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


METHODS
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.


RESULTS
Endogenous AEA was detected in the immortalized human mammary epithelial MCF-10A cells (0.034 ng per 10(6) 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
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.
Division of Experimental Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
H
H
Li
J T
JT
Wood
K M
KM
Whitten
S K
SK
Vadivel
S
S
Seng
A
A
Makriyannis
H K
HK
Avraham
D021581:Active Transport, Cell Nucleus; D000581:Amidohydrolases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001095:Arachidonic Acids / Q000378:metabolism; D001549:Benzamides / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002219:Carbamates / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids / Q000378:metabolism; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D061986:MCF-7 Cells; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D053284:Polyunsaturated Alkamides / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D000970:Antineoplastic Agents; D001095:Arachidonic Acids; D001549:Benzamides; D002219:Carbamates; D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D051547:Heme Oxygenase-1; D051267:NF-E2-Related Factor 2; D053284:Polyunsaturated Alkamides; D000099252:Fatty Acid Amide Hydrolases; C495635:NFE2L2 protein, human; C500528:cyclohexyl carbamic acid 3'-carbamoylbiphenyl-3-yl ester; C496541:HMOX1 protein, human; C078814:anandamide
FAAH enzyme; Nrf2; breast cancer; endocannabinoids; heme oxygenase 1; oxidative stress