Protective Effects of Ginkgo biloba Leaf Extracts on Trichloroethylene-Induced Human Keratinocyte Cytotoxicity and Apoptosis

Abstract

The objective of this study was to assess the protective effects of Ginkgo biloba leaf extracts (EGb) on trichloroethylene (TCE)-induced cytotoxicity and apoptosis in normal human epidermal keratinocytes (NHEK). Cytotoxicity was determined by neutral red uptake, and lipid peroxidation of the cells was assessed by malondialdehyde (MDA) and superoxide dismutase (SOD). Electron microscopy and flow cytometry were used to evaluate NHEK apoptosis. Treatment of NHEK with various concentrations of TCE caused a substantial decrease in cell viability. NR₅₀from the cytotoxicity assay was found to be 4.53 mM. TCE caused an increase in MDA, while an inhibition of SOD activity, in a concentration-dependent manner. Electron microscopic examination revealed typical morphologic changes of apoptosis in cells treated with TCE. Incubation of NHEK with TCE (0, 0.125, 0.5, 2.0 mM) for 4 h increased the proportion of apoptotic cells from control of 19.23% to nearly 44.35%. Pretreatment of EGb at 10–200 mg/l dose-dependently attenuated the cytotoxic effect of TCE, prevented TCE-induced elevation of lipid peroxidation and decline of antioxidant enzyme activities. Similar inhibition by EGb on TCE-mediated NHEK apoptosis was also observed. These results suggest that EGb can protect NHEK from TCE-induced cytotoxicity and apoptosis, which may be associated with the superoxide scavenging effect and enhancement of antioxidant enzyme activities.