The human immunodeficiency virus type 1 Tat protein enhances Cryptosporidium parvum-induced apoptosis in cholangiocytes via a Fas ligand-dependent mechanism
The human immunodeficiency virus type 1 Tat protein enhances Cryptosporidium parvum-induced apoptosis in cholangiocytes via a Fas ligand-dependent mechanism
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DOI：
10.1128/iai.01348-06
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发表时间：
2007-02-01
影响因子：
3.1
通讯作者：
LaRusso, Nicholas F.
中科院分区：
文献类型：
--
作者：
O'Hara, Steven P.;Small, Aaron J.;LaRusso, Nicholas F.
虽然免疫功能正常和免疫功能低下的人都有肠道微小隐孢子虫感染的报道，但胆道感染主要见于成年艾滋病患者，并与艾滋病胆管疾病的发展有关。然而，病原体诱导的艾滋病胆管病的发病机制尚不清楚。由于我们先前证实Fas/Fas配体(FasL)系统参与了旁分泌介导的微小弧菌对胆管细胞的致病作用，因此我们还通过半定量逆转录聚合酶链式反应(RT-PCR)、免疫印迹、免疫荧光分析和免疫金电子显微镜检测了人类免疫缺陷病毒1型(HIV-1)反式转录激活因子(TAT)介导的FasL调节对微小弧菌诱导的胆管细胞凋亡的潜在协同作用。H69细胞不表达CXCR4和CCR5，这是直接感染HIV-1病毒所需的受体。然而，重组具有生物活性的HIV-1相关TAT蛋白增加了胆管细胞胞浆中FasL的表达，而没有显著增加细胞凋亡。我们发现微小隐孢子虫诱导的细胞凋亡与细胞内FasL移位到细胞膜表面以及感染H69细胞释放全长FasL有关。TAT显著(P<；0.05)增加微小隐孢子虫诱导的旁观者细胞的凋亡，并呈剂量依赖关系。此外，TAT还促进了微小隐孢子虫诱导的FasL膜移位和全长FasL的释放。此外，FasL中和抗体NOK-1和caspase-8抑制剂Z-IETD-fmk均可阻断微小隐孢子虫诱导的胆管细胞凋亡。结果表明，HIV-1Tat通过旁分泌介导的FasL依赖机制增强微小隐孢子虫诱导的胆管细胞凋亡。我们的结果表明，同时活跃的HIV复制，伴随着Tat蛋白的产生，以及微小弧菌感染，协同增加了胆管细胞的凋亡，从而共同促进了艾滋病相关的胆管疾病。
While Cryptosporidium parvum infection of the intestine has been reported in both immunocompetent and immunocompromised individuals, biliary infection is seen primarily in adult AIDS patients and is associated with development of AIDS cholangiopathy. However, the mechanisms of pathogen-induced AIDS cholangiopathy remain unclear. Since we previously demonstrated that the Fas/Fas ligand (FasL) system is involved in paracrine-mediated C. parvum cytopathicity in cholangiocytes, we also tested the potential synergistic effects of human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat)-mediated FasL regulation on C. parvum-induced apoptosis in cholangiocytes by semiquantitative reverse transcription-PCR, immunoblotting, immunotluorescence analysis, and immunogold electron microscopy. H69 cells do not express CXCR4 and CCR5, which are receptors required for direct HIV-1 viral infection. However, recombinant biologically active HIV-1-associated Tat protein increased FasL expression in the cytoplasm of cholangiocytes without a significant increase in apoptosis. We found that C. parvum-induced apoptosis was associated with translocation of intracellular FasL to the cell membrane surface and release of full-length FasL from infected H69 cells. Tat significantly (P < 0.05) increased C. parvum-induced apoptosis in bystander cells in a dose-dependent manner. Moreover, Tat enhanced both C. parvum-induced FasL membrane translocation and release of full-length FasL. In addition, the FasL neutralizing antibody NOK-1 and the caspase-8 inhibitor Z-IETD-fmk both blocked C. parvum-induced apoptosis in cholangiocytes. The data demonstrated that HIV-1 Tat enhances C. parvum-induced cholangiocyte apoptosis via a paracrine-mediated, FasL-dependent mechanism. Our results suggest that concurrent active HIV replication, with associated production of Tat protein, and C. parvum infection synergistically increase cholangiocyte apoptosis and thus jointly contribute to AIDS-related cholangiopathies.