Alterations In Neutrophil Function Research Articles

Interplay between circulating von Willebrand factor and neutrophils: implications for inflammation, neutrophil function, and von Willebrand factor clearance.

Von Willebrand factor (VWF) plays a critical role in hemostasis, and emerging evidence suggests its involvement in inflammation. Our study aimed to investigate the interaction between circulating plasma VWF and neutrophils (polymorphonuclear cells, PMNs), elucidate the fate of VWF after binding, and explore its impact on neutrophil behavior. Neutrophils were isolated from the whole blood of healthy volunteers, and their interaction with plasma VWF was examined ex vivo. Immunofluorescence imaging revealed an enhanced binding of VWF to neutrophils following stimulation with inflammatory agents (PMA, TNFα, and IL-8) and exposure to shear forces, highlighting a previously unknown interaction. Furthermore, immunofluorescence images demonstrated increased co-localization of VWF with the early endosome marker EEA1 and the late endosome marker Rab7 over time, indicating the uptake of VWF by neutrophils subsequent to the binding. This was supported by a significant decrease in VWF antigen levels in the supernatant of cells after stimulation. Moreover, stimulated neutrophils exposed to purified plasma-derived VWF exhibited elevated expression of neutrophil surface markers CD45 and CD66b, indicative of altered neutrophil function related to cell adhesion, migration, and phagocytosis. These findings suggest that VWF binding can modulate neutrophil function, potentially influencing their role in immune responses and inflammation. In summary, our study provides novel insights into the complex interplay between VWF and neutrophils, shedding light on the multifaceted roles of VWF in inflammation. Importantly, we have identified neutrophils as potential cellular mediators involved in the clearance of VWF from circulation, introducing a novel mechanism for VWF removal.

Neutrophil phenotype, effector functions and microbicidal activity in SARS-CoV-2-associated ARDS patients.

Critically ill patients admitted to the intensive care unit (ICU) for SARS-CoV-2-induced acute respiratory distress syndrome (ARDS) are at increased risk of bacterial and fungal secondary pulmonary infections due to acquired immune dysfunction. Given that the activity of neutrophils has not been described in these patients, we aimed to investigate the function of neutrophils at ICU admission and on Day 7 (D7) post admission. Neutrophil maturation and several functional indicators were investigated. We detected a significant decrease in reactive oxygen species production at D7, but we did not observe any other significant alterations in neutrophil function. Furthermore, bronchoalveolar lavage obtained from patients displayed no inhibitory effect on the function of neutrophils from healthy donors. These findings indicate that patients admitted to the ICU for SARS-CoV-2-induced ARDS do not acquire neutrophil dysfunction within the first week of their stay, which suggests that nosocomial infections among these patients are not due to acquired neutrophil dysfunctions.

CXCR1/2 antagonism inhibits neutrophil function and not recruitment in cancer

ABSTRACT The level of tumor and circulating CXCR1/2-expressing neutrophils and CXCR1/2 ligands correlate with poor patient outcomes, inversely correlate with tumoral lymphocyte content, and predict immune checkpoint inhibitor (ICI) treatment failure. Accordingly, CXCR2-selective and CXCR1/2 dual inhibitors exhibit activity both as single agents and in combination with ICI treatment in mouse tumor models. Based on such reports, clinical trials combining CXCR1/2 axis antagonists with ICI treatment for cancer patients are underway. It has been assumed that CXCR1/2 blockade impacts tumors by blocking neutrophil chemotaxis and reducing neutrophil content in tumors. Here, we show that while CXCR2 antagonism does slow tumor growth, it does not preclude neutrophil recruitment into tumor. Instead, CXCR1/2 inhibition alters neutrophil function by blocking the polarization of transcriptional programs toward immune suppressive phenotypes and rendering neutrophils incapable of suppressing lymphocyte proliferation. This is associated with decreased release of reactive oxygen species and Arginase-1 into the extracellular milieu. Remarkably, these therapeutics do not impact the ability of neutrophils to phagocytose and kill ingested bacteria. Taken together, these results mechanistically explain why CXCR1/2 inhibition has been active in cancer but without infectious complications.

Arsenic treatment of acute promyelocytic leukemia affects neutrophil function in a compensatory manner

BackgroundArsenic (ATO) and retinoic acid (ATRA) are successfully used as chemotherapy-free regimens to treat acute APL. Compared to traditional chemotherapy approaches, this therapy evokes fewer haematological side effects, such as severe neutropenia and thrombocytopenia, but little is known about the impact of the treatment on neutrophil function.MethodsWe included three patients undergoing consolidation treatment for APL. To evaluate the functionality of neutrophils, we assessed chemotaxis, ROS production, and neutrophil extracellular trap (NET) release during different time points of the treatment and compared them with neutrophils from healthy donors.ResultsWe revealed that the chemotactic ability of neutrophils isolated from APL patients was decreased before starting each cycle of treatment. However, there was an increase in chemotactic ability in the first week of treatment compared to other time points. Additionally, we observed increased ROS production at the start of the treatment cycle. In vitro exposure of isolated neutrophils from healthy donors to ATO led to decreased chemotaxis at high ATO concentrations exceeding those achieved in vivo, while ROS production was not affected. Chemotaxis and ROS production were not altered by exposure to ATRA in vitro and neither ATO nor ATRA had an effect on neutrophils’ ability to release NETs.ConclusionsOur study suggests that ATO and ATRA therapy alter neutrophil function by increasing chemotaxis and reducing ROS production. The effect on neutrophil function does not, however, seem to impact infection susceptibility in our patients, indicating that the enhanced functionality might compensate for the lowered neutrophil count.

Neutrophil-Derived Inflammation and Pregnancy Outcomes

Inflammation, orchestrated by immune cells like neutrophils, plays a crucial role in maintaining homeostasis and protecting against pathogens. However, during pregnancy, the delicate balance of immune responses is paramount to support fetal development while safeguarding maternal health. Neutrophils, as pivotal contributors to the innate immune system, significantly influence the inflammatory milieu, yet excessive or dysregulated neutrophil-derived inflammation can impact pregnancy outcomes. This paper aims to dissect the multifaceted role of neutrophil-derived inflammation in shaping pregnancy outcomes. It delves into the mechanisms by which neutrophils orchestrate inflammatory responses during gestation and scrutinizes the implications of heightened inflammation on maternalfetal health. Specifically, it explores the association between increased neutrophil-driven inflammation and adverse outcomes such as preterm birth, preeclampsia, intrauterine growth restriction, and fetal developmental abnormalities. Examining the intricate balance between protective and detrimental roles of neutrophil-derived inflammation, this review assesses alterations in neutrophil functions, activation pathways, and the release of inflammatory mediators during normal and pathological pregnancies. Additionally, it evaluates potential regulatory mechanisms governing neutrophil-derived inflammation and identifies putative biomarkers indicative of heightened inflammatory responses linked to adverse pregnancy outcomes. The clinical implications of understanding the impact of neutrophil-derived inflammation on pregnancy outcomes are highlighted, emphasizing its significance in obstetric care, prenatal monitoring, and potential therapeutic interventions. Furthermore, this review delineates the NEWPORT INTERNATIONAL JOURNAL OF SCIENTIFIC AND EXPERIMENTAL SCIENCES (NIJSES) Volume 4 Issue 2 2023 ©NIJSES Publications Open Access ONLINE ISSN: 2992-5819 PRINT ISSN: 2992-6149 Obeagu et al., 2023 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited Page | 11 critical need for future research avenues focusing on molecular investigations, therapeutic modulation of neutrophildriven inflammation, and longitudinal studies to elucidate the long-term consequences on maternal and fetal wellbeing. In conclusion, unraveling the intricate interplay between neutrophil-derived inflammation and pregnancy outcomes is imperative. A deeper understanding of these interactions holds promise for informing clinical strategies, improving prenatal care, and ultimately optimizing maternal and fetal health.

Neutrophil heterogeneity and aging: implications for COVID-19 and wound healing.

Neutrophils play a critical role in the immune response to infection and tissue injury. However, recent studies have shown that neutrophils are a heterogeneous population with distinct subtypes that differ in their functional properties. Moreover, aging can alter neutrophil function and exacerbate immune dysregulation. In this review, we discuss the concept of neutrophil heterogeneity and how it may be affected by aging. We then examine the implications of neutrophil heterogeneity and aging for COVID-19 pathogenesis and wound healing. Specifically, we summarize the evidence for neutrophil involvement in COVID-19 and the potential mechanisms underlying neutrophil recruitment and activation in this disease. We also review the literature on the role of neutrophils in the wound healing process and how aging and neutrophil heterogeneity may impact wound healing outcomes. Finally, we discuss the potential for neutrophil-targeted therapies to improve clinical outcomes in COVID-19 and wound healing.

Systemic paracoccidioidomycosis in a patient with enzymatic myeloperoxidase deficiency and acute lymphoblastic leukemia: case report

BackgroundParacoccidioidomycosis is a systemic fungal infection that is potentially fatal, and the most prevalent of its kind in Latin America. The predisposition to infection appears to be related to abnormalities in cellular immunity, given its low prevalence in endemic regions. The role of myeloperoxidase deficiency has not been elucidated.Case presentationWe present a case of 48-year-old female patient with acute lymphoblastic leukemia, stem cell transplant candidate, who developed a fever with lymphadenopathy and lung nodules, consistent with paracoccidioidomycosis infection, in whom a myeloperoxidase deficiency was later discovered. The treatment of the hematologic malignancy had a good impact solving the enzymatic deficiency and antifungal therapy achieve controlling the infection.ConclusionsThis case lays out the possible association between acute leukemia, an alteration in neutrophil function (needed to fight fungal infections) and an infection due to Paracoccidioides brasiliensis.

Protoporphyrin IX derived from dual-species anaerobic biofilms of Fusobacterium necrophorum and Porphyromonas levii attenuates bovine neutrophil function

Host immune cells and clinical interventions often fail to eradicate biofilm-mediated infections, resulting in chronic inflammation. The role of the biofilm three-dimensional structure in this tolerant phenotype has been studied extensively; however, the impact of small molecules released from biofilm-bacteria in modulating host immune function is less well understood. A model of mixed-species biofilms composed of Fusobacterium necrophorum and Porphyromonas levii was developed to evaluate bovine neutrophil responses to bioactive molecules released from either biofilm or planktonic bacteria. We hypothesized that different soluble extracellular factors (ECFs) would be released from planktonic and biofilm bacteria, resulting in altered neutrophil function. Neutrophils exposed to ECFs from planktonic bacteria showed significantly elevated levels of reactive oxygen species (ROS). In contrast, biofilm components from these same species of bacteria failed to induce such a response. Size-exclusion filtration of ECFs revealed that the bioactive molecule causing neutrophil ROS responses was below 3 kDa. Intensive heat, nuclease, lipase, or protease treatments of the <3 kDa fractions did not alter neutrophil functional responses. Protoporphyrin IX (PPIX) is an important heme precursor and growth requirement for many anaerobes. Porphyromonas species can accumulate environmental PPIX at the cell surface as a strategy to protect the bacteria from oxidative stress and we investigated the direct interaction of bovine neutrophils with PPIX. In the present study, evidence suggests that the accumulation of protoporphyrin in these dual-species biofilm ECFs attenuates neutrophil ROS production and chemotaxis. The diminished neutrophil response to biofilm ECFs via the action of PPIX may represent a biofilm immune-evasion strategy that could assist in explaining the ineffectual host clearance of biofilm-mediated infections involving these bacteria.

Androgen exposure alters the neutrophil response to pyelonephritis

Abstract Urinary tract infections (UTIs) in men are uncommon but carry increased risk for severe upper-tract UTI (pyelonephritis) and complications including renal scarring. In preclinical models of Escherichia coli UTI, male C3H/HeN mice uniformly develop high-titer pyelonephritis (most with renal abscesses), while the majority of female C3H/HeN mice resolve renal infection within 7–14 days. We previously showed that this difference in outcomes is testosterone dependent. Here, we find that androgen exposure in female C3H/HeN mice alters the neutrophil response to UTI, increasing the propensity for severe renal inflammation and abscess formation as opposed to bacterial clearance and resolution of infection. Concordant with our prior published results, androgen exposure in C3H female mice given Escherichia coli UTI led to 3-log higher bacterial loads in the kidneys by 14 days post infection. We found that the kidneys of androgen-exposed mice harbored more neutrophils than standard females at baseline and throughout infection, correlated with higher levels of the neutrophil-recruiting chemokine CXCL1 (murine KC) in kidney tissue. In addition, the kidneys of androgen-exposed females were enriched for aged, immature neutrophils (Ly6G+, CD49d+, CD101−). Compared to their mature (CD101+) counterparts, these cells exhibited markers of increased degranulation, altered phagocytic activity, and diminished capacity for efflux from kidney tissue. These data support a model in which androgen-exposed mice, despite an apparently more robust neutrophil presence, fail to control renal bacterial infection due to altered neutrophil functions. Supported by grants from NIH (R01 DK111541, R01 DK126697, R01 AI158418)

Donor B Cells Alter Donor Neutrophil Behaviour and Protect from Lethality During Lung Allograft Reperfusion in Mice

<h3>Purpose</h3> We showed that donor B cell depletion causes mortality in a C57BL/10 (B10, H-2^b)-to-C57BL/6 (B6, H-2^b) minor alloantigen-mismatched mouse orthotopic lung transplant model with prolonged graft storage to induce ischemia-reperfusion injury (Kawashima et al. 2021 ISHLT abstract). This finding prompted us to investigate possible mechanisms by which donor B cells might augment lung injury and mortality. <h3>Methods</h3> We performed B10-to-B6 left lung transplants with prolonged (6h at 4°C followed by 45min at 37°C and 15min anastomosis time) antecedent storage using congenic donors and recipients. Donors received anti-CD20 antibody or IgG control on day -2 (Fig 1A). Necropsies were performed 1 hour after reperfusion or upon earlier recipient death. Allograft wet/dry weight ratio (W/D ratio) was assessed. Flow cytometry was used to enumerate myeloid cell populations in donor and recipient lungs given B cells and neutrophil interaction was reported elsewhere. Two-photon microscopy of precision-cut lung slices was used to observe cellular behaviour. <h3>Results</h3> Donor anti-CD20 treatment was associated with early postoperative death (p=NS), consistent with our previous report (Fig 1B). The W/D ratio of transplanted left lung was higher in the anti-CD20 group compared with normal lung control (Fig 1C, p=0.01). Anti-CD20 treatment depleted B cells from donor lungs and resulted in decreased donor neutrophils post-transplant (Fig 1D, p=0.02). Recipient myeloid cell numbers did not differ between the groups (not shown). An increase in neutrophil motility was observed in donor lungs from anti-CD20-treated mice (Fig 1E, p<0.01). <h3>Conclusion</h3> Our results suggest that altered donor neutrophil function triggered by B cell depletion may contribute to acute lung injury leading to death in a subset of recipients. Further investigation is now underway.

ADAM8 signaling drives neutrophil migration and ARDS severity.

Acute respiratory distress syndrome (ARDS) results in catastrophic lung failure and has an urgent, unmet need for improved early recognition and therapeutic development. Neutrophil influx is a hallmark of ARDS and is associated with the release of tissue-destructive immune effectors, such as matrix metalloproteinases (MMPs) and membrane-anchored metalloproteinase disintegrins (ADAMs). Here, we observed using intravital microscopy that Adam8–/– mice had impaired neutrophil transmigration. In mouse pneumonia models, both genetic deletion and pharmacologic inhibition of ADAM8 attenuated neutrophil infiltration and lung injury while improving bacterial containment. Unexpectedly, the alterations of neutrophil function were not attributable to impaired proteolysis but resulted from reduced intracellular interactions of ADAM8 with the actin-based motor molecule Myosin1f that suppressed neutrophil motility. In 2 ARDS cohorts, we analyzed lung fluid proteolytic signatures and identified that ADAM8 activity was positively correlated with disease severity. We propose that in acute inflammatory lung diseases such as pneumonia and ARDS, ADAM8 inhibition might allow fine-tuning of neutrophil responses for therapeutic gain.

Altered Mitochondrial Homeostasis during Systemic Lupus Erythematosus Impairs Neutrophil Extracellular Trap Formation Rendering Neutrophils Ineffective at Combating Staphylococcus aureus.

Inflammation involves a delicate balance between pathogen clearance and limiting host tissue damage, and perturbations in this equilibrium promote disease. Patients suffering from autoimmune diseases, such as systemic lupus erythematosus (SLE), have higher levels of serum S100A9 protein and increased risk for infection. S100A9 is highly abundant within neutrophils and modulates antimicrobial activity in response to bacterial pathogens. We reasoned that increased serum S100A9 in SLE patients reflects accumulation of S100A9 protein in neutrophils and may indicate altered neutrophil function. In this study, we demonstrate elevated S100A9 protein within neutrophils from SLE patients, and MRL/lpr mice associates with lower mitochondrial superoxide, decreased suicidal neutrophil extracellular trap formation, and increased susceptibility to Staphylococcus aureus infection. Furthermore, increasing mitochondrial superoxide production restored the antibacterial activity of MRL/lpr neutrophils in response to S. aureus These results demonstrate that accumulation of intracellular S100A9 associates with impaired mitochondrial homeostasis, thereby rendering SLE neutrophils inherently less bactericidal.

NETosis in Long-Term Type 1 Diabetes Mellitus and Its Link to Coronary Artery Disease.

BackgroundNeutrophil extracellular traps NETs have been linked to glucose and the pathogenesis of type 1 diabetes mellitus (T1DM). NETs also play a role in vascular inflammation and the development of coronary artery disease (CAD). The role of NETs in CAD progression in patients with long-term T1DM is unclear. We aimed to 1) investigate whether levels of circulating NETs markers were elevated in long-term T1DM subjects compared to controls, and 2) explore whether levels of NETs were related to the presence of CAD.Material and Methods102 patients with > 45 years of T1DM and 75 age-matched controls were enrolled in a cross-sectional study. Median age was 62 years. Computed tomography coronary angiography (CTCA) was performed in 148 subjects without established coronary heart disease. For the current study, CAD was defined as a coronary artery stenosis >50%. Double-stranded deoxyribonucleic acid (dsDNA) was measured by a nucleic acid stain, myeloperoxidase-DNA (MPO-DNA), citrullinated histone 3 (H3Cit) and peptidylarginine deiminase 4 (PAD4) by ELISAs, while gene expression of PAD4 was measured in leukocytes from PAXgene tubes.ResultsCirculating MPO-DNA levels were significantly lower in patients with T1DM than in controls (0.17 vs 0.29 OD, p<0.001), while dsDNA, H3Cit, PAD4 and gene expression of PAD4 did not differ with respect to the presence of T1DM. There were no significant associations between NETs markers and HbA1c in the T1DM group. None of the NETs markers differed according to the presence of CAD in patients with T1DM. While all circulating NETs markers correlated significantly with circulating neutrophils in the control group (r=0.292-393, p<0.014), only H3Cit and PAD4 correlated with neutrophils in the T1DM group (r= 0.330-0.449, p ≤ 0.001).ConclusionsIn this cross-sectional study of patients with long-term T1DM and age-matched controls, circulating NETs levels were not consistently associated with the presence of T1DM or glycemic status, and did not differ according to the presence of CAD in patients with T1DM. Our results entail the possibility of altered neutrophil function and reduced NETosis in T1DM. This warrants further investigation.

DNMT3A R882 Mutation in Human Haematopoietic Stem Cells Alters Differentiation Towards Neutrophils and Monocytes

Age related clonal haematopoiesis (ARCH) is defined as the clonal expansion of hematopoietic stem cells (HSCs), driven by recurrent mutations. Many of these are also commonly seen in haematological malignancies, hence termed pre-leukemic mutations (pLM). ARCH carries an increased risk of haematological malignancies and cardiometabolic disease. Further understanding of the role of pLMs in HSC function is necessary to predict and possibly prevent leukemia. DNMT3A R882 is the most common pLM observed in ARCH and is associated with poor outcomes in acute myeloid leukemia (AML). It is acquired early in life and is positively selected in HSCs. HSCs of Dnmt3a knock-out or knock-in mouse models have increased self-renewal capacity and can differentiate towards all lineages. DNMT3A R882 mutation is observed in all mature blood lineages in ARCH individuals, indicating their multipotential differentiation capacity, but the dynamics of differentiation are not known. We hypothesise that DNMT3A R882 mutation affects the differentiation dynamics of HSCs, potentially contributing to disease risk.We characterised the functional changes in HSC differentiation driven by DNMT3A R882 at single cell resolution. Single phenotypic HSCs (CD33-/CD34+/CD45dim/CD38-/CD45RA-) from 9 individuals (Table 1) were cultured in media supporting differentiation into all major blood lineages. To assess changes in differentiation capacity between DNMT3A R882 and wild-type (WT) HSCs within each individual, each single-cell colony was genotyped by targeted DNA sequencing and scored by high-throughput flow cytometry. Flow cytometry data was analysed using a novel unbiased analytical pipeline, which we have named ‘FlowPAC’, allowing generation of a two-dimensional representation of the global output of HSC differentiation by identifying clusters based on fluorochrome intensity. Four samples were underpowered for either DNMT3A R882 or WT colonies and were excluded from this analysis.We did not observe any difference in erythroid versus myeloid or lymphoid (NK) differentiation capacity between DNMT3A R882 and WT HSC. DNMT3A R882 and WT HSCs also produced similar proportions of monocytic and neutrophil colonies. However, FlowPAC analysis identified differences in their level of maturity. CD15 (neutrophil marker) expression was significantly increased in myeloid clusters of DNMT3A R882 colonies compared to WT (p=0.0043), whereas CD14 (monocyte marker) expression was decreased compared to WT (p=0.0645). We further analysed mature neutrophil differentiation using CD66b expression. Consistent with promotion of neutrophil differentiation, CD66b median fluorescence intensity was significantly increased in the CD15+ population of DNMT3A R882 colonies compared to WT. To further investigate monocyte differentiation, we performed RNAseq on colonies containing only monocytes from 1 ARCH sample. Analysis of transcriptional profiles confirmed less mature monocytes in DNMT3A R882 colonies compared to WT. Overall, our data indicate that DNMT3A R882 mutation in HSCs alters neutrophil and monocyte production.Additionally, we observed that in contrast to samples with high LSC content leading to leukemic engraftment in mice, in samples where DNMT3A R882 HSCs were able to reconstitute normal blood production, the expression of the cell surface marker CD49f, a marker of the most potent HSCs, was significantly increased in DNMT3A R882 HSCs compared to WT at the time of sorting. This may suggest unequal distribution of this pLM within the preserved normal HSC pool prior to leukemic transformation.In conclusion, DNMT3A R882 alters the dynamics of human HSC myeloid differentiation. The propensity of DNMT3A R882 derived monocytes to retain an immature phenotype relative to WT cells could represent an early change later facilitating the complete differentiation block seen in AML, driven by the acquisition of additional mutations such as NPM1. DNMT3A R882 also promoted neutrophil maturation. Altered neutrophil differentiation has been observed in patients with germline DNMT3A mutation. As altered neutrophil function plays a key role in cardiovascular disease, future studies are required to investigate whether the effect of DNMT3A R882 on neutrophil differentiation may contribute to the increased cardiovascular disease risk associated with this mutation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Brothers in arms: platelets and neutrophils in ischemic stroke.

In this review, we will describe how the combined ability of platelets and neutrophils to interact with each other drives ischemic stroke brain injury. Neutrophils are one of the first cells to respond during ischemic stroke. Although animals stroke models have indicated targeting neutrophils improves outcomes, clinical trials have failed to yield successful strategies. Platelets play a critical role in recruiting neutrophils to sites of injury by acting as a bridge to the injured endothelium. After initial platelet adhesion, neutrophils can rapidly bind platelets through P-selectin and glycoprotein Ibα. In addition, recent data implicated platelet phosphatidylserine as a novel key regulator of platelet-neutrophil interactions in the setting of ischemic stroke. Inhibition of procoagulant platelets decreases circulating platelet-neutrophil aggregates and thereby reduces infarct size. Platelet binding alters neutrophil function, which contributes to the injury associated with ischemic stroke. This includes inducing the release of neutrophil extracellular traps, which are neurotoxic and pro-thrombotic, leading to impaired stroke outcomes. Platelet-neutrophil interactions significantly contribute to the pathophysiology of ischemic stroke brain injury. Better understanding the mechanisms behind their formation and the downstream consequences of their interactions will lead to improved therapies for stroke patients.

Regulation of Neutrophil Function by Marine n-3 Fatty Acids-A Mini Review.

While normal functioning neutrophils contribute in various, critical ways to the maintenance of a stable immune system, their hypo- or hyper-activation has been implicated in the onset or exacerbation of multiple inflammatory conditions often affecting the vulnerable, aging population. As such, many would benefit from interventions capable of targeting neutrophils in disease-specific ways without disrupting their primary role in maintaining immune function. After consumption, marine omega-3 fatty acids are rapidly incorporated into the phospholipid bilayer of neutrophils, changing the fatty acid composition and consequently modifying neutrophil function. In addition to eicosanoid synthesis, the mechanisms by which marine n-3 fatty acids and their metabolites alter neutrophil function involve blockage of transcription factors that subsequently reduce pro-inflammatory gene expression by neutrophils and through the disruption of lipid rafts. In the current mini-review, a brief explanation of marine n-3 fatty acid metabolism is provided and the subsequent impact on neutrophil function is discussed. In addition, current evidence of the effects of marine n-3 fatty acid supplementation on neutrophil function from clinical trials conducted in the past 15 years is summarized.

Myeloperoxidase Modulates Inflammation in Generalized Pustular Psoriasis and Additional Rare Pustular Skin Diseases

Generalized pustular psoriasis (GPP) is a severe multi-systemic inflammatory disease characterized by neutrophilic pustulosis and triggered by pro-inflammatory IL-36 cytokines in skin. While 19%–41% of affected individuals harbor bi-allelic mutations in IL36RN, the genetic cause is not known in most cases. To identify and characterize new pathways involved in the pathogenesis of GPP, we performed whole-exome sequencing in 31 individuals with GPP and demonstrated effects of mutations in MPO encoding the neutrophilic enzyme myeloperoxidase (MPO). We discovered eight MPO mutations resulting in MPO -deficiency in neutrophils and monocytes. MPO mutations, primarily those resulting in complete MPO deficiency, cumulatively associated with GPP (p = 1.85E−08; OR = 6.47). The number of mutant MPO alleles significantly differed between 82 affected individuals and >4,900 control subjects (p = 1.04E−09); this effect was stronger when including IL36RN mutations (1.48E−13) and correlated with a younger age of onset (p = 0.0018). The activity of four proteases, previously implicated as activating enzymes of IL-36 precursors, correlated with MPO deficiency. Phorbol-myristate-acetate-induced formation of neutrophil extracellular traps (NETs) was reduced in affected cells (p = 0.015), and phagocytosis assays in MPO-deficient mice and human cells revealed altered neutrophil function and impaired clearance of neutrophils by monocytes (efferocytosis) allowing prolonged neutrophil persistence in inflammatory skin. MPO mutations contribute significantly to GPP’s pathogenesis. We implicate MPO as an inflammatory modulator in humans that regulates protease activity and NET formation and modifies efferocytosis. Our findings indicate possible implications for the application of MPO inhibitors in cardiovascular diseases. MPO and affected pathways represent attractive targets for inducing resolution of inflammation in neutrophil-mediated skin diseases.

The clinical and inflammatory relationships between periodontitis and chronic obstructive pulmonary disease.

To investigate associations between periodontitis and chronic obstructive pulmonary disease (COPD) with and without alpha-1 antitrypsin deficiency (AATD), including neutrophil functions implicated in tissue damage. The presence and severity of periodontitis (using two international criteria) and lung disease were assessed in 156 COPD patients with and without AATD accounting for common confounding factors. Saliva and systemic inflammatory markers were measured by ELISA together with neutrophil migration. COPD and AATD patients exhibited higher prevalence of periodontitis (COPD 95%; AATD 88%) than reported in unselected community-dwelling populations even when risk factors (age, smoking history, socio-economic status and dental habits) were considered. Periodontitis severity associated with lung disease severity (AATD, periodontitis versus no periodontitis; FEV1=56% versus 99% predicted; TLCO=59% versus 81% predicted, p<.0001 for both). Neutrophil migratory accuracy declined in stage II-IV periodontitis patients with COPD or AATD compared to COPD or AATD with no or stage I periodontitis. Improved dental habits appeared to be associated with a reduction in exacerbation frequency in COPD. The results support shared pathophysiology between periodontitis and COPD, especially when associated with AATD. This may reflect an amplification of neutrophilic inflammation and altered neutrophil functions, already described in periodontitis, COPD and AATD.

The effects of 17 Beta-Estradiol primed mesenchymal stem cells on the biology of co-cultured neutrophil

ObjectivesMesenchymal stem cells (MSCs) can influence immune effector cells. It is proved that MSCs respond to various Toll-like receptor (TLR) ligands, which could ultimately result in changes in their immunomodulatory effects. Neutrophils play an essential role in the first line defense system and their function can be regulated by MSCs. Estrogen is a female hormone that contributes to sex differences in several immune-related diseases. With regard to the stated facts, this research aims to elucidate the effects of estrogen treatment on the ability of TLR4-primed MSCs to regulate neutrophil functions. MethodsFollowing isolation and characterization, MSCs were stimulated with LPS as a TLR4 ligand and subsequently incubated with different concentrations (0, 10, 20 and 40 nM) of estrogen for 48 hrs. Then, MSCs were co-cultured with neutrophils to investigate the vitality and function of the co-cultured neutrophils. ResultsOur results indicated that TLR4-primed MSCs could decrease the viability and neutral red uptake potential of co-cultured neutrophils. Furthermore, neutrophils co-cultured with TLR4-primed MSCs exhibited a decrease in the respiratory burst intensity after being challenged with opsonized yeast. Interestingly, treating TLR4-primed MSCs with estrogen reversed the observed alterations in neutrophil functions. ConclusionIt appears that estrogen can alter the interaction between MSCs and neutrophils.

Vincristine, carboplatin and cisplatin increase oxidative burst induced by PAF in canine neutrophils

Myelosupression resulting from chemotherapy has been widely described in veterinary medicine; however, there is limited information relating to alterations in neutrophil function after chemotherapy in dogs with cancer. The aim of this study was to determine the non-proliferative effects of vincristine, carboplatin, and cisplatin on canine neutrophils by evaluating activation of oxidative and non-oxidative responses. Neutrophils were isolated from venous blood. Levels of reactive oxygen species (ROS) and metalloproteinase 9 (MMP-9) were measured in vitro during neutrophil exposure to these chemotherapeutic agents for 15 min followed by stimulation with platelet activating factor (PAF). ROS production was detected via luminescence, and MMP- 9 liberation was determined by zymography. The chemotherapeutic agents caused an increase in PAF-induced ROS production, but no change in the non-oxidative response was observed. These results suggest that these chemotherapeutic agents may act as priming agents by increasing the oxidative response. These effects could be beneficial for dogs with cancer by supporting their immune systems; however, excessive ROS liberation has been associated with inflammation, neutrophil-mediated cell injury, carcinogenesis, and metastasis. Clinical studies are necessary to evaluate the significance of these findings.