Gingko biloba extract (EGb 761) prevents cerebral ischemia-induced p70S6 kinase and S6 phosphorylation

Quercetin Alleviated Inflammasome-Mediated Pyroptosis and Modulated the mTOR/P70S6/P6/eIF4E/4EBP1 Pathway in Ischemic Stroke

Stroke ranks as the world's second most prevalent cause of mortality, and it represents a major public health concern with profound economic and social implications. In the present study, we elucidated the neuroprotective role of quercetin on NLRP3-associated pyroptosis, Nrf2-coupled anti-inflammatory, and mTOR-dependent downstream pathways. Male Sprague Dawley rats were subjected to 72 h of transient middle cerebral artery ischemia, followed by the administration of 10 mg/kg of quercetin. Our findings demonstrated that MCAO induced elevated ROS which were coupled to inflammasome-mediated pyroptosis and altered mTOR-related signaling proteins. We performed ELISA, immunohistochemistry, and Western blotting to unveil the underlying role of the Nrf2/HO-1 and PDK/AKT/mTOR pathways in the ischemic cortex and striatum. Our results showed that quercetin post-treatment activated the Nrf2/HO-1 cascade, reversed pyroptosis, and modulated the autophagy-related pathway PDK/AKT/mTOR/P70S6/P6/eIF4E/4EBP1. Further, quercetin enhances the sequestering effect of 14-3-3 and reversed the decrease in interaction between p-Bad and 14-3-3 and p-FKHR and 14-3-3. Our findings showed that quercetin exerts its protective benefits and rescues neuronal damage by several mechanisms, and it might be a viable neuroprotective drug for ischemic stroke therapy.

Naoxin'an capsules protect brain function and structure in patients with vascular cognitive impairment

Introduction: Vascular cognitive impairment (VCI) is one of the most common types of dementia. Naoxin'an capsule (NXA), a traditional Chinese medicine compound, has been used to treat VCI for a long time in the clinic. Previous studies proved that the NXA capsules could ameliorate the cerebral mitochondrion deficits of VCI animals. This study aimed to investigate the protectiveness of NXA on human brain structure and function in patients with VCI. Methods: In total, 100 VCI patients were enrolled in this 24-week trial and randomly divided into the NXA capsules group (n = 50) and the ginkgo biloba capsules control group (n = 50). Before and after the treatment, cognitive behavior tests and multimodal brain magnetic resonance imaging were analyzed to comprehensively evaluate the effectiveness of NXA treatment on VCI patients after 24 weeks. Results: We found that the NXA group significantly improved overall cognitive ability (Alzheimer's Disease Assessment Scale-Cognitive section, p = 0.001; Mini-Mental Status Examination, p = 0.003), memory (Rey-Osterrieth Complex Figure test, p < 0.001) and executive function (Trail Making Test-A, p = 0.024) performance after treatment compared with the control group. For brain function, the degree of centrality in the left middle frontal gyrus, right postcentral gyrus, and left supplementary motor area increased in the NXA group and decreased in the ginkgo biloba group after treatment. The fractional amplitude of low-frequency fluctuation (fALFF) of the left precentral and right superior parietal gyrus increased, and the fALFF of the right parahippocampal and left inferior temporal gyrus decreased in the NXA group after treatment. For brain structure, the gray matter density of the left postcentral gyrus increased in the NXA group after treatment, and the total volume of white matter hyperintensity showed a decreasing trend but was not statistically significant. Furthermore, the improvement effect of NXA on executive function was associated with changes in brain function. Conclusion: These findings suggest that the NXA capsules improved cognitive performance and multiregional brain function, as well as gray matter structure in the postcentral gyrus.

Casein Kinase 2 Signaling in White Matter Stroke

The growth of the aging population, together with improved stroke care, has resulted in an increase in stroke survivors and a rise in recurrent events. Axonal injury and white matter (WM) dysfunction are responsible for much of the disability observed after stroke. The mechanisms of WM injury are distinct compared to gray matter and change with age. Therefore, an ideal stroke therapeutic must restore neuronal and axonal function when applied before or after a stroke, and it must also protect across age groups. Casein kinase 2 (CK2), is expressed in the brain, including WM, and is regulated during the development and numerous disease conditions such as cancer and ischemia. CK2 activation in WM mediates ischemic injury by activating the Cdk5 and AKT/GSK3β signaling pathways. Consequently, CK2 inhibition using the small molecule inhibitor CX-4945 (Silmitasertib) correlates with preservation of oligodendrocytes, conservation of axon structure, and axonal mitochondria, leading to improved functional recovery. Remarkably, CK2 inhibition promotes WM function when applied after ischemic injury by specifically regulating the AKT/GSK3β pathways. The blockade of the active conformation of AKT confers post-ischemic protection to young and old WM by preserving mitochondria, implying AKT as a common therapeutic target across age groups. Using a NanoString nCounter miRNA expression profiling, comparative analyses of ischemic WM with or without CX-4945 treatment reveal that miRNAs are expressed at high levels in WM after ischemia, and CX-4945 differentially regulates some of these miRNAs. Therefore, we propose that miRNA regulation may be one of the protective actions of CX-4945 against WM ischemic injury. Silmitasertib is FDA approved and currently in use for cancer and Covid patients; therefore, it is plausible to repurpose CK2 inhibitors for stroke patients.

Identification of miRNAs That Mediate Protective Functions of Anti-Cancer Drugs During White Matter Ischemic Injury

We have previously shown that two anti-cancer drugs, CX-4945 and MS-275, protect and preserve white matter (WM) architecture and improve functional recovery in a model of WM ischemic injury. While both compounds promote recovery, CX-4945 is a selective Casein kinase 2 (CK2) inhibitor and MS-275 is a selective Class I histone deacetylase (HDAC) inhibitor. Alterations in microRNAs (miRNAs) mediate some of the protective actions of these drugs. In this study, we aimed to (1) identify miRNAs expressed in mouse optic nerves (MONs); (2) determine which miRNAs are regulated by oxygen glucose deprivation (OGD); and (3) determine the effects of CX-4945 and MS-275 treatment on miRNA expression. RNA isolated from MONs from control and OGD-treated animals with and without CX-4945 or MS-275 treatment were quantified using NanoString nCounter^® miRNA expression profiling. Comparative analysis of experimental groups revealed that 12 miRNAs were expressed at high levels in MONs. OGD upregulated five miRNAs (miR-1959, miR-501-3p, miR-146b, miR-201, and miR-335-3p) and downregulated two miRNAs (miR-1937a and miR-1937b) compared to controls. OGD with CX-4945 upregulated miR-1937a and miR-1937b, and downregulated miR-501-3p, miR-200a, miR-1959, and miR-654-3p compared to OGD alone. OGD with MS-275 upregulated miR-2134, miR-2141, miR-2133, miR-34b-5p, miR-153, miR-487b, miR-376b, and downregulated miR-717, miR-190, miR-27a, miR-1959, miR-200a, miR-501-3p, and miR-200c compared to OGD alone. Interestingly, miR-501-3p and miR-1959 were the only miRNAs upregulated by OGD, and downregulated by OGD plus CX-4945 and MS-275. Therefore, we suggest that protective functions of CX-4945 or MS-275 against WM injury maybe mediated, in part, through miRNA expression.

New Insight into the Mechanisms of Ginkgo Biloba Extract in Vascular Aging Prevention

BACKGROUND

Aging-associated vascular dysfunction promotes cardiovascular diseases. Recently, Ginkgo biloba extract (GBE) has attracted considerable attention in the prevention of aged vasculature.

METHODS

This review discusses the pathophysiological alterations in aged vasculature and the underlying mechanisms of GBE in vascular aging suppression.

RESULTS

Both arterial stiffening and endothelial dysfunction are critical aging-related vascular phenotypes that result in the progression of cardiovascular diseases in the general population. Consistent oxidative stress and inflammatory reaction lead to vascular dysfunction. GBE ameliorates aging-related vascular dysfunction, due to its antioxidant and anti-inflammatory properties. The main effects of GBE in aged vasculature might be associated with the longevity signaling pathways. GBE also attenuates the progression of vascular aging in diabetes mellitus via regulation of glucose and lipid metabolism.

CONCLUSION

GBE plays an important role in the prevention of vascular aging process. It is a promising therapeutic approach to ameliorate aging-related vascular dysfunction and cardiovascular diseases.

GBE attenuates arsenite-induced hepatotoxicity by regulating E2F1-autophagy-E2F7a pathway and restoring lysosomal activity

Arsenic is an environmental toxicant. Its overdose can cause liver damage. Autophagy has been reported to be involved in arsenite (iAs³⁺ ) cytotoxicity and plays a dual role in cell proliferation and cell death. However, the effect and molecular regulative mechanisms of iAs³⁺ on autophagy in hepatocytes remains largely unknown. Here, we found that iAs³⁺ exposure lead to hepatotoxicity by inducing autophagosome and autolysosome accumulation. On the one hand, iAs³⁺ promoted autophagosome synthesis by inhibiting E2F1/mTOR pathway in L-02 human hepatocytes. On the other, iAs³⁺ blocked autophagosome degradation partially via suppressing the expression of INPP5E and Rab7 as well as impairing lysosomal activity. More importantly, autophagosome and autolysosome accumulation induced by iAs³⁺ increased the protein level of E2F7a, which could further inhibit cell viability and induce apoptosis of L-02 cells. The treatment of Ginkgo biloba extract (GBE) effectively reduced autophagosome and autolysosome accumulation and thus alleviated iAs³⁺ -induced hepatotoxicity. Moreover, GBE could also protect lysosomal activity, promote the phosphorylation level of E2F1 (Ser364 and Thr433) and Rb (Ser780) as well as suppress the protein level of E2F7a in iAs³⁺ -treated L-02 cells. Taken together, our data suggested that autophagosome and autophagolysosome accumulation play a critical role for iAs³⁺ -induced hepatotoxicity, and GBE is a promising candidate for intervening iAs³⁺ induced liver damage by regulating E2F1-autophagy-E2F7a pathway and restoring lysosomal activity.

Alleviation of Simvastatin-Induced Myopathy in Rats by the Standardized Extract of Ginkgo Biloba (EGb761): Insights into the Mechanisms of Action

Statins are the most widely prescribed cholesterol-lowering drugs to reduce the risk of cardiovascular diseases. Statin-induced myopathy is the major side effect of this class of drugs. Here, we studied whether standardized leaf extracts of ginkgo biloba (EGb761) would improve simvastatin (SIM)-induced muscle changes. Sixty Wistar rats were allotted into six groups: control group, vehicle group receiving 0.5% carboxymethyl cellulose (CMC) for 30 days, SIM group receiving 80 mg/kg/day SIM in 0.5% CMC orally for 30 days, SIM withdrawal group treated with SIM for 16 days and sacrificed 14 days later, and EGb761-100 and EGb761-200 groups posttreated with either 100 or 200 mg/kg/day EGb761 orally. Muscle performance on the rotarod, serum creatine kinase (CK), coenzyme Q10 (CoQ10), serum and muscle nitrite, muscle malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were estimated. Additionally, muscle samples were processed for histopathological evaluation. We found that SIM decreased muscle performance on the rotarod, serum CoQ10, as well as muscle SOD and CAT activities while it increased serum CK, serum and muscle nitrite, as well as muscle MDA levels. SIM also induced sarcoplasmic vacuolation, splitting of myofibers, disorganization of sarcomeres, and disintegration of myofilaments. In contrast, posttreatment with EGb761 increased muscle performance, serum CoQ10, as well as muscle SOD and CAT activities while it reduced serum CK as well as serum and muscle nitrite levels in a dose-dependent manner. Additionally, EGb761 reversed SIM-induced histopathological changes with better results obtained by its higher dose. Interestingly, SIM withdrawal increased muscle performance on the rotarod, reduce serum CK and CoQ10, and reduced serum and muscle nitrite while it reversed SIM-induced histopathological changes. However, SIM withdrawal was not effective enough to restore their normal values. Additionally, SIM withdrawal did not improve SIM-induce muscle MDA, SOD, or CAT activities during the period studied. Our results suggest that EGb761 posttreatment reversed SIM-induces muscle changes possibly through its antioxidant effects, elevation of CoQ10 levels, and antagonizing mitochondrial damage.

Network topology and machine learning analyses reveal microstructural white matter changes underlying Chinese medicine Dengzhan Shengmai treatment on patients with vascular cognitive impairment

With the increasing incidence of cerebrovascular diseases and dementia, considerable efforts have been made to develop effective treatments on vascular cognitive impairment (VCI), among which accumulating practice-based evidence has shown great potential of the traditional Chinese medicine (TCM). Current randomized double-blind controlled trial has been designed to evaluate the 6-month treatment effects of Dengzhan Shengmai (DZSM) capsules, one TCM herbal preparations on VCI, and to explore the underlying neural mechanisms with graph theory-based analysis and machine learning method based on diffusion tensor imaging (DTI) data. A total of 82 VCI patients were recruited and randomly assigned to drug (45 with DZSM) and placebo (37 with placebo) groups, and neuropsychological and neuroimaging data were acquired at baseline and after 6-month treatment. After treatment, compared to the placebo group, the drug groups showed significantly improved performance in Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-cog) score (p < 0.001) and the other cognitive domains. And with the reconstruction of white matter structural network, there were more streamlines connecting the left thalamus and right hippocampus in the drug groups (p < 0.001 uncorrected), with decreasing nodal efficiency of the right olfactory associated with slower decline in the general cognition (r = -0.364, p = 0.048). Moreover, support vector machine classification analyses revealed significant white matter network alterations after treatment in the drug groups (accuracy of baseline vs. 6-month later, 68.18 %). Taking together, the present study showed significant efficacy of DZSM treatment on VCI, which might result from white matter microstructure alterations and the topological changes in brain structural network.

Dementia in China: epidemiology, clinical management, and research advances

China has the largest population of patients with dementia in the world, imposing a heavy burden on the public and health care systems. More than 100 epidemiological studies on dementia have been done in China, but the estimates of the prevalence and incidence remain inconsistent because of the use of different sampling methods. Despite improved access to health services, inadequate diagnosis and management for dementia is still common, particularly in rural areas. The Chinese Government issued a new policy to increase care facilities for citizens older than 65 years, but most patients with dementia still receive care at home. Western medicines for dementia symptoms are widely used in China, but many patients choose Chinese medicines even though they have little evidence supporting efficacy. The number of clinical trials of Chinese and western medicines has substantially increased as a result of progress in research on new antidementia drugs but international multicentre studies are few in number. Efforts are needed to establish a national system of dementia care enhance training in dementia for health professionals, and develop global collaborations to prevent and cure this disease.

Ferulic acid ameliorates cerebral infarction by activating Akt/mTOR/4E‑BP1/Bcl‑2 anti‑apoptotic signaling in the penumbral cortex following permanent cerebral ischemia in rats

The aim of the present study was to determine the effects of ferulic acid (FerA) administered immediately following the onset of permanent middle cerebral artery occlusion (MCAo) and then 7 days of ischemia, and also to explore the involvement of protein kinase B (Akt)‑induced signaling in the penumbral cortex. Immediately following the onset of MCAo, FerA was intravenously administered to rats at a dose of 60 mg/kg (FerA‑60 mg), 80 mg/kg (FerA‑80 mg), or 100 mg/kg (FerA‑100 mg). FerA‑80 mg and FerA‑100 mg effectively ameliorated cerebral infarction and neurological deficits 7 days following permanent cerebral ischemia. FerA‑80 mg and FerA‑100 mg significantly upregulated the expression of phospho‑Akt (p‑Akt), phospho‑mammalian target of rapamycin (p‑mTOR), and eukaryotic initiation factor 4E (eIF4E)‑binding protein 1 (4E‑BP1), and the phospho‑4E‑BP1 (p‑4E‑BP1)/4E‑BP1 and mitochondrial Bcl‑2/Bax ratios, and markedly downregulated the levels of cytochrome c‑, cleaved caspase‑3‑, and terminal deoxynucleotidyl transferase‑mediated dUTP‑biotin nick‑end labeling‑immunoreactive cells in the penumbral cortex at 7 days post‑ischemia. LY294002, a selective inhibitor of phosphoinositide 3‑kinase/Akt signaling, was administered 30 min prior to ischemia, which abrogated the upregulating effects of FerA‑100 mg on the expression of p‑Akt, p‑mTOR, 4E‑BP1, p‑4E‑BP1 and eIF4E, the mitochondrial Bcl‑2/Bax ratio and the ameliorating effect of FerA‑100 mg on cerebral infarction. FerA administered at doses of 80 and 100 mg/kg exerted beneficial effects against cerebral ischemia by activating Akt‑induced signaling. The effects of FerA at doses of 80 and 100 mg/kg on mitochondrial B‑cell lymphoma-2 (Bcl‑2)‑associated X protein‑related apoptosis were attributed to the activation of Akt/mTOR/4E‑BP1/Bcl‑2 anti‑apoptotic signaling, and eventually contributed to suppression of the cytochrome c/caspase‑3 activation pathway in the penumbral cortex 7 days following permanent cerebral ischemia.

Autophagy in Diabetic Retinopathy

Autophagy is an important homeostatic cellular process encompassing a number of consecutive steps indispensable for degrading and recycling cytoplasmic materials. Basically autophagy is an adaptive response that under stressful conditions guarantees the physiological turnover of senescent and impaired organelles and, thus, controls cell fate by various cross-talk signals. Diabetic retinopathy (DR) is a serious microvascular complication of diabetes and accounts for 5% of all blindness. Although, various metabolic disorders have been linked with the onset of DR, due to the complex character of this multi-factorial disease, a connection between any particular defect and DR becomes speculative. Diabetes increases inflammation, advanced glycation end products (AGEs) and oxidative stress in the retina and its capillary cells. Particularly, a great number of evidences suggest a mutual connection between oxidative stress and other major metabolic abnormalities implicated in the development of DR. In addition, the intricate networks between autophagy and apoptosis establish the degree of cellular apoptosis and the progression of DR. Growing data underline the crucial role of reactive oxygen species (ROS) in the activation of autophagy. Depending on their delicate balance both redox signaling and autophagy, being detrimental or beneficial, retain opposing effects. The molecular mechanisms of autophagy are very complex and involve many signaling pathways cooperating at various steps. This review summarizes recent advances of the possible molecular mechanisms in autophagic process that are involved in pathophysiology of DR. In-depth analysis on the molecular mechanisms leading to autophagy in the retinal pigment epithelial (RPE) will be helpful to plan new therapies aimed at preventing or improving the progression of DR.

Herbal Medicine for the Treatment of Vascular Dementia: An Overview of Scientific Evidence

Dementia is a leading cause of mental and physical disability. Vascular dementia (VaD) is the second most common cause of dementia after Alzheimer's disease (AD) constituting 10–15% of the dementia population. Currently there are no approved pharmaceutical options for VaD and the conventional anti-AD therapies provide only modest, short-term relief of symptoms associated with VaD. Herbal medicines have been used for the management of dementia-like symptoms for centuries and may provide viable therapies for VaD due to their multicomponent and multitarget approach. This review is designed to provide an updated overview on the current status of herbal medicine research, with an emphasis on Chinese herbal medicine, for the treatment of VaD or dementia. A case study is also provided to demonstrate the development process of a novel standardized complex herbal formulation for VaD. The article reveals some preliminary evidence to support the use of single and complex herbal preparations for VaD and dementia. Multiple issues in relation to clinical and preclinical research have been identified and future research directions are discussed.

Inhibition of mTOR Pathway by Rapamycin Reduces Brain Damage in Rats Subjected to Transient Forebrain Ischemia

The aims of this study are to clarify the role of mTOR in mediating cerebral ischemic brain damage and the effects of rapamycin on ischemic outcomes. Ten minutes of forebrain ischemia was induced in rats, and their brains were sampled after 3 h, 16 h, and 7 days reperfusion for histology, immunohistochemistry and biochemical analysis. Our data demonstrated that cerebral ischemia resulted in both apoptotic and necrotic neuronal death; cerebral ischemia and reperfusion led to significant increases of mRNA and protein levels of p-mTOR and its downstream p-P70S6K and p-S6; elevation of LC3-II, and release of cytochrome c into the cytoplasm in both the cortex and hippocampus. Inhibition of mTOR by rapamycin markedly reduced ischemia-induced damage; suppressed p-Akt, p-mTOR, p-P70S6K and p-S6 protein levels; decreased LC3-II and Beclin-1; and prevented cytochrome c release in the two structures. All together, these data provide evidence that cerebral ischemia activates mTOR and autophagy pathways. Inhibition of mTOR deactivates the mTOR pathway, suppresses autophagy, prevents cytochrome c release and reduces ischemic brain damage.

Current Perspectives on the Beneficial Role of Ginkgo biloba in Neurological and Cerebrovascular Disorders

Ginkgo biloba extract is an alternative medicine available as a standardized formulation, EGb 761^®, which consists of ginkgolides, bilobalide, and flavonoids. The individual constituents have varying therapeutic mechanisms that contribute to the pharmacological activity of the extract as a whole. Recent studies show anxiolytic properties of ginkgolide A, migraine with aura treatment by ginkgolide B, a reduction in ischemia-induced glutamate excitotoxicity by bilobalide, and an alternative antihypertensive property of quercetin, among others. These findings have been observed in EGb 761 as well and have led to clinical investigation into its use as a therapeutic for conditions such as cognition, dementia, cardiovascular, and cerebrovascular diseases. This review explores the therapeutic mechanisms of the individual EGb 761 constituents to explain the pharmacology as a whole and its clinical application to cardiovascular and neurological disorders, in particular ischemic stroke.

Commonly Used Dietary Supplements on Coagulation Function during Surgery

BACKGROUND

Patients who undergo surgery appear to use dietary supplements significantly more frequently than the general population. Because they contain pharmacologically active compounds, dietary supplements may affect coagulation and platelet function during the perioperative period through direct effects, pharmacodynamic interactions, and pharmacokinetic interactions. However, in this regard, limited studies have been conducted that address the pharmacological interactions of dietary supplements. To avoid possible bleeding risks during surgery, information of potential complications of dietary supplements during perioperative management is important for physicians.

METHODS

Through a systematic database search of all available years, articles were identified in this review if they included dietary supplements and coagulation/platelet function, while special attention was paid to studies published after 1990.

RESULTS

Safety concerns are reported in commercially available dietary supplements. Effects of the most commonly used natural products on blood coagulation and platelet function are systematically reviewed, including 11 herbal medicines (echinacea, ephedra, garlic, ginger, ginkgo, ginseng, green tea, kava, saw palmetto, St John's wort, and valerian) and 4 other dietary supplements (coenzyme Q₁₀, glucosamine and chondroitin sulfate, fish oil, and vitamins). Bleeding risks of garlic, ginkgo, ginseng, green tea, saw palmetto, St John's wort, and fish oil are reported. Cardiovascular instability was observed with ephedra, ginseng, and kava. Pharmacodynamic and pharmacokinetic interactions between dietary supplements and drugs used in the perioperative period are discussed.

CONCLUSIONS

To prevent potential problems associated with the use of dietary supplements, physicians should be familiar with the perioperative effects of commonly used dietary supplements. Since the effects of dietary supplements on coagulation and platelet function are difficult to predict, it is prudent to advise their discontinuation before surgery.

Protective effects of Echium amoenum Fisch. and C.A. Mey. against cerebral ischemia in the rats

Background:

This study was designed to evaluate the protective effect of Echium amoenum total anthocyanin extract (ETAE) on partial/transient cerebral ischemia in the rats.

Materials and Methods:

Rats received ETAE (50, 100 and 200 mg/kg, i.p.) 30 min before the induction of cerebral ischemia. Cerebral ischemia was induced by bilateral common carotid arteries occlusion (BCCAO) for 30 min, followed by 72 h reperfusion. The neurological deficit, brain performance, and sensory motor function were assessed 48 h and 72 h after surgery. After sacrification, the brains were evaluated for myeloperoxidase (MPO) activity and histopathological changes.

Results:

Our results showed that motor function significantly decreased in ischemia/reperfusion (I/R) group as compared to the sham group. Histopathological analysis exhibited the shrinkage and atrophy of the neurons in I/R group. ETAE at the dose of 200 mg/kg improved spontaneous activity and memory induced by cerebral ischemia compared to the control group and also decreased brain MPO activity following cerebral ischemia. However, it could not affect the ability to climbing, body proprioception, vibrissae touch and brain water content. In addition, pretreatment with ETAE at higher doses significantly reduced ischemia-induced neuronal loss of the brain.

Conclusion:

The anthocyanin rich fraction from E. amoenum was found to have protective effects against some brain damages postischemic reperfusion. However, further researches are required for investigating the exact mechanisms of the effect of this plant in the prevention of cerebral ischemia in human.

Mammalian target of rapamycin cell signaling pathway contributes to the protective effects of ischemic postconditioning against stroke

BACKGROUND AND PURPOSE

Whether the mammalian target of rapamycin (mTOR) pathway is protective against brain injury from stroke or is detrimental is controversial, and whether it is involved in the protective effects of ischemic postconditioning (IPC) against stroke is unreported. Our study focuses on the protective role of mTOR against neuronal injury after stroke with and without IPC.

METHODS

We used both an in vitro oxygen-glucose deprivation model with a mixed neuronal culture and hypoxic postconditioning, as well as an in vivo stroke model with IPC. Rapamycin, a specific pharmacological inhibitor of mTOR, and mTOR short hairpin RNA lentiviral vectors were used to inhibit mTOR activity. A lentiviral vector expressing S6K1, a downstream molecule of mTOR, was used to confirm the protective effects of mTOR. Infarct sizes were measured and protein levels were examined by Western blot.

RESULTS

We report that stroke resulted in reduced levels of phosphorylated proteins in the mTOR pathway, including S6K1, S6, and 4EBP1, and that IPC increased these proteins. mTOR inhibition, both by the mTOR inhibitor rapamycin and by mTOR short hairpin RNA, worsened ischemic outcomes in vitro and in vivo and abolished the protective effects of hypoxic postconditioning and IPC on neuronal death in vitro and brain injury size in vivo. Overexpression of S6K1 mediated by lentiviral vectors significantly attenuated brain infarction.

CONCLUSIONS

mTOR plays a crucial protective role in brain damage after stroke and contributes to the protective effects of IPC.

EGB1212 Post-treatment Ameliorates Hippocampal CA1 Neuronal Death and Memory Impairment Induced by Transient Global Cerebral Ischemia/Reperfusion

Extracts of Ginkgo biloba have been used in traditional medicines for centuries, and have potential for clinical applications in cerebral ischemia/reperfusion injury. However, standardized extracts have proven protective only as pre-treatments, and the major mechanisms of action remain unclear. We explored the potential of the novel extract EGB1212, which meets the United States Pharmacopeia (USP) 31 standardization criteria for pharmaceutical use, as a post-treatment after global cerebral ischemia/reperfusion (GCI/R) injury in a rat model. The pre-treated group was administered EGB1212 for 7 d prior to common carotid artery occlusion (i.e., ischemia, for 20 min). Post-treated rats received the same but starting 2 h after ischemia and continuing for 7 d. Seven days after GCI/R, brains of each group were processed for H&E staining of hippocampal CA1 neurons. Remaining rats underwent the Morris water maze and Y-maze tests of spatial learning and memory, beginning eight days after reperfusion. To assess hippocampal autophagy, light chain (LC)-3-I/LC3-II and Akt/pAkt were determined via a Western blot of rat hippocampi harvested 12, 24, or 72 h after reperfusion. EGB1212 pre- and post-treatments both improved neuronal survival and spatial learning and memory functions. Pre-treatment effectively reduced LC3-II levels and post-treatment resulted in significantly elevated pAkt levels. We conclude that EGB1212 exerted significant neuroprotection in GCI/R in both preventative and post-treatment settings. This extract shows great potential for clinical applications.

Gingko biloba extract (EGb 761) attenuates ischemic brain injury-induced reduction in Ca(2+) sensor protein hippocalcin

Gingko biloba extract 761 (EGb 761) protects neuronal cells from ischemic brain injury via a number of neuroprotective mechanisms. Hippocalcin is a calcium sensor protein that regulates intracellular calcium concentrations and apoptotic cell death. We investigated whether EGb 761 regulates hippocalcin expression in cerebral ischemia. Male Sprague-Dawley rats were treated with vehicle or EGb 761 (100 mg/kg) prior to middle cerebral artery occlusion (MCAO), and cerebral cortex tissues were collected 24 h after MCAO. A proteomic approach demonstrated reduction in hippocalcin expression in vehicle-treated animals during MCAO, whereas EGb 761 treatment prevented injury-induced decreases in hippocalcin expression. RT-PCR and Western blot analyses indicated that EGb 761 attenuates injury-induced decrease in hippocalcin. These results suggest that the maintenance of hippocalcin during cerebral ischemia contributes to the neuroprotective role of EGb 761.

Identification of Proteins Differentially Expressed in Cerebral Cortexes of Ginkgo biloba Extract (EGb761)-Treated Rats in a Middle Cerebral Artery Occlusion Model — A Proteomics Approach

EGb 761 is a standardized extract of Ginkgo biloba that appears to have a neuroprotective effect against neurodegenerative diseases. Adult male rats were treated with EGb 761 (100 mg/kg) or vehicle prior to middle cerebral artery occlusion (MCAO), and brains were collected 24 h after MCAO. Proteins that were differentially expressed after EGb 761 treatment during cerebral ischemia were detected using two-dimensional gel electrophoresis. Protein spots with more than a 2.5-fold change in intensity between vehicle- and EGb 761-treated groups were identified by mass spectrometry. The levels of peroxiredoxin-2 and protein phosphatase 2A subunit B were significantly decreased in the vehicle-treated group in comparison to the EGb 761-treated group. In contrast, levels of the collapsing response mediator protein 2 (CRMP2) were significantly increased in vehicle-treated animals, while EGb 761 prevented the injury-induced increase of CRMP2. These results suggest that EGb 761 protects neuronal cells against ischemic brain injury through the specific up- and down-modulation of various proteins.

Gingko biloba Extract (EGb 761) Attenuates the Focal Cerebral Ischemic Injury-Induced Decrease in Astrocytic Phosphoprotein PEA-15 Levels

EGb 761 is an extract of Gingko biloba that is neuroprotective against focal cerebral ischemic injury. PEA-15 (phosphoprotein enriched in astrocytes 15) modulates cell proliferation and apoptosis. In this study, we investigated whether EGb 761 regulates the expression of PEA-15 and two phosphorylated forms of PEA-15 (Ser 104 and Ser 116) in middle cerebral artery occlusion (MCAO)-induced injury. Adult male rats were treated with vehicle or EGb 761 (100 mg/kg) prior to MCAO and cerebral cortices were collected 24 h after MCAO. A reduction in expression of PEA-15 and its phosphorylated forms induced by MCAO injury was detected using a proteomic approach. EGb 761 pretreatment prevented the ischemic injury-induced decrease in PEA-15 expression. Western blot analysis demonstrated that EGb 761 attenuates the injury-induced reduction in PEA-15, phospho-PEA-15 (Ser 104), phospho-PEA-15 (Ser 116). Phosphorylation of PEA-15 influences its anti-apoptotic function; a decrease in PEA-15 phosphorylation induces apoptotic cell death. The maintenance of PEA-15 phosphorylation by EGb 761 pretreatment during cerebral ischemic injury indicates that EGb 761 is a neuroprotective against cerebral ischemic injury.

The functions of mTOR in ischemic diseases

Mammalian Target of Rapamycin (mTOR) is a serine/threonine kinase and that forms two multiprotein complexes known as the mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). mTOR regulates cell growth, proliferation and survival. mTORC1 is composed of the mTOR catalytic subunit and three associated proteins: raptor, mLST8/GβL and PRAS40. mTORC2 contains mTOR, rictor, mLST8/GβL, mSin1, and protor. Here, we discuss mTOR as a promising anti-ischemic agent. It is believed that mTORC2 lies down-stream of Akt and acts as a direct activator of Akt. The different functions of mTOR can be explained by the existence of two distinct mTOR complexes containing unique interacting proteins. The loss of TSC2, which is upstream of mTOR, activates S6K1, promotes cell growth and survival, activates mTOR kinase activities, inhibits mTORC1 and mTORC2 via mTOR inhibitors, and suppresses S6K1 and Akt. Although mTOR signaling pathways are often activated in human diseases, such as cancer, mTOR signaling pathways are deactivated in ischemic diseases. From Drosophila to humans, mTOR is necessary for Ser473 phosphorylation of Akt, and the regulation of Akt-mTOR signaling pathways may have a potential role in ischemic disease. This review evaluates the potential functions of mTOR in ischemic diseases. A novel mTOR-interacting protein deregulates over-expression in ischemic disease, representing a new mechanism for controlling mTOR signaling pathways and potential therapeutic strategies for ischemic diseases.