Racemization in cataractous lens from diabetic and aging individuals: analysis of Asp 58 residue in αA-crystallin.

Cataract is the leading cause of visual impairment globally. Racemization of lens proteins may contribute to cataract formation in aging individuals. As a special type of age-related cataract (ARC), diabetic cataract (DC) is characterized by the early onset of cortical opacification and finally developed into a mixed type of cortical and nuclear opacification. We compared racemization of Asp 58 residue, a hotspot position in αA-crystallin, from the cortex and nucleus of diabetic and age-matched senile cataractous lenses, by identifying L-Asp/L-isoAsp/D-Asp/D-isoAsp by mass spectrometry. Compared to nondiabetic cataractous lenses, DC lenses showed a significantly increased cortex/nucleus ratio of D-Asp 58, which originated primarily from an increased percentage of D-Asp 58 in the lens cortex of DC. Moreover, patients diagnosed with diabetes for over 10 years showed a lower cortex/nucleus ratio of D-isoAsp 58 in the lens compared with those who had a shorter duration of diabetes, which originated mainly from an increased percentage of D-isoAsp 58 in the lens nucleus of DC with increasing time of hyperglycemia. Further analysis confirmed decreased protein solubility in diabetic cataractous lenses. The different racemization pattern in DC may be distinguished from ARC and influence its phenotype over the protracted duration of diabetes.

Racemization at the Asp 58 residue in αA-crystallin from the lens of high myopic cataract patients.

Post-translational modifications in lens proteins are key causal factors in cataract. As the most abundant post-translational modification in the lens, racemization may be closely related to the pathogenesis of cataract. Racemization of αA-crystallin, a crucial structural and heat shock protein in the human lens, could significantly influence its structure and function. In previous studies, elevated racemization from l-Asp 58 to d-isoAsp58 in αA-crystallin has been found in age-related cataract (ARC) lenses compared to normal aged human lenses. However, the role of racemization in high myopic cataract (HMC), which is characterized by an early onset of nuclear cataract, remains unknown. In the current study, apparently different from ARC, significantly increased racemization from l-Asp 58 to d-Asp 58 in αA-crystallin was identified in HMC lenses. The average racemization rates for each Asp isoform were calculated in ARC and HMC group. In ARC patients, the conversion of l-Asp 58 to d-isoAsp 58, up to 31.89%, accounted for the main proportion in racemization, which was in accordance with the previous studies. However, in HMC lenses, the conversion of l-Asp 58 to d-Asp 58, as high as 35.44%, accounted for the largest proportion of racemization in αA-crystallin. The different trend in the conversion of αA-crystallin by racemization, especially the elevated level of d-Asp 58 in HMC lenses, might prompt early cataractogenesis and a possible explanation of distinct phenotypes of cataract in HMC.

Type II Peter's anomaly with histopathological proof: a case report.

BACKGROUND: Peter's anomaly is a rare congenital anterior segment dysgenesis with poor visual results. This case report describes a case of bilateral Type II Peter's anomaly with notable clinical and histopathological features. CASE PRESENTATION: A 7-year-old boy was admitted to our center with complaints of bilateral central opacification, photophobia and severe reduced vision since birth. He underwent phacoemulsification, intraocular lens (IOL) implantation and anterior vitrectomy on the right eye in another medical institution two years ago. Slit lamp examination revealed bilateral central corneal opacity, few strands of peripheral iris, irregular pupils and cloudy lens with central adhesion to posterior corneal surface in the left eye. Additionally, a history of premature birth and mental retardation was also noted. The patient was diagnosed with Peter's anomaly in the left eye, pseudophakia in the right eye and bilateral amblyopia. Similar surgery to the right one was performed on the left eye. A vesicle-like structure was found in the anterior chamber intraoperatively, which was composed mainly of immature lens and some corneal stroma as revealed by postoperative histopathological examinations. CONCLUSIONS: The exact mechanism of Peter's anomaly is not completely understood, however, the notable histopathological features of tissue obtained from the present case may provide evidence to the hypothesis of developmental anomalies.

Siderotic cataract with no signs of intraocular foreign body.

BACKGROUND: Ocular siderosis is a clinical condition induced by deposition of an iron-containing intraocular foreign body. We report a unique case of histopathologically proven lens siderosis in a young woman with a preceding history of trauma but no signs of retained intraocular foreign body. CASE PRESENTATION: A 32-year-old woman presented with an opacified lens showing brownish deposits on the anterior capsule and underwent cataract surgery. Preoperative ophthalmic examination did not show any retained intraocular foreign body. Histopathologic staining of the anterior capsule confirmed the presence of iron deposits and macrophages. Electroretinography examination performed in the postoperative period showed the changes characteristic of retinal degeneration in ocular siderosis. CONCLUSION: This case illustrates the importance of close monitoring of patients with a history of trauma or previous penetrating injury to the eye, even if there is no intraocular foreign body, because they might develop ocular siderosis at a later stage. This case report underscores the importance of electroretinography and histopathologic analysis, in addition to ophthalmic examination, in the diagnosis of ocular siderosis.

Diagnosis of pupillary block glaucoma after removal of congenital cataracts with intraoperative ultrasound biomicroscopy: a case report.

BACKGROUND: Aphakic glaucoma is a common complication after congenital cataract extraction, especially in those who have surgery during infancy. This case report describes a case of bilateral pupillary block glaucoma diagnosed with intraoperative ultrasound biomicroscopy (UBM) after removal of congenital cataract. CASE PRESENTATION: We present a case report of a 9-month-old infant with bilateral corneal enlargement and ocular hypertension after uneventful removal of congenital cataracts. Initial and follow-up examination findings were reviewed. The infant was suspected to have developmental glaucoma and schemed to have bilateral trabeculotomy until pupillary obstruction by vitreous herniation and angle closure with iris bombé were detected by intraoperative UBM. Anterior vitrectomy and goniosynechialysis were then performed as treatment. CONCLUSION: Pupillary block glaucoma is a rare type of infantile aphakic glaucoma. Application of intraoperative UBM can assist in the differential diagnosis of aphakic glaucoma in infants.

Elevated TGF-ß2 level in aqueous humor of cataract patients with high myopia: Potential risk factor for capsule contraction syndrome.

PURPOSE: To evaluate the level of transforming growth factor-ß2 (TGF-ß2) in the aqueous humor of highly myopic cataract patients and its correlation with capsule contraction syndrome. SETTING: Eye and ENT Hospital of Fudan University, Shanghai, China. DESIGN: Prospective comparative case series. METHODS: The highly myopic cataract patients were divided into the following 2 groups according to the Lens Opacity Classification System III: nuclear color (NC) 2 to 3 and NC 5 to 6. Aqueous humor TGF-ß2 concentrations were assayed in the highly myopic cataract and age-related cataract groups. The TGF-ß2, TGF-ßRII (the type II receptor for TGF-ß2), and α-smooth muscle actin (α-SMA) expressions in lens epithelial cells (LECs) were detected by real-time polymerase chain reaction and immunofluorescent staining. RESULTS: The study comprised 40 highly myopic cataract patients (40 eyes) and 20 patients (20 eyes) with age-related cataract as the control group. Compared with the control group, the highly myopic cataract group had significantly higher TGF-ß2 concentration in the aqueous humor and increased TGF-ßRII expression in LECs, especially in NC 5 to 6 cases. Expression of α-SMA was barely detectable in both groups. CONCLUSION: In highly myopic cataract patients, especially those with dark nuclei, elevated aqueous humor TGF-ß2 levels and the upregulated TGF-ßRII expression in LECs might contribute to the pathogenesis of capsule contraction syndrome through transdifferentiation of LECs into myofibroblasts. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Molecular Inflammation in the Contralateral Eye After Cataract Surgery in the First Eye.

PURPOSE: The purpose of this study was to assess the inflammatory status of the aqueous humor in the fellow eye after uneventful cataract surgery in the first eye. METHODS: At the screening stage, aqueous humor samples from 15 first-eye and 15 second-eye cataract patients were collected just before cataract surgery and assayed using human cytokine antibody array. Screened cytokines were then verified using a suspension array system with aqueous humor samples obtained from 35 first-eye and 36 second-eye cataract patients. RESULTS: The cytokine antibody array revealed that interleukin-1 receptor antagonist (Il-1ra) and macrophage inflammatory protein (MIP)-1a and MIP-1b were expressed at high levels in first-eye patients and were lower in second-eye patients, whereas opposite trends were found for monocyte chemoattractant protein 1 (MCP-1) and for regulated on activation, normal T expressed and secreted (RANTES) (all, P < 0.05, Student's t-test). However, only MCP-1 and IL-1ra were significantly different between the two groups after Bonferroni correction (both P < 0.00125). In the replication stage, the suspension cytokine array revealed that only MCP-1 expression was significantly greater in the aqueous humor of second-eye patients than in that of first-eye patients (P = 0.0067, Student's t-test). CONCLUSIONS: This study revealed that expression of MCP-1, a pain-related inflammatory chemokine, was significantly increased in aqueous humor in the contralateral eye after first-eye cataract surgery. This suggests there may be a sympathetic ophthalmic type uveitis in the contralateral eye after first-eye cataract surgery and that may help to explain why second-eye phacoemulsification is often more painful. (ClinicalTrials.gov number, NCT01824927.)

Whole-exome sequencing implicates UBE3D in age-related macular degeneration in East Asian populations.

Age-related macular degeneration (AMD) is a leading cause of irreversible central blindness among the elderly worldwide. We use exome sequencing to analyse nonsynonymous single-nucleotide variants (SNVs) across the whole genome of 216 neovascular AMD cases and 1,553 controls. As a follow-up validation, we evaluate 3,772 neovascular AMD cases and 6,942 controls from five independent cohorts in the East Asian population. Here we show strong evidence of an association at a novel, missense SNV, rs7739323, which is located in the ubiquitin protein ligase E3D (UBE3D) gene (Pmeta=1.46 × 10(-9), odds ratio (OR)=0.74, 95% confidence interval (CI): 0.63-0.88). Furthermore, ablation of the UBE3D protein lead to an abnormal amount of pigment granules deposited in retinal pigment epithelium microvilli area and an abnormal response on electroretinography (ERG) in UBE3D(+/-) heterozygous mice. Our findings indicate that the ubiquitin-proteasome system may play a role in the pathogenesis of neovascular AMD.

αA-crystallin gene CpG islands hypermethylation in nuclear cataract after pars plana vitrectomy.

PURPOSE: To investigate the DNA methylation status of αA-crystallin gene in cataract secondary to pars plana vitrectomy. METHODS: Anterior capsular membranes of 40 eyes of 40 patients with cataract secondary to vitrectomy were collected. Another 20 eyes of 20 patients who received pars plana vitrectomy and phacoemulsification in the primary procedure, were recruited as control. Methylation status of the CpG islands of αA-crystallin gene was analyzed by pyrosequencing. Expression of αA-crystallin was evaluated by real-time polymerase chain reaction and western blot. RESULTS: In the post vitrectomy group, five patients with posterior subcapsular opacity and four patients with cortical opacity were excluded from further analysis. The remaining 31 patients with nuclear cataract were assigned into two groups according to tamponade types: 19 of octafluoropropane (C3F8) and 12 of silicone oil (SiO). The average nuclear color grading was elevated both in C3F8 and SiO groups after vitrectomy. Compared to the control group, hypermethylation of the CpG islands in the αA-crystallin gene promoter was found in both post vitrectomy groups, accompanied by significantly reduced αA-crystallin expression. No statistically significant differences were found between the C3F8 and SiO groups either for DNA methylation status or αA-crystallin expression. CONCLUSIONS: CpG islands hypermethylation of αA-crystallin gene may be involved in nuclear cataract formation after pars plana vitrectomy.

Identification of proteins that interact with alpha A-crystallin using a human proteome microarray.

PURPOSE: To identify proteins interacting with alpha A-crystallin (CRYAA) and to investigate the potential role that these protein interactions play in the function of CRYAA using a human proteome (HuProt) microarray. METHODS: The active full-length CRYAA protein corresponding to amino acids 1-173 of CRYAA was recombined. A HuProt microarray composed of 17,225 human full-length proteins with N-terminal glutathione S-transferase (GST) tags was used to identify protein-protein interactions. The probes were considered detectable when the signal to noise ratio (SNR) was over 1.2. The identified proteins were subjected to subsequent bioinformatics analysis using the DAVID database. RESULTS: The HuProt microarray results showed that the signals of 343 proteins were higher in the recombinant CRYAA group than in the control group. The SNR of 127 proteins was ≥ 1.2. The SNR of the following eight proteins was > 3.0: hematopoietic cell-specific Lyn substrate 1 (HCLS1), Kelch domain-containing 6 (KLHDC6), sarcoglycan delta (SGCD), KIAA1706 protein (KIAA1706), RNA guanylyltransferase and 5'-phosphatase (RNGTT), chromosome 10 open reading frame 57 (C10orf57), chromosome 9 open reading frame 52 (C9orf52), and plasminogen activator, urokinase receptor (PLAUR). The bioinformatics analysis revealed 127 proteins associated with phosphoproteins, alternative splicing, acetylation, DNA binding, the nuclear lumen, ribonucleotide binding, the cell cycle, WD40 repeats, protein transport, transcription factor activity, GTP binding, and cellular response to stress. Functional annotation clustering showed that they belong to cell cycle, organelle or nuclear lumen, protein transport, and DNA binding and repair clusters. CRYAA interacted with these proteins to maintain their solubility and decrease the accumulation of denatured target proteins. The protein-protein interactions may help CRYAA carry out multifaceted functions. CONCLUSIONS: One-hundred and twenty-seven of 17,225 human full-length proteins were identified that interact with CRYAA. The advent of microarray analysis enables a better understanding of the functions of CRYAA as a molecular chaperone.

Epigenetic regulation of αA-crystallin in high myopia-induced dark nuclear cataract.

PURPOSE: To assess the etiology of early-onset dark nucleus in high-myopic patients and its relationship with the epigenetic regulation of αA-crystallin (CRYAA). METHODS: We reviewed clinical data from patients who underwent cataract surgery at our center in 2012. Lens epithelial samples were collected during capsulorhexis, whereas young lens epithelium was donated. Cataract type and severity were graded according to the Lens Opacity Classification System III (LOCS III). DNA methylation was analyzed by pyrosequencing the CpG islands of the CRYAA promoter in the following groups: Age-Related Cataract (ARC) Nuclear Color (NC) 2-3; High-Myopic Cataract (HMC) NC2-3; ARC NC5-6; HMC NC5-6; and in young lenses graded NC1. We analyzed CRYAA expression by real-time polymerase chain reaction (PCR), reverse transcription PCR, and immunohistochemistry. RESULTS: The odds ratio of dark nucleus in high-myopic patients was 5.16 (95% confidence interval: 3.98-6.69; p<0.001). CpG islands in lens epithelial CRYAA promoter in the HMC NC5-6 Group exhibited the highest methylation of all the groups, but no statistically significant differences were evident between the HMC NC2-3 and ARC NC2-3 Groups. Likewise, CRYAA mRNA and protein levels in the HMC NC5-6 Group were significantly lower than the ARC NC5-6 Group and high-myopic controls. CONCLUSIONS: High myopia is a risk factor for dark nucleus. Downregulation of CRYAA via the hypermethylation of CpG islands in its promoter could underlie the earlier onset of dark nucleus in high-myopic patients.

αA crystallin may protect against geographic atrophy-meta-analysis of cataract vs. cataract surgery for geographic atrophy and experimental studies.

BACKGROUND: Cataract and geographic atrophy (GA, also called advanced "dry" age-related macular degeneration) are the two major causes of visual impairment in the developed world. The association between cataract surgery and the development of GA was controversial in previous studies. METHODS/PRINCIPAL FINDINGS: We performed a meta-analysis by pooling the current evidence in literature and found that cataract is associated with an increased risk of geographic atrophy with a summary odds ratio (OR) of 3.75 (95% CI: 95% CI: 1.84-7.62). However, cataract surgery is not associated with the risk of geographic atrophy (polled OR=3.23, 95% CI: 0.63-16.47). Further experiments were performed to analyze how the αA-crystallin, the major component of the lens, influences the development of GA in a mouse model. We found that theαA-crystallin mRNA and protein expression increased after oxidative stress induced by NaIO(3) in immunohistochemistry of retinal section and western blot of posterior eyecups. Both functional and histopathological evidence confirmed that GA is more severe in αA-crystallin knockout mice compared to wild-type mice. CONCLUSIONS: Therefore, αA-crystallin may protect against geographic atrophy. This study provides a better understanding of the relationship between cataract, cataract surgery, and GA.