UVR-INDUCED DNA DAMAGE AND ANGIOGENIC GROWTH FACTORS

皮肤和眼睛是身体中唯一直接暴露于 太阳紫外线辐射(UVR)。已有研究表明干皮病 色素菌个体在DNA修复方面存在缺陷，并具有更高的 眼部对UVR所致混浊和新生血管的易感性 角膜和前眼癌。平流层臭氧的前景 枯竭和伴随而来的人类暴露在紫外线辐射下的增加使它 当务之急是我们必须了解 哺乳动物的眼睛对紫外线照射。家养有袋单胞虫是一种 独一无二的实验动物模型，适合研究血管紧张素转换酶 UVR诱导的特异性DNA损伤，嘧啶二聚体，在导致 紫外线照射眼部的病理变化。就像在表皮中一样，细胞 家蝇的角膜上皮细胞具有很高的处理能力。 UVR诱导的嘧啶二聚体的光复活修复。这个 光依赖的PR修复途径具有仅修复的独特性质 因此，如果PR降低了UVR诱导的能力 一种光生物反应，人们普遍认为，嘧啶二聚体 在某种程度上参与了这一反应的启动。 长期暴露在紫外线照射下的家蝇会导致角膜肿瘤。UVR 诱导角膜基质细胞和内皮细胞的增殖 先于肿瘤的发展。似乎有理由认为UVR在某些情况下 诱导有丝分裂和血管生成生长的合成或分泌 以自分泌或旁分泌的方式刺激的因素 角膜基质细胞和内皮细胞的增殖。建议数 研究将验证DNA中未修复的嘧啶二聚体的假设 改变有丝分裂和血管生成生长的合成和/或释放 紫外线照射下角膜的影响因素。这些早期的分子事件可能导致 在增强对UVR诱发癌症的敏感性方面。具体目标是： 1)将使用RNA印迹和标准组织学技术 测定血管生成生长因子表达的时程和 发生在慢性照射的角膜中的病理变化。印刷机 将被用来定义DNA损伤在这些过程中的作用；2)原位 杂交和免疫组织化学染色将用于鉴定 血管生成生长因子的合成和/或释放部位 慢性照射的角膜；3)作为DNA研究的延伸 角膜上皮的修复，损伤特异性核酸酶与 碱性凝胶电泳法将被用来测量切除和 紫外线诱导的晶状体中嘧啶二聚体的光复活修复 上皮性DNA。

Skin and eyes are the only organs of the body that are exposed directly to solar ultraviolet radiation (UVR). It has been shown that xeroderma pigmentosum individuals are deficient in DNA repair and have an increased susceptibility to UVR-induced opacification and neovascularization of the cornea and cancer of the anterior eye. The prospect of stratospheric ozone depletion and the accompanying increase in human exposure to UVR makes it imperative that we understand the acute and chronic responses of the mammalian eye to UVR exposure. The marsupial Monodelphis domestica is an experimental animal model uniquely suited for studies on the role of a specific UVR-induced DNA lesion, the pyrimidine dimer, in causing pathological changes in eyes exposed to UVR. As in the epidermis, cells in the corneal epithelium of M. domestica have a high capacity for the photoreactivation (PR) repair of UVR-induced pyrimidine dimers. The light-dependent PR repair pathway has the unique property of repairing only pyrimidine dimers; therefore, if PR decreases the ability of UVR to induce a photobiological response, it is generally accepted that pyrimidine dimers are in some way involved in initiating that response. Chronic UVR exposure of M. domestica induces tumors of the cornea. UVR induces proliferation of corneal stromocytes and endothelial cells which precedes tumor development. It seems reasonable to assume that UVR in some way induces the synthesis or secretion of mitogenic and angiogenic growth factors that act in an autocrine or paracrine manner to stimulate proliferation of corneal stromocytes and endothelial cells. The proposed research will lest the hypothesis that unrepaired pyrimidine dimers in DNA alters the synthesis and/or release of mitogenic and angiogenic growth factors in the UVR-exposed cornea. These early molecular events may result in enhanced susceptibility to UVR-induced cancer. The specific aims are: 1) RNA blotting and standard histological techniques will be used to determine the time course of angiogenic growth factor expression and pathological changes that occur in the chronically-irradiated cornea. PR will be used to define a role for DNA damage in these processes; 2) in situ hybridization and immunohistochemical staining will be used to identify the site of synthesis and/or release of angiogenic growth factors in the chronically irradiated cornea; and, 3) as an extension of studies on DNA repair in corneal epithelium, damage-specific nucleases in conjunction with alkaline gel electrophoresis will be used to measure the excision and photoreactivation repair of UVR-induced pyrimidine dimers in lens epithelial DNA.