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Y. Wang, M. L. Bajenaru, N. Agarwal, M. E. Fini; Laminin Increases Retinal Ganglion Cells Resistance to Glutamate Induced Oxidative Stress via the ß1-integrin Signaling Pathway. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5554.
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© ARVO (1962-2015); The Authors (2016-present)
ECM integrity in the CNS is essential for neuronal homeostasis and ECM-survival signals are transmitted to neurons through the integrin survival pathway. The purpose of this study is to explore the hypothesis that ECM-integrin survival signaling pathway can modify RGC vulnerability in glaucoma.
As an experimental paradigm of RGC apoptosis in glaucoma we exposed the RGC-5 cell line in culture to glutamate induced oxidative stress. RGC-5 cells were plated without (plastic), or on several ECM substrates: matrigel, laminin, collagen IV, and fibronectin and treated with high concentrations (2.5-25 mM) of glutamate, characteristic to glutamate oxidative stress for 24 hours. Cell survival was examined by the MTT assay. Expression levels of components of the integrin survival pathway were examined by western blotting and immunohistochemistry.
10 mM glutamate treatment of RGC-5 cells cultured on plastic results in 75% cell death. Matrigel conferred 30%, laminin 20%, and collagen IV 15% resistance to RGC-5 cells exposed to 10 mM glutamate. Fibronectin didn’t confer significant protection. Integrins are the main receptors for ECM proteins. ß1 integrin is the most abundant subfamily of integrins in the retina, and the ß1 subunit is required for intracellular signaling. We next tested if the protective effect of ECM proteins is mediated by the ß1 integrin survival pathway. Pre-incubation with ß1 integrin blocking antibodies of RGC-5 cells, cultured on the 3 protective matrices, and exposed to glutamate completely abolished the protective effect of laminin, diminished the effect of matrigel, and didn’t affect the effect of collagen IV. Consistent with that, the expression levels of components of the integrin signaling were shown to be decreased upon glutamate treatment.
These results suggest that ECM, especially laminin conferred significant RGC-5 protection against glutamate oxidative stress and this protection is mediated specifically via ß1 integrin receptors and could be attributed to increased integrin signaling.
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