Community-developed checklists for publishing images and image analyses.

Images document scientific discoveries and are prevalent in modern biomedical research. Microscopy imaging in particular is currently undergoing rapid technological advancements. However, for scientists wishing to publish obtained images and image-analysis results, there are currently no unified guidelines for best practices. Consequently, microscopy images and image data in publications may be unclear or difficult to interpret. Here, we present community-developed checklists for preparing light microscopy images and describing image analyses for publications. These checklists offer authors, readers and publishers key recommendations for image formatting and annotation, color selection, data availability and reporting image-analysis workflows. The goal of our guidelines is to increase the clarity and reproducibility of image figures and thereby to heighten the quality and explanatory power of microscopy data.

BigNeuron: a resource to benchmark and predict performance of algorithms for automated tracing of neurons in light microscopy datasets.

BigNeuron is an open community bench-testing platform with the goal of setting open standards for accurate and fast automatic neuron tracing. We gathered a diverse set of image volumes across several species that is representative of the data obtained in many neuroscience laboratories interested in neuron tracing. Here, we report generated gold standard manual annotations for a subset of the available imaging datasets and quantified tracing quality for 35 automatic tracing algorithms. The goal of generating such a hand-curated diverse dataset is to advance the development of tracing algorithms and enable generalizable benchmarking. Together with image quality features, we pooled the data in an interactive web application that enables users and developers to perform principal component analysis, t-distributed stochastic neighbor embedding, correlation and clustering, visualization of imaging and tracing data, and benchmarking of automatic tracing algorithms in user-defined data subsets. The image quality metrics explain most of the variance in the data, followed by neuromorphological features related to neuron size. We observed that diverse algorithms can provide complementary information to obtain accurate results and developed a method to iteratively combine methods and generate consensus reconstructions. The consensus trees obtained provide estimates of the neuron structure ground truth that typically outperform single algorithms in noisy datasets. However, specific algorithms may outperform the consensus tree strategy in specific imaging conditions. Finally, to aid users in predicting the most accurate automatic tracing results without manual annotations for comparison, we used support vector machine regression to predict reconstruction quality given an image volume and a set of automatic tracings.

Açaí (Euterpe oleracea Mart.) Seed Oil and Its Nanoemulsion: Chemical Characterisation, Toxicity Evaluation, Antioxidant and Anticancer Activities.

This study explores a nanoemulsion formulated with açaí seed oil, known for its rich fatty acid composition and diverse biological activities. This study aimed to characterise a nanoemulsion formulated with açaí seed oil and explore its cytotoxic effects on HeLa and SiHa cervical cancer cell lines, alongside assessing its antioxidant and toxicity properties both in vitro and in vivo. Extracted from fruits sourced in Brazil, the oil underwent thorough chemical characterization using gas chromatography-mass spectrometry. The resulting nanoemulsion was prepared and evaluated for stability, particle size, and antioxidant properties. The nanoemulsion exhibited translucency, fluidity, and stability post centrifugation and temperature tests, with a droplet size of 238.37, PDI -9.59, pH 7, and turbidity 0.267. In vitro assessments on cervical cancer cell lines revealed antitumour effects, including inhibition of cell proliferation, migration, and colony formation. Toxicity tests conducted in cell cultures and female Swiss mice demonstrated no adverse effects of both açaí seed oil and nanoemulsion. Overall, açaí seed oil, particularly when formulated into a nanoemulsion, presents potential for cancer treatment due to its bioactive properties and safety profile.

Ellman's Assay on the Surface: Thiol Quantification of Human Cofilin-1 Protein through Surface Plasmon Resonance.

Oxidative stress on cysteine (Cys)-containing proteins has been associated with physiological disorders, as suggested for the human cofilin-1 (CFL-1) protein, in which the oxidized residues are likely implicated in the aggregation process of α-synuclein, leading to severe neuronal injuries. Considering the relevance of the oxidation state of cysteine, quantification of thiols may offer a guide for the development of effective therapies. This work presents, for the very first time, thiol quantification within CFL-1 in solution and on the surface following classic and adapted versions of Ellman's assay. The 1:1 stoichiometric Ellman's reaction occurs between 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB), and the free thiol of the cysteine residue, producing two 2-nitro-5-thiobenzoate (TNB2-) ions, one of which is released into the medium. While in solution, the thiol concentration was determined by the absorbance of the released TNB2-, on the surface, the mass of the attached TNB2- ion to the protein allowed the quantification by means of the multiparametric surface plasmon resonance (MP-SPR) technique. The SPR angle change after the interaction of DTNB with immobilized CFL-1 gave a surface coverage of 26.5 pmol cm-2 for the TNB2- ions (ΓTNB2-). The ratio of this value to the surface coverage of CFL-1, ΓCFL-1 = 6.5 ± 0.6 pmol cm-2 (also determined by MP-SPR), gave 4.1 as expected for this protein, i.e., CFL-1 contains four Cys residues in its native form (reduced state). A control experiment with adsorbed oxidized protein showed no SPR angle change, thus proving the reliability of adapting Ellman's assay to the surface using the MP-SPR technique. The results presented in this work provide evidence of the heterogenization of Ellman's assay, offering a novel perspective for studying thiol-containing species within proteins. This may be particularly useful to ensure further studies on drug-like molecules that can be carried out with validated oxidized or reduced CFL-1 or other analogous systems.

Minimal Functionalization of Ruthenium Compounds with Enhanced Photoreactivity against Hard-to-Treat Cancer Cells and Resistant Bacteria.

Metallocompounds have emerged as promising new anticancer agents, which can also exhibit properties to be used in photodynamic therapy. Here, we prepared two ruthenium-based compounds with a 2,2'-bipyridine ligand conjugated to an anthracenyl moiety. These compounds coded GRBA and GRPA contain 2,2'-bipyridine or 1,10-phenathroline as auxiliary ligands, respectively, which provide quite a distinct behavior. Notably, compound GRPA exhibited remarkably high photoproduction of singlet oxygen even in water (Ï•Δ = 0.96), almost twice that of GRBA (Ï•Δ = 0.52). On the other hand, this latter produced twice more superoxide and hydroxyl radical species than GRPA, which may be due to the modulation of their excited state. Interestingly, GRPA exhibited a modest binding to DNA (Kb = 4.51 × 104), while GRBA did not show a measurable interaction only noticed by circular dichroism measurements. Studies with bacteria showed a great antimicrobial effect, including a synergistic effect in combination with commercial antibiotics. Besides that, GRBA showed very low or no cytotoxicity against four mammalian cells, including a hard-to-treat MDA-MB-231, triple-negative human breast cancer. Potent activities were measured for GRBA upon blue light irradiation, where IC50 of 43 and 13 nmol L-1 were seen against hard-to-treat triple-negative human breast cancer (MDA-MB-231) and ovarian cancer cells (A2780), respectively. These promising results are an interesting case of a simple modification with expressive enhancement of biological activity that deserves further biological studies.

Equal rates of bone healing and reduced surgical time with iliac crest allograft compared to autograft in medial opening wedge high tibial osteotomy: a randomized controlled clinical trial.

INTRODUCTION: Iliac crest autograft is frequently used to fill in bone defects after osteotomies. Nonetheless, surgery for bone autograft procurement is associated with morbidity and pain at the donor site. Alternatives to it have been explored, but there is no consensus to guide their application as a routine practice in several orthopedic procedures. Thus, this study was designed to compare the efficacy and safety between iliac crest autograft and allograft in medial opening wedge high tibial osteotomy. MATERIALS AND METHODS: Forty-seven patients with a symptomatic unilateral genu varum and an indication for high tibial osteotomy were randomly assigned to receive either autograft or allograft to fill the osteotomy site. Operative time, bone healing, and complication rates (delayed union, nonunion, superficial and deep infection, loss of correction, and hardware failure) were recorded after a one-year follow-up. Data were expressed as Mean ± Standard Deviation and considered statistically significant when p < 0.05. RESULTS: The time to radiologic union was similar between both groups (Allograft: 2.38 ± 0.97 months vs. Autograft: 2.45 ± 0.91 months; p = 0.79). Complication rates were also similar in both groups, with one infection in the allograft group and two in the autograft group, two delayed unions in the allograft group, and three in the autograft group. The operative time differed by 11 min between the groups, being lower in the allograft group (Allograft: 65.4 ± 15.1 min vs. Autograft: 76.3 ± 15.2 min; p = 0.02). CONCLUSION: Iliac crest allografts can be safely and effectively used in medial opening wedge high tibial osteotomy as it promotes the same rates of bone union as those achieved by autologous grafts, with the benefits of a shorter operative time. TRIAL REGISTRATION NUMBER: U1111-1280-0637 1 December 2022, retrospectively registered.

The Role of Cell Cycle Arrest Biomarkers for Predicting Acute Kidney Injury in Critically Ill COVID-19 Patients: A Multicenter, Observational Study.

OBJECTIVES: Patients with COVID-19-associated acute respiratory distress syndrome (ARDS) have a high risk for developing acute kidney injury (AKI) which is associated with an increased risk of death and persistent renal failure. Early prediction of AKI is crucial in order to implement preventive strategies. The purpose of this study was to investigate the predictive performance of tissue inhibitor of metalloproteinases 2 and insulin like growth factor binding protein 7 (TIMP-2) × (IGFBP7) in critically ill patients with COVID-19-associated ARDS. DESIGN: Multicenter, prospective, observational study. SETTING: Twelve centers across Europe and United Kingdom. PATIENTS: Patients with moderate or severe COVID-19-associated ARDS were included and serial measurements of (TIMP-2) × (IGFBP7) were performed. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary endpoint was the development of moderate or severe AKI according to the Kidney Disease: Improving Global Outcomes definition. Three hundred patients were available for the primary analysis, and 39 met the primary endpoint. At enrollment, urinary (TIMP-2) × (IGFBP7) had high predictive value for the primary endpoint with an area under the receiver operating characteristic curve of 0.89 (95% CI, 0.84-0.93). (TIMP-2) × (IGFBP7) was significantly higher in endpoint-positive patients at enrollment and at 12 hours. CONCLUSIONS: Urinary (TIMP-2) × (IGFBP7) predicts the occurrence of AKI in critically ill patients with COVID-19-associated ARDS.

Antimicrobial effect of quercetin against Streptococcus pneumoniae.

Streptococcus pneumoniae is a bacterium that causes serious infections, including pneumonia. The limited range of available vaccines and the rise of antibiotic-resistant bacteria mean that new treatments are needed. This study looked at the potential of quercetin as an antimicrobial agent against S. pneumoniae in both isolation and in biofilms. The researchers used microdilution tests, checkerboard assays, and death curve assays, as well as in silico and in vitro cytotoxicity evaluations. They found that quercetin at a concentration of 125.0 µg/mL had both inhibitory and bactericidal effects against S. pneumoniae, and these effects were increased when quercetin was combined with ampicillin. Quercetin also reduced the growth of pneumococcal biofilms. In addition, quercetin (absence or in combination with ampicillin) reduced the death time of Tenebrio molitor larvae compared to the infection control. The study also demonstrated that quercetin had low toxicity in both in silico and in vivo assays, suggesting that it could be a promising treatment for infections caused by S. pneumoniae.

Nitroprusside─Expanding the Potential Use of an Old Drug Using Nanoparticles.

For more than 70 years, sodium nitroprusside (SNP) has been used to treat severe hypertension in hospital emergency settings. During this time, a few other clinical uses have also emerged such as in the treatment of acute heart failure as well as improving mitral incompetence and in the intra- and perioperative management during heart surgery. This drug functions by releasing nitric oxide (NO), which modulates several biological processes with many potential therapeutic applications. However, this small molecule has a short lifetime, and it has been administered through the use of NO donor molecules such as SNP. On the other hand, SNP also has some setbacks such as the release of cyanide ions, high water solubility, and very fast NO release kinetics. Currently, there are many drug delivery strategies that can be applied to overcome many of these limitations, providing novel opportunities for the use of old drugs, including SNP. This Perspective describes some nitroprusside properties and highlights new potential therapeutic uses arising from the use of drug delivery systems, mainly silica-based nanoparticles. There is a series of great opportunities to further explore SNP in many medical issues as reviewed, which deserves a closer look by the scientific community.

MCL1 alternative polyadenylation is essential for cell survival and mitochondria morphology.

Alternative polyadenylation in the 3' UTR (3' UTR-APA) is a mode of gene expression regulation, fundamental for mRNA stability, translation and localization. In the immune system, it was shown that upon T cell activation, there is an increase in the relative expression of mRNA isoforms with short 3' UTRs resulting from 3' UTR-APA. However, the functional significance of 3' UTR-APA remains largely unknown. Here, we studied the physiological function of 3' UTR-APA in the regulation of Myeloid Cell Leukemia 1 (MCL1), an anti-apoptotic member of the Bcl-2 family essential for T cell survival. We found that T cells produce two MCL1 mRNA isoforms (pA1 and pA2) by 3' UTR-APA. We show that upon T cell activation, there is an increase in both the shorter pA1 mRNA isoform and MCL1 protein levels. Moreover, the less efficiently translated pA2 isoform is downregulated by miR-17, which is also more expressed upon T cell activation. Therefore, by increasing the expression of the more efficiently translated pA1 mRNA isoform, which escapes regulation by miR-17, 3' UTR-APA fine tunes MCL1 protein levels, critical for activated T cells' survival. Furthermore, using CRISPR/Cas9-edited cells, we show that depletion of either pA1 or pA2 mRNA isoforms causes severe defects in mitochondria morphology, increases apoptosis and impacts cell proliferation. Collectively, our results show that MCL1 alternative polyadenylation has a key role in the regulation of MCL1 protein levels upon T cell activation and reveal an essential function for MCL1 3' UTR-APA in cell viability and mitochondria dynamics.

Optimized Tourniquet Use in Primary Total Knee Arthroplasty: A Comparative, Prospective, and Randomized Study.

BACKGROUND: The results of recent studies investigating tourniquet (TNQ) use for knee arthroplasty are controversial. Therefore, this study aimed to compare patients undergoing total knee arthroplasty who did not have a TNQ to those in whom an optimized TNQ protocol was applied. METHODS: We prospectively evaluated 127 patients who had knee osteoarthritis who had undergone total knee arthroplasty and randomized them into two groups: "without TNQ" and "optimized TNQ" (TNQ inflation before skin incision, deflation after cementing, with pressure one hundred millimeters of mercury above the systolic blood pressure, and without articular suction drain usage). The means of surgery and TNQ duration, blood loss, number of blood transfusions, degree of pain, edema, range of motion (ROM), functional score over time, and postoperative complications were compared between the groups. Statistical significance was set at P < .05. RESULTS: No significant differences were found in terms of surgical timing, blood loss, thigh and knee pain, edema, ROM, functional scores, and complications between the "without TNQ" and "optimized TNQ" groups. CONCLUSION: The use of an optimized TNQ in primary total knee arthroplasty presents similar clinical results to surgery without a TNQ and did not increase the incidence of postoperative complications. Its use allowed surgery to occur with the benefits of a clean and dry surgical field provided by TNQ without increasing procedure-related comorbidities.

Decrease in CD8+CD45+CCR7+CD62L+ T cells in individuals vaccinated with Sinovac-CoronaVac following COVID-19 infection.

Vaccines induce antibodies, but T cell responses are also important for protection against Coronavirus disease 2019. Here, we analyzed the frequency of memory T cells in infected and/or vaccinated individuals and observed a decrease in central memory T cells in individuals who were vaccinated following COVID-19 infection.

Influence of type I collagen polymorphisms and risk of anterior cruciate ligament rupture in athletes: a case-control study.

BACKGROUND: Anterior cruciate ligament (ACL) rupture is a common and severe knee injury in sports and occurs mostly due to noncontact injuries. There is an increasing amount of evidence associating ACL rupture to single nucleotide polymorphisms (SNPs), and SNPs in the collagen type I genes can change its expression and tissue mechanical features. This study aimed to investigate the association between SNPs in COL1A1 and COL1A2 with sports-related ACL tears. METHODS: A total of 338 athletes from multiple sports modalities were analyzed: 146 were diagnosed with ACL rupture or underwent an ACL reconstruction surgery and 192 have no musculoskeletal injuries. SNPs were genotyped using validated TaqMan assays. The association of the polymorphisms with ACL rupture was evaluated by a multivariable logistic regression model, using odds ratios (OR) and 95% confidence intervals (CI). RESULTS: The age, sport modality, and training location were associated with an increased risk of a non-contact ACL tear. COL1A2 SNPs (rs42524 CC and rs2621215 GG) were associated with an increased risk of non-contact ACL injury (6 and 4-fold, respectively). However, no significant differences were detected in the distribution of COL1A1 rs1107946 and COL1A2 rs412777 SNPs between cases and controls. There was a protective association with ACL rupture (OR = 0.25; 95% CI = 0.07-0.96) between COL1A1 rs1107946 (GT or TT) and the wildtype genotypes of the three COL1A2 (rs412777, rs42524, rs2621215). COL1A2 rs42524 and rs2621215 SNPs were associated with non-contact ACL risk. CONCLUSION: The combined analysis of COL1A1-COL1A2 genotypes suggests a gene-gene interaction in ACL rupture susceptibility.

Modified Pulvertaft on Weave Technique Restores Full Active Knee Extension in Patients With Large Chronic Quadriceps Tendon Rupture: A Case Series.

PURPOSE: We aimed to investigate the clinical and functional outcomes, including maximal and explosive strength, after chronic quadriceps tendon rupture repair with Modified Pulvertaft on Weave (MPW) technique METHODS: Knee joint range of motion (ROM), patella height, thigh circumference, and Lysholm and International Knee Documentation Committee (IKDC) scores were assessed preoperatively and postoperatively. The knee extensors maximal (isokinetic peak torque and isometric maximal voluntary contraction (MVC) torque) and explosive strength-rate of torque development (RTD) early [RTD50 and RTD100] and late [RTD250]-were performed. We assessed the thigh circumference and vastus lateralis muscle thickness (MT) as indicators of quadriceps muscle mass, and the voluntary quadriceps activation using surface electromyography (EMG50). RESULTS: Nine patients (mean age: 53 ± 11 years) took part in the study. We observed a significant increase in the knee active ROM and a decreased extension deficit (both, P < .001), but not for pain (P = .07), IKDC (P = .07), and Lysholm (P = .21) after the surgery. We did not observe a difference between involved (n = 8) and uninvolved (n = 10) limbs for ROM, thigh circumference, and MT. We observed differences for extensors peak torque, MVC torque, and late RTD (all, P < .05). However, we did not observe differences for early RTD and EMG50. Significant positive correlations were observed for RTD50 (ρ = .80) and RTD100 (ρ = .81) vs EMG50. Both the IKDC and Lysholm were better correlated with the early than with later RTD. CONCLUSIONS: The MPW reestablished the active knee extension. The same level of quadriceps muscle mass was observed in both limbs, suggesting a lack of hypotrophy due to the injury. Although the involved limb had demonstrated lower knee extensors maximal strength, they demonstrate an equivalent early RTD when compared to the uninvolved limb. The early RTD seems to be better correlated with the patient's functionality than the later RTD and maximal strength. LEVEL OF EVIDENCE: IV, case series.

Investigation of Chloroquine Resinate Feasibility and In Vitro Taste Masking Evaluation for Pediatric Formulations.

In this study, chloroquine resinates were prepared at a 1:1 (w:w) drug-to-resin ratio using the batch method with polacrilex (PC), sodium polystyrene sulfonate (SPS), and polacrilin potassium (PP) ion exchange resins (IER). The influence of drug/resin ratio and pH of the medium on drug loading efficiency was explored. UV-VIS spectrophotometric analysis showed that SPS resin had high loading efficiency for chloroquine diphosphate (CLP), above 89%, regardless of the pH. PP resin was more effective at pH 5.0 (90.68%) than at pH 1.0 (2.09%), and PC resin had only 27.63% of CLP loading efficiency. CLP complexation with IER yielded amorphous mixtures according to results from differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD), thus indicating drug-resin interaction. The taste masking efficiency was evaluated with in vitro methods using an adapted dissolution test and an electronic tongue system. During dissolution tests, SPS released only 1.0% of CLP after 300 s, while PP released over 10% after 90 s in simulated saliva solution. The electronic tongue distinguished the samples containing CLP, resins, and resinates by using multidimensional projection techniques that indicated an effective drug taste masking. In an accelerated stability study, the drug contents did not decrease in chloroquine resinates, and there was no physical degradation of the resinates after 60 days. Using chloroquine resinates therefore represents a novel way to evaluate taste masking in vitro which is relevant for the early formulation development process.

Further Insights into the Oxidative Pathway of Thiocarbonyl-Type Antitubercular Prodrugs: Ethionamide, Thioacetazone, and Isoxyl.

A chemical activation study of the thiocarbonyl-type antitubercular prodrugs, ethionamide (ETH), thioacetazone (TAZ), and isoxyl (ISO), was performed. Biomimetic oxidation of ethionamide using H2O2 (1 equiv) led to ETH-SO as the only stable S-oxide compound, which was found to occur in solution in the preferential form of a sulfine (ETH═S═O vs the sulfenic acid tautomer ETH-S-OH), as previously observed in the crystal state. It was also demonstrated that ETH-SO is capable of reacting with amines, as the putative sulfinic derivative (ETH-SO2H) was supposed to do. Unlike ETH, oxidation of TAZ did not allow observation of the mono-oxygenated species (TAZ-SO), leading directly to the more stable sulfinic acid derivative (TAZ-SO2H), which can then lose a SOxH group after further oxidation or when placed in a basic medium. It was also noticed that the unstable TAZ-SO intermediate can lead to the carbodiimide derivative as another electrophilic species. It is suggested that TAZ-SOH, TAZ-SO2H, and the carbodiimide compound can also react with NH2-containing nucleophilic species, and therefore be involved in toxic effects. Finally, ISO showed a very complex reactivity, here assigned to the coexistence of two mono-oxygenated structures, the sulfine and sulfenic acid tautomers. The mono- and dioxygenated derivatives of ISO are also highly unstable, leading to a panel of multiple metabolites, which are still reactive and likely contribute to the toxicity of this prodrug.

QUAREP-LiMi: A community-driven initiative to establish guidelines for quality assessment and reproducibility for instruments and images in light microscopy.

A modern day light microscope has evolved from a tool devoted to making primarily empirical observations to what is now a sophisticated , quantitative device that is an integral part of both physical and life science research. Nowadays, microscopes are found in nearly every experimental laboratory. However, despite their prevalent use in capturing and quantifying scientific phenomena, neither a thorough understanding of the principles underlying quantitative imaging techniques nor appropriate knowledge of how to calibrate, operate and maintain microscopes can be taken for granted. This is clearly demonstrated by the well-documented and widespread difficulties that are routinely encountered in evaluating acquired data and reproducing scientific experiments. Indeed, studies have shown that more than 70% of researchers have tried and failed to repeat another scientist's experiments, while more than half have even failed to reproduce their own experiments. One factor behind the reproducibility crisis of experiments published in scientific journals is the frequent underreporting of imaging methods caused by a lack of awareness and/or a lack of knowledge of the applied technique. Whereas quality control procedures for some methods used in biomedical research, such as genomics (e.g. DNA sequencing, RNA-seq) or cytometry, have been introduced (e.g. ENCODE), this issue has not been tackled for optical microscopy instrumentation and images. Although many calibration standards and protocols have been published, there is a lack of awareness and agreement on common standards and guidelines for quality assessment and reproducibility. In April 2020, the QUality Assessment and REProducibility for instruments and images in Light Microscopy (QUAREP-LiMi) initiative was formed. This initiative comprises imaging scientists from academia and industry who share a common interest in achieving a better understanding of the performance and limitations of microscopes and improved quality control (QC) in light microscopy. The ultimate goal of the QUAREP-LiMi initiative is to establish a set of common QC standards, guidelines, metadata models and tools, including detailed protocols, with the ultimate aim of improving reproducible advances in scientific research. This White Paper (1) summarizes the major obstacles identified in the field that motivated the launch of the QUAREP-LiMi initiative; (2) identifies the urgent need to address these obstacles in a grassroots manner, through a community of stakeholders including, researchers, imaging scientists, bioimage analysts, bioimage informatics developers, corporate partners, funding agencies, standards organizations, scientific publishers and observers of such; (3) outlines the current actions of the QUAREP-LiMi initiative and (4) proposes future steps that can be taken to improve the dissemination and acceptance of the proposed guidelines to manage QC. To summarize, the principal goal of the QUAREP-LiMi initiative is to improve the overall quality and reproducibility of light microscope image data by introducing broadly accepted standard practices and accurately captured image data metrics.

Potential therapeutic approaches for a sleeping pathogen: tuberculosis a case for bioinorganic chemistry.

Mycobacterium tuberculosis (Mtb) has an old history as a human pathogen and still kills over one million people every year. One key feature of this bacterium is its dormancy: a phenomenon responsible for major changes in its metabolism and replication that have been associated with the need for a lengthy therapy for Mtb. This process is regulated by key heme-based sensors, particularly DosT and DevS (DosS), among other co-regulators, and also linked to nitrogen utilization (nitrate/nitrite) and stringent responses. In face of the current threat of tuberculosis, there is an urgent need to develop new therapeutic agents capable of targeting the dormant state, associated with the need for a lengthy therapy. Interestingly, many of those key proteins are indeed metallo-containing or metallo-dependent biomolecules, opening exciting bioinorganic opportunities. Here, we critically reviewed a series of small molecules targeting key proteins involved in these processes, including DosT/DevS/DevR, RegX3, MprA, MtrA, NarL, PknB, Rel, PPK, nitrate and nitrite reductases, GlnA1, aiming for new opportunities and alternative therapies. In the battle against Mycobacterium tuberculosis, new drug targets must be searched, in particular  those involved in dormancy. A series of exciting cases for drug development involving metallo-containing or metallo-dependent biomolecules are reviewed, opening great opportunities for the bioinorganic chemistry community.

Pentacyanoferrate(II) complex of pyridine-4- and pyrazine-2-hydroxamic acid as source of HNO: investigation of anti-tubercular and vasodilation activities.

A pharmacophore design approach, based on the coordination chemistry of an intimate molecular hybrid of active metabolites of pro-drugs, known to release active species upon enzymatic oxidative activation, is devised. This is exemplified by combining two anti-mycobacterial drugs: pyrazinamide (first line) and delamanid (third line) whose active metabolites are pyrazinoic acid (PyzCOOH) and likely nitroxyl (HNO (or NO.)), respectively. Aiming to generate those active species, a hybrid compound was envisaged by coordination of pyrazine-2-hydroxamic acid (PyzCONHOH) with a Na3[FeII(CN)5] moiety. The corresponding pentacyanoferrate(II) complex Na4[FeII(CN)5(PyzCONHO-)] was synthesized and characterized by several spectroscopic techniques, cyclic voltammetry, and DFT calculations. Chemical oxidation of this complex with H2O2 was shown to induce the release of the metabolite PyzCOOH, without the need of the Mycobacterium tuberculosis (Mtb) pyrazinamidase enzyme (PncA). Control experiments show that both H2O2- and N-coordinated pyrazine FeII species are required, ruling out a direct hydrolysis of the hydroxamic acid or an alternative oxidative route through chelation of a metal center by a hydroxamic group. The release of HNO was observed using EPR spectroscopy in the presence of a spin trapping agent. The devised iron metal complex of pyrazine-2-hydroxamic acid was found inactive against an actively growing/non-resistant Mtb strain; however, it showed a strong dose-dependent and reversible vasodilatory activity with mostly lesser toxic effects than the reference drug sodium nitroprussiate, unveiling thus a potential indication for acute or chronic cardiovascular pathology. This is a priori a further indirect evidence of HNO release from this metal complex, standing as a possible pharmacophore model for an alternative vasodilator drug.