Jhawar Sachin, Singh Prabhjot, Torres Daniel, Ramirez-Valle Francisco, Kassem Hania, Banerjee Trina, Dolgalev Igor, Heguy Adriana, Zavadil Jiri, Lowenstein Jerome
Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
Department of Dermatology, University of California San Francisco, San Francisco, CA, United States of America.
PLoS One. 2015 Mar 26;10(3):e0118703. doi: 10.1371/journal.pone.0118703. eCollection 2015.
Chronic renal failure is characterized by progressive renal scarring and accelerated arteriosclerotic cardiovascular disease despite what is considered to be adequate hemodialysis or peritoneal dialysis. In rodents with reduced renal mass, renal scarring has been attributed to poorly filtered, small protein-bound molecules. The best studied of these is indoxyl sulfate (IS).
We have attempted to establish whether there are uremic toxins that are not effectively removed by hemodialysis. We examined plasma from patients undergoing hemodialysis, employing global gene expression in normal human renal cortical cells incubated in pre- and post- dialysis plasma as a reporter system. Responses in cells incubated with pre- and post-dialysis uremic plasma (n = 10) were compared with responses elicited by plasma from control subjects (n = 5). The effects of adding IS to control plasma and of adding probenecid to uremic plasma were examined. Plasma concentrations of IS were measured by HPLC (high pressure liquid chromatography).
Gene expression in our reporter system revealed dysregulation of 1912 genes in cells incubated with pre-dialysis uremic plasma. In cells incubated in post-dialysis plasma, the expression of 537 of those genes returned to baseline but the majority of them (1375) remained dysregulated. IS concentration was markedly elevated in pre- and post-dialysis plasma. Addition of IS to control plasma simulated more than 80% of the effects of uremic plasma on gene expression; the addition of probenecid, an organic anion transport (OAT) inhibitor, to uremic plasma reversed the changes in gene expression.
These findings provide evidence that hemodialysis fails to effectively clear one or more solutes that effect gene expression, in our reporter system, from the plasma of patients with uremia. The finding that gene dysregulation was simulated by the addition of IS to control plasma and inhibited by addition of an OAT inhibitor to uremic plasma identifies IS as a major, poorly dialyzable, uremic toxin. The signaling pathways initiated by IS and possibly other solutes not effectively removed by dialysis may participate in the pathogenesis of renal scarring and uremic vasculopathy.
慢性肾衰竭的特征是尽管进行了所谓充分的血液透析或腹膜透析，但仍会出现进行性肾瘢痕形成和加速的动脉粥样硬化性心血管疾病。在肾质量降低的啮齿动物中，肾瘢痕形成归因于过滤不佳的、与小蛋白质结合的分子。其中研究最多的是硫酸吲哚酚（IS）。
我们试图确定是否存在血液透析无法有效清除的尿毒症毒素。我们检测了接受血液透析患者的血浆，采用在透析前和透析后血浆中孵育的正常人肾皮质细胞中的全局基因表达作为报告系统。将在透析前和透析后尿毒症血浆中孵育的细胞（n = 10）的反应与对照受试者血浆（n = 5）引发的反应进行比较。检测了向对照血浆中添加IS以及向尿毒症血浆中添加丙磺舒的效果。通过高效液相色谱法（HPLC）测量血浆中IS的浓度。
我们的报告系统中的基因表达显示，在透析前尿毒症血浆中孵育的细胞中有1912个基因失调。在透析后血浆中孵育细胞时，其中537个基因的表达恢复到基线，但大多数基因（1375个）仍失调。透析前和透析后血浆中IS浓度明显升高。向对照血浆中添加IS模拟了尿毒症血浆对基因表达的80%以上的影响；向尿毒症血浆中添加有机阴离子转运（OAT）抑制剂丙磺舒可逆转基因表达的变化。
这些发现提供了证据，表明在我们的报告系统中，血液透析未能有效清除影响尿毒症患者血浆中基因表达的一种或多种溶质。向对照血浆中添加IS模拟了基因失调，并通过向尿毒症血浆中添加OAT抑制剂而受到抑制，这一发现确定IS是一种主要的、难以透析的尿毒症毒素。由IS以及可能其他未被透析有效清除的溶质引发的信号通路可能参与肾瘢痕形成和尿毒症血管病变的发病机制。
