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Corsini E, Schubert C, Marinovich M, Galli CL: Role of mitochondria in tributyltin-induced interleukin-1alpha production in murine keratinocytes. J Invest Dermatol. 1996 Nov;107(5):720-5.
Tributyltin (TBT) salts are well known skin irritants in rodents and humans. TBT induced both the intracellular production of interleukin-1alpha (IL-1alpha) and its release into culture medium in a murine keratinocyte cell line (HEL30). Here, we report that mitochondria are important for TBT-induced IL-1alpha production. Confluent cells were treated with increasing concentrations of TBT (0--2.5 microM) or dimethylsulfoxide as vehicle control. At different times thereafter (0--24 h), nuclear extracts were analyzed for nuclear factor-(kappa) B (NF-(kappa) B) binding activity by electrophoretic mobility shift assay, and the released and cell-associated IL-1alpha was measured by enzyme-linked immunosorbent assay. TBT induced a direct and concentration-related activation of NF-(kappa) B, which peaked at 2 h and was blocked by pyrrolidinedithiocarbamate, a potent NF-(kappa) B inhibitor, and rotenone, an inhibitor of the electron entry from complex I to ubiquinone. Rotenone also induced a concentration-related inhibition of IL-1alpha synthesis induced by TBT, but rotenone did not completely abrogate TBT-induced IL-1alpha production, which suggests that other transcription factors may be involved in IL-1alpha production. Prolonged treatment with ethidium bromide, an inhibitor of mitochondrial DNA and RNA synthesis, was used to partially deplete cells of functional mitochondria. After 5 d of treatment, mitochondrial conversion of tetrazolium bromide to formazan was reduced by 50%, and IL-1alpha release was decreased by 65%, whereas no induction of intracellular IL-1alpha was observed. This effect was not due to inhibition of protein synthesis, because identical incorporation of [3H] leucine into protein in control and ethidium bromide-treated cells was identical. This impairment of mitochondrial metabolism inhibited NF-(kappa) B activation by TBT. These findings indicate that mitochondria may be the source of second messenger molecules important for TBT-induced IL-1alpha production. |
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