Regulation of AMPK and GAPDH by Transglutaminase 2 Plays a Pivotal Role in Microvascular Leakage in Diabetic Retinas

Abstract

Diabetic retinopathy is the most common microvascular complication caused by chronic hyperglycemia and is a leading cause of blindness; however, the underlying molecular mechanism has not been clearly elucidated. Therefore, we investigated whether regulation of AMPK and GAPDH by transglutaminase 2 (TGase2) is important for hyperglycemia-induced microvascular leakage in the diabetic retina. In human retinal endothelial cells (HRECs) and diabetic mouse retinas, we found that TGase2, activated by sequential elevation of intracellular Ca2+ and reactive oxygen species (ROS) levels, played an essential role in hyperglycemia-induced vascular leakage. ROS generation and TGsae2 activation were involved in hyperglycemiainduced AMPK dephosphorylation, which resulted in vascular endothelial–cadherin (VE-cadherin) disassembly and increased fluorescein isothiocyanate-dextran extravasation. Furthermore, high glucose–induced TGase2 activation suppressed GAPDH activity, determined by an on-chip activity assay, through inhibition of AMPK, which induced VEcadherin disassembly and endothelial permeability in HRECs. Overall, our findings suggest that inhibition of AMPK and GAPDH by TGase2 plays a pivotal role in hyperglycemiainduced microvascular leakage in the retinas of diabetic mice.