Masahiko Shimura

Intrinsic activation of PI3K/Akt signaling pathway and its neuroprotective effect against retinal injury.

Purpose. The aim of this study was to determine whether the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway can function as a neuroprotective pathway following induced retinal injury. Methods. The activation of Akt was assessed by immunoblot analysis, and the role of PI3K/Akt pathway was evaluated by TUNEL staining and counting the number of retrogradelylabeled retinal ganglion cells (RGCs) in the whole retina at 168 h after injury with or without PI3K specific inhibitor, LY294002. Results. Akt was induced within one hr and reached a maximum 6hrs after optic nerve clamping. The activation was observed in the RGC layer including RGCs, the inner plexiform layer, inner nuclear layer, and in the photoreceptor outer segments. The number of surviving RGCs was decreased significantly 168 hrs after injury. LY294002 partially inhibited the activation of Akt, and significantly decreased the number of surviving RGCs as compared with that of injury alone. Conclusions. These results indicate that the PI3K/Akt signaling pathway is activated intrinsically and has a neuroprotective effect on injured RGCs.

Neuroprotective effect of nipradilol on axotomized rat retinal ganglion cells

Purpose. To determine whether nipradilol, a new antiglaucoma drug, can protect retinal ganglion cells (RGCs) from secondary cell death caused by transection of the optic nerve (ON). Methods. The ON was transected 0.7mm from its exit from the eye in Sprague Dawley rats. Nipradilol (1 × 10 -8 – 10 -3 M), timolol, prazosin, or sodium nitroprusside (SNP)(1 × 10 -6 - 10 -4 M) was injected intravitreally fifteen-minutes before the ON transection. Control eyes received the same amount of phosphate buffered (PB). The RGCs were labeled retrogradely by placing gelfoam soaked in fluoro-gold (FG) on the stump of ON. RGCs density was determined by counting the FG-labeled RGCs in flat-mounted retinas 3 to 14 days post-transection. To determine whether the neuroprotective action of nipradilol was due to its NO-donor property, carboxy-PTIO, a NO-scavenger, or KT5832, a protein kinase G inhibitor, was injected with the nipradilol. Results. After ON transection, the number of surviving RGCs after intravitreal injection of 1 × 10 -4 M nipradilol was significantly higher than that following PB injection. This protective activity was dose-dependent. Neither timolol nor prazosin had a neuroprotective effect but SNP protected RGCs in a dose-dependent manner. Carboxy-PTIO and KT5832 decreased the neuroprotective effect of nipradilol. Conclusions. These results indicate that nipradilol has a possibility of neuroprotective effect on axotomized RGCs, and the effect depended mainly on its NO-donor property.

Effective treatment with topical cyclosporin A of a patient with Cogan syndrome.

The purpose of this report is to describe the effective treatment of severe anterior segment inflammation due to Cogan syndrome through the use of topical administration of cyclosporin A. A 47-year-old female patient had been experiencing headaches and difficulties with her vision. Subsequent examination revealed the sudden onset of bilateral conjunctival injection and swelling of bilateral auricles. Despite the multiple treatment (systemic and topical corticosteroid and antibiotic therapy), necrotizing scleritis had appeared bilaterally and the scleral wall was thinning. Topical administration of 1% cyclosporin A was applied to both eyes 4 times a day. After 2 months of this therapy, the epithelial tissue covered the necrotizing tissue and her symptom of ocular pain was relieved and her corrected visual acuity was improved. This is the first case exhibiting that topical cyclosporin A is an effective treatment for severe anterior segment inflammation associated with Cogan syndrome.

Molecular Genetic Analysis of ABCR Gene in Japanese Dry Form Age-Related Macular Degeneration

PURPOSE To explore whether the mutation in the retina-specific ATP-binding cassette transporter (ABCR) gene, the Stargardts disease gene, contributes to the prevalence of the dry form of age-related macular degeneration (dry AMD) in Japanese unrelated patients. METHODS Twenty-five Japanese unrelated patients with dry AMD who were diagnosed by fluorescein angiography and indocyanine green angiography were chosen as the dry AMD group. None of these cases had apparent choroidal neovascularization. To detect the mutations in the ABCR gene, genomic DNA was extracted from leukocytes of peripheral blood, and 26 exons of the ABCR gene were amplified by polymerase chain reaction (PCR). All the PCR products were then directly sequenced. When a mutation was detected, the occurrence of a mutation was compared between these AMD patients and the control group. RESULTS After direct sequencing, a point mutation in exon 29 was found in one of the 25 dry AMD patients. In addition, a polymorphism in exon 45 was found in two other patients, and three sequence variations in exon 23 were detected in all patients. The incidence in AMD patients in whom a mutation in exon 29 (4%) was detected was less than that in controls (5%). Screening of the intron-exon boundaries also led to the identification of intronic mutation in intron 33. CONCLUSION In this study we found no relationship between allelic variation in the ABCR gene and the prevalence of dry AMD in Japanese unrelated patients.

Clinical course of macular edema in two cases of interferon-associated retinopathy observed by optical coherence tomography.

BackgroundInterferon (IFN)-associated retinopathy is typically characterized by retinal hemorrhages and cotton wool spots at the posterior fundus, but visual function is usually maintained. With the use of optical coherence tomography (OCT), two patients with IFN-associated retinopathy who had developed macular edema and reduced visual acuity during the clinical course of IFN therapy were observed.CasesA 37-year-old man with chronic hepatitis C and a 59-year-old man with chronic myeloid leukemia, both of whom had received IFN therapy, were referred to our outpatient clinic. The former patient had complained once that his visual acuity had decreased after the termination of IFN therapy, and the latter patient complained twice during IFN therapy that his visual acuity had decreased.ObservationsIn both patients, at the time of the visual disturbances, macular edema was clearly observed by OCT. Hypoalbuminemia and thrombocytopenia were observed at this time also. After the remission of the hypoalbuminemia and thrombocytopenia, the macular edema observed by OCT disappeared and visual acuity returned to normal.ConclusionDuring and after IFN therapy, OCT is a useful examination technique for revealing macular edema in patients who have decreased vision. Ophthalmologists should be aware of the ocular side effects of IFN therapy and carefully monitor patients for the possible occurrence of hypoalbuminemia and thrombocytopenia. Jpn J Ophthalmol 2005;49:231–234

Choroiditis in Systemic Lupus Erythematosus: Systemic Steroid Therapy and Focal Laser Treatment

PURPOSE To report a rare case of choroiditis in association with systemic lupus erythematosus (SLE). CASE A 49-year-old woman with a 17-year history of SLE experienced acute vision impairment of her left eye during the remission stage of systemic SLE. Fundus examination revealed a gray-white subretinal exudate with serous retinal detachment. Angiographic examination disclosed choroidal inflammation at the macula and a breakdown of the blood retinal barrier. Retinal burns were applied to the subretinal exudate with an argon laser as in the treatment of central serous retinopathy. Afterward, her visual acuity showed prompt recovery due to the regression of the serous retinal detachment. However, the choroidal inflammation remained until the systemic condition was controlled with steroid therapy. RESULTS Laser treatment of a subretinal exudate was helpful for the resolution of serous detachment and the prompt improvement of visual acuity, whereas systemic steroid therapy was effective for choroidal inflammation. CONCLUSIONS Systemic steroid therapy is thought to be effective for SLE choroiditis; however, this therapy is also known to cause serous retinal detachment. Thus, in SLE choroiditis, laser photocoagulation at a leakage point, in addition to systemic steroid therapy, may be helpful for the prompt restoration of vision in patients with serous retinal detachment.

Expression and functional properties of unique inward rectifier K+ channel Kir7.1 in the porcine iris and retinal pigment epithelium

Purpose. To investigate the membrane functional properties of porcine iris pigment epithelial cells (IPE), and compare the characters of inward rectifier potassium (Kir) channel in the IPE with those in the retinal pigment epithelial cells (RPE). Methods. IPE and RPE were acutely dissociated from porcine eyes. Functional properties of Kir channels were characterized using whole cell patch clamp recording techniques. Expression of Kir7.1 mRNA in both cells was detected by reverse transcription-polymerase chain reaction (RT-PCR). Results. Whole cell current in the IPE exhibited a mild inward K + rectification, and showed little dependence on [K + ] o. Unusual high (7.04 ± 1.7) Rb + to K + inward conductance ratio indicated that Kir7.1 subunit was expressed in the IPE as the same as RPE cells. Also, Kir7.1 mRNA was detected in both porcine IPE and RPE by RT-PCR. However, functional expression of Kir conductance in IPE cells (21.7 S/F) was much smaller than that in RPE cells (205.6 S/F). Conclusions. The Kir7.1 subunit was predominantly expressed in the acutely dissociated porcine IPE and its functional properties are similar to those in the RPE. However, the current density seems too small to fulfill the task of the Kir function of RPE.

Characterization of the electrogenic Na+-K+ pump in horizontal cells isolated from the carp retina.

The electrogenic Na+-K+ pump current in horizontal cells acutely dissociated from the carp retina was investigated using a nystatin-perforated patch recording configuration under voltage-clamp conditions. In the presence of suitable blockers for known voltage-dependent Na+, K+ and Ca2+ conductances, the pump current was activated in a concentration-dependent manner by adding K+ ions to external solution. The EC50 value and Hill coefficient for the external K+ concentration were 0.66 mM and 1.39, respectively. The pump current did not show any significant voltage dependency at the physiological potential range between -90 and 20 mV either with or without external Na+ ions. In the presence of 120 mM external Na+ concentration, the addition of 3 mM K+ to the external solution induced a steady outward pump current even when the patch-pipette (internal) solution did not contain Na+. A large outward shift of the holding current was observed by removing external Na+. The result thus suggests that continuous Na+ influxes exist across the plasma membrane in the presence of external Na+. When Na+ was removed from both external and internal solutions, a transient outward pump current was observed by adding K+ to the external solution, thus indicating that the transient pump current was activated by the residual intracellular Na+ ions. The pump current was suppressed by ouabain in a concentration-dependent manner, and the ouabain-sensitive inhibition curve was fitted by two components. The IC50 values of high- and low-sensitive pump currents for ouabain were 20 nM and 10.4 microM, respectively, indicating the existence of at least two isoforms of the pump in the horizontal cells.

Gliclazide Attenuates the Intracellular Ca2+ Changes Induced In Vitro by Ischemia in the Retinal Slices of Rats with Streptozotocin-Induced Diabetes

Purpose: To investigate the dynamics of the intracellular Ca2+ concentration ([Ca2+]i) during retinal ischemia in rats with streptozotocin (STZ)-induced diabetes and the effect of gliclazide, a sulfonylurea with a potent free-radical scavenging activity on ischemia-induced [Ca2+]i dynamics. Methods: Rats with STZ (65 mg/kg) induced diabetes were divided into three groups: the untreated diabetic group, the gliclazide-treated group, and the glibenclamide-treated group. An ischemic condition was imposed in vitro on the retinal slices by perfusion with an oxygen/glucose deprived solution. The [Ca2+]i was measured in individual layers of the rat retinal slices loaded with the Ca2+ indicator fluo-3. Results: As compared to that in the normal rat retina, both the amplitude and the kinetics of the [Ca2+]i increase were suppressed in the intermediate layers of the retinal slices from the diabetic rats under the ischemic condition. These changes were attenuated by the administration of gliclazide but not by that of glibenclamide. Conclusions: Hyperglycemia influences ischemia-induced [Ca2+]i dynamics predominantly in the intermediate layers of the retina, and gliclazide, as compared to glibenclamide without a free radical scavenging activity, potently attenuates the ischemia-induced changes in the calcium dynamics.

Mononeuritis multiplex, protein-losing gastroenteropathy, and choroidopathy seen together in a case of systemic lupus erythematosus

Abstract A 43-year-old woman with systemic lupus erythematosus (SLE) had an episode of mononeuritis multiplex prior to developing protein-losing gastroenteropathy. Four years later, she had another episode of mononeuritis multiplex, followed by choroidopathy. These manifestations are uncommon in SLE, but may be attributed to vasculitis. The laboratory findings indicated that the elevation of D-dimer and thrombin–antithrombin complex levels seen in this case might be useful in evaluating vascular lesions in SLE.