Focal Functional and Microstructural Changes of Photoreceptors in Eyes with Acute Zonal Occult Outer Retinopathy

Purpose: Acute zonal occult outer retinopathy (AZOOR) is characterized by an acute zonal loss of outer retinal function with minimal ophthalmoscopic changes in one or both eyes. We present a patient with AZOOR whose ultrastructural and functional findings were followed for 8 months. Case: A 22-year-old woman developed an acute central scotoma in her right eye. Her best-corrected visual acuity (BCVA) was 0.5 OD and 1.2 OS. The ophthalmoscopic examinations, fluorescein angiography, and full-field electroretinograms (ERGs) were normal in both eyes. The amplitudes of the multifocal ERGs (mfERGs) were attenuated in the area corresponding to the scotoma. Spectral domain optical coherence tomography showed an absence of both the inner and outer segment (IS/OS) line of the photoreceptors and the cone outer segment tip (COST) line between the IS/OS line and the retinal pigment epithelium. These changes were seen in the area corresponding to the scotoma. One month later, the scotoma disappeared and the BCVA improved to 1.2 OD. The mfERGs increased to almost the same amplitude as the fellow eye. The IS/OS line became discernible but the COST line was still absent. The ophthalmological findings of the right macula remained normal during the 11-month follow-up period. Conclusions: Our findings indicate that the selective loss of the IS/OS and the COST lines is probably the morphological alterations corresponding with the reduced BCVA and the mfERGs in the areas of the visual field defects in the acute phase of AZOOR. But in the recovery phase, only the abnormality of the COST line is a subclinical sign for the disease. These findings should be important in understanding and evaluating the pathological mechanism in other outer retinal diseases

Role of nonproteolytically activated prorenin in pathologic, but not physiologic, retinal neovascularization

PURPOSE. Recently, it was revealed that the inhibition of nonproteolytic activation of prorenin led to significant suppression of ocular inflammation in endotoxin-induced uveitis. The purpose of the present study was to investigate whether nonproteolytically activated prorenin plays a role in ischemia-induced retinal neovascularization. METHODS. C57BL/6 neonatal mice were reared in an 80% concentration of oxygen from postnatal (P) day 7 to P12, followed by room-air breathing to P17 to induce ischemia-initiated retinal neovascularization. Tissue localization of activated prorenin and prorenin receptor was examined by immunohistochemistry. Animals received intraperitoneal injections of handle-region peptide (HRP), a decoy peptide corresponding to the handle region of prorenin, which inhibits prorenin receptor-mediated upregulation of the renin-angiotensin system (RAS). A concanavalin A lectin perfusion-labeling technique was used to evaluate the areas of physiologic and pathologic retinal new vessels and the number of leukocytes adhering to the vasculature. Retinal mRNA expression and protein levels of intercellular adhesion molecule (ICAM)-1, vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)-1, and VEGFR-2 were examined by RT-PCR and ELISA. RESULTS. Retinal vessels in ischemic retinopathy eyes were positive for activated prorenin and prorenin receptor. Pathologic, but not physiologic, retinal neovascularization was significantly attenuated in HRP-treated mice compared with vehicle-or control peptide-treated animals. The number of adherent leukocytes was also significantly reduced. Retinal mRNA expression and protein levels of ICAM-1, VEGF, VEGFR-1, and VEGFR-2 in ischemic retinopathy were also significantly suppressed by the application of HRP. CONCLUSIONS. The present findings suggest that nonproteolytic activation of prorenin selectively promotes pathologic, but not physiologic, retinal neovascularization through the inflammatory processes related to pathologic neovascularization. (Invest Ophthalmol Vis Sci. 2007;48:422-429) DOI:10.1167/iovs.06-0534 R etinal neovascularization is a hallmark of vision-threatening retinal diseases, including diabetic retinopathy and retinopathy of prematurity, which are major causes of blindness in adults and children, respectively. There are two distinctly different types of retinal neovascularization, physiologic and pathologic, each of which is induced by retinal ischemia. In the former, new vessels grow systematically in the retina to compensate for retinal ischemia, whereas in the latter, retinal new vessels ectopically invade the transparent vitreous, which originally lacks vasculature. Because simultaneous prevention of both types of retinal neovascularization causes retinal ischemia to be untreated, ophthalmologists await the establishment of new therapy that selectively targets pathologic neovascularization while it spares compensatory physiologic neovascularization. We have recently highlighted the molecular and cellular mechanisms differentiating pathologic from physiologic retinal neovascularization. 1-3 The influx of inflammatory cells at the growing tip of new vessels is likely to be a critical step in changing the direction of retinal neovascularization from intraretinal to extraretinal growth. Recently, we demonstrated that angiotensin II type 1 receptor (AT1-R) blockers, widely and safely used for antihypertension therapy, have an inhibitory effect on retinal neovascularization in the murine model of ischemic retinopathy. 5-8 The initial step for upregulation of the RAS is classically known as proteolytic activation, whereby prorenin is converted to an active (mature) form of renin by processing enzymes to remove the prorenin prosegment, which folds into an active-site cleft of mature renin. Renin is well known to be a rate-limiting enzyme in the RAS for the cleavage of angiotensinogen to angiotensin I, which angiotensin-converting enzyme (ACE) processes to angiotensin II, a final effector molecule that interacts with its cognate receptors AT1-R and AT2-R. In addition to the proteolytic activation of prorenin, nonproteolytic activation of prorenin, which was recently demonstrated in vitro, 9 has attracted growing attention as a local activator of the RAS, causing organ damage. In the mechanism of nonproteolytic activation, when the prorenin-binding proteins interact selectively with the handle region of the prorenin prosegment, prorenin undergoes conformational change with exposure of the active center and obtains enzymatic bioactivity of renin without cleavage of the prorenin prosegment or change in molecular weight. In vitro nonproteolytic activation of prorenin was originally observed under acidic pH or low temperature, 10 -12 which are called acid-activation and cryoFrom th

(Pro)renin Receptor Promotes Choroidal Neovascularization by Activating Its Signal Transduction and Tissue Renin-Angiotensin System

The receptor-associated prorenin system (RAPS) refers to pathogenic mechanisms whereby prorenin binding to its receptor activates both the tissue renin-angiotensin system (RAS) and RAS-independent intracellular signaling pathways. Although we found significant involvement of angiotensin II type 1 receptor (AT1-R)-mediated inflammation in choroidal neovascularization (CNV), a central abnormality of vision-threatening age-related macular degeneration, the association of receptor-associated prorenin system with CNV has not been defined. Here, (pro)renin receptor blockade in a murine model of laser-induced CNV led to the significant suppression of CNV together with macrophage infiltration and the up-regulation of intercellular adhesion molecule-1, (ICAM-1) monocyte chemotactic protein-1, (MCP-1) vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)-1, and VEGFR-2. To clarify the role of signal transduction via the (pro)renin receptor in CNV, we used mice in which renin-angiotensin system was deactivated by either the pharmacological blockade of AT1-R with losartan or the genetic ablation of AT1-R or angiotensinogen. Compared with wild-type controls, these mice exhibited significant reduction of CNV and macrophage infiltration, both of which were further suppressed by (pro)renin receptor blockade. The (pro)renin receptor and phosphorylated extracellular signal-regulated kinases (ERK) were co-localized in vascular endothelial cells and macrophages in CNV. (Pro)renin receptor blockade suppressed ERK activation and the production of MCP-1 and VEGF, but not ICAM-1, VEGFR-1, or VEGFR-2, in AT1-R-deficient mice with CNV and in losartan-treated microvascular endothelial cells and macrophages. These results indicate the significant contribution of RAPS to CNV pathogenesis

Eicosapentaenoic Acid Is Anti-Inflammatory in Preventing Choroidal Neovascularization in Mice

PURPOSE. To investigate the role of eicosapentaenoic acid (EPA), the major -3 polyunsaturated fatty acid (PUFA), in the development of choroidal neovascularization (CNV), together with underlying molecular mechanisms. METHODS. Six-week-old C57BL/6 mice were fed with laboratory chow with 5% EPA or the -6 PUFA linoleic acid (LA) for 4 weeks. Laser photocoagulation was performed to induce CNV, and the volume of CNV tissue was evaluated by volumetric measurements. The expression and production of intercellular adhesion molecule (ICAM)-1, monocyte chemotactic protein (MCP)-1, vascular endothelial growth factor (VEGF) and interleukin (IL)-6 in the retinal pigment epithelium (RPE)-choroid in vivo, and stimulated b-End3 endothelial cells and RAW264.7 macrophages in vitro were evaluated by RT-PCR and ELISA. Fatty acid composition in the serum and the RPE-choroid was analyzed by gas chromatography and high-performance liquid chromatography, respectively. Serum levels of C-reactive protein (CRP), IL-6, VEGF, MCP-1, and soluble ICAM-1 were examined by ELISA. RESULTS. The CNV volume in EPA-fed animals was significantly suppressed compared with that in control mice, whereas the LA-rich diet did not affect CNV. The mRNA expression and protein levels of ICAM-1, MCP-1, VEGF, and IL-6 after CNV induction were significantly reduced in EPA-supplemented mice. In vitro, EPA application led to significant inhibition of mRNA and protein levels of ICAM-1 and MCP-1 in endothelial cells and VEGF and IL-6 in macrophages. EPA-fed mice exhibited significantly higher levels of EPA and lower levels of the -6 PUFA arachidonic acid in the serum and the RPE-choroid than control animals. EPA supplementation also led to significant reduction of serum levels of IL-6 and CRP after CNV induction. CONCLUSIONS. The present study demonstrates for the first time that an EPA-rich diet results in significant suppression of CNV and CNV-related inflammatory molecules in vivo and in vitro. These results suggest that frequent consumption of -3 PUFAs may prevent CNV and lower the risk of blindness due to age-related macular degeneration. (Invest Ophthalmol Vis Sci

Angiotensin II Type 1 Receptor Antagonist Attenuates Lacrimal Gland, Lung, and Liver Fibrosis in a Murine Model of Chronic Graft-Versus-Host Disease

<div><p>Chronic graft-versus-host disease (cGVHD), a serious complication following allogeneic HSCT (hematopoietic stem cell transplantation), is characterized by systemic fibrosis. The tissue renin-angiotensin system (RAS) is involved in the fibrotic pathogenesis, and an angiotensin II type 1 receptor (AT1R) antagonist can attenuate fibrosis. Tissue RAS is present in the lacrimal gland, lung, and liver, and is known to be involved in the fibrotic pathogenesis of the lung and liver. This study aimed to determine whether RAS is involved in fibrotic pathogenesis in the lacrimal gland and to assess the effect of an AT1R antagonist on preventing lacrimal gland, lung, and liver fibrosis in cGVHD model mice. We used the B10.D2→BALB/c (H-2^d) MHC-compatible, multiple minor histocompatibility antigen-mismatched model, which reflects clinical and pathological symptoms of human cGVHD. First, we examined the localization and expression of RAS components in the lacrimal glands using immunohistochemistry and quantitative real-time polymerase chain reaction (PCR). Next, we administered an AT1R antagonist (valsartan; 10 mg/kg) or angiotensin II type 2 receptor (AT2R) antagonist (PD123319; 10 mg/kg) intraperitoneally into cGVHD model mice and assessed the fibrotic change in the lacrimal gland, lung, and liver. We demonstrated that fibroblasts expressed angiotensin II, AT1R, and AT2R, and that the mRNA expression of angiotensinogen was greater in the lacrimal glands of cGVHD model mice than in controls generated by syngeneic-HSCT. The inhibition experiment revealed that fibrosis of the lacrimal gland, lung, and liver was suppressed in mice treated with the AT1R antagonist, but not the AT2R antagonist. We conclude that RAS is involved in fibrotic pathogenesis in the lacrimal gland and that AT1R antagonist has a therapeutic effect on lacrimal gland, lung, and liver fibrosis in cGVHD model mice. Our findings point to AT1R antagonist as a possible target for therapeutic intervention in cGVHD.</p></div