Bradykinin alleviates DR retinal endothelial injury by regulating HMGB-1/NF-κB pathway

Y. Zhu, X.-Y. Li, J. Wang, Y.-G. Zhu

Department of Ophthalmology, Affiliated Hospital of Weifang Medical University, Weifang, Shandong, China. ek88362mq087@126.com

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• Ophthalmology

OBJECTIVE: Diabetic retinopathy (DR) is one of the most important complications of diabetes (DM) and the leading cause of blindness in adults. Bradykinin (BK) is involved in several pathophysiological processes, such as inflammation, pain, cell proliferation, and tumors. It plays a crucial role in corneal epithelial cells, corneal stromal cells, and fibroblasts. However, the role of BK in DR retinal endothelial injury remains unclear.
PATIENTS AND METHODS: Human retinal microvascular endothelial cells (hRECs) were cultured in vitro and randomly divided into 3 groups, control group in which hRECs were cultured in normal glucose concentration, high glucose group in which hRECs were cultured in the presence of high glucose, and BK group in which hRECs were cultured in the presence of high glucose with 1 μM BK. The MTT assay (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) was used to detect cell proliferation. Caspase-3 activity was adopted to detect Caspase-3 activity in hRECs. The colorimetric method was selected to determine lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, and ROS content. Western blot was used to test HMGB-1/NF-κB and vascular endothelial growth factor (VEGF) expression changes. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the secretion of inflammatory factor tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β).
RESULTS: In the presence of high glucose, hRECs cells proliferation was significantly reduced, Caspase-3 activity was enhanced, LDH and ROS levels were increased, SOD activity was declined with increased expression of HMGB-1, NF-κB, VEGF, as well as secretion of TNF-α and IL-1β compared with control group (p < 0.05). BK significantly inhibited the proliferation of hRECs cells, enhanced Caspase-3 activity, decreased the content of LDH and ROS, increased SOD activity, reduced the expressions of HMGB-1 and NF-κB protein, attenuated the expression of VEGF, and restrained the secretion of TNF-α and IL-1β compared with high glucose group (p < 0.05).
CONCLUSIONS: BK can inhibit the growth and proliferation of retinal endothelial cells by regulating HMGB-1/NF-κB signaling pathway, attenuating oxidative stress and inflammation, thereby delaying DR development and progress.

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