Effects of high-fat diet on neuronal damage, gliosis, inflammatory process and oxidative stress in the hippocampus induced by transient cerebral ischemia

Obesity induces extracellular vesicle release from the endothelium as a contributor to brain damage after cerebral ischemia in rats

OBJECTIVES

Cerebral ischemia is the most common cause of disability, the second most common cause of dementia, and the fourth most common cause of death in the developed world [Sveinsson OA, Kjartansson O, Valdimarsson EM. Heilablóðþurrð/heiladrep: Faraldsfræði, orsakir og einkenni [Cerebral ischemia/infarction - epidemiology, causes and symptoms]. Laeknabladid. 2014 May;100(5):271-9. Icelandic. doi:10.17992/lbl.2014.05.543]. Obesity has been associated with worse outcomes after ischemia in rats, triggering proinflammatory cytokine production related to the brain microvasculature. The way obesity triggers these effects remains mostly unknown. Therefore, the aim of this study was to elucidate the cellular mechanisms of damage triggered by obesity in the context of cerebral ischemia.

METHODS

We used a rat model of obesity induced by a 20% high fructose diet (HFD) and evaluated peripheral alterations in plasma (lipid and cytokine profiles). Then, we performed cerebral ischemia surgery using two-vessel occlusion (2VO) and analyzed neurological/motor performance and glial activation. Next, we treated endothelial cell line cultures with glutamate in vitro to simulate an excitotoxic environment, and we added 20% plasma from obese rats. Subsequently, we isolated EVs released from endothelial cells and treated primary cultures of astrocytes with them.

RESULTS

Rats fed a HFD had an increased BMI with dyslipidemia and high levels of proinflammatory cytokines. Glia from the obese rats exhibited altered morphology, suggesting hyperreactivity related to neurological and motor deficits. Plasma from obese rats induced activation of endothelial cells, increasing proinflammatory signals and releasing more EVs. Similarly, these EVs caused an increase in NF-κB and astrocyte cytotoxicity. Together, the results suggest that obesity activates proinflammatory signals in endothelial cells, resulting in the release of EVs that simultaneously contribute to astrocyte activation.

Improving Age-Related Cognitive Decline through Dietary Interventions Targeting Mitochondrial Dysfunction

Aging is inevitable and it is one of the major contributors to cognitive decline. However, the mechanisms underlying age-related cognitive decline are still the object of extensive research. At the biological level, it is unknown how the aging brain is subjected to progressive oxidative stress and neuroinflammation which determine, among others, mitochondrial dysfunction. The link between mitochondrial dysfunction and cognitive impairment is becoming ever more clear by the presence of significant neurological disturbances in human mitochondrial diseases. Possibly, the most important lifestyle factor determining mitochondrial functioning is nutrition. Therefore, with the present work, we review the latest findings disclosing a link between nutrition, mitochondrial functioning and cognition, and pave new ways to counteract cognitive decline in late adulthood through diet.

Experimental pretreatment with YES-10®, a plant extract rich in scutellarin and chlorogenic acid, protects hippocampal neurons from ischemia/reperfusion injury via antioxidant role

Erigeron annuus (L.) PERS. (EALP) and Clematis mandshurica RUPR. (CMR) have been used in traditional remedies due to their medicinal effects. Recently, we reported that pretreatment with 200 mg/kg of YES-10^® (a combination of extracts from leaves of EALP and CMR) displayed neuroprotective effects against brain ischemia and reperfusion injury. The present study analyzed the major ingredients of YES-10^® and investigated whether neuroprotection from YES-10^® was dependent upon antioxidant effects in the cornu ammonis 1 (CA1) field in the gerbil hippocampus, after transient forebrain ischemia for 5 min. YES-10^® was demonstrated to predominantly contain scutellarin and chlorogenic acid. Pretreatment with YES-10^® significantly increased protein levels and the immunoreactivity of copper/zinc-superoxide dismutase (SOD1) and manganese-superoxide dismutase (SOD2) was in the pyramidal neurons of the hippocampal CA1 field when these were examined prior to transient ischemia induction. The increased SODs in CA1 pyramidal neurons following YES-10^® treatment were maintained after ischemic injury. In this case, the CA1 pyramidal neurons were protected from ischemia-reperfusion injury. Oxidative stress was significantly attenuated in the CA1 pyramidal neurons, and this was determined by 4-hydroxy-2-nonenal immunohistochemistry and dihydroethidium histofluorescence staining. Taken together, the results indicated that YES-10^® significantly attenuated transient ischemia-induced oxidative stress and may be utilized for developing a protective agent against ischemic insults.

Ischemic stroke, obesity, and the anti-inflammatory role of melatonin

Obesity is a predominant risk factor in ischemic stroke and is commonly comorbid with it. Pathologies following these conditions are associated with systemic and local inflammation. Moreover, there is increasing evidence that the susceptibility for ischemic brain damage increases substantially in experimental models of ischemic stroke with concomitant obesity. Herein, we explore the proinflammatory events that occur during ischemic stroke and obesity, and we discuss the influence of obesity on the inflammatory response and cerebral damage outcomes in experimental models of brain ischemia. In addition, because melatonin is a neurohormone widely reported to exhibit protective effects in various diseases, this study also demonstrates the anti-inflammatory role and possible mechanistic actions of melatonin in both epidemic diseases. A summary of research findings suggests that melatonin administration has great potential to exert an anti-inflammatory role and provide protection against obesity and ischemic stroke conditions. However, the efficacy of this hormonal treatment on ischemic stroke with concomitant obesity, when more serious inflammation is generated, is still lacking.

Dietary Fe3O4 Nanozymes Prevent the Injury of Neurons and Blood-Brain Barrier Integrity from Cerebral Ischemic Stroke

Cerebral ischemic stroke stimulates excessive reactive oxygen species, which lead to blood-brain-barrier disruption, neuron death, and aggravated cerebral infarction. Thus, it is critical to develop an antioxidant strategy for stroke treatment. Herein, we report a dietary strategy to promote stroke healing using iron oxide (Fe₃O₄) nanoparticles with intrinsic enzyme-like activities. We find that Fe₃O₄ nanozymes exhibit triple enzyme-like activities, peroxidase, catalase, and superoxide dismutase, thus potentially possessing the ability to regulate the ROS level. Importantly, intragastric administration of PEG-modified Fe₃O₄ nanozymes significantly reduces cerebral infarction and neuronal death in a rodent model following cerebral ischemic stroke. Ex vivo analysis shows that PEG-modified Fe₃O₄ nanozymes localize in the cerebral vasculature, ameliorate local redox state with decreased malondialdehyde and increased Cu/Zn SOD, and facilitate blood-brain-barrier recovery by elevating ZO-1 and Claudin-5 in the hippocampus. Altogether, our results suggest that dietary PEG-modified Fe₃O₄ nanozymes can facilitate blood-brain-barrier reconstruction and protect neurons following ischemic stroke.

Regulation of Glycemia in the Recovery Phase After Stroke Counteracts the Detrimental Effect of Obesity-Induced Type 2 Diabetes on Neurological Recovery

The interplay between obesity and type 2 diabetes (T2D) in poststroke recovery is unclear. Moreover, the impact of glucose control during the chronic phase after stroke is undetermined. We investigated whether obesity-induced T2D impairs neurological recovery after stroke by using a clinically relevant experimental design. We also investigated the potential efficacy of two clinically used T2D drugs: the dipeptidyl peptidase 4 inhibitor linagliptin and the sulfonylurea glimepiride. We induced transient middle cerebral artery occlusion (tMCAO) in T2D/obese mice (after 7 months of high-fat diet [HFD]) and age-matched controls. After stroke, we replaced HFD with standard diet for 8 weeks to mimic the poststroke clinical situation. Linagliptin or glimepiride were administered daily from 3 days after tMCAO for 8 weeks. We assessed neurological recovery weekly by upper-limb grip strength. Brain damage, neuroinflammation, stroke-induced neurogenesis, and atrophy of parvalbumin-positive (PV⁺) interneurons were quantified by immunohistochemistry. T2D/obesity impaired poststroke neurological recovery in association with hyperglycemia, neuroinflammation, and atrophy of PV⁺ interneurons. Both drugs counteracted these effects. In nondiabetic mice, only linagliptin accelerated recovery. These findings shed light on the interplay between obesity and T2D in stroke recovery. Moreover, they promote the use of rehabilitative strategies that are based on efficacious glycemia regulation, even if initiated days after stroke.

High fat diet accelerates and exacerbates microgliosis and neuronal damage/death in the somatosensory cortex after transient forebrain ischemia in gerbils

Obesity has been known as an independent risk factor for stroke. Effects of high-fat diet (HFD)-induced obesity on neuronal damage in the somatosensory cortex of animal models of cerebral ischemia have not been studied yet. In this study, HFD-induced obesity was used to study the impact of obesity on neuronal damage/loss and microgliosis in the somatosensory cortex of a gerbil model of 5-min transient forebrain ischemia. We used gerbils fed normal diet (ND) and HFD and chronologically examined microgliosis (microglial cell activation) by ionized calcium-binding adapter molecule 1 (Iba-1) immunohistochemistry. In addition, we examined neuronal damage or death by using neuronal nuclear protein (NeuN, a neuronal marker) immunohistochemistry and Fluoro-Jade B (F-J B, a marker for neuronal degeneration) histofluorescence staining. We found that ischemia-induced microgliosis in ND-fed gerbils was increased from 2 days post-ischemia; however, ischemia-mediated microgliosis in HFD-fed gerbils increased from 1 day post-ischemia and more accelerated with time than that in the ND-fed gerbils. Ischemia-induced neuronal death/loss in the somatosensory cortex in the ND-fed gerbils was apparently found at 5 days post-ischemia. However, in the HFD-fed gerbils, neuronal death/loss was shown from 2 days post-ischemia and progressively exacerbated at 5 days post-ischemia. Our findings indicate that HFD can evoke earlier microgliosis and more detrimental neuronal death/loss in the somatosensory cortex after transient ischemia than ND evokes.

Protective effect of Hydroxysafflor Yellow A on cerebral ischemia reperfusion-injury by regulating GSK3β-mediated pathways

Ischemia-reperfusion (I/R) injury is accompanied by high mortality and morbidity. Unfortunately, there are few effective therapeutic medicines and strategies to enhance its outcome. Hydroxysafflor Yellow A (HSYA) exerts multiple biological activities and has potential protective effects against I/R injury in the brain, liver and heart. However, its underlying mechanism is still unclear. Here, we investigated whether HSYA modulates apoptosis and neuro-inflammation through the Glycogen synthase kinase-3β(GSK3β)-mediated pathway in a transient middle cerebral artery occlusion (MCAO) rat model and oxygen/glucose deprivation (OGD)-challenged primary neuronal cultures both in vivo and in vitro. Male Wistar rats were subjected to MCAO for 2 h, followed by 24 h of reperfusion. HSYA was administered 15 min after occlusion, SB216763 (GSK3β inhibitor) was injected to the left ventricle of the rat 6 h prior to MCAO. After 24 h of perfusion, apoptosis-associated protein and inflammatory markers were detected by western blotting. Meanwhile, terminal-deoxynucleotidyl transferase mediated nick end labeling(TUNEL) assay was used to evaluate the number of apoptotic cells in OGD-challenged neurons, cleaved caspase-3 were evaluated by Immunofluorescence (IF). Our data indicated that HSYA administration reduced infarct volume, decreased neurological deficit scores, elevated GSK3β phosphorylation and inhibited the activation of iNOS, NF-κB, and capase-3 in the penumbra of I/R rats. Moreover, blockade of GSK3β partly reversed the protective effect of HSYA on I/R by regulating NF-κB and caspase-3 both in vivo and in vitro. Collectively, we found that HSYA ameliorates I/R injury through its anti-inflammatory and anti-apoptotic effects via modulation of GSK-3β phosphorylation.

Obesity Drives Delayed Infarct Expansion, Inflammation, and Distinct Gene Networks in a Mouse Stroke Model

Obesity is associated with chronic peripheral inflammation, is a risk factor for stroke, and causes increased infarct sizes. To characterize how obesity increases infarct size, we fed a high-fat diet to wild-type C57BL/6J mice for either 6 weeks or 15 weeks and then induced distal middle cerebral artery strokes. We found that infarct expansion happened late after stroke. There were no differences in cortical neuroinflammation (astrogliosis, microgliosis, or pro-inflammatory cytokines) either prior to or 10 h after stroke, and also no differences in stroke size at 10 h. However, by 3 days after stroke, animals fed a high-fat diet had a dramatic increase in microgliosis and astrogliosis that was associated with larger strokes and worsened functional recovery. RNA sequencing revealed a dramatic increase in inflammatory genes in the high-fat diet-fed animals 3 days after stroke that were not present prior to stroke. Genetic pathways unique to diet-induced obesity were primarily related to adaptive immunity, extracellular matrix components, cell migration, and vasculogenesis. The late appearance of neuroinflammation and infarct expansion indicates that there may be a therapeutic window between 10 and 36 h after stroke where inflammation and obesity-specific transcriptional programs could be targeted to improve outcomes in people with obesity and stroke.

Dynamic Changes in miR-126 Expression in the Hippocampus and Penumbra Following Experimental Transient Global and Focal Cerebral Ischemia-Reperfusion

miR-126 which is considered one of the most important miRNAs for maintaining vascular integrity, plays an important role in neuroprotection after cerebral ischemia-reperfusion (I-R). Moreover, vascular endothelial growth factor A (VEGFA), sprouty-related EVH1 domain-containing protein 1 (SPRED1), and Raf-1 are also involved in physiological processes of vascular endothelial cells (ECs). This study investigated how miR-126 changes with reperfusion time in different brain tissues after global cerebral ischemia and focal cerebral ischemia and examined the underlying mechanism miR-126 involving VEGFA, SPRED1, and Raf-1 after I-R. The results indicated decreases in the levels of miR-126-3p and miR-126-5p expression in mice and gerbils after I-R, consistent with the results after oxygen and glucose deprivation and reperfusion (OGD/R) in PC12 cells. Glial cells were activated as neuronal damage gradually increased after I-R. Inhibition of miR-126-3p exacerbated the OGD/R-induced cell death and reduced cell viability. After miR-126-3p inhibition, the levels of SPRED1 and VEGFA expression were increased, and p-Raf-1 expression was decreased after OGD/R. Moreover, based on the intervention of miR-126-3p inhibition, we found that the expression of p-Raf-1 was significantly increased after the intervention of siSPRED1, while it was not statistically significant after intervention of siVEGFA. The reduction of miR-126 expression after global and focal cerebral ischemia exacerbated neuronal death, which was closely related to increasing the SPRED1 activation and inhibiting the Raf-1 expression.

Ischemia-related changes of fat-mass and obesity-associated protein expression in the gerbil hippocampus

Fat-mass and obesity-associated protein (Fto) plays important roles in energy metabolism. It also acts as a demethylase and is most abundantly found in the brain. In the present study, we examined the spatial and temporal changes of Fto immunoreactivity after five minutes of transient forebrain ischemia in the hippocampus. In the control group, Fto immunoreactivity was mainly observed in the nucleus of pyramidal cells in the CA1 and CA3 regions as well as the polymorphic layer, granule cell layer, and subgranular zone of the dentate gyrus. Fto immunoreactivity was transiently, but not significantly, increased in the hippocampal CA3 region and the dentate gyrus two days after ischemia compared to mice without ischemia in the sham-operated group. Four days after ischemia, low Fto immunoreactivity was observed in the stratum pyramidale of the CA1 region because of neuronal death, but Fto immunoreactive cells were abundantly detected in the stratum pyramidale of the CA3 region, which is relatively resistant to ischemic damage. Thereafter, Fto immunoreactivity progressively decreased in the hippocampal CA1 and CA3 regions and the dentate gyrus until ten days after ischemia. At this time-point, Fto immunoreactivity was significantly lower in the hippocampal CA1 and CA3 regions and the dentate gyrus compared to that in the sham-operated group. The reduction of Fto immunoreactive structures in the hippocampus may be associated with impairments in Fto-related hippocampal function.

Analysis of knowledge bases and research focuses of cerebral ischemia-reperfusion from the perspective of mapping knowledge domain

Cerebral ischemia-reperfusion (IR) has attracted wide attention as a serious clinical problem. So far, the field has accumulated a large amount of scientific research literature. To clarify the temporal and spatial distribution characteristics of research resources, knowledge bases and research focuses, a visual analysis was performed on 5814 articles cited in the WoS databases from 2004 to 2019. This analysis was based on bibliometrics and mapping knowledge domain (MKD) analysis with VOSviewer, and CiteSpace 5.4.R4. The results can be elaborated from four aspects. First, the volume of publications in this area is on the rise. Second, the United States and China are the active regions. The USA is the central region of cerebral ischemia-reperfusion research. Third, the knowledge bases of IR have focused on five major areas of "Suitable small-animal models", "A framework with further study", "Molecular signaling targets by oxidative stress", "Finding new potential targets for therapy" and "Protective effect of multiple transient ischemia". Fourth, the research focuses consist of three representative areas: "Oxidative stress closelyd with cerebral ischemia-reperfusion", "Neuronal apoptosis and neuronal protection", and "Neuroprotective effect of the blood-brain barrier".

A 2-Min Transient Ischemia Confers Cerebral Ischemic Tolerance in Non-Obese Gerbils, but Results in Neuronal Death in Obese Gerbils by Increasing Abnormal mTOR Activation-Mediated Oxidative Stress and Neuroinflammation

A brief episode of transient ischemia (TI) can confer cerebral ischemic tolerance against a subsequent severer TI under standard condition. The brain under obesity’s conditions is more sensitive to ischemic injury. However, the impact of a brief episode of TI under obesity’s conditions has not been fully addressed yet. Thus, the objective of this study was to determine the effect of a brief TI in the hippocampus of high-fat diet (HFD)-induced obese gerbils and related mechanisms. Gerbils were maintained on HFD or normal diet (ND) for 12 weeks and subjected to 2 min TI. HFD gerbils were heavier, with higher blood glucose, serum total cholesterol, triglycerides, and leptin levels. Massive loss of pyramidal neurons occurred in the hippocampal cornu ammonis 1 (CA1) field of HFD animals at 5 days after 2 min of TI, but 2 min of TI did not elicit death of pyramidal neurons in ND gerbils. The HFD group showed significantly increased levels of oxidative stress indicators (dihydroethidium and 4-hydroxynonenal) and proinflammatory cytokines (tumor necrosis factor-α and interleukin-1β) and microglial activation in pre- and/or post-ischemic phases compared to the ND group. Levels of mammalian target of rapamycin (mTOR) and phosphorylated-mTOR in the CA1 field of the HFD group were also significantly higher than the ND group. On the other hand, inhibition of mTOR activation by rapamycin (an allosteric mTOR inhibitor) significantly attenuated neuronal death induced by HFD, showing reduction of HFD-induced increases of oxidative stress indicators and proinflammatory cytokines, and microglia activation. Taken together, a brief episode of TI can evoke neuronal death under obesity’s conditions. It might be closely associated with an abnormal increase of mTOR activation-mediated, severe oxidative stress and neuroinflammation in pre- and/or post-ischemic phases.

Antioxidant Properties of Fucoidan Alleviate Acceleration and Exacerbation of Hippocampal Neuronal Death Following Transient Global Cerebral Ischemia in High-Fat Diet-Induced Obese Gerbils

Fucoidan, a natural sulfated polysaccharide, displays various biological activities including antioxidant properties. We examined the neuroprotective effect of fucoidan against transient global cerebral ischemia (tGCI) in high-fat diet (HFD)-induced obese gerbils and its related mechanisms. Gerbils received HFD for 12 weeks and fucoidan (50 mg/kg) daily for the last 5 days during HFD exposure, and they were subjected to 5-min tGCI. Pyramidal cell death was observed only in the CA 1 area (CA1) of the hippocampus in non-obese gerbils 5 days after tGCI. However, in obese gerbils, pyramidal cell death in the CA1 and CA2/3 occurred at 2 days and 5 days, respectively, after tGCI. In the obese gerbils, oxidative stress indicators (dihydroethidium, 8-hydroxyguanine and 4-hydroxy-2-nonenal) were significantly enhanced and antioxidant enzymes (SOD1 and SOD2) were significantly reduced in pre- and post-ischemic phases compared to the non-obese gerbils. Fucoidan treatment attenuated acceleration and exacerbation of tGCI-induced neuronal death in the CA1–3, showing that oxidative stress was significantly reduced, and antioxidant enzymes were significantly increased in pre- and post-ischemic phases. These findings indicate that pretreated fucoidan can relieve the acceleration and exacerbation of ischemic brain injury in an obese state via the attenuation of obesity-induced severe oxidative damage.

Chronic high-fat diet-induced obesity in gerbils increases pro-inflammatory cytokines and mTOR activation, and elicits neuronal death in the striatum following brief transient ischemia

Recent studies have shown that obesity and its related metabolic dysfunction exacerbate outcomes of ischemic brain injuries in some brain areas, such as the hippocampus and cerebral cortex when they are subjected to transient ischemia. However, the impact of obesity in the striatum after brief transient ischemia has not yet been addressed. The objective of this study was to investigate effects of obesity on neuronal damage and inflammation in the striatum after transient ischemia and to examine the role of mTOR which is involved in the pathogenesis of metabolic and neurological diseases. Gerbils were fed with normal diet (ND) or high-fat diet (HFD) for 12 weeks and subjected to 5 min of transient ischemia. HFD-fed gerbils showed significant increase in body weight, blood glucose level, serum triglycerides, total cholesterol and low-density lipoprotein cholesterol without affecting food intake. Neuronal death/loss in the HFD-fed gerbils occurred in the dorsolateral striatum 2 days after transient ischemia, and neuronal loss was increased 5 days after transient ischemia, although no neuronal loss was observed in ND-fed gerbils at any time after transient ischemia. The HFD-fed gerbils showed hypertrophied microglia and further increased expressions of tumor necrosis factor-alpha, interukin-1beta, mammalian target of rapamycin (mTOR) and phosphorylated-mTOR during pre- and post-ischemic phases compared with the ND-fed gerbils. Additionally, we found that treatment with mTOR inhibitor rapamycin in the HFD-fed gerbils significantly attenuated transient ischemia-induced neuronal death in the dorsolateral striatum. These findings reveal that chronic HFD-induced obesity results in severe neuroinflammation and significant increase of mTOR activation, which could contribute to neuronal death in the stratum following 5 min of transient ischemia. Especially, abnormal mTOR activation would play a key role in mediating obesity-induced severe ischemic brain injury.

Hydroxysafflor yellow a protects brain microvascular endothelial cells against oxygen glucose deprivation/reoxygenation injury: Involvement of inhibiting autophagy via class I PI3K/Akt/mTOR signaling pathway

The present study aimed to test whether Hydroxysafflor yellow A (HSYA) protects the brain microvascular endothelial cells (BMECs) injury induced by oxygen glucose deprivation/reoxygenation (OGD/R) via the PI3K/Akt/mTOR autophagy signaling pathway. Primary rat BMECs were cultured and identified by the expression of factor VIII-related antigen before being exposed to OGD/R to imitate ischemia/reperfusion (I/R) damage in vitro. The protective effect of HSYA was evaluated by assessing (1) cellular morphologic and ultrastructural changes; (2) cell viability and cytotoxicity; (3) transendothelial electrical resistance (TEER) of monolayer BMECs; (4) cell apoptosis; (5) fluorescence intensity of LC3B; (6) LC3 mRNA expression; (7) protein expressions of LC3, Beclin-1, Zonula occludens-1 (ZO-1), phospho-Akt (p-Akt), Akt, phospho-mTOR (p-mTOR) and mTOR. It was found that HSYA (20, 40, and 80 μM) and 3-MA effectively reversed the cellular morphological and ultrastructural changes, increased cell survival, normalized the permeability of BMECs, and suppressed apoptosis induced by OGD/R (2 h OGD followed by 24 h reoxygenation). Concurrently, HSYA and 3-MA also inhibited OGD/R-induced autophagy evidenced by the decreased number of autophagosomes and down-regulated levels of LC3 and Beclin-1 proteins and mRNAs. HSYA (80 μM), in combination with 3-MA showed a synergistic effect. Mechanistic studies revealed that HSYA (80 μM) markedly increased the levels of p-Akt and p-mTOR proteins. Blockade of PI3K activity by ZSTK474 abolished its anti-autophagic and pro-survival effect and lowered both Akt and mTOR phosphorylation levels. Taken together, these results suggest that HSYA protects BMECs against OGD/R-induced injury by inhibiting autophagy via the Class I PI3K/Akt/mTOR signaling pathway.

Less hippocampal neuronal death in young gerbils following transient global cerebral ischemia is associated with long‑term maintenance of insulin‑like growth factor 1 and its receptors in the hippocampal CA1 region

Insulin-like growth factor 1 (IGF-1) is a well-known growth factor with well-defined neuroprotective effects against cerebral ischemia. However, the age‑dependent differences in the expression of IGF‑1 and its receptor (IGF‑1R) in the brain following transient cerebral ischemia (TCI) have not been elucidated. In the present study, the differences in IGF‑1 and IGF‑1R in the gerbil hippocampal CA1 region of young and adult gerbils 5 min following TCI were determined. Seven days following TCI, the neuronal death in the hippocampal CA1 region of young gerbils was significantly less than that observed in adult gerbils. In addition, the immunoreactivity, and levels of IGF‑1 and IGF‑1R in the CA1 region of the normal young were higher than those in the normal adult. Four days following TCI, the immunoreactivity, and protein levels of IGF‑1 and IGF‑1R were markedly decreased in the adult group. By contrast, in the young group, the immunoreactivity and expression levels were much greater than those in the adult group. However, 7 days following TCI, all immunoreactivity and expression levels were markedly decreased when compared with those in the normal adult and young groups. In addition, the immunoreactivity and expression levels in the young groups were significantly higher than those of the adult groups. In conclusion, the present study demonstrated that the higher and sustained expression of IGF‑1 and IGF‑1R in the young gerbil hippocampal CA1 region following TCI may be associated with the reduced neuronal death compared to that in the adults.

Glial cells and energy balance

The search for new strategies and drugs to abate the current obesity epidemic has led to the intensification of research aimed at understanding the neuroendocrine control of appetite and energy expenditure. This intensified investigation of metabolic control has also included the study of how glial cells participate in this process. Glia, the most abundant cell type in the central nervous system, perform a wide spectrum of functions and are vital for the correct functioning of neurons and neuronal circuits. Current evidence indicates that hypothalamic glia, in particular astrocytes, tanycytes and microglia, are involved in both physiological and pathophysiological mechanisms of appetite and metabolic control, at least in part by regulating the signals reaching metabolic neuronal circuits. Glia transport nutrients, hormones and neurotransmitters; they secrete growth factors, hormones, cytokines and gliotransmitters and are a source of neuroprogenitor cells. These functions are regulated, as glia also respond to numerous hormones and nutrients, with the lack of specific hormonal signaling in hypothalamic astrocytes disrupting metabolic homeostasis. Here, we review some of the more recent advances in the role of glial cells in metabolic control, with a special emphasis on the differences between glial cell responses in males and females.

Obesity and stroke: Can we translate from rodents to patients?

Obesity is a risk factor for stroke and is consequently one of the most common co-morbidities found in patients. There is therefore an identified need to model co-morbidities preclinically to allow better translation from bench to bedside. In preclinical studies, both diet-induced and genetically obese rodents have worse stroke outcome, characterised by increased ischaemic damage and an altered inflammatory response. However, clinical studies have reported an 'obesity paradox' in stroke, characterised by reduced mortality and morbidity in obese patients. We discuss the potential reasons why the preclinical and clinical studies may not agree, and review the mechanisms identified in preclinical studies through which obesity may affects stroke outcome. We suggest inflammation plays a central role in this relationship, as obesity features increases in inflammatory mediators such as C-reactive protein and interleukin-6, and chronic inflammation has been linked to worse stroke risk and outcome.

YiQiFuMai Powder Injection ameliorates the oxygen-glucose deprivation-induced brain microvascular endothelial barrier dysfunction associated with the NF-κB and ROCK1/MLC signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

YiQiFuMai Powder Injection (YQFM) is a modern preparation derived from Sheng-mai San, a traditional Chinese prescription, widely used for the treatment of cardiovascular and cerebrovascular diseases. However, its potential molecular mechanism remains unclear.

AIM OF THE STUDY

The present study was designed to observe the effect of YQFM on oxygen-glucose deprivation (OGD)-induced the brain microvascular endothelial barrier dysfunction and to explore the underlying pathways in vitro.

METHODS

A mouse brain microvascular endothelial cell line (bEnd.3) was subjected to OGD (2-9h) to examine the efficacy and molecular mechanisms in the presence or absence of YQFM (100, 200 and 400 μg/ml).

RESULTS

The results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Trans-endothelial electrical resistance (TEER) assays demonstrated that treatment with YQFM increased the cell viability and TEER value, decreased even blue (EB) albumin leakage after OGD in bEnd.3 cells. Western blotting and immunofluorescence staining showed that YQFM reduced the breakage and translocation of Zonula occludens-1 (ZO-1) and claudin-5 after 4h of OGD and decreased the expression of these proteins after 9h of OGD. Moreover, YQFM significantly inhibited the expression, phosphorylation and nuclear translocation of NF-κB/p65 and decreased the expression of intercellular adhesionmolecule-1 (ICAM-1) and cyclooxygenase (COX-2) as well as production of nitric oxide (NO). In addition, real time-PCR results revealed that YQFM suppressed the mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) after 4h of OGD. Furthermore, YQFM markedly inhibited both the phosphorylation of myosin light chain (MLC) and cytoskeletal reorganization and reduced the expression of cleaved-ROCK1 in bEnd.3 cells subjected to OGD.

CONCLUSION

These findings suggest that YQFM ameliorates the OGD-induced brain microvascular endothelial cell barrier disruption associated with the NF-κB/p65 and ROCK1/MLC signaling pathways. These data provide new insights into the use of this preparation for treating cerebrovascular diseases.

The Role of bFGF in the Excessive Activation of Astrocytes Is Related to the Inhibition of TLR4/NFκB Signals

Astrocytes have critical roles in immune defense, homeostasis, metabolism, and synaptic remodeling and function in the central nervous system (CNS); however, excessive activation of astrocytes with increased intermediate filaments following neuronal trauma, infection, ischemia, stroke, and neurodegenerative diseases results in a pro-inflammatory environment and promotes neuronal death. As an important neurotrophic factor, the secretion of endogenous basic fibroblast growth factor (bFGF) contributes to the protective effect of neuronal cells, but the mechanism of bFGF in reactive astrogliosis is still unclear. In this study, we demonstrated that exogenous bFGF attenuated astrocyte activation by reducing the expression of glial fibrillary acidic protein (GFAP) and other markers, including neurocan and vimentin, but not nestin and decreased the levels of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), via the regulation of the upstream toll-like receptor 4/nuclear factor κB (TLR4/NFκB) signaling pathway. Our study suggests that the function of bFGF is not only related to the neuroprotective and neurotrophic effect but also involved in the inhibition of excessive astrogliosis and glial scarring after neuronal injury.

Differential Effects of Pioglitazone in the Hippocampal CA1 Region Following Transient Forebrain Ischemia in Low- and High-Fat Diet-Fed Gerbils

In the present study, we investigated the effects of pioglitazone (PGZ) in the hippocampal CA1 region of low- or high-fat diet (LFD or HFD) fed gerbils after transient forebrain ischemia. After 8 weeks of LFD or HFD feeding, PGZ (30 mg/kg) was intraperitoneally administered to the gerbils, following which ischemia was induced by occlusion of the bilateral common carotid arteries for 5 min. Administration of PGZ significantly reduced the ischemia-induced hyperactivity 1 day after ischemia/reperfusion in both LFD- and HFD-fed gerbils. At 4 days after ischemia/reperfusion, the neurons were significantly reduced and microglial activation was observed in the hippocampal CA1 region in LFD- and HFD-fed gerbils. The microglial activation was more prominent in the HFD-fed gerbils compared to the LFD-fed gerbils. Administration of PGZ ameliorated ischemia-induced neuronal death and microglial activation in the hippocampal CA1 region 4 days after ischemia/reperfusion in the LFD-fed gerbils, but not in the HFD-gerbils. At 6 h after ischemia/reperfusion, tumor necrosis factor-α (TNF-α) and interlukin-1β (IL-1β) levels were significantly increased in the hippocampal homogenates of LFD-fed group compared to control group, and HFD feeding further increased TNF-α and IL-1β levels. PGZ treatment significantly ameliorated the increase of TNF-α and IL-1β levels in LFD-fed gerbils, not in the HFD-fed gerbils. At 12 h after ischemia/reperfusion, superoxide dismutase (SOD) and malondialdehyde (MDA) levels in hippocampal homogenates were significantly increased in the LFD-fed group compared to the control group, and HFD feeding significantly showed relatively reduction in SOD activity and increase in MDA level. PGZ administration significantly reduced the increase in MDA levels 12 h after ischemia/reperfusion in the LFD-fed gerbils, but not in the HFD-fed gerbils. These results suggest that PGZ ameliorates the neuronal damage induced by ischemia by maintaining the TNF-α, IL-1β, SOD and MDA levels in LFD-fed gerbils. In addition, HFD feeding affects the modulation of these parameters in the hippocampus after transient forebrain ischemia.