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J.K. Krady, S.W. Levison; The Role of Microglial Reactivity in Diabetic Retinopathy . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1721.
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© ARVO (1962-2015); The Authors (2016-present)
To test the hypothesis that drugs that inhibit microglial activation, such as VP025, can reduce the increased expression of proinflammatory mediators observed early in the course of diabetic retinopathy.
Primary microglial cultures were grown in a chemically defined medium. Microglial cultures were either left untreated, stimulated with 500ng/ml LPS, or pretreated with VP025 for 2 hours prior to LPS stimulation. Eight hours following stimulation supernatants from each group were isolated and used in ELISA assays to measure secreted TNFα and IL–10 levels. Rats were given a single, i.p. dose of streptozotocin (STZ) to induce diabetes. Rats receiving VP025 were given daily injections for 6 days beginning on the same day as STZ treatment. Injections were given i.m. (0.15ml at a concentration of 1.2x107 vesicles/ml). Rats were sacrificed after 2 weeks, and mRNA was isolated from the retinas, reverse transcribed and used in real–time pcr analysis.
In vitro assays of primary microglial cultures demonstrated that VP025 could inhibit the secretion of TNFα and IL–10 observed when microglia are stimulated with LPS, suggesting that VP025 can inhibit microglial activation. RT–pcr analysis demonstrated an increase in the mRNA expression of the inflammatory mediators TNFα, IL–1ß, IL–6 and MCP–1 in the retina 2 weeks following STZ–induced diabetes. IL–1ß¸ mRNA levels increased 1.8 fold, TNFα mRNA levels increased 2 fold, IL–6 mRNA levels increased 2.5 fold and mRNA levels for MCP–1 increased 2.4 fold. In contrast diabetes led to a 50% decrease in mRNA expression in the rat retina for the anti–inflammatory cytokines IL–10 and TGFß2. For the proinflammatory mediators VP025 treatment of the diabetic rats reversed the increased mRNA expression levels seen in the retinas of untreated diabetic rats. Treatment of the diabetic rats with VP025 also increased the mRNA expression of the anti–inflammatory mediators to those seen in the retinas of control rats.
Inflammation has been implicated in the pathogenesis of diabetic retinopathy. In support of this hypothesis, mRNAs for a number of inflammatory mediators are elevated in the retinas of rats as early as 2 weeks following STZ induced diabetes which correlate with increased microglial activation immunohistochemically, Drugs that reduce microglial activation, such as VP025, alleviate inflammation within the retina, and thus may likely impede the progression of diabetic retinopathy.
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