RESUMO
A model of rabbit tracheal epithelial (RTE) cells in primary culture was used to characterize specific and repair responses of airway epithelial cells to oxidative stress. Two well-known reactive oxygen species (ROS) generating systems were used: H(2)O(2) alone or in combination with Fe(2+) to produce the hydroxyl radical. RTE cells exhibited lipid peroxidation when exposed to H(2)O(2) + Fe(2+). Moreover, catalase (CAT) activity decreased after a 1-hour treatment in 3-day-old cultures but increased in 7-day-old cultures which have higher antioxidant enzyme activities. Superoxide dismutase (SOD) activity was never affected. In addition, RTE cells displayed a repair response leading to squamous metaplasia. H(2)O(2) + Fe(2+) treatment resulted in a time-dependent increase in the steady-state level of c-myc mRNA while c-jun and c-fos were not activated. Moreover, a chronic exposure induced the expression of the squamous phenotype characterized by the expression of the cytokeratin 13 confirmed both at the message and protein levels. RTE cells in primary culture react early to H(2)O(2) + Fe(2+) exposure by an increase in c-myc expression and by modifications in CAT activity. Further, a lipid peroxidation occurs and the tracheal epithelium evolves to squamous metaplasia.
Assuntos
Peróxido de Hidrogênio/toxicidade , Oxidantes/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Traqueia/efeitos dos fármacos , Animais , Western Blotting , Catalase/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Epitélio/efeitos dos fármacos , Epitélio/enzimologia , Queratinas/metabolismo , L-Lactato Desidrogenase/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Malondialdeído/metabolismo , Metaplasia/induzido quimicamente , Metaplasia/patologia , Proteínas Oncogênicas/biossíntese , Fenótipo , RNA/análise , RNA/biossíntese , RNA/isolamento & purificação , Coelhos , Superóxido Dismutase/metabolismo , Traqueia/enzimologiaRESUMO
A model of rabbit tracheal epithelial (RTE) cells in vitro was developed in order to investigate the effects, on the airway epithelium, of reactive oxygen species (ROS) generated by H2O2 in association or not in association with Fe2+. The immediate consequence of a 24 h exposure of RTE cells to an oxidative stress was an increase in catalase activity whereas superoxide dismutase activity was not modified. A latter consequence of a chronic ROS insult was the induction of a repair mechanism which led to squamous metaplasia (SM). SM is characterized by a stratification of the epithelium, the expression of the cytokeratin 13 and the appearance of cells with cross-linked envelopes. Reversible modifications between mucociliary and squamous phenotype are modulated by retinoids. The action of retinoids is selective: metaplasia is inhibited by agonists of RAR alpha and beta receptors and not by an agonist of RAR gamma receptors.
