First description of a compensatory xylosyltransferase I induction observed after an antifibrotic UDP-treatment of normal human dermal fibroblasts

Fibrosis is a serious health problem often leading to accompanying organ failure. During the manifestation of the disease, an accumulation of different extracellular matrix (ECM) molecules, such as proteoglycans, takes place. There is no appropriate therapeutic option available to heal fibrosis to date. Current research focuses primarily on targets such as the cytokine transforming growth factor-β1 (TGF-β1), which is assumed to be one of the key mediators of fibrosis. Both xylosyltransferase isoforms, XT-I and XT-II, catalyze the rate-limiting step of the proteoglycan biosynthesis. Consequently, inhibiting XT activity could be a promising approach to treat fibrosis. It was shown in earlier studies that nucleotides and nucleosides have anti-fibrotic properties and decrease XT activity in cell-free systems. In contrast, we evaluated the mechanisms beyond an UDP-mediated induction of intracellular XT-activity in normal human dermal fibroblasts (NHDF). The observed pseudo-fibrotic XT increasement could be attributed to a compensation of decreased UDP-glucuronate decarboxylase 1 (UXS1) mRNA expression as well as a diminished intracellular UDP-xylose concentration. In summary, our results describe a so far unknown XT-inductive pathway and show that UDP could be a promising molecule for the development of an anti-fibrotic therapy. Nevertheless, XT activity has to be inhibited in parallel intracellularly.