Mechanisms of Methicillin-Resistant Staphylococcus aureus Pneumonia–Induced Intestinal Epithelial Apoptosis (original) (raw)
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JAMA, 2002
Context Increased intestinal epithelial apoptosis is present in both human autopsy studies and animal models of sepsis. Whether altering gut apoptosis decreases mortality in sepsis induced by pathogenic bacteria outside the gut is unknown. Objective To determine if decreasing levels of intestinal cell death improves survival in a murine model of Pseudomonas aeruginosa pneumonia-induced sepsis. Design and Materials Prospective study in which transgenic mice that overexpress the antiapoptotic protein Bcl-2 in their intestinal epithelium (n=25) and control littermates (n=26) were subjected to intratracheal injection of P aeruginosa. Main Outcome Measures Survival at 7 postoperative days, compared between the 2 groups. Secondary outcomes included quantification of gut epithelial apoptosis. Results Survival in transgenic mice that overexpress Bcl-2 in the intestinal epithelium was 40% (10/25) compared with 4% (1/26) in control littermates 7 days after intratracheal injection of P aeruginosa (P=.001), with differences in survival noted within 24 hours of surgery. Overexpression of Bcl-2 was associated with a decrease in gut epithelial apoptosis demonstrated by active caspase 3 staining, the terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling assay, and hematoxylin-eosin staining. Conclusions In this murine model, inhibiting gut epithelial apoptosis by overexpression of Bcl-2 was associated with a survival advantage in P aeruginosa pneumoniainduced sepsis. These results suggest that intestinal epithelial apoptosis may play a role in sepsis-related mortality.
Role of Apoptosis in Microbial Infection
Open Journal of Apoptosis, 2014
Apoptosis plays a central role in the pathogenesis of a number of human diseases. Because apoptosis represents a fundamental process in the response to such infections, it may represent a therapeutic target for their treatment. There is thus likely to be future clinical relevance in harnessing our growing knowledge both of apoptotic mechanisms, and their regulation, in the search to achieve modalities for therapeutic benefit. This brief review aims to summarize what we currently know about the role of apoptosis in response to a range of microbial infections (including bacterial and viral).
Pseudomonas aeruginosa-Induced Apoptosis Involves Mitochondria and Stress-Activated Protein Kinases
Infection and Immunity, 2001
ABSTRACTPseudomonas aeruginosa, a gram-negative facultative pathogen, causes severe infections in immunocompromised and cystic fibrosis patients. However, the molecular details of the interaction betweenP. aeruginosaand mammalian cells are still largely unknown. Here we demonstrate that infection of human conjunctiva epithelial Chang cells with the well-characterizedP. aeruginosastrain PAO-I results in rapid induction of apoptosis. Apoptosis was mediated by mitochondrial alterations, in particular mitochondrial depolarization, synthesis of reactive oxygen intermediates, and release of cytochromec, as well as an activation of Jun N-terminal kinases (JNK). Stimulation of these events was dependent on upregulation of CD95 on infected cells, and a deficiency of CD95 or the CD95 ligand prevented mitochondrial changes, JNK activation, and apoptosis upon infection. Further, efficient apoptosis of Chang epithelial cells required infection with liveP. aeruginosa, adhesion but not invasion of...
Infection and Immunity, 2004
Human peripheral blood monocytes become apoptotic following phagocytosis and killing of Staphylococcus aureus. Although this type of monocyte apoptosis is known to be initiated by Fas-Fas ligand (FasL) interactions, the downstream signaling pathway has not been determined. In this work the involvement of mitochondria and the kinetics of caspase-8 and caspase-3 activation after phagocytosis of S. aureus were studied. Caspase-8 activity was measured in cell lysates by using the fluorogenic substrate Ac-IETD-AFC. Active caspase-3 levels and mitochondrial membrane potential (⌬ m ) were measured in whole cells by flow cytometry using monoclonal antibodies reacting with activated caspase-3 and chloromethyl-X-rosamine, respectively. The results show that caspase-8 was activated shortly after phagocytosis of bacteria. Caspase-8 activation was followed by progressive disruption of ⌬ m , which is associated with the production of reactive oxygen intermediates. The irreversible caspase-8 inhibitor zIETD-FMK prevented the disruption of ⌬ m and the release of cytochrome c from S. aureus-exposed monocytes. Caspase-3 activation occurred following disruption of ⌬ m . These results strongly suggest that apoptosis of monocytes that have phagocytosed and killed S. aureus is driven by the Fas-FasL-initiated pathway, which is typical for type II cells.
American Journal of Respiratory and Critical Care Medicine, 2014
Rationale: The death receptor Fas is critical for bacterial clearance and survival of mice after Pseudomonas aeruginosa infection. Objectives: Fas ligand (FasL)-induced apoptosis is augmented by S-glutathionylation of Fas (Fas-SSG), which can be reversed by glutaredoxin-1 (Grx1). Therefore, the objective of this study was to investigate the interplay between Grx1 and Fas in regulating the clearance of P. aeruginosa infection. Methods: Lung samples from patients with bronchopneumonia were analyzed by immunofluorescence. Primary tracheal epithelial cells, mice lacking the gene for Grx1 (Glrx1 2/2), Glrx1 2/2 mice treated with caspase inhibitor, or transgenic mice overexpressing Grx1 in the airway epithelium were analyzed after infection with P. aeruginosa. Measurements and Main Results: Patient lung samples positive for P. aeruginosa infection demonstrated increased Fas-SSG compared with normal lung samples. Compared with wild-type primary lung epithelial cells, infection of Glrx1 2/2 cells with P. aeruginosa showed enhanced caspase 8 and 3 activities and cell death in association with increases in Fas-SSG. Infection of Glrx1 2/2 mice with P. aeruginosa resulted in enhanced caspase activity and increased Fas-SSG as compared with wild-type littermates. Absence of Glrx1 significantly enhanced bacterial clearance, and decreased mortality postinfection with P. aeruginosa. Inhibition of caspases significantly decreased bacterial clearance postinfection with P. aeruginosa, in association with decreased Fas-SSG. In contrast, transgenic mice that overexpress Grx1 in lung epithelial cells had significantly higher lung bacterial loads, enhanced mortality, decreased caspase activation, and Fas-SSG in the lung after infection with P. aeruginosa, compared with wild-type control animals. Conclusions: These results suggest that S-glutathionylation of Fas within the lung epithelium enhances epithelial apoptosis and promotes clearance of P. aeruginosa and that glutaredoxin-1 impairs bacterial clearance and increases the severity of pneumonia in association with deglutathionylation of Fas.
The role and regulation of apoptosis in sepsis
Journal of Endotoxin Research, 2005
Today, sepsis continues to be a growing problem in the critically ill patient population. A number of laboratories have been interested in understanding how changes in immune cell apoptosis during sepsis appear to contribute to septic morbidity. Consistently, it has been found that immune cell apoptosis is altered in a variety of tissue sites and cell populations both in experimental animals and humans. While divergent mediators, such as steroids and TNF, contribute to some of these apoptotic changes, their effects are tissue and cell population selective. Inhibition of FasL-Fas signaling (by either FasL gene deficiency, in vivo gene silencing [siRNA] or with FasL binding protein) protects septic mice from the onset of marked apoptosis and the morbidity/mortality seen in sepsis. Further, this extrinsic apoptosis response appears to utilize aspects of the Bid-induced mitochondrial pathway. This is in keeping with the findings that pan-specific caspase inhibition or the overexpression of Bcl-2 also protect these animals from the sequellae of sepsis.
A non‐death function of the mitochondrial apoptosis apparatus in immunity
The EMBO Journal, 2019
Apoptosis is a frequent form of programmed cell death, but the apoptotic signaling pathway can also be engaged at a low level, in the absence of cell death. We here report that such sub-lethal engagement of mitochondrial apoptosis signaling causes the secretion of cytokines from human epithelial cells in a process controlled by the Bcl-2 family of proteins. We further show that sub-lethal signaling of the mitochondrial apoptosis pathway is initiated by infections with all tested viral, bacterial, and protozoan pathogens and causes damage to the genomic DNA. Epithelial cells infected with these pathogens secreted cytokines, and this cytokine secretion upon microbial infection was substantially reduced if mitochondrial sub-lethal apoptosis signaling was blocked. In the absence of mitochondrial pro-apoptotic signaling, the ability of epithelial cells to restrict intracellular bacterial growth was impaired. Triggering of the mitochondrial apoptosis apparatus thus not only causes apoptosis but also has an independent role in immune defense.
Pore-Forming Toxins Induce Macrophage Necroptosis during Acute Bacterial Pneumonia
PLOS Pathogens, 2015
Necroptosis is a highly pro-inflammatory mode of cell death regulated by RIP (or RIPK)1 and RIP3 kinases and mediated by the effector MLKL. We report that diverse bacterial pathogens that produce a pore-forming toxin (PFT) induce necroptosis of macrophages and this can be blocked for protection against Serratia marcescens hemorrhagic pneumonia. Following challenge with S. marcescens, Staphylococcus aureus, Streptococcus pneumoniae, Listeria monocytogenes, uropathogenic Escherichia coli (UPEC), and purified recombinant pneumolysin, macrophages pretreated with inhibitors of RIP1, RIP3, and MLKL were protected against death. Alveolar macrophages in MLKL KO mice were also protected during S. marcescens pneumonia. Inhibition of caspases had no impact on macrophage death and caspase-1 and-3/7 were determined to be inactive following challenge despite the detection of IL-1β in supernatants. Bone marrow-derived macrophages from RIP3 KO, but not caspase-1/11 KO or caspase-3 KO mice, were resistant to PFT-induced death. We explored the mechanisms for PFT-induced necroptosis and determined that loss of ion homeostasis at the plasma membrane, mitochondrial damage, ATP depletion, and the generation of reactive oxygen species were together responsible. Treatment of mice with necrostatin-5, an inhibitor of RIP1; GW806742X, an inhibitor of MLKL; and necrostatin-5 along with co-enzyme Q 10 (N5/C 10) , which enhances ATP production; reduced the severity of S. marcescens pneumonia in a mouse intratracheal challenge model. N5/C 10 protected alveolar macrophages, reduced bacterial burden, and lessened hemorrhage in the lungs. We conclude that necroptosis is the major cell death pathway evoked by PFTs in macrophages and the necroptosis pathway can be targeted for disease intervention.
PLoS pathogens, 2009
During acute bacterial infections such as meningitis, neutrophils enter the tissue where they combat the infection before they undergo apoptosis and are taken up by macrophages. Neutrophils show pro-inflammatory activity and may contribute to tissue damage. In pneumococcal meningitis, neuronal damage despite adequate chemotherapy is a frequent clinical finding. This damage may be due to excessive neutrophil activity. We here show that transgenic expression of Bcl-2 in haematopoietic cells blocks the resolution of inflammation following antibiotic therapy in a mouse model of pneumococcal meningitis. The persistence of neutrophil brain infiltrates was accompanied by high levels of IL-1beta and G-CSF as well as reduced levels of anti-inflammatory TGF-beta. Significantly, Bcl-2-transgenic mice developed more severe disease that was dependent on neutrophils, characterized by pronounced vasogenic edema, vasculitis, brain haemorrhages and higher clinical scores. In vitro analysis of neutro...