NHMRC CKD CRE (CKD.QLD), University of Queensland, Brisbane, Australia.
School of Biomedical Sciences, Faculty of Medicine, University of Queensland, Brisbane, Australia.
Cell Death Dis. 2022 Feb 2;13(2):104. doi: 10.1038/s41419-022-04527-z.
The pathogenesis of crystal nephropathy involves deposition of intratubular crystals, tubular obstruction and cell death. The deposition of 8-dihydroxyadenine (DHA) crystals within kidney tubules, for instance, is caused by a hereditary deficiency of adenine phosphoribosyl transferase in humans or adenine overload in preclinical models. However, the downstream pathobiological patterns of tubular cell attrition in adenine/DHA-induced nephropathy remain poorly understood. In this study, we investigated: (i) the modes of adenine-induced tubular cell death in an experimental rat model and in human primary proximal tubular epithelial cells (PTEC); and (ii) the therapeutic effect of the flavonoid baicalein as a novel cell death inhibitor. In a rat model of adenine diet-induced crystal nephropathy, significantly elevated levels of tubular iron deposition and lipid peroxidation (4-hydroxynonenal; 4-HNE) were detected. This phenotype is indicative of ferroptosis, a novel form of regulated necrosis. In cultures of human primary PTEC, adenine overload-induced significantly increased mitochondrial superoxide levels, mitochondrial depolarisation, DNA damage and necrotic cell death compared with untreated PTEC. Molecular interrogation of adenine-stimulated PTEC revealed a significant reduction in the lipid repair enzyme glutathione peroxidase 4 (GPX4) and the significant increase in 4-HNE compared with untreated PTEC, supporting the concept of ferroptotic cell death. Moreover, baicalein treatment inhibited ferroptosis in adenine-stimulated PTEC by selectively modulating the mitochondrial antioxidant enzyme superoxide dismutase 2 (SOD2) and thus, suppressing mitochondrial superoxide production and DNA damage. These data identify ferroptosis as the primary pattern of PTEC necrosis in adenine-induced nephropathy and establish baicalein as a potential therapeutic tool for the clinical management of ferroptosis-associated crystal nephropathies (e.g., DHA nephropathy, oxalate nephropathy).
晶体肾病的发病机制涉及管腔内晶体沉积、管腔阻塞和细胞死亡。例如，8-二羟腺嘌呤 (DHA) 晶体在肾脏小管内的沉积是由人类腺嘌呤磷酸核糖基转移酶遗传性缺乏或临床前模型中腺嘌呤过载引起的。然而，腺嘌呤/DHA 诱导的肾病小管细胞损耗的下游病理生物学模式仍知之甚少。在这项研究中，我们研究了：（i）实验性大鼠模型和人原代近端肾小管上皮细胞（PTEC）中腺嘌呤诱导的管状细胞死亡模式；（ii）黄酮类化合物黄芩素作为一种新型细胞死亡抑制剂的治疗效果。在腺嘌呤饮食诱导的晶体肾病大鼠模型中，检测到肾小管铁沉积和脂质过氧化（4-羟基壬烯醛；4-HNE）水平显著升高。这种表型表明铁死亡是一种新的调节性坏死形式。在人原代 PTEC 的培养物中，与未处理的 PTEC 相比，腺嘌呤超负荷诱导的线粒体超氧化物水平、线粒体去极化、DNA 损伤和坏死性细胞死亡显著增加。对腺嘌呤刺激的 PTEC 的分子研究表明，脂质修复酶谷胱甘肽过氧化物酶 4（GPX4）显著减少，与未处理的 PTEC 相比，4-HNE 显著增加，支持铁死亡细胞死亡的概念。此外，黄芩素通过选择性调节线粒体抗氧化酶超氧化物歧化酶 2（SOD2）抑制腺嘌呤刺激的 PTEC 中的铁死亡，从而抑制线粒体超氧化物产生和 DNA 损伤。这些数据将铁死亡确定为腺嘌呤诱导的肾病中 PTEC 坏死的主要模式，并将黄芩素确立为治疗铁死亡相关晶体肾病（例如 DHA 肾病、草酸盐肾病）的潜在治疗工具。
