Identification of PGC-1β as novel stress response target in neovascular AMD

Abstract

Purpose : Mitochondrial-induced oxidative stress and choroidal neovascularization play a key role in AMD pathogenesis. Expression of PGC-1β, a master regulator of oxidative metabolism, in RPE was reported to be positively associated with neovascular AMD. However, the unique pathologic function of PGC-1β in RPE is unclear. We hypothesize that PGC-1β promotes AMD progression by altering RPE oxidative stress response and anti-angiogenic profile.

Methods : Matured ARPE-19s were exposed to H₂O₂, NaIO₃, oxLDL or TNFα to induce oxidative damage or activate NFkB. PGC-1β induction was controlled by infection with a Tet-responsive adenovirus (Ad-TetOn-PGC1B) and exposure to doxycycline (Dox). Reactive oxygen species (ROS) were measured with CellSox or MitoSox. RelB and PGC-1β were silenced with siRelB or Ad-shPGC1B. Choroid/RPE explants from C57bl/6J mice were infected with Ad-TetOn-PGC1B or cultured with conditional medium from PGC-1β expressing cells and the vascular sprouting area was quantified by ImageJ. Overexpression of PGC-1β in the RPE of adult WT mice was performed using a lentiviral delivery method followed by phenotypic analysis.

Results : PGC-1β expression in RPE was specifically induced by oxidative (H₂O₂, NaOI₃) and inflammatory (oxLDL, TNFα) stimuli. Silencing of the non-canonical NFkB pathway with siRelB blocked TNFα-dependent induction of PGC-1β (P<0.05). Physiological induction of PGC-1β (6.4 folds protein level, P<0.0001) in Ad-TetOn-PGC1B infected ARPE-19 treated with 20 ng/ml Dox promoted the accumulation of cytoplasmic (25%, P<0.01) and mitochondrial (300%, P<0.0001) ROS without increasing cell death. PGC-1β increased NaIO₃-dependent cell death (1.5 folds, P<0.001). Conversely, PGC-1β silencing decreased NaIO₃-induced mitoROS (71%, P<0.01) and cell death (53%, P<0.01). Both PGC-1β gene augmentation and conditional medium from PGC-1β expressing ARPE-19 significantly augmented vascular sprouting (1.5 folds, P<0.05 and 9.2 folds, P<0.001, respectively) from choroid explants by altering the RPE secretome. RPE-specific overexpression of PGC-1β in adult mice promotes a rapid degeneration of the RPE and choroidal remodeling leading to spontaneous neovascular lesions in a subset of animals.

Conclusions : Our findings identify PGC-1β as a novel mediator of RPE oxidative and inflammatory stress response promoting cellular dysfunction and choroidal neovascularization.

This is a 2020 ARVO Annual Meeting abstract.