Aims: Sulodexide (SDX) protects endothelial cells via restoring endothelial glycocalyx, but the effect of SDX on endothelial inflammation remains unknown. We showed that SDX potently inhibited the activation of NLRP3 inflammasome in diabetic retinas, but the underlying mechanism was not clear. As reactive oxygen species (ROS) activates NLRP3 inflammasome, and NADPH oxidase 4 (NOX4) is a key generator of ROS in endothelial cells, this study thus investigated if NOX4/ROS signaling mediates the effect of SDX on NLRP3 inflammasome, hoping to provide novel insights into SDX in treating diabetic retinopathy (DR).
Methods: Diabetes was induced in mice by high fat diet and streptozotocin, followed by i.p. injection of SDX (10mg/kg) every other day for 3 months. Human retinal microvascular endothelial cells were exposed to high glucose, accompanied with overexpression or knocking down of NOX4 and a serial concentration of SDX. The retinal levels of NOX4, NLRP3 inflammasome, inflammatory factors, junction components, vascular leakage and ROS levels were determined.
Results: SDX treatment dramatically suppressed the hyperglycemia-induced overexpression of NOX4 and activation of NLRP3 inflammasome in retinas compared to controls. Moreover, SDX preserved the levels of ZO-1, VE-cadherin and ameliorated the retinal vascular permeability. In addition, SDX significantly ameliorated high glucose-induced NOX4 up-regulation, ROS production and NLRP3 inflammasome activation, and restored the reduction of ZO-1 and VE-cadherin in endothelial cells. Conversely, overexpression of NOX4 exacerbated endothelial inflammation through over production of ROS and subsequent activation of NLRP3 inflammasome, which was rescued by SDX treatment.
Conclusion: Our study suggests that SDX protects the retinal microvasculature by inhibiting NOX4/ROS-induced NLRP3 inflammasome activation, thus provides novel evidence of utilizing SDX for the treatment of DR.
T. Li: None. X. He: None. R. Peng: None. X. Fu: None. G. Shi: None. Y. Chen: None.
Research and Development Plans in Key Areas of Guangdong Province (2019B020227003); National Natural Science Foundation of China (81770826); National Key Research and Development Program of China (2017YFA0105803)