RXFP1 Receptor Activation by Relaxin-2 Induces Vascular Relaxation in Mice via a Gαi2-Protein/PI3Kß/γ/Nitric Oxide-Coupled Pathway

Abstract

Background: Relaxins are small peptide hormones, which are novel candidate molecules that play important roles in cardiometablic syndrome. Relaxins are structurally related to the insulin hormone superfamily, which provide vasodilatory effects by activation of G-protein-coupled relaxin receptors (RXFPs) and stimulation of endogenous nitric oxide (NO) generation. Recently, relaxin could be demonstrated to activate Gi proteins and phosphoinositide 3-kinase (PI3K) pathways in cultured endothelial cells in vitro. However, the contribution of the Gi-PI3K pathway and their individual components in relaxin-dependent relaxation of intact arteries remains elusive.Methods: We used Gαi2- (Gnai2-/-) and Gαi3-deficient (Gnai3-/-) mice, pharmacological tools and wire myography to study G-protein-coupled signaling pathways involved in relaxation of mouse isolated mesenteric arteries by relaxins. Human relaxin-1, relaxin-2, and relaxin-3 were tested.Results: Relaxin-2 (∼50% relaxation at 10-11 M) was the most potent vasodilatory relaxin in mouse mesenteric arteries, compared to relaxin-1 and relaxin-3. The vasodilatory effects of relaxin-2 were inhibited by removal of the endothelium or treatment of the vessels with N (G)-nitro-L-arginine methyl ester (L-NAME, endothelial nitric oxide synthase (eNOS) inhibitor) or simazine (RXFP1 inhibitor). The vasodilatory effects of relaxin-2 were absent in arteries of mice treated with pertussis toxin (PTX). They were also absent in arteries isolated from Gnai2-/- mice, but not from Gnai3-/- mice. The effects were not affected by FR900359 (Gαq protein inhibitor) or PI-103 (PI3Kα inhibitor), but inhibited by TGX-221 (PI3Kβ inhibitor) or AS-252424 (PI3Kγ inhibitor). Simazine did not influence the anti-contractile effect of perivascular adipose tissue.Conclusion: Our data indicate that relaxin-2 produces endothelium- and NO-dependent relaxation of mouse mesenteric arteries by activation of RXFP1 coupled to Gi2-PI3K-eNOS pathway. Targeting vasodilatory Gi-protein-coupled RXFP1 pathways may provide promising opportunities for drug discovery in endothelial dysfunction and cardiometabolic disease.

Serelaxin activates eNOS, suppresses inflammation, attenuates developmental delay and improves cognitive functions of neonatal rats after germinal matrix hemorrhage

“…Authors also demonstrated that the stroke-induced inhibition of endothelial nitric oxide synthesis completely abolished protective effects of Relaxin 20 . Others also demonstrated that effects of both Relaxin-2 and Serelaxin are meditated by their ability to activate eNOS, but not another isoform of the NOS signaling pathway 11,45 . The activation of eNOS is neuroprotective after stroke and, as mentioned above, after GMH 46 .…”

“…It has been demonstrated before that compared to relaxin 1 and relaxin 3, relaxin 2 (Serelaxin is an analog of relaxin 2) most effectively produces endothelium relaxation and that this effect is mediated via eNOS pathway 11 . Furthermore, it has been demonstrated that cardioprotective effects of serelaxin following ischemia/reperfusion injury are mediated by eNOS mediated mechanisms 12 .…”

Circulating Relaxin-1 Level Is a Surrogate Marker of Myocardial Fibrosis in HFrEF

“…Relaxins are related to the insulin hormone superfamily and proved to have different functional activities on the cardiovascular system. Importantly, relaxins have a strong vasoactive effect, characterized as vasodilation in isolated vessel experiments (Lian et al, 2018). The most potent vasodilatory factor amongst them is RLN2.…”

Function, Regulation and Biological Roles of PI3Kγ Variants

“…Moreover, the relevance of PI3Kγ for regulating blood pressure was further demonstrated in normotensive and hypertensive mice using small- molecular inhibitors of PI3Kγ [179]. Recently, relaxin-2, a structurally insulin-related peptide, was shown to exhibit vasodilatory effects on murine mesenteric arteries through a Gα i2 -controlled PI3Kβ-and PI3Kγ-dependent pathway via production of nitric oxide (NO) [180]. Relaxins are implicated in different aspects of the cardio-metabolic syndrome.…”