title: Statins decrease Toll-like receptor 4 expression and downstream signaling in human CD14+ monocytes.
abstract: OBJECTIVE
  Anti-inflammatory effects of statins contribute to their clinical benefit. Molecular mechanisms underlying these effects have not been well explored. Because statins attenuate lipopolysaccharide (LPS) responsiveness, we hypothesized that part of the pleiotropic effects are mediated through innate immunity.
  
  
  RESULTS
  Toll-like receptor (TLR) 4 expression and downstream signaling in CD14+ monocytes after incubation with simvastatin and atorvastatin were quantified via flow-cytometry, quantitative RT-PCR, kinase assay, and enzyme-linked immunosorbent assay. Incubation with intermediates/ inhibitors of the mevalonate pathway was used to identify the mode of statin action. Statin incubation resulted in a dose-dependent reduction of TLR4 expression (53+/-7.6% reduction compared with untreated monocytes; P<0.005), transcript levels (68+/-6.3%; P<0.002), decreased IRAK phosphorylation (37+/-8.3%; P<0.05), and LPS-induced IL-6, IL-12, tumor necrosis factor (TNF)-alpha, and B7-1 expression (P<0.05). Four weeks of treatment with atorvastatin significantly reduced TLR4 expression on circulating CD14+ monocytes by 36.2+/-4.2% (P<0.05). Effects of statins were reversed by mevalonate (P=0.57). Incubation with specific inhibitors of geranylgeranyltransferase (54+/-4.3%), farnesyltransferase (57+/-5.1%), or with clostridium-difficile toxin B (58+/-6.1%, P<0.01) imitated the statin effects. Whereas wortmannin and LY294002 inhibited the statin effect (P=0.27), incubation with a specific RhoA kinase inhibitor had no effect (P=0.57).
  
  
  CONCLUSIONS
  Statins influence TLR4 expression and signaling via inhibition of protein geranylgeranylation and farnesylation. These observations imply interactions with innate immunity as one pleiotropic mechanism.
authors.affiliation: Department of Cardiology, Ludwig-Maximilians-University, Munich, Germany. hmethe@mit.edu
authors.forename: Heiko
authors.initials: H
authors.lastname: Methe
authors.forename: Jong-Oh
authors.initials: JO
authors.lastname: Kim
authors.forename: Sieglinde
authors.initials: S
authors.lastname: Kofler
authors.forename: Michael
authors.initials: M
authors.lastname: Nabauer
authors.forename: Michael
authors.initials: M
authors.lastname: Weis
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000328:Adult; D000069059:Atorvastatin; D018122:B7-1 Antigen / Q000378:metabolism; D001426:Bacterial Proteins / Q000494:pharmacology; D001427:Bacterial Toxins / Q000494:pharmacology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004347:Drug Interactions; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006538:Heptanoic Acids / Q000008:administration & dosage*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage*; D053592:Interleukin-1 Receptor-Associated Kinases; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D017368:Protein Prenylation; D011758:Pyrroles / Q000008:administration & dosage*; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000069059:Atorvastatin; D018122:B7-1 Antigen; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D016207:Cytokines; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D053592:Interleukin-1 Receptor-Associated Kinases; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D011758:Pyrroles; D012333:RNA, Messenger; D051197:Toll-Like Receptor 4; C495345:TLR4 protein, human; C031815:toxB protein, Clostridium difficile; C049347:fasudil