Bisphenol A Exposure Induces Sensory Processing Deficits in Larval Zebrafish during Neurodevelopment.

Because of their ex utero development, relatively simple nervous system, translucency, and availability of tools to investigate neural function, larval zebrafish are an exceptional model for understanding neurodevelopmental disorders and the consequences of environmental toxins. Furthermore, early in development, zebrafish larvae easily absorb chemicals from water, a significant advantage over methods required to expose developing organisms to chemical agents in utero Bisphenol A (BPA) and BPA analogs are ubiquitous environmental toxins with known molecular consequences. All humans have measurable quantities of BPA in their bodies. Most concerning, the level of BPA exposure is correlated with neurodevelopmental difficulties in people. Given the importance of understanding the health-related effects of this common toxin, we have exploited the experimental advantages of the larval zebrafish model system to investigate the behavioral and anatomic effects of BPA exposure. We discovered that BPA exposure early in development leads to deficits in the processing of sensory information, as indicated by BPA's effects on prepulse inhibition (PPI) and short-term habituation (STH) of the C-start reflex. We observed no changes in locomotion, thigmotaxis, and repetitive behaviors (circling). Despite changes in sensory processing, we detected no regional or whole-brain volume changes. Our results show that early BPA exposure can induce sensory processing deficits, as revealed by alterations in simple behaviors that are mediated by a well-defined neural circuit.

Pyrrolopyrimidine inhibitors of DNA gyrase B (GyrB) and topoisomerase IV (ParE). Part I: Structure guided discovery and optimization of dual targeting agents with potent, broad-spectrum enzymatic activity.

The bacterial topoisomerases DNA gyrase (GyrB) and topoisomerase IV (ParE) are essential enzymes that control the topological state of DNA during replication. The high degree of conservation in the ATP-binding pockets of these enzymes make them appealing targets for broad-spectrum inhibitor development. A pyrrolopyrimidine scaffold was identified from a pharmacophore-based fragment screen with optimization potential. Structural characterization of inhibitor complexes conducted using selected GyrB/ParE orthologs aided in the identification of important steric, dynamic and compositional differences in the ATP-binding pockets of the targets, enabling the design of highly potent pyrrolopyrimidine inhibitors with broad enzymatic spectrum and dual targeting activity.

Pyrrolopyrimidine inhibitors of DNA gyrase B (GyrB) and topoisomerase IV (ParE), Part II: development of inhibitors with broad spectrum, Gram-negative antibacterial activity.

The structurally related bacterial topoisomerases DNA gyrase (GyrB) and topoisomerase IV (ParE) have long been recognized as prime candidates for the development of broad spectrum antibacterial agents. However, GyrB/ParE targeting antibacterials with spectrum that encompasses robust Gram-negative pathogens have not yet been reported. Using structure-based inhibitor design, we optimized a novel pyrrolopyrimidine inhibitor series with potent, dual targeting activity against GyrB and ParE. Compounds were discovered with broad antibacterial spectrum, including activity against Pseudomonas aeruginosa, Acinetobacter baumannii and Escherichia coli. Herein we describe the SAR of the pyrrolopyrimidine series as it relates to key structural and electronic features necessary for Gram-negative antibacterial activity.

Assessing activity onset time and efficacy for clinically effective antidepressant and antimanic drugs in animal models based on dominant-submissive relationships.

There is confusion in the literature on the measurement of the drug activity onset time (AOT) for both clinical and non-clinical studies of antidepressant and antimanic drugs. The questions asked are: How often and at which time points should drug effects be measured? At what level of a drug effect should AOT be determined? Is the placebo (control) effect important for consideration of drug AOT? This paper reviews approaches taken to answer these questions and to assess drug therapeutic AOT. The first part of the paper is devoted to a review of methods used in clinical trials with depression as an indication. The second part is focused on approaches taken in animal models of depression and how they could help in assessing drug AOT. Finally, a summary of pharmacological values on which the AOT depends is presented and a new statistical approach to data analysis method proposed. The allied experimental design for pre-clinical and clinical studies may help to characterize and differentiate AOT for available and new generation of antidepressants and antimanic drugs.

Synthesis and biological evaluation of type VI beta-turn templated RGD peptidomimetics.

We report the design, synthesis, and binding affinities of a family of cyclic RGD peptides attached to type VI beta-turn scaffolds. The analogues prepared exhibit interesting binding data to the isolated receptors alphavbeta3 and alphavbeta5. The results demonstrate the utility of these type VI beta-turn scaffolds for the constraint of biologically relevant peptides.

The synthesis and evaluation of 10- and 12-membered ring benzofused enediyne amino acids.

The enediyne moiety is a versatile functional group found in natural anticancer and anti-infective agents, undergoing the Bergman cyclization reaction to afford a diradical which cleaves double-stranded DNA. We have incorporated the enediyne group into 10- (4-10) and 12-membered ring (11) cyclic amino acids and dipeptides, respectively, and explored their relative reactivity toward cyclization, varying N-substitution in the case of the 10-membered ring substrate, which gave the expected cyclization products in good yields when using either thermal conditions in the presence or absence of microwave irradiation. The N-tosyl substituted derivative (4) was shown to nick double-stranded supercoiled DNA. N-Arylsulfonyl substitution on the ring promoted the cyclization, when compared to N-mesyl or acyl substitution, possibly because of a pi-pi stacking effect as an endo-relationship of the aryl group with the enediyne was demonstrated in both the solid state and in solution. The 12-membered ring enediyne dipeptide (11) was inert to the Bergman cyclization under a variety of conditions. When this substrate was irradiated with ultraviolet light, regio- and stereospecific reduction was observed in which one of the alkynes was reduced to a Z-olefin (47).

Design, synthesis, and conformational analysis of eight-membered cyclic peptidomimetics prepared using ring closing metathesis.

As part of a program to identify novel scaffolds that adopt defined secondary structure when incorporated into peptides, we have designed and prepared a library of constrained eight-membered ring lactams based upon 7-amino-8-oxo-1,2,3,6,7-pentahydroazocine-2-carboxylic acid. Ring closing metathesis (RCM) was employed as the key step, proceeding in high yields to afford the Z olefin. In this reaction sequence, the first generation benzylidene ruthenium RCM catalyst was superior to the second-generation imidazoline catalyst, which gave extensive oligomerization at higher concentrations. Conformational analysis of the 2S,7S and 2R,7S stereoisomers revealed that the 2R,7S isomer is a Type VIa beta-turn in the solid state (X-ray crystal structure) and in water (NMR analysis). The Type VIa beta-turn is relatively rare, typically bearing the cis amide bond found in proline-containing sequences. The 2S,7S diastereomer has an extended geometry of the pendent amide chains. The corresponding saturated derivatives (7-amino-8-oxoazocane-2-carboxylic acid) were also synthesized and investigated. The 2S,7S azocane bears an extended geometry and mimics the C(+) conformer of ox-[Cys-Cys], found in a variety of naturally occurring peptides. The scaffolds described here are useful for the design of constrained peptidomimics with defined secondary structure.

Synthesis and biological evaluation of the major metabolite of atomoxetine: elucidation of a partial kappa-opioid agonist effect.

The major human metabolite of atomoxetine (4-hydroxyatomoxetine) was tested against a panel of receptors and enzymes, and was found to interact with the mu, delta, and kappa-opioid receptors based upon studies involving both binding and functional assays. 4-hydroxyatomoxetine was determined to be a partial agonist of the kappa-opioid receptor.

Noncovalent self-assembly of bicyclo[4.2.2]diketopiperazines: influence of saturation in the bridging carbacyclic ring.

[structure: see text] We have prepared 7,9-diazabicyclo[4.2.2]dec-3-ene-8,10-dione (3) and 7,9-diazabicyclo[4.2.2]decane-8,10-dione (4), which differ by virtue of the degree of unsaturation in the bridging carbacyclic tether on a 2,5-diketopiperazine. Remarkably different self-assembly patterns were observed in the solid state for the two compounds, attributed to subtle variations in the conformational constraints imposed by the tether.