Stroke neuroprotection: targeting mitochondria

Role of Brain Derived Neurotrophic Factor and Related Therapeutic Strategies in Central Post-Stroke Pain

Brain-derived neurotrophic factor (BDNF) is vital for synaptic plasticity, cell persistence, and neuronal development in peripheral and central nervous systems (CNS). Numerous intracellular signalling pathways involving BDNF are well recognized to affect neurogenesis, synaptic function, cell viability, and cognitive function, which in turn affects pathological and physiological aspects of neurons. Stroke has a significant psycho-socioeconomic impact globally. Central post-stroke pain (CPSP), also known as a type of chronic neuropathic pain, is caused by injury to the CNS following a stroke, specifically damage to the somatosensory system. BDNF regulates a broad range of functions directly or via its biologically active isoforms, regulating multiple signalling pathways through interactions with different types of receptors. BDNF has been shown to play a major role in facilitating neuroplasticity during post-stroke recovery and a pro-nociceptive role in pain development in the nervous system. BDNF-tyrosine kinase receptors B (TrkB) pathway promotes neurite outgrowth, neurogenesis, and the prevention of apoptosis, which helps in stroke recovery. Meanwhile, BDNF overexpression plays a role in CPSP via the activation of purinergic receptors P2X4R and P2X7R. The neuronal hyperexcitability that causes CPSP is linked with BDNF-TrkB interactions, changes in ion channels and inflammatory reactions. This review provides an overview of BDNF synthesis, interactions with certain receptors, and potential functions in regulating signalling pathways associated with stroke and CPSP. The pathophysiological mechanisms underlying CPSP, the role of BDNF in CPSP, and the challenges and current treatment strategies targeting BDNF are also discussed.

Rectangular method: a modified technique for sampling the ischemic border zone in a rat model of transient middle cerebral artery occlusion

To date, there have been three common methods for sampling the cerebral ischemic border zone in a rat model of transient middle cerebral artery occlusion (tMCAO): the "two o'clock method", the "diagonal method", and the "parallel line method". However, these methods have their own advantages and limitations. Here, we propose a modified technique (the "rectangular method") for sampling the ischemic border zone. A rat tMCAO model was prepared under the support of a compact small animal anesthesia machine. Cerebral blood flow was monitored by high-resolution laser Doppler to control the quality of modeling, and 2,3,5-triphenyl tetrazolium chloride (TTC) staining was used for cerebral infarction location assessment. Superoxide dismutase 2 (SOD2), cysteinyl aspartate specific proteinase (caspase)-3, caspase-9, and heat shock protein 70 (HSP70) were used to verify the reliability and reproducibility of the rectangular method. The expression of biomarkers (SOD2, caspase-3, caspase-9, and HSP70) in the traditional (two o'clock method after TTC staining) and modified (rectangular method) groups were increased. There were no significant differences between the groups. The rectangular method proposed herein is based on a modification of the diagonal method and parallel line method, which could provide a directly observable infarct borderline and a sufficient sampling area for subsequent experimental operations regardless of the cerebral infarct location. The assessed biomarkers (SOD2, caspase-3, caspase-9, and HSP70) demonstrated the reliability and reproducibility of the rectangular method, which may facilitate inter-laboratory comparisons.

FGF21 alleviates endothelial mitochondrial damage and prevents BBB from disruption after intracranial hemorrhage through a mechanism involving SIRT6

BACKGROUND

Disruption of the BBB is a harmful event after intracranial hemorrhage (ICH), and this disruption contributes to a series of secondary injuries. We hypothesized that FGF21 may have protective effects after intracranial hemorrhage (ICH) and investigated possible underlying molecular mechanisms.

METHODS

Blood samples of ICH patients were collected to determine the relationship between the serum level of FGF21 and the [Formula: see text]GCS%. Wild-type mice, SIRT6flox/flox mice, endothelial-specific SIRT6-homozygous-knockout mice (eSIRT6-/- mice) and cultured human brain microvascular endothelial cells (HCMECs) were used to determine the protective effects of FGF21 on the BBB.

RESULTS

We obtained original clinical evidence from patient data identifying a positive correlation between the serum level of FGF21 and [Formula: see text]GCS%. In mice, we found that FGF21 treatment is capable of alleviating BBB damage, mitigating brain edema, reducing lesion volume and improving neurofunction after ICH. In vitro, after oxyhemoglobin injury, we further explored the protective effects of FGF21 on endothelial cells (ECs), which are a significant component of the BBB. Mitochondria play crucial roles during various types of stress reactions. FGF21 significantly improved mitochondrial biology and function in ECs, as evidenced by alleviated mitochondrial morphology damage, reduced ROS accumulation, and restored ATP production. Moreover, we found that the crucial regulatory mitochondrial factor deacylase sirtuin 6 (SIRT6) played an irreplaceable role in the effects of FGF21. Using endothelial-specific SIRT6-knockout mice, we found that SIRT6 deficiency largely diminished these neuroprotective effects of FGF21. Then, we revealed that FGF21 might promote the expression of SIRT6 via the AMPK-Foxo3a pathway.

CONCLUSIONS

We provide the first evidence that FGF21 is capable of protecting the BBB after ICH by improving SIRT6-mediated mitochondrial homeostasis.

Ameliorative effects of 6‑gingerol in cerebral ischemia are mediated via the activation of antioxidant and anti‑inflammatory pathways

Focal ischemia occurs when an embolus or thrombus occludes an artery, causing the rapid obstruction of cerebral blood flow. Although stroke represents a main cause of disability and mortality in developing countries, therapeutic approaches available for this condition remain very limited. The aim of the present study was to examine the effects of the phytochemical, 6-gingerol, on the brain infarct volume, neuronal loss and on the oxidative stress parameters, cyclooxygenase-2 (COX-2) and interleukin (IL)-6, in an animal model of focal ischemic stroke. Male Wistar rats, weighing 250-300 g, were divided into the following six groups: i) The control; ii) right middle cerebral artery occlusion (Rt.MCAO) + vehicle; iii) Rt.MCAO + piracetam; iv) Rt.MCAO + 6-gingerol (6-Gin) at 5 mg/kg body weight (BW); v) Rt.MCAO + 6-Gin at 10 mg/kg BW; and vi) the Rt.MCAO + 6-Gin at 20 mg/kg BW group. The rats in each group received the vehicle or piracetam or 6-gingerol intraperitoneally for 7 days following Rt.MCAO. The brain infarct volume, neuronal loss and alterations in antioxidant and anti-inflammatory levels were assessed in the cortex and hippocampus. The results revealed that the brain infarct volume, malondialdehyde level and the density ratio of COX-2 and IL-6 to β-actin were significantly decreased following treatment with 6-gingerol. In addition, neuronal density and superoxide dismutase activity in the cortex and hippocampus were increased. On the whole, the findings of the present study suggest that 6-gingerol exerts antioxidant and anti-inflammatory effects in vivo, which effectively ameliorate the brain damage induced by focal cerebral ischemic strok.

Oxidative stress: A target to treat Alzheimer's disease and stroke

Oxidative stress has been established as a well-known pathological condition in several neurovascular diseases. It starts with increased production of highly oxidizing free-radicals (e.g. reactive oxygen species; ROS and reactive nitrogen species; RNS) and becomes too high for the endogenous antioxidant system to neutralize them, which results in a significantly disturbed balance between free-radicals and antioxidants levels and causes cellular damage. A number of studies have evidently shown that oxidative stress plays a critical role in activating multiple cell signaling pathways implicated in both progression as well as initiation of neurological diseases. Therefore, oxidative stress continues to remain a key therapeutic target for neurological diseases. This review discusses the mechanisms involved in reactive oxygen species (ROS) generation in the brain, oxidative stress, and pathogenesis of neurological disorders such as stroke and Alzheimer's disease (AD) and the scope of antioxidant therapies for these disorders.

Worst spasticity in patients post-stroke associated with MNSOD ALA16VAL polymorphism and interleukin-1β

The MnSOD Ala16Val single nucleotide polymorphism (SNP) has shown to be associated to risk factors of several metabolic and vascular diseases. However, little is known about interaction between MnSOD Ala16Val SNP in stroke, a frequent neurologic disease that involves clinic manifestations such as motor deficits and spasticity. In this sense, we decided to investigate the relationship between MnSOD Ala16Val SNP with spasticity in stroke and also its influence on interleukin levels, BDNF, and glycolipid parameters. Eighty post-stroke subjects and 80 healthy controls were investigated. We showed a higher spasticity, levels of total cholesterol, LDL, IL-1β, IL-6, and INF-γ in VV post-stroke group. Interesting, we found a correlation between IL-1β levels and spasticity in VV post-stroke. Triglycerides, glucose levels and caspases (1 and 3) activation were significantly higher, as well as BDNF levels were lower in VV and AV post-stroke. DNA damage was higher in post-stroke group. Thus, we can suggest that the V allele has a worse glycolipid profile, which would facilitate changes in neurovascular homeostasis. These events associated with an increase in inflammatory markers and a reduction in BDNF can contribute with the stroke and a worse clinical evolution in relation to spasticity in patients with VV genotype.

Rescuing mitochondria in traumatic brain injury and intracerebral hemorrhages - A potential therapeutic approach

Mitochondria are dynamic organelles responsible for cellular energy production. Besides, regulating energy homeostasis, mitochondria are responsible for calcium homeostasis, signal transmission, and the fate of cellular survival in case of injury and pathologies. Accumulating reports have suggested multiple roles of mitochondria in neuropathologies, neurodegeneration, and immune activation under physiological and pathological conditions. Mitochondrial dysfunction, which occurs at the initial phase of brain injury, involves oxidative stress, inflammation, deficits in mitochondrial bioenergetics, biogenesis, transport, and autophagy. Thus, development of targeted therapeutics to protect mitochondria may improve functional outcomes following traumatic brain injury (TBI) and intracerebral hemorrhages (ICH). In this review, we summarize mitochondrial dysfunction related to TBI and ICH, including the mechanisms involved, and discuss therapeutic approaches with special emphasis on past and current clinical trials.

Dihydrocapsaicin effectively mitigates cerebral ischemia-induced pathological changes in vivo, partly via antioxidant and anti-apoptotic pathways

AIMS

Ischemic stroke occurs when there is a sudden blockage of cerebral blood flow. This condition is a major cause of mortality, especially in low-income countries, and its incidence is dramatically increasing. Therapeutic strategies against stroke are therefore required. The present study explored the effects of dihydrocapsaicin on neuronal loss, brain infarct volume, and antioxidants in a rat model of permanent occlusion of the right middle cerebral artery (Rt.MCAO).

MAIN METHODS

Male Wistar rats received dihydrocapsaicin intraperitoneally for 7 days after permanent occlusion of their right middle cerebral artery (Rt.MCAO). Then, the brain infarct volume, neuronal density, and antioxidant and anti-apoptotic activities in the cortex and hippocampus were determined at the end of the study.

KEY FINDING

Dihydrocapsaicin treatment was found to significantly improve neuronal density, decrease infarct volume, reduce MDA elevation, improve CAT and SOD activities, decrease the density ratio of Bax and caspase-3, and increase the density ratio of Bcl-XL to β-actin in the cerebral cortex and hippocampus.

SIGNIFICANCE

The present study suggests that dihydrocapsaicin effectively mitigates cerebral ischemia-induced pathological changes in vivo, partly via antioxidant and anti-apoptotic pathways.

Energy Metabolism Analysis of Three Different Mesenchymal Stem Cell Populations of Umbilical Cord Under Normal and Pathologic Conditions

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are a pivotal source of therapeutically active cells for regenerative medicine due to their multipotent differentiation potential, immunomodulatory and anti-inflammatory proprieties, as well as logistical collection advantages without ethical concerns. However, it remains poorly understood whether MSCs from different compartments of the human umbilical cord are therapeutically superior than others. In this study, MSCs were isolated from Wharton’s jelly (WJ-MSCs), perivascular region (PV-MSCs) and cord lining (CL-MSCs) of hUC. These cells expressed the mesenchymal markers (CD90, CD73), stemness marker (OCT4), endothelial cell adhesion molecular marker (CD146), and the monocyte/macrophage marker (CD14) found within the MSC population implicated as a key regulator of inflammatory responses to hypoxia, was displayed by WJ-, PV-, and CL-MSCs respectively. A direct consequence of oxygen and glucose deprivation during stroke and reperfusion is impaired mitochondrial function that contributes to cellular death. Emerging findings of mitochondria transfer provide the basis for the replenishment of healthy mitochondria as a strategy for the treatment of stroke. Cell Energy Phenotype and Mito Stress tests were performed the energy metabolic profile of the three MSC populations and their mitochondrial function in both ambient and OGD cell culture conditions. PV-MSCs showed the highest mitochondrial activity. CL-MSCs were the least affected by OGD/R condition, suggesting their robust survival in ischemic environment. In this study, MSC populations in UC possess comparable metabolic capacities and good survival under normal and hypoxic conditions suggesting their potential as transplantable cells for mitochondrial-based stem cell therapy in stroke and other ischemic diseases.

Neuroprotective effects of Apium graveolens against focal cerebral ischemia occur partly via antioxidant, anti-inflammatory, and anti-apoptotic pathways

BACKGROUND

Stroke is a neurological disease caused by a sudden disturbance of cerebral blood flow to the brain, leading to loss of brain function. Recently, accumulating lines of evidence have suggested that dietary enrichment with nutritional antioxidants could reduce brain damage and improve cognitive function. In this study, we investigated the possible protective effects of Apium graveolens, a medicinal plant with putative neuroprotective activity, against oxidative-stress-related brain damage and brain damage due to inflammation induced by focal cerebral ischemia.

METHODS

Male adult Wistar rats were administered with an extract of A. graveolens orally 14 days before permanent occlusion of their right middle cerebral artery. The brain infarct volumes of rats in each group were determined by 2,3,5-triphenyltetrazolium chloride staining, and the density of neurons in the cortex and hippocampus of rats was determined by cresyl violet staining. The levels of malondialdehyde, catalase, glutathione peroxidase, and superoxide dismutase in the cerebral cortex and hippocampus of the rats were also quantified at the end of the study period.

RESULTS

Our results show that A. graveolens extract significantly decreased infarct volume and improved neuronal density in the cortex and hippocampus of rats receiving A. graveolens extract compared with those rats receiving no treatment. This neuroprotective effect was found to occur partly due to antioxidant, anti-inflammatory, and anti-apoptotic effects.

CONCLUSION

Our study demonstrates that A. graveolens helps to reduce the severity of cognitive damage caused by focal cerebral ischemia. © 2020 Society of Chemical Industry.

SkQR1 Reduces Neurologic Deficit Caused by Rat Brain Compression Ischemia

The protective effect of antioxidant SkQR1 was examined on the model of left-sided compression ischemia in rat sensorimotor cortex. The special tests aimed to determine the neurologic deficit in the limbs and assess performance of the forelimbs showed that a 2.5-min ischemia produced no disturbance in the limb functions on postsurgery days 1, 3, and 7. Elevation of compression time resulted in neurologic deficit in animals, and its severity depended on this time. A single intravenous injection of SkQR1 (250 nmol/kg body weight) performed 30 min after ischemia significantly reduced the degree of neurologic deficit. In vitro model of ischemia in surviving rat hippocampal slices showed that a 15-min-long ischemia significantly inhibited the population excitatory postsynaptic potentials, which did not restore during reperfusion. Preincubation of the slices with SkQR1 did not significantly affect recovery of these potentials.

Mitochondrial activity of human umbilical cord mesenchymal stem cells

Human umbilical cord mesenchymal stem cells (hUC-MSCs) serve as a potential cell-based therapy for degenerative disease. They provide immunomodulatory and anti-inflammatory properties, multipotent differentiation potential and are harvested with no ethical concern. It is unknown whether MSCs collected from different areas of the human umbilical cord elicit more favorable effects than others. Three MSC populations were harvested from various regions of the human umbilical cord: cord lining (CL-MSCs), perivascular region (PV-MSCs), and Wharton's jelly (WJ-MSCs). Mesenchymal markers (CD90 and CD73) were expressed by all three cell populations. Stemness marker (OCT4), endothelial cell adhesion molecular marker (CD146), and monocyte-macrophage marker (CD14) were expressed by WJ-MSCs, PV-MSCs, and CL-MSCs, respectively. Stroke presents with oxygen and glucose deprivation and leads to dysfunctional mitochondria and consequently cell death. Targeting the restoration of mitochondrial function in the stroke brain through mitochondrial transfer may be effective in treating stroke. In vitro exposure to ambient and OGD conditions resulted in CL-MSCs number decreasing the least post-OGD/R exposure, and PV-MSCs exhibiting the greatest mitochondrial activity. All three hUC-MSC populations presented similar metabolic activity and survival in normal and pathologic environments. These characteristics indicate hUC-MSCs potential as a potent therapeutic in regenerative medicine.

Extracellular Mitochondria Signals in CNS Disorders

Mitochondria actively participate in the regulation of cell respiratory mechanisms, metabolic processes, and energy homeostasis in the central nervous system (CNS). Because of the requirement of high energy, neuronal functionality and viability are largely dependent on mitochondrial functionality. In the context of CNS disorders, disruptions of metabolic homeostasis caused by mitochondrial dysfunction lead to neuronal cell death and neuroinflammation. Therefore, restoring mitochondrial function becomes a primary therapeutic target. Recently, accumulating evidence suggests that active mitochondria are secreted into the extracellular fluid and potentially act as non-cell-autonomous signals in CNS pathophysiology. In this mini-review, we overview findings that implicate the presence of cell-free extracellular mitochondria and the critical role of intercellular mitochondrial transfer in various rodent models of CNS disorders. We also discuss isolated mitochondrial allograft as a novel therapeutic intervention for CNS disorders.

Mitochondrial Transfer as a Therapeutic Strategy Against Ischemic Stroke

Stroke is a debilitating disease that remains the second leading cause of death and disability worldwide. Despite accumulating knowledge of the disease pathology, treatments for stroke are limited, and clinical translation of the neuroprotective agents has not been a complete success. Accumulating evidence links mitochondrial dysfunction to brain impairments after stroke. Recent studies have implicated the important roles of healthy mitochondria in neuroprotection and neural recovery following ischemic stroke. New and convincing studies have shown that mitochondrial transfer to the damaged cells can help revive cells energetic in the recipient cells. Hence, mitochondrial transplantation has shown to replace impaired or dysfunctional mitochondria with exogenous healthy mitochondria after ischemic stroke. We highlight the potential of mitochondrial transfer by stem cells as a therapeutic strategy for the treatment of ischemic stroke. This review captures the recent advances in the mitochondrial transfer as a novel and promising treatment for ischemic stroke.

The single intravenous administration of methylene blue after traumatic brain injury diminishes neurological deficit, blood-brain barrier disruption and decrease in the expression of S100 protein in rats

The protective effect of methylene blue (MB) was investigated on the model of focal one-sided traumatic brain injury (TBI) of the sensorimotor cortex region from 1 to 7 days after the injury. TBI caused a reliable disruption of the functions of the limbs contralateral to injury focus, an increase in the expression of S100 protein and blood-brain barrier (BBB) permeability in the ipsilateral hemisphere. The single intravenous injection of MB (1 mg/kg body weight) 30 min after TBI significantly reduced the limb function impairment as well as a TBI-induced increase in the expression of inflammatory marker S100 protein, and BBB permeability. When modeling inflammation in vitro, MB was found to protect cultured neurons from the toxic effects of lipopolysaccharide. In conclusion, the preservation of blood-brain barrier and a decrease in the expression of S100 protein may be an important mechanism by means of which MB improves neurological outcome. Our data demonstrate that MB can be a very promising pharmacological compound with neuroprotective properties for TBI treatment.

Role of Mitophagy in Cardiovascular Disease

Cardiovascular disease is the leading cause of mortality worldwide, and mitochondrial dysfunction is the primary contributor to these disorders. Recent studies have elaborated on selective autophagy-mitophagy, which eliminates damaged and dysfunctional mitochondria, stabilizes mitochondrial structure and function, and maintains cell survival and growth. Numerous recent studies have reported that mitophagy plays an important role in the pathogenesis of various cardiovascular diseases. This review summarizes the mechanisms underlying mitophagy and advancements in studies on the role of mitophagy in cardiovascular disease.

Therapeutic use of extracellular mitochondria in CNS injury and disease

In the central nervous system (CNS), neuronal functionality is highly dependent on mitochondrial integrity and activity. In the context of a damaged or diseased brain, mitochondrial dysfunction leads to reductions in ATP levels, thus impairing ATP-dependent neural firing and neurotransmitter dynamics. Restoring mitochondrial ability to generate ATP may be a basic premise to restore neuronal functionality. Recently, emerging data in rodent and human studies suggest that mitochondria and its components are surprisingly released into extracellular space and potentially transferred between cells. Transferred mitochondria may support oxidative phosphorylation in recipient cells. In this mini-review, we (a) survey recent findings in cell to cell mitochondrial transfer and the presence of cell-free extracellular mitochondria and its components, (b) review experimental details of how to detect extracellular mitochondria and mitochondrial transfer in the CNS, (c) discuss strategies and tissue sources for mitochondria isolation, and (d) explore exogenous mitochondrial transplantation as a novel approach for CNS therapies.

Astragaloside IV Protects Primary Cerebral Cortical Neurons from Oxygen and Glucose Deprivation/Reoxygenation by Activating the PKA/CREB Pathway

Stroke is one of the major leading causes of death and disability worldwide, and post-stroke cognitive impairment is a major contributor to this disability. Astragaloside IV (AST-IV) is a primary bioactive compound of Radix Astragali, which is widely used in traditional Chinese medicine to treat stroke. AST-IV was found to possess cognition-enhancing properties against ischemic stroke; however, the mechanisms underlying this effect remain largely elusive. Mitochondrial health is critical to cell viability after ischemic injury. Cyclic AMP response element-binding protein (CREB) is a transcription factor that can be activated by protein kinase A (PKA) to preserve mitochondria, regulate memory and cognitive functions. We used an in vitro model of ischemic injury via oxygen and glucose deprivation (OGD) of cultured neurons, which led to PKA inactivation and decreased CREB phosphorylation, reduced cell viability, and increased neuronal apoptosis. We hypothesized that AST-IV could protect OGD-exposed cerebral cortical neurons by modulating the PKA/CREB signaling pathway and preserving mitochondrial function. We found that the mitochondrial and cellular injuries induced by OGD were reversed following treatment with AST-IV. The activity of neuronal mitochondria was evaluated by measuring the mitochondrial potential and the levels of reactive oxygen species (ROS) and adenosine triphosphate (ATP). AST-IV significantly enhanced PKA and CREB phosphorylation and prevented OGD-induced mitochondrial dysfunction, thereby protecting neurons exposed to OGD from injury and death. Furthermore, the effects of AST-IV were partially blocked by a PKA inhibitor. Collectively, these data elucidated the molecular mechanisms underlying the protective effects of AST-IV against ischemic injury in cortical neurons.

Brain Functional Reserve in the Context of Neuroplasticity after Stroke

Stroke is the second cause of death and more importantly first cause of disability in people over 40 years of age. Current therapeutic management of ischemic stroke does not provide fully satisfactory outcomes. Stroke management has significantly changed since the time when there were opened modern stroke units with early motor and speech rehabilitation in hospitals. In recent decades, researchers searched for biomarkers of ischemic stroke and neuroplasticity in order to determine effective diagnostics, prognostic assessment, and therapy. Complex background of events following ischemic episode hinders successful design of effective therapeutic strategies. So far, studies have proven that regeneration after stroke and recovery of lost functions may be assigned to neuronal plasticity understood as ability of brain to reorganize and rebuild as an effect of changed environmental conditions. As many neuronal processes influencing neuroplasticity depend on expression of particular genes and genetic diversity possibly influencing its effectiveness, knowledge on their mechanisms is necessary to understand this process. Epigenetic mechanisms occurring after stroke was briefly discussed in this paper including several mechanisms such as synaptic plasticity; neuro-, glio-, and angiogenesis processes; and growth of axon.

Protective Effect of Anthocyanin on Neurovascular Unit in Cerebral Ischemia/Reperfusion Injury in Rats

Treating cerebral ischemia continues to be a clinical challenge. Studies have shown that the neurovascular unit (NVU), as the central structural basis, plays a key role in cerebral ischemia. Here, we report that anthocyanin, a safe and natural antioxidant, could inhibit apoptosis and inflammation to protect NVU in rats impaired by middle cerebral artery occlusion/reperfusion (MCAO/R). Administration of anthocyanin significantly reduced infarct volume and neurological scores in MCAO/R rats. Anthocyanin could also markedly ameliorate cerebral edema and reduce the concentration of Evans blue (EB) by inhibiting MMP-9. Moreover, anthocyanin alleviated apoptotic injury resulting from MCAO/R through the regulation of Bcl-2 family proteins. The levels of inflammation-related molecules including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), which were over-expressed with MCAO/R, were decreased by anthocyanin. In addition, Nuclear factor-kappa B (NF-κB) and the NLRP3 inflammasome pathway might be involved in the anti-inflammatory effect of anthocyanin. In conclusion, anthocyanin could protect the NVU through multiple pathways, and play a protective role in cerebral ischemia/reperfusion injury.

Mitophagy, a potential therapeutic target for stroke

Mitochondria autophagy, termed as mitophagy, is a mechanism of specific autophagic elimination of mitochondria. Mitophagy controls the quality and the number of mitochondria, eliminating dysfunctional or excessive mitochondria that can generate reactive oxygen species (ROS) and cause cell death. Mitochondria are centrally implicated in neuron and tissue injury after stroke, due to the function of supplying adenosine triphosphate (ATP) to the tissue, regulating oxidative metabolism during the pathologic process, and contribution to apoptotic cell death after stroke. As a catabolic mechanism, mitophagy links numbers of a complex network of mitochondria, and affects mitochondrial dynamic process, fusion and fission, reducing mitochondrial production of ROS, mediated by the mitochondrial permeability transition pore (MPTP). The precise nature of mitophagy’s involvement in stroke, and its underlying molecular mechanisms, have yet to be fully clarified. This review aims to provide a comprehensive overview of the integration of mitochondria with mitophagy, also to introduce and discuss recent advances in the understanding of the potential role, and possible signaling pathway, of mitophagy in the pathological processes of both hemorrhagic and ischemic stroke. The author also provides evidence to explain the dual role of mitophagy in stroke.

Tetrahydrocurcumin epigenetically mitigates mitochondrial dysfunction in brain vasculature during ischemic stroke

The objectives of this study are to identify the mechanism of mitochondrial dysfunction during cerebral ischemic/reperfusion (I/R) injury and the therapeutic potential of tetrahydrocurcumin (THC) to mitigate mitochondrial dysfunction in experimental stroke model. In our study, 8-10 weeks old male C57BL/6 wild-type mice were subjected to middle cerebral artery occlusion (MCAO) for 40 min, followed by reperfusion for 72 h. THC (25mg/kg-BW/day) was injected intraperitoneally once daily for 3 days after 4 h of ischemia. The experimental groups were: (i) sham, (ii) I/R and (iii) I/R + THC. We noticed that THC treatment in ischemic mice significantly improved the functional capacity and motor co-ordination along with reduced neuroscore, infarct volume, brain edema and microvascular leakage in brain parenchyma. The study revealed that level of total homocysteine (tHcy), homocysteine metabolizing enzymes, mitochondrial oxidative stress were significantly altered in I/R mice compared to sham. We also observed alteration in mitochondrial transition pore, ATP production and O₂ consumption in the ischemic brain as compared to sham. Further, elevated matrix metalloproteinases-9 (MMP-9) activity and reduced tight junction protein expressions intensified the brain vascular impairment in I/R mice compared to sham. Interestingly, we found that levels of mitophagy markers, fusion and fission proteins were significantly altered. However THC treatment in I/R mice almost normalized the above functional and molecular changes. Mechanistic study demonstrated that DNA Methyltransferase 1 (DNMT1) expression was higher and was associated with reduced mitochondrial tissue inhibitor of metalloproteinases 2 (TIMP-2) expression through hyper-methylation of CpG island of TIMP-2 promoter in I/R mice compared to sham. However, administration of epigenetic inhibitor, 5-Azacytidine (5-Aza) abrogated I/R induced hyper-methylation of TIMP-2 promoter and maintaining the extracellular matrix (ECM) integrity. In conclusion, this study suggests that THC epigenetically ameliorates mitochondrial dysfunction in brain vasculature during Ischemic Stroke.

Mitochondrial Dysfunction in Stroke: Implications of Stem Cell Therapy

Stroke is a debilitating condition which is also the second leading cause of death and disability worldwide. Despite the benefits and promises shown by numerous neuroprotective agents in animal stroke models, their clinical translation has not been a complete success. Hence, search for treatment options have directed researchers towards utilising stem cells. Mitochondria has a major involvement in the pathophysiology of stroke and a number of other conditions. Stem cells have shown the ability to transfer mitochondria to the damaged cells and to help revive cell energetics in the recipient cell. The present review discusses how stem cells could be employed to protect neurons and mitochondria in stroke and also the various mechanisms involved in neuroprotection.

Tau pathology and neurochemical changes associated with memory dysfunction in an optimised murine model of global cerebral ischaemia - A potential model for vascular dementia?

Cerebral ischemia is known to be a major cause of death and the later development of Alzheimer's disease and vascular dementia. However, ischemia induced cellular damage that initiates these diseases remain poorly understood. This is primarily due to lack of clinically relevant models that are highly reproducible. Here, we have optimised a murine model of global cerebral ischaemia with multiple markers to determine brain pathology, neurochemistry and correlated memory deficits in these animals. Cerebral ischaemia in mice was induced by bilateral common carotid artery occlusion. Following reperfusion, the mice were either fixed with 4% paraformaldehyde or decapitated under anaesthesia. Brains were processed for Western blotting or immunohistochemistry for glial (GLT1) and vesicular (VGLUT1, VGLUT2) glutamate transporters and paired helical filament (PHF1) tau. The PHF1 tau is the main component of neurofibrillary tangle, which is the pathological hallmark of Alzheimer's disease and vascular dementia. The novel object recognition behavioural assay was used to investigate the functional cognitive consequences in these mice. The results show consistent and selective neuronal and glial cell changes in the hippocampus and the cortex together with significant reductions in GLT1 (***P < 0.001), VGLUT1 (**P < 0.01) and VGLUT2 (***P < 0.001) expressions in the hippocampus in occluded mice as compared to sham-operated animals. These changes are associated with increased PHF1 (***P < 0.0001) protein and a significant impairment of performance (*p < 0.0006, N = 6/group) in the novel object recognition test. This model represents a useful tool for investigating cellular, biochemical and molecular mechanisms of global cerebral ischaemia and may be an ideal preclinical model for vascular dementia.

Oncotic Cell Death in Stroke

Oncotic cell death or oncosis represents a major mechanism of cell death in ischaemic stroke, occurring in many central nervous system (CNS) cell types including neurons, glia and vascular endothelial cells. In stroke, energy depletion causes ionic pump failure and disrupts ionic homeostasis. Imbalance between the influx of Na⁺ and Cl^- ions and the efflux of K⁺ ions through various channel proteins and transporters creates a transmembrane osmotic gradient, with ensuing movement of water into the cells, resulting in cell swelling and oncosis. Oncosis is a key mediator of cerebral oedema in ischaemic stroke, contributing directly through cytotoxic oedema, and indirectly through vasogenic oedema by causing vascular endothelial cell death and disruption of the blood-brain barrier (BBB). Hence, inhibition of uncontrolled ionic flux represents a novel and powerful strategy in achieving neuroprotection in stroke. In this review, we provide an overview of oncotic cell death in the pathology of stroke. Importantly, we summarised the therapeutically significant pathways of water, Na⁺, Cl^- and K⁺ movement across cell membranes in the CNS and their respective roles in the pathobiology of stroke.

Mesenchymal Stem Cell Therapy in Ischemic Stroke: A Meta-analysis of Preclinical Studies

Numerous preclinical studies have been carried out using mesenchymal stem cells (MSCs) therapy for ischemic stroke. The purpose of the present meta-analysis is to review the quality of preclinical studies. In all, 4,361 articles were identified, out of which 64 studies were included (excluding in vitro studies). The results were obtained across species, route, and time of administration, immunogenicity, and doses. The median quality score 4.90/10, confidence interval 95%, and large effect size were observed, which strongly supports the translation potential of MSC therapy for ischemic stroke.

Targeting mitochondrial dysfunction in CNS injury using Methylene Blue; still a magic bullet?

Complex, multi-factorial secondary injury cascades are initiated following traumatic brain injury, which makes this a difficult disease to treat. The secondary injury cascades following the primary mechanical tissue damage, are likely where effective therapeutic interventions may be targeted. One promising therapeutic target following brain injury are mitochondria. Mitochondria are complex organelles found within the cell, which act as powerhouses within all cells by supplying ATP. These organelles are also necessary for calcium cycling, redox signaling and play a major role in the initiation of cell death pathways. When mitochondria become dysfunctional, there is a tendency for the cell to loose cellular homeostasis and can lead to eventual cell death. Targeting of mitochondrial dysfunction in various diseases has proven a successful approach, lending support to mitochondria as a pivotal player in TBI cell death and loss of behavioral function. Within this mixed mini review/research article there will be a general discussion of mitochondrial bioenergetics, followed by a brief discussion of traumatic brain injury and how mitochondria play an integral role in the neuropathological sequelae following an injury. We will also give an overview of one relatively new TBI therapeutic approach, Methylene Blue, currently being studied to ameliorate mitochondrial dysfunction following brain injury. We will also present novel experimental findings, that for the first time, characterize the ex vivo effect of Methylene Blue on mitochondrial function in synaptic and non-synaptic populations of mitochondria.

Laser Acupuncture at GV20 Improves Brain Damage and Oxidative Stress in Animal Model of Focal Ischemic Stroke

The burden of stroke is high and is continually increasing due to a dramatic growth in the world's elderly population. Novel therapeutic strategies are therefore required. The present study sought to determine the effect of laser acupuncture at GV20 on brain damage, oxidative-status markers in the cerebral cortex, and superoxide dismutase in the mitochondria of an animal model of focal ischemic stroke. Wistar rats, weighing 300-350 g, were divided into the following four groups: (1) control; (2) permanent occlusion of the right middle cerebral artery (Rt.MCAO) alone; (3) Rt.MCAO plus sham laser acupuncture; and (4) Rt.MCAO plus laser-acupuncture groups. Sham laser acupuncture or laser acupuncture was performed once daily at the GV20 (Baihui) acupoint for 14 days following Rt.MCAO. Half of the rats in each group were examined by 2,3,5-triphenyltetrazolium chloride staining to determine the brain infarct volume, while the other half were examined by biochemical assays to determine the malondialdehyde level, and the glutathione peroxidase, catalase, and superoxide-dismutase activities in the brain-cortex mitochondria. The results showed that laser acupuncture at GV20 significantly decreased the brain infarct volume and malondialdehyde level, and increased the catalase, glutathione peroxidase, and superoxide-dismutase activities in cerebral ischemic rats. In conclusion, laser acupuncture at GV20 decreases the brain infarct volume in cerebral ischemic rats, at least in part due to decreased oxidative stress. Further study is warranted to investigate other possible underlying mechanisms.

Methylene blue improves mitochondrial respiration and decreases oxidative stress in a substrate-dependent manner in diabetic rat hearts

Diabetic cardiomyopathy has been systematically associated with compromised mitochondrial energetics and increased generation of reactive oxygen species (ROS) that underlie its progression to heart failure. Methylene blue is a redox drug with reported protective effects mainly on brain mitochondria. The purpose of the present study was to characterize the effects of acute administration of methylene blue on mitochondrial respiration, H₂O₂ production, and calcium sensitivity in rat heart mitochondria isolated from healthy and 2 months (streptozotocin-induced) diabetic rats. Mitochondrial respiratory function was assessed by high-resolution respirometry. H₂O₂ production and calcium retention capacity were measured spectrofluorimetrically. The addition of methylene blue (0.1 μmol·L^-1) elicited an increase in oxygen consumption of mitochondria energized with complex I and II substrates in both normal and diseased mitochondria. Interestingly, methylene blue elicited a significant increase in H₂O₂ release in the presence of complex I substrates (glutamate and malate), but had an opposite effect in mitochondria energized with complex II substrate (succinate). No changes in the calcium retention capacity of healthy or diabetic mitochondria were found in the presence of methylene blue. In conclusion, in cardiac mitochondria isolated from diabetic and nondiabetic rat hearts, methylene blue improved respiratory function and elicited a dichotomic, substrate-dependent effect on ROS production.

Comparison of Neuroprotective Effect of Bevacizumab and Sildenafil following Induction of Stroke in a Mouse Model

To evaluate the effect of bevacizumab and sildenafil on stroke parameters in a mouse model, middle cerebral artery occlusion was induced in male C57Bl/6 mice using an intra-arterial filament method. The filament was removed after 60 minutes, and the mice were immediately given a single intraperitoneal injection of saline, bevacizumab, or sildenafil. An additional group of mice (n = 7) received bevacizumab 6 h after MCAO induction. The mice were euthanized 24 hours later and evaluated for infarct area and brain edema using triphenyltetrazolium chloride staining and ImageJ. In the saline-treated mice (n = 16), total stroke volume was 19.20 ± 6.38 mm³, mean penumbra area was 4.5 ± 2.03 mm³, and hemispheric asymmetry was 106.5%. Corresponding values in the bevacizumab group (n = 19) were 17.79 ± 5.80 mm³, 7.3 ± 3.5 mm³, and 108.6%; in the delayed (6 h) bevacizumab injected mice (n = 7) they were 9.80 ± 8.00 mm³, 2.4 ± 2.0 mm³, and 98.2%; and in the sildenafil group (n = 16) they were 18.42 ± 5.41 mm³, 5.7 ± 2.02 mm³, and 109.9%. The bevacizumab group had a significantly larger mean penumbra area when given immediately and smaller total stroke area in both groups than the saline- (p = 0.03) and sildenafil-treated (p = 0.003) groups. Only delayed bevacizumab group had reduced edema. Bevacizumab, injected immediately or delayed after injury, exerts a neuroprotective/salvage effect, whereas immediate treatment with sildenafil does not. Inflammation may play a role in the neuroprotective effect.

SIRT3 Deacetylates Ceramide Synthases: IMPLICATIONS FOR MITOCHONDRIAL DYSFUNCTION AND BRAIN INJURY

Experimental evidence supports the role of mitochondrial ceramide accumulation as a cause of mitochondrial dysfunction and brain injury after stroke. Herein, we report that SIRT3 regulates mitochondrial ceramide biosynthesis via deacetylation of ceramide synthase (CerS) 1, 2, and 6. Reciprocal immunoprecipitation experiments revealed that CerS1, CerS2, and CerS6, but not CerS4, are associated with SIRT3 in cerebral mitochondria. Furthermore, CerS1, -2, and -6 are hyperacetylated in the mitochondria of SIRT3-null mice, and SIRT3 directly deacetylates the ceramide synthases in a NAD(+)-dependent manner that increases enzyme activity. Investigation of the SIRT3 role in mitochondrial response to brain ischemia/reperfusion (IR) showed that SIRT3-mediated deacetylation of ceramide synthases increased enzyme activity and ceramide accumulation after IR. Functional studies demonstrated that absence of SIRT3 rescued the IR-induced blockade of the electron transport chain at the level of complex III, attenuated mitochondrial outer membrane permeabilization, and decreased reactive oxygen species generation and protein carbonyls in mitochondria. Importantly, Sirt3 gene ablation reduced the brain injury after IR. These data support the hypothesis that IR triggers SIRT3-dependent deacetylation of ceramide synthases and the elevation of ceramide, which could inhibit complex III, leading to increased reactive oxygen species generation and brain injury. The results of these studies highlight a novel mechanism of SIRT3 involvement in modulating mitochondrial ceramide biosynthesis and suggest an important role of SIRT3 in mitochondrial dysfunction and brain injury after experimental stroke.

ConnectViz: Accelerated Approach for Brain Structural Connectivity Using Delaunay Triangulation

Stroke is a cardiovascular disease with high mortality and long-term disability in the world. Normal functioning of the brain is dependent on the adequate supply of oxygen and nutrients to the brain complex network through the blood vessels. Stroke, occasionally a hemorrhagic stroke, ischemia or other blood vessel dysfunctions can affect patients during a cerebrovascular incident. Structurally, the left and the right carotid arteries, and the right and the left vertebral arteries are responsible for supplying blood to the brain, scalp and the face. However, a number of impairment in the function of the frontal lobes may occur as a result of any decrease in the flow of the blood through one of the internal carotid arteries. Such impairment commonly results in numbness, weakness or paralysis. Recently, the concepts of brain's wiring representation, the connectome, was introduced. However, construction and visualization of such brain network requires tremendous computation. Consequently, previously proposed approaches have been identified with common problems of high memory consumption and slow execution. Furthermore, interactivity in the previously proposed frameworks for brain network is also an outstanding issue. This study proposes an accelerated approach for brain connectomic visualization based on graph theory paradigm using compute unified device architecture, extending the previously proposed SurLens Visualization and computer aided hepatocellular carcinoma frameworks. The accelerated brain structural connectivity framework was evaluated with stripped brain datasets from the Department of Surgery, University of North Carolina, Chapel Hill, USA. Significantly, our proposed framework is able to generate and extract points and edges of datasets, displays nodes and edges in the datasets in form of a network and clearly maps data volume to the corresponding brain surface. Moreover, with the framework, surfaces of the dataset were simultaneously displayed with the nodes and the edges. The framework is very efficient in providing greater interactivity as a way of representing the nodes and the edges intuitively, all achieved at a considerably interactive speed for instantaneous mapping of the datasets' features. Uniquely, the connectomic algorithm performed remarkably fast with normal hardware requirement specifications.

An introduction to the roles of purinergic signalling in neurodegeneration, neuroprotection and neuroregeneration

Purinergic signalling appears to play important roles in neurodegeneration, neuroprotection and neuroregeneration. Initially there is a brief summary of the background of purinergic signalling, including release of purines and pyrimidines from neural and non-neural cells and their ectoenzymatic degradation, and the current characterisation of P1 (adenosine), and P2X (ion channel) and P2Y (G protein-coupled) nucleotide receptor subtypes. There is also coverage of the localization and roles of purinoceptors in the healthy central nervous system. The focus is then on the roles of purinergic signalling in trauma, ischaemia, stroke and in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's diseases, as well as multiple sclerosis and amyotrophic lateral sclerosis. Neuroprotective mechanisms involving purinergic signalling are considered and its involvement in neuroregeneration, including the role of adult neural stem/progenitor cells. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

ConnectViz: Accelerated approach for brain structural connectivity using Delaunay triangulation

Stroke is a cardiovascular disease with high mortality and long-term disability in the world. Normal functioning of the brain is dependent on the adequate supply of oxygen and nutrients to the brain complex network through the blood vessels. Stroke, occasionally a hemorrhagic stroke, ischemia or other blood vessel dysfunctions can affect patients during a cerebrovascular incident. Structurally, the left and the right carotid arteries, and the right and the left vertebral arteries are responsible for supplying blood to the brain, scalp and the face. However, a number of impairment in the function of the frontal lobes may occur as a result of any decrease in the flow of the blood through one of the internal carotid arteries. Such impairment commonly results in numbness, weakness or paralysis. Recently, the concepts of brain's wiring representation, the connectome, was introduced. However, construction and visualization of such brain network requires tremendous computation. Consequently, previously proposed approaches have been identified with common problems of high memory consumption and slow execution. Furthermore, interactivity in the previously proposed frameworks for brain network is also an outstanding issue. This study proposes an accelerated approach for brain connectomic visualization based on graph theory paradigm using Compute Unified Device Architecture (CUDA), extending the previously proposed SurLens Visualization and Computer Aided Hepatocellular Carcinoma (CAHECA) frameworks. The accelerated brain structural connectivity framework was evaluated with stripped brain datasets from the Department of Surgery, University of North Carolina, Chapel Hill, United States. Significantly, our proposed framework is able to generates and extracts points and edges of datasets, displays nodes and edges in the datasets in form of a network and clearly maps data volume to the corresponding brain surface. Moreover, with the framework, surfaces of the dataset were simultaneously displayed with the nodes and the edges. The framework is very efficient in providing greater interactivity as a way of representing the nodes and the edges intuitively, all achieved at a considerably interactive speed for instantaneous mapping of the datasets' features. Uniquely, the connectomic algorithm performed remarkably fast with normal hardware requirement specifications.

Mitochondrial Targeted Antioxidant in Cerebral Ischemia

There has been much evidence suggesting that reactive oxygen species (ROS) generated in mitochondria during cerebral ischemia play a major role in programming the senescence of organism. Antioxidants dealing with mitochondria slow down the appearance and progression of symptoms in cerebral ischemia and increase the life span of organisms. The mechanisms of mitochondrial targeted antioxidants, such as SKQ1, Coenzyme Q10, MitoQ, and Methylene blue, include increasing adenosine triphosphate (ATP) production, decreasing production of ROS and increasing antioxidant defenses, providing benefits in neuroprotection following cerebral ischemia. A number of studies have shown the neuroprotective role of these mitochondrial targeted antioxidants in cerebral ischemia. Here in this short review we have compiled the literature supporting consequences of mitochondrial dysfunction, and the protective role of mitochondrial targeted antioxidants.