SEROTONIN ENHANCES THE PRODUCTION OF TYPE-IV COLLAGEN BY HUMAN MESANGIAL CELLS

Background. The plasma concentration of 5-hydroxytryptamine (5-HT) in diabetic patients is higher than that in normal subjects. Since recent reports have demonstrated the presence of 5-HT2A receptor in glomerul ar mesangial cells, it is possible that 5-HT may be involved in the de velopment of diabetic nephropathy through the 5-HT2A receptor in mesan gial cells. Because expansion of the glomerular mesangial lesion is a characteristic feature of diabetic nephropathy, we examined the effect of 5-HT on the production of type IV collagen by human mesangial cell s. Methods. Human mesangial cells were incubated with 5-HT with or wit hout 5-HT receptor antagonists, protein kinase C (PKC) inhibitor or tr ansforming growth factor-beta (TGF-beta) antibody. Type IV collagen mR NA and protein concentration in medium were measured by Northern blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. TGF-beta mRNA and bioactivity in the medium were measured by Northern blot analysis and bioassay using mink lung epithelial cells, respectiv ely. Results. 5-HT stimulated the production of type IV collagen by hu man mesangial cells, which was inhibited by ketanserin and sarpogrelat e hydrochloride, 5-HT2A receptor antagonists, but not by ondansetron, a 5-HT3 receptor antagonist. 5-HT increased the bioactivities of both active and total TGF-P. However, the 5-HT-enhanced production of type IV collagen was completely inhibited by an anti-TGF-beta antibody. Fur thermore, a PKC inhibitor, calphostin C, inhibited the 5-HT-induced in crease in type IV collagen secretion, and the activity of membrane PKC was increased by 5-HT. Phorbol ester activated type IV collagen produ ction as well as active and total TGF-beta. Calphostin C completely in hibited the 5-HT-enhanced activity of active TGF-beta, but did not inh ibit exogenous TGF-beta-induced increase in type IV collagen secretion . Conclusions. Our results suggest that 5-HT-enhanced production of ty pe TV collagen by human mesangial cells is mediated by activation of P KC and subsequent increase in active TGF-beta activity.