S1741 Milk Fat Globule EGF-8 Attenuates Intestinal Inflammation in Murine Experimental Colitis Via Inhibition of NF-κB Activation

Abstract

(Background and Aim) Milk fat globule epidermal growth factor-8 (MFG-E8) promotes efficient phagocytic clearance of apoptotic cells to maintain normal tissue homeostasis and modulate immune responses. Colitis is characterized by severe colonic inflammation with marked elevation of proinflammatory responses through involvement of the major transcription factor NF-κB. We investigated the role of MFG-E8 to improve the pathogenesis of murine experimental colitis. (Materials and Methods) Experimental acute colitis was induced in 7-week-old male BALB/c mice by giving a 2.5% dextran sulfate sodium (DSS) solution for 7 days or a single dose intrarectal administration of trinitrobenzene sulfonic acid (TNBS) (100 μl, 100 mg/kg) dissolved in 40% ethanol. MFG-E8 expression in the distal colon was checked during injury and healing stages. Further, murine wild-type and RGD mutant MFGE8 were purified with a mammalian expression system, and the functional effects of purified MFG-E8 on peritoneal macrophages were investigated based on the phagocytic potential of apoptotic thymocytes. Recombinant proteins were injected into the tail veins of mice with colitis induced by DSS or TNBS, after which a disease activity index (body weight, colon length, and histological scores), and pro-inflammatory cytokine and myeloperoxidase (MPO) profiles in inflamed tissues were determined. The In Vitro effects of recombinant MFG-E8 on inhibition of NF-κB and pro-inflammatory cytokine production were also investigated using luciferase, an electrophoreticmobility shift assay (EMSA), and an enzyme immunoassay. (Results)MFG-E8 was elevated during the healing stage after stopping theDSS administration. An increased phagocytic potential of apoptotic thymocytes was found, which indicated the functional efficiency of the purified recombinant MFG-E8. In the experimental colitis model mice, treatment with the wild-type, but not mutant MFG-E8, significantly inhibited weight loss and shortening of the colon induced by DSS or TNBS administration. In addition, histological examinations showed that lamina propria infiltration by polymorphonuclear and mononuclear cells, as well as crypt epithelial damage were markedly decreased in the wildtype recombinant MFG-E8-treated mice. MFG-E8 treatment also significantly decreased the contents of IL-1β, TNF-α, and MPO in colonic tissues of DSSand TNBS-induced colitis mice. In Vitro, transcription factor NF-κB and its regulated pro-inflammatory cytokines were inhibited in MFG-E8 treated cultured macrophages. (Conclusion) Our findings suggest that MFG-E8 is a potent therapeutic agent to attenuate intestinal inflammation in murine experimental colitis.