EFFECT OF EPIDERMAL GROWTH-FACTOR ON CU, ZN-SUPEROXIDE DISMUTASE EXPRESSION IN CULTURED FIBROBLASTS FROM RAT SKIN

The effects of epidermal growth factor (EGF) on Cu, Zn-superoxide dism utase (SOD) in cultured fibroblasts from rat skin exposed to superoxid e anions were studied. Cross-linking of [I-125]hEGF using disuccinimid yl suberate and immunoblot analysis using anti-EGF receptor antibody t o crude plasma membrane fractions of fibroblasts showed that a 170 kDa EGF receptor protein was present on the membrane, as in A431 cells wh ich over express a specific EGF receptor. The cytosolic SOD enzyme act ivity in fibroblasts exposed to superoxide anions 24 h after treatment with EGF plus nafamostat (NM), a potent protease inhibitor, was incre ased 1.6-fold compared to control-treated cells. Treatment with either EGF or NM alone, evoked little increase in SOD enzyme activity. The i ncrease in Cu, Zn-SOD protein levels corresponded to the increase in c ytosolic SOD enzyme activity in fibroblasts. The Cu, Zn-SOD mRNA level in fibroblasts treated with EGF plus NM at 3 and 6 h was higher than that of the control. Additionally, levels of [I-125]hEGF degradation p roducts released into the medium from fibroblasts exposed to superoxid e anions were significantly reduced in the presence of NM. These resul ts suggest that the stabilization of EGF by NM in culture is an import ant factor in the expression of its effects, and that EGF induces Cu, Zn-SOD expression by accelerating transcription of the Cu, Zn-SOD gene in cells, resulting in their protection from the effects of superoxid e anion radicals.