Transcriptional regulation of renal dopamine D1 receptors in hypertension during

描述(申请人提供)：氧化还原敏感的转录因子是维持细胞正常氧化环境的关键。虽然氧化还原状态的失衡与高血压有关，但这种现象与高血压之间的联系尚不清楚。此外，已有研究表明，许多生物活性化合物，即通常在食品中少量存在的营养成分(营养成分)，具有抗氧化特性和降低血压，但这些有益效果的确切机制尚不清楚。我们和其他人已经报道，肾多巴胺通过激活D1受体(D1R)在钠稳态和血压(BP)的调节中发挥重要作用。肾脏D1R功能在慢性疾病中下调，尤其是在氧化应激相关的高血压和糖尿病中。因此，识别导致D1R功能障碍的细胞分子以及饮食化合物保护肾脏D1R功能的机制将为缓解高血压提供一种新的治疗途径。AP1和SP3等转录因子在氧化应激相关的病理生理过程中发挥重要作用。相反，氧化还原敏感的转录因子Nrf2激活一个高度调节的防御系统，以对抗氧化应激，这涉及到II期防御和抗氧化基因的转录激活。我们的初步研究表明，谷胱甘肽合成途径抑制剂L-丁硫氨酸-亚磺胺处理的小鼠出现氧化应激、血压升高、肾小管D1R功能障碍以及AP1和SP3表达上调。这些现象在BSO治疗的肾近端小管特异性Nrf2基因敲除小鼠中被夸大了。更重要的是，萝卜硫素(一种多酚抗氧化剂)激活了Nrf2，减少了氧化应激，使AP1和SP3的激活正常化，保护了BSO治疗的野生型小鼠的DIR功能，并降低了血压，但未能使Nrf2基因敲除小鼠的肾脏D1R功能正常化或降低血压。对人肾细胞(一种近端肾小管上皮细胞系)的进一步实验也表明：1)BSO通过AP1激活SP3，进而下调D1R的转录表达；2)萝卜硫素通过Nrf2激活，取消BSO诱导的AP1和SP3激活以及D1R功能障碍。这些发现导致我们假设：1)氧化应激通过AP1-SP3途径下调D1R的表达和功能，从而导致钠排泄减少和高血压；2)抗氧化剂通过激活Nrf2减少氧化应激，使AP1-SP3信号和D1R功能正常化，从而降低血压。因此，萝卜硫素和白藜芦醇等多酚类物质通过激活Nrf2信号通路可能为氧化应激时保护D1R功能和缓解高血压提供了一种新的机制。这些研究将对理解抗氧化剂潜在公共健康益处的机制产生重大影响，因为最近对人类的研究表明，多酚和直接的Nrf2激动剂可以降低CKD和2型糖尿病患者的血压并改善肾功能。

DESCRIPTION (provided by applicant): Redox sensitive transcription factors are pivotal in maintaining the normal oxidative milieu of cells. While an imbalance in redox status is implicated in hypertension, the link between this phenomenon and hypertension is not clear. In addition, it has been shown that many bioactive compounds, extranutritional constituents (nutraceuticals) that typically occur in small quantities in foods, have antioxidant properties and lower blood pressure, the exact mechanism for these beneficial effects is unclear. We, and others, have reported that renal dopamine via activation of D1 receptor (D1R) plays a major role in regulation of sodium homeostasis and blood pressure (BP). Renal D1R function is down-regulated in chronic diseases, especially in oxidative stress related hypertension and diabetes. Therefore, the identification of cellular molecules which contributes to D1R dysfunction as well as the mechanism by which dietary compounds can preserve renal D1R function will provide a novel therapeutic approach to mitigate hypertension. Transcription factors such as AP1 and SP3 play an important role in oxidative stress related pathophysiological conditions. Conversely, redox sensitive transcription factor Nrf2 activates a highly regulated defense system against oxidative stress which involves transcriptional activation of phase II defense and antioxidant genes. Our preliminary studies showed that mice treated with L-buthionine-sulfoximine (BSO), a glutathione synthesis pathway inhibitor exhibited oxidative stress, high BP, renal proximal tubular D1R dysfunction and up-regulation of AP1 and SP3. These phenomena were exaggerated in BSO-treated renal proximal tubule specific Nrf2 knockout mice. More importantly, sulforaphane (a polyphenol antioxidant) activated Nrf2, reduced oxidative stress, normalized AP1 and SP3 activation, preserved DIR function and lowered BP in BSO-treated wild type mice but failed to normalize renal D1R function or reduce BP in Nrf2 knockout mice. Further experiments in human kidney cells (a proximal tubular epithelial cell line) also indicated that: 1) BSO via AP1 activated SP3 which in turn transcriptionally down-regulated D1R expression and 2) sulforaphane, via Nrf2 activation, abolished BSO-induced AP1 and SP3 activation and D1R dysfunction. These findings led us to hypothesize that: 1) oxidative stress via AP1-SP3 pathway down-regulates D1R expression and function which leads to decrease in sodium excretion and hypertension and 2) antioxidants via Nrf2 activation reduce oxidative stress and normalize AP1-SP3 signaling and D1R function which reduces BP. Therefore, it is likely that polyphenols, such as sulforaphane and resveratrol, via activation of Nrf2 signaling would provide a novel mechanism to protect D1R function and mitigate hypertension during oxidative stress. These studies will have significant impact on understanding the mechanisms for potential public health benefits of antioxidants as recent studies in humans have shown that polyphenols and direct Nrf2 activators can reduce BP and improve kidney function in CKD and type 2 diabetic patients.