Yes / Rationale: Nicotinic α7 acetylcholine receptors (nAChRs) have been highlighted as a target for cognitive enhancement in schizophrenia. Aim: To investigate whether the deficits induced by sub-chronic phencyclidine (PCP) in reversal learning and novel object recognition could be attenuated by the selective α7 nAChR full agonist, PNU-282987. Methods: Adult female hooded-Lister rats received sub-chronic PCP (2 mg/kg) or vehicle i.p. twice daily for seven days, followed by 7-days washout. In cohort 1, PCP-treated rats then received PNU-282987 (5, 10, 20 mg/kg; s.c.) or vehicle and were tested in the reversal learning task. In cohort 2, PCP-treated rats received PNU-282987 (10 mg/kg; s.c.) or saline for 15 days and were tested in the novel object recognition test on day 1 and on day 15, to test for tolerance. Results: Sub-chronic PCP produced significant deficits in both cognitive tasks (P<0.01-0.001). PNU-282987 attenuated the PCP-induced deficits in reversal learning at 10 mg/kg (P<0.01) and 20 mg/kg (P<0.001), and in novel object recognition at 10 mg/kg on day 1 (P<0.01) and on day 15 (P<0.001). Conclusions: These data show that PNU-282987 has efficacy to reverse PCP-induced deficits in two paradigms of relevance to schizophrenia. Results further suggest that 15 day daily dosing of PNU-282987 (10 mg/kg s.c.) does not cause tolerance in rat. This study suggests that activation of α7 nAChRs, may represent a suitable strategy for improving cognitive deficits of relevance to schizophrenia. / SL McLean was supported by a joint University of Bradford–GSK postgraduate studentship.

Electrical stimulation of the vagus nerve attenuates tumor necrosis factor (TNF) synthesis by macrophages and reduces the systemic inflammatory response. Current evidence suggests that the α7 nicotinic acetylcholine receptor present in the celiac/superior mesenteric ganglia is a key component in vagus nerve signaling to the spleen; however, there is currently no direct anatomical evidence that the α7 receptor is present in the murine celiac/superior mesenteric ganglia. Our study addresses this deficiency by providing anatomical evidence that the α7 receptor is expressed within the celiac/superior mesenteric ganglia and splenic nerve fibers using immunohistochemistry and quantitative polymerase chain reaction (qPCR). α7 receptor mRNA is highly expressed in the celiac/superior mesenteric ganglia and at low levels in the spleen compared to the brain. Double-labeling for α7 and tyrosine hydroxylase shows that α7 receptor protein is present on noradrenergic neurons within the ganglia and prejunctionally on noradrenergic nerve fibers within the spleen. The α7 receptor in the ganglia provides a possible location for the action of α7-selective agonists, while prejunctional α7 receptor expressed on splenic nerves may induce an increase in norepinephrine release in a positive feedback system enhanced by lymphocyte-derived acetylcholine.

The nervous system and immune system have broad and overlapping distributions in the body, and interactions of these ubiquitous systems are central to the field of neuroimmunology. Over the past two decades, there has been explosive growth in our understanding of neuroanatomical, cellular, and molecular mechanisms that mediate central modulation of immune functions through the autonomic nervous system. A major catalyst for growth in this field was the discovery that vagal nerve stimulation (VNS) caused a prominent attenuation of the systemic inflammatory response evoked by endotoxin in experimental animals. This effect was mediated by acetylcholine (ACh) stimulation of nicotinic receptors on splenic macrophages. Hence, the circuit was dubbed the “cholinergic anti-inflammatory pathway”. Subsequent work identified the α7 nicotinic ACh receptor (α7nAChR) as the crucial target for attenuation of pro-inflammatory cytokine release from macrophages and dendritic cells. Further investigation made the important discovery that cholinergic T cells within the spleen and not cholinergic nerve cells were the source of ACh that stimulated α7 receptors on splenic macrophages. Given the important role that inflammation plays in numerous disease processes, cholinergic anti-inflammatory mechanisms are under intensive investigation from a basic science perspective and in translational studies of animal models of diseases such as inflammatory bowel disease and rheumatoid arthritis. This basic work has already fostered several clinical trials examining the efficacy of VNS and cholinergic therapeutics in human inflammatory diseases. This review provides an overview of basic and translational aspects of the cholinergic anti-inflammatory response and relevant pharmacology of drugs acting at the α7nAChR.

α-conotoxins are 13–19 amino acid toxin peptides that bind various nicotinic acetylcholine receptor (nAChR) subtypes. α-conotoxin Mr1.7c (MrIC) is a 17 amino acid peptide that targets α7 nAChR. Although MrIC has no activating effect on α7 nAChR when applied by itself, it evokes a large response when co-applied with the type II positive allosteric modulator PNU-120596, which potentiates the α7 nAChR response by recovering it from a desensitized state. A lack of standalone activity, despite activation upon co-application with a positive allosteric modulator, was previously observed for molecules that bind to an extracellular domain allosteric activation (AA) site at the vestibule of the receptor. We hypothesized that MrIC may activate α7 nAChR allosterically through this site. We ran voltage-clamp electrophysiology experiments and in silico peptide docking calculations in order to gather evidence in support of α7 nAChR activation by MrIC through the AA site. The experiments with the wild-type α7 nAChR supported an allosteric mode of action, which was confirmed by the significantly increased MrIC + PNU-120596 responses of three α7 nAChR AA site mutants that were designed in silico to improve MrIC binding. Overall, our results shed light on the allosteric activation of α7 nAChR by MrIC and suggest the involvement of the AA site.

Neonatal quinpirole (NQ) treatment to rats increases dopamine D2 receptor sensitivity persistent throughout the animal’s lifetime. In Experiment 1, we analyzed the role of α7 and α4β2 nicotinic receptors (nAChRs) in nicotine behavioral sensitization and on the brain-derived neurotrophic factor (BDNF) response to nicotine in NQ- and neonatally saline (NS)-treated rats. In Experiment 2, we analyzed changes in α7 and α4β2 nAChR density in the nucleus accumbens (NAcc) and dorsal striatum in NQ and NS animals sensitized to nicotine. Male and female Sprague-Dawley rats were neonatally treated with quinpirole (1mg/kg) or saline from postnatal days (P)1-21. Animals were given ip injections of either saline or nicotine (0.5mg/kg free base) every second day from P33 to P49 and tested on behavioral sensitization. Before each injection, animals were ip administered the α7 nAChR antagonist methyllycaconitine (MLA; 2 or 4mg/kg) or the α4β2 nAChR antagonist dihydro beta erythroidine (DhβE; 1 or 3mg/kg). Results revealed NQ enhanced nicotine sensitization that was blocked by DhβE. MLA blocked the enhanced nicotine sensitization in NQ animals, but did not block nicotine sensitization. NQ enhanced the NAcc BDNF response to nicotine which was blocked by both antagonists. In Experiment 2, NQ enhanced nicotine sensitization and enhanced α4β2, but not α7, nAChR upregulation in the NAcc. These results suggest a relationship between accumbal BDNF and α4β2 nAChRs and their role in the behavioral response to nicotine in the NQ model which has relevance to schizophrenia, a behavioral disorder with high rates of tobacco smoking.

La leucémie myéloïde aiguë (AML) est une forme agressive du cancer du sang qui est caractérisée par un haut taux de mortalité, tant chez les patients plus jeunes que plus âgés. Le développement de nouveaux traitements est ardu par l’hétérogénéité de cette maladie. Dans cette perspective, les études CCC phénotypiques menées à l’IRIC visent à déceler de nouveaux composés ayant une synergie contre des souches AML primaires de patients en vue de personnaliser les thérapies selon leur profil cytogénétique. Il a été découvert que le MG624, un antagoniste des récepteurs nicotiniques α7-nAChR inhibant la prolifération des cellules cancéreuses dans les SCLC, démontrait une activité spécifique contre la souche AML5. Dans cette recherche, les voies de synthèse des analogues du MG624 sont explorées afin de concevoir une série de sondes permettant d’identifier les cibles potentielles via une approche chimioprotéomique par affinité dans le lysat cellulaire. Cette méthode a permis d’identifier trois cibles potentielles à l’aide d’un essai par compétition et de contrôles négatifs, soit XIAP, NQO2 et U119B, toutes impliquées dans différentes formes de cancer. Ces expériences ont mené à une meilleure compréhension des motifs procurant l’activité du composé chez les cellules leucémiques. La synthèse d’une sonde par photoaffinité a ensuite été élaborée pour éventuellement lier les protéines identifiées de manière covalente dans l’environnement cellulaire natif afin de valider ces cibles. / Acute myeloid leukemia (AML) is an aggressive form of blood cancer characterized by a high mortality rate in both younger and older patients. The development of new treatments is hampered by the heterogeneity of this disease, which has led to the phenotypic CCC studies carried out at IRIC to identify new compounds that exhibit synergies against primary AML patient strains to personalize therapies according to their cytogenetic profile. MG624, an α7-nAChR nicotinic receptor antagonist that inhibits cancer cell proliferation in SCLC, was found to have specific activity against AML5. In this research, the synthetic pathways of MG624 analogues are explored to design a series of probes to identify potential targets via an affinity-based chemoproteomic approach in cell lysate. This method identified three potential targets using a competitive assay and negative controls, namely XIAP, NQO2 and U119B, all implicated in different forms of cancer. These experiments led to a better understanding of the motifs that provide the compound's activity in leukemic cells. A photo-affinity probe synthesis was then developed to covalently bind the identified proteins in the native cellular environment to eventually validate these targets.