ST2/IL-33-Dependent Microglial Response Limits Acute Ischemic Brain Injury

IL-33 exerts neuroprotective effects through activation of ST2/AKT signaling axis in microglia after subarachnoid hemorrhage in rats

BACKGROUND AND PURPOSE

ST2, a member of the interleukin-1 (IL-1) receptor family, along with its ligand IL-33, plays critical roles in immune regulation and inflammatory responses. This study investigates the roles of endogenous IL-33/ST2 signaling in subarachnoid hemorrhage (SAH) and elucidates the underlying mechanisms.

METHODS

Dynamic changes in endogenous IL-33 levels were examined following SAH induction in vivo. Rats underwent the endovascular perforation model of SAH and were randomly assigned to receive either recombinant IL-33 (rIL-33) or a vehicle, administered intranasally 1 h post-SAH. ST2 siRNA or an AKT selective inhibitor was administered intraperitoneally (i.p.) 48 h prior to SAH induction to explore the potential mechanisms of IL-33-mediated neuroprotection.

RESULTS

Endogenous IL-33 and ST2 levels were elevated in in vitro models of SAH. Exogenous IL-33 significantly alleviated neuronal apoptosis, reduced brain edema, and enhanced short-term neurofunction in a dose-dependent manner following SAH in rats.

CONCLUSION

Exogenous rIL-33 alleviates SAH-induced neurological deficits by promoting M2-like polarization of microglia post-SAH. These findings suggest a potential role of the microglial ST2/AKT axis in IL-33-related neuroprotection, which warrants further investigation.

ILC2 instructs neural stem and progenitor cells to potentiate neurorepair after stroke

Stroke affects approximately 1 in 6 individuals globally and is the leading cause of adult disability, which is attributed to neuronal damage and neurological impairments. The mechanisms by which the brain tissue microenvironment supports neurogenesis and neurorepair post-stroke remain to be fully elucidated. In this study, we report that group 2 innate lymphoid cells (ILC2s) accumulate within the lesion core and subventricular zone (SVZ) during brain recovery following cerebral ischemia. Mice with ILC2 deficiency display impaired neurological scoring post-stroke. Mechanistic studies reveal that brain ILC2s enhance the proliferation of neural stem and progenitor cells (NSPCs) through the secretion of amphiregulin (Areg). Adoptive transfer of ILC2s or administration of Areg markedly improves neurological outcomes post-stroke. These findings demonstrate that ILC2s and their secreted products may represent a promising therapeutic strategy for enhancing neurorepair following brain injury.

A Data-Informed Mathematical Model of Microglial Cell Dynamics During Ischemic Stroke in the Middle Cerebral Artery

Neuroinflammation immediately follows the onset of ischemic stroke in the middle cerebral artery. During this process, microglial cells are activated in and recruited to the penumbra. Microglial cells can be activated into two different phenotypes: M1, which can worsen brain injury; or M2, which can aid in long-term recovery. In this study, we contribute a summary of experimental data on microglial cell counts in the penumbra following ischemic stroke induced by middle cerebral artery occlusion (MCAO) in mice and compile available data sets into a single set suitable for time series analysis. Further, we formulate a mathematical model of microglial cells in the penumbra during ischemic stroke due to MCAO. Through use of global sensitivity analysis and Markov Chain Monte Carlo (MCMC)-based parameter estimation, we analyze the effects of the model parameters on the number of M1 and M2 cells in the penumbra and fit identifiable parameters to the compiled experimental data set. We utilize results from MCMC parameter estimation to ascertain uncertainty bounds and forward predictions for the number of M1 and M2 microglial cells over time. Results demonstrate the significance of parameters related to M1 and M2 activation on the number of M1 and M2 microglial cells. Simulations further suggest that potential outliers in the observed data may be omitted and forecast predictions suggest a lingering inflammatory response.

Role of astrocytes connexins - pannexins in acute brain injury

Acute brain injuries (ABIs) encompass a broad spectrum of primary injuries such as ischemia, hypoxia, trauma, and hemorrhage that converge into secondary injury where some mechanisms show common determinants. In this regard, astroglial connexin and pannexin channels have been shown to play an important role. These channels are transmembrane proteins sharing similar topology and form gateways between adjacent cells named gap junctions (GJs) and pores into unopposed membranes named hemichannels (HCs). In astrocytes, GJs and HCs enable intercellular communication and have active participation in normal brain physiological processes, such as calcium waves, synapsis modulation, regional blood flow regulation, and homeostatic control of the extracellular environment, among others. However, after acute brain injury, astrocytes can change their phenotype and modify the activity of both channels and hemichannels, which can result in the amplification of danger signals, increased mediators of inflammation, and neuronal death, contributing to the expansion of brain damage and neurological deterioration. This is known as secondary brain damage. In this review, we discussed the main biological mechanism of secondary brain damage with a particular focus on astroglial connexin and pannexin participation during acute brain injuries.

Constitutive DAMPs in CNS injury: From preclinical insights to clinical perspectives

Damage-associated molecular patterns (DAMPs) are endogenous molecules released in tissues upon cellular damage and necrosis, acting to initiate sterile inflammation. Constitutive DAMPs (cDAMPs) have the particularity to be present within the intracellular compartments of healthy cells, where they exert diverse functions such as regulation of gene expression and cellular homeostasis. However, after injury to the central nervous system (CNS), cDAMPs are rapidly released by stressed, damaged or dying neuronal, glial and endothelial cells, and can trigger inflammation without undergoing structural modifications. Several cDAMPs have been described in the injured CNS, such as interleukin (IL)-1α, IL-33, nucleotides (e.g. ATP), and high-mobility group box protein 1. Once in the extracellular milieu, these molecules are recognized by the remaining surviving cells through specific DAMP-sensing receptors, thereby inducing a cascade of molecular events leading to the production and release of proinflammatory cytokines and chemokines, as well as cell adhesion molecules. The ensuing immune response is necessary to eliminate cellular debris caused by the injury, allowing for damage containment. However, seeing as some molecules associated with the inflammatory response are toxic to surviving resident CNS cells, secondary damage occurs, aggravating injury and exacerbating neurological and behavioral deficits. Thus, a better understanding of these cDAMPs, as well as their receptors and downstream signaling pathways, could lead to identification of novel therapeutic targets for treating CNS injuries such as SCI, TBI, and stroke. In this review, we summarize the recent literature on cDAMPs, their specific functions, and the therapeutic potential of interfering with cDAMPs or their signaling pathways.

IL-33/ST2 signaling in monocyte-derived macrophages maintains blood-brain barrier integrity and restricts infarctions early after ischemic stroke

BACKGROUND

Brain microglia and infiltrating monocyte-derived macrophages are vital in preserving blood vessel integrity after stroke. Understanding mechanisms that induce immune cells to adopt vascular-protective phenotypes may hasten the development of stroke treatments. IL-33 is a potent chemokine released from damaged cells, such as CNS glia after stroke. The activation of IL-33/ST2 signaling has been shown to promote neuronal viability and white matter integrity after ischemic stroke. The impact of IL-33/ST2 on blood-brain barrier (BBB) integrity, however, remains unknown. The current study fills this gap and reveals a critical role of IL-33/ST2 signaling in macrophage-mediated BBB protection after stroke.

METHODS

Transient middle cerebral artery occlusion (tMCAO) was performed to induce ischemic stroke in wildtype (WT) versus ST2 knockout (KO) male mice. IL-33 was applied intranasally to tMCAO mice with or without dietary PLX5622 to deplete microglia/macrophages. ST2 KO versus WT bone marrow or macrophage cell transplantations were used to test the involvement of ST2+ macrophages in BBB integrity. Macrophages were cocultured in transwells with brain endothelial cells (ECs) after oxygen-glucose deprivation (OGD) to test potential direct effects of IL33-treated macrophages on the BBB in vitro.

RESULTS

The ST2 receptor was expressed in brain ECs, microglia, and infiltrating macrophages. Global KO of ST2 led to more IgG extravasation and loss of ZO-1 in cerebral microvessels 3 days post-tMCAO. Intranasal IL-33 administration reduced BBB leakage and infarct severity in microglia/macrophage competent mice, but not in microglia/macrophage depleted mice. Worse BBB injury was observed after tMCAO in chimeric WT mice reconstituted with ST2 KO bone marrow, and in WT mice whose monocytes were replaced by ST2 KO monocytes. Macrophages treated with IL-33 reduced in vitro barrier leakage and maintained tight junction integrity after OGD. In contrast, IL-33 exerted minimal direct effects on the endothelial barrier in the absence of macrophages. IL-33-treated macrophages demonstrated transcriptional upregulation of an array of protective factors, suggesting a shift towards favorable phenotypes.

CONCLUSION

Our results demonstrate that early-stage IL-33/ST2 signaling in infiltrating macrophages reduces the extent of acute BBB disruption after stroke. Intranasal IL-33 administration may represent a new strategy to reduce BBB leakage and infarct severity.

Neuroprotective effects of all-trans-retinoic acid are mediated via downregulation of TLR4/NF-κB signaling in a rat model of middle cerebral artery occlusion

OBJECTIVES

To determine the effects of all-trans-retinoic acid (ATRA) on the post-stroke inflammatory response and elucidate the underlying molecular mechanisms.

METHODS

This animal experiment was conducted at Central Laboratory, the First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, China during 2020-2022. Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) for 1.5 h, and treated with ATRA at 2 and 24 h after reperfusion. Neurological deficit scores on behavioral tests, and cerebral infarct volume, microglial polarization, and the expression levels of inflammatory cytokines and proteins associated with TLR4/NF-κB signaling were assessed.

RESULTS

The ATRA administration reduced cerebral infarct volume and ameliorated neurological deficit scores in MCAO rats. Additionally, ATRA relieved cerebral edema and downregulated the secretion of proinflammatory cytokines after stroke. Finally, ATRA attenuated the polarization of the microglia toward the M1 phenotype and promoted the activation of the beneficial M2 phenotype; the underlying mechanism potentially involved the suppression of the TLR4/NF-κB signaling pathway.

CONCLUSION

The ATRA treatment promoted functional recovery in an experimental model of ischemic stroke by attenuating neural inflammation. ATRA potentially modulated microglia-mediated neuroinflammation via the downregulation of the TLR4/NF-κB signaling pathway, which makes it a candidate treatment for post-stroke neuroinflammation.

Expanding Role of Interleukin-1 Family Cytokines in Acute Ischemic Stroke

Ischemic stroke (IS) is a critical medical condition that results in significant neurological deficits and tissue damage, affecting millions worldwide. Currently, there is a significant lack of reliable tools for assessing and predicting IS outcomes. The inflammatory response following IS may exacerbate tissue injury or provide neuroprotection. This review sought to summarize current knowledge on the IL-1 family's involvement in IS, which includes pro-inflammatory molecules, such as IL-1α, IL-1β, IL-18, and IL-36, as well as anti-inflammatory molecules, like IL-1Ra, IL-33, IL-36A, IL-37, and IL-38. The balance between these opposing inflammatory processes may serve as a biomarker for determining patient outcomes and recovery paths. Treatments targeting these cytokines or their receptors show promise, but more comprehensive research is essential to clarify their precise roles in IS development and progression.

IL-33 in Ischemic Stroke: Brain vs. Periphery

Cerebrovascular disease is the second-leading cause of death and disability worldwide, with stroke being the most common cause. In ischemic stroke, several processes combine to produce immunosuppression, leaving the post-stroke body susceptible to infection, which in turn affects neuroinflammation. Interleukin-33 (IL-33), a member of the interleukin-1 family (IL-1), functions as a modulator of immune responses and inflammation, playing a crucial role in the establishment of immunologic responses. IL-33 has been shown to have a protective effect on brain injury and represents a potential target by modulating inflammatory cytokines and stimulating immune regulatory cells. With an emphasis on preclinical and clinical studies, this review covers the impact of IL-33 on immune system mechanisms following ischemic stroke.

Interleukin-33 ameliorates perioperative neurocognitive disorders by modulating microglial state

Perioperative neurocognitive disorders (PND) are cognitive dysfunctions that usually occur in elderly patients after anesthesia and surgery. Microglial overactivation is a key underlying mechanism. Interleukin-33 (IL-33) is a member of the IL-1 family that orchestrates microglial function. In the present study, we explored how IL-33, which regulates microglia, contributes to cognitive improvement in a male mouse model of PND. An exploratory laparotomy was performed to establish a PND model. The expression levels of IL-33 and its receptor ST2 were evaluated using Western blot. IL-33/ST2 secretion, microglial density, morphology, phagocytosis of synapse, and proliferation, and dystrophic microglia were assessed using immunofluorescence. Synaptic plasticity was measured using Golgi staining and long-term potentiation. The Morris water maze and open field test were used to evaluate cognitive function and anxiety. Hippocampal expression of IL-33 and ST2 were elevated on postoperative day 3. We confirmed that IL-33 was secreted by astrocytes and neurons, whereas ST2 mainly colocalized with microglia. IL-33 treatment induced microgliosis after anesthesia and surgery. These microglia had larger soma sizes and shorter and fragmented branches. Compared to the Surgery group, IL-33 treatment reduced the synaptic phagocytosis of microglia and increased microglial proliferation and dystrophic microglia. IL-33 treatment also reversed the impaired synaptic plasticity and cognitive function caused by anesthesia and surgery. In conclusion, these results indicate that IL-33 plays a key role in regulating microglial state and synaptic phagocytosis in a PND mouse model. IL-33 treatment has a therapeutic potential for improving cognitive dysfunction in PND.

Releasing Dynamic of Serum ST2 and Calprotectin in Patients with Acute Ischemic Stroke

This study investigated the releasing dynamics of serum ST2 and calprotectin in patients with acute IS. The study included acute IS patients (N = 20) with an NIH Stroke Scale score ≥8. Sampling was performed at seven time points: after admission (T0) and at the following 24 h consecutive intervals (T1-T6). Primary outcome at 90 days was evaluated using the modified Rankin scale: 0-2 for good and 3-6 for poor functional outcome. The secondary outcome was all-cause mortality after 90 days. Fifteen patients had a poor outcome, and eight died. Results showed a statistically significant difference in ST2 concentrations between good and poor outcomes at T0 (p = 0.04), T1 (p = 0.006), T2 (p = 0.01), T3 (p = 0.021), T4 (p = 0.007), T5 (p = 0.032), and for calprotectin T6 (p = 0.034). Prognostic accuracy was highest for ST2 at T1 for a cut-off > 18.9 µg/L (sensitivity 80% and specificity 100.0%) and for calprotectin at T5 for a cut-off > 4.5 mg/L (sensitivity 64.3% and specificity 100.0%). Serum ST2 and calprotectin-releasing dynamics showed a valuable prognostic accuracy for IS outcomes.

Plasmatic profiles of cytokines/chemokines, glial fibrillary acidic protein (GFAP) and MRI brain damage in neonates with hypoxic ischemic encephalopathy (HIE)

BACKGROUND

Perinatal hypoxia triggers the release of cytokines and chemokines by neurons, astrocytes and microglia. In response to hypoxia-ischemia resting/ramified microglia proliferate and undergo activation, producing proinflammatory molecules. The brain damage extension seems to be related to both the severity of hypoxia and the balance between pro and anti-inflammatory response and can be explored with neuroimaging.

AIMS

The aim of this preliminary study was to explore possible relationships between plasma levels of inflammatory cytokines/chemokines and the severe brain damage detectable by Magnetic Resonance Imaging (MRI), performed during the hospitalization.

METHODS

In 10 full terms neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH), divided into cases and controls, according to MRI results, we measured and compared the plasma levels of CCL2/MCP-1, CXCL8, GFAP, IFN y, IL-10, IL-18, IL-6, CCL3, ENOLASE2, GM-CSF, IL-1b, IL-12p70, IL-33, TNFα, collected at four different time points during TH (24, 25-48, 49-72 h of life, and 7-10 days from birth). Five of enrolled babies had pathological brain MRI (cases) and 5 had a normal MRI examination (controls). Cytokines were measured by Magnetic Luminex Assay. MRI images were classified according to Barkovich's score.

RESULTS

Mean levels of all cytokines and molecules at time T1 were not significantly different in the two groups. Comparing samples paired by day of collection, the greatest differences between cases and controls were found at times T2 and T3, during TH. At T4, levels tended to get closer again (except for IL-6, IL10 and IL18). Infants with worse MRI showed higher plasmatic GFAP levels than those with normal MRI, while their IL-18 was lower. The mean levels of CCL3MIP1alpha, GMCSF, IL1BETA overlapped throughout the observation period in both groups.

CONCLUSION

In a small number of infants with worse brain MRI, we found higher levels of GFAP and of IL-10 at T4 and a trend toward low IL-18 levels than in infants with normal MRI, considered early biomarker of brain damage and a predictor of adverse outcome, respectively. The greatest, although not significant, difference between the levels of molecules was found in cases and controls at time points T2 and T3, during TH.

Glia Maturation Factor Beta: A Novel Neuro-Impairment Prediction Factor in Toxoplasmosis

Background

Toxoplasma gondii, a neurotropic protozoan, infects up one to third of the world population. The parasite can invade a wide variety of nucleated cells but preferably glial cells. Glia maturation factor β (GMFβ), a 17KD protein expressed at high levels in the central nervous system is predominantly related to neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Multiple sclerosis. We aimed to determine the expression level of GMFβ and its relation to other pro-inflammatory factors (IL33, SDF1, and CCL2) on T. gondii infected human neuroblastoma cell line.

Methods

The human neuroblastoma (SK_NMC C535) cell line was infected by 5×106 (1:1 ratio). The supernatant was collected after cell lysis and centrifugation. Total RNA was extracted using the Yekta Tajhiz RNA extraction kit. cDNA was synthesized based on RevertAid First Strand cDNA Synthesis Kit manufacturer's protocol (Parstous, cDNA synthesis kit, Iran). The specificity of each primer pair (GMFβ, IL33, SDF1, and CCL2) was provided by NCBI BLAST. Gene expression level was measured using Real-Time PCR. All experiments were conducted at the Hamadan University of Medical Sciences, western Iran in 2022.

Results

The GMFβ increased significantly up to 1.35-fold (P=0.007). The increase in GMFβ expression in neuroblastoma cells was consistent with the increase in pro-inflammatory factors (CCL2 (0.47), IL33 (0.152) and, SDF1 (1.33)).

Conclusion

GMFβ upregulation can be a novel indicator of the destruction of nerve cells.

Xenon ameliorates chronic post-surgical pain by regulating mitophagy in microglia and rats mediated by PINK1/Parkin pathway

Background

Chronic post-surgical pain (CPSP) is one of the important causes of poor postoperative outcomes, the activation of microglia in the spinal cord is closely related to the generation, transmission and maintenance of CPSP. Xenon (Xe), an anesthetic gas, has been reported to be able to significantly reduce intraoperative analgesia and postoperative pain sensation at low doses. However, the mechanism of the regulatory effect of xenon on activated microglia after CPSP remains unclear.

Methods

In this study, CPSP model rats were treated with 50% Xe inhalation for 1 h following skin/muscle incision and retraction (SMIR), once a day for 5 consecutive days, and then the painbehavioraltests (pain behavior indexes paw withdrawal mechanical threshold, PWMT and thermal withdrawal latency, TWL), microglial activation, oxidative stress-related indexes (malondialdehyde, MDA; superoxide dismutase, SOD; hydrogen peroxide, H2O2; and catalase, CAT), mitophagy and PINK1/Parkin pathway were examined.

Results

The present results showed that a single dose of Xe treatment in SMIR rat model could significantly improve PWMT and TWL in the short-term at a single treatment and long-term at multiple treatments. Xe treatment inhibited microglia activation and oxidative stress in the spinal dorsal horn of SMIR rats, as indicated by the decrease of Iba1 and MDA/H2O2 levels and the increase of SOD/CAT levels. Compared with the control group, Xe further increased the CPSP promoted Mito-Tracker (a mitochondrial marker) and LC3 (an autophagy marker) co-localization positive spots and PINK1/Parkin/ATG5/BECN1 (autophagy-related proteins) protein expression levels, and inhibited the Mito-SOX (a mitochondrial reactive oxygen species marker) positive signal, indicating that Xe promoted microglia mitophagy and inhibited oxidative stress in CPSP. Mechanistically, we verified that Xe promoted PINK1/Parkin signaling pathway activation.

Conclusion

Xe plays a role in ameliorating chronic post-surgical pain by regulating the PINK1/Parkin pathway mediated microglial mitophagy and provide new ideas and targets for the prevention and treatment of CPSP.

ULK1 confers neuroprotection by regulating microglial/macrophages activation after ischemic stroke

Microglial activation and autophagy play a critical role in the progression of ischemic stroke and contribute to the regulation of neuroinflammation. Unc-51-like kinase 1 (ULK1) is the primary autophagy kinase involved in autophagosome formation. However, the impact of ULK1 on neuroprotection and microglial activation after ischemic stroke remains unclear. In this study, we established a photothrombotic stroke model, and administered SBI-0206965 (SBI), an ULK1 inhibitor, and LYN-1604 hydrochloride (LYN), an ULK1 agonist, to modulate ULK1 activity in vivo. We assessed sensorimotor deficits, neuronal apoptosis, and microglial/macrophage activation to evaluate the neurofunctional outcome. Immunofluorescence results revealed ULK1 was primarily localized in the microglia of the infarct area following ischemia. Upregulating ULK1 through LYN treatment significantly reduced infarct volume, improved motor function, promoted the increase of anti-inflammatory microglia. In conclusion, ULK1 facilitated neuronal repair and promoted the formation of anti-inflammatory microglia pathway after ischemic injury.

Mechanisms of immune response and cell death in ischemic stroke and their regulation by natural compounds

Ischemic stroke (IS), which is the third foremost cause of disability and death worldwide, has inflammation and cell death as its main pathological features. IS can lead to neuronal cell death and release factors such as damage-related molecular patterns, stimulating the immune system to release inflammatory mediators, thereby resulting in inflammation and exacerbating brain damage. Currently, there are a limited number of treatment methods for IS, which is a fact necessitating the discovery of new treatment targets. For this review, current research on inflammation and cell death in ischemic stroke was summarized. The complex roles and pathways of the principal immune cells (microglia, astrocyte, neutrophils, T lymphocytes, and monocytes/macrophage) in the immune system after IS in inflammation are discussed. The mechanisms of immune cell interactions and the cytokines involved in these interactions are summarized. Moreover, the cell death mechanisms (pyroptosis, apoptosis, necroptosis, PANoptosis, and ferroptosis) and pathways after IS are explored. Finally, a summary is provided of the mechanism of action of natural pharmacological active ingredients in the treatment of IS. Despite significant recent progress in research on IS, there remain many challenges that need to be overcome.

Interleukin-33 has the protective effect on oligodendrocytes against impairment induced by cuprizone intoxication

Our prior investigations have demonstrated the pivotal role of IL-33 in facilitating the maturation of oligodendrocytes (OLs), prompting our interest in exploring its potential therapeutic effects. In this study, our focus was directed towards deciphering the functions of interleukin-33 (IL-33) in established demyelinating mouse model induced by the feeding of cuprizone (CPZ)-containing diet. We observed the reduction in corpus callosal adenomatous polyposis coli (APC)+ OLs with IL-33 expression in mice subjected to CPZ feeding for durations of 6 and 8 weeks. In parallel, the levels of IL-33 in the corpus callosum declined after CPZ-containing diet. Furthermore, we conducted experiments utilizing primary oligodendrocyte precursor cells (OPCs) and mature OLs, which were exposed to CPZ. A decrease in the expression of myelin basic protein (MBP) was evident in the cultures of mature OLs after treatment with CPZ. Additionally, both IL-33 mRNA and protein levels exhibited downregulation. To counteract the diminished IL-33 levels induced by CPZ, we employed a lentiviral vector to overexpress IL-33 in OLs. Intriguingly, the overexpression of IL-33 (IL33OE) in OLs resulted in a more distinct membranous morphology following CPZ treatment when compared to that observed in OL Mock cultures. Moreover, MBP protein levels in the presence of CPZ were higher in IL33OE OLs than that detected in OL Mock cultures. These findings collectively indicate that IL-33 possesses the capability to mitigate CPZ-induced damage and bolster OL homeostasis. In summary, our study underscores the importance of IL-33 in the context of demyelinating diseases, shedding light on its potential therapeutic implications for fostering remyelination and preserving OL function.

Black Phosphorus Accelerates Bone Regeneration Based on Immunoregulation

A fundamental understanding of inflammation and tissue healing suggests that the precise regulation of the inflammatory phase, both in terms of location and timing, is crucial for bone regeneration. However, achieving the activation of early inflammation without causing chronic inflammation while facilitating quick inflammation regression to promote bone regeneration continues to pose challenges. This study reveals that black phosphorus (BP) accelerates bone regeneration by building an osteogenic immunological microenvironment. BP amplifies the acute pro-inflammatory response and promotes the secretion of anti-inflammatory factors to accelerate inflammation regression and tissue regeneration. Mechanistically, BP creates an osteoimmune-friendly microenvironment by stimulating macrophages to express interleukin 33 (IL-33), amplifying the inflammatory response at an early stage, and promoting the regression of inflammation. In addition, BP-mediated IL-33 expression directly promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which further facilitates bone repair. To the knowledge, this is the first study to reveal the immunomodulatory potential of BP in bone regeneration through the regulation of both early-stage inflammatory responses and later-stage inflammation resolution, along with the associated molecular mechanisms. This discovery serves as a foundation for the clinical use of BP and is an efficient approach for managing the immune microenvironment during bone regeneration.

Recent advances in tissue repair of the blood-brain barrier after stroke

The selective permeability of the blood-brain barrier (BBB) enables the necessary exchange of substances between the brain parenchyma and circulating blood and is important for the normal functioning of the central nervous system. Ischemic stroke inflicts damage upon the BBB, triggering adverse stroke outcomes such as cerebral edema, hemorrhagic transformation, and aggravated neuroinflammation. Therefore, effective repair of the damaged BBB after stroke and neovascularization that allows for the unique selective transfer of substances from the BBB after stroke is necessary and important for the recovery of brain function. This review focuses on four important therapies that have effects of BBB tissue repair after stroke in the last seven years. Most of these new therapies show increased expression of BBB tight-junction proteins, and some show beneficial results in terms of enhanced pericyte coverage at the injured vessels. This review also briefly outlines three effective classes of approaches and their mechanisms for promoting neoangiogenesis following a stroke.

MiR-548t-5p regulates pancreatic ductal adenocarcinoma metastasis through an IL-33-dependent crosstalk between cancer cells and M2 macrophages

IL-33 has been associated with pro- and anticancer functions in cancer. However, its role in pancreatic cancer metastasis remains unknown. This study aimed to explore the role of miR-548t-5p/IL-33 axis in the metastasis of pancreatic cancer. Luciferase activity assay, qRT-PCR, Western blot and ELISA were performed to prove whether IL-33 is the target of miR-548t-5p. In vivo metastasis assay and cellular transwell assay were performed to explore the role of miR-548t-5p/IL-33 axis in the invasion and metastasis of pancreatic cancer. Co-culture experiments and immunohistochemistry were performed to observe whether IL-33 affects cell invasion and metastasis dependent on the involvement of M2 macrophages. THP-1 cell induction experiment and flow cytometry were performed to explore the effect of IL-33 on macrophage polarization. CCK-8, colony formation, cell apoptosis, cell cycle, cell wound healing and transwell assay were performed to investigate the effect of IL-33 induced M2 macrophages on cell malignant biological behavior by coculturing pancreatic cancer cells with the conditioned medium (CM) from macrophages. We found that miR-548t-5p regulated the expression and secretion of IL-33 in pancreatic cancer cells by directly targeting IL-33 mRNA. IL-33 secreted by cancer cells promoted the recruitment and activation of macrophages to a M2-like phenotype. In turn, IL-33 induced M2 macrophages promoted the migration and invasion of cancer cells. Moreover, IL-33 affected pancreatic cancer cell invasion dependent on the involvement of M2 macrophages in the co-culture system. Thus, our study suggested that manipulation of this IL-33-dependent crosstalk has a therapeutic potential for the treatment of pancreatic cancer metastasis.

Reveal the correlation between hub hypoxia/immune-related genes and immunity and diagnosis, and the effect of SAP30 on cell apoptosis, ROS and MDA production in cerebral ischemic stroke

BACKGROUND

Cerebral ischemic stroke (CIS) is a common cerebrovascular disease. The purpose of this study was to investigate the potential mechanism of hypoxia and immune-related genes in CIS.

METHODS

All data were downloaded from public databases. Hub mRNAs was identified by differential expression analysis, WGCNA analysis and machine learning. Hub mRNAs were used to construct the classification models. Pearson correlation analysis was used to analyze the correlation between hub mRNAs and immune cell infiltration. Finally, the SAP30 was selected for verification in HMC3 cells.

RESULTS

The SVM, RF and DT classification models constructed based on 6 hub mRNAs had higher area under the curve values, which implied that these classification models had high diagnostic accuracy. Pearson correlation analysis found that Macrophage has the highest negative correlation with CCR7, while Neutrophil has the highest positive correlation with SLC2A3. Drug prediction found that ruxolitinib, methotrexate, resveratrol and resatorvid may play a role in disease treatment by targeting different hub mRNAs. Notably, inhibition of SAP30 expression can reduce the apoptosis of HMC3 cells and inhibit the production of ROS and MDA.

CONCLUSION

The identification of hub miRNAs and the construction of classification diagnosis models provide a theoretical basis for the diagnosis and management of CIS.

Montelukast sodium protects against focal cerebral ischemic injury by regulating inflammatory reaction via promoting microglia polarization

BACKGROUND

Neuroinflammation plays an important role in brain injury and repair. Regulation of post-stroke inflammation may be a reasonable strategy to treat ischemic stroke. The present study demonstrates that montelukast sodium protected brain tissue by regulating the post-stroke inflammatory reaction.

METHODS

Adult male mice underwent distal occlusion of the middle cerebral artery (d-MCAO) surgery, followed by intraperitoneal injection of montelukast sodium or equivalent saline, from day 0-7 after the operation. On the 7th day, Rotarod and adhesive-removal test were performed. M AP2 staining, and Iba1, CD206, and CD16/32 co staining were performed. BV2 microglial cell lines were co-cultured with different concentrations of montelukast sodium with or without lipopolysaccharide (LPS). Real-time polymerase chain reaction (rt-PCR) and enzyme linked immunosorbent assay (ELISA) were used to detect the mRNA expression of M1 and M2 phenotypic microglia markers and the release of cytokines representing from different phenotypes of microglia cells.

RESULTS

Montelukast sodium prolonged the time that d-MCAO mice remained on the rotating bar, shortened the time to remove the sticker on the opposite claw, and reduced the infarct volume, promoting the transformation of microglial cells/macrophages around the infarct to the M2 phenotype. Montelukast sodium increased the mRNA expression of Arg-1, CD206, TGF-β, and IL-10 in BV2 microglial cell lines stimulated by LPS, while decreased the expression of iNOS, TNF-α, and CD16/32.

CONCLUSION

Montelukast sodium can protect against focal cerebral ischemic injury by regulating inflammatory reaction via promoting microglia polarization.

IL-33 promotes sciatic nerve regeneration in mice by modulating macrophage polarization

Despite the innate regenerative capacity of peripheral nerves, regeneration after a severe injury is insufficient, and sensorimotor recovery is incomplete. As a result, finding alternative methods for improving regeneration and sensorimotor recovery is essential. In this regard, we investigated the effect of IL-33 treatment as a chemokine with neuroprotective properties. IL-33 can facilitate tissue healing by potentiating the type 2 immune response and polarizing macrophages toward the pro-healing M2 phenotype. However, its effects on nerve regeneration remain unclear. Therefore, this research aimed to evaluate the neuroprotective effects of IL-33 on sciatic nerve injury in male C57BL/6 mice. After crushing the left sciatic nerve, the animals were given 10, 25, or 50 µg/kg IL-33 intraperitoneally for seven days. The sensorimotor recovery was then assessed eight weeks after surgery. In addition, immunohistochemistry, ELISA, and real-time PCR were used to assess macrophage polarization, cytokine secretion, and neurotrophic factor expression in the injured nerves. IL-33 at 50 and 25 µg/kg doses could significantly accelerate nerve regeneration and improve sensorimotor recovery when compared to 10 µg/kg IL-33 and control groups. Furthermore, at 50 and 25 µg/kg doses, IL-33 polarized macrophages toward an M2 phenotype and reduced proinflammatory cytokines at the injury site. It also increased the mRNA expression of NGF, VEGF, and BDNF. These findings suggest that a seven-day IL-33 treatment had neuroprotective effects in a mouse sciatic nerve crush model, most likely by inducing macrophage polarization toward M2 and regulating inflammatory microenvironments.

Interleukin-33 improves the neurogenesis of neural stem cells in perinatal brain after hypoxia-ischemia

Perinatal hypoxia-ischemia (HI) insult is an important cause of neonatal encephalopathy, and the effective therapeutic approaches are currently limited. Interleukin (IL)-33 acts as a member of the IL-1 superfamily and has been shown to be neuroprotective following experimental neonatal HI and adult stroke. Here, we explore the effect of IL-33 and its specific receptor ST2 axis on endogenous neurogenesis in neonatal brain after HI. ST2 was found on the surface of NSCs, and the expression of ST2 was further enhanced after HI challenge. Delivery of IL-33 obviously repopulated the size of NSC pool, whereas ST2 deficiency worsened the neurogenesis of NSCs in neonatal brain post HI insult. Further in vivo and in vitro studies showed IL-33 regulates the survival, proliferation and differentiation of NSCs through ST2 signaling pathways. Intriguingly, IL-33 facilitated translocation of Nrf2 from the cytoplasm to the nucleus, which is involved in neural differentiation of NSCs. These data demonstrate a critical role of IL-33/ST2 axis in regulation of endogenous neurogenesis of NSCs via activation of the Nrf2 signaling, which provide a new insight into the effect of IL-33 in neonatal brain following HI injury.

Modulation of Neuroinflammation: Advances in Roles and Mechanisms of the IL-33/ST2 Axis Involved in Ischemic Stroke

Interleukin (IL)-33 was initially recognized as a constituent of the IL-1 cytokine family in 2005. It exerts pleiotropic effects by regulating immune responses via its binding to the receptor ST2 (IL-33R). The IL-33/ST2 pathway has been linked to several inflammatory disorders. In human and rodents, the broad expression of IL-33 in spinal cord tissues and brain indicates its central nervous system-specific functions. Growing evidence supports the protective effects of the IL-33/ST2 pathway in ischemic stroke, along with a better understanding of the underlying mechanisms. IL-33 plays a crucial role in the regulation of the release of inflammatory molecules from glial cells in response to neuropathological lesions. Moreover, IL-33/ST2-mediated neuroprotection following cerebral ischemia may be linked to T-cell function, specifically regulatory T cells. Soluble ST2 (sST2) acts as a decoy receptor in the IL-33/ST2 axis, blocking IL-33 signaling through the membrane ST2 receptor. sST2 has also been identified as a potential inflammatory biomarker of ischemic stroke. Targeting sST2 specifically to eliminate its inhibition of the protective IL-33/ST2 pathway in ischemic brain tissues is a promising approach for the treatment of ischemic stroke.

Roles and therapeutic potential of different extracellular vesicle subtypes on traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of injury-related disability and death around the world, but the clinical stratification, diagnosis, and treatment of complex TBI are limited. Due to their unique properties, extracellular vesicles (EVs) are emerging candidates for being biomarkers of traumatic brain injury as well as serving as potential therapeutic targets. However, the effects of different extracellular vesicle subtypes on the pathophysiology of traumatic brain injury are very different, or potentially even opposite. Before extracellular vesicles can be used as targets for TBI therapy, it is necessary to classify different extracellular vesicle subtypes according to their functions to clarify different strategies for EV-based TBI therapy. The purpose of this review is to discuss contradictory effects of different EV subtypes on TBI, and to propose treatment ideas based on different EV subtypes to maximize their benefits for the recovery of TBI patients. Video Abstract.

Transcriptomic Analyses of Neurotoxic Astrocytes Derived from Adult Triple Transgenic Alzheimer's Disease Mice

Neurodegenerative diseases such as Alzheimer's disease have been classically studied from a purely neuronocentric point of view. More recent evidences support the notion that other cell populations are involved in disease progression. In this sense, the possible pathogenic role of glial cells like astrocytes is increasingly being recognized. Once faced with tissue damage signals and other stimuli present in disease environments, astrocytes suffer many morphological and functional changes, a process referred as reactive astrogliosis. Studies from murine models and humans suggest that these complex and heterogeneous responses could manifest as disease-specific astrocyte phenotypes. Clear understanding of disease-associated astrocytes is a necessary step to fully disclose neurodegenerative processes, aiding in the design of new therapeutic and diagnostic strategies. In this work, we present the transcriptomics characterization of neurotoxic astrocytic cultures isolated from adult symptomatic animals of the triple transgenic mouse model of Alzheimer's disease (3xTg-AD). According to the observed profile, 3xTg-AD neurotoxic astrocytes show various reactivity features including alteration of the extracellular matrix and release of pro-inflammatory and proliferative factors that could result in harmful effects to neurons. Moreover, these alterations could be a consequence of stress responses at the endoplasmic reticulum and mitochondria as well as of concomitant metabolic adaptations. Present results support the hypothesis that adaptive changes of astrocytic function induced by a stressed microenvironment could later promote harmful astrocyte phenotypes and further accelerate or induce neurodegenerative processes.

Regulatory mechanisms of natural compounds from traditional Chinese herbal medicines on the microglial response in ischemic stroke

BACKGROUND

Development of clinically effective neuroprotective agents for stroke therapy is still a challenging task. Microglia play a critical role in brain injury and recovery after ischemic stroke. Traditional Chinese herbal medicines (TCHMs) are based on a unique therapeutic principle, have various formulas, and have long been widely used to treat stroke. Therefore, the active compounds in TCHMs and their underlying mechanisms of action are attracting increasing attention in the field of stroke drug development.

PURPOSE

To summarize the regulatory mechanisms of TCHM-derived natural compounds on the microglial response in animal models of ischemic stroke.

METHODS

We searched studies published until 10 April 2023 in the Web of Science, PubMed, and ScienceDirect using the following keywords: natural compounds, natural products or phytochemicals, traditional Chinese Medicine or Chinese herbal medicine, microglia, and ischemic stroke. This review was prepared according to PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analysis) guidelines.

RESULTS

Natural compounds derived from TCHMs can attenuate the M1 phenotype of microglia, which is involved in the detrimental inflammatory response, via inhibition of NF-κB, MAPKs, JAK/STAT, Notch, TLR4, P2X7R, CX3CR1, IL-17RA, the NLRP3 inflammasome, and pro-oxidant enzymes. Additionally, the neuroprotective response of microglia with the M2 phenotype can be enhanced by activating Nrf2/HO-1, PI3K/AKT, AMPK, PPARγ, SIRT1, CB2R, TREM2, nAChR, and IL-33/ST2. Several clinical trials showed that TCHM-derived natural compounds that regulate microglial responses have significant and safe therapeutic effects, but further well-designed clinical studies are needed.

CONCLUSIONS

Further research regarding the direct targets and potential pleiotropic or synergistic effects of natural compounds would provide a more reasonable approach for regulation of the microglial response with the possibility of successful stroke drug development.

Selenium supplementation enhanced the expression of selenoproteins in hippocampus and played a neuroprotective role in LPS-induced neuroinflammation

Selenium (Se) is obtained from organic and inorganic selenium food content, which mainly depends on the regional soil selenium content. Selenium deficiency and decreased selenoprotein functions have been shown to associate with the progression of cognitive decline and neurodegenerations including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Selenoproteins are well recognized for their anti-oxidative activities. Given the high oxygen consumption, mammalian brains preferent@ially supplied with Se. Here, we propose a beneficiary role for dietary supplementation of sodium selenite (300 ng per gram of body weight) in ameliorating neuroinflammation induced by bilateral intracerebroventricular injection of 1 μL LPS (1 μg/μL), evidenced by the significantly reduced oxidative stress, downregulated pro-inflammatory cytokines expression, improved integrity of blood-brain barrier, as well as suppressed glial activation and shifted microglial MI/M2 polarization in Se-sup mouse brain. Se intake also reduced neural cell death and significantly improved the cognition in Se-sup mice following LPS challenge. The neuroprotective role for supplementary Se is likely to be ascribed to the overall elevated expression of selenoproteins, especially Selenoprotein P (SELENOP) and Glutathione peroxidase 4 (GPX4), ranking on top of the change in selenoprotein expression hierarchy. The regional hierarchy of Se induced elevation of SELENOP expression was further characterized. The SELENOP expression in the mediodorsal thalamic nucleus, dendric gyrus (DG) and cornu ammonis 3 (CA3) of hippocampus and lateral habenular nucleus was highly sensitive to dietary Se intake.

Exogenous interleukin 33 enhances the brain's lymphatic drainage and toxic protein clearance in acute traumatic brain injury mice

The persistent dysregulation and accumulation of poisonous proteins from destructive neural tissues and cells activate pathological mechanisms after traumatic brain injury (TBI). The lymphatic drainage system of the brain, composed of the glymphatic system and meningeal lymphatic vessels (MLVs), plays an essential role in the clearance of toxic waste after brain injury. The neuroprotective effect of interleukin 33 (IL-33) in TBI mice has been demonstrated; however, its impact on brain lymphatic drainage is unclear. Here, we established a fluid percussion injury model to examine the IL-33 administration effects on neurological function and lymphatic drainage in the acute brain of TBI mice. We verified that exogenous IL-33 could improve the motor and memory skills of TBI mice and demonstrated that in the acute phase, it increased the exchange of cerebrospinal and interstitial fluid, reversed the dysregulation and depolarization of aquaporin-4 in the cortex and hippocampus, improved the drainage of MLVs to deep cervical lymph nodes, and reduced tau accumulation and glial activation. We speculate that the protective effect of exogenous IL-33 on TBI mice's motor and cognitive functions is related to the enhancement of brain lymphatic drainage and toxic metabolite clearance from the cortex and hippocampus in the acute stage. These data further support the notion that IL-33 therapy may be an effective treatment strategy for alleviating acute brain injury after TBI.

iPSC-sEVs alleviate microglia senescence to protect against ischemic stroke in aged mice

The polarization of microglia plays an important role in the outcome of ischemic stroke (IS). In the aged population, senescent microglia show a predominant pro-inflammatory phenotype, which leads to worse outcomes in aged ischemic stroke compared to young ischemic stroke. Recent research demonstrated that inducible pluripotent stem cell-derived small extracellular vesicles (iPSC-sEVs) possess the significant anti-ageing ability. We hypothesized that iPSC-sEVs could alleviate microglia senescence to regulate microglia polarization in aged ischemic stroke. In this study, we showed that treatment with iPSC-sEVs significantly alleviated microglia senescence as indicated by the decreased senescence-associated proteins including P16, P21, P53, and γ-H2AX as well as the activity of SA-β-gal, and inhibited pro-inflammatory activation of microglia both in vivo and in vitro. Furthermore, iPSC-sEVs shifted microglia from pro-inflammatory phenotype to anti-inflammatory phenotype, which reduced the apoptosis of neurons, and improved the outcome of aged stroke mice. Mechanism studies showed that iPSC-sEVs reversed the loss of Rictor and downstream p-AKT (s473) in senescent microglia, which was involved in the senescence and pro-inflammatory phenotype regulation of microglia. Inhibition of Rictor abolished the iPSC-sEVs-afforded phosphorylation of AKT and alleviation of inflammation of senescent microglia. Proteomics results indicated that iPSC-sEVs carried transforming growth factor-β1 (TGF-β1) to upregulate Rictor and p-AKT in senescent microglia, which could be hindered by blocking TGF-β1. Taken together, our work demonstrates iPSC-sEVs reverse the senescent characteristic of microglia in aged brains and therefore improve the outcome after stroke, at least, via delivering TGF-β1 to upregulate Rictor and p-AKT. Our data suggest that iPSC-sEVs might be a novelty therapeutic method for aged ischemic stroke and other diseases involving senescent microglia.

Immune and inflammatory mechanism of remote ischemic conditioning: A narrative review

The benefits of remote ischemic conditioning (RIC) on multiple organs have been extensively investigated. According to existing research, suppressing the immune inflammatory response is an essential mechanism of RIC. Based on the extensive effects of RIC on cardiovascular and cerebrovascular diseases, this article reviews the immune and inflammatory mechanisms of RIC and summarizes the effects of RIC on immunity and inflammation from three perspectives: (1) the mechanisms of the impact of RIC on inflammation and immunity; (2) evidence of the effects of RIC on immune and inflammatory processes in ischaemic stroke; and (3) possible future applications of this effect, especially in systemic infectious diseases such as sepsis and sepsis-associated encephalopathy. This review explores the possibility of using RIC as a treatment in more inflammation-related diseases, which will provide new ideas for the treatment of this kind of disease.

Neuroimmune mechanisms and therapies mediating post-ischaemic brain injury and repair

The nervous and immune systems control whole-body homeostasis and respond to various types of tissue injury, including stroke, in a coordinated manner. Cerebral ischaemia and subsequent neuronal cell death activate resident or infiltrating immune cells, which trigger neuroinflammation that affects functional prognosis after stroke. Inflammatory immune cells exacerbate ischaemic neuronal injury after the onset of brain ischaemia; however, some of the immune cells thereafter change their function to neural repair. The recovery processes after ischaemic brain injury require additional and close interactions between the nervous and immune systems through various mechanisms. Thus, the brain controls its own inflammation and repair processes after injury via the immune system, which provides a promising therapeutic opportunity for stroke recovery.

Microglial IL-1RA ameliorates brain injury after ischemic stroke by inhibiting astrocytic CXCL1-mediated neutrophil recruitment and microvessel occlusion

Acute ischemic stroke (AIS), one of the leading causes of mortality worldwide, is characterized by a rapid inflammatory cascade resulting in exacerbation of ischemic brain injury. Microglia are the first immune responders. However, the role of postischemic microglial activity in ischemic brain injury remains far from being fully understood. Here, using the transgenic mouse line CX₃ CR1^creER :R26^iDTR to genetically ablate microglia, we showed that microglial deletion exaggerated ischemic brain injury. Associated with this worse outcome, there were increased neutrophil recruitment, microvessel blockade and blood flow stagnation in the acute phase, accompanied by transcriptional upregulation of chemokine (C-X-C motif) ligand 1 (CXCL1). Our study showed that microglial interleukin-1 receptor antagonist (IL-1RA) suppressed astrocytic CXCL1 expression induced by oxygen and glucose deprivation and inhibited neutrophil migration. Furthermore, neutralizing antibody therapy against CXCL1 or the administration of recombinant IL-1RA protein reduced brain infarct volume and improved motor coordination performance of mice after ischemic stroke. Our study suggests that microglia protect against acute ischemic brain injury by secreting IL-1RA to inhibit astrocytic CXCL1 expression, which reduces neutrophil recruitment and neutrophil-derived microvessel occlusion.

The role of T cells in acute ischemic stroke

Acute ischemic stroke (AIS) is associated with high rates of disability and mortality, exerting a substantial impact on overall survival and health-related quality of life. Treatment of AIS remains challenging given that the underlying pathologic mechanisms remain unclear. However, recent research has demonstrated that the immune system plays a key role in the development of AIS. Numerous studies have reported infiltration of T cells into ischemic brain tissue. While some types of T cells can promote the development of inflammatory responses and aggravate ischemic damage in patients with AIS, other T cells appear to exert neuroprotective effects via immunosuppression and other mechanisms. In this review, we discuss the recent findings regarding the infiltration of T cells into ischemic brain tissue, and the mechanisms governing how T cells can facilitate tissue injury or neuroprotection in AIS. Factors influencing the function of T cells, such as intestinal microflora and sex differences, are also discussed. We also explore the recent research on the effect of non-coding RNA on T cells after stroke, as well as the potential for specifically targeting T cells in the treatment of stroke patients.

Loading neural stem cells on hydrogel scaffold improves cell retention rate and promotes functional recovery in traumatic brain injury

Neural stem cell (NSC) has gained considerable attention in traumatic brain injury (TBI) treatment because of their ability to replenish dysfunctional neurons and stimulate endogenous neurorestorative processes. However, their therapeutic effects are hindered by the low cell retention rate after transplantation into the dynamic brain. In this study, we found cerebrospinal fluid (CSF) flow after TBI is an important factor associated with cell loss following NSC transplantation. Recently, several studies have shown that hydrogels could serve as a beneficial carrier for stem cell transplantation, which provides a solution to prevent CSF flow-induced cell loss after TBI. For this purpose, we evaluated three different hydrogel scaffolds and found the gelatin methacrylate (GelMA)/sodium alginate (Alg) (GelMA/Alg) hydrogel scaffold showed the best capabilities for NSC adherence, growth, and differentiation. Additionally, we detected that pre-differentiated NSCs, which were loaded on the GelMA/Alg hydrogel and cultured for 7 days in neuronal differentiation medium (NSC [7d]), had the highest cell retention rate after CSF impact. Next, the neuroprotective effects of the NSC-loaded GelMA/Alg hydrogel scaffold were evaluated in a rat model of TBI. NSC [7d]-loaded GelMA/Alg markedly decreased microglial activation and neuronal death in the acute phase, reduced tissue loss, alleviated astrogliosis, promoted neurogenesis, and improved neurological recovery in the chronic phase. In summary, we demonstrated that the integration with the GelMA/Alg and modification of NSC differentiation could inhibit the influence of CSF flow on transplanted NSCs, leading to increased number of retained NSCs and improved neuroprotective effects, providing a promising alternative for TBI treatment.

A Preclinical Systematic Review and Meta-Analysis of Behavior Testing in Mice Models of Ischemic Stroke

Stroke remains one of the most important causes of death and disability. Preclinical research is a powerful tool for understanding the molecular and cellular response to stroke. However, a lack of standardization in animal evaluation does not always ensure reproducible results. In the present study, we wanted to identify the best strategy for evaluating animal behavior post-experimental stroke. As such, a meta-analysis was made, evaluating behavioral tests done on male C57BL/6 mice subjected to stroke or sham surgery. Overall, fifty-six studies were included. Our results suggest that different types of tests should be used depending on the post-stroke period one needs to analyze. In the hyper-acute, post-stroke period, the best quantifier will be animal examination scoring, as it is a fast and inexpensive way to identify differences between groups. When evaluating stoke mice in the acute phase, a mix of animal examination and motor tests that focus on movement asymmetry (foot-fault and cylinder testing) seem to have the best chance of picking up differences between groups. Complex tasks (the rotarod test and Morris water maze) should be used within the chronic phase to evaluate differences between the late-subacute and chronic phases.

Dl-3-n-butylphthalide promotes synaptic plasticity by activating the Akt/ERK signaling pathway and reduces the blood-brain barrier leakage by inhibiting the HIF-1α/MMP signaling pathway in vascular dementia model mice

AIMS

DL-3-n-butylphthalide (NBP) exerts beneficial effects on global cognitive functions, but the underlying molecular mechanisms are still poorly understood. The present study aimed to investigate whether NBP mediates synaptic plasticity and blood-brain barrier (BBB) function, which play a pivotal role in the pathogenesis of vascular dementia (VaD), in a mouse model of bilateral common carotid artery stenosis (BCAS).

METHODS

NBP was administered to model mice at a dose of 80 mg/kg by gavage for 28 days after surgery. Cognitive function was evaluated by behavioral tests, and hippocampal synaptic plasticity was evaluated by in vivo electrophysiological recording. Cerebral blood flow (CBF), hippocampal volume, and white matter integrity were measured with laser speckle imaging (LSI) and MRI. In addition, BBB leakage and the expression of proteins related to the Akt/ERK and HIF-1α/MMP signaling pathways were assessed by biochemical assays.

RESULTS

NBP treatment alleviated cognitive impairment, hippocampal atrophy, and synaptic plasticity impairment induced by BCAS. In addition, NBP treatment increased CBF, promoted white matter integrity, and decreased BBB leakage. Regarding the molecular mechanisms, in mice  with BCAS, NBP may activate the Akt/ERK signaling pathway, which upregulates the expression of synapse-associated proteins, and it may also inhibit the HIF-1α/MMP signaling pathway, thereby increasing the expression of tight junction (TJ) proteins.

CONCLUSION

In conclusion, our results demonstrated the therapeutic effects of NBP in improving cognitive function via a wide range of targets in mice subjected to BCAS.

The Relationship of Astrocytes and Microglia with Different Stages of Ischemic Stroke

Ischemic stroke is the predominant cause of severe morbidity and mortality worldwide. Post-stroke neuroinflammation has recently received increasing attention with the aim of providing a new effective treatment strategy for ischemic stroke. Microglia and astrocytes are major components of the innate immune system of the central nervous system. They can be involved in all phases of ischemic stroke, from the early stage, contributing to the first wave of neuronal cell death, to the late stage involving phagocytosis and repair. In the early stage of ischemic stroke, a vicious cycle exists between the activation of microglia and astrocytes (through astrocytic connexin 43 hemichannels), aggravating neuroinflammatory injury post-stroke. However, in the late stage of ischemic stroke, repeatedly activated microglia can induce the formation of glial scars by triggering reactive astrogliosis in the peri-infarct regions, which may limit the movement of activated microglia in reverse and restrict the diffusion of inflammation to healthy brain tissues, alleviating the neuroinflammatory injury poststroke. In this review, we elucidated the various roles of astrocytes and microglia and summarized their relationship with neuroinflammation. We also examined how astrocytes and microglia influence each other at different stages of ischemic stroke. Several potential therapeutic approaches targeting astrocytes and microglia in ischemic stroke have been reviewed. Understanding the details of astrocytemicroglia interaction processes will contribute to a better understanding of the mechanisms underlying ischemic stroke, contributing to the identification of new therapeutic interventions.

IL-33/ST2 axis promotes remodeling of the extracellular matrix and drives protective microglial responses in the mouse model of perioperative neurocognitive disorders

Anesthesia and surgery induce cognitive impairment via uncertain mechanisms. Increasing evidence has suggested that microglial activity mediated by IL-33 /ST2 plays a critical role in immune regulation and inflammatory responses. Yet, the implications for microglia activity mediated by IL-33 in perioperative neurocognitive disorders (PND) are not well established. We showed that IL-33 and ST2 were downregulated in the hippocampus after anesthesia and surgery, and the expression of aggrecan, remodeling by microglia, was upregulated. Meanwhile, the expression of pro-inflammatory cytokines (IL-6 and IL-1β) and M1-like microglia marker (iNOS) increased, and the expression of M2-like microglia marker (CD206) decreased. Notably, the administration of IL-33 attenuated neuroinflammation and shifted the polarization of microglia in the hippocampus after anesthesia and surgery. Furthermore, IL-33 treatment rescued the increase of aggrecan, loss of dendritic spines, and impairment of LTP, improving cognitive performance. In conclusion, our study suggests that microglia activity mediated by IL-33/ST2 plays a vital role in cognitive impairments after anesthesia and surgery, which may serve as a therapeutic target for PND.

Immunomodulatory Therapeutic Effects of Curcumin on M1/M2 Macrophage Polarization in Inflammatory Diseases

BACKGROUND

Due to their plasticity, macrophages exert critical effects on both promoting and suppressing inflammatory processes. Pathologic inflammatory conditions are frequently correlated with dynamic alterations in macrophage activation, with classically activated M1 cells associated with the promotion and maintenance of inflammation and M2 cells being linked to the resolution or smouldering of chronic inflammation. Inflammation deputes a common feature of various chronic diseases and the direct involvement in the insurgence and development of these conditions. Macrophages participate in an autoregulatory loop characterizing the inflammatory process, as they produce a wide range of biologically active mediators that exert either deleterious or beneficial effects during the inflammation. Therefore, balancing the favorable ratios of M1/M2 macrophages can help ameliorate the inflammatory landscape of pathologic conditions. Curcumin is a component of turmeric with many pharmacological properties.

OBJECTIVE

Recent results from both in-vivo and in-vitro studies have indicated that curcumin can affect polarization and/or functions of macrophage subsets in the context of inflammation-related diseases. There is no comprehensive review of the impact of curcumin on cytokines involved in macrophage polarization in the context of inflammatory diseases. The present review will cover some efforts to explore the underlying molecular mechanisms by which curcumin modulates the macrophage polarization in distant pathological inflammatory conditions, such as cancer, autoimmunity, renal inflammation, stroke, atherosclerosis, and macrophage-driven pathogenesis.

RESULTS

The accumulation of the findings from in vitro and in vivo experimental studies suggests that curcumin beneficially influences M1 and M2 macrophages in a variety of inflammatory diseases with unfavorable macrophage activation.

CONCLUSION

Curcumin not only enhances anti-tumor immunity (via shifting M polarization towards M1 phenotype and/or up-regulation of M1 markers expression) but ameliorates inflammatory diseases, including autoimmune diseases (experimental autoimmune myocarditis and Behcet's disease), nephropathy, chronic serum sickness, stroke, and atherosclerosis.

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.

Revisiting the immune landscape post spinal cord injury: More than black and white

Spinal cord injury (SCI) induced catastrophic neurological disability is currently incurable, especially in elderly patients. Due to the limited axon regeneration capacity and hostile microenvironment in the lesion site, essential neural network reconstruction remains challenging. Owing to the blood-spinal cord barrier (BSCB) created immune cells and cytokines isolation, the immune elements were incorrectly recognized as innocent bystanders during the SCI pathological process traditionally. Emerging evidence demonstrated that the central nervous system (CNS) is an "immunological quiescent" rather than "immune privileged" area, and the CNS-associated immune response played mixed roles which dedicate beneficial and detrimental contributions throughout the SCI process. Consequently, coordinating double-edged immunomodulation is vital to promote tissue repair and neurological recovery post-SCI. The comprehensive exploration and understanding of the immune landscape post-SCI are essential in establishing new avenues for further basic and clinical studies. In this context, this review summarizes the recent significant breakthroughs in key aspects of SCI-related immunomodulation, including innate and adaptive immune response, immune organ changes, and holistic immune status modification. Moreover, the currently existing immune-oriented therapies for SCI will be outlined.

Extracellular Mitochondria Activate Microglia and Contribute to Neuroinflammation in Traumatic Brain Injury

Traumatic brain injury (TBI)-induced neuroinflammation is closely associated with poor outcomes and high mortality in affected patients, with unmet needs for effective clinical interventions. A series of causal and disseminating factors have been identified to cause TBI-induced neuroinflammation. Among these are cellular microvesicles released from injured cerebral cells, endothelial cells, and platelets. In previous studies, we have put forward that cellular microvesicles can be released from injured brains that induce consumptive coagulopathy. Extracellular mitochondria accounted for 55.2% of these microvesicles and induced a redox-dependent platelet procoagulant activity that contributes to traumatic brain injury-induced coagulopathy and inflammation. These lead to the hypothesis that metabolically active extracellular mitochondria contribute to the neuroinflammation in traumatic brain injury, independent of their procoagulant activity. Here, we found that these extracellular mitochondria induced polarization of microglial M1-type pro-inflammatory phenotype, aggravating neuroinflammation, and mediated cerebral edema in a ROS-dependent manner. In addition, the effect of ROS can be alleviated by ROS inhibitor N-ethylmaleimide (NEM) in vitro experiments. These results revealed a novel pro-inflammatory activity of extracellular mitochondria that may contribute to traumatic brain injury-associated neuroinflammation.

Sulforaphane promotes white matter plasticity and improves long-term neurological outcomes after ischemic stroke via the Nrf2 pathway

AIMS

Post-stroke cognitive impairment (PSCI) is a common condition following ischemic stroke. Neuronal loss and white matter injury are among the most common neuropathological characteristics in patients with PSCI. The present study tested our hypothesis that activation of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) reduces neuronal loss, white matter injury, and neurobehavioral deficits in a mouse model of PSCI and investigated the underlying protective mechanisms.

METHODS

PSCI was modeled in wildtype (WT) and Nrf2 knockout (KO), male and female mice, by distal middle cerebral artery occlusion (dMCAO), with intraperitoneal injections of the Nrf2 activator sulforaphane (Sfn) or vehicle. Long-term (35 days) sensorimotor and cognitive performances, white matter integrity, oligodendrogenesis by BrdU incorporation, and neurite sprouting using anterograde tract-tracing were evaluated up to 35 days after dMCAO. Neuronal apoptosis was evaluated three days after dMCAO. In vitro, primary neuronal cultures were applied to validate the in vivo findings.

RESULTS

Compared to vehicle-injected controls, Sfn treatment improved long-term sensorimotor and cognitive deficits after dMCAO in WT male and female mice. Sfn-treated WT mice also had less myelin loss/axonal injury and showed evidence of Nrf2 activation. Sfn treatment failed to provide the same level of protection in Nrf2 KO mice. Mechanistically, the ability of Sfn to reduce neuronal death after ischemia in vitro and in vivo, augment axonal sprouting and enhance oligodendrogenesis after dMCAO was dependent on Nrf2 activation.

CONCLUSION

Our results support that Nrf2 is critical for Sfn-afforded neuroprotection after ischemic stroke. Thus, targeting Nrf2 may be a promising strategy for the treatment of PSCI.

Interleukin-33 regulates the functional state of microglia

Microglia, the most prominent resident immune cells, exhibit multiple functional states beyond their immunomodulatory roles. Non-immune functions such as synaptic reorganization, removal of cellular debris, and deposition of abnormal substances are mediated by phagocytosis of normal or enhanced microglia. Activation or migration of microglia occurs when environmental cues are altered. In response to pathological factors, microglia change into various phenotypes, preventing or exacerbating tissue damage. Interleukin-33 (IL-33) is an important cytokine that regulates innate immunity, and microglia are thought to be its target cells. Here, we outline the role of IL-33 in the expression of microglial functions such as phagocytosis, migration, activation, and inflammatory responses. We focus on microglial properties and diverse functional states in health and disease, including the different effects of IL-33 perturbation on microglia in vivo and in vitro. We also highlight several well-established mechanisms of microglial function mediated by IL-33, which may be initiators and regulators of microglial function and require elucidation and expansion of the underlying mechanisms.

Association of Blood Biomarkers of Inflammation With Penumbra Consumption After Mechanical Thrombectomy in Patients With Acute Ischemic Stroke

BACKGROUND AND OBJECTIVES

The objective of this study was to assess the relationship between blood biomarkers of inflammation and lesion growth within the penumbra in acute ischemic stroke (AIS) patients treated with mechanical thrombectomy (MT).

METHODS

The HIBISCUS-STROKE cohort enrolled patients admitted in the Lyon Stroke Center for an anterior circulation AIS treated with MT after brain MRI assessment. Lesion growth within the penumbra was assessed on day 6 MRI using a voxel-based nonlinear coregistration method and dichotomized into low and high according to the median value. C-reactive protein, interleukin (IL)-6, IL-8, IL-10, monocyte chemoattractant protein-1, soluble tumor necrosis factor receptor I, soluble form suppression of tumorigenicity 2 (sST2), soluble P-selectin, vascular cellular adhesion molecule-1, and matrix metalloproteinase-9 were measured in sera at 4 time points within the first 48 hours. Reperfusion was considered as successful if Thrombolysis in Cerebral Infarction score was 2b/2c/3. A multiple logistic regression model was performed to detect any association between area under the curve (AUC) of these biomarkers within the first 48 hours and a high lesion growth within the penumbra.

RESULTS

Ninety patients were included. The median lesion growth within the penumbra was 2.3 (0.7-6.2) mL. On multivariable analysis, a high sST2 AUC (OR 3.77, 95% CI 1.36-10.46), a high baseline DWI volume (OR 3.65, 95% CI 1.32-10.12), and a lack of successful reperfusion (OR 0.19, 95% CI 0.04-0.92) were associated with a high lesion growth within the penumbra. When restricting analyses to patients with successful reperfusion (n = 76), a high sST2 AUC (OR 5.03, 95% CI 1.64-15.40), a high baseline DWI volume (OR 3.74, 95% CI 1.22-11.53), and a high penumbra volume (OR 3.25, 95% CI 1.10-9.57) remained associated with a high lesion growth within the penumbra.

DISCUSSION

High sST2 levels within the first 48 hours are associated with a high lesion growth within the penumbra.

Proposed practical protocol for flow cytometry analysis of microglia from the healthy adult mouse brain: Systematic review and isolation methods’ evaluation

The aim of our study was to systematically analyze the literature for published flow cytometry protocols for microglia isolation and compare their effectiveness in terms of microglial yield, including our own protocol using sucrose for myelin removal and accutase for enzymatic digestion. For systematic review, the PubMed was searched for the terms “flow cytometry,” “microglia,” “brain,” and “mice.” Three different myelin removal methods (Percoll, sucrose, and no removal) and five protocols for enzymatic digestion (accutase, dispase II, papain, trypsin, and no enzymatic digestion) were tested for the effectiveness of microglia (CD11b⁺CD45^int cell population) isolation from the adult mouse brain using flow cytometry. Qualitative analysis of the 32 selected studies identified three most commonly used myelin removal protocols: Percoll, the use of myelin removal kit, and no removal. Nine enzymatic digestion protocols were identified, from which we selected dispase II, papain, trypsin, and no enzymatic digestion. A comparison of these myelin removal methods and digestion protocols showed the Percoll method to be preferable in removal of non-immune cells, and superior to the use of sucrose which was less effective in removal of non-immune cells, but resulted in a comparable microglial yield to Percoll myelin removal. Digestion with accutase resulted in one of the highest microglial yields, all while having the lowest variance among tested protocols. The proposed protocol for microglia isolation uses Percoll for myelin removal and accutase for enzymatic digestion. All tested protocols had different features, and the choice between them can depend on the individual focus of the research.

Multiplex array analysis of serum cytokines offers minimal predictive value for cognitive function in the subacute phase after stroke

OBJECTIVE

The effects of inflammation on post-stroke cognitive function are still unclear. This study investigated the correlation between the Th17-related cytokines in peripheral blood and post-stroke cognitive function after ischemic stroke in the subacute phase.

DESIGN

A retrospective cohort study.

SETTING

Academic acute inpatient rehabilitation facility.

PARTICIPANTS

One hundred and fourteen patients with first ischemic stroke were categorized as the poor cognitive recovery group (n = 58) or good cognitive recovery group (n = 56) based on their cognitive MRFS efficiency.

INTERVENTIONS

All subjects received routine physical, occupational, and speech-language pathology therapy.

MAIN OUTCOME MEASURES

Serum cytokines/chemokine (IL-1 β, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12p70, IL-13, IL-15, IL-17A, IL-17E, IL-17F, IL-21, IL-22, IL-23, IL-27, IL-28A, IL-31, IL-33, GM-CSF, IFN-γ, MIP-3 α, TNF-α, and TNF-β) levels were measured in duplicate using Human Th17 magnetic bead panel and multiplex array analysis (Luminex-200 system). The primary functional outcome was a gain in functional independence measure (FIM) cognitive subscore at discharge. The secondary outcome measures were FIM total score at discharge, length of stay in the hospital, and discharge destination. Cognitive Montebello Rehabilitation Factor Score (MRFS) and cognitive MRFS efficiency were calculated. Demographic and clinical characteristics were obtained from the medical record.

RESULTS

The good cognitive recovery group had an interesting trend of higher IL-13 than the poor cognitive recovery group (good cognitive recovery group 257.82 ± 268.76 vs. poor cognitive recovery group 191.67 ± 201.82, p = 0.049, unit: pg/ml). However, Pearson's correlation analysis showed no significant correlation between cytokine levels and gain of cognition, cognitive MRFS, or cognitive MRFS efficiency. Receiver operating characteristic (ROC) analysis of cytokines also suggested a low accuracy of prediction as a predictor for post-stroke cognitive recovery improvement.

CONCLUSION

Our preliminary findings suggested that the level of serum cytokines had minimal predictive value for the recovery of cognitive function during the subacute inpatient rehabilitation after stroke.

Molecular Mechanism of the Protective Effects of M2 Microglia on Neurons: A Review Focused on Exosomes and Secretory Proteins

Microglia, as innate immune cells in the brain, closely monitor changes in the internal environment and participate in the maintenance of homeostasis in the central nervous system (CNS). Microglia can be polarized to the M1 or M2 phenotype in response to various stimuli in vivo or in vitro, affecting the functions of peripheral neurons. M2 microglia have attracted increasing attention in recent years owing to their beneficial effects on various diseases and injuries of the CNS, such as traumatic brain injury, stroke, Alzheimer's disease and multiple sclerosis. They exert neuroprotective effects by various mechanisms, e.g., suppressing inflammation, promoting the degradation of misfolded and aggregated proteins, promoting neurite growth, enhancing neurogenesis, inhibiting autophagy and apoptosis, promoting myelination, maintaining blood-brain barrier integrity, and enhancing phagocytic activity.This review summarizes the molecular mechanisms by which M2 microglia exert protective effects on neurons and provides a reference for the selection of therapeutic targets for CNS diseases.