Inhibition of fatty acid amide hydrolase activates Nrf2 signalling and induces heme oxygenase 1 transcription in breast cancer cells

• Published in: British journal of pharmacology 2013-10, Vol.170 (3), p.489-505
• Main Authors: Li, H, Wood, J T, Whitten, K M, Vadivel, S K, Seng, S, Makriyannis, A, Avraham, H K
• Format: Article
• Language: English
• Subjects: Active Transport, Cell Nucleus; Amidohydrolases - antagonists & inhibitors; Amidohydrolases - genetics; Amidohydrolases - metabolism; Antineoplastic Agents - pharmacology; Arachidonic Acids - metabolism; Benzamides - pharmacology; Breast cancer; Breast Neoplasms - enzymology; Breast Neoplasms - genetics; Breast Neoplasms - pathology; Carbamates - pharmacology; Cell Survival - drug effects; Dose-Response Relationship, Drug; endocannabinoids; Endocannabinoids - metabolism; Enzyme Induction; Enzyme Inhibitors - pharmacology; FAAH enzyme; Fatty acids; Female; Gene Expression Regulation, Neoplastic; heme oxygenase 1; Heme Oxygenase-1 - genetics; Heme Oxygenase-1 - metabolism; Humans; Kinases; MCF-7 Cells; Medical research; NF-E2-Related Factor 2 - genetics; NF-E2-Related Factor 2 - metabolism; Nrf2; oxidative stress; Polyunsaturated Alkamides - metabolism; Research Papers; RNA Interference; Signal Transduction - drug effects; Transcription, Genetic - drug effects; Transfection
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/bph.12111

Background and Purpose Endocannabinoids such as anandamide (AEA) are important lipid ligands regulating cell proliferation, differentiation and apoptosis. Their levels are regulated by hydrolase enzymes, the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Here, we investigated whether FAAH or AEA are involved in NF (erythroid‐derived 2)‐like 2 (Nrf2)/antioxidant responsive element (ARE) pathway. Experimental Approach The aim of this study was to analyse the effects of AEA or FAAH inhibition by the URB597 inhibitor or FAAH/siRNA on the activation of Nrf2‐ARE signalling pathway and heme oxygenase‐1 (HO‐1) induction and transcription. Key Results Endogenous AEA was detected in the immortalized human mammary epithelial MCF‐10A cells (0.034 ng per 106 cells) but not in MCF‐7 or MDA‐MB‐231 breast cancer cells. Because breast tumour cells express FAAH abundantly, we examined the effects of FAAH on Nrf2/antioxidant pathway. We found that inhibition of FAAH by the URB597 inhibitor induced antioxidant HO‐1 in breast cancer cells and MCF‐10A cells. RNAi‐mediated knockdown of FAAH or treatment with AEA‐activated ARE‐containing reporter induced HO‐1 mRNA and protein expression, independent of the cannabinoid receptors, CB1, CB2 or TRPV1. Furthermore, URB597, AEA and siRNA‐FAAH treatments induced the nuclear translocation of Nrf2, while siRNA‐Nrf2 treatment and Keap1 expression blocked AEA, URB597 and si‐FAAH from activation of ARE reporter and HO‐1 induction. siRNA‐HO‐1 treatment decreased the viability of breast cancer cells and MCF‐10A cells. Conclusions and Implications These data uncovered a novel mechanism by which inhibition of FAAH or exposure to AEA induced HO‐1 transcripts and implicating AEA and FAAH as direct modifiers in signalling mediated activation of Nrf2‐HO‐1 pathway, independent of cannabinoid receptors.