Inhibition of LPS-stimulated pathways in macrophages by the flavonoid luteolin.
1: We have previously shown that the flavonoid luteolin inhibits the expression of pro-inflammatory molecules induced by LPS. In the present study we tested the ability of luteolin to block signalling pathways implicated in LPS-induced inflammatory gene expression in macrophages. 2: Exposure of the murine macrophage cell line RAW 264.7 to LPS increased phosphorylation of the mitogen-activated protein kinase family members ERK1/2, p38 and JNK1/2 in a time-dependent manner. Pretreatment of RAW 264.7 with luteolin inhibited the LPS-induced ERK1/2 and p38, but not JNK1/2, phosphorylation, and blocked the LPS-induced TNF-alpha release. 3: To investigate which of these pathways contribute to the inhibitory effects of luteolin on TNF-alpha release, cells were pretreated with pharmacological inhibitors of these pathways; PD98059 and SB203580 when used alone failed to inhibit TNF-alpha release, whereas pretreatment with both agents attenuated TNF-alpha release. 4: We have previously shown that luteolin blocks Akt phosphorylation in response to LPS in RAW 264.7 macrophages. To determine the role of Akt in TNF-alpha release, cells were transiently transfected with a dominant negative form of Akt (K179M). Overexpression of K179M Akt did not alter LPS-induced TNF-alpha release, suggesting that inhibition of this kinase does not mediate the inhibitory action of luteolin. 5: In addition, DRB (a pharmacological inhibitor of CK2) blocked TNF-alpha release in a concentration-dependent manner, whereas co-treatment of cells with luteolin and DRB did not have an additive effect. 6: We conclude that luteolin interferes with LPS signalling by reducing the activation of several MAPK family members and that its inhibitory action on TNF-alpha release correlates with inhibition of ERK, p38 and CK2 activation.
Xagorari
Angeliki
A
George P. Livanos Laboratory, Evangelismos Hospital, Department of Critical Care and Pulmonary Services, School of Medicine, Ploutarchou 3, 5th floor, University of Athens, Athens, Greece 10675.
Roussos
Charis
C
Papapetropoulos
Andreas
A
D000818:Animals; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005419:Flavonoids / Q000494:pharmacology*; D015870:Gene Expression; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D047311:Luteolin; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D005419:Flavonoids; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D047311:Luteolin