Effects of Dendrobium candidum polysaccharides on microRNA-125b and mitogen-activated protein kinase signaling pathways in diabetic cataract rats

Background:Diabetic cataract is a common complication and a lens disorder in diabetes.Moreover,Dendrobium officinale polysaccharide(DOP)is found to alleviate diabetes complications.Consequently,microRNA-125b and mitogen-activated protein kinase signaling pathways play significant roles in diabetes.However,the mechanism and the effect of DOP on diabetic cataract remains unknown.Methods:Wistar male rats were randomly assigned to the control,model,and DOP groups.Diabetes was induced with streptozotocin.Furthermore,DOP was orally given for 12 weeks.The Lens Opacities Classification System III was used to evaluate lens opacity by slit-lamp microscope.The lens was then harvested for testing the mRNA expression of microRNA-125b,ERK1,ERK2,Raf and Ras using reverse transcription-polymerase chain reaction.The protein expression of ERK1,ERK2,Raf,and Ras was detected using the Western blot analysis.The targets of microRNA-125b were predicted in miRWalk 2.0.These targets were obtained from the Kyoto Encyclopedia of Genes and Genomes pathway.Results:The lens opacities of the rats in the control group were almost at C0N0.Moreover,the majority of the lens opacities in the model group were C3 to C4 and N1 to N2,and were mostly at C1 to C2 and N0 to N1 in the DOP group.The difference was statistically significant(P<0.05).Furthermore,the microRNA-125b expression in the model group is significantly higher compared with the control group.Conversely,the microRNA-125b expression in the DOP group is significantly decreased(all P<0.05).The mRNA expression of ERK1,ERK2,Raf,and Ras in the model groups were upregulated compared with those of the control group.However,the ERK1 and Raf mRNA expressions of the DOP group were lower compared with the model group(all P<0.05).The protein expression of ERK1,Raf,and Ras in the model group was significantly increased compared with those of the control group.The protein expression of ERK1,Raf,and Ras in the DOP group was significantly lower compared with the model group(all P<0.05).Moreover,3,378 genes of the microRNA-125b target were gained from the miRWalk.After Kyoto Encyclopedia of Genes and Genomes pathways analysis in Gene Set Enrichment Analysis,246 items were gained including Ras(rno04014)and mitogen-activated protein kinase(rno04010)signaling pathways.A positive correlation exists between microRNA-125b and mRNA expression of ERK1,ERK2,Raf and Ras(r=0.940,0.841,0.666,and 0.768;all P<0.05).Conclusion:DOP can alleviate the severity of the opacity of the lens in diabetic cataract rats via microRNA-125b and mitogen-activated protein kinase signaling pathways.Thus,microRNA-125b has something to do with the mitogen-activated protein kinase signaling pathway.