Asymmetric dimethylarginine aggravates blood–retinal barrier breakdown of diabetic retinopathy via inhibition of intercellular communication in retinal pericytes

Blood–retinal barrier breakdown is the main pathological characteristics of diabetic retinopathy (DR). Asymmetric dimethylarginine (ADMA) was reported to be elevated in DR patients. In this study, we observed the dynamic profile of ADMA, retinal morphology and permeability of BRB at 2, 4 or 8 week of diabetic rats induced by a single intraperitoneal injection of streptozocin (60 mg/kg) and in cultured rat retinal pericytes pretreated with d-glucose (30 mM) for 1, 3, 5 and 7 days or ADMA (3, 10, 30 μM) for 24, 48 and 72 h, trying to explore the effects of ADMA on blood–retinal barrier in DR. Gap junction intercellular communication (GJIC) and the expression of blood–retinal barrier-specific component connexin 43 (Cx43) were examined in diabetic rats or cultured retinal pericytes to elucidate whether ADMA impacted blood–retinal barrier function via damaging Cx43-GJIC. The results showed that with increasing duration of diabetes, the ultrastructure of blood–retinal barrier of diabetic rats appeared cell junction damage, apoptosis of retinal pericytes and breakdown of barrier successively. The increases in retinal permeability, ADMA levels and Cx43 expression, and abnormal GJIC were observed in diabetic rats and retinal pericytes exposed to d-glucose (30 mM). A glucose-like effect was seen using ADMA or another l-arginine analogue NG-monomethyl-l-arginine or dimethylarginine dimethylaminohydrolases (DDAHs) siRNA, implicating that ADMA aggravated the breakdown of blood–retinal barrier via damaging Cx43-GJIC.