Role of transforming growth factor-β pathway in the mechanism of wound healing by saponin from Ginseng Radix rubra

Abstract

1. The effects of saponin from Ginseng Radix rubra on extracellular matrix metabolism, the activation and synthesis of TGF-β1, and the modification of TGF-β receptor in fibroblasts were examined to elucidate the contribution of the TGF-β pathway to the mechanism of wound healing by saponin.

2. Fibronectin synthesis was analysed by the immunoprecipitation method. Activation and synthesis of TGF-β1 were measured by ELISA. The expressions of TGF-β receptors in fibroblasts were examined at protein and mRNA levels by the cross-linking method and Northern blot analysis, respectively.

3. The fibronectin synthesis increased 2.3- and 3.9-fold at fibroblasts treated with 1 and 10 μg ml⁻¹ of saponin, respectively, compared with that in non-treated cells. Fibronectin synthesis stimulated with 10 μg ml⁻¹ of saponin was inhibited with 69% by 5 μg ml⁻¹ of an anti-TGF-β1 antibody. mRNA of TGF-β type I receptor increased 4.8- and 4.4-fold at fibroblasts treated with 1 and 10 μg ml⁻¹ of saponin, respectively, and that of TGF-β type II receptor also increased 3.4- and 3.2-fold at fibroblasts treated with 1 and 10 μg ml⁻¹ of saponin, respectively. The significant increases of TGF-β type I and II receptors and of fibronectin synthesis were observed at the same concentrations of saponin. TGF-β1 content increased 1.74- and 1.87-fold at conditioned medium of fibroblasts treated with 100 and 250 μg ml⁻¹ of saponin, respectively, higher concentrations than those which accelerated fibronectin synthesis. Furthermore, the active TGF-β1 content was below 10% of total TGF-β1 at each concentration of saponin.

4. These results indicate that saponin stimulates fibronectin synthesis through the changes of TGF-β receptor expressions in fibroblasts.

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