title: Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe(2+) in human monocytic U937 cells.
abstract: Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca(2+)-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30°C to 37°C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca(2+) ([Ca(2+)]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe(2+)-accumulation following pretreatment with FeSO4. Thus intracellular Fe(2+)-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe(2+)-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe(2+)-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37°C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe(2+)-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe(2+)-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2 channels by Fe(2+) may implicated in hemorrhagic brain injury via aggravation of inflammation, since Fe(2+) is released by heme degradation under intracerebral hemorrhage.
authors.affiliation: Laboratory of Pharmacology, Department of Clinical Pharmacy, Yokohama College of Pharmacy, Yokohama 245-0066, Japan; Division of Pharmacology, Faculty of Pharmaceutical Sciences, Teikyo Heisei University, Tokyo 164-8530, Japan. Electronic address: s.shimizu@thu.ac.jp.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Division of Physiology and Pathology, Department of Pharmacology, Toxicology and Therapeutics, Showa University School of Pharmacy, Tokyo 142-8555, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yonezawa
authors.affiliation: Department of Pharmacogenomics, Showa University School of Pharmacy, Tokyo 142-8555, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Negoro
authors.affiliation: Department of Molecular Cell Biology and Medicine, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima 770-8505, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Numata
authors.affiliation: Division of Physiology and Pathology, Department of Pharmacology, Toxicology and Therapeutics, Showa University School of Pharmacy, Tokyo 142-8555, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Ishii
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
authors.affiliation: Laboratory of Pharmacology, Department of Clinical Pharmacy, Yokohama College of Pharmacy, Yokohama 245-0066, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Toda
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002413:Cations, Divalent; D002460:Cell Line; D005296:Ferrous Compounds / Q000494:pharmacology; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D017136:Ion Transport; D007501:Iron / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D000067856:Poly(ADP-ribose) Polymerase Inhibitors / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D015398:Signal Transduction; D050053:TRPM Cation Channels / Q000819:agonists / Q000235:genetics* / Q000378:metabolism; D013696:Temperature
chemical_list: C508606:CXCL8 protein, human; D002413:Cations, Divalent; D005296:Ferrous Compounds; D016209:Interleukin-8; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; C020748:ferrous sulfate; D006861:Hydrogen Peroxide; D007501:Iron; D011065:Poly(ADP-ribose) Polymerases; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium
keywords: CXCL8; Ferrous iron; Hydrogen peroxide; TRPM2 channel; U937 cells