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D. Wasilewski, J. Cui, R.E. Smith, L. Rife, M. Mahmoud, S.C. Yiu; -Melanocyte-stimulating Hormone (MSH) as an Inhibitor of Traumatic Ocular Inflammation in Rats . Invest. Ophthalmol. Vis. Sci. 2003;44(13):343.
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Purpose: α-Melanocyte-stimulating hormone (α-MSH) is an endogenous neuroimmunomodulatory peptide that inhibits all major forms of experimental inflammation. We studied whether it can reduce the inflammatory reaction after induced ocular trauma in rats. Methods: Fifty-seven male Sprague Dawley rats, weighing 120g to 196g, were divided into 6 groups. All rats received a non penetrating 2 mm-long corneo-limbal incision, followed by paracentesis and aspiration of aqueous humor. Topical α-MSH (10 µL) was applied every 8 hours. Five concentrations were used (10-8M, 10-7M, 10-6M, 10-5M and 10-4M ), with each of five groups receiving a different concentration and the control group receiving balanced salt solution. Twenty-four hours after injury, we measured the protein level using the Bio-Rad reagent, counted total inflammatory cells using a hemacytometer, and measured clinical inflammation, on a scale of 1 to 4, by observing conjunctival hyperemia and edema through the operating microscope. Additional evaluation was done morphometrically using a digital camera. The aspirated aqueous humor was kept on ice and samples analyzed immediately after the study. Results: Topical α-MSH at all five concentrations reduced clinical inflammation, protein levels and total inflammatory cells in the aqueous humor. α-MSH reduced the concentration of protein and inflammatory cells in the anterior chamber in a dose-response manner. The EC50 of MSH was 12.4 nM and 17.7 nM for the inhibition of protein and inflammatory cells, respectively. The mean reduction of clinical inflammation was 75.5% in the treatment groups, versus 59.3% in the control group ( P<0.05 ). Conclusions: Topical α-MSH reduced the total number of inflammatory cells and the protein levels in aqueous humor, and it reduced the clinical signs of acute ocular inflammation. The results suggest that topical α-MSH might be a useful agent against acute ocular inflammatory reaction.
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