title: Ceramide-enriched LDL induces cytokine release through TLR4 and CD14 in monocytes. Similarities with electronegative LDL.
abstract: BACKGROUND
  In vitro ceramide-enriched LDL (CER-LDL) reproduces most of the properties of electronegative LDL (LDL(-)), a heterogeneous subfraction of LDL found in plasma. LDL(-) comprises several modifications of LDL and has an increased content in ceramide (CER). It promotes cytokine release in monocytes through CD14 and TLR4. CER-LDL also induces cytokine release in these cells but the mechanism is unknown.
  
  
  OBJECTIVE
  To evaluate TLR4 and CD14 as the putative receptors involved in cytokine release induced by CER-LDL.
  
  
  METHODS
  CER-LDL was obtained by incubating native LDL with CER-enriched liposomes. CER content in CER-LDL was assessed by thin layer chromatography of lipid extracts. CER-LDL and LDL(-) were incubated for 20 h with human monocytes in the presence or absence of a TLR4 signaling inhibitor. Both LDLs were also incubated with two human monocytic cell lines, normal and THP1 overexpressing CD14 (THP1-CD14) cells. The release of IL-6, IL-10 and MCP-1 was evaluated by ELISA in culture medium.
  
  
  RESULTS
  The release of IL-6, IL-10 and MCP-1 induced by CER-LDL in monocytes was inhibited by VIPER (90% inhibition), a specific TLR4 inhibitor. The cytokine release induced by CER-LDL was negligible in THP1, cells presenting a very low CD14 expression. In contrast, the induction of cytokine release in THP1-CD14 was high and dependent on the CER content in LDL.
  
  
  CONCLUSIONS
  CER-LDL induces IL-6, IL-10 and MCP-1 release through the activation of CD14 and TLR4 in monocytes, reproducing the behavior of LDL(-). The increased content of CER in LDL(-) is then related to the inflammatory action of LDL(-).
authors.affiliation: Biomedical Research Institute Sant Pau (IIB-Sant Pau), Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB), 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), Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Sánchez-Quesada
authors.affiliation: Biochemistry Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Ordóñez-Llanos
authors.affiliation: Biomedical Research Institute Sant Pau (IIB-Sant Pau), Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; Molecular Biology and Biochemistry Department, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain. Electronic address: sbenitez@santpau.cat.
authors.forename: Sonia
authors.initials: S
authors.lastname: Benítez
mesh_terms: D002460:Cell Line; D002518:Ceramides / Q000378:metabolism*; D018932:Chemokine CCL2 / Q000378:metabolism; D002855:Chromatography, Thin Layer; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D016753:Interleukin-10 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000097:blood*; D008081:Liposomes; D009000:Monocytes / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: C111835:CCL2 protein, human; D002518:Ceramides; D018932:Chemokine CCL2; D016207:Cytokines; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D008077:Lipoproteins, LDL; D008081:Liposomes; D051197:Toll-Like Receptor 4; C099252:oxidized low density lipoprotein; D016753:Interleukin-10
keywords: CD14; Ceramida; Ceramide; Citoquinas; Cytokines; Electronegative LDL; LDL electronegativa; Monocitos; Monocytes; TLR4