Regulation of Mitochondrial Release of Apoptosis-Inducing Factor Is a Mechanism for Neuroprotective Activity of Pigment Epithelium-Derived Factor in Retinal Degeneration

Abstract

Purpose: : To investigate the mechanism for neuroprotective activity of pigment epithelium-derived factor (PEDF) during photoreceptor apoptosis in animal models of inherited retinal degeneration.

Methods: : Royal College Surgeon (RCS) rats were used and the eyes were treated with lentiviral vector encoding hPEDF gene (SIV-hPEDF). Rat retina-derived cells (R28) were induced apoptosis by serum starvation. Z-VAD-fmk was used to inhibit caspase-dependent pathway. The localization of apoptosis-inducing factor (AIF) was assessed by immunostaining. SiRNA targeting AIF was used to knockdown the mRNA expression.

Results: : PEDF prevented R28 cell apoptosis induced by serum starvation. The cell death remained unchanged by Z-VAD-fmk, whereas that was significantly reversed by knockdown of AIF, a molecule responsible for caspase-independent apoptosis. Nuclear translocation of AIF occurred in the apoptotic R28 cells after serum starvation, and PEDF dramatically prevented the translocation. In RCS rats, AIF translocation was also associated in the apoptotic photoreceptors, and lentiviral-mediated retinal gene transfer of PEDF dramatically prevented AIF translocation, leading to prevention of the apoptotic loss of photoreceptors.

Conclusions: : These findings are clear evidence indicating that AIF is an essential executioner of photoreceptor apoptosis in inherited retinal degeneration, and that neuroprotective gene therapy using PEDF, which targets the mitochondrial AIF release, may be a reasonable therapeutic approach for preventing photoreceptor apoptosis in retinal degenerative diseases.

Keywords: retinal degenerations: hereditary • gene transfer/gene therapy • apoptosis/cell death