TREM1 Regulates Neuroinflammatory Injury by Modulate Proinflammatory Subtype Transition of Microglia and Formation of Neutrophil Extracellular Traps via Interaction With SYK in Experimental Subarachnoid Hemorrhage
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ABSTRACT:
SUBMITTER: Wu X
PROVIDER: S-EPMC8548669 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Evidence indicates that neutrophil has promoted inflammation in several central nervous system diseases. However, whether the peripheral blood levels of neutrophils are associated with the functional outcome after subarachnoid hemorrhage and its potential mechanism remain unclear. In this study, we showed that neutrophil levels in peripheral blood were higher in patients with subarachnoid hemorrhage (P < 0.001) than in healthy subjects. Neutrophil levels were positively associated with Hunt and Hess grade (P < 0.001) and modified Rankin Scale scores at 3 months after SAH (P = 0.008). In terms of the mechanism, neutrophil extracellular traps markedly increased the proinflammatory subtype transition of microglia. After treatment with DNAse I, the proinflammatory subtype transition of microglia involving CD16 positive and IL-1β positive microglia was limited (P < 0.05). This mechanism was also verified in vitro. These results indicate that the existence of neutrophil extracellular traps, released from neutrophils after subarachnoid hemorrhage, can shift microglia toward a more proinflammatory phenotype and contribute to neuroinflammation and poor outcome in subarachnoid hemorrhage.
| S-EPMC8148446 | biostudies-literature
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:Neutrophil extracellular traps (NETs) consist of decondensed nuclear chromatin that is associated with proteins and are released by neutrophils during an inflammatory response. Released NETs are able to capture pathogens, prevent their dissemination and potentially kill them via antimicrobial peptides and proteins that are associated with the decondensed chromatin. In addition to their antimicrobial functions, NETs have also been shown to exert immunomodulatory effects by activation and differentiation of macrophages, dendritic cells and T cells. However, the effect of NETs on neutrophil functions is poorly understood. Here we report the first comprehensive study regarding the effects of NETs on human primary neutrophils in vitro. NETs were isolated from cultures of PMA-exposed neutrophils. Exposure of neutrophils to isolated NETs resulted in the activation of several neutrophil functions in a concentration-dependent manner. NETs induced exocytosis of granules, the production of reactive oxygen species (ROS) by the NADPH oxidase NOX2, NOX2-dependent NET formation, increased the phagocytosis and killing of microbial pathogens. Furthermore, NETs induced the secretion of the proinflammatory chemokine IL-8 and the B-cell-activating cytokine BAFF. We could show that the NET-induced activation of neutrophils occurs by pathways that involve the phosphorylation of Akt, ERK1/2 and p38. Taken together our results provide further insights into the proinflammatory role of NETs by activating neutrophil effector function and further supports the view that NETs can amplify inflammatory events. On the one hand the amplified functions enhance the antimicrobial defense. On the other hand, NET-amplified neutrophil functions can be involved in the pathophysiology of NET-associated diseases. In addition, NETs can connect the innate and adaptive immune system by inducing the secretion of the B-cell-activating cytokine BAFF.
| S-EPMC8217666 | biostudies-literature
Project description:Aims: Extracellular vesicles (EVs) are membrane-derived vesicles that mediate intercellular communications. Neutrophils produce different subtypes of EVs during inflammatory responses. Neutrophil-derived trails (NDTRs) are generated by neutrophils migrating toward inflammatory foci, whereas neutrophil-derived microvesicles (NDMVs) are thought to be generated by neutrophils that have arrived at the inflammatory foci. However, the physical and functional characteristics of neutrophil-derived EVs are incompletely understood. In this study, we aimed to investigate the differences between NDTRs and NDMVs. Methods: The generation of neutrophil-derived EVs were visualized by live-cell fluorescence images and the physical characteristics were further analyzed using nanotracking analysis assay, scanning electron microscopic analysis, and marker expressions. Functional characteristics of neutrophil-derived EVs were analyzed using assays for bactericidal activity, monocyte chemotaxis, phenotype polarization of macrophages, and miRNA sequencing. Finally, the effects of neutrophil-derived EVs on the acute and chronic inflammation were examined in vivo. Results: Both EVs share similar characteristics including stimulators, surface marker expression, bactericidal activity, and chemoattractive effect on monocytes via MCP-1. However, the integrin-mediated physical interaction was required for generation of NDTRs whereas NDMV generation was dependent on PI3K pathway. Interestingly, NDTRs contained proinflammatory miRNAs such as miR-1260, miR-1285, miR-4454, and miR-7975, while NDMVs contained anti-inflammatory miRNAs such as miR-126, miR-150, and miR-451a. Although both EVs were easily uptaken by monocytes, NDTRs enhanced proinflammatory macrophage polarization whereas NDMVs induced anti-inflammatory macrophage polarization. Moreover, NDTRs showed protective effects against lethality in a murine sepsis model and pathological changes in a murine chronic colitis model. Conclusion: These results suggest that NDTR is a proinflammatory subtype of neutrophil-derived EVs distinguished from NDMV.
| S-EPMC7806483 | biostudies-literature
Project description:Tissue injury leads to the release of uric acid (UA). At high local concentrations, UA can form monosodium urate crystals (MSU). MSU and UA stimulate neutrophils to release extracellular traps (NET). Here, we investigated whether these NET could be involved in the development of inflammation by stimulating cytokine release by airway epithelial cells. We found that NET significantly increased the secretion of CXCL8/IL-8 and IL-6 by alveolar and bronchial epithelial cells. These effects were not observed when NETosis was inhibited by Diphenyleneiodonium, elastase inhibitor, or Cl-amidine. Similar findings were made with NET induced by cigarette smoke extract, suggesting that NET proinflammatory capacity is independent of the inducing stimulus. Furthermore, NET affected neither the viability and morphology of epithelial cells nor the barrier integrity of polarized cells. The epithelial stimulatory capacity of NET was not affected by degradation of DNA with micrococcal nuclease, treatment with heparin, or inhibition of the elastase immobilized to DNA, but it was significantly reduced by pretreatment with an anti-HMGB-1 blocking antibody. Altogether, our findings indicate that NET exert direct proinflammatory effects on airway epithelial cells that might contribute in vivo to the further recruitment of neutrophils and the perpetuation of inflammation upon lung tissue damage.
| S-EPMC6738901 | biostudies-other
Project description:Cognitive deficits after aneurysmal subarachnoid hemorrhage (SAH) are common and disabling. Patients who experience delayed deterioration associated with vasospasm are likely to have cognitive deficits, particularly problems with executive function, verbal and spatial memory. Here, we report neurophysiological and pathological mechanisms underlying behavioral deficits in a murine model of SAH. On tests of spatial memory, animals with SAH performed worse than sham animals in the first week and one month after SAH suggesting a prolonged injury. Between three and six days after experimental hemorrhage, mice demonstrated loss of late long-term potentiation (L-LTP) due to dysfunction of the NMDA receptor. Suppression of innate immune cell activation prevents delayed vasospasm after murine SAH. We therefore explored the role of neutrophil-mediated innate inflammation on memory deficits after SAH. Depletion of neutrophils three days after SAH mitigates tissue inflammation, reverses cerebral vasoconstriction in the middle cerebral artery, and rescues L-LTP dysfunction at day 6. Spatial memory deficits in both the short and long-term are improved and associated with a shift of NMDA receptor subunit composition toward a memory sparing phenotype. This work supports further investigating suppression of innate immunity after SAH as a target for preventative therapies in SAH.
| S-EPMC4828315 | biostudies-literature
Project description:Early brain injury (EBI) following subarachnoid hemorrhage (SAH) is closely associated with neuroinflammation. Microglial activation is an early event that leads to neuroinflammation after SAH. Peli1 is an E3 ubiquitin ligase that mediates the induction of pro-inflammatory cytokines in microglia. Here we report Peli1 contributions in SAH mediated brain pathology. An SAH model was induced by endovascular perforation in adult male C57BL/6J mice. Peli1 was markedly induced in mice brains in a time-dependent manner and was predominantly expressed in CD16/32-positive microglia after SAH. Using genetic approaches, we demonstrated that decreased Peli1 significantly improved neurological deficits, attenuated brain edema, reduced over-expression of pro-inflammatory cytokine IL-6 and modified apoptotic/antiapoptotic biomarkers. In addition, Peli1 downregulation suppressed ERK and JNK phosphorylation levels via the downregulation of cIAP1/2 expression, subsequently reducing inducible nitric oxide synthase (iNOS) expression after SAH. Therefore, these findings demonstrate that Peli1 contributes to microglia-mediated neuroinflammation in EBI by mediating cIAP1/2 activation, thus promoting the activation of MyD88-dependent MAPK pathway after experimental SAH. Our findings also showed that Peli1 could promote the expression of M1 microglia polarization biomarker CD16/32 and iNOS after SAH. Targeting Peli1 exerts neuroprotective effects during EBI after SAH, thus could provide potential option for prevention-therapy in high-risk individuals.
| S-EPMC5714869 | biostudies-literature
Project description:Subarachnoid hemorrhage (SAH) carries a 50% mortality rate. The extravasated erythrocytes that surround the brain contain heme, which, when released from damaged red blood cells, functions as a potent danger molecule that induces sterile tissue injury and organ dysfunction. Free heme is metabolized by heme oxygenase (HO), resulting in the generation of carbon monoxide (CO), a bioactive gas with potent immunomodulatory capabilities. Here, using a murine model of SAH, we demonstrated that expression of the inducible HO isoform (HO-1, encoded by Hmox1) in microglia is necessary to attenuate neuronal cell death, vasospasm, impaired cognitive function, and clearance of cerebral blood burden. Initiation of CO inhalation after SAH rescued the absence of microglial HO-1 and reduced injury by enhancing erythrophagocytosis. Evaluation of correlative human data revealed that patients with SAH have markedly higher HO-1 activity in cerebrospinal fluid (CSF) compared with that in patients with unruptured cerebral aneurysms. Furthermore, cisternal hematoma volume correlated with HO-1 activity and cytokine expression in the CSF of these patients. Collectively, we found that microglial HO-1 and the generation of CO are essential for effective elimination of blood and heme after SAH that otherwise leads to neuronal injury and cognitive dysfunction. Administration of CO may have potential as a therapeutic modality in patients with ruptured cerebral aneurysms.
| S-EPMC4563677 | biostudies-literature
Project description:BackgroundNeuroinflammation is closely associated with the poor prognosis in subarachnoid hemorrhage (SAH) patients. This study was aimed to determine the role of stimulator of IFN genes (STING), an essential regulator to innate immunity, in the context of SAH.MethodsA total of 344 male C57BL/6 J mice were subjected to endovascular perforation to develop a model of SAH. Selective STING antagonist C-176 and STING agonist CMA were administered at 30 min or 1 h post-modeling separately. To investigate the underlying mechanism, the AMPK inhibitor compound C was administered intracerebroventricularly at 30 min before surgery. Post-SAH assessments included SAH grade, neurological test, brain water content, western blotting, RT-PCR, and immunofluorescence. Oxygenated hemoglobin was introduced into BV2 cells to establish a SAH model in vitro.ResultsSTING was mainly distributed in microglia, and microglial STING expression was significantly increased after SAH. Administration of C-176 substantially attenuated SAH-induced brain edema and neuronal injury. More importantly, C-176 significantly alleviated both short-term and persistent neurological dysfunction after SAH. Meanwhile, STING agonist CMA remarkably exacerbated neuronal injury and deteriorated neurological impairments. Mechanically, STING activation aggravated neuroinflammation via promoting microglial activation and polarizing into M1 phenotype, evidenced by microglial morphological changes, as well as the increased level of microglial M1 markers including IL-1β, iNOS, IL-6, TNF-α, MCP-1, and NLRP3 inflammasome, while C-176 conferred a robust anti-inflammatory effect. However, all the mentioned beneficial effects of C-176 including alleviated neuroinflammation, attenuated neuronal injury and the improved neurological function were reversed by AMPK inhibitor compound C. Meanwhile, the critical role of AMPK signal in C-176 mediated anti-inflammatory effect was also confirmed in vitro.ConclusionMicroglial STING yielded neuroinflammation after SAH, while pharmacologic inhibition of STING could attenuate SAH-induced inflammatory injury at least partly by activating AMPK signal. These data supported the notion that STING might be a potential therapeutic target for SAH.
| S-EPMC7247752 | biostudies-literature
Project description:Traumatic spinal cord injury (SCI) always leads to severe neurological deficits and permanent damage. Neuroinflammation is a vital process of SCI and have become a promising target for SCI treatment. However, the neuroinflammation-targeted therapy would hinder the functional recovery of spinal cord and lead to the treatment failure. Herein, a biomimic anti-neuroinflammatory nanoplatform (DHCNPs) was developed for active neutrophil extracellular traps (NETs) targeting and SCI treatment. The curcumin-loaded liposome with the anti-inflammatory property acted as the core of the DHCNPs. Platelet membrane and neutrophil membrane were fused to form the biomimic hybrid membrane of the DHCNPs for hijacking neutrophils and neutralizing the elevated neutrophil-related proinflammatory cytokines, respectively. DNAse I modification on the hybrid membrane could achieve NETs degradation, blood spinal cord barrier, and neuron repair. Further studies proved that the DHCNPs could reprogram the multifaceted neuroinflammation and reverse the SCI process via nuclear factor kappa-B (NF-κB) pathway. We believe that the current study provides a new perspective for neuroinflammation inhibition and may shed new light on the treatment of SCI.
| S-EPMC11364920 | biostudies-literature