LncRNAs in genetic basis of glaucoma

Epigenetics in Glaucoma

Primary open angle glaucoma (POAG) is defined as a "genetically complex trait", where modifying factors act on a genetic predisposing background. For the majority of glaucomatous conditions, DNA variants are not sufficient to explain pathogenesis. Some genes are clearly underlying the more "Mendelian" forms, while a growing number of related polymorphisms in other genes have been identified in recent years. Environmental, dietary, or biological factors are known to influence the development of the condition, but interactions between these factors and the genetic background are poorly understood. Several studies conducted in recent years have led to evidence that epigenetics, that is, changes in the pattern of gene expression without any changes in the DNA sequence, appear to be the missing link. Different epigenetic mechanisms have been proven to lead to glaucomatous changes in the eye, principally DNA methylation, post-translational histone modification, and RNA-associated gene regulation by non-coding RNAs. The aim of this work is to define the principal epigenetic actors in glaucoma pathogenesis. The identification of such mechanisms could potentially lead to new perspectives on therapeutic strategies.

Long Non-Coding RNAs in Retinal Ganglion Cell Apoptosis

Traumatic optic neuropathy or other neurodegenerative diseases, including optic nerve transection, glaucoma, and diabetic retinopathy, can lead to progressive and irreversible visual damage. Long non-coding RNAs (lncRNAs), which belong to the family of non-protein-coding transcripts, have been linked to the pathogenesis, progression, and prognosis of these lesions. Retinal ganglion cells (RGCs) are critical for the transmission of visual information to the brain, damage to which results in visual loss. Apoptosis has been identified as one of the most essential modes of RGC death. Emerging evidence suggests that lncRNAs can regulate RGC degeneration by directly or indirectly modulating apoptosis-associated signaling pathways. This review presents a comprehensive overview of the role of lncRNAs in RGC apoptosis at transcriptional, post-transcriptional, translational, and post-translational levels, emphasizing on the potential mechanisms of action. The current limitations and future perspectives of exploring the connection between lncRNAs and RGC apoptosis have been summarized. Understanding the intricate molecular interaction network of lncRNAs and RGC apoptosis will open new avenues for the identification of novel diagnostic biomarkers, therapeutic targets, and molecules for prognostic evaluation of diseases related to RGC injury.

LINC01605 knockdown induces apoptosis in human Tenon's capsule fibroblasts by inhibiting autophagy

Glaucoma is an irreversible disease that causes blindness. Formation of a hypertrophic scar (HS) is the main cause of failure of glaucoma surgery. The long non-coding RNA LINC01605 is closely associated with the formation of HS; however, the function of LINC01605 in the formation and development of HS remains unclear. For this study, firstly, human Tenon's capsule fibroblasts (HTFs) and corneal epithelial cells (control cells) were collected from patients (n=5) with POAG who underwent glaucoma filtration surgery at Fuyang People's Hospital. Immunofluorescence analysis was performed to detect the expression levels of vimentin (one of the main components of medium fiber and plays an important role in the cytoskeleton and motility), keratin (the main component of cytoskeletal proteins) and LC3 (an autophagy marker). In addition, reverse transcription-quantitative PCR analysis was performed to detect LINC01605 expression. Besides, the Cell Counting Kit-8 assay was performed to assess the viability of human Tenon's capsule fibroblasts (HTFs). Next, flow cytometry was performed to detect HTF apoptosis. Furthermore, western blot analysis was performed for Bax, Bcl-2, Pro-caspase-3, cleaved caspase-3, phosphorylated (p-)Smad2, Smad2, α-SMA, MMP9, ATG7, p62, beclin 1, p-AMPK and AMPK in HTFs to determine the mechanism by which LINC01605 regulates the formation and development of HS. Moreover, a Transwell assay was performed to detect the migratory ability of HTFs. The results demonstrated that LINC01605 was significantly upregulated in HS tissues compared with that in normal (control/healthy) tissues. In addition, vimentin was highly expressed in HTFs, whereas keratin was expressed at a low level. Also, in HTFs, LINC01605 knockdown inhibited cell viability by inducing apoptosis, decreasing Smad2 activation and inhibiting autophagy. Furthermore, LINC01605 knockdown significantly inhibited the migratory ability of HTFs. Transfection with LINC01605 small interference RNAs significantly downregulated the expression levels of p-Smad2, α-SMA and MMP9 in HTFs. Furthermore, LINC01605 knockdown notably inhibited the viability and migration, and induced the apoptosis of HTFs, the effects of which were reversed following treatment with TGF-β. Taken together, the results of the present study suggested that LINC01605 knockdown may inhibit the viability of HTFs by inducing the apoptotic pathway. These findings may provide novel directions for the treatment of HS.

SNHG3 cooperates with ELAVL2 to modulate cell apoptosis and extracellular matrix accumulation by stabilizing SNAI2 in human trabecular meshwork cells under oxidative stress

Glaucoma is the main reason for irreversible blindness, and pathological increased intraocular pressure is the leading risk factor for glaucoma. It is reported that trabecular meshwork cell injury is closely associated with the elevated intraocular pressure. The current study aimed to investigate the role of small nucleolar RNA host gene 3 (SNHG3) in human trabecular meshwork (HTM) cells under oxidative stress. A series of experiments including real-time quantitative polymerase chain reaction, subcellular fractionation assay, western blot analysis, cell counting kit-8 assay, RNA pull down, flow cytometry analysis, and RNA immunoprecipitation assay were used to explore the biological function and regulatory mechanism of SNHG3 in HTM cells under oxidative stress. First, we observed that H₂ O₂ induced SNHG3 upregulation in HTM cells. Then, we found that SNHG3 silencing alleviated H₂ O₂ -induced oxidative damage in HTM cells. Moreover, snail family transcriptional repressor 2 (SNAI2) knockdown alleviated the oxidative damage induced by H₂ O₂ in HTM cells. Mechanistically, SNHG3 bound with ELAV like RNA binding protein 2 (ELAVL2) to stabilize SNAI2. Finally, SNAI2 overexpression counteracted the effect of SNHG3 silencing on H₂ O₂ -treated HTM cells. In conclusion, our results demonstrated that SNHG3 cooperated with ELAVL2 to modulate cell apoptosis and extracellular matrix accumulation by stabilizing SNAI2 in HTM cells under oxidative stress.

Long Noncoding RNA LINC01518 Modulates Proliferation and Migration in TGF-β1-Treated Human Tenon Capsule Fibroblast Cells Through the Regulation of hsa-miR-216b-5p

In this study, we investigated the expression and functions of long noncoding RNAs (LncRNAs) of LINC01518 in an in vitro model of TGF-β1-treated human Tenon capsule fibroblast (HTF) cells. qRT-PCR was used to examine LINC01518 expression in in situ human glaucoma tissues, and in vitro HTF cells treated with TGF-β1. Lentivirus-mediated LINC01518 knockdown was performed in HTF cells to investigate its effect on TGF-β1-induced cell proliferation, migration and autophagy signaling pathway. The potential ceRNA candidate of LINC01518, hsa-miR-216b-5p, was probed by dual-luciferase assay and qRT-PCR. Hsa-miR-216b-5p was also knocked down in LINC01518-downregulated HTF cells to investigate the function of this lncRNA-miRNA epigenetic axis in TGF-β1-treated HTF cells. LINC01518 was upregulated in human glaucoma tissues and cultured HTF cells. LINC01518 downregulation significantly suppressed TGF-β1-induced cell proliferation, migration and autophagy signaling pathway in HTF cells. Hsa-miR-216b-5p was confirmed to be a ceRNA target of LINC01518. Knocking down hsa-miR-216b-5p reversed the suppressing effects of LINC01518 downregulation in TGF-β1-treated HTF cells. Our study demonstrated that LINC01518 is a functional factor in regulating proliferation and migration in TGF-β1-treated HTF cells, and hsa-miR-216b -5p may also be involved. Targeting the epigenetic axis of LINC01518/hsa-miR-216b-5p may provide new insight into the pathological development of human glaucoma.

LOXL1 gene polymorphism candidates for exfoliation glaucoma are also associated with a risk for primary open-angle glaucoma in a Caucasian population from central Russia

Purpose

This study was aimed to replicate the previously reported associations of the three LOXL1 gene polymorphisms with exfoliation glaucoma (XFG) and to analyze these genetic variants for their possible contribution to primary open-angle glaucoma (POAG) in Caucasians from central Russia.

Methods

In total, 932 participants were recruited for the study, including 328 patients with XFG, 208 patients with POAG, and 396 controls. The participants were of Russian ethnicity (self-reported) and born in Central Russia. They were genotyped at three single nucleotide polymorphisms (SNPs) of the LOXL1 gene (rs2165241, rs4886776, and rs893818). The association was analyzed using logistic regression.

Results

Allele C of rs2165241 was associated with a decreased risk of XFG (odds ratio [OR] =0.27-0.45, pperm ≤5*10-6) and POAG (OR=0.35-0.47, рperm≤0.001), and allele A of rs4886776 and rs893818 were associated with a lower risk of XFG (OR=0.53-0.57, рperm≤0.001). Haplotype TGG of loci rs2165241-rs4886776-rs893818 was associated with an elevated risk of XFG (OR=2.23, рperm=0.001) and POAG (OR=2.01, рperm=0.001), haplotype CGG was also associated with a decreased risk of XFG (OR=0.45, рperm=0.001) and POAG (OR=0.35, рperm=0.001). Haplotype CAA was associated with a decreased risk of XFG only (OR=0.50, рperm=0.001).

Conclusions

Polymorphisms rs2165241, rs4886776, and rs893818 of the LOXL1 gene showed association with XFG and POAG in a Caucasian sample from central Russia.

Insights into the regulatory molecules involved in glaucoma pathogenesis

Glaucoma is an important cause of irreversible blindness, characterized by optic nerve anomalies. Increased intraocular pressure (IOP) and aging are major risk factors. Retinal ganglion cells and trabecular meshwork cells are certainly involved in the etiology of glaucoma. Glaucoma is usually a complex disease, and various genes and functions may contribute to its etiology. Among these may be genes that encode regulatory molecules. In this review, regulatory molecules including 18 transcription factors (TFs), 195 microRNAs (miRNAs), 106 long noncoding RNAs (lncRNAs), and two circular RNAs (circRNAs) that are reasonable candidates for having roles in glaucoma pathogenesis are described. The targets of the regulators are reported. Glaucoma-related features including apoptosis, stress responses, immune functions, ECM properties, IOP, and eye development are affected by the targeted genes. The targeted genes that are frequently targeted by multiple regulators most often affect apoptosis and the related features of cell death and cell survival. BCL2, CDKN1A, and TP53 are among the frequent targets of three types of glaucoma-relevant regulators, TFs, miRNAs, and lncRNAs. TP53 was itself identified as a glaucoma-relevant TF. Several of the glaucoma-relevant TFs are themselves among frequent targets of regulatory molecules, which is consistent with existence of a complex network involved in glaucoma pathogenesis.

The Genetic and Endoplasmic Reticulum-Mediated Molecular Mechanisms of Primary Open-Angle Glaucoma

Glaucoma is a heterogenous, chronic, progressive group of eye diseases, which results in irreversible loss of vision. There are several types of glaucoma, whereas the primary open-angle glaucoma (POAG) constitutes the most common type of glaucoma, accounting for three-quarters of all glaucoma cases. The pathological mechanisms leading to POAG pathogenesis are multifactorial and still poorly understood, but it is commonly known that significantly elevated intraocular pressure (IOP) plays a crucial role in POAG pathogenesis. Besides, genetic predisposition and aggregation of abrogated proteins within the endoplasmic reticulum (ER) lumen and subsequent activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dependent unfolded protein response (UPR) signaling pathway may also constitute important factors for POAG pathogenesis at the molecular level. Glaucoma is commonly known as a ‘silent thief of sight’, as it remains asymptomatic until later stages, and thus its diagnosis is frequently delayed. Thereby, detailed knowledge about the glaucoma pathophysiology is necessary to develop both biochemical and genetic tests to improve its early diagnosis as well as develop a novel, ground-breaking treatment strategy, as currently used medical therapies against glaucoma are limited and may evoke numerous adverse side-effects in patients.

LncRNAs in ocular neovascularizations

The prevalence of eye diseases worldwide is dramatically increasing and represents a major concern in underdeveloped and developed regions. Ocular diseases, previously associated with a higher depression risk, also impose a substantial economic burden on affected families, thus early detection and/or accurate treatment in order to avoid and prevent blindness should be emphasized. Ocular neovascularization (NV), the leading cause of blindness in a variety of eye diseases, is a pathologic process characterized by the formation, proliferation and infiltration of anomalous, tiny and leaky fragile blood vessels within the eye. Genetics have been suspected to play an important role in the occurrence of eye diseases, with the detection of a numbers of specific gene mutations. Long non-coding RNA (lncRNAs) are novel class of regulatory molecules previously associated with various biological processes and diseases, however the nature of the relation and pathways by which they might contribute to the development of corneal, choroidal and retinal NV have not yet been completely elucidated. In this review, we focus on the regulation and characteristics of lncRNAs, summarize results from ocular NV-related studies and discuss the implication of lncRNAs in ocular NV development.

Transthyretin Upregulates Long Non-Coding RNA MEG3 by Affecting PABPC1 in Diabetic Retinopathy

The aim of the study was to demonstrate how transthyretin (TTR) could affect long non-coding RNA (lncRNA) of maternally expressed gene 3 (MEG3) and play important roles in diabetic retinopathy (DR). A DR model in C57BL/6 mice was established after intraperitoneal injection of streptozotocin (STZ). After intravitreal injection with TTR pAAV vector, MEG3 short hairpin RNA (shRNA), scrambled shRNA, or MEG3, retinal imaging, retinal trypsin digestion, and fundus vascular permeability tests were performed. Cell counting kit-8 (CCK8), transwell, and Matrigel assays were employed to detect the proliferation and migration of human retinal microvascular endothelial cells (hRECs). The binding between long non-coding RNA of maternally expressed gene 3 (lncRNA-MEG3) and microRNA-223-3p (miR-223-3p) was observed by using luciferase reporter assays, while co-immunoprecipitation (co-IP) was employed to confirm the interaction between TTR and the target. In the DR mice model, retinal vascular leakage and angiogenesis were repressed by overexpressing TTR. In vitro, the added TTR promoted the level of lncRNA-MEG3 by interacting with poly (A) binding protein cytoplasmic 1 (PABPC1), and then repressed proliferation and angiogenesis of hRECs. In vivo, silencing or overexpressing lncRNA-MEG3 significantly affected retinal vascular phenotypes. Additionally, the interaction between lncRNA-MEG3 and miR-223-3p was confirmed, and silencing of miR-223-3p revealed similar effects on hRECs as overexpression of lncRNA-MEG3. In summary, in the DR environment, TTR might affect the lncRNA MEG3/miR-223-3p axis by the direct binding with PABPC1, and finally repress retinal vessel proliferation.

Ginkgo Biloba Extract Alleviates Methotrexate-Induced Renal Injury: New Impact on PI3K/Akt/mTOR Signaling and MALAT1 Expression

Renal injury induced by the chemotherapeutic agent methotrexate (MTX) is a serious adverse effect that has limited its use in the treatment of various clinical conditions. The antioxidant activity of Ginkgo biloba extract (GB) was reported to mitigate renal injury induced by MTX. Our research was conducted to examine the nephroprotective role of GB versus MTX-induced renal injury for the first time through its impact on the regulation of phosphatidylinositol 3-kinase/protein kinase B/ mammalian target of rapamycin (PI3K/Akt/mTOR) signaling together with the renal level of TGF-β mRNA and long non-coding RNA-metastasis-associated lung adenocarcinoma transcript-1 (MALAT1) expression. A group of adult rats was intraperitoneally (ip) injected with MTX 20 mg/kg as a single dose to induce kidney injury (MTX group). The other group of rats was orally administered with GB 60 mg/kg every day for 10 days (GB+ MTX group). The MTX increased the serum creatinine and urea levels, renal TGF-β mRNA and MALAT1 expression, in addition to dysregulation of the PI3K/Akt/mTOR signaling when compared with normal control rats that received saline only (NC group). Moreover, renal damage was reported histopathologically in the MTX group. The GB ameliorated the renal injury induced by MTX and reversed the changes of these biochemical analyses. The involvement of PI3K/Akt/mTOR signaling and downregulation of TGF-β mRNA and MALAT1 renal expressions were firstly reported in the nephroprotective molecular mechanism of GB versus MTX-induced renal injury.

Correlation between MTHFR polymorphisms and glaucoma: A meta-analysis

Background

Whether methylenetetrahydrofolate reductase (MTHFR) polymorphisms are implicated in glaucoma remains controversial. Therefore, we performed this study to better assess the relationship between MTHFR polymorphisms and the likelihood of glaucoma.

Methods

A systematic research of PubMed, Medline, and Embase was performed to retrieve relevant articles. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

Results

A total of 18 studies with 7,168 participants were analyzed. In overall analyses, a significant association with the likelihood of glaucoma was detected for the rs1801133 polymorphism in dominant (p = 0.04, OR = 0.90, 95%CI 0.81–1.00) and allele (p = 0.02, OR = 0.91, 95%CI 0.84–0.98) comparisons. Further, subgroup analyses by ethnicity revealed that both rs1801131 and rs1801133 polymorphisms were significantly associated with the likelihood of glaucoma in West Asians. However, no positive results were detected for two investigated polymorphisms in East Asians and Caucasians.

Conclusion

Our findings indicated that rs1801131 and rs1801133 polymorphisms may serve as genetic biomarkers of glaucoma in West Asians.