Background: Oligosaccharide structures and their alterations have important roles in modulating intestinal inflammation. N-Acetylglucosaminyltransferase V (GnT-V) is involved in the biosynthesis of N-acetylglucosamine (GlcNAc) by β1,6-branching on N-glycans and is induced in various pathologic processes, such as inflammation and regeneration. GnT-V alters host immune responses by inhibiting the functions of CD4(+) T cells and macrophages. The present study aimed to clarify the role of GnT-V in intestinal inflammation using GnT-V transgenic mice.
Methods: Colitis severity was compared between GnT-V transgenic mice and wild-type mice. β1,6-GlcNAc levels were investigated by phytohemagglutinin-L4 lectin blotting and flow cytometry. We investigated phagocytosis of macrophages by measuring the number of peritoneal-macrophage-ingested fluorescent latex beads by flow cytometry. Cytokine production in the culture supernatant of mononuclear cells from the spleen, mesenteric lymph nodes, and bone-marrow-derived macrophages was determined by enzyme-linked immunosorbent assay. Clodronate liposomes were intravenously injected to deplete macrophages in vivo. Chronic-colitis-associated tumorigenesis was assessed after 9 months of repeated administration of dextran sodium sulfate (DSS).
Results: DSS-induced colitis and colitis induced by trinitrobenzene sulfonic acid were markedly exacerbated in GnT-V transgenic mice compared with wild-type mice. Production of interleukin-10 and phagocytosis of macrophages were significantly impaired in GnT-V transgenic mice compared with wild-type mice. Clodronate liposome treatment to deplete macrophages blocked the exacerbation of DSS-induced colitis and impairment of interleukin-10 production in GnT-V transgenic mice. Chronic-colitis-associated tumorigenesis was significantly increased in GnT-V transgenic mice.
Conclusions: Overexpression of GnT-V exacerbated murine experimental colitis by inducing macrophage dysfunction, thereby enhancing colorectal tumorigenesis.
Keywords: Colitic cancer; Macrophage; N-Acetylglucosaminyltransferase V; Phagocytosis; Tumorigenesis.