Ji-Myong Yoo

Protein Kinase C-δ Mediates Neuronal Apoptosis in the Retinas of Diabetic Rats via the Akt Signaling Pathway

OBJECTIVE—Protein kinase C (PKC)-δ, an upstream regulator of the Akt survival pathway, contributes to cellular dysfunction in the pathogenesis of diabetes. Herein, we examined the role of PKC-δ in neuronal apoptosis through Akt in the retinas of diabetic rats. RESEARCH DESIGN AND METHODS—We used retinas from 24- and 35-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) diabetic and Long-Evans Tokushima Otsuka (LETO) nondiabetic rats. To assess whether PKC-δ affects Akt signaling and cell death in OLETF rat retinas, we examined 1) PKC-δ activity and apoptosis; 2) protein levels of phosphatidylinositol 3-kinase (PI 3-kinase) p85, heat shock protein 90 (HSP90), and protein phosphatase 2A (PP2A); 3) Akt phosphorylation; and 4) Akt binding to HSP90 or PP2A in LETO and OLETF retinas in the presence or absence of rottlerin, a highly specific PKC-δ inhibitor, or small interfering RNAs (siRNAs) for PKC-δ and HSP90. RESULTS—In OLETF retinas from 35-week-old rats, ganglion cell death, PKC-δ and PP2A activity, and Akt-PP2A binding were significantly increased and Akt phosphorylation and Akt-HSP90 binding were decreased compared with retinas from 24-week-old OLETF and LETO rats. Rottlerin and PKC-δ siRNA abrogated these effects in OLETF retinas from 35-week-old rats. HSP90 siRNA significantly increased ganglion cell death and Akt-PP2A complexes and markedly decreased HSP90-Akt binding and Akt phosphorylation in LETO retinas from 35-week-old rats compared with those from nontreated LETO rats. CONCLUSIONS—PKC-δ activation contributes to neuro-retinal apoptosis in diabetic rats by inhibiting Akt-mediated signaling pathways.

Increased O-GlcNAcylation of NF-κB Enhances Retinal Ganglion Cell Death in Streptozotocin-induced Diabetic Retinopathy

Abstract Purpose: Hyperglycemia results in increased flux through the hexoxamine biosynthetic pathway. We examined whether hyperglycemia increases O-GlcNAcylation in the diabetic retina and whether elevated O-GlcNAcylation of nuclear factor (NF)-κB increases apoptosis of retinal ganglion cells (RGCs) in diabetic retinopathy (DR). Materials and methods: Diabetes was induced in C57BL/6 mice by five consecutive intraperitoneal injections of 55 mg/kg streptozotocin. All mice were killed 2 months after injections and expression levels of O-GlcNAcylated proteins, O-linked N-acetylglucosamine transferase (OGT), β-d-N-acetylglucosaminidase and NF-κB, and the extent of RGC death were examined. Immunoprecipitations were performed to investigate whether O-GlcNAcylation of NF-κB led to its activation and RGC death in DR. Results: The expression levels of O-GlcNAcylated proteins and OGT were markedly higher in diabetic retinas than in control retinas. OGT colocalized with NeuN, a RGC-specific marker, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells in the ganglion cell layer of diabetic retinas. The p65 subunit of NF-κB was O-GlcNAcylated and the level of O-GlcNAcylated p65 was higher in diabetic retinas than in control retinas. Conclusion: The present data suggest that hyperglycemia increases O-GlcNAcylation in DR and that O-GlcNAcylation of the p65 subunit of NF-κB is involved in hyperglycemia-induced NF-κB activation and RGC death in DR.

Efficacy of systemic vitamin C supplementation in reducing corneal opacity resulting from infectious keratitis.

AbstractThe objective of this study was to determine the effect of vitamin C supplementation on reducing the size of corneal opacity resulting from infectious keratitis.The study included 82 patients (82 affected eyes), admitted for infectious keratitis from January 2009 to August 2013, who were followed for more than 3 months. Patients were divided into control, oral vitamin C (3 g/d), and intravenous vitamin C (20 g/d) groups during hospitalization. Corneal opacity sizes were measured using anterior segment photographs and Image J program (version 1.27; National Institutes of Health, Jinju, South Korea) at admission, discharge, and final follow-up. The corneal opacity size used for analysis was the measured opacity size divided by the size of the whole cornea.The corneal opacity size decreased by 0.03 ± 0.10 in the oral vitamin C group, 0.07 ± 0.22 in the intravenous vitamin C group, and 0.02 ± 0.15 in the control group. Intravenous vitamin C reduced the corneal opacity size more than oral vitamin C (P = 0.043). Intravenous vitamin C produced greater reduction in corneal opacity size in younger patients (P = 0.015) and those with a hypopyon (P = 0.036).Systemic vitamin C supplementation reduced the size of corneal opacity resulting from infectious keratitis. Intravenous vitamin C was more beneficial than oral supplementation, especially in younger patients and those with hypopyon.

Tonicity response element binding protein associated with neuronal cell death in the experimental diabetic retinopathy

AIM To study the contribution of tonicity response element binding protein (TonEBP) in retinal ganglion cell (RGC) death of diabetic retinopathy (DR). METHODS Diabetes was induced in C57BL/6 mice by five consecutive intraperitoneal injections of 55 mg/kg streptozotocin (STZ). Control mice received vehicle (phosphate-buffered saline). All mice were killed 2mo after injections, and the extent of cell death and the protein expression levels of TonEBP and aldose reductase (AR) were examined. RESULTS The TonEBP and AR protein levels and the death of RGC were significantly increased in the retinas of diabetic mice compared with controls 2mo after the induction of diabetes. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL)-positive signals co-localized with TonEBP immunoreactive RGC. These changes were increased in the diabetic retinas compared with controls. CONCLUSION The present data show that AR and TonEBP are upregulated in the DR and TonEBP may contribute to apoptosis of RGC in the DR.

Treatment With Triamcinolone Acetonide Prevents Decreased Retinal Levels of Decorin in a Rat Model of Oxygen-Induced Retinopathy

Purpose: To investigate the effect of triamcinolone acetonide (TA) on retinal expression of decorin in a rat model of oxygen-induced retinopathy (OIR). Materials and Methods: OIR was stimulated by exposing Sprague-Dawley (SD) rats to hyperoxia (80 ± 1.3% O2) from postnatal day (P) 2 to P14 and then returning them to normoxia (room air, 21 ± 1.5% O2). Control rats were maintained in normoxia. At P15, TA (40 mg/ml) was injected into the right vitreous of OIR rats and saline into the left vitreous of control rats. All rats were sacrificed at P18. RT-PCR, western blot and immunohistochemistry, TUNEL assay were performed to detect the effects of TA on molecular and morphological changes in retinal decorin levels in P18 OIR rats. Results: In P18 OIR rats, mRNA and protein of retinal levels and immunoreactivity of retinal decorin were significantly less (p-value = 0.0000000012, 0.0007, 0.000003; n = 5; respectively) than in control rats. In addition, neuronal cell death was increased in P18 OIR rats (p-value = 0.0028; n = 5) relative to controls. However, treatment with TA prevented the decrease of mRNA, protein levels, and immunoreactivity in retinal decorin in P18 OIR rats (p-value = 0.00023, 0.003, 0.000079; n = 5, respectively), and restored neuronal cell death in P18 OIR rats (p-value = 0.0022, n = 5). Conclusion: Our results suggest that decorin is involved in hypoxic retinal damage and that TA protects retinal neurons damaged by relative hypoxia from decreased decorin levels.

Effect of Dorzolamide/Timolol or Brinzolamide/Timolol Prophylaxis on Intravitreal Anti-VEGF Injection-Induced Intraocular Hypertension

ABSTRACT Purpose: To evaluate prospectively whether anti-glaucomatic drugs administered prior to intravitreal anti-vascular endothelial growth factor (VEGF) injection bevacizumab (Avastin,® Roche) or ranibizumab (Lucentis,® Novartis) prevents intraocular hypertension after the injection. Subjects and methods: In total, 166 patients (175 eyes) scheduled for intravitreal anti-VEGF injection treatment were prophylactically treated 1 hour before the procedure with Dorzolamide/Timolol (Cosopt,® MSD) (Group 1, 53 eyes) or Brinzolamide/Timolol (Elazop,® Alcon) (Group 2, 84 eyes) or left untreated (Group 3, 29 eyes). Intraocular pressure was analyzed 5 minutes prior to the injection, every 5 minutes for 30 minutes after the procedure, and 1 hour, 1 day, 7 days, and 1 month after the procedure. Results: The intraocular pressures 5 minutes before the procedure (baseline) for Groups 1, 2, and 3 were 12.06 ± 1.85, 13.98 ± 2.68, and 13.81 ± 2.24 mmHg, respectively. Five and 30 minutes after the procedure, the intraocular pressures of the three groups were 14.12 ± 4.18, 14.87 ± 3.35, and 28.21 ± 3.16 mmHg, respectively, and 10.87 ± 1.58, 14.25 ± 2.43, and 17.48 ± 2.34 mmHg, respectively. For all three groups, the changes relative to baseline 5 and 30 minutes after injection were significant. When the three groups were divided according to whether they received bevacizumab or ranibizumab and the changes in intraocular pressure relative to baseline were analyzed, all six subgroups exhibited significant changes in intraocular pressure 5 and 30 minutes after the procedure. Conclusion: The prophylactic administration of anti-glaucomatic drugs prior to intravitreal anti-VEGF injection effectively reduced the early intraocular pressure elevation. This approach was also safe and could be performed accurately.

Aralia elata prevents neuronal death by downregulating tonicity response element binding protein in diabetic retinopathy.

Background/Aims: The present study addresses the role of tonicity response element binding protein (TonEBP) in retinal ganglion cell (RGC) death in diabetic retinopathy and the impact of Aralia elata extract on the TonEBP/RGC interaction. Methods: Diabetes was induced in C57BL/6 mice by intraperitoneal injection of streptozotocin (STZ). Control mice received phosphate-buffered saline. After five injections of STZ or saline buffer, A. elata extract was administered by daily oral tube feeding for 7 weeks. All mice were killed at 2 months after the last injection of STZ or saline and the extent of cell death together with the protein expression levels of TonEBP, aldose reductase (AR) and nuclear factor-kappa B (NF-κB) were examined. Results: Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive signals were colocalized with TonEBP-immunoreactive RGCs. The apoptotic cell death of RGCs and the expression levels of TonEBP, AR and NF-κB were significantly increased in the retinas of diabetic mice compared with controls at 2 months after the induction of diabetes. However, these changes were effectively blocked by the administration of A. elata extract. Conclusions: These results indicate that A. elata prevents diabetes-induced RGC apoptosis and downregulates TonEBP expression. Therefore, A. elata extract may have therapeutic potential to prevent diabetes-induced retinal neurodegeneration in diabetic retinopathy.

Sutureless Intrascleral Pocket Technique of Transscleral Fixation of Intraocular Lens in Previous Vitrectomized Eyes

In this case series, we assessed a new technique, the intrascleral pocket procedure of transscleral fixation (TF) of the intraocular lens (IOL) in post-vitrectomized eyes. We performed the transscleral fixation of IOL in four aphakic patients who underwent pars plana vitrectomy. Two points 180° apart were marked at the limbus. A 2-mm-sized intrascleral pocket was created by lamellar dissection using a crescent blade without conjunctival dissection. A 2.8-mm clear corneal incision (CCI) was made using a keratome. Prolene sutures were exteriorized through the CCI pocket and a three-piece foldable acrylic IOL was injected via CCI and the ends of the haptics were exteriorized through the CCI. The prolene sutures for each haptic in the intrascleral pocket bed were then tied and knots were buried under scleral flaps. No patient had complaints such as conjunctival irritation, and visual acuity was almost identical to preoperative best-corrected visual acuity at day 1 postoperatively. IOLs were well placed without tilting or subluxation. They had no wound dehiscence or endophthalmitis postoperatively. The intrascleral pocket procedure of TF without the need for conjunctival dissection is a successful method for sulcus fixation in post-vitrectomized eyes predisposed to developing glaucoma.

Ultraviolet B Radiation Stimulates the Interaction between Nuclear Factor of Activated T Cells 5 (NFAT5) and Nuclear Factor-Kappa B (NF-κB) in Human Lens Epithelial Cells

ABSTRACT Purpose: Nuclear factor-kappa B (NF-κB) has been proposed as a therapeutic target for the treatment of cataracts. The authors investigated the relationship between nuclear factor of activated T cells 5 (NFAT5) and NF-κB in ultraviolet B (UVB)-irradiated human lens epithelial (HLE) cells. Methods: Human lens epithelial B-3 (HLE-B3) cells were exposed to UVB light at a dose of 10 mJ/cm2 and then incubated for 24 h. Cell viability was assessed by using the Cell Counting Kit-8 (CCK-8) assay. Gene expression level of NFAT5 was determined using real-time quantitative polymerase chain reaction (qPCR). Protein expression levels of NFAT5, NF-κB p65, and α-smooth muscle actin (α-SMA) and the association of NFAT5 with the NF-κB p65 subunit were measured by Western blot analysis and a co-immunoprecipitation assay, respectively. The cellular distribution of NFAT5 and NF-κB p65 was examined by triple immunofluorescence staining. Results: At 24 h after UVB exposure, cell viability significantly decreased in a dose-dependent manner, and UVB light (15 and 20 mJ/cm2) significantly increased the ROS generation. UVB irradiation increased NFAT5 mRNA and protein levels and increased phosphorylation of NF-κB in HLE-B3 cells. α-SMA protein levels were increased in the irradiated cells. In addition, NFAT5 and NF-κB translocated from the cytoplasm to the nucleus, and binding between the p65 subunit and NFAT5 was increased. Conclusions: Exposure to UVB radiation induces nuclear translocation and stimulates binding between NFAT5 and NF-κB proteins in HLE-B3 cells. These interactions may form part of the biochemical mechanism of cataractogenesis in UVB-irradiated HLECs.

A case of phacolytic glaucoma with anterior lens capsule disruption identified by scanning electron microscopy.

BackgroundPhacolytic glaucoma is induced by lens protein or macrophages that have leaked through a macroscopically intact anterior lens capsule. Here, we report a case of phacolytic glaucoma with anterior lens capsule disruptions visualized by scanning electron microscopy (SEM).Case presentationA 71-year-old man was referred to our institute for increased intraocular pressure (IOP) in the right eye. Slit-lamp biomicroscopic examination revealed corneal edema, the presence of inflammatory cells and iridescent crystalline in the anterior chamber, and a hypermature cataract in the right eye. Despite treatment with topical glaucoma medication (0.15% brimonidine, 1% brinzolamide/0.5% timolol, and 0.03% bimatoprost) and systemic mannitol, his IOP remained uncontrolled. Light microscopy was used to examine the aqueous humor obtained via anterior chamber paracentesis and the anterior lens capsule obtained via intracapsular cataract extraction (ICCE), which revealed that the anterior lens capsule was intact. However, SEM revealed full-thickness disruptions in the anterior lens.ConclusionThis is the first reported case of phacolytic glaucoma with disruptions of the anterior lens capsule confirmed by SEM.