Pharmaceutical induction of PGC-1α protects retinal pigment epithelium from oxidative stress

Abstract

Purpose : Retinal pigment epithelium (RPE) dysfunction due to accumulation of reactive oxygen species and oxidative damage is a key event in the development of age-related macular degeneration (AMD). Our group has previously shown that PGC-1α, a critical regulator of mitochondrial function, promotes RPE oxidative metabolism and that PGC-1α overexpression decreases RPE sensitivity to from AMD-associated pro-oxidants. Here, we examine the therapeutic potential of ZLN005, a selective PGC-1α transcriptional regulator, in protecting RPE from cytotoxic oxidative damage.

Methods : Lentiviral delivery of shRNA specific to human PGC-1α was used to silence its expression in ARPE-19 (shPGC-1a). Non-silencing shRNA was used as the negative control (shControl). LDH assays were used to quantify cell death. Changes in mitochondrial function was measured with the Seahorse extracellular flux analyzer. Quantitative PCR was performed to measure changes in gene expression. Cells were treated with 10mM of ZLN005 for 24 hours. Oxidative stress was induced by exposure to H₂O₂ (1mM for 18 hours) and NaIO₃ (2.5mg/ml for 24 hours) under serum-free conditions.

Results : ZLN005 robustly protects ARPE19 cells from cell death caused by H₂O₂ (p=1.18x10^-5, n=12) and NaIO₃ (p=5.27x10^-5, n=12) without exhibiting any cytotoxicity under basal conditions (p=0.64, n=24, compared to the vehicle control). Gene expression analysis on ARPE-19 cells treated with ZLN005 shows robust upregulation of PGC-1α (p=0.0004, N=6), its associated anti-oxidant transcription factors (ESSRA, NFE2L2, FOXO3, p < 0.05, n=6), enzymes (CAT p<0.05, GPX1, TXN2 p<0.01 and SOD2 p<0.001, n=6), and mitochondrial dynamics (FIS1 p<0.01, n=6) genes. In addition, energetic profiling shows that ZLN005 treatment also enhances mitochondrial function by increasing maximal respiration (p<0.01, n=4). To demonstrate that ZLN005 protective effects depend on PGC-1α expression, we showed that while ZLN005 treatment protects shControl cells (p=7.16x10^-6, n=12) against exposed to H₂O₂-induced cell death, this effect was loss in PGC1α-silenced cells (p=0.81, n=6).

Conclusions : Our data indicates that ZLN005 efficiently protects RPE cells from oxidative damage through selective induction of PGC-1α and its target anti-oxidant enzymes. ZLN005 may serve as a novel therapeutic agent for retinal diseases associated with RPE dystrophies.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.