Cystatin C in macular and neuronal degenerations: implications for mechanism(s) of age-related macular degeneration

Shared whole environmental etiology between Alzheimer's disease and age-related macular degeneration

The comorbidity of Alzheimer's disease (AD) and age-related macular degeneration (AMD) has been established in clinical and genetic studies. There is growing interest in determining the shared environmental factors associated with both conditions. Recent advancements in record linkage techniques enable us to identify the contributing factors to AD and AMD from a wide range of variables. As such, we first constructed a knowledge graph based on the literature, which included all statistically significant risk factors for AD and AMD. An environment-wide association study (EWAS) was conducted to assess the contribution of various environmental factors to the comorbidity of AD and AMD based on the UK biobank. Based on the conditional Q-Q plots and Bayesian algorithm, several shared environmental factors were identified, which could be categorized into the domains of health condition, biological sample parameters, body index, and attendance availability. Finally, we generated a shared etiology landscape for AD and AMD by combining existing knowledge with our novel findings.

Loss of cystatin C regulates permeability and inflammatory pathways in retina

Cystatin C has been linked to inflammation in other diseases, such as epilepsy and Alzheimer's disease. These studies were designed to investigate whether Cystatin C regulates retinal inflammation and permeability. To address this question, we used Cystatin C knockout mice in a retinal ischemia/reperfusion model to determine whether Cystatin C regulated retinal damage, as well as inflammatory mediators and retinal permeability. To support the mouse work, we also used primary retinal endothelial cells cultured in normal and high glucose. Ischemia/reperfusion in Cystatin C knockout mice caused increased formation of degenerate capillaries. Loss of Cystatin C increased fluorescein leakage in the retina, which was accompanied by reduced levels of zonula occludin 1 (ZO-1) and occludin proteins. When REC were grown in high glucose, recombinant Cystatin C decreased retinal permeability, while Cystatin C siRNA increased dextran flux compared to high glucose alone. Recombinant Cystatin C decreased levels of interleukin-1-beta (IL-1β) and high mobility group box 1 (HMGB1) levels. In conclusion, loss of Cystatin C increased vascular damage in response to ischemia/reperfusion. Cystatin C regulated permeability and inflammatory mediators in the retina in response to stressors. Cystatin C offers a new target for retinal disease therapeutic development.

Role of cystatin C in the detection of sight-threatening diabetic retinopathy in Asian Indians with type 2 diabetes

AIM

To study the association between cystatin C and sight-threatening diabetic retinopathy (STDR) in Asian Indians with type 2 diabetes (T2DM).

METHODS

In a cross-sectional study carried out at two tertiary centres in India in 2022, individuals with T2DM underwent clinical and ophthalmic assessments and estimation of serum cystatin C. Grading of DR was done by retina specialists. STDR was defined by the presence of severe non-proliferative DR (NPDR), proliferative DR (PDR) and/or diabetic macular edema. Receiver operating characteristic (ROC) curves were used to identify cystatin C cut-off value for detecting STDR.

RESULTS

Among 420 individuals with T2DM (mean age 56 ± 9 years; mean duration of diabetes 14.5 ± 7.9 years), 121 (24.1 %) had No-DR, 119 (28.3 %) had No-STDR and 200 (49.6 %) had STDR. Mean cystatin C level was significantly higher in individuals with STDR compared to those with no-STDR and No-DR (1.34 vs 1.06 vs 0.93 mg/L, p < 0.001). Cystatin C cut-off value ≥1.11 mg/L had a C statistic of 0.944 (95 % CI: 0.909-0.968, p < 0.001), 96.8 % sensitivity and 78.2 % specificity for detection of STDR.

CONCLUSION

Elevated serum cystatin C was strongly associated with STDR and could possibly be used as a biomarker for screening for sight-threatening diabetic retinopathy.

The Role of Retinal Pigment Epithelial Cells in Age-Related Macular Degeneration: Phagocytosis and Autophagy

Age-related macular degeneration (AMD) causes vision loss in the elderly population. Dry AMD leads to the formation of Drusen, while wet AMD is characterized by cell proliferation and choroidal angiogenesis. The retinal pigment epithelium (RPE) plays a key role in AMD pathogenesis. In particular, helioreceptor renewal depends on outer segment phagocytosis of RPE cells, while RPE autophagy can protect cells from oxidative stress damage. However, when the oxidative stress burden is too high and homeostasis is disturbed, the phagocytosis and autophagy functions of RPE become damaged, leading to AMD development and progression. Hence, characterizing the roles of RPE cell phagocytosis and autophagy in the pathogenesis of AMD can inform the development of potential therapeutic targets to prevent irreversible RPE and photoreceptor cell death, thus protecting against AMD.

Analysis of Wild Type and Variant B Cystatin C Interactome in Retinal Pigment Epithelium Cells Reveals Variant B Interacting Mitochondrial Proteins

Cystatin C, a secreted cysteine protease inhibitor, is abundantly expressed in retinal pigment epithelium (RPE) cells. A mutation in the protein's leader sequence, corresponding to formation of an alternate variant B protein, has been linked with an increased risk for both age-related macular degeneration (AMD) and Alzheimer's disease (AD). Variant B cystatin C displays intracellular mistrafficking with partial mitochondrial association. We hypothesized that variant B cystatin C interacts with mitochondrial proteins and impacts mitochondrial function. We sought to determine how the interactome of the disease-related variant B cystatin C differs from that of the wild-type (WT) form. For this purpose, we expressed cystatin C Halo-tag fusion constructs in RPE cells to pull down proteins interacting with either the WT or variant B form, followed by identification and quantification by mass spectrometry. We identified a total of 28 interacting proteins, of which 8 were exclusively pulled down by variant B cystatin C. These included 18 kDa translocator protein (TSPO) and cytochrome B5 type B, both of which are localized to the mitochondrial outer membrane. Variant B cystatin C expression also affected RPE mitochondrial function with increased membrane potential and susceptibility to damage-induced ROS production. The findings help us to understand how variant B cystatin C differs functionally from the WT form and provide leads to RPE processes adversely affected by the variant B genotype.

Proteomics profiling of vitreous humor reveals complement and coagulation components, adhesion factors, and neurodegeneration markers as discriminatory biomarkers of vitreoretinal eye diseases

Introduction

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are leading causes of visual impairment and blindness in people aged 50 years or older in middle-income and industrialized countries. Anti-VEGF therapies have improved the management of neovascular AMD (nAMD) and proliferative DR (PDR), no treatment options exist for the highly prevalent dry form of AMD.

Methods

To unravel the biological processes underlying these pathologies and to find new potential biomarkers, a label-free quantitative (LFQ) method was applied to analyze the vitreous proteome in PDR (n=4), AMD (n=4) compared to idiopathic epiretinal membranes (ERM) (n=4).

Results and discussion

Post-hoc tests revealed 96 proteins capable of differentiating among the different groups, whereas 118 proteins were found differentially regulated in PDR compared to ERM and 95 proteins in PDR compared to dry AMD. Pathway analysis indicates that mediators of complement, coagulation cascades and acute phase responses are enriched in PDR vitreous, whilst proteins highly correlated to the extracellular matrix (ECM) organization, platelet degranulation, lysosomal degradation, cell adhesion, and central nervous system development were found underexpressed. According to these results, 35 proteins were selected and monitored by MRM (multiple reaction monitoring) in a larger cohort of patients with ERM (n=21), DR/PDR (n=20), AMD (n=11), and retinal detachment (n=13). Of these, 26 proteins could differentiate between these vitreoretinal diseases. Based on Partial least squares discriminant and multivariate exploratory receiver operating characteristic (ROC) analyses, a panel of 15 discriminatory biomarkers was defined, which includes complement and coagulation components (complement C2 and prothrombin), acute-phase mediators (alpha-1-antichymotrypsin), adhesion molecules (e.g., myocilin, galectin-3-binding protein), ECM components (opticin), and neurodegeneration biomarkers (beta-amyloid, amyloid-like protein 2).

Salivary inflammatory biomarkers are predictive of mild cognitive impairment and Alzheimer's disease in a feasibility study

Alzheimer's disease (AD) is an insidious disease. Its distinctive pathology forms over a considerable length of time without symptoms. There is a need to detect this disease, before even subtle changes occur in cognition. Hallmark AD biomarkers, tau and amyloid-β, have shown promising results in CSF and blood. However, detecting early changes in these biomarkers and others will involve screening a wide group of healthy, asymptomatic individuals. Saliva is a feasible alternative. Sample collection is economical, non-invasive and saliva is an abundant source of proteins including tau and amyloid-β. This work sought to extend an earlier promising untargeted mass spectrometry study in saliva from individuals with mild cognitive impairment (MCI) or AD with age- and gender-matched cognitively normal from the South Australian Neurodegenerative Disease cohort. Five proteins, with key roles in inflammation, were chosen from this study and measured by ELISA from individuals with AD (n = 16), MCI (n = 15) and cognitively normal (n = 29). The concentrations of Cystatin-C, Interleukin-1 receptor antagonist, Stratifin, Matrix metalloproteinase 9 and Haptoglobin proteins had altered abundance in saliva from AD and MCI, consistent with the earlier study. Receiver operating characteristic analysis showed that combinations of these proteins demonstrated excellent diagnostic accuracy for distinguishing both MCI (area under curve = 0.97) and AD (area under curve = 0.97) from cognitively normal. These results provide evidence for saliva being a valuable source of biomarkers for early detection of cognitive impairment in individuals on the AD continuum and potentially other neurodegenerative diseases.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Cystatin C and cystatin SN as possible soluble tumor markers in malignant uveal melanoma

Background

The aim of the study was to determine the concentration of endogenous cystatin C and cystatin SN, as potential tumor biomarkers, in the serum and biological fluids of the eye in both healthy controls and patients with uveal melanoma.

Patients and methods

The concentration of both cystatins was determined in the intraocular fluid (IOF), tear fluid, and serum of patients with uveal melanoma and compared to baseline measurements in IOF, tears, serum, cerebral spinal fluid, saliva and urine of healthy controls.

Results

The concentration of cystatin C in all the biological matrices obtained from healthy controls significantly exceeded the concentration of cystatin SN and was independent of gender. Cystatin C concentrations in the tear fluid of patients with uveal melanoma (both the eye with the malignancy, as well as the contralateral, non-affected eye), were significantly greater than cystatin C concentrations in the tear fluid of healthy controls and was independent of tumor size. The concentration of cystatin SN in IOF of patients with uveal melanoma was significantly less than the corresponding concentration of cystatin SN in healthy controls.

Conclusions

The ratio of cystatins (CysC:CysSN) in both the serum and tear fluid, as well as the concentration of cystatin SN in IOF, would appear to strongly suggest the presence of uveal melanoma. It is further suggested that multiple diagnostic criteria be utilized if a patient is suspected of having uveal melanoma, such as determination of the cystatin C and cystatin SN concentrations in serum, tears, and IOF, ocular fundus and ultrasound imaging, and biopsy with histopathological evaluation.

A Novel In Silico Benchmarked Pipeline Capable of Complete Protein Analysis: A Possible Tool for Potential Drug Discovery

Simple Summary

Protein interactions govern the majority of an organism’s biological processes. Therefore, to fully understand the functionality of an organism, we must know how proteins work at a molecular level. This study assembled a protocol that enables scientists to construct a protein’s tertiary structure easily and subsequently to investigate its mechanism and function. Each step involved in prediction, validation, and functional analysis of a protein is crucial to obtain an accurate result. We have dubbed this the trifecta analysis. It was clear early in our research that no single study in the literature had previously encompassed the complete trifecta analysis. In particular, studies that recommend free, open-source tools that have been benchmarked for each step are lacking. The present study ensures that predictions are accurate and validated and will greatly benefit new and experienced scientists alike in obtaining a strong understanding of the trifecta analysis, resulting in a domino effect that could lead to drug development.

Abstract

Current in silico proteomics require the trifecta analysis, namely, prediction, validation, and functional assessment of a modeled protein. The main drawback of this endeavor is the lack of a single protocol that utilizes a proper set of benchmarked open-source tools to predict a protein’s structure and function accurately. The present study rectifies this drawback through the design and development of such a protocol. The protocol begins with the characterization of a novel coding sequence to identify the expressed protein. It then recognizes and isolates evolutionarily conserved sequence motifs through phylogenetics. The next step is to predict the protein’s secondary structure, followed by the prediction, refinement, and validation of its three-dimensional tertiary structure. These steps enable the functional analysis of the macromolecule through protein docking, which facilitates the identification of the protein’s active site. Each of these steps is crucial for the complete characterization of the protein under study. We have dubbed this process the trifecta analysis. In this study, we have proven the effectiveness of our protocol using the cystatin C and AChE proteins. Beginning with just their sequences, we have characterized both proteins’ structures and functions, including identifying the cystatin C protein’s seven-residue active site and the AChE protein’s active-site gorge via protein–protein and protein–ligand docking, respectively. This process will greatly benefit new and experienced scientists alike in obtaining a strong understanding of the trifecta analysis, resulting in a domino effect that could expand drug development.

Review of proteomics approach to eye diseases affecting the anterior segment

Visual impairment and blindness is a major health burden worldwide, and major ocular diseases causing visual impairment pertain to the anterior segment of the eye. Anterior segment ocular diseases are common, yet complex entities. Although many treatment options and surgical techniques are available for these ailments, the underlying cause and pathogenesis is still unclear. Finding ways to fundamentally treat these patients and rectify the underlying dysregulations leading to the disease may help cure patients completely without major complications. Proteomics approaches are a novel way to distinguish dysregulated proteins in a variety of biological tissues in a hypothesis-free manner, thus helping to find the responsible pathways leading to a certain disease. The aim of the current study is to review the available knowledge in scientific literature regarding the proteomics studies done on anterior segment eye diseases and suggest potential clinical implications to exploit the results of these studies. SIGNIFICANCE: Anterior segment ocular diseases are responsible for a major proportion of visual impairment and blindness worldwide. Although ophthalmologists have several treatment options that can alleviate or control the progression of these diseases, no definite cure is available for most of them. Moreover, because these diseases are progressive, prompt diagnosis is of utmost important. Proteomics studies enable us to identify and quantify the dysregulated proteins in a biological specimen in a hypothesis-free manner. Understanding the dysregulated protein pathways shines a light on the pathogenesis of the disease. Moreover, these dysregulated proteins may act as biomarkers to help in diagnosis and treatment follow-up. Hence, in this article we sought out to review the available scientific literature regarding the proteomics studies of anterior segment ocular diseases and to identify potential applications of proteomic studies in clinic.

The Diverse Roles of TIMP-3: Insights into Degenerative Diseases of the Senescent Retina and Brain

Tissue inhibitor of metalloproteinase-3 (TIMP-3) is a component of the extracellular environment, where it mediates diverse processes including matrix regulation/turnover, inflammation and angiogenesis. Rare TIMP-3 risk alleles and mutations are directly linked with retinopathies such as age-related macular degeneration (AMD) and Sorsby fundus dystrophy, and potentially, through indirect mechanisms, with Alzheimer's disease. Insights into TIMP-3 activities may be gleaned from studying Sorsby-linked mutations. However, recent findings do not fully support the prevailing hypothesis that a gain of function through the dimerisation of mutated TIMP-3 is responsible for retinopathy. Findings from Alzheimer's patients suggest a hitherto poorly studied relationship between TIMP-3 and the Alzheimer's-linked amyloid-beta (A) proteins that warrant further scrutiny. This may also have implications for understanding AMD as aged/diseased retinae contain high levels of A. Findings from TIMP-3 knockout and mutant knock-in mice have not led to new treatments, particularly as the latter does not satisfactorily recapitulate the Sorsby phenotype. However, recent advances in stem cell and in vitro approaches offer novel insights into understanding TIMP-3 pathology in the retina-brain axis, which has so far not been collectively examined. We propose that TIMP-3 activities could extend beyond its hitherto supposed functions to cause age-related changes and disease in these organs.

Association between Serum Cystatin C and Vascular Complications in Type 2 Diabetes Mellitus without Nephropathy

BACKGROUND

Recent studies have correlated serum cystatin C (CysC) with vascular complications, but few studies have investigated this correlation in diabetes patients without nephropathy. This study aimed to evaluate if higher serum CysC levels increase the risk for vascular complications in type 2 diabetes mellitus patients with normal renal function or mild renal impairment.

METHODS

A total of 806 consecutive patients with type 2 diabetes mellitus who were admitted to the diabetes center of Soonchunhyang University Hospital for blood glucose control were retrospectively reviewed. Patients with nephropathy were excluded. Subjects were categorized into quartiles of serum CysC levels (Q1, ≤0.65 mg/L; Q2, 0.66 to 0.79 mg/L; Q3, 0.80 to 0.94 mg/L; and Q4, ≥0.95 mg/L).

RESULTS

The proportion of patients with diabetic retinopathy (DR) (P for trend <0.001), coronary heart disease (CHD) (P for trend <0.001), and stroke (P for trend <0.001) increased across the serum CysC quartiles. After adjustment for confounding factors, the highest serum CysC level remained a significant risk factor for DR (odds ratio [OR], 1.929; 95% confidence interval [CI], 1.007 to 4.144; P=0.040). Compared with Q1, a significant positive association was observed between serum CysC and CHD in Q2 (OR, 7.321; 95% CI, 1.114 to 48.114; P=0.012), Q3 (OR, 6.027; 95% CI, 0.952 to 38.161; P=0.020), and Q4 (OR, 8.122; 95% CI, 1.258 to 52.453; P=0.007). No associations were observed between CysC and stroke after additional adjustment for confounding variables.

CONCLUSION

Serum CysC levels are independently associated with DR and CHD, suggesting that CysC may be useful for identifying type 2 diabetes mellitus patients without nephropathy who are at high risk for vascular complications.

Serum cystatin C as an early predictor of acute kidney injury in preterm neonates with respiratory distress syndrome

Preterm neonates with respiratory distress syndrome (RDS) are at increased risk of acute kidney injury (AKI). Our study aimed at determining whether serum cystatin C (sCysC) on day 3 of life (D3) can early predict AKI in preterm neonates with RDS. This prospective study was conducted on 75 preterm neonates; 50 with RDS and 25 without RDS. On D3, sCysC, serum creatinine (sCr) and blood urea nitrogen (BUN) were measured and estimated glomerular filtration rate (eGFR) was calculated. sCr and BUN levels were measured again on days 5 and 7. Neonates were evaluated for development of AKI during first week of life according to the modified pediatric RIFLE (pRIFLE) criteria. Thirteen neonates with RDS developed AKI (26%).There was no significant difference between RDS and control groups with respect to sCysC. RDS neonates with AKI had significantly higher sCysC than those without AKI (1.62 ± 0.12 versus 1.16 ± 0.09 mg/l; p < .001). RDS grade III-IV neonates had significantly higher sCysC than RDS grade I-II. There was a significant positive correlation between D3 sCysC and (D5 and D7 sCr and BUN). Receiver operating characteristic (ROC) curve showed that D3 sCysC can predict AKI in preterm neonates with RDS at a cutoff point of >1.3 mg/l with sensitivity of 92.30% and specificity of 96%. We conclude that neonates with RDS are at increased risk of AKI. sCysC on day 3 of life can predict AKI earlier than Cr and eGFR.

The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases

Lutein (L) and zeaxanthin (Z) are dietary carotenoids derived from dark green leafy vegetables, orange and yellow fruits that form the macular pigment of the human eyes. It was hypothesized that they protect against visual disorders and cognition diseases, such as age-related macular degeneration (AMD), age-related cataract (ARC), cognition diseases, ischemic/hypoxia induced retinopathy, light damage of the retina, retinitis pigmentosa, retinal detachment, uveitis and diabetic retinopathy. The mechanism by which they are involved in the prevention of eye diseases may be due their physical blue light filtration properties and local antioxidant activity. In addition to their protective roles against light-induced oxidative damage, there are increasing evidences that L and Z may also improve normal ocular function by enhancing contrast sensitivity and by reducing glare disability. Surveys about L and Z supplementation have indicated that moderate intakes of L and Z are associated with decreased AMD risk and less visual impairment. Furthermore, this review discusses the appropriate consumption quantities, the consumption safety of L, side effects and future research directions.

Autophagy in the eye: Development, degeneration, and aging

Autophagy is a catabolic pathway that promotes the degradation and recycling of cellular components. Proteins, lipids, and even whole organelles are engulfed in autophagosomes and delivered to the lysosome for elimination. In response to stress, autophagy mediates the degradation of cell components, which are recycled to generate the nutrients and building blocks required to sustain cellular homeostasis. Moreover, it plays an important role in cellular quality control, particularly in neurons, in which the total burden of altered proteins and damaged organelles cannot be reduced by redistribution to daughter cells through cell division. Research has only begun to examine the role of autophagy in the visual system. The retina, a light-sensitive tissue, detects and transmits electrical impulses through the optic nerve to the visual cortex in the brain. Both the retina and the eye are exposed to a variety of environmental insults and stressors, including genetic mutations and age-associated alterations that impair their function. Here, we review the main studies that have sought to explain autophagy's importance in visual function. We describe the role of autophagy in retinal development and cell differentiation, and discuss the implications of autophagy dysregulation both in physiological aging and in important diseases such as age-associated macular degeneration and glaucoma. We also address the putative role of autophagy in promoting photoreceptor survival and discuss how selective autophagy could provide alternative means of protecting retinal cells. The findings reviewed here underscore the important role of autophagy in maintaining proper retinal function and highlight novel therapeutic approaches for blindness and other diseases of the eye.

Association between Von Willebrand factor, disintegrin and metalloproteinase with thrombospondin type 1 motif member 13, d-Dimer and cystatin C levels with retinopathy in type 1 diabetes mellitus

BACKGROUND

We evaluated the association between plasma levels of VWF, ADAMTS13 and d-Dimer, which consist on endothelial dysfunction and hypercoagulability biomarkers, and cystatin C with retinopathy in type 1 diabetic patients.

METHODS

Patients were classified according to presence (n=55) or absence (n=70) of retinopathy. Plasma levels of VWF, ADAMTS13, d-Dimer and cystatin C were evaluated by ELISA and ADAMTS13 activity was evaluated by FRET.

RESULTS

Plasma levels of VWF (p=0.033), ADAMTS13 activity (p=0.014), d-Dimer (p=0.002) and cystatin C (p<0.001) were elevated in diabetic patients with retinopathy compared to those without this complication. The multivariate logistic regression analysis showed that ADAMTS13 activity (p=0.031) d-Dimer (p=0.015) and cystatin C (p=0.001) remained associated with retinopathy after adjustment for age, diabetes duration, use of statin, use of ACEi or angiotensin antagonist, use of acetylsalicylic acid and glomerular filtration rate.

CONCLUSION

ADAMTS13 activity, d-Dimer and cystatin C are associated with retinopathy in type 1 diabetic patients and are promising biomarkers for the diagnosis and monitoring of diabetic retinopathy.

Amyloid properties of the leader peptide of variant B cystatin C: implications for Alzheimer and macular degeneration

Variant B (VB) of cystatin C has a mutation in its signal peptide (A25T), which interferes with its processing leading to reduced secretion and partial retention in the vicinity of the mitochondria. There are genetic evidences of the association of VB with Alzheimer's disease (AD) and age-related macular degeneration (AMD). Here, we investigated aggregation and amyloid propensities of unprocessed VB combining computational and in vitro studies. Aggregation predictors revealed the presence of four aggregation-prone regions, with a strong one at the level of the signal peptide, which indeed formed toxic aggregates and mature amyloid fibrils in solution. In light of these results, we propose for the first time the role of the signal peptide in pathogenesis of AD and AMD.

SPP2 Mutations Cause Autosomal Dominant Retinitis Pigmentosa

Retinitis pigmentosa (RP) shows progressive loss of photoreceptors involved with heterogeneous genetic background. Here, by exome sequencing and linkage analysis on a Chinese family with autosomal dominant RP, we identified a putative pathogenic variant, p.Gly97Arg, in the gene SPP2, of which expression was detected in multiple tissues including retina. The p.Gly97Arg was absent in 800 ethnically matched chromosomes and 1400 in-house exome dataset, and was located in the first of the two highly conserved disulfide bonded loop of secreted phosphoprotein 2 (Spp-24) encoded by SPP2. Overexpression of p.Gly97Arg and another signal peptide mutation, p.Gly29Asp, caused cellular retention of both endogenous wild type and exogenous mutants in vitro, and primarily affected rod photoreceptors in zebrafish mimicking cardinal feature of RP. Taken together, our data indicate that the two mutations of SPP2 have dominant negative effects and cellular accumulation of Spp-24 might be particularly toxic to photoreceptors and/or retinal pigment epithelium. SPP2 has a new role in retinal degeneration.

Efficacy of Ethanol Extract of Fructus lycii and Its Constituents Lutein/Zeaxanthin in Protecting Retinal Pigment Epithelium Cells against Oxidative Stress: In Vivo and In Vitro Models of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a major cause of blindness worldwide. Oxidative stress plays a large role in the pathogenesis of AMD. The present study was to evaluate the effects of Fructus lycii ethanol extract on AMD in mice and to investigate whether combination of lutein and zeaxanthin, two carotenoid pigments in Fructus lycii, could protect human retinal pigment epithelial ARPE-19 cells treated with hydrogen peroxide (H₂O₂) in vitro. We found that severe sediment beneath retinal pigment epithelium and thickened Bruch membrane occurred in AMD mice. However, Fructus lycii ethanol extract improved the histopathologic changes and decreased the thickness of Bruch membrane. Furthermore, the gene and protein expression of cathepsin B and cystatin C was upregulated in AMD mice but was eliminated by Fructus lycii ethanol extract. Investigations in vitro showed that ARPE-19 cell proliferation was suppressed by H₂O₂. However, lutein/zeaxanthin not only stimulated cell proliferation but also abrogated the enhanced expression of MMP-2 and TIMP-1 in H₂O₂-treated ARPE-19 cells. These data collectively suggested that Fructus lycii ethanol extract and its active components lutein/zeaxanthin had protective effects on AMD in vivo and in vitro, providing novel insights into the beneficial role of Fructus lycii for AMD therapy.

Cellular and molecular mechanisms of age-related macular degeneration: from impaired autophagy to neovascularization

Age-related macular degeneration (AMD) is a complex, degenerative and progressive disease involving multiple genetic and environmental factors. It can result in severe visual loss e.g. AMD is the leading cause of blindness in the elderly in the western countries. Although age, genetics, diet, smoking, and many cardiovascular factors are known to be linked with this disease there is increasing evidence that long-term oxidative stress, impaired autophagy clearance and inflammasome mediated inflammation are involved in the pathogenesis. Under certain conditions these may trigger detrimental processes e.g. release of vascular endothelial growth factor (VEGF), causing choroidal neovascularization e.g. in wet AMD. This review ties together these crucial pathological threads in AMD.

Autophagy and heterophagy dysregulation leads to retinal pigment epithelium dysfunction and development of age-related macular degeneration

Age-related macular degeneration (AMD) is a complex, degenerative and progressive eye disease that usually does not lead to complete blindness, but can result in severe loss of central vision. Risk factors for AMD include age, genetics, diet, smoking, oxidative stress and many cardiovascular-associated risk factors. Autophagy is a cellular housekeeping process that removes damaged organelles and protein aggregates, whereas heterophagy, in the case of the retinal pigment epithelium (RPE), is the phagocytosis of exogenous photoreceptor outer segments. Numerous studies have demonstrated that both autophagy and heterophagy are highly active in the RPE. To date, there is increasing evidence that constant oxidative stress impairs autophagy and heterophagy, as well as increases protein aggregation and causes inflammasome activation leading to the pathological phenotype of AMD. This review ties together these crucial pathological topics and reflects upon autophagy as a potential therapeutic target in AMD.

Over-expression of human cystatin C in pterygium versus healthy conjunctiva

BACKGROUND

A prospective, non-randomised, transversal and comparative study, carried out in INOVA Vision Institute and Autonomous University of Aguascalientes. Pterygium is an important illness that affects 22% people from tropic and equatorial zones. Is an inflammatory process caused by UV rays, and it has a behavior similar to a neoplasm. For this study was taken into consideration 191 samples from the INOVA Vision Institute, Aguascalientes, Mexico. Include 73 pterygia samples, which were obtained during resection under sterile conditions. 44 normal conjunctiva samples were obtained from the same patients when harvesting the conjunctival autograft, or from other patients undergoing extracapsular cataract extraction from the superior bulbar region. Tears from patients with pterygium (n = 50) and normal volunteers (n = 24) were obtained using a calibrated glass micro capillary tube. The surgical conjunctiva and pterygia samples were subjected to reverse-transcription polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry. Tears were analyzed by enzyme-linked immunosorbent assays.

METHODS

This was a prospective, non-randomised study involving 191 biological samples taken from patients with pterygium and normal volunteers, whom were operated under local anaesthesia by either complete resection of the lesion with primary closure, or resection with conjunctival autograft. Tissue samples were fixed in 10% formaldehyde. Sections were routinely stained with hematoxylin and eosin. HCC expression was evaluated by reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and by western blotting. All tears samples were analyzed by enzyme-linked immunosorbent assays (ELISA).

RESULTS

Expression levels and distribution patterns of HCC in normal conjunctiva and pterygium. Higher levels of HCC mRNAs and proteins were detected in pterygium compared with a normal conjunctiva. Immunohistochemistry revealed that HCC was localized in the apical cells of the epithelium in the normal conjunctiva. In contrast, HCC was detected in all extension of epithelial tissue, from apical to basal cells in pterygia. The concentration of HCC protein in tears was higher in patients with pterygium versus controls.

CONCLUSION

HCC may play an important role in protecting normal conjunctiva, and regulating inflammatory conditions of the anterior ocular surface.

Age-related macular degeneration revisited--piecing the puzzle: the LXIX Edward Jackson memorial lecture

PURPOSE

To present the current understanding of age-related macular degeneration (AMD) pathogenesis, based on clinical evidence, epidemiologic data, histopathologic examination, and genetic data; to provide an update on current and emerging therapies; and to propose an integrated model of the pathogenesis of AMD.

DESIGN

Review of published clinical and experimental studies.

METHODS

Analysis and synthesis of clinical and experimental data.

RESULTS

We are closer to a complete understanding of the pathogenesis of AMD, having progressed from clinical observations to epidemiologic observations and clinical pathologic correlation. More recently, modern genetic and genomic studies have facilitated the exploration of molecular pathways. It seems that AMD is a complex disease that results from the interaction of genetic susceptibility with aging and environmental factors. Disease progression also seems to be driven by a combination of genetic and environmental factors.

CONCLUSIONS

Therapies based on pathophysiologic features have changed the paradigm for treating neovascular AMD. With improved understanding of the underlying genetic susceptibility, we can identify targets to halt early disease and to prevent progression and vision loss.

Chloroquine treatment of ARPE-19 cells leads to lysosome dilation and intracellular lipid accumulation: possible implications of lysosomal dysfunction in macular degeneration

Background

Age-related macular degeneration (AMD) is the leading cause of vision loss in elderly people over 60. The pathogenesis is still unclear. It has been suggested that lysosomal stress may lead to drusen formation, a biomarker of AMD. In this study, ARPE-19 cells were treated with chloroquine to inhibit lysosomal function.

Results

Chloroquine-treated ARPE-19 cells demonstrate a marked increase in vacuolation and dense intracellular debris. These are identified as chloroquine-dilated lysosomes and lipid bodies with LAMP-2 and LipidTOX co-localization, respectively. Dilation is an indicator of lysosomal dysfunction. Chloroquine disrupts uptake of exogenously applied rhodamine-labeled dextran by these cells. This suggests a disruption in the phagocytic pathway. The increase in LAMP protein levels, as assessed by Western blots, suggests the possible involvement in autophagy. Oxidative stress with H₂O₂ does not induce vacuolation or lipid accumulation.

Conclusion

These findings suggest a possible role for lysosomes in AMD. Chloroquine treatment of RPE cells may provide insights into the cellular mechanisms underlying AMD.