Different alpha crystallin expression in human age-related and congenital cataract lens epithelium

Truncation mutations of CRYGD gene in congenital cataracts cause protein aggregation by disrupting the structural stability of γD-crystallin

Congenital cataracts, a prevalent cause of blindness in children, are associated with protein aggregation. γD-crystallin, essential for sustaining lens transparency, exists as a monomer and exhibits excellent structural stability. In our cohort, we identified a nonsense mutation (c.451_452insGACT, p.Y151X) in the CRYGD gene. To explore the effect of truncation mutations on the structure of γD-crystallin, we examined the Y151X and T160RfsX8 mutations, both located in the Greek key motif 4 at the cellular and protein level in this study. Both truncation mutations induced protein misfolding and resulted in the formation of insoluble aggregates when overexpressed in HLE B3 and HEK 293T cells. Moreover, heat, UV irradiation, and oxidative stress increased the proportion of aggregates of mutants in the cells. We next purified γD-crystallin to estimate its structural changes. Truncation mutations led to conformational disruption and a concomitant decrease in protein solubility. Molecular dynamics simulations further demonstrated that partial deletion of the conserved domain within the Greek key motif 4 markedly compromised the overall stability of the protein structure. Finally, co-expression of α-crystallins facilitated the proper folding of truncated mutants and mitigated protein aggregation. In summary, the structural integrity of the Greek key motif 4 in γD-crystallin is crucial for overall structural stability.

Identification of spontaneous age-related cataract in Microtus fortis

OBJECTIVES

Age-related cataract is the most common type of adult cataract and a leading cause of blindness. Currently, there are few reports on the establishment of animal models for age-related cataract. During the experimental breeding of Microtus fortis (M. fortis), we first observed that M. fortis aged 12 to 15 months could naturally develop cataracts. This study aims to explore the possibility of developing them as an animal model for age-related cataract via identifing and analyzing spontaneous cataract in M. fortis.

METHODS

The 12-month-old healthy M. fortis were served as a control group and 12-month-old cataractous M. fortis were served as an experimental group. The lens transparency was observed using the slit-lamp biomicroscope. Hematoxylin and eosin staining was used to detect pathological changes in the lens. Biochemical detection methods were applied to detect blood routine, blood glucose levels, the serum activities of superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in both groups. Finally, real-time RT-PCR was used to detect the transcription levels of cataract-related genes in the lens of 2 groups.

RESULTS

Compared with the control group, the lens of cataract M. fortis showed severely visible opacity, the structure of lens was destroyed seriously, and some pathological damage, such as swelling, degeneration/necrosis, calcification, hyperplasia, and fiber liquefaction were found in lens epithelial cells (LECs). The fibrous structure was disorganized and irregularly distributed with morgagnian globules (MGs) aggregated in the degenerated lens fibers. There was no statistically significant difference in blood glucose levels between the experimental and control groups (P>0.05). However, white blood cell (WBC) count (P<0.05), lymphocyte count (P<0.01), and lymphocyte ratio (P<0.05) were significantly decreased, while neutrophil percentage (P<0.05) and monocyte ratio (P<0.01) were significantly increased. The serum activities of SOD and GSH-Px (both P<0.05) were both reduced. The mRNAs of cataract-related genes, including CRYAA, CRYBA1, CRYBB3, Bsfp1, GJA3, CRYBA2, MIP, HspB1, DNase2B, and GJA8, were significantly downregultaed in the lenses of the experimental group (all P<0.05).

CONCLUSIONS

There are significant differences in lens pathological changes, peroxidase levels, and cataract-related gene expression between cataract and healthy M. fortis. The developed cataract spontaneously in M. fortis is closely related to age, the cataract M. fortis might be an ideal animal model for the research of age-related cataract.

Celastrol regulates the oligomeric state and chaperone activity of αB-crystallin linked with protein homeostasis in the lens

Protein misfolding and aggregation are crucial pathogenic factors for cataracts, which are the leading cause of visual impairment worldwide. α-crystallin, as a small molecular chaperone, is involved in preventing protein misfolding and maintaining lens transparency. The chaperone activity of α-crystallin depends on its oligomeric state. Our previous work identified a natural compound, celastrol, which could regulate the oligomeric state of αB-crystallin. In this work, based on the UNcle and SEC analysis, we found that celastrol induced αB-crystallin to form large oligomers. Large oligomer formation enhanced the chaperone activity of αB-crystallin and prevented aggregation of the cataract-causing mutant βA3-G91del. The interactions between αB-crystallin and celastrol were detected by the FRET (Fluorescence Resonance Energy Transfer) technique, and verified by molecular docking. At least 9 binding patterns were recognized, and some binding sites covered the groove structure of αB-crystallin. Interestingly, αB-R120G, a cataract-causing mutation located at the groove structure, and celastrol can decrease the aggregates of αB-R120G. Overall, our results suggested celastrol not only promoted the formation of large αB-crystallin oligomers, which enhanced its chaperone activity, but also bound to the groove structure of its α-crystallin domain to maintain its structural stability. Celastrol might serve as a chemical and pharmacological chaperone for cataract treatment.

Expression of αA-crystallin (CRYAA) in vivo and in vitro models of age-related cataract and the effect of its silencing on HLEB3 cells

AIM

To investigate the expression of αA-crystallin (CRYAA) in age-related cataract (ARC) models and its role in lens epithelial cells (LECs).

METHODS

We used Flow cytometry to detect the apoptosis and cell cycle in HLEB3 cells and Real-time fluorescence quantitative polymerase chain reaction to detect the expression of CRYAA mRNA in HLEB3 and in rabbit lens. The expression of CRYAA in HLEB3 cells and rabbit lenses as well as the proteins related to apoptosis and autophagy in transfected cells were detected by western blotting. The lens structure in rabbits was investigated using hematoxylin-eosin staining. Protein thermostability assay was performed to detect the thermal stability of rabbit lens proteins. CCK- 8 assay was used to detect the viability of transfected cells, and the transfection was recorded by fluorescence photography.

RESULTS

Hydrogen peroxide can promote apoptosis and arrest the cell cycle in HLEB3 cells, and naphthalene can cause cataract formation and damage the structure of the lens in rabbits. Both ARC models can reduce the expression of CRYAA. The expression of CRYAA silencing increased apoptosis and autophagy in HLEB3 cells.

Relationship between expression levels of TDRD7 and CRYBB3 and development of age-related cortico-nuclear cataracts

Background

The human lens develops age-related cataracts (ARCs) because of the complicated effects of aging and stressful conditions. Under conditions involving oxidative stress, cells form stress granules (SGs). TDRD7 has been identified as an RNA granule component and an important component of SGs. TDRD7 plays a role in the post-transcriptional expression of genes, such as the crystallin gene CRYBB3. Therefore, the present study investigated TDRD7 and CRYBB3 mRNA expressions in relation to age-related cortico-nuclear cataracts.

Methods

Quantitative real-time PCR was used to determine the expression levels of TDRD7 and CRYBB3 in 52 patients with ARC and 52 healthy controls. Anterior lens capsules and peripheral blood samples from patients with ARC were included in the patient group, and peripheral blood samples from healthy subjects and human lens epithelial cells (HLE-B3) were included in the control group. Gene expression levels in the different age groups were compared. Correlation analysis was used to assess the gene expression levels and age.

Results

The expression of TDRD7 and CRYBB3 was significantly up-regulated (P < 0.0001) in anterior lens capsules compared to that in HLE-B3 cells. Similarly, the expression of TDRD7 (P = 0.0004) and CRYBB3 (P < 0.0001) was higher in the peripheral blood samples of patients with ARC than in those of healthy subjects. Significant upregulation (P < 0.05) was observed in the 71–81-year age group of patients. No correlation was found between gene expression levels and age.

Conclusion

Significantly higher expression levels of TDRD7 and CRYBB3 in patients with ARC than in controls suggest that TDRD7 and CRYBB3 are associated with the development of age-related cortico-nuclear cataracts and the aging process under chronic stress.

Dielectric response to thermal denaturation of lenses in healthy and diabetic rabbits

The relative permittivity and conductivity of healthy and alloxane-induced diabetic rabbits lenses were measured over a frequency range of 500 Hz to 100 kHz in an electric field and at temperatures from 25 to 150 °C. The dielectric spectra for both tissues showed two separate relaxations with a characteristic frequency of around 4 and 25 kHz assigned to the cortical and nuclear zones, respectively. These two dispersions are due to the interfacial polarization at the surface of the α-crystallin molecules. The denaturation temperature for the non-diabetic lens and the diabetic lens is approximately 70 and 80 °C, respectively. Moreover, the relative permittivity and conductivity values are higher in the diabetic lens than in the non-diabetic tissue at the same temperature and frequency. Our dielectric studies provide a better understanding of the thermal stability of crystallin-water complexes in normal and diseased human lenses.

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.

Loss of FYCO1 leads to cataract formation

Autophagy is a degradation process of cytoplasmic proteins and organelles trafficked to degradation vesicles known as autophagosomes. The conversion of LC3-I to LC3-II is an essential step of autophagosome formation, and FYCO1 is a LC3-binding protein that mediates autophagosome transport. The p62 protein also directly binds to LC3 and is degraded by autophagy. In the present study, we demonstrated that disrupting the FYCO1 gene in mice resulted in cataract formation. LC3 conversion decreased in eyes from FYCO1 knockout mice. Further, FYCO1 interacted with αA- and αB-crystallin, as demonstrated by yeast two-hybrid screening and immunoprecipitation analyses. In eyes from knockout mice, the soluble forms of αA- and αB-crystallin, the lens’s major protein components, decreased. In addition, p62 accumulated in eyes from FYCO1 knockout mice. Collectively, these findings suggested that FYCO1 recruited damaged α-crystallin into autophagosomes to protect lens cells from cataract formation.

Comparison of clinical outcomes between the depot gonadotrophin-releasing hormone agonist protocol and gonadotrophin-releasing hormone antagonist protocol in normal ovarian responders

BACKGROUND

The gonadotrophin-releasing hormone (GnRH) antagonist protocol has some advantages, such as a simple method, short medication duration, and low incidence of ovarian hyperstimulation syndrome, but whether the GnRH antagonist protocol is suitable for normal ovarian responders has been controversial. We compared the clinical outcomes of fresh and frozen-thawed transfer cycles between the depot GnRH agonist protocol and GnRH antagonist protocol in normal ovarian responders.

METHODS

Data of normal ovarian responders who underwent in vitro fertilization-embryo transfer (IVF-ET) or intracytoplasmic sperm injection-embryo transfer (ICSI-ET) between January 2017 and December 2018 in our hospital were retrospectively analysed. In this study, there were 1119 fresh transfer cycles, including 502 GnRH antagonist cycles (GnRH antagonist group) and 617 depot GnRH agonist cycles (depot GnRH agonist group), as well as 468 frozen-thawed transfer cycles, includng 191 GnRH antagonist cycles (GnRH antagonist group) and 277 depot GnRH agonist cycles (depot GnRH agonist group). The clinical outcomes were compared between the GnRH antagonist group and the depot GnRH agonist group.

RESULTS

With the fresh transfer cycles, there were no statistically significant differences in the anti-Mullerian hormone level, number of transferred embryos or high-quality embryo rate between the two groups. The total dosage of gonadotropin (Gn), duration of Gn stimulation, number of oocytes retrieved, clinical pregnancy rate and incidences of moderate and severe ovarian hyperstimulation syndrome (OHSS) were significantly lower but the abortion rate was significantly higher in the GnRH antagonist group than in the depot GnRH agonist group (all P < 0.05). With the frozen-thawed transfer cycles, there were no statistically significant differences in the number of transferred embryos, clinical pregnancy rate or abortion rate between the two groups (all P > 0.05).

CONCLUSIONS

With the fresh transfer cycles, the GnRH antagonist protocol had a lower clinical pregnancy rate and lower incidences of moderate and severe OHSS than the depot GnRH agonist protocol, but with the frozen-thawed transfer cycles, both protocols had similar clinical pregnancy rates. These results remain to be further confirmed through large-sample, prospective, randomized and controlled studies.

Amyloid cross-sequence interaction between Aβ(1-40) and αA(66-80) in relation to the pathogenesis of cataract

Alzheimer's disease (AD) and cataract represent two common protein misfolding diseases closely associated with aging. Growing evidence suggests that these two diseases may be interrelated with each other through cross-sequence interactions between β-amyloid (Aβ) peptide and the short aggregating peptides derived from proteolytic breakdown of α-crystallin. αΑ(66-80) is one of several peptides produced by the proteolytic breakdown of α-crystallin in aged eye lens. Although it is evident that the Aβ(1-40) and αΑ(66-80) coexist in aged eye lenses and both the peptides are known to form macromolecular assemblies, their cross-sequence interaction and the seeding behavior are not known. In this study, the aggregation behavior of αΑ(66-80) has been examined in the presence of Aβ(1-40) on using thioflavin T (ThT) based aggregation kinetics. The presence of monomeric Aβ(1-40) augmented the aggregation kinetics of αΑ(66-80) and reduced the lag time of αΑ(66-80) aggregation. However, the addition of Aβ(1-40) or αΑ(66-80) fibrils (seeds) didn't result in any change in the rate of αΑ(66-80) aggregation. In this in vitro study, we could show that the presence Aβ(1-40) has substantial effect on the aggregation of αΑ(66-80), which suggests a possible interaction between AD and cataract pathologies.

Synchrotron-based FTIR microspectroscopy of protein aggregation and lipids peroxidation changes in human cataractous lens epithelial cells

Cataract is the leading cause of blindness worldwide but the mechanisms involved in the process of cataractogenesis are not yet fully understood. Two most prevalent types of age-related cataracts are nuclear (N) and cortical (C) cataracts. A common environmental factor in most age-related cataracts is believed to be oxidative stress. The lens epithelium, the first physical and biological barrier in the lens, is build from lens epithelial cells (LECs). LECs are important for the maintenance of lens transparency as they control energy production, antioxidative mechanisms and biochemical transport for the whole lens. The purpose of this study is to characterize compounds in LECs originated from N and C cataracts, by using the synchrotron radiation-based Fourier Transform Infrared (SR-FTIR) microspectroscopy, in order to understand the functional importance of their different bio-macromolecules in cataractogenesis. We used the SR-FTIR microspectroscopy setup installed on the beamline MIRAS at the Spanish synchrotron light source ALBA, where measurements were set to achieve single cell resolution, with high spectral stability and high photon flux. The results showed that protein aggregation in form of fibrils was notably pronounced in LECs of N cataracts, while oxidative stress and the lipids peroxidation were more pronounced in LECs of C cataracts.

Therapeutic Effect of Mongolian Medicine RuXian-I on Hyperplasia of Mammary Gland Induced by Estrogen/Progesterone through CRYAB-Promoted Apoptosis

The traditional Mongolian medicine (TMM) RuXian-I is an empirical formula specifically used for treating the hyperplasia of mammary gland (HMG) in clinic based on the principles of traditional Mongolian medicine, but the treatment mechanism is not completely clear. In this paper, we elaborated the mechanism of RuXian-I in the treatment of HMG induced by estrogen and progestogen from its toxicity and activity. Firstly, RuXian-I exhibited no toxic effect on HMG rats through no changes of body weight and food intake measurement and no pathologic changes of the organs (heart, liver, spleen, lung, and kidney) detected. Secondly, RuXian-I could decrease the increased nipple height and diameter and remarkably relieve the pathologic changes of HMG rats and also alleviate serum sex hormone levels (estradiol (E₂), luteinizing hormone (LH), progesterone (P), and testosterone (T)) of HMG rats. Finally, RuXian-I could obviously inhibit the upregulation level of antiapoptotic protein CRYAB of HMG rats and promote mammary gland cell apoptosis of HMG rats via increases of promoting apoptosis protein caspases-3, 8, and 9 and Bax and tumor suppressor protein p53, decreases of antiapoptosis protein Bcl-2, and release of cytochrome c. These results suggested that RuXian-I has protective and therapeutic effects on HMG rats induced by estrogen and progestogen possibly via promoting apoptotic pathway regulated by CRYAB and is a promising agent for treating HMG.

Broccoli sprouts juice prevents lens protein aggregation in streptozotocin-induced diabetic rat

AIM

To investigate the effect of broccoli sprouts juice in preventing lens protein aggregation in diabetic rat model.

METHODS

Totally 25 male Wistar rats were divided into negative control group, diabetic group without juice treatment as positive control and diabetic group given broccoli sprouts juice 0.25, 0.5 and 1 g/d for 28d. Diabetic rat model was obtained by administering a single dose streptozotocin 65 mg/kg intraperitoneal. At the end of the study, all rats were examined for fasting blood sugar level (FBS), visual cataract score using slit lamp biomicroscope and lens αB-crystallin expression using Western blot method. Statistical analysis was performed using one way ANOVA with post hoc test, correlation test, and simple linear regression.

RESULTS

Positive control group had the highest cataract score and lens aggregated αB-crystallin expression. Broccoli sprout juice dose of 1 g/d group had the mildest cataract score, as well as the expression of lens aggregated αB-crystallin compared to treatments groups 1 and 2, opposite to lens native αB-crystallin expression. The broccoli sprout juice groups gave a significant decrease in cataract score, and also in lens aggregated αB-crystallin expression in diabetic rat models (P<0.05).

CONCLUSION

Broccoli sprout juice has a significant effect in preventing lens protein aggregation in diabetic rat model. The higher dose gives better visual cataract scores, lower lens aggregated αB-crystallin expression and higher lens native αB-crystallin expression.

High-throughput sequencing reveals novel lincRNA in age-related cataract

Age-related cataract (ARC) is a major cause of blindness. Long non-coding RNAs (lncRNAs) are a heterogeneous class of RNAs that are non-protein-coding transcripts >200 nucleotides in length. LncRNAs are involved in various critical biological processes, such as chromatin remodeling, gene transcription, and protein transport and trafficking. Furthermore, the dysregulation of lncRNAs causes a number of complex human diseases, including coronary artery diseases, autoimmune diseases, neurological disorders and various cancers. However, the role of lncRNA in cataract remains unclear. Therefore, in the present study, lens anterior capsular membrane was collected from normal subjects and patients with ARC and total RNA was extracted. High-throughput sequencing was applied to detect differentially expressed lncRNAs and mRNAs. The analysis identified a total of 42,556 candidate differentially expressed mRNAs (27,447 +15,109) and a total of 7,041 candidate differentially expressed lncRNAs (4,146 + 2,895). Through bioinformatics analysis, the significant differential expression of novel lincRNA was observed and its possible molecular mechanism was explored. Reverse transcription-quantitative polymerase chain reaction was used to validate the different expression levels of selected lncRNAs. These findings may lead to the development of novel strategies for genetic diagnosis and gene therapy.