Molecular Basis for Two Stereoselective Diels-Alderases that Produce Decalin Skeletons*

Enzymes catalyzing [4+2] cycloaddition have attracted increasing attention because of their key roles in natural product biosynthesis. Here, we solved the X-ray crystal structures of a pair of decalin synthases, Fsa2 and Phm7, that catalyze intramolecular [4+2] cycloadditions to form enantiomeric decalin scaffolds during biosynthesis of the HIV-1 integrase inhibitor equisetin and its stereochemical opposite, phomasetin. Computational modeling, using molecular dynamics simulations as well as quantum chemical calculations, demonstrates that the reactions proceed through synergetic conformational constraints assuring transition state-like substrates folds and their stabilization by specific protein-substrate interactions. Site-directed mutagenesis experiments verified the binding models. Intriguingly, the flexibility of bound substrates is largely different in two enzymes, suggesting the distinctive mechanism of dynamics regulation behind these stereoselective reactions. The proposed reaction mechanism herein deepens the basic understanding how these enzymes work but also provides a guiding principle to create artificial enzymes.

Understanding the metabolism of the tetralin degrader Sphingopyxis granuli strain TFA through genome-scale metabolic modelling

Sphingopyxis granuli strain TFA is an α-proteobacterium that belongs to the sphingomonads, a group of bacteria well-known for its degradative capabilities and oligotrophic metabolism. Strain TFA is the only bacterium in which the mineralisation of the aromatic pollutant tetralin has been completely characterized at biochemical, genetic, and regulatory levels and the first Sphingopyxis characterised as facultative anaerobe. Here we report additional metabolic features of this α-proteobacterium using metabolic modelling and the functional integration of genomic and transcriptomic data. The genome-scale metabolic model (GEM) of strain TFA, which has been manually curated, includes information on 743 genes, 1114 metabolites and 1397 reactions. This represents the largest metabolic model for a member of the Sphingomonadales order thus far. The predictive potential of this model was validated against experimentally calculated growth rates on different carbon sources and under different growth conditions, including both aerobic and anaerobic metabolisms. Moreover, new carbon and nitrogen sources were predicted and experimentally validated. The constructed metabolic model was used as a platform for the incorporation of transcriptomic data, generating a more robust and accurate model. In silico flux analysis under different metabolic scenarios highlighted the key role of the glyoxylate cycle in the central metabolism of strain TFA.

The response of Sphingopyxis granuli strain TFA to the hostile anoxic condition

Sphingomonads comprises a group of interesting aerobic bacteria because of their ubiquity and metabolic capability of degrading many recalcitrant contaminants. The tetralin-degrader Sphingopyxis granuli strain TFA has been recently reported as able to anaerobically grow using nitrate as the alternative electron acceptor and so far is the only bacterium with this ability within the sphingomonads group. To understand how strain TFA thrives under anoxic conditions, a differential transcriptomic analysis while growing under aerobic or anoxic conditions was performed. This analysis has been validated and complemented with transcription kinetics of representative genes of different functional categories. Results show an extensive change of the expression pattern of this strain in the different conditions. Consistently, the most induced operon in anoxia codes for proteases, presumably required for extensive changes in the protein profile. Besides genes that respond to lack of oxygen in other bacteria, there are a number of genes that respond to stress or to damage of macromolecules, including genes of the SOS DNA-damage response, which suggest that anoxic conditions represent a hostile environment for this bacterium. Interestingly, growth under anoxic conditions also resulted in repression of all flagellar and type IV pilin genes, which suggested that this strain shaves its appendages off while growing in anaerobiosis.

Radiosynthesis and evaluation of a fluorine-18 labeled radioligand targeting vesicular acetylcholine transporter

Vesicular acetylcholine transporter (VAChT) is a reliable biomarker for assessing the loss of cholinergic neurons in the brain that is associated with cognitive impairment of patients. 5-Hydrotetralin compound (±)-5-OH-VAT is potent (K_i = 4.64 ± 0.32 nM) and selective for VAChT (>1800-fold and 398-fold for σ₁ and σ₂ receptor, respectively) with favorable hydrophilicity (LogD = 1.78), while (-)-5-OH-VAT originally serves as the radiolabeling precursor of (-)-[¹⁸F]VAT, a promising VAChT radiotracer with a logD value of 2.56. To evaluate (-)-5-OH-[¹⁸F]VAT as a radiotracer for VAChT, we performed in vitro binding assay to determine the potency of the minus enantiomer (-)-5-OH-VAT and plus enantiomer (+)-5-OH-VAT, indicating that (-)-5-OH-VAT is a more potent VAChT enantiomer. Radiosynthesis of (-)-5-OH-[¹⁸F]VAT was explored using three strategies. (-)-5-OH-[¹⁸F]VAT was achieved with a good yield (24 ± 6%) and high molar activity (∼37 GBq/µmol, at the end of synthesis) using a microwave assisted two-step one-pot procedure that started with di-MOM protected nitro-containing precursor (-)-6. MicroPET studies in the brain of nonhuman primate (NHP) suggest that (-)-5-OH-[¹⁸F]VAT readily penetrated the blood brain barrier and specifically accumulated in the VAChT-enriched striatum with improved washout kinetics from striatum compared to [¹⁸F]VAT. Nevertheless, the lower target to non-target ratio may limit its use for in vivo measurement of the VAChT level in the brain.

Anti-cancer labdane diterpenoids from adventitious roots of Andrographis paniculata: augmentation of production prospect endowed with pathway gene expression

Andrographolide (AD) is the time-honoured pharmacologically active constituent of the traditionally renowned medicinal plant-Andrographis paniculata. Advancements in the target-oriented drug discovery process have further unravelled the immense therapeutic credibility of another unique molecule-neoandrographolide (NAD). The escalated market demand of these anti-cancer diterpenes is increasingly facing unrelenting hurdles of demand and supply disparity, attributable to their limited yield. Callus and adventitious root cultures were generated to explore their biosynthetic potentials which first time revealed NAD production along with AD. Optimization of the types and concentrations of auxins along with media form and cultivation time led to the successful tuning towards establishing adventitious roots as a superior production alternative for both AD/NAD. Supplementation of IBA to the NAA + Kn-containing MS medium boosted the overall growth and AD/NAD synthesis in the adventitious roots. Compared to control leaves, the adventitious root exhibited about 2.61- and 8.8-fold higher contents of AD and NAD, respectively. The qRT-PCR involving nine key pathway genes was studied, which revealed upregulation of GGPS1 and HMGR1/2 genes and downregulation of DXS1/2 and HDR1/2 genes in the adventitious root as compared to that in the control leaves. Such observations highlight that in vitro cultures can serve as efficient production alternatives for AD/NAD as the cytosolic genes (HMGR1/2 of MVA pathway) are competent enough to take over from the plastidial genes (DXS1/2 and HDR1/2 of MEP pathway), provided the accredited first branch-point regulatory gene (GGPS) expression and the culture requirements are optimally fulfilled.

Uptake and elimination kinetics of the biocide triclosan and the synthetic musks galaxolide and tonalide in the earthworm Dendrobaena veneta when exposed to sewage sludge

Sewage sludge is an important amendment that enriches soils with organic matter and provides plants with nutrients such as nitrogen and phosphorus. However, knowledge on the fate and effects of organic pollutants present in the sludge on soil organisms is limited. In the present study, the uptake of triclosan, galaxolide, and tonalide in the earthworm Dendrobaena veneta was measured 1 wk after amendment of agricultural soil with sewage sludge, while elimination kinetics were assessed over a 21-d period after transferring worms to clean soil. After 1-wk exposure, earthworms had accumulated 2.6 ± 0.6 μg g^-1 galaxolide, 0.04 ± 0.02 μg g^-1 tonalide, and 0.6 ± 0.2 μg g^-1 triclosan. Both synthetic musks were efficiently excreted and below the limit of quantification after 3 and 14 d of depuration for tonalide and galaxolide, respectively. Triclosan concentrations, on the other hand, did not decrease significantly over the depuration period, which may lead to the transfer of triclosan in the food web. Environ Toxicol Chem 2017;36:2068-2073. © 2017 SETAC.

Effects of Steady-State Lasofoxifene on Cyp2D6- and Cyp2E1-Mediated Metabolism

Background:

Lasofoxifene, a selective estrogen receptor modulator, may be coadministered with other drugs, raising the issue of drug–drug interactions.

Objective:

Using a 7-day, open-label, sequential study to determine whether lasofoxifene at steady-state concentration affects cytochrome P450–mediated drug metabolism.

Methods:

Lasofoxifene was tested in 18 postmenopausal women with probe drugs for CYP2E1 and CYP2D6. Changes in CYP2E1 metabolism were measured by the formation clearance of 6-hydroxychlorzoxazone (6-OHCLZ; Clf,6-OHCLZ) following a 250 mg dose of chlorzoxazone in the absence (day 1) and presence (day 6) of lasofoxifene. Changes in the dextromethorphan/dextrorphan urine metabolic ratio (MRDX) measured the effect on CYP2D6 metabolism following a 30 mg dose of dextromethorphan in the absence and presence of lasofoxifene (days 2 and 7).

Results:

Steady-state lasofoxifene did not affect the formation clearance of 6-OHCLZ or the urinary MRDX. For 6-OHCLZ, the lower boundary (87.12%) of the 90% confidence interval for the ratio (day 6/day 1) of Clf,6-OHCLZ was well above the clinically acceptable ratio of 60%. Both the individual and group mean Clf,6-OHCLZ values were comparable in the absence and presence of lasofoxifene. For MRDX, the upper boundary (129.37%) of the 90% confidence interval for the ratio (day 7/day 2) of MRDX was well below the stipulated ratio of 200%. The individual and mean MRDX values were comparable in the absence and presence of lasofoxifene. Lasofoxifene was well tolerated; adverse events were mild and transient.

Conclusions:

Lasofoxifene has no effect on CYP2E1- or CYP2D6-mediated drug metabolism and should not affect drugs metabolized by other cytochrome P450 isoenzymes.

Removal of polycyclic musks by anaerobic membrane bioreactor: biodegradation, biosorption, and enantioselectivity

This study aims to investigate the performance of anaerobic membrane bioreactor (AnMBR) for removing five polycyclic musks (PCMs), which are common active ingredients of personal care and household cleaning products. A laboratory scale AnMBR system was used in this investigation. Concentrations of the PCMs in both the liquid and biosolids phase were measured to conduct a mass balance analysis and elucidate their fate during AnMBR treatment. The AnMBR was effective for removing PCMs from the aqueous phase by a combination of biotransformation and sorption onto the biosolids. However, biotransformation was observed to be the dominant removal mechanism for all five PCMs. Enantioselective analysis of the PCMs in influent, effluent and biomass samples indicated that there was negligible enantioselectivity in the removal of these PCMs. Accordingly, all enantiomers of these PCMs can be expected to be removed by AnMBR with similar efficiency.

Modelling cometabolic biotransformation of organic micropollutants in nitrifying reactors

Cometabolism is the ability of microorganisms to degrade non-growth substrates in the presence of primary substrates, being the main removal mechanism behind the biotransformation of organic micropollutants in wastewater treatment plants. In this paper, a cometabolic Monod-type kinetics, linking biotransformation of micropollutants with primary substrate degradation, was applied to a highly enriched nitrifying activated sludge (NAS) reactor operated under different operational conditions (hydraulic retention time (HRT) and nitrifying activity). A dynamic model of the bioreactor was built taking into account biotransformation, sorption and volatilization. The micropollutant transformation capacity (Tc), the half-saturation constant (Ksc) and the solid-liquid partitioning coefficient (Kd) of several organic micropollutants were estimated at 25 °C using an optimization algorithm to fit experimental data to the proposed model with the cometabolic Monod-type biotransformation kinetics. The cometabolic Monod-type kinetic model was validated under different HRTs (1.0-3.7 d) and nitrification rates (0.12-0.45 g N/g VSS d), describing more accurately the fate of those compounds affected by the biological activity of nitrifiers (ibuprofen, naproxen, erythromycin and roxithromycin) compared to the commonly applied pseudo-first order micropollutant biotransformation kinetics, which does not link biotransformation of micropollutants to consumption of primary substrate. Furthermore, in contrast to the pseudo-first order biotransformation constant (k(biol)), the proposed cometabolic kinetic coefficients are independent of operational conditions such as the nitrogen loading rate applied. Also, the influence of the kinetic parameters on the biotransformation efficiency of NAS reactors, defined as the relative amount of the total inlet micropollutant load being biotransformed, was assessed considering different HRTs and nitrification rates.

A classical genetic solution to enhance the biosynthesis of anticancer phytochemicals in Andrographis paniculata Nees

Andrographolides, the diterpene lactones, are major bioactive phytochemicals which could be found in different parts of the medicinal herb Andrographis paniculata. A number of such compounds namely andrographolide (AG), neoandrographolide (NAG), and 14-deoxy-11,12-didehydroandrographolide (DDAG) have already attracted a great deal of attention due to their potential therapeutic effects in hard-to-treat diseases such as cancers and HIV. Recently, they have also been considered as substrates for the discovery of novel pharmaceutical compounds. Nevertheless, there is still a huge gap in knowledge on the genetic pattern of the biosynthesis of these bioactive compounds. Hence, the present study aimed to investigate the genetic mechanisms controlling the biosynthesis of these phytochemicals using a diallel analysis. The high performance liquid chromatography analysis of the three andrographolides in 210 F₁ progenies confirmed that the biosynthesis of these andrographolides was considerably increased via intraspecific hybridization. The results revealed high, moderate and low heterosis for DDAG, AG and NAG, respectively. Furthermore, the preponderance of non-additive gene actions was affirmed in the enhancement of the three andrographolides contents. The consequence of this type of gene action was the occurrence of high broad-sense and low narrow-sense heritabilities for the above mentioned andrographolides. The prevalence of non-additive gene action suggests the suitability of heterosis breeding and hybrid seed production as a preferred option to produce new plant varieties with higher andrographolide contents using the wild accessions of A. paniculata. Moreover, from an evolutionary point of view, the occurrence of population bottlenecks in the Malaysian accessions of A. paniculata was unveiled by observing a low level of additive genetic variance (V_A) for all the andrographolides.

The development of the rotigotine transdermal patch: a historical perspective

The rotigotine transdermal system is a dopamine receptor agonist delivered over a 24-hour period. It is approved for the treatment of idiopathic Parkinson's disease (PD). This article reviews the development of the rotigotine transdermal system, including rotigotine's receptor profile, steady-state pharmacokinetics, and metabolism. Preclinical studies of rotigotine in animal models of PD and proof-of-concept studies in patients with PD are reviewed. These preclinical and clinical studies established this system as an effective method for providing continuous rotigotine delivery across the skin providing the basis for continued clinical development of rotigotine for the treatment of early and advanced PD.

Effects of polycyclic musks HHCB and AHTN on steroidogenesis in H295R cells

1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(γ)-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) are widely used in personal care products. Previous studies showed that HHCB and AHTN can be found in various environmental matrices and have potential endocrine disrupting effects. However, the effects on adrenocortical function of HHCB and AHTN are not fully understood. This study evaluated the influences of HHCB and AHTN on seven steroid hormones (progesterone, aldosterone, cortisol, 17α-OH-progesterone, androstenedione, 17β-estradiol, and testosterone) and 10 genes involved in steroidogenic pathways (HMGR, StAR, CYP11A1, 3βHSD2, CYP17, CYP21, CYP11B1, CYP11B2, 17βHSD, and CYP19) using the H295R cell line in the absence and presence of 8-Br-cAMP. MC2R transcription on the cell membrane was also examined to further investigate the effects of HHCB and AHTN on adrenal steroidogenesis. The results demonstrated that HHCB and AHTN could inhibit progesterone and cortisol production mainly by the suppression of 3βHSD2 and CYP21. Meanwhile, high concentrations of AHTN can affect the sensitivity of H295R cells to ACTH by disrupting MC2R transcription. Overall, the results indicate that high concentrations of HHCB and AHTN can affect steroidogenesis in vitro using the H295R cell line.

Uptake of galaxolide, tonalide, and triclosan by carrot, barley, and meadow fescue plants

Many xenobiotics entering wastewater treatment plants are known to be persistent during wastewater treatment and tend to adsorb to sewage sludge. The application of sewage sludge as fertilizer in agriculture may pose the risk of an incorporation of xenobiotics in the cultivated plants and, finally, an inclusion into the food chain. This study was performed to investigate the uptake of common sewage sludge contaminants, galaxolide, tonalide, and triclosan, by plants used for human consumption and livestock feeding. Barley, meadow fescue, and four carrot cultivars were sown and grown in spiked soils under greenhouse conditions. After harvesting the plants, roots and leaves were analyzed separately, and the respective bioconcentration factors were calculated. In carrots, a concentration gradient of the xenobiotics became evident that decreased from the root peel via root core to the leaves. A significant influence of the differing root lipid contents on the uptake rates cannot be supported by our data, but the crucial influence of soil organic carbon content was confirmed. Barley and meadow fescue roots incorporated higher amounts of the target substances than carrots, but translocation into the leaves was negligible. The results indicated that an introduction of persistent semi- and nonpolar xenobiotics into the food chain via edible plants like carrots could be of certain relevance when sludge is applied as fertilizer. Due to low rates found for the translocation of the xenobiotics into the aerial plant parts, the entrance pathway into food products via feeding livestock is less probable.

Involvement of a putative cyclic amp receptor protein (CRP)-like binding sequence and a CRP-like protein in glucose-mediated catabolite repression of thn genes in Rhodococcus sp. strain TFB

Glucose catabolite repression of tetralin catabolic genes in Rhodococcus sp. strain TFB was shown to be exerted by a protein homologous to transcriptional regulators of the cyclic AMP receptor (CRP)-FNR family. The protein was detected bound to putative CRP-like boxes localized at the promoters of the thnA1 and thnS genes.

The "Phantom Effect" of the Rexinoid LG100754: structural and functional insights

Retinoic acid receptors (RARs) and Retinoid X nuclear receptors (RXRs) are ligand-dependent transcriptional modulators that execute their biological action through the generation of functional heterodimers. RXR acts as an obligate dimer partner in many signalling pathways, gene regulation by rexinoids depending on the liganded state of the specific heterodimeric partner. To address the question of the effect of rexinoid antagonists on RAR/RXR function, we solved the crystal structure of the heterodimer formed by the ligand binding domain (LBD) of the RARα bound to its natural agonist ligand (all-trans retinoic acid, atRA) and RXRα bound to a rexinoid antagonist (LG100754). We observed that RARα exhibits the canonical agonist conformation and RXRα an antagonist one with the C-terminal H12 flipping out to the solvent. Examination of the protein-LG100754 interactions reveals that its propoxy group sterically prevents the H12 associating with the LBD, without affecting the dimerization or the active conformation of RAR. Although LG100754 has been reported to act as a ‘phantom ligand’ activating RAR in a cellular context, our structural data and biochemical assays demonstrate that LG100754 mediates its effect as a full RXR antagonist. Finally we show that the ‘phantom ligand effect’ of the LG100754 is due to a direct binding of the ligand to RAR that stabilizes coactivator interactions thus accounting for the observed transcriptional activation of RAR/RXR.

Luzindole but not 4-phenyl-2- propionamidotetralin (4P-PDOT) diminishes the inhibitory effect of melatonin on murine Colon 38 cancer growth in vitro

OBJECTIVE

Our earlier studies have shown that MLT exerts the inhibitory effect on murine cancer via membrane and nuclear receptors. We have found that the antagonist of MT1 receptors does not diminish the antiproliferative effect of MLT on Colon 38 cells, and the contribution of MT2 receptors has been suggested to be responsible. Therefore, in the present study we have examined the influence of the 4-phenyl-2-propionamidotetralin (4P-PDOT), which is a selective antagonist of MT2 membrane receptor, and luzindole - an antagonist of both membrane receptors, on an oncostatic action of MLT.

MATERIALS AND METHODS

The murine cancer cell line Colon 38 was used in the experiments. In 48 hrs cell culture the effects of MLT, 4P-PDOT and luzindole administered alone and MLT applied jointly with either 4P-PDOT or luzindole were examined. The growth of cancer cells was assessed using the modified colorimetric Mosmann method.

RESULTS

Melatonin at both examined concentrations (10-7, 10-9 M) significantly decreased the viability of cancer cells. The selective antagonist of MT2 membrane receptor, namely 4P-PDOT and luzindole applied separately did not have an effect on the growth of Colon 38 cells. The addition of 4P-PDOT to MLT did not change the inhibitory effect of MLT, whereas luzindole given together with MLT diminished, but failed to block totally, the oncostatic properties of MLT.

CONCLUSIONS

The obtained data and our previous studies conducted on Colon 38 cancer indicate that membrane melatonin receptors are not indispensable to the oncostatic action of melatonin and thus other pathways such as nuclear signaling and receptor-independent mechanism may be also involved.

Modulation by bexarotene of mRNA expression of genes in mouse lung tumors

Bexarotene has demonstrated chemopreventive and therapeutic efficacy towards mouse lung tumors. Using specimens from our published study that demonstrated the efficacy of bexarotene, we report herein its ability to modulate mRNA expression of genes in both lung and lung tumors. Strain A/J mice were administered vinyl carbamate to induce lung tumors. This was followed by 200 mg/kg body weight of bexarotene administered by oral gavage during Wks 4-25 or 23-25. The mice were sacrificed at Wk 25. The expression of 26 genes was decreased in lung tumors, whereas only two genes, Apolipoprotein D and CYP26b, had their mRNA expression increased by bexarotene. Genes with increased mRNA expression in untreated lung tumors include: epiregulin and kininogen-1 (increased by more than 40-fold) and Caspase-3, Cyclin D1, DNA methyltransferase 3a (Dnmt-3a), E-prostanoid 3 receptor (EP3), c-myc, surfactant protein-C, and survivin (increased by 1.7- to 3.6-fold). Bexarotene decreased the mRNA expression of Caspase-3, Dnmt-3a, EP3, and survivin, as well as the expression of the Cyclin E1, estrogen receptor-alpha, and iNOS genes. Bexarotene had a greater effect in decreasing the expression of Caspase-3, Cyclin E1, Dnmt-3a, EP3, iNOS, and survivin, when administered to mice with established tumors than when administered to mice while tumors were emerging. In summary, bexarotene modulated mRNA expression of genes in mouse lung tumors, being more effective in established tumors than in emerging tumors, suggesting that modulation of expression could be useful as a biomarker for the therapeutic and chemopreventive activity of the drug, especially in established tumors.

Biotransformation of the polycyclic musks HHCB and AHTN and metabolite formation by fungi occurring in freshwater environments

Micropollutants found in aquatic environments have increasingly raised concerns with respect to their uncertain environmental fate and potentially adverse effects on human health and the environment. The biodegradability of two major representatives of the polycyclic musk fragrances, Galaxolide (HHCB) and Tonalide (AHTN), and the formation of biotransformation metabolites, were investigated with Myrioconium sp. strain UHH 1-13-18-4 and Clavariopsis aquatica, two mitosporic fungi derived from freshwater environments. A particular focus was to assess the effects of extracellular oxidoreductases such as laccases, which are produced by the investigated fungi under certain conditions, on HHCB and AHTN. The fungi converted HHCB and AHTN into various products via initial hydroxylation at different carbon positions. Further metabolism resulted in the subsequent formation of diketone, peroxide, and O-methylated derivatives. Isolated laccases of the investigated fungi were able to oxidize HHCB and AHTN and catalyzed the formation of the metabolite HHCB-lactone from HHCB. At particular environmental situations also specified within the present study, biotransformations catalyzed by fungi occurring in freshwater environments may be considered when addressing the fate of polycyclic musks in freshwater systems and potential biological effects of their degradation metabolites.

Receptor subtype involved in alpha 1-adrenergic receptor-mediated Ca2+ signaling in cardiomyocytes

AIM

The enhancement of intracellular Ca2+ signaling in response to alpha 1-adrenergic receptor (alpha 1-AR) stimulation is an essential signal transduction event in the regulation of cardiac functions, such as cardiac growth, cardiac contraction, and cardiac adaptation to various situations. The present study was intended to determine the role(s) of the alpha 1-AR subtype(s) in mediating this response.

METHODS

We evaluated the effects of subtype-specific agonists and antagonists of the alpha 1- AR on the intracellular Ca2+ signaling of neonatal rat ventricular myocytes using a confocal microscope.

RESULTS

After being cultured for 48 h, the myocytes exhibited spontaneous local Ca2+ release, sparks, and global Ca2+ transients. The activation of the alpha 1-AR with phenylephrine, a selective agonist of the alpha 1-AR, dose-dependently increased the frequency of Ca2+ transients with an EC50 value of 2.3 micromol/L. Blocking the alpha 1A-AR subtype with 5-methylurapidil (5-Mu) inhibited the stimulatory effect of phenylephrine with an IC(50) value of 6.7 nmol/L. In contrast, blockade of the alpha 1B-AR and alpha 1D-AR subtypes with chloroethylclonidine and BMY 7378, respectively, did not affect the phenylephrine effect. Similarly, the local Ca2+ spark numbers were also increased by the activation of the alpha 1-AR, and this effect could be abolished selectively by 5-Mu. More importantly, A61603, a novel selective alpha 1A-AR agonist, mimicked the effects of phenylephrine, but with more potency (EC(50) value =6.9 nmol/L) in the potentiation of Ca2+ transients, and blockade of the alpha 1A-AR by 5-Mu caused abolishment of its effects.

CONCLUSION

These results indicate that alpha 1-adrenergic stimulation of intracellular Ca2+ activity is mediated selectively by the alpha 1A-AR.

The 2.0 A crystal structure of the ERalpha ligand-binding domain complexed with lasofoxifene

Lasofoxifene is a new and potent selective estrogen receptor modulator (SERM). The structural basis of its interaction with the estrogen receptor has been investigated by crystallographic analysis of its complex with the ligand-binding domain of estrogen receptor alpha at a resolution of 2.0 A. As with other SERMs, lasofoxifene diverts the receptor from its agonist-bound conformation by displacing the C-terminal AF-2 helix into the site at which the LXXLL motif of coactivator proteins would otherwise be able to bind. Lasofoxifene achieves this effect by occupying the space normally filled by residue Leu 540, as well as by modulating the conformation of residues of helix 11 (His 524, Leu 525). A well-defined salt bridge between lasofoxifene and Asp 351 suggests that charge neutralization in this region of the receptor may explain the some of the antiestrogenic effects of lasofoxifene. The results suggest general features of ERalpha/SERM recognition, and add a new dimension to efforts to rationalize differences between the biological activity profiles exhibited by these important pharmacological agents.

Microbial transformation of neoandrographolide by Aspergillus niger (AS 3.739)

The biotransformation of neoandrographolide (1) was investigated by using Aspergillus niger (AS 3.739). Five products were obtained and identified as 8(17),13-ent-labdadien-16,15-olid-19-oic acid (2), 19-hydroxy-8(17),13-ent-labdadien-16,15-olide (3), 18-hydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid (4), 3alpha-hydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid (5) and 8beta,19-dihydroxy-ent-labd-13-en-16,15-olide (6) by spectroscopic and chemical means. Products 4, 5 and 6 are new compounds.

Integrated response to inducers by communication between a catabolic pathway and its regulatory system

Efficient gene regulation of metabolic pathways implies that the profile of molecules inducing the pathway matches that of the molecules that are metabolized. Gratuitous induction, a well-known phenomenon in catabolic pathways, is the consequence of differences in the substrate and inducer profiles. This phenomenon is particularly evident in pathways for biodegradation of organic contaminants that can be induced by a variety of molecules similar to the real substrates. Analysis of the regulation of tetralin biodegradation genes in mutant strains with mutations that affect each component of the initial dioxygenase enzymatic complex indicated that the response of the regulatory system to potential inducers is altered differently depending on the mutated component. Based on the expression phenotypes of a number of single or double mutants, we propose a model that represents an unprecedented way of communication between a catabolic pathway and its regulatory system to prevent efficient induction by a molecule that is not a real substrate. This communication allows a better fit of the substrate and inducer profiles, thus minimizing gratuitous induction, without a requirement for optimal coevolution to match the specificity of catabolic enzymes and their regulatory systems. Modulation of the regulatory system in this way not only provides a more appropriate response to potential inducers recognized by the regulatory system but also may properly adjust the levels of gene expression to the substrate availability.

Comparison of three radioligands for the labelling of human β-adrenoceptor subtypes

We have compared the ability of three radioligands, [(125)I]-cyanopindolol, [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol, to label the three human beta-adrenoceptor subtypes. Saturation and competition binding experiments were performed using membrane preparations from Chinese hamster ovary cells stably transfected with the three subtypes. While [(3)H]-CGP 12,177 had very similar affinity for beta(1)- and beta(2)-adrenoceptors (about 40 pM), [(125)I]-cyanopindolol and [(3)H]-dihydroalprenolol had 4- to 6-fold higher affinity for beta(2)- as compared to beta(1)-adrenoceptors (10 vs 45 and 187 vs 1,021 pM, respectively). The affinity of [(125)I]-cyanopindolol at beta(3)-adrenoceptors was considerably lower (440 pM) than at the other two subtypes. The beta(3)-adrenoceptor affinity of [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol was so low that it could not be estimated within the tested range of radioligand concentrations (up to 4,000 pM and 30,000 pM for [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol, respectively). We conclude that all three radioligands are ill-suited to label beta(3)-adrenoceptors, particularly in preparations co-expressing multiple subtypes. In the absence of alternatives, [(125)I]-cyanopindolol appears the least unsuitable to label beta(3)-adrenoceptors. There is a need for high-affinity radioligands which are either selective for beta(3)-adrenoceptors or reasonably non-selective among all three beta-adrenoceptor subtypes.

Polycyclic musk compounds in higher trophic level aquatic organisms and humans from the United States

Polycyclic musks, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[g]-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN), are used as fragrance ingredients in numerous consumer products such as cleaning agents and personal care products. Studies have reported the widespread occurrence of these musks in surface waters and fish from western European countries. Nevertheless, little is known about their accumulation in humans and wildlife in the United States. In this study, we measured concentrations of HHCB and AHTN in human adipose fat collected from New York City. Furthermore, tissues from marine mammals, water birds, and fish collected from US waters were analyzed to determine the concentrations of HHCB and AHTN. Concentrations of HHCB and AHTN in human adipose fat samples ranged from 12 to 798 and from <5 to 134 ng/g, on a lipid weight basis, respectively. A significant correlation existed between the concentrations of HHCB and AHTN in human adipose fat. Concentrations of HHCB and AHTN were not positively correlated with age or gender of the donors. HHCB was found in tissues of several wildlife species, but not in the livers of polar bear from the Alaskan Arctic. Among wildlife species analyzed, spinner and bottlenose dolphins collected from Florida coastal waters contained measurable concentrations of HHCB.

Privileged structure-based ligands for melanocortin receptors—tetrahydroquinolines, indoles, and aminotetralines

Substitution of the aryl sulfonamide moiety contained in MC4 agonist 1 with bicyclic heterocycles and aminotetralines produced compounds with MC4 activity. The heterocycles represent alternative privileged structures to that contained in 1. Compounds in which the polar group of the privileged structure was displayed in an endocyclic fashion were not as active as the parent agonist 1, while those with an exocyclic polar group afforded activity competitive with 1.

Effect of nolomirole on monocrotaline-induced heart failure

Neurohormonal activation has been shown to be a major factor in congestive heart failure progression and mortality. The beneficial effects obtained in clinical trials with angiotensin converting enzyme (ACE) inhibitors, beta-blockers and aldosterone antagonists have confirmed this hypothesis. 5,6-Diisobutirroyloxy-2-methyl-aminotetraline hydrochloride (nolomirole) is a selective agonist of prejunctional D(2)-dopaminergic and alpha(2)-adrenergic receptors. The stimulation of these receptors inhibits catecholamine release from sympathetic nerve endings. To confirm that this mechanism can be useful in congestive heart failure, we studied the effects of nolomirole on monocrotaline-induced congestive heart failure. The ACE inhibitor trandolapril was used as reference compound. Rats were given single intraperitoneal injection of either saline (control group; n=20) or monocrotaline (50 mg kg(-1)). Three days later, the monocrotaline-treated animals were randomly allocated (n=50 per group) to oral treatment with distilled water (vehicle group), nolomirole (0.25 mg kg(-1)) twice a day, or trandolapril (0.3 mg kg(-1)) once a day up to sacrifice. On the fourth week after monocrotaline injection, animals with signs of congestive heart failure were sacrificed for evaluation of heart hypertrophy and neuroendocrine alterations. Atrial natriuretic peptide (ANP) and alderosterone were determined by radioimmunoassay in plasma. Tissue norepinephrine concentration was quantified by high-pressure liquid chromatography. Nolomirole and trandolapril significantly reduced (a) hypertrophy of right atria and ventricles, (b) plasma levels of ANP and presence of pleural/peritoneal effusions and (c) norepinephrine depletion of right ventricle. These findings confirmed that nolomirole, like trandolapril, is able to attenuate the heart failure signs in the monocrotaline-induced congestive heart failure model.

Dopamine D3 receptor stimulation promotes the proliferation of cells derived from the post-natal subventricular zone

In the adult mammalian brain, neural stem cells persist in the subventricular zone (SVZ) where dopamine D3 receptors are expressed. Here, we demonstrate that addition of 1 microm apomorphine increases cell numbers in post-natal SVZ cell cultures. This effect was prevented by a co-treatment with haloperidol, sulpiride or U-99194A, a D3-preferring antagonist, and mimicked by the dopamine D3 receptor selective agonist 7-hydroxy-dipropylaminotetralin (7-OH-DPAT). EC50 values were 4.04 +/- 1.54 nm for apomorphine and 0.63 +/- 0.13 nm for 7-OH-DPAT, which fits the pharmacological profile of the D3 receptor. D3 receptors were detected in SVZ cells by RT-PCR and immunocytochemistry. D3 receptors were expressed in numerous beta-III tubulin immunopositive cells. The fraction of apoptotic nuclei remained unchanged following apomorphine treatment, thus ruling out any possible effect on cell survival. In contrast, proliferation was increased as both the proportion of nuclei incorporating bromo-deoxyuridine and the expression of the cell division marker cyclin D1 were enhanced. These findings provide support for a regulatory role of dopamine over cellular dynamics in post-natal SVZ.

Polycyclic musks in the Ruhr catchment area—transport, discharges of waste water, and transformations of HHCB, AHTN and HHCB-lactone

The polycyclic musk fragrance compounds HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(g)-2-benzopyran; trade name, e.g. galaxolide) and AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene, trade name, e.g. tonalide) and the transformation product of HHCB (HHCB-lactone) were analysed in surface water samples and sewage treatment plants (STP) effluents in the Ruhr megalopolis. The STPs were the dominant source for these pollutants. In the part of the river where the drinking water is extracted from the river, about 60 ng L(-1) HHCB, 10 ng L(-1) AHTN and 20-30 ng L(-1) HHCB-lactone were found as typical riverine concentrations, while none of the compounds were detected near the spring of the river. On the other hand sewage treatment plant effluents exhibited concentrations up to 600 ng L(-1). The STP's effluent resulted in elevated concentrations in some parts of the river and in the lakes into which they discharge. As some of the plants emit HHCB-lactone with a significantly changed enantiomeric pattern, biotransformation of HHCB to HHCB-lactone occurs in some waste water treatment plants operating with activated sludge. In those parts of the river where no relevant discharges of waste water or fresh water takes place neither the concentration nor the pattern changes significantly. This holds true especially for the HHCB versus HHCB-lactone ratios which indicates degradation less than 15% of the HHCB inventory in the river Ruhr itself. In other rivers, such as the Rhine, higher levels of HHCB-lactone in comparison to HHCB were detected (ratio 1 : 1).

Equisetin biosynthesis in Fusarium heterosporum

An iterative polyketide synthase-peptide synthetase hybrid assembles the HIV-1 integrase inhibitory tetramic acid, equisetin, in the filamentous fungus Fusarium heterosporum.

Regulation of tetralin biodegradation and identification of genes essential for expression of thn operons

The tetralin biodegradation genes of Sphingomonas macrogolitabida strain TFA are clustered in two closely linked and divergent operons. To analyze expression of both operons under different growth conditions, transcriptional and translational gene fusions of the first genes of each operon to lacZ have been constructed in plasmids unable to replicate in Sphingomonas and integrated by recombination into the genome of strain TFA. Expression analysis indicated that the transcription of both genes is induced in similar ways by the presence of tetralin. Gene expression in both operons is also subjected to overimposed catabolic repression. Two additional genes named thnR and thnY have been identified downstream of thnCA3A4 genes. ThnR is similar to LysR-type regulators, and mutational analysis indicated that ThnR is strictly required for expression of the thn operons. Unlike other LysR-type regulators, ThnR does not repress its own synthesis. In fact, ThnR activates its own expression, since thnR is cotranscribed with the thnCA3A4 genes. ThnY is similar to the ferredoxin reductase components of dioxygenase systems and shows the fer2 domain, binding a Cys4[2Fe-2S] iron sulfur center, and the FAD-binding domain, common to those reductases. However, it lacks the NAD-binding domain. Intriguingly, ThnY has a regulatory role, since it is also strictly required for expression of the thn operons. Given the similarity of ThnY to reductases and the possibility of its being present in the two redox states, it is tempting to speculate that ThnY is a regulatory component connecting expression of the thn operons to the physiological status of the cell.

Survival of activated human T lymphocytes is promoted by retinoic acid via induction of IL-2

At the end of an immune response, most activated T cells spontaneously undergo programmed cell death (apoptosis). In the present study we show that all-trans retinoic acid (atRA), a major vitamin A metabolite, can inhibit the spontaneous apoptosis of activated human T lymphocytes in vitro. Isolated peripheral blood T lymphocytes were activated by 12-O-tetradecanoyl phorbol 13-acetate and cultured for up to 11 days without any further stimuli. With time, a gradual increase in cell death was observed. This spontaneous death of activated T cells was apoptotic, as demonstrated by cell shrinkage, DNA fragmentation and depolarization of the mitochondrial membrane. In the presence of physiological concentrations of atRA, the percentage of T cells exhibiting these apoptotic features was significantly reduced. After 5 days of stimulation, the percentage of TUNEL+ T cells decreased from 28 to 12% in the presence of atRA. The anti-apoptotic effect of atRA was mimicked by the retinoic acid receptor (RAR)-selective agonists 4-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid and AM-580, and totally abrogated by the RAR-selective antagonist Ro 41-5253. Cytokines of the IL-2 family have been shown to improve the survival of activated T cells. Strikingly, we found that the ability of atRA to inhibit apoptosis was significantly correlated with its ability to increase the production of IL-2. Furthermore, a blocking anti-IL-2 receptor antibody completely abrogated the anti-apoptotic effect of atRA. Together, these results suggest that retinoic acid inhibits spontaneous apoptosis of activated T lymphocytes through a RAR-dependent increase in IL-2 production.

Characterization of melatonin binding sites in the brain and retina of the frog Rana perezi

The aim of this study was to characterize 2-[125I]iodomelatonin binding sites in the neural retina and central nervous system (telencephalon, diencephalon, and optic tectum) of the anuran amphibian Rana perezi. Saturation and kinetic studies and pharmacological characterization revealed the existence of a unique melatonin-binding site that belongs to the Mel 1 receptor subtype. The affinity of this site is similar in all tissues studied (Kd, 10.5-12.8 pM), but the density varied from diencephalon and optic tectum, which exhibit the highest density, to telencephalon with the lowest. Neural retina showed an intermediate receptor density. This melatonin-binding site fulfills the requirements of a real hormone receptor; the binding is saturable, reversible, and inhibited by different melatonin agonists and antagonists. The affinity order of ligands is: 2-phenyl-melatonin = 2-I-melatonin > 6-Cl-melatonin = melatoninz >> luzindole. Additionally, specific binding is decreased by non-hydrolysable GTP analogue, sodium, and by pretreatment of membranes with pertussis toxin. All these results suggest the existence of a widely distributed and pharmacologically homogeneous melatonin receptor of the subfamily Mel 1 in the nervous system of Rana perezi coupled to a Gi/o protein.

FR901512, a Novel HMG-CoA Reductase Inhibitor Produced by an Agonomycetous Fungus No. 14919: II. Biological Profiles

FR901512, a new specific inhibitor of HMG-CoA reductase, was isolated from the culture of an agonomycetous fungus No. 14919. FR901512 inhibited cholesterol synthesis from [14C] acetate in Hep G2 cells with an IC50 of 1.0 nM. An increase of cell surface LDL receptors observed on the FR901512 treated human hepatoma cell line Hep G2 cells. Single oral administration of FR901512 strongly inhibited sterol synthesis in rats. Daily oral administration of FR901512 to beagle dogs decreased plasma cholesterol levels.

Molecular Modeling of the Three-Dimensional Structure of Dopamine 3 (D3) Subtype Receptor: Discovery of Novel and Potent D3 Ligands through a Hybrid Pharmacophore- and Structure-Based Database Searching Approach

The dopamine 3 (D3) subtype receptor has been implicated in several neurological conditions, and potent and selective D3 ligands may have therapeutic potential for the treatment of drug addiction, Parkinson's disease, and schizophrenia. In this paper, we report computational homology modeling of the D3 receptor based upon the high-resolution X-ray structure of rhodopsin, extensive structural refinement in the presence of explicit lipid bilayer and water environment, and validation of the refined D3 structural models using experimental data. We further describe the development, validation, and application of a hybrid computational screening approach for the discovery of several classes of novel and potent D3 ligands. This computational approach employs stepwise pharmacophore and structure-based searching of a large three-dimensional chemical database for the identification of potential D3 ligands. The obtained hits are then subjected to structural novelty screening, and the most promising compounds are tested in a D3 binding assay. Using this approach we identified four compounds with K(i) values better than 100 nM and eight compounds with K(i) values better than 1 microM out of 20 compounds selected for testing in the D3 receptor binding assay. Our results suggest that the D3 structural models obtained from this study may be useful for the discovery and design of novel and potent D3 ligands. Furthermore, the employed hybrid approach may be more effective for lead discovery from a large chemical database than either pharmacophore-based or structure-based database screening alone.

beta3-Adrenergic stimulation produces a decrease of cardiac contractility ex vivo in mice overexpressing the human beta3-adrenergic receptor

OBJECTIVES

The regulation of cardiac function by catecholamines involves three populations of beta-adrenoceptor (beta-AR). beta(1)- and beta(2)-AR stimulations produce an increase in contractility and beta(3)-AR stimulation mediates a negative inotropic effect in human ventricular muscle. Because of the lack of suitable animal models, we have generated transgenic mice with cardiac-specific expression of the human beta(3)-AR (TG beta(3) mice).

METHODS

TG beta(3) mice were produced by microinjection of the human beta(3)-AR under the control of the alpha myosin heavy chain promoter. Phenotypic analyses comprised beta(3)-AR mRNA and protein determinations, histological studies, electrocardiogram, contractility and cyclic nucleotide measurements.

RESULTS

TG beta(3) mice presented no histological evidence of myocyte hypertrophy or fibrogenesis. In basal conditions, TG beta(3) mice were characterized by an increase in heart rate and an acceleration of twitch parameters without modification of its amplitude. beta(3)-AR agonists (CL 316243, SR 58611A) decreased contractility at low concentrations (1-100 nM). At high concentrations, the negative inotropic effect was abolished. Pretreatment with nadolol, a beta(1)/beta(2)-AR blocker, blunted the rebound in peak tension elicited by beta(3)-AR agonists suggesting a non-specific action of these compounds on beta(1)- and beta(2)-AR. The involvement of beta(3)-AR in the negative inotropic effect was confirmed by the pretreatment with bupranolol, a non-selective beta-AR antagonist, which fully abolished the effects of SR 58611A. The negative inotropic effect was associated with an increase in intracellular cGMP level.

CONCLUSIONS

We conclude that cardiac overexpression of beta(3)-AR in mice reproduces ex vivo the negative inotropic effects obtained with beta(3)-AR stimulation in human ventricular tissues.

Conformation by NMR of two tetralin-based receptor ligands

The conformation in solution of 1-phenyl-3-propionamido-1,2,3,4-tetrahydronaphthalene and 1-phenyl-3-(N,N-dimethylamino)-1,2,3,4-tetrahydronaphthalene has been determined by a combination of nuclear magnetic resonance measurements and molecular mechanics calculations. The results indicate that in the cis isomers the cyclohexene ring is in a locked conformation and the trans isomers correspond to a mixture of the two inverted half chairs. Moreover, the data allowed the identification of the two purposely-synthesized geometrical isomers of 1-phenyl-3-propionamidotetralin. Binding studies on melatonin receptor subtypes showed that the (+/-)-cis-1-phenyl-3-propionamido-1,2,3,4-tetrahydronaphthalene has higher affinity and selectivity ratio toward the MT(2) subtype than the (+/-)-trans-isomer.

Site-directed mutagenesis of an extradiol dioxygenase involved in tetralin biodegradation identifies residues important for activity or substrate specificity

The sequence of the extradiol dioxygenase ThnC, involved in tetralin biodegradation, was aligned with other extradiol dioxygenases involved in biodegradation of polycyclic compounds, and a three-dimensional model of ThnC, based on the structure of the previously crystallized 2,3-dihydroxybiphenyl dioxygenase from Burkholderia fungorum LB400, was built. In order to assess the functional importance of some non-active-site residues whose relevance could not be established by structural information, a number of positions surrounding the substrate-binding site were mutated in ThnC. Ten mutant proteins were purified and their activity towards 1,2-dihydroxytetralin, 1,2-dihydroxynaphthalene and 2,3-dihydroxybiphenyl was characterized. N213H, Q198H, G206M, A282R and A282G mutants increased k(cat)/K(m) at least twofold using 1,2-dihydroxytetralin as the substrate, thus showing that activity of ThnC is not maximized for this substrate. N213H and Q198H mutants increased k(cat)/K(m) using any of the substrates tested, thus showing the relevance for activity of these two histidines, which are highly conserved in dihydroxybiphenyl dioxygenases, but not present in dihydroxynaphthalene dioxygenases. Different substitutions in position 282 had different effects on general activity or substrate specificity, thus showing the functional importance of the most C-terminal beta-sheet of the protein. A251M and G206M mutants showed increased activity specifically for a particular substrate. N213H, G206M, A282R, A282G and Y177I substitutions resulted in enzymes more tolerant to acidic pH, the most striking effect being observed in mutant Y177I, which showed maximal activity at pH 5.5. In addition, Q198D and V175D mutants, which had altered K(m), also showed altered sensitivity to substrate inhibition, thus indicating that inhibition is exerted through the same binding site. This mutational analysis, therefore, identified conserved residues important for activity or substrate specificity, and also shed some light on the mechanism of substrate inhibition exhibited by extradiol dioxygenases.

Biological characterization of a novel, orally active small molecule gonadotropin-releasing hormone (GnRH) antagonist using castrated and intact rats

Gonadotropin-releasing hormone (GnRH) receptor antagonists have potential in treating numerous hormone-dependent pathologies including cancers of the prostate, breast, and ovary, endometriosis, and fertility disorders. An unmet clinical need exists for an orally available GnRH receptor antagonist. Guided by structure-activity relationships, ligand-based targeted library designs, and biomarker measurements, our discovery efforts have yielded a novel, small molecule GnRH receptor antagonist, 5-[(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthalenyl)methyl]-N-(2,4,6-trimethoxyphenyl)-2-furamide (CMPD1). CMPD1 bound with low nanomolar affinities to human, rat, and mouse GnRH receptors (6.0, 3.8, and 2.2 nM, respectively). CMPD1 was more than 100-fold selective for GnRH receptors versus various G-protein-coupled receptors and other enzymes and ion channels. In cells expressing recombinant rat GnRH receptors, CMPD1 was a competitive antagonist of GnRH-stimulated increases in extracellular acidification rates in Cytosensor microphysiometer assays. In cells expressing recombinant human GnRH receptors, CMPD1 was a potent inhibitor of GnRH-stimulated total inositol phosphate accumulation. The effects of CMPD1 on circulating levels of luteinizing hormone (LH) and testosterone were studied in castrated and intact male rats, respectively. Intravenous and oral administration of CMPD1 dose dependently suppressed GnRH-mediated elevations of LH in castrated male rats and testosterone in gonad-intact male rats. Moreover, CMPD1, when given at 20 mg/kg i.v. to intact male rats, inhibited the elevations of LH and testosterone stimulated by the superagonist of GnRH, [d-Ala(6), des-Gly(10)]GnRH (GnRH-A). These data suggest that CMPD1 is a potent, selective, orally active GnRH receptor antagonist that may have potential application as a therapeutic agent for treating hormone-dependent cancers and diseases.

A synthetic overview of new molecules with 5-HT1A binding affinities

The present review discusses the synthetic strategies of new ligands exhibiting mainly 5-HT(1A)binding affinities. Specifically we focused our attention in the synthesis of compounds structurally related to arylpiperazine, 2-aminotetralin, and benzopyran derivatives.

Identification and functional characterization of Sphingomonas macrogolitabida strain TFA genes involved in the first two steps of the tetralin catabolic pathway

Five genes involved in the two initial steps of the tetralin biodegradation pathway of Sphingomonas macrogolitabida strain TFA have been characterized. ThnA1A2 and ThnA3A4, components of the ring-hydroxylating dioxygenase, were encoded in divergently transcribed operons. ThnA1, ThnA2, and ThnA3 were essential for tetralin ring-hydroxylating dioxygenase activity. ThnB was identified as a dehydrogenase required for tetralin biodegradation.

Arginine of retinoic acid receptor beta which coordinates with the carboxyl group of retinoic acid functions independent of the amino acid residues responsible for retinoic acid receptor subtype ligand specificity

The biological actions of retinoic acid (RA) are mediated by retinoic acid receptors (RARalpha, RARbeta, and RARgamma) and retinoid X receptors (RXRalpha, RXRbeta, and RXRgamma). Consistent with the X-ray crystal structures of RARalpha and RARgamma, site-directed mutagenesis studies have demonstrated the importance of a conserved Arg residue (alphaArg(276), betaArg(269), and gammaArg(278)) for coordination with the carboxyl group of RA. However, mutation of Arg(269) to Ala in RARbeta causes only a 3- to 6-fold increase in the K(d) for RA and EC(50) in RA-dependent transcriptional transactivation assays while the homologous mutation in either RARalpha or RARgamma causes a 110-fold and a 45-fold increase in EC(50) value, respectively. To further investigate the nature of this difference, we prepared mutant RARs to determine the effect of conversion of betaR269A to a mutant which mimics either RARalpha ligand selectivity (betaA225S/R269A) or RARgamma ligand selectivity (betaI263M/R269A/V338A). Our results demonstrate that in RARbeta mutants that acquire either RARalpha or RARgamma ligand specificity the Arg(269) position responsible for coordination with the carboxyl group of retinoids continued to function like that of RARbeta. Furthermore, three mutant receptors (betaA225S/R269A, betaA225S/F279, and alphaF286A) were found to have a greater than wild-type affinity for the RARalpha-selective ligand Am580. Finally, a homology-based computer model of the ligand binding domain (LBD) of RARbeta and the X-ray crystal structures of the LBD of both RARalpha and RARgamma are used to describe potential mechanisms responsible for the increased affinity of some mutants for Am580 and for the difference in the effect of mutation of Arg(269) in RARbeta compared to its homologous Arg in RARalpha and RARgamma.

Effect of joint administration of imipramine and amantadine on binding of [3H]7-OH-DPAT to dopamine D3 receptors in peripheral blood lymphocytes of the patients with drug-resistant unipolar depression

Treatment of the patients suffering from therapy-resistant unipolar depression with joint administration of imipramine (twice daily, 100-150 mg/day) and amantadine (twice daily, 150 mg/day) for four to six weeks resulted in the significant increase in the binding of [3H]7-OH-DPAT to dopamine D3 receptors in the peripheral blood lymphocytes. This effect correlated well with the clinical improvement, estimated with Hamilton's Depression Rating Scale. In the light of the above data, it seems justified to postulate that joint therapy with imipramine and amantadine may be successful in the treatment-resistant unipolar depression.

Identification of a hydratase and a class II aldolase involved in biodegradation of the organic solvent tetralin

Two new genes whose products are involved in biodegradation of the organic solvent tetralin were identified. These genes, designated thnE and thnF, are located downstream of the previously identified thnD gene and code for a hydratase and an aldolase, respectively. A sequence comparison of enzymes similar to ThnE showed the significant similarity of hydratases involved in biodegradation pathways to 4-oxalocrotonate decarboxylases and established four separate groups of related enzymes. Consistent with the sequence information, characterization of the reaction catalyzed by ThnE showed that it hydrated a 10-carbon dicarboxylic acid. The only reaction product detected was the enol tautomer, 2,4-dihydroxydec-2-ene-1,10-dioic acid. The aldolase ThnF showed significant similarity to aldolases involved in different catabolic pathways whose substrates are dihydroxylated dicarboxylic acids and which yield pyruvate and a semialdehyde. The reaction products of the aldol cleavage reaction catalyzed by ThnF were identified as pyruvate and the seven-carbon acid pimelic semialdehyde. ThnF and similar aldolases showed conservation of the active site residues identified by the crystal structure of 2-dehydro-3-deoxy-galactarate aldolase, a class II aldolase with a novel reaction mechanism, suggesting that these similar enzymes are class II aldolases. In contrast, ThnF did not show similarity to 4-hydroxy-2-oxovalerate aldolases of other biodegradation pathways, which are significantly larger and apparently are class I aldolases.

Mechanisms of ligand binding and efficacy at the human D2(short) dopamine receptor

Mechanisms of ligand binding and receptor activation for the human D2(short) dopamine receptor have been probed using two homologous series of monohydroxylated and dihydroxylated agonists (phenylethylamines and 2-dipropylaminotetralins). In ligand binding studies, the majority of compounds exhibited competition curves versus [3H]spiperone that were best fitted using a two site binding model. The compounds had different abilities (potencies and maximal effects) to stimulate [35S]GTPgammaS binding and to inhibit forskolin-stimulated cAMP accumulation. From the data it can be concluded that: (i) the ability of an agonist to stabilize receptor/G protein coupling can be used to predict agonist efficacy for some groups of compounds (2-dipropylaminotetralins) but not for others (phenylethylamines); (ii) the receptor may be activated by unhydroxylated compounds; (iii) single hydroxyl groups or pairs of hydroxyl groups on the agonist may contribute to binding affinity, potency and efficacy; and (iv) for the 2-dipropylaminotetralin series two modes of agonist/receptor interaction have been identified associated with different relative efficacy.

Vibrational study of polymorphism of tetralin derivative for treatment of cardiovascular diseases

Vibrational spectroscopy coupled with thermogravimetry (TG) and differential scanning calorimetry (DSC) was used to characterize racemic propanoic acid, 2-methyl-5,6,7,8-tetrahydro-6-(methylamino)-1,2-naphthalenediyl ester hydrochloride (CHF-1035), which is a new DA2 dopaminergic receptor/alpha2 agonist and beta blocker under clinical investigation for the treatment of congestive heart failure. Raman spectroscopy disclosed at least two different CHF-1035 polymorphs; the marker bands characteristic of each form were identified. The modifications undergone by the CHF-1035 drug as a consequence of grinding and heating were investigated. Mechanical and gentle thermal treatments caused a polymorphic transformation of the drug crystal form. Raman spectroscopy proved suitable for investigating the possible presence of different polymorphic forms, their relative stability, and interconversion tendency in relation to industrial manufacturing processes undergone by the drug (i.e., grinding, compression, and heating).

A new type of prodrug of catecholamines: an opportunity to improve the treatment of Parkinson's disease

After decades of research around dopamine agonists, we have found a promising compound in S-PD148903 that represents a new type of prodrug, which in the rat is bioactivated to the catecholamine S-5,6-diOH-DPAT, known to display mixed dopamine D(1)/D(2) receptor agonist properties just like apomorphine. This prodrug has an enone structure which by an oxidative bioactivation mechanism is converted to the corresponding catechol and is delivered enantioselectively into the CNS. This novel concept has the potential to revolutionize the treatment of Parkinson's disease by competing with L-DOPA, the current treatment of choice.

Chiral capillary electrophoretic determination of the enantiomeric purity of tetrahydronaphthalenic derivatives, melatoninergic ligands, using highly sulfated beta-cyclodextrins

Using cyclodextrin capillary zone electrophoresis (CD-CZE), baseline separation of synthetic tetrahydronaphthalenic derivatives, potential melatoninergic compounds, was achieved. A method for the enantioresolution of these tetralins and determination of their enantiomeric purity was developed using anionic CDs (highly sulfated-CD or highly S-CD) as chiral selectors and capillaries dynamically coated with polyethylene oxide (PEO). Operational parameters such as the nature and concentration of the chiral selectors, buffer pH, organic modifiers, temperature and applied voltage were investigated. The use of charged CDs provides a driving force for our neutral compounds in the running buffer and enantiomeric resolution by inclusion of compounds in the CD cavity. The highly S-beta-CD was found to be the most effective complexing agent, allowing good enantiomeric resolution. The complete resolution of three tetralin compounds was obtained using 25 mM phosphate buffer at pH 2.5 containing 2.5% w/v of highly S-beta-CD at 25 degrees C with an applied field of 0.25 kV/cm. The apparent association constants of the inclusion complexes were calculated. This optimized method was validated in terms of linearity, sensitivity, accuracy and recovery. The enantiomeric purity for the three molecules was determined and the detection limit of enantiomer impurities is about 0.3-0.6%.

Theoretical determination of chromophores in the chromogenic effects of aromatic neurotoxicants

We report the first computational study of the chromophores responsible for the chromogenic effects of aromatic neurotoxicants containing a 1,2-diacetyl moiety in their oxidation metabolites. A series of ab initio electronic structure calculations was performed on two representative aromatic compounds, 1,2-diacetylbenzene (1,2-DAB) and 1,2-diacetyl tetramethyl tetralin (1,2-DATT), the putative active metabolites of the neurotoxic aromatic hydrocarbon compounds 1,2-diethylbenzene (1,2-DEB) and acetyl ethyl tetramethyl tetralin (AETT), and on the products of their possible reactions with proteins that result in chromogenic effects. The electronic excitation energies determined by three different computational approaches were found to be consistent with each other. The calculated results are consistent with the conclusion/prediction that the chromogenic effects of 1,2-DAB (or 1,2-DEB) and 1,2-DATT (or AETT) could result from ninhydrin-like reactions, rather than the formation of pyrrole-like compounds. Our pK(a) calculations further indicate that the chromophore, i.e., the product of the ninhydrin-like reaction showing the blue color, is deprotonated in neutral aqueous solution. The corresponding protonated structure has a different color as it absorbs in the blue region of the visible spectrum, and its chromogenic contribution would be significant in solution at low pH.