bims-mideyd 2025-02-23 papers

Cell Mol Biol Lett. 2025 Feb 21. 30(1): 22

Exposure of A2E to blue light promotes ferroptosis in the retinal pigment epithelium.

Bo Yang, Kunhuan Yang, Yuling Chen, Qingjian Li, Jingmeng Chen, Shiying Li, Yalin Wu.

BACKGROUND: Age-dependent accumulation of lipofuscin in the retinal pigment epithelium (RPE) is closely related to the etiology of autosomal recessive Stargardt's disease (STGD1) and dry age-related macular degeneration (AMD). N-retinylidene-N-retinylethanolamine (A2E) is a leading component of RPE lipofuscin that is highly susceptible to blue light. Ferroptosis is an iron-dependent form of non-apoptotic cell death characterized by the accumulation of lipid peroxides to a lethal level, which plays an important role in retinal diseases. However, it remains unknown whether A2E functions as a physiological trigger for eliciting blue light-induced ferroptosis of RPE cells.
METHODS: A2E-loaded RPE cells and Abca4-/-Rdh8-/- mice were exposed to blue light, respectively. Western blotting, immunofluorescence staining, reactive oxygen species (ROS) staining, intracellular iron staining, lipid peroxidation staining, fundus imaging, optical coherence tomography (OCT), hematoxylin-eosin (HE) staining, and electroretinography (ERG) were utilized to elucidate the role of blue light in A2E induced ferroptosis in the RPE and its potential mechanisms.
RESULTS: Exposure of A2E to blue light promoted ferroptotic cell death in RPE cells by elevating ferrous ion (Fe2+) levels and inhibiting the solute carrier family 7 membrane 11 (SLC7A11)-glutathione (GSH)-glutathione peroxidase 4 (GPX4) axis. GPX4 inactivation and ROS generated by Fe2+ overload and GSH depletion precipitated lipid peroxidation and subsequent ferroptosis in A2E-containing RPE cells upon exposure to blue light. In addition to GSH supplement, repressing either Fe2+ by deferiprone (DFP) or lipid peroxidation with ferrostatin-1 (Fer-1) significantly protected RPE cells against ferroptosis caused by blue light illumination of A2E. Abca4-/-Rdh8-/- mice featured by an accelerated deposition of A2E in the RPE is an animal model for STGD1 and dry AMD. It was observed that ferroptosis was indeed present in the RPE of Abca4-/-Rdh8-/- mice following exposure to blue light. Notably, alleviating ferroptosis by intraperitoneally injected Fer-1 effectively rescued retinal function and ameliorated RPE/photoreceptor degeneration in blue light-exposed Abca4-/-Rdh8-/- mice.
CONCLUSIONS: Our results suggest the importance of blue light in A2E-mediated ferroptosis in the RPE, and deeply broaden the understanding of mechanisms underlying RPE atrophy arising from lipofuscin accumulation in STGD1 and dry AMD.

Keywords: A2E; Blue light; Ferroptosis; Lipofuscin; Macular degeneration; Retinal pigment epithelium

DOI: https://doi.org/10.1186/s11658-025-00700-2

bioRxiv. 2025 Jan 28. pii: 2025.01.27.635096. [Epub ahead of print]

Cigarette smoke and biological age induce degenerative heterogeneity in retinal pigment epithelium.

Krishna Singh, Yang Jin, Ming-Wen Hu, Isabella Palazzo, Marisol Cano, Thanh Hoang, Imran Bhutto, Shusheng Wang, Debasish Sinha, Seth Blackshaw, Jiang Qian, James T Handa.

Environmental exposure such as cigarette smoke induces epigenetic changes that can induce degenerative heterogeneity and accelerate aging. In early age-related macular degeneration (AMD), the leading worldwide cause of blindness among the elderly, retinal pigment epithelial (RPE) cell heterogeneity is a key change. Since smoking is the strongest environmental risk factor for AMD, we hypothesized that cigarette smoke induces degenerative RPE heterogeneity through epigenetic changes that are distinct from aging, and that with aging, the RPE becomes vulnerable to cigarette smoke insult. We administered cigarette smoke condensate (CSC) intravitreally to young and aged mice and performed snRNA-seq and snATAC-seq on the RPE/choroid. This analysis identified separate cell clusters corresponding to healthy and abnormal, dedifferentiated RPE in both aged vehicle-treated and young CSC-treated mice. The dedifferentiated RPE were characterized by a global decrease in chromatin accessibility and decreased expression of genes in functional categories that were linked to hallmarks of aging. Notably, young, dedifferentiated RPE also exhibited a compensatory upregulation of hallmarks of aging-related genes, specifically those related to mitochondrial function and proteostasis. In contrast, aged dedifferentiated RPE did not express these compensatory changes, and did not survive CSC treatment, as experimentally verified with TUNEL labeling. These changes are relevant to early AMD because we identified through scRNA-seq, similar dedifferentiated and healthy macular RPE clusters in a donor who smoked and another with early AMD, but not from a nonsmoker. Degenerative cellular heterogeneity can include an abnormal cluster that jeopardizes cell survival and may represent an additional hallmark of ocular aging.

DOI: https://doi.org/10.1101/2025.01.27.635096

Front Immunol. 2025 ;16 1527018

The AMD-associated genetic polymorphism CFH Y402H confers vulnerability to Hydroquinone-induced stress in iPSC-RPE cells.

Angela Armento, Inga Sonntag, Ana-Cristina Almansa-Garcia, Merve Sen, Sylvia Bolz, Blanca Arango-Gonzalez, Ellen Kilger, Ruchi Sharma, Kapil Bharti, Rosario Fernandez-Godino, Berta de la Cerda, Simon J Clark, Marius Ueffing.

Introduction: Age-related macular degeneration (AMD), a degenerative disease of the macula, is caused by an interplay of diverse risk factors (genetic predisposition, age and lifestyle habits). One of the main genetic risks includes the Y402H polymorphism in complement Factor H (FH), an inhibitor of complement system activation. There has been, and continues to be, much discussion around the functional consequences of this Y402H polymorphism, whether the soluble FH protein confers its risk association, or if the cells expressing the protein themselves are affected by the genetic alteration. In our study, we examined the cell characteristics of the retinal pigment epithelium (RPE) cells, which play a major role in retinal homeostasis and stability and which are synonymously linked to AMD.
Methods: Here, we employ RPE cells derived from induced pluripotent stem cells (iPSC) generated from donors, carrying either homozygous 402Y (low risk) or 402H (high risk) variants of the CFH gene. RPE cells were treated with Hydroquinone (HQ), a component of cigarette smoke, to induce oxidative damage.
Results: Intriguingly, RPE cells carrying high genetic risk proved more vulnerable to oxidative insult when exposed to HQ, as demonstrated by increased cytotoxicity and caspase activation, compared to the low-risk RPE cells. The exposure of RPE cells to RPE conditioned medium, normal human serum (NHS) and inactivated NHS (iNHS) had minimal impact on cell cytotoxicity and caspase activation, nor did the presence of purified soluble FH rescue the observed effects. Considering the known connection of oxidative stress to proteotoxic stress and degrading processes, we investigated the unfolded protein response (UPR) and autophagy. When exposed to HQ, RPE cells showed an increase in autophagy markers; however, iPSC-RPE cells carrying high genetic risk showed an overall reduced autophagic flux.
Discussion: Our findings suggest that the degree of cellular susceptibility to oxidative stress is not conferred by soluble FH protein and other complement sources, but intercellularly because of the corresponding genetic risk predisposition. Our data support the hypothesis that RPE cells carrying high genetic risk are less resilient to oxidative stress.

Keywords: age-related macular degeneration (AMD); autophagy; complement factor H (CFH); oxidative stress; retinal pigment epithelium (RPE) cells

DOI: https://doi.org/10.3389/fimmu.2025.1527018

Aging Cell. 2025 Feb 17. e70018

Activated mTOR Signaling in the RPE Drives EMT, Autophagy, and Metabolic Disruption, Resulting in AMD-Like Pathology in Mice.

The mechanistic target of rapamycin (mTOR) complexes 1 and 2 (mTORC1/2) are crucial for various physiological functions. Although the role of mTORC1 in retinal pigmented epithelium (RPE) homeostasis and age-related macular degeneration (AMD) pathogenesis is established, the function of mTORC2 remains unclear. We investigated both complexes in RPE health and disease. Therefore, in this study, we have attempted to demonstrate that the specific overexpression of mammalian lethal with Sec13 protein 8 (mLST8) in the mouse RPE activates both mTORC1 and mTORC2, inducing epithelial-mesenchymal transition (EMT)-like changes and subretinal/RPE deposits resembling early AMD-like pathogenesis. Aging in these mice leads to RPE degeneration, causing retinal damage, impaired debris clearance, and metabolic and mitochondrial dysfunction. Inhibition of mTOR with TORIN1 in vitro or βA3/A1-crystallin in vivo normalized mTORC1/2 activity and restored function, revealing a novel role for the mTOR complexes in regulating RPE function, impacting retinal health and disease.

Keywords: RPE; epithelial–mesenchymal transition; mLST8; mTOR complex 1; mTOR complex 2; metabolic/mitochondrial changes

DOI: https://doi.org/10.1111/acel.70018