TGF-beta signaling promotes survival and repair in rat alveolar epithelial type 2 cells during recovery after hyperoxic injury.
Hyperoxic rats treated with inosine during oxygen exposure have increased levels of active transforming growth factor (TGF)-beta in the bronchoalveolar lavage (BAL), yet alveolar epithelial type 2 cells (AEC2) isolated from these animals demonstrate less hyperoxia-induced DNA damage and increased expression of active Smad2. To determine whether TGF-beta1 signaling per se protected AEC2 against hyperoxic damage, freshly isolated AEC2 from hyperoxic rats were incubated with TGF-beta1 for 24 h and assayed for DNA damage by fluorescein-activated cell sorter analysis of TdT-mediated dUTP nick end labeling. TGF-beta1 was protective over a concentration range similar to that in BAL of inosine-treated hyperoxic animals (50-5,000 pg/ml). TGF-beta1 also augmented hyperoxia-induced DNA repair activity and cell migration, stimulated autocrine secretion of fibronectin, accelerated closure of a monolayer scratch wound, and restored hyperoxia-depleted VEGF secretion by AEC2 to normoxic levels. The TGF-beta receptor type I activin-like kinase-4, -5, and -7 inhibitor peptide SB-505124 abolished the protective effect of TGF-beta on hyperoxic DNA damage and increased TdT-mediated dUTP nick end labeling in normoxic cells. These data suggest that endogenous TGF-beta-mediated Smad signaling is required for AEC2 homeostasis in vitro, while exogenous TGF-beta1 treatment of hyperoxia-damaged AEC2 results in a cell that is equipped to survive, repair, migrate, secrete matrix, and induce new blood vessel formation more efficiently than AEC2 primed by hyperoxia alone.
Buckley
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S
Developmental Biology and Regenerative Medicine and Surgery Program, Saban Research Institute of Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.
Shi
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Barsky
L
L
Warburton
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D
D000818:Animals; D052117:Benzodioxoles / Q000494:pharmacology; D018929:Cell Culture Techniques; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival; D018496:Hyperoxia / Q000503:physiopathology*; D007093:Imidazoles / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D008297:Male; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D020545:Respiratory Mucosa / Q000166:cytology* / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology* / Q000502:physiology*
C519132:2-(5-benzo(1,3)dioxol-5-yl-2-tert-butyl-3H-imidazol-4-yl)-6-methylpyridine hydrochloride; D052117:Benzodioxoles; D007093:Imidazoles; D011725:Pyridines; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta