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Rui Cheng, Kelu Zhou, Jian-Xing (Jay) Ma; PPARalpha is required for RPE metabolism and function. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1184. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear receptor regulating metabolism. We previously identified a role for PPARα in protecting retinal neurons. However, the function of PPARα in RPE cells remains unknown. This study is designed to test if PPARα is essential for RPE metabolism and function.
Fundus photographs from PPARα-deficient (Pparα-/-) and wild-type (Wt) mice were captured with the Micron IV system. RPE morphology was determined by phalloidin staining. Phagocytosis of RPE was quantified with an antibody against rhodopsin. Cell migration was evaluated by Transwell migration assay. Barrier function was assessed by transepithelial resistance (TER). Subretinal activated microglia/macrophages (MG/Mφ) were quantified using anti-iba1 staining. Mitochondrial respiratory activities were measured using the XF96 analyzer. Mitochondrial morphology was analyzed by the immunostaining using an anti-TOM20 antibody. Protein levels were determined by Western blot analysis.
Pparα-/-RPE flat-mount showed decreased cell sizes in the central RPE while enlarged cell sizes in the peripheral region. RPE cell loss was identified on Pparα-/- RPE flat-mounts. PPARα deficiency resulted in impaired cell migration, increased RPE permeability and declined phagocytosis activity of RPE. Fenofibric acid, a PPARα agonist, significantly increased the total amounts of (bound plus internal) rod outer segments in APRE-19 cells. Six-month-old Pparα-/- mice developed multiple spots in the fundus. A dramatically increased number of subretinal Iba1+ MG/Mφ was detected in 4-month-old Pparα-/-mice. Levels of C-reactive protein were significantly increased in Pparα-/- eyecup including RPE and choroid, suggesting inflammation in Pparα-/- RPE. Primary Pparα-/-RPE cells and PPARα knocking-down (KD) APRE-19 cells showed declined mitochondrial oxygen consumption rates, ATP turnover, and spare respiratory capacity, compared with control cells. PPARα KD also inhibited mitochondrial complex I- or II-mediated respiratory activity in ARPE-19 cells, without changing COXIV levels, suggesting that PPARα KD affected the mitochondrial function at Complex I and II. PPARα KD resulted in mitochondrial fragmentation by enhancing mitochondrial levels of Fis1, indicating altered mitochondrial dynamics in ARPE19 cells.
Endogenous PPARα is essential for RPE metabolism and function through modulation of mitochondrial dynamics.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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