The Changes of 8-OHdG, hOGG1, APE1 and Pol β in Lenses of Patients with Age-Related Cataract

Metformin alleviates oxidative stress-induced senescence of human lens epithelial cells via AMPK activation and autophagic flux restoration

Cataracts are the leading cause of blindness worldwide owing to the increasing proportion of elderly individuals in the population. The purpose of this study was to investigate whether metformin could alleviate the occurrence and development of age‐related cataract (ARC) and the underlying mechanism. In the present study, we established a senescence model induced by oxidative stress, which was confirmed by measuring β‐galactosidase activity, qRT‐PCR and Western blotting. In addition, we showed that metformin alleviated the oxidative stress‐induced senescence of HLE‐B3 cells via the activation of AMPK. Next, we provided evidence that oxidative stress impaired autophagic flux and induced lysosomal dysfunction. Subsequently, we found that metformin restored autophagic flux that had been impaired by oxidative stress by activating AMPK. Additionally, we found that metformin suppressed HLE‐B3 cell senescence by improving lysosomal function and inactivating mTOR. Furthermore, the inactivation of AMPK, impairment of autophagic flux and lysosomal dysfunction were observed in the human lens epithelium of ARC. In summary, our data suggest that the activation of AMPK may be a potential strategy for preventing ARC, and metformin may be an emerging candidate to alleviate the formation and development of ARC.

Cataract formation in transgenic HO-1 G143H mutant mice: Involvement of oxidative stress and endoplasmic reticulum stress

Oxidative stress and endoplasmic reticulum (ER) stress are the key contributing factors for cataract progression. In our previous studies, we demonstrated that the nuclear factor erythroid 2-like-2 (Nrf-2)/heme oxygenase-1 (HO-1)/carbon monoxide (CO) axis protects lens epithelial cells (LECs) against oxidants and ER stress. In the present study, transgenic FVB/N mice overexpressing the negative dominant mutant HO-1 G143H (TgHO-1 G143H) were generated to evaluate the crosstalk among HO-1, oxidative stress and ER stress in maintaining lens transparency. Slit-lamp examination revealed that nuclear cataracts occurred at 4 months in the TgHO-1 G143H mice, which was 5 months earlier than that of the control mice. The lenses of the transgenic mice showed an accumulation of malondialdehyde and protein carbonyl with a decrease in glutathione and protein sulfhydryl levels. Elevated concentrations of ER stress biomarkers (Bip, PERK, ATF6, IRE1, CHOP, caspase-12 and caspase-3) in the lenses of the TgHO-1 G143H mice were identified by western blotting. Furthermore, we confirmed that overexpressed HO-1 G143H in LECs resulted in oxidative insult and apoptosis in vitro. All of these data suggested that HO-1 enzymatic activity loss induces early-onset nuclear cataracts by activating oxidative stress and ER stress.

DNA damage in obesity: Initiator, promoter and predictor of cancer

Epidemiological evidence linking obesity with increased risk of cancer is steadily growing, although the causative aspects underpinning this association are only partially understood. Obesity leads to a physiological imbalance in the regulation of adipose tissue and its normal functioning, resulting in hyperglycaemia, dyslipidaemia and inflammation. These states promote the generation of oxidative stress, which is exacerbated in obesity by a decline in anti-oxidant defence systems. Oxidative stress can have a marked impact on DNA, producing mutagenic lesions that could prove carcinogenic. Here we review the current evidence for genomic instability, sustained DNA damage and accelerated genome ageing in obesity. We explore the notion of genotoxicity, ensuing from systemic oxidative stress, as a key oncogenic factor in obesity. Finally, we advocate for early, pre-malignant assessment of genome integrity and stability to inform surveillance strategies and interventions.

Lanosterol Synthase Pathway Alleviates Lens Opacity in Age-Related Cortical Cataract

Purpose

Lanosterol synthase (LSS) abnormity contributes to lens opacity in rats, mice, dogs, and human congenital cataract development. This study examined whether LSS pathway has a role in different subtypes of age-related cataract (ARC).

Methods

A total of 390 patients with ARC and 88 age-matched non-ARC patients were enrolled in this study. LSS expression was analyzed by western blot and enzyme-linked immunosorbent assay (ELISA). To further examine the function of LSS, we used U18666A, an LSS inhibitor in rat lens culture system.

Results

In lens epithelial cells (LECs), LSS expression in LECs increased with opaque degree C II, while it decreased with opaque degree C IV and C V. While in the cortex of age-related cortical cataract (ARCC), LSS expression was negatively related to opaque degree, while lanosterol level was positively correlated to opaque degree. No obvious change in both LSS and lanosterol level was found in either LECs or the cortex of age-related nuclear cataract (ARNC) and age-related posterior subcapsular cataract (ARPSC). In vitro, inhibiting LSS activity induced rat lens opacity and lanosterol effectively delayed the occurrence of lens opacity.

Conclusions

This study indicated that LSS and lanosterol were localized in the lens of human ARC, including ARCC, ARNC, and ARPSC. LSS and lanosterol level are only correlated with opaque degree of ARCC. Furthermore, activated LSS pathway in lens is protective for lens transparency in cortical cataract.

PARP-1/PAR Activity in Cultured Human Lens Epithelial Cells Exposed to Two Levels of UVB Light

This study investigated poly(ADP-ribose) polymerase-1 (PARP-1) activation in cultured human lens epithelial cells exposed to two levels of UVB light (312 nm peak wavelength), 0.014 and 0.14 J cm^-2 ("low" and "high" dose, respectively). At the low dose, PARP-1 and poly(ADP-ribose) (PAR) polymers acted to repair DNA strand breaks rapidly with no subsequent major effects on either cell morphology or viability. However, following the high UVB dose, there was a dramatic second phase of PARP-1 activation, 90 min later, which included a sudden reappearance of DNA strand breaks, bursts of reactive oxygen species (ROS) formation within both the mitochondria and nucleus, a translocation of PAR from the nucleus to the mitochondria and an ultimate 70% loss of cell viability occurring after 24 h. The results provide evidence for an important role for PARP-1 in protecting the human lens epithelium against low levels of UVB light, and possibly participating in the triggering of cell death following exposure to toxic levels of radiation.

Association between the 8-oxoguanine DNA glycosylase gene Ser326Cys polymorphism and age-related cataract: a systematic review and meta-analysis

PURPOSE

To investigate the association between the 8-oxoguanine DNA glycosylase (OGG1) gene Ser326Cys (rs1052133) polymorphism and age-related cataract (ARC).

METHODS

MEDLINE and EMBASE were searched to identify potential studies published before May 19, 2017, investigating the association between the OGG1 gene Ser326Cys polymorphism and ARC risk. The quality of eligible studies was assessed using the Newcastle-Ottawa Scale tool. The association between the OGG1 gene Ser326Cys polymorphism and ARC was analyzed using meta-analysis. Publication bias and sensitivity analyses were also performed.

RESULTS

Six studies were included in this systematic review, and five of these studies with Hardy-Weinberg equilibrium were included in a meta-analysis. The sample size of the meta-analysis was 3716, including 1831 patients with cataract and 1885 controls. Odds ratios (ORs) were 0.67 (95% confidence interval (CI) 0.52-0.85), 0.90 (95% CI 0.54-1.51), 0.52 (95% CI 0.32-0.85) and 0.72 (95% CI 0.56-0.92) for recessive, dominant, additive and allele contrast models, respectively. Sensitivity analysis indicated that the results of the meta-analysis were robust. No publication bias was observed.

CONCLUSIONS

The OGG1 gene Ser326Cys polymorphism was associated with ARC risk.

Exploiting the Ref-1-APE1 node in cancer signaling and other diseases: from bench to clinic

Reduction-oxidation factor 1-apurinic/apyrimidinic endonuclease (Ref-1/APE1) is a critical node in tumor cells, both as a redox regulator of transcription factor activation and as part of the DNA damage response. As a redox signaling protein, Ref-1/APE1 enhances the transcriptional activity of STAT3, HIF-1α, nuclear factor kappa B, and other transcription factors to promote growth, migration, and survival in tumor cells as well as inflammation and angiogenesis in the tumor microenvironment. Ref-1/APE1 is activated in a variety of cancers, including prostate, colon, pancreatic, ovarian, lung and leukemias, leading to increased aggressiveness. Transcription factors downstream of Ref-1/APE1 are key contributors to many cancers, and Ref-1/APE1 redox signaling inhibition slows growth and progression in a number of tumor types. Ref-1/APE1 inhibition is also highly effective when paired with other drugs, including standard-of-care therapies and therapies targeting pathways affected by Ref-1/APE1 redox signaling. Additionally, Ref-1/APE1 plays a role in a variety of other indications, such as retinopathy, inflammation, and neuropathy. In this review, we discuss the functional consequences of activation of the Ref-1/APE1 node in cancer and other diseases, as well as potential therapies targeting Ref-1/APE1 and related pathways in relevant diseases. APX3330, a novel oral anticancer agent and the first drug to target Ref-1/APE1 for cancer is entering clinical trials and will be explored in various cancers and other diseases bringing bench discoveries to the clinic.

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

The formation and development of age-related cataract (ARC) has been demonstrated to have the involvement of defective DNA repair in lens epithelial cells (LECs). This study aimed to investigate DNA repair genes expression in human lens cortex collected from age-related cortical cataract (ARCC) and controls during surgery. The expression levels of the genes were evaluated by xx genes microarray analysis. The results were further confirmed by Quantitative Real-Time PCR (qRT-PCR). The mRNA levels of 7 genes decreased and 4 genes out of 92 genes increased in lens cortex of ARCCs compared with controls with the fold change >1.5. Using Comet assay, we found the DNA breaks in the LECs of ARCCs were obviously severer than that of controls. The present data provide a global perspective on expression of DNA repair genes that may contribute to cataract pathogenesis. The DNA damage and repair pathway might be an effective target to delay the onset of ARC.

Associations of PARP-1 variant rs1136410 with PARP activities, oxidative DNA damage, and the risk of age-related cataract in a Chinese Han population: A two-stage case-control analysis

OBJECTIVE

To investigate whether a single nucleotide polymorphism (SNP) rs1136410 in the poly (ADP-ribose) polymerase-1 (PARP-1) gene was associated with PARP activities, 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, and the risk of age-related cataract (ARC) in a Chinese Han population.

METHODS

In this two-stage case-control study with a total of 1010 ARC patients and 1045 controls, SNP rs1136410 was genotyped by high-resolution melting analyses (HRM). PARP activities and 8-OHdG levels in peripheral blood mononuclear cells (PBMCs) were determined by ELISA kits.

RESULTS

In discovery, replication, and their merged sets, the variant genotypes (AG+GG) of SNP rs1136410 were significantly associated with an increased risk of ARC under a dominant model (Adjusted odds ratio (OR)=1.42, P_adj=0.001 for the merged set). This association was further identified in subtype analyses for cortical ARC (Adjusted OR=1.69, P_adj<0.001). In subgroup analyses, we identified a significant interaction between SNP rs1136410 and smoking habit in increasing ARC risk (P_inter=0.019). Moreover, ARC patients had lower activities of PARP and higher levels of 8-OHdG than controls. There were significant correlations of SNP rs1136410 with decreased PARP activities and increased 8-OHdG levels in controls and patients with cortical ARC.

CONCLUSIONS

This study suggests that SNP rs1136410 may confer susceptibility to ARC by affecting PARP activities and oxidative DNA damage.

Association between polymorphisms of OGG1, EPHA2 and age-related cataract risk: a meta-analysis

Background

Evidences have identified the correlation of 8-oxoguanine DNA glycosylase-1 (OGG1) and eph-receptor tyrosine kinase-type A2 (EPHA2) polymorphisms in age-related cataract (ARC) risk. However, the results were not consistent. The objective of this study was to examine the role of these two gene polymorphisms in ARC susceptibility.

Methods

Eligible case–control studies published between January 2000 and 2015 were searched and retrieved in the electronic databases. The odds ratio with 95 % confidence interval (CI) was employed to calculate the strength of the relationship.

Results

We totally screened out six articles, including 5971 cataract patients and 4189 matched controls. Three variants were contained (OGG1 rs1052133; EPHA2 rs7543472 and rs11260867). For OGG1 rs1052133, we detected a significant correlation between OGG1 polymorphism and ARC risk under the heterogenous model (CG vs. CC: OR = 1.34, 95 % CI = 1.06–1.70, P = 0.01) and dominant model (GG+CG vs. CC: OR = 1.45, 95 % CI = 1.16–1.81, P = 0.001), especially in patients with cortical cataract of subgroup analysis by phenotypes (P < 0.05). For EPHA2 rs7543472 and rs11260867, we did not find a positive association between these two mutations and ARC susceptibility in total cases. Subgroup analysis by phenotypes of cataract showed that only in cortical cataract, genotypes of rs7543472 under the allele model, homogenous model and recessive model; genotypes of rs11260867 under the heterogenous model and dominant model were associated with ARC risk.

Conclusions

OGG1 rs1052133 (CG and CG+GG genotypes) might be risk factor for ARC, particularly in cortical cataract risk. EPHA2 rs7543472 (T allele and TT genotype) and rs11260867 (CG and GG+CG genotypes) might be associated with cortical cataract.

Epigenetic Regulation of Werner Syndrome Gene in Age-Related Cataract

Purpose. To examine the promoter methylation and histone modification of WRN (Werner syndrome gene), a DNA repair gene, and their relationship with the gene expression in age-related cataract (ARC) lens. Methods. We collected the lenses after cataract surgery from 117ARC patients and 39 age-matched non-ARC. WRN expression, DNA methylation and histone modification around the CpG island were assessed. The methylation status of Human-lens-epithelium cell (HLEB-3) was chemically altered to observe the relationship between methylation and expression of WRN. Results. The WRN expression was significantly decreased in the ARC anterior lens capsules comparing with the control. The CpG island of WRN promoter in the ARC anterior lens capsules displayed hypermethylation comparing with the controls. The WRN promoter was almost fully methylated in the cortex of ARC and control lens. Acetylated H3 was lower while methylated H3-K9 was higher in ARC anterior lens capsules than that of the controls. The expression of WRN in HLEB-3 increased after demethylation of the cells. Conclusions. A hypermethylation in WRN promoter and altered histone modification in anterior lens capsules might contribute to the ARC mechanism. The data suggest an association of altered DNA repair capability in lens with ARC pathogenesis.