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

[9316426] Shick将研究海胆对太阳紫外线辐射诱导的光氧化应激的防御调控。像其他海洋生物一样，海胆含有类似霉菌素的氨基酸（MAAs），可以吸收与环境有关的紫外线波长。海胆食用的各种海藻都含有丰富的MAA，初步的色谱分析表明，海藻中的MAA含量与海胆组织，特别是卵巢中的MAA含量具有一致性。海胆对缺乏或富含MAAs的海藻的控制维持证实了海胆卵巢中MAAs的饮食积累，并提供了一种实验手段，通过这些假定的紫外线防御来强化卵。已发表的关于MAAs防紫外线作用的文献大多是间接的。因此，本研究的一个主要目的是直接测试MAAs是否能保护针鼹卵和幼虫免受自然和模拟太阳紫外线的伤害。如果MAAs确实能保护海胆免受紫外线辐射的假设是正确的，那么在饮食中强化海胆卵巢应该能使海胆卵和幼虫对紫外线有更大的抵抗力；因此，急性紫外线照射对DNA中嘧啶二聚体的形成、受精、发育和幼虫存活的影响将在富含和缺乏maa的个体中进行评估。本项目的一项比较研究旨在确定不同的太阳紫外线照射是否与MAA含量的定性和定量差异有关。将缅因州一种海胆中的MAA组成和含量与同域沙块中的进行比较。海胆在冬末成熟并产卵；因此，配子的成熟和幼虫的发育在相对低水平的紫外线照射下进行。相比之下，沙dollar是成熟的，从6月到10月反复产卵，所以它的卵和幼虫比冬季产卵的海胆暴露在更高的季节性紫外线辐射下，可能需要更强大的光氧化防御。本研究结果将对海洋食物链中天然光氧化防御的积累机制和有效性产生影响。这是一个真正令人关切的问题，因为保护臭氧层的恶化，在那里，北方海洋生物是在相对较低的太阳紫外线照射下进化的。这项研究可能对寻找天然（膳食）抗氧化剂也有重要意义，其中一些抗氧化剂可能作为抑制人类细胞肿瘤促进的抑制剂而活跃。＊＊＊

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. ***