Ca2+-sensing Receptor Cleavage by Calpain Partially Accounts for Altered Vascular Reactivity in Mice Fed a High-fat Diet

Abstract

The Ca-sensing receptor (CaSR) is expressed in endothelial and smooth muscle cells, but its role in regulating vascular reactivity is unclear, as are the effects of disease on CaSR function and expression. We studied vascular reactivity in aortic segments from healthy and diabetic mice, combined with in vitro proteolysis studies and Western blot analyses of CaSR expression in tissue samples. In endothelium-intact aortic rings, extracellular Ca elicited a nitric oxide-dependent relaxation that was attenuated by the CaSR antagonist, NPS2390. The calcimimetic, calindol, induced the endothelium-independent relaxation of aortic segments that was also sensitive to NPS2390. The antagonist failed to affect responses to acetylcholine or U46619 but attenuated contractions to phenylephrine and potassium. In mice fed a Western-type diet, phenylephrine-induced contractions and calindol-induced relaxations were markedly attenuated, and CaSR expression was decreased. The latter phenomenon could be attributed to the activation of the Ca-dependent protease, µ-calpain, and the subsequent proteolytic cleavage of the CaSR. CaSR activation in smooth muscle cells modulates vascular responsiveness to Ca-elevating agonists. These effects are blunted during metabolic stress because of the limited proteolysis of the CaSR by calpain. The loss of the CaSR function may predispose to the macrovascular late complications associated with diabetes.

The vascular Ca2+-sensing receptor regulates blood vessel tone and blood pressure

“…In line with our results of genetic ablation, Loot et al (34) have recently found that pharmacological inhibition of the CaSR attenuated vascular contraction in response to PE and high K ϩ . The congruence of these results of pharmacological CaSR inhibition in WT mice and CaSR ablation in genetically altered mice provides another line of evidence that the VSMCCaSR is indeed directly responsible for the modulation of vascular tone, rather than possible off-target effects of calcilytic drugs (35) or unexpected side-effects of the genetic ablation.…”

“…Indeed, the CaSR expression is found in the vasculature (7,54,59), but a definitive role for this receptor in blood pressure regulation has never been firmly established. In the vascular endothelium, CaSR activation is thought to stimulate nitric oxide (NO) production (34,59) and/or endothelium-derived hyperpolarization (EDH) (54). In rat subcutaneous small arteries, Ca 2ϩ o evokes a biphasic response with contraction followed by dilatation in a concentration-dependent manner (40).…”

“…In rat subcutaneous small arteries, Ca 2ϩ o evokes a biphasic response with contraction followed by dilatation in a concentration-dependent manner (40). Furthermore, activation of the endothelial CaSR in mouse aortic segments induces endothelium-dependent and -independent relaxations (34). Alteration in CaSR expression or function in vascular smooth muscle cells (VSMC) has been linked to pathological conditions such as microvascular complications during diabetes (34), vascular calcification (1), and idiopathic pulmonary arterial hypertension (55).…”

“…Furthermore, activation of the endothelial CaSR in mouse aortic segments induces endothelium-dependent and -independent relaxations (34). Alteration in CaSR expression or function in vascular smooth muscle cells (VSMC) has been linked to pathological conditions such as microvascular complications during diabetes (34), vascular calcification (1), and idiopathic pulmonary arterial hypertension (55). Allosteric CaSR activators, termed calcimimetics, have been on the market since 2004 for the treatment of hyperparathyroidism secondary to kidney failure (3).…”

The F-BAR Protein NOSTRIN Dictates the Localization of the Muscarinic M3 Receptor and Regulates Cardiovascular Function

“…High-resolution echocardiography analysis was performed using a Vevo2100-high resolution imaging system (VisualSonics, Toronto, Canada) with a 40-MHz transducer (MS-550D) as described. 34 Myograph vascular reactivity analysis of thoracic aortae and mesenteric arteries was performed on a DMT 610M small vessel myograph (Danish Myograph Technology, Aarhus, Denmark) as described 35,36 and analyzed using LabChart 7 software (AdInstruments, Oxford, United Kingdom). Hindlimb perfusion was measured as described.…”