H3 Relaxin Protects Against Myocardial Injury in Experimental Diabetic Cardiomyopathy by Inhibiting Myocardial Apoptosis, Fibrosis and Inflammation

Abstract

Background/Aims: Apoptosis, fibrosis and NLRP3 inflammasome activation are involved in the development of diabetic cardiomyopathy (DCM). Human recombinant relaxin-3 (H3 relaxin) is a novel bioactive peptide that inhibits cardiac injury; however, whether H3 relaxin prevents cardiac injury in rats with DCM and the underlying mechanisms are unknown. Methods: To investigate the effect of H3 relaxin on DCM, we performed a study using H3 relaxin treatment in male Sprague-Dawley (SD) rats with streptozotocin (STZ)-induced diabetes (DM). We measured apoptosis, fibrosis and NLRP3 inflammasome markers in the rat hearts four and eight weeks after the rats were injected with STZ (65 mg/kg) by western blot analysis. Subsequently, 2 or 6 weeks after the STZ treatment, the rats were treated with H3 relaxin [2 µg/kg/d (A group) or 0.2 µg/kg/d (B group)] for 2 weeks. Cardiac function was evaluated by echocardiography to determine the extent of myocardial injury in the DM rats. The protein levels of apoptosis, fibrosis and NLRP3 inflammasome markers were used to assess myocardial injury. In addition, we determined the plasma levels of IL-1β and IL-18 using a Milliplex MAP Rat Cytokine/Chemokine Magnetic Bead Panel kit. Results: The protein expression of cleaved caspase-8, caspase-9 and caspase-3 as well as fibrosis markers increased at 4 and 8 weeks in the STZ-induced diabetic hearts compared with the levels in the control group. Furthermore, the NLRP3 inflammasome was substantially activated in STZ-induced diabetic hearts, leading to increased IL-1β and IL-18 levels. Compared with the DM group, the A group exhibited substantially better cardiac function. The protein levels of apoptosis markers were attenuated by H3 relaxin, indicating that H3 relaxin inhibited myocardial apoptosis in the hearts of diabetic rats. The protein expression of fibrosis markers was inhibited by H3 relaxin. Additionally, the protein expression and activation of the NLRP3 inflammasome were also effectively attenuated by H3 relaxin. Conclusions: This study is the first to demonstrate that H3 relaxin plays an anti-apoptotic, anti-fibrotic and anti-inflammatory role in DCM.

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

“…Recently, it has been increasingly recognized that relaxin-3 exerts cardiac protective effects via its anti-fibrotic, anti-hypertrophic, anti-inflammatory, and vasodilatory actions (23,26). For instance, in zebrafish, relaxin-3 has been shown to be essentially involved in regulating cardiomyocyte proliferation and heart regeneration (16).…”

“…For instance, in zebrafish, relaxin-3 has been shown to be essentially involved in regulating cardiomyocyte proliferation and heart regeneration (16). Furthermore, pharmacological activation of the relaxin-3/RXFP3 pathway has been shown to exert potent anti-apoptotic, anti-fibrotic, and antihypertrophic effects in the heart (26). Indeed, relaxin peptides and their receptors have been shown to be expressed in the mouse and human heart.…”

“…Relaxin-3 was initially discovered to be predominantly expressed in the brain and play a critical role in regulating arousal, feeding, learning, and central responses to physiological stressors (17) (18) (19) (20) (21) (22). Recently, relaxin-3 thas been shown to elicit potent antiapoptotic, anti-fibrotic, and anti-hypertrophic effects in the heart (23) (24) (25) (26). Importantly, through binding to RXFP1, relaxin-3 demonstrated a synergistic effect with relaxin-2 to inhibit cardiac fibrosis (23), further suggesting that relaxin-3 is an important peptide hormone implicated in the regulation of cardiac function.…”

Identification of Energy Metabolism Changes in Diabetic Cardiomyopathy Rats Using a Metabonomic Approach

“…Rats in the control groups were injected with the same volume of sodium citrate solvent (n = 45). Two days after the injections, the blood glucose concentrations were measured using a tail nick and glucometer (One Touch Ultra, LifeScan Inc., Milpitas, CA), and rats with blood glucose levels higher than 16.70 mmol/L were classified as diabetic [21].…”

Response to letter on “Relaxin inhibits macrophage inflammation by repressing NLRP3” by Zhou et al

“…Valle Raleigh et al could elegantly delineate an eNOS-dependent decrease in caspase-1 activation, as a marker of NLRP3 inflammasome formation, following relaxin-2 application in ischemia-reperfusion [3]. In experimental diabetic cardiomyopathy relaxin-3 could attenuate inflammasome activation and plasma levels of inflammatory cytokines [4]. Furthermore, relaxin-3 led to a reduction of inflammasome activity in high glucose treated cardiac fibroblasts in vitro [5].…”