Exocytotic Secretion of Toxins from Macrophages Infected with Escherichia coli O157.

DOI Web Site Web Site PubMed 55 References
  • Shimada Osamu
    Department of Anatomy, Yamanashi Medical University, Tamaho, Yamanashi 409-3821, Japan Department of Anatomy, Gunma University School of Medicine, Maebashi, Gunma 371-8511, Japan
  • Ishikawa Harunori
    Department of Anatomy, Gunma University School of Medicine, Maebashi, Gunma 371-8511, Japan
  • Tosaka-Shimada Hisami
    Department of Anatomy, Gunma University School of Medicine, Maebashi, Gunma 371-8511, Japan
  • Atsumi Saoko
    Department of Anatomy, Yamanashi Medical University, Tamaho, Yamanashi 409-3821, Japan

Search this article

Abstract

This study examined whether macrophages are involved in the development of pathogenicity in Shiga-like toxin (SLT)-producing enterhemorrhagic Escherichia coli (EHEC) O157 : H7. Macrophages were infected with the bacteria, after which the macrophage culture medium showed a clear increase in toxicity in rats in vivo as well as in rat aortic endothelial cells in vitro. The increased toxicity resulted mainly from a rapid increase in the concentrations of SLT type I (SLT-I) and type II(SLT-II) and partly from an increase in concentrations of the proinflammatory cytokines, tumor necrosis factor α (TNFα) and interleukin-1(IL-1), in the culture medium. Most of the EHEC O157 added to the macrophage culture were quickly incorporated to form phagosomes, which then fused with lysosomes to become phagolysosomes. During this intracellular digestion process, the EHEC O157 remained alive for about 15 min, and continued synthesizing and secreting the toxins SLT-1 and SLT-II. The bacteria were then killed and digested in the phagolysosomes with significant amounts of the toxins retained. Subsequently, the contents of the phagolysosomes were exocytotically secreted from the macrophage cell membrane into the surrounding culture medium. Such a sequence of events in macrophages may occur in vivo, suggesting the active involvement of macrophages in the rapid increase in pathogenicity, such as seen in the onset of hemolytic-uremic syndrome (HUS) in patients infected with EHEC O157. The exocytotic secretion is considered to be one of the most basic cellular functions in macrophages.

Journal

References(55)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top