Melanocortins are comparable to corticosteroids as inhibitors of traumatic ocular inflammation in rabbits

Background: Melanocyte-stimulating hormone (MSH) is a known anti-inflammatory agent and we investigated whether it reduces the inflammatory reaction following ocular surgery. Methods: Rabbits received a perforating corneo-limbal cut. Treatment involved topical (10^-8M) or intramuscular (50 mg/kg/day) MSH, topical steroids or saline. The parameters studied were hyperemia, edema, aqueous protein levels and the number of inflammatory cells in the aqueous, as well as their number determined histologically in the injured cornea. Each parameter was assessed at 24 h post injury. Results: Topically and systematically applied MSH reduced edema to levels 60% and 76%, respectively, of those observed in operated saline-treated eyes (P<0.001), and their efficacy was comparable to that of topical steroids. The decrease in hyperemia brought about by MSH was more pronounced than that produced by steroids. Aqueous protein levels were reduced by a similar degree in the steroid- and MSH-treated eyes as in the saline group (P<0.001 for each treatment group); In MSH- and steroid-treated eyes the number of inflammatory cells in the aqueous was reduced by 80% and 50%, respectively. Conclusion: We demonstrated that MSH reduced the clinical signs of ocular inflammation, curtailed blood-aqueous barrier (BAB) disruption, and reduced aqueous inflammatory cell number. The efficacy of MSH applied systemically or topically was similar to that of steroids in reducing clinical signs of trauma, but MSH efficacy in maintaining BAB integrity surpassed that of steroids. We suggest that the melanocortins might be a useful anti-inflammatory agents in ocular trauma.