Luteolin suppresses inflammation-associated gene expression by blocking NF-kappaB and AP-1 activation pathway in mouse alveolar macrophages.
Luteolin, a plant flavonoid, has potent anti-inflammatory properties both in vitro and in vivo. However, the molecular mechanism of luteolin-mediated immune modulation has not been fully understood. In this study, we examined the effects of luteolin on the production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)), as well as the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) in mouse alveolar macrophage MH-S and peripheral macrophage RAW 264.7 cells. Luteolin dose-dependently inhibited the expression and production of these inflammatory genes and mediators in macrophages stimulated with lipopolysaccharide (LPS). Semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) assay further confirmed the suppression of LPS-induced TNF- alpha, IL-6, iNOS and COX-2 gene expression by luteolin at a transcriptional level. Luteolin also reduced the DNA binding activity of nuclear factor-kappa B (NF-kappaB) in LPS-activated macrophages. Moreover, luteolin blocked the degradation of IkappaB-alpha and nuclear translocation of NF-kappaB p65 subunit. In addition, luteolin significantly inhibited the LPS-induced DNA binding activity of activating protein-1 (AP-1). We also found that luteolin attenuated the LPS-mediated protein kinase B (Akt) and IKK phosphorylation, as well as reactive oxygen species (ROS) production. In sum, these data suggest that, by blocking NF-kappaB and AP-1 activation, luteolin acts to suppress the LPS-elicited inflammatory events in mouse alveolar macrophages, and this effect was mediated, at least in part, by inhibiting the generation of reactive oxygen species. Our observations suggest a possible therapeutic application of this agent for treating inflammatory disorders in lung.
Chen
Chiu-Yuan
CY
Graduate Institute of Chinese Pharmaceutical Sciences, China Medical University, Taichung 404, Taiwan, ROC.
Peng
Wen-Huang
WH
Tsai
Kuen-Daw
KD
Hsu
Shih-Lan
SL
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis; D015232:Dinoprostone / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005100:Expectorants / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000187:drug effects*; D007202:Indicators and Reagents; D007249:Inflammation / Q000235:genetics*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000633:toxicity; D047311:Luteolin / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics; D009573:Nitrites / Q000378:metabolism; D017382:Reactive Oxygen Species; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000235:genetics
D016207:Cytokines; D005100:Expectorants; D007202:Indicators and Reagents; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009573:Nitrites; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D015232:Dinoprostone; D047311:Luteolin