Chang-Hwa Song

A functional promoter polymorphism in monocyte chemoattractant protein-1 is associated with increased susceptibility to pulmonary tuberculosis.

We examined the distribution of single nucleotide polymorphisms (SNPs) in nitric oxide synthase 2A, monocyte chemoattractant protein–1 (MCP-1), regulated on activation, normal T cell expressed and secreted, and macrophage inflammatory protein–1 α genes in tuberculosis patients and healthy controls from Mexico. The odds of developing tuberculosis were 2.3- and 5.4-fold higher in carriers of MCP-1 genotypes AG and GG than in homozygous AA. Cases of homozygous GG had the highest plasma levels of MCP-1 and the lowest plasma levels of IL-12p40, and these values were negatively correlated. Furthermore, stimulation of monocytes from healthy carriers of the genotype GG with Mycobacterium tuberculosis antigens yielded higher MCP-1 and lower IL-12p40 concentrations than parallel experiments with monocytes from homozygous AA. Addition of anti–MCP-1 increased IL-12p40 levels in cultures of M. tuberculosis–stimulated monocytes from homozygous GG, and addition of exogenous MCP-1 reduced IL-12p40 production by M. tuberculosis–stimulated monocytes from homozygous AA. Furthermore, we could replicate our results in Korean subjects, in whom the odds of developing tuberculosis were 2.8- and 6.9-fold higher in carriers of MCP-1 genotypes AG and GG than in homozygous AA. Our findings suggest that persons bearing the MCP-1 genotype GG produce high concentrations of MCP-1, which inhibits production of IL-12p40 in response to M. tuberculosis and increases the likelihood that M. tuberculosis infection will progress to active pulmonary tuberculosis.

The orphan nuclear receptor SHP acts as a negative regulator in inflammatory signaling triggered by Toll-like receptors

The orphan nuclear receptor SHP (small heterodimer partner) is a transcriptional corepressor that regulates hepatic metabolic pathways. Here we identified a role for SHP as an intrinsic negative regulator of Toll-like receptor (TLR)-triggered inflammatory responses. SHP-deficient mice were more susceptible to endotoxin-induced sepsis. SHP had dual regulatory functions in a canonical transcription factor NF-κB signaling pathway, acting as both a repressor of transactivation of the NF-κB subunit p65 and an inhibitor of polyubiquitination of the adaptor TRAF6. SHP-mediated inhibition of signaling via the TLR was mimicked by macrophage-stimulating protein (MSP), a strong inducer of SHP expression, via an AMP-activated protein kinase–dependent signaling pathway. Our data identify a previously unrecognized role for SHP in the regulation of TLR signaling.

Roles of peroxiredoxin II in the regulation of proinflammatory responses to LPS and protection against endotoxin-induced lethal shock

Mammalian 2-Cys peroxiredoxin II (Prx II) is a cellular peroxidase that eliminates endogenous H2O2. The involvement of Prx II in the regulation of lipopolysaccharide (LPS) signaling is poorly understood. In this report, we show that LPS induces substantially enhanced inflammatory events, which include the signaling molecules nuclear factor κB and mitogen-activated protein kinase (MAPK), in Prx II–deficient macrophages. This effect of LPS was mediated by the robust up-regulation of the reactive oxygen species (ROS)–generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and the phosphorylation of p47phox. Furthermore, challenge with LPS induced greater sensitivity to LPS-induced lethal shock in Prx II–deficient mice than in wild-type mice. Intravenous injection of Prx II–deficient mice with the adenovirus-encoding Prx II gene significantly rescued mice from LPS-induced lethal shock as compared with the injection of a control virus. The administration of catalase mimicked the reversal effects of Prx II on LPS-induced inflammatory responses in Prx II–deficient cells, which suggests that intracellular H2O2 is attributable, at least in part, to the enhanced sensitivity to LPS. These results indicate that Prx II is an essential negative regulator of LPS-induced inflammatory signaling through modulation of ROS synthesis via NADPH oxidase activities and, therefore, is crucial for the prevention of excessive host responses to microbial products.

The Mycobacterial 38-Kilodalton Glycolipoprotein Antigen Activates the Mitogen-Activated Protein Kinase Pathway and Release of Proinflammatory Cytokines through Toll-Like Receptors 2 and 4 in Human Monocytes

ABSTRACT Although the 38-kDa glycolipoprotein of Mycobacterium tuberculosis H37Rv is known to evoke prominent cellular and humoral immune responses in human tuberculosis (TB), little information is known about intracellular regulatory mechanisms involved in 38-kDa antigen (Ag)-induced host responses. In this study, we found that purified 38-kDa glycolipoprotein activates mitogen-activated protein kinases (MAPKs; extracellular signal-regulated kinase 1/2 [ERK1/2] and p38) and induces tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) in human monocytes. When the 38-kDa Ag was applied to monocytes from TB patients and healthy controls, the activation of ERK1/2 and p38 MAPK and the subsequent cytokine secretion were greater in the monocytes from the active pulmonary TB patients than in monocytes from the healthy controls. Additionally, neutralizing antibodies for Toll-like receptor 2 (TLR2) or TLR4 significantly reduced the ERK1/2 and p38 activation induced by the 38-kDa protein when the antibodies were applied to HEK293 cells overexpressing TLR2 or TLR4 as well as human primary monocytes. Furthermore, the inhibition of TLR2 significantly, and that of TLR4 partially, decreased the 38-kDa Ag-induced secretion of TNF-α and IL-6 in human monocytes. The intact protein moieties of the 38-kDa protein were responsible for biologic activities by this Ag. These data collectively demonstrate that the 38-kDa glycolipoprotein, acting through both TLR2 and TLR4, induces the activation of the ERK1/2 and p38 MAPK pathways, which in turn play an essential role in TNF-α and IL-6 expression during mycobacterial infection.

Role of mitogen-activated protein kinase pathways in the production of tumor necrosis factor-alpha, interleukin-10, and monocyte chemotactic protein-1 by Mycobacterium tuberculosis H37Rv-infected human monocytes.

The role of mitogen-activated protein kinase (MAPK) pathways in the secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-8, and monocyte chemotactic protein-1 (MCP-1) was investigated in human monocytes that were infected with Mycobacterium tuberculosis H37Rv. Analysis of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 kinase showed rapid phosphorylation of both subfamilies in response to M. tuberculosis H37Rv. Using highly specific inhibitors of p38 (SB203580) and of MAPK kinase-1 (U0126 and PD98059), we found that both p38 and ERK were essential for M. tuberculosis H37Rv-induced TNF-α production, whereas activation of the p38 pathway, but not that of ERK, was essential for M. tuberculosis H37Rv-induced IL-10 production. Interestingly, the ERK pathway, but not that of p38, was critical for MCP-1 secretion from human monocytes that were infected with M. tuberculosis H37Rv. However, IL-8 secretion was not regulated by ERK1/2 or p38 MAPK. Collectively, these results suggest that induction of the MAPK pathway is required for the expression of TNF-α, IL-10, and MCP-1 by human monocytes during M. tuberculosis H37Rv infection.

Intracellular network of phosphatidylinositol 3-kinase, mammalian target of the rapamycin/70 kDa ribosomal S6 kinase 1, and mitogen-activated protein kinases pathways for regulating mycobacteria-induced IL-23 expression in human macrophages.

We previously demonstrated that Mycobacterium tuberculosis (M. tbc)‐induced interleukin (IL)‐12 expression is negatively regulated by the phosphatidylinositol 3‐kinase (PI3K) and extracellular signal‐regulated kinase (ERK) 1/2 pathways in human monocyte‐derived macrophages (MDMs). To extend these studies, we examined the nature of the involvement of toll‐like receptors (TLRs) and intracellular signalling pathways downstream from PI3K in M. tbc‐induced IL‐23 expression in human MDMs. M. tbc‐induced Akt activation and IL‐23 expression were essentially dependent on TLR2. Blockade of the mammalian targets of rapamycin (mTOR)/70 kDa ribosomal S6 kinase 1 (S6K1) pathway by the specific inhibitor rapamycin greatly enhanced M. tbc‐induced IL‐12/IL‐23 p40 (p40) and IL‐23 p19 (p19) mRNA and IL‐23 protein expression. In sharp contrast, p38 mitogen‐activated protein kinase (MAPK) inhibition abrogated the p40 and p19 mRNA and IL‐23 protein expression induced by M. tbc. Furthermore, the inhibition of PI3K‐Akt, but not ERK 1/2 pathway, attenuated M. tbc‐induced S6K1 phosphorylation, whereas PI3K inhibition enhanced p38 phosphorylation and apoptosis signal‐regulating kinase 1 activity during exposure to M. tbc. Although the negative or positive regulation of IL‐23 was not reversed by neutralization of IL‐10, it was significantly modulated by blocking TLR2. Collectively, these findings provide new insight into the homeostatic mechanism controlling type 1 immune responses during mycobacterial infection involving the intracellular network of PI3K, S6K1, ERK 1/2 and p38 MAPK pathways in a TLR2‐dependent manner.

Endoplasmic reticulum stress response is involved in Mycobacterium tuberculosis protein ESAT‐6‐mediated apoptosis

Mycobacterium tuberculosis (Mtb) infection leads to the induction of the apoptotic response, which is associated with bacilli killing. The early secreted mycobacterial antigen ESAT‐6 of Mtb has been shown to induce apoptosis in human macrophages and epithelial cells. In the present study, we demonstrate that the stimulation of human epithelial A549 cells by ESAT‐6 induces the endoplasmic reticulum (ER) stress response. We observed that ESAT‐6 treatment increases intracellular Ca2+ concentration, which results in ROS accumulation, and therefore induces the onset of ER stress‐induced apoptosis. Our results uncover a novel apoptotic mechanism of ESAT‐6 through ER stress responses in pathologic conditions such as tuberculosis.

Depressed Interleukin-12 (IL-12), but not IL-18, Production in Response to a 30- or 32-Kilodalton Mycobacterial Antigen in Patients with Active Pulmonary Tuberculosis

ABSTRACT The secreted 30-kDa antigen (Ag) of Mycobacterium tuberculosis directly stimulates Th1-type protective cytokine responses in healthy tuberculin reactors but not in patients with active tuberculosis (TB). To examine the cytokine profiles attributable to Th1 suppression associated with active TB, interleukin-12 (IL-12), IL-18, and IL-10 production in response to a 30- or 32-kDa Ag in 16 patients with active pulmonary TB and 24 healthy controls was investigated by enzyme-linked immunosorbent assay. In TB patients, production of IL-12 p40, as well as gamma interferon (IFN-γ), by 30- or 32-kDa Ag-stimulated peripheral blood mononuclear cells (PBMC) was significantly decreased compared with that in healthy tuberculin reactors. There were no significant differences in IL-18 production between patients and controls early during stimulation (16 h). However, PBMC from patients showed significantly enhanced IL-18 proteins after 96 h of stimulation. Similarly, higher IL-10 production was observed in the TB patients than in healthy tuberculin reactors. After 2 months of anti-TB therapy, the mean IFN-γ and IL-12 p40 production and the mean blastogenic responses were significantly increased in PBMC in the 10 TB patients who were followed up. Our findings provide evidence that depressed IL-12 in response to the 30- or 32-kDa Ag is involved in the immunopathogenesis of human active pulmonary TB.

Polymorphisms of interleukin-10 and tumour necrosis factor-alpha genes are associated with newly diagnosed and recurrent pulmonary tuberculosis.

Background and objectives:  The genetic determinants for developing TB or having recurrent TB are unknown. The present study investigated the relationship between susceptibility to tuberculosis and human tumour necrosis factor‐α (TNF‐α) and interleukin‐10 genes (IL‐10).

Protein kinase C zeta plays an essential role for Mycobacterium tuberculosis-induced extracellular signal-regulated kinase 1/2 activation in monocytes/macrophages via Toll-like receptor 2.

This study characterized the upstream signalling molecules involved in extracellular signal‐regulated kinase (ERK) 1/2 activation and determined their effects on differential tumour necrosis factor (TNF)‐α expression by monocytes/macrophages infected with virulent or avirulent mycobacteria. The avirulent Mycobacterium tuberculosis (MTB) strain H37Ra (MTBRa) induced higher levels of activation of ERK 1/2 and the upstream MAPK kinase (MEK)1 and, subsequently, higher levels of TNF‐α expression in human primary monocytes and monocyte‐derived macrophages, as compared with MTB strain H37Rv (MTBRv). The MTB‐induced activation of ERK 1/2 was not dependent on Ras or Raf. However, inhibition of the activity of atypical protein kinase C (PKC) ζ decreased the in vitro phosphorylation of MEK, ERK 1/2 activation and subsequent TNF‐α induction caused by MTBRv or MTBRa. Toll‐like receptor (TLR) 2 was found to play a major role in MTB‐induced TNF‐α expression and PKCζ phosphorylation. Co‐immunoprecipitation experiments showed that PKCζ interacts physically with TLR2 after MTB stimulation. Moreover, PKCζ phosphorylation was increased more in macrophages following MTBRa, versus MTBRv, infection. This is the first demonstration that PKCζ interacts with TLR2 to play an essential role in MTB‐induced ERK 1/2 activation and subsequent TNF‐α expression in monocytes/macrophages.