Ferroptosis drives photoreceptor degeneration in mice with defects in all-trans-retinal clearance

Abstract

The death of photoreceptor cells in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt disease (STGD1) is closely associated with disruption in all- trans -retinal (atRAL) clearance in neural retina. In this study, we reveal that the overload of atRAL leads to photoreceptor degeneration through activating ferroptosis, a nonapoptotic form of cell death. Ferroptosis of photoreceptor cells induced by atRAL resulted from increased ferrous ion (Fe 2+ ), elevated ACSL4 expression, system Xc − inhibition, and mitochondrial destruction. Fe 2+ overload, tripeptide glutathione (GSH) depletion, and damaged mitochondria in photoreceptor cells exposed to atRAL provoked reactive oxygen species (ROS) production, which, together with ACSL4 activation, promoted lipid peroxidation and thereby evoked ferroptotic cell death. Moreover, exposure of photoreceptor cells to atRAL activated COX2, a well-accepted biomarker for ferroptosis onset. In addition to GSH supplement, inhibiting either Fe 2+ by deferoxamine mesylate salt (DFO) or lipid peroxidation with ferrostatin-1 (Fer-1) protected photoreceptor cells from ferroptosis caused by atRAL. Abca4 −/− Rdh8 −/− mice exhibiting defects in atRAL clearance is an animal model for dry AMD and STGD1. We observed that ferroptosis was indeed present in neural retina of Abca4 −/− Rdh8 −/− mice after light exposure. More importantly, photoreceptor atrophy and ferroptosis in light-exposed Abca4 −/− Rdh8 −/− mice were effectively alleviated by intraperitoneally injected Fer-1, a selective inhibitor of ferroptosis. Our study suggests that ferroptosis is one of the important pathways of photoreceptor cell death in retinopathies arising from excess atRAL accumulation and should be pursued as a novel target for protection against dry AMD and STGD1.

Gasdermin E mediates photoreceptor damage by all-trans-retinal in the mouse retina

“…Moreover, GSDME-N translocates to the mitochondria where it aggregates and perforates mitochondrial membranes, which in turn accentuates pyroptosis and apoptosis through enhancing Cyt c release and caspase-3 activation. In light of current and previous studies, we conclude that photoreceptor damage by atRAL is bound up with apoptosis(6), ferroptosis (7) and pyroptosis, but is independent of necroptosis. Due to the identification of GSDME but not GSDMD as an executioner of pyroptosis and an amplifier of apoptosis in photoreceptors suffering from atRAL accumulation, GSDME may be an efficient and promising target for the therapy of photoreceptor degeneration in patients with dry AMD and STGD1.…”

“…After being washed by PBS three times, fluorescence micrographs were taken using the Leica DM2500 microscope. TEM TEM analysis of mitochondrial ultrastructures in WT or Gsdme −/− 661W photoreceptor cells incubated with 5-μM atRAL for 6 h was performed as previously described (7).…”

“…The classical visual (retinoid) cycle is a long-known enzymatic pathway which converts all-trans-retinal (atRAL) to 11-cis-retinal in rod and cone photoreceptor outer segments and the adjacent retinal pigment epithelium (RPE) for the regeneration of visual pigments (1)(2)(3). Compromised clearance of atRAL leads to an accumulation of atRAL in the cytosol of photoreceptor outer segments, which has close relation with photoreceptor degeneration in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt's disease (STGD1) (4)(5)(6)(7).…”

“…The classical visual (retinoid) cycle is a long-known enzymatic pathway that converts all- trans -retinal (atRAL) to 11- cis -retinal in rod and cone photoreceptor outer segments (OSs) and the adjacent retinal pigment epithelium (RPE) for the regeneration of visual pigments ( 1 , 2 , 3 ). Compromised clearance of atRAL leads to an accumulation of atRAL in the cytosol of photoreceptor OSs, which has close relation with photoreceptor degeneration in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt’s disease 1 (STGD1) ( 4 , 5 , 6 , 7 ). A key function for both photoreceptor-specific ABC (subfamily A, member 4) transporter (ABCA4) and all- trans -retinol (atROL) dehydrogenase 8 (RDH8) is to satisfactorily eliminate free atRAL in the visual (retinoid) cycle ( 8 , 9 , 10 ).…”

WDR45 Mutation Impairs the Autophagic Degradation of Transferrin Receptor and Promotes Ferroptosis

“…Ferroptosis is a regulated cell death driven by iron-dependent lipid peroxidation ( Dixon et al, 2012 ). Elevated Fe 2+ promotes the generation of lipid peroxidation and ROS ( Chen et al, 2020 ). We found that in WDR45 MT expressing cells, the content of MDA (an end product of lipid peroxidation) and ROS was significantly increased ( Figures 4A,B ).…”