Laura Parry

Fine-tuning the cardiac O-GlcNAcylation regulatory enzymes governs the functional and structural phenotype of the diabetic heart.

Publisher: Oxford University Press (OUP)

Date: 08-02-2022

DOI: 10.1093/CVR/CVAB043

Abstract: The glucose-driven enzymatic modification of myocardial proteins by the sugar moiety, β-N-acetylglucosamine (O-GlcNAc), is increased in pre-clinical models of diabetes, implicating protein O-GlcNAc modification in diabetes-induced heart failure. Our aim was to specifically examine cardiac manipulation of the two regulatory enzymes of this process on the cardiac phenotype, in the presence and absence of diabetes, utilising cardiac-targeted recombinant-adeno-associated viral-vector-6 (rAAV6)-mediated gene delivery. In human myocardium, total protein O-GlcNAc modification was elevated in diabetic relative to non-diabetic patients, and correlated with left ventricular (LV) dysfunction. The impact of rAAV6-delivered O-GlcNAc transferase (rAAV6-OGT, facilitating protein O-GlcNAcylation), O-GlcNAcase (rAAV6-OGA, facilitating de-O-GlcNAcylation), and empty vector (null) were determined in non-diabetic and diabetic mice. In non-diabetic mice, rAAV6-OGT was sufficient to impair LV diastolic function and induce maladaptive cardiac remodelling, including cardiac fibrosis and increased Myh-7 and Nppa pro-hypertrophic gene expression, recapitulating characteristics of diabetic cardiomyopathy. In contrast, rAAV6-OGA (but not rAAV6-OGT) rescued LV diastolic function and adverse cardiac remodelling in diabetic mice. Molecular insights implicated impaired cardiac PI3K(p110α)-Akt signalling as a potential contributing mechanism to the detrimental consequences of rAAV6-OGT in vivo. In contrast, rAAV6-OGA preserved PI3K(p110α)-Akt signalling in diabetic mouse myocardium in vivo and prevented high glucose-induced impairments in mitochondrial respiration in human cardiomyocytes in vitro. Maladaptive protein O-GlcNAc modification is evident in human diabetic myocardium, and is a critical regulator of the diabetic heart phenotype. Selective targeting of cardiac protein O-GlcNAcylation to restore physiological O-GlcNAc balance may represent a novel therapeutic approach for diabetes-induced heart failure.

Mesotocin gene expression and evidence of gene duplication in the tammar wallaby

Publisher: Wiley

Date: 05-1998

DOI: 10.1111/J.1749-6632.1998.TB10829.X

Abstract: Adolescent mental health (AMH) is a critical driver of HIV outcomes, but is often overlooked in HIV research and programming. The implementation science Exploration, Preparation, Implementation, Sustainment (EPIS) framework informed development of a questionnaire that was sent to a global alliance of adolescent HIV researchers, providers, and implementors working in sub-Saharan Africa with the aim to (1) describe current AMH outcomes incorporated into HIV research within the alliance (2) identify determinants (barriers/gaps) of integrating AMH into HIV research and care and (3) describe current AMH screening and referral systems in adolescent HIV programs in sub-Saharan Africa. Respondents reported on fourteen named studies that included AMH outcomes in HIV research. Barriers to AMH integration in HIV research and care programs were explored with suggested implementation science strategies to achieve the goal of integrated and sustained mental health services within adolescent HIV programs.

ESTIMATION OF PREGNANCY RATES AND REPRODUCTIVE FAILURE IN NEW ZEALAND FUR SEALS (ARCTOCEPHALUS FORSTERI)

Publisher: Oxford University Press (OUP)

Date: 12-2005

DOI: 10.1644/05-MAMM-A-085R.1

A Vasoactive Role for Endogenous Relaxin in Mesenteric Arteries of Male Mice

Publisher: Public Library of Science (PLoS)

Date: 22-09-2014

DOI: 10.1371/JOURNAL.PONE.0107382

Cardio-renal and metabolic adaptations during pregnancy in female rats born small: implications for maternal health and second generation fetal growth

Publisher: Wiley

Date: 10-01-2012

DOI: 10.1113/JPHYSIOL.2011.219147

Oxytocin and Estrogen Receptor Expression in the Myometrium of Pregnant Relaxin‐Deficient (Rlx^−/−) Mice

Publisher: Wiley

Date: 05-2005

DOI: 10.1196/ANNALS.1282.014

Abstract: Relaxin decreases oxytocin-stimulated rat myometrial contractions in vitro. This study used pregnant relaxin-deficient (Rlx-/-) mice to investigate the interaction between relaxin, oxytocin receptor (OTR), and estrogen receptor (ER) expression in the myometrium. Myometrial OTRs were significantly decreased on gestation day 18.5 in Rlx-/- mice than in Rlx+/+ mice. An increase in ERalpha in Rlx+/+ mice at term was correlated with a decrease in ERbeta, which was not observed in Rlx-/- mice. Treatment of Rlx-/- mice with relaxin had no effect on OTR, LGR7, or ERalpha expression, but it caused a significant decrease in ERbetas.

Gene therapy targeting cardiac phosphoinositide 3-kinase (p110α) attenuates cardiac remodeling in type 2 diabetes

Publisher: American Physiological Society

Date: 04-2020

DOI: 10.1152/AJPHEART.00632.2019

Abstract: Diabetic cardiomyopathy is a distinct form of heart disease that represents a major cause of death and disability in diabetic patients, particularly, the more prevalent type 2 diabetes patient population. In the current study, we investigated whether administration of recombinant adeno-associated viral vectors carrying a constitutively active phosphoinositide 3-kinase (PI3K)(p110α) construct (rAAV6-caPI3K) at a clinically relevant time point attenuates diabetic cardiomyopathy in a preclinical type 2 diabetes (T2D) model. T2D was induced by a combination of a high-fat diet (42% energy intake from lipid) and low-dose streptozotocin (three consecutive intraperitoneal injections of 55 mg/kg body wt), and confirmed by increased body weight, mild hyperglycemia, and impaired glucose tolerance (all P 0.05 vs. nondiabetic mice). After 18 wk of untreated diabetes, impaired left ventricular (LV) systolic dysfunction was evident, as confirmed by reduced fractional shortening and velocity of circumferential fiber shortening (Vcf c , all P 0.01 vs. baseline measurement). A single tail vein injection of rAAV6-caPI3K gene therapy (2×10 11 vector genomes) was then administered. Mice were followed for an additional 8 wk before end point. A single injection of cardiac targeted rAAV6-caPI3K attenuated diabetes-induced cardiac remodeling by limiting cardiac fibrosis (reduced interstitial and perivascular collagen deposition, P 0.01 vs. T2D mice) and cardiomyocyte hypertrophy (reduced cardiomyocyte size and Nppa gene expression, P 0.001 and P 0.05 vs. T2D mice, respectively). The diabetes-induced LV systolic dysfunction was reversed with rAAV6-caPI3K, as demonstrated by improved fractional shortening and velocity of circumferential fiber shortening (all P 0.05 vs pre-AAV measurement). This cardioprotection occurred in combination with reduced LV reactive oxygen species ( P 0.05 vs. T2D mice) and an associated decrease in markers of endoplasmic reticulum stress (reduced Grp94 and Chop, all P 0.05 vs. T2D mice). Together, our findings demonstrate that a cardiac-selective increase in PI3K(p110α), via rAAV6-caPI3K, attenuates T2D-induced diabetic cardiomyopathy, providing proof of concept for potential translation to the clinic. NEW & NOTEWORTHY Diabetes remains a major cause of death and disability worldwide (and its resultant heart failure burden), despite current care. The lack of existing management of heart failure in the context of the poorer prognosis of concomitant diabetes represents an unmet clinical need. In the present study, we now demonstrate that delayed intervention with PI3K gene therapy (rAAV6-caPI3K), administered as a single dose in mice with preexisting type 2 diabetes, attenuates several characteristics of diabetic cardiomyopathy, including diabetes-induced impairments in cardiac remodeling, oxidative stress, and function. Our discovery here contributes to the previous body of work, suggesting the cardioprotective effects of PI3K(p110α) could be a novel therapeutic approach to reduce the progression to heart failure and death in diabetes-affected patients.

Differential expression of mesotocin receptors in the uterus and ovary of the pregnant tammar wallaby

Publisher: Bioscientifica

Date: 05-2005

DOI: 10.1530/REP.1.00505

Abstract: Mesotocin, an oxytocin-like peptide, is released in highest concentrations during parturition in macropodid marsupials. In late pregnant wallabies, uterine sensitivity to mesotocin increases markedly in the myometrium of the gravid uterus. This coincides with a significant increase in myometrial mesotocin receptor concentrations 3–4 days before term. To date, there is no information on mesotocin receptor gene expression in female wallaby reproductive tissues. This study aimed to examine mesotocin receptor gene expression in the uterus and ovaries of pregnant tammar wallabies, and to localise mesotocin receptors within the uterus. An RT-PCR strategy produced a consensus nucleotide sequence of 834 bp, which encoded 278 amino acids of transmembrane domains I to VI. This protein sequence has approximately 80% homology with the bovine and rat oxytocin receptor exon 2 region. Only one mesotocin receptor was detected in the tammar genome. The myometrium and mammary gland both expressed a 4.1 kb mesotocin receptor gene transcript. Myometrial mesotocin receptor gene expression increased on day 22 of the 26-day gestation and was significantly higher in the gravid than the non-gravid uterus in late pregnancy. This pattern of mesotocin receptor gene expression paralleled mesotocin receptor concentrations. Mesotocin binding sites were localised only to the myometrium, the highest densities being observed in the gravid uterus. Finally, this study showed high expression of mesotocin receptors in the corpus luteum. The pattern of luteal mesotocin receptor expression differed from the myometrium, with a decrease in mesotocin receptors occurring on the day of expected births.

From pregnancy to cardiovascular disease: Lessons from relaxin‐deficient animals to understand relaxin actions in the vascular system

Publisher: Wiley

Date: 10-07-2019

DOI: 10.1111/MICC.12464

Abstract: Early maternal vascular adaptations to pregnancy are predominantly driven by changes in vascular tone, reactivity, and remodeling. Failure of the maternal systemic vasculature to adapt sufficiently can lead to serious complications of pregnancy. The hormone relaxin is widely recognized for its contribution to the essential renal and systemic hemodynamic adaptations in early pregnancy through direct actions on the maternal vasculature. Studies in relaxin gene knockout mice revealed that endogenous relaxin is not only a "pregnancy hormone" but has pleiotropic actions in various tissues in males and non-pregnant females. There is strong interest in relaxin's actions in the vasculature and its utility in the treatment of vascular diseases. Relaxin treatment in rodents for 2-5 days or acute intravenous injection enhances endothelium-dependent relaxation and decreases myogenic tone in resistance arteries. These vascular actions are prolonged, even in the absence of circulating relaxin, and are underpinned by the production of endothelium-derived relaxing factors including nitric oxide, endothelium-derived hyperpolarization, and prostacyclin. Relaxin is also capable of remodeling the vascular wall in a variety of blood vessels in disease conditions. Lessons learned in pregnancy research have aided studies investigating the potential therapeutic potential of relaxin in cardiovascular disease.

Relaxin deficiency attenuates pregnancy-induced adaptation of the mesenteric artery to angiotensin II in mice

Publisher: American Physiological Society

Date: 05-2016

DOI: 10.1152/AJPREGU.00506.2015

Abstract: Pregnancy is associated with reduced peripheral vascular resistance, underpinned by changes in endothelial and smooth muscle function. Failure of the maternal vasculature to adapt correctly leads to serious pregnancy complications, such as preecl sia. The peptide hormone relaxin regulates the maternal renal vasculature during pregnancy however, little is known about its effects in other vascular beds. This study tested the hypothesis that functional adaptation of the mesenteric and uterine arteries during pregnancy will be compromised in relaxin-deficient ( Rln −/− ) mice. Smooth muscle and endothelial reactivity were examined in small mesenteric and uterine arteries of nonpregnant (estrus) and late-pregnant ( day 17.5) wild-type ( Rln +/+ ) and Rln −/− mice using wire myography. Pregnancy per se was associated with significant reductions in contraction to phenylephrine, endothelin-1, and ANG II in small mesenteric arteries, while sensitivity to endothelin-1 was reduced in uterine arteries of Rln +/+ mice. The normal pregnancy-associated attenuation of ANG II-mediated vasoconstriction in mesenteric arteries did not occur in Rln −/− mice. This adaptive failure was endothelium-independent and did not result from altered expression of ANG II receptors or regulator of G protein signaling 5 ( Rgs5) or increases in reactive oxygen species generation. Inhibition of nitric oxide synthase with l-NAME enhanced ANG II-mediated contraction in mesenteric arteries of both genotypes, whereas blockade of prostanoid production with indomethacin only increased ANG II-induced contraction in arteries of pregnant Rln +/+ mice. In conclusion, relaxin deficiency prevents the normal pregnancy-induced attenuation of ANG II-mediated vasoconstriction in small mesenteric arteries. This is associated with reduced smooth muscle-derived vasodilator prostanoids.

Uteroplacental insufficiency programmes vascular dysfunction in non‐pregnant rats: compensatory adaptations in pregnancy

Publisher: Wiley

Date: 07-2012

DOI: 10.1113/JPHYSIOL.2012.230011

Relaxin mediates uterine artery compliance during pregnancy and increases uterine blood flow

Publisher: Wiley

Date: 28-06-2012

DOI: 10.1096/FJ.12-210567

Normal mammary gland growth and lactation capacity in pregnant relaxin-deficient mice

Publisher: CSIRO Publishing

Date: 2009

DOI: 10.1071/RD08243

Abstract: Pups born to mice with a targeted deletion of relaxin or its receptor (Rxfp1) die within 24 h postpartum. This has been attributed, in part, to abnormal mammary gland development in relaxin-mutant mice (Rln–/–). However, mammary development is normal in relaxin receptor-mutant (Rxfp1–/–) mice. The present study aimed to verify the mammary phenotypes in late pregnant and early lactating Rln–/– mice and to test the hypothesis that relaxin is involved in milk protein synthesis. Comparisons between late pregnant and early lactating wildtype (Rln+/+) and Rln–/– mice showed no differences in lobuloalveolar structure or ductal branching in the mammary gland. Mammary explants from Rln–/– mice also expressed β-casein and α-lactalbumin in response to lactogenic hormones at a similar level to Rln+/+ mice, implying normal milk protein synthesis. Pregnant Rln–/– mice infused with relaxin for 6 days gave birth to live pups without difficulty, and 96% of pups survived beyond 7 days. This is in contrast with the 100% pup mortality in saline-treated Rln–/– mice or 3-day relaxin-treated Rln–/– mice. Pups born to relaxin-treated Rln–/– dams weighed significantly less than Rln+/+ pups but had similar growth rates as their wildtype counterparts. In summary, relaxin is not critical for mammary gland development or β-casein and α-lactalbumin expression in late pregnant mice. In addition, Rln–/– dams did not need to be treated with relaxin postpartum for the pups to survive, suggesting that relaxin has no role in the maintenance of lactation in mice.

Relaxin Physiology in the Female Reproductive Tract during Pregnancy

Publisher: Springer New York

Date: 2007

DOI: 10.1007/978-0-387-74672-2_4

Abstract: The characteristic functions of relaxin are associated with female reproductive tract physiology. These include the regulation of biochemical processes involved in remodeling the extracellular matrix of the cervix and vagina during pregnancy and rupture of the fetal membranes at term. Such modifications enable the young to move unimpeded through the birth canal and prevent dystocia. However, relaxin's physiological actions are not limited to late gestation. New functions for this peptide hormone in implantation and placentation are also emerging. Relaxin promotes uterine and placental growth and influences vascular development and proliferation in the endometrium. This chapter provides an overview of the current literature on relaxin physiology in the uterus, cervix and vagina of pregnant females and the impact on fetal health. It also outlines the potential mechanisms of relaxin action, particularly in the cervical extracellular matrix and uterine endometrium.

Increased superoxide production and altered nitric oxide-mediated relaxation in the aorta of young but not old male relaxin-deficient mice

Publisher: American Physiological Society

Date: 15-07-2015

DOI: 10.1152/AJPHEART.00786.2014

Abstract: The vascular effects of exogenous relaxin (Rln) treatment are well established and include decreased myogenic reactivity and enhanced relaxation responses to vasodilators in small resistance arteries. These vascular responses are reduced in older animals, suggesting that Rln is less effective in mediating arterial function with aging. The present study investigated the role of endogenous Rln in the aorta and the possibility that vascular dysfunction occurs more rapidly with aging in Rln-deficient ( Rln −/− ) mice. We compared vascular function and underlying vasodilatory pathways in the aorta of male wild-type ( Rln +/+ ) and Rln −/− mice at 4 and 16 mo of age using wire myography. Superoxide production, but not nitrotyrosine or NADPH oxidase expression, was significantly increased in the aorta of young Rln −/− mice, whereas endothelial nitric oxide (NO) synthase and basal NO availability were both significantly decreased compared with Rln +/+ mice. In the presence of the cyclooxygenase inhibitor indomethacin, sensitivity to ACh was significantly decreased in young Rln −/− mice, demonstrating altered NO-mediated relaxation that was normalized in the presence of a membrane-permeable SOD or ROS scavenger. These vascular phenotypes were not exacerbated in old Rln −/− mice and, in most cases, did not differ significantly from old Rln +/+ mice. Despite the vascular phenotypes in Rln −/− mice, endothelium-dependent and -independent vasodilation were not adversely affected. Our data show a role for endogenous Rln in reducing superoxide production and maintaining NO availability in the aorta but also demonstrate that Rln deficiency does not compromise vascular function in this artery or exacerbate endothelial dysfunction associated with aging.

Animal models of preeclampsia: translational failings and why.

Publisher: American Physiological Society

Date: 04-2018

DOI: 10.1152/AJPREGU.00355.2017

Abstract: Preecl sia affects up to 8% of pregnancies worldwide and is a leading cause of both maternal and fetal morbidity and mortality. Our current understanding of the cause(s) of preecl sia is far from complete, and the lack of a single reliable animal model that recapitulates all aspects of the disease further confounds our understanding. This is partially due to the heterogeneous nature of the disease, coupled with our evolving understanding of its etiology. Nevertheless, animal models are still highly relevant and useful tools that help us better understand the pathophysiology of specific aspects of preecl sia. This review summarizes the various types and characteristics of animal models used to study preecl sia, highlighting particular features of these models relevant to clinical translation. This review points out the strengths and limitations of these models to illustrate the importance of using the appropriate model depending on the research question.

Inhibition of Oxytocin Receptor and Estrogen Receptor-α Expression, But Not Relaxin Receptors (LGR7), in the Myometrium of Late Pregnant Relaxin Gene Knockout Mice

Publisher: The Endocrine Society

Date: 10-2003

DOI: 10.1210/EN.2003-0548

Abstract: This study used relaxin (RLX) gene knockout mice (Rlx−/−) to investigate the effects of RLX on myometrial oxytocin receptor (OTR) and estrogen receptor (ER)-α gene expression in late gestation. We also characterized the temporal expression of the RLX receptor (LGR7) and demonstrated gene transcripts in the myometrium of Rlx+/+ and Rlx−/− mice. There was a significant (P & 0.05) decrease in myometrial LGR7 gene expression on d 17.5 and 18.5 post coitum (pc) compared with earlier stages of gestation, but no differences between Rlx+/+ and Rlx−/− mice. Myometrial OTR mRNA levels increased at the end of gestation in Rlx+/+ but not Rlx−/− mice. ERα gene expression was up-regulated on d 14.5 pc in Rlx+/+ mice, with mRNA levels remaining high throughout late gestation. In contrast, ERα mRNA levels were significantly lower in Rlx−/− mice on d 14.5 and 18.5 pc. These data show that the increases in myometrial OTR and ERα expression in late pregnant Rlx+/+ mice were attenuated in Rlx−/− mice. The effects of RLX on OTRs are probably mediated via activation of ERα. Finally, RLX receptor expression in the myometrium of Rlx−/− mice did not differ from wild-type mice, implying that RLX does not influence expression of its receptor.

Relaxin down-regulates renal fibroblast function and promotes matrix remodelling in vitro

Publisher: Oxford University Press (OUP)

Date: 06-02-2004

DOI: 10.1093/NDT/GFG598

Abstract: Renal fibroblasts are important effector cells in tubulointerstitial fibrosis, with experimental antifibrotic strategies focusing on the functional down-regulation of these cells. Several experimental models of fibrosis have provided evidence for the effectiveness of the polypeptide hormone relaxin as a potential antifibrotic agent. This study was conducted to further elucidate the antifibrotic mechanisms of relaxin on renal fibroblasts in vitro. Rat cortical fibroblasts were obtained from outgrowth culture of renal tissue isolated from kidneys 3 days post-unilateral ureteric obstruction and constituted 100% of cells studied. A relaxin radio-receptor assay was used to establish binding of relaxin to renal fibroblasts in vitro. Functional studies then examined the effects of H2 relaxin (0, 1, 10 and 100 ng/ml) on fibroblast kinetics, expression of alpha-smooth muscle actin (alpha-SMA), total collagen synthesis, collagenase production and collagen-I lattice contraction. CTGF mRNA expression was also measured by northern analysis. H2 relaxin bound with high affinity to rat renal fibroblasts, but receptor numbers were low. Consistent with its previously reported bimodal effect, transforming growth factor (TGF-beta 1) reduced fibroblast proliferation, an effect abrogated by H2 relaxin. Fibroblasts exposed to H2 relaxin (100 ng/ml) for 24 h demonstrated decreased immunostaining for alpha-SMA and reduced alpha-SMA protein expression compared with controls. There was a trend for a relaxin-mediated reduction in total collagen synthesis and alpha 1(I) mRNA expression with large dose-related increases in collagenase protein expression being observed. TGF-beta 1-stimulated collagen-I lattice contraction was significantly inhibited following co-incubation with 100 ng/ml relaxin. Incremental doses of H2 relaxin had no significant effect on CTGF mRNA expression. The findings of this study suggest that the antifibrotic effects of relaxin involve down-regulation of fibroblast activity, increase in collagenase synthesis and restructuring of collagen-I lattices, which are consistent with its known physiological role of matrix remodelling. Although there appears to be an interaction between TGF-beta 1 and H2 relaxin, this does not appear to involve a reduction in CTGF mRNA expression.

Steroid‐Independent Regulation of Uterine Oxytocin Receptors

Publisher: Wiley

Date: 04-2004

DOI: 10.1111/J.0953-8194.2004.01164.X

Acute Intravenous Injection of Serelaxin (Recombinant Human Relaxin‐2) Causes Rapid and Sustained Bradykinin‐Mediated Vasorelaxation

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 27-01-2014

DOI: 10.1161/JAHA.113.000493

Abstract: A recent clinical trial ( RELAX in in Acute Heart Failure [ RELAX ‐ AHF ]) demonstrated that 48 hours of continuous intravenous infusion of the vasorelaxant peptide serelaxin (recombinant human relaxin‐2) to patients with acute heart failure reduced cardiovascular mortality at 180 days. The persistence of a vasorelaxant response as a potential mechanism for this long‐term benefit and the vascular effects of a bolus intravenous injection of serelaxin have not been examined. This study investigates changes in resistance artery reactivity and passive mechanical wall properties following an intravenous serelaxin injection and whether these vascular effects persist in the absence of detectable circulating serelaxin. Male rats were injected with 13.3 μg/kg serelaxin into the tail vein mesenteric arteries were assessed 3 and 24 hours after treatment by using wire‐myography. Serelaxin increased basal nitric oxide synthase activity and reduced maximal contraction to endothelin‐1 at 3 hours after administration. Serelaxin treatment also selectively enhanced bradykinin‐mediated endothelium‐dependent relaxation. This effect was sustained for 24 hours in the absence of circulating serelaxin. Serelaxin‐mediated augmentation of bradykinin‐evoked relaxation involved endothelium‐derived hyperpolarization after 3 hours and prostacyclin‐mediated relaxation after 24 hours. Furthermore, upregulation of inducible nitric oxide synthase, phosphorylation of protein kinase B at Ser473 and endothelial nitric oxide synthase at Ser1177 was observed at 24 hours after serelaxin injection. There were no effects of serelaxin on passive arterial wall stiffness. Our data show that a bolus intravenous injection of serelaxin modulates endothelial vasodilator function 3 hours after administration, an effect that was sustained for 24 hours. The prolonged bradykinin‐mediated vasorelaxation is principally mediated through prostacyclin.

Localization of relaxin receptors in arteries and veins, and region‐specific increases in compliance and bradykinin‐mediated relaxation after in vivo serelaxin treatment

Publisher: Wiley

Date: 13-09-2013

DOI: 10.1096/FJ.13-233429

Physiological or pathological — a role for relaxin in the cardiovascular system?

Publisher: Elsevier BV

Date: 04-2003

DOI: 10.1016/S1471-4892(03)00011-0

Abstract: The omnipresent 6kDa polypeptide relaxin (RLX) is emerging as a multi-functional endocrine and paracrine factor, with a broad range of target tissues that includes the cardiovascular system. Humans and other higher primates have three RLX genes, designated H1, H2 and H3, of which H2 RLX is the major stored and circulating form. Rodents have only two RLX genes: relaxin-1 (equivalent to H2 RLX) and relaxin-3 (equivalent to H3 RLX). The recent cloning of the human RLX receptor (LGR7), a member of the leucine-rich repeat family of G-protein-coupled orphan receptors, and detection of LGR7 gene transcripts in the heart confirm this organ as a target for RLX (H2). However, evidence for production of the ligand within the cardiovascular system is limited, and few studies have clearly identified the physiological effects of RLX on cardiac function. To add to the controversy, serum concentrations and expression of RLX in the heart are elevated in chronic heart failure patients and animal models of cardiomyopathy, implying that RLX may only be a marker for pathological cardiovascular conditions, rather than normal physiology.

Marsupial relaxin: Complementary deoxyribonucleic acid sequence and gene expression in the female and male tammar wallaby, Macropus eugenii

Publisher: Oxford University Press (OUP)

Date: 07-1997

DOI: 10.1095/BIOLREPROD57.1.119

Abstract: The nucleotide and derived amino acid sequences of tammar preprorelaxin were established by combined reverse transcriptase polymerase chain reaction and 3'- and 5'-rapid lification of cDNA ends methods, using RNA from the corpus luteum of late pregnancy as template. Relaxin gene expression was then investigated in tissues at various stages of the 26-day pregnancy and in adult males. The full-length tammar relaxin preprohormone is 579 base pairs. The derived amino acid sequence contains a probable signal peptide of 26 amino acids, a B-domain of 31 amino acids, a C-domain of 111 amino acids, and an A-domain of 24 amino acids, with sequence homologies of 49%, 38%, 47%, and 47%, respectively, to dogfish, pig, and both human relaxins, for the combined A- and B-domains of the functional peptides. The conserved amino acid residues in the B-domain confirm a region shown to be essential for binding of the peptide to its receptor. A relaxin gene is expressed in several other tissues of pregnant tammars including the placenta, follicle, and hypothalamus. Northern analysis showed a 1-kilobase relaxin transcript in the corpus luteum and placenta. Using RNase protection assays, relaxin gene expression in the corpus luteum was greater in early and mid pregnancy, reduced at term, and absent postpartum. These data demonstrate relaxin biosynthesis in both the corpus luteum and placenta in this marsupial and suggest that a relaxin physiology has been conserved during mammalian evolution.

Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle

Publisher: Wiley

Date: 05-2005

DOI: 10.1196/ANNALS.1282.020

Abstract: This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.

Mesotocin receptor gene and protein expression in the prostate gland, but not testis, of the tammar wallaby, Macropus eugenii

Publisher: Oxford University Press (OUP)

Date: 11-1998

DOI: 10.1095/BIOLREPROD59.5.1101

Abstract: Evidence suggests that systemic oxytocin (OT) causes contractions of the prostate gland during ejaculation in eutherians, although functional OT receptors in this tissue have not been identified. Male marsupials secrete mesotocin (MT) from the pituitary and have relatively large, muscular prostate glands, so we examined MT receptors (MTRs) in the reproductive tract of the male tammar wallaby at the mRNA and protein level. We first obtained a partial (588 base pair) sequence of the tammar MTR cDNA that showed high homology to eutherian OT receptors (74-77%) and low homology to vasopressin receptors (38-52%). Analysis by reverse transcription-polymerase chain reaction demonstrated MTR mRNA in the adult, juvenile, and pouch young prostate and epididymis, but not testis. MTR transcripts were observed in the smooth muscle layers surrounding the urethral lumen and in the fibromuscular capsule. There was a single high-affinity 125I-D(CH2)5[Tyr(Me)2, Tyr4, Orn8, Tyr-NH29]-vasotocin (125I-OTA) binding site in the adult prostate. Competitive binding assays revealed identical ligand-binding profiles to the myometrium MTR (OTA > OT = MT > arginine vasopressin [AVP] antagonist > AVP). A lower-affinity 125I-OTA-binding site was present in the testis, with ligand-binding profiles indicating binding to vasopressin receptors. MTR concentrations in the prostate were 8-fold lower than concentrations in the myometrium. Our data demonstrate the presence of an MTR gene and functional receptor protein in the prostate gland, but not the testis, of the tammar. Localization of MTRs to the smooth muscle fibers in the capsule and surrounding the urethral lumen suggests a contractile function for MT during ejaculation.

Strain‐specific genetics, anatomy and function of enteric neural serotonergic pathways in inbred mice

Publisher: Wiley

Date: 30-01-2009

DOI: 10.1113/JPHYSIOL.2008.160416

VPAC1 receptors regulate intestinal secretion and muscle contractility by activating cholinergic neurons in guinea pig jejunum.

Publisher: American Physiological Society

Date: 05-2014

DOI: 10.1152/AJPGI.00416.2013

Abstract: In the gastrointestinal tract, vasoactive intestinal peptide (VIP) is found exclusively within neurons. VIP regulates intestinal motility via neurally mediated and direct actions on smooth muscle and secretion by a direct mucosal action, and via actions on submucosal neurons. VIP acts via VPAC 1 and VPAC 2 receptors however, the subtype involved in its neural actions is unclear. The neural roles of VIP and VPAC 1 receptors (VPAC 1 R) were investigated in intestinal motility and secretion in guinea pig jejunum. Expression of VIP receptors across the jejunal layers was examined using RT-PCR. Submucosal and myenteric neurons expressing VIP receptor subtype VPAC 1 and/or various neurochemical markers were identified immunohistochemically. Isotonic muscle contraction was measured in longitudinal muscle-myenteric plexus preparations. Electrogenic secretion across mucosa-submucosa preparations was measured in Ussing chambers by monitoring short-circuit current. Calretinin + excitatory longitudinal muscle motor neurons expressed VPAC 1 R. Most cholinergic submucosal neurons, notably NPY + secretomotor neurons, expressed VPAC 1 R. VIP (100 nM) induced longitudinal muscle contraction that was inhibited by TTX (1 μM), PG97–269 (VPAC 1 antagonist 1 μM), and hyoscine (10 μM), but not by hexamethonium (200 μM). VIP (50 nM)-evoked secretion was depressed by hyoscine or PG97–269 and involved a small TTX-sensitive component. PG97–269 and TTX combined did not further depress the VIP response observed in the presence of PG97–269 alone. We conclude that VIP stimulates ACh-mediated longitudinal muscle contraction via VPAC 1 R on cholinergic motor neurons. VIP induces Cl − secretion directly via epithelial VPAC 1 R and indirectly via VPAC 1 R on cholinergic secretomotor neurons. No evidence was obtained for involvement of other neural VIP receptors.

Human relaxin gene 3 (H3) and the equivalent mouse relaxin (M3) gene: Novel members of the relaxin peptide family

Publisher: Elsevier BV

Date: 2002

DOI: 10.1074/JBC.M107882200

Evidence for a local fetal influence on myometrial oxytocin receptors during pregnancy in the tammar wallaby (Macropus eugenii)

Publisher: Oxford University Press (OUP)

Date: 1997

DOI: 10.1095/BIOLREPROD56.1.200

Abstract: Mesotocin (MT), the oxytocin-like peptide of the tammar wallaby (Macropus eugenii) is important for delivery of live young. The tammar mesotocin receptor (MTR) was first characterized using the iodinated oxytocin receptor antagonist [125I]d(CH2)5 [Tyr(Me)2, Tyr4, Orn8, Tyr-NH(2)9]-vasotocin. MTR concentrations were then measured in matched s les of gravid and nongravid myometrium and median vagina at different stages of the 26-day pregnancy. MTR concentrations in both the gravid and nongravid myometrium changed significantly (ANOVA, p < 0.01) during pregnancy. There was no difference in MTR concentrations between uteri on Days 8-22. From Day 23 of pregnancy, MTR concentrations in the gravid myometrium increased (615.8 +/- 144.0 fmol/mg protein), whereas in the nongravid myometrium, they remained unchanged (248.6 +/- 65.5 fmol/mg protein). Receptor concentrations were high in the gravid myometrium during the last 3 days of pregnancy but decreased significantly in the nongravid myometrium. In the median vagina, MTR concentrations were low compared with myometrial tissues and did not increase at term. Changes in MTR concentrations paralleled changes in uterine responsiveness to exogenous MT in vitro. Our data show that MTR concentrations and the responsiveness to MT differ between the gravid and nongravid myometrium during pregnancy. The increase in MTRs in the gravid myometrium and the decrease in the nongravid suggest that different factors influence these receptors in the separate uteri, independent of systemic influence.

Ultrastructural localization of relaxin in the corpus luteum of the pregnant and early lactating tammar wallaby, Macropus eugenii

Publisher: Springer Science and Business Media LLC

Date: 26-11-1997

DOI: 10.1007/S004410050967

Abstract: Electron-microscope immunocytochemistry was used to determine the subcellular distribution and presence of immunoreactive relaxin throughout pregnancy and early lactation in the corpus luteum of a marsupial, the tammar wallaby. Membrane-bound, electron-dense granules were a prominent feature of the luteal cell cytoplasm. The highest numbers of granules were observed between days 20 and 24 of the 26-day gestation, with a rapid clearance immediately after birth. Relaxin immunogold particles were present only in small, electron-dense granules (200-350 nm in diameter), with no particles observed in larger granules (>400 nm diameter), nuclei or mitochondria. Relaxin immunoreactivity was low throughout early and mid pregnancy but increased markedly between days 21 and 22 and remained high over the last 4 days of pregnancy. The number of granules containing relaxin immunogold particles and the density of immunostaining were both reduced on the day of expected births (day 26). Our data demonstrate that electron-dense granules in the luteal cell cytoplasm of a pregnant marsupial contain relaxin. The peptide is produced in greatest amounts at the end of pregnancy, consistent with a role in parturition.

Time‐dependent activation of prostacyclin and nitric oxide pathways during continuous i.v. infusion of serelaxin (recombinant human H2 relaxin)

Publisher: Wiley

Date: 17-02-2016

DOI: 10.1111/BPH.13404

Mammalian mesotocin: cDNA sequence and expression of an oxytocin-like gene in a macropodid marsupial, the tammar wallaby

Publisher: Elsevier BV

Date: 05-2000

DOI: 10.1006/GCEN.2000.7464

Abstract: The oxytocin (OT)-like peptide of most Australian marsupials is mesotocin (MT), which differs from OT by substitution of isoleucine for leucine at position 8. To date, the only information on the evolution of the OT peptide in marsupials is based on the sequence of the 9-amino acid peptide itself. The main objective of this study was to obtain the nucleotide and derived amino acid sequences of a marsupial MT precursor for comparison with known OT and MT precursors of eutherians and nonmammalian vertebrates. The structural organization and sequence of the MT gene and its specific transcript were established in a macropodid marsupial, the tammar wallaby, using PCR strategies with a combination of genomic DNA and reverse-transcribed hypothalamic RNA. A consensus genomic sequence of 1221 bp was produced which, by comparison with the expressed cDNA sequence, included two intron sequences of 480 and 188 bp. The tammar MT precursor molecule consists of a 32-amino acid signal peptide, followed by the MT-encoding region and the Gly-Lys-Arg carboxy-terminal cleavage and amidation signal which separates the nonapeptide from the 92-amino acid neurophysin. At the amino acid level, the MT precursor is more similar to eutherian OT precursors than to nonmammalian MT, isotocin, or vasotocin precursors. Northern analysis demonstrated a single transcript of approximately 0.6 kB in the hypothalamus. Mesotocin mRNA is also present in several tissues of the reproductive tract, including the corpus luteum, follicle, uterus, and placenta. Within the ovary, MT transcripts are localized predominantly in the granulosa cells of antral follicles with some positive hybridization signals in cells of the theca interna. This pattern of MT gene expression in marsupials is very similar to that of OT in eutherians and suggests a conserved physiology in the mammalian ovary.

Relaxin deficiency results in increased expression of angiogenesis- and remodelling-related genes in the uterus of early pregnant mice but does not affect endometrial angiogenesis prior to implantatio

Publisher: Springer Science and Business Media LLC

Date: 22-03-2016

DOI: 10.1186/S12958-016-0148-Y

Metformin as a prevention and treatment for preeclampsia: effects on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion and endothelial dysfunction

Publisher: Elsevier BV

Date: 03-2016

DOI: 10.1016/J.AJOG.2015.12.019

Abstract: Preecl sia is associated with placental ischemia/hypoxia and secretion of soluble fms-like tyrosine kinase 1 and soluble endoglin into the maternal circulation. This causes widespread endothelial dysfunction that manifests clinically as hypertension and multisystem organ injury. Recently, small molecule inhibitors of hypoxic inducible factor 1α have been found to reduce soluble fms-like tyrosine kinase 1 and soluble endoglin secretion. However, their safety profile in pregnancy is unknown. Metformin is safe in pregnancy and is also reported to inhibit hypoxic inducible factor 1α by reducing mitochondrial electron transport chain activity. The purposes of this study were to determine (1) the effects of metformin on placental soluble fms-like tyrosine kinase 1 and soluble endoglin secretion, (2) to investigate whether the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion are regulated through the mitochondrial electron transport chain, and (3) to examine its effects on endothelial dysfunction, maternal blood vessel vasodilation, and angiogenesis. We performed functional (in vitro and ex vivo) experiments using primary human tissues to examine the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from placenta, endothelial cells, and placental villous explants. We used succinate, mitochondrial complex II substrate, to examine whether the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion were mediated through the mitochondria. We also isolated mitochondria from preterm preecl tic placentas and gestationally matched control subjects and measured mitochondrial electron transport chain activity using kinetic spectrophotometric assays. Endothelial cells or whole maternal vessels were incubated with metformin to determine whether it rescued endothelial dysfunction induced by either tumor necrosis factor-α (to endothelial cells) or placenta villous explant-conditioned media (to whole vessels). Finally, we examined the effects of metformin on angiogenesis on maternal omental vessel explants. Metformin reduced soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from primary endothelial cells, villous cytotrophoblast cells, and preterm preecl tic placental villous explants. The reduction in soluble fms-like tyrosine kinase 1 and soluble endoglin secretion was rescued by coadministration of succinate, which suggests that the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin were likely to be regulated at the level of the mitochondria. In addition, the mitochondrial electron transport chain inhibitors rotenone and antimycin reduced soluble fms-like tyrosine kinase 1 secretion, which further suggests that soluble fms-like tyrosine kinase 1 secretion is regulated through the mitochondria. Mitochondrial electron transport chain activity in preterm preecl tic placentas was increased compared with gestation-matched control subjects. Metformin improved features of endothelial dysfunction relevant to preecl sia. It reduced endothelial cell messenger RNA expression of vascular cell adhesion molecule 1 that was induced by tumor necrosis factor-α (vascular cell adhesion molecule 1 is an inflammatory adhesion molecule up-regulated with endothelial dysfunction and is increased in preecl sia). Placental conditioned media impaired bradykinin-induced vasodilation this effect was reversed by metformin. Metformin also improved whole blood vessel angiogenesis impaired by fms-like tyrosine kinase 1. Metformin reduced soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from primary human tissues, possibly by inhibiting the mitochondrial electron transport chain. The activity of the mitochondrial electron transport chain was increased in preterm preecl tic placenta. Metformin reduced endothelial dysfunction, enhanced vasodilation in omental arteries, and induced angiogenesis. Metformin has potential to prevent or treat preecl sia.

5-HT_1A, SST₁, and SST₂receptors mediate inhibitory postsynaptic potentials in the submucous plexus of the guinea pig ileum

Publisher: American Physiological Society

Date: 03-2010

DOI: 10.1152/AJPGI.00438.2009

Abstract: Vasoactive intestinal peptide (VIP) immunoreactive neurons are important secretomotor neurons in the submucous plexus. They are the only submucosal neurons to receive inhibitory inputs and exhibit both noradrenergic and nonadrenergic inhibitory synaptic potentials (IPSPs). The former are mediated by α 2 -adrenoceptors, but the receptors mediating the latter have not been identified. We used standard intracellular recording, RT-PCR, and confocal microscopy to test whether 5-HT 1A , SST 1 , and/or SST 2 receptors mediate nonadrenergic IPSPs in VIP submucosal neurons in guinea pig ileum in vitro. The specific 5-HT 1A receptor antagonist WAY 100135 (1 μM) reduced the litude of IPSPs, an effect that persisted in the presence of the α 2 -adrenoceptor antagonist idazoxan (2 μM), suggesting that 5-HT might mediate a component of the IPSPs. Confocal microscopy revealed that there were many 5-HT-immunoreactive varicosities in close contact with VIP neurons. The specific SSTR 2 antagonist CYN 154806 (100 nM) and a specific SSTR 1 antagonist SRA 880 (3 μM) each reduced the litude of nonadrenergic IPSPs and hyperpolarizations evoked by somatostatin. In contrast with the other antagonists, CYN 154806 also reduced the durations of nonadrenergic IPSPs. Effects of WAY 100135 and CYN 154806 were additive. RT-PCR revealed gene transcripts for 5-HT 1A , SST 1 , and SST 2 receptors in stripped submucous plexus preparations consistent with the pharmacological data. Although the involvement of other neurotransmitters or receptors cannot be excluded, we conclude that 5-HT 1A , SST 1 , and SST 2 receptors mediate nonadrenergic IPSPs in the noncholinergic (VIP) secretomotor neurons. This study thus provides the tools to identify functions of enteric neural pathways that inhibit secretomotor reflexes.

Peptide hormone relaxin: from bench to bedside

Publisher: American Physiological Society

Date: 06-2018

DOI: 10.1152/AJPREGU.00276.2017

Abstract: The peptide hormone relaxin has numerous roles both within and independent of pregnancy and is often thought of as a “pleiotropic hormone.” Relaxin targets several tissues throughout the body, and has many functions associated with extracellular matrix remodeling and the vasculature. This review considers the potential therapeutic applications of relaxin in cervical ripening, in vitro fertilization, preecl sia, acute heart failure, ischemia-reperfusion, and cirrhosis. We first outline the animal models used in preclinical studies to progress relaxin into clinical trials and then discuss the findings from these studies. In many cases, the positive outcomes from preclinical animal studies were not replicated in human clinical trials. Therefore, the focus of this review is to evaluate the various animal models used to develop relaxin as a potential therapeutic and consider the limitations that must be addressed in future studies. These include the use of human relaxin in animals, duration of relaxin treatment, and the appropriateness of the clinical conditions being considered for relaxin therapy.

Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle

Publisher: The Endocrine Society

Date: 07-2004

DOI: 10.1210/JC.2003-030798

Enhanced Uterine Artery Stiffness in Aged Pregnant Relaxin Mutant Mice Is Reversed with Exogenous Relaxin Treatment1

Publisher: Oxford University Press (OUP)

Date: 07-2013

DOI: 10.1095/BIOLREPROD.113.108118

Abstract: Pregnancy is associated with a progressive remodeling of the uterine artery. This adaptation is influenced by local and systemic pregnancy-dependent factors. We recently demonstrated that the peptide hormone relaxin mediates uterine artery remodeling in late pregnant rats. The objective of this study in relaxin gene knockout (Rln(-/-)) mice was to test the hypothesis that relaxin deficiency throughout pregnancy disrupts uterine artery remodeling, an effect that is exacerbated by aging and reversed with relaxin treatment. Passive mechanical wall properties and extracellular matrix components were measured using pressure myography, quantitative PCR, and zymography in uterine arteries from pregnant wild-type (Rln(+/+)) and Rln(-/-) mice aged 5 and 8 mo on Days 12.5 and 17.5 pregnancy. In a second study, 8-mo-old Rln(-/-) mice received either placebo or human recombinant relaxin subcutaneously for 5 days from Day 12.5 pregnancy. Relaxin deficiency in pregnancy did not alter uterine artery remodeling in young mice. However, remodeling was impaired in older pregnant Rln(-/-) mice, resulting in significantly stiffer uterine arteries. Uterine arteries of aged Rln(-/-) pregnant mice had increased expression of elastin, whereas several matrix metalloproteinases and cell adhesion molecules were decreased relative to Rln(+/+) mice. Fetal weight was also significantly reduced in Rln(-/-) mice in late pregnancy in both young and old dams, whereas placental weight was unchanged. Arterial stiffness and reduced fetal weight were reversed after relaxin treatment. In conclusion, relaxin deficiency compromises uterine artery remodeling in older pregnant females, increasing the risk of pregnancy complications such as hypertension and intrauterine growth restriction.

Serelaxin: A Novel Therapeutic for Vascular Diseases

Publisher: Elsevier BV

Date: 06-2016

DOI: 10.1016/J.TIPS.2016.04.001

Abstract: Vascular dysfunction is an important hallmark of cardiovascular disease. It is characterized by increased sensitivity to vasoconstrictors, decreases in the endothelium-derived vasodilators nitric oxide (NO) and prostacyclin (PGI2), and endothelium-derived hyperpolarization (EDH). Serelaxin (recombinant human relaxin) has gained considerable attention as a new vasoactive drug, largely through its beneficial therapeutic effects in acute heart failure. In this review we first describe the contribution of endogenous relaxin to vascular homeostasis. We then provide a comprehensive overview of the novel mechanisms of serelaxin action in blood vessels that differentiate it from other vasodilator drugs and explain how this peptide could be used more widely as a therapeutic to alleviate vascular dysfunction in several cardiovascular diseases.

Effects of uteroplacental restriction on the relaxin-family receptors, Lgr7 and Lgr8, in the uterus of late pregnant rats

Publisher: CSIRO Publishing

Date: 2007

DOI: 10.1071/RD07007

Abstract: The peptide hormone relaxin stimulates uterine growth and endometrial angiogenesis and inhibits myometrial contractions in a variety of species. The receptor for relaxin is a leucine-rich repeat containing G-protein-coupled receptor Lgr7 (RXFP1) that is highly expressed in the myometrium of late pregnant mice, with a significant decrease in receptor density observed at term. The present study first compared the expression of Lgr7 with another relaxin-family receptor Lgr8 (RXFP2) in the uterus and placenta of late pregnant rats. The uterus was separated into endometrial and myometrial components, and the myometrium into fetal and non-fetal sites, for further analysis. We then assessed the response of these receptors to uteroplacental restriction (UPR). Expression of the Lgr7 gene was significantly higher in the uterus compared with the placenta. Within the uterus, on Day 20 of gestation, there was equivalent expression of Lgr7 in fetal and non-fetal sites of the myometrium, as well as in the endometrium v. myometrium. The second receptor investigated, Lgr8, was also expressed in the endometrium and myometrium, but at significantly lower levels than Lgr7. Bilateral ligation of the maternal uterine blood vessels on Day 18 of gestation resulted in uteroplacental restriction, a decrease in fetal weight and litter size, and a significant upregulation in uterine, but not placental, Lgr7 and Lgr8 gene expression in UPR animals compared with controls. These data suggest that both relaxin family receptors are upregulated in response to a reduction in uteroplacental blood flow in rats.

Progesterone Withdrawal, and Not Increased Circulating Relaxin, Mediates the Decrease in Myometrial Relaxin Receptor (RXFP1) Expression in Late Gestation in Rats1

Publisher: Oxford University Press (OUP)

Date: 11-2010

DOI: 10.1095/BIOLREPROD.110.084301

Abstract: In pregnant rats, a significant decrease in myometrial relaxin family peptide receptor 1 (RXFP1) expression, indicative of a functional relaxin withdrawal for activation of myometrial contractions, occurs in late gestation and during spontaneous labor. This coincides with the highest level of circulating relaxin and a decrease in progesterone. We investigated the potential regulatory role of these two systemic factors on myometrial RXFP1 expression by examining the effects of the antiprogestin RU486 and a monoclonal antibody against rat relaxin (MCA1) in pregnant rats. Rats were injected with RU486 on Gestational Day (GD) 7, 16, or 19 and were killed on GD 8, 17, or 20. RU486 caused a significant reduction in myometrial RXFP1. Plasma progesterone and 17beta-estradiol levels were increased in RU486-treated animals compared with controls. RU486 treatment also caused significant increases in myometrial Esr1 and Vegf and a decrease in Esr2. MCA1 was administered i.v. to rats from GD 17 to GD 19. On GD 20, no significant effect of MCA1 treatment on myometrial RXFP1 expression was observed compared with controls. Furthermore, there was no change in Esr1 or Esr2. A significant reduction in myometrial Vegf, however, was observed. We suggest that blocking progesterone action with RU486 increases plasma 17beta-estradiol and myometrial Esr1 and results in decreased RXFP1 expression. In summary, myometrial RXFP1 expression is mediated mainly by progesterone and not circulating relaxin in pregnant rats.

Decreased Expression of the Rat Myometrial Relaxin Receptor (RXFP1) in Late Pregnancy Is Partially Mediated by the Presence of the Conceptus1

Publisher: Oxford University Press (OUP)

Date: 11-2010

DOI: 10.1095/BIOLREPROD.110.083931

Abstract: The actions of relaxin are mediated by relaxin family peptide receptor 1 (Rxfp1). In pregnant mice, myometrial Rxfp1 expression decreases at term, coinciding with the highest level of circulating relaxin. This down-regulation in Rxfp1 in reproductive tissues has not been investigated in other pregnant animals, nor are the regulatory mechanisms known. In the present study, we examined Rxfp1 gene and protein expression in the nonpregnant, pregnant, and postpartum rat uterus. The potential effects of local conceptus-derived factors on Rxfp1 expression were then examined in unilaterally pregnant rats. Immunoreactive RXFP1 was predominantly detected in the circular smooth muscle layer in the myometrium and in the decidualized endometrium. Rxfp1 was expressed in the rat myometrium from early to midgestation at levels similar to those in nonpregnant rat myometrium, with a significant reduction in expression at both the transcriptional and translational levels during late gestation. In unilaterally pregnant rats, myometrial Rxfp1 was higher in the nongravid compared to the gravid uterine horn, demonstrating a local negative influence of the fetal-placental unit on Rxfp1 expression. In summary, the down-regulation in myometrial Rxfp1 expression at the end of gestation in the rat is partially mediated by the fetal-placental unit and is indicative of a functional withdrawal of relaxin. This may represent a novel mechanism for the activation of spontaneous uterine contractions at labor in this species.

Differential effects of relaxin deficiency on vascular aging in arteries of male mice

Publisher: Springer Science and Business Media LLC

Date: 25-06-2015

DOI: 10.1007/S11357-015-9803-Z

Geographic Affinity, Cuticular Hydrocarbons and Colony Recognition in the Australian Meat Ant Iridomyrmex purpureus

Publisher: Springer Science and Business Media LLC

Date: 08-02-1999

DOI: 10.1007/S001140050578

Adverse vascular remodelling is more sensitive than endothelial dysfunction to hyperglycaemia in diabetic rat mesenteric arteries

Publisher: Elsevier BV

Date: 09-2016

DOI: 10.1016/J.PHRS.2016.06.025

Abstract: Increased vascular stiffness and reduced endothelial nitric oxide (NO) bioavailability are characteristic of diabetes. Whether these are evident at a more moderate levels of hyperglycaemia has not been investigated. The objectives of this study were to examine the association between the level of glycaemia and resistance vasculature phenotype, incorporating both arterial stiffness and endothelial function. Diabetes was induced in male Sprague Dawley rats with streptozotocin (STZ 55mg/kg i.v.) and followed for 8 weeks. One week post STZ, diabetic rats were allocated to either moderate (∼20mM blood glucose, 6-7U/insulins.c. daily) or severe hyperglycaemia (∼30mM blood glucose, 1-2U/insulins.c. daily as required). At study end, rats were anesthetized, and the mesenteric arcade was collected. Passive mechanical wall properties were assessed by pressure myography. Responses to the endothelium-dependent vasodilator acetylcholine (ACh) were assessed using wire myography. Our results demonstrated for the first time that mesenteric arteries from both moderate and severely hyperglycaemic diabetic rats exhibited outward hypertrophic remodelling and increased axial stiffness compared to arteries from non-diabetic rats. Secondly, mesenteric arteries from severely (∼30mM blood glucose), but not moderately hyperglycaemic (∼20mM blood glucose) rats exhibit a significant reduction to ACh sensitivity compared to their non-diabetic counterparts. This endothelial dysfunction was associated with significant reduction in endothelium-derived hyperpolarisation and endothelium-dependent NO-mediated relaxation. Interestingly, endothelium-derived nitroxyl (HNO)-mediated relaxation was intact. Therefore, moderate hyperglycaemia is sufficient to induce adverse structural changes in the mesenteric vasculature, but more severe hyperglycaemia is essential to cause endothelial dysfunction.

Linkage - International - Grant ID: LX0452118

Start Date: 01-2004

End Date: 12-2007

Amount: $39,356.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP160102404

Start Date: 01-2016

End Date: 01-2019

Amount: $354,400.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP110200543

Start Date: 02-2012

End Date: 02-2015

Amount: $335,000.00

Funder: Australian Research Council

Industrial Transformation Training Centres - Grant ID: IC170100020

Start Date: 07-2018

End Date: 12-2024

Amount: $3,279,502.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0211545

Start Date: 2002

End Date: 12-2005

Amount: $405,279.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE210100155

Start Date: 2021

End Date: 06-2022

Amount: $909,079.00

Funder: Australian Research Council