Potential influences of complement factor H in autoimmune inflammatory and thrombotic disorders

Linalool combats Saprolegnia parasitica infections through direct killing of microbes and modulation of host immune system

Saprolegnia parasitica is one of the most virulent oomycete species in freshwater aquatic environments, causing severe saprolegniasis and leading to significant economic losses in the aquaculture industry. Thus far, the prevention and control of saprolegniasis face a shortage of medications. Linalool, a natural antibiotic alternative found in various essential oils, exhibits promising antimicrobial activity against a wide range of pathogens. In this study, the specific role of linalool in protecting S. parasitica infection at both in vitro and in vivo levels was investigated. Linalool showed multifaceted anti-oomycetes potential by both of antimicrobial efficacy and immunomodulatory efficacy. For in vitro test, linalool exhibited strong anti-oomycetes activity and mode of action included: (1) Linalool disrupted the cell membrane of the mycelium, causing the intracellular components leak out; (2) Linalool prohibited ribosome function, thereby inhibiting protein synthesis and ultimately affecting mycelium growth. Surprisingly, meanwhile we found the potential immune protective mechanism of linalool in the in vivo test: (1) Linalool enhanced the complement and coagulation system which in turn activated host immune defense and lysate S. parasitica cells; (2) Linalool promoted wound healing, tissue repair, and phagocytosis to cope with S. parasitica infection; (3) Linalool positively modulated the immune response by increasing the abundance of beneficial Actinobacteriota; (4) Linalool stimulated the production of inflammatory cytokines and chemokines to lyse S. parasitica cells. In all, our findings showed that linalool possessed multifaceted anti-oomycetes potential which would be a promising natural antibiotic alternative to cope with S. parasitica infection in the aquaculture industry.

Immunodysregulation in immunodeficiency

The primary immunodeficiency diseases are often accompanied by autoimmunity, autoinflammatory, or aberrant lymphoproliferation. The paradoxical nature of this association can be explained by the multiple cells and molecules involved in immune networks that interact with each other in synergistic, redundant, antagonistic, and parallel arrangements. Because progressively more immunodeficiencies are found to have a genetic etiology, in many cases, a monogenic pathology, an understanding of why immunodeficiency is really an immune dysfunction becomes evident. Understanding the role of specific genes allows us to better understand the complete nature of the inborn error of immunity (IEI); the latter is a term generally used when a clear genetic etiology can be discerned. Autoimmune cytopenias, inflammatory bowel disease, autoimmune thyroiditis, and autoimmune liver diseases as well as lymphomas and cancers frequently accompany primary immunodeficiencies, and it is important that the practitioner be aware of this association and to expect that this is more common than not. The treatment of autoimmune or immunodysregulation in primary immunodeficiencies often involves further immunosuppression, which places the patient at even greater risk of infection. Mitigating measures to prevent such an infection should be considered as part of the treatment regimen. Treatment of immunodysregulation should be mechanism based, as much as we understand the pathways that lead to the dysfunction. Focusing on abnormalities in specific cells or molecules, e.g., cytokines, will become increasingly used to provide a targeted approach to therapy, a prelude to the success of personalized medicine in the treatment of IEIs.

Proteomics profiling reveals lipid metabolism abnormalities during oogenesis in unexplained recurrent pregnancy loss

Background

Unexplained recurrent pregnancy loss (URPL) is a clinical dilemma in reproductive fields. Its diagnosis is mainly exclusionary after extensive clinical examination, and some of the patients may still face the risk of miscarriage.

Methods

We analyzed follicular fluid (FF) from in vitro fertilization (IVF) in eight patients with URPL without endocrine abnormalities or verifiable causes of abortion and eight secondary infertility controls with no history of pregnancy loss who had experienced at least one normal pregnancy and delivery by direct data-independent acquisition (dDIA) quantitative proteomics to identify differentially expressed proteins (DEPs). In this study, bioinformatics analysis was performed using online software including g:profiler, String, and ToppGene. Cytoscape was used to construct the protein-protein interaction (PPI) network, and ELISA was used for validation.

Results

Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEPs are involved in the biological processes (BP) of complement and coagulation cascades. Apolipoproteins (APOs) are key proteins in the PPI network. ELISA confirmed that APOB was low-expressed in both the FF and peripheral blood of URPL patients.

Conclusion

Dysregulation of the immune network intersecting coagulation and inflammatory response is an essential feature of URPL, and this disequilibrium exists as early as the oogenesis stage. Therefore, earlier intervention is necessary to prevent the development of URPL. Moreover, aberrant lipoprotein regulation appears to be a key factor contributing to URPL. The mechanism by which these factors are involved in the complement and coagulation cascade pathways remains to be further investigated, which also provides new candidate targets for URPL treatment.

Factor H-related protein 1 in systemic lupus erythematosus

Background

Factor H (FH) is a major soluble inhibitor of the complement system and part of a family comprising five related proteins (FHRs 1-5). Deficiency of FHR1 was described to be linked to an elevated risk of systemic lupus erythematosus (SLE). As FHR1 can partially antagonize the functionality of FH, an altered FHR1/FH ratio could not only enhance SLE vulnerability but also affect the disease expression. This study focuses on the analysis of FH and FHR1 at a protein level, and the occurrence of anti-FH autoantibodies (anti-FH) in a large cohort of SLE patients to explore their association with disease activity and/or expression.

Methods

We assessed FH and FHR1 levels in plasma from 378 SLE patients compared to 84 healthy controls (normal human plasma, NHP), and sera from another cohort of 84 healthy individuals (normal human serum, NHS), using RayBio® CFH and CFHR1 ELISA kits. Patients were recruited by the Swiss SLE Cohort Study (SSCS). Unmeasurable FHR1 levels were all confirmed by Western blot, and in a subgroup of patients by PCR. Anti-FH were measured in SLE patients with non-detectable FHR1 levels and matched control patients using Abnova's CFH IgG ELISA kit.

Results

Overall, FH and FHR1 levels were significantly higher in healthy controls, but there was no significant difference in FHR1/FH ratios between SLE patients and NHPs. However, SLE patients showed a significantly higher prevalence of undetectable FHR1 compared to all healthy controls (35/378 SLE patients versus 6/168 healthy controls; p= 0.0214, OR=2.751, 95% CI = 1.115 - 8.164), with a consistent trend across all ethnic subgroups. Levels of FH and FHR1, FHR1/FH ratios and absence of FHR1 were not consistently associated with disease activity and/or specific disease manifestations, but absence of FHR1 (primarily equivalent to CFHR1 deficiency) was linked to the presence of anti-FH in SLE patients (p=0.039).

Conclusions

Deficiency of FHR1 is associated with a markedly elevated risk of developing SLE. A small proportion of FHR1-deficient SLE patients was found to have autoantibodies against FH but did not show clinical signs of microangiopathy.

Autoantibodies against complement proteins in patients with antiphospholipid syndrome: Prevalence and clinical associations

Seventy-seven patients with antiphospholipid syndrome were tested for autoantibodies against C1q, C3, FB, FH, and C4bp. Fifty-seven patients had at least one anti-complement antibody. IgM anti-FH positivity was associated with thrombosis when anti-C3 and anti-FB were, negatively or positively, associated with various noncriteria manifestations of antiphospholipid syndrome.

Complement-Coagulation Cross-talk: Factor H-mediated regulation of the Complement Classical Pathway activation by fibrin clots

The classical pathway of the complement system is activated by the binding of C1q in the C1 complex to the target activator, including immune complexes. Factor H is regarded as the key downregulatory protein of the complement alternative pathway. However, both C1q and factor H bind to target surfaces via charge distribution patterns. For a few targets, C1q and factor H compete for binding to common or overlapping sites. Factor H, therefore, can effectively regulate the classical pathway activation through such targets, in addition to its previously characterized role in the alternative pathway. Both C1q and factor H are known to recognize foreign or altered-self materials, e.g., bacteria, viruses, and apoptotic/necrotic cells. Clots, formed by the coagulation system, are an example of altered self. Factor H is present abundantly in platelets and is a well-known substrate for FXIIIa. Here, we investigated whether clots activate the complement classical pathway and whether this is regulated by factor H. We show here that both C1q and factor H bind to the fibrin formed in microtiter plates and the fibrin clots formed under in vitro physiological conditions. Both C1q and factor H become covalently bound to fibrin clots, and this is mediated via FXIIIa. We also show that fibrin clots activate the classical pathway of complement, as demonstrated by C4 consumption and membrane attack complex detection assays. Thus, factor H downregulates the activation of the classical pathway induced by fibrin clots. These results elucidate the intricate molecular mechanisms through which the complement and coagulation pathways intersect and have regulatory consequences.

Protective role of complement factor H against the development of preeclampsia

Pregnancy is an immunologically regulated, complex process. A tightly controlled complement system plays a crucial role in the successful establishment of pregnancy and parturition. Complement inhibitors at the feto-maternal interface are likely to prevent inappropriate complement activation to protect the fetus. In the present study, we aimed to understand the role of Factor H (FH), a negative regulator of complement activation, in normal pregnancy and in a model of pathological pregnancy, i.e. preeclampsia (PE). The distribution and expression of FH was investigated in placental tissues, various placental cells, and in the sera of healthy (CTRL) or PE pregnant women via immunohistochemistry, RT-qPCR, ELISA, and Western blot. Our results showed a differential expression of FH among the placental cell types, decidual stromal cells (DSCs), decidual endothelial cells (DECs), and extravillous trophoblasts (EVTs). Interestingly, FH was found to be considerably less expressed in the placental tissues of PE patients compared to normal placental tissue both at mRNA and protein levels. Similar results were obtained by measuring circulating FH levels in the sera of third trimester CTRL and PE mothers. Syncytiotrophoblast microvesicles, isolated from the placental tissues of PE and CTRL women, downregulated FH expression by DECs. The present study appears to suggest that FH is ubiquitously present in the normal placenta and plays a homeostatic role during pregnancy.

Complement factor H attenuates TNF-α-induced inflammation by upregulating EIF3C in rheumatoid arthritis

OBJECTIVE

To explore the role and underlying mechanism of Complement Factor H (CFH) in the peripheral and joint inflammation of RA patients.

METHODS

The levels of CFH in the serum and synovial fluid were determined by ELISA. The pyroptosis of monocytes was determined by western blotting and flow cytometry. The inflammation cytokine release was tested by ELISA. The cell migration and invasion ability of fibroblast-like synoviocytes (FLS) were tested by Wound healing Assay and transwell assay, respectively. The potential target of CFH was identified by RNA sequencing.

RESULTS

CFH levels were significantly elevated in the serum and synovial fluid from RA and associated with high sensitivity C-reactive protein (hs-CRP), erythrocyte sedimentation rate (ESR), and disease activity score 28 (DAS28). TNF-α could inhibit CFH expression, and CFH combined with TNF-α significantly decreased cell death, cleaved-caspase 3, gasdermin E N-terminal (GSDME-N), and inflammatory cytokines release (IL-1β and IL-6) of RA-derived monocytes. Stimulated with TNF-α increased CFH levels in RA FLS and CFH inhibits the migration, invasion, and TNF-α-induced production of inflammatory mediators, including proinflammatory cytokines (IL-6, IL-8) as well as matrix metalloproteinases (MMPs, MMP1 and MMP3) of RA FLSs. The RNA-seq results showed that CFH treatment induced upregulation of eukaryotic translation initiation factor 3 (EIF3C) in both RA monocytes and FLS. The migration of RA FLSs was promoted and the expressions of IL-6, IL-8, and MMP-3 were enhanced upon EIF3C knockdown under the stimulation of CFH combined with TNF-α.

CONCLUSION

In conclusion, we have unfolded the anti-inflammatory roles of CFH in the peripheral and joints of RA, which might provide a potential therapeutic target for RA patients.

Complement and coagulation crosstalk - Factor H in the spotlight

The immune complement and the coagulation systems are blood-based proteolytic cascades that are activated by pathway-specific triggers, based on protein-protein interactions and enzymatic cleavage reactions. Activation of these systems is finely balanced and controlled through specific regulatory mechanisms. The complement and coagulation systems are generally viewed as distinct, but have common evolutionary origins, and several interactions between these homologous systems have been reported. This complement and coagulation crosstalk can affect activation, amplification and regulatory functions in both systems. In this review, we summarize the literature on coagulation factors contributing to complement alternative pathway activation and regulation and highlight molecular interactions of the complement alternative pathway regulator factor H with several coagulation factors. We propose a mechanism where factor H interactions with coagulation factors may contribute to both complement and coagulation activation and regulation within the haemostatic system and fibrin clot microenvironment and introduce the emerging role of factor H as a modulator of coagulation. Finally, we discuss the potential impact of these protein interactions in diseases associated with factor H dysregulation or deficiency as well as evidence of coagulation dysfunction.

The complement system and human autoimmune diseases

Genetic deficiencies of early components of the classical complement activation pathway (especially C1q, r, s, and C4) are the strongest monogenic causal factors for the prototypic autoimmune disease systemic lupus erythematosus (SLE), but their prevalence is extremely rare. In contrast, isotype genetic deficiency of C4A and acquired deficiency of C1q by autoantibodies are frequent among patients with SLE. Here we review the genetic basis of complement deficiencies in autoimmune disease, discuss the complex genetic diversity seen in complement C4 and its association with autoimmune disease, provide guidance as to when clinicians should suspect and test for complement deficiencies, and outline the current understanding of the mechanisms relating complement deficiencies to autoimmunity. We focus primarily on SLE, as the role of complement in SLE is well-established, but will also discuss other informative diseases such as inflammatory arthritis and myositis.

Quantitative phosphoproteome analysis reveals differential whey phosphoproteins of bovine milk during lactation

Whey proteins in bovine milk, as the most widely used nutritional components for infant formulae, have been paid more attention. However, the phosphorylation of proteins in bovine whey during lactation has not been thoroughly researched. In this study, a total of 185 phosphorylation sites on 72 phosphoproteins were identified in bovine whey during lactation. 45 differentially expressed whey phosphoproteins (DEWPPs) in colostrum and mature milk were focused on by bioinformatics approaches. Gene Ontology annotation indicated that blood coagulation, extractive space, and protein binding played a key role in bovine milk. The critical pathway of DEWPPs was related to the immune system according to KEGG analysis. Our study investigated the biological functions of whey proteins from a phosphorylation perspective for the first time. The results elucidate and increase our knowledge of differentially phosphorylation sites and phosphoproteins in bovine whey during lactation. Additionally, the data might offer fresh insight into the development of whey protein nutrition.

Variation in CFHR3 determines susceptibility to meningococcal disease by controlling factor H concentrations

Neisseria meningitidis protects itself from complement-mediated killing by binding complement factor H (FH). Previous studies associated susceptibility to meningococcal disease (MD) with variation in CFH, but the causal variants and underlying mechanism remained unknown. Here we attempted to define the association more accurately by sequencing the CFH-CFHR locus and imputing missing genotypes in previously obtained GWAS datasets of MD-affected individuals of European ancestry and matched controls. We identified a CFHR3 SNP that provides protection from MD (rs75703017, p value = 1.1 × 10^-16) by decreasing the concentration of FH in the blood (p value = 1.4 × 10^-11). We subsequently used dual-luciferase studies and CRISPR gene editing to establish that deletion of rs75703017 increased FH expression in hepatocyte by preventing promotor inhibition. Our data suggest that reduced concentrations of FH in the blood confer protection from MD; with reduced access to FH, N. meningitidis is less able to shield itself from complement-mediated killing.

Atypical Hemolytic Uremic Syndrome in a Patient With Metastatic Peritoneal Serous Carcinoma: A Case Report

Atypical hemolytic uremic syndrome (HUS) is a part of a large category of diseases known as thrombotic microangiopathies that present with hemolytic anemia, thrombocytopenia, and target organ damage mostly characterized by acute kidney injury. It is a rare and challenging diagnosis due to the complex pathophysiology underlying the disease and its overlap with other conditions. We report the case of atypical hemolytic uremic syndrome in a 61-year-old female with a history of metastatic peritoneal serous carcinoma of the ovary presenting with anemia and acute renal failure. 

Cross-Talk between the Complement Pathway and the Contact Activation System of Coagulation: Activated Factor XI Neutralizes Complement Factor H

Complement factor H (CFH) is the major inhibitor of the alternative pathway of the complement system and is structurally related to beta2-glycoprotein I, which itself is known to bind to ligands, including coagulation factor XI (FXI). We observed reduced complement activation when FXI activation was inhibited in a baboon model of lethal systemic inflammation, suggesting cross-talk between FXI and the complement cascade. It is unknown whether FXI or its activated form, activated FXI (FXIa), directly interacts with the complement system. We explored whether FXI could interact with and inhibit the activity of CFH. We found that FXIa neutralized CFH by cleavage of the R341/R342 bonds. FXIa reduced the capacity of CFH to enhance the cleavage of C3b by factor I and the decay of C3bBb. The binding of CFH to human endothelial cells was also reduced after incubating CFH with FXIa. The addition of either short- or long-chain polyphosphate enhanced the capacity of FXIa to cleave CFH. FXIa also cleaved CFH that was present on endothelial cells and in the secretome from blood platelets. The generation of FXIa in plasma induced the cleavage of CFH. Moreover, FXIa reduced the cleavage of C3b by factor I in serum. Conversely, we observed that CFH inhibited FXI activation by either thrombin or FXIIa. Our study provides, to our knowledge, a novel molecular link between the contact pathway of coagulation and the complement system. These results suggest that FXIa generation enhances the activity of the complement system and thus may potentiate the immune response.

Murine Factor H Co-Produced in Yeast With Protein Disulfide Isomerase Ameliorated C3 Dysregulation in Factor H-Deficient Mice

Recombinant human factor H (hFH) has potential for treating diseases linked to aberrant complement regulation including C3 glomerulopathy (C3G) and dry age-related macular degeneration. Murine FH (mFH), produced in the same host, is useful for pre-clinical investigations in mouse models of disease. An abundance of FH in plasma suggests high doses, and hence microbial production, will be needed. Previously, Pichia pastoris produced useful but modest quantities of hFH. Herein, a similar strategy yielded miniscule quantities of mFH. Since FH has 40 disulfide bonds, we created a P. pastoris strain containing a methanol-inducible codon-modified gene for protein-disulfide isomerase (PDI) and transformed this with codon-modified DNA encoding mFH under the same promoter. What had been barely detectable yields of mFH became multiple 10s of mg/L. Our PDI-overexpressing strain also boosted hFH overproduction, by about tenfold. These enhancements exceeded PDI-related production gains reported for other proteins, all of which contain fewer disulfide-stabilized domains. We optimized fermentation conditions, purified recombinant mFH, enzymatically trimmed down its (non-human) N-glycans, characterised its functions in vitro and administered it to mice. In FH-knockout mice, our de-glycosylated recombinant mFH had a shorter half-life and induced more anti-mFH antibodies than mouse serum-derived, natively glycosylated, mFH. Even sequential daily injections of recombinant mFH failed to restore wild-type levels of FH and C3 in mouse plasma beyond 24 hours after the first injection. Nevertheless, mFH functionality appeared to persist in the glomerular basement membrane because C3-fragment deposition here, a hallmark of C3G, remained significantly reduced throughout and beyond the ten-day dosing regimen.

Complement as a Therapeutic Target in Systemic Autoimmune Diseases

The complement system (CS) includes more than 50 proteins and its main function is to recognize and protect against foreign or damaged molecular components. Other homeostatic functions of CS are the elimination of apoptotic debris, neurological development, and the control of adaptive immune responses. Pathological activation plays prominent roles in the pathogenesis of most autoimmune diseases such as systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, dermatomyositis, and ANCA-associated vasculitis. In this review, we will review the main rheumatologic autoimmune processes in which complement plays a pathogenic role and its potential relevance as a therapeutic target.

Complement-Independent Modulation of Influenza A Virus Infection by Factor H

The complement system is an ancient innate immune defense mechanism that can recognize molecular patterns on the invading pathogens. Factor H, as an inhibitor of the alternative pathway, down-regulates complement activation on the host cell surface. Locally synthesized factor H at the site of infection/injury, including lungs, can act as a pattern recognition molecule without involving complement activation. Here, we report that factor H, a sialic acid binder, interacts with influenza A virus (IAV) and modulates IAV entry, as evident from down-regulation of matrix protein 1 (M1) in H1N1 subtype-infected cells and up-regulation of M1 expression in H3N2-infected A549 cells. Far-western blot revealed that factor H binds hemagglutinin (HA, ~70 kDa), neuraminidase (NA, ~60 kDa), and M1 (~25 kDa). IAV-induced transcriptional levels of IFN-α, TNF-α, IL-12, IL-6, IFN-α, and RANTES were reduced following factor H treatment for the H1N1 subtype at 6 h post-infection. However, for the H3N2 subtype, mRNA levels of these pro-inflammatory cytokines were enhanced. A recombinant form of vaccinia virus complement control protein (VCP), which like factor H, contains CCP modules and has complement-regulatory activity, mirrored the results obtained with factor H. Both factor H (25%), and VCP (45%) were found to reduce luciferase reporter activity in MDCK cells transduced with H1N1 pseudotyped lentiviral particles. Factor H (50%) and VCP (30%) enhanced the luciferase reporter activity for H3N2, suggesting an entry inhibitory role of factor H and VCP against H1N1, but not H3N2. Thus, factor H can modulate IAV infection and inflammatory responses, independent of its complement-related functions.

Vitamin e-loaded membrane dialyzers reduce hemodialysis inflammaging

BACKGROUND

Inflammaging is a persistent, low-grade, sterile, nonresolving inflammatory state, associated with the senescence of the immune system. Such condition downregulates both innate and adaptive immune responses during chronic disorders as type II diabetes, cancer and hemodialysis, accounting for their susceptibility to infections, malignancy and resistance to vaccination. Aim of this study was to investigate hemodialysis inflammaging, by evaluating changes of several hemodialysis treatments on indoleamine 2,3-dioxygenase-1 activity and nitric oxide formation.

METHODS

We conducted a randomized controlled observational crossover trial. Eighteen hemodialysis patients were treated with 3 different hemodialysis procedures respectively: 1) Low-flux bicarbonate hemodialysis, 2) Low-flux bicarbonate hemodialysis with vitamin E - loaded dialyzers, and 3) Hemodialfitration. The control group consisted of 14 hospital staff healthy volunteers. Blood samples were collected from all 18 hemodialysis patients just after the long interdialytic interval, at the end of each hemodialysis treatment period.

RESULTS

Hemodialysis kynurenine and kynurenine/L - tryptophan blood ratio levels were significantly higher, when compared to the control group, indicating an increased indoleamine 2,3-dioxygenase-1 activity in hemodialysis patients. At the end of the low-flux bicarbonate hemodialysis with vitamin E - loaded dialyzers period, L - tryptophan serum levels remained unchanged vs both low-flux bicarbonate hemodialysis and hemodialfitration. Kynurenine levels instead decreased, resulting in a significant reduction of kynurenine/L - tryptophan blood ratio and indoleamine 2,3-dioxygenase-1 activity, when matched to both low-flux bicarbonate hemodialysis and HDF respectively. Serum nitric oxide control group levels, were significantly lower when compared to all hemodialysis patient groups. Interestingly, low-flux bicarbonate hemodialysis with vitamin E - loaded dialyzers nitric oxide serum levels from venous line blood samples taken 60 min after starting the hemodialysis session were significantly lower vs serum taken simultaneously from the arterial blood line.

CONCLUSIONS

The treatment with more biocompatible hemodialysis procedure as low-flux bicarbonate hemodialysis with vitamin E - loaded dialyzers, reduced indoleamine 2,3-dioxygenase-1 activity and nitric oxide formation when compared to both low-flux bicarbonate hemodialysis and hemodialfitration. These data suggest that low-flux bicarbonate hemodialysis with vitamin E - loaded dialyzers lowering hemodialysis inflammaging, could be associated to changes of proinflammatory signalling a regulated molecular level.

TRIAL REGISTRATION

NCT Number: NCT02981992; Other Study ID Numbers: 20100014090. First submitted: November 26, 2016. First posted: December 5, 2016. Last Update Posted: December 5, 2016.

Application of Extracellular Vesicles Proteomics to Cardiovascular Disease: Guidelines, Data Analysis, and Future Perspectives

Extracellular vesicles (EVs) are a heterogeneous population of vesicles composed of a lipid bilayer that carry a large repertoire of molecules including proteins, lipids, and nucleic acids. In this review, some guidelines for plasma-derived EVs isolation, characterization, and proteomic analysis, and the application of the above to cardiovascular disease (CVD) studies are provided. For EVs analysis, blood samples should be collected using a 21-gauge needle, preferably in citrate tubes, and plasma stored for up to 1 year at -80°, using a single freeze-thaw cycle. For proteomic applications, differential centrifugation (including ultracentrifugation steps) is a good option for EVs isolation. EVs characterization is done by transmission electron microscopy, particle enumeration techniques (nanoparticle-tracking analysis, dynamic light scattering), and flow cytometry. Regarding the proteomics strategy, a label-free and gel-free quantitative method is a good choice due to its accuracy and because it minimizes the amount of sample required for clinical applications. Besides the above, main EVs proteomic findings in cardiovascular-related diseases are presented and analyzed in this review, paying especial attention to overlapping results between studies. The latter might offer new insights into the clinical relevance and potential of novel EVs biomarkers identified to date in the context of CVD.

Selective permeability of mouse blood-aqueous barrier as determined by 15N-heavy isotope tracing and mass spectrometry

The blood-aqueous barrier plays a key role in regulating aqueous humor homeostasis by selectively restricting passage of proteins into the eye. The kinetics of aqueous flow are traditionally measured using artificial markers; however, these marker molecules do not address the barrier's selective permeability to plasma proteins. Here we applied stable isotope labeling of all serum proteins with nitrogen-15 (¹⁵N) atoms. Following systemic injection of this "heavy" serum in mice, the ¹⁵N-to-endogenous nitrogen-14 (¹⁴N) ratio of each protein in aqueous was measured by mass spectrometry. By monitoring the kinetic changes in these ratios, we determined the permeability profiles of hundreds of serum proteins. Meanwhile, we subjected one of the eyes to neoangiogenic wound healing by inflicting injury to the corneal limbus and compared the ¹⁵N proteomes between the normal eyes and the recovering eyes at 2 weeks after injury. In the injured eye, we detected markedly enhanced permeability to inhibitory complement regulator proteins, such as Cfh, Cfhr, Cfb, Cfi, Cfd, and Vtn. Many of the proteins in this group are implicated in age-related macular degeneration associated with leakage of the blood-retinal barrier due to inflammation. To rule out the possibility that the observed leakage was due simply to physical damage of the blood vessels, we separately created a neovascularization model using an alkali burn of the avascular cornea. In this latter model, elevated levels of Cfh and Cfb were evident. These findings suggest that ocular neovascularization is associated with enhanced permeability to serum complement regulators.