吡格列酮对放射性肺炎的预防作用及其机制研究

Protective effect of pioglitazone on lung injury induced by irradiation

目的过氧化物酶体增殖物激活受体γ(peroxisome proliferator-activated receptor gamma,PPARγ)是一类由配体激活的核转录因子,参与调节多种炎症介质的释放,但PPARγ是否参与调节放射性肺炎尚不清楚。本实验研究PPARγ激动剂吡格列酮(pioglitazone,PIO)对放射性肺炎的预防作用,并探讨其机制。方法将BALB/c小鼠80只随机分为正常对照组、单纯照射组、PIO治疗组及照射+PIO治疗组4组,每组20只。X射线全胸单次照射15Gy建立小鼠放射性肺炎模型,PPARγ激动剂PIO 20mg/(kg·d)于照射前1周开始灌服,1次/d,每周称体质量调整1次给药剂量,共8周。分别于照射前、照射后1、4和8周处死小鼠5只,摘取全肺,称湿重,计算肺指数;行肺脏组织学HE染色观察肺组织学变化,ELISA法检测小鼠血清中转化生长因子β1(transforming growth factor beta 1,TGF-β1)、白介素6(interleukin 6,IL-6)和肿瘤坏死因子α(tumor necrosis factor-alpha,TNF-α)在各组小鼠血清中的变化。结果各组小鼠无一例死亡。资料经Kolmogorov-Smirnov检验符合正态分布,方差齐。单纯照射组小鼠肺指数最高,F=35.82,P<0.001;照射组小鼠肺指数显著高于对照组和PIO组,均P<0.001;照射+PIO组小鼠肺指数显著低于单纯照射组,P<0.001。不同时间点各组小鼠肺指数差异无统计学意义,F=1.30,P=0.282。照射后肺组织发生广泛炎症改变,小血管和毛细血管扩张、充血,肺间隔和肺泡腔充斥大量水肿液体,使肺泡间隔增厚,肺泡腔减小。肺泡腔以及增厚的肺间质中充斥大量炎性细胞成分,包括巨噬细胞、中性粒细胞、淋巴细胞和红细胞等,表现为充血、水肿和渗出。PIO组则减轻了照射诱发的肺组织充血、水肿和渗出。单纯照射组小鼠TGF-β1、IL-6及TNF-α水平均高于其他3组,差异均有统计学意义,F值分别为128.80、79.18和135.51,均P<0.001。对照组和PIO组小鼠血清TGF-β1、IL-6及TNF-α水平差异均无统计学意义,P=1.000;照射组小鼠血清TGF-β1、IL-6及TNF-α水平均显著高于对照组和PIO组(均P<0.001),照射+PIO组小鼠血清TGF-β1、IL-6及TNF-α水平均显著低于单纯照射组(均P<0.001)。照射后4周血清TGF-β1(F=20.62,P<0.001)、IL-6(F=8.15,P=0.001)及TNF-α(F=5.96,P=0.005)水平最高,均显著高于照射后1周。但血清TGF-β1与照射后8周相比差异无统计学意义,P=0.460。血清TGF-β1、IL-6及TNF-α水平处理组与照射后时间之间无交互效应。血清中TGF-β1(r=0.486,P=0.021)、IL-6(r=0.525,P<0.001)和TNF-α(r=0.573,P=0.005)水平与肺指数呈显著正相关。结论 PPARγ激动剂PIO能减轻小鼠放射性肺炎,其作用与可能与调节TGF-β1、IL-6和TNF-α的表达水平有关。

OBJECTIVE Peroxisome proliferator-activated receptor gamma （PPART） is involved in regulating inflammatory cytokines. However, whether PPAR7 paticipates in pulmonitis induced by irradiation is not known. The aim of this study was to evaluate the protective effects of peroxisome proliferator-activated receptor gamma on lung injury induced by irradiation and the mechanism involving the process. METHODS BALB/c mice were randomly divided into 4 groups： control group, radiation group, pioglitazone group and radiation combined pioglitazone group. Fifteen Gray of X-ray dose was administered to induced lung pneumonitis. Pioglitazone was administered orally everyday by 20 mg per kilogram till 8 weeks. Mice were killed and lung index was calculated. Pathology of lung was abserved by Hematoxylin and eosin stain. Serum TGF-β1 , IL-6 and TNF-α were measured by ELISA methods. RESULTS The lung index reached a peak in radiation group compared with other three groups（F=35.82, P〈0. 001）, however, there was no difference between control group and Pioglitazone group（P= 1. 000）. The lung index of Radiation combined Pioglitazone group was lower than those of radiation group（P〈0. 001）. The difference of lung index was of no significance in 1week, 4weeks, and 8weeks after radiation（F= 1.30, P=0. 282）. The inflammatory reaction, including inflammatory cell infiltration, effusion, congestion and edema were reduced in pioglitazone combined with radiation group compared with radiation group. The levels of serum TGF-β1, IL-6, TNF-α in radiation group were all maximal during the four groups, higher than those of other three groups（F=128.80, 79.18, 135.51, all P〈0. 001）. There was no difference in serum TGF-β1, IL-6, TNF-α level between control group and pioglitazone group. However serum TGF-β1, IL-6, TNF-α levels in radiation group were higher compared with those of control group. Serum TGF-β1, IL-6, TNF-α levels of radiation combined pioglitazone group were lower than those of radiation group. The serum TGF-β1 , IL-6, TNF-α levels reach to peak at 4 weeks after radiation, higher than those of 1weeks after radiation. But the difference was no significance compared with 8 weeks after radiation. There was no interaction between group and radiation time. Serum levels of TGF-β1, IL-6, and TNF-α had positive correlations with lung index（r= 0. 486, 0. 525, 0. 573, all P〈0.05）. COUCLUSIONS Radiation pneumonitis can be relieved by peroxisome proliferator-activated receptor gamma pioglitazone and downregulation cytokines of TGF-β1 , IL-6, TNF-α may be the mechanism involved in the process.