In endothelial cells (ECs), Ca2+-activated K+ channels KCa2.3 and KCa3.1 play a crucial role in the regulation of arterial tone via producing NO and endothelium-derived hyperpolarizing factors. Since a rise in intracellular Ca2+ levels and activation of p300 histone acetyltransferase are early EC responses to laminar shear stress (LS) for the transcriptional activation of genes, we examined the role of Ca2+/calmodulin-dependent kinase kinase (CaMKK), the most upstream element of a Ca2+/calmodulin-kinase cascade, and p300 in LS-dependent regulation of KCa2.3 and KCa3.1 in ECs. Exposure to LS (15 dyn/cm2) for 24 h markedly increased KCa2.3 and KCa3.1 mRNA expression in cultured human coronary artery ECs (3.2 ± 0.4 and 45 ± 10 fold increase, respectively; P < 0.05 vs. static condition; n = 8–30), whereas oscillatory shear (OS; ± 5 dyn/cm2 × 1 Hz) moderately increased KCa3.1 but did not affect KCa2.3. Expression of KCa2.1 and KCa2.2 was suppressed under both LS and OS conditions, whereas KCa1.1 was slightly elevated in LS and unchanged in OS. Inhibition of CaMKK attenuated LS-induced increases in the expression and channel activity of KCa2.3 and KCa3.1, and in phosphorylation of Akt (Ser473) and p300 (Ser1834). Inhibition of Akt abolished the upregulation of these channels by diminishing p300 phosphorylation. Consistently, disruption of the interaction of p300 with transcription factors eliminated the induction of these channels. Thus a CaMKK/Akt/p300 cascade plays an important role in LS-dependent induction of KCa2.3 and KCa3.1 expression, thereby regulating EC function and adaptation to hemodynamic changes.

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Nuclear and mitochondrial DNA damage contribute to aging and related cardiovascular disease. To explore if the aging features are cell autonomous we compared cardiovascular function of mice with a specific DNA repair system knockout in vascular endothelial cells (EC-KO) to that of mice with specific knockout in smooth muscle cells (SMC-KO). We evaluated cardiac function by echocardiography, blood pressure by the tail cuff method and ex vivo vascular function in aorta, coronary and carotid arteries using wire myographs organ baths setups. EC-KO showed macrovascular and microvascular vasodilator dysfunction due to specific loss of endothelium-dependent nitric oxide (NO) signaling (maximal vasorelaxation response to acetylcholine in aorta: 59.0% in EC-KO vs 75.0% in WT mice; p-value lt 0.0001). The reduction of vasodilator response was associated with a temporary systolic blood pressure increase at 3 months (138 mm Hg in EC-KO vs 125 mm Hg in WT mice; p-value= 0.03). In addition, EC-KO mice showed a severely compromised microvascular barrier function in the kidney, leading to papillary necrosis. Cardiac output was slightly affected at 5 months of age (16 ml/min in EC-KO vs 18 ml/min in WT mice; p-value= 0.13) and aortic distensibility was reduced (0.2 mm in EC-KO vs 0.3 mm in WT mice; p-value =0.05), suggesting decreased cardiac contractility and increased vascular stiffness. In sharp contrast, SMC-KO mice showed a specific decrease of endothelium-independent NO-mediated relaxation (maximal vasorelaxation response to the NO donor sodium nitroprusside: 83.4% in SMC-KO vs 98.6% in WT mice; p-value lt 0.001). Furthermore, SMC-KO showed increased carotid artery stiffness (Mediastress at intraluminal pressure of 120 mm Hg: 1.44*10 6 in SMC-KO vs 1.82*10 6 dyness/cm 2 in WT mice; p-value lt 0.001), displayed aortic root dilation and regurgitation. We conclude that DNA damage in EC and VSMC each lead to specific pathological changes that are found also in human cardiovascular aging. In complement, the changes reproduce the vascular phenotype of whole body DNA repair knockout mice ( Ercc1 d/- ) previously found by us. Therefore, the cardiovascular aging effects of DNA damage are at least partly cell autonomic, and represent an important treatment target.