Vascular endothelial growth factor protects hepatoma cells against oxidative stress-induced cell death

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Background and Aim The aim of the present study was to examine coordination of the vascular endothelial growth factor (VEGF) and VEGF receptor (Flk-1) system and to study control of VEGF expression by oxidative stress, which is considered a model for chronic liver disease. Methods Cell viability was determined by test method with 3-[4, 5-dimethylthiazol-2-yl]-2, 5-dephenyl tetrazolium bromide (MTT). Expressions of cellular proteins were evaluated by Western blott analysis. Results The c-Met tyrosine phosphorylation in PLC/PRF/5 hepatoma cells was increased by treatment with 20 ng/ml Hepatocyte Growth Factor (HGF), and extracellular signal-regulated kinase (ERK) was also activated. Although Flk-1 was phosphorylated in response to VEGF (>50 ng/ml), phosphorylated ERK was not detected at these concentrations. 5.0 and 10 μM hydrogen peroxide (H2O2) caused cell death in a dose-dependent manner after 24 hours. Upon Western blott analysis at 1 hour with H2O2, rapid phosphorylation of both ERK1/2 and c-Jun NH2-terminal kinase (JNK) was observed. In first 6 hours, H2O2 induced cell death for 58.4±6.8%, whereas the presence of 100 ng/ml VEGF improved the survival rate to 77.2±4.2. VEGF significantly decreased H2O2-induced cell death after 12 hours, whereas HGF (20 ng/ml) did not have a similar effect. When cells were incubated with 5 μM H2O2, expression of VEGF protein was detected. Furthermore, H2O2-induced phosphorylation of ERK and JNK was also reduced by VEGF (100 ng/ml). In contrast, HGF did not induce phosphorylation of ERK and JNK. Conclusion Hepatoma cells might be able to survive under condition continuous oxidative stress through expression of VEGF.