Role of RIPK1 in SMAC mimetics-induced apoptosis in primary human HIV-infected macrophages

AbstractMacrophages serve as viral reservoirs due to their resistance to apoptosis and HIV-cytopathic effects. We have previously shown that inhibitor of apoptosis proteins (IAPs) confer resistance to HIV-Vpr-induced apoptosis in normal macrophages. Herein, we show that second mitochondrial activator of caspases (SMAC) mimetics (SM) induce apoptosis of monocyte-derived macrophages (MDMs) infected in vitro with a R5-tropic laboratory strain expressing heat stable antigen, chronically infected U1 cells, and ex-vivo derived MDMs from HIV-infected individuals. To understand the mechanism governing SM-induced cell death, we show that SM-induced cell death of primary HIV-infected macrophages was independent of the acquisition of M1 phenotype following HIV infection of macrophages. Instead, SM-induced cell death was found to be mediated by IAPs as downregulation of IAPs by siRNAs induced cell death of HIV-infected macrophages. Moreover, HIV infection caused receptor interacting protein kinase-1 (RIPK1) degradation which in concert with IAP1/2 downregulation following SM treatment may result in apoptosis of macrophages. Altogether, our results show that SM selectively induce apoptosis in primary human macrophages infected in vitro with HIV possibly through RIPK1. Moreover, modulation of the IAP pathways may be a potential strategy for selective killing of HIV-infected macrophages in vivo.

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Inhibitor of apoptosis, IAP, genes play a critical role in the survival of HIV-infected macrophages

10.1101/543017 ◽

2019 ◽

Author(s):

Ashok Kumar ◽

Ramon Edwin Hernandez Caballero ◽

Simon Xin Min Dong ◽

Niranjala Gajanayaka ◽

Hamza Ali ◽

...

Keyword(s):

Ex Vivo ◽

Critical Role ◽

Laboratory Strain ◽

Inhibitor Of Apoptosis ◽

Viral Reservoirs ◽

Interacting Protein ◽

Heat Stable Antigen ◽

Induced Apoptosis

Latent viral reservoirs of HIV-1 that persist despite antiretroviral therapy (ART) are major barriers for a successful cure. Macrophages serve as viral reservoirs due to their resistance to apoptosis and HIV-cytopathic effects. We have previously shown that inhibitor of apoptosis proteins (IAPs) confer resistance to HIV-Vpr-induced apoptosis in normal macrophages. Herein, we show that second mitochondrial activator of caspases (SMAC)-mimetics (SM) specifically induce apoptosis of monocyte-derived macrophages (MDMs) infected in vitro with a R5-tropic laboratory strain expressing heat stable antigen, and GFP-expressing HIV, chronically infected U1 cells, and ex-vivo derived MDMs from naïve and ART-treated HIV patients. SM-induced cell death was found to be mediated by IAPs using IAP siRNAs, was independent of endogenously produced TNFα and was attributed to the concomitant downregulation of IAP-1/2 and the receptor interacting protein kinase-1 degradation following HIV infection. Altogether, modulation of the IAP pathways may be a potential strategy for selective killing of HIV-infected macrophages in vivo.

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iPLA2β Contributes to ER Stress-Induced Apoptosis during Myocardial Ischemia/Reperfusion Injury

Cells ◽

10.3390/cells10061446 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1446

Author(s):

Tingting Jin ◽

Jun Lin ◽

Yingchao Gong ◽

Xukun Bi ◽

Shasha Hu ◽

...

Keyword(s):

Cell Death ◽

Heart Disease ◽

Myocardial Ischemia ◽

Ischemic Heart Disease ◽

Er Stress ◽

Ischemia Reperfusion ◽

Myocardial Ischemia Reperfusion ◽

Induced Apoptosis

Both calcium-independent phospholipase A2 beta (iPLA2β) and endoplasmic reticulum (ER) stress regulate important pathophysiological processes including inflammation, calcium homeostasis and apoptosis. However, their roles in ischemic heart disease are poorly understood. Here, we show that the expression of iPLA2β is increased during myocardial ischemia/reperfusion (I/R) injury, concomitant with the induction of ER stress and the upregulation of cell death. We further show that the levels of iPLA2β in serum collected from acute myocardial infarction (AMI) patients and in samples collected from both in vivo and in vitro I/R injury models are significantly elevated. Further, iPLA2β knockout mice and siRNA mediated iPLA2β knockdown are employed to evaluate the ER stress and cell apoptosis during I/R injury. Additionally, cell surface protein biotinylation and immunofluorescence assays are used to trace and locate iPLA2β. Our data demonstrate the increase of iPLA2β augments ER stress and enhances cardiomyocyte apoptosis during I/R injury in vitro and in vivo. Inhibition of iPLA2β ameliorates ER stress and decreases cell death. Mechanistically, iPLA2β promotes ER stress and apoptosis by translocating to ER upon myocardial I/R injury. Together, our study suggests iPLA2β contributes to ER stress-induced apoptosis during myocardial I/R injury, which may serve as a potential therapeutic target against ischemic heart disease.

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SMAC mimetics induce autophagy-dependent apoptosis of HIV-1-infected macrophages

Cell Death and Disease ◽

10.1038/s41419-020-02761-x ◽

2020 ◽

Vol 11 (7) ◽

Cited By ~ 1

Author(s):

Grant R. Campbell ◽

Rachel K. To ◽

Gang Zhang ◽

Stephen A. Spector

Keyword(s):

Cell Death ◽

Hiv Infection ◽

Cell Survival ◽

Acute Hiv Infection ◽

Interacting Protein ◽

Signaling Complex ◽

Hiv Eradication ◽

Smac Mimetics ◽

Smac Mimetic ◽

Latent Hiv

Abstract Human immunodeficiency type 1 (HIV)-infected macrophages (HIV-Mφ) are a reservoir for latent HIV infection and a barrier to HIV eradication. In contrast to CD4+ T cells, HIV-Mφ are resistant to the cytopathic effects of acute HIV infection and have increased expression of cell survival factors, including X-linked inhibitor of apoptosis (XIAP), baculoviral IAP repeat containing (BIRC) 2/cIAP1, beclin-1, BCL2, BCL-xl, triggering receptor expressed on myeloid cells 1, mitofusin (MFN) 1, and MFN2. DIABLO/SMAC mimetics are therapeutic agents that affect cancer cell survival and induce cell death. We found that DIABLO/SMAC mimetics (LCL-161, AT-406 (also known as SM-406 or Debio 1143), and birinapant) selectively kill HIV-Mφ without increasing bystander cell death. DIABLO/SMAC mimetic treatment of HIV-Mφ-induced XIAP and BIRC2 degradation, leading to the induction of autophagy and the formation of a death-inducing signaling complex on phagophore membranes that includes both pro-apoptotic or necroptotic (FADD, receptor-interacting protein kinase (RIPK) 1, RIPK3, caspase 8, and MLKL) and autophagy (ATG5, ATG7, and SQSTM1) proteins. Genetic or pharmacologic inhibition of early stages of autophagy, but not late stages of autophagy, ablated this interaction and inhibited apoptosis. Furthermore, DIABLO/SMAC mimetic-mediated apoptosis of HIV-Mφ is dependent upon tumor necrosis factor signaling. Our findings thus demonstrate that DIABLO/SMAC mimetics selectively induce autophagy-dependent apoptosis in HIV-Mφ.

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A Novel High-Throughput Technique for Identifying Monoclonal Antibodies capable of Death Receptor Induced Apoptosis

Journal of Cell Death ◽

10.4137/jcd.s3660 ◽

2009 ◽

Vol 2 ◽

pp. JCD.S3660

Author(s):

Hang Fai Kwok ◽

Julie A. Gormley ◽

Christopher J. Scott ◽

James A. Johnston ◽

Shane A. Olwill

Keyword(s):

Cell Death ◽

High Throughput ◽

High Throughput Screening ◽

False Negative ◽

Death Receptor ◽

Annexin V ◽

Fas Receptor ◽

Induced Apoptosis

The study of death receptor family induced apoptosis has gained momentum in recent years with the knowledge that therapeutic antibodies targeting DR4 and DR5 (death receptor's 4 and 5) have proved efficacious in multiple clinical trials. The therapeutic rationale is based on targeting and amplifying a tumour tissues normal cell death programme (apoptosis). While advances in the targeting of DR4 and DR5 have been successful the search for an agonistic antibody to another family member, the Fas receptor, has proven more elusive. This is partly due to the differing in vitro and in vivo characteristics of individual antibodies. In order to induce Fas targeted cell death an antibody must be capable of binding to and trimerising the receptor. It has been shown that antibodies capable of performing this function in vivo, with the assistance of tumour associated cells, do not always induce apoptosis in vitro. As a result the use of current methodologies to detect functional antibodies in vitro may have dismissed potential therapeutic candidates ('false negative'). Here we report a novel high throughput screening technique which artificially cross-links antibodies bound to the Fas receptor. By combining this process with Annexin-V and Prodidium Iodide (PI) staining we can select for antibodies which have the potential to induce apoptosis in vivo.

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Expression and subcellular localization of BNIP3 in hypoxic hepatocytes and liver stress

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.90526.2008 ◽

2009 ◽

Vol 296 (3) ◽

pp. G499-G509 ◽

Cited By ~ 21

Author(s):

Mallikarjuna R. Metukuri ◽

Donna Beer-Stolz ◽

Rajaie A. Namas ◽

Rajeev Dhupar ◽

Andres Torres ◽

...

Keyword(s):

Cell Death ◽

Western Blot ◽

Blot Analysis ◽

Western Blot Analysis ◽

Ischemia Reperfusion ◽

Redox Stress ◽

No Donor ◽

Interacting Protein

We have previously demonstrated that the Bcl-2/adenovirus EIB 19-kDa interacting protein 3 (BNIP3), a cell death-related member of the Bcl-2 family, is upregulated in vitro and in vivo in both experimental and clinical settings of redox stress and that nitric oxide (NO) downregulates its expression. In this study we sought to examine the expression and localization of BNIP3 in murine hepatocytes and in a murine model of hemorrhagic shock (HS) and ischemia-reperfusion (I/R). Freshly isolated mouse hepatocytes were exposed to 1% hypoxia for 6 h followed by reoxygenation for 18 h, and protein was isolated for Western blot analysis. Hepatocytes grown on coverslips were fixed for localization studies. Similarly, livers from surgically cannulated C57Bl/6 mice and from mice cannulated and subjected to 1–4 h of HS were processed for protein isolation and Western blot analysis. In hepatocytes, BNIP3 was expressed constitutively but was upregulated under hypoxic conditions, and this upregulation was countered by treatment with a NO donor. Surprisingly, BNIP3 was localized in the nucleus of normoxic hepatocytes, in the cytoplasm following hypoxia, and again in the nucleus following reoxygenation. Upregulation of BNIP3 partially required p38 MAPK activation. BNIP3 contributed to hypoxic injury in hepatocytes, since this injury was diminished by knockdown of BNIP3 mRNA. Hepatic BNIP3 was also upregulated in two different models of liver stress in vivo, suggesting that a multitude of inflammatory stresses can lead to the modulation of BNIP3. In turn, the upregulation of BNIP3 appears to be one mechanism of hepatocyte cell death and liver damage in these settings.

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Bcl-2 overexpression in type II epithelial cells does not prevent hyperoxia-induced acute lung injury in mice

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00212.2009 ◽

2010 ◽

Vol 299 (3) ◽

pp. L312-L322 ◽

Cited By ~ 8

Author(s):

Isabelle Métrailler-Ruchonnet ◽

Alessandra Pagano ◽

Stéphanie Carnesecchi ◽

Karim Khatib ◽

Pedro Herrera ◽

...

Keyword(s):

Cell Death ◽

Epithelial Cells ◽

Lung Injury ◽

Ex Vivo ◽

Lung Damage ◽

Type Ii Cells ◽

Type Ii ◽

Lung Weight

Bcl-2 is an anti-apoptotic molecule preventing oxidative stress damage and cell death. We have previously shown that Bcl-2 is able to prevent hyperoxia-induced cell death when overexpressed in a murine fibrosarcoma cell line L929. We hypothesized that its specific overexpression in pulmonary epithelial type II cells could prevent hyperoxia-induced lung injury by protecting the epithelial side of the alveolo-capillary barrier. In the present work, we first showed that in vitro Bcl-2 can rescue murine pulmonary epithelial cells (MLE12) from oxygen-induced cell apoptosis, as shown by analysis of LDH release, annexin V/propidium staining, and caspase-3 activity. We then generated transgenic mice overexpressing specifically Bcl-2 in lung epithelial type II cells under surfactant protein C (SP-C) promoter (Tg-Bcl-2) and exposed them to hyperoxia. Bcl-2 did not hinder hyperoxia-induced mitochondria and DNA oxidative damage of type II cell in vivo. Accordingly, lung damage was identical in both Tg-Bcl-2 and littermate mice strains, as measured by lung weight, bronchoalveolar lavage, and protein content. Nevertheless, we observed a significant lower number of TUNEL-positive cells in type II cells isolated from Tg-Bcl-2 mice exposed to hyperoxia compared with cells isolated from littermate mice. In summary, these results show that although Bcl-2 overexpression is able to prevent hyperoxia-induced cell death at single cell level in vitro and ex vivo, it is not sufficient to prevent cell death of parenchymal cells and to protect the lung from acute damage in mice.

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DR5 Knockout Mice Are Compromised in Radiation-Induced Apoptosis

Molecular and Cellular Biology ◽

10.1128/mcb.25.5.2000-2013.2005 ◽

2005 ◽

Vol 25 (5) ◽

pp. 2000-2013 ◽

Cited By ~ 77

Author(s):

Niklas Finnberg ◽

Joshua J. Gruber ◽

Peiwen Fei ◽

Dorothea Rudolph ◽

Anka Bric ◽

...

Keyword(s):

Cell Death ◽

Null Mouse ◽

Organ Specific ◽

Radiation Induced ◽

Induced Apoptosis ◽

The Brain ◽

Necrosis Factor

ABSTRACT DR5 (also called TRAIL receptor 2 and KILLER) is an apoptosis-inducing membrane receptor for tumor necrosis factor-related apoptosis-inducing ligand (also called TRAIL and Apo2 ligand). DR5 is a transcriptional target of p53, and its overexpression induces cell death in vitro. However, the in vivo biology of DR5 has remained largely unexplored. To better understand the role of DR5 in development and in adult tissues, we have created a knockout mouse lacking DR5. This mouse is viable and develops normally with the exception of having an enlarged thymus. We show that DR5 is not expressed in developing embryos but is present in the decidua and chorion early in development. DR5-null mouse embryo fibroblasts expressing E1A are resistant to treatment with TRAIL, suggesting that DR5 may be the primary proapoptotic receptor for TRAIL in the mouse. When exposed to ionizing radiation, DR5-null tissues exhibit reduced amounts of apoptosis compared to wild-type thymus, spleen, Peyer's patches, and the white matter of the brain. In the ileum, colon, and stomach, DR5 deficiency was associated with a subtle phenotype of radiation-induced cell death. These results indicate that DR5 has a limited role during embryogenesis and early stages of development but plays an organ-specific role in the response to DNA-damaging stimuli.

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Glucocorticoid-Induced Osteocytic Cell Death in a Hypoxic Environment Is Associated with Necroptosis

BioChem ◽

10.3390/biochem1020009 ◽

2021 ◽

Vol 1 (2) ◽

pp. 98-106

Author(s):

Shusuke Ueda ◽

Toru Ichiseki ◽

Miyako Shimasaki ◽

Hiroaki Hirata ◽

Norio Kawahara ◽

...

Keyword(s):

Cell Death ◽

Western Blotting ◽

Immunofluorescent Staining ◽

Cell Necrosis ◽

Interacting Protein ◽

Hypoxia Group ◽

Femoral Head Osteonecrosis ◽

Stress Environment

Neither the underlying pathophysiology of nor prophylactic strategies for glucocorticoid-associated femoral head osteonecrosis have yet been established. In neurovascular and cardiac ischemic disorders, necroptosis has been reported as a new concept of cell death. Here we investigated the involvement of necroptosis in glucocorticoid-induced osteonecrosis in vitro, the putative cause of which is ischemia. Murine osteocytic cells (MLO-Y4) to which 1 µM dexamethasone (Dex) was added and were cultured in 1% O2 (hypoxia) are thought to resemble the in vivo environment in which glucocorticoid-induced osteonecrosis occurs (H-D stress environment). Using such cells cultured for 24 h (Dex(+)/hypoxia(+) group), immunofluorescent staining and Western blotting were performed with receptor-interacting protein (RIP) 1 and RIP3, which are necroptosis expression factors. In addition, the necroptosis inhibitor necrostatin-1 (Nec-1) was added to Dex(+)/hypoxia(+) and cultured for 12 h and 24 h. Then using an Apoptotic/Necrotic Cells Detection Kit the numbers of apoptotic and necrotic cells were counted and compared. In Dex(+)/hypoxia(+) group, expression of both RIP1 and RIP3 was found. Additionally, in Western blotting, the addition of Nec-1 attenuated their expression. A decrease in the number of cell deaths was also found following Nec-1 administration. Necroptosis has been implicated as a cause of death in osteocytic cell necrosis. Use of the necroptosis inhibitor, Nec-1, suggests a possible approach to preventing osteocytic cell necrosis even in an H-D stress environment when given within 12 h.

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mTOR inhibition by metformin impacts monosodium urate crystal–induced inflammation and cell death in gout: a prelude to a new add-on therapy?

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2018-214656 ◽

2019 ◽

Vol 78 (5) ◽

pp. 663-671 ◽

Cited By ~ 13

Author(s):

Nadia Vazirpanah ◽

Andrea Ottria ◽

Maarten van der Linden ◽

Catharina G K Wichers ◽

Mark Schuiveling ◽

...

Keyword(s):

Cell Death ◽

Immune Cells ◽

Metabolic Diseases ◽

Ex Vivo ◽

Mtor Pathway ◽

Monosodium Urate ◽

Mtor Inhibition ◽

Msu Crystals

ObjectiveGout is the most common inflammatory arthritis worldwide, and patients experience a heavy burden of cardiovascular and metabolic diseases. The inflammation is caused by the deposition of monosodium urate (MSU) crystals in tissues, especially in the joints, triggering immune cells to mount an inflammatory reaction. Recently, it was shown that MSU crystals can induce mechanistic target of rapamycin (mTOR) signalling in monocytes encountering these crystals in vitro. The mTOR pathway is strongly implicated in cardiovascular and metabolic disease. We hypothesised that inhibiting this pathway in gout might be a novel avenue of treatment in these patients, targeting both inflammation and comorbidities.Methods We used a translational approach starting from ex vivo to in vitro and back to in vivo.ResultsWe show that ex vivo immune cells from patients with gout exhibit higher expression of the mTOR pathway, which we can mimic in vitro by stimulating healthy immune cells (B lymphocytes, monocytes, T lymphocytes) with MSU crystals. Monocytes are the most prominent mTOR expressers. By using live imaging, we demonstrate that monocytes, on encountering MSU crystals, initiate cell death and release a wide array of proinflammatory cytokines. By inhibiting mTOR signalling with metformin or rapamycin, a reduction of cell death and release of inflammatory mediators was observed. Consistent with this, we show that patients with gout who are treated with the mTOR inhibitor metformin have a lower frequency of gout attacks.ConclusionsWe propose mTOR inhibition as a novel therapeutic target of interest in gout treatment.

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Abstract 1950: Role of Superoxide, Nitric Oxide and Peroxynitrite in Doxorubicin-induced Cell Death in vitro and in vivo

Circulation ◽

10.1161/circ.116.suppl_16.ii_420-a ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Partha Mukhopadhyay ◽

Mohanraj Rajesh ◽

Sandor Bátkai ◽

György Haskó ◽

Csaba Szabo ◽

...

Keyword(s):

Cell Death ◽

Caspase 3 ◽

Superoxide Generation ◽

Cytochrome C Release ◽

Mitochondrial Superoxide ◽

Induced Apoptosis ◽

Peroxynitrite Scavengers

Although doxorubicin (DOX) is one of the most potent antitumor agents available, its clinical use is limited because of the risk of severe cardiotoxicity often leading to irreversible congestive heart failure. Apoptotic cell death is a key component in DOX-induced cardiotoxicity, but its trigger(s) and mechanisms are poorly understood. Here, we explore the role of peroxynitrite (a reactive oxidant produced from the diffusion-controlled reaction between nitric oxide and superoxide anion) in DOX-induced cell death. Using a well-established in vivo mouse model of DOX-induced acute heart failure, we demonstrate marked increases in myocardial apoptosis (caspase-3 and 9 gene expression, caspase 3 activity, cytochrome-c release, and TUNEL), iNOS but not eNOS and nNOS expression, 3-nitrotyrosine formation and a decrease in myocardial contractility following DOX treatment. Pre-treatment of mice with peroxynitrite scavengers markedly attenuated DOX-induced myocardial cell death and dysfunction without affecting iNOS expression. DOX induced increased superoxide generation and nitrotyrosine formation in the mitochondria, dissipation of mitochondrial membrane potential, apoptosis (cytochrome-C release, annexin V staining, caspase activation, nuclear fragmentation), and disruption of actin cytoskeleton structure in cardiac-derived H9c2 cells. Selective iNOS inhibitors attenuated DOX-induced apoptosis, without affecting increased mitochondrial superoxide generation, whereas NO donors increased DOX-induced cell death in vitro . The peroxynitrite scavengers FeTMPyP and MnTMPyP markedly reduced both DOX- or peroxynitrite-induced nitrotyrosine formation and cell death in vitro , without affecting DOX-induced increased mitochondrial superoxide formation. Thus, peroxynitrite is a major trigger of DOX-induced apoptosis, and its effective neutralization can be of significant therapeutic benefit.

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