Abstract
Background
Endothelial response to flow is key to vascular function in health and disease. Our earlier studies demonstrated that endothelial Kir2.1 is essential for flow-induced Akt1/eNOS signaling and for flow-induced vasodilation (FIV) but the mechanistic integration between Kir and other flow signaling pathways remained poorly understood.
Methods
We use a combination of electrophysiological recordings in real time of flow exposure, Ca 2+ imaging, pressure myography of resistance arteries, and echocardiography.
Results
We demonstrate that Kir2.1 is essential for flow-induced PI3K phosphorylation, whereas expression of myristoylated Akt1, which bypasses PI3K-dependent membrane recruitment, restores flow-induced Akt1/eNOS phosphorylation in Kir2.1-deficient endothelium. It also restores FIV in Kir2.1-deficient mesenteric arteries. We further demonstrate that Kir2.1 is essential for flow-induced Ca²⁺ influx mediated by Piezo1 and TRPV4 channels, whereas Ca²⁺ influx induced by pharmacological activation of these channels is Kir2.1 independent. Deficiency of Piezo1 does not affect endothelial Kir2.1 channels. We also discover that flow activation of endothelial Kir2.1 requires Syndecan1, thus creating a link between glycocalyx and downstream effects. Physiologically, we find that endothelial Kir2.1 is suppressed by infusion of Angiotensin-II and by advanced aging, resulting in significant impairment of FIV. In both cases, FIV is fully restored by endothelium-specific over-expression of Kir2.1.
Conclusions
Our study reveals that Kir2.1 serves as a mechanistic linker between endothelial glycocalyx to Piezo1-mediated Ca 2+ influx and downstream signaling suggesting a new integrated model of endothelial mechanotransduction. A functional loss of endothelial Kir2.1 is shown to play a significant role in FIV impairment in Angiotensin-induced hypertension and aging.
Full Text Availability
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