Inhibition of diabetes-induced Drp1 deSUMOylation prevents retinal vascular lesions associated with diabetic retinopathy

Retinal microvascular endothelial cell (RMEC) injury plays an important role in the pathophysiology diabetic retinopathy (DR). The GTPase dynamin-related protein 1 (Drp1), crucial to mitochondrial dynamics, has been implicated in hyperglycaemia-induced microvascular damage. Moreover, Drp1 can be deSUMOylated by the enzyme sentrin/SUMO-specific protease 3 (SENP3). Whether SENP3/deSUMOylated Drp1 can aggravate DR is unclear. Therefore, we designed this experiment to investigate the role of SENP3/desumoylated Drp1 in DR in vitro and in vivo. Murine RMECs (mRMECs) were classified into a control (CON), high-glucose (HG) and high-glucose + SENP3-siRNA (HG-siRNA) groups. The SENP3 and SUMOylated/deSUMOylated drp1 levels, mitochondrial morphology, mitochondrial membrane potential (MMP) and apoptosis rate were evaluated. In vivo, mice were assigned to a normal, type 2 diabetic or type 2 diabetic SENP3-siRNA mouse groups. Then, blood–retinal barrier function and retinal tissue structure were evaluated. As compared to those in the control group, the SENP3 and Drp1 levels, degree of mitochondrial fragmentation, extent of MMP loss and apoptosis rate of mRMECs were significantly increased in the HG group. However, inhibited SENP3 expression increased the level of SUMOylated Drp1 in the mRMECs and reduced the hyperglycaemia-induced mitochondrial damage and apoptosis rate. These experimental results were confirmed by diabetic animal experiments showing that inhibited SENP3 expression attenuated the increase in retinal permeability and diabetic retinopathy, suggesting that SENP3/deSUMOylated Drp1 activation aggravated DR by disrupting mitochondrial dynamics and apoptosis. Furthermore, blocking SENP3 expression significantly attenuated RMEC damage and DR.