title: Complement Factor B Production in Renal Tubular Cells and Its Role in Sodium Transporter Expression During Polymicrobial Sepsis.
abstract: OBJECTIVE
  Toll-like receptors and complement are two components of the innate immunity. Complement factor B is essential for the alternative pathway of complement activation. We have recently reported that complement factor B is significantly up-regulated in the kidney and may contribute to acute tubular injury in an animal model of sepsis. This study investigates the mechanisms responsible for the complement factor B up-regulation and its role in sodium transporter expression in tubular cells during sepsis.
  
  
  METHODS
  Animal study.
  
  
  METHODS
  Laboratory investigation.
  
  
  METHODS
  C57BL/6 J wild-type, complement factor B(-/-), and Nfkb1(tm1Bal) p50(-/-) mice.
  
  
  METHODS
  Human proximal tubular cells and mouse tubular epithelial cells were stimulated with Toll-like receptor agonists. Bay 11-7082 was used to block nuclear factor-κB pathway. Alternative pathway activation was detected by C3 zymosan deposition. Polymicrobial sepsis was created by cecal ligation and puncture. Sodium transporter gene expression was determined by quantitative reverse transcriptase-polymerase chain reaction.
  
  
  RESULTS
  The agonists for Toll-like receptor 4 (lipopolysaccharide) or Toll-like receptor 3 (polyinosinic-polycytidylic acid) induced a marked increase in complement factor B expression in human proximal tubular cells and mouse tubular epithelial cells both at gene and protein levels. The Toll-like receptor 1/2 agonist, Pam3cys, induced complement factor B production only in human proximal tubular cells, not in mouse tubular epithelial cells. The Toll-like receptor 9 ligand, CpG oligodeoxynucleotides failed to induce complement factor B production either in human proximal tubular cells or in mouse tubular epithelial cells. Lipopolysaccharide/polyinosinic-polycytidylic acid-induced complement factor B up-regulation was blocked by Bay 11-7082, a potent inhibitor of nuclear factor-κB signaling, and in mouse tubular epithelial cells deficient in p50 subunit of nuclear factor-κB. Media from the lipopolysaccharide-treated mouse tubular epithelial cell cultures contained de novo synthesized complement factor B and led to functional alternative pathway activation. In a cecal ligation and puncture model, wild-type septic mice had down-regulated expression of sodium transporters in the kidney compared with the sham. In comparison, complement factor B mice or mice treated with anti-complement factor B displayed preserved levels of Na⁺/K⁺ ATPase-α1 following sepsis.
  
  
  CONCLUSIONS
  1) Toll-like receptor 3/4 activation is sufficient to induce complement factor B production via nuclear factor-κB pathway and to enhance alternative pathway activation in the kidney tubular epithelial cells. 2) Complement factor B may contribute to the down-regulation of certain sodium transporter expression during sepsis.
authors.affiliation: 1Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA. 2Department of Anesthesia, the Third Xiangya Hospital, Xiangya School of Medicine, Changsha, China. 3Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA. 4Department of Medicine, University of Colorado School of Medicine, Aurora, CO.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Zou
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Ganqiong
authors.initials: G
authors.lastname: Xu
authors.forename: Yu
authors.initials: Y
authors.lastname: Gong
authors.forename: Gaofeng
authors.initials: G
authors.lastname: Zhao
authors.forename: Wen
authors.initials: W
authors.lastname: Ouyang
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Thurman
authors.forename: Wei
authors.initials: W
authors.lastname: Chao
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D011415:Complement Factor B / Q000096:biosynthesis*; D004195:Disease Models, Animal; D015536:Down-Regulation; D053503:Epithelial Sodium Channels / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D009570:Nitriles / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000503:physiopathology*; D015398:Signal Transduction / Q000502:physiology; D013450:Sulfones / Q000494:pharmacology; D051193:Toll-Like Receptors / Q000819:agonists / Q000235:genetics; D015854:Up-Regulation
chemical_list: C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D053503:Epithelial Sodium Channels; D016328:NF-kappa B; D009570:Nitriles; D015221:Potassium Channels; D013450:Sulfones; D051193:Toll-Like Receptors; D011415:Complement Factor B