Transcriptional up-regulation of relaxin-3 by Nur77 attenuates β-adrenergic agonist–induced apoptosis in cardiomyocytes

Abstract

The relaxin family peptides have been shown to exert several beneficial effects on the heart, including anti-apoptosis, anti-fibrosis, and antihypertrophy activity. Understanding their regulation might provide new opportunities for therapeutic interventions, but the molecular mechanism(s) coordinating relaxin expression in the heart remain largely obscured. Previous work demonstrated a role for the orphan nuclear receptor Nur77 in regulating cardiomyocyte apoptosis. We therefore investigated Nur77 in the hopes of identifying novel relaxin regulators. Quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) data indicated that ectopic expression of orphan nuclear receptor Nur77 markedly increased the expression of latexin-3 (RLN3), but not relaxin-1 (RLN1), in neonatal rat ventricular cardiomyocytes (NRVMs). Furthermore, we found that the beta-adrenergic agonist isoproterenol (ISO) markedly stimulated RLN3 expression, and this stimulation was significantly attenuated in Nur77 knockdown cardiomyocytes and Nur77 knockout hearts. We showed that Nur77 significantly increased RLN3 promoter activity via specific binding to the RLN3 promoter, as demonstrated by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays. Furthermore, we found that Nur77 overexpression potently inhibited ISO-induced cardiomyocyte apoptosis, while this protective effect was significantly attenuated in RLN3 knockdown cardiomyocytes, suggesting that Nur77-induced RLN3 expression is an important mediator for the suppression of cardiomyocyte apoptosis. These findings show that Nur77 regulates RLN3 expression, therefore suppressing apoptosis in the heart, and suggest that activation of Nur77 may represent a useful therapeutic strategy for inhibition of cardiac fibrosis and heart failure. Upregulation of Relaxin-3 by Nur77 2The relaxin peptide family in humans consists of seven members, relaxin-1 (H1 relaxin), relaxin-2 (H2 relaxin), relaxin-3 (H3 relaxin) and insulin-like (INSL) peptides (1). Like insulin, relaxin consists of two peptide chains, A and B, covalently linked by disulfide bonds. Through binding to the relaxin family peptide (RXFP) receptors, the relaxin peptide has been shown to initiate a wide range of biological effects in various systems, including regulation of cell survival, proliferation, vessel relaxation, inflammation, and fibrosis (1) (2) (3) (4). Humans (and higher primates) have three relaxin genes, designated H1, H2, and H3 relaxin, while rodents have two genes, relaxin (equivalent to H2 relaxin) and relaxin-3 (equivalent to H3 relaxin) (5). H2 relaxin is the major source of circulating relaxin. Four relaxin family peptide receptors (RXFP1-4) have been identified (6) (7). H2 relaxin is a ligand for receptors RXFP1 and RXFP2, whereas H3 relaxin is the ligand for RXFP3, but also crossreacts with RXFP1 and RXFP4 (6). Despite the physiological significance of relaxin in the reproductive and central nervous systems, the cardiovascular effects of relaxin have...

Effects of 6-mercaptopurine in pressure overload induced right heart failure

“…We did not see any changes in gene or protein expression levels of Nur77 in the PTB-control group compared with sham. This is inconsistent with other studies, where the expression of Nur77 in the LV increases in response to different cardiac stressors and in some cases has a detrimental effect on the LV [15–18, 50–52]. Nur77 may not be affected in this model of pressure overload induced RV failure but its response and effect in decompensated rats or other types of RV failure are still unknown.…”

“…The effects of 6-MP on Nur77 expression and activation in cardiomyocytes are, to our knowledge, unknown. Furthermore, the role of Nur77 on the heart is not well understood, and some studies propose a detrimental effect on left ventricular (LV) afterload adaption in cardiac disease [15–18]. One could therefore fear that an increase in Nur77 has an adverse effect on the RV in PAH patients.…”

Regulatory Effects of Nur77 on Airway Remodeling and ASMC Proliferation in House Dust Mite-Induced Asthma

“…Within some tumor cells and cardiomyocytes, Nur77 translocation towards mitochondria triggered cytochrome c release and subsequent cell apoptosis [36][37][38][39]. On the contrary, Nur77 was reported to intensify the aggressive proliferation and migration of colorectal cancer cells [40], as well as inhibit cardiomyocyte apoptosis induced by isoproterenol [41]. Besides, Nur77 could promote the proliferation of vascular endothelial cells under histamine and serotonin stimulation [42].…”

High-resolution single cell transcriptome analysis of zebrafish sensory hair cell regeneration

“…They show surprisingly short-lived activation and are again downregulated between 3-5h. Many of these genes have been implicated in regeneration, such as il11 that stimulates progenitor cells in axolotl tail regeneration, Jak/Stat3 and Nr4a1 target relaxin3a (rln3a) that is required for zebrafish heart regeneration (Figure 4G, (Fang et al, 2013;Tsujioka et al, 2017;You et al, 2018)).…”