The Involvement of Mitochondrial Biogenesis in Selenium Reduced Hyperglycemia-Aggravated Cerebral Ischemia Injury

Bibliometric insights into the inflammation and mitochondrial stress in ischemic stroke

BACKGROUND

Research in the areas of inflammation and mitochondrial stress in ischemic stroke is rapidly expanding, but a comprehensive overview that integrates bibliometric trends with an in-depth review of molecular mechanisms is lacking.

OBJECTIVE

To map the evolving landscape of research using bibliometric analysis and to detail the molecular mechanisms that underpin these trends, emphasizing their implications in ischemic stroke.

METHODS

We conducted a bibliometric analysis to identify key trends, top contributors, and focal research themes. In addition, we review recent research advances in mitochondrial stress and inflammation in ischemic stroke to gain a detailed understanding of the pathophysiological processes involved.

CONCLUSION

Our integrative approach not only highlights the growing research interest and collaborations but also provides a detailed exploration of the molecular mechanisms that are central to the pathology of ischemic stroke. This synthesis offers valuable insights for researchers and paves the way for targeted therapeutic interventions.

Mitochondrial mechanisms in Cerebral Ischemia-Reperfusion Injury: Unravelling the intricacies

Cerebral ischemic stroke is a major contributor to physical impairments and premature death worldwide. The available reperfusion therapies for stroke in the form of mechanical thrombectomy and intravenous thrombolysis increase the risk of cerebral ischemia-reperfusion (I-R) injury due to sudden restoration of blood supply to the ischemic region. The injury is manifested by hemorrhagic transformation, worsening of neurological impairments, cerebral edema, and progression to infarction in surviving patients. A complex network of multiple pathological processes has been known to be involved in the pathogenesis of I-R injury. Primarily, 3 major contributors namely oxidative stress, neuroinflammation, and mitochondrial failure have been well studied in I-R injury. A transcription factor, Nrf2 (Nuclear factor erythroid 2-related factor 2) plays a crucial defensive role in resisting the deleterious effects of I-R injury and potentiating the cellular protective mechanisms. In this review, we delve into the critical function of mitochondria and Nrf2 in the context of cerebral I-R injury. We summarized how oxidative stress, neuroinflammation, and mitochondrial anomaly contribute to the pathophysiology of I-R injury and further elaborated the role of Nrf2 as a pivotal guardian of cellular integrity. The review further highlighted Nrf2 as a putative therapeutic target for mitochondrial dysfunction in cerebral I-R injury management.

Cathodal bilateral transcranial direct-current stimulation regulates selenium to confer neuroprotection after rat cerebral ischaemia-reperfusion injury

Non-invasive transcranial direct-current stimulation (tDCS) is a safe ischaemic stroke therapy. Cathodal bilateral tDCS (BtDCS) is a modified tDCS approach established by us recently. Because selenium (Se) plays a crucial role in cerebral ischaemic injury, we investigated whether cathodal BtDCS conferred neuroprotection via regulating Se-dependent signalling in rat cerebral ischaemia-reperfusion (I/R) injury. We first showed that the levels of Se and its transport protein selenoprotein P (SEPP1) were reduced in the rat cortical penumbra following I/R, whereas cathodal BtDCS prevented the reduction of Se and SEPP1. Interestingly, direct-current stimulation (DCS) increased SEPP1 level in cultured astrocytes subjected to oxygen-glucose deprivation reoxygenation (OGD/R) but had no effect on SEPP1 level in OGD/R-insulted neurons, indicating that DCS may increase Se in ischaemic neurons by enhancing the synthesis and secretion of SEPP1 in astrocytes. We then revealed that DCS reduced the number of injured mitochondria in OGD/R-insulted neurons cocultured with astrocytes. DCS and BtDCS prevented the reduction of the mitochondrial quality-control signalling, vesicle-associated membrane protein 2 (VAMP2) and syntaxin-4 (STX4), in OGD/R-insulted neurons cocultured with astrocytes and the ischaemic brain respectively. Under the same experimental conditions, downregulation of SEPP1 blocked DCS- and BtDCS-induced upregulation of VAMP2 and STX4. Finally, we demonstrated that cathodal BtDCS increased Se to reduce infract volume following I/R. Together, the present study uncovered a molecular mechanism by which cathodal BtDCS confers neuroprotection through increasing SEPP1 in astrocytes and subsequent upregulation of SEPP1/VAMP2/STX4 signalling in ischaemic neurons after rat cerebral I/R injury. KEY POINTS: Cathodal bilateral transcranial direct-current stimulation (BtDCS) prevents the reduction of selenium (Se) and selenoprotein P in the ischaemic penumbra. Se plays a crucial role in cerebral ischaemia injury. Direct-current stimulation reduces mitochondria injury and blocks the reduction of vesicle-associated membrane protein 2 (VAMP2) and syntaxin-4 (STX4) in oxygen-glucose deprivation reoxygenation-insulted neurons following coculturing with astrocytes. Cathodal BtDCS regulates Se/VAMP2/STX4 signalling to confer neuroprotection after ischaemia.

Selenium Nanoparticles in Protecting the Brain from Stroke: Possible Signaling and Metabolic Mechanisms

Strokes rank as the second most common cause of mortality and disability in the human population across the world. Currently, available methods of treating or preventing strokes have significant limitations, primarily the need to use high doses of drugs due to the presence of the blood-brain barrier. In the last decade, increasing attention has been paid to the capabilities of nanotechnology. However, the vast majority of research in this area is focused on the mechanisms of anticancer and antiviral effects of nanoparticles. In our opinion, not enough attention is paid to the neuroprotective mechanisms of nanomaterials. In this review, we attempted to summarize the key molecular mechanisms of brain cell damage during ischemia. We discussed the current literature regarding the use of various nanomaterials for the treatment of strokes. In this review, we examined the features of all known nanomaterials, the possibility of which are currently being studied for the treatment of strokes. In this regard, the positive and negative properties of nanomaterials for the treatment of strokes have been identified. Particular attention in the review was paid to nanoselenium since selenium is a vital microelement and is part of very important and little-studied proteins, e.g., selenoproteins and selenium-containing proteins. An analysis of modern studies of the cytoprotective effects of nanoselenium made it possible to establish the mechanisms of acute and chronic protective effects of selenium nanoparticles. In this review, we aimed to combine all the available information regarding the neuroprotective properties and mechanisms of action of nanoparticles in neurodegenerative processes, especially in cerebral ischemia.

Metformin alleviates cerebral ischemia/reperfusion injury aggravated by hyperglycemia via regulating AMPK/ULK1/PINK1/Parkin pathway-mediated mitophagy and apoptosis

Stroke remains the main leading cause of death and disabilities worldwide, with diabetes mellitus being a significant independent risk factor for it. Metformin, as an efficient hypoglycemic drug in treating type 2 diabetes, has been reported to alleviate the risk of diabetes-related stroke. However, its underlying mechanisms remain unclear. This study aimed to investigate the role of mitophagy and its regulatory pathway in the neuroprotective mechanism of metformin against cerebral ischemia/reperfusion (I/R) injury aggravated by hyperglycemia. A hyperglycemic cerebral I/R animal model and a high glucose cultured oxygen-glucose deprivation/reperfusion (OGD/R) cell model were used in the experiment. The indexes of brain injury, cell activity, mitochondrial morphology and function, mitophagy, mitochondrial pathway apoptosis and the AMPK pathway were observed. In diabetic rats, metformin treatment decreased cerebral infarction volume and neuronal apoptosis, and improved neurological symptoms following I/R injury. Additionally, metformin induced activation of the AMPK/ULK1/PINK1/Parkin mitophagy pathway to have neuroprotective effects. In vitro, high glucose culture and OGD/R treatment impaired mitochondrial morphology and function, mitochondrial membrane potential, and induced apoptosis. However, metformin activated AMPK/ULK1/PINK1/Parkin mitophagy pathway, normalized mitochondrial injury. This protection was reversed by autophagy inhibitor 3-methyladenine (3MA) and AMPK inhibitor compound C. In conclusion, our present study validates the potential mechanism of metformin in alleviating hyperglycemia aggravated cerebral I/R injury by the activation of AMPK/ULK1/PINK1/Parkin mitophagy pathway.

Selenium inhibits ferroptosis in hyperglycemic cerebral ischemia/reperfusion injury by stimulating the Hippo pathway

Hyperglycemia can exacerbate cerebral ischemia/reperfusion (I/R) injury, and the mechanism involves oxidative stress, apoptosis, autophagy and mitochondrial function. Our previous research showed that selenium (Se) could alleviate this injury. The aim of this study was to examine how selenium alleviates hyperglycemia-mediated exacerbation of cerebral I/R injury by regulating ferroptosis. Middle cerebral artery occlusion (MCAO) and reperfusion models were established in rats under hyperglycemic conditions. An in vitro model of hyperglycemic cerebral I/R injury was created with oxygen-glucose deprivation and reoxygenation (OGD/R) and high glucose was employed. The results showed that hyperglycemia exacerbated cerebral I/R injury, and sodium selenite pretreatment decreased infarct volume, edema and neuronal damage in the cortical penumbra. Moreover, sodium selenite pretreatment increased the survival rate of HT22 cells under OGD/R and high glucose conditions. Pretreatment with sodium selenite reduced the hyperglycemia mediated enhancement of ferroptosis. Furthermore, we observed that pretreatment with sodium selenite increased YAP and TAZ levels in the cytoplasm while decreasing YAP and TAZ levels in the nucleus. The Hippo pathway inhibitor XMU-MP-1 eliminated the inhibitory effect of sodium selenite on ferroptosis. The findings suggest that pretreatment with sodium selenite can regulate ferroptosis by activating the Hippo pathway, and minimize hyperglycemia-mediated exacerbation of cerebral I/R injury.

MitoQ alleviates hippocampal damage after cerebral ischemia: The potential role of SIRT6 in regulating mitochondrial dysfunction and neuroinflammation

AIMS

Mitochondrial perturbations are the major culprit of the inflammatory response during the initial phase of cerebral ischemia. The present study explored the neuroprotective effect of the mitochondrial-targeted antioxidant, Mitoquinol (MitoQ), against hippocampal neuronal loss in an experimental model of brain ischemia/reperfusion (I/R) injury.

MAIN METHODS

Rats were subjected to common carotid artery occlusion for 45 min, followed by reperfusion for 24 h. MitoQ (2 mg/kg; i.p daily) was administered for 7 successive days prior to the induction of brain ischemia.

KEY FINDINGS

I/R rats exhibited hippocampal damage evidenced by aggravated mitochondrial oxidative stress, thereby enhancing mtROS and oxidized mtDNA, together with inhibiting mtGSH. Mitochondrial biogenesis and function were also affected, as reflected by the reduction of PGC-1α, TFAM, and NRF-1 levels, as well as loss of mitochondrial membrane potential (△Ψm (. These changes were associated with neuroinflammation, apoptosis, impairment of cognitive function as well as hippocampal neurodegenerative changes in histopathological examination. Notably, SIRT6 was suppressed. Pretreatment with MitoQ markedly potentiated SIRT6, modulated mitochondrial oxidative status and restored mitochondrial biogenesis and function. In addition, MitoQ alleviated the inflammatory mediators, TNF-α, IL-18, and IL-1β and dampened GFAB immunoexpression along with downregulation of cleaved caspase-3 expression. Reversal of hippocampal function by MitoQ was accompanied by improved cognitive function and hippocampal morphological aberrations.

SIGNIFICANCE

This study suggests that MitoQ preserved rats' hippocampi from I/R insults via maintenance of mitochondrial redox status, biogenesis, and activity along with mitigation of neuroinflammation and apoptosis, thereby regulating SIRT6.

Importance of Mitochondria in Cardiac Pathologies: Focus on Uncoupling Proteins and Monoamine Oxidases

On the one hand, reactive oxygen species (ROS) are involved in the onset and progression of a wide array of diseases. On the other hand, these are a part of signaling pathways related to cell metabolism, growth and survival. While ROS are produced at various cellular sites, in cardiomyocytes the largest amount of ROS is generated by mitochondria. Apart from the electron transport chain and various other proteins, uncoupling protein (UCP) and monoamine oxidases (MAO) have been proposed to modify mitochondrial ROS formation. Here, we review the recent information on UCP and MAO in cardiac injuries induced by ischemia-reperfusion (I/R) as well as protection from I/R and heart failure secondary to I/R injury or pressure overload. The current data in the literature suggest that I/R will preferentially upregulate UCP2 in cardiac tissue but not UCP3. Studies addressing the consequences of such induction are currently inconclusive because the precise function of UCP2 in cardiac tissue is not well understood, and tissue- and species-specific aspects complicate the situation. In general, UCP2 may reduce oxidative stress by mild uncoupling and both UCP2 and UCP3 affect substrate utilization in cardiac tissue, thereby modifying post-ischemic remodeling. MAOs are important for the physiological regulation of substrate concentrations. Upon increased expression and or activity of MAOs, however, the increased production of ROS and reactive aldehydes contribute to cardiac alterations such as hypertrophy, inflammation, irreversible cardiomyocyte injury, and failure.

Selenium Alleviates Cerebral Ischemia/Reperfusion Injury by Regulating Oxidative Stress, Mitochondrial Fusion and Ferroptosis

To clarify the potential role of selenium (Se) on cerebral ischemia/reperfusion (I/R) injury, we utilized mouse middle cerebral artery occlusion (MCAO) followed by reperfusion as an animal model and oxygen-glucose deprivation and reoxygenation (OGD/R) to treat N2a cells as a cell model, respectively. MCAO model was established in mice and then divided into different groups with or without Se treatment. TTC staining was used to observe whether the cerebral I/R modeling was successful, and the apoptosis level was determined by TUNEL staining. The expression of GPx-4 and p22phox was assessed by western blot. In vitro experiments, the OGD/R induced oxidative stress in N2a cells was assessed by levels of GSH/GSSG, malondialdehyde, superoxide dismutase and iron content, respectively. QRT-PCR was used to detect the mRNA levels of Cox-2, Fth1, Mfn1 and mtDNA in N2a cells. JC-1 staining and flow cytometry was performed to detect the mitochondrial membrane potential. Se treatment alleviated cerebral I/R injury and improved the survival rate of mice. Additionally, Se treatment apparently attenuated oxidative stress and inhibited iron accumulation in MCAO model mice and OGD/R model of N2a cells. In terms of its mechanism, Se could up-regulate Mfn1 expression to alleviate oxidative stress and ferroptosis by promoting mitochondrial fusion in vivo and vitro. These findings suggest that Se may have great potential in alleviating cerebral I/R injury.

Dietary supplementation with biogenic selenium nanoparticles alleviate oxidative stress-induced intestinal barrier dysfunction

Selenium (Se) is an essential micronutrient that promotes body health. Endemic Se deficiency is a major nutritional challenge worldwide. The low toxicity, high bioavailability, and unique properties of biogenic Se nanoparticles (SeNPs) allow them to be used as a therapeutic drug and Se nutritional supplement. This study was conducted to investigate the regulatory effects of dietary SeNPs supplementation on the oxidative stress-induced intestinal barrier dysfunction and its association with mitochondrial function and gut microbiota in mice. The effects of dietary SeNPs on intestinal barrier function and antioxidant capacity and its correlation with gut microbiota were further evaluated by a fecal microbiota transplantation experiment. The results showed that Se deficiency caused a redox imbalance, increased the levels of pro-inflammatory cytokines, altered the composition of the gut microbiota, and impaired mitochondrial structure and function, and intestinal barrier injury. Exogenous supplementation with biogenic SeNPs effectively alleviated diquat-induced intestinal barrier dysfunction by enhancing the antioxidant capacity, inhibiting the overproduction of reactive oxygen species (ROS), preventing the impairment of mitochondrial structure and function, regulating the immune response, maintaining intestinal microbiota homeostasis by regulating nuclear factor (erythroid-derived-2)-like 2 (Nrf2)-mediated NLR family pyrin domain containing 3 (NLRP3) signaling pathway. In addition, Se deficiency resulted in a gut microbiota phenotype that is more susceptible to diquat-induced intestinal barrier dysfunction. Supranutritional SeNPs intake can optimize the gut microbiota to protect against intestinal dysfunctions. This study demonstrates that dietary supplementation of SeNPs can prevent oxidative stress-induced intestinal barrier dysfunction through its regulation of mitochondria and gut microbiota.

Insight into Crosstalk Between Mitophagy and Apoptosis/Necroptosis: Mechanisms and Clinical Applications in Ischemic Stroke

Ischemic stroke is a serious cerebrovascular disease with high morbidity and mortality. As a result of ischemia-reperfusion, a cascade of pathophysiological responses is triggered by the imbalance in metabolic supply and demand, resulting in cell loss. These cellular injuries follow various molecular mechanisms solely or in combination with this disorder. Mitochondria play a driving role in the pathophysiological processes of ischemic stroke. Once ischemic stroke occurs, damaged cells would respond to such stress through mitophagy. Mitophagy is known as a conservatively selective autophagy, contributing to the removal of excessive protein aggregates and damaged intracellular components, as well as aging mitochondria. Moderate mitophagy may exert neuroprotection against stroke. Several pathways associated with the mitochondrial network collectively contribute to recovering the homeostasis of the neurovascular unit. However, excessive mitophagy would also promote ischemia-reperfusion injury. Therefore, mitophagy is a double-edged sword, which suggests that maximizing the benefits of mitophagy is one of the direction of future efforts. This review emphasized the role of mitophagy in ischemic stroke, and highlighted the crosstalk between mitophagy and apoptosis/necroptosis.

Features of the cytoprotective effect of selenium nanoparticles on primary cortical neurons and astrocytes during oxygen-glucose deprivation and reoxygenation

The study is aimed at elucidating the effect of selenium nanoparticles (SeNPs) on the death of cells in the primary culture of mouse cerebral cortex during oxygen and glucose deprivation (OGD). A primary cell culture of the cerebral cortex containing neurons and astrocytes was subjected to OGD and reoxygenation to simulate cerebral ischemia-like conditions in vitro. To evaluate the neuroprotective effect of SeNPs, cortical astrocytes and neurons were incubated for 24 h with SeNPs, and then subjected to 2-h OGD, followed by 24-h reoxygenation. Vitality tests, fluorescence microscopy, and real-time PCR have shown that incubation of primary cultured neurons and astrocytes with SeNPs at concentrations of 2.5–10 µg/ml under physiological conditions has its own characteristics depending on the type of cells (astrocytes or neurons) and leads to a dose-dependent increase in apoptosis. At low concentration SeNPs (0.5 µg/ml), on the contrary, almost completely suppressed the processes of basic necrosis and apoptosis. Both high (5 µg/ml) and low (0.5 µg/ml) concentrations of SeNPs, added for 24 h to the cells of cerebral cortex, led to an increase in the expression level of genes Bcl-2, Bcl-xL, Socs3, while the expression of Bax was suppressed. Incubation of the cells with 0.5 µg/ml SeNPs led to a decrease in the expression of SelK and SelT. On the contrary, 5 µg/ml SeNPs caused an increase in the expression of SelK, SelN, SelT, SelP. In the ischemic model, after OGD/R, there was a significant death of brain cells by the type of necrosis and apoptosis. OGD/R also led to an increase in mRNA expression of the Bax, SelK, SelN, and SelT genes and suppression of the Bcl-2, Bcl-xL, Socs3, SelP genes. Pre-incubation of cell cultures with 0.5 and 2.5 µg/ml SeNPs led to almost complete inhibition of OGD/R-induced necrosis and greatly reduced apoptosis. Simultaneously with these processes we observed suppression of caspase-3 activation. We hypothesize that the mechanisms of the protective action of SeNPs involve the activation of signaling cascades recruiting nuclear factors Nrf2 and SOCS3/STAT3, as well as the activation of adaptive pathways of ESR signaling of stress arising during OGD and involving selenoproteins SelK and SelT, proteins of the Bcl-2 family ultimately leading to inactivation of caspase-3 and inhibition of apoptosis. Thus, our results demonstrate that SeNPs can act as neuroprotective agents in the treatment of ischemic brain injuries.

Selenium attenuates ischemia/reperfusion injury‑induced damage to the blood‑brain barrier in hyperglycemia through PI3K/AKT/mTOR pathway‑mediated autophagy inhibition

Ischemic stroke is a leading cause of mortality and disability. Diabetes mellitus, characterized by hyperglycemia, is a common concomitant disease of ischemic stroke, which is associated with autophagy dysfunction and blood‑brain barrier (BBB) damage following cerebral ischemia/reperfusion (I/R) injury. At present, there is no effective treatment strategy for the disease. The purpose of the present study was to explore the molecular mechanisms underlying the protective effects of selenium on the BBB following I/R injury in hyperglycemic rats. Middle cerebral artery occlusion was performed in diabetic Sprague‑Dawley rats. Treatment with selenium and the autophagy inhibitor 3‑methyladenine significantly reduced cerebral infarct volume, brain water content and Evans blue leakage, while increasing the expression of tight junction (TJ) proteins and decreasing that of autophagy‑related proteins (P<0.05). In addition, selenium increased the phosphorylation levels of PI3K, AKT and mTOR (P<0.05). A mouse bEnd.3 brain microvascular endothelial cell line was co‑cultured in vitro with an MA‑h mouse astrocyte‑hippocampal cell line to simulate the BBB. The cells were then subjected to hyperglycemia, followed by oxygen‑glucose deprivation for 1 h and reoxygenation for 24 h. It was revealed that selenium increased TJ protein levels, reduced BBB permeability, decreased autophagy levels and enhanced the expression of phosphorylated (p)‑AKT/AKT and p‑mTOR/mTOR proteins (P<0.05). Treatment with wortmannin (an inhibitor of PI3K) significantly prevented the beneficial effects of selenium on the BBB, whereas insulin‑like growth factor 1 (a PI3K activator) mimicked the effects of selenium. In conclusion, the present findings indicated that selenium can inhibit autophagy by regulating the PI3K/AKT/mTOR signaling pathway, significantly preventing BBB damage following cerebral I/R injury in hyperglycemic conditions.

Mitochondrial Quality Control in Cerebral Ischemia-Reperfusion Injury

Ischemic stroke is one of the leading causes of death and also a major cause of adult disability worldwide. Revascularization via reperfusion therapy is currently a standard clinical procedure for patients with ischemic stroke. Although the restoration of blood flow (reperfusion) is critical for the salvage of ischemic tissue, reperfusion can also, paradoxically, exacerbate neuronal damage through a series of cellular alterations. Among the various theories postulated for ischemia/reperfusion (I/R) injury, including the burst generation of reactive oxygen species (ROS), activation of autophagy, and release of apoptotic factors, mitochondrial dysfunction has been proposed to play an essential role in mediating these pathophysiological processes. Therefore, strict regulation of the quality and quantity of mitochondria via mitochondrial quality control is of great importance to avoid the pathological effects of impaired mitochondria on neurons. Furthermore, timely elimination of dysfunctional mitochondria via mitophagy is also crucial to maintain a healthy mitochondrial network, whereas intensive or excessive mitophagy could exacerbate cerebral I/R injury. This review will provide a comprehensive overview of the effect of mitochondrial quality control on cerebral I/R injury and introduce recent advances in the understanding of the possible signaling pathways of mitophagy and potential factors responsible for the double-edged roles of mitophagy in the pathological processes of cerebral I/R injury.

Damage to the blood‑brain barrier and activation of neuroinflammation by focal cerebral ischemia under hyperglycemic condition

Hyperglycemia aggravates brain damage caused by cerebral ischemia/reperfusion (I/R) and increases the permeability of the blood‑brain barrier (BBB). However, there are relatively few studies on morphological changes of the BBB. The present study aimed to investigate the effect of hyperglycemia on BBB morphological changes following cerebral I/R injury. Streptozotocin‑induced hyperglycemic and citrate‑buffered saline‑injected normoglycemic rats were subjected to 30 min middle cerebral artery occlusion. Neurological deficits were evaluated. Brain infarct volume was assessed by 2,3,5‑triphenyltetrazolium chloride staining and BBB integrity was evaluated by Evans blue and IgG extravasation following 24 h reperfusion. Changes in tight junctions (TJ) and basement membrane (BM) proteins (claudin, occludin and zonula occludens‑1) were examined using immunohistochemistry and western blotting. Astrocytes, microglial cells and neutrophils were labeled with specific antibodies for immunohistochemistry after 1, 3 and 7 days of reperfusion. Hyperglycemia increased extravasations of Evan's blue and IgG and aggravated damage to TJ and BM proteins following I/R injury. Furthermore, hyperglycemia suppressed astrocyte activation and damaged astrocytic endfeet surrounding cerebral blood vessels following I/R. Hyperglycemia inhibited microglia activation and proliferation and increased neutrophil infiltration in the brain. It was concluded that hyperglycemia‑induced BBB leakage following I/R might be caused by damage to TJ and BM proteins and astrocytic endfeet. Furthermore, suppression of microglial cells and increased neutrophil infiltration to the brain may contribute to the detrimental effects of pre‑ischemic hyperglycemia on the outcome of cerebral ischemic stroke.

Effect of hyperglycemia on microglial polarization after cerebral ischemia-reperfusion injury in rats

Hyperglycemia has been shown to aggravate ischemic brain damage, in which the inflammatory reaction induced by hyperglycemia is involved in the worsening of cerebral ischemia-reperfusion injury. However, the role of microglial polarization in hyperglycemia-aggravating cerebral ischemia-reperfusion injury remains unknown. The present study investigated whether diabetic hyperglycemia inhibited or activated microglia, as well as microglial subtypes 1 and 2. Rats were used to establish the diabetic hyperglycemia and middle cerebral artery occlusion (MCAO) model. The markers CD11b, CD16, CD32, CD86, CD206, and Arg1 were used to show M1 or M2 microglia. The results revealed increased neurological deficits, infarct volume, and neural apoptosis in rats with hyperglycemia subjected to MCAO for 30 min and reperfused at 1, 3, and 7 days compared with the normoglycemic rats. Microglia and astrocyte activation and proliferation were inhibited in hyperglycemic rats. Furthermore, M1 microglia polarization was promoted, while that of M2 microglia was inhibited in hyperglycemic rats. These findings suggested that the polarization of M1 and M2 microglia is activated and inhibited, respectively, in hyperglycemic rats and may be involved in the aggravated brain damage caused by ischemia-reperfusion in diabetic hyperglycemia.

Region-specific changes in aquaporin 4 induced by hyperglycemia underlie the differences in cell swelling in the cortex and striatum after cerebral ischemia-reperfusion

Brain edema is a major cause of death in patients who suffer an ischemic stroke. Diabetes has been shown to aggravate brain edema after cerebral ischemia-reperfusion, but few studies have focused on the heterogeneity of this response across different brain regions. Aquaporin 4 plays an important role in the formation and regression of brain edema. Here, we report that hyperglycemia mainly affects the continuity of aquaporin 4 distribution around blood vessels in the cortical penumbra after ischemia-reperfusion; however, in the striatal penumbra, in addition to affecting the continuity of distribution, it also substantially affects the fluorescence intensity and the polarity distribution in astrocytes. Accordingly, hyperglycemia induces a more significant increase in the number of swelling cells in the striatal penumbra than in the cortical penumbra. These results can improve our understanding of the mechanism underlying the effects of diabetes in cerebral ischemic injury and provide a theoretical foundation for identification of appropriate therapeutic modalities.

Se-Methylselenocysteine (SMC) Improves Cognitive Deficits by Attenuating Synaptic and Metabolic Abnormalities in Alzheimer's Mice Model: A Proteomic Study

Se-methylselenocysteine (SMC) is a major selenocompound in selenium (Se) enriched plants and has been found to ameliorate neuropathology and cognitive deficits in triple-transgenic mice model of Alzheimer's disease (3 × Tg-AD mice). To explore the underlying molecular mechanisms, the present study is designed to elucidate the protein changes in the cortex of SMC-treated 3 × Tg-AD mice. After SMC supplementation, proteomic analysis revealed that 181, 271, and 41 proteins were identified as differentially expressed proteins (DEPs) between 3 × Tg-AD mice vs wild type (AD/WT group), SMC-treated AD mice vs AD (AD + SMC/AD), and AD + SMC/WT group, respectively. Among these, 138 proteins in the diseased group were reversed by SMC treatment. The DEPs in AD/WT group and AD + SMC/AD group were mainly related to metabolism, synapses, and antioxidant proteins, while their levels were decreased in AD mice but up-regulated after treating with SMC. In addition, we found reduced ATP levels and destroyed synaptic structures in the AD mice brains, which were significantly ameliorated upon SMC treatment. Our study suggests that energy metabolism disorders, abnormal amino acid metabolism, synaptic dysfunction, and oxidative stress may be the key pathogenic phenomena of AD. SMC reversed the expression of proteins associated with them, which might be the main mechanism of its intervention in AD.