Activation of the VEGF-A/ERK/PLA2 Axis Mediates Early Retinal Endothelial Cell Damage Induced by High Glucose: New Insight from an In Vitro Model of Diabetic Retinopathy

Abstract

Early blood retinal barrier (BRB) dysfunction induced by hyperglycemia was related to increased pro-inflammatory activity of phospholipase A2 (PLA2) and the upregulation of vascular endothelial growth factor A (VEGF-A). Here, we tested the role of VEGF-A in high glucose (HG)-induced damage of human retinal endothelial cells (HRECs) mediated by Ca++-dependent (cPLA2) and Ca++-independent (iPLA2) PLA2s. HRECs were treated with normal glucose (5 mM, NG) or high glucose (25 mM, HG) for 48 h with or without the VEGF-trap Aflibercept (Afl, 40 µg/mL), the cPLA2 inhibitor arachidonoyl trifluoromethyl ketone (AACOCF3; 15 µM), the iPLA2 inhibitor bromoenol lactone (BEL; 5 µM), or VEGF-A (80 ng/mL). Both Afl and AACOCF3 prevented HG-induced damage (MTT and LDH release), impairment of angiogenic potential (tube-formation), and expression of VEGF-A mRNA. Furthermore, Afl counteracted HG-induced increase of phospho-ERK and phospho-cPLA2 (immunoblot). VEGF-A in HG-medium increased glucose toxicity, through upregulation of phospho-ERK, phospho-cPLA2, and iPLA2 (about 55%, 45%, and 50%, respectively); immunocytochemistry confirmed the activation of these proteins. cPLA2 knockdown by siRNA entirely prevented cell damage induced by HG or by HG plus VEGF-A, while iPLA2 knockdown produced a milder protective effect. These data indicate that VEGF-A mediates the early glucose-induced damage in retinal endothelium through the involvement of ERK1/2/PLA2 axis activation.

Retinal Vascular Endothelial Cell Dysfunction and Neuroretinal Degeneration in Diabetic Patients

“…Many years of research have shown that hyperglycaemia plays a central role in the induction of diabetic retinopathy [ 18 , 19 , 20 ]. Studies conducted in non-obese diabetic mice (NOD mice) have demonstrated that the first changes on the fundus of the eye blood–retinal barrier breakdown are observed already in the first week of exposure to high glucose levels [ 21 ].…”

“…Studies conducted in non-obese diabetic mice (NOD mice) have demonstrated that the first changes on the fundus of the eye blood–retinal barrier breakdown are observed already in the first week of exposure to high glucose levels [ 21 ]. In the environment of high glucose concentration, hyperglycaemia causes cell dysfunction, retinal neurovascular impairment, structural defects and functional disorders which lead to further damage of the retinal cells [ 13 , 18 , 19 ]. The next active stage of pathological changes is associated with the inflammatory process [ 22 , 23 , 24 ].…”

The Mechanism of Compound Danshen Dripping Pills in the Treatment of Diabetic Retinopathy Based on Network Pharmacology and Molecular Docking

“…Hyperglycemia is an important risk factor for the occurrence and development of DR, which can cause damage to retinal microvascular system, including capillary swelling and deformation, Blood retinal barrier (BRB) damage. In the environment of high glucose concentration, hyperglycemia leads to cell dysfunction, retinal vascular and nerve damage, structural defects and further damage of retinal cells, functional disorders (31)(32)(33). Ages binding to rage induce a strong intracellular signal transduction cascade, leading to endothelial dysfunction, key pro-in ammatory cytokines and pro angiogenic factors, such as tumor necrosis factor -α (TNF -α) and nuclear transcription factor -kB (NF -kb) Activation of NFkb mediates pericyte apoptosis, vascular in ammation and angiogenesis, as well as the destruction of endogenous BRB.…”

The “Hitchhiker’s Guide to the Galaxy” of Endothelial Dysfunction Markers in Human Fertility

“…Vascular endothelial growth factor-A-encoding ( VEGF-A ) gene transcription leads to multiple alternative splicing isoforms resulting in either anti- or pro-angiogenic properties GF [ 191 , 192 ]. In humans, VEGF-A is physiologically expressed in testis, seminal vesicles, prostate, measurable in the seminal fluid, and involved in the control of male reproductive functions [ 193 ].…”