High Glucose Induces Mitochondrial Dysfunction in Retinal Müller Cells: Implications for Diabetic Retinopathy

Abstract

PurposeTo investigate whether high glucose (HG) induces mitochondrial dysfunction and promotes apoptosis in retinal Müller cells.MethodsRat retinal Müller cells (rMC-1) grown in normal (N) or HG (30 mM glucose) medium for 7 days were subjected to MitoTracker Red staining to identify the mitochondrial network. Digital images of mitochondria were captured in live cells under confocal microscopy and analyzed for mitochondrial morphology changes based on form factor (FF) and aspect ratio (AR) values. Mitochondrial metabolic function was assessed by measuring oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) using a bioenergetic analyzer. Cells undergoing apoptosis were identified by differential dye staining and TUNEL assay, and cytochrome c levels were assessed by Western blot analysis.ResultsCells grown in HG exhibited significantly increased mitochondrial fragmentation compared to those grown in N medium (FF = 1.7 ± 0.1 vs. 2.3 ± 0.1; AR = 2.1 ± 0.1 vs. 2.5 ± 0.2; P < 0.01). OCR and ECAR were significantly reduced in cells grown in HG medium compared to those grown in N medium (steady state: 75% ± 20% of control, P < 0.02; 64% ± 22% of control, P < 0.02, respectively). These cells also exhibited a significant increase (∼2-fold) in the number of apoptotic cells compared to those grown in N medium (P < 0.01), with a concomitant increase in cytochrome c levels (247% ± 94% of control, P < 0.05).ConclusionsFindings indicate that HG-induced mitochondrial morphology changes and subsequent mitochondrial dysfunction may contribute to retinal Müller cell loss associated with diabetic retinopathy.

Intraretinal changes in idiopathic versus diabetic epiretinal membranes after macular peeling

“…The combination of intraretinal gliosis and physical traction could result in the formation of CEIFLs [ 15 ]. On the contrary, it has been documented that in diabetic retinopathy there are an inner neuroretinal degeneration prior to micro-vasculopathy [ 24 ] and a high glucose (HG)-induced mitochondrial dysfunction that promotes the apoptosis of Müller cells, compromising their protective role towards neurons [ 25 ]. On the other side, since the Müller cells play an important role in the maintenance of the inner blood retinal barrier (BRB) and in retinal VEGF production [ 26 ], this can contribute to increase vascular permeability.…”

Protective Effect of Astaxanthin on Primary Retinal Cells of the GerbilPsammomys ObesusCultured in DiabeticMilieu

“…In retinal Muller cells, HG promoted mitochondrial dysfunction by inducing mitochondrial morphology changes with concomitant increase in cytochrome c and apoptosis (Tien et al . ).…”

“…Furthermore, evidence indicates that mitochondria are intimately associated with programmed cell death (Green et al 1998;Russell et al 2002). In retinal Muller cells, HG promoted mitochondrial dysfunction by inducing mitochondrial morphology changes with concomitant increase in cytochrome c and apoptosis (Tien et al 2012).…”

Long non-coding RNA nuclear paraspeckle assembly transcript 1 inhibits the apoptosis of retina Müller cells after diabetic retinopathy through regulating miR-497/brain-derived neurotrophic factor axis

“…Müller cells were essential for the maintenance of normal retina function, which supported retinal neurons and blood-retinal barrier. Studies have shown that Müller cell loss induced by apoptosis was one of the basic pathogenesis of DR, which penetrated the course of DR. 27 Both in vivo and in vitro studies confirmed that the diabetic conditions induced the apoptosis of Müller cells. 7 It has been well known that NEAT1 could regulate the downstream molecules and signalling pathways by miR-NAs and thereby influenced cell function or survival.…”