Cardiothoracic Surgery, University of Texas Health Science Center, San Antonio, TX, USA.
Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, MO, USA.
Cell Signal. 2020 Apr;68:109506. doi: 10.1016/j.cellsig.2019.109506. Epub 2019 Dec 17.
Proximal tubular epithelial cells (PTEC) in the S1 segment of the kidney abundantly express sodium-glucose co-transporters (SGLT) that play a critical role in whole body glucose homeostasis. We recently reported suppression of RECK (Reversion Inducing Cysteine Rich Protein with Kazal Motifs), a membrane anchored endogenous MMP inhibitor and anti-fibrotic mediator, in the kidneys of db/db mice, a model of diabetic kidney disease (DKD), as well as in high glucose (HG) treated human kidney proximal tubule cells (HK-2). We further demonstrated that empagliflozin (EMPA), an SGLT2 inhibitor, reversed these effects. Little is known regarding the mechanisms underlying RECK suppression under hyperglycemic conditions, and its rescue by EMPA. Consistent with our previous studies, HG (25 mM) suppressed RECK expression in HK-2 cells. Further mechanistic investigations revealed that HG induced superoxide and hydrogen peroxide generation, oxidative stress-dependent TRAF3IP2 upregulation, NF-κB and p38 MAPK activation, inflammatory cytokine expression (IL-1β, IL-6, TNF-α, and MCP-1), miR-21 induction, MMP2 activation, and RECK suppression. Moreover, RECK gain-of-function inhibited HG-induced MMP2 activation and HK-2 cell migration. Similar to HG, advanced glycation end products (AGE) induced TRAF3IP2 and suppressed RECK, effects that were inhibited by EMPA. Importantly, EMPA treatment ameliorated all of these deleterious effects, and inhibited epithelial-to-mesenchymal transition (EMT) and HK-2 cell migration. Collectively, these findings indicate that hyperglycemia and associated AGE suppress RECK expression via oxidative stress/TRAF3IP2/NF-κB and p38 MAPK/miR-21 induction. Furthermore, these results suggest that interventions aimed at restoring RECK or inhibiting SGLT2 have the potential to treat kidney inflammatory response/fibrosis and nephropathy under chronic hyperglycemic conditions, such as DKD.
肾脏 S1 段的近端肾小管上皮细胞 (PTEC) 丰富表达钠-葡萄糖协同转运蛋白 (SGLT)，这些转运蛋白在全身葡萄糖稳态中发挥关键作用。我们最近报道，糖尿病肾病 (DKD) 模型 db/db 小鼠肾脏以及高糖 (HG) 处理的人近端肾小管细胞 (HK-2) 中，膜锚定的内源性 MMP 抑制剂和抗纤维化介质 RECK (富含半胱氨酸的逆转诱导蛋白与 Kazal 基序) 受到抑制。我们进一步证明 SGLT2 抑制剂恩格列净 (EMPA) 可逆转这些作用。在高血糖条件下 RECK 抑制的机制及其被 EMPA 挽救的机制知之甚少。与我们之前的研究一致，HG (25mM) 抑制了 HK-2 细胞中 RECK 的表达。进一步的机制研究表明，HG 诱导超氧阴离子和过氧化氢的产生、氧化应激依赖的 TRAF3IP2 上调、NF-κB 和 p38 MAPK 激活、炎症细胞因子表达 (IL-1β、IL-6、TNF-α 和 MCP-1)、miR-21 的诱导、MMP2 的激活和 RECK 的抑制。此外，RECK 过表达抑制了 HG 诱导的 MMP2 激活和 HK-2 细胞迁移。与 HG 相似，糖基化终产物 (AGE) 诱导 TRAF3IP2 并抑制 RECK，这些作用被 EMPA 抑制。重要的是，EMPA 治疗改善了所有这些有害作用，并抑制了上皮间质转化 (EMT) 和 HK-2 细胞迁移。总之，这些发现表明，高血糖和相关的 AGE 通过氧化应激/TRAF3IP2/NF-κB 和 p38 MAPK/miR-21 诱导抑制 RECK 表达。此外，这些结果表明，旨在恢复 RECK 或抑制 SGLT2 的干预措施有可能在慢性高血糖条件下治疗肾脏炎症反应/纤维化和肾病，如 DKD。
