Abstract
Cannabinoids modulate nitric oxide (NO) levels in cells of the central nervous system. Here we studied the effect of cannabinoid CB(1) and CB(2) receptor agonists on the release of NO and cell toxicity induced by the human immuno-deficiency virus-1 Tat protein (HIV-1 Tat) in rat glioma C6 cells. The CB(1) and CB(2) agonist WIN 55,212-2 inhibited the expression of inducible NO synthase (iNOS) and NO release caused by treatment of C6 cells with HIV-1 Tat and interferon-gamma (IFN-gamma). The effect of WIN 55,212-2 was uniquely due to CB(1) receptors, as shown by experiments carried out with selective CB(1) and CB(2) receptor agonists and antagonists. CB(1) receptor stimulation also inhibited HIV-1 Tat + IFN-gamma-induced and NO-mediated cell toxicity. Moreover, cell treatment with HIV-1 Tat + IFN-gamma induced a significant inhibition of CB(1), but not CB(2), receptor expression. This effect was mimicked by the NO donor GSNO, suggesting that the inhibition of CB(1) expression was due to HIV-1 Tat + IFN-gamma-induced NO overexpression. HIV-1 Tat + IFN-gamma treatment also induced a significant inhibition of the uptake of the endocannabinoid anandamide by C6 cells with no effect on anandamide hydrolysis. These findings show that the endocannabinoid system, through the modulation of the l-arginine/NO pathway, reduces HIV-1 Tat-induced cytotoxicity, and is itself regulated by HIV-1 Tat.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Benzoxazines
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Camphanes / pharmacology
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Cannabinoid Receptor Modulators
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Cannabinoids / pharmacology
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Cell Survival / drug effects
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Endocannabinoids
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Gene Expression Regulation, Enzymologic / drug effects
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Gene Expression Regulation, Neoplastic / drug effects
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Gene Products, tat / toxicity*
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Glioma
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HIV-1 / pathogenicity*
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Morpholines / pharmacology
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Naphthalenes / pharmacology
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Nitric Oxide / physiology
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Nitric Oxide Donors / pharmacology
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Nitric Oxide Synthase / antagonists & inhibitors
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Nitric Oxide Synthase / genetics
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Nitric Oxide Synthase Type II
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Peptide Fragments / toxicity
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Pyrazoles / pharmacology
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Rats
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Receptor, Cannabinoid, CB2*
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Receptors, Cannabinoid
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Receptors, Drug / agonists
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Receptors, Drug / physiology*
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Reverse Transcriptase Polymerase Chain Reaction
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Tumor Cells, Cultured
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tat Gene Products, Human Immunodeficiency Virus
Substances
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Benzoxazines
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Camphanes
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Cannabinoid Receptor Modulators
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Cannabinoids
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Cnr2 protein, rat
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Endocannabinoids
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Gene Products, tat
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Morpholines
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Naphthalenes
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Nitric Oxide Donors
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Peptide Fragments
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Pyrazoles
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Receptor, Cannabinoid, CB2
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Receptors, Cannabinoid
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Receptors, Drug
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SR 144528
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tat Gene Products, Human Immunodeficiency Virus
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Nitric Oxide
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(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone
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Nitric Oxide Synthase
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Nitric Oxide Synthase Type II
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Nos2 protein, rat