Integration of Urinary Peptidome and Fecal Microbiome to Explore Patient Clustering in Chronic Kidney Disease

Millions of people worldwide currently suffer from chronic kidney disease (CKD), requiring kidney replacement therapy at the end stage. Endeavors to better understand CKD pathophysiology from an omics perspective have revealed major molecular players in several sample sources. Focusing on non-invasive sources, gut microbial communities appear to be disturbed in CKD, while numerous human urinary peptides are also dysregulated. Nevertheless, studies often focus on isolated omics techniques, thus potentially missing the complementary pathophysiological information that multidisciplinary approaches could provide. To this end, human urinary peptidome was analyzed and integrated with clinical and fecal microbiome (16S sequencing) data collected from 110 Non-CKD or CKD individuals (Early, Moderate, or Advanced CKD stage) that were not undergoing dialysis. Participants were visualized in a three-dimensional space using different combinations of clinical and molecular data. The most impactful clinical variables to discriminate patient groups in the reduced dataspace were, among others, serum urea, haemoglobin, total blood protein, urinary albumin, urinary erythrocytes, blood pressure, cholesterol measures, body mass index, Bristol stool score, and smoking; relevant variables were also microbial taxa, including Roseburia, Butyricicoccus, Flavonifractor, Burkholderiales, Holdemania, Synergistaceae, Enterorhabdus, and Senegalimassilia; urinary peptidome fragments were predominantly derived from proteins of collagen origin; among the non-collagen parental proteins were FXYD2, MGP, FGA, APOA1, and CD99. The urinary peptidome appeared to capture substantial variation in the CKD context. Integrating clinical and molecular data contributed to an improved cohort separation compared to clinical data alone, indicating, once again, the added value of this combined information in clinical practice.

Increased levels of a mycophenolic acid metabolite in patients with kidney failure negatively affect cardiomyocyte health

Chronic kidney disease (CKD) significantly increases cardiovascular risk and mortality, and the accumulation of uremic toxins in the circulation upon kidney failure contributes to this increased risk. We thus performed a screening for potential novel mediators of reduced cardiovascular health starting from dialysate obtained after hemodialysis of patients with CKD. The dialysate was gradually fractionated to increased purity using orthogonal chromatography steps, with each fraction screened for a potential negative impact on the metabolic activity of cardiomyocytes using a high-throughput MTT-assay, until ultimately a highly purified fraction with strong effects on cardiomyocyte health was retained. Mass spectrometry and nuclear magnetic resonance identified the metabolite mycophenolic acid-β-glucuronide (MPA-G) as a responsible substance. MPA-G is the main metabolite from the immunosuppressive agent MPA that is supplied in the form of mycophenolate mofetil (MMF) to patients in preparation for and after transplantation or for treatment of autoimmune and non-transplant kidney diseases. The adverse effect of MPA-G on cardiomyocytes was confirmed in vitro, reducing the overall metabolic activity and cellular respiration while increasing mitochondrial reactive oxygen species production in cardiomyocytes at concentrations detected in MMF-treated patients with failing kidney function. This study draws attention to the potential adverse effects of long-term high MMF dosing, specifically in patients with severely reduced kidney function already displaying a highly increased cardiovascular risk.

Cardiovascular Consequences of Uremic Metabolites: an Overview of the Involved Signaling Pathways

The crosstalk of the heart with distant organs such as the lung, liver, gut, and kidney has been intensively approached lately. The kidney is involved in (1) the production of systemic relevant products, such as renin, as part of the most essential vasoregulatory system of the human body, and (2) in the clearance of metabolites with systemic and organ effects. Metabolic residue accumulation during kidney dysfunction is known to determine cardiovascular pathologies such as endothelial activation/dysfunction, atherosclerosis, cardiomyocyte apoptosis, cardiac fibrosis, and vascular and valvular calcification, leading to hypertension, arrhythmias, myocardial infarction, and cardiomyopathies. However, this review offers an overview of the uremic metabolites and details their signaling pathways involved in cardiorenal syndrome and the development of heart failure. A holistic view of the metabolites, but more importantly, an exhaustive crosstalk of their known signaling pathways, is important for depicting new therapeutic strategies in the cardiovascular field.

2,8-Dihydroxyadenine-induced nephropathy causes hexosylceramide accumulation with increased mTOR signaling, reduced levels of protective SirT3 expression and impaired renal mitochondrial function

AIM

Chronic kidney disease (CKD) is accompanied by increased cardiovascular risk and heart failure (HF). In rodents, 2,8-dihydroxyadenine (DHA)-induced nephropathy is a frequently used CKD model. Cardiac and kidney tubular cells share high energy demand to guarantee constant contractive force of the heart or reabsorption/secretion of primary filtrated molecules and waste products by the kidney. Here we analyze time-dependent mechanisms of kidney damage and cardiac consequences under consideration of energetic pathways with the focus on mitochondrial function and lipid metabolism in mice.

METHODS AND RESULTS

CKD was induced by alternating dietary adenine supplementation (0.2 % or 0.05 % of adenine) in C57BL/6J mice for 9 weeks. Progressive kidney damage led to reduced creatinine clearance, kidney fibrosis and renal inflammation after 3, 6, and 9 weeks. No difference in cardiac function, mitochondrial respiration nor left ventricular fibrosis was observed at any time point. Investigating mechanisms of renal damage, protective SirT3 was decreased in CKD, which contrasted an increase in protein kinase B (AKT) expression, mechanistic target of rapamycin (mTOR) downstream signaling, induction of oxidative and endoplasmic reticulum (ER) stress. This occurred together with impaired renal mitochondrial function and accumulation of hexosylceramides (HexCer) as an established mediator of inflammation and mitochondrial dysfunction in the kidney.

CONCLUSIONS

2,8-DHA-induced CKD results in renal activation of the mTOR downstream signaling, endoplasmic reticulum stress, tubular injury, fibrosis, inflammation, oxidative stress and impaired kidney mitochondrial function in conjunction with renal hexosylceramide accumulation in C57BL/6J mice.

Urinary peptide analysis to predict the response to blood pressure medication

BACKGROUND AND HYPOTHESIS

The risk of Diabetic Kidney Disease (DKD) progression is significant despite renin-angiotensin system (RAS) blocking agents treatment. Current clinical tools cannot predict whether or not patients will respond to the treatment with RAS-inhibitors (RASi). We aimed to investigate if proteome analysis could identify urinary peptides as biomarkers that could predict the response to angiotensin-converting enzyme inhibitor (ACEi) and angiotensin receptor blockers (ARBs) treatment to avoid DKD progression. Furthermore, we investigated the comparability of the estimated glomerular filtration rate (eGFR), calculated using four different GFR-equations, for DKD progression.

METHODS

We evaluated urine samples from a discovery cohort of 199 diabetic patients treated with RASi. DKD progression was defined based on eGFR percentage slope results between visits (∼1 year) and for the entire period (∼3 year) based on the eGFR values of each GFR-equation. Urine samples were analysed using capillary electrophoresis coupled mass spectrometry. Statistical analysis was performed between the uncontrolled (patients who did not respond to RASi treatment) and controlled kidney function groups (patients who responded to the RASi treatment). Peptides were combined in a support vector machine-based model. The area under the receiver operating characteristic curve (AUC) was used to evaluate the risk prediction models in two independent validation cohorts treated with RASi.

RESULTS

The classification of patients into uncontrolled and controlled kidney function varies depending on the GFR-equation used, despite the same sample set. We identified 227 peptides showing nominal significant difference and consistent fold changes between uncontrolled and controlled patients in at least three methods of eGFR calculation. These included fragments of collagens, alpha-1-antitrypsin, antithrombin-III, CD99 antigen, and uromodulin. A model based on 189 of 227 peptides (DKDp189) showed a significant prediction of non-response to the treatment/DKD progression in two independent cohorts.

CONCLUSIONS

The DKDp189 model demonstrates potential as a predictive tool for guiding treatment with RASi in diabetic patients.

Blood Endotoxin Levels as Biomarker of Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Growing evidence supports a role of gut-derived metabolites in nonalcoholic fatty liver disease (NAFLD), but the relation of endotoxin levels with gut permeability and NAFLD stage remains unclear. This systematic review with meta-analysis aims to provide further insights.

METHODS

PubMed, Embase, and Cochrane Library were searched for studies published until January 2022 assessing blood endotoxins in patients with NAFLD. Meta-analyses and univariate/multivariate meta-regression, as well as correlation analyses, were performed for endotoxin values and potential relationships to disease stage, age, sex, parameters of systemic inflammation, and metabolic syndrome, as well as liver function and histology.

RESULTS

Forty-three studies were included, of which 34 were used for meta-analyses. Blood endotoxin levels were higher in patients with simple steatosis vs liver-healthy controls (standardized mean difference, 0.86; 95% confidence interval, 0.62-1.11) as well as in patients with nonalcoholic steatohepatitis vs patients with nonalcoholic fatty liver/non-nonalcoholic steatohepatitis (standardized mean difference, 0.81; 95% confidence interval, 0.27-1.35; P = .0078). Consistently, higher endotoxin levels were observed in patients with more advanced histopathological gradings of liver steatosis and fibrosis. An increase of blood endotoxin levels was partially attributed to a body mass index rise in patients with NAFLD compared with controls. Nevertheless, significant increases of blood endotoxin levels in NAFLD retained after compensation for differences in body mass index, metabolic condition, or liver enzymes. Increases in blood endotoxin levels were associated with increases in C-reactive protein concentrations, and in most cases, paralleled a rise in markers for intestinal permeability.

CONCLUSION

Our results support blood endotoxin levels as relevant diagnostic biomarker for NAFLD, both for disease detection as well as staging during disease progression, and might serve as surrogate marker of enhanced intestinal permeability in NAFLD. Registration number in Prospero: CRD42022311166.

Recurrent cardiovascular events in patients with type 2 diabetes and haemodialysis: analysis from the 4D Study

Background

In the 'Die Deutsche Diabetes Dialyse Studie' (4D Study), treatment of patients with type 2 diabetes mellitus (T2DM) on haemodialysis (HD) with atorvastatin compared with placebo had no significant effect on the first composite primary major adverse cardiovascular event (MACE) endpoint of death from cardiac causes, fatal stroke, non-fatal myocardial infarction or non-fatal stroke. In this study we analysed first and recurrent events in 1255 patients from the 4D Study.

Methods

We conducted an event history analysis to investigate the effects of previous clinical events on the risk of different endpoints in the total patient group and after stratification by randomization group.

Results

During a median follow-up of 4 years, a total of 548 MACEs occurred, with 469 first and 79 recurrent events. The most frequent event was sudden cardiac death, followed by death due to infection/sepsis. Of the 548 total MACEs, 260 occurred in the atorvastatin group and 288 in the placebo group [hazard ratio 0.91 (95% confidence interval 0.76-1.07), P = .266]. Interestingly, analyses of the baseline hazard functions for first and recurrent events as a function of time after randomization demonstrated that the risks of the composite primary endpoint continually increased in the placebo group with increasing time in the study, whereas the risk in the atorvastatin group remained constant after ≈1.5 years.

Conclusion

This recurrent and total event analysis from the 4D Study underscores the high risk of sudden cardiac death and death due to infection/sepsis in patients with T2DM receiving HD and raises the hypothesis that atorvastatin may stabilize cardiovascular risk only after 1-2 years in this high-risk population.

Prognosis and Personalized In Silico Prediction of Treatment Efficacy in Cardiovascular and Chronic Kidney Disease: A Proof-of-Concept Study

(1) Background: Kidney and cardiovascular diseases are responsible for a large fraction of population morbidity and mortality. Early, targeted, personalized intervention represents the ideal approach to cope with this challenge. Proteomic/peptidomic changes are largely responsible for the onset and progression of these diseases and should hold information about the optimal means of treatment and prevention. (2) Methods: We investigated the prediction of renal or cardiovascular events using previously defined urinary peptidomic classifiers CKD273, HF2, and CAD160 in a cohort of 5585 subjects, in a retrospective study. (3) Results: We have demonstrated a highly significant prediction of events, with an HR of 2.59, 1.71, and 4.12 for HF, CAD, and CKD, respectively. We applied in silico treatment, implementing on each patient's urinary profile changes to the classifiers corresponding to exactly defined peptide abundance changes, following commonly used interventions (MRA, SGLT2i, DPP4i, ARB, GLP1RA, olive oil, and exercise), as defined in previous studies. Applying the proteomic classifiers after the in silico treatment indicated the individual benefits of specific interventions on a personalized level. (4) Conclusions: The in silico evaluation may provide information on the future impact of specific drugs and interventions on endpoints, opening the door to a precision-based medicine approach. An investigation into the extent of the benefit of this approach in a prospective clinical trial is warranted.

Development, Establishment, and Validation of a Model for the Mineralization of Periodontium Remodelling Cells: Cementoblasts

Chronic kidney disease (CKD) patients undergoing dialysis are at high risk of bone fractures. CKD-induced mineral and bone disorder is extended to periodontal disease due to changes in the ionic composition of saliva in CKD patients, dysregulating mineralization, hindering regeneration and thereby promoting the progression of dental complications. Despite the importance of cementum for overall oral health, the mechanisms that regulate its development and regeneration are not well comprehended, and a lack of sufficient in vitro experimental models has hindered research progress. In this study, the impact of experimental conditions on the calcification of cementoblasts was systematically investigated, aimed at establishing a standardized and validated model for the calcification of cementoblasts. The effects of phosphate, calcium, ascorbic acid, β-glycerolphosphate, dexamethasone, and fetal calf serum on the calcification process of cementoblasts were analyzed over a wide range of concentrations and time points by investigating calcium content, cell viability, gene expression and kinase activity. Cementoblasts calcified in a concentration- and time-dependent manner with higher concentrations of supplements cause a higher degree of calcification but decreased cell viability. Phosphate and calcium have a significantly stronger effect on cementoblast calcification processes compared to osteogenic supplements: ascorbic acid, β-glycerolphosphate, and dexamethasone induce calcification over a wide range of osteogenic signalling pathways, with osteopontin being a central target of gene regulation. Conversely, treatment with ascorbic acid, β-glycerolphosphate, and dexamethasone leads to activating only selected pathways, especially promoting bone sialoprotein expression. The developed and validated cementoblast calcification protocol, incubating up to 60% confluent cementoblasts with 1.9 mmol L-1 of phosphate supplementation for a reasonable, multi-pathway calcification induction and 10 mmol L-1 β-glycerolphosphate, 75 µmol L-1 ascorbic acid and 10 nmol L-1 dexamethasone for a reasonable osteogenic differentiation-based calcification induction, provides standard in vitro experimental models for better understanding cementoblast function and regeneration.

Knockout of Bone Sialoprotein in Cementoblasts Cell Lines Affects Specific Gene Expression in Unstimulated and Mechanically Stimulated Conditions

One of the major components in cementum extracellular matrix is bone sialoprotein (BSP). BSP knockout (Ibsp) mice were reported to have a nonfunctional hypo-mineralized cementum, as well as detachment and disorganization of the periodontal ligament tissue. However, studies investigating the influence of Ibsp in cementoblasts are missing yet. This study investigates the influences of Bsp in three cementoblasts cell lines (OCCM.30-WT,Ibsp^ΔNterm, and Ibsp^KAE). The mRNA expression of cementoblast and osteoclast markers (Col1a1, Alpl, Ocn, Runx2, Ctsk, Rankl and Opg) and the cell morphology were compared. Additionally, a functional monocyte adhesion assay was performed. To understand the influence of external stimuli, the effect of Ibsp was investigated under static compressive force, mimicking the compression side of orthodontic tooth movement. Cementoblasts with genotype Ibsp^ΔNterm and Ibsp^KAE showed slight differences in cell morphology compared to OCCM.30-WT, as well as different gene expression. Under compressive force, the Ibsp cell lines presented expression pattern markers similar to the OCCM.30-WT cell line. However, Cathepsin K was strongly upregulated in Ibsp^ΔNterm cementoblasts under compressive force. This study provides insight into the role of BSP in cementoblasts and explores the influence of BSP on periodontal ligament tissues. BSP markers in cementoblasts seem to be involved in the regulation of cementum organization as an important factor for a functional periodontium. In summary, our findings provide a basis for investigations regarding molecular biology interactions of BSP in cementoblasts, and a supporting input for understanding the periodontal and cellular cementum remodeling.

Use of Computation Ecosystems to Analyze the Kidney-Heart Crosstalk

The identification of mediators for physiologic processes, correlation of molecular processes, or even pathophysiological processes within a single organ such as the kidney or heart has been extensively studied to answer specific research questions using organ-centered approaches in the past 50 years. However, it has become evident that these approaches do not adequately complement each other and display a distorted single-disease progression, lacking holistic multilevel/multidimensional correlations. Holistic approaches have become increasingly significant in understanding and uncovering high dimensional interactions and molecular overlaps between different organ systems in the pathophysiology of multimorbid and systemic diseases like cardiorenal syndrome because of pathological heart-kidney crosstalk. Holistic approaches to unraveling multimorbid diseases are based on the integration, merging, and correlation of extensive, heterogeneous, and multidimensional data from different data sources, both -omics and nonomics databases. These approaches aimed at generating viable and translatable disease models using mathematical, statistical, and computational tools, thereby creating first computational ecosystems. As part of these computational ecosystems, systems medicine solutions focus on the analysis of -omics data in single-organ diseases. However, the data-scientific requirements to address the complexity of multimodality and multimorbidity reach far beyond what is currently available and require multiphased and cross-sectional approaches. These approaches break down complexity into small and comprehensible challenges. Such holistic computational ecosystems encompass data, methods, processes, and interdisciplinary knowledge to manage the complexity of multiorgan crosstalk. Therefore, this review summarizes the current knowledge of kidney-heart crosstalk, along with methods and opportunities that arise from the novel application of computational ecosystems providing a holistic analysis on the example of kidney-heart crosstalk.

Fosl1: friend or foe?

Fos-like antigen 1 (Fosl1) is a protein that belongs to the Fos family of transcription factors. Fosl1 has an impact on (i) carcinogenesis, (ii) acute kidney injury, and (iii) fibroblast growth factor expression. Recently, the nephroprotective effect of Fosl1 by the preservation of Klotho expression was recently identified. The identification of a link between Fosl1 and Klotho expression provides an entirely new field of nephroprotection.

Role of polyphenolic compounds and their nanoformulations: a comprehensive review on cross-talk between chronic kidney and cardiovascular diseases

Chronic kidney disease (CKD) affects a huge portion of the world's population and frequently leads to cardiovascular diseases (CVDs). It might be because of common risk factors between chronic kidney disease and cardiovascular diseases. Renal dysfunction caused by chronic kidney disease creates oxidative stress which in turn leads to cardiovascular diseases. Oxidative stress causes endothelial dysfunction and inflammation in heart which results in atherosclerosis. It ends in clogging of veins and arteries that causes cardiac stroke and myocardial infarction. To develop an innovative therapeutic approach and new drugs to treat these diseases, it is important to understand the pathophysiological mechanism behind the CKD and CVDs and their interrelationship. Natural phytoconstituents of plants such as polyphenolic compounds are well known for their medicinal value. Polyphenols are plant secondary metabolites with immense antioxidant properties, which can protect from free radical damage. Nowadays, polyphenols are generating a lot of buzz in the scientific community because of their potential health benefits especially in the case of heart and kidney diseases. This review provides a detailed account of the pathophysiological link between CKD and CVDs and the pharmacological potential of polyphenols and their nanoformulations in promoting cardiovascular and renal health.

Assembly of chemically modified protein nanocages into 3D materials for the adsorption of uremic toxins

Hemodialysis fails to remove protein-bound uremic toxins that are attributed with high cardiovascular risk. Application of adsorption materials is a viable strategy, but suitable biocompatible adsorbents are still not available. Here, we demonstrate that adsorbents based on the bottom-up assembly of the intrinsically biocompatible protein cage ferritin are applicable for toxin adsorption. Due to the size-exclusion effect of its pores, only small molecules such as uremic toxins can enter the protein cage. Protein redesign techniques that target selectively the inner surface were used to introduce anchor sites for chemical modification. Porous crystalline adsorbents were fabricated by bottom-up assembly of the protein cage. Linkage of up to 96 phenylic or aliphatic molecules per container was verified by ESI-MS. Materials based on unmodified ferritin cages can already adsorb the uremic toxins. The adsorption capacity could be increased by about 50% through functionalization with hydrophobic molecules reaching 458 μg g^-1 for indoxyl sulfate. The biohybrid materials show no contamination with endotoxins and do not activate blood platelets. These findings demonstrate the great potential of protein-based adsorbents for the clearance of uremic toxins: modifications enhance toxin adsorption without diminishing the biocompatibility of the final protein-based material.

Xanthohumol exerts anti-inflammatory effects in an in vitro model of mechanically stimulated cementoblasts

Xanthohumol (XN) is a prenylated plant polyphenol that naturally occurs in hops and its products, e.g. beer. It has shown to have anti-inflammatory and angiogenesis inhibiting effects and it prevents the proliferation of cancer cells. These effects could be in particular interesting for processes within the periodontal ligament, as previous studies have shown that orthodontic tooth movement is associated with a sterile inflammatory reaction. Based on this, the study evaluates the anti-inflammatory effect of XN in cementoblasts in an in vitro model of the early phase of orthodontic tooth movement by compressive stimulation. XN shows a concentration-dependent influence on cell viability. Low concentrations between 0.2 and 0.8 µM increase viability, while high concentrations between 4 and 8 µM cause a significant decrease in viability. Compressive force induces an upregulation of pro-inflammatory gene (Il-6, Cox2, Vegfa) and protein (IL-6) expression. XN significantly reduces compression related IL-6 protein and gene expression. Furthermore, the expression of phosphorylated ERK and AKT under compression was upregulated while XN re-established the expression to a level similar to control. Accordingly, we demonstrated a selective anti-inflammatory effect of XN in cementoblasts. Our findings provide the base for further examination of XN in modulation of inflammation during orthodontic therapy and treatment of periodontitis.

Endothelial CaSR is involved in the induction of atherosclerosis by promoting cell adhesion and local inflammation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Humboldt foundation

Background

Calcium-Sensing Receptor (CaSR) is a cell surface G-protein coupled receptor that senses calcium in the extracellular environment. This receptor is widely studied in mineral homeostasis due to its presence in varied calcitropic tissues. However, CaSR is also present on the surface of vascular and hematopoietic cells and recent studies suggest that this receptor can also have pathological consequences related to cardiovascular diseases, like atherosclerosis. Since endothelial cells are crucial players in atherogenesis, we aimed to investigate which role endothelial CaSR plays in the development and progression of atherosclerosis.

Methods

We cross-bred CaSRflox/flox Apoe-/- mice with BmxCreERT2 Apoe-/- (endothelial cell specific Cre driver) mice to obtain tamoxifen-inducible mice which have an endothelial cell specific deletion of CaSR. The mice were then fed with a high fat diet (HFD) for 4 or 12 weeks, reflecting early and late atherosclerosis, respectively. We used histological and immuno-fluorescent stainings to analyse the atherosclerotic lesion size and its cellular and acellular composition. Systemic effects on leukocytes were evaluated using flow-cytometry, while intra-vital microscopy was used to study leukocyte adhesion to activated endothelium in-vivo. Further mechanistic studies were performed in human coronary artery endothelial cells (HCAECs) in-vitro.

Results

Endothelial CaSR deficiency in mice resulted in significantly smaller lesion size in early atherosclerotic stages (4 weeks HFD), whereas late atherosclerotic lesions (12 weeks HFD) were not affected by the lack of endothelial CaSR. Moreover, the phenotype of atherosclerotic plaques, characterized by macrophage, smooth muscle cell, collagen and necrotic core content remained unaltered between wild-type and endothelial cell specific CaSR knockout mice. Interestingly, leukocyte adhesion in-vivo, especially neutrophil adhesion, was significantly reduced in endothelial cell CaSR deficient mice. In line with this, overexpression of CaSR in HCAECs in-vitro increased the production of inflammatory cytokines and expression of adhesion molecules ICAM and VCAM.

Conclusion

Our results indicate that while endothelial cell specific CaSR is involved in the induction of atherosclerosis, it does not play a major role in its progression. CaSR has a major influence on endothelium-leukocyte interaction and endothelial inflammation. The increased expression of ICAM/VCAM suggest that CaSR mainly mediates such adhesive effects by modulating integrin expression. Thereby this study highlights that CaSR plays a crucial role in atherosclerosis development, rendering it a novel, so far unexplored therapeutic target.

Lipids and lipoproteins in cardiovascular diseases: a classification

Lipids and lipoproteins, their metabolism, and their transport are essential contributing factors of cardiovascular disease (CVD) as they regulate plasma cholesterol concentration, enhancing cholesterol uptake by macrophages, leading to foam cell formation and ultimately resulting in plaque formation and inflammation. However, lipids and lipoproteins have cardioprotective functions as well, such as preventing oxidation of proatherogenic molecules and downregulating inflammatory proteins.

Empagliflozin reduces markers of acute kidney injury in patients with acute decompensated heart failure

AIMS

In this prospective, placebo-controlled, double-blind, exploratory study, we examined early and more delayed effects of empagliflozin treatment on haemodynamic parameters (primary endpoint: cardiac output) and kidney function including parameters of acute kidney injury (AKI) in patients with acute decompensated heart failure (HF).

METHODS AND RESULTS

Patients with acute decompensated HF with or without diabetes were randomized to empagliflozin 10 mg or placebo for 30 days. Haemodynamic, laboratory, and urinary parameters were assessed after 6 h, 1 day, 3 days, 7 days, and 30 days of treatment. Median time between hospital admission and randomization was 72 h. Baseline characteristics were not different in the empagliflozin (n = 10) and placebo (n = 9) groups. Empagliflozin led to a significant increase in urinary glucose excretion throughout the study (baseline: 37 ± 15 mg/24 h; Day 1: 14 565 ± 8663 mg/24 h; P = 0.001). Empagliflozin did not affect the primary endpoint of cardiac index or on systemic vascular resistance index at any time point. However, empagliflozin significantly reduced parameters of AKI (urinary TIMP-2 and IGFBP7 by NephroCheck® as indicators of tubular kidney damage), which became significant after 3 days of treatment [placebo: 1.1 ± 1.1 (ng/mL)² /1000; empagliflozin: 0.3 ± 0.2 (ng/mL)² /1000; P = 0.02] and remained significant at the 7 day time point [placebo: 2.5 ± 3.8 (ng/mL)² /1000; empagliflozin: 0.3 ± 0.2 (ng/mL)² /1000; P = 0.003].

CONCLUSIONS

In this study, empagliflozin treatment did not affect haemodynamic parameters but significantly reduced markers of tubular injury in patients with acute decompensated HF.

MO453: Post-Translational Guanidinylation of Apolipoprotein C3 (APOC3) is Associated With Kidney and Vascular Injury

BACKGROUND AND AIMS

Cardiovascular diseases (CVD) and chronic kidney diseases (CKD) are highly prevalent in Western populations and account for a substantial proportion of mortality. We recently found that apolipoprotein C-3 (ApoC3), a constituent of triglyceride-rich lipoproteins, induces alternative NLRP3 inflammasome activation leading to sterile inflammation. In the present study, we aimed to assess post-translational modifications (PTMs) of ApoC3 in patients with CKD, to determine the effects of post-translationally modified ApoC3 in vitro and in vivo, and to test the relevance in a prospective clinical trial.

METHOD

Using mass-spectrometry, we screened ApoC3 for PTMs We determined the effects of modified ApoC3 on monocyte inflammatory response in vitro and assessed its effects in humanized mice subjected to a vascular injury model and unilateral ureter ligation. Finally, we assessed the association of post-translationally modified ApoC3 and cardiovascular and renal events in a prospective clinical trial of 543 CKD patients.

RESULTS

We identified post-translational guanidinylation of ApoC3 (gApoC3) in patients with CKD, which augments the proinflammatory effects of ApoC3. Mechanistically, guanidine and urea induced guanidinylation of ApoC3. gApoC3 accumulates in kidneys and plasma of mice subjected to a CKD model as determined by 2D-proteomic analyses. In humanized mice, gApoC3 promotes kidney fibrosis and impedes vascular regeneration. In the clinical trial, higher gApoC3 blood levels as determined by mass spectrometry were associated with increased mortality as well as cardiovascular and renal events.

CONCLUSION

Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, rendering gApoC3 a potential therapeutic target.

MO396: Development, Establishment and Validation of in Vitro and EX Vivo Assays of Vascular Calcification

BACKGROUND AND AIMS

Vascular calcification is one major complication in patients with chronic kidney disease (CKD), with a misbalance in calcium and phosphate metabolism playing a crucial role. The mechanisms underlying vascular calcification have not been entirely revealed to date. As studies aiming at the identification and characterization of the involved mediators are highly relevant, standardized operating protocols (SOP) for reliable assays to make different studies comparable, are needed.

METHOD

We are dealing with the following in vitro and ex vivo experimental conditions to study vascular calcifications: induction of calcification by phosphate and CaCl2, incubation time, as well as foetal calve serum concentration and ageing. Furthermore, the location and inhibition of vascular calcifications are studied. Human aortic smooth muscle cells are used for in vitro experiments and rat aorta for ex vivo experiments. The degree of calcification is estimated by quantification of calcium concentrations and by von Kossa staining.

RESULTS

As a result, a step-by-step protocol for performing experiments on vascular calcification was created.

CONCLUSION

Through the established protocol and examination of decent modifications nuances, we aim to promote standardized research on vascular calcification.

MO413: Registration of Image Modalities for Analyses of Tissue Samples Using 3D Image Modelling

BACKGROUND AND AIMS

Biopsies are a diagnostic tool for the diagnosis of histopathological, molecular biological, proteomic and imaging data, to narrow down disease patterns or identify diseases. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) provides an emerging state-of-the-art technique for molecular imaging of biological tissue. The aim of this study is the registration of MALDI MSI data sets and data acquired from different histological stainings to create a 3D model of biopsies and whole organs.

METHOD

The registration of the image modalities is achieved by using a variant of our global, deformable Schatten-q-Norm registration approach. Utilizing a connected-component segmentation for background removal followed by a principal-axis-based linear pre-registration, the images are adjusted into a homogeneous alignment. This registration approach is accompanied by the 3D reconstruction of histological and MALDI MSI data.

RESULTS

With this, a system of automatic registration for cross-process evaluation, as well as for creating 3D models, is developed and established. The registration of MALDI MSI data with different histological image data is evaluated by using the established global image registration system.

CONCLUSION

In conclusion, this multimodal image approach offers the possibility of molecular analyses of tissue specimens in clinical research and diagnosis.

MO185: Post-Translational Carbamylation of Sortilin is Associated with Cardiovascular Calcification in Chronic Kidney Disease

BACKGROUND AND AIMS

Sortilin, an intracellular sorting receptor, has been identified as a cardiovascular (CV) risk factor in the general population. Patients with chronic kidney disease (CKD) are highly susceptible to developing CV complications such as CV calcification. However, specific CKD-induced post-translational protein modifications of sortilin and their link to CV calcification remain unknown.

METHODS

Circulating sortilin isolated from two independent CKD cohorts was analysed by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF mass spectrometry). The binding partner affinity was analysed by surface plasmon resonance spectroscopy. The effect of carbamylated sortilin on vascular calcification was analysed in vitro using human coronary artery smooth muscle cells.

RESULTS

In CKD patients, targeted mass spectrometric analyses of circulating sortilin revealed an increase in carbamylated lysine residues with kidney function decline. Carbamylation did not affect dimer formation of sortilin assessed by mass spectrometry. We observed an increased affinity of interleukin 6 to in vitro carbamylated sortilin. Carbamylated sortilin increased SMC calcification in vitro that was accelerated by interleukin 6, while carbamylated albumin and collagen type I did not affect SMC calcification. Mass-spectrometry imaging of human calcified arteries revealed in situ carbamylated sortilin. In CKD patients, sortilin carbamylation was associated with coronary artery calcification volume, independent of age, kidney function and other risk factors. Moreover, patients with carbamylated sortilin displayed significantly faster coronary artery calcification progression than patients without sortilin carbamylation.

CONCLUSION

Carbamylated sortilin is a risk factor for CV calcification and may contribute to elevated CV complications in patients with CKD.

MO459: Characterization of Adrenal Gland Derived Mediators of Vascular Calcification

BACKGROUND AND AIMS

Adrenal glands participate in cardiovascular physiology and pathophysiology via the synthesis and secretion of various well-known compounds like mineralocorticoids, amine peptides and glucocorticoids. In this study, a previously unknown systemic function of adrenal glands, that is the regulation of vascular calcification processes was investigated.

METHOD

The homogenate of the bovine adrenal gland was separated using chromatographic fractionation. The fractions were analysed in aortic smooth muscle cells, aortic rings and vitamin D3 plus nicotine elastocalcinosis rat model for effects on vascular calcification processes. Potential mediators were distinguished by mass spectrometry and comparison with pertinent databases. For ease of therapeutic application, smaller fragments of the identified mediators were analysed to identify the active sites.

RESULTS

We identified a new 19aa peptide, named ‘calcification blocking factor’ (CBF), which shows a promising protective effect against vascular calcification. CBF is released from the parent protein Chromogranin A, which is released from adrenal glands via enzymatic cleavage by calpain 1 and kallikrein. CBF reduced the calcium content of cells and aortic rings in calcifying cultures. CBF downregulates vascular smooth muscle cell (VSMC) trans-differentiation into osteoblast-like cells within the vascular wall via the sodium-dependent phosphate transporter PIT-1 and by inhibiting the NF-κB activation and the subsequent BMP2/p-SMAD pathway. VDN animals treated with CBF show a significantly decreased pulse pressure as a marker of arterial stiffness. An 8aa peptide was found to have a better effect on reducing vascular calcification when compared to the original peptide.

CONCLUSION

The adrenal glands participate in cardiovascular (CV) physiology and the pathophysiology of CV diseases through their effects on sodium and water metabolism, vascular tone and cardiac function. In the present study, we identified a previously uncharacterized peptide secreted from the adrenal gland that modulates cardiovascular calcification by regulating osteoblastic differentiation in the context of vascular calcification. We show that CBF reduces calcification via PIT-1/NF-κB/BMP2/p-SMAD pathway. Further, we identified the active site of this peptide (8aa long) which can be used as a therapeutic agent. These findings suggest a novel function of adrenal glands in cardiovascular calcification.

MO379: Collagen-Derived Peptides in CKD: A Link to Fibrosis

BACKGROUND AND AIMS

Collagen is a major component of the extracellular matrix (ECM) and has an essential role in the onset and progression of fibrosis and chronic kidney disease (CKD). Collagen alpha-1(I) (col1a1) is the most abundant collagen type in humans and the involvement of col1a1in CKD onset and progression is well established. We aimed to assess in detail the association of urinary col1a1 fragments with the progression of CKD and ageing.

METHOD

About 5000 urinary peptidomic datasets from healthy participants and CKD patients were retrieved from the ‘Human Urinary Proteome Database’. Inclusion criteria were age >18 years and eGFR being available. Urinary col1a1 fragments were identified and their abundance and correlation with eGFR and age were investigated.

RESULTS

Of 707 specific col1a1 peptides, 63 were significantly and highly positively associated with eGFR, while only six peptides showed a significant and strong negative association. A similar tendency was observed for ageing, where the abundance of most of the 244 peptides significantly associated with age, decreased with increasing age. The ten most significantly correlated peptides associated with eGFR corrected for age or age in a cohort matched for eGFR are listed in the table.

CONCLUSION

The results show a strong association between the reduced abundance of urinary collagen peptides and loss of kidney function as well as ageing. The data suggest that the col1a1 peptides indicate reduced degradation of collagen in CKD and aging. The results further suggest that fibrosis, potentially also of other organs, may be the consequence of attenuation of collagen degradation, and not increased synthesis.

MicroRNA-26b Attenuates Platelet Adhesion and Aggregation in Mice

Platelets are key regulators of haemostasis, making platelet dysfunction a major driver of thrombosis. Numerous processes that determine platelet function are influenced by microRNAs (miRs). MiR-26b is one of the highest-expressed miRs in healthy platelets, and its expression in platelets is changed in a diseased state. However, the exact effect of this miR on platelet function has not been studied yet. In this study, we made use of a whole-body knockout of miR-26b in ApoE-deficient mice in order to determine its impact on platelet function, thrombus formation and platelet signalling both ex vivo and in vivo. We show that a whole-body deficiency of miR-26b exacerbated platelet adhesion and aggregation ex vivo. Additionally, in vivo, platelets adhered faster, and larger thrombi were formed in mice lacking miR-26b. Moreover, isolated platelets from miR-26b-deficient mice showed a hyperactivated Src and EGFR signalling. Taken together, we show here for the first time that miR-26b attenuates platelet adhesion and aggregation, possibly through Src and EGFR signalling.

Stimulation of the EP3 receptor causes lung edema by activation of TRPC6 in pulmonary endothelial cells

BACKGROUND

Prostaglandin E₂ (PGE₂) increases pulmonary vascular permeability by activation of the PGE₂ receptor 3 (EP₃) which may explain adverse pulmonary effects of the EP₁/EP₃ receptor agonist sulprostone in patients. PGE₂ also contributes to pulmonary edema in response to platelet-activating factor (PAF). PAF increases endothelial permeability by recruiting the cation channel transient receptor potential canonical 6 (TRPC6) to endothelial caveolae via acid sphingomyelinase (ASMase). Yet, the roles of PGE₂ and EP₃ in this pathway are unknown. We hypothesized that EP₃ receptor activation may increase pulmonary vascular permeability by activation of TRPC6, and thus, synergize with ASMase-mediated TRPC6 recruitment in PAF-induced lung edema.

METHODS

In isolated lungs, we measured increases in endothelial Ca²⁺ (ΔCa²⁺) or lung weight (Δweight), and endothelial caveolar TRPC6 abundance as well as phosphorylation.

RESULTS

PAF-induced ΔCa²⁺ and Δweight were attenuated in EP₃-deficient mice. Sulprostone replicated PAF-induced ΔCa²⁺ and Δweight which were blocked by pharmacologic/genetic inhibition of TRPC6, ASMase, or Src-family kinases (SrcFK). PAF, yet not sulprostone, increased TRPC6 abundance in endothelial caveolae. Immunoprecipitation revealed PAF- and sulprostone-induced tyrosine-phosphorylation of TRPC6 that was prevented by inhibition of phospholipase C (PLC) or SrcFK. PLC inhibition also blocked sulprostone-induced ΔCa²⁺ and Δweight, as did inhibition of SrcFK or G_i signaling.

CONCLUSIONS

EP₃ activation triggers pulmonary edema via G_i-dependent activation of PLC and subsequent SrcFK-dependent tyrosine phosphorylation of TRPC6. In PAF-induced lung edema this TRPC6 activation coincides with ASMase-dependent caveolar recruitment of TRPC6, resulting in rapid endothelial Ca²⁺ influx and barrier failure.

Urine peptidome in combination with transcriptomics analysis highlights MMP7, MMP14 and PCSK5 for further investigation in chronic kidney disease

Chronic kidney disease (CKD) is characterized by the loss of kidney function. The molecular mechanisms underlying the development and progression of CKD are still not fully understood. Among others, the urinary peptidome has been extensively studied, with several urinary peptides effectively detecting disease progression. However, their link to proteolytic events has not been made yet. This study aimed to predict the proteases involved in the generation of CKD-associated urinary excreted peptides in a well-matched (for age, sex, lack of heart disease) case-control study. The urinary peptide profiles from CKD (n = 241) and controls (n = 240) were compared and statistically analyzed. The in-silico analysis of the involved proteases was performed using Proteasix and proteases activity was predicted based on the abundance changes of the associated peptides. Predictions were cross-correlated to transcriptomics datasets by using the Nephroseq database. Information on the respective protease inhibitors was also retrieved from the MEROPS database. Totally, 303 urinary peptides were significantly associated with CKD. Among the most frequently observed were fragments of collagen types I, II and III, uromodulin, albumin and beta-2-microglobulin. Proteasix predicted 16 proteases involved in their generation. Through investigating CKD-associated transcriptomics datasets, several proteases are highlighted including members of matrix metalloproteinases (MMP7, MMP14) and serine proteases (PCSK5); laying the foundation for further studies towards elucidating their role in CKD pathophysiology.

Platelet Abnormalities in CKD and Their Implications for Antiplatelet Therapy

Patients with CKD display a significantly higher risk of cardiovascular and thromboembolic complications, with around half of patients with advanced CKD ultimately dying of cardiovascular disease. Paradoxically, these patients also have a higher risk of hemorrhages, greatly complicating patient therapy. Platelets are central to hemostasis, and altered platelet function resulting in either platelet hyper- or hyporeactivity may contribute to thrombotic or hemorrhagic complications. Different molecular changes have been identified that may underlie altered platelet activity and hemostasis in CKD. In this study, we summarize the knowledge on CKD-induced aberrations in hemostasis, with a special focus on platelet abnormalities. We also discuss how prominent alterations in vascular integrity, coagulation, and red blood cell count in CKD may contribute to altered hemostasis in these patients who are high risk. Furthermore, with patients with CKD commonly receiving antiplatelet therapy to prevent secondary atherothrombotic complications, we discuss antiplatelet treatment strategies and their risk versus benefit in terms of thrombosis prevention, bleeding, and clinical outcome depending on CKD stage. This reveals a careful consideration of benefits versus risks of antiplatelet therapy in patients with CKD, balancing thrombotic versus bleeding risk. Nonetheless, despite antiplatelet therapy, patients with CKD remain at high cardiovascular risk. Thus, deep insights into altered platelet activity in CKD and underlying mechanisms are important for the optimization and development of current and novel antiplatelet treatment strategies, specifically tailored to these patients who are high risk. Ultimately, this review underlines the importance of a closer investigation of altered platelet function, hemostasis, and antiplatelet therapy in patients with CKD.

Guanidinylated Apolipoprotein C3 (ApoC3) Associates with Kidney and Vascular Injury

BACKGROUND

Coexistent CKD and cardiovascular diseases are highly prevalent in Western populations and account for substantial mortality. We recently found that apolipoprotein C-3 (ApoC3), a major constituent of triglyceride-rich lipoproteins, induces sterile systemic inflammation by activating the NOD-like receptor protein-3 (NLRP3) inflammasome in human monocytes via an alternative pathway.

METHODS

To identify posttranslational modifications of ApoC3 in patients with CKD, we used mass spectrometry to analyze ApoC3 from such patients and from healthy individuals. We determined the effects of posttranslationally modified ApoC3 on monocyte inflammatory response in vitro, as well as in humanized mice subjected to unilateral ureter ligation (a kidney fibrosis model) and in a humanized mouse model for vascular injury and regeneration. Finally, we conducted a prospective observational trial of 543 patients with CKD to explore the association of posttranslationally modified ApoC3 with renal and cardiovascular events in such patients.

RESULTS

We identified significant posttranslational guanidinylation of ApoC3 (gApoC3) in patients with CKD. We also found that mechanistically, guanidine and urea induce guanidinylation of ApoC3. A 2D-proteomic analysis revealed that gApoC3 accumulated in kidneys and plasma in a CKD mouse model (mice fed an adenine-rich diet). In addition, gApoC3 augmented the proinflammatory effects of ApoC3 in monocytes in vitro . In humanized mice, gApoC3 promoted kidney tissue fibrosis and impeded vascular regeneration. In CKD patients, higher gApoC3 plasma levels (as determined by mass spectrometry) were associated with increased mortality as well as with renal and cardiovascular events.

CONCLUSIONS

Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, pointing to gApoC3 as a potential therapeutic target.

Effects of empagliflozin on erythropoiesis in patients with type 2 diabetes: Data from a randomized, placebo-controlled study

Sodium-glucose cotransporter-2 (SGLT2) inhibitors have been shown to significantly reduce hospitalization for heart failure (HHF) and cardiovascular (CV) mortality in various CV outcome trials in patients with and without type 2 diabetes mellitus (T2D). SGLT2 inhibition further increased haemoglobin and haematocrit levels by an as yet unknown mechanism, and this increase has been shown to be an independent predictor of the CV benefit of these agents, for example, in the EMPA-REG OUTCOME trial. The present analysis of the EMPA haemodynamic study examined the early and delayed effects of empagliflozin treatment on haemoglobin and haematocrit levels, in addition to measures of erythropoiesis and iron metabolism, to better understand the underlying mechanisms. In this prospective, placebo-controlled, double-blind, randomized, two-arm parallel, interventional and exploratory study, 44 patients with T2D were randomized into two groups and received empagliflozin 10 mg or placebo for a period of 3 months in addition to their concomitant medication. Blood and urine was collected at baseline, on Day 1, on Day 3 and after 3 months of treatment to investigate effects on haematological variables, erythropoietin concentrations and indices of iron stores. Baseline characteristics were comparable in the empagliflozin (n = 20) and placebo (n = 22) group. Empagliflozin led to a significant increase in urinary glucose excretion (baseline: 7.3 ± 22.7 g/24 h; Day 1: 48.4 ± 34.7 g/24 h; P < 0.001) as well as urinary volume (baseline: 1740 ± 601 mL/24 h; Day 1: 2112 ± 837 mL/24 h; P = 0.011) already after 1 day and throughout the 3-month study period, while haematocrit and haemoglobin were only increased after 3 months of treatment (haematocrit: baseline: 40.6% ± 4.6%; Month 3: 42.2% ±  4.8%, P < 0.001; haemoglobin: baseline: 136 ± 19 g/L; Month 3: 142 ± 25 g/L; P = 0.008). In addition, after 3 months, empagliflozin further increased red blood cell count (P < 0.001) and transferrin concentrations (P = 0.063) and there was a trend toward increased erythropoietin levels (P = 0.117), while ferritin (P = 0.017), total iron (P = 0.053) and transferrin saturation levels (P = 0.030) decreased. Interestingly, the increase in urinary glucose excretion significantly correlated with the induction of erythropoietin in empagliflozin-treated patients at the 3-month timepoint (Spearman rho 0.64; P = 0.008). Empagliflozin increased haemoglobin concentrations and haematocrit with a delayed time kinetic, which was most likely attributable to increased erythropoiesis with augmented iron utilization and not haemoconcentration. This might be attributable to reduced tubular glucose reabsorption in response to SGLT2 inhibition, possibly resulting in diminished cellular stress as a mechanism for increased renal erythropoietin secretion.

A systematic review and meta-analysis of murine models of uremic cardiomyopathy

Chronic kidney disease (CKD) triggers the risk of developing uremic cardiomyopathy as characterized by cardiac hypertrophy, fibrosis and functional impairment. Traditionally, animal studies are used to reveal the underlying pathological mechanism, although variable CKD models, mouse strains and readouts may reveal diverse results. Here, we systematically reviewed 88 studies and performed meta-analyses of 52 to support finding suitable animal models for future experimental studies on pathological kidney-heart crosstalk during uremic cardiomyopathy. We compared different mouse strains and the direct effect of CKD on cardiac hypertrophy, fibrosis and cardiac function in "single hit" strategies as well as cardiac effects of kidney injury combined with additional cardiovascular risk factors in "multifactorial hit" strategies. In C57BL/6 mice, CKD was associated with a mild increase in cardiac hypertrophy and fibrosis and marginal systolic dysfunction. Studies revealed high variability in results, especially regarding hypertrophy and systolic function. Cardiac hypertrophy in CKD was more consistently observed in 129/Sv mice, which express two instead of one renin gene and more consistently develop increased blood pressure upon CKD induction. Overall, "multifactorial hit" models more consistently induced cardiac hypertrophy and fibrosis compared to "single hit" kidney injury models. Thus, genetic factors and additional cardiovascular risk factors can "prime" for susceptibility to organ damage, with increased blood pressure, cardiac hypertrophy and early cardiac fibrosis more consistently observed in 129/Sv compared to C57BL/6 strains.

Carbamylated sortilin associates with cardiovascular calcification in patients with chronic kidney disease

Sortilin, an intracellular sorting receptor, has been identified as a cardiovascular risk factor in the general population. Patients with chronic kidney disease (CKD) are highly susceptible to develop cardiovascular complications such as calcification. However, specific CKD-induced posttranslational protein modifications of sortilin and their link to cardiovascular calcification remain unknown. To investigate this, we examined two independent CKD cohorts for carbamylation of circulating sortilin and detected increased carbamylated sortilin lysine residues in the extracellular domain of sortilin with kidney function decline using targeted mass spectrometry. Structure analysis predicted altered ligand binding by carbamylated sortilin, which was verified by binding studies using surface plasmon resonance measurement, showing an increased affinity of interleukin 6 to in vitro carbamylated sortilin. Further, carbamylated sortilin increased vascular calcification in vitro and ex vivo that was accelerated by interleukin 6. Imaging by mass spectrometry of human calcified arteries revealed in situ carbamylated sortilin. In patients with CKD, sortilin carbamylation was associated with coronary artery calcification, independent of age and kidney function. Moreover, patients with carbamylated sortilin displayed significantly faster progression of coronary artery calcification than patients without sortilin carbamylation. Thus, carbamylated sortilin may be a risk factor for cardiovascular calcification and may contribute to elevated cardiovascular complications in patients with CKD.

CCR6 Deficiency Increases Infarct Size after Murine Acute Myocardial Infarction

Ischemia-reperfusion injury after the reopening of an occluded coronary artery is a major cause of cardiac damage and inflammation after acute myocardial infarction. The chemokine axis CCL20-CCR6 is a key player in various inflammatory processes, including atherosclerosis; however, its role in ischemia-reperfusion injury has remained elusive. Therefore, to gain more insight into the role of the CCR6 in acute myocardial infarction, we have studied cardiac injury after transient ligation of the left anterior descending coronary artery followed by reperfusion in Ccr6-/- mice and their respective C57Bl/6 wild-type controls. Surprisingly, Ccr6-/- mice demonstrated significantly reduced cardiac function and increased infarct sizes after ischemia/reperfusion. This coincided with a significant increase in cardiac inflammation, characterized by an accumulation of neutrophils and inflammatory macrophage accumulation. Chimeras with a bone marrow deficiency of CCR6 mirrored this adverse Ccr6-/- phenotype, while cardiac injury was unchanged in chimeras with stromal CCR6 deficiency. This study demonstrates that CCR6-dependent (bone marrow) cells exert a protective role in myocardial infarction and subsequent ischemia-reperfusion injury, supporting the notion that augmenting CCR6-dependent immune mechanisms represents an interesting therapeutic target.

Reduction of protein-bound uraemic toxins in plasma of chronic renal failure patients: A systematic review

BACKGROUND

Protein-bound uraemic toxins (PBUTs) accumulate in patients with chronic kidney disease and impose detrimental effects on the vascular system. However, a unanimous consensus on the most optimum approach for the reduction of plasma PBUTs is still lacking.

METHODS

In this systematic review, we aimed to identify the most efficient clinically available plasma PBUT reduction method reported in the literature between 1980 and 2020. The literature was screened for clinical studies describing approaches to reduce the plasma concentration of known uraemic toxins. There were no limits on the number of patients studied or on the duration or design of the studies.

RESULTS

Out of 1274 identified publications, 101 studies describing therapeutic options aiming at the reduction of PBUTs in CKD patients were included in this review. We stratified the studies by the PBUTs and the duration of the analysis into acute (data from a single procedure) and longitudinal (several treatment interventions) trials. Reduction ratio (RR) was used as the measure of plasma PBUTs lowering efficiency. For indoxyl sulphate and p-cresyl sulphate, the highest RR in the acute studies was demonstrated for fractionated plasma separation, adsorption and dialysis system. In the longitudinal trials, supplementation of haemodialysis patients with AST-120 (Kremezin®) adsorbent showed the highest RR. However, no superior method for the reduction of all types of PBUTs was identified based on the published studies.

CONCLUSIONS

Our study shows that there is presently no technique universally suitable for optimum reduction of all PBUTs. There is a clear need for further research in this field.

Irreversible post-translational modifications - Emerging cardiovascular risk factors

Despite the introduction of lipid-lowering drugs, antihypertensives, antiplatelet and anticoagulation therapies for primary prevention of cardiovascular and heart diseases (CVD), it remains the number one cause of death globally, raising the question for novel/further essential factors besides traditional risk factors such as cholesterol, blood pressure and coagulation. With continuous identification and characterization of non-enzymatic post-translationally modified isoforms of proteins and lipoproteins, it is becoming increasingly clear that irreversible non-enzymatic post-translational modifications (nPTMs) alter the biological functions of native proteins and lipoproteins thereby transforming innate serum components into CVD mediators. In particular renal insufficiency and metabolic imbalance are major contributors to the systemically increased concentration of reactive metabolites and thus increased frequency of nPTMs, promoting multi-morbid disease development centering around cardiovascular disease. nPTMs are significantly involved in the onset and progression of cardiovascular disease and represent a significant and novel risk factor. These insights represent potentially new avenues for risk assessment, prevention and therapy. This review chapter summarizes all forms of nPTMs found in CKD and under metabolic imbalance and discusses the biochemical connections between molecular alterations and the pathological impact on increased cardiovascular risk, novel nPTM-associated non-traditional cardiovascular risk factors, and clinical implication of nPTM in cardiovascular disease.

Lipoproteins and fatty acids in chronic kidney disease: molecular and metabolic alterations

Chronic kidney disease (CKD) induces modifications in lipid and lipoprotein metabolism and homeostasis. These modifications can promote, modulate and/or accelerate CKD and secondary cardiovascular disease (CVD). Lipid and lipoprotein abnormalities - involving triglyceride-rich lipoproteins, LDL and/or HDL - not only involve changes in concentration but also changes in molecular structure, including protein composition, incorporation of small molecules and post-translational modifications. These alterations modify the function of lipoproteins and can trigger pro-inflammatory and pro-atherogenic processes, as well as oxidative stress. Serum fatty acid levels are also often altered in patients with CKD and lead to changes in fatty acid metabolism - a key process in intracellular energy production - that induce mitochondrial dysfunction and cellular damage. These fatty acid changes might not only have a negative impact on the heart, but also contribute to the progression of kidney damage. The presence of these lipoprotein alterations within a biological environment characterized by increased inflammation and oxidative stress, as well as the competing risk of non-atherosclerotic cardiovascular death as kidney function declines, has important therapeutic implications. Additional research is needed to clarify the pathophysiological link between lipid and lipoprotein modifications, and kidney dysfunction, as well as the genesis and/or progression of CVD in patients with kidney disease.

Platelet Function in CKD: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with CKD are at high risk for thrombotic and hemorrhagic complications. Abnormalities in platelet function are central to these complications, but reports on platelet function in relation to CKD are conflicting, and vary from decreased platelet reactivity to normal or increased platelet responsiveness. The direct effects of uremic toxins on platelet function have been described, with variable findings.

METHODS

To help clarify how CKD affects platelet function, we conducted a systematic review and meta-analysis of platelet activity in CKD, with a focus on nondialysis-induced effects. We also performed an extensive literature search for the effects of individual uremic toxins on platelet function.

RESULTS

We included 73 studies in the systematic review to assess CKD's overall effect on platelet function in patients; 11 of them described CKD's effect on ex vivo platelet aggregation and were included in the meta-analysis. Although findings on platelet abnormalities in CKD are inconsistent, bleeding time was mostly prolonged and platelet adhesion mainly reduced. Also, the meta-analysis revealed maximal platelet aggregation was significantly reduced in patients with CKD upon collagen stimulation. We also found that relatively few uremic toxins have been examined for direct effects on platelets ex vivo; ex vivo analyses had varying methods and results, revealing both platelet-stimulatory and inhibitory effects. However, eight of the 12 uremic toxins tested in animal models mostly induced prothrombotic effects.

CONCLUSIONS

Overall, most studies report impaired function of platelets from patients with CKD. Still, a substantial number of studies find platelet function to be unchanged or even enhanced. Further investigation of platelet reactivity in CKD, especially during different CKD stages, is warranted.

MO433IDENTIFICATION AND VALIDATION OF PEPTIDIC FEATURES IN CKD PATIENTS AND UNRAVELLING OF A POTENTIAL INFLAMMATION INDUCER

Background and Aims

Chronic Kidney Disease (CKD) is causing serious cardiovascular diseases. Creatinine quantification and eGFR estimation are suboptimal approaches for the diagnosis of CKD, especially at early stages. Therefore, there is a strong need for identification of mediators for CKD diagnosis and prediction of disease progression. In this study we follow a cohort of renal healthy patients (controls) and CKD patients (cases) for two years, defining three time points (baseline, after 12 months and after 24 months), with the aim of identifying and characterizing mediators of disease which could be an indication for the development and progression of CKD and its outcome.

Method

By the employment of liquid chromatography-mass spectrometry (LC-MS) we analyzed the plasma samples from the patients and identified the mediators1 : lysine (K), an angio-associated migratory cell protein (AAMP) peptide and an amiloride-sensitive oxidase (AOC1) peptide, which were consistently and differentially expressed in cases and controls at all time points.

Correlation analyses between the mediators and clinical markers were performed using the software R-Studio (RStudio Team (2020). RStudio: Integrated Development for R. RStudio, PBC, Boston, MA URL http://www.rstudio.com/).

The AAMP peptide was subsequently tested in a fibroblasts cells culture to investigate whether it was an inflammation inducer, its action was investigated at four different concentrations (0.1nM, 1nM, 100nM, 1000nM). Cells were stimulated for 48h and relative expression of two inflammation markers (CCL2 and IL6) was measured through PCR.

Results

Correlation analyses revealed that the AAMP peptide showed from modest to strong relations with clinical markers such as creatinine, hemoglobin, blood urea nitrogen, homocysteine, fibrinogen and parathyroid hormone.

Results showed that the peptide after 48h of stimulation did not cause an increase in the expression of gene CCL2 at any concentration, but caused a strong increase of gene IL6 (interleukin-6), a cytokine promoting inflammation and B cells maturation.

Conclusion

In conclusion, angio-associated migratory cell peptide, might be involved in CKD by inducing inflammation and driving the development of cardiovascular consequences such as atherosclerosis.

Acknowledgments

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 764474.

MO435MULTIMODAL IMAGING FOR MOLECULAR TISSUE ANALYSIS

Background and Aims

MALDI mass spectrometric imaging (MALDI MSI) is a powerful histologic tool for the analysis of biomolecules in tissue samples. MALDI MSI measurements result in a high sensitivity and accuracy of spatial distribution of biomolecules in tissue samples. For more detailed analysis of MALDI MSI data and correlation between the molecular and microscopic levels, a combination of MALDI MSI data and histological staining is essential. By combining MALDI MSI data and histological data, much more information are obtained than by analyzing both methods individually. Therefore, MALDI MSI datasets and histological staining were fused to a 3D model presenting a biomolecule distribution of the whole organ and provides more information than a single tissue section. We have developed, established and validated an algorithm for an automatic registration of MALDI data with different histological image data for cross-process evaluation of multimodal datasets to create 3D models. This multimodal imaging approach simplifies and improves molecular analyses of tissue samples in clinical research and diagnosis.

Method

The datasets for fusion and creation of a 3D model consist of mass spectrometric data, histological and immunohistochemical staining methods. Histological tissue sections of a whole mouse kidney were prepared. For MALDI MSI data, organ sections were analyzed by using a Rapiflex mass-spectrometer.

Results

A mathematical registration was used to achieve a perfect superposition of the individual histological sections of mass spectrometric data. It is feasible to combine mass spectrometric data, histological and immunohistochemical datasets in high numbers and reconstruct the measured mouse kidney. By using different imaging methods, a variety of information about tissue structure as well as tissue changes and protein distributions can be obtained. The fusion of the data also offers a virtual incision of the organ from arbitrary angle and level. The algorithms are adapted to take the data fusion automatically offering a high-throughput approach for clinical diagnostics and the possibility to involved artificial intelligence in its interpretation in research.

Conclusion

A successful fusion of MALDI MSI data and different histological and immunohistochemical staining datasets of a whole organ is performed.

MO451GUANIDINYLATED APOLIPOPROTEIN C3 (APOC3) A NOVEL PLAYER IN CKD AND CKD-ASSOCIATED CARDIOVASCULAR DISEASES

Background and Aims

Cardiovascular diseases (CVD) and chronic kidney diseases (CKD) are highly prevalent in Western populations and account for a substantial proportion of mortality. We found that apolipoprotein C-3 (ApoC3), a constituent of triglyceride-rich lipoproteins, induces alternative NLRP3 inflammasome activation in human monocytes and thus causes sterile inflammation. The aim of the present study was to screen ApoC3 for the presence of posttranslational protein modifications and to assess its relevance in vitro, in vivo, as well as in a prospective cohort of CKD patients.

Method

ApoC3 was subjected to proteomic analysis. The proinflammatory properties of ApoC3 were assessed in human monocytes and in humanized mice. Moreover, posttranslationally modified ApoC3 was quantified in prospective cohort of 543 patients with various etiologies of CKD and linked to kidney and cardiovascular outcomes.

Results

We identified posttranslational guanidinylation of lysine residues of ApoC3 (gApoC3) in patients after acute myocardial infarction and in patients with CKD. gApoC3 accumulates in kidneys and hearts after injury as determined by 2D-proteomic analyses. In human monocytes, guanidinylation enhanced the binding of ApoC3 to the cell surface and exerted substantially stronger pro-inflammatory effects as compared native ApoC3. In humanized mice, gApoC3 strongly induced kidney fibrosis and abolished the regeneration after vascular injury. In a prospective clinical trial of 543 patients, higher gApoC3 blood levels as determined by mass spectrometry were associated with increased mortality as well as cardiovascular and renal events during a long-term follow-up.

Conclusion

The present study provides evidence from preclinical models and a prospective clinical trial that gApoC3 plays an important role in the development of organ injury in patients with CKD, myocardial infarction and other clinical conditions. The clinical study represents one of the largest trials, in which the association of a specific PTM and clinically relevant outcomes was assessed. These findings highlight gApoC3 as a pathophysiologically relevant factor in development of organ dysfunction.

MO430MASS-SPECTROMETRIC IDENTIFICATION OF POST-TRANSLATIONAL GUANIDINYLATED PROTEINS IN THE CONTEXT OF SYSTEMIC LUPUS ERYTHEMATOSUS

Background and Aims

With continuous identification of post-translational modified isoforms of proteins, it is becoming increasingly clear that post-translational modifications limit or modify the biological functions of native proteins are majorly involved in development of various chronic disease. This is mostly due to technically advanced molecular identification and quantification methods, mainly based on mass spectrometry. Mass spectrometry has become one of the most powerful tools for the identification of lipids.

Method

In this study, we used sophisticated high-resolution mass-spectrometric methods to analyze the soluble ligand of receptor Notch-3, namely the Y-box protein (YB)-1, in serum from systemic lupus erythematosus (SLE) patients. In addition, kidneys of lupus-prone (MRL.lpr) mice were analyzed by mass-spectrometric imaging techniques to identify the underlying pathomechanisms. Serum YB-1 was isolated by chromatographic methods, afterwards digested by trypsin and analyzed by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The kidneys were fixed in paraffin, then kidney sections were deparaffinized, tryptic digested and analyzed by mass-spectrometric imaging techniques. Mass-spectrometry of extracellular YB-1 in SLE patient serum revealed post-translational guanidinylation of two lysine’s within the highly conserved cold shock domain (CSD) of the YB-1 protein (YB-1-2G). Patients with increased disease activity and those with active renal involvement (lupus nephritis, LN) had a higher degree of dual-guanidinylation within the CSD. Of note, at least one of these modifications was present in all analyzed LN patients, whereas single-guanidinylated YB-1 was present in only one and double modification in none of the control individuals. Mass-spectrometric imaging analyses specifically localized YB-1-2G and increases Notch-3 expression in kidney sections from MRL.lpr mice.

Results

The data from this study clearly demonstrate the high potential of high-resolution mass spectrometric methods as well as mass spectrometric imaging techniques to identify pathomechanisms of diseases like SLE/LN.

Adipocyte calcium sensing receptor is not involved in visceral adipose tissue inflammation or atherosclerosis development in hyperlipidemic Apoe-/- mice

The calcium sensing receptor (CaSR) is a G-protein coupled receptor that especially plays an important role in the sensing of extracellular calcium to maintain its homeostasis. Several in-vitro studies demonstrated that CaSR plays a role in adipose tissue metabolism and inflammation, resulting in systemic inflammation and contributing to atherosclerosis development. The aim of this study was to investigate whether adipocyte CaSR plays a role in adipose tissue inflammation in-vivo and atherosclerosis development. By using a newly established conditional mature adipocyte specific CaSR deficient mouse on a hyperlipidemic and atherosclerosis prone Apoe^−/− background it could be shown that CaSR deficiency in adipocytes does neither contribute to initiation nor to progression of atherosclerotic plaques as judged by the unchanged lesion size or composition. Additionally, CaSR deficiency did not influence gonadal visceral adipose tissue (vAT) inflammation in-vivo, although a small decrease in gonadal visceral adipose cholesterol content could be observed. In conclusion, adipocyte CaSR seems not to be involved in vAT inflammation in-vivo and does not influence atherosclerosis development in hyperlipidemic Apoe^−/− mice.