Uremic endothelial-derived extracellular vesicles: Mechanisms of formation and their role in cell adhesion, cell migration, inflammation, and oxidative stress

p-Cresyl sulfate (PCS), indoxyl sulfate (IS), and inorganic phosphate (Pi) are uremic toxins found in chronic kidney disease (CKD) that are closely related to endothelial extracellular vesicles (EVs) formation. The present study aimed to understand the role of EVs and their role in cell adhesion and migration, inflammation, and oxidative stress. Human endothelial cells were treated with PCS, IS, and Pi in pre-established uremic and kinetic recommendations. EVs were characterized using scanning electron microscopy, flow cytometry, and NanoSight assays. The concentrations of EVs were established using Alamar Blue and MTT assays. Cell adhesion to extracellular matrix proteins was analyzed using an adhesion assay. Inflammation and oxidative stress were assessed by vascular cell adhesion molecule-1 expression/monocyte migration and reactive oxygen species production, respectively. The capacity of EVs to stimulate endothelial cell migration was evaluated using a wound-healing assay. Our data showed that endothelial cells stimulated with uremic toxins can induce the formation of EVs of different sizes, quantities, and concentrations, depending on the uremic toxin used. Cell adhesion was significantly (P < 0.01) stimulated in cells exposed to PCS-induced extracellular vesicles (PCSEVs) and inorganic phosphate-induced extracellular vesicles (PiEVs). Cell migration was significantly (P < 0.05) stimulated by PCSEVs. VCAM-1 expression was evident in cells treated with PCSEVs and IS-induced extracellular vesicles (ISEVs). EVs are not able to stimulate monocyte migration or oxidative stress. In conclusion, EVs may be a biomarker of endothelial injury and the inflammatory process, playing an important role in cell-to-cell communication and pathophysiological processes, although more studies are needed to better understand the mechanisms of EVs in uremia.

Sevelamer reduces endothelial inflammatory response to advanced glycation end products

Background

Advanced glycation end products (AGEs) have been related to the pathogenesis of cardiovascular diseases (CVD), chronic kidney disease (CKD) and diabetes mellitus. We sought to investigate the binding capacity of sevelamer to both AGEs and uremic serum in vitro and then test this pharmaceutical effect as a potential vascular anti-inflammatory strategy.

Methods

AGEs were prepared by albumin glycation and characterized by absorbance and electrophoresis. Human endothelial cells were incubated in culture media containing AGEs and uremic serum with or without sevelamer. Receptor for advanced glycation end product (RAGE) expression was evaluated through immunocytochemistry and western blot to explore the interactions between AGEs and the endothelium. Inflammatory and endothelial dysfunction biomarkers, such as interleukin 6 (IL-6) and IL-8, monocyte chemoattractant protein-1 (MCP-1), plasminogen activator inhibitor-1 (PAI-1) and serum amyloid A (SAA) were also measured in cell supernatant. The chemotactic property of the supernatant was evaluated.

Results

AGEs significantly induced the expression of RAGE, inflammatory and endothelial activation biomarkers [IL-6, (P < 0.005); IL-8, MCP-1, PAI-1 and SAA (P < 0.001)] and monocyte chemotaxis as compared with controls. In addition, AGEs increased the levels of inflammatory biomarkers, which were observed after 6 h of endothelial cell incubation with uremic serum [IL-6 (P < 0.001) IL-8, MCP-1 and PAI-1 (P < 0.05)]. On the other hand, after 6 h of endothelial cell treatment with sevelamer, RAGE expression (P < 0.05) and levels of inflammatory biomarkers [IL-6 and IL-8 (P < 0.001), MCP-1 (P < 0.01), PAI-1 and SAA (P < 0.005)] significantly decreased compared with the AGEs/uremic serum treatment alone.

Conclusions

Sevelamer decreased both endothelial expression of RAGE and endothelial dysfunction biomarkers, induced by AGEs, and uremic serum. Further studies are necessary for a better understanding of the potential protective role of sevelamer on uremic serum and AGEs-mediated endothelial dysfunction.

Role of Organic Anion Transporters in the Uptake of Protein-Bound Uremic Toxins by Human Endothelial Cells and Monocyte Chemoattractant Protein-1 Expression

Organic anion transporters (OATs) are involved in the uptake of uremic toxins such as p-cresyl sulfate (PCS) and indoxyl sulfate (IS), which play a role in endothelial dysfunction in patients with chronic kidney diseases (CKD). In this study, we investigated the role of OAT1 and OAT3 in the uptake of PCS and IS into human endothelial cells. PCS was synthesized via p-cresol sulfation and characterized using analytical methods. The cells were treated with PCS and IS in the absence and presence of probenecid (Pb), an OAT inhibitor. Cell viability was assessed using the MTT assay. The absorbed toxins were analyzed using chromatography, OAT expression using immunocytochemistry and western blot, and monocyte chemoattractant protein-1 (MCP-1) expression using enzyme-linked immunosorbent assay. Cell viability decreased after toxin treatment in a dose-dependent manner. PCS and IS showed significant internalization after 60 min treatment, while no internalization was observed in the presence of Pb, suggesting that OATs are involved in the transport of both toxins. Immunocytochemistry and western blot demonstrated OAT1 and OAT3 expression in endothelial cells. MCP-1 expression increased after toxins treatment but decreased after Pb treatment. PCS and IS uptake were mediated by OATs, and OAT blockage could serve as a therapeutic strategy to inhibit MCP-1 expression.

Contribution of CT to treatment planning in patients with GIST

PURPOSE

The aim of this study was to illustrate the morphological and structural computed tomography (CT) patterns of gastrointestinal stromal tumours (GIST) and to discuss the technique's role in identifying lesions at a higher risk for malignant potential, in treatment planning and in the follow-up of patients with GIST.

MATERIALS AND METHODS

We retrospectively reviewed the CT scans of 26 patients who underwent surgery for histologically confirmed GIST of the stomach (20 cases), the duodenum (1), the caecum (1), the small bowel (2), the descending colon (1) and the rectum (1). CT exams were performed with a single-slice scanner and a 5-mm collimation before and after the intravenous administration of contrast material.

RESULTS

CT allowed us to correctly define the site, size and structure of lesions in all cases and to identify signs of invasion of neighbouring structures in some cases. The lesions exhibited solid density on the unenhanced scan and poor enhancement after contrast-medium administration; lesion structure was homogeneous in ten cases and inhomogeneous in 16; in one case, histology revealed microcalcification that had not been detected by CT.

CONCLUSIONS

CT, with its panoramic capabilities and high contrast resolution, provides essential information for treatment planning and for the follow-up of GIST patients treated with surgery or chemotherapy.

[The diagnostic and therapeutic procedures in pulmonary embolism: a survey in the Veneto Region]

BACKGROUND

Pulmonary embolism is one of the most frequent cardiopulmonary diseases, but it is often under- or misdiagnosed. In order to address this issue and to identify flow charts that are commonly used in pulmonary embolism diagnosis and treatment, 191 clinical wards of internal medicine, cardiology, geriatrics, pneumology and intensive care units, located in the Veneto Region, were surveyed.

METHODS

An anonymous questionnaire was mailed to each ward in order to collect clinical diagnostic information on all pulmonary embolisms which occurred during 1993. Among the returned questionnaires, 114 (59.6%) had usable information for the analysis.

RESULTS

The vast majority of participating centers reported in 1993 less than 10 pulmonary embolism events. No significant differences were observed between internal medicine, geriatrics, pneumology wards and intensive care units. The reported events, however, were slightly higher in the divisions of cardiology with an annual average of 12 events per center. First level diagnostic procedures, such as ECG, chest X-ray and arterial blood gas analysis were chosen and performed in all patients. Interestingly, Doppler echocardiography, which is often not included in official guidelines for pulmonary embolism diagnosis, was performed in 56% of the participating centers. On the contrary, ventilation-perfusion lung scanning, which is considered highly predictive in many diagnostic algorithms, was underutilized (35% perfusion scan, 20% ventilation scan). This underuse was probably due to technical and organizational difficulties. Pulmonary angiography, the most accurate procedure for the diagnosis of pulmonary embolism, was performed in 28% of the patients. During the acute phase, intravenous heparin was commonly used; 91% of patients received the infusion continuously, 4% intermittently. Thrombolysis was performed in 25% of the patients. The preferred drugs were recombinant tissue-plasminogen activator (67%), followed by urokinase (20%) and streptokinase (13%). To start thrombolytic therapy, 20% of the interviewed clinicians considered sufficient the evidence of clinical manifestations of pulmonary embolism confirmed by echocardiographic data. At discharge, prescription of oral anticoagulant drugs was common (78%) for at least 6 months (47%). Standardized procedures for the diagnosis and treatment of pulmonary embolism were already implemented in 13% of the participating centers.

CONCLUSIONS

These data suggest a common effort to define unanimous conventional protocols in the management of pulmonary embolism. It should be underlined, however, that a particular attention to the clinical manifestations and a productive collaboration among clinicians with different expertise are required to improve the diagnosis and treatment of pulmonary embolism.