Chung Hyunsoo, Lee Seong-Woo, Hyun Miri, Kim So Young, Cho Hyeon Gyu, Lee Eun Soo, Kang Jeong Suk, Chung Choon Hee, Lee Eun Young
College of Medicine, Soonchunhyang University, Cheonan, South Korea.
Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Cheonan, South Korea.
Front Cell Dev Biol. 2022 May 30;10:800574. doi: 10.3389/fcell.2022.800574. eCollection 2022.
Podocyte loss is well known to play a critical role in the early progression of diabetic nephropathy. A growing number of studies are paying attention to necroptosis, a programmed form of cell necrosis as a mechanism of podocyte loss. Although necroptosis is a recently established concept, the significance of receptor interacting serine/threonine kinase 3 (), a gene that encodes for the homonymous enzyme RIPK3 responsible for the progression of necroptosis, is well studied. Curcumin, a natural hydrophobic polyphenol compound responsible for the yellow color of has drawn attention due to its antioxidant and anti-inflammatory effects on cells prone to necroptosis. Nonetheless, effects of curcumin on high glucose-induced podocyte necroptosis have not been reported yet. Therefore, this study investigated RIPK3 expression in high glucose-treated podocytes to identify the involvement of necroptosis the RIPK3 pathway and the effects of curcumin treatment on RIPK3-dependent podocytopathy in a hyperglycemic environment. The study discovered that increased reactive oxygen species (ROS) in renal podocytes induced by high glucose was improved after curcumin treatment. Curcumin treatment also significantly restored the upregulated levels of VEGF, TGF-β, and CCL2 mRNAs and the downregulated level of nephrin mRNA in cultured podocytes exposed to a high glucose environment. High glucose-induced changes in protein expression of TGF-β, nephrin, and CCL2 were considerably reverted to their original levels after curcumin treatment. Increased expression of RIPK3 in high glucose-stimulated podocytes was alleviated by curcumin treatment as well as N-acetyl cysteine (NAC, an antioxidant) or GSK'872 (a RIPK3 inhibitor). Consistent with this, the increased necroptosis-associated molecules, such as RIPK3, pRIPK3, and pMLKL, were also restored by curcumin in high glucose-treated mesangial cells. DCF-DA assay confirmed that such a result was attributed to the reduction of RIPK3 through the antioxidant effect of curcumin. Further observations of DCF-DA-sensitive intracellular ROS in NAC-treated and GSK'872-treated podocyte groups showed a reciprocal regulatory relationship between ROS and RIPK3. The treatment of curcumin and GSK'872 in podocytes incubated with high glucose protected from excessive intracellular superoxide anion production. Taken together, these results indicate that curcumin treatment can protect against high glucose-induced podocyte injuries by suppressing the abnormal expression of ROS and RIPK3. Thus, curcumin might be a potential therapeutic agent for diabetic nephropathy as an inhibitor of RIPK3.
足细胞丢失在糖尿病肾病的早期进展中起着关键作用，这是众所周知的。越来越多的研究开始关注坏死性凋亡，这是一种程序性细胞坏死形式，被认为是足细胞丢失的机制。尽管坏死性凋亡是一个最近才确立的概念，但对受体相互作用丝氨酸/苏氨酸激酶3（RIPK3）的研究已经很充分，该基因编码同名酶RIPK3，负责坏死性凋亡的进展。姜黄素是一种天然的疏水性多酚化合物，因其对易发生坏死性凋亡的细胞具有抗氧化和抗炎作用而受到关注。然而，姜黄素对高糖诱导的足细胞坏死性凋亡的影响尚未见报道。因此，本研究调查了高糖处理的足细胞中RIPK3的表达，以确定坏死性凋亡在RIPK3途径中的作用，以及姜黄素处理对高血糖环境中RIPK3依赖性足细胞病变的影响。研究发现，姜黄素处理后，高糖诱导的肾足细胞中活性氧（ROS）增加的情况得到改善。姜黄素处理还显著恢复了高糖环境下培养的足细胞中血管内皮生长因子（VEGF）、转化生长因子-β（TGF-β）和趋化因子CCL2 mRNA上调水平以及nephrin mRNA下调水平。姜黄素处理后，高糖诱导的TGF-β、nephrin和CCL2蛋白表达变化显著恢复到原始水平。姜黄素处理以及N-乙酰半胱氨酸（NAC，一种抗氧化剂）或GSK'872（一种RIPK3抑制剂）均可减轻高糖刺激的足细胞中RIPK3表达的增加。与此一致，姜黄素也使高糖处理的系膜细胞中坏死性凋亡相关分子如RIPK3、磷酸化RIPK3（pRIPK3）和磷酸化混合谱系激酶结构域样蛋白（pMLKL）的增加得到恢复。2',7'-二氯二氢荧光素二乙酸酯（DCF-DA）检测证实，这一结果归因于姜黄素的抗氧化作用导致RIPK3减少。对NAC处理组和GSK'872处理组足细胞中DCF-DA敏感的细胞内ROS的进一步观察显示，ROS与RIPK3之间存在相互调节关系。在高糖培养的足细胞中，姜黄素和GSK'872处理可防止细胞内过量超氧阴离子的产生。综上所述，这些结果表明，姜黄素处理可通过抑制ROS和RIPK3的异常表达来保护足细胞免受高糖诱导的损伤。因此，姜黄素作为RIPK3抑制剂可能是治疗糖尿病肾病的潜在药物。
