Relaxin inhibits patellar tendon healing in rats: a histological and biochemical evaluation

BACKGROUND

Female patients are more likely to have tendon injuries than males, especially those who has a higher concentration of relaxin. Previous studies have demonstrated that relaxin attenuates extracellular matrix (ECM) formation. However, the mechanism of relaxin on tendon repair remains unclear. We hypothesize that relaxin inhibits tendon healing by disrupting collagen synthesis.

METHODS

A patellar tendon window defect model was established using Sprague-Dawley rats. The center of the patellar tendon was removed from the patella distal apex and inserted to the tibia tuberosity in width of 1 mm. Then, the rats were injected with saline (0.2 μg/kg/day) or relaxin (0.2 μg/kg/day) for two and four weeks, which was followed by biomechanical analysis and histological and histochemical examination.

RESULTS

Mechanical results indicated that relaxin induces a significant decrease in tear resistance, stiffness, and Young's modulus compared to those rats without relaxin treatment. In addition, it was shown that relaxin activates relaxin family peptide receptor 1(RXFP1), disturbs the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs), and reduces the deposition of collagen in injury areas.

CONCLUSIONS

Relaxin impairs tendon healing in rats. Also, relaxin might lead to tendon injury more commonly for females than males.

Intraarticular injection of relaxin-2 alleviates shoulder arthrofibrosis

Arthrofibrosis is a prevalent condition affecting greater than 5% of the general population and leads to a painful decrease in joint range of motion (ROM) and loss of independence due to pathologic accumulation of periarticular scar tissue. Current treatment options are limited in effectiveness and do not address the underlying cause of the condition: accumulation of fibrotic collagenous tissue. Herein, the naturally occurring peptide hormone relaxin-2 is administered for the treatment of adhesive capsulitis (frozen shoulder) and to restore glenohumeral ROM in shoulder arthrofibrosis. Recombinant human relaxin-2 down-regulates type I collagen and α smooth muscle actin production and increases intracellular cAMP concentration in human fibroblast-like synoviocytes, consistent with a mechanism of extracellular matrix degradation and remodeling. Pharmacokinetic profiling of a bolus administration into the glenohumeral joint space reveals the brief systemic and intraarticular (IA) half-lives of relaxin-2: 0.96 h and 0.62 h, respectively. Furthermore, using an established, immobilization murine model of shoulder arthrofibrosis, multiple IA injections of human relaxin-2 significantly improve ROM, returning it to baseline measurements collected before limb immobilization. This is in contrast to single IA (sIA) or multiple i.v. (mIV) injections of relaxin-2 with which the ROM remains constrained. The histological hallmarks of contracture (e.g., fibrotic adhesions and reduced joint space) are absent in the animals treated with multiple IA injections of relaxin-2 compared with the untreated control and the sIA- and mIV-treated animals. As these findings show, local delivery of relaxin-2 is an innovative treatment of shoulder arthrofibrosis.

Relaxin-mediated renal vasodilation in the rat is associated with falls in glomerular blood pressure

Relaxin (RLX) is a pleiotropic peptide hormone with marked renal vasodilatory actions that are physiologically important during pregnancy. RLX also has potent antifibrotic actions and is being tested therapeutically in various fibrotic diseases, including chronic kidney disease (CKD). Since renal vasodilation may expose the glomerulus to increased blood pressure [glomerular capillary pressure (PGC)], which exacerbates progression of CKD, we assessed the glomerular hemodynamic actions of acute (0.89 µg·100 g body wt-1·h-1 iv over 75 min) and chronic (1.5 µg·100 g body wt-1·h-1 sc) administration of RLX. Both acute and chronic RLX produced marked renal vasodilation and increased renal plasma flow (RPF) in euvolemic, anesthetized male rats. Glomerular filtration rate also increased with RLX, but the magnitude of the rise was much less than the increase in RPF due to concomitant decreases in filtration fraction. The fall in filtration fraction was the result of significant decreases in PGC, despite a slight increase in mean arterial blood pressure (MAP) with acute RLX and no net change in MAP with chronic RLX. This fall in PGC occurred because of the "in-series" arrangement of the afferent and efferent arteriolar resistance vessels, which can regulate PGC independently of MAP. With both acute and chronic RLX, efferent arteriolar resistance vessels relaxed to a greater extent than afferent arteriolar resistance vessels, thus producing falls in PGC. Based on this finding, RLX has a beneficial hemodynamic impact on the kidney, which, together with the antifibrotic actions of RLX, suggests a strong therapeutic potential for use in CKD.

Use of Microcomputed Tomography to Measure the Relaxin-induced Expansion of Intrapubic Ligaments in Mice

Relaxin is a 6-kDa peptide in the insulin superfamily of hormones. In addition to its effects on reproductive and musculoskeletal ligaments, relaxin has demonstrated beneficial effects on cardiac, renal, and vascular systems in preclinical models. The mouse intrapubic ligament ex vivo bioassay is the current standard for measuring in vivo relaxin bioactivity. However, this bioassay necessitates euthanasia and dissection of large cohorts to measure the intrapubic ligament at specified time points. We hypothesized that μCT imaging could be used to reduce the number of animals necessary for the intrapubic ligament bioassay by enabling a single animal to be followed longitudinally throughout the study rather than euthanizing different cohorts at established time points. Female CD1 mice were used to compare μCT imaging with the current standard. Both protocols revealed significant differences in intrapubic ligament length, with the μCT data having greater power when corrected for baseline imaging. From these data, we concluded that using μCT to measure the intrapubic ligament in mice primed with estrogen and dosed with relaxin is a viable refinement and will allow the use of fewer animals in longitudinal studies and provide more robust data, because animals can serve as their own controls.

Anti-fibrotic actions of relaxin

Fibrosis refers to the hardening or scarring of tissues that usually results from aberrant wound healing in response to organ injury, and its manifestations in various organs have collectively been estimated to contribute to around 45-50% of deaths in the Western world. Despite this, there is currently no effective cure for the tissue structural and functional damage induced by fibrosis-related disorders. Relaxin meets several criteria of an effective anti-fibrotic based on its specific ability to inhibit pro-fibrotic cytokine and/or growth factor-mediated, but not normal/unstimulated, fibroblast proliferation, differentiation and matrix production. Furthermore, relaxin augments matrix degradation through its ability to up-regulate the release and activation of various matrix-degrading matrix metalloproteinases and/or being able to down-regulate tissue inhibitor of metalloproteinase activity. Relaxin can also indirectly suppress fibrosis through its other well-known (anti-inflammatory, antioxidant, anti-hypertrophic, anti-apoptotic, angiogenic, wound healing and vasodilator) properties. This review will outline the organ-specific and general anti-fibrotic significance of exogenously administered relaxin and its mechanisms of action that have been documented in various non-reproductive organs such as the cardiovascular system, kidney, lung, liver, skin and tendons. In addition, it will outline the influence of sex on relaxin's anti-fibrotic actions, highlighting its potential as an emerging anti-fibrotic therapeutic.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Sex-Specific Effects of Chronic Administration of Relaxin-3 on Food Intake, Body Weight and the Hypothalamic-Pituitary-Gonadal Axis in Rats

The present study examined the effects of chronic central administration of relaxin-3 (RLN3) on food intake, body weight and fat mass in intact and sterilised male and female rats, as well as on hypothalamic-pituitary-gonadal (HPG) axis activity in intact male and female rats that received i.c.v. infusions of RLN3 (400 pmol/day) or vehicle during a 14-day period. The intact RLN3-injected rats displayed a higher body weight than the vehicle-treated groups, and this increase was statistically significantly stronger in female rats compared to male rats. In addition, feed efficiency and gonadal white adipose tissue weight were higher in female RLN3-injected rats. Chronic i.c.v. administration of RLN3 activated the HPG axis in intact male rats, whereas inhibition of the HPG axis was observed in intact female rats. RLN3 significantly increased the plasma levels of luteinising hormone and follicular-stimulating hormone in male rats but not in female rats. Conversely, hypothalamic expression of gonadotrophin-releasing hormone mRNA was decreased by RLN3 in female rats but not in male rats. In addition, the plasma levels of oestradiol were significantly decreased by RLN3 administration in female rats. Consequently, intact RLN3-injected female rats failed to display phasic inhibition of eating during oestrus. Sex-specific effects of RLN3 on food intake and body weight were also observed in ovariectomised female and orchidectomised male rats, suggesting that the sex-specific effects of RLN3 on energy metabolism are independent on the differential effects of RLN3 on HPG axis activity in male and female rats.

[Experience With Serelaksin for Acute Right Ventricular Failure due to Pulmonary Embolism in Acute Ischemic Stroke]

to demonstrate effects of serelaxin in treatment of acute right ventricular failure (ARVF) caused by pulmonary embolism (PE).

RLN2 regulates in vitro invasion and viability of osteosarcoma MG-63 cells via S100A4/MMP-9 signal

OBJECTIVE

Relaxin-2 (RLN2) increases cell migration, invasiveness and proliferation in vitro of osteosarcoma cells, but the molecular mechanisms of this action are still unknown. In the present study, we identified S100A4 /MMP-9 signaling as a major mediator of the actions of RLN2 in osteosarcoma cells in vitro.

MATERIALS AND METHODS

We have established stable transfectants of osteosarcoma MG-63 cells using small interfering RNA (siRNA) targeting RLN2. The stable transfectants (MG-63/RLN2 siRNA cells) were treated with 20 mM BB94 (a kind of MMP-9 activator) or 100 mM recombinant Human RLN2 (B-29/A-24) for 24 hs or transfected with S100A4 cDNA plasmid for 48 hrs or MMP-9 siRNA for 48 hrs then treated 100 mM recombinant Human RLN2 (B-29/A-24). Western blot assay was used to detect RLN2, S100A4 and MMP-9 expression. Matrigel invasion assay and wound healing assay was used to detect invasion in vitro. MTT was used to detect cell viability.

RESULTS

Knockdown of RLN2 using small interfering RNA decreases S100A4 and MMP-9 expression and inhibits invasion and cell viability in vitro. in MG-63 cells. Treatment with 100 mM recombinant Human RLN2 (B-29/A-24) for 24 hrs in MG-63/ RLN2 siRNA cells increases S100A4 and MMP-9 expression, and increases the invasion and cell viability in vitro in MG-63 cells. Transfection with S100A4 cDNA plasmid in MG-63/RLN2 siRNA cells for 48 hrs increases MMP-9 expression, and increase the invasion and cell viability of MG-63/RLN2 siRNA cells. Treatment with 20 mM BB94 (MMP-9 activator) for 24 hrs in MG-63/RLN2 siRNA cells increases MMP-9 expression, and increases the invasion and cell viability in vitro. in MG-63 cells.

CONCLUSIONS

Our results indicate that RLN2 regulats cell migration, invasiveness and proliferation of osteosarcoma cells in vitro, which may be mediated through S100A4/MMP-9 signaling.

Effects of serelaxin in subgroups of patients with acute heart failure: results from RELAX-AHF

AIM

Patients hospitalized for acute heart failure (AHF) differ with respect of many clinical characteristics which may influence their prognosis and response to treatment. We have assessed possible differences in the effects of serelaxin on dyspnoea relief, 60 Day outcomes and 180 Day mortality across patient subgroups in the RELAX-AHF trial.

METHODS AND RESULTS

Subgroups were based on pre-specified covariates (age, sex, race, geographic region, estimated glomerular filtration rate, time from presentation to randomization, baseline systolic blood pressure, history of diabetes, atrial fibrillation, ischaemic heart disease, cardiac devices, i.v. nitrates at randomization). Other covariates which may modify the efficacy of AHF treatment were also analysed. Subgroup analyses did not show any difference in the effects of serelaxin vs. placebo on dyspnoea relief or on the incidence of cardiovascular death or rehospitalizations for heart failure or renal failure at 60 days. Nominally significant interactions between some patient subgroups and the effects of serelaxin on 180 days cardiovascular and all-cause mortality were noted but should be interpreted cautiously due to the number of comparisons and the low incidence of deaths in the subgroups at lower risk.

CONCLUSION

The effects of serelaxin vs. placebo appeared to be similar across subgroups of patients in RELAX-AHF.

Efficacy and safety of oral porcine relaxin (pRLX) in adjunct to physical exercise in the treatment of peripheral arterial disease (PAD)

INTRODUCTION

PAD medical therapy has a number of limitations. RLX showed promises in experimental model mainly through NO release. Our study is the first to evaluate the efficacy and safety of RLX in PAD.

MATERIALS-METHODS

Eligible PAD La fontaine IIa-IIb patients were randomized in 2 groups. Group A was treated with physical therapy plus oral pRLX, 20 ug b.i.d for 12 weeks, group B received physical therapy alone. Pain Free Walking Distance (PFWD) and Maximum Walking Distance (MWD) at 3 and 12 wks and at follow up 3 months after treatment interruption were performed.

RESULTS

The percentage increases of PFWD in group B were 23 +/- 9, 65 +/- 17, and 35 +/- 4 respectively at 3 and at 12 weeks, and 3 months after termination. In Group A showed significantly higher percentage increases: 74 +/- 16 p < 0.01, 168 +/- 28 p < 0.001, and 122 +/- 15 p < 0.001 at the corresponding time points. The percentage increases of MWD in the B group were 29 +/- 7, 55 +/- 10 and 54 +/- 8 at the above time points, while in the A group were 55 +/- 10 p < 0.001, and 99 +/- 12 p < 0.001. The RLX patients referred a better physical and mental status. No adverse events during or after the treatment were recorded.

COMMENT

RLX resulted very effective in PAD. Our results may suggest that the observed functional benefits should come not only from hemodynamic improvement but also from positive vascular remodeling.

Anti-arthritic actions of relaxin, in combination with estrogens, in joint and bone tissue

The incidence and severity of rheumatoid arthritis decline during pregnancy. However, the role of hormones of pregnancy, including estrogens and relaxin, in attenuating the symptoms of rheumatoid arthritis, including joint inflammation and bone destruction is unknown. In rat adjuvant-induced arthritis, a model for rheumatoid arthritis, relaxin in combination with estrogens, reduced joint inflammation and circulating levels of pro-inflammatory, tumor necrosis factor alpha. In addition, relaxin together with estrogens, altered systemic levels of bone remodeling markers receptor activator of nuclear factor-kappa B, its ligand and osteoprotegerin to improve bone health when compared with arthritic controls. In vitro studies using primary rat osteoblasts and an osteoblast cell line showed a similar bon-saving response to treatment with estrogens in combination with relaxin.

Central and peripheral administration of human relaxin-2 to adult male rats inhibits food intake

AIM

Relaxin is a polypeptide hormone involved in pregnancy and lactation. It is mainly secreted by the corpus luteum and placenta, but is expressed in a number of other tissues, including heart and brain. Within the brain, relaxin is expressed in the olfactory and limbic systems, the cortex and the hypothalamic arcuate nucleus (ARC). Its cognate receptor, relaxin family peptide receptor 1 (RXFP1), is also widely expressed in the brain, including the hypothalamic ARC and paraventricular nucleus (PVN), areas important in appetite regulation. The aim of this study was to investigate whether relaxin influences food intake through central hypothalamic circuits.

METHODS

The human form of relaxin, human relaxin-2 (H2) was administered centrally and peripherally to male Wistar rats and food intake measured. Behaviour was also assessed.

RESULTS

Intracerebroventricular (ICV) administration of H2 significantly decreased 1-h food intake in the early dark phase [2.95 ± 0.45 g (saline) vs. 0.95 ± 0.18 g (180 pmol H2), p < 0.001]. ICV administration of H2 decreased feeding behaviour and increased grooming and headdown behaviour. Intraparaventricular injections of H2 significantly decreased 1-h food intake in the early dark phase [3.13 ± 0.35 g (saline) vs. 1.35 ± 0.33 g (18 pmol H2), p < 0.01, 1.61 ± 0.31 g (180 pmol H2), p < 0.05 and 1.23 ± 0.32 g (540 pmol H2), p < 0.001]. Intraperitoneal (IP) administration of H2 significantly decreased 1-h food intake in the early dark phase [4.63 ± 0.46 g (vehicle) vs. 3.08 ± 0.15 g (66 nmol H2), p < 0.01, 3.00 ± 0.17 g (200 nmol H2), p < 0.01 and 2.26 ± 0.36 g (660 nmol H2), p < 0.001].

CONCLUSIONS

Central and peripheral administration of H2 reduces the food intake in rats. This effect may be mediated via the PVN and/or other brain regions.

Relaxin for the treatment of patients with acute heart failure (Pre-RELAX-AHF): a multicentre, randomised, placebo-controlled, parallel-group, dose-finding phase IIb study

BACKGROUND

Most patients admitted for acute heart failure have normal or increase blood pressure. Relaxin is a natural human peptide that affects multiple vascular control pathways, suggesting potential mechanisms of benefit for such patients. We assessed the dose response of relaxin's effect on symptom relief, other clinical outcomes, and safety.

METHODS

In a placebo-controlled, parallel-group, dose-ranging study, 234 patients with acute heart failure, dyspnoea, congestion on chest radiograph, and increased brain natriuretic peptide (BNP) or N-terminal prohormone of BNP, mild-to-moderate renal insufficiency, and systolic blood pressure greater than 125 mm Hg were recruited from 54 sites in eight countries and enrolled within 16 h of presentation. Patients were randomly assigned, in a double-blind manner via a telephone-based interactive voice response system, to standard care plus 48-h intravenous infusion of placebo (n=62) or relaxin 10 microg/kg (n=40), 30 microg/kg (n=43), 100 microg/kg (n=39), or 250 microg/kg (n=50) per day. Several clinical endpoints were explored to assess whether intravenous relaxin should be pursued in larger studies of acute heart failure, to identify an optimum dose, and to help to assess endpoint selection and power calculations. Analysis was by modified intention to treat. This study is registered with ClinicalTrials.gov, number NCT00520806.

FINDINGS

In the modified intention-to-treat population, 61 patients were assessed in the placebo group, 40 in the relaxin 10 microg/kg per day group, 42 in the relaxin 30 microg/kg per day group, 37 in the relaxin 100 microg/kg per day group, and 49 in the relaxin 250 microg/kg per day group. Dyspnoea improved with relaxin 30 microg/kg compared with placebo, as assessed by Likert scale (17 of 42 patients [40%] moderately or markedly improved at 6 h, 12 h, and 24 h vs 14 of 61 [23%]; p=0.044) and visual analogue scale through day 14 (8214 mm x h [SD 8712] vs 4622 mm x h [9003]; p=0.053). Length of stay was 10.2 days (SD 6.1) for relaxin-treated patients versus 12.0 days (7.3) for those given placebo, and days alive out of hospital were 47.9 (10.1) versus 44.2 (14.2). Cardiovascular death or readmission due to heart or renal failure at day 60 was reduced with relaxin (2.6% [95% CI 0.4-16.8] vs 17.2% [9.6-29.6]; p=0.053). The number of serious adverse events was similar between groups.

INTERPRETATION

When given to patients with acute heart failure and normal-to-increased blood pressure, relaxin was associated with favourable relief of dyspnoea and other clinical outcomes, with acceptable safety.

Chronic Intracerebroventricular Administration of Relaxin-3 Increases Body Weight in Rats

Bolus-administered intracerebroventricular (ICV) relaxin-3 has been reported to increase feeding. In this study, to examine the role of relaxin-3 signaling in energy homeostasis, we studied the effects of chronically administered ICV relaxin-3 on body weight gain and locomotor activity in rats. Two groups of animals received vehicle or relaxin-3 at 600 pmol/head/day, delivered with Alzet osmotic minipumps. In animals receiving relaxin-3, food consumption and weight gain were statistically significantly higher than those in the vehicle group during the 14-day infusion. During the light phase on days 2 and 7 and the dark phase on days 3 and 8, there was no difference in locomotor activity between the two groups. Plasma concentrations of leptin and insulin in rats chronically injected with relaxin-3 were significantly higher than in the vehicle-injected controls. These results indicate that relaxin-3 up-regulates food intake, leading to an increase of body weight and that relaxin-3 antagonists might be candidate antiobesity agents.

Improved chemical synthesis and demonstration of the relaxin receptor binding affinity and biological activity of mouse relaxin

The primary stored and circulating form of relaxin in humans, human gene-2 (H2) relaxin, has potent antifibrotic properties with rapidly occurring efficacy. However, when administered to experimental models of fibrosis, H2 relaxin can only be applied over short-term (2-4 week) periods, due to rodents mounting an antibody response to the exogenous human relaxin, resulting in delayed clearance and, hence, increased and variable circulating levels. To overcome this problem, the current study investigated the therapeutic potential of mouse relaxin over long-term exposure in vivo. Mouse relaxin is unique among the known relaxins in that it possesses an extra residue within the C-terminal region of its A-chain. To enable a detailed assessment of its receptor interaction and biological properties, it was chemically synthesized in good overall yield by the separate preparation of each of its A- and B-chains followed by regioselective formation of each of the intramolecular and two intermolecular disulfide bonds. Murine relaxin was shown to bind with high affinity to the human, mouse, and rat RXFP1 (primary relaxin) receptor but with a slightly lower affinity to that of H2 relaxin. When administered to relaxin-deficient mice (which undergo an age-dependent progression of organ fibrosis) over a 4 month treatment period, mouse relaxin was able to significantly inhibit the progression of collagen accumulation in several organs including the lung, kidney, testis, and skin (all p < 0.05 vs untreated group), consistent with the actions of H2 relaxin. These combined data demonstrate that mouse relaxin can effectively inhibit collagen deposition and accumulation (fibrosis) over long-term treatment periods.

Relaxin improves renal function and histology in aging Munich Wistar rats

Administration of recombinant human relaxin (rhRLX) to conscious, chronically instrumented rats increases GFR and effective renal plasma flow (ERPF) and decreases effective renal vascular resistance (ERVR) with no significant change in mean arterial pressure. The Munich Wistar albino rat shows progressive chronic nephrosis with age and therefore was used to determine the functional and histologic consequences of rhRLX on matrix remodeling in the kidney of older rats. RLX-infused rats showed increased GFR and ERPF with decreased ERVR. Furthermore, in a double-blinded examination, the renal histology showed a significant decrease in glomerular and tubular collagen deposition in the rhRLX-infused aged rats. During short-term rhRLX administration (24 h), gelatinase activity was found to be essential for renal vasodilation and hyperfiltration. Surprisingly, after 20 d, improved renal function was insensitive to the inhibition of gelatinase activity, suggesting that collagen degradation in these rats had permanently altered the matrix of the renal vasculature. In conclusion, long-term administration of rhRLX improves renal function and ameliorates renal pathology in an aging rat model. The biphasic action of rhRLX on the kidney indicates that, acutely, the vessels dilate, causing increased filtration and renal blood flow with decreased vascular resistance as a result of upregulation of gelatinase activity. Subsequently, the renal vessels undergo alteration in supporting matrix, showing increased blood supply even in the face of acute matrix metalloproteinase inhibition, most likely as a result of the inhibitory properties of RLX on collagen production or increased collagen breakdown.

Clinical Use of Relaxin to Facilitate Birth: Reasons for Investigating the Premise

In the United States, both medical and nonmedical factors have driven the cesarean section rate to over 26% of all deliveries. In addition to questions of increased cost associated with operative delivery, some have questioned the ethics of performing cesarean section for nonmedical reasons. Reduction of both the duration and the pain associated with vaginal delivery would likely bring about a decline in the rate of both medical and nonmedical cesarean sections. This chapter summarizes recent findings that support the premise that through its growth-promoting and softening effects on the cervix, short-term subcutaneous administration of pharmacologic amounts of relaxin to women at term holds promise as a means of reducing the duration and discomfort associated with delivery. Two recent studies conducted in pregnant rats demonstrated that the cervix is highly responsive to relaxin during the antepartum period and that short-term subcutaneous administration of the hormone to relaxin-deficient animals not only promotes growth and softening of the cervix, but also reduces the duration of labor and delivery. Moreover, recent human clinical trials examining the influence of 24 weeks of continuous subcutaneous administration of recombinant human relaxin for the treatment of scleroderma provided evidence not only that the human reproductive tract is responsive to relaxin, but also that the administration of the hormone does not cause serious adverse side effects. It is concluded that recent findings provide an impetus for an investigation into relaxin's potential for cervical remodeling and facilitating birth in women.

Relaxin Increases Cardiac Output and Reduces Systemic Arterial Load in Hypertensive Rats

Chronic administration of recombinant human relaxin (rhRLX) to conscious, normotensive rats (male and female) increases cardiac output (CO) and global arterial compliance (ACg) and reduces systemic vascular resistance (SVR) with no change in mean arterial pressure (MAP). Effects (magnitude and temporal pattern) of relaxin on systemic hemodynamics and arterial properties in hypertensive animal models are not known. Accordingly, the major goal of the present study was to determine the cardiovascular effects of rhRLX in hypertensive rats using 2 models: Long-Evans rats chronically administered angiotensin II (AII) and spontaneously hypertensive rats (SHR). CO and systemic arterial load, as quantified by SVR and ACg, were obtained using methods reported previously by us. In rats with AII-induced hypertension, acute rhRLX administration (up to 6 hours) significantly increased CO and ACg (24.9+/-3.9 and 34.3+/-12.6% above baseline, respectively) and significantly decreased SVR (17.2+/-3.5%) without changing MAP. In contrast, acute rhRLX administration to SHR and normotensive rats for up to 6 hours failed to produce any significant changes in CO, ACg, SVR, or MAP. However, chronic rhRLX administration (1 to 7 days) to SHR yielded significant changes (24.0+/-8.1 and 22.3+/-6.6% increases in CO and ACg, respectively, and a 13.3+/-5.3% decrease in SVR, with no change in MAP). In conclusion, rhRLX increases CO and reduces arterial load in hypertensive rats without reducing MAP. However, the time course of response to rhRLX treatment is dependent on the model of hypertension such that rats characterized by AII-mediated hypertension responded more rapidly to rhRLX administration than SHR.

Recombinant human relaxin reduces hypoxic pulmonary hypertension in the rat

The fibroproliferative changes in pulmonary artery (PA) remodeling are partially prevented by antifibrotic agents. Relaxin (Rlx), a hormone involved in loosening collagen bundles in ligaments during parturition, has antifibrotic and vasodilator properties that may prevent pulmonary vascular remodeling. In the hypoxia model of pulmonary hypertension, two doses of recombinant human relaxin (rhRlx 24 [high] or 5 [low] mg X 10(-2)/kg d(-1)) were administered subcutaneously continuously for 10d to hypoxic (10% O2) rats. At day 11, right ventricular pressure (Pa X 10(2)) was reduced by rhRlx in a dose-dependent manner (15 +/- 1* control; 28 +/- 1 hypoxia; 23 +/- 1* low; 20+/-1* high; n = 10-14/group, *P < 0.05 vs. hypoxia). High rhRlx ameliorated increased collagen accumulation (mug hydroxyproline/vessel) in main PAs (87 +/- 6) vs. untreated hypoxia (102 +/- 2) (n=5/group, P < 0.05). Infusion of rhRlx had no effect on air-breathing rats, and acute administration did not alter blood pressure in hypoxic rats. Fibroblasts cultured from rat PAs spontaneously expressed collagen and fibronectin, and treatment with TGF-beta increased secretion 26- and 25 X 10(-1)-fold, respectively. Addition of rhRlx to transforming growth factor-beta-stimulated fibroblasts inhibited collagen (37%) and fibronectin (38%) secretion vs. vehicle (n = 4 per group, both P < 0.05). We conclude that rhRlx inhibits the early fibroproliferative response in hypoxic pulmonary hypertension and the mechanism may be due in part to suppression of collagen synthesis.

Central relaxin-3 administration causes hyperphagia in male Wistar rats

Relaxin-3 (INSL-7) is a recently discovered member of the insulin superfamily. Relaxin-3 mRNA is expressed in the nucleus incertus of the brainstem, which has projections to the hypothalamus. Relaxin-3 binds with high affinity to the LGR7 receptor and to the previously orphan G protein-coupled receptor GPCR135. GPCR135 mRNA is expressed predominantly in the central nervous system, particularly in the paraventricular nucleus (PVN). The presence of relaxin-3 and these receptors in the PVN led us to investigate the effect of central administration of relaxin-3 on food intake in male Wistar rats. The receptor involved in mediating these effects was also investigated. Intracerebroventricular injections of human relaxin-3 (H3) to satiated rats significantly increased food intake 1 h post administration in the early light phase [0.96 +/- 0.16 g (vehicle) vs. 1.81 +/- 0.21 g (180 pmol H3), P < 0.05] and the early dark phase [2.95 +/- 0.45 g (vehicle) vs. 4.39 +/- 0.39 g (180 pmol H3), P < 0.05]. Intra-PVN H3 administration significantly increased 1-h food intake in satiated rats in the early light phase [0.34 +/- 0.16 g (vehicle) vs. 1.23 +/- 0.30 g (18 pmol H3), P < 0.05] and the early dark phase [4.43 +/- 0.32 g (vehicle) vs. 6.57 +/- 0.42 g (18 pmol H3), P < 0.05]. Feeding behavior increased after intra-PVN H3. Equimolar doses of human relaxin-2, which binds the LGR7 receptor but not GPCR135, did not increase feeding. Hypothalamic neuropeptide Y, proopiomelanocortin, or agouti-related peptide mRNA expression did not change after acute intracerebroventricular H3. These results suggest a novel role for relaxin-3 in appetite regulation.

Responsiveness of the SF-36 and the Health Assessment Questionnaire Disability Index in a systemic sclerosis clinical trial

OBJECTIVE

This study compares the responsiveness to change of the Medical Outcomes Study Short Form Health Survey (SF-36), a measure of health related quality of life (HRQOL), and the Health Assessment Questionnaire Disability Index (HAQ-DI), a function instrument, in a randomized clinical trial for treatment of systemic sclerosis (SSc).

METHODS

A phase 2/3, multicenter, prospective, placebo controlled trial was conducted to evaluate human recombinant relaxin treatment in patients with diffuse SSc over 24 weeks. At baseline, subjects had stable, moderately severe, diffuse SSc of disease duration < or = 5 years, modified Rodnan skin score > or = 20, serum creatinine < 2.0 mg/dl, percentage forced vital capacity (% FVC) predicted > or = 50%, and % DLCO predicted > or = 40% and were not receiving concomitant disease modifying therapies. Internal consistency reliability of multi-item scales was estimated using Cronbach's alpha. Responsiveness to change of the SF-36 and HAQ-DI was computed between Weeks 0 and 24. Subjects were classified as unchanged or having a meaningful change in 4 different external measures: Change in (1) skin score > or = 30%; (2) % FVC predicted of > or = 15%; (3) self-reported patient global assessment by visual analog scale (VAS) > or = 20%; and (4) physician global assessment by VAS of > or = 20%. Responsiveness indices were computed and Cohen's effect size criteria were used to assess the magnitude of change.

RESULTS

A total of 239 patients participated in this trial, with 196 completing the 24 week trial. Cronbach's alpha for the SF-36 scales ranged from 0.76 to 0.93 and for the HAQ-DI ranged from 0.69 to 0.91 (good to excellent). The SF-36 had a larger magnitude of responsiveness in overall disease (patient and physician global assessment) compared to the HAQ-DI, while the HAQ-DI had a larger magnitude of responsiveness in clinical measures (i.e., change in skin score and % FVC predicted) than the SF-36.

CONCLUSION

These data support inclusion of both the SF-36 and HAQ-DI as outcome measures in future clinical trials of diffuse SSc.

Elastin metabolism in pelvic tissues: is it modulated by reproductive hormones?

OBJECTIVE

The purpose of this study was to investigate the effect of relaxin on extracellular matrix protein expression in pelvic fibroblasts that were cultured from women with stress urinary incontinence compared with asymptomatic control subjects.

STUDY DESIGN

Periurethral vaginal wall fibroblasts from premenopausal women with stress urinary incontinence and continent women (in both the proliferative and secretory phase of the menstrual cycle) were stimulated with increasing concentrations of relaxin (0-500 ng/mL). The supernatant was sampled for matrix metalloproteinase-2 and -9 by zymography. Tissue inhibitors of metalloproteinase-1 and -2 and alpha-1 antitrypsin were evaluated with Western blot. Total elastase activity was measured by generation of free amino groups from succinylated elastin. Increasing concentrations of alpha-1 antitrypsin were added to cell lysate to evaluate total elastase activity inhibition.

RESULTS

Proliferative-phase stress urinary incontinence fibroblasts demonstrated an increase in matrix metalloproteinase-2 and no change in matrix metalloproteinase-9 and tissue inhibitors of metalloproteinase-1 and -2 expressions with increasing relaxin concentrations. Cells from control subjects showed increased expression of matrix metalloproteinase-2 and -9, but no change in tissue inhibitors of metalloproteinases. Secretory-phase stress urinary incontinence fibroblasts showed no response in matrix metalloproteinase or tissue inhibitors of metalloproteinase expressions with relaxin stimulation. Secretory-phase control fibroblasts reacted by increasing matrix metalloproteinase-2 and -9 and tissue inhibitors of metalloproteinase-2. With respect to total elastase activity and alpha-1 antitrypsin expression, increasing doses of relaxin appear to increase elastolytic activity in stress urinary incontinence cells by decreasing the expression of alpha-1 antitrypsin in proliferative phase cells or increasing the total elastase activity in secretory phase cells. Fibroblast total elastase activity was inhibited by increasing concentrations of alpha-1 antitrypsin.

CONCLUSION

Elastase activity appears to be increased in relaxin-stimulated stress urinary incontinence fibroblasts by either decreased inhibitor (alpha-1 antitrypsin) production or increased elastase activity.

Effects of relaxin on systemic arterial hemodynamics and mechanical properties in conscious rats: sex dependency and dose response

We previously showed that chronic administration of recombinant human relaxin (rhRLX; 4 μg/h) to conscious female, nonpregnant rats to reach serum levels corresponding to early to midgestation (∼20 ng/ml) increases cardiac output (CO) and global arterial compliance (AC) and decreases systemic vascular resistance (SVR), comparable to changes observed in midterm pregnancy. The goals of this study were to test whether chronic administration of rhRLX (4 μg/h) to conscious male rats will yield similar changes in CO and systemic arterial load and to determine whether higher infusion rates of rhRLX (50 μg/h) administered to nonpregnant female rats yielding serum concentrations corresponding to late pregnancy (∼80 ng/ml) will further modify CO and SVR and global AC comparable to late gestation. CO and systemic arterial load, as quantified by SVR and AC, were obtained by using the same methods as in our previous studies. With respect to baseline, chronic rhRLX administration to male rats over 10 days at 4 μg/h increased both CO (20.5 ± 4.2%) and AC (19.4 ± 6.9%) and reduced SVR (12.7 ± 3.9%). These results were comparable to those elicited by the hormone in nonpregnant female rats. In contrast, neither acute (over 4 h) nor chronic (over 6 days) infusion of the higher dose of rhRLX administered to conscious female rats resulted in significant changes in CO, AC, or SVR from baseline. We conclude that 1) rhRLX increases CO and AC and reduces SVR irrespective of sex, and 2) the rhRLX dose response is biphasic insofar as significant alterations in CO and systemic arterial load fail to occur at high serum concentrations.

Relaxin's induction of metalloproteinases is associated with the loss of collagen and glycosaminoglycans in synovial joint fibrocartilaginous explants

Diseases of specific fibrocartilaginous joints are especially common in women of reproductive age, suggesting that female hormones contribute to their etiopathogenesis. Previously, we showed that relaxin dose-dependently induces matrix metalloproteinase (MMP) expression in isolated joint fibrocartilaginous cells. Here we determined the effects of relaxin with or without β-estradiol on the modulation of MMPs in joint fibrocartilaginous explants, and assessed the contribution of these proteinases to the loss of collagen and glycosaminoglycan (GAG) in this tissue. Fibrocartilaginous discs from temporomandibular joints of female rabbits were cultured in medium alone or in medium containing relaxin (0.1 ng/ml) or β-estradiol (20 ng/ml) or relaxin plus β-estradiol. Additional experiments were done in the presence of the MMP inhibitor GM6001 or its control analog. After 48 hours of culture, the medium was assayed for MMPs and the discs were analyzed for collagen and GAG concentrations. Relaxin and β-estradiol plus relaxin induced the MMPs collagenase-1 and stromelysin-1 in fibrocartilaginous explants – a finding similar to that which we observed in pubic symphysis fibrocartilage, but not in articular cartilage explants. The induction of these proteinases by relaxin or β-estradiol plus relaxin was accompanied by a loss of GAGs and collagen in joint fibrocartilage. None of the hormone treatments altered the synthesis of GAGs, suggesting that the loss of this matrix molecule probably resulted from increased matrix degradation. Indeed, fibrocartilaginous explants cultured in the presence of GM6001 showed an inhibition of relaxin-induced and β-estradiol plus relaxin-induced collagenase and stromelysin activities to control baseline levels that were accompanied by the maintenance of collagen or GAG content at control levels. These findings show for the first time that relaxin has degradative effects on non-reproductive synovial joint fibrocartilaginous tissue and provide evidence for a link between relaxin, MMPs, and matrix degradation.

[Induction of labour: which method to use?]

Induction of labour is a common obstetric instrument to employ when the potential risk to continue a pregnancy is higher than to terminate it. The methods of induction can be pharmacological or mechanical; the choice of the method mainly depends by the cervical ripening, as it is significantly able to influence, according to the type of induction, its final issue. The mechanical methods are: stripping and sweeping of the membranes, hand dilatation of cervix, intrauterine pressure catheters, Laminaria Japonicum, transcervical Foley catheter and amniotomy. To pharmacological methods include some agents such as the prostaglandins (PG), the most common approach to induce a labour, and used above all by vaginal way in patients with unripe cervix. They simulate the natural PG effects at the beginning of delivery and show a great efficiency. There are a lot of PG on the market, but except some of them, as Dinoprostone for PGE2 and Misoprostol for PGE1, no one of them shows the same safety in management of labour. Oxytocin, another inductive method, administered by diluted intravenous infusion, is utilized alone or mainly with other methods when the labour is started or with rupture of the membranes, because it begins or maintains the myometrial contraction.

Time course and dose response of relaxin-mediated renal vasodilation, hyperfiltration, and changes in plasma osmolality in conscious rats

The pregnancy hormone relaxin elicits renal vasodilation, hyperfiltration, and osmoregulatory changes when chronically administered to conscious, nonpregnant rats. The objective in this study was to determine the dose response and time course of hormone action, as well as the time required for recovery on stopping its administration. The threshold dose of recombinant human relaxin (rhRLX) for renal vasodilation and reduction in plasma osmolality was 0.15 microg/h when given by subcutaneous osmotic minipump for 2 days (an infusion rate that achieved circulating levels of approximately 6 ng/ml). The peak response was observed during the 0.4 microg/h infusion rate (serum rhRLX of approximately 11 ng/ml), which was comparable to our previous work using a 4.0 microg/h (serum rhRLX of approximately 20 ng/ml). In contrast, a dose of 40 microg/h was ineffective (serum rhRLX of approximately 80 ng/ml). When 4.0 microg/h rhRLX was administered by osmotic minipump for shorter periods (</=24 h), renal circulatory and osmoregulatory changes were observed by </=6 h. After removal of the osmotic minipump, these changes persisted for at least 12 h, but they were fully restored by 24 h. Even briefer administration of 4.0 microg/h rhRLX by intravenous infusion showed an onset of action in the kidney by 1-2 h. In contrast, the 40 microg/h dose of rhRLX elicited minimal effects, and comparable to our earlier report, 4.0 microg/h purified porcine relaxin was also relatively ineffective during short-term intravenous administration. In conclusion, the effect of relaxin on the renal circulation and osmoregulation is biphasic, insofar as high doses are relatively inactive, and the onset of action is more rapid than previously believed. These findings may be important to consider when evaluating relaxin in the treatment of renal disease.

Effects of recombinant human relaxin on pregnant rat uterine artery and myometrium in vitro

OBJECTIVE

The purpose of this study was to evaluate the effects of recombinant human relaxin on the uterine artery and myometrial contractility in pregnant rats.

STUDY DESIGN

Uterine artery and myometrial rings from mid and term pregnant rats were used. Relaxin effect was studied on phenylephrine-induced contraction in the presence or absence of nitric oxide synthase inhibitor, N omega-nitro-l-arginine methyl ester, soluble guanylate cyclase inhibitor, 1H-oxadiazolo-quinoxaline-1-one, or adenylate cyclase inhibitor, SQ-22,536. The myometrial inhibitory effect of relaxin was studied on spontaneous and oxytocin- or protein kinase C activator-induced contractions.

RESULTS

Uterine artery relaxation by relaxin was greater at mid pregnancy compared with term. Relaxin effect was decreased by SQ-22,536, 1H-oxadiazolo-quinoxaline-1-one and N omega-nitro-l-arginine methyl ester at mid pregnancy. Relaxin inhibited spontaneous contractions at mid pregnancy but not at term. Relaxin had no effect on oxytocin- or indolactam-V-induced contractions.

CONCLUSION

Relaxin effect is mediated by nitric oxide, soluble guanylate cyclase, and adenylate cyclase in mid pregnant uterine artery. Relaxin inhibits spontaneous uterine activity at mid pregnancy. Relaxin effect decreased at term gestation in both tissues.

Circulating relaxin acts on subfornical organ neurons to stimulate water drinking in the rat

Relaxin, a peptide hormone secreted by the corpus luteum during pregnancy, exerts actions on reproductive tissues such as the pubic symphysis, uterus, and cervix. It may also influence body fluid balance by actions on the brain to stimulate thirst and vasopressin secretion. We mapped the sites in the brain that are activated by i.v. infusion of a dipsogenic dose of relaxin (25 microg/h) by immunohistochemically detecting Fos expression. Relaxin administration resulted in increased Fos expression in the subfornical organ (SFO), organum vasculosum of the lamina terminalis (OVLT), median preoptic nucleus, and magnocellular neurons in the supraoptic and paraventricular nuclei. Ablation of the SFO abolished relaxin-induced water drinking, but did not prevent increased Fos expression in the OVLT, supraoptic or paraventricular nuclei. Although ablation of the OVLT did not inhibit relaxin-induced drinking, it did cause a large reduction in Fos expression in the supraoptic nucleus and posterior magnocellular subdivision of the paraventricular nucleus. In vitro single-unit recording of electrical activity of neurons in isolated slices of the SFO showed that relaxin (10(-7) M) added to the perfusion medium caused marked and prolonged increase in neuronal activity. Most of these neurons also responded to 10(-7) M angiotensin II. The data indicate that blood-borne relaxin can directly stimulate neurons in the SFO to initiate water drinking. It is likely that circulating relaxin also stimulates neurons in the OVLT that influence vasopressin secretion. These two circumventricular organs that lack a blood-brain barrier may have regulatory influences on fluid balance during pregnancy in rats.

Recombinant human relaxin in the treatment of scleroderma. A randomized, double-blind, placebo-controlled trial

BACKGROUND

Relaxin is a pregnancy-related hormone that has tissue remodeling and antifibrotic effects. Systemic sclerosis (scleroderma) is characterized by fibrosis of the skin, vasculature, and internal organs.

OBJECTIVE

To assess the efficacy, safety, and dose-response effect of recombinant human relaxin in patients with scleroderma.

DESIGN

Multicenter, parallel-group, randomized, double-blind, placebo-controlled trial.

SETTING

Academic referral centers.

PATIENTS

68 patients who had had stable, diffuse scleroderma (moderate to severe) for less than 5 years.

INTERVENTION

Recombinant human relaxin, 25 or 100 microg/kg of body weight per day, or placebo administered by continuous subcutaneous infusion over 24 weeks.

MEASUREMENTS

Modified Rodnan skin score was the primary efficacy measure. Secondary measurements were pulmonary function, the Health Assessment Questionnaire, and other measures of scleroderma that reflected fibrosis.

RESULTS

Patients who received 25 microg/kg of recombinant human relaxin per day had significantly lower skin scores than those who received placebo (mean change, -3.6 at 4 weeks [P = 0.021], -7.5 at 12 weeks [P < 0.001], and -8.7 at 24 weeks [P = 0.040]). Similar trends were noted in other outcome measures, including forced vital capacity, measures of oral aperture and hand extension, functional status, and global assessment. Patients who received 100 microg/kg of relaxin per day did not differ from those who received placebo. Drug-related adverse events included menometrorrhagia, reversible anemia, and complications of the subcutaneous drug administration system (site irritation and local infection).

CONCLUSIONS

Twenty-four weeks of recombinant human relaxin, 25 microg/kg per day, is associated with reduced skin thickening, improved mobility, and improved function in patients with moderate to severe diffuse scleroderma.

Expression of connexin-26, -32, and -43 gap junction proteins in the porcine cervix and uterus during pregnancy and relaxin-induced growth

Connexin (CX) proteins participate in growth, differentiation, and tissue remodeling. Relaxin-stimulated reproductive tissue growth and remodeling may be facilitated by enhanced intracellular communication. This study was an examination of the effects of relaxin in vivo on expression of CX-26, CX-32, and CX-43 in the cervix and uterus of prepubertal pigs. In addition, expression of these proteins was monitored in the sow uterus during pregnancy. Relaxin was administered to prepubertal gilts every 6 h for 54 h. CX expression was characterized by immunoblotting and localized by immunofluorescence. Significant increases in all three CXs were observed in the cervix following relaxin treatment (P < 0.05). Uterine CX proteins were also significantly higher (P < 0.05) in relaxin-treated animals compared to controls. The CX protein level in relaxin-treated animals was similar to that observed during the second half of pregnancy, but below levels found in mature, nonpregnant sows. This is the first evidence for specific CX expression in the porcine cervix, and the first study to show that relaxin increases the expression of CX proteins in the porcine uterus and cervix. The data show that CX proteins are differentially regulated in the uterus of the pig during pregnancy. These data support a role for CX-mediated communication during relaxin-induced reproductive tissue growth and remodeling.

Water drinking in rats resulting from intravenous relaxin and its modification by other dipsogenic factors

The purpose of the study was to determine whether iv infusion of relaxin would acutely stimulate water drinking in rats and, if it did, whether such drinking is affected by other dipsogenic stimuli or is blocked by centrally administered losartan. iv infusions of human gene 2 relaxin at doses of 25, 40, 55, or 80 microg/kg x h for 1 h induced dose-dependent water drinking in both male and female rats within 15-30 min of commencement of infusions. iv infusion of a nondipsogenic dose of angiotensin II (0.5 microg/h), combined with relaxin (40 microg/kg x h), almost tripled the relaxin-induced water intake. iv infusion of hypertonic (1 M) NaCl did not potentiate relaxin-induced drinking. Intracerebroventricular injection of the angiotensin AT1 antagonist losartan (10 microg) reduced water drinking induced by iv infusion of relaxin. The water drinking induced by iv infusion of relaxin in the rat suggests that blood-borne relaxin may be a dipsogenic hormone. Potentiation of this relaxin-induced drinking by moderate levels of circulating angiotensin II is additional evidence in support of this view. The results also indicate that a central angiotensinergic neural pathway, utilizing AT1 receptors, subserves relaxin-induced drinking.

Novel therapeutic strategies in scleroderma

Optimal management for scleroderma (systemic sclerosis) is likely to require treatment of the underlying disease process, which remains incompletely understood, and also of the organ-based complications of this heterogeneous condition. Clinical trials evaluating several potential agents have been completed recently, including D-penicillamine and interferon alpha. Unfortunately none of these studies has suggested significant efficacy. This article focuses on new treatment approaches using existing therapeutic agents, such as prostacyclin, and considers the potential usefulness of new agents (eg, relaxin, halofuginone) or strategies such as intensive immunosuppression with peripheral stem cell rescue. Ultimately, a better understanding of disease pathogenesis may facilitate the development of targeted therapy against key events or mediators, but for the present better evaluation of existing agents and a focus on optimizing protocols for organ-based complications, such as pulmonary vascular disease or hypertensive renal crisis, are important goals.

Relaxin stimulates expression of vascular endothelial growth factor in normal human endometrial cells in vitro and is associated with menometrorrhagia in women

Although the role of the reproductive hormone, relaxin, in rodents is well documented, its potential contribution to human reproduction is less well defined. In this study, we examine the effects of relaxin on human endometrial cells in vitro and describe the clinical effects of relaxin on menstrual flow in women. In cultured endometrial cells, relaxin specifically induces the expression of an angiogenic agent, vascular endothelial growth factor (VEGF). cAMP is implicated as a second messenger involved in VEGF stimulation. VEGF expression is temporally regulated in the endometrium, and our results suggest that relaxin, which is secreted by the corpus luteum and is present in the endometrium during the menstrual cycle and pregnancy, may be involved in regulating endometrial VEGF expression. Relaxin was recently tested in a clinical trial for efficacy in the treatment of progressive systemic sclerosis, and was administered at levels up to 10 times higher than that measured during pregnancy. The most frequent relaxin-related adverse event reported during the course of the study was the onset of menometrorrhagia, defined in this study as heavier-than-usual or irregular menstrual bleeding. The intensification of menstrual flow observed in these patients is consistent with the hypothesis that relaxin mediates neovascularization of the endometrial lining.

Relaxin is a potent renal vasodilator in conscious rats

The kidneys and other nonreproductive organs vasodilate during early gestation; however, the "pregnancy hormones" responsible for the profound vasodilation of the renal circulation during pregnancy are unknown. We hypothesized that the ovarian hormone relaxin (RLX) contributes. Therefore, we tested whether the administration of RLX elicits renal vasodilation and hyperfiltration in conscious adult, intact female rats. After several days of treatment with either purified porcine RLX or recombinant human RLX 2 (rhRLX), effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) increased by 20%-40%. Comparable renal vasodilation and hyperfiltration was also observed in ovariectomized rats, suggesting that estrogen and progesterone are unnecessary for the renal response to rhRLX. The nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester completely abrogated the increase in ERPF and GFR elicited by chronic administration of purified porcine RLX. In contrast, the renal vasoconstrictory response to angiotensin II was attenuated by the RLX treatment. Short-term infusion of purified porcine RLX to conscious rats over several hours failed to increase ERPF and GFR. Plasma osmolality was consistently reduced by the chronic administration of both RLX preparations. In conclusion, the renal and osmoregulatory effects of chronic RLX administration to conscious rats resemble the physiological changes of pregnancy in several respects: (a) marked increases in ERPF and GFR with a mediatory role for nitric oxide; (b) attenuation of the renal circulatory response to angiotensin II; and (c) reduction in plasma osmolality.

Induction of labour: new horizons

Induction of labour may be indicated in the maternal or the fetal interest, and is more likely to be successful if physiological mechanisms are replicated. Induction of labour in the presence of an unfavourable cervix presents the greatest challenge and pharmacological techniques must encourage cervical ripening if we are to advance our management of this common obstetric intervention.

Recombinant human relaxin as a cervical ripening agent

OBJECTIVE

The aim of this study was to investigate the efficacy and safety of recombinant human relaxin (rhRIx) as a cervical ripening agent in women with an unfavourable cervix before induction of labour at term.

DESIGN

A multi-centre, double-blind, placebo-controlled trial performed in Edinburgh, Glasgow and Oxford. Women were treated with 0, 1, 2 or 4 mg of rhRIx in a gel vehicle administered intravaginally. Analysis of variance tests were performed on all continuous variables, and Cochran Mantel-Haenszel tests employed for all discrete variables.

PARTICIPANTS

Ninety-six women at 37 to 42 weeks of gestation with a singleton pregnancy and a modified Bishop score of < or = 4 were recruited.

RESULTS

There was no significant difference in the change in modified Bishop score between the four treatment groups. The lengths of the first and second stages of labour were similar in all 4 groups. PGE2 and oxytocin requirements were similar in all groups, as was the mode of delivery. There was no evidence that relaxin was absorbed systemically when given in this way.

CONCLUSION

Recombinant human relaxin 1 to 4 mg, administered as an intravaginal gel, has no effect as a cervical ripening agent before induction of labour at term.

Relaxin counteracts asthma-like reaction induced by inhaled antigen in sensitized guinea pigs

In previous studies, the peptide hormone relaxin (RLX) was found to inhibit mast cell secretion and platelet activation. It has been established that the release of mediators from these cells plays a central pathogenic role in allergic asthma. This prompted us to ascertain whether RLX may counteract the respiratory and histopathological abnormalities of the asthma-like reaction to inhaled antigen in sensitized guinea pigs. Guinea pigs were sensitized with ovalbumin and challenged with the same antigen given by aerosol. Some animals received RLX (30 microg/kg BW, twice daily for 4 days) before antigen challenge. Other animals received inactivated RLX in place of authentic RLX. Respiratory abnormalities, such as cough and dyspnea, were analyzed as were light and electron microscopic features of lung specimens. RLX was shown to reduce the severity of respiratory abnormalities, as well as histological alterations, mast cell degranulation, and leukocyte infiltration in sensitized guinea pigs exposed to ovalbumin aerosol. RLX was also found to promote dilation of alveolar blood capillaries and to reduce the thickness of the air-blood barrier. This study provides evidence for an antiasthmatic property of RLX and raises the possibility of new therapeutic strategies for allergic asthma in humans.

Continuous infusion of relaxin on periparturient progesterone, oxytocin and relaxin plasma concentrations and time of parturition in beef heifers

These studies were designed to determine whether continuous i.v. infusion of increasing dosages of porcine relaxin during late pregnancy in beef heifers would influence circulating blood concentrations of relaxin, progesterone and oxytocin, and time of onset of parturition. Beef heifers were bred by artificial insemination and, on Day 277, fitted with indwelling jugular cannulas for hormone infusion and blood sampling from Day 277 to Day 286. Intravenous infusion of purified porcine relaxin (pRLX, 3000 U mg-1) was started in heifers (n = 8) at increasing dosages (200 U h-1 on Days 277 and 278, 300 U h-1 on Days 279 and 280, 500 U h-1 on Day 281, 600 U h-1 on Day 282, and 700 U h-1 on Days 283-286). Phosphate-buffered saline (PBS, 10 ml h-1) was infused during these same times to control animals (n = 6). Relaxin treatment steadily increased the circulating plasma concentration of immunoreactive relaxin to more than 120 ng ml-1 compared with less than 0.5 ng ml-1 in PBS-treated controls. Relaxin infusion in increasing dosages over the treatment time was associated with a significant decrease (P < 0.01) in plasma progesterone concentration compared with the PBS controls. The rate of change in progesterone levels between pRLX and PBS groups differed (P < 0.05) at 300 U h-1, 600 U h-1 and 700 Uh-1 dosage intervals, respectively. Plasma levels of oxytocin at 4 h intervals remained similar (P > 0.05) during the pretreatment period and throughout continuous infusion of pRLX and PBS. Mean concentrations of oxytocin in PBS control heifers peaked at 0.95 pgml-1 during the corresponding infusion of 700 Uh-1 pRLX, which peaked at 0.77 pgml-1. Although continuous i.v. infusion of relaxin resulted in a decrease in circulating blood levels of progesterone, it did not significantly reduce the interval between the beginning of pRLX treatment and parturition compared with the PBS-infused control heifers. These results indicate that continuous i.v. infusion of high levels of porcine relaxin resulted in a decrease in progesterone secretion in late pregnant beef heifers.

Relaxin and estrogen synergistically accelerate growth and development in the uterine cervix of prepubertal pigs

This study was designed to determine the development and growth-promoting effects of relaxin with or without estrogen on the uterine cervix of prepubertal gilts. Twenty littermate gilts of similar body weight (33 +/- 3 kg; mean +/- SE) at 80 days of age were randomly assigned to four treatments: Vehicle (CONTROL, 1 ml PBS and 1 ml vegetable oil, n = 5); Relaxin (Relaxin, in PBS, 1 ml, 167 micrograms ml-1, n = 5); Estradiol Benzoate (EB, in vegetable oil, 1 ml, 2 mg ml-1, n = 5); and Relaxin plus EB (Relaxin + EB, at the same doses, n = 5), total six intramuscular injections for all treatments. Twenty four hours after the last injection, hysterectomy was performed, and the uterine tissues were immediately frozen at -80 degrees C. Samples were taken from the middle portions of the cervix and the uterine horns and dried to a constant weight to determine the dry weight and water concentration. Homogenates of uterine horns and cervices were analyzed for concentrations and contents of protein, hydroxyproline (collagen index) and DNA. Relaxin alone had no significant effect on any parameters (i.e., wet weight, Relaxin vs.

CONTROL

36 +/- 5 vs. 28 +/- 3 g uterus-1, dry weight 5.6 +/- 0.6 vs. 4.4 +/- 0.4 g uterus-1). EB alone increased significantly (P < 0.05) wet weight of the uterus (EB vs.

CONTROL

85 +/- 23 vs. 28 +/- 3 g uterus-1), dry weight (EB vs.

CONTROL

14.5 +/- 3 vs. 4.4 +/- 0.4 g uterus-1), and hydroxyproline content (EB vs.

CONTROL

47.2 +/- 13 vs. 12.6 +/- 4 mg cervix-1). In the presence of EB, relaxin treatment increased all measurements compared with CONTROL (i.e., wet weight, Relaxin + EB vs. EB: 136 +/- 34 vs. 28 +/- 3 g uterus-1). Compared with EB, Relaxin + EB significantly (P < 0.05) increased the uterine wet weight (Relaxin + EB vs. EB: 136 +/- 34 vs. 85 +/- 23 g uterus-1), the hydroxyproline content (Relaxin + EB vs. EB: 91 +/- 29 vs. 47 +/- 13 mg cervix-1), and DNA content (Relaxin + EB vs. EB: 8.1 +/- 2 vs. 5.4 +/- 1 mg cervix-1). These results indicate that the growth-promoting effects of relaxin on the uterus and cervix may be, at least partly, estrogen-dependent and that the growth and development of the uterus and cervix can be accelerated by a combination of relaxin and estrogen treatment.

Relaxin and decidualization in mice: a reappraisal

The nature of the physiological stimulus inducing decidualization in the endometrium is unknown. In this study we attempted to verify a recent report that relaxin can induce decidualization in intact mice primed with a high dose of estradiol valerate (5 micrograms) and a low dose (10 micrograms) of medroxyprogesterone acetate. In our study, neither s.c. nor intrauterine relaxin, nor intraluminal arachis oil, (an established deciduogenic stimulus) were able to induce decidualization. In addition, while oil was able to induce decidualization (increased uterine weight, and positive Pontamine Sky Blue and stromal alkaline phosphatase reactions) in ovariectomized mice treated with a regimen of estradiol and medroxyprogesterone acetate designed to produce optimum uterine sensitivity, no decidualization occurred in response to either s.c. or intraluminal relaxin. This study fails to provide any support for a role for relaxin as a deciduogenic stimulus.

Twelve-month evaluation of rhesus monkey dams and infants after relaxin (hRlx-2) infusion in late pregnancy

Pregnant rhesus monkeys received daily i.v. infusions of chemically synthesized human relaxin (hRlx-2) (0.1 mg/kg/day N = 6, 2.0 mg/kg/day N = 6, vehicle control N = 7) from the onset of cervical softening to delivery (0 to 14 infusions) to simulate potential therapeutic use of this agent for cervical ripening. Reproductive fitness of dams was evaluated during the next breeding season, and infants were studied through 12 months of age. Birth weight and size, neonatal heart rate and body temperature and neurobehavioral status were not influenced by intrauterine relaxin exposure. Neonatal muscle tone was greater and responsiveness was lower in the hRlx-2 treated infants than in controls. No group differences were seen in infant postnatal growth, maturation or incidence of health problems. Maternal endpoints including uterine involution, resumption of menses, conception rate, and pregnancy outcome were similar across groups. Systemic exposure of rhesus monkeys to relatively high levels of hRlx-2 in late pregnancy did not have apparent long term effects for the measures evaluated under conditions of the experiment. Conclusions concerning adverse effects are limited by the small sample size.

Effects of relaxin on the endometrial stroma. Studies in mice

The current study was designed to elucidate the effects of relaxin, administered systemically to mice in combination with estrogen and medroxyprogesterone, on the endometrial stroma, with use of structural, ultrastructural, and immunocytochemical methods. Female, sexually mature virgin mice were placed into 4 groups and treated with estrogen, estrogen + progestin, estrogen + relaxin, and estrogen + progestin + relaxin in sequence. The results obtained show that relaxin causes a striking increase in the protein-synthesizing machinery of endometrial stromal cells, leading them to resemble closely the decidualized cells of rodent pregnant uterus. Relaxin also induces in the same cells the expression of laminin, which is regarded as a reliable marker of decidual transformation of endometrial stromal cells in mice, and which is needed for trophoblast to adhere to and invade the endometrial stroma. Moreover, relaxin seems to synergize with the steroids in promoting a growth response of the endometrial stromal cells. The above findings allow for relaxin to be regarded as an agent capable of promoting decidual transformation of endometrial stromal cells and, possibly, to participate in the events that lead to blastocyst implantation.

Pressor and bradycardic effects of centrally administered relaxin in conscious rats

The current study tested the hypothesis that centrally administered relaxin elevates arterial pressure in conscious rats and that this hypertensive effect is mediated, at least in part, by central or peripheral vasopressin. Injection of human relaxin (0.068 or 0.34 microgram in 200 nL artificial cerebrospinal fluid) into the right lateral ventricle of conscious, unrestrained Sprague-Dawley rats caused significant dose-related increases in arterial pressure and decreases in heart rat. The pressor and bradycardic responses to intracerebroventricular injections of relaxin were significantly blunted by pretreatment with either intracerebroventricular or intravenous injection of a vasopressin receptor (V1) antagonist, suggesting that the cardiovascular effects of central relaxin are mediated, at least in part, by V1 receptors in the brain and perhaps also by vasopressin released into the peripheral circulation. Neither intracerebroventricular injection of the vehicle alone nor intravenous injection of relaxin (0.34 microgram) altered arterial pressure or heart rate. In contrast to the above, intravenous injections of relaxin (40 micrograms/kg) elicited pressor and tachycardic responses that were not blunted by pretreatment with either intracerebroventricular or intravenous injection of the V1 receptor antagonist. Together, these data suggest that in the central nervous system relaxin contributes to the regulation of cardiovascular function and that the mechanisms for the cardiovascular effects of central and peripheral relaxin are distinct.

Role of the subfornical organ in the relaxin-induced prolongation of gestation in the rat

The role of the subfornical organ in the timing of birth in the rat was investigated. Animals with radiofrequency lesions of the subfornical organ made on day 12 of pregnancy gave birth significantly earlier (P < 0.05) than intact and control-lesioned rats. Animals with lesions made on day 19 of pregnancy gave birth within control times. In addition, the natural fall in plasma relaxin observed at the end of gestation in rats was prevented by i.v. infusion of porcine relaxin (4.2 micrograms/h for 5 days from day 19 of gestation), which maintained plasma relaxin levels at approximately 100 ng/ml. This rate of infusion was selected because the resultant circulating levels of relaxin reflect plasma concentrations observed on day 20 of pregnancy in rats. The effect of lesion of the subfornical organ was then studied on the timing of birth in relaxin-infused rats. Intact animals and rats with control lesions receiving an infusion of relaxin had significantly (P < 0.05) prolonged pregnancies compared with intact saline-infused controls. However, the timing of birth of rats with lesions of the subfornical organ receiving an infusion of relaxin was not significantly (P > 0.05) different from that in intact saline-infused controls. The results support the hypothesis that the subfornical organ appears to mediate the central effects of relaxin and may have a natural role in the events that lead to delivery in the rat.

Brain angiotensin-II partially mediates the effects of relaxin on vasopressin and oxytocin release in anesthetized rats

Experiments were conducted in anesthetized rats to assess the contribution of the brain angiotensin-II system in the relaxin-induced secretion of vasopressin and oxytocin. Intravenous injection of porcine relaxin (5 micrograms) caused a significant (P < 0.05, by analysis of variance) increase in plasma concentrations of both hormones. Peak concentrations of both vasopressin (75.2 +/- 2.9 pmol/liter) and oxytocin (38.4 +/- 1.2 pmol/liter) were observed 1-2.5 min after relaxin injection. Thereafter, concentrations fell significantly (P < 0.05) but remained elevated for a further 25 minutes. Continuous infusion of a specific angiotensin-II receptor antagonist into the lateral cerebral ventricle did not affect baseline levels of either vasopressin or oxytocin, but did significantly reduce (P < 0.05) the relaxin-induced release of both peptides. A significant (P < 0.05) short term increase in both plasma vasopressin and oxytocin occurred 1 min after injection of 5 micrograms relaxin, iv, in angiotensin-II-antagonized rats, but the concentrations of both neuropeptides were significantly (P < 0.05) lower than those observed in the angiotensin-intact relaxin-treated controls. These data suggest that relaxin may act through the central angiotensin-II system to induce the release of vasopressin and oxytocin.

Stimulation of prolactin secretion in the pig: central effects of relaxin and the antiprogesterone RU 486

Our previous study has shown that oral administration of a potent progesterone antagonist, RU 486, caused a marked elevation of plasma concentrations of both PRL and progesterone in hysterectomized pigs bearing aging corpora lutea. Hysterectomized pigs (hysterectomy performed on day 8; estrus = day 0) were subjected to cranial surgery for chronic placement of a head-mounted stereotaxic apparatus for intracerebroventricular (icv) administration of relaxin (300 U once daily on days 111 and 113; n = 6) and RU 486 (4 mg once daily on days 111, 113, and 115; n = 5) to test whether relaxin and RU 486 exert their actions within the central nervous system and/or pituitary gland to affect PRL and GH secretion. Control pigs (n = 3) received icv injection of vehicle. Intensive blood sampling revealed that icv injection of relaxin on day 111 markedly increased the plasma PRL concentration from 8 to 38 ng/ml within 10 min (P < 0.01). An identical icv injection of relaxin on day 113 caused only a modest increase in PRL, but the overall mean concentration of PRL after relaxin treatment was greater than that before treatment (14 vs. 8 ng/ml; P < 0.05). Intracerebroventricular injection of RU 486 on day 111 greatly elevated plasma PRL. The increase in PRL lasted more than 2 h, with several peak increases of 18-29 ng/ml (P < 0.01). The PRL response to subsequent icv infusion of RU 486 on days 113 and 115 was blunted, but the overall mean concentration of PRL (14 ng/ml) after icv injection of RU 486 remained greater (P < 0.01) than that before treatment (9 ng/ml). In contrast, PRL concentrations in the control group remained unchanged after injection. Plasma concentrations of GH, relaxin, and progesterone were significantly altered in neither hormone- nor vehicle-treated groups during this brief period of sequential blood sampling. This study provides strong evidence that relaxin has a central role in modulating PRL secretion in the pig. In addition, the antagonistic effects on progesterone receptor by RU 486 in the central nervous system and/or pituitary gland caused an abrupt increase in PRL secretion in these hysterectomized gilts.

The pharmacokinetics of recombinant human relaxin in nonpregnant women after intravenous, intravaginal, and intracervical administration

The pharmacokinetics of recombinant human relaxin (rhRlx) after intravenous (iv) bolus administration and the absorption of rhRlx after intracervical or intravaginal administration were determined in nonpregnant women. The study was conducted in two parts. In part I, 25 women received 0.01 mg/kg rhRlx iv. After a minimum 7-day washout period, these women were dosed intracervically (n = 10) or intravaginally (n = 15) with 0.75 or 1.5 mg rhRlx, respectively, in 3% methylcellulose gel. Part II was a double-blind, randomized, three-way crossover study in 26 women. At 1-month intervals, each woman received one of three intravaginal treatments consisting of 0 (placebo), 1, or 6 mg rhRlx in 3% methylcellulose gel. The serum concentrations of relaxin following iv administration were described as the sum of three exponentials. The mean (+/- SD) initial, intermediate, and terminal half-lives were 0.09 +/- 0.04, 0.72 +/- 0.11, and 4.6 +/- 1.2 hr, respectively. Most of the area under the curve was associated with the intermediate half-life. The weight-normalized clearance was 170 +/- 50 mL/hr/kg. The observed peak concentration was 98 +/- 29 ng/mL, and the weight-normalized initial volume of distribution was 78 +/- 40 mL/kg, which is approximately equivalent to the serum volume. If central compartment elimination was assumed, the volume of distribution at steady state (Vss/W) was 280 +/- 100 mL/kg, which is approximately equivalent to extracellular fluid volume. Vss/W could be as large as 1300 +/- 400 mL/kg without this assumption.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics and absorption of recombinant human relaxin in nonpregnant rabbits and rhesus monkeys after intravenous and intravaginal administration

Recombinant human relaxin (rhRlx) is being developed as a potential cervical ripening agent to be applied intravaginally or intracervically prior to parturition. The pharmacokinetics and absorption of rhRlx were determined in nonpregnant female rabbits and rhesus monkeys after intravenous bolus (iv) and intravaginal administration of 0.1 mg/kg; additionally, rabbits were dosed with 0.5 mg/kg intravaginally. In rabbits (n = 6), mean (+/- SD) peak concentrations following iv bolus administration were 1554 +/- 296 ng/mL. The weight-normalized clearance (CL/W) was 5.9 +/- 0.4 mL/min/kg, initial volume of distribution (V1/W) was 57 +/- 9 mL/kg, and volume of distribution at steady state (Vss/W), assuming central compartment elimination, was 240 +/- 20 mL/kg. Vss/W could be as large as 2000 +/- 400 mL/kg without this assumption. The estimated amounts of rhRlx absorbed in rabbits following intravaginal administration of 0.1 and 0.5 mg/kg (n = 5/dose) were 3.1 +/- 1.4 and 0.7 +/- 0.3%, respectively; peak concentrations were 600 +/- 297 and 1066 +/- 584 pg/mL, respectively. In rhesus monkeys (n = 5) after iv administration, peak concentrations were 971 +/- 277 ng/mL; CL/W was 4.1 +/- 0.6 mL/min/kg, V1/W was 78 +/- 25 mL/kg, and Vss/W, assuming central compartment elimination, was 690 +/- 220 mL/kg. The upper limit for Vss/W was 1600 +/- 200 mL/kg when no assumptions were made regarding site (compartment) of elimination. After intravaginal administration (n = 6), two monkeys had undetectable rhRlx concentrations throughout the 48-hr sampling interval; one monkey had only one sample containing measurable rhRlx (51 pg/mL) at 24 hr; and three monkeys absorbed < 2% of the 0.1 mg/kg dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of human relaxin on isolated rat and human myometrium and uteroplacental arteries

We investigated the effects of synthetic human relaxin (hRLX-2) on isolated rat and human myometrium and on uteroplacental arteries from term pregnant women. The preparations were mounted in organ baths and isometric tension was recorded. In isolated myometrium from nonpregnant rats, hRLX-2 (10(-10)-10(-7) mol/L) produced concentration-dependent inhibition of contractile activity induced by vasopressin (10(-8) mol/L). In isolated human myometrium from the fundus or isthmus, hRLX-2 (10(-10)-10(-7) mol/L) did not influence spontaneous activity or contractions induced by oxytocin (10(-9) mol/L) and prostaglandin (PG) F2 alpha (10(-5) mol/L). Nor did it influence the tension induced in small intramyometrial arteries by U46619 (10(-7) mol/L), noradrenaline (10(-5) mol/L), and endothelin (10(-9) mol/L); or the tension induced in fetal stem villus arteries by U46619 (10(-7) mol/L), endothelin (10(-9) mol/L), and PGF2 alpha (10(-5) mol/L). The inhibitory effects of hRLX-2 in preparations of rat myometrium were not influenced by the presence of human myometrium in the organ bath or by pre-incubation of hRLX-2 with human myometrium. These results suggest that direct inhibitory effects of relaxin may be of minor importance for the regulation of myometrial activity and uteroplacental circulation in term human pregnancy.