Elevated Cell Proliferation And VEGF Production By High Glucose Conditions In Müller Cells Involve XIAP

Purpose Müller cells play important roles in the pathogenesis of diabetic retinopathy(DR) by promoting cell proliferation and inducing the production of vascularendothelial growth factor (VEGF) under hyperglycemic conditions. The objective ofthis study was to determine the potential mechanism of Müller cell proliferation andVEGF production due to high glucose conditions.Methods Primary cultured rat Müller cells were incubated with medium containingvariable concentrations of glucose and/or embelin, a specific inhibitor of X-linkedinhibitor of apoptosis protein (XIAP), for72h. The proliferation of Müller cells wasassessed by the MTT assay. The expression and/or phosphorylation of146proteinswere assessed using Protein Pathway Array (PPA).Results We examined the effect of high glucose conditions on Müller cell growth usingthe MTT assay and found a dose-dependent increase of Müller cells after72h ofincubation with various concentrations of glucose (up to50mM) and the high glucoseinduced proliferation of Müller cells, which were reversed by embelin, a specificinhibitor of XIAP. High concentrations of glucose induced Müller cell proliferation andaltered expression and/or phosphorylation of47proteins that have been identified toplay key roles in several important signaling pathways (XIAP, VEGF, HIF1α, NF-κB,etc.) and are involved in the regulation of cell survival, proliferation, or apoptosis.However, Müller cell alterations induced by high glucose conditions werecounteracted by the XIAP inhibitor embelin, and26proteins/phosphorylations (out of47) were restored to their normal levels. Among146tested proteins andphosphoproteins,108were detected in protein samples from either the high or normalglucose treatments. Of which,47showed a significant difference in expression betweencells treated with high glucose. Forty proteins and phosphoproteins were overexpressedin high glucose-treated cells. These47proteins are involved in several importantsignaling pathways based on IPA, These data suggest that high glucose conditionscause a broad dysregulation of the signaling pathways in Müller cells. The PPA results showed that nine proteins, including NFκB p65, p-p38, TNF-α, uPA, CREB, IL-1β,HCAM, ERα, and p-Stat3, were involved in a regulatory network between XIAP andVEGF.Conclusions High glucose induced the significantly changes in the global network ofretinal Müller cells, which was successfully checked by PPA. The current studysuggests that XIAP may be a potential regulator that can mediate a series ofpathological changes induced by high glucose conditions in Müller cells. Wehypothesize that XIAP may regulate VEGF mainly through NFkB complex/p38cascade pathways. Therefore, embelin could be a potential agent for the prevention andtreatment of diabetic retinopathy.