Neuroprotective effect of tacrolimus (FK506) on ischemic brain damage following permanent focal cerebral ischemia in the rat

We investigated the neuroprotective effect of tacrolimus (FK506) on the ischemic cell death with respect to cytochrome c translocation and DNA fragmentation, which are pivotal events in the necrotic and apoptotic signaling pathway, using permanent focal cerebral ischemia in rats. Immunohistochemically, cytochrome c was observed in the cytoplasm as early as 1 h after middle cerebral artery (MCA) occlusion in the infarcted hemisphere. Cytosolic release of cytochrome c after MCA occlusion was also confirmed by Western blot analysis and enzyme immunoassay. Terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) showed DNA fragmentation evolving in the ipsilateral cortex and the caudate putamen after 3 and 6 h, respectively, following MCA occlusion. Tacrolimus (1 mg/kg, i.v.), administered immediately after MCA occlusion, significantly attenuated the release of cytochrome c in the ischemic region, the number of TUNEL-positive cells in the ischemic penumbra zone, and the size of cortical ischemic lesions. This study demonstrated that tacrolimus ameliorated the accumulation of cytochrome c in the cytosol and the increase of TUNEL-positive cells induced by cerebral ischemia, indicating that the neuroprotective action of tacrolimus on ischemic brain injury caused by permanent focal cerebral ischemia could partially be attributed to the attenuation of the activation of the apoptotic execution machinery.     

大鼠持续性脑缺血后小胶质细胞变化及其与神经元凋亡的关系

目的 研究成年大鼠持续性局灶脑缺血后小胶质细胞的变化及其与缺血后凋亡的关系。方法 采用单侧大脑中动脉近端民凝术建立成年大鼠持续性局灶脑缺血模型。在手术后3h、6h、12h、24h、48h、72h和120h取材,分别用IsolectinB4凝集素标记小胶质细胞和原位末端TUNEL法标记凋亡细胞。结果 缺血后凝集素阳性小胶质细胞和TUNEL阳性小胶质细胞都分布在梗死灶周边区。缺血12h在梗死灶的边缘密集分布凝集素标记阳性细胞,24－72h凝集素阳性小胶质细胞数量增加（P＜0．05）,120h阳性细胞数量减少（P＜0．01）。脑缺血48h、72h、120h在梗死灶边缘区域分布TUNEL阳性凋亡细胞,TUNEL阳性细胞以神经细胞为主。结论 持续性局灶脑缺血后活化小胶质细胞主要分布在梗死灶周边区,可能对缺血后神经元凋亡产生作用。     

Multiple modes of action of tacrolimus (FK506) for neuroprotective action on ischemic damage after transient focal cerebral ischemia in rats

While the immunosuppressant tacrolimus (FK506) is known to be neuroprotective following cerebral ischemia, the mechanisms underlying its neuroprotective properties are not fully understood. To determine the mode of action by which tacrolimus ameliorates neurodegeneration after transient focal ischemia, we therefore evaluated the effect of tacrolimus on DNA damage, release of cytochrome c, activation of microglia and infiltration of neutrophils following a 60-min occlusion of the middle cerebral artery (MCA) in rats. In this model, cortical brain damage gradually expanded until 24 h after reperfusion, whereas brain damage in the caudate putamen was fully developed within 5 h. Tacrolimus (1 mg/kg) administered immediately after MCA occlusion significantly reduced ischemic damage in the cerebral cortex, but not in the caudate putamen. Tacrolimus decreased both apoptotic and necrotic cell death at 24 h and reduced the number of cytochrome c immunoreactive cells at 8 h after reperfusion in the ischemic penumbra in the cerebral cortex. In contrast, tacrolimus did not show significant neuroprotection for necrotic cell death and reduction of cytochrome c immunoreactive cells in the caudate putamen. Tacrolimus also significantly decreased microglial activation at 8 h and inflammatory markers (cytokine-induced neutrophil chemoattractant and myeloperoxidase [MPO] activity) at 24 h after reperfusion in the ischemic cortex but not in the caudate putamen. These results collectively suggest that tacrolimus ameliorates the gradually expanded brain damage by inhibiting both apoptotic and necrotic cell death, as well as suppressing inflammatory reactions.     

Necrosis, apoptosis and hybrid death in the cortex and thalamus after barrel cortex ischemia in rats

Focal ischemia in the cerebral cortex results in acute and delayed cell death in the ischemic cortex and non-ischemic thalamus. We examined the hypothesis that neurons in ischemic and non-ischemic regions died from different mechanisms; specifically, we tested whether a mixed form of cell death containing both necrotic and apoptotic changes could be identified in individual cells.Focal barrel cortex ischemia in rats was induced by occlusion of small branches of the middle cerebral artery (MCA) corresponding to the barrel cortex, local blood flow was measured by quantitative autoradiography. Cell death was visualized by 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin-eosin (H&E) staining, the terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and caspase-3 staining 1 to 10 days after the ischemia. Electron microscopy was used for ultrastructural examination. Cell death occurred in the ipsilateral cortex 24 h after ischemia, followed by selective neuronal death in the ventrobasal (VB) thalamus 3 days later. TUNEL positive neurons were found in these two regions, but with striking morphological differences, designated as type I and type II TUNEL positive cells. The type I TUNEL positive cells in the ischemic cortex underwent necrotic changes. The type II TUNEL positive cells in the thalamus and the cortex penumbra region represented a hybrid death, featured by concurrent apoptotic and necrotic alterations in individual cells, including marked caspase-3 activation, nuclear condensation/fragmentation, but with swollen cytoplasm, damaged organelles and deteriorated membranes. Cell death in the thalamus and the cortex penumbra were attenuated by delayed administration of the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone (Z-VAD-FMK). Our data suggest that TUNEL staining should be evaluated with morphological changes, the hybrid death but not typical apoptosis occurs in the penumbra region and non-ischemic thalamus after cerebral ischemia.     

老龄大鼠局灶性脑缺血后CyclinD1表达与小胶质细胞活化、神经元凋亡间关系的研究

目的:探讨老龄大鼠局灶性脑缺血后CyclinD1表达与小胶质细胞活化、神经元凋亡之间的内在关系。方法:建立光化学诱导的老龄大鼠局灶性脑缺血模型,利用原位分子杂交、IsolectinB4免疫组织化学和原位末端标记等方法,检测缺血4、24 h和3、5 d组大鼠脑组织中的CyclinD1 mRNA阳性细胞、小胶质细胞和凋亡细胞的时空分布规律。结果:CyclinD1 mRNA阳性细胞、小胶质细胞和凋亡细胞皆分布于缺血灶周围,发布空间相互重叠。CyclinD1 mRNA在多种形态细胞中表达,以胶质细胞最为多见,其表达高峰与小胶质细胞活化高峰一致。在各时间点的病灶周围皆发现TUNEL阳性细胞,其高峰时点提前于CyclinD1 mRNA阳性细胞及小胶质细胞活化高峰。结论:CyclinD1可能参与了缺血后小胶质细胞的活化及神经元的凋亡过程。     

Ischemic intensity influences the distribution of delayed infarction and apoptotic cell death following transient focal cerebral ischemia in rats

The aim of this study was to investigate whether the apoptotic process contributes to the delayed infarction that follows a middle cerebral artery (MCA) occlusion of 20 min (mild ischemia group) and to compare this with the delayed component of infarct following 2 h of MCA occlusion (severe ischemia group). Adult male Sprague-Dawley rats underwent left MCA occlusion for either 20 min or 2 h and were reperfused for 12, 24 and 72 h. On 2,3,5-triphenyltetrazolium chloride-stained coronal sections, delayed infarction was observed to develop in the whole MCA territory after mild ischemia, and also in the frontoparietal cortex after severe ischemia. At 24 h after 20 min of MCA occlusion, characteristic apoptotic features, including chromatin condensation and apoptotic bodies were frequently observed by electron microscopy. In both ischemic groups, Hoechst 33342 staining showed typically condensed and fragmented nuclei in the area showing delayed infarction, where TdT-dUTP nick end labeling (TUNEL)-positive cells were also significantly increased. Caspase-3 activity was also found to be elevated 24 and 72 h after reperfusion and this peaked at 24 h in both groups. These findings suggest that ischemic severity may influence the distribution of delayed infarction, and that apoptosis is the underlying pathophysiologic mechanism.     

脑出血后小胶质细胞活化与神经元DNA损伤的关系

目的　探讨脑出血 (intracerebral hemorrhage,ICH )后小胶质细胞的激活与神经元 DNA损伤 (主要是凋亡 )的关系。方法　应用立体定向技术 ,将自体不凝血注入大鼠尾状核制备 ICH模型 ,将动物随机分为假手术组、ICH组 ,分别在不同时间点断头取脑 ,连续切片作 TUNEL染色和小胶质细胞组化染色。结果　 ICH后 6h血肿周边组织可见 TUNEL 阳性细胞 ,72 h达高峰 ,1周时仍有较多量表达 ;小胶质细胞在 ICH后 6h表达明显增多 ,48h达到高峰 ,2周时仍有少量表达 ,各组与假手术组之间比较差异显著 (P<0 .0 1) ;ICH后的 TUNEL阳性细胞与小胶质细胞的表达呈正相关 (r=0 .718,P<0 .0 5)。结论　 ICH后小胶质细胞的活化可导致大鼠神经细胞 DNA损伤     

Talampanel a non-competitive AMPA-antagonist attenuates caspase-3 dependent apoptosis in mouse brain after transient focal cerebral ischemia

Talampanel (IVAX) is a non-competitive AMPA-antagonist has a remarkable neuroprotection in different rodent stroke models. The focal cerebral ischemia in mice was induced by transient (60 min.) MCA occlusion and 48 h reperfusion and treated with talampanel (6 x 2 mg/kg, i.p.). The apoptotic and necrotic cells were analyzed by double immune histochemical staining on confocal laser microscope. The infarct size is decreased significantly by talampanel treatment (from 57.1+/-7.2mm(2) to 18.9+/-2.6 mm(2), p< 0.001). The number of TUNEL-positive cells localized mostly in the border zone of ischemic lesions is significantly decreased after talampanel treatment (from 962+/-13.0 to 604+/-6.9, p < 0.01). A strong, significant reduction of caspase-3 active cells was visualized. Talampanel as a neuroprotective drug candidate has a significant effect in mice transient MCA occlusion model.     

Cerebral vessels express interleukin 1β after focal cerebral ischemia

Rapid and marked increased levels of expression of interleukin 1β (IL-1β) mRNA have been detected in animal models of cerebral ischemia. However, the protein production of IL-1β and the cellular sources of IL-1β are largely undefined after cerebral ischemia. In the present study, we have measured the cellular localization of IL-1β protein in brain tissue from non-ischemic and ischemic mice using immunohistochemistry. Male C57B/6J (n=45) mice were subjected to middle cerebral artery (MCA) occlusion by a clot or a suture. The mice were sacrificed at time points spanning the period from 15 min to 24 h after onset of the MCA occlusion. Non-operated and sham-operated mice were used as control groups. A monoclonal anti-IL-1β antibody was used to detect IL-1β. In the non-operated and sham-operated mice, a few IL-1β immunoreactive cells were detected scattered throughout both hemispheres. IL-1β immunoreactive cells increased in the ischemic lesion as early as 15 min and peaked at 1 h to 2 h after MCA occlusion. IL-1β immunoreactivity was detected in the cortex of the contralateral hemisphere 1 h after ischemia. By 24 h after onset of ischemia, IL-1β immunoreactivity was mainly present adjacent to the ischemic lesion and in the non-ischemic cortex. IL-1β immunoreactivity was found on endothelial cells and microglia. This study demonstrates an early bilateral expression of IL-1β on endothelium after MCA occlusion in mice.     

成年大鼠持续性脑缺血后TGFβ_1蛋白表达与凋亡的关系

目的 :观察成年大鼠持续性局灶脑缺血后 TGFβ1 蛋白表达与缺血后凋亡的关系。方法 :单侧大脑中动脉近端电凝术建立大鼠持续性局灶脑缺血模型。缺血后 1h,实验组经尾静脉注射氟美松 (5 mg/ kg) ,对照组注射相同容积的生理盐水。缺血后 3h～ 12 0 h取材 ,分别用免疫组织化学 SP法和原位末端标记 TUNEL法标记 TGFβ1 蛋白表达细胞和凋亡细胞。结果 :持续性局灶脑缺血后 TGFβ1 蛋白呈双相性 ,主要分布在梗塞灶周围区域。TGFβ1 的表达可被氟美松抑制 ,同时缺血后神经细胞凋亡也加重。结论 :大鼠持续性局灶脑缺血后梗塞灶周围区域 TGFβ1 蛋白表达可能有减轻缺血后神经细胞凋亡的作用。     

Temporal profile of cytochrome c and caspase-3 immunoreactivities and TUNEL staining after permanent middle cerebral artery occlusion in rats

Although apoptotic pathways play important roles in ischemic neuronal injury, exact mechanism of apoptotic enzyme cascade has not been fully studied. Immunohistochemical stainings for cytochrome c and caspase-3, and histochemical staining for a terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end-labeling method (TUNEL) were examined in a rat model of permanent middle cerebral artery (MCA) occlusion. Cytochrome c was strongly induced in neurons of the ischemic penumbra from 3 h after MCA occlusion, and caspase-3 began to be induced in the same area from 3 h with a peak at 8 h. Neuronal cells in MCA area became TUNEL positive at delayed time, reaching a peak at 24 h. Thus, the peak of induction of cytochrome c preceded that of caspase-3, and these two peaks were also precedence of the peak of DNA-fragmentation. Western blot analysis showed cytosolic expression of cytochrome c from mitochondria. This study demonstrated 1. Rapid release of cytochrome c from mitochondria to the cytosol, mainly in neurons of the cortex at 3 h after ischemia. 2. Subsequent peaks of caspase-3 and TUNEL in this order. These temporal profiles suggest a serial cascadic activation of apoptotic pathways in neuronal death after permanent MCA occlusion of rats.     

Activated microglia cells express argininosuccinate synthetase and argininosuccinate lyase in the rat brain after transient ischemia

Argininosuccinate-synthetase (ASS), argininosuccinate-lyase (ASL) and nitric oxide synthase (NOS) act in the l-arginine-NO-l-citrulline cycle. In the rat brain, ASS is expressed in neurons, ASL in neurons and astroglia in the striatum, both are co-expressed with nNOS in medium-sized neurons. Microglia cells express iNOS and ASS after activation but no information is available on ASL and on ASS/ASL/iNOS co-expression in this glial population. The present aim was to ascertain, by immunohistochemistry, whether the microglia cells of the rat striatum and fronto-parietal cortex express ASL and ASS in control conditions and after transient ischemia induced by middle cerebral artery occlusion, and whether ASL and ASS are co-expressed with iNOS. The study was conducted 24, 72 and 144 h after reperfusion in two groups of ischemic rats with different tissue damage and survival. ASS and ASL are not expressed by microglia cells in controls while are present in most of the activated microglia cells in the ischemic rats. In those animals with longer survival, ASS and ASL were no more detectable at 144 h, while, in the animals with shorter survival, they were co-expressed with iNOS, but only at 72 h. In the cortex, at variance with the striatum, almost all of nNOS-positive neurons co-expressed ASS and ASL. In conclusion, only activated microglia cells express ASS and ASL, this expression precedes that of iNOS and does not necessarily imply its appearance. Therefore, local factors such as the NO produced by nNOS/ASS/ASL-positive neurons, could influence ASS/ASL-positive microglia cells avoiding or allowing the induction, in these cells, of iNOS.     

Characterization of microglial reaction after middle cerebral artery occlusion in rat brain

We have studied the microglial reaction that accompanies cortical infarction induced by middle cerebral artery occlusion (MCAO). Lectin histochemistry with the B₄-isolectin from Griffonia simplicifoliaas well as immunocytochemistry with a panel of monoclonal antibodies directed against major histocompatibility complex (MHC) and lymphocytic antigens were performed. Principal attention was focused on neocortical and thalamic regions, representative of primary and secondary ischemic damage, respectively. With the lectin procedure, activated microglial cells were abundant in the neocortex 24 hours after MCAO. In contrast, microglial activation in the thalamus was not apparent until day 2 after MCAO. On day 5, MHC class II antigen was expressed by reactive microglia in fiber tracts traversing the striatum, but was absent from activated microglia in the primary cortical infarction area. MHC class I and lymphocytic antigens were expressed differentially on microglia with class I antigens appearing early and lymphocytic antigens appearing late in the time course after focal ischemia. The findings are compatible with previous studies during global ischemia and confirm the early activation and the progressive nature of immunomolecule expression on activated microglia after an ischemic insult. In addition to neocortical and thalamic sites, our results showed an early microglial activation to be present also in forebrain regions outside of the middle cerebral artery (MCA) territory, such as the contralateral cortex and hippocampus. A unilateral microglial reaction was also detectable after long-term survival (≥4 weeks) in the pyramidal tracts, as well as in the corticospinal tracts at cervical but not lumbar spinal cord levels. Ischemia-induced neuronal damage, as evaluated by Nissl staining, was found only in cortical and thalamic regions. We conclude that the demonstration of reactive microglia indicates not only imminent ischemic neuronal damage within MCA territory but can also delineate extra-focal disturbances, possibly reflecting subtle and transitory changes in neuronal activity. © 1993 Wiley-Liss, Inc.     

Temporal profile of cytochrome c and caspase-3 immunoreactivities and TUNEL staining after permanent middle cerebral artery occlusion in rats

Abstract

Although apoptotic pathways play important roles in ischemic neuronal injury, exact mechanism of apoptotic enzyme cascade has not been fully studied. Immunohistochemical stainings for cytochrome c and caspase-3, and histochemical staining for a terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end-labeling method (TUNED were examined in a rat model of permanent middle cerebral artery (MCA) occlusion. Cytochrome c was strongly induced in neurons of the ischemic penumbra from 3 h after MCA occlusion, and caspase-3 began to be induced in the same area from 3 h with a peak at 8 h. Neuronal cells in MCA area became TUNEL positive at delayed time, reaching a peak at 24 h. Thus, the peak of induction of cytochrome c preceded that of caspase-3, and these two peaks were also precedence of the peak of DNA-fragmentation. Western blot analysis showed cytosolic expression of cytochrome c from mitochondria. This study demonstrated 7. Rapid release of cytochrome c from mitochondria to the cytosol, mainly in neurons of the cortex at 3 h after ischemia. 2. Subsequent peaks of caspase-3 and TUNEL in this order. These temporal profiles suggest a serial cascadic activation of apoptotic pathways in neuronal death after permanent MCA occlusion of rats. [Neurol Res 2000; 22: 223-228]     

Upregulation of neuronal nitric oxide synthase and mRNA, and selective sparing of nitric oxide synthase-containing neurons after local cerebral ischemia in rat

Nitric oxide synthase-containing neurons are presumed to be resistant to neurodegeneration and neurotoxicity, however this resistance has not been demonstrated after focal cerebral ischemia. We therefore measured the temporal profile of neuronal nitric oxide synthase (NOS-I) mRNA and immunoreactivity and NADPH-diaphorase reactivity over a one week period after permanent middle cerebral artery (MCA) occlusion in 48 male Wistar rats and compared these data to ischemic cell damage as evaluated on hematoxylin and eosin (H & E) stained sections by light microscopy. NOS-I mRNA increased as early as 15 min after MCA occlusion in the ipsilateral striatum and maximal expression of NOS-I was found in the ipsilateral cortex and striatum 1 h after MCA occlusion. The numbers of NOS-I-containing neurons in the ipsilateral cortex and striatum were significantly greater (P < 0.05) than NOS-I-containing neurons in the contralateral hemisphere at 2–48 h after the onset of ischemia. The number of NOS-I-containing neurons peaked at 4 h after MCA occlusion. Neurons exhibited shrinkage or were swollen at 1 to 4 h after MCA occlusion. At 24–48 h after ischemia, neurons in the ischemia lesion appeared to be eosinophilic or ghost like on H & E stained sections. However, some of these neurons retained morphological integrity on the NOS-I immunohistochemical sections. At 168 h after ischemia, all neurons within the lesion appeared necrotic on H & E stained sections; however, scatterred neurons expressed NOS-I and NADPH-diaphorase. The rapid upregulation of NOS-I and mRNA in the ischemic lesion suggests that NOS-I is involved in focal cerebral ischemic injury; the expression of NOS-I by neurons that retain their morphological structure in the area of the infarct suggests that NOS-I-containing neurons are more resistant to the ischemic insult. Our data also indicate a close association of NOS-I immunoreactivity and NADPH-diaphorase reactivity in ischemic brain.     

Expressions of neuropilin-1, neuropilin-2 and semaphorin 3A mRNA in the rat brain after middle cerebral artery occlusion

This study investigated the spatial and temporal expressions of mRNA encoding neuropilin (Npn)-1, Npn-2 and semaphorin3A (Sema3A) in the rat brain after occlusion of the middle cerebral artery (MAC) distal to the striate branches. The expression of Npn-1 mRNA was transiently upregulated in layers V and VI of the parietal cortex not entering infarction on the lesion side from 3 to 6 h after MCA occlusion. The transient up-regulation of Npn-1 mRNA expression was presumably accompanied by an increase in Npn-1 protein as shown by immunohistochemistry in combination with in situ hybridization histochemistry. Intense Npn-2 mRNA expression was noted temporarily in layer II of the parietal cortex on the lesion side from 1 to 6 h after MCA occlusion. The expression of Sema3A mRNA was upregulated in layer VI of the non-infarcted parietal cortex on the lesion side at 6 h after MCA occlusion. The above increases in mRNA expression were no longer observed at 12 h after MCA occlusion. The expressions of Npn-1, -2 and Sema3A mRNA were not detected in the ventroposterior thalamic nucleus undergoing secondary degeneration after MCA occlusion. In the infarct lesion or ischemic core, neuronal expressions of Npn-1, -2 and Sema3A disappeared by 3 days after MCA occlusion as the neurons in situ entered apoptosis or necrosis. In contrast, ED-1-positive microglia/macrophages with Npn-1 and Npn-2 mRNA were observed in the infarct lesion at 1 week after MCA occlusion. These findings suggest that the temporal up-regulation of Npn-1 and Sema 3A mRNA expressions in the non-infarcted parietal cortex on the lesion side is insufficient to induce neuronal cell death possibly because the up-regulated mRNA molecules are not fully translated and that the overexpression of Npn-1 and/or Npn-2 in the ischemic core with degenerating neurons enables activated microglial cells to contact the damaged neurons in situ for phagocytosis.     

大鼠局灶性脑缺血/再灌注后单、双链DNA断裂的实验研究

目的 :观察大鼠脑缺血 /再灌注后脑细胞单、双链DNA损伤情况 ,以揭示该病的损伤机制。方法 :分别用Klenow及TdT(TUNEL)标记染色法检测大脑中动脉阻塞 (MCAO)模型组、假手术组及正常大鼠脑细胞的单、双链DNA断裂 ,观察缺血侧、对照侧皮质及海马阳性细胞数的动态变化。结果 :MCAO模型组缺血侧皮质及海马Klenow及TUNEL阳性细胞数均逐渐增多 ,Klenow阳性细胞的出现早于TUNEL阳性细胞 ,皮质的出现早于海马。结论 :大鼠MCAO模型中DNA单、双链断裂均参与了脑损伤机制