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.

Increased cardiovascular risk in patients with chronic kidney disease

Cardiovascular disease (CVD) is highly prevalent in patients suffering from chronic kidney disease (CKD). The risk of patients with CKD developing CVD is manifested already in the early stages of CKD development. The impact of declined kidney function on increased cardiovascular risk and the underlying mechanisms are complex and multifactorial. This review discusses the impact of (a) traditional cardiovascular risk factors such as smoking, dyslipidemia, diabetes, and hypertension as well as (b) CKD-specific pathophysiological and molecular mechanisms associated with an increased cardiovascular risk. The latter include uremic toxins, post-translational modifications and uremic lipids, innate immune cell activation and inflammation, oxidative stress, endothelial cell dysfunction, increased coagulation and altered platelet responses, vascular calcification, renin-angiotensin-aldosterone-system (RAAS) and sympathetic activation, as well as anemia. Unraveling the complex interplay of different risk factors, especially in the context of patient subcohorts, will help to find new therapeutic approaches in order to reduce the increased cardiovascular risk in this vulnerable patient cohort.

Endothelial Cell Dysfunction and Increased Cardiovascular Risk in Patients With Chronic Kidney Disease

The endothelium is considered to be the gatekeeper of the vessel wall, maintaining and regulating vascular integrity. In patients with chronic kidney disease, protective endothelial cell functions are impaired due to the proinflammatory, prothrombotic and uremic environment caused by the decline in kidney function, adding to the increase in cardiovascular complications in this vulnerable patient population. In this review, we discuss endothelial cell functioning in healthy conditions and the contribution of endothelial cell dysfunction to cardiovascular disease. Further, we summarize the phenotypic changes of the endothelium in chronic kidney disease patients and the relation of endothelial cell dysfunction to cardiovascular risk in chronic kidney disease. We also review the mechanisms that underlie endothelial changes in chronic kidney disease and consider potential pharmacological interventions that can ameliorate endothelial health.

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.

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.