Selective brain hypothermia attenuates focal cerebral ischemic injury and improves long‐term neurological outcome in aged female mice

AimsThis study aimed to investigate the effects of mild selective brain hypothermia on aged female ischemic mice.MethodsA distal middle cerebral artery occlusion (dMCAO) model was established in aged female mice, who were then subjected to mild selective brain hypothermia immediately after the dMCAO procedure. Neurological behavioral examinations were conducted prior to and up to 35 days post‐ischemia. Infarct volume, brain atrophy, pro‐inflammation, and anti‐inflammation microglia/macrophages phenotype and white matter injury were evaluated by immunofluorescence staining. Correlations between neurological behaviors and histological parameters were evaluated by Pearson product linear regression analysis.ResultsSensorimotor and cognitive function tests confirmed the protective effect of mild selective brain hypothermia in elderly female ischemic mice. In addition, hypothermia decreased the infarct volume and brain atrophy induced by focal cerebral ischemia. Furthermore, hypothermia alleviated ischemia‐induced short‐term and long‐term white matter injury, which was correlated with behavioral deficits. Finally, hypothermia suppressed the harmful immunological response by promoting the transformation of pro‐inflammatory microglia/macrophages to anti‐inflammatory phenotype. This polarization was negatively correlated with neuronal loss and white matter injury.ConclusionMild selective brain hypothermia promoted long‐term functional recovery by alleviating white matter damage in an aged female mouse model of ischemia.     

Treatment with Evasin-3 reduces atherosclerotic vulnerability for ischemic stroke,but not brain injury in mice

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactivity and related neutrophilic inflammation in two mouse models of carotid atherosclerosis and ischemic stroke, respectively. In the first model, the chronic treatment with Evasin-3 as compared with Vehicle (phosphate-buffered saline (PBS)) was investigated in apolipoprotein E-deficient mice implanted of a ‘cast'' carotid device. In the second model, acute Evasin-3 treatment (5 minutes after cerebral ischemia onset) was assessed in mice subjected to transient left middle cerebral artery occlusion. Although CXCL1 and CXCL2 were upregulated in both atherosclerotic plaques and infarcted brain, only CXCL1 was detectable in serum. In carotid atherosclerosis, treatment with Evasin-3 was associated with reduction in intraplaque neutrophil and matrix metalloproteinase-9 content and weak increase in collagen as compared with Vehicle. In ischemic stroke, treatment with Evasin-3 was associated with reduction in ischemic brain neutrophil infiltration and protective oxidants. No other effects in clinical and histological outcomes were observed. We concluded that Evasin-3 treatment was associated with reduction in neutrophilic inflammation in both mouse models. However, Evasin-3 administration after cerebral ischemia onset failed to improve poststroke outcomes.     

Calcium/calmodulin‐dependent protein kinase kinase β is neuroprotective in stroke in aged mice

Stroke is a devastating neurological disease and the leading cause of long‐term disability, particularly in the elderly. Calcium/calmodulin‐dependent protein kinase kinase β (CaMKK β) is a major kinase activated by elevated levels of intracellular calcium. Our previous findings in young mice have suggested that CaMKK β is neuroprotective as KO mice had worse stroke outcomes. Because age is an important determinant of stroke outcome, we evaluated the functional role of CaMKK β in stroke in aged mice. We used middle cerebral artery occlusion to induce stroke in aged wild‐type (WT) and CaMKK β KO male mice. Lentiviral vectors carrying CaMKK β (LV‐CaMKK β) were used to overexpress CaMKK β in the mouse brain. Baseline levels of CaMKK β in the aged brain were significantly lower than those in young mice. LV‐CaMKK β treatment reduced infarcts and neurological deficits assessed 3 days after stroke. In chronic survival experiments, CaMKK β KO mice showed increased tissue loss in the ipsilateral hemisphere 3 weeks after stroke. In addition, KO mice showed poorer functional recovery during the 3‐week survival period, as measured by the rotarod test, corner test, locomotor activity assay, and novel object recognition test, compared with WT controls. The loss of blood–brain barrier proteins, inactivation of survival gene expression such as B‐cell lymphoma 2 (Bcl‐2) and an increase in inflammatory cytokines in the serum were observed after stroke with CaMKK β inhibition. We demonstrate that CaMKK β is neuroprotective in stroke in aged mice. Therefore, our data suggest that CaMKK β may be a potential target for reducing long‐term disability after stroke.     

Ubiquitin C‐terminal hydrolase‐L1 as a biomarker for ischemic and traumatic brain injury in rats

Ubiquitin C‐terminal hydrolase‐L1 (UCH‐L1), also called neuronal‐specific protein gene product 9.5, is a highly abundant protein in the neuronal cell body and has been identified as a possible biomarker on the basis of a recent proteomic study. In this study, we examined whether UCH‐L1 was significantly elevated in cerebrospinal fluid (CSF) following controlled cortical impact (CCI) and middle cerebral artery occlusion (MCAO; model of ischemic stroke) in rats. Quantitative immunoblots of rat CSF revealed a dramatic elevation of UCH‐L1 protein 48 h after severe CCI and as early as 6 h after mild (30 min) and severe (2 h) MCAO. A sandwich enzyme‐linked immunosorbent assay constructed to measure UCH‐L1 sensitively and quantitatively showed that CSF UCH‐L1 levels were significantly elevated as early as 2 h and up to 48 h after CCI. Similarly, UCH‐L1 levels were also significantly elevated in CSF from 6 to 72 h after 30 min of MCAO and from 6 to 120 h after 2 h of MCAO. These data are comparable to the profile of the calpain‐produced αII‐spectrin breakdown product of 145 kDa biomarker. Importantly, serum UCH‐L1 biomarker levels were also significantly elevated after CCI. Similarly, serum UCH‐L1 levels in the 2‐h MCAO group were significantly higher than those in the 30‐min group. Taken together, these data from two rat models of acute brain injury strongly suggest that UCH‐L1 is a candidate brain injury biomarker detectable in biofluid compartments (CSF and serum).     

Adenosine kinase determines the degree of brain injury after ischemic stroke in mice

Adenosine kinase (ADK) is the major negative metabolic regulator of the endogenous neuroprotectant and homeostatic bioenergetic network regulator adenosine. We used three independent experimental approaches to determine the role of ADK as a molecular target for predicting the brain''s susceptibility to ischemic stroke. First, when subjected to a middle cerebral artery occlusion model of focal cerebral ischemia, transgenic fb-Adk-def mice, which have increased ADK expression in striatum (164%) and reduced ADK expression in cortical forebrain (65%), demonstrate increased striatal infarct volume (126%) but almost complete protection of cortex (27%) compared with wild-type (WT) controls, indicating that cerebral injury levels directly correlate to levels of ADK in the CNS. Second, we demonstrate abrogation of lipopolysaccharide (LPS)-induced ischemic preconditioning in transgenic mice with brain-wide ADK overexpression (Adk-tg), indicating that ADK activity negatively regulates LPS-induced tolerance to stroke. Third, using adeno-associated virus-based vectors that carry Adk-sense or -antisense constructs to overexpress or knockdown ADK in vivo, we demonstrate increased (126%) or decreased (51%) infarct volume, respectively, 4 weeks after injection into the striatum of WT mice. Together, our data define ADK as a possible therapeutic target for modulating the degree of stroke-induced brain injury.     

Heterogeneous hyperactivity and distribution of ischemic lesions after focal cerebral ischemia in Mongolian gerbils

Various types of poststroke hyperactivity exist in humans, but studies of each mechanism using animal models are scarce. We aimed to analyze the heterogeneity of postischemic hyperlocomotion and to identify the ischemic lesions responsible for postischemic hyperlocomotion in rodent models of focal ischemia. Mongolian gerbils underwent right common carotid artery occlusion (CCAO) for 10 or 20 min. At 24 h, 2 days, and 7 days postischemia, we performed quantitative and qualitative locomotor analysis and correlated these results with the extent of ischemic lesions. Intermittent explosive hyperlocomotion was induced transiently in a 10‐min CCAO group at 24 h after ischemia and continual unexplosive hyperlocomotion persisted for 7 days in the 20‐min CCAO animals. Selective neuronal death, confined to the hippocampal cornu ammonis 1 (CA1), was observed in the 10‐min CCAO group and widespread cortical and basal ganglia infarction was observed in the 20‐min CCAO group. Amyloid precursor protein was transiently observed in the hippocampus at 24 h postischemia in the 10‐min CCAO animals, while it was widely distributed over the ischemic regions throughout the 7 days postischemia in the 20‐min CCAO animals. Incidence maps and correlation analysis revealed hippocampal neuronal death of the CA1 sector and widespread hemispheric infarction, including the cortex, as the region responsible for the 10‐min and 20‐min CCAO‐induced hyperactivity, respectively. Two distinct types of locomotor hyperactivity were observed that varied with regard to the distribution of the ischemic lesion, that is, hippocampal neuronal death and widespread infarction involving the cortex. These two types of locomotor hyperactivity appear to be models of the different types of poststroke hyperactivity seen in stroke patients.     

3-Nitropropionic acid-induced ischemia tolerance in the rat brain is mediated by reduced metabolic activity and cerebral blood flow

Tissue tolerance to ischemia can be achieved by noxious stimuli that are below a threshold to cause irreversible damage (‘preconditioning''). Understanding the mechanisms underlying preconditioning may lead to the identification of novel therapeutic targets for diseases such as stroke. We here used the oxidative chain inhibitor 3-nitropropionic acid (NPA) to induce ischemia tolerance in a rat middle cerebral artery occlusion (MCAO) stroke model. Cerebral blood flow (CBF) and structural integrity were characterized by longitudinal magnetic resonance imaging (MRI) in combination with behavioral, histologic, and biochemical assessment of NPA-preconditioned animals and controls. Using this approach we show that the ischemia-tolerant state is characterized by a lower energy charge potential and lower CBF, indicating a reduced baseline metabolic demand, and therefore a cellular mechanism of neural protection. Blood vessel density and structural integrity were not altered by NPA treatment. When subjected to MCAO, preconditioned animals had a characteristic MRI signature consisting of enhanced CBF maintenance within the ischemic territory and intraischemic reversal of the initial cytotoxic edema, resulting in reduced infarct volumes. Thus, our data show that tissue protection through preconditioning occurs early during ischemia and indicate that a reduced cellular metabolism is associated with tissue tolerance to ischemia.     

Latrepirdine is a potent activator of AMP-activated protein kinase and reduces neuronal excitability

Latrepirdine/Dimebon is a small-molecule compound with attributed neurocognitive-enhancing activities, which has recently been tested in clinical trials for the treatment of Alzheimer''s and Huntington''s disease. Latrepirdine has been suggested to be a neuroprotective agent that increases mitochondrial function, however the molecular mechanisms underlying these activities have remained elusive. We here demonstrate that latrepirdine, at (sub)nanomolar concentrations (0.1 nM), activates the energy sensor AMP-activated protein kinase (AMPK). Treatment of primary neurons with latrepirdine increased intracellular ATP levels and glucose transporter 3 translocation to the plasma membrane. Latrepirdine also increased mitochondrial uptake of the voltage-sensitive probe TMRM. Gene silencing of AMPKα or its upstream kinases, LKB1 and CaMKKβ, inhibited this effect. However, studies using the plasma membrane potential indicator DisBAC₂(3) demonstrated that the effects of latrepirdine on TMRM uptake were largely mediated by plasma membrane hyperpolarization, precluding a purely ‘mitochondrial'' mechanism of action. In line with a stabilizing effect of latrepirdine on plasma membrane potential, pretreatment with latrepirdine reduced spontaneous Ca²⁺ oscillations as well as glutamate-induced Ca²⁺ increases in primary neurons, and protected neurons against glutamate toxicity. In conclusion, our experiments demonstrate that latrepirdine is a potent activator of AMPK, and suggest that one of the main pharmacological activities of latrepirdine is a reduction in neuronal excitability.     

骨髓间质干细胞移植减轻犬急性脑梗死模型的缺血性脑损伤研究

目的观察骨髓间质干细胞(BMSCs)对犬急性缺血脑组织的保护作用,并探讨其可能的机制。方法将24只成年杂交犬随机分为治疗组及对照组,DSA引导下行自体血栓栓塞大脑中动脉闭塞缺血模型制作,并抽取骨髓提取BMSCs,传代并给予4’,6-二脒基-2-苯基吲哚(DAPI)标记;1周后开颅行多点脑内注射BMSCs移植;移植后1周行脑DWI序列扫描,计算梗死灶体积;4周后将犬处死,每组随机选择6只动物取脑标本行TTC染色测定梗死灶体积;另外6只动物进行HE染色、VG染色、TUNEL染色评价脑损伤情况;免疫荧光染色了解脑源性神经营养因子(BDNF)、碱性成纤维生长因子(b FGF)、胰岛素样生长因子1(IGF-1)和血管内皮生长因子(VEGF)的表达情况。结果治疗组梗死灶内广泛存在DAPI阳性细胞。治疗组的梗死灶体积明显小于对照组,P0.01。治疗组梗死灶范围、梗死灶内细胞坏死、胶质增生和胶质瘢痕均较对照组减轻。治疗组凋亡细胞明显少于对照组,P0.05。治疗组细胞因子BDNF、BFGF、IGF-1和VEGF表达阳性的细胞均显著多于对照组。结论脑梗死后给予BMSCs移植,BMSCs能存活并自行向梗死灶迁移,并发挥脑保护作用,其机制可能和分泌多种神经营养因子有关。     

Hypoxic‐ischemic brain injury exacerbates neuronal apoptosis and precipitates spontaneous seizures in glucose transporter isoform 3 heterozygous null mice

We examined the effects of 45‐min hypoxia (FiO₂ 0.08; Hx) vs. normoxia (FiO₂ 0.21; Nx) on the ipsilateral (Ipsi) and contralateral (Ctrl) sides of the brain in neuronal glucose transporter isoform 3 (Glut3) heterozygous null mice (glut3^+/−) and their wild‐type littermates (WT), undergoing unilateral carotid artery ligation. Glut3^+/− mice, under Nx, demonstrated a compensatory increase in blood–brain barrier/glial Glut1 protein concentration and a concomitant increase in neuronal nitric oxide synthase (nNOS) enzyme activity and Bax protein, with a decrease in procaspase 3 protein (P < 0.05 each). After Hx, reoxygenation in FiO₂ of 0.21 led to no comparable adaptive up‐regulation of the ipsilateral brain Glut3 or Glut1 protein at 4 hr and Glut1 at 24 hr in glut3^+/− vs. WT. These brain Glut changes in glut3^+/− but not WT mice were associated with an increase in proapoptotic Bax protein and caspase‐3 enzyme activity (P < 0.01 each) and a decline in the antiapoptotic Bcl‐2 and procaspase‐3 proteins (P < 0.05 each). Glut3^+/− mice after Hx demonstrated TUNEL‐positive neurons with nuclear pyknosis in most ipsilateral (hypoxic‐ischemia) brain regions. A subset (∼55%) of glut3^+/− mice developed spontaneous seizures after hypoxic‐ischemia, confirmed by electroencephalography, but the WT mice remained seizure‐free. Pentylenetetrazole testing demonstrated an increased occurrence of longer lasting clinical seizures at a lower threshold in glut3^+/− vs. WT mice, with no detectable differences in monamine neurotransmitters. We conclude that hypoxic‐ischemic brain injury in glut3^+/− mice exacerbates cellular apoptosis and necrosis and precipitates spontaneous seizures. © 2010 Wiley‐Liss, Inc.     

Noggin improves ischemic brain tissue repair and promotes alternative activation of microglia in mice

We previously reported that bone morphogenetic proteins (BMPs) and their endogenous antagonist noggin are expressed in the brain weeks after an ischemic insult. Here, to define their roles in ischemic brain tissue repair and remodeling, we infused recombinant BMP7 or noggin into the ipsilateral ventricle of mice for 2 weeks starting 2 weeks after transient middle cerebral artery occlusion (MCAO). Four weeks after MCAO, we measured ischemic brain volume, functional recovery, and molecules related to neurogenesis and angiogenesis such as synaptophysin, GAP-43, and VEGF. Noggin-treated mice but not BMP7-treated mice showed preserved ipsilateral brain volume and reduced neurological deficits compared with artificial cerebrospinal fluids (aCSF)-treated mice. Noggin treatment also decreased glial scar thickness, increased levels of GAP-43 and VEGF protein, and increased the number of Iba1-positive activated microglia in the ipsilateral brain. Furthermore, noggin treatment decreased M1 markers (IL-1β, TNF-α, IL-12, CCL2 and CD86) and increased M2 markers (IL-1ra, IL-10, arginase 1, CD206 and Ym1) of activated microglia, suggesting a shift from M1 to M2 phenotypes. These results suggest that noggin improves functional recovery from ischemic stroke and enhances alternatively activated microglia, thereby promoting tissue repair and remodeling.     

Osteopontin is indispensable for activation of astrocytes in injured mouse brain and primary culture

ABSTRACT

Objectives: Osteopontin (OPN) is an inflammatory cytokine inducer involved in cell proliferation and migration in inflammatory diseases or tumors. To investigate the function of OPN in astrocyte activation during brain injury, we compared OPN-deficient (OPN/KO) with wild-type (WT) mouse brains after stab wound injury and primary culture of astrocytes.

Methods: Primary cultures of astrocytes were prepared from either WT or OPN/KO postnatal mouse brains. Activation efficiency of astrocytes in primary culture was accessed using Western blotting by examining the protein levels of glial fibrillary acidic protein (GFAP) and tenascin-C (TN-C), which are markers for reactive astrocytes, following lipopolysaccharide (LPS) stimulation. Furthermore, the stab wound injury on the cerebral cortex as a brain traumatic injury model was used, and activation of astrocytes and microglial cells was investigated using immunofluorescent analysis on fixed brain sections.

Results: Primary cultures of astrocytes prepared from WT or OPN/KO postnatal mouse brains showed that only 25% of normal shaped astrocytes in a flask were produced in OPN/KO mice. The expression levels of both GFAP and TN-C were downregulated in the primary culture of astrocytes from OPN/KO mice compared with that from WT mice. By the immunofluorescent analysis on the injured brain sections, glial activation was attenuated in OPN/KO mice compared with WT mice.

Discussion: Our data suggest that OPN is essential for proper astrocytic generation in vitro culture prepared from mouse cerebral cortex. OPN is indispensable for astrocyte activation in the mouse brain injury model and in LPS stimulated primary culture.

Abbreviations: AQP4: aquaporin 4; BBB: blood brain barrier; BrdU: bromo-deoxy uridine; CNS: central nervous system; GFAP: glial fibllirary acidic protein; IgG: immunoglobulin G; LPS: lipopolysaccharide; OPN: osteopontin; OPN/KO: osteopontin-deficient; TN-C: tenascin-C     

Increased neuronal and glial expression of protein kinase C isoforms in neocortex of transgenic Tg2576 mice with amyloid pathology

We investigated the influence of five- to sevenfold neuronal overexpression of the Swedish mutation of human APP695 (APPsw) in the transgenic mouse strain Tg2576 on neocortical protein kinase C (PKC) expression and subcellular distribution. Using specific antibodies to PKC alpha, PKC beta, PKC gamma, PKC epsilon and PKC zeta isoforms for Western blot analysis, we observed increased immunoreactivity for PKC alpha and PKC gamma isoforms in crude tissue homogenates from the neocortex of 16-month-old APPsw mice as compared with nontransgenic littermates, which was not present in 6 month-old Tg2576 mice. We also observed elevated levels of PKC alpha, PKC beta, PKC gamma and PKC zeta in membrane fractions and reduced concentrations of PKC alpha and PKC gamma in cytosolic fractions of aged Tg2576 mice, indicating that these PKC isoforms are in their activated state. In young, 6-month-old Tg2576 mice, however, the increase in membrane-bound PKC isoforms and concomitant decrease in cytosolic PKC isoforms was much less pronounced, demonstrating the age-dependent nature of alterations in PKC isoforms. Immunocytochemistry of brain sections supported these findings and revealed increased neuronal labelling for PKC alpha, PKC gamma and PKC lambda isoforms in neocortex of 16-month-old APPsw mice compared with nontransgenic littermates, with the increase being strongest for PKC gamma and PKC lambda isoforms. Additionally, PKC gamma and to a lesser extent PKC lambda isoforms were induced in reactive astrocytes in proximity to amyloid plaques. Our data indicate that neuronal overexpression of APPsw causes a dynamic change in neuronal expression and activation of multiple PKC isoforms known to be regulators of proteolytic amyloid precursor protein (APP) processing (PKC alpha) and of neuronal survival (PKC lambda and PKC zeta). The induction of the PKC gamma and PKC lambda isoforms in reactive astrocytes surrounding amyloid plaques might be required for astrocyte activation and astrocytic cytokine expression in response to amyloid plaque formation.     

Baclofen is neuroprotective and prevents loss of calcium/calmodulin-dependent protein kinase II immunoreactivity in the ischemic gerbil hippocampus

Excessive release of glutamate during transient cerebral ischemia initiates a cascade of events that leads to the delayed and selective death of neurons located in the hippocampus. Activity of calcium calmodulin kinase II (CaM kinase), a protein kinase critical to neuronal functioning, disappears following ischemia. The in vivo link between glutamate excitoxicity and alterations in CaM kinase activity has not been extensively studied. Baclofen, a selective gamma-aminobutyric acid (GABA)(B) receptor agonist, has been shown to inhibit glutamate release. The present study evaluated the neuroprotective efficacy of this compound and assessed early changes in hippocampal-dependent behaviors and CaM kinase immunoreactivity following transient cerebral ischemia. Baclofen (50 mg/kg) prevented both the loss of hippocampal CA1 pyramidal cells and the reduction in hippocampal CaM kinase immunoreactivity observed in control animals following ischemic insult. Cerebral ischemia produced a significant increase in working memory errors; however, baclofen failed to attenuate this memory deficit. Results confirm that baclofen is neuroprotective and support a link between glutamate excitotoxicity and reductions in CaM kinase immunoreactivity.     

Agmatine reduces infarct area in a mouse model of transient focal cerebral ischemia and protects cultured neurons from ischemia-like injury

Agmatine is a primary amine formed by the decarboxylation of L-arginine synthesized in mammalian brain. In this study, we investigated the neuroprotective effect of agmatine on ischemic and ischemia-like insults. Primary cortical neuronal cultures were subjected to oxygen-glucose deprivation (OGD), a model of ischemia-like injury, and treated with agmatine before or at the start of OGD, or upon reperfusion. Neuronal death was reduced when agmatine was present during OGD, and this protection was associated with a reduction of nitric oxide (NO) and neuronal nitric oxide synthase (nNOS), but not inducible NOS (iNOS). Protection by agmatine was also studied at the in vivo level using a model of middle cerebral artery occlusion (MCAO) in mice. Mice were subjected to 2 h MCAO. Agmatine was administered either 30 min before ischemia, at the start of MCAO, at the start of reperfusion, or 2 or 5 h into reperfusion. Agmatine markedly reduced infarct area in all treatment groups except when treatment was delayed 5 h. The number of nNOS immunopositive cells was correlated with neuroprotection. Interestingly, immunoreactivity for iNOS was reduced only when agmatine was administered before and at the onset of MCAO. Our study suggests that agmatine may be a novel therapeutic strategy to reduce cerebral ischemic injury, and may act by inhibiting the detrimental effects of nNOS.     

Administration of N-acetylcysteine after focal cerebral ischemia protects brain and reduces inflammation in a rat model of experimental stroke

Free radicals and inflammatory mediators are involved in transient focal cerebral ischemia (FCI). Preadministration of N-acetylcysteine (NAC) has been found to attenuate the cerebral ischemia-reperfusion injury in a rat model of experimental stroke. This study was undertaken to investigate the neuroprotective potential of NAC administered after ischemic events in experimental stroke. FCI was induced for 30 min by occluding the middle cerebral artery (MCA). NAC (150 mg/kg) was administered intraperitoneally at the time of reperfusion followed by another dose 6 hr later. Animals were sacrificed after 24 hr of reperfusion. The cerebral infarct consistently involved the cortex and striatum. Infarction was assessed by staining the brain sections with 2,3,5-triphenyltetrazolium chloride. Animals treated with NAC showed a significant reduction in infarct area and infarct volume and an improvement in neurologic scores and glutathione level. Reduction in infarction was significant even when a single dose of NAC was administered at 6 hr of reperfusion. Immunohistochemical and quantitative real-time PCR studies demonstrated a reduction in the expression of proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta) and inducible nitric oxide synthase (iNOS) in NAC compared to that in vehicle-treated animals. The expression of activated macrophage/microglia (ED1) and apoptotic cell death in ischemic brain was also reduced by NAC treatment. These results indicate that in a rat model of experimental stroke, administration of NAC even after ischemia onset protected the brain from free radical injury, apoptosis, and inflammation, with a wide treatment window.     

颅脑创伤模型小鼠海马水通道蛋白1表达及作用

研究背景颅脑创伤后继发性脑损伤包括脑组织缺血、缺氧和脑水肿,可进一步加重原发性损伤,影响预后。作为选择性易损区,海马对缺血和水肿尤为敏感,易出现不可逆性损伤。水通道蛋白1(AQP1)与脑水肿的发生关系密切,但迄今尚无颅脑创伤后海马AQP1表达变化及其相关作用的报道。本研究采用闭合性颅脑创伤小鼠模型对海马水肿过程进行观察,以探讨AQP1在相关病理生理学过程中的作用机制。方法采用改良自由落体法建立BALB/c系小鼠闭合性颅脑创伤模型,于创伤后不同观察时间点(1、6、24和72 h)进行神经功能缺损程度评价和脑组织含水量测定,并通过TUNEL法观察海马神经元凋亡率、免疫组织化学染色和Western blotting法检测AQP1表达变化。结果成功制备闭合性颅脑创伤小鼠模型,并经神经功能评价和脑组织含水量测定证实存在重型颅脑创伤和脑水肿。TUNEL检测显示,模型组小鼠伤后6 h海马神经元凋亡率即升高[(44.26±15.18)%对(8.61±8.25)%;t=-9.676,P=0.002],至72 h达峰值水平[(61.62±26.55)%对(10.17±6.08)%;t=-5.018,P=0.015];免疫组织化学染色和Western blotting法观察,模型组小鼠创伤后各观察时间点海马AQP1表达水平均高于假手术组(P0.05),以伤后24 h表达水平最高(0.69±0.32对0.15±0.07,t=-4.335,P=0.023;0.46±0.19对0.14±0.04,t=-4.113,P=0.004)。结论颅脑创伤后小鼠海马AQP1表达上调可能参与了脑水肿和迟发性神经元凋亡等病理生理学过程,AQP1可能成为继发性脑损伤机制研究的新靶点。