Philipp Stiegler

Protein Carbamylation Renders High-Density Lipoprotein Dysfunctional

Carbamylation of proteins through reactive cyanate has been demonstrated to predict an increased cardiovascular risk. Cyanate is formed in vivo by breakdown of urea and at sites of inflammation by the phagocyte protein myeloperoxidase. Because myeloperoxidase (MPO) associates with high-density lipoprotein (HDL) in human atherosclerotic intima, we examined in the present study whether cyanate specifically targets HDL. Mass spectrometry analysis revealed that protein carbamylation is a major posttranslational modification of HDL. The carbamyllysine content of lesion-derived HDL was more than 20-fold higher in comparison with 3-chlorotyrosine levels, a specific oxidation product of MPO. Notably, the carbamyllysine content of lesion-derived HDL was five- to eightfold higher when compared with lesion-derived low-density lipoprotein (LDL) or total lesion protein and increased with lesion severity. The carbamyllysine content of HDL, but not of LDL, correlated with levels of 3-chlorotyrosine, suggesting that MPO mediated carbamylation in the vessel wall. Remarkably, one carbamyllysine residue per HDL-associated apolipoprotein A-I was sufficient to induce cholesterol accumulation and lipid-droplet formation in macrophages through a pathway requiring the HDL-receptor scavenger receptor class B, type I. The present results raise the possibility that HDL carbamylation contributes to foam cell formation in atherosclerotic lesions.

Sirolimus has a potential to influent viral recurrence in HCV positive liver transplant candidates.

There is in vitro proof that mTOR proteins play a role in protecting HCV infected cells from apoptosis. The aim of this cohort study was to evaluate the effect of sirolimus as an mTOR inhibitor on hepatitis C recurrence in liver transplant recipients. Hepatitis C virus positive patients were followed prospectively regarding transaminases, immunosuppressive target levels, HCV RNA and influence of donor and recipient factors on viral recurrence and survival. Viral recurrence was defined as elevated liver enzymes combined with active hepatitis diagnosed on the basis of increasing viral load and/or biopsy-proven HCV relapse in the transplanted organ. Sixty-seven HCV positive patients were included: 39 received a regimen including sirolimus; 28 patients received calcineurin inhibitors. Sirolimus patients showed a significant decrease in the HCV PCR levels (p<0.05). Survival of the sirolimus patients was significantly higher (p<0.03) than in the other patient cohort. Sirolimus has been shown to be a potent immunosuppressive agent after liver transplantation, though nothing is known about its effect on HCV. This analysis suggests that sirolimus has potential to suppress viral recurrence in HCV positive liver transplant candidates.

Image-based multi-scale modelling and validation of radio-frequency ablation in liver tumours

The treatment of cancerous tumours in the liver remains clinically challenging, despite the wide range of treatment possibilities, including radio-frequency ablation (RFA), high-intensity focused ultrasound and resection, which are currently available. Each has its own advantages and disadvantages. For non- or minimally invasive modalities, such as RFA, considered here, it is difficult to monitor the treatment in vivo. This is particularly problematic in the liver, where large blood vessels act as heat sinks, dissipating delivered heat and shrinking the size of the lesion (the volume damaged by the heat treatment) locally; considerable experience is needed on the part of the clinician to optimize the heat treatment to prevent recurrence. In this paper, we outline our work towards developing a simulation tool kit that could be used both to optimize treatment protocols in advance and to train the less-experienced clinicians for RFA treatment of liver tumours. This tool is based on a comprehensive mathematical model of bio-heat transfer and cell death. We show how simulations of ablations in two pigs, based on individualized imaging data, compare directly with experimentally measured lesion sizes and discuss the likely sources of error and routes towards clinical implementation. This is the first time that such a ‘loop’ of mathematical modelling and experimental validation in vivo has been performed in this context, and such validation enables us to make quantitative estimates of error.

Morphological and functional characterization of a pancreatic beta-cell line microencapsulated in sodium cellulose sulfate/poly(diallyldimethylammonium chloride).

Abstract:  Background:  Late diabetic complications cannot be prevented totally by current antidiabetic strategies. Therefore, new therapeutic concepts of insulin replacement such as pancreas transplantation are evolving. Due to the shortage of human donor organs, transplantation of microencapsulated xenogeneic pancreatic islet cells has attracted considerable attention. Sodium cellulose sulfate/poly(diallyldimethylammonium chloride) (NaCS/PDADMAC) is a material with favorable biogenic properties that has been used for microencapsulation of various cell types. However, there are no data on the suitability of NaCS/PDADMAC for microencapsulation of pancreatic β‐cells.

Early detection and intervention using neutrophil gelatinase-associated lipocalin (NGAL) may improve renal outcome of acute contrast media induced nephropathy: A randomized controlled trial in patients undergoing intra-arterial angiography (ANTI-CIN Study)

BackgroundPatients with pre-existing impaired renal function are prone to develop acute contrast media induced nephropathy (CIN). Neutrophil gelatinase-associated lipocalin (NGAL), a new biomarker predictive for acute kidney injury (AKI), has been shown to be useful for earlier diagnosis of CIN; however, urinary NGAL values may be markedly increased in chronic renal failure at baseline. Results from those studies suggested that urinary NGAL values may not be helpful for the clinician. An intravenous volume load is a widely accepted prophylactic measure and possibly a reasonable intervention to prevent deterioration of renal function. The aim of our study is to evaluate NGAL as an early predictor of CIN and to investigate the clinical benefit of early post-procedural i.v. hydration.Methods/DesignThe study will follow a prospective, open-label, randomized controlled design. Patients requiring intra-arterial contrast media (CM) application will be included and receive standardized, weight-based, intravenous hydration before investigation. Subjects with markedly increased urinary NGAL values after CM application will be randomized into one of two study groups. Group A will receive 3-4 ml/kg BW/h 0.9% saline intravenously for 6 hours. Group B will undergo only standard treatment consisting of unrestricted oral fluid intake. The primary outcome measure will be CIN defined by an increase greater than 25% of baseline serum creatinine. Secondary outcomes will include urinary NGAL values, cystatin C values, contrast media associated changes in cardiac parameters such as NT-pro-BNP/troponin T, changes in urinary cytology, need for renal replacement treatment, length of stay in hospital and death.We assume that 20% of the included patients will show a definite rise in urinary NGAL. Prospective statistical power calculations indicate that the study will have 80% statistical power to detect a clinically significant decrease of CIN of 40% in the treatment arm if 1200 patients are recruited into the study.DiscussionA volume expansion strategy showing a benefit from earlier intervention for patients with markedly elevated urinary NGAL values, indicating a CIN, might arise from data from this study.Trial registrationClinicalTrials.gov NCT01292317

The assessment of GFR after orthotopic liver transplantation using cystatin C and creatinine‐based equations

The measurement of kidney function after orthotopic liver transplantation (OLT) is still a clinical challenge. Cystatin C (CysC) has been proposed as a more accurate marker of renal function than serum creatinine (sCr). The aim of this study was to evaluate sCr‐ and CysC‐based equations including the Chronic kidney disease (CKD)‐EPI to determine renal function in liver transplant recipients. CysC and sCr were measured in 49 patients 24 months after OLT. The glomerular filtration rate (GFR) was calculated using the MDRD 4, the Cockroft‐Gault, Hoek, Larsson, and the CKD‐EPI equations based on sCr and/or CysC. As reference method, inulin clearance (IC) was estimated. Bias, precision, and accuracy of each equation were assessed and compared with respect to IC. Forty‐five percent had a GFR < 60 ml/min/1.73 m2 according to the IC. The Larsson, the Hoek and the CKD‐EPI‐CysC formula identified the highest percentage of patients with CKD correctly (88%, 88%, and 84%, respectively). The sCr‐based equations showed less bias than CysC‐based formulas with a similar precision. All CysC‐based equations were superior as compared with sCr‐based equations in the assessment of renal function in patients with an IC < 60 ml/min/1.73 m2.

Oxidative stress and apoptosis in a pig model of brain death (BD) and living donation (LD)

BackgroundAs organ shortage is increasing, the acceptance of marginal donors increases, which might result in poor organ function and patient survival. Mostly, organ damage is caused during brain death (BD), cold ischemic time (CIT) or after reperfusion due to oxidative stress or the induction of apoptosis. The aim of this study was to study a panel of genes involved in oxidative stress and apoptosis and compare these findings with immunohistochemistry from a BD and living donation (LD) pig model and after cold ischemia time (CIT).MethodsBD was induced in pigs; after 12 h organ retrieval was performed; heart, liver and kidney tissue specimens were collected in the BD (n = 6) and in a LD model (n = 6). PCR analysis for NFKB1, GSS, SOD2, PPAR-alpha, OXSR1, BAX, BCL2L1, and HSP 70.2 was performed and immunohistochemistry used to show apoptosis and nitrosative stress induced cell damage.ResultsIn heart tissue of BD BAX, BCL2L1 and HSP 70.2 increased significantly after CIT. Only SOD2 was over-expressed after CIT in BD liver tissue. In kidney tissue, BCL2L1, NFKB, OXSR1, SOD2 and HSP 70.2 expression was significantly elevated in LD. Immunohistochemistry showed a significant increase in activated Caspase 3 and nitrotyrosine positive cells after CIT in BD in liver and in kidney tissue but not in heart tissue.ConclusionThe up-regulation of protective and apoptotic genes seems to be divergent in the different organs in the BD and LD setting; however, immunohistochemistry revealed more apoptotic and nitrotyrosine positive cells in the BD setting in liver and kidney tissue whereas in heart tissue both BD and LD showed an increase.

Myeloperoxidase and carbonyl proteins: Promising markers for non-invasive monitoring of graft rejection after heart transplantation

BACKGROUND After heart transplantation (HTx), endomyocardial biopsy (EMB) is currently the standard method to diagnose acute graft rejection. A non-invasive marker of rejection would be desirable as an alternative or to permit more selective use of the costly and invasive EMB. METHODS In this retrospective study, outcomes of routinely taken EMBs were used to select 28 patients after HTx EMB Grade 0R (8 patients), 1R (9 patients) or 2R (11 patients). For these patients, myeloperoxidase (MPO) and carbonyl proteins (CP) in serum were measured using enzyme-linked immunoassay (ELISA). RESULTS MPO and CP levels in post-HTx patients with Grade 2R rejection were significantly (MPO: p < 0.01; CP: p < 0.001) elevated at the time of rejection compared with levels 1 month earlier. MPO and CP levels predicted Grade 2R rejection and the best cut-off point was 237.5 μg/l for MPO and 222.5 pmol/mg for CP, respectively. Clinically most important was the marked increase (doubling of basic values within 1 month) of MPO and CP levels in cases of Grade 2R rejection in post-HTx patients. CONCLUSIONS MPO and CP seem to be appropriate parameters to monitor rejection events non-invasively and to minimize the application of EMBs after HTx.

A 10 min “no-touch” time – is it enough in DCD? A DCD Animal Study

Summary Donation after cardiac death (DCD) is under investigation because of the lack of human donor organs. Required times of cardiac arrest vary between 75 s and 27 min until the declaration of the patients’ death worldwide. The aim of this study was to investigate brain death in pigs after different times of cardiac arrest with subsequent cardiopulmonary resuscitation (CPR) as a DCD paradigm. DCD was simulated in 20 pigs after direct electrical induction of ventricular fibrillation. The “no‐touch” time varied from 2 min up to 10 min; then 30 min of CPR were performed. Brain death was determined by established clinical and electrophysiological criteria. In all animals with cardiac arrest of at least 6 min, a persistent loss of brainstem reflexes and no reappearance of bioelectric brain activity occurred. Reappearance of EEG activity was found until 4.5 min of cardiac arrest and subsequent CPR. Brainstem reflexes were detectable until 5 min of cardiac arrest and subsequent CPR. According to our experiments, the suggestion of 10 min of cardiac arrest being equivalent to brain death exceeds the minimum time after which clinical and electrophysiological criteria of brain death are fulfilled. Therefore shorter “no‐touch” times might be ethically acceptable to reduce warm ischemia time.

Randomised clinical trial: the effects of a multispecies probiotic vs. placebo on innate immune function, bacterial translocation and gut permeability in patients with cirrhosis

Probiotics may correct intestinal dysbiosis and proinflammatory conditions in patients with liver cirrhosis.