β-石竹烯对小鼠脑缺血/再灌注白质损伤的保护作用研究

目的研究β-石竹烯(β-caryophyllene,BCP)对小鼠脑缺血/再灌注(cerebral ischemia-reperfusion,CIR)白质损伤的保护作用。方法随机将C57BL/6小鼠分为正常对照组(Control)、模型组(CIR)、治疗组(36、72、144 mg·kg^-1)。线栓法建立小鼠大脑中动脉栓塞(middle cerebral artery oc-clusion,MCAO)模型。缺血1 h,再灌注24 h,TTC染色确定脑梗死体积,并进行神经行为学评分;干湿重法测脑含水量;HE染色及透射电镜观察胼胝体损伤情况;Luxol Fast Blue(LFB)染色标记脑神经髓鞘;Western blot测胼胝体髓鞘碱性蛋白(mbp)、神经丝蛋白(NF)、Bcl-2、Bax和caspase-3的表达。结果与模型组比较,BCP可降低神经行为学评分,减小脑梗死体积,减轻脑水肿和胼胝体髓鞘损伤,升高髓鞘染色光密度(optical density,OD),上调mbp、NF、Bcl-2表达,降低Bax和caspase-3表达。结论BCP对小鼠脑缺血/再灌注白质损伤有保护作用,可能与Bax/Bcl-2凋亡通路有关。     

负荷-静息99Tcm-MIBI门控心肌灌注断层显像相位分析评价左室缺血心肌收缩同步性

目的 以99 Tcm-MIBI门控心肌灌注断层显像(GSMPI)相位分析探讨不同缺血灌注状态下左室心肌收缩同步性.方法 回顾性分析129例[男65例,女64例,年龄48～88(68.6±10.2)岁]行99 Tcm-MIBI两日法静息-负荷GSMPI患者的心肌灌注及心功能数据.采用17节段5分制对图像进行评分,获得负荷总积分及心肌缺血积分,分为灌注正常组及灌注异常组,后者再分为可逆性灌注缺损组及固定性灌注缺损组.采用两独立样本t检验比较分析各组间GSMPI的PSD和PHB,各组内静息与负荷PSD及PHB间差异的比较采用配对t检验.结果 129例患者中,灌注正常组66例,灌注异常组63例,其中可逆性灌注缺损组39例,固定性灌注缺损组24例.灌注异常组PSD及PHB显著大于灌注正常组,分别为18.3±7.8和14.3±6.6,68.6±30.9和50.2±20.0(t=-3.110和-3.989,均P＜0.05).尽管固定性灌注缺损组的PSD和PHB较可逆性灌注缺损组有增大趋势,但差异均无统计学意义(=-1.554～-0.408,均P＞0.05);两亚组静息和负荷PSD和PHB间亦无明显差异(t=-0.961 ～-0.114,均P＞0.05).LVEF≤60％组的静息和负荷PSD(20.4±8.1和20.8±6.4)均显著大于LVEF＞ 60％组(15.0±6.8和15.3±7.0;t=3.642和3.886,均P＜0.05);LVEF≤60％组的静息和负荷PHB (77.8±53.5和78.4±26.7)也显著大于LVEF＞60％组(53.5±23.0和55.9±24.5;t=4.567和4.302,均P＜0.05).结论 99Tcm-MIBI GSMPI相位分析能够反映血流灌注异常对心肌收缩同步性的损害及由此造成的对左室整体收缩功能的影响,可在一定程度上反映不同心肌缺血状态下左室收缩同步性的差异;就99Tcm-MIBI而言,负荷和静息GSMPI相位分析对左室收缩同步性评估的价值相当.     

Aquaporin-4 gene silencing protects injured neurons after early cerebral infarction

Aquaporin-4 regulates water molecule channels and is important in tissue regulation and water transportation in the brain. Upregulation of aquaporin-4 expression is closely related to cellular edema after early cerebral infarction. Cellular edema and aquaporin-4 expression can be determined by measuring cerebral infarct area and apparent diffusion coefficient using diffusion-weighted imaging(DWI). We examined the effects of silencing aquaporin-4 on cerebral infarction. Rat models of cerebral infarction were established by occlusion of the right middle cerebral artery and si RNA-aquaporin-4 was immediately injected via the right basal ganglia. In control animals, the area of high signal intensity and relative apparent diffusion coefficient value on T2-weighted imaging(T2WI) and DWI gradually increased within 0.5–6 hours after cerebral infarction. After aquaporin-4 gene silencing, the area of high signal intensity on T2 WI and DWI reduced, relative apparent diffusion coefficient value was increased, and cellular edema was obviously alleviated. At 6 hours after cerebral infarction, the apparent diffusion coefficient value was similar between treatment and model groups, but angioedema was still obvious in the treatment group. These results indicate that aquaporin-4 gene silencing can effectively relieve cellular edema after early cerebral infarction; and when conducted accurately and on time, the diffusion coefficient value and the area of high signal intensity on T2 WI and DWI can reflect therapeutic effects of aquaporin-4 gene silencing on cellular edema.     

Connexins in neurons and glia：targets for intervention in disease and injury

Both neurons and glia throughout the central nervous system are organized into networks by gap junctions. Among glia, gap junctions facilitate metabolic homeostasis and intercellular communication. Amo...     

Monocarboxylate transporter 4 plays a significant role in the neuroprotective mechanism of ischemic preconditioning in transient cerebral ischemia

Monocarboxylate transporters(MCTs), which carry monocarboxylates such as lactate across biological membranes, have been associated with cerebral ischemia/reperfusion process. In this study, we studied the effect of ischemic preconditioning(IPC) on MCT4 immunoreactivity after 5 minutes of transient cerebral ischemia in the gerbil. Animals were randomly designated to four groups(sham-operated group, ischemia only group, IPC + sham-operated group and IPC + ischemia group). A serious loss of neuron was found in the stratum pyramidale of the hippocampal CA1 region(CA1), not CA2/3, of the ischemia-only group at 5 days post-ischemia; however, in the IPC + ischemia groups, neurons in the stratum pyramidale of the CA1 were well protected. Weak MCT4 immunoreactivity was found in the stratum pyramidale of the CA1 in the sham-operated group. MCT4 immunoreactivity in the stratum pyramidale began to decrease at 2 days post-ischemia and was hardly detected at 5 days post-ischemia; at this time point, MCT4 immunoreactivity was newly expressed in astrocytes. In the IPC + sham-operated group, MCT4 immunoreactivity in the stratum pyramidale of the CA1 was increased compared with the sham-operated group, and, in the IPC + ischemia group, MCT4 immunoreactivity was also increased in the stratum pyramidale compared with the ischemia only group. Briefly, present findings show that IPC apparently protected CA1 pyramidal neurons and increased or maintained MCT4 expression in the stratum pyramidale of the CA1 after transient cerebral ischemia. Our findings suggest that MCT4 appears to play a significant role in the neuroprotective mechanism of IPC in the gerbil with transient cerebral ischemia.     

Delayed hippocampal neuronal death in young gerbil following transient global cerebral ischemia is related to higher and longer-term expression of p63 in the ischemic hippocampus

The tumor suppressor p63 is one of p53 family members and plays a vital role as a regulator of neuronal apoptosis in the development of the nervous system. However, the role of p63 in mature neuronal death has not been addressed yet. In this study, we first compared ischemia-induced effects on p63 expression in the hippocampal regions (CA1–3) between the young and adult gerbils subjected to 5 minutes of transient global cerebral ischemia. Neuronal death in the hippocampal CA1 region of young gerbils was significantly slow compared with that in the adult gerbils after transient global cerebral ischemia. p63 immunoreactivity in the hippocampal CA1 pyramidal neurons in the sham-operated young group was significantly low compared with that in the sham-operated adult group. p63 immunoreactivity was apparently changed in ischemic hippocampal CA1 pyramidal neurons in both ischemia-operated young and adult groups. In the ischemia-operated adult groups, p63 immunoreactivity in the hippocampal CA1 pyramidal neurons was significantly decreased at 4 days post-ischemia; however, p63 immunoreactivity in the ischemia-operated young group was significantly higher than that in the ischemia-operated adult group. At 7 days post-ischemia, p63 immunoreactivity was decreased in the hippocampal CA1 pyramidal neurons in both ischemia-operated young and adult groups. Change patterns of p63 level in the hippocampal CA1 region of adult and young gerbils after ischemic damage were similar to those observed in the immunohistochemical results. These findings indicate that higher and longer-term expression of p63 in the hippocampal CA1 region of the young gerbils after ischemia/reperfusion may be related to more delayed neuronal death compared to that in the adults.     

Endogenous level of TIGAR in brain is associated with vulnerability of neurons to ischemic injury

In previous studies,we showed that TP53-induced glycolysis and apoptosis regulator(TIGAR) protects neurons against ischemic brain injury.In the present study,we investigated the developmental changes of TIGAR level in mouse brain and the correlation of TIGAR expression with the vulnerability of neurons to ischemic injury.We found that the TIGAR level was high in the embryonic stage,dropped at birth,partially recovered in the early postnatal period,and then continued to decline to a lower level in early adult and aged mice.The TIGAR expression was higher after ischemia/reperfusion in mouse brain 8and 12 weeks after birth.Four-week-old mice had smaller infarct volumes,lower neurological scores,and lower mortality rates after ischemia than 8- and12-week-old mice.TIGAR expression also increased in response to oxygen glucose deprivation(OGD)/reoxygenation insult or H_2O_2 treatment in cultured primary neurons from different embryonic stages(E16 and E20).The neurons cultured from the early embryonic period had a greater resistance to OGD and oxidative insult.Higher TIGAR levels correlated with higher pentose phosphate pathway activity and less oxidative stress.Older mice and more mature neurons had more severe DNA and mitochondrial damage than younger mice and less mature neurons in response to ischemia/reperfusion or OGD/reoxygenation insult.Supplementation of cultured neurons with nicotinamide adenine dinuclectide phosphate(NADPH) significantly reduced ischemic injury.These results suggest that TIGAR expression changes during development and its expression level may be correlated with the vulnerability of neurons to ischemic injury.