Angiotensin II-induced MMP-2 activity and MMP-14 and basigin protein expression are mediated via the angiotensin II receptor type 1-mitogen-activated protein kinase 1 pathway in retinal pigment epithelium: implications for age-related macular degeneration

Revisiting the renin-angiotensin-aldosterone system in the eye: Mechanistic insights and pharmacological targets

The renin-angiotensin-aldosterone system (RAAS) plays a fundamental role in regulating blood pressure and fluid homeostasis through key effectors such as angiotensin II and aldosterone. These agents and their receptors have become crucial molecular targets in several cardiovascular and renal diseases. Over the past few decades, a growing body of evidence has revealed the presence of RAAS components in ocular structures, suggesting a tissue-specific RAAS within the eye. Building on this knowledge, studies have indicated that the ocular RAAS plays a significant role in the pathogenesis of various eye diseases. An impaired and overactivated RAAS contributes to the development of severe and widespread disorders affecting both the anterior and posterior segments of the eye. In this context, the current work aims to delve into the pivotal molecular pathways involving the RAAS, with an in-depth exploration of the ocular pathophysiology. It focuses on the relationship between overactivation of the RAAS and oxidative stress, as well as the exacerbation of neovascularization and inflammatory processes. The objective is to provide an updated and comprehensive understanding of the role of the RAAS in ophthalmological diseases, highlighting the therapeutic potential of RAAS modulators and discussing the controversies and challenges in this area of research.

Microinjection of angiotensin II into zebrafish embryos induces transient dilation and elastin disruption of the dorsal aorta

The effects of angiotensin II (AngII) on blood vessel development and remodeling have been extensively investigated in mice and humans. However, its action on the vessels in the zebrafish remains largely unknown. To investigate whether AngII affects vascular morphology in vivo, we administered AngII into the endothelial-specific transgenic reporter zebrafish (Tg[kdrl:EGFP]) at the 1-cell stage. The average dorsal aortic diameter of five serial positions was significantly increased by 20% in AngII-injected zebrafish compared with buffer-injected controls at 5 days post-fertilization. Histological studies in AngII-injected zebrafish at 8 weeks post-fertilization showed that elastic fiber formation was partly attenuated, with enhanced matrix metalloproteinase-2 expression in the dorsal aorta without dilation. These results suggest that AngII induced transient aortic expansion in early larvae and may affect vascular elastic fiber formation in adult zebrafish. The use of the AngII-injected zebrafish model is a potential tool to dissect the mechanisms of disruption of elastic vascular wall formation in the aorta.

Glaucoma and the ocular renin-angiotensin-aldosterone system: Update on molecular signalling and treatment perspectives

Glaucoma, a leading cause of blindness worldwide, encompasses a group of pathological conditions affecting the optic nerve and is characterized by progressive retinal ganglion cell loss, cupping of the optic nerve head, and distinct visual field defects. While elevated intraocular pressure (IOP) is the main risk factor for glaucoma, many patients do not have elevated IOP. Consequently, other risk factors, such as ocular blood flow abnormalities and immunological factors, have been implicated in its pathophysiology. Traditional therapeutic strategies primarily aim to reduce IOP, but there is growing interest in developing novel treatment approaches to improve disease management and reduce the high rates of severe visual impairment. In this context, targeting the ocular renin-angiotensin-aldosterone system (RAAS) has been found as a potential curative strategy. The RAAS contributes to glaucoma development through key effectors such as prorenin, angiotensin II, and aldosterone. Recent evidence has highlighted the potential of using RAAS modulators to combat glaucoma, yielding encouraging results. Our study aims to explore the molecular pathways linking the ocular RAAS and glaucoma, summarizing recent advances that elucidate the role of the RAAS in triggering oxidative stress, inflammation, and remodelling in the pathogenesis of glaucoma. Additionally, we will present emerging therapeutic approaches that utilize RAAS modulators and antioxidants to slow the progression of glaucoma.

Identification of the CDH18 gene associated with age-related macular degeneration using weighted gene co-expression network analysis

Purpose: Age-related macular degeneration (AMD) is a chronic and progressive macular degenerative disease that culminates in a gradual deterioration of central vision. Despite its prevalence, the key biomarkers for AMD have not yet been fully elucidated. In this study, we aimed to efficiently identify biomarkers crucial for diagnosing AMD. Methods: Three datasets pertaining to retinal pigment epithelium (RPE)/choroid tissues associated with AMD were selected from the GEO database. The GSE50195 dataset was utilized to conduct weighted gene co-expression network analysis (WGCNA) for identifying module genes linked to AMD. KEGG and GO enrichment analyses were subsequently conducted on these module genes. GSE29801 and GSE135092 datasets were subjected to differential expression analysis to pinpoint the DEGs intersecting with the module genes. Subsequently, wet AMD (wAMD) and dry AMD (dAMD) mouse models were developed, from which RPE/choroid tissues were harvested to validate the hub genes via RT-qPCR and Western blot. Results: Using the WGCNA, we selected the "antiquewhite4" module (r = 0.91 and p = 7e-07), which contains a total of 325 genes. Through the intersection of module genes with DEGs, nine hub genes were identified. Pathways involved in complement and coagulation cascades, ECM-receptor interactions, unsaturated fatty acid biosynthesis, and fatty acid elongation play important roles in AMD. Notably, CDH18 demonstrated notable variance across all three datasets. Post validation using RT-qPCR experiments revealed a significant downregulation of CDH18 in both dAMD and wAMD. EGLN3 was expressed at low levels in wAMD. In dAMD, EYA2, LTB, and PODXL were significantly downregulated, whereas APOC1 was notably upregulated. Western blot confirmed that CDH18 was lowly expressed in dAMD and wAMD mouse models. Conclusion: CDH18 was identified as the key gene involved in the pathogenesis of AMD. An imbalance of the complement and coagulation cascades is a potential mechanism of AMD. This study provides a novel idea for diagnosing and treating AMD in the future.

Current updates for hyperuricemia and gout in age-related macular degeneration

The escalating prevalence of metabolic syndrome poses a significant public health challenge, particularly among aging populations, with metabolic dysfunctions contributing to pro-inflammatory states. In this review, we delved into the less recognized association between hyperuricemia (HUA), a manifestation of metabolic syndrome and a primary risk factor for gout, and age-related macular degeneration (AMD), a sight-threatening ailment predominantly affecting the elderly. In recent years, inflammation, particularly its involvement in complement pathway dysregulation, has gained prominence in AMD pathophysiology. The contradictory role of uric acid (UA) in intercellular and intracellular environments was discussed, highlighting its antioxidant properties in plasma and its pro-oxidant effects intracellularly. Emerging evidence suggests a potential link between elevated serum uric acid levels and choroid neovascularization in AMD, providing insights into the role of HUA in retinal pathologies. Various pathways, including crystal-induced and non-crystal-induced mechanisms, were proposed to indicate the need for further research into the precise molecular interactions. The implication of HUA in AMD underscores its potential involvement in retinal pathologies, which entails interdisciplinary collaboration for a comprehensive understanding of its impact on retina and related clinical manifestations.

Hypertension facilitates age-related diseases. ~ Is hypertension associated with a wide variety of diseases?~

Hypertension, a disease whose prevalence increases with age, induces pathological conditions of ischemic vascular disorders such as cerebral infarction and myocardial infarction due to accelerated arteriosclerosis and circulatory insufficiency of small arteries and sometimes causes hemorrhagic conditions such as cerebral hemorrhage and ruptured aortic aneurysm. On the other hand, as it is said that aging starts with the blood vessels, impaired blood flow associated with vascular aging is the basis for the development of many pathological conditions, and ischemic changes in target organs associated with vascular disorders result in tissue dysfunction and degeneration, inducing organ hypofunction and dysfunction. Therefore, we hypothesized that hypertension is associated with all age-related vascular diseases, and attempted to review the relationship between hypertension and diseases for which a relationship has not been previously well reported. Following our review, we hope that a collaborative effort to unravel age-related diseases from the perspective of hypertension will be undertaken together with experts in various specialties regarding the relationship of hypertension to all pathological conditions.

RAAS in diabetic retinopathy: mechanisms and therapies

Diabetic retinopathy (DR) is a complication of diabetes with a complex pathophysiology and multiple factors involved. Recently, it has been found that the upregulation of the renin-angiotensin-aldosterone system (RAAS) leads to overexpression of angiotensin II (Ang II), which induces oxidative stress, inflammation, and angiogenesis in the retina. Therefore, RAAS may be a promising therapeutic target in DR. Notably, RAAS inhibitors are often used in the treatment of hypertension. Still, the potential role and mechanism of DR must be further studied. In this review, we discuss and summarize the pathology and potential therapeutic goals of RAAS in DR.

Short-Term Hyperuricemia Leads to Structural Retinal Changes That Can be Reversed by Serum Uric Acid Lowering Agents in Mice

Purpose

Metabolic disorders have been implicated in ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Recently, hyperuricemia (HUA) has been proposed as another risk factor for AMD, although no cause-and-effect experimental data have been published. In this study, we investigated whether HUA would initiate AMD or related retinal damages in hyperuricemic mice.

Methods

HUA was induced in male ICR mice by dietary supplements of uric acid and oxonic acid potassium salt, with or without treatments by allopurinol or benzbromarone for various durations. Serum uric acid and angiotensin II concentrations were measured by enzyme-linked immunosorbent assay (ELISA) at regular intervals. The retinal damages were assessed by hematoxylin and eosin staining, immunostaining, and TUNEL assay. The cause-and-effect of HUA was compared among the study groups.

Results

The results showed that the total thickness of photoreceptor inner and outer segments, as well as the thickness of the photoreceptor outer segment alone, were reduced under HUA. Furthermore, HUA elevated serum angiotensin II, which indicated activation of the renin–angiotensin system (RAS), leading to higher matrix metalloproteinase-2 (MMP-2) expression, and glial activation in the ganglion cell layer. HUA also led to the reduction of retinal pigment epithelium gap junction protein connexin-43 and apoptosis. Uric acid lowering agents, allopurinol or benzbromarone, were effective in ameliorating the impairments.

Conclusions

HUA may pose as a causative factor of retinal injuries. The reduction of serum uric acid may reduce the detrimental effects caused by HUA.

The Role of Metalloproteinases and Their Tissue Inhibitors on Ocular Diseases: Focusing on Potential Mechanisms

Eye diseases are associated with visual impairment, reduced quality of life, and may even lead to vision loss. The efficacy of available treatment of eye diseases is not satisfactory. The unique environment of the eye related to anatomical and physiological barriers and constraints limits the bioavailability of existing agents. In turn, complex ethiopathogenesis of ocular disorders that used drugs generally are non-disease specific and do not act causally. Therefore, there is a need for the development of a new therapeutic and preventive approach. It seems that matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have a significant role in the development and progression of eye diseases and could be used in the therapy of these disorders as pharmacological targets. MMPs and TIMPs play an important role in the angiogenesis, epithelial-mesenchymal transition, cell invasion, and migration, which occur in ocular diseases. In this review, we aim to describe the participation of MMPs and TIMPs in the eye diseases, such as age-related macular degeneration, cataract, diabetic retinopathy, dry eye syndrome, glaucoma, and ocular cancers, posterior capsule opacification focusing on potential mechanisms.

Hypertension affects the treatment of wet age-related macular degeneration

Purpose

Due to population ageing as well as the high prevalence of hypertension and age‐related macular degeneration (AMD) in elderly individuals, and the relationship between hypertension and AMD is unclear. Our research aimed to investigate the association between hypertension, wet AMD (wAMD) and the treatment strategy of wAMD patients affected by hypertension.

Methods

Data of wAMD patients at Zhongshan Ophthalmic Center, Sun Yat‐sen University, between 1 January 2002 and 30 June 2019, were extracted from the electronic healthcare information system. wAMD patients were divided into subgroups by hypertension status, age, sex, the need for vitrectomy surgery and the number of anti‐VEGF drug intravitreal injections that these were divided in 1–3 vs. >3 (available time from 1 January 2012 to 30 June 2019).

Results

A total of 3096 wAMD patients (41.7% female, 58.3% male) with an age range of 50–96 years (68.7 (SD 9.42) years) were included. wAMD was significantly associated with hypertension (p < 0.001). After adjustment for sex and age, Cox regression model showed a significant association between hypertension in wAMD patients and the number of injections (RR = 1.31, 95% CI: 1.13–1.50, p < 0.001). There was no significant association between hypertension and the need for vitrectomy (p = 0.82).

Conclusions

wet AMD was associated with hypertension status, and after the regular series of three injections, wAMD patients with hypertension were more likely to receive anti‐VEGF drug intravitreal injections than those without hypertension. These results may facilitate prospective research on the prevention of wAMD and contribute to the management of wAMD patients.

Angiotensin II is a crucial factor in retinal aneurysm formation

Retinal arterial macroaneurysms are characterized by the acquired fusiform or saccular dilatations of the retinal artery. Angiotensin II (Ang II) is a major signal molecule of the renin-angiotensin system, which exerts a range of pathogenic actions that are relevant to retinal vascular abnormalities. We aimed to study the effect of Ang II on retinal vessels and explore its relationship with retinal aneurysmal disease. C57BL/6J male mice were administered Ang II at 1000 ng/kg/min for 28 days, and the mice given saline served as controls. The mice in the treatment group were treated once daily by gastric gavage of candesartan cilexetil (an antagonist of Ang II type 1 (AT1) receptor) at 100 mg/kg/day. The in vivo imaging of murine retinas was performed using fundus photography, optical coherence tomography, fluorescein angiography, and indocyanine green angiography at 7th, 14th, and 28th days of infusion. At the end of the infusion and treatment, the morphological changes were evaluated by histopathological examination and electron microscopy; the levels of related proteins in murine retinas were examined by antibody array and Western blot analyses. We found that Ang II infusion induced aneurysm formation in mice retina, which presented as either solitary aneurysms or retinal arterial beading. The aneurysm formation was often accompanied with vessel leakage. Moreover, Ang II infusion itself may result in increased vascular permeability and ganglion cell and inner plexiform layer thickening. The blockade of AT1 receptors by systemic administration of candesartan cilexetil alleviated the Ang II-induced retinal vasculopathy. The protein level analysis further showed that Ang II upregulated IL-1β, PDGFR-β, and MMP-9 expression, and the expression of IL-1β could be inhibited by AT1 receptor antagonist. Our study provides evidence that Ang II is a crucial factor in retinal aneurysm formation and vessel leakage. It is probably the combined effect of Ang II on vessel inflammatory response, pericyte function, and extracellular matrix remodeling that predisposes the retinal arterial wall to aneurysm formation and blood-retinal barrier breakdown.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

Association of Angiotensin II Type 1 Receptor Agonistic Autoantibodies With Outcomes in Patients With Acute Aortic Dissection

IMPORTANCE

Angiotensin II is significantly associated with the pathogenesis of acute aortic dissection. Angiotensin II type 1 receptor agonistic autoantibodies (AT1-AAs) can mimic the effect of angiotensin II.

OBJECTIVE

To investigate the association between AT1-AAs and all-cause and cause-specific mortality risk in patients with acute aortic dissection.

DESIGN, SETTING, AND PARTICIPANTS

A total of 662 patients with clinically suspected aortic dissection from 3 medical centers in Wuhan, China, were enrolled in this cohort study from August 1, 2014, to July 31, 2016. Of these, 315 patients were included in the 3-year follow-up study. Follow-up was mainly performed via telephone interviews and outpatient clinic visits. Data analysis was conducted from March 1 to May 31, 2020.

MAIN OUTCOMES AND MEASURES

The primary outcomes of interest were all-cause mortality, death due to aortic dissection, and late aortic-related adverse events.

RESULTS

The full study cohort included 315 patients with AAD (mean [SD] age, 56.2 [12.7] years; 230 men [73.0%]). Ninety-two patients (29.2%) were positive for AT1-AAs. The mortality of AT1-AA-positive patients was significantly higher than that of AT1-AA-negative patients (40 [43.5%] vs 37 [16.6%]; P < .001). The mortality risk in AT1-AA-positive patients was always significantly higher than that in AT1-AA-negative patients in patients with both type A and type B dissection. Multivariable analysis showed that the risk of AT1-AA-positive patients for type A dissection was significantly higher than that of AT1-AA-negative patients (odds ratio [OR], 1.88; 95% CI, 1.12-3.13; P = .02). The Cox proportional hazards regression model showed a significant increase of all-cause mortality risk (OR, 2.27; 95% CI, 1.44-3.57; P < .001) and late aortic-related adverse events (OR, 1.58; 95% CI, 1.06-2.36; P = .03) among AT1-AA-positive patients during the follow-up period compared with AT1-AA-negative patients.

CONCLUSIONS AND RELEVANCE

This cohort study first detected AT1-AAs in patients with acute aortic dissection. The presence of AT1-AAs was associated with significantly higher all-cause and cause-specific mortality during a follow-up period of 3 years. The antibodies may be a risk factor for aortic dissection.

Atypical p38 Signaling, Activation, and Implications for Disease

The mitogen-activated protein kinase (MAPK) p38 is an essential family of kinases, regulating responses to environmental stress and inflammation. There is an ever-increasing plethora of physiological and pathophysiological conditions attributed to p38 activity, ranging from cell division and embryonic development to the control of a multitude of diseases including retinal, cardiovascular, and neurodegenerative diseases, diabetes, and cancer. Despite the decades of intense investigation, a viable therapeutic approach to disrupt p38 signaling remains elusive. A growing body of evidence supports the pathological significance of an understudied atypical p38 signaling pathway. Atypical p38 signaling is driven by a direct interaction between the adaptor protein TAB1 and p38α, driving p38 autophosphorylation independent from the classical MKK3 and MKK6 pathways. Unlike the classical MKK3/6 signaling pathway, atypical signaling is selective for just p38α, and at present has only been characterized during pathophysiological stimulation. Recent studies have linked atypical signaling to dermal and vascular inflammation, myocardial ischemia, cancer metastasis, diabetes, complications during pregnancy, and bacterial and viral infections. Additional studies are required to fully understand how, when, where, and why atypical p38 signaling is induced. Furthermore, the development of selective TAB1-p38 inhibitors represents an exciting new opportunity to selectively inhibit pathological p38 signaling in a wide array of diseases.

Angiotensin II and Angiotensin Receptors 1 and 2-Multifunctional System in Cells Biology, What Do We Know?

For years, the renin-angiotensin system (RAS) has been perceived as a system whose role is to primarily modulate the functioning of the cardiovascular system. Years of research into the role of RAS have provided the necessary data to confirm that the role of RAS is very complex and not limited to the cardiovascular system. The presence of individual elements of the renin-angiotensin (RA) system allows to control many processes, ranging from the memorization to pro-cancer processes. Maintaining the proportions between the individual axes of the RA system allows for achieving a balance, often called homeostasis. Thus, any disturbance in the expression or activity of individual RAS elements leads to pathophysiological processes.

Matrix Metalloproteinases in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a complex, multifactorial and progressive retinal disease affecting millions of people worldwide. In developed countries, it is the leading cause of vision loss and legal blindness among the elderly. Although the pathogenesis of AMD is still barely understood, recent studies have reported that disorders in the regulation of the extracellular matrix (ECM) play an important role in its etiopathogenesis. The dynamic metabolism of the ECM is closely regulated by matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). The present review focuses on the crucial processes that occur at the level of the Bruch’s membrane, with special emphasis on MMPs, TIMPs, and the polymorphisms associated with increased susceptibility to AMD development. A systematic literature search was performed, covering the years 1990–2020, using the following keywords: AMD, extracellular matrix, Bruch’s membrane, MMPs, TIMPs, and MMPs polymorphisms in AMD. In both early and advanced AMD, the pathological dynamic changes of ECM structural components are caused by the dysfunction of specific regulators and by the influence of other regulatory systems connected with both genetic and environmental factors. Better insight into the pathological role of MMP/TIMP complexes may lead to the development of new strategies for AMD treatment and prevention.

Renin-Angiotensin System Inhibitor Usage and Age-Related Macular Degeneration among Hypertensive Patients: Results from the National Health and Nutrition Examination Survey, 2005-2008

PURPOSE

To assess whether renin-angiotensin system inhibitor (RASI) utilization is associated with age-related macular degeneration (AMD) prevalence among hypertensive patients.

METHODS

A US population-based, cross-sectional study was conducted. 3,023 hypertensive participants aged 40 years and older with gradable retinal images and ascertained RASI usage in the National Health and Nutrition Examination Survey (NHANES), 2005-2008, were finally enrolled into the study. RASI usage was obtained by interview, and AMD was determined through retinal image assessment. We performed multivariable analyses to assess the relationship between utilization of RASIs and AMD prevalence. We also took drug treatment duration into account, in order to better understand the effects of RASIs.

RESULTS

Multivariable logistic regression analyses revealed that AMD prevalence had no significant association with RASI usage but was inversely correlated with RASI treatment duration (odds ratio (OR) = 0.87, 95% confidence interval (CI) = 0.78-0.98, p=0.02). Long-term usage (>5 years) of RASIs was significantly associated with not only reduced overall risk of AMD (OR = 0.23, 95% CI = 0.14-0.38, p < 0.001) but also lower propensity to have early (OR = 0.23, 95% CI = 0.14-0.37, p < 0.001) and late (OR = 0.25, 95% CI = 0.07-0.87, p=0.03) AMD. Furthermore, long-term RASI users were less prone to develop soft drusen (OR = 0.67, 95% CI = 0.45-0.99, p=0.04) and geographic atrophy (GA) (OR = 0.39, 95% CI = 0.22-0.71, p=0.003).

CONCLUSIONS

Evidence supporting that RASI utilization could directly protect against AMD in hypertensive patients was still insufficient, but long-term RASI treatment seemed to be beneficial for both early and late AMD, implicating a promising therapeutic approach that RASIs might offer for AMD prevention and management.

A novel interaction between soluble epoxide hydrolase and the AT1 receptor in retinal microvascular damage

Clinical studies have suggested that the renin-angiotensin system (RAS) may be a promising therapeutic target in treating diabetic retinopathy (DR). While AT1 receptor blockade decreased the incidence of DR in the DIRECT trial, it did not reduce the DR progression. Lack of understanding of the molecular mechanism of retinal microvascular damage induced by RAS is a critical barrier to the use of RAS blockade in preventing or treating DR. The purpose of this study is to investigate the interaction between soluble epoxide hydrolase (sEH) and the AT1 receptor in Angiotensin II (Ang II)- and diabetes-induced retinal microvascular damage. We demonstrate that Ang II increases retinal sEH levels, which is blunted by an AT1 blocker; administration of 11,12-epoxyeicosatrienoic acid (EET) exacerbates intravitreal Ang II-induced retinal albumin leakage; while sEH knockout (KO) and blockade reduce Ang II-induced retinal vascular remodeling, sEH KO causes retinal vascular leakage in Ang II-sEH KO mice; and sEH KO potentiates diabetes-induced retinal damage via promoting retinal vascular endothelial growth factor (VEGF) but reducing expression of tight junction proteins (ZO-1 and occludin). Our studies hold the promise of providing a new strategy, the use of combined EETs blockade with AT1 blocker, to prevent or reduce DR.

Bioenergetic shift and actin cytoskeleton remodelling as acute vascular adaptive mechanisms to angiotensin II in murine retina and ophthalmic artery

Ocular vascular dysfunction is a major contributing factor to the pathogenesis of glaucoma. In recent years, there has been a renewed interest in the role of angiotensin II (Ang II) in mediating the disease progression. Despite its (patho)physiological importance, the molecular mechanisms underlying Ang II-mediated oxidative stress remain largely unexplored in the ocular vasculature. Here, we provide the first direct evidence of the alterations of proteome and signalling pathways underlying Ang II-elicited oxidative insult independent of arterial pressure changes in the ophthalmic artery (OA) and retina (R) employing an in vitro experimental model. Both R and OA were isolated from male C57Bl/6J mice (n = 15/group; n = 5/biological replicate) and incubated overnight in medium containing either vehicle or Ang II (0.1 μM) at physiological conditions. Label-free quantitative mass spectrometry (MS)-based proteomics analysis identified a differential expression of 107 and 34 proteins in the R and OA, respectively. Statistical and bioinformatics analyses revealed that protein clusters involved in actin cytoskeleton and integrin-linked kinase signalling were significantly activated in the OA. Conversely, a large majority of differentially expressed retinal proteins were involved in dysregulation of numerous energy-producing and metabolic signalling pathways, hinting to a possible shift in retinal cell bioenergetics. Particularly, Ang II-mediated downregulation of septin-7 (Sept7; p < 0.01) and superoxide dismutase [Cu-Zn] (Sod1; p < 0.05), and upregulation of troponin T, fast skeletal muscle (Tnnt3; p < 0.05) and tropomyosin alpha-3 chain (Tpm3; p < 0.01) in the OA, and significant decreased expressions of two crystallin proteins (Cryab; p < 0.05 and Crybb2; p < 0.0001) in the R were verified at the mRNA level, corroborating our proteomics findings. In summary, these results demonstrated that exogenous application of Ang II over an acute time period caused impairment of retinal bioenergetics and cellular demise, and actin cytoskeleton-mediated vascular remodelling in the OA.

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Acute Ang II stimulation elicits oxidative stress in ocular vasculature without pressor effect. .

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Dysregulation of energy-producing and metabolic pathways are implicated in the retina. .

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Actin cytoskeleton remodelling are vascular adaptation processes in the ophthalmic artery. .

Bruch's membrane pathology: A mechanistic perspective

Bruch's membrane, an extracellular matrix located between the retinal pigment epithelium and the choroid, plays a vital role as structural and functional support to the retinal pigment epithelium. Dysfunction of Bruch's membrane in both age-related macular degeneration and other ocular diseases is caused mostly by extracellular matrix degeneration, deposit formation, and angiogenesis. Although these factors are dealt in greater detail with respect to the cells that are degenerated such as the retinal pigment epithelium and the endothelial cells, the pathology involving the Bruch's membrane is often underrated. Since in most of the macular degenerations early degenerative changes are also observed in the Bruch's membrane, addressing only the cellular component without the underlying membrane will not yield an ideal clinical benefit. This review aims to discuss the factors and the mechanisms affecting the integrity of the Bruch's membrane, which would aid in developing an effective therapy for these pathologies.

Molecular Mechanisms of Complement System Proteins and Matrix Metalloproteinases in the Pathogenesis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disorder affecting predominantly the older people above the age of 50 years in which the macular region of the retina deteriorates, resulting in the loss of central vision. The key factors associated with the pathogenesis of AMD are age, smoking, dietary, and genetic risk factors. There are few associated and plausible genes involved in AMD pathogenesis. Common genetic variants (with a minor allele frequency of >5% in the population) near the complement genes explain 40-60% of the heritability of AMD. The complement system is a group of proteins that work together to destroy foreign invaders, trigger inflammation, and remove debris from cells and tissues. Genetic changes in and around several complement system genes, including the CFH, contribute to the formation of drusen and progression of AMD. Similarly, Matrix metalloproteinases (MMPs) that are normally involved in tissue remodeling also play a critical role in the pathogenesis of AMD. MMPs are involved in the degradation of cell debris and lipid deposits beneath retina but with age their functions get affected and result in the drusen formation, succeeding to macular degeneration. In this review, AMD pathology, existing knowledge about the normal and pathological role of complement system proteins and MMPs in the eye is reviewed. The scattered data of complement system proteins, MMPs, drusenogenesis, and lipofusogenesis have been gathered and discussed in detail. This might add new dimensions to the understanding of molecular mechanisms of AMD pathophysiology and might help in finding new therapeutic options for AMD.

Sodium Intake and Hypertension

The close relationship between hypertension and dietary sodium intake is widely recognized and supported by several studies. A reduction in dietary sodium not only decreases the blood pressure and the incidence of hypertension, but is also associated with a reduction in morbidity and mortality from cardiovascular diseases. Prolonged modest reduction in salt intake induces a relevant fall in blood pressure in both hypertensive and normotensive individuals, irrespective of sex and ethnic group, with larger falls in systolic blood pressure for larger reductions in dietary salt. The high sodium intake and the increase in blood pressure levels are related to water retention, increase in systemic peripheral resistance, alterations in the endothelial function, changes in the structure and function of large elastic arteries, modification in sympathetic activity, and in the autonomic neuronal modulation of the cardiovascular system. In this review, we have focused on the effects of sodium intake on vascular hemodynamics and their implication in the pathogenesis of hypertension.

Expression and tissue distribution analysis of Angiotensin II in sheep (Ovis aries) skins associated with white and black coat colors

Angiotensin II (AngII) regulates pigment synthesis by tyrosinase in melanocytes. To evaluate the association between AngII and coat color formation, we detected the expression distribution of AngII in white and black sheep skins by LC-ESI-MS/MS, western blot, quantitative real-time-PCR (qPCR) and distribution of AngII by immunohistochemistry.Liquid chromatography-electrospray ionization tandem MS (LC-ESI-MS/MS) results showed that AngII was found in white and black skin tissues of sheep. Western blot results verified the LC-ESI-MS/MS results and suggested that AngII was expressed at significantly higher levels in black sheep skins compared with the white sheep skins. Quantitative real time PCR (qRT-PCR) results also revealed that the expression level of AngII mRNA was higher in black sheep skins than that in white sheep skins. Immunohistochemical analysis further demonstrated that AngII protein was localized in the hair bulb and outer root sheath of hair follicle in sheep. In summary, protein and transcripts exhibited the same expression pattern in white and black sheep skins. Furthermore, the expressions of AngII in the hair bulb and outer root sheath of black sheep were stronger than those in white sheep. These results suggested that AngII functions in sheep coat color regulation and offer a novel insight for further investigation on the role of AngII in the coat color formation in sheep.

Angiotensin II promotes ovarian cancer spheroid formation and metastasis by upregulation of lipid desaturation and suppression of endoplasmic reticulum stress

BACKGROUND

Angiotensin II (ANGII) and its receptor (AGTR1) have been proposed as significant contributors to metastasis in multiple cancers. Further, high AGTR1 levels are associated with poor epithelial ovarian cancer (EOC) outcomes. However, the mechanistic basis for these effects is unknown. Recent studies have suggested that ovarian cancer metastasis is highly dependent on the formation of multicellular spheroids (MCS). To understand the associations between the ANGII/AGTR1 pathway and cancer outcomes, we evaluated the effects of ANGII on MCS formation by ovarian cancer cells and used a proteomic approach to analyze the mechanistic basis.

METHODS

We used the data from the GENT database and immunohistochemistry staining to assess the AGTR1 expression in epithelial ovarian cancer (EOC) patients and to assess its role in cancer progression. Colony formation assay, 3D culture assay, and transwell assays were used to analyze the effect of ANGII on the MCS formation and cell migration. The signaling pathways of AGTR1 and transactivation of epidermal growth factor receptor (EGFR) transactivation were investigated by the western blotting analysis. Xenograft models were used to determine the role of AGTR1 in ovarian cancer metastasis. ANGII release from ovarian cancer cells and ANGII levels in the EOC ascites fluid were measured by immunoassay. A shotgun proteomic approach was used to explore the detail molecular mechanism. Modulation of lipid desaturation and endoplasmic reticulum stress were verified by the in vitro and in vivo functional assays.

RESULTS

AGTR1 expression was negatively correlated with EOC prognosis. AGTR1activation significantly enhanced the MCS formation and cell migration. ANGII triggered both of the classical AGTR1 pathway and the EGFR transactivation. ANGII administration increased peritoneal metastasis. In addition, ovarian cancer cells secreted ANGII and enhanced cancer metastasis in a positive feedback manner. Based on the proteomic data, lipid desaturation was activated by induction of stearoyl-CoA desaturase-1 (SCD1), which suggests that inhibition of SCD1 may significantly reduce MCS formation by increasing endoplasmic reticulum stress.

CONCLUSIONS

ANGII promotes MCS formation and peritoneal metastasis of EOC cells. AGTR1 activation increases the lipid desaturation via SCD1 upregulation, which ultimately reduces endoplasmic reticulum stress in MCS. This mechanism explained the association between high levels of AGTR1 and poor clinical outcomes in EOC patients.

Exploring the cross talk between ER stress and inflammation in age-related macular degeneration

Increasing evidence demonstrates that inflammation and endoplasmic reticulum (ER) stress is implicated in the development and progression of age-related macular degeneration (AMD), a multifactorial neurodegenerative disease. However the cross talk between these cellular mechanisms has not been clearly and fully understood. The present study investigates a possible intersection between ER stress and inflammation in AMD. In this study, we recruited two collections of involved protein markers to retrieve their interaction information from IMEx-curated databases, which are the most well- known protein-protein interaction collections, allowing us to design an intersection network for AMD that is unprecedented. In order to find expression activated subnetworks, we utilized AMD expression profiles in our network. In addition, we studied topological characteristics of the most expressed active subnetworks to identify the hubs. With regard to topological quantifications and expressional activity, we reported a list of the most pivotal hubs which are potentially applicable as probable therapeutic targets. Furthermore, we introduced MAPK signaling pathway as a significantly involved pathway in the association between ER stress and inflammation, leading to promising new directions in discovering AMD formation mechanisms and possible treatments.

ERK signaling is required for VEGF-A/VEGFR2-induced differentiation of porcine adipose-derived mesenchymal stem cells into endothelial cells

Background

Cell-based therapy that can rejuvenate the endothelium with stimulated adipose-derived mesenchymal stem cells (AMSCs) is a promising therapeutic strategy for the re-endothelialization of denuded arteries at the stenting site. Previously, we have shown that silencing of MMP-2 and MMP-14 inhibits vascular endothelial growth factor receptor type 2 (VEGFR2) cleavage, and induces differentiation of AMSCs toward the endothelial cell (EC) lineage. In this study, we examined the underlying signaling pathways that regulate differentiation of AMSCs to ECs in vitro through VEGFR2.

Methods

AMSCs were isolated from porcine abdominal adipose tissue. The isolated AMSCs were characterized by positive expression of CD29, CD44, and CD90 and negative expression of CD11b and CD45. The isolated MSCs were transfected with siRNA to silence MMP-2, MMP-14, and angiotensin receptor 2 (ATR2). Cells were suspended either in endothelial basal media (EBM) or endothelial growth media (EGM) with various treatments. Flow cytometry was performed to examine the expression of EC markers, and western blot analysis was performed to examine the expression and activity of various kinases. Scratch assay was performed to examine the cell migration. Data were analyzed by ANOVA using PRISM GraphPad.

Results

After 10 days of stimulation for EC differentiation, the morphology of AMSCs changed to a morphology similar to that of ECs. Silencing MMP-2 and MMP-14 resulted in significant decrease in the number of migrated cells compared with the EGM-only group. ATR2 siRNA transfection did not affect the migration and differentiation of AMSCs to ECs. Stimulation of AMSCs for EC differentiation with or without MMP-2 or MMP-14 siRNA resulted in significant increase in p-ERK, and significant decrease in p-JNK. There was no significant change in p-p38 in all three groups compared with the EBM group. ERK inhibition resulted in significant decrease in the expression of EC markers in the EGM, EGM + MMP-2 siRNA, and EGM + MMP-14 siRNA groups. The VEGFR2 kinase inhibitor induced a dose-dependent inhibition of ERK.

Conclusion

The ERK signaling pathway is critical for VEGF-A/VEGFR2-induced differentiation of AMSCs into ECs. These findings provide new insights into the role of the ERK signaling pathway in AMSC differentiation to ECs for potential clinical use in cardiovascular diseases.

Inhibition of Matrix Metalloproteinase 9 Enhances Rod Survival in the S334ter-line3 Retinitis Pigmentosa Model

Retinitis Pigmentosa (RP) is one of the most common forms of inherited visual loss with the initial degeneration of rod photoreceptors, followed by a progressive cone photoreceptor deterioration. Coinciding with this visual loss, the extracellular matrix (ECM) is reorganized, which alters matrix metalloproteinase (MMP) activity levels. A potential pathological role of MMPs, MMP-9 in particular, involves an excitotoxicity-mediated physiological response. In the current study, we examine the MMP-9 and MMP-2 expression levels in the rhodopsin S334ter-line3 RP rat model and investigate the impact of treatment with SB-3CT, a specific MMP-9 and MMP-2 inhibitor, on rod cell survival was tested. Retinal MMP-9 and MMP-2 expression levels were quantified by immunoblot analysis from S334ter-line3 rats compared to controls. Gelatinolytic activities of MMP-9 and MMP-2 by zymography were examined. The geometry of rod death was further evaluated using Voronoi analysis. Our results revealed that MMP-9 was elevated while MMP-2 was relatively unchanged when S334ter-line 3 retinas were compared to controls. With SB-3CT treatment, we observed gelatinolytic activity of both MMPs was decreased and diminished clustering associated with rod death, in addition to a robust preservation of rod photoreceptors. These results demonstrate that up-regulation of MMP-9 in retinas of S334ter-line3 are associated with rod death. The application of SB-3CT dramatically interferes with mechanisms leading to apoptosis in an MMP-9-dependent manner. Future studies will determine the feasibility of using SB-3CT as a potential therapeutic strategy to slow progression of vision loss in genetic inherited forms of human RP.

Therapeutic targets of renin-angiotensin system in ocular disorders

Purpose

To review current literature on the renin-angiotensin system (RAS)-mediated pathogenic mechanisms and therapeutic targets in ocular diseases.

Methods

A comprehensive literature survey was performed on PubMed, Scopus, and Google Scholar databases published from 1977 to 2016. The search terms were a RAS, angiotensin, angiotensin receptor, prorenin, pro (renin) receptor, angiotensin converting enzyme inhibitor, angiotensin receptor blocker associated with ocular disorders like cataract, glaucoma, diabetic retinopathy (DR), macular degeneration, and uveitis. Articles were reviewed on the basis of the association between ocular disorders and RAS and relevant articles were discussed.

Results

The literature revealed that the individual RAS components including renin, angiotensins, angiotensin converting enzymes, and RAS receptors have been expressed in the specific ocular tissues like retina, choroid, and ciliary body. The activation of both circulatory and local RAS potentiate the various inflammatory and angiogenic signaling molecules, including vascular endothelial growth factor (VEGF), extracellular signal-regulated kinase, and advanced glycation end products (AGE) in the ocular tissues and leads to several blinding disorders like DR, glaucoma, and macular degeneration. The classical and newer RAS inhibitors have illustrated protective effects on blinding disorders, including DR, glaucoma, macular degeneration, uveitis, and cataract.

Conclusions

The RAS components are present in the extrarenal tissues including ocular tissue and have an imperative role in the ocular pathophysiology. The clinical studies are needed to show the role of therapeutic modalities targeting RAS in the treatment of different ocular disorders.

Olmesartan, an angiotensin II receptor blocker inhibits the progression of cataract formation in cadmium chloride induced hypertensive albino rats

AIMS

Previously we found that cadmium chloride (CdCl₂) exposure substantially elevates hypertension and potentiates cataract formation. In the present study, we investigated the protective effects of olmesartan, an angiotensin II receptor blocker against cataractogenesis in the CdCl₂-induced hypertensive animal model.

MAIN METHODS

Male Sprague-Dawley albino rats (150-180g) were randomly selected and assigned to four groups (n=6). Among the four groups, one group (normal) received 0.3% carboxymethyl cellulose (10ml/kg/day, p.o.), another group (CdCl₂ control) received CdCl₂ (0.5mg/kg/day, i.p.), and remaining two groups received olmesartan at two doses level (2 and 4mg/kg/day, p.o.) concurrently with CdCl₂ for six consecutive weeks. Blood pressure and cataract formation were examined biweekly, and pathophysiological parameters in serum and eye lenses were evaluated after six weeks of the experimental protocol.

KEY FINDINGS

The olmesartan treatment significantly restored the blood pressure, lenticular opacity, serum and lens antioxidants (catalase, superoxide dismutase, glutathione peroxidase, and glutathione reduced), and malondialdehyde level. Additionally, it significantly restored the proteins, ions (Na⁺, K⁺, and Ca²⁺), and ATPase pumps activity (Na⁺K⁺ ATPase and Ca²⁺ ATPase) in the lens as compared to CdCl₂ control group.

SIGNIFICANCE

The findings demonstrate that olmesartan potentially inhibits the risk of cataract formation in the hypertensive state via restoration of lenticular oxidative stress, ATPase function, and ionic contents in the eye lenses. The results suggest that angiotensin II receptor blockers play an important role to prevent cataract formation in several pathogenic conditions like hypertension, diabetes, and oxidative stress.

Effects of matrix metalloproteinases on the fate of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have great potential as a source of cells for cell-based therapy because of their ability for self-renewal and differentiation into functional cells. Moreover, matrix metalloproteinases (MMPs) have a critical role in the differentiation of MSCs into different lineages. MSCs also interact with exogenous MMPs at their surface, and regulate the pericellular localization of MMP activities. The fate of MSCs is regulated by specific MMPs associated with a key cell lineage. Recent reports suggest the integration of MMPs in the differentiation, angiogenesis, proliferation, and migration of MSCs. These interactions are not fully understood and warrant further investigation, especially for their application as therapeutic tools to treat different diseases. Therefore, overexpression of a single MMP or tissue-specific inhibitor of metalloproteinase in MSCs may promote transdifferentiation into a specific cell lineage, which can be used for the treatment of some diseases. In this review, we critically discuss the identification of various MMPs and the signaling pathways that affect the differentiation, migration, angiogenesis, and proliferation of MSCs.

Martinique Crinkled Retinal Pigment Epitheliopathy: Clinical Stages and Pathophysiologic Insights

PURPOSE

To reappraise the autosomal dominant Martinique crinkled retinal pigment epitheliopathy (MCRPE) in light of the knowledge of its associated mutated gene mitogen-activated protein kinase-activated protein kinase 3 (MAPKAPK3), an actor in the p38 mitogen-activated protein kinase pathway.

DESIGN

Clinical and molecular study.

PARTICIPANTS

A total of 45 patients from 3 generations belonging to a family originating from Martinique with an autosomal dominant MCRPE were examined.

METHODS

Best-corrected visual acuity, fundus photographs, and spectral-domain optical coherence tomography (SD OCT) of all clinically affected patients and carriers for the causal mutation were reviewed at the initial visit and 4 years later for 10 of them. Histologic retinal lesions of Mapkapk3(-/-) mice were compared with those of the human disease.

MAIN OUTCOME MEASURES

The MCRPE natural history in view of MAPKAPK3 function and Mapkapk3(-/-) mouse retinal lesions.

RESULTS

Eighteen patients had the c.518T>C mutation. One heterozygous woman aged 20 years was asymptomatic with normal fundus and SD OCT (stage 0). All c.518T>C heterozygous patients older than 30 years of age had the characteristic dried-out soil fundus pattern (stages 1 and 2). Complications (stage 3) were observed in 7 cases, including polypoidal choroidal vasculopathy (PCV) and macular fibrosis or atrophy. One patient was homozygous and had a form with severe Bruch's membrane (BM) thickening and macular exudation with a dried-out soil pattern in the peripheral retina. The oldest heterozygous patient, who was legally blind, had peripheral nummular pigmentary changes (stage 4). After 4 years, visual acuity was unchanged in 6 of 10 patients. The dried-out soil elementary lesions radically enlarged in patients with a preferential macular extension and confluence. These findings are in line with the progressive thickening of BM noted with age in the mouse model. During follow-up, there was no occurrence of PCV.

CONCLUSIONS

MCRPE is an autosomal dominant, fully penetrant retinal dystrophy with a preclinical stage, an onset after the age of 30 years, and a preserved visual acuity until occurrence of macular complications. The natural history of MCRPE is in relation to the role of MAPKAPK3 in BM modeling, vascular endothelial growth factor activity, retinal pigment epithelial responses to aging, and oxidative stress.

Angiotensin II Induces an Increase in Matrix Metalloproteinase 2 Expression in Aortic Smooth Muscle Cells of Ascending Thoracic Aortic Aneurysms Through JNK, ERK1/2, and p38 MAPK Activation

In this study, we hypothesized that angiotensin II (Ang II) induces matrix metalloproteinase 2 (MMP-2) upregulation in aneurysmal smooth muscle cells (ASMCs) derived from ascending thoracic aortic aneurysms (ATAAs). We compared MMP-2 protein levels in ascending aortic specimens using Western blot and plasma concentrations by enzyme-linked immunosorbent assay between ATAA (n = 40) and coronary heart disease patients (n = 40). Additionally, the protein level of angiotensinogen (AGT) in the ascending aorta and the plasma concentration of Ang II were detected by Western blot and radioimmunoassay, respectively, in ATAA and coronary heart disease patients. In ATAA patients, Ang II and MMP-2 plasma levels were significantly increased (P < 0.05). Additionally, AGT and MMP-2 protein levels in the aorta of ATAA patients were higher (P < 0.01). Enhanced AGT suggested that the amount of Ang II in aneurysmal aorta specimens may be also increased, which was confirmed by immunofluorescent staining for Ang II. Moreover, we investigated the effect of Ang II on MMP-2 upregulation by ASMCs and determined the Ang II receptors and intracellular signaling pathways that are involved. Our results showed that treatment with Ang II significantly increased the expression of MMP-2 through the Ang II type 1 receptor (AT1R) and activated the 3 major mitogen-activated protein kinases (MAPKs), JNK, ERK1/2, and p38 MAPK. In conclusion, these results indicate that Ang II can induce MMP-2 expression elevation through AT1R and MAPK pathways in ASMCs and suggest that there is therapeutic potential for angiotensin receptor blocker drugs and MAPK inhibitors in the prevention and treatment of ATAAs.

Hypertension potentiates cataractogenesis in rat eye through modulation of oxidative stress and electrolyte homeostasis

Purpose

To evaluate modes of cataractogenesis in the hypertensive state by using different hypertensive animal models, including fructose, cadmium chloride (CdCl₂), N_ω-nitro-l-arginine methyl ester (l-NAME), and two-kidney, one clip (2K1C) method.

Methods

Male Sprague–Dawley albino rats (150–180 g) were divided into different groups, each group containing six animals. Hypertension was induced in animals via six weeks administration of fructose (10% solution in drinking water), CdCl₂ (0.5 mg/kg/day, i.p.), and l-NAME (20 mg/kg/day, p.o.) in their respective groups and NaCl (0.9% solution in drinking water) in the 2K1C group. The Ramipril-treated group (2 mg/kg/day, orally) served as a standard group for the 2K1C animal model. Blood pressure was measured biweekly using non-invasive blood pressure system. The biochemical parameters in serum and eye lenses were evaluated after six weeks of the experimental protocol.

Results

Hypertensive animal models showed significant induction of systolic and diastolic blood pressure and modulation of oxidative stress through depletion of antioxidants, including glutathione peroxidase, catalase, superoxide dismutase, glutathione, and elevation of malondialdehyde in serum and eye lenses. A significant elevation of ionic contents (Na⁺ and Ca²⁺) and reduction of total protein and Ca²⁺ ATPase activity in eye lenses were observed in all hypertensive animal models except l-NAME when compared with the normal group. The significant restoration of the antioxidants, Malondialdehyde (MDA) total protein, and ionic contents in the eye lenses concomitant with reduction of blood pressure were observed in the ramipril-treated group as compared to the 2K1C animal model. The results indicate that the fructose, CdCl_2, and 2K1C models showed pronounced cataractogenic effects in the rat eye lenses.

Conclusion

Based on our findings, it can be concluded that systemic hypertension significantly increases the risk of cataract formation in the rat eyes via modulation of the antioxidant defense mechanism and electrolyte homeostasis.

Vascular Fibrosis in Aging and Hypertension: Molecular Mechanisms and Clinical Implications

Aging is the primary risk factor underlying hypertension and incident cardiovascular disease. With aging, the vasculature undergoes structural and functional changes characterized by endothelial dysfunction, wall thickening, reduced distensibility, and arterial stiffening. Vascular stiffness results from fibrosis and extracellular matrix (ECM) remodelling, processes that are associated with aging and are amplified by hypertension. Some recently characterized molecular mechanisms underlying these processes include increased expression and activation of matrix metalloproteinases, activation of transforming growth factor-β1/SMAD signalling, upregulation of galectin-3, and activation of proinflammatory and profibrotic signalling pathways. These events can be induced by vasoactive agents, such as angiotensin II, endothelin-1, and aldosterone, which are increased in the vasculature during aging and hypertension. Complex interplay between the “aging process” and prohypertensive factors results in accelerated vascular remodelling and fibrosis and increased arterial stiffness, which is typically observed in hypertension. Because the vascular phenotype in a young hypertensive individual resembles that of an elderly otherwise healthy individual, the notion of “early” or “premature” vascular aging is now often used to describe hypertension-associated vascular disease. We review the vascular phenotype in aging and hypertension, focusing on arterial stiffness and vascular remodelling. We also highlight the clinical implications of these processes and discuss some novel molecular mechanisms of fibrosis and ECM reorganization.

Cross-talk between NADPH oxidase-PKCα-p(38)MAPK and NF-κB-MT1MMP in activating proMMP-2 by ET-1 in pulmonary artery smooth muscle cells

Treatment of bovine pulmonary artery smooth muscle cells with endothelin-1 (ET-1) caused an increase in the expression and activation of proMMP-2 in the cells. The present study was undertaken to determine the underlying mechanisms involved in this scenario. We demonstrated that (i) pretreatment with NADPH oxidase inhibitor, apocynin; PKC-α inhibitor, Go6976; p(38)MAPK inhibitor SB203580 and NF-κB inhibitor, Bay11-7082 inhibited the expression and activation of proMMP-2 induced by ET-1; (ii) ET-1 treatment to the cells stimulated NADPH oxidase and PKCα activity, p(38)MAPK phosphorylation as well as NF-κB activation by translocation of NF-κBp65 subunit from cytosol to the nucleus, and subsequently by increasing its DNA-binding activity; (iii) ET-1 increases MT1-MMP expression, which was inhibited upon pretreatment with apocynin, Go6976, SB293580, and Bay 11-7082; (iv) ET-1 treatment to the cells downregulated TIMP-2 level. Although apocynin and Go6976 pretreatment reversed ET-1 effect on TIMP-2 level, yet pretreatment of the cells with SB203580 and Bay 11-7082 did not show any discernible change in TIMP-2 level by ET-1. Overall, our results suggest that ET-1-induced activation of proMMP-2 is mediated via cross-talk between NADPH oxidase-PKCα-p(38)MAPK and NFκB-MT1MMP signaling pathways along with a marked decrease in TIMP-2 expression in the cells.

Angiotensin-converting enzyme 2 activator diminazene aceturate prevents lipopolysaccharide-induced inflammation by inhibiting MAPK and NF-κB pathways in human retinal pigment epithelium

Background

Retinal inflammation is a devastating pathological process in ocular diseases. Functional impairment of retinal pigment epithelium (RPE) is associated with inflammatory retinal diseases. Enhancing the protective axis namely ACE2/Ang-(1-7)/Mas by activation of ACE2 presents anti-inflammatory properties. We investigated whether diminazene aceturate (DIZE), an angiotensin-converting enzyme 2 (ACE2) activator, prevented lipopolysaccharide (LPS)-induced inflammatory response by activating the protective axis and whether the effect was mediated by inhibiting the mitogen-activated protein kinase (MAPK) and the nuclear factor-κB (NF-κB) pathways.

Methods

Cell counting kit-8 (CCK-8) assay and real-time PCR were used to determine the optimum concentration and incubation time of DIZE. ARPE-19 cells and primary cultured human retinal pigment epithelia (hRPE) were incubated with or without 10 μg/mL DIZE for 6 h before stimulated with 5 μg/mL LPS for 24 h. The mRNA expression of inflammatory cytokines, AT1R, and AT2R was analyzed. The protein level of inflammatory cytokines, Ang II, and Ang-(1-7) was detected. Phosphorylation of p38 MAPK, extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and phosphorylated transcription inhibition factor-κB-α (p-IκB-α) were measured. Inhibitors of MAPKs and NF-κB were added to verify the involvement of these pathways. A small interfering RNA (siRNA) targeted to ACE2 and a selective Ang-(1-7) antagonist A779 was used to confirm the role of ACE2 and the involvement of ACE2/Ang-(1-7)/Mas axis.

Results

DIZE remarkably increased the expression of ACE2 and inhibited the expression of IL-6, IL-8, and MCP-1 at both mRNA and protein levels in both RPE cell lines stimulated with LPS. Inhibitors of p38, ERK1/2, JNK, and NF-κB significantly decreased LPS-induced overproduction of IL-6, IL-8, and MCP-1. DIZE reduced the expression of Ang II and AT1R, whereas increased Ang-(1-7). Furthermore, DIZE downregulated the phosphorylation of p38MAPK, ERK1/2, JNK, and the activation of NF-κB upon stimulation with LPS. Downregulating ACE2 and pre-treatment with A779 abrogated the effects of DIZE on production of cytokines, the expression of Ang II, Ang-(1-7), AT1R, phosphorylation of MAPKs and activation of NF-κB.

Conclusions

DIZE inhibits LPS-induced inflammatory response by activating ACE2/Ang-(1-7)/Mas axis in human RPE cells. The protective effect is mediated by inhibiting the p38MAPK, ERK1/2, JNK, and NF-κB pathways.

Rigid and remodelled: cerebrovascular structure and function after experimental high-thoracic spinal cord transection

High-thoracic or cervical spinal cord injury (SCI) is associated with several critical clinical conditions related to impaired cerebrovascular health, including: 300-400% increased risk of stroke, cognitive decline and diminished cerebral blood flow regulation. The purpose of this study was to examine the influence of high-thoracic (T3 spinal segment) SCI on cerebrovascular structure and function, as well as molecular markers of profibrosis. Seven weeks after complete T3 spinal cord transection (T3-SCI, n = 15) or sham injury (Sham, n = 10), rats were sacrificed for either middle cerebral artery (MCA) structure and function assessments via ex vivo pressure myography, or immunohistochemical analyses. Myogenic tone was unchanged, but over a range of transmural pressures, inward remodelling occurred after T3-SCI with a 40% reduction in distensibility (both P < 0.05), and a 33% reduction in vasoconstrictive reactivity to 5-HT trending toward significance (P = 0.09). After T3-SCI, the MCA had more collagen I (42%), collagen III (24%), transforming growth factor β (47%) and angiotensin II receptor type 2 (132%), 27% less elastin as well as concurrent increased wall thickness and reduced lumen diameter (all P < 0.05). Sympathetic innervation (tyrosine hydroxylase-positive axon density) and endothelium-dependent dilatation (carbachol) of the MCA were not different between groups. This study demonstrates profibrosis and hypertrophic inward remodelling within the largest cerebral artery after high-thoracic SCI, leading to increased stiffness and possibly impaired reactivity. These deleterious adaptations would substantially undermine the capacity for regulation of cerebral blood flow and probably underlie several cerebrovascular clinical conditions in the SCI population.

A dominant mutation in MAPKAPK3, an actor of p38 signaling pathway, causes a new retinal dystrophy involving Bruch's membrane and retinal pigment epithelium

Inherited retinal dystrophies are clinically and genetically heterogeneous with significant number of cases remaining genetically unresolved. We studied a large family from the West Indies islands with a peculiar retinal disease, the Martinique crinkled retinal pigment epitheliopathy that begins around the age of 30 with retinal pigment epithelium (RPE) and Bruch's membrane changes resembling a dry desert land and ends with a retinitis pigmentosa. Whole-exome sequencing identified a heterozygous c.518T>C (p.Leu173Pro) mutation in MAPKAPK3 that segregates with the disease in 14 affected and 28 unaffected siblings from three generations. This unknown variant is predicted to be damaging by bioinformatic predictive tools and the mutated protein to be non-functional by crystal structure analysis. MAPKAPK3 is a serine/threonine protein kinase of the p38 signaling pathway that is activated by a variety of stress stimuli and is implicated in cellular responses and gene regulation. In contrast to other tissues, MAPKAPK3 is highly expressed in the RPE, suggesting a crucial role for retinal physiology. Expression of the mutated allele in HEK cells revealed a mislocalization of the protein in the cytoplasm, leading to cytoskeleton alteration and cytodieresis inhibition. In Mapkapk3-/- mice, Bruch's membrane is irregular with both abnormal thickened and thinned portions. In conclusion, we identified the first pathogenic mutation in MAPKAPK3 associated with a retinal disease. These findings shed new lights on Bruch's membrane/RPE pathophysiology and will open studies of this signaling pathway in diseases with RPE and Bruch's membrane alterations, such as age-related macular degeneration.

Regulation and involvement of matrix metalloproteinases in vascular diseases

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

Essential hypertension in the pathogenesis of age-related macular degeneration: a review of the current evidence

Age-related macular degeneration (AMD) is one of the main causes of vision loss, especially in the elderly. The involvement of essential hypertension in its pathogenesis has been well covered in the literature since it was first recognized. Hemodynamic abnormalities appear to contribute to AMD, with the renin-angiotensin system playing a significant role. Many studies have demonstrated that high blood pressure is associated with lower choroidal blood flow and disturbed vascular homeostasis in these patients. In addition, AMD is characterized by abnormal neovascularization, to which angiotensin II and growth factors make a large contribution. Most epidemiological studies have found essential hypertension to be a risk factor for AMD. However, although all agree that the strongest predisposing factors are age and smoking, overall there is some inconsistency regarding the exact role of hypertension in its pathogenesis. In particular, there are no data in the literature to support the view that antihypertensive medication and the successful management of hypertension have a positive effect on the clinical outcome of AMD. This reinforces the data indicating that the cause of AMD is multifactorial and suggests that, although essential hypertension probably plays a role, in itself it is unlikely to be a major contributor to the future occurrence of AMD.

How, with whom and when: an overview of CD147-mediated regulatory networks influencing matrix metalloproteinase activity

Matrix metalloproteinases (MMPs) comprise a family of 23 zinc-dependent enzymes involved in various pathologic and physiologic processes. In cancer, MMPs contribute to processes from tumour initiation to establishment of distant metastases. Complex signalling and protein transport networks regulate MMP synthesis, cell surface presentation and release. Earlier attempts to disrupt MMP activity in patients have proven to be intolerable and with underwhelming clinical efficacy; thus targeting ancillary proteins that regulate MMP activity may be a useful therapeutic approach. Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally characterized as a factor present on lung cancer cells, which stimulated collagenase (MMP-1) production in fibroblasts. Subsequent studies demonstrated that EMMPRIN was identical with several other protein factors, including basigin (Bsg), all of which are now commonly termed CD147. CD147 modulates the synthesis and activity of soluble and membrane-bound [membrane-type MMPs (MT-MMPs)] in various contexts via homophilic/heterophilic cell interactions, vesicular shedding or cell-autonomous processes. CD147 also participates in inflammation, nutrient and drug transporter activity, microbial pathology and developmental processes. Despite the hundreds of manuscripts demonstrating CD147-mediated MMP regulation, the molecular underpinnings governing this process have not been fully elucidated. The present review summarizes our present knowledge of the complex regulatory systems influencing CD147 biology and provides a framework to understand how CD147 may influence MMP activity.

Downregulating p22phox ameliorates inflammatory response in Angiotensin II-induced oxidative stress by regulating MAPK and NF-κB pathways in ARPE-19 cells

Oxidative stress and inflammation are two interrelated biological events implicated in the pathogenesis of many diseases. Reactive oxygen species (ROS) produced under oxidative stress play a key role in pathological conditions. Inhibition of p22phox, an indispensable component of the NADPH oxidase (NOX) complex comprising the main source of ROS, plays a protective role in many ocular conditions by inhibiting the activation of NOXs and the generation of ROS. However, little is understood regarding the role of p22phox in oxidative stress-related inflammation in the eye. We used a p22phox small interfering RNA (siRNA) to transfect the retinal pigment epithelium (RPE)-derived cell line ARPE-19, and human primary RPE (hRPE) cells, then stimulated with Ang II. We observed a potent anti-inflammatory effect and studied the underlying mechanism. Downregulating p22phox resulted in decreased ROS generation, a reduction of NOXs (NOX1, 2, 4) and a decrease in inflammatory cytokine. In addition, p22phox downregulation reduced the activation of the MAPK and NF-κB signaling pathways. We conclude that inhibition of p22phox has an anti-inflammatory effect in Ang II-induced oxidative stress. Suppressing the MAPK and NF-κB pathways is involved in this protective effect. These results suggest that p22phox may provide a promising therapeutic target for oxidative stress-induced ocular inflammation

Angiotensin II increases matrix metalloproteinase 2 expression in human aortic smooth muscle cells via AT1R and ERK1/2

Increased levels of angiotensin II (Ang II) and activated matrix metalloproteinase 2 (MMP-2) produced by human aortic smooth muscle cells (human ASMCs) have recently been implicated in the pathogenesis of thoracic aortic aneurysm (TAA). Additionally, angiotensin II type 1 receptor (AT1R)-mediated extracellular signal-regulated kinase (ERK)1/2 activation contributes to TAA development in Marfan Syndrome. However, there is scant data regarding the relationship between Ang II and MMP-2 expression in human ASMCs. Therefore, we investigated the effect of Ang II on MMP-2 expression in human ASMCs and used Western blotting to identify the Ang II receptors and intracellular signaling pathways involved. Reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence data demonstrated that Ang II receptors were expressed on human ASMCs. Additionally, Ang II increased the expression of Ang II type 2 receptor (AT2R) but not AT1R at both the transcriptional and translational levels. Furthermore, Western blotting showed that Ang II increased MMP-2 expression in human ASMCs in a dose- and time-dependent manner. This response was completely inhibited by the AT1R inhibitor candesartan but not by the AT2R blocker PD123319. In addition, Ang II-induced upregulation of MMP-2 was mediated by the activation of ERK1/2, whereas p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK) had no effect on this process. In conclusion, these results indicate that Ang II can increase the expression of MMP-2 via AT1 receptor and ERK1/2 signaling pathways in human ASMCs and suggest that antagonists of AT1R and ERK1/2 may be useful for treating TAAs.

Angiotensin II-related hypertension and eye diseases

Systemic vascular disease, especially hypertension, has been suspected as a risk factor for some eye diseases including, diabetic retinopathy and age-related macular degeneration. Hypertension can contribute to chronic diseases by hemodynamic injury and/or cellular actions induced by hypertension-related hormones or growth factors. Among the most important is Angiotensin II (Ang II), which controls blood pressure and induces different cellular functions that may be dependent or independent of its effect on blood pressure. Importantly, as is true for heart, kidney and other organs, the renin-angiotensin system (RAS) is present in the eye. So, even in the absence of hypertension, local production of Ang II could be involved in eye diseases. The goal of this manuscript is to review the most relevant scientific evidence supporting the role of the RAS activation, in the development of age-related macular degeneration and diabetic retinopathy, and highlight the importance of Ang II in the etiology of these diseases.

Role of microRNA-29b in angiotensin II-induced epithelial-mesenchymal transition in renal tubular epithelial cells

Angiotensin II (Ang II) has been proven to induce epithelial-mesenchymal transition (EMT). The aim of the present study was to determine the role of microRNA-29b (miR-29b) during Ang II-induced EMT. For this purpose, we used spontaneously hypertensive rats (SHRs) and age-matched Wistar-Kyoto (WKY) rats. The levels of Ang II and its receptor in the kidneys of the SHRs are significantly higher than those in the age-matched WKY rats. As shown by RT-qPCR, the expression of miR-29b in the renal cortex was lower in the SHRs than in the WKY rats. For in vitro experiments, NRK-52E renal tubular epithelial cells were treated with 10(-7) M Ang II; we found that the expression of miR-29b was decreased in the cells treated with Ang II. In addition, transfection of the NRK-52E cells with miR-29b inhibitor led to the downregulation of miR-29b in these cells, and increased the expression of transforming growth factor (TGF)-β, α-smooth muscle actin (α-SMA) and collagen I (Col I). Similar results were observed with the induction of Ang II expression in the NRK-52E cells. By contrast, the upregulation of miR-29b by transfection with miR-29b mimics inhibited the overexpression of these genes induced by Ang II. These results suggest that miR-29b plays an important role in Ang II-induced EMT.

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

The renin-angiotensin system (RAS) is most well-known for its role in regulation and dysregulation of blood pressure as well as fluid and electrolyte homeostasis. Due to its ability to cause cardiovascular disease, the RAS is the target of a multitude of drugs that antagonize its pathophysiological effects. While the "classical" RAS is a systemic hormonal system, there is an increasing awareness of the existence and functional significance of local RASs in a number of organs, e.g., liver, kidney, heart, lungs, reproductive organs, adipose tissue and adrenal. The eye is one of these organs where a compelling body of evidence has demonstrated the presence of a local RAS. Individual components of the RAS have been shown to be present in many structures of the eye and their potential functional significance in ocular disease states is described. Because the eye is one of the most important and complex organs in the body, this review also discusses the implications of dysregulation of the systemic RAS on the pathogenesis of ocular diseases and how pharmacological manipulation of the RAS might lead to novel or adjunctive therapies for ocular disease states.