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Scieszka D, Bolt AM, McCormick MA, Brigman JL, Campen MJ. Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality. FRONTIERS IN TOXICOLOGY 2023; 5:1267667. [PMID: 37900096 PMCID: PMC10600394 DOI: 10.3389/ftox.2023.1267667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 09/25/2023] [Indexed: 10/31/2023] Open
Abstract
Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.
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Affiliation(s)
- David Scieszka
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Alicia M. Bolt
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Mark A. McCormick
- Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Jonathan L. Brigman
- Department of Neurosciences, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Matthew J. Campen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
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Mitochondrial ROS, ER Stress, and Nrf2 Crosstalk in the Regulation of Mitochondrial Apoptosis Induced by Arsenite. Antioxidants (Basel) 2022; 11:antiox11051034. [PMID: 35624898 PMCID: PMC9137803 DOI: 10.3390/antiox11051034] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/17/2022] [Accepted: 05/20/2022] [Indexed: 02/07/2023] Open
Abstract
Long-term ingestion of arsenicals, a heterogeneous group of toxic compounds, has been associated with a wide spectrum of human pathologies, which include various malignancies. Although their mechanism of toxicity remains largely unknown, it is generally believed that arsenicals mainly produce their effects via direct binding to protein thiols and ROS formation in different subcellular compartments. The generality of these mechanisms most probably accounts for the different effects mediated by different forms of the metalloid in a variety of cells and tissues. In order to learn more about the molecular mechanisms of cyto- and genotoxicity, there is a need to focus on specific arsenic compounds under tightly controlled conditions. This review focuses on the mechanisms regulating the mitochondrial formation of ROS after exposure to low concentrations of a specific arsenic compound, NaAsO2, and their crosstalk with the nuclear factor (erythroid-2 related) factor 2 antioxidant signaling and the endoplasmic reticulum stress response.
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Crosstalk between ERO1α and ryanodine receptor in arsenite-dependent mitochondrial ROS formation. Biochem Pharmacol 2022; 198:114973. [PMID: 35189109 DOI: 10.1016/j.bcp.2022.114973] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/14/2022] [Accepted: 02/15/2022] [Indexed: 12/21/2022]
Abstract
Arsenite, a well-established human carcinogen and toxic compound, promotes the formation of mitochondrial superoxide (mitoO2-) via a Ca2+-dependent mechanism, in which an initial stimulation of the inositol 1, 4, 5-trisphosphate receptor (IP3R) is followed by the activation of the ryanodine receptor (RyR), critical for providing Ca2+ to the mitochondria. We now report that, under the same conditions, arsenite triggers endoplasmic reticulum (ER) stress and a threefold increase in ER oxidoreductin 1α (ERO1 α) levels in proliferating U937 cells. EN460, an inhibitor of ERO1 α, recapitulated all the effects associated with RyR inhibition or downregulation, including prevention of RyR-induced Ca2+ accumulation in mitochondria and the resulting O2-. formation. Quantitatively similar results were obtained in inhibitor studies performed in terminally differentiated wild type C2C12 cells. Moreover, ERO1 α knockout C2C12 myotubes responded to arsenite as their wild type counterpart supplemented with EN460. As a final note, arsenite enhanced the expression of ERO1 α via a mechanism mediated by Ca2+ release from both the IP3R and RyR. We therefore conclude that arsenite activates a positive feedback amplification cycle between Ca2+ levels and ERO1 α in the ER, by which IP3R-dependent Ca2+ induces ERO1 α and ERO1 α promotes Ca2+ release via RyR, thereby amplifying the initial Ca2+ load and causing the mitochondrial accumulation of the cation, critical for mitoO2- formation.
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Exposure to Environmental Arsenic and Emerging Risk of Alzheimer's Disease: Perspective Mechanisms, Management Strategy, and Future Directions. TOXICS 2021; 9:toxics9080188. [PMID: 34437506 PMCID: PMC8402411 DOI: 10.3390/toxics9080188] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/11/2021] [Accepted: 08/11/2021] [Indexed: 12/12/2022]
Abstract
Alzheimer’s disease (AD) is one of the most prevailing neurodegenerative diseases, characterized by memory dysfunction and the presence of hyperphosphorylated tau and amyloid β (Aβ) aggregates in multiple brain regions, including the hippocampus and cortex. The exact etiology of AD has not yet been confirmed. However, epidemiological reports suggest that populations who were exposed to environmental hazards are more likely to develop AD than those who were not. Arsenic (As) is a naturally occurring environmental risk factor abundant in the Earth’s crust, and human exposure to As predominantly occurs through drinking water. Convincing evidence suggests that As causes neurotoxicity and impairs memory and cognition, although the hypothesis and molecular mechanism of As-associated pathobiology in AD are not yet clear. However, exposure to As and its metabolites leads to various pathogenic events such as oxidative stress, inflammation, mitochondrial dysfunctions, ER stress, apoptosis, impaired protein homeostasis, and abnormal calcium signaling. Evidence has indicated that As exposure induces alterations that coincide with most of the biochemical, pathological, and clinical developments of AD. Here, we overview existing literature to gain insights into the plausible mechanisms that underlie As-induced neurotoxicity and the subsequent neurological deficits in AD. Prospective strategies for the prevention and management of arsenic exposure and neurotoxicity have also been discussed.
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Cantoni O, Zito E, Fiorani M, Guidarelli A. Arsenite impinges on endoplasmic reticulum-mitochondria crosstalk to elicit mitochondrial ROS formation and downstream toxicity. Semin Cancer Biol 2021; 76:132-138. [PMID: 34089843 DOI: 10.1016/j.semcancer.2021.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 02/08/2023]
Abstract
Arsenite is an important carcinogen and toxic compound, causing various deleterious effects through multiple mechanisms. In this review, we focused on mitochondrial ROS (mitoROS) and discussed on the mechanisms mediating their formation. The metalloid promotes direct effects in mitochondria, resulting in superoxide formation only under conditions of increased mitochondrial Ca2+ concentration ([Ca2+]m). In this perspective, the time of exposure and concentration requirements for arsenite were largely conditioned by other effects of the metalloid in specific sites of the endoplasmic reticulum (ER). Arsenite induced a slow and limited mobilization of Ca2+ from IP3R via a saturable mechanism, failing to increase the [Ca2+]m. This effect was however associated with the triggering of an intraluminal crosstalk between the IP3R and the ryanodine receptor (RyR), causing a large and concentration dependent release of Ca2+ from RyR and a parallel increase in [Ca2+]m. Thus, the Ca2+-dependent mitoO2-. formation appears to be conditioned by the spatial/functional organization of the ER/mitochondria network and RyR expression. We also speculate on the possibility that the ER stress response might regulate the above effects on the intraluminal crosstalk between the IP3R and the RyR via oxidation of critical thiols mediated by the H2O2 locally released by oxidoreductin 1α.
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Affiliation(s)
- Orazio Cantoni
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy.
| | - Ester Zito
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy
| | - Mara Fiorani
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Andrea Guidarelli
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
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Liu Z, Xu K, Xu Y, Zhang W, Jiang N, Wang S, Luo G, Liu J, Wu J, Wang H. Involvement of autophagy in realgar quantum dots (RQDs) inhibition of human endometrial cancer JEC cells. PeerJ 2020; 8:e9754. [PMID: 33150055 PMCID: PMC7587054 DOI: 10.7717/peerj.9754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 07/28/2020] [Indexed: 12/02/2022] Open
Abstract
Realgar (As4S4) has been used in traditional Chinese medicines for treatment of malignancies. The poor solubility of As4S4 hampered its clinical applications. Realgar quantum dots (RQDs) were developed to overcome these problems. Previous studies revealed that the RQDs were effective against endometrial cancer JEC cells and hepatocarcinoma HepG2 cells via inducing apoptosis.Apoptosis and autophagy are important programmed cell death pathways leading to anticancer effects. This study further examined effects of RQDs on autophagy, focusing on the formation of the autophagosome in JEC cells. CCK8 assay was used to examine cell proliferation. Flow cytometry was used to analyze cell cycle. Transmission electron microscopy (TEM) was used to examine the autophagy, cells were transfected with pEGFP-C3-MAP1LC3B plasmid to examine effects of RQDs on autophagosome via confocal microscope. Autophagy-related proteins were examined by Western blot. RQDs exhibited cytotoxicity in JEC cells in a concentration- and time- dependent manner. RQDs induced G2 and S phase arrest in JEC cells. RQDs significantly induced autophagy, with the double-membrane and autophagosome-like structures by TEM. The diffused distribution of pEGFP-C3-MAP1LC3B green fluorescence were become the punctuate pattern fluorescence after treatment with RQDs in cells transfected with pEGFP-C3-MAP1LC3B plasmid RQDs increased the expression of autophagyregulatory proteins LC3 I/II, Beclin-1, p62 and Atg12 in a concentration-dependent manner, similar to autophagy induced by serum starvation, except for p62, as induction of p62 is a characteristic of arsenic compounds. Taken together, the present study clearly demonstrated that RQDs can induce autophagy in JEC cells as one of mechanisms of anticancer effects, and indicated that RQDs may be developed as an autophagy inducer.
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Affiliation(s)
- Zhengyun Liu
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Ke Xu
- Department of Gynecology, Affiliated hospital of Zunyi Medical University, Zunyi, Guizhou, China
| | - Yan Xu
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Wanling Zhang
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Nian Jiang
- Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Shengyu Wang
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Guo Luo
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
| | - Jie Liu
- Key Laboratory for Basic Pharmacology of Ministry of Education, Zunyi Medical University, Zunyi, China
| | - Jinzhu Wu
- Department of Chemistry, School of Science, Harbin Institute of Technology, Harbin, China
| | - Huan Wang
- Key Laboratory of Infectious Disease & Biosafety, Provincial Department of Education, Zunyi Medical University, Zunyi, Guizhou, China.,Institute of Life Sciences, Zunyi Medical University, Zunyi, Guizhou, China
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Wu J, Ni Y, Yang Q, Mao J, Zhu X, Tao S, Kato K, Zhang J, Wang D, Yamanaka K, An Y. Long-term arsenite exposure decreases autophagy by increased release of Nrf2 in transformed human keratinocytes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 734:139425. [PMID: 32450402 DOI: 10.1016/j.scitotenv.2020.139425] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/07/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Autophagy dysfunction in arsenite toxicity plays critical roles in cancer development and progression. However, the precise mechanisms of arsenite-induced skin cancer by blocking autophagy remain uncertain. Herein, this study investigated molecular mechanisms of arsenite-induced autophagy dysfunction mediated by nuclear factor erythroid-2 related factor 2 (Nrf2) in human keratinocyte (HaCaT) cells. The effects of long-term arsenite exposure on Nrf2 activation and autophagy were established using a siRNA interference assay and western blots. A specific siRNA of Nrf2 was used to verify that autophagy induced by arsenite can be influenced by Nrf2. Specific inhibitors of PI3K (LY294002) and mTOR (Rapamycin) and siRNA of Nrf2 were employed to verify that upregulation of Nrf2 correlated with activating the PI3K/Akt pathway. Downstream mTOR and Bcl2 were upregulated by Nrf2 signaling, inhibiting autophagy initiation in arsenite-exposed HaCaT cells. In conclusion, our data suggest that long-term exposure to arsenite promotes Nrf2 upregulation via the PI3K/Akt pathway and, along with upregulation of downstream mTOR and Bcl2, contributes to autophagy dysfunction in transformed HaCaT cells. This work provides new insights into the mechanisms underlying arsenite-induced autophagy dysfunction in cancer promotion and malignancy progression.
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Affiliation(s)
- Jing Wu
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Yiping Ni
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Qianlei Yang
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Jiayuan Mao
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Xuerui Zhu
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Shasha Tao
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Koichi Kato
- Laboratory of Environmental Toxicology and Carcinogenesis, School of Pharmacy, Nihon University, Chiba, Japan
| | - Jie Zhang
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Dapeng Wang
- Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Department of Toxicology, Guizhou Medical University, Guiyang 550025, China.
| | - Kenzo Yamanaka
- Laboratory of Environmental Toxicology and Carcinogenesis, School of Pharmacy, Nihon University, Chiba, Japan.
| | - Yan An
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou 215123, Jiangsu, China.
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Duan T, Hu T, Wu C, Yeh YT, Lu J, Zhang Q, Li X, Jian W, Luo P. PINK1/Parkin-mediated mitophagy is involved in NaAsO 2-induced apoptosis of human hepatic cells through activation of ERK signaling. Toxicol In Vitro 2020; 66:104857. [PMID: 32278034 DOI: 10.1016/j.tiv.2020.104857] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 04/04/2020] [Accepted: 04/06/2020] [Indexed: 02/09/2023]
Abstract
Mitochondrial dysfunction has been demonstrated as one key event in arsenic-induced hepatic cell damage though the exact molecular target remains unknown. Here we examined NaAsO2-induced mitochondrial damage in the L-02 cell led to mitochondrial depolarization and cytochrome c release, mitophagy, apoptosis in a dose response manner. Mitophagy was measured by analysis of PINK1, Parkin, LC3-II and p62 protein. Apoptosis was assessed by measuring Annexin V. Using the mitophagy inhibitor cyclosporine A (CsA) or ERK inhibitor (PD98059), the balance between mitophagy and apoptosis were further explored. When CsA was used prior to cell exposure to NaAsO2, it was found that the levels of mitophagy were decreased as expected and apoptosis was increased in response. CsA alone had no effect on the apoptosis rate. When the ERK signaling inhibitor PD98059 was used, there was a similar result that mitophagy was reduced though in contrast with CsA the apoptosis rate was also decreased compared with NaAsO2 alone. This result, along with the increased levels of ERK measured here in response to NaAsO2, indicates that ERK activation is a second key molecular response to NaAsO2 through the activation of both apoptosis and mitophagy. Thus the results with CsA indicate that the likely key biological event in NaAsO2 toxicity is at the level of the mitochondria leading to cytochrome c release and apoptosis. Mitophagy is increased in response to a secondary effect of NaAsO2 on ERK signaling that activates both mitophagy and apoptosis. The activation of mitophagy allows the cell to avoid some apoptosis. When ERK signaling is inhibited by PD98059 both the levels of apoptosis and mitophagy are decreased compared with the response produced by NaAsO2 alone in comparison to the inhibition of mitophagy by CsA that reduced mitophagy but dramatically increased apoptosis in response.
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Affiliation(s)
- Tianxiao Duan
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Ting Hu
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Changyan Wu
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Yao-Tsung Yeh
- Aging and Disease Prevention Research Center, Fooyin University, Kaohsiung 83102, Taiwan
| | - Ju Lu
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Qi Zhang
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Xiaozhi Li
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Wen Jian
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China
| | - Peng Luo
- School of Public Health, The Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, Guizhou, PR China; State Key Laboratory of Functions and Applications of Medicinal Plants, Guizhou Medical University, Guiyang 550014, PR China.
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Hirano S, Kanno S. Relevance of autophagy markers to cytotoxicity of zinc compounds in macrophages. Toxicol In Vitro 2020; 65:104816. [PMID: 32126253 DOI: 10.1016/j.tiv.2020.104816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/28/2020] [Indexed: 10/24/2022]
Abstract
Autophagy molecules such as microtubule-associated protein light chain 3 (LC3) and p62/SQSTM1 have been used as biomarkers of protective or conversely adverse effects of exposure to toxicants. In the present study we show changes in LC3-II (a lipidated form of LC3-I) and p62 levels in response to zinc compounds and some other toxicants in J774.1 murine macrophages. The cytotoxicity of either ZnO or ZnSO4 largely depended on the concentration of FBS or albumin in the culture medium. Accordingly, these authophagy markers were more remarkably increased when the cells were exposed to ZnO or ZnSO4 in the absence of FBS. We next addressed lysosomal function impairment and changes in LC3-II and p62 levels following exposure to TiO2, ZnO, and ZnSO4. Lysosomal pH was quickly decreased by autolysosome inhibitors such as bafilomycin A1 and chloroquine, while TiO2, ZnO and ZnSO4 did not decrease lysosomal pH. However, the amounts of LC3-II and p62 and the LC3-II/LC3-I ratio were increased either by the lysosomal inhibitors and the Zn compounds. LC3-II and p62 levels were increased after exposure to arsenite and lipopolysaccharide (LPS). The p62 and phospho-p62 levels were also increased by either ZnSO4 and bafilomycin A1 in HEK293 cells stably expressing RFP-LC3. The current observations suggest that LC3-II and p62 levels were increased as consequences of early effects of toxicants without changing lysosomal pH.
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Affiliation(s)
- Seishiro Hirano
- Center for Health and Environmental Risk Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
| | - Sanae Kanno
- Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Japan
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Panganiban RA, Park HR, Sun M, Shumyatcher M, Himes BE, Lu Q. Genome-wide CRISPR screen identifies suppressors of endoplasmic reticulum stress-induced apoptosis. Proc Natl Acad Sci U S A 2019; 116:13384-13393. [PMID: 31213543 PMCID: PMC6613086 DOI: 10.1073/pnas.1906275116] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Sensing misfolded proteins in the endoplasmic reticulum (ER), cells initiate the ER stress response and, when overwhelmed, undergo apoptosis. However, little is known about how cells prevent excessive ER stress response and cell death to restore homeostasis. Here, we report the identification and characterization of cellular suppressors of ER stress-induced apoptosis. Using a genome-wide CRISPR library, we screen for genes whose inactivation further increases ER stress-induced up-regulation of C/EBP homologous protein 10 (CHOP)-the transcription factor central to ER stress-associated apoptosis. Among the top validated hits are two interacting components of the polycomb repressive complex (L3MBTL2 [L(3)Mbt-Like 2] and MGA [MAX gene associated]), and microRNA-124-3 (miR-124-3). CRISPR knockout of these genes increases CHOP expression and sensitizes cells to apoptosis induced by multiple ER stressors, while overexpression confers the opposite effects. L3MBTL2 associates with the CHOP promoter in unstressed cells to repress CHOP induction but dissociates from the promoter in the presence of ER stress, whereas miR-124-3 directly targets the IRE1 branch of the ER stress pathway. Our study reveals distinct mechanisms that suppress ER stress-induced apoptosis and may lead to a better understanding of diseases whose pathogenesis is linked to overactive ER stress response.
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Affiliation(s)
- Ronald A Panganiban
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115
| | - Hae-Ryung Park
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115
| | - Maoyun Sun
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115
| | - Maya Shumyatcher
- Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Blanca E Himes
- Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Quan Lu
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115;
- Department of Genetics & Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115
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Naz S, Battu S, Khan RA, Afroz S, Giddaluru J, Vishwakarma SK, Satti V, Habeeb MA, Khan AA, Khan N. Activation of integrated stress response pathway regulates IL-1β production through posttranscriptional and translational reprogramming in macrophages. Eur J Immunol 2019; 49:277-289. [PMID: 30578631 DOI: 10.1002/eji.201847513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 10/27/2018] [Accepted: 12/10/2018] [Indexed: 01/06/2023]
Abstract
Immune cells sense and programme its cellular machinery appropriately to the environmental changes through the activation of cytoprotective adaptive pathway so-called the "integrated stress response (ISR)". However, the mechanisms implicated in ISR-induced protective responses are poorly understood. Here, we show that ISR activation by arsenite (Ar) results in suppression of IL-1β production in macrophages and inhibition of DSS-induced colitis in a murine model through a novel posttranscriptional and translation regulatory (PTR) mechanism. Ar triggers PTR events through eIF2α-phosphorylation, which results in the attenuation of active polysome formation leading to the accumulation of translationally stalled IL-1β mRNAs. Translationally stalled IL-1β mRNAs recruit RNA-binding proteins (TIA-1/TIAR), resulting in the formation of RBP-RNA complexes known as stress granules (SGs). The SGs bound IL-1β mRNAs might undergo degradation through induction of autophagy. Also, we show that Ar posttranslationally impairs processing and secretion of IL-1β by diminishing inflammasome activation. Altogether, this study unveils a novel mechanism of IL-1β regulation and further suggests that pharmacological activation of cytoprotective ISR pathway might provide an effective therapeutic intervention against inflammatory diseases.
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Affiliation(s)
- Saima Naz
- Central Laboratory for Stem Cell Research and Translational Medicine, Center for Liver Research and Diagnostics, Deccan College of Medical Sciences, Hyderabad, India
| | - Srikanth Battu
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Rafiq Ahmad Khan
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Sumbul Afroz
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Jeevan Giddaluru
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Sandeep Kumar Vishwakarma
- Central Laboratory for Stem Cell Research and Translational Medicine, Center for Liver Research and Diagnostics, Deccan College of Medical Sciences, Hyderabad, India
| | | | - Md Aejaz Habeeb
- Central Laboratory for Stem Cell Research and Translational Medicine, Center for Liver Research and Diagnostics, Deccan College of Medical Sciences, Hyderabad, India
| | - Aleem Ahmed Khan
- Central Laboratory for Stem Cell Research and Translational Medicine, Center for Liver Research and Diagnostics, Deccan College of Medical Sciences, Hyderabad, India
| | - Nooruddin Khan
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
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Tillotson J, Zerio CJ, Harder B, Ambrose AJ, Jung KS, Kang M, Zhang DD, Chapman E. Arsenic Compromises Both p97 and Proteasome Functions. Chem Res Toxicol 2017; 30:1508-1514. [PMID: 28636814 PMCID: PMC5687067 DOI: 10.1021/acs.chemrestox.7b00158] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Exposure to arsenic is a worldwide problem that affects more than 200 million people. The underlying mechanisms of arsenic toxicity have been difficult to ascertain due to arsenic's pleotropic effects. A number of recent investigations have shown that arsenic can compromise protein quality control through the ubiquitin proteasome system (UPS) or the endoplasmic reticulum associated protein degradation (ERAD) pathway. In this article, a link between arsenic and protein quality control is reported. Biochemical and cellular data demonstrate a misregulation of the ATPase cycle of the ATPase associated with various cellular activities (AAA+) chaperone, p97. Interestingly, the loss of p97 activity is due to the increased rate of ATP hydrolysis, which mimics a collection of pathogenic genetic p97 lesions. Cellular studies, using a well characterized reporter of both the proteasome and p97, show the proteasome to also be compromised. This loss of both p97 and proteasome functions can explain the catastrophic protein quality control issues observed in acute, high level arsenic exposures.
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Affiliation(s)
| | | | | | | | | | | | - Donna D. Zhang
- Corresponding Authors: (D.D.Z.) University of Arizona, Department of Pharmacology and Toxicology, College of Pharmacy, 1703 East Mabel St., P.O. Box 210119, Tucson, AZ, USA 85721-0119. Tel: 520-626-9918. .; (E.C.) University of Arizona, Department of Pharmacology and Toxicology, College of Pharmacy, 1703 East Mabel St., P.O. Box 210119, Tucson, AZ, USA 85721-0207. Tel: 520-626-2740.
| | - Eli Chapman
- Corresponding Authors: (D.D.Z.) University of Arizona, Department of Pharmacology and Toxicology, College of Pharmacy, 1703 East Mabel St., P.O. Box 210119, Tucson, AZ, USA 85721-0119. Tel: 520-626-9918. .; (E.C.) University of Arizona, Department of Pharmacology and Toxicology, College of Pharmacy, 1703 East Mabel St., P.O. Box 210119, Tucson, AZ, USA 85721-0207. Tel: 520-626-2740.
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13
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Akr1 attenuates methylmercury toxicity through the palmitoylation of Meh1 as a subunit of the yeast EGO complex. Biochim Biophys Acta Gen Subj 2017; 1861:1729-1736. [DOI: 10.1016/j.bbagen.2017.03.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 03/08/2017] [Accepted: 03/14/2017] [Indexed: 02/05/2023]
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14
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Wang B, Lu D, Xuan M, Hu W. Antitumor effect of sunitinib in human prostate cancer cells functions via autophagy. Exp Ther Med 2017; 13:1285-1294. [PMID: 28413468 PMCID: PMC5377283 DOI: 10.3892/etm.2017.4134] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 11/25/2016] [Indexed: 12/25/2022] Open
Abstract
The aim of the present study was to explore sunitinib-induced autophagic effects and the specific molecular mechanisms involved, in vitro, using PC-3 and LNCaP human prostate cancer cell lines. Cells were exposed to escalating doses of sunitinib treatment and subsequent cell viability and cell cycle analyses were performed to evaluate the inhibitory effect of sunitinib in vitro. Immunofluorescence staining of microtubule associated protein 1A/1B-light chain 3 (LC3) puncta was employed to assess autophagy levels after sunitinib treatment. Western blot analysis was performed to evaluate variations in the levels of LC3, sequestosome-1, extracellular signal regulated kinase 1/2 (ERK1/2), mammalian target of rapamycin (mTOR), p70 ribosomal protein S6 kinase (p70S6K) and cleaved caspase-3 proteins. The present study revealed that sunitinib treatment inhibited cell growth and triggered autophagy in a dose-dependent manner in both cell lines. In addition, sunitinib activated ERK1/2 and inhibited mTOR/p70S6K signaling. Sunitinib-induced autophagy was notably reversed by ERK1/2 kinase inhibitor, U0126. Furthermore, inhibition of sunitinib-induced autophagy by 3-methyladenine enhanced apoptosis and exhibited improved cell viability, which indicated that sunitinib induces not only apoptosis but also autophagic cell death in prostate cancer cell lines. These results may lead to an improved understanding of the mechanism of sunitinib's cytotoxic action and may provide evidence that combined sunitinib autophagy-regulating treatment may be of benefit to anti-prostate cancer therapy.
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Affiliation(s)
- Bangqi Wang
- Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
- Department of Urology, General Hospital of Guangzhou Military Command, Guangzhou, Guangdong 510010, P.R. China
| | - Dongyuan Lu
- Graduate School of The Second Military Medical University, Shanghai 200433, P.R. China
| | - Min Xuan
- Department of Plastic Surgery, General Hospital of Guangzhou Military Command, Guangzhou, Guangdong 510010, P.R. China
| | - Weilie Hu
- Department of Urology, General Hospital of Guangzhou Military Command, Guangzhou, Guangdong 510010, P.R. China
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15
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BonakdarYazdi B, Khodagholi F, Shaerzadeh F, Sharifzadeh A, Ahmadi R, Sanati M, Mehdizadeh H, Payandehmehr B, Vali L, Jahromi MM, Taghizadeh G, Sharifzadeh M. The effect of arsenite on spatial learning: Involvement of autophagy and apoptosis. Eur J Pharmacol 2017; 796:54-61. [DOI: 10.1016/j.ejphar.2016.12.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 12/03/2016] [Accepted: 12/15/2016] [Indexed: 12/11/2022]
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16
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Escudero-Lourdes C. Toxicity mechanisms of arsenic that are shared with neurodegenerative diseases and cognitive impairment: Role of oxidative stress and inflammatory responses. Neurotoxicology 2016; 53:223-235. [DOI: 10.1016/j.neuro.2016.02.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 02/01/2016] [Accepted: 02/02/2016] [Indexed: 12/21/2022]
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17
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Affiliation(s)
- Sarmishtha Chatterjee
- Environmental Toxicology
Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan 731235, West Bengal, India
| | - Shuvasree Sarkar
- Environmental Toxicology
Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan 731235, West Bengal, India
| | - Shelley Bhattacharya
- Environmental Toxicology
Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan 731235, West Bengal, India
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18
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Guilbert C, Annis MG, Dong Z, Siegel PM, Miller WH, Mann KK. Arsenic trioxide overcomes rapamycin-induced feedback activation of AKT and ERK signaling to enhance the anti-tumor effects in breast cancer. PLoS One 2013; 8:e85995. [PMID: 24392034 PMCID: PMC3877392 DOI: 10.1371/journal.pone.0085995] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 12/03/2013] [Indexed: 11/18/2022] Open
Abstract
Inhibitors of the mammalian target of rapamycin (mTORi) have clinical activity; however, the benefits of mTOR inhibition by rapamycin and rapamycin-derivatives (rapalogs) may be limited by a feedback mechanism that results in AKT activation. Increased AKT activity resulting from mTOR inhibition can be a result of increased signaling via the mTOR complex, TORC2. Previously, we published that arsenic trioxide (ATO) inhibits AKT activity and in some cases, decreases AKT protein expression. Therefore, we propose that combining ATO and rapamycin may circumvent the AKT feedback loop and increase the anti-tumor effects. Using a panel of breast cancer cell lines, we find that ATO, at clinically-achievable doses, can enhance the inhibitory activity of the mTORi temsirolimus. In all cell lines, temsirolimus treatment resulted in AKT activation, which was decreased by concomitant ATO treatment only in those cell lines where ATO enhanced growth inhibition. Treatment with rapalog also results in activated ERK signaling, which is decreased with ATO co-treatment in all cell lines tested. We next tested the toxicity and efficacy of rapamycin plus ATO combination therapy in a MDA-MB-468 breast cancer xenograft model. The drug combination was well-tolerated, and rapamycin did not increase ATO-induced liver enzyme levels. In addition, combination of these drugs was significantly more effective at inhibiting tumor growth compared to individual drug treatments, which corresponded with diminished phospho-Akt and phospho-ERK levels when compared with rapamycin-treated tumors. Therefore, we propose that combining ATO and mTORi may overcome the feedback loop by decreasing activation of the MAPK and AKT signaling pathways.
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Affiliation(s)
- Cynthia Guilbert
- Lady Davis Institute for Medical Research, McGill University, Montreal, Canada
| | - Matthew G. Annis
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Canada
| | - Zhifeng Dong
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Canada
| | - Peter M. Siegel
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Canada
| | - Wilson H. Miller
- Lady Davis Institute for Medical Research, McGill University, Montreal, Canada
- Department of Oncology, McGill University, Montreal, Canada
| | - Koren K. Mann
- Lady Davis Institute for Medical Research, McGill University, Montreal, Canada
- Department of Oncology, McGill University, Montreal, Canada
- * E-mail:
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Weng CY, Chiou SY, Wang L, Kou MC, Wang YJ, Wu MJ. Arsenic trioxide induces unfolded protein response in vascular endothelial cells. Arch Toxicol 2013; 88:213-26. [PMID: 23892647 DOI: 10.1007/s00204-013-1101-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 07/11/2013] [Indexed: 01/13/2023]
Abstract
Chronic arsenic exposure has been linked to endothelial dysfunction and apoptosis. We investigate the involvement of unfolded protein response (UPR) signaling in the arsenic-mediated cytotoxicity of the SVEC4-10 mouse endothelial cells. The SVEC4-10 cells underwent apoptosis in response to As2O3 dose- and time-dependently, accompanied by increased accumulation of calcium, and activation of caspase-3. These phenomena were completely inhibited by α-lipoic acid (LA), which did not scavenge ROS over-production, but were only partially or not ameliorated by tiron, a potent superoxide scavenger. Moreover, arsenic activated UPR, leading to phosphorylation of eukaryotic translation initiation factor 2 subunit α (eIF2α), induction of ATF4, and processing of ATF6. Treatment with arsenic also triggered the expression of endoplasmic reticulum (ER) stress markers, GRP78 (glucose-regulated protein), and CHOP (C/EBP homologous protein). The activation of eIF2α, ATF4 and ATF6 and expression of GRP78 and CHOP are repressed by both LA and tiron, indicating arsenic-induced UPR is mediated through ROS-dependent and ROS-independent pathways. Arsenic also induced ER stress-inducible genes, BAX, PUMA (p53 upregulated modulator of apoptosis), TRB3 (tribbles-related protein 3), and SNAT2 (sodium-dependent neutral amino acid transporter 2). Consistent with intracellular calcium and cell viability data, ROS may not be important in arsenic-induced death, because tiron did not affect the expression of these pro-apoptotic genes. In addition, pretreatment with salubrinal, a selective inhibitor of eIF2α dephosphorylation, enhanced arsenic-induced GRP78 and CHOP expression and partially prevented arsenic cytotoxicity in SVEC4-10 cells. Taken together, these results suggest that arsenic-induced endothelial cytotoxicity is associated with ER stress, which is mediated by ROS-dependent and ROS-independent signaling.
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Affiliation(s)
- Ching-Yi Weng
- Department of Biotechnology, Chia Nan University of Pharmacy and Science, Tainan, 717, Taiwan
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20
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Arsenic trioxide induced endoplasmic reticulum stress in laryngeal squamous cell line Hep-2 cells. Auris Nasus Larynx 2013; 41:81-3. [PMID: 23880367 DOI: 10.1016/j.anl.2013.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 06/26/2013] [Accepted: 06/26/2013] [Indexed: 11/22/2022]
Abstract
Arsenic trioxide (As2O3) has been used in the treatment of acute promyelocytic leukemia (APL) and many malignant solid tumors. Recently, endoplasmic reticulum (ER) stress plays an important role in As2O3-treated laryngeal squamous cell line Hep-2 cells. In the present work, the expression of ER stress-related proteins was investigated in As2O3-treated Hep-2 cells. The results showed that As2O3 increased the expression of GRP78, CHOP, phosphorylated eIF2α and ATF4, all of which are the molecule of ER stress. Therefore, As2O3 induced ER stress in Hep-2 cells.
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Zhao F, Severson P, Pacheco S, Futscher BW, Klimecki WT. Arsenic exposure induces the Warburg effect in cultured human cells. Toxicol Appl Pharmacol 2013; 271:72-7. [PMID: 23648393 DOI: 10.1016/j.taap.2013.04.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 04/23/2013] [Accepted: 04/25/2013] [Indexed: 01/09/2023]
Abstract
Understanding how arsenic exacts its diverse, global disease burden is hampered by a limited understanding of the particular biological pathways that are disrupted by arsenic and underlie pathogenesis. A reductionist view would predict that a small number of basic pathways are generally perturbed by arsenic, and manifest as diverse diseases. Following an initial observation that arsenite-exposed cells in culture acidify their media more rapidly than control cells, the report here shows that low level exposure to arsenite (75ppb) is sufficient to induce aerobic glycolysis (the Warburg effect) as a generalized phenomenon in cultured human primary cells and cell lines. Expanded studies in one such cell line, the non-malignant pulmonary epithelial line, BEAS-2B, established that the arsenite-induced Warburg effect was associated with increased accumulation of intracellular and extracellular lactate, an increased rate of extracellular acidification, and inhibition by the non-metabolized glucose analog, 2-deoxy-D-glucose. Associated with the induction of aerobic glycolysis was a pathway-wide induction of glycolysis gene expression, as well as protein accumulation of an established glycolysis master-regulator, hypoxia-inducible factor 1A. Arsenite-induced alteration of energy production in human cells represents the type of fundamental perturbation that could extend to many tissue targets and diseases.
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Affiliation(s)
- Fei Zhao
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ 85724, USA
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22
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Dokladny K, Zuhl MN, Mandell M, Bhattacharya D, Schneider S, Deretic V, Moseley PL. Regulatory coordination between two major intracellular homeostatic systems: heat shock response and autophagy. J Biol Chem 2013; 288:14959-72. [PMID: 23576438 DOI: 10.1074/jbc.m113.462408] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The eukaryotic cell depends on multitiered homeostatic systems ensuring maintenance of proteostasis, organellar integrity, function and turnover, and overall cellular viability. At the two opposite ends of the homeostatic system spectrum are heat shock response and autophagy. Here, we tested whether there are interactions between these homeostatic systems, one universally operational in all prokaryotic and eukaryotic cells, and the other one (autophagy) is limited to eukaryotes. We found that heat shock response regulates autophagy. The interaction between the two systems was demonstrated by testing the role of HSF-1, the central regulator of heat shock gene expression. Knockdown of HSF-1 increased the LC3 lipidation associated with formation of autophagosomal organelles, whereas depletion of HSF-1 potentiated both starvation- and rapamycin-induced autophagy. HSP70 expression but not expression of its ATPase mutant inhibited starvation or rapamycin-induced autophagy. We also show that exercise induces autophagy in humans. As predicted by our in vitro studies, glutamine supplementation as a conditioning stimulus prior to exercise significantly increased HSP70 protein expression and prevented the expected exercise induction of autophagy. Our data demonstrate for the first time that heat shock response, from the top of its regulatory cascade (HSF-1) down to the execution stages delivered by HSP70, controls autophagy thus connecting and coordinating the two extreme ends of the homeostatic systems in the eukaryotic cell.
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Affiliation(s)
- Karol Dokladny
- Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131, USA
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