Nitroreduction: A Critical Metabolic Pathway for Drugs, Environmental Pollutants, and Explosives

Nitro-PAHs: Occurrences, ecological consequences, and remediation strategies for environmental restoration

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are persistent pollutants that have been introduced into the environment as a result of human activities. They are produced when PAHs undergo oxidation and are highly resistant to degradation, resulting in prolonged exposure and significant health risks for wildlife and humans. Nitro-PAHs' potential to induce cancer and mutations has raised concerns about their harmful effects. Furthermore, their ability to accumulate in the food chain seriously threatens the ecosystem and human health. Moreover, nitro-PAHs can disrupt the normal functioning of the endocrine system, leading to reproductive and developmental problems in humans and other organisms. Reducing nitro-PAHs in the environment through source management, physical removal, and chemical treatment is essential to mitigate the associated environmental and human health risks. Recent studies have focused on improving nitro-PAHs' phytoremediation by incorporating microorganisms and biostimulants. Microbes can break down nitro-PAHs into less harmful substances, while biostimulants can enhance plant growth and metabolic activity. By combining these elements, the effectiveness of phytoremediation for nitro-PAHs can be increased. This study aimed to investigate the impact of introducing microbial and biostimulant agents on the phytoremediation process for nitro-PAHs and identify potential solutions for addressing the environmental risks associated with these pollutants.

Protein Tyrosine Amination: Detection, Imaging, and Chemoproteomic Profiling with Synthetic Probes

Protein tyrosine nitration (PTN) by oxidative and nitrative stress is a well-known post-translational modification that plays a role in the initiation and progression of various diseases. Despite being recognized as a stable modification for decades, recent studies have suggested the existence of a reduction in PTN, leading to the formation of 3-aminotyrosine (3AT) and potential denitration processes. However, the vital functions of 3AT-containing proteins are still unclear due to the lack of selective probes that directly target the protein tyrosine amination. Here, we report a novel approach to label and enrich 3AT-containing proteins with synthetic salicylaldehyde (SAL)-based probes: SALc-FL with a fluorophore and SALc-Yn with an alkyne tag. These probes exhibit high selectivity and efficiency in labeling and can be used in cell lysates and live cells. More importantly, SALc-Yn offers versatility when integrated into multiple platforms by enabling proteome-wide quantitative profiling of cell nitration dynamics. Using SALc-Yn, 355 proteins were labeled, enriched, and identified to carry the 3AT modification in oxidatively stressed RAW264.7 cells. These findings provide compelling evidence supporting the involvement of 3AT as a critical intermediate in nitrated protein turnover. Moreover, our probes serve as powerful tools to investigate protein nitration and denitration processes, and the identification of 3AT-containing proteins contributes to our understanding of PTN dynamics and its implications in cellular redox biology.

A Multifunctional CaII-EuIII Heterometallic Organic Framework with Sensing and Selective Adsorption in Water

With increasing global industrialization, it is urgent and challenging to develop multifunctional species for detection and adsorption in the environment. For this purpose, a novel anionic heterometallic organic framework, [(CH3)2NH2][CaEu(CAM)2(H2O)2]·4H2O·4DMF (CaEuCAM), is hydrothermally synthesized based on chelidamic acid (H3CAM). Single crystal analysis shows that CaEuCAM features two different oxygen-rich channels along the c-axis in which one CAM3- bridges two sextuple-coordinated Ca2+ and two octuple-coordinated Eu3+ with a μ4-η1: η1: η1: η1: η1: η1 new chelating and bridging mode. The characteristic bright red emission and superior hydrostability of CaEuCAM under harsh acidic and basic conditions benefit it by acting as a highly sensitive sensor for Fe3+ and 3-nitrophenol (3-NP) with extremely low LODs through remarkable quenching. The combination of experiments and theoretical calculations for sensing mechanisms shows that the competitive absorption and interaction are responsible for Fe3+-induced selective emission quenching, while that for 3-NP is the result of the synergism of host-guest chemistry and the inner filter effect. Meanwhile, the assimilation of negative charge plus channels renders CaEuCAM a highly selective adsorbent for methylene blue (MB) due to a synergy of electrostatic affinity, ion-dipole interaction, and size matching. Of note is the reusability of CaEuCAM toward Fe3+/3-NP sensing and MB adsorption besides its fast response. These findings could be very useful in guiding the development of multifunctional Ln-MOFs for sensing and adsorption applications in water media.

Real-time fluorescent monitoring of phase I xenobiotic-metabolizing enzymes

This article explores the intricate landscape of advanced fluorescent probes crafted for the detection and real-time monitoring of phase I xenobiotic-metabolizing enzymes. Employing state-of-the-art technologies, such as fluorescence resonance energy transfer, intramolecular charge transfer, and solid-state luminescence enhancement, this article unfolds a multifaceted approach to unraveling the dynamics of enzymatic processes within living systems. This encompassing study involves the development and application of a diverse range of fluorescent probes, each intricately designed with tailored mechanisms to heighten sensitivity, providing dynamic insights into phase I xenobiotic-metabolizing enzymes. Understanding the role of phase I xenobiotic-metabolizing enzymes in these pathophysiological processes, is essential for both medical research and clinical practice. This knowledge can guide the development of approaches to prevent, diagnose, and treat a broad spectrum of diseases and conditions. This adaptability underscores their potential clinical applications in cancer diagnosis and personalized medicine. Noteworthy are the trifunctional fluorogenic probes, uniquely designed not only for fluorescence-based cellular imaging but also for the isolation of cellular glycosidases. This innovative feature opens novel avenues for comprehensive studies in enzyme biology, paving the way for potential therapeutic interventions. The research accentuates the selectivity and specificity of the probes, showcasing their proficiency in distinguishing various enzymes and their isoforms. The sophisticated design and successful deployment of these fluorescent probes mark significant advancements in enzymology, providing powerful tools for both researchers and clinicians. Beyond their immediate applications, these probes offer illuminating insights into disease mechanisms, facilitating early detection, and catalyzing the development of targeted therapeutic interventions. This work represents a substantial leap forward in the field, promising transformative implications for understanding and addressing complex biological processes. In essence, this research heralds a new era in the development of fluorescent probes, presenting a comprehensive and innovative approach that not only expands the understanding of cellular enzyme activities but also holds great promise for practical applications in clinical settings and therapeutic endeavors.

Recent developments and prospects of sustainable remediation treatments for major contaminants in soil: A review

Rapid industrialisation and urbanisation are contributing to the entry of emerging contaminants into the environment, posing a significant threat to soil health and quality. Therefore, several remediation technologies have been investigated and tested at a field scale to address the issue. However, these remediation technologies face challenges related to cost-effectiveness, environmental concerns, secondary pollution due to the generation of by-products, long-term pollution leaching risks, and social acceptance. Overcoming these constraints necessitates the implementation of sustainable remediation methodologies that prioritise approaches with minimal environmental ramifications and the most substantial net social and economic advantages. Hence, this review delves into diverse contaminants that threaten soil health and quality. Moreover, it outlines the research imperatives for advancing innovative remediation techniques and effective management strategies to tackle this concern. The review discusses a remediation treatment train approach that encourages resource recovery, strengthens the circular economy, and employs a Life Cycle Assessment (LCA) framework to assess the environmental impacts of different remediation strategies. Additionally, the study explores mechanisms to integrate sustainability principles into soil remediation practices. It underscores the necessity for a comprehensive and systematic approach that takes into account the economic, social, and environmental consequences of remediation methodologies in the development of sustainable solutions.

Differential DNA damage response and cell fate in human lung cells after exposure to genotoxic compounds

DNA damage can impair normal cellular functions and result in various pathophysiological processes including cardiovascular diseases and cancer. We compared the genotoxic potential of diverse DNA damaging agents, and focused on their effects on the DNA damage response (DDR) and cell fate in human lung cells BEAS-2B. Polycyclic aromatic hydrocarbons [PAHs; benzo[a]pyrene (B[a]P), 1-nitropyrene (1-NP)] induced DNA strand breaks and oxidative damage to DNA; anticancer drugs doxorubicin (DOX) and 5-bromo-2'-deoxyuridine (BrdU) were less effective. DOX triggered the most robust p53 signaling indicating activation of DDR, followed by cell cycle arrest in the G2/M phase, induction of apoptosis and senescence, possibly due to the severe and irreparable DNA lesions. BrdU not only activated p53, but also increased the percentage of G1-phased cells and caused a massive accumulation of senescent cells. In contrast, regardless the activation of p53, both PAHs did not substantially affect the cell cycle distribution or senescence. Finally, a small fraction of cells accumulated only in the G2/M phase and exhibited increased cell death after the prolonged incubation with B[a]P. Overall, we characterized differential responses to diverse DNA damaging agents resulting in specific cell fate and highlighted the key role of DNA lesion type and the p53 signaling persistence.

Investigation of the cytotoxicity, genotoxicity and antioxidant prospects of JM-20 on human blood cells: A multi-target compound with potential therapeutic applications

JM-20 is a 1,5-benzodiazepine compound fused to a dihydropyridine fraction with different pharmacological properties. However, its potential toxic effects on blood cells have not yet been reported. Thus, the present study aimed to investigate, for the first time, the possible cytotoxicity of JM-20 through cell viability, cell cycle, morphology changes, reactive species (RS) to DCFH-DA, and lipid peroxidation in human leukocytes, its hemolytic effect on human erythrocytes, and its potential DNA genotoxicity using plasmid DNA in vitro. Furthermore, the compound's ability to reduce the DPPH radical was also measured. Human blood was obtained from healthy volunteers (30 ± 10 years old), and the leukocytes or erythrocytes were immediately isolated and treated with different concentrations of JM-20. A cytoprotective effect was exhibited by 10 μM JM-20 against 1 mM tert-butyl hydroperoxide (t-but-OOH) in the leukocytes. However, the highest tested concentrations of the compound (20 and 50 μM) changed the morphology and caused a significant decrease in the cell viability of leukocytes (p < 0.05, in comparison with Control). All tested concentrations of JM-20 also resulted in a significant increase in intracellular RS as measured by DCFH-DA in these cells (p < 0.05, in comparison with Control). On the other hand, the results point out a potent antioxidant effect of JM-20, which was similar to the classical antioxidant α-tocopherol. The IC50 value of JM-20 against the lipid peroxidation induced by (FeII) was 1.051 μM ± 0.21, while the IC50 value of α-tocopherol in this parameter was 1.065 μM ± 0.34. Additionally, 50 and 100 μM JM-20 reduced the DPPH radical in a statistically similar way to the 100 μM α-tocopherol (p < 0.05, in comparison with the control). No significant hemolysis in erythrocytes, no cell cycle changes in leukocytes, and no genotoxic effects in plasmid DNA were induced by JM-20 at any tested concentration. The in silico pharmacokinetic and toxicological properties of JM-20, derivatives, and nifedipine were also studied. Here, our findings demonstrate that JM-20 and its putative metabolites exhibit similar characteristics to nifedipine, and the in vitro and in silico data support the low toxicity of JM-20 to mammals.

Electrochemistry/mass spectrometry (EC/MS) for fast generation and identification of novel reactive metabolites of two unsymmetrical bisacridines with anticancer activity

The development of a new drug requires knowledge about its metabolic fate in a living organism, regarding the comprehensive assessment of both drug therapeutic activity and toxicity profiles. Electrochemistry (EC) coupled with mass spectrometry (MS) is an efficient tool for predicting the phase I metabolism of redox-sensitive drugs. In particular, EC/MS represents a clear advantage for the generation of reactive drug transformation products and their direct identification compared to biological matrices. In this work, we focused on the characterization of novel electrochemical products of two representative unsymmetrical bisacridines (C-2028 and C-2045) with demonstrated high anticancer activity. The electrochemical thin-layer flow-through cell μ-PrepCell 2.0 (Antec Scientific) was used here for the effective metabolite electrosynthesis. The electrochemical simulation of C-2028 reductive and C-2045 oxidative metabolism resulted in the generation of new products that were not observed before. The formation of nitroso [M-O+H]+ and azoxy [2M-3O+H]+ species from C-2028, as well as a series of hydroxylated and/or dehydrogenated products, including possible quinones [M-2H+H]+ and [M+O-2H+H]+ from C-2045, was demonstrated. For the latter, a glutathione S-conjugate (m/z 935.3130) was also obtained in measurements supplemented with the excess of reduced glutathione. For the identification of the products of interest, structural confirmation based on MS/MS fragmentation experiments was performed. Novel products of electrochemical conversions of unsymmetrical bisacridines were discussed in the context of their possible biological effect on the human organism.

A Systematic Review of Polycyclic Aromatic Hydrocarbon Derivatives: Occurrences, Levels, Biotransformation, Exposure Biomarkers, and Toxicity

Polycyclic aromatic hydrocarbon (PAH) derivatives constitute a significant class of emerging contaminants that have been ubiquitously detected in diverse environmental matrixes, with some even exhibiting higher toxicities than their corresponding parent PAHs. To date, compared with parent PAHs, fewer systematic summaries and reanalyses are available for PAH derivatives with great environmental concerns. This review summarizes the current knowledge on the chemical species, levels, biotransformation patterns, chemical analytical methods, internal exposure routes with representative biomarkers, and toxicity of PAH derivatives, primarily focusing on nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs), halogenated PAHs (XPAHs), and alkylated PAHs (APAHs). A collection of 188 compounds from four categories, 44 NPAHs, 36 OPAHs, 56 APAHs, and 52 XPAHs, has been compiled from 114 studies that documented the environmental presence of PAH derivatives. These compounds exhibited weighted average air concentrations that varied from a lower limit of 0.019 pg/m3 to a higher threshold of 4060 pg/m3. Different analytical methods utilizing comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC × GC-TOF-MS), gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS), comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry (GC × GC-QQQ-MS), and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), that adopted untargeted strategies for the identification of PAH derivatives are also reviewed here. Additionally, an in-depth analysis of biotransformation patterns for each category is provided, including the likelihood of specific biotransformation reaction types. For the toxicity, we primarily summarized key metabolic activation pathways, which could result in the formation of reactive metabolites capable of covalently bonding with DNA and tissue proteins, and potential health outcomes such as carcinogenicity and genotoxicity, oxidative stress, inflammation and immunotoxicity, and developmental toxicity that might be mediated by the aryl hydrocarbon receptor (AhR). Finally, we pinpoint research challenges and emphasize the need for further studies on identifying PAH derivatives, tracking external exposure levels, evaluating internal exposure levels and associated toxicity, clarifying exposure routes, and considering mixture exposure effects. This review aims to provide a broad understanding of PAH derivatives' identification, environmental occurrence, human exposure, biotransformation, and toxicity, offering a valuable reference for guiding future research in this underexplored area.

CpxA/R-Controlled Nitroreductase Expression as Target for Combinatorial Therapy against Uropathogens by Promoting Reactive Oxygen Species Generation

The antibiotic resistances emerged in uropathogens lead to accumulative treatment failure and recurrent episodes of urinary tract infection (UTI), necessitating more innovative therapeutics to curb UTI before systematic infection. In the current study, the combination of amikacin and nitrofurantoin is found to synergistically eradicate Gram-negative uropathogens in vitro and in vivo. The mechanistic analysis demonstrates that the amikacin, as an aminoglycoside, induced bacterial envelope stress by introducing mistranslated proteins, thereby constitutively activating the cpxA/R two-component system (Cpx signaling). The activation of Cpx signaling stimulates the expression of bacterial major nitroreductases (nfsA/nfsB) through soxS/marA regulons. As a result, the CpxA/R-dependent nitroreductases overexpression generates considerable quantity of lethal reactive intermediates via nitroreduction and promotes the prodrug activation of nitrofurantoin. As such, these actions together disrupt the bacterial cellular redox balance with excessively-produced reactive oxygen species (ROS) as "Domino effect", accelerating the clearance of uropathogens. Although aminoglycosides are used as proof-of-principle to elucidate the mechanism, the synergy between nitrofurantoin is generally applicable to other Cpx stimuli. To summarize, this study highlights the potential of aminoglycoside-nitrofurantoin combination to replenish the arsenal against recurrent Gram-negative uropathogens and shed light on the Cpx signaling-controlled nitroreductase as a potential target to manipulate the antibiotic susceptibility.

Genetic and Epigenetic Basis of Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a rare but severe adverse drug reaction seen in pharmacotherapy and a major cause of postmarketing drug withdrawals. Advances in genome-wide studies indicate that genetic and epigenetic diversity can lead to inter-individual differences in drug response and toxicity. It is necessary to identify how the genetic variations, in the presence of environmental factors, can contribute to development and progression of DILI. Studies on microRNA, histone modification, DNA methylation, and single nucleotide polymorphisms related to DILI were retrieved from databases and were analyzed for the current research and updated to develop this narrative review. We have compiled some of the major genetic, epigenetic, and pharmacogenetic factors leading to DILI. Many validated genetic risk factors of DILI, such as variants of drug-metabolizing enzymes, HLA alleles, and some transporters were identified. In conclusion, these studies provide useful information in risk alleles identification and on implementation of personalized medicine.

Polymyxin-based fluorescent probes to combat Gram-negative antimicrobial resistance

Reliable diagnostic approaches especially those targeting critical Gram-negative bacteria are urgently needed for the prevention of antimicrobial resistance. Polymyxin B (PMB) which specifically targets the outer membrane of Gram-negative bacteria is the last-line antibiotic against life-threatening multidrug-resistant Gram-negative bacteria. However, increasing number of studies have reported the spread of PMB-resistant strains. With the aim to specifically detect Gram-negative bacteria and potentially reduce the irrational use of antibiotics, we herein rationally designed two Gram-negative bacteria specific fluorescent probes based on our previous activity-toxicity optimization of PMB. The in vitro probe PMS-Dns showed fast and selective labeling of Gram-negative pathogens in complex biological cultures. Subsequently, we constructed the caged in vivo fluorescent probe PMS-Cy-NO₂ by conjugating bacterial nitroreductase (NTR)-activatable positive charged hydrophobic near-infrared (NIR) fluorophore with polymyxin scaffold. Significantly, PMS-Cy-NO₂ exhibited excellent Gram-negative bacterial detection capability with the differentiation between Gram-positive and Gram-negative in a mouse skin infection model.

Role of Human Aldo-Keto Reductases and Nuclear Factor Erythroid 2-Related Factor 2 in the Metabolic Activation of 1-Nitropyrene via Nitroreduction in Human Lung Cells

1-Nitropyrene (1-NP) is a constituent of diesel exhaust and classified as a group 2A probable human carcinogen. The metabolic activation of 1-NP by nitroreduction generates electrophiles that can covalently bind DNA to form mutations to contribute to cancer causation. NADPH-dependent P450 oxidoreductase (POR), xanthine oxidase (XO), aldehyde oxidase (AOX), and NAD(P)H/quinone oxidoreductase 1 (NQO1) may catalyze 1-NP nitroreduction. We recently found that human recombinant aldo-keto reductases (AKRs) 1C1-1C3 catalyze 1-NP nitroreduction. NQO1 and AKR1C1-1C3 are genes induced by nuclear factor erythroid 2-related factor 2 (NRF2). Despite this knowledge, the relative importance of these enzymes and NRF2 to 1-NP nitroreduction is unknown. We used a combination of pharmacological and genetic approaches to assess the relative importance of these enzymes and NRF2 in the aerobic nitroreduction of 1-NP in human bronchial epithelial cells, A549 and HBEC3-KT. 1-NP nitroreduction was assessed by the measurement of 1-aminopyrene (1-AP), the six-electron reduced metabolite of 1-NP, based on its intrinsic fluorescence properties (λex and λem). We found that co-treatment of 1-NP with salicylic acid, an AKR1C1 inhibitor, or ursodeoxycholate, an AKR1C2 inhibitor, for 48 h decreased 1-AP production relative to 1-NP treatment alone (control) in both cell lines. R-Sulforaphane or 1-(2-cyano-3,12,28-trioxooleana-1,9(11)-dien-28-yl)-1H-imidazole (CDDO-Im), two NRF2 activators, each increased 1-AP production relative to control only in HBEC3-KT cells, which have inducible NRF2. Inhibitors of POR, NQO1, and XO failed to modify 1-AP production relative to control in both cell lines. Importantly, A549 wild-type cells with constitutively active NRF2 produced more 1-AP than A549 cells with heterozygous expression of NFE2L2/NRF2, which were able to produce more 1-AP than A549 cells with homozygous knockout of NFE2L2/NRF2. Together, these data show dependence of 1-NP metabolic activation on AKR1Cs and NRF2 in human lung cells. This is the second example whereby NFE2L2/NRF2 is implicated in the carcinogenicity of diesel exhaust constituents.

Role of Human Aldo-Keto Reductases in the Nitroreduction of 1-Nitropyrene and 1,8-Dinitropyrene

1-Nitropyrene (1-NP) and 1,8-dinitropyrene (1,8-DNP) are diesel exhaust constituents and are classified by the International Agency for Research on Cancer as probable (Group 2A) or possible (Group 2B) human carcinogens. These nitroarenes undergo metabolic activation by nitroreduction to result in the formation of DNA adducts. Human aldo-keto reductases (AKRs) 1C1-1C3 catalyze the nitroreduction of 3-nitrobenzanthrone (3-nitro-7H-benz[de]anthracen-7-one, 3-NBA), but the extent of AKR contribution toward the nitroreduction of additional nitroarenes, including 1-NP and 1,8-DNP, is currently unknown. In the present study, we investigated the ability of human recombinant AKRs to catalyze 1-NP and 1,8-DNP nitroreduction by measuring the formation of the respective six-electron reduced amine products in discontinuous ultraviolet-reverse phase high-performance liquid chromatography enzymatic assays. We found that AKR1C1-1C3 were able to catalyze the formation of 1-aminopyrene (1-AP) and 1-amino-8-nitropyrene (1,8-ANP) in our reactions with 1-NP and 1,8-DNP, respectively. We determined kinetic parameters (Km, kcat, and kcat/Km) and found that out of the three isoforms, AKR1C1 had the highest catalytic efficiency (kcat/Km) for 1-AP formation, whereas AKR1C3 had the highest catalytic efficiency for 1,8-ANP formation. Use of ultra-performance liquid chromatography high-resolution mass spectrometry verified amine product identity and provided evidence for the formation of nitroso- and hydroxylamino-intermediates in our reactions. Our study expands the role of AKR1C1-1C3, which are expressed in human lung cells, in the metabolic activation of nitroarenes that can lead to DNA adduct formation, mutation, and carcinogenesis.