Chen X M, Gores G J, Paya C V, LaRusso N F
Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, Rochester, Minnesota 55905, USA.
Am J Physiol. 1999 Sep;277(3):G599-608. doi: 10.1152/ajpgi.1999.277.3.G599.
Although the clinical features of sclerosing cholangitis from opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which associated pathogens, such as Cryptosporidium parvum, cause disease are obscure. Using an in vitro model of biliary cryptosporidiosis, we observed that C. parvum induces apoptosis in cultured human biliary epithelia. Both caspase protease inhibitors and neutralizing antibodies to either Fas receptor (Fas) and Fas ligand (FasL) inhibited this process; neutralizing antibodies to other apoptotic cytokines [interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta)] had no effect. C. parvum stimulated FasL membrane surface translocation, increased both FasL and Fas protein expression in infected biliary epithelia, and induced a marked increase of soluble FasL (but not IL-1beta, TNF-alpha, and TGF-beta) in supernatants from infected cells. When a coculture model is used in which infected and uninfected cell populations were physically separated by a semipermeable membrane, both uninfected biliary epithelia and uninfected Fas-sensitive Jurkat cells (but not a Fas-resistant Jurkat cell line) underwent apoptosis when cocultured with infected biliary epithelia. Moreover, both a neutralizing antibody to FasL and a metalloprotease inhibitor blocked the apoptosis in uninfected cocultured cells. Activation of caspase activity was also observed in uninfected cocultured biliary epithelia. The data suggest that C. parvum induces apoptosis in biliary epithelia by a Fas/FasL-dependent mechanism involving both autocrine and paracrine pathways. These observations may be relevant to both the pathogenesis and therapy of the cholangitis seen in AIDS patients with biliary cryptosporidiosis.
尽管获得性免疫缺陷综合征（AIDS）患者因胆管机会性感染所致硬化性胆管炎的临床特征已为人熟知，但相关病原体（如微小隐孢子虫）致病的机制仍不清楚。利用胆管隐孢子虫病的体外模型，我们观察到微小隐孢子虫可诱导培养的人胆管上皮细胞凋亡。半胱天冬酶蛋白酶抑制剂以及针对Fas受体（Fas）和Fas配体（FasL）的中和抗体均可抑制这一过程；针对其他凋亡细胞因子[白细胞介素-1β（IL-1β）、肿瘤坏死因子-α（TNF-α）和转化生长因子-β（TGF-β）]的中和抗体则无此作用。微小隐孢子虫刺激FasL膜表面易位，增加感染胆管上皮细胞中FasL和Fas蛋白表达，并导致感染细胞上清液中可溶性FasL（而非IL-1β、TNF-α和TGF-β）显著增加。当使用共培养模型，通过半透膜将感染和未感染细胞群体物理分离时，未感染的胆管上皮细胞和未感染的Fas敏感型Jurkat细胞（而非Fas抗性Jurkat细胞系）与感染的胆管上皮细胞共培养时会发生凋亡。此外，针对FasL的中和抗体和金属蛋白酶抑制剂均可阻断未感染共培养细胞中的凋亡。在未感染共培养的胆管上皮细胞中也观察到半胱天冬酶活性的激活。数据表明，微小隐孢子虫通过涉及自分泌和旁分泌途径的Fas/FasL依赖性机制诱导胆管上皮细胞凋亡。这些观察结果可能与AIDS患者胆管隐孢子虫病相关胆管炎的发病机制和治疗均有关。
