Azadirachtin Interacts with the Tumor Necrosis Factor (TNF) Binding Domain of Its Receptors and Inhibits TNF-induced Biological Responses

• Published in: The Journal of biological chemistry Vol. 285; no. 8; pp. 5888 - 5895,13556
• Main Authors: Thoh, Maikho, Kumar, Pankaj, Nagarajaram, Hampathalu A., Manna, Sunil K.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.02.2010; American Society for Biochemistry and Molecular Biology
• Subjects: Active Transport, Cell Nucleus - drug effects; Anti-Inflammatory Agents - pharmacology; Binding Sites; Cell Nucleus - metabolism; Cyclooxygenase 2 - metabolism; Cytokines; Cytokines - metabolism; Cytokines/Tumor Necrosis Factor; Gene Expression Regulation - drug effects; HeLa Cells; Humans; I-kappa B Kinase - metabolism; Insecticides - pharmacology; Limonins - pharmacology; Membrane/Biophysics; Phosphorylation - drug effects; Protein Structure, Tertiary; Protein/Protein-protein interactions; Receptors, Tumor Necrosis Factor - metabolism; Receptors/Membrane; Receptors/Regulation; Signal Transduction; Signal Transduction/Protein Kinases; TNF Receptor-Associated Death Domain Protein - metabolism; TNF Receptor-Associated Factor 2 - metabolism; TNF-Related Apoptosis-Inducing Ligand - metabolism; Transcription Factor RelA - metabolism; Transcription/Regulation; Tumor Necrosis Factor-alpha - antagonists & inhibitors; Tumor Necrosis Factor-alpha - metabolism; U937 Cells; Membrane/Biophysics; Protein/Protein-protein interactions; Cytokines; Cytokines/Tumor Necrosis Factor; Transcription/Regulation; Receptors/Regulation; Receptors/Membrane; Signal Transduction/Protein Kinases
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.065847

The role of azadirachtin, an active component of a medicinal plant Neem (Azadirachta indica), on TNF-induced cell signaling in human cell lines was investigated. Azadirachtin blocks TNF-induced activation of nuclear factor κB (NF-κB) and also expression of NF-κB-dependent genes such as adhesion molecules and cyclooxygenase 2. Azadirachtin inhibits the inhibitory subunit of NF-κB (IκBα) phosphorylation and thereby its degradation and RelA (p65) nuclear translocation. It blocks IκBα kinase (IKK) activity ex vivo, but not in vitro. Surprisingly, azadirachtin blocks NF-κB DNA binding activity in transfected cells with TNF receptor-associated factor (TRAF)2, TNF receptor-associated death domain (TRADD), IKK, or p65, but not with TNFR, suggesting its effect is at the TNFR level. Azadirachtin blocks binding of TNF, but not IL-1, IL-4, IL-8, or TNF-related apoptosis-inducing ligand (TRAIL) with its respective receptors. Anti-TNFR antibody or TNF protects azadirachtin-mediated down-regulation of TNFRs. Further, in silico data suggest that azadirachtin strongly binds in the TNF binding site of TNFR. Overall, our data suggest that azadirachtin modulates cell surface TNFRs thereby decreasing TNF-induced biological responses. Thus, azadirachtin exerts an anti-inflammatory response by a novel pathway, which may be beneficial for anti-inflammatory therapy.