Glutathione supplementation improves macrophage functions in HIV

Emerging roles of ferroptosis in infectious diseases

In living organisms, lipid peroxidation is a continuously occurring cellular process and therefore involved in various physiological and pathological contexts. Among the broad variety of lipids, polyunsaturated fatty acids (PUFA) constitute a major target of oxygenation either when released as mediators by phospholipases or when present in membranous phospholipids. The last decade has seen the characterization of an iron- and lipid peroxidation-dependent cell necrosis, namely, ferroptosis, that involves the accumulation of peroxidized PUFA-containing phospholipids. Further studies could link ferroptosis in a very large body of (physio)-pathological processes, including cancer, neurodegenerative, and metabolic diseases. In this review, we mostly focus on the emerging involvement of lipid peroxidation-driven ferroptosis in infectious diseases, and the immune consequences. We also discuss the putative ability of microbial virulence factors to exploit or to dampen ferroptosis regulatory pathways to their own benefit.

GPX4 regulates cellular necrosis and host resistance in Mycobacterium tuberculosis infection

Cellular necrosis during Mycobacterium tuberculosis (Mtb) infection promotes both immunopathology and bacterial dissemination. Glutathione peroxidase-4 (Gpx4) is an enzyme that plays a critical role in preventing iron-dependent lipid peroxidation-mediated cell death (ferroptosis), a process previously implicated in the necrotic pathology seen in Mtb-infected mice. Here, we document altered GPX4 expression, glutathione levels, and lipid peroxidation in patients with active tuberculosis and assess the role of this pathway in mice genetically deficient in or overexpressing Gpx4. We found that Gpx4-deficient mice infected with Mtb display substantially increased lung necrosis and bacterial burdens, while transgenic mice overexpressing the enzyme show decreased bacterial loads and necrosis. Moreover, Gpx4-deficient macrophages exhibited enhanced necrosis upon Mtb infection in vitro, an outcome suppressed by the lipid peroxidation inhibitor, ferrostatin-1. These findings provide support for the role of ferroptosis in Mtb-induced necrosis and implicate the Gpx4/GSH axis as a target for host-directed therapy of tuberculosis.

Fluoroquinolone heteroresistance, antimicrobial tolerance, and lethality enhancement

With tuberculosis, the emergence of fluoroquinolone resistance erodes the ability of treatment to interrupt the progression of MDR-TB to XDR-TB. One way to reduce the emergence of resistance is to identify heteroresistant infections in which subpopulations of resistant mutants are likely to expand and make the infections fully resistant: treatment modification can be instituted to suppress mutant enrichment. Rapid DNA-based detection methods exploit the finding that fluoroquinolone-resistant substitutions occur largely in a few codons of DNA gyrase. A second approach for restricting the emergence of resistance involves understanding fluoroquinolone lethality through studies of antimicrobial tolerance, a condition in which bacteria fail to be killed even though their growth is blocked by lethal agents. Studies with Escherichia coli guide work with Mycobacterium tuberculosis. Lethal action, which is mechanistically distinct from blocking growth, is associated with a surge in respiration and reactive oxygen species (ROS). Mutations in carbohydrate metabolism that attenuate ROS accumulation create pan-tolerance to antimicrobials, disinfectants, and environmental stressors. These observations indicate the existence of a general death pathway with respect to stressors. M. tuberculosis displays a variation on the death pathway idea, as stress-induced ROS is generated by NADH-mediated reductive stress rather than by respiration. A third approach, which emerges from lethality studies, uses a small molecule, N-acetyl cysteine, to artificially increase respiration and additional ROS accumulation. That enhances moxifloxacin lethality with M. tuberculosis in culture, during infection of cultured macrophages, and with infection of mice. Addition of ROS stimulators to fluoroquinolone treatment of tuberculosis constitutes a new direction for suppressing the transition of MDR-TB to XDR-TB.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Liposomal Glutathione Helps to Mitigate Mycobacterium tuberculosis Infection in the Lungs

Mycobacterium tuberculosis (M. tb), the causative agent of tuberculosis (TB), is responsible for causing significant morbidity and mortality, especially among individuals with compromised immune systems. We have previously shown that the supplementation of liposomal glutathione (L-GSH) reduces M. tb viability and enhances a Th-1 cytokine response, promoting granuloma formation in human peripheral blood mononuclear cells in vitro. However, the effects of L-GSH supplementation in modulating the immune responses in the lungs during an active M. tb infection have yet to be explored. In this article, we report the effects of L-GSH supplementation during an active M. tb infection in a mouse model of pulmonary infection. We determine the total GSH levels, malondialdehyde (MDA) levels, cytokine profiles, granuloma formation, and M. tb burden in untreated and L-GSH-treated mice over time. In 40 mM L-GSH-supplemented mice, an increase in the total GSH levels was observed in the lungs. When compared to untreated mice, the treatment of M. tb-infected mice with 40 mM and 80 mM L-GSH resulted in a reduction in MDA levels in the lungs. L-GSH treatment also resulted in a significant increase in the levels of IL-12, IFN-γ, IL-2, IL-17, and TNF-α in the lungs, while down-regulating the production of IL-6, IL-10, and TGF-β in the lungs. A reduction in M. tb survival along with a decrease in granuloma size in the lungs of M. tb-infected mice was observed after L-GSH treatment. Our results show that the supplementation of mice with L-GSH led to increased levels of total GSH, which is associated with reduced oxidative stress, increased levels of granuloma-promoting cytokines, and decreased M. tb burden in the lung. These results illustrate how GSH can help mitigate M. tb infection and provide an insight into future therapeutic interventions.

Glutathione reductase system changes in HTLV-1 infected patients

During chronic HTLV-1 infections oxidative stress occurs and contributes in viral pathogenesis. Glutaredoxin (Grx) system is one of the most effective antioxidant components. The system maintains the cellular redox and scavenges reactive oxygen species through the function of glutathione reductase (GR) enzyme, NADPH and reduced glutathione (GSH). This study was performed to investigate potential changes in GR gene expression and activity as well as GSH level, and their association with the viral load in HTLV-1 infection. Forty HTLV-1 seropositive patients divided into two groups: asymptomatic carriers (N = 20) and HAM/TSP (N = 20) with the same number of age and sex-matched healthy controls were recruited in this study. GR cellular gene expression and viral load in PBMCs were determined using Real-time PCR Technique. Enzyme activity and GSH level in sera were measured by commercial kits based on manufacturer's provided protocols. GR gene expression and GR enzyme activity, as well as GSH level, were significantly lower in HTLV-1 patients. A negative correlation between viral load and GR gene expression/enzyme activity was observed in HAM/TSP group. Similarly, a negative relationship between viral load and GSH levels was observed in both carrier and HAM/TSP groups. We also found that in profound complicated condition of HTLV-1 infection, HAM/TSP, Grx system components activity was significantly decreased compared to the controls. Such observation was not the case in clinically healthy HTLV-1 carriers. These findings may shed a light on the conditions contributing in pathogenesis of the complications and exacerbation of the disease in the HAM/TSP cases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-022-00758-y.

Liposomes as Carriers for the Delivery of Efavirenz in Combination with Glutathione—An Approach to Combat Opportunistic Infections

Human immunodeficiency virus (HIV)-infected individuals display an enhanced production of reactive oxygen species (ROS). This reduction of antioxidant capacity in host tissues has been related to the decrease in total levels of ROS scavengers such as glutathione (GSH). Prevention of opportunistic infections due to a weakened immune system is becoming a key strategy along with HIV elimination. Research in these directions is clearly warranted, especially a combination of antiretrovirals and antioxidants to ameliorate oxidative stress, improve intracellular uptake and target viral reservoirs. Hence, we aimed to formulate liposomes loaded with the antiretroviral drug efavirenz (EFA) in the presence of glutathione, as these carriers can be engineered to enhance the ability to reach the target reservoirs. The goal of the present work was to investigate the intracellular uptake of EFA-loaded liposome (with and without GSH) by human monocytic leukemia cells (THP-1 cells) and examine cell viability and ROS scavenging activity. Results obtained provided significant data as follows: (i) treatment with EFA and GSH combination could enhance the uptake and reduce cytotoxicity; (ii) encapsulation of EFA into liposomes increased its levels in the macrophages, which was further enhanced in the presence of GSH; (iii) delivery of EFA in the presence of GSH quenched the intracellular ROS, which was significantly higher when delivered via liposomes. Data revealed that a combination of EFA and GSH encompasses advantages; hence, GSH supplementation could be a safe and cost-effective treatment to slow the development of HIV infection and produce an immune-enhancing effect.

New roles for glutathione: Modulators of bacterial virulence and pathogenesis

Low molecular weight (LMW) thiols contain reducing sulfhydryl groups that are important for maintaining antioxidant defense in the cell. Aside from the traditional roles of LMW thiols as redox regulators in bacteria, glutathione (GSH) has been reported to affect virulence and bacterial pathogenesis. The role of GSH in virulence is diverse, including the activation of virulence gene expression and contributing to optimal biofilm formation. GSH can also be converted to hydrogen sulfide (H₂S) which is important for the pathogenesis of certain bacteria. Besides GSH, some bacteria produce other LMW thiols such as mycothiol and bacillithiol that affect bacterial virulence. We discuss these newer reported functions of LMW thiols modulating bacterial pathogenesis either directly or indirectly and via modulation of the host immune system.

Glutathione Deficiency in HIV-1-Infected Children with Short Stature

Objective This study was aimed to determine if glutathione (GSH) deficiency occurs in children with HIV infection and whether GSH deficiency is associated with HIV-related short stature.

Methods We conducted a cross-sectional study with two age-matched comparison groups in an inner city hospital-based pediatric AIDS/HIV outpatient clinic. Ten perinatally HIV-infected children aged 6 to 49 months with short stature (height–age percentile ≤5) were studied together with age-matched 10 HIV-infected children with normal height and 10 HIV-seronegative children with normal height. Total erythrocyte GSH (GSH and GSH disulfide) levels were determined by a modification of the 5,5′-dithiobis-2-nitrobenzoic acid glutathione disulfide reductase method. Other measures included complete blood counts, lymphocyte subset analysis, plasma albumin, cholesterol, vitamins A and E, and determination of HIV disease stage.

Discussion Erythrocyte GSH levels were lower in HIV-infected children with short stature (mean ± standard deviation [SD]: 0.639 µmol/mL ± 0.189) compared with HIV-infected children with normal height (mean ± SD: 0.860 µmol/mL ± 0.358; p < 0.05) and HIV-negative controls (mean ± SD: 0.990 µmol/mL ± 0.343; p < 0.05). Plasma levels of cholesterol, albumin, and vitamins A and E did not differ between the short-stature group and either the HIV-infected normal-height group or HIV-negative controls.

Conclusion These results demonstrate a GSH deficiency in HIV-infected children with short stature and support the hypothesis that GSH balance is important in growth among HIV-infected children.

Adjunct N-Acetylcysteine Treatment in Hospitalized Patients With HIV-Associated Tuberculosis Dampens the Oxidative Stress in Peripheral Blood: Results From the RIPENACTB Study Trial

Tuberculosis (TB) still causes significant morbidity and mortality worldwide, especially in persons living with human immunodeficiency virus (HIV). This disease is hallmarked by persistent oxidative stress and systemic inflammation. N-acetylcysteine (NAC), a glutathione (GSH) precursor, has been shown in experimental models to limit Mycobacterium tuberculosis infection and disease both by suppression of the host oxidative response and through direct antimicrobial activity. In a recent phase II randomized clinical trial (RIPENACTB study), use of NAC as adjunct therapy during the first two months of anti-TB treatment was safe. Whether adjunct NAC therapy of patients with TB-HIV coinfection in the context of anti-TB treatment could directly affect pro-oxidation and systemic inflammation has not been yet formally demonstrated. To test this hypothesis, we leveraged existing data and biospecimens from the RIPENACTB trial to measure a number of surrogate markers of oxidative stress and of immune activation in peripheral blood of the participants at pre-treatment and at the day 60 of anti-TB treatment. Upon initiation of therapy, we found that the group of patients undertaking NAC exhibited significant increase in GSH levels and in total antioxidant status while displaying substantial reduction in lipid peroxidation compared to the control group. Only small changes in plasma concentrations of cytokines were noted. Pharmacological improvement of the host antioxidant status appears to be a reasonable strategy to reduce TB-associated immunopathology.

Pathogenesis of Human Immunodeficiency Virus-Mycobacterium tuberculosis Co-Infection

Given that infection with Mycobacterium tuberculosis (Mtb) is the leading cause of death amongst individuals living with HIV, understanding the complex mechanisms by which Mtb exacerbates HIV infection may lead to improved treatment options or adjuvant therapies. While it is well-understood how HIV compromises the immune system and leaves the host vulnerable to opportunistic infections such as Mtb, less is known about the interplay of disease once active Mtb is established. This review explores how glutathione (GSH) depletion, T cell exhaustion, granuloma formation, and TNF-α upregulation, as a result of Mtb infection, leads to an increase in HIV disease severity. This review also examines the difficulties of treating coinfected patients and suggests further research on the clinical use of GSH supplementation.

HIV and the tuberculosis "set point": how HIV impairs alveolar macrophage responses to tuberculosis and sets the stage for progressive disease

As HIV has fueled a global resurgence of tuberculosis over the last several decades, there is a growing awareness that HIV-mediated impairments in both innate and adaptive immunity contribute to the heightened risk of tuberculosis in people with HIV. Since early immune responses to Mycobacterium tuberculosis (Mtb) set the stage for subsequent control or progression to active tuberculosis disease, early host-pathogen interactions following Mtb infection can be thought of as establishing a mycobacterial "set point," which we define as the mycobacterial burden at the point of adaptive immune activation. This early immune response is impaired in the context of HIV coinfection, allowing for a higher mycobacterial set point and greater likelihood of progression to active disease with greater bacterial burden. Alveolar macrophages, as the first cells to encounter Mtb in the lungs, play a critical role in containing Mtb growth and establishing the mycobacterial set point. However, a number of key macrophage functions, ranging from pathogen recognition and uptake to phagocytosis and microbial killing, are blunted in HIV coinfection. To date, research evaluating the effects of HIV on the alveolar macrophage response to Mtb has been relatively limited, particularly with regard to the critical early events that help to dictate the mycobacterial set point. A greater understanding of alveolar macrophage functions impacted by HIV coinfection will improve our understanding of protective immunity to Mtb and may reveal novel pathways amenable to intervention to improve both early immune control of Mtb and clinical outcomes for the millions of people worldwide infected with HIV.

Analysis of Tuberculosis Meningitis Pathogenesis, Diagnosis, and Treatment

Tuberculosis (TB) is the most prevalent infectious disease in the world. In recent years there has been a significant increase in the incidence of TB due to the emergence of multidrug resistant strains of Mycobacterium tuberculosis (M. tuberculosis) and the increased numbers of highly susceptible immuno-compromised individuals. Central nervous system TB, includes TB meningitis (TBM-the most common presentation), intracranial tuberculomas, and spinal tuberculous arachnoiditis. Individuals with TBM have an initial phase of malaise, headache, fever, or personality change, followed by protracted headache, stroke, meningismus, vomiting, confusion, and focal neurologic findings in two to three weeks. If untreated, mental status deteriorates into stupor or coma. Delay in the treatment of TBM results in, either death or substantial neurological morbidity. This review provides latest developments in the biomedical research on TB meningitis mainly in the areas of host immune responses, pathogenesis, diagnosis, and treatment of this disease.

Safety and efficacy of N-acetylcysteine in hospitalized patients with HIV-associated tuberculosis: An open-label, randomized, phase II trial (RIPENACTB Study)

Despite the availability of effective antimicrobials, tuberculosis (TB) is still a serious health threat. Mortality is even higher in people living with HIV who are diagnosed with TB. New therapies are needed to shorten the time required to cure TB and decrease fatality rates in this population. N-acetylcysteine (NAC) is a glutathione precursor and has shown recently in experimental setting to present in vitro and in vivo anti-mycobacterial activity. We test the hypothesis that NAC is safe, well tolerated and secondarily efficacious as adjunctive anti-TB therapy in hospitalized individuals with HIV-associated TB. Patients were enrolled sequentially in a tertiary care center, in the Brazilian Amazon. We performed a randomized, parallel group, single-center, open study trial of two arms, in hospitalized patients over 18 years of age, with microbiologically confirmed pulmonary TB in HIV: one with rifampicin, isoniazid, pyrazinamide and ethambutol at standard doses (Control Group), and a second in which NAC 600 mg bid for eight weeks was added (NAC Group). A total of 21 and 18 patients were enrolled to the Control Group and NAC Group, respectively. Adverse event rates were similar in the two arms. Our findings suggest that in the more critical population of hospitalized patients with HIV-associated TB, the use of NAC was not unsafe, despite the low sample size, and a potential impact on faster negative cultures needs to be further explored in larger studies.

N-Acetyl Cysteine as an Adjunct in the Treatment of Tuberculosis

Oxidative stress is a common feature of tuberculosis (TB), and persons with reduced antioxidants are at more risk of TB. TB patients with relatively severe oxidative stress had also more advanced disease as measured by the Karnofsky performance index. Since adverse effects from anti-TB drugs are also mediated by free radicals, TB patients are prone to side effects, such as hearing loss. In previous articles, researchers appealed for clinical trials aiming at evaluating N-acetyl cysteine (NAC) in attenuating the dreaded hearing loss during multidrug-resistant TB (MDR-TB) treatment. However, before embarking on such trials, considerations of NAC's overall impact on TB treatment are crucial. Unfortunately, such a comprehensive report on NAC is missing in the literature and this manuscript reviews the broader effect of NAC on TB treatment. This paper discusses NAC's effect on mycobacterial clearance, hearing loss, drug-induced liver injury, and its interaction with anti-TB drugs. Based on the evidence accrued to date, NAC appears to have various beneficial effects on TB treatment. However, despite the favorable interaction between NAC and first-line anti-TB drugs, the interaction between the antioxidant and some of the second-line anti-TB drugs needs further investigations.

Characterizing the Effects of Glutathione as an Immunoadjuvant in the Treatment of Tuberculosis

Mycobacterium tuberculosis is the etiological agent that is responsible for causing tuberculosis (TB), which continues to affect millions of people worldwide, and the rate of resistance of M. tuberculosis to antibiotics is ever increasing. We tested the synergistic effects of N-acetyl cysteine (NAC; the precursor molecule for the synthesis of glutathione [GSH]) and individual first-line antibiotics typically given for the treatment of TB, such as isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA), to improve the ability of macrophages to control intracellular M. tuberculosis infection.

Mycobacterium tuberculosis is the etiological agent that is responsible for causing tuberculosis (TB), which continues to affect millions of people worldwide, and the rate of resistance of M. tuberculosis to antibiotics is ever increasing. We tested the synergistic effects of N-acetyl cysteine (NAC; the precursor molecule for the synthesis of glutathione [GSH]) and individual first-line antibiotics typically given for the treatment of TB, such as isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA), to improve the ability of macrophages to control intracellular M. tuberculosis infection. GSH, a pleiotropic antioxidant molecule, has previously been shown to display both antimycobacterial and immune-enhancing effects. Our results indicate that there was not only an increase in beneficial immunomodulatory effects but also a greater reduction in the intracellular viability of M. tuberculosis when macrophages were treated with the combination of antibiotics (INH, RIF, EMB, or PZA) and NAC.

The Synergistic Effects of the Glutathione Precursor, NAC and First-Line Antibiotics in the Granulomatous Response Against Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tb), the causative bacterial agent responsible for tuberculosis (TB) continues to afflict millions of people worldwide. Although the human immune system plays a critical role in containing M. tb infection, elimination proves immensely more challenging. Consequently, there has been a worldwide effort to eradicate, and limit the spread of M. tb through the conventional use of first-line antibiotics. Unfortunately, with the emergence of drug resistant and multi-drug resistant strains of M. tb the archetypical antibiotics no longer provide the same ascendancy as they once did. Furthermore, when administered, these first-line antibiotics commonly present severe complications and side effects. The biological antioxidant glutathione (GSH) however, has been demonstrated to have a profound mycobactericidal effect with no reported adverse consequences. Therefore, we examined if N-Acetyl Cysteine (NAC), the molecular precursor to GSH, when supplemented in combination with suboptimal levels of standalone first-line antibiotics would be sufficient to completely clear M. tb infection within in vitro derived granulomas from healthy subjects and individuals with type 2 diabetes (T2DM). Our results revealed that by virtue of immune modulation, the addition of NAC to subprime levels of isoniazid (INH) and rifampicin (RIF) was indeed capable of inducing complete clearance of M. tb among healthy individuals.

Glutathione as a Marker for Human Disease

Glutathione (GSH), often referred to as "the master antioxidant," participates not only in antioxidant defense systems, but many metabolic processes, and therefore its role cannot be overstated. GSH deficiency causes cellular risk for oxidative damage and thus as expected, GSH imbalance is observed in a wide range of pathological conditions including tuberculosis (TB), HIV, diabetes, cancer, and aging. Consequently, it is not surprising that GSH has attracted the attention of biological researchers and pharmacologists alike as a possible target for medical intervention. Here, we discuss the role GSH plays amongst these pathological conditions to illuminate how it can be used as a marker for human disease.

Restoring Cytokine Balance in HIV-Positive Individuals with Low CD4 T Cell Counts

HIV infects and destroys CD4+ T cells leading to a compromised immune system. In a double-blinded study, a group of HIV-infected individuals with CD4+ T cell counts below 350 cells/mm³ were given either an empty liposomal supplement or a liposomal glutathione (L-GSH) supplement to take over a 3-month period. Baseline measurements in HIV-positive subjects show a significant decrease in levels of interleukin (IL)-12, IL-2, and interferon (IFN)-γ, along with a substantial increase in the levels of IL-6, IL-10, transforming growth factor (TGF)-β, and free radicals, compared to healthy individuals. Supplementation of HIV-positive subjects with L-GSH for 3 months resulted in a notable increase in the levels of IL-12, IL-2, and IFN-γ, with a concomitant decrease in the levels of IL-6, IL-10, and free radicals, and stabilization in the levels of TGF-β, IL-1, and IL-17, compared to their placebo counterparts. Levels of free radicals in CD4+ T cells stabilized, while GSH levels increased in the treatment group. Those in the placebo group showed no significant difference throughout the study. In summary, supplementation with L-GSH in HIV-infected individuals with CD4+ T cell counts below 350 cells/mm³ can help restore redox homeostasis and cytokine balance, therefore aiding the immune system to control opportunistic infections.

The Immune Interaction between HIV-1 Infection and Mycobacterium tuberculosis

The modulation of tuberculosis (TB)-induced immunopathology caused by human immunodeficiency virus (HIV)-1 coinfection remains incompletely understood but underlies the change seen in the natural history, presentation, and prognosis of TB in such patients. The deleterious combination of these two pathogens has been dubbed a "deadly syndemic," with each favoring the replication of the other and thereby contributing to accelerated disease morbidity and mortality. HIV-1 is the best-recognized risk factor for the development of active TB and accounts for 13% of cases globally. The advent of combination antiretroviral therapy (ART) has considerably mitigated this risk. Rapid roll-out of ART globally and the recent recommendation by the World Health Organization (WHO) to initiate ART for everyone living with HIV at any CD4 cell count should lead to further reductions in HIV-1-associated TB incidence because susceptibility to TB is inversely proportional to CD4 count. However, it is important to note that even after successful ART, patients with HIV-1 are still at increased risk for TB. Indeed, in settings of high TB incidence, the occurrence of TB often remains the first presentation of, and thereby the entry into, HIV care. As advantageous as ART-induced immune recovery is, it may also give rise to immunopathology, especially in the lower-CD4-count strata in the form of the immune reconstitution inflammatory syndrome. TB-immune reconstitution inflammatory syndrome will continue to impact the HIV-TB syndemic.

Glutathione and glutathione derivatives in immunotherapy

Reduced glutathione (GSH) is the most prevalent non-protein thiol in animal cells. Its de novo and salvage synthesis serves to maintain a reduced cellular environment, which is important for several cellular functions. Altered intracellular GSH levels are observed in a wide range of pathologies, including several viral infections, as well as in aging, all of which are also characterized by an unbalanced Th1/Th2 immune response. A central role in influencing the immune response has been ascribed to GSH. Specifically, GSH depletion in antigen-presenting cells (APCs) correlates with altered antigen processing and reduced secretion of Th1 cytokines. Conversely, an increase in intracellular GSH content stimulates IL-12 and/or IL-27, which in turn induces differentiation of naive CD4+ T cells to Th1 cells. In addition, GSH has been shown to inhibit the replication/survival of several pathogens, i.e. viruses and bacteria. Hence, molecules able to increase GSH levels have been proposed as new tools to more effectively hinder different pathogens by acting as both immunomodulators and antimicrobials. Herein, the new role of GSH and its derivatives as immunotherapeutics will be discussed.

N-acetyl-cysteine exhibits potent anti-mycobacterial activity in addition to its known anti-oxidative functions

Background

Mycobacterium tuberculosis infection is thought to induce oxidative stress. N-acetyl-cysteine (NAC) is widely used in patients with chronic pulmonary diseases including tuberculosis due to its mucolytic and anti-oxidant activities. Here, we tested whether NAC exerts a direct antibiotic activity against mycobacteria.

Methods

Oxidative stress status in plasma was compared between pulmonary TB (PTB) patients and those with latent M. tuberculosis infection (LTBI) or healthy uninfected individuals. Lipid peroxidation, DNA oxidation and cell death, as well as accumulation of reactive oxygen species (ROS) were measured in cultures of primary human monocyte-derived macrophages infected with M. tuberculosis and treated or not with NAC. M. tuberculosis, M. avium and M. bovis BCG cultures were also exposed to different doses of NAC with or without medium pH adjustment to control for acidity. The anti-mycobacterial effect of NAC was assessed in M. tuberculosis infected human THP-1 cells and bone marrow-derived macrophages from mice lacking a fully functional NADPH oxidase system. The capacity of NAC to control M. tuberculosis infection was further tested in vivo in a mouse (C57BL/6) model.

Results

PTB patients exhibited elevated levels of oxidation products and a reduction of anti-oxidants compared with LTBI cases or uninfected controls. NAC treatment in M. tuberculosis-infected human macrophages resulted in a decrease of oxidative stress and cell death evoked by mycobacteria. Importantly, we observed a dose-dependent reduction in metabolic activity and in vitro growth of NAC treated M. tuberculosis, M. avium and M. bovis BCG. Furthermore, anti-mycobacterial activity in infected macrophages was shown to be independent of the effects of NAC on the host NADPH oxidase system in vitro. Short-term NAC treatment of M. tuberculosis infected mice in vivo resulted in a significant reduction of mycobacterial loads in the lungs.

Conclusions

NAC exhibits potent anti-mycobacterial effects and may limit M. tuberculosis infection and disease both through suppression of the host oxidative response and through direct antimicrobial activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0872-7) contains supplementary material, which is available to authorized users.

Analysis of glutathione levels in the brain tissue samples from HIV-1-positive individuals and subject with Alzheimer's disease and its implication in the pathophysiology of the disease process

HIV-1 positive individuals are at high risk for susceptibility to both pulmonary tuberculosis (TB) and extra-pulmonary TB, including TB meningitis (TBM) which is an extreme form of TB. The goals of this study are to determine the mechanisms responsible for compromised levels of glutathione (GSH) in the brain tissue samples derived from HIV-1-infected individuals and individuals with Alzheimer's disease (AD), investigate the possible underlying mechanisms responsible for GSH deficiency in these pathological conditions, and establish a link between GSH levels and pathophysiology of the disease processes. We demonstrated in the autopsied human brain tissues that the levels of total and reduced forms of GSH were significantly compromised in HIV-1 infected individuals compared to in healthy subjects and individuals with AD. Brain tissue samples derived from HIV-1-positive individuals had substantially higher levels of free radicals than that derived from healthy and AD individuals. Enzymes that are responsible for the de novo synthesis of GSH such as γ-glutamate cysteine-ligase catalytic subunit (GCLC-rate limiting step enzyme) and glutathione synthetase (GSS-enzyme involved in the second step reaction) were significantly decreased in the brain tissue samples derived from HIV-1-positive individuals with low CD4 + T-cells (< 200 cells/mm³) compared to healthy and AD individuals. Levels of glutathione reductase (GSR) were also decreased in the brain tissue samples derived from HIV-1 infected individuals. Overall, our findings demonstrate causes for GSH deficiency in the brain tissue from HIV-1 infected individuals explaining the possible reasons for increased susceptibility to the most severe form of extra-pulmonary TB, TBM.

•

Total and reduced forms of GSH were significantly compromised in the brain tissues derived from HIV-1 infected individuals.

•

Brain tissue samples derived from HIV-1-positive individuals had substantially higher levels of free radicals.

•

GSH de novo synthesis enzymes were significantly decreased in HIV-1-positive individuals with low CD4 + T-cells.

•

Levels of GSR were also decreased in the brain tissue samples derived from HIV-1 infected individuals.

•

Overall, our findings demonstrate causes for GSH deficiency in the brain tissue from HIV-1 infected individuals.

Mechanisms of Control of Mycobacterium tuberculosis by NK Cells: Role of Glutathione

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tb), continues to be one of the most prevalent infectious diseases in the world. There is an upward trend in occurrence due to emerging multidrug resistant strains and an increasingly larger proportion of immunocompromised patient populations as a result of the acquired immunodeficiency syndrome pandemic. The complex and often deadly combination of multidrug resistant M. tb (MDR-M. tb) along with human immunodeficiency virus (HIV) puts a significant number of people at high risk for pulmonary and extra-pulmonary TB without sufficient therapeutic options available. Natural killer (NK) cells and macrophages are major components of the body's innate immune system, contributing significantly to the body's ability to synergistically inhibit the growth of M. tb in immune compromised individuals lacking a sufficient T cell response. Direct mechanisms of control are largely through the secretory products perforin, granulysin, and granzymes, as well as multiple membrane-bound death receptors that facilitate target directed lysis. NK cells also have a role in indirectly stimulating an immune response through activation of macrophages and monocytes with multiple signaling pathways, including both reactive oxygen species and reactive nitrogen species. Glutathione (GSH) has been shown to play a part in inhibiting the growth of intracellular M. tb through bacteriostatic mechanisms. Enhancing cellular GSH through several cytokines and N-acetyl cysteine has been shown to increase these effects, at least in part, through their action on NK cells. Taken together, there is substantial evidence for a mechanistic correlation between NK cell activity and functionality in combating M. tb in HIV infection mediated through adequate GSH production and use.

Liposomal Glutathione Supplementation Restores TH1 Cytokine Response to Mycobacterium tuberculosis Infection in HIV-Infected Individuals

Cytokines are signaling biomolecules that serve as key regulators of our immune system. CD4⁺ T-cells can be grouped into 2 major categories based on their cytokine profile: T-helper 1 (T_H1) subset and T-helper 2 (T_H2) subset. Protective immunity against HIV infection requires T_H1-directed CD4 T-cell responses, mediated by cytokines, such as interleukin-1β (IL-1β), IL-12, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). Cytokines released by the T_H1 subset of CD4 T-cells are considered important for mediating effective immune responses against intracellular pathogens such as Mycobacterium tuberculosis (M. tb). Oxidative stress and redox imbalance that occur during HIV infection often lead to inappropriate immune responses. Glutathione (GSH) is an antioxidant present in nearly all cells and is recognized for its function in maintaining redox homeostasis. Our laboratory previously reported that individuals with HIV infection have lower levels of GSH. In this study, we report a link between lower levels of GSH and dysregulation of T_H1- and T_H2-associated cytokines in the plasma samples of HIV-positive subjects. Furthermore, we demonstrate that supplementing individuals with HIV infection for 13 weeks with liposomal GSH (lGSH) resulted in a significant increase in the levels of T_H1 cytokines, IL-1β, IL-12, IFN-γ, and TNF-α. lGSH supplementation in individuals with HIV infection also resulted in a substantial decrease in the levels of free radicals and immunosuppressive cytokines, IL-10 and TGF-β, relative to those in a placebo-controlled cohort. Finally, we determined the effects of lGSH supplementation in improving the functions of immune cells to control M. tb infection by conducting in vitro assays using peripheral blood mononuclear cells collected from HIV-positive individuals at post-GSH supplementation. Our studies establish a correlation between low levels of GSH and increased susceptibility to M. tb infection through T_H2-directed response, which may be relieved with lGSH supplementation enhancing the T_H1 response.

Investigating the causes for decreased levels of glutathione in individuals with type II diabetes

Tuberculosis (TB) remains an eminent global burden with one third of the world’s population latently infected with Mycobacterium tuberculosis (M. tb). Individuals with compromised immune systems are especially vulnerable to M. tb infection. In fact, individuals with Type 2 Diabetes Mellitus (T2DM) are two to three times more susceptible to TB than those without T2DM. In this study, we report that individuals with T2DM have lower levels of glutathione (GSH) due to compromised levels of GSH synthesis and metabolism enzymes. Transforming growth factor beta (TGF-β), a cytokine that is known to decrease the expression of the catalytic subunit of glutamine-cysteine ligase (GCLC) was found in increased levels in the plasma samples from individuals with T2DM, explaining the possible underlying mechanism that is responsible for decreased levels of GSH in individuals with T2DM. Moreover, increased levels of pro-inflammatory cytokines such as interleukin-6 (IL-6) and interleukin-17 (IL-17) were observed in plasma samples isolated from individuals with T2DM. Increased levels of IL-6 and IL-17 was accompanied by enhanced production of free radicals further indicating an alternative mechanism for the decreased levels of GSH in individuals with T2DM. Augmenting the levels of GSH in macrophages isolated from individuals with T2DM resulted in improved control of M. tb infection. Furthermore, cytokines that are responsible for controlling M. tb infection at the cellular and granuloma level such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-2 (IL-2), interferon-gamma (IFN-γ), and interleukin-12 (IL-12), were found to be compromised in plasma samples isolated from individuals with T2DM. On the other hand, interleukin-10 (IL-10), an immunosuppressive cytokine was increased in plasma samples isolated from individuals with T2DM. Overall, these findings suggest that lower levels of GSH in individuals with T2DM lead to their increased susceptibility to M. tb infection.

Effect of High-Dose Cysteine Supplementation on Erythrocyte Glutathione: A Double-Blinded, Randomized Placebo-Controlled Pilot Study in Critically Ill Neonates

BACKGROUND

This study's objective was to determine if parenteral cysteine when compared with isonitrogenous noncysteine supplementation increases erythrocyte reduced glutathione (GSH) in neonates at high risk for inflammatory injury.

MATERIAL AND METHODS

Neonates with a score for neonatal acute physiology >10 requiring mechanical ventilation and parenteral nutrition (PN) were randomized in a double-blinded, placebo-controlled study to receive parenteral cysteine-HCl (CYS group) or additional PN amino acids (ISO group) at 121 mg/kg/d for ≥7 days. A 6-hour [(13)C2] glycine IV infusion was administered at study week 1 to determine the fractional synthetic rate of GSH (FSR-GSH).

RESULTS

Baseline characteristics were similar between the CYS (n = 17) and ISO groups (n = 21). Erythrocyte GSH and total glutathione concentrations, GSH:oxidized GSH (GSSG), and FSR-GSH after treatment were not different between groups. However, the CYS group had a larger individual positive change in GSH and total glutathione (infusion day - baseline) compared with the ISO group (P = .02 for each). After adjusting for treatment, a lower enrollment weight and rate of red blood cell transfusion were associated with a decreased change in total glutathione and GSH (P < .05 for each).

CONCLUSION

When compared with isonitrogenous noncysteine supplementation, high-dose cysteine supplementation for at least 1 week in critically ill neonates resulted in a larger and more positive individual change in GSH. Smaller infants and those who received transfused blood demonstrated less effective change in GSH with cysteine supplementation. The benefit of cysteine remains promising and deserves further investigation.

Randomized controlled trial of oral glutathione supplementation on body stores of glutathione

PURPOSE

Glutathione (GSH), the most abundant endogenous antioxidant, is a critical regulator of oxidative stress and immune function. While oral GSH has been shown to be bioavailable in laboratory animal models, its efficacy in humans has not been established. Our objective was to determine the long-term effectiveness of oral GSH supplementation on body stores of GSH in healthy adults.

METHODS

A 6-month randomized, double-blinded, placebo-controlled trial of oral GSH (250 or 1,000 mg/day) on GSH levels in blood, erythrocytes, plasma, lymphocytes and exfoliated buccal mucosal cells was conducted in 54 non-smoking adults. Secondary outcomes on a subset of subjects included a battery of immune markers.

RESULTS

GSH levels in blood increased after 1, 3 and 6 months versus baseline at both doses. At 6 months, mean GSH levels increased 30-35 % in erythrocytes, plasma and lymphocytes and 260 % in buccal cells in the high-dose group (P < 0.05). GSH levels increased 17 and 29 % in blood and erythrocytes, respectively, in the low-dose group (P < 0.05). In most cases, the increases were dose and time dependent, and levels returned to baseline after a 1-month washout period. A reduction in oxidative stress in both GSH dose groups was indicated by decreases in the oxidized to reduced glutathione ratio in whole blood after 6 months. Natural killer cytotoxicity increased >twofold in the high-dose group versus placebo (P < 0.05) at 3 months.

CONCLUSIONS

These findings show, for the first time, that daily consumption of GSH supplements was effective at increasing body compartment stores of GSH.

Glutathione synthesis is compromised in erythrocytes from individuals with HIV

We demonstrated that the levels of enzymes responsible for the synthesis of glutathione (GSH) such as glutathione synthase (GSS), glutamate-cysteine ligase-catalytic subunit (GCLC), and glutathione reductase (GSR) were significantly reduced in the red blood cells (RBCs) isolated from individuals with human immunodeficiency virus (HIV) infection and this reduction correlated with decreased levels of intracellular GSH. GSH content in RBCs can be used as a marker for increased overall oxidative stress and immune dysfunctions caused by HIV infection. Our data supports our hypothesis that compromised levels of GSH in HIV infected individuals’ is due to decreased levels of GSH-synthetic enzymes. The role of GSH in combating oxidative stress and improving the functions of immune cells in HIV patients’ indicates the benefit of an antioxidant supplement which can reduce the cellular damage and promote the functions of immune cells.

Deficient glutathione in the pathophysiology of mycotoxin-related illness

Evidence for the role of oxidative stress in the pathophysiology of mycotoxin-related illness is increasing. The glutathione antioxidant and detoxification systems play a major role in the antioxidant function of cells. Exposure to mycotoxins in humans requires the production of glutathione on an “as needed” basis. Research suggests that mycotoxins can decrease the formation of glutathione due to decreased gene expression of the enzymes needed to form glutathione. Mycotoxin-related compromise of glutathione production can result in an excess of oxidative stress that leads to tissue damage and systemic illness. The review discusses the mechanisms by which mycotoxin-related deficiency of glutathione may lead to both acute and chronic illnesses.

An elucidation of neutrophil functions against Mycobacterium tuberculosis infection

We characterized the functions of neutrophils in response to Mycobacterium tuberculosis (M. tb) infection, with particular reference to glutathione (GSH). We examined the effects of GSH in improving the ability of neutrophils to control intracellular M. tb infection. Our findings indicate that increasing the intracellular levels of GSH with a liposomal formulation of GSH (L-GSH) resulted in reduction in the levels of free radicals and increased acidification of M. tb containing phagosomes leading to the inhibition in the growth of M. tb. This inhibitory mechanism is dependent on the presence of TNF-α and IL-6. Our studies demonstrate a novel regulatory mechanism adapted by the neutrophils to control M. tb infection.