GLUCOCORTICOIDS AND LYMPHOCYTE CATABOLISM

这项拟议研究的长期目标是了解 肾上腺类固醇激素(糖皮质激素)对淋巴细胞和免疫的影响 一般的系统。我们将继续详细调查 糖皮质激素诱导的细胞机制最终导致 淋巴细胞死亡，从而抑制免疫功能。胸腺 去肾上腺大鼠的淋巴细胞将是我们关注的焦点。 这些细胞非常适合这些研究，因为它们是 细胞周期阶段丰富、均匀。分化状态一致， 体内外对糖皮质激素的反应及研究良好的模型 肾上腺类固醇的作用。关于以下三个开创性的观察 糖皮质激素诱导的淋巴细胞溶解作用在过去 授权期。它们是：1)糖皮质激素诱导的淋巴细胞 死亡发生在DNA降解之前；2)糖皮质激素诱导的DNA 降解不是随机的，意味着特异性；3)核 糖皮质激素诱导的核酸酶活性已被鉴定。基于 在这些观察中，我们希望提出以下假设： 糖皮质激素诱导或激活脱氧核糖核酸酶 改变基因组DNA的完整性并导致细胞死亡。为了测试 在这一假设下，我们提出了以下具体目标：1)评估 糖皮质激素诱导的DNA“断裂”是否发生在转录或 未转录的基因组序列；2)纯化到同源性 糖皮质激素“诱导”核酸酶并在体外检测其特异性；3) 糖皮质激素“诱导”核酸酶基因的克隆及其在肿瘤中的作用 通过转基因实验，糖皮质激素诱导细胞死亡；4)最后， 选择性细胞分选评价糖皮质激素的研究进展 大鼠胸腺淋巴细胞向成熟T细胞分化过程中的抗性 细胞。总而言之，这些研究应该检验提出的假设，并 为糖皮质激素诱导淋巴组织的分子基础提供数据 细胞死亡。

The long term goal of the proposed research is to understand the action of adrenal steroid hormones (glucocorticoids) on lymphocytes and the immune system in general. We will continue to investigate in detail the glucocorticoid induced cellular mechanisms which ultimately lead to lymphocyte death and thereby suppressed immune function. The thymic lymphocyte of the adrenalectomized rat will be the focus of our attention. The cells are well suited for these investigations because they are abundant, uniform in cell cycle stage. uniform in state of differentiation, responsive to glucocorticoids in vitro and in vivo and a well studied model for adrenal steroid action. Three seminal observations concerning glucocorticoid induced lymphocytolysis have been made during the past granting period. They are: 1) Glucocorticoid induced lymphocyte cell death is preceeded by DNA degradation; 2) Glucocorticoid induced DNA degradation is not random, implying specificity; 3) A nuclear glucocorticoid "induced" nuclease activity has been identified. Based on these observations, we wish to propose the following hypothesis: Glucocorticoids induce or activate a deoxyribonuclease which selectively alters the integrity of genomic DNA and causes the cells to die. To test this hypothesis, we propose the following Specific Aims: 1) To evaluate whether glucocorticoid induced "breaks" in DNA occur in transcribed or non-transcribed genomic sequences; 2) To purify to homogeneity the glucocorticoid "induced" nuclease and test its specificity in vitro; 3) To clone the glucocorticoid "induced" nuclease gene and evaluate its role in glucocorticoid induced cell death by transfection experiments; 4) Lastly, to evaluate via selective cell sorting the development of glucocorticoid resistance during the differentiation of rat thymic lymphocytes to mature T cells. Together, these studies should test the proposed hypothesis and provide data on the molecular basis for glucocorticoid induced lymphoid cell death.