Enriched environment remodels the central immune environment and improves the prognosis of acute ischemic stroke in elderly mice with chronic ischemia

Neuroprotective mechanisms of microglia in ischemic stroke: a review focused on mitochondria

Stroke encompasses a range of cerebrovascular disorders characterized by high morbidity, disability, and mortality, with ischemic stroke being the predominant type. This condition imposes significant socio-economic and healthcare burdens, and therapeutic options are currently limited. Microglia, the brain's resident immune cells, are rapidly activated following stroke-induced injury and play a pivotal role in the pathogenesis of neuroinflammation and ischemic tissues. Mitochondria participates in and influences the pathological processes of ischemic stroke, including oxidative stress, modulation of microglia phenotype, and axonal regenerative function, and is an essential and often overlooked target in the clinical management of stroke. This paper reviews recent advancements in research on microglia in ischemic stroke, specifically focusing on the contribution of the mitochondria, providing a reference for selecting therapeutic targets and guiding future research directions.

A Scoping Review of Preclinical Environmental Enrichment Protocols in Models of Poststroke to Set the Foundations for Translating the Paradigm to Clinical Settings

The translation of the highly effective Environmental Enrichment (EE) paradigm from preclinical animal models to human clinical settings has been slow and showed inconsistent results. The primary translational challenge lies in defining what constitutes an EE for humans. To tackle this challenge, this study conducted a scoping review of preclinical EE protocols to explore what constitutes EE for animal models of stroke, laying the foundation for the translation of EE to human application. A systematic search was conducted in the MEDLINE, PsycINFO, and Web of Science databases to identify studies that conducted an EE intervention in the post-stroke animal model. A total of 116 studies were included in the review. A critical reflection of the characteristics of the included studies revealed that EE for post-stroke is a strategy that frequently modifies the animals' daily environment to create a richness of spatial, structural, and/or social opportunities to engage in a variety of daily life-related motor, cognitive, and social exploratory activities. These activities are relevant to the inhabiting individual and involve the activation of the body function(s) affected by the stroke. This review also identified six principles that underpinned the EE protocols: complexity (spatial and social), variety, novelty, targeting needs, scaffolding, and integration of rehabilitation tasks. These findings can be used as steppingstones to define what constitutes EE in human clinical applications and to develop a set of principles that can inform the design of EE protocols for patients after a stroke.

The interplay between ferroptosis and inflammation: therapeutic implications for cerebral ischemia-reperfusion

Stroke ranks as the second most significant contributor to mortality worldwide and is a major factor in disability. Ischemic strokes account for 71% of all stroke incidences globally. The foremost approach to treating ischemic stroke prioritizes quick reperfusion, involving methods such as intravenous thrombolysis and endovascular thrombectomy. These techniques can reduce disability but necessitate immediate intervention. After cerebral ischemia, inflammation rapidly arises in the vascular system, producing pro-inflammatory signals that activate immune cells, which in turn worsen neuronal injury. Following reperfusion, an overload of intracellular iron triggers the Fenton reaction, resulting in an excess of free radicals that cause lipid peroxidation and damage to cellular membranes, ultimately leading to ferroptosis. The relationship between inflammation and ferroptosis is increasingly recognized as vital in the process of cerebral ischemia-reperfusion (I/R). Inflammatory processes disturb iron balance and encourage lipid peroxidation (LPO) through neuroglial cells, while also reducing the activity of antioxidant systems, contributing to ferroptosis. Furthermore, the lipid peroxidation products generated during ferroptosis, along with damage-associated molecular patterns (DAMPs) released from ruptured cell membranes, can incite inflammation. Given the complex relationship between ferroptosis and inflammation, investigating their interaction in brain I/R is crucial for understanding disease development and creating innovative therapeutic options. Consequently, this article will provide a comprehensive introduction of the mechanisms linking ferroptosis and neuroinflammation, as well as evaluate potential treatment modalities, with the goal of presenting various insights for alleviating brain I/R injury and exploring new therapeutic avenues.

Enriched Environment Inhibits Neurotoxic Reactive Astrocytes via JAK2-STAT3 to Promote Glutamatergic Synaptogenesis and Cognitive Improvement in Chronic Cerebral Hypoperfusion Rats

Chronic cerebral hypoperfusion (CCH) is a primary contributor to cognitive decline in the elderly. Enriched environment (EE) is proved to improve cognitive function. However, mechanisms involved remain unclear. The purpose of the study was exploring the mechanisms of EE in alleviating cognitive deficit in rats with CCH. To create a rat model of CCH, 2-vessel occlusion (2-VO) surgery was performed. All rats lived in standard or enriched environments for 4 weeks. Cognitive function was assessed using the novel object recognition test and Morris water maze test. The protein levels of glutamatergic synapses, neurotoxic reactive astrocytes, reactive microglia, and JAK2-STAT3 signaling pathway were measured using Western blot. The mRNA levels of synaptic regulatory factors, C1q, TNF-α, and IL-1α were identified using quantitative PCR. Immunofluorescence was used to detect glutamatergic synapses, neurotoxic reactive astrocytes, and reactive microglia, as well as the expression of p-STAT3 in astrocytes in the hippocampus. The results demonstrated that the EE mitigated cognitive impairment in rats with CCH and enhanced glutamatergic synaptogenesis. EE also inhibited the activation of neurotoxic reactive astrocytes. Moreover, EE downregulated microglial activation, levels of C1q, TNF-α and IL-1α and phosphorylation of JAK2 and STAT3. Our results suggest that inhibition of neurotoxic reactive astrocytes may be one of the mechanisms by which EE promotes glutamatergic synaptogenesis and improves cognitive function in rats with CCH. The downregulation of reactive microglia and JAK2-STAT3 signaling pathway may be involved in this process.

Neutral polysaccharide from Gastrodia elata alleviates cerebral ischemia-reperfusion injury by inhibiting ferroptosis-mediated neuroinflammation via the NRF2/HO-1 signaling pathway

AIMS

The crosstalk between ferroptosis and neuroinflammation considerably impacts the pathogenesis of cerebral ischemia-reperfusion injury (CIRI). Neutral polysaccharide from Gastrodia elata (NPGE) has shown significant effects against oxidative stress and inflammation. This study investigated the potential effects of NPGE on CIRI neuropathology.

METHODS

The effects of NPGE were studied in a mouse model of ischemic stroke (IS) and in oxygen-glucose deprivation/reperfusion (OGD/R)-induced HT22 cells.

RESULTS

NPGE treatment decreased neurological deficits, reduced infarct volume, and alleviated cerebral edema in IS mice, and promoted the survival of OGD/R-induced HT22 cells. Mechanistically, NPGE treatment alleviated neuronal ferroptosis by upregulating GPX4 levels, lowering reactive oxygen species (ROS), malondialdehyde (MDA), and Fe2+ excessive hoarding, and meliorating GSH levels and SOD activity. Additionally, it inhibited neuroinflammation by down-regulating the level of IL-1β, IL-6, TNF-α, NLRP3, and HMGB1. Meanwhile, NPGE treatment alleviated ferroptosis and inflammation in erastin-stimulated HT22 cells. Furthermore, NPGE up-regulated the expression of NRF2 and HO-1 and promoted the translocation of NRF2 into the nucleus. Using the NRF2 inhibitor brusatol, we verified that NRF2/HO-1 signaling mediated the anti-ferroptotic and anti-inflammatory properties of NPGE.

CONCLUSION

Collectively, our results demonstrate the protective effects of NPGE and highlight its therapeutic potential as a drug component for CIRI treatment.

Neurovascular protection of alisol A on cerebral ischemia mice through activating the AKT/GSK3β pathway

Alisol A, a triterpene isolated from Alisma Orientale, has been shown to exhibit anti-inflammatory effects and vascular protection. This study was designed to observe the effect of alisol A on cerebral ischemia (CI)-induced neurovascular dysfunction in the hippocampus and to further explore the potential mechanisms. The results showed that alisol A treatment improved the neurological deficits and cognitive impairment of CI mice. Alisol A reduced gliosis and improved neuronal/glial metabolism. Accordingly, alisol A inhibited inflammatory factors IL-6 and IL-1β induced by overactivation of astrocytes and microglia, thus protecting the neurovasculature. Furthermore, alisol A promoted the survival of neurons by decreasing the ratio of Bax/Bcl-2, and protected brain microvascular endothelial cells (BMECs) by upregulating the expression of ZO-1, Occludin and CD31. The phosphorylation of protein kinase B (AKT) and glycogen synthase kinase 3β (GSK3β) increased after treatment with alisol A. To explore the underlying mechanism, AKT was inhibited. As expected, the neurovascular protection of alisol A above was eliminated by AKT inhibition. The present study primarily suggested that alisol A could exert neurovascular protection in the hippocampus of CI mice by activating the AKT/GSK3β pathway and may potentially be used for the treatment of CI.