Graded reoxygenation with chemical inhibition of oxidative phosphorylation improves posthypoxic recovery in murine hippocampal slices

Abstract

Rapid and complete tissue reoxygenation is a prime goal of present stroke therapy. However, reoxygenation may trigger detrimental cascades that partially antagonize beneficial effects. It was our goal to investigate selective grading of reoxygenation with targeting of single mitochondrial complexes in murine hippocampal slices. Population spike amplitude (PSAP) and NADH were measured during hypoxic hypoxia (15 min) and recovery (45 min). With onset of reoxygenation, slices were treated for different times with amobarbital (1 mM), malonate (2 mM), or cyanide (1 mM), inhibitors of mitochondrial complex I, II, or IV, respectively. Other slices were treated with nicotinamide (1 mM). Posthypoxic recovery of PSAP increased from 32% +/- 43% of onset in control slices to 52% +/- 59% (P<.05) upon treatment with amobarbital for 1 min and to 62% +/- 37% (P <.05) upon treatment with malonate. With nicotinamide, posthypoxic recovery improved to 73% +/- 25% (P <.05). Oxidation of NADH was prolonged upon treatment with amobarbital, whereas no change in NADH oxidation was observed with malonate and nicotinamide. Thus, grading of reoxygenation with selective targeting of mitochondrial complex I or II but not of complex IV improves outcome upon reoxygenation in murine hippocampal slices.

The Oxygen Free Radicals Originating from Mitochondrial Complex I Contribute to Oxidative Brain Injury Following Hypoxia–Ischemia in Neonatal Mice

“…In our study, in opposite to the mice with inhibited C-I, the mice with inhibited C-II demonstrated exacerbation of HI brain injury, suggesting the priority of FAD-linked over NAD-linked phosphorylation in the brain recovery. An inhibition of C-I with amytal significantly prolonged recovery of NADH oxidation in murine hippocampal slices during reperfusion, yet the functional (population spike amplitude) recovery was improved compared to controls (Huber et al, 2004). …”

Nutrient-sensitized screening for drugs that shift energy metabolism from mitochondrial respiration to glycolysis

“…Previous studies have clearly demonstrated that brief, nonlethal episodes of ischemia can confer prophylaxis against subsequent stroke3,7 or myocardial infarction4,5, and studies in model systems have shown that chemical inhibition of mitochondrial respiration can mimic this protection, a process coined “chemical preconditioning”6. Having shown that meclizine, an over-the-counter drug that crosses the blood brain barrier can gently silence respiration, we sought to determine whether this drug is cardioprotective and neuroprotective in cellular and animal models.…”

“…A large body of literature demonstrates that agents that blunt respiration can offer prophylaxis against cell death following ischemia and reperfusion in the heart4,5,27 or brain3,6,26. This effect is thought to occur via suppression of oxidative injury and cell-death and may be related to protection conferred by ischemic preconditioning, though the precise molecular mechanism is not known.…”

“…For example, many cancer cells rely on aerobic glycolysis (termed the Warburg effect)1 and a recent study has shown that pharmacologically shifting their metabolism towards respiration can retard tumor growth2. Conversely, studies in animal models have shown that inhibition of mitochondrial respiration can prevent the pathological consequences of ischemia-reperfusion injury in myocardial infarction and stroke3-7.…”

Remediation of Cellular Hypoxic Damage by Pharmacological Agents

“…The third pathway -Warburg pentose-cycle or pentose phosphate pathway (hexose monophosphate shunt) -represents direct oxidation in cytosol and provides more energy but is slower compared to glycolysis. The switch from the first to the third energy production pathway may be done by using sodium oxybutirate and gamma-hydroxybutyrate, serotonin (mexamin), barbiturates, venotropic drugs and phenotiasin [86,[92][93][94][95][96]. The switch of cellular energy metabolism from the third to the first pathway may be forced by insulin, application of which in combination with glucose and potassium may be beneficial under the situation when immediate energy production is required [97].…”