title: Hypoxia-induced cytoskeleton disruption in alveolar epithelial cells.
abstract: Alveolar hypoxia, a common feature of many respiratory disorders, has been previously reported to induce functional changes, particularly a decrease of transepithelial Na and fluid transport. In polarized epithelia, cytoskeleton plays a regulatory role in transcellular and paracellular transport of ions and fluid. We hypothesized that exposure to hypoxia could damage cytoskeleton organization, which in turn, may adversely affect ion and fluid transport. Primary rat alveolar epithelial cells (AEC) were exposed to either mild (3% O(2)) or severe (0.5% O(2)) hypoxia for 18 h or to normoxia (21% O(2)). First, mild and severe hypoxia induced a disorganization of actin, a major protein of the cytoskeleton, reflected by disruption of F-actin filaments. Second, alpha-spectrin, an apical cytoskeleton protein, which binds to actin cytoskeleton and Na transport proteins, was cleaved by hypoxia. Pretreatment of AEC by a caspase inhibitor (z-VAD-fmk; 90 microM) blunted hypoxia-induced spectrin cleavage as well as hypoxia-induced decrease in surface membrane alpha-ENaC and concomitantly induced a partial recovery of hypoxia-induced decrease of amiloride-sensitive Na transport at 3% O(2). Finally, tight junctions (TJs) proteins, which are linked to actin and are a determinant of paracellular permeability, were altered by mild and severe hypoxia: hypoxia induced a mislocalization of occludin from the TJ to cytoplasm and a decrease in zonula occludens-1 protein level. These modifications were associated with modest changes in paracellular permeability at 0.5% O(2,) as assessed by small 4-kD dextran flux and transepithelial resistance measurements. Together, these findings indicate that hypoxia disrupted cytoskeleton and TJ organization in AEC and may participate, at least in part, to hypoxia-induced decrease in Na transport.
authors.affiliation: INSERM U773 Centre de Recherche Biomédicale Bichat-Beaujon (CRB3), Université Paris 7 Denis Diderot, UFR de Médecine, Site Bichat, France.
authors.forename: Diane
authors.initials: D
authors.lastname: Bouvry
authors.forename: Carole
authors.initials: C
authors.lastname: Planès
authors.forename: Laurence
authors.initials: L
authors.lastname: Malbert-Colas
authors.forename: Virginie
authors.initials: V
authors.lastname: Escabasse
authors.forename: Christine
authors.initials: C
authors.lastname: Clerici
mesh_terms: D000199:Actins / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000378:metabolism; D000860:Hypoxia; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D062793:Occludin; D018408:Patch-Clamp Techniques; D010539:Permeability; D010750:Phosphoproteins / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013049:Spectrin / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; D000590:Amino Acid Chloromethyl Ketones; D053503:Epithelial Sodium Channels; D008565:Membrane Proteins; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D013049:Spectrin; D002154:Calpain