Abstract
Excess oxidative and endoplasmic reticulum (ER) stress disrupt cellular homeostasis and promote cardiovascular disease (CVD). The endocannabinoids anandamide and 2-arachidonoyl glycerol and the potent cannabinoid Δ9-tetrahydrocannabinol increase oxidative stress and ER stress in endothelial cells. However, it remains unclear whether endocannabinoids have intrinsic capacity to ameliorate oxidative stress. In human coronary artery endothelial cells (HCAEC), anandamide, 2-arachidonoyl glycerol, and tunicamycin increased superoxide generation and nuclear factor erythroid 2-related factor 2 (NRF2) mRNA and NRF2-dependent reporter gene activity. High anandamide, 2-arachidonoyl glycerol, and tunicamycin levels also increased lipid peroxidation. Furthermore, anandamide increased NRF2-responsive hemeoxygenase 1 (HO1), thioredoxin reductase 1 (TRX1), and NAD(P)H dehydrogenase quinone 1 (NQO1) mRNA. This effect was mediated by protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK); PERK silencing utilizing siRNA suppressed NRF2 induction by anandamide and tunicamycin. In contrast, activating transcription factor 6 (ATF6) and inositol requiring enzyme 1α (IRE1α ) silencing had no effect on NRF2 mRNA or NRF2 target gene expression in tunicamycin and anandamide-treated cells. Likewise, the PERK inhibitor GSK2606414 prevented NRF2 induction by anandamide and tunicamycin while treatment with Ceapin A7 (an ATF6 inhibitor) or GSK2850163 (an IRE1α inhibitor) did not. In conclusion, endocannabinoid-related ER stress increased superoxide generation accompanied by compensatory increase in production of antioxidant enzymes thereby highlighting the cross talk between ER stress and oxidative stress.