Neuroinflammation Mediated by NLRP3 Inflammasome After Intracerebral Hemorrhage and Potential Therapeutic Targets

Cholesterol metabolism: physiological versus pathological aspects in intracerebral hemorrhage

Cholesterol is an important component of plasma membranes and participates in many basic life functions, such as the maintenance of cell membrane stability, the synthesis of steroid hormones, and myelination. Cholesterol plays a key role in the establishment and maintenance of the central nervous system. The brain contains 20% of the whole body's cholesterol, 80% of which is located within myelin. A huge number of processes (e.g., the sterol regulatory element-binding protein pathway and liver X receptor pathway) participate in the regulation of cholesterol metabolism in the brain via mechanisms that include cholesterol biosynthesis, intracellular transport, and efflux. Certain brain injuries or diseases involving crosstalk among the processes above can affect normal cholesterol metabolism to induce detrimental consequences. Therefore, we hypothesized that cholesterol-related molecules and pathways can serve as therapeutic targets for central nervous system diseases. Intracerebral hemorrhage is the most severe hemorrhagic stroke subtype, with high mortality and morbidity. Historical cholesterol levels are associated with the risk of intracerebral hemorrhage. Moreover, secondary pathological changes after intracerebral hemorrhage are associated with cholesterol metabolism dysregulation, such as neuroinflammation, demyelination, and multiple types of programmed cell death. Intracellular cholesterol accumulation in the brain has been found after intracerebral hemorrhage. In this paper, we review normal cholesterol metabolism in the central nervous system, the mechanisms known to participate in the disturbance of cholesterol metabolism after intracerebral hemorrhage, and the links between cholesterol metabolism and cell death. We also review several possible and constructive therapeutic targets identified based on cholesterol metabolism to provide cholesterol-based perspectives and a reference for those interested in the treatment of intracerebral hemorrhage.

Neuroinflammation-mediated white matter injury in Parkinson's disease and potential therapeutic strategies targeting NLRP3 inflammasome

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, severely affecting the quality of life of patients. Recent studies have shown that white matter (WM) plays a vital role in higher neurological functions such as behavior and cognition. In PD patients, neurodegeneration occurs not only in neuronal soma, but also in WM fiber bundles, which are composed of neural axons. The clinical symptoms of PD patients are related not only to the degeneration of neuronal soma, but also to the degeneration of WM. Most previous studies have focused on neuronal soma in substantia nigra (SN), while WM injury (WMI) in PD has been less studied. Moreover, most previous studies have focused on intracerebral lesions in PD, while less attention has been paid to the spinal cord distal to the brain. The above-mentioned factors may be one of the reasons for the poor treatment of previous drug outcomes. Neuroinflammation has been shown to exert a significant effect on the pathological process of brain and spinal cord neurodegeneration in PD. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome has been shown to activate and mediate neuroinflammation and exacerbate neurodegeneration in PD. NLRP3 inflammasome inhibition may be a potential strategy for the treatment of WMI in PD. This review summarizes recent advances and future directions regarding neuroinflammation-mediated WMI in PD and potential therapeutic strategies for targeting NLRP3 inflammasome in the brain and spinal cord, providing new insights for researchers to develop more effective therapeutic approaches for PD patients.

Cystatin C Attenuates Perihematomal Secondary Brain Injury by Inhibiting the Cathepsin B/NLRP3 Signaling Pathway in a Rat Model of Intracerebral Hemorrhage

Secondary brain injury (SBI) is a noticeable contributor to the high mortality and morbidity rates associated with intracerebral hemorrhage (ICH), and effective treatment options remain limited. Cystatin C (CysC) emerges as a novel candidate for SBI intervention. The therapeutic effects and underlying mechanisms of CysC in mitigating SBI following ICH were explored in the current research. An in vivo ICH rat model was established by injecting autologous blood into the right caudate nucleus. Western blotting (WB) was utilized to assess the levels of CysC, cathepsin B (CTSB), and the NLRP3 inflammasome. Subsequently, the ICH rat model was treated with exogenous CysC supplementation or CysC knockdown plasmids. Various parameters, including Evans blue (EB) extravasation, brain water content, and neurological function in rats, were examined. RT-qPCR and WB were employed to determine the expression levels of CTSB and the NLRP3 inflammasome. The co-expression of CTSB, CysC, and NLRP3 inflammasome with GFAP, NeuN, and Iba1 was assessed through double-labeled immunofluorescence. The interaction between CysC and CTSB was investigated using double-labeled immunofluorescence and co-immunoprecipitation. The findings revealed an elevation of CysC expression level, particularly at 24 h after ICH. Exogenous CysC supplementation alleviated severe brain edema, neurological deficit scores, and EB extravasation induced by ICH. Conversely, CysC knockdown produced opposite effects. The expression levels of CTSB and the NLRP3 inflammasome were significantly risen following ICH, and exogenous CysC supplement attenuated their expression levels. Double-labeled immunofluorescence illustrated that CysC, CTSB, and the NLRP3 inflammasome were predominantly expressed in microglial cells, and the interaction between CysC and CTSB was evidenced. CysC exhibited potential in ameliorating SBI following ICH via effectively suppressing the activation of the NLRP3 inflammasome mediated by CTSB specifically in microglial cells. These findings underscore the prospective therapeutic efficacy of CysC in the treatment of ICH-induced complications.

PPARβ/δ Agonist GW0742 Modulates Microglial and Astroglial Gene Expression in a Rat Model of Temporal Lobe Epilepsy

The role of astroglial and microglial cells in the pathogenesis of epilepsy is currently under active investigation. It has been proposed that the activity of these cells may be regulated by the agonists of peroxisome proliferator-activated nuclear receptors (PPARs). This study investigated the effects of a seven-day treatment with the PPAR β/δ agonist GW0742 (Fitorine, 5 mg/kg/day) on the behavior and gene expression of the astroglial and microglial proteins involved in the regulation of epileptogenesis in the rat brain within a lithium-pilocarpine model of temporal lobe epilepsy (TLE). TLE resulted in decreased social and increased locomotor activity in the rats, increased expression of astro- and microglial activation marker genes (Gfap, Aif1), pro- and anti-inflammatory cytokine genes (Tnfa, Il1b, Il1rn), and altered expression of other microglial (Nlrp3, Arg1) and astroglial (Lcn2, S100a10) genes in the dorsal hippocampus and cerebral cortex. GW0742 attenuated, but did not completely block, some of these impairments. Specifically, the treatment affected Gfap gene expression in the dorsal hippocampus and Aif1 gene expression in the cortex. The GW0742 injections attenuated the TLE-specific enhancement of Nlrp3 and Il1rn gene expression in the cortex. These results suggest that GW0742 may affect the expression of some genes involved in the regulation of epileptogenesis.

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.

Protective effects of flavonoids against intracerebral and subarachnoid hemorrhage (Review)

Intracerebral hemorrhage (ICH), known as non-traumatic cerebrovascular rupture and hemorrhage, often occurs in the deep basal brain segment. It is known for its high morbidity and mortality rates. Subarachnoid hemorrhage (SAH) is a clinical syndrome caused by the rupture of blood vessels at the base or surface of the brain that allows blood to flow directly into the subarachnoid space. It progresses quickly and typically manifests at younger ages compared with ICH. ICH and SAH are both devastating events in the category of hemorrhagic strokes and are attracting increasing attention from researchers. Flavonoids, being important natural molecules, have remarkable anti-inflammatory and antioxidant effects. Flavonoids have extensive biological activities in inflammation and oxidative stress (OS), and have protective effects in vascular function associated with cerebrovascular diseases. They have an impact on the onset of ICH and SAH by targeting various pathways, including the suppression of inflammation and OS. Recently, the role of flavonoid compounds in ICH and SAH has also received increasing interest. Thus, to serve as a resource for the prevention and treatment of ICH and SAH, the present review provided an overview of the research on flavonoid compounds in the prevention of brain damage after these two conditions have occurred.

Piezo1 inhibitor isoquercitrin rescues neural impairment mediated by NLRP3 after intracerebral hemorrhage

In intracerebral hemorrhage (ICH), the mechanical brain injury is a considerable and indispensable factor determining the neurological functions and poor outcomes. Previous studies indicate the mechanically gated ion channel-Piezo1 can transduce mechanical effects following ICH. Isoquercitrin (ISQ) is a well-studied ion channel inhibitor. Furthermore, whether the following Piezo1-mediated neurological impairment can be ameliorated by ISQ remains unclear. Herein, we constructed the hydrostatic pressure model and ICH rat model. Firstly, we found that Piezo1 agonists Yoda1 and Jedi1 facilitated extracellular calcium influx dramatically, but ISQ could depress intracellular Ca2+ overload under hydrostatic pressure in primary neurons. Then we detected the expression profile of Piezo1, NLRP3 and NF-κB p-p65 after ICH, and found that the expression of Piezo1 was much earlier than NLRP3 and NF-κB p-p65. Furthermore, by western blot and immunofluorescence, ISQ decreased the expression of Piezo1 and NLRP3 dramatically like GsMTx4, but Nigericin as a NLRP3 agonist failed to affect Piezo1. Besides, both ISQ and interfering Piezo1 suppressed the upregulated caspase-1, NF-κB p-p65, p-IκBα, Tunel-positive cells and inflammatory factors (IL-1β, IL-6 and TNF-α) in ICH. At last, the hydrostatic pressure or hematoma induced disturbed neural viability, disordered neural cytomorphology, and increased neurobehavioral and cognitive deficits, but they were improved by ISQ and GsMTx4 strongly. Therefore, ISQ could alleviate neurological injuries induced by Piezo1 via NLRP3 pathway. These observations indicated that Piezos might be the new therapeutic targets, and blocking Piezos/NLRP3 pathway by ISQ could be an auspicious strategy for the treatment of ICH.

CYR61 is Involved in Neonatal Hypoxic-ischemic Brain Damage Via Modulating Astrocyte-mediated Neuroinflammation

The activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in astrocytes has been found in the hypoxic-ischemic brain damage (HIBD) model. Cysteine rich angiogenic inducer 61 (CYR61) is secreted by reactive astrocytes. However, the effects of CYR61 on HIBD and its related mechanisms remain unclear. This study sought to explore the role of CYR61 in the activation of astrocytes and the NLRP3 inflammasome in neonatal HIBD. HIBD models were established in 7-day Sprague-Dawley rat pups. Neurobehavioral evaluation and 2,3,5-triphenyl-tetrazolium chloride staining were performed. In addition, rat primary astrocytes were used to establish the cell model of HIBD in vitro by oxygen-glucose deprivation/reperfusion (OGD/R). Then, CYR61-overexpression and sh-CYR61 viruses mediated by lentivirus were transduced into ODG/R-treated primary astrocytes. The expressions of related genes were evaluated using real-time quantitative PCR, western blot, immunofluorescence staining, and Enzyme-linked immunosorbent assay. The results showed that hypoxia-ischemia induced short-term neurological deficits, neuronal damage, and cerebral infarction in neonatal rats. In vivo, the expressions of CYR61, NLRP3, and glial fibrillary acidic protein (GFAP) were up-regulated in the HIBD model. In vitro, CYR61 exhibited high expression. CYR61 overexpression increased the expressions of GFAP and C3, whereas decreased S100A10 expression. CYR61 overexpression increased the expression of NLRP3, ASC, caspase-1 p20 and IL-1β. CYR61 overexpression activated NF-κB by promoting the phosphorylation of IκBα and p65. Thus, CYR61 is involved in neonatal HIBD progress, which may be related to the activation of astrocytes, the NLRP3 inflammasome, and the NF-κB signaling pathway.

P2Y6 Receptor Activation Aggravates NLRP3-dependent Microglial Pyroptosis via Downregulation of the PI3K/AKT Pathway in a Mouse Model of Intracerebral Hemorrhage

Pro-inflammatory signals generated after intracerebral hemorrhage (ICH) trigger a form of regulated cell death known as pyroptosis in microglia. White matter injury (WMI) refers to the condition where the white matter area of the brain suffers from mechanical, ischemic, metabolic, or inflammatory damage. Although the p2Y purinoceptor 6 (P2Y6R) plays a significant role in the control of inflammatory reactions in central nervous system diseases, its roles in the development of microglial pyroptosis and WMI following ICH remain unclear. In this study, we sought to clarify the role of P2Y6R in microglial pyroptosis and WMI by using an experimental mouse model of ICH. Type IV collagenase was injected into male C57BL/6 mice to induce ICH. Mice were then treated with MRS2578 and LY294002 to inhibit P2Y6R and phosphatidylinositol 3-kinase (PI3K), respectively. Bio-conductivity analysis was performed to examine PI3K/AKT pathway involvement in microglial pyroptosis. Quantitative Real-Time PCR, immunofluorescence staining, and western blot were conducted to examine microglial pyroptosis and WMI following ICH. A modified Garcia test, corner turning test, and forelimb placement test were used to assess neurobehavior. Hematoxylin-eosin staining (HE) was performed to detect cells damage around hematoma. Increases in the expression of P2Y6R, NLRP3, ASC, Caspase-1, and GSDMD were observed after ICH. P2Y6R was only expressed on microglia. MRS2578, a specific inhibitor of P2Y6R, attenuated short-term neurobehavioral deficits, brain edema and hematoma volume while improving both microglial pyroptosis and WMI. These changes were accompanied by decreases in pyroptosis-related proteins and pro-inflammatory cytokines both in vivo and vitro. Bioinformatic analysis revealed an association between the PI3K/AKT pathway and P2Y6R-mediated microglial pyroptosis. The effects of MRS2578 were partially reversed by treatment with LY294002, a specific PI3K inhibitor. P2Y6R inhibition alleviates microglial pyroptosis and WMI and ameliorates neurological deficits through the PI3K/AKT pathway after ICH. Consequently, targeting P2Y6R might be a promising approach for ICH treatment.

Implication of M2 macrophage on NLRP3 inflammasome signaling in mediating the neuroprotective effect of Canagliflozin against methotrexate-induced cognitive impairment

Methotrexate (MTX), a chemotherapeutic antimetabolite, has been linked to cognitive impairment in cancer patients. MTX-induced metabolic pathway disruption may result in decreased antioxidant activity and increased oxidative stress, influencing hippocampal neurogenesis and microglial activation. Nuclear factor-kappa B (NF-κB), an oxidative stress byproduct, has been linked to MTX toxicity via the activation of NLRP3 inflammasome signaling. Macrophage activation and polarization plays an important role in tissue injury. This differentiation may be mediated via either the Toll-like receptor 4 (TLR4) or NLRP3 inflammasome. Interestingly, Canagliflozin (CANA), a sodium-glucose cotransporter 2 (SGLT2) inhibitor has been recently reported to exert anti-inflammatory effects by modulating macrophage polarization balance. This study aimed to investigate CANA's protective effect against MTX-induced cognitive impairment, highlighting the possible involvement of TLR4/ NF-κB crosstalk with NLRP3 inflammasome activation and macrophage polarization. Forty-eight Male Wistar rats were divided into 4 groups; (1) received saline orally for 30 days and intravenously on days 8 and 15. (2) received Canagliflozin (CANA; 20 mg/kg/day; p.o.) for 30 days. (3) received MTX (75 mg/kg, i.v.) on day 8 and 15, then they were injected with four i.p. injections of leucovorin (LCV): the first dose was 6 mg/ kg after 18 h, and the remaining doses were 3 mg/kg after 26, 42, and 50 h of MTX administration. (4) received MTX and LCV as in group 3 in addition to CANA as in group 2. MTX-treated rats showed cognitive deficits in spatial and learning memory as evidenced in the novel object recognition and Morris water maze tests. MTX exerted an oxidative effect which was evident by the increase in MDA and decline in SOD, GSH and GPx. Moreover, it exerted an inflammatory effect via elevated caspase-1, IL-1β and IL-8. CANA treatment restored cognitive ability, reduced MTX-induced oxidative stress and neuroinflammation via attenuation of TLR4/NF-κB/NLRP3 signaling, and rebalanced macrophage polarization by promoting the M2 phenotype. Hence, targeting molecular mechanisms manipulating macrophage polarization may offer novel neuroprotective strategies for preventing or treating MTX-induced immune modulation and its detrimental sequel.

A Prospective Cohort Study of Elevated Serum NLRP1 Levels to Prognosticate Neurological Outcome After Acute Intracerebral Hemorrhage at a Single Academic Institution

Background

Nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 1 (NLRP1) participates in neuroinflammation. This study aimed to identify serum NLRP as a potential prognostic biomarker of acute intracerebral hemorrhage (ICH).

Methods

This prospective cohort study enrolled 145 patients with supratentorial ICH and 51 healthy controls. Serum NLRP1 levels were quantified on admission of all 145 patients, on days 1, 3, 5, 7, and 10 after stroke in 51 of 145 patients and at entry into the study of controls. Poststroke 6-month modified Rankin Scale (mRS) scores of 3-6 signified a poor prognosis.

Results

Compared to controls, patients had prominently increased serum NLRP1 levels until day 10 after ICH, with the highest levels at days 1 and 3. Serum NLRP1 levels were independently correlated with National Institutes of Health Stroke Scale (NIHSS) scores, hematoma volume and six-month mRS scores, and independently predicted six-month bad prognosis. A linear relationship was observed between serum NLRP1 levels and the risk of poor prognosis in a restricted cubic spline. Under the receiver operating characteristic (ROC) curve, serum NLRP levels efficiently discriminated poor prognosis. Serum NLRP1, NIHSS, and hematoma volume were merged into a prognosis prediction model, which was portrayed using a nomogram. Good performance of the model was verified using calibration curve, decision curve, and ROC curve.

Conclusion

Serum NLRP1 levels are elevated during the early period following ICH and are independently related to hemorrhagic severity and poor prognosis, suggesting that serum NLRP1 may represent a promising prognostic biomarker of ICH.

Pretreated MSCs with IronQ Transplantation Attenuate Microglia Neuroinflammation via the cGAS-STING Signaling Pathway

Background

Intracerebral hemorrhage (ICH), a devastating form of stroke, is characterized by elevated morbidity and mortality rates. Neuroinflammation is a common occurrence following ICH. Mesenchymal stem cells (MSCs) have exhibited potential in treating brain diseases due to their anti-inflammatory properties. However, the therapeutic efficacy of MSCs is limited by the intense inflammatory response at the transplantation site in ICH. Hence, enhancing the function of transplanted MSCs holds considerable promise as a therapeutic strategy for ICH. Notably, the iron-quercetin complex (IronQ), a metal-quercetin complex synthesized through coordination chemistry, has garnered significant attention for its biomedical applications. In our previous studies, we have observed that IronQ exerts stimulatory effects on cell growth, notably enhancing the survival and viability of peripheral blood mononuclear cells (PBMCs) and MSCs. This study aimed to evaluate the effects of pretreated MSCs with IronQ on neuroinflammation and elucidate its underlying mechanisms.

Methods

The ICH mice were induced by injecting the collagenase I solution into the right brain caudate nucleus. After 24 hours, the ICH mice were randomly divided into four subgroups, the model group (Model), quercetin group (Quercetin), MSCs group (MSCs), and pretreated MSCs with IronQ group (MSCs+IronQ). Neurological deficits were re-evaluated on day 3, and brain samples were collected for further analysis. TUNEL staining was performed to assess cell DNA damage, and the protein expression levels of inflammatory factors and the cGAS-STING signaling pathway were investigated and analyzed.

Results

Pretreated MSCs with IronQ effectively mitigate neurological deficits and reduce neuronal inflammation by modulating the microglial polarization. Moreover, the pretreated MSCs with IronQ suppress the protein expression levels of the cGAS-STING signaling pathway.

Conclusion

These findings suggest that pretreated MSCs with IronQ demonstrate a synergistic effect in alleviating neuroinflammation, thereby improving neurological function, which is achieved through the inhibition of the cGAS-STING signaling pathway.

New Insights on NLRP3 Inflammasome: Mechanisms of Activation, Inhibition, and Epigenetic Regulation

Inflammasomes are important modulators of inflammation. Dysregulation of inflammasomes can enhance vulnerability to conditions such as neurodegenerative diseases, autoinflammatory diseases, and metabolic disorders. Among various inflammasomes, Nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) is the best-characterized inflammasome related to inflammatory and neurodegenerative diseases. NLRP3 is an intracellular sensor that recognizes pathogen-associated molecular patterns and damage-associated patterns resulting in the assembly and activation of NLRP3 inflammasome. The NLRP3 inflammasome includes sensor NLRP3, adaptor apoptosis-associated speck-like protein (ASC), and effector cysteine protease procaspase-1 that plays an imperative role in caspase-1 stimulation which further initiates a secondary inflammatory response. Regulation of NLRP3 inflammasome ameliorates NLRP3-mediated diseases. Much effort has been invested in studying the activation, and exploration of specific inhibitors and epigenetic mechanisms controlling NLRP3 inflammasome. This review gives an overview of the established NLRP3 inflammasome assembly, its brief molecular mechanistic activations as well as a current update on specific and non-specific NLRP3 inhibitors that could be used in NLRP3-mediated diseases. We also focused on the recently discovered epigenetic mechanisms mediated by DNA methylation, histone alterations, and microRNAs in regulating the activation and expression of NLRP3 inflammasome, which has resulted in a novel method of gaining insight into the mechanisms that modulate NLRP3 inflammasome activity and introducing potential therapeutic strategies for CNS disorders.

Mitophagy in intracerebral hemorrhage: a new target for therapeutic intervention

Intracerebral hemorrhage is a life-threatening condition with a high fatality rate and severe sequelae. However, there is currently no treatment available for intracerebral hemorrhage, unlike for other stroke subtypes. Recent studies have indicated that mitochondrial dysfunction and mitophagy likely relate to the pathophysiology of intracerebral hemorrhage. Mitophagy, or selective autophagy of mitochondria, is an essential pathway to preserve mitochondrial homeostasis by clearing up damaged mitochondria. Mitophagy markedly contributes to the reduction of secondary brain injury caused by mitochondrial dysfunction after intracerebral hemorrhage. This review provides an overview of the mitochondrial dysfunction that occurs after intracerebral hemorrhage and the underlying mechanisms regarding how mitophagy regulates it, and discusses the new direction of therapeutic strategies targeting mitophagy for intracerebral hemorrhage, aiming to determine the close connection between mitophagy and intracerebral hemorrhage and identify new therapies to modulate mitophagy after intracerebral hemorrhage. In conclusion, although only a small number of drugs modulating mitophagy in intracerebral hemorrhage have been found thus far, most of which are in the preclinical stage and require further investigation, mitophagy is still a very valid and promising therapeutic target for intracerebral hemorrhage in the long run.

The NLRP3 inflammasome: a vital player in inflammation and mediating the anti-inflammatory effect of CBD

BACKGROUND

The NLRP3 inflammasome is a vital player in the emergence of inflammation. The priming and activation of the NLRP3 inflammasome is a major trigger for inflammation which is a defense response against adverse stimuli. However, the excessive activation of the NLRP3 inflammasome can lead to the development of various inflammatory diseases. Cannabidiol, as the second-most abundant component in cannabis, has a variety of pharmacological properties, particularly anti-inflammation. Unlike tetrahydrocannabinol, cannabidiol has a lower affinity for cannabinoid receptors, which may be the reason why it is not psychoactive. Notably, the mechanism by which cannabidiol exerts its anti-inflammatory effect is still unclear.

METHODS

We have performed a literature review based on published original and review articles encompassing the NLRP3 inflammasome and cannabidiol in inflammation from central databases, including PubMed and Web of Science.

RESULTS AND CONCLUSIONS

In this review, we first summarize the composition and activation process of the NLRP3 inflammasome. Then, we list possible molecular mechanisms of action of cannabidiol. Next, we explain the role of the NLRP3 inflammasome and the anti-inflammatory effect of cannabidiol in inflammatory disorders. Finally, we emphasize the capacity of cannabidiol to suppress inflammation by blocking the NLRP3 signaling pathway, which indicates that cannabidiol is a quite promising anti-inflammatory compound.

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.

Intracerebral Hemorrhage-Induced Brain Injury: the Role of Lysosomal-Associated Transmembrane Protein 5

Intracerebral hemorrhage (ICH) is a lethal stroke with high mortality or disability. However, effective therapy for ICH damage is generally lacking. Previous investigations have suggested that lysosomal protein transmembrane 5 (LAPTM5) is involved in various pathological processes, including autophagy, apoptosis, and inflammation. In this study, we aimed to identify the expression and functions of LAPTM5 in collagenase-induced ICH mouse models and hemoglobin-induced cell models. We found that LAPTM5 was highly expressed in brain tissues around the hematoma, and double immunostaining studies showed that LAPTM5 was co-expressed with microglia cells, neurons, and astrocytes. Following ICH, the mice presented increased brain edema, blood-brain barrier permeability, and neurological deficits, while pathological symptoms were alleviated after the LAPTM5 knockdown. Adeno-associated virus 9-mediated downregulation of LAPTM5 also improves ICH-induced secondary cerebral damage, including neuronal degeneration, the polarization of M1-like microglia, and inflammatory cascades. Furthermore, LAPTM5 promoted activation of the nuclear factor kappa-B (NF-κB) pathway in response to neuroinflammation. Further investigations indicated that brain injury improved by LAPTM5 knockdown was further exacerbated after the overexpression of receptor-interacting protein kinase 1 (RIP1), which is revealed to trigger the NF-κB pathway. In vitro experiments demonstrated that LAPTM5 silencing inhibited hemoglobin-induced cell function and confirmed regulation between RIP1 and LAPTM5. In conclusion, the present study indicates that LAPTM5 may act as a positive regulator in the context of ICH by modulating the RIP1/NF-κB pathway. Thus, it may be a candidate gene for further study of molecular or therapeutic targets.

The relationship between hemoglobin/red blood cell distribution width ratio and mortality in patients with intracranial hemorrhage: a possible protective effect for the elderly?

Intracranial hemorrhage (ICH) is a neurological emergency with a poor prognosis. This study aimed to understand the association between hemoglobin levels, red blood cell distribution width ratio (HRR), and mortality in patients with ICH. Information on patients with ICH was extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Cox proportional risk models were used to assess the relationship between HRR and 28-day and 90-day mortality, and constructed by adjusting for relevant covariates. Segmented regression models and smoothing curves were used to analyze the linear relationship between HRR and mortality. This study recruited 4,716 patients with ICH. The HRR Q4 group was negatively associated with the 28- and 90-day mortality. For patients aged > 65 years, the right-hand threshold inflection points of the HRR were 0.92 and 0.93, respectively, which were negatively associated with 28-day mortality (HR:0.06, 95% CI 0.01, 0.35, p = 0.0016) and with 90-day mortality (p = 0.0006). In the non-linear model, both 28-day mortality (HR, 0.17; 95% CI 0.04-0.75, p = 0.0191; HRR > 0.89) and 90-day mortality (HR, 0.13; 95% CI 0.04-0.49, p = 0.0022; HRR > 0.85) were associated in men. In the subgroup analysis, the negative association between HRR and mortality was more pronounced in patients > 65 years of age, as well as in patients with non-dementia, diabetes, and malignant cancer. We found a non-linear relationship between mortality and the HRR in elderly patients, and a higher HRR was negatively associated with mortality in patients with ICH.

Leveraging the ATP-P2X7 receptor signalling axis to alleviate traumatic CNS damage and related complications

The P2X7 receptor is an exceptional member of the P2X purinergic receptor family, with its activation requiring high concentrations of extracellular adenosine 5'-triphosphate (ATP) that are often associated with tissue damage and inflammation. In the central nervous system (CNS), it is highly expressed in glial cells, particularly in microglia. In this review, we discuss the role and mechanisms of the P2X7 receptor in mediating neuroinflammation and other pathogenic events in a variety of traumatic CNS damage conditions, which lead to loss of neurological and cognitive functions. We raise the perspective on the steady progress in developing CNS-penetrant P2X7 receptor-specific antagonists that leverage the ATP-P2X7 receptor signaling axis as a potential therapeutic strategy to alleviate traumatic CNS damage and related complications.

Inhibition of BACE1 attenuates microglia-induced neuroinflammation after intracerebral hemorrhage by suppressing STAT3 activation

Hematoma-induced neuroinflammation is the cause of poor prognosis in intracerebral hemorrhage (ICH); therefore, promoting blood clearance and blocking overactivated inflammation are rational approaches for ICH treatment. β-site amyloid precursor protein (APP) lyase-1 (BACE1) is a key molecule regulating the microglial phenotype transition in neurodegenerative diseases. Therefore, the aim of this study was to investigate the role of BACE1 in microglial phagocytosis and inflammatory features in ICH. Here, we demonstrated the unique advantages of targeting BACE1 in microglia using an autologous blood model and primary microglia hemoglobin stimulation. When BACE1 was inhibited early in ICH, fewer residual hematomas remained, consistent with an increase in genetic features that favor phagocytosis and anti-inflammation. In addition, inhibition of BACE1 enhanced the secretion of anti-inflammatory cytokines and substantially reduced the expression of proinflammatory genes, which was regulated by signal transduction and phosphorylation of activator of transcription 3 (STAT3). Further pharmacological inhibition of STAT3 phosphorylation effectively blocked the proinflammatory and weak phagocytic phenotype of microglia due to BACE1 induction. In summary, BACE1 is the critical molecule regulating the inflammatory and phagocytic phenotypes of microglia after ICH, and targeted inhibition of the BACE1/STAT3 pathway is an important strategy for the future treatment of ICH-induced neurological 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.

Prognostic significance of serum resolvin D1 levels in patients with acute supratentorial intracerebral hemorrhage: a prospective longitudinal cohort study

OBJECTIVE

Resolvin D1 (RvD1) has anti-inflammatory properties and may be neuroprotective. This study was designed to assess usability of serum RvD1 as a prognostic biomarker after intracerebral hemorrhage (ICH).

METHODS

In this prospective, observational study of 135 patients and 135 controls, serum RvD1 levels were measured. Its relations to severity, early neurologic deterioration (END) and poststroke 6-month worse outcome (modified Rankin Scale scores of 3-6) were determined via multivariate analysis. Predictive effectiveness was evaluated based on area under receiver operating characteristic curve (AUC).

RESULTS

Patients had markedly lower serum RvD1 levels than controls (median, 0.69 ng/ml versus 2.15 ng/ml). Serum RvD1 levels were independently correlated with the National Institutes of Health Stroke Scale (NIHSS) [β, -0.036; 95% confidence interval (CI), -0.060--0.013; VIF, 2.633; t=-3.025; P=0.003] and hematoma volume (β, -0.019; 95% CI, -0.056--0.009; VIF, 1.688; t=-2.703; P=0.008). Serum RvD1 levels substantially discriminated risks of END and worse outcome with AUCs at 0.762 (95% CI, 0.681-0.831) and 0.783 (95% CI, 0.704-0.850) respectively. A RvD1 cut-off value of 0.85 ng/ml was effective in predicting END with a sensitivity of 95.0% and specificity of 48.4% and its levels <0.77 ng/ml distinguished patients at risk of worse outcome with a sensitivity of 84.5% and specificity of 63.6%. Under restricted cubic spline, serum RvD1 levels were linearly related to risk of END and worse outcome (both P>0.05). Serum RvD1 levels and NIHSS scores independently predicted END with odds ratio (OR) values of 0.082 (95% CI, 0.010-0.687) and 1.280 (95% CI, 1.084-1.513) respectively. Serum RvD1 levels (OR, 0.075; 95% CI, 0.011-0.521), hematoma volume (OR, 1.084; 95% CI, 1.035-1.135) and NIHSS scores (OR, 1.240; 95% CI, 1.060-1.452) were independently associated with worse outcome. END prediction model containing serum RvD1 levels and NIHSS scores, and prognostic prediction model containing serum RvD1 levels, hematoma volumes and NIHSS scores displayed efficient predictive ability with AUCs at 0.828 (95% CI, 0.754-0.888) and 0.873 (95% CI, 0.805-0.924) respectively. Such two models were visually shown via building two nomograms. Using Hosmer-Lemeshow test, calibration curve and decision curve, the models were comparatively stable and had clinical benefit.

CONCLUSION

There is a dramatical declination of serum RvD1 levels after ICH, which is tightly related to stroke severity and is independently predictive of poor clinical outcome, implying that serum RvD1 may be of clinical significance as a prognostic marker of ICH.

Mesenchymal stem cells transplantation combined with IronQ attenuates ICH-induced inflammation response via Mincle/syk signaling pathway

BACKGROUND

Intracerebral hemorrhage (ICH) is a severe brain-injured disease accompanied by cerebral edema, inflammation, and subsequent neurological deficits. Mesenchymal stem cells (MSCs) transplantation has been used as a neuroprotective therapy in nervous system diseases because of its anti-inflammatory effect. Nevertheless, the biological characteristics of transplanted MSCs, including the survival rate, viability, and effectiveness, are restricted because of the severe inflammatory response after ICH. Therefore, improving the survival and viability of MSCs will provide a hopeful therapeutic efficacy for ICH. Notably, the biomedical applications of coordination chemistry-mediated metal-quercetin complex have been verified positively and studied extensively, including growth-promoting and imaging probes. Previous studies have shown that the iron-quercetin complex (IronQ) possesses extraordinary dual capabilities with a stimulating agent for cell growth and an imaging probe by magnetic resonance imaging (MRI). Therefore, we hypothesized that IronQ could improve the survival and viability of MSCs, displaying the anti-inflammation function in the treatment of ICH while also labeling MSCs for their tracking by MRI. This study aimed to explore the effects of MSCs with IronQ in regulating inflammation and further clarify their potential mechanisms.

METHODS

C57BL/6 male mice were utilized in this research. A collagenase I-induced ICH mice model was established and randomly separated into the model group (Model), quercetin gavage group (Quercetin), MSCs transplantation group (MSCs), and MSCs transplantation combined with IronQ group (MSCs + IronQ) after 24 h. Then, the neurological deficits score, brain water content (BWC), and protein expression, such as TNF-α, IL-6, NeuN, MBP, as well as GFAP, were investigated. We further measured the protein expression of Mincle and its downstream targets. Furthermore, the lipopolysaccharide (LPS)-induced BV2 cells were utilized to investigate the neuroprotection of conditioned medium of MSCs co-cultured with IronQ in vitro.

RESULTS

We found that the combined treatment of MSCs with IronQ improved the inflammation-induced neurological deficits and BWC in vivo by inhibiting the Mincle/syk signaling pathway. Conditioned medium derived from MSCs co-cultured with IronQ decreased inflammation, Mincle, and its downstream targets in the LPS-induced BV2 cell line.

CONCLUSIONS

These data suggested that the combined treatment exerts a collaborative effect in alleviating ICH-induced inflammatory response through the downregulation of the Mincle/syk signaling pathway following ICH, further improving the neurologic deficits and brain edema.

Hesperetin ameliorates spinal cord injury by inhibiting NLRP3 inflammasome activation and pyroptosis through enhancing Nrf2 signaling

Neuroinflammation is a prominent feature of traumatic spinal cord injuries (SCIs). Hesperetin exhibits anti-inflammatory effects in neurological disorders; however, the potential neuroprotective effects of hesperetin in cases of SCI remain unclear. Sprague-Dawley rats with C5 hemi-contusion injuries were used as an SCI model. Hesperetin was administered to the experimental rats in order to investigate its neuroprotective effects after SCI, and BV2 cells were pretreated with hesperetin or silencing of nuclear factor erythroid 2-related factor 2 (siNrf2), and then stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP). The therapeutic impact and molecular mechanism of hesperetin were elucidated in a series of in vivo and in vitro investigations conducted using a combination of experiments. The results of the present in vivo experiment indicated that hesperetin improved functional recovery and protected spinal cord tissue after SCI. Hesperetin attenuated oxidative stress and microglial activation, lowered malondialdehyde (MDA) levels, and elevated catalase (CAT), glutathione (GSH)-Px, and superoxide dismutase (SOD) levels. Moreover, hesperetin downregulated the expression of advanced oxygenation protein products (AOPPs), ionized calcium-binding adapter molecule 1 (Iba-1), NOD-like receptor protein 3 (NLRP3), and interleukin-1 beta (IL-1β), but increased the expression of Nrf2. In vitro studies have shown that hesperetin inhibits the generation of reactive oxygen species (ROS), as well as the neuroinflammation associated with the upregulation of Nrf2 and heme oxygenase-1 (HO-1) in BV2 cells. The results of the present study indicated that hesperetin inhibited BV2 cell pyroptosis and significantly blocked the expression of NLRP3 inflammasome proteins (NLRP3 Caspase-1 p10 apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain [ASC]) and pro-inflammatory mediators (IL-18, IL-1β). Furthermore, the silencing of Nrf2 by small interfering ribonucleic acid (siRNA) partially abolished its antioxidant effect in the aforementioned cell experiments. Collectively, these findings illustrate that through an increase in Nrf2 signaling hesperetin reduces oxidative stress and neuroinflammation by suppressing NLRP3 inflammasome activation and pyroptosis.

Potential preventive markers in the intracerebral hemorrhage process are revealed by serum untargeted metabolomics in mice using hypertensive cerebral microbleeds

Hypertensive cerebral microbleeds (HCMB) may be the early stage of hypertensive intracerebral hemorrhage (HICH), which is a serious threat to health due to its high mortality and disability rates. The early clinical symptoms of HCMB may not be significant. Moreover, it is difficult to achieve early diagnosis and intervention for targeted prevention of HICH. Although hypertension (HTN) is a predisposition for HCMB, it remains unclear whether there is any difference between hypertensive patients with or without HCMB. Therefore, we carried out liquid chromatography-mass spectrometry (LC-MS) to analyze early biomarkers for HCMB in mice with hypertension and to lay the foundation for early prevention of HICH in hypertensive patients. In total, 18 C57 male mice were randomly divided into the HCMB (n = 6), HTN (n = 6), and control groups (CON, n = 6). Hematoxylin-eosin and diaminobenzidine staining were used to assess the reliability of the model. The metabolite expression level and sample category stability were tested using the displacement test of orthogonal partial least squares discriminant analysis (OPLS-DA). Significant differences in metabolites were screened out using variable importance in the projection (VIP > 1), which were determined using the OPLS-DA model and the P-value of the t-test (P < 0.05) combined with the nonparametric rank-sum test. With an area under the curve (AUC) > 0.85 and a P-value of 0.05, the receiver operating characteristic curve (ROC) was used to further screen the distinct metabolites of HCMB. Compared with the HTN and CON groups, the HCMB group had significantly higher blood pressure and lower average body weight (P < 0.05). Through untargeted LC-MS analysis, 93 distinct metabolites were identified in the HCMB (P < 0.05, VIP > 1) group. Among these potential biomarkers, six significantly decreased and eight significantly increased differential metabolites were found. Meanwhile, we found that the HCMB group had statistically distinct arginine and purine metabolism pathways (P < 0.05), and citrulline may be the most significant possible biomarker of HCMB (AUC > 0.85, P < 0.05). All of these potential biomarkers may serve as early biomarkers for HICH in hypertension.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

Progress on siRNA-based gene therapy targeting secondary injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a life-threatening condition with a high mortality rate. For survivors, quality of life is determined by primary and secondary phases of injury. The prospects for injury repair and recovery after ICH are highly dependent on the extent of secondary injury. Currently, no effective treatments are available to prevent secondary injury or its long-term effects. One promising strategy that has recently garnered attention is gene therapy, in particular, small interfering RNAs (siRNA), which silence specific genes responsible for destructive effects after hemorrhage. Gene therapy as a potential treatment for ICH is being actively researched in animal studies. However, there are many barriers to the systemic delivery of siRNA-based therapy, as the use of naked siRNA has limitations. Recently, the Food and Drug Administration approved two siRNA-based therapies, and several are undergoing Phase 3 clinical trials. In this review, we describe the advancements in siRNA-based gene therapy for ICH and also summarize its advantages and disadvantages.

CNS-peripheral immune interactions in hemorrhagic stroke

Stroke is a sudden and rapidly progressing ischemic or hemorrhagic cerebrovascular disease. When stroke damages the brain, the immune system becomes hyperactive, leading to systemic inflammatory response and immunomodulatory disorders, which could significantly impact brain damage, recovery, and prognosis of stroke. Emerging researches suggest that ischemic stroke-induced spleen contraction could activate a peripheral immune response, which may further aggravate brain injury. This review focuses on hemorrhagic strokes including intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) and discusses the central nervous system-peripheral immune interactions after hemorrhagic stroke induction. First, inflammatory progression after ICH and SAH is investigated. As a part of this review, we summarize the various kinds of inflammatory cell infiltration to aggravate brain injury after blood-brain barrier interruption induced by hemorrhagic stroke. Then, we explore hemorrhagic stroke-induced systemic inflammatory response syndrome (SIRS) and discuss the interactions of CNS and peripheral inflammatory response. In addition, potential targets related to inflammatory response for ICH and SAH are discussed in this review, which may lead to novel therapeutic strategies for hemorrhagic stroke.

Engineering exosomes by three-dimensional porous scaffold culture of human umbilical cord mesenchymal stem cells promote osteochondral repair

Improving the poor microenvironment in the joint cavity has potential for treating cartilage injury, and mesenchymal stem cell (MSC)-derived exosomes (MSC-Exos), which can modulate cellular behavior, are becoming a new cell-free therapy for cartilage repair. Here, we used acellular cartilage extracellular matrix (ACECM) to prepare 3D scaffolds and 2D substrates by low-temperature deposition modeling (LDM) and tape casting. We aimed to investigate whether MSC-Exos cultured on scaffolds of different dimensions could improve the poor joint cavity microenvironment caused by cartilage injury and to explore the related mechanisms. In vitro experiments showed that exosomes derived from MSCs cultured on three-dimensional (3D) scaffolds (3D-Exos) had increased efficiency. In short-term animal experiments, compared with exosomes derived from MSCs cultured in a two-dimensional (2D) environment (2D-Exos), 3D-Exos had a stronger ability to regulate the joint cavity microenvironment. Long-term animal studies confirmed the therapeutic efficacy of 3D-Exos over 2D-Exos. Thus, 3D-Exos were applied in the rat knee osteochondral defect model after adsorption in the micropores of the scaffold and combined with subsequent articular cavity injections, and they showed a stronger cartilage repair ability. These findings provide a new strategy for repairing articular cartilage damage. Furthermore, miRNA sequencing indicated that the function of 3D-Exos may be associated with high expression of miRNAs. Thus, our study provides valuable insights for the design of 3D-Exos to promote cartilage regeneration.

Autophagy regulates inflammation in intracerebral hemorrhage: Enemy or friend?

Intracerebral hemorrhage (ICH) is the second-largest stroke subtype and has a high mortality and disability rate. Secondary brain injury (SBI) is delayed after ICH. The main contributors to SBI are inflammation, oxidative stress, and excitotoxicity. Harmful substances from blood and hemolysis, such as hemoglobin, thrombin, and iron, induce SBI. When cells suffer stress, a critical protective mechanism called "autophagy" help to maintain the homeostasis of damaged cells, remove harmful substances or damaged organelles, and recycle them. Autophagy plays a critical role in the pathology of ICH, and its function remains controversial. Several lines of evidence demonstrate a pro-survival role for autophagy in ICH by facilitating the removal of damaged proteins and organelles. However, many studies have found that heme and iron can aggravate SBI by enhancing autophagy. Autophagy and inflammation are essential culprits in the progression of brain injury. It is a fascinating hypothesis that autophagy regulates inflammation in ICH-induced SBI. Autophagy could degrade and clear pro-IL-1β and apoptosis-associated speck-like protein containing a CARD (ASC) to antagonize NLRP3-mediated inflammation. In addition, mitophagy can remove endogenous activators of inflammasomes, such as reactive oxygen species (ROS), inflammatory components, and cytokines, in damaged mitochondria. However, many studies support the idea that autophagy activates microglia and aggravates microglial inflammation via the toll-like receptor 4 (TLR4) pathway. In addition, autophagy can promote ICH-induced SBI through inflammasome-dependent NLRP6-mediated inflammation. Moreover, some resident cells in the brain are involved in autophagy in regulating inflammation after ICH. Some compounds or therapeutic targets that regulate inflammation by autophagy may represent promising candidates for the treatment of ICH-induced SBI. In conclusion, the mutual regulation of autophagy and inflammation in ICH is worth exploring. The control of inflammation by autophagy will hopefully prove to be an essential treatment target for ICH.

The NLRP3 Inflammasome in Age-Related Cerebral Small Vessel Disease Manifestations: Untying the Innate Immune Response Connection

In this narrative review, we present the evidence on nucleotide-binding and oligomerization (NOD) domain-like receptor (NLR) family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome activation for its putative roles in the elusive pathomechanism of aging-related cerebral small vessel disease (CSVD). Although NLRP3 inflammasome-interleukin (IL)-1β has been implicated in the pathophysiology of coronary artery disease, its roles in cerebral arteriothrombotic micro-circulation disease such as CSVD remains unexplored. Here, we elaborate on the current manifestations of CSVD and its' complex pathogenesis and relate the array of activators and aberrant activation involving NLRP3 inflammasome with this condition. These neuroinflammatory insights would expand on our current understanding of CSVD clinical (and subclinical) heterogenous manifestations whilst highlighting plausible NLRP3-linked therapeutic targets.

Exploring the pharmacological mechanism of Naoxueshu oral liquid in the treatment of intracerebral hemorrhage through weighted gene co-expression network analysis, network pharmacological and experimental validation

BACKGROUND

Intracerebral hemorrhage (ICH) is a life-threatening stroke subtype with high rates of disability and mortality. Naoxueshu oral liquid is a proprietary Chinese medicine that absorbs hematoma and exhibits neuroprotective effects in patients with ICH. However, the underlying mechanisms remain obscure.

PURPOSE

Exploring and elucidating the pharmacological mechanism of Naoxueshu oral liquid in the treatment of ICH.

STUDY DESIGN AND METHODS

The Gene Expression Omnibus (GEO) database was used to download the gene expression data on ICH. ICH-related hub modules were obtained by weighted gene co-expression network analysis (WGCNA) of differentially co-expressed genes (DEGs). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted using the obtained key modules to identify the ICH-related signaling pathways. Network pharmacology technology was applied to forecast the targets of Naoxueshu oral liquid and to establish a protein-protein interaction (PPI) network of overlapping targets between Naoxueshu oral liquid and ICH. Functional annotation and enrichment pathway analyses of the intersectional targets were performed using the omicsbean database. Finally, we verified the therapeutic role and mechanism of Naoxueshu oral liquid in ICH through molecular docking and experiments.

RESULTS

Through the WGCNA analysis, combined with network pharmacology, it was found that immune inflammation was closely related to the early pathological mechanism of ICH. Naoxueshu oral liquid suppressed the inflammatory response; hence, it could be a potential drug for ICH treatment. Molecular docking further confirmed that the effective components of Naoxueshu oral liquid docked well with CD163. Finally, the experimental results showed that Naoxueshu oral liquid treatment in the ICH rat model attenuated neurological deficits and neuronal injury, decreased hematoma volume, and promoted hematoma absorption. In addition, Naoxueshu oral liquid treatment also significantly increased the levels of Arg-1, CD163, Nrf2, and HO-1 around hematoma after ICH.

CONCLUSION

This study demonstrated that Naoxueshu oral liquid attenuated neurological deficits and accelerated hematoma absorption, possibly by suppressing inflammatory responses, which might be related to the regulation of Nrf2/CD163/HO-1 that interfered with the activation of M2 microglia, thus accelerating the clearance and decomposition of hemoglobin in the hematoma.

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.

Research advances in cGAS-stimulator of interferon genes pathway and central nervous system diseases: Focus on new therapeutic approaches

Cyclic GMP-AMP synthase (cGAS), a crucial innate immune sensor, recognizes cytosolic DNA and induces stimulator of interferon genes (STING) to produce type I interferon and other proinflammatory cytokines, thereby mediating innate immune signaling. The cGAS-STING pathway is involved in the regulation of infectious diseases, anti-tumor immunity, and autoimmune diseases; in addition, it plays a key role in the development of central nervous system (CNS) diseases. Therapeutics targeting the modulation of cGAS-STING have promising clinical applications. Here, we summarize the cGAS-STING signaling mechanism and the recent research on its role in CNS diseases.

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.

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 from LPS-preconditioned bone marrow MSCs accelerated peripheral nerve regeneration via M2 macrophage polarization: Involvement of TSG-6/NF-κB/NLRP3 signaling pathway

Lipopolysaccharide (LPS)-preconditioned mesenchymal stem cells (MSCs) possessed strong immunomodulatory and anti-inflammatory functions by secreting exosomes as major paracrine effectors. However, the specific effect of exosomes from LPS pre-MSCs (LPS pre-Exos) on peripheral nerve regeneration has yet to be documented. Here, we established a sciatic nerve injury model in rats and an inflammatory model in RAW264.7 cells to explore the potential mechanism between LPS pre-Exos and peripheral nerve repair. The local injection of LPS pre-Exos into the nerve injury site resulted in an accelerated functional recovery, axon regeneration and remyelination, and an enhanced M2 Macrophage polarization. Consistent with the data in vivo, LPS pre-Exos were able to shift the pro-inflammation macrophage into a pro-regeneration macrophage. Notably, TNF stimulated gene-6 (TSG-6) was found to be highly enriched in LPS pre-Exos. We obtained si TSG-6 Exo by the knockdown of TSG-6 in LPS pre-Exos to demonstrate the role of TSG-6 in macrophage polarization, and found that TSG-6 served as a critical mediator in LPS pre-Exos-induced regulatory effects through the inhibition of NF-ΚΒ and NOD-like receptor protein 3 (NLRP3). In conclusion, our findings suggested that LPS pre-Exos promoted macrophage polarization toward an M2 phenotype by shuttling TSG-6 to inactivate the NF-ΚΒ/NLRP3 signaling axis, and could provide a potential therapeutic avenue for peripheral nerve repair.

Correlation between red blood cell distribution width, neutrophil to lymphocyte ratio, and neutrophil to platelet ratio with 3-month prognosis of patients with intracerebral hemorrhage: a retrospective study

BACKGROUND

Red cell distribution width (RDW) is a parameter that indsicates the heterogeneity of red blood cell size and could be a prognostic factor in some diseases. Also, intracerebral hemorrhage (ICH) is considered a vascular event with a high mortality rate. We aimed to examine the role of RDW, neutrophil to lymphocyte ratio (NLR), and neutrophil to platelet ratio (NPR) in predicting the prognosis of patients with ICH.

METHODS

This is a retrospective cohort study conducted on 140 patients with ICH admitted to the neurology ward and intensive care unit (ICU) in Imam Reza Hospital, Tabriz, Iran. Demographic data, National Institutes of Health Stroke Scale (NIHSS), and complete blood count test parameters were evaluated within 24 h after hospitalization. These variables were collected and re-evaluated three months later.

RESULTS

The mean age of the study population was 61.14 (± 16) years and 51% were male. The mean NLR (p = 0.05), neutrophil count (p=0.04), platelet count (p = 0.05), and NIHSS (p<0.01)  had a significant difference between the deceased patients and those who partially recovered after three months. The ROC curve showed that NIHSS (area under curve (AUC): 0.902), followed by NPR (AUC: 0.682) variables had the highest AUC.

CONCLUSION

RDW could be a relevant prognostic factor and predictor in determining 3-months survival in ICH. Nevertheless, further large-scale prospective cohorts might be needed to evaluate the associations.

Inhibiting Microglia-Derived NLRP3 Alleviates Subependymal Edema and Cognitive Dysfunction in Posthemorrhagic Hydrocephalus after Intracerebral Hemorrhage via AMPK/Beclin-1 Pathway

For posthemorrhagic hydrocephalus (PHH) patients, whether occur subependymal edema indicates poor outcomes, partially manifested as cognitive impairment. In the brain, NLRP3 inflammasome mainly derived from microglia/macrophages is involved in proinflammatory and neurodeficits after hemorrhage, and autophagy is vital for neuronal homeostasis and functions. Accumulating evidence suggest that NLRP3 inflammasome and autophagy played an essential role after intracerebral hemorrhage (ICH). We aimed to dissect the mechanisms underlying subependymal edema formation and cognitive dysfunction. Here, based on the hydrocephalus secondary to ICH break into ventricular (ICH-IVH) in rats, this study investigated whether microglia/macrophage-derived NLRP3 induced subependymal edema formation and neuron apoptosis in subventricular zones (SVZ). In the acute phase of ICH-IVH, both the expression of NLRP3 inflammasome of microglia/macrophages and the autophagy of neurons were upregulated. The activated NLRP3 in microglia/macrophages promoted the release of IL-1beta to extracellular, which contributed to excessive autophagy, leading to neurons apoptosis both in vivo and in vitro through the AMPK/Beclin-1 pathway combined with transcriptomics. Administration of MCC950 (NLRP3 inflammasome specific inhibitor) after ICH-IVH significantly reduced edema formation and improved cognitive dysfunction. Thus, inhibiting NLRP3 activation in SVZ may be a promising therapeutic strategy for PHH patients that warrants further investigation.

The Role of Caspase Family in Acute Brain Injury: The Potential Therapeutic Targets in the Future

The caspase family is commonly involved in the pathophysiology of acute brain injury (ABI) through complex apoptotic, pyroptotic, and inflammatory pathways. Current translational strategies for caspase modulation in ABI primarily focus on caspase inhibitors. Because there are no caspase-inhibiting drugs approved for clinical use on the market, the development of caspase inhibitors remains an attractive challenge for researchers and clinicians. Therefore, we conducted the present review with the aim of providing a comprehensive introduction of caspases in ABI. In this review, we summarized the available evidence and potential mechanisms regarding the biological function of caspases. We also reviewed the therapeutic effects of caspase inhibitors on ABI and its subsequent complications. However, various important issues remain unclear, prompting further verification of the efficacy and safety regarding clinical application of caspase inhibitors. We believe that our work will be helpful to further understand the critical role of the caspase family and will provide novel therapeutic potential for ABI treatment.

mtDNA-STING Axis Mediates Microglial Polarization via IRF3/NF-κB Signaling After Ischemic Stroke

Neuroinflammation is initiated in response to ischemic stroke, and is usually characterized by microglial activation and polarization. Stimulator of interferon genes (STING) has been shown to play a critical role in anti-tumor immunity and inflammatory diseases. Nevertheless, the effect and underlying mechanisms of STING on microglial polarization after ischemic stroke remain unclarified. In this study, acute ischemic stroke was simulated using a model of middle cerebral artery occlusion (MCAO) at adult male C57BL/6 mice in vivo and the BV2 microglia oxygen-glucose deprivation/reperfusion (OGD/R) model in vitro. The specific STING inhibitor C-176 was administered intraperitoneally at 30min after MCAO. We found that the expression of microglial STING was increased following MCAO and OGD/R. Pharmacologic inhibition of STING with C-176 reduced the ischemia/reperfusion (I/R)-induced brain infarction, edema and neuronal injury. Moreover, blockade of STING improved neurological performance and cognitive function and attenuated neuronal degeneration in the hippocampus after MCAO. Mechanistically, both in vivo and in vitro, we delineated that STING could promote the polarization of microglia towards the M1 phenotype and restrain M2 microglia polarization via downstream pathways, including interferon regulatory factor 3 (IRF3) and nuclear factor-κB (NF-κB). In addition, mitochondrial DNA (mtDNA), which is released to microglial cytoplasm induced by I/R injury, could facilitate microglia towards M1 modality through STING signaling pathway. Treatment with C-176 abolished the detrimental effects of mtDNA on stroke outcomes. Taken together, these findings suggest that STING, activated by mtDNA, could polarize microglia to the M1 phenotype following MCAO. Inhibition of STING may serve as a potential therapeutic strategy to mitigate neuroinflammation after ischemic stroke.

Activation of RKIP Binding ASC Attenuates Neuronal Pyroptosis and Brain Injury via Caspase-1/GSDMD Signaling Pathway After Intracerebral Hemorrhage in Mice

Pyroptosis has been proven to be responsible for secondary brain injury after intracerebral hemorrhage (ICH). A recent study reported that Raf kinase inhibitor protein (RKIP) inhibited assembly and activation of inflammasome in macrophages. Our present study aimed to investigate the effects of RKIP on inflammasome-mediated neuronal pyroptosis and underlying neuroprotective mechanisms in experimental ICH. Here, we showed that RKIP expression was decreased both in cerebrospinal fluid (CSF) samples from patients with ICH and in the peri-hematoma tissues after experimental ICH. In mouse ICH model, activation of RKIP remarkably improved neurological deficits, reduced brain water content and BBB disruption, and promoted hematoma absorption at 24 h after ICH, as well as alleviated neuronal degeneration, reduced membrane pore formation, and downregulated pyroptotic molecules NLRP3, caspase-1 P20, GSDMD-N, and mature IL-1β. Besides, RKIP activation decreased the number of caspase-1 P20-positive neurons after ICH. However, RKIP inhibitor reserved the neuroprotective effects of RKIP at 24 h following ICH. Moreover, RKIP could bind with ASC, then interrupt the assembly of NLRP3 inflammasome. Mechanistically, inhibiting the caspase-1 by VX-765 attenuated brain injury and suppressed neuronal pyroptosis after RKIP inhibitor-pretreated ICH. In conclusion, our findings indicated that activation of RKIP could attenuate neuronal pyroptosis and brain injury after ICH, to some extent, through ASC/Caspase-1/GSDMD pathway. Thus, RKIP may be a potential target to attenuate brain injury via its anti-pyroptosis effect after ICH.

Extracellular vesicles derived from bone marrow mesenchymal stem cells alleviate neuroinflammation after diabetic intracerebral hemorrhage via the miR-183-5p/PDCD4/NLRP3 pathway

OBJECTIVES

Intracerebral hemorrhage (ICH) induced by diabetes results in further brain injury and nerve cell death. Bone marrow mesenchymal stem cell (BMSC) transplantation contributes to attenuating neurological deficits after ICH. This study investigated the mechanism of extracellular vesicles (EVs) derived from BMSCs in reducing neuroinflammation after diabetic ICH.

METHODS

BMSC-EVs were isolated and identified. The rat model of db/db-ICH was established and the model rats were administered with EVs. miR-183-5p expression in brain tissues of db/db-ICH rats was detected. The brain injury of db/db-ICH rats was evaluated by measuring neurobehavioral score, brain water content and inflammatory factors. BV2 cells were cultured in vitro to establish high-glucose (HG)-Hemin-BV2 cell model. The levels of reactive oxygen species (ROS) and inflammatory factors in BV2 cells were measured, and BV2 cell viability and apoptosis were assessed. The targeting relationship between miR-183-5p and PDCD4 was predicted and verified. The activation of PDCD4/NLRP3 pathway in rat brain tissues and BV2 cells was detected.

RESULTS

miR-183-5p expression was reduced in db/db-ICH rats brain tissues. BMSC-EVs ameliorated cranial nerve function, decreased brain water content and repressed inflammatory response by carrying miR-183-5p. BMSC-EVs mitigated HG-Hemin-BV2 cell injury, reduced ROS level and suppressed inflammatory response. miR-183-5p targeted PDCD4. PDCD4 promoted BV2 cell inflammation by activating the NLRP3 pathway. BMSC-EVs inhibited HG-Hemin-BV2 cell inflammation through the miR-183-5p/PDCD4/NLRP3 pathway, and inhibition of miR-183-5p reversed the protective effect of EVs.

CONCLUSION

BMSC-EVs carried miR-183-5p into db/db-ICH rat brain tissues and repressed the NLRP3 pathway by targeting PDCD4, thus alleviating neuroinflammation after diabetic ICH.

Dexmedetomidine exerts cerebral protective effects against cerebral ischemic injury by promoting the polarization of M2 microglia via the Nrf2/HO-1/NLRP3 pathway

INTRODUCTION

Cerebral ischemic injury is associated with long-term disability. Dexmedetomidine (Dex) can exert neuroprotective effects on cerebral ischemic/reperfusion injury. The present study explored the mechanism of Dex in cerebral ischemic injury.

MATERIALS AND METHODS

To this end, the permanent middle cerebral artery occlusion (p-MCAO) mouse model was established and treated with Dex or/and Nrf2 inhibitor ML385. Subsequently, microglia were subjected to oxygen-glucose deprivation (OGD) in sugar-free environment and thereafter treated with Dex, Nrf2 inhibitor, and NLRP3 lentiviral overexpression vector, respectively.

RESULTS

Dex alleviated the neurobehavioral deficit of p-MCAO mice, reduced brain water content, relieved pathological changes, and reduced cerebral infarction size. Dex promoted the polarization of microglia from M1 to M2, thus ameliorating oxidative stress and inflammatory responses. Our results showed that Dex promoted M2-polarization of microglia in vivo and in vitro by promoting HO-1 expression via Nrf2 nuclear import. Moreover, the Nrf2/HO-1 axis inhibited the activation of NLRP2 inflammasome and NLRP3 overexpression reversed the effect of Dex.

CONCLUSION

In conclusion, Dex promoted M2-polarization of microglia and attenuated oxidative stress and inflammation, and thus protected against cerebral ischemic injury by activating the Nrf2/HO-1 pathway and inhibiting NLRP3 inflammasome.

Hypoxia-preconditioned mesenchymal stem cells attenuate microglial pyroptosis after intracerebral hemorrhage

Background

Microglia plays a vital role in neuroinflammation, contributing to the pathogenesis of intracerebral hemorrhage (ICH)-induced brain injury. Mesenchymal stem cells (MSCs) hold great potential for treating ICH. We previously revealed that MSCs ameliorate the microglial pyroptosis caused by an ischemic stroke. However, whether MSCs can modulate microglial pyroptosis after ICH remains unknown. This study aimed to investigate the neuroprotective effects of hypoxia-preconditioned olfactory mucosa MSCs (OM-MSCs) on ICH and the possible mechanisms.

Methods

ICH was induced in mice via administration of collagenase IV. At 6 h post-ICH, 2-4×10⁵ normoxic/hypoxic OM-MSCs or saline were intracerebrally administered. To evaluate the neuroprotective effects, the behavioral outcome, apoptosis, and neuronal injury were measured. Microglia activation and pro-inflammatory cytokines were applied to detect neuroinflammation. Microglial pyroptosis was determined by western blotting, immunofluorescence staining, and transmission electron microscopy (TEM).

Results

The two OM-MSC-transplanted groups exhibited significantly improved functional recovery and reduced neuronal injury, especially the hypoxic OM-MSCs group. Hypoxic OM-MSCs attenuated microglial activation as well as the levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Moreover, we found that hypoxia-preconditioned OM-MSCs ameliorated pyroptosis by diminishing the levels of pyroptosis-associated proteins in peri-hematoma brain tissues, decreasing the expression of the microglial nod-like receptor family protein 3 (NLRP3) and caspase-1, and reducing the membrane pores on microglia post-ICH.

Conclusions

Our study showed that hypoxic preconditioning augments the therapeutic efficacy of OM-MSCs, and hypoxia-preconditioned OM-MSCs alleviate microglial pyroptosis in the ICH model.

Prognostic Significance of Admission Systemic Inflammation Response Index in Patients With Spontaneous Intracerebral Hemorrhage: A Propensity Score Matching Analysis

Intracerebral hemorrhage (ICH) accounts for ~15% of all strokes and is associated with high mortality and disability rates. The systemic inflammation response index (SIRI) is a novel systemic inflammatory marker based on peripheral neutrophil, monocyte, and lymphocyte counts. This study aimed to evaluate the prognostic significance of admission SIRI in patients with spontaneous ICH and compare its predictive ability with that of the neutrophil-to-lymphocyte ratio (NLR). This retrospective study was conducted based on a prospectively collected database of patients with ICH between June 2016 and January 2019. Propensity score matching (PSM) was conducted to adjust for potential imbalances in the clinical parameters. A total of 403 patients were included in the original cohort. The optimal SIRI cut-off value was 2.76. After 1:1 PSM based on potential confounding variables, a new cohort containing 262 patients was established for further analysis. In the original cohort, SIRI served as an independent predictor of 3-month functional outcome [odds ratio (OR), 1.302; 95% CI, 1.120–1.512; p = 0.001] and 1-month mortality (OR, 1.072; 95% CI, 1.020–1.126; p = 0.006), while NLR was independently associated with only 3-month functional outcomes (OR, 1.051; 95% CI, 1.004–1.100; p = 0.031) and not 1-month mortality. The same applied to the PSM cohort. Receiver operating characteristic analyses and predictive models indicated that in most instances, SIRI was superior to NLR and their components in predicting the outcomes of patients with ICH. Our study found that SIRI is determined to be an independent predictive indicator for ICH patients in 3-month functional outcomes and 1-month mortality. The prognostic predictive ability of SIRI was stronger than that of NLR.

Mechanism of Baicalein in Brain Injury After Intracerebral Hemorrhage by Inhibiting the ROS/NLRP3 Inflammasome Pathway

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke with high disability/mortality. Baicalein has strong anti-inflammatory activity. This study aims to explore the mechanism of baicalein on brain injury after ICH. The model of brain injury after ICH was established by collagenase induction, followed by the evaluation of neurological severity, brain water content, the degenerated neurons, neuronal apoptosis, and reactive oxygen species (ROS). The ICH model was treated with baicalein or silencing NLRP3 to detect brain injury. The expression of NLRP3 inflammasome was detected after treatment with ROS scavenger. The expressions of oxidative stress markers and inflammatory factors were detected, and the levels of components in NLRP3 inflammasome were detected. Baicalein reduced the damage of nervous system, lesion surface, brain water content, and apoptosis. Baicalein inhibited malondialdehyde and increased IL-10 by inhibiting ROS in brain tissue after ICH. Baicalein inhibited the high expression of NLRP3 inflammasome in ICH. ROS scavenger inhibited the NLRP3 inflammatory response by inhibiting ROS levels. Silencing NLRP3 alleviated the brain injury after ICH by inhibiting excessive oxidative stress and inflammatory factors. Overall, baicalein alleviated the brain injury after ICH by inhibiting ROS and NLRP3 inflammasome.