501
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Calado RT, Brudno J, Mehta P, Kovacs JJ, Wu C, Zago MA, Chanock SJ, Boyer TD, Young NS. Constitutional telomerase mutations are genetic risk factors for cirrhosis. Hepatology 2011; 53:1600-7. [PMID: 21520173 PMCID: PMC3082730 DOI: 10.1002/hep.24173] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED Some patients with liver disease progress to cirrhosis, but the risk factors for cirrhosis development are unknown. Dyskeratosis congenita, an inherited bone marrow failure syndrome associated with mucocutaneous anomalies, pulmonary fibrosis, and cirrhosis, is caused by germline mutations of genes in the telomerase complex. We examined whether telomerase mutations also occurred in sporadic cirrhosis. In all, 134 patients with cirrhosis of common etiologies treated at the Liver Research Institute, University of Arizona, between May 2008 and July 2009, and 528 healthy subjects were screened for variation in the TERT and TERC genes by direct sequencing; an additional 1,472 controls were examined for the most common genetic variation observed in patients. Telomere length of leukocytes was measured by quantitative polymerase chain reaction. Functional effects of genetic changes were assessed by transfection of mutation-containing vectors into telomerase-deficient cell lines, and telomerase activity was measured in cell lysates. Nine of the 134 patients with cirrhosis (7%) carried a missense variant in TERT, resulting in a cumulative carrier frequency significantly higher than in controls (P = 0.0009). One patient was homozygous and eight were heterozygous. The allele frequency for the most common missense TERT variant was significantly higher in patients with cirrhosis (2.6%) than in 2,000 controls (0.7%; P = 0.0011). One additional patient carried a TERC mutation. The mean telomere length of leukocytes in patients with cirrhosis, including six mutant cases, was shorter than in age-matched controls (P = 0.0004). CONCLUSION Most TERT gene variants reduced telomerase enzymatic activity in vitro. Loss-of-function telomerase gene variants associated with short telomeres are risk factors for sporadic cirrhosis.
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Affiliation(s)
- Rodrigo T. Calado
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Jennifer Brudno
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
- Clinical Research Training Program, National Institutes of Health, Bethesda, Maryland
| | - Paulomi Mehta
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
- Clinical Research Training Program, National Institutes of Health, Bethesda, Maryland
| | - Joseph J. Kovacs
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Colin Wu
- Office of Biostatistics Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Marco A. Zago
- Division of Hematology, Department of Internal Medicine, University of São Paulo at Ribeirão Preto Medical School, Ribeirão Preto, SP, Brazil
| | - Stephen J. Chanock
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Thomas D. Boyer
- Liver Research Institute, University of Arizona School of Medicine, Tucson, Arizona
| | - Neal S. Young
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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502
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Gu BW, Fan JM, Bessler M, Mason PJ. Accelerated hematopoietic stem cell aging in a mouse model of dyskeratosis congenita responds to antioxidant treatment. Aging Cell 2011; 10:338-48. [PMID: 21241452 DOI: 10.1111/j.1474-9726.2011.00674.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mutations in DKC1, encoding telomerase associated protein dyskerin, cause X-linked dyskeratosis congenita (DC), a bone marrow (BM) failure, and cancer susceptibility syndrome. Decreased accumulation of telomerase RNA resulting in excessive telomere shortening and premature cellular senescence is thought to be the primary cause of disease in X-linked DC. Affected tissues are those that require constant renewal by stem cell activity. We previously showed that in Dkc1(Δ15) mice, which contain a mutation that is a copy of a human mutation causing DC, mutant cells have a telomerase-dependent proliferative defect and increased accumulation of DNA damage in the first generation before the telomeres are short. We now demonstrate the presence of the growth defect in Dkc1(Δ15) mouse embryonic fibroblasts in vitro and show that accumulation of DNA damage and levels of reactive oxygen species increase with increasing population doublings. Treatment with the antioxidant, N-acetyl cysteine (NAC), partially rescued the growth disadvantage of mutant cells in vitro and in vivo. Competitive BM repopulation experiments showed that the Dkc1(Δ15) mutation is associated with a functional stem cell defect that becomes more severe with increasing age, consistent with accelerated senescence, a hallmark of DC hematopoiesis. This stem cell phenotype was partially corrected by NAC treatment. These results suggest that a pathogenic Dkc1 mutation accelerates stem cell aging, that increased oxidative stress might play a role in the pathogenesis of X-linked DC, and that some manifestations of DC may be prevented or delayed by antioxidant treatment.
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Affiliation(s)
- Bai-Wei Gu
- Division of Hematology, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO, USA
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503
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Alder JK, Cogan JD, Brown AF, Anderson CJ, Lawson WE, Lansdorp PM, Phillips JA, Loyd JE, Chen JJL, Armanios M. Ancestral mutation in telomerase causes defects in repeat addition processivity and manifests as familial pulmonary fibrosis. PLoS Genet 2011; 7:e1001352. [PMID: 21483807 PMCID: PMC3069110 DOI: 10.1371/journal.pgen.1001352] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Accepted: 02/23/2011] [Indexed: 01/05/2023] Open
Abstract
The telomerase reverse transcriptase synthesizes new telomeres onto chromosome ends by copying from a short template within its integral RNA component. During telomere synthesis, telomerase adds multiple short DNA repeats successively, a property known as repeat addition processivity. However, the consequences of defects in processivity on telomere length maintenance are not fully known. Germline mutations in telomerase cause haploinsufficiency in syndromes of telomere shortening, which most commonly manifest in the age-related disease idiopathic pulmonary fibrosis. We identified two pulmonary fibrosis families that share two non-synonymous substitutions in the catalytic domain of the telomerase reverse transcriptase gene hTERT: V791I and V867M. The two variants fell on the same hTERT allele and were associated with telomere shortening. Genealogy suggested that the pedigrees shared a single ancestor from the nineteenth century, and genetic studies confirmed the two families had a common founder. Functional studies indicated that, although the double mutant did not dramatically affect first repeat addition, hTERT V791I-V867M showed severe defects in telomere repeat addition processivity in vitro. Our data identify an ancestral mutation in telomerase with a novel loss-of-function mechanism. They indicate that telomere repeat addition processivity is a critical determinant of telomere length and telomere-mediated disease.
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Affiliation(s)
- Jonathan K. Alder
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Joy D. Cogan
- Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Andrew F. Brown
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States of America
| | - Collin J. Anderson
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - William E. Lawson
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Peter M. Lansdorp
- Terry Fox Laboratory and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - John A. Phillips
- Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - James E. Loyd
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Julian J.-L. Chen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States of America
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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504
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Syndrome complex of bone marrow failure and pulmonary fibrosis predicts germline defects in telomerase. Blood 2011; 117:5607-11. [PMID: 21436073 DOI: 10.1182/blood-2010-11-322149] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mutations in the essential telomerase components hTERT and hTR cause dyskeratosis congenita, a bone marrow failure syndrome characterized by mucocutaneous features. Some (~ 3%) sporadic aplastic anemia (AA) and idiopathic pulmonary fibrosis cases also carry mutations in hTERT and hTR. Even though it can affect clinical outcome, because the mutation frequency is rare, genetic testing is not standard. We examined whether the cooccurrence of bone marrow failure and pulmonary fibrosis in the same individual or family enriches for the presence of a telomerase mutation. Ten consecutive individuals with a total of 36 family members who fulfilled these criteria carried a germline mutant telomerase gene (100%). The mean age of onset for individuals with AA was significantly younger than that for those with pulmonary fibrosis (14 vs 51; P < .0001). Families displayed autosomal dominant inheritance and there was an evolving pattern of genetic anticipation, with the older generation primarily affected by pulmonary fibrosis and successive generations by bone marrow failure. The cooccurrence of AA and pulmonary fibrosis in a single patient or family is highly predictive for the presence of a germline telomerase defect. This diagnosis affects the choice of bone marrow transplantation preparative regimen and can prevent morbidity.
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505
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Naik PK, Moore BB. Viral infection and aging as cofactors for the development of pulmonary fibrosis. Expert Rev Respir Med 2011; 4:759-71. [PMID: 21128751 DOI: 10.1586/ers.10.73] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Idiopathic pulmonary fibrosis (IPF) is a disease of unknown origin and progression that primarily affects older adults. Accumulating clinical and experimental evidence suggests that viral infections may play a role, either as agents that predispose the lung to fibrosis or exacerbate existing fibrosis. In particular, herpesviruses have been linked with IPF. This article summarizes the evidence for and against viral cofactors in IPF pathogenesis. In addition, we review mechanistic studies in animal models that highlight the fibrotic potential of viral infection, and explore the different mechanisms that might be responsible. We also review early evidence to suggest that the aged lung may be particularly susceptible to viral-induced fibrosis and make recommendations for future research directions.
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Affiliation(s)
- Payal K Naik
- Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, MI 48109-2200, USA
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506
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Parry EM, Alder JK, Lee SS, Phillips JA, Loyd JE, Duggal P, Armanios M. Decreased dyskerin levels as a mechanism of telomere shortening in X-linked dyskeratosis congenita. J Med Genet 2011; 48:327-33. [PMID: 21415081 PMCID: PMC3088476 DOI: 10.1136/jmg.2010.085100] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dyskeratosis congenita (DC) is a premature ageing syndrome characterised by short telomeres. An X-linked form of DC is caused by mutations in DKC1 which encodes dyskerin, a telomerase component that is essential for telomerase RNA stability. However, mutations in DKC1 are identifiable in only half of X-linked DC families. A four generation family with pulmonary fibrosis and features of DC was identified. Affected males showed the classic mucocutaneous features of DC and died prematurely from pulmonary fibrosis. Although there were no coding sequence or splicing variants, genome wide linkage analysis of 16 individuals across four generations identified significant linkage at the DKC1 locus, and was accompanied by reduced dyskerin protein levels in affected males. Decreased dyskerin levels were associated with compromised telomerase RNA levels and very short telomeres. These data identify decreased dyskerin levels as a novel mechanism of DC, and indicate that intact dyskerin levels, in the absence of coding mutations, are critical for telomerase RNA stability and for in vivo telomere maintenance.
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Affiliation(s)
- Erin M Parry
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
- Medical Scientist Training Progra, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - Jonathan K Alder
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - Stella S Lee
- Pre-doctoral Training Program in Human Genetics, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
| | - John A Phillips
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - James E Loyd
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Priya Duggal
- Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Mary Armanios
- Department of Oncology and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, Maryland, USA
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507
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Selman M, Pardo A, Richeldi L, Cerri S. Emerging drugs for idiopathic pulmonary fibrosis. Expert Opin Emerg Drugs 2011; 16:341-62. [DOI: 10.1517/14728214.2011.565049] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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508
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Raghu G, Collard HR, Egan JJ, Martinez FJ, Behr J, Brown KK, Colby TV, Cordier JF, Flaherty KR, Lasky JA, Lynch DA, Ryu JH, Swigris JJ, Wells AU, Ancochea J, Bouros D, Carvalho C, Costabel U, Ebina M, Hansell DM, Johkoh T, Kim DS, King TE, Kondoh Y, Myers J, Müller NL, Nicholson AG, Richeldi L, Selman M, Dudden RF, Griss BS, Protzko SL, Schünemann HJ. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med 2011; 183:788-824. [PMID: 21471066 PMCID: PMC5450933 DOI: 10.1164/rccm.2009-040gl] [Citation(s) in RCA: 5059] [Impact Index Per Article: 389.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This document is an international evidence-based guideline on the diagnosis and management of idiopathic pulmonary fibrosis, and is a collaborative effort of the American Thoracic Society, the European Respiratory Society, the Japanese Respiratory Society, and the Latin American Thoracic Association. It represents the current state of knowledge regarding idiopathic pulmonary fibrosis (IPF), and contains sections on definition and epidemiology, risk factors, diagnosis, natural history, staging and prognosis, treatment, and monitoring disease course. For the diagnosis and treatment sections, pragmatic GRADE evidence-based methodology was applied in a question-based format. For each diagnosis and treatment question, the committee graded the quality of the evidence available (high, moderate, low, or very low), and made a recommendation (yes or no, strong or weak). Recommendations were based on majority vote. It is emphasized that clinicians must spend adequate time with patients to discuss patients' values and preferences and decide on the appropriate course of action.
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509
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Guo N, Parry EM, Li LS, Kembou F, Lauder N, Hussain MA, Berggren PO, Armanios M. Short telomeres compromise β-cell signaling and survival. PLoS One 2011; 6:e17858. [PMID: 21423765 PMCID: PMC3053388 DOI: 10.1371/journal.pone.0017858] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/11/2011] [Indexed: 01/09/2023] Open
Abstract
The genetic factors that underlie the increasing incidence of diabetes with age are poorly understood. We examined whether telomere length, which is inherited and known to shorten with age, plays a role in the age-dependent increased incidence of diabetes. We show that in mice with short telomeres, insulin secretion is impaired and leads to glucose intolerance despite the presence of an intact β-cell mass. In ex vivo studies, short telomeres induced cell-autonomous defects in β-cells including reduced mitochondrial membrane hyperpolarization and Ca2+ influx which limited insulin release. To examine the mechanism, we looked for evidence of apoptosis but found no baseline increase in β-cells with short telomeres. However, there was evidence of all the hallmarks of senescence including slower proliferation of β-cells and accumulation of p16INK4a. Specifically, we identified gene expression changes in pathways which are essential for Ca2+-mediated exocytosis. We also show that telomere length is additive to the damaging effect of endoplasmic reticulum stress which occurs in the late stages of type 2 diabetes. This additive effect manifests as more severe hyperglycemia in Akita mice with short telomeres which had a profound loss of β-cell mass and increased β-cell apoptosis. Our data indicate that short telomeres can affect β-cell metabolism even in the presence of intact β-cell number, thus identifying a novel mechanism of telomere-mediated disease. They implicate telomere length as a determinant of β-cell function and diabetes pathogenesis.
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Affiliation(s)
- Nini Guo
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Erin M. Parry
- Medical Scientist Training Program, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Luo-Sheng Li
- The Roft Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Frant Kembou
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Naudia Lauder
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Mehboob A. Hussain
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Per-Olof Berggren
- The Roft Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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510
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Koziel JE, Fox MJ, Steding CE, Sprouse AA, Herbert BS. Medical genetics and epigenetics of telomerase. J Cell Mol Med 2011; 15:457-67. [PMID: 21323862 PMCID: PMC3922369 DOI: 10.1111/j.1582-4934.2011.01276.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 02/01/2011] [Indexed: 12/13/2022] Open
Abstract
Telomerase is a specialized reverse transcriptase that extends and maintains the terminal ends of chromosomes, or telomeres. Since its discovery in 1985 by Nobel Laureates Elizabeth Blackburn and Carol Greider, thousands of articles have emerged detailing its significance in telomere function and cell survival. This review provides a current assessment on the importance of telomerase regulation and relates it in terms of medical genetics. In this review, we discuss the recent findings on telomerase regulation, focusing on epigenetics and non-coding RNAs regulation of telomerase, such as microRNAs and the recently discovered telomeric-repeat containing RNA transcripts. Human genetic disorders that develop due to mutations in telomerase subunits, the role of single nucleotide polymorphisms in genes encoding telomerase components and diseases as a result of telomerase regulation going awry are also discussed. Continual investigation of the complex regulation of telomerase will further our insight into the use of controlling telomerase activity in medicine.
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Affiliation(s)
- Jillian E Koziel
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Melanie J Fox
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Catherine E Steding
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
| | - Alyssa A Sprouse
- Department of Pharmacology and Toxicology, Indiana University School of MedicineIndianapolis, IN, USA
| | - Brittney-Shea Herbert
- Department of Medical and Molecular Genetics, Indiana University School of MedicineIndianapolis, IN, USA
- Department of Pharmacology and Toxicology, Indiana University School of MedicineIndianapolis, IN, USA
- Indiana University Melvin and Bren Simon Cancer Center, Indiana University School of MedicineIndianapolis, IN, USA
- Indiana University Center for Regenerative Biology and Medicine, Indiana University School of MedicineIndianapolis, IN, USA
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511
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Diaz de Leon A, Cronkhite JT, Yilmaz C, Brewington C, Wang R, Xing C, Hsia CCW, Garcia CK. Subclinical lung disease, macrocytosis, and premature graying in kindreds with telomerase (TERT) mutations. Chest 2011; 140:753-763. [PMID: 21349926 DOI: 10.1378/chest.10-2865] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Mutations in the human gene encoding the protein component of telomerase (TERT) are the most common genetic defect in patients with familial idiopathic pulmonary fibrosis (IPF). The subclinical phenotypes of asymptomatic members of these families have not been evaluated with respect to TERT mutation status or telomere length. METHODS We measured a variety of pulmonary, blood, skin, and bone parameters for 20 subjects with heterozygous TERT mutations (carriers) and 20 family members who had not inherited a TERT mutation (noncarriers) to identify the spectrum of phenotypes associated with mutations in this gene. The two groups were matched for sex, age, and cigarette smoking. Three TERT mutation carriers had IPF (IPF carriers). The rest of the carriers were apparently healthy (asymptomatic carriers) and were compared with the noncarriers. RESULTS Asymptomatic carriers exhibited significantly lower diffusing capacity of lung for carbon monoxide (Dlco), impaired recruitment of Dlco with exercise, radiographic signs of lung fibrosis, and increased fractional lung tissue volume quantified by high-resolution chest CT scan than noncarriers. RBC and platelet counts were significantly lower, and the mean corpuscular volume and mean corpuscular hemoglobin concentration were significantly higher in carriers than in noncarriers. Carriers reported significantly earlier graying of hair than noncarriers. TERT mutation status is more accurately predicted by short telomere lengths than any of these measured phenotypes. CONCLUSIONS TERT mutation carriers exhibit early preclinical signs of lung fibrosis, bone marrow dysfunction, and premature graying. These clinical features and short telomere lengths characterize patients with germline TERT mutations.
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Affiliation(s)
- Alberto Diaz de Leon
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jennifer T Cronkhite
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX
| | - Cuneyt Yilmaz
- Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Cecelia Brewington
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Richard Wang
- Department of Dermatology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Chao Xing
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX
| | - Connie C W Hsia
- Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Christine Kim Garcia
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX; Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Texas Southwestern Medical Center, Dallas, TX.
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512
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Xu Y. Chemistry in human telomere biology: structure, function and targeting of telomere DNA/RNA. Chem Soc Rev 2011; 40:2719-40. [DOI: 10.1039/c0cs00134a] [Citation(s) in RCA: 249] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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513
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Abstract
Telomeres are nucleoprotein structures that protect the ends of human chromosomes through the formation of a 'cap', thus preventing exonucleolytic degradation, inter- and intra-chromosomal fusion, and subsequent chromosomal instability. During aging, telomere shortening correlates with tissue dysfunction and loss of renewal capacity. In human cancer, telomere dysfunction is involved in early chromosome instability, long-term cellular proliferation, and possibly other processes related to cell survival and microenvironment. Telomeres constitute an attractive target for the development of novel small-molecule anti-cancer drugs. In particular, individual protein components of the core telomere higher-order chromatin structure (known as the telosome or 'shelterin' complex) are promising candidate targets for cancer therapy.
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514
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Minagawa S, Araya J, Numata T, Nojiri S, Hara H, Yumino Y, Kawaishi M, Odaka M, Morikawa T, Nishimura SL, Nakayama K, Kuwano K. Accelerated epithelial cell senescence in IPF and the inhibitory role of SIRT6 in TGF-β-induced senescence of human bronchial epithelial cells. Am J Physiol Lung Cell Mol Physiol 2010; 300:L391-401. [PMID: 21224216 DOI: 10.1152/ajplung.00097.2010] [Citation(s) in RCA: 219] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Reepithelialization of remodeled air spaces with bronchial epithelial cells is a prominent pathological finding in idiopathic pulmonary fibrosis (IPF) and is implicated in IPF pathogenesis. Recent studies suggest that epithelial senescence is a risk factor for development of IPF, indicating such reepithelialization may be influenced by the acceleration of cellular senescence. Among the sirtuin (SIRT) family, SIRT6, a class III histone deacetylase, has been demonstrated to antagonize senescence. We evaluated the senescence of bronchiolization in association with SIRT6 expression in IPF lung. Senescence-associated β-galactosidase staining and immunohistochemical detection of p21 were performed to evaluate cellular senescence. As a model for transforming growth factor (TGF)-β-induced senescence of abnormal reepithelialization, we used primary human bronchial epithelial cells (HBEC). The changes of SIRT6, p21, and interleukin (IL)-1β expression levels in HBEC, as well as type I collagen expression levels in fibroblasts, were evaluated. In IPF lung samples, an increase in markers of senescence and SIRT6 expression was found in the bronchial epithelial cells lining cystically remodeled air spaces. We found that TGF-β induced senescence in primary HBEC by increasing p21 expression, and, whereas TGF-β also induced SIRT6, it was not sufficient to inhibit cellular senescence. However, overexpression of SIRT6 efficiently inhibited TGF-β-induced senescence via proteasomal degradation of p21. TGF-β-induced senescent HBEC secreted increased amounts of IL-1β, which was sufficient to induce myofibroblast differentiation in fibroblasts. These findings suggest that accelerated epithelial senescence plays a role in IPF pathogenesis through perpetuating abnormal epithelial-mesenchymal interactions, which can be antagonized by SIRT6.
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Affiliation(s)
- Shunsuke Minagawa
- Division of Respiratory Diseases, Dept. of Internal Medicine, Jikei Univ. School of Medicine, Tokyo, Japan
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515
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Lawson WE, Loyd JE. Will the Genes Responsible for Familial Pulmonary Fibrosis Provide Clues to the Pathogenesis of IPF? Am J Respir Crit Care Med 2010; 182:1342-3. [DOI: 10.1164/rccm.201007-1193ed] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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516
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Perona R. The Nobel Prize in Physiology or Medicine 2009 “for telomere biology” and its relevance to cancer and related diseases. Clin Transl Oncol 2010; 12:647-9. [DOI: 10.1007/s12094-010-0572-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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517
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El-Chemaly S, Ziegler SG, Calado RT, Wilson KA, Wu HP, Haughey M, Peterson NR, Young NS, Gahl WA, Moss J, Gochuico BR. Natural history of pulmonary fibrosis in two subjects with the same telomerase mutation. Chest 2010; 139:1203-1209. [PMID: 20966039 DOI: 10.1378/chest.10-2048] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
UNLABELLED Previous studies have identified subclinical lung disease in family members of probands with familial pulmonary fibrosis, but the natural history of preclinical pulmonary fibrosis is uncertain. The purpose of this study was to determine whether individuals with preclinical lung disease will develop pulmonary fibrosis. After a 27-year interval, two subjects with manifestations of preclinical familial pulmonary fibrosis, including asymptomatic alveolar inflammation and alveolar macrophage activation, were reevaluated for lung disease. CT scans of the chest, pulmonary function tests, and BAL were performed, and genomic DNA was analyzed for mutations in candidate genes associated with familial pulmonary fibrosis. One subject developed symptomatic familial pulmonary fibrosis and was treated with oxygen; her sister remained asymptomatic but had findings of pulmonary fibrosis on high-resolution CT scan of the chest. High concentrations of lymphocytes were found in BAL fluid from both subjects. Genetic sequencing and analyses identified a novel heterozygous mutation in telomerase reverse transcriptase (TERT, R1084P), resulting in telomerase dysfunction and short telomeres in both subjects. In familial pulmonary fibrosis, asymptomatic preclinical alveolar inflammation associated with mutation in TERT and telomerase insufficiency can progress to fibrotic lung disease over 2 to 3 decades. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00071045; URL: www.clinicaltrials.gov.
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Affiliation(s)
- Souheil El-Chemaly
- Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Shira G Ziegler
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD
| | - Rodrigo T Calado
- Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Kirkland A Wilson
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD
| | - Hai Ping Wu
- Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Mary Haughey
- Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Nathan R Peterson
- Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Neal S Young
- Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - William A Gahl
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD
| | - Joel Moss
- Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, Bethesda, MD
| | - Bernadette R Gochuico
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD.
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518
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Abstract
Cellular senescence is a specialized form of growth arrest, confined to mitotic cells, induced by various stressful stimuli and characterized by a permanent growth arrest, resistance to apoptosis, an altered pattern of gene expression and the expression of some markers that are characteristic, although not exclusive, to the senescent state. Senescent cells profoundly modify neighboring and remote cells through the production of an altered secretome, eventually leading to inflammation, fibrosis and possibly growth of neoplastic cells. Mammalian aging has been defined as a reduction in the capacity to adequately maintain tissue homeostasis or to repair tissues after injury. Tissue homeostasis and regenerative capacity are nowadays considered to be related to the stem cell pool present in every tissue. For this reason, pathological and patho-physiological conditions characterized by altered tissue homeostasis and impaired regenerative capacity can be viewed as a consequence of the reduction in stem cell number and/or function. Last, cellular senescence is a double-edged sword, since it may inhibit the growth of transformed cells, preventing the occurrence of cancer, while it may facilitate growth of preneoplastic lesions in a paracrine fashion; therefore, interventions targeting this cell response to stress may have a profound impact on many age-related pathologies, ranging from cardiovascular disease to oncology. Aim of this review is to discuss both molecular mechanisms associated with stem cell senescence and interventions that may attenuate or reverse this process.
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519
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Coward WR, Saini G, Jenkins G. The pathogenesis of idiopathic pulmonary fibrosis. Ther Adv Respir Dis 2010; 4:367-88. [PMID: 20952439 DOI: 10.1177/1753465810379801] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with an appalling prognosis. The failure of anti-inflammatory therapies coupled with the observation that deranged epithelium overlies proliferative myofibroblasts to form the fibroblastic focus has lead to the emerging concept that IPF is a disease of deregulated epithelial-mesenchymal crosstalk. IPF is triggered by an as yet unidentified alveolar injury that leads to activation of transforming growth factor-β (TGF-β) and alveolar basement membrane disruption. In the presence of persisting injurious pathways, or disrupted repair pathways, activated TGF-β can lead to enhanced epithelial apoptosis and epithelial-to-mesenchymal transition (EMT) as well as fibroblast, and fibrocyte, transformation into myofibroblasts which are resistant to apoptosis. The resulting deposition of excess disrupted matrix by these myofibroblasts leads to the development of IPF.
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Affiliation(s)
- William R Coward
- Nottingham Respiratory Biomedical Research Unit, Clinical Sciences Building, Nottingham City Campus, Nottingham, UK
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520
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McGrath-Morrow SA, Gower WA, Rothblum-Oviatt C, Brody AS, Langston C, Fan LL, Lefton-Greif MA, Crawford TO, Troche M, Sandlund JT, Auwaerter PG, Easley B, Loughlin GM, Carroll JL, Lederman HM. Evaluation and management of pulmonary disease in ataxia-telangiectasia. Pediatr Pulmonol 2010; 45:847-59. [PMID: 20583220 PMCID: PMC4151879 DOI: 10.1002/ppul.21277] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ataxia-telangiectasia (A-T) is a rare autosomal recessive disorder caused by mutations in the ATM gene, resulting in faulty repair of breakages in double-stranded DNA. The clinical phenotype is complex and is characterized by neurologic abnormalities, immunodeficiencies, susceptibility to malignancies, recurrent sinopulmonary infections, and cutaneous abnormalities. Lung disease is common in patients with A-T and often progresses with age and neurological decline. Diseases of the respiratory system cause significant morbidity and are a frequent cause of death in the A-T population. Lung disease in this population is thought to exhibit features of one or more of the following phenotypes: recurrent sinopulmonary infections with bronchiectasis, interstitial lung disease, and lung disease associated with neurological abnormalities. Here, we review available evidence and present expert opinion on the diagnosis, evaluation, and management of lung disease in A-T, as discussed in a recent multidisciplinary workshop. Although more data are emerging on this unique population, many recommendations are made based on similarities to other more well-studied diseases. Gaps in current knowledge and areas for future research in the field of pulmonary disease in A-T are also outlined.
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Affiliation(s)
- Sharon A McGrath-Morrow
- Division of Pediatric Pulmonary, Department of Pediatrics, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21287-2533, USA.
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521
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Clement A, Nathan N, Epaud R, Fauroux B, Corvol H. Interstitial lung diseases in children. Orphanet J Rare Dis 2010; 5:22. [PMID: 20727133 PMCID: PMC2939531 DOI: 10.1186/1750-1172-5-22] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 08/20/2010] [Indexed: 12/30/2022] Open
Abstract
Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.
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Affiliation(s)
- Annick Clement
- Pediatric Pulmonary Department, Reference Center for Rare Lung Diseases, AP-HP, Hôpital Trousseau, Inserm UMR S-938, Université Pierre et Marie Curie-Paris 6, Paris, F-75012 France.
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522
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Huie TJ, Moss M, Frankel SK. What can biomarkers tell us about the pathogenesis of acute exacerbations of idiopathic pulmonary fibrosis? Am J Physiol Lung Cell Mol Physiol 2010; 299:L1-2. [DOI: 10.1152/ajplung.00155.2010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Tristan J. Huie
- Division of Pulmonary Science and Critical Care Medicine, University of Colorado Denver, Anschutz Medical Campus, Aurora; and
- Interstitial Lung Disease Program, National Jewish Health, Denver, Colorado
| | - Marc Moss
- Division of Pulmonary Science and Critical Care Medicine, University of Colorado Denver, Anschutz Medical Campus, Aurora; and
| | - Stephen K. Frankel
- Division of Pulmonary Science and Critical Care Medicine, University of Colorado Denver, Anschutz Medical Campus, Aurora; and
- Interstitial Lung Disease Program, National Jewish Health, Denver, Colorado
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523
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Lucid CE, Savani BN, Engelhardt BG, Shah P, Clifton C, Greenhut SL, Vaughan LA, Kassim A, Schuening F, Jagasia M. Extracorporeal photopheresis in patients with refractory bronchiolitis obliterans developing after allo-SCT. Bone Marrow Transplant 2010; 46:426-9. [PMID: 20581885 DOI: 10.1038/bmt.2010.152] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Extracorporeal photopheresis (ECP) has been shown to be a promising treatment for chronic graft-versus-host disease; however, only a few case reports are available that examine the effectiveness of ECP for bronchiolitis obliterans (BO) after allo-SCT. Because of the poor response to traditional therapies, ECP has been explored as a possible therapeutic option for severe BO after allo-SCT. Nine patients received ECP between July 2008 and August 2009 after a median follow-up of 23 months (range 9-93 months) post transplant. The primary indication for ECP was the development of BO in patients who had failed prior multidrug regimens. The median number of drugs used for BO management before ECP was 5 (range 2-7); this included immunosuppressive therapy. Six of nine (67%) patients responded to ECP after a median of 25 days (range 20-958 days). No ECP-related complications occurred. ECP seemed to stabilize rapidly declining pulmonary function tests in about two-thirds of patients with severe and heavily pretreated BO that developed after allo-SCT. This finding supports the need for a larger prospective study to confirm the impact of ECP on BO, and to consider earlier intervention with ECP to improve the outcome of BO after allo-SCT.
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Affiliation(s)
- C E Lucid
- Long-Term Follow-up Transplant Clinic, Hematology and Stem Cell Transplantation Section, Division of Hematology/Oncology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN-37232-5505, USA
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524
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Thannickal VJ. Aging, antagonistic pleiotropy and fibrotic disease. Int J Biochem Cell Biol 2010; 42:1398-400. [PMID: 20595011 DOI: 10.1016/j.biocel.2010.05.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 05/26/2010] [Accepted: 05/26/2010] [Indexed: 02/06/2023]
Abstract
Tissue fibrosis is most often referred to in its pathological context and is a major cause of progressive organ failure and death. Here, we consider fibrosis as an evolutionarily conserved, adaptive tissue response to injury. The role of NADPH oxidase 4 (Nox4) as a novel pro-fibrogenic mediator is highlighted. The concept that Nox4 may function as an antagonistically pleiotropic gene in age-associated fibrotic disorders is discussed.
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Affiliation(s)
- Victor J Thannickal
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, 1530 3rd Avenue South, THT 422, Birmingham, AL 35294-0006, United States.
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525
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526
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Diaz de Leon A, Cronkhite JT, Katzenstein ALA, Godwin JD, Raghu G, Glazer CS, Rosenblatt RL, Girod CE, Garrity ER, Xing C, Garcia CK. Telomere lengths, pulmonary fibrosis and telomerase (TERT) mutations. PLoS One 2010; 5:e10680. [PMID: 20502709 PMCID: PMC2873288 DOI: 10.1371/journal.pone.0010680] [Citation(s) in RCA: 263] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 04/23/2010] [Indexed: 11/18/2022] Open
Abstract
Background Telomerase is an enzyme that catalyzes the addition of nucleotides on the ends of chromosomes. Rare loss of function mutations in the gene that encodes the protein component of telomerase (TERT) have been described in patients with idiopathic pulmonary fibrosis (IPF). Here we examine the telomere lengths and pulmonary fibrosis phenotype seen in multiple kindreds with heterozygous TERT mutations. Methods and Findings We have identified 134 individuals with heterozygous TERT mutations from 21 unrelated families. Available medical records, surgical lung biopsies and radiographs were evaluated retrospectively. Genomic DNA isolated from circulating leukocytes has been used to measure telomere lengths with a quantitative PCR assay. We find that telomere lengths of TERT mutation carriers decrease in an age-dependent manner and show progressive shortening with successive generations of mutation inheritance. Family members without TERT mutations have a shorter mean telomere length than normal, demonstrating epigenetic inheritance of shortened telomere lengths in the absence of an inherited TERT mutation. Pulmonary fibrosis is an age-dependent phenotype not seen in mutation carriers less than 40 years of age but found in 60% of men 60 years or older; its development is associated with environmental exposures including cigarette smoking. A radiographic CT pattern of usual interstitial pneumonia (UIP), which is consistent with a diagnosis of IPF, is seen in 74% of cases and a pathologic pattern of UIP is seen in 86% of surgical lung biopsies. Pulmonary fibrosis associated with TERT mutations is progressive and lethal with a mean survival of 3 years after diagnosis. Overall, TERT mutation carriers demonstrate reduced life expectancy, with a mean age of death of 58 and 67 years for males and females, respectively. Conclusions A subset of pulmonary fibrosis, like dyskeratosis congenita, bone marrow failure, and liver disease, represents a “telomeropathy” caused by germline mutations in telomerase and characterized by short telomere lengths. Family members within kindreds who do not inherit the TERT mutation have shorter telomere lengths than controls, demonstrating epigenetic inheritance of a shortened parental telomere length set-point.
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Affiliation(s)
- Alberto Diaz de Leon
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Jennifer T. Cronkhite
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Anna-Luise A. Katzenstein
- Department of Pathology, The State University of New York Upstate Medical University, Syracuse, New York, United States of America
| | - J. David Godwin
- Department of Radiology, University of Washington Medical Center, Seattle, Washington, United States of America
| | - Ganesh Raghu
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Washington Medical Center, Seattle, Washington, United States of America
| | - Craig S. Glazer
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Randall L. Rosenblatt
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Carlos E. Girod
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Edward R. Garrity
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Chao Xing
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Christine Kim Garcia
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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527
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El-Chemaly S, Pacheco-Rodriguez G, Ikeda Y, Malide D, Moss J. Lymphatics in idiopathic pulmonary fibrosis: new insights into an old disease. Lymphat Res Biol 2010; 7:197-203. [PMID: 20143918 DOI: 10.1089/lrb.2009.0014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The lymphatic vasculature plays a key role in tissue homeostasis and immune surveillance. There is mounting evidence of a role for the lymphatic circulation and for newly formed lymphatic vessels in the pathogenesis of lung disease. Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, debilitating lung disease. In IPF, the lung parenchyma undergoes extensive remodeling. This review focuses on the current knowledge and understanding of the pathogenesis of IPF, and recent evidence of the involvement of lymphangiogenesis in lung injury and repair and the molecular and cellular pathways leading to the development of lymphatic vasculature.
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Affiliation(s)
- Souheil El-Chemaly
- Translational Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1590, USA
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528
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Abstract
The endothelin receptor-ligand system includes a family of polypeptides and G-protein-coupled receptors, which, in addition to their classic activity in the regulation of vascular tone (both directly and through the control of nitric oxide), were implicated in a wide variety of other key biological processes. In this regard, the endothelins are potent mitogens and motogens for mesenchymal cells, and can induce cell differentiation, increasing both the synthesis and deposition of extracellular matrix components and contractile ability. The endothelins are produced as inactive pre-pro-polypeptides, with gene transcription (as well as the proteolytic processing to mature active forms) under the influence of many factors, including cytokines, hypoxia, biomechanical and shear stress, pathogen products, and many growth factors. These complex regulatory events underlie the association and potential role of endothelins in a number of human diseases affecting many different target organs, including the vasculature (atherosclerosis and hypertension), kidney (renal crisis and chronic kidney disease), heart (coronary heart disease), and lungs (pulmonary fibrosis and pulmonary hypertension). This review focuses on the biochemistry of endothelin and the pathobiology of endothelin in lung fibrosis, with particular emphasis on idiopathic pulmonary fibrosis, and examines the antifibrotic potential of endothelin receptor antagonism.
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Affiliation(s)
- Carmen Fonseca
- Division of Medicine, Department of Inflammation, Centre for Rheumatology and Connective Tissue Diseases, Royal Free and University College Medical School, University College London, Rowland Hill Street, London, UK
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529
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Abstract
The inherited marrow failure syndromes are a diverse set of genetic disorders characterized by hematopoietic aplasia and cancer predisposition. The clinical phenotypes are highly variable and much broader than previously recognized. The medical management of the inherited marrow failure syndromes differs from that of acquired aplastic anemia or malignancies arising in the general population. Diagnostic workup, molecular pathogenesis, and clinical treatment are reviewed.
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530
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The IPFnet Strategy: Creating a comprehensive approach in the treatment of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med 2010; 181:527-8. [PMID: 20208036 DOI: 10.1164/rccm.200903-0483ed] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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531
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Abstract
PURPOSE OF REVIEW The lung in systemic sclerosis (scleroderma) is susceptible to fibrosis and the ensuing respiratory insufficiency contributes to significant morbidity and mortality in this disease. The lack of effective therapies for pulmonary fibrosis has spurred a re-evaluation of pathobiological paradigms and therapeutic strategies in scleroderma-associated interstitial lung disease and in idiopathic pulmonary fibrosis. The purpose of this review is to examine emerging new therapeutic targets that modulate pro-fibrotic phenotypes of tissue-resident cells and the associated aberrant tissue remodeling responses in fibrotic disorders. RECENT FINDINGS Progressive forms of tissue fibrosis, including scleroderma, are characterized by an accumulation of activated mesenchymal cells and their secreted extracellular matrix proteins in association with dysrepair of epithelial and endothelial cells. Recent studies suggest that emergence of cellular phenotypes that perpetuate loss of cellular homeostasis is characteristic of many fibrosis-related clinical syndromes. SUMMARY Therapeutic strategies that modulate the fate/phenotype of reparative structural cells, including epithelial, endothelial, and mesenchymal cells, offer new opportunities for the development of more effective drugs for the treatment of fibrosis.
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532
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Abstract
The Idiopathic Pulmonary Fibrosis (IPF) is a progressive fibrotic lung disease with poor prognosis. It is distinct from other idiopathic interstitial pneumonias by its histopathological pattern of usual interstitial pneumonia which is characterized by accumulation of fibroblasts, extracellular matrix and honeycombing. Inflammation is only scarce in true IPF. The use of anti-inflammatory therapy is still part of guidelines for IPF management, although not specifically recommended, because convincing evidence showing beneficial effects of this approach is lacking. This review provides a summary of important arguments PRO and CON using anti-inflammatory and anti-oxidant therapy for patients with IPF in form of a debate with a concluding statement of both positions at the end.
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Affiliation(s)
- Jürgen Behr
- Division of Pulmonary Diseases, Department of Internal Medicine I, Ludwig-Maximilians University of Munich, 81377 Munich, Germany.
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533
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Telomeres: protecting chromosomes against genome instability. Nat Rev Mol Cell Biol 2010; 11:171-81. [PMID: 20125188 DOI: 10.1038/nrm2848] [Citation(s) in RCA: 667] [Impact Index Per Article: 47.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The natural ends of linear chromosomes require unique genetic and structural adaptations to facilitate the protection of genetic material. This is achieved by the sequestration of the telomeric sequence into a protective nucleoprotein cap that masks the ends from constitutive exposure to the DNA damage response machinery. When telomeres are unmasked, genome instability arises. Balancing capping requirements with telomere replication and the enzymatic processing steps that are obligatory for telomere function is a complex problem. Telomeric proteins and their interacting factors create an environment at chromosome ends that inhibits DNA repair; however, the repair machinery is essential for proper telomere function.
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534
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Abstract
Cryptogenic cirrhosis remains a common clinical condition although recent advances have allowed for a better understanding of underlying conditions and associations. The evolving terminology applied to this condition has resulted in some confusion and persistent variation among pathologists and clinicians. Typical patients are middle aged with only minor liver enzyme abnormalities. Presentations range from incidentally discovered cirrhosis to complications of advanced portal hypertension and hepatocellular cancer. Clinicopathologic analysis of these patients indicates that the leading causes include previously unrecognized nonalcoholic steatohepatitis, silent autoimmune hepatitis, non-B, non-C viral hepatitis, and occult past ethanol exposure. In this article, we review these associations as well as a proposed classification system for cryptogenic cirrhosis and other lesser known genetic and syndromic associations that warrant consideration when evaluating these individuals.
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Affiliation(s)
- Stephen Caldwell
- Digestive Health Center, GI/Hepatology Division, University of Virginia Health Science Center, Charlottesville, VA 22908-0708, USA.
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535
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Fossel M, Flanary B. Telomerase and human disease: the beginnings of the ends? Rejuvenation Res 2010; 12:333-40. [PMID: 19725774 DOI: 10.1089/rej.2009.0873] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Michael Fossel
- Department of Medicine, Michigan State University, Ada, Michigan, USA
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536
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Abstract
Idiopathic pulmonary fibrosis (IPF) is the most common and most lethal diffuse fibrosing lung disease, with a mortality rate that exceeds that of many cancers. Recently, there have been many clinical trials of novel therapies for IPF. The results have mostly been disappointing, although two treatment approaches have shown some efficacy. This Review describes the difficulties of treating IPF and the approaches that have been tried or are in development, and concludes with suggestions of future therapeutic targets and strategies.
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Affiliation(s)
- R M du Bois
- National Jewish Health, 1400 Jackson Street, Denver, Colorado 80206, USA.
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537
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Chang W, Wei K, Jacobs SS, Upadhyay D, Weill D, Rosen GD. SPARC suppresses apoptosis of idiopathic pulmonary fibrosis fibroblasts through constitutive activation of beta-catenin. J Biol Chem 2010; 285:8196-206. [PMID: 20061390 DOI: 10.1074/jbc.m109.025684] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Idiopathic pulmonary fibrosis (IPF) is a poorly understood progressive disease characterized by the accumulation of scar tissue in the lung interstitium. A hallmark of the disease is areas of injury to type II alveolar epithelial cells with attendant accumulation of fibroblasts in areas called fibroblastic foci. In an effort to better characterize the lung fibroblast phenotype in IPF patients, we isolated fibroblasts from patients with IPF and looked for activation of signaling proteins, which could help explain the exaggerated fibrogenic response in IPF. We found that IPF fibroblasts constitutively expressed increased basal levels of SPARC, plasminogen activator inhibitor-1 (PAI-1), and active beta-catenin compared with control cells. Control of basal PAI-1 expression in IPF fibroblasts was regulated by SPARC-mediated activation of Akt, leading to inhibition of glycogen synthase kinase-3beta and activation of beta-catenin. Additionally, IPF fibroblasts (but not control fibroblasts) were resistant to plasminogen-induced apoptosis and were sensitized to plasminogen-mediated apoptosis by inhibition of SPARC or beta-catenin. These findings uncover a newly discovered regulatory pathway in IPF fibroblasts that is characterized by elevated SPARC, giving rise to activated beta-catenin, which regulates expression of downstream genes, such as PAI-1, and confers an apoptosis-resistant phenotype. Disruption of this pathway may represent a novel therapeutic target in IPF.
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Affiliation(s)
- Wenteh Chang
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Stanford University Medical Center, Stanford, California 94305-5236, USA
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538
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Kottmann RM, Hogan CM, Phipps RP, Sime PJ. Determinants of initiation and progression of idiopathic pulmonary fibrosis. Respirology 2009; 14:917-33. [PMID: 19740254 DOI: 10.1111/j.1440-1843.2009.01624.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
IPF is a devastating disease with few therapeutic options. The precise aetiology of IPF remains elusive. However, our understanding of the pathologic processes involved in the initiation and progression of this disease is improving. Data on the mechanisms underlying IPF have been generated from epidemiologic investigations as well as cellular and molecular studies of human tissues. Although no perfect animal model of human IPF exists, pre-clinical animal studies have helped define pathways which are likely important in human disease. Epithelial injury, fibroblast activation and repetitive cycles of injury and abnormal repair are almost certainly key events. Factors which have been associated with initiation and/or progression of IPF include viral infections, abnormal cytokine, chemokine and growth factor production, oxidant stress, autoimmunity, inhalational of toxicants and gastro-oesophageal reflux disease. Furthermore, recent evidence identifies a role for a variety of genetic and epigenetic abnormalities ranging from mutations in surfactant protein C to abnormalities in telomere length and telomerase activity. The challenge remains to identify additional inciting agents and key dysregulated pathways that lead to disease progression so that we can develop targeted therapies to treat or prevent this serious disease.
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539
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Xie M, Podlevsky JD, Qi X, Bley CJ, Chen JJL. A novel motif in telomerase reverse transcriptase regulates telomere repeat addition rate and processivity. Nucleic Acids Res 2009; 38:1982-96. [PMID: 20044353 PMCID: PMC2847249 DOI: 10.1093/nar/gkp1198] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- Mingyi Xie
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Joshua D. Podlevsky
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Xiaodong Qi
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Christopher J. Bley
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Julian J.-L. Chen
- Department of Chemistry & Biochemistry and School of Life Sciences, Arizona State University, Tempe, AZ 85287-1604, USA
- *To whom correspondence should be addressed. Tel: +1 480 965 3650; Fax: +1 480 965 2747;
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540
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Current world literature. Curr Opin Rheumatol 2009; 21:656-65. [PMID: 20009876 DOI: 10.1097/bor.0b013e3283328098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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541
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Affiliation(s)
- Rodrigo T Calado
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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542
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Waisberg DR, Barbas-Filho JV, Parra ER, Fernezlian S, de Carvalho CRR, Kairalla RA, Capelozzi VL. Abnormal expression of telomerase/apoptosis limits type II alveolar epithelial cell replication in the early remodeling of usual interstitial pneumonia/idiopathic pulmonary fibrosis. Hum Pathol 2009; 41:385-91. [PMID: 19954818 DOI: 10.1016/j.humpath.2009.08.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/21/2009] [Accepted: 08/26/2009] [Indexed: 02/08/2023]
Abstract
Idiopathic pulmonary fibrosis is a distinctive, usually fatal, type of chronic fibrosing interstitial pneumonia of unknown cause that increases in prevalence with advanced age, characterized by failure of alveolar re-epithelization and progressive scar formation. Recently, limitation of the replicative capacity of tissues determined by telomerase/apoptosis balance has been implicated in pathogenesis of age-related diseases. In this study, we validated the importance of the expression of type 2 alveolar epithelial cells telomerase protein and studied the relationships between telomerase and apoptosis in early remodeling of usual interstitial pneumonia. We determined type 2 alveolar epithelial cells density, telomerase expression, and apoptosis in surgical lung biopsies from 24 patients with usual interstitial pneumonia, and in normal lung tissues from 18 subjects. We used immunohistochemistry, deoxynucleotidyl transferase method of end labeling, electron microscopy, and histomorphometry to evaluate the amount of type 2 alveolar epithelial cells staining for surfactant-A, telomerase, and in situ detection of apoptotic cells. Unaffected areas of usual interstitial pneumonia and normal lung tissue had similar densities of type 2 alveolar epithelial cells, but a significant minor subpopulation of type 2 alveolar epithelial cells was telomerase positive and a large population was telomerase negative. A significant inverse association was found between low type 2 alveolar epithelial cell telomerase expression and high apoptosis in unaffected areas of usual interstitial pneumonia. Although type 2 alveolar epithelial cell telomerase expression was higher than apoptosis in NLT group, no significant association was found between them. Electron microscopy confirmed epithelial apoptosis, alveolar collapse, and initial fibroplasia. We conclude that abnormal type 2 alveolar epithelial cells telomerase/apoptosis balance may reduce alveolar epithelial regenerative capacity, thus contributing to the early remodeling response in usual interstitial pneumonia.
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Affiliation(s)
- Daniel Reis Waisberg
- Departament of Pathology, Faculdade de Medicina da Universidade de São Paulo, Brasil
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543
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Armanios M, Alder JK, Parry EM, Karim B, Strong MA, Greider CW. Short telomeres are sufficient to cause the degenerative defects associated with aging. Am J Hum Genet 2009; 85:823-32. [PMID: 19944403 DOI: 10.1016/j.ajhg.2009.10.028] [Citation(s) in RCA: 184] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/20/2009] [Accepted: 10/24/2009] [Indexed: 11/30/2022] Open
Abstract
Telomerase function is critical for telomere maintenance. Mutations in telomerase components lead to telomere shortening and progressive bone marrow failure in the premature aging syndrome dyskeratosis congenita. Short telomeres are also acquired with aging, yet the role that they play in mediating age-related disease is not fully known. We generated wild-type mice that have short telomeres. In these mice, we identified hematopoietic and immune defects that resembled those present in dyskeratosis congenita patients. When mice with short telomeres were interbred, telomere length was only incrementally restored, and even several generations later, wild-type mice with short telomeres still displayed degenerative defects. Our findings implicate telomere length as a unique heritable trait that, when short, is sufficient to mediate the degenerative defects of aging, even when telomerase is wild-type.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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544
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Calado RT, Regal JA, Kleiner DE, Schrump DS, Peterson NR, Pons V, Chanock SJ, Lansdorp PM, Young NS. A spectrum of severe familial liver disorders associate with telomerase mutations. PLoS One 2009; 4:e7926. [PMID: 19936245 PMCID: PMC2775683 DOI: 10.1371/journal.pone.0007926] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 10/26/2009] [Indexed: 01/06/2023] Open
Abstract
Background Telomerase is an enzyme specialized in maintaining telomere lengths in highly proliferative cells. Loss-of-function mutations cause critical telomere shortening and are associated with the bone marrow failure syndromes dyskeratosis congenita and aplastic anemia and with idiopathic pulmonary fibrosis. Here, we sought to determine the spectrum of clinical manifestations associated with telomerase loss-of-function mutations. Methodology/Principal Findings Sixty-nine individuals from five unrelated families with a variety of hematologic, hepatic, and autoimmune disorders were screened for telomerase complex gene mutations; leukocyte telomere length was measured by flow fluorescence in situ hybridization in mutation carriers and some non-carriers; the effects of the identified mutations on telomerase activity were determined; and genetic and clinical data were correlated. In six generations of a large family, a loss-of-function mutation in the telomerase enzyme gene TERT associated with severe telomere shortening and a range of hematologic manifestations, from macrocytosis to acute myeloid leukemia, with severe liver diseases marked by fibrosis and inflammation, and one case of idiopathic pulmonary fibrosis but not with autoimmune disorders. Additionally, we identified four unrelated families in which loss-of-function TERC or TERT gene mutations tracked with marrow failure, pulmonary fibrosis, and a spectrum of liver disorders. Conclusions/Significance These results indicate that heterozygous telomerase loss-of-function mutations associate with but are not determinant of a large spectrum of hematologic and liver abnormalities, with the latter sometimes occurring in the absence of marrow failure. Our findings, along with the link between pulmonary fibrosis and telomerase mutations, also suggest a common pathogenic mechanism for fibrotic diseases in which defective telomere repair plays important role.
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Affiliation(s)
- Rodrigo T Calado
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
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545
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Abstract
Telomeres and telomerase were initially discovered in pursuit of questions about how the ends of chromosomes are maintained. The implications of these discoveries to age-related disease have emerged in recent years with the recognition of a group of telomere-mediated syndromes. Telomere-mediated disease was initially identified in the context of dyskeratosis congenita, a rare syndrome of premature aging. More recently, mutations in telomerase components were identified in adults with idiopathic pulmonary fibrosis. These findings have revealed that the spectrum of telomere-mediated disease is broad and includes clinical presentations in both children and adults. We have previously proposed that these disorders be collectively considered as syndromes of telomere shortening. Here, the spectrum of these disorders and the unique telomere genetics that underlies them are reviewed. I also propose broader clinical criteria for defining telomere-mediated syndromes outside of dyskeratosis congenita, with the goal of facilitating their diagnosis and highlighting their pathophysiology.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21285, USA.
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546
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Savage SA, Dokal I, Armanios M, Aubert G, Cowen EW, Domingo DL, Giri N, Greene MH, Orchard PJ, Tolar J, Tsilou E, Van Waes C, Wong JM, Young NS, Alter BP. Dyskeratosis congenita: the first NIH clinical research workshop. Pediatr Blood Cancer 2009; 53:520-3. [PMID: 19415736 PMCID: PMC2739803 DOI: 10.1002/pbc.22061] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Dyskeratosis congenita (DC) is a heterogeneous inherited bone marrow failure syndrome, characterized by abnormally short telomeres and mutations in telomere biology genes. The spectrum of telomere biology disorders is growing and the clinical management of these patients is complex. A DC-specific workshop was held at the NIH on September 19, 2008; participants included physicians, patients with DC, their family members, and representatives from other support groups. Data from the UK's DC Registry and the NCI's DC cohort were described. Updates on the function of the known DC genes were presented. Clinical aspects discussed included androgen therapy, stem cell transplant, cancer risk, and cancer screening. Families with DC met for the first time and formed a family support group (http://www.dcoutreach.com/). Ongoing, open collaboration between the clinical, scientific, and family communities is required for continued improvement in our understanding of DC and the clinical consequences of telomeric defects.
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Affiliation(s)
- Sharon A. Savage
- Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD 20892,Corresponding author: Sharon A. Savage, MD, FAAP, Investigator, Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, 6120 Executive Blvd., EPS/7018, Rockville, MD 20892, Phone: 301-496-5785, Fax: 301-496-1854,
| | - Inderjeet Dokal
- Centre for Paediatrics, Barts and The London School of Medicine and Dentistry, Barts and The London Children’s Hospital, Queen Mary University of London, London E12AT, United Kingdom
| | - Mary Armanios
- Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Geraldine Aubert
- Terry Fox Laboratory, British Columbia Cancer Research Center, Vancouver, BC, Canada, V5Z1L3
| | - Edward W. Cowen
- Dermatology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Demetrio L. Domingo
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892
| | - Neelam Giri
- Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD 20892
| | - Mark H. Greene
- Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD 20892
| | - Paul J. Orchard
- Pediatric Blood and Marrow Transplant Program, University of Minnesota, Minneapolis, MN 55455
| | - Jakub Tolar
- Pediatric Blood and Marrow Transplant Program, University of Minnesota, Minneapolis, MN 55455
| | - Ekaterini Tsilou
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892
| | - Carter Van Waes
- Head and Neck Surgery Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892
| | - Judy M.Y. Wong
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z3
| | - Neal S. Young
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Blanche P. Alter
- Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD 20892
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547
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Abstract
The telomeres of most eukaryotes are characterized by guanine-rich repeats synthesized by the reverse transcriptase telomerase. Complete loss of telomerase is tolerated for several generations in most species, but modestly reduced telomerase levels in human beings are implicated in bone marrow failure, pulmonary fibrosis and a spectrum of other diseases including cancer. Differences in telomerase deficiency phenotypes between species most likely reflect a tumour suppressor function of telomeres in long-lived mammals that does not exist as such in short-lived organisms. Another puzzle provided by current observations is that family members with the same genetic defect, haplo-insufficiency for one of the telomerase genes, can present with widely different diseases. Here, the crucial role of telomeres and telomerase in human (stem cell) biology is discussed from a Darwinian perspective. It is proposed that the variable phenotype and penetrance of heritable human telomerase deficiencies result from additional environmental, genetic and stochastic factors or combinations thereof.
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548
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Antoniou KM, Papadaki HA, Soufla G, Siafakas NM. Short telomeres and treatment of pulmonary fibrosis: implications for early intervention. Am J Respir Crit Care Med 2009; 179:970. [PMID: 19423724 DOI: 10.1164/ajrccm.179.10.970] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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549
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Hardie WD, Glasser SW, Hagood JS. Emerging concepts in the pathogenesis of lung fibrosis. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 175:3-16. [PMID: 19497999 DOI: 10.2353/ajpath.2009.081170] [Citation(s) in RCA: 184] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fibrogenesis is an often-deadly process with increasing world-wide incidence and limited therapeutic options. Pulmonary fibrogenesis involves remodeling of the distal airspace and parenchyma of the lung, and is characterized by excessive extracellular matrix deposition and accumulation of apoptosis-resistant myofibroblasts. Recent studies have added significantly to our understanding of the complex mechanisms involved in lung fibrogenesis. Emerging concepts in this field include the critical role of the epithelium, particularly type II pneumocytes, in the initiation and perpetuation of fibrosis in response to either endogenous or exogenous stress; a growing awareness of alternative activation of macrophages in tissue remodeling; growing appreciation of the alternative origins and phenotypic plasticity of fibroblasts; the roles of epigenetic reprogramming and context-dependent signaling in profibrotic phenotype alterations; and recognition of the importance of cross talk and convergence of intracellular signaling pathways. In vitro, in vivo, and in silico approaches support a paradigm of "disordered re-development" of the lung. Designing effective antifibrotic interventions will require accurate understanding of the complex interactions among the genetic, environmental, epigenetic, biochemical, cellular, and contextual abnormalities that promote pulmonary fibrogenesis.
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Affiliation(s)
- William D Hardie
- Department of Pediatrics, Cincinnati Children's Medical Center, Cincinnati, Ohio, USA
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550
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Carroll KA, Ly H. Telomere dysfunction in human diseases: the long and short of it! INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2009; 2:528-43. [PMID: 19636400 PMCID: PMC2713453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 04/30/2009] [Indexed: 05/28/2023]
Abstract
It has been over one hundred years since the first reported case of dyskeratosis congenita (DC) and over twenty since the discovery of telomerase, an enzyme that adds telomeric DNA repeats to chromosome ends. Emerging evidence suggests that telomere dysfunction plays an important role in the pathogenesis of DC and other human disorders involving tissues that require rapid repair and renewal capacities. Yet we still do not fully understand how mutations in telomere maintenance genes contribute to disease development in affected individuals. In this review, we provide an up-to-date summary of the topic by discussing the results from genetic screens of patients, in vitro mutational analysis of involved molecules, and genetically engineered mouse models. While these data shed important light on the mechanisms underlying disease development, further investigation, particularly in an in vivo setting, is needed.
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Affiliation(s)
- Kathryn A Carroll
- Department of Pathology and Laboratory Medicine, Emory University Atlanta, GA, USA
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