Phosphoglycerate mutase 1 reduces neuronal damage in the hippocampus following ischemia/reperfusion through the facilitation of energy utilization

Phosphoglycerate kinase 1 protects against ischemic damage in the gerbil hippocampus

Phosphoglycerate kinase 1 (PGK1) is a metabolic enzyme that converts 1,3-diphosphoglycerate to 3-phosphoglycerate. In the current study, we synthesized a PEP-1-PGK1 fusion protein that can cross the blood-brain barrier and cell membrane, and the effects of PEP-1-PGK1 against oxidative stress were investigated HT22 cells and ischemic gerbil brain. The PEP-1-PGK1 protein and its control protein (Con-PGK1) were treated and permeability was evaluated HT22 cells. The PEP-1-PGK1 was introduced into HT22 cells depending on its concentration and incubation time and was gradually degraded over 36 h after treatment. PEP-1-PGK1, but not Con-PGK1, significantly ameliorated H₂O₂-induced cell damage and reactive oxygen species formation in HT22 cells. Additionally, PEP-1-PGK1, but not Con-PGK1, mitigated ischemia-induced hyperlocomotion 1 d after ischemia and 4 d after ischemia of neuronic cell death. PEP-1-PGK1 treatment significantly alleviated the raised lactate and succinate dehydrogenase activities in the early (15 min to 6 h) and late (4 and 7 d) stages of ischemia, respectively. In addition, PEP-1-PGK1 treatment ameliorated the decrease in ATP and pH levels in the late stage (2-7 d) of ischemia. Nuclear factor erythroid-2-related factor 2 (Nrf2) levels accelerated the ischemia-induced increase in the hippocampus 1 d after ischemia after PEP-1-PGK1 treatment. Neuroprotective and ameliorative effects were prominent at a low concentration (0.1 mg/kg), but not at a high concentration (1 mg/kg), of PEP-1-PGK1. Collectively, low concentrations of PEP-1-PGK1 prevented neuronal stress by increasing energy production.

The neuroprotective effects of phosphoglycerate mutase 5 are mediated by decreasing oxidative stress in HT22 hippocampal cells and gerbil hippocampus

Phosphoglycerate mutase 5 (PGAM5), a glycolytic enzyme, plays an important role in cell death and regulation of mitochondrial dynamics. In this study, we investigated the effects of PGAM5 on oxidative stress in HT22 hippocampal cells and ischemic damage in the gerbil hippocampus to elucidate the role of PGAM5 in oxidative and ischemic stress. Constructs were designed with a PEP-1 expression vector to facilitate the intracellular delivery of PGAM5 proteins. We observed time- and concentration-dependent increases in the intracellular delivery of the PEP-1-PGAM5 protein, but not its control protein (PGAM5), in HT22 cells, and morphologically demonstrated the localization of the transduced protein, which was stably expressed in the cytoplasm after 12 h of PEP-1-PGAM5 treatment. PEP-1-PGAM5 treatment significantly ameliorated cell death, reactive oxygen species formation, DNA fragmentation, and the reduction of cell proliferation induced by H₂O₂ treatment in HT22 cells. In addition, PEP-1-PGAM5 was effectively delivered to the gerbil hippocampus 8 h after treatment, and ischemia-induced hyperlocomotion and neuronal death in the hippocampal CA1 region were significantly alleviated 1 and 4 days after ischemia, respectively. Ischemia-induced microglial activation was also mitigated by treatment with 1.0 mg/kg PEP-1-PGAM5. At 3 h after ischemia, PEP-1-PGAM5 treatment significantly ameliorated the increase in lipid peroxidation, as assessed by malondialdehyde and hydroperoxide levels, and decreased glutathione levels (increases in glutathione disulfide, the oxidized form of glutathione) in the hippocampus. Two days after ischemia, treatment with PEP-1-PGAM5 significantly alleviated the ischemia-induced reduction in glutathione peroxidase activity and further increased superoxide dismutase activity in the hippocampus. The neuroprotective effects of PEP-1-PGAM5 are partially mediated by a reduction in oxidative stress, such as the formation of reactive oxygen species, and increases in the activity of antioxidants such as glutathione peroxidase and superoxide dismutase.

Neuroprotective Effects of Purpurin Against Ischemic Damage via MAPKs, Bax, and Oxidative Stress Cascades in the Gerbil Hippocampus

Purpurin has various effects, including anti-inflammatory effects, and can efficiently cross the blood-brain barrier. In the present study, we investigated the effects of purpurin on oxidative stress in HT22 cells and mild brain damage in the gerbil hippocampal CA1 region induced by transient forebrain ischemia. Oxidative stress induced by H2O2 was significantly ameliorated by treatment with purpurin, based on changes in cell death, DNA fragmentation, formation of reactive oxygen species, and pro-apoptotic (Bax)/anti-apoptotic (Bcl-2) protein levels. In addition, treatment with purpurin significantly reduced the phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK), and p38 signaling in HT22 cells. Transient forebrain ischemia in gerbils led to a significant increase in locomotor activity 1 day after ischemia and significant decrease in number of surviving cells in the CA1 region 4 days after ischemia. Administration of purpurin reduced the travel distance 1 day after ischemia and abrogates the neuronal death in the hippocampal CA1 region 4 days after ischemia based on immunohistochemical and histochemical staining for NeuN and Fluoro-Jade C, respectively. Purpurin treatment significantly decreased the activation of microglia and astrocytes as well as the increases of nuclear factor kappa-light-chain-enhancer of activated B cells p65 in the hippocampal CA1 region 4 days after ischemia and ameliorated the ischemia-induced transient increases of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the hippocampus 6 h after ischemia. In addition, purpurin significantly alleviated the ischemia-induced phosphorylation of JNK, ERK, and p38 in the hippocampus 1 day after ischemia. Furthermore, purpurin treatment significantly mitigated the increases of Bax in the hippocampus 1 day after ischemia and the lipid peroxidation based on malondialdehyde and hydroperoxides levels 2 days after ischemia. These results suggest that purpurin can be one of the potential candidates to reduce neuronal damage and inflammatory responses after oxidative stress in HT22 cells or ischemic damage in gerbils.

Cissus verticillata Extract Decreases Neuronal Damage Induced by Oxidative Stress in HT22 Cells and Ischemia in Gerbils by Reducing the Inflammation and Phosphorylation of MAPKs

In the present study, we examined the effects of Cissus verticillata leaf extracts (CVE) against hydrogen peroxide (H₂O₂)- and ischemia-induced neuronal damage in HT22 cells and gerbil hippocampus. Incubation with CVE produced concentration-dependent toxicity in HT22 cells. Significant cellular toxicity was observed with >75 μg/mL CVE. CVE treatment at 50 μg/mL ameliorated H₂O₂-induced reactive oxygen species formation, DNA fragmentation, and cell death in HT22 cells. In addition, incubation with CVE significantly mitigated the increase in Bax and decrease in Bcl-2 induced by H₂O₂ treatment in HT22 cells. In an in vivo study, the administration of CVE to gerbils significantly decreased ischemia-induced motor activity 1 d after ischemia, as well as neuronal death and microglial activation 4 d after ischemia, respectively. CVE treatment reduced the release of interleukin-1β, interleukin-6, and tumor necrosis factor-α 6 h after ischemia. Furthermore, CVE treatment significantly ameliorated ischemia-induced phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase 1/2, and p38. These results suggest that CVE has the potential to reduce the neuronal damage induced by oxidative and ischemic stress by reducing the inflammatory responses and phosphorylation of MAPKs, suggesting that CVE could be a functional food to prevent neuronal damage induced by ischemia.

P27 Protects Neurons from Ischemic Damage by Suppressing Oxidative Stress and Increasing Autophagy in the Hippocampus

p27^Kip1 (p27), a well-known cell regulator, is involved in the regulation of cell death and survival. In the present study, we observed the effects of p27 against oxidative stress induced by H₂O₂ in HT22 cells and transient ischemia in gerbils. Tat (trans-acting activator of transcription) peptide and p27 fusion proteins were prepared to facilitate delivery into cells and across the blood-brain barrier. The tat-p27 fusion protein, rather than its control protein Control-p27, was delivered intracellularly in a concentration and incubation time-dependent manner and showed its activity in HT22 cells. The localization of the delivered Tat-p27 protein was also confirmted in the HT22 cells and hippocampus in gerbils. In addition, the optimal concentration (5 μM) of Tat-p27 was determined to protect neurons from cell death induced by 1 mM H₂O₂. Treatment with 5 μM Tat-p27 significantly ameliorated H₂O₂-induced DNA fragmentation and the formation of reactive oxygen species (ROS) in HT22 cells. Tat-p27 significantly mitigated the increase in locomotor activity a day after ischemia and neuronal damage in the hippocampal CA1 region. It also reduced the ischemia-induced membrane phospholipids and ROS formation. In addition, Tat-p27 significantly increased microtubule-associated protein 1A/1B light chain 3A/3B expression and ameliorated the H₂O₂ or ischemia-induced increases of p62 and decreases of beclin-1 in the HT22 cells and hippocampus. These results suggest that Tat-p27 protects neurons from oxidative or ischemic damage by reducing ROS-induced damage and by facilitating the formation of autophagosomes in hippocampal cells.

Sugarcane (Saccharum officinarum L.) Top Extract Ameliorates Cognitive Decline in Senescence Model SAMP8 Mice: Modulation of Neural Development and Energy Metabolism

Age-related biological alterations in brain function increase the risk of mild cognitive impairment and dementia, a global problem exacerbated by aging populations in developed nations. Limited pharmacological therapies have resulted in attention turning to the promising role of medicinal plants and dietary supplements in the treatment and prevention of dementia. Sugarcane (Saccharum officinarum L.) top, largely considered as a by-product because of its low sugar content, in fact contains the most abundant amounts of antioxidant polyphenols relative to the rest of the plant. Given the numerous epidemiological studies on the effects of polyphenols on cognitive function, in this study, we analyzed polyphenolic constituents of sugarcane top and examined the effect of sugarcane top ethanolic extract (STEE) on a range of central nervous system functions in vitro and in vivo. Orally administrated STEE rescued spatial learning and memory deficit in the senescence-accelerated mouse prone 8 (SAMP8) mice, a non-transgenic strain that spontaneously develops a multisystemic aging phenotype including pathological features of Alzheimer's disease. This could be correlated with an increased number of hippocampal newborn neurons and restoration of cortical monoamine levels in STEE-fed SAMP8 mice. Global genomic analysis by microarray in cerebral cortices showed multiple potential mechanisms for the cognitive improvement. Gene set enrichment analysis (GSEA) revealed biological processes such as neurogenesis, neuron differentiation, and neuron development were significantly enriched in STEE-fed mice brain compared to non-treated SAMP8 mice. Furthermore, STEE treatment significantly regulated genes involved in neurotrophin signaling, glucose metabolism, and neural development in mice brain. Our in vitro results suggest that STEE treatment enhances the metabolic activity of neuronal cells promoting glucose metabolism with significant upregulation of genes, namely PGK1, PGAM1, PKM, and PC. STEE also stimulated proliferation of human neural stem cells (hNSCs), regulated bHLH factor expression and induced neuronal differentiation and astrocytic process lengthening. Altogether, our findings suggest the potential of STEE as a dietary intervention, with promising implications as a novel nutraceutical for cognitive health.

Phosphoglycerate Mutase 1 Prevents Neuronal Death from Ischemic Damage by Reducing Neuroinflammation in the Rabbit Spinal Cord

Phosphoglycerate mutase 1 (PGAM1) is a glycolytic enzyme that increases glycolytic flux in the brain. In the present study, we examined the effects of PGAM1 in conditions of oxidative stress and ischemic damage in motor neuron-like (NSC34) cells and the rabbit spinal cord. A Tat-PGAM1 fusion protein was prepared to allow easy crossing of the blood-brain barrier, and Control-PGAM1 was synthesized without the Tat peptide protein transduction domain. Intracellular delivery of Tat-PGAM1, not Control-PGAM1, was achieved in a time- and concentration-dependent manner. Immunofluorescent staining confirmed the intracellular expression of Tat-PGAM1 in NSC34 cells. Tat-PGAM1, but not Control-PGAM1, significantly alleviated H₂O₂-induced oxidative stress, neuronal death, mitogen-activated protein kinase, and apoptosis-inducing factor expression in NSC34 cells. After ischemia induction in the spinal cord, Tat-PGAM1 treatment significantly improved ischemia-induced neurological impairments and ameliorated neuronal cell death in the ventral horn of the spinal cord 72 h after ischemia. Tat-PGAM1 treatment significantly mitigated the ischemia-induced increase in malondialdehyde and 8-iso-prostaglandin F2α production in the spinal cord. In addition, Tat-PGAM1, but not Control-PGAM1, significantly decreased microglial activation and secretion of pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α induced by ischemia in the ventral horn of the spinal cord. These results suggest that Tat-PGAM1 can be used as a therapeutic agent to reduce spinal cord ischemia-induced neuronal damage by lowering the oxidative stress, microglial activation, and secretion of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α.

Comparison of neuronal death and expression of TNF‑α and MCT4 in the gerbil hippocampal CA1 region induced by ischemia/reperfusion under hyperthermia to those under normothermia

Monocarboxylate transporter 4 (MCT4) is a high-capacity lactate transporter in cells and the alteration in MCT4 expression harms cellular survival. The present study investigated whether hypothermia affects tumor necrosis factor-α (TNF-α) and MCT4 immunoreactivity in the subfield cornu ammonis 1 (CA1) following cerebral ischemia/reperfusion (IR) in gerbils. Hypothermia was induced for 30 min before and during ischemia. It was found that IR-induced death of pyramidal neurons was markedly augmented and occurred faster under hyperthermia than under normothermia. TNF-α immunoreactivity in the pyramidal cells started to increase at 3 h after IR and peaked at 1 day after IR under normothermia. However, in hyperthermic control and sham operated gerbils, TNF-α immunoreactivity was significantly increased compared with the normothermic gerbils, and IR under hyperthermia caused a more rapid and significant increase in TNF-α immunoreactivity in pyramidal neurons than under normothermia. In addition, in the normothermic gerbils, MCT4 immunoreactivity began to decrease in pyramidal neurons from 3 h after IR and markedly increased at 1 and 2 days after IR. On the other hand, MCT4 immunoreactivity in pyramidal neurons of the hyperthermic gerbils was significantly increased from 3 h after IR, maintained until 1 day after IR and markedly decreased at 2 days after IR. These results indicate that acceleration of IR-induced neuronal death under hyperthermia might be closely associated with early alteration of TNF-α and MCT4 protein expression in the gerbil hippocampus after IR.