American journal of respiratory cell and molecular biology
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Am. J. Respir. Cell Mol. Biol. · Jul 2013
ReviewSphingosine-1-phosphate, FTY720, and sphingosine-1-phosphate receptors in the pathobiology of acute lung injury.
Acute lung injury (ALI) attributable to sepsis or mechanical ventilation and subacute lung injury because of ionizing radiation (RILI) share profound increases in vascular permeability as a key element and a common pathway driving increased morbidity and mortality. Unfortunately, despite advances in the understanding of lung pathophysiology, specific therapies do not yet exist for the treatment of ALI or RILI, or for the alleviation of unremitting pulmonary leakage, which serves as a defining feature of the illness. A critical need exists for new mechanistic insights that can lead to novel strategies, biomarkers, and therapies to reduce lung injury. ⋯ We and others have demonstrated that S1P is a potent angiogenic factor that enhances lung endothelial cell integrity and an inhibitor of vascular permeability and alveolar flooding in preclinical animal models of ALI. In addition to S1P, S1P analogues such as 2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol (FTY720), FTY720 phosphate, and FTY720 phosphonates offer therapeutic potential in murine models of lung injury. This translational review summarizes the roles of S1P, S1P analogues, S1P-metabolizing enzymes, and S1P receptors in the pathophysiology of lung injury, with particular emphasis on the development of potential novel biomarkers and S1P-based therapies for ALI and RILI.
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Am. J. Respir. Cell Mol. Biol. · Apr 2013
ReviewEndothelial progenitor cells in regeneration after acute lung injury: do they play a role?
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common disorders in patients requiring critical care. The clinical management of these disorders is difficult and unrewarding, and thus they are among the most common causes of death in intensive care units. The activation and damage of pulmonary endothelium comprise the hallmark of ALI/ARDS. ⋯ Although initial studies suggested implantations of exogenously administered bone marrow-derived progenitor cells into damaged vessel walls, recent evidence indicates that this is rather a rare occurrence with uncertain physiologic significance. In the past few years, different populations of progenitor cells were identified, with different functional capacities. This review (1) highlights the different populations of EPCs identified or administered in different models of ALI/ARDS, (2) reports on whether beneficial effects of EPCs could be demonstrated, and (3) puts the conflicting results of different studies into perspective.
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Am. J. Respir. Cell Mol. Biol. · Jan 2013
ReviewRegulation and functional significance of autophagy in respiratory cell biology and disease.
Autophagy is a homeostatic process common to all eukaryotic cells that serves to degrade intracellular components. Among three classes of autophagy, macroautophagy is best understood, and is the subject of this Review. ⋯ This process has been extensively studied in yeast, and understanding of its functional significance in human disease is also increasing. This Review explores the basic machinery and regulation of autophagy in mammalian systems, methods employed to measure autophagic activity, and then focuses on recent discoveries about the functional significance of autophagy in respiratory diseases, including chronic obstructive pulmonary disease, cystic fibrosis, tuberculosis, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, acute lung injury, and lymphangioleiomyomatosis.
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Am. J. Respir. Cell Mol. Biol. · Apr 2012
ReviewHypercapnia: a nonpermissive environment for the lung.
Patients with severe acute and chronic lung diseases develop derangements in gas exchange that may result in increased levels of CO(2) (hypercapnia), the effects of which on human health are incompletely understood. It has been proposed that hypercapnia may have beneficial effects in patients with acute lung injury, and the concepts of "permissive" and even "therapeutic" hypercapnia have emerged. ⋯ Here we review recent research on how elevated CO(2) is sensed by cells in the lung and the potential harmful effects of hypercapnia on epithelial and endothelial barrier, lung edema clearance, innate immunity, and host defense. In view of these findings, we raise concerns about the potentially deleterious effects hypercapnia may have in patients with acute and chronic lung diseases.
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Am. J. Respir. Cell Mol. Biol. · Dec 2011
ReviewEverything prevents emphysema: are animal models of cigarette smoke-induced chronic obstructive pulmonary disease any use?
There is a very large number of experimental approaches that prevent cigarette smoke-induced emphysema in laboratory animals, but the few similar treatments that have been tried in humans have had minimal effects, leading to questions of whether animal models of chronic obstructive pulmonary disease (COPD) are of any use in developing treatments for human disease. We review possible reasons for this problem. First, humans usually get treated when they have severe (Global Initiative for Chronic Obstructive Lung Disease III/IV) COPD, but animal models only produce mild (Global Initiative for Chronic Obstructive Lung Disease I/II) disease that never progresses after smoking cessation, and never develops spontaneous exacerbations (i.e., animal models are not models of severe human disease, and probably can't be used to model treatment of severe disease). ⋯ Third, animal models are typically Day 1 of smoke exposure "prevention" models, but humans are always treated well along in the course of their disease; thus, any human treatment will be an intervention, and not a prevention. We propose that animal models should examine both emphysema and small airway remodeling, and that experiments should include a relatively late intervention arm. This approach, combined with the realization that human COPD probably needs early rather than late treatment, may make development of treatments based on animal models more relevant.