Survival or death: a dual role for autophagy in stress-induced pericyte loss in diabetic retinopathy

Abstract

Aims/hypothesisIntra-retinal extravasation and modification of LDL have been implicated in diabetic retinopathy: autophagy may mediate these effects.MethodsImmunohistochemistry was used to detect autophagy marker LC3B in human and murine diabetic and non-diabetic retinas. Cultured human retinal capillary pericytes (HRCPs) were treated with in vitro-modified heavily-oxidised glycated LDL (HOG-LDL) vs native LDL (N-LDL) with or without autophagy modulators: green fluorescent protein–LC3 transfection; small interfering RNAs against Beclin-1, c-Jun NH(2)-terminal kinase (JNK) and C/EBP-homologous protein (CHOP); autophagy inhibitor 3-MA (5 mmol/l) and/or caspase inhibitor Z-VAD-fmk (100 μmol/l). Autophagy, cell viability, oxidative stress, endoplasmic reticulum stress, JNK activation, apoptosis and CHOP expression were assessed by western blots, CCK-8 assay and TUNEL assay. Finally, HOG-LDL vs N-LDL were injected intravitreally to STZ-induced diabetic vs control rats (yielding 50 and 200 mg protein/l intravitreal concentration) and, after 7 days, retinas were analysed for ER stress, autophagy and apoptosis.ResultsIntra-retinal autophagy (LC3B staining) was increased in diabetic vs non-diabetic humans and mice. In HRCPs, 50 mg/l HOG-LDL elicited autophagy without altering cell viability, and inhibition of autophagy decreased survival. At 100–200 mg/l, HOG-LDL caused significant cell death, and inhibition of either autophagy or apoptosis improved survival. Further, 25–200 mg/l HOG-LDL dose-dependently induced oxidative and ER stress. JNK activation was implicated in autophagy but not in apoptosis. In diabetic rat retina, 50 mg/l intravitreal HOG-LDL elicited autophagy and ER stress but not apoptosis; 200 mg/l elicited greater ER stress and apoptosis.ConclusionsAutophagy has a dual role in diabetic retinopathy: under mild stress (50 mg/l HOG-LDL) it is protective; under more severe stress (200 mg/l HOG-LDL) it promotes cell death.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-016-4058-5) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Role of Autophagy in Angiogenesis Induced by a High-Glucose Condition in RF/6A Cells

“…Research showed a substantial increase in autophagic activity in retinal ganglion cells in mice with streptozotocin-induced diabetes, which indicates that cell death develops with the initial dysregulation of autophagy before the appearance of signs of vascular damage and without a strong involvement of apoptosis [27] . Further research revealed that autophagy has a dual role in DR: under mild stress, it is protective for human retinal capillary pericytes, while under more severe stress it promotes cell death [28] . Thus, the concrete mechanisms of autophagy in DR require further investigation.…”

Transthyretin Exerts Pro-Apoptotic Effects in Human Retinal Microvascular Endothelial Cells Through a GRP78-Dependent Pathway in Diabetic Retinopathy

“…These UPR branches coordinate the regulation of protein translation and transcription programs to restore ER homeostasis [35]. Unresolved ER stress activates proapoptotic and proinflammatory genes, such as those encoding CHOP, which contributes to retinal inflammation and vascular dysfunction in ischemic retinopathy and DR [36]. In endothelial cells, activation of the UPR plays a critical role in regulating cell proliferation, apoptosis and angiogenesis [37], and in this pathway, CHOP is a well-characterized marker for the cell transition from ER stress to apoptosis [38,39].…”

Association between miRNAs expression and signaling pathways of oxidative stress in diabetic retinopathy

“…Also, the retina is susceptible to ROS because of high-energy demands and exposure to light (Nita & Grzybowski, 2016 Kowluru, 2008). Therefore, oxidative stress can play an essential role in retinal capillary apoptosis (Fu et al, 2016;Kowluru, 2005).…”