低氧对大鼠肺组织结构的影响及其机制的探讨

目的观察间歇性常压低氧对SPF级SD大鼠肺组织中转化生长因子-β1(TGF-β1)、通道蛋白Smad4、Ⅰ型胶原、肿瘤坏死因子-α(TNF-α)表达及肺组织结构的影响。方法将SD大鼠置于常氧或间歇性常压低氧(101kPa,10%O2,每天低氧8h)条件下,分别于3、7、14、21d每组处死5只大鼠,HE染色观察肺组织病理改变,免疫组化染色检测肺组织TGF-β1、Ⅰ型胶原表达,RT-PCR检测TGF-β1、Ⅰ型胶原的mRNA表达量,Westernblot法检测Smad4通道蛋白的表达,ELISA法检测肺泡灌洗液中TNF-α的表达。结果 HE染色提示低氧第3d低氧组大鼠肺组织即出现轻度水肿及炎症细胞浸润,且随低氧时间延长,炎症反应加重,肺泡间隔逐渐增厚;低氧组大鼠肺组织中TGF-β1、Smad4、Ⅰ型胶原蛋白表达量及TGF-β1mRNA、Ⅰ型胶原mRNA均较对照组高(P<0.01),随低氧时间延长,各因子表达量逐渐增高,且Smad4蛋白表达水平与TGF-β1表达水平呈正相关(r=0.944,P<0.01);肺泡灌洗液中TNF-α表达量较对照组高(P<0.01)。结论低氧可能通过诱发肺组织水肿及炎症反应,上调TNF-α水平、激活TGF-β1/Smads通路从而增加Ⅰ型胶原合成,引发细胞外基质沉积,肺泡间隔增厚。

Study on the effect and mechanism of hypoxia on the histological structure of rat's lung

Objective To observe the effect of intermittent normobaric hypoxia on the expression of transforming growth factor beta1(TGFβ1),Smad4,collagen Ⅰ(Col Ⅰ),tumor necrosis factor alpha(TNF-α) and on the changes in the histological structure of SPF SD Rat’s lung.Methods Rats were placed in normal environment or intermittent normobaric hypoxia(101 kPa,10% O2,8 h every day) respectively.At the 3rd,7th,14th,21st day,5 rats from each group were killed and hematoxylin and eosin stain(HE stain) was applied to observe the pathological change in the lung of rats,immunohistochemical staining was used to detect the protein level of TGF-β1,Col Ⅰ. RT-PCR was performed to detect the mRNA levels of TGF-β1 and ColⅠ.Western blot to detect the expression of Smad4.Besides,the TNF-α in the bronchoalveolar lavage(BALF) were determined by ELISA.Results Results of HE stain demonstrated that the mild edema and inflammatory cell infiltration appeared in the lung tissue at the 3rd day,and gradually aggravated inflammation were observed as the treated time extended;meanwhile the interalveolar septum become thicker and thicker as the time of exposing to normobaric hypoxia increased.Compared with the normoxia group,not only the protein expression of TGF-β1,Smad4 and ColⅠ,but also the mRNA expression of TGF-β1 and ColⅠ were elevated(P<0.01) in normobaric hypoxia group as the treatment time extended.Besides,a positive correlation(r=0.944,P<0.01) between the protein level of TGF-β1 and Smad4 was observed and an up-regulated TNF-α in the BALF was also noticed.Conclusion Normobaric hypoxia could cause pulmonary edema and inflammation by up-regulating expression of TNFα,activating the TGF-β1/Smads Signaling Pathway,and increasing the synthesization of Col Ⅰ,the deposition of extracellular matrix as well as the interalveolar septum thickness.