EXPRESSION OF BCL 2 IN SIV INFECTED THYMIC TISSUE

BCL 2 在 SIV 感染的胸腺组织中的表达

• 批准号: 6591316
• 负责人: M ROSENZWEIG
• 金额: $ 11.11万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-05-01 至 2003-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6591316
• 关键词: AIDS; animal tissue; communicable diseases; immunology; inflammation; lymphatic system; virus

Cell death due to apoptosis plays a critical role in the development of T cells in the thymus Several intracellular molecular mechanisms have been identified that regulate apoptosis in thymocytes, including bcl-2, bcl-x, bax, R-ras and fas Retroviral infection of the thymus with HIV-1 or SIV results in selective thymocyte depletion, and apoptosis has been shown to contribute to this increase in cell death The precise mechanism whereby lentiviruses induce apoptosis remains controversial Using a novel system of in vitro T cell differentiation, we developed a multiparameter flow cytometry assay to determine the role of fas, fas-ligand and bcl-2 in apoptosis of thymocytes as a result of SIV infection We detected a 3-fold increase of apoptosis (detected by Tdt staining) in in vitro cultures 48 post infection with SIV239 Furthermore, the increase in Tdt+ cells is accompanied by a decrease in bcl-2 (2- 3-fold) expression and an increase in surface fas expressio n (4-5 fo ld) as determined by flow cytometry Fas ligand was found to be increased in single positive thymocytes in vivo, but not in the in vitro culture system This data clearly demonstrates that both the bcl-2 and fas pathways are involved in SIV induced apoptosis of thymocytes and that lentiviral infection leads to thymocyte apoptosis Using FACS we demonstrated that SIV infection results in an initial 15-20% decrease of surface fas expression in CD4+CD8+ and CD4+CD8- cells, and not CD4-CD8+ cells However, by day 7 post-infection, we observed a profound reversal of this phenomenon, with a dramatic increase (6 fold) in fas expression in CD4+CD8+ and CD4+CD8- cells, as compared to uninfected cultures These studies have been extended to examine the effects of acute SIV-infection in vivo, with respect to alterations in the thymus Data from these studies demonstrated that the surface levels of fas on thymocytes from normal neonates is generally low (1-3% of all cells), and does not demonstrate any specific phenotypic distribution After SIV infection the level of surface fas changes modestly, increasing to a maximum of 8% of thymocytes of d14 post-infection This was not accompanied by any significant alteration in surface expression of fas-ligand This observation was in contrast to the fluctuations in bcl-2 levels Uninfected neonatal thymocytes express large amounts of bcl-2, consistent with the observations of others However, rapidly during the course of SIV infection the number of bcl-2 positive cells decreases, as well as the amount of bcl-2 per cell as detected by flow cytometry The lowest levels of bcl-2 occur coincident with the largest amount of apoptosis, detected by Tdt staining By day 21 of acute SIV infection, the levels of virus begin to decline and this is associated with the resumption of normal thymic function Specifically, by d21, the number of apoptotic cells is drastically reduced, and the number of bcl-2 cells begins to approach baseline levels The level of bcl-2 on a per cell basis recovers only by day 50 post-infection Based on these observations, it would appear that dysregulation of the bcl-2 pathway is the predominant mechanism associated with the apoptosis that accompanies retroviral infection of the thymus REFERENCES Wykrzykowska JJ, Rosenzweig M, Veazey RS, Simon MA, Halvorsen K, Desrosiers RC, Johnson RP, Lackner AA Early regeneration of thymic progenitors in rhesus macaques infected with simian immunodeficiency virus J Exp Med 1998, 187:1767-1778 Gardner JP, Rosenzweig M*, Marks DF, Harper D, Gaynor K, Fallon RJ, Wall DA, Johnson RP, Scadden DT T lymphopoietic capacity of cord blood-derived CD34+ progenitor cells Exp Hematol 1998; 26:991-999

由细胞凋亡引起的细胞死亡在 胸腺T细胞在几种细胞内分子的发育 已经确定了调节胸腺细胞凋亡的机制， 包括BCL-2、BCL-x、BAX、R-ras和Fas逆转录病毒感染 带有HIV-1或SIV的胸腺会导致胸腺细胞选择性耗尽，并且 细胞凋亡已被证明是导致细胞死亡增加的原因之一 慢病毒诱导细胞凋亡的确切机制仍然存在。 使用一种新的体外T细胞分化系统存在争议， 我们建立了一种多参数流式细胞术来检测 Fas、Fas配体和bcl2在胸腺细胞凋亡中的作用 SIV感染的结果我们检测到细胞凋亡增加了3倍 (用TDT染色检测)感染后48天的体外培养 此外，TDT+细胞的增加伴随着 Bcl2表达减少(2-3倍)，表面表达增加 流式细胞术检测Fas配体表达的研究 在体内单个阳性胸腺细胞中被发现增加，但 不是在体外培养系统中，这个数据清楚地表明 Bcl2和fas信号转导通路均参与SIV诱导的细胞凋亡 慢病毒感染会导致胸腺细胞 用流式细胞仪检测细胞凋亡我们证实了SIV感染会导致 CD_4~+、CD_8~+、CD_4~+、CD_8~+细胞表面Fas表达最初下降15~20% 然而，到第7天，CD4+CD8-细胞，而不是CD4-CD8+细胞 在感染后，我们观察到这种现象发生了深刻的逆转， 随着CD4+CD8+和Fas表达的显著增加(6倍)， 与未感染的培养物相比，这些研究有 被扩展到检查体内急性SIV感染的影响， 关于这些研究中胸腺数据的变化 证明正常人胸腺细胞表面Fas的水平 新生儿通常较低(占所有细胞的1-3%)，而不是 在感染SIV后表现出任何特定的表型分布 地表FAS水平变化不大，增加到最大 感染后d14的胸腺细胞中有8%没有伴随任何 Fas配体This表面表达的显著变化 观察结果与bcl2水平的波动形成对比 未感染的新生儿胸腺细胞表达大量bcl2， 然而，与其他人的观察一致，在 在SIV感染过程中，bcl2阳性细胞数量减少， 以及流式细胞仪检测到的每个细胞bcl2的量 Bcl-2的最低水平与最高水平的 急性SIV感染第21天，TDT染色检测到细胞凋亡， 病毒水平开始下降，这与 恢复正常的胸腺功能，特别是在D21，数字 凋亡细胞的数量急剧减少，bcl2的数量 细胞开始接近基线水平，即BCL-2水平 细胞基础只有在感染后50天才能恢复 观察到，bcl2通路的失调似乎 是与细胞凋亡相关的主要机制 伴发胸腺逆转录病毒感染Wykrzykowska 首页--期刊主要分类--期刊细介绍--期刊题录与文摘-期刊详细文摘内容 Johnson RP、Lackner AA对小鼠胸腺祖细胞早期再生的影响 感染猴免疫缺陷病毒J Exp Med的恒河猴 1998,187：1767-1778 Gardner JP，Rosenzweig M*，Marks DF，Harper D， 首页--期刊主要分类--期刊细介绍--期刊题录与文摘--期刊详细文摘内容 脐带血CD34+祖细胞体外培养的能力 1998；26：991-999