Elevated cell proliferation and VEGF production by high-glucose conditions in Müller cells involve XIAP

Abstract

Purpose Mü ller cells have important roles in the pathogenesis of diabetic retinopathy by promoting cell proliferation and inducing the production of vascular endothelial growth factor (VEGF) under hyperglycemic conditions. The objective of this study was to determine the potential mechanism of Mü ller cell proliferation and VEGF production due to high-glucose conditions. Methods Primary cultured rat Mü ller cells were incubated with medium containing variable concentrations of glucose and/or embelin, a specific inhibitor of X-linked inhibitor of apoptosis protein (XIAP), for 72 h. The proliferation of Mü ller cells was assessed by the MTT assay. The expression and/or phosphorylation of 146 proteins were assessed using protein pathway array. Results High concentrations of glucoseinduced Mü ller cell proliferation and altered expression and/or phosphorylation of 47 proteins that have been identified to have key roles in several important signaling pathways (XIAP, VEGF, HIF1a, NFkB, etc) and are involved in the regulation of cell survival, proliferation, or apoptosis. However, Mü ller cell alterations induced by highglucose conditions were counteracted by the XIAP inhibitor embelin, and 26 proteins/ phosphorylations (out of 47) were restored to their normal levels. Nine proteins, including NFkB p65, p-p38, tumor necrosis factor-a, urokinase-type plasminogen activator, CREB, IL-1b, HCAM, estrogen receptor-a, and p-Stat3, were involved in regulatory networks between XIAP and VEGF. Conclusions The current study suggests that XIAP may be a potential regulator that can mediate a series of pathological changes induced by high-glucose conditions in Mü ller cells. Therefore, embelin could be a potential agent for the prevention and treatment of diabetic retinopathy.

High Glucose and Glucose Deprivation Modulate Müller Cell Viability and VEGF Secretion

“…Compared to physiological glucose (5.5mM), high glucose (30mM) increase cell viability in both Müller cell types (Figures 1 and 2). This is consistent with results of others using primary rat Müller cells [29]. In another study, the density of Müller cells in retina increased significantly in 4 week old diabetic rats [30].…”

670nm Photobiomodulation Modulates Bioenergetics And Oxidative Stress, Decreasing Inflammatory Mediator Production In An In Vitro Model Of Diabetic Retinopathy

“…The increase in NFkB activity and oxidative stress, as well as the reduction in antioxidant capacity of superoxide dismutase, was partially attenuated in diabetic rats which were treated with the antioxidant resveratrol 42 . Also, VEGF levels increased with high glucose treatment, consistent with many other reports 24,25,43,44 . Unexpectedly, we observed no change in VEGF concentration under high glucose conditions compared to high glucose cultured cells treated with 670nm light.…”

“…This data indicates that in this cell culture model of DR, VEGF and ICAM-1 are not regulated in the same manner. Regulation of VEGF can occur through multiple pathways in addition to NFkB 44 . Indeed, Sun et al reports multiple transcriptional proteins which regulate VEGF production including NFkB, p38, TNFa, CREB, vPA, IL-1B, Era, Stat3, and HCAM.…”

A journey into the retina: Müller glia commanding survival and death

“…This annexed tissue alters retinal elasticity, exerts tractional forces and recurrently causes retinal detachment and intravitreal haemorrhage. Although the mechanisms responsible for glial proliferation are not completely elucidated, the X‐linked inhibitor for apoptosis protein (XIAP) has been implicated in the induction of this process (Sun et al., ). While the migratory capacity is regulated by stimuli of a different nature, such as protease inhibitors (α 2 M), trophic factors (IGF‐1) and lipids (Sphingosine‐1‐Phosphate) (Barcelona, Jaldin‐Fincati, Sanchez, & Chiabrando, ; Lorenc et al., ; Simon, Prado Spalm, Politi, & Rotstein, ).…”