Differences between the glycosylation patterns of haptoglobin isolated from skin scales and plasma of psoriatic patients

Psoriasis: Striving for Potential Biomarkers

Psoriasis is a chronic disease that is caused by multiple factors and is identified by itchiness, unpleasant, red, or white scaly patches on the skin, particularly on regularly chafed body regions such as the lateral areas of the limbs. Reports suggest that globally around 2%-3% of the population suffers from psoriasis. In this review, we have discussed the clinical classification of psoriasis and also the ideal characteristics of the biomarkers. An overview regarding the discovery of the biomarker and method for validating the study has been discussed. A growing body of research suggests a link to certain other systemic symptoms such as cardiovascular disorder, metabolic syndrome, and few other comorbidities such as hypertension and nonalcoholic fatty liver disease. Natural killer (NK) cells are lymphocyte cells that concentrate on the destruction of virally infected and malignant cells; these tend to produce a wide range of inflammatory cytokines, some of which are associated with the etiology of psoriasis. Detailed information on the molecular pathogenesis of psoriasis in which interleukin (IL)-17, IL-23, tumor necrosis factor-α (TNF-α), and CCL20 play a very significant role in the development of psoriasis. In this review, we have discussed an overview of the recent state of the biomarkers available for the diagnosis and treatment of psoriasis by emphasizing on the available biomarkers such as epigenomic, transcriptomic, glycomic, and metabolomic. The most recent advancements in molecular-targeted therapy utilizing biologics and oral systemic therapy (methotrexate, apremilast) enable to adequately treat the most serious psoriatic symptoms and also the studies have validated the efficacy of biologic therapy such as TNF-α antagonist (infliximab, adalimumab), IL-23 antagonist (guselkumab, risankizumab), and IL-17 antagonist (secukinumab, ixekizumab). Finally, an overview about the technological opportunities as well as various challenges has been discussed.

First bioelectronic immunoplatform for quantitative secretomic analysis of total and metastasis-driven glycosylated haptoglobin

The glycosylation status of proteins is increasingly used as biomarker to improve the reliability in the diagnosis and prognosis of diseases as relevant as cancer. This feeds the need for tools that allow its simple and reliable analysis and are compatible with applicability in the clinic. With this objective in mind, this work reports the first bioelectronic immunoplatforms described to date for the determination of glycosylated haptoglobin (Hp) and the simultaneous determination of total and glycosylated Hp. The bioelectronic immunoplatform is based on the implementation of non-competitive bioassays using two different antibodies or an antibody and a lectin on the surface of commercial magnetic microcarriers. The resulting bioconjugates are labeled with the horseradish peroxidase (HRP) enzyme, and after their magnetic capture on disposable electroplatforms, the amperometric transduction using the H2O2/hydroquinone (HQ) system allows the single or multiple detection. The developed immunoplatform achieves limits of detection (LODs) of 0.07 and 0.46 ng mL−1 for total and glycosylated Hp in buffer solution, respectively. The immunoplatform allows accurate determination using simple and relatively short protocols (approx. 75 min) of total and glycosylated Hp in the secretomes of in vitro–cultured colorectal cancer (CRC) cells with different metastatic potentials, which is not feasible, due to lack of sensitivity, by means of some commercial ELISA kits and Western blot methodology.

Graphical abstract

Rapid Evaluation of the Extent of Haptoglobin Glycosylation Using Orthogonal Intact-Mass MS Approaches and Multivariate Analysis

Intact-mass measurements are becoming increasingly popular in mass spectrometry (MS) based protein characterization, as they allow the entire complement of proteoforms to be evaluated within a relatively short time. However, applications of this approach are currently limited to systems exhibiting relatively modest degrees of structural diversity, as the high extent of heterogeneity frequently prevents straightforward MS measurements. Incorporation of limited charge reduction into electrospray ionization (ESI) MS is an elegant way to obtain meaningful information on most heterogeneous systems, yielding not only the average mass of the protein but also the mass range populated by the entire complement of proteoforms. Application of this approach to characterization of two different phenotypes of haptoglobin (1-1 and 2-1) provides evidence of a significant difference in their extent of glycosylation (with the glycan load of phenotype 2-1 being notably lighter) despite a significant overlap of their ionic signals. More detailed characterization of their glycosylation patterns is enabled by the recently introduced technique of cross-path reactive chromatography (XP-RC) with online MS detection, which combines chromatographic separation with in-line reduction of disulfide bonds to generate metastable haptoglobin subunits. Application of XP-RC to both haptoglobin phenotypes confirms that no modifications are present within their light chains and provides a wealth of information on glycosylation patterns of the heavy chains. N-Glycosylation patterns of both haptoglobin phenotypes were found to be consistent with bi- and triantennary structures of complex type that exhibit significant level of fucosylation and sialylation. However, multivariate analysis of haptoglobin 1-1 reveals higher number of the triantennary structures, in comparison to haptoglobin 2-1, as well as a higher extent of fucosylation. The glycosylation patterns deduced from the XP-RC/MS measurements are in agreement with the conclusions of the intact-mass analysis supplemented by limited charge reduction, suggesting that the latter technique can be employed in situations when fast assessment of protein heterogeneity is needed (e.g., process analytical technology applications).

[Haptoglobin as a biomarker]

Haptoglobin (Hp) is a blood plasma glycoprotein that binds free hemoglobin (Hb) and plays a critical role in tissue protection and the prevention of oxidative damage. In addition, it has a number of regulatory functions. Haptoglobin is an acute phase protein, its concentration in plasma changes in pathology, and the test for its concentration is part of normal clinical practice. Haptoglobin is a conservative protein synthesized mainly in the liver and lungs and is the subject of research as a potential biomarker of many diseases, including various forms of malignant neoplasms. Haptoglobin has several unique biophysical characteristics. Only in humans, the Hp gene is polymorphic, has three structural alleles that control the synthesis of three major phenotypes of Hp, homozygous Hp1-1 and Hp2-2, and heterozygous Hp2-1, determined by a combination of allelic variants that are inherited. Numerous studies indicate that the phenotype of haptoglobin can be used to judge the individual's predisposition to various diseases. In addition, Hp undergoes various post-translational modifications (PTMs). These are structural transformations (removal of the signal peptide, cutting of the Pre-Hp precursor molecule into two subunits, α and β, limited proteolysis of α-chains, formation of disulfide bonds, multimerization), as well as chemical modifications of α-chains and glycosylation of the β-chain. Glycosylation of the β-chain of haptoglobin at four Asn sites is the most important variable PTM that regulates the structure and function of the glycoprotein. The study of modified oligosaccharides of the Hp β-chain has become the main direction in the study of pathological processes, including malignant neoplasms. Many studies are focused on the identification of PTM and changes in the level of the α2-chain of this protein in pathology. These characteristics of Hp indicate the possibility of the existence of this protein as different proteoforms, probably with different functions. This review is devoted to the description of the structural and functional diversity of Hp and its potential use as a biomarker of various pathologies.

Serum N-glycan profiling as a diagnostic biomarker for the identification and assessment of psoriasis

Background

Glycosylation is an important post‐translational modification of protein. The change in glycosylation is involved in the occurrence and development of various diseases, and this study verified that N‐glycan markers might be a diagnostic marker in psoriasis.

Methods

A total of 76 psoriasis patients were recruited. We used Psoriasis Area Severity Index (PASI) scores to evaluate the state of psoriasis, 41 of whom were divided into three subgroups: mild, moderate, and severe. At the same time, 76 healthy subjects were enrolled as a control group. We used DNA sequencer–assisted fluorophore‐assisted carbohydrate electrophoresis (DSA‐FACE) to analyze serum N‐glycan profiling.

Results

Compared with the healthy controls, the relative abundance of structures in peaks 5(NA2), 9(NA3Fb), 11(NA4), and 12(NA4Fb) was elevated (p < .05), while that in peaks 3(NG1A2F), 4(NG1A2F), 6(NA2F), and 7(NA2FB) was decreased (p < .05) in the psoriasis group. The abundance of peak 5 (NA2) increased gradually with the aggravation of disease severity though there was no statistically significant, was probably correlated with the disease severity. The best area under the receiver operating characteristic (ROC) curve (AUC) of the logistic regression model (PglycoA) to diagnose psoriasis was 0.867, with a sensitivity of 72.37%, a specificity of 85.53%, a positive predictive value(PPV) of 83.33%, a negative predictive value(NPV) of 75.58%, and an accuracy of 78.95%.

Conclusions

Our study indicated that the N‐glycan–based diagnostic model would be a new, valuable, and noninvasive alternative for diagnosing psoriasis. Furthermore, the characteristic distinctive N‐glycan marker might be correlated with the severity gradation of the psoriasis disease.

Haptoglobin as a Biomarker

Haptoglobin (Hp) is a glycoprotein that binds free hemoglobin (Hb) in plasma and plays a critical role in tissue protection and prevention of oxidative damage. Besides, it has some regulatory functions. Haptoglobin is an acute-phase protein, its concentration in plasma changes in pathology, and the test for its concentration is part of normal clinical practice. Haptoglobin is a conservative protein synthesized mainly in the liver and lungs and is the subject of research as a potential biomarker of many diseases, including various forms of malignant neoplasms. Haptoglobin has several unique biophysical characteristics. The human Нр gene is polymorphic, has three structural alleles that control the synthesis of three major phenotypes of haptoglobin: homozygous Нр1-1 and Нр2-2, and heterozygous Нр2-1, determined by a combination of allelic variants that are inherited. Numerous studies indicate that the phenotype of haptoglobin can be used to judge the individual predisposition of a person to various diseases. In addition, Hp undergoes various post-translational modifications (PTMs). These are structural transformations (removal of the signal peptide, cutting off the Pre-Hp precursor molecule into two subunits, α and β, limited proteolysis of α-chains, formation of disulfide bonds, multimerization), as well as chemical modifications of α-chains and glycosylation of the β-chain. Glycosylation of the β-chain of haptoglobin at four Asn sites is the most important variable PTM that regulates the structure and function of the glycoprotein. The study of modified oligosaccharides of the β-chain of Hp has become the main direction in the study of pathological processes, including malignant neoplasms. These characteristics indicate the possibility of the existence of Hp in the form of a multitude of proteoforms, probably performing different functions. This review is devoted to the description of the structural and functional diversity and the potential use of Hp as a biomarker of various pathologies.

Omics-Driven Biomarkers of Psoriasis: Recent Insights, Current Challenges, and Future Prospects

Advances in omics technologies have made it possible to unravel biomarkers from different biological levels. Intensive studies have been carried out to uncover the dysregulations in psoriasis and to identify molecular signatures associated with the pathogenesis of psoriasis. In this review, we presented an overview of the current status of the omics-driven biomarker research and emphasized the transcriptomic, epigenomic, proteomic, metabolomic, and glycomic signatures proposed as psoriasis biomarkers. Furthermore, insights on the limitations and future directions of the current biomarker discovery strategies were discussed, which will continue to comprehend broader visions of psoriasis research, diagnosis, and therapy especially in the context of personalized medicine.

Probing N-glycoprotein microheterogeneity by lectin affinity purification-mass spectrometry analysis

A lectin affinity purification-mass spectrometry approach to characterize lectin-reactive glycoproteoforms and elucidate lectin specificities at the intact protein level.

Lectins are carbohydrate binding proteins that recognize specific epitopes present on target glycoproteins. Changes in lectin-reactive carbohydrate repertoires are related to many biological signaling pathways and recognized as hallmarks of several pathological processes. Consequently, lectins are valuable probes, commonly used for examining glycoprotein structural and functional microheterogeneity. However, the molecular interactions between a given lectin and its preferred glycoproteoforms are largely unknown due to the inherent complexity and limitations of methods used to investigate intact glycoproteins. Here, we apply a lectin-affinity purification procedure coupled with native mass spectrometry to characterize lectin-reactive glycoproteoforms at the intact protein level. We investigate the interactions between the highly fucosylated and highly branched glycoproteoforms of haptoglobin and α1-acid glycoprotein using two different lectins Aleuria aurantia lectin (AAL) and Phaseolus vulgaris leucoagglutinin (PHA-L), respectively. Firstly we show a co-occurrence of fucosylation and N-glycan branching on haptoglobin, particularly among highly fucosylated glycoproteoforms. Secondly, we analyze the global heterogeneity of highly branched glycoproteoforms of haptoglobin and α1-acid glycoprotein and reveal that while multi-fucosylation attenuates the lectin PHA-L binding to haptoglobin, it has no impact on AGP. Taken together, our lectin affinity purification native MS approach elucidates lectin specificities between intact glycoproteins, not achievable by other methods. Moreover, since aberrant glycosylation of Hp and AGP are potential markers for many diseases, including pancreatic, hepatic and ovarian cancers, understanding their interactions with lectins will help the development of carbohydrate-centric monitoring methods to understand their pathophysiological implications.

Comparison of the methods for profiling N-glycans—hepatocellular carcinoma serum glycomics study

Monitoring serum glycomics is one of the most important emerging approaches for diagnosis of various cancers, and the majority of previous studies were based on MALDI-MS or HPLC analysis. Considering the difference of these analytical methods employed for serum glycomics, it is necessary to compare the effectiveness of different analytical methods for monitoring the aberrant changes in serum glycomics. In this study, a strategy based on machine learning was firstly applied for comparing the analysis results of MALDI-MS and HPLC on the same serum glycomics of hepatocellular carcinoma (HCC) samples. The capability of these two analytical methods for identifying HCC is demonstrated by the classification results obtained from MALDI-MS and HPLC data. In addition, by comparing glycomics which were significantly correlated with HCC based on MALDI-MS and HPLC, some N-glycans which may be the potential biomarkers for HCC were identified, validating the capability of these two analytical methods for the differentiated identification in the analysis of glycomics. Meanwhile, it is noteworthy that various physiological and environmental factors may cause the aberrant changes in glycosylation, and all these interference factors may be minimized by analyzing the same sample sets of HCC. Overall, these results showed that MALDI-MS and HPLC are complementary in qualitative and quantitative analysis of serum glycomics.

Monitoring serum glycomics is one of the most important emerging approaches for diagnosis of various cancers, and the majority of previous studies were based on MALDI-MS or HPLC analysis.

The intricacy of biomarker complexity-the identification of a genuine proteomic biomarker is more complicated than believed

Several reasons have been put forward to explain the irreproducibility of proteomic biomarker search. However, these reasons pertain to almost every part of biomarker search across the entire analytical workflow but are entirely experimental or methodological. However, in this article we point out that there is a further cause of such irreproducibility. This is not an additional methodological or experimental cause but arises directly from the biology of protein expression. It arises from the fact that disease changes the diversity within protein families. This cause of irreproducibility has been very little studied in relation to proteomic biomarker search. Gene expression is highly variable even in healthy people. Therefore, multiple proteoforms are also to be expected when gene expression is disrupted by disease, proteoforms that may be differently altered by pathology. In consequence, it is illogical to expect that the whole protein family produces a reliably usable biomarker. It is more reasonable to expect that a specific proteoform fulfills this role. Appropriate sample pre-fractionation methods and data analyses could help to identify this version, carrying the modification or the epitope required.

Acute phase proteins as promising biomarkers: Perspectives and limitations for human and veterinary medicine

Acute phase proteins (APPs) are highly conserved plasma proteins that are increasingly secreted by the liver in response to a variety of injuries, independently of their location and cause. APPs favor the systemic regulation of defense, coagulation, proteolysis, and tissue repair. Various APPs have been applied as general diagnostic parameters for a long time. Through proteomic techniques, more and more APPs have been discovered to be differentially altered. Since they are not consistently explainable by a stereotypic hepatic expression of sets of APPs, most of these results have unfortunately been neglected or attributed to the nonspecificity of the acute phase reaction. Moreover, it appears that various extrahepatic tissues are also able to express APPs. These extrahepatic APPs show focally specific roles in tissue homeostasis and repair and are released primarily into interstitial and distal fluids. Since these focal proteins might leak into the circulatory system, mixtures of hepatic and extrahepatic APP species can be expected in blood. Hence, a selective alteration of parts of APPs might be expected. There are several hints on multiple molecular forms and fragments of tissue-derived APPs. These differences offer the chance for multiple selective determinations. Thus, specific proteoforms might indeed serve as tissue-specific disease indicators.

The selected reaction monitoring/multiple reaction monitoring-based mass spectrometry approach for the accurate quantitation of proteins: clinical applications in the cardiovascular diseases

Selected reaction monitoring, also known as multiple reaction monitoring, is a powerful targeted mass spectrometry approach for a confident quantitation of proteins/peptides in complex biological samples. In recent years, its optimization and application have become pivotal and of great interest in clinical research to derive useful outcomes for patient care. Thus, selected reaction monitoring/multiple reaction monitoring is now used as a highly sensitive and selective method for the evaluation of protein abundances and biomarker verification with potential applications in medical screening. This review describes technical aspects for the development of a robust multiplex assay and discussing its recent applications in cardiovascular proteomics: verification of promising disease candidates to select only the highest quality peptides/proteins for a preclinical validation, as well as quantitation of protein isoforms and post-translational modifications.