Histones of Neutrophil Extracellular Traps Induce CD11b Expression in Brain Pericytes Via Dectin-1 after Traumatic Brain Injury

Neutrophil extracellular traps induced by neoadjuvant chemotherapy of breast cancer promotes vascular endothelial damage

BACKGROUND

The mechanisms underpinning neoadjuvant chemotherapy-induced vascular endothelial injury in breast cancer remain elusive. Our study aims to demonstrate that Neutrophil Extracellular Traps (NETs) play a pivotal role in neoadjuvant chemotherapy-induced vascular endothelial injury in breast cancer, elucidating that chemotherapy-induced upregulation of Solute Carrier 11a1 (Slc11a1) modulates Reactive Oxygen Species (ROS) generation, which may be critical for NETs formation.

METHODS

We investigated the impact of neoadjuvant chemotherapy for breast cancer on NETs formation and vascular endothelial injury by analyzing NETs dsDNA and serum markers in patients, cells, and chemotherapy mouse models. RNA sequencing of neutrophils from chemotherapy mouse models was performed to identify the potential NETs formation-associated gene Slc11a1, which was further validated through cellular and animal experiments by assessing Slc11a1 expression, intracellular ferrous ion content, and ROS levels. Knockdown of Slc11a1 in human neutrophils and mouse models were also performed to further confirm the phenotypic results.

RESULTS

Our study revealed that plasma NETs formation and endothelial injury markers were significantly elevated in breast cancer patients undergoing docetaxel & carboplatin (TCb) neoadjuvant chemotherapy, compared to controls. In these patients, NETs formation was associated with the augmentation of endothelial injury markers. Chemotherapy mouse models demonstrated that TCb treatment markedly elevated NETs formation and endothelial injury, which can be mitigated by CI-amidine, a protein-arginine deiminase inhibitor. In human neutrophils, we demonstrated that the TCb chemotherapeutic agents (combination of docetaxel and carboplatin) induced the formation of NETs, which subsequently facilitated damage to human umbilical vein endothelial cells in vitro. RNA sequencing of mouse neutrophils identified Slc11a1 as a key NETs formation-related gene, which was upregulated by TCb chemotherapy in neutrophils, leading to increased intracellular ferrous ion content and ROS generation. Knockdown of Slc11a1 in human neutrophils and mouse models demonstrated its reversal effect on TCb-induced ferrous ion upregulation, ROS generation, and NETs formation.

CONCLUSIONS

Our research underscores the capacity of TCb neoadjuvant chemotherapy in breast cancer to augment NETs formation in neutrophils through Slc11a1-mediated ROS generation, which is linked to vascular endothelial injury. Our study elucidates the potential mechanisms underlying perioperative vascular endothelial injury in breast cancer patients undergoing neoadjuvant chemotherapy, offering novel insights into perioperative therapeutic management strategies for these patients.

Recombinant human DNase treatment mitigates extracellular trap mediated damage and improves long-term recovery after spinal cord injury in male mice

After traumatic spinal cord injury (SCI), inflammation and other reactive processes exacerbate tissue damage and impair long-term motor recovery. Extracellular traps (ETs) are an immune cell effector function first described in neutrophils wherein chromatin is decondensed, decorated with cytotoxic granule enzymes, and expelled from the cell body. Recently, ETs have been linked to poor functional outcomes in SCI; however, translatable agents to prevent ET-mediated damage after SCI have yet to be explored. We assessed recombinant human (rh) DNase (trade name Pulmozyme) as a potential therapeutic that could be repurposed to break down ETs after SCI. To determine the timing of treatment, we characterized the timeline of ET formation in a thoracic contusion model of SCI in mice. We found that ETs levels increased in the injured spinal cord by 4 h post injury (hpi), peaking within 24 hpi. When rhDNase was administered at 1 hpi, DNase activity in the serum remained elevated for 24 hpi with a corresponding increase in circulating ET fragments. At 6 hpi, blood spinal cord barrier permeability was attenuated in rhDNase-treated animals. Long-term functional hind limb recovery, as assessed by the ladder rung walking test, was improved at 35 dpi in rhDNase-treated animals compared to vehicle-treated controls. RhDNase-treated animals also exhibited shorter SCI lesion lengths at 35 dpi. Altogether, our data demonstrate the potential of rhDNase as an anti-ET therapeutic to improve long-term SCI outcomes.

Novel insights into neuroinflammatory mechanisms in traumatic brain injury: Focus on pattern recognition receptors as therapeutic targets

Traumatic brain injury (TBI) is a major global health concern and a leading cause of morbidity and mortality. Neuroinflammation is a pivotal driver of both the acute and chronic phases of TBI, with pattern recognition receptors (PRRs) playing a central role in detecting damage-associated molecular patterns (DAMPs) and initiating immune responses. Key PRR subclasses, including Toll-like receptors (TLRs), NOD-like receptors (NLRs), and cGAS-like receptors (cGLRs), are abundantly expressed in central nervous system (CNS) cells and infiltrating immune cells, where they mediate immune activation, amplify neuroinflammatory cascades, and exacerbate secondary injury mechanisms. This review provides a comprehensive analysis of these PRR subclasses, detailing their distinct structural characteristics, expression patterns, and roles in post-TBI immune responses. We critically examine the molecular mechanisms underlying PRR-mediated signaling and explore their contributions to neuroinflammatory pathways and secondary injury processes. Additionally, preclinical and clinical evidence supporting the therapeutic potential of targeting PRRs to mitigate neuroinflammation and improve neurological outcomes is discussed. By integrating recent advancements, this review offers an in-depth understanding of the role of PRRs in TBI pathobiology and underscores the potential of PRR-targeted therapies in mitigating TBI-associated neurological deficits.

Early intervention with pericyte Fli-1 post-TBI attenuates hippocampal BBB disruption and subsequent neuroinflammation with neurological deficits

The ETS transcription factor Fli-1, known for regulating the vitality of pericyte in mice, has not been thoroughly investigated in traumatic brain injury (TBI). In this study, we used a mouse TBI model to demonstrate that Fli-1 expression in pericyte within the ipsilateral hippocampus is significantly increased following TBI and is associated with pericyte loss. Interfering with Fli-1 expression in pericyte disrupted their interactions with microglia, which in turn inhibited the transformation of microglia to a pro-inflammatory phenotype. Administration of Fli-1 siRNA via lateral ventricle injection reduced pericyte loss, microglial activation, and neuroinflammation induced by TBI. Additionally, Fli-1 siRNA treatment reduced neurological damage in the hippocampus and improved memory and cognitive function. Overall, our findings suggest that Fli-1 expression in pericyte is closely linked to pericyte apoptosis and pericyte-microglia interactions. Inhibiting Fli-1 could mitigate pericyte loss, neuroinflammation, blood-brain barrier disruption, and cognitive decline, indicating that targeting Fli-1 may be a viable clinical strategy for TBI intervention.

The neutrophil extracellular traps in neurological diseases: an update

Neutrophil extracellular traps (NETs) released by neutrophils are web-like DNA structures adhered to granulin proteins with bactericidal activity and can be an important mechanism for preventing pathogen dissemination or eliminating microorganisms. However, they also play important roles in diseases of other systems, such as the central nervous system. We tracked the latest advances and performed a review based on published original and review articles related to NETs and neurological diseases. Generally, neutrophils barely penetrate the blood-brain barrier into the brain parenchyma, but when pathological changes such as infection, trauma, or neurodegeneration occur, neutrophils rapidly infiltrate the central nervous system to exert their defensive effects. However, neutrophils may adversely affect the host when they uncontrollably release NETs upon persistent neuroinflammation. This review focused on recent advances in understanding the mechanisms and effects of NETs release in neurological diseases, and we also discuss the role of molecules that regulate NETs release in anticipation of clinical applications in neurological diseases.

Osteocalcin-expressing neutrophils from skull bone marrow exert immunosuppressive and neuroprotective effects after TBI

Neutrophils from skull bone marrow (Nskull) are activated under some brain stresses, but their effects on traumatic brain injury (TBI) are lacking. Here, we find Nskull infiltrates brain tissue quickly and persistently after TBI, which is distinguished by highly and specifically expressed osteocalcin (OCN) from blood-derived neutrophils (Nblood). Reprogramming of glucose metabolism by reducing glycolysis-related enzyme glyceraldehyde 3-phosphate dehydrogenase expression is involved in the antiapoptotic and proliferative abilities of OCN-expressing Nskull. The transcription factor Fos-like 1 governs the specific gene profile of Nskull including C-C motif chemokine receptor-like 2 (CCRL2), arginase 1 (Arg1), and brain-derived neurotrophic factor (BDNF) in addition to OCN. Selective knockout of CCRL2 in Nskull demonstrates that CCRL2 mediates its recruitment, whereas high Arg1 expression is consistent with its immunosuppressive effects on Nblood, and the secretion of BDNF facilitating dendritic growth contributes to its neuroprotection. Thus, our findings provide insight into the roles of Nskull in TBI.

SIRT1-Mediated HMGB1 Deacetylation Suppresses Neutrophil Extracellular Traps Related to Blood-Brain Barrier Impairment After Cerebral Venous Thrombosis

Cerebral venous thrombosis (CVT) is a neurovascular disease with recently increasing incidence. Aseptic inflammatory responses play an important role in the pathology of CVT. Recent studies report that neutrophil extracellular traps (NETs) are major triggers of thrombosis and inflammation in stroke, but their effect on brain injury in CVT requires further validation. In this study, two CVT animal models were used to simulate superior sagittal sinus thrombosis and cortical vein thrombosis. The effects of brain tissue infiltration of NETs and the molecular mechanisms associated with NET formation were deeply explored in combination with proteomics, histology, and serology. The results showed that the cortical vein thrombosis model could be combined with more severe blood-brain barrier (BBB) disruption and showed more severe cerebral hemorrhage. Decreased Sirtuin 1 (SIRT1) expression promotes high mobility group box 1 (HMGB1) acetylation, causing increased cytosolic translocation and extracellular release, and HMGB1 can promote NET formation and recruitment. In addition, corticocerebral accumulation of NETs contributes to BBB damage. This establishes a vicious cycle between BBB damage and NET accumulation. SIRT1 mediated-HMGB1 deacetylation may play a critical role in attenuating BBB damage following CVT. This study employed a combined validation using models of venous sinus thrombosis and cortical vein thrombosis to investigate the deacetylation role of SIRT1, aiming to offer new insights into the pathological mechanisms of brain injury following CVT.

Neutrophil Extracellular Traps Regulate Surgical Brain Injury by Activating the cGAS-STING Pathway

Surgical brain injury (SBI), induced by neurosurgical procedures or instruments, has not attracted adequate attention. The pathophysiological process of SBI remains sparse compared to that of other central nervous system diseases thus far. Therefore, novel and effective therapies for SBI are urgently needed. In this study, we found that neutrophil extracellular traps (NETs) were present in the circulation and brain tissues of rats after SBI, which promoted neuroinflammation, cerebral edema, neuronal cell death, and aggravated neurological dysfunction. Inhibition of NETs formation by peptidylarginine deiminase (PAD) inhibitor or disruption of NETs with deoxyribonuclease I (DNase I) attenuated SBI-induced damages and improved the recovery of neurological function. We show that SBI triggered the activation of cyclic guanosine monophosphate-adenosine monophosphate synthase stimulator of interferon genes (cGAS-STING), and that inhibition of the cGAS-STING pathway could be beneficial. It is worth noting that DNase I markedly suppressed the activation of cGAS-STING, which was reversed by the cGAS product cyclic guanosine monophosphate-adenosine monophosphate (cGMP-AMP, cGAMP). Furthermore, the neuroprotective effect of DNase I in SBI was also abolished by cGAMP. NETs may participate in the pathophysiological regulation of SBI by acting through the cGAS-STING pathway. We also found that high-dose vitamin C administration could effectively inhibit the formation of NETs post-SBI. Thus, targeting NETs may provide a novel therapeutic strategy for SBI treatment, and high-dose vitamin C intervention may be a promising translational therapy with an excellent safety profile and low cost.

Metabotropic glutamate receptor 5 promotes blood-brain barrier recovery after traumatic brain injury

Blood-brain barrier (BBB) impairment and glutamate release are two pathophysiological features of traumatic brain injury (TBI), contributing to secondary brain damage and neuroinflammation. However, our knowledge of BBB integrity damage and dysfunction are still limited due to the diverse and fluctuating expression of glutamate receptors after trauma. Here, we confirmed the downregulation of metabotropic glutamate receptor 5 (mGluR5) on microvascular endothelial cell within the acute phase of TBI, and the recovered mGluR5 levels on BBB was positively associated with blood perfusion and neurological recovery. In whole body mGluR5-knockout mice, BBB dysfunction and neurological deficiency were exacerbated after TBI compared with wild type mice. In terms of mechanism, the amino acid sequence 201-259 of cytoskeletal protein Alpha-actinin-1 (ACTN1) interacted with mGluR5, facilitating mGluR5 translocation from cytoplasmic compartment to plasma membrane in endothelial cells. Activation of plasma membrane mGluR5 triggers the PLC/PKCμ/c-Jun signaling pathway, leading to increased expression of the tight junction-actin cytoskeleton connecting protein zonula occludens-1 (ZO-1). Our findings uncover a novel mechanism mediated by membrane and cytoplasmic mGluR5 in endothelial cell integrity maintenance and repair, providing the potential therapeutic target for TBI treatment targeting at mGluR5 and mGluR5/ACTN1 complex in BBB.

FOXO1 reshapes neutrophils to aggravate acute brain damage and promote late depression after traumatic brain injury

BACKGROUND

Neutrophils are traditionally viewed as first responders but have a short onset of action in response to traumatic brain injury (TBI). However, the heterogeneity, multifunctionality, and time-dependent modulation of brain damage and outcome mediated by neutrophils after TBI remain poorly understood.

METHODS

Using the combined single-cell transcriptomics, metabolomics, and proteomics analysis from TBI patients and the TBI mouse model, we investigate a novel neutrophil phenotype and its associated effects on TBI outcome by neurological deficit scoring and behavioral tests. We also characterized the underlying mechanisms both in vitro and in vivo through molecular simulations, signaling detections, gene expression regulation assessments [including dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays], primary cultures or co-cultures of neutrophils and oligodendrocytes, intracellular iron, and lipid hydroperoxide concentration measurements, as well as forkhead box protein O1 (FOXO1) conditional knockout mice.

RESULTS

We identified that high expression of the FOXO1 protein was induced in neutrophils after TBI both in TBI patients and the TBI mouse model. Infiltration of these FOXO1high neutrophils in the brain was detected not only in the acute phase but also in the chronic phase post-TBI, aggravating acute brain inflammatory damage and promoting late TBI-induced depression. In the acute stage, FOXO1 upregulated cytoplasmic Versican (VCAN) to interact with the apoptosis regulator B-cell lymphoma-2 (BCL-2)-associated X protein (BAX), suppressing the mitochondrial translocation of BAX, which mediated the antiapoptotic effect companied with enhancing interleukin-6 (IL-6) production of FOXO1high neutrophils. In the chronic stage, the "FOXO1-transferrin receptor (TFRC)" mechanism contributes to FOXO1high neutrophil ferroptosis, disturbing the iron homeostasis of oligodendrocytes and inducing a reduction in myelin basic protein, which contributes to the progression of late depression after TBI.

CONCLUSIONS

FOXO1high neutrophils represent a novel neutrophil phenotype that emerges in response to acute and chronic TBI, which provides insight into the heterogeneity, reprogramming activity, and versatility of neutrophils in TBI.

Targeting Neutrophil Extracellular Traps in Gouty Arthritis: Insights into Pathogenesis and Therapeutic Potential

Gouty arthritis (GA) is an immune-mediated disorder characterized by severe inflammation due to the deposition of monosodium urate (MSU) crystals in the joints. The pathophysiological mechanisms of GA are not yet fully understood, and therefore, the identification of effective therapeutic targets is of paramount importance. Neutrophil extracellular traps (NETs), an intricate structure of DNA scaffold, encompassing myeloperoxidase, histones, and elastases - have gained significant attention as a prospective therapeutic target for gouty arthritis, due to their innate antimicrobial and immunomodulatory properties. Hence, exploring the therapeutic potential of NETs in gouty arthritis remains an enticing avenue for further investigation. During the process of gouty arthritis, the formation of NETs triggers the release of inflammatory cytokines, thereby contributing to the inflammatory response, while MSU crystals and cytokines are sequestered and degraded by the aggregation of NETs. Here, we provide a concise summary of the inflammatory processes underlying the initiation and resolution of gouty arthritis mediated by NETs. Furthermore, this review presents an overview of the current pharmacological approaches for treating gouty arthritis and summarizes the potential of natural and synthetic product-based inhibitors that target NET formation as novel therapeutic options, alongside elucidating the intrinsic challenges of these inhibitors in NETs research. Lastly, the limitations of HL-60 cell as a suitable substitute of neutrophils in NETs research are summarized and discussed. Series of recommendations are provided, strategically oriented towards guiding future investigations to effectively address these concerns. These findings will contribute to an enhanced comprehension of the interplay between NETs and GA, facilitating the proposition of innovative therapeutic strategies and novel approaches for the management of GA.

Neutrophil extracellular traps aggravate neuronal endoplasmic reticulum stress and apoptosis via TLR9 after traumatic brain injury

Endoplasmic reticulum (ER) stress and ER stress-mediated apoptosis play an important role during secondary brain damage after traumatic brain injury (TBI). Increased neutrophil extracellular traps (NETs) formation has been demonstrated to be associated with neurological damage after TBI. However, the correlation between ER stress and NETs remains unclear, and the specific function of NETs in neurons has not been defined. In this study, we found that the levels of NETs circulating biomarkers were remarkably elevated in the plasma of TBI patients. We then inhibited NETs formation by peptidylarginine deiminase 4 (PAD4, a critical enzyme for NETs formation) deficiency and discovered that ER stress activation and ER stress-mediated neuronal apoptosis were reduced. The degradation of NETs via DNase I showed similar outcomes. Furthermore, overexpression of PAD4 aggravated neuronal ER stress and ER stress-associated apoptosis, while TLR9 antagonist administration abrogated the damage caused by NETs. In addition to in vivo experiments, in vitro experiments revealed that treatment with a TLR9 antagonist alleviated NETs-induced ER stress and apoptosis in HT22 cells. Collectively, our results indicated that ER stress as well as the accompanying neuronal apoptosis can be ameliorated by disruption of NETs and that suppression of the TLR9-ER stress signaling pathway may contribute to positive outcomes after TBI.

Immune regulation in neurovascular units after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Survivors may experience movement disorders, memory loss, and cognitive deficits. However, there is a lack of understanding of the pathophysiology of TBI-mediated neuroinflammation and neurodegeneration. The immune regulation process of TBI involves changes in the peripheral and central nervous system (CNS) immunity, and intracranial blood vessels are essential communication centers. The neurovascular unit (NVU) is responsible for coupling blood flow with brain activity, and comprises endothelial cells, pericytes, astrocyte end-feet, and vast regulatory nerve terminals. A stable NVU is the basis for normal brain function. The concept of the NVU emphasizes that cell-cell interactions between different types of cells are essential for maintaining brain homeostasis. Previous studies have explored the effects of immune system changes after TBI. The NVU can help us further understand the immune regulation process. Herein, we enumerate the paradoxes of primary immune activation and chronic immunosuppression. We describe the changes in immune cells, cytokines/chemokines, and neuroinflammation after TBI. The post-immunomodulatory changes in NVU components are discussed, and research exploring immune changes in the NVU pattern is also described. Finally, we summarize immune regulation therapies and drugs after TBI. Therapies and drugs that focus on immune regulation have shown great potential for neuroprotection. These findings will help us further understand the pathological processes after TBI.

Traumatic brain injury: Mechanisms, manifestations, and visual sequelae

Traumatic brain injury (TBI) results when external physical forces impact the head with sufficient intensity to cause damage to the brain. TBI can be mild, moderate, or severe and may have long-term consequences including visual difficulties, cognitive deficits, headache, pain, sleep disturbances, and post-traumatic epilepsy. Disruption of the normal functioning of the brain leads to a cascade of effects with molecular and anatomical changes, persistent neuronal hyperexcitation, neuroinflammation, and neuronal loss. Destructive processes that occur at the cellular and molecular level lead to inflammation, oxidative stress, calcium dysregulation, and apoptosis. Vascular damage, ischemia and loss of blood brain barrier integrity contribute to destruction of brain tissue. This review focuses on the cellular damage incited during TBI and the frequently life-altering lasting effects of this destruction on vision, cognition, balance, and sleep. The wide range of visual complaints associated with TBI are addressed and repair processes where there is potential for intervention and neuronal preservation are highlighted.