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 nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/antioxidant responsive element (ARE) pathway.

EXPERIMENTAL APPROACH:

To analyze the effects of AEA or FAAH inhibition by the URB597 inhibitor or FAAH/siRNA on the activation of Nrf2-ARE signaling 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 (0.034ng/10(6) cells) but not in MCF-7 or MDA-MB-231 breast cancer cells. Since breast tumor cells express FAAH abundantly, we examined the effects of FAAH in 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 from 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 signaling mediated activation of Nrf2-HO-1 pathway, independent of cannabinoid receptors.
© 2013 The Authors. British Journal of Pharmacology © 2013 The British Pharmacological Society.

PMID:

 

23347118

 

[PubMed – as supplied by publisher]