Scutellarin Inhibits High Glucose–induced and Hypoxia-mimetic Agent–induced Angiogenic Effects in Human Retinal Endothelial Cells Through Reactive Oxygen Species/Hypoxia-inducible Factor-1α/Vascular Endothelial Growth Factor Pathway

Abstract

Scutellarin inhibits hypoxia-induced and moderately high glucose-induced proliferation and vascular endothelial growth factor (VEGF) expression in human retinal endothelial cells (HRECs); thus, it could be a potential therapy for diabetic retinopathy. However, how scutellarin inhibits VEGF is unknown. In our study, HRECs were treated with high glucose and/or hypoxia-mimetic agent cobalt chloride to stimulate cell proliferation, migration, and angiogenesis, and the effects of scutellarin on these processes were analyzed through cell viability assay, Transwell migration assay and endothelial tube formation assay, respectively. The inhibition of angiogenic factor VEGF by scutellarin was confirmed by reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. The mechanisms for VEGF inhibition were examined by luciferase reporter assay, Western blot, immunoprecipitation, and biochemical assays. We found that scutellarin not only concentration-dependently inhibited cell proliferation, migration, and tube formation in HRECs but also decreased their production of VEGF. The reduction of VEGF was due to increased ubiquitination and degradation of hypoxia-inducible factor (HIF)-1α by scutellarin. Furthermore, scutellarin impaired the interaction of HIF-1α with p300, which further decreased the transcriptional activity of HIF-1α. As an inducer of HIF-1α, oxidative stress was attenuated by scutellarin. Our data demonstrate that scutellarin exhibits an antiangiogenic effect via inhibition of oxidative stress, enhancement of HIF-1α degradation, and reduction of VEGF secretion.

Dietary Compound Chrysin Inhibits Retinal Neovascularization with Abnormal Capillaries in db/db Mice

“…Evidence suggests that curcumin and resveratrol may have potential in the treatment of several ocular diseases [39,40]. Scutellarin inhibits retinal angiogenesis through disturbing ROS/HIF-1α/VEGF pathway [27]. In addition, EGCG alleys ocular neovascularization and vascular permeability, congruently accompanying MMP-9 suppression and VEGF activation [26].…”

“…However, they have not been proven effective in randomized, controlled trials. Natural products may serve as specific, efficacious, and affordable agents for a potential DR therapy [26,27,28]. Epigallocatechin-3-gallate (EGCG) inhibits ocular neovascularization and vascular permeability via suppression of MMP-9 and VEGF activation [26].…”

“…Epigallocatechin-3-gallate (EGCG) inhibits ocular neovascularization and vascular permeability via suppression of MMP-9 and VEGF activation [26]. The flavone scutellarin shows potential in inhibiting retinal angiogenesis through ROS/HIF-1α/VEGF pathway [27]. Chrysin (Figure 1A) is a flavone-type flavonoid found in honey and herbs and possesses diverse pharmacological activities and multiple biological effects in the central nervous and immune systems [29,30].…”

Effect of Glucose on Retinal Endothelial Cell Viability and VEGF Secretion

“…Retinal Müller cells treated with no glucose for 24 hours resulted in a decrease in cell viability, however high glucose (30mM) increased cell viability [11]. Previous studies on primary human retinal endothelial cells show that high glucose increased cell viability [14,15]. The differences in our findings compared to those published are likely due to inter-species differences (human vs rhesus monkey) as well as the transformation of the rhesus monkey retinal endothelial cells compared to the primary human line reported by our colleagues.…”

“…Vellanki et al, 2016 showed that both high and low glucose treatments resulted in an increase in VEGF secretion into cell medium from rat and human müller cells [11]. Primary human retinal endothelial cells show that high glucose stimulates VEGF expression [14,15] and Human Umbilical Vein Endothelial Cells (HUVEC) treated with high glucose (25mM/L) resulted in a decrease in VEGF secretion in cell medium. This contrasting effect to our reports may be due to the difference in cell type and exposure time compared to our rhesus monkey cell line [17].…”