The role of cyclooxygenase inhibition in the effect of α-melanocyte-stimulating hormone on reactive oxygen species production by rat peritoneal neutrophils

Abstract The effect of α -MSH on reactive oxygen species (ROS) production by rat peritoneal neutrophils and the effect of cyclooxygenase (COX) inhibition were investigated using the chemiluminescence (CL) technique. Cells were obtained by peritoneal lavage 4 h after administration of oyster glycogen to rats and were stimulated with lipopolysaccharide (LPS) from Salmonella enderitidis and phorbol 12-myristate 13-acetate (PMA). The increasing concentrations of α -MSH (10 –12 –10 –6  M) were added to stimulated cells alone or along with the COX inhibitors indomethacin, ketorolac or nimesulide (10 −8 –10 −5  M). Luminol and lucigenin CL levels were significantly increased in cells stimulated with LPS and PMA compared to unstimulated ones. α -MSH significantly reduced lucigenin CL values and this effect was completely reversed in the presence of indomethacin (10 −8 and 10 −7  M). In conclusion, α -MSH inhibits the production of superoxide radicals by activated rat peritoneal neutrophils and COX contributes to this effect.