Effect of Hedyotis diffusa water extract on protecting human hepatocyte cells (LO2) from H2O2-induced cytotoxicity

Context: Natural products are good sources of natural dietary antioxidants that are believed to protect the body against hepatotoxic effect induced by oxidative stress. Hedyotis diffusa Willd (Rubiaceae) (HDW) is a traditional Chinese medicinal herb that has been shown to possess a variety of antioxidant properties.Objective: The present study examines and explains the cell protective property of HDW water extract (WEHDW).Materials and methods: 2,2-Diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) assay was used to measure the free radical scavenging property of WEHDW (0.001-10mg/mL). The protective effect of WEHDW (0.3-10mg/mL 2h pretreatment) against hydrogen peroxide (H2O2, 200M for 6h) induced cytotoxicity in human hepatic cells, LO2, was evaluated using cell viability assay and nuclear staining. The molecular pathway of WEHDW's effect was investigated by using Western blot assay.Results: WEHDW had a 50% scavenging concentration (SC50) at 0.153mg/mL in the DPPH assay. Exposure of LO2 cells to H2O2 resulted in apoptosis which could be markedly attenuated by pre-treating WEHDW in a concentration-dependent manner (0.5, 1, 3, 5, or 10mg/mL) (all with p<0.001, versus control). Moreover, Hoechst (nuclear) staining showed that 1mg/mL WEHDW could protect LO2 cells by attenuating apoptotic cell death mediated by H2O2. It was found that WEHDW reversed H2O2-induced activation of MEK/ERK pathway and H2O2-induced inhibition of P13-K/AKT/GSK3 pathway in LO2 cells.Discussion and conclusion: WEHDW may help to improve the antioxidant defense system, resulting in prevention of oxidative stress-related fatty liver diseases.