Resumen de Contribution of a phosphatase-independent activity of smooth muscle cell calcineurin to arterial hypertension
Arterial hypertension (AHT) is one of the most common chronic diseases in the human population, remaining the leading risk factor for cardiovascular disease (CVD) morbidity and mortality. Despite the availability of a plethora of antihypertensive drugs, a substantial proportion of patients with AHT fail to control their blood pressure to the recommended levels.
Understanding the molecular mechanisms that lead to AHT is therefore essential to improve the current therapies for AHT. Angiotensin-II (Ang-II), a critical hypertensive effector of the renin-angiotensin system, activates numerous signaling pathways, including that mediated by the serine/threonine phosphatase calcineurin (Cn). Our previous studies revealed that smooth muscle cell (SMC) Cn plays an essential structural role in vascular contractility and AHT independently of its phosphatase activity.
Here, we have investigated the mechanism underlying the structural role of SMC Cn in AHT. By using RNAseq analysis, we found that SMC Cn is required for the regulation of nearly 90% of the genes induced or repressed by Ang-II in the aorta independently of Cn enzymatic activity and that SMC Cn orchestrates a transcriptional program closely related to SMC contractility regulation and AHT. SMC Cn not only mediates the induction of AHT by Ang-II but also reverts AHT in hypertensive mice. Among the genes whose induction by Ang-II requires Cn expression in SMC, but not its activity, we identified Serpine1, the gene encoding plasminogen activator inhibitor type-1 (PAI-1), as a potential mediator of Ang-II-induced hypertension. Indeed, high PAI-1 plasma levels have been reported earlier in AHT patients and we show here that PAI-1 induction by the vasopressor stimulus Ang-II requires Cn expression in SMCs and that Cn deletion in hypertensive mice decreases PAI-1 levels. Of note, TM5441, a pharmacological inhibitor of PAI-1, nearly abolished SMC contractility and sharply reverted Ang-II-induced AHT.
We hypothesized that the structural role of Cn in AHT could be mediated by its interaction with other proteins. We therefore used high-throughput proteomics to identify the proteins co-immunoprecipitated with Cn in primary aortic smooth muscle cells and discovered that the serine/threonine-protein kinase 3 (SIK3) associates with Cn. Importantly, SIK3 silencing impaired SMC contractility, nearly blocked PAI-1 induction in SMCs and partially inhibited Ang-II-induced AHT. Together, our results suggest that the structural role of SMC Cn in AHT is mediated through the induction of PAI-1 by a Cn-SIK3 complex. These results provide the basis for developing novel pharmacological therapies for AHT, showing great translational potential
