Mutsaers H A M, Wilmer M J G, Reijnders D, Jansen J, van den Broek P H H, Forkink M, Schepers E, Glorieux G, Vanholder R, van den Heuvel L P, Hoenderop J G, Masereeuw R
Department of Pharmacology and Toxicology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Biochim Biophys Acta. 2013 Jan;1832(1):142-50. doi: 10.1016/j.bbadis.2012.09.006. Epub 2012 Sep 24.
During chronic kidney disease (CKD), drug metabolism is affected leading to changes in drug disposition. Furthermore, there is a progressive accumulation of uremic retention solutes due to impaired renal clearance. Here, we investigated whether uremic toxins can influence the metabolic functionality of human conditionally immortalized renal proximal tubule epithelial cells (ciPTEC) with the focus on UDP-glucuronosyltransferases (UGTs) and mitochondrial activity. Our results showed that ciPTEC express a wide variety of metabolic enzymes, including UGTs. These enzymes were functionally active as demonstrated by the glucuronidation of 7-hydroxycoumarin (7-OHC; K(m) of 12±2μM and a V(max) of 76±3pmol/min/mg) and p-cresol (K(m) of 33±13μM and a V(max) of 266±25pmol/min/mg). Furthermore, a wide variety of uremic toxins, including indole-3-acetic acid, indoxyl sulfate, phenylacetic acid and kynurenic acid, reduced 7-OHC glucuronidation with more than 30% as compared with controls (p<0.05), whereas UGT1A and UGT2B protein expressions remained unaltered. In addition, our results showed that several uremic toxins inhibited mitochondrial succinate dehydrogenase (i.e. complex II) activity with more than 20% as compared with controls (p<0.05). Moreover, indole-3-acetic acid decreased the reserve capacity of the electron transport system with 18% (p<0.03). In conclusion, this study shows that multiple uremic toxins inhibit UGT activity and mitochondrial activity in ciPTEC, thereby affecting the metabolic capacity of the kidney during CKD. This may have a significant impact on drug and uremic retention solute disposition in CKD patients.
在慢性肾脏病（CKD）期间，药物代谢受到影响，导致药物处置发生变化。此外，由于肾脏清除功能受损，尿毒症潴留溶质会逐渐积累。在此，我们研究了尿毒症毒素是否会影响人类条件永生化肾近端小管上皮细胞（ciPTEC）的代谢功能，重点关注尿苷二磷酸葡萄糖醛酸转移酶（UGTs）和线粒体活性。我们的结果表明，ciPTEC表达多种代谢酶，包括UGTs。这些酶具有功能活性，7-羟基香豆素（7-OHC；米氏常数为12±2μM，最大反应速度为76±3pmol/分钟/毫克）和对甲酚（米氏常数为33±13μM，最大反应速度为266±25pmol/分钟/毫克）的葡萄糖醛酸化反应证明了这一点。此外，多种尿毒症毒素，包括吲哚-3-乙酸、硫酸吲哚酚、苯乙酸和犬尿酸，与对照组相比，使7-OHC葡萄糖醛酸化反应降低了30%以上（p<0.05），而UGT1A和UGT2B蛋白表达保持不变。此外，我们的结果表明，几种尿毒症毒素抑制线粒体琥珀酸脱氢酶（即复合体II）的活性，与对照组相比降低了20%以上（p<0.05）。此外，吲哚-3-乙酸使电子传递系统的储备能力降低了18%（p<0.03）。总之，本研究表明，多种尿毒症毒素抑制ciPTEC中的UGT活性和线粒体活性，从而影响CKD期间肾脏的代谢能力。这可能对CKD患者的药物和尿毒症潴留溶质处置产生重大影响。
