L-GSH Supplementation in Conjunction With Rifampicin Augments the Treatment Response to Mycobacterium tuberculosis in a Diabetic Mouse Model

Development of a proliposomal pretomanid dry powder inhaler as a novel alternative approach for combating pulmonary tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) continue as public health concerns. Inhaled drug therapy for TB has substantial benefits in combating the causal agent of TB (Mycobacterium tuberculosis). Pretomanid is a promising candidate in an optional combined regimen for XDR-TB. Pretomanid has demonstrated high potency against M. tuberculosis in both the active and latent phases. Conventional spray drying was used to formulate pretomanid as dry powder inhalers (DPIs) for deep lung delivery using a proliposomal system with a trehalose coarse excipient to enhance the drug solubility. Co-spray drying with L-leucine protected hygroscopic trehalose in formulations and improved powder aerosolization. Higher amounts of L-leucine (40-50 % w/w) resulted in the formation of mesoporous particles with high percentages of drug content and entrapment efficiency. The aerosolized powders demonstrated both geometric and median aerodynamic diameters < 5 µm with > 90 % emitted dose and > 50 % fine particle fraction. Upon reconstitution in simulated physiological fluid, the proliposomes completely converted to liposomes, exhibiting suitable particle sizes (130-300 nm) with stable colloids and improving drug solubility, leading to higher drug dissolution compared to the drug alone. Inhalable pretomanid showed higher antimycobacterial activity than pretomanid alone. The formulations were safe for all broncho-epithelial cell lines and alveolar macrophages, thus indicating their potential suitability for DPIs targeting pulmonary TB.

Immune Responses to Mycobacterium tuberculosis Infection in the Liver of Diabetic Mice

Individuals with uncontrolled diabetes are highly susceptible to tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tb) infection. Novel treatments for TB are needed to address the increased antibiotic resistance and hepatoxicity. Previous studies showed that the administration of liposomal glutathione (L-GSH) can mitigate oxidative stress, bolster a granulomatous response, and diminish the M. tb burden in the lungs of M. tb-infected mice. Nonetheless, the impact of combining L-GSH with conventional TB treatment (RIF) on the cytokine levels and granuloma formation in the livers of diabetic mice remains unexplored. In this study, we evaluated hepatic cytokine profiles, GSH, and tissue pathologies in untreated and L-GSH, RIF, and L-GSH+RIF treated diabetic (db/db) M. tb-infected mice. Our results indicate that treatment of M. tb-infected db/db mice with L-GSH+RIF caused modulation in the levels of pro-inflammatory cytokines and GSH in the liver and mitigation in the granuloma size in hepatic tissue. Supplementation with L-GSH+RIF led to a decrease in the M. tb burden by mitigating oxidative stress, promoting the production of pro-inflammatory cytokines, and restoring the cytokine balance. These findings highlight the potential of L-GSH+RIF combination therapy for addressing active EPTB, offering valuable insights into innovative treatments for M. tb infections.

Liposomal Glutathione Augments Immune Defenses against Respiratory Syncytial Virus in Neonatal Mice Exposed in Utero to Ethanol

We previously reported that maternal alcohol use increased the risk of sepsis in premature and term newborns. In the neonatal mouse, fetal ethanol (ETOH) exposure depleted the antioxidant glutathione (GSH), which promoted alveolar macrophage (AM) immunosuppression and respiratory syncytial virus (RSV) infections. In this study, we explored if oral liposomal GSH (LGSH) would attenuate oxidant stress and RSV infections in the ETOH-exposed mouse pups. C57BL/6 female mice were pair-fed a liquid diet with 25% of calories from ethanol or maltose-dextrin. Postnatal day 10 pups were randomized to intranasal saline, LGSH, and RSV. After 48 h, we assessed oxidant stress, AM immunosuppression, pulmonary RSV burden, and acute lung injury. Fetal ETOH exposure increased oxidant stress threefold, lung RSV burden twofold and acute lung injury threefold. AMs were immunosuppressed with decreased RSV clearance. However, LGSH treatments of the ETOH group normalized oxidant stress, AM immune phenotype, the RSV burden, and acute lung injury. These studies suggest that the oxidant stress caused by fetal ETOH exposure impaired AM clearance of infectious agents, thereby increasing the viral infection and acute lung injury. LGSH treatments reversed the oxidative stress and restored AM immune functions, which decreased the RSV infection and subsequent acute lung injury.

Host-directed therapy against mycobacterium tuberculosis infections with diabetes mellitus

Tuberculosis (TB) is caused by the bacterial pathogen Mycobacterium tuberculosis (MTB) and is one of the principal reasons for mortality and morbidity worldwide. Currently, recommended anti-tuberculosis drugs include isoniazid, rifampicin, ethambutol, and pyrazinamide. TB treatment is lengthy and inflicted with severe side-effects, including reduced patient compliance with treatment and promotion of drug-resistant strains. TB is also prone to other concomitant diseases such as diabetes and HIV. These drug-resistant and complex co-morbid characteristics increase the complexity of treating MTB. Host-directed therapy (HDT), which effectively eliminates MTB and minimizes inflammatory tissue damage, primarily by targeting the immune system, is currently an attractive complementary approach. The drugs used for HDT are repositioned drugs in actual clinical practice with relative safety and efficacy assurance. HDT is a potentially effective therapeutic intervention for the treatment of MTB and diabetic MTB, and can compensate for the shortcomings of current TB therapies, including the reduction of drug resistance and modulation of immune response. Here, we summarize the state-of-the-art roles and mechanisms of HDT in immune modulation and treatment of MTB, with a special focus on the role of HDT in diabetic MTB, to emphasize the potential of HDT in controlling MTB infection.

Role of Oxidative Stress in Tuberculosis Meningitis Infection in Diabetics

Tuberculosis meningitis (TBM) is a result of the invasion of the meninges with the bacilli of Mycobacterium tuberculosis (Mtb), leading to inflammation of the meninges around the brain or spinal cord. Oxidative stress occurs when the body's cells become overwhelmed with free radicals, particularly reactive oxygen species (ROS). ROS plays a significant role in the pathogenesis of TBM due to their toxic nature, resulting in impairment of the body's ability to fight off infection. ROS damages the endothelial cells and impairs the defense mechanisms of the blood-brain barrier (BBB), which contributes to CNS susceptibility to the bacteria causing TBM. Diabetes mellitus (DM) is a common condition that is characterized by the impairment of the hormone insulin, which is responsible for modulating blood glucose levels. The increased availability of glucose in individuals with diabetes results in increased cellular activity and metabolism, leading to heightened ROS production and, in turn, increased susceptibility to TBM. In this review, we summarize our current understanding of oxidative stress and its role in both TBM and DM. We further discuss how increased oxidative stress in DM can contribute to the likelihood of developing TBM and potential therapeutic approaches that may be of therapeutic value.

Topical Absorption of Glutathione-Cyclodextrin Nanoparticle Complex in Healthy Human Subjects Improves Immune Response against Mycobacterium avium Infection

Glutathione (GSH) is an important intracellular antioxidant responsible for neutralizing reactive oxygen species (ROS). Our laboratory previously demonstrated that the oral administration of liposomal GSH improves immune function against mycobacterium infections in healthy patients along with patients with HIV and Type 2 diabetes. We aim to determine if the topical application of a glutathione-cyclodextrin nanoparticle complex (GSH-CD) confers a therapeutic effect against mycobacterium infections. In our study, healthy participants received either topical GSH-CD (n = 15) or placebo (n = 15) treatment. Subjects were sprayed four times twice a day for three days topically on the abdomen. Blood draws were collected prior to application, and at 1, 4, and 72 h post-initial topical application. GSH, malondialdehyde (MDA), and cytokine levels were assessed in the processed blood samples of study participants. Additionally, whole blood cultures from study participants were challenged with Mycobacterium avium (M. avium) infection in vitro to assess mycobacterium survival post-treatment. Topical GSH-CD treatment was observed to elevate GSH levels in peripheral blood mononuclear cells (PBMCs) and red blood cells and decrease MDA levels in PBMCs 72 h post-treatment. An increase in plasma IL-2, IFN-γ, IL-12p70, and TNF-α was observed at 72 h post-topical GSH-CD treatment. Enhanced mycobacterium clearance was observed at 4 h and 72 h post-topical GSH-CD treatment. Overall, topical GSH-CD treatment was associated with improved immune function against M. avium infection. The findings of this pilot study suggest GSH-cyclodextrin complex formulation can be used topically as a safe alternative mode of GSH delivery in the peripheral blood.

Glutathione Modulates Efficacious Changes in the Immune Response against Tuberculosis

Glutathione (GSH) is an antioxidant in human cells that is utilized to prevent damage occurred by reactive oxygen species, free radicals, peroxides, lipid peroxides, and heavy metals. Due to its immunological role in tuberculosis (TB), GSH is hypothesized to play an important part in the immune response against M. tb infection. In fact, one of the hallmark structures of TB is granuloma formation, which involves many types of immune cells. T cells, specifically, are a major component and are involved in the release of cytokines and activation of macrophages. GSH also serves an important function in macrophages, natural killer cells, and T cells in modulating their activation, their metabolism, proper cytokine release, proper redox activity, and free radical levels. For patients with increased susceptibility, such as those with HIV and type 2 diabetes, the demand for higher GSH levels is increased. GSH acts as an important immunomodulatory antioxidant by stabilizing redox activity, shifting of cytokine profile toward Th1 type response, and enhancing T lymphocytes. This review compiles reports showing the benefits of GSH in improving the immune responses against M. tb infection and the use of GSH as an adjunctive therapy for TB.

Inhibition of indoleamine dioxygenase leads to better control of tuberculosis adjunctive to chemotherapy

The expression of indoleamine 2,3-dioxygenase (IDO), a robust immunosuppressant, is significantly induced in macaque tuberculosis (TB) granulomas, where it is expressed on IFN-responsive macrophages and myeloid-derived suppressor cells. IDO expression is also highly induced in human TB granulomas, and products of its activity are detected in patients with TB. In vivo blockade of IDO activity resulted in the reorganization of the granuloma with substantially greater T cells being recruited to the core of the lesions. This correlated with better immune control of TB and reduced lung M. tuberculosis burdens. To study if the IDO blockade strategy can be translated to a bona fide host-directed therapy in the clinical setting of TB, we studied the effect of IDO inhibitor 1-methyl-d-tryptophan adjunctive to suboptimal anti-TB chemotherapy. While two-thirds of controls and one-third of chemotherapy-treated animals progressed to active TB, inhibition of IDO adjunctive to the same therapy protected macaques from TB, as measured by clinical, radiological, and microbiological attributes. Although chemotherapy improved proliferative T cell responses, adjunctive inhibition of IDO further enhanced the recruitment of effector T cells to the lung. These results strongly suggest the possibility that IDO inhibition can be attempted adjunctive to anti-TB chemotherapy in clinical trials.

Differential Role of Type 2 Diabetes as a Risk Factor for Tuberculosis in the Elderly versus Younger Adults

The elderly are understudied despite their high risk of tuberculosis (TB). We sought to identify factors underlying the lack of an association between TB and type 2 diabetes (T2D) in the elderly, but not adults. We conducted a case-control study in elderly (≥65 years old; ELD) vs. younger adults (young/middle-aged adults (18-44/45-64 years old; YA|MAA) stratified by TB and T2D, using a research study population (n = 1160) and TB surveillance data (n = 8783). In the research study population the adjusted odds ratio (AOR) of TB in T2D was highest in young adults (AOR 6.48) but waned with age becoming non-significant in the elderly. Findings were validated using TB surveillance data. T2D in the elderly (vs. T2D in younger individuals) was characterized by better glucose control (e.g., lower hyperglycemia or HbA1c), lower insulin resistance, more sulphonylureas use, and features of less inflammation (e.g., lower obesity, neutrophils, platelets, anti-inflammatory use). We posit that differences underlying glucose dysregulation and inflammation in elderly vs. younger adults with T2D, contribute to their differential association with TB. Studies in the elderly provide valuable insights into TB-T2D pathogenesis, e.g., here we identified insulin resistance as a novel candidate mechanism by which T2D may increase active TB risk.