Physiology/pathophysiology of intestinal vitC uptake: Cell/molecular mechanisms

 描述（由申请人提供）：维生素C是正常人类健康和福祉不可或缺的微量营养素。维生素C缺乏导致各种临床异常。维生素作为一种有效的抗氧化剂和几种酶的辅因子，细胞内水平低会导致氧化应激，这是许多人类疾病的驱动因素。因此，旨在优化整体维生素C体内稳态的研究非常重要。人类已经失去了内源性合成维生素C的能力，必须通过肠道吸收来获得。 肠吸收过程涉及人钠依赖性维生素C转运蛋白1和2（hSVCT 1和hSVCT 2），其中hSVCT 1仅在极化肠细胞的顶膜表达，而hSVCT 2定位于基底外侧。本提案的目的是继续我们的调查，以分子生理学/细胞生物学的维生素C摄取过程中，并解决其病理生理学的具体方面，以及确定外部/内部因素对摄取过程的影响。我们新的初步研究表明，microRNA和表观遗传机制参与了hSVCT 1表达的调控，确定了推定的新型hSVCT 1相互作用伴侣，并显示了暴露于特定肠道病原体（EPEC和ETEC），促炎细胞因子和细菌LPS后对维生素C摄取的显著抑制。基于这些发现，我们的工作假设是：i）microRNA和表观遗传机制调节SVCT 1的表达和功能; ii）hSVCT 1具有影响其生理学/细胞生物学的相互作用伴侣;以及iii） 暴露于肠道病原体、促炎细胞因子和细菌LPS导致肠道维生素C摄取的显著抑制。提出了三个具体目标来测试这些假设，并将利用最先进的细胞/分子方法。这些调查的结果应提供有价值的信息，在正常生理条件下的肠道维生素C的吸收过程，以及这种情况是如何受到特定的病理生理因素。这最终将帮助我们设计有效的策略来优化正常的维生素C体内稳态，特别是在缺乏/次优水平的情况下。

 DESCRIPTION (provided by applicant): Vitamin C is an indispensable micronutrient for normal human health and well-being. Vitamin C deficiency leads to a variety of clinical abnormalities. The vitamin acts as a potent antioxidant and a cofactor for several enzymes, with low intracellular levels causing oxidative stress, a driver for many human diseases. Therefore, studies designed to optimize overall vitamin C body homeostasis are important. Humans have lost the ability to synthesis vitamin C endogenously, and must obtain it via intestinal absorption. The intestinal absorption process involves the human sodium-dependent vitamin C transporters-1 & 2 (hSVCT1& hSVCT2), where hSVCT1 is exclusively expressed at the apical membrane of the polarized enterocytes whereas hSVCT2 is localized basolaterally. The objectives of this proposal are to continue our investigations into the molecular physiology/cell biology of intestina vitamin C uptake process, and to address specific aspects of its pathophysiology as well as to determine the effect of external/internal factors on the uptake process. Our new preliminary studies suggest the involvement of microRNA and epigenetic mechanism(s) in the regulation of hSVCT1 expression, identified putative novel hSVCT1 interacting partners, and show a significant inhibition in vitamin C uptake upon exposure to specific enteric pathogens (EPEC and ETEC), pro-inflammatory cytokines, and to bacterial LPS. Based on these findings, our working hypotheses are: i) microRNA and epigenetic mechanism(s) regulate SVCT1 expression and function; ii) hSVCT1 has interacting partners that affect its physiology/cell biology; and iii) exposure to enteric pathogens, pro- inflammatory cytokines, and to bacterial LPS leads to a significant inhibition in intestinal vitamin C uptake. Three specific aims are proposed to test these hypotheses and will utilize state-of- the-art cell/molecular approaches. Results of these investigations should provide valuable information regarding the intestinal vitamin C absorption process under normal physiological conditions, and how this event is affected by specific pathophysiological factors. This should ultimately help us in designing effective strategies to optimize normal vitamin C body homeostasis, especially in conditions of deficiency/sub-optimal levels.