am-356 and Multiple-Sclerosis

The aim of this study was to characterize inhibitory mechanisms on T cell receptor signaling mediated by the cannabinoid receptors CB1 and CB2. Both receptors are coupled to G(i/o) proteins, which are associated with inhibition of cyclic AMP formation. In human primary and Jurkat T lymphocytes, activation of CB1 by R(+)-methanandamide, CB2 by JWH015, and both by Delta9-tetrahydrocannabinol induced a short decrease in cyclic AMP lasting less than 1 h. However, this decrease was followed by a massive (up to 10-fold) and sustained (at least up to 48 h) increase in cyclic AMP. Mediated by the cyclic AMP-activated protein kinase A and C-terminal Src kinase, the cannabinoids induced a stable phosphorylation of the inhibitory Tyr-505 of the leukocyte-specific protein tyrosine kinase (Lck). By thus arresting Lck in its inhibited form, the cannabinoids prevented the dephosphorylation of Lck at Tyr-505 in response to T cell receptor activation, which is necessary for the subsequent initiation of T cell receptor signaling. In this way the cannabinoids inhibited the T cell receptor-triggered signaling, i.e. the activation of the zeta-chain-associated protein kinase of 70 kDa, the linker for activation of T cells, MAPK, the induction of interleukin-2, and T cell proliferation. All of the effects of the cannabinoids were blocked by the CB1 and CB2 antagonists AM281 and AM630. These findings help to better understand the immunosuppressive effects of cannabinoids and explain the beneficial effects of these drugs in the treatment of T cell-mediated autoimmune disorders like multiple sclerosis.

Topics: Arachidonic Acids; Cannabinoids; Cell Proliferation; CSK Tyrosine-Protein Kinase; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Dronabinol; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; GTP-Binding Protein alpha Subunits, Gi-Go; Humans; Indoles; Interleukin-2; Jurkat Cells; Lymphocyte Activation; Lymphocyte Specific Protein Tyrosine Kinase p56(lck); Morpholines; Multiple Sclerosis; Phosphorylation; Protein-Tyrosine Kinases; Psychotropic Drugs; Pyrazoles; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Receptors, Antigen, T-Cell; Signal Transduction; src-Family Kinases; T-Lymphocytes

Activation of cannabinoid receptors causes inhibition of spasticity, in a mouse model of multiple sclerosis, and of persistent pain, in the rat formalin test. The endocannabinoid anandamide inhibits spasticity and persistent pain. It not only binds to cannabinoid receptors but is also a full agonist at vanilloid receptors of type 1 (VR1). We found here that vanilloid VR1 receptor agonists (capsaicin and N-N'-(3-methoxy-4-aminoethoxy-benzyl)-(4-tert-butyl-benzyl)-urea [SDZ-249-665]) exhibit a small, albeit significant, inhibition of spasticity that can be attenuated by the vanilloid VR1 receptor antagonist, capsazepine. Arvanil, a structural "hybrid" between capsaicin and anandamide, was a potent inhibitor of spasticity at doses (e.g. 0.01 mg/kg i.v.) where capsaicin and cannabinoid CB(1) receptor agonists were ineffective. The anti-spastic effect of arvanil was unchanged in cannabinoid CB(1) receptor gene-deficient mice or in wildtype mice in the presence of both cannabinoid and vanilloid receptor antagonists. Likewise, arvanil (0.1-0.25 mg/kg) exhibited a potent analgesic effect in the formalin test, which was not reversed by cannabinoid and vanilloid receptor antagonists. These findings suggest that activation by arvanil of sites of action different from cannabinoid CB(1)/CB(2) receptors and vanilloid VR1 receptors leads to anti-spastic/analgesic effects that might be exploited therapeutically.

Topics: Animals; Arachidonic Acids; Benzoxazines; Camphanes; Cannabinoid Receptor Modulators; Capsaicin; Disease Models, Animal; Dose-Response Relationship, Drug; Genotype; Mice; Mice, Inbred Strains; Mice, Knockout; Morpholines; Multiple Sclerosis; Muscle Spasticity; Naphthalenes; Pain; Pain Measurement; Piperidines; Pyrazoles; Receptors, Cannabinoid; Receptors, Drug; Rimonabant