Studying ultrastructural changes could reveal novel pathophysiology of obese-asthmatic condition as existing concepts in asthma pathogenesis are based on the histological changes of the diseased airway. While asthma is defined in functional terms, the potential of electron microscopy (EM) in providing cellular and subcellular detail is underutilized. With this view, we have performed transmission EM in the lungs from allergic mice that show key features of asthma and high-fat- or high-fructose-fed mice that mimicked metabolic syndrome to illustrate the ultrastructural changes. The primary focus was epithelial injury and metaplasia, which are cardinal features of asthma and initiate airway remodeling. EM findings of the allergically inflamed mouse lungs correlate with known features of human asthma such as increased mitochondria in airway smooth muscle, platelet activation and subepithelial myofibroblasts. Interestingly, we found a clear and unambiguous evidence to suggest that ciliated cells can become goblet cells using immunoelectron microscopy. Additionally, we show for the first time the stressed mitochondria in the bronchial epithelia of high-fat- or high-fructose-fed mice even without allergen exposure. These results may stimulate interest in using EM in understanding novel pathological mechanisms for different subtypes of asthma including obese asthma. 1. Introduction Asthma, a chronic airway disease, is characterized by reversible airflow obstruction, airway inflammation, airway hyperresponsiveness (AHR), and structural changes referred to as airway remodeling [1, 2]. Asthma can be described in clinical, physiological, immunological, and pathological terms, each providing its own unique context in understanding asthma pathogenesis. Though this description seems to be simple, various endotypes/phenotypes of asthma have been recently demonstrated indicating the complexity of asthma [3–5]. Similar complexity also exists in the responsiveness to available antiasthma medications. The difficult-to-treat or severe or refractory asthmatics are responsible for significant health and economic burden of asthma even though they are just 10% of all asthmatics [6–9]. In this context, it has been demonstrated that asthma severity correlates very well with increased body mass index [10, 11]. As obese-asthmatic condition does not fall in the description of general asthma, there is necessity to understand the novel mechanisms for this condition. Muscular disease, inflammation dominant disease, airway remodeling, and epithelial injury are the historical
References
[1]
A. B. Kay, “Pathology of mild, severe, and fatal asthma,” American Journal of Respiratory and Critical Care Medicine, vol. 154, no. 2, pp. S66–S69, 1996.
[2]
D. E. Davies, “The role of the epithelium in airway remodeling in asthma,” Proceedings of the American Thoracic Society, vol. 6, no. 8, pp. 678–682, 2009.
[3]
T. Y. Lin, A. H. Poon, and Q. Hamid, “Asthma phenotypes and endotypes,” Current Opinion in Pulmonary Medicine, vol. 19, no. 1, pp. 18–23, 2013.
[4]
S. Wenzel, “Severe asthma: from characteristics to phenotypes to endotypes,” Clinical and Experimental Allergy, vol. 42, no. 5, pp. 650–658, 2012.
[5]
J. L？tvall, C. A. Akdis, L. B. Bacharier et al., “Asthma endotypes: a new approach to classification of disease entities within the asthma syndrome,” Journal of Allergy and Clinical Immunology, vol. 127, no. 2, pp. 355–360, 2011.
[6]
W. W. Busse, S. Banks-Schlegel, and S. E. Wenzel, “Pathophysiology of severe asthma,” Journal of Allergy and Clinical Immunology, vol. 106, no. 6, pp. 1033–1042, 2000.
[7]
S. Papiris, A. Kotanidou, K. Malagari, and C. Roussos, “Clinical review: severe asthma,” Critical Care, vol. 6, no. 1, pp. 30–44, 2002.
[8]
S. E. Wenzel and W. W. Busse, “Severe asthma: lessons from the Severe Asthma Research Program,” Journal of Allergy and Clinical Immunology, vol. 119, no. 1, pp. 14–21, 2007.
[9]
S. Wenzel, “Severe asthma in adults,” American Journal of Respiratory and Critical Care Medicine, vol. 172, no. 2, pp. 149–160, 2005.
[10]
R. Varraso, V. Siroux, J. Maccario, I. Pin, and F. Kauffmann, “Asthma severity is associated with body mass index and early menarche in women,” American Journal of Respiratory and Critical Care Medicine, vol. 171, no. 4, pp. 334–339, 2005.
[11]
B. Taylor, D. Mannino, C. Brown, D. Crocker, N. Twum-Baah, and F. Holguin, “Body mass index and asthma severity in the National Asthma Survey,” Thorax, vol. 63, no. 1, pp. 14–20, 2008.
[12]
S. T. Holgate, “A brief history of asthma and its mechanisms to modern concepts of disease pathogenesis,” Allergy, Asthma and Immunology Research, vol. 2, no. 3, pp. 165–171, 2010.
[13]
S. T. Holgate, “Has the time come to rethink the pathogenesis of asthma?” Current Opinion in Allergy and Clinical Immunology, vol. 10, no. 1, pp. 48–53, 2010.
[14]
S. T. Holgate, “Epithelium dysfunction in asthma,” Journal of Allergy and Clinical Immunology, vol. 120, no. 6, pp. 1233–1244, 2007.
[15]
S. R. Hays and J. V. Fahy, “The role of mucus in fatal asthma,” American Journal of Medicine, vol. 115, no. 1, pp. 68–69, 2003.
[16]
J. A. Elias, C. G. Lee, T. Zheng, B. Ma, R. J. Homer, and Z. Zhu, “New insights into the pathogenesis of asthma,” Journal of Clinical Investigation, vol. 111, no. 3, pp. 291–297, 2003.
[17]
E. Crimi, A. Spanevello, M. Neri, P. W. Ind, G. A. Rossi, and V. Brusasco, “Dissociation between airway inflammation and airway hyperresponsiveness in allergic asthma,” American Journal of Respiratory and Critical Care Medicine, vol. 157, no. 1, pp. 4–9, 1998.
[18]
R. J. Homer and J. A. Elias, “Airway remodeling in asthma: Therapeutic implications of mechanisms,” Physiology, vol. 20, no. 1, pp. 28–35, 2005.
[19]
E. D. Fixman, A. Stewart, and J. G. Martin, “Basic mechanisms of development of airway structural changes in asthma,” European Respiratory Journal, vol. 29, no. 2, pp. 379–389, 2007.
[20]
T. Mauad, E. H. Bel, and P. J. Sterk, “Asthma therapy and airway remodeling,” Journal of Allergy and Clinical Immunology, vol. 120, no. 5, pp. 997–1009, 2007.
[21]
R. He and R. S. Geha, “Thymic stromal lymphopoietin,” Annals of the New York Academy of Sciences, vol. 1183, pp. 13–24, 2010.
[22]
L. Borish and J. W. Steinke, “Interleukin-33 in asthma: how big of a role does it play?” Current Allergy and Asthma Reports, vol. 11, no. 1, pp. 7–11, 2011.
[23]
M. Suzukawa, H. Morita, A. Nambu, et al., “Epithelial cell-derived IL-25, but not Th17 cell-Derived IL-17 or IL-17F, is crucial for murine asthma,” Journal of Immunology, vol. 189, no. 7, pp. 3641–3652, 2012.
[24]
J. A. Elias, Z. Zhu, G. Chupp, and R. J. Homer, “Airway remodeling in asthma,” Journal of Clinical Investigation, vol. 104, no. 8, pp. 1001–1006, 1999.
[25]
P. M. D'Agostino and C. S. Reiss, “A confocal and electron microscopic comparison of interferon β-induced changes in vesicular stomatitis virus infection of neuroblastoma and nonneuronal cells,” DNA and Cell Biology, vol. 29, no. 3, pp. 103–120, 2010.
[26]
U. Mabalirajan, A. K. Dinda, S. Kumar et al., “Mitochondrial structural changes and dysfunction are associated with experimental allergic asthma,” Journal of Immunology, vol. 181, no. 5, pp. 3540–3548, 2008.
[27]
U. Mabalirajan, T. Ahmad, G. D. Leishangthem et al., “Beneficial effects of high dose of L-arginine on airway hyperresponsiveness and airway inflammation in a murine model of asthma,” Journal of Allergy and Clinical Immunology, vol. 125, no. 3, pp. 626–635, 2010.
[28]
U. Mabalirajan, R. Rehman, T. Ahmad, et al., “Linoleic acid metabolite drives severe asthma by causing airway epithelial injury,” Scientific Reports, vol. 3, article 1349, 2013.
[29]
U. Mabalirajan, R. Rehman, T. Ahmad T, et al., “12/15-lipoxygenase expressed in non-epithelial cells causes airway epithelial injury in asthma,” Scientific Reports, vol. 3, article 1540, 2013.
[30]
J. Aich, U. Mabalirajan, T. Ahmad, A. Agrawal, and B. Ghosh, “Loss-of-function of inositol polyphosphate-4-phosphatase reversibly increases the severity of allergic airway inflammation,” Nature Communications, vol. 3, p. 877, 2012.
[31]
M. Kumar, T. Ahmad, A. Sharma et al., “Let-7 microRNA-mediated regulation of IL-13 and allergic airway inflammation,” Journal of Allergy and Clinical Immunology, vol. 128, no. 5, pp. 1077–e10, 2011.
[32]
T. Ahmad, U. Mabalirajan, D. A. Joseph et al., “Exhaled nitric oxide estimation by a simple and efficient noninvasive technique and its utility as a marker of airway inflammation in mice,” Journal of Applied Physiology, vol. 107, no. 1, pp. 295–301, 2009.
[33]
G. Leishangthem, U. Mabalirajan, T. Ahmad, et al., “Use of transmission electron microscopy for studying airway remodeling in a chronic ovalbumin mice model of allergic asthma,” in Microscopy: Science, Technology, Applications and Education, A. Méndez-Vilas and J. Díazs, Eds., pp. 347–353, 2010.
[34]
L. N. A. Gamage, C. Charavaryamath, T. L. Swift, and B. Singh, “Lung inflammation following a single exposure to swine barn air,” Journal of Occupational Medicine and Toxicology, vol. 2, no. 1, article 18, 2007.
[35]
M. Malm-Erjef？lt, C. G. A. Persson, and J. S. Erjef？lt, “Degranulation status of airway tissue eosinophils in mouse models of allergic airway inflammation,” American Journal of Respiratory Cell and Molecular Biology, vol. 24, no. 3, pp. 352–359, 2001.
[36]
S. C. Pitchford, S. Momi, S. Baglioni et al., “Allergen induces the migration of platelets to lung tissue in allergic asthma,” American Journal of Respiratory and Critical Care Medicine, vol. 177, no. 6, pp. 604–612, 2008.
[37]
M. J. Sanderson, E. R. Dirksen, and P. Satir, “Electron Microscopy of respiratory tract cilia,” in Lung Biology in Health and Disease (Electron Microscopy of the Lung), D. E. Schraufnagel, Ed., vol. 48, pp. 47–69, Marcel Dekker, New York, NY, USA, 1990.
[38]
J. E. Boers, A. W. Ambergen, and F. B. J. M. Thunnissen, “Number and proliferation of Clara cells in normal human airway epithelium,” American Journal of Respiratory and Critical Care Medicine, vol. 159, no. 5, pp. 1585–1591, 1999.
[39]
A. Agrawal, S. Rengarajan, K. B. Adler et al., “Inhibition of mucin secretion with MARCKS-related peptide improves airway obstruction in a mouse model of asthma,” Journal of Applied Physiology, vol. 102, no. 1, pp. 399–405, 2007.
[40]
D. F. Rogers, “Airway goblet cell hyperplasia in asthma: hypersecretory and anti-inflammatory?” Clinical and Experimental Allergy, vol. 32, no. 8, pp. 1124–1127, 2002.
[41]
J. R. Reader, J. S. Tepper, E. S. Schelegle et al., “Pathogenesis of mucous cell metaplasia in a murine asthma model,” American Journal of Pathology, vol. 162, no. 6, pp. 2069–2078, 2003.
[42]
C. M. Evans, O. W. Williams, M. J. Tuvim et al., “Mucin is produced by clara cells in the proximal airways of antigen-challenged mice,” American Journal of Respiratory Cell and Molecular Biology, vol. 31, no. 4, pp. 382–394, 2004.
[43]
P. J. Barnes, “Pathophysiology of asthma,” British Journal of Clinical Pharmacology, vol. 42, no. 1, pp. 3–10, 1996.
[44]
S. A. A. Comhair, W. Xu, S. Ghosh et al., “Superoxide dismutase inactivation in pathophysiology of asthmatic airway remodeling and reactivity,” American Journal of Pathology, vol. 166, no. 3, pp. 663–674, 2005.
[45]
S. Shahana, E. Bj？rnsson, D. L. Lúdvíksdóttir, et al., “Ultrastructure of bronchial biopsies from patients with allergic and non-allergic asthma,” Respiratory Medicine, vol. 99, no. 4, pp. 429–443, 2005.
[46]
B. A. Raby, B. Klanderman, A. Murphy et al., “A common mitochondrial haplogroup is associated with elevated total serum IgE levels,” Journal of Allergy and Clinical Immunology, vol. 120, no. 2, pp. 351–358, 2007.
[47]
E. Zifa, Z. Daniil, E. Skoumi et al., “Mitochondrial genetic background plays a role in increasing risk to asthma,” Molecular Biology Reports, vol. 39, no. 4, pp. 4697–4708, 2012.
[48]
E. M. Schauberger, S. L. Ewart, S. H. Arshad et al., “Identification of ATPAF1 as a novel candidate gene for asthma in children,” Journal of Allergy and Clinical Immunology, vol. 128, no. 4, pp. 753.e11–760.e11, 2011.
[49]
L. Aguilera-Aguirre, A. Bacsi, A. Saavedra-Molina, A. Kurosky, S. Sur, and I. Boldogh, “Mitochondrial dysfunction increases allergic airway inflammation,” Journal of Immunology, vol. 183, no. 8, pp. 5379–5387, 2009.
[50]
B. N. Lambrecht and H. Hammad, “The airway epithelium in asthma,” Nature Medicine, vol. 18, no. 5, pp. 684–692, 2012.
[51]
M. Swamy, C. Jamora, W. Havran, and A. Hayday, “Epithelial decision makers: in search of the 'epimmunome',” Nature Immunology, vol. 11, no. 8, pp. 656–665, 2010.
[52]
C. S. Nunemaker, M. Chen, H. Pei et al., “12-Lipoxygenase-knockout mice are resistant to inflammatory effects of obesity induced by western diet,” American Journal of Physiology—endocrinology and Metabolism, vol. 295, no. 5, pp. E1065–E1075, 2008.
[53]
B. K. Cole, M. A. Morris, W. J. Grzesik, K. A. Leone, and J. L. Nadler, “Adipose tissue-specific deletion of 12/15-lipoxygenase protects mice from the consequences of a high-fat diet,” Mediators of Inflammation, vol. 2012, Article ID 851798, 13 pages, 2012.
[54]
D. D. Sears, P. D. Miles, J. Chapman et al., “12/15-Lipoxygenase is equired for the early onset of high fat diet-induced adipose tissue inflammation and insulin resistance in mice,” PLoS One, vol. 4, no. 9, Article ID e7250, 2009.
[55]
S. A. Shore, “Obesity and asthma: Lessons from animal models,” Journal of Applied Physiology, vol. 102, no. 2, pp. 516–528, 2007.
[56]
R. A. Johnston, T. A. Theman, F. L. Lu, R. D. Terry, E. S. Williams, and S. A. Shore, “Diet-induced obesity causes innate airway hyperresponsiveness to methacholine and enhances ozone-induced pulmonary inflammation,” Journal of Applied Physiology, vol. 104, no. 6, pp. 1727–1735, 2008.
[57]
S. A. Shore, “Obesity, airway hyperresponsiveness, and inflammation,” Journal of Applied Physiology, vol. 108, no. 3, pp. 735–743, 2010.
[58]
S. T. Holgate, “The airway epithelium is central to the pathogenesis of asthma,” Allergology International, vol. 57, no. 1, pp. 1–10, 2008.
[59]
H. Tanaka, M. Komai, K. Nagao et al., “Role of interleukin-5 and eosinophils in allergen-induced airway remodeling in mice,” American Journal of Respiratory Cell and Molecular Biology, vol. 31, no. 1, pp. 62–68, 2004.
[60]
S.-Y. Leung, P. Eynott, A. Noble, P. Nath, and K. F. Chung, “Resolution of allergic airways inflammation but persistence of airway smooth muscle proliferation after repeated allergen exposures,” Clinical and Experimental Allergy, vol. 34, no. 2, pp. 213–220, 2004.
[61]
A. L. James, P. D. Pare, and J. C. Hogg, “The mechanics of airway narrowing in asthma,” The American Review of Respiratory Disease, vol. 139, no. 1, pp. 242–246, 1989.
[62]
B. R. Wiggs, C. Bosken, P. D. Paré, A. James, and J. C. Hogg, “A model of airway narrowing in asthma and in chronic obstructive pulmonary disease,” The American Review of Respiratory Disease, vol. 145, no. 6, pp. 1251–1258, 1992.
[63]
P. K. Jeffery, A. J. Wardlaw, F. C. Nelson, J. V. Collins, and A. B. Kay, “Bronchial biopsies in asthma. An ultrastructural, quantitative study and correlation with hyperreactivity,” The American Review of Respiratory Disease, vol. 140, no. 6, pp. 1745–1753, 1989.
[64]
W. R. Roche, R. Beasley, J. H. Williams, and S. T. Holgate, “Subepithelial fibrosis in the bronchi of asthmatics,” The Lancet, vol. 1, no. 8637, pp. 520–524, 1989.
[65]
L. Pini, Q. Hamid, J. Shannon et al., “Differences in proteoglycan deposition in the airways of moderate and severe asthmatics,” European Respiratory Journal, vol. 29, no. 1, pp. 71–77, 2007.
[66]
P. Bradding, A. E. Redington, and S. T. Holgate, “Airway wall remodelling in the pathogenesis of asthma: cytokine expression in the airways,” in Airway Wall Remodelling in Asthma, A. G. Stewart, Ed., pp. 29–63, CRC Press, Boca Raton, Fla, USA, 1997.
[67]
A. Laitinen, E.-M. Karjalainen, A. Altraja, and L. A. Laitinen, “Histopathologic features of early and progressive asthma,” Journal of Allergy and Clinical Immunology, vol. 105, no. 2, pp. S509–S513, 2000.
[68]
C. E. Brewster, P. H. Howarth, R. Djukanovic, J. Wilson, S. T. Holgate, and W. R. Roche, “Myofibroblasts and subepithelial fibrosis in bronchial asthma,” American Journal of Respiratory Cell and Molecular Biology, vol. 3, no. 5, pp. 507–511, 1990.
[69]
M. J. Gizycki, E. ？delroth, A. V. Rogers, P. M. O'Byrne, and P. K. Jeffery, “Myofibroblast involvement in the allergen-induced late response in mild atopic asthma,” American Journal of Respiratory Cell and Molecular Biology, vol. 16, no. 6, pp. 664–673, 1997.
[70]
P. G. Woodruff, G. M. Dolganov, R. E. Ferrando et al., “Hyperplasia of smooth muscle in mild to moderate asthma without changes in cell size or gene expression,” American Journal of Respiratory and Critical Care Medicine, vol. 169, no. 9, pp. 1001–1006, 2004.
[71]
M. Ebina, H. Yaegashi, R. Chiba, T. Takahashi, M. Motomiya, and M. Tanemura, “Hyperreactive site in the airway tree of asthmatic patients revealed by thickening of bronchial muscles. A morphometric study,” The American Review of Respiratory Disease, vol. 141, no. 5, part 1, pp. 1327–1332, 1990.
[72]
S. J. McMillan and C. M. Lloyd, “Prolonged allergen challenge in mice leads to persistent airway remodelling,” Clinical and Experimental Allergy, vol. 34, no. 3, pp. 497–507, 2004.
