Proinflammatory Cytokines Down-Regulate Intestinal Selenoprotein P Biosynthesis Via NOS2 Induction

Selenoprotein P (SeP), serving as selenium transporter and extracellular antioxidant, is assumed to have a protective role in the gastrointestinal tract, which is particularly susceptible to oxidative damage. Decreased SeP mRNA levels have been found in colon cancer; however, information on the control of intestinal SeP biosynthesis is scarce. We analyzed SeP biosynthesis in human intestinal epithelial Caco-2 cells subject to differentiation from crypt- to villous-like enterocytes. In the course of Caco-2 cell differentiation, SeP mRNA expression and secretion increased concomitant with three regulators of SeP transcription: hepatocyte nuclear factor-4alpha, forkhead box class O1a, and peroxisomal proliferator-activated receptor-gamma coactivator 1alpha. Treatment of differentiated Caco-2 cells with the proinflammatory cytokines IL-1beta, TNF-alpha, and IFN-gamma caused a down-regulation of SeP biosynthesis, resulting from induction of nitric oxide synthase 2. These observations were corroborated by decreased SeP mRNA levels in the colon of dextran sodium sulfate-treated mice, an animal model of experimental colitis. We conclude that inflammation of the intestinal mucosa causes a decline in locally produced selenoprotein P in the colon that eventually may contribute to the emergence of inflammatory bowel disease-related colorectal cancer.