Glutamate as a potential "survival factor" in an in vitro model of neuronal hypoxia/reoxygenation injury: leading role of the Na+/Ca2+ exchanger

EAAT3 impedes oligodendrocyte remyelination in chronic cerebral hypoperfusion-induced white matter injury

BACKGROUND

Chronic cerebral hypoperfusion-induced demyelination causes progressive white matter injury, although the pathogenic pathways are unknown.

METHODS

The Single Cell Portal and PanglaoDB databases were used to analyze single-cell RNA sequencing experiments to determine the pattern of EAAT3 expression in CNS cells. Immunofluorescence (IF) was used to detect EAAT3 expression in oligodendrocytes and oligodendrocyte progenitor cells (OPCs). EAAT3 levels in mouse brains were measured using a western blot at various phases of development, as well as in traumatic brain injury (TBI) and intracerebral hemorrhage (ICH) mouse models. The mouse bilateral carotid artery stenosis (BCAS) model was used to create white matter injury. IF, Luxol Fast Blue staining, and electron microscopy were used to investigate the effect of remyelination. 5-Ethynyl-2-Deoxy Uridine staining, transwell chamber assays, and IF were used to examine the effects of OPCs' proliferation, migration, and differentiation in vivo and in vitro. The novel object recognition test, the Y-maze test, the rotarod test, and the grid walking test were used to examine the impact of behavioral modifications.

RESULTS

A considerable amount of EAAT3 was expressed in OPCs and mature oligodendrocytes, according to single-cell RNA sequencing data. During multiple critical phases of mouse brain development, there were no substantial changes in EAAT3 levels in the hippocampus, cerebral cortex, or white matter. Furthermore, neither the TBI nor ICH models significantly affected the levels of EAAT3 in the aforementioned brain areas. The chronic white matter injury caused by BCAS, on the other hand, resulted in a strikingly high level of EAAT3 expression in the oligodendroglia and white matter. Correspondingly, blocking EAAT3 assisted in the recovery of cognitive and motor impairment as well as the restoration of cerebral blood flow following BCAS. Furthermore, EAAT3 suppression was connected to improved OPCs' survival and proliferation in vivo as well as faster OPCs' proliferation, migration, and differentiation in vitro. Furthermore, this study revealed that the mTOR pathway is implicated in EAAT3-mediated remyelination.

CONCLUSIONS

Our findings provide the first evidence that abnormally high levels of oligodendroglial EAAT3 in chronic cerebral hypoperfusion impair OPCs' pro-remyelination actions, hence impeding white matter repair and functional recovery. EAAT3 inhibitors could be useful in the treatment of ischemia demyelination.

Exploring the Role of NCX1 and NCX3 in an In Vitro Model of Metabolism Impairment: Potential Neuroprotective Targets for Alzheimer's Disease

Alzheimer's disease (AD) is a widespread neurodegenerative disorder, affecting a large number of elderly individuals worldwide. Mitochondrial dysfunction, metabolic alterations, and oxidative stress are regarded as cooperating drivers of the progression of AD. In particular, metabolic impairment amplifies the production of reactive oxygen species (ROS), resulting in detrimental alterations to intracellular Ca²⁺ regulatory processes. The Na⁺/Ca²⁺ exchanger (NCX) proteins are key pathophysiological determinants of Ca²⁺ and Na⁺ homeostasis, operating at both the plasma membrane and mitochondria levels. Our study aimed to explore the role of NCX1 and NCX3 in retinoic acid (RA) differentiated SH-SY5Y cells treated with glyceraldehyde (GA), to induce impairment of the default glucose metabolism that typically precedes Aβ deposition or Tau protein phosphorylation in AD. By using an RNA interference-mediated approach to silence either NCX1 or NCX3 expression, we found that, in GA-treated cells, the knocking-down of NCX3 ameliorated cell viability, increased the intracellular ATP production, and reduced the oxidative damage. Remarkably, NCX3 silencing also prevented the enhancement of Aβ and pTau levels and normalized the GA-induced decrease in NCX reverse-mode activity. By contrast, the knocking-down of NCX1 was totally ineffective in preventing GA-induced cytotoxicity except for the increase in ATP synthesis. These findings indicate that NCX3 and NCX1 may differently influence the evolution of AD pathology fostered by glucose metabolic dysfunction, thus providing a potential target for preventing AD.

Rapidly Inhibiting the Inflammatory Cytokine Storms and Restoring Cellular Homeostasis to Alleviate Sepsis by Blocking Pyroptosis and Mitochondrial Apoptosis Pathways

Pyroptosis, systemic inflammation, and mitochondrial apoptosis are the three primary contributors to sepsis's multiple organ failure, the ultimate cause of high clinical mortality. Currently, the drugs under development only target a single pathogenesis, which is obviously insufficient. In this study, an acid-responsive hollow mesoporous polydopamine (HMPDA) nanocarrier that is highly capable of carrying both the hydrophilic drug NAD⁺ and the hydrophobic drug BAPTA-AM, with its outer layer being sealed by the inflammatory targeting peptide PEG-LSA, is developed. Once targeted to the region of inflammation, HMPDA begins depolymerization, releasing the drugs NAD⁺ and BAPTA-AM. Depletion of polydopamine on excessive reactive oxygen species production, promotion of ATP production and anti-inflammation by NAD⁺ replenishment, and chelation of BAPTA (generated by BA-AM hydrolysis) on overloaded Ca²⁺ can comprehensively block the three stages of sepsis, i.e., precisely inhibit the activation of pyroptosis pathway (NF-κB-NLRP3-ASC-Casp-1), inflammation pathway (IL-1β, IL-6, and TNF-α), and mitochondrial apoptosis pathway (Bcl-2/Bax-Cyt-C-Casp-9-Casp-3), thereby restoring intracellular homeostasis, saving the cells in a state of "critical survival," further reducing LPS-induced systemic inflammation, finally restoring the organ functions. In conclusion, the synthesis of this agent provides a simple and effective synergistic drug delivery nanosystem, which demonstrates significant therapeutic potential in a model of LPS-induced sepsis.

Mitochondrial oxidative stress in brain microvascular endothelial cells: Triggering blood-brain barrier disruption

Blood-brain barrier disruption plays an important role in central nervous system diseases. This review provides information on the role of mitochondrial oxidative stress in brain microvascular endothelial cells in cellular dysfunction, the disruption of intercellular junctions, transporter dysfunction, abnormal angiogenesis, neurovascular decoupling, and the involvement and aggravation of vascular inflammation and illustrates related molecular mechanisms. In addition, recent drug and nondrug therapies targeting cerebral vascular endothelial cell mitochondria to repair the blood-brain barrier are discussed. This review shows that mitochondrial oxidative stress disorder in brain microvascular endothelial cells plays a key role in the occurrence and development of blood-brain barrier damage and may be critical in various pathological mechanisms of blood-brain barrier damage. These new findings suggest a potential new strategy for the treatment of central nervous system diseases through mitochondrial modulation of cerebral vascular endothelial cells.

The hepato-protective effect of H2S-modified and non-modified mesenchymal stem cell exosomes on liver ischemia-reperfusion injury in mice: The role of MALAT1

INTRODUCTION

Ischemia-reperfusion injury (IRI) by causing histopathological changes is considered one of the most important causes of liver failure and dysfunction after surgery which affect graft outcomes. Stem cells are new promising approaches to treating different diseases. One of the critical strategies to improve their function is the preconditioning of their culture medium. This study compared the effect of NaHS-modified and non-modified mesenchymal stem cell exosomes on liver ischemia-reperfusion injury in mice.

METHODS

Human umbilical cord-derived MSC (MSC) cultured in a 75 cm3 flask and when confluency reached about 80%, the culture medium replaced with a serum-free medium, and 48 h later supernatants collected, concentrated, and then MSC-Exo extracted. To obtain H2S-Exo, MSC was treated with NaHS (1 μmol),the supernatant collected after 48 h, concentrated and exosomes extracted. Twenty-four male mice were randomly divided into four groups (n = 6) including: 1-ischemia, 2-sham-operated, 3- MSC-Exo, and 4- H2S-Exo. To induce ischemia, the hepatic artery and portal vein clamped using an atraumatic clip for 60 min followed by 3 h of reperfusion. Just upon ending the time of ischemia (removal of clamp artery), animals in MSC-Exo, and H2S-Exo groups received 100 μg exosomes in 100 μl PBS via tail vein. At the end of reperfusion, blood, and liver samples were collected for further serological, molecular, and histological analyses.

RESULTS

Administration of both MSC-Exo and H2S-Exo improved liver function by reducing inflammatory cytokines, cellular apoptosis, liver levels of total oxidant status, and liver aminotransferases. The results showed that protecting effect of MSC exosomes enhanced following NaHS preconditioning of cell culture medium.

CONCLUSION

MSC-Exo and H2S-Exo had hepato-protective effects against injuries induced by ischemia-reperfusion in mice. NaHS preconditioning of mesenchymal stem cells could enhance the therapeutic effects of MSC-derived exosomes.

Calcium signaling in neurodevelopment and pathophysiology of autism spectrum disorders

BACKGROUND

Autism spectrum disorder (ASD) covers a group of neurodevelopmental disorders with complex genetic background. Several genetic mutations, epigenetic alterations, copy number variations and single nucleotide polymorphisms have been reported that cause ASD or modify its phenotype. Among signaling pathways that influence pathogenesis of ASD, calcium signaling has a prominent effect.

METHODS

We searched PubMed and Google Scholar databases with key words "Calcium signaling" and "Autism spectrum disorder".

CONCLUSION

This type of signaling has essential roles in the cell physiology. Endoplasmic reticulum and mitochondria are the key organelles involved in this signaling. It is vastly accepted that organellar disorders intensely influence the central nervous system (CNS). Several lines of evidence indicate alterations in the function of calcium channels in polygenic disorders affecting CNS. In the current review, we describe the role of calcium signaling in normal function of CNS and pathophysiology of ASD.

Control of Ca2+ and metabolic homeostasis by the Na+/Ca2+ exchangers (NCXs) in health and disease

Spatial and temporal control of calcium (Ca²⁺) levels is essential for the background rhythms and responses of living cells to environmental stimuli. Whatever other regulators a given cellular activity may have, localized and wider scale Ca²⁺ events (sparks, transients, and waves) are hierarchical determinants of fundamental processes such as cell contraction, excitability, growth, metabolism and survival. Different cell types express specific channels, pumps and exchangers to efficiently generate and adapt Ca²⁺ patterns to cell requirements. The Na⁺/Ca²⁺ exchangers (NCXs) in particular contribute to Ca²⁺ homeostasis by buffering intracellular Ca²⁺ loads according to the electrochemical gradients of substrate ions - i.e., Ca²⁺ and sodium (Na⁺) - and under a dynamic control of redundant regulatory processes. An interesting feature of NCX emerges from the strict relationship that connects transporter activity with cell metabolism: on the one hand NCX operates under constant control of ATP-dependent regulatory processes, on the other hand the ion fluxes generated through NCX provide mechanistic support for the Na⁺-driven uptake of glutamate and Ca²⁺ influx to fuel mitochondrial respiration. Proof of concept evidence highlights therapeutic potential of preserving a timed and balanced NCX activity in a growing rate of diseases (including excitability, neurodegenerative, and proliferative disorders) because of an improved ability of stressed cells to safely maintain ion gradients and mitochondrial bioenergetics. Here, we will summarize and review recent works that have focused on the pathophysiological roles of NCXs in balancing the two-way relationship between Ca²⁺ signals and metabolism.

Biomarkers of Oxidative Stress Tethered to Cardiovascular Diseases

Cardiovascular disease (CVD) is a broad term that incorporated a group of conditions that affect the blood vessels and the heart. CVD is a foremost cause of fatalities around the world. Multiple pathophysiological mechanisms are involved in CVD; however, oxidative stress plays a vital role in generating reactive oxygen species (ROS). Oxidative stress occurs when the concentration of oxidants exceeds the potency of antioxidants within the body while producing reactive nitrogen species (RNS). ROS generated by oxidative stress disrupts cell signaling, DNA damage, lipids, and proteins, thereby resulting in inflammation and apoptosis. Mitochondria is the primary source of ROS production within cells. Increased ROS production reduces nitric oxide (NO) bioavailability, which elevates vasoconstriction within the arteries and contributes to the development of hypertension. ROS production has also been linked to the development of atherosclerotic plaque. Antioxidants can decrease oxidative stress in the body; however, various therapeutic drugs have been designed to treat oxidative stress damage due to CVD. The present review provides a detailed narrative of the oxidative stress and ROS generation with a primary focus on the oxidative stress biomarker and its association with CVD. We have also discussed the complex relationship between inflammation and endothelial dysfunction in CVD as well as oxidative stress-induced obesity in CVD. Finally, we discussed the role of antioxidants in reducing oxidative stress in CVD.

Glutamate-aspartate transporter 1 attenuates oxygen-glucose deprivation-induced injury by promoting glutamate metabolism in primary cortical neurons

Ischemic stroke is a common cerebral disease. However, the treatment for the disease is limited. Daurian ground squirrel (GS; Spermophilus dauricus), a hibernating mammalian species, is highly tolerant to ischemia. In the present study, GS neurons in a non-hibernating state were found to be more resistant to oxygen-glucose deprivation (OGD), an ischemic model in vitro. We leveraged the differences in the endurance capacity of GS and rats to investigate the mechanisms of resistance to ischemia in GS neurons. We first identified glutamate-aspartate transporter 1 (GLAST) as a cytoprotective factor that contributed to tolerance against OGD injury of GS neurons. The expression of GLAST in GS neurons was much higher than that in rat neurons. Overexpression of GLAST rescued viability in rat neurons, and GS neurons exhibited decreased viability following GLAST knockdown under OGD conditions. Mechanistically, more glutamate was transported into neurons after GLAST overexpression and served as substrates for ATP production. Furthermore, eukaryotic transcription initiation factor 4E binding protein 1 was downregulated by GLAST to rescue neuronal viability. Our findings not only revealed an important molecular mechanism underlying the survival of hibernating mammals but also suggested that neuronal GLAST may be a potential target for ischemic stroke therapy.

SLC1A1-mediated cellular and mitochondrial influx of R-2-hydroxyglutarate in vascular endothelial cells promotes tumor angiogenesis in IDH1-mutant solid tumors

Mutant isocitrate dehydrogenase 1 (mIDH1) drives tumorigenesis via producing oncometabolite R-2-hydroxyglutarate (R-2-HG) across various tumor types. However, mIDH1 inhibitors appear only effective in hematological tumors. The therapeutic benefit in solid tumors remains elusive, likely due to the complex tumor microenvironment. In this study, we discover that R-2-HG produced by IDH1-mutant tumor cells is preferentially imported into vascular endothelial cells and remodels mitochondrial respiration to promote tumor angiogenesis, conferring a therapeutic vulnerability in IDH1-mutant solid tumors. Mechanistically, SLC1A1, a Na⁺-dependent glutamate transporter that is preferentially expressed in endothelial cells, facilitates the influx of R-2-HG from the tumor microenvironment into the endothelial cells as well as the intracellular trafficking of R-2-HG from cytoplasm to mitochondria. R-2-HG hijacks SLC1A1 to promote mitochondrial Na⁺/Ca²⁺ exchange, which activates the mitochondrial respiratory chain and fuels vascular endothelial cell migration in tumor angiogenesis. SLC1A1 deficiency in mice abolishes mIDH1-promoted tumor angiogenesis as well as the therapeutic benefit of mIDH1 inhibitor in solid tumors. Moreover, we report that HH2301, a newly discovered mIDH1 inhibitor, shows promising efficacy in treating IDH1-mutant cholangiocarcinoma in preclinical models. Together, we identify a new role of SLC1A1 as a gatekeeper of R-2-HG-mediated crosstalk between IDH1-mutant tumor cells and vascular endothelial cells, and demonstrate the therapeutic potential of mIDH1 inhibitors in treating IDH1-mutant solid tumors via disrupting R-2-HG-promoted tumor angiogenesis.

Knocking Down Peroxiredoxin 6 Aggravates Cerebral Ischemia-Reperfusion Injury by Enhancing Mitophagy

Cerebral ischemia-reperfusion injury (IRI) is caused by reperfusion following ischemia. Mitophagy is closely related to cerebral IRI. Mitophagy disorder or excess may be harmful and lead to neuronal apoptosis. Peroxiredoxin 6 (PRDX6) is an antioxidant protein and plays an important role in ischemic stroke. However, the relationship between PRDX6 and mitophagy is not clear at present. In order to explore and solve this problem. We have established a middle cerebral artery occlusion (MCAO) model of cerebral ischemia-reperfusion in SD rats and knockdown PRDX6 and PINK1 with lentivirus. Knocking down PRDX6 led to further aggravation of cerebral IRI. Our research found that knockdown PRDX6 increased the expression of mitophagy-related and apoptosis-related proteins. Knocking down PINK1 relieved mitophagy and apoptosis caused by knocking down PRDX6. In conclusion, knockdown of PRDX6 could aggravate cerebral IRI by enhancing PINK1/PARKIN pathway mediated mitophagy, and this effect could increase neuronal apoptosis.

A beneficial role for elevated extracellular glutamate in Amyotrophic Lateral Sclerosis and cerebral ischemia

This hypothesis proposes that increased extracellular glutamate in Amyotrophic Lateral Sclerosis (ALS) and cerebral ischemia, currently viewed as a trigger for excitotoxicity, is actually beneficial as it stimulates the utilization of glutamate as metabolic fuel. Renewed appreciation of glutamate oxidation by ischemic neurons has raised questions regarding the role of extracellular glutamate in ischemia. Is it detrimental, as suggested by excitotoxicity in early in vitro studies, or beneficial, as suggested by its oxidation in later in vivo studies? The answer may depend on the activity of N-methyl-D-aspartate (NMDA) glutamate receptors. Early in vitro procedures co-activated NMDA receptors (NMDARs) containing 2A (GluN2A) and 2B (GluN2B) subunits, an event now believed to trigger excitotoxicity; however, during in vivo ischemia D-serine and zinc molecules are released and these ensure only GluN2B receptors are stimulated. This not only prevents excitotoxicity but also initiates signaling cascades that allow ischemic neurons to import and oxidize glutamate.

Different Expressions of HIF-1α and Metabolism in Brain and Major Visceral Organs of Acute Hypoxic Mice

Hypoxia is associated with clinical diseases. Extreme hypoxia leads to multiple organs failure. However, the different effects of hypoxia on brain and visceral organs still need to be clarified, and moreover, characteristics in vulnerable organs suffering from hypoxia remain elusive. In the present study, we first aimed to figure out the hypoxic sensitivity of organs. Adult male mice were exposed to 6% O2 or 8% O2 for 6 h. Control mice were raised under normoxic conditions. In vivo and in vitro imaging of anti-HIF-1α-NMs-cy5.5 nanocomposites showed that the expression level of hypoxia-inducible factor (HIF-1α) was the highest in the liver, followed by kidney and brain. HIF-1α was detected in the hepatocytes of liver, distal convoluted tubules of kidney and neurons of cerebral cortex. The liver, kidney and brain showed distinct metabolic profiles but an identical change in glutamate. Compared with kidney and brain, the liver had more characteristic metabolites and more disturbed metabolic pathways related to glutaminolysis and glycolysis. The level of O-phosphocholine, GTP, NAD and aspartate were upregulated in hypoxic mice brain, which displayed significant positive correlations with the locomotor activity in control mice, but not in hypoxic mice with impaired locomotor activities. Taken together, the liver, kidney and brain are the three main organs of the body that are strongly respond to acute hypoxia, and the liver exhibited the highest hypoxic sensitivity. The metabolic disorders appear to underlie the physiological function changes.

Platelet Mitochondria Transplantation Rescues Hypoxia/Reoxygenation-Induced Mitochondrial Dysfunction and Neuronal Cell Death Involving the FUNDC2/PIP3/Akt/FOXO3a Axis

Mitochondrial transplantation emerges as a novel therapeutic solution for ischemia/reperfusion injury (IRI) in various tissues. Platelets have recently been used in mitochondrial transplantation as readily-available donors of small-size platelet mitochondria (plt-mito). Interestingly, FUN14 Domain Containing 2 (FUNDC2), a protein highly-expressed in the outer membrane (OMM) of plt-mito, has been identified to maintain platelet survival under hypoxic condition. The current study determined whether and how FUNDC2 contributed to the therapeutic effect of plt-mito transplantation for hypoxia/reoxygenation (HR) injury. The results showed that incorporation of human plt-mito into SH-SY5Y cells rescued HR-induced mitochondrial malfunction and mitochondrial apoptotic pathway. Mechanistically, plt-mito transplantation led to an increased expression of FUNDC2 in the recipient cells. This protein induced mitochondrial translocation of phosphatidylinositol-3,4,5-trisphosphate (PIP3) via its N-term, resulting in the stimulation of the protein kinase B (Akt)/forkhead box O3a (FOXO3a) pathway, which inhibited HR-induced mitochondrial accumulation of a mitochondrial target of FOXO3a, Bim, also known as a pro-apoptotic protein. Therefore, the FUNDC2/PIP3/Akt/FOXO3a axis may facilitate the incorporated plt-mito to restore mitochondrial function and cell viability of the recipient cells, and platelets may serve as readily-available sources of donor mitochondria that afford therapeutic benefits against IRI.

Mito-Tempo suppresses autophagic flux via the PI3K/Akt/mTOR signaling pathway in neuroblastoma SH-SY5Y cells

The generation of excessive mitochondrial reactive oxygen species (mtROS) is associated with glutamate-stimulated neurotoxicity and pathogenesis of Alzheimer's disease (AD). Impaired mitochondrial function is accompanied with oxidative stress that is a significant contributor to initiate autophagy, but the underlying mechanisms are not fully understood. The present study aimed to investigate the neuroprotective effects of Mito-Tempo on glutamate-induced neuroblastoma SH-SY5Y cell toxicity. SH-SY5Y cells were treated with 100 μM glutamate in the presence or absence of 50 and 100 μM Mito-Tempo for 24 h. Changes in cell viability were measured by MTT assay. Cytotoxicity and intracellular ROS accumulation were also evaluated using lactate dehydrogenase (LDH) activity assay and 2,7-dichlorofluorescein diacetate (DCFDA) Reactive Oxygen Species Assay kit, respectively. Mitochondrial membrane potential was analyzed by tetraethylbenzimidazoly-lcarbocyanine iodide (JC-1) staining. Expression of PI3K/AKT/mTOR pathway and autophagy markers, including LC3 (LC3-I/-II) and p62 (SQSTM1) were performed using Western blot analysis. Our results demonstrated that glutamate-exposed cells significantly increased cellular oxidative stress by enhancing ROS production. Glutamate treatment also increased LDH release follows the loss of mitochondrial membrane potential, caused cell viability loss. Treatment with Mito-Tempo not only attenuated the generation of ROS and improved mitochondrial membrane potential but also reduced the neurotoxicity of glutamate in a concentration-dependent manner, which leads to increased cell viability and decreased LDH release. Mito-Tempo has a greater protective effect by enhancing superoxide dismutase (SOD) activity and PI3K/AKT/mTOR phosphorylation. Moreover, Mito-Tempo treatment altered the autophagy process resulting in the decline in the ratio of the autophagy markers LC3-I/-II and p62 (SQSTM1). We propose that Mito-Tempo can improve neuronal properties against glutamate cytotoxicity through its direct free radical scavenging activity and inhibit excessive autophagy signaling pathway, therefore, allow for further studies to investigate the therapeutic potentials of Mito-Tempo in animal disease models and human.

Blockage of miR-485-5p on Cortical Neuronal Apoptosis Induced by Oxygen and Glucose Deprivation/Reoxygenation Through Inactivating MAPK Pathway

This study is designed to explore the role of miR-485-5p in hypoxia/reoxygenation-induced neuronal injury in primary rat cortical neurons. Hypoxia/reoxygenation model was established through oxygen and glucose deprivation/reoxygenation (OGD/R). RN-c cells were transfected with miR-485-5p mimics, miR-485-5p inhibitors, si-SOX6, pCNDA3.1-SOX6 or miR-485-5p + pCDNA3.1-SOX6, in which cell viability, apoptosis, lactate dehydrogenase (LDH) release rate were assessed. Western blot detected the protein expressions of apoptotic-related proteins (caspase3, Bcl-2, Bax) and the phosphorylated level of ERK1/2. The potential binding sites between miR-485-5p and SOX6 were predicted by STARBASE and identified using dual luciferase reporter gene assay. OGD/R-treated RN-c cell presented increases in apoptosis and LDH release rate as well as a decrease in cell viability. miR-485-5p was downregulated while SOX6 was upregulated in OGD/R-treated RN-c cells. Overexpression of miR-485-5p or SOX6 knockdown rescued cell viability and Bcl-2 expression, while attenuated apoptosis, LDH release rate, expression of SOX6 and the phosphorylated level of ERK1/2. Consistently, miR-485-5p inhibition led to the reverse pattern. Co-transfection of miR-485-5p and SOX6 reversed the protective effect of miR-485-5p on OGD/R-induced neuronal apoptosis. miR-485-5p can directly target SOX6. Together, miR-485-5p inhibited SOX6 to alleviate OGD/R-induced apoptosis. Collectively, miR-485-5p protects primary cortical neurons against hypoxia injury through downregulating SOX6 and inhibiting MAPK pathway.

Pharmacodynamic Effects of Standard versus High Caffeine Doses in the Developing Brain of Neonatal Rats Exposed to Intermittent Hypoxia

(1) Background: Caffeine citrate, at standard doses, is effective for reducing the incidence of apnea of prematurity (AOP) and may confer neuroprotection and decrease neonatal morbidities in extremely low gestational age neonates (ELGANs) requiring oxygen therapy. We tested the hypothesis that high-dose caffeine (HiC) has no adverse effects on the neonatal brain. (2) Methods: Newborn rat pups were randomized to room air (RA), hyperoxia (Hx) or neonatal intermittent hypoxia (IH), from birth (P0) to P14 during which they received intraperitoneal injections of LoC (20 mg/kg on P0; 5 mg/kg/day on P1-P14), HiC (80 mg/kg; 20 mg/kg), or equivalent volume saline. Blood gases, histopathology, myelin and neuronal integrity, and adenosine receptor reactivity were assessed. (3) Results: Caffeine treatment in Hx influenced blood gases more than treatment in neonatal IH. Exposure to neonatal IH resulted in hemorrhage and higher brain width, particularly in layer 2 of the cerebral cortex. Both caffeine doses increased brain width in RA, but layer 2 was increased only with HiC. HiC decreased oxidative stress more effectively than LoC, and both doses reduced apoptosis biomarkers. In RA, both caffeine doses improved myelination, but the effect was abolished in Hx and neonatal IH. Similarly, both doses inhibited adenosine 1A receptor in all oxygen environments, but adenosine 2A receptor was inhibited only in RA and Hx. (4) Conclusions: Caffeine, even at high doses, when administered in normoxia, can confer neuroprotection, evidenced by reductions in oxidative stress, hypermyelination, and increased Golgi bodies. However, varying oxygen environments, such as Hx or neonatal IH, may alter and modify pharmacodynamic actions of caffeine and may even override the benefits caffeine.

Neuroprotective effects of human amniotic fluid stem cells-derived secretome in an ischemia/reperfusion model

Stem cells offer the basis for the promotion of robust new therapeutic approaches for a variety of human disorders. There are still many limitations to be overcome before clinical therapeutic application, including a better understanding of the mechanism by which stem cell therapies may lead to enhanced recovery. In vitro investigations are necessary to dissect the mechanisms involved and to support the potential development in stem cell-based therapies. In spite of growing interest in human amniotic fluid stem cells, not much is known about the characteristics of their secretome and regarding the potential neuroprotective mechanism in different pathologies, including stroke. To get more insight on amniotic fluid cells therapeutic potential, signal transduction pathways activated by human amniotic fluid stem cells (hAFSCs)-derived secretome in a stroke in vitro model (ischemia/reperfusion [I/R] model) were investigated by Western blot. Moreover, miRNA expression in the exosomal fraction of the conditioned medium was analyzed. hAFSCs-derived secretome was able to activate pro-survival and anti-apoptotic pathways. MicroRNA analysis in the exosomal component revealed a panel of 16 overexpressed miRNAs involved in the regulation of coherent signaling pathways. In particular, the pathways of relevance in ischemia/reperfusion, such as neurotrophin signaling, and those related to neuroprotection and neuronal cell death, were analyzed. The results obtained strongly point toward the neuroprotective effects of the hAFSCs-conditioned medium in the in vitro stroke model here analyzed. This can be achieved by the modulation and activation of pro-survival processes, at least in part, due to the activity of secreted miRNAs.

Refinement of a differentiation protocol using neuroblastoma SH-SY5Y cells for use in neurotoxicology research

Since most models used to study neuronal dysfunction display disadvantages and ethical concerns, a fast and reproducible in vitro model to study mitochondria-related neurodegeneration is required. Here, we optimized and characterized a 3-day retinoic acid-based protocol to differentiate the SH-SY5Y cell line into a neuronal-like phenotype and investigated alterations in mitochondrial physiology and distribution. Differentiation was associated with p21-linked cell cycle arrest and an increase in cell mass and area, possibly associated with the development of neurite-like extensions. Notably, increased expression of mature neuronal markers (neuronal-specific nuclear protein, microtubule-associated protein 2, βIII tubulin and enolase 2) was observed in differentiated cells. Moreover, increased mitochondrial content and maximal area per cell suggests mitochondrial remodeling. To demonstrate that this model is appropriate to study mitochondrial dysfunction, cells were treated for 6 h with mitochondrial toxicants (rotenone, antimycin A, carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP) and 6-hydroxydopamine (6-OHDA)). Differentiated cells were more susceptible to increasing concentrations of FCCP, antimycin A, and rotenone, while 6-OHDA showed a distinct dose-dependent neurotoxicity pattern. Even though differentiated cells did not exhibit a fully mature/differentiated neuronal phenotype, the protocol developed can be used to study neurotoxicity processes, mitochondrial dynamics, and bioenergetic impairment, representing an alternative to study mitochondrial impairment-related pathologies in vitro.

Peripheral blood-derived monocytes show neuronal properties and integration in immune-deficient rd1 mouse model upon phenotypic differentiation and induction with retinal growth factors

BACKGROUND

Cell therapy is one of the most promising therapeutic interventions for retinitis pigmentosa. In the current study, we aimed to assess if peripheral blood-derived monocytes which are highly abundant and accessible could be utilized as a potential candidate for phenotypic differentiation into neuron-like cells.

METHODS

The peripheral blood-derived monocytes were reconditioned phenotypically using extrinsic growth factors to induce pluripotency and proliferation. The reconditioned monocytes (RM) were further incubated with a cocktail of growth factors involved in retinal development and growth to induce retinal neuron-like properties. These cells, termed as retinal neuron-like cells (RNLCs) were characterized for their morphological, molecular and functional behaviour in vitro and in vivo.

RESULTS

The monocytes de-differentiated in vitro and acquired pluripotency with the expression of prominent stem cell markers. Treatment of RM with retinal growth factors led to an upregulation of neuronal and retinal lineage markers and downregulation of myeloid markers. These cells show morphological alterations resembling retinal neuron-like cells and expressed photoreceptor (PR) markers. The induced RNLCs also exhibited relative membrane potential change upon light exposure suggesting that they have gained some neuronal characteristics. Further studies showed that RNLCs could also integrate in an immune-deficient retinitis pigmentosa mouse model NOD.SCID-rd1 upon sub-retinal transplantation. The RNLCs engrafted in the inner nuclear layer (INL) and ganglion cell layer (GCL) of the RP afflicted retina. Mice transplanted with RNLCs showed improvement in depth perception, exploratory behaviour and the optokinetic response.

CONCLUSIONS

This proof-of-concept study demonstrates that reconditioned monocytes can be induced to acquire retinal neuron-like properties through differentiation using a defined growth media and can be a potential candidate for cell therapy-based interventions and disease modelling for ocular diseases.

Gateways for Glutamate Neuroprotection in Parkinson's Disease (PD): Essential Role of EAAT3 and NCX1 Revealed in an In Vitro Model of PD

Increasing evidence suggests that metabolic alterations may be etiologically linked to neurodegenerative disorders such as Parkinson's disease (PD) and in particular empathizes the possibility of targeting mitochondrial dysfunctions to improve PD progression. Under different pathological conditions (i.e., cardiac and neuronal ischemia/reperfusion injury), we showed that supplementation of energetic substrates like glutamate exerts a protective role by preserving mitochondrial functions and enhancing ATP synthesis through a mechanism involving the Na⁺-dependent excitatory amino acid transporters (EAATs) and the Na⁺/Ca²⁺ exchanger (NCX). In this study, we investigated whether a similar approach aimed at promoting glutamate metabolism would be also beneficial against cell damage in an in vitro PD-like model. In retinoic acid (RA)-differentiated SH-SY5Y cells challenged with α-synuclein (α-syn) plus rotenone (Rot), glutamate significantly improved cell viability by increasing ATP levels, reducing oxidative damage and cytosolic and mitochondrial Ca²⁺ overload. Glutamate benefits were strikingly lost when either EAAT3 or NCX1 expression was knocked down by RNA silencing. Overall, our results open the possibility of targeting EAAT3/NCX1 functions to limit PD pathology by simultaneously favoring glutamate uptake and metabolic use in dopaminergic neurons.

NCX1 and EAAC1 transporters are involved in the protective action of glutamate in an in vitro Alzheimer's disease-like model

Increasing evidence suggests that metabolic dysfunctions are at the roots of neurodegenerative disorders such as Alzheimer's disease (AD). In particular, defects in cerebral glucose metabolism, which have been often noted even before the occurrence of clinical symptoms and histopathological lesions, are now regarded as critical contributors to the pathogenesis of AD. Hence, the stimulation of energy metabolism, by enhancing the availability of specific metabolites, might be an alternative way to improve ATP synthesis and to positively affect AD progression. For instance, glutamate may serve as an intermediary metabolite for ATP synthesis through the tricarboxylic acid (TCA) cycle and the oxidative phosphorylation. We have recently shown that two transporters are critical for the anaplerotic use of glutamate: the Na⁺-dependent Excitatory Amino Acids Carrier 1 (EAAC1) and the Na⁺-Ca²⁺ exchanger 1 (NCX1). Therefore, in the present study, we established an AD-like phenotype by perturbing glucose metabolism in both primary rat cortical neurons and retinoic acid (RA)-differentiated SH-SY5Y cells, and we explored the potential of glutamate to halt cell damage by monitoring neurotoxicity, AD markers, ATP synthesis, cytosolic Ca²⁺ levels and EAAC1/NCX1 functional activities. We found that glutamate significantly increased ATP production and cell survival, reduced the increase of AD biomarkers (amyloid β protein and the hyperphosphorylated form of tau protein), and recovered the increase of NCX reverse-mode activity. The RNA silencing of either EAAC1 or NCX1 caused the loss of the beneficial effects of glutamate, suggesting the requirement of a functional interplay between these transporters for glutamate-induced protection. Remarkably, our results indicate, as proof-of-principle, that facilitating the use of alternative fuels, like glutamate, may be an effective approach to overcome deficits in glucose utilization and significantly slow down neuronal degenerative process in AD.

Oxidative Stress-Mediated Blood-Brain Barrier (BBB) Disruption in Neurological Diseases

The blood-brain barrier (BBB), as a crucial gate of brain-blood molecular exchange, is involved in the pathogenesis of multiple neurological diseases. Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the scavenger system. Since oxidative stress plays a significant role in the production and maintenance of the BBB, the cerebrovascular system is especially vulnerable to it. The pathways that initiate BBB dysfunction include, but are not limited to, mitochondrial dysfunction, excitotoxicity, iron metabolism, cytokines, pyroptosis, and necroptosis, all converging on the generation of ROS. Interestingly, ROS also provide common triggers that directly regulate BBB damage, parameters including tight junction (TJ) modifications, transporters, matrix metalloproteinase (MMP) activation, inflammatory responses, and autophagy. We will discuss the role of oxidative stress-mediated BBB disruption in neurological diseases, such as hemorrhagic stroke, ischemic stroke (IS), Alzheimer’s disease (AD), Parkinson’s disease (PD), traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and cerebral small vessel disease (CSVD). This review will also discuss the latest clinical evidence of potential biomarkers and antioxidant drugs towards oxidative stress in neurological diseases. A deeper understanding of how oxidative stress damages BBB may open up more therapeutic options for the treatment of neurological diseases.

BRAF and NRAS mutated melanoma: Different Ca2+ responses, Na+/Ca2+ exchanger expression, and sensitivity to inhibitors

Calcium is a ubiquitous intracellular second messenger, playing central roles in the regulation of several biological processes. Alterations in Ca²⁺ homeostasis and signaling are an important feature of tumor cells to acquire proliferative and survival advantages, which include structural and functional changes in storage capacity, channels, and pumps. Here, we investigated the differences in Ca²⁺ homeostasis in vemurafenib-responsive and non-responsive melanoma cells. Also, the expression of the Na⁺/Ca²⁺ exchanger (NCX) and the impact of its inhibition were studied. For this, it was used B-RAF^V600E and NRAS^Q61R-mutated human melanoma cells. The intracellular Ca²⁺ chelator BAPTA-AM decreased the viability of SK-MEL-147 but not of SK-MEL-19 and EGTA sensitized NRAS^Q61R-mutated cells to vemurafenib. These cells also presented a smaller response to thapsargin and ionomycin regarding the cytosolic Ca²⁺ levels in relation to SK-MEL-19, which was associated to an increased expression of NCX1, NO basal levels, and sensitivity to NCX inhibitors. These data highlight the differences between B-RAF^V600E and NRAS^Q61R-mutated melanoma cells in response to Ca²⁺ stimuli and point to the potential combination of clinically used chemotherapeutic drugs, including vemurafenib, with NCX inhibitors as a new therapeutic strategy to the treatment of melanoma.

Dual benefit of combined neuroprotection: Cholesterol depletion restores membrane microviscosity but not lipid order and enhances neuroprotective action of hypothermia in rat cortex nerve terminals

Here, both neuroprotectants, i.e. cholesterol depletion of the plasma membrane of rat brain nerve terminals (synaptosomes) using methyl-β-cyclodextrin (MβCD) and deep/propound hypothermia, were analyzed during their combined administration and regarding additive neuroprotective effect. The extracellular synaptosomal level of L-[¹⁴C]glutamate significantly increased after treatment with MβCD in both deep and profound hypothermia. Cholesterol depletion gradually enhanced inhibiting effect of deep and profound hypothermia on glutamate uptake and "excitotoxic" transporter-mediated release of L-[¹⁴C]glutamate. A decrease in L-[¹⁴C]glutamate release via heteroexchange from nerve terminals in deep and profound hypothermia was enhanced by cholesterol deficiency that confirmed previous result. Fluorometric studies with probes NR12S and DCVJ revealed oppositely directed effects of cholesterol depletion and hypothermia on synaptosomal membrane lipid order and microviscosity showing that cholesterol depletion can normalise up to the control hypothermia-induced increase in microviscosity, but not the lipid order of the synaptosomal membrane. Dynamics of changes in exocytosis in nerve terminals, which involved membrane fusion stage, was different from transporter-dependent ones. Hypothermia did not augment effects of cholesterol depletion on exocytotic L-[¹⁴C]glutamate release and lowering cholesterol enhanced the impact of deep, but not profound hypothermia on this parameter. Therefore, dual benefit of combined neuroprotection was demonstrated. Cholesterol depletion enhanced neuroprotective effects of hypothermia intensifying inhibition of "excitotoxic" transporter-mediated glutamate release and can normalise a hypothermia-induced increase in microviscosity of the synaptosomal membrane. This feature is prospective in mitigation of side effects of therapeutic hypothermia, and also for brain conservation preserving normal physical and chemical properties of the cellular membranes.

NCX and EAAT transporters in ischemia: At the crossroad between glutamate metabolism and cell survival

Energy metabolism impairment is a central event in the pathophysiology of ischemia. The limited availability of glucose and oxygen strongly affects mitochondrial activity, thus leading to ATP depletion. In this setting, the switch to alternative energy sources could ameliorate cells survival by enhancing ATP production, thus representing an attractive strategy for ischemic treatment. In this regard, some studies have recently re-evaluated the metabolic role of glutamate and its potential to promote cell survival under pathological conditions. In the present review, we discuss the ability of glutamate to exert an "energizing role" in cardiac and neuronal models of hypoxia/reoxygenation (H/R) injury, focusing on the Na⁺/Ca²⁺ exchanger (NCX) and the Na⁺-dependent excitatory amino acid transporters (EAATs) as key players in this metabolic pathway.

Excitatory Amino Acid Transporters (EAATs): Glutamate Transport and Beyond

Na⁺-dependent excitatory amino acid transporters (EAATs) are the major transport mechanisms for extracellular glutamate removal in the central nervous system (CNS). The primary function assigned to EAATs is the maintenance of low extracellular glutamate levels, thus allowing glutamate to be used as a signaling molecule in the brain and to avoid excitotoxicity. However, glutamate has other recognized functions. For instance, it is a key anaplerotic substrate for the tricarboxylic acid (TCA) cycle, as it can be converted to α-ketoglutarate by transaminases or glutamate dehydrogenase. Furthermore, glutamate is a precursor of the main antioxidant glutathione, which plays a pivotal role in preventing oxidative cell death. Therefore, glutamate signaling/use is at the crossroad of multiple metabolic pathways and accordingly, it can influence a plethora of cell functions, both in health and disease. Here, we provide an overview of the main functions of glutamate and its transport systems, analyzing its role as a neurotransmitter and at the same time, the possible metabolic fates it can undergo in the intracellular milieu. Specifically, the metabolic role of glutamate and the molecular machinery proposed to metabolically support its transport will be further analyzed.

Novel application of amino-acid buffered solution for neuroprotection against ischemia/reperfusion injury

Ischemic neuron loss contributes to brain dysfunction in patients with cardiac arrest (CA). Histidine–tryptophan–ketoglutarate (HTK) solution is a preservative used during organ transplantation. We tested the potential of HTK to protect neurons from severe hypoxia (SH) following CA. We isolated rat primary cortical neurons and induced SH with or without HTK. Changes in caspase-3, hypoxia-inducible factor 1-alpha (HIF-1α), and nicotinamide adenine dinucleotide phosphate oxidase-4 (NOX4) expression were evaluated at different time points up to 72 h. Using a rat asphyxia model, we induced CA-mediated brain damage and then completed resuscitation. HTK or sterile saline was administered into the left carotid artery. Neurological deficit scoring and mortality were evaluated for 3 days. Then the rats were sacrificed for evaluation of NOX4 and H₂O₂ levels in blood and brain. In the in vitro study, HTK attenuated SH- and H₂O₂-mediated cytotoxicity in a volume- and time-dependent manner, associated with persistent HIF-1α expression and reductions in procaspase-3 activation and NOX4 expression. The inhibition of HIF-1α abrogated HTK’s effect on NOX4. In the in vivo study, neurological scores were significantly improved by HTK. H₂O₂ level, NOX4 activity, and NOX4 gene expression were all decreased in the brain specimens of HTK-treated rats. Our results suggest that HTK acts as an effective neuroprotective solution by maintaining elevated HIF-1α level, which was associated with inhibited procaspase-3 activation and decreased NOX4 expression.

Simvastatin Alleviates Intestinal Ischemia/Reperfusion Injury by Modulating Omi/HtrA2 Signaling Pathways

PURPOSE

The objective of this research was to survey the therapeutic action of simvastatin (Sim) on intestinal ischemia/reperfusion injury (II/RI) by modulating Omi/HtrA2 signaling pathways.

METHODS

Sprague Dawley rats were pretreated with 40 mg/kg Sim and then subjected to 1 hour of ischemia and 3 hours of reperfusion. The blood and intestinal tissues were collected, pathologic injury was observed, the contents of serum tumor necrosis factor-α and interleukin-6 (IL-6) were estimated, and superoxide dismutase, methane dicarboxylic aldehyde, and cysteinyl aspartate specific proteinase-3 (caspase-3) levels, as well as the expressions of Omi/HtrA2 and caspase-3, were measured in the intestinal tissues.

RESULTS

Sim preconditioning mitigated the damnification of intestinal tissues by decreasing oxidative stress, inflammatory damage, and apoptosis and downregulating the expression of Omi/HtrA2 compared to the ischemia/reperfusion group, while Sim+Ucf-101 significantly augmented this effect.

CONCLUSION

These results suggest that Sim may alleviate intestinal ischemia/reperfusion injury by modulating Omi/HtrA2 signaling pathways.

The dual face of glutamate: from a neurotoxin to a potential survival factor-metabolic implications in health and disease

Glutamate is the major excitatory neurotransmitter in the central nervous system. Beyond this function, glutamate also plays a key role in intermediary metabolism in all organs and tissues, linking carbohydrate and amino acid metabolism via the tricarboxylic acid cycle. Under both physiological and pathological conditions, we have recently found that the ability of glutamate to fuel cell metabolism selectively relies on the activity of two main transporters: the sodium-calcium exchanger (NCX) and the sodium-dependent excitatory amino-acid transporters (EAATs). In ischemic settings, when glutamate is administered at the onset of the reoxygenation phase, the coordinate activity of EAAT and NCX allows glutamate to improve cell viability by stimulating ATP production. So far, this phenomenon has been observed in both cardiac and neuronal models. In this review, we focus on the most recent findings exploring the unusual activity of glutamate as a potential survival factor in different settings.

A Metabonomics Investigation into the Therapeutic Effects of BuChang NaoXinTong Capsules on Reversing the Amino Acid-Protein Interaction Network of Cerebral Ischemia

Background

Amino acids (AAs) in cerebrospinal fluid (CSF) play a pivotal role in cerebral ischemia (CI). BuChang NaoXinTong Capsules (BNC) are widely prescribed in Chinese medicine for the treatment of cerebrovascular and cardiovascular diseases.

Methods

In order to investigate the therapeutic effects and pharmacological mechanisms of BNC on reversing CI from a system level, an amino acid-protein interaction imbalanced network of CI containing metabolites of AAs, key regulatory enzymes, and proteins was constructed for the first time. Furthermore, a novel method for detecting the ten AAs in CSF was developed by UPLC-QQQ-MS in an effort to validate the imbalanced networks and the therapeutic effects of BNC via analysis of metabolites.

Results

Based on a middle cerebral artery occlusion (MCAO) rat model, the dynamic levels of amino acids in CSF 3, 6, 12, and 24 h after MCAO were analyzed. Up to 24 h, the accumulated nine AA biomarkers were found to significantly change in the MCAO group compared to the sham group and exhibited an obvious tendency for returning to baseline values after BNC treatment. In addition, based on the imbalanced network of CI, four key enzymes that regulate the generation of BNC-mediated AA biomarkers were selected and validated using an enzyme-linked immunosorbent assay and western blotting. Finally, aromatic-L-amino-acid decarboxylase (AADC) was found to be one of the putative targets for BNC-mediated protection against CI.

Conclusion

This study provides new strategies to explore the mechanism of cerebral ischemia and help discover the potential mechanism of BNC.

Selective inhibition of mitochondrial sodium-calcium exchanger protects striatal neurons from α-synuclein plus rotenone induced toxicity

Progressive accumulation of α-synuclein (α-syn) and exposure to environmental toxins are risk factors that may both concur to Parkinson’s disease (PD) pathogenesis. Electrophysiological recordings of field postsynaptic potentials (fEPSPs) and Ca²⁺ measures in striatal brain slices and differentiated SH-SY5Y cells showed that co-application of α-syn and the neurotoxic pesticide rotenone (Rot) induced Ca²⁺ dysregulation and alteration of both synaptic transmission and cell function. Interestingly, the presence of the mitochondrial NCX inhibitor CGP-37157 prevented these alterations. The specific involvement of the mitochondrial NCX was confirmed by the inability of the plasma membrane inhibitor SN-6 to counteract such phenomenon. Of note, using a siRNA approach, we found that NCX1 was the isoform specifically involved. These findings suggested that NCX1, operating on the mitochondrial membrane, may have a critical role in the maintenance of ionic Ca²⁺ homeostasis in PD and that its inhibition most likely exerts a protective effect in the toxicity induced by α-syn and Rot.