Solvent Fractions of Daniellia oliveri ((Rolfe) Stem Bark Modulate Rat Liver Mitochondrial Permeability Transition Pore

Abstract

Mitochondrial-dependent cell death is initiated by the release of cytochrome c due to the opening of the mitochondrial permeability transition (mPT) pore, a pharmacological target for drug development in the treatment of diseases associated with dysregulated apoptosis. Daniellia oliveri (DO) is traditionally used in management of breast tumours, sickle cell anaemia and diabetes. This study evaluated the effects of solvent fractions of D. oliveri stem bark extract on the modulation of the mPT pore. The crude ethanol extract (EEDO) of the stem bark was partitioned successively with n – hexane (HFDO), chloroform (CFDO), ethyl acetate (EAFDO) and ethanol (EFDO) to obtain their respective fractions. Mitochondrial permeability transition (mPT), mitochondrial ATPase (mATPase) activity, cytochrome c release and mitochondrial lipid peroxidation were assessed spectrophotometrically. The EEDO and EFDO significantly induced (p < 0.05) mPT pore opening with induction folds of 15.4 and 12.2 folds, respectively at the highest concentration (420 μg/ml) in the absence of calcium while inductive effects of CFDO and EAFDO were not significant. The inductive effect of EFDO resulted in significant release of cytochrome c to the cytosol. In contrast, all fractions of DO had mild inhibitory effects on calcium-induced opening of the mPT pore except CFDO that displayed strong reversal of pore opening (86%) greater than spermine (73%), a standard inhibitor. Furthermore, at pH 7.4, all solvent fractions of D. oliveri stem bark significantly (p < 0.05) inhibited Fe2+ - induced lipid peroxidation in a concentration-dependent manner and EFDO showed maximum enhancement effect of mATPase activity compared to control and other fractions. In this regard, enhancement effect of 63% was obtained at 420 μg/ml of EFDO which was comparable to 2, 4-dinitrophenol (68%), the standard uncoupler of oxidative phosphorylation These findings show clearly that Daniellia oliveri contains bioactive agents that either induce or inhibit calcium-induced opening of the mPT pore and therefore modulate mitochondrial-mediated cell death and this justifies the use of the plant in management of diseases associated with dysregulated cell death. Further studies on the isolation and characterization of the compounds responsible for modulating the mitochondrial permeability transition pore will therefore yield positive results in drug design in situations or diseases associated with dysregulated cell death