3-Nitrotyrosine quantification methods: Current concepts and future challenges

Overview and trends in electrochemical sensors, biosensors and cellular antioxidant assays for oxidant and antioxidant determination in food

Screening and quantifying antioxidants from food samples, their antioxidant activity, as well as the assessment of food oxidation is critical, not only for ensuring food quality and safety, but also to understand and relate these parameters to the shelf life, sensory attributes, and health aspects of food products. For this purpose, several methods have been developed and used for decades, which regardless of their effectiveness, present a certain number of drawbacks mainly related to extensive sample preparation and technical complexity, time requirements, and the use of hazardous chemicals. Electrochemical sensors and biosensors are gaining popularity in food analysis due to their high sensitivity, specificity, rapid response times, and potential for miniaturisation and portability. Furthermore, other modern methods using whole living cells such as the cellular antioxidant activity assay, the antioxidant power 1 assay, and the catalase-like assays, may interpret more realistic antioxidant results rather than just reporting the ability to scavenge free radicals in isolated systems with extrapolation to reality. This paper provides an overview of electrochemical sensors, biosensors, and cellular antioxidant assays, and reviews the latest advancements and emerging trends in these techniques for determining oxidants and antioxidants in complex food matrices. The performances of different strategies are described for each of these approaches to provide insights into the extent to which these methods can be exploited in the field and inspire new research to fill the current gaps.

Biomolecular Dynamics of Nitric Oxide Metabolites and HIF1α in HPV Infection

INTRODUCTION

Viral infections cause oxygen deprivation, leading to hypoxia or anoxia in certain tissues. The limitation of mitochondrial respiration is one of the major events during hypoxia that induces alternative metabolic activities and increased levels of certain biomolecules such as nitric oxide (NO) metabolites. In this study, we aimed to investigate the role of NO metabolites and hypoxia in HPV infection.

MATERIALS AND METHODS

We included 36 patients with palmoplantar warts and 36 healthy subjects and performed serum determinations of NO metabolites (direct nitrite, total nitrite, nitrate, and 3-nitrotyrosine) and HIF1α, a marker of hypoxia.

RESULTS

We found elevated serum levels in NO metabolites and HIF1α, and decreased direct nitrite/nitrate ratios in patients with warts versus controls. Additionally, we identified statistically significant positive correlations between NO metabolites and HIF1α levels, except for 3-nitrotyrosine.

CONCLUSIONS

Our findings show that HPV infection causes hypoxia and alterations in NO metabolism and suggest a link between wart development and cellular stress. Our research could provide new insights for a comprehensive understanding of the pathogenesis of cutaneous HPV infections.

Surface-active agent enhanced FRET effect Cu-doped NH2-MIL-88(Fe) for highly sensitive detection of 3-nitro-L-tyrosine

In this study, Cu-doped NH2-MIL-88(Fe) metal-organic frameworks (MOF) were synthesized via a one-step method. Characterization techniques such as XPS, XRD and FTIR confirmed the successful incorporation of Cu2+ into NH2-MIL-88(Fe), naming this MOF as NH2-MIL-88(Fe)@Cu2+. This MOF was employed to develop a highly sensitive fluorescence sensing platform for detecting 3-nitro-L-tyrosine(3-NT). The potential for fluorescence resonance energy transfer (FRET) was suggested by the spectral overlap between NH2-MIL-88(Fe)@Cu2+'s emission and 3-NT's UV absorption. To augment this effect, cationic surfactant hexadecyltrimethylammonium bromide (CTAB), which self-assembled into nanostructured microspheres above its critical micelle concentration, was utilized. The charged surface of these microspheres, formed by the self-assembly of CTAB, is bound to the MOF surface through electrostatic force and simultaneously attracts 3-NT. Adjusting the solution's pH strengthened the interaction between NH2-MIL-88(Fe)@Cu2+ and 3-NT, thereby enhancing their mutual FRET interaction. Experimental results indicated that CTAB's introduction markedly improved the FRET effects, potentially converting a weak FRET into a strong one and enhancing detection sensitivity and accuracy. Under optimal conditions, NH2-MIL-88(Fe)@Cu2+ detected 3-NT within 0-30 μM range, with a limit of detection (LOD, S/N = 3) of 41.1 nM. Finally, the applicability of the sensor is tested by calibrating measurements in fetal bovine serum samples, achieving good performance in terms of sensitivity, selectivity and reproducibility. This research provides a method for efficient and highly sensitive 3-NT detection and insights into the FRET effect between MOF and target molecules, likely advancing related fields and inspiring future fluorescence sensor designs.

α-Tocotrienol Protects Neurons by Preventing Tau Hyperphosphorylation via Inhibiting Microtubule Affinity-Regulating Kinase Activation

In the pathological process of Alzheimer's disease, neuronal cell death is closely related to the accumulation of reactive oxygen species. Our previous studies have found that oxidative stress can activate microtubule affinity-regulating kinases, resulting in elevated phosphorylation levels of tau protein specifically at the Ser262 residue in N1E-115 cells that have been subjected to exposure to hydrogen peroxide. This process may be one of the pathogenic mechanisms of Alzheimer's disease. Vitamin E is a fat-soluble, naturally occurring antioxidant that plays a crucial role in biological systems. This study aimed to examine the probable processes that contribute to the inhibiting effect on the abnormal phosphorylation of tau protein and the neuroprotective activity of a particular type of vitamin E, α-tocotrienol. The experimental analysis revealed that α-tocotrienol showed significant neuroprotective effects in the N1E-115 cell line. Our data further suggest that one of the mechanisms underlying the neuroprotective effects of α-tocotrienol may be through the inhibition of microtubule affinity-regulated kinase activation, which significantly reduces the oxidative stress-induced aberrant elevation of p-Tau (Ser262) levels. These results indicate that α-tocotrienol may represent an intriguing strategy for treating or preventing Alzheimer's disease.

Layer-by-Layer Assembly of Renal-Targeted Polymeric Nanoparticles for Robust Arginase-2 Knockdown and Contrast-Induced Acute Kidney Injury Prevention

The mitochondrial enzyme arginase-2 (Arg-2) is implicated in the pathophysiology of contrast-induced acute kidney injury (CI-AKI). Therefore, Arg-2 represents a candid target for CI-AKI prevention. Here, layer-by-layer (LbL) assembled renal-targeting polymeric nanoparticles are developed to efficiently deliver small interfering RNA (siRNA), knockdown Arg-2 expression in renal tubules, and prevention of CI-AKI is evaluated. First, near-infrared dye-loaded poly(lactic-co-glycolic acid) (PLGA) anionic cores are electrostatically coated with cationic chitosan (CS) to facilitate the adsorption and stabilization of Arg-2 siRNA. Next, nanoparticles are coated with anionic hyaluronan (HA) to provide protection against siRNA leakage and shielding against early clearance. Sequential electrostatic layering of CS and HA improves loading capacity of Arg-2 siRNA and yields LbL-assembled nanoparticles. Renal targeting and accumulation is enhanced by modifying the outermost layer of HA with a kidney targeting peptide (HA-KTP). The resultant kidney-targeting and siRNA loaded nanoparticles (PLGA/CS/HA-KTP siRNA) exhibit proprietary accumulation in kidneys and proximal tubular cells at 24 h post-tail vein injection. In iohexol-induced in vitro and in vivo CI-AKI models, PLGA/CS/HA-KTP siRNA delivery alleviates oxidative and nitrification stress, and rescues mitochondrial dysfunction while reducing apoptosis, thereby demonstrating a robust and satisfactory therapeutic effect. Thus, PLGA/CS/HA-KTP siRNA nanoparticles offer a promising candidate therapy to protect against CI-AKI.

Protein Oxidative Modifications in Neurodegenerative Diseases: From Advances in Detection and Modelling to Their Use as Disease Biomarkers

Oxidation-reduction post-translational modifications (redox-PTMs) are chemical alterations to amino acids of proteins. Redox-PTMs participate in the regulation of protein conformation, localization and function, acting as signalling effectors that impact many essential biochemical processes in the cells. Crucially, the dysregulation of redox-PTMs of proteins has been implicated in the pathophysiology of numerous human diseases, including neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. This review aims to highlight the current gaps in knowledge in the field of redox-PTMs biology and to explore new methodological advances in proteomics and computational modelling that will pave the way for a better understanding of the role and therapeutic potential of redox-PTMs of proteins in neurodegenerative diseases. Here, we summarize the main types of redox-PTMs of proteins while providing examples of their occurrence in neurodegenerative diseases and an overview of the state-of-the-art methods used for their detection. We explore the potential of novel computational modelling approaches as essential tools to obtain insights into the precise role of redox-PTMs in regulating protein structure and function. We also discuss the complex crosstalk between various PTMs that occur in living cells. Finally, we argue that redox-PTMs of proteins could be used in the future as diagnosis and prognosis biomarkers for neurodegenerative diseases.

Uncommon posttranslational modifications in proteomics: ADP-ribosylation, tyrosine nitration, and tyrosine sulfation

Posttranslational modifications (PTMs) are covalent modifications of proteins that modulate the structure and functions of proteins and regulate biological processes. The development of various mass spectrometry-based proteomics workflows has facilitated the identification of hundreds of PTMs and aided the understanding of biological significance in a high throughput manner. Improvements in sample preparation and PTM enrichment techniques, instrumentation for liquid chromatography-tandem mass spectrometry (LC-MS/MS), and advanced data analysis tools enhance the specificity and sensitivity of PTM identification. Highly prevalent PTMs like phosphorylation, glycosylation, acetylation, ubiquitinylation, and methylation are extensively studied. However, the functions and impact of less abundant PTMs are not as well understood and underscore the need for analytical methods that aim to characterize these PTMs. This review focuses on the advancement and analytical challenges associated with the characterization of three less common but biologically relevant PTMs, specifically, adenosine diphosphate-ribosylation, tyrosine sulfation, and tyrosine nitration. The advantages and disadvantages of various enrichment, separation, and MS/MS techniques utilized to identify and localize these PTMs are described.

Oligomerization and tyrosine nitration enhance the allergenic potential of the birch and grass pollen allergens Bet v 1 and Phl p 5

Protein modifications such as oligomerization and tyrosine nitration alter the immune response to allergens and may contribute to the increasing prevalence of allergic diseases. In this mini-review, we summarize and discuss relevant findings for the major birch and grass pollen allergens Bet v 1 and Phl p 5 modified with tetranitromethane (laboratory studies), peroxynitrite (physiological processes), and ozone and nitrogen dioxide (environmental conditions). We focus on tyrosine nitration and the formation of protein dimers and higher oligomers via dityrosine cross-linking and the immunological effects studied.

L-glutathione 1% promotes neuroprotection of nitrergic neurons and reduces the oxidative stress in the jejunum of rats with Walker-256-bearing tumor

AIMS

Our main goals were to investigate the effects of L-glutathione (1%) treatment in Walker-256 tumor-bearing rats by analyzing immunoreactive neurons (IR), responsive to the nNOS enzyme and 3-Nitrotyrosine, in their jejunum myenteric plexus. Moreover, the oxidative state and inflammatory process in these animals were investigated.

METHODS

Four experimental groups were utilized: control (C), control treated with L-glutathione (CGT), Walker-256 tumor-bearing rats (TW), and Walker-256 tumor-bearing rats treated with L-glutathione (TWGT). After 14 days of tumor inoculation, the jejunum was collected for immunohistochemical techniques and assessment of oxidative status. Plasma was collected to evaluate oxidative status and measure cytokines.

RESULTS

The TW group exhibited a decrease of reduced glutathione in their jejunum, which was prevented in the L-glutathione treated TWGT group. TW animals presented pronounced oxidative stress by increasing levels of lipoperoxidation in their jejunum and malondialdehyde in their plasma; however, the L-glutathione treatment in TWGT group was not able to avoid it. The total antioxidant capacity was altered in groups TW and TWGT, yet the last one had a better index in their plasma. The IL-10, and TNF-α levels increased in TWGT animals. The nNOS-IR neuron density decreased in the jejunum myenteric plexus of the TW group, which was avoided in the TWGT group. The nNOS +3-Nitrotyrosine neurons quantification did not show significative alterations.

CONCLUSION

The treatment with L-glutathione (1%) imposed an important defense to some parameters of oxidative stress induced by TW-256, leading to neuroprotection to the loss in the nNOS-IR neuron density.

The Role of Potential Oxidative Biomarkers in the Prognosis of Acute Ischemic Stroke and the Exploration of Antioxidants as Possible Preventive and Treatment Options

Ischemic strokes occur when the blood supply to a part of the brain is interrupted or reduced due to arterial blockage, and it often leads to damage to brain cells or death. According to a myriad of experimental studies, oxidative stress is an important pathophysiological mechanism of ischemic stroke. In this narrative review, we aimed to identify how the alterations of oxidative stress biomarkers could suggest a severity-reflecting diagnosis of ischemic stroke and how these interactions may provide new molecular targets for neuroprotective therapies. We performed an eligibility criteria-based search on three main scientific databases. We found that patients with acute ischemic stroke are characterized by increased oxidative stress markers levels, such as the total antioxidant capacity, F2-isoprostanes, hydroxynonenal, total and perchloric acid oxygen radical absorbance capacity (ORACTOT and ORACPCA), malondialdehyde (MDA), myeloperoxidase, and urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine. Thus, acute ischemic stroke is causing significant oxidative stress and associated molecular and cellular damage. The assessment of these molecular markers could be useful in diagnosing ischemic stroke, finding its causes, predicting its severity and outcomes, reducing its impact on the cellular structures of the brain, and guiding preventive treatment towards antioxidant-based therapy as novel therapeutic alternatives.

Biomarkers of oxidative stress and reproductive complications

Oxidative stress is the result of an imbalance between the formation of reactive oxygen species (ROS) and the levels of enzymatic and non-enzymatic antioxidants. The assessment of biological redox status is performed by the use of oxidative stress biomarkers. An oxidative stress biomarker is defined as any physical structure or process or chemical compound that can be assessed in a living being (in vivo) or in solid or fluid parts thereof (in vitro), the determination of which is a reproducible and reliable indicator of oxidative stress. The use of oxidative stress biomarkers allows early identification of the risk of developing diseases associated with this process and also opens up possibilities for new treatments. At the end of the last century, interest in oxidative stress biomarkers began to grow, due to evidence of the association between the generation of free radicals and various pathologies. Up to now, a significant number of studies have been carried out to identify and apply different oxidative stress biomarkers in clinical practice. Among the most important oxidative stress biomarkers, it can be mentioned the products of oxidative modifications of lipids, proteins, nucleic acids, and uric acid as well as the measurement of the total antioxidant capacity of fluids in the human body. In this review, we aim to present recent advances and current knowledge on the main biomarkers of oxidative stress, including the discovery of new biomarkers, with emphasis on the various reproductive complications associated with variations in oxidative stress levels.

Oxidative Damage by 3-nitrotyrosine in Young Adults with Obesity: Its Implication in Chronic and Contagious Diseases

INTRODUCTION

Cellular damage by oxidation occurs in numerous chronic diseases, such as obesity, type II diabetes, cardiovascular disease, nonalcoholic fatty liver, etc. The oxidized compound 3-nitrotyrosine is a marker of oxidative stress and protein oxidation damage.

OBJECTIVE

The article aims to assess whether 3-nitrotyrosine levels are higher in young people with obesity than in the same population without obesity.

METHODS

Anthropometry and blood chemistry analyses were performed on 24 young Mexican participants (18-30 years old), categorized into two groups based on their waist circumference: Withobesity (≥ 80 cm women; ≥ 90 cm men) and without-obesity (<80 cm women; <90 cm men). Additionally, 3-nitrotyrosine blood values were quantified by ELISA.

RESULTS

Except for HDL-cholesterol, the mean values of lipids increased in women and men with obesity (p<0.05), and 3-nitrotyrosine concentration (nM/μg total protein) was higher by 60% in the group with-obesity compared to the group without-obesity, both for women (66.21 ± 23.85 vs. 40.69 ± 16.25, p<0.05) and men (51.72 ± 20.56 vs. 30.52 ± 5.21, p<0.05).

CONCLUSION

Oxidative damage measured by compound 3-nitrotyrosine was higher in the group with obesity than in the group without obesity, which, if not controlled, could lead to a chronic oxidative condition and thereby to a degree of cellular aging with adverse health effects.

Ellagic Acid Triggers the Necrosis of Differentiated Human Enterocytes Exposed to 3-Nitro-Tyrosine: An MS-Based Proteomic Study

To study the molecular basis of the toxicological effect of a dietary nitrosated amino acid, namely, 3-nitrotyrosine (3-NT), differentiated human enterocytes were exposed to dietary concentrations of this species (200 μM) and analyzed for flow cytometry, protein oxidation markers and MS-based proteomics. The possible protective role of a dietary phytochemical, ellagic acid (EA) (200 μM), was also tested. The results revealed that cell viability was significantly affected by exposure to 3-NT, with a concomitant significant increase in necrosis (p < 0.05). 3-NT affected several biological processes, such as histocompatibility complex class II (MHC class II), and pathways related to type 3 metabotropic glutamate receptors binding. Addition of EA to 3-NT-treated cells stimulated the toxicological effects of the latter by reducing the abundance of proteins involved in mitochondrial conformation. These results emphasize the impact of dietary nitrosated amino acids in intestinal cell physiology and warn about the potential negative effects of ellagic acid when combined with noxious metabolites.

A Fluorescent Cage for Supramolecular Sensing of 3-Nitrotyrosine in Human Blood Serum

3-Nitrotyrosine (NT) is generated by the action of peroxynitrite and other reactive nitrogen species (RNS), and as a consequence it is accumulated in inflammation-associated conditions. This is particularly relevant in kidney disease, where NT concentration in blood is considerably high. Therefore, NT is a crucial biomarker of renal damage, although it has been underestimated in clinical diagnosis due to the lack of an appropriate sensing method. Herein we report the first fluorescent supramolecular sensor for such a relevant compound: Fluorescence by rotational restriction of tetraphenylethenes (TPE) in a covalent cage is selectively quenched in human blood serum by 3-nitrotyrosine (NT) that binds to the cage with high affinity, allowing a limit of detection within the reported physiological concentrations of NT in chronic kidney disease.

Evaluation and optimization of nanosuspensions of Chrysanthemum coronarium and Azadirachta indica using Response Surface Methodology for pest management

The rapidly emerging field of nanotechnology is considered an important achievement in the agriculture sector to increase the pest mortality rate and improve the crop production. The present study evaluates the novel pesticidal and anti-microbial activities of Chrysanthemum coronarium and Azadirachta indica in the nano-suspensions form. The anti-solvent precipitation method was used to formulate nano-suspensions proposed by Response Surface Methodology (RSM). Physicochemical nature of plant extracts and nano-suspensions was characterized through analysis of Zeta-sizer, FT-IR, and HPLC. Characterization results revealed a minimum particle size of 121.1 and 170.1 nm for Chrysanthemum coronarium and Azadirachta indica, respectively. The pesticidal activity of nano-suspension was performed against red flour beetle (RFB) and lesser grain borer (LGB) pests, which showed the maximum mortality rate of 100% with 100% concentration of plant extracts and nano-suspensions of Chrysanthemum coronarium and Azadirachta indica against both insects. In comparison, the combination of these both plant extracts revealed the maximum 100% mortality with a 50% concentration of nano-suspensions (mixing ratio 1:1) after 72 h. The antibacterial activity showed the maximum zone inhibition of 9.96 ± 0.17 and 14.17 ± 0.50 mm against S.aureus and E. coli with nano-suspension of Chrysanthemum coronarium, and 12.09 ± 0.11 and 14.10 ± 0.49 mm with nano-suspension of Azadirachta indica, respectively. It is concluded that individual nano-suspensions showed better pesticidal as well as antimicrobial activities than combinations. However, the constructed nanosuspension can be applied to control the plant pests and diseases simultaneously.

Evaluation of the Biological Potential of Himanthalia elongata (L.) S.F.Gray and Eisenia bicyclis (Kjellman) Setchell Subcritical Water Extracts

Neuroprotection is a need that remains unmet in treating chronic neurodegenerative disorders, despite decades of extensive research. To find new neuroprotective compounds, extracts of Himanthalia elongata (L.) S.F.Gray and of Eisenia bicyclis (Kjellman) Setchell were obtained through subcritical water extraction applying a four-step temperature gradient. The fractions obtained were screened against brain enzymes involved in neurodegenerative etiology, namely in Alzheimer’s and Parkinson’s diseases, and against reactive oxygen and nitrogen species, all contributing factors to the progression of neurodegeneration. Results showed no significant enzyme inhibition but strong radical scavenging activities, particularly in the fourth fraction, extracted at the highest temperature (250 °C), highlighting their ability to retard oxidative and nitrosative stresses. At higher temperatures, fractions were composed of phenolic compounds and Maillard reaction products, a combination that contributed to their antioxidant activity and, consequently, their neuroprotective properties. All fractions were evaluated for the presence of iodine, 14 organochlorine and 7 organophosphorus pesticides, and pharmaceuticals used in Alzheimer’s and Parkinson’s diseases (14), psychiatric drugs (8), and metabolites (8). The fractions studied did not present any of the screened contaminants, and only fraction 1 of E. bicyclis should be used with caution due to iodine content.

Nrf2 Deficiency Attenuates Testosterone Efficiency in Ameliorating Mitochondrial Function of the Substantia Nigra in Aged Male Mice

Reduced testosterone level is a common feature of aging in men. Aging, as a risk factor for several neurodegenerative disorders, shows declined mitochondrial function and downregulated mitochondrial biogenesis and mitochondrial dynamics. Mitochondrial biogenesis and mitochondrial dynamics are crucial in maintaining proper mitochondrial function. Supplementation with testosterone is conducive to improving mitochondrial function of males during aging. Nuclear factor erythroid 2-related factor 2 (Nrf2), a regulator of redox homeostasis, is involved in the ameliorative effects of testosterone supplementation upon aging. To explore Nrf2 role in the effects of testosterone supplementation on mitochondrial function during aging, we studied the efficiency of testosterone supplementation in improving mitochondrial function of Nrf2 knockout- (KO-) aged male mice by analyzing the changes of mitochondrial biogenesis and mitochondrial dynamics. It was found that wild-type- (WT-) aged male mice showed low mitochondrial function and expression levels of PGC-1α, NRF-1\NRF-2, and TFAM regulating mitochondrial biogenesis, as well as Drp1, Mfn1, and OPA1 controlling mitochondrial dynamics in the substantia nigra (SN). Nrf2 KO aggravated the defects above in SN of aged male mice. Testosterone supplementation to WT-aged male mice significantly ameliorated mitochondrial function and upregulated mitochondrial biogenesis and mitochondrial dynamics, which were not shown in Nrf2 KO-aged male mice due to Nrf2 deficiency. Testosterone deficiency by gonadectomy (GDX) decreased mitochondrial function, downregulated mitochondrial biogenesis, and altered mitochondrial dynamics balance in young male mice. Supplementation with testosterone to Nrf2 KO-GDX mice only ameliorated the alterations above but did not reverse them to sham level. Nrf2 deficiency attenuated testosterone efficiency in ameliorating mitochondrial function in the SN of aged male mice through mitochondrial biogenesis and mitochondrial dynamics to some extent. Activation of Nrf2 might contribute to testosterone-upregulating mitochondrial biogenesis and mitochondrial dynamics in the SN during aging to produce efficient mitochondria for ATP production.

Protein tyrosine nitration in atherosclerotic endothelial dysfunction

Accumulation of reactive oxygen species (ROS) can induce both protein tyrosine nitration and endothelial dysfunction in atherosclerosis. Endothelial dysfunction refers to impaired endothelium-dependent vasorelaxation that can be triggered by an imbalance in nitric oxide (NO) production and consumption. ROS reacts with NO to generate peroxynitrite, decreasing NO bioavailability. Peroxynitrite also promotes protein tyrosine nitration in vivo that can affect protein structure and function and further damage endothelial function. In this review, we discuss the process of protein tyrosine nitration, increased expression of nitrated proteins in cardiovascular disease and their association with endothelial dysfunction, and the interference of tyrosine nitration with antioxidants and the protective role in endothelial dysfunction. These may lead us to the conception that protein tyrosine nitration may be one of the causes of endothelial dysfunction, and help us gain information about the mechanism of endothelial dysfunction underlying atherosclerosis.

A highly selective and sensitive spectrofluorimetric method for the assessment of 3-nitrotyrosine in serum using (Eu(TTA)3Phen) photo probe

A simple, accurate and fast method was developed for the assessment of 3-nitrotyrosine as a biomarker for the early diagnosis of liver cirrhosis with minimal hepatic encephalopathy (MHE) using a (Eu(TTA)₃Phen) photo probe. 3-Nitrotyrosine can remarkably quench the luminescence intensity of the (Eu(TTA)₃Phen) complex in DMSO at pH = 9 and λ_em = 617 nm. The quenching of the luminescence intensity of (Eu(TTA)₃Phen) complex particularly the electrical emission band at λ_em = 617 nm is used for the assessment of 3-nitrotyrosine in different serum samples of patients with liver cirrhosis.

A simple, accurate and fast method was developed for the assessment of 3-nitrotyrosine as a biomarker for the early diagnosis of liver cirrhosis with minimal hepatic encephalopathy (MHE) using a (Eu(TTA)₃Phen) photo probe.

Smart sensor for assessment of oxidative/nitrative stress biomarkers using a dual-imprinted electrochemical paper-based analytical device

We present a novel dual-imprinted electrochemical paper-based analytical device (Di-ePAD) to simultaneously determine 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 3-nitrotyrosine (3-NT) and assess oxidative and nitrative biomarkers in urine and plasma samples. The Di-ePAD was designed with hydrophobic barrier layers formed on filter paper to provide three-dimensional circular reservoirs and assembled electrodes. The molecularly imprinted polymer (MIP) was synthesized using a silica nanosphere decorated with silver nanoparticles (SiO₂@AgNPs) as a core covered with dual-analyte imprinted sites on the polymer to recognize selectively and bind the target biomarkers. This strategy drives monodispersity and enhances the conductivity of the resulting MIP core-shell products. 3-NT-MIP and 8-OHdG-MIP were synthesized by successively coating the surface of SiO₂@AgNPs with l-Cysteine via the thiol group, then terminating with MIP shells. The dual imprinted core-shell composites possess attractive properties for the target biomarkers' sensing, including catalytic activity, selectivity, and good conductivity. The Di-ePAD revealed excellent linear dynamic ranges of 0.01-500 μM for 3-NT and 0.05-500 μM for 8-OHdG, with detection limits of 0.0027 μM for 3-NT and 0.0138 μM for 8-OHdG. This newly developed method based on the synergistic effects of SiO₂@AgNPs combined with promising properties of MIP offers outstanding selectivity, sensitivity, reproducibility, simplicity, and low cost for quantitative analysis of 3-NT and 8-OHdG. The proposed Di-ePAD showed good accuracy and precision when applied to actual samples, including urine and serum samples validated by a conventional HPLC method.

Association between intestinal lymphangiectasia and expression of inducible nitric oxide synthase in dogs with lymphoplasmacytic enteritis

Intestinal lymphangiectasia (IL) is a common complication in dogs. Since nitric oxide (NO) is known to relax the lymphatic vessel, we evaluated inducible NO synthase (iNOS) expression using immunohistochemistry in 13 dogs with lymphoplasmacytic enteritis (LPE) with or without IL. The duodenal iNOS expressing cells were significantly increased in dogs with IL-negative or IL-positive LPE dogs (P=0.025, P=0.007) compared with control dogs. However, there was no significant difference in iNOS expression between IL-positive and IL-negative tissues. Based on these results, there is no clear evidence for the NO overproduction in the pathogenesis of IL in dogs with LPE. Factors other than NO could, thus, contribute to IL in dogs with LPE.

A Review of Oxidative Stress Products and Related Genes in Early Alzheimer's Disease

Oxidative stress is associated with the progression of Alzheimer’s disease (AD). Reactive oxygen species can modify lipids, DNA, RNA, and proteins in the brain. The products of their peroxidation and oxidation are readily detectable at incipient stages of disease. Based on these oxidation products, various biomarker-based strategies have been developed to identify oxidative stress levels in AD. Known oxidative stress-related biomarkers include lipid peroxidation products F2-isoprostanes, as well as malondialdehyde and 4-hydroxynonenal which both conjugate to specific amino acids to modify proteins, and DNA or RNA oxidation products 8-hydroxy-2’-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG), respectively. The inducible enzyme heme oxygenase type 1 (HO-1) is found to be upregulated in response to oxidative stress-related events in the AD brain. While these global biomarkers for oxidative stress are associated with early-stage AD, they generally poorly differentiate from other neurodegenerative disorders that also coincide with oxidative stress. Redox proteomics approaches provided specificity of oxidative stress-associated biomarkers to AD pathology by the identification of oxidatively damaged pathology-specific proteins. In this review, we discuss the potential combined diagnostic value of these reported biomarkers in the context of AD and discuss eight oxidative stress-related mRNA biomarkers in AD that we newly identified using a transcriptomics approach. We review these genes in the context of their reported involvement in oxidative stress regulation and specificity for AD. Further research is warranted to establish the protein levels and their functionalities as well as the molecular mechanisms by which these potential biomarkers are involved in regulation of oxidative stress levels and their potential for determination of oxidative stress and disease status of AD patients.

Protein oxidation - Formation mechanisms, detection and relevance as biomarkers in human diseases

Generation of reactive oxygen species and related oxidants is an inevitable consequence of life. Proteins are major targets for oxidation reactions, because of their rapid reaction rates with oxidants and their high abundance in cells, extracellular tissues, and body fluids. Additionally, oxidative stress is able to degrade lipids and carbohydrates to highly reactive intermediates, which eventually attack proteins at various functional sites. Consequently, a wide variety of distinct posttranslational protein modifications is formed by protein oxidation, glycoxidation, and lipoxidation. Reversible modifications are relevant in physiological processes and constitute signaling mechanisms ("redox signaling"), while non-reversible modifications may contribute to pathological situations and several diseases. A rising number of publications provide evidence for their involvement in the onset and progression of diseases as well as aging processes. Certain protein oxidation products are chemically stable and formed in large quantity, which makes them promising candidates to become biomarkers of oxidative damage. Moreover, progress in the development of detection and quantification methods facilitates analysis time and effort and contributes to their future applicability in clinical routine. The present review outlines the most important classes and selected examples of oxidative protein modifications, elucidates the chemistry beyond their formation and discusses available methods for detection and analysis. Furthermore, the relevance and potential of protein modifications as biomarkers in the context of disease and aging is summarized.

Regulation of Mitochondrial Dynamics in Parkinson's Disease-Is 2-Methoxyestradiol a Missing Piece?

Mitochondria, as "power house of the cell", are crucial players in cell pathophysiology. Beyond adenosine triphosphate (ATP) production, they take part in a generation of reactive oxygen species (ROS), regulation of cell signaling and cell death. Dysregulation of mitochondrial dynamics may lead to cancers and neurodegeneration; however, the fusion/fission cycle allows mitochondria to adapt to metabolic needs of the cell. There are multiple data suggesting that disturbed mitochondrial homeostasis can lead to Parkinson's disease (PD) development. 2-methoxyestradiol (2-ME), metabolite of 17β-estradiol (E2) and potential anticancer agent, was demonstrated to inhibit cell growth of hippocampal HT22 cells by means of nitric oxide synthase (NOS) production and oxidative stress at both pharmacologically and also physiologically relevant concentrations. Moreover, 2-ME was suggested to inhibit mitochondrial biogenesis and to be a dynamic regulator. This review is a comprehensive discussion, from both scientific and clinical point of view, about the influence of 2-ME on mitochondria and its plausible role as a modulator of neuron survival.

A high-performance genetically encoded fluorescent biosensor for imaging physiological peroxynitrite

Peroxynitrite is a reactive nitrogen species (RNS) that plays critical roles in signal transduction, stress response, and numerous human diseases. Advanced molecular tools that permit the selective, sensitive, and noninvasive detection of peroxynitrite are essential for understanding its pathophysiological functions. Here, we present pnGFP-Ultra, a high-performance, reaction-based, genetically encodable biosensor for imaging peroxynitrite in live cells. pnGFP-Ultra features a p-boronophenylalanine-modified chromophore as the sensing moiety and exhibits a remarkable ~110-fold fluorescence turn-on response toward peroxynitrite while displaying virtually no cross-reaction with other reactive oxygen/nitrogen species. To facilitate the expression of pnGFP-Ultra in mammalian cells, we engineered an efficient noncanonical amino acid (ncAA) expression system that is broadly applicable to the mammalian expression of ncAA-containing proteins. pnGFP-Ultra robustly detected peroxynitrite production in activated macrophages and primary glial cells. pnGFP-Ultra fills an important technical gap and represents a valuable addition to the molecular toolbox for probing RNS biology.

Deleterious Effects of an Air Pollutant (NO2) on a Selection of Commensal Skin Bacterial Strains, Potential Contributor to Dysbiosis?

The skin constitutes with its microbiota the first line of body defense against exogenous stress including air pollution. Especially in urban or sub-urban areas, it is continuously exposed to many environmental pollutants including gaseous nitrogen dioxide (gNO₂). Nowadays, it is well established that air pollution has major effects on the human skin, inducing various diseases often associated with microbial dysbiosis. However, very few is known about the impact of pollutants on skin microbiota. In this study, a new approach was adopted, by considering the alteration of the cutaneous microbiota by air pollutants as an indirect action of the harmful molecules on the skin. The effects of gNO₂ on this bacterial skin microbiota was investigated using a device developed to mimic the real-life contact of the gNO₂ with bacteria on the surface of the skin. Five strains of human skin commensal bacteria were considered, namely Staphylococcus aureus MFP03, Staphylococcus epidermidis MFP04, Staphylococcus capitis MFP08, Pseudomonas fluorescens MFP05, and Corynebacterium tuberculostearicum CIP102622. Bacteria were exposed to high concentration of gNO₂ (10 or 80 ppm) over a short period of 2 h inside the gas exposure device. The physiological, morphological, and molecular responses of the bacteria after the gas exposure were assessed and compared between the different strains and the two gNO₂ concentrations. A highly significant deleterious effect of gNO₂ was highlighted, particularly for S. capitis MFP08 and C. tuberculostearicum CIP102622, while S. aureus MFP03 seems to be the less sensitive strain. It appeared that the impact of this nitrosative stress differs according to the bacterial species and the gNO₂ concentration. Thus the exposition to gNO₂ as an air pollutant could contribute to dysbiosis, which would affect skin homeostasis. The response of the microbiota to the nitrosative stress could be involved in some pathologies such as atopic dermatitis.

Recent progress in the LC-MS/MS analysis of oxidative stress biomarkers

The presence of a dynamic and balanced equilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and the in-house antioxidant defense mechanisms is characteristic for a healthy body. During oxidative stress (OS), this balance is switched to increased production of ROS and RNS, exceeding the capacity of physiological antioxidant systems. This can cause damage to biological molecules, leading to loss of function and even cell death. Nowadays, there is increasing scientific and clinical interest in OS and the associated parameters to measure the degree of OS in biofluids. An increasing number of reports using LC-MS/MS methods for the analysis of OS biomarkers can be found. Since bioanalysis is usually complicated by matrix effects, various types of cleanup procedures are used to effectively separate the biomarkers from the matrix. This is an essential part of the analysis to prepare a reproducible and homogenous solution suitable for injection onto the column. The present review gives a summary of the chromatographic methods used for the determination of OS biomarkers in both urine and plasma, serum, and whole blood samples. The first part mainly describes the biological background of the different OS biomarkers, while the second part reports examples of chromatographic methods for the analysis of different metabolites connected with OS in biofluids, covering a period from 2015 till early 2020. The selected examples mainly include LC-MS/MS methods for isoprostanes, oxidized proteins, oxidized lipoproteins, and DNA/RNA biomarkers. The last part explains the clinical relevance of this review.

The Potential Benefit of Monitoring Oxidative Stress and Inflammation in the Prevention of Non-Communicable Diseases (NCDs)

The significant increase in worldwide morbidity and mortality from non-communicable diseases (NCDs) indicates that the efficacy of existing strategies addressing this crisis may need improvement. Early identification of the metabolic irregularities associated with the disease process may be a key to developing early intervention strategies. Unhealthy lifestyle behaviours are well established drivers of the development of several NCDs, but the impact of such behaviours on health can vary considerably between individuals. How can it be determined if an individual's unique set of lifestyle behaviours is producing disease? Accumulating evidence suggests that lifestyle-associated activation of oxidative and inflammatory processes is primary driver of the cell and tissue damage which underpins the development of NCDs. However, the benefit of monitoring subclinical inflammation and oxidative activity has not yet been established. After reviewing relevant studies in this context, we suggest that quantification of oxidative stress and inflammatory biomarkers during the disease-free prodromal stage of NCD development may have clinical relevance as a timely indicator of the presence of subclinical metabolic changes, in the individual, portending the development of disease. Monitoring markers of oxidative and inflammatory activity may therefore enable earlier and more efficient strategies to both prevent NCD development and/or monitor the effectiveness of treatment.

Simultaneous LC-MS/MS-Based Quantification of Free 3-Nitro-l-tyrosine, 3-Chloro-l-tyrosine, and 3-Bromo-l-tyrosine in Plasma of Colorectal Cancer Patients during Early Postoperative Period

Quantification with satisfactory specificity and sensitivity of free 3-Nitro-l-tyrosine (3-NT), 3-Chloro-l-tyrosine (3-CT), and 3-Bromo-l-tyrosine (3-BT) in biological samples as potential inflammation, oxidative stress, and cancer biomarkers is analytically challenging. We aimed at developing a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for their simultaneous analysis without an extract purification step by solid-phase extraction. Validation of the developed method yielded the following limits of detection (LOD) and quantification (LOQ) for 3-NT, 3-BT, and 3-CT: 0.030, 0.026, 0.030 ng/mL (LODs) and 0.100, 0.096, 0.098 ng/mL (LOQs). Coefficients of variation for all metabolites and tested concentrations were <10% and accuracy was within 95-105%. Method applicability was tested on colorectal cancer patients during the perioperative period. All metabolites were significantly higher in cancer patients than healthy controls. The 3-NT was significantly lower in advanced cancer and 3-BT showed a similar tendency. Dynamics of 3-BT in the early postoperative period were affected by type of surgery and presence of surgical site infections. In conclusion, a sensitive and specific LC-MS/MS method for simultaneous quantification of free 3-NT, 3-BT, and 3-CT in human plasma has been developed.

Hepatitis C virus eradication by direct antiviral agents abates oxidative stress in patients with advanced liver fibrosis

BACKGROUND AND AIMS

HCV eradication improves non-hepatic outcomes such as cardiovascular diseases, although without clearly defined mechanisms. In this study we aimed to assess whether improvement of carotid atherosclerosis may be linked to a reduction in systemic oxidative stress after viral clearance.

METHODS

We studied a retrospective cohort of 105 patients (age 62.4 ± 11.2 years; 62 men) with F3/F4 fibrosis, characterized by carotid ultrasonography at baseline and at sustained virologic response (SVR) follow-up. Levels of 8-iso-prostaglandin F_2α (F₂ -isoprostanes) and other oxidative stress markers were measured on frozen sera. Association between change (denoted as Δ) in oxidative stress markers (exposures) and change in carotid intima-media thickness (cIMT) (outcome) was examined using multiple linear regression.

RESULTS

Subclinical atherosclerosis, defined as the presence of carotid plaque and/or cIMT ≥ 0.9, was present in 72% of the cohort. All patients achieved SVR that led to reduction in cIMT (0.92 ± 0.20 vs 0.83 ± 0.21 mm, P < .001). HCV eradication markedly decreased serum levels of F₂ -isoprostanes (620.5 [143.2; 1904.1] vs 119.51 [63.2; 400.6] pg/mL, P < .0001), lipid hydroperoxides (13.8 [6.3; 20.7] vs 4.9 [2.3; 9.6] nmol/μl, P < .0001) and 8-hydroxy-2'-deoxyguanosine (558.9 [321.0; 6301.2] vs 294.51 [215.31; 408.95] pg/mL, P < .0001), whereas increased serum GPx activity (10.44 [4.6; 16.3] vs 13.75 [9.42; 20.63] nmol/min/mL, P = .001). By multiple linear regression analysis ΔcIMT was independently associated with ΔF₂ -isoprostanes (β: 1.746 [0.948; 2.543]; P < .0001) after adjustment for age, baseline F₂ -isoprostanes and baseline IMT.

CONCLUSIONS

Besides association of lipid peroxidation with severity of liver disease, the reduction in F₂ -isoprostanes may be involved in the improvement of atherosclerosis after HCV eradication.

Monitoring the Redox Status in Multiple Sclerosis

Worldwide, over 2.2 million people suffer from multiple sclerosis (MS), a multifactorial demyelinating disease of the central nervous system. MS is characterized by a wide range of motor, autonomic, and psychobehavioral symptoms, including depression, anxiety, and dementia. The blood, cerebrospinal fluid, and postmortem brain samples of MS patients provide evidence on the disturbance of reduction-oxidation (redox) homeostasis, such as the alterations of oxidative and antioxidative enzyme activities and the presence of degradation products. This review article discusses the components of redox homeostasis, including reactive chemical species, oxidative enzymes, antioxidative enzymes, and degradation products. The reactive chemical species cover frequently discussed reactive oxygen/nitrogen species, infrequently featured reactive chemicals such as sulfur, carbonyl, halogen, selenium, and nucleophilic species that potentially act as reductive, as well as pro-oxidative stressors. The antioxidative enzyme systems cover the nuclear factor erythroid-2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) signaling pathway. The NRF2 and other transcriptional factors potentially become a biomarker sensitive to the initial phase of oxidative stress. Altered components of the redox homeostasis in MS were discussed in search of a diagnostic, prognostic, predictive, and/or therapeutic biomarker. Finally, monitoring the battery of reactive chemical species, oxidative enzymes, antioxidative enzymes, and degradation products helps to evaluate the redox status of MS patients to expedite the building of personalized treatment plans for the sake of a better quality of life.

Detecting Oxidative Stress Biomarkers in Neurodegenerative Disease Models and Patients

Oxidative stress is prominent in many neurodegenerative diseases. Along with mitochondrial dysfunction and pathological protein aggregation, increased levels of reactive oxygen and nitrogen species, together with impaired antioxidant defense mechanisms, are frequently observed in Alzheimer's, Parkinson's, Huntington's disease and amyotrophic lateral sclerosis. The presence of oxidative stress markers in patients' plasma and cerebrospinal fluid may aid early disease diagnoses, as well as provide clues regarding the efficacy of experimental disease-modifying therapies in clinical trials. In preclinical animal models, the detection and localization of oxidatively damaged lipids, proteins and nucleic acids helps to identify most vulnerable neuronal populations and brain areas, and elucidate the molecular pathways and the timeline of pathology progression. Here, we describe the protocol for the detection of oxidative stress markers using immunohistochemistry on formaldehyde-fixed, paraffin-embedded tissue sections, applicable to the analysis of postmortem samples and tissues from animal models. In addition, we provide a simple method for the detection of malondialdehyde in tissue lysates and body fluids, which is useful for screening and the identification of tissues and structures in the nervous system which are most affected by oxidative stress.

Occupational exposure to volatile organic compounds affects microRNA profiling: Towards the identification of novel biomarkers

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Exposure to volatile organic compounds represents a threat for workers' health and safety, even using protective equipment.

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Spray-painting exposure is at higher risk than roller-painting.

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Exposure to organic solvents may induce DNA and RNA oxidation, urine metabolite excretion and miRNA up- or down-regulation.

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miR-589-5p and miR-941, miR-146b-3p and miR-27a-3p have been identified as potential biomarkers of effect in exposed workers.

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KEGG pathway analysis showed that miRNA-1, related to lung cancer, is significantly downregulated in exposed workers.

In the framework of a project aimed at finding novel predictive biomarkers of VOCs exposure-related diseases, the effect of exposure to ethylbenzene, toluene, and xylene has been analyzed in a group of painters (spray- and roller-painters) working in the shipyard industry. Airborne levels of solvents were higher in spray- than in roller-painters, and comparable to the Occupational Exposure Limits (OELs), particularly for toluene and xylene. The urinary concentration of each volatile organic compound (VOC) and of the corresponding metabolites were also concurrently measured. A set of oxidative stress biomarkers, i.e., the products of DNA and RNA oxidation, RNA methylation, and protein nitration, were measured, and found significantly higher at the end of the work shift. MicroRNA (MiRNA) expression was analyzed in the VOC-exposed workers and in a control group, finding 56 differentially expressed (DE) miRNAs at a statistically significant level (adjusted p ≤ 0.01). The Receiver-Operating Characteristic curves, computed for each identified miRNA, showed high sensitivity and specificity. A pathway analysis in the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that miRNA-1, which was found downregulated in exposed workers, is involved in the lung cancer oncogenesis. A subset of 10 miRNAs (out of the 56 DE) was selected, including those with the highest correlation to the urinary dose biomarkers measured at the end of work-shift. Multivariate ANOVA analysis showed a statistically significant correlation between the urinary dose biomarkers (both the VOCs urinary concentration and the VOCs’ metabolite concentration), and the identified miRNA subset, indicating that the exposure to low VOC doses may be sufficient to activate the miRNA response. Four miRNAs belonging to the subset strongly related to the VOCs and VOCs’ metabolites concentration were individuated, miR-589-5p, miR-941, miR-146b-3p and miR-27a-3p, with well-known implications in oxidative stress and inflammation processes.

3-Nitrotyrosine: a versatile oxidative stress biomarker for major neurodegenerative diseases

Reactive oxygen species are generated as a by-product of routine biochemical reactions. However, dysfunction of the antioxidant system or mutations in gene function may result in the elevated production of the pro-oxidant species. Modified endogenous molecules due to chemical interactions with increased levels of reactive oxygen and nitrogen species in the cellular microenvironment can be termed as biomarkers of oxidative stress. 3-Nitrotyrosine is one such promising biomarker of oxidative stress formed due to nitration of protein-bound and free tyrosine residues by reactive peroxynitrite molecules. Nitration of proteins at the subcellular level results in conformational alterations that damage the cytoskeleton and result in neurodegeneration. In this review, we summarized the role of oxidative/nitrosative processes as a contributing factor for progressive neurodegeneration in Alzheimer's disease, Parkinson's disease, Huntington's disease, Lou Gehrig's disease and Prion disease. The selective tyrosine protein nitration of the major marker proteins in related pathologies has been discussed. The alteration in 3-Nitrotyrosine profile occurs well before any symptoms appear and can be considered as a potential target for early diagnosis of neurodegenerative diseases. Furthermore, the reduction in 3-Nitrotyrosine levels in response to treatment with neuroprotective has been highlighted which is indicative of the importance of this particular marker in oxidative stress-related brain and central nervous system pathologies.

Protective Role of Hydrogen Gas on Oxidative Damage and Apoptosis in Intestinal Porcine Epithelial Cells (IPEC-J2) Induced by Deoxynivalenol: A Preliminary Study

To explore the protective role of hydrogen gas (H2) on oxidative damage and apoptosis in intestinal porcine epithelial cells (IPEC-J2) induced by deoxynivalenol (DON), cells were assigned to four treatment groups, including control, 5 μM DON, H2-saturated medium, and 5 μM DON + H2-saturated medium treatments. After 12 h of different treatments, the cell viability, biomarkers of cell redox states, and gene expression of antioxidant enzymes and apoptosis were observed and detected. Furthermore, caspase-3 and Bax protein expressions were measured by Western blot analysis. Our results demonstrated that the 5 μM DON significantly caused cytotoxicity to IPEC-J2 cells by reducing cell viability and increasing lactate dehydrogenase release in culture supernatants. Moreover, DON treatments significantly increased levels of 8-hydroxy-2'-deoxyguanosine, 3-nitrotyrosine, and malonaldehyde; however, they decreased total superoxide dismutase and catalase activities and downregulated messenger RNA (mRNA) expression related to antioxidant enzymes in cells. The 5 μM DON treatment also downregulated Bcl-2 expression and upregulated caspase-3 and Bax expression. However, the H2-saturated medium significantly improved cell growth status and reversed the change of redox states and expression of genes and proteins related to apoptosis induced by DON in IPEC-J2 cells. In conclusion, H2 could protect IPEC-J2 cells from DON-induced oxidative damage and apoptosis in vitro.

Persistent Oxidative Stress in Vestibular Schwannomas After Stereotactic Radiation Therapy

OBJECTIVE

Stereotactic radiation therapy is increasingly used to treat vestibular schwannomas (VSs) primarily and to treat tumor remnants following microsurgery. Little data are available regarding the effects of radiation on VS cells. Tyrosine nitrosylation is a marker of oxidative stress following radiation in malignant tumors. It is not known how long irradiated tissue remains under oxidative stress, and if such modifications occur in benign neoplasms such as VSs treated with significantly lower doses of radiation. We immunostained sections from previously radiated VSs with an antibody that recognizes nitrosylated tyrosine residues to assess for ongoing oxidative stress.

STUDY DESIGN

Immunohistochemical analysis.

METHODS

Four VSs, which recurred after excision, were treated with stereotactic radiation therapy. Ultimately each tumor required salvage reresection for regrowth. Histologic sections of each tumor before and after radiation were immunolabeled with a monoclonal antibody specific to nitrotyrosine and compared. Two VSs that underwent reresection of a growing tumor remnant without previous radiation therapy served as additional controls.

RESULTS

Irradiated tumors enlarged in volume by 3.16 to 8.62 mL following radiation. Preradiation sections demonstrated little to no nitrotyrosine immunostaining. Three of four of irradiated VSs demonstrated increased nitrotyrosine immunostaining in the postradiation sections compared with preradiation tumor sections. Nonirradiated VSs did not label with the antinitrotyrosine antibody.

CONCLUSIONS

VSs exhibit oxidative stress up to 7 years after radiotherapy, yet these VSs continued to enlarge. Thus, VSs that grow following radiation appear to possess mechanisms for cell survival and proliferation despite radiation-induced oxidative stress.

Reformulating Pro-Oxidant Microglia in Neurodegeneration

In neurodegenerative diseases, microglia-mediated neuroinflammation and oxidative stress are central events. Recent genome-wide transcriptomic analyses of microglial cells under different disease conditions have uncovered a new subpopulation named disease-associated microglia (DAM). These studies have challenged the classical view of the microglia polarization state's proinflammatory M1 (classical activation) and immunosuppressive M2 (alternative activation). Molecular signatures of DAM and proinflammatory microglia (highly pro-oxidant) have shown clear differences, yet a partial overlapping gene profile is evident between both phenotypes. The switch activation of homeostatic microglia into reactive microglia relies on the selective activation of key surface receptors involved in the maintenance of brain homeostasis (a.k.a. pattern recognition receptors, PRRs). Two relevant PRRs are toll-like receptors (TLRs) and triggering receptors expressed on myeloid cells-2 (TREM2), whose selective activation is believed to generate either a proinflammatory or a DAM phenotype, respectively. However, the recent identification of endogenous disease-related ligands, which bind to and activate both TLRs and TREM2, anticipates the existence of rather complex microglia responses. Examples of potential endogenous dual ligands include amyloid β, galectin-3, and apolipoprotein E. These pleiotropic ligands induce a microglia polarization that is more complicated than initially expected, suggesting the possibility that different microglia subtypes may coexist. This review highlights the main microglia polarization states under disease conditions and their leading role orchestrating oxidative stress.

An Azo Coupling Strategy for Protein 3-Nitrotyrosine Derivatization

Herein, a strategy for the selective derivatization of 3-nitrotyrosine-containing proteins using the classic azo coupling reaction as the key step is described. This novel approach featured multiple advantages and was successfully applied to detect picomole levels of protein tyrosine nitration in biological samples.