Regulation of neutrophil survival/apoptosis by Mcl-1

MNDA, a PYHIN factor involved in transcriptional regulation and apoptosis control in leukocytes

Inflammation control is critical during the innate immune response. Such response is triggered by the detection of molecules originating from pathogens or damaged host cells by pattern-recognition receptors (PRRs). PRRs subsequently initiate intra-cellular signalling through different pathways, resulting in i) the production of inflammatory cytokines, including type I interferon (IFN), and ii) the initiation of a cascade of events that promote both immediate host responses as well as adaptive immune responses. All human PYRIN and HIN-200 domains (PYHIN) protein family members were initially proposed to be PRRs, although this view has been challenged by reports that revealed their impact on other cellular mechanisms. Of relevance here, the human PYHIN factor myeloid nuclear differentiation antigen (MNDA) has recently been shown to directly control the transcription of genes encoding factors that regulate programmed cell death and inflammation. While MNDA is mainly found in the nucleus of leukocytes of both myeloid (neutrophils and monocytes) and lymphoid (B-cell) origin, its subcellular localization has been shown to be modulated in response to genotoxic agents that induce apoptosis and by bacterial constituents, mediators of inflammation. Prior studies have noted the importance of MNDA as a marker for certain forms of lymphoma, and as a clinical prognostic factor for hematopoietic diseases characterized by defective regulation of apoptosis. Abnormal expression of MNDA has also been associated with altered levels of cytokines and other inflammatory mediators. Refining our comprehension of the regulatory mechanisms governing the expression of MNDA and other PYHIN proteins, as well as enhancing our definition of their molecular functions, could significantly influence the management and treatment strategies of numerous human diseases. Here, we review the current state of knowledge regarding PYHIN proteins and their role in innate and adaptive immune responses. Emphasis will be placed on the regulation, function, and relevance of MNDA expression in the control of gene transcription and RNA stability during cell death and inflammation.

Maresins as novel anti-inflammatory actors and putative therapeutic targets in sepsis

Sepsis, a complex clinical syndrome characterized by an exaggerated host response to infection, often necessitates hospitalization and intensive care unit admission. Delayed or inaccurate diagnosis of sepsis, coupled with suboptimal treatment strategies, can result in unfavorable outcomes, including mortality. Maresins, a newly discovered family of lipid mediators synthesized from docosahexaenoic acid by macrophages, have emerged as key players in promoting inflammation resolution and the termination of inflammatory processes. Extensive evidence has unequivocally demonstrated the beneficial effects of maresins in modulating the inflammatory response associated with sepsis; however, their bioactivity and functions exhibit remarkable diversity and complexity. This article presents a comprehensive review of recent research on the role of maresins in sepsis, aiming to enhance our understanding of their effectiveness and elucidate the specific mechanisms underlying their actions in sepsis treatment. Furthermore, emerging insights into the management of patients with sepsis are also highlighted.

Complexation of fungal extracellular nucleic acids by host LL-37 peptide shapes neutrophil response to Candida albicans biofilm

Candida albicans remains the predominant cause of fungal infections, where adhered microbial cells form biofilms - densely packed communities. The central feature of C. albicans biofilms is the production of an extracellular matrix (ECM) consisting of polymers and extracellular nucleic acids (eDNA, eRNA), which significantly impedes the infiltration of host cells. Neutrophils, as crucial players in the innate host defense, employ several mechanisms to eradicate the fungal infection, including NETosis, endocytosis, or the release of granules containing, among others, antimicrobial peptides (AMPs). The main representative of these is the positively charged peptide LL-37 formed from an inactive precursor (hCAP18). In addition to its antimicrobial functions, this peptide possesses a propensity to interact with negatively charged molecules, including nucleic acids. Our in vitro studies have demonstrated that LL-37 contacting with C. albicans nucleic acids, isolated from biofilm, are complexed by the peptide and its shorter derivatives, as confirmed by electrophoretic mobility shift assays. We indicated that the generation of the complexes induces discernible alterations in the neutrophil response to fungal nucleic acids compared to the effects of unconjugated molecules. Our analyses involving fluorescence microscopy, flow cytometry, and Western blotting revealed that stimulation of neutrophils with DNA:LL-37 or RNA:LL-37 complexes hamper the activation of pro-apoptotic caspases 3 and 7 and fosters increased activation of anti-apoptotic pathways mediated by the Mcl-1 protein. Furthermore, the formation of complexes elicits a dual effect on neutrophil immune response. Firstly, they facilitate increased nucleic acid uptake, as evidenced by microscopic observations, and enhance the pro-inflammatory response, promoting IL-8 production. Secondly, the complexes detection suppresses the production of reactive oxygen species and attenuates NETosis activation. In conclusion, these findings may imply that the neutrophil immune response shifts toward mobilizing the immune system as a whole, rather than inactivating the pathogen locally. Our findings shed new light on the intricate interplay between the constituents of the C. albicans biofilm and the host's immune response and indicate possible reasons for the elimination of NETosis from the arsenal of the neutrophil response during contact with the fungal biofilm.

A variety of death modes of neutrophils and their role in the etiology of autoimmune diseases

Neutrophils are important in the context of innate immunity and actively contribute to the progression of diverse autoimmune disorders. Distinct death mechanisms of neutrophils may exhibit specific and pivotal roles in autoimmune diseases and disease pathogenesis through the orchestration of immune homeostasis, the facilitation of autoantibody production, the induction of tissue and organ damage, and the incitement of pathological alterations. In recent years, more studies have provided in-depth examination of various neutrophil death modes, revealing nuances that challenge conventional understanding and underscoring their potential clinical utility in diagnosis and treatment. This review explores the multifaceted processes and characteristics of neutrophil death, with a focus on tailored investigations within various autoimmune diseases. It also highlights the potential interplay between neutrophil death and the landscape of autoimmune disorders. The review encapsulates the pertinent pathways implicated in various neutrophil death mechanisms across diverse autoimmune diseases while also charts possible avenues for future research.

Blockade of Syk modulates neutrophil immune-responses via the mTOR/RUBCNL-dependent autophagy pathway to alleviate intestinal inflammation in ulcerative colitis

Background

Ulcerative colitis (UC) is a progressive chronic inflammatory disorder. Neutrophils play a critical role in regulating intestinal mucosal homeostasis in UC. Spleen tyrosine kinase (Syk) is involved in several inflammatory diseases. Here, we evaluated the effects and underlying mechanisms of Syk on neutrophil immune-responses in UC.

Methods

Syk expression in the colonic tissues of patients with UC was determined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry. Colonic biopsies from patients with UC were obtained for single-cell RNA-sequencing. Neutrophils isolated from peripheral blood were pre-treated with R788 (a Syk inhibitor) and gene differences were determined using RNA sequencing. Neutrophil functions were analyzed using qRT-PCR, flow cytometry, and Transwell assay. R788 was administered daily to mice with dextran sulfate sodium (DSS)-induced colitis to verify the effects of Syk on intestinal inflammation.

Results

Syk expression was increased in inflamed mucosa and neutrophils of patients with UC and positively correlated with disease activity. Pharmacological inhibition of Syk in neutrophils decreased the production of pro-inflammatory cytokines, chemokines, neutrophil extracellular traps, reactive oxygen species, and myeloperoxidase. Apoptosis and migration of neutrophils were suppressed by Syk blockade. Syk blockade ameliorated mucosal inflammation in DSS-induced murine colitis by inhibiting neutrophil-associated immune responses. Mechanistically, Syk regulated neutrophil immune-responses via the mammalian target of rapamycin kinase/rubicon-like autophagy enhancer-dependent autophagy pathway.

Conclusions

Our findings indicate that Syk facilitates specific neutrophil functional responses to mucosal inflammation in UC, and its inhibition ameliorates mucosal inflammation in DSS-induced murine colitis, suggesting its potential as a novel therapeutic target for UC treatment.

Jinhua Qinggan granules attenuates acute lung injury by promotion of neutrophil apoptosis and inhibition of TLR4/MyD88/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Acute lung injury (ALI) is one of the fatal complications of respiratory virus infections such as influenza virus and coronavirus, which has high clinical morbidity and mortality. Jinhua Qinggan granules (JHQG) has been approved by China Food and Drug Administration in the treatment of H1N1 influenza and mild or moderate novel coronavirus disease 2019 (COVID-19), which is an herbal formula developed based on Maxingshigan decoction and Yinqiao powder that have been used to respiratory diseases in China for thousands of years. However, the underlying mechanism of JHQG in treating infectious diseases remains unclear.

AIM OF THE STUDY

This study investigated the effects of JHQG on neutrophil apoptosis and key signaling pathways in lipopolysaccharide (LPS) -induced ALI mice in order to explore its mechanism of anti-inflammation.

MATERIALS AND METHODS

The effect of JHQG on survival rate was observed in septic mouse model by intraperitoneal injection of LPS (20 mg/kg). To better pharmacological evaluation, the mice received an intratracheal injection of 5 mg/kg LPS. Lung histopathological changes, wet-to-dry ratio of the lungs, and MPO activity in the lungs and total protein concentration, total cells number, TNF-α, IL-1β, IL-6, and MIP-2 levels in BALF were assessed. Neutrophil apoptosis rate was detected by Ly6G-APC/Annexin V-FITC staining. Key proteins associated with apoptosis including caspase 3/7 activity, Bcl-xL and Mcl-1 were measured by flow cytometry and confocal microscope, respectively. TLR4 receptor and its downstream signaling were analyzed by Western blot assay and immunofluorescence, respectively.

RESULTS

JHQG treatment at either 6 or 12 g/kg/day resulted in 20% increase of survival in 20 mg/kg LPS-induced mice. In the model of 5 mg/kg LPS-induced mice, JHQG obviously decreased the total protein concentration in BALF, wet-to-dry ratio of the lungs, and lung histological damage. It also attenuated the MPO activity and the proportion of Ly6G staining positive neutrophils in the lungs, as well as the MIP-2 levels in BALF were reduced. JHQG inhibited the expression of Mcl-1 and Bcl-xL and enhanced caspase-3/7 activity, indicating that JHQG partially acted in promoting neutrophil apoptosis via intrinsic mitochondrial apoptotic pathway. The levels of TNF-α, IL-1β, and IL-6 were significantly declined in LPS-induced mice treated with JHQG. Furthermore, JHQG reduced the protein expression of TLR4, MyD88, p-p65 and the proportion of nuclei p65, suggesting that JHQG treatment inhibited TLR4/MyD88/NF-κB pathway.

CONCLUSION

JHQG reduced pulmonary inflammation and protected mice from LPS-induced ALI by promoting neutrophil apoptosis and inhibition of TLR4/MyD88/NF-κB pathway, suggesting that JHQG may be a promising drug for treatment of ALI.

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

Stroke is among the leading causes of death and disability worldwide. Restoring blood flow through recanalization is currently the only acute treatment for cerebral ischemia. Unfortunately, many patients that achieve a complete recanalization fail to regain functional independence. Recent studies indicate that activation of peripheral immune cells, particularly neutrophils, may contribute to microcirculatory failure and futile recanalization. Stroke primarily affects the elderly population, and mortality after endovascular therapies is associated with advanced age. Previous analyses of differential gene expression across injury status and age identify ischemic stroke as a complex age-related disease. It also suggests robust interactions between stroke injury, aging, and inflammation on a cellular and molecular level. Understanding such interactions is crucial in developing effective protective treatments. The global stroke burden will continue to increase with a rapidly aging human population. Unfortunately, the mechanisms of age-dependent vulnerability are poorly defined. In this review, we will discuss how neutrophil-specific gene expression patterns may contribute to poor treatment responses in stroke patients. We will also discuss age-related transcriptional changes that may contribute to poor clinical outcomes and greater susceptibility to cerebrovascular diseases.

Maresin-1 and Its Receptors RORα/LGR6 as Potential Therapeutic Target for Respiratory Diseases

Maresin-1 is one of the representative specialized pro-resolving mediators that has shown beneficial effects in inflammatory disease models. Recently, two distinct types of receptor molecules were discovered as the targets of maresin-1, further revealing the pro-resolution mechanism of maresin-1. One is retinoic acid-related orphan receptor α (RORα) and the another one is leucine-rich repeat domain-containing G protein-coupled receptor 6 (LGR6). In this review, we summarized the detailed role of maresin-1 and its two different receptors in respiratory diseases. RORα and LGR6 are potential targets for the treatment of respiratory diseases. Future basic research and clinical trials on MaR1 and its receptors should provide useful information for the treatment of respiratory diseases.

The Role of Zinc in GM-CSF-Induced Signaling in Human Polymorphonuclear Leukocytes

SCOPE

Zinc is suggested to be necessary for functional signaling induced by certain growth factors. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key factor for differentiation and activation of myeloid cells. This report analyses the impact of different zinc concentrations on GM-CSF-induced signaling in mature polymorphonuclear leukocytes (PMN).

METHODS AND RESULTS

As measured by flow cytometry, zinc increases surface GM-CSF receptor (GM-CSFR) in PMN, whereas monocytes respond with decreased GM-CSFR surface expression. Since total cellular GM-CSFR expression remains unaffected, the observed zinc-induced GM-CSFR surface dynamics may be explained by receptor redistribution. In PMN, zinc enhanced phosphorylation of mitogen-activated protein kinases (MAPK) in a dose-dependent manner as found in western blot. Zinc-induced MAPK phosphorylation is additionally augmented by moderate GM-CSF stimulation.

CONCLUSION

The present study demonstrates the opposing influence of zinc on GM-CSFR surface expression in monocytes and PMN. Zinc and GM-CSF, use in optimized concentrations, augment MAPK signaling, and increase expression of MAPK-induced myeloid cell leukemia-1 (Mcl-1) in PMN. Thus, this study concludes that zinc strengthens growth factor-induced signaling. Hence, the study provides a basis for further in vivo studies, focusing on the therapeutic value of zinc in patients with a disturbed GM-CSF signaling.

Neutrophil Functional Heterogeneity and Implications for Viral Infections and Treatments

Evidence suggests that neutrophils exert specialized effector functions during infection and inflammation, and that these cells can affect the duration, severity, and outcome of the infection. These functions are related to variations in phenotypes that have implications in immunoregulation during viral infections. Although the complexity of the heterogeneity of neutrophils is still in the process of being uncovered, evidence indicates that they display phenotypes and functions that can assist in viral clearance or augment and amplify the immunopathology of viruses. Therefore, deciphering and understanding neutrophil subsets and their polarization in viral infections is of importance. In this review, the different phenotypes of neutrophils and the roles they play in viral infections are discussed. We also examine the possible ways to target neutrophil subsets during viral infections as potential anti-viral treatments.

Molecular Basis for Paradoxical Activities of Polymorphonuclear Neutrophils in Inflammation/Anti-Inflammation, Bactericide/Autoimmunity, Pro-Cancer/Anticancer, and Antiviral Infection/SARS-CoV-II-Induced Immunothrombotic Dysregulation

Polymorphonuclear neutrophils (PMNs) are the most abundant white blood cells in the circulation. These cells act as the fast and powerful defenders against environmental pathogenic microbes to protect the body. In addition, these innate inflammatory cells can produce a number of cytokines/chemokines/growth factors for actively participating in the immune network and immune homeostasis. Many novel biological functions including mitogen-induced cell-mediated cytotoxicity (MICC) and antibody-dependent cell-mediated cytotoxicity (ADCC), exocytosis of microvesicles (ectosomes and exosomes), trogocytosis (plasma membrane exchange) and release of neutrophil extracellular traps (NETs) have been successively discovered. Furthermore, recent investigations unveiled that PMNs act as a double-edged sword to exhibit paradoxical activities on pro-inflammation/anti-inflammation, antibacteria/autoimmunity, pro-cancer/anticancer, antiviral infection/COVID-19-induced immunothrombotic dysregulation. The NETs released from PMNs are believed to play a pivotal role in these paradoxical activities, especially in the cytokine storm and immunothrombotic dysregulation in the recent SARS-CoV-2 pandemic. In this review, we would like to discuss in detail the molecular basis for these strange activities of PMNs.

PI3K Isoforms in Cell Signalling and Innate Immune Cell Responses

Phosphoinositide-3-kinases (PI3Ks) are enzymes involved in signalling and modification of the function of all mammalian cells. These enzymes phosphorylate the 3-hydroxyl group of the inositol ring of phosphatidylinositol, resulting in lipid products that act as second messengers responsible for coordinating many cellular functions, including activation, chemotaxis, proliferation and survival. The identification of the functions that are mediated by a specific PI3K isoform is complex and depends on the specific cell type and inflammatory context. In this chapter we will focus on the role of PI3K isoforms in the context of innate immunity, focusing on the mechanisms by which PI3K signalling regulates phagocytosis, the activation of immunoglobulin, chemokine and cytokines receptors, production of ROS and cell migration, and how PI3K signalling plays a central role in host defence against infections and tissue injury.

Anti-inflammatory effect of traditional Chinese medicine preparation Penyanling on pelvic inflammatory disease

ETHNOPHARMACOLOGICAL RELEVANCE

Penyanling is made up of Smilacis Glabrae Rhizoma (SG, from Smilar glabra Roxb.), Angelicae Sinensis Radix (AS, from Angelica sinensis (Oliv.) Diels), Salviae Miltiorrhizae Radix et Rhizoma (SM, from Salvia miltiorrhiza Bunge), Sargentodoxae Caulis (SC, from Sargentodoxa cuneata (Oliv.) Rehd.et Wils.), Linderae Radix (LR, from Lindera aggregata (Sims) Kosterm.), Paeoniae Radix Rubra (PR, from Paeonia lactiflora Pall.), Sparganii Rhizoma (SR, from Sparganium stoloniferum (Graebn.) Buch.-Ham.), Corydalis Rhizoma (CoR, from Corydalis yanhusuo W. T. Wang), Cyperi Rhizoma (CyR, from Cyperus rotundus Linn.), Glycyrrhizae Radix et Rhizoma (GR, from Glycyrrhiza uralensis Fisch.), and Patrinia Scabiosaefolia (PS, from Patrinia scabiosaefolia Fisch. ex Trev.) recorded in Chinese Pharmacopoeia. It has been used on pelvic inflammatory disease (PID) for more than twenty years.

AIM OF THE STUDY

This study was carried out to illustrate its pharmacological action and clarify its substantial composition.

MATERIALS AND METHODS

The anti-inflammatory effects of Penyanling were studied on a PID rat model and a lipopolysaccharides (LPS)-stimulated THP-1 cell line. Histological changes and levels of inflammatory factors in the uterine tube of the PID rat were examined. Levels of nuclear factor-kappa B (NF-κB) in the nuclear of THP-1 cells and NF-κB, IκB-α, and FPR2 in the cytoplasm were tested by Western blot analysis. Substances within Penyanling were scanned with liquid chromatography-quadrupole-time of flight-mass spectrometry (LC-Q-TOF-MS). The contents of total flavonoids, phenolics, and saponins were quantified.

RESULTS

The anti-inflammatory effects of Penyanling were observed on PID rats, such as suppressing the infiltrations of lymphocytes and neutrophils in the uterine tube, decreasing the release of interleukin (IL)-1β, IL-6, IL-8, and monocyte chemotactic protein (MCP)-1, and promoting the production of lipoxin A₄ (LXA₄). On the other hand, Penyanling regulated the activity of NF-κB signal pathway on the LPS-stimulated THP-1 cell line, which suggested the potential mechanism of its anti-inflammatory effect. Besides, it could promote the expression of formyl peptide receptor 2 (FPR2), which suggested its effect on enhancing the resolution of inflammation. Seventy-six substances were identified by their accurate molecular weights, mass fragment patterns, retention times, and standards if available. Most of these substances were flavonoids, phenolics, saponins, and alkaloids. The contents of total flavonoids, phenolics, and saponins within Penyanling were 0.186, 1.371, and 4.321 mg/mL, respectively.

CONCLUSION

Penyanling showed an anti-inflammatory effect on PID, and its potential mechanism involved suppressing NF-κB signal pathway and promoting the resolution of inflammation. The main substances within it were flavonoids, phenolics, saponins, and alkaloids.

In Vitro and In Vivo Antitumor Activity of Cucurbitacin C, a Novel Natural Product From Cucumber

Cucurbitacin C (CuC), a novel analogue of triterpenoids cucurbitacins, confers a bitter taste in cucumber. Genes and signaling pathways responsive for biosynthesis of CuC have been identified in the recent years. In the present study, we explored the anti-cancer effects of CuC against human cancers in vitro and in vivo. CuC inhibited proliferation and clonogenic potential of multiple cancer cells in a dose-dependent manner. Low-dose CuC treatment induced cell cycle arrest at G1 or G2/M stage in different cancer lines, whereas high-dose treatment of CuC caused apoptosis in cancer cells. PI3K-Akt signaling pathway was found to be one of the major pathways involved in CuC-induced cell growth arrest and apoptosis by RNA-Seq and Western blotting. Mechanistic dissection further confirmed that CuC effectively inhibited the Akt signaling by inhibition of Akt phosphorylation at Ser473. In vivo CuC treatment (0.1 mg/kg body weight) effectively inhibited growth of cancer cell-derived xenograft tumors in athymic nude mice and caused significant apoptosis. Our findings for the first time demonstrated the potential therapeutic significance of CuC against human cancers.

Low human and murine Mcl-1 expression leads to a pro-apoptotic plaque phenotype enriched in giant-cells

The anti-apoptotic protein myeloid cell leukemia 1 (Mcl-1) plays an important role in survival and differentiation of leukocytes, more specifically of neutrophils. Here, we investigated the impact of myeloid Mcl-1 deletion in atherosclerosis. Western type diet fed LDL receptor-deficient mice were transplanted with either wild-type (WT) or LysMCre Mcl-1^fl/fl (Mcl-1^−/−) bone marrow. Mcl-1 myeloid deletion resulted in enhanced apoptosis and lipid accumulation in atherosclerotic plaques. In vitro, Mcl-1 deficient macrophages also showed increased lipid accumulation, resulting in increased sensitivity to lipid-induced cell death. However, plaque size, necrotic core and macrophage content were similar in Mcl-1^−/− compared to WT mice, most likely due to decreased circulating and plaque-residing neutrophils. Interestingly, Mcl-1^−/− peritoneal foam cells formed up to 45% more multinucleated giant cells (MGCs) in vitro compared to WT, which concurred with an increased MGC presence in atherosclerotic lesions of Mcl-1^−/− mice. Moreover, analysis of human unstable atherosclerotic lesions also revealed a significant inverse correlation between MGC lesion content and Mcl-1 gene expression, coinciding with the mouse data. Taken together, these findings suggest that myeloid Mcl-1 deletion leads to a more apoptotic, lipid and MGC-enriched phenotype. These potentially pro-atherogenic effects are however counteracted by neutropenia in circulation and plaque.

Post-Translational Modifications in NETosis and NETs-Mediated Diseases

Neutrophils undergo a unique form of cell death that generates neutrophil extracellular traps (NETs) that may help to neutralize invading pathogens and restore homeostasis. However, uncontrolled NET formation (NETosis) can result in numerous diseases that adversely affect health. Recent studies further elucidate the mechanistic details of the different forms of NETosis and their common end structure, as NETs were constantly found to contain DNA, modified histones and cytotoxic enzymes. In fact, emerging evidence reveal that the post translational modifications (PTMs) of histones in neutrophils have a critical role in regulating neutrophil death. Histone citrullination is shown to promote a rapid form of NET formation independent of NADPH oxidase (NOX), which relies on calcium influx. Interestingly, few studies suggest an association between histone citrullination and other types of PTMs to control cell survival and death, such as histone methylation. Even more exciting is the finding that histone acetylation has a biphasic effect upon NETosis, where histone deacetylase (HDAC) inhibitors promote baseline, NOX-dependent and -independent NETosis. However, increasing levels of histone acetylation suppresses NETosis, and to switch neutrophil death to apoptosis. Interestingly, in the presence of NETosis-promoting stimuli, high levels of HDACis limit both NETosis and apoptosis, and promote neutrophil survival. Recent studies also reveal the importance of the PTMs of neutrophils in influencing numerous pathologies. Histone modifications in NETs can act as a double-edged sword, as they are capable of altering multiple types of neutrophil death, and influencing numerous NET-mediated diseases, such as acute lung injury (ALI), thrombosis, sepsis, systemic lupus erythematosus, and cancer progression. A clear understanding of the role of different PTMs in neutrophils would be important for an understanding of the molecular mechanisms of NETosis, and to appropriately treat NETs-mediated diseases.

MicroRNA-105 promotes epithelial-mesenchymal transition of nonsmall lung cancer cells through upregulating Mcl-1

BACKGROUND

A growing number of microRNAs have been proved to play significant roles in limiting tumor growth and the epithelial-mesenchymal transition (EMT) process of nonsmall cell lung cancer (NSCLC). Present work aims to study the function of microRNA (miR)-105 in EMT of NSCLC cells, which is unrevealed yet.

METHODS

Two NSCLC cell lines A549 and Calu-3 were transfected with miR-105 mimic, inhibitor, or scrambled control. And then the effects of miR-105 were evaluated by performing trypan blue staining, transwell assay, ANNEXIN-FITC/propidium iodide (PI) double staining and Western blot analysis. The expression levels of myeloid cell leukemia-1 (Mcl-1) after transfection were tested by real-time quantitative polymerase chain reaction and Western blot analysis. Whether Mcl-1 was a downstream effector of miR-105, and the involvement of mammalian target of Rapamycin (mTOR) and p38 mitogen-activated protein kinase (p38MAPK) signaling pathways were assessed.

RESULTS

The overexpression of miR-105 significantly increased the viability and migration of A549 and Calu-3, but had no impacts on cell apoptosis. Meanwhile, E-cadherin was remarkably downregulated, and N-cadherin, Vimentin, ZEB1, and Snail were upregulated by miR-105 overexpression. Mcl-1 was positively regulated by miR-105, and the effects of miR-105 overexpression on A549 and Calu-3 cells viability, migration and EMT were all flattened by Mcl-1 silence. Both mTOR and p38MAPK pathways were activated in miR-105-overexpressing and Mcl-1-overexpressing cells. Besides, inhibition of mTOR and p38MAPK pathways by using Rapamycin and VX-702 abolished the regulatory effects of Mcl-1 on EMT.

CONCLUSION

Our study underlines the importance of miR-105 in modulating NSCLC cells EMT. miR-105 promoted the EMT of NSCLC cells possibly via upregulation of Mcl-1 and thereby activation of mTOR and p38MAPK signaling.

The CDK inhibitor purvalanol A induces neutrophil apoptosis and increases the turnover rate of Mcl-1: potential role of p38-MAPK in regulation of Mcl-1 turnover

Human neutrophils are terminally differentiated cells that do not replicate and yet express a number of enzymes, notably cell cycle-dependent kinases (CDKs), that are associated normally with control of DNA synthesis and cell cycle progression. In neutrophils, CDKs appear to function mainly to regulate apoptosis, although the mechanisms by which they regulate this process are largely unknown. Here we show that the CDK2 inhibitor, purvalanol A, induces a rapid decrease in myeloid cell leukaemia factor-1 (Mcl-1) levels in human neutrophils and peripheral blood mononuclear cells (PBMCs), but only induces apoptosis in neutrophils which are dependent upon expression on this protein for survival. This rapid decrease in cellular Mcl-1 protein levels was due to a purvalanol A-induced decrease in stability, with the half-life of the protein decreasing from approximately 2 h in control cells to just over 1 h after addition of the CDK2 inhibitor: it also blocked the granulocyte-macrophage colony-stimulating factor (GM-CSF)-dependent stabilization of Mcl-1. Purvanalol A blocked GM-CSF-stimulated activation of extracellular-regulated kinase (Erk) and signal transducer and activator of transcription (STAT)-3, and stimulated an additive activation of protein kinase B (Akt) with GM-CSF. Purvalanol A alone stimulated a rapid and sustained activation of p38-mitogen-activated protein kinase (MAPK) and the pan p38-MAPK inhibitor, BIRB796, partly blocked the purvalanol A-induced apoptosis and Mcl-1 loss. These novel effects of purvalanol A may result, at least in part, from blocking GM-CSF-mediated Erk activation. In addition, we propose that purvalanol A-induced activation of p38-MAPK is, at least in part, responsible for its rapid effects on Mcl-1 turnover and acceleration of neutrophil apoptosis.

MicroRNA-30 inhibits antiapoptotic factor Mcl-1 in mouse and human hematopoietic cells after radiation exposure

We previously reported that microRNA-30 (miR-30) expression was initiated by radiation-induced proinflammatory factor IL-1β and NFkB activation in mouse and human hematopoietic cells. However, the downstream effectors of miR-30 and its specific role in radiation-induced cell death are not well understood. In the present study, we evaluated effects of radiation on miR-30 expression and activation of intrinsic apoptotic pathway Bcl-2 family factors in in vivo mouse and in vitro human hematopoietic cells. CD2F1 mice and human CD34+ cells were exposed to different doses of gamma-radiation. In addition to survival studies, mouse blood, bone marrow (BM) and spleen cells and human CD34+ cells were collected at 4 h, and 1, 3 and 4 days after irradiation to determine apoptotic and stress response signals. Our results showed that mouse serum miR-30, DNA damage marker γ-H2AX in BM, and Bim, Bax and Bak expression, cytochrome c release, and caspase-3 and -7 activation in BM and/or spleen cells were upregulated in a radiation dose-dependent manner. Antiapoptotic factor Mcl-1 was significantly downregulated, whereas Bcl-2 was less changed or unaltered in the irradiated mouse cells and human CD34+ cells. Furthermore, a putative miR-30 binding site was found in the 3′ UTR of Mcl-1 mRNA. miR-30 directly inhibits the expression of Mcl-1 through binding to its target sequence, which was demonstrated by a luciferase reporter assay, and the finding that Mcl-1 was uninhibited by irradiation in miR-30 knockdown CD34+ cells. Bcl-2 expression was not affected by miR-30. Our data suggest miR-30 plays a key role in radiation-induced apoptosis through directly targeting Mcl-1in hematopoietic cells.

The total terpenoids of Celastrus orbiculatus (TTC) inhibit NOX-dependent formation of PMA-induced neutrophil extracellular traps (NETs)

Previously, we identified that Celastrus orbiculatus, a traditional Chinese herbal medicine, exhibited prominent anti-inflammatory and anti-tumor activities. More recently, the formation of neutrophil extracellular traps (NETs) or NETosis has been recognized as a critical pathological event in the development of inflammatory and autoimmune diseases. The present study is aimed to explore the pharmacological effect of the total terpenoids from the stems of C. orbiculatus (TTC) on NETosis and underlying mechanisms, which may provide fundamental knowledge for future utilization of the Chinese medicine. Human neutrophils were isolated by density gradient centrifugation; lactase dehydrogenase (LDH) assay was used to detect cytotoxic effect of TTC on neutrophils. Moreover, we established phorbol-12-myristate-13-acetate (PMA)-induced NETosis. Quantitative and qualitative study of PMA-induced NET release was labeled by SYTOX™ Green. ROS production was determined by flow cytometry. The neutrophil NADPH oxidase (NOX) activity was assessed by lucigenin chemiluminescence assay, and the phosphorylation of NOX subunit was analyzed by immunoblot assay. TTC (5–80 μg.mL−1) had no predominant neutrophil cytotoxicity after 4 h exposure. PMA (200 ng.mL−1) significantly induced the formation of NETs after 4 h stimulus, whereas TTC dose-dependently (5–80 μg.mL−1) inhibited the process. TTC (40 μg.mL−1) blocked neutrophil elastase (NE) and myeloperoxidase (MPO) translocation from cytoplasm to nucleus and disrupted the formation of NET-associated deoxyribonucleic acid (DNA)–MPO and DNA–NE complexes. Moreover, TTC dose-dependently blocked PMA-mediated ROS production, and inhibited the NOX enzymatic activity of neutrophils upon PMA stimulus for 1 h. Finally, TTC suppressed PMA-induced phosphorylation of NOX subunit p40phox on Thr154 residue. TTC inhibited PMA-induced NOX phosphorylation, thereby suppressing NOX enzymatic activity and ROS generation in neutrophils undergoing NETosis. Consequently, TTC disrupted NETosis in the early stage of NOX-dependent NETs formation, which might serve as a promising anti-inflammatory agent by targeting suicidal NETosis.

PRN473, an inhibitor of Bruton's tyrosine kinase, inhibits neutrophil recruitment via inhibition of macrophage antigen-1 signalling

BACKGROUND AND PURPOSE

Following inflammatory stimuli, neutrophils are recruited to sites of inflammation and exert effector functions that often have deleterious effects on tissue integrity, which can lead to organ failure. Bruton's tyrosine kinase (Btk) is expressed in neutrophils and constitutes a promising pharmacological target for neutrophil-mediated tissue damage. Here, we evaluate a selective reversible inhibitor of Btk, PRN473, for its ability to dampen neutrophil influx via inhibition of adhesion receptor signalling pathways.

EXPERIMENTAL APPROACH

In vitro assays were used to assess fMLP receptor 1 (Fpr-1)-mediated binding of ligands to the adhesion receptors macrophage antigen-1 (Mac-1) and lymphocyte function antigen-1. Intravital microscopy of the murine cremaster was used to evaluate post-adhesion strengthening and endoluminal crawling. Finally, neutrophil influx was visualized in a clinically relevant model of sterile liver injury in vivo. Btk knockout animals were used as points of reference for Btk functions.

KEY RESULTS

Pharmacological inhibition of Btk by PRN473 reduced fMLP-induced phosphorylation of Btk and Mac-1 activation. Biochemical experiments demonstrated the specificity of the inhibitor. PRN473 (20 mg·kg^-1 ) significantly reduced intravascular crawling and neutrophil recruitment into inflamed tissue in a model of sterile liver injury, down to levels seen in Btk-deficient animals. A higher dose did not provide additional reduction of intravascular crawling and neutrophil recruitment.

CONCLUSIONS AND IMPLICATIONS

PRN473, a highly selective inhibitor of Btk, potently attenuates sterile liver injury by inhibiting the activation of the β₂ -integrin Mac-1 and subsequently neutrophil recruitment into inflamed tissue.

Age is the work of art? Impact of neutrophil and organism age on neutrophil extracellular trap formation

Neutrophil extracellular traps or NETs are released by highly activated neutrophils in response to infectious agents, sterile inflammation, autoimmune stimuli and cancer. In the cells, the nuclear envelop disintegrates and decondensation of chromatin occurs that depends on peptidylarginine deiminase 4 (PAD4) and neutrophil elastase (NE). Subsequently, proteins from neutrophil granules (e.g., NE, lactoferrin and myeloperoxidase) and the nucleus (histones) bind to decondensed DNA and the whole structure is ejected from the cell. The DNA decorated with potent antimicrobials and proteases can act to contain dissemination of infection and in sterile inflammation NETs were shown to degrade cytokines and chemokines via serine proteases. On the other hand, overproduction of NETs, or their inadequate removal and prolonged presence in vasculature or tissues, can lead to bystander damage or even initiation of diseases. Considering the pros and cons of NET formation, it is of relevance if the stage of neutrophil maturation (immature, mature and senescent cells) affects the capacity to produce NETs as the cells of different age-related phenotypes dominate in given (pathological) conditions. Moreover, the immune system of neonates and elderly individuals is weaker than in adulthood. Is the same pattern followed when it comes to NETs? The overall importance of individual and neutrophil age on the capacity to release NETs is reviewed in detail and the significance of these facts is discussed.

Angiotensin-(1-7) Promotes Resolution of Neutrophilic Inflammation in a Model of Antigen-Induced Arthritis in Mice

Defective resolution of inflammation may be crucial for the initiation and development of chronic inflammatory diseases, such as arthritis. Therefore, it has been suggested that therapeutic strategies based on molecules that facilitate inflammation resolution present great potential for the treatment of chronic inflammatory diseases. In this study, we investigated the effects and role of angiotensin-(1-7) [Ang-(1-7)] in driving resolution of neutrophilic inflammation in a model of arthritis. For this purpose, male C57BL/6 mice were subjected to antigen-induced arthritis and treated with Ang-(1-7) at the peak of the inflammatory process. Analysis of the number of inflammatory cells, apoptosis, and immunofluorescence for NF-κB was performed in the exudate collected from the knee cavity. Neutrophil accumulation in periarticular tissue was measured by assaying myeloperoxidase activity. Apoptosis of human neutrophil after treatment with Ang-(1-7) was evaluated morphologically and by flow cytometry, and NF-κB phosphorylation by immunofluorescence. Efferocytosis was evaluated in vivo. Therapeutic treatment with Ang-(1-7) at the peak of inflammation promoted resolution, an effect associated with caspase-dependent neutrophils apoptosis and NF-κB inhibition. Importantly, Ang-(1-7) was also able to induce apoptosis of human neutrophils, an effect associated with NF-κB inhibition. The pro-resolving effects of Ang-(1-7) were inhibited by the Mas receptor antagonist A779. Finally, we showed that Ang-(1-7) increased the efferocytic ability of murine macrophages. Our results clearly demonstrate that Ang-(1-7) resolves neutrophilic inflammation in vivo acting in two key step of resolution: apoptosis of neutrophils and their removal by efferocytosis. Ang-(1-7) is a novel mediator of resolution of inflammation.

Proliferating cell nuclear antigen in neutrophil fate

The life span of a neutrophil is a tightly regulated process as extended survival is beneficial for pathogen elimination and cell death necessary to prevent cytotoxic content release from activated neutrophils at the inflammatory site. Therefore, the control between survival and death must be a dynamic process. We have previously described that proliferating cell nuclear antigen (PCNA) which is known as a nuclear protein pivotal in DNA synthesis, is a key element in controlling neutrophil survival through its association with procaspases. Contrary to the dogma which asserted that PCNA has a strictly nuclear function, in mature neutrophils, PCNA is present exclusively within the cytosol due to its nuclear export at the end of the granulocytic differentiation. More recent studies are consistent with the notion that the cytosolic scaffold of PCNA is aimed at modulating neutrophil fate rather than simply preventing death. Ultimately, targeting neutrophil survival might have important applications not just in the field of immunology and inflammation, but also in hematology and transfusion. The neutrophil emerges as a unique and powerful cellular model to unravel the basic mechanisms governing the cell cycle-independent functions of PCNA and should be considered as a leader of the pack.

Harnessing Neutrophil Survival Mechanisms during Chronic Infection by Pseudomonas aeruginosa: Novel Therapeutic Targets to Dampen Inflammation in Cystic Fibrosis

More than two decades after cloning the cystic fibrosis transmembrane regulator (CFTR) gene, the defective gene in cystic fibrosis (CF), we still do not understand how dysfunction of this ion channel causes lung disease and the tremendous neutrophil burden which persists within the airways; nor why chronic colonization by Pseudomonas aeruginosa develops in CF patients who are thought to be immunocompetent. It appears that the microenvironment within the lung of CF patients provides favorable conditions for both P. aeruginosa colonization and neutrophil survival. In this context, the ability of bacteria to induce hypoxia, which in turn affects neutrophil survival is an additional level of complexity that needs to be accounted for when controlling neutrophil fate in CF. Recent studies have underscored the importance of neutrophils in innate immunity and their functions appear to extend far beyond their well-described role in antibacterial defense. Perhaps a disturbance in neutrophil reprogramming during the course of an infection severely modulates the inflammatory response in CF. Furthermore there is an emerging concept that the CFTR itself may be an immune modulator and stimulating CFTR function in CF patients could promote neutrophil and macrophages antimicrobial function. Fostering the resolution of inflammation by favoring neutrophil apoptosis could preserve their microbicidal activities but decrease their proinflammatory potential. In this context, triggering neutrophil apoptosis with roscovitine may be a potential therapeutic option and this is currently being evaluated in CF patients. In the present review we discuss how neutrophils functions are disturbed in CF and how this may relate to chronic infection with P. aeuginosa and we propose novel research directions aimed at modulating neutrophil survival, dampening lung inflammation and ultimately leading to an amelioration of the lung disease.

The resolution of acute inflammation induced by cyclic AMP is dependent on annexin A1

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein known for its anti-inflammatory and pro-resolving effects. We have shown previously that the cAMP-enhancing compounds rolipram (ROL; a PDE4 inhibitor) and Bt₂cAMP (a cAMP mimetic) drive caspase-dependent resolution of neutrophilic inflammation. In this follow-up study, we investigated whether AnxA1 could be involved in the pro-resolving properties of these compounds using a model of LPS-induced inflammation in BALB/c mice. The treatment with ROL or Bt₂cAMP at the peak of inflammation shortened resolution intervals, improved resolution indices, and increased AnxA1 expression. In vitro studies showed that ROL and Bt₂cAMP induced AnxA1 expression and phosphorylation, and this effect was prevented by PKA inhibitors, suggesting the involvement of PKA in ROL-induced AnxA1 expression. Akin to these in vitro findings, H89 prevented ROL- and Bt₂cAMP-induced resolution of inflammation, and it was associated with decreased levels of intact AnxA1. Moreover, two different strategies to block the AnxA1 pathway (by using N-t-Boc-Met-Leu-Phe, a nonselective AnxA1 receptor antagonist, or by using an anti-AnxA1 neutralizing antiserum) prevented ROL- and Bt₂cAMP-induced resolution and neutrophil apoptosis. Likewise, the ability of ROL or Bt₂cAMP to induce neutrophil apoptosis was impaired in AnxA-knock-out mice. Finally, in in vitro settings, ROL and Bt₂cAMP overrode the survival-inducing effect of LPS in human neutrophils in an AnxA1-dependent manner. Our results show that AnxA1 is at least one of the endogenous determinants mediating the pro-resolving properties of cAMP-elevating agents and cAMP-mimetic drugs.

Serum α-1 Antitrypsin (AAT) antagonizes intrinsic apoptosis induction in neutrophils from patients with systemic inflammatory response syndrome

Excessive neutrophil activation accompanied by delayed apoptotic cell death in inflammatory conditions causes progressive damage of cells and tissues, leading to life-threatening multiple organ dysfunction syndrome. Previous work suggested that circulating serum factors during inflammation are critically involved in the suppression of neutrophil cell death although the identity of these antiapoptotic mediators remained elusive. In this study, we identified the acute phase protein α-1 Antitrypsin (AAT) as a potent suppressor of staurosporine (STS)-induced apoptosis in human neutrophils through a mechanism implicating caspases-independent pathways. We show here that serum levels of AAT, potentially in part released by stimulated neutrophils, are markedly elevated in major trauma patients suffering from systemic inflammatory response syndrome (SIRS). Notably, AAT depletion from serum increased sensitivity of human neutrophils for STS-induced cell death. In fact, AAT was demonstrated to confer intrinsic apoptosis resistance by preventing PKC/Akt inactivation and subsequent proteasomal degradation of antiapoptotic Mcl-1 protein in response to STS treatment. Neither MAP kinase ERK1/2 nor caspases were found to be involved in AAT-triggered antiapoptotic pathways in neutrophils. In summary, these results establish a novel pivotal role of circulating AAT in mediating survival by antagonizing the proapoptotic action of the PKC inhibitor STS and should be considered for AAT augmentation therapies in future.

Rhizoma Smilacis Glabrae inhibits pathogen-induced upper genital tract inflammation in rats through suppression of NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Smilacis Glabrae (RSG) is traditionally used to treat gynecological disease, which is simply recorded in Chinese Pharmacopoeia. However, whether it has effect on upper genital tract inflammation (UGTI) is unclear.

AIM OF THE STUDY

To evaluate the pharmacological effect of RSG on UGTI in rats and analyze its phytochemistry characteristics.

MATERIALS AND METHODS

The substances in RSG extract was qualified by LC-Q-TOF-MS method, and 11 substances were further quantified. The RSG extract, at dose of 241, 482 (clinical dose) and 964mg/kg/day, was orally administered to UGTI rats whose upper genital tracts were multi-infected with pathogens. Infiltrations of neutrophil and lymphocyte and productions of IL-1β, IL-6, CXCL-1, MCP-1, RANTES, PGE2, COX-2, NF-κB p65 and IκB-α in upper genital tract were examined to evaluate the effects of RSG and its potential mechanism.

RESULTS

A total of 77 substances were detected in RSG extract, with 50 substances putatively identified, most of which were flavonoids, phenolic acids and phenylpropanoids. The quantification analysis showed flavonoid had a relative high amount. In pharmacological study, RSG extract suppressed infiltrations of inflammatory cells, reduced over-productions of factors involved in inflammation and pelvic pain. A potential mechanism of these effects was blocking NF-κB signal pathway.

CONCLUSIONS

The RSG extract exhibited anti-inflammatory effect on UGTI, with a potential mechanism of blocking the activation of NF-κB signal pathway. The effect may be involved in the presence of substances, such as flavonoids and phenolic acids.

Pretreatment neutrophil-lymphocyte count ratio may associate with gastric cancer presence

BACKGROUND

Inflammation plays a pivotal role in cancer development and progression. Neutrophil-lymphocyte count ratio (NLR) is an indicator of systemic inflammatory response which is supposedly associated with gastric cancer (GC) development and progression. Since this parameter can be easily obtained from routine blood examination, it will be a great economic relief to gastric patients if we can bring it into clinical application.

OBJECTIVE

The current study aims to evaluate the pretreatment NLR in gastric cancer patients through retrospectively reviewing the medical records.

METHODS

A total of 327 patients hospitalized on a tertiary care hospital were retrospectively investigated and divided into two groups. Gastric cancer group were composed of patients with newly diagnosed, pathologically confirmed GC and the control group were patients with gastric polyp or benign gastric stromal tumor. The value of NLR in the presence and stage of gastric cancer was investigated in the entire gastric cancer group.

RESULTS

Our study showed levels of NLR were significantly higher in gastric cancer cohort (2.17 (1.63-3.09) versus 1.62 (0.85-2.32), p< 0.001). After all the known confounders were excluded, NLR was an independent predicator of GC (OR = 1.446, 95%CI (1.121-1.866), and P= 0.005). Area under ROC curve (AUC) of NLR was 0.694. In addition, the results of Spearman's correlation showed NLR may have a positive correlation with size of tumor, N-stage, distant metastasis, and overall stage (r = 0.256, 0.256, 0.161 and 0.171, resp., all p < 0.05).

CONCLUSIONS

The current study demonstrated that pre-treatment NLR may be a useful biomarker in the health care of gastric cancer patients.

The anti-inflammatory effect of Andrographis paniculata (Burm. f.) Nees on pelvic inflammatory disease in rats through down-regulation of the NF-κB pathway

BACKGROUND

Andrographis paniculata (Burm. f.) Nees (APN), a principal constituent of a famous traditional Chinese medicine Fukeqianjin tablet which is used for the treatment of pelvic inflammatory disease (PID), has been reported to have anti-inflammatory effect in vitro. However, whether it has pharmacological effect on PID in vivo is unclear. Therefore, the aim of this study is to test the anti-inflammatory effect of APN and illuminate a potential mechanism.

METHODS

Thirty-six female specific pathogen-free SD rats were randomly divided into control group, PID group, APN1 group, APN2 group, APN3 group and prednisone group. Pathogen-induced PID rats were constructed. The APN1, APN2 and APN3 group rats were orally administrated with APN extract at different levels. The prednisone group rats were administrated with prednisone. Eight days after the first infection, the histological examination of upper genital tract was carried out, and enzyme-linked immunosorbent assay (ELISA) was carried out using homogenate of the uterus and fallopian tube. Furthermore, immunohistochemical evaluations of NF-κB p65 and IκB-α in uterus was conducted.

RESULTS

APN obviously suppressed the infiltrations of neutrophils and lymphocytes, and it could significantly reduce the excessive production of cytokines and chemokines including IL-1β, IL-6, CXCL-1, MCP-1 and RANTES in a dose-dependent manner. Furthermore, APN could block the pathogen-induced activation of NF-κB pathway.

CONCLUSION

APN showed potent anti-inflammatory effect on pathogen-induced PID in rats, with a potential mechanism of inhibiting the NF-κB signal pathway.

Hyperbaric Oxygen Reduces Production of Reactive Oxygen Species in Neutrophils from Polytraumatized Patients Yielding in the Inhibition of p38 MAP Kinase and Downstream Pathways

Trauma represents the leading cause of death among young people in western countries. Among the beneficial role of neutrophils in host defence, excessive priming and activation of neutrophils after major trauma lead to an overwhelming inflammatory response and secondary host tissue injury due to the release of toxic metabolites and enzymes. Hyperbaric oxygen (HBO) therapy has been proposed to possess antiinflammatory effects and might represent an appropriate therapeutic option to lower inflammation in a broad range of patients. Here, we studied the effects of HBO on the activity of neutrophils isolated from severely injured patients (days 1–2 after trauma), in fact on the production of reactive oxygen species (ROS) and release of neutrophil extracellular traps (NETs). We found exposure to HBO therapy to significantly diminish phorbol-12-myristate-13-acetate (PMA)-induced ROS production in neutrophils isolated from patients and healthy volunteers. At the same time, marked decrease in NETs release was found in control cells and a less pronounced reduction in patient neutrophils. Impaired ability to produce ROS following exposure to HBO was demonstrated to be linked to a strong downregulation of the activity of p38 MAPK. Only slight suppression of ERK activity could be found. In addition, HBO did not influence neutrophil chemotaxis or apoptosis, respectively. Collectively, this study shows for the first time that HBO therapy suppresses ROS production in inflammatory human neutrophils, and thus might impair ROS-dependent pathways, e.g. kinases activation and NETs release. Thus, HBO might represent a feasible therapy for patients suffering from systemic inflammation, including those with multiple trauma.

Dihydroartemisinin and its derivative induce apoptosis in acute myeloid leukemia through Noxa-mediated pathway requiring iron and endoperoxide moiety

Anti-apoptotic protein Mcl-1 plays an important role in protecting cell from death in acute myeloid leukemia (AML). The apoptosis blocking activity of Mcl-1 is inhibited by BH3-only protein Noxa. We found that dihydroartemisinin (DHA) and its derivative X-11 are potent apoptosis inducers in AML cells and act through a Noxa-mediate pathway; X-11 is four-fold more active than DHA. DHA and X-11-induced apoptosis is associated with induction of Noxa; apoptosis is blocked by silencing Noxa. DHA and X-11 induce Noxa expression by upregulating the transcription factor FOXO3a in a reactive oxygen species-mediated pathway. Interfering with the integrity of the endoperoxide moiety of DHA and X-11, as well as chelating intracellular iron with deferoxamine, diminish apoptosis and Noxa induction. AML cells expressing Bcl-xL, or with overexpression of Bcl-2, have decreased sensitivity to DHA and X-11-induced apoptosis which could be overcome by addition of Bcl-2/Bcl-xL inhibitor ABT-737. DHA and X-11 represent a new group of AML cells-apoptosis inducing compounds which work through Noxa up-regulation utilizing the specific endoperoxide moiety and intracellular iron.

Francisella tularensis Modulates a Distinct Subset of Regulatory Factors and Sustains Mitochondrial Integrity to Impair Human Neutrophil Apoptosis

Tularemia is a disease characterized by profound neutrophil accumulation and tissue destruction. The causative organism, Francisella tularensis, is a facultative intracellular bacterium that replicates in neutrophil cytosol, inhibits caspase activation and profoundly prolongs cell lifespan. Here, we identify unique features of this infection and provide fundamental insight into the mechanisms of apoptosis inhibition. Mitochondria are critical regulators of neutrophil apoptosis. We demonstrate that F. tularensis significantly inhibits Bax translocation and Bid processing during 24-48 h of infection, and in this manner sustains mitochondrial integrity. Downstream of mitochondria, X-linked inhibitor of apoptosis protein (XIAP) and proliferating cell nuclear antigen (PCNA) inhibit caspase-9 and caspase-3 by direct binding. Notably, we find that PCNA disappeared rapidly and selectively from infected cells, thereby demonstrating that it is not essential for neutrophil survival, whereas upregulation of calpastatin correlated with diminished calpain activity and reduced XIAP degradation. In addition, R-roscovitine is a cyclin-dependent kinase inhibitor developed for the treatment of cancer; it also induces neutrophil apoptosis and can promote the resolution of several infectious and inflammatory disorders. We confirm the ability of R-roscovitine to induce neutrophil apoptosis, but also demonstrate that its efficacy is significantly impaired by F. tularensis. Collectively, our findings advance the understanding of neutrophil apoptosis and its capacity to be manipulated by pathogenic bacteria.

Proresolving Actions of Synthetic and Natural Protease Inhibitors Are Mediated by Annexin A1

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein endowed with anti-inflammatory and proresolving properties. Intact AnxA1 is a 37-kDa protein that may be cleaved in vivo at the N-terminal region by neutrophil proteases including elastase and proteinase-3, generating the 33-kDa isoform that is largely inactive. In this study, we investigated the dynamics of AnxA1 expression and the effects of synthetic (sivelestat [SIV]; Eglin) and natural (secretory leukocyte protease inhibitor [SLPI]; Elafin) protease inhibitors on the resolution of LPS-induced inflammation. During the settings of LPS inflammation AnxA1 cleavage associated closely with the peak of neutrophil and elastase expression and activity. SLPI expression increased during resolving phase of the pleurisy. Therapeutic treatment of LPS-challenge mice with recombinant human SLPI or Elafin accelerated resolution, an effect associated with increased numbers of apoptotic neutrophils in the pleural exudates, inhibition of elastase, and modulation of the survival-controlling proteins NF-κB and Mcl-1. Similar effects were observed with SIV, which dose-dependently inhibited neutrophil elastase and shortened resolution intervals. Mechanistically, SIV-induced resolution was caspase-dependent, associated to increased levels of intact AnxA1 and decreased expression of NF-κB and Mcl-1. The proresolving effect of antiproteases was also observed in a model of monosodium urate crystals-induced inflammation. SIV skewed macrophages toward resolving phenotypes and enhanced efferocytosis of apoptotic neutrophils. A neutralizing antiserum against AnxA1 and a nonselective antagonist of AnxA1 receptor abolished the accelerated resolution promoted by SIV. Collectively, these results show that elastase inhibition not only inhibits inflammation but actually promotes resolution, and this response is mediated by protection of endogenous intact AnxA1 with ensuing augmentation of neutrophil apoptosis.

Leishmania donovani Exploits Myeloid Cell Leukemia 1 (MCL-1) Protein to Prevent Mitochondria-dependent Host Cell Apoptosis

Apoptosis is one of the mechanisms used by host cells to remove unwanted intracellular organisms, and often found to be subverted by pathogens through use of host anti-apoptotic proteins. In the present study, with the help of in vitro and in vivo approaches, we documented that the macrophage anti-apoptotic protein myeloid cell leukemia 1 (MCL-1) is exploited by the intra-macrophage parasite Leishmania donovani to protect their "home" from actinomycin D-induced mitochondria-dependent apoptosis. Among all the anti-apoptotic BCL-2 family members, infection preferentially up-regulated expression of MCL-1 at both the mRNA and protein levels and compared with infected control, MCL-1-silenced infected macrophages documented enhanced caspase activity and increased apoptosis when subjected to actinomycin D treatment. Phosphorylation kinetics and ChIP assay demonstrated that infection-induced MCL-1 expression was regulated by transcription factor CREB (cAMP-response element-binding protein) and silencing of CREB resulted in reduced expression of MCL-1 and increased apoptosis. During infection, MCL-1 was found to be localized in mitochondria and this was significantly reduced in Tom70-silenced macrophages, suggesting the active role of TOM70 in MCL-1 transport. In the mitochondria, MCL-1 interacts with the major pro-apoptotic protein BAK and prevents BAK-BAK homo-oligomer formation thereby preventing cytochrome c release-mediated mitochondrial dysfunction. Silencing of MCL-1 in the spleen of infected mice showed decreased parasite burden and increased induction of splenocyte apoptosis. Collectively our results showed that L. donovani exploited the macrophage anti-apoptotic protein MCL-1 to prevent BAK-mediated mitochondria-dependent apoptosis thereby protecting its niche, which is essential for disease progression.

TIIA attenuates LPS-induced mouse endometritis by suppressing the NF-κB signaling pathway

Endometritis is one of the main diseases that harms the dairy cow industry. Tanshinone IIA (TIIA), a fat-soluble alkaloid isolated from Salviae miltiorrhizae, has been reported to have potent anti-inflammatory properties. However, the anti-inflammatory effects of TIIA on a mouse model of lipopolysaccharide (LPS)-induced endometritis remain to be elucidated. The purpose of the present study was to investigate the effects of TIIA on LPS-induced mouse endometritis. TIIA was intraperitoneally injected 1 h before and 12 h after perfusion of LPS into the uterus. A histological examination was then performed, and the concentrations of myeloperoxidase (MPO) and nitric oxide (NO) in the uterine tissue were determined. The levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in a homogenate of the uterus were detected by enzyme-linked immunosorbent assay. The extent of phosphorylation of IκBα and p65 was detected by Western blotting. TIIA markedly reduced the infiltration of neutrophils, suppressed MPO activity and the concentration of NO, and attenuated the expression of TNF-α and IL-1β. Furthermore, TIIA inhibited the phosphorylation of the nuclear factor-kappa B (NF-κB) p65 subunit and the degradation of its inhibitor IκBα. All the results suggest that TIIA has strong anti-inflammatory effects on LPS-induced mouse endometritis.

Host and pathogen hyaluronan signal through human siglec-9 to suppress neutrophil activation

Inhibitory CD33-related Siglec receptors regulate immune cell activation upon engaging ubiquitous sialic acids (Sias) on host cell surface glycans. Through molecular mimicry, Sia-expressing pathogen group B Streptococcus binds inhibitory human Siglec-9 (hSiglec-9) to blunt neutrophil activation and promote bacterial survival. We unexpectedly discovered that hSiglec-9 also specifically binds high molecular weight hyaluronan (HMW-HA), another ubiquitous host glycan, through a region of its terminal Ig-like V-set domain distinct from the Sia-binding site. HMW-HA recognition by hSiglec-9 limited neutrophil extracellular trap (NET) formation, oxidative burst, and apoptosis, defining HMW-HA as a regulator of neutrophil activation. However, the pathogen group A Streptococcus (GAS) expresses a HMW-HA capsule that engages hSiglec-9, blocking NET formation and oxidative burst, thereby promoting bacterial survival. Thus, a single inhibitory lectin receptor detects two distinct glycan "self-associated molecular patterns" to maintain neutrophil homeostasis, and two leading human bacterial pathogens have independently evolved molecular mimicry to exploit this immunoregulatory mechanism.

KEY MESSAGE

HMW-HA is the first example of a non-sialic acid containing glycan to be recognized by CD33-related Siglecs. HMW-HA engagement of hSiglec-9 attenuates neutrophil activation. Group A Streptococcus exploits hSiglec-9 recognition via its polysaccharide HMW-HA capsule to subvert neutrophil killing.

Glucocorticoid-Induced Leucine Zipper Is Expressed in Human Neutrophils and Promotes Apoptosis through Mcl-1 Down-Regulation

Glucocorticoid-induced leucine zipper (GILZ) is a potent anti-inflammatory protein, the expression of which is mainly induced by glucocorticoids (GCs) in haematopoietic cells. GILZ regulates signal transduction pathways of inflammation and plays a role in cell survival. The objective of this study was to evaluate the expression and mechanisms of action of GILZ in the apoptosis of human neutrophils. GILZ expression was induced by GCs in human neutrophils, enhanced upon phosphatidylinositol 3-kinase inhibition and resulted in apoptosis amplification. We then stably transfected PLB-985 cells with the human gilz gene and differentiated both control and GILZ-overexpressing clones in neutrophil-like cells. GILZ overexpression in PLB-985 cells led to an exacerbated apoptosis, associated with caspase-3, caspase-9 and caspase-8 activations, and a loss of mitochondrial potential, suggesting that GILZ-induced apoptosis used the mitochondrial pathway. The expression of BH3 interacting domain death agonist, Bcl-2 interacting mediator of cell death, annexin-A1 and Bcl-2-associated X was not affected in PLB-985-GILZ clones, but phosphorylation and subsequent proteasomal degradation of myeloid cell leukemia-1 (Mcl-1) were observed. Noteworthy, Mcl-1 phosphorylation was related to a significant and sustained activation of c-Jun N-terminal kinase (JNK) in PLB-985-GILZ clones. These results reveal GILZ to be a new actor in apoptosis regulation in neutrophil-like cells involving JNK and Mcl-1.

Apoptotic Effect of Galbanic Acid via Activation of Caspases and Inhibition of Mcl-1 in H460 Non-Small Lung Carcinoma Cells

Galbanic acid (GBA), a major compound of Ferula assafoetida, was known to have cytotoxic, anti-angiogenic and apoptotic effects in prostate cancer and murine Lewis lung cancer cells; the underling apoptotic mechanism of GBA still remains unclear so far. Thus, in the present study, the apoptotic mechanism of GBA was investigated mainly in H460 non-small cell lung carcinoma (NSCLC) cells because H460 cells were most susceptible to GBA than A549, PC-9 and HCC827 NSCLC cells. Galbanic acid showed cytotoxicity in wild EGFR type H460 and A549 cells better than other mutant type PC-9 and HCC827 NSCLC cells. Also, GBA significantly increased the number of Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells and sub G1 population in H460 cells. Western blotting revealed that GBA cleaved poly (ADP-ribose) polymerase (PARP), activated Bax and caspase 9, attenuated the expression of Bcl-2, Bcl-x(L), and Myeloid cell leukemia 1 (Mcl-1) in H460 cells. However, interestingly, overexpression of Mcl-1 blocked the ability of GBA to exert cytotoxicity, activate caspase9 and Bax, cleave PARP, and increase sub G1 accumulation in H460 cells. Overall, these findings suggest that GBA induces apoptosis in H460 cells via caspase activation and Mcl-1 inhibition in H460 cells as a potent anticancer agent for NSCLC treatment.

Extracellular NAD(+) inhibits human neutrophil apoptosis

Regulation of neutrophil apoptosis plays a critical role in the inflammatory response. Inflammation has previously been shown to increase levels of extracellular β-nicotinamide adenine dinucleotide (NAD(+)). The present study demonstrates that extracellular NAD(+) at concentrations found in the inflamed tissues profoundly delays spontaneous apoptosis of human neutrophils as was evidenced by inhibition of phosphatidylserine (PS) exposure, DNA fragmentation and caspase-3 activation. The effect was abrogated by NF157, an antagonist of P2Y11 receptor, and was pertussis toxin-insensitive. The NAD(+)-mediated delay of neutrophil apoptosis was reversed by 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, and Rp-8-Br-cAMPS, an inhibitor of type I cAMP-dependent protein kinase A (PKA). Blocking of NAD(+)-induced influx of extracellular Ca(2+) with EGTA did not abolish the pro-survival effect of NAD(+). Extracellular NAD(+) inhibited proteasome-dependent degradation of Mcl-1 upstream of caspase activation and, furthermore, suppressed Bax translocation to the mitochondria and attenuated both dissipation of mitochondrial transmembrane potential (ΔΨm) and cytochrome c release from the mitochondria into the cytosol. Finally, we found that extracellular NAD(+) inhibited spontaneous activation of caspase-9, but not caspase-8, and the pro-survival effect of extracellular NAD(+) was abrogated by the inhibitor of caspase-9, but not by the inhibitor of caspase-8. Together, these results demonstrate that extracellular NAD(+) inhibits neutrophil apoptosis via P2Y11 receptor and cAMP/PKA pathway by regulating Mcl-1 level, Bax targeting to the mitochondria and mitochondrial apoptotic pathway. Thus, extracellular NAD(+) acts as a neutrophil survival factor that can contribute to prolonged neutrophil lifespan in inflammatory response.

The mystery of BCL2 family: Bcl-2 proteins and apoptosis: an update

Apoptosis is a critically important biological process that plays an essential role in cell fate and homeostasis. An important component of the apoptotic pathway is the family of proteins commonly known as the B cell lymphoma-2 (Bcl-2). The primary role of Bcl-2 family members is the regulation of apoptosis. Although the structure of Bcl-2 family of proteins was reported nearly 10 years ago, however, it still surprises us with its structural and functional complexity and diversity. A number of studies have demonstrated that Bcl-2 family influences many other cellular processes beyond apoptosis which are generally independent of the regulation of apoptosis, suggesting additional roles for Bcl-2. The disruption of the regulation of apoptosis is a causative event in many diseases. Since the Bcl-2 family of proteins is the key regulator of apoptosis, the abnormalities in its function have been implicated in many diseases including cancer, neurodegenerative disorders, ischemia and autoimmune diseases. In the past few years, our understanding of the mechanism of action of Bcl-2 family of proteins and its implications in various pathological conditions has enhanced significantly. The focus of this review is to summarize the current knowledge on the structure and function of Bcl-2 family of proteins in apoptotic cellular processes. A number of drugs have been developed in the past few years that target different Bcl-2 members. The role of Bcl-2 proteins in the pathogenesis of various diseases and their pharmacological significance as effective molecular therapeutic targets is also discussed.

Insights into the apoptotic death of immune cells in sepsis

Sepsis with subsequent multiple-organ dysfunction is a distinct systemic inflammatory response to concealed or obvious infection, and it is a leading cause of death in intensive care units. Thus, one of the key goals in critical care medicine is to develop novel therapeutic strategies that will affect favorably on outcome of septic patients. In addition to systemic response to infection, apoptosis is implicated to be an important mechanism of the death of immune cells, including neutrophils, macrophages, T lymphocytes, and dendritic cells, and it is usually followed by the development of multiple-organ failure in sepsis. The implication of apoptosis of immune cells is now highlighted by multiple studies that demonstrate that prevention of cell apoptosis can improve survival in relevant animal models of severe sepsis. In this review, we focus on major apoptotic death pathways and molecular mechanisms that regulate apoptosis of different immune cells, and advances in these areas that may be translated into more promising therapies for the prevention and treatment of severe sepsis.

IL-32γ delays spontaneous apoptosis of human neutrophils through MCL-1, regulated primarily by the p38 MAPK pathway

IL-32γ is a multifunctional cytokine involved in various inflammatory and auto-immune diseases in which neutrophils can affect the evolution of these diseases. To persist at inflammatory sites, neutrophils require inhibition of their rapid and constitutive apoptosis, an inhibitory effect that phlogogenic cytokines support. To date, the effects of IL-32γ on neutrophils remain unknown. We demonstrate that IL-32γ delays, in a dose-dependent manner, the spontaneous apoptosis of human blood neutrophils by activating mainly p38 MAPK through rapid p38 phosphorylation. PI3-K and ERK1/2 MAPK are also involved, but to a lesser extent. Most of cytokines that induce retardation of neutrophil apoptosis activate the expression of MCL-1 at both mRNA and protein levels. IL-32γ added to human blood neutrophils in vitro is associated with sustained levels of MCL-1 protein. This effect in neutrophils corresponds to a decrease of MCL-1 protein degradation without any effect on MCL-1 mRNA levels. The sustained levels of MCL-1 induced by IL-32γ are only abrogated by the p38β MAPK inhibitor SB202190. Additionally, IL-32γ induces a reduction in caspase 3 activity in neutrophils. In conclusion, IL-32γ affects human blood neutrophils in vitro by increasing their survival, suggesting that this cytokine could have profound effects on the deleterious functions of neutrophils in several diseases.

Adiponectin inhibits neutrophil apoptosis via activation of AMP kinase, PKB and ERK 1/2 MAP kinase

Neutrophils are abundant, short-lived leukocytes that play a key role in the immune defense against microbial infections. These cells die by apoptosis following activation and uptake of microbes and will also enter apoptosis spontaneously at the end of their lifespan if they do not encounter a pathogen. Adiponectin exerts anti-inflammatory effects on neutrophil antimicrobial functions, but whether this abundant adipokine influences neutrophil apoptosis is unknown. Here we report that adiponectin in the physiological range (1–10 μg/ml) reduced apoptosis in resting neutrophils, decreasing caspase-3 cleavage and maintaining Mcl-1 expression by stabilizing this anti-apoptotic protein. We show that adiponectin induced phosphorylation of AMP-activated kinase (AMPK), protein kinase B (PKB), extracellular signal-regulated kinase (ERK 1/2) and p38 mitogen activated protein kinase (MAPK). Pharmacological inhibition of AMPK, PKB and ERK 1/2 ablated the pro-survival effects of adiponectin and treatment of neutrophils with an AMPK specific activator (AICAR) and AMPK inhibitor (compound C) respectively decreased and increased apoptosis. Finally, activation of AMPK by AICAR or adiponectin also decreased ceramide accumulation in the neutrophil cell membrane, a process involved in the early stages of spontaneous apoptosis, giving another possible mechanism downstream of AMPK activation for the inhibition of neutrophil apoptosis.

Regulation of human neutrophil apoptosis and lifespan in health and disease

Neutrophils (also called polymorphonuclear leukocytes, PMNs) are the most abundant white blood cells in humans and play a central role in innate host defense. Another distinguishing feature of PMNs is their short lifespan. Specifically, these cells survive for less than 24 hours in the bloodstream and are inherently pre-programed to die by constitutive apoptosis. Recent data indicate that this process is regulated by intracellular signaling and changes in gene expression that define an “apoptosis differentiation program.” Infection typically accelerates neutrophil turnover, and as such, phagocytosis-induced cell death (PICD) and subsequent clearance of the corpses by macrophages are essential for control of infection and resolution of the inflammatory response. Herein we reprise recent advances in our understanding of the molecular mechanisms of neutrophil apoptosis with a focus on regulatory factors and pathway intermediates that are specific to this cell type. In addition, we summarize mechanisms whereby perturbation of PMN death contributes directly to the pathogenesis of many infectious and inflammatory disease states.

Radio-sensitization of human leukaemic MOLT-4 cells by DNA-dependent protein kinase inhibitor, NU7441

We studied the effect of pre-incubation with NU7441, a specific inhibitor of DNA-dependent protein kinase (DNA-PK), on molecular mechanisms triggered by ionizing radiation (IR). The experimental design involved four groups of human T-lymphocyte leukaemic MOLT-4 cells: control, NU7441-treated (1 μM), IR-treated (1 Gy), and combination of NU7441 and IR. We used flow cytometry for apoptosis assessment, Western blotting and ELISA for detection of proteins involved in DNA repair signalling and epifluorescence microscopy for detection of IR-induced phosphorylation of histone H2A.X. We did not observe any major changes in the amount of DNA-PK subunits Ku70/80 caused by the combination of NU7441 and radiation. Their combination led to an increased phosphorylation of H2A.X, a hallmark of DNA damage. However, it did not prevent up-regulation of neither p53 (and its phosphorylation at Ser 15 and 392) nor p21. We observed a decrease in the levels of anti-apoptotic Mcl-1, cdc25A phosphatase, cleavage of PARP and a significant increase in apoptosis in the group treated with combination. In conclusion, the combination of NU7441 with IR caused increased phosphorylation of H2A.X early after irradiation and subsequent induction of apoptosis. It was efficient in MOLT-4 cells in 10× lower concentration than the inhibitor NU7026. NU7441 proved as a potent radio-sensitizing agent, and it might provide a platform for development of new radio-sensitizers in radiotherapy.