Apoptosis-inducing effects of Terminalia phanerophlebia leaf extracts on human renal cells

Abstract

The study investigated the toxicogenic effects and molecular mechanisms of Terminalia phanerophlebia on human renal cells. The methylthiazol tetrazolium (MTT) assay was used to assess the cytotoxicity of a crude leaf extract of Terminalia phanerophlebia in Hek293 cells. Luminometry was used to determine caspase activity, phosphatidylserine externalization and necrosis. The comet assay evaluated DNA fragmentation and the lactate dehydrogenase (LDH) assay was used to assess membrane integrity. Western blotting measured the expression of bcl-2-like protein 4 (Bax), inhibitors of apoptosis proteins (IAP), cleaved poly (ADP-ribose) polymerase (cPARP), p53 and nuclear factor kappa B (NF-κB) in treated Hek293 cells. A reduction in cell viability was observed with a half maximal inhibitory concentration (IC50) of 1.36 mg/ml. At this concentration, Terminalia phanerophlebia decreased initiator and executioner caspase activity. Phosphatidylserine validated apoptosis in IC25-treated cells, while necrosis was observed in all treated cells. Comet formation indicated that there was DNA fragmentation. High levels of p53 resulted in upregulation of Bax in IC25-treated cells, while the opposite was noted in IC50-treated cells. Upregulation of NF-κB is associated with decreased caspase-3 and cPARP and further supported by an increase in IAP indicating that Hek293 cell death was mainly through apoptosis and necrosis. The findings suggest that while Terminalia phanerophlebia is a good extract for tuberculosis therapeutic intervention, it may exert toxic effects on kidney cells via the apoptotic pathway.