Differential Lysyl oxidase like 1 expression in pseudoexfoliation glaucoma is orchestrated via DNA methylation.

Pseudoexfoliation syndrome (PXF) is the most common cause of secondary open angle glaucoma worldwide. Single nucleotide polymorphisms (SNPs) in the gene Lysyl oxidase like 1 (LOXL1) are strongly associated with the development of pseudoexfoliation glaucoma (PXFG). However, these SNPs are also present in 50-80% of the general population, suggestive of other factors being involved in the pathogenesis of PXFG. In this study, we aimed to investigate the influence of epigenetic regulation, specifically DNA methylation, on LOXL1 expression in PXFG using human tenons fibroblasts (HTFs), aqueous humour and serum samples from donors with and without PXFG. LOXL1 expression in HTFs was measured by qPCR and Western Blotting and LOXL1 concentration in aqueous humour was determined by ELISA. Global DNA methylation levels were quantified using an ELISA for 5-methylcytosine. MeDIP assays assessed the methylation status of the LOXL1 promoter region. Expression of methylation-associated enzymes (DNMT1, DNMT3a and MeCP2) were determined by qPCR and inhibited by 0.3 µM 5-azacytidine (5-aza). Results showed that LOXL1 expression was significantly decreased in PXFG HTFs compared with Control HTFs at gene (Fold change 0.37 ± 0.05, P < 0.01) level and showed a decrease, when measured at the protein level (Fold change 0.65 ± 0.42, P = 0.22), however this was not found to be significant. LOXL1 concentration was increased in the aqueous of PXFG patients compared with Controls (2.76 ± 0.78 vs. 1.79 ± 0.33 ng/ml, P < 0.01). Increased global methylation (56.07% ± 4.87% vs. 32.39% ± 4.29%, P < 0.01) was observed in PXFG HTFs compared with Control HTFs, as was expression of methylation-associated enzymes (DNMT1 1.58 ± 0.30, P < 0.05, DNMT3a 1.89 ± 0.24, P < 0.05, MeCP2 1.63 ± 0.30, P < 0.01). Methylation-associated enzymes were also increased when measured at protein level (DNMT1 5.70 ± 2.64, P = 0.04, DNMT3a 1.79 ± 1.55, P = 0.42, MeCP2 1.64 ± 1.33, P = 0.45). LOXL1 promoter methylation was increased in patients with PXFG compared to Control patients in both blood (3.98 ± 2.24, 2.10 ± 1.29, P < 0.05) and HTF cells (37.31 ± 22.0, 8.66 ± 10.40, P < 0.01). Treatment of PXFG HTFs with in 5-azacytidine increased LOXL1 expression when compared with untreated PXFG HTFs (Fold change 2.26 ± 0.67, P < 0.05). These data demonstrate that LOXL1 expression is altered in PXFG via DNA methylation and that reversal of these epigenetic changes may represent future potential therapeutic targets in the management of PXFG.

The role of lamina cribrosa tissue stiffness and fibrosis as fundamental biomechanical drivers of pathological glaucoma cupping.

The primary biomechanical driver of pathological glaucomatous cupping remains unknown. Finite element modeling indicates that stress and strain play key roles. In this article, primarily a review, we utilize known biomechanical data and currently unpublished results from our lab to propose a three-stage, tissue stiffness-based model to explain glaucomatous cupping occurring at variable levels of translaminar pressure (TLP). In stage 1, a short-term increase in TLP gradient induces a transient increase in lamina cribrosa (LC) strain. Beyond a critical level of strain, the tissue stiffness rises steeply provoking cellular responses via integrin-mediated mechanotransduction. This early mechanoprotective cellular contraction reduces strain, which reduces tissue stiffness by return of the posteriorly deflected LC to baseline. In stage 2 a prolonged period of TLP increase elicits extracellular matrix (ECM) production leading to fibrosis, increasing baseline tissue stiffness and strain and diminishing the contractile ability/ability to return to the baseline LC position. This is supported by our three-dimensional collagen contraction assays, which show significantly reduced capacity to contract in glaucoma compared with normal LC cells. Second, 15% cyclic strain in LC cells over 24 h elicits a typical increase in ECM profibrotic genes in normal LC cells but a highly blunted response in glaucoma LC cells. Stage 3 is characterized by persistent fibrosis causing further stiffening and inducing a feed-forward ECM production cycle. Repeated cycles of increased strain and stiffness with profibrotic ECM deposition prevent optic nerve head (ONH) recoil from the new deflected position. This incremental maladaptive modeling leads to pathological ONH cupping.

Lysyl Oxidase Like 1: Biological roles and regulation.

Lysyl Oxidase Like 1 (LOXL1) is a gene that encodes for the LOXL1 enzyme. This enzyme is required for elastin biogenesis and collagen cross-linking, polymerising tropoelastin monomers into elastin polymers. Its main role is in elastin homeostasis and matrix remodelling during injury, fibrosis and cancer development. Because of its vast range of biological functions, abnormalities in LOXL1 underlie many disease processes. Decreased LOXL1 expression is observed in disorders of elastin such as Cutis Laxa and increased expression is reported in fibrotic disease such as Idiopathic Pulmonary Fibrosis. LOXL1 is also downregulated in the lamina cribrosa in pseudoexfoliation glaucoma and genetic variants in the LOXL1 gene have been linked with an increased risk of developing pseudoexfoliation glaucoma and pseudoexfoliation syndrome. However the two major risk alleles are reversed in certain ethnic groups and are present in a large proportion of the normal population, implying complex genetic and environmental regulation is involved in disease pathogenesis. It also appears that the non-coding variants in intron 1 of LOXL1 may be involved in the regulation of LOXL1 expression. Gene alteration may occur via a number of epigenetic and post translational mechanisms such as DNA methylation, long non-coding RNAs and microRNAs. These may represent future therapeutic targets for disease. Environmental factors such as hypoxia, oxidative stress and ultraviolet radiation exposure alter LOXL1 expression, and it is likely a combination of these genetic and environmental factors that influence disease development and progression. In this review, we discuss LOXL1 properties, biological roles and regulation in detail with a focus on pseudoexfoliation syndrome and glaucoma.

Increased Substrate Stiffness Elicits a Myofibroblastic Phenotype in Human Lamina Cribrosa Cells.

Purpose: Alteration in the extracellular matrix (ECM) of the optic nerve head (ONH) causes lamina cribrosa (LC) fibrosis and affects the mechanical integrity of the ONH. Increased ECM tissue stiffness drives myofibroblast activation leading to tissue fibrosis throughout the body. Here using primary human LC cells, we investigate the effect of substrate stiffness on profibrotic changes, which might be a key molecular mechanism driving ECM remodeling of the LC in primary open-angle glaucoma (POAG) glaucoma. Methods: Primary human LC cells from normal and age-matched POAG glaucoma donors were cultured on substrates with defined mechanical properties of 5 and 100 kPa to replicate the range of mechanical microenvironments that cells may experience in vivo. Cell morphology, spread area, actin stress fibers, vinculin-focal adhesion formation, and α-smooth muscle actin (α-SMA) signal were examined using immunofluorescence staining. The elastic modulus of cells was measured using atomic force microscopy (AFM). Results: Significantly greater cell spread area along with increased actin filament development, and vinculin-focal adhesion formation (number and size) were found in both normal and glaucoma LC cells cultured on stiff substrates. These changes were positively associated with elevated cell stiffness measured by AFM. Changes in spreading and cytoskeleton organization of glaucoma LC cells were significantly more pronounced than those in normal cells. The transformation to a myofibroblast-like cell phenotype was identified in both LC cells exposed to stiffer substrates, as indicated by an increased α-SMA signal and its colocalization with the actin stress fibers. Conclusions: These findings demonstrated that a stiffer cell microenvironment activates a myofibroblastic transformation in human LC cells, and therefore contributes to LC remodelling and fibrosis in glaucoma.

Early Subretinal Allograft Rejection Is Characterized by Innate Immune Activity.

Successful subretinal transplantation is limited by considerable early graft loss despite pharmacological suppression of adaptive immunity. We postulated that early innate immune activity is a dominant factor in determining graft survival and chose a nonimmunosuppressed mouse model of retinal pigment epithelial (RPE) cell transplantation to explore this. Expression of almost all measured cytokines by DH01 RPE cells increased significantly following graft preparation, and the neutrophil chemoattractant KC/GRO/CINC was most significantly increased. Subretinal allografts of DH01 cells (C57BL/10 origin) into healthy, nonimmunosuppressed C57BL/6 murine eyes were harvested and fixed at 1, 3, 7, and 28 days postoperatively and subsequently cryosectioned and stained. Graft cells were detected using SV40 large T antigen (SV40T) immunolabeling and apoptosis/necrosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Sections were also immunolabeled for macrophage (CD11b and F4/80), neutrophil (Gr1 Ly-6G), and T-lymphocyte (CD3-ɛ) infiltration. Images captured with an Olympus FV1000 confocal microscope were analyzed using the Imaris software. The proportion of the subretinal bolus comprising graft cells (SV40T+) was significantly (p < 0.001) reduced between postoperative day (POD) 3 (90 ± 4%) and POD 7 (20 ± 7%). CD11b+, F4/80+, and Gr1 Ly-6G+ cells increased significantly (p < 0.05) from POD 1 and predominated over SV40T+ cells by POD 7. Colabeling confocal microscopic analysis demonstrated graft engulfment by neutrophils and macrophages at POD 7, and reconstruction of z-stacked confocal images confirmed SV40T inside Gr1 Ly-6G+ cells. Expression of CD3-ɛ was low and did not differ significantly between time points. By POD 28, no graft cells were detectable and few inflammatory cells remained. These studies reveal, for the first time, a critical role for innate immune mechanisms early in subretinal graft rejection. The future success of subretinal transplantation will require more emphasis on techniques to limit innate immune-mediated graft loss, rather than focusing exclusively on suppression of the adaptive immune response.

Increased Global DNA Methylation and Decreased TGFß1 Promoter Methylation in Glaucomatous Lamina Cribrosa Cells.

BACKGROUND: Glaucoma is an optic neuropathy that affects 60 million people worldwide. There is an underlying fibrosis associated with the lamina cribrosa (LC) in glaucoma. DNA methylation is well established in regulating fibrosis and may be a therapeutic target for glaucoma. The purpose of this study was to compare global DNA methylation levels in primary human normal (NLC) and glaucomatous (GLC) cells, and to investigate DNA methylation in driving fibrosis through regulation of transforming growth factor ß1 (TGFß1). MATERIALS AND METHODS: LC cells were cultured from normal and glaucomatous human donors. Global methylation was assessed by ELISA. qPCR was conducted for DNA methyltransferases (DNMTs), methyl-CpG-binding protein 2 (MeCP2), TGFß 1 and 2, collagen 1α1 (COL1A1), and α-smooth muscle actin (αSMA). TGFß1 and DNMT1 were examined by immunofluorescence. Methylation of the TGFß1 promoter was determined by methylation-specific PCR (MSP). RESULTS: Global DNA methylation demonstrated an increase in GLC compared with NLC cells (P<0.05). The previously mentioned methylation and matrix genes were increased in GLC compared with NLC cells (P<0.05). Immunofluorescence showed increased TGFß1 and DNMT1 in GLC compared with NLC cells. MSP showed increased unmethylated DNA in the TGFß1 promoter of GLC compared with NLC cells. CONCLUSIONS: We found increased expression of fibrotic genes in GLC cells and demonstrated an increase in global DNA methylation and in associated enzymes in GLC cells. Furthermore, we showed decreased promoter methylation of TGFß1 in GLC cells. Determining a role for methylation in glaucoma and in regulating TGFß1 may provide a novel therapeutic approach.

Hypoxia-Induced Changes in DNA Methylation Alter RASAL1 and TGFß1 Expression in Human Trabecular Meshwork Cells.

PURPOSE: Fibrosis and a hypoxic environment are associated with the trabecular meshwork (TM) region in the blinding disease glaucoma. Hypoxia has been shown to alter DNA methylation, an epigenetic mechanism involved in regulating gene expression such as the pro-fibrotic transforming growth factor (TGF) ß1 and the anti-fibrotic Ras protein activator like 1 (RASAL1). The purpose of this study was to compare DNA methylation levels, and the expression of TGFß1 and RASAL1 in primary human normal (NTM) with glaucomatous (GTM) cells and in NTM cells under hypoxic conditions. METHODS: Global DNA methylation was assessed by ELISA in cultured age-matched NTM and GTM cells. qPCR was conducted for TGFß1, collagen 1α1 (COL1A1), and RASAL1 expression. Western immunoblotting was used to determine protein expression. For hypoxia experiments, NTM cells were cultured in a 1%O2, 5%CO2 and 37°C environment. NTM and GTM cells were treated with TGFß1 (10ng/ml) and the methylation inhibitor 5-azacytidine (5-aza) (0.5µM) respectively to determine their effects on DNA Methyltransferase 1 (DNMT1) and RASAL1 expression. RESULTS: We found increased DNA methylation, increased TGFß1 expression and decreased RASAL1 expression in GTM cells compared to NTM cells. Similar results were obtained in NTM cells under hypoxic conditions. TGFß1 treatment increased DNMT1 and COL1A1, and decreased RASAL1 expression in NTM cells. 5-aza treatment decreased DNMT1, TGFß1 and COL1A1 expression, and increased RASAL1 expression in GTM cells. CONCLUSIONS: TGFß1 and RASAL1 expression, global DNA methylation, and expression of associated methylation enzymes were altered between NTM and GTM cells. We found that hypoxia in NTM cells induced similar results to the GTM cells. Furthermore, DNA methylation, TGFß1 and RASAL1 appear to have an interacting relationship that may play a role in driving pro-fibrotic disease progression in the glaucomatous TM.

The role of lamina cribrosa cells in optic nerve head fibrosis in glaucoma.

Glaucoma is a chronic progressive optic neuropathy. There are extracellular matrix (ECM) changes associated with optic disc cupping in the optic nerve head (ONH) and subsequent visual field defects. The primary risk factor for onset and progression of glaucoma is raised intraocular pressure (IOP). Elevated IOP causes deformation at the ONH specifically at the lamina cribrosa (LC) region where there is also deposition of ECM causing the LC to initially undergo thickening and posterior migration with eventual shearing and collapse of the LC plates leading to a thin fibrotic connective tissue structure/scar. Cells that populate the LC region of the ONH are those cells that are positive for GFAP (the astrocytes) and those negative for GFAP (the LC cells). The LC cell plays an integral role in ECM remodelling producing ECM when exposed to high level mechanical stretch, TGF- ß1 and a hypoxic environment.

The Function of Matricellular Proteins in the Lamina Cribrosa and Trabecular Meshwork in Glaucoma.

PURPOSE: To review the current literature regarding the role of matricellular proteins in glaucoma, specifically in the lamina cribrosa (LC) region of the optic nerve head (ONH) and the trabecular meshwork (TM). METHODS: A literature search was performed for published articles describing the expression and function of matricellular proteins such as thrombospondin (TSP), connective tissue growth factor (CTGF), secreted protein acidic and rich in cysteine (SPARC), and periostin in glaucoma. RESULTS: In glaucoma, there are characteristic extracellular matrix (ECM) changes associated with optic disc cupping in the ONH and subsequent visual field defects. Matricellular proteins are a family of nonstructural secreted glycoproteins, which enable cells to communicate with their surrounding ECM, including CTGF, also known as CCN2, TSPs, SPARC, periostin, osteonectin, and tenascin-C and -X, and other ECM proteins. Such proteins appear to play a role in fibrosis and increased ECM deposition. Importantly, most are widely expressed in tissues particularly in the TM and ONH, and deficiency of TSP1 and SPARC has been shown to lower intraocular pressure in mouse models of glaucoma through enhanced outflow facility. CONCLUSION: This article highlights the role of matricellular proteins in glaucoma pathology. The potential role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC region and might therefore be potential targets for therapeutic intervention in glaucoma.

Lipofuscin accumulation and autophagy in glaucomatous human lamina cribrosa cells.

BACKGROUND: Disease associated alterations in the phenotype of lamina cribrosa (LC) cells are implicated in changes occurring at the optic nerve head (ONH) in glaucoma. Lipofuscin, the formation of which is driven by reactive oxygen species (ROS), is an intralysosomal, non-degradable, auto-fluorescent macromolecule which accumulates with age and can affect autophagy - the lysosomal degradation of a cell's constituents. We aimed to compare the content of lipofuscin-like material and markers of autophagy in LC cells from normal and glaucoma donor eyes. METHODS: The number and size of peri-nuclear lysosomes were examined by transmission electron microscopy (TEM). Cellular auto-fluorescence was quantified by flow cytometry. Cathepsin K mRNA levels were assessed by PCR. Autophagy protein 5 (Atg5) mRNA and protein levels were analysed by PCR and Western blot. Protein levels of subunits of the microtubule associated proteins (MAP) 1A and 1B, light chain 3 (LC3) I and II were analysed by Western blot. Immunohistochemical staining of LC3-II in ONH sections from normal and glaucomatous donor eyes was performed. RESULTS: A significant increase in the number of peri-nuclear lysosomes [4.1 × 10,000 per high power field (h.p.f.) ± 1.9 vs. 2.0 × 10,000 per h.p.f. ± 1.3, p = 0.002, n = 3] and whole cell auto-fluorescence (83.62 ± 45.1 v 41.01 ± 3.9, p = 0.02, n = 3) was found in glaucomatous LC cells relative to normal LC cells. Glaucomatous LC cells possessed significantly higher levels of Cathepsin K mRNA and Atg5 mRNA and protein. Enhanced levels of LC3-II were found in both LC cells and optic nerve head sections from glaucoma donors. CONCLUSIONS: Increased lipofuscin formation is characteristic of LC cells from donors with glaucoma. This finding confirms the importance of oxidative stress in glaucoma pathogenesis. Intracellular lipofuscin accumulation may have important effects on autophagy the modification of which could form the basis for future novel glaucoma treatments.

The role of matricellular proteins in glaucoma.

Glaucoma is an optic neuropathy affecting approximately 60million people worldwide and is the second most common cause of irreversible blindness. Elevated intraocular pressure (IOP) is the main risk factor for developing glaucoma and is caused by impaired aqueous humor drainage through the trabecular meshwork (TM) and Schlemm's canal (SC). In primary open angle glaucoma (POAG), this elevation in IOP in turn leads to deformation at the optic nerve head (ONH) specifically at the lamina cribrosa (LC) region where there is also a deposition of extracellular matrix (ECM) molecules such as collagen and fibronectin. Matricellular proteins are non-structural secreted glycoproteins that help cells communicate with their surrounding ECM. This family of proteins includes connective tissue growth factor (CTGF), also known as CCN2, thrombospondins (TSPs), secreted protein acidic and rich in cysteine (SPARC), periostin, osteonectin, and Tenascin-C and -X and other ECM proteins. All members appear to play a role in fibrosis and increased ECM deposition. Most are widely expressed in tissues particularly in the TM and ONH and deficiency of TSP1 and SPARC have been shown to lower IOP in mouse models of glaucoma through enhanced outflow facility. The role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC regions and might therefore be potential targets for therapeutic intervention in glaucoma.

Anti-connective tissue growth factor antibody treatment reduces extracellular matrix production in trabecular meshwork and lamina cribrosa cells.

PURPOSE: We have previously demonstrated elevated levels of connective tissue growth factor (CTGF/CCN2) in the aqueous humor (AqH) of pseudoexfoliation glaucoma (PXFG) patients when compared with cataract controls. Furthermore, there is a significant trabecular meshwork (TM) and lamina cribrosa (LC) fibrotic phenotype associated with glaucoma, possibly driven by CTGF. The purpose of this study was to investigate the potential of anti-CTGF immunotherapy in glaucoma. METHODS: Primary TM and LC cells were cultured from human donors with (GTM/GLC) and without (NTM/NLC) primary open angle glaucoma (POAG). Aqueous humor samples from PXFG, POAG, and control cataract patients were applied to N/GTM and N/GLC cells in the presence or absence of a therapeutic, humanized monoclonal anti-CTGF antibody FG-3019 (10 µg/mL). Hydrogen peroxide (H2O2) was also used as a stimulus. Expression of fibrotic genes (fibronectin-1, fibrillin-1, CTGF, collagen type I α1, and α-smooth muscle actin) was assessed by q-PCR. Protein expression of collagen 1A1 and α-smooth muscle actin was examined in N/G TM cells by SDS-PAGE. The modulatory effect of FG-3019 (10 µg/mL) and IgG (10 µg/mL) were also assessed. RESULTS: Treatment of cells with AqH from PXFG and POAG patients and H2O2 induced a significant (P < 0.05) increase in expression of profibrotic genes, which was significantly reduced by pretreatment with FG-3019 (P < 0.05). FG-3019 also reduced expression of α-smooth muscle actin and collagen 1A1 protein expression in N/GTM cells. CONCLUSIONS: FG-3019 is effective in blocking extracellular matrix production in TM and LC cells, thus supporting a role for the use of anti-CTGF immunotherapy in the treatment of glaucoma.

Elevated maxi-K(+) ion channel current in glaucomatous lamina cribrosa cells.

The connective tissue plates of the lamina cribrosa (LC) region are continuously exposed to a mechanically dynamic environment. To study how the LC cells respond to these mechanical forces, we measured the mechano-sensitive calcium dependent maxi-K(+) ion channel current in the cell membrane of LC cells of glaucoma and normal subjects. Primary culture LC cells from 7 normal and 7 age matched glaucoma donors were studied. Perfusion of cells with hypotonic solution was used to stretch the cell membrane. Whole-cell patch-clamp technique was used to measure the basal (non stretched) and hypotonic stretch-induced changes in maxi-K(+) ion channel activity in normal and glaucoma LC cells. The role of membrane-type Ca(2+) entry channel inhibition (verapamil) and internal Ca(2+) store re-uptake blockade (2-APB) on maxi-K(+) activity was also examined. Basal and stretched-induced maxi-K(+) current were significantly elevated in the glaucoma LC cells compared to normal controls (p < 0.05). In normal LC cells hypotonic stretch elevated the mean maxi-K(+) current from 18.5 ± 5.7 pA/pF (at Vp = +100 mV) to 88.4 ± 12.4 pA/pF (P < 0.05), and from 39.5 ± 7.3 pA/pF to 133.1 ± 18.5 pA/pF in glaucoma LC cells (P < 0.02). Verapamil and 2-APB significantly reduced basal maxi-K(+) current in glaucoma LC cells (33.1 ± 8.2 pA/pF to 17.9 ± 5.6 pA/pF; and 32.2 ± 8.3 pA/pF to 17.3 ± 5.4 pA/pF, P < 0.05, respectively) but not in normal LC cells (P > 0.05). Following hypotonic stretch, verapamil and 2-APB significantly (P < 0.05) reduced the maxi-K(+) current in both normal and glaucoma LC cells. Baseline and hypotonic stretch induced Ca(2+)-dependent maxi-K(+) channel activity are elevated in LC cells of glaucoma patients, which may result from the abnormally high levels of intracellular calcium in glaucoma LC cells.

Preparation of pre-confluent retinal cells increases graft viability in vitro and in vivo: a mouse model.

PURPOSE: Graft failure remains an obstacle to experimental subretinal cell transplantation. A key step is preparing a viable graft, as high levels of necrosis and apoptosis increase the risk of graft failure. Retinal grafts are commonly harvested from cell cultures. We termed the graft preparation procedure "transplant conditions" (TC). We hypothesized that culture conditions influenced graft viability, and investigated whether viability decreased following TC using a mouse retinal pigment epithelial (RPE) cell line, DH01. METHODS: Cell viability was assessed by trypan blue exclusion. Levels of apoptosis and necrosis in vitro were determined by flow cytometry for annexin V and propidium iodide and Western blot analysis for the pro- and cleaved forms of caspases 3 and 7. Graft viability in vivo was established by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and cleaved caspase 3 immunolabeling of subretinal allografts. RESULTS: Pre-confluent cultures had significantly less nonviable cells than post-confluent cultures (6.6%±0.8% vs. 13.1%±0.9%, p<0.01). Cell viability in either group was not altered significantly following TC. Caspases 3 and 7 were not altered by levels of confluence or following TC. Pre-confluent cultures had low levels of apoptosis/necrosis (5.6%±1.1%) that did not increase following TC (4.8%±0.5%). However, culturing beyond confluence led to progressively increasing levels of apoptosis and necrosis (up to 16.5%±0.9%). Allografts prepared from post-confluent cultures had significantly more TUNEL-positive cells 3 hours post-operatively than grafts of pre-confluent cells (12.7%±3.1% vs. 4.5%±1.4%, p<0.001). Subretinal grafts of post-confluent cells also had significantly higher rates of cleaved caspase 3 than pre-confluent grafts (20.2%±4.3% vs. 7.8%±1.8%, p<0.001). CONCLUSION: Pre-confluent cells should be used to maximize graft cell viability.

Protein macroarray profiling of serum autoantibodies in pseudoexfoliation glaucoma.

PURPOSE: Complex repertoires of IgG autoantibodies have been detected against ocular antigens in patients with glaucoma. The goal was to identify and characterize the IgG autoantibody repertoires in sera of patients with pseudoexfoliation glaucoma (PXFG) with protein macroarrays. METHODS: Serum samples of 21 patients with PXFG and 19 age- and sex-matched control subjects were profiled on high-density colony protein macroarrays expressing His-tagged recombinant human proteins derived from a human fetal brain cDNA library. Statistically prevalent expression clones in the PXFG group were sequenced. mRNA expression of identified antigens was examined in the rat ganglion cell line RGC-5 and in human brain and optic nerve cDNA. The IgG immunoreactivity of the sera of 20 control and 26 PXFG patients to purified C6orf129 was analyzed in a reverse enzyme-linked immunosorbent assay. RESULTS: An increased prevalence was detected among the PXFG patients of serum antibodies to seven proteins: C6orf129; stathmin-like 4; transmembrane protein 9 domain family, member B; fibroblast growth factor receptor 3; cleft lip and palate transmembrane protein 1; EH-domain-containing protein 1; and eukaryotic translation elongation factor 2. All antigens were expressed in the RGC-5 cells and in cDNA from human brain and optic nerve, with the exception of stathmin-like 4, which was not expressed in the RGC-5 cells. The patients with PXFG had increased anti-C6orf129 IgG immunoreactivity compared with that in the control subjects (P < 0.05). CONCLUSIONS: Screening high-density protein arrays identifies unique antibody profiles that may discriminate between patients with and without PXFG. Characterization of the autoantibody repertoire may provide new insights into the pathophysiology of PXFG.

Rosiglitazone acts as a neuroprotectant in retinal cells via up-regulation of sestrin-1 and SOD-2.

Rosiglitazone is a member of the thiazolidinedione family of synthetic peroxisome proliferator-activated receptor (PPAR) agonists. It is a selective ligand of the PPARgamma subtype and functions by regulating the transcription of insulin-responsive genes. A screen of FDA-approved compounds identified rosiglitazone as a novel anti-apoptotic agent in retinal cells both in vitro and in vivo, functioning as a neuroprotectant in response to oxidative and calcium stress. We have found that the likely mechanism of action is via increased protein expression of the antioxidant enzymes superoxide dismutase 2 (SOD-2) and sestrin-1, boosting antioxidant defences. Transcription of both genes appears to be mediated by PPARgamma as their up-regulation is reversed by the PPARgamma antagonist GW9662 and proliferator hormone response elements were found in the putative promoter regions of mouse SOD-2 and sestrin-1. However, further investigation revealed that p53 expression was also induced in response to rosiglitazone and chromatin immunoprecipitation assays confirm that it is a bona fide target of PPARgamma. Furthermore, inhibition of p53 partially blocks the observed increase in SOD-2 and sestrin-1 expression indicating that p53 expression is upstream of both antioxidants. We conclude that rosiglitazone may increase cell survival in retinal diseases and potentially other neuronal diseases in which oxidative stress is a key factor.

Histone deacetylase activity in conjunction with E2F-1 and p53 regulates Apaf-1 expression in 661W cells and the retina.

Apaf-1 and the cysteine proteases known as caspases are genes central to the intrinsic apoptotic pathway in the retina. Previously, we have shown that histone deacetylase (HDAC) activity regulates Apaf-1 expression in the retina. In this study, we unravel the detailed molecular mechanism of HDAC-mediated regulation of Apaf-1 initially by use of a cell line (661W), which expresses some cone-specific genes and then by means of an ex vivo retinal explant system. Inhibition of HDAC activity by trichostatin A (TSA) up-regulates Apaf-1 expression, which precedes the induction of apoptosis. Furthermore, by a bioinformatics approach, we identify E2F-1 and p53 binding sites on the mouse Apaf-1 promoter and show by chromatin immunoprecipitation assays that these sites are occupied in vitro and that treatment with TSA results in increased binding of E2F-1 and p53 to the Apaf-1 promoter. By performing siRNA to these transcription factors, we illustrate that they govern Apaf-1 expression levels in vitro. Finally, in a retinal explant system, we show that similar to our 661W results, E2F-1 and p53 are up-regulated after inhibition of HDAC activity in the retina. This correlates with our previous observation in the explant system that Apaf-1 expression increases significantly and leads to an induction of apoptosis after inhibition of HDAC activity. Overall, we propose a role for HDAC activity, E2F-1, and p53 in the regulation of Apaf-1 expression in 661W cells; initial data also indicate a regulatory role in the retina.

A novel antioxidant function for the tumor-suppressor gene p53 in the retinal ganglion cell.

PURPOSE: Recent evidence has suggested that the tumor-suppressor gene p53 has a role in regulating antioxidant response in cancer cells. This study was conducted to determine whether p53 regulates redox enzymes in a neuronal context in RGCs and whether this regulation contributes to an increased survival signal. METHODS: The expression of p53, and its putative responsive antioxidant enzymes sestrin 2, catalase, Cu/ZnSOD, and MnSOD were evaluated in the developing rat retina by immunohistochemistry and Western blot. Small interfering (si)RNA to p53 was used in an RGC cell line, RGC-5, and downstream effects on antioxidants observed by Western blot. Transcription factor-analysis software was used to identify p53 binding sites on the catalase promoter, and chromatin immunoprecipitation (ChIP) assays on whole retina to demonstrate in vivo binding. The effect of p53 deficiency on basal reactive oxygen species levels (ROS) within the RGC and on susceptibility to oxidative-signaling-induced apoptosis was measured by flow cytometry. RESULTS: Developmental expression patterns of p53 and catalase mirrored each other. p53 knockdown resulted in a significant decrease in catalase. p53-binding sites were identified on the rat catalase promoter and confirmed in vivo. p53 knockdown resulted in a corresponding increase in basal cellular ROS levels and increased susceptibility to oxidative-signaling-induced cell death. CONCLUSIONS: The results suggest a novel regulating influence of p53 on catalase in the retina--more specifically in the RGC--and an influence of p53 on the susceptibility of the cell to oxidative-signaling-induced apoptosis, which could implicate p53 as a potential neuroprotectant for the RGC.

Histone deacetylase activity regulates apaf-1 and caspase 3 expression in the developing mouse retina.

PURPOSE: Apoptosis is a form of programmed cell death essential for both tissue development and maintenance of tissue homeostasis. Apoptosis protease activating factor (Apaf)-1 and caspase 3 are downregulated in the retina during postnatal development. The decreased expression of these genes is potentially a critical survival strategy adopted to protect against accidental cell death. The purpose of this study was to investigate the transcriptional mechanism involved in the downregulation of Apaf-1 and caspase 3. METHODS: SDS-polyacrylamide gel electrophoresis and semiquantitative PCR were used to examine Apaf-1 and caspase 3 expression levels during development. TdT-mediated dUTP nick-end labeling (TUNEL) and DNA laddering were used to identify cells undergoing apoptosis. RESULTS: A decrease in expression of Apaf-1 and caspase 3 during retinal development correlated with a decreased susceptibility to an apoptotic stimulus. Furthermore, treatment with a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), resulted in widespread hyperacetylation in the retina, coinciding with transcriptional activation of Apaf-1 and caspase 3 and subsequent induction of apoptosis in postnatal day (P)5 and P15 retinas. However, inhibition of HDAC activity is not sufficient to induce apoptosis in the mature retina (P60). CONCLUSIONS: Overall, these results elicit the conclusion that downregulation of Apaf-1 and caspase 3 in the developing retina correlates with a decreased susceptibility to apoptotic stimuli and ensures the survival of the retina. Furthermore, the authors propose that, in the early postnatal retina, HDAC activity governs the transcriptional regulation of these genes. Upregulation of Apaf-1 and caspase 3 coincides with an induction of apoptosis. In the mature retina transcriptional activation of these genes or induction of apoptosis was not observed.

Rab11-FIP4 interacts with Rab11 in a GTP-dependent manner and its overexpression condenses the Rab11 positive compartment in HeLa cells.

We have recently identified Rab11-FIP4 as the sixth member of the Rab11-FIP family of Rab11 interacting proteins. Here, we demonstrate that Rab11-FIP4 interacts with Rab11 in a GTP-dependent manner and that its C-terminal region allows the protein to self-interact and interact with pp75/Rip11, Rab11-FIP2, and Rab11-FIP3. However, Rab11-FIP4 does not appear to interact directly with Rab coupling protein (RCP). We investigated the subcellular localisation of Rab11-FIP4 in HeLa cells and show that it colocalises extensively with transferrin and with Rab11. Furthermore, when overexpressed, it causes a condensation of the Rab11 compartment in the perinuclear region. We demonstrate that the carboxy-terminal region of Rab11-FIP4 (Rab11-FIP4(C-ter)) is necessary and sufficient for its endosomal membrane association. Expression of Rab11-FIP4(C-ter) causes a dispersal of the Rab11 compartment towards the cell periphery and does not inhibit transferrin recycling in HeLa cells. It is likely that Rab11-FIP4 serves as a Rab11 effector in a Rab11 mediated function other than transferrin recycling.