Regulation Of Neutrophil Function Research Articles

Tumor-Activated Neutrophils Promote Lung Cancer Progression through the IL-8/PD-L1 Pathway.

Lung cancer remains a major global health threat due to its complex microenvironment, particularly the role of neutrophils, which are crucial for tumor development and immune evasion mechanisms. This study aimed to delve into the impact of lung cancer cell-conditioned media on neutrophil functions and their potential implications for lung cancer progression. Employing in vitro experimental models, this study has analyzed the effects of lung cancer cell-conditioned media on neutrophil IL-8 and IFN-γ secretion, apoptosis, PD-L1 expression, and T-cell proliferation by using techniques, such as ELISA, flow cytometry, immunofluorescence, and CFSE proliferation assay. The roles of IL-8/PD-L1 in regulating neutrophil functions were further explored using inhibitors for IL-8 and PD-L1. Lung cancer cell lines were found to secrete higher levels of IL-8 compared to normal lung epithelial cells. The conditioned media from lung cancer cells significantly reduced apoptosis in neutrophils, increased PD-L1 expression, and suppressed T-cell proliferation and IFN-γ secretion. These effects were partially reversed in the presence of IL-8 inhibitors in Tumor Tissue Culture Supernatants (TTCS), while being further enhanced by IL-8. Both apoptosis and PD-L1 expression in neutrophils demonstrated dose-dependency to TTCS. Additionally, CFSE proliferation assay results further confirmed the inhibitory effect of lung cancer cell-conditioned media on T-cell proliferation. This study has revealed lung cancer cell-conditioned media to modulate neutrophil functions through regulating factors, such as IL-8, thereby affecting immune regulation and tumor progression in the lung cancer microenvironment.

PPARα suppresses growth of hepatocellular carcinoma in a high-fat diet context by reducing neutrophil extracellular traps release

Background & AimsThe role of infiltrating neutrophils in hepatocellular carcinoma (HCC) is modulated by cellular metabolism, specifically lipid homeostasis. Throughout the progression of HCC, alterations in lipid metabolism are intricately linked with various signaling that regulate neutrophil function and the release of neutrophil extracellular traps (NETs). However, the dependence of high-fat diet (HFD) on NETs for regulating the development of HCC and the potential interplay between NETs and other leukocytes remains uncertain. MethodsIn this study, the molecular mechanism of NETs release and the potential improvement of the HCC microenvironment by PPARα agonists were explored through proteomics, metabolomics, tissue microarray, immunofluorescence, flow cytometry, Western blot, and dual-luciferase reporter gene assay (n = 6 per group). ResultsOur study demonstrated a notable inhibition of PPARα signaling in HCC. Furthermore, the disruption of PPARα-mediated lipid metabolism was responsible for the release of NETs. The presence of HFD was observed to induce mitochondrial impairment in neutrophils, leading to the activation of cGAS-STING by oxidized mitochondrial DNA (Ox-mtDNA). Consequently, this activation triggered the release of NETs containing Ox-mtDNA through the enhancement of NLRP3-GSDMD-N in a NF-κB-dependent manner. Moreover, the release of NETs within HCC tissues effectively isolated cytotoxic leukocytes in the outer regions of HCC cells. ConclusionsOur study not only enriched the relationship between lipid metabolism disorders and NETs’ tumor-promoting function, but also provided an important strategic reference for multi-target or combined immunotherapy of HCC. Impact and implicationsWe have identified PPARα and its agonists as therapeutic targets for controlling the neutrophil extracellular traps associated with high lipid metabolism. Results from preclinical models suggest that PPARα can limit mitochondrial oxidative stress, inhibit cGAS-STING-NF-κB signaling, and limit the release of neutrophil extracellular traps, thereby increasing the contact of anti-tumor leukocytes and hepatocellular cancer cells, thereby limiting tumor growth.

Abstract We070: The role of neutrophil YAP in cardiac inflammation and injury

Background: There is a growing appreciation that neutrophils demonstrate plasticity, not unlike the macrophage, and can modulate both inflammation and repair following organ injury. Neutrophils are rapidly recruited to the heart after acute myocardial infarction (MI) and participate in cardiac inflammation and remodeling. Nevertheless, mechanisms regulating neutrophil function during heart injury remain largely unknown. Research Question/Aim: Previous work demonstrated that Yes-Associated Protein (YAP) regulates macrophage function during heart injury. However, whether YAP regulates neutrophil function in any context, including reperfused MI (I/R), remains unexplored. Approach: We generated neutrophil-specific YAP KO mice (MRP8 Cre ) and subjected them to I/R to elicit inflammation and injury. Cell-based experiments were performed using primary isolated mouse neutrophils. We utilized flow cytometry, single-cell RNAseq, and histological and biochemical assays to investigate underlying mechanisms. Results: Neutrophils isolated from the blood and heart of WT mice subjected to I/R revealed increased YAP expression. Compared to control mice, neutrophil YAP KO hearts had decreased infarct size after 24 hours reperfusion, and better cardiac function after 2 weeks. Single-cell RNAseq of heart leukocytes indicated suppression of inflammatory, migratory, and superoxide production pathways in YAP KO neutrophils. Characterization of neutrophils by flow cytometry indicated a shift toward reparative polarization in YAP KO mice during early reperfusion. Bone marrow-derived neutrophils (BMDNs) from KO mice had attenuated inflammatory gene expression and ROS production compared to control cells. Pharmacological inhibition of YAP using verteporfin produced comparable results. Ongoing experiments are investigating how YAP modulates neutrophil inflammatory function, and will determine the therapeutic potential of targeted YAP inhibition for I/R injury. Conclusion: These results suggest that YAP regulates neutrophil function during I/R injury in the heart and that suppression of neutrophil YAP affords cardioprotection.

Abstract Tu148: cGAS-STING pathway promotes granulopoiesis and neutrophil differentiation in acute ischemia

Contemporary evidence supports neutrophils' complex roles beyond being the simple and powerful destruction tools in MI. However, our understanding remains limited. We especially lack the knowledge of how cGAS-STING regulates neutrophil functions in acute ischemia. The cGAS-STING pathway senses cytosolic DNA to produce IFN and ISGs and is a pillar of innate immunity. Early evidence suggested neutrophils did not express cGAS. Taking advantage of the improved detecting method, we revisited this topic because this pathway can play an essential role in neutrophil function in MI. Using purified neutrophils from WT and knockout mice (as control), we detected cGAS, STING, and IRF3 in these cells. To determine if cGAS-STING regulates neutrophil function, we first generated MI model in cGAS -/- , STING -/- mice, and their WT littermates and performed flow cytometry and RNA-seq analyses. We uncovered that inhibiting cGAS-STING decreases neutrophil production in bone marrow (BM) after ischemia. Interestingly, cGAS- and STING-deficient neutrophils express significantly higher levels of primary granule molecules such as MPO, Prtn3, Elane, Cts- (s, g, b, l) but much lower levels of the secondary and tertiary granule components , including Mmp9, Mmp8, Olfm4, Cd177, Lyz2, and Lyz1. Neutrophils acquire granules sequentially during differentiation. Therefore, our data suggest inhibiting cGAS-STING leads to a stagnated neutrophil differentiation in the BM and mobilizes CD101 - immature neutrophils into the circulation and MI hearts. Consistently, cGAS- and STING-deficient neutrophils release less MMP8 and MMP9 into the ischemic area. Ischemia does not trigger the degranulation of primary granules, as indicated by the minimal changes of CD63. Our data further suggest that TF C/EBP𝜹 functions downstream of cGAS-STING to promote neutrophil differentiation. Adoptive transfer experiments suggest the neutrophil-specific function of cGAS-STING. In conclusion, we identify cGAS-STING as a novel mechanism promoting emergency granulopoiesis and neutrophil differentiation after MI and uncover its functional implications in ischemia-induced remodeling. Studies using Mrp8-Cre-mediated cGAS-STING deletion in granulocyte/macrophage progenitors are in progress.

Signaling by Neutrophil G Protein-Coupled Receptors that Regulate the Release of Superoxide Anions.

In human peripheral blood, the neutrophil granulocytes (neutrophils) are the most-abundant white blood cells. These professional phagocytes are rapidly recruited from the bloodstream to inflamed tissues by chemotactic factors that signal danger. Neutrophils, which express many receptors that are members of the large family of G protein-coupled receptors (GPCRs), are critical for the elimination of pathogens and inflammatory insults, as well as for the resolution of inflammation leading to tissue repair. Danger-signaling molecular patterns such as the N-formylated peptides that are formed during bacterial and mitochondrial protein synthesis and recognized by formyl peptide receptors (FPRs) and free fatty acids recognized by free fatty acid receptors (FFARs) regulate neutrophil functions. Short peptides and short chain fatty acids activate FPR1 and FFA2R, respectively, while longer peptides and fatty acids activate FPR2 and GPR84, respectively. The activation profiles of these receptors include the release of reactive oxygen species (ROS) generated by the NADPH oxidase. Activation of the oxidase and the production of ROS are processes that are regulated by proinflammatory mediators, including TNFα and GM-CSF. The receptors have signaling and functional similarities, although there are also important differences, not only between the two closely related neutrophil FPRs, but also between the FPRs and the FFARs. In neutrophils, these receptors never walk alone, and additional mechanistic insights into the regulation of the GPCRs and the novel regulatory mechanisms underlying the activation of NADPH oxidase advance our understanding of the role of receptor transactivation in the regulation of inflammatory reactions.

Abstract 105: Neutrophil Cracr2a Is Crucial For Calcium Signaling And Enhances Neutrophil Adhesive Function Under Thromboinflammatory Conditions

Ca 2+ release-activated channel regulator 2A (CRACR2A) is a Ca 2+ -binding protein that facilitates store-operated Ca 2+ entry during T cell activation. However, it is unknown whether neutrophil CRACR2A regulates neutrophil functions in inflammation. Our confocal intravital microscopy (IVM) revealed that compared to wild-type (WT) mice, myeloid-specific cracr2a conditional knockout (CKO, cracr2a fl/fl;Lyz-cre ) mice exhibited a significant increase in neutrophil rolling and a decrease in neutrophil adhesion, crawling, and transmigration on ear and cremaster venules in TNF-α-induced inflammation. Deletion of neutrophil cracr2a impaired β2 integrin function without affecting the expression of L-selectin, PECAM-1, and JAM-A. Neutrophil cracr2a increased Ca 2+ mobilization after stimulation with fMLP, A23187, and thapsigargin by its rapid interaction with STIM1. Due to the lack of CRACR2A inhibitors, we generated CRACR2A-deleted HL60 cells using CRISPR/Cas9. CRACR2A deletion in differentiated HL60 cells recapitulated the defects seen in cracr2a-null neutrophils, including reduced β2 integrin function and Ca 2+ mobilization after agonist stimulation. Since excessively recruited neutrophils cause brain damage in ischemic stroke, we examined whether neutrophil cracr2a contributes to stroke pathology. Using a transient middle cerebral artery occlusion (tMCAO)-induced ischemic stroke model, we found that compared to WT mice, cracr2a CKO mice exhibited improved neurological deficits and reduced infarct volume. Longitudinal 4D IVM of mouse brain revealed that neutrophil cracr2a is crucial for neutrophil adhesion and transmigration on cerebral vessels 16-24 hours after tMCAO and upregulated αMβ2 integrin on adherent neutrophils. Further, single-cell behavior analysis of 4D IVM showed that a proinflammatory subset of neutrophils arise in WT mice, but not cracr2a CKO mice, after tMCAO. We observed that the number of circulating pro-inflammatory neutrophils was markedly decreased 24 hours after tMCAO in cracr2a CKO mice compared with WT mice. Our findings indicate that neutrophil CRACR2A is a key regulator for Ca 2+ signaling and enhances neutrophil pro-inflammatory and adhesive activities in vascular inflammation and ischemic stroke.

Grass carp Il-2 promotes neutrophil extracellular traps formation via inducing ROS production and autophagy in vitro

Interleukin (IL)-2 has been reported to regulate neutrophil functions in humans, mice, pigs and chicken although it is a key regulator of T cells. Consistently, we found that grass carp (Ctenopharyngodon idellus) interleukin-2 (gcIl-2) is capable of modulating the antimicrobial activities of neutrophils via regulating granzyme B- and perforin-like gene expression in our previous study. In the present study, stimulation of gcIl-2 on neutrophil extracellular traps (NETs) formation in grass carp neutrophils was demonstrated by detecting free DNA release, histone H3 citrullination and morphological changes of the cells. Further investigation revealed that reactive oxygen species (ROS) production from NADPH oxidase but not mitochondria was involved in NETosis induced by gcIl-2. Aside from ROS, autophagy was disclosed to be indispensable for NETosis induced by gcIl-2. These converging lines of evidence suggested that fish Il-2 could induce NETs formation via NADPH oxidase-derived ROS- and autophagy-dependent pathways in fish species which is evolutionarily conserved with that in mammals. It is noteworthy that these two pathways did not interplay with each other in Il-2-stimulated NETosis. The mechanisms governing autophagy induced by Il-2 were also explored in the present study, showing that Il-2 modulated the action of high mobility group box 1 (HMGB1) protein to stimulate autophagy, leading to NETs formation in fish neutrophils. These results provided a new insight to the function of Il-2 in fish neutrophils, and a clue about the regulation of NETosis in the lower vertebrates.

Nonfunctional TGF-β/ALK1/ENG signaling pathway supports neutrophil proangiogenic activity in hereditary hemorrhagic telangiectasia.

The transforming growth factor β (TGF-β)/ALK1/ENG signaling pathway maintains quiescent state of endothelial cells, but at the same time, it regulates neutrophil functions. Importantly, mutations of this pathway lead to a rare autosomal disorder called hereditary hemorrhagic telangiectasia (HHT), characterized with abnormal blood vessel formation (angiogenesis). As neutrophils are potent regulators of angiogenesis, we investigated how disturbed TGF-β/ALK1/ENG signaling influences angiogenic properties of these cells in HHT. We could show for the first time that not only endothelial cells, but also neutrophils isolated from such patients are ENG/ALK1 deficient. This deficiency obviously stimulates proangiogenic switch of such neutrophils. Elevated proangiogenic activity of HHT neutrophils is mediated by the increased spontaneous degranulation of gelatinase granules, resulting in high release of matrix-degrading matrix metalloproteinase 9 (MMP9). In agreement, therapeutic disturbance of this process using Src tyrosine kinase inhibitors impaired proangiogenic capacity of such neutrophils. Similarly, inhibition of MMP9 activity resulted in significant impairment of neutrophil-mediated angiogenesis. All in all, deficiency in TGF-β/ALK1/ENG signaling in HHT neutrophils results in their proangiogenic activation and disease progression. Therapeutic strategies targeting neutrophil degranulation and MMP9 release and activity may serve as a potential therapeutic option for HHT.

The Mechanism of IL-17 Regulating Neutrophils Participating in Host Immunity of RVVC Mice.

Vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC) are the most common lower genital tract infections in reproductive women. In recent years, the research on its pathogenesis mainly focuses on vaginal local immunity and IL-17 as key factors in adaptive immunity, attracting much attention. However, the role of IL-17 in local immunity in VVC and RVVC is poorly understood. At the same time, neutrophils are considered the most effective way to control and eliminate candidal infection and have a controversial role in VVC and RVVC. In this study, we built a mouse RVVC model. After analyzing the vaginal lavage solution of RVVC mice with an inflammatory factor antibody chip and ELISA, we found that IL-17 may play a protective role in RVVC. The experiment of constructing RVVC mice with different concentrations of IL-17 using halofuginone and comparing the vaginal fungi load and vaginal epithelial damage verified that IL-17 had a protective effect in RVVC. In addition, in vitro and in vivo studies found that IL-17 can promote neutrophil apoptosis and recruit neutrophils in the vagina. The neutrophils in the vagina can secrete IL-17 in an autocrine manner. These two may be why IL-17 plays a protective role in RVVC. In summary, the study suggests that IL-17-mediated regulation of neutrophil function is involved in host immune response to RVVC, which helps us to further understand the potential mechanism of IL-17 in RVVC.

GPR84 regulates pulmonary inflammation by modulating neutrophil functions

Acute lung injury (ALI) is an acute, progressive hypoxic respiratory failure that could develop into acute respiratory distress syndrome (ARDS) with very high mortality rate. ALI is believed to be caused by uncontrolled inflammation, and multiple types of immune cells, especially neutrophils, are critically involved in the development of ALI. The treatment for ALI/ARDS is very limited, a better understanding of the pathogenesis and new therapies are urgently needed. Here we discover that GPR84, a medium chain fatty acid receptor, plays critical roles in ALI development by regulating neutrophil functions. GPR84 is highly upregulated in the cells isolated from the bronchoalveolar lavage fluid of LPS-induced ALI mice. GPR84 deficiency or blockage significantly ameliorated ALI mice lung inflammation by reducing neutrophils infiltration and oxidative stress. Further studies reveal that activation of GPR84 strongly induced reactive oxygen species production from neutrophils by stimulating Lyn, AKT and ERK1/2 activation and the assembly of the NADPH oxidase. These results reveal an important role of GPR84 in neutrophil functions and lung inflammation and strongly suggest that GPR84 is a potential drug target for ALI.

GPR120 promotes neutrophil control of intestinal bacterial infection

ABSTRACT G-protein coupled receptor 120 (GPR 120) has been implicated in anti-inflammatory functions. However, how GPR120 regulates the neutrophil function remains unknown. This study investigated the role of GPR120 in the regulation of neutrophil function against enteric bacteria. 16S rRNA sequencing was used for measuring the gut microbiota of wild-type (WT) mice and Gpr120 −/− mice. Citrobacter rodentium infection and dextran sulfate sodium (DSS)-induced colitis models were performed in WT and Gpr120 −/− mice. Mouse peritoneal-derived primary neutrophils were used to determine the neutrophil functions. Gpr120 −/− mice showed altered microbiota composition. Gpr120 −/− mice exhibited less capacity to clear intestinal Citrobacter rodentium and more severe intestinal inflammation upon infection or DSS insults. Depletion of neutrophils decreased the intestinal clearance of Citrobacter rodentium. GPR120 agonist, CpdA, enhanced WT neutrophil production of reactive oxygen species (ROS) and extracellular traps (NETs), and GPR120-deficient neutrophils demonstrated a lower level of ROS and NETs. CpdA-treated neutrophils showed an enhanced capacity to inhibit the growth of Citrobacter rodentium, which was abrogated by the inhibition of either NETs or ROS. CpdA promoted neutrophil inhibition of the growth of commensal bacteria Escherichia coli O9:H4 and pathobiont Escherichia coli O83:H1 isolated from a Crohn’s disease patient. Mechanically, mTOR activation and glycolysis mediated GPR120 induction of ROS and NETs in neutrophils. Additionally, CpdA promoted the neutrophil production of IL-17 and IL-22, and treatment with a conditioned medium of GPR120-activated neutrophils increased intestinal epithelial cell barrier functions. Our study demonstrated the critical role of GPR120 in neutrophils in protection against enteric bacterial invasion.

The protective role of HMGB1 in affecting the balance between autophagy and pyroptosis to maintain neutrophils homeostasis during β-glucan-induced mice lung inflammation

Fungal contamination is omnipresent, and inhalation of fungi-contaminated organic dust leads to hypersensitivity pneumonitis (HP), in which neutrophils played a pivotal role. Existing studies have suggested that cell homeostasis is crucial for the pathogenesis of the inflammatory disease. Although HMGB1 has been shown to contribute to suppressing HP, there is a lack of studies on its mechanisms, especially the regulation of neutrophil homeostasis. This study aims to investigate how HMGB1 regulates neutrophil function by affecting neutrophil homeostasis, and then affects lung inflammation induced by β-glucan, the exposure marker of fungi. Our results showed that deficient HMGB1 led to neutrophil death by disrupting the balance between autophagy and pyroptosis after β-glucan treatment. And HMGB1 deficiency exacerbated the β-glucan-induced lung inflammation and neutrophil dysfunction both in vivo and in vitro. Furthermore, HMGB1 contributed to remodeling neutrophil function by restricting autophagy and aggravating pyroptosis β-glucan exposure. Our funding suggested that HMGB1 deficiency could break the balance between autophagy and pyroptosis towards pyroptosis to cause neutrophil dysfunction during the exacerbated inflammatory response, which provides insights into the pathogenesis of HP and the potential biological targets for its treatment. Data AvailabilityThe datasets used during the current study are available from the corresponding author on reasonable request

Hyaluronic Acid in Synovial Fluid Prevents Neutrophil Activation in Spondyloarthritis

Spondyloarthritis (SpA) patients suffer from joint inflammation resulting in tissue damage, characterized by the presence of numerous neutrophils in the synovium and synovial fluid (SF). As it is yet unclear to what extent neutrophils contribute to the pathogenesis of SpA, we set out to study SF neutrophils in more detail. We analyzed the functionality of SF neutrophils of 20 SpA patients and 7 disease controls, determining ROS production and degranulation in response to various stimuli. In addition, the effect of SF on neutrophil function was determined. Surprisingly, our data show that SF neutrophils in SpA patients have an inactive phenotype, despite the presence of many neutrophil-activating stimuli such as GM-CSF and TNF in SF. This was not due to exhaustion as SF neutrophils readily responded to stimulation. Therefore, this finding suggests that one or more inhibitors of neutrophil activation may be present in SF. Indeed, when blood neutrophils from healthy donors were activated in the presence of increasing concentrations of SF from SpA patients, degranulation and ROS production were dose-dependently inhibited. This effect was independent of diagnosis, gender, age, and medication in the patients from which the SF was isolated. Treatment of SF with the enzyme hyaluronidase strongly reduced the inhibitory effect of SF on neutrophil activation, indicating that hyaluronic acid that is present in SF may be an important factor in preventing SF neutrophil activation. This finding provides novel insights into the role of soluble factors in SF regulating neutrophil function and may lead to the development of novel therapeutics targeting neutrophil activation via hyaluronic acid or associated pathways.

Unique insertion/deletion polymorphisms within histidine-rich region of histidine-rich glycoprotein in Thoroughbred horses

Histidine-rich glycoprotein (HRG) is abundant plasma protein with various effects on angiogenesis, coagulation, and immune responses. Previously, we identified the base and amino acid sequences of equine HRG (eHRG) and revealed that eHRG regulates neutrophil functions. In this study, we first conducted a large-scale gene analysis with DNA samples extracted from 1700 Thoroughbred horses and identified unique insertion/deletion polymorphisms in the histidine-rich region (HRR) of eHRG. Here we report two types of polymorphisms (deletion type 1 [D1] and deletion type 2 [D2]) containing either a 45 bp or 90 bp deletion in the HRR of eHRG, and five genotypes of eHRG (insertion/insertion [II], ID1, ID2, D1D1, and D1D2) in Thoroughbred horses. Allele frequency of I, D1, and D2, was 0.483, 0.480, and 0.037 and the incidence of each genotype was II: 23.4%, ID1: 46.2%, ID2: 3.6%, D1D1: 23.1%, and D1D2: 3.7%, respectively. The molecular weights of each plasma eHRG protein collected from horses with each genotype was detected as bands of different molecular size, which corresponded to the estimated amino acid sequence. The nickel-binding affinity of the D1 or D2 deletion eHRG was reduced, indicating a loss of function at the site. eHRG proteins show a variety of biological and immunological activities in vivo, and HRR is its active center, suggesting that genetic polymorphisms in eHRG may be involved in the performance in athletic ability, productivity, and susceptibility to infectious diseases in Thoroughbred horses.

Myeloperoxidase: Regulation of Neutrophil Function and Target for Therapy.

Neutrophils, the most abundant white blood cells in humans, are critical for host defense against invading pathogens. Equipped with an array of antimicrobial molecules, neutrophils can eradicate bacteria and clear debris. Among the microbicide proteins is the heme protein myeloperoxidase (MPO), stored in the azurophilic granules, and catalyzes the formation of the chlorinating oxidant HOCl and other oxidants (HOSCN and HOBr). MPO is generally associated with killing trapped bacteria and inflicting collateral tissue damage to the host. However, the characterization of non-enzymatic functions of MPO suggests additional roles for this protein. Indeed, evolving evidence indicates that MPO can directly modulate the function and fate of neutrophils, thereby shaping immunity. These actions include MPO orchestration of neutrophil trafficking, activation, phagocytosis, lifespan, formation of extracellular traps, and MPO-triggered autoimmunity. This review scrutinizes the multifaceted roles of MPO in immunity, focusing on neutrophil-mediated host defense, tissue damage, repair, and autoimmunity. We also discuss novel therapeutic approaches to target MPO activity, expression, or MPO signaling for the treatment of inflammatory and autoimmune diseases.

MCPIP-1-Mediated Immunosuppression of Neutrophils Exacerbates Acute Bacterial Peritonitis and Liver Injury

Monocyte chemotactic protein-1-induced protein-1 (MCPIP-1) is highly expressed in activated immune cells and negatively regulates immune responses, while the mechanisms underlying the immunoregulation of neutrophils in acute bacterial infection and liver injury remain elusive. Here, we examined the role of MCPIP-1 in regulating neutrophil functions during acute bacterial peritonitis and liver injury. Mice with myeloid cell-specific overexpression (McpipMye-tg) or knockout (McpipΔMye) of MCPIP-1 were generated. We found that reactive oxygen species and myeloperoxidase production, formation of neutrophil extracellular traps, and migratory capacity were deficient in McpipMye-tg neutrophils but enhanced in McpipΔMye neutrophils. The recruitment of neutrophils and pathogen clearance were markedly suppressed in McpipMye-tg mice following intraperitoneal infection with Salmonella typhimurium while intensified in McpipΔMye mice. Severe acute S. typhimurium-infected peritonitis and liver injury occurred in McpipMye-tg mice but were alleviated in McpipΔMye mice. RNA sequencing, RNA-binding protein immunoprecipitation and qPCR analysis revealed that MCPIP-1 downregulated the protective functions of neutrophils via degrading the mRNA of cold inducible RNA-binding protein. Consistently, MCPIP-1 was highly expressed in neutrophils of patients with acute infectious diseases, especially in those with liver injury. Collectively, we uncover that MCPIP-1 negatively regulates the antibacterial capacities of neutrophils, leading to exacerbating severe acute bacterial peritonitis and liver injury. It may serve as a candidate target for maintaining neutrophil homeostasis to control acute infectious diseases.

Hypoxia inducible-factor 1 alpha regulates neutrophil recruitment during fungal-elicited granulomatous inflammation.

Chronic pulmonary aspergillosis (CPA) is a devastating disease with increasing prevalence worldwide. The characteristic granulomatous-like inflammation poses as the major setback to effective antifungal therapies by limiting drug access to fungi. These inflammatory lung structures are reported to be severely hypoxic; nevertheless, the underlying mechanisms whereby these processes contribute to fungal persistence remain largely unknown. Hypoxia-inducible factor 1 alpha (HIF-1α), besides being the major cellular response regulator to hypoxia, is a known central immune modulator. Here, we used a model of Aspergillus fumigatus airway infection in myeloid-restricted HIF-1α knock-out (mHif1α-/- ) mice to replicate the complex structures resembling fungal granulomas and evaluate the contribution of HIF-1α to antifungal immunity and disease development. We found that fungal-elicited granulomas in mHif1α-/- mice had significantly smaller areas, along with extensive hyphal growth and increased lung fungal burden. This phenotype was associated with defective neutrophil recruitment and an increased neutrophil death, therefore highlighting a central role for HIF-1α-mediated regulation of neutrophil function in the pathogenesis of chronic fungal infection. These results hold the promise of an improved capacity to manage the progression of chronic fungal disease and open new avenues for additional therapeutic targets and niches of intervention.

Roles of mitochondria in neutrophils.

Neutrophils are the most abundant leukocyte in human blood. They are critical for fighting infections and are involved in inflammatory diseases. Mitochondria are indispensable for eukaryotic cells, as they control the biochemical processes of respiration and energy production. Mitochondria in neutrophils have been underestimated since glycolysis is a major metabolic pathway for fuel production in neutrophils. However, several studies have shown that mitochondria are greatly involved in multiple neutrophil functions as well as neutrophil-related diseases. In this review, we focus on how mitochondrial components, metabolism, and related genes regulate neutrophil functions and relevant diseases.

The role of N-acetyl cysteine and some other clinical antidotes in the treatment of patients with COVID-19; review of the current evidence

Anti-viral and anti-cytokine drugs have been proven to be inadequate in ceasing the progression of the novel coronavirus disease, and severe cases are often associated with death or severe chronic injuries. In this respect, N-acetyl cysteine (NAC) has anti-oxidant, anti-inflammatory, and immune-modulating effects and has been revealed to be beneficial in the treatment and prevention of this virus. High-dose oral NAC (1200 mg) can improve adaptive immunity by increasing lymphocyte glutathione levels and regulating neutrophil function during the COVID-19 development. Given that the majority of these patients suffer from hypoxemic respiratory failure and require oxygen supplementation in hospitals, hyperbaric oxygen therapy (HBOT) appears to be an alternative treatment. In fact, HBOT can increase the circulation and delivery of oxygen under high pressures, making the tissue uptake more efficient and improving hypoxia in patients with COVID-19. In addition, low-doses of naltrexone can interact with angiotensin-converting enzyme 2 (ACE2), disrupt the binding of ACE2 to the receptor-binding domain, and have anti-inflammatory and suppressive properties of pro-inflammatory cytokines. Therefore, due to the ability of the low-dose of this drug in preventing the progression of this disease, it can be recommended as an adjunct drug with an immunomodulatory role in combination with other anti-viral drugs in patients with COVID-19. Finally, there appears to be a significant association between vitamin K and thiamine deficiency with the severity of COVID-19. These vitamins play an important role in the coagulation system and suppress inflammation. Therefore, they can be used as a supplement or treatment to improve the outcomes of COVID-19.

The Regulation of Neutrophil Function and Trafficking in Pulmonary Fibrosis

The Regulation of Neutrophil Function and Trafficking in Pulmonary Fibrosis