Assessing health risks from bioaccessible PM2.5-bound toxic metals in Nanchang metro: Implications for metro workers and emissions control.

High concentrations of PM2.5 with enriched levels of metallic constituents could significantly affect the health and comfort of metro employees. To avoid overestimating the exposure risks, we investigated the bioaccessibility of toxic metals (TMs) bound in PM2.5 from the Nanchang metro using Gamble's solution method, and qualitatively analyzed the impact of valence state and various sources on the bioaccessibility of TMs bound to PM2.5. The results showed that the bioaccessibility of the studied TMs ranged from 2.1% to 88.1%, with As, Ba, Co and Pb being the most bioaccessible and V, Fe and Cr being the less bioaccessible. The bioaccessibility of TMs in our subway PM2.5 samples varied based on their valence and species, showing higher valence states associated with increased bioaccessibility. Vehicle traffic, secondary aerosols and wheel/rail sources were found to be significantly and positively associated with the bioaccessibility of several TMs, implying a severe potential risk from these three sources. Although both non-carcinogenic and carcinogenic risks associated with total TMs were found to be high, only As and Cr(VI) posed a considerable carcinogenic risk to metro workers based on the bioaccessible fractions and were therefore priority pollutants. In addition, potential carcinogenic risk was found to be more severe in platform than that in ticket counter. The results indicate that considerable efforts are required to control and manage PM2.5 and the associated TMs in the Nanchang subway, particularly from traffic, wheel/rail and secondary sources, to protect the health of metro staff and the public.

Design, synthesis and biological evaluation of structurally new 4-indolyl quinazoline derivatives as highly potent, selective and orally bioavailable EGFR inhibitors.

Targeting the epidermal growth factor receptor (EGFR) has been recognized as an effective strategy for treating non-small-cell lung cancer (NSCLC). Although several representative EGFR inhibitors have been approved for clinical use, it is highly desirable to develop highly potent and selective EGFR inhibitors with novel scaffolds because of the occurrence of acquired resistance after treatment. Here we first demonstrate that the 4-indolyl quinazoline derivatives could potently inhibit EGFR in vitro and in vivo, of which YS-67 effectively and selectively inhibits EGFR[WT] (IC50 = 5.2 nM), EGFR[d746-750] (IC50 = 9.6 nM) and EGFR[L858R] (IC50 = 1.9 nM). The TREEspot™ kinase interaction map further reveals the binding selectivity toward 468 kinases. YS-67 not only potently suppresses p-EGFR and p-AKT, but also effectively inhibits proliferation of A549 (IC50 = 4.1 µM), PC-9 (IC50 = 0.5 µM) and A431 cells (IC50 = 2.1 µM). YS-67 treatment also causes colony formation inhibition, arrests cell cycle progression at G0/G1 phases and induces apoptosis. More importantly, YS-67 is well tolerated in A431 xenograft model after oral administration, showing effective tumor growth suppression and low toxicity. Collectively, YS-67 represents an underexplored scaffold for developing new EGFR inhibitors.

New ε-N-thioglutaryl-lysine derivatives as SIRT5 inhibitors: Chemical synthesis, kinetic and crystallographic studies.

SIRT5 has been implicated in various physiological processes and human diseases, including cancer. Development of new highly potent, selective SIRT5 inhibitors is still needed to investigate disease-related mechanisms and therapeutic potentials. We here report new ε-N-thioglutaryllysine derivatives, which were designed according to SIRT5-catalysed deacylation reactions. These ε-N-thioglutaryllysine derivatives displayed potent SIRT5 inhibition, of which the potential photo-crosslinking derivative 8 manifested most potent inhibition with an IC50 value of 120 nM to SIRT5, and low inhibition to SIRT1-3 and SIRT6. The enzyme kinetic assays revealed that the ε-N-thioglutaryllysine derivatives inhibit SIRT5 by lysine-substrate competitive manner. Co-crystallographic analyses demonstrated that 8 binds to occupy the lysine-substate binding site by making hydrogen-bonding and electrostatic interactions with SIRT5-specific residues, and is likely positioned to react with NAD+ and form stable thio-intermediates. Compound 8 was observed to have low photo-crosslinking probability to SIRT5, possibly due to inappropriate position of the diazirine group as observed in SIRT5:8 crystal structure. This study provides useful information for developing drug-like inhibitors and cross-linking chemical probes for SIRT5-related studies.

Structure-Based Design of the Indole-Substituted Triazolopyrimidines as New EED-H3K27me3 Inhibitors for the Treatment of Lymphoma.

Interrupting the embryonic ectoderm development (EED)-H3K27me3 interaction represents a promising strategy to allosterically inhibit polycomb repressive complex 2 (PRC2) for cancer therapy. In this work, we report the structure-based design of new triazolopyrimidine-based EED inhibitors, which structurally feature the electron-rich indole ring at the C8 position. Particularly, ZJH-16 directly binds to EED (HTRF IC50 = 2.72 nM, BLI KD = 4.4 nM) and potently inhibits the growth of KARPAS422 and Pfeiffer cells. In both cells, ZJH-16 is selectively engaged with EED and reduces H3K27 trimethylation levels. ZJH-16 inhibits the gene silencing function of PRC2 in KARPAS422 cells. ZJH-16 possesses favorable pharmacokinetic (PK) profiles with an excellent oral bioavailability (F = 94.7%). More importantly, ZJH-16 shows robust tumor regression in the KARPAS422 xenograft model after oral administration with the tumor growth inhibition reaching nearly 100%. The robust antitumor efficacy and favorable PK profiles of ZJH-16 warrant further advanced preclinical development for lymphoma treatment.

4,6-Disubstituted-1H-Indazole-4-Amine derivatives with immune-chemotherapy effect and in vivo antitumor activity.

Tryptophan-2,3-dioxygenase (TDO) and indoleamine-2, 3-dioxygenase 1 (IDO1) are the important tumor immune checkpoints and TDO and IDO1 inhibition may present a potential approach to activate the T cell-mediated antitumor immune response during cancer treatment. Herein, we designed and synthesized a series of nitro-aryl 1H-indazole derivatives. SARs analysis showed that the nitro-aryl at the C-4 position of 1H-indazole was beneficial for TDO inhibition and directly tumoricidal effect and the substituents at C-6 position of 1H-indazole significantly affected the activity and selectivity of IDO1/TDO. Among these derivatives, HT-28 and HT-30 demonstrated nanomolar potency and excellent selectivity against TDO with IC50 values of 0.62 µM and 0.17 µM respectively, and HT-37 showed the IDO1 and TDO dual-target inhibitory activity with IC50 values of 0.91 µM and 0.46 µM against IDO1 and TDO. Moreover, HT-28 showed the significant tumoricidal effect on six tumor cell lines, while HT-30 and HT-37 had almost no cytotoxic activity on these tumor cells. In the CT-26 allograft BALB/c mice, HT-28 had the significant in vivo antitumor activity at a lower dose. IHC staining assay indicated that HT-28 could reduce the expression of Foxp3 and enhance the expression of CD8 and TNF-α in tumor tissue. In summary, we developed a difunctional monomer with immune-chemotherapy effect to obtain the better in anti-tumor activity.

Contribution of Na/K Doping to the Activity and Mechanism of Low-Temperature COS Hydrolysis over TiO2-Al2O3 Based Catalyst in Blast Furnace Gas.

As an organic sulfur pollutant generated in blast furnace gas, carbonyl sulfide (COS) has attracted more attention due to its negative effects on the environment and economy. The TiO2-Al2O3 composite metal oxide (Ti0.5Al) with uniformly dispersed particles was prepared by the co-precipitation method. And on this basis, a series of Na/K-doped catalysts were prepared separately. The activity evaluation results showed that the introduction of Na/K significantly improved the low-temperature COS hydrolysis activity, which exhibited a COS conversion of 98% and H2S yield of 95% at 75 °C with 24,000 h-1. And K showed a better promoting effect than Na. Brunauer-Emmett-Teller (BET) results revealed the increased mesopore proportion of Na/K-modified catalysts. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that Na and K formed prismatic and nanorod-like structures, respectively. More weakly basic sites with enhanced intensity and decreased Oads/Olat content contributed to the excellent catalytic activity, as certified by the results of CO2 temperature-programmed desorption (CO2-TPD) and X-ray photoelectron spectroscopy (XPS). It was also proposed that the decrease of weakly basic sites ultimately deactivated catalyst activity. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the introduction of Na/K enhanced the dissociation of H2O, and the generated abundant hydroxyl groups promoted the adsorption of COS and formed surface transition species, such as HSCO2 - and HCO3 -.

Potential synthetic lethality for breast cancer: A selective sirtuin 2 inhibitor combined with a multiple kinase inhibitor sorafenib.

Sorafenib is a clinically useful multiple kinase inhibitor for the treatment of kidney cancer, liver cancer and acute myelocytic leukemia, while it has shown weak efficacy in suppressing breast cancer. Since sirtuin2 (SIRT2) is an important epigenetic regulator and associated with several cancer types including breast cancer, development and evaluation of new SIRT2 inhibitors to probe their therapeutic potentials is currently desirable. A highly selective SIRT2 inhibitor named I was previously developed by us, which showed activity to inhibit non-small cell lung cancer cell lines in vitro. We herein report expanded screening of I and its structurally similar inactive compound II against other cancer cell lines, and found that I had a wide spectrum of anticancer activity while II had no such effects. The I-sorafenib combination treatment exerted obvious synergistic reduction on cell viability of MCF-7 cells. We observed that the combination treatment could suppress cell proliferation, survival and migration, arrest cell cycle at G0/G1 phase, and induce apoptosis in MCF-7 cells, when compared with the single treatment. In vivo studies revealed that the combination treatment showed stronger tumor growth inhibition (87%), comparing with I-(42.8%) or sorafenib-solely-treated groups (61.1%) in MCF-7 xenograft model. In conclusion, this work clearly revealed a potential synthetic lethality effect for I combined with sorafenib, and will probably offer a new strategy at least for breast cancer treatment.

Discovery of New 4-Indolyl Quinazoline Derivatives as Highly Potent and Orally Bioavailable P-Glycoprotein Inhibitors.

The major drawbacks of P-glycoprotein (P-gp) inhibitors at the clinical stage make the development of new P-gp inhibitors challenging and desirable. In this study, we reported our structure-activity relationship studies of 4-indolyl quinazoline, which led to the discovery of a highly effective and orally active P-gp inhibitor, YS-370. YS-370 effectively reversed multidrug resistance (MDR) to paclitaxel and colchicine in SW620/AD300 and HEK293T-ABCB1 cells. YS-370 bound directly to P-gp, did not alter expression or subcellular localization of P-gp in SW620/AD300 cells, but increased the intracellular accumulation of paclitaxel. Furthermore, YS-370 stimulated the P-gp ATPase activity and had moderate inhibition against CYP3A4. Significantly, oral administration of YS-370 in combination with paclitaxel achieved much stronger antitumor activity in a xenograft model bearing SW620/Ad300 cells than either drug alone. Taken together, our data demonstrate that YS-370 is a promising P-gp inhibitor capable of overcoming MDR and represents a unique scaffold for the development of new P-gp inhibitors.

Discovery of new human Sirtuin 5 inhibitors by mimicking glutaryl-lysine substrates.

Human sirtuin 5 (SIRT5) plays pivotal roles in metabolic pathways and other biological processes, and is involved in several human diseases including cancer. Development of new potent and selective SIRT5 inhibitors is currently desirable to provide potential therapeutics for related diseases. Herein, we report a series of new 3-thioureidopropanoic acid derivatives, which were designed to mimic the binding features of SIRT5 glutaryl-lysine substrates. Structure-activity relationship studies revealed several compounds with low micromolar inhibitory activities to SIRT5. Computational and biochemical studies indicated that these compounds exhibited competitive SIRT5 inhibition with respect to the glutaryl-lysine substrate rather than nicotinamide adenine dinucleotide cofactor. Moreover, they showed high selectivity for SIRT5 over SIRT1-3 and 6 and could stabilize SIRT5 proteins as revealed by thermal shift analyses. This work provides an effective substrate-mimicking strategy for future inhibitor design, and offers new inhibitors to investigate their therapeutic potentials in SIRT5-associated disease models.

X-ray Structure-Guided Discovery of a Potent, Orally Bioavailable, Dual Human Indoleamine/Tryptophan 2,3-Dioxygenase (hIDO/hTDO) Inhibitor That Shows Activity in a Mouse Model of Parkinson's Disease.

Human indoleamine 2,3-dioxygenase 1 (hIDO1) and tryptophan 2,3-dioxygenase (hTDO) have been closely linked to the pathogenesis of Parkinson's disease (PD); nevertheless, development of dual hIDO1 and hTDO inhibitors to evaluate their potential efficacy against PD is still lacking. Here, we report biochemical, biophysical, and computational analyses revealing that 1H-indazole-4-amines inhibit both hIDO1 and hTDO by a mechanism involving direct coordination with the heme ferrous and ferric states. Crystal structure-guided optimization led to 23, which manifested IC50 values of 0.64 and 0.04 µM to hIDO1 and hTDO, respectively, and had good pharmacokinetic properties and brain penetration in mice. 23 showed efficacy against the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse motor coordination deficits, comparable to Madopar, an anti-PD medicine. Further studies revealed that different from Madopar, 23 likely has specific anti-PD mechanisms involving lowering IDO1 expression, alleviating dopaminergic neurodegeneration, reducing inflammatory cytokines and quinolinic acid in mouse brain, and increasing kynurenic acid in mouse blood.

Sensitive fluorogenic substrates for sirtuin deacylase inhibitor discovery.

Sirtuins (SIRTs) are NAD+-dependent lysine deacylases, regulating many important biological processes such as metabolism and stress responses. SIRT inhibitors may provide potential benefits against SIRT-driven human diseases. Development of efficient assay platforms based on fluorogenic substrates will facilitate the discovery of high-quality SIRT inhibitors. We here report 16 new fluorogenic peptide substrates (P1-P16) designed with structurally diverse tetrapeptides and acyl modifications. Tests of P1-P16 against SIRT isoforms identified several sensitive substrates for SIRT1, SIRT2, SIRT3 and SIRT5, which manifested lower KM values and higher catalytic efficiency, and particularly had less signal interference in inhibitor screening compared with our previously reported internally quenched fluorescent substrates. Co-crystallization of sensitive substrates P13 and P15 with SIRT5 revealed an unexpected binding mode, involving interactions with residues from active site bordering surfaces, different from that observed for other peptides derived from natural protein substrates. By using SIRT5 sensitive substrates, we found that TW-37, a Bcl-2 inhibitor, displayed low micromolar inhibition to SIRT5, which was further validated by isothermal titration calorimetry analyses, offering a new point to develop dual-action SIRT5/Bcl-2 inhibitors against cancers. This work provides assay platform and structural basis for developing new substrates and inhibitors targeting human SIRTs.

Principles and current strategies targeting metallo-ß-lactamase mediated antibacterial resistance.

Resistance to ß-lactam antibacterials is commonly associated with the production of the serine ß-lactamases (SBLs) and/or metallo-ß-lactamases (MBLs). Although clinically useful inhibitors for the SBLs have been developed, no equivalent inhibitors are available for the MBLs, which can hydrolyze almost all ß-lactam antibiotics, including the so-called "last resort" carbapenems. It is still a challenging task to develop a clinically useful inhibitor that should be broad-spectrum targeting multiple clinically relevant MBL enzymes that differ in their active site features. This review provides a detailed description of interaction modes of substrates and small-molecule inhibitors with various MBL enzymes and highlights the importance of metal- and "anchor residue"-binding features to achieve broad-spectrum MBL inhibition. Recently emerging active site interference strategies include metal ion deprivation, metal ion replacement, and cysteine modification as challenging, but worth experimenting directions for inhibitor development. The metalloenzyme selectivity, metal-binding pharmacophore, and cellular permeability and accumulation should be properly considered in the further development of clinically useful inhibitors to combat MBL-mediated antibacterial resistance.

Structure-Based Development of (1-(3'-Mercaptopropanamido)methyl)boronic Acid Derived Broad-Spectrum, Dual-Action Inhibitors of Metallo- and Serine-ß-lactamases.

The emergence and spread of bacterial pathogens acquired metallo-ß-lactamase (MBL) and serine-ß-lactamase (SBL) medicated ß-lactam resistance gives rise to an urgent need for the development of new dual-action MBL/SBL inhibitors. Application of a pharmacophore fusion strategy led to the identification of (2'S)-(1-(3'-mercapto-2'-methylpropanamido)methyl)boronic acid (MS01) as a new dual-action inhibitor, which manifests broad-spectrum inhibition to representative MBL/SBL enzymes, including the widespread VIM-2 and KPC-2. Guided by the VIM-2:MS01 and KPC-2:MS01 complex structures, further structural optimization yielded new, more potent dual-action inhibitors. Selectivity studies indicated that the inhibitors had no apparent inhibition to human angiotensin-converting enzyme-2 and showed selectivity across serine hydrolyases in E. coli and human HEK293T cells labeled by the activity-based probe TAMRA-FP. Moreover, the inhibitors displayed potentiation of meropenem efficacy against MBL- or SBL-positive clinical isolates without apparent cytotoxicity. This work will aid efforts to develop new types of clinically useful dual-action inhibitors targeting MBL/SBL enzymes.

X-ray crystal structure guided discovery of new selective, substrate-mimicking sirtuin 2 inhibitors that exhibit activities against non-small cell lung cancer cells.

Human sirtuin 2 (SIRT2) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacylase, and is implicated in human diseases including cancer. Selective small-molecule inhibitors for SIRT2 are sought as chemical tools and potential therapeutics. Here we report the X-ray crystal structure guided structure-activity relationship studies of new N-(3-(phenoxymethyl)phenyl)acetamide derivatives with SIRT2, which led to the identification of potent, selective SIRT2 inhibitors. Crystallographic analyses reveal that the new inhibitors act via inducing the formation of an enlarged hydrophobic pocket and particularly mimicking the interactions made by myristoylated-lysine substrates. The most potent inhibitor 24a could dose-dependently elevate the acetylation level of α-tubulin in the non-small cell lung cancer H441 cells, which have a high expression level of SIRT2 as determinated by Western blotting analyses. Further cellular assays reveal that 24a restrains cell growth mainly through inhibiting cellular proliferation rather than inducing apoptosis. Moreover, 24a could suppress the migration and invasion of H441 cells. These results provide an excellent basis for further development of new potent, selective, and cell active SIRT2 inhibitors as chemical tools and potential therapeutics for SIRT2-driven non-small cell lung cancers.

Virtual target screening reveals rosmarinic acid and salvianolic acid A inhibiting metallo- and serine-ß-lactamases.

Rosmarinic acid (RA), a polyphenolic phytochemical, has broad-spectrum biological and pharmacological activity. A virtual target screening method termed IFPTarget combined with enzyme inhibition assays led to the identification of the clinically relevant metallo-ß-lactamase (MBL) VIM-2 as one of unexploited targets of RA. The enzyme kinetic studies indicated that RA is a fully reversible, substrate-competitive VIM-2 inhibitor. The isothermal titration calorimetry (ITC) analyses revealed that the initial binding of RA to VIM-2 is mainly due to enthalpy contribution. Further inhibition assays with RA related compounds revealed that salvianolic acid A, a derivative of RA, manifests potent inhibition to VIM-2, more interestingly, which shows inhibitory activity against the NDM-1, another clinically relevant MBL subtype, and the serine-ß-lactamase TEM-1 that is structurally and mechanistically distinct from the VIM-2 and NDM-1.

Structure-based discovery of new maternal embryonic leucine zipper kinase inhibitors.

Maternal embryonic leucine zipper kinase (MELK), a serine/threonine protein kinase, has oncogenic properties and plays a key functional role in various cancer cells. Although MELK may not be a cancer addiction target, the development of specific MELK inhibitors would provide useful chemical tools for synthetic lethal investigation. Herein, we identified several hit compounds using a customized structure-based virtual screening, among which compounds 4 and 16 showed the most potent inhibition to MELK with IC50 values of 3.52 µM and 178.3 nM, respectively. In vitro cell-based assays revealed that 16 has no effect on the growth of various types of cancer cells, but has the potential to inhibit cancer cell migration and invasion. Western blotting analyses revealed that 16 suppresses the phosphorylation of focal adhesion kinase (FAK), a downstream molecule of MELK, which is a key kinase in regulating cancer cell migration and invasion.

Heterocyclic-Fused Pyrimidines as Novel Tubulin Polymerization Inhibitors Targeting the Colchicine Binding Site: Structural Basis and Antitumor Efficacy.

We report the design, synthesis, and biological evaluation of heterocyclic-fused pyrimidines as tubulin polymerization inhibitors targeting the colchicine binding site with significantly improved therapeutic index. Additionally, for the first time, we report high-resolution X-ray crystal structures for the best compounds in this scaffold, 4a, 4b, 6a, and 8b. These structures not only confirm their direct binding to the colchicine site in tubulin and reveal their detailed molecular interactions but also contrast the previously published proposed binding mode. Compounds 4a and 6a significantly inhibited tumor growth in an A375 melanoma xenograft model and were accompanied by elevated levels of apoptosis and disruption of tumor vasculature. Finally, we demonstrated that compound 4a significantly overcame clinically relevant multidrug resistance in a paclitaxel resistant PC-3/TxR prostate cancer xenograft model. Collectively, these studies provide preclinical and structural proof of concept to support the continued development of this scaffold as a new generation of tubulin inhibitors.

Mechanism of microtubule stabilization by taccalonolide AJ.

As a major component of the cytoskeleton, microtubules consist of αß-tubulin heterodimers and have been recognized as attractive targets for cancer chemotherapy. Microtubule-stabilizing agents (MSAs) promote polymerization of tubulin and stabilize the polymer, preventing depolymerization. The molecular mechanisms by which MSAs stabilize microtubules remain elusive. Here we report a 2.05 Å crystal structure of tubulin complexed with taccalonolide AJ, a newly identified taxane-site MSA. Taccalonolide AJ covalently binds to ß-tubulin D226. On AJ binding, the M-loop undergoes a conformational shift to facilitate tubulin polymerization. In this tubulin-AJ complex, the E-site of tubulin is occupied by GTP rather than GDP. Biochemical analyses confirm that AJ inhibits the hydrolysis of the E-site GTP. Thus, we propose that the ß-tubulin E-site is locked into a GTP-preferred status by AJ binding. Our results provide experimental evidence for the connection between MSA binding and tubulin nucleotide state, and will help design new MSAs to overcome taxane resistance.

NMR-filtered virtual screening leads to non-metal chelating metallo-ß-lactamase inhibitors.

There are no clinically useful inhibitors of metallo-ß-lactamases (MBLs), which are a growing problem because they hydrolyse almost all ß-lactam antibacterials. Inhibition by most reported MBL inhibitors involves zinc ion chelation. A structure-based virtual screening approach combined with NMR filtering led to the identification of inhibitors of the clinically relevant Verona Integron-encoded MBL (VIM)-2. Crystallographic analyses reveal a new mode of MBL inhibition involving binding adjacent to the active site zinc ions, but which does not involve metal chelation. The results will aid efforts to develop new types of clinically useful inhibitors targeting MBLs/MBL-fold metallo-enzymes involved in antibacterial and anticancer drug resistance.