目的研究抗氧化剂叔丁基对苯二酚(tBHQ)对早期糖尿病大鼠视网膜结构和功能的保护作用及其机制。
方法选取8周龄健康清洁级雄性SD大鼠45只，采用随机数字表法将其分为正常对照组、糖尿病模型组和tBHQ干预组，每组15只；糖尿病模型组和tBHQ干预组采用一次性腹腔内注射链脲佐菌素(STZ)诱导糖尿病模型，正常对照组大鼠腹腔内注射等容量枸橼酸钠缓冲液；tBHQ干预组在STZ注射前2周喂食质量分数为1% tBHQ添加饲料，其余2个组大鼠喂食普通饲料；分别于造模后72 h、2周和4周尾静脉采血用于血糖检测。取造模成功的大鼠于造模后4周行视网膜电图(ERG)检测；采用苏木精－伊红染色法观察大鼠视网膜组织形态结构变化；采用TUNEL法观察视网膜组织各层细胞凋亡情况；Western blot法检测视网膜组织中蛋白激酶B(Akt)、p-Akt、内皮型一氧化氮合酶(eNOS)和p-eNOS的表达情况。另取体外培养的Müller细胞系rMC-1进行分组。正常对照组、甘露醇对照组、高糖组细胞分别在正常培养基、含5.5 mmol/L葡萄糖+24.5 mmol/L甘露醇的培养基、高糖培养基中培养72 h。tBHQ干预组细胞先于含5 μmol/L tBHQ的正常糖培养基中预处理24 h，然后于含5 μmol/L tBHQ的高糖培养基中继续培养72 h；磷脂酰肌醇3激酶(PI3K)抑制剂组细胞先于含5 μmol/L LY294002的正常糖培养基中预处理6 h，然后于含5 μmol/L LY294002及5 μmol/L tBHQ的正常糖培养基中继续培养24 h，最后于含5 μmol/L LY294002及5 μmol/L tBHQ的高糖培养基中继续培养72 h，收集各组细胞提取蛋白，Western blot法检测Akt、p-Akt、eNOS和p-eNOS的表达情况。
结果造模后72 h、2周和4周，糖尿病模型组大鼠血糖较正常对照组和tBHQ干预组高，差异均有统计学意义(均 P<0.01)。造模后4周糖尿病模型组大鼠暗适应ERG的a波、b波振幅较正常对照组和tBHQ干预组下降，差异均有统计学意义(均 P<0.05)。组织病理学染色结果显示，与正常对照组相比，糖尿病模型组视网膜神经节细胞数目减少，内丛状层水肿增厚，内核层及外核层变薄，结构疏松且排列紊乱，而tBHQ干预组各结构较糖尿病模型组有所改善。TUNEL染色结果显示，糖尿病模型组大鼠视网膜细胞凋亡指数较正常对照组和tBHQ干预组高，差异均有统计学意义(均 P<0.05)，且凋亡细胞主要存在于外核层。Western blot法检测结果显示，正常对照组、糖尿病模型组和tBHQ干预组大鼠视网膜组织p-Akt/Akt的相对表达量分别为0.76±0.11、0.52±0.10和1.14±0.31，p-eNOS/eNOS的相对表达量分别为0.83±0.06、0.52±0.08和1.03±0.13，糖尿病模型组大鼠视网膜组织p-Akt/Akt、p-eNOS/eNOS的相对表达量均较正常对照组和tBHQ干预组降低，差异均有统计学意义(均 P<0.01)；正常对照组、甘露醇对照组、高糖组、tBHQ干预组和PI3K抑制剂组细胞p-Akt/Akt的相对表达量分别为0.95±0.38、0.94±0.27、0.33±0.25、1.32±0.37和0.24±0.09，p-eNOS/eNOS的相对表达量分别为0.86±0.11、0.74±0.29、0.45±0.29、1.28±0.22和0.73±0.29，高糖组细胞p-Akt/Akt、p-eNOS/eNOS的相对表达量较正常对照组和tBHQ干预组显著降低，差异均有统计学意义(均 P<0.05)，PI3K抑制剂组p-Akt/Akt、p-eNOS/eNOS的相对表达量较tBHQ干预组明显降低，差异均有统计学意义(均 P<0.01)。
结论tBHQ对早期糖尿病大鼠视网膜结构和功能均具有保护作用，其保护作用机制可能与Akt/eNOS信号通路的活化有关。
ObjectiveTo investigate the protective effects of an antioxidant tert-butylhydroquinone (tBHQ) on the morphology and function of retina in early-stage experimental diabetic rats, and to explore the mechanism of its protective effect.
MethodsForty-five healthy SD rats of clean degree were randomized into normal control group, diabetes model group and tBHQ intervention group, with 15 rats in each group according to a random number table.The diabetes model was established via a single intraperitoneal injection of streptozotocin (STZ) in diabetes model group and tBHQ intervention group.Normal control group was intraperitoneally administered with an equal-volume injection of sodium citrate buffer.Rats in the tBHQ intervention group maintained a diet with 1% tBHQ for 2 weeks before the STZ injection, and the other two groups were fed with normal rat food only.Blood from tail vein was collected to assay the blood glucose level at 72 hours, 2 weeks and 4 weeks following modeling.Rat electroretinogram (ERG) was detected at 4 weeks after modeling.Morphological changes of rat retina were observed by hematoxylin and eosin staining.The apoptosis of retinal cells in different layers was detected by TUNEL assay.The expression of protein kinase B (Akt), p-Akt, endothelial nitric oxide synthase (eNOS) and p-eNOS was detected by Western blot.Müller cell line rMC-1 cells cultured in vitro were divided into 5 groups, including normal control group (72-hour culturing in normal medium), mannitol control group (72-hour culturing in medium containing 5.5 mmol/L glucose and 24.5 mmol/L mannitol), high glucose group (72-hour culturing in high-glucose medium), tBHQ intervention group (24-hour culturing in normal-glucose medium containing 5 μmol/L tBHQ, 72-hour culturing in high-glucose medium containing 5 μmol/L tBHQ), and phosphoinositide 3-kinase (PI3K) inhibitor group (6-hour culturing in normal medium containing 5 μmol/L LY294002, 24-hour culturing in normal-glucose medium containing 5 μmol/L LY294002 and 5 μmol/L tBHQ, 72-hour culturing in high-glucose medium containing 5 μmol/L LY294002 and 5 μmol/L tBHQ). The expression of Akt, p-Akt, eNOS and p-eNOS in the cells was detected by western blot.The use and care of animals complied with Regulations for the Administration of Laboratory Animals in Southwest Medical University.The study protocol was approved by the Animal Ethics Committee of Southwest Medical University (No.201711189).
ResultsThe blood glucose level at 72 hours, 2 weeks and 4 weeks after modeling was higher in diabetic model group than tBHQ intervention group and normal control group (all at P<0.01). Four weeks after modeling, the scotopic ERG a-wave and b-wave amplitudes of diabetic model group were lower than those of normal control group and tBHQ intervention group (all at P<0.05). With edema and thickening of inner plexiform layer, thinning of inner nuclear layer and outer nuclear layer, as well as loosely arrangement and disorder of retinal layers, the number of retinal ganglion cells was decreased in diabetic model group in comparison with normal control group, all of which were improved in tBHQ intervention group in comparison with diabetic model group.There were more apoptotic retinal cells in diabetic model group than normal control group and tBHQ intervention group (both at P<0.05), which mainly existed in the outer nuclear layer.The relative expressions of p-Akt/Akt and p-eNOS/eNOS in rat retina of normal control group, diabetic model group and tBHQ intervention group were 0.76±0.11 and 0.83±0.06, 0.52±0.10 and 0.52±0.08, 1.14±0.31 and 1.03±0.13, respectively.The relative expressions of p-Akt/Akt and p-eNOS/eNOS in diabetic model group were lower than those of normal control group and tBHQ intervention group (all at P<0.01). The relative expressions of p-Akt/Akt and p-eNOS/eNOS in normal glucose group, mannitol control group, high glucose group, tBHQ intervention group and PI3K inhibitor group were 0.95±0.38 and 0.86±0.11, 0.94±0.27 and 0.74±0.29, 0.33±0.25 and 0.45±0.29, 1.32±0.37 and 1.28±0.22, 0.24±0.09 and 0.73±0.29, respectively.The relative expressions of p-Akt/Akt and p-eNOS/eNOS were significantly lower in high glucose group than those in normal glucose group and tBHQ intervention group (all at P<0.05), which were significantly lower in PI3K inhibitor group compared with tBHQ intervention group (both at P<0.01).
ConclusionstBHQ has protective effects on the morphology and function of retina in early diabetic rats, and the mechanism may be related to the activation of Akt/eNOS signaling pathway.
王娟,韦芳,曹阳,等. 叔丁基对苯二酚对早期糖尿病模型大鼠视网膜结构和功能的保护作用及其机制[J]. 中华实验眼科杂志,2022,40(09)：796-803.
DOI:10.3760/cma.j.cn115989-20191225-00555版权归中华医学会所有。
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王娟：参与选题与实验设计、实验操作、数据整理、统计分析、论文撰写及修改；韦芳：参与实验设计、实验指导与实验操作；曹阳、田敏：参与实验选题、实验设计、实验指导；吕红彬：参与实验选题、实验指导、论文修改及定稿
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