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S. He, G. Prasanna, T. Yorio; Involvement of ERK–MAPK and PKC in the Expression of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of Metalloproteinases (TIMPs) in Astrocytes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2214.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Remodeling of the extracellular matrix (ECM) of the optic nerve head and cupping of the optic disc are characteristics of glaucoma. Endothelin–1 levels are increased in aqueous & vitreous humor in glaucoma patients and animal models of glaucoma. Whether the elevated ET–1 induces ECM remodeling resulting in pathological changes in the optic nerve head is still unknown. In the present study, the expression of MMPs and TIMPs in ET–1–activated astrocytes and the role of ERK–MAPK and PKC were determined. Methods: A zymography assay was used for quantifying the activity of MMP–2,3 and 9. Western Blot was employed to determine the expression of MMP–2, 3, 9 and TIMP–1, 2. Phosphorylation of ERK1/2 was detected by Western blot analysis. Results: ET–1 caused a rapid phosphorylation of ERK1/2, which could be blocked by treatment with U0126 (a MEK1/2 inhibitor), in both U373MG cells and hONA cells. ET–1 increased the expression and activity of MMP2, which could be blocked by U0126. U0126 blocked even basal expression as compared with vehicle–treated control. In hONAs, expression of MMP3 was not detectable in Western Blot, however, activity of MMP3 was seen using casein zymography. Blockade of ERK–MAPK by U0126 and PKC by chelerythrine increased the activity of MMP3. In U373MG cells, there was no detectable MMP3 by both zymography and Western Blot. In both cell types, treatment of ET–1 increased the expression of TIMP–1 and 2. ERK–MAPK blockade by U0126 not only abolished the ET–1 effects, but also lowered the basal level of expression of TIMP–1 and 2. Furthermore, there were no apparent differences in the profile of expression of MMPs and TIMPs in hONA cells form normal human and POAG patients. Conclusions: ET–1 activated phosphorylation of ERK1/2, which plays an important role in proliferation and reactivation for hONAs and U373MG astrocytoma cells. ET–1 also increased the expression of MMP2 and TIMP–1, 2. ERK–MAPK and PKC are involved in the regulation of remodeling of ECM in both cell types. Balance of MMPs/TIMPs may be important relative to ET–1 treatment. In future studies, the temporal and spatial regulation of MMPs and TIMPs induced by ET–1 will be investigated.
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