Modulation of the lipopolysaccharide receptor complex (CD14, TLR4, MD-2) and toll-like receptor 2 in systemic inflammatory response syndrome-positive patients with and without infection: relationship to tolerance.
The lipopolysaccharide (LPS) receptor complex consists of two interacting receptors (CD14 and TLR4) and an associated protein (MD-2). When engaged by LPS, as in gram-negative infection, this complex transduces a signal detected by MyD88 and passed onward by a cascade of the IRAKs, TRAF6, and NIK, resulting in activation of NF-kappaB. A similar cascade, mediated by TLR2, occurs with ligands derived from gram-positive bacteria. In vitro studies of human monocytes have shown that TLR4 mRNA is paradoxically upregulated in response to "tolerizing" doses of LPS. This study evaluated changes in vivo of blood monocyte CD14, TLR4, TLR2, and MD-2 mRNA by reverse transcription followed by real-time polymerase chain reaction in surgical intensive care unit patients and in normal controls. In addition cell-surface receptor expression of TLR2, TLR4, and CD14 was assessed by flow cytometry in patients and normal controls. Inflammation-induced acute tolerance to LPS was evaluated by ex vivo whole blood tumor necrosis factor alpha production and was significantly reduced in patients compared with controls, confirming LPS hyporesponsiveness. Monocyte mRNA and cell-surface receptor expression of TLR4 were increased 2.4-fold (P < 0.05) and 1.7-fold (P <.002), respectively, in patients compared with normal controls. Monocyte TLR2 mRNA, MD-2 mRNA and CD14 and TLR2 cell-surface expression were not significantly changed compared with controls. The present study suggests that the acute inflammatory condition associated with peripheral cellular LPS hyporesponsiveness is neither specific to prior infectious challenge nor can be ascribed to significant alterations in expression of the cell-surface LPS binding complex proteins.
Calvano
Jacqueline E
JE
Division of Surgical Sciences, Department of Surgery, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey 08903, USA.
Agnese
Doreen M
DM
Um
John Y
JY
Goshima
Masahiro
M
Singhal
Ritu
R
Coyle
Susette M
SM
Reddell
Michael T
MT
Kumar
Ashwini
A
Calvano
Steve E
SE
Lowry
Stephen F
SF
D000954:Antigens, Surface / Q000235:genetics; D001424:Bacterial Infections / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D016905:Gram-Negative Bacterial Infections / Q000378:metabolism / Q000503:physiopathology; D016908:Gram-Positive Bacterial Infections / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D009000:Monocytes / Q000737:chemistry / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D018746:Systemic Inflammatory Response Syndrome / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000378:metabolism
D000954:Antigens, Surface; C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha