Injury to axons and oligodendrocytes following endothelin-1-induced middle cerebral artery occlusion in conscious rats

Clinical Features, Risk Factors, and Early Prognosis for Wallerian Degeneration in the Descending Pyramidal Tract after Acute Cerebral Infarction

BACKGROUND

Wallerian degeneration(WD) occurs in the descending pyramidal tract(DPT) after cerebral infarction commonly, but studies of its degree evaluation, influencing factors and effects on nervous function are still limited.

OBJECTIVES

The purpose of this study was to describe these findings and estimate their clinical significance.

METHODS

In total, 133 patients confirmed acute cerebral infarction and restricted diffusion in the DPT of the cerebral peduncle by MRI scans. These cases were retrospectively reviewed. We describe their clinical characteristics and analyze influence factors of WD, including the timespan from symptom onset to MRI and TOAST classification. Their NIHSS scores at admission and first 7 days NIHSS improvement rate after admission were also analyzed.

RESULTS

These patients were divided into three groups by timespan ≤7 days(n = 45),7-14 days(n = 70) and >14 days(n = 18). The mean WD degree (%)of these three groups was 44.41 ± 22.51,52.35 ± 22.61and 44.31 ± 19.35,respectively(p = 0.122).According to the TOAST classification, the mean WD degree(%) of the cardioembolism group(n = 28, 62.80 ± 25.12) was significantly different from both the large-artery atherosclerosis group(n = 73,45.08 ± 20.03,p = 0.000) and the small-vessel occlusion group(n = 23,39.68 ± 16.95,p = 0.000). The mean NIHSS score upon admission of the WD degree≤50% group(n = 82,8.17 ± 5.87) was different from that of the >50% group(n = 51,11.31 ± 7.00)(p = 0.006). However, the mean 7 days NIHSS improvement rate(%) of the WD degree≤50% group(n = 79,11.83 ± 23.76)and >50% group(n = 50,13.40 ± 27.88) was not significantly different(p = 0.733).

CONCLUSIONS

Early WD in ischemic stroke patients has a correlation with serious baseline functional defects. Therefore, we should give close attention to imaging change, especially in those with cardioembolism .

Focal cerebral ischemia induces changes in oligodendrocytic tau isoforms in the damaged area

Ischemic stroke is a major cause of death and the first leading cause of long-term disability worldwide. The only therapeutic strategy available to date is reperfusion and not all the patients are suitable for this treatment. Blood flow blockage or reduction leads to considerable brain damage, affecting both gray and white matter. The detrimental effects of ischemia have been studied extensively in the former but not in the latter. Previous reports indicate that preservation of white matter integrity reduces deleterious effect of ischemia on the brain. Oligodendrocytes are sensitive to ischemic damage, however, some reports demonstrate that oligodendrogenesis occurs after ischemia. These glial cells have a complex cytoskeletal network, including tau, that plays a key role to proper myelination. 4R-Tau/3R-Tau, which differ in the presence/absence of Exon 10, are found in oligodendrocytes; but the precise role of each isoform is not understood. Using permanent middle cerebral artery occlusion model and immunofluorescence, we demonstrate that cerebral ischemia induces an increase in 3R-Tau versus 4R-Tau in oligodendrocytes in the damaged area. In addition, cellular distribution of Tau undergoes a change after ischemia, with some oligodendrocytic processes showing positive staining for 3R-Tau. This occurs simultaneously with the amelioration of neurological damage in ischemic rats. We propose that ischemia triggers an endogenous mechanism involving 3R-Tau, that induces colonization of the ischemic damaged area by oligodendrocytes in an attempt to myelinate-injured axons. Understanding the molecular mechanism of this phenomenon could pave the way for the design of therapeutic strategies that exploit glial cells for the treatment of ischemia.

Comparative Therapeutic Effects of Minocycline Treatment and Bone Marrow Mononuclear Cell Transplantation following Striatal Stroke

We explored the comparative effects of minocycline treatment and intrastriatal BMMC transplantation after experimental striatal stroke in adult rats. Male Wistar adult rats were divided as follows: saline-treated (N = 5), minocycline-treated (N = 5), and BMMC-transplanted (N = 5) animals. Animals received intrastriatal microinjections of 80 pmol of endothelin-1 (ET-1). Behavioral tests were performed at 1, 3, and 7 days postischemia. Animals were treated with minocycline (50 mg/kg, i.p.) or intrastriatal transplants of 106 BMMCs at 24 h postischemia. Animals were perfused at 7 days after ischemic induction. Coronal sections were stained with cresyl violet for gross histopathological analysis and immunolabeled for the identification of neuronal bodies (NeuN), activated microglia/macrophages (ED1), and apoptotic cells (active caspase-3). BMMC transplantation and minocycline reduced the number of ED1+ cells (p < 0.05, ANOVA-Tukey), but BMMC afforded better results. Both treatments afforded comparable levels of neuronal preservation compared to control (p > 0.05). BMMC transplantation induced a higher decrease in the number of apoptotic cells compared to control and minocycline treatment. Both therapeutic approaches improved functional recovery in ischemic animals. The results suggest that BMMC transplantation is more effective in modulating microglial activation and reducing apoptotic cell death than minocycline, although both treatments are equally efficacious on improving neuronal preservation.

Indomethacin treatment reduces microglia activation and increases numbers of neuroblasts in the subventricular zone and ischaemic striatum after focal ischaemia

Neuroblasts from the subventricular zone (SVZ) migrate to striatum following stroke, but most of them die in the ischaemic milieu and this can be related to exacerbated microglial activation. Here, we explored the effects of the non-steroidal anti-inflammatory indomethacin on microglial activation, neuronal preservation and neuroblast migration following experimental striatal stroke in adult rats. Animals were submitted to endothelin-1 (ET-1)-induced focal striatal ischaemia and were treated with indomethacin or sterile saline (i.p.) for 7 days, being perfused after 8 or 14 days. Immunohistochemistry was performed to assess neuronal loss (anti-NeuN), microglial activation (anti-Iba1, ED1) and migrating neuroblasts (anti-DCX) by counting NeuN, ED1 and DCX-positive cells in the ischaemic striatum or SVZ. Indomethacin treatment reduced microglia activation and the number of ED1+ cells in both 8 and 14 days post injury as compared with controls. There was an increase in the number of DCX+ cells in both SVZ and striatum at the same survival times. Moreover, there was a decrease in the number of NeuN+ cells in indomethacin-treated animals as compared with the control group at 8 days but not after 14 days post injury. Our results suggest that indomethacin treatment modulates microglia activation, contributing to increased neuroblast proliferation in the SVZ and migration to the ischaemic striatum following stroke.

Neurodegeneration and Glial Response after Acute Striatal Stroke: Histological Basis for Neuroprotective Studies

Stroke is a leading cause of death and neurological disability worldwide and striatal ischemic stroke is frequent in humans due to obstruction of middle cerebral artery. Several pathological events underlie damage progression and a comprehensive description of the pathological features following experimental stroke in both acute and chronic survival times is a necessary step for further functional studies. Here, we explored the patterns of microglial activation, astrocytosis, oligodendrocyte damage, myelin impairment, and Nogo-A immunoreactivity between 3 and 30 postlesion days (PLDs) after experimental striatal stroke in adult rats induced by microinjections of endothelin-1 (ET-1). The focal ischemia induced tissue loss concomitant with intense microglia activation between 3 and 14 PLDs (maximum at 7 PLDs), decreasing afterward. Astrocytosis was maximum around 7 PLDs. Oligodendrocyte damage and Nogo-A upregulation were higher at 3 PLDs. Myelin impairment was maximum between 7 and 14 PLDs. Nogo-A expression was higher in the first week in comparison to control. The results add important histopathological features of ET-1 induced stroke in subacute and chronic survival times. In addition, the establishment of the temporal evolution of these neuropathological events is an important step for future studies seeking suitable neuroprotective drugs targeting neuroinflammation and white matter damage.

Ameliorative Effects of Antioxidants on the Hippocampal Accumulation of Pathologic Tau in a Rat Model of Blast-Induced Traumatic Brain Injury

Traumatic brain injury (TBI) can lead to early onset dementia and other related neurodegenerative diseases. We previously demonstrated that damage to the central auditory pathway resulting from blast-induced TBI (bTBI) could be significantly attenuated by a combinatorial antioxidant treatment regimen. In the current study, we examined the localization patterns of normal Tau and the potential blast-induced accumulation of neurotoxic variants of this microtubule-associated protein that are believed to potentiate the neurodegenerative effects associated with synaptic dysfunction in the hippocampus following three successive blast overpressure exposures in nontransgenic rats. We observed a marked increase in the number of both hyperphosphorylated and oligomeric Tau-positive hilar mossy cells and somatic accumulation of endogenous Tau in oligodendrocytes in the hippocampus. Remarkably, a combinatorial regimen of 2,4-disulfonyl α-phenyl tertiary butyl nitrone (HPN-07) and N-acetylcysteine (NAC) resulted in striking reductions in the numbers of both mossy cells and oligodendrocytes positively labeled for these pathological Tau immunoreactivity patterns in response to bTBI. This treatment strategy represents a promising therapeutic approach for simultaneously reducing or eliminating both primary auditory injury and nonauditory changes associated with bTBI-induced hippocampal neurodegeneration.

The back and forth of axonal injury and repair after stroke

PURPOSE OF REVIEW

The axon plays a central role in both the injury and repair phases after stroke. This review highlights emerging principles in the study of axonal injury in stroke and the role of the axon in neural repair after stroke.

RECENT FINDINGS

Ischemic stroke produces a rapid and significant loss of axons in the acute phase. This early loss of axons results from a primary ischemic injury that triggers a wave of calcium signaling, activating proteolytic mechanisms and downstream signaling cascades. A second progressive phase of axonal injury occurs during the subacute period and damages axons that survive the initial ischemic insult but go on to experience a delayed axonal degeneration driven in part by changes in axoglial contact and axonal energy metabolism. Recovery from stroke is dependent on axonal sprouting and reconnection that occurs during a third degenerative/regenerative phase. Despite this central role played by the axon, comparatively little is understood about the molecular pathways that contribute to early and subacute axonal degeneration after stroke. Recent advances in axonal neurobiology and signaling suggest new targets that hold promise as potential molecular therapeutics including axonal calcium signaling, axoglial energy metabolism and cell adhesion as well as retrograde axonal mitogen-activated protein kinase pathways. These novel pathways must be modeled appropriately as the type and severity of axonal injury vary by stroke subtype.

SUMMARY

Stroke-induced injury to axons occurs in three distinct phases each with a unique molecular underpinning. A wealth of new data about the molecular organization and molecular signaling within axons is available but not yet robustly applied to the study of axonal injury after stroke. Identifying the spatiotemporal patterning of molecular pathways within the axon that contribute to injury and repair may offer new therapeutic strategies for the treatment of stroke.

What drives progressive motor deficits in patients with acute pontine infarction?

Progressive motor deficits are relatively common in acute pontine infarction and frequently associated with increased functional disability. However, the factors that affect the progression of clinical motor weakness are largely unknown. Previous studies have suggested that pontine infarctions are caused mainly by basilar artery stenosis and penetrating artery disease. Recently, lower pons lesions in patients with acute pontine infarctions have been reported to be related to progressive motor deficits, and ensuing that damage to the corticospinal tracts may be responsible for the worsening of neurological symptoms. Here, we review studies on motor weakness progression in pontine infarction and discuss the mechanisms that may underlie the neurologic worsening.

Effects of hypothermia on oligodendrocyte precursor cell proliferation, differentiation and maturation following hypoxia ischemia in vivo and in vitro

Hypoxic-ischemia (HI) not only causes gray matter injury but also white matter injury, leading to severe neurological deficits and mortality, and only limited therapies exist. The white matter of animal models and human patients with HI-induced brain injury contains increased oligodendrocyte precursor cells (OPCs). However, little OPC can survive and mature to repair the injured white matter. Here, we test the effects of mild hypothermia on OPC proliferation, differentiation and maturation. Animals suffered to left carotid artery ligation followed by 8% oxygen for 2h in 7-day-old rats. They were divided into a hypothermic group (rectal temperature 32-33 °C for 48 h) and a normothermic group (36-37 °C for 48 h), then animals were sacrificed at 3, 7, 14 and 42 days after HI surgery. Our results showed that hypothermia successfully enhanced early OL progenitors (NG2(+)) and its proliferation in the corpus callosum (CC) after HI. Late OL progenitor (O4(+)) accumulation decreased accompanied with increased OL maturation which is detected by myelin basic protein (MBP) and proteolipid protein. (PLP) immunostaining and immunoblotting in hypothermia compared to normothermia. Additionally, using an in vitro hypoxic-ischemia model-oxygen glucose deprivation (OGD), we demonstrated that hypothermia decreased preOL accumulation and promoted OPC differentiation and maturation. Further data indicated that OPC death was significantly suppressed by hypothermia in vitro. The myelinated axons and animal behavior both markedly increased in hypothermic- compared to normothermic-animals after HI. In summary, these data suggest that hypothermia has the effects to protect OPC and to promote OL maturation and myelin repair in hypoxic-ischemic events in the neonatal rat brain. This study proposed new aspects that may contribute to elucidate the mechanism of hypothermic neuroprotection for white matter injury in neonatal rat brain injury.

Short-term effects of hypothermia on axonal injury, preoligodendrocyte accumulation and oligodendrocyte myelination after hypoxia-ischemia in the hippocampus of immature rat brain

Hypothermia is known to improve neurological recovery of animals and humans exposed to hypoxic-ischemic (HI) injury. However, the underlying mechanisms of the neuroprotective effects of hypothermia are only partially understood, including decreased excitotoxicity and apoptosis, and suppressed inflammation. There are few studies about the hypothermic effects on axonal injury and oligodendrocyte (OL) lineage degeneration, which are important components of neonatal brain injuries that cause cognitive disability. We hypothesized that mild hypothermia would reduce axonal injury and increase myelination in the hippocampus after HI. We performed left carotid artery ligation followed by 8% oxygen for 2 h in 7-day-old rats. Animals were divided into a hypothermic group (rectal temperature 32-33°C for 24 h) and a normothermic group (36-37°C for 24 h) immediately after HI. Animals were sacrificed at 1, 3 and 7 days for immunohistochemistry or Western blot analysis. We detected neuron loss by microtubule-associated protein 2 labeling and axonal injury by non-phosphorylated neurofilament (SMI32) with neurofilament 200 (NF200) double staining. We examined early OL progenitors by A2B5 or NG2, preoligodendrocytes (preOLs) by O4, and mature OLs by 2,3-cyclic nucleotide 3-phosphodiesterase (CNPase) and glutathione S-transferase (GST)-pi staining. Apoptosis was studied by active caspase-3. Hypothermia was associated with a significant elevation of neurons and axons in the hippocampal CA1 region after HI. Early OL progenitors (A2B5(+)) were elevated, but preOLs (O4(+)) and active caspase-3 were dramatically reduced in the hypothermic rat brain. Further study showed that the apoptotic rate of preOLs (caspase-3(+)-O4(+)/O4(+)) was markedly attenuated by hypothermic treatment compared to normothermic animals. The immunoreactivity of CNPase and GST-pi and the protein level of the myelin basic protein significantly increased in the hippocampus of hypothermia-treated rat brain. Axonal myelination also increased in hypothermic animals, which were tested by myelin basic protein and NF200 double staining and electron microscopy. These results showed that hypothermia reduced HI damage to axons and OL myelination coincided with increased early OL progenitor proliferation and decreased preOL accumulation and apoptosis. This study suggested new aspects that may contribute to elucidate the mechanism of hypothermic neuroprotection in neonatal rat brain.

Neuroprotective effect of kaempferol glycosides against brain injury and neuroinflammation by inhibiting the activation of NF-κB and STAT3 in transient focal stroke

BACKGROUND

Ischemic brain injury is associated with neuroinflammatory response, which essentially involves glial activation and neutrophil infiltration. Transcription factors nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) contribute to ischemic neuroinflammatory processes and secondary brain injury by releasing proinflammatory mediators. Kaempferol-3-O-rutinoside (KRS) and kaempferol-3-O- glucoside (KGS) are primary flavonoids found in Carthamus tinctorius L. Recent studies demonstrated that KRS protected against ischemic brain injury. However, little is known about the underlying mechanisms. Flavonoids have been reported to have antiinflammatory properties. Herein, we explored the effects of KRS and KGS in a transient focal stroke model.

METHODOLOGY/PRINCIPAL FINDINGS

Rats were subjected to middle cerebral artery occlusion for 2 hours followed by 22 h reperfusion. An equimolar dose of KRS or KGS was administered i.v. at the beginning of reperfusion. The results showed that KRS or KGS significantly attenuated the neurological deficits, brain infarct volume, and neuron and axon injury, reflected by the upregulation of neuronal nuclear antigen-positive neurons and downregulation of amyloid precursor protein immunoreactivity in the ipsilateral ischemic hemisphere. Moreover, KRS and KGS inhibited the expression of OX-42, glial fibrillary acidic protein, phosphorylated STAT3 and NF-κB p65, and the nuclear content of NF-κB p65. Subsequently, these flavonoids inhibited the expression of tumor necrosis factor α, interleukin 1β, intercellular adhesion molecule 1, matrix metallopeptidase 9, inducible nitric oxide synthase, and myeloperoxidase.

CONCLUSION/SIGNIFICANCE

Our findings suggest that postischemic treatment with KRS or KGS prevents ischemic brain injury and neuroinflammation by inhibition of STAT3 and NF-κB activation and has the therapeutic potential for the neuroinflammation-related diseases, such as ischemic stroke.

Endothelin-1-induced down-regulation of NaV1.7 expression in adrenal chromaffin cells: attenuation of catecholamine secretion and tau dephosphorylation

Endothelin-1 and voltage-dependent sodium channels are involved in control and suppression of neuropathological factors, which contribute to sculpting the neuronal network. We previously demonstrated that veratridine-induced NaV1.7 sodium channel activation caused intracellular calcium elevation, catecholamine secretion and tau dephosphorylation in adrenal chromaffin cells. The aim of this study was to examine whether endothelin-1 could modulate NaV1.7. Our results indicated that endothelin-1 decreased the protein level of NaV1.7 and the veratridine-induced increase in intracellular calcium. In addition, it also abolished the veratridine-induced dephosphorylation of tau and the phosphorylation of glycogen synthase kinase-3β and extracellular signal-regulated kinase. These findings suggest that the endothelin-1-induced down-regulation of NaV1.7 diminishes NaV1.7-related catecholamine secretion and dephosphorylation of tau.

Impaired axoplasmic transport is the dominant injury induced by an impact acceleration injury device: an analysis of traumatic axonal injury in pyramidal tract and corpus callosum of rats

Traumatic axonal injury (TAI) involves neurofilament compaction (NFC) and impaired axoplasmic transport (IAT) in distinct populations of axons. Previous quantification studies of TAI focused on limited areas of pyramidal tract (Py) but not its entire length. Quantification of TAI in corpus callosum (CC) and its comparison to that in Py is also lacking. This study assessed and compared the extent of TAI in the entire Py and CC of rats following TBI. TBI was induced by a modified Marmarou impact acceleration device in 31 adult male Sprague Dawley rats by dropping a 450 gram impactor from either 1.25 m or 2.25 m. Twenty-four hours after TBI, TAI was assessed by beta amyloid precursor protein (β-APP-IAT) and RMO14 (NFC) immunocytochemistry. TAI density (β-APP and RMO14 axonal swellings, retraction balls and axonal profiles) was counted from panoramic images of CC and Py. Significantly high TAI was observed in 2.25 m impacted rats. β-APP immunoreactive axons were significantly higher in number than RMO14 immunoreactive axons in both the structures. TAI density in Py was significantly higher than in CC. Based on our parallel biomechanical studies, it is inferred that TAI in CC may be related to compressive strains and that in Py may be related to tensile strains. Overall, IAT appears to be the dominant injury type induced by this model and injury in Py predominates that in CC.

Consistent injury to medium spiny neurons and white matter in the mouse striatum after prolonged transient global cerebral ischemia

A reproducible transient global cerebral ischemia (tGCI) mouse model has not been fully established. Although striatal neurons and white matter are recognized to be vulnerable to ischemia, their injury after tGCI in mice has not been elucidated. The purpose of this study was to evaluate injuries to striatal neurons and white matter after tGCI in C57BL/6 mice, and to develop a reproducible tGCI model. Male C57BL/6 mice were subjected to tGCI by bilateral common carotid artery occlusion (BCCAO). Mice whose cortical cerebral blood flow after BCCAO decreased to less than 13% of the pre-ischemic value were used. Histological analysis showed that at 3 days after 22 min of BCCAO, striatal neurons were injured more consistently than those in other brain regions. Quantitative analysis of cytochrome c release into the cytosol and DNA fragmentation in the striatum showed consistent injury to the striatum. Immunohistochemistry and Western blot analysis revealed that DARPP-32-positive medium spiny neurons, the majority of striatal neurons, were the most vulnerable among the striatal neuronal subpopulations. The striatum (especially medium spiny neurons) was susceptible to oxidative stress after tGCI, which is probably one of the mechanisms of vulnerability. SMI-32 immunostaining showed that white matter in the striatum was also consistently injured 3 days after 22 min of BCCAO. We thus suggest that this is a tGCI model using C57BL/6 mice that consistently produces neuronal and white matter injury in the striatum by a simple technique. This model can be highly applicable for elucidating molecular mechanisms in the brain after global ischemia.

Lycium barbarum polysaccharides reduce neuronal damage, blood-retinal barrier disruption and oxidative stress in retinal ischemia/reperfusion injury

Neuronal cell death, glial cell activation, retinal swelling and oxidative injury are complications in retinal ischemia/reperfusion (I/R) injuries. Lycium barbarum polysaccharides (LBP), extracts from the wolfberries, are good for “eye health” according to Chinese medicine. The aim of our present study is to explore the use of LBP in retinal I/R injury. Retinal I/R injury was induced by surgical occlusion of the internal carotid artery. Prior to induction of ischemia, mice were treated orally with either vehicle (PBS) or LBP (1 mg/kg) once a day for 1 week. Paraffin-embedded retinal sections were prepared. Viable cells were counted; apoptosis was assessed using TUNEL assay. Expression levels of glial fibrillary acidic protein (GFAP), aquaporin-4 (AQP4), poly(ADP-ribose) (PAR) and nitrotyrosine (NT) were investigated by immunohistochemistry. The integrity of blood-retinal barrier (BRB) was examined by IgG extravasations. Apoptosis and decreased viable cell count were found in the ganglion cell layer (GCL) and the inner nuclear layer (INL) of the vehicle-treated I/R retina. Additionally, increased retinal thickness, GFAP activation, AQP4 up-regulation, IgG extravasations and PAR expression levels were observed in the vehicle-treated I/R retina. Many of these changes were diminished or abolished in the LBP-treated I/R retina. Pre-treatment with LBP for 1 week effectively protected the retina from neuronal death, apoptosis, glial cell activation, aquaporin water channel up-regulation, disruption of BRB and oxidative stress. The present study suggests that LBP may have a neuroprotective role to play in ocular diseases for which I/R is a feature.

Role of glial cells in neurotoxin-induced animal models of Parkinson's disease

Dopaminergic neurons are selectively vulnerable to oxidative stress and inflammatory attack. The neuronal cell loss in the substantia nigra is associated with a glial response composed markedly of activated microglia and, to a lesser extent, of reactive astrocytes although these glial responses may be the source of neurotrophic factors and can protect against oxidative stress such as reactive oxygen species and reactive nitrogen species. However, the glial response can also mediate a variety of deleterious events related to the production of pro-inflammatory, pro-oxidant reactive species, prostaglandins, cytokines, and so on. In this review, we discuss the possible protective and deleterious effects of glial cells in the neurodegenerative diseases and examine how these factors may contribute to the pathogenesis of Parkinson's disease. This review suggests that further investigation concerning glial reaction in Parkinson's disease may lead to disease-modifying therapeutic approaches and may contribute to the pathogenesis of this disease.

Endothelin-1 as a neuropeptide: neurotransmitter or neurovascular effects?

Endothelin-1 (ET-1) is an endothelium-derived peptide that also possesses potent mitogenic activity. There is also a suggestion the ET-1 is a neuropeptide, based mainly on its histological identification in both the central and peripheral nervous system in a number of species, including man. A neuropeptide role for ET-1 is supported by studies showing a variety of effects caused following its administration into different regions of the brain and by application to peripheral nerves. In addition there are studies proposing that ET-1 is implicated in a number of neural circuits where its transmitter affects range from a role in pain and temperature control to its action on the hypothalamo-neurosecretory system. While the effect of ET-1 on nerve tissue is beyond doubt, its action on nerve blood flow is often ignored. Here, we review data generated in a number of species and using a variety of experimental models. Studies range from those showing the distribution of ET-1 and its receptors in nerve tissue to those describing numerous neurally-mediated effects of ET-1.

Human umbilical cord blood cells directly suppress ischemic oligodendrocyte cell death

Previous reports have shown that human umbilical cord blood cells (HUCBCs) administered intravenously 48 hr following middle cerebral artery occlusion reduce infarct area and behavioral deficits of rodents. This cellular therapy is potently neuroprotective and antiinflammatory. This study investigates the effect of HUCBC treatment on white matter injury and oligodendrocyte survival in a rat model of ischemia. Intravenous infusion of 10(6) HUCBCs 48 hr poststroke reduced the amount of white matter damage in vivo as seen by quantification of myelin basic protein staining in tissue sections. To determine whether HUCBC treatment was protective via direct effects on oligodendrocytes, cultured oligodendrocytes were studied in an in vitro model of oxygen glucose deprivation. Active caspase 3 immunohistochemistry and the lactate dehydrogenase assay for cytotoxicity were used to determine that HUCBCs provide protection to oligodendrocytes in vitro. Based on these results, it is likely that HUCBC administration directly protects oligodendrocytes and white matter. This effect is likely to contribute to the increased behavioral recovery observed with HUCBC therapy.

Progression of pathological changes in the middle cerebellar peduncle by diffusion tensor imaging correlates with lesser motor gains after pontine infarction

BACKGROUND

Wallerian degeneration in pyramidal tract following supratentorial stroke has been detected by some studies using diffusion tensor imaging (DTI), but the Wallerian degeneration in middle cerebellar peduncle after pontine infarction and its potential clinical significance remain to be confirmed.

METHODS

Seventeen patients with a recent focal pontine infarct underwent 3 DTIs at week 1 (W1), week 4 (W4), and week 12 (W12) after onset. Seventeen age-matched and gender-matched controls underwent DTI one time. Mean diffusivity and fractional anisotropy (FA) were measured in the basis pontis and bilateral middle cerebellar peduncles. Neurological deficit, motor deficit, functional independence, and limbs ataxia were assessed with the National Institutes of Health (NIH) Stroke Scale, Fugl-Meyer scale, Barthel Index, and the second part of International Cooperative Ataxia Rating Scale.

RESULTS

FA values at the bilateral middle cerebellar peduncles decreased significantly from W1 to W12 progressively (P<.01). The patients improved on the NIH Stroke Scale, Fugl-Meyer scale, and Barthel Index over time (P<.01). Greater absolute value of percentage reduction of FA at the bilateral middle peduncles, however, was associated with the less absolute value of percentage reduction of the NIH Stroke Scale and less increase in the Fugl-Meyer scale, as well as greater ataxia over time.

CONCLUSIONS

Wallerian degeneration in the middle cerebellar peduncle revealed by DTI may hinder the process of neurological recovery following a focal pontine infarct.

Bone marrow stromal cells protect oligodendrocytes from oxygen-glucose deprivation injury

Oligodendrocyte (OLG) damage leads to demyelination, which is frequently observed in ischemic cerebrovascular diseases. In this study, we investigated the effect of bone marrow stromal cells (BMSCs) on OLGs subjected to oxygen-glucose deprivation (OGD). N20.1 cells (mouse OLG cell line) were transferred into an anaerobic chamber for 3 hr in glucose-free and serum-free medium. After OGD incubation, OLG cultures were divided into the following groups: 1) OGD alone, 2) OLG cocultured with BMSCs, 3) treatment with the phosphoinostide 3-kinase (PI3k) inhibitor LY294002, 4) LY294002-treated OLGs with BMSC cocultured, and 5) anti-p75 antibody-treated OLGs. After an additional 3 hr of reoxygenation incubation, OLG viability and apoptosis were measured. The mRNA expression in the BMSCs and OLGs was analyzed using quantitative real-time PCR (RT-PCR). Serine/threonine-specific protein kinase (Akt), phosphorylated Akt (p-Akt), p75, and caspase 3 protein expressions in OLGs were measured by Western blot. Our results suggest that BMSCs produce growth factors, activate the Akt pathway, and increase the survival of OLGs. BMSCs also reduce p75 and caspase 3 expressions in the OGD-OLGs, which leads to decreased OLG apoptosis. BMSCs participate in OLG protection that may occur with promoting growth factors/PI3K/Akt and inhibiting the p75/caspase pathways. Our study provides insight into white matter damage and the therapeutic benefits of BMSC-based remyelinating therapy after stroke and demyelinating diseases.

Spatiotemporal expression of Dexras1 after spinal cord transection in rats

Dexras1, a brain-enriched member of the Ras subfamily of GTPases, as a novel physiologic nitric oxide (NO) effector, anchor neuronal nitric oxide synthase (nNOS) that increased after spinal cord injury (SCI), to specific targets to enhance NO signaling, and is strongly and rapidly induced during treatment with dexamethasone. It is unknown how the central nervous system (CNS) trauma affects the expression of Dexras1. Here we used spinal cord transection (SCT) model to detect expression of Dexras1 at mRNA and protein level in spinal cord homogenates by real-time PCR and Western blot analysis. The results showed that Dexras1 mRNA upregulated at 3 day, 5 day, and 7 day significantly (P < 0.05) that was consistent with the protein level except at 7 day. Immunofluorescence revealed that both neurons and glial cells showed Dexras1 immunoreactivivty (IR) around SCT site, but the proportion is different. Importantly, injury-induced expression of Dexras1 was co-labeled by caspase-3 (apoptotic marker) and Tau-1 (marker for pathological oligodendrocyte). Furthermore, colocalization of Dexras1, carboxy-terminal PSD95/DLG/ZO-1 (PDZ) ligand of nNOS (CAPON) and nNOS was observed in neurons and glial cells, supporting the existence of ternary complexes in this model. Thus, the results that the transient high expression of Dexras1 which localized in apoptotic neurons and pathological oligodendrocytes might provide new insight into the secondary response after SCT.

Spatiotemporal patterns of SSeCKS expression after rat spinal cord injury

Src suppressed C kinase substrate (SSeCKS) was identified as a PKC substrate/PKC-binding protein, which plays a role in mitogenic regulatory activity and has a function in the control of cell signaling and cytoskeletal arrangement. However its distribution and function in the central nervous system (CNS) lesion remain unclear. In this study, we mainly investigated the mRNA and protein expression and cellular localization of SSeCKS during spinal cord injury (SCI). Real-time PCR and Western blot analysis revealed that SSeCKS was present in normal whole spinal cord. It gradually increased, reached a peak at 3 days for its mRNA level and 5 days for its protein level after SCI, and then declined during the following days. In ventral horn, the expression of SSeCKS underwent a temporal pattern that was similar with the whole spinal cord in both mRNA and protein level. However, in dorsal horn, the mRNA and protein for SSeCKS expression were significantly increased at 1 day for its mRNA level and 3 days for its protein level, and then gradually declined to the baseline level, ultimately up-regulated again from 7 to 14 days. The protein expression of SSeCKS was further analysed by immunohistochemistry. The positively stained areas for SSeCKS changed with the similar pattern to that of protein expression detected by immunoblotting analysis. Double immunofluorescence staining showed that SSeCKS immunoreactivity (IR) was found in neurons, astrocytes, oligodendrocytes of spinal cord tissues within 5 mm from the lesion site. Importantly, injury-induced expression of SSeCKS was co-labeled by active caspase-3 (apoptotic marker), Tau-1 (the marker for pathological oligodendrocyte) and beta-1,4-galactosyltransferase 1 (GalT). All the results suggested that SSeCKS might play important roles in spinal cord pathophysiology and further research is needed to have a good understanding of its function and mechanism.

Spatiotemporal patterns of postsynaptic density (PSD)-95 expression after rat spinal cord injury

AIMS

Postsynaptic density (PSD)-95 is a scaffolding protein linking the N-methyl-D-aspartate receptor with neuronal nitric oxide synthase (nNOS), which contributes to many physiological and pathological actions. We here investigated whether PSD-95 was involved in the secondary response following spinal cord injury (SCI).

METHODS

Spinal cord contusion (SCC) and spinal cord transection (SCT) models at thoracic (T) segment 9 (T(9)) were established in adults rats. Real-time polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence were used to detect the temporal profile and spatial distribution of PSD-95 after SCI. The association between PSD-95 and nNOS in the injured cords was also assessed by coimmmunoprecipation and double immunofluorescent staining.

RESULTS

The mRNA and protein for PSD-95 expression were significantly increased at 2 h or 8 h, and then gradually declined to the baseline level, ultimately up-regulated again from 5 days to 7 days for its mRNA level and at 7 days or 14 days for its protein level after either SCC or SCT. PSD-95 immunoreactivity was found in neurones, oligodendrocytes and synaptic puncta of spinal cord tissues within 5 mm from the lesion site. Importantly, injury-induced expression of PSD-95 was colabelled by active caspase-3 (apoptotic marker), Tau-1 (the marker for pathological oligodendrocytes) and nNOS.

CONCLUSIONS

Accompanied by the spatio-temporal changes for PSD-95 expression, the association between PSD-95 and nNOS undergoes substantial alteration after SCI. These two molecules are likely to form a complex on apoptotic neurones and pathological oligodendrocytes, which may in turn be involved in the secondary response after SCI.

Damage to oligodendrocytes in the striatum after MPTP neurotoxicity in mice

We investigated the alteration of oligodendrocytes in comparison with that of astrocytes and microglia in the mouse striatum after MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropridine) treatment under the same conditions using Western blot analysis and Immunohistochemistry. In our Western blot analysis, four administrations of MPTP at 2-h intervals to mice produced the remarkable loss of TH (tyrosine hydroxylase) protein levels in the striatum after 3 and 7 days. In contrast, GFAP (glial fibrillary acidic protein) and Iba-1 protein in the striatum showed a significant increase of GFAP and Iba-1 protein levels 3 and 7 days after MPTP treatment. On the other hand, the levels of CNPase (2', 3'-cyclic nucleotide 3'-phosphodiesterase) protein were decreased significantly in the striatum 3 and 7 days after MPTP treatment. In our immunohistochemical study, a significant decrease in the area of expression of CNPase-positive profiles was observed in the striatum 3 and 7 days after MPTP treatment. These results demonstrate that oligodendrocytes in the striatum are damaged after MPTP treatment. Thus our present findings provide valuable information for the pathogenesis of Parkinson's disease.