Excessive ATP hydrolysis in ischemic myocardium by mitochondrial F₁F₀-ATPase: effect of selective pharmacological inhibition of mitochondrial ATPase hydrolase activity

Abstract

Mitochondrial F(1)F(0)-ATPase normally synthesizes ATP in the heart, but under ischemic conditions this enzyme paradoxically causes ATP hydrolysis. Nonselective inhibitors of this enzyme (aurovertin, oligomycin) inhibit ATP synthesis in normal tissue but also inhibit ATP hydrolysis in ischemic myocardium. We characterized the profile of aurovertin and oligomycin in ischemic and nonischemic rat myocardium and compared this with the profile of BMS-199264, which only inhibits F(1)F(0)-ATP hydrolase activity. In isolated rat hearts, aurovertin (1-10 microM) and oligomycin (10 microM), at concentrations inhibiting ATPase activity, reduced ATP concentration and contractile function in the nonischemic heart but significantly reduced the rate of ATP depletion during ischemia. They also inhibited recovery of reperfusion ATP and contractile function, consistent with nonselective F(1)F(0)-ATPase inhibitory activity, which suggests that upon reperfusion, the hydrolase activity switches back to ATP synthesis. BMS-199264 inhibits F(1)F(0) hydrolase activity in submitochondrial particles with no effect on ATP synthase activity. BMS-199264 (1-10 microM) conserved ATP in rat hearts during ischemia while having no effect on preischemic contractile function or ATP concentration. Reperfusion ATP levels were replenished faster and necrosis was reduced by BMS-199264. ATP hydrolase activity ex vivo was selectively inhibited by BMS-199264. Therefore, excessive ATP hydrolysis by F(1)F(0)-ATPase contributes to the decline in cardiac energy reserve during ischemia and selective inhibition of ATP hydrolase activity can protect ischemic myocardium.

Oligomycin, an F1FO-ATPase Inhibitor, Protects Against Ischemic Acute Kidney Injury in Male but Not in Female Rats

“…Moreover, Grover et al (12) reported that excessive ATP hydrolysis by F 1 F O -ATPase contributed to the decline in cardiac energy reserve during ischemia and that selective inhibition of ATP hydrolase activity could protect ischemic myocardium in male rats. Taken together, it seems likely that the pre-ischemic treatment of male rats with oligomycin would prevent ischemiainduced renal ATP depletion through inhibition of ATP hydrolysis by F 1 F O -ATPase and exerts a protective effect on ischemia/reperfusion-induced renal damage.…”

“…In addition, proteomic analysis showed that the b subunit of F 1 F O -ATPase was significantly up-regulated 2 h after the reperfusion in ischemia/reperfusion-treated male rat kidneys, but not in female kidneys (10). F 1 F O -ATPase has been reported to play a role in the pathophysiology of myocardial ischemia/reperfusion injury in isolated male rat hearts (11,12). Taken together, there is a possibility that F 1 F O -ATPase is a key component of the sex difference in ischemic acute kidney injury.…”

“…However, oxygen deprivation, which collapses the mitochondrial electrochemical gradient, switches F 1 F O -ATPase from ATP synthesis to ATP hydrolysis. Several studies showed that an F 1 F O -ATPase inhibitor oligomycin reduced the rate of ATP depletion during ischemia in isolated hearts, suggesting that ATP hydrolysis by F 1 F O -ATPase partly contributes to ischemiainduced ATP depletion (11,12). Additionally, Zheng and Ramirez (13,14) have shown that a subunit of the F 1 F O -ATPase, oligomycin-sensitivity-conferring protein, is a novel estradiol binding protein, and 17b-estradiol preferentially inhibits the rat brain mitochondrial F 1 F OATPase activity.…”

Cell death: A dynamic response concept

“…104 In the ischaemic myocardium it is demonstrated that ATP levels at reperfusion are replenished faster and necrosis is reduced when using an ATP-hydrolase inhibitor. 105 In glucose-deprived rat neonatal cardiac myocytes exposed to hypoxia, a positive correlation between myocyte ATP concentration and the percentage of apoptotic cells is described. By increasing the glucose concentration, apoptosis progressively replaces necrotic cells, 106 underlining the importance of substrate availability in the cell death decisionmaking process.…”

Impact of Ischemia on Cellular Metabolism

“…During ischemia, the proton-translocating F0F1-ATP synthase, which normally produces ATP, becomes an F0F1-ATPase and consumes ATP in order to pump protons from the matrix to the intermembrane space and maintain the mitochondrial membrane potential. [39], [40] The mitochondria therefore become a site of ATP consumption produced by anaerobic glycolysis.…”