SIRT1介导的七氟醚后处理对失血性休克复苏小鼠学习与记忆损伤的保护作用

目的探究沉默信息调节因子(silent information regulation 1,SIRT1)介导的凋亡相关通路在七氟醚后处理对失血性休克复苏小鼠海马神经元损伤中的保护作用。方法建立失血性休克与复苏小鼠模型,雄性C57BL/6J小鼠60只随机分为:假手术组(Sham组)、HSR组(Shock组)、七氟醚处理组(Sevo组)、七氟醚联合SIRT1特异性抑制剂处理组(EX527+Sevo组)以及EX527处理组(EX527组)。通过TTC染色法检测小鼠脑梗死体积,TUNEL染色法检测各组小鼠海马神经细胞的变化,水迷宫实验检测小鼠学习记忆能力,Western blot检测SIRT1和凋亡相关蛋白Bcl-2、Bax、Cleaved caspase-3的表达。结果造模小鼠在水迷宫检测中到达平台的潜伏期延长,在目标象限的运动距离减少,脑梗死体积增大,TUNEL染色阳性细胞数增多,SIRT1、Bcl-2蛋白表达降低,Bax、Cleaved-caspase3蛋白表达增加;七氟醚处理后改善了失血性休克与复苏小鼠的神经损伤情况,七氟醚与SIRT1抑制剂EX527联合处理后,七氟醚对失血性休克与复苏小鼠的神经损伤保护作用减弱。结论七氟醚可能通过SIRT1介导的凋亡相关通路发挥对失血性休克复苏引起的海马神经元损伤的保护作用。

C-peptide and Diabetic Encephalopathy

With the changes of life style, diabetes and its complications have become a major cause of morbidity and mortality. It is reasonable to anticipate a continued rise in the incidence of diabetes and its complications along with the aging of the population, increase in adult obesity rate, and other risk factors. Diabetic en- cephalopathy is one of the severe microvascular complications of diabetes, characterized by impaired cogni- tive functions, and electrophysiological, neurochemical, and structural abnormalities. It may involve direct neuronal damage caused by intracellular glucose. However, the pathogenesis of this disease is complex and its diagnosis is not very clear. Previous researches have suggested that chronic metabolic alterations, vascular changes, and neuronal apoptosis may play important roles in neuronai loss and damaged cognitive functions. Multiple factors are responsible for neuronal apoptosis, such as disturbed insulin growth factor （IGF） system, hyperglycemia, and the aging process. Recent data suggest that insulin/C-peptide deficiency may exert a primary and key effect in diabetic encephalopathy. Administration of C-peptide partially improves the condition of the IGF system in the brain and prevents neuronal apoptosis in the hippocampus of diabetic patients. Those findings provide a basis for application of C-peptide as a potentially effective therapy for diabetes and diabetic encephalopathy.

Cbl negatively regulates JNK activation and cell death

Here, we explore the role of Cbl proteins in regulation of neuronal apoptosis. In two paradigms of neuron apoptosis -- nerve growth factor （NGF） deprivation and DNA damage -- cellular levels of c-Cbl and Cbl-b fell well before the onset of cell death. NGF deprivation also induced rapid loss of tyrosine phosphorylation （and most likely, activation） of c-Cbl. Targeting c-Cbl and Cbl-b with siRNAs to mimic their loss/inactivation sensitized neuronal cells to death promoted by NGF deprivation or DNA damage. One potential mechanism by which Cbl proteins might affect neuronal death is by regulation of apoptotic c-Jun N-terminal kinase （JNK） signaling. We demonstrate that Cbl proteins interact with the JNK pathway components mixed lineage kinase （MLK） 3 and POSH and that knockdown of Cbl proteins is sufficient to increase JNK pathway activity. Furthermore, expression of c-Cbl blocks the ability of MLKs to signal to downstream components of the kinase cascade leading to JNK activation and protects neuronal cells from death induced by MLKs, but not from downstream JNK activators. On the basis of these findings, we propose that Cbls suppress cell death in healthy neurons at least in part by inhibiting the ability of MLKs to activate JNK signaling. Apoptotic stimuli lead to loss of Cbl protein/activity, thereby removing a critical brake on JNK activation and on cell death.

Spinal cord decompression reduces rat neural cell apoptosis secondary to spinal cord injury

Objective： To determine whether spinal cord decompression plays a role in neural cell apoptosis after spinal cord injury. Study design： We used an animal model of compressive spinal cord injury with incomplete paraparesis to evaluate neural cell apoptosis after decompression. Apoptosis and cellular damage were assessed by staining with terminal deoxynucleotidyl transferase （TdT）-mediated deoxyuridine triphosphate nick-end labelling （TUNEL） and immunostaining for caspase-3, Bcl-2 and Bax. Methods： Experiments were conducted in male Sprague-Dawley rats （n-78） weighing 300-400 g. The spinal cord was compressed posteriorly at T10 level using a custom-made screw for 6 h, 24 h or continuously, followed by decompression by removal of the screw. The rats were sacrificed on Day I or 3 or in Week 1 or 4 post-decompression. The spinal cord was removed en bloc and examined at lesion site, rostral site and caudal site （7.5 mm away from the lesion）. Results： The numbers of TUNEL-positive cells were significantly lower at the site of decompression on Day 1, and also at the rostral and caudal sites between Day 3 and Week 4 post-decompression, compared with the persistently compressed group. The numbers of cells between Day 1 and Week 4 were immunoreactive to caspase-3 and B-cell lymphoma-2 （Bcl-2）-associated X-protein （Bax）, but not to Bcl-2, correlated with those of TUNEL-positive cells. Conclusion： Our results suggest that decompression reduces neural cell apoptosis following spinal cord injury.