Effect of TNF-alpha on Raji cells at different cellular levels estimated by various methods.

Tumor necrosis factor (TNF)-alpha, a pleiotropic cytokine, has been shown to induce diverse and opposite effects on lymphoid malignancy depending on TNF receptor system expression. Based on this, we investigated its in vitro dose- and time-related effect on the malignant B-cell line Raji, derived from Burkitt lymphoma patients, at different intracellular levels. The membrane alteration was estimated by lactate dehydrogenase (LDH) release and by flow cytometry; intracellular metabolic energy by determination of the total intracellular LDH activity; total cytosole protein mass by sulforhodamine B assay; and cell growth by incorporation of [3H]thymidine into DNA. Significant increase of LDH through cell membrane alteration was accompanied by decrease of intracellular metabolized energy and total protein mass. TNF-alpha at lower concentrations (125 and 250 pg/ml) significantly induced cell proliferation in comparison with 1,000 pg/ml of TNF-alpha, which induced more cell death. TNF-alpha induced maximal apoptosis rate up to 30% after 24 h, showing more effects for a necrotic form of cell death. Here we reported opposite and diverse effects of TNF-alpha at different intracellular levels in Raji cells, when applied in different assays, showing characteristics for every cellular compartment.