The effect of melanin on the proteolytic potential of blood under alkali esophageal burn

Caustic esophageal burns are among serious medical problems of global significance. Due to a key role in biological processes proteolytic enzymes actively involved in the pathological mechanisms underpinning the development and progression of burn-related complications. Since melanin possesses a broad spectrum of biological activities we have investigated whether this compound can influence the proteolytic activity and level of proteinase inhibitors in the blood of rats with an alkali esophageal burn. Alkaline esophageal burns, which correspond to the first and second degree of burn, were induced by 10% and 20% NaOH, respectively. White, nonlinear, immature (4 weeks old) rats were used in the experiment. Total proteolytic activity was measured using casein as a substrate. The activities of α1- antitrypsin and α2-macroglobulin were measured considering the degree of inhibition of hydrolysis of N-benzoyl-L-arginineethyl ester. The fraction of serine proteinases was obtained by affinity chromatography on a benzamidine sepharose column. The qualitative composition of serine proteinases fraction was analyzed by zymography technique. According to the data obtained, the pathogenesis of alkaline esophageal burn is accompanied by a significant increase in the total proteolytic activity, activity of serine proteinases, and activity of α1-antitrypsin and α2-macroglobulin compared with the control rats. The present results clearly indicated that melanin is able to normalize the proteolytic homeostasis by affecting the activity of serine proteinases and the level of proteinase inhibitors in the plasma of rats with alkali esophageal burns.