Induction of intracellular calcium elevation by Delta9-tetrahydrocannabinol in T cells involves TRPC1 channels.
We have reported previously that Delta9-tetrahydrocannabinol (Delta9-THC) treatment of resting human and murine splenic T cells robustly elevated intracellular calcium ([Ca2+]i). The objective of the present investigation was to examine the putative role of [Ca2+]i store depletion and store-operated calcium (SOC) and receptor-operated cation (ROC) channels in the mechanism by which Delta9-THC increases [Ca2+]i in the cannabinoid-2 receptor-expressing human peripheral blood-acute lymphoid leukemia (HPB-ALL) human T cell line. By using the smooth endoplasmic reticulum Ca2+-ATPase pump inhibitor, thapsigargin, and the ryanodine receptor antagonist, 8-bromo-cyclic adenosine diphosphate ribose, we demonstrate that the Delta9-THC-mediated elevation in [Ca2+]i occurs independently of [Ca2+]i store depletion. Furthermore, the ROC channel inhibitor, SK&F 96365 was more efficacious at attenuating the Delta9-THC-mediated elevation in [Ca2+]i than SOC channel inhibitors, 2-aminoethoxydiphenyl borate and La3+. Recently, several members of the transient receptor potential canonical (TRPC) channel subfamily have been suggested to operate as SOC or ROC channels. In the present studies, treatment of HPB-ALL cells with 1-oleoyl-2-acetyl-sn-glycerol (OAG), a cell-permeant analog of diacylglycerol (DAG), which gates several members of the TRPC channel subfamily, rapidly elevated [Ca2+]i, as well as prevented a subsequent, additive elevation in [Ca2+]i by Delta9-THC, independent of protein kinase C. Reverse transcriptase-polymerase chain reaction analysis for TRPC1-7 showed that HPB-ALL cells express detectable mRNA levels of only TRPC1. Finally, small interference RNA knockdown of TRPC1 attenuated the Delta9-THC-mediated elevation of [Ca2+]i. Collectively, these results suggest that Delta9-THC-induced elevation in [Ca2+]i is attributable entirely to extracellular calcium influx, which is independent of [Ca2+]i store depletion, and is mediated, at least partially, through the DAG-sensitive TRPC1 channels.
Rao
Gautham K
GK
Department of Pharmacology & Toxicology, Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824-1317, USA.
Kaminski
Norbert E
NE
D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D045744:Cell Line, Tumor; D013759:Dronabinol / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism / Q000473:pathology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000096:biosynthesis; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism* / Q000473:pathology; D050052:TRPC Cation Channels / Q000378:metabolism*
D018712:Analgesics, Non-Narcotic; D004791:Enzyme Inhibitors; D043885:Receptor, Cannabinoid, CB2; D019837:Ryanodine Receptor Calcium Release Channel; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D013759:Dronabinol; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D002118:Calcium