Identification and biochemical analyses of selective CB2 agonists

Abstract

Cannabinoid CB 1 and CB 2 receptors are activated by Δ 9-tetrahydrocannabinol, a psychoactive component of marijuana. The cannabinoid CB 1 receptor is primarily located in the brain and is responsible for the psychoactive side effects, whereas the cannabinoid CB 2 receptor is located in immune cells and is an attractive target for immune-related maladies. We identify small molecules that selectively bind to the cannabinoid CB 2 receptor and can be further developed into therapeutics. The affinity of three molecules, ABK5, ABK6, and ABK7, to the cannabinoid CB 2 receptor was determined with radioligand competition binding. The potency of G-protein coupling was determined with GTPγS binding. The three compounds bound selectively to the cannabinoid CB 2 receptor, and no binding to the cannabinoid CB 1 receptor was detected up to 10 μM. Immunoblotting studies show that the amount of ERK1/2 and MEK phosphorylation increased in a G i/o-dependent manner. Furthermore, an immune cell line (Jurkat cells) was treated with ABK5, and as a result, inhibited cell proliferation. These three compounds are novel cannabinoid CB 2 receptor agonists and hold promise to be further developed to treat inflammation and the oftenassociated pain.

Characterization of Subtype Selective Cannabinoid CB2 Receptor Agonists as Potential Anti-Inflammatory Agents

“…Although studies reported that activation of CB 2 can reduce pain through anti-inflammation [ 7 , 28 , 29 ], there is still no CB 2 -subtype selective agonist on the market. Previously, we identified a compound, ABK5, which was originally found to activate CB 2 in a high throughput screening [ 25 ], and to be a CB 2 -subtype selective agonist [ 23 ]. ABK5 inhibited IL-2 and TNF-α production in Jurkat cells and MOLT-4 cells, and mitigated inflammation in a Complete Freund’s adjuvant treated inflammatory pain model in rats [ 24 ].…”

“…d N.D.: K i or EC 50 value was not determined. e Parameters of ABK5 were determined previously and are shown for comparison [ 23 ].…”

“…Previously, we identified a CB 2 subtype selective agonist, ABK5, which is a structurally distinct compound from plant-derived or synthetic cannabinoid receptor agonists such as THC and CP55,940 [ 23 ]. ABK5 is a strong CB 2 binder with K i value of 16 nM, while no CB 1 binding was detected up to 10 μM [ 23 ].…”

“…Previously, we identified a CB 2 subtype selective agonist, ABK5, which is a structurally distinct compound from plant-derived or synthetic cannabinoid receptor agonists such as THC and CP55,940 [ 23 ]. ABK5 is a strong CB 2 binder with K i value of 16 nM, while no CB 1 binding was detected up to 10 μM [ 23 ]. We also demonstrated that this compound has anti-inflammatory effects through inhibition of proliferation, IL-2 and TNF-α production, and chemotaxis in human T cell lines [ 23 ].…”

“…ABK5 is a strong CB 2 binder with K i value of 16 nM, while no CB 1 binding was detected up to 10 μM [ 23 ]. We also demonstrated that this compound has anti-inflammatory effects through inhibition of proliferation, IL-2 and TNF-α production, and chemotaxis in human T cell lines [ 23 ]. Moreover, ABK5, showed an anti-inflammatory effect in inflammatory pain model rats [ 24 ].…”