INCREASED MATRIX METALLOPROTEINASES IN THE AQUEOUS-HUMOR OF PATIENTS AND EXPERIMENTAL-ANIMALS WITH UVEITIS

Purpose. Matrix metalloproteinases (MMPs) play a major role in connect ive tissue remodelling, wound healing and embryogenesis. They have als o been implicated in pathological tissue degradation in diseases such as rheumatoid arthritis (RA), osteoarthritis (OA), and tumor invasion. The aim of this study was to define the potential role of MMPs in the inflammatory process of uveitis by identifying these proteases in the aqueous humor (AH) of patients with uveitis and in rabbits with endot oxin-induced uveitis (EIU). Methods. Aqueous humor samples from 6 pati ents with uveitis and 5 control patients who had undergone elective ca taract surgery were examined. The profile of MMPs in the AH of experim entally-induced acute anterior uveitis in rabbits was also assessed. W estern blot analysis and SDS-PAGE substrate zymography were used to de tect metalloenzymes and their natural inhibitor, tissue inhibitor of m etalloproteinase (TIMP-1) in aqueous samples. Results. Aqueous humor f rom all patient contained interstitial collagenase (MMP-1), stromelysi n (MMP-3), gelatinase B (MMP-9) and TIMP-1. Although the amount of MMP s varied considerably, TIMP-1 levels remained unchanged in the aqueous of uveitis patients. Using substrate gel zymography, we were able to reveal several gelatinolytic bands, including one major band at approx imately 92-kDa whose activity differed between uveitis and cataract AH . The gelatinase activity found in human AH samples was shown to be in hibited by 10mM EDTA and activated in vitro by APMA, indicating that t hese enzymes were indeed of the metalloproteinase class. Aqueous humor samples from the rabbit EIU model revealed a 100-kDa molecular weight species likely to correspond to gelatinase B. This gelatinolytic acti vity was maximal at 6 hours after the lipopolysaccharide (LPS) injecti on, declined at 12 and 24 hours post LPS, and was absent at later time points. The induction of gelatinase activity in rabbit AH preceded th e increase in cell number during the inflammatory process in the anter ior chamber. Conclusions. Metalloproteinases found in normal human AH may participate in physiological turnover of extracellular matrix in t he eye. Elevated levels of MMPs were found in the AH of patients with uveal inflammation and animals with LPS-induced uveitis, where they ar e likely to be critical to tissue destructive and repair processes. It is likely that pro-inflammatory cytokines such as tumor necrosis fact or-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha), which are k nown modulators of MMPs, induce their secretion in acute anterior uvei tis.