霍乱毒素对受损视网膜环磷酸腺苷和节细胞存活及凋亡的影响

THE EFFECTS OF CHOLERA TOXIN ON THE cAMP LEVEL OF THE RETINA AND THE SURVIVAL AS WELL AS THE APOPTOSIS OF THE RETINAL GANGLION CELLS AFTER DISTAL AXOTOMY OF THE OPTIC NERVE

目的 研究霍乱毒素 (CTx)对视网膜cAMP水平及视网膜节细胞存活及凋亡的影响。 方法 视神经远端 (颅内 )切断 ,玻璃体内注射CTx,采用荧光逆行示踪技术及原位末端标记 (TUNEL)技术显示存活的视网膜节细胞及节细胞层凋亡的细胞 ,Brown放射免疫法测定各时间点视网膜cAMP的水平。 结果 远端切断视神经后各时间点cAMP水平均低于玻璃体内注射霍乱毒素组。视神经远端切断后视网膜节细胞平均密度明显下降 ,玻璃体内注射霍乱毒素后 ,节细胞平均密度明显提高 ,细胞凋亡数也明显少于单纯视神经切断组。 结论 表明霍乱毒素可提高成年金黄地鼠视网膜cAMP水平并具有促受损视网膜节细胞存活及抗凋亡作用。

Objective To investigate the effects of Cholera Toxin(CTx)on the cAMP level and the survival as well as the apoptosis of retinal ganglion cells (RGCs) after distal axotomy of the optic nerve.Method After transecting the optic nerve intracranially, CTx was injected intravitreally. Fluorescent retrograde tracing method and TUNEL(TdT-mediated dUTP nick end labeling)technique were used to show the surviving RGCs and the apoptotic cells in the ganglion cell layer. The Brown's radioimmunoassay method was used to measure the cAMP level of the retina. Result The cAMP level of the normal retina was 6.22±2.02pmol/g/retina. The mean density of RGCs in the normal retina was 2 192±66/mm 2 and it decreased to 1 520±116/mm 2、736±39/mm 2 and 466±53/mm 2 at 1W、2W and 3W respectively after distal axotomy. The densities of RGCs in the distal axotomy groups treated with CTx and killed at 1W、2W and 3W were 1 642±122/mm 2、1 091±107/mm 2、 748±35/mm 2 respectively and were significantly higher than those of distal axotomy group without CTx treatment. Conclusions The results show that CTx can elevate cAMP level of the retina and promote the survival of RGCs and inhibit the apoptosis of RGCs after distal axotomy of the optic nerve in adult hamsters.