Kudo Akiko, Fukuda Akihiro, Gotoh Koro, Shibata Hirotaka
Department of Endocrinology, Metabolism, Rheumatology and Nephrology, Faculty of Medicine, Oita University, Yufu, JPN.
Faculty of Welfare and Health Science, Oita University, Oita, JPN.
Cureus. 2024 Dec 6;16(12):e75236. doi: 10.7759/cureus.75236. eCollection 2024 Dec.
The uremic toxin indoxyl sulfate (IS) is an important factor in chronic kidney disease (CKD) progression. Inhibitors of the renin-angiotensin system and add-on therapy with mineralocorticoid receptor (MR) antagonists can help reduce proteinuria and suppress CKD progression. However, the association between IS and MR activation remains unknown.
experiments utilized the 5/6 nephrectomy model to assess mineralocorticoid receptor (MR) activation in chronic kidney disease (CKD). The clinical parameters and immunohistochemical analysis of IS and MR proteins were investigated. experiments involved transfecting COS-7 cells with MR expression plasmids and MR response element-luciferase reporter plasmids. The cells were then treated with aldosterone (10⁻¹⁰ mol/L), indoxyl sulfate (IS, 500 μmol/L), and α-lipoic acid (10⁻³ mol/L). MR transcriptional activity was investigated by luciferase assays, and protein levels were measured by Western blotting.
In the 5/6 nephrectomy model, the serum IS concentration was significantly increased; however, the plasma aldosterone levels were decreased. Immunohistochemistry showed that the expression of IS protein increased in injured tubular cells in the 5/6 nephrectomy group compared with that in the sham group. Furthermore, evaluations of serial kidney sections revealed that the expression site of IS protein was colocalized with the distal nephron, where the expression of MR protein was observed. MR-mediated transcriptional activity in COS-7 cells was increased in an aldosterone concentration-dependent manner. IS increased MR-mediated transcriptional activity and protein levels with and without aldosterone, and α-lipoic acid attenuated this increase.
IS could enhance MR transactivation by increasing MR protein levels through oxidative stress in CKD rats, indicating that treatment with MR antagonists and antioxidants may play a permissive role in inhibiting IS-induced CKD progression.
尿毒症毒素硫酸吲哚酚（IS）是慢性肾脏病（CKD）进展的重要因素。肾素 - 血管紧张素系统抑制剂及联合盐皮质激素受体（MR）拮抗剂治疗有助于减少蛋白尿并抑制CKD进展。然而，IS与MR激活之间的关联尚不清楚。
实验采用5/6肾切除模型评估慢性肾脏病（CKD）中盐皮质激素受体（MR）的激活情况。研究了IS和MR蛋白的临床参数及免疫组化分析。实验包括用MR表达质粒和MR反应元件 - 荧光素酶报告质粒转染COS - 7细胞。然后用醛固酮（10⁻¹⁰ mol/L）、硫酸吲哚酚（IS，500 μmol/L）和α - 硫辛酸（10⁻³ mol/L）处理细胞。通过荧光素酶测定研究MR转录活性，并用蛋白质印迹法测量蛋白质水平。
在5/6肾切除模型中，血清IS浓度显著升高；然而，血浆醛固酮水平降低。免疫组化显示，与假手术组相比，5/6肾切除组损伤肾小管细胞中IS蛋白表达增加。此外，对连续肾脏切片的评估显示，IS蛋白的表达位点与远端肾单位共定位，在该部位观察到MR蛋白的表达。COS - 7细胞中MR介导的转录活性以醛固酮浓度依赖性方式增加。无论有无醛固酮，IS均增加MR介导的转录活性和蛋白质水平，而α - 硫辛酸减弱了这种增加。
IS可通过氧化应激增加MR蛋白水平来增强CKD大鼠中MR的反式激活，表明用MR拮抗剂和抗氧化剂治疗可能在抑制IS诱导的CKD进展中起允许作用。
