PTEN Reduced UVB-Mediated Apoptosis in Retinal Pigment Epithelium Cells

Enhancing ocular protection against UVB: The role of irigenin in modulating oxidative stress and apoptotic pathways In Vivo

Oxidative damage contributes to age-related macular degeneration. Irigenin possesses diverse pharmacologic properties, including antioxidative and antiapoptotic effects. Our in vivo experiments indicated that irigenin mitigates UVB-induced histopathologic changes and oxidative DNA damage. Histologic analyses and TUNEL staining revealed that this compound dose-dependently ameliorated UVB-induced retinal damage and apoptosis. Furthermore, irigenin substantially reduced the level of 8-hydroxyguanosine, a biomarker of UVB-induced oxidative DNA damage. We further explored the molecular mechanisms that mediate the protective effects of irigenin. Our findings suggested that UVB-induced generation of ROS disrupts the stability of the mitochondrial membrane, activating intrinsic apoptotic pathways; the underlying mechanisms include the release of cytochrome c, activation of caspase-9 and caspase-3, and subsequent degradation of PARP-1. Notably, irigenin reversed mitochondrial disruption and apoptosis. It also modulated the Bax and Bcl-2 expression but influenced the mitochondrial apoptotic pathways. Our study highlights the role of the Nrf2 pathway in mitigating the effects of oxidative stress. We found that UVB exposure downregulated, but irigenin treatment upregulated the expression of Nrf2 and antioxidant enzymes. Therefore, irigenin activates the Nrf2 pathway to address oxidative stress. In conclusion, irigenin exhibits protective effects against UVB-induced ocular damage, evidenced by the diminution of histological alterations. It mitigates oxidative DNA damage and apoptosis in the retinal tissues by modulating the intrinsic apoptotic pathways and the AIF mechanisms. Furthermore, irigenin effectively reduces lipid peroxidation, enhancing the activity of antioxidant enzymes by stimulating the Nrf2 pathway. This protective mechanism underscores the potential benefit of irigenin in combating UVB-mediated ocular damage.

PRDX1 exerts a photoprotection effect by inhibiting oxidative stress and regulating MAPK signaling on retinal pigment epithelium

BACKGROUND

The purpose of this study was to investigate the photoprotection effect of peroxiredoxin 1 (PRDX1) protein in ultraviolet B (UVB) irradiation-induced damage of retinal pigment epithelium (RPE) and its possible molecular mechanism.

METHODS

ARPE-19 cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect the PRDX1 expression. The corresponding kits were employed to measure the levels or activities of lactate dehydrogenase (LDH), 8-hydroxy-2-deoxyguanosine (8-OHdG), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD). Western blotting was applied to examine PRDX1 expression and mitogen-activated protein kinase (MAPK) signaling pathway-related proteins.

RESULTS

After exposure to 20 mJ/cm2 intensity of UVB irradiation for 24 h, ARPE-19 cells viability was decreased, the leakage degree of LDH and 8-OHdG were increased, and cell apoptosis was elevated. The expression of PRDX1 was significantly down-regulated in UVB-induced ARPE-19 cells. The low expression of PRDX1 was involved in high irradiation intensity. Overexpression of PRDX1 increased cell activity, decreased cell apoptosis, and LDH as well as 8-OHdG leakage in UVB-induced ARPE-19 cells. In addition to alleviating UVB-induced cell damage, PRDX1 overexpression also inhibited UVB-induced oxidative stress (down-regulation of ROS and MDA levels, up-regulation of GSH-Px and SOD activities) and the activation of MAPK signaling pathway in ARPE-19 cells.

CONCLUSION

PRDX1 exerts a photoprotection effect on RPE by attenuating UVB-induced cell damage and inhibiting oxidative stress, which can be attributed to the inhibition of MAPK signaling pathway activation.

Molecular Signatures Integral to Natural Reprogramming in the Pigment Epithelium Cells after Retinal Detachment in Pleurodeles waltl

The reprogramming of retinal pigment epithelium (RPE) cells into retinal cells (transdifferentiation) lies in the bases of retinal regeneration in several Urodela. The identification of the key genes involved in this process helps with looking for approaches to the prevention and treatment of RPE-related degenerative diseases of the human retina. The purpose of our study was to examine the transcriptome changes at initial stages of RPE cell reprogramming in adult newt Pleurodeles waltl. RPE was isolated from the eye samples of day 0, 4, and 7 after experimental surgical detachment of the neural retina and was used for a de novo transcriptome assembly through the RNA-Seq method. A total of 1019 transcripts corresponding to the differently expressed genes have been revealed in silico: the 83 increased the expression at an early stage, and 168 increased the expression at a late stage of RPE reprogramming. We have identified up-regulation of classical early response genes, chaperones and co-chaperones, genes involved in the regulation of protein biosynthesis, suppressors of oncogenes, and EMT-related genes. We revealed the growth in the proportion of down-regulated ribosomal and translation-associated genes. Our findings contribute to revealing the molecular mechanism of RPE reprogramming in Urodela.

Silibinin Prevents TGFβ-Induced EMT of RPE in Proliferative Vitreoretinopathy by Inhibiting Stat3 and Smad3 Phosphorylation

Purpose

The purpose of this study was to investigate the effects of silibinin on epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) and proliferative vitreoretinopathy (PVR) formation, as well as its underlying molecular mechanism.

Methods

Cellular morphological change and EMT molecular markers were evaluated by using phase contrast imaging, qPCR, and Western blot (WB) to investigate the impact of silibinin on the EMT of ARPE-19 cells. Scratch assay and transwell assay were used to study the effect of silibinin on cell migration. An intravitreally injected RPE-induced rat PVR model was used to assess the effect of silibinin on PVR in vivo. RNA-seq was applied to study the molecular mechanism of silibinin-mediated PVR prevention.

Results

Silibinin inhibited TGFβ1-induced EMT and migration of RPE in a dose-dependent manner in vitro. Moreover, silibinin prevented proliferative membrane formation in an intravitreal injected RPE-induced rat PVR model. In line with these findings, RNA-seq revealed a global suppression of TGFβ1-induced EMT and migration-related genes by silibinin in RPEs. Mechanistically, silibinin reduced TGFβ1-induced phosphorylation levels of Smad3 and Stat3, and Smad3 nuclear translocation in RPE.

Conclusions

Silibinin inhibits the EMT of RPE cells in vitro and prevents the formation of PVR membranes in vivo. Mechanistically, silibinin inhibits Smad3 phosphorylation and suppresses Smad3 nuclear translocation through the inhibition of Stat3 phosphorylation. These findings suggest that silibinin may serve as a potential treatment for PVR.

Oxidative stress-induced lncRNA CYLD-AS1 promotes RPE inflammation via Nrf2/miR-134-5p/NF-κB signaling pathway

Oxidative stress-induced damage to and dysfunction of retinal pigment epithelium (RPE) cells are important pathogenetic factors of age-related macular degeneration (AMD); however, the underlying molecular mechanism is not fully understood. Long noncoding RNAs (lncRNAs) have important roles in various biological processes. In this study, using an oxidative damage model in RPE cells, we identified a novel oxidation-related lncRNA named CYLD-AS1. We further revealed that the expression of CYLD-AS1 was increased in RPEs during oxidative stress. Depletion of CYLD-AS1 promoted cell proliferation and mitochondrial function and protected RPE cells against hydrogen peroxide (H₂ O₂ )-induced damage. Mechanistically, CYLD-AS1 also regulated the expression of NRF2, which is related to oxidative stress, and NF-κB signaling pathway members, which are related to inflammation. Remarkably, these two signaling pathways were mediated by the CYLD-AS1 interactor miR-134-5p. Moreover, exosomes secreted by CYLD-AS1 knockdown RPE cells had a lower proinflammatory effect than those secreted by control cells. In summary, our study revealed that CYLD-AS1 affects the oxidative stress-related and inflammatory functions of RPE cells by sponging miR-134-5p to mediate NRF2/NF-κB signaling pathway activity, suggesting that targeting CYLD-AS1 could be a promising strategy for the treatment of AMD and related diseases.

Arbutin Protects Retinal Pigment Epithelium Against Oxidative Stress by Modulating SIRT1/FOXO3a/PGC-1α/β Pathway

Age-related macular degeneration (AMD), which is the leading cause of blindness among the elderly in western societies, is majorly accompanied by retinal pigment epithelium (RPE) degeneration. Because of the irreversible RPE cell loss among oxidative stress, it is crucial to search for available drugs for atrophic (dry) AMD. RNA-Seq analysis revealed that genes related to aging and mitochondrial health were differentially expressed under Arbutin treatment, whereas compared to oxidative injury, our study demonstrated that Arbutin substantially abrogated oxidative stress-induced cell senescence and apoptosis linked to intracellular antioxidant enzyme system homeostasis maintenance, restored mitochondrial membrane potential (MMP), and reduced the SA-β-GAL accumulation in RPE. Furthermore, Arbutin alleviated oxidative stress-mediated cell apoptosis and senescence via activation of SIRT1, as evidenced by the increase of the downstream FoxO3a and PGC-1α/β that are related to mitochondrial biogenesis, and the suppression of NF-κB p65 inflammasome, whereas rehabilitation of oxidative stress by SIRT1 inhibitor attenuated the protective effect of Arbutin. In conclusion, we validated the results in an in vivo model constructed by NAIO₃-injured mice. OCT and HE staining showed that Arbutin sustained retinal integrity in the case of oxidative damage in vivo, and the disorder of RPE cytochrome was alleviated through fundus observation. In summary, our findings identified that oxidative stress-induced mitochondrial malfunction and the subsequent senescence acceleration in RPE cells, whereas Arbutin inhibited TBHP-induced RPE degeneration via regulating the SIRT1/Foxo3a/PGC-1α/β signaling pathway. These findings suggested that Arbutin is a new agent with potential applications in the development of AMD diseases.

METTL3 attenuates proliferative vitreoretinopathy and epithelial-mesenchymal transition of retinal pigment epithelial cells via wnt/β-catenin pathway

Proliferative vitreoretinopathy (PVR) is a refractory vitreoretinal fibrosis disease, and epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is the key pathological mechanism of PVR. However, few studies focused on the role of METTL3, the dominating methyltransferase for m6A RNA modification in PVR pathogenesis. Immunofluorescence staining and qRT-PCR were used to determine the expression of METTL3 in human tissues. Lentiviral transfection was used to stably overexpress and knockdown METTL3 in ARPE-19 cells. MTT assay was employed to study the effects of METTL3 on cell proliferation. The impact of METTL3 on the EMT of ARPE-19 cells was assessed by migratory assay, morphological observation and expression of EMT markers. Intravitreal injection of cells overexpressing METTL3 was used to assess the impact of METTL3 on the establishment of the PVR model. We found that METTL3 expression was less in human PVR membranes than in the normal RPE layers. In ARPE-19 cells, total m6A abundance and the METTL3 expression were down-regulated after EMT. Additionally, METTL3 overexpression inhibited cell proliferation through inducing cell cycle arrest at G0/G1 phase. Furthermore, METTL3 overexpression weakened the capacity of TGFβ1 to trigger EMT by regulating wnt/β -catenin pathway. Oppositely, knockdown of METTL3 facilitated proliferation and EMT of ARPE-19 cells. In vivo, intravitreal injection of METTL3-overexpressing cells delayed the development of PVR compared with injection of control cells. In summary, this study suggested that METTL3 is involved in the PVR process, and METTL3 overexpression inhibits the EMT of ARPE-19 cells in vitro and suppresses the PVR process in vivo.

m6 A methyltransferase METTL3 promotes retinoblastoma progression via PI3K/AKT/mTOR pathway

Retinoblastoma (RB) is a common intraocular malignancy in children. Due to the poor prognosis of RB, it is crucial to search for efficient diagnostic and therapeutic strategies. Studies have shown that methyltransferase-like 3 (METTL3), a major RNA N (6)-adenosine methyltransferase, is closely related to the initiation and development of cancers. Nevertheless, whether METTL3 is associated with RB remains unexplored. Therefore, we investigated the function and mechanisms of METTL3 in the regulation of RB progression. We manipulated METTL3 expression in RB cells. Then, cell proliferation, apoptosis, migration and invasion were analysed. We also analysed the expression of PI3K/AKT/mTOR pathway members. Finally, we incorporated subcutaneous xenograft mouse models into our studies. The results showed that METTL3 is highly expressed in RB patients and RB cells. We found that METTL3 knockdown decreases cell proliferation, migration and invasion of RB cells, while METTL3 overexpression promotes RB progression in vitro and in vivo. Moreover, two downstream members of the PI3K/AKT/mTOR pathway, P70S6K and 4EBP1, were affected by METTL3. Our study revealed that METTL3 promotes the progression of RB through PI3K/AKT/mTOR pathways in vitro and in vivo. Targeting the METTL3/PI3K/AKT/mTOR signalling axis could be a promising therapeutic strategy for the treatment of RB.

Detrimental Effects of UVB on Retinal Pigment Epithelial Cells and Its Role in Age-Related Macular Degeneration

Retinal pigment epithelial (RPE) cells are an essential part of the human eye because they not only mediate and control the transfer of fluids and solutes but also protect the retina against photooxidative damage and renew photoreceptor cells through phagocytosis. However, their function necessitates cumulative exposure to the sun resulting in UV damage, which may lead to the development of age-related macular degeneration (AMD). Several studies have shown that UVB induces direct DNA damage and oxidative stress in RPE cells by increasing ROS and dysregulating endogenous antioxidants. Activation of different signaling pathways connected to inflammation, cell cycle arrest, and intrinsic apoptosis was reported as well. Besides that, essential functions like phagocytosis, osmoregulation, and water permeability of RPE cells were also affected. Although the melanin within RPE cells can act as a photoprotectant, this photoprotection decreases with age. Nevertheless, the changes in lens epithelium-derived growth factor (LEDGF) and autophagic activity or application of bioactive compounds from natural products can reverse the detrimental effect of UVB. Additionally, in vivo studies on the whole retina demonstrated that UVB irradiation induces gene and protein level dysregulation, indicating cellular stress and aberrations in the chromosome level. Morphological changes like retinal depigmentation and drusen formation were noted as well which is similar to the etiology of AMD, suggesting the connection of UVB damage with AMD. Therefore, future studies, which include mechanism studies via in vitro or in vivo and other potential bioactive compounds, should be pursued for a better understanding of the involvement of UVB in AMD.

Circular Noncoding RNA NR3C1 Acts as a miR-382-5p Sponge to Protect RPE Functions via Regulating PTEN/AKT/mTOR Signaling Pathway

Age-related macular degeneration (AMD) is a universal leading cause for irreversible blindness in the elderly population. Dedifferentiation of retinal pigment epithelium (RPE) cells initiates early pathological events in atrophic AMD. Herein, we aim to investigate effects of a circular RNA derived from the NR3C1 gene (circNR3C1) on regulating RPE function and AMD pathogenesis. circNR3C1 expression was consistently upregulated along with RPE differentiation and was downregulated in dysfunctional RPE and blood serum of AMD patients. Silencing of circNR3C1 reduced RPE characteristic transcripts and proteins, interrupted phagocytosis, accelerated intracellular reactive oxygen species (ROS) generation, and promoted RPE proliferation in vitro. circN3C1 silencing also decreased expressions of RPE characteristic markers and disturbed the ultrastructure of RPE in vivo, as shown by a thickened RPE with twisted basal infoldings and outer segments. Mechanistically, circNR3C1 acted as an endogenous microRNA-382-5p (miR-382-5p) sponge to sequester its activity, which increased phosphatase and tensin homolog on chromosome 10 (PTEN) expression and inhibited the protein kinase B/mammalian target of rapamycin (AKT/mTOR) pathway. miR-382-5p overexpression and PTEN silencing mimicked effects of circNR3C1 silencing on RPE phenotypes in vivo and in vitro. In conclusion, circNR3C1 prevents AMD progression and protects RPE by directly sponging miR-382-5p to block its interaction with PTEN and subsequently blocks the AKT/mTOR pathway. Pharmacological circNR3C1 supplementations are promising therapeutic options for atrophic AMD.

miR-132-3p boosts caveolae-mediated transcellular transport in glioma endothelial cells by targeting PTEN/PI3K/PKB/Src/Cav-1 signaling pathway

Blood-brain tumor barrier (BTB) impedes the transportation of antitumor therapeutic drugs into brain tumors. Its mechanism is still unknown, but learning how to improve the BTB permeability is critical for drug intervention. Recently, microRNAs (miRNAs) have appeared as regulation factors of numerous biologic processes and therapeutic targets of diverse diseases. In this study, we have identified that miR-132-3p is an essential miRNA by increasing the transcellular transport through the BTB. We found that miR-132-3p expression was significantly up-regulated in glioma endothelial cells (GECs). Furthermore we showed that miR132-3p⁺ greatly induced the endocytosis of cholera toxin subunit B and FITC-bovine serum albumin and up-regulated the expression of p-PKB, p-Src and Tyr14 phosphorylation of caveolin-1 (p-Cav-1), while phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression was markedly down-regulated in GECs. Our results identify PTEN as a direct and functional downstream target of miR-132-3p, which is involved in the regulation of p-PKB, p-Src, and p-Cav-1. The inhibitors for PI3K and Src significantly reversed the increase of p-Cav-1 induced by miR-132-3p. Moreover, overexpression of PTEN greatly reduced the endocytosis of cholera toxin subunit B and the up-regulation of p-Cav-1 induced by agomiR132-3p, suggesting that miR132-3p⁺ increases the endothelial permeability by inhibition of PTEN expression. In addition, miR132-3p⁺ significantly increased the delivery of doxorubicin across the BTB in vitro and contributed to the accumulation of doxorubicin within the brain tumor tissue. Our results show that miR-132-3p contributes to the increased permeability of BTB by targeting PTEN/PI3K/PKB/Src/Cav-1, thereby revealing a novel drug target for the treatment of brain gliomas.-Gu, Y., Cai, R., Zhang, C., Xue, Y., Pan, Y., Wang, J., Zhang, Z. miR-132-3p boosts caveolae-mediated transcellular transport in glioma endothelial cells by targeting PTEN/PI3K/PKB/Src/Cav-1 signaling pathway.

ID2 protects retinal pigment epithelium cells from oxidative damage through p-ERK1/2/ID2/NRF2

Age-related macular degeneration (AMD) is the leading cause of blindness during aging. The degeneration of retinal pigment epithelium (RPE) is the main pathologic characteristic of AMD. ID2 is a member of the Inhibitor of DNA binding proteins (ID) family and is involved in regulation of cell proliferation and differentiation. However, currently the role of ID2 in oxidative injury response in RPE cells remains unknown. Here we showed that oxidative stress increased ID2 expression in RPE cells. Knockdown of ID2 promoted cell apoptosis and increased ROS level in RPE cells that were subjected to oxidative damage. In addition, over-expression of ID2 attenuated the oxidative damage response in RPE cells. Mechanistically, ID2 protected RPE cells from oxidative damage through activating NRF2. Furthermore, phosphorylation of ERK1/2 positively regulated the protective function of ID2. Finally, we confirmed that the oxidative damage increased Id2 expression and over-expression of Id2 elevated Nrf2 expression in primary mouse RPE cells. Therefore, ID2 protects RPE cells from oxidative damage through the p-ERK1/2/ID2/NRF2 pathway. Our study contributes to a better understanding of the mechanisms underlying oxidative stress in AMD and may present a new strategy for AMD treatment.

MiR-340/iASPP axis affects UVB-mediated retinal pigment epithelium (RPE) cell damage

Long-term exposure to ultraviolet B (UVB) light increases the risk of UVB damage due to increased UVB absorption by the retina and may further lead to age-related eye diseases. The retinal pigment epithelium (RPE) cell is a main target of UVB reaching the retina; its degeneration is an essential event in UVB-mediated age-related macular degeneration (AMD). Herein, we first evaluated the expression and effect of iASPP, an inhibitory regulator of apoptosis, in UVB-induced RPE cell damage. Through the mechanism of RNA interference at the post-transcriptional level, miRNA affects a variety of cellular processes, including UVB-mediated cell damage. We next screened for upstream candidate miRNAs that may regulate iASPP expression. Among 8 candidate miRNAs, UVB significantly increased miR-340 levels. We also confirmed the direct binding of miR-340 to the 3'UTR of iASPP, and assessed the combined effect of miR-340 and iASPP on UVB-induced RPE cell damage. Taken together, we demonstrated the possible mechanisms involved in UVB-induced retinal damage. In RPE cells, UVB irradiation inhibits iASPP expression through inducing miR-340 expression, thereby promoting RPE cell apoptosis and suppressing cell viability via affecting p53, p21 and caspase-3 protein expression. Targeting miR-340 to rescue iASPP expression in RPE cells may help treat UVB-mediated retinal damage.

Diastereoselective synthesis of chiral 1,3-cyclohexadienals

A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner.