Phosphatase-independent activity of smooth-muscle calcineurin orchestrates a gene expression program leading to hypertension

Abstract

STRUCTURED ABSTRACTObjective: Angiotensin-II (Ang-II) drives pathological vascular wall remodeling in hypertension and abdominal aortic aneurysm (AAA). Previous studies showed that the phosphatase activity of calcineurin (Cn) mediates Ang-II-induced AAA, but the cell type involved in the action of Cn in AAA formation remained unknown. Methods: Smooth muscle cell (SMC)-specific and endothelial cell (EC)-specific Cn-deficient mice (SM-Cn-/- and EC-Cn-/- mice, respectively) were created and assessed for Ang-II-induced AAA formation and hypertension vs controls. Osmotic minipumps were used to administer Ang-II and cyclosporine A (CsA), a pharmaceutical Cn inhibitor. AAA formation and hypertension were monitored by ultrasonography, arterial blood pressure monitoring, and histological analysis. Deep RNA sequencing was used to identify the Ang-II-regulated transcriptome sensitive to Cn deletion or pharmacological inhibition. Arterial and SMC contractility were also assessed. Results: Cn expressed in SMCs, but not ECs, was required for Ang-II-induced AAA. Unexpectedly, SMC Cn played a structural role in the early onset and maintenance of Ang-II-induced hypertension independently of Cn phosphatase activity. Nearly 90% of the genes regulated by Ang-II in the aorta required Cn expression in SMCs. Cn orchestrated, independently of its enzymatic activity, the induction by Ang-II of a gene expression program closely related to SMC contractility and hypertension. Cn deletion in SMCs, but not its pharmacological inhibition, impaired the regulation of arterial contractility. Among the genes whose regulation by Ang-II required Cn expression but not its phosphatase activity, we discovered that Serpine1 was critical for Ang-II-induced hypertension. Indeed, pharmacological inhibition of PAI-1, the protein encoded by Serpine1, impaired SMCs contractility and readily regressed hypertension. Conclusions: Whereas the phosphatase activity of Cn mediates Ang-II-induced AAA, a phosphatase-independent action of SMC Cn mediates hypertension by orchestrating a gene expression program closely related to contractility and blood pressure regulation. Our results urge the evaluation of PAI-1 as a candidate therapeutic target for hypertension.