title: Toll-like receptor-4 signaling mediates pulmonary neutrophil sequestration in response to gram-positive bacterial enterotoxin.
abstract: BACKGROUND
  Toll-like receptors (TLRs) serve as mediators of innate immune responses to pathogen-associated molecular patterns (PAMPs) which include lipopolysaccharide (LPS) and staphylococcal enterotoxin B (SEB). TLR-4 is thought to act as the primary effector of LPS recognition and TLR-2 is thought to mediate responses to Gram-positive bacterial proteins. Chemokines such as macrophage inflammatory protein (MIP-2) are peptides that are responsible for lung neutrophil (PMN) sequestration following an infectious or inflammatory insult. Given the Gram-positive origin of SEB, we hypothesized that mice with altered TLR-4 signaling would exhibit no difference in lung PMN sequestration following SEB when compared to wild-type mice.
  
  
  METHODS
  Wild-type and TLR-4 mutant mice were administered intratracheal saline, LPS (Escherichia coli 0.1 mg/kg), or SEB (1 mg/kg). After 24 h, lung PMN accumulation was determined by myeloperoxidase (MPO) assay and bronchoalveolar lavage fluid cell count (BALfcc). Total lung and BALf MIP-2 was measured by enzyme-linked immunosorbent assay.
  
  
  RESULTS
  There was an increase in lung PMN accumulation (by both MPO and BALfcc) and MIP-2 following LPS and SEB in wild-type mice compared to saline-treated controls. In contrast, TLR-4 mice failed to exhibit an increase in lung MIP-2 or PMN accumulation following either LPS or SEB compared to wild-type mice.
  
  
  CONCLUSIONS
  TLR-4 mutant mice are unresponsive to intratracheal LPS. SEB elicited an increase in lung MIP-2 and PMN accumulation in wild-type mice. However, TLR-4 mutant mice were protected from this process. This suggests that TLR-4 signaling may mediate the responses to other PAMPs in addition to LPS.
authors.affiliation: Department of Surgery, University of Colorado Health Sciences Center and Veterans Affairs Hospital, Denver, USA.
authors.forename: Casey M
authors.initials: CM
authors.lastname: Calkins
authors.forename: Katherine
authors.initials: K
authors.lastname: Barsness
authors.forename: Denis D
authors.initials: DD
authors.lastname: Bensard
authors.forename: Andres
authors.initials: A
authors.lastname: Vasquez-Torres
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Raeburn
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Meng
authors.forename: Robert C
authors.initials: RC
authors.lastname: McIntyre
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D054426:Chemokine CXCL2; D029721:Drosophila Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008168:Lung / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D015846:Monokines / Q000032:analysis / Q000378:metabolism; D009504:Neutrophils / Q000473:pathology*; D009195:Peroxidase / Q000032:analysis; D011650:Pulmonary Alveoli / Q000473:pathology; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014132:Trachea
chemical_list: D054426:Chemokine CXCL2; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D015846:Monokines; D011956:Receptors, Cell Surface; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D009195:Peroxidase