Division of Ophthalmology, Department of Surgery, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
Exp Eye Res. 2010 Jan;90(1):17-25. doi: 10.1016/j.exer.2009.09.003. Epub 2009 Sep 11.
Evidence is mounting that not only microangiopathy, but also neurodegenerative events occur in the retinas of humans and rodents with early diabetes. Diverse pathologies are known to alter the amount and/or location of glial expression of the water-selective channels aquaporins (AQPs) 1 and 4. However, the temporal relationships among glial activation, the altered expression of the AQP proteins and neuronal death in the retinas of diabetic animals remains to be investigated. Male spontaneously diabetic Torii (SDT) rats reportedly develop diabetes by 40 weeks of age at the latest and manifest proliferative diabetic retinopathy at 50 weeks or later. This study compared temporal changes in neuroretinal apoptosis, glial fibrillary acidic protein (GFAP) expression and the expression of AQPs 1 and 4 between SDT rat retinas and age-matched Sprague-Dawley (SD) rat retinas. Cell death was detected by terminal deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate nick end-labeling on retinal flatmounts and activated caspase 3 immunofluorescence of retinal cryosections. The expression of GFAP and AQPs 1 and 4 was assessed by immunohistochemistry of cryosections and retinal flatmounts. Diabetes started to develop around 15 weeks in SDT rats. Apoptotic cells in the ganglion cell layer and the inner nuclear layer were significantly more numerous in 40-week-old SDT rat retinas than in either age-matched SD rat retinas or 10-week-old SDT rats. GFAP immunoreactivity was confined to the nerve fiber layer both in SD and SDT rats at 10 weeks, whereas it spanned the whole retina in SDT rats, but not in SD rats, at 40 weeks. AQP1 was expressed in the outer retina, whereas AQP4 was expressed in the perivascular and end feet of Müller cells and astrocytes in the inner retina in the control SD rats and the SDT rats at 10 weeks. The perivascular AQPs shifted from AQP4 to AQP1 in 40-week-old SDT rats that exhibited marked hyperglycemia. Thus, the development of diabetes increases neuroretinal apoptosis, and this coincides with an altered expression pattern of GFAP and water-selective channels AQPs 1 and 4 in SDT rats.
越来越多的证据表明，不仅微血管病变，而且神经退行性事件也发生在早期糖尿病患者的人和啮齿动物的视网膜中。众所周知，各种病理学改变会改变水选择性通道水通道蛋白（AQP）1 和 4 的胶质表达量和/或位置。然而，糖尿病动物视网膜中胶质细胞激活、AQP 蛋白表达改变和神经元死亡之间的时间关系仍有待研究。据报道，雄性自发性糖尿病 Torii（SDT）大鼠最迟在 40 周龄时发生糖尿病，并在 50 周龄或之后表现出增生性糖尿病性视网膜病变。本研究比较了 SDT 大鼠视网膜和年龄匹配的 Sprague-Dawley（SD）大鼠视网膜之间神经视网膜细胞凋亡、胶质纤维酸性蛋白（GFAP）表达和 AQP1 和 4 表达的时间变化。在视网膜平片上通过末端脱氧核苷酸转移酶介导的脱氧尿嘧啶三磷酸缺口末端标记法检测细胞死亡，并通过视网膜冷冻切片上的活化半胱天冬酶 3 免疫荧光法检测细胞死亡。通过冷冻切片和视网膜平片的免疫组织化学评估 GFAP 和 AQP1 和 4 的表达。SDT 大鼠的糖尿病大约在 15 周时开始发展。40 周龄 SDT 大鼠视网膜的节细胞层和内核层中的凋亡细胞明显多于年龄匹配的 SD 大鼠视网膜或 10 周龄 SDT 大鼠。10 周龄时，GFAP 免疫反应性仅限于 SD 和 SDT 大鼠的神经纤维层，而 40 周龄时，GFAP 免疫反应性在 SDT 大鼠中跨越整个视网膜，但在 SD 大鼠中则不然。AQP1 在视网膜外区表达，而 AQP4 在对照组 SD 大鼠和 10 周龄 SDT 大鼠的内视网膜血管周围和 Müller 细胞和星形胶质细胞的足突中表达。40 周龄 SDT 大鼠表现出明显的高血糖，血管周围的 AQP 从 AQP4 转变为 AQP1。因此，糖尿病的发展增加了神经视网膜细胞凋亡，这与 SDT 大鼠中 GFAP 和水选择性通道 AQP1 和 4 的表达模式改变一致。
