NOS2 and colitis: In the acute phase of dextran sulfate sodium (DSS)-induced colitis, one study reported exacerbated colitis in OPN-deficient mice compared to wild-type mice with reduced nitric oxide synthase (NOS) expression and impaired phagocytic activity in intestinal macrophages, whereas another study reported attenuated colitis with reduced macrophage migration in the inflamed colonic tissues of OPN-deficient mice [11, 17].