WITHDRAWN: GRP75 modulates endoplasmic reticulum-mitochondria coupling and accelerates Ca 2+ -dependent endothelial cells apoptosis in diabetic retinopathy

Abstract

Background Endoplasmic reticulum (ER) and mitochondrial dysfunction play fundamental roles in the pathogenesis of diabetic retinopathy (DR). The communication between the mitochondria and the ER is mediated by a functional subdomain referred to as the mitochondria-associated membrane (MAM). However, the mechanism underlying material exchange between the ER and mitochondria are poorly understood. This study aimed to explore the role of IP3R1-GRP75-VDAC1 axis in modulating Ca2+ homeostasis in RMECs. Methods In this study, we established high glucose (HG) and advanced glycosylation end products (AGEs)-induced human retinal vascular endothelial cells (RMECs) models in vitro, and streptozotocin (STZ)-induced DR model in vivo. CCK8 assay and Calcein-AM/PI double stain were used to detect cell viability.The ER-Tracker Red Kit and MitoTracker-Green are used to co-localize ER and mitochondria. Mitochondrial Ca2+ was detected using Rhod-2 AM. Co-immunoprecipitation (co-IP) was used to examine the interaction between IP3R1, GRP75 and VDAC1. MitoSOX™ Red Probe, mPTP Assay, and JC-1 Assay are used to measure mitochondrial function. Evans blue dye, retinal PAS staining, and TUNEL assay were used to assess retinal function. Results Our data demonstrated that there was increased ER-mitochondria coupling in the RMECs, which was accompanied by elevated mitochondrial calcium ions (Ca2+) and mitochondrial dysfunction (mitochondrial membrane potential, ΔΨm; and mitochondrial ROS) under HG or AGEs transferred ER Ca2+ into the mitochondria. Elevated mitochondrial Ca2+ concentrations led to an increase in mitochondrial ROS and a decline in mitochondrial membrane potential. These events resulted in mitochondrial dysfunction and elevation of mitochondrial permeability, which induced cytoplasmic Cyt c/Caspase-3-mediated cell apoptosis. The above phenomenon was reversed by BAPTA-AM (an intracellular calcium chelator) and tunicamycin (TUN), a common ERS inducer. In addition, 4-PBA, (an ERS inhibitor), was shown to reverse retinal dysfunction in STZ-induced DR rats. Conclusions Our findings demonstrated that DR fuels the formation of ER-mitochondria coupling via the IP3R1-GRP75-VDAC1 axis, which facilitates transport of Ca2+ from the ER to the mitochondria, eventually leading to mitochondrial dysfunction and apoptosis of endothelial cells. Our results demonstrated that inhibition of ER-mitochondrial coupling, including inhibition of GRP75 or Ca2+ overload, may be a potential therapeutic target in DR.

Phenotypic age and biological age mediate the association between Life's Essential 8 and diabetic retinopathy among US adults

“…As a result of diabetes, many metabolic changes occur within the cell, leading to an increased level of oxidative stress, which may contribute to the regression of telomere length [45] . There was also an association between DR and increased oxidative stress and activation of proin ammatory signaling pathways [19,46] . As a result of chronic hyperglycemia induces a set of metabolic abnormalities that enhance ROS generation and ultimately lead to oxidative stress in the retina, resulting in retinal cell apoptosis and irregular function of the retina [47] .…”

“…The occurrence of age-related cardiovascular events is in uenced by several aging biomarkers, including telomere length, DNA methylation age, somatic cell mutations, and in ammatory markers [16] . Research progress has indicated that a number of factors contribute to the pathogenesis of DR, including senescence-associated secretory phenotypes, advanced glycation end products, oxidative stress on the endoplasmic reticulum, and impaired autophagy [17][18][19] . CVH is an appropriate prevention and management strategy for reducing the burden of DR due to its close association with established cardiovascular disease (CVD) risk factors.…”