Colchicine induces apoptosis in organotypic hippocampal slice cultures

The microtubule-disrupting agent colchicine is known to be particular toxic for certain types of neurons, including the granule cells of the dentate gyrus. In this study we investigated whether colchicine could induce such neuron-specific degeneration in developing (1 week in vitro) and mature (3 weeks in vitro) organotypic hippocampal slice cultures and whether the induced cell death was apoptotic and/or necrotic. When applied to 1-week-old cultures for 48 h, colchicine induced primarily apoptotic, but also a minor degree of necrotic cell death in the dentate granule cells, as investigated by cellular uptake of the fluorescent dye propidium iodide (PI), immunostaining for active caspase 3 and c-Jun/AP-1 (N) and fragmentation of nuclei as seen in Hoechst 33342 staining. All four markers appeared after 12 h of colchicine exposure. Two of them, active caspase 3 and c-Jun/AP-1 (N) displayed a similar time course and reached a maximum after 24 h of exposure, 24 h ahead of both PI uptake and Hoechst 33342 staining, which together displayed similar time profiles and a close correlation. In 3-week-old cultures, colchicine did not induce apoptotic or necrotic cell death. Attempts to interfere with the colchicine-induced apoptosis in 1-week-old cultures showed that colchicine-induced PI uptake and formation of apoptotic nuclei were temporarily prevented by coapplication of the protein synthesis inhibitor cycloheximide. Application of the pancaspase inhibitor z-VAD-fmk almost completely abolished the formation of active caspase 3 protein and apoptotic nuclei induced by colchicine, but the formation of necrotic nuclei increased correspondingly and the PI uptake was unaffected. We conclude that colchicine induces caspase 3-dependent apoptotic cell death of dentate granule cells in hippocampal brain slice cultures, but the apoptotic cell death is highly dependent on the developmental stage of the cultures.     

Inhibition of caspases promotes long-term survival and reinnervation by axotomized spinal motoneurons of denervated muscle in newborn rats

We examined whether (1) a pan-caspase inhibitor, Boc-D-FMK, exerts long-term neuroprotective effects on spinal motoneurons (MNs) after root avulsion in neonatal rats and (2) whether the rescued spinal MNs regenerate their axons into a peripheral nerve (PN) graft and reinnervate a previously denervated target muscle. Eight weeks after root avulsion, 67% of spinal MNs remained in the Boc-D-FMK-treated group, whereas all MNs died in the sham control group. By 12 weeks postinjury, however, all Boc-D-FMK treated MNs died. In the regeneration experiment, a PN graft was implanted at different times after injury. The animals were allowed to survive for 4 weeks following the operation. Without caspase inhibition, MNs did not regenerate at any time point. In animals treated with Ac-DEVD-CHO, a caspase-3-specific inhibitor, and Boc-D-FMK, 44 and 62% of MNs, respectively, were found to regenerate their axons into a PN graft implanted immediately after root avulsion. When the PN graft was implanted 2 weeks after injury, however, MNs failed to regenerate following Ac-DEVD-CHO treatment, whereas 53% of MNs regenerated their axons into the graft after treatment with Boc-D-FMK. No regeneration was observed when a PN graft was implanted later than 2 weeks after injury. In the reinnervation study, injured MNs and the target biceps muscle were reconnected by a PN bridge implanted 2 weeks after root avulsion with administration of Boc-D-FMK. Eight weeks following the operation, 39% of MNs reinnervated the biceps muscle. Morphologically normal synapses and motor endplates were reformed in the muscle fibers. Collectively, these data provide evidence that injured neonatal motoneurons can survive and reinnervate peripheral muscle targets following inhibition of caspases.     

Dilinoleoylphosphatidylcholine reproduces the antiapoptotic actions of polyenylphosphatidylcholine against ethanol-induced hepatocyte apoptosis

BACKGROUND: Polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines extracted from soybeans, attenuates hepatocyte apoptosis induced by ethanol feeding of rats. Our aims were to evaluate whether dilinoleoylphosphatidylcholine (DLPC), the main component of PPC, reproduces the antiapoptotic actions of PPC against alcohol-induced apoptosis and to identify the apoptotic proteins that are affected by PPC and DLPC. METHODS: Rats were fed Lieber-DeCarli liquid diets containing ethanol (35% of energy) or an isocaloric amount of carbohydrate for 4 weeks. Another group of rats were given the ethanol diet supplemented with PPC (3 g/liter) or DLPC (1.5 and 3 g/liter). Hepatocyte apoptosis was assessed by terminal transferase-mediated dUTP nick end labeling staining and by caspase 3 enzyme activity. Activity of caspases 3 and 9 was assayed by using fluorogenic peptide substrates. Cytochrome c was quantified by enzyme-linked immunosorbent assay. The protein contents of cytochrome c, procaspase 3, caspase 3, Bcl-x(L), and Bax were analyzed by Western blot and quantified by densitometry. Lobular localization of active caspase 3 was examined by immunoperoxidase staining. RESULTS: PPC and DLPC decreased ethanol-induced increases in hepatocyte apoptosis, cytosolic cytochrome c, and caspase 3 content and its activity. Caspase 3 activity correlated with the number of apoptotic hepatocytes. Active caspase 3 was present predominantly in perivenular hepatocytes, and ethanol feeding extended it to lobular hepatocytes; this ethanol effect was reduced by PPC and DLPC. Ethanol significantly decreased Bcl-x(L) in homogenate, mitochondria, and cytosol, and there was a trend for increased Bcl-x(L) in these fractions after PPC and DLPC supplementation. Microsomal Bcl-x(L) did not differ between treatment groups. Bax was detected in homogenate and cytosol, and its level was not affected by ethanol. CONCLUSIONS: DLPC, at a dose contained in PPC, reproduces the antiapoptotic actions of PPC through a reduction in cytosolic cytochrome c concentration and caspase 3 activity, possibly in association with up-regulation of Bcl-x(L) expression. Because DLPC is a pure and well defined compound, it may be more suitable than PPC for intervention against alcohol-induced apoptosis.     

Styrene 7,8-oxide induces caspase activation and regular DNA fragmentation in neuronal cells

Neurobehavioral changes have been described in workers occupationally exposed to styrene vapors. Alterations of neurotransmitters and loss of neurons have been observed in brains of styrene-exposed rats. However, the mechanisms of neuronal damage are not yet clearly understood. We have characterized the cellular alterations induced by the main reactive intermediate of styrene metabolism, styrene 7,8-oxide (SO) in the human neuroblastoma SK-N-MC cell line and primary culture of rat cerebellar granule cells (CGC). SK-N-MC cells exposed to SO (0.3-1 mM) displayed apoptotic morphology, together with chromatin condensation and DNA cleavage into high molecular weight fragments of regular size. These features were accompanied by the activation of class II caspases, as detected with the DEVD assay, by following the cleavage of the caspase-substrate poly (ADP-ribose) polymerase (PARP) and by detection of the active fragment of caspase-3. Pre-incubation of the cells with the caspase inhibitor z-VAD-fmk reduced the cellular damage induced by SO, suggesting that caspases play an important role in SO toxicity. Increased proteolysis by class II caspases was detected also in primary culture of CGC exposed to SO. In addition, the presence of the 150-kDa cleavage product of alpha-fodrin suggests a possible activation of calpains in SK-N-MC cells. Moreover, SO did not affect the level of expression of the p53 protein, even though it is known to cause DNA damage. The identified intracellular pathways affected by SO exposure provides end-points that can be used in future studies for the evaluation of the neurotoxic effect of styrene in vivo.     

Caspase与细胞凋亡

目的了解Caspase家族及其与细胞凋亡关系的研究进展。方法复习国内外相关文献,综述Caspase家族成员、功能、激活、调节及其在细胞凋亡中的作用。结果Caspase不仅与真核细胞凋亡密切相关,还参与了细胞因子的成熟、细胞生长和分化。结论Caspase在介导细胞凋亡中起重要作用。对Caspase的结构、特性及生理作用研究的不断深入,有助于研究细胞凋亡机制,为肿瘤和许多慢性疾病的防治和药物开发提供更多选择。     

Caspase-6,8在骨关节炎软骨细胞中的表达及意义

目的探讨Caspase-6,8在骨关节炎软骨细胞中的表达及意义。方法用免疫组化SP法、原位末端标记技术(TUNEL)等方法检测Caspase-6,8在22例骨关节炎患者关节软骨细胞中的表达和软骨细胞凋亡情况,并探讨基因表达与细胞凋亡之间的关系。结果在软骨细胞中Caspase-6,8的表达实验组阳性率均高于对照组(P<0.05);实验组软骨细胞凋亡程度与Caspase-6,8的表达均呈正相关(P<0.05)。结论Caspase-6,8的表达与骨关节炎发生发展有密切关系。     

丙戊酸诱导白血病U937细胞凋亡机理的实验研究

目的从分子水平探索丙戊酸(VPA)诱导白血病U937细胞凋亡的机制,为临床治疗提供理论依据。方法将U937细胞分为1mmol/LVPA作用组、1mmol/LVPA 1μmol/LzVAD-fmk作用组和空白对照组,作用72h后进行Annixin-ⅴ及PI双重染色,在流式细胞仪上检测细胞凋亡;采用流式细胞仪检测处理前后各组细胞Bcl-2、Bax和Bcl-xl的平均荧光指数(MFI)以及胱冬肽酶(caspase)3、8和9的含量。结果1mmol/LVPA诱导U937凋亡率为(75.78±4.20)%(P<0.01);多cas-pase抑制剂zVAD-fmk可全部抑制U937凋亡,凋亡率为(2.89±0.36)%(P<0.01)。细胞内Bcl-2、Bax和Bcl-xl的MFI无明显变化。VPA作用后U937中caspase3由(14.09±1.19)%上升至(32.30±2.47)%,caspase8由(4.58±1.41)%上升至(86.47±3.26)%(P均<0.01),caspase9变化不显著。结论VPA通过激活caspase3和caspase8诱导U937凋亡;VPA诱导U937凋亡并非通过改变细胞中Bcl-2等的含量实现。     

Caspase活化的细胞凋亡在非小细胞肺癌组织中的表达

目的：观察非小细胞肺癌（NSCLC）组织中Caspase活化的癌细胞凋亡与临床病理特征的关系。方法：对手术切的NSCLC组织标本50例（其中鳞癌24例，腺癌26例），采用Caspase特异的单克隆抗体－M30 CytoDEATH免疫组化染色方法 显示凋亡细胞，计算凋亡指数（AI），结果：28．0％（14／50）的肺癌组织标中中可见不同程度的M30表达，其中肺鳞癌组织的M30阳性表达率（41．7％）明显高于肺腺癌（15．3％），有显著性差异（P＜05），肺鳞癌组织的AI亦高于腺癌，有显著性差异（P＜0．05），低分化NSCLC 组织的AI高于中，高分化的NSCLC组织，有显著性差异（P＜0．05），低分化鳞癌组织的AI明显高于中高分化的鳞癌，有显著性差异（P＜0．05），M30的表达与其它临床病理学特征无相关性。结论：非小细胞肺癌组织中存在Caspase活化的自发性癌细胞凋亡控制，且Caspase的表达与组织类型及组织分化程度有关。     

Suppression of Postmitochondrial Signaling and Delayed Response to UV-induced Nuclear Apoptosis in HeLa Cells

Activation of postmitochondrial pathways by UV irradiation was examined using mouse lymphoma 3SB and human leukemic Jurkat cells and two human carcinoma cell lines (HeLa and MCF-7). Exposure of 3SB and Jurkat cells resulted in large amounts of cytochrome c and apoptosis-inducing factor (AIF) being released into the cytosol, and a clear laddering pattern of DNA fragments was observed within 3 h of incubation after irradiation. Simultaneously, activation of caspase-9 and its downstream caspases was detected. HeLa and MCF-7 cells also showed extensive release of mitochondrial factors and caspase-9 activation at 4 to 6 h after exposure, but apoptotic nuclear changes appeared much later. Compared with 3SB and Jurkat cells, these carcinoma cell lines exhibited reduced activation of caspase-9-like proteolytic activity by UV radiation, and levels of caspase-3-like activity in HeLa cells were extremely low, similar to those in caspase-3-deficient MCF-7 cells. These results suggest that the delayed response to UV-induced nuclear apoptosis in HeLa cells is due to a reduced activation of the caspase cascade downstream of cytochrome c release and suppression of caspase-3 activity.     

Induction of Apoptosis in Hepatocellular Carcinoma Cell Lines by Emodin

Previous experiments have shown that emodin is highly active in suppressing the proliferation of several tumor cell lines. However, it is not clear that emodin can induce growth inhibition of hepatoma cells. We have found that emodin induces apoptotic responses in the human hepatocellular carcinoma cell lines (HCC) Mahlavu, PLC/PRF/5 and HepG2. The addition of emodin to these three cell lines led to inhibition of growth in a time-and dose-dependent manner. Emodin generated reactive oxygen species (ROS) in these cells which brought about a reduction of the intracellular mitochondrial transmembrane potential (Δ Ψ _m), followed by the activation of caspase–9 and caspase–3, leading to DNA fragmentation and apoptosis. Our findings demonstrate that ROS and the resulting oxidative stress play a pivotal role in apoptosis. Preincubation of hepatoma cell lines with the hydrogen peroxide-scavenging enzyme, catalase (CAT) and cyclosporin A (CsA), partially inhibited apoptosis. These results demonstrate that enhancement of generation of ROS, Δ Ψ _mdisruption and caspase activation may be involved in the apoptotic pathway induced by emodin.