Sources and Functions of Defenses Against Solar UV Radiationand Photooxidative Stress in Sea Urchins

9316426 Shick将在海胆中研究对太阳紫外线辐射诱导的光氧化应激的防御调节。像其他海洋生物一样，海胆含有类似霉菌的氨基酸(MAAs)，可以吸收与环境相关的波长的紫外线。海胆食用的各种海藻都含有丰富的MAA，初步的层析分析表明，海藻和海胆组织，特别是卵巢中的MAA水平是一致的。对缺乏或富含MAAs的海藻进行受控维护，证实了海胆卵巢中MAAs的饮食积累，并提供了一种实验方法，通过这些假定的紫外线防御来增强海胆的卵子。已发表的关于MAAS防紫外线作用的文献在很大程度上是间接的。因此，拟议研究的一个主要目标是直接测试MAAS是否能保护棘球体卵和幼虫免受自然和模拟太阳紫外线的照射。如果MAA确实提供了对紫外线辐射的保护的假设是正确的，海胆卵巢的饮食强化应该在卵和仔鱼中对紫外线具有更大的抵抗力；因此，在MAA丰富和MAA缺乏的个体中，急性紫外线暴露对DNA中嘧啶二聚体的形成、受精、发育和幼虫存活的影响将被评估。该项目的一项比较研究旨在确定太阳紫外线辐射的不同暴露是否与MAA含量的质和量差异有关。缅因州海胆的MAA组成和含量将与同域沙洲海胆的MAA组成和含量进行比较。海胆在冬末成熟产卵，因此配子成熟和幼虫发育是在相对较低的紫外线照射下进行的。相比之下，沙海胆是成熟的，从6月到10月反复产卵，因此它的卵和幼虫暴露在比冬季产卵的海胆更高的季节性紫外线辐射中，可能需要更强大的光氧化防御。这项研究的结果将对海洋食物链中天然光氧化防御的积累和有效性的机制产生影响。这是一个真正令人担忧的问题，因为保护臭氧层的恶化，北方海洋生物是在相对较低的太阳紫外线照射下进化出来的。这项研究在寻找天然(饮食)抗氧化剂方面也可能具有重要意义，其中一些抗氧化剂可能在人类细胞中具有促进肿瘤的活性。***

9316426 Shick The regulation of defenses against solar ultraviolet radiation-induced photooxidative stress will be studied in sea urchins. Like other marine organisms, sea urchins contain mycosporine-like amino acids (MAAs) which absorb environmentally relevant wavelengths of UV. Various seaweeds eaten by sea urchins are rich in MAAs, and preliminary chromatographic analyses indicate concordance between the MAA levels in seaweed and in sea urchin tissues, especially ovaries. Controlled maintenance of sea urchins on seaweeds lacking or rich in MAAs confirms dietary accumulation of MAAs in the urchins' ovaries, and provides an experimental means to fortify the eggs with these presumptive UV defenses. Published documentation of a UV-protective effect of MAAs is largely circumstantial. Thus, a major objective of the proposed research is to test directly whether MAAs protect echinoid eggs and larvae from exposure to natural and simulated solar UV. If the hypothesis that MAAs do confer protection against UV radiation is correct, dietary fortification of sea urchin ovaries should confer a greater resistance to UV in eggs and larvae; therefore, effects of acute UV exposure on pyrimidine dimer formation in DNA, fertilization, development, and larval survival will be assessed in MAA-rich and MAA-deficient individuals. A comparative study in this project is aimed at determining whether different exposures to solar UV radiation are associated with qualitative and quantitative differences in MAA content. MAA composition and content in a Maine species of sea urchin will be compared with those in a sympatric sand dollar. The sea urchin species matures and spawns in late winter; thus gamete maturation and larval development take place under relatively low levels of UV exposure. In contrast, the sand dollar is mature and spawns repeatedly from June through October, so its eggs and larvae are exposed to higher seasonal UV radiation than the winter- spawning se a urchin and may require more robust photooxidative defenses. The results of this study will have implications for the mechanism of accumulation and effectiveness of natural photooxidative defenses in marine food chains. This is a genuine concern because of deterioration of the protective ozone layer, where boreal marine organisms have evolved under relatively low solar UV exposure. The research may also have importance in the search for natural (dietary) antioxidants, some of which may be active as inhibitors of tumor promotion in human cells. ***