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

Abstract

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.

Cyclic Peptide [R4W4] in Improving the Ability of First-Line Antibiotics to Inhibit Mycobacterium tuberculosis Inside in vitro Human Granulomas

“…There was a 2.5-fold increase in IFN-γ production in the supernatants from in vitro granulomas treated with 4 µg/ml concentration of [R 4 W 4 ] (p = 0.0161) compared to sham control ( Figure 2D). In our previously published study (18), we demonstrated that IFN-γ increase was associated with enhanced phagosome acidification and improved killing of M. tb in the in vitro granulomas. Therefore, higher amounts of the IFNγ release may therefore serve as an additional effector mechanism by which in vitro granulomas treated with 4 µg/ml of [R 4 W 4 ] control M. tb infection.…”

“…In comparison to the untreated granulomas, the fold reduction in the levels of TNF-α was 2 and 3.3 for granulomas treated with [R 4 W 4 ] at 4 and 8 µg/ml, respectively. TNF-α, a pro-inflammatory cytokine, activates the effector immune functions and causes recruitment of immune cells to form a solid and stable granuloma to contain M. tb infection (14)(15)(16)(17)(18). Excess TNF-α can cause cell death by necrosis, leading to inflammation (19,20).…”

“…Although the combination of INH + [R 4 W 4 ] did not increase the expression of LC3B when compared to treatment with INH alone, INH + [R 4 W 4 ] treatment downregulated the intensity of CellROX staining and diminished the production of TNF-α and IL-10. Although TNF-α plays a central role in the formation and maintenance of granulomas, overexpression of TNF-α has also been linked to many inflammatory and autoimmune diseases (14)(15)(16)(17)(18)(19)(20). IL-10, an immunosuppressive cytokine, can 05 is not considered significant, one symbol (*, #, or $) denotes significant difference below 0.05, two symbols (**, ##, or $$) denote significant difference below 0.005, three symbols (***, ###, or $$$) denote significant difference below 0.0005, and four symbols (****, ####, or $$$$) denote significant difference below 0.0001.…”

Therapeutic host-directed strategies to improve outcome in tuberculosis

“…This occurs by suppressing the host oxidative response, along with direct anti-mycobacterial affects. 40,41 Therefore, beneficial effects of NAC as HDT is not limited to use in symptomatic TB disease and post-TB lung disease, but also to clear Mtb in healthy latently infected individuals. NAC has subsequently been tested in a prospective randomized control trial, demonstrating significantly faster sputum conversion with improved lung pathology in TB patients receiving daily NAC treatment during the intensive phase of DOTS.…”

The effects of anti-inflammatory agents as host-directed adjunct treatment of tuberculosis in humans: a systematic review and meta-analysis

“…Recombinant human interleukin, used as HDT, also enhances both the bacterial clearance and immune response when administered twice daily for 30 days [25]. N-acetylcysteine, another HDT molecule, effectively increases glutathione (GSH), which is usually low in TB patients due to oxidative stress [26,27]. Increased levels of GSH have been demonstrated to play a positive role in phagocytosis, T-cell activation responses and balancing in TB [28].…”