Association of Tumour Microenvironment with Protein Glycooxidation, DNA Damage, and Nitrosative Stress in Colorectal Cancer

Gut microbiota in cancer: From molecular mechanisms to precision medicine applications

The gut microbiota-cancer interaction functions through multi-level biological mechanisms, forming the basis for both diagnostic and therapeutic applications. Current technical and biological challenges drive the field toward precision medicine approaches, aiming to integrate multi-dimensional data for optimized, personalized cancer treatments.

Preoperative and Postoperative Neutrophil-Lymphocyte Ratio and Platelet-Lymphocyte Ratio Measured From the Peripheral Blood of Patients with Colorectal Cancer

Background

The neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) have been confirmed to be related to the clinicopathological features and prognosis of colorectal cancer (CRC) patients. However, the results have been inconsistent, and few studies have focused on a specific point in time during surgery and dynamic changes prior to and after surgery.

Methods

We conducted a retrospective analysis of 349 CRC patients and explored the value of NLR, PLR and their dynamic changes in predicting clinicopathological variables and prognosis in CRC.

Results

Preoperative NLR (Pre-NLR) was correlated with CEA, CA199 levels, tumor location and tumor stage (P=0.041, P=0.002, P=0.001 and P=0.012, respectively), whereas postoperative NLR (post-NLR) was relevant to age, sex, CA125 levels and T stage significantly (P=0.032, P=0.002, P=0.026, P=0.019, respectively). When comparing post- and pre-NLR values, there was a positive connection between increases in NLR and BMI, tumor location, T stage, and tumor stage (P=0.034, P=0.005, P=0.023, P=0.023, respectively). In addition, Preoperative PLR (pre-PLR) was correlated with sex, smoke and drink history, CEA and CA199 levels, tumor location, T stage and tumor stage (P=0.006, P=0.037, P=0.040, P=0.006, P=0.005, P<0.001, P=0.007, P=0.003 respectively), while postoperativePLR (post-PLR) was only associated with tumor location (P=0.010). Increases in PLR were significantly related to sex, smoking history, tumor location and differentiation (P=0.001, P=0.002, P<0.001, P=0.034, respectively). Patients with CRC who had a high post-PLR experienced significantly shorter relapse-free survival (RFS) compared to other patients (HR 0.607 (0.381-0.968), P=0.036). Furthermore, this high post-PLR has tendency association with shorter overall survival (OS) (HR 0.596 (0.338-1.050), P=0.076).

Conclusion

These findings suggest that levels and changes in NLR/PLR are associated with several unfavorable clinicopathological features in CRC patients. Furthermore, patients with high levels of post-PLR exhibit a worse prognosis.

Oxidative stress index-based scoring for prediction of long-term prognosis in patients with colorectal cancer with liver metastases

Oxidative stress has been implicated as a pivotal factor in the pathogenesis of numerous malignancies. However, the association between oxidative stress and the prognosis of patients with colorectal cancer liver metastasis (CRCLM) is not well elucidated. We conducted a retrospective analysis of 424 patients with CRCLM who underwent primary resection at the Union Hospital, Tongji Medical College, Wuhan, between July 2013 and September 2018. Patients were randomly divided into a training set (n = 300) and a test set (n = 124) in a 7:3 ratio.To develop the CRCLM-integrated Oxidative Stress Score (CLIOSS) for CRCLM, we utilized individual oxidative stress markers. The overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method, and the log-rank test was employed to assess prognostic factors.To validate the predictive performance of CLIOSS, we constructed Receiver Operating Characteristic (ROC) curves and calculated the Area Under the Curve (AUC) values. Additionally, Decision Curve Analysis (DCA) and calibration plots were used to evaluate the clinical utility and predictive consistency of the model. The CLIOSS prognostic model was constructed based on the following variables and their corresponding β coefficients: 0.042 × total bilirubin (TBIL, µmol/L) + 0.032 × blood urea nitrogen (BUN, mmol/L) - 0.001 × uric acid (UA, µmol/L). Higher CLIOSS were associated with poorer OS (2.934;95% CI 2.167-3.974;P < 0.001) and DFS(2.707; 95% CI 2.000-3.664; P  < 0.001. The 3-year OS AUC values were 0.803 in the training set and 0.851 in the testset, while the 3-year DFS AUC values were 0.892 and 0.898, respectively. Decision curve analysis demonstrated that both predictive models have significant clinical utility in practice. CLIOSS is a comprehensive prognostic index derived from oxidative stress markers, designed to predict long-term survival in patients with CRCLM. Our study shows that higher CLIOSS are significantly associated with poorer outcomes, making it an important tool for assessing patient risk.

The antiglycation potential of H1 receptor antagonists - in vitro studies in bovine serum albumin model and in silico molecular docking analyses

The H1 receptor belongs to the family of rhodopsin-like G-protein-coupled receptors activated by the biogenic amine histamine. H1 receptor antagonists are widely used in the treatment of allergies. However, these drugs could have a much broader spectrum of activity, including hypoglycemic effects, which can broaden the spectrum of their use. The aim of the study was to evaluate the antiglycation potential of twelve H1 receptor antagonists (diphenhydramine, antazoline, promethazine, ketotifen, clemastine, pheniramine, cetirizine, levocetirizine, bilastine, fexofenadine, desloratadine, and loratadine). Bovine serum albumin (BSA) was glycated with sugars (glucose, fructose, galactose, and ribose) and aldehydes (glyoxal and methylglyoxal) in the presence of H1 blockers. The tested substances did not induce a significant decrease in the content of albumin glycation end-products, and the inhibition rate of glycoxidation was not influenced by the chemical structure or generation of H1 blockers. None of the tested H1 receptor antagonists exhibited strong antiglycation activity. Antiglycemic potential of H1 blockers could be attributed to their antioxidant and anti-inflammatory activity, as well as their effects on carbohydrate metabolism/metabolic balance at the systemic level.

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives: An update

1-Amino-1-deoxy-d-fructose (fructosamine, FN) derivatives are omnipresent in all living organisms, as a result of non-enzymatic condensation and Amadori rearrangement reactions between free glucose and biogenic amines such as amino acids, polypeptides, or aminophospholipids. Over decades, steady interest in fructosamine was largely sustained by its role as a key intermediate structure in the Maillard reaction that is responsible for the organoleptic and nutritional value of thermally processed foods, and for pathophysiological effects of hyperglycemia in diabetes. New trends in fructosamine research include the discovery and engineering of FN-processing enzymes, development of advanced tools for hyperglycemia monitoring, and evaluation of the therapeutic potential of both fructosamines and FN-recognizing proteins. This article covers developments in the field of fructosamine and its derivatives since 2010 and attempts to ascertain challenges in future research.

Serum Oxidative and Nitrosative Stress Markers in Clear Cell Renal Cell Carcinoma

Oxidative stress is believed to be a factor in the development and progression of renal cell carcinoma (RCC). The identification of the oxidative and nitrosative modification of proteins and the definition of their roles in clear cell RCC (ccRCC) may be helpful in the elaboration of targeted therapeutic approaches to mitigate protein damage. This study aimed to investigate the status of oxidative/nitrosative stress and to explore its role in the development and progression. The studied group consisted of 48 newly diagnosed ccRCC and 30 healthy controls. Serum levels of oxidative stress markers-advanced oxidation protein products (AOPP), thiol groups, Amadori reaction products, 3-nitrotyrosine, nitrate/nitrite, malondialdehyde (MDA), 4-hydroxy-2-nonenal and total antioxidant capacity (TAC)-were determined. Additionally, associations between tumour stage assessed according to TNM classification, histological grade, and the effect of the presence of angioinvasion on the level of stress markers were evaluated. The levels of Amadori products, 3-nitrotyrosine, and nitrate/nitrite were elevated, while the levels of thiol groups and TAC decreased in the ccRCC group. The levels of AOPP, Amadori, and 3-nitrotyrosine increased, and thiol groups and TAC levels decreased with the increasing pathological stage of the tumour. In the case of advanced histological assessment of the tumour, we found decreasing levels of thiol groups and increasing levels of MDA. In patients with angioinvasion, nitrate/nitrite and MDA levels were significantly elevated compared to those in patients without angioinvasion. Oxidative stress increased with the progression of the disease assessed according to the TNM and histological grade. These results demonstrate systemic oxidative stress in ccRCC, suggesting the therapeutic application of antioxidants.

Could circulating biomarkers of nitrosative stress and protein glycoxidation be useful in patients with gastric cancer?

Background

Nitrosative stress leads to protein glycoxidation, but both processes may be strongly related to the cancer development. Therefore, the aim of this study was to assess the nitrosative stress and protein glycoxidation products in patients with gastric cancer in comparison with healthy controls. We are also the first to evaluate the diagnostic utility of nitrosative stress and protein glycoxidation markers in gastric cancer patients in respect to histopathological classifications (TNM, Lauren's and Goseki's classification) and histopathological parameters such as histological type, histological differentiation grade, presence of vascular or neural invasion, desmoplasia and Helicobacter pylori infection.

Methods

The study included 50 patients with gastric cancer and 50 healthy controls matched for sex and age. Nitrosative stress parameters and protein glycoxidation products were measured colorimetrically/fluorometrically in plasma or serum samples. Student's t-test or Mann-Whitney U-test were used for statistical analysis.

Results

NO, S-nitrosothiols, nitrotyrosine, kynurenine, N-formylkynurenine, dityrosine, AGE and Amadori products were significantly increased whereas tryptophan fluorescence was decreased in patients with gastric cancer compared to the healthy control. Nitrosative stress and glycoxidation products may be useful in diagnosis of gastric cancer because they differentiate patients with gastric cancer from healthy individuals with high sensitivity and specificity. Some of the determined parameters are characterised by high AUC value in differentiation of GC patients according to the histopathological parameters.

Conclusions

Gastric cancer is associated with enhanced circulating nitrosative stress and protein glycation. Although further research on a tissue model is needed, plasma/serum biomarkers may be dependent on tumour size, histological type, tumour invasion depth, presence of lymph node and distant metastasis, vascular and neural invasion and Helicobacter pylori infection. Thus, circulating biomarkers of nitrosative stress/protein glycoxidation may have potential diagnostic significance in gastric cancer patients.

Indole metabolites and colorectal cancer: Gut microbial tryptophan metabolism, host gut microbiome biomarkers, and potential intervention mechanisms

Tryptophan (Trp) functions in host-disease interactions. Its metabolism is a multi-pathway process. Indole and its derivatives are Trp metabolites unique to the human gut microbiota. Changes in Trp metabolism have also been detected in colorectal cancer (CRC). Here, combined with the existing CRC biomarkers, we ascribed it to the altered bacteria having the indole-producing ability by making a genomic prediction. We also reviewed the anti-inflammatory and possible anti-cancer mechanisms of indoles, including their effects on tumor cells, the ability to repair the gut barrier, regulation of the host immune system, and provide resistance against oxidative stress. Indole and its derivatives, along with related bacteria, could be targeted as auxiliary strategies to restrain cancer development in the future.

Oxidative Stress, Inflammation and Colorectal Cancer: An Overview

Colorectal cancer (CRC) represents the second leading cause of cancer-related deaths worldwide. The pathogenesis of CRC is a complex multistep process. Among other factors, inflammation and oxidative stress (OS) have been reported to be involved in the initiation and development of CRC. Although OS plays a vital part in the life of all organisms, its long-term effects on the human body may be involved in the development of different chronic diseases, including cancer diseases. Chronic OS can lead to the oxidation of biomolecules (nucleic acids, lipids and proteins) or the activation of inflammatory signaling pathways, resulting in the activation of several transcription factors or the dysregulation of gene and protein expression followed by tumor initiation or cancer cell survival. In addition, it is well known that chronic intestinal diseases such as inflammatory bowel disease (IBD) are associated with an increased risk of cancer, and a link between OS and IBD initiation and progression has been reported. This review focuses on the role of oxidative stress as a causative agent of inflammation in colorectal cancer.

The role of oxidative stress, tumor and inflammatory markers in colorectal cancer patients: A one-year follow-up study

Oxidative stress (OS) and inflammation are known to play an important role in colorectal cancer (CRC). This study analyzed tumor, inflammatory and OS markers in CRC patients and in a control group. In addition, the evolution of these markers was evaluated after one-year of follow-up treatment. This was a longitudinal and prospective, observational study in 80 CRC patients who were candidates for tumor resection surgery and/or chemo-radiotherapy treatment and a healthy control group (n = 60). Subsequently, catalase (CAT), reduced glutathione (GSH), oxidized glutathione (GSSG) and GSSG/GSH ratio in serum and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and F2-IsoProstanes (F2-IsoPs) in urine at 1, 6 and 12 months after treatment was analyzed. Tumor markers (CEA and CA 19.9), as well as inflammatory markers-leukocytes, neutrophils, neutrophil/lymphocyte (N/L) index, platelets, fibrinogen, C-reactive protein (CRP), and interleukin 6 (IL6)- were also analyzed. As expected, levels of CEA and CA 19.9 and markers of inflammation, except CRP, were significantly higher in CRC compared to the control group. Regarding OS markers, a decrease in CAT and GSH and an increase in GSSG, GSSG/GSH ratio, 8-oxodG and F2-IsoPs were found in CRC patients compared to healthy controls at baseline. After treatment, an improvement of their inflammation profile was accompanied by a progressive recovery of antioxidant enzyme activities and the decline of oxidative byproducts both in serum and urine. Based on the results obtained, we propose the assay of urinary 8-oxodG and F2-IsoPs, as well as serum CAT, GSH, GSSG as a marker for the evaluation of OS and the clinical follow-up of CRC patients.

Fashionable, but What is Their Real Clinical Usefulness? NLR, LMR, and PLR as a Promising Indicator in Colorectal Cancer Prognosis: A Systematic Review

The link between inflammation and cancer is still an attractive subject of many studies because systemic inflammatory response has been proven to play a pivotal role in cancer progression and metastasis. The strongest relationship between chronic inflammation and cancer development is observed in colorectal cancer (CRC). The evaluation of ratios derived from the routinely performed inflammatory biomarkers shows limited performances and limited clinical utility when individually used as prognostic factors for patients with CRC. In this review, we would like to summarize the latest knowledge about the diagnostic utility of systemic inflammatory ratios: neutrophil/lymphocyte (NLR), lymphocyte/monocyte (LMR), and platelet/lymphocyte (PLR) in CRC. We focused on the papers that assessed the diagnostic utility of blood cell parameters on the basis of the area under the ROC curve published in the recent 6 years. Identification of biomarkers that are significantly associated with prognostic in cancer would help the selection of patients with a high risk of poor outcomes.

Diagnostic significance and utility of circulating redox biomarkers in patients with gastric cancer - preliminary study

BACKGROUND

This study aimed to evaluate the redox status, antioxidant barrier, and oxidative damage to proteins, lipids, and DNA in patients with gastric cancer (GC). We are also the first to assess the diagnostic utility of redox parameters in patients with GC with respect to histopathological parameters.

METHODS

Fifty patients with gastric cancer and 50 healthy controls matched for sex and age were included in the study. The antioxidant barrier, redox status, and oxidative damage products were measured in serum/plasma samples using colorimetric or spectrophotometric methods.

RESULTS

The activity of superoxide dismutase - SOD (p < 0.05) was significantly higher, whereas the activities of catalase - CAT (p < 0.0001), glutathione peroxidase - GPx (p < 0.0001), glutathione reductase - GR (p < 0.0001), and reduced glutathione - GSH (p < 0.05) were considerably lower in GC patients than in the control group. The levels of total oxidant status - TOS (p < 0.0001), oxidative stress index - OSI (p < 0.0001), advanced oxidation protein products - AOPP (p < 0.0001), ischaemia modified albumin - IMA (p < 0.01), lipid hydroperoxides - LOOH (p < 0.0001), 8-IsoProstane - 8-Iso-P (p < 0.0001), and DNA/RNA (p < 0.0001) were significantly higher, and the levels of total antioxidant capacity - TAC (p < 0.0001) and total thiols (p < 0.0001) were considerably lower in patients compared to the healthy controls. Some redox parameters are characterized by high AUC values in patients with differentiated GC according to histopathological parameters.

CONCLUSIONS

Gastric cancer is strongly linked to a systemic redox imbalance and increased oxidative damage to proteins, lipids, and DNA. Redox biomarkers are potential diagnostic indicators of gastric cancer advancement.

Do Circulating Redox Biomarkers Have Diagnostic Significance in Alcohol-Intoxicated People?

The toxic properties of ethanol are inextricably linked to oxidative stress. Despite many reports on the effects of alcohol dependence on blood redox homeostasis, there are no data on the oxidative stress profile in alcohol-poisoned cases. There are also no data on the diagnostic usefulness of redox biomarkers determined post-mortem in various biological fluids. This work investigates the utility of enzymatic and non-enzymatic antioxidant barrier, redox status, and oxidative/nitrosative stress biomarkers in different biological fluids (such as blood, urine, vitreous humor, and cerebrospinal fluid) in the post-mortem study of patients with acute alcohol intoxication. The study group included those who died due to acute ethanol intoxication (n = 22). The research showed a significant increase in glutathione peroxidase activity, total antioxidant status, ferric reducing antioxidant power, and tryptophan concentration only in the study group’s urine compared to the control. In other circulating fluids, both antioxidant enzyme activities and glycoxidation product concentrations were not significantly different in individuals who died of alcohol overdose compared with those who died suddenly. We also did not observe a connection between oxidation–reduction balance and the amount of alcohol consumed before death. These unexpected observations may be caused by irreversible post-mortem changes occurring at the cellular level due to autolysis and putrefaction. In summary, the use of circulating body fluids to assess redox homeostasis is limited in the post-mortem analysis. Our results indicate the increased stability of urine collected post mortem compared to other circulating bioliquids. Further studies are needed to assess the intensity of oxidative and carbonyl stress in ethanol-damaged organs and the effects of post-mortem processes on cellular redox balance.

May the Nitrosative and Carbonyl Stress Promote Inflammation in Patients with Colorectal Cancer?

Purpose

Overproduction of reactive nitrogen species (RNS) causes the nitrosative stress, which plays a vital role in the development of metabolic, inflammatory, and cancerous diseases. However, the role of nitrosative and carbonyl stress in the biology of colorectal cancer (CRC) is still not well understood. Therefore, this study evaluated nitrosative stress, protein and DNA oxidation/glycoxidation, and pro- and anti-inflammatory cytokines in CRC patients compared with healthy controls.

Patients and Methods

Fifty-five CRC patients (21 women, 34 men) and 55 healthy controls matched for sex and age were included in the experiment. Nitrosative stress parameters (nitric oxide (NO), peroxynitrite, S-nitrosothiols, and nitrotyrosine), protein oxidation (total thiols) and glycoxidation products (kynurenine N-formylkynurenine, dityrosine, Amadori products, and amyloid), and DNA damage markers (8-hydroxydeoxyguanosine (8-OHdG)), as well as levels of pro- and anti-inflammatory cytokines, were measured in serum or plasma samples.

Results

The levels of NO, peroxynitrite, S-nitrosothiols, nitrotyrosine, total thiols, kynurenine, N-formylkynurenine, dityrosine, Amadori product, amyloid, and 8-OHdG, as well as IL1α, IL1β, IL6, IL10, and TNF-α, were significantly higher in CRC patients than in controls. Oxidation and glycoxidation products were positively correlated with pro-inflammatory (IL1α, IL1β, IL6, TNFα) and anti-inflammatory cytokines (IL10), indicating that redox damages may promote inflammation in CRC patients. Many redox biomarkers differentiate patients with CRC from healthy individuals with high sensitivity and specificity.

Conclusion

Correlations of chosen oxidative products with pro-inflammatory (IL1α, IL1β, IL6, TNFα) and anti-inflammatory cytokines (IL10) suggest that redox damages may promote inflammation in CRC patients. Thus, our research is the first point for further clinical trials focusing on the evaluation of the diagnostic utility of nitrosative stress biomarkers in a larger group of CRC patients.

Adherence to the Mediterranean Diet Has a Protective Role against Metabolic and DNA Damage Markers in Colorectal Cancer Patients

Oxidative stress (OS) and inflammation have been related to colorectal cancer (CRC), but the influence of the Mediterranean diet (MD) on these parameters is unknown. Therefore, the aim of this study was to determine the association between adherence to the MD and markers of OS and DNA damage in CRC patients and to study the influence of adherence to the MD on metabolic and tumor-related factors. This prospective observational study included a total of 80 patients diagnosed with CRC. Adherence to the MD was estimated by the 14-item Mediterranean Diet Adherence Screener (MEDAS) questionnaire. The levels of OS markers (catalase, glutathione peroxidase, and glutathione system in serum; 8-oxo-7'8-dihydro-2'-deoxyguanosine and F2-isoprotanes in urine) and tumor and metabolic factors were determined. A total of 51.2% of our CRC patients showed a high adherence to the MD. These patients presented decreased levels of 8-oxodG, increased GPX and HDL-cholesterol levels, and a downward trend in the GSSG/GSH ratio with respect to patients with low adherence to the MD. In addition, a high adherence to the MD was associated with a lower histological grade of the tumor and a lower presence of synchronous adenomas. We conclude that a high adherence to the MD has a protective role against metabolic and oxidative DNA damage and improves antioxidant systems in CRC patients.

Oxidation, Glycation, and Carbamylation of Salivary Biomolecules in Healthy Children, Adults, and the Elderly: Can Saliva Be Used in the Assessment of Aging?

Background

Aging is inextricably linked to oxidative stress, inflammation, and posttranslational protein modifications. However, no studies evaluate oxidation, glycation, and carbamylation of salivary biomolecules as biomarkers of aging. Saliva collection is non-invasive, painless, and inexpensive, which are advantages over other biofluids.

Methods

The study enrolled 180 healthy subjects divided into six groups according to age: 6–13, 14–19, 20–39, 40–59, 60–79, and 80–100 years. The number of individuals was determined a priori based on our previous experiment (power of the test = 0.8; α = 0.05). Non-stimulated saliva and plasma were collected from participants, in which biomarkers of aging were determined by colorimetric, fluorometric, and ELISA methods.

Results

The study have demonstrated that modifications of salivary proteins increase with age, as manifested by decreased total thiol levels and increased carbonyl groups, glycation (Nε-(carboxymethyl) lysine, advanced glycation end products (AGE)) and carbamylation (carbamyl-lysine) protein products in the saliva of old individuals. Oxidative modifications of lipids (4-hydroxynonenal) and nucleic acids (8-hydroxy-2’-deoxyguanosine (8-OHdG)) also increase with age. Salivary redox biomarkers correlate poorly with their plasma levels; however, salivary AGE and 8-OHdG generally reflect their blood concentrations. In the multivariate regression model, they are a predictor of aging and, in the receiver operating characteristic (ROC) analysis, significantly differentiate children and adolescents (under 15 years old) from the working-age population (15–64 years) and the older people (65 years and older).

Conclusion

Salivary AGE and 8-OHdG have the most excellent diagnostic utility in assessing the aging process. Saliva can be used to evaluate the aging of the body.

Effect of Normobaric Hypoxia on Alterations in Redox Homeostasis, Nitrosative Stress, Inflammation, and Lysosomal Function following Acute Physical Exercise

Hypoxia is a recognized inducer of oxidative stress during prolonged physical activity. Nevertheless, previous studies have not systematically examined the effects of normoxia and hypoxia during acute physical exercise. The study is aimed at evaluating the relationship between enzymatic and nonenzymatic antioxidant barrier, total antioxidant/oxidant status, oxidative and nitrosative damage, inflammation, and lysosomal function in different acute exercise protocols under normoxia and hypoxia. Fifteen competitive athletes were recruited for the study. They were subjected to two types of acute cycling exercise with different intensities and durations: graded exercise until exhaustion (GE) and simulated 30 km individual time trial (TT). Both exercise protocols were performed under normoxic and hypoxic ( $\text{Fi}{\text{O}}_2=16.5\%$ ) conditions. The number of subjects was determined based on our previous experiment, assuming the test $\text{power}=0.8$ and $\alpha =0.05$ . We demonstrated enhanced enzymatic antioxidant systems during hypoxic exercise (GE: ↑ catalase (CAT), ↑ superoxide dismutase; TT: ↑ CAT) with a concomitant decrease in plasma reduced glutathione. In athletes exercising in hypoxia, redox status was shifted in favor of oxidation reactions (GE: ↑ total oxidant status, ↓ redox ratio), leading to increased oxidation/nitration of proteins (GE: ↑ advanced oxidation protein products (AOPP), ↑ ischemia-modified albumin, ↑ 3-nitrotyrosine, ↑ S-nitrosothiols; TT: ↑ AOPP) and lipids (GE: ↑ malondialdehyde). Concentrations of nitric oxide and its metabolites (peroxynitrite) were significantly higher in the plasma of hypoxic exercisers with an associated increase in inflammatory mediators (GE: ↑ myeloperoxidase, ↑ tumor necrosis factor-alpha) and lysosomal exoglycosidase activity (GE: ↑ N-acetyl-β-hexosaminidase, ↑ β-glucuronidase). Our study indicates that even a single intensive exercise session disrupts the antioxidant barrier and leads to increased oxidative and nitrosative damage at the systemic level. High-intensity exercise until exhaustion (GE) alters redox homeostasis more than the less intense exercise (TT, near the anaerobic threshold) of longer duration ( $20.2\pm 1.9$  min vs. $61.1\pm 5.4$  min—normoxia; $18.0\pm 1.9$  min vs. $63.7\pm 3.0$  min—hypoxia), while hypoxia significantly exacerbates oxidative stress, inflammation, and lysosomal dysfunction in athletic subjects.