Upregulation of EphA2 is associated with apoptosis in response to H2O2 and UV radiation-induced cataracts.

In this article, we examine the role of erythropoietin-producing hepatocellular receptor A2 (EphA2) in the apoptosis of lens epithelial cells (LECs) in H2O2 and UV radiation-induced cataracts. We treated SRA01/04 cells with H2O2 or ultraviolet (UV) radiation to create a cataract cell model. We constructed a cataract lens model by exposing mice to UV radiation. We used CCK8 assays, Annexin V-FITC analysis, and immunohistochemical staining to explore proliferation and apoptosis of the cataract model. Thereafter, we used quantitative real-time PCR (qPCR) analysis, Western blot assays, and immunofluorescence to determine gene and protein expression levels. We also employed Crispr/Cas9 gene editing to create an EphA2 knockout in SRA01/04 cells. Results: H2O2 or UV radiation induced SRA01/04 cells showed EphA2 gene upregulation. CCK8 and apoptosis assays showed that EphA2 over-expression (OE) reduced epithelial cell apoptosis, but knockout of EphA2 induced it in response to H2O2 and UV radiation, respectively. Mutation of the EphA2 protein kinase domain (c.2003G > A, p. G668D) had a limited effect on cell apoptosis. In vivo, the EphA2 protein level increased in the lenses of UV-treated mice. Our results showed that EphA2 was upregulated in SRA01/04 cells in response to H2O2 and UV radiation. Mutation of the EphA2 protein kinase domain (c.2003G > A, p. G668D) had a limited effect on H2O2 and UV radiation-induced cell apoptosis. We confirmed this change with an experiment on UV-treated mice. The present study established a novel association between EphA2 and LEC apoptosis.

Long-term PM2.5 exposure disrupts corneal epithelial homeostasis by impairing limbal stem/progenitor cells in humans and rat models.

BACKGROUND: Limbal stem/progenitor cells (LSPCs) play a crucial role in maintaining corneal health by regulating epithelial homeostasis. Although PM2.5 is associated with the occurrence of several corneal diseases, its effects on LSPCs are not clearly understood. METHODS: In this study, we explored the correlation between PM2.5 exposure and human limbal epithelial thickness measured by Fourier-domain Optical Coherence Tomography in the ophthalmologic clinic. Long- and short-term PM2.5 exposed-rat models were established to investigate the changes in LSPCs and the associated mechanisms. RESULTS: We found that people living in regions with higher PM2.5 concentrations had thinner limbal epithelium, indicating the loss of LSPCs. In rat models, long-term PM2.5 exposure impairs LSPCs renewal and differentiation, manifesting as corneal epithelial defects and thinner epithelium in the cornea and limbus. However, LSPCs were activated in short-term PM2.5-exposed rat models. RNA sequencing implied that the circadian rhythm in LSPCs was perturbed during PM2.5 exposure. The mRNA level of circadian genes including Per1, Per2, Per3, and Rev-erbα was upregulated in both short- and long-term models, suggesting circadian rhythm was involved in the activation and dysregulation of LSPCs at different stages. PM2.5 also disturbed the limbal microenvironment as evidenced by changes in corneal subbasal nerve fiber density, vascular density and permeability, and immune cell infiltration, which further resulted in the circadian mismatches and dysfunction of LSPCs. CONCLUSION: This study systematically demonstrates that PM2.5 impairs LSPCs and their microenvironment. Moreover, we show that circadian misalignment of LSPCs may be a new mechanism by which PM2.5 induces corneal diseases. Therapeutic options that target circadian rhythm may be viable options for improving LSPC functions and alleviating various PM2.5-associated corneal diseases.

Acute and continuous exposure of airborne fine particulate matter (PM2.5): diverse outer blood-retinal barrier damages and disease susceptibilities.

BACKGROUND: The association between air pollution and retinal diseases such as age-related macular degeneration (AMD) has been demonstrated, but the pathogenic correlation is unknown. Damage to the outer blood-retinal barrier (oBRB), which consists of the retinal pigment epithelium (RPE) and choriocapillaris, is crucial in the development of fundus diseases. OBJECTIVES: To describe the effects of airborne fine particulate matter (PM2.5) on the oBRB and disease susceptibilities. METHODS: A PM2.5-exposed mice model was established through the administration of eye drops containing PM2.5. Optical coherence tomography angiography, transmission electron microscope, RPE immunofluorescence staining and Western blotting were applied to study the oBRB changes. A co-culture model of ARPE-19 cells with stretching vascular endothelial cells was established to identify the role of choroidal vasodilatation in PM2.5-associated RPE damage. RESULTS: Acute exposure to PM2.5 resulted in choroidal vasodilatation, RPE tight junctions impairment, and ultimately an increased risk of retinal edema in mice. These manifestations are very similar to the pachychoroid disease represented by central serous chorioretinopathy (CSC). After continuous PM2.5 exposure, the damage to the RPE was gradually repaired, but AMD-related early retinal degenerative changes appeared under continuous choroidal inflammation. CONCLUSION: This study reveals oBRB pathological changes under different exposure durations, providing a valuable reference for the prevention of PM2.5-related fundus diseases and public health policy formulation.

CHAC1 as a Novel Contributor of Ferroptosis in Retinal Pigment Epithelial Cells with Oxidative Damage.

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the elderly population. With aging and the accumulated effects of environmental stress, retinal pigment epithelial (RPE) cells are particularly susceptible to oxidative damage, which can lead to retinal degeneration. However, the underlying molecular mechanisms of how RPE responds and progresses under oxidative damage are still largely unknown. Here, we reveal that exogenous oxidative stress led to ferroptosis characterized by Fe2+ accumulation and lipid peroxidation in RPE cells. Glutathione specific gamma-glutamylcyclotransferase 1 (Chac1), as a component of the unfolded protein response (UPR) pathway, plays a pivotal role in oxidative-stress-induced cell ferroptosis via the regulation of glutathione depletion. These results indicate the biological significance of Chac1 as a novel contributor of oxidative-stress-induced ferroptosis in RPE, suggesting its potential role in AMD.

Characterization of mechanical stress in the occurrence of cortical opacification in age-related cataracts using three-dimensional finite element model of the human lens and RNA-seq.

Cataract is the leading cause of blindness across the world. Age-related cataract (ARC) is the most common type of cataract, but its pathogenesis is not fully understood. Using three-dimensional finite element modeling combining experimental biotechnology, our study demonstrates that external forces during accommodation cause mechanical stress predominantly in lens cortex, basically matching the localization of opacities in cortical ARCs. We identified the cellular senescence and upregulation of PIEZO1 mRNA in HLECs under mechanical stretch. This mechano-induced senescence in HLECs might be mediated by PIEZO1-related pathways, portraying a potential biomechanical cause of cortical ARCs. Our study updates the fundamental insight towards cataractogenesis, paving the way for further exploration of ARCs pathogenesis and nonsurgical treatment.

Airborne fine particulate matter (PM2.5) damages the inner blood-retinal barrier by inducing inflammation and ferroptosis in retinal vascular endothelial cells.

This study was the first to explore the effect of airborne fine particulate matter (PM2.5) exposure on the inner blood-retinal barrier (iBRB). In this study, retinal vascular permeability and diameter were enhanced in the PM2.5-exposed animal model (1 mg/mL PM2.5, 10 µL per eye, 4 times per day, 3 days), together with observable retinal edema and increased inflammation level in retina. PM2.5-induced cell damage in human retinal microvascular endothelial cells (HRMECs) occurred in a time- and dose-dependent manner. Decreased cell viability, proliferation, migration, and angiogenesis, as well as increased apoptosis and inflammation, were observed. Iron overload and excessive lipid oxidation were also discovered after PM2.5 exposure (25, 50, and 100 µg/mL PM2.5 for 24 h), along with significantly altered expression of ferroptosis-related genes, such as prostaglandin-endoperoxide synthase 2, glutathione peroxidase 4, and ferritin heavy chain 1. Moreover, Ferrostatin-1, an inhibitor of ferroptosis, evidently alleviated the PM2.5-induced cytotoxicity of HRMECs. The present study investigated the in vivo effects of PM2.5 on retinas, revealing that PM2.5 exposure induced retinal inflammation, vascular dilatation, and caused damage to the iBRB. The crucial role of ferroptosis was discovered during PM2.5-induced HRMEC cytotoxicity and dysfunction, indicating a potential precautionary target in air pollution-associated retinal vascular diseases.