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Induction of intracellular calcium elevation by Δ 9 ‐tetrahydrocannabinol in T cells involves TRPC1 channels
Author(s) -
Rao Gautham K.,
Kaminski Norbert E.
Publication year - 2006
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.0505274
Subject(s) - trpc , thapsigargin , trpc1 , biology , transient receptor potential channel , ryanodine receptor , voltage dependent calcium channel , microbiology and biotechnology , endocrinology , medicine , intracellular , receptor , calcium , biochemistry
We have reported previously that Δ 9 ‐tetrahydrocannabinol (Δ 9 ‐THC) treatment of resting human and murine splenic T cells robustly elevated intracellular calcium ([Ca 2 + ] i ). The objective of the present investigation was to examine the putative role of [Ca 2 + ] i store depletion and store‐operated calcium (SOC) [1] and receptor‐operated cation (ROC) channels in the mechanism by which Δ 9 ‐THC increases [Ca 2 + ] i in the cannabinoid‐2 receptor‐expressing human peripheral blood‐acute lymphoid leukemia (HPB‐ALL) human T cell line. By using the smooth endoplasmic reiculum Ca 2 + ‐ATPase pump inhibitor, thapsigargin, and the ryanodine receptor antagonist, 8‐bromo‐cyclic adenosine diphosphate ribose, we demonstrate that the Δ 9 ‐THC‐mediated elevation in [Ca 2 + ] i occurs independently of [Ca 2 + ] i store depletion. Furthermore, the ROC channel inhibitor, SK&F 96365 was more efficacious at attenuating the Δ 9 ‐THC‐mediated elevation in [Ca 2 + ] i than SOC channel inhibitors, 2‐aminoethoxydiphenyl borate and La 3 + . 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 [Ca 2 + ] i , as well as prevented a subsequent, additive elevation in [Ca 2 + ] i by Δ 9 ‐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 Δ 9 ‐THC‐mediated elevation of [Ca 2 + ] i . Collectively, these results suggest that Δ 9 ‐THC‐induced elevation in [Ca 2 + ] i is attributable entirely to extracellular calcium influx, which is independent of [Ca 2 + ] i store depletion, and is mediated, at least partially, through the DAG‐sensitive TRPC1 channels.