BLM can regulate cataract progression by influencing cell vitality and apoptosis

DCLRE1A Contributes to DNA Damage Repair and Apoptosis in Age-Related Cataracts by Regulating the lncRNA/miRNA/mRNA Axis

PURPOSE

Age-related cataract (ARC) is associated with the deregulation of transcription and defects in DNA repair in lens epithelial cells (LECs). DCLRE1A acted in DNA interstrand cross-links pathway to improve DNA replication and transcription. The aim of this study was to examined the further regulatory effect on DCLRE1A in the lncRNA-miRNA-mRNA network using a cell model of DCLRE1A overexpression (OE-DCLRE1A) in LECs.

METHODS

The expression level of DCLRE1A in ARC tissues and SRA01/04 cells after H2O2 treatment was measured as protein and mRNA by qRT-PCR and Western Blot(WB). CCK8, and TUNEL assays detected the change in cell viability and apoptosis, respectively. Furthermore, Immunofluorescence assays detect the expression of DNA damaged and repair marker proteins after OE-DCLRE1A. The global expression profiles of lncRNAs, miRNAs, and mRNAs were determined using high-throughput sequencing. KEGG and GO enrichment analysis disclose the possible function of differentially expressed (DE) lncRNA, miRNA, and mRNA.

RESULTS

The protein and mRNA of DCLRE1A were decreased in the anterior capsule of ARC and SRA01/04 cells treated by H2O2. OE-DCLRE1A improved damaged-DNA repair and enhanced cell viability against apoptosis after H2O2 treatment. Furthermore, we demonstrated the DE-molecules between the OE-DCLRE1A and control groups including 595 DE-lncRNAs, 221 DE-miRNAs, and 4718 DE-mRNAs. Next, bioinformatics analysis not only found that the DE-mRNAs are mainly involved in DNA repair-related signaling pathways after OE-DCLRE1A, but also screened two lncRNA-miRNA-mRNA networks focusing on DNA damage activated by OE-DCLRE1A, which involved 2 lncRNAs, 2 miRNAs, and 53 mRNAs.

CONCLUSION

We revealed that DCLRE1A activated the lncRNA/miRNA/DNA-repair network to take part in DNA repair processes, which not only represents a new regulatory mechanism employed by DCLRE1A but also uncovers the screening lncRNA may hold potential therapeutic values in ARC formation. However, these conclusions will need to be confirmed by future studies in vitro and in vivo models.

Candidate genes identification and RNA-seq based pathway analysis associated with primary angle-closure glaucoma with cataract

BACKGROUND

Cataract is commonly observed in patients with primary angle-closure glaucoma; however, its underlying pathological mechanisms remain unclear. This study aimed to improve our knowledge on the pathological processes involved in primary angle-closure glaucoma (PACG) by identifying potential prognostic genes associated with cataract progression.

METHODS

Thirty anterior capsular membrane samples were collected from PACG patients with cataracts and age-related cataracts. Differentially expressed genes (DEGs) between these two cohorts were analyzed using high-throughput sequencing. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed to screen the DEGs, and potential prognostic markers and their coexpression network were then predicted by bioinformatic analyses. The DEGs were further validated by reverse transcription-quantitative polymerase chain reaction.

RESULTS

A total of 399 DEGs were found to be specifically associated with cataracts development in PACG patients, among which 177 and 221 DEGs were upregulated and downregulated, respectively. STRING and Cytoscape network analyses revealed seven genes-CTGF, FOS, CAV1, CYR61, ICAM1, EGR1, and NR4A1-that were remarkably enriched and mainly involved in the MAPK, PI3K/Akt, Toll-like receptor, and TNF signaling pathways. RT-qPCR-based validation further confirmed that the sequencing results were accurate and reliable.

CONCLUSIONS

Herein, we identified seven genes and their signaling pathways that may contribute to cataract progression in patients with high intraocular pressure. Taken together, our findings highlight new molecular mechanisms that may explain the high incidence of cataracts in PACG patients. In addition, the genes identified herein may represent new foundations for the development of therapeutic strategies for PACG with cataract.

Age-related cataract: GSTP1 ubiquitination and degradation by Parkin inhibits its anti-apoptosis in lens epithelial cells

PURPOSE

Oxidative stress-induced apoptosis of lens epithelial cells (LECs) contributes to the pathogenesis of age-related cataract (ARC). The purpose of this research is to underlie the potential mechanism of E3 ligase Parkin and its oxidative stress-associated substrate in cataractogenesis.

METHODS

The central anterior capsules were obtained from patients with ARC, Emory mice, and corresponding controls. SRA01/04 cells were exposed to H₂O₂ combined with cycloheximide (a translational inhibitor), MG-132 (a proteasome inhibitor), chloroquine (an autophagy inhibitor), Mdivi-1 (a mitochondrial division inhibitor), respectively. Co-immunoprecipitation was employed to detect protein-protein interactions and ubiquitin-tagged protein products. Levels of proteins and mRNA were evaluated by western blotting and quantitative RT-PCR assays.

RESULTS

Glutathione-S-transferase P1 (GSTP1) was identified as a novel Parkin substrate. Compared with corresponding controls, GSTP1 was significantly decreased in the anterior lens capsules obtained from human cataracts and Emory mice. Similarly, GSTP1 was declined in H₂O₂-stimulated SRA01/04 cells. Ectopic expression of GSTP1 mitigated H₂O₂-induced apoptosis, whereas silencing GSTP1 aggregated apoptosis. In addition, H₂O₂ stimulation and Parkin overexpression could promote the degradation of GSTP1 through the ubiquitin-proteasome system, autophagy-lysosome pathway, and mitophagy. After co-transfection with Parkin, the non-ubiquitinatable GSTP1 mutant maintained its anti-apoptotic function, while wildtype GSTP1 failed. Mechanistically, GSTP1 might promote mitochondrial fusion through upregulating Mitofusins 1/2 (MFN1/2).

CONCLUSION

Oxidative stress induces LECs apoptosis via Parkin-regulated degradation of GSTP1, which may provide potential targets for ARC therapy.

METTL3-mediated m6A modification of has_circ_0007905 promotes age-related cataract progression through miR-6749-3p/EIF4EBP1

Many cases of blindness are caused by age-related cataracts (ARCs). N6-methyladenosine (m6A)-modified circRNA widely participates in disease progression. However, the role of m6A modification of circRNA in ARC is unclear. We mined and elucidated the functions and mechanisms of key circRNAs with m6A modification involved in ARC progression. The GSE153722 dataset was used to mine m6A-mediated key circRNA. Loss-of-function assays and rescue assays were used to explore the effect and mechanism of circRNA on ARC cell proliferation and apoptosis. Has_circ_0007905 was a hypermethylated and upregulated expression in the ARC group relative to the control group both in vivo and in vitro. Silencing of has_circ_0007905 promoted proliferation and inhibited the apoptosis of HLE-B3 cells. METTL3 was upregulated in HLE-B3 cells after ARC modeling and had four binding sites with has_circ_0007905 and a mediated m6A modification of has_circ_0007905. Proliferation was significantly inhibited and apoptosis of HLE-B3 cells was facilitated by METTL3 overexpression, whereas these effects were prevented by has_circ_0007905 silencing. Silencing of has_circ_0007905 led to an alteration in the transcriptome landscape. Differentially expressed genes were mainly involved in immune-related processes and pathways. EIF4EBP1 overexpression promoted apoptosis and suppressed proliferation, and also significantly reversed effects of has_circ_0007905 silencing. Moreover, miR-6749-3p significantly decreased the luciferase activities of wild type plasmids with both of has_circ_0007905 and EIF4EBP1. MiR-6749-3p inhibitor blocked elevation in proliferation and reduced EIF4EBP1 expression and apoptosis conferred by has_circ_0007905 silencing. We reveal for the first time that the commitment of ARC progression is guided by METTL3/has_circ_0007905/miR-6749-3p/EIF4EBP1 axis, and the results provide new insights into ARC pathology.

Exosomal microRNA-222-3p increases UVB sensitivity of lens epithelium cells by suppressing MGMT

BACKGROUND

Age-related cataract (ARC) is a leading cause of blindness worldwide with multiple pathogenic factors. Oxidative damage of lens epithelium cells (LECs) is one of the well-accepted pathogenesis of ARC which can be regulated by DNA repair genes (DRGs). The present research aimed to clarify the regulatory mechanism of exosomal microRNAs (miRNAs) on DRGs in LECs.

METHODS

The LECs oxidative damage model was established by UVB-irradiation on SRA01/04 (human lens epithelium cell line). Exosomes from UVB-irradiated cells (UVB-exo) and exosomes from normal control cells (NC-exo) were collected from the culture medium. To explore the functions of LECs exosomes, SRA01/04 were incubated with UVB-exo/NC-exo. Then, we detected SRA01/04 proliferation, viability and apoptosis respectively using 5'-ethynyl-2'-deoxyuridine (EdU), cell-counting kit-8 (CCK-8) and TdT-mediated dUTP Nick-End Labeling (TUNEL) assay. Next, the miRNA expression profiles of UVB-exo and NC-exo were identified by miRNA microarrays. RNA expression in exosomes, cells, and clinical samples was verified by qRT-PCR. The location and expression of MGMT and CD63 proteins were detected by immunofluorescence and western blot. The 3'UTR regulation of miR-222-3p to MGMT was verified by luciferase analyses.

RESULTS

MGMT down-regulated while miR-222-3p up-regulated in LECs sub-central anterior capsule from ARC lenses. MGMT and miR-222-3p expressions in central and peripheral LECs from anterior lens capsules were differential. UVB-exo can transport the up-regulated miR-222-3p from oxidative-damaged LECs to normal LECs, which could suppress MGMT expression and increase UVB sensitivity of LECs.

CONCLUSIONS

Findings on exosomal miRNA functions provided novel insights into pathogenesis of ARC. Exosomal miR-222-3p can be a potential target for prevention and cure of ARC.

miR-125a-3p regulates apoptosis by suppressing TMBIM4 in lens epithelial cells

PURPOSE

To explore the regulatory effect of miR-125a-3p on lens epithelial cells (LECs) under ultraviolet radiation B (UVB) irradiation.

METHODS

The expression of miR-125a-3p in age-related cataract (ARC) specimens and cell models was detected by qRT-PCR. UVB was utilized to establish DNA damage model of LECs. Cell count kit-8 was applied in detecting cell viability. Cell apoptosis ratio was analyzed by flow cytometry. Dual luciferase reports were applied to analyze the mechanism between miRNA and target genes. Nanoparticle tracking analysis, and Western blot were used to identify whether the exosomes were typical exosomes.

RESULTS

miR-125a-3p was upregulated in ARC tissues and LECs treated with UVB. Knockdown of miR-125a-3p in LECs significantly decreased apoptosis and increased viability of UVB-irradiated LECs. We predicted that miR-125a-3p could regulate transmembrane Bax inhibitor motif containing 4 (TMBIM4) by the bioinformatics databases TargetScan, miRBase, and miRWalk. Luciferase reporter assays demonstrated that miR-125a-3p may suppress TMBIM4 protein translation by binding to 3'UTR of TMBIM4 mRNA. Overexpression of miR-125a-3p decreased TMBIM4, which suggested that miR-125a-3p could inhibit TMBIM4. Moreover, knockdown of TMBIM4 decreased cell viability and enhanced cell apoptosis during UVB irradiation. In addition, the exosome secretion of LECs irradiated by UVB was enhanced, and the expression of miR-125a-3p was high. Cell viability was significantly decreased, and cell apoptosis was increased during UVB-exos treatment.

CONCLUSION

This study indicated that miR-125a-3p regulated apoptosis by suppressing TMBIM4 in LECs under oxidative damage, providing a new idea for clinical therapeutic target of cataract.

MSLN Correlates With Immune Infiltration and Chemoresistance as a Prognostic Biomarker in Ovarian Cancer

Mesothelin (MSLN) is a glycoprotein with various expression degrees in different tumors including mesothelioma, ovarian cancer, pancreatic cancer, etc. MSLN is considered to play an important role in cell survival, proliferation, and tumor progression. Although the expression of MSLN in tumors makes it a potential therapeutic target, its mechanism of action is still unclear, especially its correlation with immune cells infiltration in the tumor microenvironment has not been investigated. In this study, we detected the overexpression of MSLN in ovarian cancer using database analysis and tissue-array staining. We further evaluated the diagnostic value of MSLN and found it was associated with poor overall survival in ovarian cancer. In addition, the high expression of MSLN was significantly related to the immune-related genes and chemoresistant genes. We confirmed the overexpression of MSLN in the chemoresistant ovarian cancer cell lines. Our research suggests that MSLN participates in a variety of pathways related to the suppression of immune activation and promotion of chemoresistance, leading to a poor prognosis in ovarian cancer.

Diosmetin attenuates oxidative stress-induced damage to lens epithelial cells via the mitogen-activated protein kinase (MAPK) pathway

Cataract is a global ophthalmic disease that blinds the eye, and oxidative stress is one of its primary causes. Apoptosis of lens epithelial cells (LECs) is considered the major cytological basis of many cataracts except congenital cataracts. The purpose of this study was to investigate whether diosmetin could reduce oxidative stress-induced damage to LECs, and explore its regulatory pathway. Lens epithelial cell line SRA01/04 was used as the object of study. Using ultraviolet B (UVB) and hydrogen peroxide (H₂O₂) as sources of oxidative stress, the protective effects of diosmetin at different concentrations on cells were investigated, including inhibition of proliferation, apoptosis, and oxidative stress. Molecular docking was then used to predict the target proteins and validation was performed at the cellular and protein levels. The oxidative stress of SRA01/04 was induced by UVB and H₂O₂, and inhibition of proliferation and apoptosis were observed. Here, diosmetin has a dose-dependent cell-protecting effect. This effect is achieved by targeting the MEK2 protein and inhibiting the MAPK signaling. In conclusion, diosmetin reduces H₂O₂- and UVB-induced inhibition of SRA01/04 proliferation and apoptosis by reducing oxidative stress-induced activation of the MAPK pathway.

SYVN1-mediated ubiquitination and degradation of MSH3 promotes the apoptosis of lens epithelial cells

The pathology of age-related cataract (ARC) mainly involves the misfolding and aggregation of proteins, especially oxidative damage repair proteins, in the lens, induced by ultraviolet-B (UVB). MSH3, as a key member of the mismatch repair family, primarily maintains genome stability. However, the function of MSH3 and the mechanism by which cells maintain MSH3 proteostasis during cataractogenesis remains unknown. In the present study, the protein expression levels of MSH3 were found to be attenuated in ARC specimens and SRA01/04 cells under UVB exposure. The ectopic expression of MSH3 notably impeded UVB-induced apoptosis, whereas the knockdown of MSH3 promoted apoptosis. Protein half-life assay revealed that UVB irradiation accelerated the decline of MSH3 by ubiquitination and degradation. Subsequently, we found that E3 ubiquitin ligase synoviolin (SYVN1) interacted with MSH3 and promoted its ubiquitination and degradation. Of note, the expression and function of SYVN1 were contrary to those of MSH3 and SYVN1 regulated MSH3 protein degradation via the ubiquitin-proteasome pathway and the autophagy-lysosome pathway. Based on these findings, we propose a mechanism for ARC pathogenesis that involves SYVN1-mediated degradation of MSH3 via the ubiquitin-proteasome pathway and the autophagy-lysosome pathway, and suggest that interventions targeting SYVN1 might be a potential therapeutic strategy for ARC.

Identification and Integrated Analysis of the miRNA-mRNA Regulatory Network in Lens from an H2O2-Induced Zebrafish Cataract Model

PURPOSE

This study aimed to explore the regulatory mechanisms of age-related cataract (ARC) formation.

METHODS

Cataracts in zebrafish were induced by injecting hydrogen peroxide into the fish anterior chamber. The mRNA and miRNA expression profiles of the lens from H₂O₂-injected and PBS-injected zebrafishes were detected by RNA sequencing. The LIMMA package was applied to identify differentially expressed genes (DEGs). Gene Ontology categories were enriched by the R "cluster Profiler" package and Kyoto Encyclopedia of Genes and Genomes pathway enrichment was performed based on hypergeometric distribution using the R "phyper" function. The protein-protein interaction network of DEGs was built via the STRING. Target genes of differentially expressed miRNAs (DEmiRs) were predicted by miRanda. Furthermore, DEGs were selected as DEmiR targets and a DEmiR-DEG regulatory network was constructed via Cytoscape.

RESULTS

In total, 3689 DEGs (such as opn1mw4, LOC103908930, si:dkeyp-1h4.8, crispld1b, cyp1a, and gdpd3a) including 2478 upregulated and 1211 downregulated genes were identified. 177 DEmiRs (such as dre-miR-96-3p, dre-miR-182-5p, dre-miR-9-7-3p, and dre-miR-124-4-5p) including 108 upregulated and 69 downregulated miRNAs were detected. The DEGs are involved in cell death, DNA repair, and cell development-related pathways. A protein-protein interaction network including 79 node genes was constructed to explore the interactions of DEGs. Furthermore, a DEmiR-DEG regulatory network focusing on the DNA repair process was constructed, including 21 hub DEGs and 15 hub DEmiRs.

CONCLUSIONS

We identified several DEGs and constructed a miRNA-mRNA regulatory network related to the DNA repair process in a zebrafish cataract model. These genes participate in the oxidative stress response of lens epithelium cells and finally contribute to the formation of zebrafish cataracts. The hub DEGs and hub DEmiRs could be potential therapeutic targets for ARC.

XRCC5 downregulated by TRIM25 is susceptible for lens epithelial cell apoptosis

Exposure of the lens to UVB can lead to oxidative stress, which would result in age-related cataract (ARC) formation. In this study, we investigate the regulatory mechanism of tripartite motif containing 25 (TRIM25) in ARC. The protein level of TRIM25 was elevated in ARC specimens and UVB-exposed SRA01/04 cells. Bioinformatic analysis indicated that X-ray repair cross complementing 5 (XRCC5) might interact with TRIM25, and the interaction was validated via immunoprecipitation. TRIM25 interacted with XRCC5 and ubiquitinated it for degradation. Further studies showed that XRCC5 overexpression notably repressed UVB-induced apoptosis, while XRCC5 knockdown promoted apoptosis. Of note, ubiquitination of XRCC5 mediated by TRIM25 overexpression facilitated apoptosis. Attenuation of XRCC5 ubiquitination by mutant with substitution of lysine residues with arginine residues rescued its anti-apoptosis effect. Moreover, we observed that TRIM25-mediated XRCC5 degradation was reversed by proteasome inhibitor MG-132 or lysosome inhibitor 3-MA. In conclusion, TRIM25 mediates ubiquitination of XRCC5 to regulate the function and degradation of XRCC5, suggesting that interventions targeting TRIM25 might be a promising therapeutic strategy for ARC.

Changes in DNA methylation hallmark alterations in chromatin accessibility and gene expression for eye lens differentiation

Background

Methylation at cytosines (mCG) is a well-known regulator of gene expression, but its requirements for cellular differentiation have yet to be fully elucidated. A well-studied cellular differentiation model system is the eye lens, consisting of a single anterior layer of epithelial cells that migrate laterally and differentiate into a core of fiber cells. Here, we explore the genome-wide relationships between mCG methylation, chromatin accessibility and gene expression during differentiation of eye lens epithelial cells into fiber cells.

Results

Whole genome bisulfite sequencing identified 7621 genomic loci exhibiting significant differences in mCG levels between lens epithelial and fiber cells. Changes in mCG levels were inversely correlated with the differentiation state-specific expression of 1285 genes preferentially expressed in either lens fiber or lens epithelial cells (Pearson correlation r = − 0.37, p < 1 × 10^–42). mCG levels were inversely correlated with chromatin accessibility determined by assay for transposase-accessible sequencing (ATAC-seq) (Pearson correlation r = − 0.86, p < 1 × 10^–300). Many of the genes exhibiting altered regions of DNA methylation, chromatin accessibility and gene expression levels in fiber cells relative to epithelial cells are associated with lens fiber cell structure, homeostasis and transparency. These include lens crystallins (CRYBA4, CRYBB1, CRYGN, CRYBB2), lens beaded filament proteins (BFSP1, BFSP2), transcription factors (HSF4, SOX2, HIF1A), and Notch signaling pathway members (NOTCH1, NOTCH2, HEY1, HES5). Analysis of regions exhibiting cell-type specific alterations in DNA methylation revealed an overrepresentation of consensus sequences of multiple transcription factors known to play key roles in lens cell differentiation including HIF1A, SOX2, and the MAF family of transcription factors.

Conclusions

Collectively, these results link DNA methylation with control of chromatin accessibility and gene expression changes required for eye lens differentiation. The results also point to a role for DNA methylation in the regulation of transcription factors previously identified to be important for lens cell differentiation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13072-022-00440-z.

Long Noncoding RNA OIP5-AS1 Promotes Cell Apoptosis and Cataract Formation by Blocking POLG Expression Under Oxidative Stress

Purpose

Cataract, a clouding of the intraocular lens, is the leading cause of blindness. The lens-expressed long noncoding RNA OIP5-AS1 was upregulated in lens epithelial cells from patients with cataracts, suggesting its pathogenic role in cataracts. We investigated the regulatory role of OIP5-AS1 in the development of cataracts as well as potential RNA binding proteins, downstream target genes, and upstream transcription factors.

Methods

Clinical capsules and ex vivo and in vitro cataract models were used to test OIP5-AS1 expression. Cell apoptosis was detected using Western blots, JC-1 staining, and flow cytometry. Ribonucleoprotein immunoprecipitation-qPCR was performed to confirm the interaction of OIP5-AS1 and POLG. Chromatin immunoprecipitation-qPCR was used to determine the binding of TFAP2A and the OIP5-AS1 promoter region.

Results

OIP5-AS1 was upregulated in cataract lenses and B3 cells under oxidative stress. OIP5-AS1 knockdown protected B3 cells from H₂O₂-induced apoptosis and alleviated lens opacity in the ex vivo cataract model. HuR functioned as a scaffold carrying OIP5-AS1 and POLG mRNA and mediated the decay of POLG mRNA. POLG was downregulated in the cataract lens and oxidative-stressed B3 cells, and POLG depletion decreased the mtDNA copy number and MMP, increased reactive oxygen species production, and sensitized B3 cells to oxidative stress-induced apoptosis. POLG overexpression reversed these effects. TFAP2A bound the OIP5-AS1 promoter and contributed to OIP5-AS1 expression.

Conclusions

We demonstrated that OIP5-AS1, activated by TFAP2A, contributed to cataract formation by inhibiting POLG expression mediated by HuR, thus leading to increased apoptosis of lens epithelial cells and aggravated lens opacity, suggesting that OIP5-AS1 is a potential target for cataract treatment.

MicroRNA Let-7c-5p-Mediated Regulation of ERCC6 Disrupts Autophagic Flux in Age-Related Cataract via the Binding to VCP

Purpose: DNA damage contributes to the pathogenesis of age-related cataract (ARC) and is repaired through the nucleotide excision repair (NER) pathway, which includes ERCC6. Evidence has demonstrated that defective autophagy leads to lens organelle degradation and cataract. This study aimed to investigate the effects of ERCC6 on autophagy and determine its mechanisms in ARC.Methods: The clinical case-control study comprised 30 patients with ARC and 30 age-matched controls who received transparent lens extraction. Transmission electron microscopy was used to assess the ultrastructure of autophagic vesicles in lens anterior capsule tissues and lens epithelial cell line (SRA01/04). Real-time polymerase chain reaction and western blot analyses were performed to measure relative gene expression levels. Gene expression levels and localization were assessed by immunofluorescence. A coimmunoprecipitation assay was used to investigate the relationship between CSB which encoded by ERCC6 and VCP. ERCC6-siRNA and let-7 c-5p mimic were used to alter the expression of ERCC6 and let-7 c-5p.Results: Autophagy induction occurred in lens anterior capsule tissues of patients with ARC and in UVB-induced SRA01/04 cells, where the number of LC3B puncta was increased. Consistent with this result, the expression of beclin1 (BECN1) and LC3B, in addition to that of p62, was increased. Additionally, ERCC6 expression decreased, and silencing ERCC6 induced increases in the expression of BECN1, LC3B and p62. Moreover, CSB interacted with VCP, and let-7 c-5p induced dysregulation of autophagy by targeting ERCC6.Conclusion: In ARC, Let-7 c-5p-mediated downregulation of ERCC6 might prevent the degradation of autophagic vacuoles. CSB binds to VCP, inducing autophagosomes to combine with lysosomes and be degraded.

Identification and Characterization of N6-Methyladenosine CircRNAs and Methyltransferases in the Lens Epithelium Cells From Age-Related Cataract

Purpose

To explore the involvement of N⁶-methyladenosine (m⁶A) modification in circular RNAs (circRNAs) and relevant methyltransferases in the lesion of lens epithelium cells (LECs) under the circumstances of age-related cataract (ARC).

Methods

LECs were collected from normal subjects and patients with cortical type of ARC (ARCC). M⁶A-tagged circRNAs and circRNAs expression were analyzed by m⁶A-modified RNA immunoprecipitation sequencing (m⁶A-RIP-seq) and RNA sequencing (RNA-seq). Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to predict possible functions of the m⁶A-circRNAs. Expression of m⁶A-related methyltransferase and demethytransferase was measured by quantitative real-time polymerase chain reaction. Expression and location of AlkB homolog 5 RNA demethylase (ALKBH5), a key component of m⁶A demethytransferase, were determined by Western blot and immunostaining.

Results

All 4646 m⁶A peaks within circRNAs had different abundances, with 2472 enriched and 2174 subdued. The level of m⁶A abundance in total circRNAs was decreased in the LECs from ARCCs in comparison with the controls. We also found that the expression of highly m6A-tagged circRNAs was mostly decreased in comparison with non-m⁶A-tagged circRNAs. The bioinformatics analysis predicted the potential functions of m⁶A modified circRNAs and the relevant pathways that may be associated with m⁶A modified circRNAs. Among five major methyltransferases, ALKBH5 was significantly upregulated in LECs of ARCCs.

Conclusions

Our data provided novel evidence regarding the involvement of circRNAs m⁶A modifications in ARC. The altered expression of methyltransferases in lens tissue might selectively change the epigenetic profile of lens genome through regulating genes that host the circRNAs, thus enhance the susceptibility to ARC. The results might provide a new insight in the molecular target of ARC pathogenesis.

Ganoderic acid A protects lens epithelial cells from UVB irradiation and delays lens opacity

A contributory role of oxidative stress and protection by antioxidant nutrients have been suspected in cataract formation. Ganoderic acid A (GAA), an effective lanostane triterpene, is widely reported as an antioxidant. The aim of this study is to investigate the potential effects of GAA on cataract formation. After lens epithelial cells (LECs) were exposed to UVB radiation for different periods, cell viability, apoptosis-related protein levels, malondialdehyde (MDA) and superoxide dismutase (SOD) activities were monitored. We found that cell viability, the Bcl-2/Bax ratio and SOD activity were increased, while Cleaved caspase-3 levels and MDA activity were decreased compared with those in UVB-impaired LECs after GAA treated. Furthermore, GAA activated PI3K/AKT in UVB-impaired LECs and effectively delayed the occurrence of lens opacity in vitro. In conclusion, these findings demonstrated that GAA exhibited protective functions in SRA01/04 cells and rat lenses against UVB-evoked impairment through elevating cell viability and antioxidant activity, inhibiting cell apoptosis, activating the PI3K/AKT pathway and delaying lens opacity.

Comprehensive Profiling of Proteome and Ubiquitome Changes in Human Lens Epithelial Cell Line after Ultraviolet-B Irradiation

Ultraviolet-B (UVB) is a recognized risk factor for age-related cataract (ARC) and can cause various changes, including ubiquitination, in lens epithelial cells (LECs). However, the relationship between ubiquitination and ARC is unclear. Herein, we used UVB-irradiated human lens epithelial cell line (SRA01/04) representing the cell model of ARC to investigate the profile changes in the proteome and ubiquitome. A total of 552 differentially expressed proteins (DEPs) and 871 differentially ubiquitinated proteins (DUPs) were identified, and 9 ubiquitination motifs were found. Bioinformatics analysis revealed diverse pathways and biological processes of differential proteins and several DNA damage repair proteins that were potentially mediated via ubiquitin-proteasome pathway. We validated the decreased protein expression of DNA-directed RNA polymerase II subunit RPB2 (POLR2B) in both human cataract capsule tissues and UVB-treated SRA01/04 cells and found that treatment with proteasome inhibitor (MG-132) could reverse the protein level of POLR2B in UVB-irradiated SRA01/04 cells. Our data provide novel information regarding protein expressions and ubiquitination modifications in UVB-induced oxidative damage model. This study might offer a cell-level reference to further investigate the pathogenesis of ARC.

Long non-coding RNA MEG3 promotes cataractogenesis by upregulating TP53INP1 expression in age-related cataract

Age-related cataract (ARC) is the leading cause of visual impairment or even blindness among the aged population globally. Long non-coding RNA (LncRNA) has been proven to be the potential regulator of ARC. The latest study reveals that maternally expressed gene 3 (MEG3) promotes the apoptosis and inhibits the proliferation of multiple cancer cells. However, the expression and role of MEG3 in ARC are unclear. In this study, we investigated the effects of MEG3 in ARC and explored the regulatory mechanisms underlying these effects. We observed that MEG3 expression was up-regulated in the age-related cortical cataract (ARCC) lens capsules and positively correlated with the histological degree of ARCC. The pro-apoptosis protein, active caspase-3 and Bax increased in the anterior lens capsules of ARCC tissue, while the anti-apoptotic protein Bcl-2 decreased compared to normal lens. Knockdown of MEG3 increased the viability and inhibited the apoptosis of LECs upon the oxidative stress induced by H₂O₂. MEG3 was localized in both nucleus and cytoplasm in LECs. MEG3 facilitated TP53INP1 expression via acting as miR-223 sponge and promoting P53 expression. Additionally, TP53INP1 knockdown alleviated H₂O₂-induced lens turbidity. In summary, MEG3 promoted ARC progression by up-regulating TP53INP1 expression through suppressing miR-223 and promoting P53 expression, which would provide a novel insight into the pathogenesis of ARC.

Protective Effects of Lanosterol Synthase Up-Regulation in UV-B-Induced Oxidative Stress

UV-B radiation may be an important risk factor in cataract etiology. After exposure to UV-B radiation, cells show imbalances in the repair of DNA damage, which induce changes in the levels of certain proteins, including alpha-crystallin, which is the most abundant protein in the lens and crucial for the maintenance of lens transparency. Lanosterol synthase (LSS), an essential rate-limiting enzyme in cholesterol biosynthesis, might play significant roles in oxidative stress and in the maintenance of lens transparency. However, the roles of LSS in UV-B-induced apoptosis are not well understood. Therefore, we irradiated female Sprague-Dawley rats with ultraviolet radiation to establish an animal model for exploring the variations in LSS expression during the early stages of UV-B exposure. In addition, we cultured human lens epithelial (HLE) cells that overexpress LSS and exposed them to UV-B radiation to explore the function of increased LSS expression in UV-B-induced apoptosis. The data demonstrated that UV-B exposure induced oxidative stress and apoptosis in rat lens epithelial cells and that irradiance exposure increased the level of lenticular damage. Additionally, UV-B exposure decreased the alpha-crystallin content and increased the expressions of Bax and cleaved caspase-3 compared with the control levels. After exposure to UV-B, the apoptosis-related index of HLE cells overexpressing LSS was lower than that of the control cells. Furthermore, ROS overproduction might activate the sirtuin 1 (Sirt1) pathway, which induced protein expressions of sterol regulatory element-binding transcription factor 2 (SREBF2), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), and LSS. However, the specific mechanism of the Sirt1 pathway needed to be further studied. In summary, UV-B exposure induced oxidative injury and resulted in crystallin denaturation and apoptosis in lens epithelial cells, and LSS might play a protective role during the early stages of this process and could be an important target in the cataract prevention.

lncRNA H19 contributes to oxidative damage repair in the early age-related cataract by regulating miR-29a/TDG axis

Age‐related cataract (ARC) is caused by the exposure of the lens to UVB which promotes oxidative damage and cell death. This study aimed to explore the role of lncRNA H19 in oxidative damage repair in early ARC. lncRNAs sequencing technique was used to identify different lncRNAs in the lens of early ARC patients. Human lens epithelial cells (HLECs) were exposed to ultraviolet irradiation; and 8‐OHdG ELISA, Cell counting kit 8 (CCK8), EDU, flow cytometry and TUNEL assays were used to detect DNA damage, cell viability, proliferation and apoptosis. Luciferase assay was used to examine the interaction among H19, miR‐29a and thymine DNA glycosylase (TDG) 3'UTR. We found that lncRNA H19 and TDG were highly expressed while miR‐29a was down‐regulated in the three types of early ARC and HLECs exposed to ultraviolet irradiation, compared to respective controls. lncRNA H19 knockdown aggravated oxidative damage, reduced cell viability and proliferation, and promoted apoptosis in HLECs, while lncRNA H19 overexpression led to opposite effects in HLECs. Mechanistically, miR‐29a bound TDG 3'UTR to repress TDG expression. lncRNA H19 up‐regulated the expression of TDG by repressing miR‐29a because it acted as ceRNA through sponging miR‐29a. In conclusion, the interaction among lncRNA H19, miR‐29a and TDG is involved in early ARC. lncRNA H19 could be a useful marker of early ARC and oxidative damage repair pathway of lncRNA H19/miR‐29a/TDG may be a promising target for the treatment of ARC.