Project description:The Ca2+/calmodulin-dependent kinase II is expressed in smooth muscle and believed to mediate intracellular calcium handling and calcium-dependent gene transcription. CaMKII is activated by Angiotensin-II. The multifunctional calcium/calmodulin-dependent kinase II (CaMKII) is activated by Angiotensin-II (Ang-II) in vascular smooth muscle cells (VSMC), but its impact on hypertension remains unknown. In our transgenic mice that express the inhibitor peptide CaMKIIN in smooth muscle (TG SM-CaMKIIN), the blood pressure response to chronic Ang-II infusion was significantly reduced as compared to littermate controls. Surprisingly, examination of blood pressure and heart rate under ganglionic blockade revealed a key role for VSMC CaMKII in efferent sympathetic outflow in response to Ang II hypertension. Consistently, the efferent splanchnic nerve activity and plasma phenylephrine concentrations were significantly lower in TG SM-CaMKIIN mice as compared to littermates. Moreover, the aortic depressor nerve activity was reset in hypertensive wild type animals, but not in TG SM-CaMKIIN mice, suggesting that changes in baroreceptor wall activity may be responsible for the blood pressure difference in Ang-II hypertension. The pulse wave velocity, a measure of vascular wall stiffness in vivo, was increased in aortas of hypertensive compared to normotensive WT animals. However, Ang-II infusion did not alter the pulse wave velocity in transgenic mice, suggesting that CaMKII in VSMC controls structural smooth muscle genes. Accordingly, analysis of gene expression changes in aortas from wild type and TG SM-CaMKIIN hypertensive mice demonstrated that CaMKII inhibition mainly altered the expression of muscle contractile proteins. In contrast, TG SM-CaMKIIN aortas were protected from the Ang-II induced upregulation of genes linked to proliferation, suggesting that CaMKII inhibition prevents the Ang-II-induced reprogramming of smooth muscle cell gene expression towards a proliferative phenotype.

Project description: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.

Project description:The Ca2+/calmodulin-dependent kinase II is expressed in smooth muscle and believed to mediate intracellular calcium handling and calcium-dependent gene transcription. CaMKII is activated by Angiotensin-II. The multifunctional calcium/calmodulin-dependent kinase II (CaMKII) is activated by Angiotensin-II (Ang-II) in vascular smooth muscle cells (VSMC), but its impact on hypertension remains unknown. In our transgenic mice that express the inhibitor peptide CaMKIIN in smooth muscle (TG SM-CaMKIIN), the blood pressure response to chronic Ang-II infusion was significantly reduced as compared to littermate controls. Surprisingly, examination of blood pressure and heart rate under ganglionic blockade revealed a key role for VSMC CaMKII in efferent sympathetic outflow in response to Ang II hypertension. Consistently, the efferent splanchnic nerve activity and plasma phenylephrine concentrations were significantly lower in TG SM-CaMKIIN mice as compared to littermates. Moreover, the aortic depressor nerve activity was reset in hypertensive wild type animals, but not in TG SM-CaMKIIN mice, suggesting that changes in baroreceptor wall activity may be responsible for the blood pressure difference in Ang-II hypertension. The pulse wave velocity, a measure of vascular wall stiffness in vivo, was increased in aortas of hypertensive compared to normotensive WT animals. However, Ang-II infusion did not alter the pulse wave velocity in transgenic mice, suggesting that CaMKII in VSMC controls structural smooth muscle genes. Accordingly, analysis of gene expression changes in aortas from wild type and TG SM-CaMKIIN hypertensive mice demonstrated that CaMKII inhibition mainly altered the expression of muscle contractile proteins. In contrast, TG SM-CaMKIIN aortas were protected from the Ang-II induced upregulation of genes linked to proliferation, suggesting that CaMKII inhibition prevents the Ang-II-induced reprogramming of smooth muscle cell gene expression towards a proliferative phenotype. 5 WT C57Bl/6 and 5 mice that express the Ca2+/calmodulin-dependent kinase II peptide inhibitor CaMKIIN in smooth muscle only (TG SM-CaMKIIN) were infused with 1.25 ug/kg/min Angiotensin-II by osmotic minipump for 14 days. 5 WT and 5 transgenic mice infused with normal saline served as controls. The mice were sacrificed on day 14 and the thoracic aortas isolated. RNA was isolated and pooled for the following groups: WT (wild type), C (TG SM-CaMKIIN), WT-A (WT with Angiotensin-II), C-A (TG SM-CaMKIIN + Angiotensin-II)

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Cardiovascular consequences of K(ATP) dysfunction in Cantu Syndrome arising from in mutations Kir6.1 (KCNJ8) and SUR2 (ABCC9)

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