Downregulation of decorin expression in dermal fibroblasts by interleukin-4

Decorin, a chondroitin/dermatan sulphate proteoglycan, plays an important role in the assembly of extracellular matrix components. In this study, we investigated the influence of interleukin-4 (IL-4) on the expression of decorin and sulphated glycosamino-glycans (GAGs) in cultures of human skin fibroblasts. IL-4 inhibited the expression of decorin mRNA and its core protein synthesis. IL-4 stimulated dermatan sulphate but decreased chondroitin sulphate synthesis without altering the total amount of sulphated GAGs. IL-4 had no effect on the initiation activity of the dermatan sulphate and chondroitin sulphate chains, as evaluated by the effect of exogenous beta-xyloside that acts as an artificial chain initiator for dermatan sulphate and chondroitin sulphate biosynthesis. Type I collagen mRNA levels and protein synthesis were increased by this IL-4. Therefore, the effects of IL-4 on decorin and GAGs as well as type I collagen may have important implications for wound healing and for the treatment of several fibrosing diseases.