Nutritional concentration of genistein protects human dermal fibroblasts from oxidative stress-induced collagen biosynthesis inhibition through IGF-I receptor-mediated signaling.

The effects of genistein, a soy isoflavone phytoestrogen and antioxidant, on collagen and DNA biosynthesis (measured by the 5-[3H]proline and the [3H]thymidine incorporation assays), prolidase activity (colorimetric method) and expression (determined by Western immunoblot) of the beta1-integrin receptor, focal adhesion kinase pp125(FAK) (FAK), Src, the insulin-like growth factor-I (IGF-I) receptor, Shc, growth-factor receptor-bound protein 2 (Grb2), son of sevenless protein (Sos) and phosphorylated mitogen activated protein (MAP) kinases, extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) were examined in normal human dermal fibroblasts (CRL-1474) exposed to oxidative stress. Subconfluent cells were subjected to repetitive stress with 30 microM t-butylhydroperoxide (t-BHP) in combination with 1-100 microM genistein for 1 h per day over the course of 5 days. Also, the cells were treated with t-BHP alone or with t-BHP in combination with 1-100 microM ascorbate. It was found that genistein at 1 microM counteracted the inhibition of collagen biosynthesis evoked by t-BHP in fibroblasts, more effectively than ascorbate at the same concentration. At 10 microM, genistein exerted significantly diminished protective effect on collagen biosynthesis in fibroblasts, while at 100 microM it induced inhibition of this process. The protective effect of genistein on collagen biosynthesis was not related to modulation of prolidase activity or the expression of the beta1-integrin receptor, FAK, Src or Grb2. It was found that genistein, at 1 microM, diminished t-BHP-induced down-regulation of the IGF-I receptor, Shc, Sos and phosphorylated ERK1/ERK2 expression in fibroblasts. Simultaneously, genistein counteracted the antiproliferative activity of the oxidant. These results suggest that the mechanism of the protective effect of genistein on collagen biosynthesis in t-BHP-treated fibroblasts may be due to prevention of disturbances in the IGF-I receptor-mediated, ERK1/ERK2-associated signaling pathway evoked by the oxidant.