A Celecoxib Derivative Eradicates Antibiotic-Resistant Staphylococcus aureus and Biofilms by Targeting YidC2 Translocase.

The treatment of Staphylococcus aureus infections is impeded by the prevalence of MRSA and the formation of persisters and biofilms. Previously, we identified two celecoxib derivatives, Cpd36 and Cpd46, to eradicate MRSA and other staphylococci. Through whole-genome resequencing, we obtained several lines of evidence that these compounds might act by targeting the membrane protein translocase YidC2. Our data showed that ectopic expression of YidC2 in S. aureus decreased the bacterial susceptibility to Cpd36 and Cpd46, and that the YidC2-mediated tolerance to environmental stresses was suppressed by both compounds. Moreover, the membrane translocation of ATP synthase subunit c, a substrate of YidC2, was blocked by Cpd46, leading to a reduction in bacterial ATP production. Furthermore, we found that the thermal stability of bacterial YidC2 was enhanced, and introducing point mutations into the substrate-interacting cavity of YidC2 had a dramatic effect on Cpd36 binding via surface plasmon resonance assays. Finally, we demonstrated that these YidC2 inhibitors could effectively eradicate MRSA persisters and biofilms. Our findings highlight the potential of impeding YidC2-mediated translocation of membrane proteins as a new strategy for the treatment of bacterial infections.

Therapeutic Opportunities of Targeting Histone Deacetylase Isoforms to Eradicate Cancer Stem Cells.

Cancer stem cells (CSCs), or tumor-initiating cells, are a small subset of cancer cells with the capacity for self-renewal and differentiation, which have been shown to drive tumor initiation, progression, and metastasis in many types of cancer. Moreover, therapeutic regimens, such as cisplatin and radiation were reported to induce the enrichment of CSCs, thereby conferring chemoresistance on cancer cells. Therefore, therapeutic targeting of CSCs represents a clinical challenge that needs to be addressed to improve patient outcome. In this context, the effectiveness of pan or class-I histone deacetylase (HDAC) inhibitors in suppressing the CSC population is especially noteworthy in light of the new paradigm of combination therapy. Evidence suggests that this anti-CSC activity is associated with the ability of HDAC inhibitors to target multiple signaling pathways at different molecular levels. Beyond chromatin remodeling via histone acetylation, HDAC inhibitors can also block key signaling pathways pertinent to CSC maintenance. Especially noteworthy is the ability of different HDAC isoforms to regulate the protein stability and/or activity of a series of epithelial-mesenchymal transition (EMT)-inducing transcription factors, including HIF-1α, Stat3, Notch1, ß-catenin, NF-κB, and c-Jun, each of which plays a critical role in regulating CSCs. From the translational perspective, these mechanistic links constitute a rationale to develop isoform-selective HDAC inhibitors as anti-CSC agents. Thus, this review aims to provide an overview on the roles of HDAC isoforms in maintaining CSC homeostasis via distinct signaling pathways independent of histone acetylation.

Adsorption Behavior and Mechanism of Antibiotic Sulfamethoxazole on Carboxylic-Functionalized Carbon Nanofibers-Encapsulated Ni Magnetic Nanoparticles.

In this work we developed a one-step process for synthesizing carboxylic-functionalized carbon nanofibers (CNFs)-encapsulated Ni magnetic nanoparticles (Ni@CNFs) that exhibit an excellent magnetic response and a large content of hydrophilic carboxylate groups with a negative charge (RCOO(-)) on the carbon surface. The carbon-encapsulated magnetic Ni nanoparticles could be rapidly separated from water, and they showed high efficiency for adsorption of the antibiotic sulfamethoxazole (SMX) in aqueous solution. The adsorption of SMX on Ni@CNFs as a function of pH was investigated, and the greatest adsorption occurred at pH 7.0. The adsorption isotherms for SMX on Ni@CNFs depended on different pH values. A Monte Carlo simulation was used to probe the relationship between molecular conformation and π-π interaction. The high adsorption of SMX on Ni@CNFs at pH 7.0 could be ascribed to deprotonated SMX being easily converted to a planar-like conformation, thereby resulting in the formation of π rings that were approximately parallel to the graphite surface and that enhanced strong π-π interaction. Electrostatic and π-π interactions both contributed to deprotonated SMX adsorption at pH 7.0, and they influenced the adsorption isotherm toward the Freundlich model. However, in weakly acidic environments (pH 2.0 and 4.0), the electrostatic interaction alone could induce an adsorption pattern that was similar to the Langmuir model.

Effect of Ti3+ on TiO2-supported Cu catalysts used for CO oxidation.

In this paper, we have shown that Cu/TiO(2) catalysts are highly active in CO oxidation. For instance, a 3.4% Cu/TiO(2) catalyst exhibits a higher turnover rate for the effective removal of CO in air than 3-5% Pt/TiO(2) and 20% Cu/ZnO/Al(2)O(3) catalysts. A small amount of Cu(+) species is formed during the calcination treatment at 225 °C, which is the main active phase for the CO oxidation. However, it is proposed that some highly dispersed CuO can also form in the TiO(2) lattice during the calcination treatment. Furthermore, a strong electron interaction between Cu(2+) in highly dispersed CuO and Ti(3+) on rutile TiO(2) (Cu(2+)+Ti(3+)→Cu(+)+Ti(4+)) has been shown to occur. Overall, the reduction of Cu(+) is a major factor that contributes to the reaction rate of the CO oxidation.

Effects of potassium on Ni-K/Al2O3 catalysts in the synthesis of carbon nanofibers by catalytic hydrogenation of CO2.

Commercially available Ni/Al(2)O(3) samples containing various concentrations of potassium were used to achieve carbon deposition from CO(2) via catalytic hydrogenation. Experimental results show that K additives can induce the formation of carbon nanofibers or carbon deposition on Ni/Al(2)O(3) during the reverse water-gas shift reaction. This work proposes that the formation rate of carbon deposition depends closely on ensemble control, suggesting that the ensemble size necessary to form carbon may be approximately 0.5 potassium atoms. The results of CO(2) temperature-programmed desorption provide strong evidence that the new adsorption sites for CO(2) created on Ni-K/Al(2)O(3) closely depend upon the synthesis of carbon nanofibers. It is found that some potassium-related active phases obtained by calcination and reduction pretreatments can participate in the carbon deposition reaction. The formation pathway for carbon deposition suggests that the main source of carbon deposition is CO(2) and that the pathway is independent of the reaction products CO and CH(4) in the reverse water-gas shift reaction.

Targeting YAP Degradation by a Novel 1,2,4-Oxadiazole Derivative via Restoration of the Function of the Hippo Pathway.

Recent evidence has linked the dysregulation of the Hippo pathway to tumorigenesis and cancer progression due to its pivotal role in regulating the stability of the oncoprotein YAP. Based on an unexpected finding from the SAR study of a recently reported oxadiazole-based EGFR/c-Met dual inhibitor (compound 1), we identified a closely related derivative, compound 2, which exhibited cogent antitumor activities while devoid of compound 1's ability to promote EGFR/c-Met degradation. Compound 2 acted, in part, by facilitating YAP degradation through activation of its upstream kinase LATS1. However, it did not alter the phosphorylation status of MST1/2, a LATS1 kinase, suggesting an alternative mechanism for LATS1 activation. Orally administered compound 2 was effective in suppressing MDA-MB-231 xenograft tumor growth while exhibiting a satisfactory safety profile. From a therapeutic perspective, compound 2 might help foster new therapeutic strategies for cancer treatment by restoring the Hippo pathway regulatory function to facilitate YAP degradation.

1,2,4-Oxadiazole derivatives targeting EGFR and c-Met degradation in TKI resistant NSCLC.

Development of small-molecule agents with the ability to facilitate oncoprotein degradation has emerged as a promising strategy for cancer therapy. Since EGFR and c-Met are both implicated in oncogenesis and tumor progression, we initiated a screening program by using an in-house library to identify agents capable of inducing the concomitant suppression of EGFR and c-Met expression, which led to the identification of compound 1, a 1,2,4-oxadiazole derivative. Based on the scaffold of 1, we developed a series of derivatives to assess their efficacies in facilitating the downregulation of EGFR and c-Met, among which compound 48 represented the optimal agent. 48 showed equipotent antiproliferative activity against a panel of five NSCLC cell lines with different EGFR mutational status (IC50 = 0.2-0.6 µM), while the same panel exhibited differential sensitivity to different EGFR kinase inhibitors tested. Cell cycle analysis indicated that the antiproliferative activity of 48 was associated with its ability to cause G2/M arrest and, to a lesser extent, apoptosis. Western blot and RT-PCR analyses revealed that 48 facilitated the downregulation of EGFR and c-Met at the protein level. In vivo data showed that oral administration of 48 was effective in suppressing gefitinib-resistant H1975 xenograft tumor growth in nude mice, and at a suboptimal dose, could sensitize H1975 tumors to gefitinib. Based on these findings, 48 represents a promising candidate for further development to target EGFR TKI-resistant NSCLC via dual inhibition of EGFR and c-Met oncoproteins.

p21-Activated kinase 3 promotes cancer stem cell phenotypes through activating the Akt-GSK3ß-ß-catenin signaling pathway in pancreatic cancer cells.

Relative to several other p21-activated kinase (PAK) family members, the role of PAK3 in regulating cancer cell functions remains unclear. Our study obtained evidence that PAK3 regulates the Akt-GSK3ß-ß-catenin signaling by acting as Ser473-Akt kinase in several pancreatic cancer cell lines. Specifically, knockdown of PAK3 or overexpression of dominant-negative PAK3 inhibited the phosphorylation of Ser473-Akt and GSK3ß, resulting in the proteasomal degradation of ß-catenin. Conversely, overexpression of PAK3 led to activation of Akt signaling and increased ß-catenin expression. These changes, however, were not noted with the silencing and/or overexpression of PAK1, PAK2, or PAK4, which underlies the impetus of PAK3 as a key effector in governing malignant phenotypes in these pancreatic cancer cells, including cancer stem cell (CSC) expansion. Accordingly, PAK3 depletion effectively suppresses tumorsphere formation, ALDH activity, and the expression of CSC surface markers. Moreover, we used a stable knockdown clone of AsPC-1 cells to demonstrate the in vivo efficacy of PAK3 inhibition in suppressing tumorigenesis and xenograft tumor growth. Together, these findings suggest the potential role of PAK3 as a target for pancreatic cancer therapy, which warrants further investigations.

Loxapine, an antipsychotic drug, suppresses intracellular multiple-antibiotic-resistant Salmonella enterica serovar Typhimurium in macrophages.

BACKGROUND: The emergence of multiple-antibiotic-resistant (MAR) Salmonella has been a serious threat worldwide. Salmonella can invade into host cells and evade the attacks of host humoral defenses and antibiotics. Thus, a new antibacterial agent capable of inhibiting intracellular Salmonella is highly needed. METHODS: The anti-intracellular activity and cytotoxicity of drugs on intracellular bacteria and macrophages were assayed using intracellular CFU assay and MTT cell viability assay, respectively. The uptake of gentamicin into macrophage and the effect of autophagy inhibitor on loxapine's anti-intracellular Salmonella activity were assessed by using image-based high-content system. The expression of bacterial genes was measured by real-time PCR. The efflux pump activity of bacteria was measured by Hoechst accumulation assays. RESULTS: With our efforts, an antipsychotic drug, loxapine, was identified to exhibit high potency in suppressing intracellular MAR S. Typhimurium, Staphylococcus aureus, Shigella flexneri or Yersinia enterocolitica. Subsequent investigations indicated that loxapine's anti-intracellular bacteria activity was not associated with increased penetration of gentamicin into bacteria and macrophages. Loxapine didn't inhibit bacterial growth in broth at concentration up to 500 µM and has no effect on Salmonella's type III secretion system genes' expression. Blockage of autophagy also didn't reverse loxapine's anti-intracellular activity. Lastly, loxapine suppressed bacterial efflux pump activity in all bacteria tested. CONCLUSION: Altogether, our data suggested that loxapine might suppress intracellular bacteria through inhibiting of bacterial efflux pumps. In light of its unique activity, loxapine represents a promising lead compound with translational potential for the development of a new antibacterial agent against intracellular bacteria.

Development of Novel Irreversible Pyruvate Kinase M2 Inhibitors.

As cancer cells undergo metabolic reprogramming in the course of tumorigenesis, targeting energy metabolism represents a promising strategy in cancer therapy. Among various metabolic enzymes examined, pyruvate kinase M2 type (PKM2) has received much attention in light of its multifaceted function in promoting tumor growth and progression. In this study, we reported the development of a novel irreversible inhibitor of PKM2, compound 1, that exhibits a differential tumor-suppressive effect among an array of cancer cell lines. We further used a clickable activity-based protein profiling (ABPP) probe and SILAC coupled with LC-MS/MS to identify the Cys-317 and Cys-326 residues of PKM2 as the covalent binding sites. Equally important, compound 1 at 10 mg/kg was effective in suppressing xenograft tumor growth in nude mice without causing acute toxicity by targeting both metabolic and oncogenic functions. Together, these data suggest its translational potential to foster new strategies for cancer therapy.

Novel AR-12 derivatives, P12-23 and P12-34, inhibit flavivirus replication by blocking host de novo pyrimidine biosynthesis.

The genus Flavivirus contains many important pathogens, including dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV). AR-12 is a celecoxib-derived anticancer agent that possesses antiviral activity against a broad range of viruses. We pharmacologically exploited this unique activity to develop additional antiviral agents, resulting in the production of the AR-12 derivatives P12-23 and P12-34. At nanomolar concentrations, these compounds were effective in suppressing DENV, ZIKV and JEV replication, exhibiting 10-fold improvements in the efficacy and selectivity indices as compared to AR-12. Regarding the mode of antiviral action, P12-23 and P12-34 inhibited viral RNA replication but had no effect on viral binding, entry or translation. Moreover, these AR-12 derivatives co-localized with mitochondrial markers, and their antiviral activity was lost in mitochondria-depleted cells. Interestingly, exogenous uridine or orotate, the latter being a metabolite of the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH), abolished the antiviral activity of AR-12 and its derivatives. As DHODH is a key enzyme in the de novo pyrimidine biosynthesis pathway, these AR-12 derivatives may act by targeting pyrimidine biosynthesis in host cells to inhibit viral replication. Importantly, treatment with P12-34 significantly improved the survival of mice that were subcutaneously challenged with DENV. Thus, P12-34 may warrant further evaluation as a therapeutic to control flaviviral outbreaks.

Properties of Cu(thd)2 as a precursor to prepare Cu/SiO2 catalyst using the atomic layer epitaxy technique.

The new Cu/SiO2 catalyst is developed by the atomic layer epitaxy (ALE) method. The ALE-Cu/SiO2 catalyst with high dispersion and nanoscale Cu particles appears to have very different catalytic properties from those of the typical Cu-based catalysts, which have satisfactory thermal stability to resist the sintering of Cu particles at 773 K. Due to the formation of small Cu particles, the ALE-Cu/SiO2 can strongly bind CO and give high catalytic activity for CO2 converted to CO in the reverse water-gas-shift reaction. The catalytic activity decreases in the order of 2.4% ALE-Cu/SiO2 =... 2% Pt/SiO2 > 2% Pd/SiO2 > 10.3% IM-Cu/SiO2.