scholarly journals Coxiella burnetii Inhibits Apoptosis in Human THP-1 Cells and Monkey Primary Alveolar Macrophages

2007 ◽  
Vol 75 (9) ◽  
pp. 4263-4271 ◽  
Author(s):  
Daniel E. Voth ◽  
Dale Howe ◽  
Robert A. Heinzen
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Coxiella Burnetii ◽  
Alveolar Macrophages ◽  
Q Fever ◽  
Apoptotic Cell ◽  
Parp Cleavage ◽  
Potent Inducer ◽  
Infected Cells ◽  
Infectious Cycle

ABSTRACT Coxiella burnetii, the cause of human Q fever, is an aerosol-borne, obligate intracellular bacterium that targets host alveolar mononuclear phagocytic cells during infection. In all cell types examined, C. burnetii establishes a replicative niche in a lysosome-like parasitophorous vacuole where it carries out a lengthy infectious cycle with minimal cytopathic effects. The persistent and mild nature of C. burnetii infection in vitro suggests that the pathogen modulates apoptosis to sustain the host cell. In the current study, we examined the ability of C. burnetii to inhibit apoptotic cell death during infection of human THP-1 monocyte-derived macrophages and primary monkey alveolar macrophages. C. burnetii-infected cells demonstrated significant protection from death relative to uninfected cells following treatment with staurosporine, a potent inducer of intrinsic apoptosis. This protection correlated with reduced cleavage of caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP), all proteolytic events that occur during apoptosis. Reduced PARP cleavage was also observed in cells treated with tumor necrosis factor alpha to induce extrinsic apoptosis. Apoptosis inhibition was a C. burnetii-driven process as infected cells treated with rifampin or chloramphenicol, inhibitors of bacterial RNA and protein synthesis, respectively, showed significantly reduced protection against staurosporine-induced apoptosis. C. burnetii infection affected the expression of multiple apoptosis-related genes and resulted in increased synthesis of the antiapoptotic proteins A1/Bfl-1 and c-IAP2. Collectively, these data suggest that C. burnetii modulates apoptotic pathways to inhibit host cell death, thus providing a stable, intracellular niche for the course of the pathogen's infectious cycle.

scholarly journals Coxiella burnetii Inhibits Activation of Host Cell Apoptosis through a Mechanism That Involves Preventing Cytochrome c Release from Mitochondria

2007 ◽  
Vol 75 (11) ◽  
pp. 5282-5289 ◽  
Author(s):  
Anja Lührmann ◽  
Craig R. Roy
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Coxiella Burnetii ◽  
Mammalian Cells ◽  
Q Fever ◽  
Host Cells ◽  
Intracellular Pathogen ◽  
Obligate Intracellular ◽  
Cell Death Pathway ◽  
Obligate Intracellular Pathogen

ABSTRACT Coxiella burnetii is an obligate intracellular pathogen and the etiological agent of the human disease Q fever. C. burnetii infects mammalian cells and then remodels the membrane-bound compartment in which it resides into a unique lysosome-derived organelle that supports bacterial multiplication. To gain insight into the mechanisms by which C. burnetii is able to multiply intracellularly, we examined the ability of host cells to respond to signals that normally induce apoptosis. Our data show that mammalian cells infected with C. burnetii are resistant to apoptosis induced by staurosporine and UV light. C. burnetii infection prevented caspase 3/7 activation and limited fragmentation of the host cell nucleus in response to agonists that induce apoptosis. Inhibition of bacterial protein synthesis reduced the antiapoptotic effect that C. burnetii exerted on infected host cells. Inhibition of apoptosis in C. burnetii-infected cells did not correlate with the degradation of proapoptotic BH3-only proteins involved in activation of the intrinsic cell death pathway; however, cytochrome c release from mitochondria was diminished in cells infected with C. burnetii upon induction of apoptosis. These data indicate that C. burnetii can interfere with the intrinsic cell death pathway during infection by producing proteins that either directly or indirectly prevent release of cytochrome c from mitochondria. It is likely that inhibition of apoptosis by C. burnetii represents an important virulence property that allows this obligate intracellular pathogen to maintain host cell viability despite inducing stress that would normally activate the intrinsic death pathway.

scholarly journals Chinese Giant Salamander (Andrias davidianus) Iridovirus Infection Leads to Apoptotic Cell Death through Mitochondrial Damage, Caspases Activation, and Expression of Apoptotic-Related Genes

2019 ◽  
Vol 20 (24) ◽  
pp. 6149 ◽  
Author(s):  
Yiqun Li ◽  
Nan Jiang ◽  
Yuding Fan ◽  
Yong Zhou ◽  
Wenzhi Liu ◽  
...  
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Mitochondrial Damage ◽  
Apoptotic Cell Death ◽  
Economic Losses ◽  
P53 Expression ◽  
Andrias Davidianus ◽  
Chinese Giant Salamander ◽  
Infected Cells ◽  
Apoptotic Genes

Chinese giant salamander iridovirus (GSIV) is the causative pathogen of Chinese giant salamander (Andrias davidianus) iridovirosis, leading to severe infectious disease and huge economic losses. However, the infection mechanism by GSIV is far from clear. In this study, a Chinese giant salamander muscle (GSM) cell line is used to investigate the mechanism of cell death during GSIV infection. Microscopy observation and DNA ladder analysis revealed that DNA fragmentation happens during GSIV infection. Flow cytometry analysis showed that apoptotic cells in GSIV-infected cells were significantly higher than that in control cells. Caspase 8, 9, and 3 were activated in GSIV-infected cells compared with the uninfected cells. Consistently, mitochondria membrane potential (MMP) was significantly reduced, and cytochrome c was released into cytosol during GSIV infection. p53 expression increased at an early stage of GSIV infection and then slightly decreased late in infection. Furthermore, mRNA expression levels of pro-apoptotic genes participating in the extrinsic and intrinsic pathway were significantly up-regulated during GSIV infection, while those of anti-apoptotic genes were restrained in early infection and then rose in late infection. These results collectively indicate that GSIV induces GSM apoptotic cell death involving mitochondrial damage, caspases activation, p53 expression, and pro-apoptotic molecules up-regulation.

scholarly journals Coxiella burnetii Alters Cyclic AMP-Dependent Protein Kinase Signaling during Growth in Macrophages

2012 ◽  
Vol 80 (6) ◽  
pp. 1980-1986 ◽  
Author(s):  
Laura J. MacDonald ◽  
Richard C. Kurten ◽  
Daniel E. Voth
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Coxiella Burnetii ◽  
Alveolar Macrophages ◽  
Q Fever ◽  
Parasitophorous Vacuole ◽  
Dependent Protein Kinase ◽  
Content Type ◽  
Bacterial Agent ◽  
Dependent Protein

ABSTRACTCoxiella burnetiiis the bacterial agent of human Q fever, an acute, flu-like illness that can present as chronic endocarditis in immunocompromised individuals. Following aerosol-mediated transmission,C. burnetiireplicates in alveolar macrophages in a unique phagolysosome-like parasitophorous vacuole (PV) required for survival. The mechanisms ofC. burnetiiintracellular survival are poorly defined and a recent Q fever outbreak in the Netherlands emphasizes the need for better understanding this unique host-pathogen interaction. We recently demonstrated that inhibition of host cyclic AMP-dependent protein kinase (PKA) activity negatively impacts PV formation. In the current study, we confirmed PKA involvement in PV biogenesis and probed the role of PKA signaling duringC. burnetiiinfection of macrophages. Using PKA-specific inhibitors, we found the kinase was needed for biogenesis of prototypical PV andC. burnetiireplication. PKA and downstream targets were differentially phosphorylated throughout infection, suggesting prolonged regulation of the pathway. Importantly, the pathogen actively triggered PKA activation, which was also required for PV formation by virulentC. burnetiiisolates during infection of primary human alveolar macrophages. A subset of PKA-specific substrates were differentially phosphorylated duringC. burnetiiinfection, suggesting the pathogen uses PKA signaling to control distinct host cell responses. Collectively, the current results suggest a versatile role for PKA inC. burnetiiinfection and indicate virulent organisms usurp host kinase cascades for efficient intracellular growth.

Reactive oxygen species and caspase activation mediate silica-induced apoptosis in alveolar macrophages

2001 ◽  
Vol 280 (1) ◽  
pp. L10-L17 ◽  
Author(s):  
Han-Ming Shen ◽  
Zhuo Zhang ◽  
Qi-Feng Zhang ◽  
Choon-Nam Ong
Keyword(s):  
Reactive Oxygen Species ◽  
Cell Death ◽  
Alveolar Macrophages ◽  
Caspase 3 ◽  
Reactive Oxygen ◽  
Parp Cleavage ◽  
Oxygen Species ◽  
Caspase Activation ◽  
Caspase 9 ◽  
Induced Apoptosis

Alveolar macrophages (AMs) are the principal target cells of silica and occupy a key position in the pathogenesis of silica-related diseases. Silica has been found to induce apoptosis in AMs, whereas its underlying mechanisms involving the initiation and execution of apoptosis are largely unknown. The main objective of the present study was to examine the form of cell death caused by silica and the mechanisms involved. Silica-induced apoptosis in AMs was evaluated by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling assay and cell cycle/DNA content analysis. The elevated level of reactive oxygen species (ROS), caspase-9 and caspase-3 activation, and poly(ADP-ribose) polymerase (PARP) cleavage in silica-treated AMs were also determined. The results showed that there was a temporal pattern of apoptotic events in silica-treated AMs, starting with ROS formation and followed by caspase-9 and caspase-3 activation, PARP cleavage, and DNA fragmentation. Silica-induced apoptosis was significantly attenuated by a caspase-3 inhibitor, N-acetyl-Asp-Glu-Val-Asp aldehyde, and ebselen, a potent antioxidant. These findings suggest that apoptosis is an important form of cell death caused by silica exposure in which the elevated ROS level that results from silica exposure may act as an initiator, leading to caspase activation and PARP cleavage to execute the apoptotic process.

scholarly journals Cell Entry-Independent Role for the Reovirus μ1 Protein in Regulating Necroptosis and the Accumulation of Viral Gene Products

2019 ◽  
Vol 93 (11) ◽  
Author(s):  
Katherine E. Roebke ◽  
Pranav Danthi
Keyword(s):  
Cell Death ◽  
Capsid Protein ◽  
Apoptotic Cell ◽  
Guanidine Hydrochloride ◽  
Viral Gene ◽  
Gene Products ◽  
Minus Strand ◽  
Outer Capsid Protein ◽  
Infected Cells ◽  
Outer Capsid

ABSTRACTThe reovirus outer capsid protein μ1 regulates cell death in infected cells. To distinguish between the roles of incoming, capsid-associated, and newly synthesized μ1, we used small interfering RNA (siRNA)-mediated knockdown. Loss of newly synthesized μ1 protein does not affect apoptotic cell death in HeLa cells but enhances necroptosis in L929 cells. Knockdown of μ1 also affects aspects of viral replication. We found that, while μ1 knockdown results in diminished release of infectious viral progeny from infected cells, viral minus-strand RNA, plus-strand RNA, and proteins that are not targeted by the μ1 siRNA accumulate to a greater extent than in control siRNA-treated cells. Furthermore, we observed a decrease in sensitivity of these viral products to inhibition by guanidine hydrochloride (GuHCl) (which targets minus-strand synthesis to produce double-stranded RNA) when μ1 is knocked down. Following μ1 knockdown, cell death is also less sensitive to treatment with GuHCl. Our studies suggest that the absence of μ1 allows enhanced transcriptional activity of newly synthesized cores and the consequent accumulation of viral gene products. We speculate that enhanced accumulation and detection of these gene products due to μ1 knockdown potentiates receptor-interacting protein 3 (RIP3)-dependent cell death.IMPORTANCEWe used mammalian reovirus as a model to study how virus infections result in cell death. Here, we sought to determine how viral factors regulate cell death. Our work highlights a previously unknown role for the reovirus outer capsid protein μ1 in limiting the induction of a necrotic form of cell death called necroptosis. Induction of cell death by necroptosis requires the detection of viral gene products late in infection; μ1 limits cell death by this mechanism because it prevents excessive accumulation of viral gene products that trigger cell death.

scholarly journals Activation and Antagonism of the OAS–RNase L Pathway

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 14
Author(s):  
Susan R. Weiss
Keyword(s):  
Cell Death ◽  
Antiviral Activity ◽  
Apoptotic Cell ◽  
Early Response ◽  
Apoptotic Cell Death ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Viral Genomes ◽  
L System ◽  
Infected Cells

The oligoadenylate synthetase–ribonuclease L (OAS–RNase L) system is a potent antiviral pathway that severely limits the pathogenesis of many viruses. Upon sensing dsRNA, OASs produce 2′,5′-oligoadenylates (2-5A) that activate RNase L to cleave both host and viral single-stranded RNA, thereby limiting protein production, virus replication and spread, leading to apoptotic cell death. Endogenous host dsRNA, which accumulates in the absence of adenosine deaminase acting on RNA (ADAR)1, can also activate RNase L and lead to apoptotic cell death. RNase L activation and antiviral activity during infections with several types of viruses in human and bat cells is dependent on OAS3 but independent of virus-induced interferon (IFN) and, thus, RNase L can be activated even in the presence of IFN antagonists. Differently from other human viruses examined, Zika virus is resistant to the antiviral activity of RNase L and instead utilizes RNase L to enhance its replication factories to produce more infectious virus. Some betacoronaviruses antagonize RNase L activation by expressing 2′,5′-phosphodiesterases (PDEs) that cleave 2-5A and thereby antagonize activation of RNase L. The best characterized of these PDEs is the murine coronavirus (MHV) NS2 accessory protein. Enzymatically active NS2 is required for replication in myeloid cells and in the liver. Interestingly, while wild type mice clear MHV from the liver by 7–10 days post-infection, RNase L knockout mice fail to effectively clear MHV, probably due to diminished apoptotic death of infected cells. We suggest that RNase L antiviral activity stems from direct cleavage of viral genomes and cessation of protein synthesis as well as through promoting death of infected cells, limiting the spread of virus. Importantly, OASs are pattern recognition receptors and the OAS–RNase L pathway is a primary innate response pathway to viruses, capable of early response, coming into play before IFN is induced or when the virus shuts down IFN signaling.

scholarly journals Coxiella burnetii Expresses a Functional Δ24 Sterol Reductase

2010 ◽  
Vol 192 (23) ◽  
pp. 6154-6159 ◽  
Author(s):  
Stacey D. Gilk ◽  
Paul A. Beare ◽  
Robert A. Heinzen
Keyword(s):  
Host Cell ◽  
Coxiella Burnetii ◽  
Fluorescent Protein ◽  
De Novo ◽  
Cholesterol Metabolism ◽  
Q Fever ◽  
Parasitophorous Vacuole ◽  
Cholesterol Biosynthesis ◽  
Brefeldin A ◽  
Ergosterol Biosynthesis

ABSTRACT Coxiella burnetii, the etiological agent of human Q fever, occupies a unique niche inside the host cell, where it replicates in a modified acidic phagolysosome or parasitophorous vacuole (PV). The PV membrane is cholesterol-rich, and inhibition of host cholesterol metabolism negatively impacts PV biogenesis and pathogen replication. The precise source(s) of PV membrane cholesterol is unknown, as is whether the bacterium actively diverts and/or modifies host cell cholesterol or sterol precursors. C. burnetii lacks enzymes for de novo cholesterol biosynthesis; however, the organism encodes a eukaryote-like Δ24 sterol reductase homolog, CBU1206. Absent in other prokaryotes, this enzyme is predicted to reduce sterol double bonds at carbon 24 in the final step of cholesterol or ergosterol biosynthesis. In the present study, we examined the functional activity of CBU1206. Amino acid alignments revealed the greatest sequence identity (51.7%) with a Δ24 sterol reductase from the soil amoeba Naegleria gruberi. CBU1206 activity was examined by expressing the protein in a Saccharomyces cerevisiae erg4 mutant under the control of a galactose-inducible promoter. Erg4 is a yeast Δ24 sterol reductase responsible for the final reduction step in ergosterol synthesis. Like Erg4-green fluorescent protein (GFP), a CBU1206-GFP fusion protein localized to the yeast endoplasmic reticulum. Heterologous expression of CBU1206 rescued S. cerevisiae erg4 sensitivity to growth in the presence of brefeldin A and cycloheximide and resulted in new synthesis of ergosterol. These data indicate CBU1206 is an active sterol reductase and suggest the enzyme may act on host sterols during C. burnetii intracellular growth.

scholarly journals Ginkgo biloba Prevents Oxidative Stress-Induced Apoptosis Blocking p53 Activation in Neuroblastoma Cells

Antioxidants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 279 ◽  
Author(s):  
Francesco Di Meo ◽  
Rossana Cuciniello ◽  
Sabrina Margarucci ◽  
Paolo Bergamo ◽  
Orsolina Petillo ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Neurodegenerative Diseases ◽  
Ginkgo Biloba ◽  
Apoptotic Cell ◽  
Neuroblastoma Cells ◽  
Apoptotic Cell Death ◽  
Parp Cleavage ◽  
Egb 761 ◽  
Induced Apoptosis

Oxidative stress has been associated to neuronal cell loss in neurodegenerative diseases. Neurons are post-mitotic cells that are very sensitive to oxidative stress—especially considering their limited capacity to be replaced. Therefore, reduction of oxidative stress, and inhibiting apoptosis, will potentially prevent neurodegeneration. In this study, we investigated the neuroprotective effect of Ginkgo biloba extract (EGb 761) against H2O2 induced apoptosis in SK-N-BE neuroblastoma cells. We analysed the molecular signalling pathway involved in the apoptotic cell death. H2O2 induced an increased acetylation of p53 lysine 382, a reduction in mitochondrial membrane potential, an increased BAX/Bcl-2 ratio and consequently increased Poly (ADP-ribose) polymerase (PARP) cleavage. All these effects were blocked by EGb 761 treatment. Thus, EGb 761, acting as intracellular antioxidant, protects neuroblastoma cells against activation of p53 mediated pathway and intrinsic mitochondrial apoptosis. Our results suggest that EGb 761, protecting against oxidative-stress induced apoptotic cell death, could potentially be used as nutraceutical for the prevention and treatment of neurodegenerative diseases.

scholarly journals Sustained Activation of Akt and Erk1/2 Is Required for Coxiella burnetii Antiapoptotic Activity

2008 ◽  
Vol 77 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Daniel E. Voth ◽  
Robert A. Heinzen
Keyword(s):  
Host Cell ◽  
Coxiella Burnetii ◽  
Stress Responses ◽  
Mammalian Cells ◽  
Apoptotic Cell ◽  
Parasitophorous Vacuole ◽  
Critical Role ◽  
Bacterial Pathogen ◽  
Human Macrophage ◽  
Antiapoptotic Activity

ABSTRACT Coxiella burnetii is an obligate intracellular bacterial pathogen that directs biogenesis of a lysosome-like, parasitophorous vacuole in mammalian cells. We recently reported that C. burnetii inhibits apoptotic cell death in macrophages, presumably as a mechanism to sustain the host for completion of its lengthy infectious cycle. In the current study, we further investigated C. burnetii manipulation of host cell signaling and apoptosis by examining the effect of C. burnetii infection on activation of 15 host proteins involved in stress responses, cytokine production, and apoptosis. C. burnetii infection of THP-1 human macrophage-like cells caused increased levels of phosphorylated c-Jun, Hsp27, Jun N-terminal protein kinase, and p38 at 2 h postinfection (hpi), and this activation rapidly decreased to near basal levels by 24 hpi. The prosurvival kinases Akt and Erk1/2 (extracellular signal-regulated kinases 1 and 2) were also activated at 2 to 6 hpi; however, the phosphorylation of these proteins increased coincident with C. burnetii replication through at least 72 hpi. Sustained phosphorylation of Akt and Erk1/2 was abolished by treatment of infected cells with rifampin, indicating their activation is a C. burnetii-directed event requiring pathogen RNA synthesis. Moreover, pharmacological inhibition of Akt or Erk1/2 significantly decreased C. burnetii antiapoptotic activity. Collectively, these results indicate the importance of C. burnetii modulation of host signaling and demonstrate a critical role for Akt and Erk1/2 in successful intracellular parasitism and maintenance of host cell viability.

scholarly journals Coxiella burnetiiblocks intracellular IL-17 signaling in macrophages

2018 ◽  
Author(s):  
Tatiana M. Clemente ◽  
Minal Mulye ◽  
Anna V. Justis ◽  
Srinivas Nallandhighal ◽  
Tuan M. Tran ◽  
...  
Keyword(s):  
Host Cell ◽  
Q Fever ◽  
Protective Role ◽  
Effector Proteins ◽  
Antimicrobial Protein ◽  
Dependent Manner ◽  
Cell Infection ◽  
Protein Levels ◽  
Host Cytoplasm ◽  
Infected Cells

AbstractCoxiella burnetiiis an obligate intracellular bacterium and the etiological agent of Q fever. Successful host cell infection requires theCoxiellaType IVB Secretion System (T4BSS), which translocates bacterial effector proteins across the vacuole membrane into the host cytoplasm, where they manipulate a variety of cell processes. To identify host cell targets ofCoxiellaT4BSS effector proteins, we determined the transcriptome of murine alveolar macrophages infected with aCoxiellaT4BSS effector mutant. We identified a set of inflammatory genes that are significantly upregulated in T4BSS mutant-infected cells compared to mock-infected cells or cells infected with wild type (WT) bacteria, suggestingCoxiellaT4BSS effector proteins downregulate expression of these genes. In addition, the IL-17 signaling pathway was identified as one of the top pathways affected by the bacteria. While previous studies demonstrated that IL-17 plays a protective role against several pathogens, the role of IL-17 duringCoxiellainfection is unknown. We found that IL-17 kills intracellularCoxiellain a dose-dependent manner, with the T4BSS mutant exhibiting significantly more sensitivity to IL-17 than WT bacteria. In addition, quantitative PCR confirmed increased expression of IL-17 downstream signaling genes in T4BSS mutant-infected cells compared to WT or mock-infected cells, including the pro-inflammatory cytokinesI11a, Il1bandTnfa, the chemokinesCxcl2andCcl5, and the antimicrobial proteinLcn2. We further confirmed that theCoxiellaT4BSS downregulates macrophage CXCL2/MIP-2 and CCL5/RANTES protein levels following IL-17 stimulation. Together, these data suggest thatCoxielladownregulates IL-17 signaling in a T4BSS-dependent manner in order to escape the macrophage immune response.

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