title: Importance of Toll-like receptor 2 in mitochondrial dysfunction during polymicrobial sepsis.
abstract: BACKGROUND
  Toll-like receptor 2 (TLR2) contributes to sepsis pathogenesis such as deleterious systemic inflammation, cardiac dysfunction, and high mortality in animal studies. Mitochondrial dysfunction is a key molecular event that is associated with organ injury in sepsis. The role of TLR2 in sepsis-induced mitochondrial dysfunction remains unclear.
  
  
  METHODS
  Intracellular hydrogen peroxide (H2O2), mitochondrial superoxide (O2), mitochondrial membrane potential (ΔΨm), and intracellular adenosine triphosphate (ATP) were measured in peritoneal leukocytes. A mouse model of polymicrobial sepsis was generated by cecum ligation and puncture (CLP). Wild-type and TLR2-deficient (TLR2) mice were subjected to sham or CLP. Mitochondrial functions including reactive oxygen species (ROS), ΔΨm, intracellular ATP, and complex III activity were measured.
  
  
  RESULTS
  TLR2/1 activation by Pam3Cys enhanced intracellular H2O2 and mitochondrial O2 production in leukocytes, but had no effect on mitochondrial ΔΨm and ATP production. The effect was specific for TLR2/1 as TLR3 or TLR9 ligands did not induce ROS production. Polymicrobial sepsis induced mitochondrial dysfunction in leukocytes, as demonstrated by increased H2O2 and mitochondrial O2- production (CLP vs. sham; H2O2: 3,173±498, n=5 vs. 557±38, n=4; O2-: 707±66, n=35 vs. 485±35, n=17, mean fluorescence intensity, mean±SEM), attenuated complex III activity (13±2, n=16 vs. 30±3, n=7, millioptical densities/min), loss of mitochondrial ΔΨm, and depletion of intracellular ATP (33±6, n=11 vs. 296±29, n=4, nmol/mg protein). In comparison, there was significant improvement in mitochondrial function in septic TLR2-/- mice as evidenced by attenuated mitochondrial ROS production, better-maintained mitochondrial ΔΨm, and higher cellular ATP production.
  
  
  CONCLUSIONS
  TLR2 signaling plays a critical role in mediating mitochondrial dysfunction in peritoneal leukocytes during polymicrobial sepsis.
authors.affiliation: From the Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts (Y.G., L.Z., Y.F., D.L., J.C., W.C.); and Key Laboratory for Major Obstetric Diseases, Institute of Gynecology and Obstetrics, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China (Y.G., D.C.).
authors.forename: Yu
authors.initials: Y
authors.lastname: Gong
authors.forename: Lin
authors.initials: L
authors.lastname: Zou
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.forename: Jiayan
authors.initials: J
authors.lastname: Cai
authors.forename: Dunjin
authors.initials: D
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Chao
mesh_terms: D000818:Animals; D001202:Ascitic Fluid / Q000473:pathology; D051546:Cyclooxygenase 2 / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D006609:High Mobility Group Proteins / Q000235:genetics; D007962:Leukocytes; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D028361:Mitochondrial Diseases / Q000209:etiology / Q000503:physiopathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D018805:Sepsis / Q000150:complications / Q000503:physiopathology*; D051195:Toll-Like Receptor 2 / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D017382:Reactive Oxygen Species; C081930:Tfam protein, mouse; D051195:Toll-Like Receptor 2; D051546:Cyclooxygenase 2