Background The decrease of surfactant protein （SP） secreted by the alveolar type Ⅱ cell is one of the important causes of limiting air of pulmonary emphysema. However, the SP-A gene and protein changes in this disease are rarely studied. This study was undertaken to investigate alterations in SP-A gene activity and protein, and to explore their roles in the pathogenesis of emphysematous changes. Methods Twenty Wistar rats were divided randomly into a normal control group （n=10） and a cigarette smoking （CS） ＋ lipopolysaccharide （LPS） group （n=10）. Ultra-structural changes were observed under an electron microscope. The number of cells positive for SP-A was measured by immunohistochemistry. The mRNA expression and protein level of SP-A in the lung tissues were determined by quantitative polymerase chain reaction （qPCR） and Western blot separately. The protein level of SP-A in lavage fluid was determined by Western blot. Results The number of cells positive for SP-A of the CS＋LPS group （0.35±0.03） was lower than that of the blank control group （0.72±0.06, P 〈0.05）. The level of SP-A in the lung tissues of rats in the CS＋LPS group （0.2765±0.0890） was lower than that in the blank control group （0.6875±0.1578, P 〈0.05）. The level of SP-A in the lavage fluid of rats in the CS＋LPS group （0.8567±0.1458） was lower than that in the blank control group （1.3541±0.2475, P 〈0.05）. The lung tissues of rats in the CS＋LPS group showed an approximate increase （0.4-fold） in SP-A mRNA levels relative to β-actin mRNA （P 〈0.05）. Conclusions The changes of SP-A may be related to emphysematous changes in the lung. And cigarette smoke and LPS alter lung SP-A gene activity and protein homeostasis.
HU Qiong-jie XIONG Sheng-dao ZHANG Hui-lan SHI Xue-mei XU Yong-jian ZHANG Zhen-xiang ZHEN Guo-hua ZHAO Jian-ping
In order to confirm the alteration and significance of cigarette smoke exposure on SP-A in rats, 20 Wistar rats were assigned randomly to two groups： an N group （n=10）, and an S group （n=10）. The ultra-structural change was observed by electron microscopy. The number of cells positive for SPA was by immunohistochemically measured. The mRNA expression in the lung tissues was determined by reverse transcription polymerase chain reaction （RT-PCR）. The number of cells positive for SPA of the S group （0.52±0.05） was lower than that of the N group （0.72±0.06） （P〈0.05）. The levels of mRNA of SPA in the lung tissues of the S group （0.3522±0.0512） was significantly lower than that of the N group （0.4432± 0.05628） （P〈0.05）. It is concluded that cigarette smoke alone decreased the level of SP-A and that might have an important effect on surfactant metabolism and the host defense functions of surfactant in the peripheral airways, which might play a crucial role in the development of chronic obstructive lung disease.
