Human recombinant relaxin-2 (serelaxin) regulates the proteome, lipidome, lipid metabolism and inflammatory profile of rat visceral adipose tissue

Recombinant human relaxin-2 (serelaxin) has been widely proven as a novel drug with myriad effects at different cardiovascular levels, which support its potential therapeutic efficacy in several cardiovascular diseases (CVD). Considering these effects, together with the influence of relaxin-2 on adipocyte physiology and adipokine secretion, and the connection between visceral adipose tissue (VAT) dysfunction and the development of CVD, we could hypothesize that relaxin-2 may regulate VAT metabolism. Our objective was to evaluate the impact of a 2-week serelaxin treatment on the proteome and lipidome of VAT from Sprague-Dawley rats. We found that serelaxin increased 1 polyunsaturated fatty acid and 6 lysophosphatidylcholines and decreased 4 triglycerides in VAT employing ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) based platforms, and that regulates 47 phosphoproteins using SWATH/MS analysis. Through RT-PCR, we found that serelaxin treatment also caused an effect on VAT lipolysis through an increase in the mRNA expression of hormone-sensitive lipase (HSL) and a decrease in the expression of adipose triglyceride lipase (ATGL), together with a reduction in the VAT expression of the fatty acid transporter cluster of differentiation 36 (Cd36). Serelaxin also caused an anti-inflammatory effect in VAT by the decrease in the mRNA expression of tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), chemerin, and its receptor. In conclusion, our results highlight the regulatory role of serelaxin in the VAT proteome and lipidome, lipolytic function, and inflammatory profile, suggesting the implication of several mechanisms supporting the potential benefit of serelaxin for the prevention of obesity and metabolic disorders.

Serelaxin Protects H9c2 Cardiac Myoblasts against Hypoxia and Reoxygenation-Induced Damage through Activation of AMP Kinase/Sirtuin1: Further Insight into the Molecular Mechanisms of the Cardioprotection of This Hormone

Serelaxin (RLX), namely the human recombinant Relaxin-2 hormone, protects the heart from ischemia/reperfusion (I/R)-induced damage due to its anti-inflammatory, anti-apoptotic and antioxidant properties. RLX acts by binding to its specific RXFP1 receptor whereby it regulates multiple transduction pathways. In this in vitro study, we offer the first evidence for the involvement of the AMP kinase/Sirtuin1 (AMPK/SIRT1) pathway in the protection by RLX against hypoxia/reoxygenation (H/R)-induced damage in H9c2 cells. The treatment of the H/R-exposed cells with RLX (17 nmol L-1) enhanced SIRT1 expression and activity. The inhibition of SIRT1 signaling with EX527 (10 µmol L-1) reduced the beneficial effect of the hormone on mitochondrial efficiency and cell apoptosis. Moreover, RLX upregulated the AMPK pathway, as shown by the increase in the expression of phospho-AMPK-activated protein. Finally, AMPK pathway inhibition by Compound C (10 and 20 μmol L-1) abrogated the increase in SIRT1 expression induced by RLX, thus suggesting the involvement of the AMPK pathway in this effect of RLX. These results strengthen the concept that RLX exerts its cardioprotective effects against H/R-induced injury through multiple pathways which also include AMPK/SIRT1. These new findings support the use of RLX or RLX-derived molecules as a promising therapeutic for those diseases in which I/R and oxidative stress play a pathogenic role.

Cardiovascular effects of relaxin-2: therapeutic potential and future perspectives

The hormone relaxin-2 has emerged as a promising player in regulating the physiology of the cardiovascular system. Through binding to the relaxin family peptide receptor 1 (RXFP1), this hormone elicits multiple physiological responses including vasodilation induction, reduction of inflammation and oxidative stress, and angiogenesis stimulation. The role of relaxin-2, or its recombinant human form known as serelaxin, has been investigated in preclinical and clinical studies as a potential therapy for cardiovascular diseases, especially heart failure, whose current therapy is still unoptimized. However, evidence from past clinical trials has been inconsistent and further research is needed to fully understand the potential applications of relaxin-2. This review provides an overview of serelaxin use in clinical trials and discusses future directions in the development of relaxin-2 mimetics, which may offer new therapeutic options for patients with heart failure.

Disconnect between the effects of serelaxin on renal function and outcome in acute heart failure

BACKGROUND

We aimed to study whether improvement in renal function by serelaxin in patients who were hospitalized for acute heart failure (HF) might explain any potential effect on clinical outcomes.

METHODS

We included 6318 patients from the RELAXin in AHF-2 (RELAX-AHF2) study. Improvement in renal function was defined as a decrease in serum creatinine of ≥ 0.3 mg/dL and ≥ 25%, or increase in estimated glomerular filtration rate of ≥ 25% between baseline and day 2. Worsening renal function (WRF) was defined as the reverse. We performed causal mediation analyses regarding 180-day all-cause mortality (ACM), cardiovascular death (CVD), and hospitalization for HF/renal failure.

RESULTS

Improvement in renal function was more frequently observed with serelaxin when compared with placebo [OR 1.88 (95% CI 1.64-2.15, p < 0.0001)], but was not associated with subsequent clinical outcomes. WRF occurred less frequent with serelaxin [OR 0.70 (95% CI 0.60-0.83, p < 0.0001)] and was associated with increased risk of ACM, worsening HF and the composite of CVD and HF or renal failure hospitalization. Improvement in renal function did not mediate the treatment effect of serelaxin [CVD HR 1.01 (0.99-1.04), ACM HR 1.01 (0.99-1.03), HF/renal failure hospitalization HR 0.99 (0.97-1.00)].

CONCLUSIONS

Despite the significant improvement in renal function by serelaxin in patients with acute HF, the potential beneficial treatment effect was not mediated by improvement in renal function. These data suggest that improvement in renal function might not be a suitable surrogate marker for potential treatment efficacy in future studies with novel relaxin agents in acute HF. Central illustration. Conceptual model explaining mediation analysis; treatment efficacy of heart failure therapies mediated by renal function.

Characteristics and clinical outcomes of patients with acute heart failure with a supranormal left ventricular ejection fraction

AIM

Recent data suggest that guideline-directed medical therapy of patients with heart failure (HF) with reduced ejection fraction (HFrEF) might improve clinical outcomes in patients with HF up to a left ventricular ejection fraction (LVEF) of 55-65%, whereas patients with higher LVEF do not seem to benefit. Recent data have shown that LVEF may have a U-shaped relation with outcome, with poorer outcome also in patients with supranormal values. This suggests that patients with supranormal LVEF may be a distinctive group of patients.

METHODS AND RESULTS

RELAX-AHF-2 was a multicentre, placebo-controlled trial on the effects of serelaxin on 180-day cardiovascular (CV) mortality and worsening HF at day 5 in patients with acute HF. Echocardiograms were performed at hospital admission in 6128 patients: 155 (2.5%) patients were classified as HF with supranormal ejection fraction (HFsnEF; LVEF >65%), 1440 (23.5%) as HF with preserved ejection fraction (HFpEF; LVEF 50-65%), 1353 (22.1%) as HF with mildly reduced ejection fraction (HFmrEF; LVEF 41-49%) and 3180 (51.9%) as HFrEF (LVEF <40%). Patients with HFsnEF compared to HFpEF were more often women, had higher prevalence of non-ischaemic HF, had lower levels of natriuretic peptides, were less likely to be treated with beta-blockers and had higher blood urea nitrogen plasma levels. All-cause mortality was not statistically different between groups, although patients with HFsnEF had the highest numerical rate. A declining trend was seen in the proportion of 180-day deaths due to CV causes from HFrEF (290/359, 80.8%) to HFsnEF (14/24, 58.3%). The reverse was observed with death from non-CV causes. No treatment effect of serelaxin was observed in any of the subgroups.

CONCLUSIONS

In this study, only 2.5% of patients were classified as HFsnEF. HFsnEF was primarily characterized by female sex, lower natriuretic peptides and a higher risk of non-CV death.

Relaxin in hepatic fibrosis: What is known and where to head?

Relaxin (RLX) is a heterodimeric, polypeptide hormone that has natural anti-fibrotic activity in many organs. During the chronic liver injury, hepatic stellate cells (HSCs) are phenotypically transformed into myofibroblasts. This process is known as activation of HSCs. Activated HSCs play a central role in hepatic fibrosis. Quiescent HSCs were shown to express low levels of RLX receptors such as RXFP1 and RXFP2. Upon chronic liver injury, HSCs are activated and express high levels of the RLX receptors. ML290, an agonist of RXFP1 has been reported to have antifibrotic effect in vitro as well as in vivo. Serelaxin, a recombinant human RLX-2 treatment has reduced hepatic fibrosis and portal hypertension in experimental models due to its vasodilation properties by inducing intrahepatic nitric oxide level. Serelaxin has also produced a neutral effect when studied against human cirrhosis-related portal hypertension in clinical trials. RLX is a potent collagen synthesis inhibitor and it has extracellular matrix (ECM) remodeling properties by promoting matrix metalloproteinases and downregulating expression of metalloproteinases inhibitors. Available reports suggest that RLX could induce ECM remodeling and suppress the profibrogenic transforming growth factor-β signaling and thereby regress hepatic fibrosis. Though RLX has natural antifibrotic activity, its antifibrotic molecular mechanisms especially in hepatic fibrosis condition are not reported. This review exclusively focuses antifibrotic effect of RLX on hepatic fibrosis.

Pulmonary myeloid cell uptake of biodegradable nanoparticles conjugated with an anti-fibrotic agent provides a novel strategy for treating chronic allergic airways disease

Asthma (chronic allergic airways disease, AAD) is characterized by airway inflammation (AI), airway remodeling (AWR) and airway hyperresponsiveness (AHR). Current treatments for AAD mainly focus on targeting AI and its contribution AHR, with the use of corticosteroids. However, there are no therapies for the direct treatment of AWR, which can contribute to airway obstruction, AHR and corticosteroid resistance independently of AI. The acute heart failure drug, serelaxin (recombinant human gene-2 relaxin, RLX), has potential anti-remodeling and anti-fibrotic effects but only when continuously infused or injected to overcome its short half-life. To alleviate this limitation, we conjugated serelaxin to biodegradable and noninflammatory nanoparticles (NP-RLX) and evaluated their therapeutic potential on measures of AI, AWR and AHR, when intranasally delivered to a preclinical rodent model of chronic AAD and TGF-β1-stimulated collagen gel contraction from asthma patient-derived myofibroblasts. NP-RLX was preferentially taken-up by CD206⁺-infiltrating and CD68⁺-tissue resident alveolar macrophages. Furthermore, NP-RLX ameliorated the chronic AAD-induced AI, pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), chemokines (CCL2, CCL11) and the pro-fibrotic TGF-β1/IL-1β axis on AWR and resulting AHR, as well as human myofibroblast-induced collagen gel contraction, to a similar extent as unconjugated RLX. Hence, NP-RLX represents a novel strategy for treating the central features of asthma.

A phase 2 randomised controlled trial of serelaxin to lower portal pressure in cirrhosis (STOPP)

BACKGROUND

In preclinical models, recombinant human relaxin-2 (serelaxin) had anti-fibrotic effects and ameliorated portal hypertension (PH). A small exploratory study in patients with cirrhosis also suggested that serelaxin could reduce portal pressure.

METHODS

In a phase 2, double-blind, randomised controlled study conducted in a single centre (Royal Infirmary of Edinburgh, UK), male and female adult participants with cirrhosis and clinically significant PH (CSPH; hepatic venous pressure gradient (HVPG) > 10 mmHg) were enrolled. Participants were allocated to serelaxin or placebo in a 3:1 ratio. The placebo was matched to serelaxin on appearance and administration protocol to create and maintain blinding. The primary endpoint was the change from baseline in fasting HVPG after 2 h of peripheral i.v. serelaxin infusion (80 μg/kg/day for 60 min followed by 30 μg/kg/day for at least 60 min). Secondary endpoints included the change from baseline in hepatic blood flow and systemic haemodynamics (cardiac index, systemic vascular resistance index and aortic pulse wave velocity). Short-term safety and tolerability of serelaxin were assessed.

RESULTS

A total of 17 participants were screened, 15 were randomised and 11 completed the study (n = 9 serelaxin, n = 2 placebo). Reasons for withdrawal were baseline HVPG < 10 mmHg (n = 2) and technical failure (n = 2). The trial ended early due to manufacturer discontinuation of the study drug. The median age was 56 (range 43-69) years and 73% of participants were male. Alcohol was the commonest cirrhosis aetiology (n = 10). Participants had a median Model for End-Stage Liver Disease score of 10 (range 6-14). The mean baseline HVPG was 16.3 (range 10.3-21.7) mmHg. Individual responses were variable, but overall there was no statistically significant change in HVPG after 2 h of i.v. serelaxin (arithmetic mean of difference ± SD was 0.4 ± 3.5 mmHg (95% CI -2.3, 3.1; p = 0.76)). There were also no substantial changes from baseline in hepatic or systemic haemodynamics. We recorded 12 adverse events in 7 participants treated with serelaxin; none were significant, and most were unrelated to the investigational medicinal product. There were no serious adverse events.

CONCLUSION

In a small randomised, phase 2, proof-of-concept study in patients with cirrhosis and CSPH, serelaxin infusion was safe and well-tolerated but had a neutral effect on HVPG.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02669875. Registered on 1 February 2016.

Serelaxin alleviates cardiac fibrosis through inhibiting endothelial-to-mesenchymal transition via RXFP1

Rationale: Cardiac fibrosis is an integral constituent of every form of chronic heart disease, and persistence of fibrosis reduces tissue compliance and accelerates the progression to heart failure. Relaxin-2 is a human hormone, which has various physiological functions such as mediating renal vasodilation in pregnancy. Its recombinant form Serelaxin has recently been tested in clinical trials as a therapy for acute heart failure but did not meet its primary endpoints. The aim of this study is to examine whether Serelaxin has an anti-fibrotic effect in the heart and therefore could be beneficial in chronic heart failure. Methods: We utilized two different cardiac fibrosis mouse models (ascending aortic constriction (AAC) and Angiotensin II (ATII) administration via osmotic minipumps) to assess the anti-fibrotic potential of Serelaxin. Histological analysis, immunofluorescence staining and molecular analysis were performed to assess the fibrosis level and indicate endothelial cells which are undergoing EndMT. In vitro TGFβ1-induced endothelial-to-mesenchymal transition (EndMT) assays were performed in human coronary artery endothelial cells and mouse cardiac endothelial cells (MCECs) and were examined using molecular methods. Chromatin immunoprecipitation-qPCR assay was utilized to identify the Serelaxin effect on chromatin remodeling in the Rxfp1 promoter region in MCECs. Results: Our results demonstrate a significant and dose-dependent anti-fibrotic effect of Serelaxin in the heart in both models. We further show that Serelaxin mediates this effect, at least in part, through inhibition of EndMT through the endothelial Relaxin family peptide receptor 1 (RXFP1). We further demonstrate that Serelaxin administration is able to increase its own receptor expression (RXFP1) through epigenetic regulation in form of histone modifications by attenuating TGFβ-pSMAD2/3 signaling in endothelial cells. Conclusions: This study is the first to identify that Serelaxin increases the expression of its own receptor RXFP1 and that this mediates the inhibition of EndMT and cardiac fibrosis, suggesting that Serelaxin may have a beneficial effect as anti-fibrotic therapy in chronic heart failure.

Vascular effects of serelaxin in patients with stable coronary artery disease: a randomized placebo-controlled trial

AIMS

The effects of serelaxin, a recombinant form of human relaxin-2 peptide, on vascular function in the coronary microvascular and systemic macrovascular circulation remain largely unknown. This mechanistic, clinical study assessed the effects of serelaxin on myocardial perfusion, aortic stiffness, and safety in patients with stable coronary artery disease (CAD).

METHODS AND RESULTS

In this multicentre, double-blind, parallel-group, placebo-controlled study, 58 patients were randomized 1:1 to 48 h intravenous infusion of serelaxin (30 µg/kg/day) or matching placebo. The primary endpoints were change from baseline to 47 h post-initiation of the infusion in global myocardial perfusion reserve (MPR) assessed using adenosine stress perfusion cardiac magnetic resonance imaging, and applanation tonometry-derived augmentation index (AIx). Secondary endpoints were: change from baseline in AIx and pulse wave velocity, assessed at 47 h, Day 30, and Day 180; aortic distensibility at 47 h; pharmacokinetics and safety. Exploratory endpoints were the effect on cardiorenal biomarkers [N-terminal pro-brain natriuretic peptide (NT-proBNP), high-sensitivity troponin T (hsTnT), endothelin-1, and cystatin C]. Of 58 patients, 51 were included in the primary analysis (serelaxin, n = 25; placebo, n = 26). After 2 and 6 h of serelaxin infusion, mean placebo-corrected blood pressure reductions of -9.6 mmHg (P = 0.01) and -13.5 mmHg (P = 0.0003) for systolic blood pressure and -5.2 mmHg (P = 0.02) and -8.4 mmHg (P = 0.001) for diastolic blood pressure occurred. There were no between-group differences from baseline to 47 h in global MPR (-0.24 vs. -0.13, P = 0.44) or AIx (3.49% vs. 0.04%, P = 0.21) with serelaxin compared with placebo. Endothelin-1 and cystatin C levels decreased from baseline in the serelaxin group, and there were no clinically relevant changes observed with serelaxin for NT-proBNP or hsTnT. Similar numbers of serious adverse events were observed in both groups (serelaxin, n = 5; placebo, n = 7) to 180-day follow-up.

CONCLUSION

In patients with stable CAD, 48 h intravenous serelaxin reduced blood pressure but did not alter myocardial perfusion.

Efficacy and safety of serelaxin when added to standard of care in patients with acute heart failure: results from a PROBE study, RELAX-AHF-EU

AIM

Serelaxin is a recombinant human relaxin-2 hormone, which confers receptor-mediated vasodilatation in a tissue-specific fashion. The RELAX-AHF-EU study assessed the effect of serelaxin when added to standard-of-care (SoC) therapy on worsening heart failure (WHF)/all-cause death through Day 5 in patients hospitalised for acute heart failure (AHF) in Europe.

METHODS AND RESULTS

This multicentre, prospective, randomised, open-label, blinded-endpoint validation study enrolled hospitalised AHF patients and randomised (2:1) eligible patients (mild-to-moderate renal impairment and systolic blood pressure ≥ 125 mmHg) within 16 h of presentation with signs/symptoms of AHF, to receive 48 h intravenous infusion of 30 μg/kg/day serelaxin + SoC or SoC alone. The primary endpoint was adjudicated WHF/all-cause death through Day 5. Of 3183 patients targeted, 2666 were randomised when the study was terminated early by the sponsor due to the neutral results of the pivotal RELAX-AHF-2 study. Adjudicated WHF/all-cause death through Day 5 was significantly reduced in the serelaxin + SoC vs. SoC group (5.0% vs. 6.9%; hazard ratio 0.71; 95% confidence interval 0.51-0.98; P = 0.0172) (absolute risk reduction 1.9%, number needed to treat 53). The difference between treatment groups was not significant for WHF/all-cause death/heart failure rehospitalisation through Day 14 and length of hospital stay. A significantly smaller proportion of patients in the serelaxin + SoC vs. SoC group experienced persistent heart failure signs/symptoms at each visit until Day 4, or renal deterioration through Day 5 (all P ≤ 0.01). Overall incidence of treatment-emergent adverse events was comparable between treatment groups. Hypotension and decrease in haemoglobin/haematocrit were more frequent in the serelaxin + SoC group.

CONCLUSION

When added to SoC, serelaxin reduced adjudicated WHF or all-cause death through Day 5 in AHF patients. The results from this open-label study should be considered in the context of the totality of the double-blind, randomised evidence on serelaxin in AHF.

Relaxin activates AMPK-AKT signaling and increases glucose uptake by cultured cardiomyocytes

PURPOSE

Many evidences show that the hormone relaxin plays a pivotal role in the physiology and pathology of the cardiovascular system. This pleiotropic hormone exerts regulatory functions through specific receptors in cardiovascular tissues: in experimental animal models it was shown to induce coronary vasodilation, prevent cardiac damage induced by ischemia/reperfusion and revert cardiac hypertrophy and fibrosis. A tight relationship between this hormone and important metabolic pathways has been suggested, but it is at present unknown if relaxin could regulate cardiac metabolism. Our aim was to study the possible effects of relaxin on cardiomyocyte metabolism.

METHODS

Neonatal rat cardiomyocytes were treated with relaxin and (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays (MTT) were performed to assess metabolic activity; while 2-deoxy-D-[³H] glucose and BODIPY-labelled fatty acid incorporations were analyzed to measure glucose and fatty acid uptakes, and western blot was utilized to study the intracellular signaling pathways activated by the hormone.

RESULTS

We observed that relaxin at 10 ng/ml was able to increase the level of metabolic activity of cultured neonatal rat cardiomyocytes; the rate of 2-deoxy-D-[³H]glucose incorporation demonstrated that relaxin also induced an increase in glucose uptake. First evidence is also offered that relaxin can activate the master energy sensor and regulator AMPK in cardiomyocytes. Moreover, the treatment of cardiomyocytes with relaxin also induced dose-dependent increases in ERK1/2, AKT, and AS160 phosphorylation. That raise in AS160 phosphorylation induced by relaxin was prevented by the pretreatment with AMPK and AKT pathways inhibitors, indicating that both molecules play important roles in the relaxin effects reported.

CONCLUSION

Relaxin can regulate cardiomyocyte metabolism and activate AMPK, the central sensor of energy status that maintains cellular energy homeostasis, and also ERK and AKT, two molecular sensing nodes that coordinate dynamic responses of the cell's metabolic responses.

Reperfusion therapy with recombinant human relaxin-2 (Serelaxin) attenuates myocardial infarct size and NLRP3 inflammasome following ischemia/reperfusion injury via eNOS-dependent mechanism

Aims

The preconditioning-like infarct-sparing and anti-inflammatory effects of the peptide hormone relaxin following ischemic injury have been studied in the heart. Whether reperfusion therapy with recombinant human relaxin-2, serelaxin, reduces myocardial infarct size and attenuates the subsequent NLRP3 inflammasome activation leading to further loss of functional myocardium following ischemia/reperfusion (I/R) injury is unknown.

Methods and results

After baseline echocardiography, adult male wild-type C57BL or eNOS knockout mice underwent myocardial infarction (MI) by coronary artery ligation for 30 min followed by 24 h reperfusion. Mice were treated with either serelaxin (10 µg/kg; sc) or saline 1 h prior to ischemia or 5 min before reperfusion. In both pre-treatment and reperfusion therapy arms, serelaxin improved survival at 24 h post MI in wild-type mice (79% and 82%) as compared with controls (46% and 50%, P = 0.01), whereas there was no difference in survival between serelaxin- and saline-treated eNOS knockout mice. Moreover, serelaxin significantly reduced infarct size (64% and 67% reduction, P < 0.05), measured with TTC staining, and preserved LV fractional shortening (FS) and end-systolic diameter (LVESD) in wild-type mice as compared with controls (P < 0.05). Interestingly, caspase-1 activity in the heart tissue, a measure of inflammasome formation, was markedly reduced in serelaxin-treated wild-type mice compared with controls at 24 h post-MI in both treatment modalities (P < 0.05). Genetic deletion of eNOS abolished the infarct-sparing and anti-inflammatory effects of serelaxin as well as functional preservation. Serelaxin plasma levels assessed at 5 min and 1 h after treatment, using ELISA, approximated physiologic relaxin levels during pregnancy in mice and parallels that in humans.

Conclusion

Serelaxin attenuates myocardial I/R injury and the subsequent caspase-1 activation via eNOS-dependent mechanism.

Serelaxin inhibits differentiation and fibrotic behaviors of cardiac fibroblasts by suppressing ALK-5/Smad2/3 signaling pathway

Serelaxin, a recombinant form of human relaxin-2, is currently regarded as a novel drug for treatment of acute heart failure. However, whether therapeutic effects of serelaxin are achieved by inhibiting cardiac fibrosis remains unclear. In this study, we investigate effects of serelaxin on inhibiting cardiac fibrosis. Cardiac fibroblasts (CFs) were isolated from the hearts of adult rats. Effects of serelaxin on differentiation of CFs towards myofibroblasts (MFs) and their fibrotic behaviors after induction with TGF-β1 were examined. Synthesis and degradation of collagens, secretion of IL-10, and expression of ALK-5 and p-Smad2/3 of TGF-β1-induced cells were assessed after treatment with serelaxin. Serelaxin inhibited differentiation of TGF-β1-induced CFs towards MFs, and reduced proliferation and migration of the induced cells. Moreover, serelaxin down-regulated expression of collagen I/III and TIMP-2, and up-regulated expression of MMP-2 and MMP-9 in the cells. After treatment with serelaxin, activity of MMP-2 and MMP-9 and secretion of IL-10 increased, expression of ALK-5 and the level of Smad2/3 phosphorylation was reduced significantly. These results suggest that serelaxin can inhibit differentiation of TGF-β1-induced CFs towards MFs, reduce production of collagens by suppressing ALK-5/Smad2/3 signaling pathway, and enhance extracellular matrix degradation by increasing MMP-2/TIMP-2 ratio and IL-10 secretion. Serelaxin may be a potential therapeutic drug for inhibiting cardiac fibrosis.

Early Anti-inflammatory and Pro-angiogenic Myocardial Effects of Intravenous Serelaxin Infusion for 72 H in an Experimental Rat Model of Acute Myocardial Infarction

Sprague Dawley rats were subjected to acute myocardial infarction (AMI) by permanent ligation of the left anterior descending coronary artery. At the time of AMI, a subcutaneous mini-osmotic pump was implanted and animals were randomized into three groups, according to the intravenous therapy received during the first 72 h: placebo-treated (saline), serelaxin10-treated (SRLX10 = 10 μg/kg/day), or serelaxin30-treated (SRLX30 = 30 μg/kg/day). Treatment with SRLX30 reduced the expression of inflammatory cytokines and chemokines, as well as the infiltration of macrophages, and increased the expression of pro-angiogenic markers and vessel density in the infarcted myocardium after 7 days. SRLX30 did not reduce early myocardial fibrosis but reduced myocardial levels of sST2 and galectin-3. No significant effects were observed with SRLX10 treatment. A significant correlation was observed between plasma levels of serelaxin and effect measures. The results suggest serelaxin has a protective effect in early processes of cardiac remodeling after AMI.

Differences in the renal antifibrotic cGMP/cGKI-dependent signaling of serelaxin, zaprinast, and their combination

Renal fibrosis is an important factor for end-stage renal failure. However, only few therapeutic options for its treatment are established. Zaprinast, a phosphodiesterase 5 inhibitor, and serelaxin, the recombinant form of the naturally occurring hormone relaxin, are differently acting modulators of cyclic guanosine monophosphate (cGMP) signaling. Both agents enhance cGMP availability in kidney tissue. These substances alone or in combination might interfere with the development of kidney fibrosis. Therefore, we compared the effects of combination therapy with the effects of monotherapy on renal fibrosis. Renal fibrosis was induced by unilateral ureteral obstruction (UUO) for 7 days in wild-type (WT) and cGKI knockout (KO) mice. Renal antifibrotic effects were assessed after 7 days. In WT, zaprinast and the combination of zaprinast and serelaxin significantly reduced renal interstitial fibrosis assessed by α-SMA, fibronectin, collagen1A1, and gelatinases (MMP2 and MMP9). Intriguingly in cGKI-KO, mRNA and protein expression of fibronectin and collagen1A1 were reduced by zaprinast, in contrast to serelaxin. Gelatinases are not regulated by zaprinast. Although both substances showed similar antifibrotic properties in WT, they distinguished in their effect mechanisms. In contrast to serelaxin which acts both on Smad2 and Erk1, zaprinast did not significantly diminish Erk1/2 phosphorylation. Interestingly, the combination of serelaxin/zaprinast achieved no additive antifibrotic effects compared to the monotherapy. Due to antifibrotic effects of zaprinast in cGKI-KO, we hypothesize that additional cGKI-independent mechanisms are supposed for antifibrotic signaling of zaprinast.

Serelaxin treatment promotes adaptive hypertrophy but does not prevent heart failure in experimental peripartum cardiomyopathy

AIMS

Peripartum cardiomyopathy (PPCM) is a systolic left ventricular dysfunction developing in the peripartum phase in previously healthy women. Relaxin-2 is a pregnancy hormone with potential beneficial effects in heart failure patients. We evaluated Relaxin-2 as a potential diagnostic marker and/or a therapeutic agent in PPCM.

METHODS AND RESULTS

In healthy peripartum women, serum Relaxin-2 levels (measured by ELISA in the second half of pregnancy) were elevated showing a decreasing trend in the first postpartum week and returned to non-pregnant levels thereafter. In PPCM patients diagnosed in the first postpartum week, serum Relaxin-2 levels were lower compared to healthy postpartum stage-matched controls. In PPCM patients diagnosed later (0.5-10 months postpartum) Relaxin-2 levels were in the range of non-pregnant controls and not different from healthy postpartum stage-matched controls. In mice, serum Relaxin-1 (functional equivalent of human Relaxin-2) was increased late in pregnancy and rapidly cleared in the first postpartum week. In mice with PPCM due to a cardiomyocyte-specific knockout of STAT3 (CKO) neither low nor high dose of recombinant Relaxin-2 (serelaxin, sRlx-LD: 30 µg/kg/day; sRlx-HD: 300 µg/kg/day) affected cardiac fibrosis, inflammation and heart failure but sRlx-HD increased capillary/cardiomyocyte ratio. sRlx-HD significantly increased heart/body weight ratio and cardiomyocyte cross-sectional area in postpartum CKO and wild-type mice without changing the foetal gene expression program (ANP or β-MHC). sRlx-HD augmented plasma Prolactin levels in both genotypes, which induced cardiac activation of STAT5. In vitro analyses showed that Prolactin induces cardiomyocyte hypertrophy via activation of STAT5.

CONCLUSION

Although Relaxin-2 levels seemed lower in PPCM patients diagnosed early postpartum, we observed a high pregnancy-related variance of serum Relaxin-2 levels peripartum making it unsuitable as a biomarker for this condition. Supplementation with sRlx may contribute to angiogenesis and compensatory hypertrophy in the diseased heart, but the effects are not sufficient to prevent heart failure in an experimental PPCM model.

Serelaxin in addition to standard therapy in acute heart failure: rationale and design of the RELAX-AHF-2 study

Patients admitted for acute heart failure (AHF) experience high rates of in-hospital and post-discharge morbidity and mortality despite current therapies. Serelaxin is recombinant human relaxin-2, a hormone with vasodilatory and end-organ protective effects believed to play a central role in the cardiovascular and renal adaptations of human pregnancy. In the phase 3 RELAX-AHF trial, serelaxin met its primary endpoint of improving dyspnoea through day 5 in patients admitted for AHF. Compared to placebo, serelaxin also reduced worsening heart failure (WHF) by 47% through day 5 and both all-cause and cardiovascular mortality by 37% through day 180. RELAX-AHF-2 ( ClinicalTrials.gov NCT01870778) is designed to confirm serelaxin's effect on these clinical outcomes. RELAX-AHF-2 is a multicentre, randomized, double-blind, placebo-controlled, event-driven, phase 3 trial enrolling ∼6800 patients hospitalized for AHF with dyspnoea, congestion on chest radiograph, increased natriuretic peptide levels, mild-to-moderate renal insufficiency, and systolic blood pressure ≥125 mmHg. Patients are randomized within 16 h of presentation to 48 h intravenous infusions of serelaxin (30 µg/kg/day) or placebo, both in addition to standard of care treatments. The primary objectives are to demonstrate that serelaxin is superior to placebo in reducing: (i) 180 day cardiovascular death, and (ii) occurrence of WHF through day 5. Key secondary endpoints include 180 day all-cause mortality, composite of 180 day combined cardiovascular mortality or heart failure/renal failure rehospitalization, and in-hospital length of stay during index AHF. The results from RELAX-AHF-2 will provide data on the potential beneficial effect of serelaxin on cardiovascular mortality and WHF in selected patients with AHF.

Serelaxin in acute heart failure patients with and without atrial fibrillation: a secondary analysis of the RELAX-AHF trial

BACKGROUND

Atrial fibrillation (AFib) is a common comorbidity in HF and affects patients' outcome. We sought to assess the effects of serelaxin in patients with and without AFib.

METHODS

In a post hoc analysis of the RELAX-AHF trial, we compared the effects of serelaxin on efficacy end points, safety end points and biomarkers in 1161 patients with and without AFib on admission electrocardiogram.

RESULTS

AFib was present in 41.3% of patients. Serelaxin had a similar effect in patients with and without AFib, including dyspnea relief by visual analog scale through day 5 [mean change in area under the curve, 541.11 (33.79, 1048.44), p = 0.0366 in AFib versus 361.80 (-63.30, 786.90), p = 0.0953 in non-AFib, interaction p = 0.5954] and all-cause death through day 180 [HR = 0.42 (0.23, 0.77), p = 0.0051 in AFib versus 0.90 (0.53, 1.52), p = 0.6888 in non-AFib, interaction p = 0.0643]. Serelaxin was similarly safe in the two groups and induced similar reductions in biomarkers of cardiac, renal and hepatic damage. Stroke occurred more frequently in AFib patients (2.8 vs. 0.8%, p = 0.0116) and there was a trend for lower stroke incidence in the serelaxin arm in AFib patients (odds ratios, 0.31, p = 0.0759 versus 3.88, p = 0.2255 in non-AFib, interaction p = 0.0518).

CONCLUSIONS

Serelaxin was similarly safe and efficacious in improving short- and long-term outcomes and inducing organ protection in acute HF patients with and without AFib.

Sex differences in early dyspnea relief between men and women hospitalized for acute heart failure: insights from the RELAX-AHF study

AIMS

Women with heart failure are typically older, and more often have hypertension and a preserved left ventricular ejection fraction as compared with men. We sought to analyze if these sex differences influence the course and outcome of acute heart failure.

METHODS AND RESULTS

We analyzed sex differences in acute heart failure in 1161 patients enrolled in the RELAX-AHF study. The pre-specified study endpoints were used. At baseline, women (436/1161 patients) were older, had a higher left ventricular ejection fraction, a higher rate of hypertension, and were treated differently from men. Early dyspnea improvement (moderate or marked dyspnea improvement measured by Likert scale during the first 24 h) was greater in women. However, dyspnea improvement over the first 5 days (change from baseline in the visual analog scale area under the curve (VAS AUC) to day 5) was similar between men and women. Women reported greater improvements in general wellbeing by Likert, but no such benefits were evident with the VAS score. Multi-variable predictors of moderate or marked dyspnea improvement were female sex (p = 0.0011), lower age (p = 0.0026) and lower diuretic dose (p = 0.0067). The additional efficacy endpoints of RELAX-AHF were similar between men and women and serelaxin was equally effective in men and women.

CONCLUSIONS

Women exhibit better earlier dyspnea relief and improvement in general wellbeing compared with men, even adjusted for age and left ventricular ejection fraction. However, in-hospital and post-discharge clinical outcomes were similar between men and women. This trial is registered at ClinicalTrials.gov, NCT00520806.

Evaluating the Efficacy, Safety, and Tolerability of Serelaxin When Added to Standard Therapy in Asian Patients With Acute Heart Failure: Design and Rationale of RELAX-AHF-ASIA Trial

BACKGROUND

Acute heart failure (AHF), a common and growing health concern worldwide, is associated with high risk of post-discharge rehospitalization and mortality. Existing evidence indicates potential therapeutic benefits of serelaxin in Caucasian AHF patients, but corresponding data in Asians remain scarce. RELAX-AHF-ASIA, a multinational, randomized, double-blind, placebo-controlled, phase III trial, will evaluate the effects of serelaxin on symptom relief and clinical outcomes in Asian AHF patients, with the use of novel assessments.

METHODS AND RESULTS

Patients with AHF, systolic blood pressure ≥125 mm Hg, and mild to moderate renal dysfunction will be randomized within 16 hours of presentation to receive 48-hour intravenous infusion of 30 µg ⋅ kg^-1 ⋅ d^-1 serelaxin or placebo in addition to standard therapy. The composite primary end point includes: (1) treatment success (moderate/marked improvement in patient-reported dyspnea and physician-assessed signs of congestion on day 2); (2) treatment failure (in-hospital worsening of signs and/or symptoms of heart failure [HF] requiring intensification of intravenous HF therapy or mechanical ventilation, renal/circulatory support, rehospitalization due to HF/renal-failure, or death through day 5); and (3) unchanged status. Secondary end points include time to in-hospital worsening HF through day 5 and all-cause and cardiovascular deaths through day 180.

CONCLUSIONS

RELAX-AHF-ASIA, the largest randomized clinical trial in Asian AHF patients to date, has a novel composite primary end point and the potential to become a hallmark of AHF trials.

Recombinant human relaxin versus placebo for cervical ripening: a double-blind randomised trial in pregnant women scheduled for induction of labour

Background

Nonclinical studies indicate that the hormone relaxin is a good candidate for a safe cervical ripening agent that does not cause uterine contractions.

Methods

This Phase II study (conducted November 2, 2005–October 20, 2006) was a randomised, double blind, placebo controlled trial testing 24-h intravenous infusion of serelaxin (recombinant human relaxin) or placebo for cervical ripening in 72 healthy, primiparous women. Eligible subjects had a singleton pregnancy ≥40 weeks, were planned for elective induction, had vertex presentation of the fetus, intact membranes and a Bishop score at screening ≤4. In Part A of the study, safety evaluation of three escalating doses of serelaxin (7.5, 25 or 75 μg/kg/day) or placebo was performed in 22 subjects admitted to the hospital 24 h prior to scheduled induction (n = 7, 4, 4, and 7 subjects, respectively). The highest safe dose from Part A and placebo were then tested in Part B for safety and cervical ripening (n = 25 subjects/arm). Planned randomisation ratio was of 4:2 (serelaxin:placebo) for each dose group in Part A and 1:1 for Part B. For analysis, subjects in Part B were pooled with those receiving the same dose in Part A and all subjects receiving placebo were pooled. The primary efficacy endpoint was change from baseline in Bishop score at 6, 12 and 24 h or end of study drug administration. Maternal safety evaluations included adverse events and vital signs through 4 weeks. Fetal assessments included serial heart rate monitoring and nonstress testing. Neonatal assessments included Apgar scores, NICU admissions, and adverse events through 4 weeks.

Results

Overall, 74 subjects were randomized and 72 were treated. There were no significant differences between the groups receiving the highest safe dose of serelaxin (75 μg/kg/day) and placebo in the primary or secondary efficacy endpoints. Changes from baseline in Bishop score at 24 h were 4.19 ± 1.9 and 3.26 ± 2.26 in the pooled placebo and serelaxin groups, respectively (p = 0.2507). Serelaxin was well tolerated and no anti-serelaxin antibodies were detected in either subjects or neonates.

Conclusion

Serelaxin infusion at the end of pregnancy was well tolerated but did not advance cervical ripening.

Trial registration

Clinicaltrials.gov identifier NCT00259103 (15 November 2005).

Increase of cortical cerebral blood flow and further cerebral microcirculatory effects of Serelaxin in a sheep model

Serelaxin, recombinant human relaxin-2, modulates endothelial vasodilatory functionality and is under evaluation for treatment of acute heart failure. Little is known about acute effects on cerebral perfusion. We tested the hypothesis that Serelaxin might also have effects on the cerebral microcirculation in a sheep model, which resembles human brain structure quite well. We used laser Doppler flowmetry and sidestream dark-field (SDF) imaging techniques, which are reliable tools to continuously assess dynamic changes in cerebral perfusion. Laser Doppler flowmetry shows that bolus injection of 30 μg Serelaxin/kg body wt induces an increase (P = 0.006) to roughly 150% of cortical cerebral blood flow (CBF), whereas subcortical CBF remains unchanged (P = 0.688). The effects on area-dependent CBF were significantly different after the bolus injection (P = 0.042). Effects on cortical CBF were further confirmed by SDF imaging. The bolus injection of Serelaxin increased total vessel density to 127% (P = 0.00046), perfused vessel density to 145% (P = 0.024), and perfused capillary density to 153% (P = 0.024). Western blotting confirmed the expression of relaxin receptors RXFP1 and truncated RXFP2-variants in the respective brain regions, suggesting a possible contribution of RXFP1 on the effects of Serelaxin. In conclusion, the injection of a high dose of Serelaxin exerts quick effects on the cerebral microcirculation. Therefore, Serelaxin might be suitable to improve cortical microcirculation and exert neuroprotective effects in clinically relevant scenarios that involve cortical hypoperfusion. These findings need to be confirmed in relevant experimental settings involving cerebral cortical hypoperfusion and can possibly be translated into clinical practice.

Anti-atherosclerotic effects of serelaxin in apolipoprotein E-deficient mice

BACKGROUND AND AIMS

Serelaxin (SLX) is a recombinant form of human relaxin-2, a naturally occurring peptide that regulates maternal cardiovascular adaptations to pregnancy. It is unclear whether SLX has a therapeutic effect on atherosclerosis. Therefore, we investigated direct vascular effects of SLX in a mouse model of atherosclerosis.

METHODS

6-8 week-old female apolipoprotein E-deficient mice were fed a high-fat, cholesterol-rich diet for 6 weeks and additionally received a continuous treatment with vehicle or SLX (0.05 or 0.1 μg/h), during the last 4 weeks, via subcutaneously implanted osmotic mini-pumps. Vascular oxidative stress, vasorelaxation and atherosclerotic plaque development were assessed.

RESULTS

Vascular oxidative stress was reduced in SLX-treated mice (vehicle: 322.67 RLU/s, SLX 0.05 μg/h: 119.76 RLU/s (p < 0.001 vs. vehicle), SLX 0.1 μg/h: 109.33 RLU/s (p < 0.001 vs. vehicle; p = 0.967 vs. 0.05 μg/h SLX)). Further SLX improved endothelium-dependent vasodilatation without influencing endothelium-independent vasorelaxation. Atherosclerotic plaque development was significantly reduced by SLX (vehicle: 0.38 ± 0.02 mm(2), 0.05 μg/h SLX: 0.32 ± 0.02 mm(2) (p = 0.047 vs. vehicle), 0.1 μg/h SLX: 0.29 ± 0.02 mm(2) (p = 0.002 vs. vehicle; p = 0.490 vs. 0.05 μg/h SLX)). Neither vascular macrophage, T-cell or neutrophil infiltration, nor collagen/vascular smooth muscle cell content differed between the groups. We observed a significant down-regulation of the angiotensin II type 1a receptor and a decrease in IL-6 and an increase in IL-10 plasma concentrations.

CONCLUSIONS

Our data demonstrates novel pleiotropic effects of SLX on vascular oxidative stress, endothelial dysfunction and atherosclerotic plaque burden. Therefore, SLX could serve as a new drug for the treatment of atherosclerosis-related diseases.

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

BACKGROUND

Serelaxin showed beneficial effects on clinical outcome and trajectories of renal markers in patients with acute heart failure. We aimed to study the interaction between renal function and the treatment effect of serelaxin.

METHODS

In the current post hoc analysis of the RELAX-AHF trial, we included all patients with available estimated glomerular filtration rate (eGFR) at baseline (n = 1132). Renal impairment was defined as an eGFR <60 ml/min/1.73 m(2) estimated by creatinine.

RESULTS

817 (72.2 %) patients had a baseline eGFR <60 ml/min/1.73 m(2). In placebo-treated patients, baseline renal impairment was related to a higher 180 day cardiovascular (HR 3.12, 95 % CI 1.33-7.30) and all-cause mortality (HR 2.81, 95 % CI 1.34-5.89). However, in serelaxin-treated patients, the risk of cardiovascular and all-cause mortality was less pronounced (HR 1.19, 95 % CI 0.54 -2.64; p for interaction = 0.106, and HR 1.15 95 % CI 0.56-2.34 respectively; p for interaction = 0.088). In patients with renal impairment, treatment with serelaxin resulted in a more pronounced all-cause mortality reduction (HR 0.53, 95 % CI 0.34-0.83), compared with patients without renal impairment (HR 1.30, 95 % CI 0.51-3.29).

CONCLUSION

Renal dysfunction was associated with higher cardiovascular and all-cause mortality in placebo-treated patients, but not in serelaxin-treated patients. The observed reduction in (cardiovascular) mortality in RELAX-AHF was more pronounced in patients with renal dysfunction. These observations need to be confirmed in the ongoing RELAX-AHF-2 trial.

Serelaxin (recombinant human relaxin-2) prevents high glucose-induced endothelial dysfunction by ameliorating prostacyclin production in the mouse aorta

Diabetes-induced endothelial dysfunction is a critical initiating factor in the development of cardiovascular complications. Treatment with relaxin improves tumour necrosis factor α-induced endothelial dysfunction by enhancing endothelial nitric oxide synthase (eNOS) activity and restoring superoxide dismutase 1 protein in rat aortic rings ex vivo. It is, therefore, possible that relaxin treatment could alleviate endothelial dysfunction in diabetes. This study aimed to test the hypothesis that serelaxin (recombinant human relaxin-2) prevents high glucose-induced vascular dysfunction in the mouse aorta. Abdominal aortae were isolated from C57BL/6 male mice and incubated in M199 media for 3days with either normal glucose (5.5mM) or high glucose (30mM), and co-incubated with placebo (20mM sodium acetate) or 10nM serelaxin at 37°C in 5% CO2. Vascular function was analysed using wire-myography. High glucose significantly reduced the sensitivity to the endothelium-dependent agonist, acetylcholine (ACh) (pEC50; normal glucose=7.66±0.10 vs high glucose=7.29±0.10, n=11-12, P<0.05) and the contraction induced by NOS inhibitor, L-NAME (200μM) (normal glucose=59.9±8.3% vs high glucose=38.7±4.3%, n=6, P<0.05), but had no effect on the endothelium-independent agonist, sodium nitroprusside (SNP)-mediated relaxation. Treatment with serelaxin restored endothelial function (pEC50; 7.83±0.11, n=11) but not NO availability. The presence of the cyclooxygenase (COX) inhibitor, indomethacin (1μM) (pEC50; control=7.29±0.10 vs indo=7.74±0.18, n=6-12, P<0.05) and a superoxide dismutase mimetic, tempol (10μM) (pEC50; control=7.29±0.10 vs tempol=7.82±0.05, n=6-12, P<0.01) significantly improved sensitivity to ACh in high glucose treated aortae, but had no effect in serelaxin treated aortae. This suggests that high glucose incubation alters the superoxide and COX-sensitive pathway, which was normalized by co-incubation with serelaxin. Neither high glucose incubation nor serelaxin treatment had an effect on cyclooxygenase 1 and 2 (Ptgs1, Ptgs2), prostacyclin synthase (PTGIS) and receptor (Ptgir) as well as thromboxane A2 receptor (Tbxa2r) mRNA expression. Importantly, production of prostacyclin was significantly (P<0.05) attenuated in high glucose treated aortae, which was prevented by serelaxin treatment. Our data show that serelaxin treatment for 3 days restores high glucose-induced endothelial dysfunction by ameliorating vasodilator prostacyclin production and possibly through the reduction of superoxide in the mouse aorta.

Serelaxin for the treatment of acute heart failure: a review with a focus on end-organ protection

Acute heart failure (AHF) is a complex clinical syndrome characterized by fluid overload and haemodynamic abnormalities (short-term clinical consequences) and the development of end-organ damage (long-term consequences). Current therapies for the treatment of AHF, such as loop diuretics and vasodilators, help to relieve haemodynamic imbalance and congestion, but have not been shown to prevent (and may even contribute to) end-organ damage, or to provide long-term clinical benefit. Serelaxin is the recombinant form of human relaxin-2, a naturally occurring hormone involved in mediating haemodynamic changes during pregnancy. Preclinical and clinical studies have investigated the effects mediated by serelaxin and the suitability of this agent for the treatment of patients with AHF. Data suggest that serelaxin acts via multiple pathways to improve haemodynamics at the vascular, cardiac, and renal level and provide effective congestion relief. In addition, this novel agent may protect the heart, kidneys, and liver from damage by inhibiting inflammation, oxidative stress, cell death, and tissue fibrosis, and stimulating angiogenesis. Serelaxin may therefore improve both short- and long-term outcomes in patients with AHF. In this review, we examine the unique mechanisms underlying the potential benefits of serelaxin for the treatment of AHF, in particular, those involved in mediating end-organ protection.

Targeted biological therapies reach the heart: the case of serelaxin for heart failure

Acute heart failure (AHF) is one of the most important causes of mortality, morbidity and rising healthcare costs. Despite this, there has been minimal advancement in the management of AHF and the treatment continues to focus on symptomatic improvement using vasodilators, diuretics and inotropes, none of which have shown any mortality benefits. Though originally thought of as a reproductive hormone, relaxin is now recognized as a potent vasodilator that modulates systemic and renal vascular tone, resulting in pre- and after-load reduction and a decrease in cardiac workload. A single intravenous infusion of relaxin over 48 hours has been shown to provide significant dyspnea relief among AHF patients, with an ongoing study to evaluate its potential for mortality benefit. This article provides an insight into the pharmacology of this novel therapy for AHF with an eye towards future clinical applications.

Mesenchymal stem cells and serelaxin synergistically abrogate established airway fibrosis in an experimental model of chronic allergic airways disease

This study determined if the anti-fibrotic drug, serelaxin (RLN), could augment human bone marrow-derived mesenchymal stem cell (MSC)-mediated reversal of airway remodeling and airway hyperresponsiveness (AHR) associated with chronic allergic airways disease (AAD/asthma). Female Balb/c mice subjected to the 9-week model of ovalbumin (OVA)-induced chronic AAD were either untreated or treated with MSCs alone, RLN alone or both combined from weeks 9-11. Changes in airway inflammation (AI), epithelial thickness, goblet cell metaplasia, transforming growth factor (TGF)-β1 expression, myofibroblast differentiation, subepithelial and total lung collagen deposition, matrix metalloproteinase (MMP) expression, and AHR were then assessed. MSCs alone modestly reversed OVA-induced subepithelial and total collagen deposition, and increased MMP-9 levels above that induced by OVA alone (all p<0.05 vs OVA group). RLN alone more broadly reversed OVA-induced epithelial thickening, TGF-β1 expression, myofibroblast differentiation, airway fibrosis and AHR (all p<0.05 vs OVA group). Combination treatment further reversed OVA-induced AI and airway/lung fibrosis compared to either treatment alone (all p<0.05 vs either treatment alone), and further increased MMP-9 levels. RLN appeared to enhance the therapeutic effects of MSCs in a chronic disease setting; most likely a consequence of the ability of RLN to limit TGF-β1-induced matrix synthesis complemented by the MMP-promoting effects of MSCs.

Investigation of interactions at the extracellular loops of the relaxin family peptide receptor 1 (RXFP1)

Relaxin, an emerging pharmaceutical treatment for acute heart failure, activates the relaxin family peptide receptor (RXFP1), which is a class A G-protein-coupled receptor. In addition to the classic transmembrane (TM) domain, RXFP1 possesses a large extracellular domain consisting of 10 leucine-rich repeats and an N-terminal low density lipoprotein class A (LDLa) module. Relaxin-mediated activation of RXFP1 requires multiple coordinated interactions between the ligand and various receptor domains including a high affinity interaction involving the leucine-rich repeats and a predicted lower affinity interaction involving the extracellular loops (ELs). The LDLa is essential for signal activation; therefore the ELs/TM may additionally present an interaction site to facilitate this LDLa-mediated signaling. To overcome the many challenges of investigating relaxin and the LDLa module interactions with the ELs, we engineered the EL1 and EL2 loops onto a soluble protein scaffold, mapping specific ligand and loop interactions using nuclear magnetic resonance spectroscopy. Key EL residues were subsequently mutated in RXFP1, and changes in function and relaxin binding were assessed alongside the RXFP1 agonist ML290 to monitor the functional integrity of the TM domain of these mutant receptors. The outcomes of this work make an important contribution to understanding the mechanism of RXFP1 activation and will aid future development of small molecule RXFP1 agonists/antagonists.

Serelaxin in acute heart failure patients with preserved left ventricular ejection fraction: results from the RELAX-AHF trial

AIMS

Serelaxin is effective in relieving dyspnoea and improving multiple outcomes in acute heart failure (AHF). Many AHF patients have preserved ejection fraction (HFpEF). Given the lack of evidence-based therapies in this population, we evaluated the effects of serelaxin according to EF in RELAX-AHF trial.

METHODS AND RESULTS

RELAX-AHF randomized 1161 AHF patients to 48-h serelaxin (30 μg/kg/day) or placebo within 16 h from presentation. We compared the effects of serelaxin on efficacy endpoints, safety endpoints, and biomarkers of organ damage between preserved (≥50%) and reduced (<50%, HFrEF) EF. HFpEF was present in 26% of patients. Serelaxin induced a similar dyspnoea relief in HFpEF vs. HFrEF patients by visual analogue scale-area under the curve (VAS-AUC) through Day 5 [mean change, 461 (-195, 1117) vs. 397 (10, 783) mm h, P = 0.87], but had possibly different effects on the proportion of patients with moderately or markedly dyspnoea improvement by Likert scale at 6, 12, and 24 h [odds ratio for favourable response, 1.70 (0.98, 2.95) vs. 0.85 (0.62, 1.15), interaction P = 0.030]. No differences were encountered in the effect of serelaxin on short- or long-term outcome between HFpEF and HFrEF patients including cardiovascular death or hospitalization for heart/renal failure through Day 60, cardiovascular death through Day 180, and all-cause death through Day 180. Similar safety and changes in biomarkers (high-sensitivity troponin T, cystatin-C, and alanine/aspartate aminotransferases) were found in both groups.

CONCLUSIONS

In AHF patients with HFpEF compared with those with HFrEF, serelaxin was well tolerated and effective in relieving dyspnoea and had a similar effect on short- and long-term outcome, including survival improvement.

A randomized, double-blind, placebo-controlled, multicentre study to assess haemodynamic effects of serelaxin in patients with acute heart failure

Aims

The aim of this study was to evaluate the haemodynamic effects of serelaxin (30 µg/kg/day 20-h infusion and 4-h post-infusion period) in patients with acute heart failure (AHF).

Methods and results

This double-blind, multicentre study randomized 71 AHF patients with pulmonary capillary wedge pressure (PCWP) ≥18 mmHg, systolic blood pressure (BP) ≥115 mmHg, and estimated glomerular filtration rate ≥30 mL/min/1.73 m² to serelaxin (n = 34) or placebo (n = 37) within 48 h of hospitalization. Co-primary endpoints were peak change from baseline in PCWP and cardiac index (CI) during the first 8 h of infusion. Among 63 patients eligible for haemodynamic analysis (serelaxin, n = 32; placebo, n = 31), those treated with serelaxin had a significantly higher decrease in peak PCWP during the first 8 h of infusion (difference vs. placebo: −2.44 mmHg, P = 0.004). Serelaxin showed no significant effect on the peak change in CI vs. placebo. Among secondary haemodynamic endpoints, a highly significant reduction in pulmonary artery pressure (PAP) was observed throughout the serelaxin infusion (largest difference in mean PAP vs. placebo: −5.17 mmHg at 4 h, P < 0.0001). Right atrial pressure, systemic/pulmonary vascular resistance, and systolic/diastolic BP decreased from baseline with serelaxin vs. placebo and treatment differences reached statistical significance at some time points. Serelaxin administration improved renal function and decreased N-terminal pro-brain natriuretic peptide levels vs. placebo. Treatment with serelaxin was well tolerated with no apparent safety concerns.

Conclusion

The haemodynamic effects of serelaxin observed in the present study provide plausible mechanistic support for improvement in signs and symptoms of congestion observed with this agent in AHF patients.

ClinicalTrials.gov identifier NCT01543854.

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.