Cadmium Induces Thymocyte Apoptosis via Caspase‐Dependent and Caspase‐Independent Pathways

Based on our recent findings that 25  µ M cadmium triggers oxidative stress–mediated caspase‐dependent apoptosis in murine thymocytes, this study is designed to explore whether Cd also induces caspase‐independent apoptosis. We found that pretreatment with caspase inhibitors fails to prevent Cd‐induced apoptosis completely, suggesting the possibility of an additional pathway. Western blot and flow cytometry techniques indicated marked expression of apoptosis‐inducing factor and endonuclease G in nuclear fraction, signifying their translocation from mitochondria to nucleus. Intracellular Ca²⁺ and reactive oxygen species (ROS) levels significantly raised by Cd were restored by ruthenium red, which had no influence on mitochondrial membrane depolarization and caspase activity and apoptosis. Using cyclosporin A, ROS formation and mitochondrial membrane depolarization were completely abolished, whereas apoptosis was partly attenuated. These results clearly demonstrate more than one apoptotic pathway in thymocytes and support the role of mitochondrial permeability transition pore in the regulation of caspase‐independent cell death triggered by Cd. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:193‐203, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21468     

Treatment of pregnant BALB/c mice with sulphadoxine pyrimethamine or chloroquine abrogates Plasmodium berghei induced placental pathology

Malaria infection during pregnancy is a risk factor for foetus survival and is associated with abortion, premature delivery and low birth weight of infants in malaria endemic regions. In these regions, prophylactic measures and treatment mainly rely on chloroquine and sulphadoxine pyrimethamine, but their efficacy in reducing the placental pathology has not been studied. Therefore, the present study was designed to assess the effectiveness of chloroquine and sulphadoxine pyrimethamine treatment in reducing the placental pathology of Plasmodium berghei infected BALB/c mice. It was observed that pregnant-infected mice, treated either with chloroquine or sulphadoxine pyrimethamine had significantly lower percent parasitaemia, 100% survival and delivered normally compared with untreated pregnant-infected mice. Interestingly, antimalarial treatment significantly reduced malondialdehyde (MDA) levels, measure of lipid peroxidation and number of apoptotic cells in the placentae of pregnant-infected treated mice. Histologically also no morphological and cellular alterations were observed in the placentae of pregnant-infected treated mice. Taken together, the study shows the effectiveness of chloroquine and sulphadoxine pyrimethamine treatment, when administered in second trimester in abrogating malaria induced oxidative stress, apoptosis and histopathological alterations in the placenta, leading to normal foetal development.     

Direct activation of mitochondrial apoptosis machinery by c-Jun N-terminal kinase in adult cardiac myocytes.

Although oxidative stress causes activation of c-Jun N-terminal kinase (JNK) and apoptosis in many cell types, how the JNK pathway is connected to the apoptosis pathway is unclear. The molecular mechanism of JNK-mediated apoptosis was investigated in adult rat cardiac myocytes in culture as a model system that is sensitive to oxidative stress. Oxidative stress caused JNK activation, cytochrome c release, and apoptosis without new protein synthesis. Oxidative stress-induced apoptosis was abrogated by dominant negative stress-activated protein kinase/extracellular signal-regulated kinase kinase-1 (SEK1)-mediated inhibition of the JNK pathway, whereas activation of the JNK pathway by constitutively active SEK1 was sufficient to cause apoptosis. Inhibition of caspase-9, an apical caspase in the mitochondrial apoptosis pathway, suppressed oxidative stress-induced apoptosis, whereas inhibition of caspase-8 had no effect, indicating that both the JNK pathway and the mitochondrial apoptosis machinery are central to oxidative stress-induced apoptosis. Both JNK and SEK1 localized on mitochondria where JNK was activated by oxidative stress. Furthermore, active JNK caused the release of apoptogenic factors such as cytochrome c from isolated mitochondria in a cell-free assay. These findings indicate that the JNK pathway is a direct activator of mitochondrial death machinery without other cellular components and provide a molecular linkage from oxidative stress to the mitochondrial apoptosis machinery.     

Overexpression of Endogenous Anti-Oxidants with Selenium Supplementation Protects Trophoblast Cells from Reactive Oxygen Species-Induced Apoptosis in a Bcl-2-Dependent Manner

The human placenta provides life support for the developing foetus, and a healthy placenta is a prerequisite to a healthy start to life. Placental tissue is subject to oxidative stress which can lead to pathological conditions of pregnancy such as preeclampsia, preterm labour and intrauterine growth restriction. Up-regulation of endogenous anti-oxidants may alleviate placental oxidative stress and provide a therapy for these complications of pregnancy. In this study, selenium supplementation, as inorganic sodium selenite (NaSel) or organic selenomethionine (SeMet), was used to increase the protein production and cellular activity of the important redox active proteins glutathione peroxidase (GPx) and thioredoxin reductase (Thx-Red). Placental trophoblast cell lines, BeWo, JEG-3 and Swan-71, were cultured in various concentrations of NaSel or SeMet for 24 h and cell extracts prepared for western blots and enzyme assays. Rotenone and antimycin were used to stimulate mitochondrial reactive oxygen species (ROS) production and induce apoptosis. Trophoblast cells supplemented with 100 nM NaSel and 500 nM SeMet exhibited significantly enhanced expression and activity of both GPx and Thx-Red. Antimycin and rotenone were found to generate ROS when measured by 2′,7′-dichlorofluorescein diacetate (DCFDA) assay, and selenium supplementation was shown to reduce ROS production in a dose-dependent manner. Rotenone, 100 μM treatment for 4 h, caused trophoblast cell apoptosis as evidenced by increased Annexin V binding and decreased expression of Bcl-2. In both assays of apoptosis, selenium supplementation was able to prevent apoptosis, preserve Bcl-2 expression and protect trophoblast cells from mitochondrial oxidative stress. This data suggests that selenoproteins such as GPx and Thx-Red have an important role in protecting trophoblast cells from mitochondrial oxidative stress and that selenium supplementation may be important in treating some placental pathologies.     

GSH extrusion and and the mitochondrial pathway of apoptotic signalling

New evidence suggests that physiological and damaging agents activate two different pathways of apoptotic signalling, which are mediated by protein-protein interactions and mitochondrial alterations respectively. The two pathways converge at the activation of caspase 3, the key effector of the execution phase of apoptosis, thus giving similar final results. The knowledge that different biochemical routes exist allows us to re-evaluate previous apparently contradictory results concerning the events occurring during apoptosis, and their respective roles. In particular, this applies to the role of oxidative stress and redox imbalance in the signal transduction events of apoptosis. It now appears that oxidative alterations are absent, or at least unnecessary, for the development of the physiological pathway. Instead, clear indications are emerging showing that redox imbalance is required for the damage-induced mitochondrial pathway. This is suggested by the finding that the depletion of glutathione, a common event in damage-induced apoptosis, is necessary and sufficient to induce cytochrome c release, the key event of this pathway. A model is proposed with GSH efflux as the backbone of the damage-induced apoptotic pathway.     

Role of the mitochondrial signaling pathway in murine coronavirus-induced oligodendrocyte apoptosis

A previous study demonstrated that infection of rat oligodendrocytes by mouse hepatitis virus (MHV) resulted in apoptosis, which is caspase dependent (Y. Liu, Y. Cai, and X. Zhang, J. Virol. 77:11952-11963, 2003). Here we determined the involvement of the mitochondrial pathway in MHV-induced oligodendrocyte apoptosis. We found that caspase-9 activity was 12-fold higher in virus-infected cells than in mock-infected cells at 24 h postinfection (p.i.). Pretreatment of cells with a caspase-9 inhibitor completely blocked caspase-9 activation and partially inhibited the apoptosis mediated by MHV infection. Analyses of cytochrome c release further revealed an activation of the mitochondrial apoptotic pathway. Stable overexpression of the two antiapoptotic proteins Bcl-2 and Bcl-xL significantly, though only partially, blocked apoptosis, suggesting that activation of the mitochondrial pathway is partially responsible for the apoptosis. To identify upstream signals, we determined caspase-8 activity, cleavage of Bid, and expression of Bax and Bad by Western blotting. We found a drastic increase in caspase-8 activity and cleavage of Bid at 24 h p.i. in virus-infected cells, suggesting that Bid may serve as a messenger to relay the signals from caspase-8 to mitochondria. However, treatment with a caspase-8 inhibitor only slightly blocked cytochrome c release from the mitochondria. Furthermore, we found that Bax but not Bad was significantly increased at 12 h p.i. in cells infected with both live and UV-inactivated viruses and that Bax activation was partially blocked by treatment with the caspase-8 inhibitor. These results thus establish the involvement of the mitochondrial pathway in MHV-induced oligodendrocyte apoptosis.     

Staphylococcus aureus alpha-toxin induces apoptosis in peripheral blood mononuclear cells: role of endogenous tumour necrosis factor-alpha and the mitochondrial death pathway

Staphylococcus aureus infections can result in septic and toxic shock with depletion of immune cells and massive cytokine production. Recently, we showed that, in S. aureus-infected Jurkat T cells, alpha-toxin is the major mediator of caspase activation and apoptosis. Here, we investigated the mechanisms of cell death induced by alpha-toxin in peripheral blood mononuclear cells (MNC). We show that alpha-toxin is required and sufficient for S. aureus-induced cell death not only in transformed Jurkat T cells but also in MNC. Low alpha-toxin doses (3-30 ng ml-1) dose- and time-dependently induced apoptosis in both cell types, which was completely blocked by the caspase inhibitor zVAD-fmk. In Jurkat T cells and MNC, alpha-toxin induced the breakdown of the mitochondrial membrane potential and the intrinsic activation of caspase-3, -8 and -9. Interestingly, unlike in Jurkat T cells, apoptosis in MNC was additionally mediated by a caspase-9-independent component. MNC, but not Jurkat T cells, produced tumour necrosis factor (TNF)-alpha upon alpha-toxin stimulation. Blocking endogenous TNF-alpha with a TNF-alpha receptor antagonist partially decreased apoptosis in MNC. Our data therefore suggest that, whereas in Jurkat T cells apoptosis is solely mediated by the mitochondrial pathway, in MNC endogenous TNF-alpha and a death receptor-dependent pathway are also involved, which may contribute to depletion of immune cells during S. aureus infection.     

Malarial infection develops mitochondrial pathology and mitochondrial oxidative stress to promote hepatocyte apoptosis

Activation of the mitochondrial apoptosis pathway by oxidative stress has been implicated in hepatocyte apoptosis during malaria. Because mitochondria are the source and target of reactive oxygen species (ROS), we have investigated whether hepatocyte apoptosis is linked to mitochondrial pathology and mitochondrial ROS generation during malaria. Malarial infection induces mitochondrial pathology by inhibiting mitochondrial respiration, dehydrogenases, and transmembrane potential and damaging the ultrastructure as evident from transmission electron microscopic studies. Mitochondrial GSH depletion and formation of protein carbonyl indicate that mitochondrial pathology is associated with mitochondrial oxidative stress. Fluorescence imaging of hepatocytes documents intramitochondrial superoxide anion (O₂^?) generation during malaria. O₂^? inactivates mitochondrial aconitase to release iron from iron–sulfur clusters, which forms the hydroxyl radical (OH) interacting with H₂O₂ produced concurrently. Malarial infection inactivates mitochondrial aconitase, and carbonylation of aconitase is evident from Western immunoblotting. The release of iron has been documented by fluorescence imaging of hepatocytes using Phen Green SK, and mitochondrial OH generation has been confirmed. During malaria, the depletion of cardiolipin and formation of the mitochondrial permeability transition pore favor cytochrome c release to activate caspase-9. Interestingly, mitochondrial OH generation correlates with the activation of both caspase-9 and caspase-3 with the progress of malarial infection, indicating the critical role of OH.     

Caspase-9-dependent pathway to murine germ cell apoptosis: mediation by oxidative stress,BAX, and caspase 2

Ischemia-reperfusion (IR) of the testis results in germ-cell-specific apoptosis (GCA) and a reduction in daily sperm production. This has been correlated with and is dependent upon neutrophil recruitment to the testis. In a rat model of testicular IR, this has also been correlated with an increase in reactive oxygen species (ROS). We have investigated ROS in the mouse testis after IR and determined whether the observed GCA is mediated via a mitochondrial caspase-9-dependent pathway involving the upstream mediators caspase 2 and BAX. Mice were subjected to a 2-h period of testicular ischemia followed by reperfusion. An accumulation of 8-isoprostane, a marker of oxidative stress, occurred 4 h after reperfusion. Activation of a mitochondrial dependent pathway to GCA after testicular IR was determined based on the observations that both BAX and caspase 2 translocated to the mitochondria, and that an increase occurred in cytoplasmic cytochrome c. Moreover, microinfusion of a specific caspase 9 inhibitor significantly reduced active caspase 3 after testicular IR and the number of apoptotic germ cells. These results suggest that oxidative stress products accumulate in the testis following IR and demonstrate that the observed GCA is stimulated through a mitochondrial caspase-9-dependent pathway. The identification of the germ-cell apoptotic pathway induced after testicular IR, including the key players in the pathway subsequent to ROS (BAX, caspase 9, and caspase 2), aids our understanding of IR injury in the testis and provides a wider background for the development of therapeutic interventions to rescue testis function. The work was supported by grants P50 DK45179 and DK53072.     

Plasmodium berghei: influence of infection on the oxidant and antioxidants levels in pregnant BALB/c mice

Malarial infection during pregnancy has been associated with maternal anemia and death, abortion, still-birth and is a major cause of low birth weight, an important risk factor for infant morbidity and mortality in endemic areas. The present study was designed to delineate the oxidative stress in various organs (liver, spleen, kidney, brain and placenta) of pregnant Plasmodium berghei infected BALB/c mice. It was observed that pregnant-infected mice had higher parasitaemia than nonpregnant-infected mice. Most notably, levels of malondialdehyde (MDA), a measure of lipid peroxidation, reduced glutathione (GSH) and superoxide dismutase (SOD) levels were significantly higher in the liver, spleen, kidney and brain of pregnant-infected mice compared with pregnant mice. Although MDA levels were significantly higher, GSH and SOD levels remained unaltered in the placenta of pregnant-infected mice compared with pregnant mice. Furthermore, catalase activity was significantly lower in all the organs of pregnant-infected mice compared with pregnant mice. Histopathological observations in the organs clearly show the cellular and morphological alterations that may be occurring due to increased lipid peroxidation. Taken together, the data suggest that the increased severity of malarial infection during pregnancy may be due to accentuated oxidative stress.     

Bcl-2 protects against hyperoxia-induced apoptosis through inhibition of the mitochondria-dependent pathway

Bcl-2 is an antiapoptotic molecule that prevents oxidative stress damage and cell death. We investigated the possible protective mechanisms mediated by Bcl-2 during hyperoxia-induced cell death in L929 cells. In these cells, hyperoxia promoted apoptosis without DNA fragmentation. Overexpression of Bcl-2 significantly protected cells from oxygen-induced apoptosis, as shown by measurement of lactate dehydrogenase release, quantification of apoptotic nuclei, and detection of Annexin-V-positive cells. Bcl-2 partially prevented mitochondrial damage and interfered with the mitochondrial proapoptotic signaling pathway: it reduced Bax translocation to mitochondria, decreased the release of cytochrome c, and inhibited caspase 3 activation. However, treatment with the caspase inhibitor Z-VAD.fmk failed to rescue the cells from death, indicating that protection provided by Bcl-2 was due not only to caspase inhibition. Bcl-2 also prevented the release of mitochondrial apoptotic inducing factor, a mediator of caspase-independent apoptosis, correlating with the absence of oligonucleosomal DNA fragmentation. In addition, Bcl-2-overexpressing cells showed significantly higher intracellular amounts of glutathione after 72 h of oxygen exposure. In conclusion, our results demonstrate that the overexpression of Bcl-2 is able to prevent hyperoxia-induced cell death, by affecting mitochondria-dependent apoptotic pathways and increasing intracellular antioxidant compounds.     

Herpes simplex virus 1 blocks caspase-3-independent and caspase-dependent pathways to cell death

Earlier reports have shown that herpes simplex virus 1 (HSV-1) mutants induce programmed cell death and that wild-type HSV blocks the execution of the cell death program triggered by viral gene products, by the effectors of the immune system such as the Fas and tumor necrosis factor pathways, or by nonspecific stress agents such as either osmotic shock induced by sorbitol or thermal shock. A report from this laboratory showed that caspase inhibitors do not block DNA fragmentation induced by infection with the HSV-1 d120 mutant. To identify the events in programmed cell death induced and blocked by HSV-1, we examined cells infected with wild-type virus or the d120 mutant or cells infected and exposed to sorbitol. We report that: (i) the HSV-1 d120 mutant induced apoptosis by a caspase-3-independent pathway inasmuch as caspase 3 was not activated and DNA fragmentation was not blocked by caspase inhibitors even though the virus caused cytochrome c release and depolarization of the inner mitochondrial membrane. (ii) Cells infected with wild-type HSV-1 exhibited none of the manifestations associated with programmed cell death assayed in these studies. (iii) Uninfected cells exposed to osmotic shock succumbed to caspase-dependent apoptosis inasmuch as cytochrome c was released, the inner mitochondrial potential was lost, caspase-3 was activated, and chromosomal DNA was fragmented. (iv) Although caspase-3 was activated in cells infected with wild-type HSV-1 and exposed to sorbitol, cytochrome c outflow, depolarization of the inner mitochondrial membrane, and DNA fragmentation were blocked. We conclude that although d120 induces apoptosis by a caspase-3-independent pathway, the wild-type virus blocks apoptosis induced by this pathway and also blocks the caspase-dependent pathway induced by osmotic shock. The block in the caspase-dependent pathway may occur downstream of caspase-3 activation.     

Higher expression of ferritin protects Chlamydia trachomatis infected HeLa 229 cells from reactive oxygen species mediated cell death

Apoptosis plays an important role in modulating the pathogenesis of a variety of infectious diseases. Chlamydial infection protects cells against different forms of apoptosis: extrinsic, intrinsic, and granzyme B mediated. Redox reactions are central to the life and death decision of cells and pathogens and an intimate relationship exists between oxidative stress and iron metabolism. The link between redox status and ferritin was largely unexplored in chlamydia-infected cells. In the present study, we showed that Chlamydia trachomatis (CT) infection induced FHC protein in HeLa cells. FHC induction by CT-infected cells stably expressing FHC blunted ROS production compared with mock infected cells, and the infected cells were relatively resistant to apoptosis induced by H?O?. We also demonstrated that endogenous FHC overexpression correlates well with the stabilization of the mitochondrial membrane potential in CT-infected cells. Increased expression of FHC is independent of iron supplementation (FAC) and depletion (DFO) in CT-infected cells. These data suggest that FHC up-regulation is an acute response of HeLa cells against CT infection and that FHC exerts anti-apoptotic activity against oxidative stress.     

Critical contribution of RIPK1 mediated mitochondrial dysfunction and oxidative stress to compression-induced rat nucleus pulposus cells necroptosis and apoptosis

The aim of this study was to investigate whether RIPK1 mediated mitochondrial dysfunction and oxidative stress contributed to compression-induced nucleus pulposus (NP) cells necroptosis and apoptosis, together with the interplay relationship between necroptosis and apoptosis in vitro. Rat NP cells underwent various periods of 1.0 MPa compression. To determine whether compression affected mitochondrial function, we evaluated the mitochondrial membrane potential, mitochondrial permeability transition pore (mPTP), mitochondrial ultrastructure and ATP content. Oxidative stress-related indicators reactive oxygen species, superoxide dismutase and malondialdehyde were also assessed. To verify the relevance between oxidative stress and necroptosis together with apoptosis, RIPK1 inhibitor necrostatin-1(Nec-1), mPTP inhibitor cyclosporine A (CsA), antioxidants and small interfering RNA technology were utilized. The results established that compression elicited a time-dependent mitochondrial dysfunction and elevated oxidative stress. Nec-1 and CsA restored mitochondrial function and reduced oxidative stress, which corresponded to decreased necroptosis and apoptosis. CsA down-regulated mitochondrial cyclophilin D expression, but had little effects on RIPK1 expression and pRIPK1 activation. Additionally, we found that Nec-1 largely blocked apoptosis; whereas, the apoptosis inhibitor Z-VAD-FMK increased RIPK1 expression and pRIPK1 activation, and coordinated regulation of necroptosis and apoptosis enabled NP cells survival more efficiently. In contrast to Nec-1, SiRIPK1 exacerbated mitochondrial dysfunction and oxidative stress. In summary, RIPK1-mediated mitochondrial dysfunction and oxidative stress play a crucial role in NP cells necroptosis and apoptosis during compression injury. The synergistic regulation of necroptosis and apoptosis may exert more beneficial effects on NP cells survival, and ultimately delaying or even retarding intervertebral disc degeneration.     

Hepatitis C virus infection induces apoptosis through a Bax-triggered, mitochondrion-mediated, caspase 3-dependent pathway

We previously reported that cells harboring the hepatitis C virus (HCV) RNA replicon as well as those expressing HCV NS3/4A exhibited increased sensitivity to suboptimal doses of apoptotic stimuli to undergo mitochondrion-mediated apoptosis (Y. Nomura-Takigawa, et al., J. Gen. Virol. 87:1935-1945, 2006). Little is known, however, about whether or not HCV infection induces apoptosis of the virus-infected cells. In this study, by using the chimeric J6/JFH1 strain of HCV genotype 2a, we demonstrated that HCV infection induced cell death in Huh7.5 cells. The cell death was associated with activation of caspase 3, nuclear translocation of activated caspase 3, and cleavage of DNA repair enzyme poly(ADP-ribose) polymerase, which is known to be an important substrate for activated caspase 3. These results suggest that HCV-induced cell death is, in fact, apoptosis. Moreover, HCV infection activated Bax, a proapoptotic member of the Bcl-2 family, as revealed by its conformational change and its increased accumulation on mitochondrial membranes. Concomitantly, HCV infection induced disruption of mitochondrial transmembrane potential, followed by mitochondrial swelling and release of cytochrome c from mitochondria. HCV infection also caused oxidative stress via increased production of mitochondrial superoxide. On the other hand, HCV infection did not mediate increased expression of glucose-regulated protein 78 (GRP78) or GRP94, which are known as endoplasmic reticulum (ER) stress-induced proteins; this result suggests that ER stress is not primarily involved in HCV-induced apoptosis in our experimental system. Taken together, our present results suggest that HCV infection induces apoptosis of the host cell through a Bax-triggered, mitochondrion-mediated, caspase 3-dependent pathway(s).     

Chlamydia heat shock protein 60 induces trophoblast apoptosis through TLR4

Intrauterine infection affects placental development and function, and subsequently may lead to complications such as preterm delivery, intrauterine growth retardation, and preeclampsia; however, the molecular mechanisms are not clearly known. TLRs mediate innate immune responses in placenta, and recently, TLR2-induced trophoblast apoptosis has been suggested to play a role in infection-induced preterm delivery. Chlamydia trachomatis is the etiological agent of the most prevalent sexually transmitted bacterial infection in the United States. In this study, we show that in vitro chlamydial heat shock protein 60 induces apoptosis in primary human trophoblasts, placental fibroblasts, and the JEG3 trophoblast cell line, and that TLR4 mediates this event. We observed a host cell type-dependent apoptotic response. In primary placental fibroblasts, chlamydial heat shock protein 60-induced apoptosis was caspase dependent, whereas in JEG3 trophoblast cell lines it was caspase independent. These data suggest that TLR4 stimulation induces apoptosis in placenta, and this could provide a novel mechanism of pathogenesis for poor fertility and pregnancy outcome in women with persistent chlamydia infection.     

Astaxanthin inhibits apoptosis in alveolar epithelial cells type II in vivo and in vitro through the ROS‐dependent mitochondrial signalling pathway

Oxidative stress is an important molecular mechanism underlying lung fibrosis. The mitochondrion is a major organelle for oxidative stress in cells. Therefore, blocking the mitochondrial signalling pathway may be the best therapeutic manoeuver to ameliorate lung fibrosis. Astaxanthin (AST) is an excellent antioxidant, but no study has addressed the pathway of AST against pulmonary oxidative stress and free radicals by the mitochondrion‐mediated signalling pathway. In this study, we investigated the antioxidative effects of AST against H₂O₂‐ or bleomycin (BLM)‐induced mitochondrial dysfunction and reactive oxygen species (ROS) production in alveolar epithelial cells type II (AECs‐II) in vivo and in vitro. Our data show that AST blocks H₂O₂‐ or BLM‐induced ROS generation and dose‐dependent apoptosis in AECs‐II, as characterized by changes in cell and mitochondria morphology, translocation of apoptotic proteins, inhibition of cytochrome c (Cyt c) release, and the activation of caspase‐9, caspase‐3, Nrf‐2 and other cytoprotective genes. These data suggest that AST inhibits apoptosis in AECs‐II cells through the ROS‐dependent mitochondrial signalling pathway and may be of potential therapeutic value in lung fibrosis treatment.     

铁蛋白介导细胞凋亡的作用机制

铁蛋白是生物体广泛存在且高度保守的可溶性蛋白质,在铁离子稳态维持、胚胎发育调控、细胞增殖以及细胞凋亡等过程中具有重要作用。过量的铁离子能通过芬顿反应产生活性氧,过量的活性氧会造成氧化应激并直接损害DNA、脂质和蛋白质,最终导致细胞凋亡。铁蛋白能够螯合铁离子,进而保护细胞免受氧化应激诱导的细胞凋亡。铁蛋白表达受阻时,细胞内不稳定铁水平升高并诱导氧化应激,最终造成细胞凋亡。同时,氧化应激可在转录和翻译水平调节铁蛋白表达,升高的铁蛋白则参与维持机体氧化还原水平的稳定。本文主要从线粒体途径和死亡受体途径阐明铁蛋白介导细胞凋亡的分子机制,为深入研究铁蛋白功能以及相关疾病治疗提供理论支持。     

Induction of apoptosis by Legionella pneumophila in mammalian cells requires the mitochondrial pathway for caspase activation

Legionella pneumophila, the agent of human Legionnaire's disease is a Gram-negative, rod-shaped bacterium. During infection, the bacteria invade human cells and replicate intracellularly. L. pneumophila can induce apoptosis in human myeloid and epitheloid cells and this may contribute to the development of pathology and disease. However, the molecular mechanism of apoptosis induction is still uncertain. Here we investigate this process. Legionella efficiently induced apoptosis in myeloid cells, T cells and fibroblasts. Induction of apoptosis involved activation of the initiator caspase-9 and effector caspases. Caspase activity was required for cell death. Analysis of mutant cells showed that the death receptor pathway was not involved in Legionella-induced apoptosis. Surprisingly, caspase activity was found almost exclusively in cells that did not harbor bacteria. Infection with Legionella caused the activation of the pro-apoptotic protein Bax and the release of cytochrome c. Mouse embryonic fibroblasts deficient for Bax and/or Bak were protected from Legionella-induced caspase activation. These results show a clear contribution of the mitochondrial pathway to Legionella-induced apoptosis.     

Pregnancy outcome and placenta pathology in Plasmodium berghei ANKA infected mice reproduce the pathogenesis of severe malaria in pregnant women

Pregnancy-associated malaria (PAM) is expressed in a range of clinical complications that include increased disease severity in pregnant women, decreased fetal viability, intra-uterine growth retardation, low birth weight and infant mortality. The physiopathology of malaria in pregnancy is difficult to scrutinize and attempts were made in the past to use animal models for pregnancy malaria studies. Here, we describe a comprehensive mouse experimental model that recapitulates many of the pathological and clinical features typical of human severe malaria in pregnancy. We used P. berghei ANKA-GFP infection during pregnancy to evoke a prominent inflammatory response in the placenta that entails CD11b mononuclear infiltration, up-regulation of MIP-1 alpha chemokine and is associated with marked reduction of placental vascular spaces. Placenta pathology was associated with decreased fetal viability, intra-uterine growth retardation, gross post-natal growth impairment and increased disease severity in pregnant females. Moreover, we provide evidence that CSA and HA, known to mediate P. falciparum adhesion to human placenta, are also involved in mouse placental malaria infection. We propose that reduction of maternal blood flow in the placenta is a key pathogenic factor in murine pregnancy malaria and we hypothesize that exacerbated innate inflammatory responses to Plasmodium infected red blood cells trigger severe placenta pathology. This experimental model provides an opportunity to identify cell and molecular components of severe PAM pathogenesis and to investigate the inflammatory response that leads to the observed fetal and placental blood circulation abnormalities.