title: Inhibition of activator protein 1 by barbiturates is mediated by differential effects on mitogen-activated protein kinases and the small G proteins ras and rac-1.
abstract: Barbiturates are known to suppress protective immunity, and their therapeutic use is associated with nosocomial infections. Although barbiturates inhibit T cell proliferation, differentiation, and cytokine synthesis, only thiobarbiturates markedly reduce the activation of immune regulatory transcription factors such as nuclear factor-kappaB and nuclear factor of activated T cells. In this study, we investigated barbiturate-mediated effects on the regulation of the transcription factor activator protein 1 (AP-1) in primary T lymphocytes. We show that both thiobarbiturates and their oxy-analogs inhibit AP-1-dependent gene expression and AP-1 complex formation at clinically relevant doses. Furthermore, mitogen-activated protein (MAP) kinase activity, which transcriptionally and posttranslationally regulates AP-1 complex formation, is suppressed by most barbiturates. CD3/CD28- or phorbol 12-myristate 13-acetate (PMA)/ionomycin-induced p38 and extracellular signal-regulated kinase 1/2 phosphorylation or c-jun NH2-terminal kinase (JNK) 1/2 kinase activity was significantly diminished by pentobarbital, thiamylal, secobarbital, or methohexital treatment. These barbiturates also inhibited the initiators of the MAP kinase cascade, the small G proteins ras and rac-1, and prevented binding to their partners raf-1 and PAK, respectively. Thiopental, unlike the other barbiturates, only reduced ras and JNK activity upon direct CD3/CD28 receptor engagement. Contrarily, upon PMA/ionomycin stimulation, thiopental blocked AP-1-dependent gene expression independently of the small G protein ras and MAP kinases, thus suggesting an additional, unknown mechanism of AP-1 regulation. In conclusion, our results contribute to the explanation of a clinically manifested immune suppression in barbiturate-treated patients and support the idea of a MAP kinase-independent regulation of AP-1 by PKC and calcium in human T cells.
authors.affiliation: Anaesthesiologische Universitätsklinik, Hugstetterstrasse 55, D-79106 Freiburg, Germany.
authors.forename: Matjaz
authors.initials: M
authors.lastname: Humar
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Andriopoulos
authors.forename: Soeren E
authors.initials: SE
authors.lastname: Pischke
authors.forename: Torsten
authors.initials: T
authors.lastname: Loop
authors.forename: Rene
authors.initials: R
authors.lastname: Schmidt
authors.forename: Alexander
authors.initials: A
authors.lastname: Hoetzel
authors.forename: Martin
authors.initials: M
authors.lastname: Roesslein
authors.forename: Heike L
authors.initials: HL
authors.lastname: Pahl
authors.forename: Klaus K
authors.initials: KK
authors.lastname: Geiger
authors.forename: Benedikt H J
authors.initials: BH
authors.lastname: Pannen
mesh_terms: D001463:Barbiturates / Q000494:pharmacology*; D017252:CD3 Complex / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D048670:MAP Kinase Kinase 4; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D009479:Neuropeptides / Q000187:drug effects*; D009687:Nuclear Proteins / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000187:drug effects*; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins / Q000187:drug effects*
chemical_list: D001463:Barbiturates; D017252:CD3 Complex; D009479:Neuropeptides; D009687:Nuclear Proteins; D016755:Proto-Oncogene Proteins c-jun; C107953:RAC1 protein, human; D018808:Transcription Factor AP-1; D008156:Luciferases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins