Sexually dimorphic microglia and ischemic stroke

Gut-Brain Axis: Focus on Sex Differences in Neuroinflammation

In recent years, there has been a growing interest in the concept of the "gut-brain axis". In addition to well-studied diseases associated with an imbalance in gut microbiota, such as cancer, chronic inflammation, and cardiovascular diseases, research is now exploring the potential role of gut microbial dysbiosis in the onset and development of brain-related diseases. When the function of the intestinal barrier is altered by dysbiosis, the aberrant immune system response interacts with the nervous system, leading to a state of "neuroinflammation". The gut microbiota-brain axis is mediated by inflammatory and immunological mechanisms, neurotransmitters, and neuroendocrine pathways. This narrative review aims to illustrate the molecular basis of neuroinflammation and elaborate on the concept of the gut-brain axis by virtue of analyzing the various metabolites produced by the gut microbiome and how they might impact the nervous system. Additionally, the current review will highlight how sex influences these molecular mechanisms. In fact, sex hormones impact the brain-gut microbiota axis at different levels, such as the central nervous system, the enteric nervous one, and enteroendocrine cells. A deeper understanding of the gut-brain axis in human health and disease is crucial to guide diagnoses, treatments, and preventive interventions.

Acrobatic training prevents motor deficits and neuronal loss in male and female rats following chronic cerebral hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion in vascular dementia leads to memory and motor deficits; Physical exercise improves these aspects and promotes neuroprotection. Sexual dimorphism may significantly influence both ischemic and exercise outcomes.

AIMS

The aim of this study was to investigate the effects of 2VO (Two-Vessel occlusion) and the acrobatic training on motor function, functional performance, and tissue loss in male and female rats.

METHODS

Male and female rats were randomly divided into 4 groups: sham acrobatic, sham sedentary, 2VO acrobatic and 2VO sedentary. After 45 days of 2VO surgery, the animals received 4 weeks of acrobatic training. At the end, open field, beam balance and horizontal ladder tests were performed. Brain samples were taken for histological and morphological evaluation.

RESULTS

Spontaneous motor activity in the open field was not affected by 2VO, on the other hand, an impairment in forelimb placement was observed after 2VO and acrobatic training prevented errors and improved hindlimb placement. Neuronal loss was found in the motor cortex and striatum after 2VO, especially in females, which was prevented by acrobatic training.

CONCLUSION

Mild motor damage was found in animals after 2VO when refined movement was evaluated, probably associated to neuronal death in the motor cortex and striatum. The acrobatic exercise showed a neuroprotective effect, promoting neuronal survival and attenuating the motor deficit.

STING mediates microglial pyroptosis via interaction with NLRP3 in cerebral ischaemic stroke

BACKGROUND

Ischaemia-evoked neuroinflammation is a critical pathogenic event following ischaemic stroke. Gasdermin D (GSDMD)-associated pyroptosis represents a type of inflammation-associated programmed cell death, which can exacerbate neuroinflammatory responses and brain damage. Stimulator of interferon genes (STING) was recently described as a vital innate immune adaptor protein associated with neuroinflammation. Nevertheless, the regulatory effects of STING on microglial pyroptosis post-stroke have not been well elaborated.

METHODS

STING-knockout and wild-type (WT) mice were subjected to middle cerebral artery occlusion (MCAO). STING small interfering RNA (siRNA) was transfected into BV2 cells before oxygen-glucose deprivation/reoxygenation (OGD/R). STING-overexpressing adeno-associated virus (AAV) and NOD-like receptor family pyrin domain containing 3 (NLRP3) siRNA were administered by stereotaxic injection. 2,3,5-Triphenyl tetrazolium chloride (TTC) staining, TdT-mediated dUTP nick end labeling (TUNEL) staining, Fluoro-Jade C (FJC) staining, neurobehavioural tests, immunohistochemistry, cytokine antibody array assay, transmission electron microscopy, immunoblot, Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR) were carried out. Co-immunoprecipitation assays were used to investigate the interplay between STING and NLRP3.

RESULTS

STING expression was increased after MCAO and mainly detected on microglia. STING deletion alleviated brain infarction, neuronal damage and neurobehavioural impairment in mice subjected to MCAO. STING knockout suppressed microglial activation and the secretion of inflammatory chemokines, accompanied by mitigation of microglial pyroptosis. Specific upregulation of microglial STING by AAV-F4/80-STING aggravated brain injury and microglial pyroptosis. Mechanistically, co-immunoprecipitation showed that STING bound to NLRP3 in microglia. Supplementation of NLRP3 siRNA reversed AAV-F4/80-STING-induced deterioration of microglial pyroptosis.

CONCLUSIONS

The current findings indicate that STING modulates NLRP3-mediated microglial pyroptosis following MCAO. STING may serve as a therapeutic target in neuroinflammation induced by cerebral ischaemic/reperfusion (I/R) injury.

Sex Dependent Disparities in the Central Innate Immune Response after Moderate Spinal Cord Contusion in Rat

Subacute spinal cord injury (SCI) displays a complex pathophysiology associated with pro-inflammation and ensuing tissue damage. Microglia, the resident innate immune cells of the CNS, in concert with infiltrating macrophages, are the primary contributors to SCI-induced inflammation. However, subpopulations of activated microglia can also possess immunomodulatory activities that are essential for tissue remodeling and repair, including the production of anti-inflammatory cytokines and growth factors that are vital for SCI recovery. Recently, reports have provided convincing evidence that sex-dependent differences exist in how microglia function during CNS pathologies and the extent to which these cells contribute to neurorepair and endogenous recovery. Herein we employed flow cytometry and immunohistochemical methods to characterize the phenotype and population dynamics of activated innate immune cells within the injured spinal cord of age-matched male and female rats within the first week (7 days) following thoracic SCI contusion. This assessment included the analysis of pro- and anti-inflammatory markers, as well as the expression of critical immunomodulatory kinases, including P38 MAPK, and transcription factors, such as NFκB, which play pivotal roles in injury-induced inflammation. We demonstrate that activated microglia from the injured spinal cord of female rats exhibited a significantly diminutive pro-inflammatory response, but enhanced anti-inflammatory activity compared to males. These changes included lower levels of iNOS and TLR4 expression but increased levels of ARG-1 and CD68 in females after SCI. The altered expression of these markers is indicative of a disparate secretome between the microglia of males and females after SCI and that the female microglia possesses higher phagocytic capabilities (increased CD68). The examination of immunoregulatory kinases and transcription factors revealed that female microglia had higher levels of phosphorylated P38Thr180/Tyr182 MAPK and nuclear NFκB pp50Ser337 but lower amounts of nuclear NFκB pp65Ser536, suggestive of an attenuated pro-inflammatory phenotype in females compared to males after SCI. Collectively, this work provides novel insight into some of the sex disparities that exist in the innate immune response after SCI and indicates that sex is an important variable when designing and testing new therapeutic interventions or interpretating positive or negative responses to an intervention.

Repurposing of pexidartinib for microglia depletion and renewal

Pexidartinib (PLX3397) is a small molecule receptor tyrosine kinase inhibitor of colony stimulating factor 1 receptor (CSF1R) with moderate selectivity over other members of the platelet derived growth factor receptor family. It is approved for treatment of tenosynovial giant cell tumors (TGCT). CSF1R is highly expressed by microglia, which are macrophages of the central nervous system (CNS) that defend the CNS against injury and pathogens and contribute to synapse development and plasticity. Challenged by pathogens, apoptotic cells, debris, or inflammatory molecules they adopt a responsive state to propagate the inflammation and eventually return to a homeostatic state. The phenotypic switch may fail, and disease-associated microglia contribute to the pathophysiology in neurodegenerative or neuropsychiatric diseases or long-lasting detrimental brain inflammation after brain, spinal cord or nerve injury or ischemia/hemorrhage. Microglia also contribute to the growth permissive tumor microenvironment of glioblastoma (GBM). In rodents, continuous treatment for 1-2 weeks via pexidartinib food pellets leads to a depletion of microglia and subsequent repopulation from the remaining fraction, which is aided by peripheral monocytes that search empty niches for engraftment. The putative therapeutic benefit of such microglia depletion or forced renewal has been assessed in almost any rodent model of CNS disease or injury or GBM with heterogeneous outcomes, but a tendency of partial beneficial effects. So far, microglia monitoring e.g. via positron emission imaging is not standard of care for patients receiving Pexidartinib (e.g. for TGCT), so that the depletion and repopulation efficiency in humans is still largely unknown. Considering the virtuous functions of microglia, continuous depletion is likely no therapeutic option but short-lasting transient partial depletion to stimulate microglia renewal or replace microglia in genetic disease in combination with e.g. stem cell transplantation or as part of a multimodal concept in treatment of glioblastoma appears feasible. The present review provides an overview of the preclinical evidence pro and contra microglia depletion as a therapeutic approach.

Comprehensive review on sexual dimorphism to improve scalp acupuncture in nervous system disease

BACKGROUND

With the development of modern medicine, the Traditional Chinese Medicine (TCM) combined with western medicine began to be produced and applied. Scalp acupuncture (SA) as a Chinese medicine based on neurological theory, has a great advantage compared with TCM in the treatment of nervous system diseases.

METHOD

In this paper, we analyze the physiological and pathological manifestations of sexual dimorphism (SD) to illustrate the necessity of SD treatment. In addition, we review the factors that can affect SD and analyze in physiological structure, function, and pathological neurons. Diseases (pathological basis, pathological manifestations, and incidence) and factors leading to gender differences, which to analyze the possibility of gender differences in SA.

RESULT

Furthermore, we creatively a new insight of SD-SA and provide the complete SD treatment cases on the basis of the existing SA in different kinds of diseases including stroke, migraine, attention deficit hyperactivity disorder (ADHD), and depression.

CONCLUSION

In summary, we believe that it is feasible to improve the clinical effectiveness of SA, which is able to promote the development of SA, and then provides an actionable evidence for the promotion of precision medicine in the future.

Mechanism of Microglial Cell Activation in the Benzophenone-3 Exposure Model

Benzophenone-3 (BP-3) is the most commonly used UV filter in cosmetics, which is absorbed through the skin and crosses the blood-brain barrier. This compound increases extracellular glutamate concentrations, lipid peroxidation, the number of microglia cells and induces process of apoptosis. The aim of this study was to determine the effect of BP-3 on the activation and polarization of microglial cells in the frontal cortex and hippocampus of adult male rats exposed to BP-3 prenatally and then for two weeks in adulthood. It has been found, that exposure to BP-3 reduced the expression of the marker of the M2 phenotype of glial cells in both examined brain structures. An increase in the CD86/CD206 microglial phenotype ratio, expression of transcription factor NFκB and activity of caspase-1 were observed only in the frontal cortex, whereas BP-3 increased the level of glucocorticoid receptors in the hippocampus. The in vitro study conducted in the primary culture of rat frontal cortical microglia cells showed that BP-3 increased the LPS-stimulated release of pro-inflammatory cytokines IL-1α, IL-1β, TNFα, but in cultures without LPS there was decreased IL-1α, IL-6 and TNFα production, while the IL-18 and IP-10 was elevated. The obtained results indicate that differences in the level of immunoactivation between the frontal cortex and the hippocampus may result from the action of this compound on glucocorticoid receptors. In turn, changes in cytokine production in microglial cells indicate that BP-3 aggravates the LPS-induced immunoactivation.

NLRP3 inflammasome in cognitive impairment and pharmacological properties of its inhibitors

Cognitive impairment is a multifactorial and multi-step pathological process that places a heavy burden on patients and the society. Neuroinflammation is one of the main factors leading to cognitive impairment. The inflammasomes are multi-protein complexes that respond to various microorganisms and endogenous danger signals, helping to initiate innate protective responses in inflammatory diseases. NLRP3 inflammasomes produce proinflammatory cytokines (interleukin IL-1β and IL-18) by activating caspase-1. In this review, we comprehensively describe the structure and functions of the NLRP3 inflammasome. We also explore the intrinsic relationship between the NLRP3 inflammasome and cognitive impairment, which involves immune cell activation, cell apoptosis, oxidative stress, mitochondrial autophagy, and neuroinflammation. Finally, we describe NLRP3 inflammasome antagonists as targeted therapies to improve cognitive impairment.

Pterostilbene as a Therapeutic Alternative for Central Nervous System Disorders: A Review of the Current Status and Perspectives

Neurological disorders are diverse, have complex causes, and often result in disability; yet, effective treatments remain scarce. The resveratrol derivative pterostilbene possesses numerous physiological activities that hold promise as a novel therapy for the central nervous system (CNS) disorders. This review aimed to summarize the protective mechanisms of pterostilbene in in vitro and in vivo models of CNS disorders and the pharmacokinetics and safety to assess its possible effects on CNS disorders. Available evidence supports the protective effects of pterostilbene in CNS disorders involving mechanisms such as antioxidant and anti-inflammatory activity, regulation of lipid metabolism and vascular smooth muscle cell proliferation, improvement of synaptic function and neurogenesis, induction of glioma cell cycle arrest, and inhibition of glioma cell migration and invasion. Studies have identified possible molecular targets and pathways for the protective actions of pterostilbene in CNS disorders including the AMPK/STAT3, Akt, NF-κB, MAPK, and ERK signaling pathways. The possible pharmacological effects and molecular pathways of pterostilbene in CNS disorders are critically discussed in this review. Future studies should aim to increase our understanding of pterostilbene in animal models and humans to further evaluate its role in CNS disorders and the detailed mechanisms.

LXA4 attenuates perioperative neurocognitive disorders by suppressing neuroinflammation and oxidative stress

Perioperative neurocognitive disorder (PND) is a common complication that increases morbidity and mortality in elderly patients undergoing surgery. Abnormal microglia activation causes neuroinflammation and contributes to the development of PND. Growing evidence shows that lipoxin A4 (LXA4), a lipid mediator, possesses potent anti-inflammatory activities. In this study, we investigated whether LXA4 exerted a protective effect against surgery-induced neurocognitive deficits and explored the underlying mechanisms. Mice were subjected to laparotomy under sevoflurane anesthesia to establish an animal model of PND. LXA4 (15 μg/kg/d, ip) was administered three days prior surgery. We showed that LXA4 significantly alleviated surgery-induced cognitive impairments, attenuated neuroinflammation and microglial activation in hippocampus. In BV2 microglial cells treated with LPS (100 ng/mL), pre-application of LXA4 (100 nΜ) significantly inhibited M1 polarization and promoted M2 polarization, and decreased the levels of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and increased the levels of anti-inflammatory cytokine (IL-10). LXA4 also mitigated LPS-regulated expression of HO-1, NOX2, and SOD1, elevated SOD activity, and attenuated ROS production. Furthermore, we revealed that LXA4 increased the expression of SIRT1 and decreased the protein level of acetylated NF-κB p65. SIRT1 inhibitor EX-527 abolished the anti-inflammatory and antioxidant response effects of LXA4 in BV2 microglial cells. Hence, LXA4 is a potential therapeutic agent for surgery-induced neuroinflammation, oxidative stress, and cognitive deficit, and the effect of LXA4 is probably mediated by the activation of the SIRT1/NF-κB signaling pathway in microglia.

Controlled Decompression Alleviates Motor Dysfunction by Regulating Microglial Polarization via the HIF-1α Signaling Pathway in Intracranial Hypertension

Decompressive craniectomy (DC) is a major form of surgery that is used to reduce intracranial hypertension (IH), the most frequent cause of death and disability following severe traumatic brain injury (sTBI) and stroke. Our previous research showed that controlled decompression (CDC) was more effective than rapid decompression (RDC) with regard to reducing the incidence of complications and improving outcomes after sTBI; however, the specific mechanisms involved have yet to be elucidated. In the present study, we investigated the effects of CDC in regulating inflammation after IH and attempted to identify the mechanisms involved. Analysis showed that CDC was more effective than RDC in alleviating motor dysfunction and neuronal death in a rat model of traumatic intracranial hypertension (TIH) created by epidural balloon pressurization. Moreover, RDC induced M1 microglia polarization and the release of pro-inflammatory cytokines. However, CDC treatment resulted in microglia primarily polarizing into the M2 phenotype and induced the significant release of anti-inflammatory cytokines. Mechanistically, the establishment of the TIH model led to the increased expression of hypoxia-inducible factor-1α (HIF-1α); CDC ameliorated cerebral hypoxia and reduced the expression of HIF-1α. In addition, 2-methoxyestradiol (2-ME2), a specific inhibitor of HIF-1α, significantly attenuated RDC-induced inflammation and improved motor function by promoting M1 to M2 phenotype transformation in microglial and enhancing the release of anti-inflammatory cytokines. However, dimethyloxaloylglycine (DMOG), an agonist of HIF-1α, abrogated the protective effects of CDC treatment by suppressing M2 microglia polarization and the release of anti-inflammatory cytokines. Collectively, our results indicated that CDC effectively alleviated IH-induced inflammation, neuronal death, and motor dysfunction by regulating HIF-1α-mediated microglial phenotype polarization. Our findings provide a better understanding of the mechanisms that underlie the protective effects of CDC and promote clinical translational research for HIF-1α in IH.

Preferential pruning of inhibitory synapses by microglia contributes to alteration of the balance between excitatory and inhibitory synapses in the hippocampus in temporal lobe epilepsy

BACKGROUND

A consensus has formed that neural circuits in the brain underlie the pathogenesis of temporal lobe epilepsy (TLE). In particular, the synaptic excitation/inhibition balance (E/I balance) has been implicated in shifting towards elevated excitation during the development of TLE.

METHODS

Sprague Dawley (SD) rats were intraperitoneally subjected to kainic acid (KA) to generate a model of TLE. Next, electroencephalography (EEG) recording was applied to verify the stability and detectability of spontaneous recurrent seizures (SRS) in rats. Moreover, hippocampal slices from rats and patients with mesial temporal lobe epilepsy (mTLE) were assessed using immunofluorescence to determine the alterations of excitatory and inhibitory synapses and microglial phagocytosis.

RESULTS

We found that KA induced stable SRSs 14 days after status epilepticus (SE) onset. Furthermore, we discovered a continuous increase in excitatory synapses during epileptogenesis, where the total area of vesicular glutamate transporter 1 (vGluT1) rose considerably in the stratum radiatum (SR) of cornu ammonis 1 (CA1), the stratum lucidum (SL) of CA3, and the polymorphic layer (PML) of the dentate gyrus (DG). In contrast, inhibitory synapses decreased significantly, with the total area of glutamate decarboxylase 65 (GAD65) in the SL and PML diminishing enormously. Moreover, microglia conducted active synaptic phagocytosis after the formation of SRSs, especially in the SL and PML. Finally, microglia preferentially pruned inhibitory synapses during recurrent seizures in both rat and human hippocampal slices, which contributed to the synaptic alteration in hippocampal subregions.

CONCLUSIONS

Our findings elaborately characterize the alteration of neural circuits and demonstrate the selectivity of synaptic phagocytosis mediated by microglia in TLE, which could strengthen the comprehension of the pathogenesis of TLE and inspire potential therapeutic targets for epilepsy treatment.

Novel CH25H+ and OASL+ microglia subclusters play distinct roles in cerebral ischemic stroke

BACKGROUND

Microglial polarization is one of the most promising therapeutic targets for multiple central nervous system (CNS) disorders, including ischemic stroke. However, detailed transcriptional alteration of microglia following cerebral ischemic stroke remains largely unclear.

METHODS

Focal cerebral ischemia was induced by transient middle cerebral artery occlusion (tMCAO) for 60 min in mice. Single-cell RNA sequencing (scRNA-seq) was performed using ischemic brain tissues from tMCAO and sham mice 3 days after surgery. Ch25h^-/- mice were used to investigate the role of specific microglia subcluster on post-stroke infarct volume and neuroinflammation.

RESULTS

We identified a relatively homeostatic subcluster with enhanced antigen processing and three "ischemic stroke associated microglia" (ISAM): MKI67⁺, CH25H⁺ and OASL⁺ subclusters. We found the MKI67⁺ subcluster undergo proliferation and differentiation into CH25H⁺ and OASL⁺ subclusters. CH25H⁺ microglia was a critical subcluster of ISAM that exhibited increased phagocytosis and neuroprotective property after stroke. Ch25h^-/- mice developed significantly increased infarct volume following ischemic stroke compared to Ch25h^+/-. Meanwhile, the OASL⁺ subcluster accumulated in the ischemic brain and was associated with the evolving of neuroinflammation after stroke, which was further aggravated in the aged mice brain.

CONCLUSIONS

Our data reveal previously unrecognized roles of the newly defined CH25H⁺ and OASL⁺ microglia subclusters following ischemic stroke, with novel insights for precise microglia modulation towards stroke therapy.

Sex differences in the inflammatory response to stroke

Ischemic stroke is a leading cause of morbidity and mortality and disproportionally affects women, in part due to their higher longevity. Older women have poorer outcomes after stroke with high rates of cognitive deficits, depression, and reduced quality of life. Post-stroke inflammatory responses are also sexually dimorphic and drive differences in infarct size and recovery. Factors that influence sex-specific immune responses can be both intrinsic and extrinsic. Differences in gonadal hormone exposure, sex chromosome compliment, and environmental/social factors can drive changes in transcriptional and metabolic profiles. In addition, how these variables interact, changes across the lifespan. After the onset of ischemic injury, necrosis and apoptosis occur, which activate microglia and other glial cells within the central nervous system, promoting the release of cytokines and chemokines and neuroinflammation. Cells involved in innate and adaptive immune responses also have dual functions after stroke as they can enhance inflammation acutely, but also contribute to suppression of the inflammatory cascade and later repair. In this review, we provide an overview of the current literature on sex-specific inflammatory responses to ischemic stroke. Understanding these differences is critical to identifying therapeutic options for both men and women.

Complexity of Sex Differences and Their Impact on Alzheimer's Disease

Sex differences are present in brain morphology, sex hormones, aging processes and immune responses. These differences need to be considered for proper modelling of neurological diseases with clear sex differences. This is the case for Alzheimer's disease (AD), a fatal neurodegenerative disorder with two-thirds of cases diagnosed in women. It is becoming clear that there is a complex interplay between the immune system, sex hormones and AD. Microglia are major players in the neuroinflammatory process occurring in AD and have been shown to be directly affected by sex hormones. However, many unanswered questions remain as the importance of including both sexes in research studies has only recently started receiving attention. In this review, we provide a summary of sex differences and their implications in AD, with a focus on microglia action. Furthermore, we discuss current available study models, including emerging complex microfluidic and 3D cellular models and their usefulness for studying hormonal effects in this disease.

β-Adrenoceptor Blockade Moderates Neuroinflammation in Male and Female EAE Rats and Abrogates Sexual Dimorphisms in the Major Neuroinflammatory Pathways by Being More Efficient in Males

Our previous studies showed more severe experimental autoimmune encephalomyelitis (EAE) in male compared with female adult rats, and moderating effect of propranolol-induced β-adrenoceptor blockade on EAE in females, the effect associated with transcriptional stimulation of Nrf2/HO-1 axis in spinal cord microglia. This study examined putative sexual dimorphism in propranolol action on EAE severity. Propranolol treatment beginning from the onset of clinical EAE mitigated EAE severity in rats of both sexes, but to a greater extent in males exhibiting higher noradrenaline levels and myeloid cell β₂-adrenoceptor expression in spinal cord. This correlated with more prominent stimulatory effects of propranolol not only on CX3CL1/CX3CR1/Nrf2/HO-1 cascade, but also on Stat3/Socs3 signaling axis in spinal cord microglia/myeloid cells (mirrored in the decreased Stat3 and the increased Socs3 expression) from male rats compared with their female counterparts. Propranolol diminished the frequency of activated cells among microglia, increased their phagocyting/endocyting capacity, and shifted cytokine secretory profile of microglia/blood-borne myeloid cells towards an anti-inflammatory/neuroprotective phenotype. Additionally, it downregulated the expression of chemokines (CCL2, CCL19/21) driving T-cell/monocyte trafficking into spinal cord. Consequently, in propranolol-treated rats fewer activated CD4+ T cells and IL-17+ T cells, including CD4+IL17+ cells coexpressing IFN-γ/GM-CSF, were recovered from spinal cord of propranolol-treated rats compared with sex-matched saline-injected controls. All the effects of propranolol were more prominent in males. The study as a whole disclosed that sexual dimorphism in multiple molecular mechanisms implicated in EAE development may be responsible for greater severity of EAE in male rats and sexually dimorphic action of substances affecting them. Propranolol moderated EAE severity more effectively in male rats, exhibiting greater spinal cord noradrenaline (NA) levels and myeloid cell β₂-adrenoceptor (β₂-AR) expression than females. Propranolol affected CX3CR1/Nrf2/HO-1 and Stat3/Socs3 signaling axes in myeloid cells, favored their anti-inflammatory/neuroprotective phenotype and, consequently, reduced Th cell reactivation and differentiation into highly pathogenic IL-17/IFN-γ/GM-CSF-producing cells.

Adrenoceptors as potential target for add-on immunomodulatory therapy in multiple sclerosis

This review summarizes recent findings related to the role of the sympathetic nervous system (SNS) in pathogenesis of multiple sclerosis (MS) and its commonly used experimental model - experimental autoimmune encephalomyelitis (EAE). They indicate that noradrenaline, the key end-point mediator of the SNS, acting through β-adrenoceptor, has a contributory role in the early stages of MS/EAE development. This stage is characterized by the SNS hyperactivity (increased release of noradrenaline) reflecting the net effect of different factors, such as the disease-associated inflammation, stress, vitamin D hypovitaminosis, Epstein-Barr virus infection and dysbiosis. Thus, the administration of propranolol, a non-selective β-adrenoceptor blocker, readily crossing the blood-brain barrier, to experimental rats before the autoimmune challenge and in the early (preclinical/prodromal) phase of the disease mitigates EAE severity. This phenomenon has been ascribed to the alleviation of neuroinflammation (due to attenuation of primarily microglial activation/proinflammatory functions) and the diminution of the magnitude of the primary CD4+ T-cell autoimmune response (the effect associated with impaired autoantigen uptake by antigen presenting cells and their migration into draining lymph nodes). The former is partly related to breaking of the catecholamine-dependent self-amplifying microglial feed-forward loop and the positive feedback loop between microglia and the SNS, leading to down-regulation of the SNS hyperactivity and its enhancing influence on microglial activation/proinflammatory functions and the magnitude of autoimmune response. The effects of propranolol are shown to be more prominent in male EAE animals, the phenomenon important as males (like men) are likely to develop clinically more severe disease. Thus, these findings could serve as a firm scientific background for formulation of a new sex-specific immune-intervention strategy for the early phases of MS (characterized by the SNS hyperactivity) exploiting anti-(neuro)inflammatory and immunomodulatory properties of propranolol and other relatively cheap and safe adrenergic drugs with similar therapeutic profile.

MCC950 Regulates Stem Cells Destiny Through Modulating SIRT3-NLRP3 Inflammasome Dynamics During Oxygen Glucose Deprivation

Ischemic stroke is the major cause of death and morbidity worldwide. Stem cell treatment is at the forefront of ischemic therapeutic interventions. However, the fate of these cells following transplantation is mostly unknown. The current study examines the influence of oxidative and inflammatory pathological events associated with experimental ischemic stroke (oxygen glucose deprivation (OGD)) on the stem cell population (human Dental Pulp Stem Cells, and human Mesenchymal Stem Cells) through the involvement of the NLRP3 inflammasome. We explored the destiny of the above-mentioned stem cells in the stressed micro (-environment) and the ability of MCC950 to reverse the magnitudes. An enhanced expression of NLRP3, ASC, cleaved caspase1, active IL-1β and active IL-18 in OGD-treated DPSC and MSC was observed. The MCC950 significantly reduced NLRP3 inflammasome activation in the aforementioned cells. Further, in OGD groups, oxidative stress markers were shown to be alleviated in the stem cells under stress, which was effectively relieved by MCC950 supplementation. Interestingly, whereas OGD increased NLRP3 expression, it decreased SIRT3 levels, implying that these two processes are intertwined. In brief, we discovered that MCC950 inhibits NLRP3-mediated inflammation by inhibiting the NLRP3 inflammasome and increasing SIRT3. To conclude, according to our findings, inhibiting NLRP3 activation while enhancing SIRT3 levels with MCC950 reduces oxidative and inflammatory stress in stem cells under OGD-induced stress. These findings shed light on the causes of hDPSC and hMSC demise following transplantation and point to strategies to lessen therapeutic cell loss under ischemic-reperfusion stress.

Genetic and Epigenetic Sexual Dimorphism of Brain Cells during Aging

In recent years, much of the attention paid to theoretical and applied biomedicine, as well as neurobiology, has been drawn to various aspects of sexual dimorphism due to the differences that male and female brain cells demonstrate during aging: (a) a dimorphic pattern of response to therapy for neurodegenerative disorders, (b) different age of onset and different degrees of the prevalence of such disorders, and (c) differences in their symptomatic manifestations in men and women. The purpose of this review is to outline the genetic and epigenetic differences in brain cells during aging in males and females. As a result, we hereby show that the presence of brain aging patterns in males and females is due to a complex of factors associated with the effects of sex chromosomes, which subsequently entails a change in signal cascades in somatic cells.

Immune regulation based on sex differences in ischemic stroke pathology

Ischemic stroke is one of the world's leading causes of death and disability. It has been established that gender differences in stroke outcomes prevail, and the immune response after stroke is an important factor affecting patient outcomes. However, gender disparities lead to different immune metabolic tendencies closely related to immune regulation after stroke. The present review provides a comprehensive overview of the role and mechanism of immune regulation based on sex differences in ischemic stroke pathology.

Sexual Dimorphism in Neurodegenerative Diseases and in Brain Ischemia

Epidemiological studies and clinical observations show evidence of sexual dimorphism in brain responses to several neurological conditions. It is suggested that sex-related differences between men and women may have profound effects on disease susceptibility, pathophysiology, and progression. Sexual differences of the brain are achieved through the complex interplay of several factors contributing to this phenomenon, such as sex hormones, as well as genetic and epigenetic differences. Despite recent advances, the precise link between these factors and brain disorders is incompletely understood. This review aims to briefly outline the most relevant aspects that differ between men and women in ischemia and neurodegenerative disorders (AD, PD, HD, ALS, and SM). Recognition of disparities between both sexes could aid the development of individual approaches to ameliorate or slow the progression of intractable disorders.

Microglial angiotensin type 2 receptors mediate sex-specific expression of inflammatory cytokines independently of circulating estrogen

There are sex differences in microglia, which can maintain sex-related gene expression and functional differences in the absence of circulating sex steroids. The angiotensin type 2 (AT2) receptors mediate anti-inflammatory actions in different tissues, including brain. In mice, we performed RT-PCR analysis of microglia isolated from adult brains and RNA scope in situ hybridization from males, females, ovariectomized females, orchiectomized males and brain masculinized females. We also compared wild type and AT2 knockout mice. The expression of AT2 receptors in microglial cells showed sex differences with much higher AT2 mRNA expression in females than in males, and this was not dependent on circulating gonadal hormones, as observed using ovariectomized females, brain masculinized females and orchiectomized males. These results suggest genomic reasons, possibly related to sex chromosome complement, for sex differences in AT2 expression in microglia, as the AT2 receptor gene is located in the X chromosome. Furthermore, sex differences in expression of AT2 receptors were associated to sex differences in microglial expression of key anti-inflammatory cytokines such as interleukin-10 and pro-inflammatory cytokines such as interleukin-1β and interleukin-6. In conclusion, sex differences in microglial AT2 receptor expression appear as a major factor contributing to sex differences in the neuroinflammatory responses beyond the effects of circulating steroids.

Hyperbaric oxygen improves depression-like behaviors in chronic stress model mice by remodeling gut microbiota and regulating host metabolism

AIMS

There is growing evidence that the gut microbiota plays a significant part in the pathophysiology of chronic stress. The dysbiosis of the gut microbiota closely relates to dysregulation of microbiota-host cometabolism. Composition changes in the gut microbiota related to perturbations in metabolic profiles are vital risk factors for disease development. Hyperbaric oxygen therapy is commonly applied as an alternative or primary therapy for various diseases. Therefore, a metabolic and gut bacteria perspective is essential to uncover possible mechanisms of chronic stress and the therapeutic effect of hyperbaric oxygenation. We determined that there were significantly disturbed metabolites and disordered gut microbiota between control and chronic stress group. The study aims to offer further information on the interactions between host metabolism, gut microbiota, and chronic stress.

METHODS

At present, chronic unpredictable mild stress is considered the most widespread method of modeling chronic stress in animals, so we used a chronic unpredictable mild stress mouse model to characterize changes in the metabolome and microbiome of depressed mice by combining 16S rRNA gene sequencing and UHPLC-MS/MS-based metabolomics. Pearson's correlation-based clustering analysis was performed with above metabolomics and fecal microbiome data to determine gut microbiota-associated metabolites.

RESULTS

We found that 18 metabolites showed a significant correlation with campylobacterota. Campylobacterota associated metabolites were significantly enriched mainly in the d-glutamate and d-glutamine metabolism. Hyperoxia treatment may improve depression-like behaviors in chronic stress model mice through regulating the disrupted metabolites.

CONCLUSIONS

Hyperbaric oxygen improves depression-like behaviors in chronic stress model mice by remodeling Campylobacterota associated metabolites.

Female-specific neuroprotection after ischemic stroke by vitronectin-focal adhesion kinase inhibition

We found that blood vitronectin (VTN) leaks into the brain and exacerbates tissue loss after stroke by increasing pro-inflammatory IL-6 expression in female, but not male, mice. VTN signals through integrins and downstream focal adhesion kinase (FAK). Here, a two day systemic treatment with a small molecule FAK inhibitor starting 6 h after middle cerebral artery occlusion reduced ipsilateral brain injury size by ∼40-45% at 7 and 14 d, as well as inflammation and motor dysfunction in wild-type female, but not male, mice. FAK inhibition also reduced IL-6 expression in the injured female striatum at 24 h by 62%. Inducible selective gene deletion of FAK in astrocytes also reduced acute IL-6 expression by 72% only in females, and mitigated infarct size by ∼80% and inflammation at 14 d after stroke. Lastly, VTN-/- females had better outcomes, but FAK inhibitor treatment had no additional protective or anti-inflammatory effects. Altogether, this suggests that VTN is detrimental in females primarily through FAK and that FAK inhibition provides neuroprotection (cerebroprotection) by reducing VTN-induced IL-6 expression in astrocytes. Thus, VTN signaling can be targeted to mitigate harmful inflammation with relevance to treatments for women with ischemic stroke, who often have worse outcomes than men.

The multiple faces of extracellular vesicles released by microglia: Where are we 10 years after?

As resident component of the innate immunity in the central nervous system (CNS), microglia are key players in pathology. However, they also exert fundamental roles in brain development and homeostasis maintenance. They are extremely sensitive and plastic, as they assiduously monitor the environment, adapting their function in response to stimuli. On consequence, microglia may be defined a heterogeneous community of cells in a dynamic equilibrium. Extracellular vesicles (EVs) released by microglia mirror the dynamic nature of their donor cells, exerting important and versatile functions in the CNS as unbounded conveyors of bioactive signals. In this review, we summarize the current knowledge on EVs released by microglia, highlighting their heterogeneous properties and multifaceted effects.

NG2-glia crosstalk with microglia in health and disease

Neurodegenerative diseases are increasingly becoming a global problem. However, the pathological mechanisms underlying neurodegenerative diseases are not fully understood. NG2‐glia abnormalities and microglia activation are involved in the development and/or progression of neurodegenerative disorders, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, and cerebrovascular diseases. In this review, we summarize the present understanding of the interaction between NG2‐glia and microglia in physiological and pathological states and discuss unsolved questions concerning their fate and potential fate. First, we introduce the NG2‐glia and microglia in health and disease. Second, we formulate the interaction between NG2‐glia and microglia. NG2‐glia proliferation, migration, differentiation, and apoptosis are influenced by factors released from the microglia. On the other hand, NG2‐glia also regulate microglia actions. We conclude that NG2‐glia and microglia are important immunomodulatory cells in the brain. Understanding the interaction between NG2‐glia and microglia will help provide a novel method to modulate myelination and treat neurodegenerative disorders.

A novel severe cerebral venous thrombosis rat model based on semi-ligation combined with ferric chloride and thrombin

AIMS

An applicable cerebral venous sinus thrombosis (CVST) model is imperative for exploring its pathophysiology. We established a novel severe CVST model using semi-ligation, ferric chloride, and thrombin.

METHODS

A total of 138 male Sprague-Dawley rats were randomly divided into semi-ligation (n = 75) and non-semi-ligation (n = 63) groups. A sham group (n = 46) was also included. We compared short-term and long-term neurological and cognitive dysfunction, mortality rates, thrombus load, venous infarction volume, the blood-brain barrier permeability, brain water content, and microglia activation among the three groups.

RESULTS

Thrombi involving multiple venous sinuses appeared in all semi-ligation rats within 2 days postoperatively. Compared with the non-semi-ligation group, short-term and long-term neurological dysfunction were more severe (p < 0.05), and thrombus weight, venous infarction volumes, and microglia activation were more significant (p < 0.05) in the semi-ligation group. Further, the cognitive function of the semi-ligation group significantly decreased (p < 0.05) on postoperative day 21. Cumulative mortality rates between the semi-ligation and non-semi-ligation groups did not differ significantly.

CONCLUSION

Semi-ligation combined with ferric chloride and thrombin can produce a severe CVST model with multiple venous sinus involvement, which is suitable for short- and long-term neurological and cognitive dysfunction assessment.

Role of Rph3A in brain injury induced by experimental cerebral ischemia-reperfusion model in rats

Aim

The aim was to study the role of Rph3A in neuronal injury induced by cerebral ischemia‐reperfusion.

Methods

The protein and mRNA levels of Rph3A in penumbra were detected by Western blot. The localization of Rph3A in different cell types in penumbra was detected by immunofluorescence. Apoptosis in the brain was detected by TUNEL staining. We tested neurobehavioral evaluation using rotarod test, adhesive‐removal test, and Morris Water maze test. We examined the expression and localization of Rph3A in cultured neurons and astrocytes in vitro by Western blot and ELISA, respectively.

Results

The mRNA and protein levels of Rph3A had significantly increased in brain penumbra of the rat MCAO/R model. Rph3A was mainly distributed in neurons and astrocytes and was significantly increased by MCAO/R. We downregulated Rph3A and found that it further worsened the cerebral infarct, neuronal death and behavioral, cognitive, and memory impairments in rats after MCAO/R. We also found that ischemia‐reperfusion upregulated the in vitro protein level and secretion of Rph3A in astrocytes but led to a decrease in the protein level of Rph3A in neurons.

Conclusion

The increase in Rph3A in the brain penumbra may be an endogenous protective mechanism against ischemia‐reperfusion injury, which is mainly dominated by astrocytes.

Phagocytic microglia and macrophages in brain injury and repair

AIMS

Phagocytosis is the cellular digestion of extracellular particles, such as pathogens and dying cells, and is a key element in the evolution of central nervous system (CNS) disorders. Microglia and macrophages are the professional phagocytes of the CNS. By clearing toxic cellular debris and reshaping the extracellular matrix, microglia/macrophages help pilot the brain repair and functional recovery process. However, CNS resident and invading immune cells can also magnify tissue damage by igniting runaway inflammation and phagocytosing stressed-but viable-neurons.

DISCUSSION

Microglia/macrophages help mediate intercellular communication and react quickly to the "find-me" signals expressed by dead/dying neurons. The activated microglia/macrophages then migrate to the injury site to initiate the phagocytic process upon encountering "eat-me" signals on the surfaces of endangered cells. Thus, healthy cells attempt to avoid inappropriate engulfment by expressing "do not-eat-me" signals. Microglia/macrophages also have the capacity to phagocytose immune cells that invade the injured brain (e.g., neutrophils) and to regulate their pro-inflammatory properties. During brain recovery, microglia/macrophages engulf myelin debris, initiate synaptogenesis and neurogenesis, and sculpt a favorable extracellular matrix to support network rewiring, among other favorable roles. Here, we review the multilayered nature of phagocytotic microglia/macrophages, including the molecular and cellular mechanisms that govern microglia/macrophage-induced phagocytosis in acute brain injury, and discuss strategies that tap into the therapeutic potential of this engulfment process.

CONCLUSION

Identification of biological targets that can temper neuroinflammation after brain injury without hindering the essential phagocytic functions of microglia/macrophages will expedite better medical management of the stroke recovery stage.

Interleukin 13 promotes long-term recovery after ischemic stroke by inhibiting the activation of STAT3

BACKGROUND

Microglia/macrophages are activated after cerebral ischemic stroke and can contribute to either brain injury or recovery by polarizing microglia/macrophage into distinctive functional phenotypes with pro- or anti-inflammatory properties. Interleukin-13 (IL-13) is an anti-inflammatory cytokine that regulates microglia/macrophage polarization toward an anti-inflammatory phenotype. However, it is not clear whether IL-13 is beneficial after ischemic stroke long-term and the underlying molecular mechanism(s) remain unknown. Thus, we examined the effect of IL-13 on long-term recovery and microglia/macrophage polarization in mice with transient middle cerebral artery occlusion model (tMCAO).

METHODS

tMCAO was induced in adult male C57BL/6J mice. IL-13 (60 μg/kg) was administered intranasally starting 2 h after stroke and continued for seven consecutive days. Sensorimotor function, spatial learning and memory function, as well as brain infarct volume were assessed up to 35 days after stroke. White matter integrity was evaluated by electrophysiology, immunofluorescence staining, and transmission electron microscopy. Microglia/macrophage activation was assessed using immunofluorescence staining and quantitative real-time polymerase chain reaction. Changes in immune cells in the brain and the periphery, and expression of IL-13 receptors in different brain cells were detected by flow cytometry. Primary neuron/microglia co-cultures and a STAT3 inhibitor were used for mechanistic studies.

RESULTS

Post-treatment with IL-13 improved long-term neurofunctional recovery and decreased brain tissue atrophy after stroke. Intranasal delivery of IL-13 enhanced the structural and functional integrity of white matter after stroke. Furthermore, the neuroprotection afforded by IL-13 administration was not due to a direct effect on neurons, but by indirectly regulating the anti-inflammatory phenotype of microglia/macrophages. IL-13 treatment also had no effect on peripheral immune cells. Mechanistically, IL-13 improved the long-term outcome after ischemic stroke by promoting the polarization of microglia/macrophages toward the anti-inflammatory phenotype at least partially by inhibiting the phosphorylation of STAT3.

CONCLUSIONS

IL-13 promotes white matter repair and improves neurofunctional outcomes after ischemic stroke by modulating microglia/macrophages via inhibition of STAT3 phosphorylation.

Sex-Specific Immune Responses in Stroke

In both acute and chronic diseases, functional differences in host immune responses arise from a multitude of intrinsic and extrinsic factors. Two of the most important factors affecting the immune response are biological sex and aging. Ischemic stroke is a debilitating disease that predominately affects older individuals. Epidemiological studies have shown that older women have poorer functional outcomes compared with men, in part due to the older age at which they experience their first stroke and the increased comorbidities seen with aging. The immune response also differs in men and women, which could lead to altered inflammatory events that contribute to sex differences in poststroke recovery. Intrinsic factors including host genetics and chromosomal sex play a crucial role both in shaping the host immune system and in the neuroimmune response to brain injury. Ischemic stroke leads to altered intracellular communication between astrocytes, neurons, and resident immune cells in the central nervous system. Increased production of cytokines and chemokines orchestrate the infiltration of peripheral immune cells and promote neuroinflammation. To maintain immunosurveillance, the host immune and central nervous system are highly regulated by a diverse population of immune cells which are strategically distributed within the neurovascular unit and become activated with injury. In this review, we provide a comprehensive overview of sex-specific host immune responses in ischemic stroke.

Sex-Associated Differences in Neurovascular Dysfunction During Ischemic Stroke

Neurovascular units (NVUs) are basic functional units in the central nervous system and include neurons, astrocytes and vascular compartments. Ischemic stroke triggers not only neuronal damage, but also dissonance of intercellular crosstalk within the NVU. Stroke is sexually dimorphic, but the sex-associated differences involved in stroke-induced neurovascular dysfunction are studied in a limited extend. Preclinical studies have found that in rodent models of stroke, females have less neuronal loss, stronger repairing potential of astrocytes and more stable vascular conjunction; these properties are highly related to the cerebroprotective effects of female hormones. However, in humans, these research findings may be applicable only to premenopausal stroke patients. Women who have had a stroke usually have poorer outcomes compared to men, and because stoke is age-related, hormone replacement therapy for postmenopausal women may exacerbate stroke symptoms, which contradicts the findings of most preclinical studies. This stark contrast between clinical and laboratory findings suggests that understanding of neurovascular differences between the sexes is limited. Actually, apart from gonadal hormones, differences in neuroinflammation as well as genetics and epigenetics promote the sexual dimorphism of NVU functions. In this review, we summarize the confirmed sex-associated differences in NVUs during ischemic stroke and the possible contributing mechanisms. We also describe the gap between clinical and preclinical studies in terms of sexual dimorphism.

Electro-acupuncture and its combination with adult stem cell transplantation for spinal cord injury treatment: A summary of current laboratory findings and a review of literature

The incidence and disability rate of spinal cord injury (SCI) worldwide are high, imposing a heavy burden on patients. Considerable research efforts have been directed toward identifying new strategies to effectively treat SCI. Governor Vessel electro‐acupuncture (GV‐EA), used in traditional Chinese medicine, combines acupuncture with modern electrical stimulation. It has been shown to improve the microenvironment of injured spinal cord (SC) by increasing levels of endogenous neurotrophic factors and reducing inflammation, thereby protecting injured neurons and promoting myelination. In addition, axons extending from transplanted stem cell‐derived neurons can potentially bridge the two severed ends of tissues in a transected SC to rebuild neuronal circuits and restore motor and sensory functions. However, every single treatment approach to severe SCI has proven unsatisfactory. Combining different treatments—for example, electro‐acupuncture (EA) with adult stem cell transplantation—appears to be a more promising strategy. In this review, we have summarized the recent progress over the past two decades by our team especially in the use of GV‐EA for the repair of SCI. By this strategy, we have shown that EA can stimulate the nerve endings of the meningeal branch. This would elicit the dorsal root ganglion neurons to secrete excess amounts of calcitonin gene‐related peptide centrally in the SC. The neuropeptide then activates the local cells to secrete neurotrophin‐3 (NT‐3), which mediates the survival and differentiation of donor stem cells overexpressing the NT‐3 receptor, at the injury/graft site of the SC. Increased local production of NT‐3 facilitates reconstruction of host neural tissue such as nerve fiber regeneration and myelination. All this events in sequence would ultimately strengthen the cortical motor‐evoked potentials and restore the motor function of paralyzed limbs. The information presented herein provides a basis for future studies on the clinical application of GV‐EA and adult stem cell transplantation for the treatment of SCI.

Protective Effect of Mild Hypothermia on Spinal Cord Ischemia-Induced Delayed Paralysis and Spinal Cord Injury

To explore the mechanism regarding the regulation of spinal cord ischemia (SCI) in rats by mild hypothermia. A SCI rat model was established through aorta occlusion, and in some cases, the rats were intervened with mild hypothermia, after which motor function, microglia activation, and M1/M2 polarization in rats were measured. Also, the expression of inflammatory cytokines (IL-1β, IL-6 and TNF-α) and neuronal apoptosis were examined. Lipopolysaccharide (LPS)-induced M1 microglia and IL-4-induced M2 microglia were intrathecally injected into rats to evaluate the effect of microglial polarization on SCI. In in vitro experiments, primary microglial cells were treated under hypothermic condition, in which M1/M2 polarization and microglia apoptosis, the levels of iNOS, CD86, CD206, Arg-1 and inflammatory cytokines were assessed. Western blot analysis detected the activation of the TLR4/NF-κB pathway to investigate the role of this pathway in M1/M2 polarization. SCI treatment impaired motor function, induced higher M1 microglia proportion, and increased the levels of pro-inflammatory cytokines in rats, and mild hypothermic treatment attenuated these trends. Moreover, injection of M1 microglia increased M1 microglia proportion and increased the levels of pro-inflammatory cytokines, while injection of M2 microglia induced the reverse results, i.e. decreased M1 microglia proportion and reduced pro-inflammatory cytokine levels. In LPS-induced microglial cells, mild hypothermia treatment increased M2 microglia proportion and decreased pro-inflammatory cytokine levels, relative to normothermia. Mild hypothermia inactivated the TLR4/NF-κB pathway in LPS-treated microglia. TLR4 overexpression reversed the function of mild hypothermia in LPS-stimulated microglia, and under normal condition, TLR4/NF-κB pathway suppressed microglial M2 polarization. Mild hypothermia inhibits TLR4/NF-κB pathway and promotes microglial M2 polarization, thus attenuating SCI-induced injury and inflammation.

Polaryzacja mikrogleju i makrofagów w wybranych chorobach degeneracyjnych i zapalnych układu nerwowego

Makrofagi to komórki efektorowe układu odpornościowego zdolne do polaryzacji, czyli zmiany fenotypu powiązanej ze zmianą aktywności. Można wyróżnić: polaryzację klasyczną (M1), która służy obronie przed patogenami, a makrofagi M1 mają aktywność ogólnie prozapalną, oraz polaryzację alternatywną (M2), która sprzyja wygaszaniu stanu zapalnego i regeneracji tkanki. Makrofagi zasiedlają niemal cały organizm, więc zjawisko ich polaryzacji ma wpływ na wiele procesów zachodzących w różnych tkankach. W układzie nerwowym reprezentacją osiadłych makrofagów jest mikroglej. Jednak w wielu sytuacjach patologicznych w mózgu pojawiają się także makrofagi rekrutowane z monocytów krążących we krwi. Choroby neurodegeneracyjne, urazy i choroby autoimmunologiczne są związane z reakcją układu odpornościowego, która może mieć istotny wpływ na dalszy przebieg choroby i na tempo regeneracji tkanki. Polaryzacja makrofagów ma w związku z tym znaczenie w chorobach centralnego układu nerwowego. Aktywność komórek M1 i M2 może bowiem różnie wpływać na przeżywalność neuronów i oligodendrocytów, na wzrost aksonów, na proces demielinizacji czy na szczelność bariery krew–mózg. Wynika to z różnic między fenotypami w wytwarzaniu reaktywnych form tlenu i tlenku azotu, wydzielaniu cytokin i czynników wzrostu, bezpośrednich oddziaływaniach na sąsiednie komórki i zdolnościach do fagocytozy. W artykule omówiono to zagadnienie w: udarze mózgu, urazie rdzenia kręgowego, chorobie Alzheimera, stwardnieniu zanikowym bocznym i stwardnieniu rozsianym. W wielu spośród tych patologii obserwuje się gradient czasowy lub przestrzenny rozmieszczenia w tkance poszczególnych fenotypów mikrogleju i/lub makrofagów. Wydaje się zatem, że zmiany polaryzacji makrofagów mogą potencjalnie sprzyjać regeneracji tkanki lub hamować rozwój chorób neurodegeneracyjnych.

BMPER alleviates ischemic brain injury by protecting neurons and inhibiting neuroinflammation via Smad3-Akt-Nrf2 pathway

Aims

Bone morphogenetic proteins (BMPs) are a group of proteins related to bone morphogenesis. BMP‐binding endothelial regulator (BMPER), a secreted protein that interacts with BMPs, is known to be involved in ischemic injuries. Here, we explored the effects of BMPER on cerebral ischemia and its mechanism of action.

Methods

A mouse model of brain ischemia was induced by middle cerebral artery occlusion (MCAO). An in vitro ischemic model was established by subjecting primary cultured neurons to oxygen‐glucose deprivation/reperfusion (OGD/R). Serum levels of BMPs/BMPER were measured in MCAO mice and in patients with acute ischemic stroke (AIS). Brain damages were compared between BMPER‐ and vehicle‐treated mice. Quantitative polymerase chain reaction (qPCR), immunohistochemistry, and immunofluorescence staining were performed to examine neuroinflammation and cell death. BMPER‐related pathways were assessed by Western blotting.

Results

BMPER level was elevated in MCAO mice and AIS patients. BMPER administration reduced mortality, infarct size, brain edema, and neurological deficit after MCAO. Neuroinflammation and cell death after ischemia were alleviated by BMPER both in vivo and in vitro. BMPER activated the Smad3/Akt/Nrf2 pathway in OGD/R‐challenged neurons.

Conclusion

BMPER is a neuroprotective hormone that alleviates ischemic brain injury via activating the Smad3/Akt/Nrf2 pathway. These findings may provide potential therapeutic strategies for stroke.

Microglial deactivation by adeno-associated virus expressing small-hairpin GCH1 has protective effects against neuropathic pain development in a spinothalamic tract-lesion model

AIMS

Neuropathic pain after spinal cord injury is one of the most difficult clinical problems after the loss of mobility, and pharmacological or neuromodulation therapy showed limited efficacy. In this study, we examine the possibility of pain modulation by a recombinant adeno-associated virus (rAAV) encoding small-hairpin RNA against GCH1 (rAAV-shGCH1) in a spinal cord injury model in which neuropathic pain was induced by a spinothalamic tract (STT) lesion.

METHODS

Micro-electric lesioning was used to damage the left STT in rats (n = 32), and either rAAV-shGCH1 (n = 19) or rAAV control (n = 6) was injected into the dorsal horn of the rats at the same time. On postoperative days 3, 7, and 14, we evaluated neuropathic pain using a behavioral test and microglial activation by immunohistochemical staining.

RESULTS

A pain modulation effect of shGCH1 was observed from postoperative days 3 to 14. The mechanical withdrawal threshold was 13.0 ± 0.95 in the shGCH1 group, 4.3 ± 1.37 in the control group, and 3.49 ± 0.85 in sham on postoperative day 3 (p < 0.0001) and continued to postoperative day 14 (shGCH1 vs. control: 11.4 ± 1.1 vs. 2.05 ± 0.60, p < 0.001 and shGCH1 vs. sham: 11.4 ± 1.1 vs. 1.43 ± 0.54, p < 0.001). Immunohistochemical staining of the spinal cord dorsal horn showed deactivation of microglia in the shGCH1 group without any change of delayed pattern of astrocyte activation as in STT model.

CONCLUSIONS

Neuropathic pain after spinal cord injury can be modulated bilaterally by deactivating microglial activation after a unilateral injection of rAAV-shGCH1 into the dorsal horn of a STT lesion spinal cord pain model. This new attempt would be another therapeutic approach for NP after SCI, which once happens; there is no clear curative options still now.

The promise of exosome applications in treating central nervous system diseases

Exosomes (EXs), a type of extracellular vesicles, are secreted from virtually all types of cells. EXs serve as cell-to-cell communicators by conveying proteins and nucleic acids with regulatory functions. Increasing evidence shows that EXs are implicated in the pathogenesis of central nervous system (CNS) diseases. Moreover, EXs have recently been highlighted as a new promising therapeutic strategy for in vivo delivery of nucleotides and drugs. Studies have revealed that infusion of EXs elicits beneficial effects on the CNS injury animal models. As compared to cell-based therapy, EXs-based therapy for CNS diseases has unique advantages, opening a new path for neurological medicine. In this review, we summarized the current state of knowledge of EXs, the roles and applications of EXs as a viable pathological biomarker, and EX-based therapy for CNS diseases.

A nerve conduit filled with Wnt5a-loaded fibrin hydrogels promotes peripheral nerve regeneration

Aims

Peripheral nerve injury is a significant clinical problem with a substantial impact on quality of life, for which no optimal treatment has been found. This study aimed to analyze the effect and mechanism of Wnt5a‐loaded fibrin hydrogel on a 10‐mm rat sciatic nerve defect.

Methods

The Wnt5a‐loaded fibrin hydrogel was synthesized by mixing a Wnt5a solution with thrombin and fibrinogen solutions. The loading capacity and release profile of Wnt5a‐loaded fibrin hydrogel and the effect of Wnt5a on Schwann cells were evaluated in vitro. We also assessed the in vivo repair status via histological analysis of the regenerative nerve and gastrocnemius muscle, electrophysiological examination, gait analysis, and muscle wet weight.

Results

We developed a nerve conduit filled with Wnt5a‐loaded fibrin hydrogel (Fn) as a sustained‐release system to repair a 10‐mm rat sciatic nerve defect. In vitro, Wnt5a could promote SC proliferation and the gene expression of vascular endothelial growth factor (VEGF), nerve growth factor (NGF), and cholinergic neurotrophic factor (CNTF), as well as the protein secretion of VEGF and NGF. In vivo, the Wnt5a/Fn group was superior to the hollow, fibrin hydrogel, and Wnt5a groups in terms of axonal growth, myelination, electrophysiological recovery, target organ innervation, and motor function recovery 12 weeks after the operation.

Conclusion

The Wnt5a/Fn nerve conduit can promote peripheral nerve defect regeneration, with potential clinical applications. The mechanism for this may be the facilitation of multiple neurotrophin secretion, combining vascularization and neurotrophic growth cues.

Intranasal delivery of interleukin-4 attenuates chronic cognitive deficits via beneficial microglial responses in experimental traumatic brain injury

Traumatic brain injury (TBI) is commonly followed by long-term cognitive deficits that severely impact the quality of life in survivors. Recent studies suggest that microglial/macrophage (Mi/MΦ) polarization could have multidimensional impacts on post-TBI neurological outcomes. Here, we report that repetitive intranasal delivery of interleukin-4 (IL-4) nanoparticles for 4 weeks after controlled cortical impact improved hippocampus-dependent spatial and non-spatial cognitive functions in adult C57BL6 mice, as assessed by a battery of neurobehavioral tests for up to 5 weeks after TBI. IL-4-elicited enhancement of cognitive functions was associated with improvements in the integrity of the hippocampus at the functional (e.g., long-term potentiation) and structural levels (CA3 neuronal loss, diffusion tensor imaging of white matter tracts, etc.). Mechanistically, IL-4 increased the expression of PPARγ and arginase-1 within Mi/MΦ, thereby driving microglia toward a global inflammation-resolving phenotype. Notably, IL-4 failed to shift microglial phenotype after TBI in Mi/MΦ-specific PPARγ knockout (mKO) mice, indicating an obligatory role for PPARγ in IL-4-induced Mi/MΦ polarization. Accordingly, post-TBI treatment with IL-4 failed to improve hippocampal integrity or cognitive functions in PPARγ mKO mice. These results demonstrate that administration of exogenous IL-4 nanoparticles stimulates PPARγ-dependent beneficial Mi/MΦ responses, and improves hippocampal function after TBI.

A high fat, sugar, and salt Western diet induces motor-muscular and sensory dysfunctions and neurodegeneration in mice during aging: Ameliorative action of metformin

Aims

To explore the novel linkage between a Western diet combining high saturated fat, sugar, and salt (HFSS) and neurological dysfunctions during aging as well as Metformin intervention, we assessed cerebral cortex abnormalities associated with sensory and motor dysfunctions and cellular and molecular insights in brains using HFSS‐fed mice during aging. We also explored the effect of Metformin treatment on these mice.

Methods

C57BL/6 mice were fed with HFSS and treated with metformin from 20 to 22 months of age, resembling human aging from 56 to 68 years of age (an entry phase of the aged portion of lifespan).

Results

The motor and sensory cortexes in mice during aging after HFSS diet showed: (A) decreased motor‐muscular and sensory functions; (B) reduced inflammation‐resolving Arg‐1⁺ microglia; (C) increased inflammatory iNOs⁺ microglia and TNFα levels; (D) enhanced abundance of amyloid‐β peptide and of phosphorylated Tau. Metformin attenuated these changes.

Conclusion

A HFSS‐combined diet caused motor‐muscular and sensory dysfunctions, neuroinflammation, and neurodegeneration, whereas metformin counteracted these effects. Our findings show neuroinflammatory consequences of a HFSS diet in aging. Metformin curbs the HFSS‐related neuroinflammation eliciting neuroprotection.

Inhibitory Effect of Gualou Guizhi Decoction on Microglial Inflammation and Neuron Injury by Promoting Anti-Inflammation via Targeting mmu-miR-155

Gualou Guizhi decoction (GLGZD) treatment exerts neuroprotective effects and promotes spasticity following ischemic stroke. However, the molecular mechanism of GLGZD treatment on ischemic stroke remains unclear. Our previous study indicated that GLGZD ameliorates neuronal damage caused by secondary inflammatory injury induced by microglia. In the present study, we investigate the potential mechanism of GLGZD treatment on neuron damage induced by neuroinflammation via mmu-miR-155 in vitro. The HT22 cell line and the BV2 cell line were exposed to oxygen/glucose-deprive (OGD) conditions; the conditioned medium was prepared using the supernatants from OGD-stimulated BV2 cells after pretreating with GLGZD. Cell viability was determined by MTT assays; levels of released inflammatory cytokines were assessed using the BioPlex system. mmu-miR-155 and its targeting genes were detected using real-time reverse transcription polymerase chain reaction (RT-PCR). The expression of anti-inflammatory proteins was evaluated by Western blotting. DAPI staining was used to test the apoptotic cells. Our results showed that GLGZD pretreatment significantly induced IL10 release and decreased the production of TNF-α, IL6, and IFN-γ. In addition, GLGZD markedly attenuated mmu-miR-155 expression and its downstream SOCS1, SMAD2, SHIP1, and TAB2 expression levels. The DAPI-stained apoptotic cell death and caspase-3 activation in HT22 cells exposed to the conditioned medium were reversed by GLGZD treatment. Our findings suggested that GLGZD pretreatment downregulates the mmu-miR-155 signaling, which inhibits microglial inflammation, thereby resulting in the suppression of neuron apoptosis after OGD stress. The underlying mechanisms may provide the support for GLGZD treatment of cerebral ischemic injury.

Genetic Modulators of Traumatic Brain Injury in Animal Models and the Impact of Sex-Dependent Effects

Traumatic brain injury (TBI) is a major health problem causing disability and death worldwide. There is no effective treatment, due in part to the complexity of the injury pathology and factors affecting its outcome. The extent of brain injury depends on the type of insult, age, sex, lifestyle, genetic risk factors, socioeconomic status, other co-injuries, and underlying health problems. This review discusses the genes that have been directly tested in TBI models, and whether their effects are known to be sex-dependent. Sex differences can affect the incidence, symptom onset, pathology, and clinical outcomes following injury. Adult males are more susceptible at the acute phase and females show greater injury in the chronic phase. TBI is not restricted to a single sex; despite variations in the degree of symptom onset and severity, it is important to consider both female and male animals in TBI pre-clinical research studies.

The killifish visual system as an in vivo model to study brain aging and rejuvenation

Worldwide, people are getting older, and this prolonged lifespan unfortunately also results in an increased prevalence of age-related neurodegenerative diseases, contributing to a diminished life quality of elderly. Age-associated neuropathies typically include diseases leading to dementia (Alzheimer's and Parkinson's disease), as well as eye diseases such as glaucoma and age-related macular degeneration. Despite many research attempts aiming to unravel aging processes and their involvement in neurodegeneration and functional decline, achieving healthy brain aging remains a challenge. The African turquoise killifish (Nothobranchius furzeri) is the shortest-lived reported vertebrate that can be bred in captivity and displays many of the aging hallmarks that have been described for human aging, which makes it a very promising biogerontology model. As vision decline is an important hallmark of aging as well as a manifestation of many neurodegenerative diseases, we performed a comprehensive characterization of this fish's aging visual system. Our work reveals several aging hallmarks in the killifish retina and brain that eventually result in a diminished visual performance. Moreover, we found evidence for the occurrence of neurodegenerative events in the old killifish retina. Altogether, we introduce the visual system of the fast-aging killifish as a valuable model to understand the cellular and molecular mechanisms underlying aging in the vertebrate central nervous system. These findings put forward the killifish for target validation as well as drug discovery for rejuvenating or neuroprotective therapies ensuring healthy aging.

Sevoflurane preconditioning protects experimental ischemic stroke by enhancing anti-inflammatory microglia/macrophages phenotype polarization through GSK-3β/Nrf2 pathway

Aims

Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro‐inflammatory state to anti‐inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition.

Methods

Mouse primary microglia with SPC were challenged by oxygen‐glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro‐inflammatory/anti‐inflammatory factors were analyzed. GSK‐3β phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro‐inflammatory/anti‐inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro‐inflammatory/anti‐inflammatory microglia/macrophages, and the generation of super‐oxidants were examined after SPC or GSK‐3β inhibitor TDZD treatment with or without Nrf2 deficiency.

Results

Sevoflurane preconditioning promoted anti‐inflammatory and inhibited pro‐inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK‐3β phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro‐inflammatory microglia/macrophages markers expression, promoted anti‐inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti‐inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro‐inflammatory positive cells and super‐oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown.

Conclusions

Our results indicated that SPC exerts brain ischemic tolerance and promotes anti‐inflammatory microglia/macrophages polarization by GSK‐3β‐dependent Nrf2 activation, which provides a novel mechanism for SPC‐induced neuroprotection.

Janus Kinase Inhibition Ameliorates Ischemic Stroke Injury and Neuroinflammation Through Reducing NLRP3 Inflammasome Activation via JAK2/STAT3 Pathway Inhibition

Background

Inflammatory responses play a multiphase role in the pathogenesis of cerebral ischemic stroke (IS). Ruxolitinib (Rux), a selective oral JAK 1/2 inhibitor, reduces inflammatory responses via the JAK2/STAT3 pathway. Based on its anti-inflammatory and immunosuppressive effects, we hypothesized that it may have a protective effect against stroke. The aim of this study was to investigate whether inhibition of JAK2 has a neuroprotective effect on ischemic stroke and to explore the potential molecular mechanisms.

Methods

Rux, MCC950 or vehicle was applied to middle cerebral artery occlusion (MCAO) mice in vivo and an oxygen-glucose deprivation/reoxygenation (OGD/R) model in vitro. After 3 days of reperfusion, neurological deficit scores, infarct volume and brain water content were assessed. Immunofluorescence staining and western blots were used to measure the expression of NLRP3 inflammasome components. The infiltrating cells were investigated by flow cytometry. Proinflammatory cytokines were assessed by RT-qPCR. The expression of the JAK2/STAT3 pathway was measured by western blots. Local STAT3 deficiency in brain tissue was established with a lentiviral vector carrying STAT3 shRNA, and chromatin immunoprecipitation (ChIP) assays were used to investigate the interplay between NLRP3 and STAT3 signaling.

Results

Rux treatment improved neurological scores, decreased the infarct size and ameliorated cerebral edema 3 days after stroke. In addition, immunofluorescence staining and western blots showed that Rux application inhibited the expression of proteins related to the NLRP3 inflammasome and phosphorylated STAT3 (P-STAT3) in neurons and microglia/macrophages. Furthermore, Rux administration inhibited the expression of proinflammatory cytokines, including TNF-α, IFN-γ, HMGB1, IL-1β, IL-2, and IL-6, suggesting that Rux may alleviate IS injury by inhibiting proinflammatory reactions via JAK2/STAT3 signaling pathway regulation. Infiltrating macrophages, B, T, cells were also reduced by Rux. Local STAT3 deficiency in brain tissue decreased histone H3 and H4 acetylation on the NLRP3 promoter and NLRP3 inflammasome component expression, indicating that the NLRP3 inflammasome may be directly regulated by STAT3 signaling. Rux application suppressed lipopolysaccharide (LPS)-induced NLRP3 inflammasome secretion and JAK2/STAT3 pathway activation in the OGD/R model in vitro.

Conclusion

JAK2 inhibition by Rux in MCAO mice decreased STAT3 phosphorylation, thus inhibiting the expression of downstream proinflammatory cytokines and the acetylation of histones H3 and H4 on the NLRP3 promoter, resulting in the downregulation of NLRP3 inflammasome expression.

Spinal microglial β-endorphin signaling mediates IL-10 and exenatide-induced inhibition of synaptic plasticity in neuropathic pain

AIM

This study aimed to investigate the regulation of pain hypersensitivity induced by the spinal synaptic transmission mechanisms underlying interleukin (IL)-10 and glucagon-like peptide 1 receptor (GLP-1R) agonist exenatide-induced pain anti-hypersensitivity in neuropathic rats through spinal nerve ligations.

METHODS

Neuropathic pain model was established by spinal nerve ligation of L5/L6 and verified by electrophysiological recording and immunofluorescence staining. Microglial expression of β-endorphin through autocrine IL-10- and exenatide-induced inhibition of glutamatergic transmission were performed by behavioral tests coupled with whole-cell recording of miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) through application of endogenous and exogenous IL-10 and β-endorphin.

RESULTS

Intrathecal injections of IL-10, exenatide, and the μ-opioid receptor (MOR) agonists β-endorphin and DAMGO inhibited thermal hyperalgesia and mechanical allodynia in neuropathic rats. Whole-cell recordings of bath application of exenatide, IL-10, and β-endorphin showed similarly suppressed enhanced frequency and amplitude of the mEPSCs in the spinal dorsal horn neurons of laminae II, but did not reduce the frequency and amplitude of mIPSCs in neuropathic rats. The inhibitory effects of IL-10 and exenatide on pain hypersensitive behaviors and spinal synaptic plasticity were totally blocked by pretreatment of IL-10 antibody, β-endorphin antiserum, and MOR antagonist CTAP. In addition, the microglial metabolic inhibitor minocycline blocked the inhibitory effects of IL-10 and exenatide but not β-endorphin on spinal synaptic plasticity.

CONCLUSION

This suggests that spinal microglial expression of β-endorphin mediates IL-10- and exenatide-induced inhibition of glutamatergic transmission and pain hypersensitivity via presynaptic and postsynaptic MORs in spinal dorsal horn.

Galectin-1 ameliorates perioperative neurocognitive disorders in aged mice

Introduction

The incidence of perioperative neurocognitive disorders (PND) is higher in the elderly patients undergoing surgery. Microglia activation‐mediated neuroinflammation is one of the hallmarks of PND. Galectin‐1 has been identified as a pivotal modulator in the central nervous system (CNS), while the role of galectin‐1 in PND induced by microglia‐mediated neuroinflammation is still undetermined.

Methods

An exploratory laparotomy model anesthetized with isoflurane was employed to investigate the role of galectin‐1 on PND in aged mice. Open field test and Morris water maze were used to test the cognitive function 3‐ or 7‐days post‐surgery. The activation of microglia in the hippocampus of aged mice was tested by immunohistochemistry. Western blot, enzyme‐linked immunosorbent assay (ELISA), and quantitative real‐time polymerase chain reaction (qRT‐PCR) were employed to elucidate the underlying mechanisms.

Results

Galectin‐1 attenuated the cognitive dysfunction induced by surgery in aged mice and inhibited microglial activity. Moreover, galectin‐1 decreased the expression level of inflammatory proteins (interleukin‐1β, interleukin‐6, and tumor necrosis factor‐α), and prevented neuronal loss in the hippocampus. Galectin‐1 inhibited the inflammation of BV2 microglial cells induced by lipopolysaccharide via decreasing the translocation of NF‐κB p65 and c‐Jun, while this kind of inhibition was rescued when overexpressing IRAK1.

Conclusion

Our findings provide evidence that galectin‐1 may inhibit IRAK1 expression, thus suppressing inflammatory response, inhibiting neuroinflammation, and improving ensuing cognitive dysfunction. Collectively, these findings unveil that galectin‐1 may elicit protective effects on surgery‐induced neuroinflammation and neurocognitive disorders.

Role of glial cells in the generation of sex differences in neurodegenerative diseases and brain aging

Diseases and aging-associated alterations of the nervous system often show sex-specific characteristics. Glial cells play a major role in the endogenous homeostatic response of neural tissue, and sex differences in the glial transcriptome and function have been described. Therefore, the possible role of these cells in the generation of sex differences in pathological alterations of the nervous system is reviewed here. Studies have shown that glia react to pathological insults with sex-specific neuroprotective and regenerative effects. At least three factors determine this sex-specific response of glia: sex chromosome genes, gonadal hormones and neuroactive steroid hormone metabolites. The sex chromosome complement determines differences in the transcriptional responses in glia after brain injury, while gonadal hormones and their metabolites activate sex-specific neuroprotective mechanisms in these cells. Since the sex-specific neuroprotective and regenerative activity of glial cells causes sex differences in the pathological alterations of the nervous system, glia may represent a relevant target for sex-specific therapeutic interventions.