Abstract

Matrix metalloproteinases participate in the degradation of the extracellular matrix proteins and are regulated mainly by their respective tissue inhibitors. In a variety of inflammatory connective tissue diseases, variations in the tissue content of both metalloproteinases and tissue inhibitors have been reported. The purpose of this study was to determine the serum levels of metalloproteinases and tissue inhibitors in patients with autoimmune diseases and compare with those of healthy individuals of similar age. The metalloproteinase content was analyzed by zymography and it was found that the serum levels of metalloproteinase-2 and metalloproteinase-9 of all autoimmune disease samples were decreased, in all diseases examined and independently of clinical activity, while those of active metalloproteinase-9 were significantly elevated. Both tissue inhibitors were quantitated by direct enzyme-linked immunosorbent assay and were also found decreased in autoimmune disease samples, confirming the balance that should exist in the secretion of metalloproteinases and tissue inhibitors. These results suggested that the increased active form of metalloproteinase-9, together with the decreased concentration of tissue inhibitor-2, could be used for diagnostic purposes and for the follow-up of patients with autoimmune diseases.