All-trans-retinal (atRAL)-induced photoreceptor atrophy and retinal degeneration are hallmark features of dry age-related macular degeneration (AMD) and Stargardt disease type 1 (STGD1). The toxicity of atRAL is closely related to the generation of reactive oxygen species (ROS). Quercetin, a natural product, is known for its potent antioxidant properties; however, its effects in mitigating atRAL-mediated retinal damage remains unclear. This study investigated the protective effects of quercetin against atRAL-induced photoreceptor damage. Using atRAL-loaded 661W photoreceptor cells, we evaluated cell viability, ROS generation, and endoplasmic reticulum (ER) stress under quercetin treatment. Quercetin significantly restored the cell viability (to 70%) and reduced ROS generation in atRAL-treated 661W cells. Additionally, Western blot analysis demonstrated that quercetin mitigated protein kinase RNA-like ER kinase (PERK) signaling, preventing ER stress-induced apoptosis. Importantly, in Abca4^−/−Rdh8^−/− mice, an animal model of light-induced atRAL accumulation in the retina, quercetin treatment effectively alleviated light-exposed photoreceptor atrophy and retinal degeneration by attenuating PERK signaling. Thus, quercetin protected photoreceptor cells from atRAL-induced damage by inhibiting ROS generation and PERK signaling, which suggests its potential as a therapeutic agent for atRAL-related retinal degeneration.

Background Type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) are prevalent metabolic disorders with overlapping pathophysiological mechanisms. A comprehensive understanding of the shared molecular pathways involved in these conditions can advance the development of effective therapeutic interventions. Methods We used two datasets sourced from the Gene Expression Omnibus (GEO) database to identify common differentially expressed genes (DEGs) between T2D and NAFLD. Subsequently, we conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to identify the enriched biological processes and signaling pathways. In addition, we performed a protein-protein interaction (PPI) network analysis to identify hub genes with pivotal roles. To validate our findings, we established a type 2 diabetic mouse model with NAFLD. Results Our analysis identified 53 DEGs shared between T2D and NAFLD. Enrichment analysis revealed their involvement in signal transduction, transcriptional regulation, and cell proliferation as well as in the ferroptosis signaling pathways. PPI network analysis identified ten hub genes, namely CD44, CASP3, FYN, KLF4, HNRNPM, HNRNPU, FUBP1, RUNX1, NOTCH3, and ANXA2. We validated the differential expression of FYN, HNRNPU, and FUBP1 in liver tissues of a type 2 diabetic mouse model with NAFLD. Conclusions Our study offers valuable insights into the shared molecular mechanisms underlying T2D and NAFLD. The identified hub genes and pathways present promising prospects as therapeutic targets to address these prevalent metabolic disorders.

Age-related macular degeneration (AMD) is a common disease contributing to vision loss in the elderly. All-trans-retinal (atRAL) is a retinoid in the retina, and its abnormal accumulation exhibits toxicity to the retina and promotes oxidative stress-induced photoreceptor degeneration, which plays a crucial role in AMD progression. Crocin is a natural product extracted from saffron, which displays significant antioxidant and anti-inflammatory effects. The present study elucidates the protective effects of crocin on photoreceptor cell damage by atRAL and its potential mechanisms. The results revealed that crocin significantly attenuated cytotoxicity by repressing oxidative stress, mitochondrial injury, and DNA damage in atRAL-loaded photoreceptor cells. Moreover, crocin visibly inhibited DNA damage-induced apoptosis and gasdermin E (GSDME)-mediated pyroptosis in photoreceptor cells after exposure to atRAL. It was also observed that crocin distinctly prevented an increase in Fe²⁺ levels and lipid peroxidation caused by atRAL via suppressing the Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor-erythroid 2-related factor 2 (NRF2)/heme oxygenase-1 (HO-1) signaling pathway, thereby ameliorating photoreceptor cell ferroptosis. In short, these findings provide new insights that crocin mitigates atRAL-induced toxicity to photoreceptor cells by inhibiting oxidative stress, apoptosis, pyroptosis, and ferroptosis.

Impaired clearance of all-trans-retinal (atRAL) during the visual cycle leads to retinal degeneration, which is closely associated with autosomal recessive Stargardt disease (STGD1) and dry age-related macular degeneration (dry AMD). Transient activation of activating transcription factor 4 (ATF4) generally supports cellular adaptation to stress, whereas excessive ATF4 expression or prolonged activation can become maladaptive and promote oxidative and metabolic disturbances. Here, we reported that activation of ATF4 promoted atRAL-induced photoreceptor damage through mitochondria-caspase/DNA damage-dependent apoptosis and gasdermin E (GSDME)-dependent pyroptosis and apoptosis, and identified ATF4 as an upstream transcriptional regulator of GSDME. Genetic ablation of Atf4 or pharmacological attenuation of ATF4 signaling with the integrated stress response inhibitor ISRIB visibly preserved the viability and morphology of atRAL-treated 661W cone photoreceptor cells. Both interventions lowered GSDME N-terminal fragment (GSDME-N) abundance, decreased intracellular and mitochondrial reactive oxygen species (ROS) production, and blunted damage to mitochondria and DNA. Notably, pharmacologically suppressing ATF4 expression in the neural retina effectively prevented retinal function loss and structural injury as well as photoreceptor apoptosis and pyroptosis in light-exposed Abca4^−/−Rdh8^−/− mice, which exhibit severe defects in atRAL clearance and recapitulate key features of STGD1 and dry AMD. Our findings demonstrate that ATF4 is a critical mediator of atRAL-induced retinal atrophy, suggesting that ATF4 inhibition represents a promising therapeutic strategy for STGD1 and dry AMD.