Modulation of C3 gene expression in HepG2 human hepatoma cells

Inflammation elicits an acute phase response, which includes changes in plasma concentrations of a number of cytokines, reflecting changes in their gene transcription in the liver. In this study, the induction of complement factor 3 (C3) was investigated in HepG2 cells, a human hepatoma cell line often used as a model system for cytokine-dependent expression of acute phase proteins of the liver. By using a very sensitive RT-PCR assay, the amount of mRNA for C3 was measured after induction with lipopolysaccharide (LPS) and interleukin-6 (IL-6). Both substances were found to up-regulate C3 gene expression. C3 mRNA level was lower in LPS-treated cells compared to IL-6 induction and also reached maximum expression at an earlier time point. These findings suggest a coordinate stimulation of C3 expression in the hepatocytes, which then maintains the host response to infectious agents.