Decorin Protects The Inner Blood-retinal Barrier In Diabetic Conditions By Inhibiting The P38 MAPK Signaling Pathway

Objective:To evaluate the protective effect of decorin(DCN)on the inner blood-retinal barrier(i BRB)function under diabetic conditions,and explore the potential mechanisms mediated this effect.Methods:(1)In vivo part:We constructed a lentiviral vector and confirmed its transduction efficiency both in vivo and in vitro.Diabetic rats were induced by using streptozotocin and assigned to receive intravitreal injections.After 12 weeks,function of the retinal vessels was assessed by the Evans blue permeability test and retinal whole mounts.The general structure and ultrastructure of the retinas were assessed using hematoxylin and eosin staining and transmission electron microscopy.The expression of decorin,content of tight junction proteins,including claudin-5,occludin,and zonula occludens-1,nuclear factor-?B,and p38 mitogen-activated protein kinase phosphorylation were measured using western blot.(2)In vitro part:The effect of different concentrations of DCN on the cell viability of human umbilical vein endothelial cells(HUVEC)was determined by the cell counting kit-8 assay.At 6,12,24,48 h after incubation under high glucose and hypoxia conditions,the suppression effect of various concentrations of DCN on the vascular endothelial growth factor(VEGF)expression of HUVEC was detected by enzyme-linked immunosorbent assay.HUVEC were divided into normal control group,diabetic group,mannitol group and DCN treatment group.HUVEC barrier function was evaluated by measuring transepithelial electrical resistance(TER)and the permeability of fluorescein isothiocyanate-dextran(FITC-dextran).The content of tight junction proteins(claudin-5,occludin,and ZO-1)and p38mitogen-activated protein kinase(MAPK)phosphorylation was detected by Western blot.Results:(1)In vivo part:Decorin significantly reversed the effects of increased Evans blue permeability,decreased TJs and ganglion cells,and inhibited the activation of p38mitogen-activated protein kinase induced by diabetes.(2)In vitro part:DCN showed no significant effect on HUVEC survival(P>0.05).The VEGF concentration increased significantly under high-glucose plus hypoxia conditions,and this effect was inhibited in the presence of 100-200nmol·L-1 DCN(all P< 0.05).Under high-glucose plus hypoxia conditions,the TER of diabetic group was significantly lower than that of the DCN treatment group(P<0.05).The FITC-dextran of diabetic group increased significantly.DCN reversed this effect(P<0.05).The results of Western blot showed that diabetic condition-induced the reduction of claudin-5,occludin and ZO-1 was also reversed by DCN.DCN prevented the activation of p38 MAPK induced by diabetic conditions(P<0.05).Conclusion: DCN could protect the i BRB function under diabetic conditions and suppress the activation of p38 MAPK signaling pathway.So it may be used to treat diabetic retinopathy.