Tumor Necrosis Factor-α Production by Human Hepatoma Cell Lines Is Resistant to Drugs That Are Inhibitory to Macrophages

Abstract

Little is known about the potential of immunomodulatory agents to lower tumor necrosis factor-α(TNF-α) synthesis in tissues of nonmonocytic origin. We studied effects of diverse drugs on the formation of immunoreactive TNF-α in the human hepatoma cell lines HepG2 and Hep3B, in which TNF-α production was induced by treatment (3 h incubation periods) with interleukin-1β (IL-1β, 300 pg/ml) or phorbol myristate acetate (PMA, 100 nmol/l). TNF-α production in IL-1β-stimulated or PMA-stimulated hepatocyte cultures was not altered following the addition of dihydrocortisone (≤ 1 μg/ml), dibutyryl-cAMP (db-cAMP,≤ 100 μmol/1), adenosine (≤ 1 mmol/l), thalidomide (≤ 25 μg/ml), or cyclosporine (≤ 300 ng/ml). TNF-α production was inhibited by taurolidine (≥300 μg/ml), but this inhibition was associated with reduced cell viability. Pentoxifylline (1 mg/ml) did not influence PMA-induced TNF-α production, but it augmented IL-1β-induced TNF-α production. Measurements of TNF-α mRNA by RT-PCR indicated that pentoxifylline exerted its effect posttranscriptionally. Additional studies with PMA-treated human whole blood cultures confirmed that pentoxifylline, db-cAMP, and adenosine reduced TNF-α production by leukocytes. These results provide first evidence to assume cell type-specific effects of immunomodulatory drugs on TFN-α synthesis, which may be relevant with respect to their clinical application.