Sustained activation of the unfolded protein response induces cell death in Fuchs' endothelial corneal dystrophy

Purpose: The unfolded protein response (UPR) is believed to play a role in the pathogenesis of Fuchs' endothelial corneal dystrophy (FECD). The purpose of this study was to investigate whether unfolded proteins accumulate in the corneal endothelium in FECD and if they are involved in triggering cell death. Methods: Descemet's membranes with corneal endothelial cells (CECs) were obtained during keratoplasty, and expression of aggresomes, type 1 collagen, fibronectin, and agrin was evaluated. Endoplasmic reticulum (ER) stress of immortalized human CECs from non-FECD subjects and from FECD patients (iHCEC and iFECD, respectively) were evaluated. The effect of MG132-mediated aggresome formation on the UPR and intrinsic pathway and the effect of mitochondrial damage on UPR were also examined. The effect of CHOP knockdown on the ER stress–mediated intrinsic pathway was also evaluated. Results: Aggresome formation was higher in iFECD than in iHCEC and was colocalized with type 1 collagen, fibronectin, and agrin. GRP78, phosphorylated IRE1, PERK, and CHOP showed higher activation in iFECD than in iHCEC. MG132-mediated aggresome formation upregulated ER stress sensors, the mitochondrial membrane potential drop, cytochrome c release to the cytoplasm, and activation of caspase-9 and -3. By contrast, staurosporine-mediated mitochondrial damage did not induce ER stress. Knockdown of CHOP attenuated the ER stress-induced cleavage of caspase-9, which is caused by intrinsic pathway activation. Conclusions: Excessive synthesis of extracellular matrix proteins induced unfolded protein accumulation in FECD. Prolonged ER stress–mediated cell death, occurring via the intrinsic apoptotic signaling pathway, therefore might be associated with the pathogenesis of FECD

Effect of trinucleotide repeat expansion on the expression of TCF4 mRNA in Fuchs' endothelial corneal dystrophy

Purpose: CTG trinucleotide repeat (TNR) expansion is frequently found in transcription factor 4 (TCF4) in Fuchs' endothelial corneal dystrophy (FECD), though the effect of TNR expansion on FECD pathophysiology remains unclear. The purpose of this study was to evaluate the effect of TNR expansion on TCF4 expression in corneal endothelium of patients with FECD. Methods: Peripheral blood DNA and Descemet membrane with corneal endothelium were obtained from 203 German patients with FECD. The CTG TNR repeat length in TCF4 was determined by short tandem repeat (STR) assays and Southern blotting using genomic DNA. Genotyping of rs613872 in TCF4 was performed by PCR. TCF4 mRNA levels in corneal endothelium were evaluated by quantitative PCR using three different probes. Control corneal endothelial samples were obtained from 35 non-FECD subjects. Results: The STR assay and Southern blotting showed that 162 of the 203 patients with FECD (80%) harbored CTG trinucleotide repeat lengths larger than 50. Quantitative PCR using all three probes demonstrated that TCF4 mRNA is significantly upregulated in the corneal endothelium of patients with FECD, regardless of the presence of TNR expansion. However, the length of the TNR tended to show a positive correlation with TCF4 expression level. No correlation was shown between the genotype of TCF4 SNP, rs613872, and the level of TCF4 expression. Conclusions: Our findings showed that TCF4 mRNA is upregulated in the corneal endothelium of patients with FECD. Further studies on the effects of TCF4 upregulation on corneal endothelial cell function will aid in understanding the pathophysiology of FECD

Preventive Effects of Omega-3 and Omega-6 Fatty Acids on Peroxide Mediated Oxidative Stress Responses in Primary Human Trabecular Meshwork Cells

Pathologic processes in glaucoma include increased apoptosis, accumulation of extracellular material in the trabecular meshwork and optic nerve, condensations of the cytoskeleton and precocious cellular senescence. Oxidative stress was shown to generate these alterations in primary ocular cells. Fatty acids omega-3 and -6 are alleged to constitute a prophylaxis against these deleterious effects. Here, we tested actual preventive effects omega-3 and -6 against peroxide induced stress responses in primary human trabecular meshwork cells. Changes of mitochondrial activity, proliferation, heat shock proteins, extracellular matrix components, and inflammatory markers were evaluated. Alterations of the cytoskeleton were evaluated by phalloidin labeling. Here we report a repressive effect of omega-6 on metabolic activity and proliferation, which was not detected for omega-3. Both agents were able to prevent the anti-proliferative effect of H2O2, but only omega-3 prevented metabolic repression. Expression of heat shock protein 27 was unaltered by both fatty acids, whereas heat shock protein 90 was significantly induced by both. Omega-6 increased fibronectin and connective tissue growth factor synthesis, as well as the amount of secreted fibronectin. Omega-3, instead, induced plasminogen activator inhibitor 1 synthesis. H2O2 further increased fibronectin production in omega-6 supplemented cells, which was not the case in omega-3 treated cells. H2O2 stimulation of plasminogen activator inhibitor 1 and connective tissue growth factor was repressed by both fatty acids. Both fatty acids appeared to abolish H2O2 mediated stimulation of nuclear factor κB and IL-6, but not IL-1α and IL-8. H2O2 induced formation of cross-linked actin networks and stress fibers, which was reduced by preemptive application of omega-3. Omega-6, in contrast, had no protective effect on that, and even seemed to promote condensation. Based on the observed side effects of omega-6, omega-3 appears to be the more beneficial fatty acid in respect of prophylactic intake for prevention of a glaucomatous disease

Pressure-induced interlamellar stromal keratitis after laser in situ keratomileusis

To describe a patient with interlamellar stromal keratitis induced by increased intraocular pressure (IOP) [Pressure-induced interlamellar stromal keratitis (PISK)] after laser in situ keratomileusis (LASIK) surgery. Case report and review of the literature. We report a case of interlamellar stromal keratitis induced by increased IOP after LASIK surgery. A 42-year-old man presented with persistent interface haze after uneventful LASIK. The patient described onset of decreased visual acuity after the first 2 postoperative weeks, failed to improve with high-dose topical steroid drops, and had significantly elevated IOP values up to 48 mm Hg. IOP was resistant to maximal topical antiglaucomatous therapy. The patient showed both improvement in visual acuity and decrease in interface haze after discontinuation of topical steroids and lowering of IOP by both topical and systemic treatment. Slit-lamp optical coherence tomography ruled out a fluid accumulation in the interface. PISK appears clinically almost identical to diffuse lamellar keratitis after LASIK. It is important to measure the IOP and be suspicious when a diffuse interface haze occurs after the first postoperative week, is resistant to or even exacerbates in response to an increase in topical steroid treatment, and is not associated with other causative events. Slit-lamp optical coherence tomography is a valuable tool that allows differentiation between space-occupying interface fluid collection and non-space-occupying interface fluid collection to avoid falsely low or normal IOP measurements in PISK

Use of Accidentally Torn Descemet Membrane to Successfully Complete Descemet Membrane Endothelial Keratoplasty

Purpose:To describe the use of an accidentally torn Descemet membrane (DM) to successfully complete Descemet membrane endothelial keratoplasty (DMEK) surgery.Methods:Retrospective, observational case series of 3 eyes of 3 patients undergoing DMEK with a DM accidentally torn into 2 pieces during graft preparation. The mean outcome measures included best-corrected visual acuity, endothelial cell density, and central corneal thickness, before and at 1, 3, and 6 months after the DMEK surgery was performed.Results:During graft preparation, immediately before transplantation, a large tear within the 8.0-mm marking line of the DM occurred, resulting in a DM torn into 2 pieces. In all the eyes, both pieces were successfully implanted into the anterior chamber, unfolded and attached to the posterior corneal stroma, one after the other. Six months after the surgery was performed, the best-corrected visual acuity ranged between 20/30 and 20/25. Endothelial cell loss was about 30% (range 28%-32%) 6 months after the surgery. Pachymetry findings showed normal corneal thickness 6 months after the surgery. All corneas remained clear without any signs of graft failure within 6 months of follow-up.Conclusions:DMEK surgery can be successfully completed despite the accidental tearing of donor DMs during the preparation of DMEK grafts by the sequential implantation of both DM pieces

Hsp27 and Hsp90 expression analysis.

<p>(<b>A</b>) Quantification of realtime PCR expression analysis of Hsp27 and Hsp90 mRNAs in controls, ω-6 and ω-3 fatty acids pre-treated hTM normalized to controls. (<b>B</b>) Western blot detection of cellular Hsp27, Hsp90 and actin protein in controls, ω-6 and ω-3 fatty acids pre-treated hTM. (<b>C</b>) Plot of densitometric quantifications of Hsp27 and Hsp90 protein expression in controls, ω-6 and ω-3 fatty acids pre-treated hTM adjusted to actin expression and normalized to controls. Values represent m.a. ± sd of three independent experiments performed on cells of three different donors (n = 9); asterisks: p-values of statistical significances (*p≤0.05; **p≤0.01; ***p≤0.001).</p

Interleukin 1α, -6 and -8 expression analysis.

<p>Quantitative realtime PCR expression analysis of interleukins (<b>A</b>) -1α, (<b>B</b>) -6 and (<b>C</b>) -8 mRNAs in controls, hTM pre-treated with ω-6 and ω-3 before and after H₂O₂ exposition. ELISA quantification of (<b>D</b>) IL-6 and (<b>E</b>) IL-8 medium contents. Values are normalized to untreated controls and represent m.a. folds ± sd of three independent experiments performed on cells of three different donors (n = 9); asterisks: <i>p</i>-values of statistical significances (*<i>p</i>≤0.05; **<i>p</i>≤0.01; ***<i>p</i>≤0.001).</p

Primers used for realtime PCR.

<p>Primers used for realtime PCR.</p

FN, PAI-1 and CTGF expression analysis.

<p>Quantitative realtime PCR expression analysis of FN, PAI-1 and CTGF mRNAs in controls, ω-6 and ω-3 fatty acids pre-treated hTM normalized to controls (<b>A</b>) before and (<b>B</b>) after H₂O₂ exposition. (<b>C</b>) Western blot detection of cellular FN, PAI-1, CTGF, and actin in controls, ω-6 and ω-3 fatty acids pre-treated hTM. Plots of densitometric quantifications to deduce fold expressions of intracellular (<b>D</b>) FN, (<b>E</b>) PAI-1 and (<b>F</b>) CTGF, before and after H₂O₂ exposition. (<b>G</b>) ELISA quantification of FN medium contents normalized to controls. Values represent m.a. folds ± sd of three independent experiments performed on cells of three different donors (n = 9); asterisks: <i>p</i>-values of statistical significances (*<i>p</i>≤0.05; **<i>p</i>≤0.01; ***<i>p</i>≤0.001).</p