Expression Of Peptidylarginine Deiminase 4 Research Articles

Ferroptosis Induces gut microbiota and metabolic dysbiosis in Collagen-Induced arthritis mice via PAD4 enzyme

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation and joint destruction, with emerging evidence implicating gut microbiota dysbiosis in its pathogenesis. The current study explores the role of ferroptosis, a form of regulated cell death driven by iron-dependent lipid peroxidation, in modulating gut microbiota and metabolic dysregulation through the enzyme peptidyl arginine deiminase 4 (PAD4) in collagen-induced arthritis (CIA) mouse model. Our findings demonstrate that ferroptosis exacerbates RA-related inflammatory responses and joint damage by upregulating PAD4 expression, which, in turn, influences the gut microbial composition and associated metabolite profiles. Erastin, a known ferroptosis agonist, significantly increased the relative abundance of pro-inflammatory bacteria such as Proteobacteria while reducing beneficial taxa like Firmicutes and Bacteroidetes. This microbial shift was associated with heightened oxidative stress and an imbalance in key metabolites, such as lysophosphatidyl ethanolamine 14:0 (LysoPE 14:0), further exacerbated by ferroptosis. Co-treatment with GSK484, a PAD4 inhibitor, reversed these effects, restoring microbial homeostasis and reducing joint inflammation. This study suggests that ferroptosis-mediated PAD4 activity contributes to RA pathogenesis by disrupting the gut-joint axis, providing novel insights into potential therapeutic targets for RA. Our results highlight the intricate interplay between immune-mediated cell death, gut microbiota, and systemic inflammation, emphasizing the importance of ferroptosis as a therapeutic target in mitigating RA progression.

Circulating levels of neutrophil extracellular traps reflects local neutrophil activity but not fibrinolytic activity in coronary thrombi from patients with ST-elevation myocardial infarction

Abstract Introduction Neutrophil extracellular traps (NETs) are associated with impaired fibrinolysis in ischemic stroke, while NETs degradation enhances lysis of coronary thrombi in ex vivo experiments. Whether circulating NET markers are associated with local fibrinolytic activity in patients with ST-elevation myocardial infarction (STEMI) has not been reported. Purpose We investigated associations between circulating NET markers and gene expression of fibrinolytic markers in aspirated coronary thrombi from patients with STEMI. Furthermore, we explored whether local upregulation of NET formation by peptidylarginine deiminase 4 (PAD4) was reflected in the circulation. Methods Coronary thrombi from 35 STEMI patients undergoing primary percutaneous coronary intervention (PCI) were aspirated and promptly snap-frozen to -80°C. Peripheral blood samples were collected simultaneously. Median time from start of symptoms to PCI was 152 min. Thrombus gene expression of tissue Plasminogen Activator (tPA), urinary-type Plasminogen Activator (uPA), plasminogen-activation inhibitor type 1 (PAI-1) and PAD4 were quantified with RT-PCR. Gene expression of PAD4 was also measured in circulating leukocytes. Circulating NET markers were measured by a fluorescent nucleic acid stain using fluorometry (dsDNA), an in-house ELISA technique (MPO-DNA) and commercial ELISA (H3Cit). Correlations were tested using Spearman’s rho. Results There were no correlations between any of the circulating NET markers and gene expression of the fibrinolytic markers tPA, uPA and PAI-1 in the thrombus. Of the circulating NET markers, dsDNA correlated with thrombus gene expression of PAD4 (rs=0.491 p=0.006), whereas none of the NET markers correlated with gene expression of PAD4 in circulating leukocytes. Conclusion Circulating NET markers were not associated with gene expression of fibrinolytic activity in thrombi from patients with STEMI. Local NET formation in the thrombi, measured as PAD4 expression, was associated with the circulating NET marker dsDNA. These findings suggest that circulating NET markers have limited utility for assessing local fibrinolytic activity, but might reflect PAD4-dependent NET formation in coronary thrombi.

Berbamine ameliorates DSS-induced colitis by inhibiting peptidyl-arginine deiminase 4-dependent neutrophil extracellular traps formation

Ulcerative colitis (UC) is a chronic inflammatory bowel disease with immune dysregulation affecting colon inflammatory response. Recent studies have highlighted that neutrophil extracellular traps (NETs) play an important role in the pathogenesis of UC. Berbamine (BBM), one of the bioactive ingredients extracted from Chinese herbal medicine Berberis vulgaris L, has attracted intensive attentions due to its significant anti-inflammatory activity and a marketing drug for treating leukemia in China. However, the exact role and potential molecular mechanism of BBM against UC remains elusive. In the present study, our results showed that BBM could markedly improve the pathological phenotype and the colon inflammation in mice with dextran sulfate sodium (DSS)-induced colitis. Then, comprehensive approaches combining network pharmacology and molecular docking analyses were employed to predict the therapeutic potential of BBM in treating UC by peptidyl-arginine deiminase 4 (PAD4), a crucial molecule involved in NETs formation. The molecular docking results showed BBM had a high affinity for PAD4 with a binding energy of −9.3 kcal/mol Moreover, PAD4 expression and NETs productions, including citrullination of histone H3 (Cit-H3), neutrophil elastase (NE), myeloperoxidase (MPO) in both neutrophils and colonic tissue were reduced after BBM administration. However, in the mice with DSS-induced colitis pretreated with GSK484, a PAD4-specific inhibitor, BBM could not further reduce disease related indexes, expression of PAD4 and NETs productions. Above all, the identification of PAD4 as a potential target for BBM to inhibit NETs formation in colitis provides novel insights into the development of BBM-derived drugs for the clinical management of UC.

Computational analysis of curcumin-mediated alleviation of inflammation in periodontitis patients with experimental validation in mice.

Using network pharmacology and experimental validation to explore the therapeutic efficacy and mechanism of curcumin (Cur) in periodontitis treatment. Network pharmacology was utilized to predict target gene interactions of Cur-Periodontitis. Molecular docking was used to investigate the binding affinity of Cur for the predicted targets. A mouse model with ligature-induced periodontitis (LIP) was used to verify the therapeutic effect of Cur. Microcomputed tomography (micro-CT) was used to evaluate alveolar bone resorption, while western blotting, haematoxylin-eosin staining and immunohistochemistry were used to analyse the change in immunopathology. SYTOX Green staining was used to assess the in vitro effect of Cur in a mouse bone marrow-isolated neutrophil model exposed to lipopolysaccharide. Network pharmacology identified 114 potential target genes. Enrichment analysis showed that Cur can modulate the production of neutrophil extracellular traps (NETs). Molecular docking experiments suggested that Cur effectively binds to neutrophil elastase (ELANE), peptidylarginine deiminase 4 (PAD4) and cathepsin G, three enzymes involved in NETs. In LIP mice, Cur alleviated alveolar bone resorption and reduced the expression of ELANE and PAD4 in a time-dependent but dose-independent manner. Cur can directly inhibit NET formation in the cell model. Our research suggested that Cur may alleviate experimental periodontitis by inhibiting NET formation.

Attenuation of Pulmonary Damage Associated with COPD in a Cadmium-Exposed Model Due to the Administration of a siRNA Targeting PAD4

Chronic obstructive pulmonary disease (COPD), characterised by persistent airflow limitation during breathing, is considered to be the third leading cause of death worldwide. Among the mechanisms involved in this pathology is the excessive generation of neutrophil extracellular traps (NETs), which can induce an unwanted inflammatory response. These traps have been reported to be generated by the enzyme peptidyl arginine deiminase 4 (PAD4). The aim of this work is therefore to evaluate the effect of the administration of a siRNA targeting PAD4 on lung damage in a COPD animal model. Wistar rats weighing 300–350 g were administered cadmium chloride (5 mg/kg i.p.) every 24 h. Then, following one week of the administration of cadmium chloride, the PAD4-targeted siRNA was administered, and at the second week, lung function was measured, as were lung and heart weights, as well as PAD4 expression by RT-PCR. Our results showed that cadmium administration generated a COPD model, which increased PAD4 expression and decreased lung and heart weights and respiratory function. SiRNA administration partially reversed the changes associated with the COPD model. In conclusion, our results suggest that administration of an siRNA targeting PAD4 could improve respiratory function by decreasing lung and heart damage.

Do neutrophil extracellular traps implicate in atheromatous plaques from carotid endarterectomy? Re-analyzes of cDNA microarray data by surgeons.

Carotid artery stenosis is the cause of 15% of strokes. Neutrophil extracellular traps (NETs) and peptidyl arginine deiminase 4 (PAD4) are believed to be involved in thrombosis. This pilot study described the differential expression profile of NETs between atheromatous plaques and surrounding tissues. Microarray datasets of carotid plaques were obtained from Gene Expression Omnibus. The normalized data were processed into comma-separated value matrix files using spreadsheet software. Analyzes of microarray data were conducted using integrated differential expression and pathway analysis. The clustering results illustrated that the classifications of plaque and control had reasonable biological validity. Pathway analysis revealed the relevance of immune response, cell signaling, and other pathways. Differentially expressed genes were detected between carotid plaques and control specimens. However, enrichment analyzes did not reveal a difference in PAD4 expression between the groups and that NET implication was only found in one cDNA microarray dataset. This pilot study does not necessarily dismiss the possibility of a relationship between NETs and atherothrombotic stroke. Gene expression could differ between endothelial cells and atheromas, and further studies are needed.

EQUOL, A SOYBEAN METABOLITE WITH ESTROGEN-LIKE FUNCTIONS, DECREASES LIPOPOLYSACCHARIDE-INDUCED HUMAN NEUTROPHIL EXTRACELLULAR TRAPS IN VITRO.

Objective: Neutrophil extracellular traps (NETs) defend against acute infections. However, their overexpression causes organ failure during sepsis. Control of NET formation may improve the outcomes of patients with sepsis. Equol, a soybean isoflavone, is a female hormone analog, which prevents inflammation. We evaluated the effects of equol on NET formation in human neutrophils during inflammatory stimulation in vitro . Methods: Healthy volunteers provided blood samples. An enzyme-linked immunosorbent assay assessed serum equol concentrations. Neutrophil extracellular trap formation in neutrophils was induced by lipopolysaccharide treatment. Enzyme-linked immunosorbent assay quantified DNA-binding elastase, and immunostaining assessed NET formation. Reverse-transcription quantitative polymerase chain reaction and Western blotting detected G-protein-coupled receptor 30 (GPR30) or peptidyl arginine deiminase 4 (PAD4) expression. Flow cytometry assessed neutrophil phagocytic ability with inactivated Escherichia coli . Results: In neutrophils derived from males with low-serum equol levels (low-serum equol group), equol significantly decreased DNA-binding elastase levels and NET formation. Equol did not decrease NETs in neutrophils from males with high-serum equol levels. GPR30 expression of neutrophils was higher in the low-serum than in the high-serum equol group. PAD4 mRNA levels and nuclear PAD4 protein expression also decreased more than the vehicle control in the low-serum equol group. Equol did not alter the phagocytic ability of neutrophils. In neutrophils from young females, equol had no inhibitory effect on NET formation. Conclusions: Equol decreases lipopolysaccharide-induced NET formation in neutrophils from males via inhibition of PAD4 expression. Our findings provide a rationale for investigating a new therapeutic approach using equol to control neutrophil activity during sepsis.

Interleukin-8 and neutrophil extracellular traps in children with lupus nephritis and vitamin C deficiency.

Vitamin C is a potent scavenger of reactive oxygen species, which induce neutrophil extracellular trap (NET) formation. NETs are a major source of autoantigens and are involved in systemic lupus erythematosus (SLE) pathogenesis. We determined vitamin C status and evaluated NET formation and inflammatory cytokines in children with lupus nephritis. Serum vitamin C was measured in 46 patients (82.6% females, mean age 14.5 ± 0.3years). Vitamin C levels < 0.3mg/dL indicated vitamin C deficiency. Patients were divided into two groups according to serum vitamin C levels: normal and low (< 0.3mg/dL). We compared NET formation and levels of SLE-related cytokines, including interleukin (IL)-8, IL-10, and tumor necrosis factor-α (TNF-α), between groups. NET formation was determined through measurement of serum citrullinated histone 3 levels and mRNA expression of peptidyl arginine deiminase-4 and assessment of the percentage of neutrophils with NETs by immunofluorescence. Nine patients (19.6%) had vitamin C deficiency. Kidney pathology assessment at disease onset revealed that histological activity index and number of kidney biopsies containing crescentic glomeruli were higher in vitamin C-deficient patients, but chronicity index was not. NET formation and serum IL-8 were more prominent in vitamin C-deficient patients. Serum IL-8 levels were 12.9 ± 5.2pg/mL in low vitamin C group and 5.2 ± 0.9pg/mL in normal vitamin C group (p = 0.03). Serum IL-10 and TNF-α were similar between groups. Our study demonstrated correlation among vitamin C deficiency, increased NET formation, and IL-8 upregulation in children with lupus nephritis. A prospective study is required to evaluate cause‒effect relationships of vitamin C status, NET formation and IL-8 expression.

Investigating the cell membrane localization of PADI4 in breast cancer cells and inhibition of anti-PADI4 monoclonal antibody

BackgroundPeptidyl arginine deiminase 4 (PADI4) is a post-translational modification enzymecan that converts arginine in protein into citrulline in the presence of calcium ions, which is called citrullination. PADI4 has been reported to be expressed in the cytoplasm and nucleus in a variety of malignant tumors. Based on the GeneCards database and our previous research, it is speculated that PADI4 may also be expressed on the cell membrane. This study aimed to confirm the membrane expression of PADI4 and the effect of anti-PADI4 antibodies on cell membrane PADI4. This may be another mechanism of action of anti-PADI4 monoclonal antibodies in the treatment of breast cancer.MethodsThe subcellular localizations of PADI4 in MDA-MB-231 and MCF-7 breast cancer cells were determined by immunofluorescence, immunoelectron microscopy, and Western blot analysis. The tumor cells were treated with PADI4 antibody, and cell proliferation, migration, colony formation, apoptosis, glycolysis, and epithelial-mesenchymal transition (EMT) were measured as well as the expression of some essential tumor genes.ResultsPADI4 was not only localized in the nucleus and cytoplasm of breast cancer cells but was also detected on the cell membrane. Following PADI4 antibody treatment, cell proliferation, migration, colony formation, EMT, and ATP production through glycolysis were decreased, and the mRNA expression of MYC proto-oncogene (MYC), FAT atypical cadherin 1 (FAT1), nuclear factor kappa B subunit 1 (NFκB), and tumor necrosis factor (TNF-α) in breast cancer cells was downregulated, while the mRNA expression of tumor protein p63 (TP63) was upregulated.ConclusionsPADI4 is expressed on the cell membrane in breast cancer cells. Anti-PADI4 antibodies can affect the biological functions of cell membrane PADI4, including proliferation, migration, apoptosis, and glycolysis, thereby inhibiting tumor progression.Graphical abstract

The role of protein arginine deiminase 4-dependent neutrophil extracellular traps formation in ulcerative colitis.

Neutrophil extracellular traps (NETs) play an important role in the development and progression of ulcerative colitis (UC). Peptidyl arginine deiminase 4 (PAD4) is essential for the formation of NETs via catalyzing histone citrullination. This study mainly to explore the role of PAD4-mediated NETs in intestinal inflammation of dextran sulfate sodium (DSS)-induced UC. Acute and chronic colitis mouse models were established by supplementing DSS in drinking water. Colon tissues from colitis mice were analyzed for the level of PAD4 expression, citrullinated histone H3(Cit-H3), intestinal histopathology, and inflammatory cytokines secretion. Serum samples were tested for systemic neutrophil activation biomarkers. Colitis mice administered with Cl-amidine, a PAD4 inhibitor, and PAD4 knockout mice were investigated to detect NETs formation, intestinal inflammation, and barrier function. We found the formation of NETs significantly increased in DSS-induced colitis mice and was correlated with disease markers. Blocking NETs formation by Cl-amidine or PAD4 genetic knockout could alleviate clinical colitis index, intestinal inflammation, and barrier dysfunction. This study provided a research basis for the role of PAD4-mediated NETs formation in the pathogenesis of UC and suggested that inhibition of PAD4 activity and the formation of NETs may be helpful for the prevention and treatment of UC.

Simvastatin Reduces NETosis to Attenuate Severe Asthma by Inhibiting PAD4 Expression.

Patients with severe asthma respond poorly to corticosteroids, and their care accounts for more than 60% of the total costs attributed to asthma. Neutrophils form neutrophil extracellular traps (NETs), which play a crucial role in severe asthma. Statins have shown anti-inflammatory effects by reducing NETosis. In this study, we investigate if simvastatin can attenuate severe asthma by reducing NETosis and the underlying mechanism. Mice were concomitantly sensitized with ovalbumin (OVA), house dust mite (HDM), and lipopolysaccharide (LPS) during sensitization to establish a mouse model of severe asthma with neutrophil predominant inflammation (OVA+LPS mice) and treated with or without simvastatin. In inflammatory response, proportions of Th2, Th17, and Treg cells in lung tissue were detected by flow cytometry, and the levels of cytokines, dsDNA, and MPO-DNA in bronchoalveolar lavage fluid (BALF) were analyzed by ELISA. Citrullinated histone H3 (CitH3) and peptidyl arginine deiminase 4 (PAD4) in lung tissue were determined by Western blot and immunofluorescence imaging. PAD4 mRNA was determined by quantitative PCR (qPCR). HL-60 cells were differentiated into neutrophil-like cells by 1.25% DMSO. The neutrophil-like cells were treated with or without LPS, and simvastatin was then stimulated with PMA. CitH3 and PAD4 expressions were determined. Sensitization with OVA, HDM, and LPS resulted in neutrophilic inflammation and the formation of NETs in the lungs. Simvastatin treatment reduced the inflammation score, cytokine levels, total cells, and neutrophil counts in the BALF and reduced proportions of Th2 and Th17 but increased Treg cells in lungs of OVA+LPS mice. Simvastatin-treated OVA+LPS mice show reduced NET formation in BALF and lung tissue compared to control mice. Adoptive transfer of neutrophils was sufficient to restore NETosis and neutrophilic inflammation in simvastatin-treated OVA+LPS mice. Simvastatin reduced PAD4 mRNA and protein expression in lung tissues and neutrophils isolated from lungs of OVA+LPS mice and consequent NET formation. In vitro, simvastatin reduced LPS-induced PAD4 upregulation and NETosis in HL-60-differentiated neutrophil-like cells. Furthermore, PAD4-overexpressed lentiviral transduction was sufficient to restore PAD4 protein expression and NETosis in simvastatin-treated HL-60-differentiated neutrophil-like cells. Simvastatin reduces Th17-mediated neutrophilic inflammation and airway hyperreactivity by reducing PAD4 expression and inhibiting NETosis in a mouse model of severe asthma. Severe asthmatic patients with high levels of circulating NETs or sputum NETs may show improved responses to statin treatment.

S-07-6: NEUTROPHIL EXTRACELLULAR TRAPS AS MEDIATORS OF ENDOTHELIAL DAMAGE IN HYPERTENSION AND DIABETES

Objective: Endothelial dysfunction (ED) plays a key role in the pathogenesis of hypertension and diabetes, yet its molecular determinants are poorly understood. Concomitant hypertension and diabetes can synergistically increase damage to the vasculature, with increasing evidence suggesting that resulting immune dysregulation may contribute to endothelial injury. Neutrophil extracellular traps (NETs), networks of chromatin and protein-containing extracellular fibers released to fight infection, are generated from neutrophils following activation of the citrullinating enzyme peptidylarginine deiminase 4 (PAD4). PAD4 has been shown to be upregulated in atherosclerosis, vasculitis, and various inflammatory autoimmune diseases, leading to NET-induced endothelial injury. Whether NETs could contribute to hypertension- and diabetes-induced ED has not been established. The objective of the present study is to investigate the impact of hypertension and diabetes on PAD4 activity and the contribution of NETs to resulting vascular injury. Design and Methods: Promyelocytic HL-60 cells were differentiated to neutrophil-like cells and treated with angiotensin II (10−7 M) and/or high glucose (25 mM) for 24 hours, with or without subsequent NET-inducing PMA stimulation (500 nM). NETs were isolated from the culture medium by differential centrifugation and assessed by Western blot analysis of citrullinated histone H3 (citH3, a primary NET component). Isolated NETs were used to treat Human Umbilical Vein Endothelial Cells (HUVECs) at 0.5–500 ng/ml for 24 hours, after which cell viability (XTT cell assay) and proliferation (BrdU assay) were measured. We also assessed NETosis in mice expressing human renin in the liver (TTRhRen) intercrossed with OVE26 diabetic mice [i.e. hypertensive-diabetic, HD mice], compared with wild-type (WT) FVBN/J mice. We examined kidney levels of citH3, neutrophil elastase (NE), and PAD4 expression by immunohistochemistry. Results: Treatment with high glucose, but not angiotensin II, increased citH3 levels in neutrophil-like cells. NETs isolated from PMA-stimulated cells decreased HUVEC viability by ∼2-fold at 5 ng/ml (P = &lt; 0.0001), and dose dependently decreased proliferation from 0.5–500 ng/ml, with a ∼80% decrease at 500 ng/ml. In HD mice, we observed a significant increase in kidney levels of citH3 (P &lt; 0.0001), NE (P &lt; 0.0001), and PAD4 (P &lt; 0.0001), which was associated with the presence of albuminuria and increased blood pressure levels. Conclusion: These results suggest that NETs are upregulated in hypertension and diabetes and may contribute to endothelial damage and microvascular injury.

IFI204 protects host defense against Staphylococcus aureus-induced pneumonia by promoting extracellular traps formation

Interferon-inducible protein 204 (IFI204) is an intracellular DNA receptor that can recognize DNA viruses and intracellular bacteria. Extracellular traps (ETs) have been recognized as an indispensable antimicrobial barrier that play an indispensable role in bacterial, fungal, parasitic, and viral infections. However, how ETs form and the mechanisms by which IFI204 function in Staphylococcus aureus pneumonia are still unclear. Moreover, by in vitro experiments, we proved that IFI204 deficiency decreases the formation of ETs induced by Staphylococcus aureus in a NOX-independent manner. More importantly, Deoxyribonuclease I (DNase I) treatment significantly inhibited the formation of ETs. IFI204 contributed to ETs formation by promoting citrullination of histone H3 and the expression of PAD4 (peptidylarginine deiminase 4). Altogether, these findings highlight the potential importance of IFI204 for host defense against S. aureus USA300-TCH1516 infection.

Forsythiaside B ameliorates coagulopathies in a rat model of sepsis through inhibition of the formation of PAD4-dependent neutrophil extracellular traps.

Forsythiaside B (FTB) is one of the main components of Forsythia suspensa (Thunb.) Vahl and exerts anti-inflammatory and anti-oxidative effects. However, its mechanism of action as a treatment for sepsis remains unclear. In this study, we developed a rat model of sepsis using cecal ligation and puncture (CLP) to investigate the effects of FTB on sepsis-associated coagulopathies. Using rats with sepsis, we investigated the effects of FTB on neutrophil extracellular trap (NETs) formation and peptidylarginine deiminase 4 (PAD4) expression in neutrophils. NET (DNase1) and PAD4 (Cl-amidine) inhibitors were used to further investigate whether FTB mitigates sepsis-associated coagulopathies by inhibiting PAD4-dependent NETs production. Our results showed that treatment with FTB increased the survival rate, ameliorated the CLP-induced inflammatory response and multiple organ dysfunction, and reduced CLP-induced pathological changes. FTB also alleviated the associated coagulopathies. Additionally, we demonstrated that treatment with FTB inhibited NETs formation and downregulated PAD4 expression in peripheral neutrophils. The effects of FTB on coagulopathies were similar to those of monotherapy with NET or PAD4 inhibitors. In conclusion, our study confirmed that FTB can alleviate coagulopathies in rats with sepsis. The underlying mechanism of FTB's effect consists in inhibition of PAD4-dependent NETs formation.

PAD4-dependent citrullination of nuclear translocation of GSK3β promotes colorectal cancer progression via the degradation of nuclear CDKN1A

Peptidylarginine deiminase 4 (PAD4), a Ca2+-dependent enzyme, catalyzes the conversion of arginine to citrulline and has been strongly associated with many malignant tumors. However, the molecular mechanisms of PAD4 in the development and progression of colorectal cancer (CRC) remain unclearly defined. In our study, PAD4 expression was increased in CRC tissues and cells, and was closely related to tumor size, lymph node metastasis. Moreover, the transcription factor KLF9 directly bound to PADI4 gene promoter, leading to overexpression of PAD4 in CRC cells, which augmented cell growth and migration. We revealed that PAD4 interacted with and citrullinated glycogen synthase kinase-3β (GSK3β) in CRC cells, and GSK3β Arg-344 was the dominating PAD4-citrullination site. Furthermore, IgL2 and catalytic domains of PAD4 directly bound to the kinase domain of GSK3β in CRC cells. Mechanistically, PAD4 promoted the transport of GSK3β from the cytoplasm to the nucleus, thereby increasing the ubiquitin-dependent proteasome degradation of nuclear cyclin-dependent kinase inhibitor 1 (CDKN1A). Our study is the first to reveal the details of a critical PAD4/GSK3β/CDKN1A signaling axis for CRC progression, and provides evidence that PAD4 is a potential diagnosis biomarker and therapeutic target in CRC.

P075 Neutrophils prevent rectal bleeding in Ulcerative Colitis by peptidyl-arginine deiminase-4-dependent immunothrombosis

Abstract Background Bleeding ulcers and erosions are hallmarks of active ulcerative colitis (UC). However, the mechanisms controlling bleeding and mucosal haemostasis remain elusive. Methods We used high resolution endoscopy and colon tissue samples of active UC (n = 36) as well as experimental models of physical and chemical mucosal damage in mice deficient for peptidyl-arginine deiminase-4 (PAD4), gnotobiotic mice and controls. We employed endoscopy, histochemistry, live-cell microscopy and flow cytometry to study eroded mucosal surfaces during mucosal haemostasis. Results Erosions and ulcerations in UC were covered by fresh blood, haematin or fibrin visible by endoscopy. Fibrin layers rather than fresh blood or haematin on erosions were inversely correlated with rectal bleeding in UC. Fibrin layers contained ample amounts of neutrophils co-aggregated with neutrophil extracellular traps (NETs) with detectable activity of peptidyl-arginine deiminases (PAD). Transcriptome analyses showed significantly elevated PAD4 expression in active UC. In experimentally inflicted wounds, we found that neutrophils underwent NET formation in a PAD4-dependent manner hours after formation of primary blood clots, and remodelled clots to immunothrombi containing citrullinated histones, even in the absence of microbiota. PAD4-deficient mice experienced an exacerbated course of DSS-induced colitis with markedly increased rectal bleeding (96 % vs 10 %) as compared to controls. PAD4-deficient mice failed to remodel blood clots on mucosal wounds eliciting impaired healing. Thus, NET-associated immunothrombi are protective in acute colitis, while insufficient immunothrombosis is associated with rectal bleeding. Conclusion Our findings uncover that neutrophils induce secondary immunothrombosis by PAD4-dependent mechanisms. Insufficient immunothrombosis may favor rectal bleeding in UC.

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

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

Neutrophils prevent rectal bleeding in ulcerative colitis by peptidyl-arginine deiminase-4-dependent immunothrombosis

ObjectiveBleeding ulcers and erosions are hallmarks of active ulcerative colitis (UC). However, the mechanisms controlling bleeding and mucosal haemostasis remain elusive.DesignWe used high-resolution endoscopy and colon tissue samples of active...

CML-271: Neutrophil Extracellular Traps Are Increased in Chronic Myeloid Leukemia and Are Differentially Affected by Tyrosine Kinase Inhibitors

Context: Cardiovascular (CVS) complications are increasingly reported with the use of certain tyrosine kinase inhibitors (TKIs) to treat chronic myeloid leukemia (CML). Neutrophil extracellular traps (NETs) have previously been implicated in the pathogenesis of cancer-associated thrombosis. Objective: To assess NET formation in neutrophils from patients with CML, to characterize the role of reactive oxygen species (ROS) and peptidyl arginine deiminase 4 (PAD4) in NET formation in CML, and to assess the effects of TKIs on NET formation in CML. Design: Blood samples were obtained from patients with newly diagnosed CML and from age/gender-matched controls. NETs were assessed after stimulation with phorbol 12-myristate 13-acetate (PMA) or ionomycin (IO), with or without pre-treatment with imatinib, ponatinib, nilotinib, and dasatinib at clinically relevant concentrations. NET formation was assessed by morphology, immunofluorescence (IF), and the expression of proteins known to be associated with NET formation (NET-associated elastase, citrullinated histone H3 [H3cit], etc.). ER-HoxB8 conditionally immortalized murine myeloid progenitor cell line was differentiated into functional neutrophils and transduced with a BCR-ABL1 oncogene (or empty vector control). Results: Neutrophils isolated from treatment-naive patients with CML showed a significant increase in NET formation compared to matched controls at baseline and after stimulation with IO as assessed by IF and after stimulation with PMA as assessed by NET-associated elastase expression. Expression of H3cit, PAD4, and ROS was significantly higher in CML samples compared to controls. Pre-treatment of neutrophils with TKIs was associated with a differential effect on NET formation. Exposure to ponatinib significantly augmented NET-associated elastase and ROS levels as compared to control and other TKIs in neutrophils derived from patients with CML. BCR-ABL1 retrovirally transduced HoxB8-neutrophils demonstrated increased H3cit and myeloperoxidase expression, consistent with excess NET formation. This was inhibited by Cl-amidine, a PAD4 inhibitor, but not by the NADPH inhibitor diphenyleneiodonium (DPI). Ponatinib and nilotinib pre-exposure significantly increased H3cit expression in HoxB8-BCR-ABL1 cells after stimulation with IO. Conclusions: CML is associated with increased NET formation, which is further augmented by ponatinib and nilotinib, suggesting a possible role for NETs in promoting vascular toxicity in CML. In the ER-HoxB8-BCR-ABL1 model, NET formation is PAD4- but not ROS-dependent.

Effect of PADI4 on the Expression of Inflammatory Cytokines During NB4 Cells Differentiation

To investigate the expression of peptidylarginine deiminase 4 (PADI4) during the process of differentiation into granulocyte of NB4 cells induced by all-trans-retinoic acid (ATRA) and whether PADI4 is involved in the inflammatory cytokines expression. Granulocyte differentiation model of NB4 cells induced by ATRA was established. The cell morphology changes were observed by Wright-Giemsa staining. The expression of cell differentiation marker CD11b was analyzed by flow cytometry. The mRNA and protein expression of PADI4 was detected by RT-PCR and Western blot, respectively. The expression of tumor necrosis factor (TNF) α and interleukin (IL) 1β was analyzed by ELISA, and also examined with the knockdown of PADI4 expression by siRNA. After NB4 cells induced by ATRA, the cytoplasm increased and the ratio of nuclear to cytoplasmic was reduced. Nuclear dented, and rod-shaped nucleus, lobulated phenomenon increased (P<0.05). Flow cytometry analysis results showed that the cell surface molecule CD11b expression increased (P<0.01). RT-PCR and Western blot showed the expression of PADI4 increased at both transcriptional and translational levels during the process of the differentiation. ELISA showed TNF-α and IL-1β secretion increased in differentiated macrophages, while they could be inhibited by PADI4-specific siRNA. During the differentiation into granulocyte of NB4 cells induced by ATRA, PADI4 expression increased. Furthermore, PADI4 appeared to play a critical role in inflammatory cytokines secretion.