Tissue factor-thrombin signaling enhances the fibrotic activity of myofibroblasts in systemic sclerosis through up-regulation of endothelin receptor A

Higher gamma-glutamyl transferase levels are associated with an increased risk of incident systemic sclerosis: a nationwide population-based study

Gamma-glutamyl transferase (GGT) is known to promote oxidative stress. As oxidative stress is a key component in the pathogenesis of systemic sclerosis (SSc), we investigated whether GGT levels are associated with the risk of incident SSc. A cohort of individuals without SSc who underwent national health examination in 2009 were extracted from the Korean National Health Insurance Service database. The incidence rate of SSc during the observation period, between 2009 and 2019, was estimated. GGT levels measured in 2009 were categorized into quartiles (Q1 [lowest], Q2, Q3, and Q4 [highest]). Multivariable Cox proportional hazard models were used to estimate the risk of incident SSc according to the quartiles of GGT, using Q1 as the reference. A total of 6,091,788 individuals were included. Incidence rate of SSc was 1.16 per 100,000 person-years over a mean observation period of 9.2 years. After adjusting for age, sex, body mass index, economic income, smoking status, alcohol consumption, physical activity, hypertension, type 2 diabetes, dyslipidemia, and chronic kidney disease, higher quartiles of GGT levels were significantly associated with a higher risk of incident SSc (Q4: adjusted hazard ratio [aHR] 1.807, 95% confidence interval CI 1.446-2.259; Q3: aHR 1.221, 95% CI 0.971-1.536; and Q2: aHR 1.034, 95% CI 0.807-1.324; p for trend < 0.001). Higher GGT levels were associated with a higher risk of incident SSc. These findings could lead to a closer monitoring for high risk individuals and an earlier diagnosis and treatment.

Ιnterleukin-17A-Enriched Neutrophil Extracellular Traps Promote Immunofibrotic Aspects of Childhood Asthma Exacerbation

Childhood asthma is a chronic inflammatory airway disorder that can drive tissue remodeling. Neutrophils are amongst the most prominent inflammatory cells contributing to disease manifestations and may exert a potent role in the progression of inflammation to fibrosis. However, their role in asthma exacerbation is still understudied. Here, we investigate the association between neutrophil extracellular traps (NETs) and lung fibroblasts in childhood asthma pathophysiology using serum samples from pediatric patients during asthma exacerbation. Cell-based assays and NETs/human fetal lung fibroblast co-cultures were deployed. Increased levels of NETs and interleukin (IL)-17A were detected in the sera of children during asthma exacerbation. The in vitro stimulation of control neutrophils using the sera from pediatric patients during asthma exacerbation resulted in IL-17A-enriched NET formation. The subsequent co-incubation of lung fibroblasts with in vitro-generated IL-17A-enriched NETs led fibroblasts to acquire a pre-fibrotic phenotype, as assessed via enhanced CCN2 expression, migratory/healing capacity, and collagen release. These data uncover the important pathogenic role of the NET/IL-17A axis in asthma exacerbation, linking lung inflammation to fibroblast dysfunction and fibrosis.

Down-regulation of KLF2 in lung fibroblasts is linked with COVID-19 immunofibrosis and restored by combined inhibition of NETs, JAK-1/2 and IL-6 signaling

Kruppel-like factor 2 (KLF2) has been linked with fibrosis and neutrophil-associated thromboinflammation; however, its role in COVID-19 remains elusive. We investigated the effect of disease microenvironment on the fibrotic potential of human lung fibroblasts (LFs) and its association with KLF2 expression. LFs stimulated with plasma from severe COVID-19 patients down-regulated KLF2 expression at mRNA/protein and functional level acquiring a pre-fibrotic phenotype, as indicated by increased CCN2/collagen levels. Pre-incubation with the COMBI-treatment-agents (DNase I and JAKs/IL-6 inhibitors baricitinib/tocilizumab) restored KLF2 levels of LFs to normal abolishing their fibrotic activity. LFs stimulated with plasma from COMBI-treated patients at day-7 expressed lower CCN2 and higher KLF2 levels, compared to plasma prior-to-treatment, an effect not observed in standard-of-care treatment. In line with this, COMBI-treated patients had better outcome than standard-of-care group. These data link fibroblast KLF2 with NETosis and JAK/IL-6 signaling, suggesting the potential of combined therapeutic strategies in immunofibrotic diseases, such as COVID-19.

Combined administration of inhaled DNase, baricitinib and tocilizumab as rescue treatment in COVID-19 patients with severe respiratory failure

Aiming to reduce mortality in COVID-19 with severe respiratory failure we administered a combined rescue treatment (COMBI) on top of standard-of-care (SOC: dexamethasone/heparin) consisted of inhaled DNase to dissolve thrombogenic neutrophil extracellular traps, plus agents against cytokine-mediated hyperinflammation, namely anti-IL-6-receptor tocilizumab and JAK1/2 inhibitor baricitinib. Patients with PaO2/FiO2 < 100 mmHg were analysed. COMBI group (n = 22) was compared with similar groups that had received SOC alone (n = 26) or SOC plus monotherapy with either IL-1-receptor antagonist anakinra (n = 19) or tocilizumab (n = 11). COMBI was significantly associated with lower in-hospital mortality and intubation rate, shorter duration of hospitalization, and prolonged overall survival after a median follow-up of 110 days. In vitro, COVID-19 plasma induced tissue factor/thrombin pathway in primary lung fibroblasts. This effect was inhibited by the immunomodulatory agents of COMBI providing a mechanistic explanation for the clinical observations. These results support the conduct of randomized trials using combined immunomodulation in COVID-19 to target multiple interconnected pathways of immunothrombosis.

Angiotensin II triggers neutrophil extracellular traps release linking thromboinflammation with essential hypertension

Innate immunity and chronic inflammation are involved in atherosclerosis and atherothrombosis leading to target organ damage in essential hypertension (EH). However, the role of neutrophils in EH is still elusive. We investigated the association between angiotensin II (Ang II) and neutrophil extracellular traps (NETs) in pathogenesis of EH. Plasma samples, kidney biopsies and surgical specimens of abdominal aortic aneurysms (AAA) from EH patients were used. Cell-based assays, NETs/human aortic endothelial cells co-cultures and in situ studies were performed. Increased plasma levels of NETs and tissue factor (TF) activity were detected in untreated, newly-diagnosed, EH patients. Stimulation of control neutrophils with plasma from untreated EH patients generated TF-enriched NETs promoting endothelial collagen production. Ang II induced NETosis in vitro via a reactive oxygen species (ROS)/peptidylarginine deiminase type 4 and autophagy-dependent pathway. Circulating NETs and thrombin generation levels were reduced significantly in EH patients starting treatment with Ang II receptor blockers, whereas their plasma was unable to trigger procoagulant NETs. Moreover, TF-bearing NETotic neutrophils/remnants were accumulated in sites of interstitial renal fibrosis and in the subendothelial layer of AAA. These data reveal the important pathogenic role of Ang II/ROS/NETs/TF axis in EH, linking thromboinflammation with endothelial dysfunction and fibrosis.

Endothelial cells, neutrophils and platelets: getting to the bottom of an inflammatory triangle

Severe fibrotic and thrombotic events permeate the healthcare system, causing suffering for millions of patients with inflammatory disorders. As late-state consequences of chronic inflammation, fibrosis and thrombosis are the culmination of pathological interactions of activated endothelium, neutrophils and platelets after vessel injury. Coupling of these three cell types ensures a pro-coagulant, cytokine-rich environment that promotes the capture, activation and proliferation of circulating immune cells and recruitment of key pro-fibrotic cell types such as myofibroblasts. As the first responders to sterile inflammatory injury, it is important to understand how endothelial cells, neutrophils and platelets help create this environment. There has been a growing interest in this intersection over the past decade that has helped shape the development of therapeutics to target these processes. Here, we review recent insights into how neutrophils, platelets and endothelial cells guide the development of pathological vessel repair that can also result in underlying tissue fibrosis. We further discuss recent efforts that have been made to translate this knowledge into therapeutics and provide perspective as to how a compound or combination therapeutics may be most efficacious when tackling fibrosis and thrombosis that is brought upon by chronic inflammation.

Progressive fibrosing interstitial lung disease associated with systemic autoimmune diseases

Interstitial lung disease (ILD) is a common manifestation of systemic autoimmune diseases and a leading cause of death in these patients. A proportion of patients with autoimmune ILDs develop a progressive fibrosing form of ILD, characterized by increasing fibrosis on high-resolution computed tomography, worsening of lung function, and early mortality. Autoimmune disease-related ILDs have a variable clinical course and not all patients will require treatment, but all patients should be monitored for signs of progression. Apart from systemic sclerosis-associated ILD, the limited evidence to support the efficacy of immunosuppression as a treatment for ILDs is based mainly on small retrospective series and expert opinion. Non-clinical data suggest that there are commonalities in the mechanisms that drive progressive fibrosis in ILDs with an immunological trigger as in other forms of progressive fibrosing ILD. This suggests that nintedanib and pirfenidone, drugs known to slow disease progression in patients with idiopathic pulmonary fibrosis, may also slow the progression of ILD associated with systemic autoimmune diseases. In the SENSCIS® trial, nintedanib reduced the rate of ILD progression in patients with systemic sclerosis-associated ILD. The results of other large clinical trials will provide further insights into the role of anti-fibrotic therapies in the treatment of autoimmune disease-related ILDs.

Cytokine Receptor Profiling in Human Colonic Subepithelial Myofibroblasts: A Differential Effect of Th Polarization-Associated Cytokines in Intestinal Fibrosis

BACKGROUND

Colonic subepithelial myofibroblasts (cSEMFs) are mesenchymal cells with a pivotal role in the pathophysiology of Crohn's disease (CD) fibrosis. Here, we demonstrate for the first time a complete expression mapping of cytokine receptors, implicated in inflammatory bowel diseases, in primary human cSEMFs and how pro-inflammatory cytokines regulate this expression. Furthermore, we show the effect of Th1-, Th2-, Th17- and Treg-related cytokines on a fibrosis-related phenotype of cSEMFs.

METHODS

Colonic subepithelial myofibroblasts were isolated from healthy individuals' colonic biopsies. Interleukin (IL)-1α- and/or tumor necrosis factor (TNF)-α-induced mRNA and protein expression of cytokine receptors was assayed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence, respectively. Th-related cytokine effects on mRNA and protein profibrotic factor expression were analyzed by qRT-PCR and/or colorimetric assays and on the wound-healing capacity of cSEMFs by scratch test.

RESULTS

In cSEMFs, we observed basal cytokine receptor expression, which was modified by IL-1α and TNF-α. Th1-related cytokines upregulated tissue factor (TF), collagen, fibronectin and matrix metalloproteinase (MMP)-1 and downregulated α-smooth muscle actin (α-SMA), MMP-9, and wound healing rate. Th2-related cytokines upregulated collagen, TF, α-SMA, MMP-1, and wound healing rate and downregulated fibronectin and MMP-9. IL-17 and IL-23 upregulated fibronectin, and IL-22 downregulated TF. IL-17 and IL-22 decreased wound healing rate. Similar to TGF-β, IL-23 upregulated MMP-1, tissue inhibitor of metalloproteinases-1, collagen expression, and wound healing rates.

CONCLUSIONS

Our results suggest that cSEMFs have a central role in inflammation and fibrosis, as they express a great variety of Th-related cytokine receptors, making them responsive to pro-inflammatory cytokines, abundant in the inflamed mucosa of CD patients.

Clarithromycin Enhances the Antibacterial Activity and Wound Healing Capacity in Type 2 Diabetes Mellitus by Increasing LL-37 Load on Neutrophil Extracellular Traps

Background: Type 2 diabetes mellitus (T2D) is characterized by susceptibility to bacterial infections and impaired wound healing. Neutrophil extracellular traps (NETs) and the cathelicidin antimicrobial peptide LL-37 have been implicated both in defense against bacterial infections and in wound healing process. Recently, it was shown that macrolide antibiotic clarithromycin induces the release of LL-37-bearing NETs. In T2D there has not been identified any link between NETs and LL-37 and the effect of clarithromycin in neutrophils/NETs is unknown yet. Methods: Peripheral blood neutrophils were obtained from treatment-naive hyperglycemic T2D patients (naive), normoglycemic T2D patients under antidiabetic treatment (well-controlled) and healthy donors (controls). NET release and NET proteins were studied. Co-culture systems of NET structures with E. coli NCTC 9001 and primary skin fibroblasts were deployed to examine the in vitro antibacterial and fibrotic NET properties, respectively. The effect of clarithromycin was also investigated. Analysis was performed using immunofluorescence confocal microscopy, myeloperoxidase-DNA complex and LL-37 ELISA, immunoblotting and qRT-PCR. Results: NETs were characterized by the presence of LL-37, however they lacked antibacterial activity, in both groups of T2D patients. Clarithromycin significantly increased the externalization of LL-37 on NETs generated from well-controlled T2D neutrophils, thus restoring NET antibacterial capacity and promoting the wound healing process via fibroblast activation and differentiation. Conclusion: This study suggests that clarithromycin may add further advantage to well-controlled T2D patients, by enhancing their antibacterial defense and improving wound healing capacity of fibroblasts, through upregulation of LL-37 on NET structures.

Thrombin induces protease-activated receptor 1 signaling and activation of human atrial fibroblasts and dabigatran prevents these effects

BACKGROUND

Data with animal cells and models suggest that thrombin activates cardiac fibroblasts (Fib) to myofibroblasts (myoFib) via protease-activated receptor 1 (PAR1) cleavage, and in this way promotes adverse atrial remodeling and, thereby, atrial fibrillation (AF).

OBJECTIVE

Here, we explored the effects of thrombin on human atrial Fib and whether they are antagonized by the clinically available direct thrombin inhibitor, dabigatran.

METHODS

Fib isolated from atrial appendages of patients without AF undergoing elective cardiac surgery were evaluated for PAR expression and treated with thrombin with or without dabigatran. PAR1 cleavage, downstream signaling and myoFib markers were investigated by immunofluorescence and Western blot. Collagen synthesis, activity of matrix metalloprotease (MMP)-2 and proliferation were assessed by Picro-Sirius red staining, gelatinolytic zymography and BrdU incorporation, respectively. Fib function was studied as capability to contract a collagen gel and stimulate the chemotaxis of peripheral blood monocytes from healthy volunteers.

RESULTS

Primary human atrial Fib expressed PAR1, while levels of the other PARs were very low. Thrombin triggered PAR1 cleavage and phosphorylation of ERK1/2, p38 and Akt, elicited a switch to myoFib enriched for αSMA, fibronectin and type I collagen, and induced paracrine/autocrine transforming growth factor beta-1, cyclooxygenase-2, endothelin-1 and chemokine (C-C motif) ligand 2 (CCL2); conversely, MMP-2 activity decreased. Thrombin-primed cells displayed enhanced proliferation, formed discrete collagen-containing cellular nodules, and stimulated the contraction of a collagen gel. Furthermore, their conditioned medium caused monocytes to migrate. All these effects were prevented by dabigatran.

CONCLUSION

These results with human cells complete the knowledge about thrombin actions on cardiac Fib and strengthen the translational potential of the emerging paradigm that pharmacological blockade of thrombin may counteract molecular and cellular events underlying AF.

Lung fibrosis-associated soluble mediators and bronchoalveolar lavage from idiopathic pulmonary fibrosis patients promote the expression of fibrogenic factors in subepithelial lung myofibroblasts

Idiopathic pulmonary fibrosis (IPF) is characterized by infiltration of inflammatory cells, excessive collagen production and accumulation of myofibroblasts. We explored the possible role of subepithelial lung myofibroblasts (SELMs) in the development of fibrosis in IPF. SELMs, isolated from surgical specimens of healthy lung tissue, were cultured with pro-inflammatory factors or bronchoalveolar lavage fluid (BALF) from patients with IPF or idiopathic non-specific interstitial pneumonia (iNSIP) and their fibrotic activity was assessed. Stimulation of SELMs with pro-inflammatory factors induced a significant increase of Tissue Factor (TF) and Tumor necrosis factor-Like cytokine 1 A (TL1A) expression and collagen production in culture supernatants. Stimulation with BALF from IPF patients with mild to moderate, but not severe disease, and from iNSIP patients induced a significant increase of TF expression. BALF from all IPF patients induced a significant increase of TL1A expression and collagen production, while BALF from iNSIP patients induced a significant increase of TL1A, but not of collagen production. Interestingly, TGF-β1 and BALF from all IPF, but not iNSIP patients, induced a significant increase in SELMs migration. In conclusion, BALF from IPF patients induces fibrotic activity in lung myofibroblasts, similar to mediators associated with lung fibrosis, indicating a key role of SELMs in IPF.

Immunomodulatory Role of Clarithromycin in Acinetobacter baumannii Infection via Formation of Neutrophil Extracellular Traps

Macrolide antibiotics have been shown to act as immunomodulatory molecules in various immune cells. However, their effect on neutrophils has not been extensively investigated. In this study, we investigated the role of macrolide antibiotics in the generation of neutrophil extracellular traps (NETs). By assessing ex vivo and in vivo NET formation, we demonstrated that clarithromycin is able to induce NET generation both in vitro and in vivo. Clarithromycin utilizes autophagy in order to form NETs, and these NETs are decorated with antimicrobial peptide LL-37. Clarithromycin-induced NETs are able to inhibit Acinetobacter baumannii growth and biofilm formation in an LL-37-dependent manner. Additionally, LL-37 antimicrobial function depends on NET scaffold integrity. Collectively, these data expand the knowledge on the immunomodulatory role of macrolide antibiotics via the generation of LL-37-bearing NETs, which demonstrate LL-37-dependent antimicrobial activity and biofilm inhibition against A. baumannii.

Neutrophil extracellular traps regulate IL-1β-mediated inflammation in familial Mediterranean fever

OBJECTIVE

Inflammatory attacks of familial Mediterranean fever (FMF) are characterised by circulation and influx of high number of polymorphonuclear neutrophils (PMN) in the affected sites and profound therapeutic effect of IL-1β inhibitors. We investigated the role of neutrophil extracellular traps (NET) in the pathogenesis of FMF, and their involvement in IL-1β production.

METHODS

Blood samples were obtained from six FMF patients during remissions and from three patients during attacks. NET formation and NET components were studied by fluorescence techniques, immunobloting and MPO-DNA complex ELISA.

RESULTS

PMNs from patients released NETs decorated with IL-1β during disease attacks. On the other hand, PMNs from patients during remission were resistant to inflammatory stimuli that induce NET release in PMNs from control subjects. Lower basal autophagy levels were identified in PMNs during remission, while induction of autophagy facilitated NET release, suggesting that autophagy is involved in the regulation of NET release. During the resolution of attacks, inhibition of NET formation by negative feedback mechanism was also observed. The anti-inflammatory agents, colchicine and DNAse I, inhibited IL-1β production in PMNs and IL-1β activity in NETs, respectively.

CONCLUSIONS

We suggest two additive events for triggering the FMF attack; the production of IL-1β by PMNs and its release through NETs. At the same time NETs, homeostatically, downregulate further NETosis, facilitating the resolution of attack. Compensatorly, lower basal autophagy of PMNs may protect from crises by attenuating the release of pro-inflammatory NETs.

Neutrophil extracellular traps promote differentiation and function of fibroblasts

Neutrophil activation by inflammatory stimuli and the release of extracellular chromatin structures (neutrophil extracellular traps - NETs) have been implicated in inflammatory disorders. Herein, we demonstrate that NETs released by neutrophils treated either with fibrosis-related agents, such as cigarette smoke, magnesium silicate, bleomycin, or with generic NET inducers, such as phorbol 12-myristate 13-acetate, induced activation of lung fibroblasts (LFs) and differentiation into myofibroblast (MF) phenotype. Interestingly, the aforementioned agents or IL-17 (a primary initiator of inflammation/fibrosis) had no direct effect on LF activation and differentiation. MFs treated with NETs demonstrated increased connective tissue growth factor expression, collagen production, and proliferation/migration. These fibrotic effects were significantly decreased after degradation of NETs with DNase1, heparin or myeloperoxidase inhibitor, indicating the key role of NET-derived components in LF differentiation and function. Furthermore, IL-17 was expressed in NETs and promoted the fibrotic activity of differentiated LFs but not their differentiation, suggesting that priming by DNA and histones is essential for IL-17-driven fibrosis. Additionally, autophagy was identified as the orchestrator of NET formation, as shown by inhibition studies using bafilomycin A1 or wortmannin. The above findings were further supported by the detection of NETs in close proximity to alpha-smooth muscle actin (α-SMA)-expressing fibroblasts in biopsies from patients with fibrotic interstitial lung disease or from skin scar tissue. Together, these data suggest that both autophagy and NETs are involved not only in inflammation but also in the ensuing fibrosis and thus may represent potential therapeutic targets in human fibrotic diseases.

Tissue factor expression in neutrophil extracellular traps and neutrophil derived microparticles in antineutrophil cytoplasmic antibody associated vasculitis may promote thromboinflammation and the thrombophilic state associated with the disease

OBJECTIVES

Antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is characterised by neutrophil activation. An elevated prevalence of venous thromboembolic events has been reported in AAV. Because of the critical role of neutrophils in inflammation associated thrombosis, we asked whether neutrophil tissue factor (TF) may be implicated in the thrombotic diathesis in AAV.

METHODS

Neutrophils from four patients and sera from 17 patients with ANCA associated vasculitis with active disease and remission were studied. TF expression was assessed by immunoblotting and confocal microscopy. Circulating DNA levels were evaluated. TF expressing microparticles (MPs) were measured by flow cytometry and thrombin-antithrombin complex levels by ELISA.

RESULTS

Peripheral blood neutrophils from four patients with active disease expressed elevated TF levels and released TF expressing neutrophil extracellular traps (NETs) and MPs. TF positive NETs were released by neutrophils isolated from the bronchoalveolar lavage and were detected in nasal and renal biopsy specimens. Elevated levels of circulating DNA and TF expressing neutrophil derived MPs were further observed in sera from patients with active disease. Induction of remission attenuated the aforementioned effects. Control neutrophils treated with sera from patients with active disease released TF bearing NETs and MPs which were abolished after IgG depletion. Treatment of control neutrophils with isolated IgG from sera from patients with active disease also resulted in the release of TF bearing NETs. TF implication in MP dependent thrombin generation was demonstrated by antibody neutralisation studies.

CONCLUSIONS

Expression of TF in NETs and neutrophil derived MPs proposes a novel mechanism for the induction of thrombosis and inflammation in active AAV.