A NIR fluorescence probe for monitoring Cys upregulation induced by balsam pear polysaccharide and imaging in zebrafish.

In this work, we introduced the acrylate recognition group into dicyanoisophorone derivative DCI-C-OH to construct the NIR fluorescent probe DCI-C-Cys with a large Stokes shift (240 nm). DCI-C-Cys could specifically respond to Cys, resulting in a 22-fold increase in fluorescence intensity at 702 nm. Meanwhile, the probe has the advantages of good water solubility, high sensitivity (93 nM), and excellent biocompatibility. Moreover, DCI-C-Cys successfully monitored endogenous and exogenous Cys in HepG2 cells and zebrafish. Most importantly, we found that balsam pear polysaccharide could lead to the increase of intracellular Cys levels, which might be conducive to the further study of the antioxidant mechanism of balsam pear polysaccharide.

Selective Activation of a Prodrug by Thioredoxin Reductase Providing a Strategy to Target Cancer Cells.

Elevated reactive oxygen species and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. As a major regulator of the cellular redox homeostasis, the selenoprotein thioredoxin reductase (TrxR) is increasingly considered as a promising target for anticancer drug development. The current approach to inhibit TrxR predominantly relies on the modification of the selenocysteine residue in the C-terminal active site of the enzyme, in which it is hard to avoid the off-target effects. By conjugating the anticancer drug gemcitabine with a 1,2-dithiolane scaffold, an unprecedented prodrug strategy is disclosed that achieves a specific release of gemcitabine by TrxR in cells. As overexpression of TrxR is frequently found in different types of tumors, the TrxR-dependent prodrugs are promising for further development as cancer chemotherapeutic agents.

An ultrafast turn-on thiol probe for protein labeling and bioimaging.

A novel turn-on type of ultrafast biothiol fluorescent probe, Naph-EA-mal, was designed, synthesized and evaluated. The probe contains a naphthalimide moiety as a fluorophore, a maleimide unit as a thiol acceptor, and 1,2-ethylenediamine as a linker. Naph-EA-mal displays high selectivity and a fast response toward thiols in aqueous solution. The reaction mechanism of the probe with thiols was confirmed by 1H NMR and HRMS. Test strips were fabricated and a sharp color change was observed by the naked-eye. Furthermore, Naph-EA-mal was successfully applied to label protein thiols, image thiols in living cells, quantify thiol content in cells lysate, and determine the reversible protein thiols oxidation in fixed cells.

Selective selenol fluorescent probes: design, synthesis, structural determinants, and biological applications.

Selenium (Se) is an essential micronutrient element, and the biological significance of Se is predominantly dependent on its incorporation as selenocysteine (Sec), the genetically encoded 21st amino acid in protein synthesis, into the active site of selenoproteins, which have broad functions, ranging from redox regulation and anti-inflammation to the production of active thyroid hormones. Compared to its counterpart Cys, there are only limited probes for selective recognition of Sec, and such selectivity is strictly restricted at low pH conditions. We reported herein the design, synthesis, and biological evaluations of a series of potential Sec probes based on the mechanism of nucleophilic aromatic substitution. After the initial screening, the structural determinants for selective recognition of Sec were recapitulated. The follow-up studies identified that probe 19 (Sel-green) responds to Sec and other selenols with more than 100-fold increase of emission in neutral aqueous solution (pH 7.4), while there is no significant interference from the biological thiols, amines, or alcohols. Sel-green was successfully applied to quantify the Sec content in the selenoenzyme thioredoxin reductase and image endogenous Sec in live HepG2 cells. With the aid of Sel-green, we further demonstrated that the cytotoxicity of different selenocompounds is correlated to their ability metabolizing to selenols in cells. To the best of our knowledge, Sel-green is the first selenol probe that works under physiological conditions. The elucidation of the structure-activity relationship for selective recognition of selenols paves the way for further design of novel probes to better understand the pivotal role of Sec as well as selenoproteins in vivo.

Highly selective off-on fluorescent probe for imaging thioredoxin reductase in living cells.

The first fluorescent probe for mammalian thioredoxin reductase (TrxR), TRFS-green, was designed, synthesized, and fully evaluated. The probe features a 1,2-dithiolane scaffold with a quenched naphthalimide fluorophore. TRFS-green displays a green fluorescence off-on change induced by the TrxR-mediated disulfide cleavage and subsequent intramolecular cyclization to liberate the masked naphthalimide fluorophore. It was demonstrated in vitro that TRFS-green manifests high selectivity toward TrxR over other related enzymes and various small molecule thiols as well as biological reducing molecules. HPLC analyses indicated that TRFS-green was exclusively converted to naphthalimide catalyzed by TrxR. The ability in triggering on the fluorescence signal by cellular protein extracts correlates well with the endogenous TrxR activity in different cells. Furthermore, inhibition of TrxR by 2,4-dinitrochlorobenzene or depletion of TrxR by immunoprecipitation remarkably decreases the reduction of TRFS-green by cellular protein extracts. Finally, TRFS-green was successfully applied in imaging TrxR activity in living cells. The fluorescence signal of TRFS-green in living cells was inhibited by pretreating the cells with TrxR inhibitor in a dose-dependent manner, potentiating the development of living cell-based screening assay for identifying TrxR inhibitors. We expect the novel fluorescent probe TRFS-green would facilitate the discovery of TrxR-targeting small molecules for potential therapeutic agents and provide significant advances in understanding the physiological/pathophysiological functions of TrxR in vivo.

Nitrogen-Doped Carbon Quantum Dots Activated Dandelion-Like Hierarchical WO3 for Highly Sensitive and Selective MEMS Sensors in Diabetes Detection.

High sensitivity, low concentration, and excellent selectivity are pronounced primary challenges for semiconductor gas sensors to monitor acetone from exhaled breath. In this study, nitrogen-doped carbon quantum dots (N-CQDs) with high reactivity were used to activate dandelion-like hierarchical tungsten oxide (WO3) microspheres to construct an efficient and stable acetone gas sensor. Benefiting from the synergistic effect of both the abundant active sites provided by the unique dandelion-like hierarchical structure and the high reaction potential generated by the sensitization of the N-CQDs, the resulting 16 wt % N-CQDs/WO3 sensor shows an ultrahigh response value (Ra/Rg = 74@1 ppm acetone), low detection limit (0.05 ppm), outstanding selectivity, and reliable stability to acetone at the optimum working temperature of 210 °C. Noteworthy that the N-CQDs facilitate the carrier migration and intensify the reaction between acetone and WO3 during the sensing process. Considering the above advantages, N-CQDs as a sensitizer to achieve excellent gas-sensitive properties of WO3 are a promising new strategy for achieving accurate acetone detection in real time and facilitating the development of portable human-exhaled gas sensors.

H2O2-triggered controllable carbon monoxide delivery for photothermally augmented gas therapy.

Carbon monoxide (CO) gas therapy has shown great potential as a very promising approach in the ongoing fight against tumors. However, delivering unstable CO to the tumor site and safely releasing it for maximum efficacy still have unsatisfactory outcomes. In this study, we've developed nanotheranostics (IN-DPPCO NPs) based on conjugated polymer IN-DPP and carbon monoxide (CO) carrier polymer mPEG(CO) for photothermal augmented gas therapy. The IN-DPPCO NPs can release CO with the hydrogen peroxide (H2O2) overexpressed in the tumor microenvironment. Meanwhile, IN-DPPCO NPs exhibit strong absorption in the near-infrared window, showing a high photothermal conversion efficiency of up to 41.5% under 808 nm laser irradiation. In vitro and in vivo experiments demonstrate that these nanotheranostics exhibit good biocompatibility. Furthermore, the synergistic CO/photothermal therapy shows enhanced therapeutic efficacy compared to gas therapy alone. This work highlights the great promise of conjugated polymer nanoparticles as versatile nanocarriers for spatiotemporally controlled and on-demand delivery of gaseous messengers to achieve precision cancer theranostics.

Dual blockade of CD47 and CD24 signaling using a novel bispecific antibody fusion protein enhances macrophage immunotherapy.

CD47 and its receptor signal regulatory protein α (SIRPα) act as a dominant antiphagocytic, "don't eat me" signal. Recent studies reveal CD24 as a novel target for cancer immunotherapy by macrophages in ovarian cancer and breast cancer. However, whether simultaneous blockade of CD47 and CD24 by a bispecific antibody may result in a potential synergy is still unclear. In the present study, we for the first time designed and developed a bispecific antibody fusion protein, PPAB001 for cotargeting CD47 and CD24. Data demonstrate that simultaneous blockade of CD47/SIRPα and CD24/Siglec-10 signaling by PPAB001 potently promoted macrophage phagocytosis of tumor cells. Compared to single CD47 or CD24 targeting agents, PPAB001 was more effective in inhibiting tumor growth in both mouse 4T-1 syngeneic and human SK-OV-3 xenogeneic tumor models. Mechanistically, we found that PPAB001 therapy markedly increased the proportion of tumor-infiltrating macrophages and upregulated interleukin-6 and tumor necrosis factor-α levels that were representative macrophage inflammatory cytokines. Notably, an increased ratio of M1/M2 in tumor-infiltrating macrophages in the mice treated with PPAB001 suggested that the dual blockade may promote the transition of macrophages from M2 to M1. Taken together, our data supported the development of PPAB001 as a novel immunotherapeutic in the treatment of CD47 and CD24 double-positive cancers.

NIR-II Absorbing Conjugated Polymer Nanotheranostics for Thermal Initiated NO Enhanced Photothermal Therapy.

Photothermal therapy (PTT) has received constant attention as a promising cancer treatment. However, PTT-induced inflammation can limit its effectiveness. To address this shortcoming, we developed second near-infrared (NIR-II) light-activated nanotheranostics (CPNPBs), which include a thermosensitive nitric oxide (NO) donor (BNN6) to enhance PTT. Under a 1064 nm laser irradiation, the conjugated polymer in CPNPBs serves as a photothermal agent for photothermal conversion, and the generated heat triggers the decomposition of BNN6 to release NO. The combination of hyperthermia and NO generation under single NIR-II laser irradiation allows enhanced thermal ablation of tumors. Consequently, CPNPBs can be exploited as potential candidates for NO-enhanced PTT, holding great promise for their clinical translational development.

A novel synthetic chalcone derivative, 2,4,6-trimethoxy-4'-nitrochalcone (Ch-19), exerted anti-tumor effects through stimulating ROS accumulation and inducing apoptosis in esophageal cancer cells.

Esophageal cancer has always been associated with poor prognosis and a low five-year survival rate. Chalcone, a flavonoid family member, has shown anti-tumor property in several types of cancer. However, few studies reported the potency and mechanisms of action of synthetic Chalcone derivatives against esophageal squamous cell carcinoma. In this study, we designed and synthesized a series of novel chalcone analogs and Ch-19 was selected for its superior anti-tumor potency. Results indicated that Ch-19 shows a dose- and time-dependent anti-tumor activity in both KYSE-450 and Eca-109 esophageal cancer cells. Moreover, treatment of Ch-19 resulted in the regression of KYSE-450 tumor xenografts in nude mice. Furthermore, we investigated the potential mechanism involved in the effective anti-tumor effects of Ch-19. As a result, we observed that Ch-19 treatment promoted ROS accumulation and caused G2/M phase arrest in both Eca-109 and KYSE-450 cancer cell lines, thereby resulting in cell apoptosis. Taken together, our study provided a novel synthetic chalcone derivative as a potential anti-tumor therapeutic candidate for treating esophageal cancer.

Peroxymonosulfate activation by Co3O4/SnO2 for efficient degradation of ofloxacin under visible light.

In this work, Co3O4/SnO2 catalyst was prepared by a one-pot hydrothermal method and applied in the activation of peroxymonosulfate (PMS) for the degradation of the target pollutant ofloxacin (OFX). The results showed that the PMS/Co3O4/SnO2-8% system had a 92% OFX degradation efficiency after 30 min of catalytic reaction, which was 46 times higher than that of PMS/SnO2 alone, and the degradation efficiency could be maintained in a wide pH range (5-11). In addition, reactive oxygen species quenching experiments and electron spin resonance spectra confirmed that sulfate radicals, superoxide radicals, hydroxyl radicals and singlet oxygen were the dominant active groups. The excellent recyclability and stability of the as-prepared catalyst were confirmed by cycling experiments and characterization results. Finally, a possible degradation pathway of OFX was suggested, and the intermediate toxicity of this system was identified and analyzed by a quantitative structure-activity relationship (QSAR).

The Nrf2 inhibitor brusatol synergistically enhances the cytotoxic effect of lapatinib in HER2-positive cancers.

The dual tyrosine kinase (EGFR/HER2) inhibitor lapatinib is currently used to clinically treat HER2-positive breast cancer. However, a majority of patients do not respond to lapatinib therapy within 6 months. Therefore, potentiating the anti-tumor effect of lapatinib by combination treatment has a great potential to overcome the obstacle. Herein, we aim to investigate the anti-tumor activity of lapatinib in combination with brusatol and explore the potential mechanism involved in the combinatorial treatment. Our findings revealed that the Nrf2 inhibitor brusatol potently enhanced the anti-tumor effect of lapatinib against SK-BR-3, SK-OV-3 and AU565 cancer cells in a synergistic manner. Furthermore, we found that lapatinib plus brusatol more effectively decreased Nrf2 level and induced ROS generation in both SK-BR-3 and SK-OV-3 cells. Moreover, we also observed a significant reduction on the phosphorylation of HER2, EGFR, AKT and ERK1/2 in SK-BR-3 and SK-OV-3 cells when treated with lapatinib plus brusatol compared to either agent alone. More importantly, brusatol significantly augmented the anti-tumor effects of lapatinib in the SK-OV-3 xenograft model. In summary, these data provide a potential rationale for the combination of brusatol and lapatinib on the treatment of HER2-positive cancers.

Red-emitting fluorescent turn-on probe with specific isothiocyanate recognition site for cysteine imaging in living systems.

Cysteine (Cys) is an effective biomarker in life systems and is closely related to a variety of diseases, so developing a specific and efficient detection method for Cys is of great significance. To date, extensive work has been undertaken toward this goal. However, the differentiation of Cys from other biothiols still represents a challenge from an experimental point of view. Toward this end, a selective and sensitive red-emitting probe (TMN-NCS) with an isothiocyanate (ITC)-based structure was proposed in this paper. A large Stokes shift (210 nm) was observed upon addition of Cys to a solution of TMN-NCS. In addition, TMN-NCS showed low toxicity, a low detection limit (120 nM), and excellent cell permeability. The results suggested that TMN-NCS holds great promise for biological applications.

Palladium-Catalyzed C-H Allylation of Electron-Deficient Polyfluoroarenes with gem-Difluorinated Cyclopropanes.

A palladium-catalyzed C-H allylation of electron-deficient polyfluoroarenes with gem-difluorinated cyclopropanes is reported. It provides a useful and facile approach to 2-fluoroallylic polyfluoroarenes in moderate to excellent yields with high Z-selectivity. In addition, this new approach has good functional group compatibility and broad substrate scope.

A novel NIR fluorescence probe with cysteine-activated structure for specific detection of cysteine and its application in vitro and in vivo.

Cysteine (Cys) as a vital antioxidant molecule and an effective biomarker for illness, plays an essential role in physiological functions and pathological processes. Extensive work has been done to explore the physiological functions of Cys and develop probes for detection of biothiols. However, the challenge to differentiate Cys from glutathione and homocystine remains. In this work, we constructed a novel near-infrared (NIR) probe, termed TMN-Cys, using TMN-NH2 and thionoesters. The probe could selectively detect Cys over homocysteine and glutathione in solution. It displayed a large Stokes shift (210 nm) upon treatment with Cys, and its detection limit was as low as 79 nM. Moreover, this probe showed low toxicity and was successfully employed in monitoring endogenous Cys in living cells and mice.

Metabolomics Study Reveals Inhibition and Metabolic Dysregulation in Staphylococcus aureus Planktonic Cells and Biofilms Induced by Carnosol.

Staphylococcus aureus (S. aureus) is a global health threat accompanied by increasing in drug resistance. To combat this challenge, there is an urgent need to find alternative antimicrobial agents against S. aureus. This study investigated the antimicrobial efficacy of carnosol against S. aureus using an in vitro model. The effects of carnosol were determined based on the antimicrobial effects or formation and disruption of biofilms. Finally, metabolomics of S. aureus grown as planktonic cells and biofilms with carnosol treatment were analyzed using gas chromatography-mass spectrometry. The minimum inhibitory concentrations (MICs) of carnosol were 32 to 256 µg/mL against the sixteen tested S. aureus strains. Among the biofilms, we observed a reduction in bacterial motility of the S. aureus, biofilm development and preformed biofilm after carnosol treatment. Moreover, the significantly altered metabolic pathways upon carnosol treatment in S. aureus planktonic cells and biofilms were highly associated with the perturbation of glyoxylate and dicarboxylate metabolism, glycine, serine and threonine metabolism, arginine and proline metabolism, alanine, aspartate and glutamate metabolism, arginine biosynthesis, and aminoacyl-tRNA biosynthesis. In addition, glutathione metabolism, D-glutamine and D-glutamate metabolism were significantly changed in the biofilms. This study establishes the antibacterial and antibiofilm properties of carnosol, and will provide an alternative strategy for overcoming the drug resistance of S. aureus.

Aloe-emodin induces autophagy and apoptotic cell death in non-small cell lung cancer cells via Akt/mTOR and MAPK signaling.

Lung cancer has a relatively poor prognosis, and the clinical efficacy of targeted drugs remains unsatisfactory. Therefore, the search for safe and efficient novel antitumor drugs has become an urgent problem in the treatment of lung cancer. Aloe-emodin (AE), a medicinal herb, has been demonstrated to exhibit many pharmacological effects on tumor cells, such as lung cancer cells. However, the anticancer properties of AE have not been fully exploited by modern medicine, as their mechanisms of action are not yet known. In this study, the bioassay results demonstrated that AE reduced the viability of the non-small cell lung cancer cell line A549 and NCI-H1299 in a dose- and time-dependent manner. Moreover, AE induced caspase-dependent apoptosis and autophagy. AE induced autophagy through activation of MAPK signaling and inhibition of the Akt/mTOR pathway. We also found that AE-induced autophagy was attenuated by the reactive oxygen species scavenger N-acetylcysteine, indicating that reactive oxygen species played a key role in AE-mediated autophagy in A549 and NCI-H1299 cells. Furthermore, AE induced reactive oxygen species-dependent autophagy in A549 and NCI-H1299 cells, which triggered apoptosis. Additionally, AE showed synergistic cytotoxic effects with the antitumor drug gemcitabine in A549 and NCI-H1299 cells. In brief, these results showed that AE might be useful for developing a therapeutic candidate for lung cancer complications.

Xanthohumol, a polyphenol chalcone present in hops, activating Nrf2 enzymes to confer protection against oxidative damage in PC12 cells.

Xanthohumol (2',4',4-trihydroxy-6'-methoxy-3'-prenylchalcone, Xn), a polyphenol chalcone from hops (Humulus lupulus), has received increasing attention due to its multiple pharmacological activities. As an active component in beers, its presence has been suggested to be linked to the epidemiological observation of the beneficial effect of regular beer drinking. In this work, we synthesized Xn with a total yield of 5.0% in seven steps and studied its neuroprotective function against oxidative-stress-induced neuronal cell damage in the neuronlike rat pheochromocytoma cell line PC12. Xn displays moderate free-radical-scavenging capacity in vitro. More importantly, pretreatment of PC12 cells with Xn at submicromolar concentrations significantly upregulates a panel of phase II cytoprotective genes as well as the corresponding gene products, such as glutathione, heme oxygenase, NAD(P)H: quinone oxidoreductase, thioredoxin, and thioredoxin reductase. A mechanistic study indicates that the α,ß-unsaturated ketone structure in Xn and activation of the transcription factor Nrf2 are key determinants for the cytoprotection of Xn. Targeting the Nrf2 by Xn discloses a previously unrecognized mechanism underlying the biological action of Xn. Our results demonstrate that Xn is a novel small-molecule activator of Nrf2 in neuronal cells and suggest that Xn might be a potential candidate for the prevention of neurodegenerative disorders.

Synthesis of xanthohumol analogues and discovery of potent thioredoxin reductase inhibitor as potential anticancer agent.

The selenoprotein thioredoxin reductases (TrxRs) are attractive targets for anticancer drugs development. Xanthohumol (Xn), a naturally occurring polyphenol chalcone from hops, has received increasing attention because of its multiple pharmacological activities. We synthesized Xn and its 43 analogues and discovered that compound 13n displayed the highest cytotoxicity toward HeLa cells (IC50 = 1.4 µM). Structure-activity relationship study indicates that the prenyl group is not necessary for cytotoxicity, and introducing electron-withdrawing group, especially on the meta-position, is favored. In addition, methylation of the phenoxyl groups generally improves the potency. Mechanistic study revealed that 13n selectively inhibits TrxR and induces reactive oxygen species and apoptosis in HeLa cells. Cells overexpressing TrxR are resistant to 13n insult, while knockdown of TrxR sensitizes cells to 13n treatment, highlighting the physiological significance of targeting TrxR by 13n. The clarification of the structural determinants for the potency would guide the design of novel potent molecules for future development.

A thiol-thiosulfonate reaction providing a novel strategy for turn-on thiol sensing.

The first thiol-specific turn-on probe, BODIPY-TS, utilizing a thiosulfonate scaffold as the thiol recognition unit was reported. BODIPY-TS displays low toxicity, and features high sensitivity, fast response and quantitative reaction towards thiols. The structural novelty of BODIPY-TS would guide the development of novel thiol probes.