The ocular renin-angiotensin system: a therapeutic target for the treatment of ocular disease

(Pro)Renin Receptor Decoy Peptide PRO20 Protects against Oxidative Renal Damage Induced by Advanced Oxidation Protein Products

Chronic kidney disease (CKD) is associated with advanced oxidation protein products (AOPPs). A recent study has shown that AOPP-induced renal tubular injury is mediated by the (pro)renin receptor (PRR). However, it is unclear whether the PRR decoy inhibitor PRO20 can protect against renal damage related to AOPPs in vivo. In this study, we examined the role of the PRR in rats with AOPP-induced renal oxidative damage. Male SD rats were subjected to unilateral nephrectomy, and after a four-day recuperation period, they were randomly divided into four groups (n = 6/group) for four weeks: control (CTR), unmodified rat serum albumin (RSA, 50 mg/kg/day via tail-vein injection), AOPPs-RSA (50 mg/kg/day via tail-vein injection), and AOPPs-RSA + PRO20 (50 mg/kg/day via tail-vein injection + 500 μg/kg/day via subcutaneous injection) groups. PRO20 was administered 3 days before AOPPs-RSA injection. Renal histopathology evaluation was performed by periodic acid–Schiff (PAS) staining, and biochemical parameters related to renal injury and oxidative stress biomarkers were evaluated. The expression of related indicators was quantified by RT-qPCR and immunoblotting analysis. In the results, rats in the AOPPs-RSA group exhibited higher levels of albuminuria, inflammatory cell infiltration, and tubular dilation, along with upregulation of oxidative stress, profibrotic and proinflammatory factors, and elevation of AOPP levels. Meanwhile, in the PRO20 group, these were significantly reduced. Moreover, the levels of almost all components of the renin-angiotensin system (RAS) and Nox4-dependent H2O2 production in urine and the kidneys were elevated by AOPPs-RSA, while they were suppressed by PRO20. Furthermore, AOPPs-RSA rats showed elevated kidney expression of the PRR and soluble PRR (sPRR) and increased renal excretion of sPRR. In summary, these findings suggest that PRR inhibition may serve as a protective mechanism against AOPP-induced nephropathy by inhibiting the intrarenal RAS and Nox4-derived H2O2 mechanisms.

A Cross Talk between the Endocannabinoid System and Different Systems Involved in the Pathogenesis of Hypertensive Retinopathy

The prognosis of hypertension leads to organ damage by causing nephropathy, stroke, retinopathy, and cardiomegaly. Retinopathy and blood pressure have been extensively discussed in relation to catecholamines of the autonomic nervous system (ANS) and angiotensin II of the renin–angiotensin aldosterone system (RAAS) but very little research has been conducted on the role of the ECS in the regulation of retinopathy and blood pressure. The endocannabinoid system (ECS) is a unique system in the body that can be considered as a master regulator of body functions. It encompasses the endogenous production of its cannabinoids, its degrading enzymes, and functional receptors which innervate and perform various functions in different organs of the body. Hypertensive retinopathy pathologies arise normally due to oxidative stress, ischemia, endothelium dysfunction, inflammation, and an activated renin–angiotensin system (RAS) and catecholamine which are vasoconstrictors in their biological nature. The question arises of which system or agent counterbalances the vasoconstrictors effect of noradrenaline and angiotensin II (Ang II) in normal individuals? In this review article, we discuss the role of the ECS and its contribution to the pathogenesis of hypertensive retinopathy. This review article will also examine the involvement of the RAS and the ANS in the pathogenesis of hypertensive retinopathy and the crosstalk between these three systems in hypertensive retinopathy. This review will also explain that the ECS, which is a vasodilator in its action, either independently counteracts the effect produced with the vasoconstriction of the ANS and Ang II or blocks some of the common pathways shared by the ECS, ANS, and Ang II in the regulation of eye functions and blood pressure. This article concludes that persistent control of blood pressure and normal functions of the eye are maintained either by decreasing systemic catecholamine, ang II, or by upregulation of the ECS which results in the regression of retinopathy induced by hypertension.

Azilsartan suppresses the antiapoptotic biomarker and pro-inflammatory cytokines in rat model of cisplatin-induced retinal and optic nerve toxicity

BACKGROUND

The local renin-angiotensin system has been discovered in the eyes; thus, this study evaluates the Azilsartan effect in the retina and optic nerve toxicity induced by Cisplatin in vivo.

METHODOLOGY

Forty-eight male rats were randomly assigned into six groups of 8 animals. Group 1 was healthy control that received 0.5 mL/day of 0.5% carboxymethyl cellulose (CMC) orally (PO). Group 2 received a single dose of the 7.0 mg/kg CIS intraperitoneally with 0.5 mL/day of 0.5% CMC-PO. Groups 3 and 4 received 3.5 and 7.0 mg/kg/day of AZIL-PO, respectively. Groups 5 and 6 received 3.5 and 7.0 mg/kg/day of AZIL-PO, respectively together with a single dose of 7.0 mg/kg of CIS-IP. The ocular tissue and serum estimated the TNF-α, NF-kβ, and Casp-3. A complete blood count was also measured, and the eye was sent for histological examination.

RESULTS

The administration of the 3.5 mg/kg AZIL significantly (p < 0.05) reduced the ocular tissue and serum TNF-α, NF-kB, and Casp-3 levels, when given to CIS treated group, while the 7.0 mg/kg AZIL does not. Additionally, azilsartan shows no negative impact on the CBC in rats. Finally, the eye histological examination showed a significant (p < 0.05) drop in the signs of inflammation and cellular degeneration, particularly after administration of the 3.5 mg/kg AZIL to the CIS-treated group.

CONCLUSION

A low dose of AZIL exerts an anti-inflammation and an anti-apoptotic effect through significant suppression of the pro-inflammatory mediators and an apoptotic biomarker by blocking the local angiotensin II type.

Сases of lacrimal system affection after Coronavirus infection

In the present article, cases of lacrimal apparatus conditions emerging after a new Coronavirus infection COVID-19. The aim of the study is to determine the causes of epiphora in patients after Coronavirus infection. 26 patients (30 eyes) were examined, aged from 28 to 70 years, complaining of tearing, which emerged for the first time ever not earlier than 514 days from the onset of the laboratory-confirmed Coronavirus infection COVID-19, which had a mild or a moderately severe course and was accompanied by anosmia. In patients, following conditions of the lacrimal system were revealed: in 22 patients, there were pathological changes of the horizontal portion of lacrimal pathways; in 6 people dry eye syndrome was diagnosed: in 3 people, it was of mild severity, manifested by hyperlacrimia, 3 people had moderate severity of the dry eye syndrome. As concomitant, following signs were revealed: in 7 patients rhinologic conditions were present, in 2 people neurologic signs. In the examined group of patients with epiphora, we found that in 1.53 month after Coronavirus infection COVID-19 with anosmia, as a common sign of the disease in more than a half of cases, a development of pathological changes of the horizontal portion of lacrimal pathways was revealed.

Cardiovascular aspects of the (pro)renin receptor: Function and significance

Cardiovascular diseases (CVDs), including all types of disorders related to the heart or blood vessels, are the major public health problems and the leading causes of mortality globally. (Pro)renin receptor (PRR), a single transmembrane protein, is present in cardiomyocytes, vascular smooth muscle cells, and endothelial cells. PRR plays an essential role in cardiovascular homeostasis by regulating the renin-angiotensin system and several intracellular signals such as mitogen-activated protein kinase signaling and wnt/β-catenin signaling in various cardiovascular cells. This review discusses the current evidence for the pathophysiological roles of the cardiac and vascular PRR. Activation of PRR in cardiomyocytes may contribute to myocardial ischemia/reperfusion injury, cardiac hypertrophy, diabetic or alcoholic cardiomyopathy, salt-induced heart damage, and heart failure. Activation of PRR promotes vascular smooth muscle cell proliferation, endothelial cell dysfunction, neovascularization, and the progress of vascular diseases. In addition, phenotypes of animals transgenic for PRR and the hypertensive actions of PRR in the brain and kidney and the soluble PRR are also discussed. Targeting PRR in local tissues may offer benefits for patients with CVDs, including heart injury, atherosclerosis, and hypertension.

Association between chronic kidney disease and open-angle glaucoma in South Korea: a 12-year nationwide retrospective cohort study

Various non-intraocular pressure factors have been identified as possible risk factors for open-angle glaucoma (OAG). However, there is still controversy around the association between OAG and chronic kidney disease (CKD). In this study, we used a nationwide cohort to investigate the risk of OAG in the 12 years following a diagnosis of CKD. This retrospective cohort study included 1,103,302 subjects from the Korean National Health Insurance Service National Sample Cohort database. The CKD group (n = 1318) included patients who were initially diagnosed with CKD between 2003 and 2008. The subjects in the comparison group were matched at a 1:5 ratio using propensity scores. In multivariate Cox regression analysis, a diagnosis of CKD was significantly associated with an increased incidence of OAG (hazard ratio [HR] = 1.546, 95% confidence interval [CI] 1.363–1.754, p < 0.001). Further analysis revealed that the risk of OAG increased with the severity of CKD (mild to moderate CKD [CKD stage 1–3]: HR = 1.280, 95% CI 1.077–1.521, p = 0.005; advanced CKD [CKD stage 4–5]: HR = 1.861, 95% CI 1.589–2.180, p < 0.001). In subgroup analysis, female CKD patients had a greater risk of developing OAG than males, and subjects with CKD aged ≥ 40 years were more likely to develop OAG compared with those aged < 40 years. Our study demonstrates that CKD is a significant risk factor for OAG and that severe CKD is associated with an increased risk of developing OAG.

AGTR1 blocker attenuates activation of Tenon's capsule fibroblasts after glaucoma filtration surgery via the NF-κB signaling pathway

Activation of Tenon's capsule fibroblasts limits the success rate of glaucoma filtration surgery (GFS), the most efficacious therapy for patients with glaucoma. Angiotensin type 1 receptor (AGTR1) is involved in tissues remodeling and fibrogenesis. However, whether AGTR1 is involved in the progress of fibrogenesis after GFS is not fully elucidated. The aim of this study was to investigate the role of an AGTR1 in scar formation after GFS and the potential anti-fibrosis effect of AGTR1 blocker. AGTR1 expression level was increased in subconjunctival tissues in a rat model of GFS and transforming growth factor-beta 2 (TGF-β2)-induced human Tenon's capsule fibroblasts (HTFs). AGTR1 blocker treatment suppressed TGF-β2-induced HTF migration and α-smooth muscle actin (α-SMA) and fibronectin (FN) expression. AGTR1 blocker treatment also attenuated collagen deposition and α-SMA and FN expression in subconjunctival tissues of the rat model after GFS. Moreover, AGTR1 blocker decreased TGF-β2-induced P65 phosphorylation, P65 nuclear translocation, and nuclear factor kappa B (NF-κB) luciferase activity. Additionally, BAY 11-7082 (an NF-κB inhibitor) significantly suppressed HTF fibrosis. In conclusion, our results indicate that AGTR1 is involved in scar formation after GFS. The AGTR1 blocker attenuates subconjunctival fibrosis after GFS by inhibiting the NF-κB signaling pathway. These findings indicate that targeting AGTR1 is a potential approach to attenuate fibrosis after GFS.

Alterations in Gene Expression of Renin-Angiotensin System Components and Related Proteins in Colorectal Cancer

MATERIALS AND METHODS

Quantitative expression of the RNA of these 17 genes in normal and cancerous tissues obtained using chip arrays from the public functional genomics data repository, Gene Expression Omnibus (GEO) application, was compared statistically.

RESULTS

Expression of four genes, AGT (angiotensinogen), ENPEP (aminopeptidase A) MME (neprilysin), and PREP (prolyl endopeptidase), was significantly upregulated in CRC specimens. Expression of REN (renin), THOP (thimet oligopeptidase), NLN (neurolysin), PRCP (prolyl carboxypeptidase), ANPEP (aminopeptidase N), and MAS1 (Mas receptor) was downregulated in CRC specimens.

CONCLUSIONS

Presuming gene expression parallel protein expression, these results suggest that increased production of the angiotensinogen precursor of angiotensin (ANG) peptides, with the reduction of the enzymes that metabolize it to ANG II, can lead to accumulation of angiotensinogen in CRC tissues. Downregulation of THOP, NLN, PRCP, and MAS1 gene expression, whose proteins contribute to the ACE2/ANG 1-7/Mas axis, suggests that reduced activity of this RAS branch could be permissive for oncogenicity. Components of the RAS may be potential therapeutic targets for treatment of CRC.

(Pro)renin receptor antagonist PRO20 attenuates nephrectomy-induced nephropathy in rats via inhibition of intrarenal RAS and Wnt/β-catenin signaling

Introduction

(Pro)renin receptor has emerged as a new member of the renin‐angiotensin system implicated in the pathogenesis of chronic kidney disease (CKD). Herein we report characterization of the therapeutic potential of (pro)renin receptor (PRR) antagonist PRO20 in 5/6 nephrectomy (5/6Nx) rats.

Methods

Male Wistar rats underwent 5/6Nx followed by treatment with vehicle or received daily injections of a PRR inhibitor PRO20 (700 μg/kg) via the 3 s.c. Sham group served as a control.

Results

As compared with the sham control, the 5/6Nx rats exhibited significant increases in proteinuria, glomerulosclerosis, tubular injury, and interstitial inflammation in the remnant kidneys. Treatment with PRO20 significantly attenuated these abnormalities, as evidenced by reduced expression of fibronectin, α‐SMA, collagen 1, TGF‐β1, IL‐6, IL‐8, IL‐1β, MCP‐1 and increased expression of E‐cadherin. Increased urinary/renal levels of renin activity, angiotensinogen (AGT), and Angiotensin II (Ang II) by 5/6Nx, which were all ameliorated by PRO20. Renal PRR, the secreted proteolytic fragment of PRR (sPRR) in renal and urinary, were all elevated in 5/6Nx rats. Moreover, our results revealed that renal Wnt3A and β‐catenin expression were upregulated during 5/6Nx, which were all attenuated by PRO20.

Conclusions

Overall we conclude that in vivo antagonism of PRR with PRO20 will improve 5/6Nx‐induced CKD mainly through inhibition of intrarenal RAS and Wnt/β‐catenin signaling pathway.

Emerging importance of ACE2 in external stratified epithelial tissues

Angiotensin converting enzyme 2 (ACE2), a component of the renin-angiotensin system (RAS), has been identified as the receptor for the SARS-CoV-2. Several RAS components including ACE2 and its substrate Ang II are present in both eye and skin, two stratified squamous epithelial tissues that isolate organisms from external environment. Our recent findings in cornea and others in both skin and eye suggest contribution of this system, and specifically of ACE2 in variety of physiological and pathological responses of these organ systems. This review will focus on the role RAS system plays in both skin and cornea, and will specifically discuss our recent findings on ACE2 in corneal epithelial inflammation, as well as potential implications of ACE2 in patients with COVID-19.

Association Between Chronic Renal Disease and the Risk of Glaucoma Development: A 12-year Nationwide Cohort Study

Purpose

The purpose of this study was to present the results of our investigation into the risk of glaucoma development in patients with chronic renal disease (CRD).

Methods

The present retrospective cohort study used the Korean National Health Insurance Service data, which consisted of 1,025,340 random subjects who were tracked from 2002 to 2013. Newly diagnosed glaucoma and CRD were included on the basis of the Korean Classification of Disease codes. The CRD group consisted of patients who received an initial CRD diagnosis between January 2003 and December 2007 as an index period (n = 3640). The control group (n = 17,971) was selected using 1:5 propensity-score matching using social and demographic factors, along with the year of enrollment. Each group subject was followed until 2013. We used multivariate Cox proportional hazard regression analysis to compare the risk of glaucoma development between the two groups.

Results

Glaucoma consecutively developed in 4.3% in the CRD group and 2.8% in the control group (P < 0.0001). CRD increased the risk of glaucoma development (hazard ratio [HR] = 1.63, 95% confidence interval [CI] = 1.34–1.98] after adjusting for age, sex, comorbidities, residence, household income, and the year of enrollment. In multivariate Cox regression analysis, patients with comorbidity of hypertension, diabetes mellitus, or aged ≥ 50 years showed a significantly higher risk of glaucoma development (all P < 0.008).

Conclusions

A significant association between CRD and following development of glaucoma was revealed after adjusting the potential confounding factors.

Role of the renin-angiotensin system in the development of cataract formation in angiotensin-II-induced experimental rats

Previously, we established several facts regarding hypertension-associated cataractogenesis. As a follow-on study, we evaluated the role of the renin-angiotensin system (RAS) in angiotensin-II (Ang-II)-induced cataract formation in experimental hypertensive rats. Sprague-Dawley male albino rats (150-180 g) were used for the present experiment. The animals were divided into four groups, with six animals in each group. During the 12 weeks of the experimental protocol, the normal group received sterile water (1 ml/kg/day, subcutaneously (sc), and the Ang-II control group received angiotensin (1 mg/kg/day) subcutaneously. The ARB (O) group received olmesartan (2 mg/kg/day) orally, and the ARB (T) group received two drops of olmesartan (5 mM) topically on the cornea; concurrently, both groups were treated with Ang-II (1 mg/kg/day, sc) to induce hypertension. Biweekly, the systolic and the diastolic blood pressures were recorded, and the eyes were examined; moreover, cataractogenic parameters, such as oxidative stress markers and protein contents in the lenses, were evaluated after completion of the experimental protocol. Twelve weeks of olmesartan administered, orally or topically, significantly reduced the progression of cataract formation and restored antioxidants, lipid peroxidation, nitrite content, and protein contents in the lenses of the mice in groups O and T, respectively, as compared with those in the Ang-II control group. On the basis of our results, we conclude that the ocular RAS exacerbates the lenticular oxidative stress that may lead to cataract formation. The results showed that the RAS has an independent and important role in cataract formation under hypertensive conditions.

SARS-COV-2 and Ocular Surface: From Physiology to Pathology, a Route to Understand Transmission and Disease

Coronaviruses gained public attention during the severe acute respiratory syndrome (SARS) outbreak in East Asia in 2003 and spread of Middle Eastern respiratory syndrome (MERS) in 2012. Direct human-to-human contact and droplet are the main methods of transmission. Viral stability in aerosols on different surfaces supports evidence on indirect viral acquisition from fomites through the mucous membranes of the mouth, nose, and eyes. Given the pandemic circumstances, the level of evidence in COVID-19 and ophthalmology regarding eye infection, conjunctival transmission, and viral shedding through tears is insufficient. Presently, conjunctival transmission of coronaviruses has not been confirmed and remains controversial. Considering the physiology of the lacrimal system and ocular surface, the eyes are considered an immunoprotective site, with several antiviral molecules and anti-inflammatory proteins. Nevertheless, they represent an interface with the exterior world and face daily putative aggressors. Understanding the host's ocular surface immunological and protective environment is crucial to clarify the potential of the conjunctiva as an entry route for SARS-CoV-2 and as part of this viral infection. We will discuss hypothetical ocular surface transmission mechanisms and related counterarguments addressed to both angiotensin-converting enzyme 2 receptors found on the conjunctival and corneal epithelia and lactoferrin, lysozyme, lipocalin and secretory IgA levels in the tear film. Hopefully, we will promote better understanding of this organ in COVID-19 infection and the potential transmission route that can be helpful in setting recommendations on best practices and protective guidelines to mitigate the disease spread.

Telmisartan Prevents Alveolar Bone Loss by Decreasing the Expression of Osteoclasts Markers in Hypertensive Rats With Periodontal Disease

Periodontal disease (PD) is a prevalent inflammatory disease with the most severe consequence being the loss of the alveolar bone and teeth. We therefore aimed to evaluate the effects of telmisartan (TELM), an angiotensin II type 1 receptor (Agtr1) antagonist, on the PD-induced alveolar bone loss, in Wistar (W) and Spontaneous Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk, and 10 mg/kg TELM was concomitantly administered for 15 days. The hemimandibles were subjected to microtomography, ELISA was used for detecting tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), CXCL3, and CCL2, while qRT-PCR was used for analyzing expression of components of renin-angiotensin system (RAS) (Agt, Ace, Agt1r, Agt2r, Ace2, and Masr), and bone markers (Runx2, Osx, Catnb, Alp, Col1a1, Opn, Ocn, Bsp, Bmp2, Trap, Rank, Rankl, CtsK, Mmp-2, Mmp-9, and osteoclast-associated receptor (Oscar)). The SHR + PD group showed greater alveolar bone loss than the W + PD group, what was significantly inhibited by treatment with TELM, especially in the SHR group. Additionally, TELM reduced the production of TNF-α, IL-1β, and CXCL3 in the SHR group. The expression of Agt increased in the groups with PD, while Agtr2 reduced, and TELM reduced the expression of Agtr1 and increased the expression of Agtr2, in W and SHRs. PD did not induce major changes in the expression of bone formation markers, except for the expression of Alp, which decreased in the PD groups. The bone resorption markers expression, Mmp9, Ctsk, and Vtn, was higher in the SHR + PD group, compared to the respective control and W + PD group. However, TELM attenuated these changes and increased the expression of Runx2 and Alp. Our study suggested that TELM has a protective effect on the progression of PD, especially in hypertensive animals, as evaluated by the resorption of the lower alveolar bone. This can be partly explained by the modulation in the expression of Angiotensin II receptors (AT1R and AT2R), reduced production of inflammatory mediators, the reduced expression of resorption markers, and the increased expression of the bone formation markers.

Human coronaviruses: ophthalmic manifestations

The 2019 novel coronavirus which causes severe acute respiratory syndrome (SARS) known as SARS-CoV-2 still remains as a global pandemic since its discovery and continues to spread across the world, given how highly contagious the virus is. We reviewed various articles that explore eye involvement in COVID-19 and other human coronaviruses, its human manifestations in comparison to animal studies and potential mechanism of viral entry into the eye surface. Evidence of animal studies depicted various complications of coronaviruses infection into the eyes, in both anterior and posterior segments of the eye. Conjunctival inflammation remains uncommon in association with COVID-19, with other ophthalmic findings. The risk of transmission via the ocular surface remains likely low, though it is inarguably present based on preliminary finding of viral load in ocular samples and expression of ACE2 on the ocular surface. Testing the tears sample for diagnosing SARS-CoV-2 was unreliable due to limitations of the testing kits and conflicting evidence of the viral titre in the ocular samples. Further larger, more precise and specific studies are required to allow us to better understand the pattern of virulence underlying the associations of SARS-CoV-2 in the eye despite its rare occurrence. This review article aims to enhance better awareness among clinicians regarding ocular manifestations associated with COVID-19 and necessary precautions should be implemented to minimise the risk of person-to-person especially in the nosocomial setting.

Therapeutic effects of various renin angiotensin modulators on hyperglycemia-induced cataract formation in Sprague Dawley rats

Objects:

Our previous research work reported the beneficial effects of angiotensin receptor blockers (ARBs) for the treatment of diabetes associated cataract which was induced by streptozotocin (STZ). The current study, evaluated the effects of topical administration of various renin angiotensin modulators on STZ-induced cataracts in rats.

Methods:

Single dose of STZ (60 mg/kg, i.p.) was administered in the rats to induce diabetes. Animals were divided into normal and diabetic rats. Normal rats were administered with single dose of sodium citrate buffer (0.1 M, 10ml/kg, i.p.). Diabetic animals were divided into various treatment groups, each group contains six animals and received aliskiren, olmesartan, enalapril, and angiotensin 1–7 at a dose of 0.5% w/v topically on the cornea of the eye for a period of 8 weeks. During experimental protocol morphology of the eyes and lenticular opacity were monitored. Animals were sacrificed after 8 weeks of drug treatment, and various cataractogenic biochemical parameters were assessed.

Results:

Topical administrations with aliskiren, enalapril, olmesartan, and angiotensin 1–7 showed non-significant alterations in the blood glucose level, but significantly decreased lenticular opacity, restored antioxidant level, restored MDA level and Nitrite content, and decreased the onset of cataract formation.

Conclusion:

Overall, our findings suggest that topical treatment with renin angiotensin modulators delayed the onset of diabetes-induced cataract formation.

Unfolding COVID-19: Lessons-in-Learning in Ophthalmology

Importance

An observant Chinese doctor Li Wenliang became the first physician to alert the world about COVID-19. Being an ophthalmologist himself, he has put the additional onus on us. The fact that the ocular manifestation could be the first presenting feature of novel coronavirus pneumonia should not be ignored and the possibility of spread of SARS-CoV-2 through the ocular secretions cannot be ruled out. However, with breakthroughs still evolving about this disease, the calls are now louder for closer examination on the pathogenesis of conjunctivitis associated with it. Hence, we conducted a scoping review of all available literature till date to fill in the "potential" gaps in currently available knowledge on ocular manifestations of SARS-CoV-2 infection in an attempt to establish continuity in the "chain of information" from December 2019 till April 2020. We also summarize a possible hypothesis on much less understood and highly debated topics on regard to the etiopathogenesis of ocular involvement in SARS-CoV-2 based on either presence or absence of ACE2 receptor in the ocular surface.

Methods

We conducted a scoping review search of published and unpublished SARS-CoV-2-related English language articles from December 2019 till mid of April 2020 from the online databases. The findings were summarized using text, tables, diagrams, and flowcharts.

Results

The commonest ocular manifestation in SARS-CoV-2 infection is follicular conjunctivitis and has been the first manifestation of SARS-CoV-2 infection in 3 reported cases till date. The ocular surface inoculated with the SARS-CoV-2 leads to the facilitation of the virus to the respiratory system via the lacrimal passage. RT-PCR analysis of the ocular secretions has shown the presence of the SARS-CoV-2 nucleotides indicating the possibility of infection of ocular secretions. ACE2 receptors and its expression on the ocular mucosal surface are linked behind the etiopathogenesis of conjunctivitis.

Conclusion

Conjunctivitis can be the presenting manifestation but may go unnoticed due to its mild nature. The ocular surface could serve as the entry gateway for the virus and ocular secretions could play a role in virus shed. The eye care personnel, as well as the general people, need to be more vigilant and adopt protective eye measures.

Local ocular renin-angiotensin-aldosterone system: any connection with intraocular pressure? A comprehensive review

The renin-angiotensin system (RAS) is one of the oldest and most extensively studied human peptide cascades, well-known for its role in regulating blood pressure. When aldosterone is included, RAAS is involved also in fluid and electrolyte homeostasis. There are two main axes of RAAS: (1) Angiotensin (1-7), angiotensin converting enzyme 2 and Mas receptor (ACE2-Ang(1-7)-MasR), (2) Angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor (ACE1-AngII-AT1R). In its entirety, RAAS comprises dozens of angiotensin peptides, peptidases and seven receptors. The first mentioned axis is known to counterbalance the deleterious effects of the latter axis. In addition to the systemic RAAS, tissue-specific regulatory systems have been described in various organs, evidence that RAAS is both an endocrine and an autocrine system. These local regulatory systems, such as the one present in the vascular endothelium, are responsible for long-term regional changes. A local RAAS and its components have been detected in many structures of the human eye. This review focuses on the local ocular RAAS in the anterior part of the eye, its possible role in aqueous humour dynamics and intraocular pressure as well as RAAS as a potential target for anti-glaucomatous drugs.KEY MESSAGESComponents of renin-angiotensin-aldosterone system have been detected in different structures of the human eye, introducing the concept of a local intraocular renin-angiotensin-aldosterone system (RAAS).Evidence is accumulating that the local ocular RAAS is involved in aqueous humour dynamics, regulation of intraocular pressure, neuroprotection and ocular pathology making components of RAAS attractive candidates when developing new effective ways to treat glaucoma.

Primary Open-angle Glaucoma and Increased Risk of Chronic Kidney Disease

PRECIS

The association between primary open-angle glaucoma (POAG) and subsequent development of chronic kidney disease (CKD) was investigated using a nationwide, population-based, retrospective cohort in South Korea. POAG increases the risk of subsequent CKD development.

PURPOSE

The purpose of this study was to investigate the risk of subsequent CKD development in patients with POAG.

METHODS

In this nationwide, population-based longitudinal cohort, 1,025,340 beneficiaries in the 2002-2013 Korean National Health Insurance database were included. We identified patients with incident POAG and evaluated the risk of subsequent CKD development using diagnostic codes from the database after 2-year wash-out periods. We applied time-varying covariate Cox regression analyses to determine the effect of POAG on the development of CKD: Model 1 included only POAG as a time-varying covariate; Model 2 included Model 1 and demographic information; and Model 3 included Model 2, comorbidity, comedication, and the Charlson Comorbidity Index score.

RESULTS

The fixed cohort included 478,303 eligible subjects, and of these subjects, 1749 suffered incident POAG, and 3157 developed CKD. POAG was associated with an increased risk of CKD development [hazard ratio (HR)=7.63; 95% confidence interval (CI), 5.89-9.87] in Model 1; HR=3.54 (95% CI, 2.73-4.58) in Model 2; and HR=2.90 (95% CI, 2.24-3.76) in Model 3].

CONCLUSION

POAG increased the risk of subsequent CKD in the general population, suggesting that POAG and CKD might share a common pathogenic mechanism.

Angiotensin receptor expression revealed by reporter mice and beneficial effects of AT2R agonist in retinal cells

The renin-angiotensin system (RAS) plays a vital role in cardiovascular physiology and body homeostasis. In addition to circulating RAS, a local RAS exists in the retina. Dysfunction of local RAS, resulting in increased levels of Angiotensin II (Ang II) and activation of AT1R-mediated signaling pathways, contributes to tissue pathophysiology and end-organ damage. Activation of AT2R on other hand is known to counteract the effects of AT1R activation and produce anti-inflammatory and anti-oxidative effects. We examined the expression of angiotensin receptors in the retina by using transgenic dual reporter mice and by real-time RT-PCR. We further evaluated the effects of C21, a selective agonist of AT2R, in reducing Ang II, lipopolysaccharide (LPS) and hydrogen peroxide induced oxidative stress and inflammatory responses in cultured human ARPE-19 cells. We showed that both AT1Ra and AT2R positive cells are detected in different cell types of the eye, including the RPE/choroid complex, ciliary body/iris, and neural retina. AT1Ra is more abundantly expressed than AT2R in mouse retina, consistent with previous reports. In the neural retina, AT1Ra are also detected in photoreceptors whereas AT2R are mostly expressed in the inner retinal neurons and RGCs. In cultured human RPE cells, activation of AT2R with C21 significantly blocked Ang II, LPS and hydrogen peroxide -induced NF-κB activation and inflammatory cytokine expression; Ang II and hydrogen peroxide-induced reactive oxygen species (ROS) production and MG132-induced apoptosis, comparable to the effects of Angiotensin-(1-7) (Ang-(1-7)), another protective component of the RAS, although C21 is more potent in reducing some of the effects induced by Ang II, whereas Ang-(1-7) is more effective in reducing some of the LPS and hydrogen peroxide-induced effects. These results suggest that activation of AT2R may represent a new therapeutic approach for retinal diseases.

Human umbilical cord mesenchymal stem cells pretreated with Angiotensin-II attenuate pancreas injury of rats with severe acute pancreatitis

Mesenchymal stem cells (MSCs) pretreatment is an effective route for improving cell-based therapy of endothelial cell survival, vascular stabilization, and angiogenesis. We hypothesized that the application of human umbilical cord-MSCs (hUC-MSCs) pretreated with angiotensin-II (Ang-II) might be a potential therapeutic approach for severe acute pancreatitis (SAP). Therefore, the effect of Ang-II pretreated hUC-MSCs on SAP was investigated in vitro and in vivo.

METHODS

In the present study, human umbilical cord-derived MSCs pretreated with or without Ang-II were delivered through the tail vein of rats 12 h after induction of SAP. Pancreatitis severity scores and serum lipase levels, as well as the levels of VEGF and VEGFR2 were evaluated.

RESULTS

We found that the administration of Ang-II-MSCs significantly inhibited pancreatic injury, as reflected by reductions of pancreatitis severity scores, serum amylase and serum lipase levels. Furthermore, the reduced apoptotic rate and increased tube formation in human umbilical vein endothelial Cells (HUVEC) were found resulting from the administration of Ang-II-MSC-CM. Moreover, knockdown of VEGFR2 can block the effect of Ang-II-MSC-CM on preventing HUVEC from apoptosis, as well as the capacity of tube formation was also suppressed. In addition, the expression of increased Bcl-2 and alleviated caspase-3 were observed in HUVEC and HUVEC transfectants exposure to Ang-II-MSC-CM.

CONCLUSION

Collectively, these results elucidated that the pretreatment of hUC-MSCs with Ang-II improved the outcome of MSC-based therapy for SAP via enhancing angiogenesis and ameliorating endothelial cell dysfunction in a VEGFR2 dependent manner.

Angiotensin II triggers autophagy and apoptosis in PC12 cell line: An in vitro Alzheimer's disease model

OBJECTIVE

The activation of renin angiotensin system is involved in multiple pathological processes. Growing evidence reveal that Angiotensin II (Ang II) contributes to the pathogenesis of Alzheimer disease (AD). However, the underlying mechanisms are still not fully understood.

METHODS

In this study, the effect of Ang II on Aβ_1-42 induced neurotoxicity was evaluated in PC12 cells. Apoptosis was examined by flow cytometry analysis and caspase-3 activity assay. Autophagy-related markers were also measured in each group.

RESULTS

The results indicated that Ang II activated autophagy and triggered apoptosis in PC12 cells in a dose-dependent manner, as demonstrated byincreased LC3 II/I ratio and decreased p62 expression. Moreover, inhibition of autophagy by 3-methyladenine markedly attenuated the apoptosis caused by Ang II. In addition, an AT1R antagonist losartan, rather than the AT2R antagonist PD123319, completely reversed the Ang II induced autophagic activation and subsequent cell apoptosis.

CONCLUSIONS

Taken together, our study strengthen the crucial function of Ang II/AT1R axis in the pathogenesis of AD in vitro. These findings have deepened our understanding on the role of Ang II in the pathogenesis of AD and support the use of AT1R antagonists for the treatment of this devastating neurodegenerative disease.

The skeletal renin-angiotensin system: A potential therapeutic target for the treatment of osteoarticular diseases

The classical renin-angiotensin system (RAS) is known to be a key regulator of blood pressure as well as fluid and electrolyte homeostasis. Additionally, it is now evident that components of the RAS are produced and act locally in many tissues, including liver, kidney, heart, lung, eye, bone, reproductive organ, adipose, and adrenal tissue, and these components are collectively known as tissue RAS. Recently, several studies have shown that local bone RAS is directly involved in bone metabolism, and activation of skeletal RAS plays an important role in bone diseases, such as osteoporosis, arthritis, and deterioration as well as in fracture healing. Based on the identification of RAS components in bone, we examined a new therapeutic approach to attenuate bone diseases through RAS inhibitors: renin inhibitor, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers. In this paper, we provide a systematic review of the skeletal RAS in the pathophysiology of bone diseases and the beneficial effect of RAS inhibitors on bone tissue.

Role of (pro)renin receptor in albumin overload-induced nephropathy in rats

Proteinuria is not only a common feature of chronic kidney diseases (CKD) but also an independent risk factor promoting CKD progression to end-stage renal failure. However, the underlying molecular mechanisms for protein overload-induced renal injury remain elusive. The present study examined the role of (pro)renin receptor (PRR) in pathogenesis of albumin overload (AO)-induced nephropathy and activation of the intrarenal renin-angiotensin system (RAS) in rats. Wistar rats underwent unilateral nephrectomy and were treated for 7 wk with vehicle, bovine serum albumin (5 g·kg^-1·day^-1 via a single ip injection), alone or in conjunction with the PRR decoy inhibitor PRO20 (500 μg·kg^-1·day^-1 via 3 sc injections). The AO rat model exhibited severe proteinuria, tubular necrosis, and interstitial fibrosis, oxidative stress, and inflammation, accompanied by elevated urinary N-acetyl-β-d-glucosaminidase activity and urinary β₂-microglobulin secretion, all of which were significantly attenuated by PRO20. Urinary and renal levels of renin, angiotensinogen, and ANG II were elevated by AO and suppressed by PRO20, contrasting to largely unaltered plasma levels of the RAS parameters. The AO model also showed increased renal expression of full-length PRR and soluble PRR (sPRR) and urinary excretion of sPRR. Taken together, we conclude that PRR antagonism with PRO20 alleviates AO-induced nephropathy via inhibition of intrarenal RAS.

Azilsartan ameliorates apoptosis of dopaminergic neurons and rescues characteristic parkinsonian behaviors in a rat model of Parkinson's disease

Loss of dopaminergic neurons within the substantia nigra (SN) is a pathological hallmark of Parkinsons disease (PD), which leads to the onset of motor symptoms. Previously, our in vitro studies revealed that Angiotensin II (Ang II) induced apoptosis of dopaminergic neurons through its type 1 receptor (AT1R), but these findings needed to be confirmed via animal experiments. Here, using a rotenone-induced rat model of PD, we observed an overactivation of Ang II/AT1R axis in the SN, since Ang II level and AT1R expression were markedly increased. Furthermore, we provided in vivo evidence that Ang II directly elicited apoptosis of dopaminergic neurons via activation of AT1R in the SN of rats. More importantly, we showed for the first time that oral administration of azilsartan, a newly developed AT1R blocker approved by the U.S. Food and Drug Administration for hypertension treatment, rescued the apoptosis of dopaminergic neurons and relieved the characteristic parkinsonian symptoms in PD rats. These results support the application of AT1R blockers in PD therapy, and strengthen the notion that many therapeutic agents may possess pleiotropic action in addition to their main applications.

Utility of angiotensin-converting enzyme activity in aqueous humor in the diagnosis of ocular sarcoidosis

Purpose:

Many studies include elevated activity of angiotensin-converting enzyme (ACE) in serum in sarcoidosis and in ocular sarcoidosis as well, but there are only a few analyzing ACE activities in aqueous humor. The aim of this study is to illuminate the diagnostic value of ACE in aqueous humor in patients with ocular sarcoidosis.

Methods:

We analyzed twenty patients with ocular sarcoidosis and 18 patients with nonocular involvement. All patients have biopsy-positive sarcoidosis of the lungs and/or mediastinal lymph nodes. Blood samples for ACE serum levels were obtained from all patients. Aqueous humor samples were taken by paracentesis with a 25-gauge needle in local anesthesia. With appropriate statistical tests, we compared ACE activity in serum and aqueous humor in patients with and without ocular sarcoidosis.

Results:

The majority of our patients with ocular sarcoidosis were female (12/20), also in the group with systemic sarcoidosis and without ocular involvement (12/6). Mean age of the whole analyzed group of sarcoidosis patients was 45 ± 6 years. There is no statistically significant difference in ACE activity in serum between two groups of patients (with and without ocular sarcoidosis). There is statistically significant difference in ACE activity in aqueous humor among patients with ocular and nonocular sarcoidosis. ACE activity in aqueous humor is significantly higher in patients with ocular sarcoidosis.

Conclusion:

Increased ACE activity in aqueous humor can point to a diagnosis of ocular sarcoidosis, without the need for ocular biopsy.

Knobloch syndrome associated with Polymicrogyria and early onset of retinal detachment: two case reports

Background

Knobloch Syndrome (KS) is a rare congenital syndrome characterized by occipital skull defects and vitreoretinal degeneration. Retinal detachment (RD) often occurs at the end of the first decade of life or later. Aside from occipital skull defects, central nervous system abnormalities are uncommon.

Case presentations

We report on two siblings with KS. The first, a seven month old male, presented with nystagmus and was found to have a serous RD and a tessellated retinal appearance. His sister had a history of multiple visual abnormalities and had a similar retinal appearance although no signs of RD, but retina staphylomas. Genetic testing performed on both siblings showed a mutation in COL18A1, diagnostic of KS. MRI of both siblings demonstrated polymicrogyria but did not show occipital defects.

Conclusions

Although several families with KS have been described previously, our case is noteworthy for several reasons. The RD observed in our first patient occurred at an early age, and we find evidence of only one patient with KS who had an RD identified at an earlier age. The findings of polymicrogyria are not characteristic of KS, and we found only a few previous reports of this association. Additionally, we review potential treatment options for this condition.

Diurnal opposite variation between angiotensinase activities in photo-neuro-endocrine tissues of rats

Central and peripheral renin-angiotensin systems (RASs) act in a coordinated manner for the physiologic functions regulated by neuroendocrine events. However, whereas the diurnal rhythm of peripheral circulatory and tissue RASs is well known, the circadian behaviour of their components in central photo-neuro-endocrine structures, key elements for the control of circadian rhythms, has been barely studied. In the present study, we analysed the aspartyl- (AspAP) and glutamyl-aminopeptidase (GluAP) (aminopeptidase A) activities, the angiotensinases responsible for the metabolism of Ang I to Ang 2-10 and Ang II to Ang III, respectively, in the retina, anterior hypothalamus and pituitary at different light and dark time-points of a 12:12 h light:dark cycle (7-19 h light), using arylamide derivatives as substrates. The results demonstrated that while retina and pituitary exhibited their highest levels of AspAP activity in the light period and the lowest in the dark one, the contrary occurred in the hypothalamus - the lowest levels were observed in light conditions and the highest in darkness. The outcome for GluAP showed the highest levels in the light period and the lowest in the dark one in the three tissues analysed. In conclusion, changes in angiotensinase activities throughout the daytime may cause changes of their respective substrates and derived peptides and, consequently, in their functions. This observation may have implications for the treatment of hypertension.

Effect of angiotensin II type 1 receptor blocker and angiotensin converting enzyme inhibitor on the intraocular growth factors and their receptors in streptozotocin-induced diabetic rats

AIM

To investigate the effect of angiotensin II type 1 receptor blocker (ARB) and angiotensin converting enzyme inhibitor (ACEI) on intraocular growth factors and their receptors in streptozotocin-induced diabetic rats.

METHODS

Forty Sprague-Dawley rats were divided into 4 groups: control, diabetes mellitus (DM), candesartan-treated DM, and enalapril-treated DM (each group, n=10). After the induction of DM by streptozotocin, candesartan [ARB, 5 mg/(kg·d)] and enalapril [ACEI, 10 mg/(kg·d)] were administered to rats orally for 4wk. Vascular endothelial growth factor (VEGF) and angiotensin II (Ang II) concentrations in the vitreous were measured using enzyme-linked immunosorbent assays, and VEGF receptor 2 and angiotensin II type 1 receptor (AT1R) levels were assessed at week 4 by Western blotting.

RESULTS

Vitreous Ang II levels were significantly higher in the DM group and candesartan-treated DM group than in the control (P=0.04 and 0.005, respectively). Vitreous AT1R increased significantly in DM compared to the other three groups (P<0.007). Candesartan-treated DM rats showed higher vitreal AT1R concentration than the enalapril-treated DM group and control (P<0.001 and P=0.005, respectively). No difference in vitreous Ang II and AT1R concentration was found between the enalapril-treated DM group and control. VEGF and its receptor were below the minimum detection limit in all 4 groups.

CONCLUSION

Increased Ang II and AT1R in the hyperglycemic state indicate activated the intraocular renin-angiotensin system, which is inhibited more effectively by systemic ACEI than systemic ARB.

Many Faces of Renin-angiotensin System - Focus on Eye

The renin-angiotensin system (RAS), that is known for its role in the regulation of blood pressure as well as in fluid and electrolyte homeostasis, comprises dozens of angiotensin peptides and peptidases and at least six receptors. Six central components constitute the two main axes of the RAS cascade. Angiotensin (1-7), an angiotensin converting enzyme 2 and Mas receptor axis (ACE2-Ang(1-7)-MasR) counterbalances the harmful effects of the angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor axis (ACE1-AngII-AT1R) Whereas systemic RAS is an important factor in blood pressure regulation, tissue-specific regulatory system, responsible for long term regional changes, that has been found in various organs. In other words, RAS is not only endocrine but also complicated autocrine system. The human eye has its own intraocular RAS that is present e.g. in the structures involved in aqueous humor dynamics. Local RAS may thus be a target in the development of new anti-glaucomatous drugs. In this review, we first describe the systemic RAS cascade and then the local ocular RAS especially in the anterior part of the eye.

Integrated Approaches to Drug Discovery for Oxidative Stress-Related Retinal Diseases

Excessive oxidative stress induces dysregulation of functional networks in the retina, resulting in retinal diseases such as glaucoma, age-related macular degeneration, and diabetic retinopathy. Although various therapies have been developed to reduce oxidative stress in retinal diseases, most have failed to show efficacy in clinical trials. This may be due to oversimplification of target selection for such a complex network as oxidative stress. Recent advances in high-throughput technologies have facilitated the collection of multilevel omics data, which has driven growth in public databases and in the development of bioinformatics tools. Integration of the knowledge gained from omics databases can be used to generate disease-related biological networks and to identify potential therapeutic targets within the networks. Here, we provide an overview of integrative approaches in the drug discovery process and provide simple examples of how the approaches can be exploited to identify oxidative stress-related targets for retinal diseases.

Vaccination via Chloroplast Genetics: Affordable Protein Drugs for the Prevention and Treatment of Inherited or Infectious Human Diseases

Plastid-made biopharmaceuticals treat major metabolic or genetic disorders, including Alzheimer's, diabetes, hypertension, hemophilia, and retinopathy. Booster vaccines made in chloroplasts prevent global infectious diseases, such as tuberculosis, malaria, cholera, and polio, and biological threats, such as anthrax and plague. Recent advances in this field include commercial-scale production of human therapeutic proteins in FDA-approved cGMP facilities, development of tags to deliver protein drugs to targeted human cells or tissues, methods to deliver precise doses, and long-term stability of protein drugs at ambient temperature, maintaining their efficacy. Codon optimization utilizing valuable information from sequenced chloroplast genomes enhanced expression of eukaryotic human or viral genes in chloroplasts and offered unique insights into translation in chloroplasts. Support from major biopharmaceutical companies, development of hydroponic production systems, and evaluation by regulatory agencies, including the CDC, FDA, and USDA, augur well for advancing this novel concept to the clinic and revolutionizing affordable healthcare.

Neuroprotection as a Therapeutic Target for Diabetic Retinopathy

Diabetic retinopathy (DR) is a multifactorial progressive disease of the retina and a leading cause of vision loss. DR has long been regarded as a vascular disorder, although neuronal death and visual impairment appear before vascular lesions, suggesting an important role played by neurodegeneration in DR and the appropriateness of neuroprotective strategies. Upregulation of vascular endothelial growth factor (VEGF), the main target of current therapies, is likely to be one of the first responses to retinal hyperglycemic stress and VEGF may represent an important survival factor in early phases of DR. Of central importance for clinical trials is the detection of retinal neurodegeneration in the clinical setting, and spectral domain optical coherence tomography seems the most indicated technique. Many substances have been tested in animal studies for their neuroprotective properties and for possible use in humans. Perhaps, the most intriguing perspective is the use of endogenous neuroprotective substances or nutraceuticals. Together, the data point to the central role of neurodegeneration in the pathogenesis of DR and indicate neuroprotection as an effective strategy for treating this disease. However, clinical trials to determine not only the effectiveness and safety but also the compliance of a noninvasive route of drug administration are needed.

Activation of endogenous angiotensin converting enzyme 2 prevents early injuries induced by hyperglycemia in rat retina

Diabetic retinopathy (DR) is a serious complication of diabetes mellitus that may result in blindness. We evaluated the effects of activation of endogenous angiotensin converting enzyme (ACE) 2 on the early stages of DR. Rats were administered an intravenous injection of streptozotocin to induce hyperglycemia. The ACE2 activator 1-[[2-(dimethylamino) ethyl] amino]-4-(hydroxymethyl)-7-[[(4-methylphenyl) sulfonyl] oxy]-9H-xanthone 9 (XNT) was administered by daily gavage. The death of retinal ganglion cells (RGC) was evaluated in histological sections, and retinal ACE2, caspase-3, and vascular endothelial growth factor (VEGF) expressions were analyzed by immunohistochemistry. XNT treatment increased ACE2 expression in retinas of hyperglycemic (HG) rats (control: 13.81±2.71 area%; HG: 14.29±4.30 area%; HG+XNT: 26.87±1.86 area%; P<0.05). Importantly, ACE2 activation significantly increased the RCG number in comparison with HG animals (control: 553.5±14.29; HG: 530.8±10.3 cells; HG+XNT: 575.3±16.5 cells; P<0.05). This effect was accompanied by a reduction in the expression of caspase-3 in RGC of the HG+XNT group when compared with untreated HG rats (control: 18.74±1.59; HG: 38.39±3.39 area%; HG+XNT: 27.83±2.80 area%; P<0.05). Treatment with XNT did not alter the VEGF expression in HG animals (P>0.05). Altogether, these findings indicate that activation of ACE2 reduced the death of retinal ganglion cells by apoptosis in HG rats.

Ocular renin-angiotensin system with special reference in the anterior part of the eye

The renin-angiotensin system (RAS) regulates blood pressure (BP) homeostasis, systemic fluid volume and electrolyte balance. The RAS cascade includes over twenty peptidases, close to twenty angiotensin peptides and at least six receptors. Out of these, angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor (AngII-ACE1-AT1R) together with angiotensin (1-7), angiotensin converting enzyme 2 and Mas receptor (Ang(1-7)-ACE2-MasR) are regarded as the main components of RAS. In addition to circulating RAS, local RA-system exists in various organs. Local RA-systems are regarded as tissue-specific regulatory systems accounting for local effects and long term changes in different organs. Many of the central components such as the two main axes of RAS: AngII-ACE1-AT1R and Ang(1-7)-ACE2-MasR, have been identified in the human eye. Furthermore, it has been shown that systemic antihypertensive RAS- inhibiting medications lower intraocular pressure (IOP). These findings suggest the crucial role of RAS not only in the regulation of BP but also in the regulation of IOP, and RAS potentially plays a role in the development of glaucoma and antiglaucomatous drugs.

Activation of Autophagy Contributes to the Angiotensin II-Triggered Apoptosis in a Dopaminergic Neuronal Cell Line

Our recent study indicated that angiotensin II (Ang II), the main component of renin-angiotensin system, participated in the pathogenesis of Parkinson's disease (PD) by triggering the apoptosis of dopaminergic neuronal cells. However, the underlying mechanisms are still not fully understood. In this study, by using CATH.a cells, a dopaminergic neuronal cell line stably expressing angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R), we tested the hypothesis that activation of autophagy contributed to the apoptosis triggered by Ang II. We showed that Ang II activated autophagy and triggered apoptosis in CATH.a cells in a dose-dependent manner. More importantly, inhibition of autophagy by 3-methyladenine markedly attenuated the apoptosis caused by Ang II in CATH.a cells. In addition, the Ang II-induced autophagy and subsequent cell apoptosis could be fully abolished by an AT1R antagonist losartan rather than PD1223319, an antagonist for AT2R. Taken together, our study provides the first evidence that Ang II triggers apoptosis via activation of autophagy in a dopaminergic neuronal cell line through an AT1R-mediated manner. These findings have deepened our understanding on the role of Ang II in the pathogenesis of PD and support the use of AT1R antagonists for the treatment of this devastating neurodegenerative disease.

Angiotensin(1-7) and ACE2, "The Hot Spots" of Renin-Angiotensin System, Detected in the Human Aqueous Humor

Background:

The main purpose of the study was to establish whether essential components of the renin-angiotensin system (RAS) exist in the human aqueous humor.

Methods:

Forty-five patients ≥ 60 (74±7) years of age undergoing cataract surgery at Tampere University Hospital were randomly selected for the prospective study. The exclusion criterion was the use of oral antihypertensive medicine acting via renin-angiotensin system. Aqueous humor samples were taken at the beginning of normal cataract extraction. The samples were frozen and stored at -80 °C. The concentrations of intraocular endogenous RAS components Ang(1-7), ACE2, and ACE1 were measured using ELISA.

Results:

Concentration medians of Ang(1-7), ACE2, and ACE1 in the aqueous humor were: Ang(1-7) 4.08 ng/ml, ACE2 2.32 ng/ml and ACE1 0.35 ng/ml. The concentrations were significantly higher in glaucomatous than in non-glaucomatous eyes, ACE1 (p=0.014) and Ang(1-7) (p=0.026) vs non-glaucomatous eyes.

Conclusions:

Ang(1-7), ACE2 and ACE1 are found in the human aqueous humor. The observations are consistent with the conception that local tissue-RAS exists in the human eye and it might have a role in the control of intraocular pressure.

The expression of Mas-receptor of the renin-angiotensin system in the human eye

PURPOSE

The local renin-angiotensin system has been held to be expressed in many organs, including the eye. It has an important role in the regulation of local fluid homeostasis, cell proliferation, fibrosis, and vascular tone. Mas-receptor (Mas-R) is a potential receptor acting mainly opposite to the well-known angiotensin II receptor type 1. The aim of this study was to determine if Mas-R is expressed in the human eye.

METHODS

Seven enucleated human eyes were used in immunohistochemical detection of Mas-R and its endogenous ligand angiotensin (1-7) [Ang(1-7)]. Both light microscopy and immunofluorescent detection methods were used. A human kidney preparation sample was used as control.

RESULTS

The Mas-R was found to have nuclear localization, and localized in the retinal nuclear layers and in the structures of the anterior segment of the eye. A cytoplasmic immunostaining pattern of Ang(1-7) was found in the inner and outer nuclear and plexiform layers of the retina and in the ciliary body.

CONCLUSION

To the best of our knowledge, this is the first report showing Mas-R expression in the human eye. Its localization suggests that it may have a role in physiological and pathological processes in the anterior part of the eye and in the retina.

Angiotensin II triggers apoptosis via enhancement of NADPH oxidase-dependent oxidative stress in a dopaminergic neuronal cell line

Numerous studies reveal that Angiotensin II (Ang II), the main effector of renin-angiotensin system, contributes to the pathogenesis of Parkinson's disease (PD) via triggering dopaminergic cell loss. However, the underlying mechanisms remain largely unclear. In the current study, by using CATH.a cell, a dopaminergic neuronal cell line stably expressing Angiotensin II type 1 receptor (AT1R) and Angiotensin II type 2 receptor (AT2R), we showed that Ang II treatment triggered cell apoptosis in a dose-dependent manner, providing the first evidence that apoptotic cell death contributed to the dopaminergic cell loss induced by Ang II. Ang II treatment also led to a significant increment in intracellular reactive oxygen species generation, which could be fully abolished by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors apocynin or diphenylene iodonium, indicating that Ang II enhanced oxidative stress via a NADPH oxidase-dependent manner. More importantly, inhibition of oxidative stress by NADPH oxidase inhibitors partially attenuated cell apoptosis caused by Ang II, implying that the enhancement of NADPH oxidase-dependent oxidative stress contributed to the cell apoptosis triggered by Ang II. Furthermore, the Ang II-induced oxidative stress and subsequent apoptosis could be completely abolished by AT1R blocker losartan rather than AT2R blocker PD1223319, suggesting that the aforementioned detrimental effects of Ang II are mediated by AT1R. In summary, these findings have deepened our understanding on the role of Ang II in PD pathogenesis, and support the use of AT1R blockers in the treatment of this devastating disease.