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Li L, Xu X, Xiao M, Huang C, Cao J, Zhan S, Guo J, Zhong T, Wang L, Yang L, Zhang H. The Profiles and Functions of RNA Editing Sites Associated with High-Altitude Adaptation in Goats. Int J Mol Sci 2023; 24:3115. [PMID: 36834526 PMCID: PMC9964554 DOI: 10.3390/ijms24043115] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 01/27/2023] [Accepted: 01/28/2023] [Indexed: 02/08/2023] Open
Abstract
High-altitude environments dramatically influenced the genetic evolution of vertebrates. However, little is known about the role of RNA editing on high-altitude adaptation in non-model species. Here, we profiled the RNA editing sites (RESs) of heart, lung, kidney, and longissimus dorsi muscle from Tibetan cashmere goats (TBG, 4500 m) and Inner Mongolia cashmere goats (IMG, 1200 m) to reveal RNA editing-related functions of high-altitude adaptation in goats. We identified 84,132 high-quality RESs that were unevenly distributed across the autosomes in TBG and IMG, and more than half of the 10,842 non-redundant editing sites were clustered. The majority (62.61%) were adenosine-to-inosine (A-to-I) sites, followed by cytidine-to-uridine (C-to-U) sites (19.26%), and 32.5% of them had a significant correlation with the expression of catalytic genes. Moreover, A-to-I and C-to-U RNA editing sites had different flanking sequences, amino acid mutations, and alternative splicing activity. TBG had higher editing levels of A-to-I and C-to-U than IMG in the kidney, whereas a lower level was found in the longissimus dorsi muscle. Furthermore, we identified 29 IMG and 41 TBG population-specific editing sites (pSESs) and 53 population-differential editing sites (pDESs) that were functionally involved in altering RNA splicing or recoding protein products. It is worth noting that 73.3% population-differential, 73.2% TBG-specific, and 80% IMG-specific A-to-I sites were nonsynonymous sites. Moreover, the pSESs and pDESs editing-related genes play critical functions in energy metabolisms such as ATP binding molecular function, translation, and adaptive immune response, which may be linked to goat high-altitude adaptation. Our results provide valuable information for understanding the adaptive evolution of goats and studying plateau-related diseases.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Liu Yang
- Farm Animal Genetic Resources Exploration Innovation Key Laboratory of Sichuan Province, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Hongping Zhang
- Farm Animal Genetic Resources Exploration Innovation Key Laboratory of Sichuan Province, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
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2
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Alharbi Y, Kapur A, Felder M, Barroilhet L, Pattnaik BR, Patankar MS. Oxidative stress induced by the anti-cancer agents, plumbagin, and atovaquone, inhibits ion transport through Na +/K +-ATPase. Sci Rep 2020; 10:19585. [PMID: 33177587 PMCID: PMC7659016 DOI: 10.1038/s41598-020-76342-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 10/05/2020] [Indexed: 11/23/2022] Open
Abstract
Oxidative stress inhibits Na+/K+-ATPase (NKA), the ion channel that maintains membrane potential. Here, we investigate the role of oxidative stress-mediated by plumbagin and atovaquone in the inhibition of NKA activity. We confirm that plumbagin and atovaquone inhibit the proliferation of three human (OVCAR-3, SKOV-3, and TYKNu) and one mouse (ID8) ovarian cancer cell lines. The oxygen radical scavenger, N-acetylcysteine (NAC), attenuates the chemotoxicity of plumbagin and atovaquone. Whole-cell patch clamping demonstrates that plumbagin and atovaquone inhibit outward and the inward current flowing through NKA in SKOV-3 and OVCAR-3. Although both drugs decrease cellular ATP; providing exogenous ATP (5 mM) in the pipet solution used during patch clamping did not recover NKA activity in the plumbagin or atovaquone treated SKOV-3 and OVCAR-3 cells. However, pretreatment of the cells with NAC completely abrogated the NKA inhibitory activity of plumbagin and atovaquone. Exposure of the SKOV-3 cells to either drug significantly decreases the expression of NKA. We conclude that oxidative stress caused by plumbagin and atovaquone degrades NKA, resulting in the inability to maintain ion transport. Therefore, when evaluating compounds that induce oxidative stress, it is important to consider the contribution of NKA inhibition to their cytotoxic effects on tumor cells.
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Affiliation(s)
- Yousef Alharbi
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792, USA.,Department of Veterinary Medicine, Qassim University, Qassim, Saudi Arabia
| | - Arvinder Kapur
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Mildred Felder
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Lisa Barroilhet
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Bikash R Pattnaik
- Department of Pediatrics, Ophthalmology and Visual Sciences, McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - Manish S Patankar
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, 53792, USA.
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Leslie TK, James AD, Zaccagna F, Grist JT, Deen S, Kennerley A, Riemer F, Kaggie JD, Gallagher FA, Gilbert FJ, Brackenbury WJ. Sodium homeostasis in the tumour microenvironment. Biochim Biophys Acta Rev Cancer 2019; 1872:188304. [PMID: 31348974 PMCID: PMC7115894 DOI: 10.1016/j.bbcan.2019.07.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 12/17/2022]
Abstract
The concentration of sodium ions (Na+) is raised in solid tumours and can be measured at the cellular, tissue and patient levels. At the cellular level, the Na+ gradient across the membrane powers the transport of H+ ions and essential nutrients for normal activity. The maintenance of the Na+ gradient requires a large proportion of the cell's ATP. Na+ is a major contributor to the osmolarity of the tumour microenvironment, which affects cell volume and metabolism as well as immune function. Here, we review evidence indicating that Na+ handling is altered in tumours, explore our current understanding of the mechanisms that may underlie these alterations and consider the potential consequences for cancer progression. Dysregulated Na+ balance in tumours may open opportunities for new imaging biomarkers and re-purposing of drugs for treatment.
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Affiliation(s)
- Theresa K Leslie
- Department of Biology, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
| | - Andrew D James
- Department of Biology, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
| | - Fulvio Zaccagna
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - James T Grist
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Surrin Deen
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Aneurin Kennerley
- York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK; Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
| | - Frank Riemer
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Joshua D Kaggie
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Ferdia A Gallagher
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Fiona J Gilbert
- Department of Radiology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - William J Brackenbury
- Department of Biology, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK.
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4
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Lang J, Zhao X, Wang X, Zhao Y, Li Y, Zhao R, Cheng K, Li Y, Han X, Zheng X, Qin H, Geranpayehvaghei M, Shi J, Anderson GJ, Hao J, Ren H, Nie G. Targeted Co-delivery of the Iron Chelator Deferoxamine and a HIF1α Inhibitor Impairs Pancreatic Tumor Growth. ACS NANO 2019; 13:2176-2189. [PMID: 30676731 DOI: 10.1021/acsnano.8b08823] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Rapidly growing cancer cells exhibit a strong dependence on iron for their survival. Thus, iron-removing drugs, iron chelators, have potential applications in cancer treatment. Deferoxamine (DFO) is an efficient iron chelator, but its short circulation half-life and ability to induce hypoxia-inducible factor 1α (HIF1α) overexpression restricts its use as an antitumor agent. In the present study, we first found that a pattern of iron-related protein expression favoring higher intracellular iron closely correlates with shorter overall and relapse-free survival in pancreatic cancer patients. We subsequently found that a combination of DFO and the HIF1α inhibitor, lificiguat (also named YC1), significantly enhanced the antitumor efficacy of DFO in vitro. We then employed transferrin receptor 1 (TFR1) targeting liposomes to codeliver DFO and YC1 to pancreatic tumors in a mouse model. The encapsulation of DFO prolonged its circulation time, improved its accumulation in tumor tissues via the enhanced permeability and retention (EPR) effect, and facilitated efficient uptake by cancer cells, which express high level of TFR1. After entering the tumor cells, the encapsulated DFO and YC1 were released to elicit a synergistic antitumor effect in subcutaneous and orthotopic pancreatic cancer xenografts. In summary, our work overcame two major obstacles in DFO-based cancer treatment through a simple liposome-based drug delivery system. This nanoencapsulation and targeting paradigm lays the foundation for future application of iron chelation in cancer therapy.
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Affiliation(s)
- Jiayan Lang
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- Sino-Danish Center for Education and Research/Sino-Danish College of UCAS , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xiao Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- Department of Pancreatic Carcinoma , Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy , Tianjin 300060 , China
| | - Xiuchao Wang
- Department of Pancreatic Carcinoma , Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy , Tianjin 300060 , China
| | - Ying Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Yiye Li
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Ruifang Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Keman Cheng
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Yao Li
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Xuexiang Han
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xiaowei Zheng
- Department of Pancreatic Carcinoma , Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy , Tianjin 300060 , China
| | - Hao Qin
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Marzieh Geranpayehvaghei
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- Department of Nanobiotechnology, Faculty of Biological Sciences , Tarbiat Modares University , Tehran , Iran
| | - Jian Shi
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
| | - Gregory J Anderson
- Iron Metabolism Laboratory , QIMR Berghofer Medical Research Institute , Brisbane , Queensland 4006 , Australia
| | - Jihui Hao
- Department of Pancreatic Carcinoma , Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy , Tianjin 300060 , China
| | - He Ren
- Department of Pancreatic Carcinoma , Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy , Tianjin 300060 , China
- Affiliated Hospital of Qingdao University , Qingdao 266000 , China
| | - Guangjun Nie
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology of China , 11 Beiyitiao , Zhongguancun , Beijing 100190 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
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Magnani ND, Dada LA, Sznajder JI. Ubiquitin-proteasome signaling in lung injury. Transl Res 2018; 198:29-39. [PMID: 29752900 PMCID: PMC6986356 DOI: 10.1016/j.trsl.2018.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 04/15/2018] [Accepted: 04/16/2018] [Indexed: 12/21/2022]
Abstract
Cell homeostasis requires precise coordination of cellular proteins function. Ubiquitination is a post-translational modification that modulates protein half-life and function and is tightly regulated by ubiquitin E3 ligases and deubiquitinating enzymes. Lung injury can progress to acute respiratory distress syndrome that is characterized by an inflammatory response and disruption of the alveolocapillary barrier resulting in alveolar edema accumulation and hypoxemia. Ubiquitination plays an important role in the pathobiology of acute lung injury as it regulates the proteins modulating the alveolocapillary barrier and the inflammatory response. Better understanding of the signaling pathways regulated by ubiquitination may lead to novel therapeutic approaches by targeting specific elements of the ubiquitination pathways.
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Affiliation(s)
- Natalia D Magnani
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois
| | - Laura A Dada
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois
| | - Jacob I Sznajder
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois.
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6
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HIF and HOIL-1L-mediated PKCζ degradation stabilizes plasma membrane Na,K-ATPase to protect against hypoxia-induced lung injury. Proc Natl Acad Sci U S A 2017; 114:E10178-E10186. [PMID: 29109255 DOI: 10.1073/pnas.1713563114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Organisms have evolved adaptive mechanisms in response to stress for cellular survival. During acute hypoxic stress, cells down-regulate energy-consuming enzymes such as Na,K-ATPase. Within minutes of alveolar epithelial cell (AEC) exposure to hypoxia, protein kinase C zeta (PKCζ) phosphorylates the α1-Na,K-ATPase subunit and triggers it for endocytosis, independently of the hypoxia-inducible factor (HIF). However, the Na,K-ATPase activity is essential for cell homeostasis. HIF induces the heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), which leads to PKCζ degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKCζ degradation allows plasma membrane Na,K-ATPase stabilization at ∼50% of normoxic levels, preventing its excessive down-regulation and cell death. Mice lacking HOIL-1L in lung epithelial cells (CreSPC/HOIL-1Lfl/fl ) were sensitized to hypoxia because they express higher levels of PKCζ and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an α1-Na,K-ATPase construct bearing an S18A (α1-S18A) mutation, which precludes PKCζ phosphorylation, stabilized the Na,K-ATPase at the plasma membrane and prevented hypoxia-induced cell death even in the absence of HOIL-1L. Adenoviral overexpression of the α1-S18A mutant Na,K-ATPase in vivo rescued the enhanced sensitivity of CreSPC/HOIL-1Lfl/fl mice to hypoxic lung injury. These data suggest that stabilization of Na,K-ATPase during severe hypoxia is a HIF-dependent process involving PKCζ degradation. Accordingly, we provide evidence of an important adaptive mechanism to severe hypoxia, whereby halting the exaggerated down-regulation of plasma membrane Na,K-ATPase prevents cell death and lung injury.
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Zhou Q, Dai J, Chen T, Dada LA, Zhang X, Zhang W, DeCamp MM, Winn RA, Sznajder JI, Zhou G. Downregulation of PKCζ/Pard3/Pard6b is responsible for lung adenocarcinoma cell EMT and invasion. Cell Signal 2017; 38:49-59. [PMID: 28652146 PMCID: PMC5555371 DOI: 10.1016/j.cellsig.2017.06.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 06/08/2017] [Accepted: 06/20/2017] [Indexed: 12/24/2022]
Abstract
Atypical protein kinase C ζ (PKCζ) forms an apico-basal polarity complex with Partitioning Defective (Pard) 3 and Pard6 to regulate normal epithelial cell apico-basolateral polarization. The dissociation of the PKCζ/Pard3/Pard6 complex is essential for the disassembly of the tight/adherens junction and epithelial-mesenchymal transition (EMT) that is critical for tumor spreading. Loss of cell polarity and epithelial organization is strongly correlated with malignancy and tumor progression in some other cancer types. However, it is unclear whether the PKCζ/Pard3/Pard6 complex plays a role in the progression of non-small-cell lung cancer (NSCLC). We found that hypoxia downregulated the PKCζ/Pard3/Pard6 complex, correlating with induction of lung cancer cell migration and invasion. Silencing of the PKCζ/Pard3/Pard6 polarity complex components induced lung cancer cell EMT, invasion, and colonization in vivo. Suppression of Pard3 was associated with altered expression of genes regulating wound healing, cell apoptosis/death and cell motility, and particularly upregulation of MAP3K1 and fibronectin which are known to contribute to lung cancer progression. Human lung adenocarcinoma tissues expressed less Pard6b and PKCζ than the adjacent normal tissues and in experimental mouse lung adenocarcinoma, the levels of Pard3 and PKCζ were also decreased. In addition, we showed that a methylation locus in the gene body of Pard3 is positively associated with the expression of Pard3 and that methylation of the Pard3 gene increased cellular sensitivity to carboplatin, a common chemotherapy drug. Suppression of Pard3 increased chemoresistance in lung cancer cells. Together, these results suggest that reduced expression of PKCζ/Pard3/Pard6 contributes to NSCLC EMT, invasion, and chemoresistance.
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Affiliation(s)
- Qiyuan Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL, USA
| | - Jingbo Dai
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL, USA
| | - Tianji Chen
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL, USA
| | - Laura A Dada
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Xu Zhang
- Division of Hematology and Oncology, University of Illinois at Chicago, Chicago, IL, USA
| | - Wei Zhang
- Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Malcolm M DeCamp
- The Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; Division of Thoracic Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Robert A Winn
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA; Cancer Center, University of Illinois at Chicago, Chicago, IL, USA
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Guofei Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL, USA; Cancer Center, University of Illinois at Chicago, Chicago, IL, USA; State Key Laboratory of Respiratory Diseases, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.
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8
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Vadász I, Sznajder JI. Gas Exchange Disturbances Regulate Alveolar Fluid Clearance during Acute Lung Injury. Front Immunol 2017; 8:757. [PMID: 28725223 PMCID: PMC5495863 DOI: 10.3389/fimmu.2017.00757] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 06/15/2017] [Indexed: 01/07/2023] Open
Abstract
Disruption of the alveolar-capillary barrier and accumulation of pulmonary edema, if not resolved, result in poor alveolar gas exchange leading to hypoxia and hypercapnia, which are hallmarks of acute lung injury and the acute respiratory distress syndrome (ARDS). Alveolar fluid clearance (AFC) is a major function of the alveolar epithelium and is mediated by the concerted action of apically-located Na+ channels [epithelial Na+ channel (ENaC)] and the basolateral Na,K-ATPase driving vectorial Na+ transport. Importantly, those patients with ARDS who cannot clear alveolar edema efficiently have worse outcomes. While hypoxia can be improved in most cases by O2 supplementation and mechanical ventilation, the use of lung protective ventilation settings can lead to further CO2 retention. Whether the increase in CO2 concentrations has deleterious or beneficial effects have been a topic of significant controversy. Of note, both low O2 and elevated CO2 levels are sensed by the alveolar epithelium and by distinct and specific molecular mechanisms impair the function of the Na,K-ATPase and ENaC thereby inhibiting AFC and leading to persistence of alveolar edema. This review discusses recent discoveries on the sensing and signaling events initiated by hypoxia and hypercapnia and the relevance of these results in identification of potential novel therapeutic targets in the treatment of ARDS.
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Affiliation(s)
- István Vadász
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center, Giessen, Germany
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
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Chen T, Zhou Q, Tang H, Bozkanat M, Yuan JXJ, Raj JU, Zhou G. miR-17/20 Controls Prolyl Hydroxylase 2 (PHD2)/Hypoxia-Inducible Factor 1 (HIF1) to Regulate Pulmonary Artery Smooth Muscle Cell Proliferation. J Am Heart Assoc 2016; 5:e004510. [PMID: 27919930 PMCID: PMC5210422 DOI: 10.1161/jaha.116.004510] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/08/2016] [Indexed: 12/20/2022]
Abstract
BACKGROUND Previously we found that smooth muscle cell (SMC)-specific knockout of miR-17~92 attenuates hypoxia-induced pulmonary hypertension. However, the mechanism underlying miR-17~92-mediated pulmonary artery SMC (PASMC) proliferation remains unclear. We sought to investigate whether miR-17~92 regulates hypoxia-inducible factor (HIF) activity and PASMC proliferation via prolyl hydroxylases (PHDs). METHODS AND RESULTS We show that hypoxic sm-17~92-/- mice have decreased hematocrit, red blood cell counts, and hemoglobin contents. The sm-17~92-/- mouse lungs express decreased mRNA levels of HIF targets and increased levels of PHD2. miR-17~92 inhibitors suppress hypoxia-induced levels of HIF1α, VEGF, Glut1, HK2, and PDK1 but not HIF2α in vitro in PASMC. Overexpression of miR-17 in PASMC represses PHD2 expression, whereas miR-17/20a inhibitors induce PHD2 expression. The 3'-UTR of PHD2 contains a functional miR-17/20a seed sequence. Silencing of PHD2 induces HIF1α and PCNA protein levels, whereas overexpression of PHD2 decreases HIF1α and cell proliferation. SMC-specific knockout of PHD2 enhances hypoxia-induced vascular remodeling and exacerbates established pulmonary hypertension in mice. PHD2 activator R59949 reverses vessel remodeling in existing hypertensive mice. PHDs are dysregulated in PASMC isolated from pulmonary arterial hypertension patients. CONCLUSIONS Our results suggest that PHD2 is a direct target of miR-17/20a and that miR-17~92 contributes to PASMC proliferation and polycythemia by suppression of PHD2 and induction of HIF1α.
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Affiliation(s)
- Tianji Chen
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL
| | - Qiyuan Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL
| | - Haiyang Tang
- Department of Medicine, University of Arizona, Tucson, AZ
| | - Melike Bozkanat
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL
| | - Jason X-J Yuan
- Department of Medicine, University of Arizona, Tucson, AZ
| | - J Usha Raj
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL
- Children's Hospital University of Illinois, University of Illinois Hospital and Health Sciences System, Chicago, IL
| | - Guofei Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL
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10
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Zimmer AD, Walbrecq G, Kozar I, Behrmann I, Haan C. Phosphorylation of the pyruvate dehydrogenase complex precedes HIF-1-mediated effects and pyruvate dehydrogenase kinase 1 upregulation during the first hours of hypoxic treatment in hepatocellular carcinoma cells. HYPOXIA 2016; 4:135-145. [PMID: 27800515 PMCID: PMC5085306 DOI: 10.2147/hp.s99044] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The pyruvate dehydrogenase complex (PDC) is an important gatekeeper enzyme connecting glycolysis to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS). Thereby, it has a strong impact on the glycolytic flux as well as the metabolic phenotype of a cell. PDC activity is regulated via reversible phosphorylation of three serine residues on the pyruvate dehydrogenase (PDH) E1α subunit. Phosphorylation of any of these residues by the PDH kinases (PDKs) leads to a strong decrease in PDC activity. Under hypoxia, the inactivation of the PDC has been described to be dependent on the hypoxia-inducible factor 1 (HIF-1)-induced PDK1 protein upregulation. In this study, we show in two hepatocellular carcinoma cell lines (HepG2 and JHH-4) that, during the adaptation to hypoxia, PDH is already phosphorylated at time points preceding HIF-1-mediated transcriptional events and PDK1 protein upregulation. Using siRNAs and small molecule inhibitor approaches, we show that this inactivation of PDC is independent of HIF-1α expression but that the PDKs need to be expressed and active. Furthermore, we show that reactive oxygen species might be important for the induction of this PDH phosphorylation since it correlates with the appearance of an altered redox state in the mitochondria and is also inducible by H2O2 treatment under normoxic conditions. Overall, these results show that neither HIF-1 expression nor PDK1 upregulation is necessary for the phosphorylation of PDH during the first hours of the adaptation to hypoxia.
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Affiliation(s)
| | - Geoffroy Walbrecq
- Life Sciences Research Unit, University of Luxembourg, Belvaux, Luxembourg
| | - Ines Kozar
- Life Sciences Research Unit, University of Luxembourg, Belvaux, Luxembourg
| | - Iris Behrmann
- Life Sciences Research Unit, University of Luxembourg, Belvaux, Luxembourg
| | - Claude Haan
- Life Sciences Research Unit, University of Luxembourg, Belvaux, Luxembourg
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11
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Zhou Q, Chen T, Zhang W, Bozkanat M, Li Y, Xiao L, van Breemen RB, Christman JW, Sznajder JI, Zhou G. Suppression of von Hippel-Lindau Protein in Fibroblasts Protects against Bleomycin-Induced Pulmonary Fibrosis. Am J Respir Cell Mol Biol 2016; 54:728-39. [PMID: 26488390 PMCID: PMC4942192 DOI: 10.1165/rcmb.2015-0111oc] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/16/2015] [Indexed: 12/20/2022] Open
Abstract
We have reported that von Hippel-Lindau protein (pVHL) expression is elevated in human and mouse fibrotic lungs and that overexpression of pVHL stimulates fibroblast proliferation. We sought to determine whether loss of pVHL in fibroblasts prevents injury and fibrosis in mice that are treated with bleomycin. We generated heterozygous fibroblast-specific pVHL (Fsp-VHL) knockdown mice (Fsp-VHL(+/-)) and homozygous Fsp-VHL knockout mice (Fsp-VHL(-/-)) by crossbreeding vhlh 2-lox mice (VHL(fl/fl)) with Fsp-Cre recombinase mice. Our data show that Fsp-VHL(-/-) mice, but not Fsp-VHL(+/-) mice, have elevated red blood cell counts, hematocrit, hemoglobin content, and expression of hypoxia-inducible factor (HIF) targets, indicating HIF activation. To examine the role of pVHL in bleomycin-induced lung injury and fibrosis in vivo, we administered PBS or bleomycin to age-, sex-, and strain-matched 8-week-old VHL(fl/fl), Fsp-VHL(+/-), and Fsp-VHL(-/-) mice. In Fsp-VHL(+/-) and Fsp-VHL(-/-) mice, bleomycin-induced collagen accumulation, fibroblast proliferation, differentiation, and matrix protein dysregulation were markedly attenuated. Suppression of pVHL also decreased bleomycin-induced Wnt signaling and prostaglandin E2 signaling but did not affect bleomycin-induced initial acute lung injury and lung inflammation. These results indicate that pVHL has a pivotal role in bleomycin-induced pulmonary fibrosis, possibly via an HIF-independent pathway. Paradoxically, pVHL does not affect bleomycin-induced lung injury and inflammation, indicating a separation of the mechanisms involved in injury/inflammation from those involved in pulmonary fibrosis.
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Affiliation(s)
| | | | - Wei Zhang
- Department of Preventive Medicine and
| | | | | | - Lei Xiao
- Department of Medicine, Division of Pulmonary, Critical Care, Sleep, and Allergy, and
| | | | - John W. Christman
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Ohio State University, Columbus, Ohio
| | - Jacob I. Sznajder
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois; and
| | - Guofei Zhou
- Departments of Pediatrics and
- Cancer Center, University of Illinois at Chicago, Chicago, Illinois
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12
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Lim TKY, Shi XQ, Johnson JM, Rone MB, Antel JP, David S, Zhang J. Peripheral nerve injury induces persistent vascular dysfunction and endoneurial hypoxia, contributing to the genesis of neuropathic pain. J Neurosci 2015; 35:3346-59. [PMID: 25716835 PMCID: PMC6605560 DOI: 10.1523/jneurosci.4040-14.2015] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 01/09/2015] [Accepted: 01/12/2015] [Indexed: 12/22/2022] Open
Abstract
Nerve injury is associated with microvascular disturbance; however, the role of the vascular system has not been well characterized in the context of neuropathic pain. Furthermore, ischemia is thought to play a role in a number of neuropathic pain conditions, and yet the role of hypoxia has also not been characterized in neuropathic pain conditions. In this study, we observed the presence of persistent endoneurial hypoxia in a mouse model of traumatic peripheral nerve injury, causing painful mononeuropathy. We attribute the ongoing hypoxia to microvascular dysfunction, endoneurial fibrosis, and increased metabolic requirements within the injured nerve. Increased lactate levels were observed in injured nerves, as well as increased oxygen consumption and extracellular acidification rates, suggesting that anaerobic glycolysis is required to maintain cellular ATP levels. Hypoxia causes a reduction in levels of the Na(+)/K(+) ATPase ion transporter in both cultured primary dorsal root ganglion neurons and injured peripheral nerve. A reduction of Na(+)/K(+) ATPase ion transporter levels likely contributes to the hyperexcitability of injured nerves. Physiological antagonism of hypoxia with hyperbaric oxygen alleviated mechanical allodynia in nerve-injured animals. These results suggest that hypoxia and the Na(+)/K(+) ATPase ion transporter may be a novel mechanistic target for the treatment of neuropathic pain. In addition, the findings support the possibility of using hypoxia activated pro-drugs to localize treatments for neuropathic pain and nerve injury to injured nerves.
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Affiliation(s)
- Tony K Y Lim
- Neurology and Neurosurgery, Alan Edwards Centre for Research on Pain, and
| | - Xiang Q Shi
- Alan Edwards Centre for Research on Pain, and
| | | | | | | | - Samuel David
- Neurology and Neurosurgery, Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada, H3G 1A4
| | - Ji Zhang
- Neurology and Neurosurgery, Alan Edwards Centre for Research on Pain, and Faculty of Dentistry, McGill University, Montreal Quebec, Canada H3A 0G4, and
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13
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Zhou Q, Chen T, Bozkanat M, Ibe JCF, Christman JW, Raj JU, Zhou G. Intratracheal instillation of high dose adenoviral vectors is sufficient to induce lung injury and fibrosis in mice. PLoS One 2014; 9:e116142. [PMID: 25551570 PMCID: PMC4281082 DOI: 10.1371/journal.pone.0116142] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 12/03/2014] [Indexed: 12/23/2022] Open
Abstract
RATIONALE Replication deficient adenoviruses (Ad) vectors are common tools in gene therapy. Since Ad vectors are known to activate innate and adaptive immunity, we investigated whether intratracheal administration of Ad vectors alone is sufficient to induce lung injury and pulmonary fibrosis. METHODS We instilled Ad viruses ranging from 107 to 1.625×109 ifu/mouse as well as the same volume of PBS and bleomycin. 14 and 21 days after administration, we collected bronchoalveolar lavage fluid (BALF) and mouse lung tissues. We measured the protein concentration, total and differential cell counts, and TGF-β1 production, performed Trichrome staining and Sircol assay, determined gene and protein levels of profibrotic cytokines, MMPs, and Wnt signaling proteins, and conducted TUNEL staining and co-immunofluorescence for GFP and α-SMA staining. RESULTS Instillation of high dose Ad vectors (1.625×109 ifu/mouse) into mouse lungs induced high levels of protein content, inflammatory cells, and TGF-β1 in BALF, comparable to those in bleomycin-instilled lungs. The collagen content and mRNA levels of Col1a1, Col1a2, PCNA, and α-SMA were also increased in the lungs. Instillation of both bleomycin and Ad vectors increased expression levels of TNFα and IL-1β but not IL-10. Instillation of bleomycin but not Ad increased the expression of IL-1α, IL-13 and IL-16. Treatment with bleomycin or Ad vectors increased expression levels of integrin α1, α5, and αv, MMP9, whereas treatment with bleomycin but not Ad vectors induced MMP2 expression levels. Both bleomycin and Ad vectors induced mRNA levels of Wnt2, 2b, 5b, and Lrp6. Intratracheal instillation of Ad viruses also induced DNA damages and Ad viral infection-mediated fibrosis is not limited to the infection sites. CONCLUSIONS Our results suggest that administration of Ad vectors induces an inflammatory response, lung injury, and pulmonary fibrosis in a dose dependent manner.
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Affiliation(s)
- Qiyuan Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Tianji Chen
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Melike Bozkanat
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Joyce Christina F. Ibe
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Children’s Hospital University of Illinois, Chicago, Illinois, United States of America
| | - John W. Christman
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - J. Usha Raj
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Children’s Hospital University of Illinois, Chicago, Illinois, United States of America
| | - Guofei Zhou
- Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America
- University of Illinois Cancer Center, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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14
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Queisser MA, Dada LA, Deiss-Yehiely N, Angulo M, Zhou G, Kouri FM, Knab LM, Liu J, Stegh AH, DeCamp MM, Budinger GRS, Chandel NS, Ciechanover A, Iwai K, Sznajder JI. HOIL-1L functions as the PKCζ ubiquitin ligase to promote lung tumor growth. Am J Respir Crit Care Med 2014; 190:688-98. [PMID: 25118570 DOI: 10.1164/rccm.201403-0463oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
RATIONALE Protein kinase C zeta (PKCζ) has been reported to act as a tumor suppressor. Deletion of PKCζ in experimental cancer models has been shown to increase tumor growth. However, the mechanisms of PKCζ down-regulation in cancerous cells have not been previously described. OBJECTIVES To determine the molecular mechanisms that lead to decreased PKCζ expression and thus increased survival in cancer cells and tumor growth. METHODS The levels of expression of heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), HOIL-1-interacting protein (HOIP), Shank-associated RH domain-interacting protein (SHARPIN), and PKCζ were analyzed by Western blot and/or quantitative real-time polymerase chain reaction in different cell lines. Coimmunoprecipitation experiments were used to demonstrate the interaction between HOIL-1L and PKCζ. Ubiquitination was measured in an in vitro ubiquitination assay and by Western blot with specific antibodies. The role of hypoxia-inducible factor (HIF) was determined by gain/loss-of-function experiments. The effect of HOIL-1L expression on cell death was investigated using RNA interference approaches in vitro and on tumor growth in mice models. Increased HOIL-1L and decreased PKCζ expression was assessed in lung adenocarcinoma and glioblastoma multiforme and documented in several other cancer types by oncogenomic analysis. MEASUREMENTS AND MAIN RESULTS Hypoxia is a hallmark of rapidly growing solid tumors. We found that during hypoxia, PKCζ is ubiquitinated and degraded via the ubiquitin ligase HOIL-1L, a component of the linear ubiquitin chain assembly complex (LUBAC). In vitro ubiquitination assays indicate that HOIL-1L ubiquitinates PKCζ at Lys-48, targeting it for proteasomal degradation. In a xenograft tumor model and lung cancer model, we found that silencing of HOIL-1L increased the abundance of PKCζ and decreased the size of tumors, suggesting that lower levels of HOIL-1L promote survival. Indeed, mRNA transcript levels of HOIL-1L were elevated in tumor of patients with lung adenocarcinoma, and in a lung adenocarcinoma tissue microarray the levels of HOIL-1L were associated with high-grade tumors. Moreover, we found that HOIL-1L expression was regulated by HIFs. Interestingly, the actions of HOIL-1L were independent of LUBAC. CONCLUSIONS These data provide first evidence of a mechanism of cancer cell adaptation to hypoxia where HIFs regulate HOIL-1L, which targets PKCζ for degradation to promote tumor survival. We provided a proof of concept that silencing of HOIL-1L impairs lung tumor growth and that HOIL-1L expression predicts survival rate in cancer patients suggesting that HOIL-1L is an attractive target for cancer therapy.
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15
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Ward JBJ, Keely SJ, Keely SJ. Oxygen in the regulation of intestinal epithelial transport. J Physiol 2014; 592:2473-89. [PMID: 24710059 DOI: 10.1113/jphysiol.2013.270249] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The transport of fluid, nutrients and electrolytes to and from the intestinal lumen is a primary function of epithelial cells. Normally, the intestine absorbs approximately 9 l of fluid and 1 kg of nutrients daily, driven by epithelial transport processes that consume large amounts of cellular energy and O2. The epithelium exists at the interface of the richly vascularised mucosa, and the anoxic luminal environment and this steep O2 gradient play a key role in determining the expression pattern of proteins involved in fluid, nutrient and electrolyte transport. However, the dynamic nature of the splanchnic circulation necessitates that the epithelium can evoke co-ordinated responses to fluctuations in O2 availability, which occur either as a part of the normal digestive process or as a consequence of several pathophysiological conditions. While it is known that hypoxia-responsive signals, such as reactive oxygen species, AMP-activated kinase, hypoxia-inducible factors, and prolyl hydroxylases are all important in regulating epithelial responses to altered O2 supply, our understanding of the molecular mechanisms involved is still limited. Here, we aim to review the current literature regarding the role that O2 plays in regulating intestinal transport processes and to highlight areas of research that still need to be addressed.
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Affiliation(s)
- Joseph B J Ward
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Simon J Keely
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle NSW, Australia
| | - Stephen J Keely
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
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16
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Chen T, Sun M, Zhou G. Von Hippel-Lindau protein and respiratory diseases. World J Respirol 2013; 3:48-56. [DOI: 10.5320/wjr.v3.i3.48] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 07/09/2013] [Accepted: 07/19/2013] [Indexed: 02/06/2023] Open
Abstract
Von Hippel-Lindau protein (pVHL) was first identified as a tumor suppressor gene as mutations in the VHL gene predispose individuals to systemic benign or malignant tumors and cysts in many organs, including renal cell carcinoma of the clear-cell type and hemangioblastoma. Although pVHL is best known to act as a component of ubiquitin protein ligase for the proteasomal degradation of hypoxia inducible factor (HIF)-α, pVHL also interacts with extracellular matrix proteins and cytoskeleton, regulating extracellular matrix assembly, cell signaling, and many other cellular functions. Recent studies suggest that pVHL contributes to many lung diseases, including pulmonary arterial hypertension, lung cancer, pulmonary fibrosis, and acute respiratory distress syndrome. Mutation or loss of function of pVHL activates HIF and induced expression of vascular endothelial growth factor, endothelin-1, and FoxM1, leading to pulmonary arterial hypertension. Loss of pVHL in lung cancer cells promotes epithelial-mesenchymal transition and cancer migration and invasion while decreasing lung cancer cell proliferation and colonization. In patients of idiopathic pulmonary fibrosis, elevated expression of pVHL induces expression of fibronectin/integrin α5β1/focal adhesion kinase signaling, resulting in fibroproliferation and fibrosis. In alveolar epithelial cells, pVHL mediates Na-K-ATPase degradation in an HIF independent pathway, causing decreased edema clearance during hypoxia. These studies suggest that pVHL plays key roles in the pathogenesis of many lung diseases, and further investigations are warranted to elucidate the underlying molecular mechanisms.
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17
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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18
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Weathington NM, Sznajder JI, Mallampalli RK. The emerging role of the ubiquitin proteasome in pulmonary biology and disease. Am J Respir Crit Care Med 2013; 188:530-7. [PMID: 23713962 DOI: 10.1164/rccm.201304-0754pp] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Derangements in normal cellular homeostasis at the protein level can cause or be the consequence of initiation and progression of pulmonary diseases related to genotype, infection, injury, smoking, toxin exposure, or neoplasm. We discuss one of the fundamental mechanisms of protein homeostasis, the ubiquitin proteasome system (UPS), as it relates to lung disease. The UPS effects selective degradation of ubiquitinated target proteins via ubiquitin ligase activity. Important pathobiological mechanisms relating to the UPS and lung disease have been the focus of research, with inappropriate cellular proteolysis now a validated therapeutic target. We review the contributions of this system in various lung diseases, and discuss the exciting area of UPS-targeting drug development for pulmonary disease.
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Affiliation(s)
- Nathaniel M Weathington
- Acute Lung Injury Center of Excellence, Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh, Pennsylvania, USA
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19
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Weathington NM, Mallampalli RK. New insights on the function of SCF ubiquitin E3 ligases in the lung. Cell Signal 2013; 25:1792-8. [PMID: 23680451 DOI: 10.1016/j.cellsig.2013.05.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 05/06/2013] [Indexed: 12/01/2022]
Abstract
Recent developments in pulmonary cell biology have shown that the maintenance of protein concentrations, proteostasis, is an integral process of all biologic systems. The balance of available protein is the sum total of three key elements of cell metabolism: production by transcription and translation, compartmentalization through processing and sorting, and proteolytic degradation of proteins at any stage of their life-span. Considerable advances are constantly made in each of these three essential fields, and our appreciation for the diversity of mechanisms of protein degradation has expanded greatly in the last decade. The ubiquitin proteasome system (UPS) has emerged as the predominant protein degradation pathway in eukaryotes, with the large cullin-RING family of E3 ligases responsible for ubiquitination of a broad array of proteins to be degraded. The Skip-Cullin-F-box (SCF) ubiquitin E3 ligase superfamily is the largest family of cullin-RING ligases, with interchangeable F-box proteins orchestrating the trafficking proteins for ubiquitination and degradation. We will discuss the best characterized and most recent developments in the role of this intriguing family of proteins in normal physiology and disorders of the lungs.
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Affiliation(s)
- Nathaniel M Weathington
- Department of Medicine, Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, PA 15213, USA
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20
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Shaikh D, Zhou Q, Chen T, Ibe JCF, Raj JU, Zhou G. cAMP-dependent protein kinase is essential for hypoxia-mediated epithelial-mesenchymal transition, migration, and invasion in lung cancer cells. Cell Signal 2012; 24:2396-406. [PMID: 22954688 DOI: 10.1016/j.cellsig.2012.08.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 08/19/2012] [Accepted: 08/20/2012] [Indexed: 12/31/2022]
Abstract
Lung cancer is the leading cause of cancer-related death worldwide. Hypoxia is known to increase cancer cell migration and invasion. We have previously reported that hypoxia induces epithelial-mesenchymal transition (EMT) in lung cancer cells. However, it is unknown whether hypoxia promotes lung cancer cell migration and invasion via EMT and whether cyclic AMP (cAMP) dependent protein kinase (PKA) plays a role in this process. We found that hypoxia increased PKA activity and induced mRNA and protein expression of PKA catalytic subunit α (PKACA), and regulatory subunits R1A and R1B. Knockdown of HIF-1/2α prevented hypoxia-mediated induction of PKACA mRNA expression and PKA activity. Inhibition of PKA activity with chemical inhibitors prevented EMT induced by hypoxia and tumor growth factor β1. However, activation of PKA by forskolin and 8-Br-cAMP did not induce EMT. Furthermore, treatment with H89 and knockdown of PKACA prevented hypoxia-mediated, EMT, cell migration, and invasion, whereas overexpression of mouse PKACA rescued hypoxia-mediated migration and invasion in PKACA deficient cancer cells. Our results suggest that hypoxia enhances PKA activity by upregulating PKA gene expression in a HIF dependent mechanism and that PKA plays a key role in hypoxia-mediated EMT, migration, and invasion in lung cancer cells.
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Affiliation(s)
- Dooniya Shaikh
- Department of Pediatrics, University of Illinois at Chicago, Chicago, IL 60612, USA
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21
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Gou D, Ramchandran R, Peng X, Yao L, Kang K, Sarkar J, Wang Z, Zhou G, Zhou G, Raj JU. miR-210 has an antiapoptotic effect in pulmonary artery smooth muscle cells during hypoxia. Am J Physiol Lung Cell Mol Physiol 2012; 303:L682-91. [PMID: 22886504 DOI: 10.1152/ajplung.00344.2011] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
MicroRNAs (miRNAs) were recently reported to play an important role in the pathogenesis of pulmonary arterial hypertension (PAH), but it is not clear which miRNAs are important or what pathways are involved in the process. Because hypoxia is an important stimulus for human pulmonary artery smooth muscle cell (HPASMC) proliferation and PAH, we performed miRNA microarray assays in hypoxia-treated and control HPASMC. We found that miR-210 is the predominant miRNA induced by hypoxia in HPASMC. Induction of miR-210 was also observed in whole lungs of mice with chronic hypoxia-induced PAH. We found that transcriptional induction of miR-210 in HPASMC is hypoxia-inducible factor-1α dependent. Inhibition of miR-210 in HPASMC caused a significant decrease in cell number due to increased apoptosis. We found that miR-210 appears to mediate its antiapoptotic effects via the regulation of transcription factor E2F3, a direct target of miR-210. Our results have identified miR-210 as a hypoxia-inducible miRNA both in vitro and in vivo, which inhibits pulmonary vascular smooth muscle cell apoptosis in hypoxia by specifically repressing E2F3 expression.
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Affiliation(s)
- Deming Gou
- College of Life Sciences, Shenzhen University, Shenzhen 518060 China.
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22
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Vadász I, Weiss CH, Sznajder JI. Ubiquitination and proteolysis in acute lung injury. Chest 2012; 141:763-771. [PMID: 22396561 DOI: 10.1378/chest.11-1660] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Ubiquitination is a posttranslational modification that regulates a variety of cellular functions depending on timing, subcellular localization, and type of tagging, as well as modulators of ubiquitin binding leading to proteasomal or lysosomal degradation or nonproteolytic modifications. Ubiquitination plays an important role in the pathogenesis of acute lung injury (ALI) and other lung diseases with pathologies secondary to inflammation, mechanical ventilation, and decreased physical mobility. Particularly, ubiquitination has been shown to affect alveolar epithelial barrier function and alveolar edema clearance by targeting the Na,K-ATPase and epithelial Na(+) channels upon lung injury. Notably, the proteasomal system also exhibits distinct functions in the extracellular space, which may contribute to the pathogenesis of ALI and other pulmonary diseases. Better understanding of these mechanisms may ultimately lead to novel therapeutic modalities by targeting elements of the ubiquitination pathway.
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Affiliation(s)
- István Vadász
- Department of Internal Medicine, University of Giessen Lung Center, Justus Liebig University, Giessen, Germany.
| | - Curtis H Weiss
- Division of Pulmonary and Critical Care Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL
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23
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Knockdown of von Hippel-Lindau protein decreases lung cancer cell proliferation and colonization. FEBS Lett 2012; 586:1510-5. [PMID: 22673518 DOI: 10.1016/j.febslet.2012.04.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/19/2012] [Accepted: 04/07/2012] [Indexed: 12/31/2022]
Abstract
Although von Hippel-Lindau protein (pVHL) is known as a tumor suppressor in kidney and other organs, it remains unclear whether pVHL plays a role in lung cancer development. We investigated the role of pVHL in lung cancer cell proliferation, migration, and colonization using stable A549 cells with knockdown of pVHL. We found that knockdown of pVHL promotes epithelial-mesenchymal transition (EMT) in lung cancer cells. Knockdown of pVHL decreased tumor colonization in a tail-vein injection model and decreased cell proliferation, whereas overexpression of constitutive active HIF increased tumor colonization, suggesting a HIF-independent function of pVHL in lung. Knockdown of pVHL decreased phosphorylation of FAK and expression of integrin, suggesting that pVHL regulates lung cancer development via integrin/FAK signaling pathway.
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24
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Yu L, Hales CA. Long-term exposure to hypoxia inhibits tumor progression of lung cancer in rats and mice. BMC Cancer 2011; 11:331. [PMID: 21812995 PMCID: PMC3199866 DOI: 10.1186/1471-2407-11-331] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 08/03/2011] [Indexed: 12/24/2022] Open
Abstract
Background Hypoxia has been identified as a major negative factor for tumor progression in clinical observations and in animal studies. However, the precise role of hypoxia in tumor progression has not been fully explained. In this study, we extensively investigated the effect of long-term exposure to hypoxia on tumor progression in vivo. Methods Rats bearing transplanted tumors consisting of A549 human lung cancer cells (lung cancer tumor) were exposed to hypoxia for different durations and different levels of oxygen. The tumor growth and metastasis were evaluated. We also treated A549 lung cancer cells (A549 cells) with chronic hypoxia and then implanted the hypoxia-pretreated cancer cells into mice. The effect of exposure to hypoxia on metastasis of Lewis lung carcinoma in mice was also investigated. Results We found that long-term exposure to hypoxia a) significantly inhibited lung cancer tumor growth in xenograft and orthotopic models in rats, b) significantly reduced lymphatic metastasis of the lung cancer in rats and decreased lung metastasis of Lewis lung carcinoma in mice, c) reduced lung cancer cell proliferation and cell cycle progression in vitro, d) decreased growth of the tumors from hypoxia-pretreated A549 cells, e) decreased Na+-K+ ATPase α1 expression in hypoxic lung cancer tumors, and f) increased expression of hypoxia inducible factors (HIF1α and HIF2α) but decreased microvessel density in the lung cancer tumors. In contrast to lung cancer, the growth of tumor from HCT116 human colon cancer cells (colon cancer tumor) was a) significantly enhanced in the same hypoxia conditions, accompanied by b) no significant change in expression of Na+-K+ ATPase α1, c) increased HIF1α expression (no HIF2α was detected) and d) increased microvessel density in the tumor tissues. Conclusions This study demonstrated that long-term exposure to hypoxia repressed tumor progression of the lung cancer from A549 cells and that decreased expression of Na+-K+ ATPase was involved in hypoxic inhibition of tumor progression. The results from this study provide new insights into the role of hypoxia in tumor progression and therapeutic strategies for cancer treatment.
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Affiliation(s)
- Lunyin Yu
- Pulmonary and Critical Care Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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25
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Abstract
Adaptation to lowering oxygen levels (hypoxia) requires coordinated downregulation of metabolic demand and supply to prevent a mismatch in ATP utilization and production that might culminate in a bioenergetic collapse. Hypoxia diminishes ATP utilization by downregulating protein translation and the activity of the Na-K-ATPase. Hypoxia diminishes ATP production in part by lowering the activity of the electron transport chain through activation of the transcription factor hypoxia-inducible factor-1. The decrease in electron transport limits the overproduction of reactove oxygen species during hypoxia and slows the rate of oxygen depletion to prevent anoxia. In this review, we discuss these mechanisms that diminish metabolic supply and demand for adaptation to hypoxia.
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Affiliation(s)
- William W Wheaton
- Division of Pulmonary & Critical Care Medicine, 240 East Huron Ave., McGraw M-334, Chicago, IL 60611-2909, USA
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26
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Abstract
During acute lung injury edema accumulates in the alveolar space, resulting in hypoxemia due to intrapulmonary shunt. The alveolar Na,K-ATPase, by effecting active Na(+) transport, is essential for removing edema from the alveolar spaces. However, during hypoxia it is endocytosed and degraded, which results in decreased Na,K-ATPase function and impaired lung edema clearance. Na,K-ATPase endocytosis and degradation require the phosphorylation and subsequent ubiquitination of the Na,K-ATPase. These events are the results of cross-talk between post-translational modifications, and how ubiquitination of a specific protein can result from injurious extracellular stimuli. Here, we review current knowledge on the regulation of Na,K-ATPase activity during lung injury, focusing on the role of Na,K-ATPase ubiquitination during hypoxia. A better understanding of these signaling pathways can be of relevance for the design of novel treatments to ameliorate the deleterious effects of acute lung injury.
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Harrington MG, Fonteh AN, Arakaki X, Cowan RP, Ecke LE, Foster H, Hühmer AF, Biringer RG. Capillary endothelial Na(+), K(+), ATPase transporter homeostasis and a new theory for migraine pathophysiology. Headache 2010; 50:459-78. [PMID: 19845787 PMCID: PMC8020446 DOI: 10.1111/j.1526-4610.2009.01551.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Cerebrospinal fluid sodium concentration ([Na(+)](csf)) increases during migraine, but the cause of the increase is not known. OBJECTIVE Analyze biochemical pathways that influence [Na(+)](csf) to identify mechanisms that are consistent with migraine. METHOD We reviewed sodium physiology and biochemistry publications for links to migraine and pain. RESULTS Increased capillary endothelial cell (CEC) Na(+), K(+), -ATPase transporter (NKAT) activity is probably the primary cause of increased [Na(+)](csf). Physiological fluctuations of all NKAT regulators in blood, many known to be involved in migraine, are monitored by receptors on the luminal wall of brain CECs; signals are then transduced to their abluminal NKATs that alter brain extracellular sodium ([Na(+)](e)) and potassium ([K(+)](e)). CONCLUSIONS We propose a theoretical mechanism for aura and migraine when NKAT activity shifts outside normal limits: (1) CEC NKAT activity below a lower limit increases [K(+)](e), facilitates cortical spreading depression, and causes aura; (2) CEC NKAT activity above an upper limit elevates [Na(+)](e), increases neuronal excitability, and causes migraine; (3) migraine-without-aura may arise from CEC NKAT over-activity without requiring a prior decrease in activity and its consequent spreading depression; (4) migraine triggers disturb, and treatments improve, CEC NKAT homeostasis; (5) CEC NKAT-induced regulation of neural and vasomotor excitability coordinates vascular and neuronal activities, and includes occasional pathology from CEC NKAT-induced apoptosis or cerebral infarction.
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Affiliation(s)
- Michael G Harrington
- Huntington Medical Research Institutes - Molecular Neurology, Pasadena, CA 91101, USA
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28
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Abstract
The transcription factors hypoxia inducible factors 1 and 2 (HIF-1 and HIF-2) regulate multiple responses to physiological hypoxia such as transcription of the hormone erythropoietin to enhance red blood cell proliferation, vascular endothelial growth factor to promote angiogenesis and glycolytic enzymes to increase glycolysis. Recent studies indicate that HIFs also regulate mitochondrial respiration and mitochondrial oxidative stress. Interestingly, mitochondrial metabolism, respiration and oxidative stress also regulate activation of HIFs. In this review, we examine the evidence that mitochondria and HIFs are intimately connected to regulate each other resulting in appropriate responses to hypoxia.
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Affiliation(s)
- Kathryn V Tormos
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, Northwestern University Medical School, Chicago, IL 60611-2909, USA
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29
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Abstract
Solid tumours invariably exhibit regions of hypoxia and up-regulation of receptor tyrosine kinases (RTKs) that trigger multiple signal pathways, including those that govern cell proliferation, survival and motility, ultimately contributing to oncogenesis. Although past studies have shown hypoxia-dependent transcriptional and translational induction of several RTK expression and their respective ligands, recent evidence suggests that hypoxia regulates RTK signalling through endocytosis, a major deactivation pathway of RTKs. Hypoxia-mediated endocytosis is also thought to modulate the activity of a growing list of other membrane-associated proteins such as integrins and Na,K-ATPase. These recent discoveries underscore the emergence of endocytosis as an important hypoxia-mediated regulatory process in cancer.
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Affiliation(s)
- Yi Wang
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
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30
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Zhou G, Dada LA, Wu M, Kelly A, Trejo H, Zhou Q, Varga J, Sznajder JI. Hypoxia-induced alveolar epithelial-mesenchymal transition requires mitochondrial ROS and hypoxia-inducible factor 1. Am J Physiol Lung Cell Mol Physiol 2009; 297:L1120-30. [PMID: 19801454 DOI: 10.1152/ajplung.00007.2009] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Patients with acute lung injury develop hypoxia, which may lead to lung dysfunction and aberrant tissue repair. Recent studies have suggested that epithelial-mesenchymal transition (EMT) contributes to pulmonary fibrosis. We sought to determine whether hypoxia induces EMT in alveolar epithelial cells (AEC). We found that hypoxia induced the expression of alpha-smooth muscle actin (alpha-SMA) and vimentin and decreased the expression of E-cadherin in transformed and primary human, rat, and mouse AEC, suggesting that hypoxia induces EMT in AEC. Both severe hypoxia and moderate hypoxia induced EMT. The reactive oxygen species (ROS) scavenger Euk-134 prevented hypoxia-induced EMT. Moreover, hypoxia-induced expression of alpha-SMA and vimentin was prevented in mitochondria-deficient rho(0) cells, which are incapable of ROS production during hypoxia. CoCl(2) and dimethyloxaloylglycine, two compounds that stabilize hypoxia-inducible factor (HIF)-alpha under normoxia, failed to induce alpha-SMA expression in AEC. Furthermore, overexpression of constitutively active HIF-1alpha did not induce alpha-SMA. However, loss of HIF-1alpha or HIF-2alpha abolished induction of alpha-SMA mRNA during hypoxia. Hypoxia increased the levels of transforming growth factor (TGF)-beta1, and preincubation of AEC with SB431542, an inhibitor of the TGF-beta1 type I receptor kinase, prevented the hypoxia-induced EMT, suggesting that the process was TGF-beta1 dependent. Furthermore, both ROS and HIF-alpha were necessary for hypoxia-induced TGF-beta1 upregulation. Accordingly, we have provided evidence that hypoxia induces EMT of AEC through mitochondrial ROS, HIF, and endogenous TGF-beta1 signaling.
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Lecuona E, Sun H, Vohwinkel C, Ciechanover A, Sznajder JI. Ubiquitination participates in the lysosomal degradation of Na,K-ATPase in steady-state conditions. Am J Respir Cell Mol Biol 2009; 41:671-9. [PMID: 19286978 DOI: 10.1165/rcmb.2008-0365oc] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The alveolar epithelial cell (AEC) Na,K-ATPase contributes to vectorial Na(+) transport and plays an important role in keeping the lungs free of edema. We determined, by cell surface labeling with biotin and immunofluorescence, that approximately 30% of total Na,K-ATPase is at the plasma membrane of AEC in steady-state conditions. The half-life of the plasma membrane Na,K-ATPase was about 4 hours, and the incorporation of new Na,K-ATPase to the plasma membrane was Brefeldin A sensitive. Both protein kinase C (PKC) inhibition with bisindolylmaleimide (10 microM) and infection with an adenovirus expressing dominant-negative PKCzeta prevented Na,K-ATPase degradation. In cells expressing the Na,K-ATPase alpha1-subunit lacking the PKC phosphorylation sites, the plasma membrane Na,K-ATPase had a moderate increase in half-life. We also found that the Na,K-ATPase was ubiquitinated in steady-state conditions and that proteasomal inhibitors prevented its degradation. Interestingly, mutation of the four lysines described to be necessary for ubiquitination and endocytosis of the Na,K-ATPase in injurious conditions did not have an effect on its half-life in steady-state conditions. Lysosomal inhibitors prevented Na,K-ATPase degradation, and co-localization of Na,K-ATPase and lysosomes was found after labeling and chasing the plasma membrane Na,K-ATPase for 4 hours. Accordingly, we provide evidence suggesting that phosphorylation and ubiquitination are necessary for the steady-state degradation of the plasma membrane Na,K-ATPase in the lysosomes in alveolar epithelial cells.
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Affiliation(s)
- Emilia Lecuona
- Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, 240 E. Huron, McGaw M300, Chicago, IL 60611, USA.
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Clerici C, Planès C. Gene regulation in the adaptive process to hypoxia in lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 2008; 296:L267-74. [PMID: 19118091 DOI: 10.1152/ajplung.90528.2008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lung alveolar epithelial cells are normally very well oxygenated but may be exposed to hypoxia in many pathological conditions such as pulmonary edema, acute respiratory distress syndrome, chronic obstructive pulmonary diseases, or in some environmental conditions such ascent to high altitude. The ability of alveolar epithelial cells to cope with low oxygen tensions is crucial to maintain the structural and functional integrity of the alveolar epithelium. Alveolar epithelial cells appear to be remarkably tolerant to oxygen deprivation as they are able to maintain adequate cellular ATP content during prolonged hypoxic exposure when mitochondrial oxidative phosphorylation is limited. This property mostly relies on the ability of the cells to rapidly modify their gene expression program, stimulating the expression of genes involved in anaerobic energy supply and repressing expression of genes involved in some ATP-consuming cellular processes. This adaptive strategy of the cells is mostly, but not entirely, dependent on the expression of hypoxia-inducible factors (HIFs), known to be responsible for orchestrating a large number of hypoxia-sensitive genes. This review focuses on the role of HIF isoforms expressed in alveolar epithelial cells exposed to hypoxia and on the specific hypoxic gene regulation that takes place in alveolar epithelial cells either through HIF-dependent or -independent pathways.
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Affiliation(s)
- Christine Clerici
- Service de Physiologie-Explorations Fonctionnelles, Paris cedex 18, France.
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