Novel acetylcholine and carbamoylcholine analogues: development of a functionally selective alpha4beta2 nicotinic acetylcholine receptor agonist

A series of carbamoylcholine and acetylcholine analogues were synthesized and characterized pharmacologically at neuronal nicotinic acetylcholine receptors (nAChRs). Several of the compounds displayed low nanomolar binding affinities to the alpha4beta2 nAChR and pronounced selectivity for this subtype over alpha3beta4, alpha4beta4, and alpha7 nAChRs. The high nAChR activity of carbamoylcholine analogue 5d was found to reside in its R-enantiomer, a characteristic most likely true for all other compounds in the series. Interestingly, the pronounced alpha4beta2 selectivities exhibited by some of the compounds in the binding assays translated into functional selectivity. Compound 5a was a fairly potent partial alpha4beta2 nAChR agonist with negligible activities at the alpha3beta4 and alpha7 subtypes, thus being one of the few truly functionally selective alpha4beta2 nAChR agonists published to date. Ligand-protein docking experiments using homology models of the amino-terminal domains of alpha4beta2 and alpha3beta4 nAChRs identified residues Val111(beta2)/Ile113(beta4), Phe119(beta2)/Gln121(beta4), and Thr155(alpha4)/Ser150(alpha3) as possible key determinants of the alpha4beta2/alpha3beta4-selectivity displayed by the analogues.     

Bioactivation of diclofenac in vitro and in vivo: correlation to electrochemical studies

Diclofenac is widely used in the treatment of, for example, arthritis and muscle pain. The use of diclofenac has been associated with hepatotoxicity, which has been linked to the formation of reactive metabolites. Diclofenac can be metabolized to 4'-OH- and 5-OH-diclofenac, both of which are able to form quinone imines capable of reacting with, for example, GSH and nucleophilic groups in proteins. Electrochemistry has been shown to be a suitable tool for mimicking some types of oxidative drug metabolism and for studying the formation of reactive metabolites. In these studies, the electrochemical oxidation of diclofenac to a +16 Da metabolite was shown to be identical to a synthetic standard of 5-OH-diclofenac. Furthermore, two different experimental designs were investigated with respect to the electrochemical oxidation of 4'-OH- and 5-OH-diclofenac. In the first approach, the oxidized sample was collected in an aqueous solution of GSH, whereas in the other approach, GSH was added to the sample before the oxidation was performed. From these electrochemical oxidations, a range of GSH conjugates of 4'-OH- and 5-OH-diclofenac were observed and characterized by MS/MS. This allowed the development of sensitive LC-MS methods in order to detect the GSH conjugates from in vivo (rat bile) and in vitro (human liver microsomes (HLM), rat liver microsomes (RLM), and rat hepatocytes) samples. A wide range of mono-, di-, and triglutathionyl conjugates were detected in the in vitro and in vivo samples. It was also observed that 5-OH-diclofenac formed GSH conjugates with RLM and HLM without addition of NADPH, whereas GSH conjugate formation of 4'-OH-diclofenac was NADPH-dependent. This indicated that 5-OH-diclofenac was prone to auto-oxidation. The oxidation potentials of the two hydroxy metabolites were determined by cyclic voltammetry. A difference of 69 mV was observed between the two oxidation potentials, which in part may explain the extent of auto-oxidation for 5-OH-diclofenac. In conclusion, it was shown that electrochemical oxidation was capable of mimicking the metabolic hydroxylation of diclofenac to 5-OH-diclofenac. Furthermore, electrochemical oxidation was used to generate a range of GSH conjugates of 4'-OH- and 5-OH-diclofenac and a number of these conjugates were also detected in metabolism studies with microsomes (HLM/RLM) and freshly isolated rat hepatocytes, and in vivo in rat bile.     

Differential modulation of inflammatory pain by a selective estrogen receptor beta agonist

To understand the contribution of the estrogen receptor beta, the potent and selective agonist ERb-131 was evaluated in animal models of inflammatory pain. In paradigms of acute and persistent inflammatory pain, ERb-131 did not alleviate the nociception induced by either carrageenan or formalin. However, in the chronic complete Freund's adjuvant model, ERb-131 resolved both inflammatory and hyperalgesic components. Thus, ERb-131 is sufficient to alleviate chronic but not acute inflammatory pain states.     

Identification of the first synthetic steroidogenic factor 1 inverse agonists: pharmacological modulation of steroidogenic enzymes

Steroidogenic factor SF-1, a constitutively active nuclear hormone receptor, is essential to the development of adrenal and gonadal glands and acts as a shaping factor of sexual determination and differentiation. Its effects are exerted primarily through the control of the synthesis of steroid hormones. The functional cell-based assay Receptor Selection and Amplification Technology (R-SAT) was used to identify potent and selective SF-1 inverse agonists through the screening of a chemical library of drug-like small-molecule entities. Among them, 4-(heptyloxy)phenol (AC-45594), a prototype inverse agonist lead, was used to show that SF-1 constitutive activity can be pharmacologically modulated by a synthetic ligand. In a physiological system of endocrine function, the expression of several reported SF-1 target genes, including SF-1 itself, was inhibited by treatment with AC-45594 and analogs. Thus, pharmacological modulation of SF-1 is critical to its function as an endocrine master regulator and has potentially important consequences to diseases in which SF-1 activity is critical.     

ACToR--Aggregated Computational Toxicology Resource

ACToR (Aggregated Computational Toxicology Resource) is a database and set of software applications that bring into one central location many types and sources of data on environmental chemicals. Currently, the ACToR chemical database contains information on chemical structure, in vitro bioassays and in vivo toxicology assays derived from more than 150 sources including the U.S. Environmental Protection Agency (EPA), Centers for Disease Control (CDC), U.S. Food and Drug Administration (FDA), National Institutes of Health (NIH), state agencies, corresponding government agencies in Canada, Europe and Japan, universities, the World Health Organization (WHO) and non-governmental organizations (NGOs). At the EPA National Center for Computational Toxicology, ACToR helps manage large data sets being used in a high-throughput environmental chemical screening and prioritization program called ToxCast^™.