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.

Characterization of dendritic cell and regulatory T cell functions against Mycobacterium tuberculosis infection.

Glutathione (GSH) is a tripeptide that regulates intracellular redox and other vital aspects of cellular functions. GSH plays a major role in enhancing the immune system. Dendritic cells (DCs) are potent antigen presenting cells that participate in both innate and acquired immune responses against microbial infections. Regulatory T cells (Tregs) play a significant role in immune homeostasis. In this study, we investigated the effects of GSH in enhancing the innate and adaptive immune functions of DCs against Mycobacterium tuberculosis (M. tb) infection. We also characterized the functions of the sub-populations of CD4+T cells such as Tregs and non-Tregs in modulating the ability of monocytes to control the intracellular M. tb infection. Our results indicate that GSH by its direct antimycobacterial activity inhibits the growth of intracellular M. tb inside DCs. GSH also increases the expressions of costimulatory molecules such as HLA-DR, CD80 and CD86 on the cell surface of DCs. Furthermore, GSH-enhanced DCs induced a higher level of T-cell proliferation. We also observed that enhancing the levels of GSH in Tregs resulted in downregulation in the levels of IL-10 and TGF- ß and reduction in the fold growth of M. tb inside monocytes. Our studies demonstrate novel regulatory mechanisms that favor both innate and adaptive control of M. tb infection.

Glutathione supplementation improves macrophage functions in HIV.

In this study, we determined the effects of glutathione (GSH)-enhancing agents in restoring the levels of GSH in isolated macrophages from individuals with HIV infection thereby resulting in improved control of Mycobacterium tuberculosis. Our results indicate that treatment with N-acetyl cysteine or a liposomal formulation of glutathione (lGSH) resulted in replenishment of reduced also known as free GSH (rGSH), and correlated with a decrease in the intracellular growth of M. tuberculosis. Finally, we observed differences in the amount of the catalytic subunit of glutamine-cysteine ligase (GCLC), glutathione synthase, and glutathione reductase present in macrophages derived from healthy and HIV-infected individuals. These changes correlated with changes in free radicals as well as rGSH levels. Our results indicate that HIV infection leads to increased production of free radicals and decreased production of GCLC resulting in depletion of rGSH and this may lead, in part, to the loss of innate immune function observed in HIV patients. These findings represent a novel mechanism for control of M. tuberculosis infection, and a possible supplement to current HIV treatments.

Glutathione and infection.

BACKGROUND: The tripeptide γ-glutamylcysteinylglycine or glutathione (GSH) has demonstrated protective abilities against the detrimental effects of oxidative stress within the human body, as well as protection against infection by exogenous microbial organisms. SCOPE OF REVIEW: In this review we describe how GSH works to modulate the behavior of many cells including the cells of the immune system, augmenting the innate and the adaptive immunity as well as conferring protection against microbial, viral and parasitic infections. This article unveils the direct antimicrobial effects of GSH in controlling Mycobacterium tuberculosis (M. tb) infection within macrophages. In addition, we summarize the effects of GSH in enhancing the functional activity of various immune cells such as natural killer (NK) cells and T cells resulting in inhibition in the growth of M. tb inside monocytes and macrophages. Most importantly we correlate the decreased GSH levels previously observed in individuals with pulmonary tuberculosis (TB) with an increase in the levels of pro-inflammatory cytokines which aid in the growth of M. tb. MAJOR CONCLUSIONS: In conclusion, this review provides detailed information on the protective integral effects of GSH along with its therapeutic effects as they relate to the human immune system and health. GENERAL SIGNIFICANCE: It is important to note that the increases in the levels of pro-inflammatory cytokines are not only detrimental to the host due to the sequel that follow such as fever and cachexia, but also due to the alteration in the functions of immune cells. The additional protective effects of GSH are evident after sequel that follows the depletion of this antioxidant. This is evident in a condition such as Cystic Fibrosis (CF) where an increased oxidant burden inhibits the clearance of the affecting organism and results in oxidant-induced anti-protease inhibition. GSH has a similar protective effect in protozoans as it does in human cells. Thus GSH is integral to the survival of some of the protozoans because some protozoans utilize the compound trypanothione [T(SH)2] as their main antioxidant. T(SH)2 in turn requires GSH for its production. Hence a decrease in the levels of GSH (by a known inhibitor such as buthionine sulfoximine [BSO] can have adverse effects of the protozoan parasites. This article is part of a Special Issue entitled Cellular functions of glutathione.

Unveiling the mechanisms for decreased glutathione in individuals with HIV infection.

We examined the causes for decreased glutathione (GSH) in individuals with HIV infection. We observed lower levels of intracellular GSH in macrophages from individuals with HIV compared to healthy subjects. Further, the GSH composition found in macrophages from HIV(+) subjects heavily favors oxidized glutathione (GSSG) which lacks antioxidant activity, over free GSH which is responsible for GSH's antioxidant activity. This decrease correlated with an increase in the growth of Mycobacterium tuberculosis (M. tb) in macrophages from HIV(+) individuals. In addition, we observed increased levels of free radicals, interleukin-1 (IL-1), interleukin-17 (IL-17) and transforming growth factor-ß (TGF-ß) in plasma samples derived from HIV(+) individuals compared to healthy subjects. We observed decreased expression of the genes coding for enzymes responsible for de novo synthesis of GSH in macrophages derived from HIV(+) subjects using quantitative PCR (qPCR). Our results indicate that overproduction of proinflammatory cytokines in HIV(+) individuals lead to increased production of free radicals. This combined with the decreased expression of GSH synthesis enzymes leads to a depletion of free GSH and may lead in part to the loss of immune function observed in HIV patients.