Anandamide induces apoptosis in human cells via vanilloid receptors - Evidence for a protective role of cannabinoid receptors

The endocannabinoid anandamide (AEA) is shown to induce apoptotic bodies fo rmation and DNA fragmentation, hallmarks of programmed cell death, in human neuroblastoma CHP100 and lymphoma U937 cells. RNA and protein synthesis in hibitors like actinomycin D and cycloheximide reduced to one-fifth the numb er of apoptotic bodies induced by AEA, whereas the AEA transporter inhibito r AM404 or the AEA hydrolase inhibitor ATFMK significantly increased the nu mber of dying cells. Furthermore, specific antagonists of cannabinoid or va nilloid receptors potentiated or inhibited cell death induced by AEA, respe ctively. Other endocannabinoids such as 2-arachidonoylglycerol, linoleoylet hanolamide, oleoylethanolamide, and palmitoylethanolamide did not promote c ell death under the same experimental conditions. The formation of apoptoti c bodies induced by AEA was paralleled by increases in intracellular calciu m (3-fold over the controls), mitochondrial uncoupling (6-fold), and cytoch rome c release (3-fold). The intracellular calcium chelator EGTA-AM reduced the number of apoptotic bodies to 40% of the controls, and electrotransfer red anti-cytochrome c monoclonal antibodies fully prevented apoptosis induc ed by AEA, Moreover, 5-lipoxygenase inhibitors 5,8,11,14-eicosatetraynoic a cid and MK886, cyclooxygenase inhibitor indomethacin, caspase-3 and caspase -9 inhibitors Z-DEVD-FMK and Z-LEHD-FMK, but not nitric oxide synthase inhi bitor Nw-nitro-L-arginine methyl ester, significantly reduced the cell deat h-inducing effect of AEA. The data presented indicate a protective role of cannabinoid receptors against apoptosis induced by AEA via vanilloid recept ors.