Apigenin blocks lipopolysaccharide-induced lethality in vivo and proinflammatory cytokines expression by inactivating NF-kappaB through the suppression of p65 phosphorylation.
LPS stimulates monocytes/macrophages through the activation of signaling events that modulate the production of inflammatory cytokines. Apigenin, a flavonoid abundantly found in fruits and vegetables, exhibits anti-proliferative and anti-inflammatory activities through poorly defined mechanisms. In this study, we demonstrate that apigenin inhibits the production of proinflammatory cytokines IL-1beta, IL-8, and TNF in LPS-stimulated human monocytes and mouse macrophages. The inhibitory effect on proinflammatory cytokine production persists even when apigenin is administered after LPS stimulation. Transient transfection experiments using NF-kappaB reporter constructs indicated that apigenin inhibits the transcriptional activity of NF-kappaB in LPS-stimulated mouse macrophages. The classical proteasome-dependent degradation of the NF-kappaB inhibitor IkappaBalpha was observed in apigenin LPS-stimulated human monocytes. Using EMSA, we found that apigenin does not alter NF-kappaB-DNA binding activity in human monocytes. Instead we show that apigenin, as part of a non-canonical pathway, regulates NF-kappaB activity through hypophosphorylation of Ser536 in the p65 subunit and the inactivation of the IKK complex stimulated by LPS. The decreased phosphorylation on Ser536 observed in LPS-stimulated mouse macrophages treated with apigenin was overcome by the over-expression of IKKbeta. In addition, our studies indicate that apigenin inhibits in vivo LPS-induced TNF and the mortality induced by lethal doses of LPS. Collectively, these findings suggest a molecular mechanism by which apigenin suppresses inflammation and modulates the immune response in vivo.
Nicholas
Courtney
C
Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA.
Batra
Sanjay
S
Vargo
Melissa A
MA
Voss
Oliver H
OH
Gavrilin
Mikhail A
MA
Wewers
Mark D
MD
Guttridge
Denis C
DC
Grotewold
Erich
E
Doseff
Andrea I
AI
D000818:Animals; D047310:Apigenin / Q000494:pharmacology*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology*; D006801:Humans; D051550:I-kappa B Kinase / Q000276:immunology / Q000378:metabolism; D020672:I-kappa B Proteins / Q000276:immunology / Q000378:metabolism; D007249:Inflammation / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000276:immunology / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects* / Q000276:immunology; D051996:Transcription Factor RelA / Q000276:immunology* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology
D016207:Cytokines; D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D047310:Apigenin; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496562:Ikbkb protein, mouse; D046988:Proteasome Endopeptidase Complex