铁皮石斛多糖对糖尿病性白内障大鼠氧化应激及ERK信号通路的影响

Effects of dendrobium officinale polysaccharides on oxidative stress and ERK signaling pathway in diabetic cataract rats

目的探讨铁皮石斛多糖(DOP)对糖尿病性白内障大鼠血清氧化应激产物及晶状体组织ERK1、ERK2、MEK、Raf、Ras mRNA水平的影响。方法将Wistar大鼠50只随机分为5组:对照组(CG)、模型组(MG)、铁皮石斛多糖低(DOPL)、中(DOPM)、高(DOPH)3个剂量组。以腹腔注射链脲菌素制备糖尿病大鼠模型。铁皮石斛多糖各剂量分别灌胃,对照组和模型组按相同容量生理盐水灌胃,每日2次,连续12周。检测各组大鼠血清丙二醛(MDA)、超氧化物岐化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)含量及晶状体组织中ERK1、ERK2、MEK、Raf、Ras mRNA水平。结果(1)晶状体混浊评定:对照组晶状体混浊评定几乎都在C0N0,保持透明;模型组绝大多数晶状体混浊程度在C3-4和N1-2,几乎完全混浊;DOP组晶状体混浊程度评定大部分在C1-2和N0-1,DOPH组晶状体出现絮状、片状等部分混浊,混浊程度较模型组明显减轻,3组之间差异有统计学意义(χ皮质^(2)=49.401,χ核^(2)=43.914,均P=0.000);(2)氧化应激指标:(1)MDA含量,模型组MDA含量较对照组明显升高(t=4.615,P=0.000),DOP作用后MDA较模型组明显下降,且存在量效关系(tDOPL=4.046,tDOPM=6.504,tDOPH=6.587,均P=0.000);(2)SOD活力,模型组SOD活力较对照组明显降低(t=9.809,P=0.000),DOPM、DOPH组均较模型组升高(tDOPM=2.914,P=0.007;tDOPH=13.305,P=0.000);(3)GSH-Px活力,DOPH组GSH-Px较DOPL组和对照组明显升高(tCG=2.728,P=0.011;tDOPL=2.068,P=0.048);(3)ERK1、ERK2、MEK、Raf、Ras基因表达:模型组ERK1、ERK2、MEK、Raf、Ras mRNA表达均较对照组增高(P<0.05);随着DOP浓度增高,ERK1、ERK2和Raf mRNA表达水平逐渐降低,其中DOPH组的ERK1较模型组显著降低,差异有统计学意义(t=7.849,P=0.000);与对照组比较,DOP3个剂量组的MEK mRNA表达增强,差异均有统计学意义(tDOPL=4.046,P=0.001;tDOPM=4.493,P=0.000;tDOPH=4.403,P=0.000)。结论DOP延缓糖尿病性白内障可能是通过降低糖尿病大鼠血清中MDA含量,提高血清中SOD的活力,增强其抗氧化能力实现的,其中氧化应激介导的ERK/Raf信号通路可能是DOP延缓糖尿病性白内障的重要机制。

OBJECTIVE To investigate the effect of dendrobium officinale polysaccharide(DOP)on serum oxidative stress products and the mRNA levels of ERK1,ERK2,MEK,Raf,Ras in lens tissue of diabetic cataract rats.METHODS Fifty Wistar rats were randomly divided into 5 groups:control group(CG),model group(MG),low-dose DOP group(DOPL),medium-dose DOP group(DOPM),and high-dose DOP group(DOPH).The diabetic rat model was prepared by intraperitoneal injection of streptozotocin.Rats in low,medium,and high-dose DOP groups were given different doses of DOP by gavage respectively.The control group and model group were given the same capacity of normal saline by gavage,2 times every day for 12 consecutive weeks.The levels of serum malondialdehyde,superoxide dismutase,glutathione peroxidase and the mRNA levels of ERK1,ERK2,MEK,Raf,Ras in lens tissue were detected in rats of each group.RESULTS(1)Assessment of lens opacification:In the control group,most lens opacification was C0N0 which meant transparent;In model group,lens opacification were C3-4 and N1-2 which meant feculent;In DOP group lens opacification were C1-2,N0-1.The lens of DOP group appeared flocculent and lamellar opacity,and the turbidity level was less than that of the model group.Differences were statistically significant(χcortex^(2)=49.401,χnuclear^(2)=43.914,all P=0.000);(2)Indicators of oxidative stress:(1)MDA,Serum MDA of rats in the model group was significantly higher than the control group(t=4.615,P=0.000).The MDA in DOP group was significantly lower than the model group,and there was a dose-effect relationship(tDOPL=4.046,tDOPM=6.504,tDOPH=6.587,all P=0.000);(2)SOD,Compared with the control group,the serum SOD activity of rats in model group decreased significantly(t=9.809,P=0.000).The levels in DOPM,DOPH group were higher than that in model group(tDOPM=2.914,P=0.007,tDOPH=13.305,P=0.000);(3)GSH-Px,The serum GSH-Px of rats in DOPH group was significantly higher that of DOPL group and the control group(tCG=2.728,P=0.011,tDOPL=2.068,P=0.048);(3)Gene expression of ERK1,ERK2,MEK,Raf,Ras:The mRNA expression of ERK1,ERK2,MEK,Raf,Ras in the model group were higher than those in the control group(P<0.05).As the concentrations of DOP increased,the level of ERK1,ERK2 and Raf mRNA expression decreased gradually.And ERK1 of DOPH group was significantly lower than that of the model group.The difference was statistically significant(t=7.849,P=0.000).Compared with the control group,the MEK mRNA expression in DOP groups all increased.Differences were statistically significant(tDOPL=4.046,P=0.001;tDOPM=4.493,P=0.000;tDOPH=4.403,P=0.000).CONCLUSIONS Dendrobium officinale polysaccharides delayed development of diabetic cataract possibly through reducing MDA in the serum of diabetic rats,increasing the activity of SOD in the serum and enhancing their antioxidant capacity.Among them,the signaling pathway about ERK/Raf mediated by oxidative stress may be an important mechanism of dendrobium officinale polysaccharide in delaying development of diabetic cataract.