Nicotinic acetylcholine receptors (nAChRs) are longstanding targets for a next generation of pain therapeutics, but the nAChR subtypes that govern analgesia remain unknown. We tested a series of nicotinic agonists, including many molecules used or tried clinically, on a panel of cloned neuronal nAChRs for potency and selectivity using patch-clamp electrophysiology and a live cell-based fluorescence assay. Nonselective nicotinic agonists as well as compounds selective either for α4β2 or for α7 nAChRs were then tested in the formalin and complete Freund’s adjuvant models of pain. Nonselective nAChR agonists ABT-594 and varenicline were effective analgesics. By contrast, the selective α4β2 agonist ispronicline and a novel α4β2-selective potentiator did not appear to produce analgesia in either model. α7-selective agonists reduced the pain-related endpoint, but the effect could be ascribed to nonspecific reduction of movement rather than to analgesia. Neither selective nor nonselective α7 nicotinic agonists affected the release of pro-inflammatory cytokines in response to antigen challenge. Electrophysiological recordings from spinal cord slice showed a strong nicotine-induced increase in inhibitory synaptic transmission that was mediated partially by α4β2 and only minimally by α7 subtypes. Taken with previous studies, the results suggest that agonism of α4β2 nAChRs is necessary but not sufficient to produce analgesia, and that the spinal cord is a key site where the molecular action of nAChRs produces analgesia.

The discovery of a series of small molecule alpha4beta2 nAChR potentiators is reported. The structure-activity relationship leads to potent compounds selective against nAChRs including alpha3beta2 and alpha3beta4 and optimized for CNS penetrance. Compounds increased currents through recombinant alpha4beta2 nAChRs, yet did not compete for binding with the orthosteric ligand cytisine. High potency and efficacy on the rat channel combined with good PK properties will allow testing of the alpha4beta2 potentiator mechanism in animal models of disease.

The synthesis and structure–activity relationship of a series of carbamate potentiators of α4β2 nAChR is reported herein. These compounds were highly selective for α4β2 over other nAChR subtypes. In addition, compounds increased the response of α4β2 nAChRs to acetylcholine, as measured with patch–clamp electrophysiology.

We have identified and cloned a novel human cytokine with homology to cytokines of the interleukin-17 (IL-17) family, which we have termed human IL-17E (hIL-17E). With the identification of several IL-17 family members, it is critical to understand the in vivo function of these molecules. We have generated transgenic mice overexpressing hIL-17E using an apolipoprotein E (ApoE) hepatic promoter. These mice displayed changes in the peripheral blood, particularly, a 3-fold increase in total leukocytes consisting of increases in eosinophils, lymphocytes, and neutrophils. Splenomegaly and lymphoadenopathy were predominant and included marked eosinophil infiltrates and lymphoid hyperplasia. CCR3(+) eosinophils increased in the blood and lymph nodes of the transgenic mice by 50- and 300-fold, respectively. Eosinophils also increased 8- to 18-fold in the bone marrow and spleen, respectively. In the bone marrow, most of the eosinophils had an immature appearance. CD19(+) B cells increased 2- to 5-fold in the peripheral blood, 2-fold in the spleen, and 10-fold in the lymph nodes of transgenic mice, whereas CD4(+) T lymphocytes increased 2-fold in both blood and spleen. High serum levels of the cytokines IL-2, IL-4, IL-5, granulocyte colony-stimulating factor, eotaxin, and interferon gamma were observed. Consistent with B-lymphocyte increases, serum immunoglobulin (Ig) M, IgG, and IgE were significantly elevated. Antigenic challenge of the transgenic mice with keyhole limpet hemocyanin (KLH) resulted in a decrease in anti-KLH IgG accompanied by increases of anti-KLH IgA and IgE. In situ hybridization of transgenic tissues revealed that IL-17Rh1 (IL-17BR/Evi27), a receptor that binds IL-17E, is up-regulated. Taken together, these data indicate that IL-17E regulates hematopoietic and immune functions, stimulating the development of eosinophils and B lymphocytes. The fact that hIL-17E overexpression results in high levels of circulating eosinophils, IL-4, IL-5, eotaxin, and IgE suggests that IL-17E may be a proinflammatory cytokine favoring Th2-type immune responses.