title: Inhibition of TNF-alpha-induced neutrophil apoptosis by crystals of calcium pyrophosphate dihydrate is mediated by the extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways up-stream of caspase 3.
abstract: The role of protein kinases in the inhibition of TNF-alpha associated apoptosis of human neutrophils by crystals of calcium pyrophosphate dihydrate (CPPD) (25 mg/ml) was investigated. We monitored the activities of the p44 extracellular signal-regulated kinase 1 (ERK1) and p42 ERK2 mitogen-activated protein (MAP) kinases and phosphatidylinositol 3-kinase (PI3-K)-regulated protein kinase B (Akt) in neutrophils incubated with TNF-alpha and CPPD crystals, separately and in combination, in parallel with the endogenous caspase 3 activity and DNA fragmentation. CPPD crystals were observed to induce a robust and transient activation of ERK1, ERK2, and Akt, whereas TNF-alpha produced only a modest and delayed activation of Akt. In the presence of TNF-alpha, Akt activity was enhanced, and CPPD crystal-induced activation of ERK1 and ERK2 was more sustained than with CPPD crystals alone, but TNF-alpha itself reduced the basal phosphotransferase activities of these MAP kinases. Preincubation with the MAP kinase kinase (MEK1) inhibitors PD98059 (20 ng/ml) and U0126 (250 nM), or the PI3-K inhibitors wortmannin (100 nM) and LY294002 (50 microM) repressed the activation of ERK1, ERK2, and Akt in association with CPPD crystal incubation, in the absence or presence of TNF-alpha. Furthermore, the inhibition of the Mek1/Mek2-->ERK1/ERK2 or PI3-K/Akt pathways reversed CPPD crystal-associated suppression of TNF-alpha-induced caspase 3 activation and neutrophil apoptosis. Together, these results indicate that CPPD crystals function to induce acute inflammatory responses through ERK1/ERK2 and PI3-K/Akt-mediated stimulation of neutrophil activation and repression of apoptosis.
authors.affiliation: Faculty of Pharmaceutical Sciences, and Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Tudan
authors.forename: J K
authors.initials: JK
authors.lastname: Jackson
authors.forename: L
authors.initials: L
authors.lastname: Blanis
authors.forename: S L
authors.initials: SL
authors.lastname: Pelech
authors.forename: H M
authors.initials: HM
authors.lastname: Burt
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D002131:Calcium Pyrophosphate / Q000494:pharmacology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D003460:Crystallization; D053938:DNA Fragmentation / Q000187:drug effects / Q000276:immunology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004790:Enzyme Induction / Q000187:drug effects / Q000276:immunology; D004794:Enzyme Repression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D002131:Calcium Pyrophosphate; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D014409:Tumor Necrosis Factor-alpha; C494918:AKT1 protein, human; C505407:CASP3 protein, human