Apoptotic Cell Death in the Pathogenesis of Infectious Diseases

Apoptosis is a physiological process critical for tissue homeostasis. It is essential for the regulation of immune responses. A series of molecules transduce apoptoic signals and induce the characteristic morphological appearances of apoptotic cells. Infectious diseases modulate apoptosis and this contributes to disease pathogenesis. Infection with HIV results in enhanced levels of CD4 T-lymphocyte apoptosis in both directly infected cells and in uninfected bystander cells. A variety of HIV proteins including gp120 contribute to this process. A number of different pathways induce HIV-associated CD4 T-lymphocyte apoptosis and apoptosis of uninfected bystander cells is particularly associated with increased susceptibility to Fas. Other viruses including hepatitis viruses and the human herpesviruses also modulate apoptosis. Bacterial infection induces apoptosis which is frequently mediated by the direct activation of caspases in the absence of death receptor ligation. Bacterial induction of apoptosis may either be due to bacterial factors such as the invasin IpaB of Shigella flexneri or be the result of host immune responses which control infection as demonstrated in infections due to Mycobacterium spp. Apoptosis may be modulated by therapeutic strategies, such as antiretroviral therapy, and an improved understanding of infection-associated apoptosis modulation will aid the design of novel therapeutic approaches to control infectious diseases.     

Ethanol Increases Apoptotic Cell Death of Thymocytes in Vitro

Exposure of animals to ethanol causes thymic atrophy in adults and fetuses. Whether direct effects of ethanol contribute to thymic atrophy or whether indirect effects are entirely responsible is at present unknown. In the normal animal, large numbers of thymocytes undergo a physiological form of cell death referred to as "apoptosis." To determine if ethanol affects the process of apoptosis, studies were undertaken in which mouse thymocytes were cultured overnight in the presence or absence of ethanol. Apoptotic cell death was analyzed by flow cytometric quantitation of apoptotic nuclei, by fluorometric measurement of DNA fragments, and by gel electrophoretic analysis of DNA fragments. Ethanol in concentrations of 0.2% to 0.8% produced significantly higher levels of apoptosis than were seen in control cultures. The DNA fragmentation was characterized as apoptotic on the basis of inhibition by aurintricarboxylic acid (an inhibitor of nucleases) and by the presence of characteristic oligonucleosomal-sized fragments of DNA. The effect of ethanol on apoptosis was additive to that induced by immobilized anti-CD3 monoclonal antibody. CD4⁺CD8⁺ cells underwent apoptosis as indicated by reduction in CD4 and CD8 surface antigen expression. An inhibitor of protein kinases (H-7) reduced the DNA degradation induced by ethanol and by anti-CD3. These results suggest that direct effects of ethanol contribute to thymic atrophy in alcohol-consuming animals.     

急慢性血管损伤中的血管细胞凋亡和再狭窄的机制

血管细胞凋亡是血管重构的一个主要特点，细胞凋亡贯串在血管发生，发展及死亡的全过程中，对急慢性血管损伤后的血管重构起重要的作用，尤其是对血管机械性损伤后的再狭窄有重要的影响。     

血管外膜成纤维细胞在冠脉损伤后重构及再狭窄中的作用

经皮冠状动脉腔内成形术 (PTCA)已广泛地应用于冠心病的治疗 ,但术后 3～ 6个月内的高再狭窄率(30 %～ 5 0 % )严重影响了其临床的有效应用。关于再狭窄的发病机制仍有许多不明之处 ,目前认为再狭窄可能是新生内膜增生和不利的血管重构共同作用的结果[1] 。血管外膜过去被认为是无活性的 ,近来研究发现冠脉损伤后伴随有外膜的激活 [2 ,3] 。血管外膜成纤维细胞 (vascular adventitial fibroblasts,VAF)具有增殖、迁移、表型转化及合成大量细胞外基质的能力 ,因而在促冠脉损伤后重构及再狭窄的发生中发挥重要作用。本文就此作一综述。1　…     

Factors Involved in the Apoptotic Cell Death Mechanism in Yellow Fever Hepatitis

Yellow fever (YF), a non-contagious infectious disease, is endemic or enzootic to the tropical regions of the Americas and Africa. Periodic outbreaks or epidemics have a significant impact on public health. Programmed cell death, or apoptosis, is generally characterised by distinct morphological changes and energy-dependent biochemical pathways. In this study, we performed immunohistochemistry analysis to identify and quantify proteases and protein targets involved in the cascade that triggers apoptosis in YF virus (YFV)-infected human hepatocytes. Liver tissue samples were collected from 26 individuals, among whom 21 were diagnosed as YF-positive, and five were flavivirus-negative and died due to other causes. The histopathological alterations in YFV-positive cases were characterised by the presence of apoptotic bodies, steatosis, cellular swelling, and extensive necrosis and haemorrhage in the hepatic lobules. Additionally, we observed an abundance of inflammatory infiltrates in the portal tract. The expression of various apoptotic markers in the hepatic parenchyma, including CASPASE 3, CASPASE 8, BAX, FAS, FASL, GRANZYME B, and SURVIVIN, differed between YFV-positive cases and controls. Collectively, this study confirmed the complexity of YFV infection-induced apoptosis in situ. However, our data suggest that apoptosis in liver parenchyma lesions may significantly contribute to the pathogenesis of fatal YF in humans.     

ICE重组质粒转染血管平滑肌细胞及其促凋亡作用的观察

目的：观察转染白介素－１β－转换酶（ＩＣＥ）基因对血管平滑肌细胞的促凋亡作用。方法通过阳离子脂质体介导的方法将重组质粒及报告质粒ＰＳＶ－β－ｇａｌ共转染体外培养的血管平滑肌细胞,运用生化染色、电镜观察、流式细胞仪及ＤＮＡ凝胶电泳等检测方法了解细胞转染后的凋亡发生情况。结果：ＩＣＥ转染阳性的细胞具有凋亡的形态学变化,且试验组的凋亡百分率较正常对照组及空白粒对照组显著升高。结论：ＩＣＥ基因可诱导体外培     

ICE重组质粒转染血管平滑肌细胞及其促凋亡作用的观察

目的:观察转染白介素-1β-转换酶(ICE)基因对血管平滑肌细胞的促凋亡作用.方法:通过阳离子脂质体介导的方法将重组质粒及报告质粒PSV-β-gal共转染体外培养的血管平滑肌细胞,运用生化染色、电镜观察、流式细胞仪及DNA凝胶电泳等检测方法了解细胞转染后的凋亡发生情况.结果:ICE转染阳性的细胞具有凋亡的典型形态学变化,且试验组的凋亡百分率较正常对照组及空白质粒对照组显著升高.结论:ICE基因可诱导体外培养的平滑肌细胞发生凋亡.     

Aspirin-Induced Mucosal Cell Death in Human Gastric Cells: Evidence Supporting an Apoptotic Mechanism

This study was undertaken to define the role that apoptosis may play in inducing cellular injury and death in gastric mucosa exposed to aspirin. Apoptosis was characterized by DNA gel electrophoresis, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and DNA-histone-associated complex formation. A human gastric cell line (AGS) was exposed to physiologic concentrations (3 to 50 mM) of aspirin. Both time- and concentration-dependent effects on apoptosis were noted, which were effectively prevented by the caspase inhibitor z-VAD-fmk. Accordingly, the role of caspases in aspirin-induced apoptosis was also evaluated. Early activation of caspase-8 and caspase-9 was demonstrated, indicating a role for both receptor and mitochondrial pathways, respectively, in the apoptotic process. Corresponding activation of effector caspases-3, -6, and -7 was also evident, as was cleavage of PARP. We conclude that physiologically relevant concentrations of aspirin induces apoptosis in human gastric cells through a caspase-mediated mechanism.     

In Utero Ethanol Exposure Causes Mitochondrial Dysfunction, Which Can Result in Apoptotic Cell Death in Fetal Brain: A Potential Role for 4-Hydroxynonenal

BACKGROUND: In utero ethanol exposure causes abnormal fetal brain development that may partly be due to enhanced cell death. The mechanisms underlying this remain to be defined, but ethanol-induced oxidative stress may play a role. The following studies investigated the effects of short-term in utero ethanol exposure on fetal brain mitochondrial events that are known to elicit apoptotic cell death. Evidence is presented suggesting that 4-hydroxynonenal (HNE), a toxic product of lipid oxidation, is a causal factor in the observed mitochondrial damage. METHODS: Mitochondria were isolated from control and ethanol-exposed fetal brains (days 17 and 18 of gestation). Permeability transition was determined spectrophotometrically, and cytochrome c and apoptosis-inducing factor (AIF) release were assessed by Western blotting. Caspase-3 activity and DNA fragmentation were determined both as markers for mitochondrially mediated apoptosis and as consequences of cytochrome c and AIF release. RESULTS: Maternal ethanol intake caused an increase in mitochondrial permeability transition, and this was accompanied by cytochrome c and AIF release from fetal brain mitochondria that exceeded control values by 62 and 25%, respectively (p < 0.05). In utero ethanol exposure resulted in a 30% increase in caspase-3 activity and a 25% increase in DNA fragmentation (p < 0.05) in the fetal brain. HNE levels were increased by 23% (p < 0.05) in mitochondria by in vivo ethanol exposure. In vitro treatment of fetal brain mitochondria with HNE (25-100 microM) also caused increases in mitochondrial permeability transition, as well as dose-dependent releases of cytochrome c and AIF. CONCLUSIONS: These studies illustrate that in utero ethanol exposure can elicit a cascade of events in the fetal brain that are consistent with mitochondrially mediated apoptotic cell death. Additionally, the increase in mitochondrial content of HNE after ethanol intake and the ability of HNE added to fetal brain mitochondria to mimic these effects of in vivo ethanol exposure support a potential role for HNE in the proapoptotic responses to ethanol.     

三七总皂苷对血管内皮细胞凋亡及凋亡调控基因的影响

目的探讨血管紧张素Ⅱ(Ang Ⅱ)在不同浓度和不同作用时间下对内皮细胞凋亡率及凋亡调控基因(Fas)的作用及三七总皂苷对其影响.方法采用流式细胞技术测定在血管紧张素Ⅱ不同浓度和不同作用时间下,内皮细胞凋亡率及Fas和Bcl-2表达量的变化.结果血管紧张素Ⅱ可明显促进凋亡率及Fas的表达量,且其作用呈剂量依赖性和时间依赖性;经药物处理后的内皮细胞对AngⅡ的反应完全不同,凋亡率明显降低,同时Fas的表达量随药物浓度增加和作用时间延长而降低,Bcl-2则增高.结论血管紧张素Ⅱ具有明显的促进细胞凋亡和凋亡基因表达的作用;三七总皂苷对细胞凋亡和Fas表达有一定的调节作用.     

Increased Cell Death and Reduced Neural Crest Cell Numbers in Ethanol-Exposed Embryos: Partial Basis for the Fetal Alcohol Syndrome Phenotype

Fetal alcohol syndrome (FAS) is characterized by growth retardation, craniofacial malformations, and heart and neural defects; the cellular and molecular mechanism(s) responsible for ethanol's teratogenicity remains unknown. Although the phenotype suggests that prenatal ethanol exposure perturbs neural crest cell development, direct proof that these cells are an in utero target is still lacking. Previous research suggested that cranial neural crest cells are eliminated by ethanol-induced apoptosis. We tested this hypothesis using a chick embryo model of FAS. A single dose of ethanol, chosen to achieve a concentration of 35–42 mg/dl, was injected in ovo at gastrulation and resulted in growth retardation, craniofacial foreshortening, and disrupted hindbrain segmentation. Ethanol exposure enhanced cell death within areas populated by cranial neural crest cells, particularly in the hindbrain and craniofacial mesenchyme. In contrast, control embryos had limited cell death within these regions. Subsequent immunolabeling with neural crest cell-specific antibody revealed that ethanol treatment resulted in fewer neural crest cell numbers, whereas neural crest migration patterns were unaffected by ethanol. These results suggest that prenatal ethanol exposure leads to loss of cranial neural crest cells. Such a loss could result, in part, in the phenotype characteristic of FAS.     

程序性细胞死亡与血管钙化关系的研究进展

血管钙化是多种疾病的并发症之一,并参与疾病的发生发展。而血管平滑肌细胞死亡是钙化过程中的必然伴随现象。已有研究证明血管平滑肌细胞的凋亡明确参加血管钙化的发生,而对于另一种程序性细胞死亡方式——自噬是否参与血管平滑肌细胞钙化研究近年来也有报道。本文就当今凋亡和自噬两种常见细胞程序性死亡参与血管平滑肌钙化的作用及可能机制以及影响因素的研究进展作一综述。     

Sirolimus-Eluting Versus Bare-Metal Stents for the Reduction of Coronary Restenosis

PURPOSE: The GERSHWIN study (German Stent Health Outcome and Economics Within Normal Practice) was designed to evaluate long-term effects of treatment of coronary artery disease (CAD) with sirolimus-eluting stents (SES), as compared to bare-metal stents (BMS). PATIENTS AND METHODS: Within a multicenter, prospective intervention study in 35 hospitals throughout Germany, CAD patients with coronary stenosis and elective percutaneous coronary intervention (PCI) indication were treated either with SES or BMS (sequential control design with a case-to-control ratio of 2 : 1). Standardized questionnaires were completed by patients and their physicians at baseline, 3, 6, 12, and 18 months following PCI to document re-PCI for restenosis, myocardial infarction (MI), coronary bypass surgery (CABG), and death. Angiographic PCI documentation was evaluated by an independent expert. RESULTS: From April 2003 until June 2005, 658 patients were treated with SES (mean age 63 +/- 9 years, 87% male) and 294 patients with BMS (mean age 64 +/- 10 years, 79% male). Significant baseline differences were found by age, gender, household status, three vessel disease, and number of implanted stents. After 18 months, 8% of the SES versus 17% of the BMS group had undergone target vessel revascularization (p adjusted < 0.0001). There were no significant differences between BMS and SES regarding MI, CABG, or death. Re-PCI of target and new non-target vessel lesions was performed at a significantly lower degree of stenosis in SES than in BMS. CONCLUSION: Compared to patients with BMS, patients with implantation of SES experienced considerably fewer target vessel revascularizations. The threshold to perform re-PCI appeared lower in SES than in BMS. An extended evaluation of the effects of SES will be available from the 3-year follow-up of the GERSHWIN study.     

血管内皮生长因子对过氧化氢诱导的内皮细胞凋亡的影响及其机制

目的研究血管内皮生长因子对过氧化氢诱导的血管内皮细胞凋亡的影响,同时检测凋亡相关基因Bcl-2 mRNA与Fas mRNA表达的变化。方法体外培养人脐静脉内皮细胞,随机分成对照组、过氧化氢组和过氧化氢 血管内皮生长因子组,12 h后,采用原位末端标记法和流式细胞仪分别观察各组细胞的凋亡数和凋亡率,通过逆转录聚合酶链反应观察各组细胞中凋亡相关基因Bcl-2 mRNA与Fas mRNA表达的变化。结果过氧化氢组凋亡细胞数(27.83±2.14)明显高于对照组(2.50±1.05)(P<0.01)和过氧化氢 血管内皮生长因子组(13.00±2.10)(P<0.01)。过氧化氢组细胞凋亡率(14.17%±0.45%)明显高于对照组(1.55%±0.87%)(P<0.01)和过氧化氢 血管内皮生长因子组(5.69%±0.38%)(P<0.01)。与过氧化氢组比较,过氧化氢 血管内皮生长因子组Fas mRNA表达明显减少(40.67%±2.16%比94.50%±3.45%,P<0.01),而Bcl-2 mRNA表达明显增加(60.33%±1.75%比23.17%±1.17%,P<0.01)。结论血管内皮生长因子能拮抗过氧化氢诱导的内皮细胞凋亡,其抗凋亡的机制可能与上调Bcl-2 mRNA表达与下调Fas mRNA表达有关。     

Potential Role of Apoptosis and Apoptotic Regulatory Proteins in Colorectal Neoplasia: Correlations with Clinico-Pathological Parameters and Survival

An imbalance between apoptotic and proliferative processes is believed to underlie colorectal neoplasia. We evaluated the expression of bcl-2, p53, mdm2 proteins, and apoptosis in colorectal neoplasms, as well as their correlation with clinico-pathological parameters, using image analysis. Biopsies from 46 colorectal cancers, 121 adenomas, and 25 controls were studied using monoclonal antibodies against p53, bcl-2, mdm2 and the terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) method for apoptosis. P53 and bcl2 protein expression was higher in adenomas ≥1 cm (P < 0.03) and tubulovillous-villous adenomas (P < 0.03), and correlated with dysplasia (P < 0.03). In Cox regression analysis, Dukes’ stage was the most significant independent prognostic indicator of a worse survival (P < 0.019), whereas when stage was eliminated, bcl-2 expression was also a powerful predictor for bad prognosis (P = 0.02). In conclusion, both bcl-2 and p53 immunohistochemical profiles may be useful adjuncts in detecting adenomas with a malignant potential, whereas bcl-2 could be used in combination with Dukes’ stage as a predictor of prognosis in colorectal cancer.     

Critical Role of P-Selectin and Lymphocyte Function Antigen-1 in Radiation-Induced Leukocyte-Endothelial Cell Interactions in the Colon

Purpose

Radiation therapy is frequently used in treating different types of tumors, although associated with serious side effects, such as fibrosis and complicated diarrhea. This study was designed to define the adhesive mechanisms behind radiotherapy-induced leukocyte recruitment in the colon.

Methods

All mice, except control animals, were radiated with a single dose of 20 Gy. Mice were pretreated with an isotype-matched control antibody or a monoclonal antibody directed against P-selectin. In separate experiments, lymphocyte function antigen-1–deficient animals were used. Leukocyte rolling and firm adhesion were determined by use of inverted intravital fluorescence microscopy 16 hours after radiation.

Results

It was found that immunoneutralization of P-selectin reduced leukocyte rolling by 83 percent and adhesion by 87 percent in radiated mice. Moreover, radiation-induced leukocyte adhesion in LFA-1-deficient mice was decreased by 94 percent compared with wild-type animals.

Conclusions

This study demonstrates that leukocyte rolling is mediated by P-selectin and that firm leukocyte adhesion is supported by lymphocyte function antigen-1 in radiation-induced enteritis. Moreover, P-selectin-dependent leukocyte rolling is a precondition for subsequent leukocyte adhesion in radiation-induced intestinal injury. Thus, targeting P-selectin and/or lymphocyte function antigen-1 may protect against pathologic inflammation in the colon induced by radiotherapy.

     

血管内皮生长因子预防血管成形术后再狭窄的机理

为探讨血管内皮生长因子预防血管成形术后再狭窄的机理 ,构建含人血管内皮生长因子 165基因的重组腺病毒 ,感染体外培养的血管平滑肌细胞 ,将人脐静脉内皮细胞和血管平滑肌细胞分别分成对照组、H2 O2 处理组和H2 O2 +血管内皮生长因子处理组 ,采用WST 1比色法、原位末端标记法及流式细胞术检测各组细胞光密度值和凋亡发生情况。结果发现 ,人脐静脉内皮细胞中 ,与对照组和H2 O2 +血管内皮生长因子处理组比较 ,H2 O2 处理组光密度值降低 ,凋亡细胞明显增加 ;血管平滑肌细胞中上述改变相反。提示H2 O2 能促进平滑肌细胞增殖 ,诱导内皮细胞凋亡 ,抑制内皮细胞增殖及平滑肌细胞凋亡 ,促进再狭窄的发生 ,而血管内皮生长因子能拮抗H2 O2 的作用 ,有利于再狭窄的防治 ,为血管内皮生长因子预防再狭窄提供新的理论依据     

Apoptotic Cell Death in Cultured Cardiomyocytes Following Exposure to Low Concentrations of 4-Hydroxy-2-nonenal

Lipid peroxidation (LP), induced by oxidative stress, is associated with degenerative processes. 4-Hydroxy-2-nonenal (HNE), a highly reactive diffusible product of LP, is considered by-product and mediator of oxidative stress. Its level increases under pathological conditions such as cardiovascular diseases. In this study, we partially characterized the mechanisms of HNE-mediated cytotoxicity in cardiomyocytes. After establishing that pathophysiological doses of HNE trigger cell death dependent on the incubation time and dose of HNE (LD₅₀ = 4.4 μM), we tackled the mechanisms that underlie the cell death induced by HNE. Our results indicate that HNE rapidly increases intracellular Ca²⁺; it also increases the rate of reactive oxygen species generation and causes a loss of mitochondrial membrane potential (ΔΨm) as well as a decrease in the ATP and GSH levels. Such alterations result in the activation of caspase-3 and DNA breakdown, both characteristic features of apoptotic cell death, as well as disruption of the cytoskeleton. Moreover, the nucleophilic compounds N-acetyl-cysteine and β-mercapto-propionyl-glycine, and the synthetic antioxidant Trolox exert a potent antioxidant action against HNE damage; this suggests its use as effective compounds in order to reduce the damage occurred as consequence of cardiovascular disorders in which oxidative stress and hence LP take place.