title: GSK-3β/CREB axis mediates IGF-1-induced ECM/adhesion molecule expression, cell cycle progression and monolayer permeability in retinal capillary endothelial cells: Implications for diabetic retinopathy.
abstract: Various growth factors and cytokines are implicated in endothelial dysfunction and blood-retinal barrier (BRB) breakdown in early diabetic retinopathy (DR). However, cellular and molecular mechanisms that may underlie the pathology of DR are not fully understood yet. We therefore examined the effect of insulin-like growth factor (IGF)-1 on ECM/adhesion molecule expression, cell cycle regulation and monolayer permeability in an endothelial cell line (TR-iBRB2). We investigate whether the action of IGF-1 (1) involves glycogen synthase kinase 3beta (GSK-3β) and cAMP responsive transcription factor (CREB) and (2) alters ECM/adhesion molecule gene expression. Treatment of TR-iBRB2 cell with IGF-1 (100ng/ml for 0-24h) increases phosphorylation of (i) Akt Thr308, and its substrates including GSK-3β at Ser9, which inactivates its kinase function, and (ii) CREB at Ser133 (activation). These phosphorylations correlate positively with enhanced expression of CREB targets such as ECM protein fibronectin and cell cycle progression factor cyclin D1. However, stable transfection of a mutant GSK3β(S9A) or a dominant negative K-CREB in TR-iBRB2 prevents IGF-1-induced fibronectin and cyclin D1 expression. Furthermore, IGF-1 reduces the level of intercellular adherence molecule VE-cadherin and increases monolayer permeability in TR-iBRB2 cells when measured by FITC-dextran leakage. The effect of IGF-1 on VE-cadherin and membrane permeability is absent in TR-iBRB2 cells expressing the GSK-3β(S9A). Similarly, K-CREB reverses IGF-1 down-regulation of VE-cadherin and up-regulation of fibronectin. These results indicate that GSK-3β/CREB axis alters ECM/adhesion molecule expression and cell cycle progression in retinal endothelial cells, and may potentially contribute to endothelial dysfunction and BRB leakage in DR.
authors.affiliation: Departments of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48202, USA.
authors.forename: Takhellambam S
authors.initials: TS
authors.lastname: Devi
authors.forename: Lalit P
authors.initials: LP
authors.lastname: Singh
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Hosoya
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Terasaki
mesh_terms: D000818:Animals; D001813:Blood-Retinal Barrier / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology*; D003930:Diabetic Retinopathy / Q000503:physiopathology; D042783:Endothelial Cells / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051381:Rats; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D015815:Cell Adhesion Molecules; D017362:Cyclic AMP Response Element-Binding Protein; D007334:Insulin-Like Growth Factor I; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3