Extracellular thiols and thiol/disulfide redox in metabolism

A Chemiluminescent Hydrogen Sulfide Probe with Multimodal Validation for Inflammation Diagnosis in Vivo

Probes capable of simultaneously detecting and differentiating biothiols is crucial yet challenging in optical chemical sensing. In this study, we design a multimodal probe, CL-NBD, through integrating chemiluminescence (high sensitivity and signal-to-noise ratio), absorption (visual discrimination by the naked eye), and fluorescence to distinguish various biothiol species. CL-NBD exhibits distinct signal response modes for hydrogen sulfide (H2S), cysteine/homocysteine (Cys/Hcy), and glutathione. Upon activation by biothiols, CL-NBD produces chemiluminescence and enhances fluorescence at 515 nm, allowing for selective biothiol detection over other reactive species. Additionally, the probe reveals specific absorbance enhancement at 531 nm for H2S, facilitating its selective detection. For Cys/Hcy, the probe enhances absorbance at 475 nm and fluorescence at 550 nm, enabling distinctive detection capabilities. Remarkably, CL-NBD was applied to visualize biothiol levels both at the cellular level and in vivo.

PyDNA-templated AgNPs coupled with poly (β‑cyclodextrin) enhanced fluorescence: A facile platform for signal amplification detection of biothiols in living cells and zebrafish

Accurate and sensitive fluorescence imaging of biothiols is essential for understanding the mechanism underlying some physiological and pathological events, as well as the prevention and diagnosis of diseases. However, low signal transduction efficiency and poor biocompatibility of fluorescence tags associated with current sensors hinder their potential utilizations. Herein, a smart biothiols sensitive vivo imaging platform on the basis of amplifying nanoprobe has been designed. The as-prepared nanoprobe are composed of 5'-pyrene-labeled single-stranded DNA with C-rich (PyDNA), DNA-templated silver nanoparticles (AgNPs) and amplification carrier β-cyclodextrin-based polymer (βCDP). PyDNA was not only used as a signal tag, but also as a templated DNA for in situ growth of silver nanoparticles (PyDNA-AgNPs), resulting in fluorescence quenching of PyDNA through FRET. In the presence of GSH as a model biothiol, replace PyDNA off from the surface of AgNPs owing to the interact intensely between biothiol and AgNPs by forming S-Ag bonds, resulting in a fluorescence enhancement. Simultaneously, the released PyDNA was able to form a host-guest inclusion complex with βCDP to achieve signal amplification (10.1-fold enhancement). The obtained nanoprobe exhibits high sensitivity and selectivity to glutathione (GSH) with a detection limit as low as 71 nM. Using HeLa cells as a model, this nanoprobe not only realizes the highly sensitive amplifying detection and imaging of GSH in living cells, but also applies in vivo monitoring of exogenous GSH level in zebrafish. Further use of probes to reveal the overexpression of GSH with the high-contrast imaging in the tumor tissues from the lung disease model mice and clinical lung cancer patients was successfully demonstrated. It provides a facile tool for highly sensitive biothiols imaging and may pave a new avenue for the early and accurate diagnosis of tumors.

NF-κB-mediated EAAT3 upregulation in antioxidant defense and ferroptosis sensitivity in lung cancer

Cellular glutathione (GSH) in lung cancer cells represents the most abundant antioxidant. GSH production is regulated not only by upregulated cystine/glutamate exchanger (xCT) but also by the involvement of glutamate transporters, specifically excitatory amino acid transporter 3 (EAAT3). Our prior research established that the uptake of glutamate via EAAT3 plays a pivotal role in driving cystine uptake through xCT, contributing to GSH biosynthesis during lung tumorigenesis. Nevertheless, the underlying mechanism governing the upregulation of EAAT3 remains enigmatic. In this study, we conducted a comprehensive reanalysis of publicly available data and employed the Gprc5a-/-/SR-IκB mouse model alongside in vitro cell experiments to elucidate the correlations between NF-κB and EAAT3 in lung cancer. We observed that EAAT3 knockdown, similar to NF-κB inhibition, led to the accumulation of reactive oxygen species (ROS) and increased sensitivity to ferroptosis induction by RAS-selective lethal 3 (RSL3). Mechanistic insights were obtained through chromatin immunoprecipitation and luciferase reporter assays, revealing that NF-κB induces EAAT3 expression via two putative cis-elements within its promoter. Furthermore, our investigation unveiled the upregulation of EAAT3 in a subset of clinical non-small cell lung cancer (NSCLC) tissues, exhibiting a positive correlation with the P65 protein. In addition, the inflammatory factor of smoking was found to augment EAAT3 expression in both human and murine experimental models. These findings collectively emphasize the pivotal role of the NF-κB/EAAT3 axis in managing antioxidant stress and influencing lung cancer development. Moreover, this research offers insights into the potential for a combined ferroptosis therapy strategy in lung cancer treatment.

Simultaneous Quantitation of Multiple Biological Thiols Using Reactive Ionization and Derivatization with Charged Mass Tags

The biologically important thiols (cysteine, homocysteine, N-acetyl cysteine, and glutathione) are key species in redox homeostasis, and there is a clinical need to measure them rapidly, accurately, and simultaneously at low levels in complex biofluids. The solution to the challenge presented here is based on a new derivatizing reagent that combines a thiol-selective unit to optimize the chemical transformation and a precharged pyridinium unit chosen to maximize sensitivity in mass spectrometry. Derivatization is performed simultaneously with ionization ("reactive ionization"), and mass spectrometry is used to record and characterize the thiol reaction products. The method is applicable over the concentration range from 1 μM to 10 mM and is demonstrated for 25 blood serum, 1 plasma, and 3 types of tissue samples. The experiment is characterized by limited sample preparation (<4 min) and short analysis time (<1 min). High precision and accuracy (both better than 8%) are validated using independent HPLC-MS analysis. Cystine-cysteine redox homeostasis can be monitored by introducing an additional reduction step, and the accuracy and precision of these results are also validated by HPLC-MS.

Regulation of Kv1.2 Redox-Sensitive Gating by the Transmembrane Lectin LMAN2

Voltage gated potassium (Kv)1.2 channels influence excitability and action potential propagation in the nervous system. Unlike closely related Kv1 channels, Kv1.2 exhibits highly variable voltage-dependence of gating, attributed to regulation by unidentified extrinsic factors. Variability of Kv1.2 gating is strongly influenced by the extracellular redox potential, and we demonstrate that Kv1.2 currents in dorsal root ganglion sensory neurons exhibit similar variability and redox sensitivity as observed when the channel is heterologously expressed in cell lines. We used a functional screening approach to test the effects of candidate regulatory proteins on Kv1.2 gating, using patch clamp electrophysiology. Among 52 candidate genes tested, we observed that co-expression with the transmembrane lectin LMAN2 led to a pronounced gating shift of Kv1.2 activation to depolarized voltages in CHO and L(tk-) cell lines, accompanied by deceleration of activation kinetics. Overexpression of LMAN2 promoted a slow gating mode of Kv1.2 that mimics the functional outcomes of extracellular reducing conditions, and enhanced sensitivity to extracellular reducing agents. In contrast, shRNA-mediated knockdown of endogenous LMAN2 in cell lines reduced Kv1.2 redox sensitivity and gating variability. Kv1.2 sensitivity to LMAN2 is abolished by mutation of neighboring residues F251 and T252 in the intracellular S2-S3 linker, and these also abolish redox-dependent gating changes, suggesting that LMAN2 influences the same pathway as redox for Kv1.2 modulation. In conclusion, we identified LMAN2 as a candidate regulatory protein that influences redox-dependent modulation of Kv1.2, and clarified the structural elements of the channel that are required for sensitivity.

Gold Nanorod Amalgamation: Machine Learning Empowered Discrimination of Biothiol and Thiol Ratios

Biothiols, characterized by thiol groups, exhibit remarkable affinity for certain metals, playing pivotal roles in intracellular and extracellular biological processes. Fluctuations in their levels profoundly impact overall physiological health. Despite the development of various probes for biothiol detection and quantification, their inability to monitor thiol-to-disulfide state transitions persists as a limitation. Given their association with pathologies, early detection remains imperative. Gold nanorod (AuNR)-based colorimetric probes have garnered attention for their utility in visual diagnostic assays. Herein, we present a cost-effective, and sensitive multicolor ratio measuring probe enabling on-site simultaneous identification, discrimination, and quantification of essential biothiols─cysteine (CYS), glutathione (GSH), cystine (CYSS), and glutathione disulfide (GSSG)─while also quantifying thiol-to-disulfide ratios. Our investigation clarifies the probe's functionality, elucidating etching and antietching mechanisms based on sulfhydryl group coordination with Hg2+. This coordination impedes gold amalgam formation, facilitating discriminative detection via AuNR size and aspect ratio modulation, validated by transmission electron microscopy. Notably, distinct rainbow-like fingerprint patterns were discernible both visually and spectroscopically for the aforementioned biothiols and their respective thiol-to-disulfide ratios. Subsequent qualitative and quantitative analyses via linear discriminant analysis (LDA) and partial least squares regression revealed linear correlations over broad concentration ranges (CYS: 1.9-40 μmol L-1, GSH: 3.2-200.0 μmol L-1, CYSS: 2.0-70.0 μmol L-1, GSSG: 3.7-100.0 μmol L-1), with detection limits of 0.66 μmol L-1 (CYS), 1.07 μmol L-1 (GSH), 0.69 μmol L-1 (CYSS), and 1.24 μmol L-1 (GSSG). Moreover, thiol-to-disulfide ratios exhibited linear patterns within 0.2-5 μmol L-1, with detection limits of 0.13 and 0.09 μmol L-1, and exceptional analytical sensitivities of 32.648 and 49.782 for (CYS/CYSS) and (GSH/GSSG), respectively. Lastly, we evaluated the probe's performance in complex matrices relative to aqueous media, both quantitatively and qualitatively.

Reactive oxygen species activate the Drosophila TNF receptor Wengen for damage-induced regeneration

Tumor necrosis factor receptors (TNFRs) control pleiotropic pro-inflammatory functions that range from apoptosis to cell survival. The ability to trigger a particular function will depend on the upstream cues, association with regulatory complexes, and downstream pathways. In Drosophila melanogaster, two TNFRs have been identified, Wengen (Wgn) and Grindelwald (Grnd). Although several reports associate these receptors with JNK-dependent apoptosis, it has recently been found that Wgn activates a variety of other functions. We demonstrate that Wgn is required for survival by protecting cells from apoptosis. This is mediated by dTRAF1 and results in the activation of p38 MAP kinase. Remarkably, Wgn is required for apoptosis-induced regeneration and is activated by the reactive oxygen species (ROS) produced following apoptosis. This ROS activation is exclusive for Wgn, but not for Grnd, and can occur after knocking down Eiger/TNFα. The extracellular cysteine-rich domain of Grnd is much more divergent than that of Wgn, which is more similar to TNFRs from other animals, including humans. Our results show a novel TNFR function that responds to stressors by ensuring p38-dependent regeneration.

Modification of extracellular matrix proteins by oxidants and electrophiles

The extracellular matrix (ECM) is critical to biological architecture and determines cellular properties, function and activity. In many situations it is highly abundant, with collagens and elastin being some of the most abundant proteins in mammals. The ECM comprises of multiple different protein species and sugar polymers, with both different isoforms and post-translational modifications (PTMs) providing a large variety of microenvironments that play a key role in determining tissue structure and health. A number of the PTMs (e.g. cross-links) present in the ECM are critical to integrity and function, whereas others are deleterious to both ECM structure and associated cells. Modifications induced by reactive oxidants and electrophiles have been reported to accumulate in some ECM with increasing age. This accumulation can be exacerbated by disease, and in particular those associated with acute or chronic inflammation, obesity and diabetes. This is likely to be due to higher fluxes of modifying agents in these conditions. In this focused review, the role and effects of oxidants and other electrophiles on ECM are discussed, with a particular focus on the artery wall and atherosclerotic cardiovascular disease. Modifications generated on ECM components are reviewed, together with the effects of these species on cellular properties including adhesion, proliferation, migration, viability, metabolic activity, gene expression and phenotype. Increasing data indicates that ECM modifications are both prevalent in human and mammalian tissues and play an important role in disease development and progression.

Did diet compliance and remission reduce oxidative stress in celiac patients?

OBJECTIVE

We aimed to examine the effect of remission status on thiol-disulfide homeostasis in celiac patients and thus to indirectly determine the effect of oxidative stress and inflammation caused by non-compliance with the diet.

METHODS

Between February 2019 and December 2021, 117 patients diagnosed with celiac disease were included in this prospective randomized and controlled study. In addition to routine tests of celiac patients, thiol and disulfide measurements were made from the blood both at the beginning of the study and at the end of the first year.

RESULTS

While 52 of the patients (44.4%) were in remission, 65 patients (55.6%) were not. There was an evident increase in native thiol levels of the patients who were initially not in remission but went into at the end of the first year (347.4±46.7 μmol/L vs. 365.3±44.0 μmol/L; p=0.001). Mean plasma disulfide levels of patients with celiac going into remission became reduced in the first year from the level of 14.5±5.1 μmol/L down to 8.9±4.2 μmol/L (p<0.001). In celiac patients who entered remission, disulfide and anti-tissue transglutaminase immunoglobulin A levels decreased in a correlation (r=0.526; p<0.001).

CONCLUSION

Not being in remission in celiac disease leads to increased oxidative stress, and thiol-disulfide homeostasis is an indirect indicator of this. Additionally, providing remission in celiac patients reduces oxidative stress.

A ratiometric upconversion nanoprobe enables super-resolution imaging sensing of biothiols in living cells

We have developed an upconversion luminescent ratiometric nanoprobe, specifically designed for detection of biothiols with high sensitivity (∼25 nM) at the single-particle level. Using a single-particle localization and rendering method, this nanoprobe enables super-resolution imaging sensing of biothiols within a confined 22 nm space in living cells.

Effects of redox modulation on quiescin/sulfhydryl oxidase activity of melanoma cells

Secreted quiescin/sulfhydryl oxidase (QSOX) is overexpressed in many tumor cell lines, including melanoma, and is usually associated with a pro-invasive phenotype. Our previous work described that B16-F10 cells enter in a quiescent state as a protective mechanism against damage generated by reactive oxygen species (ROS) during melanogenesis stimulation. Our present results show that QSOX activity was two-fold higher in cells with stimulated melanogenesis when compared to control cells. Considering that glutathione (GSH) is one of the main factor responsible for controlling redox homeostasis in cells, this work also aimed to investigate the relationship between QSOX activity, GSH levels and melanogenesis stimulation in B16-F10 murine melanoma cell line. The redox homeostasis was impaired by treating cells with GSH in excess or depleting its intracellular levels through BSO treatment. Interestingly, GSH-depleted cells without stimulation of melanogenesis kept high levels of viability, suggesting a possible adaptive mechanism of survival even under low GSH levels. They also showed lower extracellular activity of QSOX, and higher QSOX intracellular immunostaining, suggesting that this enzyme was less excreted from cells and corroborating with a diminished extracellular QSOX activity. On the other hand, cells under melanogenesis stimulation showed a lower GSH/GSSG ratio (8:1) in comparison with control (non-stimulated) cells (20:1), indicating a pro-oxidative state after stimulation. This was accompanied by decreased cell viability after GSH-depletion, no alterations in QSOX extracellular activity, but higher QSOX nucleic immunostaining. We suggest that melanogenesis stimulation and redox impairment caused by GSH-depletion enhanced the oxidative stress in these cells, contributing to additional alterations of its metabolic adaptive response.

Current advances in the development of bioluminescent probes toward spatiotemporal trans-scale imaging

Bioluminescence imaging has recently attracted great attention as a highly sensitive and non-invasive analytical method. However, weak signal and low chemical stability of the luciferin are conventional drawbacks of bioluminescence imaging. In this review article, we describe the recent progress on the development and applications of bioluminescent probes for overcoming the aforementioned limitations, thereby enabling spatiotemporal trans-scale imaging. The detailed molecular design for manipulation of their luminescent properties and functions enabled a variety of applications, including in vivo deep tissue imaging, long-term imaging, and chemical sensor.

Gasotransmitter-Mediated Cysteinome Oxidative Posttranslational Modifications: Formation, Biological Effects, and Detection

Significance: Gasotransmitters, including nitric oxide (NO), hydrogen sulfide (H2S) and sulfur dioxide (SO2), participate in various cellular processes via corresponding oxidative posttranslational modifications (oxiPTMs) of specific cysteines. Recent Advances: Accumulating evidence has clarified the mechanisms underlying the formation of oxiPTMs derived from gasotransmitters and their biological functions in multiple signal pathways. Because of the specific existence and functional importance, determining the sites of oxiPTMs in cysteine is crucial in biology. Recent advances in the development of selective probes, together with upgraded mass spectrometry (MS)-based proteomics, have enabled the quantitative analysis of cysteinome. To date, several cysteine residues have been identified as gasotransmitter targets. Critical Issues: To clearly understand the underlying mechanisms for gasotransmitter-mediated biological processes, it is important to identify modified targets. In this review, we summarize the chemical formation and biological effects of gasotransmitter-dependent oxiPTMs and highlight the state-of-the-art detection methods. Future Directions: Future studies in this field should aim to develop the next generation of probes for in situ labeling to improve spatial resolution and determine the dynamic change of oxiPTMs, which can lay the foundation for research on the molecular mechanisms and clinical translation of gasotransmitters. Antioxid. Redox Signal. 40, 145-167.

Uncoupled redox stress: how a temporal misalignment of redox-regulated processes and circadian rhythmicity exacerbates the stressed state

Diurnal and seasonal rhythmicity, entrained by environmental and nutritional cues, is a vital part of all life on Earth operating at every level of organization; from individual cells, to multicellular organisms, whole ecosystems and societies. Redox processes are intrinsic to physiological function and circadian regulation, but how they are integrated with other regulatory processes at the whole-body level is poorly understood. Circadian misalignment triggered by a major stressor (e.g. viral infection with SARS-CoV-2) or recurring stressors of lesser magnitude such as shift work elicit a complex stress response that leads to desynchronization of metabolic processes. This in turn challenges the system's ability to achieve redox balance due to alterations in metabolic fluxes (redox rewiring). We infer that the emerging 'alternative redox states' do not always revert readily to their evolved natural states; 'Long COVID' and other complex disorders of unknown aetiology are the clinical manifestations of such rearrangements. To better support and successfully manage bodily resilience to major stress and other redox challenges needs a clear perspective on the pattern of the hysteretic response for the interaction between the redox system and the circadian clock. Characterization of this system requires repeated (ideally continuous) recording of relevant clinical measures of the stress responses and whole-body redox state (temporal redox phenotyping). The human/animal body is a complex 'system of systems' with multi-level buffering capabilities, and it requires consideration of the wider dynamic context to identify a limited number of stress-markers suitable for routine clinical decision making. Systematically mapping the patterns and dynamics of redox biomarkers along the stressor/disease trajectory will provide an operational model of whole-body redox regulation/balance that can serve as basis for the identification of effective interventions which promote health by enhancing resilience.

Investigation of inflammation, oxidative stress, and DNA damage in COVID-19 patients

COVID-19 disease, which spreads worldwide, is a disease characterized by widespread inflammation and affects many organs, especially the lungs. The resulting inflammation can lead to reactive oxygen radicals, leading to oxidative DNA damage. The pneumonia severity of 95 hospitalized patients with positive RT-PCR test was determined and divided into three groups: mild, moderate, and severe/critical. Inflammation markers (neutrophil-lymphocyte ratio, serum reactive protein, procalcitonin, etc.) were determined, and IL-10 and IFN-γ measurements were analyzed using the enzyme-linked immunosorbent assay method. In evaluating oxidative damage, total thiol, native thiol, disulfide, and ischemia-modified albumin (IMA) levels were determined by measuring spectrophotometrically. The comet assay method's percentage of tail DNA obtained was used to determine oxidative DNA damage. As a result, when the mild and severe/critical groups were compared, we found that total thiol, native thiol, and disulfide levels decreased significantly in the severe/critical group due to the increase in inflammation markers and cytokine levels (p < 0.05). We could not detect any significance in IMA levels between the groups (p > 0.05). At the same time, we determined an increase in the tail DNA percent level, that is, DNA damage, due to the increased oxidative effect. As a result, we determined that inflammation and oxidative stress increased in patients with severe pneumonia, and there was DNA damage in these patients.

Skeletal muscle and erythrocyte redox status is associated with dietary cysteine intake and physical fitness in healthy young physically active men

PURPOSE

To investigate the association between redox status in erythrocytes and skeletal muscle with dietary nutrient intake and markers of physical fitness and habitual physical activity (PA).

METHODS

Forty-five young physically active men were assessed for body composition, dietary nutrient intake, muscle strength, cardiorespiratory capacity and habitual PA. Blood and muscle samples were collected to estimate selected redox biomarkers. Partial correlation analysis was used to evaluate the independent relationship of each factor with redox biomarkers.

RESULTS

Dietary cysteine intake was positively correlated (p < 0.001) with both erythrocyte (r = 0.697) and muscle GSH (0.654, p < 0.001), erythrocyte reduced/oxidized glutathione ratio (GSH/GSSG) (r = 0.530, p = 0.001) and glutathione reductase (GR) activity (r = 0.352, p = 0.030) and inversely correlated with erythrocyte protein carbonyls (PC) levels (r = - 0.325; p = 0.046). Knee extensors eccentric peak torque was positively correlated with GR activity (r = 0.355; p = 0.031) while, one-repetition maximum in back squat exercise was positively correlated with erythrocyte GSH/GSSG ratio (r = 0.401; p = 0.014) and inversely correlated with erythrocyte GSSG and PC (r = - 0.441, p = 0.006; r = - 0.413, p = 0.011 respectively). Glutathione peroxidase (GPx) activity was positively correlated with step count (r = 0.520; p < 0.001), light (r = 0.406; p = 0.008), moderate (r = 0.417; p = 0.006), moderate-to-vigorous (r = 0.475; p = 0.001), vigorous (r = 0.352; p = 0.022) and very vigorous (r = 0.326; p = 0.035) PA. Muscle GSSG inversely correlated with light PA (r = - 0.353; p = 0.022).

CONCLUSION

These results indicate that dietary cysteine intake may be a critical element for the regulation of glutathione metabolism and redox status in two different tissues pinpointing the independent significance of cysteine for optimal redox regulation. Musculoskeletal fitness and PA levels may be predictors of skeletal muscle, but not erythrocyte, antioxidant capacity.

TRIAL REGISTRATION

Registry: ClinicalTrials.gov, identifier: NCT03711838, date of registration: October 19, 2018.

Intramuscular administration of glyoxylate rescues swine from lethal cyanide poisoning and ameliorates the biochemical sequalae of cyanide intoxication

Cyanide-a fast-acting poison-is easy to obtain given its widespread use in manufacturing industries. It is a high-threat chemical agent that poses a risk of occupational exposure in addition to being a terrorist agent. FDA-approved cyanide antidotes must be given intravenously, which is not practical in a mass casualty setting due to the time and skill required to obtain intravenous access. Glyoxylate is an endogenous metabolite that binds cyanide and reverses cyanide-induced redox imbalances independent of chelation. Efficacy and biochemical mechanistic studies in an FDA-approved preclinical animal model have not been reported. Therefore, in a swine model of cyanide poisoning, we evaluated the efficacy of intramuscular glyoxylate on clinical, metabolic, and biochemical endpoints. Animals were instrumented for continuous hemodynamic monitoring and infused with potassium cyanide. Following cyanide-induced apnea, saline control or glyoxylate was administered intramuscularly. Throughout the study, serial blood samples were collected for pharmacokinetic, metabolite, and biochemical studies, in addition, vital signs, hemodynamic parameters, and laboratory values were measured. Survival in glyoxylate-treated animals was 83% compared with 12% in saline-treated control animals (p < .01). Glyoxylate treatment improved physiological parameters including pulse oximetry, arterial oxygenation, respiration, and pH. In addition, levels of citric acid cycle metabolites returned to baseline levels by the end of the study. Moreover, glyoxylate exerted distinct effects on redox balance as compared with a cyanide-chelating countermeasure. In our preclinical swine model of lethal cyanide poisoning, intramuscular administration of the endogenous metabolite glyoxylate improved survival and clinical outcomes, and ameliorated the biochemical effects of cyanide.

Value of thiol and ischemia modified albumin (IMA) in predicting mortality in serious COVID-19 pneumonia

Background/aim

Viral infections of the respiratory tract are generally related to many factors such as excessive production of cytokines, inflammation, cellular death, redox imbalance or oxidative stress. The aim of this study was to determine the serum levels of thiol and IMA in patients with severe COVID-19 pneumonia to evaluate oxidative stress.

Study design

This was a prospective, sectional cohort study conducted at a pandemics hospital between 01.01.2022 and 01.02.2022.

Methods

A total of 153 patients who had been confirmed with severe COVID-19 pneumonia in the emergency unit were prospectively analyzed. The control group was formed by 50 healthy volunteers with similar age and no chronic disease history. Thiol and IMA levels were statistically compared both in the patient and the control groups, and within the patient groups (survived and non-survival).

Results

While 96 out of 153 patients had survived, 57 patients had non-survival. There was a statistically significant distinction between the survived and non-survival patients with regard to Thiol and IMA levels (p < 0.001). The thiol levels in the patient group were significantly lower compared to the control group, and the IMA levels were significantly higher (p < 0.001). The sensitivity, specificity and NPV were 70.2%, 86.5% and 83% when thiol cut-off value was ≤345.2 μmol/L (AUC: 0.886, p < 0.001). The sensitivity, specificity and NPV were 70.2%, 85.4% and 82.8% when the IMA cut-off was >302.9 ABSU (AUC: 0.875, p < 0.001).

Conclusions

Our results demonstrate that thiol and IMA levels may be used as bioindicators for risk classification and mortality in patients with serious COVID-19 pneumonia.

Reduced Nucleotides, Thiols and O2 in Cellular Redox Balance: A Biochemist's View

In the present review, which is aimed at researchers, teachers and students in life sciences, we try to show how the physicochemical properties of the elements and molecules define the concept of redox balance. Living organism are open systems traversed by fluxes of energy and matter. During catabolic oxidative metabolism, matter-mostly hydrogenated organic molecules-is oxidized and ultimately released as CO₂. Electrons are passed over to coupling molecules, such as NAD+ and FAD, whose reduced forms serve as electrons donors in anabolic reactions. Early photosynthetic activity led to the accumulation of O₂ and the transformation of the reduction to an oxidizing atmosphere, favoring the development of oxidative metabolism in living organisms. We focus on the specific properties of O₂ that provide the chemical energy for the combustion reactions occurring in living cells. We explain the concepts of redox potential and redox balance in complex systems such as living cells, we present the main redox couples involved in cellular redox balance and we discuss the chemical properties underlying their cellular roles and, in particular, their antioxidant properties in the defense against reactive oxygen species (ROS). Finally, we try to provide an integrative view emphasizing the interplay between metabolism, oxidative stress and metabolic compartmentation in mammalian cells.

How Aging and Oxidative Stress Influence the Cytopathic and Inflammatory Effects of SARS-CoV-2 Infection: The Role of Cellular Glutathione and Cysteine Metabolism

SARS-CoV-2 infection can cause a severe respiratory distress syndrome with inflammatory and thrombotic complications, the severity of which increases with patients’ age and presence of comorbidity. The reasons for an age-dependent increase in the risk of severe COVID-19 could be many. These include defects in the homeostatic processes that control the cellular redox and its pivotal role in sustaining the immuno-inflammatory response to the host and the protection against oxidative stress and tissue degeneration. Pathogens may take advantage of such age-dependent abnormalities. Alterations of the thiol redox balance in the lung tissue and lining fluids may influence the risk of infection, and the host capability to respond to pathogens and to avoid severe complications. SARS-CoV-2, likewise other viruses, such as HIV, influenza, and HSV, benefits in its replication cycle of pro-oxidant conditions that the same viral infection seems to induce in the host cell with mechanisms that remain poorly understood. We recently demonstrated that the pro-oxidant effects of SARS-CoV-2 infection are associated with changes in the cellular metabolism and transmembrane fluxes of Cys and GSH. These appear to be the consequence of an increased use of Cys in viral protein synthesis and to ER stress pathway activation that interfere with transcription factors, as Nrf2 and NFkB, important to coordinate the metabolism of GSH with other aspects of the stress response and with the pro-inflammatory effects of this virus in the host cell. This narrative review article describes these cellular and molecular aspects of SARS-CoV-2 infection, and the role that antivirals and cytoprotective agents such as N-acetyl cysteine may have to limit the cytopathic effects of this virus and to recover tissue homeostasis after infection.

Changing Perspectives from Oxidative Stress to Redox Signaling-Extracellular Redox Control in Translational Medicine

Extensive research has changed the understanding of oxidative stress that has been linked to every major disease. Today we distinguish oxidative eu- and distress, acknowledging that redox modifications are crucial for signal transduction in the form of specific thiol switches. Long underestimated, reactive species and redox proteins of the Thioredoxin (Trx) family are indeed essential for physiological processes. Moreover, extracellular redox proteins, low molecular weight thiols and thiol switches affect signal transduction and cell–cell communication. Here, we highlight the impact of extracellular redox regulation for health, intermediate pathophenotypes and disease. Of note, recent advances allow the analysis of redox changes in body fluids without using invasive and expensive techniques. With this new knowledge in redox biochemistry, translational strategies can lead to innovative new preventive and diagnostic tools and treatments in life sciences and medicine.

The Intestinal Redox System and Its Significance in Chemotherapy-Induced Intestinal Mucositis

Chemotherapy-induced intestinal mucositis (CIM) is a significant dose-limiting adverse reaction brought on by the cancer treatment. Multiple studies reported that reactive oxygen species (ROS) is rapidly produced during the initial stages of chemotherapy, when the drugs elicit direct damage to intestinal mucosal cells, which, in turn, results in necrosis, mitochondrial dysfunction, and ROS production. However, the mechanism behind the intestinal redox system-based induction of intestinal mucosal injury and necrosis of CIM is still undetermined. In this article, we summarized relevant information regarding the intestinal redox system, including the composition and regulation of redox enzymes, ROS generation, and its regulation in the intestine. We innovatively proposed the intestinal redox "Tai Chi" theory and revealed its significance in the pathogenesis of CIM. We also conducted an extensive review of the English language-based literatures involving oxidative stress (OS) and its involvement in the pathological mechanisms of CIM. From the date of inception till July 31, 2021, 51 related articles were selected. Based on our analysis of these articles, only five chemotherapeutic drugs, namely, MTX, 5-FU, cisplatin, CPT-11, and oxaliplatin were shown to trigger the ROS-based pathological mechanisms of CIM. We also discussed the redox system-mediated modulation of CIM pathogenesis via elaboration of the relationship between chemotherapeutic drugs and the redox system. It is our belief that this overview of the intestinal redox system and its role in CIM pathogenesis will greatly enhance research direction and improve CIM management in the future.

The Impact of Alcohol Use Disorder on Tuberculosis: A Review of the Epidemiology and Potential Immunologic Mechanisms

Globally, an estimated 107 million people have an alcohol use disorder (AUD) leading to 2.8 million premature deaths each year. Tuberculosis (TB) is one of the leading causes of death globally and over 8% of global TB cases are estimated to be attributable to AUD. Social determinants of health such as poverty and undernutrition are often shared among those with AUD and TB and could explain the epidemiologic association between them. However, recent studies suggest that these shared risk factors do not fully account for the increased risk of TB in people with AUD. In fact, AUD has been shown to be an independent risk factor for TB, with a linear increase in the risk for TB with increasing alcohol consumption. While few studies have focused on potential biological mechanisms underlying the link between AUD and TB, substantial overlap exists between the effects of alcohol on lung immunity and the mechanisms exploited by Mycobacterium tuberculosis (Mtb) to establish infection. Alcohol misuse impairs the immune functions of the alveolar macrophage, the resident innate immune effector in the lung and the first line of defense against Mtb in the lower respiratory tract. Chronic alcohol ingestion also increases oxidative stress in the alveolar space, which could in turn facilitate Mtb growth. In this manuscript, we review the epidemiologic data that links AUD to TB. We discuss the existing literature on the potential mechanisms by which alcohol increases the risk of TB and review the known effects of alcohol ingestion on lung immunity to elucidate other mechanisms that Mtb may exploit. A more in-depth understanding of the link between AUD and TB will facilitate the development of dual-disease interventions and host-directed therapies to improve lung health and long-term outcomes of TB.

Multi-parametric functional imaging of cell cultures and tissues with a CMOS microelectrode array

Electrode-based impedance and electrochemical measurements can provide cell-biology information that is difficult to obtain using optical-microscopy techniques. Such electrical methods are non-invasive, label-free, and continuous, eliminating the need for fluorescence reporters and overcoming optical imaging's throughput/temporal resolution limitations. Nonetheless, electrode-based techniques have not been heavily employed because devices typically contain few electrodes per well, resulting in noisy aggregate readouts. Complementary metal-oxide-semiconductor (CMOS) microelectrode arrays (MEAs) have sometimes been used for electrophysiological measurements with thousands of electrodes per well at sub-cellular pitches, but only basic impedance mappings of cell attachment have been performed outside of electrophysiology. Here, we report on new field-based impedance mapping and electrochemical mapping/patterning techniques to expand CMOS-MEA cell-biology applications. The methods enable accurate measurement of cell attachment, growth/wound healing, cell-cell adhesion, metabolic state, and redox properties with single-cell spatial resolution (20 μm electrode pitch). These measurements allow the quantification of adhesion and metabolic differences of cells expressing oncogenes versus wild-type controls. The multi-parametric, cell-population statistics captured by the chip-scale integrated device opens up new avenues for fully electronic high-throughput live-cell assays for phenotypic screening and drug discovery applications.

Cysteine as a Multifaceted Player in Kidney, the Cysteine-Related Thiolome and Its Implications for Precision Medicine

In this review encouraged by original data, we first provided in vivo evidence that the kidney, comparative to the liver or brain, is an organ particularly rich in cysteine. In the kidney, the total availability of cysteine was higher in cortex tissue than in the medulla and distributed in free reduced, free oxidized and protein-bound fractions (in descending order). Next, we provided a comprehensive integrated review on the evidence that supports the reliance on cysteine of the kidney beyond cysteine antioxidant properties, highlighting the relevance of cysteine and its renal metabolism in the control of cysteine excess in the body as a pivotal source of metabolites to kidney biomass and bioenergetics and a promoter of adaptive responses to stressors. This view might translate into novel perspectives on the mechanisms of kidney function and blood pressure regulation and on clinical implications of the cysteine-related thiolome as a tool in precision medicine.

Sensitivity and Selectivity Analysis of Fluorescent Probes for Hydrogen Sulfide Detection

Hydrogen sulfide (H₂S) is a gasotransmitter known to regulate physiological and pathological processes. Abnormal H₂S levels have been associated with a range of conditions, including Parkinson's and Alzheimer's diseases, cardiovascular and renal diseases, bacterial and viral infections, as well as cancer. Therefore, fast and sensitive H₂S detection is of significant clinical importance. Fluorescent H₂S probes hold great potential among the currently developed detection methods because of their high sensitivity, selectivity, and biocompatibility. However, many proposed probes do not provide a gold standard for proper use and selection. Consequently, issues arise when applying the probes in different conditions. Therefore, we systematically evaluated four commercially available probes (WSP‐1, WSP‐5, CAY, and P3), considering their detection range, sensitivity, selectivity, and performance in different environments. Furthermore, their capacity for endogenous H₂S imaging in live cells was demonstrated.

Cloning, Functional Characterization and Response to Cadmium Stress of the Thioredoxin-like Protein 1 Gene from Phascolosoma esculenta

Cadmium (Cd) is a heavy metal toxicant and is widely distributed in aquatic environments. It can cause excessive production of reactive oxygen species (ROS) in the organism, which in turn leads to a series of oxidative damages. Thioredoxin (Trx), a highly conserved disulfide reductase, plays an important role in maintaining the intracellular redox homeostasis in eukaryotes and prokaryotes. Phascolosoma esculenta is an edible marine worm, an invertebrate that is extensively found on the mudflats of coastal China. To explore the molecular response of Trx in mudflat organisms under Cd stress, we identified a new Trx isoform (Trx-like protein 1 gene) from P. esculenta for the first time, designated as PeTrxl. Molecular and structural characterization, as well as multiple sequence and phylogenetic tree analysis, demonstrated that PeTrxl belongs to the Trx superfamily. PeTrxl transcripts were found to be ubiquitous in all tissues, and the highest expression level occurred in the coelomic fluid. Exposure to three sublethal concentrations of Cd resulted in the upregulation and then downregulation of PeTrxl expression levels over time in coelomic fluid of P. esculenta. The significant elevation of PeTrxl expression after 12 and 24 h of Cd exposure at 6 and 96 mg/L, respectively, might reflect its important role in the resistance to Cd stress. Recombinant PeTrxl (rPeTrxl) showed prominent dose-dependent insulin-reducing and ABTS free radical-scavenging abilities. After exposure to 96 mg/L Cd for 24 h, the ROS level increased significantly in the coelomic fluid, suggesting that Cd induced oxidative stress in P. esculenta. Furthermore, the injection of rPeTrxl during Cd exposure significantly reduced the ROS in the coelomic fluid. Our data suggest that PeTrxl has significant antioxidant capacity and can protect P. esculenta from Cd-induced oxidative stress.

Simultaneous Quantification of Biothiols and Deciphering Diverse GSH Stability in Different Live Cells by 19F-Tag

GSH, Cys, Hcy, and H₂S are important biothiols and play important roles in the living systems. Quantitative and simultaneous determination of these biothiols under physiological conditions is still a challenge. Herein, we developed an effective ¹⁹F-reactive tag that readily interacts with these four biothiols for the generation of stable thioether products that have distinguishable ¹⁹F-chemical shifts. These thioester compounds encode the characteristic fingerprint profiles of each biothiols, allowing one to simultaneously quantify and determine these biothiols by 1D ¹⁹F NMR spectroscopy. The intra-/extracellular GSH in live cells was assessed by the established strategy, and remarkable variations in the GSH stability were determined between the normal mammalian cells and cancer cells. It is notable that GSH hydrolyzes efficiently in the out-membrane of the cancer cells and the lysates. In contrast, GSH remains stable in the tested normal cells.

Gender-Specific Behaviour in Obesity Stages I-II: Imbalance of Aminothiol Status and Adipomyokine Profile in Subjects with Different Insulin Resistance Severity

The hyperproduction of oxidative stress and inflammatory biomarkers, which is paralleled by decreased levels of antioxidant and anti-inflammatory mediators, is part of cellular mechanisms that contribute to the disruption of metabolic homeostasis in obesity. Whether gender-specific alterations and gender-restricted associations in these biomarkers underlie the increased cardiometabolic risk in men compared to women is unclear. We enrolled 31 women and 29 men, aged ≥50 and ≤70 years and with body mass index ≥ 30 and <40 kg/m². We assessed the concentrations of aminothiols (cysteine, homocysteine, and glutathione), expression of oxidant/antioxidant balance, adipomyokines (leptin, adiponectin, myostatin, and interleukin-6), markers of chronic inflammation, and vitamin D, an index of nutritional state, in plasma and serum samples by using HPLC, ELISA, and chemiluminescent immunoassay methods. We measured insulin resistance (IR) by the homeostasis model assessment (HOMA) index. Despite comparable levels of visceral adiposity, IR, and a similar dietary regimen, men showed, with respect to women, higher oxidant concentrations and lower antioxidant levels, which paralleled IR severity. Myostatin levels correlated with prooxidant aminothiols among men only. Gender-specific alterations in aminothiol status and adipomyokine profile and the gender-restricted association between these biomarkers and metabolic derangement are consistent with an increased cardiometabolic risk in men compared to age-matched women with stage I-II obesity. Strict control of redox and inflammatory status, even addressing gender-specific nutritional targets, may be useful to prevent obesity-related metabolic alterations and comorbidities.

Dynamic thiol disulphide homeostasis in patients with surfer's eye: a case-control study

PURPOSE

The role of oxidative stress in the pathogenesis of pterygium is still unclear. However, abnormal thiol disulfide homeostasis levels are involved in the pathogenesis of various systemic or ocular diseases. We aim to analyze dynamic thiol disulphide homeostasis in patients suffering from conjunctival pterygium using a contemporary technique.

METHODS

Thirty-eight subjects suffering from pterygium and 35 age-gender matched healthy volunteers were recruited for the study. For each case, total thiol, disulfide and native thiol levels in blood were obtained. Additionally, the ratio of disulfide over total thiol, native thiol over total thiol and disulfide over native thiol were computed.

RESULTS

The level of median native thiol was lower in pterygium group (318.2 µmol/L vs. 333.4 µmol/L) and median disulfide was slightly higher in pterygium group (24.3 µmol/L vs. 22.8 µmol/L) compared to control group. Both disulfide over total thiol and disulfide over native thiol ratios were higher in pterygium group, ratio of native thiol over total thiol was found to be higher in control group. Nevertheless, none of those differences were statistically significant at 95% confidence level. Notably, correlation test pointed to a negative correlation both between pterygium grade and native thiol and between total thiol and pterygium grade in pterygium group (P = 0.03 and 0.02, respectively).

CONCLUSION

A negative correlation hinting that slightly weakened dynamic thiol disulphide homeostasis in subjects with pterygium, a local ocular disease. Further studies with larger sample sizes may shed light on this potential relationship and justify systemic antioxidant therapies in these cases.

COVID-19: A Redox Disease-What a Stress Pandemic Can Teach Us About Resilience and What We May Learn from the Reactive Species Interactome About Its Treatment

Significance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), affects every aspect of human life by challenging bodily, socioeconomic, and political systems at unprecedented levels. As vaccines become available, their distribution, safety, and efficacy against emerging variants remain uncertain, and specific treatments are lacking. Recent Advances: Initially affecting the lungs, COVID-19 is a complex multisystems disease that disturbs the whole-body redox balance and can be long-lasting (Long-COVID). Numerous risk factors have been identified, but the reasons for variations in susceptibility to infection, disease severity, and outcome are poorly understood. The reactive species interactome (RSI) was recently introduced as a framework to conceptualize how cells and whole organisms sense, integrate, and accommodate stress. Critical Issues: We here consider COVID-19 as a redox disease, offering a holistic perspective of its effects on the human body, considering the vulnerability of complex interconnected systems with multiorgan/multilevel interdependencies. Host/viral glycan interactions underpin SARS-CoV-2's extraordinary efficiency in gaining cellular access, crossing the epithelial/endothelial barrier to spread along the vascular/lymphatic endothelium, and evading antiviral/antioxidant defences. An inflammation-driven "oxidative storm" alters the redox landscape, eliciting epithelial, endothelial, mitochondrial, metabolic, and immune dysfunction, and coagulopathy. Concomitantly reduced nitric oxide availability renders the sulfur-based redox circuitry vulnerable to oxidation, with eventual catastrophic failure in redox communication/regulation. Host nutrient limitations are crucial determinants of resilience at the individual and population level. Future Directions: While inflicting considerable damage to health and well-being, COVID-19 may provide the ultimate testing ground to improve the diagnosis and treatment of redox-related stress diseases. "Redox phenotyping" of patients to characterize whole-body RSI status as the disease progresses may inform new therapeutic approaches to regain redox balance, reduce mortality in COVID-19 and other redox diseases, and provide opportunities to tackle Long-COVID. Antioxid. Redox Signal. 35, 1226-1268.

Molecular characterization and functional analysis of Trx and Trp14 in roughskin sculpin (Trachidermus fasciatus)

Thioredoxins (Trxs) are a family of small and highly conserved proteins which play crucial roles in the maintenance and regulation of the cellular redox homeostasis. In this study, the full-length cDNAs of thioredoxin 1 (TfTrx1) and thioredoxin-related protein of 14 kDa (TfTrp14) were isolated from roughskin sculpin (Trachidermus fasciatus). TfTrx1 is 662 bp in length with a 336-bp open reading frame (ORF) that encodes for a peptide with 111 amino acids, and TfTrp14 consists of 1066 bp with a 372-bp ORF that is translated to 123 amino acids. TfTrx1 and TfTrp14 contain highly conserved catalytic site motif CGPC and CPDC, respectively. Tissue distribution analysis indicated that both genes were broadly expressed in all examined tissues with the highest expression of TfTrx1 in the blood and TfTrp14 in the brain. In post-LPS and heavy metal challenge, the mRNA of both genes was significantly increased in the skin, liver, spleen, and brain at various times. The results of western blot detection displayed that the time of the induced maximum protein expression was 6-h post-LPS injection in the skin and liver, which were slightly delayed compared with that of 2 h at mRNA level. The recombinant TfTrp14 and TfTrx1 proteins were expressed in E. coli BL21 (DE3). The increase of the fluorescence intensity in rTfTrx1 and rTfTrp14 suggested the redox state changes in the microenvironment around tryptophan residues. Both of the recombinant proteins exhibited concentration-dependent disulfide reductase activity towards insulin, and the catalytic activity of rTfTrx1 was much higher than that of rTfTrp14.

Aryl Hydrocarbon Receptor and Cysteine Redox Dynamics Underlie (Mal)adaptive Mechanisms to Chronic Intermittent Hypoxia in Kidney Cortex

We hypothesized that an interplay between aryl hydrocarbon receptor (AhR) and cysteine-related thiolome at the kidney cortex underlies the mechanisms of (mal)adaptation to chronic intermittent hypoxia (CIH), promoting arterial hypertension (HTN). Using a rat model of CIH-HTN, we investigated the impact of short-term (1 and 7 days), mid-term (14 and 21 days, pre-HTN), and long-term intermittent hypoxia (IH) (up to 60 days, established HTN) on CYP1A1 protein level (a sensitive hallmark of AhR activation) and cysteine-related thiol pools. We found that acute and chronic IH had opposite effects on CYP1A1 and the thiolome. While short-term IH decreased CYP1A1 and increased protein-S-thiolation, long-term IH increased CYP1A1 and free oxidized cysteine. In addition, an in vitro administration of cystine, but not cysteine, to human endothelial cells increased Cyp1a1 expression, supporting cystine as a putative AhR activator. This study supports CYP1A1 as a biomarker of obstructive sleep apnea (OSA) severity and oxidized pools of cysteine as risk indicator of OSA-HTN. This work contributes to a better understanding of the mechanisms underlying the phenotype of OSA-HTN, mimicked by this model, which is in line with precision medicine challenges in OSA.

Sources and triggers of oxidative damage in neurodegeneration

Neurodegeneration describes a group of more than 300 neurological diseases, characterised by neuronal loss and intra- or extracellular protein depositions, as key neuropathological features. Multiple factors play role in the pathogenesis of these group of disorders: mitochondrial dysfunction, membrane damage, calcium dyshomeostasis, metallostasis, defect clearance and renewal mechanisms, to name a few. All these factors, without exceptions, have in common the involvement of immensely increased generation of free radicals and occurrence of oxidative stress, and as a result - exhaustion of the scavenging potency of the cellular redox defence mechanisms. Besides genetic predisposition and environmental exposure to toxins, the main risk factor for developing neurodegeneration is age. And although the "Free radical theory of ageing" was declared dead, it is undisputable that accumulation of damage occurs with age, especially in systems that are regulated by free radical messengers and those that oppose oxidative stress, protein oxidation and the accuracy in protein synthesis and degradation machinery has difficulties to be maintained. This brief review provides a comprehensive summary on the main sources of free radical damage, occurring in the setting of neurodegeneration.

Thiol level and total oxidant/antioxidant status in patients with COVID-19 infection

Background

Accumulating evidence suggests that oxidative stress is closely related to the pathogenesis and severity of COVID-19 infection. Here, we attempted to compare thiol, total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) levels between COVID-19 patients who need and do not need intensive care unit (ICU) support, and determine whether these markers could be used as predictors of ICU admission.

Methods

We recruited 86 patients with COVID-19 infection and classified them into two groups according to the level of care: ICU group (n = 40) and non-ICU group (n = 46). Thiol, TAS, TOS, and OSI levels were determined and compared between the two groups.

Results

The levels of thiol and TAS in serum were markedly lower in ICU patients than in the non-ICU patients. On the contrary, TOS and OSI levels were markedly higher. Inflammatory markers, including white blood cell, neutrophil, C-reactive protein, procalcitonin, and ferritin, were negatively correlated with the thiol and TAS, and positively correlated with the TOS and OSI. We determined that areas under the ROC curve for thiol, TAS, TOS, and OSI were 0.799, 0.778, 0.713, and 0.780, respectively.

Conclusions

Our results revealed that the increase in oxidative stress and decrease in antioxidant levels in COVID-19-infected patients were associated with worsening of disease. Thiol, TAS, TOS, and OSI parameters can be used to distinguish between ICU patients and those who do not, among which thiol was the best predictor of ICU requirement.

Oxidant and antioxidant balance in patients with COVID-19

BACKGROUND

A crucial balance exists between oxidant and antioxidant mechanisms in the functional immune system. We aimed to evaluate the contributions of balance between these systems to coronavirus disease 2019 (COVID-19), a devastating pandemic caused by viral infection.

METHOD

We analyzed serum oxidant and antioxidant stress parameters according to the clinical and demographic characteristics of children and adults with COVID-19 and compared them against the values of healthy controls. Serum native thiol (NT), total thiol (TT), disulfide, total antioxidant status, total oxidant status, and ischemia-modified albumin levels were evaluated and compared between groups.

RESULTS

A total of 79 children and 74 adults were evaluated in the present study, including 46 children and 40 adults with COVID-19, 33 healthy children, and 34 healthy adults. TT, NT, and disulfide levels were significantly lower in the adult COVID-19 group than in all other groups (p = .001, p = .001, and p = .005, respectively). Additionally, TT and NT levels were significantly lower in both pediatric and adult COVID-19 cases with severe disease course than mild/moderate course. TT and NT levels were identified as predictors for the diagnosis of the adult COVID-19 cases and as independent predictors for disease severity in both children and adults with COVID-19.

CONCLUSION

Parameters that reveal the oxidant and antioxidant capacity, including TT and NT, appear to be good candidates for the accurate prediction of the clinical course among patients with COVID-19.

Thiol/disulfide homeostasis in medication-naive children and adolescents with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) causes significant psychic distress and affects children's social and academic functioning. Approximately 80% of OCD cases begin in childhood. Earlier onset is associated with more severe OC symptoms, poorer treatment response, and a more unfavorable clinical course. A particular oxidative stress marker, thiol/disulfide homeostasis, using a new, comparatively inexpensive, easily calculated, easily accessible, repeatable, and fully automated method was investigated between pediatric patients diagnosed with OCD and a healthy control group in this study. This study is the first to address this subject in pediatric patients with OCD and aims to contribute to our knowledge of the etiopathogenesis and treatment of pediatric OCD. The study included children with OCD (n = 35, 52.2%) (drug free, comorbidity free) between 11 and 18 years of age and age- and sex-matched healthy controls (n = 32, 47.8%). The total thiol (p = 0.025) and disulfide (p = 0.001) levels and the disulfide/native thiol (p = 0.001) and disulfide/total thiol ratios (p = 0.001) were significantly different between the groups. Also, in the patient group, biochemical analysis revealed that the disulfide level (p = 0.05) and the disulfide/native thiol (p = 0.034) and disulfide/total thiol ratios (p = 0.039) differed significantly according to the presence of a family history of psychiatric disorders. Consequently, the results of our study show that thiol/disulfide homeostasis may affect the etiopathogenesis of pediatric OCD and can be utilized as a new method when evaluating oxidative stress.

Self-stabilized Pt(IV) amphiphiles by precise regulation of branch length for enhanced chemotherapy

A surge of platinum(IV) compounds are utilized or investigated in cancer treatment but their therapeutic outcomes have been greatly compromised by remaining adverse effects and limited antitumor performance, attributable to nonspecific distribution and insufficient activation in tumor site. Herein, we designed a series of disulfide bond introduced Pt(IV)-lipid prodrugs with different branch length, all of which are able to self-stabilize into nanomedicine and be activated by high intracellular glutathione (GSH) level. The impact of precise modification of these prodrugs on their assembly stability, pharmacokinetics and cytotoxicity was probed to establish a connection between chemical structure and antiproliferation efficiency. With optimal assembly manner and delivery efficacy, the longest axial branched Pt(IV) prodrug CSS18 exhibited the most impressive therapeutic outcome, providing a potential path to more efficient nanocarriers for chemotherapeutic agents by chemical modulation and, giving insights into the rational design of reduction responsive platinum delivery system.

Effects of antiviral drug therapy on dynamic thiol/disulphide homeostasis and nitric oxide levels in COVID-19 patients

The novel coronavirus disease 2019 (COVID-19) has led to a serious global pandemic. Although an oxidative stress imbalance occurs in COVID-19 patients, the contributions of thiol/disulphide homeostasis and nitric oxide (NO) generation to the pathogenesis of COVID-19 have been poorly identified. Therefore, the aim of this study was to evaluate the effects of antiviral drug therapy on the serum dynamics of thiol/disulphide homeostasis and NO levels in COVID-19 patients. A total of 50 adult patients with COVID-19 and 43 sex-matched healthy control subjects were enrolled in this prospective study. Venous blood samples were collected immediately on admission to the hospital within 24 h after the diagnosis (pre-treatment) and at the 15th day of drug therapy (post-treatment). Serum native thiol and total thiol levels were measured, and the amounts of dynamic disulphide bonds and related ratios were calculated. The average pre-treatment total and native thiol levels were significantly lower than the post-treatment values (P < 0.001 for all). We observed no significant changes in disulphide levels or disulphide/total thiol, disulphide/native thiol, or native thiol/total thiol ratios between pre- and post-treatments. There was also a significant increase in serum NO levels in the pre-treatment values when compared to control (P < 0.001) and post-treatment measurements (P < 0.01). Our results strongly suggest that thiol/disulphide homeostasis and nitrosative stress can contribute to the pathogenesis of COVID-19. This study was the first to show that antiviral drug therapy can prevent the depletion in serum thiol levels and decrease serum NO levels in COVID-19 patients.

A sensitive indicator for the severity of COVID-19: thiol

Background/aim

Thiol status is a good reflector of the cellular redox and have vital roles in various cellular signaling pathways. The purpose of the study was to investigate thiol status in patients with SARS-CoV-2 infection.

Materials and methods

A total of 587 subjects (517 patients/70 healthy controls) were enrolled in the study.The patients were categorized into the groups regarding to the severity of disease (mild, moderate, severe, and critical).Thiol status of all groups were compared.

Results

The patients had significantly diminished thiol levels compared to controls. Thiol levels were gradually decreased as the severity of the disease increased. Logistic regression analyses identified that thiol concentrations were an independent risk factor for the disease severity in each phase (mild group OR 0.975, 95%CI 0.965-0.986; moderate group, OR 0.964, 95%CI 0.953-0.976; severe group OR 0.953, 95%CI 0.941-0.965; critical group OR 0.947, 95%CI 0.935-0.960).Thiol test exhibited the largest area under the curve at 0.949, with the highest sensitivity (98.6%) and specificity (80.4%).

Conclusions

Depleted thiol status was observed in SARS-CoV-2 infection. Decline of the thiol levels by degrees while the severity of infection increased was closely related to the progression of the disease. This outcome highlights that thiols could be an impressible biomarker for predicting of the severity of COVID-19.

Fluorescent Probes for Live Cell Thiol Detection

Thiols play vital and irreplaceable roles in the biological system. Abnormality of thiol levels has been linked with various diseases and biological disorders. Thiols are known to distribute unevenly and change dynamically in the biological system. Methods that can determine thiols' concentration and distribution in live cells are in high demand. In the last two decades, fluorescent probes have emerged as a powerful tool for achieving that goal for the simplicity, high sensitivity, and capability of visualizing the analytes in live cells in a non-invasive way. They also enable the determination of intracellular distribution and dynamitic movement of thiols in the intact native environments. This review focuses on some of the major strategies/mechanisms being used for detecting GSH, Cys/Hcy, and other thiols in live cells via fluorescent probes, and how they are applied at the cellular and subcellular levels. The sensing mechanisms (for GSH and Cys/Hcy) and bio-applications of the probes are illustrated followed by a summary of probes for selectively detecting cellular and subcellular thiols.

Pathophysiological roles of cell surface and extracellular protein disulfide isomerase and their molecular mechanisms

Protein disulfide isomerase (PDI) is the prototypic member of the thiol isomerase family that catalyses disulfide bond rearrangement. Initially identified in the endoplasmic reticulum as folding catalysts, PDI and other members in its family have also been widely reported to reside on the cell surface and in the extracellular matrix. Although how PDI is exported and retained on the cell surface remains a subject of debate, this unique pool of PDI is developing into an important mechanism underlying the redox regulation of protein sulfhydryls that are critical for the cellular activities under various disease conditions. This review aims to provide an overview of the pathophysiological roles of surface and extracellular PDI and their underlying molecular mechanisms. Understanding the involvement of extracellular PDI in these diseases will advance our knowledge in the molecular aetiology to facilitate the development of novel pharmacological strategies by specifically targeting PDI in extracellular compartments.

The age-dependent decline of the extracellular thiol-disulfide balance and its role in SARS-CoV-2 infection

SARS-CoV-2 (COVID-19) infection can cause a severe respiratory distress syndrome. The risk of severe manifestations and mortality characteristically increase in the elderly and in the presence of non-COVID-19 comorbidity. We and others previously demonstrated that the low molecular weight (LMW) and protein thiol/disulfide ratio declines in human plasma with age and such decline is even more rapid in the case of inflammatory and premature aging diseases, which are also associated with the most severe complications of COVID-19 infection. The same decline with age of the LMW thiol/disulfide ratio observed in plasma appears to occur in the extracellular fluids of the respiratory tract and in association with many pulmonary diseases that characteristically reduce the concentrations and adaptive stress response of the lung glutathione. Early evidence in literature suggests that the thiol to disulfide balance of critical Cys residues of the COVID-19 spike protein and the ACE-2 receptor may influence the risk of infection and the severity of the disease, with a more oxidizing environment producing the worst prognosis. With this hypothesis paper we propose that the age-dependent decline of LMW thiol/disulfide ratio of the extracellular fluids, could play a role in promoting the physical (protein-protein) interaction of CoV-2 and the host cell in the airways. Therefore, this redox-dependent interaction is expected to affect the risk of severe infection in an age-dependent manner. The hypothesis can be verified in experimental models of in vitro CoV-2 infection and at the clinical level in that LMW thiols and protein thiolation can now be investigated with standardized, reliable and versatile laboratory protocols. Presenting the verification strategy of our hypothesis, we also discuss available nutritional and ancillary pharmacological strategies to intervene on the thiol/disulfide ratio of extracellular fluids of subjects at risk of infection and COVID-19 patients.

Disulfide Bridging Strategies in Viral and Nonviral Platforms for Nucleic Acid Delivery

Self-assembled nanostructures that are sensitive to environmental stimuli are promising nanomaterials for drug delivery. In this class, disulfide-containing redox-sensitive strategies have gained enormous attention because of their wide applicability and simplicity of nanoparticle design. In the context of nucleic acid delivery, numerous disulfide-based materials have been designed by relying on covalent or noncovalent interactions. In this review, we highlight major advances in the design of disulfide-containing materials for nucleic acid encapsulation, including covalent nucleic acid conjugates, viral vectors or virus-like particles, dendrimers, peptides, polymers, lipids, hydrogels, inorganic nanoparticles, and nucleic acid nanostructures. Our discussion will focus on the context of the design of materials and their impact on addressing the current shortcomings in the intracellular delivery of nucleic acids.

Cysteine metabolic circuitries: druggable targets in cancer

To enable survival in adverse conditions, cancer cells undergo global metabolic adaptations. The amino acid cysteine actively contributes to cancer metabolic remodelling on three different levels: first, in its free form, in redox control, as a component of the antioxidant glutathione or its involvement in protein s-cysteinylation, a reversible post-translational modification; second, as a substrate for the production of hydrogen sulphide (H2S), which feeds the mitochondrial electron transfer chain and mediates per-sulphidation of ATPase and glycolytic enzymes, thereby stimulating cellular bioenergetics; and, finally, as a carbon source for epigenetic regulation, biomass production and energy production. This review will provide a systematic portrayal of the role of cysteine in cancer biology as a source of carbon and sulphur atoms, the pivotal role of cysteine in different metabolic pathways and the importance of H2S as an energetic substrate and signalling molecule. The different pools of cysteine in the cell and within the body, and their putative use as prognostic cancer markers will be also addressed. Finally, we will discuss the pharmacological means and potential of targeting cysteine metabolism for the treatment of cancer.

Protein thiolation index in microvolumes of plasma

Protein Thiolation Index (PTI) has been recently proposed as a new biomarker of oxidative stress. It is calculated by measuring both free thiols and S-thiolated proteins in plasma with the assumption that this redox ratio is altered by a pro-oxidant stimulus. Here the original protocol was modified and adapted to the use of microvolumes of blood collected by finger prick and down to 3 μl blood was shown to be the lowest volume suitable for this kind of analysis. The new procedure was used to evaluate both the circadian rhythm and the annual fluctuations of PTI in healthy humans.