“Retina Neuroscience Session 2: Muller cells"

SANCHEZ MC; SARTHY VIJAY

Buenos Aires

Simposio; XVII International Congress of Eye Research 2006; 2006

Glial Müller cells (MC) are involved in retinal neovascularization, but very little is known of the contribution of these cells to this process. Hypoxia and growth factors are postulated to be involved in the development of retinal neovascularization through the regulation of extracellular proteinase production. However, the factors and mechanisms that regulate the expression of these enzymes are not well characterized. Previously we demonstrated that matrix metalloproteinases (MMPs) are elevated in the retina during the neovascularization process. Herein we investigated the a2-M effect on intracellular signaling pathways in primary cultures of MC that express LRP-1, evaluating the potential role of these transduction pathways as a regulator of MMPs. MC were isolated from C57BL/6 mice and the LRP-1 expression was detected by Western blotting and immunocytochemistry. MAPK-ERK1/2 and PKB pathways were analyzed by Western blotting in MC cultured in presence of a2-M. The role of α2-M in stimulating retinal glial cell proteinase production was evaluated by zymographic  analysis. We showed that nearly 95-100% of MC expressed LRP-1. In MC cultures, the α2-M-induced ERK1/2 phosphorylation exhibited distinct profiles throughout the times and concentrations examined. For 15 min, a2-M 180 nM showed a maximal activation of phosphorylated forms of ERK1/2, whereas a2-M concentrations lower than 20 nM reached maximal ERK1/2 phosphorylation for 5 min remaining activated up to 10 min. On the other hand, a2-M did not induce a significant Akt phosphorylation. Finally, a2-M increased the MMP-2 gelatinolytic activity after 24 hours of stimulation. The present study demonstrates that α2-M induces MAPK-ERK1/2 activation and MMP-2 activity in MC, suggesting that the a2-M/LRP-1 system is involved in the regulation of extracellular proteinase production during retinal neovascularization.