Exercise-induced neuroprotection against cerebral ischemia/reperfusion injury is mediated via alleviating inflammasome-induced pyroptosis

Exercise preconditioning alleviates ischemia-induced memory deficits by increasing circulating adiponectin

JOURNAL/nrgr/04.03/01300535-202505000-00027/figure1/v/2024-07-28T173839Z/r/image-tiff Cerebral ischemia is a major health risk that requires preventive approaches in addition to drug therapy. Physical exercise enhances neurogenesis and synaptogenesis, and has been widely used for functional rehabilitation after stroke. In this study, we determined whether exercise training before disease onset can alleviate the severity of cerebral ischemia. We also examined the role of exercise-induced circulating factors in these effects. Adult mice were subjected to 14 days of treadmill exercise training before surgery for middle cerebral artery occlusion. We found that this exercise pre-conditioning strategy effectively attenuated brain infarct area, inhibited gliogenesis, protected synaptic proteins, and improved novel object and spatial memory function. Further analysis showed that circulating adiponectin plays a critical role in these preventive effects of exercise. Agonist activation of adiponectin receptors by AdipoRon mimicked the effects of exercise, while inhibiting receptor activation abolished the exercise effects. In summary, our results suggest a crucial role of circulating adiponectin in the effects of exercise pre-conditioning in protecting against cerebral ischemia and supporting the health benefits of exercise.

GIV/Girdin Modulation of Microglial Activation in Ischemic Stroke: Impact of FTO-Mediated m6A Modification

Ischemic stroke (IS) is one of the most common causes of death in the world. The lack of effective pharmacological treatments for IS was primarily due to a lack of understanding of its pathogenesis. Gα-Interacting vesicle-associated protein (GIV/Girdin) is a multi-modular signal transducer and guanine nucleotide exchange factor that controls important signaling downstream of multiple receptors. The purpose of this study was to investigate the role of GIV in IS. In the present study, we found that GIV is highly expressed in the central nervous system (CNS). GIV protein level was decreased, while GIV transcript level was increased in the middle cerebral artery occlusion reperfusion (MCAO/R) mice model. Additionally, GIV was insensitive lipopolysaccharide (LPS) exposure. Interestingly, we found that GIV overexpression dramatically restrained microglial activation, inflammatory response, and M1 polarization in BV-2 microglia induced by oxygen-glucose deprivation and reoxygenation (OGD/R). On the contrary, GIV knockdown had the opposite impact. Mechanistically, we found that GIV activated the Wnt/β-catenin signaling pathway by interacting with DVL2 (disheveled segment polarity protein 2). Notably, m6A demethylase fat mass and obesity-associated protein (FTO) decreased the N6-methyladenosine (m6A) modification-mediated increase of GIV expression and attenuated the inflammatory response in BV-2 stimulated by OGD/R. Taken together, our results demonstrate that GIV inhibited the inflammatory response via activating the Wnt/β-catenin signaling pathway which expression regulated in an FTO-mediated m6A modification in IS. These results broaden our understanding of the role of the FTO-GIV axis in IS development.

Changes in Type 1 Diabetes-Associated Gut Microbiota Aggravate Brain Ischemia Injury by Affecting Microglial Polarization Via the Butyrate-MyD88 Pathway in Mice

People with type 1 diabetes (T1D) have a significantly elevated risk of stroke, but the mechanism through which T1D worsens ischemic stroke remains unclear. This study was aimed at investigating the roles of T1D-associated changes in the gut microbiota in aggravating ischemic stroke and the underlying mechanism. Fecal 16SrRNA sequencing indicated that T1D mice and mice with transplantation of T1D mouse gut microbiota had lower relative abundance of butyric acid producers, f_Erysipelotrichaceae and g_Allobaculum, and lower content of butyric acid in feces. After middle cerebral artery occlusion (MCAO), these mice had poorer neurological outcomes and more severe inflammation, but higher expression of myeloid differentiation factor 88 (MyD88) in the ischemic penumbra; moreover, the microglia were inclined to polarize toward the pro-inflammatory type. Administration of butyrate to T1D mice in the drinking water alleviated the neurological damage after MCAO. Butyrate influenced the response and polarization of BV2 and decreased the production of inflammatory cytokines via MyD88 after oxygen-glucose deprivation/reoxygenation. Knocking down MyD88 in the brain alleviated neurological outcomes and decreased the concentrations of inflammatory cytokines in the brain after stroke in mice with transplantation of T1D mouse gut microbiota. Poor neurological outcomes and aggravated inflammatory responses of T1D mice after ischemic stroke may be partly due to differences in microglial polarization mediated by the gut microbiota-butyrate-MyD88 pathway. These findings provide new ideas and potential intervention targets for alleviating neurological damage after ischemic stroke in T1D.

New insights into the function of the NLRP3 inflammasome in sarcopenia: mechanism and therapeutic strategies

Sarcopenia is one of the most common skeletal muscle disorders and is characterized by infirmity and disability. While extensive research has focused on elucidating the mechanisms underlying the progression of sarcopenia, further comprehensive insights into its pathogenesis are necessary to identify new preventive and therapeutic approaches. The involvement of inflammasomes in sarcopenia is widely recognized, with particular emphasis on the NLRP3 (NLR family pyrin domain containing 3) inflammasome. In this review, we aim to elucidate the underlying mechanisms of the NLRP3 inflammasome and its relevance in sarcopenia of various etiologies. Furthermore, we highlight interventions targeting the NLRP3 inflammasome in the context of sarcopenia and discuss the current limitations of our knowledge in this area.

High-intensity interval training ameliorates postnatal immune activation-induced mood disorders through KDM6B-regulated glial activation

Postnatal immune activation (PIA) induces persistent glial activation in the brain and causes various neuropathologies in adults. Exercise training improves stress-related mood disorders; however, the role of exercise in psychiatric disorders induced by early-life immune activation and the association between exercise training and glial activation remain unclear. We compared the effects of different exercise intensities on the PIA model, including high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT). Both HIIT and MICT in adolescent mice inhibited neuroinflammation, remodeled synaptic plasticity, and improved PIA-induced mood disorders in adulthood. Importantly, HIIT was superior to MICT in terms of reducing inflammation and increasing body weight. RNA-seq of prefrontal cortex (PFC) tissues revealed a gene expression pattern, confirming that HIIT was more effective than MICT in improving brain glial cell activation through epigenetic modifications of KDM6B. We investigated the role of KDM6B, a specific histone lysine demethylation enzyme - histone 3 lysine 27 demethylase, in inhibiting glial activation against PIA-induced depression and anxiety by regulating the expression of IL-4 and brain-derived neurotrophic factor (BDNF). Overall, our data support the idea that HIIT improves PIA-induced mood disorders by regulating KDM6B-mediated epigenetic mechanisms and indicate that HIIT might be superior to MICT in improving mood disorders with PIA in mice. Our findings provide new insights into the treatment of anxiety and depression disorders.

Can Methamphetamine-Induced Cardiotoxicity be Ameliorated by Aerobic Training and Nutrition Bio-shield Superfood Supplementation in Rats After Withdrawal?

The abuse of methamphetamine is a significant threat to cardiovascular health and has detrimental effects on the myocardium. The present study aims to explore potential interventions that can mitigate myocardial pyroptosis in rats following methamphetamine withdrawal. A total of 104 male Wistar rats were randomly assigned to eight groups. The rats underwent a methamphetamine administration protocol, receiving intraperitoneal injections of 10 mg/kg during the 1st week, followed by a weekly dose escalation of 1 mg/kg from the second to the 6th week and two times per day. Concurrently, the rats engaged in 6 weeks of moderate-intensity treadmill aerobic training, lasting 60 min per day, 5 days a week. Simultaneously, the Nutrition bio-shield Superfood (NBS) supplement was administered at a dosage of 25 g/kg daily for 6 weeks. The study assessed the expression levels of Caspase-1, Interleukin-1beta (IL-1β), and Interleukin-18 (IL-18) genes in myocardial tissue. Data analysis utilized a one-way analysis of variance (p ≤ 0.05). The findings revealed that methamphetamine usage significantly elevated the expression of Caspase-1, IL-1β, and IL-18 genes (p ≤ 0.05). Conversely, methamphetamine withdrawal led to a notable reduction in the expression of these genes (p ≤ 0.05). Noteworthy reductions in Caspase-1, IL-1β, and IL-18 expression were observed following aerobic training, supplementation, and the combined approach (p ≤ 0.05). The chronic use of methamphetamine was associated with cardiac tissue damage. This study highlights the potential of aerobic training and NBS Superfood supplementation in mitigating the harmful effects of methamphetamine-induced myocardial pyroptosis. The observed reductions in gene expression levels indicate promising interventions to address the cardiovascular consequences of methamphetamine abuse. The findings of this study suggest that a combination of aerobic exercise and NBS Superfood supplementation can provide a promising approach to mitigate the deleterious effects of methamphetamine on the heart. These findings can be useful for healthcare professionals and policymakers to design effective interventions to prevent and manage the adverse effects of methamphetamine abuse.

Physical exercise regulates microglia in health and disease

There is a well-established link between physical activity and brain health. As such, the effectiveness of physical exercise as a therapeutic strategy has been explored in a variety of neurological contexts. To determine the extent to which physical exercise could be most beneficial under different circumstances, studies are needed to uncover the underlying mechanisms behind the benefits of physical activity. Interest has grown in understanding how physical activity can regulate microglia, the resident immune cells of the central nervous system. Microglia are key mediators of neuroinflammatory processes and play a role in maintaining brain homeostasis in healthy and pathological settings. Here, we explore the evidence suggesting that physical activity has the potential to regulate microglia activity in various animal models. We emphasize key areas where future research could contribute to uncovering the therapeutic benefits of engaging in physical exercise.

Effects of a novel regimen of repetitive transcranial magnetic stimulation (rTMS) on neural remodeling and motor function in adult male mice with ischemic stroke

Neuroinflammation caused by excessive microglial activation plays a key role in the pathogenesis of ischemic stroke. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulatory technique that has recently been reported to regulate microglial functions and exert anti-inflammatory effects. The intermittent burst stimulation (iTBS) regimen in rTMS improves neuronal excitability. However, whether iTBS exerts its anti-inflammatory effects by stimulating neurons and thereby modulating microglial polarization remains unclear. Motor function was assessed after 1 week of rTMS (iTBS regimen) treatment in adult male mice with occlusion/reperfusion of the middle cerebral artery (MCAO/r) injury. We also investigated the molecular biological alterations associated with microglial polarization using a cell proliferation assay, multiplex cytokine bioassays, and immunofluorescence staining. iTBS regimen can improve balance and motor coordination function, increase spontaneous movement, and improve walking function in mice with early cerebral ischemia injury. Expression levels of IL-1β, TNF-α, and IL-10 increased significantly in mice with MCAO injury. Especially, rTMS significantly increased the number of proliferating cells in the infarcted cortex. The fluorescence intensity of MAP2 in the peri-infarct area of MCAO injured mice was low, but the signal was broader. Compared with MCAO group, the fluorescence intensity of MAP2 in rTMS group was significantly increased. rTMS inhibited pro-inflammatory M1 activation (Iba1+/CD86+) and improved anti-inflammatory M2 activation (Iba1+/CD206+) in the peri-infarct zone, thus significantly changing the phenotypic ratio M1/M2. rTMS improves motor dysfunction and neuroinflammation after cerebral I/R injury in mice by regulating microglial polarization.

Purinergic signaling influences the neuroinflammatory outcomes of a testosterone-derived synthetic in female rats: Resistance training protective effects on brain health

Physical exercise is recognized as a non-pharmacological approach to treat and protect against several neuroinflammatory conditions and thus to prevent brain disorders. However, the interest in ergogenic resources by athletes and bodybuilding practitioners is widespread and on the rise. These substances shorten the process of performance gain and improve aesthetics, having led to the prominent use and abuse of hormones in the past years. Recent evidence has shown that the purinergic system, composed of adenine nucleotides, nucleosides, enzymes, and receptors, participates in a wide range of processes within the brain, such as neuroinflammation, neuromodulation, and cellular communication. Here, we investigated the effects of the anabolic androgenic steroid (AAS) testosterone (TES) at a dose of 70 mg/kg/week in female rats and the neuroprotective effect of resistance exercise related to the purinergic system and oxidative stress parameters. Our findings showed a decrease in ATP and ADO hydrolysis in treated and trained animals. Furthermore, there was an increase in the density of purinoceptors (P2X7 and A2A) and inflammatory markers (IBA-1, NRLP3, CASP-1, IL-1β, and IL-6) in the cerebral cortex of animals that received AAS. On the other hand, exercise reversed neuroinflammatory parameters such as IBA-1, NLRP3, CASP-1, and IL-1β and improved antioxidant response and anti-inflammatory IL-10 cytokine levels. Overall, this study shows that the use of TES without indication or prescription disrupts brain homeostasis, as demonstrated by the increase in neuroinflammation, and that the practice of exercise can protect brain health.

Pharmacological inhibition of ICOS attenuates the protective effect of exercise on cardiac fibrosis induced by isoproterenol

AIMS

To investigate the cardioprotective mechanism of exercise or exercise combined with inducible costimulatory molecules (ICOS) monoclonal antibody (mAb) therapy against isoproterenol (ISO)-induced cardiac remodeling.

MAIN METHODS

Totally 24 male C57BL/6J mice were randomly divided into four groups: the control group (normal saline treatment), ISO group (subcutaneous injection of isoproterenol, 10 mg/kg/day, once daily for 5 consecutive days), the exercise with subcutaneous ISO injection group (EPI), and the exercise with injected with ISO and ICOS mAb group (EPII). The mice in EPI and EPII group were trained on a small animal treadmill for 4 weeks (13 m/min, 0% grade, 60min/day).

KEY FINDINGS

Exercise significantly attenuated CD45+, Mac-2 inflammatory cell infiltration, cardiac fibrosis and inhibited the RIPK1/RIPK3/MLKL/CaMKII and cardiomyocyte pyroptosis pathways to counter ISO-induced severe cardiac injury. The administration of the ICOS mAb may inhibit the cardioprotection of exercise against ISO-induced heart damage. Compared to those in EPI, our data showed that the increasing levels of myocardial fibrosis, the leukocyte infiltration of cardiac tissue and proteins expression of cardiac myocyte necrosis and pyroptosis signaling pathways in the EPII group.

SIGNIFICANCE

Our results demonstrated that exercise decreased leukocyte infiltration in heart, inhibited the cardiomyocyte pyroptosis and necroptosis signaling pathways, and attenuated inflammatory responses to alleviate ISO-induced cardiac fibrosis. However, the antifibrotic effects of combined treatment with exercise and ICOS mAb intervention did not exhibit synergistic enhancement.

TAT-W61 peptide attenuates neuronal injury through blocking the binding of S100b to the V-domain of Rage during ischemic stroke

Ischemic stroke is a devastative nervous system disease associated with high mortality and morbidity rates. Unfortunately, no clinically effective neuroprotective drugs are available now. In ischemic stroke, S100 calcium-binding protein b (S100b) binds to receptor for advanced glycation end products (Rage), leading to the neurological injury. Therefore, disruption of the interaction between S100B and Rage can rescue neuronal cells. Here, we designed a peptide, termed TAT-W61, derived from the V domain of Rage which can recognize S100b. Intriguingly, TAT-W61 can reduce the inflammatory caused by ischemic stroke through the direct binding to S100b. The further investigation demonstrated that TAT-W61 can improve pathological infarct volume and reduce the apoptotic rate. Particularly, TAT-W61 significantly improved the learning ability, memory, and motor dysfunction of the mouse in the ischemic stroke model. Our study provides a mechanistic insight into the abnormal expression of S100b and Rage in ischemic stroke and yields an invaluable candidate for the development of drugs in tackling ischemic stroke. KEY MESSAGES: S100b expression is higher in ischemic stroke, in association with a high expression of many genes, especially of Rage. S100b is directly bound to the V-domain of Rage. Blocking the binding of S100b to Rage improves the injury after ischemic stroke.

Exercise, Spinal Microglia and Neuropathic Pain: Potential Molecular Mechanisms

As one of the most common neuropathic disorders, neuropathic pain often has a negative impact on patients with persistent pain, mood disorders and sleep disturbances. Currently, neuropathic pain is not treated with any specific drug, instead, drugs for other diseases are used as replacements in clinics, but most have adverse effects. In recent years, the role of spinal cord microglia in the pathogenesis of neuropathic pain has been widely recognized, and they are being explored as potential therapeutic targets. Spinal microglia are known to be involved in the pathogenic mechanisms of neuropathic pain through purine signaling, fractalkine signaling, and p38 MAPK signaling. Exercise is a safe and effective treatment, and numerous studies have demonstrated its effectiveness in improving neurological symptoms. Nevertheless, it remains unclear what the exact molecular mechanism is. This review summarized the specific molecular mechanisms of exercise in alleviating neuropathic pain by mediating the activity of spinal microglia and maintaining the phenotypic homeostasis of spinal microglia through purine signaling, fractalkine signaling and p38 MAPK signaling. In addition, it has been proposed that different intensities and types of exercise affect the regulation of the above-mentioned signaling pathways differently, providing a theoretical basis for the improvement of neuropathic pain through exercise.

Pharmacological intervention of curcumin via the NLRP3 inflammasome in ischemic stroke

Ischemic-induced neuronal injury arises due to low oxygen/nutrient levels and an inflammatory response that exacerbates neuronal loss. NOD-like receptor family pyrin domain-containing 3 (NLRP3) is an important regulator of inflammation after ischemic stroke, with its inhibition being involved in nerve regeneration. Curcumin, a main active ingredient in Chinese herbs, plays a positive role in neuronal repair and neuroprotection by regulating the NLRP3 signaling pathway. Nevertheless, the signaling mechanisms relating to how curcumin regulates NLRP3 inflammasome in inflammation and neural restoration following ischemic stroke are unknown. In this report, we summarize the main biological functions of the NLRP3 inflammasome along with the neuroprotective effects and underlying mechanisms of curcumin via impairment of the NLRP3 pathway in ischemic brain injury. We also discuss the role of medicinal interventions that target the NLRP3 and potential pathways, as well as possible directions for curcumin therapy to penetrate the blood-brain barrier (BBB) and hinder inflammation in ischemic stroke. This report conclusively demonstrates that curcumin has neuroprotective properties that inhibit inflammation and prevent nerve cell loss, thereby delaying the progression of ischemic brain damage.

Spatial and temporal mapping of neuron-microglia interaction modes in acute ischemic stroke

Ischemic stroke (IS) is a major cause of morbidity and mortality worldwide, accounting for 75-80% of all strokes. Under conditions of ischemia and hypoxia, neurons suffer damage or death, leading to a series of secondary immune reactions. Microglia, the earliest activated immune cells, can exert neurotoxic or neuroprotective effects on neurons through secretion of factors. There exists a complex interaction between neurons and microglia during this process. Moreover, the interaction between them becomes even more complex due to differences in the infarct area and reperfusion time. This review first elaborates on the differences in neuronal death modes between the ischemic core and penumbra, and then introduces the differences in microglial markers across different infarct areas with varying reperfusion time, indicating distinct functions. Finally, we focus on exploring the interaction modes between neurons and microglia in order to precisely target beneficial interactions and inhibit harmful ones, thus providing new therapeutic strategies for the treatment of IS.

Mechanisms underlying the beneficial effects of physical exercise on multiple sclerosis: focus on immune cells

Multiple sclerosis (MS) is a prevalent neuroimmunological illness that leads to neurological disability in young adults. Although the etiology of MS is heterogeneous, it is well established that aberrant activity of adaptive and innate immune cells plays a crucial role in its pathogenesis. Several immune cell abnormalities have been described in MS and its animal models, including T lymphocytes, B lymphocytes, dendritic cells, neutrophils, microglia/macrophages, and astrocytes, among others. Physical exercise offers a valuable alternative or adjunctive disease-modifying therapy for MS. A growing body of evidence indicates that exercise may reduce the autoimmune responses triggered by immune cells in MS. This is partially accomplished by restricting the infiltration of peripheral immune cells into the central nervous system (CNS) parenchyma, curbing hyperactivation of immune cells, and facilitating a transition in the balance of immune cells from a pro-inflammatory to an anti-inflammatory state. This review provides a succinct overview of the correlation between physical exercise, immune cells, and MS pathology, and highlights the potential benefits of exercise as a strategy for the prevention and treatment of MS.

Astragaloside IV alleviates stroke-triggered early brain injury by modulating neuroinflammation and ferroptosis via the Nrf2/HO-1 signaling pathway

PURPOSE

Stroke is an acute cerebrovascular disease. Astragaloside IV (AS-IV) is an active ingredient extracted from Astragalus membranaceus with an established therapeutic effect on central nervous system diseases. This study examined the neuroprotective properties and possible mechanisms of AS-IV in stroke-triggered early brain injury (EBI) in a rat transient middle cerebral artery occlusion (MCAO) model.

METHODS

The neurological scores and brain water content were analyzed. 2,3,5-triphenyl tetrazolium chloride (TTC) staining was utilized to determine the infarct volume, neuroinflammatory cytokine levels, and ferroptosis-related genes and proteins, and neuronal damage and molecular mechanisms were evaluated by terminal deoxynucleotidyl transferase dutp nick-end labeling (TUNEL) staining, western blotting, and real-time polymerase chain reaction.

RESULTS

AS-IV administration decreased the infarct volume, brain edema, neurological deficits, and inflammatory cytokines TNF-α, interleukin-1β (IL-1β), IL-6, and NF-κB, increased the levels of SLC7A11 and glutathione peroxidase 4 (GPX4), decreased lipid reactive oxygen species (ROS) levels, and prevented neuronal ferroptosis. Meanwhile, AS-IV triggered the Nrf2/HO-1 signaling pathway and alleviated ferroptosis due to the induction of stroke.

CONCLUSIONS

Hence, the findings of this research illustrate that AS-IV administration can improve delayed ischemic neurological deficits and decrease neuronal death by modulating nuroinflammation and ferroptosis via the Nrf2/HO-1 signaling pathway.

The Implications of Microglial Regulation in Neuroplasticity-Dependent Stroke Recovery

Stroke causes varying degrees of neurological deficits, leading to corresponding dysfunctions. There are different therapeutic principles for each stage of pathological development. Neuroprotection is the main treatment in the acute phase, and functional recovery becomes primary in the subacute and chronic phases. Neuroplasticity is considered the basis of functional restoration and neurological rehabilitation after stroke, including the remodeling of dendrites and dendritic spines, axonal sprouting, myelin regeneration, synapse shaping, and neurogenesis. Spatiotemporal development affects the spontaneous rewiring of neural circuits and brain networks. Microglia are resident immune cells in the brain that contribute to homeostasis under physiological conditions. Microglia are activated immediately after stroke, and phenotypic polarization changes and phagocytic function are crucial for regulating focal and global brain inflammation and neurological recovery. We have previously shown that the development of neuroplasticity is spatiotemporally consistent with microglial activation, suggesting that microglia may have a profound impact on neuroplasticity after stroke and may be a key therapeutic target for post-stroke rehabilitation. In this review, we explore the impact of neuroplasticity on post-stroke restoration as well as the functions and mechanisms of microglial activation, polarization, and phagocytosis. This is followed by a summary of microglia-targeted rehabilitative interventions that influence neuroplasticity and promote stroke recovery.

Alternate-day fasting for the protection of cognitive impairment in c57BL/6J mice following whole-brain radiotherapy

NLRP3 inflammasome activation is implicated in irradiation-induced cognitive dysfunction. Alternate-day fasting (ADF) has been demonstrated to improve neuroinflammation as a non-pharmacological intervention. However, the exact mechanism and the anti-inflammatory effect in irradiation-induced cognitive dysfunction still need further in-depth study. The present study examined the effects of eight-week ADF on the cognitive functions of mice as well as inflammasome-mediated hippocampal neuronal loss following irradiation in mouse models of irradiation-induced cognitive deficits using seven-week-old male C57BL/6J mice. The behavioral results of novel place recognition and object recognition tasks revealed that ADF ameliorated cognitive functions in irradiation-induced cognitive dysfunction mice. ADF inhibited the expression of components of the NLRP3 inflammasome (NLRP3, ASC, and Cl.caspase-1), the downstream inflammatory factor (IL-1β and IL-18), and apoptosis-related proteins (caspase-3) via western blotting. Furthermore, an increased number of neurons and activated astrocytes were observed in the hippocampus using immunohistochemistry and Sholl analysis, which was jointly confirmed by western blotting. According to our study, this is the first time we found that ADF improved cognitive dysfunction induced by irradiation, and the anti-inflammatory effect of ADF could be due to inhibition in NLRP3-mediated hippocampal neuronal loss by suppressing astrocyte activation.

Pyroptosis: A Newly Discovered Therapeutic Target for Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury, uncommon among patients suffering from myocardial infarction, stroke, or acute kidney injury, can result in cell death and organ dysfunction. Previous studies have shown that different types of cell death, including apoptosis, necrosis, and autophagy, can occur during I/R injury. Pyroptosis, which is characterized by cell membrane pore formation, pro-inflammatory cytokine release, and cell burst, and which differentiates itself from apoptosis and necroptosis, has been found to be closely related to I/R injury. Therefore, targeting the signaling pathways and key regulators of pyroptosis may be favorable for the treatment of I/R injury, which is far from adequate at present. This review summarizes the current status of pyroptosis and its connection to I/R in different organs, as well as potential treatment strategies targeting it to combat I/R injury.

Exercise Preconditioning Ameliorates Cognitive Impairment in Mice with Ischemic Stroke by Alleviating Inflammation and Modulating Gut Microbiota

Several studies have demonstrated that exercise preconditioning is an effective means of alleviating poststroke cognitive impairment (PSCI). Mechanisms of regulating cognitive function have not been fully elucidated. Herein, the present study is aimed at exploring the effect of the microbiota-gut-inflammasome-brain axis in the process of exercise preconditioning moderating cognitive impairment after ischemic stroke. We observed that exercise preconditioning decreased infarct size, reduced the degree of neuronal damage, and alleviated cognitive impairment in mice with ischemic stroke. In addition, exercise preconditioning also reduced the expression of inflammatory cytokines, as well as NLRP3, Caspase-1, IL-18, and IL-1β protein expressions. Ischemic stroke could downregulate the abundance of Roseburia while increasing the abundance of the Helicobacter at the level of genus. As a comparison, exercise preconditioning increased the abundance of the Lactobacillus, which was beneficial for mice at the genus level. In conclusion, exercise preconditioning can improve cognitive dysfunction after ischemic stroke through alleviating inflammation and regulating the composition and diversity of the gut microbiota, which might provide a new strategy for the prevention of PSCI.

Exercise Intervention Modulates Synaptic Plasticity by Inhibiting Excessive Microglial Activation via Exosomes

Background

Exosomes can activate microglia to modulate neural activity and synaptic plasticity by phagocytosis of neural spines or synapses. Our previous research found that an early 4-week exercise intervention in middle cerebral artery occlusion (MCAO) rats can promote the release of exosomes and protect the brain. This study intended to further explore the intrinsic mechanism of neuroprotection by exosome release after exercise.

Methods

Rats were randomly divided into four groups: the sham operation (SHAM), middle cerebral artery occlusion (MCAO) with sedentary intervention (SED-MCAO), MCAO with exercise intervention (EX-MCAO), and MCAO with exercise intervention and exosome injection (EX-MCAO-EXO). Modified neurological severity score (mNSS), cerebral infarction volume ratio, microglial activation, dendritic complexity, and expression of synaptophysin (Syn) and postsynaptic density protein 95 (PSD-95) were detected after 28 days of intervention.

Results

(1) The exercise improved body weight and mNSS score, and the survival state of the rats after exosome infusion was better. (2) Compared with the SED-MCAO group, the EX-MCAO (P = 0.039) and EX-MCAO-EXO groups (P = 0.002) had significantly lower cerebral infarct volume ratios (P < 0.05), among which the EX-MCAO-EXO group had the lowest (P = 0.031). (3) Compared with the SED-MCAO group, the EX-MCAO and EX-MCAO-EXO groups had a significantly decreased number of microglia (P < 0.001) and significantly increased process length/cell (P < 0.01) and end point/cell (P < 0.01) values, with the EX-MCAO-EXO group having the lowest number of microglia (P = 0.036) and most significantly increased end point/cell value (P = 0.027). (4) Compared with the SED-MCAO group, the total number of intersections and branches of the apical and basal dendrites in the EX-MCAO and EX-MCAO-EXO groups was increased significantly (P < 0.05), and the increase was more significant in the EX-MCAO-EXO group (P < 0.05). (5) The expression levels of Syn and PSD-95 in the EX-MCAO (P_Syn = 0.043, P_PSD−95 = 0.047) and EX-MCAO-EXO groups were significantly higher than those in the SED-MCAO group (P < 0.05), and the expression levels in the EX-MCAO-EXO group were significantly higher than those in the EX-MCAO group (P < 0.05).

Conclusion

Early exercise intervention after stroke can inhibit the excessive activation of microglia and regulate synaptic plasticity by exosome release.

Intermittent theta-burst stimulation improves motor function by inhibiting neuronal pyroptosis and regulating microglial polarization via TLR4/NFκB/NLRP3 signaling pathway in cerebral ischemic mice

Background

Neuronal pyroptosis and neuroinflammation with excess microglial activation are widely involved in the early pathological process of ischemic stroke. Repetitive transcranial magnetic stimulation (rTMS), as a non-invasive neuromodulatory technique, has recently been reported to be anti-inflammatory and regulate microglial function. However, few studies have elucidated the role and mechanism of rTMS underlying regulating neuronal pyroptosis and microglial polarization.

Methods

We evaluated the motor function in middle cerebral artery occlusion/reperfusion (MCAO/r) injury mice after 1-week intermittent theta-burst rTMS (iTBS) treatment in the early phase with or without depletion of microglia by colony-stimulating factor 1 receptor (CSF1R) inhibitor treatment, respectively. We further explored the morphological and molecular biological alterations associated with neuronal pyroptosis and microglial polarization via Nissl, EdU, TTC, TUNEL staining, electron microscopy, multiplex cytokine bioassays, western blot assays, immunofluorescence staining and RNA sequencing.

Results

ITBS significantly protected against cerebral ischemia/reperfusion (I/R) injury-induced locomotor deficits and neuronal damage, which probably relied on the regulation of innate immune and inflammatory responses, as evidenced by RNA sequencing analysis. The peak of pyroptosis was confirmed to be later than that of apoptosis during the early phase of stroke, and pyroptosis was mainly located and more severe in the peri-infarcted area compared with apoptosis. Multiplex cytokine bioassays showed that iTBS significantly ameliorated the high levels of IL-1β, IL-17A, TNF-α, IFN-γ in MCAO/r group and elevated the level of IL-10. ITBS inhibited the expression of neuronal pyroptosis-associated proteins (i.e., Caspase1, IL-1β, IL-18, ASC, GSDMD, NLRP1) in the peri-infarcted area rather than at the border of infarcted core. KEGG enrichment analysis and further studies demonstrated that iTBS significantly shifted the microglial M1/M2 phenotype balance by curbing proinflammatory M1 activation (Iba1⁺/CD86⁺) and enhancing the anti-inflammatory M2 activation (Iba1⁺/CD206⁺) in peri-infarcted area via inhibiting TLR4/NFκB/NLRP3 signaling pathway. Depletion of microglia using CSF1R inhibitor (PLX3397) eliminated the motor functional improvements after iTBS treatment.

Conclusions

rTMS could alleviate cerebral I/R injury induced locomotor deficits and neuronal pyroptosis by modulating the microglial polarization. It is expected that these data will provide novel insights into the mechanisms of rTMS protecting against cerebral I/R injury and potential targets underlying neuronal pyroptosis in the early phase of stroke.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02501-2.

rTMS significantly ameliorated cerebral ischemia/reperfusion injury-induced locomotor deficits and neuronal damage in the early phase probably through the anti-inflammatory mechanism.

The peak of pyroptosis was later than that of apoptosis during the early phase of stroke, and pyroptosis was mainly located and more severe in the peri-infarcted area compared with apoptosis.

rTMS inhibited neuronal pyroptosis in the peri-infarcted area rather than at the border of infarcted core.

rTMS modulated microglial polarization in the peri-infarcted area via inhibiting TLR4/NFκB/NLRP3 signaling pathway.

Depletion of microglia eliminated the motor functional improvements after rTMS treatment.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

Angiotensin Type-1 Receptor Inhibition Reduces NLRP3 Inflammasome Upregulation Induced by Aging and Neurodegeneration in the Substantia Nigra of Male Rodents and Primary Mesencephalic Cultures

The tissue renin–angiotensin system (RAS) has been shown to be involved in prooxidative and proinflammatory changes observed in aging and aging-related diseases such as dopaminergic degeneration in Parkinson’s disease (PD). We studied the activation of the NLRP3 inflammasome in the substantia nigra with aging and early stages of dopaminergic degeneration in PD models and, particularly, if the brain RAS, via its prooxidative proinflammatory angiotensin II (AngII) type 1 (AT1) receptors, mediates the inflammasome activation. Nigras from aged rats and mice and 6-hydroxydopamine PD models showed upregulation in transcription of inflammasome-related components (NLRP3, pro-IL1β and pro-IL18) and IL1β and IL18 protein levels, which was inhibited by the AT1 receptor antagonist candesartan. The role of the AngII/AT1 axis in inflammasome activation was further confirmed in rats intraventricularly injected with AngII, and in primary mesencephalic cultures treated with 6-hydroxydopamine, which showed inflammasome activation that was blocked by candesartan. Observations in the nigra of young and aged AT1 and AT2 knockout mice confirmed the major role of AT1 receptors in nigral inflammasome activation. In conclusion, the inflammasome is upregulated by aging and dopaminergic degeneration in the substantia nigra, possibly related with a decrease in dopamine levels, and it is mediated by the AngII/AT1 axis.