Endoplasmic reticulum-targeted fluorescent probe with aggregation-induced emission features for imaging peroxynitrite in drug-induced liver injury model.

Drug-induced liver injury (DILI) poses a severe threat to public health. Endoplasmic reticulum (ER) stress contributes significantly to DILI pathogenesis, with peroxynitrite (ONOO-) identified as a pivotal indicator. However, the temporal and spatial fluctuations of ONOO- associated with ER stress in the pathogenesis of DILI remain unclear. Herein, a novel ER-specific near-infrared (NIR) probe (QM-ONOO) with aggregation-induced emission (AIE) features for monitoring ONOO- fluctuations in DILI was elaborately constructed. QM-ONOO exhibited excellent ER-targeting specificity, a large Stoke's shift, and a low detection limit (26.9 nM) toward ONOO-. QM-ONOO performed well in imaging both exogenous and endogenous ONOO- in HepG2 cells. Furthermore, molecular docking calculations validated the ER-targeting mechanism of QM-ONOO. Most importantly, using this probe allowed us to intuitively observe the dynamic fluctuations of ONOO- during the formation and remediation processes of DILI in the acetaminophen (APAP)-induced mouse model. Consequently, this work provides a promising tool for in-depth research of ONOO- associated pathological processes in DILI.

Eicosapentaenoic Acid Improves Endothelial Nitric Oxide Bioavailability Via Changes in Protein Expression During Inflammation.

BACKGROUND: Endothelial cell (EC) dysfunction involves reduced nitric oxide (NO) bioavailability due to NO synthase uncoupling linked to increased oxidation and reduced cofactor availability. Loss of endothelial function and NO bioavailability are associated with inflammation, including leukocyte activation. Eicosapentaenoic acid (EPA) administered as icosapent ethyl reduced cardiovascular events in REDUCE-IT (Reduction of Cardiovascular Events With Icosapent Ethyl-Intervention Trial) in relation to on-treatment EPA blood levels. The mechanisms of cardiovascular protection for EPA remain incompletely elucidated but likely involve direct effects on the endothelium. METHODS AND RESULTS: In this study, human ECs were treated with EPA and challenged with the cytokine IL-6 (interleukin-6). Proinflammatory responses in the ECs were confirmed by ELISA capture of sICAM-1 (soluble intercellular adhesion molecule-1) and TNF-α (tumor necrosis factor-α). Global protein expression was determined using liquid chromatography-mass spectrometry tandem mass tag. Release kinetics of NO and peroxynitrite were monitored using porphyrinic nanosensors. IL-6 challenge induced proinflammatory responses from the ECs as evidenced by increased release of sICAM-1 and TNF-α, which correlated with a loss of NO bioavailability. ECs pretreated with EPA modulated expression of 327 proteins by >1-fold (P<0.05), compared with IL-6 alone. EPA augmented expression of proteins involved in NO production, including heme oxygenase-1 and dimethylarginine dimethylaminohydrolase-1, and 34 proteins annotated as associated with neutrophil degranulation. EPA reversed the endothelial NO synthase uncoupling induced by IL-6 as evidenced by an increased [NO]/[peroxynitrite] release ratio (P<0.05). CONCLUSIONS: These direct actions of EPA on EC functions during inflammation may contribute to its distinct cardiovascular benefits.

The Ubiquity of the Reaction of the Labile Iron Pool That Attenuates Peroxynitrite-Dependent Oxidation Intracellularly.

Although the labile iron pool (LIP) biochemical identity remains a topic of debate, it serves as a universal homeostatically regulated and essential cellular iron source. The LIP plays crucial cellular roles, being the source of iron that is loaded into nascent apo-iron proteins, a process akin to protein post-translational modification, and implicated in the programmed cell death mechanism known as ferroptosis. The LIP is also recognized for its reactivity with chelators, nitric oxide, and peroxides. Our recent investigations in a macrophage cell line revealed a reaction of the LIP with the oxidant peroxynitrite. In contrast to the LIP's pro-oxidant interaction with hydrogen peroxide, this reaction is rapid and attenuates the peroxynitrite oxidative impact. In this study, we demonstrate the existence and antioxidant characteristic of the LIP and peroxynitrite reaction in various cell types. Beyond its potential role as a ubiquitous complementary or substitute protection system against peroxynitrite for cells, the LIP and peroxynitrite reaction may influence cellular iron homeostasis and ferroptosis by changing the LIP redox state and LIP binding properties and reactivity.

Dual NIR-channel fluorescent probe for detecting ONOO- in vitro and vivo.

As one of endogenous reactive oxygen species (ROS), peroxynitrite (ONOO-) performs various functions in both pathological and physiological mechanisms. In this work, an optical and near-infrared (NIR) fluorescent probe (NX), which based on 3-dihydro-1H-xanthene and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) group was designed and prepared to detect ONOO-. This probe revealed an obvious optical and a fluorescent response when ONOO- was present and it exhibited higher selectivity over other ROS. Especially, the dual NIR fluorescence changes at 660 and 800 nm allowed quantitative detection of ONOO- in the range of 15-40 µM, and the detection limit was 82 nM. Finally, the probe was effectively employed to visualize exogenous and endogenous ONOO- in HepG2 cells and zebrafish, respectively. All the results indicated the dual NIR-channel probe could serve as a potent detecting tools in studying ONOO- in vitro and in vivo.

Visulization of peroxynitrite variation for accurate diagnosis and assessing treatment response of hepatic fibrosis using a Golgi-targetable ratiometric fluorescent probe.

Hepatic fibrosis (HF) is caused by persistent inflammation, which is closely associated with hepatic oxidative stress. Peroxynitrite (ONOO-) is significantly elevated in HF, which would be regarded as a potential biomarker for the diagnosis of HF. Research has shown that ONOO- in the Golgi apparatus can be overproduced in HF, and it can induce hepatocyte injury by triggering Golgi oxidative stress. Meanwhile, the ONOO- inhibitors could effectively relieve HF by inhibiting Golgi ONOO-, but as yet, no Golgi-targetable fluorescent probe available for diagnosis and assessing treatment response of HF through sensing Golgi ONOO-. To this end, we reported a ratiometric fluorescent probe, Golgi-PER, for diagnosis and assessing treatment response of HF through monitoring the Golgi ONOO-. Golgi-PER displayed satisfactory sensitivity, low detection limit, and exceptional selectivity to ONOO-. Combined with excellent biocompatibility and good Golgi-targeting ability, Golgi-PER was further used for ratiometric monitoring the Golgi ONOO- fluctuations and screening of ONOO- inhibitors from polyphenols in living cells. Meanwhile, using Golgi-PER as a probe, the overexpression of Golgi ONOO- in HF and the treatment response of HF to the screened rosmarinic acid were precisely visualized for the first time. Furthermore, the screened RosA has a remarkable therapeutic effect on HF, which may be a new strategy for HF treatment. These results demonstrated the practicability of Golgi-PER for monitoring the occurrence, development, and personalized treatment response of HF.

Anti-Quenching NIR-II Excitation Phenylboronic Acid Modified Conjugated Polyelectrolyte for Intracellular Peroxynitrite-Enhanced Chemo-Photothermal Therapy.

Multidrug resistance to clinical chemotherapeutic drugs severely limits antitumor efficacy and patient survival. The integration of chemotherapy with photothermal therapy (PTT) and reactive nitrogen species has become a major strategy to enhance cancer treatment efficacy. Herein, a multifunctional peroxynitrite (ONOO-) nanogenerator (PBT/NO/Pt) for NIR-II fluorescence (NIR-II FL)/NIR-II photoacoustic (NIR-II PA) imaging-guided chemo/NIR-II PTT/ONOO- combination therapy is reported. The multifunction nanogenerator is developed by co-loading a pH-sensitive nitric oxide donor (DETA NONOate) and nicotinamide adenine dinucleotide phosphate oxidases trigger superoxide (O2 •-) generator chemotherapy drug (CDDP) to an NIR-II excitation-conjugated polyelectrolyte (PNC11BA). PNC11BA has non-conjugated alkyl chain segments in the polymer backbone and abundant positively charged phenylboronic acid in its side chains, which support the anti-quenching of NIR-II FL and the integration of DETA NONOate and CDDP into PBT/NO/Pt. In the acidic tumor microenvironment, the coordination bonds between CDDP and PNC11BA are cleaved, releasing CDDP for chemotherapeutic activity. The simultaneous release of nitric oxide (NO) and O2 •- rapidly leads to the in situ generation of the more cytotoxic reactive physiological nitrogen species ONOO-. In vitro and in vivo results prove that PBT/NO/Pt exhibited a markedly ONOO- enhanced chemo-photothermal synergistic therapy for SKOV3/DDP tumor by downregulating the intracellular glutathione and increasing CDDP-DNA adducts.

Peroxynitrite: a multifaceted oxidizing and nitrating metabolite.

Peroxynitrite, a short-lived and reactive oxidant, emerges from the diffusion-controlled reaction between the superoxide radical and nitric oxide. Evidence shows that peroxynitrite is a critical mediator in physiological and pathological processes such as the immune response, inflammation, cancer, neurodegeneration, vascular dysfunction, and aging. The biochemistry of peroxynitrite is multifaceted, involving one- or two-electron oxidations and nitration reactions. This minireview highlights recent findings of peroxynitrite acting as a metabolic mediator in processes ranging from oxidative killing to redox signaling. Selected examples of nitrated proteins (i.e., 3-nitrotyrosine) are surveyed to underscore the role of this post-translational modification on cell homeostasis. While accumulated evidence shows that large amounts of peroxynitrite participates of broad oxidation and nitration events in invading pathogens and host tissues, a closer look supports that low to moderate levels selectively trigger signal transduction cascades. Peroxynitrite probes and redox-based pharmacology are instrumental to further understand the biological actions of this reactive metabolite.

Apigenin Provides Structural Protection to Human Fibrinogen against Nitrosative Stress: Biochemical and Molecular Insights.

BACKGROUND: Peroxynitrite (ONOO-) is an oxidant linked with several human pathologies. Apigenin, a natural flavonoid known for its health benefits, remains unexplored in relation to ONOO- effects. This study investigated the potential of apigenin to structurally protect fibrinogen, an essential blood clotting factor, from ONOO--induced damage. METHODS: Multi-approach analyses were carried out where fibrinogen was exposed to ONOO- generation while testing the efficacy of apigenin. The role of apigenin against ONOO--induced modifications in fibrinogen was investigated using UV spectroscopy, tryptophan or tyrosine fluorescence, protein hydrophobicity, carbonylation, and electrophoretic analyses. RESULTS: The findings demonstrate that apigenin significantly inhibits ONOO--induced oxidative damage in fibrinogen. ONOO- caused reduced UV absorption, which was reversed by apigenin treatment. Moreover, ONOO- diminished tryptophan and tyrosine fluorescence, which was effectively restored by apigenin treatment. Apigenin also reduced the hydrophobicity of ONOO--damaged fibrinogen. Moreover, apigenin exhibited protective effects against ONOO--induced protein carbonylation. SDS-PAGE analyses revealed that ONOO-treatment eliminated bands corresponding to fibrinogen polypeptide chains Aα and γ, while apigenin preserved these changes. CONCLUSIONS: This study highlights, for the first time, the role of apigenin in structural protection of human fibrinogen against peroxynitrite-induced nitrosative damage. Our data indicate that apigenin offers structural protection to all three polypeptide chains (Aα, Bß, and γ) of human fibrinogen. Specifically, apigenin prevents the dislocation or breakdown of the amino acids tryptophan, tyrosine, lysine, arginine, proline, and threonine and also prevents the exposure of hydrophobic sites in fibrinogen induced by ONOO-.

A Sequentially Activated Probe for Imaging of Superoxide Anion and Peroxynitrite in PC12 Cells under Oxidative Stress.

Superoxide anion (O2·-) and peroxynitrite (ONOO-), two important oxidants under oxidative stress, coexist in complex cell and organism systems, playing crucial roles in various physiological and pathological processes, particularly in neurodegenerative diseases. Despite the absence of robust molecular tools capable of simultaneously visualizing O2·- and ONOO- in biosystems, the relationship between these two species remains understudied. Herein, we present sequentially activated fluorescent probe, DHX-SP, which exhibits exceptional selectivity and sensitivity toward O2·- and ONOO-. This probe enables precise imaging of these species in living PC12 cells under oxidative stress conditions using distinct fluorescence signal combinations. Furthermore, the probe DHX-SP has the ability to visualize changes in O2·- and ONOO- levels during ferroptosis of PC12 cells and in the Parkinson's disease model. These findings establish a connection between the crosstalk of the phosphorus group of O2·- and ONOO- in PC12 cells under oxidative stress.

Multifunctional fluorescent probe for simultaneous revealing Cys and ONOO- dynamic correlation in the ferroptosis.

Ferroptosis is a type of lipid peroxidation-induced apoptosis brought on by imbalances in iron metabolism and redox. It involves both the thiol-associated anti-ferroptosis pathway and the excessive buildup of reactive oxygen species (ROS), which stimulates the ferroptosis pathway. Determining the precise control mechanism of ferroptosis requires examining the dynamic connection between reactive sulfur species (RSS) and ROS. Cysteine (Cys) and peroxynitrite (ONOO-) are highly active redox species in organisms and play dynamic roles in the ferroptosis process. In this study, a coumarin dye was conjugated with specific response sites for Cys and ONOO-, enabling the simultaneous detection of Cys and ONOO- through the green and red fluorescence channels, respectively (λem = 498 nm for Cys and λem = 565 nm for ONOO-). Using the probe LXB, we monitored the changes in Cys and ONOO- levels in the ferroptosis pathway induced by erastin. The results demonstrate a significant generation of ONOO- and a noticeable decrease in intracellular Cys levels at the beginning upon erastin treatment and finally maintains a relatively low level. This study presents the first probe to investigate the intracellular redox modulation and control between Cys and ONOO- during ferroptosis, providing valuable insights into the potential mutual correlation between Cys and ONOO- in this process.

Simultaneous Visualization and Depletion of Peroxynitrite by a Simple Aggregation-Induced Emission Nanoprobe for Preventing Breast Cancer Metastasis after Surgery.

Inflammation has been confirmed to be closely related to the development of tumors, while peroxynitrite (ONOO-) is one of the most powerful oxidative pro-inflammatory factors. Although ONOO- can kill bacteria through oxidation, it will activate matrix metalloproteinases (MMPs), accelerate the degradation of the extracellular matrix (ECM), and subsequently lead to the activation and release of other tumor promotion factors existing in the ECM, promoting tumor metastasis and invasion. Herein, we report a simple aggregation-induced emission (AIE) nanoprobe (NP), TPE-4NMB, that can simultaneously visualize and deplete ONOO-. The probe can light up the endogenous and exogenous ONOO- in cells and selectively inhibit the proliferation and migration of 4T1 cells by inducing an intracellular redox homeostasis imbalance through ONOO- depletion. After being modified with DSPE-PEG2000, the TPE-4NMB NPs can be used to image ONOO- induced by various models in vivo; especially, it can monitor the dynamic changes of ONOO- level in the residual tumor after surgery, which can provide evidence for clarifying the association between surgery, ONOO-, and cancer metastasis. Excitingly, inhibited tumor volume growth and decreased counts of lung metastases were observed in the TPE-4NMB NPs group, which can be attributed to the downregulated expression of MMP-9 and transforming growth factor-ß (TGF-ß), increased cell apoptosis, and inhibited epithelial-mesenchymal transition (EMT) mediated by ONOO-. The results will provide new evidence for clarifying the relationship between surgery, ONOO-, and tumor metastasis and serve as a new intervention strategy for preventing tumor metastasis after tumor resection.

A highly sensitive and selective chemiluminescent probe for peroxynitrite detection in vitro, in vivo and in human liver cancer tissue.

Peroxynitrite (ONOO-) is one of the important active nitrogen/reactive oxygen species that plays various roles in biological processes, such as inducing apoptosis and necrosis. Recent studies have shown that a significant increases in ONOO- content during tumor development, which is closely related to the level of oxidative stress within the tumor. It has been found that herbicide paraquat (PQ) can significantly increase the level of ONOO- in cells. Therefore, accurate monitoring abnormal changes in ONOO- caused by environmental hazardous materials and tumors is helpful in promoting the diagnosis and treatment of oxidative stress diseases (tumors), evenly environmental detection. Currently, traditional fluorescent probes for ONOO- detection have background interference. To address this, we developed a chemiluminescent probe (CL-1) and a fluorescent probe (Flu-1), using diphenyl phosphonate as a recognition group. CL-1 shows extremely sensitivity (9.8 nM), a high signal-to-noise(S/N) ratio (502), and excellent bioimaging capabilities compared to fluorescent probe (Flu-1). We have successfully used CL-1 to detect ONOO- produced by PQ stimulated cells, as well as endogenous ONOO- in tumor cells, mice, and human liver cancer tissues. Therefore, CL-1 can not only be a valuable tool for visualizing tumor and studying the role of ONOO- in tumor pathology, but the probe has the potential to be a powerful molecular imaging tool for exploring the complex biological role of ONOO- in a variety of biological Settings.

Several lines of antioxidant defense against oxidative stress: antioxidant enzymes, nanomaterials with multiple enzyme-mimicking activities, and low-molecular-weight antioxidants.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well recognized for playing a dual role, since they can be either deleterious or beneficial to biological systems. An imbalance between ROS production and elimination is termed oxidative stress, a critical factor and common denominator of many chronic diseases such as cancer, cardiovascular diseases, metabolic diseases, neurological disorders (Alzheimer's and Parkinson's diseases), and other disorders. To counteract the harmful effects of ROS, organisms have evolved a complex, three-line antioxidant defense system. The first-line defense mechanism is the most efficient and involves antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). This line of defense plays an irreplaceable role in the dismutation of superoxide radicals (O2•-) and hydrogen peroxide (H2O2). The removal of superoxide radicals by SOD prevents the formation of the much more damaging peroxynitrite ONOO- (O2•- + NO• → ONOO-) and maintains the physiologically relevant level of nitric oxide (NO•), an important molecule in neurotransmission, inflammation, and vasodilation. The second-line antioxidant defense pathway involves exogenous diet-derived small-molecule antioxidants. The third-line antioxidant defense is ensured by the repair or removal of oxidized proteins and other biomolecules by a variety of enzyme systems. This review briefly discusses the endogenous (mitochondria, NADPH, xanthine oxidase (XO), Fenton reaction) and exogenous (e.g., smoking, radiation, drugs, pollution) sources of ROS (superoxide radical, hydrogen peroxide, hydroxyl radical, peroxyl radical, hypochlorous acid, peroxynitrite). Attention has been given to the first-line antioxidant defense system provided by SOD, CAT, and GPx. The chemical and molecular mechanisms of antioxidant enzymes, enzyme-related diseases (cancer, cardiovascular, lung, metabolic, and neurological diseases), and the role of enzymes (e.g., GPx4) in cellular processes such as ferroptosis are discussed. Potential therapeutic applications of enzyme mimics and recent progress in metal-based (copper, iron, cobalt, molybdenum, cerium) and nonmetal (carbon)-based nanomaterials with enzyme-like activities (nanozymes) are also discussed. Moreover, attention has been given to the mechanisms of action of low-molecular-weight antioxidants (vitamin C (ascorbate), vitamin E (alpha-tocopherol), carotenoids (e.g., ß-carotene, lycopene, lutein), flavonoids (e.g., quercetin, anthocyanins, epicatechin), and glutathione (GSH)), the activation of transcription factors such as Nrf2, and the protection against chronic diseases. Given that there is a discrepancy between preclinical and clinical studies, approaches that may result in greater pharmacological and clinical success of low-molecular-weight antioxidant therapies are also subject to discussion.

Shedding light on ONOO- detection: the emergence of a fast-response fluorescent probe for biological systems.

ONOO-, a bioactive molecule, plays a critical role in inflammation-related signaling pathways and pathological mechanisms. Numerous studies have established a direct correlation between elevated ONOO- levels and tumor progression. Therefore, investigating ONOO- levels in inflammation and tumors is of utmost importance. Fluorescence imaging presents a highly sensitive, non-invasive, easily operable, selective, and efficient method for ONOO- detection in situ. In this study, we designed and synthesized a rhodamine-based probe, NRho, which effectively identifies tumors, inflammatory cells, tissues, and organs by detecting ONOO- content. The synthesis process of NRho is simple, yielding a probe with favorable spectral characteristics and rapid response. Our cell imaging analysis has provided novel insights, revealing distinct ONOO- levels among different types of cancer cells, with hepatocellular carcinoma cells exhibiting higher ONOO- content than the others. This observation marks the proposal of such variations in ONOO- levels across cancer cell types. Furthermore, our study has showcased the practicality of our probe in live organ imaging, enabling the identification of tumors from living organs within a brief 5-minute incubation period. Additionally, our findings highlight the rapid detection capability of the probe NRho in various tissue samples, effectively identifying inflammation. This research holds important promise in advancing biomedical research and clinical diagnosis.

Multifunctional fluorescence probe for simultaneous detection of viscosity, polarity, and ONOO- and its bioimaging in vitro and vivo.

Intracellular microenvironment (viscosity and polarity) and peroxynitrite ions (ONOO-) are involved in maintaining cell morphology, cell function, and signaling so that it is crucial to explore their level changes in vitro and vivo. In this work, we designed and synthesized a mitochondria-targeted fluorescence probe XBL for monitoring the dynamic changes of viscosity, polarity, and ONOO- based on TICT and ICT mechanism. The fluorescence spectra showed obvious changes for polarity at 500 nm as well as ONOO- and viscosity at 660 nm, respectively. The XBL can image simultaneously viscosity, polarity, and ONOO- in cells, and the results showed excess ONOO- leaded to the increase of viscosity in mitochondrial. The ferroptosis process was accompanied by increase of intracellular viscosity and ONOO- levels (or decrease of polarity), which allowed us to better understand the relevant physiological and pathological processes. The XBL can distinguish normal cells and cancerous cells by the fluorescence intensity changes in green and red channels, and image viscosity in inflamed mice. Thus, XBL can provided the chemical tool to understand the physiological and pathological mechanisms of disease by simultaneous detection of viscosity, polarity and ONOO-.

Characterization of leucine aminopeptidase (LAP) activity in sweet pepper fruits during ripening and its inhibition by nitration and reducing events.

KEY MESSAGE: Pepper fruits contain two leucine aminopeptidase (LAP) genes which are differentially modulated during ripening and by nitric oxide. The LAP activity increases during ripening but is negatively modulated by nitration. Leucine aminopeptidase (LAP) is an essential metalloenzyme that cleaves N-terminal leucine residues from proteins but also metabolizes dipeptides and tripeptides. LAPs play a fundamental role in cell protein turnover and participate in physiological processes such as defense mechanisms against biotic and abiotic stresses, but little is known about their involvement in fruit physiology. This study aims to identify and characterize genes encoding LAP and evaluate their role during the ripening of pepper (Capsicum annuum L.) fruits and under a nitric oxide (NO)-enriched environment. Using a data-mining approach of the pepper plant genome and fruit transcriptome (RNA-seq), two LAP genes, designated CaLAP1 and CaLAP2, were identified. The time course expression analysis of these genes during different fruit ripening stages showed that whereas CaLAP1 decreased, CaLAP2 was upregulated. However, under an exogenous NO treatment of fruits, both genes were downregulated. On the contrary, it was shown that during fruit ripening LAP activity increased by 81%. An in vitro assay of the LAP activity in the presence of different modulating compounds including peroxynitrite (ONOO-), NO donors (S-nitrosoglutathione and nitrosocyteine), reducing agents such as reduced glutathione (GSH), L-cysteine (L-Cys), and cyanide triggered a differential response. Thus, peroxynitrite and reducing compounds provoked around 50% inhibition of the LAP activity in green immature fruits, whereas cyanide upregulated it 1.5 folds. To our knowledge, this is the first characterization of LAP in pepper fruits as well as of its regulation by diverse modulating compounds. Based on the capacity of LAP to metabolize dipeptides and tripeptides, it could be hypothesized that the LAP might be involved in the GSH recycling during the ripening process.

Exploration of Nitrotyrosine-Containing Proteins and Peptides by Antibody-Based Enrichment Strategies.

Nitrotyrosine, or 3-nitrotyrosine, is an oxidative post-translational modification induced by reactive nitrogen species. Although nitrotyrosine is considered a marker of oxidative stress and has been associated with inflammation, neurodegeneration, cardiovascular disease, and cancer, identification of nitrotyrosine-modified proteins remains challenging owing to its low stoichiometric levels in biological samples. To facilitate a comprehensive analysis of proteins and peptides containing nitrotyrosine, we optimized an immunoprecipitation-based enrichment workflow using a cell line model. The identification of proteins and peptides containing nitrotyrosine residues was carried out after peroxynitrite treatment of cell lysates, which generated modified nitrotyrosine residues on susceptible sites on proteins. We evaluated the efficacy of enriching nitrotyrosine-modified proteins and peptides by employing four different commercially available monoclonal antibodies directed against nitrotyrosine. LC-MS/MS analysis resulted in the identification of 1377 and 1624 nitrotyrosine-containing peptides from protein- and peptide-based enrichment experiments, respectively. Although the yield of nitrotyrosine-containing peptides was higher in experiments where peptides rather than proteins were enriched, we found a substantial proportion (37-65%) of identified nitrotyrosine-containing peptides contained nitrotyrosine at the N-terminus. However, in protein-based immunoprecipitation <9% of nitrotyrosine-containing peptides had nitrotyrosine modification at the N-terminus of the peptide. Overall, our study resulted in the identification of 2603 nitrotyrosine-containing peptides of which >2000 have not previously been reported. We synthesized 101 novel nitrotyrosine-containing peptides identified in our analysis and analyzed them by LC-MS/MS to validate our findings. We have confirmed the validity of 70% of these peptides, as they demonstrated a similarity score exceeding 0.7 when compared to peptides identified through experimental methods. Finally, we also validated the presence of nitrotyrosine modification on PKM and EF2 proteins in peroxynitrite-treated samples by immunoblot analysis. The large catalog presented in this study along with the workflow should facilitate the investigation of nitrotyrosine as an oxidative modification in a variety of settings in greater detail.

Photocleavable Visible Light-Triggered Anthraquinone-Derived Water-Soluble Block Copolymer for Peroxynitrite Generation in Cancer Therapy.

We report a facile stimuli-responsive strategy to generate reactive oxygen and nitrogen species (ROS and RNS) in the biological milieu from a photocleavable water-soluble block copolymer under visible light irradiation (427 nm, 2.25 mW/cm2). An anthraquinone-based water-soluble polymeric nitric oxide (NO) donor (BCPx-NO) is synthesized, which exhibits NO release in the range of 40-65 µM within 10 h of photoirradiation with a half-life of 30-103 min. Additionally, BCPx-NO produces peroxynitrite (ONOO-) and singlet oxygen (1O2) under photoirradiation. To understand the mechanism of NO release and photolysis of the functional group under blue light, we prepared a small-molecule anthraquinone-based N-nitrosamine (NOD). The cellular investigation of the effect of spatiotemporally controlled ONOO- and 1O2 generation from the NO donor polymeric nanoparticles in a triple negative breast adenocarcinoma (MDA-MB-231) under visible light irradiation (white light, 5.83 mW/cm2; total dose 31.5 J/cm2) showed an IC50 of 0.6 mg/mL. The stimuli-responsive strategy using a photolabile water-soluble block copolymer employed to generate ROS and RNS in a biological setting widens the horizon for their potential in cancer therapy.

Kisspeptin-10 Improves Testicular Redox Status but Does Not Alter the Unfolded Protein Response (UPR) That Is Downregulated by Hypothyroidism in a Rat Model.

Hypothyroidism compromises the testicular redox status and is associated with reduced sperm quality and infertility in men. In this regard, studies have demonstrated the antioxidant potential of kisspeptin in reproductive and metabolic diseases. In this study, we evaluate the effects of kisspeptin-10 (Kp10) on the testicular redox, as well as mediators of the unfolded protein response (UPR) in adult rats with hypothyroidism. Adult male Wistar rats were randomly separated into the Control (n = 15), Hypo (n = 13) and Hypo + Kp10 (n = 14) groups, and hypothyroidism was induced with 6-propyl-2-thiouracil (PTU) for three months. In the last month, half of the hypothyroid animals received Kp10. Testis samples were collected for enzymatic, immunohistochemical and/or gene evaluation of mediators of oxidative stress (TBARs, lipid hydroperoxides (LOOH), ROS, peroxynitrite, SOD, CAT and GPX), endoplasmic reticulum stress (GRP78, ATF6, PERK, CHOP, HO-1 and sXBP1) and antiapoptocytes (BCL-2). Hypothyroidism increased apoptosis index, TBARS and LOOH concentrations, and reduced testicular gene expression of Sod1, Sod2 and Gpx1, as well as the expression of Grp78, Atf6, Ho1 and Chop. Treatment with Kp10, in turn, reduced testicular apoptosis and the production of peroxynitrite, while increased SOD1 and GPX ½ expression, and enzymatic activity of CAT, but did not affect the lower expression of UPR mediators caused by hypothyroidism. This study demonstrated that hypothyroidism causes oxidative stress and dysregulated the UPR pathway in rat testes and that, although Kp10 does not influence the low expression of UPR mediators, it improves the testicular redox status, configuring it as an important antioxidant factor in situations of thyroid dysfunction.

High Contrast Bioimaging of Tumor and Inflammation with a Bicyclic Dioxetane Chemiluminescent Probe.

The link between inflammation and the evolution of cancer is well established. Visualizing and tracking both tumor proliferation and the associated inflammatory response within a living organism are vital for dissecting the nexus between these two processes and for crafting precise treatment modalities. We report the creation and synthesis of an advanced NIR chemiluminescence probe that stands out for its exceptional selectivity, extraordinary sensitivity at nanomolar concentrations, swift detection capabilities, and broad application prospects. Crucially, this probe has been successfully utilized to image endogenous ONOO- across different inflammation models, including abdominal inflammation triggered by LPS, subcutaneous inflammatory conditions, and tumors grafted onto mice. These findings highlight the significant promise of chemiluminescence imaging in enhancing our grasp of the intricate interplay between cancer and inflammation and in steering the development of potent, targeted therapeutic strategies.