Expression of DNA repair genes in lens cortex of age-related cortical cataract

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.

TGF-β2-induced NEAT1 regulates lens epithelial cell proliferation, migration and EMT by the miR-26a-5p/FANCE axis

AIM

To explore the regulatory mechanism of nuclear paraspeckle assembly transcript 1 (NEAT1) in the pathogenesis of posterior capsule opacification (PCO).

METHODS

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was executed to analyze NEAT1 and microRNA (miR)-26a-5p expression in transforming growth factor-beta 2 (TGF-β2)-disposed lens epithelial cells (LECs). The proliferation, cell cycle progression, apoptosis, and migration of TGF-β2-disposed LECs were evaluated. The relationship between NEAT1 or fanconi anemia (FA) complementation group E (FANCE) and miR-26a-5p was verified by dual-luciferase reporter assay.

RESULTS

TGF-β2 induced NEAT1 expression in LECs. NEAT1 inhibition accelerated apoptosis, cell cycle arrest, decreased proliferation, epithelial-mesenchymal transition (EMT), and migration of TGF-β2-disposed LECs. NEAT1 sponged miR-26a-5p to further regulate FANCE expression. Rescue experiments presented that miR-26a-5p downregulation overturned NEAT1 silencing-mediated impacts on TGF-β2-disposed LEC biological behaviors. Additionally, FANCE overexpression reversed miR-26a-5p mimic-mediated impacts on TGF-β2-disposed LEC biological behaviors.

CONCLUSION

TGF-β2-induced NEAT1 facilitates LEC proliferation, migration, and EMT by upregulating FANCE via sequestering miR-26a-5p.

Profiling and Integrated Analysis of the ERCC6-regulated circRNA-miRNA-mRNA Network in Lens Epithelial Cells

Purpose: To explore the regulatory role of ERCC6 in the circRNA-miRNA-mRNA network using a cellular ERCC6 overexpression model (OE-ERCC6) in lens epithelial cells.Methods: The expression profiles of circRNAs, miRNAs and mRNAs were determined by RNA-seq, and a regulatory circRNA-miRNA-mRNA network was constructed via bioinformatics. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used for the functional annotation of circRNA host genes, differentially expressed (DE) genes, and miRNA targets.Results: The DE molecules between the OE-ERCC6 and control groups included 269 circRNAs, 241 miRNAs and 3500 mRNAs. We validated 5 selected DE reads of circRNAs (hsa_circ_0001009, hsa_circ_0002024, hsa_circ_0004592, hsa_circ_0001900 and hsa_circ_0001017). Subsequent bioinformatics analysis revealed that the DE circRNAs are mainly involved in oxidative stress- and cell death-related signaling pathways. Finally, a circRNA-miRNA-mRNA network focusing on DNA damage and cell death, which involved 5 circRNAs, 13 miRNAs and 107 mRNAs, was constructed.Conclusion: We constructed a circRNA-miRNA-mRNA network that is regulated by ERCC6. DE circRNAs have the potential to become therapeutic targets related to the lens lesions observed in ARC. The establishment of related in vivo and in vitro models could be a future direction to confirm these hypotheses.

Radiation-induced DNA Damage and Repair in Lens Epithelial Cells of both Ptch1(+/-) and Ercc2(+/-) Mutated Mice

Epidemiological studies suggest an increased incidence and risk of cataract after low-dose (<2 Gy) ionizing radiation exposures. However, the biological mechanism(s) of this process are not fully understood. DNA damage and repair are thought to have a contributing role in radiation-induced cataractogenesis. Recently we have reported an inverse dose-rate effect, as well as the low-dose response, of DNA damage and repair in lens epithelial cells (LECs). Here, we present further initial findings from two mutated strains (Ercc2+/- and Ptch1+/-) of mice, both reportedly susceptible to radiation-induced cataract, and their DNA damage and repair response to low-dose and low-dose-rate gamma rays. Our results support the hypothesis that the lens epithelium responds differently to radiation than other tissues, with reported radiation susceptibility to DNA damage not necessarily translating to the LECs. Genetic predisposition and strain(s) of mice have a significant role in radiation-induced cataract susceptibility.

CircMRE11A_013 binds to UBXN1 and integrates ATM activation enhancing lens epithelial cells senescence in age-related cataract

Ultraviolet B (UVB) irradiation could trigger DNA double-strand breaks (DDSBs) and senescence in lens epithelial cells (LECs), thus inducing age-related cortical cataract (ARCC) formation. Cell-cycle irreversible arrest induced by DDSBs depended on excessive activation of ataxia-telangiectasia mutated kinase (ATM). We studied the up-regulated circular RNA circMRE11A_013 (circMRE11A) in LECs of ARCC and SRA01/04 cell lines under UVB exposure. In vitro, knockdown of circMRE11A in SRA01/04 cell lines enhanced cell viability and cell cycle, while over-expression of circMRE11A exhibited an opposite trend. Additionally, circMRE11A could bind to UBX domain-containing protein 1 (UBXN1), which might enhance excessive activation of ATM and initiate ATM/p53/p21 signaling pathway causing LECs cell-cycle arrest and senescence. In vivo, recombinant adeno-associated virus vectors (rAAV-2) virions of circMRE11A (circMRE11A-AAV2) was injected to Institute of Cancer Research mouse vitreous cavity. The circMRE11A-AAV2 could express in mouse lens at 4 weeks. The LECs aging and opacity lens were observed at 8 weeks after the injection. Together, our findings reveal a previously unidentified role of circMRE11A interacting with UBXN1 in enhancing ATM activity and inhibiting LECs cell-cycle in ARCC formation. The findings might give us a better understanding of ARC pathology and provide a novel and more effective therapeutic approaches for ARC treatment.

Phototoxicity of environmental radiations in human lens: revisiting the pathogenesis of UV-induced cataract

The magnitude of cataract pathology is indeed significant as it is the principal cause of blindness worldwide. Also, the prominence of this concept escalates with the current aging population. The burden of the disease is more tangible in developing countries than developed ones. Regarding this concern, there is a gap in classifying the pathogenesis of the ultraviolet (UV) radiation-induced cataracts and explaining the possible cellular and subcellular pathways. In this review, we aim to revisit the effect of UV radiation on cataracts categorizing the cellular pathways involved. This may help for better pharmaceutical treatment alternatives and their wide-reaching availability. Also, in the last section, we provide an overview of the protecting agents utilized as UV shields. Further studies are required to enlighten new treatment modalities for UV radiation-induced pathologies in human lens.

The comet assay applied to cells of the eye

The human eye is relatively unexplored as a source of cells for investigating DNA damage. There have been some clinical studies, using cells from surgically removed tissues, and altered DNA bases as well as strand breaks have been measured using the comet assay. Tissues examined include corneal epithelium and endothelium, lens capsule, iris and retinal pigment epithelium. For the purpose of biomonitoring for exposure to potential mutagens in the environment, the eye-relatively unprotected as it is compared with the skin-would be a valuable object for study; non-invasive techniques exist to collect lachrymal duct cells from tears, or cells from the ocular surface by impression cytology, and these methods should be further developed and validated.

MicroRNA binding mediated Functional sequence variant in 3'-UTR of DNA repair Gene XPC in Age-related Cataract

DNA oxidative damage repair is strongly involved in the pathogenesis of age-related cataract (ARC). The sequence variants of in coding region of DNA repair genes have been shown to be associated with ARC. It is known that single nucleotide polymorphisms (SNPs) in the 3′-terminal untranslated region (3′-UTR) can alter the gene expression by binding with microRNAs (miRNAs). We hypothesize that SNP(s) in miRNA binding site of certain DNA oxidative damage repair genes might associate with ARC risk. We examined 10 miRNA binding SNPs in 3′-UTR of 7 oxidative damage genes and revealed the XPC- rs2229090 C allele was associated with nuclear type of ARC (ARNC) risk in Chinese population. The individuals with the variant G allele (CG and GG) of XPC- rs2229090 had higher XPC mRNA expression compared to individuals carrying CC genotype. The in vitro assay showed that luciferase reporter gene expression can be down regulated by hsa-miR-589-5p in cells transfected with rs2229090 C allele compared to G allele. These results suggested that the C allele of XPC-2229090 increase the risk with ARNC. The mechanism underlying might be due to the stronger interation of the C allele with hsa-miR-589-5p, resulting in lower XPC expression and DNA repair capability than the individuals carring G allele in lens.