姜黄素对糖尿病大鼠视网膜中巨噬细胞游走抑制因子表达的影响

Effects of curcumin on expression of macrophage migration inhibitory factor in retina of diabetic rats

目的检测巨噬细胞游走抑制因子(MIF)在糖尿病大鼠视网膜中的表达,探讨MIF在糖尿病视网膜病变(DR)中的作用及姜黄素早期干预对其表达的影响。方法对30只清洁级SD大鼠行腹腔注射质量分数1%链脲佐菌素(STZ)诱导建立糖尿病动物模型,选取其中的20只随机分为糖尿病组和姜黄素治疗组,各10只,另取10只正常匹配的大鼠作为正常对照组。姜黄素治疗组自STZ注射后3d起给予含羧甲基纤维素的姜黄素200mg/(kg.d)灌胃,共8周,正常对照组和糖尿病组给予等量的羧甲基纤维素灌胃。动物处死后收集各组大鼠眼球,苏木精-伊红染色观察大鼠视网膜组织的病理变化;采用ELISA法检测各组大鼠视网膜组织中MIF的表达;应用免疫组织化学法观察各实验组大鼠视网膜中MIF的表达及定位;透射电镜下观察大鼠视网膜超微结构的改变。结果与正常对照组比较,糖尿病组大鼠和姜黄素治疗组大鼠血糖明显升高,差异均有统计学意义(P<0.01);姜黄素治疗组大鼠血糖水平明显低于糖尿病组,差异有统计学意义(P<0.01)。与正常对照组比较,糖尿病组和姜黄素治疗组大鼠体重明显下降,差异均有统计学意义(P<0.01);姜黄素治疗组大鼠体重明显大于糖尿病组,差异有统计学意义(P<0.01)。糖尿病组大鼠视网膜变薄,但姜黄素治疗组大鼠视网膜接近正常。免疫组织化学检测表明,糖尿病组视网膜组织中含有大量MIF阳性细胞,姜黄素治疗组视网膜中MIF表达明显少于糖尿病组(P<0.01)。ELISA法检测结果显示,糖尿病组MIF的表达较正常对照组显著升高(P<0.01);姜黄素治疗组MIF的表达较糖尿病组明显下降(P<0.01)。透射电镜下糖尿病组大鼠视网膜光感受器内外节水肿,毛细血管内皮细胞和周细胞染色体边集;姜黄素治疗组大鼠视网膜超微结构的改变轻微。结论 DR与视网膜的炎性改变有关,视网膜组织中MIF的高表达参与早期DR的发生发展。姜黄素可下调MIF的表达,其早期干预可延缓DR的发病进程。

Background Studies showed that diabetic retinopathy is a chronic inflammatory disease,and curcumin has good therapeutic effect on a variety of inflammatory diseases.Therefore,curcumin has been widely used in clinic.But at present,the effect of curcumin on prevention and treatment of diabetic retinopathy is rarely reported in China and abroad.ObjectiveThis study was to explore the role and significance of macrophage migration inhibitory factor（MIF）in pathogenesis of diabetic retinopathy and investigate the influence of curcumin on expression of MIF in retina.MethodsThirty clean male SD rats were divided into normal control group,diabetes mellitus（DM）group and curcumin group.0.1% streptozotocin（STZ）was intraperitonealy injected to induce the diabetic models in 20 rats and were then randomly allocated to diabetic group and curcumin group.Curcumin 200mg/（kg·d）containing carboxymethylcellulose was administered intragastrically at the third day after injection of STZ for 8 weeks in curcumin group,and only carboxymethylcellulose was used at the same way in DM group and normal control group.The animals were sacrificed and eyeballs were obtained for retinal histopathological examination.Expression of MIF in retina tissue was detected by immunohistochemistry.Content of MIF in retina of every group was evaluated using ELISA.Retinal ultrastructural change was examined under the transmission electron microscope.ResultsThe blood glucose level was significantly higher in DM group and curcumin group than the normal control group（P0.01）,and that of curcumin group was evidently lower than DM group（P0.01）.The body weight was considerably higher in normal group compared with DM group and curcumin group（P0.01）,and significantly increased weight was seen in curcumin group compared with DM group（P0.01）.Normal retinal structure was seen in normal group,and that of curcumin group was almost normal under the light microscope.But in DM group,retinal thickness was decreased.Lots of MIF positive cells were found in retinal inner and outer nuclear layer and capillary endothelial cells in DM group,but less MIF positive cells were seen in curcumin group.ELISA test results showed that MIF content was significantly higher in DM group than the control group（P0.01）,and that of curcumin group was lower than the DM group（P0.01）.Obvious ultrastructure changes were exhibited under the transmission electron microscope in DM group,including the enlarging of space of disc membrane in outer segment and edema of mitochondria in inner segment of photoreceptors,margin of chromosome of capillary endothelial cells and peripherial cells.However,the ultrastructural damage was evidently mild and retinal capillary was normal in curcumin group.ConclusionThese results indicate that diabetic retinopathy is associated with retinal inflammatory change.MIF may participate in the pathological process of early diabetic retinopathy.Curcumin can down-regulate the expression of MIF in retina and therefore delay the pathogenesis of diabetic retinopathy.