title: Mechanisms of endotoxin tolerance in human intestinal microvascular endothelial cells.
abstract: Lipopolysaccharide (endotoxin) tolerance is well described in monocytes and macrophages, but is less well characterized in endothelial cells. Because intestinal microvascular endothelial cells exhibit a strong immune response to LPS challenge and play a critical regulatory role in gut inflammation, we sought to characterize the activation response of these cells to repeated LPS exposure. Primary cultures of human intestinal microvascular endothelial cells (HIMEC) were stimulated with LPS over 6-60 h and activation was assessed using U937 leukocyte adhesion, expression of E-selectin, ICAM-1, VCAM-1, IL-6, IL-8, manganese superoxide dismutase, HLA-DR, and CD86. Effect of repeat LPS stimulation on HIMEC NF-kappaB and mitogen-activated protein kinase (MAPK) activation, generation of superoxide anion, and Toll-like receptor 4 expression was characterized. LPS pretreatment of HIMEC for 24-48 h significantly decreased leukocyte adhesion after subsequent LPS stimulation. LPS pretreatment inhibited expression of E-selectin, VCAM-1, IL-6, and CD86, while ICAM-1, IL-8, and HLA-DR were not altered. Manganese superoxide dismutase expression increased with repeated LPS stimulation, with a reduction in intracellular superoxide. NF-kappaB activation was transiently inhibited by LPS pretreatment for 6 h, but not at later time points. In contrast, p44/42 MAPK, p38 MAPK, and c-Jun N-terminal kinase activation demonstrated inhibition by LPS pretreatment 24 or 48 h prior. Toll-like receptor 4 expression on HIMEC was not altered by LPS. HIMEC exhibit endotoxin tolerance after repeat LPS exposure in vitro, characterized by diminished activation and intracellular superoxide anion concentration, and reduced leukocyte adhesion. HIMEC possess specific mechanisms of immunoregulatory hyporesponsiveness to repeated LPS exposure.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Surgery, Milwaukee Veterans Administration Medical Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ogawa
authors.forename: Parvaneh
authors.initials: P
authors.lastname: Rafiee
authors.forename: Jan
authors.initials: J
authors.lastname: Heidemann
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Fisher
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Johnson
authors.forename: Mary F
authors.initials: MF
authors.lastname: Otterson
authors.forename: Balaraman
authors.initials: B
authors.lastname: Kalyanaraman
authors.forename: Kirkwood A
authors.initials: KA
authors.lastname: Pritchard
authors.forename: David G
authors.initials: DG
authors.lastname: Binion
mesh_terms: D000276:Adjuvants, Immunologic / Q000633:toxicity; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001666:Binding Sites, Antibody; D001667:Binding, Competitive / Q000276:immunology; D002448:Cell Adhesion / Q000276:immunology; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000276:immunology; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D004306:Dose-Response Relationship, Immunologic; D004730:Endothelium, Vascular / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007108:Immune Tolerance; D018928:Immunity, Mucosal / Q000276:immunology; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D007413:Intestinal Mucosa / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology* / Q000633:toxicity*; D020935:MAP Kinase Signaling System / Q000276:immunology; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D008833:Microcirculation / Q000201:enzymology / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000276:immunology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000096:biosynthesis; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D020298:U937 Cells
chemical_list: D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D016207:Cytokines; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D013481:Superoxides