title: Inhibition of the phosphoinositide 3-kinase pathway decreases innate resistance to lipopolysaccharide toxicity in TLR4 deficient mice.
abstract: BACKGROUND
  Upon lipopolysaccharide (LPS) stimulation, activation of both the Toll-like receptor 4 (TLR4) and phosphoinositide 3-kinase (PI3K) pathways serves to balance proinflammatory and anti-inflammatory responses. Although the antagonist to TLR4 represents an emerging promising target for the treatment of sepsis; however, the role of the PI3K pathway under TLR4-null conditions is not well understood. This goal of this study was to investigate the effect of inhibition of PI3K on innate resistance to LPS toxicity in a murine model.
  
  
  RESULTS
  The overall survival of the cohorts receiving intraperitoneal injections of 100, 500, or 1000 μg LPS from Escherichia coli serotype 026:B6 after 7 d was 100%, 10%, and 10%, respectively. In contrast, no mortality was noted after 500-μg LPS injection in Tlr4-/- mice. When the PI3K inhibitor LY294002 was injected (1 mg/25 g body weight) 1 h prior to the administration of LPS, the overall survival of the Tlr4-/- mice was 30%. In the Tlr4-/- mice, the LPS injection induced no NF-κB activation but an increased Akt phosphorylation in the lung and liver, when compared to that of the C57BL/6 mice. Injection of 500 μg LPS led to a significant induction in O₂⁻ detected by electron paramagnetic resonance (EPR) spin trapping spectroscopy in the lung and liver at 3 and 6 h in C57BL/6 but not Tlr4-/- mice. Addition of LY294002 only significantly increased the O₂⁻ level in the lung and liver of the Tlr4-/- mice but not in the C57BL/6 mice following 500-μg LPS injection. In addition, the serum IL-1β and IL-2 levels were more elevated in C57BL/6 mice than in Tlr4-/- mice. Notably, IL-1β and IL-2 were significantly increased in Tlr4-/- mice but not in the C57BL/6 mice when the PI3K pathway was inhibited by LY294002 prior to LPS injection.
  
  
  CONCLUSIONS
  In this study, we demonstrate that innate resistance to LPS toxicity in Tlr4-/- mice is impaired by inhibition of the PI3K pathway, with a corresponding increase in mortality and production of tissue O₂⁻ and inflammatory cytokines.
authors.forename: Johnson Chia-Shen
authors.initials: JC
authors.lastname: Yang
authors.forename: Shao-Chun
authors.initials: SC
authors.lastname: Wu
authors.forename: Cheng-Shyuan
authors.initials: CS
authors.lastname: Rau
authors.forename: Tsu-Hsiang
authors.initials: TH
authors.lastname: Lu
authors.forename: Yi-Chan
authors.initials: YC
authors.lastname: Wu
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Lin
authors.forename: Siou-Ling
authors.initials: SL
authors.lastname: Tzeng
authors.forename: Chia-Jung
authors.initials: CJ
authors.lastname: Wu
authors.affiliation: Department of Plastic and Reconstructive Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, No,123, Ta-Pei Road, Niao-Sung District, Kaohsiung City 833, Taiwan. m93chinghua@gmail.com.
authors.forename: Ching-Hua
authors.initials: CH
authors.lastname: Hsieh
mesh_terms: D000818:Animals; D006801:Humans; D053583:Interleukin-1beta / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000633:toxicity*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000235:genetics*
chemical_list: D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010100:Oxygen; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D051197:Toll-Like Receptor 4; C493487:Tlr4 protein, mouse