Eszter Tóth

Comparison of Dialysis and Clinical Characteristics of Patients with Frequent and Occasional Hemodialysis-Associated Hypotension

Background: Symptomatic dialysis hypotension (DH) continues to be a common problem. By comparing patients prone and resistant to DH, several dialysis session and patient related characteristics have been identified that confer susceptibility to DH. Less is known, however, about the comparison of patients with frequent and only occasional DH. The aim of the study was to compare clinical and dialysis-session- (complicated by hypotension) related data between those with frequent (fDH) and those with occasional dialysis hypotension (oDH). Methods: Nine hundred and fifty-eight patients at 11 dialysis units were followed for 10 months and characteristics of patients with fDH (≧10 hypotensive events necessitating medical intervention) (n = 96) were compared to that of patients with oDH (1 or 2 events/10 months) (n = 130). Significant and independent predictors of fDH were obtained by multivariate logistic regression. Results: Significant differences between fDH vs. oDH patients were older age (64.4 vs. 56.9 years, p < 0.001), more females (66 vs. 46%, p < 0.005) in fDH. More fDH patients had diabetes (27 vs. 15%, p < 0.05) and less had glomerulonephritis (15 vs. 35%, p < 0.001) as the cause for ESRD. Coronary artery disease (68 vs. 50%, p < 0.01) and long-acting nitrate treatment (51 vs. 30%, p < 0.001) was more frequent while treatment with ACEI (33 vs. 48%, p < 0.05) or Ca-channel blockers (40 vs. 53%, p < 0.05) were less frequent in patients with fDH. Patients with fDH had higher serum phosphorus levels (1.99 vs. 1.79 mmol, p < 0.005). Dialysis session related data were similar but the hypotensive episode occurred earlier during dialysis in fDH (136 vs. 156 min, p < 0.01). In multivariate analysis, significant independent predictors of fDH were older age (OR = 1.04 [1.02–1.07]), lack of glomerulonephritis as renal diagnosis (2.63 [1.18–5.87]), high phosphorus levels (5.0 [2.45–10.0]), lack of use of Ca-channel blockers (2.09 [1.12–3.91]), and the use of nitrates (2.38 [1.24–4.55]). Conclusion: Features of the dialysis sessions complicated by DH seem to be similar between patients with fDH and oDH, while patient characteristics such as older age, renal diagnosis other than glomerulonephritis, higher serum phosphorus levels, use of nitrates, and lack of use of calcium channel blockers are significantly and independently associated with fDH.

Mast cell secretome: Soluble and vesicular components

Mast cells are multifunctional master cells implicated in both innate and adaptive immune responses. Their role has been best characterized in allergy and anaphylaxis; however, emerging evidences support their contribution to a wide variety of human diseases. Mast cells, being capable of both degranulation and subsequent recovery, have recently attracted substantial attention as also being rich sources of secreted extracellular vesicles (including exosomes and microvesicles). Along with secreted de novo synthesized soluble molecules and secreted preformed granules, the membrane-enclosed extracellular vesicles represent a previously unexplored part of the mast cell secretome. In this review article we summarize available data regarding the different soluble molecules and membrane-enclosed structures secreted by mast cells. Furthermore, we provide an overview of the release mechanisms including degranulation, piecemeal degranulation, transgranulation, and secretion of different types of extracellular vesicles. Finally, we aim to give a summary of the known biological functions associated with the different mast cell-derived secretion products. The increasingly recognized complexity of mast cell secretome may provide important novel clues to processes by which mast cells contribute to the development of different pathologies and are capable of orchestrating immune responses both in health and disease.

Monocyte activation drives preservation of membrane thiols by promoting release of oxidised membrane moieties via extracellular vesicles

Abstract The redox state of cellular exofacial molecules is reflected by the amount of available thiols. Furthermore, surface thiols can be considered as indicators of immune cell activation. One group of thiol containing proteins, peroxiredoxins, in particular, have been associated with inflammation. In this study, we assessed surface thiols of the U937 and Thp1 monocyte cell lines and primary monocytes in vitro upon inflammatory stimulation by irreversibly labelling the cells with a fluorescent derivative of maleimide. We also investigated exofacial thiols on circulating blood mononuclear cells in patients with rheumatoid arthritis and healthy controls. When analysing extracellular vesicles, we combined thiol labelling with the use of antibodies to specific CD markers to exclude extracellular vesicle mimicking signals from thiol containing protein aggregates. Furthermore, differential detergent lysis was applied to confirm the vesicular nature of the detected extracellular events in blood plasma. We found an increase in exofacial thiols on monocytes upon in vitro stimulation by LPS or TNF, both in primary monocytes and monocytic cell lines (p<0.0005). At the same time, newly released extracellular vesicles showed a decrease in their exofacial thiols compared with those from unstimulated cells (p<0.05). We also found a significant elevation of surface thiols on circulating monocytes in rheumatoid arthritis patients (p<0.05) and newly released extracellular vesicles of isolated CD14+ cells from rheumatoid arthritis patients had decreased thiol levels compared with healthy subjects (p<0.01). Exofacial peroxiredoxin 1 was demonstrated on the surface of primary and cultured monocytes, and the number of peroxiredoxin 1 positive extracellular vesicles was increased in rheumatoid arthritis blood plasma (p<0.05). Furthermore, an overoxidised form of peroxiredoxin was detected in extracellular vesicle‐enriched preparations from blood plasma. Our data show that cell surface thiols play a protective role and reflect oxidative stress resistance state in activated immune cells. Furthermore, they support a role of extracellular vesicles in the redox regulation of human monocytes, possibly representing an antioxidant mechanism. Graphical abstract Figure. No Caption available. HighlightsRedox state of extracellular vesicles (EVs) was detected by dual labelling.Monocyte surface thiols were found to be enhanced after stimulation.In contrast, surface thiols of secreted EVs were decreased.Overoxidised Prdx was detected in EVs.EV secretion thus, may serve as an antioxidant mechanism.

Molecular interactions at the surface of extracellular vesicles

Extracellular vesicles such as exosomes, microvesicles, apoptotic bodies, and large oncosomes have been shown to participate in a wide variety of biological processes and are currently under intense investigation in many different fields of biomedicine. One of the key features of extracellular vesicles is that they have relatively large surface compared to their volume. Some extracellular vesicle surface molecules are shared with those of the plasma membrane of the releasing cell, while other molecules are characteristic for extracellular vesicular surfaces. Besides proteins, lipids, glycans, and nucleic acids are also players of extracellular vesicle surface interactions. Being secreted and present in high number in biological samples, collectively extracellular vesicles represent a uniquely large interactive surface area which can establish contacts both with cells and with molecules in the extracellular microenvironment. Here, we provide a brief overview of known components of the extracellular vesicle surface interactome and highlight some already established roles of the extracellular vesicle surface interactions in different biological processes in health and disease.

Changes of protein glycosylation in the course of radiotherapy

This is the first study of changes in protein glycosylation due to exposure of human subjects to ionizing radiation. Site specific glycosylation patterns of 7 major plasma proteins were analyzed; 171 glycoforms were identified; and the abundance of 99 of these was followed in the course of cancer radiotherapy in 10 individual patients. It was found that glycosylation of plasma proteins does change in response to partial body irradiation (∼ 60 Gy), and the effects last during follow-up; the abundance of some glycoforms changed more than twofold. Both the degree of changes and their time-evolution showed large inter-individual variability.

Effect of angiotensin-converting enzyme gene insertion/deletion polymorphism and angiotensin-converting enzyme inhibition on erythropoiesis in patients on haemodialysis.

Background: Angiotensin-converting enzyme inhibitors (ACEis) improve survival; however, their effect on erythropoiesis remains a matter of debate in this population. Since insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene largely influences serum ACE activity, its effect on erythropoiesis is also anticipated. Method: In this multicentre, cross-sectional study of 660 patients on maintenance haemodialysis, we analysed the effect of ACEi use and ACE gene I/D polymorphism on haemoglobin levels and erythropoietin resistance. Patients were allocated in groups based on genotype and ACEi therapy. We identified 128 matched pairs with I/I and D/D genotypes. Result: There was no difference in haemoglobin levels between genotype groups. Haemoglobin levels were lower in patients on ACEi therapy in the entire cohort (95.5±12.1 g/l vs 97.4±13.4 g/l, p=0.02) and patients with I/D (95.2±11 g/l vs 98.2±11.9 g/l, p=0.04) and D/D (93.3±13.2 g/l vs 97.4±14.2 g/l, p=0.02) genotypes. In patient pairs treated with ACEi therapy, subjects with D/D genotype had lower Haemoglobin level (93.0±12.8 g/l vs 98.2±11.9 g/l, p=0.006) and higher erythropoietin resistance index (ERI) (199.1 vs 175.0, p=0.046) than individuals with I/I genotype. Conclusion: These results indicate that ACEi therapy may increase erythropoietin resistance and worsen erythropoiesis in haemodialysis patients with the D allele.

Simple correction improving long-term reproducibility of HPLC-MS

Chromatographic peak areas in long series of high-performance liquid chromatography-MS experiments often vary, which decrease reproducibility and may cause bias in the results. It was found that the sensitivity of various components change differently; in our case, variability is in the order of 20-40%, and it is most likely due to changing conditions in electrospray ionization (ESI). The most often used peak area correction methods do not take this effect into account. The change in peak areas can be well described by a polynomial function; we found that a fourth-order polynomial is most often suitable. We suggest a simple correction algorithm based on polynomial fitting. When the experiments were inherently well reproducible, this correction improved reproducibility from 12% to 3% (on average for various components). When random errors were larger, this improvement was less significant (15% to 12% in nano-ESI) but nevertheless essential in order to avoid possible bias in the results.