Abstract
Abstract: :
Purpose: To characterize changes in nuclear gene expression induced by mitochondrial (MT) dysfunction in retinal pigment epithelial cells. Methods: ARPE19 cells were depleted of mitochondrial DNA by passaging cells in 50 nM ethidium bromide. RNA was isolated and quantitative real time RT–PCR was used to measure changes in the expression of approximately 120 nuclear genes involved in glycolytic, TCA, peroxisomal, mitochondrial biogenesis extracllular matrix, transcriptional activation and stress response pathways. Changes in nuclear gene expression were measures against that of PPIA (Cyclophillin A) as a housekeeping gene. Results: MT–DNA minus (rho0) ARPE19 cannot respire normally and exhibit a decreased growth rate, increased lactic acidosis in culture, reduced mitochondrial membrane potential and an inability to grow in the absence of pyruvate and uridine when compared to untreated controls. A number of genes showed significantly significant expression differences when compared to the untreated control cells. These included genes in the glycolytic, TCA and stress response pathways. Changes in nuclear gene expression included induction of glycolysis pathway genes GLUT1 and ENO1, induction of SDHA and PC, induction of the stress genes HSF1, HMOX1, SOD2, IGF1, VEGFa and PPARγ, increases in the extracellular matrix genes COL1A1 and LAMB1, and a decreased expression of COL4A1 and CAT (catalase). Conclusion: The results indicate that the RPE cell responds to disruptions in mitochondrial energy metabolism by increases in gene expression to compensate for loss of MT function and also by the induction of stress genes. This approach should be useful in explaining changes in phenotypes brought on by mitochondrial gene dysfunction from mutations or deletions in RPE mitochondrial DNA such as those seen in LHON and Kearns–Sayre syndrome and may explain some of the clinical changes seen in the RPE due to aging where loss of MT function due to oxidative damage to MT–DNA is presumed. Commercial Relationship: M.V. Miceli, None; S.M. Jazwinski, None.
Keywords: age–related macular degeneration • retinal pigment epithelium • gene/expression