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. Thus, we investigated whether regulation of AMP-activated protein kinase (AMPK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by transglutaminase 2 (TGase2) is important for hyperglycemia-induced microvascular leakage in the diabetic retina. In 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 hyperglycemia-induced AMPK dephosphorylation, which resulted in 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 VE-cadherin disassembly and endothelial permeability in HRECs. Overall, our findings suggest that inhibition of AMPK and GAPDH by TGase2 plays a pivotal role in hyperglycemia-induced microvascular leakage in the retinas of diabetic mice. Highlights • ROS-mediated activation of TGase2 inhibited AMPK in the diabetic retina. • AMPK inhibition resulted in VE-cadherin disassembly and microvascular leakage. • TGase2 suppressed GAPDH activity and induced endothelial permeability through AMPK inhibition. • Inhibition of AMPK and GAPDH by TGase2 is important for microvascular leakage in the diabetic retina.