Patients with chronic kidney disease (CKD) have a high prevalence of hyperphosphatemia, where uremic toxins like inorganic phosphate (Pi) induce a cardiovascular remodeling. Related disorders like ...atherosclerosis bear the risk of increased morbidity and mortality. We previously found that Pi stimulates the synthesis and sulfation of the negatively charged glycosaminoglycans (GAGs) heparan sulfate and chondroitin sulfate in vascular smooth muscle cells (VSMC). Similar GAG alterations were detected in VSMC-derived exosome-like extracellular vesicles (EV). These EV showed a strong interaction with very small superparamagnetic iron oxide particles (VSOP), which are used as imaging probes for experimental magnetic resonance imaging (MRI). Hyaluronic acid (HA) represents another negatively charged GAG which is supposed to function as binding motif for VSOP as well. We investigated the effects of Pi on the amounts of HA in cells and EV and studied the HA-dependent interaction between VSOP with cells and EV. Rat VSMC were treated with elevated concentrations of Pi. CKD in rats was induced by adenine feeding. EV were isolated from culture supernatants and rat plasma. We investigated the role of HA in binding VSOP to cells and EV via cell-binding studies, proton relaxometry, and analysis of cellular signaling, genes, proteins, and HA contents. Due to elevated HA contents, VSMC and EV showed an increased interaction with VSOP after Pi stimulation. Amongst others, Pi induced hyaluronan synthase (HAS)2 expression and activation of the Wnt pathway in VSMC. An alternative upregulation of HA by iloprost and an siRNA-mediated knockdown of HAS2 confirmed the importance of HA in cells and EV for VSOP binding. The in vitro-derived data were validated by analyses of plasma-derived EV from uremic rats. In conclusion, the inorganic uremic toxin Pi induces HA synthesis in cells and EV, which leads to an increased interaction with VSOP. HA might therefore be a potential molecular target structure for improved detection of pathologic tissue changes secondary to CKD like atherosclerosis or cardiomyopathy using EV, VSOP and MRI.
During the development of cancer, changes in cellular glycosylation are observed, indicating that alterations of the glycome occur in extracellular fluids as well as in serum and could therefore ...serve as tumor biomarkers. In the case of epithelial ovarian cancer (EOC), common tumor markers such as CA125 are known to have poor specificity; therefore, better biomarkers are needed. The aim of this work was to identify new potential glycan biomarkers in EOC-patients. N-Glycans were cleaved from serum glycoproteins from 63 preoperative primary EOC-patients along with 33 age-matched healthy women, permethylated, and analyzed using MALDI-TOF mass spectrometry. A value named GLYCOV was calculated from the relative areas of the 11 N-glycan biomarkers revealed by SPSS statistical analyses, namely four high-mannose and seven complex-type fucosylated N-glycans. GLYCOV diagnosed primary EOC with a sensitivity of 97% and a specificity of 98.4% whereas CA-125 showed a sensitivity of 97% and a specificity of 88.9%. Our study is the first one to compare glycan values with the established tumor marker CA125 and to give better results. Therefore, the N-glycome could potentially be used as a biomarker.
Inflammatory bowel diseases (IBD) comprise mainly ulcerative colitis (UC) and Crohn´s disease (CD). Both forms present with a chronic inflammation of the (gastro) intestinal tract, which induces ...excessive changes in the composition of the associated extracellular matrix (ECM). In UC, the inflammation is limited to the colon, whereas it can occur throughout the entire gastrointestinal tract in CD. Tools for early diagnosis of IBD are still very limited and highly invasive and measures for standardized evaluation of structural changes are scarce. To investigate an efficient non-invasive way of diagnosing intestinal inflammation and early changes of the ECM, very small superparamagnetic iron oxide nanoparticles (VSOPs) in magnetic resonance imaging (MRI) were applied in two mouse models of experimental colitis: the dextran sulfate sodium (DSS)-induced colitis and the transfer model of colitis. For further validation of ECM changes and inflammation, tissue sections were analyzed by immunohistochemistry. For in depth
ex-vivo
investigation of VSOPs localization within the tissue, Europium-doped VSOPs served to visualize the contrast agent by imaging mass cytometry (IMC). VSOPs accumulation in the inflamed colon wall of DSS-induced colitis mice was visualized in T
2
* weighted MRI scans. Components of the ECM, especially the hyaluronic acid content, were found to influence VSOPs binding. Using IMC, co-localization of VSOPs with macrophages and endothelial cells in colon tissue was shown. In contrast to the DSS model, colonic inflammation could not be visualized with VSOP-enhanced MRI in transfer colitis. VSOPs present a potential contrast agent for contrast-enhanced MRI to detect intestinal inflammation in mice at an early stage and in a less invasive manner depending on hyaluronic acid content.
Alzheimer’s disease (AD) is the most common neurodegenerative disorder, affecting a growing number of elderly people. In order to improve the early and differential diagnosis of AD, better biomarkers ...are needed. Glycosylation is a protein post-translational modification that is modulated in the course of many diseases, including neurodegeneration. Aiming to improve AD diagnosis and differential diagnosis through glycan analytics methods, we report the glycoprotein glycome of cerebrospinal fluid (CSF) isolated from a total study cohort of 262 subjects. The study cohort consisted of patients with AD, healthy controls and patients suffering from other types of dementia. CSF free-glycans were also isolated and analyzed in this study, and the results reported for the first time the presence of 19 free glycans in this body fluid. The free-glycans consisted of complete or truncated N-/O-glycans as well as free monosaccharides. The free-glycans Hex1 and HexNAc1Hex1Neu5Ac1 were able to discriminate AD from controls and from patients suffering from other types of dementia. Regarding CSF N-glycosylation, high proportions of high-mannose, biantennary bisecting core-fucosylated N-glycans were found, whereby only about 20% of the N-glycans were sialylated. O-Glycans and free-glycan fragments were less sialylated in AD patients than in controls. To conclude, this comprehensive study revealed for the first time the biomarker potential of free glycans for the differential diagnosis of AD.
Glycosaminoglycans (GAGs) are considered to be the most difficult type of glycoconjugates to analyze as they are constituted of linear long polysaccharidic chains having molecular weights reaching up ...to several million daltons. Bottom-up analysis of glycosaminoglycans from biological samples is a long and work-extensive procedure due to the many preparation steps involved. In addition, so far, only few research articles have been dedicated to the analysis of GAGs by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) because their intact ionization can be problematic due to the presence of labile sulfate groups. In this work, we had the aim of exploring the sulfation pattern of monosulfated chondroitin/dermatan sulfate (CS/DS) disaccharides in human tissue samples because they represent the most abundant form of sulfation in disaccharides. We present here an optimized strategy to analyze on-target derivatized CS/DS disaccharides via MALDI-TOF-MS using a fast workflow that does not require any purification after enzymatic cleavage. For the first time, we show that MALDI-TOF/TOF experiments allow for discrimination between monosulfated CS disaccharide isomers via specific fragments corresponding to glycosidic linkages and to cross-ring cleavages. This proof of concept is illustrated via the analysis of CS/DS disaccharides of atherosclerotic lesions of different histological origins, in which we were able to identify their monosulfation patterns.
Glycosaminoglycans are long polysaccharidic chains, which are mostly present in connective tissues. Modified GAG expression in tissues surrounding malignant cells has been shown to contribute to ...tumor progression, aggressive status and metastasis in many types of cancer. Ovarian cancer is one of the most lethal gynecological malignancies due to its late diagnosis because of the absence of clear symptoms and unavailability of early disease markers. We investigated for the first time GAG changes at the molecular level as a novel biomarker for primary epithelial ovarian cancer. To this end, serum of a cohort of 68 samples was digested with chondroitinase ABC, which releases chondroitin sulfate into disaccharides. After labeling and purification, they were measured by HPLC, yielding a profile of eight disaccharides. We proposed a novel GAG-based score named “CS- bio” from the measured abundance of disaccharides present that were of statistical relevance. CS-bio’s performance was compared with CA125, the clinically used serum tumor marker in routine diagnostics. CS-bio had a better sensitivity and specificity than CA125. It was more apt in differentiating early-stage patients from healthy controls, which is of high interest for oncologists.
Glycoconjugates on extracellular vesicles (EVs) play a vital role in internalization and mediate interaction as well as regulation of the host immune system by viruses, bacteria, and parasites. ...During their intraerythrocytic life‐cycle stages, malaria parasites, Plasmodium falciparum (Pf) mediate the secretion of EVs by infected red blood cells (RBCs) that carry a diverse range of parasitic and host‐derived molecules. These molecules facilitate parasite‐parasite and parasite‐host interactions to ensure parasite survival.
To date, the number of identified Pf genes associated with glycan synthesis and the repertoire of expressed glycoconjugates is relatively low. Moreover, the role of Pf glycans in pathogenesis is mostly unclear and poorly understood. As a result, the expression of glycoconjugates on Pf‐derived EVs or their involvement in the parasite life‐cycle has yet to be reported.
Herein, we show that EVs secreted by Pf‐infected RBCs carry significantly higher sialylated complex N‐glycans than EVs derived from healthy RBCs. Furthermore, we reveal that EV uptake by host monocytes depends on N‐glycoproteins and demonstrate that terminal sialic acid on the N‐glycans is essential for uptake by human monocytes. Our results provide the first evidence that Pf exploits host sialylated N‐glycans to mediate EV uptake by the human immune system cells.
The classical function of human chorionic gonadotropin (hCG) is its role in supporting pregnancy. hCG is a dimer consisting of two highly glycosylated subunits, alpha (CGA) and beta (CGB). The ...beta-hCG protein is encoded by
CGB3, CGB5, CGB7
and
CGB8
genes.
CGB3
,
5
and
8
code for an identical protein, CGB3/5/8, whereas CGB7 differs in three amino acids from CGB3/5/8. We had observed earlier that CGB7 and CGB3/5/8 display very distinct tissue expression patterns and that the tumor suppressor and transcription factor p53 can activate expression of
CGB7
but not of
CGB3/5/8
genes. Here, we investigate the glycan structures and possible functional differences of the two CGB variants. To this end, we established a system to produce and isolate recombinant CGA, CGB7 and CGB3/5/8 proteins. We found that N- and O-glycosylation patterns of CGB7 and CGB3/5/8 are quite similar. Functional assays were performed by testing activation of the ERK1/2 pathway and demonstrated that CGB7 and CGB5/5/8 appear to be functionally redundant isoforms, although a slight difference in the kinetics of ERK1/2 pathway activation was observed. This is the first time that biological activity of CGB7 is shown. In summary, the results lead to the hypothesis that CGB7 and CGB3/5/8 do not hold significant functional differences but that timing and cell type of their expression is the key for understanding their divergent evolution.
Epithelial ovarian cancer (EOC) is worldwide the sixth most lethal form of cancer occurring in women. More than one third of ovarian patients have ascites at the time of diagnosis and almost all of ...them have it when recurrence occurs. Although its effect on tumor cell microenvironment remains poorly understood, its presence is correlated with bad diagnosis. In previous studies, we proposed a novel glycan-based biomarker for the diagnosis of EOC, which showed an improved sensitivity and specificity at any stage of the disease and an improved discrimination between malignant and benign ovarian tumors. In this work, we report for the first time the N-glycome profiles of ascitic fluid from primary serous EOC patients and compare them with the serum N-glycomes of the same patients as well as of healthy controls. N-Glycans were digested from equivalent amount of ascites and serum from 18 EOC patients and from serum of 20 age-matched controls and measured by MALDI-TOF-MS. Ascites N-glycome showed increased antennarity, branching, sialylation and LewisX motives compared to healthy serum. In addition, a correlation was established between ascites volume and degree of sialylation.
Malignant ascitic fluid is the build-up of large volumes of fluid in the peritoneal cavity secondary to cancer. At least one-third of ovarian cancer patients develop ascites, a generally voluminous fluid containing cells of tumor origin, in the course of cancer and almost all when recurrence occurs. The proteome of ascites is known to be as complex as that of serum and contains high amount of proteins shed from inflammatory cells as well as from tumor cells. Although many attempts have been made to provide molecular insight into the proteomic and peptidomic content of malignant ascites, no data about the N-glycome of the ascitic fluid fraction from cancer patients has been reported to date.
In this study, the N-glycosylation profile of ascites from 20 patients suffering from epithelial ovarian cancer (EOC) was analyzed by MALDI-TOF-mass spectrometry and compared to the pathologically modified N-glycan pattern obtained from serum of the same patients as well as to the pattern of serum from healthy individuals. Significant quantitative differences were observed in the ascites of EOC patients when compared to the serum of healthy subjects. The glycome of ascites shows typical features of inflammatory conditions, what was also found in the serum of patients suffering from EOC when compared to healthy serum. In addition, a correlation was established between ascites volume and degree of sialylation, showing that the high-volume ascites contains a higher amount of sialylated structures than the low-volume ascites.
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•first glycome study on ascitic fluid using MALDI-TOF-MS•comparison between serum, ascitic fluid and serum of healthy controls•serum and ascites were taken from the same patients to overcome the patient’s specific•glycome modulations, previously detected in EOC serum, were also present in ascites•a correlation was established between ascites volume and degree of sialylation
Alzheimer’s disease (AD) is the most common neurodegenerative disorder, affecting a growing number of elderly people. In order to improve the early and differential diagnosis of AD, better biomarkers ...are needed. Glycosylation is a protein post-translational modification that is modulated in the course of many diseases, including neurodegeneration. Aiming to improve AD diagnosis and differential diagnosis through glycan analytics methods, we report the glycoprotein glycome of cerebrospinal fluid (CSF) isolated from a total study cohort of 262 subjects. The study cohort consisted of patients with AD, healthy controls and patients suffering from other types of dementia. CSF free-glycans were also isolated and analyzed in this study, and the results reported for the first time the presence of 19 free glycans in this body fluid. The free-glycans consisted of complete or truncated N-/O-glycans as well as free monosaccharides. The free-glycans Hexsub.1 and HexNAcsub.1Hexsub.1Neu5Acsub.1 were able to discriminate AD from controls and from patients suffering from other types of dementia. Regarding CSF N-glycosylation, high proportions of high-mannose, biantennary bisecting core-fucosylated N-glycans were found, whereby only about 20% of the N-glycans were sialylated. O-Glycans and free-glycan fragments were less sialylated in AD patients than in controls. To conclude, this comprehensive study revealed for the first time the biomarker potential of free glycans for the differential diagnosis of AD.
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