Stimulation of collagen gene expression and protein synthesis in murine mesangial cells by high glucose is mediated by autocrine activation of transforming growth factor-β

Previous investigations have demonstrated that growing mesangial cells in high glucose concentration stimulates extracellular matrix synthesis and also increases the expression of TGF-β. We tested whether the stimulation of extracellular matrix production is mediated by autocrine activation of TGF- β, a known prosclerotic cytokine. Addition of neutralizing anti-TGF-β antibody, but not normal rabbit IgG, significantly reduced the high glucose- stimulated incorporation of ³[H]proline. Denaturing SDS-PAGE revealed that mainly collagen types I and IV were stimulated by high (450 mg/dl) D-glucose. This high glucose-mediated increase in collagen synthesis was reduced by the anti-TGF-β antibody. Treatment of mesangial cells grown in normal (100 mg/dl) D-glucose with 2 ng/ml recombinant TGF-β₁ mimicked the effects of high glucose. Furthermore, the anti-TGF-β antibody significantly reduced the increase in mRNA levels encoding α2(I) and α1(IV) collagens induced by high glucose. Thus, the high glucose-stimulated increase of collagen production in mesangial cells is mediated, at least in part, by autocrine TGF-β activation. We postulate that the interception of the glomerular activity of TGF-β may be an effective intervention in the management of diabetic nephropathy.