Apoptotic cell death in rat lung following mustard gas inhalation

To investigate apoptosis as a mechanism of sulfur mustard (SM) inhalation injury in animals, we studied different caspases (caspase-8, -9, -3, and -6) in the lungs from a ventilated rat SM aerosol inhalation model. SM activated all four caspases in cells obtained from bronchoalveolar lavage fluid (BALF) as early as 6 h after exposure. Caspase-8, which is known to initiate the extrinsic Fas-mediated pathway of apoptosis, was increased fivefold between 6 and 24 h, decreasing to the unexposed-control level at 48 h. The initiator, caspase-9, in the intrinsic mitochondrial pathway of apoptosis as well as the executioner caspases, caspase-3 and -6, all peaked ( P < 0.01) at 24 h; caspase-3 and -6 remained elevated, but caspase-9 decreased to unexposed-control level at 48 h. To study further the Fas pathway, we examined soluble as well as membrane-bound Fas ligand (sFas-L and mFas-L, respectively) and Fas receptor (Fas-R) in both BALF cells and BALF. At 24 h after SM exposure, sFas-L increased significantly in both BALF cells ( P < 0.01) and BALF ( P < 0.05). However, mFas-L increased only in BALF cells between 24 and 48 h ( P < 0.1 and P < 0.001, respectively). Fas-R increased only in BALF cells by 6 h ( P < 0.01) after SM exposure. Apoptosis in SM-inhaled rat lung specimens was also confirmed by both immunohistochemical staining using cleaved caspase-3 and -9 antibodies and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining as early as 6 h in the proximal trachea and bronchi, but not before 48 h in distal airways. These findings suggest pathogenic mechanisms at the cellular and molecular levels and logical therapeutic target(s) for SM inhalation injury in animals.

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Nrf2 Inhibits Periodontal Ligament Stem Cell Apoptosis under Excessive Oxidative Stress

10.20944/preprints201704.0016.v1 ◽

2017 ◽

Author(s):

Yanli Liu ◽

Hongxu Yang ◽

Yinhua Zhao ◽

Min Zhang ◽

Yongjin Chen

Keyword(s):

Oxidative Stress ◽

Periodontal Ligament ◽

Caspase 3 ◽

Oxidative Enzymes ◽

Tunel Staining ◽

Caspase 8 ◽

Caspase 9 ◽

Periodontal Ligament Stem Cells ◽

H2o2 Treatment ◽

Periodontal Ligament Stem Cell

The present study aimed to analyze novel mechanisms underlying Nrf2-mediated anti-apoptosis in periodontal ligament stem cells (PDLSCs) in the periodontitis oxidative microenvironment. We created an oxidative stress model with H2O2-treated PDLSCs. Herein, we used real-time PCR, western blotting, TUNEL staining, fluorogenic assay and transfer genetics to confirm the degree of oxidative stress and apoptosis as well as the Nrf2 function. Surprisingly, we demonstrated that with up-regulated ROS and MDA levels, the effect of oxidative stress was obvious under H2O2 treatment. Anti-oxidative molecules were changed after the H2O2 exposure, whereby the anti-oxidative signaling of Nrf2 was activated with the increase of its downstream effectors, HO-1, NQO1 and γ-GCS. Additionally, the apoptosis levels gradually increased with oxidative stress and changes in the caspase-9, caspase-3, Bax and c-Fos levels, but not with caspase-8 and down-regulated Bcl-2. The enhanced antioxidant effect could not resist the occurrence of apoptosis. Furthermore, Nrf2 overexpression effectively improved the anti-oxidative levels and increased cell proliferation. At the same time, overexpression effectively restrained TUNEL staining and decreased the molecular levels of caspase-9, caspase-3, et al, but not that of caspase-8. By contrast, silencing the expression Nrf2 levels had the opposite effect. Collectively, Nrf2 alleviates PDLSCs via its effects on anti-oxidative and anti-intrinsic apoptosis by the activation of anti-oxidative enzymes.

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Suppression of Fas-Mediated Signaling Pathway is Involved in Zinc Inhibition of Ethanol-Induced Liver Apoptosis

Experimental Biology and Medicine ◽

10.1177/153537020322800411 ◽

2003 ◽

Vol 228 (4) ◽

pp. 406-412 ◽

Cited By ~ 29

Author(s):

Jason C. Lambert ◽

Zhanxiang Zhou ◽

Y. James Kang

Keyword(s):

Electron Microscopy ◽

Caspase 3 ◽

Fas Ligand ◽

Morphological Changes ◽

Alcohol Exposure ◽

Terminal Deoxynucleotidyl Transferase ◽

Caspase 8 ◽

Intragastric Administration ◽

Induced Apoptosis ◽

Zinc Inhibition

Apoptosis is critically involved in hepatic pathogenesis induced by acute alcohol exposure. This study was undertaken to test the hypothesis that zinc interferes with an important Fas ligand-mediated pathway in the liver, leading to the inhibition of ethanol-induced apoptosis. Male 129/SvPCJ mice were injected subcutaneously with ZnSO4 (5 mg of Zn ion/kg) in 12-hr intervals for 24 hr before intragastric administration of ethanol (5 g/kg) in 12-hr intervals for 36 hr. Ethanol-induced apoptosis in the liver was detected by a terminal deoxynucleotidyl transferase nick-end labeling assay and was further confirmed by electron microscopy. The number of apoptotic cells in the livers pretreated with zinc was significantly decreased, being only 15% of that found in the animals treated with ethanol only. Characteristic apoptotic morphological changes observed by electron microscopy were also inhibited by zinc. Importantly, zinc inhibited ethanol-induced activation of caspase-3, the primary executioner protease responsible for alcohol-induced liver apoptosis, and caspase-8 as determined by enzymatic assay. Immunohistochemical analysis revealed that zinc inhibited ethanol-induced endogenous Fas ligand activation, which is a key component in signaling pathways leading to hepatic caspase-8 and subsequent caspase-3 activation and apoptosis. These results demonstrate that zinc is a potent inhibitor of acute ethanol-induced liver apoptosis, and this effect occurs primarily through zinc interference with Fas ligand pathway and the suppression of caspase-3.

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Increased cell death in osteopontin-deficient cardiac fibroblasts occurs by a caspase-3-independent pathway

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00098.2004 ◽

2004 ◽

Vol 287 (4) ◽

pp. H1730-H1739 ◽

Cited By ~ 37

Author(s):

Ron Zohar ◽

Baoqian Zhu ◽

Peter Liu ◽

Jaro Sodek ◽

C. A. McCulloch

Keyword(s):

Cell Death ◽

Caspase 3 ◽

Cardiac Fibroblasts ◽

Chromatin Condensation ◽

Terminal Deoxynucleotidyl Transferase ◽

Tunel Staining ◽

Wild Type ◽

Nuclear Fragmentation ◽

A Cell

Reperfusion-induced oxidative injury to the myocardium promotes activation and proliferation of cardiac fibroblasts and repair by scar formation. Osteopontin (OPN) is a proinflammatory cytokine that is upregulated after reperfusion. To determine whether OPN enhances fibroblast survival after exposure to oxidants, cardiac fibroblasts from wild-type (WT) or OPN-null (OPN−/−) mice were treated in vitro with H2O2to model reperfusion injury. Within 1 h, membrane permeability to propidium iodide (PI) was increased from 5 to 60% in OPN−/−cells but was increased to only 20% in WT cells. In contrast, after 1–8 h of treatment with H2O2, the percent of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-stained cells was more than twofold higher in WT than OPN−/−cells. Electron microscopy of WT cells treated with H2O2showed chromatin condensation, nuclear fragmentation, and cytoplasmic and nuclear shrinkage, which are consistent with apoptosis. In contrast, H2O2-treated OPN−/−cardiac fibroblasts exhibited cell and nuclear swelling and membrane disruption that are indicative of cell necrosis. Treatment of OPN−/−and WT cells with a cell-permeable caspase-3 inhibitor reduced the percentage of TUNEL staining by more than fourfold in WT cells but decreased staining in OPN−/−cells by ∼30%. Although the percentage of PI-permeable WT cells was reduced threefold, the percent of PI-permeable OPN−/−cells was not altered. Restoration of OPN expression in OPN−/−fibroblasts reduced the percentage of PI-permeable cells but not TUNEL staining after H2O2treatment. Thus H2O2-induced cell death in OPN-deficient cardiac fibroblasts is mediated by a caspase-3-independent, necrotic pathway. We suggest that the increased expression of OPN in the myocardium after reperfusion may promote fibrosis by protecting cardiac fibroblasts from cell death.

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Inclusion Complex of Zerumbone with Hydroxypropyl-β-Cyclodextrin Induces Apoptosis in Liver Hepatocellular HepG2 Cells via Caspase 8/BID Cleavage Switch and Modulating Bcl2/Bax Ratio

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2013/810632 ◽

2013 ◽

Vol 2013 ◽

pp. 1-16 ◽

Cited By ~ 13

Author(s):

Nabilah Muhammad Nadzri ◽

Ahmad Bustamam Abdul ◽

Mohd Aspollah Sukari ◽

Siddig Ibrahim Abdelwahab ◽

Eltayeb E. M. Eid ◽

...

Keyword(s):

Inclusion Complex ◽

Mitochondrial Membrane ◽

Morphological Study ◽

Caspase 3 ◽

Anticancer Agent ◽

Caspase 8 ◽

Caspase 9 ◽

Solubility In Water ◽

Anticancer Effects ◽

First Time

Zerumbone (ZER) isolated fromZingiber zerumbetwas previously encapsulated with hydroxypropyl-β-cyclodextrin (HPβCD) to enhance ZER’s solubility in water, thus making it highly tolerable in the human body. The anticancer effects of this new ZER-HPβCD inclusion complex via apoptosis cell death were assessed in this study for the first time in liver hepatocellular cells, HepG2. Apoptosis was ascertained by morphological study, nuclear stain, and sub-G1 cell population accumulation with G2/M arrest. Further investigations showed the release of cytochrome c and loss of mitochondrial membrane potential, proving mitochondrial dysfunction upon the ZER-HPβCD treatment as well as modulating proapoptotic and anti-apototic Bcl-2 family members. A significant increase in caspase 3/7, caspase 9, and caspase 8 was detected with the depletion of BID cleaved by caspase 8. Collectively, these results prove that a highly soluble inclusion complex of ZER-HPβCD could be a promising anticancer agent for the treatment of hepatocellular carcinoma in humans.

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The Antioxidant, Anti-Inflammatory and Anti-Apoptotic Activities of the Bauhinia Championii Flavone are Connected with Protection Against Myocardial Ischemia/Reperfusion Injury

Cellular Physiology and Biochemistry ◽

10.1159/000443080 ◽

2016 ◽

Vol 38 (4) ◽

pp. 1365-1375 ◽

Cited By ~ 15

Author(s):

Jie Jian ◽

Feifei Xuan ◽

Feizhang Qin ◽

Renbin Huang

Keyword(s):

Myocardial Ischemia ◽

Caspase 3 ◽

Ischemia Reperfusion Injury ◽

Myocardial Infarct ◽

Ischemia Reperfusion ◽

Terminal Deoxynucleotidyl Transferase ◽

Enzyme Linked Immunosorbent Assay ◽

Tunel Staining ◽

Myocardial Infarct Size ◽

Myocardial Ischemia Reperfusion

Background/Aims: Previous studies have demonstrated that Bauhinia championii flavone (BCF) exhibits anti-oxidative, anti-hypoxic and anti-stress properties. This study was designed to investigate whether BCF has a cardioprotective effect against myocardial ischemia/reperfusion (I/R) injuries in rats and to shed light on its possible mechanism. Methods: The model of I/R was established by ligating the left anterior descending coronary artery for 30 min, then reperfusing for 180 min. Hemodynamic changes were continuously monitored. The content of malondialdehyde (MDA) as well as the lactate dehydrogenase (LDH), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were assessed. The release of interleukin-6 (IL-6) was measured by enzyme-linked immunosorbent assay (ELISA). Apoptosis of cardiomyocytes was determined by caspase-3 activity and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The expression of TLR4, NF-κBp65, Bcl-2 and Bax were detected by western blotting. Results: Pretreatment with BCF significantly reduced the serum levels of LDH, MDA and IL-6, but increased the activities of SOD and GSH-Px. It also attenuated myocardial infarct size, reduced the apoptosis rate and preserved cardiac function. Furthermore, BCF inhibited caspase-3 activity and the expression of TLR4, phosphorylated NF-κBp65 and Bax, but enhanced the expression of Bcl-2. Conclusion: These results provide substantial evidence that BCF exerts a protective effect on myocardial I/R injury, which may be attributed to attenuating lipid peroxidation, the inflammatory response and apoptosis.

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Protective Effects of Shenfuyixin Granule on H2O2-Induced Apoptosis in Neonatal Rat Cardiomyocytes

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2021/6654457 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Xinlu Wang ◽

Xuanxuan Hao ◽

Youping Wang ◽

Bin Li ◽

Lin Cui ◽

...

Keyword(s):

Membrane Potential ◽

Caspase 3 ◽

Neonatal Rat ◽

Caspase 8 ◽

Caspase 9 ◽

Rat Cardiomyocytes ◽

Expression Levels ◽

Apoptosis Rate ◽

Neonatal Rat Cardiomyocytes ◽

Mitochondrion Membrane Potential

Shenfuyixin granule (SFYXG, i.e., Xinshuaikang granule) is a prescription, commonly used in the clinical experience, which plays a significant role in the treatment of heart failure. The purpose of this present research was to investigate the protective effect of SFYXG, and the mechanism about anti-H2O2-induced oxidative stress and apoptosis in the neonatal rat cardiomyocytes. Myocardial cells, as is well known, were divided into 4 groups: normal, model, SFYXG, and coenzyme Q10 group, respectively. Cells viability was determined by MTT assay. Flow cytometry and AO/EB staining were implemented to test the apoptosis rate and intracellular reactive oxygen species (ROS) level. Mitochondrion membrane potential (MMP) was evaluated by JC-1 fluorescence probe method. The myocardial ultrastructure of mitochondrion was measured by electron microscope. The related mRNA expression levels of Bax, Bcl-2, Caspase-3, caspase-8, and caspase-9 were detected by real-time polymerase chain reaction (PCR). Also, the expression levels of Bax and Bcl-2 protein were detected by Western blot, and the expression levels of caspase-3, caspase-8, and caspase-9 protein were tested by caspase-Glo®3 Assay, caspase-Glo®8 Assay, and caspase-Glo®9 Assay, respectively. GAPDH was used as the internal reference gene/protein. The results revealed that SFYXG (0.5 mg/ml) raised the viability of myocardial cell, weakened the apoptosis rate and ROS level, corrected the mitochondrion membrane potential stability, and improved cell morphology and ultrastructure of myocardial mitochondrion. Furthermore, SFYXG upregulated the antiapoptosis gene of Bcl-2, but downregulated the proapoptosis genes of Bax, caspase-3, and caspase-9. In conclusion, SFYXG could appear to attenuate myocardial injury by its antioxidative and antiapoptosis effect.

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Antiproliferative and Apoptotic Effects of Red Beetroot and Betanin on Human Colorectal Cancer Cell Lines

10.21203/rs.3.rs-955140/v1 ◽

2021 ◽

Author(s):

Amir Saber ◽

Nasim Abedimanesh ◽

Mohammad-Hossein Somi ◽

Ahmad Yari Khosroushahi

Keyword(s):

Colorectal Cancer ◽

Cell Lines ◽

Caspase 3 ◽

Caspase 8 ◽

Alcoholic Extract ◽

Caspase 9 ◽

Dapi Staining ◽

Normal Cells ◽

Colorectal Cancer Cell Lines ◽

Ht 29

Abstract Background: Colorectal cancer (CRC) is the third most common type of cancer worldwide. Fruit and vegetables have some active compounds such as flavonoids and polyphenols that protect against malignancies through their antioxidative, anti-inflammatory, anti-proliferative, neuro, and hepatoprotective properties. Red beetroot (Beta vulgaris) contains red (betacyanins) and yellow (betaxanthins) pigments known as betalains. Betanin makes up 75-95% of the total betacyanins, possessed a wide range of favorable biological effects such as chemopreventive, anticarcinogenic, anti-tumorogenic, antiangiogenic, and proapoptotic effects. Methods: Red beetroot hydro-alcoholic extract and betanin were used to treat Caco-2 and HT-29 colorectal cancer cells, as well as KDR/293 normal epithelial cells. The half-maximal inhibitory concentration (IC50) was determined by prescreening MTT tests in the range of 20 to 140 µg/ml at 24 and 48 h. The cytotoxicity and apoptosis-inducing evaluations were performed via MTT assay, DAPI staining, and FACS-flow cytometry tests using determined times and doses. Moreover, the expression level of six important genes involving in the apoptosis pathway (Bcl-2, BAD, Caspase-3, Caspase-8, Caspase-9, and Fas-R) were determined using the real-time polymerase chain reaction (RT-PCR) method.Results: The IC50 doses for HT-29 and Caco-2 cell lines were determined to be about 92 μg/mL, 107 μg/mL for beetroot hydro-alcoholic extract, and 64 μg/mL, 90 μg/mL for betanin at 48 h, respectively. Our findings showed that beetroot extract and betanin significantly inhibit the growth of HT-29 and Caco-2 cell lines, time and dose-dependently, without considerable adverse effects on KDR/293 normal cells. Moreover, DAPI staining and flow cytometry results revealed significant apoptosis symptoms in treated cancerous cell lines. The expression level of pro-apoptotic genes involved in intrinsic and extrinsic apoptosis pathways (BAD, Caspase-3, Caspase-8, Caspase-9, and Fas-R) in treated HT-29 and Caco-2 cells was higher than untreated and normal cells, whereas the anti-apoptotic gene (Bcl-2) was downregulated. Conclusion: Beetroot hydro-alcoholic extract and betanin significantly inhibited cell proliferation and induced cell apoptosis (intrinsic and extrinsic pathways) via modification of effective genes in both colorectal cancer cell lines with no significant cytotoxic effects on KDR/293 normal cells. The mechanism of the anticancer effects of red beetroot extract and betanin needs to be further studied.

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p53-Dependent Apoptosis in the Inhibition of Spermatogonial Differentiation in Juvenile Spermatogonial Depletion (Utp14bjsd) Mice

Endocrinology ◽

10.1210/en.2007-1338 ◽

2008 ◽

Vol 149 (6) ◽

pp. 2773-2781 ◽

Cited By ~ 13

Author(s):

Gunapala Shetty ◽

Shan H. Shao ◽

Connie C. Y. Weng

Keyword(s):

Double Mutant ◽

Fas Ligand ◽

Type A ◽

Terminal Deoxynucleotidyl Transferase ◽

Seminiferous Tubules ◽

Caspase 9 ◽

Apoptotic Pathway ◽

Independent Process ◽

Old Mice ◽

Type A Spermatogonia

In adult male mice homozygous for the juvenile spermatogonial depletion (Utp14bjsd) mutation in the Utp14b gene, type A spermatogonia proliferate, but in the presence of testosterone and at scrotal temperatures, these spermatogonia undergo apoptosis just before differentiation. In an attempt to delineate this apoptotic pathway in jsd mice and specifically address the roles of p53- and Fas ligand (FasL) /Fas receptor-mediated apoptosis, we produced jsd mice deficient in p53, Fas, or FasL. Already at the age of 5 wk, less degeneration of spermatogenesis was observed in p53-null-jsd mice than jsd single mutants, and in 8- or 12-wk-old mice, the percentage of seminiferous tubules showing differentiated germ cells [tubule differentiation index (TDI)] was 26–29% in the p53-null-jsd mice, compared with 2–4% in jsd mutants with normal p53. The TDI in jsd mice heterozygous for p53 showed an intermediate TDI of 8–13%. The increase in the differentiated tubules in double-mutant and p53 heterozygous jsd mice was mostly attributable to intermediate and type B spermatogonia; few spermatocytes were present. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining showed that most of these differentiated spermatogonia still underwent apoptosis, thereby blocking further continuation of spermatogenesis. In contrast, the percentage of tubules that were differentiated was not significantly altered in either adult Fas null-jsd mice or adult FasL defective gld-jsd double mutant mice as compared with jsd single mutants. Furthermore, caspase-9, but not caspase-8 was immunochemically localized in the adult jsd mice spermatogonia undergoing apoptosis. The results show that p53, but not FasL or Fas, is involved in the apoptosis of type A spermatogonia before/during differentiation in jsd mice that involves the intrinsic pathway of apoptosis. However, apoptosis in the later stages must be a p53-independent process.

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JS-K, a Novel Nitric Oxide (NO) Generator, Induces Cytochrome c Release and Caspase Activation in HL-60 Myeloid Leukemia Cells.

Blood ◽

10.1182/blood.v104.11.3415.3415 ◽

2004 ◽

Vol 104 (11) ◽

pp. 3415-3415

Author(s):

Paul J. Shami ◽

Vidya Udupi ◽

Margaret Yu ◽

Swati Malaviya ◽

Joseph E. Saavedra ◽

...

Keyword(s):

Cytochrome C ◽

Caspase 3 ◽

Myelogenous Leukemia ◽

Leukemia Cells ◽

Caspase 8 ◽

Caspase 9 ◽

Cytochrome C Release ◽

Dose Dependent Fashion ◽

Acute Myelogenous ◽

Dose Dependent

Abstract NO induces differentiation and apoptosis in Acute Myelogenous Leukemia (AML) cells. Glutathione S-Transferases (GST) play an important role in multidrug resistance and are upregulated in 90% of AML cells. We have designed a novel prodrug class that releases NO on metabolism by GST. O2-(2,4-Dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K, a member of this class) has potent antileukemic activity. We have previously shown that JS-K induces apoptosis in HL-60 cells by a caspase dependent mechanism (Molecular Cancer Therapeutics2:409-417,2003). The purpose of this study was to determine the pathway through which JS-K induces apoptosis. Western blot analysis showed that treatment of HL-60 cells with JS-K (0 – 1 μM) for 6 hours results in release of Cytochrome c from mitochondria in a dose dependent fashion. Treatment with JS-K resulted in a dose dependent activation of Caspase 9. Sixteen and 24 hours after exposure to 1 μM JS-K, Caspase 9 activity was induced by 393 ± 93% and 237 ± 13% of control, respectively (p = 0.03 at the 24 hours time point). Treatment with JS-K resulted in a dose dependent activation of Caspase 3. Twenty four hours after exposure to 1 μM JS-K, Caspase 3 activity was 208 ± 3.4 % of control (p = 0.02). Treatment with JS-K also resulted in a dose dependent activation of Caspase 8, but to a lesser extent than Caspase 9 and 3. Twenty four hours after exposure to 1 μM JS-K, Caspase 8 activity was 144 ± 5.3 % of control (p = 0.04). We conclude that JS-K activates the intrinsic pathway of apoptosis in leukemia cells by inducing the release of Cytochrome c from mitochondria. (NO1-CO-12400).

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

Blood ◽

10.1182/blood.v116.21.2177.2177 ◽

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.

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