TY - JOUR T1 - Protein Kinase C Downregulation Enhanced Ca2+-Induced Relaxation of Isolated Mesenteric Arteries from Aged Dahl Salt-Sensitive Rats JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther DO - 10.1124/jpet.119.258475 SP - jpet.119.258475 AU - Samuel O Odutola AU - Lakeesha E Bridges AU - Emmanuel M Awumey Y1 - 2019/01/01 UR - http://jpet.aspetjournals.org/content/early/2019/06/13/jpet.119.258475.abstract N2 - The Ca2+-sensing receptor (CaSR) detects small changes in extracellular calcium (Ca2+e) concentration ([Ca2+]e) and transduce the signal into modulation of various signaling pathways. Ca2+-induced relaxation of isolated phenylephrine-contracted mesenteric arteries is mediated by the perivascular nerve CaSR. Elucidation of the regulatory mechanisms involved in vascular CaSR signaling may provide insights into the physiological functions of the receptor and identify targets for the development of new treatments for cardiovascular pathologies such as hypertension. Protein kinase Cα(PKCα) is a critical regulator of multiple signaling pathways and can phosphorylate the CaSR leading to receptor desensitization. In this study, we investigated the effects of CaSR mutation and siRNA downregulation of PKCα on CaSR-mediated relaxation of phenylephrine (PE)-contracted mesenteric arteries from aged Dahl salt-sensitive rats, on a low salt diet, using automated wire myography. The data show minimal relaxation responses of arteries to Ca2+e in wild type (SS) and CaSR mutant (SS-Casrem1Mcwi) rats. Mutation of the CaSR gene had no significant effect on relaxation. PKCα expression was similar in wild type and mutant rats and small interfering RNA downregulation of PKCα and/or inhibition of PKC with the Ca2+-sensitive Gӧ 6976 resulted in >80% increase in relaxation. Significant differences in EC50 values were observed between treated and untreated controls (p < 0.05; ANOVA). The results indicate that PKCα plays an important role in the regulation of CaSR-mediated relaxation of mesenteric arteries and its downregulation or pharmacological inhibition may lead to increased Ca2+ sensitivity of the receptor and reverse age-related changes in vascular tone.SIGNIFICANCE STATEMENT G protein-coupled CaSR signaling leads to the regulation of vascular tone and may, therefore play a vital role in blood pressure regulation. The receptor has several PKC phosphorylation sites in the C-terminal intracellular tail that mediate desensitization. We have previously shown that activation of the CaSR in neuronal cells leads to PKC phosphorylation indicating that protein kinase C is an important regulator of CaSR function. Therefore, PKC in the CaSR signaling pathway in mesenteric arteries is a potential target for the development of new therapeutic approaches to treat hypertension and age-related vascular dysfunction. The present studies show that siRNA downregulation of PKCa and pharmacological inhibition of PKC enhanced CaSR-mediated relaxation of phenylephrine-contracted mesenteric arteries from aged Dahl salt-sensitive rats. ER -