Hyperoxia induces the apoptosis of alveolar epithelial cells and changes of pulmonary surfactant proteins.

OBJECTIVE

To explore the changes of surfactant protein C, D (SP-C, SP-D) and apoptosis of alveolar epithelial cells (AEC) in the lung injury of neonatal rats induced by hyperoxia.

MATERIALS AND METHODS

We divided neonatal rats within 24 hours into two groups randomly: the air group (n = 50) and the hyperoxia group (n = 50). Rats in the air group and hyperoxia group were bred conventionally and in tanks with normal pressure and 90% concentration of oxygen, respectively. On the 1st, 3rd, 7th, 10th, and 14th day after exposure, lung tissue of 8 rats in each group was collected and stained with hematoxylin and eosin (HE). We observed and recorded pathologic changes of lung tissue and detected apoptosis rate of alveolar epithelial cells by TUNEL (TdT-mediated dUTP nick end labeling). We detected the content of SP-C, SP-D in bronchoalveolar lavage fluid (BALF) by ELISA (enzyme-linked immunosorbent assay).

RESULTS

In the air group, the alveolar formed gradually with equable size and regular shape during growth. While the amount of alveolar decreased gradually and we observed small vessels dilation and increasing hemorrhage as well as increasing interstitial cells and swollen lung tissue in the hyperoxia group. In the air group, the content of SP-C in the BALF reduced during growth. However, the content of SP-C in the hyperoxia group was lower than that in the air group on the first day, higher on the third day, reached the peak on the seventh day and began to decrease on the tenth day and more obviously on the fourteenth day. The level of SP-D in the air group declined gradually with growing. On the first day, the content of SP-D in the hyperoxia group was similar to that in the air group. It began to increase on the third day, reached its peak on the seventh day, and began to decrease on the tenth day, more obviously on the fourteenth day.

CONCLUSIONS

Long-term exposure to hyperoxia inhibits the development of alveolar. The apoptosis of alveolar epithelial cells increased and the content of SP-C, SP-D in the lung tissue first increased and then decreased with the increase of exposure time.