Azadirachtin interacts with retinoic acid receptors and inhibits retinoic acid-mediated biological responses.
Considering the role of retinoids in regulation of more than 500 genes involved in cell cycle and growth arrest, a detailed understanding of the mechanism and its regulation is useful for therapy. The extract of the medicinal plant Neem (Azadirachta indica) is used against several ailments especially for anti-inflammatory, anti-itching, spermicidal, anticancer, and insecticidal activities. In this report we prove the detailed mechanism on the regulation of retinoic acid-mediated cell signaling by azadirachtin, active components of neem extract. Azadirachtin repressed all trans-retinoic acid (ATRA)-mediated nuclear transcription factor κB (NF-κB) activation, not the DNA binding but the NF-κB-dependent gene expression. It did not inhibit IκBα degradation, IκBα kinase activity, or p65 phosphorylation and its nuclear translocation but inhibited NF-κB-dependent reporter gene expression. Azadirachtin inhibited TRAF6-mediated, but not TRAF2-mediated NF-κB activation. It inhibited ATRA-induced Sp1 and CREB (cAMP-response element-binding protein) DNA binding. Azadirachtin inhibited ATRA binding with retinoid receptors, which is supported by biochemical and in silico evidences. Azadirachtin showed strong interaction with retinoid receptors. It suppressed ATRA-mediated removal of retinoid receptors, bound with DNA by inhibiting ATRA binding to its receptors. Overall, our data suggest that azadirachtin interacts with retinoic acid receptors and suppresses ATRA binding, inhibits falling off the receptors, and activates transcription factors like CREB, Sp1, NF-κB, etc. Thus, azadirachtin exerts anti-inflammatory and anti-metastatic responses by a novel pathway that would be beneficial for further anti-inflammatory and anti-cancer therapies.
Laboratory of Immunology, Centre for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad 500001, India.
Maikho
M
Thoh
Banaganapalli
B
Babajan
Pongali B
PB
Raghavendra
Chitta
C
Sureshkumar
Sunil K
SK
Manna
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D031601:Azadirachta / Q000737:chemistry*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D036701:Limonins / Q000737:chemistry / Q000494:pharmacology*; D000072000:NF-KappaB Inhibitor alpha; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2 / Q000235:genetics / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D020298:U937 Cells
D000893:Anti-Inflammatory Agents; D000970:Antineoplastic Agents; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D020672:I-kappa B Proteins; D007306:Insecticides; D036701:Limonins; C000606204:NFKBIA protein, human; C498143:RELA protein, human; D018168:Receptors, Retinoic Acid; D016329:Sp1 Transcription Factor; D047992:TNF Receptor-Associated Factor 2; D048029:TNF Receptor-Associated Factor 6; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D014212:Tretinoin; C010329:azadirachtin