Fig. 2.

HepG2 cells and primary human hepatocytes are sensitized to TNF cytotoxicity by pre-treatment with the combination of adenosine and homocysteine (Ado+Hcy). (A) HepG2 cells were pre-treated for 2 hours with medium alone (DMEM), 500 µM adenosine (Ado), 500 µMhomocysteine (Hcy) or the combination (Ado+Hcy; 500 µM each), then exposed to 10 ng/ml TNF (light bars) or vehicle (DMEM; dark bars) for an additional 24 hours. MTT was added during the final hour of exposure to assess cell viability. Actinomycin D (ActD; 0.4 µg/ml) was included as a positive control for sensitization to TNF cytotoxicity. (B) Primary human hepatocytes were pre-treated with the indicated concentrations of Ado+Hcy, then exposed to 100 ng/ml TNF (light bars) or vehicle (DMEM; dark bars) for an additional 24 hours. MTT was added during the final hour of exposure to assess cell viability. The experiments were performed in triplicate using hepatocytes from 2 different donors, and the data from both donors was pooled for statistical analyses. Data show mean ± s.d. of the pooled data. *- Significantly different (p<0.05) compared to no TNF control.