Apoptosis of airway epithelial cells in response to meconium

Meconium aspiration syndrome (MAS) is common among newborn children but its mechanism is unclear. The syndrome is known to produce a strong inflammatory reaction in the lungs resulting in massive cell death. In this work we studied lung cell death by apoptosis after meconium aspiration in forty two-week-old rabbit pups. Analyzing lung samples by ISEL-DNA end labeling demonstrated the specific spread of apoptotic bodies throughout the lungs. These bodies were shrunken and smaller in size compared to normal cells and many of them were lacking cell membranes. About 70% of all apoptotic bodies were found among the airway epithelium cell eight hours after meconium instillation. In comparison, among lung alveolar cells, only about 20% cells were apoptotic in the same animals. In meconium-treated lungs and A549 cells, a significant increase of angiotensinogen mRNA and Caspase-3 expression were observed. The pretreatment of cells with Caspase-3 inhibitor ZVAD-fmk significantly inhibited meconium-induced lung cell death by apoptosis. These findings demonstrate the apoptotic process in meconium-instilled lungs or A549 cells in culture. Our results show lung airway epithelial and A549 cell apoptosis after meconium instillation. We suggest that studies of lung airway epithelial cell death are essential to understanding the pathophysiology of MAS and may present a key point in future therapeutic applications.     

Characterization of serine/cysteine protease inhibitor alpha1-antitripsin from meconium-instilled rabbit lungs

We have recently purified from meconium-instilled rabbit lungs a novel serine proteinase inhibitor, with an apparent molecular mass of 50 kDa, which we assign to be alpha1-antitripsin. We hypothesize that serpin may attenuate pulmonary inflammation and improve surfactant function after meconium aspiration. Alpha1-antitripsin is a member of the proteinase inhibitor (serpin) superfamily and inhibitor of neutrophil elastase, and it can be identified as a member of the family by its amino acid sequence due to the high degree of conserved residues. Alpha1-antitripsin is synthesized by epithelial cells, macrophages, monocytes, and neutrophils. Deficiency in alpha1-antitripsin leads to exposure of lungs to uncontrolled proteolytic attack from neutrophil elastase or other damaging factors culminating in lung destruction and cell apoptosis. We hypothesize that accumulation of alpha1-antitripsin in the lungs serves as a predisposed protection against meconium-induced lung injury. In this paper, we show how this knowledge can lead to the development of novel therapeutic approaches for treatment of MAS.     

Apoptosis Induction Influences Reovirus Replication and Virulence in Newborn Mice

Apoptosis is a type of controlled cell death that is essential for development and tissue homeostasis. It also serves as a robust host response against infection by many viruses. The capacity of neurotropic viruses to induce apoptosis strongly correlates with virulence. However, the precise function of apoptosis in viral infection is not well understood. Reovirus is a neurotropic virus that induces apoptosis in a variety of cell types, including central nervous system neurons, leading to fatal encephalitis in newborn mice. To determine the effect of apoptosis on reovirus replication in the host, we generated two otherwise isogenic viruses that differ in a single amino acid in viral capsid protein μ1 that segregates with apoptotic capacity. Apoptosis-proficient and apoptosis-deficient viruses were compared for replication, dissemination, tropism, and tissue injury in newborn mice and for the capacity to spread to uninfected littermates. Our results indicate that apoptotic capacity enhances reovirus replication in the brain and consequent neurovirulence but reduces transmission efficiency. The replication advantage of the apoptosis-proficient strain is limited to the brain and correlates with enhanced infectivity of neurons. These studies reveal a new cell type-specific determinant of reovirus virulence.     

Deciphering the pathways of death of Histoplasma capsulatum-infected macrophages: implications for the immunopathogenesis of early infection

Apoptosis of leukocytes is known to strongly influence the immunopathogenesis of infection. In this study, we dissected the death pathways of murine macrophages (MΦs) infected with the intracellular pathogen Histoplasma capsulatum. Yeast cells caused apoptosis of MΦs at a wide range of multiplicity of infection, but smaller inocula resulted in delayed detection of apoptosis. Upon infection, caspases 3 and 1 were activated, and both contributed to cell death; however, only the former was involved in apoptosis. The principal driving force for apoptosis involved the extrinsic pathway via engagement of TNFR1 by TNF-α. Infected MΦs produced IL-10 that dampened apoptosis. The chronology of TNF-α and IL-10 release differed in vitro. The former was detected by 2 h postinfection, and the latter was not detected until 8 h postinfection. In vivo, the lungs of TNFR1(-/-) mice infected for 1 d contained fewer apoptotic MΦs than wild-type mice, whereas the lungs of IL-10(-/-) mice exhibited more. Blockade of apoptosis by a pan-caspase inhibitor or by simvastatin sharply reduced the release of TNF-α but enhanced IL-10. However, these treatments did not modify the fungal burden in vitro over 72 h. Thus, suppressing cell death modulated cytokine release but did not alter the fungal burden. These findings provide a framework for the early pathogenesis of histoplasmosis in which yeast cell invasion of lung MΦs engenders apoptosis, triggered in part in an autocrine TNF-α-dependent manner, followed by release of IL-10 that likely prevents apoptosis of newly infected neighboring phagocytes.     

Streptococcus pneumoniae: the role of apoptosis in host defense and pathogenesis

Programmed cell death or apoptosis is a recognised feature of infection with Streptococcus pneumoniae, and is observed during pneumococcal meningitis and pneumonia. The cholesterol-dependent cytolysin, pneumolysin, is a major trigger of apoptosis in the brain in association with pneumococcal production of hydrogen peroxide. Pneumococcal cell wall is also an important stimulus for apoptosis. Microbial factors and host factors combine in causing apoptosis in the brain, with hippocampal neurons being particularly susceptible. In pulmonary infection epithelial cell apoptosis contributes to tissue injury but macrophage apoptosis may benefit the host, aiding microbial killing and downregulating the inflammatory response. During sepsis lymphocyte apoptosis may be harmful to the host while dendritic cell apoptosis may limit the generation of an adaptive immune response during infection. Apoptosis induction may be harmful or potentially beneficial during pneumococcal infection and understanding its function in each setting is essential to allow specific therapeutic intervention.     

Lymphocyte apoptosis in murine Pneumocystis pneumonia

Background

Apoptosis of lymphocytes is important in the termination of an immune response to infection but has also been shown to have detrimental effects in animal models of systemic infection and sepsis. We sought to characterize lymphocyte apoptosis in an animal model of pneumonia due to Pneumocystis murina, an infection localized to the lungs.

Methods

Control mice and mice depleted of CD4+ lymphocytes were inoculated with Pneumocystis. Apoptosis of lung and spleen lymphocytes was assayed by flow cytometry and PCR assay of apoptotic proteins.

Results

In control mice, apoptosis of lung lymphocytes was maximal just after the infection was cleared from lung tissue and then declined. However, in CD4-depleted mice, apoptosis was also upregulated in recruited lymphocytes in spite of progressive infection. In splenic lymphocytes, apoptosis was observed early at 1 week after inoculation and then declined. Apoptosis of lung lymphocytes in control mice was associated with a decrease in mRNA for Bcl-2 and an increase in mRNA for Bim. In CD4-depleted mice, lavaged CD8+ cells did change intracellular Bcl-2 but showed increased mRNA for Bim.

Conclusion

Apoptosis of both pulmonary and extrapulmonary lymphocytes is part of the normal host response to Pneumocystis but is also triggered in CD4-deficient animals with progressive infection. In normal mice apoptosis of pulmonary lymphocytes may serve to terminate the immune response in lung tissue. Apoptosis of lung lymphocytes takes place via both the intrinsic and extrinsic apoptotic pathways and is associated with changes in both pro- and anti-apoptotic proteins.     

Apoptotic signaling in mouse odontogenesis

Apoptosis is an important morphogenetic event in embryogenesis as well as during postnatal life. In the last 2 decades, apoptosis in tooth development (odontogenesis) has been investigated with gradually increasing focus on the mechanisms and signaling pathways involved. The molecular machinery responsible for apoptosis exhibits a high degree of conservation but also organ and tissue specific patterns. This review aims to discuss recent knowledge about apoptotic signaling networks during odontogenesis, concentrating on the mouse, which is often used as a model organism for human dentistry. Apoptosis accompanies the entire development of the tooth and corresponding remodeling of the surrounding bony tissue. It is most evident in its role in the elimination of signaling centers within developing teeth, removal of vestigal tooth germs, and in odontoblast and ameloblast organization during tooth mineralization. Dental apoptosis is caspase dependent and proceeds via mitochondrial mediated cell death with possible amplification by Fas-FasL signaling modulated by Bcl-2 family members.     

神经酰胺与细胞凋亡

细胞凋亡 (apoptosis) 又称细胞的程序性死亡,参与机体许多生理和病理过程.近年来的研究表明细胞凋亡与鞘脂质代谢有密切的关系,鞘磷脂的水解产物神经酰胺作为脂质第二信使在诱导和抑制细胞凋亡中起着重要的作用.     

Apoptosis in yeast--a monocellular organism exhibits altruistic behaviour

Apoptosis is a highly regulated form of programmed cell death crucial for life and health in metazoan animals. Apoptosis is defined by a set of cytological alterations. The recent discovery of these markers in yeast indicates the presence of the basic mechanisms of apoptosis already in unicellular eukaryotes. Oxygen radicals regulate both mammalian and yeast apoptosis. We suggest that apoptosis originated in unicellular organisms as an altruistic response to severe oxidative damage. Later, cells developed mechanisms to purposely produce reactive oxygen species as a regulator of apoptosis. Yeast may become an important model to investigate the conserved steps of apoptosis.     

Hyperoxia-induced apoptosis and Fas/FasL expression in lung epithelial cells

Alveolar epithelial apoptosis is an important feature of hyperoxia-induced lung injury in vivo and has been described in the early stages of bronchopulmonary dysplasia (chronic lung disease of preterm newborn). Molecular regulation of hyperoxia-induced alveolar epithelial cell death remains incompletely understood. In view of functional involvement of Fas/FasL system in physiological postcanalicular type II cell apoptosis, we speculated this system may also be a critical regulator of hyperoxia-induced apoptosis. The aim of this study was to investigate the effects of hyperoxia on apoptosis and apoptotic gene expression in alveolar epithelial cells. Apoptosis was studied by TUNEL, electron microscopy, DNA size analysis, and caspase assays. Fas/FasL expression was determined by Western blot analysis and RPA. We determined that in MLE-12 cells exposed to hyperoxia, caspase-mediated apoptosis was the first morphologically and biochemically recognizable mode of cell death, followed by necrosis of residual adherent cells. The apoptotic stage was associated with a threefold upregulation of Fas mRNA and protein expression and increased susceptibility to direct Fas receptor activation, concomitant with a threefold increase of FasL protein levels. Fas gene silencing by siRNAs significantly reduced hyperoxia-induced apoptosis. In murine fetal type II cells, hyperoxia similarly induced markedly increased Fas/FasL protein expression, confirming validity of results obtained in transformed MLE-12 cells. Our findings implicate the Fas/FasL system as an important regulator of hyperoxia-induced type II cell apoptosis. Elucidation of regulation of hyperoxia-induced lung apoptosis may lead to alternative therapeutic strategies for perinatal or adult pulmonary diseases characterized by dysregulated type II cell apoptosis.     

Caspase-dependent apoptosis and -independent poly(ADP-ribose) polymerase cleavage induced by transforming growth factor beta1

Apoptosis is an important cell suicide program which involves the caspases activation and is implicated in physiological and pathological processes. Poly(ADP-ribose) polymerase (PARP) cleavage is often associated with apoptosis and has been served as one hallmark of apoptosis and caspase activation. In this study, we aimed to determine TGF-beta1-induced apoptosis and to examine the involvement of caspases and its relationship with PARP cleavage. TGF-beta1 induces strong apoptosis of AML-12 cells which can be detected by DNA fragmentation, FACS, and morphological assays. Z-VAD-fmk, a selective caspase inhibitor, partially inhibits the TGF-beta1-induced apoptosis; but has no effect on TGF-beta1-induced DNA fragmentation and PARP cleavage. However, BD-fmk, a broad-spectrum caspase inhibitor, completely suppresses TGF-beta1-induced apoptosis, but unexpectedly does not inhibit TGF-beta1-induced PARP cleavage. Furthermore, Z-VAD-fmk treatment is able to completely inhibit the daunorubicin-induced apoptosis in A-431 cells, but only slightly blocks the daunorubicin-induced PARP cleavage, whereas BD-fmk can inhibit both daunorubicin-induced apoptosis and PARP cleavage completely. In addition, we observed that both TGF-beta1-induced apoptosis and PARP degradation in AML-12 cells can be completely blocked by inhibiting the protein synthesis with cycloheximide. These results demonstrate for the first time that TGF-beta1-induced caspase-dependent apoptosis is associated with caspase-independent PARP cleavage that requires the TGF-beta1-induced synthesis of new proteins. The results indicate that caspase-3 is not a major caspase involved in TGF-beta1-induced apoptosis in AML-12 cells, and is not required for apoptosis-associated DNA fragmentation. The results also suggest that PARP cleavage may occur as an independent event that can be disassociated with cell apoptosis.     

人外周血淋巴细胞凋亡与年龄及p21~(WAF1)的关系

 分别从老年人和新生儿外周血中分离淋巴细胞 ,用形态观察、DNA断裂电泳图谱、流式细胞仪分析凋亡峰等手段检测其在体外培养过程中发生凋亡的情况 .结果表明 ,不论是自发凋亡还是用1 0 mmol/L的丁酸钠诱导其凋亡 ,老年人淋巴细胞的凋亡率均高于新生儿组 .进一步检测淋巴细胞凋亡时 p2 1 WAF1的表达变化 ,结果表明老年人淋巴细胞 p2 1 WAF1的下调幅度明显大于新生儿组 .提示老年人淋巴细胞凋亡率高与其 p2 1 WAF1表达容易下调有关 .     

运动对细胞凋亡的影响

细胞凋亡是一种由基因控制的细胞自主性死亡过程,其性质为生理性细胞死亡。细胞凋亡的研究已成为生物医学领域中最热门的课题之一。运动可以诱导细胞凋亡,细胞凋亡发生的比率和程度与运动形式、运动强度和运动持续时间有关,其机制可能主要包括以下方面：影响凋亡相关基因、自由基的介导使氧化与抗氧化系统失衡,损伤线粒体的结构和功能以及机械损伤。为此就运动对细胞凋亡影响的一些新的研究进展进行了综述。     

细胞凋亡（Apoptosis）与癌基因

细胞凋亡是细胞衰老、死亡过程的主要形式.最近研究发现有多种癌基因与抑癌基因参与细胞凋亡过程.因此目前认为癌基因与抑癌基因不仅控制细胞增殖、分化,而且调节细胞凋亡.细胞凋亡受阻或缺陷可能是肿瘤发生的基础之一.     

运动对细胞凋亡的影响

细胞凋亡是一种由基因控制的细胞自主性死亡过程,其性质为生理性细胞死亡。细胞凋亡的研究已成为生物医学领域中最热门的课题之一。运动可以诱导细胞凋亡,细胞凋亡发生的比率和程度与运动形式、运动强度和运动持续时间有关,其机制可能主要包括以下方面:影响凋亡相关基因、自由基的介导使氧化与抗氧化系统失衡,损伤线粒体的结构和功能以及机械损伤。为此就运动对细胞凋亡影响的一些新的研究进展进行了综述。     

Lessons from genetically engineered animal models. VII. Apoptosis in intestinal epithelium: lessons from transgenic and knockout mice

Apoptosis plays an important role in homeostasis of intestinal epithelia and is also a stress response to toxic stimuli. Transgenic and knockout mice have provided insights into the regulation of intestinal epithelial apoptosis that could not have been obtained by cell culture techniques. Two broad types of apoptosis have been characterized: spontaneous apoptosis, which occurs continuously at low levels in the normal, unstressed intestine, and stress-induced apoptosis, which occurs after genotoxic insult such as exposure to gamma radiation or DNA-damaging drugs. Spontaneous apoptosis occurs at the base of the crypt at or near the position of epithelial stem cells. Knockout studies have shown that spontaneous apoptosis is independent of p53 and Bax in both small and large intestine, whereas Bcl2 only regulates spontaneous apoptosis in the colon. Little is known about the regulation of the specialized form of cell death at the villus tip. In contrast, knockout studies have demonstrated that both p53 and Bcl2 are important regulators of stress-induced apoptosis but that there are significant differences between early and late time points. Bax plays only a minor role in the regulation of stress-induced apoptosis. The cumulative effect of stress-induced apoptosis on tissue architecture is not straightforward, and cell cycle arrest also plays a critical role. Nevertheless, p53 is an important determinant of the histopathological damage induced by 5-fluorouracil in murine intestinal epithelium. These studies have important implications for the development of more effective treatment for inflammatory bowel disease and cancer.     

Extremely rapid and intense induction of apoptosis in human eosinophils by anti-CD30 antibody treatment in vitro

Apoptosis is an important cellular mechanism for controlling cell viability and proliferation. With respect to eosinophils, cytokines prolong their survival, whereas corticosteroids reduce their survival in vitro. CD30, a member of the TNFR family, is expressed on the surface of many cell types, including Hodgkin's lymphoma cells. CD30 is capable of inducing apoptosis after Ab treatment in some cell lines. To determine whether this surface structure is involved in apoptosis of human eosinophils, we examined its expression and the effect of anti-CD30 Ab treatment on the viability of eosinophils. Purified human eosinophils expressed low, but consistently detectable, levels of CD30. Immobilized, but not soluble, forms of anti-CD30 Abs (HRS-4 and Ber-H8) or recombinant mouse CD30 ligand exhibited an extremely rapid and intense survival-reducing effect on the eosinophils in the presence of exogenous IL-5; this effect was both concentration and time dependent. Furthermore, high concentrations of IL-5 could not reverse the reduced survival rates. After treatment with anti-CD30 Ab, gel electrophoresis of DNA extracted from the eosinophils demonstrated changes consistent with apoptosis. The immobilized F(ab')(2) of the anti-CD30 Ab failed to induce eosinophil apoptosis. The addition of anti-CD18 Ab also completely abrogated the induction of eosinophil apoptosis. Further examination using specific signal transduction inhibitors suggested the involvement of p38, mitogen-activated protein kinase kinase 1/2, and specific tyrosine kinase, but not NF-kappaB, in the induction of CD30-mediated eosinophil apoptosis. These data demonstrate that CD30 can modify eosinophil survival by causing an extremely rapid and intense induction of apoptosis through a tightly regulated intracellular signaling pathway.     

细胞凋亡中的钙离子调控

凋亡是细胞的一种生理性、主动性的自杀行为,它使机体能够有效清除多余或病态的细胞。作为细胞内普遍存在的第二信使,Ca2 在信号转导过程中发挥重要作用。它能够将细胞感受的刺激转化为其在不同细胞组分间的分布差异及自身浓度的振荡,这种在细胞内和细胞间的波动协调了细胞生命活动的各个方面。以往的研究认为细胞内Ca2 浓度的升高是凋亡进行到后期的结果,而最近的研究发现Ca2 也可以在凋亡通路的各个层次,通过不同的方式精细调控凋亡的进程,这构成了凋亡中复杂的钙调控网络。现对钙离子和线粒体凋亡途径中分子间的复杂联系以及钙调控细胞凋亡研究的最新进展进行综述。     

Early inhaled nitric oxide treatment decreases apoptosis of endothelial cells in neonatal rat lungs after vascular endothelial growth factor inhibition

Vascular endothelial growth factor (VEGF) receptor blockade impairs lung growth and decreases nitric oxide (NO) production in neonatal rat lungs. Inhaled NO (iNO) treatment after VEGF inhibition preserves lung growth in infant rats by unknown mechanisms. We hypothesized that neonatal VEGF inhibition disrupts lung growth by causing apoptosis in endothelial cells, which is attenuated by early iNO treatment. Three-day-old rats received SU-5416, an inhibitor of VEGF receptor, or its vehicle and were raised in room air with or without iNO (10 ppm). SU-5416 reduced alveolar counts and lung vessel density by 28% (P < 0.005) and 21% (P < 0.05), respectively, as early as at 7 days of age. SU-5416 increased lung active caspase-3 protein by 60% at 5 days of age (P < 0.05), which subsided by 7 days of age, suggesting a transient increase in lung apoptosis after VEGF blockade. Apoptosis primarily colocalized to lung vascular endothelial cells, and SU-5416 increased endothelial cell apoptotic index by eightfold at 5 days of age (P <0.0001). iNO treatment after SU-5416 prevented the increases in lung active caspase-3 and in endothelial cell apoptotic index. There was no difference in alveolar type 2 cell number between control and SU-5416-treated rats. We conclude that neonatal VEGF receptor inhibition causes transient apoptosis in pulmonary endothelium, which is followed by persistently impaired lung growth. Early iNO treatment after VEGF inhibition reduces endothelial cell apoptosis in neonatal lungs. We speculate that enhancing endothelial cell survival after lung injury may preserve neonatal lung growth in bronchopulmonary dysplasia.