Modulation of rat liver mitochondrial membrane permeability transition pore by fruit extracts of Citrullus lanatus (Thunb.)

Abstract

Background: Medicinal plants possess potential phytochemicals that have been proven to induce cell death in a wide variety of cancer via the induction of the Mitochondrial Membrane Permeability Transition (MMPT) pore. Citrullus lanatus (CL) is a tropical medicinal plant used in treating cancer, gonorrhoea, kidney and urethral diseases. However, its use in treating cancer has not been scientifically proven.

Objective: This study investigated the effect of fruit extracts of Citrullus lanatus on rat liver MMPT pore and Mitochondrial ATPase activity (mATPase).

Methods: Chopped fruit (1kg) was soaked in distilled water to obtain the Aqueous Fruit Extract (AECL), and 2 kilogram of chopped fruit was serially extracted with Methanol and water to obtain the Methanol Fraction (MFCL) and Aqueous Fraction (AFCL) respectively. For in vitro study, the effects of the extracts and fractions were assessed on isolated rat liver mitochondrial. For in vivo study, 25 male Wistar rats (130g±10g) were randomly assigned into 5 groups of five animals per group and orally treated with only the AECL for fourteen days, respectively. Group 1 (distilled water), Group 2 (50 mg/kg AECL), Group 3 (100 mg /kg AECL), Group 4 (200 mg/kg AECL) and Group 5 (400 mg/kg AECL). Rat liver mitochondria were obtained by differential centrifugation. The MMPT, Fe²⁺- induced mitochondrial lipid peroxidation and mATPase were assayed spectrophotometrically. Data were analysed using one way analysis of variance.

Results: The AECL and MFCL induced MMPT pore opening significantly in a concentration-dependent manner at 200, 600, 1000 and 1400 μg/ml. Specifically, AECL induced pore opening by 1.1, 3.5, 7.6, 14.8 folds, respectively. In like manner, the MFCL induced MMPT pore opening significantly only at 1000 and 1400μg/ml by 2.6 and 5.3 folds respectively. However, the AFCL had no inductive effect on MMPT pore of rat liver mitochondria. Similarly, the AECL had no inductive effect on the mitochondria of rats orally treated with AECL for fourteen days. The AECL inhibited Fe²⁺-induced mitochondrial lipid peroxidation by 45% and also stimulated mATPase by 21% at 1400μg/ml.

Conclusion: These findings suggest that potential phytochemicals that could induce MMPT pore opening and stimulate mitochondrial ATPase activity are present in the extracts of the Citrullus lanatus. Further studies on the extracts will help to determine the exact nature of the bioactive components present in Citrullus lanatus and may be useful in drug development.

Keyword: Apoptosis, Cancer, Citrullus lanatus, Mitochondrial ATPase, Mitochondrial Membrane Permeability Transition (MMPT)