Factors affecting responsiveness of vadadustat in patients with anemia associated with chronic kidney disease: a post-hoc subgroup analysis of Japanese phase 3 randomized studies

BACKGROUND

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor developed for treating anemia in chronic kidney disease (CKD). The purpose of this post-hoc analysis was to investigate the factors affecting the responsiveness to vadadustat in anemia patients with nondialysis-dependent (NDD) or hemodialysis-dependent (HDD) CKD in two Japanese phase 3 studies.

METHODS

Of 151 and 162 patients enrolled in NDD-CKD and HDD-CKD studies, 136 and 140 patients, respectively, were included and divided into subgroups for the analysis. To assess vadadustat responsiveness, the resistance index was defined as the mean body weight-adjusted dose of vadadustat (mg/kg) at weeks 20-24 divided by the mean hemoglobin (g/dL) at weeks 20-24. Multivariate analysis was performed to identify the variables affecting the resistance index.

RESULTS

Independent factors identified as determinants for better response to vadadustat were as follows: high baseline hemoglobin, low baseline eGFR, high week-20-24 ferritin, and CKD not caused by autoimmune disease/glomerulonephritis/vasculitis in NDD-CKD; and male sex, high baseline C-reactive protein, and low baseline erythropoiesis-stimulating agent resistance index (ERI) in HDD-CKD.

CONCLUSIONS

In this post-hoc analysis, several factors were identified as affecting the response to vadadustat. These results may provide useful information leading to an appropriate dose modification for vadadustat.

CLINICAL TRIAL REGISTRATION

NCT03329196 (MT-6548-J01) and NCT03439137 (MT-6548-J03).

A Dual-Mode Fluorescent Nanoprobe for the Detection and Visual Screening of Pathogenic Bacterial Spores

Bacterial vegetative cells turn into metabolically dormant spores in certain environmental situations. Once suitable conditions trigger the germination of spores belonging to the pathogenic bacterial category, public safety and environmental hygiene will be threatened, and lives will even be endangered when encountering fatal ones. Instant identification of pathogenic bacterial spores remains a challenging task, since most current approaches belonging to complicated biological methods unsuitable for onsite sensing or emerging alternative chemical techniques are still inseparable from professional instruments. Here we developed a polychromatic fluorescent nanoprobe for ratiometric detection and visual inspection of the pathogenic bacterial spore biomarker, dipicolinic acid (DPA), realizing rapidly accurate screening of pathogenic bacterial spores such as Bacillus anthracis spores. The nanoprobe is made of aminoclay-coated silicon nanoparticles and functionalized with europium ions, exhibiting selective and sensitive response toward DPA and Bacillus subtilis spores (simulants for Bacillus anthracis spores) with excellent linearity. The proposed sensing strategy allowing spore determination of as few as 0.3 × 105 CFU/mL within 10 s was further applied to real environmental sample detection with good accuracy and reliability. Visual quantitative determination can be achieved by analyzing the RGB values of the corresponding test solution color via a color recognition APP on a smartphone. Different test samples can be photographed at the same time, hence the efficient accomplishment of examining bulk samples within minutes. Potentially employed in various on-site sensing occasions, this strategy may develop into a powerful means for distinguishing hazardous pathogens to facilitate timely and proper actions of dealing with multifarious security issues.

Targeting of G-quadruplex DNA with 99mTc(I)/Re(I) Tricarbonyl Complexes Carrying Pyridostatin Derivatives

The main goal of this work was to elucidate the potential relevance of (radio)metal chelates of 99mTc and Re targeting G-quadruplex structures for the design of new tools for cancer theranostics. 99mTc provides the complexes with the ability to perform single-photon-emission computed tomography imaging studies, while the Re complexes should act as anticancer agents upon interaction with specific G4 DNA or RNA structures present in tumor tissues. Towards this goal, we have developed isostructural 99mTc(I) and Re(I) tricarbonyl complexes anchored by a pyrazolyl-diamine (Pz) chelator carrying a pendant pyridostatin (PDS) fragment as the G4-binding motif. The interaction of the PDF-Pz-Re (8) complex with different G4-forming oligonucleotides was studied by circular dichroism, fluorescence spectroscopy and FRET-melting assays. The results showed that the Re complex retained the ability to bind and stabilize G4-structures from different DNA or RNA sequences, namely those present on the SRC proto-oncogene and telomeric RNA (TERRA sequence). PDF-Pz-Re (8) showed low to moderate cytotoxicity in PC3 and MCF-7 cancer cell lines, as typically observed for G4-binders. Biodistribution studies of the congener PDF-Pz-99mTc (12) in normal mice showed that the complex undergoes a fast blood clearance with a predominant hepatobiliary excretion, pointing also for a high in vitro stability.

Spatial confinement of styryl pyridine salt derivative in MCM-22 molecular sieve network for boosted fluorescence emission and stable ratiometric sensing of bacillus anthracis biomarkers

In this work, a stable ratiometric nanofluorescent probe for the detection of 2,6-dipicolinic acid (DPA), a Bacillus anthracis biomarker, was developed based on confinement-induced emission enhancement of cationic styrylpyridine salt derivative L in MCM-22 molecular sieve pores. The cationic L and the lanthanide Tb3+ were loaded into the pores of the molecular sieve by electrostatic interaction with the negatively charged AlO4 tetrahedron unit, and L exhibited enhanced red fluorescence emission as a stable fluorescence reference mark in the nanoprobe platform due to the restricted molecular torsion of L in the pores of MCM-22. At the same time, the characteristic green fluorescence emission of Tb3+ can be excited by energy transfer due to the "antenna effect" of DPA. The prepared Tb-L@MCM-22 nanoprobe showed specific selectivity and stable fluorescence ratiometric detection of DPA in tap water, lake water, bovine serum and actual bacterial spores. Benefiting from the confinement-induced fluorescence enhancement effect of L in the MCM-22 molecular sieve pores, the obtained Tb-L@MCM-22 can provide a stable reference signal for the fluorescence ratiometric detection of DPA with a limit of detection (LOD) of 78.6 nM and 1.310 × 104 spores per mL. More importantly, combining of the Tb-L@MCM-22 based DPA detection test strips with a smartphone app demonstrated a stable, convenient and rapid method for detecting of anthrax biomarkers.

Pulmonary RNA interference against acute lung injury mediated by mucus- and cell-penetrating nanocomplexes

Trans-mucosal delivery of anti-inflammatory siRNA into alveolar macrophages represents a promising modality for the treatment of acute lung injury (ALI). However, its therapeutic efficacy is often hurdled by the lack of effective carriers that can simultaneously overcome the mucosal barrier and cell membrane barrier. Herein, we developed mucus/cell membrane dual-penetrating, macrophage-targeting polyplexes which enabled efficient intratracheal delivery of TNF-α siRNA (siTNF-α) to attenuate pulmonary inflammation against lipopolysaccharide (LPS)-induced ALI. P-G@Zn, a cationic helical polypeptide bearing both guanidine and zinc dipicolylamine (Zn-DPA) side charged groups, was designed to condense siTNF-α and promote macrophage internalization due to its helicity-dependent membrane activity. Coating of the polyplexes with charge-neutralizing carboxylated mannan (Man-COOH) greatly enhanced the mucus penetration potency due to shielding of the electrostatic adhesive interactions with the mucus, and it cooperatively enabled active targeting to alveolar macrophages to potentiate the intracellular delivery efficiency of siTNF-α. As such, intratracheally administered Man-COOH/P-G@Zn/siTNF-α polyplexes provoked notable TNF-α silencing by ∼75 % in inflamed lung tissues at 500 μg siRNA/kg, and demonstrated potent anti-inflammatory performance to treat ALI. This study provides an effective tool for the synchronized trans-mucosal delivery of siRNA into macrophages, and the unique properties of the polyplexes render remarkable potentials for anti-inflammatory therapy against ALI. STATEMENT OF SIGNIFICANCE: siRNA-mediated anti-inflammatory management of acute lung injury (ALI) is greatly challenged by the insufficient delivery across the mucus layer and cell membrane. To address such critical issue, mucus/cell membrane dual-penetrating, macrophage-targeting polyplexes are herein developed, which are comprised of an outer shell of carboxylated mannan (Man-COOH) and an inner nanocore formed by TNF-α siRNA (siTNF-α) and a cationic helical polypeptide P-G@Zn. Man-COOH coating endowed the polyplexes with high mucus-penetrating capability and macrophage-targeting ability, while P-G@Zn bearing both guanidine and zinc dipicolylamine afforded potent siTNF-α condensation capacity and high intracellular delivery efficiency with reduced cytotoxicity. Intratracheally administered polyplexes solicit pronounced TNF-α silencing and anti-inflammatory efficiencies in ALI mice. This study renders an effective example for overcoming the multiple barriers against trans-mucosal delivery of siRNA into macrophages, and holds profound potentials for gene therapy against ALI.

Development and validation of a simple and efficient method for the analysis of commercial formulations containing clopyralid, picloram and aminopyralid as active ingredients

Liquid chromatography plays a pivotal role in evaluating pesticide formulations as it enables the determination of multiple active substances in plant protection products. An adaptable separation technique has been developed, enabling the qualitative and quantitative analysis of clopyralid, picloram, and aminopyralid within pesticide formulations in line with SANCO/3030/99 rev. 5 guidelines. This article offers an insight into the validation procedure encompassing key aspects such as selectivity, linearity, accuracy, precision, and recovery. It places emphasis on critical stages, including sample preparation, chromatographic separation, detection, quantification, and data analysis. The active ingredients are separated using chromatography with isocratic elution, utilizing a mobile phase consisting of a mixture of water, acetonitrile, and acetic acid in a specific ratio (83:15:2 v/v/v). This separation is carried out on a YMC-Pack ODS-AQ column (250 mm x 4.6 mm, 5 μm) at a flow rate of 1.5 mL/min. The method's validation parameters have produced satisfactory outcomes. The recovery rates for each individual compound were found to be in the range of 98.6% to 101.0%. Precision, as indicated by the relative standard deviation (%RSD), was lower than the values predicted by the modified Horwitz equation. Furthermore, the correlation coefficients assessing the linearity of the response exceeded 0.99.

Dipicolylamine-Zn Induced Targeting and Photo-Eliminating of Pseudomonas aeruginosa and Drug-Resistance Gram-Positive Bacteria

The emergence of drug-resistant bacteria, particularly resistant strains of Gram-negative bacteria, such as Pseudomonas aeruginosa, poses a significant threat to public health. Although antibacterial photodynamic therapy (APDT) is a promising strategy for combating drug-resistant bacteria, actively targeted photosensitizers (PSs) remain unknown. In this study, a PS based on dipicolylamine (DPA), known as WZK-DPA-Zn, is designed for the selective identification of P. aeruginosa and drug-resistant Gram-positive bacteria. WZK-DPA-Zn exploits the synergistic effects of DPA-Zn2+ coordination and cellular uptake, which could effectively anchor P. aeruginosa within a brief period (10 min) without interference from other Gram-negative bacteria. Simultaneously, the cationic nature of WZK-DPA-Zn enhances its interaction with Gram-positive bacteria via electrostatic forces. Compared to traditional clinical antibiotics, WZK-DPA-Zn shows exceptional antibacterial activity without inducing drug resistance. This effectiveness is achieved using the APDT strategy when irradiated with white light or sunlight. The combination of WZK-DPA-Zn with Pluronic-based thermosensitive hydrogel dressings (WZK-DPA-Zn@Gel) effectively eliminates mixed bacterial infections and accelerates wound healing, thereby achieving a synergistic effect where "1+1>2." In summary, this study proposes a precise strategy employing DPA-Zn as the targeting moiety of a PS, facilitating the rapid elimination of P. aeruginosa and drug-resistant Gram-positive bacteria using APDT.

The Interaction Mechanism of Picolinamide Fungicide Targeting on the Cytochrome bc1 Complex and Its Structural Modification

Picolinamide fungicides, structurally related to UK-2A and antimycin-A, bind into the Qi-site in the bc1 complex. However, the detailed binding mode of picolinamide fungicides remains unknown. In the present study, antimycin-A and UK-2A were selected to study the binding mode of picolinamide inhibitors with four protonation states in the Qi-site by integrating molecular dynamics simulation, molecular docking, and molecular mechanics Generalized Born surface area (MM/GBSA) calculations. Subsequently, a series of new picolinamide derivatives were designed and synthesized to further understand the effects of substituents on the tail phenyl ring. The computational results indicated that the substituted aromatic rings in antimycin-A and UK-2A were the pharmacophore fragments and made the primary contribution when bound to a protein. Compound 9g-hydrolysis formed H-bonds with Hie201 and Ash228 and showed an IC50 value of 6.05 ± 0.24 μM against the porcine bc1 complex. Compound 9c, with a simpler chemical structure, showed higher control effects than florylpicoxamid against cucumber downy mildew and expanded the fungicidal spectrum of picolinamide fungicides. The structural and mechanistic insights obtained from the present study will provide a valuable clue for the future designing of new promising Qi-site inhibitors.

Ratiometric fluorescent and electrochemiluminescent dual modal assay for detection of 2,6-pyridinedicarboxylic acid as an anthrax biomarker

2,6-pyridinedicarboxylic acid (DPA) is an excellent biomarker of Bacillus anthracis (B. anthracis). The sensitive detection of DPA, especially through visual point-of-care testing, was significant for accurate and rapid diagnosis of anthrax to timely prevent anthrax disease or biological terrorist attack. Herein, a ratiometric fluorescent (R-FL) and electrochemiluminescent (ECL) dual-mode detection platform with a lanthanide ion-based metal-organic framework (Ln-MOF, i.e., M/Y-X: M = Eu, Y = Tb, and X = 4,4',4″-s-triazine-1,3,5-triyltri-m-aminobenzoic acid) was developed. Eu/Tb-TATAB nanoparticles were constructed to identify DPA. The R-FL detection platform quantitatively detected DPA by monitoring the I545/I617 ratio of the characteristic fluorescence peak intensities of Tb3+ ions and Eu3+ ions. The ECL sensing platform successfully quantified DPA by exploiting the burst effect of DPA on the ECL signal. The above methods had highly sensitive and rapid detection of DPA in water and serum samples. The results showed that this dual-mode detection platform may be projected to be a powerful instrument for preventing related biological warfare and bio-terrorism.

Magnetic separation-enhanced photoluminescence detection of dipicolinic acid and quenching detection of Cu(II) ions

Dipicolinic acid (DPA) is a chelate capable of binding to a variety of lanthanide ions to make them luminescent in the visible range. Based on this property and also assisted by magnetic separation, we report a strategy for the sensitive detection of DPA. Poly(acrylic acid)-coated iron oxide nanoparticles (IONPs) serve as a magnetic carrier to deliver only a necessary amount of Tb3+ ions to DPA in a sample solution. This enables photoluminescence measurement of the Tb3+-DPA complex with minimal background noise. The obtained detection limit, which is as low as 0.236 nM, is more than two orders of magnitude lower than that of the assay not assisted by magnetic separation. Not only does this method possess a potential for diagnosing anthrax, given that DPA is a major constituent of Bacillus anthracis spores, but it is also useful for detecting aqueous Cu2+ ions through the luminescence quenching effect. High sensitivity with a detection limit of 54 nM [Cu2+] is demonstrated using the Eu3+-DPA complex.

Self-calibrated HAp:Tb-EDTA paper-based probe with dual emission ratio fluorescence for binary visual and fluorescent detection of anthrax biomarker

Development of the portable device is significant for sensitive and rapid detection of an anthrax biomarker dipicolinic acid (DPA), existing in the B. anthracis. In this work, a novel HAp:Tb-EDTA paper-based ratiometric fluorescent sensor was obtained by a simple one-pot method for rapid and sensitive DPA detection. With the increased DPA concentration, the luminescence intensity of HAp (hydroxyapatite) remained constant, and thus applied as the stable reference signal, while the luminescence signal of Tb3+-EDTA was significantly enhanced due to the antenna effect. Therefore, the HAp:Tb-EDTA paper-based sensor was endowed with self-calibrated and ratiometric fluorescent detection performance for DPA. The proposed sensor showed excellent detection performance with a detection limit as low as 10.8 nM in the linear range of 0.5-30 μM. After combination with a smartphone, rapid visual and fluorescent detection of DPA was achieved. The proposed sensor was successfully applied to detect DPA from B. subtilis spore real samples, showing the application prospects of the paper-based sensors and opening a new horizon to develop novel paper-based point-of-care testing (POCT) devices.

Design, Synthesis and Gene Modulation Insights into Pigments Derived from Tryptophan-Betaxanthin, Which Act against Tumor Development in Caenorhabditis elegans

The use of betalains, which are nitrogenous plant pigments, by the food industry is widespread and reflects their safety after intake. The recent research showed outstanding results for L-tryptophan-betaxanthin, a phytochemical present in traditional Chinese medicine, as an antitumoral agent when the activity was evaluated in the animal model Caenorhabditis elegans. Thus, L-tryptophan-betaxanthin is now presented as a lead compound, from which eleven novel structurally related betaxanthins have been designed, biotechnologically produced, purified, and characterized. The antitumoral effect of the derived compounds was evaluated on the JK1466 tumoral strain of C. elegans. All the tested molecules significantly reduced the tumoral gonad sizes in a range between 31.4% and 43.0%. Among the novel compounds synthesized, tryptophan methyl ester-betaxanthin and tryptophan benzyl ester-betaxanthin, which are the first betalains to contain an ester group in their structures, caused tumor size reductions of 43.0% and 42.6%, respectively, after administration to the model animal. Since these were the two most effective molecules, their mechanism of action was investigated by microarray analysis. Differential gene expression analysis showed that tryptophan methyl ester-betaxanthin and tryptophan benzyl ester-betaxanthin were able to down-regulate the key genes of the mTOR pathway, such as daf-15 and rict-1.

H3 Derivatives Possessing Picolyl and Picolinate Pendants for Ga3+ Coordination and 67Ga3+ Radiolabeling

We synthesized, thanks to the regiospecific N-functionalization using an orthoamide intermediate, two 1,4,7-triazacyclononane derivatives containing an acetate arm and either a methylpyridine or a picolinic acid group, respectively, Hnoapy and H2noapa, as new Ga3+ chelators for potential use in nuclear medicine. The corresponding Ga3+ complexes were synthesized and structurally characterized in solution by 1H and 13C NMR. The [Ga(noapy)]2+ complex appears to exist in solution as two diasteroisomeric pairs of enantiomers, as confirmed by density functional theory (DFT) calculations, while for [Ga(noapa)]+, a single species is present in solution. Solid-state investigations were possible for the [Ga(noapa)]+ complex, which crystallized from water as a pair of enantiomers. The average length of the N-Ga bonds of 2.090 Å is identical with that found for the [Ga(nota)] complex, showing that the presence of the picolinate arm does not hinder the coordination of the ligand to the metal ion. Protonation constants of noapy- and noapa2- were determined by potentiometric titrations, providing an overall basicity ∑log KiH (i = 1-4) that increases in the order noapy- < noapa2- < nota3- with increases in the negative charge of the ligand. Stability constants determined by pH-potentiometric titrations supplemented with 71Ga NMR data show that the stabilities of [Ga(noapy)]2+ and [Ga(noapa)]+ are lower compared to that of [Ga(nota)] but higher than those of other standards such as [Ga(aazta)]-. 67Ga radiolabeling studies were performed in order to demonstrate the potential of these chelators for 67/68Ga-based radiopharmaceuticals. The labelings of Hnoapy and H2noapa were nearly identical, outperforming H3nota. Stability studies were conducted in phosphate-buffered saline and in the presence of human serum transferrin, revealing no significant decomplexation of [67Ga][Ga(noapy)]2+ and [67Ga][Ga(noapa)]+ compared to [67Ga][Ga(nota)]. Finally, all complexes were found to be highly hydrophilic, with calculated log D7.4 values of -3.42 ± 0.05, -3.34 ± 0.04, and -3.00 ± 0.23 for Hnoapy, H2noapa, and H3nota, respectively, correlating with the charge of each complex and the electrostatic potentials obtained with DFT.

Fluorescent silica nanoparticles as nano-chemosensors for the sequential detection of Pb2+ ions and bacterial-spore biomarker dipicolinic acid (DPA) in aqueous solution

Herein, we report fluorescein-labelled silica nanoparticles (FSNP) which serve as fluorescent nano-chemosensors for sequential detection of Pb2+ (which is a toxic heavy metal) and dipicolinic acid (DPA) (which is a distinctive indicator biomarker of bacterial spores) with high sensitivity and selectivity. The fluorescence of FSNP is quenched because of the complex formation between Pb2+ ions and surface amide groups, however, the fluorescence is recovered in contact with DPA, resulting from the association of DPA with surface bound Pb2+ ions. FSNP-Pb2+ complexes show high sensitivity towards DPA with a low detection limit of 850 nM which is approximately seventy times lower than the infectious dosage of bacterial spores (60 μM). Lateral flow test platform was further developed to show the applicability and practicability of our system.

Pd-Catalyzed Picolinamide-Directed Late-Stage Chalcogenation of Tryptophan-Containing Peptides

This report describes the Pd-catalyzed late-stage chalcogenation of tryptophan-containing peptides with disulfides/diselenides in moderate to good yields. It comprises broad substrate scope, functional group diversity, late-stage modification of drug molecules, and various valuable synthetic transformations, including room temperature easy removal of the picolinamide auxiliary, which could be applicable to tune the structure and function of peptides.

Determination of 2, 6-dipicolinic acid as an Anthrax biomarker based on the enhancement of copper nanocluster fluorescence by reversible aggregation-induced emission

The weak fluorescence efficiency of copper nanoclusters (Cu NCs) limits their wide applications in biosensing and bioimaging areas, while the aggregation-induced emission (AIE) effect is anticipated to increase their luminescence intensity. Herein, the weak red emission of Cu NCs is increased considerably by the addition of lanthanide Tb³⁺, ascribed to the AIE effect. Monitoring of spores contamination can be carried out by determining the level of 2, 6-dipicolinic acid (DPA), which is a marker of spores. Due to the stronger synergy between DPA and Tb³⁺ for its clamped configuration of adjacent pyridine nitrogen group with the carboxylic acid group, the addition of DPA leads Tb³⁺ to be taken away from Cu NCs through a stronger coordination effect, causing Cu NCs to return to the dispersed state and weakened fluorescence. Based on this, an "off-on-off" fluorescent probe for DPA sensing was built, in which Tb³⁺ was used as a bridge to achieve AIE enhanced fluorescence effect on Cu NCs as well as a specific recognizer of DPA. The detection range for DPA was 0.1-60 μM and the detection limit was 0.06 μM, which was much lower than the infectious dose of anthrax spores. Since DPA is a unique biomarker for bacterial spores, the method was applied to the detection of actual bacterial spores and satisfactory results were obtained with a detection limit of 4.9*10³ CFU mL^-1.

Dual-mode strategy for 2,6-dipicolinic acid detection based on the fluorescence property and peroxidase-like activity inhibition of Fe-MIL-88NH2

This work designed a fluorometric/colorimetric dual-mode sensor for detecting 2,6-dipicolinic acid (DPA) based on the blue emission property and peroxidase-like activity of Fe-MIL-88NH₂. The fluorescence of Fe-MIL-88NH₂ was obviously turned off by Cu²⁺, but DPA was able to bring it back because it has a strong chelate bond with Cu²⁺. Fe-MIL-88NH₂ also displayed high peroxidase-like activity, which accelerated the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to the blue oxidation product (oxTMB) when H₂O₂ was present. When DPA was added, it efficiently inhibited the peroxidase-like activity of Fe-MIL-88NH₂, causing less oxTMB and less absorbance at 652 nm. The fluorescence recovery of Fe-MIL-88NH₂ and the change in absorbance at 652 nm were used as analytical signals for dual-mode detection of DPA. The linear responses in the range of 10-60 μM and 60-160 μM were achieved for the fluorometric mode, and the limit of detection (LOD) was 1.46 μM. The respective values of linear range and LOD for the colorimetric mode were 5-25 μM and 3.00 μM, respectively. In summary, the dual-mode testing strategy successfully detected DPA in aqueous environmental samples, suggesting great potential in disease prevention and environmental analysis.

Dual-ligand lanthanide metal-organic framework for ratiometric fluorescence detection of the anthrax biomarker dipicolinic acid

Dipicolinic acid (DPA) is a unique biomarker of Bacillus anthracis. Development of a simple, fast, sensitive and timely DPA detection method is of great importance and interest for preventing mass disease outbreaks and treatment of anthrax. In this work, a novel lanthanide-doped fluorescence probe was constructed by coordination of Eu³⁺ with bifunctional UiO-66-(COOH)₂-NH₂ MOFs materials for efficient monitoring DPA. UiO-66-(COOH)₂-NH₂ MOFs were prepared using Zr⁴⁺ as a metal node, 1,2,4,5-benzenetetracarboxylic acid (H₄BTC) and 2-aminoterephthalic acid (NH₂-BDC) as bridging ligand through a simple one-pot synthesis method. By virtue their abundant carboxyl groups, UiO-66-(COOH)₂-NH₂ can readily grasp Eu³⁺ to form UiO-66-(COOH)₂-NH₂/Eu with coordinated water molecules at Eu sites. Upon interaction with DPA molecules, the coordinated H₂O molecules were replaced by DPA molecules which transfer energy to Eu³⁺ in UiO-66-(COOH)₂-NH₂/Eu and sensitize Eu³⁺ luminescence. Meanwhile, DPA has a characteristic absorption band at 270 nm, which overlapped with the excitation spectrum of NH₂-BDC, allowing the fluorescence of UiO-66-(COOH)₂-NH₂/Eu at 453 nm to be greatly quenched by DPA through inner filter effect (IFE). Therefore, the rationally designed UiO-66-(COOH)₂-NH₂/Eu complex not only exhibits strong hydrophilicity and high dispersion, but also serves as ratiometric fluorescence sensing platform for monitoring DPA concentration. This sensing platform showed a satisfactory linear relationship from 0.2 μM to 40 μM with a limit of detection of 25.0 nM and a noticeable fluorescence color change from blue to red, holding a great promise in practical applications.

Application of Molecular-Modeling, Scaffold-Hopping, and Bioisosteric Approaches to the Discovery of New Heterocyclic Picolinamides

Macrocyclic natural products and their derivatives are a valuable source for biologically active crop protection products and have had significant impact on the development of conventional agrochemicals. However, they can be challenging starting points for lead-generation efforts because of their size, structural complexity, and developability. Using molecular modeling and electrostatic analysis, alternative bicyclic isosteres were identified as replacements for the antifungal nine-membered macrocycle UK-2A. By application of a structure-based conformational approach, a series of heterocyclic replacements were derivatized to deliver promising fungicidal activity and scaffold bioisosteres were further diversified to investigate structure-activity relationships.

Erythropoietic effects of vadadustat in patients with anemia associated with chronic kidney disease

Patients with chronic kidney disease (CKD) develop anemia largely because of inappropriately low erythropoietin (EPO) production and insufficient iron available to erythroid precursors. In four phase 3, randomized, open-label, clinical trials in dialysis-dependent and non-dialysis-dependent patients with CKD and anemia, the hypoxia-inducible factor prolyl hydroxylase inhibitor, vadadustat, was noninferior to the erythropoiesis-stimulating agent, darbepoetin alfa, in increasing and maintaining target hemoglobin concentrations. In these trials, vadadustat increased the concentrations of serum EPO, the numbers of circulating erythrocytes, and the numbers of circulating reticulocytes. Achieved hemoglobin concentrations were similar in patients treated with either vadadustat or darbepoetin alfa, but compared with patients receiving darbepoetin alfa, those receiving vadadustat had erythrocytes with increased mean corpuscular volume and mean corpuscular hemoglobin, while the red cell distribution width was decreased. Increased serum transferrin concentrations, as measured by total iron-binding capacity, combined with stable serum iron concentrations, resulted in decreased transferrin saturation in patients randomized to vadadustat compared with patients randomized to darbepoetin alfa. The decreases in transferrin saturation were associated with relatively greater declines in serum hepcidin and ferritin in patients receiving vadadustat compared with those receiving darbepoetin alfa. These results for serum transferrin saturation, hepcidin, ferritin, and erythrocyte indices were consistent with improved iron availability in the patients receiving vadadustat. Thus, overall, vadadustat had beneficial effects on three aspects of erythropoiesis in patients with anemia associated with CKD: increased endogenous EPO production, improved iron availability to erythroid cells, and increased reticulocytes in the circulation.

Identification of New Fusarium sulawense Strains Causing Soybean Pod Blight in China and Their Control Using Carbendazim, Dipicolinic Acid and Kojic Acid

Soybean plants are highly susceptible to Fusarium species, which significantly reduce soybean production and quality. Several Fusarium species have been reported to synthesize mycotoxins, such as trichothecene, which have been related to major human diseases. In November 2021, soybean pods in Nantong municipality, China, showed black necrotic lesions during the harvest stage. The disease incidence reached 69%. The pathogen was identified as Fusarium sulawense via morphological analysis and sequencing of ITS, EF1-α and RPB2 genes. A PCR assay with primers targeting the trichothecene biosynthesis genes suggested that the three isolates could synthesize trichothecenes. The effectiveness of fungicide carbendazim and natural metabolites dipicolinic acid and kojic acid was screened for the management of F. sulawense on postharvest soybean pods. The highest efficacy was obtained when combining 3.8 mg/mL carbendazim and 0.84 mg/mL dipicolinic acid (curative efficacy: 49.1% lesion length inhibition; preventive efficacy: 82.7% lesion length inhibition), or 1.9 mg/mL carbendazim and 0.71 mg/mL kojic acid (preventive efficacy: 84.9% lesion length inhibition). Collectively, this report will lead to a better understanding of the safety hazards found in soybean products in China and reveals the application of dipicolinic and kojic acids to reduce the use of carbendazim.

Bioaccumulation of dietary CrPic, Cr(III) and Cr(VI) in juvenile coral trout (Plectropomus leopardus)

The form of chromium (Cr) is an important factor that influences its bioavailability and potential toxicity, while the difference of Cr bioaccumulation between organic and inorganic Cr has been rarely investigated. The present study compared the bioaccumulation of organic Cr (e.g., chromium picolinate (CrPic)) and inorganic Cr (e.g., trivalent (Cr(III)) and hexavalent (Cr(VI))) in juvenile coral trout (Plectropomus leopardus). The fish were exposed to a gradient level of different forms of dietary Cr for 66 days. Then the Cr bioaccumulation in fish were comparatively quantified between CrPic, Cr(VI) and Cr(III) groups. The results showed that the Cr bioaccumulation was form- and tissue-specific, dose- and time-dependent. Specifically, the newly bioaccumulated Cr in fish generally increased with the increasing dietary Cr level and exposure time, while the CrPic groups accumulated the highest Cr in most cases, followed by Cr(VI) and Cr(III) groups. The highest Cr content was observed in gut for CrPic groups, while it was highest in heart for Cr(VI) and Cr(III) groups, followed by kidney, skin, fin, liver, gill, bone, eyes and muscle in order. Overall, the results here firstly demonstrated that the dietary organic Cr(III) had significantly higher bioaccumulation than inorganic Cr (Cr(III) and Cr(VI)). Our findings suggested the complexity and variability of form-specific Cr bioavailability and toxicity should be cautiously evaluated in aquatic environments, which has been largely overlooked previously.

Itaconate alleviates β2-microglobulin-induced cognitive impairment by enhancing the hippocampal amino-β-carboxymuconate-semialdehyde-decarboxylase/picolinic acid pathway

β₂-microglobulin (B₂M) has been established to impair cognitive function. However, no treatment is currently available for B₂M-induced cognitive dysfunction. Itaconate is a tricarboxylic acid (TCA) cycle intermediate that exerts neuroprotective effects in several neurological diseases. The amino-β-carboxymuconate-semialdehyde-decarboxylase (ACMSD)/picolinic acid (PIC) pathway is a crucial neuroprotective branch in the kynurenine pathway (KP). The present study sought to investigate whether Itaconate attenuates B₂M-induced cognitive impairment and examine the mediatory role of the hippocampal ACMSD/PIC pathway. We demonstrated that 4-Octyl Itaconate (OI, an itaconate derivative) significantly alleviated B₂M-induced cognitive dysfunction and hippocampal neurogenesis impairment. OI treatment also increased the expression of ACMSD, elevated the concentration of PIC, and decreased the level of 3-HAA in the hippocampus of B₂M-exposed rats. Furthermore, inhibition of ACMSD by TES-991 significantly abolished the protections of Itaconate against B₂M-induced cognitive impairment and neurogenesis deficits. Exogenous PIC supplementation in hippocampus also improved cognitive performance and hippocampal neurogenesis in B₂M-exposed rats. These findings demonstrated that Itaconate alleviates B₂M-induced cognitive impairment by upregulation of the hippocampal ACMSD/PIC pathway. This is the first study to document Itaconate as a promising therapeutic agent to ameliorate cognitive impairment. Moreover, the mechanistic insights into the ACMSD/PIC pathway improve our understanding of it as a potential therapeutic target for neurological diseases beyond B₂M-associated neurocognitive disorders.

Mn(II) Acceleration of the Picolinic Acid-Assisted Fenton Reaction: New Insight into the Role of Manganese in Homogeneous Fenton AOPs

The homogeneous Fe-catalyzed Fenton reaction remains an attractive advanced oxidation process for wastewater treatment, but sustaining the Fe(III)/Fe(II) redox cycle at a convenient pH without the costly input of energy or reductants remains a challenge. Mn(II) is known to accelerate the Fenton reaction, yet the mechanism has never been confidently established. We report a systematic kinetic and spectroscopic investigation into Mn(II) acceleration of atrazine or 2,4,6-trichlorophenol degradation by the picolinic acid (PICA)-assisted Fenton reaction at pH 4.5-6.0. Mn(II) accelerates Fe(III) reduction, superoxide radical (HO₂^•/O₂^•-) formation, and hydroxyl radical (HO^•) formation. A Mn(II/III)-H₂O₂ redox cycle as an independent source of reactive oxygen species, as proposed in the literature, is shown to be insignificant. Rather, Mn(II) assists by participating directly and catalytically in the Fe(III)/Fe(II) redox cycle. Initially, Mn(II) (as Mn^II(PICA)⁺) complexes with a ferric hydroperoxo species, PICA-Fe^III-OOH. The resulting binuclear complex undergoes intramolecular electron transfer to give Fe(II), which later generates HO^• from H₂O₂, plus MnO₂⁺, which later decomposes to HO₂^•/O₂^•- (an Fe(III) reductant) and Mn(II), completing the catalytic cycle. This scheme may apply to other Fenton-type systems that go through an Fe^III-OOH intermediate. The findings here will inform the design of practical and sustainable Fenton-based AOPs employing Mn(II) in combination with chelating agents.

Rare-Earth hydroxide nanosheets based ratio fluorescence nanoprobe for dipicolinic acid detection

We demonstrate a novel ratio fluorescence nanoprobe for dipicolinic acid (DPA) as an anthrax biomarker based on layered rare-earth hydroxide (LRH). 3-Amino-benzenesulfonic acid (AS) was intercalated into layered terbium hydroxide to form composite and then delaminated into nanosheets in formamide. The monolayer nanosheets were beneficial to expose the Ln³⁺ luminescence centers to the environment more completely, contributing a high sensitive detection to the environment. With the increase of DPA concentration, the emission intensity of AS kept constant which worked as a stable internal reference, while the fluorescence of Tb³⁺ was enhanced obviously due to the antenna effect. In the 0.05-5.0 μM concentration range, the I₅₄₄/I₃₆₀ fluorescence ratio changed with the DPA concentration, which exhibited a good linear relationship (R² = 0.999) and an ultralow detection limit of 3.8 nM. In addition, the probe showed high selectivity and sensitivity to the DPA detection as an anthrax biomarker, which can be applied in real tap water with good performances. This work could extend the applications of LRH nanosheets in detection and offer an extremely effective and easy technique for detecting DPA.

The multi-targeted tyrosine kinase inhibitor SKLB610 resensitizes ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs

The overexpression of ATP-binding cassette (ABC) transporter ABCB1 (P-glycoprotein) or ABCG2 (BCRP/MXR/ABCP) in cancer cells is frequently associated with the development of multidrug resistance (MDR) in cancer patients, which remains a major obstacle to effective cancer treatment. By utilizing energy derived from ATP hydrolysis, both transporters have been shown to reduce the chemosensitivity of cancer cells by actively effluxing cytotoxic anticancer drugs out of cancer cells. Knowing that there are presently no approved drugs or other therapeutics for the treatment of multidrug-resistant cancers, in recent years, studies have investigated the repurposing of tyrosine kinase inhibitors (TKIs) to act as agents against MDR mediated by ABCB1 and/or ABCG2. SKLB610 is a multi-targeted TKI with potent activity against vascular endothelial growth factor receptor 2 (VEGFR2), platelet-derived growth factor receptor (PDGFR), and fibroblast growth factor receptor 2 (FGFR2). In this study, we investigate the interaction of SKLB610 with ABCB1 and ABCG2. We discovered that neither ABCB1 nor ABCG2 confers resistance to SKLB610, but SKLB610 selectively sensitizes ABCG2-overexpressing multidrug-resistant cancer cells to cytotoxic anticancer agents in a concentration-dependent manner. Our data indicate that SKLB610 reverses ABCG2-mediated MDR by attenuating the drug-efflux function of ABCG2 without affecting its total cell expression. These findings are further supported by results of SKLB610-stimulated ABCG2 ATPase activity and in silico docking of SKLB610 in the drug-binding pocket of ABCG2. In summary, we reveal the potential of SKLB610 to overcome resistance to cytotoxic anticancer drugs, which offers an additional treatment option for patients with multidrug-resistant cancers and warrants further investigation.

Enhanced Degradation of Micropollutants in a Peracetic Acid-Fe(III) System with Picolinic Acid

Activation of peracetic acid (PAA) with iron species is an emerging advanced oxidation process (AOP). This study investigates the use of the chelating agent picolinic acid (PICA) to extend the pH range and enhance the performance of the PAA-Fe(III) AOP. Compared to the PAA-Fe(III) system, the PAA-Fe(III)-PICA system degrades various micropollutants (MPs: methylene blue, naproxen, sulfamethoxazole, carbamazepine, trimethoprim, diclofenac, and bisphenol-A) much more rapidly at higher pH, achieving almost complete removal of parent compounds within 10 min. PAA significantly outperforms the coexistent H₂O₂ and is the key oxidant for rapid compound degradation. Other chelating agents, EDTA, NTA, citric acid, proline, and nicotinic acid, could not enhance MP degradation in the PAA-Fe(III) system, while 2,6-pyridinedicarboxylic acid with a structure similar to PICA moderately enhanced MP degradation. Experiments with scavengers (tert-butyl alcohol and methyl phenyl sulfoxide) and a probe compound (benzoic acid) confirmed that high-valent iron species [Fe(IV) and/or Fe(V)], rather than radicals, are the major reactive species contributing to MP degradation. The oxidation products of methylene blue, naproxen, and sulfamethoxazole by PAA-Fe(III)-PICA were characterized and supported the proposed mechanism. This work demonstrates that PICA is an effective complexing ligand to assist the Fenton reaction of PAA by extending the applicable pH range and accelerating the catalytic ability of Fe(III).

Laser induced degradation of bacterial spores during micro-Raman spectroscopy

Micro-Raman spectroscopy combined with optical tweezers is a powerful method to analyze how the biochemical composition and molecular structures of individual biological objects change with time. In this work we investigate laser induced effects in the trapped object. Bacillus thuringiensis spores, which are robust organisms known for their resilience to light, heat, and chemicals are used for this study. We trap spores and monitor the Raman peak from CaDPA (calcium dipicolinic acid), which is a chemical protecting the spore core. We see a correlation between the amount of laser power used in the trap and the release of CaDPA from the spore. At a laser power of 5 mW, the CaDPA from spores in water suspension remain intact over the 90 min experiment, however, at higher laser powers an induced effect could be observed. SEM images of laser exposed spores (after loss of CaDPA Raman peak was confirmed) show a notable alteration of the spores' structure. Our Raman data indicates that the median dose exposure to lose the CaDPA peak was ∼60 J at 808 nm. For decontaminated/deactivated spores, i.e., treated in sodium hypochlorite or peracetic acid solutions, the sensitivity on laser power is even more pronounced and different behavior could be observed on spores treated by the two chemicals. Importantly, the observed effect is most likely photochemical since the increase of the spore temperature is in the order of 0.1 K as suggested by our numerical multiphysics model. Our results show that care must be taken when using micro-Raman spectroscopy on biological objects since photoinduced effects may substantially affect the results.

OUP accepted manuscript

Pyridostatin (PDS) is a well-known G-quadruplex (G4) inducer and stabilizer, yet its target genes have remained unclear. Herein, applying MS proteomics strategy, we revealed PDS significantly downregulated 22 proteins but upregulated 16 proteins in HeLa cancer cells, of which the genes both contain a number of G4 potential sequences, implying that PDS regulation on gene expression is far more complicated than inducing/stabilizing G4 structures. The PDS-downregulated proteins consequently upregulated 6 proteins to activate cyclin and cell cycle regulation, suggesting that PDS itself is not a potential anticancer agent, at least toward HeLa cancer cells. Importantly, SUB1, which encodes human positive cofactor and DNA lesion sensor PC4, was downregulated by 4.76-fold. Further studies demonstrated that the downregulation of PC4 dramatically promoted the cytotoxicity of trans-[PtCl₂(NH₃)(thiazole)] (trans-PtTz) toward HeLa cells to a similar level of cisplatin, contributable to retarding the repair of 1,3-trans-PtTz crosslinked DNA lesion mediated by PC4. These findings not only provide new insights into better understanding on the biological functions of PDS but also implicate a strategy for the rational design of novel multi-targeting platinum anticancer drugs via conjugation of PDS as a ligand to the coordination scaffold of transplatin for battling drug resistance to cisplatin.

Florylpicoxamid, a new picolinamide fungicide with broad spectrum activity

BACKGROUND

Following the introduction of fenpicoxamid, a natural product-based fungicide targeting the Qi site of mitochondrial cytochrome bc1 complex, a second generation fully synthetic picolinamide, florylpicoxamid, was discovered and its biological activity and attributes were characterized.

RESULTS

In vitro fungal growth inhibition assays and in planta glasshouse biological activity evaluations showed florylpicoxamid was active against 21 different plant pathogenic fungi within the phyla Ascomycota and Basidiomycota. Among the pathogens evaluated, florylpicoxamid was most potent against Zymoseptoria tritici, the causal organism of wheat leaf blotch, providing 80% growth inhibition in vitro at 0.0046 mg L^-1 and 80% disease control in planta at 0.03 mg L^-1 when applied as a preventative treatment. Florylpicoxamid was more efficacious than epoxiconazole, fluxapyroxad, and benzovindiflupyr versus a Z. tritici wild-type isolate when applied as curative and preventative treatments, with superior 10-day curative reachback activity. Analytical studies and in planta tests demonstrated that florylpicoxamid partitioned into plants quickly and showed good systemicity and translaminar activity on both monocot and dicot plants. No cross-resistance was observed between florylpicoxamid and strobilurin or azole fungicides. Florylpicoxamid exerts its preventative effect by preventing spore germination on the leaf surface and curative activity by arresting mycelial growth and pycnidia development in leaf tissue.

CONCLUSIONS

With strong broad spectrum fungicidal activity, florylpicoxamid delivers an innovative solution for growers to sustain high productivity and quality of many crops, and also provides a new option for developing effective strategies for fungicide resistance management. © 2021 Society of Chemical Industry.

Biomass and salt-dependent effects of Bacillus spores on radionuclide migration from the Waste Isolation Pilot Plant

Spores of a Bacillus sp., isolated from radioactive waste, were tested for their ability to influence the fate and transport of neodymium (Nd³⁺) under high salt conditions expected at the Waste Isolation Pilot Plant (WIPP) nuclear waste repository. Spores were suspended in neodymium-spiked saline solutions up to 4 M NaCl, and concentrations of Nd and the complexing agent dipicolinic acid (DPA), a component of spores, were monitored along with optical densities and spore numbers. Results support neodymium bioassociation that is dependent upon biomass, with more apparent adsorption occurring at higher spore concentrations. However, probable spore lysis in 2 and 4 M NaCl solutions and possible germination at 0.15 M NaCl appear to drive the release of DPA and subsequent return of Nd to solution. The implications of this work for the WIPP will depend on actual biomass levels and the ionic strength of the repository brines.

Cytotoxic and genotoxic effects of clopyralid herbicide on Allium cepa roots

Clopyralid is one of the synthetic pyridine-carboxylate auxin herbicides and used to control perennial and annual broadleaf weeds in wheat, sugar beets, canola, etc. In this study, dose-dependent cytotoxicity and genotoxicity of clopyralid at different concentrations (25, 50, and 100 μg/mL) have been evaluated on the Allium cepa roots. The evaluation has been performed at macroscopic (root growth) and microscopic levels [mitotic index (MI), chromosome aberrations (CAs) in ana-telophase cells, and DNA damage] using root growth inhibition, Allium ana-telophase, and comet tests. The percentage of root growth inhibition and concentration of reducing root growth by 50% (EC₅₀) of clopyralid were determined compared with the negative control by using various concentrations of clopyralid (6.25-1000 μg/L). The 96 h EC₅₀ of clopyralid was recorded as 50 μg/L. The gradual decrease in root growth and the MI reveals the cytotoxic effects of clopyralid. All the tested concentrations of clopyralid induced total CAs (polyploidy, stickiness, anaphase bridges, chromosome laggards, and disturbed ana-telophase) and DNA damage dose and time dependently. These results confirm the cytotoxic and genotoxic effects of clopyralid on non-target organism.

The Fenton Reaction in Water Assisted by Picolinic Acid: Accelerated Iron Cycling and Co-generation of a Selective Fe-Based Oxidant

The Fenton reaction is limited by a narrow acidic pH range, the slow reduction of Fe(III), and susceptibility of the nonselective hydroxyl radical (HO^•) to scavenging by water constituents. Here, we employed the biodegradable chelating agent picolinic acid (PICA) to address these concerns. Compared to the classical Fenton reaction at pH 3.0, PICA greatly accelerated the degradation of atrazine, sulfamethazine, and various substituted phenols at pH 5.0 in a reaction with autocatalytic characteristics. Although HO^• served as the principal oxidant, a high-spin, end-on hydroperoxo intermediate, tentatively identified as PICA-Fe^III-OOH, also exhibited reactivity toward several test compounds. Chloride release from the oxidation of 2,4,6-trichlorophenol and the positive slope of the Hammett correlation for a series of halogenated phenols were consistent with PICA-Fe^III-OOH reacting as a nucleophilic oxidant. Compared to HO^•, PICA-Fe^III-OOH is less sensitive to potential scavengers in environmental water samples. Kinetic analysis reveals that PICA facilitates Fe(III)/Fe(II) transformation by accelerating Fe(III) reduction by H₂O₂. Autocatalysis is ascribed to the buildup of Fe(II) from the reduction of Fe(III) by H₂O₂ as well as PICA oxidation products. PICA assistance in the Fenton reaction may be beneficial to wastewater treatment because it favors iron cycling, extends the pH range, and balances oxidation universality with selectivity.

Design, synthesis and mode of action of novel 3-chloro-6-pyrazolyl picolinate derivatives as herbicide candidates

BACKGROUND

Picolinate/picolinic acid compounds are an important class of synthetic auxin herbicides. To explore the herbicidal activity of 6-pyrazolyl picolinate compounds, a series of 3-chloro-6-pyrazolyl-picolinate derivatives was designed and synthesized.

RESULTS

Twenty-five 3-chloro-6-pyrazolyl-picolinate derivatives synthesized were tested for herbicidal activity and the IC₅₀ value of compound c5 to the growth of Arabidopsis thaliana root was 27 times lower than that of the commercial herbicide clopyralid. Compound c5 displayed better post-emergence herbicidal activity and broader (Picloram, Clopyralid, Aminopyralid) herbicidal spectrum at a dosage of 400 g ha^-1 in comparison with clopyralid; it also was safe to wheat and maize at this dosage. Arabidopsis thaliana phenotypes and expression of auxin-response genes demonstrated that compound c5 might be a novel auxin-type herbicide. Molecular docking analyses revealed that compound c5 had stronger binding ability to receptor AFB5 (auxin signaling F-box protein 5) than clopyralid.

CONCLUSION

These 6-pyrazolyl picolinate compounds could be used as potential lead structures for the discovery of a novel synthetic auxin herbicide. © 2021 Society of Chemical Industry.

Fluorescent detection of dipicolinic acid as a biomarker in bacterial spores employing terbium ion-coordinated magnetite nanoparticles

Anthrax is a bioterror agent because of its toxicity and the tolerance of its bacterial spores. Thus, researchers have attempted to develop various nanomaterials to detect dipicolinic acid (DPA), a biomarker of bacterial spores. Nanomaterials containing lanthanide ions have received considerable attention, owing to their potential to exhibit high sensitivity and selectivity in the detection of DPA via chelation with molecules. However, the fluorescent signals of the lanthanide complex are quenchable because the nanomaterials simultaneously absorb the excitation and emission light. For the precise detection of DPA, pure signals have to be obtained from the complex by alleviating the quenching effect of the nanomaterials. In this study, we develop a structure with terbium ion (Tb³⁺)-coordinated magnetite (Fe₃O₄) nanoparticle to detect DPA. Tb³⁺ can be detached from the magnetite during chelation with the DPA, and the complex can emit the unencumbered signals with improved detection limit through the application of a magnetic field. The detection system exhibits a significantly lower detection limit (5.4 nM) than the infectious dosage of anthrax (60 μM) with high selectivity and chemical stability. This study informs the improvement of detection limits via the separation of nanomaterials and lanthanide complex.

Positron Emission Tomography-Magnetic Resonance Imaging Pharmacokinetics, In Vivo Biodistribution, and Whole-Body Elimination of Mn-PyC3A

OBJECTIVES

Mn-PyC3A is an experimental manganese (Mn)-based extracellular fluid magnetic resonance imaging (MRI) contrast agent that is being evaluated as a direct replacement for clinical gadolinium (Gd)-based contrast agents. The goals of this study were to use simultaneous positron emission tomography (PET)-MRI to (1) compare the whole-body pharmacokinetics, biodistribution, and elimination of Mn-PyC3A with the liver-specific contrast agent mangafodipir (Mn-DPDP), (2) determine the pharmacokinetics and fractional excretion of Mn-PyC3A in a rat model of renal impairment, and (3) compare whole-body elimination of Mn-PyC3A to gadoterate (Gd-DOTA) in a rat model of renal impairment.

METHODS

Mn-PyC3A and Mn-DPDP were radiolabeled with the positron emitting isotope Mn-52 via Mn2+ exchange with 52MnCl2. Dynamic simultaneous PET-MRI was used to measure whole-body pharmacokinetics and biodistribution of Mn-52 immediately and out to 7 days after an intravenous 0.2 mmol/kg dose of [52Mn]Mn-PyC3A to normal or to 5/6 nephrectomy rats or a 0.01 mmol/kg dose of [52Mn]Mn-DPDP to normal rats. The fractional excretion and 1- and 7-day biodistribution in rats after the injection of 2.0 mmol/kg [52Mn]Mn-PyC3A (n = 11 per time point) or 2.0 mmol/kg Gd-DOTA (n = 8 per time point) were quantified by gamma counting or Gd elemental analysis, respectively. Comparisons of Mn-PyC3A pharmacokinetics and in vivo biodistribution in normal and 5/6 nephrectomy rats and comparisons of ex vivo Mn versus Gd biodistribution data in 5/6 nephrectomy were made with an unpaired t test.

RESULTS

Dynamic PET-MRI data demonstrate that both [52Mn]Mn-PyC3A and [52Mn]Mn-DPDP were eliminated by mixed renal and hepatobiliary elimination but that a greater fraction of [52Mn]Mn-PyC3A was eliminated by renal filtration. Whole-body PET images show that Mn-52 from [52Mn]Mn-PyC3A was efficiently eliminated from the body, whereas Mn-52 from [52Mn]Mn-DPDP was retained throughout the body. The blood elimination half-life of [52Mn]Mn-PyC3A in normal and 5/6 nephrectomy rats was 13 ± 3.5 minutes and 23 ± 12 minutes, respectively (P = 0.083). Area under the curve between 0 and 60 minutes postinjection (AUC0-60) in the bladder of normal and 5/6 nephrectomy rats was 2600 ± 1700 %ID/cc*min and 750 ± 180 %ID/cc*min, respectively (P = 0.024), whereas AUC0-60 in the liver of normal and 5/6 nephrectomy rats was 33 ± 13 %ID/cc*min and 71 ± 16 %ID/cc*min, respectively (P = 0.011), indicating increased hepatobiliary elimination in 5/6 nephrectomy rats. The %IDs of Mn from [52Mn]Mn-PyC3A and Gd from Gd-DOTA recovered from 5/6 nephrectomy rats 1 day after injection were 2.0 ± 1.1 and 1.3 ± 0.34, respectively (P = 0.10) and 7 days after injection were 0.14 ± 0.11 and 0.41 ± 0.24, respectively (P = 0.0041).

CONCLUSIONS

Mn-PyC3A has different pharmacokinetics and is more efficiently eliminated than Mn-DPDP in normal rats. Mn-PyC3A is efficiently eliminated from both normal and 5/6 nephrectomy rats, with increased fractional hepatobiliary excretion from 5/6 nephrectomy rats. Mn-PyC3A is more completely eliminated than Gd-DOTA from 5/6 nephrectomy rats after 7 days.

Spectroscopic characterization of dipicolinic acid and its photoproducts as thymine photosensitizers

Dipicolinic acid (DPA), present in large amount in bacterial spores, has been proposed to act as an endogenous photosensitizer in spore photoproduct formation. The proposed mechanism involves a triplet-triplet energy transfer from DPA to thymine. However, up to now, no spectroscopic studies have been performed to determine the interaction between the endogenous compound and the nucleobase, probably due to its photolability in aqueous solutions. Here, triplet excited state properties of DPA are reported together with its bimolecular quenching rate constant by thymidine, k_q of ca. 5.3 × 10⁹ M^-1 s^-1. To run more reliable studies, a stable methyl ester derivative of DPA, which exhibits the same spectroscopic properties as the parent compound, is also described. Finally, DPA photoproducts are characterized. Studies of their triplet excited state properties have demonstrated that, interestingly, one of them is able to photosensitize thymidine triplet excited state formation.

Mild Cu(OTf)2-Mediated C-Glycosylation with Chelation-Assisted Picolinate as a Leaving Group

C-Glycosylation reactions of glycosyl picolinates with allyltrimethylsilane or silyl enol ethers were developed. Picolinate as a chelation-assisted leaving group could be activated by Cu(OTf)2 and avoided the use of harsh Lewis acids. The glycosylations were operated under mild neutral conditions and gave the corresponding C-glycosides in up to 95% yield with moderate to excellent stereoselectivities.

Selective Coordination of Cu2+ and Subsequent Anion Detection Based on a Naphthalimide-Triazine-(DPA)2 Chemosensor

A new fluorescent chemosensor for copper (II) and subsequent anion sensing was designed and fully characterized. The sensor consisted of a 1,8-naphthalimide core, bearing two terminal dipicolylamine (DPA) receptor units for binding metal cations, and an ethoxyethanol moiety for enhanced water solubility. The DPA units are connected to position 4 of the fluorophore via a triazine-ethylenediamine spacer. Fluorescence titration studies of the chemosensor revealed a high selectivity for Cu²⁺ over other divalent ions, the emissions were strongly quenched upon binding, and a stability constant of 5.52 log units was obtained. Given the distance from DPA chelating units and the fluorophore, quenching from the Cu²⁺ complexation suggests an electron transfer or an electronic energy transfer mechanism. Furthermore, the Cu²⁺-sensor complex proved to be capable of sensing anionic phosphate derivatives through the displacement of the Cu²⁺ cation, which translated into a full recovery of the luminescence from the naphthalimide. Super-resolution fluorescence microscopy studies performed in HeLa cells showed there was a high intracellular uptake of the chemosensor. Incubation in Cu²⁺ spiked media revealed a strong fluorescent signal from mitochondria and cell membranes, which is consistent with a high concentration of ATP at these intracellular sites.

Discovery of a Potent Picolinamide Antibacterial Active against Clostridioides difficile

A major challenge for chemotherapy of bacterial infections is perturbation of the intestinal microbiota. Clostridioides difficile is a Gram-positive bacterium of the gut that can thrive under this circumstance. Its production of dormant and antibiotic-impervious spores results in chronic disruption of normal gut flora and debilitating diarrhea and intestinal infection. C. difficile is responsible for 12,800 deaths per year in the United States. Here, we report the discovery of 2-(4-(3-(trifluoromethoxy)phenoxy)picolinamido)benzo[d]oxazole-5-carboxylate as an antibacterial with potent and selective activity against C. difficile. Its MIC₅₀ and MIC₉₀ (the concentration required to inhibit the growth of 50% and 90% of all the tested strains, respectively) values, documented across 101 strains of C. difficile, are 0.12 and 0.25 μg/mL, respectively. The compound targets cell wall biosynthesis, as assessed by macromolecular biosynthesis assays and by scanning electron microscopy. Animals infected with a lethal dose of C. difficile and treated with compound 1 had a similar survival compared to treatment with vancomycin, which is the frontline antibiotic used for C. difficile infection.

Biodegradability improvement of clopyralid wastes through electrolysis using different diamond anodes

The use of boron-doped (BDDs) anodes for efficient removal of complex organic molecules, such as organochlorine compounds, is well stated in the literature. However, the role of the different characteristics of this anode on the transformation of these type of contaminants into more biodegradable molecules is a topic of interest that need to be clarified when aimed an efficient combination of an electrochemical system as a previous step to biological treatment. In this work, improvement in the biodegradability of synthetic wastes polluted with clopyralid, as an organochlorine model compound, is studied after electrolysis with different BDDs in the presence of the two most common supporting electrolytes (containing sulfate or chloride ions). For that, clopyralid removal, mineralization, aromatics intermediates, short-chain carboxylic acids, and inorganic ions were monitored. Improved results were found in sulfate media for BDD with 200 ppm, capable of removing 88.7% of contaminants and 85% of TOC, resulting in an improvement in biodegradability of almost 7-fold compared to the initial sample. These findings point out that lower doping levels are preferable when coupling studied technologies.

Identification of New Betalains in Separated Betacyanin and Betaxanthin Fractions from Ulluco (Ullucus tuberosus Caldas) by HPLC-DAD-ESI-MS

An improved methodology of achieving an accurate separation of pure fractions of betacyanins and betaxanthins from Ullucus tuberosus Caldas has been carried out. For that purpose, an in-depth chemical identification of each betalain fraction using HPLC-DAD-ESI-MS was developed. This procedure allowed to evaluate the fractionation efficiency and also identify a large number of betalains, most of which have not been described so far in this raw material: betanidin- and isobetanidin-5-O-(4'-O-malonyl-β-glucoside), 2-decarboxy-phyllocactin, betanidin- and isobetanidin-6-O-(6'-O-feruloyl)-β-glucoside (gomphrenin and isogomphrenin III), dehydro-phyllocactin and isophyllocactin, and arginine and glycine-betaxanthins (portulacaxanthin III). Moreover, the availability of pure betalain fractions by the proposed methodology permitted to establish the total betalain content and the antioxidant activity of both separated betacyanin and betaxanthin fractions of ulluco for the first time. The results suggest Ullucus tuberosus as an underutilized food bioactive source with a high concentration of total betaxanthins (21.8 μg indicaxanthin/g fresh ulluco) and betacyanins (44.5 μg betanin/g fresh ulluco), strongly correlated to the Folin-Ciocalteau reduction capacity.

Picolinic acid, a tryptophan oxidation product, does not impact bone mineral density but increases marrow adiposity

Tryptophan is an essential amino acid catabolized initially to kynurenine (kyn), an immunomodulatory metabolite that we have previously shown to promote bone loss. Kyn levels increase with aging and have also been associated with neurodegenerative disorders. Picolinic acid (PA) is another tryptophan metabolite downstream of kyn. However, in contrast to kyn, PA is reported to be neuroprotective and further, to promote osteogenesis in vitro. Thus, we hypothesized that PA might be osteoprotective in vivo. In an IACUC-approved protocol, we fed PA to aged (23-month-old) C57BL/6 mice for eight weeks. In an effort to determine potential interactions of PA with dietary protein we also fed PA in a low-protein diet (8%). The mice were divided into four groups: Control (18% dietary protein), +PA (700 ppm); Low-protein (8%), +PA (700 ppm). The PA feedings had no impact on mouse weight, body composition or bone density. At sacrifice bone and stem cells were collected for analysis, including μCT and RT-qPCR. Addition of PA to the diet had no impact on trabecular bone parameters. However, marrow adiposity was significantly increased in PA-fed mice, and in bone marrow stromal cells isolated from these mice increases in the expression of the lipid storage genes, Plin1 and Cidec, were observed. Thus, as a downstream metabolite of kyn, PA no longer showed kyn's detrimental effects on bone but instead appears to impact energy balance.

New insights into clopyralid degradation by sulfate radical: Pyridine ring cleavage pathways

Contamination by herbicides such as clopyralid (CLP) poses a significant threat to human health and ecological systems. In the present study, efficient removal of CLP was achieved by thermo activated persulfate, among which sulfate radical was identified as the predominant oxidizing species responsible for the decontamination. Based on high resolution LC-MS, derivatization method and density functional theory (DFT) computation, the detailed oxidation pathways and mechanisms were proposed. The primary oxidation pathways included dechlorination-hydroxylation, decarboxylation and the formation of quinone-like moieties. Afterwards, numerous intermediate byproducts ranging from high molecular to very small ones were identified, suggesting the pyridine ring was damaged during the thermo activated persulfate process. The detected products containing six and five carbons indicated the pyridine ring cleavage would take place on the quinone-structure intermediate. Further oxidation could continue by breaking each bond on the ring-cleavage product, yielding a series of short-chain carbonyl chemicals, carboxylic acids and inorganic ions. In addition, the presence of dissolved oxygen (DO) was favorable to CLP degradation, indicating DO played an important role in applying such technology. The degradation rate constants of CLP increased appreciably with increasing temperature, and acidic pH facilitated the CLP degradation. The results obtained in this work would increase our understanding on the environmental fates of nitrogen heterocyclic compounds during sulfate radical (SO₄^•-)-based advanced oxidation processes (SR-AOPs).

Small-molecule G-quadruplex stabilizers reveal a novel pathway of autophagy regulation in neurons

Guanine-rich DNA sequences can fold into four-stranded G-quadruplex (G4-DNA) structures. G4-DNA regulates replication and transcription, at least in cancer cells. Here, we demonstrate that, in neurons, pharmacologically stabilizing G4-DNA with G4 ligands strongly downregulates the Atg7 gene. Atg7 is a critical gene for the initiation of autophagy that exhibits decreased transcription with aging. Using an in vitro assay, we show that a putative G-quadruplex-forming sequence (PQFS) in the first intron of the Atg7 gene folds into a G4. An antibody specific to G4-DNA and the G4-DNA-binding protein PC4 bind to the Atg7 PQFS. Mice treated with a G4 stabilizer develop memory deficits. Brain samples from aged mice contain G4-DNA structures that are absent in brain samples from young mice. Overexpressing the G4-DNA helicase Pif1 in neurons exposed to the G4 stabilizer improves phenotypes associated with G4-DNA stabilization. Our findings indicate that G4-DNA is a novel pathway for regulating autophagy in neurons.

A luminescent europium-dipicolinic acid nanohybrid for the rapid and selective sensing of pyrophosphate and alkaline phosphatase activity

As a ubiquitous hydrolysis enzyme in phosphate metabolism, alkaline phosphatase (ALP) is a significant biomarker in laboratory research and clinic diagnosis. Herein, we report a highly water-soluble Eu(DPA)3@Lap nanohybrid material for the rapid and selective assay of PPi and ALP through a luminescence off-on recognition process. Eu(DPA)3@Lap was successfully prepared in an aqueous solution, and it exhibited strong luminescence emission, high photostability, and long lifetime. More interestingly, the strong luminescence of Eu(DPA)3@Lap can be remarkably quenched by Cu2+ due to the high impetus of coordination between the DPA ligand and Cu2+ ion. Using Cu2+ as a signal transducer, the luminescence could be recovered upon the addition of PPi ion owing to the formation of a Cu2+-PPi complex; thus, a luminescence turn-on assay for PPi ions was realized. Utilizing the ability of Cu2+ to differentiate between PPi and Pi, a convenient and straightforward luminescence assay for ALP activity was accomplished based on the specific dephosphorylation of PPi to Pi. To the best of our knowledge, this elaborate luminescence sensing system constitutes the first luminescent nanohybrid material based on a europium organic complex for ALP activity assay. Furthermore, the recognition process of PPi and ALP was completed in a convenient and facile mix-and-readout manner, and it revealed significant potential in point of care testing.

Isolation of a 2-picolinic acid-assimilating bacterium and its proposed degradation pathway

Burkholderia sp. ZD1, aerobically utilizes 2-picolinic acid as a source of carbon, nitrogen and energy, was isolated. ZD1 completely degraded 2-picolinic acid when the initial concentrations ranged from 25 to 300mg/L. Specific growth rate (μ) and specific consumption rate (q) increased continually in the concentration range of 25-100mg/L, and then declined. Based on the Haldane model and Andrew's model, μ_max and q_max were calculated as 3.9 and 16.5h^-1, respectively. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to determine the main intermediates in the degradation pathway. Moreover, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was innovatively used to deduce the ring cleavage mechanism of N-heterocycle of 2-picolinic acid. To our knowledge, this is the first report on not only the utilization of 2-picolinic acid by a Burkholderia sp., but also applying FT-ICR-MS and ATR-FTIR for exploring the biodegradation pathway of organic compounds.

Purification and Characterization of Plantaricin JLA-9: A Novel Bacteriocin against Bacillus spp. Produced by Lactobacillus plantarum JLA-9 from Suan-Tsai, a Traditional Chinese Fermented Cabbage

Bacteriocins are ribosomally synthesized peptides with antimicrobial activity produced by numerous bacteria. A novel bacteriocin-producing strain, Lactobacillus plantarum JLA-9, isolated from Suan-Tsai, a traditional Chinese fermented cabbage, was screened and identified by its physiobiochemical characteristics and 16S rDNA sequence analysis. A new bacteriocin, designated plantaricin JLA-9, was purified using butanol extraction, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular mass of plantaricin JLA-9 was shown to be 1044 Da by MALDI-TOF-MS analyses. The amino acid sequence of plantaricin JLA-9 was predicted to be FWQKMSFA by MALDI-TOF-MS/MS, which was confirmed by Edman degradation. This bacteriocin exhibited broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, especially Bacillus spp., high thermal stability (20 min, 121 °C), and narrow pH stability (pH 2.0-7.0). It was sensitive to α-chymotrypsin, pepsin, alkaline protease, and papain. The mode of action of this bacteriocin responsible for outgrowth inhibition of Bacillus cereus spores was studied. Plantaricin JLA-9 had no detectable effects on germination initiation over 1 h on monitoring the hydration, heat resistance, and 2,6-pyridinedicarboxylic acid (DPA) release of spores. Rather, germination initiation is a prerequisite for the action of plantaricin JLA-9. Plantaricin JLA-9 inhibited growth by preventing the establishment of oxidative metabolism and disrupting membrane integrity in germinating spores within 2 h. The results suggest that plantaricin JLA-9 has potential applications in the control of Bacillus spp. in the food industry.