Coupled Calcium and Zinc Dyshomeostasis and Oxidative Stress in Cardiac Myocytes and Mitochondria of Rats With Chronic Aldosteronism

A dyshomeostasis of extra- and intracellular Ca2+ and Zn2+ occurs in rats receiving chronic aldosterone/salt treatment (ALDOST). Herein, we hypothesized that the dyshomeostasis of intracellular Ca2+ and Zn2+ is intrinsically coupled that alters the redox state of cardiac myocytes and mitochondria, with Ca2+ serving as a pro-oxidant and Zn2+ as all antioxidant. Toward this end, we liar-vested hearts from rats receiving 4 weeks of ALDOST alone or cotreatment with either spironolactone (Spiro), an aldosterone receptor antagonist, or amlodipine (Amlod), an L-type Ca2+ channel blocker, and from age/sex-matched untreated controls. In each group, we monitored cardiomyocyte [Ca2+](i) and [Zn2+](i) and mitochondrial [Ca2+](m) and [Zn2+](m); biomarkers of oxidative stress and antioxidant defenses; expression of Zn transporters, Zip1 and ZnT-1; metallothionein-1, a Zn2+-binding protein; and metal response element transcription factor-1, a [Zn2+](i) sensor and regulator of antioxidant defenses. Compared with controls, at 4-week ALDOST, we found the following: (a) increased [Ca2+](i) and [Zn2+](i), together with increased [Ca2+](m) and [Zn2+](m), each of which could be prevented by Spiro and attenuated with Amlod; (b) increased levels of 3-nitrotyrosine and 4-hydroxy-2-nonenal in cardiomyocytes, together with increased H2O2 production, malondialdehyde, and oxidized glutathione in mitochondria that were coincident with increased activities of Cu/Zn superoxide dismutase and glutathione peroxidase; and (c) increased expression of metallothionein-1, Zip1 and ZnT-1, and metal response element transcription factor-1, attenuated by Spiro. Thus, ail intrinsically coupled dyshomeostasis of intracellular Ca2+ and Zn2+ occurs in cardiac myocytes and mitochondria in rats receiving ALDOST, where it serves to alter their redox state through a respective induction of oxidative stress and generation of antioxidant defenses. The importance of therapeutic strategies that can uncouple these two divalent cations and modulate their ratio in favor of sustained antioxidant defenses is therefore suggested.