Pathologic Roles of Receptor-Associated Prorenin System in Idiopathic Epiretinal Membrane

Blood inflammatory biomarkers in participants with idiopathic epiretinal membrane: A retrospective case series study

The objective was to evaluate the levels of monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in patients with idiopathic epiretinal membrane (iERM). This retrospective case series study comprised of participants with iERM and participants with cataract. The values of MLR, NLR, PLR and from participants' peripheral blood were assessed among groups. The best cutoff value of MLR, NLR, and PLR in iERM was found by performing a receiver operating characteristic curve analysis and determining the optimum cutoff value for each variable. In total, 95 participants with iERM were included in the study group, and 61 participants with senile cataract were included as controls. The lymphocyte count in the iERM group was significantly lower than the control group (1.69 ± 0.63 vs. 1.95 ± 0.53, P = .003). The monocyte count in the iERM group was significantly higher than the control group (0.39 ± 0.11 vs. 0.31 ± 0.10, P < .001). The area under the curve of MLR, NLR, and PLR in differentiating patients with IERM and controls was 0.782, 0.645, and 0.657, respectively, according to receiver operating characteristic. The best cutoff value of MLR was > 0.18, with sensitivity and specificity of 74.7% and 75.4%, respectively. The NLR was > 2.06, with a sensitivity and specificity of 50.5% and 83.6%, respectively. The PLR was > 95.89, with a sensitivity and specificity of 86.3% and 41.0%, respectively. The findings of this study suggest that systemic inflammation may be associated with iERM. IERM patients may be prone to have high MLR, NLR, and PLR values.

Involvement of Müller Glial Autoinduction of TGF-β in Diabetic Fibrovascular Proliferation Via Glial-Mesenchymal Transition

Purpose

Müller glial–mesenchymal transition (GMT) is reported as the fibrogenic mechanism promoted by TGF-β–SNAIL axis in Müller cells transdifferentiated into myofibroblasts. Here we show the multifaceted involvement of TGF-β in diabetic fibrovascular proliferation via Müller GMT and VEGF-A production.

Methods

Surgically excised fibrovascular tissues from the eyes of patients with proliferative diabetic retinopathy were processed for immunofluorescence analyses of TGF-β downstream molecules. Human Müller glial cells were used to evaluate changes in gene and protein expression with real-time quantitative PCR and ELISA, respectively. Immunoblot analyses were performed to detect TGF-β signal activation.

Results

Müller glial cells in patient fibrovascular tissues were immunopositive for GMT-related molecular markers, including SNAIL and smooth muscle protein 22, together with colocalization of VEGF-A and TGF-β receptors. In vitro administration of TGF-β1/2 upregulated TGFB1 and TGFB2, both of which were suppressed by inhibitors for nuclear factor-κB, glycogen synthase kinase-3, and p38 mitogen-activated protein kinase. Of the various profibrotic cytokines, TGF-β1/2 application exclusively induced Müller glial VEGFA mRNA expression, which was decreased by pretreatment with small interfering RNA for SMAD2 and inhibitors for p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Supporting these findings, TGF-β1/2 stimulation to Müller cells increased the phosphorylation of these intracellular signaling molecules, all of which were also activated in Müller glial cells in patient fibrovascular tissues.

Conclusions

This study underscored the significance of Müller glial autoinduction of TGF-β as a pathogenic cue to facilitate diabetic fibrovascular proliferation via TGF-β–driven GMT and VEGF-A–driven angiogenesis.

Receptor-Associated Prorenin System in the Trabecular Meshwork of Patients with Primary Open-Angle Glaucoma and Neovascular Glaucoma

The receptor-associated prorenin system (RAPS) is associated with several pathologic conditions, including diabetic retinopathy, age-related macular degeneration, and uveitis. Here, we show the involvement of RAPS in the trabecular meshwork (TM) from patients with primary open-angle glaucoma (POAG) and neovascular glaucoma (NVG) due to proliferative diabetic retinopathy. Anterior chamber (AC) levels of prorenin significantly increased in both POAG and NVG, as did those of angiotensin II in NVG alone, compared to cataract. In surgically excised TM tissues, (pro)renin receptor ((P)RR) and angiotensin II type 1 receptor (AT1R) co-localized with prorenin and angiotensinogen, respectively. In screening for various genes related to glaucoma, prorenin stimulation to human TM cells exclusively upregulated cell junction constituents connexin 43 and zona occludens 1, while downregulating an extracellular matrix-degrading enzyme tissue plasminogen activator, all of which were reversed by (P)RR blockade. In contrast, angiotensin II application upregulated a pro-angiogenic factor placental growth factor alone, which was abolished by AT1R blockade. Consistently, (P)RR and AT1R co-localized with these corresponding proteins in patient TM tissues. Oxidative stress, a known etiology for glaucoma, induced the expression of prorenin and angiotensinogen in human TM cells. These data suggest the contribution of RAPS to the molecular pathogenesis of POAG and NVG through TM tissue remodeling and AC angle angiogenesis.

Suppression of Choroidal Neovascularization and Fibrosis by a Novel RNAi Therapeutic Agent against (Pro)renin Receptor

The receptor-associated prorenin system refers to the pathogenic mechanism whereby prorenin binding to (pro)renin receptor [(P)RR] dually activates the tissue renin-angiotensin system (RAS) and RAS-independent signaling, and its activation contributes to the molecular pathogenesis of various ocular diseases. We recently developed a new single-stranded RNAi agent targeting both human and mouse (P)RR ((P)RR-proline-modified short hairpin RNA [(P)RR-PshRNA]), and confirmed its therapeutic effect on murine models of ocular inflammation. Here, we investigated the efficacy of (P)RR-PshRNA against laser-induced choroidal neovascularization (CNV) and subretinal fibrosis, both of which are involved in the pathogenesis of age-related macular degeneration (AMD). Administration of (P)RR-PshRNA in mice significantly reduced CNV formation, together with the expression of inflammatory molecules, macrophage infiltration, and extracellular signal-regulated kinase (ERK) 1/2 activation. In addition, (P)RR-PshRNA attenuated subretinal fibrosis, together with epithelial-mesenchymal transition (EMT)-related markers including phosphorylated SMAD2. The suppressive effect of (P)RR-PshRNA is comparable with aflibercept, an anti-vascular endothelial growth factor drug widely used for AMD therapy. AMD patient specimens demonstrated (P)RR co-localization with phosphorylated ERK1/2 in neovascular endothelial cells and retinal pigment epithelial cells. These results indicate that (P)RR contributes to the ocular pathogenesis of both inflammation-related angiogenesis and EMT-driven fibrosis, and that (P)RR-PshRNA is a promising therapeutic agent for AMD.

TGF-β-SNAIL axis induces Müller glial-mesenchymal transition in the pathogenesis of idiopathic epiretinal membrane

The epithelial-mesenchymal transition (EMT) is a key process in fibrogenic diseases where transdifferentiated myofibroblasts produce excessive amounts of extracellular matrix, resulting in organ dysfunction. Idiopathic epiretinal membrane (iERM) is a vision-threatening disorder characterized by fibrocellular proliferation and contraction on the central retina. Müller glial cells, which regulate retinal physiology and structure, are the major cellular components in the iERM tissue; however, the pathological role of this cell type remains incompletely understood. Here we revealed the involvement of Müller glial-mesenchymal transition (GMT), as an alternative to EMT, in the pathogenesis of iERM lacking epithelial contribution in nature. Of various pro-fibrotic cytokines, transforming growth factor (TGF)-β1 stimulation to human Müller glial cells exclusively increased mRNA and protein levels of several EMT-related molecular markers, together with the transcription factor SNAIL but not SLUG or TWIST. TGF-β1-stimulated Müller cells also exhibited EMT-related cell motility, while reducing the expression of glutamine synthetase (GS), a Müller glial marker. Notably, all of these TGF-β-induced EMT features were reversed by SNAI1 knockdown in Müller cells. iERM patient specimens demonstrated co-immunolocalization of SNAIL with TGF-β1, GS, and smooth muscle protein 22. Our data implicated a critical role of the TGF-β-SNAIL axis in Müller GMT to promote iERM formation.

(Pro)renin receptor: Involvement in diabetic retinopathy and development of molecular targeted therapy

The renin-angiotensin system (RAS), a crucial regulator of systemic blood pressure (circulatory RAS), plays distinct roles in pathological angiogenesis and inflammation in various organs (tissue RAS), such as diabetic microvascular complications. Using ocular clinical samples and animal disease models, we elucidated molecular mechanisms in which tissue RAS excites the expression of vascular endothelial growth factor (VEGF)-A responsible for retinal inflammation and angiogenesis, the two major pathological events in diabetic retinopathy (DR). Furthermore, we showed the involvement of (pro)renin receptor [(P)RR] in retinal RAS activation and its concurrent intracellular signal transduction (e.g., extracellular signal-regulated kinase); namely, the (P)RR-induced dual pathogenic bioactivity referred to as the receptor-associated prorenin system. Indeed, neovascular endothelial cells in the fibrovascular tissue collected from eyes with proliferative DR were immunoreactive for the receptor-associated prorenin system components including prorenin, (P)RR, phosphorylated extracellular signal-regulated kinase and VEGF-A. Protein levels of soluble (P)RR increased with its positive correlations with prorenin, renin enzymatic activity and VEGF in the vitreous of proliferative DR eyes, suggesting a close link between (P)RR and VEGF-A-driven angiogenic activity. Furthermore, we revealed an unsuspected, PAPS-independent role of (P)RR in glucose-induced oxidative stress. Recently, we developed an innovative single-strand ribonucleic acid interference molecule selectively targeting human and mouse (P)RR, and confirmed its efficacy in suppressing diabetes-induced retinal inflammation in mice. Our data using clinical samples and animal models suggested the significant implication of (P)RR in the pathogenesis of DR, and the potential usefulness of the ribonucleic acid interference molecule as a therapeutic agent to attenuate ocular inflammation and angiogenesis.