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Y Nakai, A Sawada, MZ Karim, K Kawase, K-I Takahashi, Y Okano, T Yamamoto; A Long Term Effect of Increased IOP on Alteration of HSP-70 mRNA Expression using a Rat Glaucoma Model . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2191.
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Purpose: Glaucoma is characterized by selective retinal ganglion cell loss, typical optic nerve damage and specific pattern of visual field defect. Increased intraocular pressure is one of the most important risk factors in triggering and progression of glaucoma. But the precise mechanism of the glaucomatous change has not been determined yet. HSP-70, a member of heat-shock proteins, is induced during preconditioning stress and is known to be responsible for the cell survival from the various metabolic stresses such as ischemia and hyperthermia in neuronal tissues. In this study, we employed a rat glaucoma model and performed semi-quantitative RT-PCR to determine the alteration of the expression level of HSP-70 mRNA in the retina. Methods: The right eye of each rat was used to make the glaucoma model. To make the glaucoma model, cauterization of three episcleral vessels was carried out. The left eye of each rat was served as control. Then the retina was collected to extract mRNA 4, 14, 30 and 90 days after the cauterization. Thereafter RT-PCR was performed to detect HSP-70. Results: In the cauterized eye, IOP was moderately elevated measured by a pneumatonometer and no additional cauterization was necessary throughout the experimental period. The amount of mRNA encoding HSP-70 extracted from the retina of the cauterized eyes collected between 4 days and 30 days after the treatment was increased compared with the control eyes. On the other hand, the expression level of HSP-70 mRNA was decreased in the sample collected 90 days after the cauterization. Conclusion: In the rat eye, the expression of mRNA of HSP-70 was increased by moderately elevated IOP up to one month period. But the eyes exposed to increased IOP for 3 months showed decrease in the amount of the HSP-70 mRNA. This finding suggested that the decreased level of HSP-70 in the retina exposed to the chronically increased IOP could be related to the lack of neuroprotective effect of HSP-70 and subsequent progression of the glaucomatous neuronal degeneration in the eye.
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