Yan Chao, Wang Lin, Li Bo, Zhang Bei-Bei, Zhang Bo, Wang Yan-Hong, Li Xiang-Yang, Chen Jia-Xu, Tang Ren-Xian, Zheng Kui-Yang
Department of Pathogenic Biology and Immunology, Laboratory of Infection and Immunity, Xuzhou Medical College, Xuzhou, Jiangsu Province, 221004, PR China.
Laboratory of Parasite and Vector Biology, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, 200025, PR China.
Parasit Vectors. 2015 Feb 4;8:70. doi: 10.1186/s13071-015-0675-y.
Liver fibrosis is a hallmark of clonorchiasis suffered by millions people in Eastern Asian countries. Recent studies showed that the activation of TGF-β/Smad signaling pathway can potently regulate the hepatic fibrogenesis including Schistosoma spp. and Echinococcus multilocularis-caused liver fibrosis. However, little is known to date about the expression of transforming growth factor-β (TGF-β) and other molecules in TGF-β/Smad signaling pathway which may play an important role in hepatic fibrosis caused by C. sinensis.
A total of 24 mice were individually infected orally with 45 metacercariae, both experimental mice and mocked-infected control mice were anesthetized at 4 week post-infection (wk p.i.), 8 wk p.i. and 16 wk p.i., respectively. For each time-point, the liver and serum from each animal were collected to analyze histological findings and various fibrotic parameters including TGF-β₁, TGF-β receptors and down-stream Smads activation, as well as fibrosis markers expression.
The results showed that collagen deposition indicated by hydroxyproline content and Masson's trichrome staining was increased gradually with the development of infection. The expression of collagen type α1 (Col1a) mRNA transcripts was steadily increased during the whole infection. The mRNA levels of Smad2, Smad3 as well as the protein of Smad3 in the liver of C. sinensis-infected mice were increased after 4 wk p.i. (P < 0.05, compared with normal control) whereas the TGF-β₁, TGF-β type I receptor (TGFβRI) and TGF-β type II receptor (TGFβRII) mRNA expression in C. sinensis-infected mice were higher than those of normal control mice after 8 wk p.i. (P < 0.05). However, the gene expression of Smad4 and Smad7 were peaked at 4 wk p.i. (P < 0.05), and thereafter dropped to the basal level at 8 wk p.i., and 16 wk p.i., respectively. The concentrations of TGF-β₁ in serum in the C. sinensis-infected mice at 8 wk p.i. and 16 wk p.i (P < 0.05) were significantly higher than those in the control mice.
The results of the present study indicated for the first time that the activation of TGF-β/Smad signaling pathway might contribute to the synthesis of collagen type I which leads to liver fibrosis caused by C. sinensis.
肝纤维化是东亚国家数百万人感染华支睾吸虫病的一个标志。最近的研究表明，转化生长因子-β（TGF-β）/Smad信号通路的激活可有效调节包括血吸虫属和多房棘球绦虫引起的肝纤维化在内的肝纤维化形成。然而，迄今为止，关于TGF-β/Smad信号通路中可能在华支睾吸虫引起的肝纤维化中起重要作用的转化生长因子-β（TGF-β）和其他分子的表达情况知之甚少。
将24只小鼠分别经口感染45个囊蚴，分别在感染后4周（p.i.）、8周和16周对实验小鼠和假感染对照小鼠进行麻醉。对于每个时间点，收集每只动物的肝脏和血清，以分析组织学结果和各种纤维化参数，包括TGF-β₁、TGF-β受体和下游Smad激活，以及纤维化标志物表达。
结果表明，羟脯氨酸含量和Masson三色染色所示的胶原沉积随着感染的发展而逐渐增加。在整个感染过程中，Ⅰ型胶原（Col1a）mRNA转录本的表达稳步增加。感染华支睾吸虫的小鼠肝脏中Smad2、Smad3的mRNA水平以及Smad3蛋白在感染后4周升高（与正常对照相比，P<0.05），而感染华支睾吸虫的小鼠中TGF-β₁、Ⅰ型TGF-β受体（TGFβRI）和Ⅱ型TGF-β受体（TGFβRII）mRNA表达在感染后8周高于正常对照小鼠（P<0.05）。然而，Smad4和Smad7的基因表达在感染后4周达到峰值（P<0.05），此后分别在感染后8周和16周降至基础水平。感染华支睾吸虫的小鼠在感染后8周和16周时血清中TGF-β₁的浓度（P<0.05）显著高于对照小鼠。
本研究结果首次表明，TGF-β/Smad信号通路的激活可能有助于Ⅰ型胶原的合成，从而导致华支睾吸虫引起的肝纤维化。
