One-pot tandem reduction and site-selective halogenation of nitroarenes.

Halogenated aryl amines are a widely used chemical feedstock in the pharmaceutical and agrochemical industries. Achieving a single regioselective product from the para-selective halogenation of the aryl ring is significantly challenging because of the presence of several C-H bonds with similar reactivities. In this study, single para-halogenated aniline derivatives were prepared by the cascade para-selective halogenation (Cl, Br) and reduction of nitrobenzene derivatives using a mixture of SnCl2/SnCl4 salts. The mechanistic study confirmed that the noncovalent interactions between the chalcogen bond and Sn salt were pivotal for achieving regioselectivity. This synthetic method was applied for the development of potent and highly selective positron emission tomography molecular probes for serotonin transporters.

Differential roles of serotonin receptor subtypes in regulation of neurotrophin receptor expression and intestinal hypernociception.

OBJECTIVES: Aberrant serotonin (5-hydroxytryptamine, 5-HT) metabolism and neurite outgrowth were associated with abdominal pain in irritable bowel syndrome (IBS). We previously demonstrated that 5-HT receptor subtype 7 (5-HT7) was involved in visceral hypersensitivity of IBS-like mouse models. The aim was to compare the analgesic effects of a novel 5-HT7 antagonist to reference standards in mouse models and investigate the mechanisms of 5-HT7-dependent neuroplasticity. METHODS: Two mouse models, including Giardia post-infection combined with water avoidance stress (GW) and post-resolution of trinitrobenzene sulfonic acid-induced colitis (PT) were used. Mice were orally administered CYY1005 (CYY, a novel 5-HT7 antagonist), alosetron (ALN, a 5-HT3 antagonist), and loperamide (LPM, an opioid receptor agonist) prior to measurement of visceromotor responses (VMR). Levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin receptors (NTRs) were assessed. RESULTS: Peroral CYY was more potent than ALN or LPM in reducing VMR values in GW and PT mice. Increased mucosal 5-HT7-expressing nerve fibers were associated with elevated Gap43 levels in the mouse colon. We observed higher colonic Ntrk2 and Ngfr expression in GW mice, and increased Bdnf expression in PT mice compared with control mice. Human SH-SY5Y cells stimulated with mouse colonic supernatant or exogenous serotonin exhibited longer nerve fibers, which CYY dose-dependently inhibited. Serotonin increased Ntrk1 and Ngfr expression via 5-HT7 but not 5-HT3 or 5-HT4, while Ntrk2 upregulation was dependent on all three 5-HT receptor subtypes. CONCLUSIONS: Stronger analgesic effects by peroral CYY were observed compared with reference standards in two IBS-like mouse models. The 5-HT7-dependent NTR upregulation and neurite elongation may be involved in intestinal hypernociception.

Synthesis and biological evaluation of C-4 substituted phenoxazine-bearing hydroxamic acids with potent class II histone deacetylase inhibitory activities.

Class II histone deacetylases (HDACs) are considered as potential targets to treat Alzheimer's disease (AD). Previously, C-3 substituted phenothiazine-containing compounds with class II HDAC-inhibiting activities was found to promote neurite outgrowth. This study replaced phenothiazine moiety with phenoxazine that contains many C-3 and C-4 substituents. Some resulting compounds bearing the C-4 substituent on a phenoxazine ring displayed potent class II HDAC inhibitory activities. Structure-activity relationship (SAR) of these compounds that inhibited HDAC isoenzymes was disclosed. Molecular modelling analysis demonstrates that the potent activities of C-4 substituted compounds probably arise from π-π stacked interactions between these compounds and class IIa HDAC enzymes. One of these, compound 7d exhibited the most potent class II HDAC inhibition (IC50= 3-870 nM). Notably, it protected neuron cells from H2O2-induced neuron damage at sub-µM concentrations, but with no significant cytotoxicity. These findings show that compound 7d is a lead compound for further development of anti-neurodegenerative agents.

5-HT7 receptor-dependent intestinal neurite outgrowth contributes to visceral hypersensitivity in irritable bowel syndrome.

Irritable bowel syndrome (IBS) is characterized by visceral hypersensitivity (VH) associated with abnormal serotonin/5-hydroxytryptamine (5-HT) metabolism and neurotrophin-dependent mucosal neurite outgrowth. The underlying mechanisms of VH remain poorly understood. We investigated the role of 5-HT7 receptor in mucosal innervation and intestinal hyperalgesia. A high density of mucosal nerve fibres stained for 5-HT7 was observed in colonoscopic biopsy specimens from IBS patients compared with those from healthy controls. Staining of 5-HT3 and 5-HT4 receptors was observed mainly in colonic epithelia with comparable levels between IBS and controls. Visceromotor responses to colorectal distension were evaluated in two mouse models, one postinfectious with Giardia and subjected to water avoidance stress (GW) and the other postinflammatory with trinitrobenzene sulfonic acid-induced colitis (PT). Increased VH was associated with higher mucosal density of 5-HT7-expressing nerve fibres and elevated neurotrophin and neurotrophin receptor levels in the GW and PT mice. The increased VH was inhibited by intraperitoneal injection of SB-269970 (a selective 5-HT7 antagonist). Peroral multiple doses of CYY1005 (a novel 5-HT7 ligand) decreased VH and reduced mucosal density of 5-HT7-expressing nerve fibres in mouse colon. Human neuroblastoma SH-SY5Y cells incubated with bacteria-free mouse colonic supernatant, 5-HT, nerve growth factor, or brain-derived neurotrophic factor exhibited nerve fibre elongation, which was inhibited by 5-HT7 antagonists. Gene silencing of HTR7 also reduced the nerve fibre length. Activation of 5-HT7 upregulated NGF and BDNF gene expression, while stimulation with neurotrophins increased the levels of tryptophan hydroxylase 2 and 5-HT7 in neurons. A positive-feedback loop was observed between serotonin and neurotrophin pathways via 5-HT7 activation to aggravate fibre elongation, whereby 5-HT3 and 5-HT4 had no roles. In conclusion, 5-HT7-dependent mucosal neurite outgrowth contributed to VH. A novel 5-HT7 antagonist could be used as peroral analgesics for IBS-related pain.

Synthesis and biological evaluation of phenothiazine derivative-containing hydroxamic acids as potent class II histone deacetylase inhibitors.

The pathogenesis of Alzheimer's disease (AD) has been associated with dysregulation of histone deacetylases (HDACs). Previously, acridine-based HDAC inhibitors have shown potential in ameliorating HDAC activity and enhancing neurite outgrowth. In this study, the acridine ring was modified using various phenothiazine derivatives. Several resulting compounds exhibited potent enzyme-inhibiting activity towards class II HDACs when compared to the clinically approved HDAC inhibitor SAHA. Compound 4f demonstrated the highest class II HDAC inhibition (IC50 = 4.6-600 nM), as well as promotion of neurite outgrowth. Importantly, compound 4f displayed no cytotoxicity against neuron cells. Compound 4f was further evaluated for cellular effects. Altogether, these findings show a potential strategy in HDAC inhibition for treatment of the neurological disease.

Inhibitor development of MTH1 via high-throughput screening with fragment based library and MTH1 substrate binding cavity.

MutT Homolog 1 (MTH1) has been proven to hydrolyze oxidized nucleotide triphosphates during DNA repair. It can prevent the incorporation of wrong nucleotides during DNA replication and mitigate cell apoptosis. In a cancer cell, abundant reactive oxygen species can lead to substantial DNA damage and DNA mutations by base-pairing mismatch. MTH1 could eliminate oxidized dNTP and prevent cancer cells from entering cell death. Therefore, inhibition of MTH1 activity is considered to be an anti-cancer therapeutic target. In this study, high-throughput screening techniques were combined with a fragment-based library containing 2,313 compounds, which were used to screen for lead compounds with MTH1 inhibitor activity. Four compounds with MTH1 inhibitor ability were selected, and compound MI0639 was found to have the highest effective inhibition. To discover the selectivity and specificity of this action, several derivatives based on the MTH1 and MI0639 complex structure were synthesized. We compared 14 complex structures of MTH1 and the various compounds in combination with enzymatic inhibition and thermodynamic analysis. Nanomolar-range IC50 inhibition abilities by enzyme kinetics and Kd values by thermodynamic analysis were obtained for two compounds, named MI1020 and MI1024. Based on structural information and compound optimization, we aim to provide a strategy for the development of MTH1 inhibitors with high selectivity and specificity.

Synthesis and analysis of 4-(3-fluoropropyl)-glutamic acid stereoisomers to determine the stereochemical purity of (4S)-4-(3-[18F]fluoropropyl)-L-glutamic acid ([18F]FSPG) for clinical use.

(4S)-4-(3-[18F]Fluoropropyl)-L-glutamic acid ([18F]FSPG) is a positron emission tomography (PET) imaging agent for measuring the system xC- transporter activity. It has been used for the detection of various cancers and metastasis in clinical trials. [18F]FSPG is also a promising diagnostic tool for evaluation of multiple sclerosis, drug resistance in chemotherapy, inflammatory brain diseases, and infectious lesions. Due to the very short half-life (110 min) of 18F nuclide, [18F]FSPG needs to be produced on a daily basis; therefore, fast and efficient synthesis and analytical methods for quality control must be established to assure the quality and safety of [18F]FSPG for clinical use. To manufacture cGMP-compliant [18F]FSPG, all four nonradioactive stereoisomers of FSPG were prepared as reference standards for analysis. (2S,4S)-1 and (2R,4R)-1 were synthesized starting from protected L- and D-glutamate derivatives in three steps, whereas (2S,4R)-1 and (2R,4S)-1 were prepared in three steps from protected (S)- and (R)-pyroglutamates. A chiral HPLC method for simultaneous determination of four FSPG stereoisomers was developed by using a 3-cm Chirex 3126 column and a MeCN/CuSO4(aq) mobile phase. In this method, (2R,4S)-1, (2S,4S)-1, (2R,4R)-1, and (2S,4R)-1 were eluted in sequence with sufficient resolution in less than 25 min without derivatization. Scale-up synthesis of intermediates for the production of [18F]FSPG in high optical purity was achieved via stereo-selective synthesis or resolution by recrystallization. The enantiomeric excess of intermediates was determined by HPLC using a Chiralcel OD column and monitored at 220 nm. The nonradioactive precursor with >98% ee can be readily distributed to other facilities for the production of [18F]FSPG. Based on the above accomplishments, cGMP-compliant [18F]FSPG met the acceptance criteria in specifications and was successfully manufactured for human use. It has been routinely prepared and used in several pancreatic ductal adenocarcinoma metastasis-related clinical trials.

Synthesis and evaluation of 2-(2'-((dimethylamino)methyl)-4'-(2-fluoroethoxy-substituted)phenylthio)benzenamine derivatives as potential positron emission tomography imaging agents for serotonin transporters.

A series of diphenylsulfide derivatives with various substitutions at the 4-position on phenyl ring A and different lengths of the 2-fluoroethoxy-substituted side-chain at the 4'-position on ring B were synthesized and evaluated as potential positron emission tomography (PET) imaging agents for serotonin transporters (SERT). These ligands exhibited high SERT binding affinities (Ki = 0.11-1.3 nM) and the 4-methyl-substituted (4-Me) compounds 7a and 8a displayed excellent selectivity for SERT versus norepinephrine transporters (NET) (392- and 700-fold, respectively). In the parallel artificial membrane permeability assay (PAMPA), these ligands demonstrated moderate to high brain penetration, and the 4-Me analogs showed higher BBB permeability than the corresponding 4-F analogs. The 2-fluoroethoxy-substituted ligands showed higher metabolic stability and lower lipophilicity than 4-F-ADAM. [18F]7a-c were readily prepared using an automatic synthesizer and exhibited significant uptake and slow washout in rat brains. At 120 min after iv injection, [18F]7a exhibited the highest uptake in the midbrain, whereas [18F]7b exhibited the highest uptake in the hypothalamus and midbrain. After treatment with citalopram, a SERT-selective ligand, the uptake of [18F]7a in the hypothalamus and striatum was significantly decreased. The potent and highly selective SERT binding and the selective and reversible accumulation in SERT-rich brain regions suggested that [18F]7a is a promising lead for the further development of novel [18F]-labeled PET imaging agents for SERT binding sites in the brain.

A novel isoquinoline derivative exhibits anti-inflammatory properties and improves the outcomes of endotoxemia.

BACKGROUND: Sepsis initiates an inflammatory response that causes widespread injury, and candidates for related myocardial depressant factors include cytokines and nitric oxide (NO). Nuclear factor kappa-B (NF-κB) stimulated by toll-like receptor 4 activation in sepsis mediates the transcription of multiple proinflammatory genes. These inflammatory mediators can cause myocardial dysfunction, which may deteriorate sepsis outcomes. To address this risk, we investigated the potential beneficial effects of a novel isoquinolines derivative, CYY054c, in LPS-induced inflammatory response leading to endotoxemia. METHODS: The effects of CYY054c on cytokine and inflammatory-related protein production were evaluated in lipopolysaccharide (LPS)-stimulated macrophages. To determine whether CYY054c alleviates inflammatory storm-induced myocardial dysfunction in vivo, LPS was injected in rats, and cardiac function was measured by a pressure-volume loop. RESULTS: CYY054c inhibited LPS-induced NF-κB expression in macrophages and reduced the release of tumor necrosis factor-alpha (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6), as well as the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In the animal studies, CYY054c alleviated LPS-upregulated plasma TNF-α, IL-1ß, IL-6, and NO concentrations, as well as cardiac monocyte chemotactic protein-1, iNOS, and COX-2 expression in rats, contributing to the improvement of cardiac function during endotoxemia. CONCLUSIONS: The reduction of NF-κB-mediated inflammatory mediators and the maintenance of hemodynamic performance by CYY054c improved the outcomes during endotoxemia. CYY054c may be a potential therapeutic agent for sepsis.

An one-pot two-step automated synthesis of [18F]T807 injection, its biodistribution in mice and monkeys, and a preliminary study in humans.

[18F]T807 is a potent tau protein imaging agent. In order to fulfill the demand from preclinical and clinical studies, we developed an automated one-pot two-step synthesis of this potent tau imaging agent and studied its stability, and dosimetry in mice and monkeys. We also conducted a preliminary study of this imaging agent in humans. Using this one-pot two-step method, the radiochemical yield (RCY) of [18F]T807 was 20.5 ± 6.1% (n = 15) at the end of bombardment (EOB) in a synthesis time of 70±5 min. The chemical and radiochemical purities were >90% and the specific activities were 151 ± 52 GBq/µmol. The quality of [18F]T807 synthesized by this method met the U.S. Pharmacopoeia (USP) criteria. The stability test showed that the [18F]T807 injection was stable at room temperature for up to 4 h after the end of synthesis (EOS). The estimated effective dose of the [18F]T807 injection extrapolated from monkeys was 19 µSv/MBq (n = 2), while the estimated effective doses of the [18F]T807 injection extrapolated from fasted and non-fasted mice were 123 ± 27 (n = 3) and 94 ± 19 (n = 4) µSv/MBq, respectively. This one-pot two-step automated method produced the [18F]T807 injection with high reproducibility and high quality. PET imaging and radiation dosimetry evaluation in mice and Formosan rock monkeys suggested that the [18F]T807 injection synthesized by this method is suitable for use in human PET imaging studies. Thus, this method could fulfill the demand for the [18F]T807 injection in both preclinical and clinical studies of tauopathies, especially for nearby study sites without cyclotrons.

High-selective HDAC6 inhibitor promotes HDAC6 degradation following autophagy modulation and enhanced antitumor immunity in glioblastoma.

Glioblastoma is the most fatal type of primary brain cancer, and current treatments for glioblastoma are insufficient. HDAC6 is overexpressed in glioblastoma, and siRNA-mediated knockdown of HDAC6 inhibits glioma cell proliferation. Herein, we report a high-selective HDAC6 inhibitor, J22352, which has PROTAC (proteolysis-targeting chimeras)-like property resulted in both p62 accumulation and proteasomal degradation, leading to proteolysis of aberrantly overexpressed HDAC6 in glioblastoma. The consequences of decreased HDAC6 expression in response to J22352 decreased cell migration, increased autophagic cancer cell death and significant tumor growth inhibition. Notably, J22352 reduced the immunosuppressive activity of PD-L1, leading to the restoration of host anti-tumor activity. These results demonstrate that J22352 promotes HDAC6 degradation and induces anticancer effects by inhibiting autophagy and eliciting the antitumor immune response in glioblastoma. Therefore, this highly selective HDAC6 inhibitor can be considered a potential therapeutic for the treatment of glioblastoma and other cancers.

Prospective comparison of (4S)-4-(3-18F-fluoropropyl)-L-glutamate versus 18F-fluorodeoxyglucose PET/CT for detecting metastases from pancreatic ductal adenocarcinoma: a proof-of-concept study.

PURPOSE: (4S)-4-(3-18F-Fluoropropyl)-L-glutamate (FSPG) positron emission tomography (PET) reflects system xC- transporter (xCT) expression. FSPG PET has been used to detect brain, lung, breast and liver cancer with only modest success. There is no report on the use of FSPG PET in pancreatic ductal adenocarcinoma (PDAC), presumably because of normal xCT expression in the pancreas. Nonetheless, the tissue-specific expression of xCT in the pancreas suggests that FSPG PET may be ideal for identifying metastasized PDAC. METHODS: The performance of FSPG in detecting PDAC metastases was compared with that of 18F-fluorodeoxyglucose (FDG) in small-animal PET studies in seven PDAC tumour-bearing mice and in prospective PET/computed tomography (CT) studies in 23 patients with tissue-confirmed PDAC of stage III or stage IV. All PET/CT results were correlated with the results of histopathology or contrast-enhanced CT (ceCT) performed 3 and 6 months later. RESULTS: In the rodent model, FSPG PET consistently found more PDAC metastases earlier than FDG PET. FSPG PET showed a trend for a higher sensitivity, specificity and diagnostic accuracy than FDG PET in detecting PDAC metastases in a patient-based analysis: 95.0%, 100.0% and 95.7%, and 90.0%, 66.7% and 90.0%, respectively. In a lesion-based analysis, FSPG PET identified significantly more PDAC metastases, especially in the liver, than FDG PET (109 vs. 95; P = 0.0001, 95% CI 4.9-14.6). The tumour-to-background ratios for FSPG and FDG uptake on positive scans were similar (FSPG 4.2 ± 4.3, FDG 3.6 ± 3.0; P = 0.44, 95% CI -1.11 to 0.48), despite a lower tumour maximum standardized uptake value in FSPG-avid lesions (FSPG 4.2 + 2.3, FDG 7.7 + 5.7; P = 0.002, 95% CI 0.70-4.10). Because of the lower physiological activity of FSPG in the liver, FSPG PET images of the liver are more easy to interpret than FDG PET images, and therefore the use of FSPG improves the detection of liver metastasis. CONCLUSION: FSPG PET is superior to FDG PET in detecting metastasized PDAC, especially in the liver.

Targeting breast cancer stem cells by novel HDAC3-selective inhibitors.

Although histone deacetylase (HDAC) inhibitors have been known to suppress the cancer stem cell (CSC) population in multiple types of cancer cells, it remains unclear which HDAC isoforms and corresponding mechanisms contribute to this anti-CSC activity. Pursuant to our previous finding that HDAC8 regulates CSCs in triple-negative breast cancer (TNBC) cells by targeting Notch1 stability, we investigated related pathways and found HDAC3 to be mechanistically linked to CSC homeostasis by increasing ß-catenin expression through the Akt/GSK3ß pathway. Accordingly, we used a pan-HDAC inhibitor, AR-42 (1), as a scaffold to develop HDAC3-selective inhibitors, obtaining the proof-of-concept with 18 and 28. These two derivatives exhibited high potency and isoform selectivity in HDAC3 inhibition. Equally important, they showed in vitro and/or in vivo efficacy in suppressing the CSC subpopulation of TNBC cells via the downregulation of ß-catenin.

Identification of Buctopamine and Mebuctopamine, a ß2 Receptor Agonist and Its Metabolite, in Swine Hair and Feed Additives.

4-[2-(t-Butylamino)-1-hydroxyethyl]phenol (buctopamine, 4), a new ß2 receptor agonist (ß2-agonist), was found to be an adulterant in feed additives for swine in Taiwan, where using ß2-agonists in food-production animals is prohibited. Buctopamine and its metabolite, 4-[2-(t-butylamino)-1-hydroxyethyl]-2-methoxyphenol (mebuctopamine, 2), were detected in swine hair specimens. Authentic compounds 2 and 4 were synthesized with 98.6% and 97.7% purity, respectively, as reference standards for analysis, and both compounds were more hydrophilic than ractopamine and clenbuterol. In a preliminary pharmacological evaluation, compounds 2 and 4 exhibited moderate human ß2 receptor binding affinity and did not show significant affinities for the human α1, α2, ß1, and ß3 receptors. After addition of compounds 2-4 into the ß2-agonist library, a multiresidue analysis of 26 ß2-agonists by using triple quadrupole LC/MS/MS for routine screening conducted by regulatory authorities was established, in which the common limits of quantification for the 26 ß2-agonists in swine feed and hair are 10 and 25 ng/g, respectively. In addition, the illegal use of buctopamine (4) has been effectively prevented. The results of this study are also useful for controlling the illegal use of new ß2-agonists in food-production animals.

Fast and Facile Synthesis of 4-Nitrophenyl 2-Azidoethylcarbamate Derivatives from N-Fmoc-Protected α-Amino Acids as Activated Building Blocks for Urea Moiety-Containing Compound Library.

A fast and facile synthesis of a series of 4-nitrophenyl 2-azidoethylcarbamate derivatives as activated urea building blocks was developed. The N-Fmoc-protected 2-aminoethyl mesylates derived from various commercially available N-Fmoc-protected α-amino acids, including those having functionalized side chains with acid-labile protective groups, were directly transformed into 4-nitrophenyl 2-azidoethylcarbamate derivatives in 1 h via a one-pot two-step reaction. These urea building blocks were utilized for the preparation of a series of urea moiety-containing mitoxantrone-amino acid conjugates in 75-92% yields and parallel solution-phase synthesis of a urea compound library consisted of 30 members in 38-70% total yields.

A Novel Potential Positron Emission Tomography Imaging Agent for Vesicular Monoamine Transporter Type 2.

In the early 1990s, 9-(+)-11C-dihydrotetrabenazine (9-(+)-11C-DTBZ) was shown to be a useful positron emission tomography (PET) imaging agent for various neurodegenerative disorders. Here, we described the radiosynthesis and evaluation of the 9-(+)-11C-DTBZ analog, 10-(+)-11C-DTBZ, as a vesicular monoamine transporter 2 (VMAT2) imaging agent and compare it with 9-(+)-11C-DTBZ. 10-(+)-11C-DTBZ was obtained by 11C-MeI methylation with its 10 hydroxy precursor in the presence of 5 M NaOH. It had a slightly better average radiochemical yield of 35.3 ± 3.6% (decay-corrected to end of synthesis (EOS)) than did 9-(+)-11C-DTBZ (30.5 ± 2.3%). MicroPET studies showed that 10-(+)-11C-DTBZ had a striatum-to-cerebellum ratio of 3.74 ± 0.21 at 40 min post-injection, while the ratio of 9-(+)-11C-DTBZ was 2.50 ± 0.33. This indicated that 10-(+)-11C-DTBZ has a higher specific uptake in VMAT2-rich brain regions, and 10-(+)-11C-DTBZ may be a potential VMAT2 radioligand. Our experiment is the first study of 10-(+)-11C-DTBZ to include dynamic brain distribution in rat brains.

Mechanisms of amphetamine action illuminated through optical monitoring of dopamine synaptic vesicles in Drosophila brain.

Amphetamines elevate extracellular dopamine, but the underlying mechanisms remain uncertain. Here we show in rodents that acute pharmacological inhibition of the vesicular monoamine transporter (VMAT) blocks amphetamine-induced locomotion and self-administration without impacting cocaine-induced behaviours. To study VMAT's role in mediating amphetamine action in dopamine neurons, we have used novel genetic, pharmacological and optical approaches in Drosophila melanogaster. In an ex vivo whole-brain preparation, fluorescent reporters of vesicular cargo and of vesicular pH reveal that amphetamine redistributes vesicle contents and diminishes the vesicle pH-gradient responsible for dopamine uptake and retention. This amphetamine-induced deacidification requires VMAT function and results from net H(+) antiport by VMAT out of the vesicle lumen coupled to inward amphetamine transport. Amphetamine-induced vesicle deacidification also requires functional dopamine transporter (DAT) at the plasma membrane. Thus, we find that at pharmacologically relevant concentrations, amphetamines must be actively transported by DAT and VMAT in tandem to produce psychostimulant effects.

Activation of serotonin 5-HT7 receptor induces coronary flow increase in isolated rat heart.

Serotonin (5-Hydroxytryptamine, 5-HT) can elicit both vasoconstrictive and relaxant responses on rat coronary artery. The constrictive response has been well discussed, but the mechanism of relaxant response is less studied. In the present study, we found serotonin (0.3 and 1 µM) increased coronary flow on isolated rat hearts, and treatment of nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) 300 µM reduced but not totally blocked this coronary flow increasing effect. In L-NAME 10 µM treated heart, treatment of selective serotonin 5-HT7 receptor antagonist SB269970 0.1 µM blocked serotonin induced coronary flow increasing response, and in the presence of 1 µM SB269970, serotonin turned into reducing coronary flow. Treatment of TCW295 (8-(2,4-Dimethoxyphenyl)-6-methoxy-2-phenethyl-1,2,3,4-tetrahydroisoquinolin-7-ol hydrochloride), a novel serotonin 5-HT2A/7 receptor antagonist, inhibited both serotonin induced coronary flow increasing and decreasing effects. In conclusion, we found serotonin increases coronary flow of isolated rat heart by activating serotonin 5-HT7 receptor activation, and this effect can be, at least partially, resistant to L-NAME.

Topoisomerase II inhibition suppresses the proliferation of telomerase-negative cancers.

Telomere maintenance is required for chromosome stability, and telomeres are typically elongated by telomerase following DNA replication. In both tumor and yeast cells that lack telomerase, telomeres are maintained via an alternative recombination mechanism. Previous studies have indicated that yeast Sgs1 and Top3 may work together to remove highly negative supercoils that are generated from recombination. However, the mechanism by which cells eradicate highly positive supercoils during recombination remains unclear. In the present study, we demonstrate that TOP2 is involved in telomere-telomere recombination. Disturbance of telomeric structure by RIF1 or RIF2 deletion alleviates the requirement for TOP2 in telomere-telomere recombination. In human telomerase-negative alternative lengthening of telomere (ALT) cells, TOP2α or TOP2ß knockdown decreases ALT-associated PML bodies, increases telomere dysfunction-induced foci and triggers telomere shortening. Similar results were observed when ALT cells were treated with ICRF-193, a TOP2 inhibitor. Importantly, ICRF-193 treatment blocks ALT-associated phenotypes in vitro, causes telomere shortening, and inhibits ALT cell proliferation in mice. Taken together, these findings imply that TOP2 is involved in the ALT pathway, perhaps by resolving the highly positive supercoil structure at the front of the helicase. Inhibition of topoisomerase II may be a promising therapeutic approach that can be used to prevent cell proliferation in ALT-type cancer cells.

Quinazolin-4-one derivatives as selective histone deacetylase-6 inhibitors for the treatment of Alzheimer's disease.

Novel quinazolin-4-one derivatives containing a hydroxamic acid moiety were designed and synthesized. All compounds were subjected to histone deacetylase (HDAC) enzymatic assays to identify selective HDAC6 inhibitors with nanomolar IC50 values. (E)-3-(2-Ethyl-7-fluoro-4-oxo-3-phenethyl-3,4-dihydroquinazolin-6-yl)-N-hydroxyacrylamide, 4b, is the most potent HDAC6 inhibitor (IC50, 8 nM). In vitro, these compounds induced neurite outgrowth accompanied by growth-associated protein 43 expression, and they enhanced the synaptic activities of PC12 and SH-SY5Y neuronal cells without producing toxic or mitogenic effects. Several of the compounds dramatically increased nonhistone protein acetylation, specifically of α-tubulin. Some of the more potent HDAC6 inhibitors decreased zinc-mediated ß-amyloid aggregation in vitro. N-Hydroxy-3-(2-methyl-4-oxo-3-phenethyl-3,4-dihydro-quinazolin-7-yl)-acrylamide, 3f, the most promising drug candidate, selectively inhibits HDAC6 (IC50, 29 nM), practically does not affect human ether-a-go-go-related membrane channel activity (IC50 >10 µM) or cytochrome P450 activity (IC50 >6.5 µM) in vitro, and significantly improves learning-based performances of mice with ß-amyloid-induced hippocampal lesions.