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Evidence has emerged suggesting a role for the cannabinoid CB2 receptor in immune cell motility. This provides a rationale for a novel and generalized immunoregulatory role for cannabinoid CB2 receptor-specific compounds. In support of this possibility, we will review the biology of a class of cannabinoid CB2 receptor-specific inverse agonist, the triaryl bis-sulfones. We will show that one candidate, Sch.414319, is potent and selective for the cannabinoid CB2 receptor, based on profiling studies using biochemical assays for 45 enzymes and 80 G-protein coupled receptors and ion channels. We will describe initial mechanistic studies using this optimized triaryl bis-sulfone, showing that the compound exerts a broad effect on cellular protein phosphorylations in human monocytes. This profile includes the down regulation of a required phosphorylation of the monocyte-specific actin bundling protein L-plastin. We suggest that this observation may provide a mechanism for the observed activity of Sch.414319 in vivo. Our continued analysis of the in vivo efficacy of this compound in diverse disease models shows that Sch.414319 is a potent modulator of immune cell mobility in vivo, can modulate bone damage in antigen-induced mono-articular arthritis in the rat, and is uniquely potent at blocking experimental autoimmune encephalomyelitis in the rat.

We report that the addition of human macrophage inflammatory protein-3 beta (MIP-3 beta) to cultures of human PBMCs that have been activated with LPS or PHA results in a significant enhancement of IL-10 production. This effect was concentration-dependent, with optimal MIP-3 beta concentrations inducing more than a 5-fold induction of IL-10 from LPS-stimulated PBMCs and a 2- to 3-fold induction of IL-10 from PHA-stimulated PBMCs. In contrast, no significant effect on IL-10 production was observed when 6Ckine, the other reported ligand for human CCR7, or other CC chemokines such as monocyte chemoattractant protein-1, RANTES, MIP-1 alpha, and MIP-1 beta were added to LPS- or PHA-stimulated PBMCs. Similar results were observed using activated purified human peripheral blood monocytes or T cells. Addition of MIP-3 beta to nonactivated PBMCs had no effect on cytokine production. Enhancement of IL-10 production by MIP-3beta correlated with the inhibition of IL-12 p40 and TNF-alpha production by monocytes and with the impairment of IFN-gamma production by T cells, which was reversed by addition of anti-IL-10 Abs to the cultures. The ability of MIP-3 beta to augment IL-10 production correlated with CCR7 mRNA expression and stimulation of intracellular calcium mobilization in both monocytes and T cells. These data indicate that MIP-3 beta acts directly on human monocytes and T cells and suggest that this chemokine is unique among ligands binding to CC receptors due to its ability to modulate inflammatory activity via the enhanced production of the anti-inflammatory cytokine IL-10.

The CC chemokine known as 6Ckine (SLC, Exodus-2, or TCA4) has been identified as a ligand for CCR7. Mouse 6Ckine has also been shown to signal through mouse CXCR3 and share some of the activities of IFN-gamma inducible protein 10 and monokine induced by IFN-gamma. Nonetheless, human 6Ckine has not been shown to bind CXCR3 receptor or have angiostatic activity. In this study, we report that human 6Ckine does not induce a calcium flux in either human CXCR3 or mouse CXCR3 transfected cells, although it is an equally potent agonist as mouse 6Ckine and human macrophage inflammatory protein-3beta in human CCR7 transfected cells. Mouse 6Ckine (but not human 6Ckine) is capable of competing with radiolabeled IFN-gamma inducible protein 10 for human CXCR3. In addition, radiolabeled human 6Ckine does not bind to either human CXCR3 or mouse CXCR3. Together these data suggest that human CC chemokine 6Ckine is not a ligand for the human or mouse CXC chemokine receptor CXCR3.