Abstract
Activation of CB2 has been demonstrated to induce directed immune cell migration. However, the ability of CB2 to act as a chemoattractant receptor in macrophages remains largely unexplored. Using a real-time chemotaxis assay and a panel of chemically diverse and widely used CB2 agonists, we set out to examine whether CB2 modulates primary murine macrophage chemotaxis. We report that of 12 agonists tested, only JWH133, HU308, L-759,656 and L-759,633 acted as macrophage chemoattractants. Surprisingly, neither pharmacological inhibition nor genetic ablation of CB2 had any effect on CB2 agonist-induced macrophage chemotaxis. As chemotaxis was pertussis toxin sensitive in both WT and CB2-/- macrophages, we concluded that a non-CB1/CB2, Gi/o-coupled GPCR must be responsible for CB2 agonist-induced macrophage migration. The obvious candidate receptors GPR18 and GPR55 could not mediate JWH133 or HU308-induced cytoskeletal rearrangement or JWH133-induced β-arrestin recruitment in cells transfected with either receptor, demonstrating that neither are the unidentified GPCR. Taken together our results conclusively demonstrate that CB2 is not a chemoattractant receptor for murine macrophages. Furthermore we show for the first time that JWH133, HU308, L-759,656 and L-759,633 have off-target effects of functional consequence in primary cells and we believe that our findings have wide ranging implications for the entire cannabinoid field.
Highlights
This expression profile led to the hypothesis that CB2 acts as an immunomodulatory receptor
Steffens et al demonstrated that Δ 9-THC treatment of murine macrophages inhibits their chemotaxis towards CCL225, whilst a parallel report by Raborn et al found that Δ 9-THC and CP55,940 inhibit macrophage migration towards CCL526
This negative role seems to be at odds with CB2 behaving as a chemoattractant receptor in other leukocyte populations and further complexity is added by the finding that, in contrast to 2-AG, JWH015, CP55,940 and Δ 9-THC are unable to inhibit neutrophil chemotaxis toward fMLP27,28, suggesting that functional selectivity may impact this process as well
Summary
This expression profile led to the hypothesis that CB2 acts as an immunomodulatory receptor. 2-AG acts as a chemoattractant, the mixed CB1/CB2 agonists WIN,55212-2 and CP55,940 fail to elicit directed cellular migration[14,17], hinting that functional selectivity may impact CB2-mediated chemotaxis This phenomenon, known as biased agonism, is defined as the ability of different ligands at the same receptor to activate distinct downstream signalling pathways[18] and has already been documented for ligands acting at CB219,20. Steffens et al demonstrated that Δ 9-THC treatment of murine macrophages inhibits their chemotaxis towards CCL225, whilst a parallel report by Raborn et al found that Δ 9-THC and CP55,940 inhibit macrophage migration towards CCL526 This negative role seems to be at odds with CB2 behaving as a chemoattractant receptor in other leukocyte populations and further complexity is added by the finding that, in contrast to 2-AG, JWH015, CP55,940 and Δ 9-THC are unable to inhibit neutrophil chemotaxis toward fMLP27,28, suggesting that functional selectivity may impact this process as well. We conclude that CB2 is not a chemoattractant receptor in murine macrophages, and that chemotaxis elicited by CB2 agonists occurs via an off-target effect at a non-CB1/CB2 Gi/o-coupled GPCR
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
