Role of cytokines and nitric oxide in the induction of tuberculostatic macrophage functions

Abstract

The aim of this study was to determine phenotypic differences when BCG invades macrophages. Bacilli prepared from the same BCG primary seed, but produced in different culture media, were analysed with respect to the ability to stimulate macrophages and the susceptibility to treatment with cytokines and nitric oxide (NO). Tumour necrosis factor (TNF) activity was assayed by measuring its cytotoxic activity on L-929 cells, interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) were assayed by enzyme-linked immunosorbent assay (ELISA), whereas NO levels were detected by Griess colorimetric reactions in the culture supernatant of macrophages incubated with IFN-gamma, TNF or NO and subsequently exposed to either BCG-I or BCG-S. We found that BCG-I and BCG-S bacilli showed different ability to simulate peritoneal macrophages. Similar levels of IL-6 were detected in stimulated macrophages with lysate from two BCG samples. The highest levels of TNF and IFN-gamma were observed in macrophages treated with BCG-S and BCG-I, respectively. The highest levels of NO were observed in cultures stimulated for 48 h with BCG-S. We also found a different susceptibility of the bacilli to exogenous treatment with IFN-gamma and TNF which were capable of killing 60 and 70% of both bacilli, whereas NO was capable of killing about 98 and 47% of BCG-I and BCG-S, respectively. The amount of bacilli proportionally decreased with IFN-gamma and TNF, suggesting a cytokine-related cytotoxic effect. Moreover, NO also decreased the viable number of bacilli. Interestingly, NO levels of peritoneal macrophages were significantly increased after cytokine treatment. This indicates that the treatment of macrophages with cytokines markedly reduced bacilli number and presented effects on NO production. The results obtained here emphasize the importance of adequate stimulation for guaranteeing efficient killing of bacilli. In this particular case, the IFN-gamma and TNF were involved in the activation of macrophage bactericidal activity.

Interleukin-10 inhibitsMycobacterium bovisbacillus Calmette–Guérin (BCG)-induced macrophage cytotoxicity against bladder cancer cells

“…These observations were consistent with previous observations that macrophages are capable of producing TNF-a and NO in response to BCG stimulation [6,[20][21][22][23][24][25], which were tumoricidal for human and murine bladder cancer cells [6,24,25,51,52]. TNF-a is known to act as an autocrine cytokine essential for macrophage activation and NO production [22,53,54], whereas NO is known to be required for macrophage activation and TNF-a production [53]. Thus, production of these two effector molecules provided a positive feedback loop for macrophage activation and cytotoxicity induction.…”

Role of Th1-stimulating cytokines in bacillus Calmette–Guérin (BCG)-induced macrophage cytotoxicity against mouse bladder cancer MBT-2 cells

“…They were also found to be cytotoxic toward MBT‐2 cells in this study. Both cytokines are also known to be a potent inducer of NO, a macrophage effector molecule [33,34]. IL‐6 may contribute to BCG‐induced PEC cytotoxicity through its influence on secretion of cytotoxic cytokines [35].…”

Murine cytokine responses following multiple oral immunizations using lipid‐formulated mycobacterial antigens

“…In contrast, IL‐4 production can signify a Th2 bias in the immune response to mycobacterial antigens signifying the onset of a non‐protective immune response 11 . TNF‐α is also an important cytokine with pluripotent roles, 14 in that the early presence of TNF‐α (along with IL‐12 and IFN‐γ) during an immune response is necessary for effective macrophage activation and pathogen control 15 whereas during mycobacterial infection, TNF‐α plays a pivotal role in modulating immunopathogenesis and tissue damage 16 . In the present study, we have identified that antigen‐induced IL‐2 and IFN‐γ (but not IL‐4) are components of the cytokine response following single or multiple oral immunizations with lipid‐formulated live BCG, and that while TNF‐α is produced by PPD‐stimulated murine cells, levels of this cytokine are not significantly elevated in mice that have received prior BCG oral priming.…”