title: Discharge of solubilized and Dectin-1-reactive β-glucan from macrophage cells phagocytizing insoluble β-glucan particles: involvement of reactive oxygen species (ROS)-driven degradation.
abstract: Phagocytes engulf pathogenic microbes, kill them and degrade their cellular macromolecules by hydrolytic enzymes in phagolysosomes. However, such enzymes are unable to degrade some microbial polysaccharides, and fate of such indigestible polysaccharides in phagocytes remains uncertain. Using the extracellular domain of Dectin-1 as β-glucan-specific probes, we succeeded in detection of soluble and Dectin-1-reactive β-glucan discharged from mouse RAW 264.7 and human THP-1 macrophage cell lines as well as mouse peritoneal macrophages, which had phagocytized insoluble β-glucan particles. The RAW 264.7 cell culture-supernatant containing the discharged β-glucan stimulated naïve RAW 264.7 cells, resulting in the induction of cytokine expression. Such discharge of Dectin-1-reactive β-glucan from macrophage cells was inhibited by either NADPH oxidase inhibitors (apocynin and diphenylene iodonium) or radical scavengers (N-acetyl cysteine and MCI-186). Moreover, reactive oxygen species (ROS) produced by a Cu(2+)/ascorbic acid system solubilized insoluble β-glucan particles in vitro, and a part of the solubilized β-glucan was Dectin-1 reactive and biologically active in macrophage activation. The soluble and biologically active β-glucan was degraded further during prolonged exposure to ROS. These results suggest that degraded but Dectin-1-reactive β-glucan is discharged from macrophage cells phagocytizing insoluble β-glucan particles and stimulates not only themselves again but also the other naïve phagocytes, leading to the effective elimination of infecting microbes and the ultimate breakdown and inactivation of metabolically resistant β-glucan.
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Hino
authors.forename: Aki
authors.initials: A
authors.lastname: Kito
authors.forename: Remi
authors.initials: R
authors.lastname: Yokoshima
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sugino
authors.forename: Kenzi
authors.initials: K
authors.lastname: Oshima
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Morita
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Okajima
authors.forename: Daita
authors.initials: D
authors.lastname: Nadano
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Matsuda
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000983:Antipyrine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D000077553:Edaravone; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D037181:Lectins, C-Type / Q000276:immunology*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D010587:Phagocytosis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012995:Solubility; D047071:beta-Glucans / Q000032:analysis / Q000276:immunology*; D000099181:Dectin-1
chemical_list: D000098:Acetophenones; D000111:Acetylcysteine; D000983:Antipyrine; D000077553:Edaravone; D037181:Lectins, C-Type; D017382:Reactive Oxygen Species; D047071:beta-Glucans; D000099181:Dectin-1; C056165:acetovanillone