葛根素对大鼠糖尿病视网膜病变的抑制作用

目的　探讨葛根素对大鼠糖尿病视网膜病变（diabetic retinopathy，DR）的抑制作用。方法　取SPF级健康Wistar大鼠60只，随机分为正常对照组20只、模型组20只和葛根素组20只，模型组和葛根素组大鼠均接受链脲佐菌素左下腹腔注射建立糖尿病模型，正常对照组大鼠注射同样体积的枸橼酸盐溶液。造模后1周，葛根素组大鼠每天给予100 mg·kg^-1葛根素单侧腹腔注射治疗，连续治疗6周。正常对照组和模型组大鼠每天给予等量生理盐水腹腔注射。观察并比较各组大鼠体质量、血糖及血-视网膜屏障的损伤情况。应用TUNEL法检测大鼠的视网膜组织神经节细胞凋亡情况；采用ELISA检测各组大鼠白细胞介素1（interleukin-1,IL-1)β、肿瘤坏死因子α（tumor necrosis factor α,TNF-α)的水平；采用硫代巴比妥酸法检测丙二醛 （malonaldehyde，MDA）水平；采用黄嘌呤氧化酶法检测超氧化物歧化酶（superoxide dismutase，SOD）水平；Western blot法检测磷酸化细胞外信号调节蛋白激酶（phospho-extracellular signal-regulated kinase，p-ERK）、B淋巴细胞瘤-2（B-cell lymphoma-2，Bcl-2）、E2核因子相关因子2（nuclear factor-erythroid 2-related factor-2，Nrf2）、细胞外调节p-ERK的总蛋白（t-ERK）及P53的表达情况。结果　模型组大鼠的体质量低于正常对照组，血糖高于正常对照组（P＜0.05）；而葛根素组大鼠体质量高于模型组，血糖低于模型组（P＜0.05）。模型组大鼠视网膜组织伊凡斯兰渗透量为（10.63±3.21）μg·g^-1，高于正常对照组［（2.87±1.09）μg·g^-1］，差异有统计学意义（P＜0.05）；而葛根素组伊凡斯兰渗透量为（5.56±2.71）μg·g^-1，低于模型组，但高于正常对照组，差异均有统计学意义（均为P＜0.05）。模型组大鼠神经节细胞凋亡指数高于正常对照组，而葛根素组低于模型组，但高于正常对照组，差异均有统计学意义（均为P<0.05）。模型组大鼠视网膜组织中IL-1β、TNF-α及MDA水平高于正常对照组，SOD水平低于正常对照组，差异均有统计学意义（均为P＜0.05）。而葛根素组大鼠视网膜组织中IL-1β、TNF-α及MDA水平低于模型组，SOD水平高于模型组，差异均有统计学意义（均为P＜0.05）。模型组大鼠Nrf2、p-ERK蛋白的表达水平高于正常对照组，差异均有统计学意义（均为P＜0.05）。而葛根素组大鼠Nrf2、p-ERK的表达水平低于模型组，差异均有统计学意义（均为P＜0.05）。各组大鼠t-ERK 的蛋白表达水平差异无统计学意义（P>0.05）。模型组大鼠的Bcl-2表达水平低于正常对照组，P53高于正常对照组，差异均有统计学意义（均为P<0.05）；葛根素组大鼠Bcl-2表达水平高于模型组，P53低于模型组，差异均有统计学意义（均为P<0.05）。结论　葛根素可有效减缓2型糖尿病大鼠视网膜神经节细胞的凋亡，改善2型DR的进程，其机制可能与抑制Nrf2/ERK通路的激活，减轻视网膜组织的炎性反应及氧化应激损伤有关。

Inhibitory effects of puerarin on retinopathy of diabetic rats by regulating activation of Nrf2/ERK signaling pathway

Objective　To investigate the inhibitory effect of puerarin on diabetic retinopathy （DR）.Methods　Totally 60 healthy Wistar rats were randomly divided into normal control group （n=20），model group （n=20） and puerarin group （n=20）.A diabetes model in the model group and puerarin group was established by intraperitoneal injection of streptozotocin in the lower left abdomen and rats in the normal control group were injected with the same volume of citrate solution.One week after model establishment，rats in the puerarin group were given unilateral intraperitoneal injection of 100 mg·kg^-1 per day for 6 weeks.Rats in the normal control group and the model group were given an equal amount of normal saline per day.The body weight，blood glucose and blood-retinal barrier damage of the rats in each group were observed and compared.The apoptosis of retinal tissue ganglion cells was detected by TUNEL method.The levels of IL-1β and TNF-α in each group were detected by ELISA.The level of malonaldehyde （MDA） was detected by thiobarbituric acid method.Superoxide dismutase （SOD） levels were detected by xanthine oxidase method；phospho-extracellular signal-regulated kinase （p-ERK），B-cell lymphoma-2 （Bcl-2），E2 nuclear factor-erythroid 2-related factor-2 （Nrf2），extracellular regulation of p-ERK total protein （t-ERK） and P53 antibody were detected by Western blot.Results　The body weight of the model group was lower than that of the normal control group，and the blood glucose was higher than that of the normal control group （P<0.05）.The body weight of the puerarin group was higher than that of the model group，and the blood glucose was lower than the model group （P<0.05）.The permeation of Evans blue in the retinal tissue of the model group was （10.63±3.21）μg·g^-1，which was higher than （2.87±1.09）μg·g^-1 of the normal control group，and the difference was statistically significant （P<0.05）.The penetration of Evans blue in puerarin group was （5.56±2.71）μg·g^-1，which was lower than the model group，but higher than the normal control group，the difference was statistically significant （both P<0.05）.The apoptotic index of ganglion cells in the model group was higher than that in the normal control group，but the puerarin group was lower than the model group，but higher than the normal control group，the differences were statistically significant （all P<0.05）.The levels of IL-1β，TNF-α and MDA in the retinal tissue of the model group were higher than those in the normal control group，and the SOD level was lower than that in the normal control group （all P<0.05）.The expression levels of Nrf2 and p-ERK protein in the model group were higher than those in the normal control group，and the differences were statistically significant （both P<0.05）.The expression levels of Nrf2 and p-ERK in the puerarin group were lower than those in the model group，and the differences were statistically significant （both P<0.05）.There was no significant difference in the protein expression levels of t-ERK between the groups （P>0.05）.The expression level of Bcl-2 in the model group was lower than that in the normal control group，and the P53 was higher than the normal control group，and the difference was statistically significant （both P<0.05）.The expression level of Bcl-2 in the puerarin group was higher than that in the model group，and the P53 was low.In the model group，and the difference was statistically significant （both P<0.05）.Conclusion　Puerarin can effectively alleviate the apoptosis of retinal ganglion cells in type 2 diabetic rats and improve the progression of type 2 DR.The mechanism may be related to inhibiting the activation of Nrf2/ERK pathway and reducing the inflammatory response and oxidation of retinal tissue.