Proanthocyanidins Attenuate The Mechanism Of Diabetic Retinopathy By Inhibiting The Activity Of MMP-9

Diabetic retinopathy(DR)is a common chronic diabetic microvascular complication and it is also an important cause of blindness in diabetic patients.Its pathological manifestations are: apoptotic retinal cells,retinal nerve dysfunction,and massive production of new blood vessels.Although a large number of hypotheses about DR have been reported,the exact mechanism of DR remains unclear.Studies have shown that inflammation is involved in the process of retinopathy,and retinal muller cells participate in the development of DR disease.Retinal muller cells are key factors involved in the inflammatory process.Matrix metalloproteinases,which are capable of degrading extracellular matrix,are hydrolytic enzymes that act extracellularly.They not only mediate a series of normal physiological processes but also maintain homeostasis in cells,particularly matrix metalloproteinase-9,participate in the destruction of the blood-retinal barrier(BRB).Proanthocyanidins,a safe and effective natural product that has been used clinically,have a strong immunomodulatory effect on retinal muller cells.We believe that procyanidins can inhibit the elevated MMP-9 of retinal muller cells induced by high glucose stimulation and explore the possible anti-inflammatory mechanisms of procyanidins.Part I: High Glucose Increases MMP-9 Activity Through the P38-NFκB Pathway Leads to Retinopathy OBJECTIVE: To study the mechanism of diabetic retinopathy caused by MMP-9.\ METHODS: High glucose was used to stimulate retinal muller cells to establish a diabetic retinopathy model;intraperitoneal injection of streptozotocin(STZ)was used to establish a mouse model of diabetes;Gelatin zymography was used to detect changes in the activity of MMP-9;immunoenzymatic imprinting was used.The level of protein expression in the signal pathway was detected;P65 NF-κB inhibitors and P38 inhibitors were used to detect the reversal of inflammation;HE staining was used to observe the changes in the morphological structure of the mouse retina.RESULTS: In the STZ-induced diabetic mouse model,MMP-9 was activated,and STZ could induce changes in the morphological structure of diabetic retina.High glucose can induce MMP-9 activation in retinal muller cells.This increase can be mediated by Toll-like receptor 4(TLR-4)inhibitors,p38 mitogen-activated protein kinase(MAPK P38)inhibitors,and nuclear transcription factor-κB.(NF-κB)inhibitors are eliminated.TLR-4 inhibitors can reduce high glucose-induced phosphorylation of P38 in retinal muller cells.At the same time,high glucose can cause elevated levels of p-AMPK,p-AKT,and p-ERK.CONCLUSION: High glucose activates MMP-9 in retinal mullerian cells through activation of HMGB1-TLR4-NF-κB signaling pathway,thereby destroying BRB and causing DR.Part 2.Proanthocyanidins alleviate diabetic retinopathy by inhibiting MMP-9 OBJECTIVE:To study the protective mechanism of procyanidins on diabetic retinopathy.METHODS: High glucose was used to stimulate retinal muller cells to establish a diabetic retinopathy model;intraperitoneal injection of streptozotocin(STZ)was used to establish a mouse model of diabetes;Gelatin zymography was used to detect changes in the activity of MMP-9;immunoenzymatic imprinting was used.The level of protein expression in the signal pathway was detected;P65 immunofluorescence was used to detect nuclear transcription of NF-κB.RESULTS: Proanthocyanidins can alleviate high glucose-induced retinopathy by inhibiting the expression of MMP-9 in retinal muller cells.In an STZ-induced diabetic mouse model,procyanidins can reduce MMP-9 activation.Procyanidins can inhibit the expression of HSP70 and HMGB1 induced by high glucose stimulated retinal muller cells.Procyanidins can inhibit the activation of p-AMPK,p-AKT and p-ERK induced by high glucose-stimulated retinal muller cells.In vitro incubation with procyanidins can inhibit MMP-9 activity in a dose-dependent manner.Proanthocyanidins inhibit LPS-mediated microglia activation by inhibiting the p38-MAPK/NF-κB pathway.CONCLUSION: Procyanidins can alleviate DR by inhibiting the activation of p-AMPK,p-AKT,p-ERK and inhibiting the activation of MMP-9 by inhibiting p38-MAPK/NF-κB signaling pathway.