Azuma Mitsuyoshi, Sakamoto-Mizutani Kanako, Nakajima Takeshi, Kanaami-Daibo Sayaka, Tamada Yoshiyuki, Shearer Thomas R
Research Laboratories, Senju Pharmaceutical Co. Ltd., 1-5-4, Murotani, Nishiku, Kobe, Hyogo, 651-2241, Japan.
Comp Med. 2004 Oct;54(5):533-42.
Results of our recent studies in rats suggested that calpains play an important role in retinal cell death induced by ischemia-reperfusion in vivo and by hypoxia in vitro. Study of spontaneous animal models could help determine the involvement of calpains in human retinopathy. The WBN/Kob rat is such a model for spontaneous retinal degeneration. The purpose of the study reported here was to determine the involvement of calpain isoforms during retinal degeneration in WBN/Kob rats. Histologic and functional retinal degeneration in WBN/Kob rats was observed by use of light microscopy and electroretinography, respectively. Proteolysis of alpha-spectrin in the retina was detected by use of immunoblot analysis in aging WBN/Kob rats. This proteolysis was associated with the increases of retinal calcium content and caseinolytic activity for calpains 1 and 2. Expression of calpain 1, calpain 2, and calpastatin mRNAs in the retina, as measured by use of reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, were only slightly up-regulated at 24 weeks of age. In contrast, expression of retina-specific calpains, such as Rt88, Rt88', and Rt90 mRNA, was markedly down-regulated at 12 weeks of age. Expression of calpain 10 mRNA in the retina was only slightly down-regulated at 12 weeks of age. In contrast to mRNA expression, various expression patterns of calpain 10 proteins were observed. Increased retinal calcium content, leading to activation of calpains 1 and 2, may be an important event in the sequential changes leading to degeneration of the retina in WBN/Kob rats. Activated calpain causing proteolysis of alpha-spectrin and changes in Rt88, Rt88', Rt90 and calpain 10 may also contribute to retinal degeneration.
我们最近在大鼠身上进行的研究结果表明，钙蛋白酶在体内缺血再灌注和体外缺氧诱导的视网膜细胞死亡中起重要作用。对自发动物模型的研究有助于确定钙蛋白酶在人类视网膜病变中的作用。WBN/Kob大鼠就是这样一种自发视网膜变性的模型。本文报道的这项研究的目的是确定钙蛋白酶同工型在WBN/Kob大鼠视网膜变性过程中的作用。分别通过光学显微镜和视网膜电图观察WBN/Kob大鼠视网膜的组织学和功能性变性。在衰老的WBN/Kob大鼠中，通过免疫印迹分析检测视网膜中α-血影蛋白的蛋白水解情况。这种蛋白水解与视网膜钙含量的增加以及钙蛋白酶1和2的酪蛋白水解活性的增加有关。通过逆转录聚合酶链反应（RT-PCR）分析测定，视网膜中钙蛋白酶1、钙蛋白酶2和钙蛋白酶抑制蛋白mRNA的表达在24周龄时仅略有上调。相比之下，视网膜特异性钙蛋白酶如Rt88、Rt88'和Rt90 mRNA的表达在12周龄时明显下调。视网膜中钙蛋白酶10 mRNA的表达在12周龄时仅略有下调。与mRNA表达不同，观察到钙蛋白酶10蛋白的各种表达模式。视网膜钙含量增加导致钙蛋白酶1和2激活，这可能是WBN/Kob大鼠视网膜变性一系列变化中的一个重要事件。激活的钙蛋白酶导致α-血影蛋白的蛋白水解以及Rt88、Rt88'、Rt90和钙蛋白酶10的变化，也可能导致视网膜变性。
