Role of microglia-mediated neuronal injury in neurodegenerative diseases / 中国组织工程研究

BACKGROUND: Microglia are resident immune cells of the central nervous system that normally perform sensing, housekeeping, and defense functions. In the context of neurodegenerative diseases, the dysfunction of microglia leads to or aggravates neuronal injury. OBJECTIVE: To investigate the mechanism of microglia-mediated neuronal injury in neurodegenerative diseases. METHODS: The first author searched for relevant articles published from January 2001 to January 2020 in PubMed, CNKI, Wanfang database, and VIP database with the key words of “microglia; neurodegenerative diseases; neuronal injury”. RESULTS AND CONCLUSION: In neurodegenerative diseases, microglia perform excessive sensing due to toxic substances during normal function, leading to increasing activation of microglia, accompanied with hyperfunction of housekeeping and intense neuroinflammation causing neuronal impairment. The dysregulation can also be manifested as dysfunction of sensing and housekeeping due to specific gene mutations, which bring about accumulation of toxic substances, aggravating the dysregulation of defense function and inducing apoptosis or necrosis of neurons as a result. Further exploration on the mechanism of microglia-mediated neuronal injury in neurodegenerative diseases may provide several targets for the treatment of neurodegenerative disease.

Transient forebrain ischemia induces impairment in cognitive performance prior to extensive neuronal cell death in Mongolian gerbil (Meriones unguiculatus)

In Mongolian gerbils, bilateral common carotid artery occlusion (BCCAO) for several minutes induces ischemia, due to an incomplete circle of Willis, resulting in delayed neuronal cell death in the Cornet d'Ammon 1 (CA1) region of the hippocampus. Neuronal cell death in the hippocampus and changes in behavior were examined after BCCAO was performed for 5 min in the gerbils. One day after BCCAO, the pyramidal neurons of the CA1 region of the hippocampus showed degenerative changes (clumped chromatin in nuclei). At 5 and 10 days after BCCAO, extensive neuronal cell death was observed in the hippocampal CA1 region. Cognitive performance was evaluated by using the radial maze and passive avoidance tests. In the radial maze test, which examines win-stay performance, the number of errors was significantly higher in ischemic gerbils than in sham-operated gerbils on days 1 and 2 post-operation. In the passive avoidance test, the latency and freezing times were significantly shorter in ischemic gerbils than in sham-operated gerbils on the days 1, 2, and 4–6 post-operation. These results indicate that transient forebrain ischemia impairs cognitive performance, even immediately after the ischemic insult when there are only subtle signs of neuronal cell death.

Intracerebroventricular Kainic Acid-Induced Damage Affects Blood Glucose Level in d-glucose-fed Mouse Model

We have previously reported that the intracerebroventricular (i.c.v.) administration of kainic acid (KA) results in significant neuronal damage on the hippocampal CA3 region. In this study, we examined possible changes in the blood glucose level after i.c.v. pretreatment with KA. The blood glucose level was elevated at 30 min, began to decrease at 60 min and returned to normal at 120 min after D-glucose-feeding. We found that the blood glucose level in the KA-pretreated group was higher than in the saline-pretreated group. The up-regulation of the blood glucose level in the KA-pretreated group was still present even after 1~4 weeks. The plasma corticosterone and insulin levels were slightly higher in the KA-treated group. Corticosterone levels decreased whereas insulin levels were elevated when mice were fed with D-glucose. The i.c.v. pretreatment with KA for 24 hr caused a significant reversal of D-glucose-induced down-regulation of corticosterone level. However, the insulin level was enhanced in the KA-pretreated group compared to the vehicle-treated group when mice were fed with D-glucose. These results suggest that KA-induced alterations of the blood glucose level are related to cell death in the CA3 region whereas the up-regulation of blood glucose level in the KA-pretreated group appears to be due to a reversal of D-glucose feeding-induced down-regulation of corticosterone level.

Calbindin-D28K Prevents Staurosporin-induced Bax Cleavage and Membrane Permeabilization

Calbindin-D28K has been implicated in the regulation of neuronal cell death. Previously, we demonstrated that calbindin-D28K prevents staurosporine (STS)-induced caspase activation and subsequent apoptosis in a neuronal cell line. However, the role of calbindin-D28K in STS-induced activation of calpain and necrotic cell death was not identified. Staurosporine induced the elevation of intracellular calcium after 1 hr of treatment. Overexpression of calbindin-D28K and presence of a calcium chelator, BAPTA, prevented the increase of calcium in STS-treated cells. Cleavage of Bax by calpain was prevented by the overexpressed calbindin-D28K. Permeabilization of the plasma membrane, a factor in necrosis, as well as apoptotic change of the nucleolus induced by STS, was prevented by calbindin-D28K. Thus, our study suggests that calbindin-D28K may exert its protective functions by preventing calpain activation in necrotic cell death, in addition to its effect on the caspase-apoptosis pathway.

Interleucina-1ß, crisis convulsivas y muerte neuronal / Interleukin-1ß, seizures and neuronal cell death

La epilepsia es un trastorno neurológico que afecta aproximadamente al 1% de la población mundial. Estudios realizados en humanos y animales de experimentación sugieren que mediadores de inflamación, como las citocinas, participan en la fisiopatología de la epilepsia; entre ellos, la interleucina-1beta (IL-1ß) podría participar en la susceptibilidad para generar crisis convulsivas así como en la muerte neuronal causada por las convulsiones, aunque algunos hallazgos son contradictorios. En este documento se revisa el conocimiento actual que establece una relación entre la IL-1ß, las crisis convulsivas y la muerte neuronal.

Epilepsy is a neurological disorder affecting almost 1% of the world population. Experimental human and animal studies suggest that inflammation mediators, like cytokines, participate in the physiopathology of epilepsy. Interleukin-1beta (IL-1ß) could influence susceptibility for seizures, as well as neuronal death caused by seizures, although some findings are contradictory. This document reviews the current knowledge establishing a connection between IL-1ß, seizures and neuronal death.

Oxygen/Glucose Deprivation and Reperfusion Cause Modifications of Postsynaptic Morphology and Activity in the CA3 Area of Organotypic Hippocampal Slice Cultures

Brain ischemia leads to overstimulation of N-methyl-D-aspartate (NMDA) receptors, referred as excitotoxicity, which mediates neuronal cell death. However, less attention has been paid to changes in synaptic activity and morphology that could have an important impact on cell function and survival following ischemic insult. In this study, we investigated the effects of reperfusion after oxygen/glucose deprivation (OGD) not only upon neuronal cell death, but also on ultrastructural and biochemical characteristics of postsynaptic density (PSD) protein, in the stratum lucidum of the CA3 area in organotypic hippocampal slice cultures. After OGD/reperfusion, neurons were found to be damaged; the organelles such as mitochondria, endoplasmic reticulum, dendrites, and synaptic terminals were swollen; and the PSD became thicker and irregular. Ethanolic phosphotungstic acid staining showed that the density of PSD was significantly decreased, and the thickness and length of the PSD were significantly increased in the OGD/reperfusion group compared to the control. The levels of PSD proteins, including PSD-95, NMDA receptor 1, NMDA receptor 2B, and calcium/calmodulin-dependent protein kinase II, were significantly decreased following OGD/reperfusion. These results suggest that OGD/reperfusion induces significant modifications to PSDs in the CA3 area of organotypic hippocampal slice cultures, both morphologically and biochemically, and this may contribute to neuronal cell death and synaptic dysfunction after OGD/reperfusion.

Effects of Pilocarpine-induced Seizures on the Neuronal Cell Death, Mossy Fiber Sprouting and Neurogensis in the Hippocampus of Mice / 체질인류학회지

Present study was performed to delineate the inter-relationship among neuronal death, mossy fiber sprouting (MFS) and neurogenesis in hippocampal formation of pilocarpine-treated mice. Status epilepticus was induced by intraperitoneal administration of 300 mg/kg pilocarpine in male ICR and C57BL/6 mouse. The severity of seizure was evaluated using 5 grades of Racine scales for first 4 hr after pilocarpine injection. Fluro-Jade C (FJC) staing, NeoTimm's staining and immunohistochemistry for BrdU were employed to evaluate neuronal cell death, MFS and neurogenesis, respectively. All animals in the present study induced seizures over grade 3 of Racine scale by pilocarpine injection. ICR mice show higher seizure severity (mean Racine scale; 4.37) than C57BL/6 mice do (mean Racine scale; 3.22), while the latency times for the first seizure over Racine scale grade 3 are from 15 min to 20 min and showed no difference between the 2 strains. In ICR mouse, numerous FJC-positive cells in hilus of hippocampus were detected at 4 h after pilocarpine injection, while they were not detected at that time in C57BL/6 mouse. The number of FJC-positive neuronal cells, which were densely found in the pyramidal layer of CA1, CA3 and hilus polymorphic regions of hippocampus, reached peak at 3 days after injection and then few cells were found at 7 days after injection in both strains. In control animals, BrdU positive cells in dentate subgranular layer which represent the hippocampal neurogenesis were more numerous in C57BL/6 than in ICR. The number of BrdU positive cells significantly increased at 2 days after pilocarpine injection and reached the peak at 8 days after injection and returned to control level at 15 day after injection in both strains. The percent increase of the BrdU positive cell was more prominent in ICR mouse. MFS was found at 2 weeks after the injection and the intensity of MFS was getting strong at 4 weeks after injection. There was no differences in MFS grading between 2 strains. These results suggest that there are some inter-relationships among the seizure severity, hippocampal neuronal cell death and hippocampal neurogenesis, but they don't have any significant relationships with the mossy fiber sprouting from dentate granule cells.

Agmatine Attenuates Nitric Oxide Synthesis and Protects ER-structure from Global Cerebral Ischemia in Rats / 대한해부학회지

In ischemic strokes, apoptosis is caused by excitotoxicity, ionic imbalance, oxidative/nitrosative stress, and apoptotic-like pathways. Nitric oxide (NO), a free radical, is elevated after ischemic insult. NO, which is generated primarily by neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS), promotes neuronal damage following ischemia. Evidence obtained in recent years has demonstrated that endoplasmic reticulum (ER)-mediated cell death plays an important role in cerebral ischemia. Agmatine is an endogenous substance synthesized from L-arginine by arginine decarboxylase (ADC) and is present in mammalian brain. We had previously reported that agmatine contributes to neuroprotection against ischemic injury. In continuation of our earlier work, we intended to investigate whether agmatine protects brain from transient global ischemia, and also tried to determine the neuroprotective mechanism of agmatine. Twenty minutes of transient global ischemia was induced by 4 vessel occlusion (4-VO). Agmatine (100 mg/kg, IP) was administered simultaneously with reperfusion. Samplings of brain were done at 6, 24, 48, and 72 h after reperfusion to determine the effect of agmatine on ischemic injured hippocampus. ER-damage was also investigated using electron microscope. Results showed that agmatine treatment prevented delayed neuronal cell death in hippocampal CA1 neurons after global cerebral ischemia. It also blocked NOS expression in the rat brain. Agmatine induced the increased expression of glucose-regulated protein 78 (Grp78). These results suggest that agmatine inhibits the production of NO by decreasing the expression of nNOS and iNOS on global forebrain ischemia and the neuroprotective effect of agmatine were concerned with the ER stress-mediated condition.

Extracellular HMGB1 Released after Zinc-treatment Induces Neuronal Death in Primary Cortical Cultures / 대한해부학회지

As a nonhistone DNA-binding protein, high mobility group box 1 (HMGB1) is released in large amounts into the extracellular space immediately after ischemic insult and plays a role in the release of proinflammatory cytokines. Here, we the examined cytokine-like or signaling molecule-like function of extracellular HMGB1 in primary cortical cultures. We found that a large amount of HMGB1 was released following zinc-induced neuronal cell death in primary cortical cultures and that this extracellular HMGB1 might aggravate neuronal damage. The conditioned media collected from zinc-treated primary cortical cultures decreased neuronal cell survival to 69.6+/-1.4% of control values when added to fresh primary cortical cultures. In contrast, treatment with HMGB1-depleted conditioned media produced by cultures treated with an HMGB1 siRNA-expression vector suppressed the induction of neuronal death. A mutant HMGB1 siRNA-expression vector did not suppress the induction of neuronal death, demonstrating a role of HMGB1 in neuronal death. Moreover, HMGB1-depletion in media conditioned by cotreatment with anti-HMGB1 antibody or with anti-RAGE antibody, a potential receptor for HMGB1, recovered neuronal cell survival to 81.0+/-4.0% and 79.0+/-4.0%, respectively, when added to fresh primary cortical cultures. These results indicate that extracellular HMGB1 released after zinc treatment induces neuronal death, which might aggravate zinc toxicity.

Effects of Recombinant EPO on Death of Cortical Neuron in Chronic Hypoxia / 체질인류학회지

Chronic hypoxia has been associated with change in neurovascular behavior, mediated, in part, by erythropoietin (EPO). EPO, a hematopoietic growth factor, could act as a neurotrophic factor. In the present study, we investigated the characteristics of EPO and erythropoietin receptor (EPOR) expressions by cortical neuron in vivo and in vitro and tested the hypothesis that EPO serves protective functions under chronic hypoxia. E18, P5 and P7 mice for 3 days and primary cultured neurons for 6 days were incubated in hypoxic conditions consisted of a mixture of 10% O2, 5% CO2, 85% N2. To study expressions of EPO, EPOR, caspases, pAKT, pERK, and PARP, immunohistochemical stainning and western blotting were carried out. In addition to expressing EPO and EPOR under normoxic conditions, neurons increased their expression of EPO and EPOR under hypoxia. The effects of recombinant EPO appeared to be mediated via the phosphatidylinositol (PI) 3- kinase-AKT pathway, correlated directly with activation of caspase 3. Also recombinant EPO decreased expression of caspase 8, but not caspase 9. Finally, recombinant EPO decreased apoptosis of cultured neurons as evaluated by expression of PARP. These data support a role for EPO in maintenance of cortical neuron under chronic hypoxia.

Studies on Signal Transduction Mechanism of Alcohol-induced Neuronal Cell Death and Protective Effect / 체질인류학회지

Excessive use of alcohol is a serious problem in our society and induces various, severe alcohol related diseases. The cytotoxicities of ethanol are still largely unknown. We studied the molecular mechanisms of EtOH-induced SK-N-SH neuronal cell death and protective effects of baicalein and gramineus against EtOH-induced cytotoxicities. In our results, the cell death by EtOH showed morphologic features of apoptosis like as membrane blebbing, nuclear condensation and fragmentation. Furthermore, pretreated baicalein attenuated EtOH-induced neuronal cell death effectively. EtOH increased expression levels of p53 and both p53 antisense oligonucleotide and Pifithrin protected the cell death against EtOH. Also, EtOH induced mitochondrial event, collapse of mitochondrial membrane potential ( delta psi m ) and caspase cascade as a downstream of mitochondria. Interestingly, baicalein decreased expression levels of p53 and inhibited collapse of mitochondrial membrane potential. These results suggest that baicalein reduces mitochondrial dysfunction induced by EtOH through down-regulation of p53 expression levels. Also, baicalein attenuated activation of caspase, which was triggered by mitochondrial malfunction. But gramineus didn't have any protective effect. These results imply that baicalein significantly protects EtOH-induced neuronal cell death through regulating p53, mitochondrial dysfunction and caspase activation.

Studies on Signal Transduction Mechanism of Alcohol-induced Neuronal Cell Death and Protective Effect / 체질인류학회지

Excessive use of alcohol is a serious problem in our society and induces various, severe alcohol related diseases. The cytotoxicities of ethanol are still largely unknown. We studied the molecular mechanisms of EtOH-induced SK-N-SH neuronal cell death and protective effects of baicalein and gramineus against EtOH-induced cytotoxicities. In our results, the cell death by EtOH showed morphologic features of apoptosis like as membrane blebbing, nuclear condensation and fragmentation. Furthermore, pretreated baicalein attenuated EtOH-induced neuronal cell death effectively. EtOH increased expression levels of p53 and both p53 antisense oligonucleotide and Pifithrin protected the cell death against EtOH. Also, EtOH induced mitochondrial event, collapse of mitochondrial membrane potential ( delta psi m ) and caspase cascade as a downstream of mitochondria. Interestingly, baicalein decreased expression levels of p53 and inhibited collapse of mitochondrial membrane potential. These results suggest that baicalein reduces mitochondrial dysfunction induced by EtOH through down-regulation of p53 expression levels. Also, baicalein attenuated activation of caspase, which was triggered by mitochondrial malfunction. But gramineus didn't have any protective effect. These results imply that baicalein significantly protects EtOH-induced neuronal cell death through regulating p53, mitochondrial dysfunction and caspase activation.

Caspase is Regulated by ROS in CT Induced Neuronal Cell Death / 대한해부학회지

Carboxy-terminal fragment of amyloid precusor protein (CT) is a candidate of causal molecule in the pathogenesis of Alzheimer's disease. Although it has been identified that CT shows cytotoxicity in various types of cells, little is known about the molecular mechanism of the cytotoxic on neuronal cells by CT. In the present study, we investigated the relevance of reactive oxygen species (ROS) generation to CT induced cell death in SK-N-SH cells. We showed CT induced ROS production and antioxidant GSH inhibited the increase of ROS production, thereby preventing neuronal cell death. These results indicate that CT induce neuronal cell death through mediation of ROS. Furthermore, increase of caspase activity resulted from CT reduced by GSH. It is implicate that caspase-3 may act downstream of ROS in the pathway neuronal cell death induced by CT.

The Protective Role of Estrogen by Down -regulation of Bax in Ceramide Induced Neuronal Cell Death / 대한해부학회지

In the present study, we investigated effects of estrogen on cell death induced by ceramide in human neuroblastoma SK -N -SH. Estrogen, attenuated ceramide -induced cell death. To determine the molecular mechanism of protective effect of estrogen, we investigated the effect of estrogen on the increase of Bax by ceramide. Estrogen decreased Bax expression. Moreover, estrogen showed the inhibitory effect on the caspase activation by ceramide. These results suggest that estrogen attenuate ceramide -induced neuronal cell death by downregulation of Bax and subsequent inhibition of caspase activation.