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Norris AC, Mansueto AJ, Jimenez M, Yazlovitskaya EM, Jain BK, Graham TR. Flipping the script: Advances in understanding how and why P4-ATPases flip lipid across membranes. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119700. [PMID: 38382846 DOI: 10.1016/j.bbamcr.2024.119700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 11/15/2023] [Accepted: 02/16/2024] [Indexed: 02/23/2024]
Abstract
Type IV P-type ATPases (P4-ATPases) are a family of transmembrane enzymes that translocate lipid substrates from the outer to the inner leaflet of biological membranes and thus create an asymmetrical distribution of lipids within membranes. On the cellular level, this asymmetry is essential for maintaining the integrity and functionality of biological membranes, creating platforms for signaling events and facilitating vesicular trafficking. On the organismal level, this asymmetry has been shown to be important in maintaining blood homeostasis, liver metabolism, neural development, and the immune response. Indeed, dysregulation of P4-ATPases has been linked to several diseases; including anemia, cholestasis, neurological disease, and several cancers. This review will discuss the evolutionary transition of P4-ATPases from cation pumps to lipid flippases, the new lipid substrates that have been discovered, the significant advances that have been achieved in recent years regarding the structural mechanisms underlying the recognition and flipping of specific lipids across biological membranes, and the consequences of P4-ATPase dysfunction on cellular and physiological functions. Additionally, we emphasize the requirement for additional research to comprehensively understand the involvement of flippases in cellular physiology and disease and to explore their potential as targets for therapeutics in treating a variety of illnesses. The discussion in this review will primarily focus on the budding yeast, C. elegans, and mammalian P4-ATPases.
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Affiliation(s)
- Adriana C Norris
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | | | - Mariana Jimenez
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | | | - Bhawik K Jain
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Todd R Graham
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
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Radak M, Ghamari N, Fallahi H. Common factors among three types of cells aged in mice. Biogerontology 2023; 24:363-375. [PMID: 37081236 DOI: 10.1007/s10522-023-10035-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 04/05/2023] [Indexed: 04/22/2023]
Abstract
The greatest risk factor for the formation of numerous significant chronic disorders is aging. Understanding the core molecular underpinnings of aging can help to slow down the inevitable process. Systematic study of gene expression or DNA methylation data is possible at the transcriptomics and epigenetics levels. DNA methylation and gene expression are both affected by aging. Gene expression is an important element in the aging of Homo sapiens. In this work, we evaluated the expression of differentially expressed genes (DEGs), proteins, and transcription factors (TFs) in three different types of cells in mice: antibody-secreting cells, cardiac mesenchymal stromal cells, and skeletal muscle cells. The goal of this article is to uncover a common cause during aging among these cells in order to increase understanding about establishing complete techniques for preventing aging and improving people's quality of life. We conducted a comprehensive network-based investigation to establish which genes and proteins are shared by the three different types of aged cells. Our findings clearly indicated that aging induces gene dysregulation in immune, pharmacological, and apoptotic pathways. Furthermore, our research developed a list of hub genes with differential expression in aging responses that should be investigated further to discover viable anti-aging treatments.
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Affiliation(s)
- Mehran Radak
- Department of Biology, School of Sciences, Razi University, Baq-e-Abrisham, 6714967346, Kermanshah, Islamic Republic of Iran
| | - Nakisa Ghamari
- Department of Biology, School of Sciences, Razi University, Baq-e-Abrisham, 6714967346, Kermanshah, Islamic Republic of Iran
| | - Hossein Fallahi
- Department of Biology, School of Sciences, Razi University, Baq-e-Abrisham, 6714967346, Kermanshah, Islamic Republic of Iran.
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Soundararajan R, Hernández-Cuervo H, Stearns TM, Griswold AJ, Patil SS, Fukumoto J, Narala VR, Galam L, Lockey R, Kolliputi N. A-Kinase Anchor Protein 1 deficiency causes mitochondrial dysfunction in mouse model of hyperoxia induced acute lung injury. Front Pharmacol 2022; 13:980723. [PMID: 36263130 PMCID: PMC9574061 DOI: 10.3389/fphar.2022.980723] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 08/30/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Critically ill patients on supplemental oxygen therapy eventually develop acute lung injury (ALI). Reactive oxygen species (ROS) produced during ALI perturbs the mitochondrial dynamics resulting in cellular damage. Genetic deletion of the mitochondrial A-kinase anchoring protein 1 (Akap1) in mice resulted in mitochondrial damage, Endoplasmic reticulum (ER) stress, increased expression of mitophagy proteins and pro-inflammatory cytokines, exacerbating hyperoxia-induced Acute Lung Injury (HALI).Objective: Despite a strong causal link between mitochondrial dysfunction and HALI, the mechanisms governing the disease progression at the transcriptome level is unknown.Methods: In this study, RNA sequencing (RNA-seq) analysis was carried out using the lungs of Akap1 knockout (Akap1−/−) mice exposed to normoxia or 48 h of hyperoxia followed by quantitative real time PCR and Ingenuity pathway analysis (IPA). Western blot analysis assessed mitochondrial dysfunction, OXPHOS complex (I-V), apoptosis and antioxidant proteins. Mitochondrial enzymatic assays was used to measure the aconitase, fumarase, citrate synthase activities in isolated mitochondria from Akap1−/− vs. Wt mice exposed to hyperoxia.Results: Transcriptome analysis of Akap1−/− exposed to hyperoxia reveals increases in transcripts encoding electron transport chain (ETC) and tricarboxylic acid cycle (TCA) proteins. Ingenuity pathway analysis (IPA) shows enrichment of mitochondrial dysfunction and oxidative phosphorylation in Akap1−/− mice. Loss of AKAP1, coupled with oxidant injury, significantly decreases the activities of TCA enzymes. Mechanistically, a significant loss of dynamin-related protein 1 (Drp1) phosphorylation at the protein kinase A (PKA) site Serine 637 (Ser637), decreases in Akt phosphorylation at Serine 437 (Ser47) and increase in the expression of pro-apoptotic protein Bax indicate mitochondrial dysfunction. Heme oxygenase-1 (HO-1) levels significantly increased in CD68 positive alveolar macrophages in Akap1−/− lungs, suggesting a strong antioxidant response to hyperoxia.Conclusion: Overall these results suggest that AKAP1 overexpression and modulation of Drp1 phosphorylation at Ser637 is an important therapeutic strategy for acute lung injury.
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Affiliation(s)
- Ramani Soundararajan
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Helena Hernández-Cuervo
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
- University of South Florida, Department of Molecular Medicine, Morsani College of Medicine, Tampa, FL, United States
| | | | - Anthony J Griswold
- John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL, United States
| | - Sahebgowda Sidramagowda Patil
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Jutaro Fukumoto
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | | | - Lakshmi Galam
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Richard Lockey
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Narasaiah Kolliputi
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
- University of South Florida, Department of Molecular Medicine, Morsani College of Medicine, Tampa, FL, United States
- *Correspondence: Narasaiah Kolliputi,
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Matrix Metalloproteinase 7 Expression and Apical Epithelial Defects in Atp8b1 Mutant Mouse Model of Pulmonary Fibrosis. Biomolecules 2022; 12:biom12020283. [PMID: 35204783 PMCID: PMC8961514 DOI: 10.3390/biom12020283] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 01/27/2022] [Accepted: 02/03/2022] [Indexed: 02/04/2023] Open
Abstract
Abnormalities in airway epithelia and lung parenchyma are found in Atp8b1 mutant mice, which develop pulmonary fibrosis after hyperoxic insult. Microarray and ingenuity pathway analysis (IPA) show numerous transcripts involved in ciliogenesis are downregulated in 14-month (14 M) -old Atp8b1 mouse lung compared with wild-type C57BL/6. Lung epithelium of Atp8b1 mice demonstrate apical abnormalities of ciliated and club cells in the bronchial epithelium on transmission electron microscopy (TEM). Matrix metalloproteinase 7 (MMP7) regulates of ciliogenesis and is a biomarker for idiopathic pulmonary fibrosis (IPF) in humans. Mmp7 transcript and protein expression are significantly upregulated in 14 M Atp8b1 mutant mouse lung. MMP7 expression is also increased in bronchoalveolar lavage fluid (BAL). Immunohistochemistry is localized MMP7 to bronchial epithelial cells in the Atp8b1 mutant. In conclusion, MMP7 is upregulated in the aged Atp8b1 mouse model, which displays abnormal ciliated cell and club cell morphology. This mouse model can facilitate the exploration of the role of MMP7 in epithelial integrity and ciliogenesis in IPF. The Atp8b1 mutant mouse is proposed as a model for IPF.
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Wang J, Fan Q, Yu T, Zhang Y. Identifying the hub genes for Duchenne muscular dystrophy and Becker muscular dystrophy by weighted correlation network analysis. BMC Genom Data 2021; 22:57. [PMID: 34922439 PMCID: PMC8684282 DOI: 10.1186/s12863-021-01014-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 11/19/2021] [Indexed: 12/14/2022] Open
Abstract
Background The goal of this study is to identify the hub genes for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) via weighted correlation network analysis (WGCNA). Methods The gene expression profile of vastus lateralis biopsy samples obtained in 17 patients with DMD, 11 patients with BMD and 6 healthy individuals was downloaded from the Gene Expression Omnibus (GEO) database (GSE109178). After obtaining different expressed genes (DEGs) via GEO2R, WGCNA was conducted using R package, modules and genes that highly associated with DMD, BMD, and their age or pathology were screened. Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment analysis and protein–protein interaction (PPI) network analysis were also conducted. Hub genes and highly correlated clustered genes were identified using Search Tool for the Retrieval of Interacting Genes (STRING) and Cystoscape software. Results One thousand four hundred seventy DEGs were identified between DMD and control, with 1281 upregulated and 189 downregulated DEGs. Four hundred and twenty DEGs were found between BMD and control, with 157 upregulated and 263 upregulated DEGs. Fourteen modules with different colors were identified for DMD vs control, and 7 modules with different colors were identified for BMD vs control. Ten hub genes were summarized for DMD and BMD respectively, 5 hub genes were summarized for BMD age, 5 and 3 highly correlated clustered genes were summarized for DMD age and BMD pathology, respectively. In addition, 20 GO enrichments were found to be involved in DMD, 3 GO enrichments were found to be involved in BMD, 3 GO enrichments were found to be involved in BMD age. Conclusion In DMD, several hub genes were identified: C3AR1, TLR7, IRF8, FYB and CD33(immune and inflammation associated genes), TYROBP, PLEK, AIF1(actin reorganization associated genes), LAPTM5 and NT5E(cell death and arterial calcification associated genes, respectively). In BMD, a number of hub genes were identified: LOX, ELN, PLEK, IKZF1, CTSK, THBS2, ADAMTS2, COL5A1(extracellular matrix associated genes), BCL2L1 and CDK2(cell cycle associated genes).
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Smith JC, Sausville EL, Girish V, Yuan ML, Vasudevan A, John KM, Sheltzer JM. Cigarette Smoke Exposure and Inflammatory Signaling Increase the Expression of the SARS-CoV-2 Receptor ACE2 in the Respiratory Tract. Dev Cell 2020; 53:514-529.e3. [PMID: 32425701 PMCID: PMC7229915 DOI: 10.1016/j.devcel.2020.05.012] [Citation(s) in RCA: 276] [Impact Index Per Article: 69.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 04/26/2020] [Accepted: 05/12/2020] [Indexed: 01/06/2023]
Abstract
The factors mediating fatal SARS-CoV-2 infections are poorly understood. Here, we show that cigarette smoke causes a dose-dependent upregulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 receptor, in rodent and human lungs. Using single-cell sequencing data, we demonstrate that ACE2 is expressed in a subset of secretory cells in the respiratory tract. Chronic smoke exposure triggers the expansion of this cell population and a concomitant increase in ACE2 expression. In contrast, quitting smoking decreases the abundance of these secretory cells and reduces ACE2 levels. Finally, we demonstrate that ACE2 expression is responsive to inflammatory signaling and can be upregulated by viral infections or interferon treatment. Taken together, these results may partially explain why smokers are particularly susceptible to severe SARS-CoV-2 infections. Furthermore, our work identifies ACE2 as an interferon-stimulated gene in lung cells, suggesting that SARS-CoV-2 infections could create positive feedback loops that increase ACE2 levels and facilitate viral dissemination.
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Affiliation(s)
- Joan C Smith
- Google, Inc., New York City, NY 10011, USA; Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Erin L Sausville
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Vishruth Girish
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Stony Brook University, Stony Brook, NY 11794, USA
| | - Monet Lou Yuan
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Johns Hopkins University, Baltimore, MD 21218, USA
| | - Anand Vasudevan
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Kristen M John
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Hofstra University, Hempstead, NY 11549, USA
| | - Jason M Sheltzer
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
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Cho HY, Kleeberger SR. Mitochondrial biology in airway pathogenesis and the role of NRF2. Arch Pharm Res 2019; 43:297-320. [PMID: 31486024 DOI: 10.1007/s12272-019-01182-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 08/14/2019] [Indexed: 12/12/2022]
Abstract
A constant improvement in understanding of mitochondrial biology has provided new insights into mitochondrial dysfunction in human disease pathogenesis. Impaired mitochondrial dynamics caused by various stressors are characterized by structural abnormalities and leakage, compromised turnover, and reactive oxygen species overproduction in mitochondria as well as increased mitochondrial DNA mutation frequency, which leads to modified energy production and mitochondria-derived cell signaling. The mitochondrial dysfunction in airway epithelial, smooth muscle, and endothelial cells has been implicated in diseases including chronic obstructive lung diseases and acute lung injury. Increasing evidence indicates that the NRF2-antioxidant response element (ARE) pathway not only enhances redox defense but also facilitates mitochondrial homeostasis and bioenergetics. Identification of functional or potential AREs further supports the role for Nrf2 in mitochondrial dysfunction-associated airway disorders. While clinical reports indicate mixed efficacy, NRF2 agonists acting on respiratory mitochondrial dynamics are potentially beneficial. In lung cancer, growth advantage provided by sustained NRF2 activation is suggested to be through increased cellular antioxidant defense as well as mitochondria reinforcement and metabolic reprogramming to the preferred pathways to meet the increased energy demands of uncontrolled cell proliferation. Further studies are warranted to better understand NRF2 regulation of mitochondrial functions as therapeutic targets in airway disorders.
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Affiliation(s)
- Hye-Youn Cho
- Immunity, Inflammation, and Disease Laboratory, National Institute of Environmental Health Sciences, 111 TW Alexander Dr., Research Triangle Park, NC, 27709, USA.
| | - Steven R Kleeberger
- Immunity, Inflammation, and Disease Laboratory, National Institute of Environmental Health Sciences, 111 TW Alexander Dr., Research Triangle Park, NC, 27709, USA
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Fukumoto J, Sidramagowda Patil S, Krishnamurthy S, Saji S, John I, Narala VR, Hernández-Cuervo H, Alleyn M, Breitzig MT, Galam L, Soundararajan R, Chaudhari UK, Hansen BC, Lockey RF, Kolliputi N. Altered expression of p63 isoforms and expansion of p63- and club cell secretory protein-positive epithelial cells in the lung as novel features of aging. Am J Physiol Cell Physiol 2019; 316:C492-C508. [PMID: 30649915 PMCID: PMC6482668 DOI: 10.1152/ajpcell.00330.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 01/04/2019] [Accepted: 01/05/2019] [Indexed: 12/20/2022]
Abstract
Aging is a key contributor for subclinical progression of late-onset lung diseases. Basal, club, and type II alveolar epithelial cells (AECs) are lung epithelial progenitors whose capacities of differentiation are extensively studied. The timely transition of these cells in response to environmental changes helps maintain the intricate organization of lung structure. However, it remains unclear how aging affects their behavior. This paper demonstrates that the protein expression profiles of a type II AEC marker, prosurfactant protein C (pro-SPC), and a basal cell marker, p63, are altered in the lungs of 14-mo-old versus 7- to 9-wk-old mice. Expression of NH2-terminal-truncated forms of p63 (ΔNp63), a basal cell marker, and claudin-10, a club cell marker, in cytoplasmic extracts of lungs of 14-mo-old mice was upregulated. In contrast, nuclear expression of full-length forms of p63 (TAp63) decreases with age. These alterations in protein expression profiles coincide with dramatic changes in lung functions including compliance. Whole tissue lysates of middle-aged versus aged rhesus monkey lungs display similar age-associated alterations in pro-SPC expression. An age-associated decrease of TAp63 in nuclear lysates was observed in aged monkey group. Moreover, the lungs of 14-mo-old versus 7- to 9-wk-old mice display a wider spreading of ΔNp63-positive CCSP-positive bronchiolar epithelial cells. This expansion did not involve upregulation of Ki67, a representative proliferation marker. Collectively, it is postulated that 1) this expansion is secondary to a transition of progenitor cells committed to club cells from ΔNp63-negative to ΔNp63-positive status, and 2) high levels of cytoplasmic ΔNp63 expression trigger club cell migration.
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Affiliation(s)
- Jutaro Fukumoto
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Sahebgowda Sidramagowda Patil
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Sudarshan Krishnamurthy
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Smita Saji
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Irene John
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Venkata Ramireddy Narala
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
- Department of Zoology, Yogi Vemana University, Kadapa, India
| | - Helena Hernández-Cuervo
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Matthew Alleyn
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Mason T Breitzig
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Lakshmi Galam
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Ramani Soundararajan
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Uddhav K Chaudhari
- Departments of Internal Medicine and Pediatrics, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Barbara C Hansen
- Departments of Internal Medicine and Pediatrics, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Richard F Lockey
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Narasaiah Kolliputi
- Division of Allergy and Immunology, Department of Internal Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida , Tampa, Florida
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Traver G, Mont S, Gius D, Lawson WE, Ding GX, Sekhar KR, Freeman ML. Loss of Nrf2 promotes alveolar type 2 cell loss in irradiated, fibrotic lung. Free Radic Biol Med 2017; 112:578-586. [PMID: 28870520 PMCID: PMC5623074 DOI: 10.1016/j.freeradbiomed.2017.08.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/28/2017] [Accepted: 08/31/2017] [Indexed: 12/21/2022]
Abstract
The development of radiation-induced pulmonary fibrosis represents a critical clinical issue limiting delivery of therapeutic doses of radiation to non-small cell lung cancer. Identification of the cell types whose injury initiates a fibrotic response and the underlying biological factors that govern that response are needed for developing strategies that prevent or mitigate fibrosis. C57BL/6 mice (wild type, Nrf2 null, Nrf2flox/flox, and Nrf2Δ/Δ; SPC-Cre) were administered a thoracic dose of 12Gy and allowed to recover for 250 days. Whole slide digital and confocal microscopy imaging of H&E, Masson's trichrome and immunostaining were used to assess tissue remodeling, collagen deposition and cell renewal/mobilization during the regenerative process. Histological assessment of irradiated, fibrotic wild type lung revealed significant loss of alveolar type 2 cells 250 days after irradiation. Type 2 cell loss and the corresponding development of fibrosis were enhanced in the Nrf2 null mouse. Yet, conditional deletion of Nrf2 in alveolar type 2 cells in irradiated lung did not impair type 2 cell survival nor yield an increased fibrotic phenotype. Instead, radiation-induced ΔNp63 stem/progenitor cell mobilization was inhibited in the Nrf2 null mouse while the propensity for radiation-induced myofibroblasts derived from alveolar type 2 cells was magnified. In summary, these results indicate that Nrf2 is an important regulator of irradiated lung's capacity to maintain alveolar type 2 cells, whose injury can initiate a fibrotic phenotype. Loss of Nrf2 inhibits ΔNp63 stem/progenitor mobilization, a key event for reconstitution of injured lung, while promoting a myofibroblast phenotype that is central for fibrosis.
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Affiliation(s)
- Geri Traver
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Stacey Mont
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - David Gius
- Department of Radiation Oncology, Driskill Graduate Program in Life Sciences, Department of Pharmacology, Robert Lurie Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - William E Lawson
- Division of Pulmonary & Critical Care, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Konjeti R Sekhar
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Michael L Freeman
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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