Selective Expression of the MAPK Phosphatase Dusp9/MKP-4 in Mouse Plasmacytoid Dendritic Cells and Regulation of IFN-β Production

Methionine- and Choline-Deficient Diet Identifies an Essential Role for DNA Methylation in Plasmacytoid Dendritic Cell Biology

Diet plays an important role in lifestyle disorders associated with the disturbed immune system. During the study of methionine- and choline-deficient diet-induced nonalcoholic fatty liver disease, we observed a specific decrease in the plasmacytoid dendritic cell (pDC) fraction from murine spleens. While delineating the role for individual components, we identified that l-methionine supplementation correlates with representation of the pDC fraction. S-adenosylmethionine (SAM) is a key methyl donor, and we demonstrate that supplementation of methionine-deficient medium with SAM but not homocysteine reverses the defect in pDC development. l-Methionine has been implicated in maintenance of methylation status in the cell. Based on our observed effect of SAM and zebularine on DC subset development, we sought to clarify the role of DNA methylation in pDC biology. Whole-genome bisulfite sequencing analysis from the splenic DC subsets identified that pDCs display differentially hypermethylated regions in comparison with classical DC (cDC) subsets, whereas cDC1 and cDC2 exhibited comparable methylated regions, serving as a control in our study. We validated differentially methylated regions in the sorted pDC, CD8α⁺ cDC1, and CD4⁺ cDC2 subsets from spleens as well as FL-BMDC cultures. Upon analysis of genes linked with differentially methylated regions, we identified that differential DNA methylation is associated with the MAPK pathway such that its inhibition guides DC development toward the pDC subtype. Overall, our study identifies an important role for methionine in pDC biology.

Prolonged high-intensity exercise induces fluctuating immune responses to herpes simplex virus infection via glucocorticoids

BACKGROUND

Epidemiologic studies have yielded conflicting results regarding the influence of a single bout of prolonged high-intensity exercise on viral infection.

OBJECTIVE

We sought to learn whether prolonged high-intensity exercise either exacerbates or ameliorates herpes simplex virus type 2 (HSV-2) infection according to the interval between virus exposure and exercise.

METHODS

Mice were intravaginally infected with HSV-2 and exposed to run on the treadmill.

RESULTS

Prolonged high-intensity exercise 17 hours after infection impaired the clearance of HSV-2, while exercise 8 hours after infection enhanced the clearance of HSV-2. These impaired or enhanced immune responses were related to a transient decrease or increase in the number of blood-circulating plasmacytoid dendritic cells. Exercise-induced glucocorticoids transiently decreased the number of circulating plasmacytoid dendritic cells by facilitating their homing to the bone marrow via the CXCL12-CXCR4 axis, which led to their subsequent increase in the blood.

CONCLUSION

A single bout of prolonged high-intensity exercise can be either deleterious or beneficial to antiviral immunity.

EEF1A2 and ERN2 could potentially discriminate metastatic status of mediastinal lymph node in lung adenocarcinomas harboring EGFR 19Del/L858R mutations

Background

Early data has indicated that EGFR 19Del mutation and EGFR L585R mutation are two different types of non‐small cell lung cancer (NSCLC). However, how the different molecular mechanisms participate in the process of mediastinal lymph node metastasis (MLNM) in lung adenocarcinoma (LA) harboring EGFR 19Del and EGFR L858R mutation remains unknown. We thus explored the genes responsible for MLNM in LA with EGFR 19Del or L858R mutation.

Methods

We performed transcriptome sequencing and bioinformatics analysis from 10 patients with LA resection specimens of primary tumors. Quantitative reverse transcription‐polymerase chain reaction was used to validate gene expressions.

Results

There were 69 mRNAs upregulated and 100 mRNAs downregulated in five samples with MLNM compared with samples without MLN metastasis. EEF1A2 and ERN2 were observed exhibiting different expression patterns in EGFR 19Del and EGFR L858R samples with MLNM. In samples harboring EGFR 19Del mutation, the expression of EEF1A2 gene in samples with MLNM was significantly lower compared with samples without MLN metastasis, and in samples with EGFR L858R, it was significantly higher in samples with MLNM. The expression pattern of ERN2 was opposite to EEF1A2. In addition, several other genes including SLC6A11, IGHV3‐48, IGHV3‐43, DUSP9, and HOXA9 were also shown to be associated with invasion and metastasis and exhibited an expression pattern similar to EEF1A2 and ERN2 in EGRF 19Del and L858R mutation tumors.

Conclusions

EEF1A2 and ERN2 were for the first time observed exhibiting distinct expression patterns in MLNM in lung adenocarcinomas harboring EGFR 19Del and EGFR L858R mutation by interindividual DEGs analysis.

Key points

Significant findings of the study

In our study, we focused on the mechanisms of metastasis and invasion that different EGFR mutations conferred and identified two critical genes separately involved in this process in EGFR 19Del and L858R mutation tumors.

What this study adds

Our findings not only reinforced theoretical foundations that the EGFR 19Del and L858R mutation tumors should be considered as two kinds of diseases, but also laid the fundamentals for precise determination of the mediastinal lymph node radiation field and improvement of clinical outcome.

Dual-Specificity Phosphatases in Immunity and Infection: An Update

Kinase activation and phosphorylation cascades are key to initiate immune cell activation in response to recognition of antigen and sensing of microbial danger. However, for balanced and controlled immune responses, the intensity and duration of phospho-signaling has to be regulated. The dual-specificity phosphatase (DUSP) gene family has many members that are differentially expressed in resting and activated immune cells. Here, we review the progress made in the field of DUSP gene function in regulation of the immune system during the last decade. Studies in knockout mice have confirmed the essential functions of several DUSP-MAPK phosphatases (DUSP-MKP) in controlling inflammatory and anti-microbial immune responses and support the concept that individual DUSP-MKP shape and determine the outcome of innate immune responses due to context-dependent expression and selective inhibition of different mitogen-activated protein kinases (MAPK). In addition to the canonical DUSP-MKP, several small-size atypical DUSP proteins regulate immune cells and are therefore also reviewed here. Unexpected and complex findings in DUSP knockout mice pose new questions regarding cell type-specific and redundant functions. Another emerging question concerns the interaction of DUSP-MKP with non-MAPK binding partners and substrate proteins. Finally, the pharmacological targeting of DUSPs is desirable to modulate immune and inflammatory responses.

Regulation of p38MAPK-mediated dendritic cell functions by the deubiquitylase otubain 1

Dendritic cells (DCs) are professional antigen presenting cells (APCs) that represent the essential link between innate and acquired immunity. Otubain (OTUB) 1 is shown to deubiquitinate TRAFs to suppress virus-induced inflammatory response. MAPK, a downstream molecule of TRAFs, is involved in regulating LPS-induced immune reactions and its activation is sensitive to the presence of OTUB1. Little is known about contributions of OTUB1 to changes in biological properties of DCs. The present study, therefore, explored whether DC functions are influenced by OTUB1. To this end, DCs were isolated and cultured with GM-CSF to attain bone marrow-derived DCs (BMDCs) and followed by treatment with lipopolysaccharide (LPS) in the presence or absence of OTUB1 siRNA. Expression of markers of cellular maturation and proliferation were analyzed by flow cytometry, and secretion of inflammatory cytokines and ability to stimulate CD4⁺ T-cells in allogenic mixed leukocyte reaction (allo-MLR) by ELISA, cell migration by a transwell migration assay and phagocytic capacity by FITC-dextran uptake measurement. As a result, treatment of the cells with OTUB1 siRNA prolonged activation of p38MAPK, increased CD54 expression and IL-6 release and reduced FITC-dextran uptake. Moreover, cytokine release produced from CD4⁺ T-cells in allo-MLR was different. The enhanced level of IFN-γ, but not other cytokine production was observed in the presence of siRNA OTUB1. All the effects were completely abolished when the cells were exposed with p38MAPK inhibitor SB203580. In conclusion, OTUB1 prevents the prolonged activation of p38MAPK, which in turn compromises DC functions.

Dual-specificity MAP kinase phosphatases in health and disease

It is well established that a family of dual-specificity MAP kinase phosphatases (MKPs) play key roles in the regulated dephosphorylation and inactivation of MAP kinase isoforms in mammalian cells and tissues. MKPs provide a mechanism of spatiotemporal feedback control of these key signalling pathways, but can also mediate crosstalk between distinct MAP kinase cascades and facilitate interactions between MAP kinase pathways and other key signalling modules. As our knowledge of the regulation, substrate specificity and catalytic mechanisms of MKPs has matured, more recent work using genetic models has revealed key physiological functions for MKPs and also uncovered potentially important roles in regulating the pathophysiological outcome of signalling with relevance to human diseases. These include cancer, diabetes, inflammatory and neurodegenerative disorders. It is hoped that this understanding will reveal novel therapeutic targets and biomarkers for disease, thus contributing to more effective diagnosis and treatment for these debilitating and often fatal conditions.

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A comprehensive review of the dual-specificity MAP kinase Phosphatases (MKPs)

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Focus is on MKPs in the regulation of MAPK signalling in health and disease.

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Covers roles of MKPs in inflammation, obesity/diabetes, cancer and neurodegeneration

Functional Impairment of Murine Dendritic Cell Subsets following Infection with Infective Larval Stage 3 of Brugia malayi

Filarial parasites cause functional impairment of host dendritic cells (DCs). However, the effects of early infection on individual DC subsets are not known. In this study, we infected BALB/c mice with infective stage 3 larvae of the lymphatic filarial parasite Brugia malayi (Bm-L3) and studied the effect on fluorescence-activated cell sorter (FACS)-sorted DC subsets. While myeloid DCs (mDCs) accumulated by day 3 postinfection (p.i.), lymphoid DCs (LDCs) and CD8⁺ plasmacytoid DCs (pDCs) peaked at day 7 p.i. in the spleens and mesenteric lymph nodes (mLNs) of infected mice. Increased tumor necrosis factor alpha (TNF-α) but reduced interleukin 12 (IL-12) and Toll-like receptor 4 (TLR4), -6, and -9 and reciprocal secretion of IL-4 and IL-10 were also observed across all DC subsets. Interestingly, Bm-L3 increased the expression of CD80 and CD86 across all DC subsets but decreased that of major histocompatibility complex class II (MHC-II) on mDCs and pDCs, resulting in their impaired antigen uptake and presentation capacities, but maximally attenuated the T-cell proliferation capacity of only mDCs. Furthermore, Bm-L3 increased phosphorylated p38 (p-p38), but not p-ERK, in mDCs and LDCs but downregulated them in pDCs, along with differential modulation of protein tyrosine phosphatases SHP-1, TCPTP, PTEN, and PTP1B across all DC subsets. Taken together, we report hitherto undocumented effects of early Bm-L3 infection on purified host DC subsets that lead to their functional impairment and attenuated host T-cell response.

l-arginine and docetaxel synergistically enhance anti-tumor immunity by modifying the immune status of tumor-bearing mice

l-arginine (l-Arg) supplementation has been reported to enhance the function of immune cells, including dendritic cells (DCs) and T lymphocytes, in cancer models thereby countering the suppressive effects of myeloid-derived suppressor cells (MDSCs). The balance of the active immune cells is one factor that determines the progression of cancers in vivo. Docetaxel (DTX), an immunomodulatory chemotherapeutic agent, is now widely used in several types of malignancies including breast cancer. We hypothesized that the combination of DTX and l-Arg would elicit a more robust antitumor response than either molecule alone. To test this hypothesis we utilized BALB/c mice inoculated with 4T1 mammary carcinoma cells. DTX and l-Arg synergistically limited tumor growth in vivo and moderately increased the life span of tumor bearing mice. The anti-tumor effects were associated with the proliferation of splenic CD8(+) CTL and CD4(+) Th1 effector cells, as well as increased serum levels of interferon gamma. More importantly, DTX+l-Arg effectively increased anti-tumor immunity within the tumor microenvironment. Furthermore, the combined therapy increased the number of myeloid (mDCs) and plasmacytoid (pDCs) dendritic cells, potent activators of the T cell response, and enhanced expression of the maturation markers CD86 and MHC II (required for antigen presentation). The combination therapy also reduced the proliferation of MDSCs. These data suggest that DTX+l-Arg may be a novel therapeutic strategy for breast cancer patients.