摘要
背景：糖尿病视网膜病变（DR）是一种常见的糖尿病微血管并发症，也是糖尿病患者视力丧失的主要原因。视网膜色素上皮（RPE）细胞通过释放细胞因子和长非编码 RNAs（lncRNAs）等外泌体货物，调节局部免疫反应、维持视网膜免疫平衡并影响巨噬细胞极化，从而在糖尿病视网膜病变的病理生理学中发挥着至关重要的作用。最近的研究表明，lncRNA 癌症易感性候选因子 2（CASC2）可能参与了 DR 进展的调控。然而，CASC2 与 RPE 细胞之间的调控机制及其在巨噬细胞极化中的作用仍未得到充分了解：方法：在正常葡萄糖和高葡萄糖条件下培养各种类型的细胞，包括人视网膜色素上皮细胞（ARPE-19）、THP-1 单核细胞和其他视网膜细胞系。ARPE-19 细胞暴露于氧化应激、炎症刺激或缺氧条件下。从 DR 患者和糖尿病对照组收集血浆和水样。从 AREP-19 细胞中提取外泌体并进行表征。利用定量反转录聚合酶链反应、Western 印迹、免疫荧光、流式细胞术、酶联免疫吸附测定和组织学染色等技术进行了各种基因和蛋白质表达分析。细胞增殖和迁移分别采用细胞计数试剂盒-8测定法和Transwell迁移测定法进行评估。利用 RNA 免疫沉淀和双荧光素酶报告实验探讨了 CASC2、细胞因子信号抑制因子 6（SOCS6）和 U2 小核 RNA 辅助因子 2（U2AF2）之间的相互作用。结果发现：与无视网膜病变的糖尿病患者相比，DR 患者血浆和水样液中 lncRNA CASC2 的表达水平明显较低。CASC2的过表达在体外和体内都能明显减轻DR和炎症损伤。我们证实，来自 ARPE-19 细胞的外泌体 CASC2 通过抑制 M1 极化和促进 M2 极化来介导巨噬细胞极化。我们的研究结果表明，CASC2通过U2AF2稳定SOCS6 mRNA来调节这种极化：结论：源自 RPE 细胞的 CASC2 被转运至巨噬细胞，通过招募 U2AF2 稳定 SOCS6 mRNA，从而诱导 M2 极化。这项研究可为开发新的 DR 治疗策略奠定基础。Background: Diabetic retinopathy (DR) is a prevalent microvascular complication of diabetes and a leading cause of vision loss among diabetic individuals. Retinal pigment epithelium (RPE) cells play a crucial role in the pathophysiology of DR by releasing cytokines and exosomal cargo, such as long non-coding RNAs (lncRNAs), that modulate local immune responses, maintain retinal immune homeostasis and influence macrophage polarisation. Recent studies suggest that lncRNA cancer susceptibility candidate 2 (CASC2) may be involved in the regulation of DR progression. However, the regulatory mechanisms linking CASC2 with RPE cells and its role in macrophage polarisation remain insufficiently understood.
Methods: Various types of cells, including human retinal pigment epithelial cells (ARPE-19), THP-1 monocytes and additional retinal cell lines, were cultured under normal glucose and high glucose conditions. ARPE-19 cells were exposed to oxidative stress, inflammatory stimulation, or hypoxic conditions. Plasma and aqueous humour samples were collected from DR patients and diabetic controls. Exosomes were extracted from AREP-19 cells and characterised. Various gene and protein expression analyses were performed using techniques including quantitative reverse transcription polymerase chain reaction, Western blot, immunofluorescence, flow cytometry, enzyme-linked immunosorbent assay, and histological staining. Cell proliferation and migration were assessed using Cell Counting Kit-8 assays and Transwell migration assays, respectively. The interactions among CASC2, suppressor of cytokine signalling 6 (SOCS6), and U2 small nuclear RNA auxiliary factor 2 (U2AF2) were explored using RNA immunoprecipitation and dual-luciferase reporter assays. An in vivo diabetic rat model was established.
Results: lncRNA CASC2 expression levels were significantly lower in plasma and aqueous humour from DR patients compared to those from diabetic patients without retinopathy. Overexpression of CASC2 significantly attenuated DR and inflammatory damage both in vitro and in vivo. We demonstrated that exosomal CASC2 from ARPE-19 cells mediated macrophage polarisation by inhibiting M1 polarisation and promoting M2 polarisation. Our findings suggest that CASC2 regulates this polarisation through the stabilisation of SOCS6 mRNA via U2AF2.
Conclusion: CASC2 derived from RPE cells was transported to macrophages, inducing M2 polarisation by stabilising SOCS6 mRNA through the recruitment of U2AF2. This research may provide a foundation for developing novel therapeutic strategies for DR.
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