title: Inflammatory intracellular pathways activated by electronegative LDL in monocytes.
abstract: Electronegative LDL (LDL(-)) is a plasma LDL subfraction that induces cytokine release in monocytes through toll-like receptor 4 (TLR4) activation. However, the intracellular pathways induced by LDL(-) downstream TLR4 activation are unknown. We aimed to identify the pathways activated by LDL(-) leading to cytokine release in monocytes.
  
  
  
  We determined LDL(-)-induced activation of several intracellular kinases in protein extracts from monocytes using a multikinase ELISA array. LDL(-) induced higher p38 mitogen-activated protein kinase (MAPK) phosphorylation than native LDL. This was corroborated by a specific cell-based assay and it was dependent on TLR4 and phosphoinositide 3-kinase (PI3k)/Akt pathway. P38 MAPK activation was involved in cytokine release promoted by LDL(-). A specific ELISA showed that LDL(-) activated cAMP response-element binding (CREB) in a p38 MAPK dependent manner. P38 MAPK was also involved in the nuclear factor kappa-B (NF-kB) and activating protein-1 (AP-1) activation by LDL(-). We found that NF-kB, AP-1 and CREB inhibitors decreased LDL(-)-induced cytokine release, mainly on MCP1, IL6 and IL10 release, respectively.
  
  
  
  LDL(-) promotes p38 MAPK phosphorylation through TLR4 and PI3k/Akt pathways. Phosphorylation of p38 MAPK is involved in NF-kB, AP-1 and CREB activation, leading to LDL(-)-induced cytokine release in monocytes.
authors.affiliation: Biomedical Research Institute Sant Pau (IIB-Sant Pau), Barcelona, Spain, C/Sant Antoni M. Claret 167, 08025 Barcelona, Spain. Electronic address: mestruch@santpau.cat.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Estruch
authors.affiliation: Biomedical Research Institute Sant Pau (IIB-Sant Pau), Barcelona, Spain, C/Sant Antoni M. Claret 167, 08025 Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB) Faculty of Medicine, Building M. Cerdanyola del Vallès, Spain. Electronic address: jsanchezq@santpau.cat.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Sanchez-Quesada
authors.affiliation: Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB) Faculty of Medicine, Building M. Cerdanyola del Vallès, Spain; Biochemistry Department, Hospital de la Santa Creu i Sant Pau Barcelona, C/Sant Quintí 89, 08026 Barcelona, Spain. Electronic address: jordonez@santpau.cat.
authors.forename: Jordi
authors.initials: J
authors.lastname: Ordoñez-Llanos
authors.affiliation: Biomedical Research Institute Sant Pau (IIB-Sant Pau), Barcelona, Spain, C/Sant Antoni M. Claret 167, 08025 Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB) Faculty of Medicine, Building M. Cerdanyola del Vallès, Spain. Electronic address: sbenitez@santpau.cat.
authors.forename: Sonia
authors.initials: S
authors.lastname: Benitez
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis / Q000235:genetics; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D053492:Elafin / Q000235:genetics; D006801:Humans; D008077:Lipoproteins, LDL / Q000096:biosynthesis / Q000097:blood*; D009000:Monocytes / Q000378:metabolism*; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000096:biosynthesis / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D016207:Cytokines; D053492:Elafin; D008077:Lipoproteins, LDL; D016328:NF-kappa B; C506806:PI3 protein, human; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D018808:Transcription Factor AP-1; C099252:oxidized low density lipoprotein; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Cell signaling; Cytokines; Electronegative LDL; MAP kinases; Toll-like receptor (TLR); Transcription factors