Three-dimensional choroidal vascularity index and choroidal thickness in fellow eyes of acute and chronic primary angle-closure using swept-source optical coherence tomography.

AIM: To compare the three-dimensional choroidal vascularity index (CVI) and choroidal thickness between fellow eyes of acute primary angle-closure (F-APAC) and chronic primary angle-closure glaucoma (F-CPACG) and the eyes of normal controls. METHODS: This study included 37 patients with unilateral APAC, 37 with asymmetric CPACG without prior treatment, and 36 healthy participants. Using swept-source optical coherence tomography (SS-OCT), the macular and peripapillary choroidal thickness and three-dimensional CVI were measured and compared globally and sectorally. Pearson's correlation analysis and multivariate regression models were used to evaluate choroidal thickness or CVI with related factors. RESULTS: The mean subfoveal CVIs were 0.35±0.10, 0.33±0.09, and 0.29±0.04, and the mean subfoveal choroidal thickness were 315.62±52.92, 306.22±59.29, and 262.69±45.55 µm in the F-APAC, F-CPACG, and normal groups, respectively. All macular sectors showed significantly higher CVIs and choroidal thickness in the F-APAC and F-CPACG eyes than in the normal eyes (P<0.05), while there were no significant differences between the F-APAC and F-CPACG eyes. In the peripapillary region, the mean overall CVIs were 0.21±0.08, 0.20±0.08, and 0.19±0.05, and the mean overall choroidal thickness were 180.45±54.18, 174.82±50.67, and 176.18±37.94 µm in the F-APAC, F-CPACG, and normal groups, respectively. There were no significant differences between any of the two groups in all peripapillary sectors. Younger age, shorter axial length, and the F-APAC or F-CPACG diagnosis were significantly associated with higher subfoveal CVI and thicker subfoveal choroidal thickness (P<0.05). CONCLUSION: The fellow eyes of unilateral APAC or asymmetric CPACG have higher macular CVI and choroidal thickness than those of the normal controls. Neither CVI nor choroidal thickness can distinguish between eyes predisposed to APAC or CPACG. A thicker choroid with a higher vascular volume may play a role in the pathogenesis of primary angle-closure glaucoma.

Publication trends of primary angle-closure disease during 1991-2022: a bibliometric analysis.

AIM: To perform a bibliometric analysis in the field of primary angle-closure disease (PACD) research to characterize current global trends and compare contributions from different countries, institutions, journals, and authors. METHODS: All PACD-related publications from 1991 to 2022 from the Web of Science Core Collection database were extracted. Microsoft Excel and VOSviewer were used to collect publication data, analyze publication trends, and visualize relevant results. RESULTS: A total of 1721 publications with 34 591 citations were identified. China produced the most publications (554) while ranking third in citations (8220 times). The United States contributed the most citations (12 315 times) with publications (362) ranking second. The Investigative Ophthalmology Visual Science was the most productive journal concerning PACD, and Aung Tin was the author with the highest number of publications in the field. Keywords were classified into three clusters, epidemiology and pathogenesis research, optical coherence tomography (OCT) and other imaging examinations, and glaucoma surgery treatment. Genome-wide association, susceptibility loci, OCT, and combined phacoemulsification have become new hot research topics in recent years since 2015. CONCLUSION: China, the United States, and Singapore make the most outstanding contributions in the field of PACD research. OCT, combined phacoemulsification, and gene mutation-related study, are considered the potential focus for future research.

Safety profile of 0.0015% tafluprost eye drops in China: a post-marketing observational study.

AIM: To investigate the treatment pattern and safety of tafluprost for glaucoma and ocular hypertension (OH) in clinical practice in China. METHODS: This post-marketing observational study included patients who received tafluprost to lower intraocular pressure (IOP) within 30d between September 2017 and March 2020 in 20 hospitals in China. Adverse drug reactions (ADRs) during tafluprost treatment and within 30d after the treatment were collected. RESULTS: A total of 2544 patients were included in this study, of them 58.5% (1488/2544) had primary open angle glaucoma (POAG), 21.9% (556/2544) had OH and 19.7% (500/2544) used tafluprost for other reasons. Of 359 ADRs occurred in 10.1% (258/2544) patients, and no serious adverse event occurred. The most common ADR was conjunctival hyperemia (128 ADRs in 124 patients, 4.9%). Totally 1670 participants (65.6%) combined tafluprost with carbonic anhydrase inhibitors (CAIs; 37.1%, 620/1670), sympathomimetics (33.5%, 559/1670), ß-blockers (33.2%, 555/1670), other prostaglandin analogs (PGAs; 15.6%, 260/1670) and other eye drops (15.1%, 253/1670). The highest incidence of conjunctival hyperemia was noted in patients who received tafluprost in combination with other PGAs (23 ADRs in 23 patients, 8.8%, 23/260) and the lowest was in combination with CAIs (16 ADRs in 16 patients, 2.6%, 16/620). Tafluprost was applied in primary angle-closure glaucoma (41.6%, 208/500), after glaucoma surgery (17.8%, 89/500) and after non-glaucoma surgery (15.8%, 79/500). CONCLUSION: Tafluprost is safe for POAG and OH, and tolerable when combined with other eye drops and under various clinical circumstances.

EphA4/ephrinA3 reverse signaling induced Müller cell gliosis and production of pro-inflammatory cytokines in experimental glaucoma.

Previous work showed that ephrinA3/EphA4 forward signaling contributed to retinal ganglion cell (RGC) damage in experimental glaucoma. Since up-regulated patterns of ephrinA3 and EphA4 were observed in Müller cells and RGCs, an EphA4/ephrinA3 reverse signaling may exist in Müller cells of chronic ocular hypertension (COH) retina. We investigated effects of EphA4/ephrinA3 reverse signaling activation on Müller cells in COH retina. Intravitreal injection of the ephrinA3 agonist EphA4-Fc increased glial fibrillary acidic protein (GFAP) levels in normal retinas, suggestive of Müller cell gliosis, which was confirmed in purified cultured Müller cells treated with EphA4-Fc. These effects were mediated by intracellular STAT3 signaling pathway as phosphorylated STAT3 (p-STAT3) levels and ratios of p-STAT3/STAT3 were significantly increased in both COH retinas and EphA4-Fc intravitreally injected retinas, as well as in EphA4-Fc treated purified cultured Müller cells. The increase of GFAP protein levels in EphA4-Fc-injected retinas and EphA4-Fc treated purified cultured Müller cells could be partially eliminated by stattic, a selective STAT3 blocker. Co-immunoprecipitation results testified to the presence of interaction between ephrinA3 and STAT3/p-STAT3. In addition, intravitreal injection of EphA4-Fc or EphA4-Fc treatment of cultured Müller cells significantly up-regulated mRNA and protein contents of pro-inflammatory cytokines. Moreover, intravitreal injection of EphA4-Fc increased the number of apoptotic RGCs, which could be reversed by the tyrosine kinase blocker PP2. Overall, EphA4/ephrinA3 reverse signaling may induce Müller cell gliosis and increases release of pro-inflammatory factors, which could contribute to RGC death in glaucoma. Inhibition of EphA4/ephrinA3 signaling may provide an effective neuroprotection in glaucoma.

L- and T-type Ca2+ channels dichotomously contribute to retinal ganglion cell injury in experimental glaucoma.

Retinal ganglion cell apoptotic death is the main pathological characteristic of glaucoma, which is the leading cause of irreversible blindness. Disruption of Ca2+ homeostasis plays an important role in glaucoma. Voltage-gated Ca2+ channel blockers have been shown to improve vision in patients with glaucoma. However, whether and how voltage-gated Ca2+ channels are involved in retinal ganglion cell apoptotic death are largely unknown. In this study, we found that total Ca2+ current densities in retinal ganglion cells were reduced in a rat model of chronic ocular hypertension experimental glaucoma, as determined by whole-cell patch-clamp electrophysiological recordings. Further analysis showed that L-type Ca2+ currents were downregulated while T-type Ca2+ currents were upregulated at the later stage of glaucoma. Western blot assay and immunofluorescence experiments confirmed that expression of the CaV1.2 subunit of L-type Ca2+ channels was reduced and expression of the CaV3.3 subunit of T-type Ca2+ channels was increased in retinas of the chronic ocular hypertension model. Soluble tumor necrosis factor-α, an important inflammatory factor, inhibited the L-type Ca2+ current of isolated retinal ganglion cells from control rats and enhanced the T-type Ca2+ current. These changes were blocked by the tumor necrosis factor-α inhibitor XPro1595, indicating that both types of Ca2+ currents may be mediated by soluble tumor necrosis factor-α. The intracellular mitogen-activated protein kinase/extracellular signal-regulated kinase pathway and nuclear factor kappa-B signaling pathway mediate the effects of tumor necrosis factor-α. TUNEL assays revealed that mibefradil, a T-type calcium channel blocker, reduced the number of apoptotic retinal ganglion cells in the rat model of chronic ocular hypertension. These results suggest that T-type Ca2+ channels are involved in disrupted Ca2+ homeostasis and apoptosis of retinal ganglion cells in glaucoma, and application of T-type Ca2+ channel blockers, especially a specific CaV3.3 blocker, may be a potential strategy for the treatment of glaucoma.

Clinical and Genetic Analysis of Retinitis Pigmentosa with Primary Angle Closure Glaucoma in the Chinese Population.

PURPOSE: Retinitis pigmentosa (RP) constitutes a class of common inherited retinal dystrophies. Patients with RP and comorbid primary angle-closure glaucoma (PACG) have been described, but the relationship between the diseases remains unclear. This study investigated the clinical and genetic characteristics of Chinese patients with RP and comorbid PACG. METHODS: Of 1356 patients with RP, we analyzed the genetic features of 39 RP patients with PACG using next-generation sequencing and reviewed their clinical characteristics. RESULTS: In total, 18 patients with acute PACG and 21 patients with chronic PACG were included in this study; their age at examination was 50.54 ± 12.99 years (range, 25.0-71.0 years), and their age at PACG onset was 46.04 ± 14.50 years (range, 24.9-68.0 years). Additionally, the mean lens thickness (LT) was 4.49 ± 0.44 µm, and the mean axial length (AL) was 22.63 ± 1.17 mm. Notably, the prevalence of PACG in patients with RP was 2.88%; this was higher than the prevalence in the general population. This could be explained by nanophthalmos, thickened lentis, ectopia lentis, or zonular insufficiency. Furthermore, patients with a shorter AL, a greater LT, iridociliary cysts, or nanophthalmos exhibited earlier development of PACG. Overall, 30 disease-causing variants spanning 17 genes were identified in 56.41% of the patients, and PRPH2 was the most common mutation gene. CONCLUSIONS: Our findings revealed that there is a strong association between RP and PACG. Furthermore, intraocular pressure (IOP) should be measured in patients with RP to protect them from the aggravated damage of an elevated IOP.

Neuroprotective effect of the somatostatin receptor 5 agonist L-817,818 on retinal ganglion cells in experimental glaucoma.

Somatostatin plays important roles in modulating neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Previous studies have demonstrated that sst5 were expressed in retinal ganglion cells (RGCs) and sst5 agonist attenuated the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid-induced retinal neurotoxicity. In this study, we investigated effects and underlying mechanisms of the sst5 agonist L-817,818 on RGC injury induced by elevated intraocular pressure (COH) in experimental glaucoma. Our results showed that intraperitoneal administration of L-817,818 significantly reduced RGC loss and decreased the number of terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL)-positive RGCs in COH retinas, suggesting that L-817,818 may attenuate RGC apoptosis. Consistently, in COH retinas with L-817,818 administration, both the down-regulated mRNA and protein levels of anti-apoptotic Bcl-2 and the up-regulated mRNA and protein levels of pro-apoptotic Bax were partially reversed. L-817,818 administration downregulated the expression of apoptosis-related proteins caspase-9 and caspase-3 in COH retinas. In addition, L-817,818 administration reduced the concentrations of reactive oxygen species/reactive nitrogen species and malondialdehyde, and ameliorated the functions of mitochondrial respiratory chain complex (MRCC). Our results imply that administration of the sst5 agonist L-817,818 reduces RGC loss in COH rats through decreasing RGC apoptosis, which is mediated by regulating Bcl-2/Bax balance, reducing oxidative stress and rescuing activities of MRCC. Activation of sst5 may provide neuroprotective roles for RGCs in glaucoma.

Activated ephrinA3/EphA4 forward signaling induces retinal ganglion cell apoptosis in experimental glaucoma.

Previous studies have demonstrated that EphA4 participates in neuronal injury, and there is a strong interaction between ephrinA3 and EphA4. In this study, we showed that in a rat chronic ocular hypertension (COH) experimental glaucoma model, expression of EphA4 and ephrinA3 proteins was increased in retinal cells, including retinal ganglion cells (RGCs) and Müller cells, which may result in ephrinA3/EphA4 forward signaling activation on RGCs, as evidenced by increased p-EphA4/EphA4 ratio. Intravitreal injection of ephrinA3-Fc, an activator of EphA4, mimicked the effect of COH on p-EphA4/EphA4 and induced an increase in TUNEL-positive signals in normal retinas, which was accompanied by dendritic spine retraction and thinner dendrites in RGCs. Furthermore, Intravitreal injection of ephrinA3-Fc increased the levels of phosphorylated src and GluA2 (p-src and p-GluA2). Co-immunoprecipitation assay demonstrated interactions between EphA4, p-src and GluA2. Intravitreal injection of ephrinA3-Fc reduced the expression of GluA2 proteins on the surface of normal retinal cells, which was prevented by intravitreal injection of PP2, an inhibitor of src-family tyrosine kinases. Pre-injection of PP2 or the Ca2+-permeable GluA2-lacking AMPA receptor inhibitor Naspm significantly and partially reduced the number of TUNEL-positive RGCs in the ephrinA3-Fc-injected and COH retinas. Our results suggest that activated ephrinA3/EphA4 forward signaling promoted GluA2 endocytosis, then resulted in dendritic spine retraction of RGCs, thus contributing to RGC apoptosis in COH rats. Attenuation of the strength of ephrinA/EphA signaling in an appropriate manner may be an effective way for preventing the loss of RGCs in glaucoma.

Measurement of the depths at different regions of the anterior chamber in healthy Chinese adults.

AIM: To measure the depths of different regions of the anterior chamber (AC) in healthy Chinese adults, and to explore possible correlations with age or gender. METHODS: The AC was imaged by swept-source optical coherence tomography in healthy Chinese adults. The horizontal scan of the right eye was used to measure the anterior chamber depth (ACD) at 199 points. RESULTS: A total of 309 images from 309 subjects were analyzed. The ACD values at nearly all locations were negatively correlated with age (all P<0.05), except for ACD1, 2, 198, and 199 (correspond to the iris roots). The mean annual decrease 0.013±0.005 mm/y for all ACDs combined, 0.008±0.004 mm/y for the peripheral region, 0.017±0.003 mm/y for the middle peripheral region, and 0.014±0.001 mm/y for the central region. The mean annual decrease was significantly different among these three regions (P<0.001). The ACD was greater in males than in females (P<0.05). The mean difference in ACD between males and females was 0.081±0.025 mm. CONCLUSION: This study showed that optical coherence tomography can be used to measure the ACD of different regions of the AC. We found reductions in ACD with age, although the reduction varied among different points, in healthy Chinese adults.

Somatostatin receptor 5-mediated modulation of outward K+ currents in rat retinal ganglion cells.

Somatostatin participants in multiple physiological functions by activating the five distinct G-protein-coupled receptors (sst1-sst5). In this study, we investigated the effect of sst5 activation on outward K currents in acutely isolated rat retinal ganglion cells using whole-cell patch-clamp techniques. Extracellular application of L-817,818, a specific sst5 agonist, significantly reduced outward K currents which was mainly the 4-aminopyridine and glybenclamide sensitive current components, but not the tetraethylammonium-sensitive one. The L-817,818 effect was mediated by sst5 since the suppression was eliminated when intracellular dialysis of the G-protein inhibitor GDP-ß-S or extracellular application of the sst5 antagonist BIM-23056. Intracellular phospholipase C/protein kinase C signaling pathway was involved in the L-817,818 effect because the L-817,818 effect on K currents was inhibited when rat retinal ganglion cells were pretreated with U73122 or chelerythrine chloride. However, L-817,818 persisted to reduce the K currents when cAMP/protein kinase A, calcium/calmodulin-dependent protein kinase II and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling pathways were blocked respectively. These results suggest that sst5 activation suppresses 4-aminopyridine and glybenclamide-sensitive K currents in rat retinal ganglion cells by stimulating intracellular phospholipase C/protein kinase C signaling pathway, thereby regulating the rat retinal ganglion cell excitability.

Morphological alterations of intrinsically photosensitive retinal ganglion cells after ablation of mouse photoreceptors with selective photocoagulation.

In this work, we investigated changes in the morphology of intrinsically photosensitive retinal ganglion cells (ipRGCs), M1 subtype, and pupillary light reflex following local and selective ablation of photoreceptors in mice. Laser photocoagulation was used to selectively destroy four patches of photoreceptors per eye at around 4 papillary diameters from the optic disc and at the 3, 6, 9, and 12 o'clock positions between the retinal vessels in the adult mouse retina, leaving cells in the inner retina intact. Morphological parameters of individual M1 cells specifically labeled by the antibody against melanopsin (PA1-780), including dendritic field size, total dendritic length, and dendritic branch number, were examined 1, 2, 4, and 8 weeks after photocoagulation with Neurolucida software. A considerable reduction in these parameters in M1 cells in the "lesioned areas" was found at all the four time points after photocoagulation, as compared with those in the "unlesioned areas". Although M1 cells in the lesioned areas showed significant changes as early as 1 week after laser treatment and the changes gradually increased, reaching a peak value at 2 weeks, morphological restoration was clearly seen in these cells over time. However, no difference in the morphological parameters of M1 cells was observed between the unlesioned areas of laser-treated mice and the corresponding areas of age-matched normal mice without laser lesions. Fluorescence intensity of the somata of melanopsin-positive M1 cells located inside the lesioned areas was significantly decreased at all the four time points after photocoagulation, whereas no changes in pupillary light reflex were detected at different light irradiations, indicating that photocoagulation-induced local photoreceptor loss and alterations of ipRGCs may be insufficient to cause abnormalities in non-image-forming (NIF) visual functions. The results suggest that intact photoreceptors could be crucial for maintaining the expression levels of melanopsin and normal morphology of M1 cells.

Green Tea Extract Ameliorates Ischemia-Induced Retinal Ganglion Cell Degeneration in Rats.

PURPOSE: Oxidative stress induced by reduced blood circulation is a critical pathological damage to retinal ganglion cells (RGCs) in glaucoma. We previously showed that green tea extract (GTE) and its catechin constituents alleviate sodium iodate-induced retinal degeneration in rats. Here, we investigated the therapeutic effect of GTE on ischemia-induced RGC degeneration in rats. METHODS: RGC degeneration was induced by ischemic reperfusion in adult Fischer F344 rats. Green tea extract (Theaphenon E) was intragastrically administered 4 times within 48 hours after ischemia. RGC survival, pupillary light reflex, expressions of cell apoptosis, oxidative stress, and inflammation-related proteins were studied. RESULTS: Ischemic reperfusion significantly induced apoptotic RGCs, RGC loss, and larger constricted pupil area compared to the untreated normal rats. Expressions of activated caspase-3 and caspase-8, Sod2, and inflammation-related proteins as well as p38 phosphorylation were significantly upregulated in the ischemia-injured rats. Compared to the saline-fed ischemic rats, significantly higher number of surviving RGCs, less apoptotic RGCs, and smaller constricted pupil area were observed in the GTE-fed ischemic rats. GTE also reduced the increased protein expressions caused by ischemic injury but enhanced the Jak phosphorylation in the retina. Notably, green tea extract did not affect the survival of RGCs in the uninjured normal rats. CONCLUSIONS: In summary, GTE offers neuroprotection to RGCs under ischemic challenge, suggesting a potential therapeutic strategy for glaucoma and optic neuropathies.

Activation of somatostatin receptor 5 suppresses T-type Ca2+ channels through NO/cGMP/PKG signaling pathway in rat retinal ganglion cells.

Somatostatin has been shown to modulate a variety of neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Here, effects of sst5 receptor activation on T-type Ca2+ channels in acutely isolated retinal ganglion cells (RGCs) of rats were investigated using whole-cell patch-clamp techniques. The sst5 receptor specific agonist L-817,818 significantly and reversibly suppressed T-type Ca2+ currents, and shifted inactivation curve of the channels toward hyperpolarization direction. The effect of L-817,818 was in a dose-dependent manner, with an IC50 being 8.8 µM. Pertussis toxin-sensitive Gi/o protein mediated intracellular nitric oxide (NO)/cGMP/protein kinase G (PKG) signaling cascade was involved in the L-817,818 effect on Ca2+ currents because pharmacological interference of each of these signaling molecules abolished the L-817,818 effect. In contrast, neither phospholipase C/protein kinase C nor cAMP/protein kinase A signal pathways seemed likely to be involved because the L-817,818 effect persisted when these signaling pathways were blocked by U73122, bisindolylmaleimide IV, chelerythrine chloride, and Rp-cAMP, respectively. These results suggest that activation of sst5 receptors suppresses T-type Ca2+ currents in rat RGCs through intracellular NO/cGMP/PKG signaling pathway, which may provide a potential mechanism for protecting RGCs against injury.

EphrinB/EphB forward signaling in Müller cells causes apoptosis of retinal ganglion cells by increasing tumor necrosis factor alpha production in rat experimental glaucomatous model.

It was previously shown that EphB/ephrinB reverse signaling in retinal ganglion cells (RGCs) is activated and involved in RGC apoptosis in a rat chronic ocular hypertension (COH) model. In the present work, we first show that ephrinB/EphB forward signaling was activated in COH retinas, and RGC apoptosis in COH retinas was reduced by PP2, an inhibitor of ephrinB/EphB forward signaling. We further demonstrate that treatment of cultured Müller cells with ephrinB1-Fc, an EphB1 activator, or intravitreal injection of ephrinB1-Fc in normal rats induced an increase in phosphorylated EphB levels in these cells, indicating the activation of ephrinB/EphB forward signaling, similar to those in COH retinas. The ephrinB1-Fc treatment did not induce Müller cell gliosis, as evidenced by unchanged GFAP expression, but significantly up-regulated mRNA and protein levels of tumor necrosis factor-α (TNF-α) in Müller cells, thereby promoting RGC apoptosis. Production of TNF-α induced by the activation of ephrinB/EphB forward signaling was mediated by the NR2B subunit of NMDA receptors, which was followed by a distinct PI3K/Akt/NF-κB signaling pathway, as pharmacological interference of each step of this pathway caused a reduction of TNF-α production, thus attenuating RGC apoptosis. Functional analysis of forward and reverse signaling in such a unique system, in which ephrin and Eph exist respectively in a glial element and a neuronal element, is of theoretical importance. Moreover, our results also raise a possibility that suppression of ephrinB/EphB forward signaling may be a new strategy for ameliorating RGC apoptosis in glaucoma.

Melatonin concentrations in serum of primary glaucoma patients.

AIM: To determine whether glaucoma patients exhibit an abnormal melatonin concentration in serum and the effects of psychiatric disorders caused by glaucoma in melatonin secretion. METHODS: A sample of 80 primary angle-closure glaucoma (PACG) patients, 120 primary open angle glaucoma (POAG) patients, and 120 normal controls were enrolled in this study. All the participants were asked to complete the following questionnaires: Pittsburgh sleep quality index (PSQI), self-rating anxiety scale (SAS), and self-rating depression scale (SDS). Variance analysis was used to compare the subscores between the groups. After that, we chose 58 patients with primary glaucoma and 20 non-glaucoma control patients to collect their serum samples at 7-10 a.m. Serum melatonin levels were measured using enzyme linked immunosorbent assay (ELISA). RESULTS: Of all participants, the scores of PSQI, SAS, and SDS in PACG and POAG group were 9.38±0.40, 46.08±8.99, 51.11±10.72 and 7.43±0.35, 45.42±9.87, 49.04±12.24 respectively, significantly higher than those in control group (4.16±0.28, 35.49±9.18, 40.31±13.08). The serum melatonin levels in PACG (37.29±2.99 pg/mL) and POAG (35.97±3.64 pg/mL) were significantly higher than the controls (29.96±3.94 pg/mL) (P<0.001). But no difference was found between the PACG and POAG (P=0.216). Glaucoma patients with sleep disorders, anxiety and depression were more likely resulting in the increase of melatonin levels. CONCLUSION: There is a significant increase in serum melatonin levels in glaucoma patients compared to the controls especially in glaucoma patients with psychiatric disorders such as sleep disorders, anxiety and depression.

Circular RNA-ZNF609 regulates retinal neurodegeneration by acting as miR-615 sponge.

Glaucoma is a major cause of visual impairment characterized by progressive retinal neurodegeneration. Circular RNAs are a class of endogenous noncoding RNAs that regulate gene expression in eukaryotes. In this study, we investigated the role of cZNF609 in retinal neurodegeneration induced by glaucoma. Methods: qRT-PCR and Sanger sequencing were conducted to detect cZNF609 expression pattern during retinal neurodegeneration. Immunofluorescence staining was conducted to detect the effect of cZNF609 silencing on retinal neurodegeneration in vivo. MTT assay, Ki67 staining, and PI staining were conducted to detect the effect of cZNF609 silencing on retinal glial cells and RGC function in vitro. Bioinformatics analysis, RNA pull-down assays, and in vitro studies were conducted to reveal the mechanism of cZNF609-mediated retinal neurodegeneration. Results: cZNF609 expression was significantly up-regulated during retinal neurodegeneration. cZNF609 silencing reduced retinal reactive gliosis and glial cell activation, and facilitated RGC survival in vivo. cZNF609 silencing directly regulated Müller cell function but indirectly regulated RGC function in vitro. cZNF609 acted as an endogenous miR-615 sponge to sequester and inhibit miR-615 activity, which led to increased METRN. METRN overexpression could partially rescue cZNF609 silencing-mediated inhibitory effects on retinal glial cell proliferation. Conclusion: Intervention of cZNF609 expression is a promising therapeutic strategy for retinal neurodegeneration.

Dopamine D1 receptor-mediated upregulation of BKCa currents modifies Müller cell gliosis in a rat chronic ocular hypertension model.

Müller cell gliosis is a common response in many retinal pathological conditions. We previously demonstrated that downregulation of Kir channels contributes to Müller cell gliosis in a rat chronic ocular hypertension (COH) model. Here, the possible involvement of outward K+ currents in Müller cell gliosis was investigated. Outward K+ current densities in Müller cells isolated from COH rats, as compared with those in normal rats, showed a significant increase, which was mainly contributed by large-conductance Ca2+ -activated K+ (BKCa ) channels. The involvement of BKCa channels in Müller cell gliosis is suggested by the fact that glial fibrillary acidic protein (GFAP) levels were augmented in COH retinas when these channels were suppressed by intravitreal injections of iberiotoxin. In COH retinas an increase in dopamine (DA) D1 receptor (D1R) expression in Müller cells was revealed by both immunohistochemistry and Western blotting. Moreover, protein levels of tyrosine hydroxylase were also increased, and consistent to this, retinal DA contents were elevated. SKF81297, a selective D1R agonist, enhanced BKCa currents of normal Müller cells through intracellular cAMP-PKA signaling pathway. Furthermore, GFAP levels were increased by the D1R antagonist SCH23390 injected intravitreally through eliminating the BKCa current upregulation in COH retinas, but partially reduced by SKF81297. All these results strongly suggest that the DA-D1R system may be activated to a stronger extent in COH rat retinas, thus increasing BKCa currents of Müller cells. The upregulation of BKCa channels may antagonize the Kir channel inhibition-induced depolarization of Müller cells, thereby attenuating the gliosis of these cells.

K+ Channels of Müller Glial Cells in Retinal Disorders.

BACKGROUND & OBJECTIVE: Müller cell is the major type of glial cell in the vertebrate retina. Müller cells express various types of K+ channels, such as inwardly rectifying K+ (Kir) channels, big conductance Ca2+-activated K+ (BKCa) channels, delayed rectifier K+ channels (KDR), and transient A-type K+ channels. These K+ channels play important roles in maintaining physiological functions of Müller cells. Under some retinal pathological conditions, the changed expression and functions of K+ channels may contribute to retinal pathogenesis. CONCLUSION: In this article, we reviewed the physiological properties of K+ channels in retinal Müller cells and the functional changes of these channels in retinal disorders.

Involvement of mGluR I in EphB/ephrinB reverse signaling activation induced retinal ganglion cell apoptosis in a rat chronic hypertension model.

EphB/ephrinB reverse signaling is involved in retinal ganglion cell (RGC) apoptosis in experimental glaucoma. Here, we further investigated the mechanisms underlying EphB/ephrinB reverse signaling activation induced RGC apoptosis in a rat chronic ocular hypertension (COH) model, using patch-clamp techniques in retinal slices. In COH retinas, RGCs showed higher spontaneous firing frequency and much more depolarized membrane potential as compared to control, which was mimicked by intravitreally injection of EphB2-Fc, an activator of ephrinB2. The changes in RGC spontaneous firing and membrane potential could be reversed by the tyrosine kinase inhibitor PP2, suggesting that EphB/ephrinB reverse signaling activation induced RGC hyperexcitability. Intravitreal pre-injection of either LY367385 or MPEP, selective mGluR1 and mGluR5 antagonists, also blocked the changes in RGC spontaneous firing and membrane potential. Co-immunoprecipitation experiments showed an interaction between ephrinB2 and group I metabotropic glutamate receptor (mGluR I) (mGluR1/mGluR5). Furthermore, intravitreal pre-injection of the mixture of L-NAME (an NO synthase inhibitor) and XPro1595 (a selective inhibitor of soluble TNF-α) could reduce the EphB2-Fc injection induced increase in RGC firing, suggesting that Müller cells might be involved in EphB/ephrinB reverse signaling activation induced change in RGC hyperexcitability. In addition, LY367385/MPEP reduced the numbers of TUNEL-positive RGCs both in EphB2-Fc injected and COH retinas. All results suggest that activation of EphB/ephrinB reverse signaling induces RGC hyperexcitability and apoptosis by interacting with mGluR I in COH rats. Appropriate reduction of EphB/ephrinB reverse signaling could alleviate the loss of RGCs in glaucoma.