Inhibition by N-acetyl-L-cysteine of interleukin-6 mRNA induction and activation of NF kappa B by tumor necrosis factor alpha in a mouse fibroblastic cell line, Balb/3T3.

Redox-based modulation plays a role in transcriptional control of gene expression. In the present study, we investigated the possible role of reactive oxygen species in the induction of interleukin-6 (IL-6) mRNA and in increases in NF kappa B binding activity by tumor necrosis factor (TNF) alpha using a mouse fibroblastic cell line, Balb/3T3. Expression of IL-6 mRNA is known to be dependent upon NF kappa B that binds to the 5'-flanking region of the IL-6 gene. We found that: (i) TNF alpha increased IL-6 mRNA levels and this increase was inhibited by N-acetyl-L-cysteine (NAC), a scavenger of reactive oxygen species. (ii) NF kappa B binding activity in this cell line was also increased by TNF alpha, and the increase was inhibited in the presence of NAC. (iii) The treatment of cells with low doses of hydrogen peroxide increased the NF kappa B binding activity. (iv) Expression of a reporter gene in which the chloramphenicol acetyltransferase (CAT) gene was under the control of NF kappa B binding sites was induced by hydrogen peroxide. These results suggest that the induction of IL-6 mRNA is regulated by a mechanism involving reactive oxygen species and that NF kappa B, whose activity is sensitive to the cellular redox state, plays an important role in this induction in a fibroblastic cell line, Balb/3T3, stimulated with TNF alpha.