Bcl-2 Family Gene Expression during Severe Hyperoxia Induced Lung Injury

Department of Pediatrics, School of Medicine and Dentistry, Children's Hospital at Strong, University of Rochester, New York 14642, USA.
Laboratory Investigation (Impact Factor: 3.68). 01/2001; 80(12):1845-54. DOI: 10.1038/labinvest.3780195
Source: PubMed


Exposure of the lung to severe hyperoxia induces terminal transferase dUTP end-labeling (TUNEL) indicative of DNA damage or apoptosis and increases expression of the tumor suppressor p53 and of members of the Bcl-2 gene family. Because cell survival and apoptosis are regulated, in part, by the relative abundance of proteins of the Bcl-2 family, we hypothesized that lung cells dying during exposure would show increased expression of pro-apoptotic members, such as Bax, whereas surviving cells would have increased expression of anti-apoptotic members, such as Bcl-X(L). The hypothesis is tested in the current study by determining which Bcl-2 genes are regulated by hyperoxia, with specific focus on correlating expression of Bax and Bcl-X(L) with morphologic evidence of apoptosis or necrosis. Adult mice exposed to greater than 95% oxygen concentrations for 48 to 88 hours had increased whole-lung mRNA levels of Bax and Bcl-X(L), no change in Bak, Bad, or Bcl-2, and decreased levels of Bcl-w and Bfl-1. In situ hybridization revealed that hyperoxia induced Bax and Bcl-X(L) mRNA in uniform and overlapping patterns of expression throughout terminal bronchioles and parenchyma, coinciding with TUNEL staining. Electron microscopy and DNA electrophoresis, however, suggested relatively little classical apoptosis. Unexpectedly, Western analysis demonstrated increased Bcl-X(L), but not Bax, protein in response to hyperoxia. Bax and Bfl-1 were not altered by hyperoxia in p53 null mice; however, oxygen toxicity was not lessened by p53 deficiency. These findings suggest that oxygen-induced lung injury does not depend on the relative expression of these Bcl-2 members.

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Available from: Michael B LoMonaco, Mar 26, 2014
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    • "A high concentration of oxygen is a main stay in preterm infants with respiratory distress since birth. However, exposure to a high concentration of oxygen (> 40%) for prolonged periods causes lung injuries, which is a major contributing factor to the development of bronchopulmonary dysplasia (Barazzone et al., 2000; O'Reilly et al., 2000; Ward et al., 2000). Alveolar type II cells act as stem cells for alveolar epithelial restoration after lung injuries and during normal tissue turnover (Rama et al., 1997) and must be the critical target of hyperoxia-induced lung injury. "
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    ABSTRACT: Alveolar type II cells are main target of hyperoxia-induced lung injury. The authors investigated whether lysosomal protease, cathepsin B (CB), is activated in fetal alveolar type II cells in the transitional period from the canalicular to saccular stages during 65%-hyperoxia and whether CB is related to fetal alveolar type II cell (FATIIC) death secondary to hyperoxia. FATIICs were isolated from embryonic day 19 rats and exposed to 65%-oxygen for 24 h and 36 h. The cells exposed to room air were used as controls. Cell cytotoxicity was assessed by lactate dehydrogenase-release and flow cytometry, and apoptosis was analyzed by TUNEL assay and flow cytometry. CB activity was assessed by colorimetric assay, qRT-PCR and western blots. 65%-hyperoxia induced FATIIC death via necrosis and apoptosis. Interestingly, caspase-3 activities were not enhanced in FATIICs during 65%-hyperoxia, whereas CB activities were greatly increased during 65%-hyperoxia in a time-dependent manner, and similar findings were observed with qRT-PCR and western blots. In addition, the preincubation of CB inhibitor prior to 65%-hyperoxia reduced FATIIC death significantly. Our studies suggest that CB activation secondary to hyperoxia might have a relevant role in executing the cell death program in FATIICs during the acute stage of 65%-hyperoxia.
    Experimental and Molecular Medicine 03/2011; 43(4):223-9. DOI:10.3858/emm.2011.43.4.027 · 3.45 Impact Factor
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    • "Email: michael_oreilly@urmc.rochester.edu. TOXICOLOGICAL SCIENCES 63, 214 –222 (2001) Copyright © 2001 by the Society of Toxicology (Barazzone et al., 1998; OReilly et al., 2000 "

    Toxicological Sciences 10/2001; 63(2):214-222. DOI:10.1093/toxsci/63.2.214 · 3.85 Impact Factor
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    ABSTRACT: Pulmonary cell death may contribute significantly to acute and chronic lung injuries caused by various adverse environmental agents. Pulmonary cells may die by necrosis, apoptosis, and other forms of regulated cell death. Apoptosis exerts a homeostatic function in lung defense and development, through the removal of dysfunctional cells and by regulating cellular proliferation. Lung cell apoptosis can occur as a response to oxidative stress, mechanical ventilation, ischemia/reperfusion, cigarette smoke exposure, and other forms of acute and chronic lung injuries. The role of apoptosis in the pathogenesis of chronic lung disease remains controversial. Apoptosis may act as an adaptive process, by removing dysfunctional cells, limiting inflammation in damaged tissue, and preventing cell proliferation. On the other hand, excessive apoptosis may contribute to the depletion of critical cell populations, resulting in loss of function, as in emphysema, or in undesirable cell proliferation, as in fibrosis and pulmonary hypertension. An understanding of the cell-type-specific regulation and function of apoptosis in the lung may facilitate the development of therapeutic strategies for the treatment of lung pathologies. This chapter reviews the current evidence for the regulation and function of apoptosis in specific lung diseases, with an emphasis on chronic obstructive lung disease and acute respiratory distress syndrome.
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