Selective NLRP3 (Pyrin Domain-Containing Protein 3) Inflammasome Inhibitor Reduces Brain Injury After Intracerebral Hemorrhage

Exploring the correlation between innate immune activation of inflammasome and regulation of pyroptosis after intracerebral hemorrhage: From mechanism to treatment

Stroke has emerged as the primary cause of disability and death globally in recent years. Intracerebral hemorrhage (ICH), a particularly severe kind of stroke, is occurring in an increasing number of people. The two main clinical treatments for ICH now in use are conservative pharmaceutical therapy and surgical intervention, both of which have risks and drawbacks. Consequently, it is crucial to look into the pathophysiology of ICH and consider cutting-edge therapeutic approaches. Recent research has revealed that pyroptosis is a newly identified type of cell death distinguished by the break of the cell membrane and the discharge of pro-inflammatory substances through different routes. Following ICH, glial cells experience pyroptosis, which worsens neuroinflammation. Hence, the onset and progression of ICH are strongly linked to pyroptosis, which is facilitated by different inflammasomes. It is essential to conduct a comprehensive investigation of ICH damage processes and uncover new targets for treatment. The impact and function of pyroptosis in ICH, as well as the activation and regulation of inflammasomes and their mediated pyroptosis pathways will be fully discussed in this review.

Inhibition of the NLRP3/caspase-1 cascade related pyroptosis relieved propofol-induced neuroinflammation and cognitive impairment in developing rats

BACKGROUND

Numerous preclinical studies have demonstrated that prolonged exposure to propofol (A general anaesthetics) can lead to hippocampus injury in immature brains and impact long-term learning and memory functions. Neuroinflammation plays a pivotal role in the impairment of brain function associated with early exposure to anesthetic drugs. Nevertheless, the involvement of hippocampal pyroptosis and neuroinflammation mediated by the NLRP3/caspase-1 signaling cascade in propofol-induced developmental neurotoxicity remains unclear.

METHODS

Postnatal day (PND) 7 SD rats, PC12 cells, and HAPI cells were used to establish propofol neurotoxicity models in vivo and in vitro, respectively. We examined the potential hippocampal injury and cognitive dysfunction caused by propofol in neonatal rats through the NLRP3/caspase-1 signaling pathway using MCC950 and VX765 to inhibit the pathway. This investigation involved assessing histological changes in the hippocampus, behavioral performance in adulthood, NLRP3-related pyroptosis indicators, and neuroinflammatory cytokines.

RESULTS

Both in vivo and in vitro studies have demonstrated that exposure to propofol activates the NLRP3/caspase-1 signaling cascade in the hippocampus of PND7 rats, leading to pyroptosis, neuroinflammation, and subsequent hippocampal injury and behavioral changes in adulthood. However, MCC950 and VX765 inhibit the NLRP3/caspase-1 signaling cascade, reversing the developmental neurotoxicity of propofol.

CONCLUSION

Our study findings suggest that negative regulation of NLRP3/caspase-1 activation may serve as a potential therapeutic strategy for developmental neuroinflammation induced by propofol.

New targets in spontaneous intracerebral hemorrhage

PURPOSE OF REVIEW

Intracerebral hemorrhage (ICH) is a devastating stroke with limited medical treatments; thus, timely exploration of emerging therapeutic targets is essential. This review focuses on the latest strategies to mitigate secondary brain injury post-ICH other than targeting surgery or hemostasis, addressing a significant gap in clinical practice and highlighting potential improvements in patient outcomes.

RECENT FINDINGS

Promising therapeutic targets to reduce secondary brain injury following ICH have recently been identified, including attenuation of iron toxicity and inhibition of ferroptosis, enhancement of endogenous resorption of hematoma, and modulation of perihematomal inflammatory responses and edema. Additionally, novel insights suggest the lymphatic system of the brain may potentially play a role in hematoma clearance and edema management. Various experimental and early-phase clinical trials have demonstrated these approaches may potentially offer clinical benefits, though most research remains in the preliminary stages.

SUMMARY

Continued research is essential to identify multifaceted treatment strategies for ICH. Clinical translation of these emerging targets could significantly enhance the efficacy of therapeutic interventions and potentially reduce secondary brain damage and improve neurological recovery. Future efforts should focus on large-scale clinical trials to validate these approaches, to pave the way for more effective treatment protocols for spontaneous ICH.

The dual role of microglia in intracerebral hemorrhage

Intracerebral hemorrhage has the characteristics of high morbidity, disability and mortality, which has caused a heavy burden to families and society. Microglia are resident immune cells in the central nervous system, and their activation plays a dual role in tissue damage after intracerebral hemorrhage. The damage in cerebral hemorrhage is embodied in the following aspects: releasing inflammatory factors and inflammatory mediators, triggering programmed cell death, producing glutamate induced excitotoxicity, and destroying blood-brain barrier; The protective effect is reflected in the phagocytosis and clearance of harmful substances by microglia, and the secretion of anti-inflammatory and neurotrophic factors. This article summarizes the function of microglia and its dual regulatory mechanism in intracerebral hemorrhage. In the future, drugs, acupuncture and other clinical treatments can be used to intervene in the activation state of microglia, so as to reduce the harm of microglia.

Microglial repopulation induced by PLX3397 protects against ischemic brain injury by suppressing neuroinflammation in aged mice

As the resident immune cells in the central nervous system, microglia exhibit a 'sensitized' or 'primed' phenotype with dystrophic morphology and dysregulated functions in aged brains. Although studies have demonstrated the inflammatory profile of aged microglia in several neurological diseases, this issue is largely uncertain in stroke. Consequently, this study investigated the effects of primed and repopulated microglia on post-ischemic brain injury in aged mice. We replaced primed microglia with newly repopulated microglia through pharmacological administration and withdrawal of the colony-stimulating factor 1 receptor (CSF1R) inhibitor, PLX3397. Further, we performed a series of behavioral tests and flow cytometry in mouse models of middle cerebral artery occlusion (MCAO) to study the effects of microglial replacement on ischemic injury in the aged brain. With depletion and subsequent repopulation of microglia in MCAO mice, microglial replacement in aged mice improved neurological function and decreased brain infarction. This protective effect was accompanied by the reduction of peripheral immune cells infiltrating into brains. We showed that the repopulated microglia expressed elevated neuroprotective factors (including Cluster of Differentiation 206, transforming growth factor-β, and interleukin-10) and diminished expression of inflammatory markers (including Cluster of Differentiation 86, interleukin-6, and tumor necrosis factor α). Moreover, microglial replacement protected the blood-brain barrier and relieved neuronal death in aged mice subjected to 60 min of MCAO. These results imply that the replacement of microglia in the aged brain may alleviate brain damage and neuroinflammation, and therefore, ischemic brain damage. Thus, targeting microglia could be a promising therapeutic strategy for ischemic stroke.

Veliparib exerts protective effects in intracerebral hemorrhage mice by inhibiting the inflammatory response and accelerating hematoma resolution

Poly (ADP-ribose) polymerase (PARP) inhibitors have potent anti-inflammatory effects, including the suppression of brain microglial activation. Veliparib, a well-known PARP1/2 inhibitor, exhibits particularly high brain penetration, but its effects on stroke outcome is unknown. Here, the effects of veliparib on the short-term outcome of intracerebral hemorrhage (ICH), the most lethal type of stroke, were investigated. Collagenase-induced mice ICH model was applied, and the T2-weighted magnetic resonance imaging was performed to evaluate lesion volume. Motor function and hematoma volume were also measured. We further performed immunofluorescence, enzyme linked immunosorbent assay, flow cytometry, and blood-brain barrier assessment to explore the potential mechanisms. Our results demonstrated veliparib reduced the ICH lesion volume dose-dependently and at a dosage of 5 mg/kg, veliparib significantly improved mouse motor function and promoted hematoma resolution at days 3 and 7 post-ICH. Veliparib inhibited glial activation and downregulated the production of pro-inflammatory cytokines. Veliparib significantly decreased microglia counts and inhibited peripheral immune cell infiltration into the brain on day 3 after ICH. Veliparib improved blood-brain barrier integrity at day 3 after ICH. These findings demonstrate that veliparib improves ICH outcome by inhibiting inflammatory responses and may represent a promising novel therapy for ICH.

TYROBP serve as potential immune-related signature genes in the acute phase of intracerebral hemorrhage

The development of intracerebral hemorrhage (ICH) is a dynamic process and intervention during the acute phase of ICH is critical for subsequent recovery. Therefore, it is crucial to screen potential signature genes and therapeutic target genes in the acute phase of ICH. In this study, based on the results of mRNA sequencing in mouse ICH and mRNA sequencing of human ICH from online databases, top five potential signature genes after ICH, Tyrobp, Itgb2, Tlr2, Ptprc and Itgam, were screened. Quantitative PCR results showed higher mRNA expression of Tyrobp, Itgb2, Tlr2, Ptprc, and Itgam in the 1-, 3- and 5-day mouse ICH groups compared to the sham-operated group. Immune infiltration correlation analysis shows that the top-ranked signature gene, Tyrobp, is negatively correlated with M2 macrophages and plasma cells, and Western blot analysis shows higher expression of the Tyrobp protein in the 1-, 3-, and 5-day mouse ICH groups compared to the sham-operated group. Furthermore, immunohistochemistry revealed that TYROBP protein expression was significantly higher in human ICH tissues than in normal brain tissues. Our results suggest that Tyrobp is a signature gene in the acute phase of ICH and may be a potential target for the treatment of the acute phase of ICH.

MCC950 as a promising candidate for blocking NLRP3 inflammasome activation: A review of preclinical research and future directions

The NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome is a key component of the innate immune system that triggers inflammation and pyroptosis and contributes to the development of several diseases. Therefore, blocking the activation of the NLRP3 inflammasome has therapeutic potential for the treatment of these diseases. MCC950, a selective small molecule inhibitor, has emerged as a promising candidate for blocking NLRP3 inflammasome activation. Ongoing research is focused on elucidating the specific targets of MCC950 as well as assessfing its metabolism and safety profile. This review discusses the diseases that have been studied in relation to MCC950, with a focus on stroke, Alzheimer's disease, liver injury, atherosclerosis, diabetes mellitus, and sepsis, using bibliometric analysis. It then summarizes the potential pharmacological targets of MCC950 and discusses its toxicity. Furthermore, it traces the progression from preclinical to clinical research for the treatment of these diseases. Overall, this review provides a solid foundation for the clinical therapeutic potential of MCC950 and offers insights for future research and therapeutic approaches.

The critical role of NLRP3 inflammasome activation in Streptococcus suis-induced blood-brain barrier disruption

Streptococcus suis (S. suis) type 2 (SS2) is an important zoonotic pathogen causing severe neural infections in pigs and causes serious threat to public health. Inflammasome activation plays an important role in the host against microbial infection but the role of inflammasome activation in the blood-brain barrier (BBB) integrity during S. suis infection is rarely studied. This study investigated the mechanism by which S. suis-induced NLRP3 inflammasome activation led to BBB disruption. Our results showed that S. suis infection activated NLRP3 inflammasome in brain microvascular endothelial cells (BMECs) leading to the secretion of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) and chemokines (CCL-2 and CXCL-2) as well as the cleavage of Gasdermin D (GSDMD) which were significantly attenuated by inflammasome inhibitor MCC950. Furthermore, S. suis infection significantly downregulated expression of tight junctions (TJs) proteins and trans-endothelial electrical resistance (TEER) while NLRP3 inhibition rescued S. suis-induced degradation of TJs proteins and significantly reduced the number of S. suis crossing BBB in transwell infection model. Moreover, recombinant IL-1β exacerbated the reduction of TJs proteins in BMECs. In murine S. suis-infection model, MCC950 reduced the bacterial load and the excessive inflammatory response in mice brain. In addition, the integrity of the BBB was protected with increased TJ proteins expression and decreased pathological injury after the inhibition of NLRP3 inflammasome, indicating NLRP3 inflammasome plays a destructive role in meningitis induced by S. suis. Our study expands the understanding on the role of NLRP3 inflammasome in bacterial meningitis, which provide the valuable information for the development of anti-infective agents targeting NLRP3 to treat bacterial meningitis.

Bibliometric insights into the inflammation and mitochondrial stress in ischemic stroke

BACKGROUND

Research in the areas of inflammation and mitochondrial stress in ischemic stroke is rapidly expanding, but a comprehensive overview that integrates bibliometric trends with an in-depth review of molecular mechanisms is lacking.

OBJECTIVE

To map the evolving landscape of research using bibliometric analysis and to detail the molecular mechanisms that underpin these trends, emphasizing their implications in ischemic stroke.

METHODS

We conducted a bibliometric analysis to identify key trends, top contributors, and focal research themes. In addition, we review recent research advances in mitochondrial stress and inflammation in ischemic stroke to gain a detailed understanding of the pathophysiological processes involved.

CONCLUSION

Our integrative approach not only highlights the growing research interest and collaborations but also provides a detailed exploration of the molecular mechanisms that are central to the pathology of ischemic stroke. This synthesis offers valuable insights for researchers and paves the way for targeted therapeutic interventions.

Multiple sclerosis: the NLRP3 inflammasome, gasdermin D, and therapeutics

Multiple sclerosis (MS) stands as a chronic inflammatory disease characterized by its neurodegenerative impacts on the central nervous system. The complexity of MS and the significant challenges it poses to patients have made the exploration of effective treatments a crucial area of research. Among the various mechanisms under investigation, the role of inflammation in MS progression is of particular interest. Inflammatory responses within the body are regulated by various cellular mechanisms, one of which involves the nucleotide-binding oligomerization domain (NOD)-, leucine-rich repeat (LRR)-, and pyrin domains (PYD)-containing protein 3 (NLRP3). NLRP3 acts as a sensor within cells, playing a pivotal role in controlling the inflammatory response. Its activation is a critical step leading to the assembly of the NLRP3 inflammasome complex, a process that has profound implications for inflammatory diseases like MS. The NLRP3 inflammasome's activation is intricately linked to the subsequent activation of caspase 1 and gasdermin D (GsdmD), signaling pathways that are central to the inflammatory process. GsdmD, a prominent member of the Gasdermin protein family, is particularly noteworthy for its role in pyroptotic cell death, a form of programmed cell death that is distinct from apoptosis and is characterized by its inflammatory nature. This pathway's activation contributes significantly to the pathology of MS by exacerbating inflammatory responses within the nervous system. Given the detrimental effects of unregulated inflammation in MS, therapeutics targeting these inflammatory processes offer a promising avenue for alleviating the symptoms experienced by patients. This review delves into the intricacies of the pyroptotic pathways, highlighting how the formation of the NLRP3 inflammasome induces such pathways and the potential intervention points for therapeutic agents. By inhibiting key steps within these pathways, it is possible to mitigate the inflammatory response, thereby offering relief to those suffering from MS. Understanding these mechanisms not only sheds light on the pathophysiology of MS but also paves the way for the development of novel therapeutic strategies aimed at controlling the disease's progression through the modulation of the body's inflammatory response.

Diagnostic value of serum NLRP3, metalloproteinase-9 and interferon-γ for postoperative hydrocephalus and intracranial infection in patients with severe craniocerebral trauma

Traumatic brain injury (TBI) is a major cause of morbidity and mortality globally. We unveiled the diagnostic value of serum NLRP3, metalloproteinase-9 (MMP-9) and interferon-γ (IFN-γ) levels in post-craniotomy intracranial infections and hydrocephalus in patients with severe craniocerebral trauma to investigate the high risk factors for these in patients with TBI, and the serological factors predicting prognosis, which had a certain clinical predictive value. Study subjects underwent bone flap resection surgery and were categorized into the intracranial infection/hydrocephalus/control (without postoperative hydrocephalus or intracranial infection) groups, with their clinical data documented. Serum levels of NLRP3, MMP-9 and IFN-γ were determined using ELISA kits, with their diagnostic efficacy on intracranial infections and hydrocephalus evaluated by receiver operating characteristic curve analysis. The independent risk factors affecting postoperative intracranial infections and hydrocephalus were analysed by logistic multifactorial regression. The remission after postoperative symptomatic treatment was counted. The intracranial infection/control groups had significant differences in Glasgow Coma Scale (GCS) scores, opened injury, surgical time and cerebrospinal fluid leakage, whereas the hydrocephalus and control groups had marked differences in GCS scores, cerebrospinal fluid leakage and subdural effusion. Serum NLRP3, MMP-9 and IFN-γ levels were elevated in patients with post-craniotomy intracranial infections/hydrocephalus. The area under the curve values of independent serum NLRP3, MMP-9, IFN-γ and their combination for diagnosing postoperative intracranial infection were 0.822, 0.722, 0.734 and 0.925, respectively, and for diagnosing hydrocephalus were 0.865, 0.828, 0.782 and 0.957, respectively. Serum NLRP3, MMP-9 and IFN-γ levels and serum NLRP3 and MMP-9 levels were independent risk factors influencing postoperative intracranial infection and postoperative hydrocephalus, respectively. Patients with hydrocephalus had a high remission rate after postoperative symptomatic treatment. Serum NLRP3, MMP-9 and IFN-γ levels had high diagnostic efficacy in patients with postoperative intracranial infection and hydrocephalus, among which serum NLRP3 level played a major role.

CSF1R blockade slows progression of cerebral hemorrhage by reducing microglial proliferation and increasing infiltration of CD8 + CD122+ T cells into the brain

Microglia play a pivotal role in the neuroinflammatory response after brain injury, and their proliferation is dependent on colony-stimulating factors. In the present study, we investigated the effect of inhibiting microglia proliferation on neurological damage post intracerebral hemorrhage (ICH) in a mouse model, an aspect that has never been studied before. Using a colony-stimulating factor-1 receptor antagonist (GW2580), we observed that inhibition of microglia proliferation significantly ameliorated neurobehavioral deficits, attenuated cerebral edema, and reduced hematoma volume after ICH. This intervention was associated with a decrease in pro-inflammatory factors in microglia and an increased infiltration of peripheral regulatory CD8 + CD122+ T cells into the injured brain tissue. The CXCR3/CXCL10 axis is the mechanism of brain homing of regulatory CD8 + CD122+ T cells, and the high expression of IL-10 is the hallmark of their synergistic anti-inflammatory effect with microglia. And activated astrocytes around the insult site are a prominent source of CXCL10. Thus, inhibition of microglial proliferation offers a new perspective for clinical translation. The cross-talk between multiple cells involved in the regulation of the inflammatory response highlights the comprehensive nature of neuroimmunomodulation.

Inhibition of piezo1 prevents chronic cerebral hypoperfusion-induced cognitive impairment and blood brain barrier disruption

Chronic cerebral hypoperfusion (CCH) plays a critical role in the onset and progression of vascular dementia (VD), which is now recognized as the second most common form of dementia after Alzheimer's disease (AD). The mechanosensitive piezo1 channel has been identified to play important roles in several neurological disorders. However, the roles and possible mechanisms of piezo1 in CCH-induced cognitive decline and blood brain barrier (BBB) disruption, as well as the underlying mechanisms remain elusive. In this study, the CCH model was established by bilateral common carotid artery occlusion in rats and by oxygen and glucose deprivation/reoxygenation (OGD/R) in bEnd.3 cells. The results demonstrated that the antagonist of piezo1 GsMTx4 ameliorated CCH-induced cognitive dysfunction and mitigated cerebral edema. Furthermore, this study indicated that GsMTx4 improved the permeability and integrity of BBB and protected cerebral microvasculature after CCH. In vitro, GsMTx4 improved cell viability, promoted the ability of cell motility and migration, and inhibited the degradation of BBB integrity-related proteins by inhibiting NLRP3 inflammasome activation. In addition, NLRP3 agonist abolished the beneficial effects of GsMTx4. Collectively, our results demonstrate that piezo1 might be involved in CCH-induced cognitive impairment and BBB damage, which may be at least partially mediated through regulation of NLRP3 inflammasome.

The NLRP3 inhibitor, OLT1177 attenuates brain injury in experimental intracerebral hemorrhage

BACKGROUND AND PURPOSE

It has been reported activation of NLRP3 inflammasome after intracerebral hemorrhage (ICH) ictus exacerbates neuroinflammation and brain injury. We hypothesized that inhibition of NLRP3 by OLT1177 (dapansutrile), a novel NLRP3 inflammasome inhibitor, could reduce brain edema and attenuate brain injury in experimental ICH.

METHODS

ICH was induced by injection of autologous blood into basal ganglia in mice models. Sixty-three C57Bl/6 male mice were randomly grouped into the sham, vehicle, OLT1177 (Dapansutrile, 200 mg/kg intraperitoneally) and treated for consecutive three days, starting from 1 h after ICH surgery. Behavioral test, brain edema, brain water content, blood-brain barrier integrity and vascular permeability, cell apoptosis, and NLRP3 and its downstream protein levels were measured.

RESULTS

OLT1177 significantly reduced cerebral edema after ICH and contributed to the attenuation of neurological deficits. OLT1177 could preserve blood-brain barrier integrity and lessen vascular leakage. In addition, OLT1177 preserved microglia morphological shift and significantly inhibited the activation of caspase-1 and release of IL-1β. We also found that OLT1177 can protect against neuronal loss in the affected hemisphere.

CONCLUSIONS

OLT1177 (dapansutrile) could significantly attenuate the brain edema after ICH and effectively alleviate the neurological deficit. This result suggests that the novel NLRP3 inhibitor, OLT1177, might serve as a promising candidate for the treatment of ICH.

Hippocampal and gut AMPK activation attenuates enterocolitis-like symptoms and co-occurring depressive-like behavior in ulcerative colitis model mice: Involvement of brain-gut autophagy

Patients with inflammatory bowel disease, including ulcerative colitis (UC) and Crohn's disease, have a high incidence of psychiatric disorders, including depression and anxiety. However, the underlying pathogenic mechanism remains unknown. Dextran sulfate sodium (DSS)-treated mice, a model of UC, exhibit depressive-like behavior and reduced adenosine monophosphate-activated protein kinase (AMPK) activity, which regulates various physiological functions in the brain and gut. However, comprehensive studies on UC pathophysiology with co-occurring depression focused on brain-gut AMPK activity are lacking. Therefore, we aimed to investigate whether resveratrol (RES), an AMPK activator, prevented DSS-induced UC-like symptoms and depressive-like behavior. DSS treatment induced UC-like pathology and depressive-like behavior, as assessed via the tail suspension test. Moreover, western blotting and immunohistochemical studies revealed that DSS increased p-p70S6 kinase (Thr389), p62, tumor necrosis factor-α, interleukin (IL)-1β, IL-18, NLR family pyrin domain containing 3 (NLRP3), cleaved caspase-1, cleaved Gasdermin-D (GSDMD), and cleaved caspase-3 expression levels in the rectum and hippocampus, and increased CD40, iNOS, and Kelch-like ECH-associated protein 1 expression levels, and the number of Iba1-positive cells in the hippocampus, and decreased p-AMPK and LC3II/I expression levels, and the number of NF-E2-related factor 2 (Nrf2)-positive cells, and reduced neurogenesis in the hippocampus. These changes were reversed by the RES administration. RES also enhanced PGC1α and SOD1 expression in the hippocampus of DSS-treated male mice. Moreover, NLRP3 staining was observed in the neurons and microglia, and cleaved GSDMD staining in neurons in the hippocampus of DSS-treated mice. Notably, RES prevented UC-like pathology and depressive-like behavior and enhancement of autophagy, decreased rectal and hippocampal inflammatory cytokines and inflammasome, and induced the Nrf2-PGC1α-SOD1 pathway in the hippocampus, resulting in neurogenesis in the hippocampal dentate gyrus. Our findings suggest that brain-gut AMPK activation may be an important therapeutic strategy in patients with UC and depression.

The role of gut microorganisms and metabolites in intracerebral hemorrhagic stroke: a comprehensive review

Intracerebral hemorrhagic stroke, characterized by acute hemorrhage in the brain, has a significant clinical prevalence and poses a substantial threat to individuals' well-being and productivity. Recent research has elucidated the role of gut microorganisms and their metabolites in influencing brain function through the microbiota-gut-brain axis (MGBA). This article provides a comprehensive review of the current literature on the common metabolites, short-chain fatty acids (SCFAs) and trimethylamine-N-oxide (TMAO), produced by gut microbiota. These metabolites have demonstrated the potential to traverse the blood-brain barrier (BBB) and directly impact brain tissue. Additionally, these compounds have the potential to modulate the parasympathetic nervous system, thereby facilitating the release of pertinent substances, impeding the buildup of inflammatory agents within the brain, and manifesting anti-inflammatory properties. Furthermore, this scholarly analysis delves into the existing dearth of investigations concerning the influence of gut microorganisms and their metabolites on cerebral functions, while also highlighting prospective avenues for future research.

Inflammasomes in neurological disorders - mechanisms and therapeutic potential

Inflammasomes are molecular scaffolds that are activated by damage-associated and pathogen-associated molecular patterns and form a key element of innate immune responses. Consequently, the involvement of inflammasomes in several diseases that are characterized by inflammatory processes, such as multiple sclerosis, is widely appreciated. However, many other neurological conditions, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, stroke, epilepsy, traumatic brain injury, sepsis-associated encephalopathy and neurological sequelae of COVID-19, all involve persistent inflammation in the brain, and increasing evidence suggests that inflammasome activation contributes to disease progression in these conditions. Understanding the biology and mechanisms of inflammasome activation is, therefore, crucial for the development of inflammasome-targeted therapies for neurological conditions. In this Review, we present the current evidence for and understanding of inflammasome activation in neurological diseases and discuss current and potential interventional strategies that target inflammasome activation to mitigate its pathological consequences.

TMT-based quantitative proteomics reveals the protective mechanism of tenuigenin after experimental intracerebral hemorrhage in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Tenuigenin (TNG) is an extract obtained from Polygalae Radix. It possesses anti-inflammatory, antioxidant, and neuroprotective properties. However, the potential mechanism of TNG in intracerebral hemorrhage (ICH) has not been well studied.

AIM OF THE STUDY

In the present study, we aimed to identify the prospective mechanism of TNG in treating ICH.

MATERIALS AND METHODS

A total of 120 mice were divided into five groups: Sham group, ICH + vehicle group, ICH + TNG(8 mg/kg), ICH + TNG(16 mg/kg), and ICH + TNG(32 mg/kg). The modified Garcia test and beam walking test were carried out at 24 h and 72 h after ICH. Brain water content, haematoma volume and hemoglobin content examinations were performed at 72 h after ICH. TMT-based quantitative proteomics combined with bioinformatics analysis methods was used to distinguish differentially expressed proteins (DEPs) to explore potential pharmacological mechanisms. Western blotting was performed to validate representative proteins.

RESULTS

Our results showed that the optimal dose of TNG was 16 mg/kg, which could markedly improve neurological functions, and reduce cerebral oedema, haematoma volume and hemoglobin levels 72 h after ICH. A total of 404 DEPs (353 up-and 51 downregulated) were identified in the ICH + vehicle vs. sham group, while 342 DEPs (306 up-and 36 downregulated) and 76 DEPs (28 up-and 48 downregulated) were quantified in the TNG vs. sham group and TNG vs. ICH + vehicle group, respectively. In addition, a total of 26 DEPs were selected according to strict criteria. Complement and coagulation cascades were the most significantly enriched pathways, and two proteins (MBL-C and Car1) were further validated as hub molecules.

CONCLUSIONS

Our results suggested that the therapeutic effects of TNG on ICH were closely associated with the complement system, and that MBL-C and Car1 might be potential targets of TNG for the treatment of ICH.

Cofilin Inhibitor Improves Neurological and Cognitive Functions after Intracerebral Hemorrhage by Suppressing Endoplasmic Reticulum Stress Related-Neuroinflammation

Neuroinflammation after intracerebral hemorrhage (ICH) is a crucial factor that determines the extent of the injury. Cofilin is a cytoskeleton-associated protein that drives neuroinflammation and microglia activation. A novel cofilin inhibitor (CI) synthesized and developed in our lab has turned out to be a potential therapeutic agent for targeting cofilin-mediated neuroinflammation in an in vitro model of ICH and traumatic brain injury. The current study aims to examine the therapeutic potential of CI in a mouse collagenase model of ICH and examine the neurobehavioral outcomes and its mechanism of action. Male mice were subjected to intrastriatal collagenase injection to induce ICH, and sham mice received needle insertion. Various concentrations (25, 50, and 100 mg/kg) of CI were administered to different cohorts of the animals as a single intravenous injection 3 h following ICH and intraperitoneally every 12 h for 3 days. The animals were tested for neurobehavioral parameters for up to 7 days and sacrificed to collect brains for hematoma volume measurement, Western blotting, and immunohistochemistry. Blood was collected for cofilin, TNF-α, and IL-1β assessments. The results indicated that 50 mg/kg CI improved neurological outcomes, reversed post-stroke cognitive impairment, accelerated hematoma resolution, mitigated cofilin rods/aggregates, and reduced microglial and astrocyte activation in mice with ICH. Microglia morphological analysis demonstrated that CI restored the homeostasis ramification pattern of microglia in mice treated with CI. CI suppressed endoplasmic reticulum stress-related neuroinflammation by inhibiting inflammasomes and cell death signaling pathways. We also showed that CI prevented synaptic loss by reviving the pre- and post-synaptic markers. Our results unveil a novel therapeutic approach to treating ICH and open a window for using CI in clinical practice.

Role of Crosstalk between Glial Cells and Immune Cells in Blood-Brain Barrier Damage and Protection after Acute Ischemic Stroke

Blood-brain barrier (BBB) damage is the main pathological basis for acute ischemic stroke (AIS)-induced cerebral vasogenic edema and hemorrhagic transformation (HT). Glial cells, including microglia, astrocytes, and oligodendrocyte precursor cells (OPCs)/oligodendrocytes (OLs) play critical roles in BBB damage and protection. Recent evidence indicates that immune cells also have an important role in BBB damage, vasogenic edema and HT. Therefore, regulating the crosstalk between glial cells and immune cells would hold the promise to alleviate AIS-induced BBB damage. In this review, we first introduce the roles of glia cells, pericytes, and crosstalk between glial cells in the damage and protection of BBB after AIS, emphasizing the polarization, inflammatory response and crosstalk between microglia, astrocytes, and other glia cells. We then describe the role of glial cell-derived exosomes in the damage and protection of BBB after AIS. Next, we specifically discuss the crosstalk between glial cells and immune cells after AIS. Finally, we propose that glial cells could be a potential target for alleviating BBB damage after AIS and we discuss some molecular targets and potential strategies to alleviate BBB damage by regulating glial cells after AIS.

CD22 blockade modulates microglia activity to suppress neuroinflammation following intracerebral hemorrhage

Microglia are first responders to acute brain insults and initiate neuroinflammation to drive secondary tissue injury. Yet the key molecular switches in control of the inflammatory activity of microglia remain poorly understood. Intracerebral hemorrhage (ICH) is a devastating stroke subtype whereby a hematoma is formed within the brain parenchyma and associated with high mortality. Using a mouse model of ICH, we found upregulation of CD22 that predominantly occurred in microglia. Antibody blockade of CD22 led to a reduction in neurological deficits, brain lesion and hematoma volume. This was accompanied by reduced inflammatory activity, increased expression of alternative activation markers (CD206 and IL-10) and enhanced phagocytosis activity in microglia after ICH. CD22 blockade also led to an increase of phosphorylated SYK and AKT after ICH. Notably, the benefits of CD22 blockade were ablated in ICH mice subjected to microglial depletion with a colony-stimulating factor 1 receptor inhibitor PLX5622. Additionally, the protective effects of CD22 blockade was diminished in ICH mice receiving a SYK inhibitor R406. Together, our findings highlight CD22 as a key molecular switch to control the detrimental effects of microglia after acute brain injury, and provide a novel strategy to improve the outcome of ICH injury.

Periventricular Microglia Polarization and Morphological Changes Accompany NLRP3 Inflammasome-Mediated Neuroinflammation after Hypoxic-Ischemic White Matter Damage in Premature Rats

White matter damage (WMD) is a primary cause of cerebral palsy and cognitive impairment in preterm infants, and no effective treatments are available. Microglia are a major component of the innate immune system. When activated, they form typical pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes and regulate myelin development and synapse formation. Therefore, they may play a pivotal role in hypoxic-ischemic (HI) WMD. Herein, we investigated neural inflammation and long-term microglia phenotypic polarization in a neonatal rat model of hypoxia-ischemia-induced WMD and elucidated the underlying pathophysiological processes. We exposed 3-day-old (P3) Sprague-Dawley rats to hypoxia (8% oxygen) for 2.5 hr after unilateral common carotid artery ligation. The activation of NLRP3 inflammatory bodies, microglia M1/M2 polarization, myelination, and synaptic development in our model were monitored 7, 14, and 21 days after birth. In addition, the Morris water maze test was performed on postnatal Day 28. We confirmed myelination disturbance in the periventricular white matter, abnormal synaptic development, and behavioral changes in the periventricular area during the development of HI WMD. In addition, we found an association between the occurrence and development of HI WMD and activation of the NLRP3 inflammasome, microglial M1/M2 polarization, and the release of inflammatory factors. NLRP3 inhibition can play an anti-inflammatory role by inhibiting the differentiation of microglia into the M1 phenotype, thereby improving myelination and synapse formation. In conclusion, microglia are key mediators of the inflammatory response and exhibit continuous phenotypic polarization 7-21 days after HI-induced WMD. This finding can potentially lead to a new treatment regimen targeting the phenotypic polarization of microglia early after HI-induced brain injury.

Induced neural stem cells suppressed neuroinflammation by inhibiting the microglial pyroptotic pathway in intracerebral hemorrhage rats

Intracerebral hemorrhage usually manifests as strong neuroinflammation and neurological deficits. There is an urgent need to explore effective methods for the treatment of intracerebral hemorrhage. The therapeutic effect and the possible mechanism of induced neural stem cell transplantation in an intracerebral hemorrhage rat model are still unclear. Our results showed that transplantation of induced neural stem cells could improve neurological deficits by inhibiting inflammation in an intracerebral hemorrhage rat model. Additionally, induced neural stem cell treatment could effectively suppress microglial pyroptosis, which might occur through inhibiting the NF-κB signaling pathway. Induced neural stem cells could also regulate the polarization of microglia and promote the transition of microglia from pro-inflammatory phenotypes to anti-inflammatory phenotypes to exert their anti-inflammatory effects. Overall, induced neural stem cells may be a promising tool for the treatment of intracerebral hemorrhage and other neuroinflammatory diseases.

The NLRP3 inflammasome: contributions to inflammation-related diseases

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines interleukin (IL)-1β and IL-18. Multiple studies have demonstrated the importance of the NLRP3 inflammasome in the development of immune and inflammation-related diseases, including arthritis, Alzheimer's disease, inflammatory bowel disease, and other autoimmune and autoinflammatory diseases. This review first explains the activation and regulatory mechanism of the NLRP3 inflammasome. Secondly, we focus on the role of the NLRP3 inflammasome in various inflammation-related diseases. Finally, we look forward to new methods for targeting the NLRP3 inflammasome to treat inflammation-related diseases, and provide new ideas for clinical treatment.

Microglial exosomes alleviate intermittent hypoxia-induced cognitive deficits by suppressing NLRP3 inflammasome

Intermittent hypoxia is the best predictor of developing cognitive decline and Alzheimer's disease progression in patients with obstructive sleep apnea. The nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome has been poorly studied as a regulator of neuroinflammation in cognitive impairment caused by intermittent hypoxia. As critical inflammatory cells, exosomes secreted by microglia have been found to affect the spread of pathologic proteins and neuropathology in neurodegenerative diseases. However, the effects of microglial exosomes on neuroinflammation and cognitive outcomes after intermittent hypoxia remain unclear. In this study, the role of miRNAs in microglial exosomes in improving cognitive deficits in mice exposed to intermittent hypoxia was investigated. We demonstrated that miR-146a-5p fluctuated over time in microglial exosomes of mice exposed to intermittent hypoxia for different periods of time, which could regulate neuronal NLRP3 inflammasome and neuroinflammation. In primary neurons, we found that miR-146a-5p regulated mitochondrial reactive oxygen species by targeting HIF1α, thus affecting the NLRP3 inflammasome and secretion of inflammatory factors. Similarly, further studies showed that inhibition of NLRP3 by administering overexpressed miR-146a-5p in microglial exosomes and MCC950 has improved neuroinflammation and cognitive dysfunction in mice after intermittent hypoxia. In conclusion, NLRP3 inflammasome may be a regulatory target for ameliorating cognitive impairment caused by intermittent hypoxia, and microglial exosomal miR-146a-5p may be a promising therapeutic strategy.

Transmission of NLRP3-IL-1β Signals in Cerebral Ischemia and Reperfusion Injury: from Microglia to Adjacent Neuron and Endothelial Cells via IL-1β/IL-1R1/TRAF6

The pyrin domain-containing protein 3 (NLRP3) inflammasome drives the profound cerebral ischemia and reperfusion injury (I/R) and mediates the secretion of IL-1β (interleukin-1β), which exerts a subsequent cascade of inflammatory injury. The NLRP3-activated-microglial manipulation in adjacent neuronal and endothelial NLRP3 activation has been confirmed in our previous studies. In the present study, we extended the cognition of how microglia mediated neuronal and endothelial NLRP3-IL-1β signaling during cerebral ischemia and reperfusion injury. In vitro, Neuro-2a and bEND3 cells were cultured alone or co-cultured with BV2 cells and oxygen-glucose deprivation/reoxygenation (OGD/R) was performed. In vivo, transient middle cerebral artery occlusion (tMCAO) rat models and lentiviral silencing targeting IL-1R1 were performed. The NLRP3 inflammasome activation was evaluated by enzyme-linked immunosorbent assay, western blotting, immunoprecipitation, immunohistochemistry, and immunofluorescence. In the co-culture system after OGD/R treatment, NLRP3 inflammasomes in neurons and endothelial cells were activated by microglial IL-1β via IL-1β/IL-1R1/TRAF6 signaling pathway, with the basal protein level of NLRP3. In addition, ruptured lysosomes engulfing ASC specks which were possibly secreted from microglia triggered the enhanced NLRP3 expression. In cortices of tMCAO rats at 24 h of reperfusion, silencing IL-1R1, mainly presented in neurons and endothelial cells, was efficient to block the subsequent inflammatory damage and leukocyte brain infiltration, leading to better neurological outcome. Neuronal and endothelial NLRP3 inflammasomes were activated by microglia in cerebral ischemia and reperfusion injury mainly via IL-1β/IL-1R1/TRAF6 signaling, which might be therapeutically targetable.

The Potential of NLRP3 Inflammasome as a Therapeutic Target in Neurological Diseases

NLRP3 (NLRP3: NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome is the best-described inflammasome that plays a crucial role in the innate immune system and a wide range of diseases. The intimate association of NLRP3 with neurological disorders, including neurodegenerative diseases and strokes, further emphasizes its prominence as a clinical target for pharmacological intervention. However, after decades of exploration, the mechanism of NLRP3 activation remains indefinite. This review highlights recent advances and gaps in our insights into the regulation of NLRP3 inflammasome. Furthermore, we present several emerging pharmacological approaches of clinical translational potential targeting the NLRP3 inflammasome in neurological diseases. More importantly, despite small-molecule inhibitors of the NLRP3 inflammasome, we have focused explicitly on Chinese herbal medicine and botanical ingredients, which may be splendid therapeutics by inhibiting NLRP3 inflammasome for central nervous system disorders. We expect that we can contribute new perspectives to the treatment of neurological diseases.

Intranasal Delivery of Gene-Edited Microglial Exosomes Improves Neurological Outcomes after Intracerebral Hemorrhage by Regulating Neuroinflammation

Neural inflammatory response is a crucial pathological change in intracerebral hemorrhage (ICH) which accelerates the formation of perihematomal edema and aggravates neural cell death. Although surgical and drug treatments for ICH have advanced rapidly in recent years, therapeutic strategies that target and control neuroinflammation are still limited. Exosomes are important carriers for information transfer among cells. They have also been regarded as a promising therapeutic tool in translational medicine, with low immunogenicity, high penetration through the blood-brain barrier, and ease of modification. In our previous research, we have found that exogenous administration of miRNA-124-overexpressed microglial exosomes (Exo-124) are effective in improving post-injury cognitive impairment. From this, we evaluated the potential therapeutic effects of miRNA-124-enriched microglial exosomes on the ICH mice in the present study. We found that the gene-edited exosomes could attenuate neuro-deficits and brain edema, improve blood-brain barrier integrity, and reduce neural cell death. Moreover, the protective effect of Exo-124 was abolished in mice depleted of Gr-1⁺ myeloid cells. It suggested that the exosomes exerted their functions by limiting the infiltration of leukocyte into the brain, thus controlling neuroinflammation following the onset of ICH. In conclusion, our findings provided a promising therapeutic strategy for improving neuroinflammation in ICH. It also opens a new avenue for intranasal delivery of exosome therapy using miRNA-edited microglial exosomes.

Cytotoxic Edema and Adverse Clinical Outcomes in Patients with Intracerebral Hemorrhage

BACKGROUND

Cytotoxic edema (CE) is an important form of perihematomal edema (PHE), which is a surrogate marker of secondary injury after intracerebral hemorrhage (ICH). However, knowledge about CE after ICH is insufficient. Whether CE has adverse effects on clinical outcomes of patients with ICH remains unknown. Therefore, we aimed to investigate the temporal pattern of CE and its association with clinical outcomes in patients with ICH.

METHODS

Data were derived from a randomized controlled study (comparing the deproteinized calf blood extract with placebo in patients with ICH). Intervention in this original study did not show any impact on hematoma and PHE volume, presence of CE, or clinical outcomes. We conducted our analysis in 20 patients who underwent magnetic resonance imaging with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) images at day 3 and within 7-12 days after symptom onset. CE was defined as an elevated DWI b1000 signal and an ADC value reduced by > 10% compared with the mirror area of interest in the perihematomal region. The modified Rankin Scale (mRS), National Institutes of Health Stroke Scale (NIHSS), and Barthel Index (BI) were performed face to face at 30-day and 90-day follow-ups after ICH onset to assess the clinical outcomes of the patients.

RESULTS

CE was detected in nearly two thirds of patients with ICH in our study and seemed to be reversible. CE within 7-12 days, rather than at day 3 after symptom onset, was associated with poor clinical outcome (mRS 3-6) at the 30-day follow-up (P = 0.020). In addition, compared with those without CE, patients with CE within 7-12 days had more severe neurological impairment measured by NIHSS score (P = 0.024) and worse daily life quality measured by BI (P = 0.004) at both the 30- and 90-day follow-ups.

CONCLUSIONS

CE appears in the acute phase of ICH and might be reversible. CE within 7-12 days post ICH was related to poor outcomes, which provides a novel therapeutic target for ICH intervention.

LDC7559 inhibits microglial activation and GSDMD-dependent pyroptosis after subarachnoid hemorrhage

Mounting evidence indicates that inhibition of microglial activation and neuronal pyroptosis plays important roles in brain function recovery after subarachnoid hemorrhage (SAH). LDC7559 is a newly discovered gasdermin D (GSDMD) inhibitor. Previous studies have demonstrated that LDC7559 could inhibit microglial proliferation and pyroptosis. However, the beneficial effects of LDC7559 on SAH remain obscure. Based on this background, we investigated the potential role and the mechanism of LDC7559 on SAH-induced brain damage both in vivo and in vitro. The findings revealed that microglial activation and neuronal pyroptosis were evidently increased after SAH, which could be markedly suppressed by LDC7559 both in vivo and in vitro. Meanwhile, LDC7559 treatment reduced neuronal apoptosis and improved behavior function. Mechanistically, LDC7559 decreased the levels of GSDMD and cleaved GSDMD after SAH. In contrast, nod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome activation by nigericin increased GSDMD-mediated pyroptosis and abated the beneficial effects of LDC7559 on SAH-induced brain damage. However, LDC7559 treatment did not significantly affect the expression of NLRP3 after SAH. Taken together, LDC7559 might suppress neuronal pyroptosis and microglial activation after SAH by inhibiting GSDMD, thereby promoting brain functional recovery.

Ozanimod-Dependent Activation of SIRT3/NF-κB/AIM2 Pathway Attenuates Secondary Injury After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is characterized by poor prognosis and high mortality rates. To date, satisfactory therapeutic approaches for ICH remain limited, so it is urgently needed to develop a safer and more effective prescription. Secondary inflammatory response has been acknowledged as an aggravating factor to neurological deterioration after ICH. As a component of inflammasome sensors, absent in melanoma 2 (AIM2) plays an important role in the neuroinflammation process. Here, ozanimod, a novel selective sphingosine 1-phosphate receptor modulator, has gained much attention, which alleviates the resultant neuroinflammation and improves functional recovery derived from ICH. In this study, ozanimod improved neurological functions of ICH mice via reduction of hematoma size. Furthermore, both microglial and AIM2 inflammasome activations were reversed by ozanimod, which are confirmed by the downregulation of related inflammatory proteins and cytokines (IL-1β, IL-6, and TNF-α), coupled with the upregulation of SIRT3, by leveraging the Western blot and enzyme-linked immunosorbent assay. Additionally, we find that ozanimod decreases nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) expression. Notably, in vitro cell experiments induced by lipopolysaccharide confirms that the anti-inflammatory effect of ozanimod could be abolished by the SIRT3 inhibitor. In conclusion, these results indicate that ozanimod mitigates ICH-induced secondary inflammatory responses by modulating AIM2 inflammasome mediated by SIRT3/NF-κB/AIM2 pathway. This demonstrates ozanimod orchestrates ICH-induced neuroinflammation and could be a targeted therapy for improving prognosis of ICH.

NLRP3 inflammasome in traumatic brain injury: Its implication in the disease pathophysiology and potential as a therapeutic target

Traumatic brain injury (TBI), an acquired brain injury imparted by a mechanical trauma to the head, has significant ramifications in terms of long-term disability and cost of healthcare. TBI is characterized by an initial phase of cell death owing to direct mechanical injury, followed by a secondary phase in which neuroinflammation plays a pivotal role. Activation of inflammasome complexes triggers a cascade that leads to activation of inflammatory mediators such as caspase-1, Interleukin (IL)-18, and IL-1β, eventually causing pyroptosis. NLRP3 inflammasome, a component of the innate immune response, has been implicated in a number of neurodegenerative diseases, including TBI. Recent findings indicate that NLRP3 inhibitors can potentially ameliorate neuroinflammation and improve cognition and motor function in TBI. The NLRP3 inflammasome also holds potential as a predictive biomarker for the long-term sequelae following TBI. Although several therapeutic agents have shown promising results in pre-clinical studies, none of them have been effective in human trials for TBI, to date. Thus, it is imperative that such promising therapeutic candidates are evaluated in clinical trials to assess their efficacy in alleviating neurological impairments in TBI. This review offers an insight into the pathophysiology of TBI, with an emphasis on neuroinflammation in the aftermath of TBI. We highlight the NLRP3 inflammasome and explore its role in the neuroinflammatory cascade in TBI. We also shed light on its potential as a prospective biomarker and therapeutic target for TBI management.

Role of Inflammatory Processes in Hemorrhagic Stroke

Hemorrhagic stroke is the deadliest form of stroke and includes the subtypes of intracerebral hemorrhage and subarachnoid hemorrhage. A common cause of hemorrhagic stroke in older individuals is cerebral amyloid angiopathy. Intracerebral hemorrhage and subarachnoid hemorrhage both lead to the rapid collection of blood in the central nervous system and generate inflammatory immune responses that involve both brain resident and infiltrating immune cells. These responses are complex and can contribute to both tissue recovery and tissue injury. Despite the interconnectedness of these major subtypes of hemorrhagic stroke, few reviews have discussed them collectively. The present review provides an update on inflammatory processes that occur in response to intracerebral hemorrhage and subarachnoid hemorrhage, and the role of inflammation in the pathophysiology of cerebral amyloid angiopathy-related hemorrhage. The goal is to highlight inflammatory processes that underlie disease pathology and recovery. We aim to discuss recent advances in our understanding of these conditions and identify gaps in knowledge with the potential to develop effective therapeutic strategies.

Maraviroc promotes recovery from traumatic brain injury in mice by suppression of neuroinflammation and activation of neurotoxic reactive astrocytes

Neuroinflammation and the NACHT, LRR, and PYD domains-containing protein 3 inflammasome play crucial roles in secondary tissue damage following an initial insult in patients with traumatic brain injury (TBI). Maraviroc, a C-C chemokine receptor type 5 antagonist, has been viewed as a new therapeutic strategy for many neuroinflammatory diseases. We studied the effect of maraviroc on TBI-induced neuroinflammation. A moderate-TBI mouse model was subjected to a controlled cortical impact device. Maraviroc or vehicle was injected intraperitoneally 1 hour after TBI and then once per day for 3 consecutive days. Western blot, immunohistochemistry, and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) analyses were performed to evaluate the molecular mechanisms of maraviroc at 3 days post-TBI. Our results suggest that maraviroc administration reduced NACHT, LRR, and PYD domains-containing protein 3 inflammasome activation, modulated microglial polarization from M1 to M2, decreased neutrophil and macrophage infiltration, and inhibited the release of inflammatory factors after TBI. Moreover, maraviroc treatment decreased the activation of neurotoxic reactive astrocytes, which, in turn, exacerbated neuronal cell death. Additionally, we confirmed the neuroprotective effect of maraviroc using the modified neurological severity score, rotarod test, Morris water maze test, and lesion volume measurements. In summary, our findings indicate that maraviroc might be a desirable pharmacotherapeutic strategy for TBI, and C-C chemokine receptor type 5 might be a promising pharmacotherapeutic target to improve recovery after TBI.

Inflammasomes as biomarkers and therapeutic targets in traumatic brain injury and related-neurodegenerative diseases: A comprehensive overview

Given the ambiguity surrounding traumatic brain injury (TBI) pathophysiology and the lack of any Food and Drug Administration (FDA)-approved neurotherapeutic drugs, there is an increasing need to better understand the mechanisms of TBI. Recently, the roles of inflammasomes have been highlighted as both potential therapeutic targets and diagnostic markers in different neurodegenerative disorders. Indeed, inflammasome activation plays a pivotal function in the central nervous system (CNS) response to many neurological conditions, as well as to several neurodegenerative disorders, specifically, TBI. This comprehensive review summarizes and critically discusses the mechanisms that govern the activation and assembly of inflammasome complexes and the major methods used to study inflammasome activation in TBI and its implication for other neurodegenerative disorders. Also, we will review how inflammasome activation is critical in CNS homeostasis and pathogenesis, and how it can impact chronic TBI sequalae and increase the risk of developing neurodegenerative diseases. Additionally, we discuss the recent updates on inflammasome-related biomarkers and the potential to utilize inflammasomes as putative therapeutic targets that hold the potential to better diagnose and treat subjects with TBI.

Brain edema formation and therapy after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) accounts for about 10% of all strokes in the United States of America causing a high degree of disability and mortality. There is initial (primary) brain injury due to the mechanical disruption caused by the hematoma. There is then secondary injury, triggered by the initial injury but also the release of various clot-derived factors (e.g., thrombin and hemoglobin). ICH alters brain fluid homeostasis. Apart from the initial hematoma mass, ICH causes blood-brain barrier disruption and parenchymal cell swelling, which result in brain edema and intracranial hypertension affecting patient prognosis. Reducing brain edema is a critical part of post-ICH care. However, there are limited effective treatment methods for reducing perihematomal cerebral edema and intracranial pressure in ICH. This review discusses the mechanisms underlying perihematomal brain edema formation, the effects of sex and age, as well as how edema is resolved. It examines progress in pharmacotherapy, particularly focusing on drugs which have been or are currently being investigated in clinical trials.

What type of cell death occurs in chronic cerebral hypoperfusion? A review focusing on pyroptosis and its potential therapeutic implications

Chronic cerebral hypoperfusion (CCH) is a major global disease with chronic cerebral blood flow reduction. It is also the main cause of cognitive impairment and neurodegenerative diseases. Pyroptosis, a novel form of cell death, is characterized by the rupture of the cell membrane and the release of pro-inflammatory mediators. In recent years, an increasing number of studies have identified the involvement of pyroptosis and its mediated inflammatory response in the pathological process of CCH. Therefore, preventing the activation of pyroptosis following CCH is beneficial to inhibit the inflammatory cascade and reduce brain injury. In this review, we discuss the research progress on the relationship between pyroptosis and CCH, in order to provide a reference for research in related fields.

Secondary White Matter Injury Mediated by Neuroinflammation after Intracerebral Hemorrhage and Promising Therapeutic Strategies of Targeting the NLRP3 Inflammasome

Intracerebral hemorrhage (ICH) is a neurological disease with high mortality and disability. Recent studies showed that white matter injury (WMI) plays an important role in motor dysfunction after ICH. WMI includes WMI proximal to the lesion and WMI distal to the lesion, such as corticospinal tract injury located at the cervical enlargement of the spinal cord after ICH. Previous studies have tended to focus only on gray matter (GM) injury after ICH, and fewer studies have paid attention to WMI, which may be one of the reasons for the poor outcome of previous drug treatments. Microglia and astrocyte-mediated neuroinflammation are significant mechanisms responsible for secondary WMI following ICH. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome activation, has been shown to exacerbate neuroinflammation and brain injury after ICH. Moreover, NLRP3 inflammasome is activated in microglia and astrocytes and exerts a vital role in microglia and astrocytes-mediated neuroinflammation. We speculate that NLRP3 inflammasome activation is closely related to the polarization of microglia and astrocytes and that NLRP3 inflammasome activation may exacerbate WMI by polarizing microglia and astrocytes to the pro-inflammatory phenotype after ICH, while NLRP3 inflammasome inhibition may attenuate WMI by polarizing microglia and astrocytes to the anti-inflammatory phenotype following ICH. Therefore, NLRP3 inflammasome may act as leveraged regulatory fulcrums for microglia and astrocytes polarization to modulate WMI and WM repair after ICH. This review summarized the possible mechanisms by which neuroinflammation mediated by NLRP3 inflammasome exacerbates secondary WMI after ICH and discussed the potential therapeutic targets.

Glial Cells Response in Stroke

As the second-leading cause of death, stroke faces several challenges in terms of treatment because of the limited therapeutic interventions available. Previous studies primarily focused on metabolic and blood flow properties as a target for treating stroke, including recombinant tissue plasminogen activator and mechanical thrombectomy, which are the only USFDA approved therapies. These interventions have the limitation of a narrow therapeutic time window, the possibility of hemorrhagic complications, and the expertise required for performing these interventions. Thus, it is important to identify the contributing factors that exacerbate the ischemic outcome and to develop therapies targeting them for regulating cellular homeostasis, mainly neuronal survival and regeneration. Glial cells, primarily microglia, astrocytes, and oligodendrocytes, have been shown to have a crucial role in the prognosis of ischemic brain injury, contributing to inflammatory responses. They play a dual role in both the onset as well as resolution of the inflammatory responses. Understanding the different mechanisms driving these effects can aid in the development of therapeutic targets and further mitigate the damage caused. In this review, we summarize the functions of various glial cells and their contribution to stroke pathology. The review highlights the therapeutic options currently being explored and developed that primarily target glial cells and can be used as neuroprotective agents for the treatment of ischemic stroke.

Therapeutic effects of CD133 + Exosomes on liver function after stroke in type 2 diabetic mice

Background and purpose

Non-alcoholic fatty liver disease (NAFLD) is known to adversely affect stroke recovery. However, few studies investigate how stroke elicits liver dysfunction, particularly, how stroke in type 2 diabetes mellitus (T2DM) exacerbates progression of NAFLD. In this study, we test whether exosomes harvested from human umbilical cord blood (HUCBC) derived CD133 + cells (CD133 + Exo) improves neuro-cognitive outcome as well as reduces liver dysfunction in T2DM female mice.

Methods

Female, adult non-DM and T2DM mice subjected to stroke presence or absence were considered. T2DM-stroke mice were randomly assigned to receive PBS or Exosome treatment group. CD133 + Exo (20 μg/200 μl PBS, i.v.) was administered once at 3 days after stroke. Evaluation of neurological (mNSS, adhesive removal test) and cognitive function [novel object recognition (NOR) test, odor test] was performed. Mice were sacrificed at 28 days after stroke and brain, liver, and serum were harvested.

Results

Stroke induces severe and significant short-term and long-term neurological and cognitive deficits which were worse in T2DM mice compared to non-DM mice. CD133 + Exo treatment of T2DM-stroke mice significantly improved neurological function and cognitive outcome indicated by improved discrimination index in the NOR and odor tests compared to control T2DM-stroke mice. CD133 + Exo treatment of T2DM stroke significantly increased vascular and white matter/axon remodeling in the ischemic brain compared to T2DM-stroke mice. However, there were no differences in the lesion volume between non-DM stroke, T2DM-stroke and CD133 + Exo treated T2DM-stroke mice. In T2DM mice, stroke induced earlier and higher TLR4, NLRP3, and cytokine expression (SAA, IL1β, IL6, TNFα) in the liver compared to heart and kidney, as measured by Western blot. T2DM-stroke mice exhibited worse NAFLD progression with increased liver steatosis, hepatocellular ballooning, fibrosis, serum ALT activity, and higher NAFLD Activity Score compared to T2DM mice and non-DM-stroke mice, while CD133 + Exo treatment significantly attenuated the progression of NAFLD in T2DM stroke mice.

Conclusion

Treatment of female T2DM-stroke mice with CD133 + Exo significantly reduces the progression of NAFLD/NASH and improves neurological and cognitive function compared to control T2DM-stroke mice.

Oxymatrine ameliorates white matter injury by modulating gut microbiota after intracerebral hemorrhage in mice

INTRODUCTION

White matter injury (WMI) significantly affects neurobehavioral recovery in intracerebral hemorrhage (ICH) patients. Gut dysbiosis plays an important role in the pathogenesis of neurological disorders. Oxymatrine (OMT) has therapeutic effects on inflammation-mediated diseases. Whether OMT exerts therapeutic effects on WMI after ICH and the role of gut microbiota involved in this process is largely unknown.

METHODS

Neurological deficits, WMI, gut microbial composition, intestinal barrier function, and systemic inflammation were investigated after ICH. Fecal microbiota transplantation (FMT) was performed to elucidate the role of gut microbiota in the pathogenesis of ICH.

RESULTS

OMT promoted long-term neurological function recovery and ameliorated WMI in the peri-hematoma region and distal corticospinal tract (CST) region after ICH. ICH induced significant and persistent gut dysbiosis, which was obviously regulated by OMT. In addition, OMT alleviated intestinal barrier dysfunction and systemic inflammation. Correlation analysis revealed that gut microbiota alteration was significantly correlated with inflammation, intestinal barrier permeability, and neurological deficits after ICH. Moreover, OMT-induced gut microbiota alteration could confer protection against neurological deficits and intestinal barrier disruption.

CONCLUSIONS

Our study demonstrates that OMT ameliorates ICH-induced WMI and neurological deficits by modulating gut microbiota.

Therapeutic strategies for intracerebral hemorrhage

Stroke is the second highest cause of death globally, with an increasing incidence in developing countries. Intracerebral hemorrhage (ICH) accounts for 10-15% of all strokes. ICH is associated with poor neurological outcomes and high mortality due to the combination of primary and secondary injury. Fortunately, experimental therapies are available that may improve functional outcomes in patients with ICH. These therapies targeting secondary brain injury have attracted substantial attention in their translational potential. Here, we summarize recent advances in therapeutic strategies and directions for ICH and discuss the barriers and issues that need to be overcome to improve ICH prognosis.

Inhibition of Dectin-1 Alleviates Neuroinflammatory Injury by Attenuating NLRP3 Inflammasome-Mediated Pyroptosis After Intracerebral Hemorrhage in Mice: Preliminary Study Results

BACKGROUND

Neuroinflammation plays an important role following intracerebral hemorrhage (ICH). NLRP3 inflammasome-mediated pyroptosis contributes to the mechanism of neuroinflammation. It has been reported that dendritic cell-associated C-type lectin-1 (Dectin-1) activation triggers inflammation in neurological diseases. However, the role of Dectin-1 on NLRP3 inflammasome-mediated pyroptosis after ICH remains unclear. Here, we aimed to explore the effect of Dectin-1 on NLRP3 inflammasome-mediated pyroptosis and neuroinflammation after ICH.

METHODS

Adult male C57BL/6 mice were used to establish the ICH model. Laminarin, an inhibitor of Dectin-1, was administered for intervention. Expression of Dectin-1 was evaluated by Western blot and immunofluorescence. Brain water content and neurobehavioral function were tested to assess brain edema and neurological performance. Western blot was conducted to evaluate the level of GSDMD-N. ELISA kits were used to measure the levels of IL-1β and IL-18. qRT-PCR and Western blot were performed to evaluate the expressions of NLRP3 inflammasome, IL-1β, and IL-18.

RESULTS

The expression of Dectin-1 increased following ICH, and Dectin-1 was expressed on microglia. In addition, inhibition of Dectin-1 by laminarin decreased brain edema and neurological impairment after ICH. Moreover, inhibition of Dectin-1 decreased the expression of pyroptosis-related protein, GSDMD-N, and inflammatory cytokines (IL-1β and IL-18). Mechanistically, Dectin-1 blockade inhibits NLRP3 inflammasome activation, thereby alleviating neuroinflammatory injury by attenuating NLRP3 inflammasome-mediated pyroptosis both in vivo and in vitro.

CONCLUSION

Our study indicates that the inhibition of Dectin-1 alleviates neuroinflammation by attenuating NLRP3 inflammasome-mediated pyroptosis after ICH.

Emerging trends and hot spots of NLRP3 inflammasome in neurological diseases: A bibliometric analysis

Background: NLRP3 inflammasome has been of great interest in the field of neurological diseases. To visualize the research hotspots and evolutionary trends in this area, we collected the relevant articles in the Web of Science Core Collection database from 2010 to 2022 and analyzed them using CiteSpace software.

Methods: We performed a systematic search of the literature within the Web of Science Core Collection database using the strategy described below: TS = NLRP3 inflammasome AND TS = neurological diseases OR TS = neurological disorder OR TS = brain disorder OR TS = brain injury OR TS = central nervous system disease OR TS = CNS disease OR TS = central nervous system disorder OR TS = CNS disorder AND Language = English from 2010 to 2022. The type of literature was limited to articles and reviews. The data were processed using CiteSpace software (version 5.8. R3).

Results: A total of 1,217 literature from 67 countries/regions and 337 research institutions was retrieved. Publications in this area have increased rapidly since 2013. China presents the highest number of published articles, but the United States has a higher centrality and h-index. The top five most published institutions and authors are from China, Zhejiang University and Li Y ranking first, respectively. Of the ten most cited articles, Prof. Heneka MT and colleagues accounted for three of them. In terms of the co-occurrence keyword diagram, the five most frequent keywords are “nlrp3 inflammasome”, “activation”, “oxidative stress”, “expression”, and “alzheimers disease”.

Conclusion: The research of NLRP3 inflammasome in neurological disorders is overall developing well. Chinese scholars contributed the most significant number of articles, while researchers from developed countries presented more influential papers. The importance of NLRP3 inflammasome in neurological diseases is widely appreciated, and the mechanism is under study. Moreover, NLRP3 inflammasome is emerging as a promising therapeutic target in treating neurological disorders. However, despite decades of research, our understanding of NLRP3 inflammasome in central nervous system diseases is still lacking. More and more profound research is needed in the future.

Perspectives on the mechanism of pyroptosis after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a highly harmful neurological disorder with high rates of mortality, disability, and recurrence. However, effective therapies are not currently available. Secondary immune injury and cell death are the leading causes of brain injury and a poor prognosis. Pyroptosis is a recently discovered form of programmed cell death that differs from apoptosis and necrosis and is mediated by gasdermin proteins. Pyroptosis is caused by multiple pathways that eventually form pores in the cell membrane, facilitating the release of inflammatory substances and causing the cell to rupture and die. Pyroptosis occurs in neurons, glial cells, and endothelial cells after ICH. Furthermore, pyroptosis causes cell death and releases inflammatory factors such as interleukin (IL)-1β and IL-18, leading to a secondary immune-inflammatory response and further brain damage. The NOD-like receptor protein 3 (NLRP3)/caspase-1/gasdermin D (GSDMD) pathway plays the most critical role in pyroptosis after ICH. Pyroptosis can be inhibited by directly targeting NLRP3 or its upstream molecules, or directly interfering with caspase-1 expression and GSDMD formation, thus significantly improving the prognosis of ICH. The present review discusses key pathological pathways and regulatory mechanisms of pyroptosis after ICH and suggests possible intervention strategies to mitigate pyroptosis and brain dysfunction after ICH.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Promote Angiogenesis in Ischemic Stroke Mice via Upregulation of MiR-21-5p

Exosomes derived from bone mesenchymal stem cells (BMSC-Exos) are one of the main factors responsible for the therapeutic effects of BMSCs. The study aimed to investigate whether BMSC-Exos could promote angiogenesis in ischemic stroke mice via miR-21-5p. In ischemic stroke mice, the therapeutic effects of BMSC-Exos were evaluated by neurological functions and infarct volume. Microvessel density was detected by BrdU/vWF immunofluorescence staining. In in vitro experiments, the proangiogenic effects of BMSC-Exos were assessed via proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs). The miR-21-5p inhibitor was transfected into BMSCs using Lipofectamine 2000. miR-21-5p expression was detected by qRT-PCR. The expression levels of VEGF, VEGFR2, Ang-1, and Tie-2 were determined by Western blot. BMSC-Exos significantly improved neurological functions and reduced infarct volume, upregulated microvessel density, and miR-21-5p expression after cerebral ischemia. In vitro assays revealed that BMSC-Exos enhanced HUVECs functions including proliferation, migration, and tube formation. BMSC-Exos increased the expression levels of VEGF, VEGFR2, Ang-1, and Tie-2. However, the proangiogenic effects of BMSC-Exos on HUVECs were reversed by the miR-21-5p inhibitor. These results suggest that BMSC-Exos could promote angiogenesis via miR-21-5p upregulation, making them an attractive treatment strategy for stroke recovery.

NLRP3 inflammasome-mediated choroid plexus hypersecretion contributes to hydrocephalus after intraventricular hemorrhage via phosphorylated NKCC1 channels

Background

Hydrocephalus is a severe complication of intracerebral hemorrhage with ventricular extension (ICH-IVH) and causes cerebrospinal fluid (CSF) accumulation. The choroid plexus epithelium plays an important role in CSF secretion and constitutes the blood–CSF barrier within the brain–immune system interface. Although the NLRP3 inflammasome, as a key component of the innate immune system, promotes neuroinflammation, its role in the pathogenesis of hydrocephalus after hemorrhage has not been investigated. Therefore, this study aimed to investigate the potential mechanism of NLRP3 in hydrocephalus to discover a potential marker for targeted therapy.

Methods

A rat model of hydrocephalus after ICH-IVH was developed through autologous blood infusion in wild-type and Nlrp3^−/− rats. By studying the features and processes of the model, we investigated the relationship between the NLRP3 inflammasome and CSF hypersecretion in the choroid plexus.

Results

The ICH-IVH model rats showed ventricular dilation accompanied by CSF hypersecretion for 3 days. Based on the choroid plexus RNA-seq and proteomics results, we found that an inflammatory response was activated. The NLRP3 inflammasome was investigated, and the expression levels of NLRP3 inflammasome components reached a peak at 3 days after ICH-IVH. Inhibition of NLRP3 by an MCC950 inflammasome inhibitor or Nlrp3 knockout decreased CSF secretion and ventricular dilation and attenuated neurological deficits after ICH-IVH. The mechanism underlying the neuroprotective effects of NLRP3 inhibition involved decreased phosphorylation of NKCC1, which is a major protein that regulates CSF secretion by altering Na⁺- and K⁺-coupled water transport, via MCC950 or Nlrp3 knockout. In combination with the in vitro experiments, this experiment confirmed the involvement of the NLRP3/p-NKCC1 pathway and Na⁺ and K⁺ flux.

Conclusions

This study demonstrates that NKCC1 phosphorylation in the choroid plexus epithelium promotes NLRP3 inflammasome-mediated CSF hypersecretion and that NLRP3 plays an important role in the pathogenesis of hydrocephalus after hemorrhage. These findings provide a new therapeutic strategy for treating hydrocephalus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02530-x.

Activating cGAS-STING axis contributes to neuroinflammation in CVST mouse model and induces inflammasome activation and microglia pyroptosis

Background

Neuroinflammation-induced injury is intimately associated with poor prognosis in patients with cerebral venous sinus thrombosis (CVST). The cyclic GMP-AMP synthase–stimulator of interferon gene (cGAS–STING) axis is a cytoplasmic double-stranded DNA (dsDNA) sensing pathway has recently emerged as a crucial mediator of neuroinflammation in ischemic stroke. However, the role of the cGAS–STING pathway in modulating post-CVST inflammation and the underlying mechanisms involved remain unclear.

Methods

A CVST model was induced by ferric chloride in male C57BL/6J mice. The selective cGAS inhibitor RU.521, STING agonist 2′3′-cGAMP, and STING siRNA were delivered by intranasal administration or intraventricular injection. Post-CVST assessments included rotarod test, TUNEL staining, Fluoro-Jade C staining, dihydroethidium staining, western blotting, qPCR, immunofluorescence, immunohistochemistry, ELISA and flow cytometry.

Results

cGAS, STING, NLRP3 and GSDMD were significantly upregulated after CVST and mostly in the microglia of the mouse brain. CVST triggered the release of dsDNA into the cytoplasm and elicited an inflammatory response via activating the cGAS–STING axis. RU.521 decreased the levels of 2′3′-cGAMP, STING and downstream inflammatory cytokines, and suppressed the expressions of NLRP3 inflammasome and pyroptosis-pertinent components containing cleaved caspase-1, GSDMD, GSDMD-C, pro- and cleaved IL-1β, and cleaved IL-1β/pro-IL-1β. Besides, RU.521 treatment also reduced oxidative stress, lessened the numbers of microglia and neutrophils, and ameliorated neuronal apoptosis, degeneration along with neurological deficits post-CVST. 2′3'-cGAMP delivery enhanced the expressions of STING and related inflammatory mediators, NLRP3 inflammasome and pyroptosis-relevant proteins, whereas these alterations were significantly abrogated by the silencing of STING by siRNA.

Conclusions

Our data demonstrate that repression of the cGAS–STING pathway diminishes the neuroinflammatory burden of CVST and highlight this approach as a potential therapeutic tactic in CVST-mediated pathologies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02511-0.