Pathological induction of PGC‐1β by RelB/NF‐κB promotes RPE oxidative damage and choroidal neovascularization
Authors: Saint-Geniez Magali , Cai Siwei , Satish Sangeeta , Senthilkumar Ilakya , Shu Daisy Y. , Butcher Erik , Frank Scott 
Published: April 2020

Mitochondrial dysfunction and oxidative stress play a central role in the onset and progression of numerous age‐associated retinal pathologies such as AMD. Our previous work indicates that the master metabolic regulators, PGC‐1α and PGC‐1β, exert contrasting functions in RPE homeostasis and implicates PGC‐1β as a novel disease‐associated target in AMD. In this study, we characterized the molecular regulation and biological consequences of pathological PGC‐1β induction in RPE. First, we show that PGC‐1β is specifically induced in RPE by AMD‐associated pro‐oxidative and pro‐inflammatory stimuli. NF‐kB is a primary regulator of RPE stress response known to promote RPE dysfunction in AMD. Activation of the NF‐κB pathway by TNFα promotes PGC‐1β expression in RPE. NF‐κB‐dependent transcriptional induction of PGC‐1β was abrogated by silencing of the RelB/NF‐κB non canonical pathway. In order to evaluate the effect of PGC‐1β induction at physiological levels observed in vitro and in humans, we developed an adenoviral Tet‐on expression system able to tightly control PGC‐1β overexpression in RPE. Comparative analysis of PGC‐1β expressing cells (PGC1B‐Dox+) and controls (PGC1B‐Dox− and GFP‐Dox+) shows that physiological PGC‐1β induction promotes mitoROS production and reduces the cells’ anti‐oxidative capacity under both basal and challenged conditions. Conversely, we demonstrate that PGC‐1β silencing protects cells from mitochondrial targeting pro‐oxidants. As recent transcriptome analysis show that PGC‐1β (but not PGC‐1α) expression is increased in neovascular AMD patients compared to unaffected controls, we examined PGC‐1β pro‐angiogenic effect in choroidal neovascularization. Using an ex vivo choroid explant sprouting model, we demonstrate that gene augmentation of PGC1β in RPE significantly enhances choroidal vessels sprouting. A similar pro‐angiogenic effect was observed when explants were exposed to conditioned media from PGC1B‐Dox+ cells but not from PGC1B‐Dox− or GFP‐Dox+ cells. Protein array analysis indicates that PGC‐1β increases the secretion by RPE of pro‐angiogenic factors (PlGF, FGF2, Leptin, HB‐EGF) while repressing anti‐angiogenic ones (Thrombospondin, Endostatin, Angiostatin). Finally, we confirmed our in vitro data by overexpressing PGC‐1β in the RPE of adult mice using a lentiviral delivery method. RPE‐specific expression of PGC‐1β promotes a rapid disorganization and dysfunction of the RPE leading to spontaneous formation of neovascular lesions in the subretinal space. These findings highlight PGC‐1β as a major regulator of RPE stress response and validate human data associating PGC‐1β induction in RPE to neovascular AMD.Support or Funding InformationThis work was funded by donations to the Macular Degeneration Research, a program of the BrightFocus Foundation (MSG), the Grimshaw‐Gudewicz Charitable Foundation (MSG), the Iraty Award (MSG), the China Scholarship Council (SC), and the NEI Core Grant P30EYE003790.