Expression of proinflammatory and regulatory cytokines via NF-κB and MAPK-dependent and IFN regulatory factor-3-independent mechanisms in human primary monocytes infected by Mycobacterium tuberculosis

Mycobacterium tuberculosis PPE7 Enhances Intracellular Survival of Mycobacterium smegmatis and Manipulates Host Cell Cytokine Secretion Through Nuclear Factor Kappa B and Mitogen-Activated Protein Kinase Signaling

The PE/PPE family proteins of Mycobacterium tuberculosis have been associated with its virulence and interaction with the host immune system. The highly virulent modern lineage of M. tuberculosis possesses a lineage-specific PPE gene (PPE7), which arises from an ancestral mutation and is rarely studied. Here we examined the role of PPE7 in mycobacterial pathogenicity and survival by expressing M. tuberculosis PPE7 in Mycobacterium smegmatis. We show that, PPE7 activates host inflammation by increasing expression of pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6, while suppressing the expression of anti-inflammatory cytokines such as IL-10, possibly through the nuclear factor kappa B, ERK1/2, and p38 mitogen-activated protein kinase pathways. Overexpressing PPE7 in M. smegmatis could enhance bacterial intracellular survival of infected macrophages. Furthermore, higher level of bacterial persistence, higher levels of TNF-α, IL-1β, and IL-6 cytokines, and more injury in the lung, liver, and spleen tissues of infected mice has been discovered. In conclusion, PPE7 could manipulate host immune response and increase bacterial persistence.

Characterization of immune responses of human PBMCs infected with Mycobacterium tuberculosis H37Ra: Impact of donor declared BCG vaccination history on immune responses and M. tuberculosis growth

This study characterized the immune responses in early Mycobacterium tuberculosis (Mtb) H37Ra infection of human peripheral blood mononuclear cell (PBMC)-collagen matrix culture and the impact of Bacille Calmette-Guérin (BCG) vaccination history of donor PBMCs on the immune responses to Mtb infection. Aggregates of PBMCs were initially observed on day 3 and the size of aggregates continued to increase on day 8 post-infection, where macrophages and T cell subsets were identified to be present. Similarly, mycobacterial load progressively increased in infected PBMCs during the 8 days of culture but were significantly lower in infected PBMCs from BCG vaccinated (BCG+) donors compared to unvaccinated (BCG-) donors. The levels of INF-γ, TNF-α, IL-4, IL-6, IL-10 and IL-17 in the supernatants of Mtb-infected PBMCs peaked at day 3 and decreased on days 5 and 8. The levels of these cytokines except IL-10 were significantly lower in Mtb-infected PBMCs from BCG+ donors compared to infected PBMCs from BCG- donors. The percentages of activated naïve Th cells, activated effector memory Th cells and activated central memory Tc cells were significantly higher in Mtb-infected PBMCs compared to uninfected PBMCs at day 8 post-infection. Further, the proportion of activated central memory Tc cells was significantly higher in infected PBMCs from BCG+ donors compared to the BCG- donors. This study highlights the possibility that BCG vaccination may confound results that utilize human PBMCs to study Mtb infection.

Elemental Ingredients in the Macrophage Cocktail: Role of ZIP8 in Host Response to Mycobacterium tuberculosis

Tuberculosis (TB) is a global epidemic caused by the infection of human macrophages with the world's most deadly single bacterial pathogen, Mycobacterium tuberculosis (M.tb). M.tb resides in a phagosomal niche within macrophages, where trace element concentrations impact the immune response, bacterial metal metabolism, and bacterial survival. The manipulation of micronutrients is a critical mechanism of host defense against infection. In particular, the human zinc transporter Zrt-/Irt-like protein 8 (ZIP8), one of 14 ZIP family members, is important in the flux of divalent cations, including zinc, into the cytoplasm of macrophages. It also has been observed to exist on the membrane of cellular organelles, where it can serve as an efflux pump that transports zinc into the cytosol. ZIP8 is highly inducible in response to M.tb infection of macrophages, and we have observed its localization to the M.tb phagosome. The expression, localization, and function of ZIP8 and other divalent cation transporters within macrophages have important implications for TB prevention and dissemination and warrant further study. In particular, given the importance of zinc as an essential nutrient required for humans and M.tb, it is not yet clear whether ZIP-guided zinc transport serves as a host protective factor or, rather, is targeted by M.tb to enable its phagosomal survival.

Bone Marrow-Derived Mesenchymal Stem Cells-Mediated Protection Against Organ Dysfunction in Disseminated Intravascular Coagulation Is Associated With Peripheral Immune Responses

Disseminated intravascular coagulation (DIC) is a fatal thrombohemorrhagic disorder. Bone marrow-derived mesenchymal stem cells (BMSCs) are multipotent stem cells that have tremendous therapeutic effect. Our aim was to explore whether the immune mechanisms were associated with BMSCs-afforded protection against DIC. We generated a rat model of DIC by lipopolysaccharide (LPS, 3 mg/kg) injection via the tail vein. In the treatment group, rats were pre-treated with 1 × l0³ , 1 × l0⁴ , 1 × l0⁵ , and 1 × l0⁶ allogeneic BMSCs before LPS injection. Blood sample was withdrawn from the abdominal aorta at 0 (before), 4, and 8 h after LPS injection and used for biochemical analyses. After experiments, the mice were sacrificed and their organs were harvested and observed by H&E and PTAH staining. Continuous infusion of LPS into the rats gradually impaired the hemostatic parameters and damaged organ functions. However, pre-treatment with BMSCs dose-dependently improved the hemostatic parameters. Meanwhile, the treatment significantly suppressed the fibrin microthrombi formation and alleviated liver, heart, lung, and renal injuries. Flow cytometry analysis demonstrated that BMSCs pre-treatment inhibited LPS-induced upregulation of CD3⁺ CD8⁺ T cells and CD3⁺ /CD161a⁺ NKT cells in the peripheral blood. BMSCs pre-treatment reversed the upregualtion of the B-cell population and the percentage of CD43⁺ /CD172a⁺ monocytes in the DIC models. Finally, BMSCs pre-treatment decreased the levels of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), and interleukin-6 (IL-6) and increased the levels of interleukin-10 (IL-10) in LPS-induced DIC models. Pre-treatment with BMSCs can reduce coagulation and alleviate organ dysfunction via peripheral immune responses in LPS-induced DIC rat model. J. Cell. Biochem. 118: 3184-3192, 2017. © 2017 Wiley Periodicals, Inc.

Interleukin-10 Family and Tuberculosis: An Old Story Renewed

The interleukin-10 (IL-10) family of cytokines consists of six immune mediators, namely IL-10, IL-19, IL-20, IL-22, IL-24 and IL-26. IL-10, IL-22, IL-24 and IL-26 are critical for the regulation of host defense against Mycobacterium tuberculosis infections. Specifically, IL-10 and IL-26 can suppress the antimycobacterial immunity and promote the survival of pathogen, while IL-22 and IL-24 can generate protective responses and inhibit the intracellular growth of pathogen. Knowledge about the new players in tuberculosis immunology, namely IL-10 family, can inform novel immunity-based countermeasures and host directed therapies against tuberculosis.

Canonical pathways, networks and transcriptional factor regulation by clinical strains of Mycobacterium tuberculosis in pulmonary alveolar epithelial cells

Limited knowledge exists on pathways, networks and transcriptional factors regulated within epithelial cells by diverse Mycobacterium tuberculosis genotypes. This study aimed to elucidate these mechanisms induced in A549 epithelial cells by dominant clinical strains in KwaZulu-Natal, South Africa. RNA for sequencing was extracted from epithelial cells at 48 h post-infection with 5 strains at a multiplicity of infection of approximately 10:1. Bioinformatics analysis performed with the RNA-Seq Tuxedo pipeline identified differentially expressed genes. Changes in pathways, networks and transcriptional factors were identified using Ingenuity Pathway Analysis (IPA). The interferon signalling and hepatic fibrosis/hepatic stellate cell activation pathways were among the top 5 canonical pathways in all strains. Hierarchical clustering for enrichment of cholesterol biosynthesis and immune associated pathways revealed similar patterns for Beijing and Unique; F15/LAM4/KZN and F11; and, F28 and H37Rv strains, respectively. However, the induction of top scoring networks varied among the strains. Among the transcriptional factors, only EHL, IRF7, PML, STAT1, STAT2 and VDR were induced by all clinical strains. Activation of the different pathways, networks and transcriptional factors revealed in the current study may be an underlying mechanism that results in the differential host response by clinical strains of M. tuberculosis.

Type I, II, and III Interferons: Regulating Immunity to Mycobacterium tuberculosis Infection

Interferons (IFNs) are cytokines released by host cells in response to the presence of pathogens or tumor cells. The aim of this review was to present the previously known and new findings about the role of interferons type I and II, and recently discovered type III in Mycobacterium tuberculosis (M. tuberculosis) infection control. Infection of various cell types with M. tuberculosis induce both IFN-α and IFN-β synthesis. The majority of the studies support the findings that IFN type I actually promotes infection with M. tuberculosis. It has been well establish that IFN-γ has protective function against M. tuberculosis and the other mycobacteria and that the primary source of this cytokine are CD4(+) and CD8(+) T cells. Recently, it has been shown that also the innate lymphocytes, γδ T cells, natural killer (NK) T cells, and NK cells can also be the source of IFN-γ in response to mycobacterial infection. Several studies have shown that CD4(+) T cells protect mice against M. tuberculosis independently of IFN-γ. The balance between IFN-γ and different cytokines such as IL-10 and other Th2 cell cytokines is likely to influence disease outcome. Type I IFN appears to be detrimental through at least three separate, but overlapping, type I IFN-mediated mechanisms: induction of excessive apoptosis, specific suppression of Th1 and IFN-γ responses, and dampening of the immune response by strong IL-10 induction. Recently it has been found that M. tuberculosis infection in A549 lung epithelial cells stimulate up-regulation of IFN-λ genes in vitro. IFN-λs also have a role in modulation of Th1/Th2 response. IFN-λs are not essential for M. tuberculosis infection control, but can give some contribution in immune response to this pathogen.

A mycobacterial phosphoribosyltransferase promotes bacillary survival by inhibiting oxidative stress and autophagy pathways in macrophages and zebrafish

Mycobacterium tuberculosis employs various strategies to modulate host immune responses to facilitate its persistence in macrophages. The M. tuberculosis cell wall contains numerous glycoproteins with unknown roles in pathogenesis. Here, by using Concanavalin A and LC-MS analysis, we identified a novel mannosylated glycoprotein phosphoribosyltransferase, encoded by Rv3242c from M. tuberculosis cell walls. Homology modeling, bioinformatic analyses, and an assay of phosphoribosyltransferase activity in Mycobacterium smegmatis expressing recombinant Rv3242c (MsmRv3242c) confirmed the mass spectrometry data. Using Mycobacterium marinum-zebrafish and the surrogate MsmRv3242c infection models, we proved that phosphoribosyltransferase is involved in mycobacterial virulence. Histological and infection assays showed that the M. marinum mimG mutant, an Rv3242c orthologue in a pathogenic M. marinum strain, was strongly attenuated in adult zebrafish and also survived less in macrophages. In contrast, infection with wild type and the complemented ΔmimG:Rv3242c M. marinum strains showed prominent pathological features, such as severe emaciation, skin lesions, hemorrhaging, and more zebrafish death. Similarly, recombinant MsmRv3242c bacteria showed increased invasion in non-phagocytic epithelial cells and longer intracellular survival in macrophages as compared with wild type and vector control M. smegmatis strains. Further mechanistic studies revealed that the Rv3242c- and mimG-mediated enhancement of intramacrophagic survival was due to inhibition of autophagy, reactive oxygen species, and reduced activities of superoxide dismutase and catalase enzymes. Infection with MsmRv3242c also activated the MAPK pathway, NF-κB, and inflammatory cytokines. In summary, we show that a novel mycobacterial mannosylated phosphoribosyltransferase acts as a virulence and immunomodulatory factor, suggesting that it may constitute a novel target for antimycobacterial drugs.

Tupistra chinensis extract attenuates murine fulminant hepatitis with multiple targets against activated T lymphocytes

OBJECTIVES

The extract of Tupistra chinensis (TCE) is traditionally used for the treatment of inflammatory diseases in southwestern China for hundreds of years. The present study was designed to investigate the effects of the TCE against experimental hepatitis and to illustrate its potential mechanisms.

METHODS

Effects of TCE were investigated on Con A-induced hepatitis. Profiles of multiple cytokines were measured with biometric immuno-sandwich ELISA. Proliferation, activation and apoptosis of T lymphocytes were evaluated using Western blot, MTT analysis and flow cytometry.

KEY FINDINGS

TCE significantly inhibited levels of serum transaminases and lactic dehydrogenase in mice with Con A-induced hepatitis, accompanied with marked alleviation of the liver microscopic appearances. Moreover, it decreased levels of inflammatory cytokines in a concentration-dependent manner both in vivo and in vitro. It also suppressed mitogen-activated protein kinases and NF-κB-signalling in liver. These effects of TCE are attributed to its inhibition on activated T cells but not to hepatocytes protection. Flow cytometry and immunoblot assay data showed its effects on STAT1/NF-κB-signalling blockage and apoptosis induction in activated T cells.

CONCLUSION

Our findings illustrate the significant potential of TCE as a novel approach for treatment of T cell-mediated inflammatory diseases.

Intranasal pyrrolidine dithiocarbamate decreases brain inflammatory mediators and provides neuroprotection after brain hypoxia-ischemia in neonatal rats

Brain injury due to birth asphyxia is the major cause of death and long-term disabilities in newborns. We determined whether intranasal pyrrolidine dithiocarbamate (PDTC) could provide neuroprotection in neonatal rats after brain hypoxia-ischemia (HI). Seven-day old male and female Sprague-Dawley rats were subjected to brain HI. They were then treated with intranasal PDTC. Neurological outcomes were evaluated 7 or 30 days after the brain HI. Brain tissues were harvested 6 or 24 h after the brain HI for biochemical analysis. Here, PDTC dose-dependently reduced brain HI-induced brain tissue loss with an effective dose (ED)50 at 27 mg/kg. PDTC needed to be applied within 45 min after the brain HI for this neuroprotection. This treatment reduced brain tissue loss and improved neurological and cognitive functions assessed 30 days after the HI. PDTC attenuated brain HI-induced lipid oxidative stress, nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells, and various inflammatory mediators in the brain tissues. Inhibition of inducible nitric oxide synthase after brain HI reduced brain tissue loss. Our results suggest that intranasal PDTC provides neuroprotection possibly via reducing inflammation and oxidative stress. Intranasal PDTC may have a potential to provide neuroprotection to human neonates after birth asphyxia.

Isoflurane postconditioning reduces ischemia-induced nuclear factor-κB activation and interleukin 1β production to provide neuroprotection in rats and mice

Application of isoflurane, a volatile anesthetic, after brain ischemia can reduce ischemic brain injury in rodents (isoflurane postconditioning). This study is designed to determine whether isoflurane postconditioning improves long-term neurological outcome after focal brain ischemia and whether this protection is mediated by attenuating neuroinflammation. Adult male Sprague-Dawley rats were subjected to a 90-min middle cerebral arterial occlusion (MCAO). Isoflurane postconditioning was performed by exposing rats to 2% isoflurane for 60min immediately after the MCAO. Isoflurane postconditioning reduced brain infarct volumes, apoptotic cells in the ischemic penumbral brain tissues and neurological deficits of rats at 4weeks after the MCAO. Isoflurane postconditioning reduced brain ischemia/reperfusion-induced nuclear transcription factor (NF)-κB (NF-κB) activation as well as interleukin 1β (IL-1β) and interleukin-6 production in the ischemic penumbral brain tissues at 24h after the MCAO. IL-1β deficient mice had smaller brain infarct volumes and better neurological functions than wild-type mice at 24h after a 90-min focal brain ischemia. Isoflurane posttreatment failed to induce neuroprotection in the IL-1β deficient mice. Our results suggest that isoflurane postconditioning improved long-term neurological outcome after transient focal brain ischemia. This protection may be mediated by inhibiting NF-κB activation and the production of the proinflammatory cytokine IL-1β.

Is RORγ a therapeutic target for treating Mycobacterium tuberculosis infections?

A link is hypothesized between inhibition of the retinoic acid receptor-related orphan receptor γ (RORγ) and treatment of Mycobacterium tuberculosis (Mtb) infection. An unexpected overlap was found between inhibitors of both Mtb H37Rv with RORγ in PubChem. Since RORγ is not present in Mtb, a commonality was reasoned to be cholesterol. Gemfibrozil is a RORγ inhibitor that was inactive against Mtb cells. Yet, gemfibrozil has been shown to inhibit Mtb growth in macrophages, supporting the hypothesis that RORγ inhibitors could show therapeutic benefit in Mtb infection.(7).