Proviral integration site for Moloney murine leukemia virus 1, but not phosphatidylinositol-3 kinase, is essential in the antiapoptotic signaling cascade initiated by IL-5 in eosinophils

Syntaxin-4 and SNAP23 are involved in neutrophil degranulation, but not in the release of mitochondrial DNA during NET formation

Neutrophils are a specialized subset of white blood cells, which have the ability to store pre-formed mediators in their cytoplasmic granules. Neutrophils are well-known effector cells involved in host protection against pathogens through diverse mechanisms such as phagocytosis, degranulation, extracellular traps, and oxidative burst. In this study, we provide evidence highlighting the significance of the SNARE proteins syntaxin-4 and synaptosomal-associated protein (SNAP) 23 in the release of azurophilic granules, specific granules, and the production of reactive oxygen species in human neutrophils. In contrast, the specific blockade of either syntaxin-4 or SNAP23 did not prevent the release of mitochondrial dsDNA in the process of neutrophil extracellular trap (NET) formation. These findings imply that degranulation and the release of mitochondrial dsDNA involve at least partially distinct molecular pathways in neutrophils.

Ventilagolin Suppresses Migration, Invasion and Epithelial-Mesenchymal Transition of Hepatocellular Carcinoma Cells by Downregulating Pim-1

Objective

Inhibition of tumor metastasis is a useful strategy to improve the efficacy of cancer therapy. Ventilagolin, a natural 1, 4-naphthoquinone derivative extracted from Ventilago leiocarpa Benth, has shown promising antitumor effects in previous studies. However, the effects and underlying mechanisms of Ventilagolin against migration, invasion and epithelial-mesenchymal transition (EMT) of hepatocellular carcinoma (HCC) remain unclear. The present study has examined these effects and determined whether the proto-oncogene Pim-1 is involved.

Methods

The effects of Ventilagolin on migration, invasion, Pim-1 and EMT-related proteins (eg, E-cadherin, N-cadherin, Vimentin) expression were assessed by scratch wound healing, Transwell, qRT-PCR and Western blot assays, respectively. Pim-1 stably overexpressed HepG2 and SMMC-7721 cells were generated to explore whether Ventilagolin inhibited migration, invasion and EMT of HCC cells via regulating Pim-1. Subcutaneous xenograft tumor model in nude mice was established. Histopathological changes of tumor tissues were examined by H&E staining and expressions of Pim-1 and EMT-related proteins were detected by immunohistochemistry.

Results

Ventilagolin significantly (P < 0.01) reduced the expression of Pim-1 levels in HepG2 and SMMC-7721 cells. Compared with the control group, the migration and invasion abilities of Pim-1-overexpressing HepG2 and SMMC-7721 cells were significantly (P < 0.05, P < 0.01) enhanced, the expression of E-cadherin was decreased (P < 0.01), and the levels of N-cadherin and Vimentin were upregulated (P < 0.05, P < 0.01). Ventilagolin treatment effectively reversed these effects of Pim-1 overexpression. In vivo experiments showed that Ventilagolin could effectively suppress HCC tumor growth, downregulate Pim-1, N-cadherin and Vimentin expression, and upregulate E-cadherin expression.

Conclusion

Ventilagolin suppresses HCC cell proliferation, migration and invasion and reverses EMT process by downregulating Pim-1, suggesting Ventilagolin is a potential therapeutic agent for treatment of HCC.

Spectrum of T-lymphocyte activities regulating allergic lung inflammation

Despite advances in the treatment of asthma, optimization of symptom control remains an unmet need in many patients. These patients, labeled severe asthma, are responsible for a substantial fraction of the disease burden. In these patients, research is needed to define the cellular and molecular pathways contributing to disease which in large part are refractory to corticosteroid treatment. The causes of steroid-resistant asthma are multifactorial and result from complex interactions of genetics, environmental factors, and innate and adaptive immunity. Adaptive immunity, addressed here, integrates the activities of distinct T-cell subsets and by definition is dynamic and responsive to an ever-changing environment and the influences of epigenetic modifications. These T-cell subsets exhibit different susceptibilities to the actions of corticosteroids and, in some, corticosteroids enhance their functional activation. Moreover, these subsets are not fixed in lineage differentiation but can undergo transcriptional reprogramming in a bidirectional manner between protective and pathogenic effector states. Together, these factors contribute to asthma heterogeneity between patients but also in the same patient at different stages of their disease. Only by carefully defining mechanistic pathways, delineating their sensitivity to corticosteroids, and determining the balance between regulatory and effector pathways will precision medicine become a reality with selective and effective application of targeted therapies.

Eosinophil resistance to glucocorticoid-induced apoptosis is mediated by the transcription factor NFIL3

The mainstay of asthma therapy, glucocorticoids (GCs) exert their therapeutic effects through the inhibition of inflammatory signaling and induction of eosinophil apoptosis. However, laboratory and clinical observations of GC-resistant asthma suggest that GCs' effects on eosinophil viability may depend on the state of eosinophil activation. In the present study we demonstrate that eosinophils stimulated with IL-5 show impaired pro-apoptotic response to GCs. We sought to determine the contribution of GC-mediated transactivating (TA) and transrepressing (TR) pathways in modulation of activated eosinophils' response to GC by comparing their response to the selective GC receptor (GR) agonist Compound A (CpdA) devoid of TA activity to that upon treatment with Dexamethasone (Dex). IL-5-activated eosinophils showed contrasting responses to CpdA and Dex, as IL-5-treated eosinophils showed no increase in apoptosis compared to cells treated with Dex alone, while CpdA elicited an apoptotic response regardless of IL-5 stimulation. Proteomic analysis revealed that both Nuclear Factor IL-3 (NFIL3) and Map Kinase Phosphatase 1 (MKP1) were inducible by IL-5 and enhanced by Dex; however, CpdA had no effect on NFIL3 and MKP1 expression. We found that inhibiting NFIL3 with specific siRNA or by blocking the IL-5-inducible Pim-1 kinase abrogated the protective effect of IL-5 on Dex-induced apoptosis, indicating crosstalk between IL-5 anti-apoptotic pathways and GR-mediated TA signaling occurring via the NFIL3 molecule. Collectively, these results indicate that (1) GCs' TA pathway may support eosinophil viability in IL-5-stimulated cells through synergistic upregulation of NFIL3; and (2) functional inhibition of IL-5 signaling (anti-Pim1) or the use of selective GR agonists that don't upregulate NFIL3 may be effective strategies for the restoring pro-apoptotic effect of GCs on IL-5-activated eosinophils.

Pim1 kinase activity preserves airway epithelial integrity upon house dust mite exposure

Most patients with allergic asthma are sensitized to house dust mite (HDM). The allergenicity of HDM largely depends on disruption of the integrity and proinflammatory activation of the airway epithelium. In this study, we hypothesized that Pim1 kinase activity attenuates HDM-induced asthma by preserving airway epithelial integrity. The effects of Pim1 kinase activity on barrier function and release of the proinflammatory mediators IL-1α and CCL20 were studied in vitro in 16HBE and primary bronchial epithelial cells (PBECs). Pim1-proficient and -deficient mice were exposed to a HDM-driven model of allergic asthma, and airway hyperresponsiveness (AHR) was measured upon methacholine challenge. Airway inflammation and proinflammatory mediators in lung tissue and BAL fluid were determined. We observed that inhibition of Pim1 kinase prolongs the HDM-induced loss of barrier function in 16HBE cells and sensitizes PBECs to HDM-induced barrier dysfunction. Additionally, inhibition of Pim1 kinase increased the HDM-induced proinflammatory activity of 16HBE cells as measured by IL-1α secretion. In line herewith, HDM exposure induced an enhanced production of the proinflammatory chemokines CCL17 and CCL20 in Pim1-deficient mice compared with wild-type controls. While we observed a marked increase in eosinophilic and neutrophilic granulocytes as well as mucus cell metaplasia and AHR to methacholine in mice exposed to HDM, these parameters were independent of Pim1 kinase activity. In contrast, levels of the Th2-cytokines IL-5 and IL-10 were significantly augmented in HDM-treated Pim1-deficient mice. Taken together, our study shows that Pim1 kinase activity maintains airway epithelial integrity and protects against HDM-induced proinflammatory activation of the airway epithelium.

Determinants of eosinophil survival and apoptotic cell death

Eosinophils (Eos) are potent inflammatory cells and abundantly present in the sputum and lung of patients with allergic asthma. During both transit to and residence in the lung, Eos contact prosurvival cytokines, particularly IL-3, IL-5 and GM-CSF, that attenuate cell death. Cytokine signaling modulates the expression and function of a number of intracellular pro- and anti-apoptotic molecules. Both intrinsic mitochondrial and extrinsic receptor-mediated pathways are affected. This article discusses the fundamental role of the extracellular and intracellular molecules that initiate and control survival decisions by human Eos and highlights the role of the cis-trans isomerase, Pin1 in controlling these processes.

Cholesterol selectively regulates IL-5 induced mitogen activated protein kinase signaling in human eosinophils

Eosinophils function contributes to human allergic and autoimmune diseases, many of which currently lack curative treatment. Development of more effective treatments for eosinophil-related diseases requires expanded understanding of eosinophil signaling and biology. Cell signaling requires integration of extracellular signals with intracellular responses, and is organized in part by cholesterol rich membrane microdomains (CRMMs), commonly referred to as lipid rafts. Formation of these organizational membrane domains is in turn dependent upon the amount of available cholesterol, which can fluctuate widely with a variety of disease states. We tested the hypothesis that manipulating membrane cholesterol content in primary human peripheral blood eosinophils (PBEos) would selectively alter signaling pathways that depend upon membrane-anchored signaling proteins localized within CRMMs (e.g., mitogen activated protein kinase [MAPK] pathway), while not affecting pathways that signal through soluble proteins, like the Janus Kinase/Signal Transducer and Activator of Transcription [JAK/STAT] pathway. Cholesterol levels were increased or decreased utilizing cholesterol-chelating methyl-β-cyclodextrin (MβCD), which can either extract membrane cholesterol or add exogenous membrane cholesterol depending on whether MβCD is preloaded with cholesterol. Human PBEos were pretreated with MβCD (cholesterol removal) or MβCD+Cholesterol (MβCD+Chol; cholesterol delivery); subsequent IL-5-stimulated signaling and physiological endpoints were assessed. MβCD reduced membrane cholesterol in PBEos, and attenuated an IL-5-stimulated p38 and extracellular-regulated kinase 1/2 phosphorylation (p-p38, p-ERK1/2), and an IL-5-dependent increase in interleukin-1β (IL-1β) mRNA levels. In contrast, MβCD+Chol treatment elevated PBEos membrane cholesterol levels and basal p-p38, but did not alter IL-5-stimulated phosphorylation of ERK1/2, STAT5, or STAT3. Furthermore, MβCD+Chol pretreatment attenuated an IL-5-induced increase in cell survival at 48 hours, measured as total cellular metabolism. The reduction in cell survival following cholesterol addition despite unaltered STAT phosphorylation contradicts the current dogma in which JAK/STAT activation is sufficient to promote eosinophil survival, and suggests an additional, unidentified mechanism critically regulates IL-5-mediated human PBEos survival.

Mechanism of Siglec-8-mediated cell death in IL-5-activated eosinophils: role for reactive oxygen species-enhanced MEK/ERK activation

BACKGROUND

Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is expressed on human eosinophils, where its ligation induces cell death. Paradoxically, Siglec-8-mediated cell death is markedly enhanced by the presence of the activation and survival factor IL-5 and becomes independent of caspase activity.

OBJECTIVE

In this report we investigate the mechanism of Siglec-8-mediated cell death in activated eosinophils.

METHODS

Human peripheral blood eosinophils were treated with agonistic anti-Siglec-8 antibody and IL-5, and cell death was determined by using flow cytometry and morphology. Phosphorylation of mitogen-activated protein kinase (MAPK) was determined by using phosphoLuminex, flow cytometry, and Western blotting. Reactive oxygen species (ROS) accumulation was determined by using dihydrorhodamine fluorescence.

RESULTS

Costimulation with anti-Siglec-8 and IL-5 significantly increased the rate and proportion of cell death by means of necrosis accompanied by granule release compared with that seen after stimulation with anti-Siglec-8 alone, in which apoptosis predominated. Together with the caspase-independent mode of cell death in costimulated cells, these findings suggest the activation of a specific and distinct biochemical pathway of cell death during anti-Siglec-8/IL-5 costimulation. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and MAPK-ERK kinase (MEK) 1 was significantly enhanced and sustained in costimulated cells compared with that seen in cells stimulated with IL-5 alone; anti-Siglec-8 alone did not cause ERK1/2 phosphorylation. MEK1 inhibitors blocked anti-Siglec-8/IL-5-induced cell death. ROS accumulation was induced by Siglec-8 ligation in a MEK-independent manner. In contrast, an ROS inhibitor prevented the anti-Siglec-8/IL-5-induced enhancement of ERK phosphorylation and cell death. Exogenous ROS mimicked stimulation by anti-Siglec-8 and was sufficient to induce enhanced cell death in IL-5-treated cells. Collectively, these data suggest that the enhancement of ERK phosphorylation is downstream of ROS generation.

CONCLUSIONS

In activated eosinophils ligation of Siglec-8 leads to ROS-dependent enhancement of IL-5-induced ERK phosphorylation, which results in a novel mode of biochemically regulated eosinophil cell death.

Living and dying for inflammation: neutrophils, eosinophils, basophils

Neutrophils, eosinophils, and basophils play essential roles during microbe-induced and sterile inflammation. The severity of such inflammatory processes is controlled, at least in part, by factors that regulate cell death and survival of granulocytes. In recent years, major progress has been made in understanding the molecular mechanisms of granulocyte cell death and in identifying novel damage- and pathogen-associated molecular patterns as well as regulatory cytokines impacting granulocyte viability. Furthermore, an increased interest in innate immunity has boosted our overall understanding of granulocyte biology. In this review, we describe and compare factors and mechanisms regulating neutrophil, eosinophil, and basophil lifespan. Because dysregulation of death pathways in granulocytes can contribute to inflammation-associated immunopathology, targeting granulocyte lifespan could be therapeutically promising.

Inhibition of Pim1 kinase activation attenuates allergen-induced airway hyperresponsiveness and inflammation

Pim kinases are a family of serine/threonine kinases whose activity can be induced by cytokines involved in allergy and asthma. These kinases play a role in cell survival and proliferation, but have not been examined, to the best of our knowledge, in the development of allergic disease. This study sought to determine the role of Pim1 kinase in the development of allergic airway responses. Mice were sensitized and challenged with antigen (primary challenge), or were sensitized, challenged, and rechallenged with allergen in a secondary model. To assess the role of Pim1 kinase, a small molecule inhibitor was administered orally after sensitization and during the challenge phase. Airway responsiveness to inhaled methacholine, airway and lung inflammation, cell composition, and cytokine concentrations were assessed. Lung Pim1 kinase concentrations were increased after ovalbumin sensitization and challenge. In the primary allergen challenge model, treatment with the Pim1 kinase inhibitor after sensitization and during airway challenges prevented the development of airway hyperresponsiveness, eosinophilic airway inflammation, and goblet cell metaplasia, and increased Th2 cytokine concentrations in bronchoalveolar fluid in a dose-dependent manner. These effects were also demonstrated after a secondary allergen challenge, where lung allergic disease was established before treatment. After treatment with the inhibitor, a significant reduction was evident in the number of CD4(+) and CD8(+) T cells and concentrations of cytokines in the airways. The inhibition of Pim1 kinase was effective in preventing the development of airway hyperresponsiveness, airway inflammation, and cytokine production in allergen-sensitized and allergen-challenged mice. These data identify the important role of Pim1 kinase in the full development of allergen-induced airway responses.

The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 modulates cytokine expression in macrophages via p50 nuclear factor κB inhibition, in a PI3K-independent mechanism

The Phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002 (LY2), has been previously reported to inhibit nuclear factor κB (NFκB) activity, in a PI3K-independent mechanism. The goals of the current research were to determine the specificity of LY2 regarding NFκB subunits, and to identify relevant modulation of cytokine expression in LPS-stimulated macrophages. We found that LY2 specifically diminished the level of p50, but not p65, NFκB in the nucleus of LPS-stimulated mouse RAW264.7 macrophages and human THP-1 monocytes. This activity of LY2 was mimicked by its PI3K-inert analog LY303511 (LY3), but not by another PI3K inhibitor - wortmannin. We further show that LY2 inhibited LPS-induced IL-10 expression by RAW264.7 macrophages, in a PI3K-independent mechanism. Moreover, using a deletion mutant of an IL-10 promoter reporter gene we demonstrate that the activity of the NFκB enhancer site at the IL-10 promoter is regulated by LY2 in a PI3K-independent manner. Finally, both LY2 and LY3 elevated TNFα production in the LPS tolerant state which is regulated by p50 NFκB homodimers, but not before tolerance development. The effects of LY2 and LY3 on p50 translocation and on cytokine production in LPS-stimulated macrophages are thus consistent with specific PI3K-independent inhibition of p50 NFκB homodimer activity by LY2.

Inflammation-associated autophagy-related programmed necrotic death of human neutrophils characterized by organelle fusion events

The most common form of neutrophil death, under both physiological and inflammatory conditions, is apoptosis. In this study, we report a novel form of programmed necrotic cell death, associated with cytoplasmic organelle fusion events, that occurs in neutrophils exposed to GM-CSF and other inflammatory cytokines upon ligation of CD44. Strikingly, this type of neutrophil death requires PI3K activation, a signaling event usually involved in cellular survival pathways. In the death pathway reported in this study, PI3K is required for the generation of reactive oxygen species, which somehow trigger the generation of large cytoplasmic vacuoles, generated by the fusion of CD44-containing endosomes with autophagosomes and secondary, but not primary, granules. Neutrophils demonstrating vacuolization undergo rapid cell death that depends on receptor-interacting protein 1 kinase activity and papain family protease(s), but not caspases, that are most likely activated and released, respectively, during or as a consequence of organelle fusion. Vacuolized neutrophils are present in infectious and autoimmune diseases under in vivo conditions. Moreover, isolated neutrophils from such patients are highly sensitive toward CD44-mediated PI3K activation, reactive oxygen species production, and cell death, suggesting that the newly described autophagy-related form of programmed neutrophil necrosis plays an important role in inflammatory responses.

Why target PIM1 for cancer diagnosis and treatment?

The highly conserved proto-oncogenic protein PIM1 is an unusual serine or threonine kinase, in part because it is constitutively active. Overexpression of PIM1 experimentally leads to tumor formation in mice, while complete knockout of the protein has no observable phenotype. It appears to contribute to cancer development in three major ways when it is overexpressed; by inhibiting apoptosis, by promoting cell proliferation and by promoting genomic instability. Expression in normal tissues is nearly undetectable. However, in hematopoietic malignancies and in a variety of solid tumors, increased PIM1 expression has been shown to correlate with the stage of disease. This characteristic suggests it can serve as a useful biomarker for cancer diagnosis and prognosis. Several specific and potent inhibitors of PIM1&#x2019;s kinase activity have also been shown to induce apoptotic death of cancer cells, to sensitize cancer cells to chemotherapy and to synergize with other anti-tumor agents, thus making it an attractive therapeutic target.

Analysis of microRNA transcriptome by deep sequencing of small RNA libraries of peripheral blood

Background

MicroRNAs are a class of small non-coding RNAs that regulate mRNA expression at the post - transcriptional level and thereby many fundamental biological processes. A number of methods, such as multiplex polymerase chain reaction, microarrays have been developed for profiling levels of known miRNAs. These methods lack the ability to identify novel miRNAs and accurately determine expression at a range of concentrations. Deep or massively parallel sequencing methods are providing suitable platforms for genome wide transcriptome analysis and have the ability to identify novel transcripts.

Results

The results of analysis of small RNA sequences obtained by Solexa technology of normal peripheral blood mononuclear cells, tumor cell lines K562 and HL60 are presented. In general K562 cells displayed overall low level of miRNA population and also low levels of DICER. Some of the highly expressed miRNAs in the leukocytes include several members of the let-7 family, miR-21, 103, 185, 191 and 320a. Comparison of the miRNA profiles of normal versus K562 or HL60 cells revealed a specific set of differentially expressed molecules. Correlation of the miRNA with that of mRNA expression profiles, obtained by microarray, revealed a set of target genes showing inverse correlation with miRNA levels. Relative expression levels of individual miRNAs belonging to a cluster were found to be highly variable. Our computational pipeline also predicted a number of novel miRNAs. Some of the predictions were validated by Real-time RT-PCR and or RNase protection assay. Organization of some of the novel miRNAs in human genome suggests that these may also be part of existing clusters or form new clusters.

Conclusions

We conclude that about 904 miRNAs are expressed in human leukocytes. Out of these 370 are novel miRNAs. We have identified miRNAs that are differentially regulated in normal PBMC with respect to cancer cells, K562 and HL60. Our results suggest that post - transcriptional processes may play a significant role in regulating levels of miRNAs in tumor cells. The study also provides a customized automated computation pipeline for miRNA profiling and identification of novel miRNAs; even those that are missed out by other existing pipelines. The Computational Pipeline is available at the website: http://mirna.jnu.ac.in/deep_sequencing/deep_sequencing.html