Presence of autoantibodies to the glycolytic enzyme alpha-enolase in sera from patients with early rheumatoid arthritis

Clinical correlates of a subset of anti-fibroblast antibodies in systemic sclerosis

Anti-fibroblast antibodies (AFA) have been reported in systemic sclerosis (SSc) and are known to promote fibroblast activation. Aim of this study was to characterize the fine specificity of AFA and to analyze any correlations with clinical parameters associated to fibrosis. To this end, AFA were affinity-purified from a patient with diffuse cutaneous SSc (dcSSc) and interstitial lung disease (ILD). Panning of a phage display peptide library with purified AFA identified the motif . The peptide p121, bearing the AFA-specific motif, was used in ELISA to screen sera from 186 SSc patients and 81 healthy donors. Anti-p121 Ab serum levels were statistically higher in SSc than in healthy groups, and directly associated with dcSSc, reduced FVC (FVC < 70), and ILD. Given these clinical correlates, this study lays the groundwork for the identification of the antigen recognized by anti-p121 Ab, which might represent a novel therapeutic target for ILD.

Non-invasive diagnosis of endometriosis: Immunologic and genetic markers

Endometriosis, a benign gynecologic and chronic inflammatory disease, is defined by the presence of endometrial tissue outside the uterus characterized mainly by pelvic pain and infertility. Because endometriosis affects approximately 10% of females, it represents a significant socioeconomic burden worldwide having tremendous impact on daily quality of life. Accurate and prompt diagnosis is crucial for the management of this debilitating disorder. Unfortunately, diagnosis is typically delayed to lack of specific symptoms and readily accessible biomarkers. Although histopathologic examination remains the current gold standard, this approach is highly invasive and not applicable for early screening. Recent work has focused on the identification of reliable biomarkers including immunologic, ie, immune cells, antibodies and cytokines, as well as genetic and biochemical markers, ie, microRNAs, lncRNAs, circulating and mitochondrial nucleic acids, along with some hormones, glycoproteins and signaling molecules. Confirmatory research studies are, however, needed to more fully establish these markers in the diagnosis, progression and staging of these endometrial lesions.

The effects of maternal anti-alpha-enolase antibody expression on the brain development in offspring

Anti-alpha-enolase autoantibodies have not only been found to play an important role in autoimmune diseases but also cause neurological damage in adults. In this study, a pregnant mouse model with high serum alpha-enolase (ENO1)-specific antibody (ENO1Ab) was established by immunization with ENO1 protein to explore the effects of maternal circulatory ENO1Ab on the brain development in offspring. The pups showed impaired learning and memory abilities with obviously thinner tight junctions in the brain tissue. IgG deposits colocalized with both ENO1 protein and complement 3 (C3), and the membrane attack complex was obviously detectable in the brain tissues of pups from dams with high serum ENO1Ab expression. Our findings suggest that highly expressed ENO1Ab in the maternal circulation can pass through the blood-placenta-barrier and the compromised blood-brain barrier into the brain tissues of offspring and may cause neurological development impairment mainly through complement-dependent cytotoxicity.

Identification of crucial salivary proteins/genes and pathways involved in pathogenesis of temporomandibular disorders

Temporomandibular disorder (TMD) is a collective term for a group of conditions that lead to impairment of the function of the temporomandibular joint. The proteins/genes and signaling pathways associated with TMD are still poorly understood. The aim of this study was to identify key differentially expressed salivary proteins/genes (DEGs) associated with TMD progression using LC-MS/MS coupled with a bioinformatics approach. The protein–protein interaction network was obtained from the STRING database and the hub genes were identified using Cytoscape including cytoHubba and MCODE plug-ins. In addition, enrichment of gene ontology functions and the Reactome signaling pathway was performed. A total of 140 proteins/genes were differentially expressed. From cluster analysis, a set of 20 hub genes were significantly modulated: ALB, APOA1, B2M, C3, CAT, CLU, CTSD, ENO1, GSN, HBB, HP, HSPA8, LTF, LYZ, MMP9, S100A9, SERPINA1, TF, TPI1, and TXN. Two enriched signaling pathways, glycolysis and gluconeogenesis, and tryptophan signaling pathway involving the hub genes CAT, ENO1, and TPI1 have been identified. The rest of the hub genes were mainly enriched in the innate immune system and antimicrobial peptides signaling pathways. In summary, hub DEGs and the signaling pathways identified here have elucidated the molecular mechanisms of TMD pathogenesis.

Redox-Mediated Carbamylation As a Hapten Model Applied to the Origin of Antibodies to Modified Proteins in Rheumatoid Arthritis

Significance: The production of antibodies to posttranslationally modified antigens is a hallmark in rheumatoid arthritis (RA). In particular, the presence of citrullination-associated antibodies, targeting both citrullinating enzymes (the peptidylarginine deiminases [PADs]) and citrullinated antigens (anticitrullinated protein antibodies [ACPAs]), has suggested that dysregulated citrullination is relevant for disease pathogenesis. Antibodies to other protein modifications with physicochemical similarities to citrulline, such as carbamylated-lysine and acetylated-lysine, have also gained interest in RA, but their mechanistic relation to ACPAs remains unclear. Recent Advances: Recent studies using RA-derived monoclonal antibodies have found that ACPAs are cross-reactive to carbamylated and acetylated peptides, challenging our understanding of the implications of such cross-reactivity. Critical Issues: Analogous to the classic antibody response to chemically modified proteins, we examine the possibility that antibodies to modified proteins in RA are more likely to resemble antihapten antibodies rather than autoantibodies. This potential shift in the autoantibody paradigm in RA offers the opportunity to explore new mechanisms involved in the origin and cross-reactivity of pathogenic antibodies in RA. In contrast to citrullination, carbamylation is a chemical modification associated with oxidative stress, it is highly immunogenic, and is considered in the group of posttranslational modification-derived products. We discuss the possibility that carbamylated proteins are antigenic drivers of cross-reacting antihapten antibodies that further create the ACPA response, and that ACPAs may direct the production of antibodies to PAD enzymes. Future Directions: Understanding the complexity of autoantibodies in RA is critical to develop tools to clearly define their origin, identify drivers of disease propagation, and develop novel therapeutics. Antioxid. Redox Signal. 36, 389-409.

An auto-antibody identified from phenotypic directed screening platform shows host immunity against EV-A71 infection

Background

Enterovirus A71 (EV-A71) is a neurotropic virus which may cause severe neural complications, especially in infants and children. The clinical manifestations include hand-foot-and-mouth disease, herpangina, brainstem encephalitis, pulmonary edema, and other severe neurological diseases. Although there are some vaccines approved, the post-marketing surveillance is still unavailable. In addition, there is no antiviral drugs against EV-A71 available.

Methods

In this study, we identified a novel antibody that could inhibit viral growth through a human single chain variable fragment (scFv) library expressed in mammalian cells and panned by infection with lethal dose of EV-A71.

Results

We identified that the host protein α-enolase (ENO1) is the target of this scFv, and anti-ENO1 antibody was found to be more in mild cases than severe EV-A71 cases. Furthermore, we examined the antiviral activity in a mouse model. We found that the treatment of the identified 07-human IgG₁ antibody increased the survival rate after virus challenge, and significantly decreased the viral RNA and the level of neural pathology in brain tissue.

Conclusions

Collectively, through a promising intracellular scFv library expression and screening system, we found a potential scFv/antibody which targets host protein ENO1 and can interfere with the infection of EV-A71. The results indicate that the usage and application of this antibody may offer a potential treatment against EV-A71 infection.

Evaluation of autoantibodies against vimentin and α-enolase in rheumatoid arthritis patients

Introduction

Rheumatoid arthritis (RA) is categorized as an autoimmune disease with a frequency of 0.2–1% worldwide. It is reported that various autoantibodies are produced in the RA population, particularly against citrullinated peptides. Among various candidate markers for RA diagnosis, the citrullinated proteins have the highest specificity and sensitivity for both diagnosis and prognosis of RA. Anti-mutated citrullinated vimentin and α-enolase constitute a new class of autoantibodies for early detection of RA.

Material and methods

45 serum samples and 19 synovial fluid (SF) specimens collected from RA patients were considered for American College of Rheumatology criteria and 20 serum samples and 10 SF specimens were provided from healthy subjects as a control group. To assess the quantity of anti-citrullinated protein antibodies (ACPA), anti-mutated citrullinated vimentin (MCV) and anti-α-enolase in the serum and SF of RA patients were determined by the enzyme-linked immunosorbent assay (ELISA) method. For the evaluation of disease activity and joint destruction, we used the Disease Activity Score of 28 joints based on erythrocyte sedimentation rate (ESR) Disease Activity Score 28 (DAS28). Furthermore, to measure the molecular weight of vimentin and α-enolase, electrophoresis on 10% SDS-PAGE was performed as described before.

Results

The anti-α-enolase level among serum samples from RA patients was significantly higher than in healthy subjects (4.49 ±0.20 ng/ml vs. 0.76 ±0.12 ng/ml) (p < 0.001). There was a direct relation between α-enolase quantity and (rheumatoid factor) RF and C-reactive protein (CRP) levels. The mean ESR value in positive and negative ACPA patients was 38.2 ±22.6 mm/h and 9.2 ±5.8 mm/h respectively (p < 0.0001). The mean DAS28-ESR was 3.3. The level of anti-MCV in the serum of RA patients (244.6 ±53.3 U/ml) was higher than in serum of the healthy group (148.73 ±71.8) (p < 0.0001). The level of anti-MCV in the SF of patients was 687.5 ±148.4 U/ml.

Conclusions

In conclusion, both autoantibodies against MCV and α-enolase are two important markers that increase in serum and SF of RA patients and are specific for diagnosis of RA disease.

Insights into the autoimmune aspect of premature ovarian insufficiency

Premature ovarian insufficiency (POI) refers to a continuum of decreasing ovarian function in women before the age of 40. To date, the cause of POI in the majority of cases remain unresolved. Many cases has been linked to genetic, toxic, infections, enzymatic and iatrogenic causes. A key function of the immune system is to identify and differentiate "self" and "non self" i.e. tolerance. Loss of self-tolerance results in an immune response against self-tissues and thus autoimmunity. Various investigations have highlighted the role of autoimmunity and its pertinence to POI. Several potential immune antigenic targets in the ovary have been reported to be involved in autoantibody induced autoimmune attack. The presence of lymphocytic oöphorits in ovarian samples of patients with POI provides histopathological evidence of autoimmune ovarian involvement. Finally, POI is strongly associated with other autoimmune conditions including for instance Addison disease, autoimmune polyglandular syndrome (APS) -1, APS-4, hypothyroidism, and diabetes mellitus among other autoimmune diseases. Taken together, these lines of evidence provide strong basis that support the role of autoimmunity as a potential cause of disease etiopathogenesis. Continuing research is increasingly providing more insight into the complex disease process. The aim of this review is to summarize the current literature related to the autoimmune nature of POI.

Reaction of antibodies to Campylobacter jejuni and cytolethal distending toxin B with tissues and food antigens

BACKGROUND

The bacteria Campylobacter jejuni (C. jejuni) is commonly associated with Guillane-Barré syndrome (GBS) and irritable bowel syndrome (IBS), but studies have also linked it with Miller Fisher syndrome, reactive arthritis and other disorders, some of which are autoimmune. It is possible that C. jejuni and its toxins may be cross-reactive with some human tissues and food antigens, potentially leading to autoimmune responses.

AIM

To measure the immune reactivity of C. jejuni and C. jejuni cytolethal distending toxin (Cdt) antibodies with tissue and food antigens to examine their role in autoimmunities.

METHODS

Using enzyme-linked immunosorbent assay (ELISA) methodology, specific antibodies made against C. jejuni and C. jejuni Cdt were applied to a variety of microwell plates coated with 45 tissues and 180 food antigens. The resulting immunoreactivities were compared to reactions with control wells coated with human serum albumin (HSA) which were used as negative controls and with wells coated with C. jejuni lysate or C. jejuni Cdt which served as positive controls.

RESULTS

At 3 SD above the mean of control wells coated with HSA or 0.41 OD, the mouse monoclonal antibody made against C. jejuni showed moderate to high reactions with zonulin, somatotropin, acetylcholine receptor, β-amyloid and presenilin. This immune reaction was low with an additional 25 tissue antigens including asialoganglioside, and the same antibody did not react at all with another 15 tissue antigens. Examining the reaction between C. jejuni antibody and 180 food antigens, we found insignificant reactions with 163 foods but low to high immune reactions with 17 food antigens. Similarly, we examined the reaction of C. jejuni Cdt with the same tissues and food antigens. The strongest reactions were observed with zonulin, intrinsic factor and somatotropin. The reaction was moderate with 9 different tissue antigens including thyroid peroxidase, and reaction was low with another 10 different antigens, including neuronal antigens. The reaction of C. jejuni Cdt antibody with an additional 23 tissue antigens was insignificant. Regarding the reaction of C. jejuni Cdt antibody with different food antigens, 160 out of 180 foods showed insignificant reactions, while 20 foods showed reactions ranging from low to high.

CONCLUSION

Our findings indicate that C. jejuni and its Cdt may play a role in inflammation and autoimmunities beyond the gut.

Hypoxia, oxidative stress and inflammation

Inflammatory Arthritis is characterized by synovial proliferation, neovascularization and leukocyte extravasation leading to joint destruction and functional disability. Efficiency of oxygen supply to the synovium is poor due to the highly dysregulated synovial microvasculature. This along with the increased energy demands of activated infiltrating immune cells and inflamed resident cells leads to an hypoxic microenvironment and mitochondrial dysfunction. This favors an increase of reactive oxygen species, leading to oxidative damage which further promotes inflammation. In this adverse microenvironment synovial cells adapt to generate energy and switch their cell metabolism from a resting regulatory state to a highly metabolically active state which allows them to produce essential building blocks to support their proliferation. This metabolic shift results in the accumulation of metabolic intermediates which act as signaling molecules that further dictate the inflammatory response. Understanding the complex interplay between hypoxia-induced signaling pathways, oxidative stress and mitochondrial function will provide better insight into the underlying mechanisms of disease pathogenesis.

A set of conformationally well-defined L/D-peptide epitopes provides a serological bar code for autoantibody subtypes

Which conformational parameters lead to an antibody-affine peptide antigen? And in how many different conformations can we actually present the respective conformational epitope? To provide answers from a chemical point of view, we direct the bending and tethering of peptide backbones by the utilisation of a hydrophobic cluster, disulfides, and d-amino acids. Each mutation is employed pairwise on directly opposite sides of a β-hairpin. In combination, these synthetic modules guide the formation of complementary β-sheet-like structures, whereby the oppositely configured (l/d-)bi-disulfide pairs form with high regioselectivity. The conformational properties of the peptides are assessed by NMR spectroscopy and correlated with their antibody affinity in ELISA. From a pool of thus designed peptide antigens with distinctive complementary affinities against known rheumatoid arthritis (RA) autoantibodies, we select a set of epitopes for an immunoassay with sera of RA patients. We want to put emphasis on the idea, that the different conformational properties of the chosen antigens, containing the same epitope sequence, are mirrored in the distribution of autoantibody subtypes (or of the antibody polyclonality, respectively). Such directly comparable information can only be delivered by a set of peptides, rather than a single one. The hairpin-restriction technology of l/d-configured bi-disulfide amino acid pairs is not limited to RA but applicable to other shape-persistent hairpin motifs which are supposed to identify subgroups of protein receptors.

Methodology and Applications of Disease Biomarker Identification in Human Serum

Biomarkers are biomolecules that serve as indicators of biological and pathological processes, or physiological and pharmacological responses to a drug treatment. Because of the high abundance of albumin and heterogeneity of plasma lipoproteins and glycoproteins, biomarkers are difficult to identify in human serum. Due to the clinical significance the identification of disease biomarkers in serum holds great promise for personalized medicine, especially for disease diagnosis and prognosis. This review summarizes some common and emerging proteomics techniques utilized in the separation of serum samples and identification of disease signatures. The practical application of each protein separation or identification technique is analyzed using specific examples. Biomarkers of cancers of prostate, breast, ovary, and lung in human serum have been reviewed, as well as those of heart disease, arthritis, asthma, and cystic fibrosis. Despite the advancement of technology few biomarkers have been approved by the Food and Drug Administration for disease diagnosis and prognosis due to the complexity of structure and function of protein biomarkers and lack of high sensitivity, specificity, and reproducibility for those putative biomarkers. The combination of different types of technologies and statistical analysis may provide more effective methods to identify and validate new disease biomarkers in blood.

Nutrition and fasting mimicking diets in the prevention and treatment of autoimmune diseases and immunosenescence

Complex and coordinated signals are necessary to initiate and sustain the activation, proliferation, and differentiation of lymphocytes. These signals, which are known to determine T-cell fate and function, also depend on the metabolic state of the organism. Recent studies indicate that both the type and levels of nutrients can influence the generation, survival and function of lymphocytes and therefore can affect several autoimmune diseases. Here, we review the dysregulation of lymphocytes during autoimmunity and aging, the mechanisms associated with loss of immune function, and how fasting mimicking diets and other dietary interventions affect autoimmunity and immunosenescence.

Immunometabolism of human autoimmune diseases: from metabolites to extracellular vesicles

Immunometabolism focuses on the mechanisms regulating the impact of metabolism on lymphocyte activity and autoimmunity outbreak. The adipose tissue is long known to release adipokines, either pro- or anti-inflammatory factors bridging nutrition and immune function. More recently, adipocytes were discovered to also release extracellular vesicles (EVs) containing a plethora of biological molecules, including metabolites and microRNAs, which can regulate cell function/metabolism in distant tissues, suggesting that immune regulatory function by the adipose tissue may be far more complex than originally thought. Moreover, EVs were also identified as important mediators of immune cell-to-cell communication, adding a further microenvironmental mechanism of plasticity to fine-tune specific lymphocyte responses. This Review will first focus on the known mechanisms by which metabolism impacts immune function, presenting a systemic (nutrition and long-ranged adipokines) and a cellular point of view (metabolic pathway derangement in autoimmunity). It will then discuss the new discoveries concerning how EVs may act as nanometric vehicles integrating immune/metabolic responses at the level of the extracellular environment and affecting pathological processes.

Impact of Autoantibodies against Glycolytic Enzymes on Pathogenicity of Autoimmune Retinopathy and Other Autoimmune Disorders

Autoantibodies (AAbs) against glycolytic enzymes: aldolase, α-enolase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase are prevalent in sera of patients with blinding retinal diseases, such as paraneoplastic [cancer-associated retinopathy (CAR)] and non-paraneoplastic autoimmune retinopathies, as well as in many other autoimmune diseases. CAR is a degenerative disease of the retina characterized by sudden vision loss in patients with cancer and serum anti-retinal AAbs. In this review, we discuss the widespread serum presence of anti-glycolytic enzyme AAbs and their significance in autoimmune diseases. There are multiple mechanisms responsible for antibody generation, including the innate anti-microbial response, anti-tumor response, or autoimmune response against released self-antigens from damaged, inflamed tissue. AAbs against enolase, GADPH, and aldolase exist in a single patient in elevated titers, suggesting their participation in pathogenicity. The lack of restriction of AAbs to one disease may be related to an increased expression of glycolytic enzymes in various metabolically active tissues that triggers an autoimmune response and generation of AAbs with the same specificity in several chronic and autoimmune conditions. In CAR, the importance of serum anti-glycolytic enzyme AAbs had been previously dismissed, but the retina may be without pathological consequence until a failure of the blood–retinal barrier function, which would then allow pathogenic AAbs access to their retinal targets, ultimately leading to damaging effects.

Metabolic control of immune tolerance in health and autoimmunity

The filed that links immunity and metabolism is rapidly expanding. The adipose tissue, by secreting a series of immune regulators called adipokines, represents the common mediator linking metabolic processes and immune system functions. The dysregulation of adipokine secretion, occurring in obese individuals or in conditions of malnutrition or dietary restriction, affects the activity of immune cells resulting in inflammatory autoimmune responses or increased susceptibility to infectious diseases. Alterations of cell metabolism that characterize several autoimmune diseases strongly support the idea that the immune tolerance is also regulated by metabolic pathways. The comprehension of the molecular mechanisms underlying these alterations may lead to the development of novel therapeutic strategies to control immune cell differentiation and function in conditions of autoimmunity.

Rhamnose Links Moonlighting Proteins to Membrane Phospholipid in Mycoplasmas

Many proteins that have a primary function as a cytoplasmic protein are known to have the ability to moonlight on the surface of nearly all organisms. An example is the glycolytic enzyme enolase, which can be found on the surface of many types of cells from bacteria to human. Surface enolase is not enzymatic because it is monomeric and oligomerization is required for glycolytic activity. It can bind various molecules and activate plasminogen. Enolase lacks a signal peptide and the mechanism by which it attaches to the surface is unknown. We found that treatment of whole cells of the murine pathogen Mycoplasma pulmonis with phospholipase D released enolase and other common moonlighting proteins. Glycostaining suggested that the released proteins were glycosylated. Cytoplasmic and membrane-bound enolase was isolated by immunoprecipitation. No post-translational modification was detected on cytoplasmic enolase, but membrane enolase was associated with lipid, phosphate and rhamnose. Treatment with phospholipase released the lipid and phosphate from enolase but not the rhamnose. The site of rhamnosylation was identified as a glutamine residue near the C-terminus of the protein. Rhamnose has been found in all species of mycoplasma examined but its function was previously unknown. Mycoplasmas are small bacteria with have no peptidoglycan, and rhamnose in these organisms is also not associated with polysaccharide. We suggest that rhamnose has a central role in anchoring proteins to the membrane by linkage to phospholipid, which may be a general mechanism for the membrane association of moonlighting proteins in mycoplasmas and perhaps other bacteria.

Soluble alpha-enolase activates monocytes by CD14-dependent TLR4 signalling pathway and exhibits a dual function

Rheumatoid arthritis (RA) is the most common form of chronic inflammatory rheumatism. Identifying auto-antigens targeted by RA auto-antibodies is of major interest. Alpha-enolase (ENO1) is considered to be a pivotal auto-antigen in early RA but its pathophysiologic role remains unknown. The main objective of this study was to investigate the in vitro effects of soluble ENO1 on peripheral blood mononuclear cells (PBMC) from healthy donors and RA patients in order to determine the potential pathogenic role of ENO1. ELISA, transcriptomic analysis, experiments of receptor inhibition and flow cytometry analysis were performed to determine the effect, the target cell population and the receptor of ENO1. We showed that ENO1 has the ability to induce early production of pro-inflammatory cytokines and chemokines with delayed production of IL-10 and to activate the innate immune system. We demonstrated that ENO1 binds mainly to monocytes and activates the CD14-dependent TLR4 pathway both in healthy subjects and in RA patients. Our results establish for the first time that ENO1 is able to activate in vitro the CD14-dependent TLR4 pathway on monocytes involving a dual mechanism firstly pro-inflammatory and secondly anti-inflammatory. These results contribute to elucidating the role of this auto-antigen in the pathophysiologic mechanisms of RA.

Targeting of surface alpha-enolase inhibits the invasiveness of pancreatic cancer cells

Pancreatic Ductal Adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by rapid progression, invasiveness and resistance to treatment. We have previously demonstrated that most PDAC patients have circulating antibodies against the glycolytic enzyme alpha-enolase (ENO1), which correlates with a better response to therapy and survival. ENO1 is a metabolic enzyme, also expressed on the cell surface where it acts as a plasminogen receptor. ENO1 play a crucial role in cell invasion and metastasis by promoting plasminogen activation into plasmin, a serine-protease involved in extracellular matrix degradation. The aim of this study was to investigate the role of ENO1 in PDAC cell invasion. We observed that ENO1 was expressed on the cell surface of most PDAC cell lines. Mouse anti-human ENO1 monoclonal antibodies inhibited plasminogen-dependent invasion of human PDAC cells, and their metastatic spreading in immunosuppressed mice was inhibited. Notably, a single administration of Adeno-Associated Virus (AAV)-expressing cDNA coding for 72/1 anti-ENO1 mAb reduced the number of lung metastases in immunosuppressed mice injected with PDAC cells. Overall, these data indicate that ENO1 is involved in PDAC cell invasion, and that administration of an anti-ENO1 mAb can be exploited as a novel therapeutic option to increase the survival of metastatic PDAC patients.

Antibodies to native and citrullinated RA33 (hnRNP A2/B1) challenge citrullination as the inciting principle underlying loss of tolerance in rheumatoid arthritis

BACKGROUND

Anti-citrullinated protein antibodies (ACPAs) are the hallmark of rheumatoid arthritis (RA). Protein citrullination is believed to drive autoantigen selection in RA. Nonetheless, several autoantigens in RA are targeted as native (unmodified) proteins. Here, the study of hnRNP A2/B1 (RA33) provides a framework to understand the humoral response to native and citrullinated autoantigens in RA.

METHODS

RA synovial fluid (SF) cells were analysed by immunoblotting and mass spectrometry. RA33 was cloned from RASF cells and splice variants expressed as recombinant proteins. Antibodies against native and citrullinated RA33 were characterised by ELISA, immunoblotting and immunoprecipitation.

RESULTS

RA33 is citrullinated in the rheumatoid joint and targeted either as a citrullinated or native protein in distinct patient subsets with RA. A novel splice variant (hnRNP B1b) previously associated with disease initiation in experimental arthritis was identified in the RA joint and acts as the major target of the anti-RA33 response. Antibodies exclusively targeting citrullinated RA33 were positively associated with disease duration and erosive disease. In contrast, anti-(native) RA33 antibodies were detected almost exclusively in early RA and identified patients with low radiographic erosion scores. Finally, a unique subset of double-reactive patients demonstrated intermediate severity, but rapid disease progression, suggesting a transitional disease phase in the evolution of an anti-native protein antibody to ACPA response in RA.

CONCLUSIONS

These data suggest that native and citrullinated proteins targeted by autoantibodies in RA may be part of a single antibody system and challenge the paradigm of citrullination as the unifying principle underlying loss of tolerance in RA.

Circulating antibodies to α-enolase and phospholipase A2 receptor and composition of glomerular deposits in Japanese patients with primary or secondary membranous nephropathy

Background

Phospholipase A₂ receptor (PLA₂R) is recognized as a target antigen in primary membranous nephropathy (MN); Anti-α-enolase antibody in primary and secondary MN has been proposed, however, little is known about the potential contribution of α-enolase to the pathogenesis of MN.

Methods

We evaluated circulating antibodies to α-enolase by a dot blotting system and PLA₂R by indirect immunofluorescence, and glomerular deposition of these proteins in 25 patients with primary MN, 20 patients with secondary MN, 44 patients with collagen disease or severe infection, 60 patients with nephritis (each ten patients of IgA nephropathy, focal segmental gloemrulosclerosis, minimal change nephrotic syndrome, membranoproliferative glomeurlonephritis, diabetic glomerulosclerosis, and tubulointerstitial nephritis) as disease control, and 20 healthy subjects.

Results

In primary MN, 18 of 25 sera (72 %) showed anti-α-enolase antibody (IgG1 and IgG4, 11 pts; IgG4 alone, six pts; IgG1 alone, one pt). In secondary MN, 15 of 20 sera (75 %) contained anti-α-enolase antibody (IgG1 and IgG3, 13 pts; IgG3 alone, two pts). No circulating anti-α-enolase antibody was found in 44 collagen diseases or septic patients, 60 nephritis without MN, and 20 healthy subjects. Twelve of 25 sera (48 %) from patients with primary MN were positive for anti-PLA₂R antibody, whereas all patients with secondary MN were negative. Eight of the 12 PLA₂R-positive patients (67 %) with primary MN also had anti α-enolase antibody. Although PLA₂R antigen was present in a subepithelial pattern in 10 of 19 (52 %) patients with primary MN, α-enolase was never detected in glomerular deposits in 19 and ten patients with primary and secondary MN, respectively.

Conclusions

Circulating anti-α-enolase antibodies are highly present in both primary and secondary MN (about 70 %, respectively), while anti-PLA₂R antibodies are specific for primary MN (48 %) with a prevalence apparently lower in the Japanese population than in Chinese and Caucasian populations. The absence of α-enolase from subepithelial immune deposits suggests that anti-α-enolase antibodies do not contribute directly to immune-deposit formation, although they may have other pathogenic effects.

Electronic supplementary material

The online version of this article (doi:10.1007/s10157-016-1235-2) contains supplementary material, which is available to authorized users.

The Anti-inflammatory Effect of GV1001 Mediated by the Downregulation of ENO1-induced Pro-inflammatory Cytokine Production

GV1001 is a peptide derived from the human telomerase reverse transcriptase (hTERT) sequence that is reported to have anti-cancer and anti-inflammatory effects. Enolase1 (ENO1) is a glycolytic enzyme, and stimulation of this enzyme induces high levels of pro-inflammatory cytokines from concanavalin A (Con A)-activated peripheral blood mononuclear cells (PBMCs) and ENO1-expressing monocytes in healthy subjects, as well as from macrophages in rheumatoid arthritis (RA) patients. Therefore, this study investigated whether GV1001 downregulates ENO1-induced pro-inflammatory cytokines as an anti-inflammatory peptide. The results showed that GV1001 does not affect the expression of ENO1 in either Con A-activated PBMCs or RA PBMCs. However, ENO1 stimulation increased the production of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, and these cytokines were downregulated by pretreatment with GV1001. Moreover, p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB were activated when ENO1, on the surface of Con A-activated PBMCs and RA PBMCs, was stimulated, and they were successfully suppressed by pre-treatment with GV1001. These results suggest that GV1001 may be an effective anti-inflammatory peptide that downregulates the production of pro-inflammatory cytokines through the suppression of p38 MAPK and NF-κB activation following ENO1 stimulation.

A GC-MS Based Metabonomics Study of Rheumatoid Arthritis and the Interventional Effects of the Simiaowan in Rats

Simiaowan (SMW) is a famous Chinese prescription widely used in clinical treatment of rheumatoid arthritis (RA). The aim of the present study is to determine novel biomarkers to increase the current understanding of RA mechanisms, as well as the underlying therapeutic mechanism of SMW, in RA-model rats. Plasma extracts from control, RA model, and SMW-treated rats were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). An orthogonal partial least-square discriminant analysis (OPLS-DA) model was created to detect metabolites that were expressed in significantly different amounts between the RA model and the control rats and investigate the therapeutic effect of SMW. Metabonomics may prove to be a valuable tool for determining the efficacy of complex traditional prescriptions.

New autoantibodies associated with rheumatoid arthritis recognize posttranslationally modified self-proteins

Citrullination, carbamylation and oxidation are posttranslational modifications of proteins that produce neoepitopes. Rheumatoid arthritis (RA) is an autoimmune disease of which one distinctive feature is the development of B-cell-mediated immunity against these neoepitopes. Antibodies to citrullinated proteins (ACPAs) were identified nearly two decades ago and are now widely used in clinical practice. The identification of additional citrullinated proteins as potential autoantibody targets has suggested new pathophysiological hypotheses and prompted studies of potential associations with disease severity or specific disease patterns. Carbamylation is a nonenzymatic posttranslational modification that produces homocitrullines, against which newly identified autoantibodies different from ACPAs have been found in over 15% of patients with RA. Finally, the development of antibodies to oxidized type II collagen reflects immunization against collagen modified by oxidation in relation to intraarticular oxidative stress. These new autoantibodies are both sensitive and specific and may therefore serve as early disease markers and as useful tools for therapeutic monitoring.

Discovery of serum proteomic biomarkers for prediction of response to moxibustion treatment in rats with collagen-induced arthritis: an exploratory analysis

OBJECTIVE

To examine the possible impact of moxibustion on the serum proteome of the collagen-induced arthritis (CIA) rat model.

MATERIALS AND METHODS

Thirty-six male Sprague-Dawley rats were included in this experiment. The CIA animal model was prepared by injection of type II bovine collagen in Freund's adjuvant on the first and seventh day. The 36 rats were randomly divided into two groups: the untreated CIA group (control), and the CIA plus treatment with moxibustion (CIA+moxi) group. Moxibustion was administered daily at ST36 and BL23 for 7, 14 or 21 days (n=12 rats each). Arthritis score was used to assess the severity of arthritis. At the end of each 7 day treatment, blood samples from the control group and the CIA+moxi group were collected. After removal of high abundance proteins from serum samples, two-dimensional gel combined with matrix-assisted laser desorption ionisation time-of-flight MS/MS (MALDI-TOF-MS/MS) techniques were performed to examine serum protein expression patterns of the CIA rat model with and without moxibustion treatment. In addition, the relevant proteins were further analysed with the use of bioinformatics analysis.

RESULTS

Moxibustion significantly decreased arthritis severity in the rats in the CIA+moxi group, when compared with the rats in the CIA group 35 days after the first immunisation (p=0.001). Seventeen protein spots which changed >1.33 or <0.77 at p<0.05 using Bonferonni correction for multiple testing were found to be common to all three comparisons, and these proteins were used for classification of functions using the Gene Ontology method. Consequently, with the use of the Ingenuity Pathway Analysis, the top canonical pathways and a predicted proteomic network related to the moxibustion effect of CIA were established.

CONCLUSIONS

Using the proteomics technique, we have identified novel candidate proteins that may be involved in the mechanisms of action underlying the beneficial effects of moxibustion in rats with CIA. Our findings suggest that immune responses and metabolic processes may be involved in mediating the effects of moxibustion. Moreover, periodxiredoxin I (PRDX1) and inositol 1,4,5-triphosphate receptor (IP3R) may be potential targets.

Prophylactic Injection of Recombinant Alpha-Enolase Reduces Arthritis Severity in the Collagen-Induced Arthritis Mice Model

Objective

To evaluate the ability of the glycolytic enzyme alpha-enolase (ENO1) or its immunodominant peptide (pEP1) to reduce the severity of CIA in DBA/1 mice when injected in a prophylactic way.

Methods

Mice were treated with mouse ENO1 or pEP1 one day prior to collagen II immunization. Clinical assessment was evaluated using 4 parameters (global and articular scores, ankle thickness and weight). Titers of serum anti-ENO1, anti-cyclic citrullinated peptides (anti-CCP) and anti-CII (total IgG and IgG1/IgG2a isotypes) antibodies were measured by ELISA at different time-points. Disease activity was assessed by histological analysis of both anterior and hind paws at the end of experimentation.

Results

Prophylactic injection of 100 μg of ENO1 reduced severity of CIA. Serum levels of anti-CII antibodies were reduced in ENO1-treated mice. Concordantly, ENO1-treated mice joints presented less severe histological signs of arthritis. ENO1 did not induce a shift toward a Th2 response since IgG1/IgG2a ratio of anti-CII antibodies remained unchanged and IL-4 serum levels were similar to those measured in the control group.

Conclusions

Pre-immunization with ENO1 or its immunodominant peptide pEP1 reduces CIA severity at the clinical, immunological and histological levels. Effects of pEP1 were less pronounced. This immunomodulatory effect is associated with a reduction in anti-CII antibodies production but is not due to a Th1/Th2 shift.

Association between anti-Porphyromonas gingivalis or anti-α-enolase antibody and severity of periodontitis or rheumatoid arthritis (RA) disease activity in RA

Background

Periodontitis (PD) has been reported to be associated with rheumatoid arthritis (RA). Porphyromonas gingivalis (P. gingivalis) is a gram-negative anaerobic bacterium that is recognized as one of the major pathogenic organisms in PD and is the only bacterium known to express peptidylarginine deiminase (PAD). Antibody against human α-enolase (ENO1) is one of the autoantibodies in RA. ENO1 is a highly conserved protein, and could be a candidate molecule for molecular mimicry between bacterial and human proteins. In the present study, we measured serum antibody against P. gingivalis and human ENO1 in patients with RA and investigated their association with the severity of PD or disease activity of RA.

Methods

Two hundred, forty-eight patients with RA and 85 age- and sex-matched healthy controls were evaluated by rheumatologic and periodontal examinations. The serum levels of anti-P. gingivalis and anti-ENO1 antibodies were measured by an enzyme-linked immunosorbent assay (ELISA).

Results

Patients with RA had significantly higher levels of anti-P. gingivalis and anti-ENO1 antibody titers than the controls (p = 0.002 and 0.0001, respectively). Anti-P. gingivalis antibody titers significantly correlated with anti-ENO1 antibody titers in RA patients (r = 0.30, p < 0.0001). There were significant correlations between anti-P. gingivalis antibody titers and the gingival index (GI), probing pocket depth (PPD), bleeding on probing (BOP) and clinical attachment level (CAL) (p = 0.038, 0.004, 0.004 and 0.002, respectively) in RA. Anti-P. gingivalis antibody titers were not correlated with disease activity score 28 (DAS28) or anti-CCP titer. However, anti-ENO1 antibody titers were significantly correlated not only with the periodontal indices, such as PPD, BOP, and CAL (p = 0.013, 0.023 and 0.017, respectively), but also RA clinical characteristics, such as DAS28, anti-CCP titer, and ESR (p = 0.009, 0.015 and 0.001, respectively).

Conclusion

Anti-P. gingivalis and anti-ENO1 antibody titers were correlated with the severity of PD in RA. Anti-ENO1 antibody titers, but not anti-P. gingivalis antibody titers, were further associated with RA disease activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0647-6) contains supplementary material, which is available to authorized users.

An Optimized Fluorescence-Based Bidimensional Immunoproteomic Approach for Accurate Screening of Autoantibodies

Serological proteome analysis (SERPA) combines classical proteomic technology with effective separation of cellular protein extracts on two-dimensional gel electrophoresis, western blotting, and identification of the antigenic spot of interest by mass spectrometry. A critical point is related to the antigenic target characterization by mass spectrometry, which depends on the accuracy of the matching of antigenic reactivities on the protein spots during the 2D immunoproteomic procedures. The superimposition, based essentially on visual criteria of antigenic and protein spots, remains the major limitation of SERPA. The introduction of fluorescent dyes in proteomic strategies, commonly known as 2D-DIGE (differential in-gel electrophoresis), has boosted the qualitative capabilities of 2D electrophoresis. Based on this 2D-DIGE strategy, we have improved the conventional SERPA by developing a new and entirely fluorescence-based bi-dimensional immunoproteomic (FBIP) analysis, performed with three fluorescent dyes. To optimize the alignment of the different antigenic maps, we introduced a landmark map composed of a combination of specific antibodies. This methodological development allows simultaneous revelation of the antigenic, landmark and proteomic maps on each immunoblot. A computer-assisted process using commercially available software automatically leads to the superimposition of the different maps, ensuring accurate localization of antigenic spots of interest.

Characterization of proteins regulated by interleukin-4 in 3T3-L1 adipocytes

Obesity is closely associated with metabolic syndrome, type 2 diabetes mellitus (T2DM) and cardiovascular diseases. Our previous reports uncover the significant associations between interleukin-4 (IL-4)/IL-4 receptor genotypes and T2DM, as well as IL-4 genotypes and high density lipoprotein-cholesterol. Theses observations suggest that IL-4 harbors the capacity to regulate lipid metabolism. The present study is aimed at further elucidating regulatory roles of IL-4 to lipid metabolism by identifying putative proteins in 3T3-L1 adipocytes which are differentially expressed under IL-4 treatment. Proteins in mature 3T3-L1 adipocytes with altered expression levels under IL-4 treatment were identified by proteomic strategy. Our results revealed that IL-4 up-regulated levels of ATP synthase δ chain, Cytochrome c reductase, Pyrophsphatase and Vimentin, whereas, Alpha-enolase, Gelsolin, Vinculin and Valosin were down-regulated. These observations suggest that IL-4 promotes energy metabolism and inhibit lipid deposits in adipocytes by up-regulating proteins accelerating ATP synthesis. Our results suggest that IL-4 facilitates adipocytes metabolism to catabolism with a favorable condition for lipolysis. These catabolized lipids in adipocytes triggered by IL-4 might either be released into periphery or metabolized intracellularlly, and modulate systemic energy metabolism.

The danger model approach to the pathogenesis of the rheumatic diseases

The danger model was proposed by Polly Matzinger as complement to the traditional self-non-self- (SNS-) model to explain the immunoreactivity. The danger model proposes a central role of the tissular cells' discomfort as an element to prime the immune response processes in opposition to the traditional SNS-model where foreignness is a prerequisite. However recent insights in the proteomics of diverse tissular cells have revealed that under stressful conditions they have a significant potential to initiate, coordinate, and perpetuate autoimmune processes, in many cases, ruling over the adaptive immune response cells; this ruling potential can also be confirmed by observations in several genetically manipulated animal models. Here, we review the pathogenesis of rheumatic diseases such as systemic lupus erythematous, rheumatoid arthritis, spondyloarthritis including ankylosing spondylitis, psoriasis, and Crohn's disease and provide realistic approaches based on the logic of the danger model. We assume that tissular dysfunction is a prerequisite for chronic autoimmunity and propose two genetically conferred hypothetical roles for the tissular cells causing the disease: (A) the Impaired cell and (B) the paranoid cell. Both roles are not mutually exclusive. Some examples in human disease and in animal models are provided based on current evidence.

T-cell metabolism in autoimmune disease

Cancer cells have long been known to fuel their pathogenic growth habits by sustaining a high glycolytic flux, first described almost 90 years ago as the so-called Warburg effect. Immune cells utilize a similar strategy to generate the energy carriers and metabolic intermediates they need to produce biomass and inflammatory mediators. Resting lymphocytes generate energy through oxidative phosphorylation and breakdown of fatty acids, and upon activation rapidly switch to aerobic glycolysis and low tricarboxylic acid flux. T cells in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) have a disease-specific metabolic signature that may explain, at least in part, why they are dysfunctional. RA T cells are characterized by low adenosine triphosphate and lactate levels and increased availability of the cellular reductant NADPH. This anti-Warburg effect results from insufficient activity of the glycolytic enzyme phosphofructokinase and differentiates the metabolic status in RA T cells from those in cancer cells. Excess production of reactive oxygen species and a defect in lipid metabolism characterizes metabolic conditions in SLE T cells. Owing to increased production of the glycosphingolipids lactosylceramide, globotriaosylceramide and monosialotetrahexosylganglioside, SLE T cells change membrane raft formation and fail to phosphorylate pERK, yet hyperproliferate. Borrowing from cancer metabolomics, the metabolic modifications occurring in autoimmune disease are probably heterogeneous and context dependent. Variations of glucose, amino acid and lipid metabolism in different disease states may provide opportunities to develop biomarkers and exploit metabolic pathways as therapeutic targets.

Mycoplasma synoviae enolase is a plasminogen/fibronectin binding protein

Background

Mycoplasma synoviae is an avian pathogen that can lead to respiratory tract infections and arthritis in chickens and turkeys, resulting in serious economic losses to the poultry industry. Enolase reportedly plays important roles in several bacterial pathogens, but its role in M. synoviae has not been established. Therefore, in this study, the enolase encoding gene (eno) of M. synoviae was amplified from strain WVU1853 and expressed in E. coli BL21 cells. Then the enzymatic activity, immunogenicity and binding activity with chicken plasminogen (Plg) and human fibronectin (Fn) was evaluated.

Results

We demonstrated that the recombinant M. synoviae enolase protein (rMsEno) can catalyze the conversion of 2-phosphoglycerate (2-PGA) to phosphoenolpyruvate (PEP), the Km and Vmax values of rMsEno were 1.1 × 10⁻³ M and 0.739 μmol/L/min, respectively. Western blot and immuno-electron microscopy analyses confirmed that enolase was distributed on the surface and within the cytoplasm of M. synoviae cells. The binding assays demonstrated that rMsEno was able to bind to chicken Plg and human Fn proteins. A complement-dependent mycoplasmacidal assay demonstrated that rabbit anti–rMsEno serum had distinct mycoplasmacidal efficacy in the presence of complement, which also confirmed that enolase was distributed on the surface of M. synoviae. An inhibition assay showed that the adherence of M. synoviae to DF-1 cells pre-treated with Plg could be effectively inhibited by treatment with rabbit anti-rMsEno serum.

Conclusion

These results reveal that M. synoviae enolase has good catalytic activity for conversion of 2-PGA to PEP, and binding activity with chicken Plg and human Fn. Rabbit anti–rMsEno serum displayed an obvious complement-dependent mycoplasmacidal effect and adherent inhibition effect. These results suggested that the M. synoviae enolase plays an important role in M. synoviae metabolism, and could potentially impact M. synoviae infection and immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-014-0223-6) contains supplementary material, which is available to authorized users.

Differential proteomic analysis of synovial fluid from rheumatoid arthritis and osteoarthritis patients

Background

Rheumatoid arthritis and osteoarthritis are two common musculoskeletal disorders that affect the joints. Despite high prevalence rates, etiological factors involved in these disorders remain largely unknown. Dissecting the molecular aspects of these disorders will significantly contribute to improving their diagnosis and clinical management. In order to identify proteins that are differentially expressed between these two conditions, a quantitative proteomic profiling of synovial fluid obtained from rheumatoid arthritis and osteoarthritis patients was carried out by using iTRAQ labeling followed by high resolution mass spectrometry analysis.

Results

We have identified 575 proteins out of which 135 proteins were found to be differentially expressed by ≥3-fold in the synovial fluid of rheumatoid arthritis and osteoarthritis patients. Proteins not previously reported to be associated with rheumatoid arthritis including, coronin-1A (CORO1A), fibrinogen like-2 (FGL2), and macrophage capping protein (CAPG) were found to be upregulated in rheumatoid arthritis. Proteins such as CD5 molecule-like protein (CD5L), soluble scavenger receptor cysteine-rich domain-containing protein (SSC5D), and TTK protein kinase (TTK) were found to be upregulated in the synovial fluid of osteoarthritis patients. We confirmed the upregulation of CAPG in rheumatoid arthritis synovial fluid by multiple reaction monitoring assay as well as by Western blot. Pathway analysis of differentially expressed proteins revealed a significant enrichment of genes involved in glycolytic pathway in rheumatoid arthritis.

Conclusions

We report here the largest identification of proteins from the synovial fluid of rheumatoid arthritis and osteoarthritis patients using a quantitative proteomics approach. The novel proteins identified from our study needs to be explored further for their role in the disease pathogenesis of rheumatoid arthritis and osteoarthritis.

Sartaj Ahmad and Raja Sekhar Nirujogi contributed equally to this article.

Proteomic Surveillance of Autoantigens in Relapsing Polychondritis

Relapsing polychondritis (RP) is a systemic inflammatory disease, in which autoimmunity to cartilage-related components is thought to be involved in its pathogenesis. However, the autoimmune profile in RP has not been studied fully. We therefore investigated autoantibodies/autoantigens in RP comprehensively, by 2-dimensional electrophoresis (2DE), subsequent western blotting (WB) and mass spectrometry, using cell-extracted proteins as the antigen source. As a result, we detected 15 autoantigens on 2DE-WB, and further identified five of them. On average, one RP serum recognized approximately 8 out of the 15 autoantigens. Frequencies of the autoantibodies to the 5 identified antigens of tubulin alpha ubiquitous/6, vimentin, alpha enolase, calreticulin, and colligin-1/-2 were 91%, 46%, 36%, 82%, and 36%, respectively. ELISA using recombinant proteins for them revealed that frequencies of the autoantibodies to tubulin alpha ubiquitous, vimentin, alpha enolase, calreticulin, and colligin-1 were 36%, 64%, 46%, 27%, and 18%, respectively. Our data demonstrated that the autoimmune reaction was not restricted to cartilagerelated components, rather a variety of autoimmune responses occurred in patients with RP, which may be involved in the pathophysiology of RP. In addition, the proteomic approach using cell-extracted proteins would be a powerful way to investigate autoantigens.

Identification of parvalbumin and two new thermolabile major allergens of Thunnus tonggol using a proteomics approach

BACKGROUND

The longtail tuna (Thunnus tonggol) is widely consumed in Asia. Parvalbumin, the main major allergen of fish, has been well identified in multiple fish species, yet little is known about the allergenic proteins in T. tonggol. Thus, the aim of this study was to characterize the major allergens of T. tonggol using a proteomics approach.

METHODS

Raw and boiled extracts of the fish were prepared. Fish proteins were separated by means of SDS-PAGE and two-dimensional (2-DE) electrophoresis. 1-DE immunoblotting of raw extract was performed with sera from fish-allergic patients. Ten sera were further analysed by 2-DE immunoblotting. Selected major allergenic protein spots were excised, trypsin digested and analysed by means of mass spectrometry.

RESULTS

SDS-PAGE of raw extract revealed 26 protein fractions, while boiled extract demonstrated fewer bands. The 2-DE gel profile of the raw extract further fractionated the protein bands to more than 100 distinct protein spots. 1-DE immunoblotting of raw extract exhibited two thermolabile protein fractions of 42 and 51 kDa as the major allergens, while the boiled extract only revealed a single IgE-binding band at 151 kDa. 2-DE immunoblotting of raw extract further detected numerous major IgE-reactive spots of 11-13, 42 and 51 kDa. Mass spectrometry analysis of the peptides generated from the 12, 42 and 51 kDa digested spots indicated that these spots were parvalbumin, creatine kinase and enolase, respectively.

CONCLUSIONS

In addition to parvalbumin, two new thermolabile allergens were identified as major allergenic proteins of T. tonggol. This study proved that both thermostable and thermolabile proteins are important in local tuna allergy and should be included in diagnostic strategies.

Interaction of aldehydes derived from lipid peroxidation and membrane proteins

A great variety of compounds are formed during lipid peroxidation of polyunsaturated fatty acids of membrane phospholipids. Among them, bioactive aldehydes, such as 4-hydroxyalkenals, malondialdehyde (MDA) and acrolein, have received particular attention since they have been considered as toxic messengers that can propagate and amplify oxidative injury. In the 4-hydroxyalkenal class, 4-hydroxy-2-nonenal (HNE) is the most intensively studied aldehyde, in relation not only to its toxic function, but also to its physiological role. Indeed, HNE can be found at low concentrations in human tissues and plasma and participates in the control of biological processes, such as signal transduction, cell proliferation, and differentiation. Moreover, at low doses, HNE exerts an anti-cancer effect, by inhibiting cell proliferation, angiogenesis, cell adhesion and by inducing differentiation and/or apoptosis in various tumor cell lines. It is very likely that a substantial fraction of the effects observed in cellular responses, induced by HNE and related aldehydes, be mediated by their interaction with proteins, resulting in the formation of covalent adducts or in the modulation of their expression and/or activity. In this review we focus on membrane proteins affected by lipid peroxidation-derived aldehydes, under physiological and pathological conditions.

Surface α-enolase promotes extracellular matrix degradation and tumor metastasis and represents a new therapeutic target

In previous research, we found α-enolase to be inversely correlated with progression-free and overall survival in lung cancer patients and detected α-enolase on the surface of lung cancer cells. Based on these findings, we hypothesized that surface α-enolase has a significant role in cancer metastasis and tested this hypothesis in the current study. We found that α-enolase was co-immunoprecipitated with urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor, and plasminogen in lung cancer cells and interacted with these proteins in a cell-free dot blotting assay, which can be interrupted by α-enolase-specific antibody. α-Enolase in lung cancer cells co-localized with these proteins and was present at the site of pericellular degradation of extracellular matrix components. Treatment with antibody against α-enolase in vitro suppressed cell-associated plasminogen and matrix metalloproteinase activation, collagen and gelatin degradation, and cell invasion. Examination of the effect of treatment with shRNA plasmids revealed that down regulation of α-enolase decreases extracellular matrix degradation by and the invasion capacity of lung cancer cells. Adoptive transfer of α-enolase-specific antibody to mice resulted in accumulation of antibody in subcutaneous tumor and inhibited the formation of tumor metastasis in lung and bone. This study demonstrated that surface α-enolase promotes extracellular matrix degradation and invasion of cancer cells and that targeting surface α-enolase is a promising approach to suppress tumor metastasis.

Anti-citrullinated glucose-6-phosphate isomerase peptide antibodies in patients with rheumatoid arthritis are associated with HLA-DRB1 shared epitope alleles and disease activity

To identify and characterize anti-citrullinated glucose-6-phosphate isomerase (GPI) peptide antibodies in patients with rheumatoid arthritis (RA). Nine GPI arginine-bearing peptides in human GPI protein were selected and cyclic citrullinated GPI peptides (CCG-1-9) were constructed. Samples were obtained from RA (n = 208), systemic lupus erythematosus (SLE) (n = 101), Sjögren's syndrome (SS; n = 101) and healthy controls (n = 174). Antibodies against CCG-1-9 were measured, and anti-citrullinated α-enolase-1 (CEP-1), -cyclic citrullinated peptides (CCP) and -GPI proteins antibodies were also examined. Patients with RA were genotyped for HLA-DRB1. The numbers of shared epitope (SE) alleles were counted and compared with those of the autoantibodies. Rabbit GPI was citrullinated with rabbit peptidylarginine deiminase and immunoblot analysis of RA sera performed. The levels of autoantibodies were compared before and after treatment with TNF antagonists in 58 RA patients. Anti-CCG-2, -4 and -7 antibodies were detected in 25·5, 33·2 and 37·0% patients with RA, respectively, and these antibodies were very specific for RA (specificity, 98·1-99·7%). Altogether, 44·2, 86·1 and 13·9% of RA sera were positive for anti-CEP-1, -CCP and -GPI protein antibodies, respectively. Anti-CCG-2, -4 and -7 antibodies were correlated with anti-CCP and anti-CEP-1 antibodies and with the presence of HLA-DRB1 SE alleles. Citrullinated GPI protein was detected using RA sera. Treatment with tumour necrosis factor antagonists reduced significantly the levels of anti-CCG-2 and -7 but not of anti-CEP-1 antibodies. This is the first report documenting the presence of anti-CCG antibodies in RA. Anti-CCG-2 and -7 antibodies could be considered as markers for the diagnosis of RA and its disease activity.

Bovine neonatal pancytopenia--comparative proteomic characterization of two BVD vaccines and the producer cell surface proteome (MDBK)

Background

Bovine neonatal pancytopenia (BNP) is a disease syndrome in newborn calves of up to four weeks of age, first observed in southern Germany in 2006. By now, cases have been reported in several countries around the globe. Many affected calves die within days due to multiple haemorrhages, thrombocytopenia, leukocytopenia and bone marrow depletion. A certain vaccine directed against Bovine Virus Diarrhoea Virus (BVDV) was recently shown to be associated with BNP pathogenesis. Immunized cows develop alloantibodies that are transferred to newborn calves via colostrum intake. In order to further elucidate BNP pathogenesis, the purpose of this study was to characterize and compare the protein composition of the associated vaccine to another vaccine directed against BVDV not related to BNP and the cell surface proteome of MDBK (Madin-Darby Bovine Kidney) cells, the cell line used for production of the associated vaccine.

Results

By SDS-PAGE and mass spectrometry, we were able to detect several coagulation-related and immune modulatory proteins, as well as cellular and serum derived molecules being shared between the associated vaccine and MDBK cells. Furthermore, the number of proteins identified in the BNP related vaccine was almost as high as the number of surface proteins detected on MDBK cells and exceeded the amount of proteins identified in the non-BNP related vaccine over 3.5 fold. The great amount of shared cellular and serum derived proteins confirm that the BNP associated vaccine contained many molecules originating from MDBK cells and vaccine production.

Conclusions

The respective vaccine was not purified enough to prevent the development of alloantibodies. To narrow down possible candidate proteins, those most likely to represent a trigger for BNP pathogenesis are presented in this study, giving a fundament for further analysis in future research.

Clues to the etiology of bile duct injury in biliary atresia

Biliary atresia (BA) is an infantile obstructive cholangiopathy of unknown etiology with suboptimal therapy, which is responsible for 40 to 50% of all pediatric liver transplants. Although the etiology of bile duct injury in BA in unknown, it is postulated that a pre- or perinatal viral infection initiates cholangiocyte apoptosis and release of antigens that trigger a Th1 immune response that leads to further bile duct injury, inflammation, and obstructive fibrosis. Humoral immunity and activation of the innate immune system may also play key roles in this process. Moreover, recent investigations from the murine BA model and human data suggest that regulatory T cells and genetic susceptibility factors may orchestrate autoimmune mechanisms. What controls the coordination of these events, why the disease only occurs in the first few months of life, and why a minority of infants with perinatal viral infections develop BA are remaining questions to be answered.

α-Enolase, a multifunctional protein: its role on pathophysiological situations

α-Enolase is a key glycolytic enzyme in the cytoplasm of prokaryotic and eukaryotic cells and is considered a multifunctional protein. α-enolase is expressed on the surface of several cell types, where it acts as a plasminogen receptor, concentrating proteolytic plasmin activity on the cell surface. In addition to glycolytic enzyme and plasminogen receptor functions, α-Enolase appears to have other cellular functions and subcellular localizations that are distinct from its well-established function in glycolysis. Furthermore, differential expression of α-enolase has been related to several pathologies, such as cancer, Alzheimer's disease, and rheumatoid arthritis, among others. We have identified α-enolase as a plasminogen receptor in several cell types. In particular, we have analyzed its role in myogenesis, as an example of extracellular remodelling process. We have shown that α-enolase is expressed on the cell surface of differentiating myocytes, and that inhibitors of α-enolase/plasminogen binding block myogenic fusion in vitro and skeletal muscle regeneration in mice. α-Enolase could be considered as a marker of pathological stress in a high number of diseases, performing several of its multiple functions, mainly as plasminogen receptor. This paper is focused on the multiple roles of the α-enolase/plasminogen axis, related to several pathologies.