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Cannabinoid CB1 and CB2 receptors are members of the G protein-coupled receptor family, which is the largest class of membrane proteins in the human genome. As part of the endocannabinoid system, they have many regulatory functions in the human body. Their malfunction therefore triggers a diverse set of undesired conditions, such as pain, neuropathy, nephropathy, pruritus, osteoporosis, cachexia and Alzheimer’s disease. Although drugs targeting the system exist, the molecular and functional mechanisms involved are still poorly understood, preventing the development of better therapeutics with fewer undesired effects. One path toward the development of better and safer medicines targeting cannabinoid receptors relies on the ability of some compounds to activate a subset of pathways engaged by the receptor while sparing or even inhibiting the others, a phenomenon known as biased signaling. To take advantage of this phenomenon for drug development, a better profiling of the pathways engaged by the receptors is required. Using a BRET-based signaling detection platform, we systematically analyzed the primary signaling cascades activated by CB1 and CB2 receptors, including 9 G protein and 2 β-arrestin subtypes. Given that biased signaling is driven by ligand-specific distinct active conformations of the receptor, establishing a link between the signaling profiles elicited by different drugs and their chemotypes may help designing compounds that selectively activate beneficial pathways while avoiding those leading to undesired effects. We screened a selection of 35 structurally diverse ligands, including endocannabinoids, phytocannabinoids and synthetic compounds structurally similar or significantly different from natural cannabinoids. Our data show that biased signaling is a prominent feature of the cannabinoid receptor system and that, as predicted, ligands with different chemotypes have distinct signaling profiles. The study therefore allows for better understanding of cannabinoid receptors signaling and provides the information about tool compounds that can now be used to link signaling pathways to biological outcomes, aiding the design of improved therapeutics.

(1) Background: The cannabinoid 2 receptor (CB2R) is a promising anti-inflammatory drug target and development of selective CB2R ligands may be useful for treating sight-threatening ocular inflammation. (2) Methods: This study examined the pharmacology of three novel chemically-diverse selective CB2R ligands: CB2R agonists, RO6871304, and RO6871085, as well as a CB2R inverse agonist, RO6851228. In silico molecular modelling and in vitro cell-based receptor assays were used to verify CB2R interactions, binding, cell signaling (&szlig, arrestin and cAMP) and early absorption, distribution, metabolism, excretion, and toxicology (ADMET) profiling of these receptor ligands. All ligands were evaluated for their efficacy to modulate leukocyte-neutrophil activity, in comparison to the reported CB2R ligand, HU910, using an in vivo mouse model of endotoxin-induced uveitis (EIU) in wild-type (WT) and CB2R-/- mice. The actions of RO6871304 on neutrophil migration and adhesion were examined in vitro using isolated neutrophils from WT and CB2R-/- mice, and in vivo in WT mice with EIU using adoptive transfer of WT and CB2R-/- neutrophils, respectively. (3) Results: Molecular docking studies indicated that RO6871304 and RO6871085 bind to the orthosteric site of CB2R. Binding studies and cell signaling assays for RO6871304 and RO6871085 confirmed high-affinity binding to CB2R and selectivity for CB2R &gt, CB1R, with both ligands acting as full agonists in cAMP and &szlig, arrestin assays (EC50s in low nM range). When tested in EIU, topical application of RO6871304 and RO6871085 decreased leukocyte-endothelial adhesion and this effect was antagonized by the inverse agonist, RO6851228. The CB2R agonist, RO6871304, decreased in vitro neutrophil migration of WT neutrophils but not neutrophils from CB2R-/-, and attenuated adhesion of adoptively-transferred leukocytes in EIU. (4) Conclusions: These unique ligands are potent and selective for CB2R and have good immunomodulating actions in the eye. RO6871304 and RO6871085, as well as HU910, decreased leukocyte adhesion in EIU through inhibition of resident ocular immune cells. The data generated with these three structurally-diverse and highly-selective CB2R agonists support selective targeting of CB2R for treating ocular inflammatory diseases.

Astrocytes are involved in non-cell-autonomous pathogenic cascades in amyotrophic lateral sclerosis (ALS); however, their role is still debated. We show that astrocytic NF-κB activation drives microglial proliferation and leukocyte infiltration in the SOD1 (G93A) ALS model. This response prolongs the presymptomatic phase, delaying muscle denervation and decreasing disease burden, but turns detrimental in the symptomatic phase, accelerating disease progression. The transition corresponds to a shift in the microglial phenotype showing two effects that can be dissociated by temporally controlling NF-κB activation. While NF-κB activation in astrocytes induced a Wnt-dependent microglial proliferation in the presymptomatic phase with neuroprotective effects on motoneurons, in later stage, astrocyte NF-κB-dependent microglial activation caused an accelerated disease progression. Notably, suppression of the early microglial response by CB ₂ R agonists had acute detrimental effects. These data identify astrocytes as important regulators of microglia expansion and immune response. Therefore, stage-dependent microglia modulation may be an effective therapeutic strategy in ALS.

The cannabinoid receptor 2 (CB2) system is described to modulate various pathological conditions, including inflammation and fibrosis. A series of new heterocyclic small-molecule CB2 receptor agonists were identified from a high-throughput screen. Lead optimization gave access to novel, highly potent, and selective (over CB1) triazolopyrimidine derivatives. A preliminary structure-activity relationship was established, and physicochemical properties in this compound class were significantly improved toward better solubility, lipophilicity, and microsomal stability. An optimized triazolopyrimidine derivative, (3S)-1-[5-tert-butyl-3-[(1-cyclopropyltetrazol-5-yl)methyl]triazolo[4,5-d]pyrimidin-7-yl]pyrrolidin-3-ol (39), was tested in a kidney ischemia-reperfusion model, in which it showed efficacy at a dose of 10 mg kg(-1) (p.o.). A significant depletion of the three measured kidney markers indicated a protective role of CB2 receptor activation toward inflammatory kidney damage. Compound 39 was also protective in a model of renal fibrosis. Oral treatment with 39 at 3 mg kg(-1) per day significantly decreased the amount of fibrosis by ∼ 40% which was induced by unilateral ureter obstruction.

Development of efficient methods for preparation of bioactive nonribosomal peptides, containing densely functionalized nonproteinogenic amino acids, is an important task in organic synthesis. We have employed a concise synthesis for such amino acids by asymmetric aldol addition coupled with an isomeric resolution via diastereoselective cyclization. This approach is successfully applied to the first total synthesis of the cyclic hexapeptide aglycone of the mannopeptimycins, a group of glycopeptides known for potent activity against drug-resistant bacteria. The facile preparation of the key amino acids and the synthesis of the aglycone pave the way for further studies on this class of antibiotics and the development of new lead compounds with therapeutic potential. In addition, our studies have led to the revision of the stereochemistry of the β-methylphenylalanine residue in the mannopeptimycin aglycone.

A series of highly potent & selective adamantane derived CB2 agonists was identified in a high-throughput screen. A SAR was established and physicochemical properties were significantly improved. This was accompanied by potency of the compounds on the Q63R variant and varying β-arrestin data which will support the insight into their relevance for the in vivo situation.