Kim Byung Oh, Liu Ying, Zhou Betty Y, He Johnny J
Department of Microbiology and Immunology, Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
J Immunol. 2004 Feb 1;172(3):1888-95. doi: 10.4049/jimmunol.172.3.1888.
HIV-1 Tat has been proposed as a key agent in many AIDS-related disorders, including HIV-1-associated neurological diseases. We have recently shown that Tat expression induces a significant increase in T lymphocytes in the brains of Tat transgenic mice. The CNS infiltration of T lymphocytes has been noted in AIDS patients. In the present study using this unique genetic system we attempted to understand the underlying mechanisms of Tat expression-induced infiltration of T lymphocytes by examining chemokine expression. RNase protection assay revealed that in addition to CCL2 (monocyte chemoattractant protein-1), CCL3 (macrophage inflammatory protein-1alpha (MIP-1alpha)), CCL4 (MIP-1beta), CCL5 (RANTES), CXCL2 (MIP-2), and CXCL10 (inducing protein-10), XCL1 (lymphotactin/single C motif-1alpha/activation-induced, T cell-derived and chemokine-related cytokine) was identified to be up-regulated by Tat expression. XCL1 is a C chemokine and plays a specific and important role in tissue-specific recruitment of T lymphocytes. Thus, we further determined the relationship between Tat and XCL1 expression. Tat-induced XCL1 expression was further confirmed by XCL1-specific RT-PCR and ELISA. Combined in situ hybridization and immunohistochemical staining identified astrocytes, monocytes, and macrophages/microglia as XCL1-producing cells in vivo. Using human astrocytes, U87.MG cells, as an in vitro model, activation of XCL1 expression was positively correlated with Tat expression. Moreover, the XCL1 promoter-driven reporter gene assay showed that Tat-induced XCL1 expression occurred at the transcriptional level. Taken together, these results demonstrate that Tat directly trans-activated XCL1 expression and suggest potential roles of Tat-induced XCL1 expression in the CNS infiltration of T lymphocytes during HIV-1 infection and subsequent HIV-1-induced neurological diseases.
HIV-1反式激活因子（Tat）被认为是许多与艾滋病相关疾病的关键因子，包括与HIV-1相关的神经疾病。我们最近发现，Tat表达可导致Tat转基因小鼠大脑中的T淋巴细胞显著增加。艾滋病患者中已观察到T淋巴细胞的中枢神经系统浸润。在本研究中，我们利用这个独特的遗传系统，通过检测趋化因子表达，试图了解Tat表达诱导T淋巴细胞浸润的潜在机制。核糖核酸酶保护试验显示，除了CCL2（单核细胞趋化蛋白-1）、CCL3（巨噬细胞炎性蛋白-1α（MIP-1α））、CCL4（MIP-1β）、CCL5（调节激活正常T细胞表达和分泌因子）、CXCL2（MIP-2）和CXCL10（诱导蛋白-10）外，XCL1（淋巴细胞趋化因子/单C基序-1α/激活诱导的、T细胞来源的趋化因子相关细胞因子）也被确定因Tat表达而上调。XCL1是一种C类趋化因子，在T淋巴细胞的组织特异性募集中发挥特定且重要的作用。因此，我们进一步确定了Tat与XCL1表达之间的关系。XCL1特异性逆转录-聚合酶链反应（RT-PCR）和酶联免疫吸附测定（ELISA）进一步证实了Tat诱导的XCL1表达。原位杂交和免疫组织化学染色相结合，确定星形胶质细胞、单核细胞以及巨噬细胞/小胶质细胞是体内产生XCL1的细胞。以人星形胶质细胞U87.MG细胞作为体外模型，XCL1表达的激活与Tat表达呈正相关。此外，XCL1启动子驱动的报告基因试验表明，Tat诱导的XCL1表达发生在转录水平。综上所述，这些结果表明Tat直接反式激活XCL1表达，并提示Tat诱导的XCL1表达在HIV-1感染及后续HIV-1诱导的神经疾病过程中T淋巴细胞的中枢神经系统浸润中可能发挥的作用。
