Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece.
Biomolecules. 2021 Oct 15;11(10):1522. doi: 10.3390/biom11101522.
Ischemia-reperfusion injury is the commonest form of acute kidney injury (AKI). Tubular epithelial cell senescence contributes to incomplete recovery from AKI and predisposes to subsequent chronic kidney disease. In cultures of primary proximal renal tubular epithelial cells (RPTECs) subjected to anoxia or reoxygenation, we evaluated the role of indoleamine 2,3-dioxygenase 1 (IDO) in cellular senescence. Proteins of interest were assessed with Western blotting or enzyme-linked immunosorbent assay or histochemically. Under anoxia or reoxygenation, IDO expression and activity were increased. Moreover, the two IDO-derived pathways, the general control nonderepressible 2 kinase (GCN2K) pathway and the aryl-hydrocarbon receptor (AhR) pathway, were also activated. A DNA damage response (DDR) took place and led to increased levels of the cell-cycle inhibitors p21 and p16, and senescence-associated β-galactosidase (SA-β-Gal) activity. Cell proliferation was inhibited, and more IL-6 was produced. The IDO inhibitor 1-DL-methyl-tryptophan ameliorated the DDR; decreased p21, p16, and SA-β-Gal activity; restored cell proliferation; and decreased IL-6 production. The AhR inhibitor CH223191 did not affect the above parameters. In conclusion, anoxia and the subsequent reoxygenation upregulate IDO. IDO depletes tryptophan and activates GCN2K. The latter enhances the anoxia- or reoxygenation-induced DDR, resulting in increased p21 and p16 expression and eventually leading to RPTEC senescence. Since cellular senescence affects AKI outcome, the role of IDO in cellular senescence and the possible therapeutic role of IDO inhibitors deserve further investigation.
缺血再灌注损伤是急性肾损伤（AKI）最常见的形式。肾小管上皮细胞衰老导致 AKI 不完全恢复，并易继发慢性肾脏病。在缺氧或复氧培养的原代近端肾小管上皮细胞（RPTEC）中，我们评估了色氨酸 2,3-双加氧酶 1（IDO）在细胞衰老中的作用。用 Western blot 或酶联免疫吸附试验或组织化学法评估感兴趣的蛋白。在缺氧或复氧下，IDO 表达和活性增加。此外，两种 IDO 衍生途径，一般控制非抑制 2 激酶（GCN2K）途径和芳香烃受体（AhR）途径，也被激活。发生 DNA 损伤反应（DDR），导致细胞周期抑制剂 p21 和 p16 水平升高，以及衰老相关 β-半乳糖苷酶（SA-β-Gal）活性增加。细胞增殖受到抑制，更多的 IL-6 产生。IDO 抑制剂 1-DL-甲基-色氨酸改善了 DDR；降低了 p21、p16 和 SA-β-Gal 活性；恢复了细胞增殖；并减少了 IL-6 的产生。AhR 抑制剂 CH223191 不影响上述参数。总之，缺氧和随后的复氧上调 IDO。IDO 消耗色氨酸并激活 GCN2K。后者增强了缺氧或复氧诱导的 DDR，导致 p21 和 p16 表达增加，最终导致 RPTEC 衰老。由于细胞衰老影响 AKI 结局，IDO 在细胞衰老中的作用以及 IDO 抑制剂的可能治疗作用值得进一步研究。
