title: 5, 8, 11, 14-eicosatetraynoic acid suppresses CCL2/MCP-1 expression in IFN-γ-stimulated astrocytes by increasing MAPK phosphatase-1 mRNA stability.
abstract: BACKGROUND
  The peroxisome proliferator-activated receptor (PPAR)-α activator, 5,8,11,14-eicosatetraynoic acid (ETYA), is an arachidonic acid analog. It is reported to inhibit up-regulation of pro-inflammatory genes; however, its underlying mechanism of action is largely unknown. In the present study, we focused on the inhibitory action of ETYA on the expression of the chemokine, CCL2/MCP-1, which plays a key role in the initiation and progression of inflammation.
  
  
  METHODS
  To determine the effect of ETYA, primary cultured rat astrocytes and microglia were stimulated with IFN-γ in the presence of ETYA and then, expression of CCL2/MCP-1 and MAPK phosphatase (MKP-1) were determined using RT-PCR and ELISA. MKP-1 mRNA stability was evaluated by treating actinomycin D. The effect of MKP-1 and human antigen R (HuR) was analyzed by using specific siRNA transfection system. The localization of HuR was analyzed by immunocytochemistry and subcellular fractionation experiment.
  
  
  RESULTS
  We found that ETYA suppressed CCL2/MCP-1 transcription and secretion of CCL2/MCP-1 protein through up-regulation of MKP-1mRNA levels, resulting in suppression of c-Jun N-terminal kinase (JNK) phosphorylation and activator protein 1 (AP1) activity in IFN-γ-stimulated brain glial cells. Moreover, these effects of ETYA were independent of PPAR-α. Experiments using actinomycin D revealed that the ETYA-induced increase in MKP-1 mRNA levels reflected an increase in transcript stability. Knockdown experiments using small interfering RNA demonstrated that this increase in MKP-1 mRNA stability depended on HuR, an RNA-binding protein known to promote enhanced mRNA stability. Furthermore, ETYA-induced, HuR-mediated mRNA stabilization resulted from HuR-MKP-1 nucleocytoplasmic translocation, which served to protect MKP-1 mRNA from the mRNA degradation machinery.
  
  
  CONCLUSIONS
  ETYA induces MKP-1 through HuR at the post-transcriptional level in a receptor-independent manner. The mechanism revealed here suggests eicosanoids as potential therapeutic modulators of inflammation that act through a novel target.
authors.affiliation: Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon 442-721, Korea. if7979@hotmail.com
authors.forename: Jee Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Hyunmi
authors.initials: H
authors.lastname: Kim
authors.forename: Joo Hong
authors.initials: JH
authors.lastname: Woo
authors.forename: Eun-hye
authors.initials: EH
authors.lastname: Joe
authors.forename: Ilo
authors.initials: I
authors.lastname: Jou
mesh_terms: D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D018932:Chemokine CCL2 / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics*; D051959:ELAV Proteins; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D017628:Microglia / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection
chemical_list: D018932:Chemokine CCL2; D051959:ELAV Proteins; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D015117:5,8,11,14-Eicosatetraynoic Acid; D007371:Interferon-gamma; D054638:Dual Specificity Phosphatase 1