# Glutathione Depletion Exacerbates Hepatic Mycobacterium tuberculosis Infection

## TL;DR

Low levels of glutathione in the liver and spleen worsen tuberculosis infections in mice, suggesting antioxidants may help treat the disease.

## Contribution

This study reveals that glutathione depletion impairs immune responses and increases Mycobacterium tuberculosis burden in the liver and spleen.

## Key findings

- DEM-induced GSH depletion increased M.tb burden and oxidative stress in the liver and spleen of mice.
- Reduced GSH levels were linked to altered cytokine profiles and disorganized lymphocyte infiltrates in hepatic tissues.
- Glutathione depletion impaired granuloma formation and worsened EPTB in mice.

## Abstract

Extrapulmonary tuberculosis (EPTB) makes up 17% of all tuberculosis cases worldwide. Immunocompromised patients, such as those with HIV or type 2 diabetes, are more likely to obtain EPTB. Studies show that these individuals often have lower levels of glutathione (GSH), a key antioxidant. In experiments with mice, depleting GSH in the lungs led to more severe tuberculosis infections. This study examined how GSH depletion affects tuberculosis in the liver and spleen. Mice with diminished GSH levels had higher levels of oxidative stress, inflammation, and M.tb burden in the liver and spleen. These findings highlight the important role of GSH in modulating the granulomatous response against EPTB.

Extrapulmonary tuberculosis (EPTB) accounts for approximately 17% of all Mycobacterium tuberculosis (M.tb) infections globally. Immunocompromised individuals, such as those with HIV infection or type 2 diabetes mellitus (T2DM), are at an increased risk for EPTB. Previous studies have demonstrated that patients with HIV and T2DM exhibit diminished synthesis of glutathione (GSH) synthesizing enzymes. In a murine model, we showed that the diethyl maleate (DEM)-induced depletion of GSH in the lungs led to increased M.tb burden and an impaired pulmonary granulomatous response to M.tb infection. However, the effects of GSH depletion during active EPTB in the liver and spleen have yet to be elucidated. In this study, we evaluated hepatic GSH and malondialdehyde (MDA) levels, as well as cytokine profiles, in untreated and DEM-treated M.tb-infected wild-type (WT) C57BL/6 mice. Additionally, we assessed hepatic and splenic M.tb burdens and tissue pathologies. DEM treatment resulted in a significant decrease in the levels of the reduced form of GSH and an increase in MDA, oxidized GSH, and interleukin (IL)-6 levels. Furthermore, DEM-induced GSH decrease was associated with decreased production of IL-12 and IL-17 and elevated production of interferon-gamma (IFN-γ), tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β. A significant increase in M.tb growth was detected in the liver and spleen in DEM-treated M.tb-infected mice. Large, disorganized lymphocyte infiltrates were detected in the hepatic tissues of DEM-treated mice. Overall, GSH diminishment impaired the granulomatous response to M.tb in the liver and exacerbated M.tb growth in both the liver and spleen. These findings provide critical insights into the immunomodulatory role of GSH in TB pathogenesis and suggest potential therapeutic avenues for the treatment of extrapulmonary M.tb infections.