Mechanism of staurosporine-induced apoptosis in murine hepatocytes

2002 ◽  
Vol 282 (5) ◽  
pp. G825-G834 ◽  
Author(s):  
Guoping Feng ◽  
Neil Kaplowitz
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Caspase 3 ◽  
Nuclear Translocation ◽  
Nuclear Factor Κb ◽  
Jurkat Cells ◽  
Primary Hepatocytes ◽  
Iκb Kinase ◽  
Apoptosis Protein ◽  
Induced Apoptosis

Staurosporine (STS) induces apoptosis in various cell lines. We report in this study that primary cultured mouse hepatocytes are less sensitive to STS compared with Jurkat cells and Huh-7 cells. In contrast to the cell lines, no apparent release of cytochrome c or loss of mitochondrial transmembrane potential was detected in primary hepatocytes undergoing STS-induced apoptosis. Caspase-3 was activated in primary hepatocytes by STS treatment, but caspase-9 and -12 were not activated, and caspase-3 activation is not dependent on caspase-8. These findings point to a novel pathway for caspase-3 activation by STS in primary hepatocytes. Pretreatment with caspase inhibitor converted STS-induced apoptosis of hepatocytes to necrotic cell death without significantly changing total cell death. Thus STS causes hepatocytes to commit to death upstream of the activation of caspases. We also demonstrated that STS dramatically sensitized primary hepatocytes to tumor necrosis factor-α-induced apoptosis. STS activated IκB kinase and nuclear factor-κB (NF-κB) nuclear translocation and DNA binding but inhibited transactivation of IκB-α, inducible nitric oxide synthase, and inhibitor of apoptosis protein-1 in hepatocytes and NF-κB reporter in transfected Huh-7 cells.

Biologic sequelae of nuclear factor–κB blockade in multiple myeloma: therapeutic applications

Blood ◽  
2002 ◽  
Vol 99 (11) ◽  
pp. 4079-4086 ◽  
Author(s):  
Nicholas Mitsiades ◽  
Constantine S. Mitsiades ◽  
Vassiliki Poulaki ◽  
Dharminder Chauhan ◽  
Paul G. Richardson ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Nuclear Translocation ◽  
Nuclear Factor Κb ◽  
Inhibitor Of Apoptosis ◽  
Caspase 8 ◽  
Nuclear Factor ◽  
Inhibitor Of Apoptosis Protein ◽  
Tnf Α ◽  
Apoptosis Protein ◽  
Induced Apoptosis

The transcription factor nuclear factor–κB (NF-κB) confers significant survival potential in a variety of tumors. Several established or novel anti–multiple myeloma (anti-MM) agents, such as dexamethasone, thalidomide, and proteasome inhibitors (PS-341), inhibit NF-κB activity as part of their diverse actions. However, studies to date have not delineated the effects of specific inhibition of NF-κB activity in MM. We therefore investigated the effect of SN50, a cell-permeable specific inhibitor of NF-κB nuclear translocation and activity, on MM cells. SN50 induced apoptosis in MM cell lines and patient cells; down-regulated expression of Bcl-2, A1, X-chromosome–linked inhibitor-of-apoptosis protein (XIAP), cellular inhibitor-of-apoptosis protein 1 (cIAP-1), cIAP-2, and survivin; up-regulated Bax; increased mitochondrial cytochromec release into the cytoplasm; and activated caspase-9 and caspase-3, but not caspase-8. We have previously demonstrated that tumor necrosis factor–α (TNF-α) is present locally in the bone marrow microenvironment and induces NF-κB–dependent up-regulation of adhesion molecules on both MM cells and bone marrow stromal cells, with resultant increased adhesion. In this study, TNF-α alone induced NF-κB nuclear translocation, cIAP-1 and cIAP-2 up-regulation, and MM cell proliferation; in contrast, SN50 pretreatment sensitized MM cells to TNF-α–induced apoptosis and cleavage of caspase-8 and caspase-3, similar to our previous finding of SN50-induced sensitization to apoptosis induced by the TNF-α family member TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L. Moreover, SN50 inhibited TNF-α–induced expression of another NF-κB target gene, intercellular adhesion molecule–1. Although the p38 inhibitor PD169316 did not directly kill MM cells, it potentiated the apoptotic effect of SN50, suggesting an interaction between the p38 and NF-κB pathways. Our results therefore demonstrate that NF-κB activity in MM cells promotes tumor-cell survival and protects against apoptotic stimuli. These studies provide the framework for targeting NF-κB activity in novel biologically based therapies for MM.

SMAC-Mimetic BV-6 Sensitizes Therapeutic Agents-Induced Apoptosis In AML Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2177-2177
Author(s):  
Duncan H Mak ◽  
Christa Manton ◽  
Michael Andreeff ◽  
Bing Z Carter
Keyword(s):  
Cell Death ◽  
Vector Control ◽  
Caspase 3 ◽  
Jurkat Cells ◽  
Leukemic Cells ◽  
Caspase 8 ◽  
Caspase 9 ◽  
Smac Mimetic ◽  
P53 Activation ◽  
Induced Apoptosis

Abstract Abstract 2177 The antiapoptotic function of the inhibitors of apoptosis family of proteins (IAPs) is antagonized by mitochondria-released SMAC protein. The IAP-member XIAP suppresses apoptosis by directly binding and inhibiting caspase-9 and caspase-3, while cIAP1, a component of the cytoplasmic signaling complex containing TNF receptor associated factors, suppresses apoptosis via the caspase-8-mediated pathway. BV-6 (Genentech) is a bivalent SMAC-mimetic and has been shown to promote cell death by inducing cIAP autoubiquitination, NF-κB activation, and TNFα-dependent apoptosis. We examined its effect on leukemic cells and found that BV-6 only moderately induced apoptosis. The EC50 was found to be 15.3±5.1 μM at 48 hours in OCI-AML3 cells which are relatively sensitive. We then determined whether BV-6 sensitizes leukemic cells to the HDM2-inhibitor nutlin-3a and to Ara-C. p53 modulates the expression and activity of Bcl-2 family proteins and promotes the mitochondrial-mediated apoptosis. We showed previously that activation of p53 by nutlin-3a sensitizes AML cells to XIAP inhibition induced-death in part by promoting the release of SMAC from mitochondrion (Carter BZ et al., Blood 2010). We treated OCI-AML3 cells with BV-6, nutlin-3a or Ara-C, and BV-6+nutlin-3a or BV-6+Ara-C and found that the combination of BV-6 and nutlin-3a or BV-6 and Ara-C synergistically induced cell death in OCI-AML3 cells with a combination index (CI) of 0.27±0.11 and 0.22±0.05 (48 hours), respectively. To demonstrate that p53 activation is essential for the synergism of BV-6+nutlin-3a combination, we treated OCI-AML3 vector control and p53 knockdown cells with these two agents and found that the combination synergistically promoted cell death in the vector control (CI=0.47±0.15) but not in the p53 knockdown cells, as expected, while BV6+Ara-C was synergistic in both vector control and p53 knockdown cells (CI=0.15±0.03 and 0.08±0.03, respectively, 48 hours). BV-6 induced activation of caspase-8, caspase-9, and caspase-3 and decreased XIAP levels, but did not cause rapid cIAP1 degradation, as reported by others. To assess the contribution of death receptor-mediated apoptosis in BV-6-induced cell death, we treated Jurkat and caspase-8 mutated Jurkat cells (JurkatI9.2) with BV-6 and found that BV-6 induced cell death and significantly potentiated TRAIL-induced apoptosis in Jurkat cells (CI=0.14±0.08, 48 hours). Caspase-8 mutated JurkatI9.2 cells were significantly less sensitive to BV-6 than Jurkat cells and as expected, JurkatI9.2 was completely resistant to TRAIL. Collectively, we showed that the bivalent SMAC-mimetic BV-6 potentiates p53 activation-, chemotherapy-, and TRAIL-induced cell death, but has only minimal activity by itself in leukemic cells. SMAC-mimetics could be useful in enhancing the efficacy of different classes of therapeutic agents used in AML therapy. Disclosures: No relevant conflicts of interest to declare.

scholarly journals NF-κB Inducers Upregulate cFLIP, a Cycloheximide-Sensitive Inhibitor of Death Receptor Signaling

2001 ◽  
Vol 21 (12) ◽  
pp. 3964-3973 ◽  
Author(s):  
Sebastian Kreuz ◽  
Daniela Siegmund ◽  
Peter Scheurich ◽  
Harald Wajant
Keyword(s):  
Cell Lines ◽  
Death Receptor ◽  
Jurkat Cells ◽  
Negative Regulator ◽  
Inhibitory Protein ◽  
Iκb Kinase ◽  
Low Concentrations ◽  
Death Receptor Signaling ◽  
Induced Apoptosis ◽  
Necrosis Factor

ABSTRACT The caspase 8 homologue FLICE-inhibitory protein (cFLIP) is a potent negative regulator of death receptor-induced apoptosis. We found that cFLIP can be upregulated in some cell lines under critical involvement of the NF-κB pathway, but NF-κB activation was clearly not sufficient for cFLIP induction in all cell lines. Treatment of SV80 cells with the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG-132) or geldanamycin, a drug interfering with tumor necrosis factor (TNF)-induced NF-κB activation, inhibited TNF-induced upregulation of cFLIP. Overexpression of a nondegradable IκBα mutant (IκBα-SR) or lack of IκB kinase γ expression completely prevented phorbol myristate acetate-induced upregulation of cFLIP mRNA in Jurkat cells. These data point to an important role for NF-κB in the regulation of the cFLIP gene. SV80 cells normally show resistance to TNF-related apoptosis-inducing ligand (TRAIL) and TNF, as apoptosis can be induced only in the presence of low concentrations of cycloheximide (CHX). However, overexpression of IκBα-SR rendered SV80 cells sensitive to TRAIL-induced apoptosis in the absence of CHX, and cFLIP expression was able to reverse the proapoptotic effect of NF-κB inhibition. Western blot analysis further revealed that cFLIP, but not TRAF1, A20, and cIAP2, expression levels rapidly decrease upon CHX treatment. In conclusion, these data suggest a key role for cFLIP in the antiapoptotic response of NF-κB activation.

scholarly journals IKKα plays a major role in canonical NF-kB signalling in colorectal cells

2022 ◽  
Author(s):  
Jack A Prescott ◽  
Kathryn Balmanno ◽  
Jennifer P Mitchell ◽  
Hanneke Okkenhaug ◽  
Simon J Cook
Keyword(s):  
Cell Lines ◽  
Nuclear Translocation ◽  
Transcriptional Response ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Knock Out ◽  
Iκb Kinase ◽  
Sw620 Cells ◽  
Hct116 Cells

Inhibitor of kappa B (IκB) kinase β (IKKβ) has long been viewed as the dominant IKK in the canonical nuclear factor-κB (NF-κB) signalling pathway, with IKKα being more important in non-canonical NF-κB activation. Here we have investigated the role of IKKα and IKKβ in canonical NF-κB activation in colorectal cells using CRISPR-Cas9 knock-out cell lines, siRNA and selective IKKβ inhibitors. IKKα and IKKβ were redundant for IκBα phosphorylation and turnover since loss of IKKα or IKKβ alone had little (SW620 cells) or no (HCT116 cells) effect. However, in HCT116 cells IKKα was the dominant IKK required for basal phosphorylation of p65 at S536, stimulated phosphorylation of p65 at S468, nuclear translocation of p65 and the NF-κB-dependent transcriptional response to both TNFα and IL-1α. In these cells IKKβ was far less efficient at compensating for the loss of IKKα than IKKα was able to compensate for the loss of IKKβ. This was confirmed when siRNA was used to knock-down the non-targeted kinase in single KO cells. Critically, the selective IKKβ inhibitor BIX02514 confirmed these observations in WT cells and similar results were seen in SW620 cells. Notably, whilst IKKα loss strongly inhibited TNFα-dependent p65 nuclear translocation, IKKα and IKKβ contributed equally to c-Rel nuclear translocation indicating that different NF-κB subunits exhibit different dependencies on these IKKs. These results demonstrate a major role for IKKα in canonical NF-κB signalling in colorectal cells and may be relevant to efforts to design IKK inhibitors, which have focused largely on IKKβ to date.

Motexafin Gadolinium Induces Apoptosis in Lymphoid Cell Lines and Demonstrates Enhanced Biological Activity with Akt Kinase Inhibitors.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3406-3406
Author(s):  
Louie Naumovski ◽  
Jason Ramos ◽  
Jun Chen ◽  
Mint Sirisawad ◽  
David Lucas ◽  
...  
Keyword(s):  
Cell Death ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Lines ◽  
Specific Inhibitor ◽  
Annexin V ◽  
Lymphocytic Leukemia ◽  
Jurkat Cells ◽  
Motexafin Gadolinium ◽  
Akt Phosphorylation ◽  
Induced Apoptosis

Abstract Motexafin gadolinium (MGd, Xcytrin®) is a tumor-selective redox mediator that catalytically oxidizes intracellular reducing metabolites and produces reactive oxygen species (ROS). In this report, we demonstrate that MGd induces apoptosis or growth inhibition in several hematopoietic tumor-derived cell lines and tumor cells from patients with chronic lymphocytic leukemia. Lymphoma (HF-1, Ramos, DHL-4, DB, Hut78 and Raji) and leukemia (Jurkat, HL-60) cell lines were cultured in RPMI 1640 media with 10% heat inactivated fetal bovine serum with or without 50 uM MGd. MGd inhibited the growth of 6 of the cell lines (HF-1, Ramos, HL-60, DHL-4, Jurkat and DB) and was cytotoxic to HF-1. ROS were implicated in MGd-induced cell death since their presence was detected by dichlorofluorescein diacetate staining and peroxiredoxin oxidation in MGd treated HF-1 cells that undergo apoptosis, but not in Jurkat cells that do not undergo MGd-induced apoptosis. MGd triggered an apoptotic pathway in HF-1 cells as demonstrated by loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, activation of caspases, cleavage of PARP and annexin-V binding. MGd also induced cell death and activated caspases in vitro in primary chronic lymphocytic leukemia cells. Protein lysates from cultured cell lines (HF-1, Ramos) were subjected to immunoblot analysis to determine caspase cleavage patterns, and the phosphorylation status of Akt, a kinase that regulates survival pathways. In MGd treated HF-1, phospho-Akt protein levels initially increased 2–3 fold between 30 min and 1 hr (n=4) and then decreased to 40–50% of control levels by 24–48 hrs (n=4). The drop in phospho-Akt protein coincided with an increase in apoptotic cell death as indicated by morphology, staining with Annexin-V and activation of caspases. Addition of a specific inhibitor of Akt phosphorylation (SH-5) reduced Akt phosphorylation in MGd treated HF-1 cells by 90% and enhanced the cytotoxic effect of MGd. In Ramos cells, which do not undergo apoptosis when treated with MGd, co-treatment with MGd and SH-5 decreased phospho Akt levels by only 15% and did not result in cytotoxicity. These data point to a potential role for Akt in MGd-induced apoptosis and suggest that MGd activity may be enhanced by inhibition of Akt. These data show that the pro-apoptotic effects of MGd involve caspase activation and provide a rationale to evaluate MGd in the treatment of lymphoma and leukemia patients.

Inhibition of NF-κB essentially contributes to arsenic-induced apoptosis

Blood ◽  
2003 ◽  
Vol 102 (3) ◽  
pp. 1028-1034 ◽  
Author(s):  
Stephan Mathas ◽  
Andreas Lietz ◽  
Martin Janz ◽  
Michael Hinz ◽  
Franziska Jundt ◽  
...  
Keyword(s):  
Cell Lines ◽  
Target Genes ◽  
Nuclear Factor Κb ◽  
Model Systems ◽  
Direct Role ◽  
Iκb Kinase ◽  
Transient Overexpression ◽  
Induced Apoptosis ◽  
Necrosis Factor

Abstract Arsenic can induce apoptosis and is an efficient drug for the treatment of acute promyelocytic leukemia. Currently, clinical studies are investigating arsenic as a therapeutic agent for a variety of malignancies. In this study, Hodgkin/Reed-Sternberg (HRS) cell lines served as model systems to characterize the role of nuclear factor–κB (NF-κB) in arsenic-induced apoptosis. Arsenic rapidly down-regulated constitutive IκB kinase (IKK) as well as NF-κB activity and induced apoptosis in HRS cell lines containing functional IκB proteins. In these cell lines, apoptosis was blocked by inhibition of caspase-8 and caspase-3–like activity. Furthermore, arsenic treatment down-regulated NF-κB target genes, including tumor necrosis factor-αreceptor–associated factor 1 (TRAF1), c-IAP2, interleukin-13 (IL-13), and CCR7. In contrast, cell lines with mutated, functionally inactive IκB proteins or with a weak constitutive IKK/NF-κB activity showed no alteration of the NF-κB activity and were resistant to arsenic-induced apoptosis. A direct role of the NF-κB pathway in arsenic-induced apoptosis is shown by transient overexpression of NF-κB–p65 in L540Cy HRS cells, which protected the cells from arsenic-induced apoptosis. In addition, treatment of NOD/SCID mice with arsenic trioxide induced a dramatic reduction of xenotransplanted L540Cy Hodgkin tumors concomitant with NF-κB inhibition. We conclude that inhibition of NF-κB contributes to arsenic-induced apoptosis. Furthermore, pharmacologic inhibition of the IKK/NF-κB activity might be a powerful treatment option for Hodgkin lymphoma.

scholarly journals Jasplakinolide Induces Apoptosis in Various Transformed Cell Lines by a Caspase-3-Like Protease-Dependent Pathway

2000 ◽  
Vol 7 (6) ◽  
pp. 947-952 ◽  
Author(s):  
Chikako Odaka ◽  
Miranda L. Sanders ◽  
Phillip Crews
Keyword(s):  
T Cells ◽  
Cell Death ◽  
Cell Lines ◽  
Caspase 3 ◽  
Dependent Manner ◽  
Jurkat T Cells ◽  
Transformed Cell ◽  
Induced Apoptosis ◽  
Transformed Cell Lines ◽  
Dependent Pathway

ABSTRACT To clarify the mechanisms underlying the antiproliferative effects of jasplakinolide, a cyclic depsipeptide from marine sponges, we examined whether jasplakinolide induces apoptosis in a variety of transformed and nontransformed cells. Jasplakinolide inhibited proliferation of human Jurkat T cells, resulting in cell death. This was accompanied by chromatin condensation and DNA cleavage at the linker regions between the nucleosomes. When caspase-3-like activity in the cytosolic extracts of Jurkat T cells was examined with a fluorescent substrate, DEVD-MAC (N-acetyl-Asp-Glu-Val-Asp-4-methyl-coumaryl-7-amide), the activity in the cells treated with jasplakinolide was remarkably increased in a time-dependent manner. Pretreatment of Jurkat T cells with the caspase inhibitor zVAD [benzyloxycarbonyl(Cbz)-Val-Ala-β-Asp(OMe)-fluoromethylketone] or DEVD-CHO (N-acetyl-Asp-Glu-Val-Asp-1-aldehyde) prevented the induction of apoptosis by jasplakinolide. Moreover, exposure of various murine transformed cell lines to jasplakinolide resulted in cell death, which was inhibited by zVAD. Although it has been well established that murine immature thymocytes are sensitive to apoptosis when exposed to various apoptotic stimuli, these cells as well as mature T lymphocytes were resistant to jasplakinolide-induced apoptosis. The results suggest that jasplakinolide induces apoptotic cell death through a caspase-3-like protease-dependent pathway. Another important outcome is that transformed cell lines were more susceptible to jasplakinolide-induced apoptosis than normal nontransformed cells.

scholarly journals SUMOylation protects against IL-1β-induced apoptosis in INS-1 832/13 cells and human islets

2014 ◽  
Vol 307 (8) ◽  
pp. E664-E673 ◽  
Author(s):  
Catherine Hajmrle ◽  
Mourad Ferdaoussi ◽  
Gregory Plummer ◽  
Aliya F. Spigelman ◽  
Krista Lai ◽  
...  
Keyword(s):  
Cell Death ◽  
Insulin Secretion ◽  
Caspase 3 ◽  
Nuclear Translocation ◽  
Human Islets ◽  
Inos Expression ◽  
Β Cell ◽  
Intracellular Ca ◽  
Induced Apoptosis ◽  
The Impact

Posttranslational modification by the small ubiquitin-like modifier (SUMO) peptides, known as SUMOylation, is reversed by the sentrin/SUMO-specific proteases (SENPs). While increased SUMOylation reduces β-cell exocytosis, insulin secretion, and responsiveness to GLP-1, the impact of SUMOylation on islet cell survival is unknown. Mouse islets, INS-1 832/13 cells, or human islets were transduced with adenoviruses to increase either SENP1 or SUMO1 or were transfected with siRNA duplexes to knockdown SENP1. We examined insulin secretion, intracellular Ca2+ responses, induction of endoplasmic reticulum stress markers and inducible nitric oxide synthase (iNOS) expression, and apoptosis by TUNEL and caspase 3 cleavage. Surprisingly, upregulation of SENP1 reduces insulin secretion and impairs intracellular Ca2+ handling. This secretory dysfunction is due to SENP1-induced cell death. Indeed, the detrimental effect of SENP1 on secretory function is diminished when two mediators of β-cell death, iNOS and NF-κB, are pharmacologically inhibited. Conversely, enhanced SUMOylation protects against IL-1β-induced cell death. This is associated with reduced iNOS expression, cleavage of caspase 3, and nuclear translocation of NF-κB. Taken together, these findings identify SUMO1 as a novel antiapoptotic protein in islets and demonstrate that reduced viability accounts for impaired islet function following SENP1 up-regulation.

Tumor-induced apoptosis of T lymphocytes: elucidation of intracellular apoptotic events

Blood ◽  
2000 ◽  
Vol 95 (6) ◽  
pp. 2015-2023 ◽  
Author(s):  
Brian R. Gastman ◽  
Daniel E. Johnson ◽  
Theresa L. Whiteside ◽  
Hannah Rabinowich
Keyword(s):  
T Cells ◽  
Cell Death ◽  
T Cell ◽  
T Lymphocytes ◽  
Tumor Cells ◽  
Caspase 3 ◽  
Jurkat Cells ◽  
Caspase 8 ◽  
Induced Apoptosis ◽  
Fluoromethyl Ketone

Abstract Our recent studies suggest that human squamous cell carcinoma of the head and neck (SCCHN) is capable of activating an intrinsic mechanism of programmed-cell death in interacting lymphocytes in situ and in vitro. The current study used Jurkat T-cell line as a model to investigate intracellular apoptotic events in T cells interacting with SCCHN. Apoptosis induced in T lymphocytes by tumor cells was in part Fas-mediated, since it was partially, but significantly, inhibited in the presence of anti-Fas ligand Ab or in Fas-resistant Jurkat cells. The synthetic caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) and N-benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-FMK), effectively blocked apoptosis of Jurkat cells co-incubated with SCCHN cell lines, suggesting the involvement of caspases in tumor-induced apoptosis of lymphocytes. Overexpression of CrmA, an inhibitor of caspase-1 and caspase-8, partially inhibited tumor-induced T-cell death. Caspase-8 and caspase-3 were identified as effector molecules in the execution of tumor-induced T-cell death, since the proform enzymes were processed into active subunits during co-incubation of T cells with tumor cells. Furthermore, co-incubation with tumor cells resulted in cleavage of poly(ADP-ribose) polymerase (PARP), a common caspase-3 substrate, and in cleavage of TcR-ζ chain, shown by us to be a T-cell specific caspase-3 substrate. Overexpression of Bcl-2 did not provide protection of T cells from SCCHN-induced DNA degradation. Instead, the Bcl-2 protein was cleaved in the target T cells during their co-incubation with tumor cells. These findings demonstrate that tumor cells can trigger in T lymphocytes caspase-dependent apoptotic cascades, which are not effectively protected by Bcl-2.

scholarly journals Pneumolysin Causes Neuronal Cell Death through Mitochondrial Damage

2007 ◽  
Vol 75 (9) ◽  
pp. 4245-4254 ◽  
Author(s):  
Johann S. Braun ◽  
Olaf Hoffmann ◽  
Miriam Schickhaus ◽  
Dorette Freyer ◽  
Emilie Dagand ◽  
...  
Keyword(s):  
Cell Death ◽  
Caspase 3 ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Mitochondrial Damage ◽  
Cell Death Pathways ◽  
Apoptosis Protein ◽  
Mitochondrial Toxin ◽  
Induced Apoptosis ◽  
Apoptosis Inducing Factor

ABSTRACT Bacterial toxins such as pneumolysin are key mediators of cytotoxicity in infections. Pneumolysin is a pore-forming toxin released by Streptococcus pneumoniae, the major cause of bacterial meningitis. We found that pneumolysin is the pneumococcal factor that accounts for the cell death pathways induced by live bacteria in primary neurons. The pore-forming activity of pneumolysin is essential for the induction of mitochondrial damage and apoptosis. Pneumolysin colocalized with mitochondrial membranes, altered the mitochondrial membrane potential, and caused the release of apoptosis-inducing factor and cell death. Pneumolysin induced neuronal apoptosis without activating caspase-1, -3, or -8. Wild-type pneumococci also induced apoptosis without activation of caspase-3, whereas pneumolysin-negative pneumococci activated caspase-3 through the release of bacterial hydrogen peroxide. Pneumolysin caused upregulation of X-chromosome-linked inhibitor of apoptosis protein and inhibited staurosporine-induced caspase activation, suggesting the presence of actively suppressive mechanisms on caspases. In conclusion, our results indicate additional functions of pneumolysin as a mitochondrial toxin and as a determinant of caspase-independent apoptosis. Considering this, blocking of pneumolysin may be a promising cytoprotective strategy in pneumococcal meningitis and other infections.

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