Ceramide is a mediator of apoptosis in retina photoreceptors
Ceramide is a mediator of apoptosis in retina photoreceptors
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DOI：
10.1167/iovs.05-1310
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发表时间：
2006-04-01
影响因子：
4.4
通讯作者：
Rotstein, NP
中科院分区：
文献类型：
--
作者：
German, OL;Miranda, GE;Rotstein, NP
目的。光感受器细胞凋亡的确切机制尚不清楚。在本研究中，神经酰胺是一种神经鞘磷脂前体，在细胞应激下诱导细胞凋亡，与光感受器细胞死亡的激活有关。方法：用神经酰胺类似物乙酰鞘氨醇(C-2-神经酰胺)和葡萄糖神经酰胺合成酶抑制剂处理有或没有二十二碳六烯酸(DHA)的大鼠视网膜神经元培养。用[H-3]棕榈酸酯评价氧化剂百草枯处理培养物中神经酰胺的合成。研究神经酰胺新生合成抑制剂伏马菌素B1和环丝氨酸对光感受器细胞凋亡的影响。结果：加入C-2-神经酰胺后，光感受器细胞发生凋亡。与对照组相比，百草枯增加了光感受器中[H-3]神经酰胺的形成，而在百草枯处理前立即抑制神经酰胺的合成，阻止了百草枯诱导的光感受器凋亡。伏马菌素在体外发育早期也能减少光感受器的凋亡。DHA是视网膜的主要多不饱和脂肪酸，它可以保护光感受器免受氧化应激诱导的细胞凋亡，并完全阻止C-2-神经酰胺诱导的光感受器死亡，同时增加Bcl-2的表达。在神经酰胺或百草枯处理前抑制催化神经酰胺糖基化的葡萄糖神经酰胺合成酶可阻断DHA的保护作用。结论氧化应激刺激神经酰胺水平升高，从而诱导感光细胞凋亡。DHA通过上调Bcl2的表达和糖基化神经酰胺，从而降低其细胞内浓度，从而预防氧化应激和神经酰胺损伤。这首次表明神经酰胺是触发哺乳动物视网膜光感受器凋亡的关键介质，并提示调节神经酰胺水平可能为预防神经退行性疾病的光感受器死亡提供一种治疗工具。
PURPOSE. The precise mechanisms involved in photoreceptor apoptosis are still unclear. in the present study, the role of ceramide, a sphingolipid precursor that induces apoptosis on cellular stress, was investigated in relation to the activation of cell death in photoreceptors.METHODS. Rat retina neuronal cultures, with or without docosahexaenoic acid (DHA), were treated with the ceramide analogue acetylsphingosine (C-2-ceramide), and with a glucosylceramide synthase inhibitor. Ceramide synthesis in cultures treated with the oxidant paraquat was evaluated with [H-3]palmitate. The effect of inhibitors of ceramide de novo synthesis, fumonisin B1 and cycloserine, on photoreceptor apoptosis was investigated. Apoptosis, mitochondrial membrane potential, and Bcl-2 expression were determined.RESULTS. Addition of C-2-Ceramide induced photoreceptor apoptosis. Paraquat increased formation of [H-3]ceramide in photoreceptors, compared with the control, whereas inhibition of ceramide synthesis, immediately before paraquat treatment, prevented paraquat-induced photoreceptor apoptosis. Fumonisin also reduced photoreceptor apoptosis during early development in vitro. DHA, the retina major polyunsaturated fatty acid, which protects photoreceptors from oxidative stress-induced apoptosis, completely blocked C-2-ceramide-induced photoreceptor death, simultaneously increasing Bcl-2 expression. Inhibiting glucosylceramide synthase, which catalyzes ceramide glucosylation, before ceramide or paraquat treatment blocked DHA's protective effect.CONCLUSIONS. The results suggest that oxidative stress stimulated an increase in ceramide levels that induced photoreceptor apoptosis. DHA prevented oxidative stress and ceramide damage by upregulating Bcl-2 expression and glucosylating ceramide, thus decreasing its intracellular concentration. This shows for the first time that ceramide is a critical mediator for triggering photoreceptor apoptosis in mammalian retina and suggests that modulating ceramide levels may provide a therapeutic tool for preventing photoreceptor death in neurodegenerative diseases.