Retinoic Acid Could Accommodate The Expression Of Smad3 And Repress The Radiation-induced Lung Injury

ObjectiveTo investigate the effect of retinoic acid (RA) on the change of pathology and the expression of Smad3 in the pulmonary tissue of radiation-induced lung injury rat model.MethodEighty Wistar rats were randomly divided into four groups, with twenty rats in each group, including control group(group A), RA treatment group(group B), radiation group(group C), and radiation with RA treatment group(group D). Rats in group C and group D were radiated with 6MV-X ray of linear accelaretor at dose of 15Gy thoracically, rats in group B and group D were given RA by gastrogavage at dose of 20 mg/(kg-d), and group A and group C were given physiological saline at the same dose until they were killed. In 1,2,4,8 week after radiation, HE staining and Massion staining were used to detecte the pathological change of pulmonary tissues, immunohistochemistry staining was use to measure the expression of Smad3 level, and the results of immunohistochemistry staining were measured by image analysis system.ResultHE and Massion staining suggested that the alveolar spaces have inflammatory cells exudation one week after radiation, followed by interstitial edema, and they shrink and even with destroyed structure, local consol, and collagen fibers appearing in pulmonary interstitial at 4 and 8 week. No significant difference of pathology was seen between the simple treatment group and the control group, but obviously decreased was seen between group C and group D. The expression of Smad3 was enhanced significantly in group C and D group at 1,2,4,8 week(P<0.0001), compared with group A, while was weakened in group D compared with group C, especially at 4,8 week. However, no statistical difference was observed between group A and group B.ConclusionSmad3 participated in the process of radiation induced lung injury while RA repress the expression of Smad3 in protein level.