The Experts below are selected from a list of 200211 Experts worldwide ranked by ideXlab platform
Mark D Wewers - One of the best experts on this subject based on the ideXlab platform.
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mononuclear phagocyte derived microparticulate Caspase 1 induces pulmonary vascular endothelial cell injury
PLOS ONE, 2015Co-Authors: Srabani Mitra, Mark D Wewers, Anasuya SarkarAbstract:Lung endothelial cell apoptosis and injury occurs throughout all stages of acute lung injury (ALI/ARDS) and impacts disease progression. Lung endothelial injury has traditionally been focused on the role of neutrophil trafficking to lung vascular integrin receptors induced by proinflammatory cytokine expression. Although much is known about the pathogenesis of cell injury and death in ALI/ARDS, gaps remain in our knowledge; as a result of which there is currently no effective pharmacologic therapy. Enzymes known as Caspases are essential for completion of the apoptotic program and secretion of pro-inflammatory cytokines. We hypothesized that Caspase-1 may serve as a key regulator of human pulmonary microvascular endothelial cell (HPMVEC) apoptosis in ALI/ARDS. Our recent experiments confirm that microparticles released from stimulated monocytic cells (THP1) induce lung endothelial cell apoptosis. Microparticles pretreated with the Caspase-1 inhibitor, YVAD, or pan-Caspase inhibitor, ZVAD, were unable to induce cell death of HPMVEC, suggesting the role of Caspase-1 or its substrate in the induction of HPMVEC cell death. Neither un-induced microparticles (control) nor direct treatment with LPS induced apoptosis of HPMVEC. Further experiments showed that Caspase-1 uptake into HPMVEC and the induction of HPMVEC apoptosis was facilitated by Caspase-1 interactions with microparticulate vesicles. Altering vesicle integrity completely abrogated apoptosis of HPMVEC suggesting an encapsulation requirement for target cell uptake of active Caspase-1. Taken together, we confirm that microparticle centered Caspase-1 can play a regulator role in endothelial cell injury.
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monocyte Caspase 1 is released in a stable active high molecular weight complex distinct from the unstable cell lysate activated Caspase 1
PLOS ONE, 2015Co-Authors: Obada R Shamaa, Srabani Mitra, Mikhail A Gavrilin, Mark D WewersAbstract:Mononuclear phagocytes utilize Caspase-1 activation as a means to respond to danger signals. Although Caspase-1 was discovered using highly concentrated cell extracts that spontaneously activate Caspase-1, it is now clear that in live cell models Caspase-1 activation occurs in the process of its cellular release and is not an intracellular event. Therefore, we compared the characteristics of Caspase-1 activation in the cell lysate model to that of Caspase-1 that is released in response to exogenous inflammasome activation. Whereas both models generated active Caspase-1, the cell-lysate induced Caspase-1 required highly concentrated cell lysates and had a short half-life (~15 min) whereas, the activation induced released Caspase-1 required 2-3 log fold fewer cells and was stable for greater than 12 h. Both forms were able to cleave proIL-1beta but unexpectedly, the released activity was unable to be immunodepleted by Caspase-1 antibodies. Size exclusion chromatography identified two antigenic forms of p20 Caspase-1 in the activation induced released Caspase-1: one at the predicted size of tetrameric, p20/p10 Caspase-1 and the other at >200 kDa. However, only the high molecular weight form had stable functional activity. These results suggest that released Caspase-1 exists in a unique complex that is functionally stable and protected from immunodepletion whereas cell-extract generated active Caspase-1 is rapidly inhibited in the cytosolic milieu.
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microvesicular Caspase 1 mediates lymphocyte apoptosis in sepsis
PLOS ONE, 2014Co-Authors: Matthew C Exline, Mark D Wewers, Steven E Justiniano, Jennifer L Hollyfield, Freweine Berhe, Beth Y Besecker, S Das, Anasuya SarkarAbstract:Objective Immune dysregulation during sepsis is poorly understood, however, lymphocyte apoptosis has been shown to correlate with poor outcomes in septic patients. The inflammasome, a molecular complex which includes Caspase-1, is essential to the innate immune response to infection and also important in sepsis induced apoptosis. Our group has recently demonstrated that endotoxin-stimulated monocytes release microvesicles (MVs) containing Caspase-1 that are capable of inducing apoptosis. We sought to determine if MVs containing Caspase-1 are being released into the blood during human sepsis and induce apoptosis.. Design Single-center cohort study Measurements 50 critically ill patients were screened within 24 hours of admission to the intensive care unit and classified as either a septic or a critically ill control. Circulatory MVs were isolated and analyzed for the presence of Caspase-1 and the ability to induce lymphocyte apoptosis. Patients remaining in the ICU for 48 hours had repeated measurement of Caspase-1 activity on ICU day 3. Main Results Septic patients had higher microvesicular Caspase-1 activity 0.05 (0.04, 0.07) AFU versus 0.0 AFU (0, 0.02) (p<0.001) on day 1 and this persisted on day 3, 0.12 (0.1, 0.2) versus 0.02 (0, 0.1) (p<0.001). MVs isolated from septic patients on day 1 were able to induce apoptosis in healthy donor lymphocytes compared with critically ill control patients (17.8±9.2% versus 4.3±2.6% apoptotic cells, p<0.001) and depletion of MVs greatly diminished this apoptotic signal. Inhibition of Caspase-1 or the disruption of MV integrity abolished the ability to induce apoptosis. Conclusion These findings suggest that microvesicular Caspase-1 is important in the host response to sepsis, at least in part, via its ability to induce lymphocyte apoptosis. The ability of microvesicles to induce apoptosis requires active Caspase-1 and intact microvesicles.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria 111 33
Journal of Immunology, 2011Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Irina A Leaf, Piper M Treuting, Dat P Mao, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of IL-1β and IL-18. While wild type Salmonella typhimurium infection is lethal to mice, a strain that persistently expresses flagellin was cleared by the cytosolic flagellin detection pathway via NLRC4 activation of Caspase-1; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1 induced pyroptotic cell death released bacteria from macrophages, exposing them to uptake and killing by reactive oxygen species in neutrophils. Similarly, Caspase-1 cleared Legionella and Burkholderia by cytokine independent mechanisms. Our results show, for the first time, that Caspase-1 can clear intracellular bacteria in vivo independent of IL-1β and IL-18, and establish pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria
Nature Immunology, 2010Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Sarah E. Warren, Irina A Leaf, Piper M Treuting, Dat P Mao, Monica Dors, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of Caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of Caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of Caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
Anasuya Sarkar - One of the best experts on this subject based on the ideXlab platform.
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mononuclear phagocyte derived microparticulate Caspase 1 induces pulmonary vascular endothelial cell injury
PLOS ONE, 2015Co-Authors: Srabani Mitra, Mark D Wewers, Anasuya SarkarAbstract:Lung endothelial cell apoptosis and injury occurs throughout all stages of acute lung injury (ALI/ARDS) and impacts disease progression. Lung endothelial injury has traditionally been focused on the role of neutrophil trafficking to lung vascular integrin receptors induced by proinflammatory cytokine expression. Although much is known about the pathogenesis of cell injury and death in ALI/ARDS, gaps remain in our knowledge; as a result of which there is currently no effective pharmacologic therapy. Enzymes known as Caspases are essential for completion of the apoptotic program and secretion of pro-inflammatory cytokines. We hypothesized that Caspase-1 may serve as a key regulator of human pulmonary microvascular endothelial cell (HPMVEC) apoptosis in ALI/ARDS. Our recent experiments confirm that microparticles released from stimulated monocytic cells (THP1) induce lung endothelial cell apoptosis. Microparticles pretreated with the Caspase-1 inhibitor, YVAD, or pan-Caspase inhibitor, ZVAD, were unable to induce cell death of HPMVEC, suggesting the role of Caspase-1 or its substrate in the induction of HPMVEC cell death. Neither un-induced microparticles (control) nor direct treatment with LPS induced apoptosis of HPMVEC. Further experiments showed that Caspase-1 uptake into HPMVEC and the induction of HPMVEC apoptosis was facilitated by Caspase-1 interactions with microparticulate vesicles. Altering vesicle integrity completely abrogated apoptosis of HPMVEC suggesting an encapsulation requirement for target cell uptake of active Caspase-1. Taken together, we confirm that microparticle centered Caspase-1 can play a regulator role in endothelial cell injury.
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microvesicular Caspase 1 mediates lymphocyte apoptosis in sepsis
PLOS ONE, 2014Co-Authors: Matthew C Exline, Mark D Wewers, Steven E Justiniano, Jennifer L Hollyfield, Freweine Berhe, Beth Y Besecker, S Das, Anasuya SarkarAbstract:Objective Immune dysregulation during sepsis is poorly understood, however, lymphocyte apoptosis has been shown to correlate with poor outcomes in septic patients. The inflammasome, a molecular complex which includes Caspase-1, is essential to the innate immune response to infection and also important in sepsis induced apoptosis. Our group has recently demonstrated that endotoxin-stimulated monocytes release microvesicles (MVs) containing Caspase-1 that are capable of inducing apoptosis. We sought to determine if MVs containing Caspase-1 are being released into the blood during human sepsis and induce apoptosis.. Design Single-center cohort study Measurements 50 critically ill patients were screened within 24 hours of admission to the intensive care unit and classified as either a septic or a critically ill control. Circulatory MVs were isolated and analyzed for the presence of Caspase-1 and the ability to induce lymphocyte apoptosis. Patients remaining in the ICU for 48 hours had repeated measurement of Caspase-1 activity on ICU day 3. Main Results Septic patients had higher microvesicular Caspase-1 activity 0.05 (0.04, 0.07) AFU versus 0.0 AFU (0, 0.02) (p<0.001) on day 1 and this persisted on day 3, 0.12 (0.1, 0.2) versus 0.02 (0, 0.1) (p<0.001). MVs isolated from septic patients on day 1 were able to induce apoptosis in healthy donor lymphocytes compared with critically ill control patients (17.8±9.2% versus 4.3±2.6% apoptotic cells, p<0.001) and depletion of MVs greatly diminished this apoptotic signal. Inhibition of Caspase-1 or the disruption of MV integrity abolished the ability to induce apoptosis. Conclusion These findings suggest that microvesicular Caspase-1 is important in the host response to sepsis, at least in part, via its ability to induce lymphocyte apoptosis. The ability of microvesicles to induce apoptosis requires active Caspase-1 and intact microvesicles.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria 111 33
Journal of Immunology, 2011Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Irina A Leaf, Piper M Treuting, Dat P Mao, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of IL-1β and IL-18. While wild type Salmonella typhimurium infection is lethal to mice, a strain that persistently expresses flagellin was cleared by the cytosolic flagellin detection pathway via NLRC4 activation of Caspase-1; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1 induced pyroptotic cell death released bacteria from macrophages, exposing them to uptake and killing by reactive oxygen species in neutrophils. Similarly, Caspase-1 cleared Legionella and Burkholderia by cytokine independent mechanisms. Our results show, for the first time, that Caspase-1 can clear intracellular bacteria in vivo independent of IL-1β and IL-18, and establish pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria
Nature Immunology, 2010Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Sarah E. Warren, Irina A Leaf, Piper M Treuting, Dat P Mao, Monica Dors, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of Caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of Caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of Caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
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monocyte derived microvesicles deliver a cell death message via encapsulated Caspase 1
PLOS ONE, 2009Co-Authors: Anasuya Sarkar, Srabani Mitra, Sonya Mehta, Raquel M Raices, Mark D WewersAbstract:Apoptosis depends upon the activation of intracellular Caspases which are classically induced by either an intrinsic (mitochondrial based) or extrinsic (cytokine) pathway. However, in the process of explaining how endotoxin activated monocytes are able to induce apoptosis of vascular smooth muscle cells when co-cultured, we uncovered a transcellular apoptosis inducing pathway that utilizes Caspase-1 containing microvesicles. Endotoxin stimulated monocytes induce the cell death of VSMCs but this activity is found in 100,000 g pellets of cell free supernatants of these monocytes. This activity is not a direct effect of endotoxin, and is inhibited by the Caspase-1 inhibitor YVADcmk but not by inhibitors of Fas-L, IL-1beta and IL-18. Importantly, the apoptosis inducing activity co-purifies with 100 nm sized microvesicles as determined by TEM of the pellets. These microvesicles contain Caspase-1 and Caspase-1 encapsulation is required since disruption of microvesicular integrity destroys the apoptotic activity but not the Caspase-1 enzymatic activity. Thus, monocytes are capable of delivering a cell death message which depends upon the release of microvesicles containing functional Caspase-1. This transcellular apoptosis induction pathway describes a novel pathway for inflammation induced programmed cell death.
Alan Aderem - One of the best experts on this subject based on the ideXlab platform.
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Caspase 1 induced pyroptotic cell death
Immunological Reviews, 2011Co-Authors: Edward A Miao, Jayant V Rajan, Alan AderemAbstract:Programmed cell death is a necessary part of development and tissue homeostasis enabling the removal of unwanted cells. In the setting of infectious disease, cells that have been commandeered by microbial pathogens become detrimental to the host. When macrophages and dendritic cells are compromised in this way, they can be lysed by pyroptosis, a cell death mechanism that is distinct from apoptosis and oncosis/necrosis. Pyroptosis is triggered by Caspase-1 after its activation by various inflammasomes and results in lysis of the affected cell. Both pyroptosis and apoptosis are programmed cell death mechanisms but are dependent on different Caspases, unlike oncosis. Similar to oncosis and unlike apoptosis, pyroptosis results in cellular lysis and release of the cytosolic contents to the extracellular space. This event is predicted to be inherently inflammatory and coincides with interleukin-1β (IL-1β) and IL-18 secretion. We discuss the role of distinct inflammasomes, including NLRC4, NLRP3, and AIM2, as well as the role of the ASC focus in Caspase-1 signaling. We further review the importance of pyroptosis in vivo as a potent mechanism to clear intracellular pathogens.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria 111 33
Journal of Immunology, 2011Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Irina A Leaf, Piper M Treuting, Dat P Mao, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of IL-1β and IL-18. While wild type Salmonella typhimurium infection is lethal to mice, a strain that persistently expresses flagellin was cleared by the cytosolic flagellin detection pathway via NLRC4 activation of Caspase-1; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1 induced pyroptotic cell death released bacteria from macrophages, exposing them to uptake and killing by reactive oxygen species in neutrophils. Similarly, Caspase-1 cleared Legionella and Burkholderia by cytokine independent mechanisms. Our results show, for the first time, that Caspase-1 can clear intracellular bacteria in vivo independent of IL-1β and IL-18, and establish pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
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Caspase 1 induced pyroptosis is an innate immune effector mechanism against intracellular bacteria
Nature Immunology, 2010Co-Authors: Edward A Miao, Mark D Wewers, Anasuya Sarkar, Sarah E. Warren, Irina A Leaf, Piper M Treuting, Dat P Mao, Monica Dors, Alan AderemAbstract:Macrophages mediate crucial innate immune responses via Caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of Caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, Caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of Caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of Caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.
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Multiple Nod-Like Receptors Activate Caspase 1 during Listeria monocytogenes Infection
Journal of Immunology, 2008Co-Authors: Sarah E. Warren, Edward A Miao, April E. Rodriguez, Alan AderemAbstract:Listeria monocytogenes escapes from the phagosome of macrophages and replicates within the cytosolic compartment. The macrophage responds to L. monocytogenes through detection pathways located on the cell surface (TLRs) and within the cytosol (Nod-like receptors) to promote inflammatory processes aimed at clearing the pathogen. Cytosolic L. monocytogenes activates Caspase 1, resulting in post-translational processing of the cytokines IL-1β and IL-18 as well as Caspase 1-dependent cell death (pyroptosis). We demonstrate that the presence of L. monocytogenes within the cytosolic compartment induces Caspase 1 activation through multiple Nod-like receptors, including Ipaf and Nalp3. Flagellin expression by cytosolic L. monocytogenes was detected through Ipaf in a dose-dependent manner. Concordantly, detection of flagellin promoted bacterial clearance in a murine infection model. Finally, we provide evidence that suggests cytosolic L. monocytogenes activates Caspase 1 through a third pathway, which signals through the adaptor protein ASC. Thus, L. monocytogenes activates Caspase 1 in macrophages via multiple pathways, all of which detect the presence of bacteria within the cytosol.
Richard Groves - One of the best experts on this subject based on the ideXlab platform.
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functional Caspase 1 is required for langerhans cell migration and optimal contact sensitization in mice
Journal of Immunology, 2001Co-Authors: Christos Antonopoulos, Rebecca Jane Dearman, Marie Cumberbatch, Richard J Daniel, Ian Kimber, Richard GrovesAbstract:Langerhans cell (LC) migration from epidermis to draining lymph node is a critical first step in cutaneous immune responses. Both TNF-α and IL-1β are important signals governing this process, but the potential regulatory role of IL-1α processing by Caspase-1 is unknown. In wild-type (WT) mice, application of the contact allergens 2,4-dinitrofluorobenzine and oxazolone lead to a marked reduction in epidermal LC numbers, but in Caspase-1-deficient mice this reduction was not observed. Moreover, although intradermal injection of TNF-α (50 ng) induced epidermal LC migration in WT mice, this cytokine failed to induce LC migration in Caspase-1-deficient mice. Intradermal IL-1β (50 ng) caused a similar reduction in epidermal LC numbers in both WT and Caspase-1-deficient mice, indicating that, given an appropriate signal, Caspase-1-deficient epidermal LC are capable of migration. Contact hypersensitivity to both 2,4-dinitrofluorobenzine and oxazolone was inhibited in Caspase-1-deficient mice, indicating a functional consequence of the LC migration defect. In organ culture the Caspase-1 inhibitor Ac-YVAD-cmk, but not control peptide, potently inhibited the epidermal LC migration that occurs in this system, and reduced spontaneous migration of LC was observed in skin derived from Caspase-1-deficient mice. Moreover, Ac-YVAD-cmk applied to BALB/c mouse skin before application of contact sensitizers inhibited LC migration and contact hypersensitivity in vivo. Taken together, these data indicate that Caspase-1 may play a central role in the regulation of LC migration and suggest that the activity of this enzyme is amenable to control by specific inhibitors both in vivo and in vitro.
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functional Caspase 1 is required for langerhans cell migration and optimal contact sensitization in mice
Journal of Immunology, 2001Co-Authors: Christos Antonopoulos, Rebecca Jane Dearman, Marie Cumberbatch, Richard J Daniel, Ian Kimber, Richard GrovesAbstract:Langerhans cell (LC) migration from epidermis to draining lymph node is a critical first step in cutaneous immune responses. Both TNF-alpha and IL-1 beta are important signals governing this process, but the potential regulatory role of IL-1 alpha processing by Caspase-1 is unknown. In wild-type (WT) mice, application of the contact allergens 2,4-dinitrofluorobenzine and oxazolone lead to a marked reduction in epidermal LC numbers, but in Caspase-1-deficient mice this reduction was not observed. Moreover, although intradermal injection of TNF-alpha (50 ng) induced epidermal LC migration in WT mice, this cytokine failed to induce LC migration in Caspase-1-deficient mice. Intradermal IL-1 beta (50 ng) caused a similar reduction in epidermal LC numbers in both WT and Caspase-1-deficient mice, indicating that, given an appropriate signal, Caspase-1-deficient epidermal LC are capable of migration. Contact hypersensitivity to both 2,4-dinitrofluorobenzine and oxazolone was inhibited in Caspase-1-deficient mice, indicating a functional consequence of the LC migration defect. In organ culture the Caspase-1 inhibitor Ac-YVAD-cmk, but not control peptide, potently inhibited the epidermal LC migration that occurs in this system, and reduced spontaneous migration of LC was observed in skin derived from Caspase-1-deficient mice. Moreover, Ac-YVAD-cmk applied to BALB/c mouse skin before application of contact sensitizers inhibited LC migration and contact hypersensitivity in vivo. Taken together, these data indicate that Caspase-1 may play a central role in the regulation of LC migration and suggest that the activity of this enzyme is amenable to control by specific inhibitors both in vivo and in vitro.
Brad T Cookson - One of the best experts on this subject based on the ideXlab platform.
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the yersinia virulence effector yopm binds Caspase 1 to arrest inflammasome assembly and processing
Cell Host & Microbe, 2012Co-Authors: Christopher N Larock, Brad T CooksonAbstract:Inflammasome assembly activates Caspase-1 and initiates the inflammatory cell death program pyroptosis, which is protective against numerous pathogens. Consequently, several pathogens, including the plague causing bacterium Yersinia pestis, avoid activating this pathway to enhance their virulence. However, bacterial molecules that directly modulate the inflammasome have yet to be identified. Examining the contribution of Yersinia type III secretion effectors to Caspase-1 activation, we identified the leucine-rich repeat effector YopM as a potent antagonist of both Caspase-1 activity and activation. YopM directly binds Caspase-1, which both inhibits Caspase-1 activity and sequesters it to block formation of the mature inflammasome. Caspase-1 activation antagonizes Yersinia survival in vivo, and consequently YopM inhibition of Caspase-1 is required for Yersinia pathogenesis. Thus, a bacterium obstructs pyroptosis utilizing a direct mechanism of Caspase-1 inhibition that is distinct from known viral or host inhibitors.
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coordinated host responses during pyroptosis Caspase 1 dependent lysosome exocytosis and inflammatory cytokine maturation
Journal of Immunology, 2011Co-Authors: Tessa Bergsbaken, Susan L Fink, Andreas Den B Hartigh, Wendy P Loomis, Brad T CooksonAbstract:Activation of Caspase-1 leads to pyroptosis, a program of cell death characterized by cell lysis and inflammatory cytokine release. Caspase-1 activation triggered by multiple nucleotide-binding oligomerization domain-like receptors (NLRs; NLRC4, NLRP1b, or NLRP3) leads to loss of lysosomes via their fusion with the cell surface, or lysosome exocytosis. Active Caspase-1 increased cellular membrane permeability and intracellular calcium levels, which facilitated lysosome exocytosis and release of host antimicrobial factors and microbial products. Lysosome exocytosis has been proposed to mediate secretion of IL-1β and IL-18; however, blocking lysosome exocytosis did not alter cytokine processing or release. These studies indicate two conserved secretion pathways are initiated by Caspase-1, lysosome exocytosis, and a parallel pathway resulting in cytokine release, and both enhance the antimicrobial nature of pyroptosis.
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anthrax lethal toxin and salmonella elicit the common cell death pathway of Caspase 1 dependent pyroptosis via distinct mechanisms
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Susan L Fink, Tessa Bergsbaken, Brad T CooksonAbstract:Caspase-1 cleaves the inactive IL-1β and IL-18 precursors into active inflammatory cytokines. In Salmonella-infected macrophages, Caspase-1 also mediates a pathway of proinflammatory programmed cell death termed “pyroptosis.” We demonstrate active Caspase-1 diffusely distributed in the cytoplasm and localized in discrete foci within macrophages responding to either Salmonella infection or intoxication by Bacillus anthracis lethal toxin (LT). Both stimuli triggered Caspase-1-dependent lysis in macrophages and dendritic cells. Activation of Caspase-1 by LT required binding, uptake, and endosome acidification to mediate translocation of lethal factor (LF) into the host cell cytosol. Catalytically active LF cleaved cytosolic substrates and activated Caspase-1 by a mechanism involving proteasome activity and potassium efflux. LT activation of Caspase-1 is known to require the inflammasome adapter Nalp1. In contrast, Salmonella infection activated Caspase-1 through an independent pathway requiring the inflammasome adapter Ipaf. These distinct mechanisms of Caspase-1 activation converged on a common pathway of Caspase-1-dependent cell death featuring DNA cleavage, cytokine activation, and, ultimately, cell lysis resulting from the formation of membrane pores between 1.1 and 2.4 nm in diameter and pathological ion fluxes that can be blocked by glycine. These findings demonstrate that distinct activation pathways elicit the conserved cell death effector mechanism of Caspase-1-mediated pyroptosis and support the notion that this pathway of proinflammatory programmed cell death is broadly relevant to cell death and inflammation invoked by diverse stimuli.
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Caspase 1 dependent pore formation during pyroptosis leads to osmotic lysis of infected host macrophages
Cellular Microbiology, 2006Co-Authors: Susan L Fink, Brad T CooksonAbstract:Salmonella enterica serovar Typhimurium invades host macrophages and induces a unique Caspase-1-dependent pathway of cell death termed pyroptosis, which is activated during bacterial infection in vivo. We demonstrate DNA cleavage during pyroptosis results from Caspase-1-stimulated nuclease activity. Although poly(ADP-ribose) polymerase (PARP) activation by fragmented DNA depletes cellular ATP to cause lysis during oncosis, the rapid lysis characteristic of Salmonella-infected macrophages does not require PARP activity or DNA fragmentation. Membrane pores between 1.1 and 2.4 nm in diameter form during pyroptosis of host cells and cause swelling and osmotic lysis. Pore formation requires host cell actin cytoskeleton rearrangements and Caspase-1 activity, as well as the bacterial type III secretion system (TTSS); however, insertion of functional TTSS translocons into the host membrane is not sufficient to directly evoke pore formation. Concurrent with pore formation, inflammatory cytokines are released from infected macrophages. This mechanism of Caspase-1-mediated cell death provides additional experimental evidence supporting pyroptosis as a novel pathway of inflammatory programmed cell death.