Li Yan, Roth Steven, Laser Martin, Ma Jian-xing, Crosson Craig E
Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Invest Ophthalmol Vis Sci. 2003 Mar;44(3):1299-304. doi: 10.1167/iovs.02-0235.
Brief periods of ischemia have been shown to protect the retina from potentially damaging periods of ischemia. This phenomenon has been termed ischemic preconditioning or ischemic tolerance. In the present study the cellular changes in levels of heat shock protein (Hsp)27, -70, and -90 mRNA and expression of Hsp in the rat retina associated with ischemic preconditioning were evaluated.
Unilateral retinal ischemia was created in Long-Evans and Sprague-Dawley rats for 5 minutes. Rats were then left for 1 hour to 7 days, to allow the retina to reperfuse. Retinas were dissected, the mRNA and protein isolated, and Northern and Western blot analyses conducted to detect changes in expression of Hsp27, -70, and -90. Immunohistochemical studies were used to identify retinal regions where Hsp changes occurred. Selected animals were subjected to a second ischemic event, 60 minutes in duration, to correlate the changes in expression of Hsp with functional protection of the retina from ischemic injury.
In control and sham-treated animals retinal Hsp27, -70, and -90 mRNAs were detectable. Five hours after retinal preconditioning, levels of Hsp27 mRNA were elevated above control levels, and 24 hours later, mRNA levels increased 200% over basal levels. Hsp27 expression remained elevated for up to 72 hours and then began to return to control levels. Hsp27 protein levels were increased by 200% over basal levels 24 hours after retinal preconditioning, remained at this level for 72 hours, and then returned to control levels. In contrast, no consistent change in Hsp70 or -90 mRNA or protein levels was observed during the course of the study. Immunohistochemical studies demonstrated that the increase in expression of Hsp27 was localized to neuronal and non-neuronal cells in the inner layers of the retina. Electroretinography studies demonstrated a strong correlation between the protection of retinal function from ischemic injury and the expression of Hsp27.
These results provide evidence that the induction of Hsp27 is a gene-specific event associated with ischemic preconditioning in the retina. This increase in expression of Hsp27 occurs in both neuronal and non-neuronal retinal cells, and appears to be one component of the neuroprotective events induced by ischemic preconditioning in the retina.
短暂的缺血已被证明可保护视网膜免受潜在的缺血性损伤。这种现象被称为缺血预处理或缺血耐受。在本研究中，评估了与缺血预处理相关的大鼠视网膜中热休克蛋白（Hsp）27、-70和-90 mRNA水平的细胞变化以及Hsp的表达。
在Long-Evans和Sprague-Dawley大鼠中造成单侧视网膜缺血5分钟。然后让大鼠存活1小时至7天，以使视网膜再灌注。解剖视网膜，分离mRNA和蛋白质，并进行Northern和Western印迹分析以检测Hsp27、-70和-90表达的变化。免疫组织化学研究用于确定发生Hsp变化的视网膜区域。对选定的动物进行持续60分钟的第二次缺血事件，以将Hsp表达的变化与视网膜对缺血性损伤的功能保护相关联。
在对照和假手术处理的动物中可检测到视网膜Hsp27、-70和-90 mRNA。视网膜预处理5小时后，Hsp27 mRNA水平升高至对照水平以上，24小时后，mRNA水平比基础水平增加200%。Hsp27表达持续升高至72小时，然后开始恢复到对照水平。视网膜预处理24小时后，Hsp27蛋白水平比基础水平增加200%，在该水平维持72小时，然后恢复到对照水平。相比之下，在研究过程中未观察到Hsp70或-90 mRNA或蛋白水平的一致变化。免疫组织化学研究表明，Hsp27表达的增加定位于视网膜内层的神经元和非神经元细胞。视网膜电图研究表明，视网膜功能免受缺血性损伤的保护与Hsp27的表达之间存在很强的相关性。
这些结果提供了证据，表明Hsp27的诱导是与视网膜缺血预处理相关的基因特异性事件。Hsp27表达的这种增加发生在视网膜的神经元和非神经元细胞中，并且似乎是视网膜缺血预处理诱导的神经保护事件的一个组成部分。
