Modulation of Neutrophil Apoptosis and the Resolution of Inflammation through β2 Integrins

Blockade of neutrophil extracellular trap components ameliorates cholestatic liver disease in Mdr2 (Abcb4) knockout mice

Primary sclerosing cholangitis (PSC) is an (auto)immune-mediated cholestatic liver disease with a yet unclear etiology. Increasing evidence points to an involvement of neutrophils in chronic liver inflammation and cirrhosis but also liver repair. Here, we investigate the role of the neutrophil extracellular trap (NET) component myeloperoxidase (MPO) and the therapeutic potential of DNase I and of neutrophil elastase (NE) inhibitor GW311616A on disease outcome in the multidrug resistance 2 knockout (Mdr2-/-) mouse, a PSC animal model. Initially, we observed the recruitment of MPO expressing cells and the formation of NETs in liver biopsies of PSC patients and in Mdr2-/- livers. Furthermore, sera of Mdr2-/- mice contained perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA)-like reactivity similar to PSC patient sera. Also, hepatic NE activity was significantly higher in Mdr2-/- mice than in wild type littermates. Flow cytometry analyses revealed that during disease development a highly active neutrophil subpopulation established specifically in the liver of Mdr2-/- mice. However, absence of their MPO activity, as in MPO-deficient Mdr2-/- mice, showed no effect on hepatobiliary disease severity. In contrast, clearance of extracellular DNA by DNase I reduced the frequency of liver-resident neutrophils, plasmacytoid dendritic cells (pDCs) and CD103+ conventional DCs and decreased cholangiocyte injury. Combination of DNase I with a pDC-depleting antibody was additionally hepatocyte-protective. Most importantly, GW311616A, an orally bioavailable inhibitor of human NE, attenuated hepatobiliary injury in a TNFα-dependent manner and damped hyperproliferation of biliary epithelial cells. Further, hepatic immigration and activity of CD11b+ DCs as well as the secretion of IFNγ by hepatic CD4 and CD8 T cells were reduced. Our findings delineate neutrophils as important participants in the immune cell crosstalk that drives cholestatic liver disease and identify NET components as potential therapeutic targets.

NMDAR activation attenuates the protective effect of BM-MSCs on bleomycin-induced ALI via the COX-2/PGE2 pathway

N-methyl-d-aspartate (NMDA) receptor (NMDAR) activation mediates glutamate (Glu) toxicity and involves bleomycin (BLM)-induced acute lung injury (ALI). We have reported that bone marrow-derived mesenchymal stem cells (BM-MSCs) are NMDAR-regulated target cells, and NMDAR activation inhibits the protective effect of BM-MSCs on BLM-induced pulmonary fibrosis, but its effect on ALI remains unknown. Here, we found that Glu release was significantly elevated in plasma of mice at d 7 after intratracheally injected with BLM. BM-MSCs were pretreated with NMDA (the selective agonist of NMDAR) and transplanted into the recipient mice after the BLM challenge. BM-MSCs administration significantly alleviated the pathological changes, inflammatory response, myeloperoxidase activity, and malondialdehyde content in the damaged lungs, but NMDA-pretreated BM-MSCs did not ameliorate BLM-induced lung injury in vivo. Moreover, NMDA down-regulated prostaglandin E2 (PGE2) secretion and cyclooxygenase (COX)-2 expression instead of COX-1 expression in BM-MSCs in vitro. We also found that NMDAR1 expression was increased and COX-2 expression was decreased, but COX-1 expression was not changed in primary BM-MSCs of BLM-induced ALI mice. Further, the cultured supernatants of lipopolysaccharide (LPS)-pretreated RAW264.7 macrophages were collected to detect inflammatory factors after co-culture with NMDA-pretreated BM-MSCs. The co-culture experiments showed that NMDA precondition inhibited the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation, and PGE2 could partially alleviate this inhibition. Our findings suggest that NMDAR activation attenuated the protective effect of BM-MSCs on BLM-induced ALI in vivo. NMDAR activation inhibited COX-2 expression and PGE2 secretion in BM-MSCs and weakened the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation in vitro. In conclusion, NMDAR activation attenuates the protective effect of BM-MSCs on BLM-induced ALI via the COX-2/PGE2 pathway. Keywords: Acute Lung Injury, BM-MSCs, NMDA receptor, COX-1/2, PGE2.

Perturbational phenotyping of human blood cells reveals genetically determined latent traits associated with subsets of common diseases

Although genome-wide association studies (GWAS) have successfully linked genetic risk loci to various disorders, identifying underlying cellular biological mechanisms remains challenging due to the complex nature of common diseases. We established a framework using human peripheral blood cells, physical, chemical and pharmacological perturbations, and flow cytometry-based functional readouts to reveal latent cellular processes and performed GWAS based on these evoked traits in up to 2,600 individuals. We identified 119 genomic loci implicating 96 genes associated with these cellular responses and discovered associations between evoked blood phenotypes and subsets of common diseases. We found a population of pro-inflammatory anti-apoptotic neutrophils prevalent in individuals with specific subsets of cardiometabolic disease. Multigenic models based on this trait predicted the risk of developing chronic kidney disease in type 2 diabetes patients. By expanding the phenotypic space for human genetic studies, we could identify variants associated with large effect response differences, stratify patients and efficiently characterize the underlying biology.

The effect of local anaesthetics on apoptosis and NETosis of human neutrophils in vitro: comparison between lidocaine and ropivacaine

There are immunological consequences to the method by which neutrophils undergo cell death. Neutrophil apoptosis, called silent death, leads to the resolution of inflammation, while NETosis deepens and prolongs the inflammatory response and is associated with a worse prognosis of severe infections, e.g., sepsis. Besides nociceptive inhibition, local anaesthetics modulate leukocyte functions, even at low, clinically relevant concentrations. There is currently no data on ropivacaine NETosis, and this study aimed to evaluate the impact of clinical concentrations of ropivacaine (0.0007, 0.007 and 1.4 mmol/L) and lidocaine (0.002, 0.02 and 4 mmol/L) on apoptosis and NETosis of adult peripheral blood neutrophils after 2 h of incubation. Neutrophil identification, apoptosis and NETosis were evaluated by flow cytometry using forward and side scatter characteristics and fluorescent labelling: CD15 for neutrophils identification; Annexin V and propidium iodide for apoptosis and citrullinated histone H3 and myeloperoxidase for NETosis. Lidocaine (4 mmol/L) and ropivacaine (1.4 mmol/L) induced early apoptosis in resting but not in stimulated neutrophils. Low doses of ropivacaine (0.0007 and 0.007 mmol/L) decreased the number of late apoptotic neutrophils, and the lowest dose slightly increased their viability. None of the drugs induced NETosis in resting neutrophils but decreased NETosis at clinical concentrations compared to PMA-stimulated 4 mM lidocaine, PMA-stimulated control, and 1.4 mM ropivacaine. The effect of lidocaine and ropivacaine on apoptosis and NETosis depended on neutrophil stimulation and drug concentrations. Ropivacaine tends to be cytoprotective at concentrations observed in plasma under local anaesthesia. Lidocaine enhanced NETosis at high concentration only in stimulated neutrophils. Thus, both drugs have the ability to change the course of inflammation.

Transport by circulating myeloid cells drives liposomal accumulation in inflamed synovium

The therapeutic potential of liposomes to deliver drugs into inflamed tissue is well documented. Liposomes are believed to largely transport drugs into inflamed joints by selective extravasation through endothelial gaps at the inflammatory sites, known as the enhanced permeation and retention effect. However, the potential of blood-circulating myeloid cells for the uptake and delivery of liposomes has been largely overlooked. Here we show that myeloid cells can transport liposomes to inflammatory sites in a collagen-induced arthritis model. It is shown that the selective depletion of the circulating myeloid cells reduces the accumulation of liposomes up to 50-60%, suggesting that myeloid-cell-mediated transport accounts for more than half of liposomal accumulation in inflamed regions. Although it is widely believed that PEGylation inhibits premature liposome clearance by the mononuclear phagocytic system, our data show that the long blood circulation times of PEGylated liposomes rather favours uptake by myeloid cells. This challenges the prevailing theory that synovial liposomal accumulation is primarily due to the enhanced permeation and retention effect and highlights the potential for other pathways of delivery in inflammatory diseases.

A subset of type-II collagen-binding antibodies prevents experimental arthritis by inhibiting FCGR3 signaling in neutrophils

Rheumatoid arthritis (RA) involves several classes of pathogenic autoantibodies, some of which react with type-II collagen (COL2) in articular cartilage. We previously described a subset of COL2 antibodies targeting the F4 epitope (ERGLKGHRGFT) that could be regulatory. Here, using phage display, we developed recombinant antibodies against this epitope and examined the underlying mechanism of action. One of these antibodies, R69-4, protected against cartilage antibody- and collagen-induced arthritis in mice, but not autoimmune disease models independent of arthritogenic autoantibodies. R69-4 was further shown to cross-react with a large range of proteins within the inflamed synovial fluid, such as the complement protein C1q. Complexed R69-4 inhibited neutrophil FCGR3 signaling, thereby impairing downstream IL-1β secretion and neutrophil self-orchestrated recruitment. Likewise, human isotypes of R69-4 protected against arthritis with comparable efficiency. We conclude that R69-4 abrogates autoantibody-mediated arthritis mainly by hindering FCGR3 signaling, highlighting its potential clinical utility in acute RA.

Trail Formation Alleviates Excessive Adhesion and Maintains Efficient Neutrophil Migration

Migrating neutrophils are found to leave behind subcellular trails in vivo, but the underlying mechanisms remain unclear. Here, an in vitro cell migration test plus an in vivo observation was applied to monitor neutrophil migration on intercellular cell adhesion molecule-1 (ICAM-1) presenting surfaces. Results indicated that migrating neutrophils left behind long-lasting, chemokine-containing trails. Trail formation tended to alleviate excessive cell adhesion enhanced by the trans-binding antibody and maintain efficient cell migration, which was associated with differential instantaneous edge velocity between the cell front and rear. CD11a and CD11b worked differently in inducing trail formation with polarized distributions on the cell body and uropod. Trail release at the cell rear was attributed to membrane ripping, in which β2-integrin was disrupted from the cell membrane through myosin-mediated rear contraction and integrin-cytoskeleton dissociation, potentiating a specialized strategy of integrin loss and cell deadhesion to maintain efficient migration. Moreover, neutrophil trails left on the substrate served as immune forerunners to recruit dendritic cells. These results provided an insight in elucidating the mechanisms of neutrophil trail formation and deciphering the roles of trail formation in efficient neutrophil migration.

Salmonella Typhimurium induces genome-wide expression and phosphorylation changes that modulate immune response, intracellular survival and vesicle transport in infected neutrophils

Salmonella Typhimurium is a food-borne pathogen that causes salmonellosis. When in contact with the host, neutrophils are rapidly recruited to act as first line of defense. To better understand the pathogenesis of this infection, we used an in vitro model of neutrophil infection to perform dual RNA-sequencing (both host and pathogen). In addition, and given that many pathogens interfere with kinase-mediated phosphorylation in host signaling, we performed a phosphoproteomic analysis. The immune response was overall diminished in infected neutrophils, mainly JAK/STAT and toll-like receptor signaling pathways. We found decreased expression of proinflammatory cytokine receptor genes and predicted downregulation of the mitogen-activated protein (MAPK) signaling pathway. Also, Salmonella infection inhibited interferons I and II signaling pathways by upregulation of SOCS3 and subsequent downregulation of STAT1 and STAT2. Additionally, phosphorylation of PSMC2 and PSMC4, proteasome regulatory proteins, was decreased in infected neutrophils. Cell viability and survival was increased by p53 signaling, cell cycle arrest and NFkB-proteasome pathways activation. Combined analysis of RNA-seq and phosphoproteomics also revealed inhibited vesicle transport mechanisms mediated by dynein/dynactin and exocyst complexes, involved in ER-to-Golgi transport and centripetal movement of lysosomes and endosomes. Among the overexpressed virulence genes from Salmonella we found potential effectors responsible of these dysregulations, such as spiC, sopD2, sifA or pipB2, all of them involved in intracellular replication. Our results suggest that Salmonella induces (through overexpression of virulence factors) transcriptional and phosphorylation changes that increases neutrophil survival and shuts down immune response to minimize host response, and impairing intracellular vesicle transport likely to keep nutrients for replication and Salmonella-containing vacuole formation and maintenance.

Possibility of averting cytokine storm in SARS-COV 2 patients using specialized pro-resolving lipid mediators

Fatal "cytokine storms (CS)" observed in critically ill COVID-19 patients are consequences of dysregulated host immune system and over-exuberant inflammatory response. Acute respiratory distress syndrome (ARDS), multi-system organ failure, and eventual death are distinctive symptoms, attributed to higher morbidity and mortality rates among these patients. Consequent efforts to save critical COVID-19 patients via the usage of several novel therapeutic options are put in force. Strategically, drugs being used in such patients are dexamethasone, remdesivir, hydroxychloroquine, etc. along with the approved vaccines. Moreover, it is certain that activation of the resolution process is important for the prevention of chronic diseases. Until recently Inflammation resolution was considered a passive process, rather it's an active biochemical process that can be achieved by the use of specialized pro-resolving mediators (SPMs). These endogenous mediators are an array of atypical lipid metabolites that include Resolvins, lipoxins, maresins, protectins, considered as immunoresolvents, but their role in COVID-19 is ambiguous. Recent evidence from studies such as the randomized clinical trial, in which omega 3 fatty acid was used as supplement to resolve inflammation in COVID-19, suggests that direct supplementation of SPMs or the use of synthetic SPM mimetics (which are still being explored) could enhance the process of resolution by regulating the aberrant inflammatory process and can be useful in pain relief and tissue remodeling. Here we discussed the biosynthesis of SPMs, & their mechanistic pathways contributing to inflammation resolution along with sequence of events leading to CS in COVID-19, with a focus on therapeutic potential of SPMs.

Anti-DEspR antibody treatment improves survival and reduces neurologic deficits in a hypertensive, spontaneous intracerebral hemorrhage (hsICH) rat model

Progressive secondary brain injury-induced by dysregulated neuroinflammation in spontaneous intracerebral hemorrhage (sICH)-underlies high sICH-mortality and remains without FDA-approved pharmacotherapy. Clinical insight that hematoma-directed interventions do not improve mortality prioritizes resolving acute secondary brain injury in sICH. As neutrophils are implicated in sICH secondary brain injury, we tested whether inhibition of a rogue neutrophil-subset expressing the dual endothelin-1/signal peptide receptor (DEspR) and associated with secondary tissue injury, DEspR+ CD11b+ immunotype, will attenuate mortality in a hypertensive-sICH (hsICH) rat model. We confirmed sICH-related deaths in hsICH-rats by T2*-weighted 9.4 T MRI and DEspR+ neutrophils in hsICH-rat brain perihematomal areas by immunostaining. At acute sICH, anti-DEspR muIgG1-antibody, mu10a3, treatment increased median survival in hsICH rats vs controls (p < 0.0001). In pre-stroke sICH, weekly 10a3-treatment did not predispose to infection and delayed sICH-onset vs controls (p < 0.0001). As potential sICH-therapeutic, we tested humanized anti-DEspR IgG4^S228P-mAb, hu6g8. In vitro, hu6g8 reversed delayed-apoptosis in DEspR+ CD11b+ neutrophils. In vivo, hu6g8 increased median survival and reduced neurologic symptoms in male/female hsICH-rats vs controls (p < 0.0001). Altogether, preclinical efficacy of inhibition of DEspR+ CD11b+ neutrophils in acute sICH-without infection complications, supports the potential of anti-DEspR therapy in sICH. Data provide basis for clinical study of DEspR+ CD11b+ neutrophil-subset in sICH patients.

Cardiac repair after myocardial infarction: A two-sided role of inflammation-mediated

Myocardial infarction is the leading cause of death and disability worldwide, and the development of new treatments can help reduce the size of myocardial infarction and prevent adverse cardiovascular events. Cardiac repair after myocardial infarction can effectively remove necrotic tissue, induce neovascularization, and ultimately replace granulation tissue. Cardiac inflammation is the primary determinant of whether beneficial cardiac repair occurs after myocardial infarction. Immune cells mediate inflammatory responses and play a dual role in injury and protection during cardiac repair. After myocardial infarction, genetic ablation or blocking of anti-inflammatory pathways is often harmful. However, enhancing endogenous anti-inflammatory pathways or blocking endogenous pro-inflammatory pathways may improve cardiac repair after myocardial infarction. A deficiency of neutrophils or monocytes does not improve overall cardiac function after myocardial infarction but worsens it and aggravates cardiac fibrosis. Several factors are critical in regulating inflammatory genes and immune cells' phenotypes, including DNA methylation, histone modifications, and non-coding RNAs. Therefore, strict control and timely suppression of the inflammatory response, finding a balance between inflammatory cells, preventing excessive tissue degradation, and avoiding infarct expansion can effectively reduce the occurrence of adverse cardiovascular events after myocardial infarction. This article reviews the involvement of neutrophils, monocytes, macrophages, and regulatory T cells in cardiac repair after myocardial infarction. After myocardial infarction, neutrophils are the first to be recruited to the damaged site to engulf necrotic cell debris and secrete chemokines that enhance monocyte recruitment. Monocytes then infiltrate the infarct site and differentiate into macrophages and they release proteases and cytokines that are harmful to surviving myocardial cells in the pre-infarct period. As time progresses, apoptotic neutrophils are cleared, the recruitment of anti-inflammatory monocyte subsets, the polarization of macrophages toward the repair phenotype, and infiltration of regulatory T cells, which secrete anti-inflammatory factors that stimulate angiogenesis and granulation tissue formation for cardiac repair. We also explored how epigenetic modifications regulate the phenotype of inflammatory genes and immune cells to promote cardiac repair after myocardial infarction. This paper also elucidates the roles of alarmin S100A8/A9, secreted frizzled-related protein 1, and podoplanin in the inflammatory response and cardiac repair after myocardial infarction.

CHL1-Deficient and Wild-Type Male Mice do Not Differ in Locomotor Recovery from Spinal Cord Injury

CHL1 is a close homolog of L1, a cell adhesion molecule that plays major roles in neural and tumor cell functions. We had found that young adult female mice deficient in CHL1 recovered better than their wild-type female littermates after thoracic Spinal Cord Injury (SCI). This observation was surprising, because CHL1 increases neurite outgrowth in vitro. Injury of adult mouse central and peripheral nervous systems upregulate CHL1 expression in neurons and astrocytes, consistent with CHL1's pro-active, homophilic interaction between CHL1 surface molecules in wild-type mice. After SCI, CHL1 expression was observed to increase in the glial scar, areas of axonal regrowth and remodeling of neural circuits. These observations were made only in females, and we therefore sought to analyze SCI in CHL1-deficient male mice. We now show that CHL1-deficient males did not recover better or worse than their male wild-type littermates. Primary and secondary lesion volumes were similar in the two genotypes, as seen in female mice which were studied in parallel with male mice. Assessment of peripheral leukocytes showed a significant increase in numbers of blood neutrophils at 24 h after SCI in males, but not in females. Lymphocyte numbers in mutant males increased slightly, but numbers of lymphocytes or monocytes did not differ significantly between males or females. These results indicate that CHL1-deficient males and females differ in the number of neutrophils but not lymphocytes or monocytes, suggesting that the difference between males and females is unlikely due to differences in leukocytes.

Lipoxin alleviates oxidative stress: a state-of-the-art review

OBJECTIVE

This review aims to summarize the capability of lipoxin in regulating oxidative stress.

BACKGROUND

Oxidative stress is defined as an imbalance between the production of free radicals and the antioxidant system, and it is associated with the existence of a large number of oxidation products, such as reactive oxygen species (ROS) and reaction nitrogen species (RNS), causing damage to human tissues through immunoinflammatory responses. Therefore, reducing oxidative stress is vital to alleviate pathological damage. Lipoxin, an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. Previous studies have shown that lipoxin is associated with a variety of biological functions, including anti-inflammatory, regulating immune responses, promoting the repair of damaged cells, etc. The deficiency of lipoxin is a critical pathological mechanism in different diseases. Moreover, the ability of lipoxin to attenuate oxidative stress is noteworthy, thereby protecting the human body from diverse diseases.

METHODS

We searched papers from PubMed database using search terms, such as lipoxin, lipoxin A4, oxidative stress, and other relevant terms.

RESULTS

A total of 103 articles published over the past 20 years were identified for inclusion. We summarized the capability of lipoxin in regulating oxidative stress and mechanism.

CONCLUSION

Lipoxin is provided with a protective role in attenuating oxidative stress.

Lack of Functional P110δ Affects Expression of Activation Marker CD80 but Does Not Influence Functions of Neutrophils

Neutrophils are specialized immune cells that are essential constituents of the innate immune response. They defend the organism against pathogens through various mechanisms. It was reported that phosphatidylinositols are key players in neutrophil functions, especially in the activity of class-I phosphoinositide 3-kinases (PI3Ks). P110δ, one of the PI3K subunits, is mostly expressed in immune cells, and its activity plays an important role in inflammatory responses. The aim of this study was to investigate the role of p110δ in neutrophil antimicrobial functions, activation status and cytokine production. To this end, we used bone marrow and splenic neutrophils isolated from a murine model expressing catalytically inactive p110δ^D910A/D910A. The level of phagocytosis and degranulation, the expressions of activation markers and cytokine production were determined by flow cytometry. ROS generation and NET release were assessed by fluorometry and fluorescent microscopy. We observed a significantly higher percentage of CD80-positive cells among the splenic granulocytes and found granulocytes subpopulations of differing phenotypes between WT and p110δ^D910A/D910A mice by multiparametric tSNE analysis. Moreover, we detected some differences in the expressions of activation markers, intracellular production of cytokines and bacterial killing. However, we did not observe any alterations in the selected neutrophil functions in p110δ mutant mice. Altogether, our data suggest that the catalytic p110 subunit(s), other than p110δ, is a key player in most neutrophil functions in mice. A follow-up study to correlate these in vitro results with in vivo observations is highly recommended.

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

The metamorphosis of neutrophil transcriptional program during Leishmania infection

The role of neutrophils in the course of Leishmania infection remains controversial, displaying tremendous variability depending on the species of parasite, stage of infection, host genetic background, and methodological discrepancies among studies. Although neutrophils have long been categorized as short-lived cells with limited capacity to express proteins de novo, recent advances have revealed significant plasticity in neutrophil transcriptional programs and intrapopulation heterogeneity, which can be regulated by both intrinsic and extrinsic factors that together determine the profile of neutrophil effector response. In this review, we focus on the current understanding of neutrophil transcriptional plasticity, neutrotime, evidence of Leishmania-mediated alterations in neutrophil transcriptome leading to the rise of subpopulations, and finally, functional implications of those findings to the course of Leishmania infection.

Immune cells in cardiac repair and regeneration

The immune system is fundamental to tissue homeostasis and is the first line of defense following infection, injury or disease. In the damaged heart, large numbers of immune cells are recruited to the site of injury. These cells play an integral part in both repair by scar formation and the initiation of tissue regeneration. They initially assume inflammatory phenotypes, releasing pro-inflammatory cytokines and removing dead and dying tissue, before entering a reparative stage, replacing dead muscle tissue with a non-contractile scar. In this Review, we present an overview of the innate and adaptive immune response to heart injury. We explore the kinetics of immune cell mobilization following cardiac injury and how the different innate and adaptive immune cells interact with one another and with the damaged tissue. We draw on key findings from regenerative models, providing insight into how to support a robust immune response permissible for cardiac regeneration. Finally, we consider how the latest technological developments can offer opportunities for a deeper and unbiased functional understanding of the immune response to heart disease, highlighting the importance of such knowledge as the basis for promoting regeneration following cardiac injury in human patients.

A targetable ‘rogue’ neutrophil-subset, [CD11b+DEspR+] immunotype, is associated with severity and mortality in acute respiratory distress syndrome (ARDS) and COVID-19-ARDS

Neutrophil-mediated secondary tissue injury underlies acute respiratory distress syndrome (ARDS) and progression to multi-organ-failure (MOF) and death, processes linked to COVID-19-ARDS. This secondary tissue injury arises from dysregulated neutrophils and neutrophil extracellular traps (NETs) intended to kill pathogens, but instead cause cell-injury. Insufficiency of pleiotropic therapeutic approaches delineate the need for inhibitors of dysregulated neutrophil-subset(s) that induce subset-specific apoptosis critical for neutrophil function-shutdown. We hypothesized that neutrophils expressing the pro-survival dual endothelin-1/VEGF-signal peptide receptor, DEspR, are apoptosis-resistant like DEspR+ cancer-cells, hence comprise a consequential pathogenic neutrophil-subset in ARDS and COVID-19-ARDS. Here, we report the significant association of increased peripheral DEspR+CD11b+ neutrophil-counts with severity and mortality in ARDS and COVID-19-ARDS, and intravascular NET-formation, in contrast to DEspR[-] neutrophils. We detect DEspR+ neutrophils and monocytes in lung tissue patients in ARDS and COVID-19-ARDS, and increased neutrophil RNA-levels of DEspR ligands and modulators in COVID-19-ARDS scRNA-seq data-files. Unlike DEspR[-] neutrophils, DEspR+CD11b+ neutrophils exhibit delayed apoptosis, which is blocked by humanized anti-DEspR-IgG4^S228P antibody, hu6g8, in ex vivo assays. Ex vivo live-cell imaging of Rhesus-derived DEspR+CD11b+ neutrophils showed hu6g8 target-engagement, internalization, and induction of apoptosis. Altogether, data identify DEspR+CD11b+ neutrophils as a targetable ‘rogue’ neutrophil-subset associated with severity and mortality in ARDS and COVID-19-ARDS.

Myeloperoxidase Deficiency Alters the Process of the Regulated Cell Death of Polymorphonuclear Neutrophils

Polymorphonuclear neutrophils (PMNs) play a key role in host defense. However, their massive accumulation at the site of inflammation can delay regenerative healing processes and can initiate pathological inflammatory processes. Thus, the efficient clearance of PMNs mediated by the induction of regulated cell death is a key process preventing the development of these pathological conditions. Myeloperoxidase (MPO), a highly abundant enzyme in PMN granules, primarily connected with PMN defense machinery, is suggested to play a role in PMN-regulated cell death. However, the contribution of MPO to the mechanisms of PMN cell death remains incompletely characterized. Herein, the process of the cell death of mouse PMNs induced by three different stimuli – phorbol 12-myristate 13-acetate (PMA), opsonized streptococcus (OST), and N-formyl-met-leu-phe (fMLP) – was investigated. MPO-deficient PMNs revealed a significantly decreased rate of cell death characterized by phosphatidylserine surface exposure and cell membrane permeabilization. An inhibitor of MPO activity, 4-aminobenzoic acid hydrazide, did not exhibit a significant effect on PMA-induced cell death compared to MPO deficiency. Interestingly, only the limited activation of markers related to apoptotic cell death was observed (e.g. caspase 8 activation, Bax expression) and they mostly did not correspond to phosphatidylserine surface exposure. Furthermore, a marker characterizing autophagy, cleavage of LC3 protein, as well as histone H3 citrullination and its surface expression was observed. Collectively, the data show the ability of MPO to modulate the life span of PMNs primarily through the potentiation of cell membrane permeabilization and phosphatidylserine surface exposure.

2-Styrylchromones: Cytotoxicity and Modulation of Human Neutrophils' Oxidative Burst

Neutrophils are polymorphonuclear leukocytes recruited to sites of acute inflammation, in response to pathogen invasion and tissue injury. The modulation of their activity, especially oxidative burst, may be important to control the inflammatory process. 2-Styrylchromones (2-SC) are derived from chromones and despite their recognized multiple biological activities, their anti-inflammatory and antioxidant properties are still poorly explored. Therefore, in this study, 43 structurally related 2-SC were evaluated concerning their effects on freshly isolated human neutrophils’ viability and oxidative burst. The studied 2-SC were divided into eight groups according to their substitution at C-4′ on B-ring (none, -OH, -OCH3, -OBn, -CH3, and -NO2), existence and location of -Cl on B-ring, and presence of -Br at C-3 on C-ring. Overall, most of the studied 2-SC did not affect neutrophils’ viability, at physiological relevant concentrations. The ones belonging to B group were the most effective (IC50 values < 2 μM), and present one -OH group at C-4′ or a catechol group at C-3′ and C-4′ on B-ring. These substituents seem to play an important role in the modulatory activity of human neutrophils’ oxidative burst. These results reinforce the great potential of 2-SC’s scaffold for the development of new anti-inflammatory agents.

THE VIABILITY OF LEUKOCYTES AND REACTIVE OXYGEN SPECIES GENERATION BY THEM IN RATS WITH CHRONIC COLITIS

OBJECTIVE

The aim: To assess reactive oxygen species production by leukocytes and their viability in rats with chronic colitis.

PATIENTS AND METHODS

Materials and methods: Reactive oxygen species production was estimated in leukocytes, isolated from rats with Dextran Sulfate Sodium-induced chronic colitis and control rats, by flow cytometry using the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate. Leukocyte viability and apoptosis stages were assessed by flow cytometry using annexin V and 7-aminoactinomycin D staining. White blood cell counting was carried out with using Hematology Analyzer.

RESULTS

Results: The increased fluorescence intensity of 2',7'-dichlorofluorescein in viable leukocytes by 36.7% was revealed in rats with chronic colitis compared control rats. A significant decrease in the percentage of viable cells and an increase in apoptotic cells were found compared to intact animals. Leukocytes, granulocytes, monocytes, lymphocytes counts in blood of experimental group animals were significantly higher compared to control those.

CONCLUSION

Conclusions: Our findings indicate that Dextran Sulfate Sodium-induced chronic colitis increases an intracellular production of reactive oxygen species by leukocytes. Despite of increased leukopoiesis it reduces viability of white blood cells and promotes their apoptosis via stimulation of oxidative stress.

Maternal Iron Deficiency Alters Trophoblast Differentiation and Placental Development in Rat Pregnancy

Iron deficiency, which occurs when iron demands chronically exceed intake, is prevalent in pregnant women. Iron deficiency during pregnancy poses major risks for the baby, including fetal growth restriction and long-term health complications. The placenta serves as the interface between a pregnant mother and her baby, and it ensures adequate nutrient provisions for the fetus. Thus, maternal iron deficiency may impact fetal growth and development by altering placental function. We used a rat model of diet-induced iron deficiency to investigate changes in placental growth and development. Pregnant Sprague-Dawley rats were fed either a low-iron or iron-replete diet starting 2 weeks before mating. Compared with controls, both maternal and fetal hemoglobin were reduced in dams fed low-iron diets. Iron deficiency decreased fetal liver and body weight, but not brain, heart, or kidney weight. Placental weight was increased in iron deficiency, due primarily to expansion of the placental junctional zone. The stimulatory effect of iron deficiency on junctional zone development was recapitulated in vitro, as exposure of rat trophoblast stem cells to the iron chelator deferoxamine increased differentiation toward junctional zone trophoblast subtypes. Gene expression analysis revealed 464 transcripts changed at least 1.5-fold (P < 0.05) in placentas from iron-deficient dams, including altered expression of genes associated with oxygen transport and lipoprotein metabolism. Expression of genes associated with iron homeostasis was unchanged despite differences in levels of their encoded proteins. Our findings reveal robust changes in placentation during maternal iron deficiency, which could contribute to the increased risk of fetal distress in these pregnancies.

Metabolite G-Protein Coupled Receptors in Cardio-Metabolic Diseases

G protein-coupled receptors (GPCRs) have originally been described as a family of receptors activated by hormones, neurotransmitters, and other mediators. However, in recent years GPCRs have shown to bind endogenous metabolites, which serve functions other than as signaling mediators. These receptors respond to fatty acids, mono- and disaccharides, amino acids, or various intermediates and products of metabolism, including ketone bodies, lactate, succinate, or bile acids. Given that many of these metabolic processes are dysregulated under pathological conditions, including diabetes, dyslipidemia, and obesity, receptors of endogenous metabolites have also been recognized as potential drug targets to prevent and/or treat metabolic and cardiovascular diseases. This review describes G protein-coupled receptors activated by endogenous metabolites and summarizes their physiological, pathophysiological, and potential pharmacological roles.

An Autophagy Modulator Peptide Prevents Lung Function Decrease and Corrects Established Inflammation in Murine Models of Airway Allergy

The involvement of autophagy and its dysfunction in asthma is still poorly documented. By using a murine model of chronic house dust mite (HDM)-induced airway inflammation, we tested the expression of several autophagy markers in the lung and spleen of asthma-like animals. Compared to control mice, in HDM-sensitized and challenged mice, the expression of sequestosome-1/p62, a multifunctional adaptor protein that plays an important role in the autophagy machinery, was raised in the splenocytes. In contrast, its expression was decreased in the neutrophils recovered from the bronchoalveolar fluid, indicating that autophagy was independently regulated in these two compartments. In a strategy of drug repositioning, we treated allergen-sensitized mice with the therapeutic peptide P140 known to target chaperone-mediated autophagy. A single intravenous administration of P140 in these mice resulted in a significant reduction in airway resistance and elastance, and a reduction in the number of neutrophils and eosinophils present in the bronchoalveolar fluid. It corrected the autophagic alteration without showing any suppressive effect in the production of IgG1 and IgE. Collectively, these findings show that autophagy processes are altered in allergic airway inflammation. This cellular pathway may represent a potential therapeutic target for treating selected patients with asthma.

Increased Neutrophil-Subset Associated With Severity/Mortality In ARDS And COVID19-ARDS Expresses The Dual Endothelin-1/VEGFsignal-Peptide Receptor (DEspR): An Actionable Therapeutic Target

Neutrophil-mediated secondary tissue injury underlies acute respiratory distress syndrome (ARDS) and progression to multi-organ-failure (MOF) and death, processes linked to severe COVID19. This 'innocent bystander' tissue injury arises in dysregulated hyperinflammatory states from neutrophil functions and neutrophil extracellular traps (NETs) intended to kill pathogens, but injure cells instead, causing MOF. Insufficiency of prior therapeutic approaches suggest need to identify dysregulated neutrophil-subset(s) and induce subset-specific apoptosis critical for neutrophil function-shutdown and clearance. We hypothesized that neutrophils expressing the pro-survival dual endothelin-1/signal peptide receptor, DEspR, are apoptosis-resistant just like DEspR+ cancer cells, hence comprise a consequential pathogenic neutrophil-subset in ARDS and COVID19-ARDS. Here, we report correlation of circulating DEspR+CD11b+ activated neutrophils (DESpR+actNs) and NETosing-neutrophils with severity in ARDS and in COVID19-ARDS, increased DEspR+ neutrophils and monocytes in post-mortem ARDS-patient lung sections, and neutrophil DEspR/ET1 receptor/ligand autocrine loops in severe COVID19. Unlike DEspR[-] neutrophils, ARDS patient DEspR+actNs exhibit apoptosis-resistance, which decreased upon ex vivo treatment with humanized anti-DEspR-IgG4S228P antibody, hu6g8. Ex vivo live-cell imaging of non-human primate DEspR+actNs showed hu6g8 target-engagement, internalization, and induction of apoptosis. Altogether, data differentiate DEspR+actNs as a targetable neutrophil-subset associated with ARDS and COVID19-ARDS severity, and suggest DEspR-inhibition as a potential therapeutic paradigm.

Der f 38 Is a Novel TLR4-Binding Allergen Related to Allergy Pathogenesis from Dermatophagoides farinae

It is difficult to treat allergic diseases including asthma completely because its pathogenesis remains unclear. House dust mite (HDM) is a critical allergen and Toll-like receptor (TLR) 4 is a member of the toll-like receptor family, which plays an important role in allergic diseases. The purpose of this study was to characterize a novel allergen, Der f 38 binding to TLR4, and unveil its role as an inducer of allergy. Der f 38 expression was detected in the body and feces of Dermatophagoides farinae (DF). Electron microscopy revealed that it was located in the granule layer, the epithelium layer, and microvilli of the posterior midgut. The skin prick test showed that 60% of allergic subjects were Der f 38-positive. Der f 38 enhanced surface 203c expression in basophils of Der f 38-positive allergic subjects. By analysis of the model structure of Der p 38, the expected epitope sites are exposed on the exterior side. In animal experiments, Der f 38 triggered an infiltration of inflammatory cells. Intranasal (IN) administration of Der f 38 increased neutrophils in the lung. Intraperitoneal (IP) and IN injections of Der f 38 induced both eosinophils and neutrophils. Increased total IgE level and histopathological features were found in BALB/c mice treated with Der f 38 by IP and IN injections. TLR4 knockout (KO) BALB/c mice exhibited less inflammation and IgE level in the sera compared to wild type (WT) mice. Der f 38 directly binds to TLR4 using biolayer interferometry. Der f 38 suppressed the apoptosis of neutrophils and eosinophils by downregulating proteins in the proapoptotic pathway including caspase 9, caspase 3, and BAX and upregulating proteins in the anti-apoptotic pathway including BCL-2 and MCL-1. These findings might shed light on the pathogenic mechanisms of allergy to HDM.

Image-Based Identification and Genomic Analysis of Single Circulating Tumor Cells in High Grade Serous Ovarian Cancer Patients

Simple Summary

Ovarian Cancer (OC) is one of the leading causes of death among gynecological tumors and there is still an insufficient understanding of its evolution. Blood, as a minimal invasive tool, allows multiple sampling over the treatment course and genomic single circulating tumor cell (sCTC) data provide the opportunity to investigate the genetic tumor evolution. CTC detection in OC remains difficult, due to epithelial-mesenchymal transition (EMT). This proof of principle study presents a workflow to generate sCTC genomic data, with the need of further studies to improve the CTC detection rate and enable insights into tumor evolution on a sCTC resolution to identify new treatment targets and/or biomarkers for an early treatment intervention.

Abstract

In Ovarian Cancer (OC), the analysis of single circulating tumor cells (sCTCs) might help to investigate genetic tumor evolution during the course of treatment. Since common CTC identification features failed to reliably detect CTCs in OC, we here present a workflow for their detection and genomic analysis. Blood of 13 high-grade serous primary OC patients was analyzed, using negative immunomagnetic enrichment, followed by immunofluorescence staining and imaging for Hoechst, ERCC1, CD45, CD11b and cytokeratin (CK) and sCTC sorting with the DEPArray^TM NxT. The whole genome of single cells was amplified and profiled for copy number variation (CNV). We detected: Type A-cells, epithelial (Hoechst^pos, ERCC1^pos, CD45^neg, CD11b^pos, CK^pos); Type B-cells, potentially epithelial (Hoechst^pos, ERCC1^pos, CD45^neg, CD11b^pos, CK^neg) and Type C-cells, potentially mesenchymal (Hoechst^pos, ERCC1^pos, CD45^neg, CD11b^neg, CK^neg). In total, we identified five (38.5%) patients harboring sCTCs with an altered CN profile, which were mainly Type A-cells (80%). In addition to inter-and intra-patient genomic heterogeneity, high numbers of Type B- and C-cells were identified in every patient with their aberrant character only confirmed in 6.25% and 4.76% of cases. Further identification markers and studies in the course of treatment are under way to expand sCTC analysis for the identification of tumor evolution in OC.

Usnic Acid and Usnea barbata (L.) F.H. Wigg. Dry Extracts Promote Apoptosis and DNA Damage in Human Blood Cells through Enhancing ROS Levels

Nowadays, numerous biomedical studies performed on natural compounds and plant extracts aim to obtain highly selective pharmacological activities without unwanted toxic effects. In the big world of medicinal plants, Usnea barbata (L) F.H. Wigg (U. barbata) and usnic acid (UA) are well-known for their therapeutical properties. One of the most studied properties is their cytotoxicity on various tumor cells. This work aims to evaluate their cytotoxic potential on normal blood cells. Three dry U. barbata extracts in various solvents: ethyl acetate (UBEA), acetone (UBA), and ethanol (UBE) were prepared. From UBEA we isolated usnic acid with high purity by semipreparative chromatography. Then, UA, UBA, and UBE dissolved in 1% dimethyl sulfoxide (DMSO) and diluted in four concentrations were tested for their toxicity on human blood cells. The blood samples were collected from a healthy non-smoker donor; the obtained blood cell cultures were treated with the tested samples. After 24 h, the cytotoxic effect was analyzed through the mechanisms that can cause cell death: early and late apoptosis, caspase 3/7 activity, nuclear apoptosis, autophagy, reactive oxygen species (ROS) level and DNA damage. Generally, the cytotoxic effect was directly proportional to the increase of concentrations, usnic acid inducing the most significant response. At high concentrations, usnic acid and U. barbata extracts induced apoptosis and DNA damage in human blood cells, increasing ROS levels. Our study reveals the importance of prior natural products toxicity evaluation on normal cells to anticipate their limits and benefits as potential anticancer drugs.

Role of Neutrophils in Cardiac Injury and Repair Following Myocardial Infarction

Neutrophils are first-line responders of the innate immune system. Following myocardial infarction (MI), neutrophils are quickly recruited to the ischemic region, where they initiate the inflammatory response, aiming at cleaning up dead cell debris. However, excessive accumulation and/or delayed removal of neutrophils are deleterious. Neutrophils can promote myocardial injury by releasing reactive oxygen species, granular components, and pro-inflammatory mediators. More recent studies have revealed that neutrophils are able to form extracellular traps (NETs) and produce extracellular vesicles (EVs) to aggravate inflammation and cardiac injury. On the contrary, there is growing evidence showing that neutrophils also exert anti-inflammatory, pro-angiogenic, and pro-reparative effects, thus facilitating inflammation resolution and cardiac repair. In this review, we summarize the current knowledge on neutrophils’ detrimental roles, highlighting the role of recently recognized NETs and EVs, followed by a discussion of their beneficial effects and molecular mechanisms in post-MI cardiac remodeling. In addition, emerging concepts about neutrophil diversity and their modulation of adaptive immunity are discussed.

β2 Integrin Regulation of Neutrophil Functional Plasticity and Fate in the Resolution of Inflammation

Neutrophils act as the first line of cellular defense against invading pathogens or tissue injury. Their rapid recruitment into inflamed tissues is critical for the elimination of invading microorganisms and tissue repair, but is also capable of inflicting damage to neighboring tissues. The β₂ integrins and Mac-1 (CD11b/CD18, α_Mβ₂ or complement receptor 3) in particular, are best known for mediating neutrophil adhesion and transmigration across the endothelium and phagocytosis of microbes. However, Mac-1 has a broad ligand recognition property that contributes to the functional versatility of the neutrophil population far beyond their antimicrobial function. Accumulating evidence over the past decade has demonstrated roles for Mac-1 ligands in regulating reverse neutrophil transmigration, lifespan, phagocytosis-induced cell death, release of neutrophil extracellular traps and efferocytosis, hence extending the traditional β₂ integrin repertoire in shaping innate and adaptive immune responses. Understanding the functions of β₂ integrins may partly explain neutrophil heterogeneity and may be instrumental to develop novel therapies specifically targeting Mac-1-mediated pro-resolution actions without compromising immunity. Thus, this review details novel insights on outside-in signaling through β₂ integrins and neutrophil functional heterogeneity pertinent to the resolution of inflammation.

Neutrophils in the Pathogenesis of Rheumatoid Arthritis and Systemic Lupus Erythematosus: Same Foe Different M.O

Dysregulated neutrophil activation contributes to the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Neutrophil-derived reactive oxygen species (ROS) and granule proteases are implicated in damage to and destruction of host tissues in both conditions (cartilage in RA, vascular tissue in SLE) and also in the pathogenic post-translational modification of DNA and proteins. Neutrophil-derived cytokines and chemokines regulate both the innate and adaptive immune responses in RA and SLE, and neutrophil extracellular traps (NETs) expose nuclear neoepitopes (citrullinated proteins in RA, double-stranded DNA and nuclear proteins in SLE) to the immune system, initiating the production of auto-antibodies (ACPA in RA, anti-dsDNA and anti-acetylated/methylated histones in SLE). Neutrophil apoptosis is dysregulated in both conditions: in RA, delayed apoptosis within synovial joints contributes to chronic inflammation, immune cell recruitment and prolonged release of proteolytic enzymes, whereas in SLE enhanced apoptosis leads to increased apoptotic burden associated with development of anti-nuclear auto-antibodies. An unbalanced energy metabolism in SLE and RA neutrophils contributes to the pathology of both diseases; increased hypoxia and glycolysis in RA drives neutrophil activation and NET production, whereas decreased redox capacity increases ROS-mediated damage in SLE. Neutrophil low-density granulocytes (LDGs), present in high numbers in the blood of both RA and SLE patients, have opposing phenotypes contributing to clinical manifestations of each disease. In this review we will describe the complex and contrasting phenotype of neutrophils and LDGs in RA and SLE and discuss their discrete roles in the pathogenesis of each condition. We will also review our current understanding of transcriptomic and metabolomic regulation of neutrophil phenotype in RA and SLE and discuss opportunities for therapeutic targeting of neutrophil activation in inflammatory auto-immune disease.

LL-37-mediated activation of host receptors is critical for defense against group A streptococcal infection

Group A Streptococcus (GAS) causes diverse human diseases, including life-threatening soft-tissue infections. It is accepted that the human antimicrobial peptide LL-37 protects the host by killing GAS. Here, we show that GAS extracellular protease ScpC N-terminally cleaves LL-37 into two fragments of 8 and 29 amino acids, preserving its bactericidal activity. At sub-bactericidal concentrations, the cleavage inhibits LL-37-mediated neutrophil chemotaxis, shortens neutrophil lifespan, and eliminates P2X7 and EGF receptors' activation. Mutations at the LL-37 cleavage site protect the peptide from ScpC-mediated splitting, maintaining all its functions. The mouse LL-37 ortholog CRAMP is neither cleaved by ScpC nor does it activate P2X7 or EGF receptors. Treating wild-type or CRAMP-null mice with sub-bactericidal concentrations of the non-cleavable LL-37 analogs promotes GAS clearance that is abolished by the administration of either P2X7 or EGF receptor antagonists. We demonstrate that LL-37-mediated activation of host receptors is critical for defense against GAS soft-tissue infections.

Therapeutic Targeting of Neutrophil Extracellular Traps Improves Primary and Secondary Intention Wound Healing in Mice

Background

Neutrophils are the first responders in wound healing after injury that mediate pro- and anti-inflammatory activities i.a. through the formation of extracellular traps (NETs). However, excessive NETs presence in wound tissue can cause local hyperinflammation and -coagulation resulting in delayed wound healing. To improve wound healing, we aimed to examine the role of NETs and DNase1 on primary and secondary wound healing.

Methods

The study included 93 C57BL/6 mice, with 3 different genotypes: wildtype, Pad4-, and DNase1-Knockout (KO). Pad4-KO mice show limited NETs formation, while DNase1-KO mice cannot disintegrate them. All 3 genotypes were included in (1) a laparotomy group and (2) a thermal injury group. Animals in both groups either received DNase1 or a vehicle i.p. post wound induction and wound assessment and euthanasia were conducted. Laparotomy and burn scars were assessed using the stony brook scar evaluation scale and modified Yeong scale respectively. Tissue was analyzed histologically using H&E staining. Ly6g, Collagen I and III, SMA, and Fibrinogen were visualized and neutrophils activation (NE, MPO) and NETs (H3cit) formation assessed.

Results

All animals survived with no complications. DNase1 treatment led to a significantly improved scar appearance in both groups, which was also seen in Pad4-KO mice. In the laparotomy group DNase1 improved collagen deposition and fibrin concentration was significantly reduced by DNase1 treatment. Markers of neutrophil activation were significantly reduced in the treatment and Pad4-KO group. In the thermal injury group wound closure time was significantly reduced after DNase1 treatment and in the Pad4-KO group. Even though inflammation remained high in the thermal injury model over time, neutrophil activation and NETs formation were significantly reduced by DNase1 treatment compared to controls.

Discussion

Primary and secondary intention wound healing is improved by targeting NETs through DNase1 treatment or genetic KO, as assessed by wound closure time and scar appearances. Additionally, wound stability was not affected by DNASE treatment. The results suggest that overall wound healing is accelerated and DNase1 appears to be a promising option to reduce scar formation; which should be evaluated in humans.

BMP Receptor Inhibition Enhances Tissue Repair in Endoglin Heterozygous Mice

Hereditary hemorrhagic telangiectasia type 1 (HHT1) is a severe vascular disorder caused by mutations in the TGFβ/BMP co-receptor endoglin. Endoglin haploinsufficiency results in vascular malformations and impaired neoangiogenesis. Furthermore, HHT1 patients display an impaired immune response. To date it is not fully understood how endoglin haploinsufficient immune cells contribute to HHT1 pathology. Therefore, we investigated the immune response during tissue repair in Eng+/- mice, a model for HHT1. Eng+/- mice exhibited prolonged infiltration of macrophages after experimentally induced myocardial infarction. Moreover, there was an increased number of inflammatory M1-like macrophages (Ly6Chigh/CD206-) at the expense of reparative M2-like macrophages (Ly6Clow/CD206+). Interestingly, HHT1 patients also showed an increased number of inflammatory macrophages. In vitro analysis revealed that TGFβ-induced differentiation of Eng+/- monocytes into M2-like macrophages was blunted. Inhibiting BMP signaling by treating monocytes with LDN-193189 normalized their differentiation. Finally, LDN treatment improved heart function after MI and enhanced vascularization in both wild type and Eng+/- mice. The beneficial effect of LDN was also observed in the hind limb ischemia model. While blood flow recovery was hampered in vehicle-treated animals, LDN treatment improved tissue perfusion recovery in Eng+/- mice. In conclusion, BMPR kinase inhibition restored HHT1 macrophage imbalance in vitro and improved tissue repair after ischemic injury in Eng+/- mice.

Actinobacillus pleuropneumoniae exotoxin ApxI induces cell death via attenuation of FAK through LFA-1

ApxI exotoxin is an important virulence factor derived from Actinobacillus pleuropneumoniae that causes pleuropneumonia in swine. Here, we investigate the role of lymphocyte function-associated antigen 1 (LFA-1, CD11a/CD18), a member of the β₂ integrin family, and the involvement of the integrin signaling molecules focal adhesion kinase (FAK) and Akt in ApxI cytotoxicity. Using Western blot analysis, we found that ApxI downregulated the activity of FAK and Akt in porcine alveolar macrophages (AMs). Preincubation of porcine AMs with an antibody specific for porcine CD18 reduced ApxI-induced cytotoxicity as measured by a lactate dehydrogenase release assay and decreased ApxI-induced FAK and Akt attenuation, as shown by Western blot analysis. Pretreatment with the chemical compounds PMA and SC79, which activate FAK and Akt, respectively, failed to overcome the ApxI-induced attenuation of FAK and Akt and death of porcine AMs. Notably, the transfection experiments revealed that ectopic expression of porcine LFA-1 (pLFA-1) conferred susceptibility to ApxI in ApxI-insensitive cell lines, including human embryonic kidney 293T cells and FAK-deficient mouse embryonic fibroblasts (MEFs). Furthermore, ectopic expression of FAK significantly reduced ApxI cytotoxicity in pLFA-1-cotransfected FAK-deficient MEFs. These findings show for the first time that pLFA-1 renders cells susceptible to ApxI and ApxI-mediated attenuation of FAK activity via CD18, thereby contributing to subsequent cell death.

Role of Neutrophils in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of liver disorders, from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Compared with fatty liver, NASH is characterized by increased liver injury and inflammation, in which liver-infiltrating immune cells, with neutrophil infiltration as a hallmark of NASH, play a critical role in promoting the progression of fatty liver to NASH. Neutrophils are the first responders to injury and infection in various tissues, establishing the first line of defense through multiple mechanisms such as phagocytosis, cytokine secretion, reactive oxygen species production, and neutrophil extracellular trap formation; however, their roles in the pathogenesis of NASH remain obscure. The current review summarizes the roles of neutrophils that facilitate the progression of fatty liver to NASH and their involvement in inflammation resolution during NASH pathogenesis. The notion that neutrophils are potential therapeutic targets for the treatment of NASH is also discussed.

Pro-Resolving Lipid Mediator Resolvin E1 Mitigates the Progress of Diethylnitrosamine-Induced Liver Fibrosis in Sprague-Dawley Rats by Attenuating Fibrogenesis and Restricting Proliferation

Liver fibrosis is a complex process associated to most types of chronic liver disease, which is characterized by a disturbance of hepatic tissue architecture and the excessive accumulation of extracellular matrix. Resolvin E1 (RvE1) is a representative member of the eicosapentaenoic omega-3 lipid derivatives, and is a drug candidate of the growing family of endogenous resolvins. Considering the aforementioned, the main objective of this study was to analyze the hepatoprotective effect of RvE1 in a rat model of liver fibrosis. Male Sprague-Dawley rats received diethylnitrosamine (DEN, 70 mg/mg body weight intraperitoneally (i.p)) as an inductor of liver fibrosis once weekly and RvE1(100 ng/body weight i.p) twice weekly for four weeks. RvE1 suppressed the alterations induced by DEN, normalizing the levels of alanine aminotransferase (ALT), albumin, and lactate dehydrogenase (LDH), and ameliorated DEN injury by decreasing the architecture distortion, inflammatory infiltration, necrotic areas, and microsteatosis. RvE1 also limited DEN-induced proliferation through a decrease in Ki67-positive cells and cyclin D1 protein expression, which is related to an increase of the levels of cleaved caspase-3. Interestingly, we found that RvE1 promotes higher nuclear translocation of nuclear factor κB (NF-κB)p65 than DEN. RvE1 also increased the levels of nuclear the nuclear factor erythroid 2-related factor 2 (Nrf2), but with no antioxidant effect, measured as an increase in glutathione disulfide (GSSG) and a decrease in the ratio of glutathione (GSH)/GSSG. Taken together, these results suggest that RvE1 modulates the fibrogenesis, steatosis, and cell proliferation in a model of DEN induced fibrosis.

Alpha 1 Antitrypsin-Deficient Macrophages Have Impaired Efferocytosis of Apoptotic Neutrophils

Alpha 1 antitrypsin deficiency (AATD) is an autosomal co-dominant disorder characterized by a low level of circulating AAT, which significantly reduces protection for the lower airways against proteolytic burden caused by neutrophils. Neutrophils, which are terminally differentiated innate immune cells and play a critical role to clear pathogens, accumulate excessively in the lung of AATD individuals. The neutrophil burden in AATD individuals increases the risk for early-onset destructive lung diseases by producing neutrophil products such as reactive oxygen radicals and various proteases. The level of AAT in AATD individuals is not sufficient to inhibit the activity of neutrophil chemotactic factors such as CXCL-8 and LTB4, which could lead to alveolar neutrophil accumulation in AATD individuals. However, as neutrophils have a short lifespan, and apoptotic neutrophils are rapidly cleared by alveolar macrophages that outnumber the apoptotic neutrophils in the pulmonary alveolus, the increased chemotaxis activity does not fully explain the persistent neutrophil accumulation and the resulting chronic inflammation in AATD individuals. Here, we propose that the ability of alveolar macrophages to clear apoptotic neutrophils is impaired in AATD individuals and it could be the main driver to cause neutrophil accumulation in their lung. This study demonstrates that Z-AAT variant significantly increases the expression of pro-inflammatory cytokines including CXCL-8, CXCL1, LTB4, and TNFα in LPS-treated macrophages. These cytokines play a central role in neutrophil recruitment to the lung and in clearance of apoptotic neutrophils by macrophages. Our result shows that LPS treatment significantly reduces the efferocytosis ability of macrophages with the Z-AAT allele by inducing TNFα expression. We incubated monocyte-derived macrophages (MDMs) with apoptotic neutrophils and found that after 3 h of co-incubation, the expression level of CXCL-8 is reduced in M-MDMs but increased in Z-MDMs. This result shows that the expression of inflammatory cytokines could be increased by impaired efferocytosis. It indicates that the efferocytosis ability of macrophages plays an important role in regulating cytokine expression and resolving inflammation. Findings from this study would help us better understand the multifaceted effect of AAT on regulating neutrophil balance in the lung and the underlying mechanisms.

Topical insulin application accelerates diabetic wound healing by promoting anti-inflammatory macrophage polarization

Besides regulating glucose levels, insulin has been reported to participate actively in many other functions, including modulating inflammatory reactions. In this study we investigated how topical insulin application would affect the diabetic wound healing process. We found that the excessive expression of insulin-degrading enzyme led to insufficient insulin levels in diabetic skin during wound healing, which ultimately reduced the recovery rate of diabetic wounds. We confirmed that topical insulin application could reverse the impaired inflammation reaction in the diabetic wound environment and promote healing of diabetic wounds. Our study revealed that insulin promoted apoptosis of neutrophils and subsequently triggered polarization of macrophages. Both in vivo and in vitro studies verified that insulin re-established phagocytosis function and promoted the process of phagocytosis-induced apoptosis in neutrophils. Furthermore, we found that insulin treatment also promoted efferocytosis of the apoptosed neutrophils by macrophages, and thus induced macrophages to change their polarization state from M1 to M2. In conclusion, our studies proved that the exogenous application of insulin could improve diabetic wound healing via the restoration of the inflammatory response.

Complement Receptor 3 Contributes to the Sexual Dimorphism in Neutrophil Killing of Staphylococcus aureus

We previously reported sex differences in innate susceptibility to Staphylococcus aureus skin infection and that bone marrow neutrophils (BMN) from female mice have an enhanced ability to kill S. aureus ex vivo compared with those of male mice. However, the mechanism(s) driving this sex bias in neutrophil killing have not been reported. Given the role of opsonins such as complement, as well as their receptors, in S. aureus recognition and clearance, we investigated their contribution to the enhanced bactericidal capacity of female BMN. We found that levels of C3 in the serum and CR3 (CD11b/CD18) on the surface of BMN were higher in female compared with male mice. Consistent with increased CR3 expression following TNF-α priming, production of reactive oxygen species (ROS), an important bactericidal effector, was also increased in female versus male BMN in response to serum-opsonized S. aureus Furthermore, blocking CD11b reduced both ROS levels and S. aureus killing by murine BMN from both sexes. However, at the same concentration of CD11b blocking Ab, S. aureus killing by female BMN was greatly reduced compared with those from male mice, suggesting CR3-dependent differences in bacterial killing between sexes. Overall, this work highlights the contributions of CR3, C3, and ROS to innate sex bias in the neutrophil response to S. aureus Given that neutrophils are crucial for S. aureus clearance, understanding the mechanism(s) driving the innate sex bias in neutrophil bactericidal capacity could identify novel host factors important for host defense against S. aureus.

The Septic Neutrophil-Friend or Foe

ABSTRACT

Neutrophils play a critical role in the eradication of pathogenic organisms, particularly bacteria. However, in the septic patient the prolonged activation and accumulation of neutrophils may augment tissue and organ injury. This review discusses the different activation states and chemotaxis of neutrophils in septic patients. Neutrophil killing of bacteria and the formation of neutrophil extracellular traps represent important components of the innate immune response and they become dysregulated during sepsis, possibly through changes in their metabolism. Delayed neutrophil apoptosis may contribute to organ injury, or allow better clearance of pathogens. Neutrophils provide a friendly immune response to clear infections, but excessive activation and recruitment has the potential to turn them into potent foes.

Pulmonary Innate Immune Response Determines the Outcome of Inflammation During Pneumonia and Sepsis-Associated Acute Lung Injury

The lung is a primary organ for gas exchange in mammals that represents the largest epithelial surface in direct contact with the external environment. It also serves as a crucial immune organ, which harbors both innate and adaptive immune cells to induce a potent immune response. Due to its direct contact with the outer environment, the lung serves as a primary target organ for many airborne pathogens, toxicants (aerosols), and allergens causing pneumonia, acute respiratory distress syndrome (ARDS), and acute lung injury or inflammation (ALI). The current review describes the immunological mechanisms responsible for bacterial pneumonia and sepsis-induced ALI. It highlights the immunological differences for the severity of bacterial sepsis-induced ALI as compared to the pneumonia-associated ALI. The immune-based differences between the Gram-positive and Gram-negative bacteria-induced pneumonia show different mechanisms to induce ALI. The role of pulmonary epithelial cells (PECs), alveolar macrophages (AMs), innate lymphoid cells (ILCs), and different pattern-recognition receptors (PRRs, including Toll-like receptors (TLRs) and inflammasome proteins) in neutrophil infiltration and ALI induction have been described during pneumonia and sepsis-induced ALI. Also, the resolution of inflammation is frequently observed during ALI associated with pneumonia, whereas sepsis-associated ALI lacks it. Hence, the review mainly describes the different immune mechanisms responsible for pneumonia and sepsis-induced ALI. The differences in immune response depending on the causal pathogen (Gram-positive or Gram-negative bacteria) associated pneumonia or sepsis-induced ALI should be taken in mind specific immune-based therapeutics.

A review of Sulfur Mustard-induced pulmonary immunopathology: An Alveolar Macrophage Approach

Despite many studies investigating the mechanism of Sulfur Mustard (SM) induced lung injury, the underlying mechanism is still unclear. Inflammatory and subsequent fibroproliferative stages of SM-toxicity are based upon several highly-related series of events controlled by the immune system. The inhalation of SM gas variably affects different cell populations within the lungs. Various studies have shown the critical role of macrophages in triggering a pulmonary inflammatory response as well as its maintenance, resolution, and repair. Importantly, macrophages can serve as either pro-inflammatory or anti-inflammatory populations depending on the present conditions at any pathological stage. Different characteristics of macrophages, including their differentiation, phenotypic, and functional properties, as well as interactions with other cell populations determine the outcomes of lung diseases and the extent of long- or short-term pulmonary damage induced by SM. In this paper, we summarize the current state of knowledge regarding the role of alveolar macrophages and their mediators in the pathogenesis of SM in pulmonary injury. Investigating the specific cells and mechanisms involved in SM-lung injury may be useful in finding new target opportunities for treatment of this injury.

A C-terminal fragment of adhesion protein Fibulin7 regulates neutrophil migration and functions and improves survival in LPS induced systemic inflammation

Accumulation of hyperactive neutrophils in the visceral organs was shown to be associated with sepsis-induced multi-organ failure. Recently, a C-terminal fragment of secreted glycoprotein Fibulin7 (Fbln7-C) was shown to inhibit angiogenesis and regulate monocyte functions in inflammatory conditions. However, its effects on neutrophil functions and systemic inflammation induced lethality remain unknown. In this study, we show that human peripheral blood neutrophils adhered to Fbln7-C in a dose-dependent manner via integrin β1. Moreover, the presence of Fbln7-C inhibited spreading, and fMLP mediated random migration of neutrophils on fibronectin. Significant reduction in ROS and inflammatory cytokine production (i.e., IL-6, IL-1β) was observed, including a reduction in ERK1⁄2 phosphorylation in neutrophils stimulated with LPS and fMLP in the presence of Fbln7-C compared to untreated controls. In an in vivo model of endotoxemia, the administration of Fbln7-C (10 μg/dose) significantly improved survival and reduced the infiltration of neutrophils to the site of inflammation. Additionally, neutrophils infiltrating into the inflamed peritoneum of Fbln7-C administered animals expressed lower levels CD11b marker, IL-6, and produced lower levels of ROS upon stimulation with PMA compared to untreated controls. In conclusion, our results show that Fbln7-C could bind to the integrin β1 on the neutrophil surface and regulate their inflammatory functions.

The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction

Sepsis remains a significant health care burden, with high morbidities and mortalities. Patients with sepsis often require general anesthesia for procedures and imaging studies. Knowing that anesthetic drugs can pose immunomodulatory effects, it would be critical to understand the impact of anesthetics on sepsis pathophysiology. The volatile anesthetic sevoflurane is a common general anesthetic derived from ether as a prototype. Using a murine sepsis model induced by cecal ligation and puncture surgery, we examined the impact of sevoflurane on sepsis outcome. Different from volatile anesthetic isoflurane, sevoflurane exposure significantly improved the outcome of septic mice. This was associated with less apoptosis in the spleen. Because splenic apoptosis was largely attributed to the apoptosis of neutrophils, we examined the effect of sevoflurane on FasL-induced neutrophil apoptosis. Sevoflurane exposure significantly attenuated apoptosis. Sevoflurane did not affect the binding of FasL to the extracellular domain of Fas receptor. Instead, in silico analysis suggested that sevoflurane would bind to the interphase between Fas death domain (DD) and Fas-associated DD (FADD). The effect of sevoflurane on Fas DD-FADD interaction was examined using fluorescence resonance energy transfer (FRET). Sevoflurane attenuated FRET efficiency, indicating that sevoflurane hindered the interaction between Fas DD and FADD. The predicted sevoflurane binding site is known to play a significant role in Fas DD-FADD interaction, supporting our in vitro and in vivo apoptosis results.-Koutsogiannaki, S., Hou, L., Babazada, H., Okuno, T., Blazon-Brown, N., Soriano, S. G., Yokomizo, T., Yuki, K. The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction.

MSC: immunoregulatory effects, roles on neutrophils and evolving clinical potentials

Mesenchymal stem cells (MSCs) are multipotent, non-hematopoietic stem cells capable of differentiating into varieties of mature cell types such as osteoblasts, chondrocytes, adipocytes, and myoblasts. MSCs can be isolated from different kinds of tissues and cultivated in vitro for amplification and passage easily. These cells have drawn researcher's attention lately due to their ability of tissue repair, properties of hematopoiesis support and function of immunoregulation through the secretion of a variety of cytokines and growth factors that have both paracrine and autocrine activities. MSCs can regulate the proliferation of T cells, the antibodies secretion of B cells, maturation of DC, polarization of macrophages and also have many effects on neutrophils such as the suppression of NO secretion, inhibition of apoptosis, reduction of their infiltration, decreasing of N-Formy l-L-Methionine-L-leucy l-L-phenylalanine, induction of respiratory bursts and promotion of survivals. In some conditions, MSCs exert their function of treatment through immunoregulation. We reviewed the multifaceted roles of MSCs in communicating with immune cells mainly neutrophils in both in vivo and in vitro experiments. MSCs may provide promising trends for cell therapy in future.

Anhydroglucitol-core gallotannins from red maple buds modulate viability of human blood neutrophils

Apoptosis of neutrophils is an essential checkpoint for the resolution of inflammation by shutting down the deleterious functions of these immune cells. This study investigated the role of anhydroglucitol-core gallotannins (ACGs) in apoptosis increase of human blood neutrophils treated by the hot water extract from red maple buds (RMB). Fractions obtained by liquid-liquid partitioning (ethyl acetate, butanol and water-remaining fractions) of the hot water extract from RMB were assessed for their effects on neutrophil viability by using flow cytometry. These fractions were then phytochemically analyzed to investigate the ability of major compounds to induce neutrophil apoptosis individually. Ethyl acetate and butanol fractions that contained the major ACGs ginnalin A, ginnalin 3,6 and ginnalin C stimulated the apoptosis of neutrophils. The three ACGs at 100 μM significantly increased the rate of the late apoptotic cells. When differentially combined, these ACGs have additive or antagonist effects. These effects are related to the concentrations of the constituents in the mixtures studied, especially so for ginnalin C. GinA increased FADD, phospho-Rad17, SMAC/Diablo and cytochrome C, while decreasing the anti-apoptotic protein catalase. These compounds could be useful for the development of novel therapeutic approaches that facilitate resolution of neutrophil-mediated inflammatory diseases.

The cytokine environment influence on human skin-derived T cells

Skin resident T cells provide immediate immunologic responses at their specific location and play a role in the pathogenesis of skin diseases such as psoriasis. Recently, IL-9-producing T cells were described as a major T-cell subtype present in the skin, but knowledge on the biology and in situ regulation of this T-cell subtype is scarce. Here, we investigated the cytokine influence on skin T cells with focus on IL-9-producing T cells because a better understanding of their biology may identify novel therapeutic approaches. Healthy human skin biopsies were cultured either in the presence of IL-2, IL-4, and TGF-β [T helper (T_h)9-promoting condition (T_h9-PC)] or IL-2 and IL-15 [standard condition (SC)]. Paired analysis of enzymatically isolated skin T cells and emigrated T cells after 4 wk of skin culture showed significant alterations of T-cell phenotypes, cytokine production, and IL-9-producing T-cell frequency. RNA sequencing analysis revealed differentially regulated pathways and identified CXCL8 and CXCL13 as top up-regulated genes in T_h9-PC compared with SC. Functionally supernatant of stimulated skin-derived T cells, CXCL8 and CXCL13 increased neutrophil survival. We report that the cytokine environment alters skin-derived T-cell phenotype and functional properties.-Kienzl, P., Polacek, R., Reithofer, M., Reitermaier, R., Hagenbach, P., Tajpara, P., Vierhapper, M., Gschwandtner, M., Mildner, M. Jahn-Schmid, B., Elbe-Bürger, A. The cytokine environment influence on human skin-derived T cells.