Kalesnykas G, Niittykoski M, Rantala J, Miettinen R, Salminen A, Kaarniranta K, Uusitalo H
Department of Ophthalmology, Institute of Clinical Medicine, University of Kuopio, P.O. Box 1627, Kuopio FIN-70211, Finland.
Neuroscience. 2007 Dec 12;150(3):692-704. doi: 10.1016/j.neuroscience.2007.09.078. Epub 2007 Oct 11.
The heat shock protein 27 kDa (HSP27) is a member of proteins that are highly inducible under various forms of cellular stress. This study describes constitutive HSP27 expression in rat retina and stress-associated expression of HSP27 in an experimental rat glaucoma model. Glaucoma was induced unilaterally using laser photocoagulation of the episcleral and limbal veins. Three and seven days after the elevation of intraocular pressure (IOP), groups of rats were killed. The second laser treatment was performed for those rats killed 14 and 21 days after the first laser treatment. The RGCs were labeled with a retrograde tracer 7 days before kill. The expression of HSP27 was analyzed by Western blotting in retinas of rats killed on day 14 after the first laser treatment. Retinal astrocytes, Müller cells and HSP27-positive cells were visualized using immunohistochemical methods both from retinal whole-mounts and paraffin sections. The total number of retrogradely labeled RGCs decreased by 23.2% after 7 days, 28% after 14 days, and 29.3% after 21 days of elevated IOP when compared with controls. A significant decrease of glial fibrillary acidic protein (GFAP)-immunoreactive retinal astrocytes in laser-treated eyes was observed compared with the controls (accounted for 44.9%, 38.2% and 35% of the control values in the 7-day, 14-day and 21-day groups, respectively). The expression of HSP27 in RGCs and retinal astrocytes was also increased in laser-treated eyes when compared with controls in all groups. However, glycinergic and cholinergic cells in the inner nuclear layer and the highest number of RGCs and astrocytes that expressed HSP27 were found in the 14-day group of rats. The constitutive expression of HSP27 was observed only in retinal astrocytes and Müller cells. This study suggests that constitutive HSP27 expression is a cell-type specific phenomenon in the rat retina. However, at the same time, HSP27 might be considered as a marker for neuronal injury in the rat glaucoma model.
27 kDa热休克蛋白（HSP27）是在各种细胞应激形式下高度可诱导的蛋白质成员之一。本研究描述了大鼠视网膜中HSP27的组成性表达以及实验性大鼠青光眼模型中HSP27与应激相关的表达。通过激光光凝巩膜上静脉和角膜缘静脉单侧诱导青光眼。在眼压（IOP）升高后3天和7天，处死几组大鼠。对在第一次激光治疗后14天和21天处死的大鼠进行第二次激光治疗。在处死前7天用逆行示踪剂标记视网膜神经节细胞（RGCs）。通过蛋白质印迹法分析第一次激光治疗后第14天处死的大鼠视网膜中HSP27的表达。使用免疫组织化学方法从视网膜全层和石蜡切片中观察视网膜星形胶质细胞、穆勒细胞和HSP27阳性细胞。与对照组相比，IOP升高7天后逆行标记的RGCs总数减少了23.2%，14天后减少了28%，21天后减少了29.3%。与对照组相比，激光治疗眼的胶质纤维酸性蛋白（GFAP）免疫反应性视网膜星形胶质细胞显著减少（7天、14天和21天组分别占对照值的44.9%、38.2%和35%）。与所有组的对照组相比，激光治疗眼的RGCs和视网膜星形胶质细胞中HSP27的表达也增加。然而，在内核层的甘氨酸能和胆碱能细胞以及表达HSP27的RGCs和星形胶质细胞数量最多的是在14天龄的大鼠组中。仅在视网膜星形胶质细胞和穆勒细胞中观察到HSP27的组成性表达。本研究表明，HSP27的组成性表达是大鼠视网膜中一种细胞类型特异性现象。然而，与此同时，HSP27可能被视为大鼠青光眼模型中神经元损伤的标志物。
