title: PKC-epsilon and TLR4 synergistically regulate resistin-mediated inflammation in human macrophages.
abstract: Resistin has been associated with atherosclerotic inflammation and cardiovascular complications. We and others have previously shown that PKC-epsilon (PKCε) is involved in resistin-induced smooth muscle cell (VSMC) dysfunction at a high pathological concentration. This study aimed to evaluate the role and potential pathways of resistin at a physiological concentration, in atherosclerosis-related inflammation.
  
  
  
  Plasma from patients with atherosclerosis was analyzed for resistin concentration. Patients were divided into tertiles based on resistin levels and cytokines were compared between tertiles. Macrophages were then treated with resistin in the presence or absence of PKCε inhibitor and/or TLR4 blocking-antibody, and their inflammatory state was evaluated with ELISA, RT-PCR, immunocytochemistry, and Western blot.
  
  
  
  We observed significant associations between plasma resistin levels and TNF-α, IL-6, IL-12, MIP-1α, MIP-1β, and CD40L. Our in vitro analyses revealed that resistin activated PKCε via TLR4. This was followed by NF-kB activation and induction of a pro-inflammatory phenotype in macrophages, significantly upregulating CD40, downregulating CD206 and stimulating gene expression and secretion of the inflammatory cytokines, for which we found association in our plasma analysis. Resistin also induced persistent TRAM and CD40L upregulation up to 36 h after resistin treatment. PKCε and TLR4 inhibitors suppressed gene expression to levels similar to control, especially when used in combination.
  
  
  
  Resistin, at a physiological concentration, exacerbates the inflammatory response of macrophages. PKCε is a key upstream mediator in resistin-induced inflammation that may interact synergistically with TLR4 to promote NF-kB activation, while TRAM is an important signal. PKCε and TRAM may represent novel molecular targets for resistin-associated chronic atherosclerotic inflammation.
authors.affiliation: Department of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, CA, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Zuniga
authors.affiliation: Department of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, CA, USA.
authors.forename: Gayatri
authors.initials: G
authors.lastname: Raghuraman
authors.affiliation: Department of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, CA, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hitchner
authors.affiliation: Department of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, CA, USA; Division of Immunology and Rheumatology, Department of Medicine, Stanford University, Stanford, CA, USA.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Weyand
authors.affiliation: Department of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, CA, USA; Division of Immunology and Rheumatology, Department of Medicine, Stanford University, Stanford, CA, USA.
authors.forename: William
authors.initials: W
authors.lastname: Robinson
authors.affiliation: Division of Vascular Surgery, Department of Surgery, University of Arizona, Tucson, AZ, USA; Department of Vascular Surgery, Southern Arizona VA Health Care System, Tucson, AZ, USA. Electronic address: zhouw@email.arizona.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D050197:Atherosclerosis / Q000097:blood* / Q000201:enzymology / Q000276:immunology / Q000517:prevention & control; D023201:CD40 Ligand / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood* / Q000201:enzymology / Q000276:immunology / Q000517:prevention & control; D018836:Inflammation Mediators / Q000097:blood*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D010641:Phenotype; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D052243:Resistin / Q000097:blood*; D015398:Signal Transduction; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000893:Anti-Inflammatory Agents; D016207:Cytokines; D018836:Inflammation Mediators; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; C499624:RETN protein, human; D052243:Resistin; C480228:TICAM2 protein, human; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D023201:CD40 Ligand; C497255:PRKCE protein, human; D051744:Protein Kinase C-epsilon
keywords: Atherosclerosis; Cytokine; Macrophage; Protein kinase C epsilon; Resistin; Toll-like receptor 4