铜对大鼠肝细胞凋亡的影响以及姜黄素的保护作用

目的：探讨铜对大鼠肝细胞（BRL细胞）凋亡的诱导作用及其机制，研究姜黄素对BRL细胞铜损伤时的影响。方法：对硫酸铜（CuSO4）和姜黄素干预培养的BRL细胞，采用荧光探针DCFH-DA进行活性氧(ROS)测定，MTT法检测细胞活力，Hoechst染色和Annexin V-FITC/PI流式细胞术检测细胞凋亡。Western blot法检测磷酸化应激激活的蛋白激酶（JNK/SAPK）蛋白水平。结果：铜处理后6 h BRL细胞ROS和凋亡率达到高峰，分别为711.70±68.33，（45.08±1.87）%，铜处理后24 h JNK磷酸化率上升至（63.36±2.24）%，与正常对照组相比差异有显著性（P<0.01）；姜黄素组ROS、凋亡百分率和JNK磷酸化率均较相应对照组下降(P<0.01)。结论：一定浓度的铜可以诱导BRL细胞的凋亡且与活性氧的产生有关；姜黄素对铜损伤BRL的保护作用与抗氧化和抑制磷酸化JNK的表达有关。［中国当代儿科杂志，2007，9（6）：567-570］     

凋亡调控因子在凝血酶诱导海马神经元凋亡中的变化

目的探讨凝血酶（TM）对海马神经元凋亡调控凶子Bcl-2、Bax及c-jun氨基末端激酶（JNK）表达的影响，阐明TM诱导凋亡的机制。方法海马神经元经40U／mLTM作用0h、6h、12h、24h、48h、72h后终止培养，应用免疫细胞化学方法检测Bcl-2及Bax蛋白表达，Western blot检测磷酸化JNK（P—JNK）及JNK蛋白表达。结果TM作用6h后，Bcl-2蛋白表达增加，12h后开始下降，到48h达到最低值（P〈0．01），72h后Bcl-2蛋白表达开始回升。TM作用6h后，Bax蛋白表达增加，随作用时间的延长，Bax蛋白表达水平逐渐上升，到48h达到最高值（P〈0．01）。Bcl-2／Bax比值逐渐降低，在48h达最低。TM作用0h时P-JNK蛋白无表达，6h后开始表达，与0h组比较差异存在显著性（P〈0．011，12h时达高峰（P〈0．01），并持续到24h，48h后逐渐降低。0h组可见有少量JNK蛋白表达，6h后JNK蛋白表达显著增加（P〈0．01），随TM作用时间的延长，JNK蛋白表达无明显变化。结论TM可能是通过抑制Bcl-2的表达，增强Bax的表达，降低Bcl-2和Bax的比值，激活JNK信号传导通路导致海马神经元凋亡。     

Oxidative stress, ER stress, and the JNK pathway in type 2 diabetes

Pancreatic -cell dysfunction and insulin resistance are observed in type 2 diabetes. Under diabetic conditions, oxidative stress and ER stress are induced in various tissues, leading to activation of the JNK pathway. This JNK activation suppresses insulin biosynthesis and interferes with insulin action. Indeed, suppression of the JNK pathway in diabetic mice improves insulin resistance and ameliorates glucose tolerance. Thus, the JNK pathway plays a central role in pathogenesis of type 2 diabetes and may be a potential target for diabetes therapy.     

Genetic approaches for the identification of apoptotic components

Jun amino-terminal kinase (JNK) mediates a physiological stress signal that leads to cell death. However, the role of the JNK pathway in intrinsic cell death execution mechanisms is largely unknown. In a genetic screen for dominant suppressors of Reaper (Rpr)-induced cell death, we identified Drosophila chromosomal regions that contain genes which are homologous to apoptosis signal-regulating kinase (ASK1) and Drosophila tumor necrosis factor receptor-associated factor 1 (DTRAF1). We present evidence that the killer signal initiates the JNK pathway via proteasome-mediated degradation of Drosophila inhibitor of apoptosis protein 1 (DIAP1) to promote cell death.     

凝聚态Aβ 25～35可通过JNK/p38 MAPK途径诱导胎鼠皮层神经元Tau蛋白过度磷酸化

目的 探讨JNK/p38 MAPK在β淀粉样蛋白多肽片段25～35(Aβ25～35)诱导的阿尔茨海默病(AD)样胎鼠皮层神经元Tau蛋白过度磷酸化中的作用.方法 应用蛋白免疫印迹和免疫细胞化学染色的方法,观察Tau蛋白磷酸化和JNK/p38丝裂原活化的蛋白激酶(JNK/p38 MAPK)的表达情况.结果 凝聚态Aβ25～35(20μmol/L)作用于皮层神经元12h,Tau蛋白Ser396、Ser199/202、Thr205位点的磷酸化水平明显增高,同时JNK/p38 MAPK的总量及其活性形式-磷酸化JNK/p38 MAPK的蛋白表达水平也增加.结论 Aβ25～35可通过激活JNK/p38 MAPK使Tau蛋白的磷酸化水平增高.     

The mechanism of Ara-C-induced apoptosis of differentiating cerebellar granule neurons

Neurotoxicity is one of the side-effects of the therapeutically useful antitumour agent, Ara-C (or 1-beta-d-arabinofuranosyl-cytosine, cytarabine). This agent is also reported to induce cell death of cultured neurons. In this study, we show that Ara-C-induced death of differentiating rat cerebellar granule neurons is prevented by cycloheximide at concentrations corresponding to its action in preventing protein synthesis. The death is accompanied by cleavage of the caspase substrate poly ADP ribose polymerase (PARP) and c-Abl-dependent activation of the stress-activated protein kinases c-Jun N-terminal kinase and p38. However, c-Jun levels do not rise and the activation of the stress-activated protein kinases is not required for this form of neuronal death. Cyclin-dependent kinase (cdk) activity and inappropriate cell-cycle re-entry have been implicated in some forms of death in differentiated neurons. Here we show that Ara-C-induced death of cerebellar granule neurons is prevented by an inhibitor of cdk4, whereas inhibition of cdk1, -2 and -5 mimics the death, and non-cdk4/6 cdks are inhibited by Ara-C treatment. Cdk1 and -2 are dramatically down-regulated during neuronal differentiation, and neither Ara-C nor inhibition of these cdks induces death in mature neurons. This mechanism could also play a significant role in the neurotoxicity associated with the therapeutic use of Ara-C, as cdk levels can be upregulated in stressed neurons of adult brain. We propose that the balance between cdk4/6 and cdk1/2/5 activity may determine the survival of early differentiating neurons, and that DNA-damaging agents may induce neuronal death by inhibiting cdk1/2/5 under conditions which require these activities for survival.     

Spatial, temporal and subcellular localization of islet-brain 1 (IB1), a homologue of JIP-1, in mouse brain

Islet-brain 1 (IB1) was recently identified as a DNA-binding protein of the GLUT2 gene promoter. The mouse IB1 is the rat and human homologue of the Jun-interacting protein 1 (JIP-1) which has been recognized as a key player in the regulation of c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) pathways. JIP-1 is involved in the control of apoptosis and may play a role in brain development and aging. Here, IB1 was studied in adult and developing mouse brain tissue by in situ hybridization, Northern and Western blot analysis at cellular and subcellular levels, as well as by immunocytochemistry in brain sections and cell cultures. IB1 expression was localized in the synaptic regions of the olfactory bulb, retina, cerebral and cerebellar cortex and hippocampus in the adult mouse brain. IB1 was also detected in a restricted number of axons, as in the mossy fibres from dentate gyrus in the hippocampus, and was found in soma, dendrites and axons of cerebellar Purkinje cells. After birth, IB1 expression peaks at postnatal day 15. IB1 was located in axonal and dendritic growth cones in primary telencephalon cells. By biochemical and subcellular fractionation of neuronal cells, IB1 was detected both in the cytosolic and membrane fractions. Taken together with previous data, the restricted neuronal expression of IB1 in developing and adult brain and its prominent localization in synapses suggest that the protein may be critical for cell signalling in developing and mature nerve terminals.