NOS2 and colitis: In experimental colitis in rats, melatonin has been shown to reduce colon injury by influencing numerous events, including the enzymatic activities of matrix metalloproteinase (MMP)-9 and caspase-3, by suppressing the activities of cyclooxygenase (COX)-2 and iNOS, inhibiting the expression of nuclear factor-κB (NF-κB), and acting as a radical scavenger (25,26).