title: Effects of taraxasterol on iNOS and COX-2 expression in LPS-induced RAW 264.7 macrophages.
abstract: BACKGROUND
  Taraxasterol was isolated from the Chinese medicinal herb Taraxacum officinale which has been frequently used as a remedy for inflammatory diseases. Our previous study has shown that taraxasterol inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production in RAW 264.7 macrophages. To elucidate the underlying mechanism responsible for these effects, in the present study, we investigated the effects of taraxasterol on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, and mitogen-activated protein kinases (MAPKs) signaling pathway in LPS-induced RAW 264.7 macrophages.
  
  
  METHODS
  RAW 264.7 cells were pretreated with 2.5, 5 and 12.5 μg/ml of taraxasterol 1 h prior to treatment with 1 μg/ml of LPS. The mRNA expression levels of iNOS and COX-2 were examined by RT-PCR. The protein expression levels of iNOS and COX-2, and the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), p38 and c-Jun N-terminal kinase (JNK) MAPKs were measured by Western blot.
  
  
  RESULTS
  The mRNA and protein expression levels of iNOS and COX-2 were inhibited by taraxasterol in a concentration-dependent manner. Further studies revealed that taraxasterol suppressed the phosphorylation of ERK1/2 and p38 in LPS-induced RAW 264.7 macrophages.
  
  
  CONCLUSIONS
  These results indicate that taraxasterol inhibits iNOS and COX-2 expression by blocking ERK1/2 and p38 MAPKs signaling pathway.
authors.affiliation: Department of Animal Medicine, Agricultural College of Yanbian University, Gongyuan Street, Yanji, Jilin 133002, PR China.
authors.forename: Huanzhang
authors.initials: H
authors.lastname: Xiong
authors.affiliation: Department of Animal Medicine, Agricultural College of Yanbian University, Gongyuan Street, Yanji, Jilin 133002, PR China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Animal Medicine, Agricultural College of Yanbian University, Gongyuan Street, Yanji, Jilin 133002, PR China.
authors.forename: Xian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Animal Medicine, Agricultural College of Yanbian University, Gongyuan Street, Yanji, Jilin 133002, PR China. Electronic address: zhangxm@ybu.edu.cn.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008516:Medicine, Chinese Traditional / Q000379:methods; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics*; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013261:Sterols / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D031205:Taraxacum / Q000737:chemistry; D014315:Triterpenes / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D013261:Sterols; D014315:Triterpenes; D009569:Nitric Oxide; C079988:taraxasterol; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Cyclooxygenase-2 (COX-2); Inducible nitric oxide synthase (iNOS); Mitogen-activated protein kinase (MAPK); Taraxasterol