title: Alkaline phosphatase protects against renal inflammation through dephosphorylation of lipopolysaccharide and adenosine triphosphate.
abstract: OBJECTIVE
  Recently, two phase-II trials demonstrated improved renal function in critically ill patients with sepsis-associated acute kidney injury treated with the enzyme alkaline phosphatase. Here, we elucidated the dual active effect on renal protection of alkaline phosphatase.
  
  
  METHODS
  The effect of human recombinant alkaline phosphatase (recAP) on LPS-induced renal injury was studied in Sprague-Dawley rats. Renal function was assessed by transcutaneous measurement of FITC-sinistrin elimination in freely moving, awake rats. The mechanism of action of recAP was further investigated in vitro using conditionally immortalized human proximal tubular epithelial cells (ciPTEC).
  
  
  RESULTS
  In vivo, LPS administration significantly prolonged FITC-sinistrin half-life and increased fractional urea excretion, which was prevented by recAP co-administration. Moreover, recAP prevented LPS-induced increase in proximal tubule injury marker, kidney injury molecule-1 expression and excretion. In vitro, LPS-induced production of TNF-α, IL-6 and IL-8 was significantly attenuated by recAP. This effect was linked to dephosphorylation, as enzymatically inactive recAP had no effect on LPS-induced cytokine production. RecAP-mediated protection resulted in increased adenosine levels through dephosphorylation of LPS-induced extracellular ADP and ATP. Also, recAP attenuated LPS-induced increased expression of adenosine A2A receptor. However, the A2A receptor antagonist ZM-241385 did not diminish the effects of recAP.
  
  
  CONCLUSIONS
  These results indicate that the ability of recAP to reduce renal inflammation may account for the beneficial effect observed in septic acute kidney injury patients, and that dephosphorylation of ATP and LPS are responsible for this protective effect.
authors.affiliation: Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands.|Department of Pharmacology and Toxicology, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Peters
authors.affiliation: Medical Research Center, University of Heidelberg, Mannheim, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Geraci
authors.affiliation: Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands.|Department of Pharmacology and Toxicology, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Heemskerk
authors.affiliation: Department of Pharmacology and Toxicology, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: M J
authors.initials: MJ
authors.lastname: Wilmer
authors.affiliation: Department of Pharmacology and Toxicology, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Bilos
authors.affiliation: Medical Research Center, University of Heidelberg, Mannheim, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Kraenzlin
authors.affiliation: Medical Research Center, University of Heidelberg, Mannheim, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Gretz
authors.affiliation: Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Pickkers
authors.affiliation: Department of Pharmacology and Toxicology, Radboud university medical center, Nijmegen, The Netherlands.|Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Masereeuw
mesh_terms: D058186:Acute Kidney Injury / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008070:Lipopolysaccharides; D008297:Male; D009844:Oligosaccharides / Q000378:metabolism; D020011:Protective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D011687:Purines / Q000652:urine; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D016207:Cytokines; D005452:Fluoresceins; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D020011:Protective Agents; D011687:Purines; D011994:Recombinant Proteins; D014227:Triazines; D014230:Triazoles; C097270:ZM 241385; C576250:fluorescein-isothiocyanate sinistrin; D000469:Alkaline Phosphatase