Renal function, uraemia and early arteriovenous fistula failure

Background Guidance varies regarding the optimal timing of arteriovenous fistula (AVF) creation. The aim of this study was to evaluate the association between uraemia, haemodialysis and early AVF failure. Methods Immunoblotting and cell proliferation assays were performed on vascular smooth muscle cells (VSM) cells isolated from long saphenous vein samples to evaluate the cells’ ability to proliferate when stimulated with uraemic (post-dialysis) and hyperuraemic (pre-dialysis) serum. Clinical data was collected prospectively for 569 consecutive radiocephalic (RCF) and brachiocephalic (BCF) fistulae. The primary outcome was AVF failure at 6 weeks. Dialysis status (haemodialysis (HD); pre-dialysis (Pre-D)), eGFR and serum urea were evaluated to determine if they affected early AVF failure. Results Human VSM cells demonstrated increased capacity to proliferate when stimulated with hyperuraemic serum. There was no significant difference in early failure rate of either RCF or BCF depending on dialysis status (pre-D RCF 31.4% (n = 188); pre-D BCF 22.4% (n = 165); HD RCF 29.3% (n = 99); HD BCF 25.9% (n = 116); p = 0.34). There was no difference in mean eGFR between those patients with early AVF failure and those without (11.2+/-0.2 ml/min/1.73 m2 vs. 11.6+/-0.4 ml/min/1.73 m2; p = 0.47). Uraemia was associated with early AVF failure (serum urea: 35.0+/-0.7 mg/dl vs. 26.6+/-0.3 mg/dl (p &lt; 0.001)). Conclusions We present the first in vivo evidence of an association between adverse early AVF outcomes and uraemia. This is supported mechanistically by in vitro work demonstrating a pro-mitogenic effect of hyperuraemic serum. We hypothesise that uraemia-driven upregulation of VSM cell proliferation at the site of surgical insult in contributes to higher early AVF failure rates.</p

Threshold of peroxynitrite cytotoxicity in bovine pulmonary artery endothelial and smooth muscle cells

Peroxynitrite is widely reported as highly cytotoxic; yet recent evidence indicates that at certain concentrations, it can induce pulmonary cell hyper-proliferation and tissue remodelling. This study aimed to establish the threshold concentration of peroxynitrite to induce functional impairment of bovine pulmonary artery endothelial (PAEC) and smooth muscle cells (PASMC). PAEC or PASMC were exposed to solution of peroxynitrite or 3-morpholinosydnonimine (SIN-1). Twenty-four hour cell viability, DNA synthesis, and protein biochemistry were assessed by trypan blue dye exclusion, [(3)H] thymidine incorporation and western blot analysis, respectively. Threshold concentration of peroxynitrite to significantly impair viability of PAEC and PASMC was 2μM peroxynitrite. In PASMC and PAEC, low concentrations of peroxynitrite (2nM-0.2μM) increased cell proliferation and did not activate p38 MAP kinase. The decrease in DNA synthesis and cell viability caused by 2μM peroxynitrite was associated with caspase-3 cleavage but not p38 activation. Also, 2-20μM peroxynitrite significantly activated poly ADP ribose polymerase and stress activated kinase JNK in PAEC. However, the higher concentration of 20μM peroxynitrite did cause a threefold increase in p38 activation. In conclusion, the threshold for the cytotoxic effects of peroxynitrite was 2μM; which caused apoptotic cell death independent of p38 MAP kinase activation in pulmonary artery cells

Adventitial ablation technique that permits the assessment of adventitial-dependent contribution to microvascular contractile function

Resistance arteries have been implicated as major contributing factor in the sequela of disease conditions such as hypertension and diabetes and as such are a major focus of cardiovascular research. The paracrine influence of the intimal endothelial layer of resistance arteries is well established. Considering the growing body of evidence substantiating a functionally relevant vascular adventitia in this present study we have established a technique which permits determination of the functional influence of the adventitial layer on resistance artery tone. Isolating adventitial-dependent function, analogous to isolating endothelial function, has potentially significant implication for studying the as yet unexplored role of the microvascular adventitial layer in modulating acute vascular contractile function

Untargeted metabolic profiling cell-based approach of pulmonary artery smooth muscle cells in response to high glucose and the effect of the antioxidant vitamins D and E

Pulmonary arterial hypertension (PAH) is a multi-factorial disease characterized by the hyperproliferation of pulmonary artery smooth muscle cells (PASMCs). Excessive reactive oxygen species (ROS) formation resulted in alterations of the structure and function of pulmonary arterial walls, leading to right ventricular failure and death. Diabetes mellitus has not yet been implicated in pulmonary hypertension. However, recently, variable studies have shown that diabetes is correlated with pulmonary hypertension pathobiology, which could participate in the modification of pulmonary artery muscles. The metabolomic changes in PASMCs were studied in response to 25 mM of D-glucose (high glucose, or HG) in order to establish a diabetic-like condition in an in vitro setting, and compared to five mM of D-glucose (normal glucose, or LG). The effect of co-culturing these cells with an ideal blood serum concentration of cholecalciferol-D3 and tocopherol was also examined. The current study aimed to examine the role of hyperglycemia in pulmonary arterial hypertension by the quantification and detection of the metabolomic alteration of smooth muscle cells in high-glucose conditions. Untargeted metabolomics was carried out using hydrophilic interaction liquid chromatography and high-resolution mass spectrometry. Cell proliferation was assessed by cell viability and the [³H] thymidine incorporation assay, and the redox state within the cells was examined by measuring reactive oxygen species (ROS) generation. The results demonstrated that PASMCs in high glucose (HG) grew, proliferated faster, and generated higher levels of superoxide anion (O₂·-) and hydrogen peroxide (H₂O₂). The metabolomics of cells cultured in HG showed that the carbohydrate pathway, especially that of the upper glycolytic pathway metabolites, was influenced by the activation of the oxidation pathway: the pentose phosphate pathway (PPP). The amount of amino acids such as aspartate and glutathione reduced via HG, while glutathione disulfide, N6-Acetyl-L-lysine, glutamate, and 5-aminopentanoate increased. Lipids either as fatty acids or glycerophospholipids were downregulated in most of the metabolites, with the exception of docosatetraenoic acid and PG (16:0/16:1(9Z)). Purine and pyrimidine were influenced by hyperglycaemia following PPP oxidation. The results in addition showed that cells exposed to 25 mM of glucose were oxidatively stressed comparing to those cultured in five mM of glucose. Cholecalciferol (D3, or vitamin D) and tocopherol (vitamin E) were shown to restore the redox status of many metabolic pathways

Improving arteriovenous fistula patency : transdermal delivery of diclofenac reduces cannulation-dependent neointimal hyperplasia via AMPK activation

Creation of an autologous arteriovenous fistula (AVF) for vascular access in haemodialysis is the modality of choice. However neointimal hyperplasia and loss of the luminal compartment result in AVF patency rates of ~60% at 12months. The exact cause of neointimal hyperplasia in the AVF is poorly understood. Vascular trauma has long been associated with hyperplasia. With this in mind in our rabbit model of AVF we simulated cannulation autologous to that undertaken in vascular access procedures and observed significant neointimal hyperplasia as a direct consequence of cannulation. The neointimal hyperplasia was completely inhibited by topical transdermal delivery of the non-steroidal anti-inflammatory (NSAID) diclofenac. In addition to the well documented anti-inflammatory properties we have identified novel anti-proliferative mechanisms demonstrating diclofenac increases AMPK-dependent signalling and reduced expression of the cell cycle protein cyclin D1. In summary prophylactic transdermal delivery of diclofenac to the sight of AVF cannulation prevents adverse neointimal hyperplasic remodelling and potentially offers a novel treatment option that may help prolong AVF patency and flow rates

Interhospital variation in the RATPAC trial (Randomised Assessment of Treatment using Panel Assay of Cardiac markers)

Background: The RATPAC trial showed that using a point-of-care panel of CK-MB(mass), myoglobin and troponin at baseline and 90 min increased the proportion of patients successfully discharged home, leading to reduced median length of initial hospital stay. However, it did not change mean hospital stay and may have increased mean costs per patient. The aim of this study was to explore variation in outcome and costs between participating hospitals. Methods: RATPAC was a pragmatic multicentre randomised controlled trial (N=2243) and economic analysis comparing diagnostic assessment using the panel to standard care for patients with acute chest pain due to suspected myocardial infarction at six hospitals. The difference in the proportion of patients successfully discharged (primary outcome) and mean costs per patient between the participating hospitals was compared. Results: Point-of-care assessment led to a higher proportion of successful discharges in four hospitals, a lower proportion in one and was equivocal in another. The OR (95% CI) for the primary outcome varied from 0.12 (0.01 to 1.03) to 11.07 (6.23 to 19.66) with significant heterogeneity between the centres (

Improving arteriovenous fistula patency : transdermal delivery of diclofenac reduces cannulation-dependent neointimal hyperplasia via AMPK activation

Creation of an autologous arteriovenous fistula (AVF) for vascular access in haemodialysis is the modality of choice. However neointimal hyperplasia and loss of the luminal compartment result in AVF patency rates of ~60% at 12months. The exact cause of neointimal hyperplasia in the AVF is poorly understood. Vascular trauma has long been associated with hyperplasia. With this in mind in our rabbit model of AVF we simulated cannulation autologous to that undertaken in vascular access procedures and observed significant neointimal hyperplasia as a direct consequence of cannulation. The neointimal hyperplasia was completely inhibited by topical transdermal delivery of the non-steroidal anti-inflammatory (NSAID) diclofenac. In addition to the well documented anti-inflammatory properties we have identified novel anti-proliferative mechanisms demonstrating diclofenac increases AMPK-dependent signalling and reduced expression of the cell cycle protein cyclin D1. In summary prophylactic transdermal delivery of diclofenac to the sight of AVF cannulation prevents adverse neointimal hyperplasic remodelling and potentially offers a novel treatment option that may help prolong AVF patency and flow rates

Monitoring of biomarkers in heart failure.

The role of biomarkers is increasingly recognized in heart failure (HF) management, for diagnosis, prognostication, and screening of high-risk patients. Beyond natriuretic peptides and troponins, the utility of novel, emerging biomarkers is less established. This document reflects the key points of a Heart Failure Association of the European Society of Cardiology (ESC) consensus meeting on biomarker monitoring in HF