INHIBITION OF PRO-OXIDANT-INDUCED MITOCHONDRIAL PYRIDINE-NUCLEOTIDE HYDROLYSIS AND CALCIUM RELEASE BY 4-HYDROXYNONENAL

Intra- and extra-mitochondrial Ca2+ participates in vital cellular processes. This work investigates the influences of 4-hydroxynonenal (HNE) on pro-oxidant-induced Ca2+ release from rat liver mitochondria. Ca2+ movements across the mitochondrial inner membrane, the pyridine nucleotide redox state and pyridine (nicotinamide) nucleotide hydrolysis were analysed. HNE did not influence Ca2+ uptake by mitochondria, but inhibited in a concentration-dependent manner Ca2+ release induced by t-butylhydroperoxide (tbh). Total inhibition was achieved with about 50 μM-HNE. Ca2+ release induced by the pro-oxidant alloxan was also inhibited by HNE. Oxidation of pyridine nucleotide, induced by tbh through the concerted action of glutathione peroxidase, glutathione reductase and the energy-linked transhydrogenase, was not affected by up to 50 μM-HNE. In contrast, HNE inhibited pyridine nucleotide hydrolysis in a concentration-dependent manner. The data suggest that HNE toxicity may be in part attributed to an impaired intramitochondrial Ca2+ homeostasis.