Eosinophils control the resolution of inflammation and draining lymph node hypertrophy through the proresolving mediators and CXCL13 pathway in mice

Novel IL-4/HB-EGF-dependent crosstalk between eosinophils and macrophages controls liver regeneration after ischaemia and reperfusion injury

OBJECTIVE

Previous studies indicate that eosinophils are recruited into the allograft following orthotopic liver transplantation and protect from ischaemia reperfusion (IR) injury. In the current studies, we aim to explore whether their protective function could outlast during liver repair.

DESIGN

Eosinophil-deficient mice and adoptive transfer of bone marrow-derived eosinophils (bmEos) were employed to investigate the effects of eosinophils on tissue repair and regeneration after hepatic IR injury. Aside from exogenous cytokine or neutralising antibody treatments, mechanistic studies made use of a panel of mouse models of eosinophil-specific IL-4/IL-13-deletion, cell-specific IL-4rα-deletion in liver macrophages and hepatocytes and macrophage-specific deletion of heparin-binding epidermal growth factor-like growth factor (hb-egf).

RESULT

We observed that eosinophils persisted over a week following hepatic IR injury. Their peak accumulation coincided with that of hepatocyte proliferation. Functional studies showed that eosinophil deficiency was associated with a dramatic delay in liver repair, which was normalised by the adoptive transfer of bmEos. Mechanistic studies demonstrated that eosinophil-derived IL-4, but not IL-13, was critically involved in the reparative function of these cells. The data further revealed a selective role of macrophage-dependent IL-4 signalling in liver regeneration. Eosinophil-derived IL-4 stimulated macrophages to produce HB-EGF. Moreover, macrophage-specific hb-egf deletion impaired hepatocyte regeneration after IR injury.

CONCLUSION

Together, these studies uncovered an indispensable role of eosinophils in liver repair after acute injury and identified a novel crosstalk between eosinophils and macrophages through the IL-4/HB-EGF axis.

The SWI/SNF chromatin-remodeling subunit DPF2 facilitates NRF2-dependent antiinflammatory and antioxidant gene expression

During emergency hematopoiesis, hematopoietic stem cells (HSCs) rapidly proliferate to produce myeloid and lymphoid effector cells, a response that is critical against infection or tissue injury. If unresolved, this process leads to sustained inflammation, which can cause life-threatening diseases and cancer. Here, we identify a role of double PHD fingers 2 (DPF2) in modulating inflammation. DPF2 is a defining subunit of the hematopoiesis-specific BAF (SWI/SNF) chromatin-remodeling complex, and it is mutated in multiple cancers and neurological disorders. We uncovered that hematopoiesis-specific Dpf2-KO mice developed leukopenia, severe anemia, and lethal systemic inflammation characterized by histiocytic and fibrotic tissue infiltration resembling a clinical hyperinflammatory state. Dpf2 loss impaired the polarization of macrophages responsible for tissue repair, induced the unrestrained activation of Th cells, and generated an emergency-like state of HSC hyperproliferation and myeloid cell-biased differentiation. Mechanistically, Dpf2 deficiency resulted in the loss of the BAF catalytic subunit BRG1 from nuclear factor erythroid 2-like 2-controlled (NRF2-controlled) enhancers, impairing the antioxidant and antiinflammatory transcriptional response needed to modulate inflammation. Finally, pharmacological reactivation of NRF2 suppressed the inflammation-mediated phenotypes and lethality of Dpf2Δ/Δ mice. Our work establishes an essential role of the DPF2-BAF complex in licensing NRF2-dependent gene expression in HSCs and immune effector cells to prevent chronic inflammation.

Regulation of short-chain fatty acids in the immune system

A growing body of research suggests that short-chain fatty acids (SCFAs), metabolites produced by intestinal symbiotic bacteria that ferment dietary fibers (DFs), play a crucial role in the health status of symbiotes. SCFAs act on a variety of cell types to regulate important biological processes, including host metabolism, intestinal function, and immune function. SCFAs also affect the function and fate of immune cells. This finding provides a new concept in immune metabolism and a better understanding of the regulatory role of SCFAs in the immune system, which impacts the prevention and treatment of disease. The mechanism by which SCFAs induce or regulate the immune response is becoming increasingly clear. This review summarizes the different mechanisms through which SCFAs act in cells. According to the latest research, the regulatory role of SCFAs in the innate immune system, including in NLRP3 inflammasomes, receptors of TLR family members, neutrophils, macrophages, natural killer cells, eosinophils, basophils and innate lymphocyte subsets, is emphasized. The regulatory role of SCFAs in the adaptive immune system, including in T-cell subsets, B cells, and plasma cells, is also highlighted. In addition, we discuss the role that SCFAs play in regulating allergic airway inflammation, colitis, and osteoporosis by influencing the immune system. These findings provide evidence for determining treatment options based on metabolic regulation.

Investigating the role of obstructive pulmonary diseases and eosinophil count at admission on all-cause mortality in SARS-CoV-2 patients : A single center registry-based retrospective cohort study

INTRODUCTION

The impact of asthma and chronic obstructive pulmonary disease (COPD) in the setting of severe acute respiratory syndrome coronavirus 2 (SARS-CoV‑2) infection is not clearly defined. Blood eosinophil count is a standard diagnostic test which, according to the previously published literature, might have a potential prognostic role on mortality in patients with SARS-CoV‑2 infection.

AIM

To investigate the potential prognostic value of peripheral blood eosinophil count on all-cause mortality of patients hospitalized with SARS-CoV‑2 infection, as well as to assess the impact of asthma or COPD premorbidity on all-cause mortality.

MATERIAL AND METHODS

We conducted a retrospective registry-based cohort study. Survival analysis was performed by employing the Cox proportional hazards regression model at 30 days of follow-up. Prognostic value of eosinophil count on all-cause mortality was assessed using receiver-operating characteristic (ROC) curve analysis.

RESULTS

A total of 5653 participants were included in the study. Our model did not reveal that pre-existing asthma or COPD is a statistically significant covariate for all-cause mortality but, indicated that higher eosinophil count at admission might have a protective effect (hazard ratio, HR 0.13 (95% confidence interval, CI 0.06-0.27), p = 0.0001). ROC curve analysis indicates cut-off value of 20 cells/mm³ (81% specificity; 30.9% sensitivity).

CONCLUSION

Our results indicate that eosinophil count at hospital admission might have a potential prognostic role for all-cause mortality at 30 days of follow-up; however this was not demonstrated for pre-existing obstructive lung diseases.

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

Eosinophils are typically a minority population of circulating granulocytes being released from the bone-marrow as terminally differentiated cells. Besides their function in the defense against parasites and in promoting allergic airway inflammation, regulatory functions have now been attributed to eosinophils in various organs. Although eosinophils are involved in the inflammatory response to allergens, it remains unclear whether they are drivers of the asthma pathology or merely recruited effector cells. Recent findings highlight the homeostatic and pro-resolving capacity of eosinophils and raise the question at what point in time their function is regulated. Similarly, eosinophils from different physical locations display phenotypic and functional diversity. However, it remains unclear whether eosinophil plasticity remains as they develop and travel from the bone marrow to the tissue, in homeostasis or during inflammation. In the tissue, eosinophils of different ages and origin along the inflammatory trajectory may exhibit functional diversity as circumstances change. Herein, we outline the inflammatory time line of allergic airway inflammation from acute, late, adaptive to chronic processes. We summarize the function of the eosinophils in regards to their resident localization and time of recruitment to the lung, in all stages of the inflammatory response. In all, we argue that immunological differences in eosinophils are a function of time and space as the allergic inflammatory response is initiated and resolved.

Emerging Role of Eosinophils in Resolution of Arthritis

Eosinophils are a minor component of circulating granulocytes, which are classically viewed as end-stage effector cells in host defense against helminth infection and promoting allergic responses. However, a growing body of evidence has emerged showing that eosinophils are versatile leukocytes acting as an orchestrator in the resolution of inflammation. Rheumatoid arthritis (RA) is the most common chronic inflammatory disease characterized by persistent synovitis that hardly resolves spontaneously. Noteworthy, a specific population of eosinophils, that is, regulatory eosinophils (rEos), was identified in the synovium of RA patients, especially in disease remission. Mechanistically, the rEos in the synovium display a unique pro-resolving signature that is distinct from their counterpart in the lung. Herein, we summarize the latest understanding of eosinophils and their emerging role in promoting the resolution of arthritis. This knowledge is crucial to the design of new approaches to rebalancing immune homeostasis in RA, considering that current therapies are centered on inhibiting pro-inflammatory cytokines and mediators rather than fostering the resolution of inflammation.

Longitudinal urinary biomarkers of immunological activation in covid-19 patients without clinically apparent kidney disease versus acute and chronic failure

Kidney function is affected in COVID-19, while kidney itself modulates the immune response. Here, hypothesize if COVID-19 urine biomarkers level can assess immune activation vs. clinical trajectory. Considering the kidney's critical role in modulating the immune response, we sought to analyze activation markers in patients with pre-existing dysfunction. This was a cross-sectional study of 68 patients. Blood and urine were collected within 48 h of hospital admission (H1), followed by 96 h (H2), seven days (H3), and up to 25 days (H4) from admission. Serum level ferritin, procalcitonin, IL-6 assessed immune activation overall, while the response to viral burden was gauged with serum level of spike protein and αspike IgM and IgG. 39 markers correlated highly between urine and blood. Age and race, and to a lesser extend gender, differentiated several urine markers. The burden of pre-existing conditions correlated with urine DCN, CAIX and PTN, but inversely with IL-5 or MCP-4. Higher urinary IL-12 and lower CAIX, CCL23, IL-15, IL-18, MCP-1, MCP-3, MUC-16, PD-L1, TNFRS12A, and TNFRS21 signified non-survivors. APACHE correlated with urine TNFRS12, PGF, CAIX, DCN, CXCL6, and EGF. Admission urine LAG-3 and IL-2 predicted death. Pre-existing kidney disease had a unique pattern of urinary inflammatory markers. Acute kidney injury was associated, and to a certain degree, predicted by IFNg, TWEAK, MMP7, and MUC-16. Remdesavir had a more profound effect on the urine biomarkers than steroids. Urinary biomarkers correlated with clinical status, kidney function, markers of the immune system activation, and probability of demise in COVID-19.

Cellular and molecular mediators of lymphangiogenesis in inflammatory bowel disease

Background

Recent studies reporting the intricate crosstalk between cellular and molecular mediators and the lymphatic endothelium in the development of inflammatory bowel diseases (IBD) suggest altered inflammatory cell drainage and lymphatic vasculature, implicating the lymphatic system as a player in the occurrence, development, and recurrence of intestinal diseases. This article aims to review recent data on the modulatory functions of cellular and molecular components of the IBD microenvironment on the lymphatic system, particularly lymphangiogenesis. It serves as a promising therapeutic target for IBD management and treatment. The interaction with gut microbiota is also explored.

Main text

Evidence shows that cells of the innate and adaptive immune system and certain non-immune cells participate in the complex processes of inflammatory-induced lymphangiogenesis through the secretion of a wide spectrum of molecular factors, which vary greatly among the various cells. Lymphangiogenesis enhances lymphatic fluid drainage, hence reduced infiltration of immunomodulatory cells and associated-inflammatory cytokines. Interestingly, some of the cellular mediators, including mast cells, neutrophils, basophils, monocytes, and lymphatic endothelial cells (LECs), are a source of lymphangiogenic molecules, and a target as they express specific receptors for lymphangiogenic factors.

Conclusion

The effective target of lymphangiogenesis is expected to provide novel therapeutic interventions for intestinal inflammatory conditions, including IBD, through both immune and non-immune cells and based on cellular and molecular mechanisms of lymphangiogenesis that facilitate inflammation resolution.

12/15-Lipoxygenase Regulates IL-33-Induced Eosinophilic Airway Inflammation in Mice

Dysregulated fatty acid metabolism is clinically associated with eosinophilic allergic diseases, including severe asthma and chronic rhinosinusitis. This study aimed to demonstrate the role of 12/15-lipoxygenase (12/15-LOX) in interleukin (IL)-33-induced eosinophilic airway inflammation; to this end, we used 12/15-LOX-deficient mice, which displayed augmented IL-33-induced lung inflammation, characterized by an increased number of infiltrated eosinophils and group 2 innate lymphoid cells (ILC2s) in the airway. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based lipidomics revealed that the levels of a series of 12/15-LOX-derived metabolites were significantly decreased, and application of 14(S)-hydroxy docosahexaenoic acid (HDoHE), a major 12/15-LOX-derived product, suppressed IL-33-mediated eosinophilic inflammation in 12/15-LOX-deficient mice. Using bioactive lipid screening, we found that 14(S)-HDoHE and 10(S),17(S)-diHDoHE markedly attenuated ILC2 proliferation and cytokine production at micromolar concentration in vitro. In addition, maresin 1 (MaR1) and resolvin D1 (RvD1), 12/15-LOX-derived specialized proresolving mediators (SPMs), inhibited cytokine production of ILC2s at nanomolar concentration. These findings demonstrate the protective role of endogenous 12/15-LOX-derived lipid mediators in controlling ILC2-mediated eosinophilic airway inflammation and related diseases. Thus, 12/15-LOX-derived lipid mediators may represent a potential therapeutic strategy for ameliorating airway inflammation-associated conditions.

12-Hydroxyeicosapentaenoic acid inhibits foam cell formation and ameliorates high-fat diet-induced pathology of atherosclerosis in mice

Atherosclerosis is a chronic inflammatory disease associated with macrophage aggregate and transformation into foam cells. In this study, we sought to investigate the impact of dietary intake of ω3 fatty acid on the development of atherosclerosis, and demonstrate the mechanism of action by identifying anti-inflammatory lipid metabolite. Mice were exposed to a high-fat diet (HFD) supplemented with either conventional soybean oil or α-linolenic acid-rich linseed oil. We found that as mice became obese they also showed increased pulsatility and resistive indexes in the common carotid artery. In sharp contrast, the addition of linseed oil to the HFD improved pulsatility and resistive indexes without affecting weight gain. Histological analysis revealed that dietary linseed oil inhibited foam cell formation in the aortic valve. Lipidomic analysis demonstrated a particularly marked increase in the eicosapentaenoic acid-derived metabolite 12-hydroxyeicosapentaenoic acid (12-HEPE) in the serum from mice fed with linseed oil. When we gave 12-HEPE to mice with HFD, the pulsatility and resistive indexes was improved. Indeed, 12-HEPE inhibited the foamy transformation of macrophages in a peroxisome proliferator-activated receptor (PPAR)γ-dependent manner. These results demonstrate that the 12-HEPE-PPARγ axis ameliorates the pathogenesis of atherosclerosis by inhibiting foam cell formation.

Role of Short Chain Fatty Acids and Apolipoproteins in the Regulation of Eosinophilia-Associated Diseases

Eosinophils are key components of our host defense and potent effectors in allergic and inflammatory diseases. Once recruited to the inflammatory site, eosinophils release their cytotoxic granule proteins as well as cytokines and lipid mediators, contributing to parasite clearance but also to exacerbation of inflammation and tissue damage. However, eosinophils have recently been shown to play an important homeostatic role in different tissues under steady state. Despite the tremendous progress in the treatment of eosinophilic disorders with the implementation of biologics, there is an unmet need for novel therapies that specifically target the cytotoxic effector functions of eosinophils without completely depleting this multifunctional immune cell type. Recent studies have uncovered several endogenous molecules that decrease eosinophil migration and activation. These include short chain fatty acids (SCFAs) such as butyrate, which are produced in large quantities in the gastrointestinal tract by commensal bacteria and enter the systemic circulation. In addition, high-density lipoprotein-associated anti-inflammatory apolipoproteins have recently been shown to attenuate eosinophil migration and activation. Here, we focus on the anti-pathogenic properties of SCFAs and apolipoproteins on eosinophil effector function and provide insights into the potential use of SCFAs and apolipoproteins (and their mimetics) as effective agents to combat eosinophilic inflammation.

Specialized Pro-Resolving Mediators and the Lymphatic System

Diminished lymphatic function and abnormal morphology are common in chronic inflammatory diseases. Recent studies are investigating whether it is possible to target chronic inflammation by promoting resolution of inflammation, in order to enhance lymphatic function and attenuate disease. Resolution of inflammation is an active process regulated by bioactive lipids known as specialized pro-resolving mediators (SPMs). SPMs can modulate leukocyte migration and function, alter cytokine/chemokine release, modify autophagy, among other immune-related activities. Here, we summarize the role of the lymphatics in resolution of inflammation and lymphatic impairment in chronic inflammatory diseases. Furthermore, we discuss the current literature describing the connection between SPMs and the lymphatics, and the possibility of targeting the lymphatics with innovative SPM therapy to promote resolution of inflammation and mitigate disease.

Formation of atherosclerotic lesions is independent of eosinophils in male mice

BACKGROUND AND AIMS

Oxidation of low-density lipoprotein (LDL) and oxidized LDL-mediated activation of the innate immune system have been recognized as early key events during the pathogenesis of atherosclerosis. Recent evidence identified eosinophils as a major source of enzymatic lipid oxidation and suggested a potential role of type 2 immunity in atherogenesis. However, the involvement of individual type 2 immune cell subsets involved in this process has been incompletely defined. We therefore sought to determine the role of eosinophils during LDL oxidation and the pathogenesis of this disease.

METHODS

Using eosinophil-deficient dblGATA1 mice, we studied the role of eosinophils in two established mouse models of atherosclerosis.

RESULTS

These experiments revealed that the presence of eosinophils did neither affect biomarkers of LDL oxidation nor atherosclerotic lesion development.

CONCLUSIONS

The obtained results show that LDL oxidation and development of atherosclerosis are largely independent of eosinophils or eosinophil-mediated LDL oxidation.

Eosinophil diversity in asthma

Eosinophils are a type of granulated innate immune cells that have long been implicated in a specific type of asthma, referred to as eosinophilic asthma. Several immunotherapeutics that target and deplete eosinophils or limit their numbers are currently widely used and provide improved disease outcome in severe eosinophilic asthma. Current clinical results provide conclusive evidence of a generally detrimental role of eosinophils in asthma. Yet, a small but growing body of reports suggests that eosinophils may be more diverse than currently appreciated. In this review, we explore pre-clinical and clinical evidence that suggests the existence of eosinophil subsets with potentially distinct functional roles in asthma. We conclude by discussing state-of-the-art strategies for deciphering heterogeneity of this complex cell type, and argue this knowledge could translate into the improved personalized treatment of severe eosinophilic asthma.

Association between the cytokine storm, immune cell dynamics, and viral replicative capacity in hyperacute HIV infection

INTRODUCTION

Immunological damage in acute HIV infection (AHI) may predispose to detrimental clinical sequela. However, studies on the earliest HIV-induced immunological changes are limited, particularly in sub-Saharan Africa. We assessed the plasma cytokines kinetics, and their associations with virological and immunological parameters, in a well-characterized AHI cohort where participants were diagnosed before peak viremia.

METHODS

Blood cytokine levels were measured using Luminex and ELISA assays pre-infection, during the hyperacute infection phase (before or at peak viremia, 1-11 days after the first detection of viremia), after peak viremia (24-32 days), and during the early chronic phase (77-263 days). Gag-protease-driven replicative capacities of the transmitted/founder viruses were determined using a green fluorescent reporter T cell assay. Complete blood counts were determined before and immediately following AHI detection before ART initiation.

RESULTS

Untreated AHI was associated with a cytokine storm of 12 out of the 33 cytokines analyzed. Initiation of ART during Fiebig stages I-II abrogated the cytokine storm. In untreated AHI, virus replicative capacity correlated positively with IP-10 (rho = 0.84, P < 0.001) and IFN-alpha (rho = 0.59, P = 0.045) and inversely with nadir CD4⁺ T cell counts (rho = - 0.58, P = 0.048). Hyperacute HIV infection before the initiation of ART was associated with a transient increase in monocytes (P < 0.001), decreased lymphocytes (P = 0.011) and eosinophils (P = 0.003) at Fiebig stages I-II, and decreased eosinophils (P < 0.001) and basophils (P = 0.007) at Fiebig stages III-V. Levels of CXCL13 during the untreated hyperacute phase correlated inversely with blood eosinophils (rho = - 0.89, P < 0.001), basophils (rho = - 0.87, P = 0.001) and lymphocytes (rho = - 0.81, P = 0.005), suggesting their trafficking into tissues. In early treated individuals, time to viral load suppression correlated positively with plasma CXCL13 at the early chronic phase (rho = 0.83, P = 0.042).

CONCLUSION

While commencement of ART during Fiebig stages I-II of AHI abrogated the HIV-induced cytokine storm, significant depletions of eosinophils, basophils, and lymphocytes, as well as transient expansions of monocytes, were still observed in these individuals in the hyperacute phase before the initiation of ART, suggesting that even ART initiated during the onset of viremia does not abrogate all HIV-induced immune changes.

Resolution metabolomes activated by hypoxic environment

Targeting hypoxia-sensitive pathways in immune cells is of interest in treating diseases. Here, we demonstrate that physiologic hypoxia (1% O₂), as encountered in bone marrow and spleen, accelerates human M2 macrophage efferocytosis of apoptotic-neutrophils and senescent erythrocytes via lipolysis-dependent biosynthesis of specialized pro-resolving mediators (SPMs), i.e. resolvins, protectins, maresins and lipoxin. SPM-production was enhanced via hypoxia in M2 macrophages interacting with neutrophils and erythrocytes enabling structural elucidation of a novel eicosapentaenoic acid (EPA)-derived resolvin, resolvin E4 (RvE4) that stimulates efferocytosis of senescent erythrocytes and more potently than aspirin in mouse hemorrhagic exudates. In hypoxia, glycolysis inhibition enhanced neutrophil RvE4-SPM biosynthesis. Human macrophage-erythrocyte co-incubations in physiologic hypoxia produced RvE4-SPM from erythrocyte stores of omega-3 fatty acids. These results indicate that hypoxic environments, including bone marrow and spleen as well as sites of inflammation, activate SPM-biosynthetic circuits that in turn stimulate resolution and clearance of senescent erythrocytes and apoptotic neutrophils.

A novel myeloid cell in murine spleen defined through gene profiling

A novel myeloid antigen presenting cell can be generated through in vitro haematopoiesis in long‐term splenic stromal cocultures. The in vivo equivalent subset was recently identified as phenotypically and functionally distinct from the spleen subsets of macrophages, conventional (c) dendritic cells (DC), resident monocytes, inflammatory monocytes and eosinophils. This novel subset which is myeloid on the basis of cell surface phenotype, but dendritic‐like on the basis of cell surface marker expression and antigen presenting function, has been tentatively labelled “L‐DC.” Transcriptome analysis has now been employed to determine the lineage relationship of this cell type with known splenic cDC and monocyte subsets. Principal components analysis showed separation of “L‐DC” and monocytes from cDC subsets in the second principal component. Hierarchical clustering then indicated a close lineage relationship between this novel subset, resident monocytes and inflammatory monocytes. Resident monocytes were the most closely aligned, with no genes specifically expressed by the novel subset. This subset, however, showed upregulation of genes reflecting both dendritic and myeloid lineages, with strong upregulation of several genes, particularly CD300e. While resident monocytes were found to be dependent on Toll‐like receptor signalling for development and were reduced in number in Myd88‐/‐ and Trif‐/‐ mutant mice, both the novel subset and inflammatory monocytes were unaffected. Here, we describe a novel myeloid cell type closely aligned with resident monocytes in terms of lineage but distinct in terms of development and functional capacity.

Dysregulated fatty acid metabolism in nasal polyp-derived eosinophils from patients with chronic rhinosinusitis

BACKGROUND

Eosinophils are multifunctional granulocytes capable of releasing various cytokines, chemokines, and lipid mediators. We previously reported dysregulated fatty acid metabolism in peripheral blood-derived eosinophils from patients with severe asthma. However, functional characteristics of eosinophils present in allergic inflammatory tissues remain largely uncharacterized.

METHODS

We established a method for isolating CD69^hi CCR3^low CXCR4^- siglec-8^int eosinophils from nasal polyps of patients with eosinophilic rhinosinusitis (NP-EOS). Multi-omics analysis including lipidomics, proteomics, and transcriptomics was performed to analyze NP-EOS as compared to peripheral blood-derived eosinophils from healthy subjects (PB-EOS).

RESULTS

Lipidomic analysis revealed impaired synthesis of prostaglandins and 15-lipoxygenase (15-LOX)-derived mediators, and selective upregulation of leukotriene D₄ production. Furthermore, proteomics and transcriptomics revealed changes in the expression of specific enzymes (GGT5, DPEP2, and 15-LOX) responsible for dysregulated lipid metabolism. Ingenuity pathway analysis indicated the importance of type 2 cytokines and pattern recognition receptor pathways. Stimulation of PB-EOS with eosinophil activators IL-5, GM-CSF, and agonists of TLR2 and NOD2 mimicked the observed changes in lipid metabolism.

CONCLUSION

Inflammatory tissue-derived eosinophils possess a specific phenotype with dysregulated fatty acid metabolism that may be targeted therapeutically to control eosinophilic inflammatory diseases.

Enzymatically oxidized phospholipids assume center stage as essential regulators of innate immunity and cell death

Enzymatically oxidized phospholipids (eoxPLs) are formed through regulated processes by which eicosanoids or prostaglandins are attached to phospholipids (PLs) in immune cells. These eoxPLs comprise structurally diverse families of biomolecules with potent bioactivities, and they have important immunoregulatory roles in both health and disease. The formation of oxPLs through enzymatic pathways and their signaling capabilities are emerging concepts. This paradigm is changing our understanding of eicosanoid, prostaglandin, and PL biology in health and disease. eoxPLs have roles in cellular events such as ferroptosis, apoptosis, and blood clotting and diseases such as arthritis, diabetes, and cardiovascular disease. They are increasingly recognized as endogenous bioactive mediators and potential targets for drug development. This review will describe recent evidence that places eoxPLs and their biosynthetic pathways center stage in immunoregulation.

Specialized Proresolving Mediators in Innate and Adaptive Immune Responses in Airway Diseases

Airborne pathogens and environmental stimuli evoke immune responses in the lung. It is critical to health that these responses be controlled to prevent tissue damage and the compromise of organ function. Resolution of inflammation is a dynamic process that is coordinated by biochemical and cellular mechanisms. Recently, specialized proresolving mediators (SPMs) have been identified in resolution exudates. These molecules orchestrate anti-inflammatory and proresolving actions that are cell type specific. In this review, we highlight SPM biosynthesis, the influence of SPMs on the innate and adaptive immune responses in the lung, as well as recent insights from SPMs on inflammatory disease pathophysiology. Uncovering these mediators and cellular mechanisms for resolution is providing new windows into physiology and disease pathogenesis.

CXCL13 produced by macrophages due to Fli1 deficiency may contribute to the development of tissue fibrosis, vasculopathy and immune activation in systemic sclerosis

CXCL13, a chemokine for B cells, follicular T cells, T helper 17 cells, and regulatory T cells, is reported to contribute to the development of systemic sclerosis (SSc), reflecting aberrant activation of immune system. To better understand the role of CXCL13 in SSc, we investigated the influence of Fli1 deficiency, a potential predisposing factor of this disease, on CXCL13 expression and assessed the clinical correlation of serum CXCL13 levels by multivariate regression analysis. Haploinsufficient loss of Fli1 remarkably induced CXCL13 expression in murine peritoneal macrophages, while gene silencing of FLI1 did not affect the expression of CXCL13 in human dermal fibroblasts and human dermal microvascular endothelial cells. Serum CXCL13 levels were elevated in SSc patients compared with healthy controls and correlated positively with skin score and negatively with pulmonary function test results. SSc patients with elevated serum CXCL13 levels had longer disease duration, diffuse cutaneous involvement, interstitial lung disease (ILD), heart involvement, pulmonary arterial hypertension, Raynaud's phenomenon, pitting scars, digital ulcers, telangiectasia, and high serum IgG levels more frequently than the other patients. In particular, serum CXCL13 levels were associated with ILD and digital ulcers by multivariate regression analysis. Taken together, these results indicate that CXCL13 expression is upregulated by Fli1 deficiency in macrophages, potentially contributing to the development of tissue fibrosis, vasculopathy and immune activation in SSc, especially ILD and digital ulcers.

Tumor necrosis factor-α, interleukin-8 and eosinophil cationic protein as serum markers of glucocorticoid efficacy in the treatment of bronchial asthma

BACKGROUND

Bronchial asthma (BA) is a common chronic respiratory disease that has exhibited a rising global incidence in recent years. Glucocorticoids are used for the treatment of BA. Emerging evidence has demonstrated the roles of tumor necrosis factor (TNF-α), interleukin-8 (IL-8) and eosinophil cationic protein (ECP) in BA. The present study investigated whether TNF-α, IL-8 and ECP were associated with the clinical stages and severity of BA and the efficacy of glucocorticoids in the treatment of BA.

METHODS

A total of 199 patients with BA and 174 healthy individuals were included in this study. Patients with BA underwent glucocorticoid treatment, and the TNF-α, IL-8 and ECP levels and lung functions of the subjects were measured. The correlations of the TNF-α, IL-8 and ECP levels with BA severity, clinical staging and lung functions were assessed. We investigated whether the TNF-α, IL-8 and ECP levels aided in evaluating the efficacy of using glucocorticoids for the treatment of BA.

RESULTS

TNF-α, IL-8 and ECP exhibited high levels in patients with BA, and glucocorticoid treatment notably decreased these levels. The TNF-α, IL-8 and ECP levels were positively correlated with the clinical stages and severity of BA and negatively correlated with lung function. TNF-α, IL-8 and ECP can be used as serum markers to predict the efficacy of glucocorticoids in the treatment of BA.

CONCLUSION

The key findings of this study collectively support a role for TNF-α, IL-8 and ECP in BA development, and TNF-α, IL-8 and ECP can be used as serum markers of glucocorticoid efficacy in BA.

Enzymatic lipid oxidation by eosinophils propagates coagulation, hemostasis, and thrombotic disease

Blood coagulation is essential for physiological hemostasis but simultaneously contributes to thrombotic disease. However, molecular and cellular events controlling initiation and propagation of coagulation are still incompletely understood. In this study, we demonstrate an unexpected role of eosinophils during plasmatic coagulation, hemostasis, and thrombosis. Using a large-scale epidemiological approach, we identified eosinophil cationic protein as an independent and predictive risk factor for thrombotic events in humans. Concurrent experiments showed that eosinophils contributed to intravascular thrombosis by exhibiting a strong endogenous thrombin-generation capacity that relied on the enzymatic generation and active provision of a procoagulant phospholipid surface enriched in 12/15-lipoxygenase-derived hydroxyeicosatetraenoic acid-phosphatidylethanolamines. Our findings reveal a previously unrecognized role of eosinophils and enzymatic lipid oxidation as regulatory elements that facilitate both hemostasis and thrombosis in response to vascular injury, thus identifying promising new targets for the treatment of thrombotic disease.

Eosinophil polyunsaturated fatty acid metabolism and its potential control of inflammation and allergy

Polyunsaturated fatty acids (PUFAs) exhibit a range of biological effects, many of which are mediated through the formation and actions of their bioactive metabolites. It is well appreciated that dietary PUFA balance affects inflammation and/or allergic diseases, and recent advances in liquid chromatography tandem mass spectrometry (LC-MS/MS)-based mediator lipidomics have revealed a potential link between PUFA metabolism and biological phenotypes. This review presents insights into the emerging roles of eosinophil PUFA metabolism in controlling inflammatory responses and its potential involvement in allergy control.

Single-cell analysis reveals new subset markers of murine peritoneal macrophages and highlights macrophage dynamics upon Staphylococcus aureus peritonitis

Resident macrophages play a central role in maintaining tissue homeostasis and immune surveillance. Here, we used single cell-based qPCR coupled with flow cytometry analysis to further define the phenotypes of large and small resident peritoneal macrophages (LPMs and SPMs, respectively) in mice. We demonstrated that the expression of Cxcl13, IfngR1, Fizz-1 and Mrc-1 clearly distinguished between LPMs and SPMs subsets. Using these markers, the dynamics of peritoneal macrophages in a Staphylococcus aureus-induced peritonitis model were analyzed. We found that S. aureus infection triggers a massive macrophage disappearance reaction in both subsets. Thereafter, inflammatory monocytes rapidly infiltrated the cavity and differentiated to replenish the SPMs. Although phenotypically indistinguishable from resident SPMs by flow cytometry, newly recruited SPMs had a different pattern of gene expression dominated by M2 markers combined with M1 associated features (inos expression). Interestingly, S. aureus elicited SPMs showed a robust expression of Cxcl13, suggesting that these cells may endorse the role of depleted LPMs and contribute to restoring peritoneal homeostasis. These data provide information on both resident and recruited macrophages dynamics upon S. aureus infection and demonstrate that single-cell phenotyping is a promising and highly valuable approach to unraveling macrophage diversity and plasticity.

Innate immunity is a key factor for the resolution of inflammation in asthma

The resolution of inflammation is an integral and natural part of the physiological response to tissue injury, infection and allergens or other noxious stimuli. Resolution is now recognised as an active process with highly regulated cellular and biochemical events. Recent discoveries have highlighted that innate inflammatory cells have bimodal effector functions during the inflammatory response, including active roles during the resolution process. Several mediators displaying potent pro-resolving actions have recently been uncovered. Lipoxin A4, the lead member of this new class of pro-resolving mediators, has anti-inflammatory actions on type 2 innate lymphoid cells and pro-resolving actions through natural killer cells in asthma immunobiology. Eosinophils are also able to control crucial aspects of resolution through the generation of pro-resolving mediators. Uncontrolled asthma has been associated with a defect in the generation of specialised pro-resolving mediators, including lipoxin A4 and protectin D1. Thus, bioactive stable analogue mimetics of these mediators that can harness endogenous resolution mechanisms for inflammation may offer new therapeutic strategies for asthma and airway inflammation associated diseases.

The resolution of inflammation: Principles and challenges

The concept that chemokines, cytokines and pro-inflammatory mediators act in a co-ordinated fashion to drive the initiation of the inflammatory reaction is well understood. The significance of such networks acting during the resolution of inflammation however is poorly appreciated. In recent years, specific pro-resolving mediators were discovered which activate resolution pathways to return tissues to homeostasis. These mediators are diverse in nature, and include specialized lipid mediators (lipoxins, resolvins, protectins and maresins) proteins (annexin A1, galectins) and peptides, gaseous mediators including hydrogen sulphide, a purine (adenosine), as well as neuromodulator release under the control of the vagus nerve. Functionally, they can act to limit further leukocyte recruitment, induce neutrophil apoptosis and enhance efferocytosis by macrophages. They can also switch macrophages from classical to alternatively activated cells, promote the return of non-apoptotic cells to the lymphatics and help initiate tissue repair mechanisms and healing. Within this review we highlight the essential cellular aspects required for successful tissue resolution, briefly discuss the pro-resolution mediators that drive these processes and consider potential challenges faced by researchers in the quest to discover how inflammation resolves and why chronic inflammation persists.

Rebamipide suppresses TNF-α mediated inflammation in vitro and attenuates the severity of dermatitis in mice

Rebamipide is a routine drug for the treatment of gastritis in a clinical setting. Recently, it has been shown to protect against various inflammatory diseases, and has provided a potential therapy for these diseases. However, whether rebamipide has a role in dermatitis remains to be elucidated. Here, we found that rebamipide alleviated the inflammatory reaction induced by tumor necrosis factor-α in RAW264.7, a stable macrophage cell line. Furthermore, rebamipide treatment repressed activation of nuclear factor-kappaB signaling, a well-established inflammatory signaling pathway. Moreover, an oxazolone-induced dermatitis mouse model was established to investigate the role of rebamipide in vivo. PBS control group exhibited typical skin inflammation, whereas treatment with rebamipide remarkably attenuated a dermatitis phenotype in this mouse model. The protective role of rebamipide in dermatitis in vivo was probably due to its inhibition of nuclear factor-kappaB signaling. Collectively, rebamipide may represent a promising molecular target for the prevention and treatment of inflammatory skin diseases.