Induction of Mitochondrial Membrane Permeability Transition Pore Opening and Cytochrome C Release by Fractions of Drymaria cordata

Abstract

Inducers or inhibitors of opening of the Mitochondrial Membrane Permeability Transition (MMPT) Pore are targets of drug development for conditions arising from dysregulated apoptosis. In this study, the effects of various fractions of the methanol extract of Drymaria cordata (DC), a medicinal plant were investigated on (MMPT) pore in the presence and absence of calcium. The defatted methanol extract of the whole plant (MEDC) was partitioned in succession between chloroform, ethylacetate and water. The fractions were concentrated at 400C to obtain chloroform (CFDC), ethylacetate (EFDC) and aqueous (AFDC) fractions. Varying concentrations of the fractions in the absence of calcium significantly induced pore opening by 2.5, 4.6,10 and 13 folds for MEDC and 3.6, 13, 15, 18 and 17 folds for CFDC, respectively, while EFDC and AFDC did not have any significant effect at lower concentrations but induced pore opening at 90μg/ml by 3.1 and 1.8 folds, respectively. Also, all the solvent fractions caused the release of cytochrome c in a concentration-dependent manner with CFDC giving the highest release of cytochrome c. In contrast, Ca2+-induced MMPT pore opening was inhibited by MEDC and CFDC. At concentrations of 10, 30, 50, 70 and 90μg/ml, the percentage inhibition was 38, 48, 50, 57 and 65% for MEDC and 7, 14, 15, 28 and 34% for CFDC , respectively, when compared with the effect of spermine, a standard inhibitor. EFDC and AFDC fractions however, did not inhibit pore opening but rather had synergistic effect with calcium. FIFO-ATPase activity was enhanced by all the fractions with CFDC having the highest effect. Also, all the fractions ameliorated ferrous-induced mitochondrial membrane lipid peroxidation. These results suggest that the chloroform fraction is the most potent and possibly contains the bioactive agent that may induce mitochondrial-mediated apoptosis..