Calcitonin Gene-Related Peptide Protects Against Cardiovascular Dysfunction Independently of Nitric Oxide In Vivo

Abstract

The neuropeptide CGRP (calcitonin gene-related peptide) is a potent vasodilator, with a cardioprotective role, although the precise mechanisms are unclear. Here we show the ability of endogenous and exogenous CGRP to restore blood pressure, when nitric oxide synthesis is blocked, in a model of cardiovascular disease associated with endothelial dysfunction and impaired nitric oxide production. Male wild-type and αCGRP knockout mice received L-nitro-arginine methyl ester (150 mg/kg in drinking water) to induce a sustained hypertension with evidence of cardiovascular remodeling. The hypertensive response was exacerbated in L-nitro-arginine methyl ester-treated αCGRP knockouts, indicating that endogenous αCGRP acts in a protective manner, when nitric oxide production is diminished. Exogenous CGRP rescued αCGRP knockout mice from both hypertension and cardiovascular remodeling. Further studies using a nonrecovery protocol with a CGRP receptor antagonist (BIBN4096 BS) revealed that CGRP acts via the canonical CGRP receptor (CLR [calcitonin-like receptor]/RAMP1 [receptor activity-modifying protein]); with no effect of an antagonist (AC187) of a second CGRP-responsive receptor (the amylin-1 receptor, CTR [calcitonin receptor]/RAMP1). Blood flow, in resistance vessels of the exteriorised mesentery, was investigated. Noradrenaline–induced vasoconstriction with recovery, in L-nitro-arginine methyl ester-treated wild-type mice. However, αCGRP knockout, or BIBN4096 BS-treated wild-type mice demonstrated a similar constrictor response to noradrenaline, but significantly impaired blood flow recovery. The combined findings highlight that αCGRP protects against cardiovascular dysfunction, signaling via the canonical CGRP receptor and acting when nitric oxide production is lost, such as in endothelial dysfunction associated with vascular disease. These in vivo results support the proposal that CGRP provides a novel treatment for cardiovascular disease.

The Vascular-Dependent and -Independent Actions of Calcitonin Gene-Related Peptide in Cardiovascular Disease

“…However, there is very limited evidence of this in vivo. We demonstrated that α-CGRP KO mice develop exacerbated hypertension and present with dysfunctional blood flow recovery in mesenteric vessels in vivo after chronic L-NAME administration (Argunhan et al, 2021) indicating that α-CGRP can induce vasodilation and hence attenuate hypertension independently of NOS. These findings suggest that α-CGRP may be able to offer protection to compensate for pathophysiological processes such as endothelial dysfunction, which contributes to hypertension and cardiovascular disease.…”

“…Our research group has reported that, despite a lack of vascular tone modulation at baseline, α-CGRP-specific KO mice display elevated blood pressure after AngII or L-NAME treatment (Smillie et al, 2014;Argunhan et al, 2021). α-CGRP KO mice present with hypertrophic vascular remodeling in their aortic tissues and increased mRNA levels of inflammatory and oxidative stress markers after 14 or 28 days of AngII treatment (Smillie et al, 2014).…”

“…It has been difficult to study α-CGRP in vivo due to its peptide nature, therefore the use of genetically engineered mice has been fitting. Genetic deletion of CGRP has been reported to cause elevated baseline blood pressure in some (Gangula et al, 2000;Oh-hashi et al, 2001;Li et al, 2004;Mai et al, 2014) but not all studies (Smillie et al, 2014;Argunhan et al, 2021). This is likely due to differences in methodology, such as differences in the precise genetic deletion site when generating knockout (KO) mouse lines, particular strains preserving unique hemodynamic phenotypes, and the utilization of various different blood pressure measurement techniques.…”

“…The current consensus is that, upon neuronal depolarization, αor β-CGRP is released from sensory neurons via calciumdependent exocytosis to bind to its receptor situated on the plasma membrane of several cell types including, but not limited to, smooth muscle cells (Argunhan et al, 2021), endothelial cells (Gray and Marshall, 1992a) and cardiomyocytes (Clark et al, 2021). The receptor complex is composed of a seven domain G-protein coupled receptor (GPCR) known as calcitonin receptor-like receptor (CRLR) and a single transmembrane protein recognized as receptor activity modifying protein-1 (RAMP1).…”

Roles of calcitonin gene-related peptide in the skin, and other physiological and pathophysiological functions

“…NO plays a role in maintaining low blood pressure and healthy heart function. It was also shown that when vascular NO production is not fully functional, alpha-CGRP can act via the canonical CGRP receptor to protect against cardiovascular dysfunction by promoting mesenteric regulation of blood flow ( Argunhan et al., 2021 ).…”