Department of Medicine, Xizang Minzu University, Xianyang 712082, Shaanxi, PR China.
School of Medicine, Xinjiang Tarim University, Alar 843300, Xinjiang, PR China.
Immunol Lett. 2024 Jun;267:106862. doi: 10.1016/j.imlet.2024.106862. Epub 2024 May 1.
Diabetic retinopathy (DR) stands as a prominent complication of diabetes. Berberine (BBR) has reported to be effective to ameliorate the retinal damage of DR. Studying the potential immunological mechanisms of BBR on the streptozotocin (STZ) induced DR mouse model will explain the therapeutic mechanisms of BBR and provide theoretical basis for the clinical application of this drug.
C57BL/6 J mice were induced into a diabetic state using a 50 mg/(kg·d) dose of STZ over a 5-day period. Subsequently, they were subjected to a high-fat diet (HFD) for one month. Following a 5-week treatment with 100 mg/(kg·d) BBR, the concentrations of inflammatory factors in the mice's peripheral blood were determined using an enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin staining was employed to scrutinize pathological changes in the mice's retinas, while flow cytometry assessed the proportions of T-lymphocyte subsets and the activation status of dendritic cells (DCs) in the spleen and lymph nodes. CD4T cells and DC2.4 cell lines were utilized to investigate the direct and indirect effects of BBR on T cells under high glucose conditions in vitro.
Following 5 weeks of BBR treatment in the streptozotocin (STZ) mouse model of DR, we observed alleviation of retinal lesions and a down-regulation in the secretion of inflammatory cytokines, namely TNF-α, IL-1β, and IL-6, in the serum of these mice. And in the spleen and lymph nodes of these mice, BBR inhibited the proportion of Th17 cells and promoted the proportion of Treg cells, thereby down-regulating the Th17/Treg ratio. Additionally, in vitro experiments, BBR directly inhibited the expression of the transcription factor RORγt and promoted the expression of the transcription factor Foxp3 in T cells, resulting in a down-regulation of the Th17/Treg ratio. Furthermore, BBR indirectly modulated the Th17/Treg ratio by suppressing the secretion of TNF-α, IL-1β, and IL-6 by DCs and enhancing the secretion of indoleamine 2,3-dioxygenase (IDO) and transforming growth factor-beta (TGF-β) by DCs. This dual action inhibited Th17 cell differentiation while promoting Treg cells.
Our findings indicate that BBR regulate T cell subpopulation differentiation, reducing the Th17/Treg ratio by directly or indirectly pathway. This represents a potential therapeutic avenue of BBR for improving diabetic retinopathy.
糖尿病视网膜病变（DR）是糖尿病的主要并发症之一。黄连素（BBR）已被报道可有效改善 DR 的视网膜损伤。研究 BBR 在链脲佐菌素（STZ）诱导的 DR 小鼠模型中的潜在免疫机制将解释 BBR 的治疗机制，并为该药物的临床应用提供理论依据。
使用 50mg/（kg·d）剂量的 STZ 诱导 C57BL/6 J 小鼠 5 天，使其产生糖尿病状态。随后，它们接受高脂肪饮食（HFD）1 个月。用 100mg/（kg·d）BBR 治疗 5 周后，使用酶联免疫吸附试验（ELISA）测定小鼠外周血中炎症因子的浓度。用苏木精-伊红染色观察小鼠视网膜的病理变化，用流式细胞术检测脾和淋巴结中 T 淋巴细胞亚群的比例和树突状细胞（DC）的激活状态。利用 CD4T 细胞和 DC2.4 细胞系，在体外高糖条件下研究 BBR 对 T 细胞的直接和间接作用。
在 DR 的 STZ 小鼠模型中，经过 5 周的 BBR 治疗后，我们观察到视网膜病变减轻，血清中 TNF-α、IL-1β和 IL-6 等炎症因子的分泌下调。在这些小鼠的脾和淋巴结中，BBR 抑制 Th17 细胞的比例，促进 Treg 细胞的比例，从而下调 Th17/Treg 比值。此外，在体外实验中，BBR 直接抑制 T 细胞中转录因子 RORγt 的表达，促进转录因子 Foxp3 的表达，从而下调 Th17/Treg 比值。此外，BBR 通过抑制 DC 分泌 TNF-α、IL-1β和 IL-6，增强 IDO 和 TGF-β的分泌，间接调节 Th17/Treg 比值。这种双重作用抑制了 Th17 细胞的分化，同时促进了 Treg 细胞的分化。
我们的研究结果表明，BBR 通过直接或间接途径调节 T 细胞亚群分化，降低 Th17/Treg 比值。这代表了 BBR 改善糖尿病视网膜病变的一种潜在治疗途径。
