Topics on the Na+/Ca2+ Exchanger: Role of Vascular NCX1 in Salt-Dependent Hypertension

概要

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Excess salt intake is a major risk factor for hypertension. However, the molecular mechanisms underlying salt-dependent hypertension remain obscure. Our recent studies using selective Na+/Ca2+ exchange inhibitors and genetically engineered mice provide compelling evidence that salt-dependent hypertension is triggered by Ca2+ entry through Na+/Ca2+ exchanger type 1 (NCX1) in arterial smooth muscle. Endogenous cardiac glycosides, which may contribute to salt-dependent hypertension, seem to be necessary for NCX1-mediated hypertension. Intriguingly, recent studies by Dostanic-Larson et al. using knock-in mice with modified cardiac glycoside binding affinity of Na+,K+-ATPases demonstrate that this binding site plays an important physiological role in blood pressure control. Thus, when cardiac glycosides inhibit Na+,K+-ATPase in arterial smooth muscle cells, the elevation of local Na+ on the submembrane area is believed to facilitate Ca2+ entry through NCX1, resulting in vasoconstriction. This proposed pathway may have enabled us to explain how to link dietary salt to hypertension.