Dept. of Neurosurgery, Univ. of Kentucky, Lexington, 40536, USA.
Am J Physiol Heart Circ Physiol. 2010 Apr;298(4):H1136-45. doi: 10.1152/ajpheart.01126.2009. Epub 2010 Feb 5.
Telomerase, via its catalytic component telomerase reverse transcriptase (TERT), extends telomeres of eukaryotic chromosomes. The importance of this reaction is related to the fact that telomere shortening is a rate-limiting mechanism for human life span that induces cell senescence and contributes to the development of age-related pathologies. The aim of the present study was to evaluate whether the modulation of telomerase activity can influence human immunodeficiency virus type 1 (HIV-1)-mediated dysfunction of human brain endothelial cells (hCMEC/D3 cells) and transendothelial migration of HIV-1-infected cells. Telomerase activity was modulated in hCMEC/D3 cells via small interfering RNA-targeting human TERT (hTERT) or by using a specific pharmacological inhibitor of telomerase, TAG-6. The inhibition of hTERT resulted in the upregulation of HIV-1-induced overexpression of intercellular adhesion molecule-1 via the nuclear factor-kappaB-regulated mechanism and induced the transendothelial migration of HIV-1-infected monocytic U937 cells. In addition, the blocking of hTERT activity potentiated a HIV-induced downregulation of the expression of tight junction proteins. These results were confirmed in TERT-deficient mice injected with HIV-1-specific protein Tat into the cerebral vasculature. Further studies revealed that the upregulation of matrix metalloproteinase-9 is the underlying mechanisms of disruption of tight junction proteins in hCMEC/D3 cells with inhibited TERT and exposed to HIV-1. These results indicate that the senescence of brain endothelial cells may predispose to the HIV-induced upregulation of inflammatory mediators and the disruption of the barrier function at the level of the brain endothelium.
端粒酶通过其催化成分端粒酶逆转录酶（TERT）延长真核染色体的端粒。这种反应的重要性与以下事实有关：端粒缩短是人类寿命的限速机制，会诱导细胞衰老，并导致与年龄相关的病理发生。本研究旨在评估端粒酶活性的调节是否会影响人类免疫缺陷病毒 1（HIV-1）介导的人脑微血管内皮细胞（hCMEC/D3 细胞）功能障碍和 HIV-1 感染细胞的跨内皮迁移。通过靶向人 TERT（hTERT）的小干扰 RNA 或使用端粒酶的特异性药理学抑制剂 TAG-6 来调节 hCMEC/D3 细胞中的端粒酶活性。hTERT 的抑制导致 HIV-1 诱导的细胞间黏附分子-1 的过表达通过核因子-κB 调节的机制上调，并诱导 HIV-1 感染的单核细胞 U937 细胞的跨内皮迁移。此外，hTERT 活性的阻断增强了 HIV 诱导的紧密连接蛋白表达下调。这些结果在向脑血管内注射 HIV-1 特异性蛋白 Tat 的 TERT 缺陷型小鼠中得到了证实。进一步的研究表明，基质金属蛋白酶-9 的上调是 hCMEC/D3 细胞中紧密连接蛋白破坏的潜在机制，这些细胞中 TERT 被抑制并暴露于 HIV-1 下。这些结果表明，脑内皮细胞的衰老可能使 HIV 诱导的炎症介质上调和血脑屏障功能障碍易于发生。
