Oxidative Stress-Mediated Induction of MMP-1 and MMP-3 in Human RPE Cells

PURPOSE. In early exudative age-related macular degeneration (AMD), segmental thinning of Bruch's membrane is associated with ingrowth of choroidal neovascularization into the subretinal space. To determine whether there is a link between oxidative stress and extracellular matrix (ECM) degradation by the retinal pigment epithelium, the present study focused on the effect of oxidative stress on MMP-1 and MMP-3 expression, two enzymes with substrate specificity for components of Bruch's membrane. METHODS. Cultured human RPE cells were exposed to oxidative stress. To investigate the role of signal transduction proteins, cells were pretreated with the specific inhibitors SB202190 or PD98059. Secreted MMP-1 and MMP-3 were detected by ELISA, MMP-2, and MMP-9 by zymography. Expression of mRNA was determined by quantitative real-time RT-PCR. ECM degradation by retinal pigment epithelium was assessed by immunofluorescence microscopy. RESULTS. Oxidative stress increased MMP-1 and MMP-3 protein release but reduced MMP-2 activity. Real-time RT-PCR disclosed increases of MMP-1 and MMP-3 mRNA after oxidative stress with no modulation of TIMP-1. MMP-2 and MMP-9 mRNA was slightly enhanced. PD98059, an inhibitor of ERK1/2, markedly reduced MMP-1 expression, whereas SB202190, an inhibitor of p38 MAPK, was less effective. MMP-3 expression was attenuated by both inhibitors. Oxidative stress-stimulated type I collagen degradation by RPE cells was reduced by simultaneous treatment with a synthetic MMP-inhibitor or a neutralizing antibody against MMP-1. CONCLUSIONS. MMP-1 and MMP-3 in the retinal pigment epithelium are inducible by oxidative stress. The directional shift in the MMP-1,-3/TIMP-1 ratio is associated with increased type I collagen degradation. This may be an important mechanism contributing to the pathogenesis of early exudative AMD. (Invest Ophthalmol Vis Sci. 2009;50:5495-5503) DOI: 10.1167/iovs.08-3193