Role of Glutathionylation in Infection and Inflammation

Exploring Immune Redox Modulation in Bacterial Infections: Insights into Thioredoxin-Mediated Interactions and Implications for Understanding Host-Pathogen Dynamics

Bacterial infections trigger a multifaceted interplay between inflammatory mediators and redox regulation. Recently, accumulating evidence has shown that redox signaling plays a significant role in immune initiation and subsequent immune cell functions. This review addresses the crucial role of the thioredoxin (Trx) system in the initiation of immune reactions and regulation of inflammatory responses during bacterial infections. Downstream signaling pathways in various immune cells involve thiol-dependent redox regulation, highlighting the pivotal roles of thiol redox systems in defense mechanisms. Conversely, the survival and virulence of pathogenic bacteria are enhanced by their ability to counteract oxidative stress and immune attacks. This is achieved through the reduction of oxidized proteins and the modulation of redox-sensitive signaling pathways, which are functions of the Trx system, thereby fortifying bacterial resistance. Moreover, some selenium/sulfur-containing compounds could potentially be developed into targeted therapeutic interventions for pathogenic bacteria. Taken together, the Trx system is a key player in redox regulation during bacterial infection, and contributes to host-pathogen interactions, offering valuable insights for future research and therapeutic development.

Ginkgo biloba attenuated detrimental inflammatory and oxidative events due to Trypanosoma brucei rhodesiense in mice treated with melarsoprol

BACKGROUND

The severe late stage Human African Trypanosomiasis (HAT) caused by Trypanosoma brucei rhodesiense (T.b.r) is characterized by damage to the blood brain barrier, severe brain inflammation, oxidative stress and organ damage. Melarsoprol (MelB) is currently the only treatment available for this disease. MelB use is limited by its lethal neurotoxicity due to post-treatment reactive encephalopathy. This study sought to assess the potential of Ginkgo biloba (GB), a potent anti-inflammatory and antioxidant, to protect the integrity of the blood brain barrier and ameliorate detrimental inflammatory and oxidative events due to T.b.r in mice treated with MelB.

METHODOLOGY

Group one constituted the control; group two was infected with T.b.r; group three was infected with T.b.r and treated with 2.2 mg/kg melarsoprol for 10 days; group four was infected with T.b.r and administered with GB 80 mg/kg for 30 days; group five was given GB 80mg/kg for two weeks before infection with T.b.r, and continued thereafter and group six was infected with T.b.r, administered with GB and treated with MelB.

RESULTS

Co-administration of MelB and GB improved the survival rate of infected mice. When administered separately, MelB and GB protected the integrity of the blood brain barrier and improved neurological function in infected mice. Furthermore, the administration of MelB and GB prevented T.b.r-induced microcytic hypochromic anaemia and thrombocytopenia, as well as T.b.r-driven downregulation of total WBCs. Glutathione analysis showed that co-administration of MelB and GB prevented T.b.r-induced oxidative stress in the brain, spleen, heart and lungs. Notably, GB averted peroxidation and oxidant damage by ameliorating T.b.r and MelB-driven elevation of malondialdehyde (MDA) in the brain, kidney and liver. In fact, the co-administered group for the liver, registered the lowest MDA levels for infected mice. T.b.r-driven elevation of serum TNF-α, IFN-γ, uric acid and urea was abrogated by MelB and GB. Co-administration of MelB and GB was most effective in stabilizing TNFα levels. GB attenuated T.b.r and MelB-driven up-regulation of nitrite.

CONCLUSION

Utilization of GB as an adjuvant therapy may ameliorate detrimental effects caused by T.b.r infection and MelB toxicity during late stage HAT.

Whey Protein, Vitamins C and E Decrease Interleukin-10 in Chronic Hemodialysis Patients: A Pioneer, Randomized, Double-Blind Pilot Trial

OBJECTIVE

To evaluate the effects of supplementation with whey protein combined with vitamins C and E on inflammatory markers in hemodialysis (HD) patients.

DESIGN AND METHODS

This was a pioneer, randomized and double-blinded study. Patients were randomized into two groups and stratified by HD frequency. The supplementation group received 20 g of whey protein, 250 mg of vitamin C, and 600 IU of vitamin E; the placebo group, 20 g of rice flour, and microcrystalline cellulose capsules. The interventions were given after HD, 3 times a week, for 8 weeks. The inflammatory markers were assessed: interleukin (IL) IL-12p70, IL-10, IL-6, IL-8, and tumor necrosis factor alpha. For statistical analysis, the χ2 test, Student's t-test, Mann-Whitney test, analysis of variance for repeated two-way measurements, paired t test, and Wilcoxon test were performed. P < .05 was considered statistically significant.

RESULTS

Twenty-three patients completed the study. No significant differences were found in inflammatory markers when comparing the groups postintervention. In the intragroup was a decrease in IL-10 in the supplementation group after 8 weeks (P = .0382). IL-6 tended to decrease by 810.95% in the supplementation group and increased by 732.8% (nonsignificant) in the placebo group.

CONCLUSION

Whey protein combined with vitamins C and E significantly reduced IL-10 in the supplementation group and could be beneficial to reduce IL-6 in HD patients. Future studies are suggested with a larger sample size, different supplementation doses, and longer interventions.

Topical glutathione amino acid precursors protect skin against environmental and oxidative stress

BACKGROUND

Although glutathione (GSH) has long been considered a master antioxidant, poor stability and bioavailability limit its application in skin protection. To overcome the challenges, Unilever R&D formulated a Glutathione Amino acid Precursors blend (named GAP) to boost GSH de novo synthesis.

OBJECTIVE

Determine whether GAP can boost GSH levels and provide skin protection against stressors.

METHODS

Normal human epidermal keratinocytes were treated with GAP, with or without stressors, namely, menadione, blue light or pollutants. Ascorbic acid was used as a benchmark. The levels of GSH, glutathione disulfide (GSSG), adenosine triphosphate (ATP) and reactive oxygen species (ROS) were quantified. A placebo-controlled clinical study was conducted on 21 female subjects who received product applications and subsequent UV radiation. Tape strip samples were collected from the subjects for GSH and GSSG quantification using ultra-performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS). The UV-protective effect of GAP was investigated using ex vivo skin. Biomarkers related to DNA damage and the skin barrier were analysed using immunohistochemistry.

RESULTS

Glutathione amino acid precursors significantly increased the GSH levels and GSH/GSSG ratio in normal human epidermal keratinocytes. Menadione treatment resulted in excessive ROS production and a decline in ATP levels, which were effectively abrogated by GAP. The protective effects of GAP against menadione-induced oxidative stress were superior to those of ascorbic acid. In addition, GAP effectively protected the cells against blue light-induced ROS production and pollutant-induced ATP depletion. Topical application of the GAP formulation significantly elevated the skin GSH/GSSG ratio in a clinical study. Ex vivo skin treated with the GAP formulation displayed a reduction in DNA damage and high levels of barrier proteins after UV exposure.

CONCLUSIONS

Glutathione amino acid precursors effectively increases cellular GSH levels to protect the skin from oxidative and environmental stresses.

Age-related influence on DNA damage, proteomic inflammatory markers and oxidative stress in hospitalized COVID-19 patients compared to healthy controls

COVID-19 infections are accompanied by adverse changes in inflammatory pathways that are also partly influenced by increased oxidative stress and might result in elevated DNA damage. The aim of this case-control study was to examine whether COVID-19 patients show differences in oxidative stress-related markers, unconjugated bilirubin (UCB), an inflammation panel and DNA damage compared to healthy, age-and sex-matched controls. The Comet assay with and without the treatment of formamidopyrimidine DNA glycosylase (FPG) and H2O2 challenge was used to detect DNA damage in whole blood. qPCR was applied for gene expression, UCB was analyzed via HPLC, targeted proteomics were applied using Olink® inflammation panel and various oxidative stress as well as clinical biochemistry markers were analyzed in plasma. Hospitalized COVID-19 patients (n = 48) demonstrated higher serum levels of 55 inflammatory proteins (p < 0.001), including hs-C-reactive protein levels (p < 0.05), compared to healthy controls (n = 48). Interestingly, significantly increased age-related DNA damage (%-DNA in tail) after formamidopyrimidine DNA glycosylase (FPG) treatment was measured in younger (n = 24, average age 55.7 years; p < 0.05) but not in older COVID-19 patients (n = 24, average age 83.5 years; p > 0.05). Although various oxidative stress markers were not altered (e.g., FRAP, malondialdehyde, p > 0.05), a significant increased ratio of oxidized to reduced glutathione was detected in COVID-19 patients compared to healthy controls (p < 0.05). UCB levels were significantly lower in individuals with COVID-19, especially in younger COVID-19 patients (p < 0.05). These results suggest that COVID-19 infections exert effects on DNA damage related to age in hospitalized COVID-19 patients that might be driven by changes in inflammatory pathways but are not altered by oxidative stress parameters.

Robust AMBER Force Field Parameters for Glutathionylated Cysteines

S-glutathionylation is an oxidative post-translational modification, which is involved in the regulation of many cell signaling pathways. Increasing amounts of studies show that it is crucial in cell homeostasis and deregulated in several pathologies. However, the effect of S-glutathionylation on proteins' structure and activity is poorly understood, and a drastic lack of structural information at the atomic scale remains. Studies based on the use of molecular dynamics simulations, which can provide important information about modification-induced modulation of proteins' structure and function, are also sparse, and there is no benchmarked force field parameters for this modified cysteine. In this contribution, we provide robust AMBER parameters for S-glutathionylation, which we tested extensively against experimental data through a total of 33 μs molecular dynamics simulations. We show that our parameter set efficiently describes the global and local structural properties of S-glutathionylated proteins. These data provide the community with an important tool to foster new investigations into the effect of S-glutathionylation on protein dynamics and function, in a common effort to unravel the structural mechanisms underlying its critical role in cellular processes.

Glutathione: Lights and Shadows in Cancer Patients

In cases of cellular injury, there is an observed increase in the production of reactive oxygen species (ROS). When this production becomes excessive, it can result in various conditions, including cancerogenesis. Glutathione (GSH), the most abundant thiol-containing antioxidant, is fundamental to re-establishing redox homeostasis. In order to evaluate the role of GSH and its antioxi-dant effects in patients affected by cancer, we performed a thorough search on Medline and EMBASE databases for relevant clinical and/or preclinical studies, with particular regard to diet, toxicities, and pharmacological processes. The conjugation of GSH with xenobiotics, including anti-cancer drugs, can result in either of two effects: xenobiotics may lose their harmful effects, or GSH conjugation may enhance their toxicity by inducing bioactivation. While being an interesting weapon against chemotherapy-induced toxicities, GSH may also have a potential protective role for cancer cells. New studies are necessary to better explain the relationship between GSH and cancer. Although self-prescribed glutathione (GSH) implementation is prevalent among cancer patients with the intention of reducing the toxic effects of anticancer treatments and potentially preventing damage to normal tissues, this belief lacks substantial scientific evidence for its efficacy in reducing toxicity, except in the case of cisplatin-related neurotoxicity. Therefore, the use of GSH should only be considered under medical supervision, taking into account the appropriate timing and setting.

Chemistry and biology of enzymes in protein glutathionylation

Protein S-glutathionylation is emerging as a central oxidation that regulates redox signaling and biological processes linked to diseases. In recent years, the field of protein S-glutathionylation has expanded by developing biochemical tools for the identification and functional analyses of S-glutathionylation, investigating knockout mouse models, and developing and evaluating chemical inhibitors for enzymes involved in glutathionylation. This review will highlight recent studies of two enzymes, glutathione transferase omega 1 (GSTO1) and glutaredoxin 1 (Grx1), especially introducing their glutathionylation substrates associated with inflammation, cancer, and neurodegeneration and showcasing the advancement of their chemical inhibitors. Lastly, we will feature protein substrates and chemical inducers of LanC-like protein (LanCL), the first enzyme in protein C-glutathionylation.

Downregulation of Bmal1 Expression in Celiac Ganglia Protects against Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (HIRI) significantly contributes to liver dysfunction following liver transplantation and hepatectomy. However, the role of the celiac ganglion (CG) in HIRI remains unclear. Adeno-associated virus was used to silence Bmal1 expression in the CG of twelve beagles that were randomly assigned to the Bmal1 knockdown group (KO-Bmal1) and the control group. After four weeks, a canine HIRI model was established, and CG, liver tissue, and serum samples were collected for analysis. The virus significantly downregulated Bmal1 expression in the CG. Immunofluorescence staining confirmed a lower proportion of c-fos⁺ and NGF⁺ neurons in TH⁺ cells in the KO-Bmal1 group than in the control group. The KO-Bmal1 group exhibited lower Suzuki scores and serum ALT and AST levels than the control group. Bmal1 knockdown significantly reduced liver fat reserve, hepatocyte apoptosis, and liver fibrosis, and it increased liver glycogen accumulation. We also observed that Bmal1 downregulation inhibited the hepatic neurotransmitter norepinephrine, neuropeptide Y levels, and sympathetic nerve activity in HIRI. Finally, we confirmed that decreased Bmal1 expression in CG reduces TNF-α, IL-1β, and MDA levels and increases GSH levels in the liver. The downregulation of Bmal1 expression in CG suppresses neural activity and improves hepatocyte injury in the beagle model after HIRI.

Coenzyme Q10 prevented Trypanosoma brucei rhodesiense-mediated breach of the blood brain barrier, inflammation and organ damage in late stage of Human African Trypanosomiasis

During the late stage of Human African Trypanosomiasis (HAT), there is severe cytokine-driven inflammation, oxidative stress and organ damage. Controlling inflammation and oxidative damage presents unique therapeutic opportunities to improve treatment outcome. The current study sought to determine the putative impact of Coenzyme-Q10 (Co-Q10), a potent antioxidant and anti-inflammatory, on adverse inflammatory and oxidative events during Trypanosoma brucei rhodesiense (T.b.r) infection. Group one constituted the control; the second group was infected with T.b.r; the third group was orally administered with 200 mg/kg Co-Q10 for two weeks; thereafter, Co-Q10 administration continued after infection with T.b.r. Co-Q10 improved the survival rate of infected mice and prevented full blown parasite driven splenomegaly and hepatomegaly. Co-Q10 prevented characteristic T.b.r-driven breach of the blood brain barrier and improved neurological integrity among T.b.r infected mice. Co-Q10 protected from T.b.r-induced microcytic hypochromic anaemia and thrombocytopenia. T.b.r-induced oxidative stress in the vital organs was assuaged following exposure to Co-Q10. Co-Q10 blocked T.b.r-induced derangement of high density lipoprotein and triglyceride levels. Co-Q10 significantly abrogated T.b.r-driven elevation of serum TNF-α and IFN-γ levels. Moreover, T.b.r-induced kidney and liver damage was assuaged by Co-Q10 administration. Co-Q10 administration downregulated T.b.r-induced elevation of uric acid and C-reactive protein. Likewise, T.b.r infected mice receiving Co-Q10 exhibited normal brain architecture. In conclusion, treatment with Co-Q10 may be useful in protecting against T.b.r-mediated organ injury, lethal inflammation and oxidative stress commonly present in severe late stage HAT; and presents unique opportunities for an adjunct therapy for late stage HAT.

The C-glucosyl flavone isoorientin pretreatment attenuates the methylglyoxal-induced mitochondrial dysfunction in the human neuroblastoma SH-SY5Y cells: role for the AMPK-PI3K/Akt/Nrf2/γ-GCL/GSH axis

The reactive dicarbonyl methylglyoxal (MG) behaves as a pro-oxidant agent, causing redox dysfunction and cell death by different mechanisms in mammalian cells. MG is also a mitochondrial toxicant, impairing the oxidative phosphorylation (OXPHOS) system and leading to bioenergetics and redox collapses. MG induces glycation and exerts an important role in neurodegenerative and cardiovascular diseases. Isoorientin (ISO), a C-glucosyl flavone found in Aspalathus linearis, Fagopyrum esculentum, and Passiflora edulis, among others, is an antioxidant and anti-inflammatory molecule. ISO is a potent inducer of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), the master modulator of the redox environment in mammals. We investigated here whether ISO would prevent the mitochondria-related redox and bioenergetics impairments induced by MG in the human neuroblastoma SH-SY5Y cells. The cells were administrated with ISO at 20 μM for 18 h prior to the exposure to MG at 500 μM for further 24 h. It was observed that ISO efficiently prevented the mitochondrial impairments caused by MG. ISO upregulated the activity of the enzyme γ-glutamate-cysteine ligase (γ-GCL), consequently stimulating the synthesis of glutathione (GSH). The inhibition of γ-GCL, adenosine monophosphate-activated protein kinase (AMPK), and phosphoinositide 3-kinase/Akt (PI3K/Akt) suppressed the beneficial effects induced by ISO on the MG-challenged cells. Moreover, silencing of Nrf2 blocked the ISO-dependent γ-GCL and GSH upregulation and the effects on the mitochondria of the MG-challenged cells. Then, ISO caused mitochondrial protection by an AMPK-PI3K/Akt/Nrf2/γ-GCL/GSH-dependent manner in MG-administrated SH-SY5Y cells.

Emerging chemistry and biology in protein glutathionylation

Protein S-glutathionylation serves a regulatory role in proteins and modulates distinct biological processes implicated in health and diseases. Despite challenges in analyzing the dynamic and reversible nature of S-glutathionylation, recent chemical and biological methods have significantly advanced the field of S-glutathionylation, culminating in selective identification and detection, structural motif analysis, and functional studies of S-glutathionylation. This review will highlight emerging studies of protein glutathionylation, beginning by introducing biochemical tools that enable mass spectrometric identification and live-cell imaging of S-glutathionylation. Next, it will spotlight recent examples of S-glutathionylation regulating physiology and inflammation. Lastly, we will feature two emerging lines of glutathionylation research in cryptic cysteine glutathionylation and protein C-glutathionylation.

Recent Developments in the Understanding of Immunity, Pathogenesis and Management of COVID-19

Coronaviruses represent a diverse family of enveloped positive-sense single stranded RNA viruses. COVID-19, caused by Severe Acute Respiratory Syndrome Coronavirus-2, is a highly contagious respiratory disease transmissible mainly via close contact and respiratory droplets which can result in severe, life-threatening respiratory pathologies. It is understood that glutathione, a naturally occurring antioxidant known for its role in immune response and cellular detoxification, is the target of various proinflammatory cytokines and transcription factors resulting in the infection, replication, and production of reactive oxygen species. This leads to more severe symptoms of COVID-19 and increased susceptibility to other illnesses such as tuberculosis. The emergence of vaccines against COVID-19, usage of monoclonal antibodies as treatments for infection, and implementation of pharmaceutical drugs have been effective methods for preventing and treating symptoms. However, with the mutating nature of the virus, other treatment modalities have been in research. With its role in antiviral defense and immune response, glutathione has been heavily explored in regard to COVID-19. Glutathione has demonstrated protective effects on inflammation and downregulation of reactive oxygen species, thereby resulting in less severe symptoms of COVID-19 infection and warranting the discussion of glutathione as a treatment mechanism.

Redox Imbalance and Its Metabolic Consequences in Tick-Borne Diseases

One of the growing global health problems are vector-borne diseases, including tick-borne diseases. The most common tick-borne diseases include Lyme disease, tick-borne encephalitis, human granulocytic anaplasmosis, and babesiosis. Taking into account the metabolic effects in the patient’s body, tick-borne diseases are a significant problem from an epidemiological and clinical point of view. Inflammation and oxidative stress are key elements in the pathogenesis of infectious diseases, including tick-borne diseases. In consequence, this leads to oxidative modifications of the structure and function of phospholipids and proteins and results in qualitative and quantitative changes at the level of lipid mediators arising in both reactive oxygen species (ROS) and ROS enzyme–dependent reactions. These types of metabolic modifications affect the functioning of the cells and the host organism. Therefore, links between the severity of the disease state and redox imbalance and the level of phospholipid metabolites are being searched, hoping to find unambiguous diagnostic biomarkers. Assessment of molecular effects of oxidative stress may also enable the monitoring of the disease process and treatment efficacy.

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.

Plasma Proteomic Profile of Patients with Tick-Borne Encephalitis and Co-Infections

Despite the increasing number of patients suffering from tick-borne encephalitis (TBE), Lyme disease, and their co-infection, the mechanisms of the development of these diseases and their effects on the human body are still unknown. Therefore, the aim of this study was to evaluate the changes in the proteomic profile of human plasma induced by the development of TBE and to compare it with changes in TBE patients co-infected with other tick-borne pathogens. The results obtained by proteomic analysis using a nanoLC-Q Exactive HF mass spectrometer showed that the most highly elevated groups of proteins in the plasma of TBE patients with co-infection were involved in the pro-inflammatory response and protein degradation, while the antioxidant proteins and factors responsible for protein biosynthesis were mainly downregulated. These results were accompanied by enhanced GSH- and 4-HNE-protein adducts formation, observed in TBE and co-infected patients at a higher level than in the case of patients with only TBE. In conclusion, the differences in the proteomic profiles between patients with TBE and co-infected patients indicate that these diseases are significantly diverse and, consequently, require different treatment, which is particularly important for further research, including the development of novel diagnostics tools.

The Role of Glutathione-S Transferase in Psoriasis and Associated Comorbidities and the Effect of Dimethyl Fumarate in This Pathway

Psoriasis vulgaris is a chronic inflammatory skin disease characterized by well-demarcated scaly plaques. Oxidative stress plays a crucial role in the psoriasis pathogenesis and is associated with the disease severity. Dimethyl fumarate modulates the activity of the pro-inflammatory transcription factors. This is responsible for the downregulation of inflammatory cytokines and an overall shift from a pro-inflammatory to an anti-inflammatory/regulatory response. Both steps are necessary for the amelioration of psoriatic inflammation, although additional mechanisms have been proposed. Several studies reported a long-term effectiveness and safety of dimethyl fumarate monotherapy in patients with moderate-to-severe psoriasis. Furthermore, psoriasis is a chronic disease often associated to metabolic comorbidities, as obesity, diabetes, and cardiovascular diseases, in which glutathione-S transferase deregulation is present. Glutathione-S transferase is involved in the antioxidant system. An increase of its activity in psoriatic epidermis in comparison with the uninvolved and normal epidermal biopsies has been reported. Dimethyl fumarate depletes glutathione-S transferase by formation of covalently linked conjugates. This review investigates the anti-inflammatory role of dimethyl fumarate in oxidative stress and its effect by reducing oxidative stress. The glutathione-S transferase regulation is helpful in treating psoriasis, with an anti-inflammatory effect on the keratinocytes hyperproliferation, and in modulation of metabolic comorbidities.

Carbonic Anhydrases in Metazoan Model Organisms: Molecules, Mechanisms, and Physiology

During the past three decades, mice, zebrafish, fruit flies, and Caenorhabditis elegans have been the primary model organisms used for the study of various biological phenomena. These models have also been adopted and developed to investigate the physiological roles of carbonic anhydrases (CAs) and carbonic anhydrase-related proteins (CARPs). These proteins belong to eight CA families and are identified by Greek letters: α, β, γ, δ, ζ, η, θ, and ι. Studies using model organisms have focused on two CA families, α-CAs and β-CAs, which are expressed in both prokaryotic and eukaryotic organisms with species-specific distribution patterns and unique functions. This review covers the biological roles of CAs and CARPs in light of investigations performed in model organisms. Functional studies demonstrate that CAs are not only linked to the regulation of pH homeostasis, the classical role of CAs but also contribute to a plethora of previously undescribed functions.

New insights into the regulatory roles of glutathione in NLRP3-inflammasome-mediated immune and inflammatory responses

Glutathione (GSH) is the most abundant non-protein thiol (-SH) in mammalian cells. Its synthesis and metabolism serve to maintain cellular reduction-oxidation (redox) homeostasis, which is important for multiple cellular processes including proliferation, differentiation, and death. An accumulating body of evidence suggests that the essential roles of GSH extended far beyond its oxidant and electrophile scavenger activities and regulatory role in the lifespan of cells. Recent findings revealed that altered GSH levels are closely associated with a wide range of pathologies including bacterial and viral infections, neurodegenerative diseases, and autoimmune disorders, all of which are also characterized by aberrant activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. As a result of these findings, GSH was assigned a central role in influencing the activation of the NLRP3 inflammasome. To expand on our recent advances in understanding this process, we discuss here the emerging roles of GSH in activation of the NLRP3 inflammasome, and the therapeutic potential of GSH in its associated pathologies.

Therapeutic Potential of Alpha-Lipoic Acid in Viral Infections, including COVID-19

Oxidative stress (OS), resulting from a disrupted balance between reactive oxygen species (ROS) and protective antioxidants, is thought to play an important pathogenetic role in several diseases, including viral infections. Alpha-lipoic acid (LA) is one of the most-studied and used natural compounds, as it is endowed with a well-defined antioxidant and immunomodulatory profile. Owing to these properties, LA has been tested in several chronic immunoinflammatory conditions, such as diabetic neuropathy and metabolic syndrome. In addition, a pharmacological antiviral profile of LA is emerging, that has attracted attention on the possible use of this compound for the cotreatment of several viral infections. Here, we will review the emerging literature on the potential use of LA in viral infections, including COVID-19.

Fluorescein Based Fluorescence Sensors for the Selective Sensing of Various Analytes

Fluorescein molecules are extensively used to develop fluorescent probes for various analytes due to their excellent photophysical properties and the spirocyclic structure. The main structural modification of fluorescein occurs at the carboxyl group where different groups can be easily introduced to produce the spirolactam structure which is non-fluorescent. The spirolactam ring opening accounts for the fluorescence and the dual sensing of analytes using fluorescent sensors is still a topic of high interest. There is an increase in the number of dual sensors developed in the past five years and quite a good number of fluorescein derivatives were also reported based on reversible mechanisms. This review analyses environmentally and biologically important cations such as Cu²⁺, Hg²⁺, Fe³⁺, Pd²⁺, Zn²⁺, Cd²⁺, and Mg²⁺; anions (F^-, OCl^-) and small molecules (thiols, CO and H₂S). Structural modifications, binding mechanisms, different strategies and a comparative study for selected cations, anions and molecules are outlined in the article.

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.

SARS-CoV2 infection impairs the metabolism and redox function of cellular glutathione

Viral infections sustain their replication cycle promoting a pro-oxidant environment in the host cell. In this context, specific alterations of the levels and homeostatic function of the tripeptide glutathione have been reported to play a causal role in the pro-oxidant and cytopathic effects (CPE) of the virus. In this study, these aspects were investigated for the first time in SARS-CoV2-infected Vero E6 cells, a reliable and well-characterized in vitro model of this infection. SARS-CoV2 markedly decreased the levels of cellular thiols, essentially lowering the reduced form of glutathione (GSH). Such an important defect occurred early in the CPE process (in the first 24 hpi). Thiol analysis in N-acetyl-Cys (NAC)-treated cells and membrane transporter expression data demonstrated that both a lowered uptake of the GSH biosynthesis precursor Cys and an increased efflux of cellular thiols, could play a role in this context. Increased levels of oxidized glutathione (GSSG) and protein glutathionylation were also observed along with upregulation of the ER stress marker PERK. The antiviral drugs Remdesivir (Rem) and Nelfinavir (Nel) influenced these changes at different levels, essentially confirming the importance or blocking viral replication to prevent GSH depletion in the host cell. Accordingly, Nel, the most potent antiviral in our in vitro study, produced a timely activation of Nrf2 transcription factor and a GSH enhancing response that synergized with NAC to restore GSH levels in the infected cells. Despite poor in vitro antiviral potency and GSH enhancing function, Rem treatment was found to prevent the SARS-CoV2-induced glutathionylation of cellular proteins. In conclusion, SARS-CoV2 infection impairs the metabolism of cellular glutathione. NAC and the antiviral Nel can prevent such defect in vitro.

Role of protein S-Glutathionylation in cancer progression and development of resistance to anti-cancer drugs

The survival, functioning and proliferation of mammalian cells are highly dependent on the cellular response and adaptation to changes in their redox environment. Cancer cells often live in an altered redox environment due to aberrant neo-vasculature, metabolic reprogramming and dysregulated proliferation. Thus, redox adaptations are critical for their survival. Glutathione plays an essential role in maintaining redox homeostasis inside the cells by binding to redox-sensitive cysteine residues in proteins by a process called S-glutathionylation. S-Glutathionylation not only protects the labile cysteine residues from oxidation, but also serves as a sensor of redox status, and acts as a signal for stimulation of downstream processes and adaptive responses to ensure redox equilibrium. The present review aims to provide an updated overview of the role of the unique redox adaptations during carcinogenesis and cancer progression, focusing on their dependence on S-glutathionylation of specific redox-sensitive proteins involved in a wide range of processes including signalling, transcription, structural maintenance, mitochondrial functions, apoptosis and protein recycling. We also provide insights into the role of S-glutathionylation in the development of resistance to chemotherapy. Finally, we provide a strong rationale for the development of redox targeting drugs for treatment of refractory/resistant cancers.

Regulation of the Dimerization and Activity of SARS-CoV-2 Main Protease through Reversible Glutathionylation of Cysteine 300

SARS-CoV-2 encodes main protease (M^pro), an attractive target for therapeutic interventions. We show M^pro is susceptible to glutathionylation leading to inhibition of dimerization and activity. Activity of glutathionylated M^pro could be restored with reducing agents or glutaredoxin. Analytical studies demonstrated that glutathionylated M^pro primarily exists as a monomer and that a single modification with glutathione is sufficient to block dimerization and loss of activity. Proteolytic digestions of M^pro revealed Cys300 as a primary target of glutathionylation, and experiments using a C300S M^pro mutant revealed that Cys300 is required for inhibition of activity upon M^pro glutathionylation. These findings indicate that M^pro dimerization and activity can be regulated through reversible glutathionylation of Cys300 and provides a novel target for the development of agents to block Mpro dimerization and activity. This feature of M^pro may have relevance to human disease and the pathophysiology of SARS-CoV-2 in bats, which develop oxidative stress during flight.

Carnosic acid depends on glutathione to promote mitochondrial protection in methylglyoxal-exposed SH-SY5Y cells

Methylglyoxal (MG) is an endogenously produced toxicant that induces mitochondrial dysfunction leading to impaired redox biology homeostasis, bioenergetics collapse, and cell death in mammalian cells. However, MG toxicity is particularly relevant to neurons and glia given their chemical and metabolic characteristics. Here, we have investigated whether a pretreatment with carnosic acid (CA) would be able to promote mitochondrial protection in human neuroblastoma SH-SY5Y cells exposed to MG. We found that a pretreatment with CA at 1 μM for 12 h prevented the MG-induced lipid peroxidation and protein carbonylation and nitration in the membranes of mitochondria obtained from the SH-SY5Y cells. CA also prevented the MG-elicited Complexes I and V dysfunction, adenosine triphosphate (ATP) levels decline, and loss of mitochondrial membrane potential (MMP). Moreover, CA also reduced the mitochondrial production of the radical anion superoxide (O₂^-•) in the MG-challenged cells. We found that CA upregulated the synthesis of glutathione (GSH) by increasing the activity of the γ-glutamylcysteine ligase (γ-GCL). Inhibition of the GSH synthesis by buthionine sulfoximine (BSO) abolished the CA-induced mitochondrial protection. Besides, inhibition of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, as well as silencing of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), suppressed the CA-stimulated protection and the synthesis of GSH. Thus, CA promoted mitochondrial protection by a PI3K/Akt/Nrf2/γ-GCL/GSH axis in MG-treated SH-SY5Y cells.

Targeting spectrin redox switches to regulate the mechanoproperties of red blood cells

The mechanical properties of red blood cells (RBCs) are fundamental for their physiological role as gas transporters. RBC flexibility and elasticity allow them to survive the hemodynamic changes in the different regions of the vascular tree, to dynamically contribute to the flow thereby decreasing vascular resistance, and to deform during the passage through narrower vessels. RBC mechanoproperties are conferred mainly by the structural characteristics of their cytoskeleton, which consists predominantly of a spectrin scaffold connected to the membrane via nodes of actin, ankyrin and adducin. Changes in redox state and treatment with thiol-targeting molecules decrease the deformability of RBCs and affect the structure and stability of the spectrin cytoskeleton, indicating that the spectrin cytoskeleton may contain redox switches. In this perspective review, we revise current knowledge about the structural and functional characterization of spectrin cysteine redox switches and discuss the current lines of research aiming to understand the role of redox regulation on RBC mechanical properties. These studies may provide novel functional targets to modulate RBC function, blood viscosity and flow, and tissue perfusion in disease conditions.

S-glutathionylation, friend or foe in cardiovascular health and disease

Glutathione is a low molecular weight thiol that is present at high levels in the cell. The high levels of glutathione in the cell make it one of the most abundant antioxidants contributing to cellular redox homeostasis. As a general rule, throughout cardiovascular disease and progression there is an imbalance in redox homeostasis characterized by reactive oxygen species overproduction and glutathione underproduction. As research into these imbalances continues, glutathione concentrations are increasingly being observed to drive various physiological and pathological signaling responses. Interestingly in addition to acting directly as an antioxidant, glutathione is capable of post translational modifications (S-glutathionylation) of proteins through both chemical interactions and enzyme mediated events. This review will discuss both the chemical and enzyme-based S-glutathionylation of proteins involved in cardiovascular pathologies and angiogenesis.

Glutaredoxin 1 regulates macrophage polarization through mediating glutathionylation of STAT1

Background

Macrophage polarization affects tumor growth, metabolism, and many other tumor processes. M1 macrophages can promote antitumor immunity response. Signal transducer and activator of transcription 1 (STAT1) is one of the critical transcription factors in this process, which promotes the expression of a series of inflammatory molecules. STAT1 has been reported as a potential target of reactive oxygen species (ROS)‐induced glutathionylation, while the glutathionylation of STAT1 in macrophages and its underlying regulatory mechanism remains unclear. Glutaredoxin 1 (Grx1) functions as a deglutathionylation enzyme, which regulates the activities of many proteins through reversing glutathionylation.

Methods

GeneChip and RT‐qPCR was first applied to test the mRNA level of Grx1 in M1 macrophages. Western blot was then used to evaluate the variations of the Grx1 protein expression in M1 macrophages. Next, immunoprecipitation was used to investigate the glutathionylated STAT1 in both wild‐type and Grx1^−/− mouse macrophages. Finally, the induced alterations of STAT1 activity and function by Grx1 in M1 macrophage were examined by western blot and RT‐qPCR.

Results

In M1‐type macrophages, the levels of Grx1 were elevated. Glutathionylation of STAT1 was negatively regulated by Grx1. Furthermore, depletion of Grx1 increased the activity of STAT1, and thereby promoted the mRNA level of C‐X‐C motif chemokine ligand 9 (CXCL9) during M1‐type polarization of macrophages.

Conclusions

Grx1 controlled deglutathionylation of STAT1, which in turn might regulate M1‐type polarization of macrophages.

S-glutathionylation proteome profiling reveals a crucial role of a thioredoxin-like protein in interspecies competition and cariogenecity of Streptococcus mutans

S-glutathionylation is an important post-translational modification (PTM) process that targets protein cysteine thiols by the addition of glutathione (GSH). This modification can prevent proteolysis caused by the excessive oxidation of protein cysteine residues under oxidative or nitrosative stress conditions. Recent studies have suggested that protein S-glutathionylation plays an essential role in the control of cell-signaling pathways by affecting the protein function in bacteria and even humans. In this study, we investigated the effects of S-glutathionylation on physiological regulation within Streptococcus mutans, the primary etiological agent of human dental caries. To determine the S-glutathionylated proteins in bacteria, the Cys reactive isobaric reagent iodoacetyl Tandem Mass Tag (iodoTMT) was used to label the S-glutathionylated Cys site, and an anti-TMT antibody-conjugated resin was used to enrich the modified peptides. Proteome profiling identified a total of 357 glutathionylated cysteine residues on 239 proteins. Functional enrichment analysis indicated that these S-glutathionylated proteins were involved in diverse important biological processes, such as pyruvate metabolism and glycolysis. Furthermore, we studied a thioredoxin-like protein (Tlp) to explore the effect of S-glutathionylation on interspecies competition between oral streptococcal biofilms. Through site mutagenesis, it was proved that glutathionylation on Cys41 residue of Tlp is crucial to protect S. mutans from oxidative stress and compete with S. sanguinis and S. gordonii. An addition rat caries model showed that the loss of S-glutathionylation attenuated the cariogenicity of S. mutans. Taken together, our study provides an insight into the S-glutathionylation of bacterial proteins and the regulation of oxidative stress resistance and interspecies competition.

Redox-Modulating Agents in the Treatment of Viral Infections

Viruses use cell machinery to replicate their genome and produce viral proteins. For this reason, several intracellular factors, including the redox state, might directly or indirectly affect the progression and outcome of viral infection. In physiological conditions, the redox balance between oxidant and antioxidant species is maintained by enzymatic and non-enzymatic systems, and it finely regulates several cell functions. Different viruses break this equilibrium and induce an oxidative stress that in turn facilitates specific steps of the virus lifecycle and activates an inflammatory response. In this context, many studies highlighted the importance of redox-sensitive pathways as novel cell-based targets for therapies aimed at blocking both viral replication and virus-induced inflammation. In the review, we discuss the most recent findings in this field. In particular, we describe the effects of natural or synthetic redox-modulating molecules in inhibiting DNA or RNA virus replication as well as inflammatory pathways. The importance of the antioxidant transcription factor Nrf2 is also discussed. Most of the data reported here are on influenza virus infection. We believe that this approach could be usefully applied to fight other acute respiratory viral infections characterized by a strong inflammatory response, like COVID-19.

Protein S-glutathionylation reactions as a global inhibitor of cell metabolism for the desensitization of hydrogen peroxide signals

The pathogenesis of many human diseases has been attributed to the over production of reactive oxygen species (ROS), particularly superoxide (O₂^●-) and hydrogen peroxide (H₂O₂), by-products of metabolism that are generated by the premature reaction of electrons with molecular oxygen (O₂) before they reach complex IV of the respiratory chain. To date, there are 32 known ROS generators in mammalian cells, 16 of which reside inside mitochondria. Importantly, although these ROS are deleterious at high levels, controlled and temporary bursts in H₂O₂ production is beneficial to mammalian cells. Mammalian cells use sophisticated systems to take advantage of the second messaging properties of H₂O₂. This includes controlling its availability using antioxidant systems and negative feedback loops that inhibit the genesis of ROS at sites of production. At its core, ROS production depends on fuel metabolism. Therefore, desensitizing H₂O₂ signals would also require the temporary inhibition of fuel combustion and fluxes through metabolic pathways that promote ROS production. Additionally, this would also demand the diversion of fuels and nutrients into pathways that generate NADPH and other molecules required to maintain cellular redox buffering capacity. Therefore, fuel selection and metabolic flux plays an integral role in dictating the strength and duration of cellular redox signals. In the present review I provide an updated view on the function of protein S-glutathionylation, a ubiquitous redox sensitive modification involving the formation of a disulfide between the small molecular antioxidant glutathione and a cysteine residue, in the regulation of cellular metabolism on a global scale. To date, these concepts have mostly been reviewed at the level of mitochondrial bioenergetics in the contexts of health and disease. Careful examination of the literature revealed that glutathionylation is a temporary inhibitor of most metabolic pathways including glycolysis, the Krebs cycle, oxidative phosphorylation, amino acid metabolism, and fatty acid combustion, resulting in the diversion of fuels towards NADPH-producing pathways and the inhibition of ROS production. Armed with this information, I propose that protein S-glutathionylation reactions desensitize H₂O₂ signals emanating from catabolic pathways using a three-pronged regulatory mechanism; 1) inhibition of metabolic flux through pathways that promote ROS production, 2) diversion of metabolites towards pathways that support antioxidant defenses, and 3) direct inhibition of ROS-generating enzymes.