Infected U937 Cells Research Articles

Attenuated Cytokine-Induced Memory-Like Natural Killer Cell Responses to Mycobacterium tuberculosis in Tuberculosis Patients.

This study aimed to investigate the phenotype, proliferation and functional alterations of cytokine-induced memory-like natural killer (CIML NK) cells from healthy subjects and TB patients, and assessed the efficacy of CIML NK cells in response to H37Rv-infected U937 cells in vitro. Fresh peripheral blood mononuclear cells (PBMCs) were isolated from healthy people and tuberculosis patients and activated for 16h using low-dose IL-15, or IL-12, IL-15, IL-18 combination or IL-12, IL-15, IL-18 and MTB H37Rv lysates, respectively, followed by low-dose IL-15 maintenance for another 7 days. Then, the PBMCs were co-cultured with K562 and H37Rv-infected U937, and the purified NK cells were co-cultured with H37Rv infected U937. The phenotype, proliferation and response function of CIML NK cells were assessed using flow cytometry. Finally, colony forming units were enumerated to confirm the survival of intracellular MTB. CIML NK phenotypes from TB patients were similar to healthy controls. CIML NK cells undergo higher rates of proliferation after IL-12/15/18 pre-activation. Moreover, the poor expansion potential of CIML NK cells co-stimulated with MTB lysates. CIML NK cells from healthy individuals showed enhanced IFN-γ functional to H37Rv infected U937 cells, along with significantly enhanced killing of H37Rv. However, the CIML NK cells from TB patients show attenuated IFN-γ production and now enhanced the ability of killing intracellular MTB compared to those from healthy donors after co-cultured with H37Rv infected U937. CIML NK cells from healthy individuals exist the increased ability of IFN-γ secretion and boosted anti-MTB activity in vitro, which from TB patients show impaired IFN-γ production and no enhanced anti-MTB activity compared to those from healthy donors. Additionally, we observe the poor expansion potential of CIML NK cells co-stimulated with antigens from MTB. These results open up new possibilities for NK cell-based anti-tuberculosis immunotherapeutic strategies.

Detection of artemisinin effect on macrophage inducible nitric oxide gene expression in macrophage infected with Leishmania donovani.

Leishmaniosis is a parasitic infection spreads to humans by sand flies. Over 20 different species of Leishmania are responsible for the disease, which infect over 14 million people around the world. Chemotherapy is one of the most effective treatments for leishmaniosis, however it is restricted by the high cost and/or toxicity. In this study, the possible effect of artemisinin (ART) was detected on intracellular amastigotes of Iraqi strain of Leishmania donovani in ex vivo condition in U937 macrophage cell line. Gene expression of inducible nitric oxide synthase (iNOS) in U937 macrophage was investigated, before and after treatment with artemisinin. Kinetic result by real-time PCR demonstrated that the iNOS expression folding reached the maximum at concentration of 500 μM after 24 hours, at 750 μM after 48 hours and at 1000 μM after 72 hours, which was 56, 11, and 6, respectively. The copy number of iNOS gene expression was also significantly higher in treated infected U937 cells compared to both non-treated-infected cells and intact macrophages, under different concentration of ART along the three times of follow-up. Moreover, stained macrophages with fluorescent DAPI proved that the percentage of intracellular infective amastigotes was decreased to the minimum in treated U937 cells, in comparison to non-treated cells. The minimal amastigote-invasion percentage was recorded at 1000 μM, which was 26%, 27%, 21% compared to 61%, 87%, 75% in untreated cells after 24, 48, 72 hours respectively. These findings demonstrated ART positive efficacy against iNOS expression and this compound can be further studied as novel therapeutic rather than toxic available chemotherapies.

Role of RIPK1 in SMAC mimetics-induced apoptosis in primary human HIV-infected macrophages

Macrophages serve as viral reservoirs due to their resistance to apoptosis and HIV-cytopathic effects. We have previously shown that inhibitor of apoptosis proteins (IAPs) confer resistance to HIV-Vpr-induced apoptosis in normal macrophages. Herein, we show that second mitochondrial activator of caspases (SMAC) mimetics (SM) induce apoptosis of monocyte-derived macrophages (MDMs) infected in vitro with a R5-tropic laboratory strain expressing heat stable antigen, chronically infected U1 cells, and ex-vivo derived MDMs from HIV-infected individuals. To understand the mechanism governing SM-induced cell death, we show that SM-induced cell death of primary HIV-infected macrophages was independent of the acquisition of M1 phenotype following HIV infection of macrophages. Instead, SM-induced cell death was found to be mediated by IAPs as downregulation of IAPs by siRNAs induced cell death of HIV-infected macrophages. Moreover, HIV infection caused receptor interacting protein kinase-1 (RIPK1) degradation which in concert with IAP1/2 downregulation following SM treatment may result in apoptosis of macrophages. Altogether, our results show that SM selectively induce apoptosis in primary human macrophages infected in vitro with HIV possibly through RIPK1. Moreover, modulation of the IAP pathways may be a potential strategy for selective killing of HIV-infected macrophages in vivo.

Campylobacter coli strains from Brazil can invade phagocytic and epithelial cells and induce IL-8 secretion.

Campylobacter spp. have been a predominant cause of bacterial foodborne gastroenteritis worldwide, causing substantial costs to public healthcare systems. This study aimed to assess the invasion and pro-inflammatory cytokine production capacity of Campylobacter coli strains isolated in Brazil. A total of 50 C. coli isolated from different sources in Brazil were analyzed for their capacity of invasion in Caco-2 and U-937 cell lines. The production of pro-inflammatory cytokines was quantitatively measured in response to C. coli. All the strains studied showed invasion percentage ≥ 40% in polarized Caco-2 cells. In U-937 cells assay, 35 of 50 C. coli strains studied showed invasion percentage ≥ 50%. A significant increase in IL-8 production by infected U-937 cells was observed for 17.5% of the C. coli isolates. The high percentages of invasion in Caco-2 and U-937 cells observed for all studied strains, plus the increased production of IL-8 by U-937 cells against some strains, highlighted the pathogenic potential of the C. coli studied and bring extremely relevant data since it has never been reported for strains isolated in Brazil and there are a few data for C. coli in the literature.

Activation of hypoxia-inducible factor 1 (Hif-1) enhanced bactericidal effects of macrophages to Mycobacterium tuberculosis

BackgroundTuberculosis is chronic infection caused by Mycobacterium tuberculosis (M.tb), which infects specifically macrophages. Hif-1, hypoxia-inducible factor-1, was reported to act as master regulator of killing functions in macrophages. AimTo investigate whether Hif-1 activation would enhance bactericidal effect of macrophages and anti-tuberculosis effect of chemical reagent. MethodsHif-1 and LC3B were detected in tissues from pulmonary tuberculosis. U937, human monocytic leukemia cell line, was stimulated with PMA and differentiated into macrophages. Cells were pretreated with Hif-1 chemical inhibitor YC-1, stimulated with CoCl2 (Hif-1 activator), to detect LC3B with Western blot and confocal microscopy. Cells were infected with M. tb H37Rv strain, stimulated with CoCl2, following rifampine treatment. Expression of autophagy markers was detected using Western blot. IL-6 and TNF-α were detected in cell supernatant with ELISA. Acid-fast staining and CFU assay were performed to evaluate intracellular bacterial load. Results and conclusionsHif-1 and LC3B increased in tissues of pulmonary tuberculosis. Hif-1 activation enhanced autophagy in M. tb infected U937 cells and production of IL-6 and TNF-α. Data from acid-fast staining and CFU indicated that Hif-1 activation enhanced anti-tuberculosis effect of rifampine in macrophages. Conclusively, to activate Hif-1 would strengthen bactericidal effect of macrophages, to further enhance anti-tuberculosis effect of chemical reagent.

Phosphoproteomic analysis of dengue virus infected U937 cells and identification of pyruvate kinase M2 as a differentially phosphorylated phosphoprotein

Dengue virus (DENV) is an arthropod-borne Flavivirus that can cause a range of symptomatic disease in humans. There are four dengue viruses (DENV 1 to 4) and infection with one DENV only provides transient protection against a heterotypic virus. Second infections are often more severe as the disease is potentiated by antibodies from the first infection through a process known as antibody dependent enhancement (ADE) of infection. Phosphorylation is a major post-translational modification that can have marked effects on a number of processes. To date there has been little information on the phosphorylation changes induced by DENV infection. This study aimed to determine global phosphoproteome changes induced by DENV 2 in U937 cells infected under an ADE protocol. A 2-dimensional electrophoretic approach coupled with a phosphoprotein-specific dye and mass spectroscopic analysis identified 15 statistically significant differentially phosphorylated proteins upon DENV 2 infection. One protein identified as significantly differentially phosphorylated, pyruvate kinase M2 (PKM2) was validated. Treatment with a PKM2 inhibitor modestly reduced levels of infection and viral output, but no change was seen in cellular viral protein levels, suggesting that PKM2 acts on exocytic virus release. While the effect of inhibition of PKM2 was relatively modest, the results highlight the need for a greater understanding of the role of phosphoproteins in DENV infection.

The Opposite Effects of Kynurenic Acid and Different Kynurenic Acid Analogs on Tumor Necrosis Factor-α (TNF-α) Production and Tumor Necrosis Factor-Stimulated Gene-6 (TSG-6) Expression.

Purpose: The investigation of anti-inflammatory and immunosuppressive functions of Kynurenic acid (KYNA) is now in focus. There is also substantial evidence that TSG-6 has an anti-inflammatory activity. Therefore, in the present study, we compared the effects of newly synthetized KYNA analogs on the TNF-α production in U-937 monocytic cells in correlation with the effects on the TSG-6 expression.Methods: TNF-α production was measured by ELISA, the TSG-6 expression was determined by RTqPCR method. As cytokine inducers Staphylococcus aureus and Chlamydia pneumoniae were used.Results: KYNA and KYNA analogs attenuated TNF-α production and increased TSG-6 mRNA expression in U-937 cells stimulated by heat inactivated Staphylococcus aureus. In contrast, KYNA and some of the KYNA analogs increased the TNF-α production of C. pneumoniae infected U-937 cells; however, the newly synthetized analogs (SZR104, SZR 105, and SZR 109) exerted significant inhibitory effects on the TNF-α synthesis. The inhibitory and stimulatory effects correlated inversely with the TSG-6 expression.Conclusions: TSG-6 expression following activation with bacterial components could participate in the suppression of inflammatory cytokines, such as TNF-α, We suppose that the elevation of the TSG-6 expression by KYNA and especially by new KYNA analogs might be one of the mechanisms that are responsible for their suppressive effect on TNF-α production as a feedback mechanism. KYNA and KYNA analogs have an important role in influencing TSG-6 expression, and there is a possible benefit of targeting TSG-6 expression by kynurenines in inflammatory conditions following infections.

PR8 virus harbouring H5N1 NS gene contributed for THP-1 cell tropism.

Innate immune cells are key player in immune response to influenza virus infection. Influenza infected monocytes exacerbate the disease pathology. However, monocytes differ in susceptibilities to influenza virus infection. Herein, susceptibilities of U937 and THP-1 monocytic cells to PR8 virus infection, the associated cellular factor- sialic acid (SA) receptor distribution and viral factor were determined. Moreover, amino acid sequences in hemagglutinin (HA) receptor binding domain (RBD) of PR8 virus that determine SA preferences were analysed. PR8 infected U937 cells express significantly higher numbers of nucleoprotein positive cells suggesting U937 cells being more susceptible to influenza virus than THP-1 cells. Lectin staining suggested similar pattern of SA receptor distribution in both cells. Interestingly, sequence analysis of RBD suggested their preferences for alpha 2,3 SA receptors suggesting RBD sequences are not always determining for SA preferences. Furthermore, the resistance barrier on THP-1 cells was overcome by H5N1 NS gene. In conclusion, the study demonstrated that decreased susceptibility of THP-1 cells to PR8 virus could not be related to the SA receptor distribution, and H5N1 NS gene was sufficient to determine tropism for THP-1 cells. Hence, mechanistic basis of NS gene on cell tropism and contribution of other internal genes remained to be determined.

Epithelial Cells Attenuate Toll-Like Receptor-Mediated Inflammatory Responses in Monocyte-Derived Macrophage-Like Cells to Mycobacterium tuberculosis by Modulating the PI3K/Akt/mTOR Signaling Pathway.

Both alveolar macrophages (AMs) and alveolar epithelial cells (AECs) are main targets of Mycobacterium tuberculosis (M. tuberculosis (Mtb)). Intercellular communications between mucosal AECs and AMs have important implications in cellular responses to exogenous insults. However, molecular mechanisms underpinning interactions responding to Mtb remain largely unknown. In this study, impacts of AECs on Toll-like receptor- (TLR-) mediated inflammatory responses of AMs to Mtb virulent strain H37Rv were interrogated using an air-liquid interface (ALI) coculture model of epithelial A549 cells and U937 monocyte-derived macrophage-like cells. Results showed that Mtb-activated TLR-mediated inflammatory responses in U937 cells were significantly alleviated when A549 cells were coinfected with H37Rv, in comparison with the infection of U937 cells alone. Mechanistically, PI3K/Akt/mTOR signaling was involved in the epithelial cell-modulated Mtb-activated TLR signaling. The epithelial cell-attenuated TLR signaling in U937s could be reversed by PI3K inhibitor LY294002 and mTOR inhibitor rapamycin, but not glycogen synthase kinase 3β inhibitor LiCl, suggesting that the epithelially modulated-TLR signaling in macrophages was in part caused by inhibiting the TLR-triggered PI3K/Akt/mTOR signaling pathway. Together, this study demonstrates that mucosal AEC-derived signals play an important role in modulating inflammatory responses of AMs to Mtb, which thus also offers an insight into cellular communications between AECs and AMs to Mtb infections.

Identification, structural modification, and dichotomous effects on human immunodeficiency virus type 1 (HIV-1) replication of ingenane esters from Euphorbia kansui

Euphorbia kansui showed potent anti-HIV-1 activity during screening of a library composed of plant extracts from Euphorbiaceae and Thymelaeaceae families. Bioassay-guided isolation led to identification of ingenane esters as the active compounds. Further chemical modification resulted in 3-(2-naphthoyl)ingenol (23), which exhibited the most potent anti-HIV-1 activity. Compound 23 also acted as an HIV-1-latency-reversing agent on activation of HIV-1 replication in a latently infected U1 cell model and a T cell latent HIV-1 model JLat-A2.

Resistance to apoptosis in Leishmania infantum-infected human macrophages: a critical role for anti-apoptotic Bcl-2 protein and cellular IAP1/2.

Apoptosis is essential for maintaining tissue homoeostasis in multi-cellular organisms, also occurring as a defence mechanism against a number of infectious agents, such as parasites. Among intracellular protozoan parasites reported to interfere with the apoptotic machinery of the host cell, Leishmania (L.) sp. have been described, although the various species might activate different pathways in their host cells. Since until now it is not yet well clarified the signalling pathway involved in the apoptosis modulation by L. infantum, the aim of this work was to investigate the role of the anti-apoptotic protein, Bcl-2, and the inhibitors of apoptosis IAP1/2 (cIAP1/2) in cell death resistance showed in L. infantum-infected human macrophages. We observed that actinomycin D-induced apoptosis in U-937 cells, evaluated by Annexin V-CY3, DNA fragmentation and caspase-3, caspase-8, caspase-9 activation assays, was inhibited in the presence of L. infantum promastigotes and that, in these conditions, Bcl-2 protein expression resulted significantly upregulated. Interestingly, L. infantum infection in combination with the Bcl-2 inhibitor, ABT-737, significantly increased the apoptotic process in actinomycin D-treated cells, suggesting a role for Bcl-2 in the anti-apoptotic regulation of human macrophages induced by L. infantum infection. Moreover, Western blotting analysis demonstrated not only a significantly upregulation of cIAP1/2 in infected U-937 cells, but also that the inhibition of cIAPs, employing specific siRNAs, restored the apoptotic effect of actinomycin in infected macrophages. These results clearly support the hypothesis that Bcl-2 and cIAPs are strongly involved in the anti-apoptotic action played by L. infantum in human macrophages.

The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages.

Previously, we reported that mutants of Legionella pneumophila lacking a type II secretion (T2S) system elicit higher levels of cytokines (e.g., interleukin-6 [IL-6]) following infection of U937 cells, a human macrophage-like cell line. We now show that this effect of T2S is also manifest upon infection of human THP-1 macrophages and peripheral blood monocytes but does not occur during infection of murine macrophages. Supporting the hypothesis that T2S acts to dampen the triggering of an innate immune response, we observed that the mitogen-activated protein kinase (MAPK) and nuclear transcription factor kappa B (NF-κB) pathways are more highly stimulated upon infection with the T2S mutant than upon infection with the wild type. By using short hairpin RNA to deplete proteins involved in specific pathogen-associated molecular pattern (PAMP) recognition pathways, we determined that the dampening effect of the T2S system was not dependent on nucleotide binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible protein I (RIG-I)-like receptors (RLRs), double-stranded RNA (dsRNA)-dependent protein kinase receptor (PKR), or TIR domain-containing adaptor inducing interferon beta (TRIF) signaling or an apoptosis-associated speck-like protein containing a CARD (ASC)- or caspase-4-dependent inflammasome. However, the dampening effect of T2S on IL-6 production was significantly reduced upon gene knockdown of myeloid differentiation primary response 88 (MyD88), TANK binding kinase 1 (TBK1), or Toll-like receptor 2 (TLR2). These data indicate that the L. pneumophila T2S system dampens the signaling of the TLR2 pathway in infected human macrophages. We also document the importance of PKR, TRIF, and TBK1 in cytokine secretion during L. pneumophila infection of macrophages.

Effects of PTPN11 on the Biological Characteristics of AML Cells

To detect the expression of PTPN11 gene in acute myeloid leukemia (AML) cell line and to explore the effects of PTPN11 over expressing on proliferation and apotosis of AML cell lines. The expression of PTPN11 in AML cell lines（HEL,U937, K562, KG-1, HL -60） was detected by RT-PCR, Q-PCR and Western blot. The PTPN11 gene was amplified by RT-PCR. PTPN11 DNA fragement and the lentiviral vector PCDH-CD513B were digested by BamHI and EcoRI, and then ligated by T4 DNA ligase. Recombinant lentivirus was generated by co-transfection of three-plasmids into 293FT cells using lipofectamine 2000. Then Q-PCR and Western blot were used to detect the expression of PTPN11 in the lentivirus infected HEL and U937 cells. The CCK-8 and Annexin V/7-AAD assays were performed to evaluate effects of PTPN11 on proliferation, apoptosis of HEL and U937 cells. All 5 AML cell lines expressed the PTPN11 gene, restriction analysis and gene sequencing confirmed that recombinant lentiviral vector was successfully constructed. After transfection of cells with the lentivirus, the recombinant plasmid could stably up-regulate the expression of PTPN11. Analysis of the proliferation and apoptosis of transfected AML cells indicated that as compared with the control group, the OD values of over-expression group were significantly higher and the apoptotic rates were significantly lower (P<0.05). PTPN11 is expressed in all the 5 AML cell lines. The lentiviral expression vector carrying human PTPN11 and the engineered HEL and U937 cell lines stably up-regulating PTPN11 gene expression are successfully obtained. Over-expression of PTPN11 promotes the proliferation of AML cell lines and inhibit then apoptosis.

Effect of Hippophae Rhamnoides Leaf Extract against Dengue Virus Infection in U937 Cells

Hippophae rhamnoides (Seabuckthorn) (Family: Elaegnaceae), a medicinal plant from Himalayas, traditionally used for health promotion. The study has been designed to investigate the effect of Sea buckthorn leaf alcoholic extract and other well-known medicinal plants, in Dengue infected U-937 cells (Human Monocytic cell line), as monocytes are the host cells for Dengue virus. Significantly high anti-dengue activity of Seabuckthorn was observed indicating it as a potential candidate for management of Dengue infection.

Extracellular ATP induces the rapid release of HIV-1 from virus containing compartments of human macrophages

HIV type 1 (HIV-1) infects CD4(+) T lymphocytes and tissue macrophages. Infected macrophages differ from T cells in terms of decreased to absent cytopathicity and for active accumulation of new progeny HIV-1 virions in virus-containing compartments (VCC). For these reasons, infected macrophages are believed to act as "Trojan horses" carrying infectious particles to be released on cell necrosis or functional stimulation. Here we explored the hypothesis that extracellular ATP (eATP) could represent a microenvironmental signal potentially affecting virion release from VCC of infected macrophages. Indeed, eATP triggered the rapid release of infectious HIV-1 from primary human monocyte-derived macrophages (MDM) acutely infected with the CCR5-dependent HIV-1 strain. A similar phenomenon was observed in chronically infected promonocytic U1 cells differentiated to macrophage-like cells (D-U1) by costimulation with phorbol esters and urokinase-type plasminogen activator. Worthy of note, eATP did not cause necrotic, apoptotic, or pyroptotic cell death, and its effect on HIV-1 release was suppressed by Imipramine (an antidepressant agent known to inhibit microvesicle formation by interfering with membrane-associated acid sphingomyelinase). Virion release was not triggered by oxidized ATP, whereas the effect of eATP was inhibited by a specific inhibitor of the P2X7 receptor (P2X7R). Thus, eATP triggered the discharge of virions actively accumulating in VCC of infected macrophages via interaction with the P2X7R in the absence of significant cytopathicity. These findings suggest that the microvesicle pathway and P2X7R could represent exploitable targets for interfering with the VCC-associated reservoir of infectious HIV-1 virions in tissue macrophages.

Molecular mechanisms linking high dose medroxyprogesterone with HIV-1 risk.

BackgroundEpidemiological studies suggest that medroxyprogesterone acetate (MPA) may increase the risk of HIV-1. The current studies were designed to identify potential underlying biological mechanisms.MethodsHuman vaginal epithelial (VK2/E6E7), peripheral blood mononuclear (PBMC), and polarized endometrial (HEC-1-A) cells were treated with a range of concentrations of MPA (0.015-150 μg/ml) and the impact on gene expression, protein secretion, and HIV infection was evaluated.ResultsTreatment of VK2/E6E7 cells with high doses (>15μg/ml] of MPA significantly upregulated proinflammatory cytokines, which resulted in a significant increase in HIV p24 levels secreted by latently infected U1 cells following exposure to culture supernatants harvested from MPA compared to mock-treated cells. MPA also increased syndecan expression by VK2/E6E7 cells and cells treated with 15 μg/ml of MPA bound and transferred more HIV-1 to T cells compared to mock-treated cells. Moreover, MPA treatment of epithelial cells and PBMC significantly decreased cell proliferation resulting in disruption of the epithelial barrier and decreased cytokine responses to phytohaemagglutinin, respectively.ConclusionWe identified several molecular mechanisms that could contribute to an association between DMPA and HIV including proinflammatory cytokine and chemokine responses that could activate the HIV promoter and recruit immune targets, increased expression of syndecans to facilitate the transfer of virus from epithelial to immune cells and decreased cell proliferation. The latter could impede the ability to maintain an effective epithelial barrier and adversely impact immune cell function. However, these responses were observed primarily following exposure to high (15-150 μg/ml) MPA concentrations. Clinical correlation is needed to determine whether the prolonged MPA exposure associated with contraception activates these mechanisms in vivo.

Role of Bruton's tyrosine kinase inhibitors in HIV-1-infected cells.

Many cellular cofactors have been documented to be critical for various stages of viral replication. Using high-throughput proteomic assays, we have previously identified Bruton's tyrosine kinase (BTK) as a host protein that was uniquely upregulated in the plasma membrane of human immunodeficiency virus (HIV-1)-infected T cells. Here, we have further characterized the BTK expression in HIV-1 infection and show that this cellular factor is specifically expressed in infected myeloid cells. Significant upregulation of the phosphorylated form of BTK was observed in infected cells. Using size exclusion chromatography, we found BTK to be virtually absent in the uninfected U937 cells; however, new BTK protein complexes were identified and distributed in both high molecular weight (∼600 kDa) and a small molecular weight complex (∼60-120 kDa) in the infected U1 cells. BTK levels were highest in cells either chronically expressing virus or induced/infected myeloid cells and that BTK translocated to the membrane following induction of the infected cells. BTK knockdown in HIV-1-infected cells using small interfering RNA (siRNA) resulted in selective death of infected, but not uninfected, cells. Using BTK-specific antibody and small-molecule inhibitors including LFM-A13 and a FDA-approved compound, ibrutinib (PCI-32765), we have found that HIV-1-infected cells are sensitive to apoptotic cell death and result in a decrease in virus production. Overall, our data suggests that HIV-1-infected cells are sensitive to treatments targeting BTK expressed in infected cells.

Different behaviours of promoters in Mycobacterium tuberculosis H37Rv and H37Ra.

Mycobacterium tuberculosis H37Rv and H37Ra are two closely-related bacterial strains in which the former is virulent whereas the latter is not. Although the genetic differences between these strains are known, our understanding of how they control the difference in virulence characteristics is incomplete. In this work, we tested the activities of different mycobacterium gene promoters in the two strains using a gfp reporter gene. The promoter activities were compared between growth in vitro and growth of bacteria residing in U937 cells (a-macrophage-like cell line). The promoters tested included M. tuberculosis isocitrate lyase (icl), alpha crystalline homolog (hspX) and moeZ, and the M. avium macrophage-induced gene (mig) promoter. Two hspX constructs with different lengths of the promoter sequence were tested. All promoters except the shorter hspX construct were active in the H37Ra strain in both liquid culture and in U937 cells. In the H37Rv strain, the shorter hspX and icl constructs were induced in infected U937 cells relative to liquid culture, whereas the mig construct was active in both conditions. In conclusion, the inducible properties of the shorter hspX and the icl promoters evident in H37Rv appeared to be lost in the H37Ra strain. Furthermore, sequence further upstream of the hspX gene appears to modulate the inducible property of the hspX promoter in a strain-dependent manner.

Proteomic analysis of U937 cells expressing Mycobacterium tuberculosis heat shock protein 16.3

To compare the protein expression differences between U937 macrophages expressing M. tuberculosis (MTB) Hsp16.3 protein and U937 macrophages expressing green fluorescent protein (GFP), and therefore to explore the protein expressions related to latent TB infection(LTBI). U937 macrophages were infected with an integrase-deficient Lentivirus vector to transiently express MTB Hsp16.3, and green fluorescent protein (GFP) as a control. 2-DE was used to compare the differentially expressed proteins in the infected U937 cells. Then 5 significantly different expressed protein spots were identified by using mass spectrometry. The data of 6 protein spots in gel obtained from peptide mass fingerprinting were retrieved in protein database. They were identified as heat shock protein 70, actin, elongation factor I, peptidyl-prolyl cis-trans isomerase, ubiquitin-conjugation enzyme E2, and milk acyl glutathione lyase. The results showed that MTB specific protein intrusion resulted in changes of macrophage proteome expression, and this finding may help in understanding of the interaction between macrophages and MTB specific proteins.

Measuring Glutathione Redox Potential of HIV-1-infected Macrophages

Redox signaling plays a crucial role in the pathogenesis of human immunodeficiency virus type-1 (HIV-1). The majority of HIV redox research relies on measuring redox stress using invasive technologies, which are unreliable and do not provide information about the contributions of subcellular compartments. A major technological leap emerges from the development of genetically encoded redox-sensitive green fluorescent proteins (roGFPs), which provide sensitive and compartment-specific insights into redox homeostasis. Here, we exploited a roGFP-based specific bioprobe of glutathione redox potential (E(GSH); Grx1-roGFP2) and measured subcellular changes in E(GSH) during various phases of HIV-1 infection using U1 monocytic cells (latently infected U937 cells with HIV-1). We show that although U937 and U1 cells demonstrate significantly reduced cytosolic and mitochondrial E(GSH) (approximately -310 mV), active viral replication induces substantial oxidative stress (E(GSH) more than -240 mV). Furthermore, exposure to a physiologically relevant oxidant, hydrogen peroxide (H2O2), induces significant deviations in subcellular E(GSH) between U937 and U1, which distinctly modulates susceptibility to apoptosis. Using Grx1-roGFP2, we demonstrate that a marginal increase of about ∼25 mV in E(GSH) is sufficient to switch HIV-1 from latency to reactivation, raising the possibility of purging HIV-1 by redox modulators without triggering detrimental changes in cellular physiology. Importantly, we show that bioactive lipids synthesized by clinical drug-resistant isolates of Mycobacterium tuberculosis reactivate HIV-1 through modulation of intracellular E(GSH). Finally, the expression analysis of U1 and patient peripheral blood mononuclear cells demonstrated a major recalibration of cellular redox homeostatic pathways during persistence and active replication of HIV.