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Choo Z, Koh X, Wong MRE, Ashokan RM, Ali Ahamed NSB, Kang C, Kuick CH, Chang KTE, Larisch S, Loh AHP, Chen ZX. Targeted Degradation of XIAP is Sufficient and Specific to Induce Apoptosis in MYCN-overexpressing High-risk Neuroblastoma. CANCER RESEARCH COMMUNICATIONS 2023; 3:2386-2399. [PMID: 37874199 PMCID: PMC10681007 DOI: 10.1158/2767-9764.crc-23-0082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 07/22/2023] [Accepted: 10/16/2023] [Indexed: 10/25/2023]
Abstract
XIAP, the most potent mammalian inhibitor of apoptosis protein (IAP), critically restricts developmental culling of sympathetic neuronal progenitors, and is correspondingly overexpressed in most MYCN-amplified neuroblastoma tumors. Because apoptosis-related protein in the TGFβ signaling pathway (ARTS) is the only XIAP antagonist that directly binds and degrades XIAP, we evaluated the preclinical effectiveness and tolerability of XIAP antagonism as a novel targeting strategy for neuroblastoma. We found that antagonism of XIAP, but not other IAPs, triggered apoptotic death in neuroblastoma cells. XIAP silencing induced apoptosis while overexpression conferred protection from drug-induced apoptosis. From a screen of IAP inhibitors, first-in-class ARTS mimetic A4 was most effective against high-risk and high XIAP-expressing neuroblastoma cells, and least toxic toward normal liver- and bone marrow-derived cells, compared with pan-IAP antagonists. On target engagement assays and nuclear magnetic resonance spectroscopy, A4 was observed to degrade rather than inhibit XIAP, catalyzing rapid degradation of XIAP through the ubiquitin-proteasome pathway. In MYCN-amplified neuroblastoma patient-derived xenografts, A4 significantly prolonged survival as a single agent, and demonstrated synergism with standard-of-care agents to reduce their effective required doses 3- to 6-fold. Engagement and degradation of XIAP by ARTS mimetics is a novel targeting strategy for neuroblastoma that may be especially effective against MYCN-amplified disease with intrinsically high XIAP expression. First-in-class ARTS mimetic A4 demonstrates preclinical efficacy and warrants further development and study. SIGNIFICANCE XIAP degradation is sufficient to kill MYCN-amplified neuroblastoma which overexpresses and relies on XIAP as a brake against cell death, without affecting normal cells.
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Affiliation(s)
- Zhang'E Choo
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- NUS Centre for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Xiaoying Koh
- Experimental Drug Development Centre, A*STAR, Singapore
| | - Megan Rui En Wong
- VIVA-KKH Paediatric Brain and Solid Tumour Programme, Children's Blood and Cancer Centre, KK Women's and Children's Hospital, Singapore
| | - Ruth Minothini Ashokan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- NUS Centre for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Nurul Suhana Binte Ali Ahamed
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- NUS Centre for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - CongBao Kang
- Experimental Drug Development Centre, A*STAR, Singapore
| | - Chik Hong Kuick
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore
| | - Kenneth Tou En Chang
- VIVA-KKH Paediatric Brain and Solid Tumour Programme, Children's Blood and Cancer Centre, KK Women's and Children's Hospital, Singapore
- Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore
- Duke NUS Medical School, Singapore
| | - Sarit Larisch
- Cell Death and Cancer Research Laboratory, Department of Human Biology and Medical Sciences, University of Haifa, Haifa, Israel
| | - Amos Hong Pheng Loh
- VIVA-KKH Paediatric Brain and Solid Tumour Programme, Children's Blood and Cancer Centre, KK Women's and Children's Hospital, Singapore
- Duke NUS Medical School, Singapore
- Cell Death and Cancer Research Laboratory, Department of Human Biology and Medical Sciences, University of Haifa, Haifa, Israel
- Department of Paediatric Surgery, KK Women's and Children's Hospital, Singapore
| | - Zhi Xiong Chen
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- NUS Centre for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- VIVA-KKH Paediatric Brain and Solid Tumour Programme, Children's Blood and Cancer Centre, KK Women's and Children's Hospital, Singapore
- National University Cancer Institute, Singapore, National University Health System, Singapore
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2
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p53 is required for nuclear but not mitochondrial DNA damage-induced degeneration. Cell Death Dis 2021; 12:104. [PMID: 33473103 PMCID: PMC7817838 DOI: 10.1038/s41419-020-03373-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 12/18/2022]
Abstract
While the consequences of nuclear DNA damage have been well studied, the exact consequences of acute and selective mitochondrial DNA (mtDNA) damage are less understood. DNA damaging chemotherapeutic drugs are known to activate p53-dependent apoptosis in response to sustained nuclear DNA damage. While it is recognized that whole-cell exposure to these drugs also damages mtDNA, the specific contribution of mtDNA damage to cellular degeneration is less clear. To examine this, we induced selective mtDNA damage in neuronal axons using microfluidic chambers that allow for the spatial and fluidic isolation of neuronal cell bodies (containing nucleus and mitochondria) from the axons (containing mitochondria). Exposure of the DNA damaging drug cisplatin selectively to only the axons induced mtDNA damage in axonal mitochondria, without nuclear damage. We found that this resulted in the selective degeneration of only the targeted axons that were exposed to DNA damage, where ROS was induced but mitochondria were not permeabilized. mtDNA damage-induced axon degeneration was not mediated by any of the three known axon degeneration pathways: apoptosis, axon pruning, and Wallerian degeneration, as Bax-deficiency, or Casp3-deficiency, or Sarm1-deficiency failed to protect the degenerating axons. Strikingly, p53, which is essential for degeneration after nuclear DNA damage, was also not required for degeneration induced with mtDNA damage. This was most evident when the p53-deficient neurons were globally exposed to cisplatin. While the cell bodies of p53-deficient neurons were protected from degeneration in this context, the axons farthest from the cell bodies still underwent degeneration. These results highlight how whole cell exposure to DNA damage activates two pathways of degeneration; a faster, p53-dependent apoptotic degeneration that is triggered in the cell bodies with nuclear DNA damage, and a slower, p53-independent degeneration that is induced with mtDNA damage.
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Choo Z, Loh AHP, Chen ZX. Destined to Die: Apoptosis and Pediatric Cancers. Cancers (Basel) 2019; 11:cancers11111623. [PMID: 31652776 PMCID: PMC6893512 DOI: 10.3390/cancers11111623] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 10/20/2019] [Accepted: 10/22/2019] [Indexed: 01/10/2023] Open
Abstract
Apoptosis (programmed cell death) is a systematic and coordinated cellular process that occurs in physiological and pathophysiological conditions. Sidestepping or resisting apoptosis is a distinct characteristic of human cancers including childhood malignancies. This review dissects the apoptosis pathways implicated in pediatric tumors. Understanding these pathways not only unraveled key molecules that may serve as potential targets for drug discovery, but also molecular nodes that integrate with other signaling networks involved in processes such as development. This review presents current knowledge of the complex regulatory system that governs apoptosis with respect to other processes in pediatric cancers, so that fresh insights may be derived regarding treatment resistance or for more effective treatment options.
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Affiliation(s)
- Zhang'e Choo
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore.
| | - Amos Hong Pheng Loh
- VIVA-KKH Pediatric Brain and Solid Tumor Program, KK Women's and Children's Hospital, Singapore 229899, Singapore.
- Department of Pediatric Surgery, KK Women's and Children's Hospital, Singapore 229899, Singapore.
| | - Zhi Xiong Chen
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore.
- VIVA-KKH Pediatric Brain and Solid Tumor Program, KK Women's and Children's Hospital, Singapore 229899, Singapore.
- National University Cancer Institute, Singapore, Singapore 119074, Singapore.
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4
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Chen YJ, Liu YC, Liu YW, Lee YB, Huang HC, Chen YY, Shih YH, Lee YC, Cheng CF, Meng TC. Nitrite Protects Neurons Against Hypoxic Damage Through S-nitrosylation of Caspase-6. Antioxid Redox Signal 2019; 31:109-126. [PMID: 30417658 DOI: 10.1089/ars.2018.7522] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Aims: The coordination of neurons to execute brain functions requires plenty of oxygen. Thus, it is not surprising that the chronic hypoxia resulting from chronic obstructive pulmonary diseases (COPD) can cause neuronal damage. Injury in the cortex can give rise to anxiety and cognitive dysfunction. This study investigated what causes hypoxia-induced neuronal injury and what strategies might be used to protect neurons against such damage. Results: This study found that hypoxia in primary cortical neurons caused neurite retraction, a caspase-6-dependent process. The hypoxic stress activated caspase-6 within the neurite, leading to microtubule disassembly and neurite retraction. The effect of hypoxia on caspase-6 activation, microtubule disassembly, and neurite retraction was alleviated by nitrite treatment. The protective role of nitrite was further supported by the observation that the active-site Cys146 of caspase-6 was S-nitrosylated in hypoxic neuro-2a cells treated with nitrite. We further validated the beneficial effect of nitrite on neuronal function against hypoxic stress in vivo. Using the wild-type or Apo E-/- mice exposed to chronic hypoxia as a model, we demonstrated that supplementing drinking water with nitrite suppressed active caspase-6 in the cortex of the brain, concomitant with the prevention of hypoxia-induced anxiety in the animals. Innovation: These results are the first evidence of a new pathway for the activation of caspase-6 and the first to indicate that nitrite can protect neurons against chronic hypoxic insult. Conclusion: Our findings suggest that nitrite holds great potential for the treatment of diseases such as COPD associated with hypoxia-induced neuronal injury.
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Affiliation(s)
- Yen-Jung Chen
- 1 Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.,2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yun-Chung Liu
- 1 Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.,2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yu-Wen Liu
- 2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yu-Bin Lee
- 2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Hsin-Chieh Huang
- 2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yi-Yun Chen
- 2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | | | - Ying-Chu Lee
- 2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Ching-Feng Cheng
- 4 Department of Medical Research, Tzu Chi University, Hualien, Taiwan.,5 Department of Pediatrics, Tzu Chi General Hospital, Hualien, Taiwan.,6 Institutes of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Tzu-Ching Meng
- 1 Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.,2 Institutes of Biological Chemistry, Academia Sinica, Taipei, Taiwan
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5
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Kyriakou S, Mitsiogianni M, Mantso T, Cheung W, Todryk S, Veuger S, Pappa A, Tetard D, Panayiotidis MI. Anticancer activity of a novel methylated analogue of L-mimosine against an in vitro model of human malignant melanoma. Invest New Drugs 2019; 38:621-633. [PMID: 31240512 PMCID: PMC7211211 DOI: 10.1007/s10637-019-00809-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 06/05/2019] [Indexed: 12/18/2022]
Abstract
The anticancer activity of a series of novel synthesized, hydroxypyridone-based metal chelators (analogues of L-mimosine) was evaluated in an in vitro model of melanoma consisting of malignant melanoma (A375), non-melanoma epidermoid carcinoma (A431) and immortalized non-malignant keratinocyte (HaCaT) cells. More specifically, we have demonstrated that the L-enantiomer of a methylated analogue of L-mimosine (compound 22) can exert a potent anticancer effect in A375 cells when compared to either A431 or HaCaT cells. Moreover, we have demonstrated that this analogue has the ability to i) promote increased generation of reactive oxygen species (ROS), ii) activate both intrinsic and extrinsic apoptosis and iii) induce perturbations in cell cycle growth arrest. Our data highlights the potential of compound 22 to act as a promising therapeutic agent against an in vitro model of human malignant melanoma.
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Affiliation(s)
- Sotiris Kyriakou
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Melina Mitsiogianni
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Theodora Mantso
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - William Cheung
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Stephen Todryk
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Stephany Veuger
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Aglaia Pappa
- Department of Molecular Biology & Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - David Tetard
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
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6
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Geden MJ, Romero SE, Deshmukh M. Apoptosis versus axon pruning: Molecular intersection of two distinct pathways for axon degeneration. Neurosci Res 2018; 139:3-8. [PMID: 30452947 DOI: 10.1016/j.neures.2018.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 11/02/2018] [Accepted: 11/07/2018] [Indexed: 12/16/2022]
Abstract
Neurons are capable of degenerating their axons for the physiological clearance and refinement of unnecessary connections via the programmed degenerative pathways of apoptosis and axon pruning. While both pathways mediate axon degeneration they are however distinct. Whereas in apoptosis the entire neuron, both axons and cell body, degenerates, in the context of axon pruning only the targeted axon segments are selectively degenerated. Interestingly, the molecular pathways mediating axon degeneration in these two contexts have significant mechanistic overlap but also retain distinct differences. In this review, we describe the peripheral neuronal cell culture models used to study the molecular pathways of apoptosis and pruning. We outline what is known about the molecular mechanisms of apoptosis and axon pruning and focus on highlighting the similarities and differences of these two pathways.
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Affiliation(s)
- Matthew J Geden
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, 27599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Selena E Romero
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, 27599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Mohanish Deshmukh
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, 27599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
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7
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Riley JS, Quarato G, Cloix C, Lopez J, O'Prey J, Pearson M, Chapman J, Sesaki H, Carlin LM, Passos JF, Wheeler AP, Oberst A, Ryan KM, Tait SW. Mitochondrial inner membrane permeabilisation enables mtDNA release during apoptosis. EMBO J 2018; 37:e99238. [PMID: 30049712 PMCID: PMC6120664 DOI: 10.15252/embj.201899238] [Citation(s) in RCA: 287] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 06/11/2018] [Accepted: 06/18/2018] [Indexed: 12/16/2022] Open
Abstract
During apoptosis, pro-apoptotic BAX and BAK are activated, causing mitochondrial outer membrane permeabilisation (MOMP), caspase activation and cell death. However, even in the absence of caspase activity, cells usually die following MOMP Such caspase-independent cell death is accompanied by inflammation that requires mitochondrial DNA (mtDNA) activation of cGAS-STING signalling. Because the mitochondrial inner membrane is thought to remain intact during apoptosis, we sought to address how matrix mtDNA could activate the cytosolic cGAS-STING signalling pathway. Using super-resolution imaging, we show that mtDNA is efficiently released from mitochondria following MOMP In a temporal manner, we find that following MOMP, BAX/BAK-mediated mitochondrial outer membrane pores gradually widen. This allows extrusion of the mitochondrial inner membrane into the cytosol whereupon it permeablises allowing mtDNA release. Our data demonstrate that mitochondrial inner membrane permeabilisation (MIMP) can occur during cell death following BAX/BAK-dependent MOMP Importantly, by enabling the cytosolic release of mtDNA, inner membrane permeabilisation underpins the immunogenic effects of caspase-independent cell death.
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Affiliation(s)
- Joel S Riley
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Giovanni Quarato
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Catherine Cloix
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Jonathan Lopez
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Jim O'Prey
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Matthew Pearson
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - James Chapman
- Ageing Research Laboratories, Newcastle University Institute for Ageing, LLHW Centre for Ageing and Vitality, Campus for Ageing and Vitality, Newcastle University, Newcastle upon Tyne, UK
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Leo M Carlin
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - João F Passos
- Ageing Research Laboratories, Newcastle University Institute for Ageing, LLHW Centre for Ageing and Vitality, Campus for Ageing and Vitality, Newcastle University, Newcastle upon Tyne, UK
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Ann P Wheeler
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK
| | - Andrew Oberst
- Department of Immunology, University of Washington, Seattle, WA, USA
- Center for Innate Immunity and Immune Disease, University of Washington, Seattle, WA, USA
| | - Kevin M Ryan
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Stephen Wg Tait
- Cancer Research UK Beatson Institute, Glasgow, UK
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
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8
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MicroRNA-146a down-regulation correlates with neuroprotection and targets pro-apoptotic genes in cerebral ischemic injury in vitro. Brain Res 2016; 1648:136-143. [PMID: 27449900 DOI: 10.1016/j.brainres.2016.07.034] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 07/11/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022]
Abstract
MicroRNAs (miRNAs) are short, non-coding RNAs that negatively regulate target gene expression, and play an important role in cerebral ischemic injury. MiR-146a has been reported to be highly related to cell invasion, metastasis, immunity, inflammation and apoptosis. Previous studies have indicated that miR-146a can either inhibit or promote apoptosis through different pathophysiological processes. In our previous study, miR-146a in the blood was down-regulated during acute ischemic stroke. However, the connection between miR-146a and acute cerebral ischemic injury and the mechanism underlying the connection remain unclear. Here, we aimed to investigate the role of miR-146a and its possible target genes in human SK-N-SH cells subjected to 16h of oxygen-glucose deprivation and 12h of reperfusion (OGD/R) injury. Cells were transfected with miR-146a mimic or inhibitor to alter the expression of miR-146a. MiR-146a in the SK-N-SH cells was down-regulated after OGD/R injury. Moreover, bioinformatics analysis and dual luciferase assays demonstrated that miR-146a directly recognized the 3'-UTR of the pro-apoptotic genes, Caspase7 and Bcl-2-associated transcription factor 1 (Bclaf1). Furthermore, miR-146a over-expression effectively decreased the mRNA and protein expression of Caspase7 and Bclaf1, and aggravated OGD/R-induced cell apoptosis; in contrast, miR-146a down-regulation was neuroprotective. In conclusion, our study revealed that miR-146a contributes to OGD/R injury in vitro, while negatively regulating the pro-apoptotic genes, Caspase7 and Bclaf1. This special mechanism provides new insight into miRNA regulatory networks. In addition, miR-146a may offer a potential therapeutic approach to cerebral ischemic injury.
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9
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Axon degeneration: context defines distinct pathways. Curr Opin Neurobiol 2016; 39:108-15. [PMID: 27197022 DOI: 10.1016/j.conb.2016.05.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/02/2016] [Accepted: 05/03/2016] [Indexed: 12/29/2022]
Abstract
Axon degeneration is an essential part of development, plasticity, and injury response and has been primarily studied in mammalian models in three contexts: 1) Axotomy-induced Wallerian degeneration, 2) Apoptosis-induced axon degeneration (axon apoptosis), and 3) Axon pruning. These three contexts dictate engagement of distinct pathways for axon degeneration. Recent advances have identified the importance of SARM1, NMNATs, NAD+ depletion, and MAPK signaling in axotomy-induced Wallerian degeneration. Interestingly, apoptosis-induced axon degeneration and axon pruning have many shared mechanisms both in signaling (e.g. DLK, JNKs, GSK3α/β) and execution (e.g. Puma, Bax, caspase-9, caspase-3). However, the specific mechanisms by which caspases are activated during apoptosis versus pruning appear distinct, with apoptosis requiring Apaf-1 but not caspase-6 while pruning requires caspase-6 but not Apaf-1.
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10
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Satheesh NJ, Büsselberg D. The role of intracellular calcium for the development and treatment of neuroblastoma. Cancers (Basel) 2015; 7:823-48. [PMID: 26010602 PMCID: PMC4491686 DOI: 10.3390/cancers7020811] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Accepted: 05/05/2015] [Indexed: 12/16/2022] Open
Abstract
Neuroblastoma is the second most common paediatric cancer. It developsfrom undifferentiated simpatico-adrenal lineage cells and is mostly sporadic; however, theaetiology behind the development of neuroblastoma is still not fully understood. Intracellularcalcium ([Ca2+]i) is a secondary messenger which regulates numerous cellular processesand, therefore, its concentration is tightly regulated. This review focuses on the role of[Ca2+]i in differentiation, apoptosis and proliferation in neuroblastoma. It describes themechanisms by which [Ca2+]i is regulated and how it modulates intracellular pathways.Furthermore, the importance of [Ca2+]i for the function of anti-cancer drugs is illuminatedin this review as [Ca2+]i could be a target to improve the outcome of anti-cancer treatmentin neuroblastoma. Overall, modulations of [Ca2+]i could be a key target to induce apoptosisin cancer cells leading to a more efficient and effective treatment of neuroblastoma.
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Affiliation(s)
- Noothan Jyothi Satheesh
- Weill Cornell Medical College in Qatar, Qatar Foundation-Education City, POB 24144, Doha, Qatar.
| | - Dietrich Büsselberg
- Weill Cornell Medical College in Qatar, Qatar Foundation-Education City, POB 24144, Doha, Qatar.
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11
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Mitochondria-derived reactive oxygen species mediate caspase-dependent and -independent neuronal deaths. Mol Cell Neurosci 2014; 63:13-23. [PMID: 25239010 DOI: 10.1016/j.mcn.2014.09.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 09/03/2014] [Accepted: 09/12/2014] [Indexed: 01/04/2023] Open
Abstract
Mitochondrial dysfunction and oxidative stress are implicated in many neurodegenerative diseases. Mitochondria-targeted drugs that effectively decrease oxidative stress, protect mitochondrial energetics, and prevent neuronal loss may therefore lend therapeutic benefit to these currently incurable diseases. To investigate the efficacy of such drugs, we examined the effects of mitochondria-targeted antioxidants MitoQ10 and MitoE2 on neuronal death induced by neurotrophin deficiency. Our results indicate that MitoQ10 blocked apoptosis by preventing increased mitochondria-derived reactive oxygen species (ROS) and subsequent cytochrome c release, caspase activation, and mitochondrial damage in nerve growth factor (NGF)-deprived sympathetic neurons, while MitoE2 was largely ineffective. In this paradigm, the most proximal point of divergence was the ability of MitoQ10 to scavenge mitochondrial superoxide (O2(-)). MitoQ10 also prevented caspase-independent neuronal death in these cells demonstrating that the mitochondrial redox state significantly influences both apoptotic and nonapoptotic pathways leading to neuronal death. We suggest that mitochondria-targeted antioxidants may provide tools for delineating the role and significance of mitochondrial ROS in neuronal death and provide a new therapeutic approach for neurodegenerative conditions involving trophic factor deficits and multiple modes of cell death.
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12
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Chen B, Zhao L, Li X, Ji YS, Li N, Xu XF, Chen ZY. Syntaxin 8 modulates the post-synthetic trafficking of the TrkA receptor and inflammatory pain transmission. J Biol Chem 2014; 289:19556-69. [PMID: 24872407 DOI: 10.1074/jbc.m114.567925] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Nerve growth factor (NGF) promotes the survival, maintenance, and neurite outgrowth of sensory and sympathetic neurons, and the effects are mediated by TrkA receptor signaling. Thus, the cell surface location of the TrkA receptor is crucial for NGF-mediated functions. However, the regulatory mechanism underlying TrkA cell surface levels remains incompletely understood. In this study, we identified syntaxin 8 (STX8), a Q-SNARE protein, as a novel TrkA-binding protein. Overexpression and knockdown studies showed that STX8 facilitates TrkA transport from the Golgi to the plasma membrane and regulates the surface levels of TrkA but not TrkB receptors. Furthermore, STX8 modulates downstream NGF-induced TrkA signaling and, consequently, the survival of NGF-dependent dorsal root ganglia neurons. Finally, knockdown of STX8 in rat dorsal root ganglia by recombinant adeno-associated virus serotype 6-mediated RNA interference led to analgesic effects on formalin-induced inflammatory pain. These findings demonstrate that STX8 is a modulator of TrkA cell surface levels and biological functions.
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Affiliation(s)
- Bing Chen
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Ling Zhao
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Xian Li
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Yun-Song Ji
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Na Li
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Xu-Feng Xu
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
| | - Zhe-Yu Chen
- From the Department of Neurobiology, Shandong Provincial Key Laboratory of Mental Disorders, School of Medicine, Shandong University, Number 44 Wenhua Xi Road, Jinan, Shandong 250012, China
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Kristiansen M, Ham J. Programmed cell death during neuronal development: the sympathetic neuron model. Cell Death Differ 2014; 21:1025-35. [PMID: 24769728 PMCID: PMC4207485 DOI: 10.1038/cdd.2014.47] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 03/05/2014] [Accepted: 03/13/2014] [Indexed: 01/08/2023] Open
Abstract
Developing sympathetic neurons of the superior cervical ganglion are one of the best studied models of neuronal apoptosis. These cells require nerve growth factor (NGF) for survival at the time that they innervate their final target tissues during late embryonic and early postnatal development. In the absence of NGF, developing sympathetic neurons die by apoptosis in a transcription-dependent manner. Molecular studies of sympathetic neuron apoptosis began in the 1980s. We now know that NGF withdrawal activates the mitochondrial (intrinsic) pathway of apoptosis in sympathetic neurons cultured in vitro, and the roles of caspases, Bcl-2 (B-cell CLL/lymphoma 2) family proteins and XIAP (X-linked inhibitor of apoptosis protein) have been extensively studied. Importantly, a considerable amount has also been learned about the intracellular signalling pathways and transcription factors that regulate programmed cell death in sympathetic neurons. In this article, we review the key papers published in the past few years, covering all aspects of apoptosis regulation in sympathetic neurons and focusing, in particular, on how signalling pathways and transcription factors regulate the cell death programme. We make some comparisons with other models of neuronal apoptosis and describe possible future directions for the field.
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Affiliation(s)
- M Kristiansen
- Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - J Ham
- Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
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14
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Morton CC, Aitchison AJ, Gehrig K, Ridgway ND. A mechanism for suppression of the CDP-choline pathway during apoptosis. J Lipid Res 2013; 54:3373-84. [PMID: 24136823 DOI: 10.1194/jlr.m041434] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Inhibition of the CDP-choline pathway during apoptosis restricts the availability of phosphatidylcholine (PtdCho) for assembly of membranes and synthesis of signaling factors. The N-terminal nuclear localization signal (NLS) in CTP:phosphocholine cytidylyltransferase (CCT)α is removed during apoptosis but the caspase(s) involved and the contribution to suppression of the CDP-choline pathway is unresolved. In this study we utilized siRNA silencing of caspases in HEK293 cells and caspase 3-deficient MCF7 cells to show that caspase 3 is required for CCTα proteolysis and release from the nucleus during apoptosis. CCTα-Δ28 (a caspase-cleaved mimic) expressed in CCTα-deficient Chinese hamster ovary cells was cytosolic and had increased in vitro activity. However, [³H]choline labeling experiments in camptothecin-treated MCF7 cells and MCF7 cells expressing caspase 3 (MCF7-C3) revealed a global suppression of the CDP-choline pathway that was consistent with inhibition of a step prior to CCTα. In camptothecin-treated MCF7 and MCF7-C3 cells, choline kinase activity was unaffected; however, choline transport into cells was reduced by 30 and 60%, respectively. We conclude that caspase 3-mediated removal of the CCTα NLS contributes minimally to the inhibition of PtdCho synthesis during DNA damage-induced apoptosis. Rather, the CDP-choline pathway is inhibited by caspase 3-independent and -dependent suppression of choline transport into cells.
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Affiliation(s)
- Craig C Morton
- Departments of Pediatrics and Biochemistry and Molecular Biology, Atlantic Research Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
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15
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Abstract
Neurons completely transform how they regulate cell death over the course of their lifetimes. Developing neurons freely activate cell death pathways to fine-tune the number of neurons that are needed during the precise formation of neural networks. However, the regulatory balance between life and death shifts as neurons mature beyond early development. Mature neurons promote survival at all costs by employing multiple, often redundant, strategies to prevent cell death by apoptosis. This dramatic shift from permitting cell death to ensuring cellular survival is critical, as these post-mitotic cells must provide neuronal circuitry for an organism's entire lifetime. Importantly, as many neurodegenerative diseases afflict adult neuronal populations, the survival mechanisms in mature neurons are likely to be either reversed or circumvented during neurodegeneration. Examining the adaptations for inhibiting apoptosis during neuronal maturation is key to comprehending not just how neurons survive long term, but may also provide insight for understanding how neuronal toxicity in various neurodegenerative diseases may ultimately lead to cell death.
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Affiliation(s)
- A J Kole
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA
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16
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Li Y, Nakagawara A. Apoptotic cell death in neuroblastoma. Cells 2013; 2:432-59. [PMID: 24709709 PMCID: PMC3972687 DOI: 10.3390/cells2020432] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 05/30/2013] [Accepted: 06/08/2013] [Indexed: 12/16/2022] Open
Abstract
Neuroblastoma (NB) is one of the most common malignant solid tumors in childhood, which derives from the sympathoadrenal lineage of the neural crest and exhibits extremely heterogeneous biological and clinical behaviors. The infant patients frequently undergo spontaneous regression even with metastatic disease, whereas the patients of more than one year of age who suffer from disseminated disease have a poor outcome despite intensive multimodal treatment. Spontaneous regression in favorable NBs has been proposed to be triggered by nerve growth factor (NGF) deficiency in the tumor with NGF dependency for survival, while aggressive NBs have defective apoptotic machinery which enables the tumor cells to evade apoptosis and confers the resistance to treatment. This paper reviews the molecules and pathways that have been recently identified to be involved in apoptotic cell death in NB and discusses their potential prospects for developing more effective therapeutic strategies against aggressive NB.
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Affiliation(s)
- Yuanyuan Li
- Division of Biochemistry and Innovative Cancer Therapeutics, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuoh-ku, Chiba 260-8717, Japan.
| | - Akira Nakagawara
- Division of Biochemistry and Innovative Cancer Therapeutics, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuoh-ku, Chiba 260-8717, Japan.
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17
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Saburi S, Hester I, Goodrich L, McNeill H. Functional interactions between Fat family cadherins in tissue morphogenesis and planar polarity. Development 2012; 139:1806-20. [PMID: 22510986 DOI: 10.1242/dev.077461] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The atypical cadherin fat (ft) was originally discovered as a tumor suppressor in Drosophila and later shown to regulate a form of tissue patterning known as planar polarity. In mammals, four ft homologs have been identified (Fat1-4). Recently, we demonstrated that Fat4 plays a role in vertebrate planar polarity. Fat4 has the highest homology to ft, whereas other Fat family members are homologous to the second ft-like gene, ft2. Genetic studies in flies and mice imply significant functional differences between the two groups of Fat cadherins. Here, we demonstrate that Fat family proteins act both synergistically and antagonistically to influence multiple aspects of tissue morphogenesis. We find that Fat1 and Fat4 cooperate during mouse development to control renal tubular elongation, cochlear extension, cranial neural tube formation and patterning of outer hair cells in the cochlea. Similarly, Fat3 and Fat4 synergize to drive vertebral arch fusion at the dorsal midline during caudal vertebra morphogenesis. We provide evidence that these effects depend on conserved interactions with planar polarity signaling components. In flies, the transcriptional co-repressor Atrophin (Atro) physically interacts with Ft and acts as a component of Fat signaling for planar polarity. We find that the mammalian orthologs of atro, Atn1 and Atn2l, modulate Fat4 activity during vertebral arch fusion and renal tubular elongation, respectively. Moreover, Fat4 morphogenetic defects are enhanced by mutations in Vangl2, a 'core' planar cell polarity gene. These studies highlight the wide range and complexity of Fat activities and suggest that a Fat-Atrophin interaction is a conserved element of planar polarity signaling.
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Affiliation(s)
- Sakura Saburi
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, M5G 1X5, Canada.
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18
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Ichim G, Tauszig-Delamasure S, Mehlen P. Neurotrophins and cell death. Exp Cell Res 2012; 318:1221-8. [PMID: 22465479 DOI: 10.1016/j.yexcr.2012.03.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 03/07/2012] [Accepted: 03/10/2012] [Indexed: 11/18/2022]
Abstract
The neurotrophins - NGF, BDNF, NT-3 - are secreted proteins that play a major role in neuron survival, differentiation and axon wiring toward target territories. They do so by interacting with their main tyrosine kinase receptors TrkA, TrkB, TrkC and p75(NTR). Even though there is a general consensus on the view that neurotrophins are survival factors, there are two fundamentally different views on how they achieve this survival activity. One prevailing view is that all neurons and more generally all normal cells are naturally committed to die unless a survival factor blocks this death. This death results from the engagement of a "default" apoptotic cell program. The minority report supports, on the opposite, that neurotrophin withdrawal is associated with an active signal of cell death induced by unbound dependence receptors. We will discuss here how neurotrophins regulate cell death and survival and how this has implications not only during nervous system development but also during cancer progression.
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Affiliation(s)
- Gabriel Ichim
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée La Ligue, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, Lyon, France
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19
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Kristiansen M, Menghi F, Hughes R, Hubank M, Ham J. Global analysis of gene expression in NGF-deprived sympathetic neurons identifies molecular pathways associated with cell death. BMC Genomics 2011; 12:551. [PMID: 22067274 PMCID: PMC3256215 DOI: 10.1186/1471-2164-12-551] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 11/08/2011] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Developing sympathetic neurons depend on nerve growth factor (NGF) for survival and die by apoptosis after NGF withdrawal. This process requires de novo gene expression but only a small number of genes induced by NGF deprivation have been identified so far, either by a candidate gene approach or in mRNA differential display experiments. This is partly because it is difficult to obtain large numbers of sympathetic neurons for in vitro studies. Here, we describe for the first time, how advances in gene microarray technology have allowed us to investigate the expression of all known genes in sympathetic neurons cultured in the presence and absence of NGF. RESULTS We have used Affymetrix Exon arrays to study the pattern of expression of all known genes in NGF-deprived sympathetic neurons. We identified 415 up- and 813 down-regulated genes, including most of the genes previously known to be regulated in this system. NGF withdrawal activates the mixed lineage kinase (MLK)-c-Jun N-terminal kinase (JNK)-c-Jun pathway which is required for NGF deprivation-induced death. By including a mixed lineage kinase (MLK) inhibitor, CEP-11004, in our experimental design we identified which of the genes induced after NGF withdrawal are potential targets of the MLK-JNK-c-Jun pathway. A detailed Gene Ontology and functional enrichment analysis also identified genetic pathways that are highly enriched and overrepresented amongst the genes expressed after NGF withdrawal. Five genes not previously studied in sympathetic neurons - trib3, ddit3, txnip, ndrg1 and mxi1 - were validated by real time-PCR. The proteins encoded by these genes also increased in level after NGF withdrawal and this increase was prevented by CEP-11004, suggesting that these genes are potential targets of the MLK-JNK-c-Jun pathway. CONCLUSIONS The sympathetic neuron model is one of the best studied models of neuronal apoptosis. Overall, our microarray data gives a comprehensive overview of, and provides new information about, signalling pathways and transcription factors that are regulated by NGF withdrawal.
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Affiliation(s)
- Mark Kristiansen
- Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
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20
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Caspase-3 is a target gene of c-Jun:ATF2 heterodimers during apoptosis induced by activity deprivation in cerebellar granule neurons. Neurosci Lett 2011; 505:76-81. [PMID: 21996423 DOI: 10.1016/j.neulet.2011.09.060] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 09/07/2011] [Accepted: 09/24/2011] [Indexed: 01/29/2023]
Abstract
Caspase-3, a key executor of neuronal apoptosis, is up-regulated and activated during apoptosis induced by activity deprivation in cerebellar granule neurons (CGNs). However, the transcriptional mechanism regulating caspase-3 during CGN apoptosis remains unknown. Here, we show that the caspase-3 gene is transactivated and its induction is preceded by c-Jun NH(2)-terminal kinase (JNK)/c-Jun:ATF2 pathway activation following activity deprivation in CGNs. We observed that caspase-3 induction is abolished by pharmacological inhibition of the JNK/c-Jun:ATF2 pathway. Destroying c-Jun:ATF2 heterodimers with dominant negative mutants of c-Jun and ATF2 or knockdown by small RNA interference reduced caspase-3 promoter activity and mRNA level. Furthermore, chromatin immunoprecipitation showed increased binding of c-Jun:ATF2 heterodimers to the caspase-3 promoter in response to activity deprivation in vivo. Site-directed mutagenesis of the caspase-3 promoter revealed that caspase-3 transcriptional activation depends primarily on an ATF site -233 to -225 nucleotides upstream of the start site. Taken together, these data demonstrate that caspase-3 is a target gene of c-Jun:ATF2 heterodimers during apoptosis induced by activity deprivation in CGNs.
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Abstract
Two principal pathways exist by which cells can undergo apoptotic death, known as the extrinsic and the intrinsic pathways. Binding of a ligand to a death receptor activates the extrinsic pathway. In the intrinsic pathway, an apoptotic stimulus, such as neurotrophin withdrawal or exposure to a toxin, causes a proapoptotic member of the Bcl-2 family of proteins, such as Bax, to permeabilize the outer mitochondrial membrane. This allows redistribution of cytochrome c from the mitochondrial intermembrane space into the cytoplasm, where it causes activation of caspase proteases and, subsequently, cell death. A dramatic increase occurs in mitochondria-derived reactive oxygen species (ROS) during the apoptotic death of sympathetic, cerebellar granule, and cortical neurons. These ROS lie downstream of Bax in each cell type. Here I review possible mechanisms by which Bax causes increased ROS during neuronal apoptosis. I also discuss evidence that these ROS are an important part of the apoptotic cascade in these cells. Finally, I discuss evidence that suggests that neurotrophins prevent release of cytochrome c in neurons through activation of an antioxidant pathway.
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Affiliation(s)
- James L Franklin
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 250 Green St., Athens, GA 30602, USA.
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22
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Malik S, Khalique H, Buch S, Seth P. A growth factor attenuates HIV-1 Tat and morphine induced damage to human neurons: implication in HIV/AIDS-drug abuse cases. PLoS One 2011; 6:e18116. [PMID: 21483469 PMCID: PMC3063804 DOI: 10.1371/journal.pone.0018116] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 02/25/2011] [Indexed: 01/03/2023] Open
Abstract
The neuropathological abnormalities of human immunodeficiency virus (HIV)-1 patients abusing illicit drugs suggest extensive interactions between the two agents, thereby leading to increased rate of progression to neurodegeneration. The role of HIV-1 transactivating protein, Tat has been elucidated in mediating neuronal damage via apoptosis, a hallmark of HIV-associated dementia (HAD), however the underlying mechanisms involved in enhanced neurodegeneration by illicit drugs remain elusive. In this study, we demonstrated that morphine enhances HIV-Tat induced toxicity in human neurons and neuroblastoma cells. Enhanced toxicity by Tat and morphine was accompanied by increased numbers of TUNEL positive apoptotic neurons, elevated caspase-3 levels and decreased ratio of anti- and pro-apoptotic proteins, Bcl2/Bax. Tat and morphine together elicited high levels of reactive oxygen species that were NADPH dependent. Significant alterations in mitochondrial membrane homeostasis were also observed with co-exposure of these agents. Extensive studies of mitogen activated protein kinase (MAPK) signaling pathways revealed the involvement of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase-1/2 (ERK1/2) pathways in enhanced toxicity of Tat and morphine. In addition to this, we found that pre-treatment of cells with platelet derived growth factor (PDGF-BB) protected neurons from HIV-Tat and morphine induced damage. PDGF-BB alleviated ROS production, maintained mitochondrial membrane potential, decreased caspase-3 activation and hence protected the cells from undergoing apoptosis. PDGF-BB mediated protection against Tat and morphine involved the phosphatidylinositol–3 kinase (PI3K) pathway, as specific inhibitor of PI3K abrogated the protection conferred by PDGF-BB. This study demonstrates the mechanism of enhanced toxicity in human neurons subjected to co-exposure of HIV protein Tat and morphine, thus implying its importance in HIV positive drug abusers, where damage to the brain is reported to be more severe than non-drug abusers. We have also showed for the first time that PDGF-BB can protect against simultaneous exposure of Tat and morphine, strengthening its role as a neuroprotective agent that could be considered for therapeutic intervention.
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Affiliation(s)
- Shaily Malik
- Cellular and Molecular Neuroscience, National Brain Research Center, Manesar, Gurgaon, Haryana, India
| | - Hena Khalique
- Cellular and Molecular Neuroscience, National Brain Research Center, Manesar, Gurgaon, Haryana, India
| | - Shilpa Buch
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Pankaj Seth
- Cellular and Molecular Neuroscience, National Brain Research Center, Manesar, Gurgaon, Haryana, India
- * E-mail:
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Bax regulates production of superoxide in both apoptotic and nonapoptotic neurons: role of caspases. J Neurosci 2011; 30:16114-27. [PMID: 21123558 DOI: 10.1523/jneurosci.2862-10.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A Bax- and, apparently, mitochondria-dependent increase in superoxide (O(2)(·-)) and other reactive oxygen species (ROS) occurs in apoptotic superior cervical ganglion (SCG) and cerebellar granule (CG) neurons. Here we show that Bax also lies upstream of ROS produced in nonapoptotic neurons and present evidence that caspases partially mediate the pro-oxidant effect of Bax. We used the O(2)(·-)-sensitive dye MitoSOX to monitor O(2)(·-) in neurons expressing different levels of Bax and mitochondrial superoxide dismutase (SOD2). Basal and apoptotic O(2)(·-) levels in both SCG and CG neurons were reduced in SOD2 wild-type (WT) cells having lower Bax concentrations. Apoptotic and nonapoptotic neurons from Bax-WT/SOD2-null but not Bax-null/SOD2-null mice had increased O(2)(·-) levels. A caspase inhibitor inhibited O(2)(·-) in both apoptotic and nonapoptotic SCG neurons. O(2)(·-) production increased when WT, but not Bax-null, SCG neurons were permeabilized and treated with active caspase 3. There was no apoptosis and little increase in O(2)(·-) in SCG neurons from caspase 3-null mice exposed to an apoptotic stimulus. O(2)(·-) levels in nonapoptotic caspase 3-null SCG neurons were lower than in WT cells but not as low as in caspase inhibitor-treated cells. These data indicate that Bax lies upstream of most O(2)(·-) produced in neurons, that caspase 3 is required for increased O(2)(·-) production during neuronal apoptosis, that caspase 3 is partially involved in O(2)(·-) production in nonapoptotic neurons, and that other caspases may also be involved in Bax-dependent O(2)(·-) production in nonapoptotic cells.
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Mkp1 is a c-Jun target gene that antagonizes JNK-dependent apoptosis in sympathetic neurons. J Neurosci 2010; 30:10820-32. [PMID: 20702711 DOI: 10.1523/jneurosci.2824-10.2010] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Developing sympathetic neurons depend on NGF for survival. When sympathetic neurons are deprived of NGF in vitro, a well documented series of events, including c-Jun N-terminal kinase (JNK) pathway activation, release of cytochrome c from the mitochondria, and caspase activation, culminates in the death of the neuron by apoptosis within 24-48 h. This process requires de novo gene expression, suggesting that increased expression of specific genes activates the cell death program. Using rat gene microarrays, we found that NGF withdrawal induces the expression of many genes, including mkp1, which encodes a MAPK phosphatase that can dephosphorylate JNKs. The increase in mkp1 mRNA level requires the MLK-JNK-c-Jun pathway, and we show that Mkp1 is an important regulator of JNK-dependent apoptosis in sympathetic neurons. In microinjection experiments, Mkp1 overexpression can inhibit JNK-mediated phosphorylation of c-Jun and protect sympathetic neurons from apoptosis, while Mkp1 knockdown accelerates NGF withdrawal-induced death. Accordingly, the number of superior cervical ganglion (SCG) neurons is reduced in mkp1-/- mice at P1 during the period of developmental sympathetic neuron death. We also show that c-Jun and ATF2 bind to two conserved ATF binding sites in the mkp1 promoter in vitro and in chromatin. Both of these ATF sites contribute to basal promoter activity and are required for mkp1 promoter induction after NGF withdrawal. These results demonstrate that Mkp1 is part of a negative feedback loop induced by the MLK-JNK-c-Jun signaling pathway that modulates JNK activity and the rate of neuronal death in rat sympathetic neurons following NGF withdrawal.
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Detectable levels of cytochrome C and activated caspase-9 in cerebrospinal fluid after human traumatic brain injury. Neurocrit Care 2010; 12:337-41. [PMID: 20087688 DOI: 10.1007/s12028-009-9328-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND The intrinsic pathway of apoptosis has been proposed as one mechanism of cell death after traumatic brain injury (TBI). This study tested the hypothesis that cytochrome c and activated caspase-9 are released into the cerebrospinal fluid (CSF) after severe TBI and that their presence correlates with mitochondrial injury and severity of neurologic outcome. METHODS Nine adult patients with severe TBI (GCS < or = 8) underwent placement of intraventricular catheters for monitoring and management of intracranial pressure. CSF was sampled at catheter insertion (2-26 h after injury) and at intervals of 24, 48, and 72 h thereafter. Control samples were obtained from patients undergoing spinal anesthesia (ASA1). CSF levels of cytochrome c and activated caspase-9 were measured using ELISA. RESULTS Cytochrome c was detected in 18 (51.4%) samples, in the range of 0.08-5 ng/ml; mean value for cytochrome c was 0.44 ng/ml (SD +/- 0.632). Activated caspase-9 was detected in 10 samples (28.6%); mean value was 0.28 ng/ml (SD +/- 0.39). R (s) between cytochrome c and Glasgow outcome score (GOS) was -0.25 (P = 0.14), and between GOS and activated caspase-9 was -0.35 (P = 0.04). R calculated based on linear regression of activated caspase-9 and cytochrome c concentrations was 0.18. Control CSF samples had no detectable levels of either marker (detection level for cytochrome c was 0.08 ng/ml and 0.20 for activated caspase-9). CONCLUSIONS We concluded that activated caspase-9 and cytochrome c are present in the CSF of patients with severe TBI. Activated caspase-9 shows weak correlation with poor neurologic outcome.
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26
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Oh-hashi K, Imai K, Koga H, Hirata Y, Kiuchi K. Knockdown of transmembrane protein 132A by RNA interference facilitates serum starvation-induced cell death in Neuro2a cells. Mol Cell Biochem 2010; 342:117-23. [PMID: 20455009 DOI: 10.1007/s11010-010-0475-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 04/17/2010] [Indexed: 10/19/2022]
Abstract
Transmembrane protein 132A (TMEM132A) is a novel GRP78 binding protein that we recently discovered. However, the biological functions of TMEM132A are merely characterized because it does not encode any known structural domains. In this study, we down regulated intrinsic TMEM132A by RNA interference and identified a variety of genes that fluctuated during TMEM132A gene silencing using microarray analysis. TMEM132A-knockdown in Neuro2a cells caused neurite-like projection without any stimuli and enhanced the expression of ATF6 mRNA, an ER stress transducer, and GADD153 mRNA, a stress inducible gene. Under serum-deprived condition, TMEM132A-knockdown cells gradually retarded neurite-like projection and decreased cell viability. Moreover, TMEM132A knockdown markedly induced GADD153 expression due to serum starvation without affecting the level of cleaved caspase-3. Our data suggest that TMEM132A is an important factor of cell survival in regulating certain ER stress-related gene expression in neuronal cells.
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Affiliation(s)
- Kentaro Oh-hashi
- Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu, Japan.
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27
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Bao XQ, Liu GT. Bicyclol protects HepG2 cells against D-galactosamine-induced apoptosis through inducing heat shock protein 27 and mitochondria associated pathway. Acta Pharmacol Sin 2010; 31:219-26. [PMID: 20139905 DOI: 10.1038/aps.2009.194] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
AIM To study the inducing effect of bicyclol on heat shock protein 27 (HSP27) and its role on anti-apoptosis in HepG2 cells intoxicated with D-galactosamine (D-GaIN). METHODS HepG2 cells were treated with various concentrations of bicyclol and then subjected to D-GaIN intoxication. Apoptosis was assayed by hoechst 33258 staining and flow cytometry analysis. HSP27, cytochrome c, apoptosis inducing factor (AIF) and c-Jun N-terminal kinase (JNK) were assayed by Western blot. Heat shock factor 1 (HSF1) was determined by electrophoretic mobility shift assay and the interactions of HSP27 with cytochrome c and AIF were detected by co-immunoprecipitation. RESULTS The results showed that bicyclol induced HSP27 protein and mRNA expression in HepG2 cells in both time- and dose-dependent manners (the maximal response: 1.23 fold increase at 100 micromol/L). Bicyclol treatment stimulated HSF1 activation and increased the HSF1-HSE binding activity (the maximal response: 2.1 fold increase at 100 micromol/L). This inducing effect of bicyclol on HSP27 and HSF1 was markedly blocked by quercetin. Pretreatment of the cells with bicyclol markedly attenuated D-GaIN-induced apoptosis and the release of cytochrome c and AIF from mitochondria. The induced HSP27 by bicyclol suppressed the activity of caspase-3 and the phosphorylation of JNK caused by D-GaIN in HepG2 cells. All the above effect of bicyclol against D-GaIN-induced hepatocytes apoptosis were significantly reversed by quercetin. CONCLUSION HSP27 is involved in the anti-hepatocytes apoptosis of bicyclol, and this effect of bicyclol-induced HSP27 is mainly through inhibition of mitochondria and JNK apoptotic pathways.
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28
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A retrograde apoptotic signal originating in NGF-deprived distal axons of rat sympathetic neurons in compartmented cultures. Cell Res 2009; 19:546-60. [PMID: 19188931 DOI: 10.1038/cr.2009.11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Previous investigations of retrograde survival signaling by nerve growth factor (NGF) and other neurotrophins have supported diverse mechanisms, but all proposed mechanisms have in common the generation of survival signals retrogradely transmitted to the neuronal cell bodies. We report the finding of a retrograde apoptotic signal in axons that is suppressed by local NGF signaling. NGF withdrawal from distal axons alone was sufficient to activate the pro-apoptotic transcription factor, c-jun, in the cell bodies. Providing NGF directly to cell bodies, thereby restoring a source of NGF-induced survival signals, could not prevent c-jun activation caused by NGF withdrawal from the distal axons. This is evidence that c-jun is not activated due to loss of survival signals at the cell bodies. Moreover, blocking axonal transport with colchicine inhibited c-jun activation caused by NGF deprivation suggesting that a retrogradely transported pro-apoptotic signal, rather than loss of a retrogradely transported survival signal, caused c-jun activation. Additional experiments showed that activation of c-jun, pro-caspase-3 cleavage, and apoptosis were blocked by the protein kinase C inhibitors, rottlerin and chelerythrine, only when applied to distal axons suggesting that they block the axon-specific pro-apoptotic signal. The rottlerin-sensitive mechanism was found to regulate glycogen synthase kinase 3 (GSK3) activity. The effect of siRNA knockdown, and pharmacological inhibition of GSK3 suggests that GSK3 is required for apoptosis caused by NGF deprivation and may function as a retrograde carrier of the axon apoptotic signal. The existence of a retrograde death signaling system in axons that is suppressed by neurotrophins has broad implications for neurodevelopment and for discovering treatments for neurodegenerative diseases and neurotrauma.
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Abstract
The elimination of unwanted cells by programmed cell death is a common feature of animal development. Genetic studies in the nematode Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and the mouse have not only revealed the molecular machineries that cause the programmed demise of specific cells, but have also allowed us to get a glimpse of the types of pathways that regulate these machineries during development. Rather than serving as a broad overview of programmed cell death during development, this review focuses on recent advances in our understanding of the regulation of specific programmed cell death events during nematode, fly, and mouse development. Recent studies have revealed that many of the regulatory pathways involved play additional important roles in development, which confirms that the programmed cell death fate is an integral aspect of animal development.
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Affiliation(s)
- Barbara Conradt
- Department of Genetics, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
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30
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Lockshin RA. An attempt to understand the multiparametric control of the initiation of apoptosis. Apoptosis 2008; 13:1195-7. [DOI: 10.1007/s10495-008-0251-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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31
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Abstract
Cytochrome c is primarily known for its function in the mitochondria as a key participant in the life-supporting function of ATP synthesis. However, when a cell receives an apoptotic stimulus, cytochrome c is released into the cytosol and triggers programmed cell death through apoptosis. The release of cytochrome c and cytochrome-c-mediated apoptosis are controlled by multiple layers of regulation, the most prominent players being members of the B-cell lymphoma protein-2 (BCL2) family. As well as its role in canonical intrinsic apoptosis, cytochrome c amplifies signals that are generated by other apoptotic pathways and participates in certain non-apoptotic functions.
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32
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Wang Y, Sun L, Xia C, Ye L, Wang B. P38MAPK regulates caspase-3 by binding to caspase-3 in nucleus of human hepatoma Bel-7402 cells during anti-Fas antibody- and actinomycin D-induced apoptosis. Biomed Pharmacother 2008; 63:343-50. [PMID: 18640003 DOI: 10.1016/j.biopha.2008.05.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 05/21/2008] [Indexed: 10/21/2022] Open
Abstract
Anti-Fas antibody- and actinomycin D (FA/AD) has been shown to have anti-tumor activity in some tumor cells. However, many of the molecular mechanism of FA/AD-induced apoptosis of human hepatoma Bel-7402 cells have not been fully clarified. In the present study, therefore, the effect of FA/AD in presence or absence of p38MAPK inhibitor SB203580 on the proliferation, apoptosis, p38MAPK, caspase-3, location of p38MAPK and caspase-3, and interaction between p38MAPK and caspase-3 in Bel-7402 cell was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), annexin V-FITC/propidium iodide (PI) double staining, electron microscopy, immunoblot, immunofluorescence and immunoprecipitation/immunoblot assay, respectively. We found that FA/AD significantly resulted in the inhibition of proliferation, induction of apoptosis, activation and up-regulation of p38MAPK, activation and up-regulation of caspase-3, translocation of p38MAPK and caspase-3 from cytosol to nucleus, and formation of p38MAPK/caspase-3 complex in Bel-7402 cells. In contrast, SB203580, a p38MAPK-specific inhibitor, apparently blocked induction of apoptosis, activation and up-regulation of p38MAPK, activation and up-regulation of caspase-3, and translocation of p38MAPK and caspase-3 from cytosol to nucleus in FA/AD-treated Bel-7402 cells. Taken together, we conclude that p38MAPK regulates caspase-3 by binding to caspase-3 in nucleus of Bel-7402 cells during FA/AD-induced apoptosis.
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Affiliation(s)
- Yu Wang
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang 110001, PR China
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33
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Peng F, Dhillon N, Callen S, Yao H, Bokhari S, Zhu X, Baydoun HH, Buch S. Platelet-derived growth factor protects neurons against gp120-mediated toxicity. J Neurovirol 2008; 14:62-72. [PMID: 18300076 DOI: 10.1080/13550280701809084] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The human immunodeficiency virus (HIV)-1 envelope glycoprotein gp120 has been implicated in mediating neuronal apoptosis, a hallmark feature of HIV-associated dementia (HAD). Mitigation of the toxic effects of gp120 could thus be a potential mechanism for reducing HIV toxicity in the brain. In this study the authors hypothesized that neurotrophic factor, such as platelet-derived growth factor (PDGF), could protect the neurons against gp120-mediated apoptosis. SH-SY5Y cells treated with gp120 exhibited increased cell death when measured by lactate dehydrogenase (LDH) and deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay, with concomitant loss of neurites and increased cell rounding. Pretreatment with PDGF-BB, however, reduced gp120-associated neurotoxicity and rescued the neurite outgrowth. Additionally, gp120-mediated activation of caspase-3 was also significantly reduced in cells pretreated with PDGF-BB. Antiapoptotic effects of PDGF-BB were also confirmed by monitoring levels of anti- and proapoptotic genes, Bcl-xL and Bax, respectively. Furthermore, PDGF-mediated protection against gp120 involved the phosphoinositide (PI) 3-kinase/Akt pathway. Taken together these findings lead us to suggest that PDGF-BB could be considered as a therapeutic agent that can mitigate gp120-mediated neurotoxicity in HAD.
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Affiliation(s)
- Fuwang Peng
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
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34
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Developing postmitotic mammalian neurons in vivo lacking Apaf-1 undergo programmed cell death by a caspase-independent, nonapoptotic pathway involving autophagy. J Neurosci 2008; 28:1490-7. [PMID: 18256270 DOI: 10.1523/jneurosci.4575-07.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Previous studies have shown that caspases and Apaf-1 are required for the normal programmed cell death (PCD) in vivo of immature postmitotic neurons and mitotically active neuronal precursor cells. In contrast, caspase activity is not necessary for the normal PCD of more mature postmitotic neurons that are establishing synaptic connections. Although normally these cells use caspases for PCD, in the absence of caspase activity these neurons undergo a distinct nonapoptotic type of degeneration. We examined the survival of these more mature postmitotic neuronal populations in mice in which Apaf-1 has been genetically deleted and find that they exhibit quantitatively normal PCD of developing postmitotic neurons. We next characterized the morphological mode of PCD in these mice and show that the neurons degenerate by a caspase-independent, nonapoptotic pathway that involves autophagy. However, autophagy does not appear to be involved in the normal PCD of postmitotic neurons in which caspases and Apaf-1 are present and functional because quantitatively normal neuronal PCD occurred in the absence of a key gene required for autophagy (ATG7). Finally, we examined the possible role of another caspase-independent type of neuronal PCD involving the apoptosis-inducing factor (AIF). Mice deficient in AIF also exhibit quantitatively normal PCD of postmitotic neurons after caspase inhibition. Together, these data indicate that, when key components of the type 1 apoptotic pathway (i.e., caspases and Apaf-1) are perturbed in vivo, developing postmitotic neurons nonetheless undergo quantitatively normal PCD by a caspase-independent pathway involving autophagy and not requiring AIF.
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35
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Wright KM, Smith MI, Farrag L, Deshmukh M. Chromatin modification of Apaf-1 restricts the apoptotic pathway in mature neurons. ACTA ACUST UNITED AC 2007; 179:825-32. [PMID: 18056406 PMCID: PMC2099178 DOI: 10.1083/jcb.200708086] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although apoptosis has been extensively studied in developing neurons, the dynamic changes in this pathway after neuronal maturation remain largely unexplored. We show that as neurons mature, cytochrome c– mediated apoptosis progresses from inhibitor of apoptosis protein–dependent to –independent regulation because of a complete loss of Apaf-1 expression. However, after DNA damage, mature neurons resynthesize Apaf-1 through the cell cycle–related E2F1 pathway and restore their apoptotic potential. Surprisingly, we find that E2F1 is sufficient to induce Apaf-1 expression in developing but not mature neurons. Rather, Apaf-1 up-regulation in mature neurons requires both chromatin derepression and E2F1 transcriptional activity. This differential capacity of E2F1 to induce Apaf-1 transcription is because of the association of the Apaf-1 promoter with active chromatin in developing neurons and repressed chromatin in mature neurons. These data specifically illustrate how the apoptotic pathway in mature neurons becomes increasingly restricted by a novel mechanism involving the regulation of chromatin structure.
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Affiliation(s)
- Kevin M Wright
- Neuroscience Center and 2Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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36
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Vaughn AE, Deshmukh M. Essential postmitochondrial function of p53 uncovered in DNA damage-induced apoptosis in neurons. Cell Death Differ 2007; 14:973-81. [PMID: 17218959 DOI: 10.1038/sj.cdd.4402084] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In postmitotic sympathetic neurons, unlike most mitotic cells, death by apoptosis requires not only the release of cytochrome c from the mitochondria, but also an additional step to relieve X-linked inhibitor of apoptosis protein (XIAP)'s inhibition of caspases. Here, we examined the mechanism by which XIAP is inactivated following DNA damage and found that it is achieved by a mechanism completely different from that following apoptosis by nerve growth factor (NGF) deprivation. NGF deprivation relieves XIAP by selectively degrading it, whereas DNA damage overcomes XIAP via a p53-mediated induction of Apaf-1. Unlike wild-type neurons, p53-deficient neurons fail to overcome XIAP and remain resistant to cytochrome c after DNA damage. Restoring Apaf-1 induction in p53-deficient neurons is sufficient to overcome XIAP and sensitize cells to cytochrome c. Although a role for p53 in apoptosis upstream of cytochrome c release has been well established, this study uncovers an additional, essential role for p53 in regulating caspase activation downstream of mitochondria following DNA damage in neurons.
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Affiliation(s)
- A E Vaughn
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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