Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, USA.
Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, USA; Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania, USA.
J Biol Chem. 2023 Aug;299(8):104991. doi: 10.1016/j.jbc.2023.104991. Epub 2023 Jun 29.
Increasing evidence supports a role for inflammation in the early development and progression of retinal complications caused by diabetes. We recently demonstrated that the stress response protein regulated in development and DNA damage response 1 (REDD1) promotes diabetes-induced retinal inflammation by sustaining canonical activation of nuclear transcription factor, NF-κB. The studies here were designed to identify signaling events whereby REDD1 promotes NF-κB activation in the retina of diabetic mice. We observed increased REDD1 expression in the retina of mice after 16 weeks of streptozotocin (STZ)-induced diabetes and found that REDD1 was essential for diabetes to suppress inhibitory phosphorylation of glycogen synthase kinase 3β (GSK3β) at S9. In human retinal MIO-M1 Müller cell cultures, REDD1 deletion prevented dephosphorylation of GSK3β and increased NF-κB activation in response to hyperglycemic conditions. Expression of a constitutively active GSK3β variant restored NF-κB activation in cells deficient for REDD1. In cells exposed to hyperglycemic conditions, GSK3β knockdown inhibited NF-κB activation and proinflammatory cytokine expression by preventing inhibitor of κB kinase complex autophosphorylation and inhibitor of κB degradation. In both the retina of STZ-diabetic mice and in Müller cells exposed to hyperglycemic conditions, GSK3 inhibition reduced NF-κB activity and prevented an increase in proinflammatory cytokine expression. In contrast with STZ-diabetic mice receiving a vehicle control, macrophage infiltration was not observed in the retina of STZ-diabetic mice treated with GSK3 inhibitor. Collectively, the findings support a model wherein diabetes enhances REDD1-dependent activation of GSK3β to promote canonical NF-κB signaling and the development of retinal inflammation.
越来越多的证据表明，炎症在糖尿病引起的视网膜并发症的早期发生和进展中起作用。我们最近证明，应激反应蛋白发育和 DNA 损伤反应 1（REDD1）通过维持核转录因子 NF-κB 的经典激活，促进糖尿病诱导的视网膜炎症。本研究旨在确定 REDD1 通过何种信号事件促进糖尿病小鼠视网膜中 NF-κB 的激活。我们观察到，16 周链脲佐菌素（STZ）诱导的糖尿病后，小鼠视网膜中 REDD1 的表达增加，并且发现 REDD1 对于糖尿病抑制糖原合酶激酶 3β（GSK3β）在 S9 的抑制性磷酸化是必需的。在人视网膜 MIO-M1 Müller 细胞培养物中，REDD1 缺失阻止了 GSK3β 的去磷酸化，并增加了 NF-κB 在高血糖条件下的激活。组成型激活 GSK3β 变体的表达恢复了 REDD1 缺失细胞中 NF-κB 的激活。在暴露于高血糖条件的细胞中，GSK3β 敲低通过阻止 IKK 激酶复合物自身磷酸化和 IκB 降解抑制 NF-κB 激活和促炎细胞因子表达。在 STZ 糖尿病小鼠的视网膜和暴露于高血糖条件的 Müller 细胞中，GSK3 抑制降低了 NF-κB 活性并防止了促炎细胞因子表达的增加。与接受载体对照的 STZ 糖尿病小鼠相比，在接受 GSK3 抑制剂治疗的 STZ 糖尿病小鼠的视网膜中未观察到巨噬细胞浸润。总之，这些发现支持了一种模型，即糖尿病增强 REDD1 依赖性 GSK3β 的激活，以促进经典的 NF-κB 信号传导和视网膜炎症的发展。
