Purpose: Matrix metalloproteinases have been shown to play a role in active uveitis. Transcription of MMPs is induced by a number of growth factors and cytokines. This study investigates the role of MMPs in chronic uveitis and correlates the amounts of MMP-2 and -9 in intraocular samples to the intraocular levels of proinflammatory cytokines (Interleukin-1 [IL-1], Interleukin-12 [IL-12] and Interleukin-1 receptor antagonist [IL-1ra]).
Methods: Aqueous humor of 16 patients was collected during surgical or diagnostic procedures (control group: cataract patients). MMP-2 and -9 were measured using zymography. IL-1beta, IL-12 and IL-1ra were evaluated by ELISA.
Results: We found MMP-2 and -9 in all of our uveitis patients. In the control group only MMP-2 was seen. Higher levels of MMP-2 and -9 were found in patients with higher activity of uveitis (p < 0.014 for MMP-2, p < 0.0054 for MMP-9). The amounts of IL-1beta, IL-12 and IL-1ra detected in our uveitis patients correlated with levels of MMP-2 (p < 0.07, p < 0.0004, p < 0.03) and MMP-9 (p < 0. 003, p < 0.0001, p < 0.002), and IL-12 (p < 0.004, p < 0.0001). Patients with moderately active uveitis presented with twice the level of MMP-2 as the control group; MMP-9 levels reached up to 92% of the amounts found in patients with active uveitis. Two patients in remission for almost one year still had detectable intraocular MMP-9 levels.
Conclusion: Our data suggests that the high levels of MMPs found in patients with chronic uveitis might contribute to the damage often seen in these eyes. Since MMPs are capable of releasing proinflammatory cytokines bound to components of the extracellular matrix, and facilitate the secretion of active TNF-alpha by cleavage of the membrane bound form, it is conceivable that MMPs contribute to the chronicity of some uveitis cases.