Involvement of the ubiquitin-proteasome system in the expression of extracellular matrix genes in retinal pigment epithelial cells

SPI1-mediated macrophage polarization aggravates age-related macular degeneration

Objective

This study revealed a core regulator and common upstream mechanisms for the multifaceted pathological processes of age-related macular degeneration (AMD) and provided proof-of-concept for this new therapeutic target.

Methods

Comprehensive gene expression analysis was performed using RNA sequencing of eye cup from old mice as well as laser-induced choroidal neovascularization (CNV) mouse model. Through integrative analysis and protein-protein interaction (PPI) analysis, common pathways and key transcription factor was identified simultaneously engaged in age-related retinal degeneration and CNV, the two typical pathological process of AMD. Subsequently, the expression changes of Spi1, the key regulator, as well as the alternation of the downstream mechanisms were validated in both models through qRT-PCR, Elisa, flow cytometry and immunofluorescence. Further, we assessed the impact of Spi1 knockdown in vitro and in vivo using gene intervention vectors carried by adeno-associated virus or lentivirus to test its potential as a therapeutic target.

Results

Compared to corresponding controls, we found 1,939 and 1,319 genes differentially expressed in eye cups of old and CNV mice respectively. The integrative analysis identified a total of 275 overlapping DEGs, of which 150 genes were co-upregulated. PPI analysis verified a central transcription factor, SPI1. The significant upregulation of Spi1 expression was then validated in both models, accompanied by macrophage polarization towards the M1 phenotype. Finally, SPI1 suppression significantly inhibited M1 polarization of BMDMs and attenuated neovascularization in CNV mice.

Conclusion

This study demonstrates that SPI1 exerts a pivotal role in AMD by regulation of macrophage polarization and innate immune response, offering promise as an innovative target for treating AMD.

Soluble CD147 regulates endostatin via its effects on the activities of MMP-9 and secreted proteasome 20S

During progression of rheumatoid arthritis (RA), angiogenesis provides oxygen and nutrients for the cells' increased metabolic demands and number. To turn on angiogenesis, pro-angiogenic factors must outweigh anti-angiogenic factors. We have previously shown that CD147/extracellular matrix metalloproteinase inducer (EMMPRIN) can induce the expression of the pro-angiogenic factors vascular endothelial growth factor (VEGF) and matrix metallopeptidase 9 (MMP-9) in a co-culture of the human HT1080 fibrosarcoma and U937 monocytic-like cell lines. However, whether CD147 influences anti-angiogenic factors was not known. We now show that relative to single cultures, the co-culture of these cells not only enhanced pro-angiogenic factors but also decreased the anti-angiogenic factors endostatin and thrombospondin-1 (Tsp-1), generally increasing the angiogenic potential as measured by a wound assay. Using anti-CD147 antibody, CD147 small interfering RNA (siRNA), and recombinant CD147, we demonstrate that CD147 hormetically regulates the generation of endostatin but has no effect on Tsp-1. Since endostatin is cleaved from collagen XVIII (Col18A), we applied different protease inhibitors and established that MMP-9 and proteasome 20S, but not cathepsins, are responsible for endostatin generation. MMP-9 and proteasome 20S collaborate to synergistically enhance endostatin generation, and in a non-cellular system, CD147 enhanced MMP-9 activity and hormetically regulated proteasome 20S activity. Serum samples obtained from RA patients and healthy controls mostly corroborated these findings, indicating clinical relevance. Cumulatively, these findings suggest that secreted CD147 mediates a possibly allosteric effect on MMP-9 and proteasome 20S activities and can serve as a switch that turns angiogenesis on or off, depending on its ambient concentrations in the microenvironment.

The impact of early RPE cell junction loss on VEGF, Ang-2, and TIMP secretion in vitro

Purpose

The retinal pigment epithelium (RPE) is an important tissue for maintaining a healthy retina. Retinal pigment epithelial cells help regulate nutrient transport to photoreceptors and are heavily pigmented to prevent light scattering. These cells also have junction proteins to form monolayers. Monolayers are key players in pathologies such as age-related macular degeneration (AMD), a leading cause of vision loss in older adults. During AMD, RPE cell detachment can occur, resulting in a loss of junctions. Losing junctions can increase the expression of pro-angiogenic vascular endothelial growth factor (VEGF). This overexpression can cause abnormal blood vessel growth or angiogenesis in the retina. Age-related macular degeneration treatments target VEGF to slow angiogenesis progression. However, other proteins, such as angiopoietin-2 (Ang-2) and the tissue inhibitor of metalloproteinase-1 (TIMP-1), may also play important roles, making them potential targets for treatment. Controlling RPE junction formation will help elucidate the relationship between RPE cell detachment and additional angiogenic factor secretion, lead to more therapeutics, and increase the efficacy of current treatments.

Methods

Micropatterning was used to control the spatial arrangement of primary porcine RPE cells using polydimethylsiloxane (PDMS) stencils. Patterns were formed into PDMS stencils to mimic 10%, 25%, and 50% overall detachment of the RPE monolayer. Zonula-occludens-1 (ZO-1), Ang-2, and VEGF were visualized using immunocytochemical (ICC) staining. An enzyme-linked immunosorbent assay (ELISA) was used to quantify extracellular Ang-2, VEGF, TIMP-1, and TIMP-2 levels. A rod outer segment (OS) phagocytosis assay was performed to determine how RPE junction loss directly affects photoreceptor support.

Results

The growth of primary porcine RPE cells was successfully controlled using stencils. Morphological changes and a decrease in pigmentation were observed, showing a decline in barrier and light absorption functions as degeneration increased. One day after stencil removal, junction proteins were delocalized, and angiogenic factor secretions were correlated with increased levels of detachment. Secretion levels of Ang-2 and TIMP-1 were significantly increased, whereas VEGF and TIMP-2 concentrations were not as affected by varying levels of detachment. OS phagocytosis appeared lower in RPE cells when ZO-1 was affected.

Conclusions

These results suggest a correlation between loss of junctions, abnormal angiogenic protein secretion, and reduced OS phagocytosis. Furthermore, Ang-2 and TIMP-1 proteins might be beneficial targets for AMD treatments, and their roles in retinal diseases deserve further investigation.

Whole-Exome sequencing analysis identified TMSB10/TRABD2A locus to be associated with carfilzomib-related cardiotoxicity among patients with multiple myeloma

Background

Proteasome inhibitor Carfilzomib (CFZ) is effective in treating patients with refractory or relapsed multiple myeloma (MM) but has been associated with cardiovascular adverse events (CVAE) such as hypertension, cardiomyopathy, and heart failure. This study aimed to investigate the contribution of germline genetic variants in protein-coding genes in CFZ-CVAE among MM patients using whole-exome sequencing (WES) analysis.

Methods

Exome-wide single-variant association analysis, gene-based analysis, and rare variant analyses were performed on 603,920 variants in 247 patients with MM who have been treated with CFZ and enrolled in the Oncology Research Information Exchange Network (ORIEN) at the Moffitt Cancer Center. Separate analyses were performed in European Americans and African Americans followed by a trans-ethnic meta-analysis.

Results

The most significant variant in the exome-wide single variant analysis was a missense variant rs7148 in the thymosin beta-10/TraB Domain Containing 2A (TMSB10/TRABD2A) locus. The effect allele of rs7148 was associated with a higher risk of CVAE [odds ratio (OR) = 9.3 with a 95% confidence interval of 3.9-22.3, p = 5.42*10^-7]. MM patients with rs7148 AG or AA genotype had a higher risk of CVAE (50%) than those with GG genotype (10%). rs7148 is an expression quantitative trait locus (eQTL) for TRABD2A and TMSB10. The gene-based analysis also showed TRABD2A as the most significant gene associated with CFZ-CVAE (p = 1.06*10^-6).

Conclusions

We identified a missense SNP rs7148 in the TMSB10/TRABD2A as associated with CFZ-CVAE in MM patients. More investigation is needed to understand the underlying mechanisms of these associations.

Non-coding RNAs and related molecules associated with form-deprivation myopia in mice

The role of miRNAs and its regulatory mechanism in myopia are indeterminate. Our study aimed to investigate potential myopia‐associated non‐coding RNAs and related molecules by performing a comprehensive bioinformatic analysis of miRNA expression profile of mice with form‐deprivation myopia (FDM). Differentially expressed miRNAs in two raw microarray data sets (GSE58124 and GSE84220) from Gene Expression Omnibus (GEO) database were comprehensively analysed using GEO2R. Target genes were predicted using miRDB and enriched with Metascape online tool. Protein‐protein interaction (PPI) networks were constructed utilizing STRING and Cytoscape. Significant differentially expressed miRNAs were validated by real‐time polymerase chain reaction (qRT‐PCR) using RNA extracted from monocular FDM ocular tissues. As result, we identified three upregulated miRNAs (mmu‐miR‐1936, mmu‐miR‐338‐5p, and mmu‐miR‐673‐3p) significantly associated with myopia in the two microarray data sets (p < 0.05 and |Log (Fold Change) |>1). GO functional analysis suggested these three miRNAs were targeted in genes mostly enriched in morphogenesis and developmental growth of retinal tissues. Enrichment analysis revealed top eight transcription factors, including PAX6 and Smad3, related to myopia. Ten hub genes, including Rbx1, Fbxl3, Fbxo27, Fbxl7, Fbxo4, Cul3, Cul2, Klhl5, Fbxl16 and Klhl42, associated with ubiquitin conjugation were identified. qRT‐PCR confirmed the increased expression of mmu‐miR‐1936 and mmu‐miR‐338‐5p (p < 0.05), but no statistical difference was observed in mmu‐miR‐673‐3p expression in myopic retinas. Our findings indicated mmu‐miR‐1936, mmu‐miR‐338‐5p and mmu‐miR‐673‐3p upregulation may be associated with myopia development via post‐transcriptional gene regulation, and identified potential molecules that could be further explored in future studies of the mechanism in myopia.

Bortezomib Inhibits Lung Fibrosis and Fibroblast Activation Without Proteasome Inhibition

The FDA-approved proteasomal inhibitor bortezomib (BTZ) has attracted interest for its potential anti-fibrotic actions. However, neither its in vivo efficacy in lung fibrosis nor its dependence on proteasome inhibition has been conclusively defined. In this study, we assessed the therapeutic efficacy of BTZ in a mouse model of pulmonary fibrosis, developed an in vitro protocol to define its actions on diverse fibroblast activation parameters, determined its reliance on proteasome inhibition for these actions in vivo and in vitro and explored alternative mechanisms of action. The therapeutic administration of BTZ diminished the severity of pulmonary fibrosis without reducing proteasome activity in the lung. In experiments designed to mimic this lack of proteasome inhibition in vitro, BTZ reduced fibroblast proliferation, differentiation into myofibroblasts, and collagen synthesis. It promoted de-differentiation of myofibroblasts and overcame their characteristic resistance to apoptosis. Mechanistically, BTZ inhibited kinases important for fibroblast activation while inducing expression of dual-specificity phosphatase 1 or DUSP1, and knockdown of DUSP1 abolished its anti-fibrotic actions in fibroblasts. Collectively, these findings suggest that BTZ exhibits a multidimensional profile of robust inhibitory actions on lung fibroblasts as well as anti-fibrotic actions in vivo. Unexpectedly, these actions appear to be independent of proteasome inhibition, and instead attributable to induction of DUSP1.

Sex-stratified gene-by-environment genome-wide interaction study of trauma, posttraumatic-stress, and suicidality

Epidemiologic studies recognize that trauma and posttraumatic stress are associated with heightened suicidal behavior severity, yet examination of these associations from a genetic perspective is limited. We performed a multivariate gene-by-environment genome-wide interaction study (GEWIS) of suicidality in 123,633 individuals using a covariance matrix based on 26 environments related to traumatic experiences, posttraumatic stress, social support, and socioeconomic status. We discovered five suicidality risk loci, including the male-associated rs2367967 (CWC22), which replicated in an independent cohort. All GEWIS-significant loci exhibited interaction effects where at least 5% of the sample had environmental profiles conferring opposite SNP effects from the majority. We identified PTSD as a primary driving environment for GxE at suicidality risk loci. The male suicidality GEWIS was enriched for three middle-temporal-gyrus inhibitory neuron transcriptomic profiles: SCUBE- and PVALB-expressing cells (β = 0.028, p = 3.74 × 10-4), OPRM1-expressing cells (β = 0.030, p = 0.001), and SPAG17-expressing cells (β = 0.029, p = 9.80 × 10-4). Combined with gene-based analyses (CNTN5 p association  = 2.38 × 10-9, p interaction  = 1.51 × 10-3; PSMD14 p association  = 2.04 × 10-7, p interaction  = 7.76 × 10-6; HEPACAM p association  = 2.43 × 10-6, p interaction  = 3.82 × 10-7) including information about brain chromatin interaction profiles (UBE2E3 in male neuron p = 1.07 × 10-5), our GEWIS points to extracellular matrix biology and synaptic plasticity as biological interactors with the effects of potentially modifiable lifetime traumatic experiences on genetic risk for suicidality. Characterization of molecular basis for the effects of traumatic experience and posttraumatic stress on risk of suicidal behaviors may help to identify novel targets for which more effective treatments can be developed for use in high-risk populations.

Small-Molecule Modulation of PPARs for the Treatment of Prevalent Vascular Retinal Diseases

Vascular-related retinal diseases dramatically impact quality of life and create a substantial burden on the healthcare system. Age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity are leading causes of irreversible blindness. In recent years, the scientific community has made great progress in understanding the pathology of these diseases and recent discoveries have identified promising new treatment strategies. Specifically, compelling biochemical and clinical evidence is arising that small-molecule modulation of peroxisome proliferator-activated receptors (PPARs) represents a promising approach to simultaneously address many of the pathological drivers of these vascular-related retinal diseases. This has excited academic and pharmaceutical researchers towards developing new and potent PPAR ligands. This review highlights recent developments in PPAR ligand discovery and discusses the downstream effects of targeting PPARs as a therapeutic approach to treating retinal vascular diseases.

Legumain is a predictor of all-cause mortality and potential therapeutic target in acute myocardial infarction

The prognostic impact of extracellular matrix (ECM) modulation and its regulatory mechanism post-acute myocardial infarction (AMI), require further clarification. Herein, we explore the predictive role of legumain—which showed the ability in ECM degradation—in an AMI patient cohort and investigate the underlying mechanisms. A total of 212 AMI patients and 323 healthy controls were enrolled in the study. Moreover, AMI was induced in mice by permanent ligation of the left anterior descending artery and fibroblasts were adopted for mechanism analysis. Based on the cut-off value for the receiver-operating characteristics curve, AMI patients were stratified into low (n = 168) and high (n = 44) plasma legumain concentration (PLG) groups. However, PLG was significantly higher in AMI patients than that in the healthy controls (median 5.9 μg/L [interquartile range: 4.2–9.3 μg/L] vs. median 4.4 μg/L [interquartile range: 3.2–6.1 μg/L], P < 0.001). All-cause mortality was significantly higher in the high PLG group compared to that in the low PLG group (median follow-up period, 39.2 months; 31.8% vs. 12.5%; P = 0.002). Multivariate Cox regression analysis showed that high PLG was associated with increased all-cause mortality after adjusting for clinical confounders (HR = 3.1, 95% confidence interval (CI) = 1.4–7.0, P = 0.005). In accordance with the clinical observations, legumain concentration was also increased in peripheral blood, and infarcted cardiac tissue from experimental AMI mice. Pharmacological blockade of legumain with RR-11a, improved cardiac function, decreased cardiac rupture rate, and attenuated left chamber dilation and wall thinning post-AMI. Hence, plasma legumain concentration is of prognostic value in AMI patients. Moreover, legumain aggravates cardiac remodelling through promoting ECM degradation which occurs, at least partially, via activation of the MMP-2 pathway.

A Tale of Two Proteolytic Machines: Matrix Metalloproteinases and the Ubiquitin-Proteasome System in Pulmonary Fibrosis

Pulmonary fibrosis is a chronic and progressive lung disease characterized by the activation of fibroblasts and the irreversible deposition of connective tissue matrices that leads to altered pulmonary architecture and physiology. Multiple factors have been implicated in the pathogenesis of lung fibrosis, including genetic and environmental factors that cause abnormal activation of alveolar epithelial cells, leading to the development of complex profibrotic cascade activation and extracellular matrix (ECM) deposition. One class of proteinases that is thought to be important in the regulation of the ECM are the matrix metalloproteinases (MMPs). MMPs can be up- and down- regulated in idiopathic pulmonary fibrosis (IPF) lungs and their role depends upon their location and function. Furthermore, alterations in the ubiquitin-proteosome system (UPS), a major intracellular protein degradation complex, have been described in aging and IPF lungs. UPS alterations could potentially lead to the abnormal accumulation and deposition of ECM. A better understanding of the specific roles MMPs and UPS play in the pathophysiology of pulmonary fibrosis could potentially drive to the development of novel biomarkers that can be as diagnostic and therapeutic targets. In this review, we describe how MMPs and UPS alter ECM composition in IPF lungs and mouse models of pulmonary fibrosis, thereby influencing the alveolar epithelial and mesenchymal cell behavior. Finally, we discuss recent findings that associate MMPs and UPS interplay with the development of pulmonary fibrosis.

Eyeing the Extracellular Matrix in Vascular Development and Microvascular Diseases and Bridging the Divide between Vascular Mechanics and Function

The extracellular matrix (ECM) is critical in all aspects of vascular development and health: supporting cell anchorage, providing structure, organization and mechanical stability, and serving as a sink for growth factors and sustained survival signals. Abnormal changes in ECM protein expression, organization, and/or properties, and the ensuing changes in vascular compliance affect vasodilator responses, microvascular pressure transmission, and collateral perfusion. The changes in microvascular compliance are independent factors initiating, driving, and/or exacerbating a plethora of microvascular diseases of the eye including diabetic retinopathy (DR) and vitreoretinopathy, retinopathy of prematurity (ROP), wet age-related macular degeneration (AMD), and neovascular glaucoma. Congruently, one of the major challenges with most vascular regenerative therapies utilizing localized growth factor, endothelial progenitor, or genetically engineered cell delivery, is the regeneration of blood vessels with physiological compliance properties. Interestingly, vascular cells sense physical forces, including the stiffness of their ECM, through mechanosensitive integrins, their associated proteins and the actomyosin cytoskeleton, which generates biochemical signals that culminate in a rapid expression of matricellular proteins such as cellular communication network 1 (CCN1) and CCN2 (aka connective tissue growth factor or CTGF). Loss or gain of function of these proteins alters genetic programs of cell growth, ECM biosynthesis, and intercellular signaling, that culminate in changes in cell behavior, polarization, and barrier function. In particular, the function of the matricellular protein CCN2/CTGF is critical during retinal vessel development and regeneration wherein new blood vessels form and invest a preformed avascular neural retina following putative gradients of matrix stiffness. These observations underscore the need for further in-depth characterization of the ECM-derived cues that dictate structural and functional properties of the microvasculature, along with the development of new therapeutic strategies addressing the ECM-dependent regulation of pathophysiological stiffening of blood vessels in ischemic retinopathies.

Effect of Curcumin on Protein Damage Induced by Rotenone in Dopaminergic PC12 Cells

Oxidative stress is considered to be a key factor of the pathogenesis of Parkinson's disease, a multifactorial neurodegenerative disorder characterized by reduced dopaminergic neurons in the substantia nigra pars compacta and accumulated protein aggregates. Rotenone is a worldwide-used pesticide that induces the most common features of Parkinson's by direct inhibition of the mitochondrial complex I. Rotenone-induced Parkinson's models, as well as brain tissues from Parkinson's patients, are characterized by the presence of both lipid peroxidation and protein oxidation markers resulting from the increased level of free radical species. Oxidation introduces several modifications in protein structure, including carbonylation and nitrotyrosine formation, which severely compromise cell function. Due to the link existing between oxidative stress and Parkinson's disease, antioxidant molecules could represent possible therapeutic tools for this disease. In this study, we evaluated the effect of curcumin, a natural compound known for its antioxidant properties, in dopaminergic PC12 cells treated with rotenone, a cell model of Parkinsonism. Our results demonstrate that the treatment of PC12 cells with rotenone causes severe protein damage, with formation of both carbonylated and nitrotyrosine-derived proteins, whereas curcumin (10 µM) co-exposure exerts protective effects by reducing the levels of oxidized proteins. Curcumin also promotes proteasome activation, abolishing the inhibitory effect exerted by rotenone on this degradative system.

Ocular Surface Changes in Prostaglandin Analogue-Treated Patients

Glaucoma is the second leading cause of blindness globally. Reducing intraocular pressure (IOP) has been acknowledged to be the main therapy for glaucoma. Prostaglandin analogues (PGAs) have become the first-line therapy for patients with glaucoma due to their powerful efficacy for lowering (IOP). However, usage of PGAs can also cause several notable side effects, including the changes in ocular surface. The relationship between PGAs and ocular surface changes is complicated and still remains unclear. In the present review, we summarize the recent studies of the effects of PGAs on ocular changes as well as the possible mechanisms that might provide new considerations during clinical medication.

Interplay between Autophagy and the Ubiquitin-Proteasome System and Its Role in the Pathogenesis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a complex eye disease with many pathogenesis factors, including defective cellular waste management in retinal pigment epithelium (RPE). Main cellular waste in AMD are: all-trans retinal, drusen and lipofuscin, containing unfolded, damaged and unneeded proteins, which are degraded and recycled in RPE cells by two main machineries—the ubiquitin-proteasome system (UPS) and autophagy. Recent findings show that these systems can act together with a significant role of the EI24 (etoposide-induced protein 2.4 homolog) ubiquitin ligase in their action. On the other hand, E3 ligases are essential in both systems, but E3 is degraded by autophagy. The interplay between UPS and autophagy was targeted in several diseases, including Alzheimer disease. Therefore, cellular waste clearing in AMD should be considered in the context of such interplay rather than either of these systems singly. Aging and oxidative stress, two major AMD risk factors, reduce both UPS and autophagy. In conclusion, molecular mechanisms of UPS and autophagy can be considered as a target in AMD prevention and therapeutic perspective. Further work is needed to identify molecules and effects important for the coordination of action of these two cellular waste management systems.