Neutrophil extracellular traps in acrolein promoted hepatic ischemia reperfusion injury: Therapeutic potential of NOX2 and p38MAPK inhibitors

Bulk and single-cell RNA sequencing analysis with 101 machine learning combinations reveal neutrophil extracellular trap involvement in hepatic ischemia-reperfusion injury and early allograft dysfunction

BACKGROUND

Hepatic ischaemia-reperfusion injury (HIRI) is a major clinical concern during the perioperative period and is closely associated with early allograft dysfunction (EAD), acute rejection (AR) and long-term graft survival. Neutrophil extracellular traps (NETs) are extracellular structures formed by the release of decondensed chromatin and granular proteins following neutrophil stimulation. There is growing evidence that NETs are involved in the progression of various liver transplantation complications, including ischaemia-reperfusion injury (IRI). This study aimed to comprehensively analyse the expression patterns of NET-related genes (NRGs) in HIRI, identify HIRI subtypes with distinct characteristics, and develop a reliable EAD prediction model.

METHODS

Microarray, bulk RNA-seq, and single-cell sequencing datasets were obtained from the GEO database. Initially, differentially expressed NRGs (DE-NRGs) were identified using differential gene expression analyses. We then utilised a non-negative matrix factorisation (NMF) algorithm to classify HIRI samples. Subsequently, we employed machine learning algorithms to screen the hub NRGs related to EAD and developed an EAD prediction model based on these hub NRGs. Concurrently, we assessed the expression patterns of hub NRGs at the single-cell level using the HIRI. Additionally, we validated C5AR1 expression and its effect on HIRI and NETs formation in a rat orthotopic liver transplantation (OLT) model.

RESULTS

In this study, we identified 11 DE-NRGs in the HIRI context. Based on these 11 DE-NRGs, HIRI samples were classified into two distinct clusters. Cluster1 exhibited a low expression of DE-NRGs, minimal neutrophil infiltration, mild inflammation, and a low incidence of EAD. Conversely, Cluster2 displayed the opposite phenotype, with an activated inflammatory subtype and a higher incidence of EAD. Furthermore, an EAD prediction model was developed using the four hub NRGs associated with EAD. Based on risk scores, HIRI samples were classified into high- and low-risk groups. The OLT model confirmed substantial upregulation of C5AR1 expression in the liver tissue, accompanied by increased formation of NETs. Treatment with a C5AR1 antagonist improved liver function, reduced tissue inflammation, and decreased NETs formation.

CONCLUSIONS

This study distinguished two apparent HIRI subtypes, established a predictive model for EAD, and validated the effect of C5AR1 on HIRI. These findings provide novel perspectives for the development of advanced clinical strategies to enhance the outcomes of liver transplant recipients.

Targeting neutrophil extracellular traps: A novel strategy in hematologic malignancies

Neutrophil extracellular traps (NETs) have emerged as a critical factor in malignant hematologic disease pathogenesis. These structures, comprising DNA, histones, and cytoplasmic proteins, were initially recognized for their role in immune defense against microbial threats. Growing evidence suggests that NETs contribute to malignant cell progression and dissemination, representing a double-edged sword. However, there is a paucity of reports on its involvement in hematological disorders. A comprehensive understanding of the intricate relationship between malignant cells and NETs is necessary to explore effective therapeutic strategies. This review highlights NET formation and mechanisms underlying disease pathogenesis. Moreover, we discuss recent advancements in targeted inhibitor development for selective NET disruption, empowering precise design and efficacious therapeutic interventions for malignant hematologic diseases.

Imp7 siRNA nanoparticles protect against mechanical ventilation-associated liver injury by inhibiting HMGB1 production and NETs formation

Mechanical ventilation (MV) has the potential to induce extra-pulmonary organ damage by adversely affecting the lungs and promoting the secretion of inflammatory cytokines. High-mobility group box 1 protein (HMGB1) is a pro-inflammatory mediator in ventilator-induced lung injury (VILI), but its effect on MV-associated liver injury and the mechanisms are poorly understood. In the present study, mice were subjected to high-volume MV (20 ml/kg) to induce VILI. MV-induced HMGB1 prompted neutrophil extracellular traps (NETs) formation and PANoptosis within the liver. Inhibiting NETs formation by DNase I or PAD4 inhibitor, or by HMGB1 neutralizing ameliorated the liver injury. HMGB1 activated neutrophils to form NETs through TLR4/MyD88/TRAF6 pathway. Importantly, Importin7 siRNA nanoparticles inhibited HMGB1 release and protected against MV-associated liver injury. These data provide evidence of MV-induced HMGB1 prompted NETs formation and PANoptosis in the liver via the TLR4/MyD88/TRAF6 pathway. HMGB1 is a potential therapeutic target for MV-associated liver injury.

The oncolytic bacteria-mediated delivery system of CCDC25 nucleic acid drug inhibits neutrophil extracellular traps induced tumor metastasis

BACKGROUND

Neutrophil extracellular traps (NETs), antibacterial weapons of neutrophils (NEs), have been found to play a crucial role in cancer metastasis in recent years. More and more cancer research is focusing on anti-NETs. However, almost all anti-NETs treatments have limitations such as large side effects and limited efficacy. Therefore, exploring new anti-NETs therapeutic strategies is a long-term goal.

RESULTS

The transmembrane protein coiled-coil domain containing 25 (CCDC25) on tumor cell membranes can bind NETs-DNA with high specificity and affinity, enabling tumor cells to sense NETs and thus promote distant metastasis. We transformed shCCDC25 into VNP20009 (VNP), an oncolytic bacterium, to generate VNP-shCCDC25 and performed preclinical evaluation of the inhibitory effect of shCCDC25 on cancer metastasis in B16F10 lung metastasis and 4T1 orthotopic lung metastasis models. VNP-shCCDC25 effectively blocked the downstream prometastatic signaling pathway of CCDC25 at tumor sites and reduced the formation of NETs while recruiting more neutrophils and macrophages to the tumor core, ultimately leading to excellent metastasis inhibition in the two lung metastasis models.

CONCLUSION

This study is a pioneer in focusing on the effect of anti-NET treatment on CCDC25. shCCDC25 is effectively delivered to tumor sites via the help of oncolytic bacteria and has broad application in the inhibition of cancer metastasis via anti-NETs.

Intrahepatic neutrophil accumulation and extracellular trap formation are associated with posthepatectomy liver failure

BACKGROUND

Posthepatectomy liver failure (PHLF) represents a life-threatening complication with limited therapeutic options. Neutrophils play a critical and dynamic role during regeneratory processes, but their role in human liver regeneration is incompletely understood, especially as underlying liver disease, detectable in the majority of patients, critically affects hepatic regeneration. Here we explored intrahepatic neutrophil accumulation and neutrophil extracellular traps (NETs) in patients with PHLF and validated the functional relevance of NETs in a murine partial hepatectomy (PHx) model.

METHODS

We investigated the influx of neutrophils, macrophages, eosinophils, and mast cells and the presence of their respective extracellular traps in liver biopsies of 35 patients undergoing hepatectomy (10 patients with PHLF) before and after the initiation of liver regeneration by fluorescence microscopy. In addition, NET formation and neutrophil activation were confirmed by plasma analysis of 99 patients (24 patients with PHLF) before and up to 5 days after surgery. Furthermore, we inhibited NETs via DNase I in a murine PHx model of mice with metabolically induced liver disease.

RESULTS

We detected rapid intrahepatic neutrophil accumulation, elevated levels of myeloperoxidase release, and NET formation in regenerating human livers, with a significantly higher increase of infiltrating neutrophils and NETs in patients with PHLF. Circulating markers of neutrophil activation, including elastase, myeloperoxidase, and citrullinated histone H3, correlated with markers of liver injury. In a murine PHx model, we showed that the inhibition of NET accelerated hepatocyte proliferation and liver regeneration.

CONCLUSIONS

Patients with PHLF showed accelerated intrahepatic neutrophil infiltration and NET formation, which were associated with liver damage. Further, we identified postsurgical myeloperoxidase levels as predictive markers for adverse outcomes and observed that blocking NETs in a murine PHx model accelerated tissue regeneration.

Neutrophil extracellular traps regulating tumorimmunity in hepatocellular carcinoma

As a component of the innate immune system, there is emerging evidence to suggest that neutrophils may play a critical role in the initiation and progression of hepatocellular carcinoma (HCC). Neutrophil extracellular traps (NETs) are web-like chromatin structures that protrude from the membranes during neutrophil activation. Recent research has shown that NETs, which are at the forefront of the renewed interest in neutrophil studies, are increasingly intertwined with HCC. By exploring the mechanisms of NETs in HCC, we aim to improve our understanding of the role of NETs and gain deeper insights into neutrophil biology. Therefore, this article provides a summary of key findings and discusses the emerging field of NETs in HCC.

Curcumin Alleviates Hepatic Ischemia-Reperfusion Injury by Inhibiting Neutrophil Extracellular Traps Formation

BACKGROUND

Hepatic ischemia-reperfusion injury (IRI) is a common innate immune-mediated sterile inflammatory response in liver transplantation and liver tumor resection. Neutrophil extracellular traps (NETs) can aggravate liver injury and activates innate immune response in the process of liver IRI. However, Curcumin (Cur) can reverse this damage and reduce NETs formation. Nevertheless, the specific regulatory mechanism is still unclear in liver IRI. This study aimed to explore the potential mechanisms that how does Cur alleviate hepatic IRI by inhibits NETs production and develop novel treatment regimens.

METHODS

We established a hepatic IRI model by subjecting C57BL/6J mice to 60 min of ischemia, followed by reperfusion for 2 h, 6 h, 12 h, and 24 h respectively. Subsequently, we were separated into 5 groups, namely the I/R group, Cur group, DNase-1 group, Cur + DNase1 group and sham operation group. Serum alanine aminotransferase (ALT) and aspartate transaminase (AST), Hematoxylin-eosin staining, immunofluorescence, and TUNEL analysis were applied to assess liver injury degree and NETs levels. Western blot assay was used to detect the protein levels of apoptosis-related proteins and MEK pathway proteins.

RESULTS

Cur could alleviate hepatic IRI by inhibiting the generation of NETs via suppressing the MEK/ERK pathway. In addition, this study also revealed that DNase-1 is vital for alleviating hepatic IRI by reducing the generation of NETs.

CONCLUSIONS

Cur combined with DNase-1 was more effective than the two drugs administered alone in alleviating hepatic IRI by inhibiting the generation of NETs. These results also suggested that curcumin combined with DNase-1 was a potential therapeutic strategy to mitigate hepatic IRI.

Acrolein produced by glioma cells under hypoxia inhibits neutrophil AKT activity and suppresses anti-tumoral activities

Acrolein, which is the most reactive aldehyde, is a byproduct of lipid peroxidation in a hypoxic environment. Acrolein has been shown to form acrolein-cysteine bonds, resulting in functional changes in proteins and immune effector cell suppression. Neutrophils are the most abundant immune effector cells in circulation in humans. In the tumor microenvironment, proinflammatory tumor-associated neutrophils (TANs), which are termed N1 neutrophils, exert antitumor effects via the secretion of cytokines, while anti-inflammatory neutrophils (N2 neutrophils) support tumor growth. Glioma is characterized by significant tissue hypoxia, immune cell infiltration, and a highly immunosuppressive microenvironment. In glioma, neutrophils exert antitumor effects early in tumor development but gradually shift to a tumor-supporting role as the tumor develops. However, the mechanism of this anti-to protumoral switch in TANs remains unclear. In this study, we found that the production of acrolein in glioma cells under hypoxic conditions inhibited neutrophil activation and induced an anti-inflammatory phenotype by directly reacting with Cys310 of AKT and inhibiting AKT activity. A higher percentage of cells expressing acrolein adducts in tumor tissue are associated with poorer prognosis in glioblastoma patients. Furthermore, high-grade glioma patients have increased serum acrolein levels and impaired neutrophil functions. These results suggest that acrolein suppresses neutrophil function and contributes to the switch in the neutrophil phenotype in glioma.

Ganoderma lucidum polysaccharide peptides GL-PPSQ2 alleviate intestinal ischemia-reperfusion injury via inhibiting cytotoxic neutrophil extracellular traps

Ganoderma lucidum polysaccharides peptides (GLPP) are the main effective ingredients from G. lucidum (Leyss. ex Fr.) Karst with anti-inflammatory, antioxidant, and immunoregulatory activities. We extracted and characterized a novel GLPP, named GL-PPSQ₂, which were found to have 18 amino acids and 48 proteins, connected by O-glycosidic bonds. The monosaccharide composition of GL-PPSQ₂ was determined to be composed of fucose, mannose, galactose and glucose with a molar ratio of 1: 1.45:2.37:16.46. By using asymmetric field-flow separation technique, GL-PPSQ₂ were found to have a highly branched structure. Moreover, in an intestinal ischemia-reperfusion (I/R) mouse model, GL-PPSQ₂ significantly increased the survival rate and alleviated intestinal mucosal hemorrhage, pulmonary permeability, and pulmonary edema. Meanwhile, GL-PPSQ₂ significantly promoted intestinal tight junction, decreased inflammation, oxidative stress and cellular apoptosis in the ileum and lung. Analysis with Gene Expression Omnibus series indicates that neutrophil extracellular trap (NET) formation plays an important role in intestinal I/R injury. GL-PPSQ₂ remarkedly inhibited NETs-related protein myeloperoxidase (MPO) and citrulline-Histone H3 (citH3) expression. GL-PPSQ₂ could alleviate intestinal I/R and its induced lung injury via inhibiting oxidative stress, inflammation, cellular apoptosis, and cytotoxic NETs formation. This study proves that GL-PPSQ₂ is a novel drug candidate for preventing and treating intestinal I/R injury.

Neutrophil extracellular traps and complications of liver transplantation

Many end-stage liver disease etiologies are attributed to robust inflammatory cell recruitment. Neutrophils play an important role in inflammatory infiltration and neutrophil phagocytosis, oxidative burst, and degranulation. It has also been suggested that neutrophils may release neutrophil extracellular traps (NETs) to kill pathogens. It has been proven that neutrophil infiltration within the liver contributes to an inflammatory microenvironment and immune cell activation. Growing evidence implies that NETs are involved in the progression of numerous complications of liver transplantation, including ischemia-reperfusion injury, acute rejection, thrombosis, and hepatocellular carcinoma recurrence. NETs are discussed in this comprehensive review, focusing on their effects on liver transplantation complications. Furthermore, we discuss NETs as potential targets for liver transplantation therapy.

Ferritin triggers neutrophil extracellular trap-mediated cytokine storm through Msr1 contributing to adult-onset Still's disease pathogenesis

Hyperferritinemic syndrome, an overwhelming inflammatory condition, is characterized by high ferritin levels, systemic inflammation and multi-organ dysfunction, but the pathogenic role of ferritin remains largely unknown. Here we show in an animal model that ferritin administration leads to systemic and hepatic inflammation characterized by excessive neutrophil leukocyte infiltration and neutrophil extracellular trap (NET) formation in the liver tissue. Ferritin-induced NET formation depends on the expression of peptidylarginine deiminase 4 and neutrophil elastase and on reactive oxygen species production. Mechanistically, ferritin exposure increases both overall and cell surface expression of Msr1 on neutrophil leukocytes, and also acts as ligand to Msr1 to trigger the NET formation pathway. Depletion of neutrophil leukocytes or ablation of Msr1 protect mice from tissue damage and the hyperinflammatory response, which further confirms the role of Msr1 as ferritin receptor. The relevance of the animal model is underscored by the observation that enhanced NET formation, increased Msr1 expression and signalling on neutrophil leukocytes are also characteristic to adult-onset Still's disease (AOSD), a typical hyperferritinemic syndrome. Collectively, our findings demonstrate an essential role of ferritin in NET-mediated cytokine storm, and suggest that targeting NETs or Msr1 may benefit AOSD patients.

Comprehensive analysis of transient receptor potential channels-related signature for prognosis, tumor immune microenvironment, and treatment response of colorectal cancer

BACKGROUND

Transient receptor potential channels (TRPC) play critical regulatory functions in cancer occurrence and progression. However, knowledge on its role in colorectal cancer (CRC) is limited. In addition, neoadjuvant treatment and immune checkpoint inhibitors (ICIs) have increasing roles in CRC management, but not all patients benefit from them. In this study, a TRPC related signature (TRPCRS) was constructed for prognosis, tumor immune microenvironment (TIME), and treatment response of CRC.

METHODS

Data on CRC gene expression and clinical features were retrospectively collected from TCGA and GEO databases. Twenty-eight TRPC regulators (TRPCR) were retrieved using gene set enrichment analysis. Different TRPCR expression patterns were identified using non-negative matrix factorization for consensus clustering, and a TRPCRS was established using LASSO. The potential value of TRPCRS was assessed using functional enrichment analysis, tumor immune analysis, tumor somatic mutation analysis, and response to preoperative chemoradiotherapy or ICIs. Moreover, an external validation was conducted using rectal cancer samples that received preoperative chemoradiotherapy at Fujian Cancer Hospital (FJCH) via qRT-PCR.

RESULTS

Among 834 CRC samples in the TCGA and meta-GEO cohorts, two TRPCR expression patterns were identified, which were associated with various immune infiltrations. In addition, 266 intersected genes from 5564 differentially expressed genes (DEGs) between two TRPC subtypes, 4605 DEGs between tumor tissue and adjacent non-tumor tissue (all FDR< 0.05, adjusted P< 0.001), and 1329 prognostic related genes (P< 0.05) were identified to establish the TRPCRS, which was confirmed in the TCGA cohort, two cohorts from GEO, and one qRT-PCR cohort from FJCH. According to the current signature, the high-TRPC score group had higher expressions of PD-1, PD-L1, and CTLA4, lower TIDE score, and improved response to anti-PD-1 treatment with better predictive ability. Compared to the high-TRPC score group, the low-TRPC score group comprised an immunosuppressive phenotype with increased infiltration of neutrophils and activated MAPK signaling pathway, but was more sensitive to preoperative chemoradiotherapy and associated with improved prognosis.

CONCLUSIONS

The current TRPCRS predicted the prognosis of CRC, evaluated the TIME in CRC, and anticipated the response to immune therapy and neoadjuvant treatment.

The role of extracellular traps in ischemia reperfusion injury

In response to strong signals, several types of immune cells release extracellular traps (ETs), which are web-like structures consisting of DNA decorated with various protein substances. This process is most commonly observed in neutrophils. Over the past two decades, ET formation has been recognized as a unique mechanism of host defense and pathogen destruction. However, the role of ETs in sterile inflammation has only been studied extensively in recent years. Ischemia reperfusion injury (IRI) is a type of sterile inflammatory injury. Several studies have reported that ETs have an important role in IRI in various organs. In this review, we describe the release of ETs by various types of immune cells and focus on the mechanism underlying the formation of neutrophil ETs (NETs). In addition, we summarize the role of ETs in IRI in different organs and their effects on tumors. Finally, we discuss the value of ETs as a potential therapeutic target for organ IRI and present possible challenges in conducting studies on IRI-related ETs as well as future research directions and prospects.

Neutrophil Activated by the Famous and Potent PMA (Phorbol Myristate Acetate)

This review will briefly outline the major signaling pathways in PMA-activated neutrophils. PMA is widely used to understand neutrophil pathways and formation of NETs. PMA activates PKC; however, we highlight some isoforms that contribute to specific functions. PKC α, β and δ contribute to ROS production while PKC βII and PKC ζ are involved in cytoskeleton remodeling. Actin polymerization is important for the chemotaxis of neutrophils and its remodeling is connected to ROS balance. We suggest that, although ROS and production of NETs are usually observed together in PMA-activated neutrophils, there might be a regulatory mechanism balancing both. Interestingly, we suggest that serine proteases might determine the PAD4 action. PAD4 could be responsible for the activation of the NF-κB pathway that leads to IL-1β release, triggering the cleavage of gasdermin D by serine proteases such as elastase, leading to pore formation contributing to release of NETs. On the other hand, when serine proteases are inhibited, NETs are formed by citrullination through the PAD4 pathway. This review puts together results from the last 31 years of research on the effects of PMA on the neutrophil and proposes new insights on their interpretation.

HMGB1-Mediated Neutrophil Extracellular Trap Formation Exacerbates Intestinal Ischemia/Reperfusion-Induced Acute Lung Injury

Influx of activated neutrophils into the lungs is the histopathologic hallmark of acute lung injury (ALI) after intestinal ischemia/reperfusion (I/R). Neutrophils can release DNA and granular proteins to form cytotoxic neutrophil extracellular traps (NETs), which promotes bystander tissue injury. However, whether NETs are responsible for the remote ALI after intestinal I/R and the mechanisms underlying the dissemination of harmful gut-derived mediators to the lungs are unknown. In the C57BL/6J mouse intestinal I/R model, DNase I-mediated degradation and protein arginine deiminase 4 (PAD4) inhibitor-mediated inhibition of NET treatments reduced NET formation, tissue inflammation, and pathological injury in the lung. High-mobility group protein B1 (HMGB1) blocking prevented NET formation and protected against tissue inflammation, as well as reduced cell apoptosis and improved survival rate. Moreover, recombinant human HMGB1 administration further drives NETs and concurrent tissue toxic injury, which in turn can be reversed by neutrophil deletion via anti-Ly6G Ab i.p. injection. Furthermore, global MyD88 deficiency regulated NET formation and alleviated the development of ALI induced by intestinal I/R. Thus, HMGB1 released from necroptotic enterocytes caused ALI after intestinal I/R by inducing NET formation. Targeting NETosis and the HMGB1 pathway might extend effective therapeutic strategies to minimize intestinal I/R-induced ALI.

NETosis in ischemic/reperfusion injuries: An organ-based review

Neutrophil extracellular trap (NETosis), the web-like structures induced by neutrophil death, is an important inflammatory mechanism of the immune system leading to reactive oxygen species production/coagulopathy, endothelial dysfunction, atherosclerosis, and ischemia. NETosis exerts its role through different mechanisms such as triggering Toll-like receptors, inflammatory cytokines, platelet aggregation, neutrophil activation/infiltration, and vascular impairment. NETosis plays a key role in the prognosis of coronary artery disease, ischemic injury of kidney, lung, gastrointestinal tract and skeletal muscles. In this review, we explored the molecular mechanisms involved in NETosis, and ischemic/reperfusion injuries in body organs.

Sex-dependent acrolein sensitivity in mice is associated with differential lung cell, protein, and transcript changes

Acrolein is a reactive inhalation hazard. Acrolein's initial interaction, which in itself can be function-altering, is followed by time-dependent cascade of complex cellular and pulmonary responses that dictate the severity of the injury. To investigate the pathophysiological progression of sex-dependent acrolein-induced acute lung injury, C57BL/6J mice were exposed for 30 min to sublethal, but toxic, and lethal acrolein. Male mice were more sensitive than female mice. Acrolein of 50 ppm was sublethal to female but lethal to male mice, and 75 ppm was lethal to female mice. Lethal and sublethal acrolein exposure decreased bronchoalveolar lavage (BAL) total cell number at 3 h after exposure. The cell number decrease was followed by progressive total cell and neutrophil number and protein increases. The BAL total cell number in female mice exposed to a sublethal, but not lethal dose, returned to control levels at 16 h. In contrast, BAL protein content and neutrophil number were higher in mice exposed to lethal compared to sublethal acrolein. RNASeq pathway analysis identified greater increased lung neutrophil, glutathione metabolism, oxidative stress responses, and CCL7 (aka MCP-3), CXCL10 (aka IP-10), and IL6 transcripts in males than females, whereas IL10 increased more in female than male mice. Thus, the IL6:IL10 ratio, an indicator of disease severity, was greater in males than females. Further, H3.3 histone B (H3F3B) and pro-platelet basic protein (PPBP aka CXCL7), transcripts increased in acrolein exposed mouse BAL and plasma at 3 h, while H3F3B protein that is associated with neutrophil extracellular traps formation increased at 12 h. These results suggest that H3F3B and PPBP transcripts increase may contribute to extracellular H3F3B and PPBP proteins increase.

Biogenic Selenium Nanoparticles: Potential Solution to Oxidative Stress Mediated Inflammation in Rheumatoid Arthritis and Associated Complications

Rheumatoid arthritis (RA) is a common chronic inflammation-mediated disorder having systematic complications. RA triggers a self-directed inflammatory and immunological cascade that culminates in joint destruction. Though a range of treatment options are available, none of them are without adverse effects and this has led researchers to search for alternative solutions. Nanomedicine has emerged as a powerful therapeutic alternative, and selenium (Se) is an essential micronutrient trace element that has a crucial role in human health and disease. Selenium nanoparticles (SeNPs) derived from biological sources, such as plants, bacteria, fungi, and proteins, have exhibited remarkable candidate properties and toxicological profiles, and hence have shown potential to be used as antirheumatic agents. The potential of SeNPs can be attributed to the effect of functional groups bound to them, concentration, and most importantly to their nano range size. The antirheumatic effect of SeNPs is considerable due to its potential in amelioration of oxidative stress-mediated inflammation via downregulation of radical and nonradical species, markers of inflammation, and upregulation of inherent antioxidant defenses. The size and concentration impact of SeNPs has been shown in the subsequent antioxidant and anti-inflammatory properties. Moreover, the article emphasizes the role of these biogenic SeNPs as a notable option in the nanomedicine arena that needs to be further studied as a prospective remedial alternative to cure RA and medication-related adverse events.

Neutrophil-Induced Liver Injury and Interactions Between Neutrophils and Liver Sinusoidal Endothelial Cells

Neutrophils are the most abundant type of leukocytes with diverse functions in immune defense including production of reactive oxygen species, bacteriocidal proteins, neutrophil extracellular traps, and pro-inflammatory mediators. However, aberrant accumulation of neutrophils in host tissues and excessive release of bacteriocidal compounds can lead to unexpected injury to host organs. Neutrophil-mediated liver injury has been reported in various types of liver diseases including liver ischemia/reperfusion injury, nonalcoholic fatty liver disease, endotoxin-induced liver injury, alcoholic liver disease, and drug-induced liver injury. Yet the mechanisms of neutrophil-induced hepatotoxicity in different liver diseases are complicated. Current knowledge of these mechanisms are summarized in this review. In addition, a substantial body of evidence has emerged showing that liver sinusoidal endothelial cells (LSECs) participate in several key steps of neutrophil-mediated liver injury including neutrophil recruitment, adhesion, transmigration, and activation. This review also highlights the current understanding of the interactions between LSECs and neutrophils in liver injury. The future challenge is to explore new targets for selectively interfering neutrophil-induced liver injury without impairing host defense function against microbial infection. Further understanding the role of LSECs in neutrophil-induced hepatotoxicity would aid in developing more selective therapeutic approaches for liver disease.

Gut-Liver Axis: Liver Sinusoidal Endothelial Cells Function as the Hepatic Barrier in Colitis-Induced Liver Injury

Background

Based on the gut–liver axis theory, a leaky gut can aggravate liver injury. However, clinical studies suggest that although gut mucosa damage is commonly observed in inflammatory bowel disease (IBD), it seldom leads to severe liver injury. We hypothesize that there is a hepatic barrier in the gut–liver axis, which protects the liver against gut-derived invasive factors.

Methods

Colitis was induced by dextran sulfate sodium (DSS) in eight different liver injury models in Sprague–Dawley rats. Liver sinusoidal endothelial cell (LSEC) injury was evaluated by a scanning and transmission electron microscope. Neutrophils were depleted by injection of anti-rat polymorphonuclear serum. Two pneumonia models were also induced to investigate the mechanism of neutrophil recruitment and activation. LSECs isolated from rat liver were used to investigate the effect on neutrophil recruitment and activation.

Results

Among eight liver injury models, DSS colitis had no effect on liver injury in three models with normal LSECs. In the other five models with LSEC rupture, liver injury was significantly exacerbated by colitis, and increased hepatic neutrophil accumulation was observed. When neutrophils were depleted, colitis-induced liver injury was significantly attenuated. In pneumonia, liver injury, and colitis models, the level of CXCL1 correlated with the recruitment of neutrophils in different tissues, while DSS colitis and LSEC injury synergistically contributed to increased CXCL1 expression in the liver. In colitis-induced liver injury, neutrophils were activated in the liver. Injured LSECs showed both structural and functional changes, with significantly increased expression of CXCL1 and TNF-α under the stimulation of lipopolysaccharide (LPS). The combination of gut-derived LPS and LSEC-derived TNF-α led to the activation of neutrophils, characterized by enhanced production of reactive oxygen species, pro-inflammatory cytokines, and the formation of neutrophil extracellular traps.

Conclusion

LSECs constitute a vitally important barrier in the gut–liver axis, defending the liver against colitis-induced injury. When LSECs are damaged, they can turn into a pro-inflammatory pattern under the stimulation of LPS. LSEC injury and colitis-derived LPS synergistically contribute to the recruitment and activation of hepatic neutrophils. Neutrophils play a pivotal role as a downstream effector in colitis-induced liver injury.

Naringin alleviates methotrexate-induced liver injury in male albino rats and enhances its antitumor efficacy in HepG2 cells

Methotrexate (MTX) is an efficient chemotherapeutic and immunosuppressant drug, but the hepatotoxicity of MTX limits its clinical use. Naringin (Nar) is a flavonoid derived from Citrus paradise, and has been shown to possess several pharmacological activities, including free-radical scavenging and antioxidant properties. In the present study, we first tested the possible protective effects of multiple doses of Nar against MTX-induced acute hepatotoxicity in rats, and then we investigated the growth inhibition and apoptotic effects of MTX and/or Nar against the HepG2 hepatocarcinoma cell line. Our in vivo results showed that Nar significantly reduced MTX-induced increases in serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin levels. Nar also reduced MTX-induced oxidative stress by significantly reducing liver malondialdehyde (MDA) and nitric oxide (NO) content and increasing superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione (GSH). In addition, Nar significantly counteracted MTX-induced increases in hepatic interleukin-6 and tumor necrosis factor-α (TNF-α). Further, Nar greatly protected hepatocyte ultrastructure against MTX-induced injury. In contrast, in vitro MTX and/or Nar treatment of HepG2 cells for 48 h exhibited a cytotoxic effect and induced apoptosis in a dose-dependent manner mediated by a significant increase in the Bax/Bcl-2 protein expression ratio. Noticeably, Nar potentiated the MTX effect on the Bax/Bcl-2 ratio. In conclusion, Nar decreased MTX-induced functional and ultrastructural liver damage in a tumor-free animal model. Also, our data introduce MTX and Nar as promising antiproliferative agents with a distinctive mode of action, inducing apoptosis in HepG2 tumor cells through activation of Bax and down-regulation of Bcl-2 protein expression.

The Roles of Neutrophils in the Pathogenesis of Liver Diseases

Neutrophils are the largest population of circulating leukocytes and the first responder against invading pathogens or other danger signals. Sophisticated machineries help them play critical roles in immunity and inflammation, including phagocytosis, superoxide production, cytokine and chemokine production, degranulation, and formation of neutrophil extracellular traps (NETs). After maturation and release from the bone marrow, neutrophils migrate to inflamed tissues in response to many stimuli. Increasing evidences indicate that neutrophils are critically involved in the pathogenesis of liver diseases, including liver cancer, thus making them promising target for the treatment of liver diseases. Here, we would like to provide the latest finding about the role of neutrophils in liver diseases and discuss the potentiality of neutrophils as target for liver diseases.

Orchestration of Neutrophil Extracellular Traps (Nets), a Unique Innate Immune Function during Chronic Obstructive Pulmonary Disease (COPD) Development

Morbidity, mortality and economic burden caused by chronic obstructive pulmonary disease (COPD) is a significant global concern. Surprisingly, COPD is already the third leading cause of death worldwide, something that WHO had not predicted to occur until 2030. It is characterized by persistent respiratory symptoms and airway limitation due to airway and/or alveolar abnormalities usually caused by significant exposure to noxious particles of gases. Neutrophil is one of the key infiltrated innate immune cells in the lung during the pathogenesis of COPD. Neutrophils during pathogenic attack or injury decide to undergo for a suicidal death by releasing decondensed chromatin entangled with antimicrobial peptides to trap and ensnare pathogens. Casting neutrophil extracellular traps (NETs) has been widely demonstrated to be an effective mechanism against invading microorganisms thus controlling overwhelming infections. However, aberrant and massive NETs formation has been reported in several pulmonary diseases, including chronic obstructive pulmonary disease. Moreover, NETs can directly induce epithelial and endothelial cell death resulting in impairing pulmonary function and accelerating the progression of the disease. Therefore, understanding the regulatory mechanism of NET formation is the need of the hour in order to use NETs for beneficial purpose and controlling their involvement in disease exacerbation. For example, DNA neutralization of NET proteins using protease inhibitors and disintegration with recombinant human DNase would be helpful in controlling excess NETs. Targeting CXC chemokine receptor 2 (CXCR2) would also reduce neutrophilic inflammation, mucus production and neutrophil-proteinase mediated tissue destruction in lung. In this review, we discuss the interplay of NETs in the development and pathophysiology of COPD and how these NETs associated therapies could be leveraged to disrupt NETopathic inflammation as observed in COPD, for better management of the disease.

The Role of Pancreatic Infiltrating Innate Immune Cells in Acute Pancreatitis

Acute pancreatitis (AP) is a leading cause of gastrointestinal-related hospital admissions with significant morbidity and mortality. Although the underlying pathophysiology of AP is rather complex, which greatly limits the treatment options, more and more studies have revealed that infiltrating immune cells play a critical role in the pathogenesis of AP and determine disease severity. Thus, immunomodulatory therapy targeting immune cells and related inflammatory mediators is expected to be a novel treatment modality for AP which may improve the prognosis of patients. Cells of the innate immune system, including macrophages, neutrophils, dendritic cells, and mast cells, represent the majority of infiltrating cells during AP. In this review, an overview of different populations of innate immune cells and their role during AP will be discussed, with a special focus on neutrophils and macrophages.

Circulating Neutrophil Extracellular Traps Signature for Identifying Organ Involvement and Response to Glucocorticoid in Adult-Onset Still's Disease: A Machine Learning Study

Adult-onset Still’s disease (AOSD) is an autoinflammatory disease with multisystem involvement. Early identification of patients with severe complications and those refractory to glucocorticoid is crucial to improve therapeutic strategy in AOSD. Exaggerated neutrophil activation and enhanced formation of neutrophil extracellular traps (NETs) in patients with AOSD were found to be closely associated with etiopathogenesis. In this study, we aim to investigate, to our knowledge for the first time, the clinical value of circulating NETs by machine learning to distinguish AOSD patients with organ involvement and refractory to glucocorticoid. Plasma samples were used to measure cell-free DNA, NE-DNA, MPO-DNA, and citH3-DNA complexes from training and validation sets. The training set included 40 AOSD patients and 24 healthy controls (HCs), and the validation set included 26 AOSD patients and 16 HCs. Support vector machines (SVM) were used for modeling and validation of circulating NETs signature for the diagnosis of AOSD and identifying patients refractory to low-dose glucocorticoid treatment. The training set was used to build a model, and the validation set was used to test the predictive capacity of the model. A total of four circulating NETs showed similar trends in different individuals and could distinguish patients with AOSD from HCs by SVM (AUC value: 0.88). Circulating NETs in plasma were closely correlated with systemic score, laboratory tests, and cytokines. Moreover, circulating NETs had the potential to distinguish patients with liver and cardiopulmonary system involvement. Furthermore, the AUC value of combined NETs to identify patients who were refractory to low-dose glucocorticoid was 0.917. In conclusion, circulating NETs signature provide added clinical value in monitoring AOSD patients. It may provide evidence to predict who is prone to be refractory to low-dose glucocorticoid and help to make efficient therapeutic strategy.

Destruction of Neutrophil Extracellular Traps Promotes the Apoptosis and Inhibits the Invasion of Gastric Cancer Cells by Regulating the Expression of Bcl-2, Bax and NF-κB

Introduction

This study aimed to investigate the effects of Neutrophil extracellular traps (NETs) destruction on the apoptosis and invasion of gastric cancer cells and the involved mechanisms.

Methods

Primary human neutrophils were isolated and co-cultured with three gastric cancer cells (BGC-823, SGC7901 and MKN28), and phorbol-12-myristate-13-acetate was added to generate NETs. Expression of NETs (SPINK5/LEKTI) and Cit Histone H3 were examined by immunofluorescent analysis and Western blot. Cancer cells were then divided into five groups: Control, NETs, Neutrophil, Amidine and DNase I. Cell apoptosis and invasion were examined by Transwell assay and flow cytometry, respectively. Expression of NF-κB p65, Bcl-2 and Bax was determined by RT-PCR, immunofluorescent analysis and Western blot.

Results

The expression of NETs (SPINK5/LEKTI) and Cit Histone H3 after co-culture increased significantly (P < 0.05), suggesting that gastric cancer cells could promote NETs generation. The Control, NETs and Neutrophil groups exhibited similar apoptosis and invasion of gastric cancer cells and similar mRNA and protein levels of NF-κB p65, Bcl-2 and Bax. However, compared with the Control group, the apoptosis and invasion of gastric cancer cells in both Amidine and DNase I groups were enhanced and weakened, respectively (P < 0.05). Moreover, both Amidine and DNase I groups showed much higher mRNA and protein levels of NF-κB p65 and Bax and lower mRNA and protein levels of Bcl-2 than the Control group (P < 0.05).

Conclusion

NETs destruction promoted the apoptosis and inhibited the invasion of gastric cancer cells by regulating the expression of Bcl-2, Bax and NF-κB.

Extracellular histones play a pathogenic role in primary graft dysfunction after human lung transplantation

Primary graft dysfunction (PGD) causes early mortality and late graft failure after lung transplantation. The mechanisms of PGD are not fully understood but ischemia/reperfusion (I/R) injury may be involved. Extracellular histones have recently been identified as major contributors to I/R injury. Hence, we investigated whether extracellular histones are associated with PGD after lung transplantation. In total, 65 lung transplant patients were enrolled into this study. Blood samples were collected from patients before and serially after transplantation (24 h, 48 h, and 72 h) and measured for extracellular histones, myeloperoxidase (MPO), lactate dehydrogenase (LDH), and multiple cytokines. Besides, the patients' sera were cultured with human pulmonary artery endothelial cells (HPAEC) and human monocyte cell line (THP1) cells, respectively, and cellular viability and cytokine production were determined. Heparin or anti-histone antibody were used to study the effects of histone-neutralized interventions. The results showed that extracellular histones increased markedly after lung transplantation, peaked by 24 h and tended to decrease thereafter, but still retained high levels up to 72 h. Extracellular histones were more abundant in patients with PGD (n = 8) than patients without PGD (n = 57) and linearly correlated with MPO, LDH, and most detected cytokines. Ex vivo studies showed that the patients' sera collected within 24 h after transplantation were very damaging to HPAEC cells and promoted cytokine production in cultured THP1 cells, which could be largely prevented by heparin or anti-histone antibodies. These data suggested a pathogenic role for extracellular histones in PGD after lung transplantation. Targeting extracellular histones may serve as a preventive and therapeutic strategy for PGD following lung transplantation.

Inhibition of peptidyl arginine deiminase-4 protects against myocardial infarction induced cardiac dysfunction

Peptidyl arginine deiminase-4 (PAD4), a PAD enzyme family member, catalyzes the posttranslational conversion of arginine residues to citrulline in target proteins. Although PAD4 is believed to play a crucial role in various pathological conditions such as infectious diseases, autoimmune diseases, and ischemic conditions, the effect of PAD4 in myocardial infarction (MI)-induced cardiac injury remains to be examined. Here, we hypothesize that PAD4 contributes to cardiac ischemic injury by exacerbating the inflammatory response and promoting neutrophil extracellular trap (NET) formation after MI. Permanent left coronary artery ligation, a condition that mimics MI, was performed on male C57BL/6 mice. [(3S,4R)-3-amino-4-hydroxy-1-piperidinyl] [2-[1-(cyclopropylmethyl)-1H-indol-2-yl]-7-methoxy-1-methyl-1H-benzimidazol-5-yl]-methanone (GSK484), an inhibitor of PAD4, was delivered via intraperitoneal injection to inhibit PAD4 activity. Cardiac PAD4 expression, tissue injury scoring, neutrophil infiltration, cit-H3 expression, NET formation, inflammatory cytokine secretion, apoptosis, and cardiac function were analyzed. In the current study, we discovered the protective effect of PAD4 inhibition using the PAD4-specific inhibitor GSK484 in cardiomyocytes challenged by MI. GSK484-mediated PAD4 inhibition can moderately preserve ventricle histological structure and myocardium integrity after MI, thereby reducing the infarct size and decreasing myocardial enzyme levels in serum. PAD4 inhibition also effectively protects cardiomyocytes from MI-induced NET formation and inflammatory cytokine secretion, in turn alleviating cardiac ischemia-induced apoptosis of cardiomyocytes. Collectively, these findings demonstrate the efficacy of specific PAD4 inhibition in reducing MI-induced neutrophil infiltration, NET formation, inflammatory reaction, and cardiomyocyte apoptosis, thereby increasing overall cardiac function improvement. These results provide novel insights for the development of new strategies to treat cardiovascular dysfunction in MI patients.

Upregulation of FSHR and PCNA by administration of coenzyme Q10 on cyclophosphamide-induced premature ovarian failure in a mouse model

Cyclophosphamide (CTX) has been broadly used in the clinic for the treatment of autoimmune disorders and ovarian cancer. The process of chemotherapy has significant toxicity in the reproductive system as it has detrimental effects on folliculogenesis, which leads to an irreversible premature ovarian failure (POF). Coenzyme Q10 (CoQ10) has positive impacts on the reproductive system due to its antioxidant properties, protecting the cells from free-radical oxidative damage and apoptosis. However, little is known about the possible synergistic effect of CTX and CoQ10 on the expression of genes involved in folliculogenesis, such as proliferation cell nuclear antigen (PCNA) and follicle-stimulating hormone receptor (FSHR). A total of 32 NMRI mice were applied and divided into four groups, including healthy control, CTX, CTX + CoQ10, and CoQ10 groups. The effects of CoQ10 on CTX-induced ovarian injury and folliculogenesis were examined by histopathological and real-time quantitative reverse transcription-polymerase chain reaction analyses. The rates of fertilization (in vitro fertilization), embryo development, as well as the level of reactive oxygen species (ROS) in metaphase II (MII) mouse oocytes after PMSG/HCC treatment were also assessed. Results showed that the treatment with CTX decreased the mRNA expression of PCNA and FSHR, IVF rate, and embryo development whereas the application of CoQ10 successfully reversed those factors. CoQ10 administration significantly enhanced histological morphology and decreased ROS levels and the number of atretic follicles in the ovary of CTX-treated mice. In conclusion, it seems that the protective effect of CoQ10 is exerted via the antioxidant and proliferative properties of this substance on CTX-induced ovarian damage.

Mechanisms of Environmental Contributions to Fatty Liver Disease

PURPOSE

Fatty liver disease (FLD) affects over 25% of the global population and may lead to liver-related mortality due to cirrhosis and liver cancer. FLD caused by occupational and environmental chemical exposures is termed "toxicant-associated steatohepatitis" (TASH). The current review addresses the scientific progress made in the mechanistic understanding of TASH since its initial description in 2010.

RECENT FINDINGS

Recently discovered modes of actions for volatile organic compounds and persistent organic pollutants include the following: (i) the endocrine-, metabolism-, and signaling-disrupting chemical hypotheses; (ii) chemical-nutrient interactions and the "two-hit" hypothesis. These key hypotheses were then reviewed in the context of the steatosis adverse outcome pathway (AOP) proposed by the US Environmental Protection Agency. The conceptual understanding of the contribution of environmental exposures to FLD has progressed significantly. However, because this is a new research area, more studies including mechanistic human data are required to address current knowledge gaps.

Extracellular DNA traps in inflammation, injury and healing

Following strong activation signals, several types of immune cells reportedly release chromatin and granular proteins into the extracellular space, forming DNA traps. This process is especially prominent in neutrophils but also occurs in other innate immune cells such as macrophages, eosinophils, basophils and mast cells. Initial reports demonstrated that extracellular traps belong to the bactericidal and anti-fungal armamentarium of leukocytes, but subsequent studies also linked trap formation to a variety of human diseases. These pathological roles of extracellular DNA traps are now the focus of intensive biomedical research. The type of pathology associated with the release of extracellular DNA traps is mainly determined by the site of trap formation and the way in which these traps are further processed. Targeting the formation of aberrant extracellular DNA traps or promoting their efficient clearance are attractive goals for future therapeutic interventions, but the manifold actions of extracellular DNA traps complicate these approaches.

Interaction of volatile organic compounds and underlying liver disease: a new paradigm for risk

Occupational and environmental exposures to industrial chemicals are known to cause hepatotoxicity and liver injury, in humans and in animal models. Historically, research has focused on severe acute liver injury (e.g. fulminant liver failure) or endstage diseases (e.g. cirrhosis and HCC). However, it has become recently recognized that toxicants can cause more subtle changes to the liver. For example, toxicant-associated steatohepatitis, characterized by hepatic steatosis, and inflammation, was recently recognized in an occupational cohort exposed to vinyl chloride. At high occupational levels, toxicants are sufficient to cause liver damage and disease even in healthy subjects with no comorbidities for liver injury. However, it is still largely unknown how exposure to toxicants initiate and possibly more importantly exacerbate liver disease, when combined with other factors, such as underlying non-alcoholic fatty liver disease caused by poor diet and/or obesity. With better understanding of the mechanism(s) and risk factors that mediate the initiation and progression of toxicant-induced liver disease, rational targeted therapy can be developed to better predict risk, as well as to treat or prevent this disease. The purpose of this review is to summarize established and proposed mechanisms of volatile organic compound-induced liver injury and to highlight key signaling events known or hypothesized to mediate these effects.

NETopathic Inflammation in Chronic Obstructive Pulmonary Disease and Severe Asthma

Neutrophils play a central role in innate immunity, inflammation, and resolution. Unresolving neutrophilia features as a disrupted inflammatory process in the airways of patients with chronic obstructive pulmonary disease (COPD) and severe asthma. The extent to which this may be linked to disease pathobiology remains obscure and could be further confounded by indication of glucocorticoids or concomitant respiratory infections. The formation of neutrophil extracellular traps (NETs) represents a specialized host defense mechanism that entrap and eliminate invading microbes. NETs are web-like scaffolds of extracellular DNA in complex with histones and neutrophil granular proteins, such as myeloperoxidase and neutrophil elastase. Distinct from apoptosis, NET formation is an active form of cell death that could be triggered by various microbial, inflammatory, and endogenous or exogenous stimuli. NETs are reportedly enriched in neutrophil-dominant refractory lung diseases, such as COPD and severe asthma. Evidence for a pathogenic role for respiratory viruses (e.g., Rhinovirus), bacteria (e.g., Staphylococcus aureus) and fungi (e.g., Aspergillus fumigatus) in NET induction is emerging. Dysregulation of this process may exert localized NET burden and contribute to NETopathic lung inflammation. Disentangling the role of NETs in human health and disease offer unique opportunities for therapeutic modulation. The chemokine CXCR2 receptor regulates neutrophil activation and migration, and small molecule CXCR2 antagonists (e.g., AZD5069, danirixin) have been developed to selectively block neutrophilic inflammatory pathways. NET-stabilizing agents using CXCR2 antagonists are being investigated in proof-of-concept studies in patients with COPD to provide mechanistic insights. Clinical validation of this type could lead to novel therapeutics for multiple CXCR2-related NETopathologies. In this Review, we discuss the emerging role of NETs in the clinicopathobiology of COPD and severe asthma and provide an outlook on how novel NET-stabilizing therapies via CXCR2 blockade could be leveraged to disrupt NETopathic inflammation in disease-specific phenotypes.

Characterisation of small molecule ligands 4CMTB and 2CTAP as modulators of human FFA2 receptor signalling

Short chain fatty acids (SCFAs) are protective against inflammatory diseases. Free fatty acid receptor 2 (FFA2), is a target of SCFAs however, their selectivity for FFA2 over other FFA receptors is limited. This study aimed to functionally characterise 2-(4-chlorophenyl)-3-methyl-N-(thiazole-2-yl)butanamide (4CMTB) and 4-((4-(2-chlorophenyl)thiazole-2-yl)amino)-4oxo-3-phenylbutanoic acid (2CTAP), and their enantiomers, in modulating FFA2 activity. The racemic mixture (R/S) and its constituents (R-) and (S-) 4CMTB or 2CTAP were used to stimulate human (h)FFA2 in the absence or presence of acetate. Calcium ions (Ca²⁺), phosphorylated extracellular signal-regulated kinase 1 and 2 (pERK1/2) and cyclic adenosine monophosphate (cAMP) were measured. R/S-4CMTB is a functionally selective ago-allosteric ligand that enhances Ca²⁺ response to acetate. Both R/S-4CMTB and S-4CMTB are more potent activators of pERK1/2 and inhibitors of forskolin-induced cAMP than acetate. S-4CMTB increased neutrophil infiltration in intestinal ischemia reperfusion injury (IRI). 2CTAP inhibited constitutive Ca²⁺ levels, antagonised acetate-induced pERK1/2 and prevented damage following IRI. This study characterises enantiomers of functionally selective ligands for FFA2 in cells stably expressing hFFA2. It highlights the novel roles of selective FFA2 enantiomers 4CMTB and 2CTAP on Ca²⁺, pERK1/2 and cAMP and their roles as allosteric modulators which, may assist in efforts to design novel therapeutic agents for FFA2-driven inflammatory diseases.

E-Cigarette Use Causes a Unique Innate Immune Response in the Lung, Involving Increased Neutrophilic Activation and Altered Mucin Secretion

RATIONALE

E-cigarettes have become increasingly popular and little is known about their potential adverse health effects.

OBJECTIVES

To determine the effects of e-cigarette use on the airways.

METHODS

Induced sputum samples from cigarette smokers, e-cigarette users, and nonsmokers were analyzed by quantitative proteomics, and the total and individual concentrations of mucins MUC5AC and MUC5B were determined by light scattering/refractometry and labeled mass spectrometry, respectively. Neutrophil extracellular trap (NET) formation rates were also determined for the same groups.

MEASUREMENTS AND MAIN RESULTS

E-cigarette users exhibited significant increases in aldehyde-detoxification and oxidative stress-related proteins associated with cigarette smoke compared with nonsmokers. The levels of innate defense proteins associated with chronic obstructive pulmonary disease, such as elastase and matrix metalloproteinase-9, were significantly elevated in e-cigarette users as well. E-cigarette users' sputum also uniquely exhibited significant increases in neutrophil granulocyte-related and NET-related proteins, such as myeloperoxidase, azurocidin, and protein-arginine deiminase 4, despite no significant elevation in neutrophil cell counts. Peripheral neutrophils from e-cigarette users showed increased susceptibility to phorbol 12-myristate 13-acetate-induced NETosis. Finally, a compositional change in the gel-forming building blocks of airway mucus (i.e., an elevated concentration of mucin MUC5AC) was observed in both cigarette smokers and e-cigarette users.

CONCLUSIONS

Together, our results indicate that e-cigarette use alters the profile of innate defense proteins in airway secretions, inducing similar and unique changes relative to cigarette smoking. These data challenge the concept that e-cigarettes are a healthier alternative to cigarettes.