title: Apigenin, a dietary flavonoid, sensitizes human T cells for activation-induced cell death by inhibiting PKB/Akt and NF-kappaB activation pathway.
abstract: Resistance of T cells to activation-induced cell death (AICD) is associated with autoimmunity and lymphoproliferation. We found that apigenin (4',5,7-trihydroxyflavone), a non-mutagenic dietary flavonoid, augmented both extrinsic and intrinsic pathways of apoptosis in recurrently activated, but not in primarily stimulated, human blood CD4+ T cells. Apigenin potentiated AICD by inhibiting NF-kappaB activation and suppressing NF-kappaB-regulated anti-apoptotic molecules, cFLIP, Bcl-x(L), Mcl-1, XIAP and IAP, but not Bcl-2. Apigenin suppressed NF-kappaB translocation to nucleus and inhibited IkappaBalpha phosphorylation and degradation in response to TCR stimulation in reactivated peripheral blood CD4 T cells, as well as in leukemic Jurkat T cell lines. Among the pathways that lead to NF-kappaB activation upon TCR stimulation, apigenin selectively inhibited PI3K-PKB/Akt, but not PKC-theta activation in the human T cells, and synergized with a PI3K inhibitor to markedly augment AICD. Apigenin also suppressed expression of anti-apoptotic cyclooxygenase 2 (COX-2) protein in activated human T cells, but it did not affect activation of Erk MAPKinase. Thus, in chronically activated human T cells, relatively non-toxic apigenin can suppress anti-apoptotic pathways involving NF-kappaB activation, and especially cFLIP and COX-2 expression that are important for functioning and maintenance of immune cells in inflammation, autoimmunity and lymphoproliferation.
authors.affiliation: Division of Rheumatology, Departments of Medicine and Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, 240 East Huron, St. McGaw #M300, Chicago, IL 60611, United States.
authors.forename: Luting
authors.initials: L
authors.lastname: Xu
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Anne M
authors.initials: AM
authors.lastname: Bertucci
authors.forename: Richard M
authors.initials: RM
authors.lastname: Pope
authors.forename: Syamal K
authors.initials: SK
authors.lastname: Datta
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D047310:Apigenin / Q000008:administration & dosage*; D017209:Apoptosis / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology*; D049109:Cell Proliferation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004032:Diet; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D008213:Lymphocyte Activation; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002867:Chromones; D009025:Morpholines; D016328:NF-kappa B; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D047310:Apigenin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase