Derivatives of 1,4-dihydropyridines as modulators of ascorbate-induced lipid peroxidation and high-amplitude swelling of mitochondria, caused by ascorbate, sodium linoleate and sodium pyrophosphate

A group of 26 2,6-dimethyl-3,5-disubstituted and 2,6-dimethyl-3,4, 5-trisubstituted-1,4-dihydropyridines (1,4-H(2)Py=1,4-DHPs) and five related pyridines were studied as inhibitors of rat liver mitochondrial swelling and O(2) uptake by ascorbic acid-dependent lipid peroxidation (LP) and as modulators of mitochondrial swelling induced by Na(+)-linoleate or Na(+)-pyrophosphate. 1,4-DHPs studied include 4-unsubstituted and 4-methyl- and 4-phenyl-substituted 3, 5-dialkoxycarbonylderivatives of 2,6-dimethyl-1,4-DHP with variations in alkoxy chain length and composition, 4-unsubstituted and 4-methyl-, 4-aryl- and 4-pyridyl-substituted 3, 5-dianilidocarbonylderivatives, and a structurally related group of 3,5-dipyridylamidocarbonylderivatives. Many 1,4-DHPs possess marked antioxidant (AO) and membrane stabilizing activity, expressed as the mitochondrial swelling (deltaA(520)/t) and/or O(2) uptake rate decrease (V(0)/V) as well as prolongation of the induction period (tau/tau(0)) of mitochondrial swelling and/or O(2) uptake at ascorbic acid-dependent LP of rat liver mitochondria. 4-Unsubstituted 3,5-dialkoxycarbonyl-2,6-dimethyl-1,4-DHPs, as well as 4-unsubstituted or those possessing lipophylic 4-aryl- groups 3, 5-diamido-2,6-dimethyl-1,4-DHPs, reveal marked AO and membrane stabilizing properties. Oxidized (heteroaromatized) derivatives have minimal activity. Perhaps 1,4-DHPs preferably act as antioxidants on stages of initiation and prolongation of LP chain reactions at low concentrations: IC(50) (when V(0)/V or tau/tau(0)=2) are 0.1 microM to 100 microM. At 100 microM 3,5-di-p-hydroxyphenoxycarbonyl- and 3, 5-di-p-tolyloxycarbonyl-2,6-dimethyl-1,4-DHPs, as well as 3, 5-diethoxycarbonyl-2,6-dimethylpyridine (oxidized form of Hantzsch ester) and 3,5-diamyloxycarbonyl-2,6-dimethylpyridine, alter the mitochondrial swelling rate in the presence of natural protonophore Na(+)-linoleate (0.063 mM and 0.125 mM). 3,5-Di-n-butyloxycarbonyl-2, 6-dimethyl-1,4-DHP at 100 microM completely stops mitochondrial swelling in the presence of 0.8 mM Na(+)-pyrophosphate. In the presence of many of the 1,4-DHPs, the lipid peroxidation process was inhibited. However, the swelling process could be prolonged, promoted, accelerated or inhibited-depending on 1,4-DHPs structure, concentration, the type of initiators of the swelling process and the medium composition.