Interferon- γ-dependent induction of manganese superoxide dismutase activity of SV40-transformed human keratinocytes by anti-Fas antibody and by TNF- α

Abstract

It has been reported that cellular oxidative stress induces apoptosis, that may be inhibited by scavengers of reactive oxygen intermediates (ROIs). Superoxide dismutase (SOD) is among the most active scavengers of ROIs, providing defense against the cellular oxidative stress. Fas antigen and tumor necrosis factor (TNF) receptor are the cell surface proteins, stimulation of which induces apoptosis of keratinocytes. Using SV40-transformed human keratinocytes (SVHK cells), we investigated the effects of anti-Fas antibody and TNF- α on the SOD activity. Treatment of SVHK cells with anti-Fas antibody or TNF- α in the presence of interferon- γ (IFN- γ) resulted in an increase in Mn-SOD activity, Cu,Zn-SOD activity was not affected. In the absence of IFN- γ, no increase in Mn-SOD activity was detected. The induction of IFN- γ-dependent Mn-SOD activity by anti-Fas antibody or TNF- α was concentration-dependent; the maximal effect was observed at 1–10 μg/ml and 5–10 ng/ml, respectively. The increase in Mn-SOD activity was observed at 6 h following the treatment and remained for at least 48 h. Northern blot analyses showed that Mn-SOD mRNA increased within 3 h without a significant change in Cu,Zn-SOD mRNA. The addition of both anti-Fas antibody and TNF- α in the presence of IFN- γ resulted in an additive increase in Mn-SOD activity. Although the addition of 12- o-tetradecanoylphorbol-13-acetate (TPA) singly to the incubation medium had no effect on either Mn-, or Cu,Zn-SOD activity, it significantly augmented the IFN- γ-dependent induction of Mn-SOD activity by anti-Fas antibody or by TNF- α. The protein kinase C inhibitor, 1-(5-isoquinoline-sulfonyl)-2-methyl piperazine dihydrochloride (H-7), significantly inhibited the TPA-dependent increase in Mn-SOD activity. These results indicate that the stimulation of Fas antigen or TNF receptor increases Mn-SOD activity of SVHK cells in the presence of IFN- γ and that TPA augments the process through the activation of protein kinase C.