Iterations in Ca 2+ and Mg 2+ balance accompany aldosteronism (inappropriate for dietary Na + intake). Increased Zn excretion and Zn translocation to injured tissues, including the heart, also occurs. Several causes and consequences of Zn dyshomeostasis in rats receiving aldosterone/salt treatment (ALDOST) were examined: 1) the role of urinary acidification in promoting hyperzincuria, acetazolamide (75 mg/kg), a carbonic anhydrase inhibitor, was used as cotreatment to raise urinary HCO 3 − excretion; 2) assess Zn levels in the heart, including cardiomyocyte cytosolic free [Zn 2+ ] i and mitochondrial Zn, the expression of metallothionein (MT-I), a Zn binding protein, and biomarkers of oxidative stress; and 3) monitor oxidative stress and cardiac pathology in response to ZnSO 4 supplement (40 mg/day). Compared to controls, at 4 wks ALDOST we found: an acidification of urine and metabolic alkalosis associated with increased urinary Zn excretion and hypozincemia, each of which were prevented by acetazolamide; a rise in cardiac Zn including increased [Zn 2+ ] i and mitochondrial Zn, associated with increased tissue MT-I, 8-isoprostane, malondialdehyde, and gp91 phox , coupled with oxidative stress in plasma and urine; and ZnSO 4 prevented hypozincemia, but not ionized hypocalcemia, and attenuated oxidative stress and microscopic scarring without preventing the vasculitis and perivascular fibrosis of intramural coronary arteries. Thus, the hyperzincuria seen with ALDOST is due to urinary acidification. The oxidative stress that appears in the heart is accompanied by increased tissue Zn serving as an antioxidant. Cotreatment with ZnSO 4 attenuated cardiomyocyte necrosis, however, polynutrient supplement may be required to counteract the dyshomeostasis of all 3 cations that accompanies aldosteronism and contribute to cardiac pathology.

Intracellular Ca(2+) overloading, coupled to induction of oxidative stress, is present at 4-wk aldosterone/salt treatment (ALDOST). This prooxidant reaction in cardiac myocytes and mitochondria accounts for necrotic cell death and subsequent myocardial scarring. It is intrinsically linked to increased intracellular zinc concentration ([Zn(2+)](i)) serving as an antioxidant. Herein, we addressed the temporal responses in coupled Ca(2+) and Zn(2+) dyshomeostasis, reflecting the prooxidant-antioxidant equilibrium, by examining preclinical (week 1) and pathological (week 4) stages of ALDOST to determine whether endogenous antioxidant defenses would be ultimately overwhelmed to account for this delay in cardiac remodeling. We compared responses in cardiomyocyte free [Ca(2+)](i) and [Zn(2+)](i) and mitochondrial total [Ca(2+)](m) and [Zn(2+)](m), together with biomarkers of oxidative stress and antioxidant defenses, during 1- and 4-wk ALDOST. At week 1 and compared with controls, we found: 1) elevations in [Ca(2+)](i) and [Ca(2+)](m) were coupled with [Zn(2+)](i) and [Zn(2+)](m); 2) increased mitochondrial H(2)O(2) production, cardiomyocyte xanthine oxidase activity, and cardiac and mitochondrial 8-isoprostane levels, counterbalanced by increased activity of antioxidant proteins, enzymes, and the nonenzymatic antioxidants that can be considered as cumulative antioxidant capacity; some of these enzymes and proteins (e.g., metallothionein-1, Cu/Zn-superoxide, glutathione synthase) are regulated by metal-responsive transcription factor-1; and 3) although these augmented antioxidant defenses were sustained at week 4, they fell short in combating the persistent intracellular Ca(2+) overloading and marked rise in cardiac tissue 8-isoprostane and mitochondrial transition pore opening. Thus a coupled Ca(2+) and Zn(2+) dyshomeostasis occurs early during ALDOST in cardiac myocytes and mitochondria that regulate redox equilibrium until week 4 when ongoing intracellular Ca(2+) overloading and prooxidants overwhelm antioxidant defenses.

Intracellular [Ca2+]i overloading in cardiomyocytes is a fundamental pathogenic event associated with chronic aldosterone/salt treatment (ALDOST) and accounts for an induction of oxidative stress that leads to necrotic cell death and consequent myocardial scarring. This prooxidant response to Ca2+ overloading in cardiac myocytes and mitochondria is intrinsically coupled to simultaneous increased Zn2+ entry serving as an antioxidant. Herein, we investigated whether Ca2+ and Zn2+ dyshomeostasis and prooxidant:antioxidant dysequilibrium seen at 4 wks, the pathologic stage of ALDOST, could be uncoupled in favor of antioxidants, using cotreatment with a ZnSO4 supplement, pyrrolidine dithiocarbamate (PDTC), a Zn2+ ionophore, or ZnSO4 in combination with amlodipine (Amlod), a Ca2+ channel blocker. We monitored and compared responses in cardiomyocyte free [Ca2+]i and [Zn2+]i together with biomarkers of oxidative stress in cardiac myocytes and mitochondria. At wk 4 ALDOST and compared to controls, we found: i) an elevation in [Ca2+]i coupled with [Zn2+]i; and ii) increased mitochondrial H2O2 production, and increased mitochondrial and cardiac 8-isoprostane levels. Cotreatment with the ZnSO4 supplement alone, PDTC, or ZnSO4+Amlod augmented the rise in cardiomyocyte [Zn2+]i beyond that seen with ALDOST alone, while attenuating the rise in [Ca2+]i which together served to reduce oxidative stress. Thus, a coupled dyshomeostasis of intracellular Ca2+ and Zn2+ was demonstrated in cardiac myocytes and mitochondria during 4 wks ALDOST, where prooxidants overwhelm antioxidant defenses. This intrinsically coupled Ca2+ and Zn2+ dyshomeostasis could be uncoupled in favor of antioxidant defenses by selectively increasing free [Zn2+]i and/or reducing [Ca2+]i using cotreatment with ZnSO4 or PDTC alone or ZnSO4+Amlod in combination.

Fibrosis is a fundamental component of the adverse structural remodeling of myocardium present in the failing heart. Replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium, but not without adverse functional consequences. The extensive nature of this microscopic scarring suggests cardiomyocyte necrosis is widespread and the loss of these contractile elements, combined with fibrous tissue deposition in the form of a stiff in-series and in-parallel elastic elements, contributes to the progressive failure of this normally efficient muscular pump. Cellular and molecular studies into the signaltransducer-effector pathway involved in cardiomyocyte necrosis have identified the crucial pathogenic role of intracellular Ca 2+ overloading and subsequent induction of oxidative stress, Correspondence to: Karl T. Weber, KTWeber@uthsc.edu. NIH Public Access Author ManuscriptHeart Fail Rev. Author manuscript; available in PMC 2012 January 1. Published in final edited form as:Heart Fail Rev. 2011 January ; 16(1): 23-34. doi:10.1007/s10741-010-9169-3. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript predominantly confined within its mitochondria, to be followed by the opening of the mitochondrial permeability transition pore that leads to the destruction of these organelles and cells. It is now further recognized that Ca 2+ overloading of cardiac myocytes and mitochondria serves as a prooxidant and which is counterbalanced by an intrinsically coupled Zn 2+ entry serving as antioxidant. The prospect of raising antioxidant defenses by increasing intracellular Zn 2+ with adjuvant nutriceuticals can, therefore, be preferentially exploited to uncouple this intrinsically coupled Ca 2+ -Zn 2+ dyshomeostasis. Hence, novel yet simple cardioprotective strategies may be at hand that deserve to be further explored.

Despite today's standard of care, aimed at containing homeostatic neurohormonal activation, 1 in every 5 patients recently hospitalized with congestive heart failure (CHF) will be readmitted within 30 days of discharge because of a recurrence of their symptoms and signs. In light of recent pathophysiologic insights, it is now propitious to revisit CHF with a view toward complementary and evolving management strategies. CHF is a progressive systemic illness. Its features include: oxidative stress in diverse tissues; an immunostimulatory state with circulating proinflammatory cytokines; a wasting of soft tissues; and a resorption of bone. Its origins are rooted in homeostatic mechanisms gone awry to beget dyshomeostasis. For example, marked excretory losses of Ca 2+ and Mg 2+ accompany renin-angiotensin-aldosterone system (RAAS) activation, causing ionized hypocalcemia and hypomagnesemia that lead to secondary hyperparathyroidism (SHPT) with consequent bone resorption and a propensity to atraumatic fractures. Parathyroid hormone (PTH) accounts for paradoxical intracellular Ca 2+ overloading in diverse tissues and consequent systemic induction of oxidative stress. In cardiac myocytes and mitochondria these events orchestrate opening of the mitochondrial membrane permeability transition pore (mPTP) with an ensuing osmotic-based destruction of these organelles and resultant cardiomyocyte necrosis with myocardial scarring. Contemporaneous with Ca 2+ and Mg 2+ dyshomeostasis is hypozincemia and hyposelenemia, which compromise metalloenzyme-based antioxidant defenses while hypovitaminosis D threatens Ca 2+ stores needed to prevent SHPT. An intrinsically coupled dyshomeostasis of intracellular Ca 2+ and Zn 2+ , representing prooxidant and antioxidant, respectively, is integral to regulating mitochondrial redox state; it can be uncoupled by a Zn 2+ supplement in favor of antioxidant defenses. Hence, the complementary use of nutriceuticals to nullify dyshomeostatic responses involving macro-and micronutrients should be considered. Evolving strategies with mitochondria-targeted interventions interfering with their uptake of Ca 2+ or serving as selective antioxidant or mPTP inhibitor may also prove efficacious in the overall management of CHF.