title: IL-4 induces apoptosis in A549 lung adenocarcinoma cells: evidence for the pivotal role of 15-hydroxyeicosatetraenoic acid binding to activated peroxisome proliferator-activated receptor gamma transcription factor.
abstract: The proinflammatory cytokine IL-4 is secreted in large amounts during allergic inflammatory response in asthma and plays a pivotal role in the airway inflammation. IL-4 has been shown to up-regulate 15-lipoxygenase and produce 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) in A549 cells via the Janus kinase/STAT6 pathway under coactivation of CREB binding protein/p300. IL-4 has also been shown to up-regulate peroxisome proliferator-activated receptor gamma (PPARgamma) nuclear receptors in macrophages and A549 cells. In this study we demonstrate that 15(S)-HETE binds to PPARgamma nuclear receptors and induces apoptosis in A549 cells. Moreover, pretreatment of cells with nordihydroguaiaretic acid, a 15-lipoxygenase inhibitor, prevented PPARgamma activation and apoptosis. The latter was accomplished by the interaction of the 15(S)-HETE/PPARgamma complex with the adapter protein Fas-associating protein with death domain and caspase-8, as shown by transfection of Fas-associating protein with death domain dominant negative vector and cleavage of caspase 8 to active subunits p41/42 and p18. Whereas IL-4 and PPARgamma ligands failed to induce cleavage of Bid and release of cytochrome c from mitochondria, they caused translocation of the proapoptotic protein Bax from cytoplasm to mitochondria with a concomitant decrease in the Bcl-x(L) level. We therefore believe that in unstimulated cells Bcl-x(L) and Bax form a heterodimer, in which Bcl-x(L) dominates and prevents the induction of apoptosis, whereas in IL-4-stimulated cells the 15(S)-HETE/PPARgamma complex down-regulates Bcl-x(L), and the resulting overweight of Bax commits the cell to apoptosis via caspase-3. However, this pathway does not rule out the direct caspase-8-mediated activation of caspase-3. In conclusion, IL-4-induced apoptosis may contribute to severe loss of alveolar structures and infiltration of eosinophils, mononuclear phagocytes, etc., into the lung tissue of chronic asthma patients.
authors.affiliation: Eicosanoid and Lipid Research Division, Department of Gynecology, University Medical Center Benjamin Franklin, Free University Berlin, Germany.
authors.forename: Pattabhiraman
authors.initials: P
authors.lastname: Shankaranarayanan
authors.forename: Santosh
authors.initials: S
authors.lastname: Nigam
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000276:immunology*; D051023:BH3 Interacting Domain Death Agonist Protein; D001665:Binding Sites / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D015536:Down-Regulation / Q000276:immunology; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D006868:Hydrolysis; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism* / Q000502:physiology; D015847:Interleukin-4 / Q000502:physiology*; D008024:Ligands; D008175:Lung Neoplasms / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology; D014157:Transcription Factors / Q000378:metabolism* / Q000502:physiology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000276:immunology; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D006893:Hydroxyeicosatetraenoic Acids; D008024:Ligands; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D015847:Interleukin-4; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases