Nuclear and Mitochondrial DNA of Age-Related Cataract Patients Are Susceptible to Oxidative Damage

CircRNA HLCS regulates lens epithelial cell apoptosis via miR-338-3p/BPNT1 axis

PURPOSE

The purpose of this study was to investigate the effect of circ_HLCS on age-related cataract (ARC).

METHODS

Circ_HLCS, microRNA (miR)-338-3p, and bisphosphate 3'-nucleotidase 1 (BPNT1) were quantified by quantitative real-time polymerase chain reaction or western blot. Cell proliferation and cell viability were assessed by the 5-Ethynyl-2'-deoxyuridinr and cell counting kit-8 assays. Cell apoptosis was detected by flow cytometry. Targeted correlations among circ_HLCS, miR-338-3p, and BPNT1 were verified by the dual-luciferase reporter and RNA pull-down assays.

RESULTS

circ_HLCS was diminished in ARC tissues and UV-treated SRA01/04 cells. Elevated content of circ_HLCS undermined UV-induced cell proliferation inhibition and apoptosis. Mechanistically, circ_HLCS directly targeted miR-338-3p, and circ_HLCS regulated BPNT1 expression through miR-338-3p. Furthermore, reduction of miR-338-3p ameliorated UV-induced SRA01/04 cell damage by increasing BPNT1 expression.

CONCLUSION

Taken together, these data suggested that circ_HLCS inhibited apoptosis of UV-treated SRA01/04 cells by miR-338-3p/BPNT1 axis. Therefore, circ_HLCS might be a potential therapeutic target for ARC.

Comparative proteomics in captive giant pandas to identify proteins involved in age-related cataract formation

Approximately 20% of aged captive giant pandas (Ailuropoda melanoleuca) have cataracts that impair their quality of life. To identify potential biomarkers of cataract formation, we carried out a quantitative proteomics analysis of 10 giant pandas to find proteins differing in abundance between healthy and cataract-bearing animals. We identified almost 150 proteins exceeding our threshold for differential abundance, most of which were associated with GO categories related to extracellular localization. The most significant differential abundance was associated with components of the proteasome and other proteins with a role in proteolysis or its regulation, most of which were depleted in pandas with cataracts. Other modulated proteins included components of the extracellular matrix or cytoskeleton, as well as associated signaling proteins and regulators, but we did not find any differentially expressed transcription factors. These results indicate that the formation of cataracts involves a complex post-transcriptional network of signaling inside and outside lens cells to drive stress responses as a means to address the accumulation of protein aggregates triggered by oxidative damage. The modulated proteins also indicate that it should be possible to predict the onset of cataracts in captive pandas by taking blood samples and testing them for the presence or absence of specific protein markers.

The Role of Oxidative Stress in the Aging Eye

Given the expanding elderly population in the United States and the world, it is important to understand the processes underlying both natural and pathological age-related changes in the eye. Both the anterior and posterior segment of the eye undergo changes in biological, chemical, and physical properties driven by oxidative stress. With advancing age, changes in the anterior segment include dermatochalasis, blepharoptosis, thickening of the sclera, loss of corneal endothelial cells, and stiffening of the lens. Changes in the posterior segment include lowered viscoelasticity of the vitreous body, photoreceptor cell loss, and drusen deposition at the macula and fovea. Age-related ocular pathologies including glaucoma, cataracts, and age-related macular degeneration are largely mediated by oxidative stress. The prevalence of these diseases is expected to increase in the coming years, highlighting the need to develop new therapies that address oxidative stress and slow the progression of age-related pathologies.

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.

The human lens: An antioxidant-dependent tissue revealed by the role of caffeine

Cataract is the leading cause of blindness worldwide and surgery is the only option to treat the disease. Although the surgery is considered to be relatively safe, complications may occur in a subset of patients and access to ophthalmic care may be limited. Due to a growing and ageing population, an increase in cataract prevalence is expected and its management will become a socioeconomic challenge. Hence, there is a need for an alternative to cataract surgery. It is well known that oxidative stress is one of the main pathological processes leading to the generation of the disease. Antioxidant supplementation may, therefore, be a strategy to delay or to prevent the progression of cataract. Caffeine is a widely consumed high-potency antioxidant and may be of interest for the prevention of the disease. This review aims to give an overview of the anatomy and function of the lens, its antioxidant and reactive oxygen species (ROS) composition, and the role of oxidative stress in cataractogenesis. Also, the pharmacokinetics and -dynamics of caffeine will be described and the literature will be reviewed to give an overview of its anti-cataract potential and its possible role in the prevention of the disease.

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.

LncRNA KCNQ1OT1 promotes apoptosis and oxidative stress of human lens epithelial cells through epigenetic regulation of WRN

PURPOSE

Long non-coding RNA KCNQ1OT1 is fundamental to age-related cataract (ARC), whereas the underlying mechanism is still unknown. Here, we explored the possible mechanism of KCNQ1OT1 in ARC.

METHODS

The expression of KCNQ1OT1 in ARC patients and H₂O₂-treated human lens epithelial cell line SRA01/04 was detected. Gene and protein expression were examined by quantitative real-time PCR and western blot. Cell viability and apoptosis were detected by CCK-8 assay and flow cytometry. The content of reactive oxygen species (ROS) was assessed by fluorescent probe DCFH-DA. The relationship among KCNQ1OT1, G9a, H3K9me1/2 and WRN was verified by RNA pull down and Chromatin immunoprecipitation.

RESULTS

KCNQ1OT1 was up-regulated in the anterior lens capsule tissues of ARC patients and H₂O₂-treated SRA01/04 cells. KCNQ1OT1 overexpression suppressed cell viability and facilitated apoptosis in H₂O₂-treated SRA01/04 cells. KCNQ1OT1 up-regulation enhanced the levels of ROS and malondialdehyde (MDA), and reduced the levels of superoxide dismutase (SOD) and catalase (CAT) in H₂O₂-treated SRA01/04 cells. WRN up-regulation led to a result opposite to KCNQ1OT1 overexpression. The influence of WRN up-regulation on cell viability, apoptosis and oxidative stress of SRA01/04 cells was rescued by KCNQ1OT1 overexpression. Additionally, KCNQ1OT1 interacted with G9a. Both G9a and H3K9me1/2 interacted with WRN promoter. G9a deficiency significantly enhanced WRN expression and repressed H3K9me1/2 expression in SRA01/04 cells, which was abrogated by KCNQ1OT1 up-regulation.

CONCLUSION

This study demonstrated that KCNQ1OT1 promoted apoptosis and oxidative stress of human LECs through G9a-driven epigenetic regulation of WRN. This work highlights a novel lncRNA involving key regulators of ARC.

An Eye in the Replication Stress Response: Lessons From Tissue-Specific Studies in vivo

Several inherited human syndromes that severely affect organogenesis and other developmental processes are caused by mutations in replication stress response (RSR) genes. Although the molecular machinery of RSR is conserved, disease-causing mutations in RSR-genes may have distinct tissue-specific outcomes, indicating that progenitor cells may differ in their responses to RSR inactivation. Therefore, understanding how different cell types respond to replication stress is crucial to uncover the mechanisms of RSR-related human syndromes. Here, we review the ocular manifestations in RSR-related human syndromes and summarize recent findings investigating the mechanisms of RSR during eye development in vivo. We highlight a remarkable heterogeneity of progenitor cells responses to RSR inactivation and discuss its implications for RSR-related human syndromes.

RNA-Seq analysis in giant pandas reveals the differential expression of multiple genes involved in cataract formation

BACKGROUND

The giant panda (Ailuropoda melanoleuca) is an endangered mammalian species native to China. Fewer than 2500 giant pandas are known to exist, many of which are bred in captivity as a means to preserve and repopulate the species. Like other captive mammals, giant pandas acquire age-related cataracts, reducing their quality of life. Recent comparative genome-wide methylation analysis revealed 110 differentially methylated genes associated with cataract formation including six also associated with the formation of age-related cataracts in humans.

RESULTS

To investigate the pathological pathway in greater detail, here we used RNA-Seq analysis to investigate the differential expression profiles of genes in three giant pandas with cataracts and three healthy controls. We identified more than 700 differentially expressed genes, 29 of which were selected for further analysis based on their low q-value. We found that many of the genes encoded regulatory and signaling proteins associated with the control of cell growth, migration, differentiation and apoptosis, supporting previous research indicating a key role for apoptosis in cataract formation.

CONCLUSION

The identification of genes involved in the formation of age-related cataracts could facilitate the development of predictive markers, preventative measures and even new therapies to improve the life of captive animals.

Connexin Gap Junctions and Hemichannels in Modulating Lens Redox Homeostasis and Oxidative Stress in Cataractogenesis

The lens is continuously exposed to oxidative stress insults, such as ultraviolet radiation and other oxidative factors, during the aging process. The lens possesses powerful oxidative stress defense systems to maintain its redox homeostasis, one of which employs connexin channels. Connexins are a family of proteins that form: (1) Hemichannels that mediate the communication between the intracellular and extracellular environments, and (2) gap junction channels that mediate cell-cell communication between adjacent cells. The avascular lens transports nutrition and metabolites through an extensive network of connexin channels, which allows the passage of small molecules, including antioxidants and oxidized wastes. Oxidative stress-induced post-translational modifications of connexins, in turn, regulates gap junction and hemichannel permeability. Recent evidence suggests that dysfunction of connexins gap junction channels and hemichannels may induce cataract formation through impaired redox homeostasis. Here, we review the recent advances in the knowledge of connexin channels in lens redox homeostasis and their response to cataract-related oxidative stress by discussing two major aspects: (1) The role of lens connexins and channels in oxidative stress and cataractogenesis, and (2) the impact and underlying mechanism of oxidative stress in regulating connexin channels.

Hallmarks of lens aging and cataractogenesis

Lens homeostasis and transparency are dependent on the function and intercellular communication of its epithelia. While the lens epithelium is uniquely equipped with functional repair systems to withstand reactive oxygen species (ROS)-mediated oxidative insult, ROS are not necessarily detrimental to lens cells. Lens aging, and the onset of pathogenesis leading to cataract share an underlying theme; a progressive breakdown of oxidative stress repair systems driving a pro-oxidant shift in the intracellular environment, with cumulative ROS-induced damage to lens cell biomolecules leading to cellular dysfunction and pathology. Here we provide an overview of our current understanding of the sources and essential functions of lens ROS, antioxidative defenses, and changes in the major regulatory systems that serve to maintain the finely tuned balance of oxidative signaling vs. oxidative stress in lens cells. Age-related breakdown of these redox homeostasis systems in the lens leads to the onset of cataractogenesis. We propose eight candidate hallmarks that represent common denominators of aging and cataractogenesis in the mammalian lens: oxidative stress, altered cell signaling, loss of proteostasis, mitochondrial dysfunction, dysregulated ion homeostasis, cell senescence, genomic instability and intrinsic apoptotic cell death.

Circular RNA circZNF292 regulates H2 O2 -induced injury in human lens epithelial HLE-B3 cells depending on the regulation of the miR-222-3p/E2F3 axis

Circular RNAs (circRNAs) play important roles in the pathogenesis of age-related cataract (ARC). CircRNA zinc finger protein 292 (circZNF292, hsa_circ_0004058) is downregulated in ARC lens capsules. Here, we focused on its precise roles in oxidative stress underlying the pathogenesis of ARC. CircZNF292, microRNA (miR)-222-3p, and E2F transcription factor 3 (E2F3) were quantified by quantitative real-time polymerase chain reaction or western blot. Cell viability was assessed by the cell counting kit-8 assay. Cell cycle distribution and apoptosis were detected by flow cytometry. The activities of superoxide dismutase, catalase, and malondialdehyde were measured using the corresponding assay kit. Targeted correlations among circZNF292, miR-222-3p, and E2F3 were verified by the dual-luciferase reporter, RNA immunoprecipitation and RNA pull-down assays. Our data showed that circZNF292 was downregulated in ARC tissues and H₂ O₂ -treated human lens epithelial B3 (HLE-B3) cells. Increased expression of circZNF292 alleviated H₂ O₂ -induced cell viability suppression, apoptosis promotion, and oxidative stress enhancement. Mechanistically, circZNF292 directly targeted miR-222-3p, and circZNF292 regulated E2F3 expression through miR-222-3p. MiR-222-3p was a functional mediator of circZNF292 in modulating H₂ O₂ -induced injury in HLE-B3 cells. Furthermore, reduced level of miR-222-3p ameliorated H₂ O₂ -induced HLE-B3 cell damage by upregulating E2F3. Our present study demonstrated that increased expression of circZNF292 ameliorated H₂ O₂ -induced injury in HLE-B3 cells at least in part through the miR-222-3p/E2F3 axis, highlighting a novel insight into the involvement of circRNAs in the pathogenesis of ARC.

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.

Long non‑coding RNA NONHSAT143692.2 is involved in oxidative DNA damage repair in the lens by regulating the miR‑4728‑5p/OGG1 axis

Age-related cataract (ARC) is the leading cause of blindness worldwide. Oxidative DNA damage is a biochemical feature of ARC pathogenesis. The present study investigated the role of long non-coding RNAs in the DNA repair of oxidative damage, partially the regulation of the DNA repair gene, 8-oxoguanine DNA glycosylase (OGG1), in lens affected by ARC. The ogg1 mutant zebrafish model was constructed to verify the role of ogg1 in the lens. A high-throughput lncRNA profiling was performed on human lens epithelial cells (LECs) following oxidative stress. The lncRNAs with the OGG1 target gene were analyzed for possible differentiated expression levels. The lens capsule samples of patients with ARC were collected to further verify the screening results. lncRNA was then overexpressed and knocked down in LECs to observe cell proliferation and apoptosis. The association between lncRNA, miRNA and the OGG1 mRNA 3′UTR were analyzed. The ogg1 mutant zebrafish developed more severe lens lesions following oxidative challenge. lncRNA NONHSAT143692.2 was distinctly expressed in various disease models. The knockdown of NONHSAT143692.2 downregulated the expression of OGG1 mRNA (P<0.001) and OGG1 protein (P<0.001), aggravated oxidative damage to LECs, increased apoptosis (P<0.001) and decreased cell proliferation (P<0.01). The overexpression of NONHSAT143692.2 reversed the above-mentioned outcomes. miR-4728-5p was predicted to bind to NONHSAT143692.2 and OGG1 mRNA 3′UTR. The overexpression of miR-4728-5p downregulated the expression of NONHSAT143692.2 (P<0.001), OGG1 mRNA (P<0.001) and OGG1 protein (P<0.001). The knockdown of miR-4728-5p reversed the above-mentioned outcomes. Overall, the findings of the present study demonstrate that the NONHSAT143692.2/miR-4728-5p/OGG1 axis may play an important role in the development of ARC. This novel concept may provide new insight into the molecular diagnosis and treatment of ARC.

A Mitochondrial Genome-Wide Association Study of Cataract in a Latino Population

Purpose

Over 9.5 million Latinos could be affected by cataracts by 2050. However, no known cataract genetic risk alleles have been identified in Latinos. Moreover, no mitochondrial genome-wide association studies (MiWAS) have been conducted on cataracts in a Latino cohort despite the association between mitochondrial dysfunction and cataracts. Our purpose was to identify a mitochondrial DNA variant that associated with cataracts in a large-scale Latino population.

Methods

We conducted an MiWAS to identify mitochondrial single-nucleotide polymorphisms that modify cataract risk in nearly 3500 individuals enrolled in the Los Angles Latino Eye Study cohort, the largest Latino-specific cohort with comprehensive cataract data. Our analytic strategy for MiWAS included logistic regression on cataract occurrence while controlling for mitochondrial genetic ancestry, age, and biological sex.

Results

We found that MitoG228A (rs41323649) alternative allele carriers experienced a five times greater risk for cataracts compared with reference allele carriers. Alternative allele carriers also developed cataracts earlier in life compared with reference allele carriers. Intracohort cross-validation with 10-fold resampling and five repeats showed that the effect of MitoG228A remained significant.

Conclusions

MitoG228A increased risk for cataracts five-fold in approximately 3500 Latinos. To the best of our knowledge, this is the first cataract MiWAS on a large-scale Latino population. This association needs to be validated in an independent cohort.

Translational Relevance

Our discovery hypothesis-generating study suggest MitoG228A has potential to be used as a risk factor in the clinic and as a target for therapeutics. With validation via an independent cohort, MitoG228A could be used to estimate cataract risk for a Latino to reduce complications later in life.

Effects of Eurya japonica extracts on human corneal epithelial cells and experimental dry eye

Eurya japonica (EJ) leaves have been indicated to exert anti-oxidative and anti-inflammatory effects. Dry eye disease (DED) is a chronic inflammatory disease and oxidative stress is closely associated with DED. The aim of the present study was to analyze the therapeutic efficacy of EJ in DED using human corneal epithelial (HCE) cells and a mouse model of experimental dry eye (EDE). EJ extracts (0.001, 0.01 and 0.1%) were used to treat HCE cells. Cell viability and mitochondrial function were detected using a EZ-Cytox cell viability assay kit and mitochondrial membrane potential assays. Dichlorofluorescein diacetate (DCF-DA) assay was used to measure cellular reactive oxygen species (ROS) levels. Subsequently, eye drops consisting of BSS or 0.001%, 0.01 and 0.1% EJ extracts were applied for treatment of EDE. At 7 days, conjunctival ROS production was measured using a DCF-DA assay. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, 10 kDa interferon gamma-induced protein 10 (IP-10) and monokine induced by interferon-γ (MIG) levels in the conjunctiva were analyzed using a multiplex immunobead assay. Tear film and ocular surface parameters were measured. Treatment with EJ extracts in HCE cells effectively improved cell viability, ROS levels and mitochondrial function. Mice treated with 0.01 and 0.1% EJ extracts indicated a significant decrease in ROS, TNF-α, IL-1β, IP-10 and MIG levels compared with the EDE or BSS groups. Furthermore, a significant improvement in all clinical parameters was observed in the 0.01 and 0.1% EJ extract groups. EJ extracts could decrease cytotoxicity and ROS production in HCE cells. Additionally, topical EJ extracts reduced oxidative damage and inflammation and improved clinical signs of EDE, suggesting that EJ extracts may be used as an adjunctive therapy for DED.

Effect of SOD2 methylation on mitochondrial DNA4834-bp deletion mutation in marginal cells under oxidative stress

Presbycusis, or age-related hearing loss, is a prevalent disease that severely affects the physical and mental health of the elderly. Oxidative stress and mitochondrial (mt)DNA deletion mutation are considered as major factors in the pathophysiology of age-related hearing loss. The 4977-bp deletion in human mtDNA (common deletion, corresponding to the 4834-bp mtDNA deletion in rats) is suggested to be closely associated with the pathogenesis of age-related hearing loss. Superoxide dismutase 2 (SOD2), an isoform of SOD that is exclusively expressed in the intracellular mitochondrial matrix, plays a crucial role in oxidative resistance against mitochondrial superoxide. Previous research has shown that methylation of the promoter region of the SOD2 gene decreased the expression of SOD2 in marginal cells (MCs) extracted from the inner ear of rats subjected to D-galactose-induced mtDNA4834 deletion. However, the relationship between SOD2 methylation and mtDNA4834 deletion under oxidative stress remains to be elucidated. Herein, an oxidative damage model was established in the extracted MCs using hydrogen peroxide (H2O2), which increased the methylation level of SOD2 and the copy number of mtDNA4834 mutation in MCs. Decreasing the methylation level of SOD2 using 5-azacytidine, a DNA methylation inhibitor, reduced oxidative stress and the copy number of mtDNA4834 mutation and inhibited H2O2-induced apoptosis. The present work demonstrates that decreasing the methylation of SOD2 suppresses the mtDNA4834 deletion in MCs under oxidative stress and provides potential insights to the intervention therapy of aging-related hearing loss.

Genome-wide analysis of methylation in giant pandas with cataract by methylation-dependent restriction-site associated DNA sequencing (MethylRAD)

The giant panda (Ailuropoda melanoleuca) is a native species to China. They are rare and endangered and are regarded as the 'national treasure' and 'living fossil' in China. For the time being, there are only about 2500 giant pandas in the world. Therefore, we still have to do much more efforts to protect the giant pandas. In captive wildlife, the cataract incidence of mammalian always increases with age. Currently, in China, the proportion of elderly giant pandas who suffering from cataract has reached 20%. The eye disorder thus has a strong influence on the physical health and life quality of the elderly giant pandas. To discover the genes associated with the pathogenesis of cataract in the elderly giant panda and achieve the goal of early assessment and diagnosis of cataract in giant pandas during aging, we performed whole genome methylation sequencing in 3 giant pandas with cataract and 3 healthy giant pandas using methylation-dependent restriction-site associated DNA sequencing (MethylRAD). In the present study, we obtained 3.62M reads, on average, for each sample, and identified 116 and 242 differentially methylated genes (DMGs) between the two groups under the context of CCGG and CCWGG on genome, respectively. Further KEGG and GO enrichment analyses determined a total of 110 DMGs that are involved in the biological functions associated with pathogenesis of cataract. Among them, 6 DMGs including EEA1, GARS, SLITRK4, GSTM3, CASP3, and EGLN3 have been linked with cataract in old age.

Pigment epithelial-derived factor in the lens anterior capsule of patients with senile cataract with pseudoexfoliation

BACKGROUND

This study sought to evaluate pigment epithelial-derived factor (PEDF) levels in lens anterior capsule material taken during cataract surgery from patients with senile cataract with pseudoexfoliation.

METHODS

The study included 90 eyes of 86 patients who were diagnosed with, and underwent surgery for, cataracts. Sixty of the eyes included in the study had senile cataract. Thirty eyes of 30 young patients with other forms of cataract were included as a control group. Pseudoexfoliation was present in 21 patients with senile cataract. PEDF levels in the lens anterior capsule material - extracted with capsulorhexis in the classical phacoemulsification procedure - were measured by the enzyme-linked immunosorbent assay method and compared between the groups.

RESULTS

The PEDF level in the lens anterior capsule in the senile cataract patient group was 149.36 ± 17.46 pg/ml. A statistically significant lower level of PEDF was found in the lens anterior capsule of patients with senile cataract compared with the other groups. In the patient group with pseudoexfoliation, the PEDF level in the lens anterior capsule was found to be statistically significantly lower than the patient group without pseudoexfoliation.

CONCLUSION

PEDF levels decrease with senile cataract and pseudoexfoliation. These findings may clarify the pathogenesis of these conditions and point toward alternative treatment modalities.

The Effect of a Mediterranean Diet on the Incidence of Cataract Surgery

BACKGROUND

Cataract is a leading cause of vision impairment worldwide, and surgery is the only available treatment. The process that initiates lens opacification is dependent on the oxidative stress experienced by the lens components. A healthy overall dietary pattern, with the potential to reduce oxidative stress, has been suggested as a means to decrease the risk of developing cataract. We aimed to investigate the hypothesis that an intervention with a Mediterranean diet (MedDiet) rather than a low-fat diet could decrease the incidence of cataract surgery in elderly subjects.

METHODS

We included 5802 men and women (age range: 55-80 years) from the Prevención con Dieta Mediterránea study (multicenter, parallel-group, randomized controlled clinical trial) who had not undergone cataract surgery. They were randomly assigned to one of three intervention groups: (1) a MedDiet enriched with extra-virgin olive oil (EVOO) (n = 1998); (2) a MedDiet enriched with nuts (n = 1914), and a control group recommended to follow a low-fat diet (n = 1890). The incidence of cataract surgery was recorded yearly during follow-up clinical evaluations. Primary analyses were performed on an intention-to-treat basis. Cox regression analyses were used to assess the relationship between the nutritional intervention and the incidence of cataract surgery.

RESULTS

During a follow-up period of 7.0 years (mean follow-up period: 5.7 years; median: 5.9 years), 559 subjects underwent cataract surgery. Two hundred and six participants from the MedDiet + EVOO group, 174 from the MedDiet + Nuts group, and 179 from the control group underwent cataract surgery. We did not observe a reduction in the incidence of cataract surgery in the MedDiet groups compared to the control group. The multivariable adjusted hazard ratios were 1.03 (95% confidence interval [CI]: 0.84-1.26, p = 0.79) for the control group versus the MedDiet + EVOO group and 1.06 (95% CI: 0.86-1.31, p = 0.58) for the control group versus the MedDiet + Nuts group.

CONCLUSIONS

To our knowledge, this is the first large randomized trial assessing the role of a MedDiet on the incidence of cataract surgery. Our results showed that the incidence of cataract surgery was similar in the MedDiet with EVOO, MedDiet with nuts, and low-fat diet groups. Further studies are necessary to investigate whether a MedDiet could have a preventive role in cataract surgery.

Decreased Integrity, Content, and Increased Transcript Level of Mitochondrial DNA Are Associated with Keratoconus

Oxidative stress may play an important role in the pathogenesis of keratoconus (KC). Mitochondrial DNA (mtDNA) is involved in mitochondrial function, and the mtDNA content, integrity, and transcript level may affect the generation of reactive oxygen species (ROS) and be involved in the pathogenesis of KC. We designed a case-control study to research the relationship between KC and mtDNA integrity, content and transcription. One-hundred ninety-eight KC corneas and 106 normal corneas from Chinese patients were studied. Quantitative real-time PCR was used to measure the relative mtDNA content, transcript levels of mtDNA and related genes. Long-extension PCR was used to detect mtDNA damage. ROS, mitochondrial membrane potential and ATP were measured by respective assay kit, and Mito-Tracker Green was used to label the mitochondria. The relative mtDNA content of KC corneas was significantly lower than that of normal corneas (P = 9.19×10⁻²⁴), possibly due to decreased expression of the mitochondrial transcription factor A (TFAM) gene (P = 3.26×10⁻³). In contrast, the transcript levels of mtDNA genes were significantly increased in KC corneas compared with normal corneas (NADH dehydrogenase subunit 1 [ND1]: P = 1.79×10⁻³; cytochrome c oxidase subunit 1 [COX1]: P = 1.54×10⁻³; NADH dehydrogenase subunit 1, [ND6]: P = 4.62×10⁻³). The latter may be the result of increased expression levels of mtDNA transcription-related genes mitochondrial RNA polymerase (POLRMT) (P = 2.55×10⁻⁴) and transcription factor B2 mitochondrial (TFB2M) (P = 7.88×10⁻⁵). KC corneas also had increased mtDNA damage (P = 3.63×10⁻¹⁰), higher ROS levels, and lower mitochondrial membrane potential and ATP levels compared with normal corneas. Decreased integrity, content and increased transcript level of mtDNA are associated with KC. These changes may affect the generation of ROS and play a role in the pathogenesis of KC.