Isoeugenol suppression of inducible nitric oxide synthase expression is mediated by down-regulation of NF-kappaB, ERK1/2, and p38 kinase.
Isoeugenol, which is a naturally occurring o-methoxyphenol in a variety of foods and essential oils, is known to have anti-inflammatory effects, although the mechanism is not clear. In the present study, we investigated the effect of isoeugenol on NF-kappaB signaling leading to inducible nitric oxide synthase (iNOS) expression in RAW 264.7 murine macrophages stimulated with lipopolysaccharide (LPS). Isoeugenol markedly inhibited nitric oxide (NO) production in dose- and time-dependent manners. The decrease in NO production was found to correlate with a decrease in iNOS expression, as determined by Western blot analysis and real-time RT-PCR. To characterize further the inhibitory mechanisms of isoeugenol at the transcriptional level, we examined the DNA-binding and transcriptional activities of NF-kappaB. Isoeugenol inhibited NF-kappaB-dependent transcriptional activity and DNA-binding activity by decreasing the nuclear translocation of p65, which is a component of NF-kappaB. In addition, isoeugenol blocked signaling upstream of NF-kappaB activation, such as degradation of I-kappaBalpha and the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK), in LPS-stimulated RAW 264.7 cells. The isoeugenol analogues eugenol and allylbenzene also inhibited LPS-induced NF-kappaB signaling and iNOS expression, albeit with less potency than isoeugenol. These results suggest that isoeugenol and its analogues inhibit NO production and iNOS expression in LPS-stimulated RAW 264.7 cells, and that these effects are mediated, at least in part, by blocking the phosphorylation of ERK1/2 and p38 kinase, degradation of I-kappaBalpha, and activation of NF-kappaB.
Choi
Chun Yeon
CY
Department of Biochemistry, College of Medicine, Inje University, Busan 614-735, Republic of Korea.
Park
Kyung-Ran
KR
Lee
Jung-Hee
JH
Jeon
Young Jin
YJ
Liu
Kwang-Hyeon
KH
Oh
Sangtaek
S
Kim
Dong-Eun
DE
Yea
Sung Su
SS
D000498:Allyl Compounds / Q000494:pharmacology*; D000818:Animals; D001555:Benzene Derivatives / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D005054:Eugenol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter / Q000235:genetics; D020672:I-kappa B Proteins / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D000081248:Allylbenzene Derivatives
D000498:Allyl Compounds; D001555:Benzene Derivatives; D005054:Eugenol; D020672:I-kappa B Proteins; D020928:Mitogen-Activated Protein Kinases; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites; D012333:RNA, Messenger; C000606205:Nfkbia protein, mouse; C102347:allylbenzene; D000081248:Allylbenzene Derivatives; C036643:isoeugenol; C496317:Nos2 protein, mouse