Effect of Retinoic Acid on the Primary Rat Embryonic Type II Alveolar Epithelial Cell and Lung Fibroblasts Proliferation and Apoptosis Exposed to Hyperoxia

Abstract: To explore the effect of hyperoxia exposure on proliferation and apoptosis of the primary rat embryonic type II alveolar epithelial cells (AECII) and lung fibroblasts (LFs)， and the protective effect of retinoic acid (RA) on hyperoxia lung injury. The primary rat embryonic AECII and LFs (gestation 19-20 d) were cultured in vitro. For the study of RA effects， AECII and LFs were exposed to hyperoxia in the presence or absence of RA for 12 h. Their apoptosis were analyzed by annexin V/propidium iodide (PI) double Staining and flow cytometry. The expression of PCNA， p53 and caspase-3 in AECII and that of PCNA in LFs were determined by Western blot. Results showed that: (1) Quantitative data from flow cytometry analyses (PI/annexin V double staining) demonstrated that there was a significant increase in positive cells of both annexin V (+) PI (-) and annexin V (+) PI (+) after 12 h of hyperoxia in AECII (14.41±1.15 vs 2.80±0.19， P<0.01; 61.07±3.06 vs 1.49±0.11， P<0.01). RA had no effect on apoptosis and necrosis of AECII exposed in room air， but markedly decreased hyperoxia-induced AECII apoptosis and necrosis(8.04±0.79 vs 14.41±1.15， P<0.01; 27.57±2.32 vs 61.07±3.06， P<0.01). (2) The apoptosis and necrosis of LFs were not changed by hyperoxia exposure and/or RA treatment. (3) Western blot analyses showed that， after 12 h of hyperoxia， PCNA was reduced markedly (P<0.01)， p53 and active fragment of caspase-3 (17 kDa) were increased in AECII (P<0.01). In hyperoxia exposure， RA decreased the expression of p53 and active fragment of caspase-3 markedly (P<0.01)， improved the expression of PCNA (P<0.01). (4) Hyperoxia exposure and/or RA treatment had no effect on the expression of PCNA in LFs. It was concluded that， hyperoxia exposure lead to numerous AECII apoptosis and necrosis and inhibited AECII proliferation， but did not change LFs survival， both of which were involved in abnormal lung remodeling; RA had a protective effect on hyperoxia lung injury by which declined AECII apoptosis and necrosis.

CSTR: 32200.14.cjcb.2007.01.0023