Neutrophil extracellular traps, released from neutrophil, promote microglia inflammation and contribute to poor outcome in subarachnoid hemorrhage.
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ABSTRACT:
SUBMITTER: Hanhai Z
PROVIDER: S-EPMC8148446 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Background: Subarachnoid hemorrhage (SAH) caused by rupture of an intracranial aneurysm, is a life-threatening emergency that is associated with substantial morbidity and mortality. Emerging evidence suggests involvement of the innate immune response in secondary brain injury, and a potential role of neutrophil extracellular traps (NETs) for SAH-associated neuroinflammation. In this study, we investigated the spatiotemporal patterns of NETs in SAH and the potential role of the RNase A (the bovine equivalent to human RNase 1) application on NET burden. Methods: A total number of n=81 male C57Bl/6 mice were operated utilizing a filament perforation model to induce SAH, and Sham operation was performed for the corresponding control groups. To confirm the bleeding and exclude stroke and intracerebral hemorrhage, the animals received MRI after 24h. Mice were treated with intravenous injection of RNase A (42μg/kg body weight) or saline solution for the control groups, respectively. Quadruple-immunofluorescence (IF) staining for cell nuclei (DAPI), F-actin (phalloidin), citrullinated H3, and neurons (NeuN) was analyzed by confocal imaging and used to quantify NET abundance in the subarachnoid space (SAS) and brain parenchyma. To quantify NETs in human SAH patients, cerebrospinal spinal fluid (CSF) and blood samples from day 1, 2, 7, and 14 after bleeding onset were analyzed for double-stranded DNA (dsDNA) via Sytox Green. Results: Neutrophil extracellular traps are released upon subarachnoid hemorrhage in the SAS on the ipsilateral bleeding site 24h after ictus. Over time, NETs showed progressive increase in the parenchyma on both ipsi- and contralateral site, peaking on day 14 in periventricular localization. In CSF and blood samples of patients with aneurysmal SAH, NETs also increased gradually over time with a peak on day 7. RNase application significantly reduced NET accumulation in basal, cortical, and periventricular areas. Conclusion: Neutrophil extracellular trap formation following SAH originates in the ipsilateral SAS of the bleeding site and spreads gradually over time to basal, cortical, and periventricular areas in the parenchyma within 14days. Intravenous RNase application abrogates NET burden significantly in the brain parenchyma, underpinning a potential role in modulation of the innate immune activation after SAH.
| S-EPMC8481772 | biostudies-literature
Project description:Intracerebral hemorrhage associated with thrombolytic therapy with tissue plasminogen activator (tPA) in acute ischemic stroke continues to present a major clinical problem. Here, we report that infusion of tPA resulted in a significant increase in markers of neutrophil extracellular traps (NETs) in the ischemic cortex and plasma of mice subjected to photothrombotic middle cerebral artery occlusion. Peptidylarginine deiminase 4 (PAD4), a critical enzyme for NET formation, is also significantly upregulated in the ischemic brains of tPA-treated mice. Blood-brain barrier (BBB) disruption after ischemic challenge in an in vitro model of BBB was exacerbated after exposure to NETs. Importantly, disruption of NETs by DNase I or inhibition of NET production by PAD4 deficiency restored tPA-induced loss of BBB integrity and consequently decreased tPA-associated brain hemorrhage after ischemic stroke. Furthermore, either DNase I or PAD4 deficiency reversed tPA-mediated upregulation of the DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS). Administration of cGAMP after stroke abolished DNase I-mediated downregulation of the STING pathway and type 1 interferon production and blocked the antihemorrhagic effect of DNase I in tPA-treated mice. We also show that tPA-associated brain hemorrhage after ischemic stroke was significantly reduced in cGas-/- mice. Collectively, these findings demonstrate that NETs significantly contribute to tPA-induced BBB breakdown in the ischemic brain and suggest that targeting NETs or cGAS may ameliorate thrombolytic therapy for ischemic stroke by reducing tPA-associated hemorrhage.
| S-EPMC8288643 | biostudies-literature
Project description:Neuroinflammation is a key process in the pathogenesis of subarachnoid hemorrhage (SAH) and contributes to poor outcome in patients. The purpose of this study is to explore the effect of triggering receptor expressed on myeloid cells 1 (TREM1) in the SAH, as well as its potential mechanism. In our study, plasma levels of soluble TREM1 was increased significantly after SAH and correlated to SAH severity and serum C-reactiveprotein. TREM1 inhibitory peptide LP17 alleviated the neurological deficits, attenuated brain water content, and reduced neuronal damage after SAH. Meanwhile, TREM1 inhibitory peptide decreased neuroinflammation (evidenced by the decreased levels of markers including IL-6, IL-1β, TNF-α) by attenuating proinflammatory subtype transition of microglia (evidenced by the decreased levels of markers including CD68, CD16, CD86) and decreasing the formation of neutrophil extracellular traps (evidenced by the decreased levels of markers including CitH3, MPO, and NE). Further mechanistic study identified that TREM1 can activate downstream proinflammatory pathways through interacting with spleen tyrosine kinase (SYK). In conclusion, inhibition of TREM1 alleviates neuroinflammation by attenuating proinflammatory subtype transition of microglia and decreasing the formation of neutrophil extracellular traps through interacting with SYK after SAH. TREM1 may be a a promising therapeutic target for SAH.
| S-EPMC8548669 | biostudies-literature
Project description:TH17 cell subpopulations have been defined that contribute to inflammation and homeostasis, yet the characteristics of TH17 cells that contribute to host defense against infection are not clear. To elucidate the antimicrobial machinery of the TH17 subset, we studied the response to Cutibacterium acnes, a skin commensal that is resistant to IL-26, the only known TH17-secreted protein with direct antimicrobial activity. We generated C. acnes-specific antimicrobial TH17 clones (AMTH17) with varying antimicrobial activity against C. acnes, which we correlated by RNA sequencing to the expression of transcripts encoding proteins that contribute to antimicrobial activity. Additionally, we validated that AMTH17-mediated killing of C. acnes and bacterial pathogens was dependent on the secretion of granulysin, granzyme B, perforin, and histone H2B. We found that AMTH17 cells can release fibrous structures composed of DNA decorated with histone H2B that entangle C. acnes that we call T cell extracellular traps (TETs). Within acne lesions, H2B and IL-17 colocalized in CD4+ T cells, in proximity to TETs in the extracellular space composed of DNA decorated with H2B. This study identifies a functionally distinct subpopulation of TH17 cells with an ability to form TETs containing secreted antimicrobial proteins that capture and kill bacteria.
| S-EPMC7810473 | biostudies-literature
Project description:Varicella pneumonia is the most common and severe complication of primary varicella-zoster virus (VZV) infection in adults. Pathogenesis of varicella pneumonia is largely unknown, mainly due to limited availability of clinical specimens and lack of appropriate VZV animal models. Simian varicella virus (SVV) infection of nonhuman primates closely recapitulates clinical and pathogenic features of human VZV disease. This study aimed to elucidate the virus and host factors that contribute to the pathogenesis of varicella pneumonia. The deposited data present changes in gene expression in the lung of SVV-infected cynomolgus macaques (Macaca fascicularis) at 3, 6 and 9 days after infection, and mock-infected control macaques at 3 days after infection.
2020-09-01 | E-MTAB-8485 | biostudies-arrayexpress
Project description:Neovascularization and vascular remodeling are functionally important for brain repair after stroke. We show that neutrophils accumulate in the peri-infarct cortex during all stages of ischemic stroke. Neutrophils producing intravascular and intraparenchymal neutrophil extracellular traps (NETs) peak at 3-5 days. Neutrophil depletion reduces blood-brain barrier (BBB) breakdown and enhances neovascularization at 14 days. Peptidylarginine deiminase 4 (PAD4), an enzyme essential for NET formation, is upregulated in peri-ischemic brains. Overexpression of PAD4 induces an increase in NET formation that is accompanied by reduced neovascularization and increased BBB damage. Disruption of NETs by DNase 1 and inhibition of NET formation by genetic ablation or pharmacologic inhibition of PAD increases neovascularization and vascular repair and improves functional recovery. Furthermore, PAD inhibition reduces stroke-induced STING-mediated production of IFN-?, and STING knockdown and IFN receptor-neutralizing antibody treatment reduces BBB breakdown and increases vascular plasticity. Collectively, our results indicate that NET release impairs vascular remodeling during stroke recovery.
| S-EPMC7237502 | biostudies-literature
Project description:The majority of patients with cancer undergo at least one surgical procedure as part of their treatment. Severe postsurgical infection is associated with adverse oncologic outcomes; however, the mechanisms underlying this phenomenon are unclear. Emerging evidence suggests that neutrophils, which function as the first line of defense during infections, facilitate cancer progression. Neutrophil extracellular traps (NETs) are extracellular neutrophil-derived DNA webs released in response to inflammatory cues that trap and kill invading pathogens. The role of NETs in cancer progression is entirely unknown. We report that circulating tumor cells become trapped within NETs in vitro under static and dynamic conditions. In a murine model of infection using cecal ligation and puncture, we demonstrated microvascular NET deposition and consequent trapping of circulating lung carcinoma cells within DNA webs. NET trapping was associated with increased formation of hepatic micrometastases at 48 hours and gross metastatic disease burden at 2 weeks following tumor cell injection. These effects were abrogated by NET inhibition with DNAse or a neutrophil elastase inhibitor. These findings implicate NETs in the process of cancer metastasis in the context of systemic infection and identify NETs as potential therapeutic targets.
| S-EPMC3726160 | biostudies-literature
Project description:Low back pain following spine surgery is a major complication due to excessive epidural fibrosis, which compresses the lumbar nerve. The mechanisms of epidural fibrosis remain largely elusive. In the drainage samples from patients after spine operation, neutrophil extracellular traps (NETs) and NETs inducer high-mobility group box 1 were significantly increased. In a mouse model of laminectomy, NETs developed in the wound area post epidural operation, accompanied with macrophage infiltration. In vitro, macrophages ingested NETs and thereby increased the elastase from NETs via the receptor for advanced glycation end product. Moreover, NETs boosted the expression of fibronectin in macrophages, which was dependent on elastase and could be partially blocked by DNase. NF-κB p65 and Smad pathways contributed to the increased expression fibronectin in NETs-treated macrophages. In the mouse spine operation model, post-epidural fibrosis was significantly mitigated with the administration of DNase I, which degraded DNA and cleaved NETs. Our study shed light on the roles and mechanisms of NETs in the scar formation post spine operation.
| S-EPMC7599244 | biostudies-literature
Project description:Actinobacillus pleuropneumoniae (A.pp) causes severe pneumonia associated with enormous economic loss in pigs. Peracute diseased pigs die in <24 h with pneumonia. Neutrophils are the prominent innate immune cell in this infection that massively infiltrate the infected lung. Here we show that neutrophils release neutrophil extracellular traps (NETs) as response to A.pp infection. Numerous NET-markers were identified in bronchoalveolar lavage fluid (BALF) of A.pp-infected piglets in vivo, however, most NET fibers are degraded. Importantly, A.pp is able to enhance its growth rate in the presence of NETs that have been degraded by nucleases efficiently. A.pp itself releases no nuclease, but we identified host nucleases as sources that degrade NETs after A.pp infection. Furthermore, the nucleases of co-infecting pathogens like Streptococcus suis increase growth of A.pp in presence of porcine NETs. Thus, A.pp is not only evading the antimicrobial activity of NETs, A.pp is rather additionally using parts of NETs as growth factor thereby taking advantage of host nucleases as DNase1 or nucleases of co-infecting bacteria, which degrade NETs. This effect can be diminished by inhibiting the bacterial adenosine synthase indicating that degraded NETs serve as a source for NAD, which is required by A.pp for its growth. A similar phenotype was found for the human pathogen Haemophilus (H.) influenzae and its growth in the presence of human neutrophils. H. influenzae benefits from host nucleases in the presence of neutrophils. These data shed light on the detrimental effects of NETs during host immune response against certain bacterial species that require and/or efficiently take advantage of degraded DNA material, which has been provided by host nuclease or nucleases of other co-infecting bacteria, as growth source.
| S-EPMC6736959 | biostudies-literature
Project description:Neutrophil extracellular traps (NETs) are upregulated and promote thrombosis in Behçet's disease (BD). However, whether NETs promote autoinflammation in BD remains unclear. This study aimed to investigate the potential role of NETs in promoting macrophage activation in BD. Firstly, we quantified NETs by measuring double-stranded DNA (dsDNA) using PicoGreen and calculating the proportion of NETosis. Then macrophages were stimulated with BD- or healthy controls (HC)-derived NETs, and IL-8 and TNF-α production and IFN-γ+ CD4+ T cells differentiation were measured using ELISA and flow cytometry, respectively. The protein components in NETs were analyzed by western blot. Macrophages were stimulated with Histone H4 neutralized NETs, and IL-8 and TNF-α production were measured using ELISA. The level of 8-hydroxydeoxyguanosine (8-OHdG) DNA in NETs was measured using ELISA. The levels of reactive oxygen species (ROS) in serum and neutrophils were measured using ROS probes by a microplate reader and flow cytometry. We found that circulating NETs and neutrophil-derived NETs were significantly higher in BD than HC. BD NETs stimulated macrophages produced higher levels of IL-8 and TNF-α, and promoted IFN-γ+ CD4+ T cells differentiation. BD NETs were enriched in Histone H4, and neutralizing Histone H4 abrogated the BD NETs-mediated IL-8 production by macrophages, but not TNF-α. Also, BD neutrophils produced more 8-OHdG DNA than HC neutrophils, and the percentage of 8-OHdG DNA in dsDNA from BD neutrophils was also higher than that of HC neutrophils. The ROS levels in serum and neutrophils were both higher in BD than HC. Our findings suggested that excessive BD NETs promoted macrophages activation and facilitated IFN-γ+ CD4+ T cells differentiation. Higher levels of Histone H4 and oxidized DNA in BD NETs might mediate macrophages hyperactivation.
| S-EPMC7901995 | biostudies-literature