title: Molecular mechanisms of macrophage activation and deactivation by lipopolysaccharide: roles of the receptor complex.
abstract: Bacterial lipopolysaccharide (LPS), the major structural component of the outer wall of Gram-negative bacteria, is a potent activator of macrophages. Activated macrophages produce a variety of inflammatory cytokines. Excessive production of cytokines in response to LPS is regarded as the cause of septic shock. On the other hand, macrophages exposed to suboptimal doses of LPS are rendered tolerant to subsequent exposure to LPS and manifest a profoundly altered response to LPS. Increasing evidence suggests that monocytic cells from patients with sepsis and septic shock survivors have characteristics of LPS tolerance. Thus, an understanding of the molecular mechanisms underlying activation and deactivation of macrophages in response to LPS is important for the development of therapeutics for septic shock and the treatment of septic shock survivors. Over the past several years, significant progress has been made in identifying and characterizing several key molecules and signal pathways involved in the regulation of macrophage functions by LPS. In this paper, we summarize the current findings of the functions of the LPS receptor complex, which is composed of CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation protein-2 (MD-2), and the signal pathways of this LPS receptor complex with regard to both activation and deactivation of macrophages by LPS. In addition, recent therapeutic approaches for septic shock targeting the LPS receptor complex are described.
authors: Japanese Red Cross, Hokkaido Red Cross Blood Center, Yamanote 2-2, Nishi-ku, Sapporo 063-0002, Japan. fujihara@hokkaido.bc.jrc.or.jp
authors: Mitsuhiro
authors: M
authors: Fujihara
authors: Masashi
authors: M
authors: Muroi
authors: Ken-ichi
authors: K
authors: Tanamoto
authors: Tsuneo
authors: T
authors: Suzuki
authors: Hiroshi
authors: H
authors: Azuma
authors: Hisami
authors: H
authors: Ikeda
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007108:Immune Tolerance; D008050:Lipid A / Q000037:antagonists & inhibitors; D018950:Lipopolysaccharide Receptors / Q000276:immunology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism*; D051218:Lymphocyte Antigen 96; D008262:Macrophage Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism*; D012772:Shock, Septic / Q000188:drug therapy / Q000276:immunology; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D000954:Antigens, Surface; C495377:LY96 protein, human; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors