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Kyle Trudeau, Anthony J. Molina, Sayon Roy; High Glucose Affects Mitochondrial Metabolic Capacity and Extracellular Acidification in Retinal Pericytes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3566.
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Mitochondrial dysfunction plays a significant role in diabetic retinopathy; however it is unknown if high glucose (HG) affects mitochondrial metabolic capacity and apoptosis in retinal pericytes, and whether cells enact any compensatory mechanism. To investigate HG effects on mitochondrial metabolic capacity and apoptosis in bovine retinal pericytes (BRPs), we assessed cellular oxygen consumption, mitochondrial membrane potential (MMP), extracellular acidification, terminal dUTP nick-end labeled (TUNEL) cells, and mitochondrial content.
To assess HG-induced changes in mitochondrial metabolic capacity, BRPs grown for 7 days in normal or HG conditions were measured for rates of oxygen consumption and extracellular acidification by XF24 bioenergetic assay. Changes in MMP were analyzed in cells grown for 7 days in normal or HG using differential staining and live cell imaging through confocal microscopy. To assess mitochondrial content of RRECs grown in N or HG medium for 7 days, whole cell extract was assessed for VDAC1 expression by Western blot, while apoptosis was measured by TUNEL assay.
BRPs exposed to HG for 7 days showed significantly decreased steady state oxygen consumption level (36.2 vs. 50.0 pmol O2/min/million cells, p<0.05); the maximal oxygen consumption measured by sequential injection of oligomycin and FCCP was also significantly reduced in BRPs exposed to HG (88.1 vs. 132 pmol O2/min/million cells, p<0.05). A significant decrease in MMP was observed for BRPs grown in HG (84 ± 11% of control, p<0.05). BRPs grown in HG for 7 days displayed a significant decrease in extracellular acidification (60.5±24% of control, p<0.05), and VDAC1 expression was not altered. Finally, BRPs grown in HG for 7 days showed greater number of TUNEL-positive cells (243±63% of control, p<0.01).
The findings suggest that in retinal pericytes, HG decreases mitochondrial metabolic capacity without change in mitochondrial content, and that pericytes exhibit weak compensatory response to the decrease in mitochondrial metabolic capacity. The results provide mechanistic insight into mitochondrial dysfunction underlying pericyte loss in diabetic retinopathy.
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