Peripheral DNA damage in active pulmonary tuberculosis

Functional Polymorphism in the NFE2L2 Gene Associated With Tuberculosis Susceptibility

Background

Nuclear transcription factor erythroid 2 p45-related factor 2 (Nrf2), encoded by NFE2L2, functions as a key transcription factor and regulates expression of antioxidant genes. Our study aimed to investigate the association of single nucleotide polymorphisms of NFE2L2 with tuberculosis (TB) and latent tuberculosis infection (LTBI) and the underlying causal mechanisms.

Methods

1950 unrelated Chinese Han participants were included in our two independent study groups. Five tag polymorphisms were selected and genotyped. The functional effects of the rs13005431 polymorphism were confirmed by dual-luciferase reporter assays and mRNA level comparisons.

Results

Rs13005431_C and rs2364723_G were associated with increased TB susceptibility (P = 0.010 and P = 0.041) after adjustment for confounding factors. rs6726395_A was associated with increased risk of active TB (P=0.035) in a comparison with the LTBI group. The frequency of haplotype rs1049751- rs13005431 AC was higher in the TB group (P =0.013), while frequency of haplotype AT was higher in the healthy control group (P =0.025). The luciferase activity of a plasmid with the rs13005431C-promoter was significantly lower than that of the rs13005431T-promoter. In addition, neutrophils with the CC/TC genotypes which were activated by GM-CSF showed a decreased level of NFE2L2 mRNA when compared with the rs13005431 TT genotype.

Conclusions

Our study suggests that allele C of rs13005431 might increase the susceptibility to TB by down-regulating the transcriptional activity of NFE2L2.

Total oxidant and antioxidant status and paraoxonase 1 levels of children with noncystic fibrosis bronchiectasis

Background/aim

To evaluate total oxidant status (TOS), total antioxidant capacity (TAC), and paraoxonase 1 (PON1) levels in children with noncystic fibrosis (CF) bronchiectasis (BE), and to compare these levels with those of healthy controls. The study parameters were also evaluated according to some demographic, anthropometric, and clinical characteristics, as well as lung functions.

Materials and methods

Enrolled in the study were 118 children with non-CF BE and 68 healthy controls. Serum TOS, TAC, and PON1 levels were determined. Lung function tests were performed by spirometry.

Results

Serum TOS was higher in the patients [median 9.54 (IQR 25–75 = 7.05–13.30) μmol H2O2 Eq/L] than in the healthy subjects [6.64 (5.45–9.53) μmol H2O2 Eq/L] (P < 0.001). TAC was higher in patients with non-CF BE [1.07 (1.0–1.07) mmol Trolox Eq/L] than in the healthy controls [0.87 (0.77–0.98) mmol Trolox Eq/L] (P < 0.001). In addition, serum PON1 levels were significantly higher in the patients [106.5 (42.5–154.2) U/L] than in the controls [47.7 (27.5–82.1) U/L] (P < 0.001). The patients with low FEV1 had decreased TAC when compared to those who had normal FEV1 in non-CF BE.

Conclusion

The present study demonstrated that compared with the control group the children with non-CF BE had elevated oxidative status, antioxidant defenses parameters, and PON1 values.

Mycobacterium tuberculosis promotes genomic instability in macrophages

BACKGROUND

Mycobacterium tuberculosis is an intracellular pathogen, which may either block cellular defensive mechanisms and survive inside the host cell or induce cell death. Several studies are still exploring the mechanisms involved in these processes.

OBJECTIVES

To evaluate the genomic instability of M. tuberculosis-infected macrophages and compare it with that of uninfected macrophages.

METHODS

We analysed the possible variations in the genomic instability of Mycobacterium-infected macrophages using the DNA breakage detection fluorescence in situ hybridisation (DBD-FISH) technique with a whole human genome DNA probe.

FINDINGS

Quantitative image analyses showed a significant increase in DNA damage in infected macrophages as compared with uninfected cells. DNA breaks were localised in nuclear membrane blebs, as confirmed with DNA fragmentation assay. Furthermore, a significant increase in micronuclei and nuclear abnormalities were observed in infected macrophages versus uninfected cells.

MAIN CONCLUSIONS

Genomic instability occurs during mycobacterial infection and these data may be seminal for future research on host cell DNA damage in M. tuberculosis infection.

Mycobacterium tuberculosis Induction of Heme Oxygenase-1 Expression Is Dependent on Oxidative Stress and Reflects Treatment Outcomes

The antioxidant enzyme heme oxygenase-1 (HO-1) is implicated in the pathogenesis of tuberculosis (TB) and has been proposed as a biomarker of active disease. Nevertheless, the mechanisms by which Mycobacterium tuberculosis (Mtb) induces HO-1 as well as how its expression is affected by HIV-1 coinfection and successful antitubercular therapy (ATT) are poorly understood. We found that HO-1 expression is markedly increased in rabbits, mice, and non-human primates during experimental Mtb infection and gradually decreased during ATT. In addition, we examined circulating concentrations of HO-1 in a cohort of 130 HIV-1 coinfected and uninfected pulmonary TB patients undergoing ATT to investigate changes in expression of this biomarker in relation to HIV-1 status, radiological disease severity, and treatment outcome. We found that plasma levels of HO-1 were elevated in untreated HIV-1 coinfected TB patients and correlated positively with HIV-1 viral load and negatively with CD4⁺ T cell count. In both HIV-1 coinfected and Mtb monoinfected patients, HO-1 levels were substantially reduced during successful TB treatment but not in those who experienced treatment failure or subsequently relapsed. To further delineate the molecular mechanisms involved in induction of HO-1 by Mtb, we performed a series of in vitro experiments using mouse and human macrophages. We found that Mtb-induced HO-1 expression requires NADPH oxidase-dependent reactive oxygen species production induced by the early-secreted antigen ESAT-6, which in turn triggers nuclear translocation of the transcription factor NRF-2. These observations provide further insight into the utility of HO-1 as a biomarker of both disease and successful therapy in TB monoinfected and HIV-TB coinfected patients and reveal a previously undocumented pathway linking expression of the enzyme with oxidative stress.

Role of mitochondrial oxidative stress on lymphocyte homeostasis in patients diagnosed with extra-pulmonary tuberculosis

Extra-pulmonary tuberculosis is often an underrated illness. Recent clinical studies have pointed out that lymphocyte homeostasis is dramatically disturbed as revealed through a series of signs and symptoms. Lymphocytes, the known effector cells of our immune system, play an important role in providing immunologic resistance against Mycobacterium infection. It is important to have quantitative insights into the lifespan of these cells; therefore, we aimed to study the precise effect of gastrointestinal tuberculosis infection on peripheral blood lymphocyte subpopulations and function. Our results indicated that gastrointestinal tuberculosis could increase mitochondrial oxidative stress, lower mitochondrial DNA copy number, promote nuclear DNA damage and repair response, decrease mitochondrial respiratory chain enzyme activities, and upregulate Bcl-2 and caspase-3 gene expression in lymphocytes. We further revealed that Mycobacterium infection induces autophagy for selective sequestration and subsequent degradation of the dysfunctional mitochondrion before activating cellular apoptosis in the peripheral lymphocyte pool. Together, these observations uncover a new role of mitochondrial-nuclear crosstalk that apparently contributes to lymphocyte homeostasis in gastrointestinal tuberculosis infection.

Analysis of Toll-like receptors, iNOS and cytokine profiles in patients with pulmonary tuberculosis during anti-tuberculosis treatment

Toll-like receptors (TLRs) play an important role in mycobacterial infection, although little is known about the roles of these receptors, cytokines and nitric oxide during anti-tuberculosis treatment. Our objective was to evaluate the mRNA and cell surface expression of TLR2 and TLR4; inducible nitric oxide synthase (iNOS) expression; and cytokine Th1, Th2 and Th17 profiles in pulmonary tuberculosis patients at different time points of anti-tuberculosis treatment. Peripheral blood mononuclear cells (PBMCs) were obtained from PPD⁺ healthy controls and from patients receiving anti-tuberculosis treatment. Gene expression quantification was performed by qPCR, cell surface expression was assessed using flow cytometry, and cytokine quantification was conducted using the CBA technique. The treated patients presented higher gene expression and higher numbers of receptors on the cell surface of lymphocytes and monocytes than did control individuals. IL-12 and IFN-γ levels increased after the start of treatment, whereas TNF-α levels were reduced. TGF-β presented the highest levels during treatment. IL-10 and IL-17 expression and production tended to increase during treatment. iNOS gene expression was reduced throughout treatment in patients. Our results suggest that anti-tuberculosis treatment modulates the immune response, inducing an increase in the expression of TLRs and pro- and anti-inflammatory cytokines to combat bacteria and reduce the inflammatory process.