Astragalus polysaccharide attenuates metabolic memory-triggered ER stress and apoptosis via regulation of miR-204/SIRT1 axis in retinal pigment epithelial cells

Abstract

Background: ‘Metabolic memory’ of early hyperglycaemic environment has been frequently suggested in the progression of diabetic retinopathy (DR). Retinal pigment epithelial (RPE) cells are crucial targets for DR initiation following hyperglycaemia. Astragalus polysaccharides (APS) has been long used as a traditional Chinese medicine in treating diabetes. In the present study, the preventive effects and mechanisms of APS on metabolic memory-induced RPE cell death were investigated. Methods: The expressions of miR-204 and SIRT1 were determined by reverse transcription quantitative PCR (RT-qPCR). Dual luciferase assay was applied to detect the potential targeting effects of miR-204 on SIRT1. SIRT1, ER stress and apoptosis related proteins were monitored using Western blotting. Apoptosis was assessed by TUNEL assay and Annexin V/PI staining followed by flow cytometry analysis. MiR-204 mimics and shSIRT1 were applied for miR-204 overexpression and SIRT1 knockdown, respectively. Results: High glucose exposure induced metabolic memory, which was accompanied with sustained dysregulation of miR-204/SIRT1 axis, high level of ER stress and activation of apoptotic pathway even after replacement with normal glucose. Pre-treatment with APS concentration-dependently reversed miR-204 expression, leading to disinhibition of SIRT1 and alleviation of ER stress-induced apoptosis indicated by decreased levels of p-PERK, p-IRE-1, cleaved-ATF6, Bax, cleaved caspase-12, -9, -3, and increased levels of Bcl-2 and unleaved PARP. The effects of APS on RPE cells were reversed by either miR-204 overexpression or SIRT1 knockdown. Conclusions: We concluded that APS inhibited ER stress and subsequent apoptosis via regulating miR-204/SIRT1 axis in metabolic memory model of RPE cells.

Protective Effects of Astragalus Polysaccharide on Sepsis-Induced Acute Kidney Injury

“…It has been suggested that sepsis is related to endoplasmic reticulum activation, that is, the disorder of intracellular homeostasis caused by sepsis can destroy the homeostasis of the endoplasmic reticulum, thereby causing ERS [ 25 , 27 ]. Previous studies have found that APS can inhibit ERS by regulating the miR-204/SIRT1 axis of retinal pigment epithelial cells [ 28 ]. The results of this study show that LPS can induce ERS in HK-2 cells and increase the expression of ERS-related markers CHOP and GRP78, while APS pretreatment inhibited the increase of mRNA and protein expression of CHOP and GRP78 in HK-2 cells.…”

Mitochondrial Ceramide Effects on the Retinal Pigment Epithelium in Diabetes

“…These effects have been shown to occur in animal models as well as in cell culture models. Cells isolated from diabetic donor retinas or animal models retain their diabetic metabolic phenotype for several passages [40][41][42][43][44][45]. Human control and diabetic donor cells were previously shown to display metabolic memory characteristics right after the isolation and for up to eight passages [40].…”

Roles and Therapeutic Implications of Endoplasmic Reticulum Stress and Oxidative Stress in Cardiovascular Diseases

“…Evidence shows that ER stress contributes to endothelial cell inflammatory responses and apoptosis in diabetic retinopathy [ 95 , 96 ]. In streptozotocin (STZ)-induced type 1 diabetic mice, retinal inflammation and vascular leakage are attributed to ATF4 activation of STAT3 [ 97 , 98 ].…”