title: Release of TNF-alpha during myocardial reperfusion depends on oxidative stress and is prevented by mast cell stabilizers.
abstract: OBJECTIVE
  Our study sought to elucidate the role of oxidative stress for shedding of tumor necrosis factor-alpha (TNF-alpha) and for activating TNF-alpha-converting enzyme (TACE).
  
  
  BACKGROUND
  TNF-alpha, a central inflammatory cytokine, is discussed as one of the mediators of reperfusion injury. Shedding of membrane-bound pro-TNF-alpha is thought to be largely due to TNF-alpha-converting enzyme (TACE).
  
  
  METHODS
  Release of TNF-alpha and TACE dependency were studied in isolated rat hearts and in the human mast cell line HMC-1.
  
  
  RESULTS
  In reperfused hearts, interstitial release of TNF-alpha occurred in two phases (2-10 and >45 min). It depended on the presence of oxygen during reperfusion and was attenuated by reduced glutathione. Infusion of the oxidants H(2)O(2) or HOCl elicited release in non-ischemic hearts. TNF-alpha release was inhibited in hearts treated with degranulation inhibitors ketotifen or cromoglycate, suggesting mast cells as major source for myocardial TNF-alpha. This was confirmed by tissue staining. Post-ischemic release of histamine, however, did not parallel that of TNF-alpha. Heart tissue contained mainly mature TACE. HMC-1 expressed abundant pro-TACE and cleaved the pro-TNF-alpha-peptide Ac-SPLAQAVRSSSR-NH(2). However, cleavage was nonspecific and only partly inhibited by TACE inhibitor TAPI-2 (10-100 micromol/l), while it was stimulated by H(2)O(2) and HOCl and fully blocked by the nonspecific metalloprotease inhibitor o-phenanthroline.
  
  
  CONCLUSIONS
  The mechanism underlying TNF-alpha release from post-ischemic myocardium is oxidation-dependent but largely independent of activation of TACE. Mast cell stabilizers may be useful in preventing TNF-alpha release during reperfusion.
authors.affiliation: Department of Physiology, University of Munich, Schillerstr. 44, 80336 Munich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Gilles
authors.forename: Stefan
authors.initials: S
authors.lastname: Zahler
authors.forename: Ulrich
authors.initials: U
authors.lastname: Welsch
authors.forename: Christian P
authors.initials: CP
authors.lastname: Sommerhoff
authors.forename: Bernhard F
authors.initials: BF
authors.lastname: Becker
mesh_terms: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D000818:Animals; D002460:Cell Line; D006632:Histamine / Q000378:metabolism; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D007665:Ketotifen / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D017202:Myocardial Ischemia / Q000378:metabolism*; D015425:Myocardial Reperfusion; D018384:Oxidative Stress; D010477:Perfusion; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: D006634:Histamine H1 Antagonists; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D006632:Histamine; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606464:Adam17 protein, rat; D007665:Ketotifen