Activation of the Cancer Preventive Nrf2-ARE Pathway by Seaweed

描述（由申请人提供）： 海藻（海洋藻类）是亚洲国家，特别是日本的主要饮食来源。已经报道了食用海藻的许多有益效果，但其中只有一些归因于个别化学成分。海藻促进健康作用的一个明显共同点是抗氧化活性，它可以抵消致癌氧化应激引起的损伤。与此同时，日本几种癌症的发病率极低，并且据报道与海藻摄入量呈负相关。特别是在日本，前列腺癌的风险几乎可以忽略不计。前列腺癌的特征在于一种谷胱甘肽-S-转移酶（GST）基因（一种II期解毒酶）的沉默。II相和其他抗氧化酶通常由转录因子Nrf 2激活的抗氧化反应元件（ARE）调节。Nrf 2-ARE通路的激活是一种有效的癌症预防策略，萝卜硫素是西兰花的一种成分，是通过这种机制发挥作用的癌症预防天然产物的最著名的例子。初步数据表明，某些海藻提取物激活了IMR-32人类神经母细胞瘤细胞中的ARE-荧光素酶报告基因。这里假设一些海藻能够激活Nrf 2-ARE癌症预防信号通路，并且一些有益的，特别是抗氧化特性，可以通过ARE激活来介导。首先，将在佛罗里达沿海栖息地进行小规模的海藻采集。然后制备各种浸提液并进行简单分级。将粗提物和级分排列在96孔板中，然后使用ARE报告基因测定在细胞模型中筛选氧化应激和癌症预防。通过引起氧化应激或毒性激活ARE的天然产物混合物将在计数器屏幕中被消除。将使用各种二级生化测定进一步优先考虑命中。在重新收集最有希望的海藻物种之后，然后使用ARE报告小鼠测试相应的提取物或级分在体内激活ARE的能力，这用作优先化的附加层。将执行生物测定引导的分级分离以从体内活性混合物中分离纯ARE激活剂。然后通过分析技术（主要是NMR）对活性成分进行结构鉴定。PI实验室正在进行的研究补充了拟议的研究，该研究旨在表征Nrf 2-ARE途径，并已产生通过该机制起作用的癌症预防和抗变性药物的潜在分子靶标。这一应用符合NIH确定有效疾病预防策略的目标。氧化应激导致致癌细胞损伤，可通过增强内源性防御系统来减轻或预防。海藻是一种膳食来源，在这里假设通过特定的信号传导途径提高人类抗氧化和解毒因子的水平。确定预防癌症的海藻和单个活性成分可能成为开发新的健康促进策略的基础。

DESCRIPTION (provided by applicant): Project Summary/Abstract Seaweed (marine algae) is a major dietary source in Asian countries, particularly in Japan. Numerous beneficial effects of seaweed consumption have been reported, but only some of which have been attributed to individual chemical components. An apparent common denominator of seaweed's health-promoting effects is the antioxidant activity which may counteract cancer-causing oxidative stress induced damage. Concomitantly, the incidence of several types of cancer is extremely low in Japan and inverse correlations with seaweed consumption have been reported. Prostate cancer risk in particular is almost negligible in Japan. Prostate cancer is characterized by the silencing of one glutathione-S-transferase (GST) gene, a phase II detoxification enzyme. Phase II and other antioxidant enzymes are commonly regulated by the antioxidant response element (ARE) which is activated by transcription factor Nrf2. The activation of the Nrf2-ARE pathway is a valid cancer preventive strategy, and sulforaphane, a constituent of broccoli, is the best known example of a cancer preventive natural product that acts through this mechanism. Preliminary data indicate that certain seaweed extracts activate the ARE-luciferase reporter in IMR-32 human neuroblastoma cells. It is hypothesized here that some seaweeds are able to activate the Nrf2-ARE cancer preventive signaling pathway and that some of the beneficial, particularly antioxidant properties, may be mediated through ARE activation. First, small-scale collections of seaweed will be carried out in Florida coastal habitats. Various extracts will then be prepared and briefly fractionated. Crude extracts and fractions are arrayed in 96-well plates and then screened in cellular models for oxidative stress and cancer prevention using an ARE reporter gene assay. Natural product mixtures that activate the ARE by causing oxidative stress or toxicity will be eliminated in counter screens. Hits will be further prioritized using a variety of secondary biochemical assays. Following re- collections of most promising seaweed species, the corresponding extracts or fractions will then be tested for their ability to activate the ARE in vivo using ARE reporter mice, which serves as an additional layer of prioritization. Bioassay-guided fractionation will be executed to isolate pure ARE activators from in vivo active mixtures. The active principle(s) will then be structurally identified by analytical techniques, primarily NMR. The proposed study is complemented by ongoing research in the PI's laboratory which aims in characterizing the Nrf2-ARE pathway and which has been yielding potential molecular targets for cancer preventive and anti- degenerative agents acting through this mechanism. This application is in line with NIH's goal to identify effective disease-preventive strategies. PUBLIC HEALTH RELEVANCE Oxidative stress results in cancer-causing cellular damage which can be attenuated or prevented by boosting the endogenous defense system. Seaweed is a dietary source that is hypothesized here to enhance levels of humans' antioxidant and detoxification factors through a specific signaling pathway. The identification of cancer-preventing seaweeds and of individual active components may become the basis for the development of new health-promoting strategies.