细胞外信号调节激酶和转化生长因子β1在哮喘气道重塑中的作用以及糖皮质激素的调控

The role of external signal regulated kinase and transforming growth factor β_1 in asthma airway remodeling and regulation of glucocorticoids

目的研究细胞外信号调节激酶(ERK)和转化生长因子β1(TGF-β1)在哮喘气道重塑中的作用,探讨糖皮质激素对 ERK、TGF-β1及哮喘气道重塑的调控。方法建立慢性哮喘动物模型,将30只 SD 大鼠随机分对照组、哮喘组、地塞米松干预组(DM 组)。免疫组化测定肺组织中磷酸化的 ERK(P-ERK),ELISA 测定血清中 TGF-β1含量。体外培养大鼠气道上皮细胞,以 BB 型血小板源性生长因子(PDGF-BB)、U0126、布地奈德(BUD)作为工具药干预细胞,Western 印迹检测细胞 ERK磷酸化水平,ELISA 法检测细胞上清液 TGF-β1含量。结果哮喘组 P-ERK 平均吸光度和 TGF-β1含量[分别为(31.1±2.2)和(28.1±7.4)μg/L]均较对照组[(12.8±2.4)和(13.6±2.7)μg/L]高(P<0.01),DM 组[分别为(18.7±3.1)和(15.0±3.2)μg/L]较哮喘组低(P 均<0.01)。ERK 的磷酸化与 PDGF-BB 存在浓度依赖关系,50μg/L 时 ERK 磷酸化水平最高,高于对照组(P<0.01);U0126和 BUD 均可抑制 ERK 的磷酸化;各处理组细胞上清 TGF-β1差异无统计学意义。结论 ERK磷酸化、TGF-β1在支气管哮喘气道重塑中起重要作用;PDGF-BB 不能通过 ERK 磷酸化诱导正常大鼠气管上皮细胞产生释放 TGF-β1;糖皮质激素能抑制 ERK 磷酸化。

Objective To study role of external signal regulated kinase （ ERK ） and transforming growth factor β1 （TGF-β1） in asthma airway remodeling and to explore the regulation of glucocorticoids on ERK , TGF-β1, and airway remodeling. Methods Thirty SD rats were randomly divided into 3 equal groups： control group; asthma group, undergoing intra-peritoneal injection of ovalbumin （OVA） on days 1 and 8 and inhalation of OVA every other day for 8 weeks since day 15 to establish chronic asthma models; dexamethasone （DM） intervention group, undergoing intra-peritoneal injection of DM 30 min before every inhalation instigation ; and control group, receiving normal saline instead of DM. 1 -2 hours after the last instigation the left lungs were taken out. The total bronchial wall thickness （Wat） and smooth muscle thickness （Warn） were measured by image analysis system. Phosphorylated ERK （P-ERK） was detected by immunohistochemistry. 1 -2 hours after the last instigation blood samples were collected from the femoral artery. The concentration of transforming growth factor （TGF）-β1 in the serum was measured by sandwich ELISA. Rat airway epithelial cells were cultured, stimulated with platelet-derived growth factor-BB （ PDGF- BB, 1, 10, 25, or 50 μg/L）, U0126 （specific inhibitor of phosphorylation of ERK）, or budesonide （BUD）. Western blotting was used to detect the P-ERK level. The level of TGF-β1 in the cell culture supernatant was detected by sandwich ELISA. Results The Wat and Wam of the asthma group was significantly higher than those of the control group （both P 〈0.01 ）, and the War and Wam of the DM group were both significantly lower than those of the asthma group （ both P 〈 0.01 ）. The mean optical density of P- ERK and concentration of TGF-β1 in the serum of the asthma group were 31.1 ±2.2 and 28.1 ±7.4 μg/L respectively, both significantly higher than those of the control group （ 12.8 ±2.4 and 13.6 ±2.7 μg/L respectively, both P 〈0.01 ）, and the mean optical density of P-ERK and concentration of TGF-β1 in the serum of the DM group were 18.7 ± 3.1 and 15.0 ± 3.2μg/L respectively, both significantly lower than those asthma group （both P 〈0. 01 ）. In the PDGF-BB （25 μg/L） stimulated cells marked phosphorylation of ERK occurred 15 min later, the level of P-ERK remained high up to 8 hour later, and the maximal activation occurred at the period of 2 h - 4 h later, 6.5±0. 4 times that of the control value （ P 〈 0.01 ）. The phosphorylation levels of ERK depended on the concentration of PDGF-BB and the maximal level phosphorylation was detected with the concentration of PDGF-BB of 50 μg/L, which was 4.1 ±0. 3 times that of the control value （P 〈0.01 ）. U0126 and BUD inhibited the phosphorylation of ERK in the cells stimulated by PDGF-BB of the concentration of 25 μg/L. there was no difference in the level of TGF-β1in the cell culture supernatant among different groups. Conclusion Phosphorylation of ERK and TGF-β1 have an important role in asthma airway remodeling; PDGF-BB does not induce normal rat airway epithelial cells to product or release TGF-β1 by phosphorylation of ERK. Glucocorticoids can inhibit phosphorylation of ERK.