Heat-shock protein-27 and sex-selective regulation of muscarinic and PAR2 receptor-mediated Vasodilation: Differential sensitivity to eNOS inhibition

Background and Purpose Previously, we demonstrated that exogenous Heat Shock Protein 27 (HSP27/gene, HSPB1) treatment of human endothelial progenitor cells (EPCs) increases the synthesis and secretion of VEGF, improves EPC-migration/re-endothelialization and decreases neo-intima formation, suggesting a role for HSPB1 in regulating EPC function. We hypothesized that HSPB1 could also affect mature endothelial cells (ECs) to alter EC-mediated vasoreactivity in vivo. Our work focused on eNOS/NO-dependent relaxation caused by acetylcholine and the coagulation pathway-activated receptor, proteinase-activated receptor-2 (PAR2). Experimental Approach/ResultsMethods Aorta rings from male and female wild-type, HSPB1-null, and HSPB1 over-expressing (HSPB1o/e) mice were contracted with phenylephrine (PE) and NOS-dependent relaxation responses to acetylcholine and a PAR2 agonist, 2-furoyl-LIGRLO-NH2 (2-fLI), were measured without and with L-NAME and ODQ, either alone or in combination to block NO synthesis/action. Tissues from female HSPB1-null mice were treated in vitro with recombinant HSP27 (rHSP27) and then used for bioassay as above. Furthermore, estrogen-specific effects were evaluated using a bioassay of aorta isolated from ovariectomized mice. Results Relative to males, HSPB1-null female mice exhibited an increased L-NAME-resistant relaxation caused by activation either PAR2 or the muscarinic acetylcholine receptor, that was blocked in the concurrent presence of both L-NAME and ODQ. mRNAs (qPCR) for eNOS and ODQ-sensitive guanylyl-cyclase were increased in females versus males. Treatment of isolated aorta tissue with HSPB1 improved tissue responsiveness in the presence of L-NAME. Ovariectomy didn’t affect NO-sensitivity, supporting an estrogen-independent role for HSPB1. Conclusion HSPB1 can regulate intact vascular endothelial function to affect NO-mediated vascular relaxation, especially in females.