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LOXL1 expression in lens capsule tissue specimens from individuals with pseudoexfoliation syndrome and glaucoma.

ABSTRACT: To study lysyl oxidase-like 1 (LOXL1) expression in freshly collected lens capsules from pseudoexfoliation syndrome (XFS), pseudoexfoliation glaucoma (XFG), and normal cataract control individuals. We also investigated the effects of four glaucoma drug medications on LOXL1 expression in primary human lens epithelial cell cultures to see if they could affect LOXL1 expression.Lens capsules were collected at the time of cataract surgery. Controls were matched to age, sex, and ethnicity. Total RNA was isolated from individual lens capsule samples and real-time PCR was performed on each sample using primers flanking the sixth exon of the LOXL1 gene. Cell cultures were grown to confluence in four separate six-well plates at 37 °C in 5% CO2. Each plate was then treated with one of four different glaucoma drugs (brinzolamide 1%, brimonidine tartrate 0.1%, timolol maleate 0.5%, and latanoprost 0.005%) once daily for seven days (at both 1:1,000 and 1:100 concentrations relative to media). Controls were not treated with any drug but media was changed in the same manner. After one week of treatment, cells were harvested and total RNA isolated. Real-time PCR was performed on each group of cells.Seven XFS, seven XFG, and ten cataract control specimens were analyzed. LOXL1 expression was detected in the lens capsule specimens from each of the four groups. Significant expression differences were found between the control and XFG groups and XFS and XFG groups. No significant difference was observed between the control and XFS group. No significant decrease in LOXL1 expression was seen with drug incubation of the four medications (Brinzolamide, Timolol, Latanoprost, and Brimonidine) at the 1:1,000 drug:media concentrations versus controls. At 10-fold higher concentrations (1:100 drug:media), brinzolamide, timolol maleate, and latanoprost showed small increases in LOXL1 expression relative to controls. This effect was not observed with brimonidine tartrate.These results establish that LOXL1 expression is reduced in lens capsule specimens from XFG individuals but not XFS. The drug treatment incubation studies suggest that the change in LOXL1 expression observed in XFG is not attributable to glaucoma drug therapy. If a causative functional relationship can be validated, modification of LOXL1 expression in affected tissues may represent a novel treatment strategy for this disorder.

SUBMITTER: Khan TT

PROVIDER: S-EPMC2994419 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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LOXL1 expression in lens capsule tissue specimens from individuals with pseudoexfoliation syndrome and glaucoma.

Khan Tanya T TT Li Guorong G Navarro Iris D ID Kastury Rama D RD Zeil Carol J CJ Semchyshyn Taras M TM Moya Frank J FJ Epstein David L DL Gonzalez Pedro P Challa Pratap P

Molecular vision 20101102

<h4>Purpose</h4>To study lysyl oxidase-like 1 (LOXL1) expression in freshly collected lens capsules from pseudoexfoliation syndrome (XFS), pseudoexfoliation glaucoma (XFG), and normal cataract control individuals. We also investigated the effects of four glaucoma drug medications on LOXL1 expression in primary human lens epithelial cell cultures to see if they could affect LOXL1 expression.<h4>Methods</h4>Lens capsules were collected at the time of cataract surgery. Controls were matched to age, ...[more]

PMID: 21139690

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Project description:BACKGROUND: LOXL1 gene is the most important genetic risk factor known so far for pseudoexfoliation glaucoma (XFG). Our purpose was to evaluate the potential association of individual genetic variants of the lysyl oxidase-like 1 (LOXL1) gene and haplotypes with XFG in Spanish patients. METHODS: Blood samples were collected from a total of 105 Spanish patients with XFG and 200 healthy controls. The entire LOXL1 gene along with the promoter, coding and non-coding regions including the 5'- and 3'-untranslated regions, were sequenced using next-generation sequencing in 99 XFG patients. SNPs rs16958477 (promoter), rs1048661 (exon 1), rs3825942 (exon 1), rs2165241 (intron 1) and rs3522 (exon 7) in LOXL1 were genotyped by restriction fragment-length polymorphism (RFLP) in all Spanish control participants and in six additional XFG patients, and a case-control association study was performed. Comparisons of the allelic and genotypic frequencies were performed using standard ?(2) test with Bonferroni and Pearson corrections. Logistic regression analyses were permormed using Sigmaplot v11. Haplotypes frequencies were performed using HaploView 4.0. RESULTS: Sequencing of the LOXL1 gene in XFG participants identified a total of 212 SNPs, of which 49 exhibited allelic frequencies with significant differences between cases and controls, and 66 were not previously described. The allele frequencies of SNPs rs16958477, rs1048661, rs3825942, rs2165241, were significantly associated with an increased risk for XFG, however the SNP rs3522 was not. The haplotype frequencies of SNPs rs16958477, rs1048661, rs3825942 and rs2165241 and their association with XFG indicated that the CGGT haplotype, containing all four risk alleles, and the AGGT haplotype, which carries the protective allele of rs16958477 and three risk alleles of the other three SNPs, were significantly associated with XFG (p?=?4.5×10(-6), and p?=?8.8×10(-6)), conferring more than 2-fold increased disease susceptibility. CONCLUSIONS: SNPs of the LOXL1 gene are associated with XFG in the Spanish population. This information adds new support to the distinct risk association frequencies of LOXL1 alleles with XFG in Western European and Asian populations. Identification and validation of additional SNPs along the entire LOXL1 gene of XFG cases may provide insightful information on their potential role in the pathogenesis of this disease.

Project description:Pseudoexfoliation (PEX) syndrome, one of the most common causes of glaucoma, represents a complex, multifactorial, late-onset disease of worldwide significance. The etiopathogenesis involves both genetic and non-genetic factors. The PEX-specific tissue alterations are caused by a generalized fibrotic matrix process, which has been characterized as a stress-induced elastosis associated with the excessive production and abnormal cross-linking of elastic microfibrils into fibrillar PEX aggregates. The identification of lysyl oxidase-like 1 (LOXL1) as a major genetic risk factor for PEX syndrome and PEX glaucoma further supports a role of elastogenesis and elastosis in the pathophysiology of PEX, as LOXL1 is a pivotal cross-linking enzyme in elastic fiber formation and stabilization. The available data suggest that LOXL1 is markedly dysregulated depending on the stage of the fibrotic process. While transient upregulation of LOXL1 during the early stages of PEX fibrogenesis participates in the formation and aggregation of abnormal PEX fiber deposits, the decreased expression of LOXL1 during the advanced stages of the disease may affect elastin metabolism and promote elastotic processes, e.g. in the lamina cribrosa, predisposing to glaucoma development. However, in view of the low penetrance of the PEX-associated risk variants of LOXL1, other genetic and/or environmental factors must contribute to the risk of developing the PEX phenotype. Some evidence exists for the contribution of additional genes with relatively small effects, e.g. clusterin (CLU), contactin-associated protein-like 2 (CNTNAP2), apolipoprotein E (APOE), glutathione S-transferases (GSTs), and tumor necrosis factor-alpha (TNFA), in certain study populations. Several environmental conditions associated with PEX, such as oxidative stress as well as pro-fibrotic cytokines and growth factors, can regulate expression of LOXL1 and elastic proteins in vitro and may therefore act as co-modulating external factors. Ultimately, both detection and functional characterization of yet unidentified genetic and non-genetic factors may lead to the development of more precise screening tools for the risk of PEX glaucoma.

Dataset Information

LOXL1 expression in lens capsule tissue specimens from individuals with pseudoexfoliation syndrome and glaucoma.

Publications

LOXL1 expression in lens capsule tissue specimens from individuals with pseudoexfoliation syndrome and glaucoma.

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