Phosphatase-independent activity of smooth-muscle calcineurin orchestrates a gene expression program leading to arterial hypertension
Objective: 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. SMC Cn also played an unexpected 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, Serpine1 was critical for Ang-II-induced hypertension. Indeed, pharmacological inhibition of PAI-1, the protein encoded by Serpine1, impaired SMCs contractility and regressed hypertension. Conclusions: Whereas the phosphatase activity of Cn mediates Ang-II-induced AAA, a phosphatase-independent action of SMC Cn underlies blood pressure regulation by orchestrating a gene expression program closely related to contractility regulation and hypertension. Overall design: For RNAseq 1: Aortic samples from Cn-Ctl and SM-Cn-/- male mice treated or non-treated with Ang-II for 2h, 6h or 24h. For RNAseq 2: Aortic samples from WT and WT male mice treated with Cyclosporin A, both treated or non-treated with Ang-II for 2h or 24h.