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Liu B, Henry AP, Azimi S, Miller S, Lee FK, Lee JC, Probert K, Kotlikoff MI, Sayers I, Hall IP. Exposure to lipopolysaccharide (LPS) reduces contractile response of small airways from GSTCD-/- mice. PLoS One 2019; 14:e0221899. [PMID: 31513609 PMCID: PMC6742219 DOI: 10.1371/journal.pone.0221899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 08/17/2019] [Indexed: 11/25/2022] Open
Abstract
Introduction Genome-Wide Association Studies suggest glutathione S transferase C terminal domain (GSTCD) may play a role in development of Chronic Obstructive Pulmonary Disease. We aimed to define the potential role of GSTCD in airway inflammation and contraction using precision cut lung slice (PCLS) from wild-type (GSTCD+/+) and GSTCD knockout mice (GSTCD-/-). Methods PCLS from age and gender matched GSTCD+/+ and GSTCD-/- mice were prepared using a microtome. Contraction was studied after applying either a single dose of Methacholine (Mch) (1 μM) or different doses of Mch (0.001 to 100 μM). Each slice was then treated with lipopolysaccharide (LPS) or vehicle (PBS) for 24 hours. PCLS contraction in the same airway was repeated before and after stimulation. Levels of TNFα production was also measured. Results There were no differences in contraction of PCLS from GSTCD+/+ and GSTCD-/- mice in response to Mch (EC50 of GSTCD+/+ vs GSTCD-/- animals: 100.0±20.7 vs 107.7±24.5 nM, p = 0.855, n = 6 animals/group). However, after LPS treatment, there was a 31.6% reduction in contraction in the GSTCD-/- group (p = 0.023, n = 6 animals). There was no significant difference between PBS and LPS treatment groups in GSTCD+/+ animals. We observed a significant increase in TNFα production induced by LPS in GSTCD-/- lung slices compared to the GSTCD+/+ LPS treated slices. Conclusion GSTCD knockout mice showed an increased responsiveness to LPS (as determined by TNFα production) that was accompanied by a reduced contraction of small airways in PCLS. These data highlight an unrecognised potential function of GSTCD in mediating inflammatory signals that affect airway responses.
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Affiliation(s)
- Bo Liu
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
| | - Amanda P. Henry
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
- * E-mail:
| | - Sheyda Azimi
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
| | - Suzanne Miller
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
| | - Frank K. Lee
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Jane C. Lee
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Kelly Probert
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
| | - Michael I. Kotlikoff
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Ian Sayers
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
| | - Ian P. Hall
- Division of Respiratory Medicine, & National Institute for Health Medicine, Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, England, United Kingdom
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Park K, Jung Y, Son T, Cho YJ, Jeon NL, Kim W, Kim HY. Optimal diameter reduction ratio of acinar airways in human lungs. PLoS One 2019; 14:e0204191. [PMID: 30703086 PMCID: PMC6354962 DOI: 10.1371/journal.pone.0204191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 01/16/2019] [Indexed: 11/18/2022] Open
Abstract
In the airway network of a human lung, the airway diameter gradually decreases through multiple branching. The diameter reduction ratio of the conducting airways that transport gases without gas exchange is 0.79, but this reduction ratio changes to 0.94 in acinar airways beyond transitional bronchioles. While the reduction in the conducting airways was previously rationalized on the basis of Murray’s law, our understanding of the design principle behind the acinar airways has been far from clear. Here we elucidate that the change in gas transfer mode is responsible for the transition in the diameter reduction ratio. The oxygen transfer rate per unit surface area is maximized at the observed geometry of acinar airways, which suggests the minimum cost for the construction and maintenance of the acinar airways. The results revitalize and extend the framework of Murray’s law over an entire human lung.
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Affiliation(s)
- Keunhwan Park
- Institute of Advanced Machines and Design, Seoul National University, Seoul, Korea
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - Yeonsu Jung
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea
| | - Taeho Son
- Institute of Advanced Machines and Design, Seoul National University, Seoul, Korea
| | - Young-Jae Cho
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Noo Li Jeon
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea
| | - Wonjung Kim
- Department of Mechanical Engineering, Sogang University, Seoul, Korea
- * E-mail: (WK); (HYK)
| | - Ho-Young Kim
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea
- * E-mail: (WK); (HYK)
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Abstract
Background and objective The mortality rate for patients requiring mechanical ventilation is about 35% and this rate increases to about 53% for the elderly. In general, with increasing age, the dynamic lung function and respiratory mechanics are compromised, and several experiments are being conducted to estimate these changes and understand the underlying mechanisms to better treat elderly patients. Materials and methods Human tracheobronchial (G1 ~ G9), bronchioles (G10 ~ G22) and alveolar sacs (G23) geometric models were developed based on reported anatomical dimensions for a 50 and an 80-year-old subject. The aged model was developed by altering the geometry and material properties of the model developed for the 50-year-old. Computational simulations using coupled fluid-solid analysis were performed for geometric models of bronchioles and alveolar sacs under mechanical ventilation to estimate the airflow and lung function characteristics. Findings The airway mechanical characteristics decreased with aging, specifically a 38% pressure drop was observed for the 80-year-old as compared to the 50-year-old. The shear stress on airway walls increased with aging and the highest shear stress was observed in the 80-year-old during inhalation. A 50% increase in peak strain was observed for the 80-year-old as compared to the 50-year-old during exhalation. The simulation results indicate that there is a 41% increase in lung compliance and a 35%-50% change in airway mechanical characteristics for the 80-year-old in comparison to the 50-year-old. Overall, the airway mechanical characteristics as well as lung function are compromised due to aging. Conclusion Our study demonstrates and quantifies the effects of aging on the airflow dynamics and lung capacity. These changes in the aging lung are important considerations for mechanical ventilation parameters in elderly patients. Realistic geometry and material properties need to be included in the computational models in future studies.
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Affiliation(s)
- JongWon Kim
- College of Engineering, University of Georgia, Athens, Georgia, United States of America
| | - Rebecca L. Heise
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia, United States of America
- The VCU Johnson Center, Virginia Commonwealth University Medical Center, Richmond, Virginia, United States of America
| | - Angela M. Reynolds
- The VCU Johnson Center, Virginia Commonwealth University Medical Center, Richmond, Virginia, United States of America
- Department of Mathematics & Applied Mathematics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Ramana M. Pidaparti
- College of Engineering, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
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López IP, Piñeiro-Hermida S, Pais RS, Torrens R, Hoeflich A, Pichel JG. Involvement of Igf1r in Bronchiolar Epithelial Regeneration: Role during Repair Kinetics after Selective Club Cell Ablation. PLoS One 2016; 11:e0166388. [PMID: 27861515 PMCID: PMC5115747 DOI: 10.1371/journal.pone.0166388] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 10/27/2016] [Indexed: 12/14/2022] Open
Abstract
Regeneration of lung epithelium is vital for maintaining airway function and integrity. An imbalance between epithelial damage and repair is at the basis of numerous chronic lung diseases such as asthma, COPD, pulmonary fibrosis and lung cancer. IGF (Insulin-like Growth Factors) signaling has been associated with most of these respiratory pathologies, although their mechanisms of action in this tissue remain poorly understood. Expression profiles analyses of IGF system genes performed in mouse lung support their functional implication in pulmonary ontogeny. Immuno-localization revealed high expression levels of Igf1r (Insulin-like Growth Factor 1 Receptor) in lung epithelial cells, alveolar macrophages and smooth muscle. To further understand the role of Igf1r in pulmonary homeostasis, two distinct lung epithelial-specific Igf1r mutant mice were generated and studied. The lack of Igf1r disturbed airway epithelial differentiation in adult mice, and revealed enhanced proliferation and altered morphology in distal airway club cells. During recovery after naphthalene-induced club cell injury, the kinetics of terminal bronchiolar epithelium regeneration was hindered in Igf1r mutants, revealing increased proliferation and delayed differentiation of club and ciliated cells. Amid airway restoration, lungs of Igf1r deficient mice showed increased levels of Igf1, Insr, Igfbp3 and epithelial precursor markers, reduced amounts of Scgb1a1 protein, and alterations in IGF signaling mediators. These results support the role of Igf1r in controlling the kinetics of cell proliferation and differentiation during pulmonary airway epithelial regeneration after injury.
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Affiliation(s)
- Icíar P López
- Centro de Investigación Biomédica de la Rioja (CIBIR), Fundación Rioja Salud, Logroño, Spain
| | - Sergio Piñeiro-Hermida
- Centro de Investigación Biomédica de la Rioja (CIBIR), Fundación Rioja Salud, Logroño, Spain
| | - Rosete S Pais
- Centro de Investigación Biomédica de la Rioja (CIBIR), Fundación Rioja Salud, Logroño, Spain
| | - Raquel Torrens
- Centro de Investigación Biomédica de la Rioja (CIBIR), Fundación Rioja Salud, Logroño, Spain
| | - Andreas Hoeflich
- Institute of Genome Biology, Leibniz-Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
| | - José G Pichel
- Centro de Investigación Biomédica de la Rioja (CIBIR), Fundación Rioja Salud, Logroño, Spain
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Ortega-Martínez M, Rodríguez-Flores LE, Ancer-Arellano A, Cerda-Flores RM, de-la-Garza-González C, Ancer-Rodríguez J, Jaramillo-Rangel G. Analysis of Cell Turnover in the Bronchiolar Epithelium Through the Normal Aging Process. Lung 2016; 194:581-7. [PMID: 27164984 DOI: 10.1007/s00408-016-9890-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 05/02/2016] [Indexed: 11/26/2022]
Abstract
PURPOSE Aging is associated with changes in the lung that leads to a decrease in its function. Alterations in structure and function in the small airways are well recognized in chronic lung diseases. The aim of this study was the assessment of cell turnover in the bronchiolar epithelium of mouse through the normal aging process. METHODS Lungs from CD1 mice at the age of 2, 6, 12, 18, or 24 months were fixed in neutral-buffered formalin and paraffin-embedded. Proliferating cell nuclear antigen was examined by immunohistochemistry. Apoptosis was analyzed by in situ end-labeling of fragmented DNA. Epithelial dimensions were analyzed by morphometry. RESULTS The 2-month-old mice showed significantly higher number of proliferating cells when compared with mice at all other age groups. The number of apoptotic cells in mice at 24 months of age was significantly greater than in mice at all other age groups. Thus, the number of epithelial cells decreased as the age of the subject increased. We also found reductions in both area and height of the bronchiolar epithelium in mice at 18 and 24 months of age. CONCLUSIONS We found a decrease in the total number of epithelial cells in the aged mice, which was accompanied by a thinning of the epithelium. These changes reflect a dysregulated tissue regeneration process in the bronchiolar epithelium that might predispose to respiratory diseases in elderly subjects.
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Affiliation(s)
- Marta Ortega-Martínez
- Department of Pathology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Laura E Rodríguez-Flores
- Department of Pathology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Adriana Ancer-Arellano
- Department of Pathology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Ricardo M Cerda-Flores
- School of Nursing, Autonomous University of Nuevo Leon, Ave. Gonzalitos 1500 Nte., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Carlos de-la-Garza-González
- Department of Embryology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Jesús Ancer-Rodríguez
- Department of Pathology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico
| | - Gilberto Jaramillo-Rangel
- Department of Pathology, School of Medicine, Autonomous University of Nuevo Leon, Ave. Madero y Dr. Eduardo Aguirre P., Colonia Mitras Centro, 64460, Monterrey, Nuevo León, Mexico.
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Hogan BLM, Barkauskas CE, Chapman HA, Epstein JA, Jain R, Hsia CCW, Niklason L, Calle E, Le A, Randell SH, Rock J, Snitow M, Krummel M, Stripp BR, Vu T, White ES, Whitsett JA, Morrisey EE. Repair and regeneration of the respiratory system: complexity, plasticity, and mechanisms of lung stem cell function. Cell Stem Cell 2014; 15:123-38. [PMID: 25105578 PMCID: PMC4212493 DOI: 10.1016/j.stem.2014.07.012] [Citation(s) in RCA: 605] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Respiratory disease is the third leading cause of death in the industrialized world. Consequently, the trachea, lungs, and cardiopulmonary vasculature have been the focus of extensive investigations. Recent studies have provided new information about the mechanisms driving lung development and differentiation. However, there is still much to learn about the ability of the adult respiratory system to undergo repair and to replace cells lost in response to injury and disease. This Review highlights the multiple stem/progenitor populations in different regions of the adult lung, the plasticity of their behavior in injury models, and molecular pathways that support homeostasis and repair.
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Affiliation(s)
- Brigid L M Hogan
- Department of Cell Biology, Duke Medicine, Durham, NC 27705, USA.
| | - Christina E Barkauskas
- Division of Pulmonary, Allergy and Critical Care Medicine, Duke Medicine, Durham, NC 27705, USA
| | - Harold A Chapman
- Division of Pulmonary and Critical Care, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Jonathan A Epstein
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Rajan Jain
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Connie C W Hsia
- Department of Internal Medicine, University of Texas, Southwestern Medical Center, Dallas, TX 75390, USA
| | - Laura Niklason
- Departments of Anesthesiology and Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - Elizabeth Calle
- Department of Cell Biology, Duke Medicine, Durham, NC 27705, USA
| | - Andrew Le
- Department of Cell Biology, Duke Medicine, Durham, NC 27705, USA
| | - Scott H Randell
- Department of Cell Biology and Physiology, The University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Jason Rock
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Melinda Snitow
- Perleman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew Krummel
- Division of Pulmonary and Critical Care, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Barry R Stripp
- Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Thiennu Vu
- Division of Pulmonary and Critical Care, Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Eric S White
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jeffrey A Whitsett
- Section of Neonatology, Perinatal and Pulmonary Biology, Department of Pediatrics, Cincinnati Children's Hospital Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Edward E Morrisey
- Departments of Medicine and Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Hou C, Mayo M. Pulmonary diffusional screening and the scaling laws of mammalian metabolic rates. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 84:061915. [PMID: 22304124 DOI: 10.1103/physreve.84.061915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Indexed: 05/31/2023]
Abstract
Theoretical considerations suggest that the mammalian metabolic rate is linearly proportional to the surface areas of mitochondria, capillary, and alveolar membranes. However, the scaling exponents of these surface areas to the mammals' body mass (approximately 0.9-1) are higher than exponents of the resting metabolic rate (RMR) to body mass (approximately 0.75), although similar to the one of exercise metabolic rate (EMR); the underlying physiological cause of this mismatch remains unclear. The analysis presented here shows that discrepancies between the scaling exponents of RMR and the relevant surface areas may originate from, at least for the system of alveolar membranes in mammalian lungs, the facts that (i) not all of the surface area is involved in the gas exchange and (ii) that larger mammals host a smaller effective surface area that participates in the material exchange rate. A result of these facts is that lung surface areas unused at rest are activated under heavy breathing conditions (e.g., exercise), wherein larger mammals support larger activated surface areas that provide a higher capability to increase the gas-exchange rate, allowing for mammals to meet, for example, the high energetic demands of foraging and predation.
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Affiliation(s)
- Chen Hou
- Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri 65409, USA
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Kitaoka H. [The origin of frequency dependence of respiratory resistance: airflow simulation study by the use of a 4D pulmonary lobule model]. Nihon Kokyuki Gakkai Zasshi 2011; 49:629-635. [PMID: 22073606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND AND OBJECTIVE The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity, however it is unclear which components in the respiratory system generate the frequency dependence. The author constructed a 4D pulmonary lobule model and analyzed relationships between airflow rate, pressure and airway resistance by the use of computational fluid dynamics (CFD). METHODS The lobule model contained bifurcated bronchioles with two adjacent acini in which deformable inter-acinar septa and alveolar duct walls were designed. Constrictive conditions of respective bronchioles were designed, too. 4D finite element models for CFD were generated and airflow simulations were performed under moving boundary conditions of the arbitrary Lagrangean-Eulerean method. From the simulation results, airway resistances for various conditions were calculated. RESULTS Tissue resistance emerged under the condition of different acinar pressures caused by unequal airway resistances. If the inter-acinar septum was shifted so as to cancel the pressure difference, the acinar pressures were equal in spite of unequal airway resistances, and hence, tissue resistances did not emerge. Therefore, the tissue resistance in the former case is thought to be an index of alveolar pressure inequality (which could be canceled by mechanical interaction of lung parenchyma), rather than a material property of the tissue itself. CONCLUSIONS Inequality of alveolar pressure decreases as the input oscillatory frequency increases. Therefore, frequency dependence of the respiratory resistance should be regarded as a conditional index of the alveolar pressure inequality caused by heterogeneous changes in the intra-pulmonary airway and/or the lung parenchyma.
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Churg A, Zhou S, Preobrazhenska O, Tai H, Wang R, Wright JL. Expression of profibrotic mediators in small airways versus parenchyma after cigarette smoke exposure. Am J Respir Cell Mol Biol 2009; 40:268-76. [PMID: 18723441 DOI: 10.1165/rcmb.2007-0367oc] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cigarette smoke-induced lung disease presents a morphologic contradiction in that the small airways become fibrotic but the parenchyma becomes emphysematous over time. To examine the mechanisms behind these phenomena, we exposed mice to cigarette smoke for up to 6 months and isolated small airways from histologic sections by laser capture microdissection. We then removed residual airway tissue and vessels, and collected the remaining parenchymal tissue. Gene expression of 13 fibrogenic growth/signaling factors (particularly TGF-beta-related genes), matrix proteins, or enzymes involved in matrix production was examined by real-time RT-PCR. Combining present and previously published data from our laboratory, in the airways over the long term there was a sustained and marked increase in expression of almost all of these genes. By contrast, in the parenchyma, expression of most genes was elevated at 2 and 24 hours after initial exposure, and all were elevated at 1 month; but by 6 months, when emphysema was present, most genes (9/13) were either at control values or down-regulated below control. At 3 months, several genes that were considerably elevated at 1 month were back to control levels, suggesting that loss of the parenchymal response precedes the development of emphysema. We conclude that with smoke exposure the airways demonstrate an ongoing profibrotic/proelastogenic response and the parenchyma a generally anti-fibrotic/anti-elastogenic response, but one that develops only with long-term exposure to smoke. These observations support the idea that the parenchyma largely fails to repair smoke-induced matrix damage, but this phenomenon is a relatively late event.
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Affiliation(s)
- Andrew Churg
- Department of Pathology, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC, V6T 2B5 Canada.
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Abstract
In addition to the core circadian oscillator, located within the suprachiasmatic nucleus, numerous peripheral tissues possess self-sustaining circadian timers. In vivo these are entrained and temporally synchronized by signals conveyed from the core oscillator. In the present study, we examine circadian timing in the lung, determine the cellular localization of core clock proteins in both mouse and human lung tissue, and establish the effects of glucocorticoids (widely used in the treatment of asthma) on the pulmonary clock. Using organotypic lung slices prepared from transgenic mPER2::Luc mice, luciferase levels, which report PER2 expression, were measured over a number of days. We demonstrate a robust circadian rhythm in the mouse lung that is responsive to glucocorticoids. Immunohistochemical techniques were used to localize specific expression of core clock proteins, and the glucocorticoid receptor, to the epithelial cells lining the bronchioles in both mouse and human lung. In the mouse, these were established to be Clara cells. Murine Clara cells retained circadian rhythmicity when grown as a pure population in culture. Furthermore, selective ablation of Clara cells resulted in the loss of circadian rhythm in lung slices, demonstrating the importance of this cell type in maintaining overall pulmonary circadian rhythmicity. In summary, we demonstrate that Clara cells are critical for maintaining coherent circadian oscillations in lung tissue. Their coexpression of the glucocorticoid receptor and core clock components establishes them as a likely interface between humoral suprachiasmatic nucleus output and circadian lung physiology.
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Affiliation(s)
- J E Gibbs
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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