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Activated T cells differentiate into functional subsets with distinct metabolic programs. Glutaminase (GLS) converts glutamine to glutamate to support the tricarboxylic acid cycle and redox and epigenetic reactions. Here, we identify a key role for GLS in T cell activation and specification. Though GLS deficiency diminished initial T cell activation and proliferation and impaired differentiation of Th17 cells, loss of GLS also increased Tbet to promote differentiation and effector function of CD4 Th1 and CD8 CTL cells. This was associated with altered chromatin accessibility and gene expression, including decreased PIK3IP1 in Th1 cells that sensitized to IL-2-mediated mTORC1 signaling. In vivo, GLS null T cells failed to drive Th17-inflammatory diseases, and Th1 cells had initially elevated function but exhausted over time. Transient GLS inhibition, however, led to increased Th1 and CTL T cell numbers. Glutamine metabolism thus has distinct roles to promote Th17 but constrain Th1 and CTL effector cell differentiation.
Copyright © 2018 Elsevier Inc. All rights reserved.
Histological chorioamnionitis (HCA) is an intrauterine inflammatory condition that increases the risk for preterm birth, death, and disability because of persistent systemic and localized inflammation. The immunological mechanisms sustaining this response in the preterm newborn remain unclear. We sought to determine the consequences of HCA exposure on the fetal CD4 T lymphocyte exometabolome. We cultured naive CD4 T lymphocytes from HCA-positive and -negative preterm infants matched for gestational age, sex, race, prenatal steroid exposure, and delivery mode. We collected conditioned media samples before and after a 6-h in vitro activation of naive CD4 T lymphocytes with soluble staphylococcal enterotoxin B and anti-CD28. We analyzed samples by ultraperformance liquid chromatography ion mobility-mass spectrometry. We determined the impact of HCA on the CD4 T lymphocyte exometabolome and identified potential biomarker metabolites by multivariate statistical analyses. We discovered that: 1) CD4 T lymphocytes exposed to HCA exhibit divergent exometabolomic profiles in both naive and activated states; 2) ∼30% of detected metabolites differentially expressed in response to activation were unique to HCA-positive CD4 T lymphocytes; 3) metabolic pathways associated with glutathione detoxification and tryptophan degradation were altered in HCA-positive CD4 T lymphocytes; and 4) flow cytometry and cytokine analyses suggested a bias toward a T1-biased immune response in HCA-positive samples. HCA exposure primes the neonatal adaptive immune processes by inducing changes to the exometabolomic profile of fetal CD4 T lymphocytes. These exometabolomic changes may link HCA exposure to T1 polarization of the neonatal adaptive immune response.
Copyright © 2017 by The American Association of Immunologists, Inc.
We reported that arginase 2 (ARG2) deletion results in increased gastritis and decreased bacterial burden during Helicobacter pylori infection in mice. Our studies implicated a potential role for inducible nitric oxide (NO) synthase (NOS2), as Arg2 (-/-) mice exhibited increased NOS2 levels in gastric macrophages, and NO can kill H. pylori. We now bred Arg2 (-/-) to Nos2 (-/-) mice, and infected them with H. pylori. Compared to wild-type mice, both Arg2 (-/-) and Arg2 (-/-) ;Nos2 (-/-) mice exhibited increased gastritis and decreased colonization, the latter indicating that the effect of ARG2 deletion on bacterial burden was not mediated by NO. While Arg2 (-/-) mice demonstrated enhanced M1 macrophage activation, Nos2 (-/-) and Arg2 (-/-) ;Nos2 (-/-) mice did not demonstrate these changes, but exhibited increased CXCL1 and CXCL2 responses. There was an increased expression of the Th1/Th17 cytokines, interferon gamma and interleukin 17, in gastric tissues and splenic T-cells from Arg2 (-/-), but not Nos2 (-/-) or Arg2 (-/-) ;Nos2 (-/-) mice. Gastric tissues from infected Arg2 (-/-) mice demonstrated increased expression of arginase 1, ornithine decarboxylase, adenosylmethionine decarboxylase 1, spermidine/spermine N (1)-acetyltransferase 1, and spermine oxidase, along with increased spermine levels. These data indicate that ARG2 deletion results in compensatory upregulation of gastric polyamine synthesis and catabolism during H. pylori infection, which may contribute to increased gastric inflammation and associated decreased bacterial load. Overall, the finding of this study is that ARG2 contributes to the immune evasion of H. pylori by restricting M1 macrophage activation and polyamine metabolism.
Mycobacterium tuberculosis, the causative agent of tuberculosis, is an ancient pathogen and a major cause of death worldwide. Although various virulence factors of M. tuberculosis have been identified, its pathogenesis remains incompletely understood. TlyA is a virulence factor in several bacterial infections and is evolutionarily conserved in many Gram-positive bacteria, but its function in M. tuberculosis pathogenesis has not been elucidated. Here, we report that TlyA significantly contributes to the pathogenesis of M. tuberculosis. We show that a TlyA mutant M. tuberculosis strain induces increased IL-12 and reduced IL-1β and IL-10 cytokine responses, which sharply contrasts with the immune responses induced by wild type M. tuberculosis. Furthermore, compared with wild type M. tuberculosis, TlyA-deficient M. tuberculosis bacteria are more susceptible to autophagy in macrophages. Consequently, animals infected with the TlyA mutant M. tuberculosis organisms exhibited increased host-protective immune responses, reduced bacillary load, and increased survival compared with animals infected with wild type M. tuberculosis. Thus, M. tuberculosis employs TlyA as a host evasion factor, thereby contributing to its virulence.
© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
Long noncoding RNAs (lncRNAs), critical regulators of protein-coding genes, are likely to be coexpressed with neighboring protein-coding genes in the genome. How the genome integrates signals to achieve coexpression of lncRNA genes and neighboring protein-coding genes is not well understood. The lncRNA Tmevpg1 (NeST, Ifng-AS1) is critical for Th1-lineage-specific expression of Ifng and is coexpressed with Ifng. In this study, we show that T-bet guides epigenetic remodeling of Tmevpg1 proximal and distal enhancers, leading to recruitment of stimulus-inducible transcription factors, NF-κB and Ets-1, to the locus. Activities of Tmevpg1-specific enhancers and Tmevpg1 transcription are dependent upon NF-κB. Thus, we propose that T-bet stimulates epigenetic remodeling of Tmevpg1-specific enhancers and Ifng-specific enhancers to achieve Th1-lineage-specific expression of Ifng.
Copyright © 2014 by The American Association of Immunologists, Inc.
Helicobacter pylori incites a futile inflammatory response, which is the key feature of its immunopathogenesis. This leads to the ability of this bacterial pathogen to survive in the stomach and cause peptic ulcers and gastric cancer. Myeloid cells recruited to the gastric mucosa during H. pylori infection have been directly implicated in the modulation of host defense against the bacterium and gastric inflammation. Heme oxygenase-1 (HO-1) is an inducible enzyme that exhibits anti-inflammatory functions. Our aim was to analyze the induction and role of HO-1 in macrophages during H. pylori infection. We now show that phosphorylation of the H. pylori virulence factor cytotoxin-associated gene A (CagA) in macrophages results in expression of hmox-1, the gene encoding HO-1, through p38/NF (erythroid-derived 2)-like 2 signaling. Blocking phagocytosis prevented CagA phosphorylation and HO-1 induction. The expression of HO-1 was also increased in gastric mononuclear cells of human patients and macrophages of mice infected with cagA(+) H. pylori strains. Genetic ablation of hmox-1 in H. pylori-infected mice increased histologic gastritis, which was associated with enhanced M1/Th1/Th17 responses, decreased regulatory macrophage (Mreg) response, and reduced H. pylori colonization. Gastric macrophages of H. pylori-infected mice and macrophages infected in vitro with this bacterium showed an M1/Mreg mixed polarization type; deletion of hmox-1 or inhibition of HO-1 in macrophages caused an increased M1 and a decrease of Mreg phenotype. These data highlight a mechanism by which H. pylori impairs the immune response and favors its own survival via activation of macrophage HO-1.
Copyright © 2014 by The American Association of Immunologists, Inc.
Tuberculosis remains the biggest infectious threat to humanity with one-third of the population infected and 1.4 million deaths and 8.7 million new cases annually. Current tuberculosis therapy is lengthy and consists of multiple antimicrobials, which causes poor compliance and high treatment dropout, resulting in the development of drug-resistant variants of tuberculosis. Therefore, alternate methods to treat tuberculosis are urgently needed. Mycobacterium tuberculosis evades host immune responses by inducing T helper (Th)2 and regulatory T (Treg) cell responses, which diminish protective Th1 responses. Here, we show that animals (Stat-6(-/-)CD4-TGFβRIIDN mice) that are unable to generate both Th2 cells and Tregs are highly resistant to M. tuberculosis infection. Furthermore, simultaneous inhibition of these two subsets of Th cells by therapeutic compounds dramatically reduced bacterial burden in different organs. This treatment was associated with the generation of protective Th1 immune responses. As these therapeutic agents are not directed to the harbored organisms, they should avoid the risk of promoting the development of drug-resistant M. tuberculosis variants.
© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.
CD4(+) T cells developing toward a Th2 fate express IL-4, IL-5, and IL-13 while inhibiting production of cytokines associated with other Th types, such as the Th1 cytokine IFN- γ. IL-4-producing Th2 effector cells give rise to a long-lived memory population committed to reactivation of the Th2 cytokine gene expression program. However, reactivation of these effector-derived cells under Th1-skewing conditions leads to production of IFN-γ along with IL-4 in the same cell. We now show that this flexibility ("plasticity") of cytokine expression is preceded by a loss of the repressive DNA methylation of the Ifng promoter acquired during Th2 polarization yet requires STAT4 along with T-box expressed in T cells. Surprisingly, loss of either STAT4 or T-box expressed in T cells increased Ifng promoter CpG methylation in both effector and memory Th2 cells. Taken together, our data suggest a model in which the expression of IFN-γ by Th2-derived memory cells involves attenuation of epigenetic repression in memory Th2 cells, combined with Th1-polarizing signals after their recall activation.