M. Sallée

Indolic uremic solutes increase tissue factor production in endothelial cells by the aryl hydrocarbon receptor pathway.

In chronic kidney disease (CKD), uremic solutes accumulate in blood and tissues. These compounds probably contribute to the marked increase in cardiovascular risk during the progression of CKD. The uremic solutes indoxyl sulfate and indole-3-acetic acid (IAA) are particularly deleterious for endothelial cells. Here we performed microarray and comparative PCR analyses to identify genes in endothelial cells targeted by these two uremic solutes. We found an increase in endothelial expression of tissue factor in response to indoxyl sulfate and IAA and upregulation of eight genes regulated by the transcription factor aryl hydrocarbon receptor (AHR). The suggestion by microarray analysis of an involvement of AHR in tissue factor production was confirmed by siRNA inhibition and the indirect AHR inhibitor geldanamycin. These observations were extended to peripheral blood mononuclear cells. Tissue factor expression and activity were also increased by AHR agonist dioxin. Finally, we measured circulating tissue factor concentration and activity in healthy control subjects and in patients with CKD (stages 3-5d), and found that each was elevated in patients with CKD. Circulating tissue factor levels were positively correlated with plasma indoxyl sulfate and IAA. Thus, indolic uremic solutes increase tissue factor production in endothelial and peripheral blood mononuclear cells by AHR activation, evoking a dioxin-like effect. This newly described mechanism of uremic solute toxicity may help understand the high cardiovascular risk of CKD patients.

The Aryl Hydrocarbon Receptor-Activating Effect of Uremic Toxins from Tryptophan Metabolism: A New Concept to Understand Cardiovascular Complications of Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have a higher risk of cardiovascular diseases and suffer from accelerated atherosclerosis. CKD patients are permanently exposed to uremic toxins, making them good candidates as pathogenic agents. We focus here on uremic toxins from tryptophan metabolism because of their potential involvement in cardiovascular toxicity: indolic uremic toxins (indoxyl sulfate, indole-3 acetic acid, and indoxyl-β-d-glucuronide) and uremic toxins from the kynurenine pathway (kynurenine, kynurenic acid, anthranilic acid, 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and quinolinic acid). Uremic toxins derived from tryptophan are endogenous ligands of the transcription factor aryl hydrocarbon receptor (AhR). AhR, also known as the dioxin receptor, interacts with various regulatory and signaling proteins, including protein kinases and phosphatases, and Nuclear Factor-Kappa-B. AhR activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin and some polychlorinated biphenyls is associated with an increase in cardiovascular disease in humans and in mice. In addition, this AhR activation mediates cardiotoxicity, vascular inflammation, and a procoagulant and prooxidant phenotype of vascular cells. Uremic toxins derived from tryptophan have prooxidant, proinflammatory, procoagulant, and pro-apoptotic effects on cells involved in the cardiovascular system, and some of them are related with cardiovascular complications in CKD. We discuss here how the cardiovascular effects of these uremic toxins could be mediated by AhR activation, in a “dioxin-like” effect.

The Cardiovascular Effect of the Uremic Solute Indole-3 Acetic Acid

In CKD, uremic solutes may induce endothelial dysfunction, inflammation, and oxidative stress, leading to increased cardiovascular risk. We investigated whether the uremic solute indole-3 acetic acid (IAA) predicts clinical outcomes in patients with CKD and has prooxidant and proinflammatory effects. We studied 120 patients with CKD. During the median study period of 966 days, 29 patients died and 35 experienced a major cardiovascular event. Kaplan-Meier analysis revealed that mortality and cardiovascular events were significantly higher in the higher IAA group (IAA>3.73 µM) than in the lower IAA group (IAA<3.73 µM). Multivariate Cox regression analysis demonstrated that serum IAA was a significant predictor of mortality and cardiovascular events after adjustments for age and sex; cholesterol, systolic BP, and smoking; C-reactive protein, phosphate, body mass index, and albumin; diastolic BP and history of cardiovascular disease; and uremic toxins p-cresyl sulfate and indoxyl sulfate. Notably, IAA level remained predictive of mortality when adjusted for CKD stage. IAA levels were positively correlated with markers of inflammation and oxidative stress: C-reactive protein and malondialdehyde, respectively. In cultured human endothelial cells, IAA activated an inflammatory nongenomic aryl hydrocarbon receptor (AhR)/p38MAPK/NF-κB pathway that induced the proinflammatory enzyme cyclooxygenase-2. Additionally, IAA increased production of endothelial reactive oxygen species. In conclusion, serum IAA may be an independent predictor of mortality and cardiovascular events in patients with CKD. In vitro, IAA induces endothelial inflammation and oxidative stress and activates an inflammatory AhR/p38MAPK/NF-κB pathway.

Thrombocytopenia is not mandatory to diagnose haemolytic and uremic syndrome

BackgroundHemolytic and uremic syndrome (HUS) diagnosis involves association of non immune hemolytic anemia, thrombocytopenia, and renal failure. HUS without thrombocytopenia has been observed, we call it partial HUS. Its real frequency and outcome are unknown. The aim of this study was to determine the prevalence of patients with normal platelets count in two HUS cohorts and to compare their outcome to patients with thrombocytopenia.MethodsWe retrospectively identified HUS diagnosis in two different cohorts. The first cohort was from a single center and consisted of all cases of HUS whatever the aetiology, the second was multicentric and consisted of atypical HUS patients. These cohorts were divided into two groups depending on the presence or absence of thrombocytopenia. Clinical and biological data were compared between thrombopenic and non thrombopenic group.ResultsWe identified 13% (20/150) of patients with normal platelets count: 10 episodes (18%) of HUS in six patients (14%) in the monocentric cohort and 14 patients (13%) with 17 episodes (12%) in the multicentric cohort of atypical HUS. Groups differed in platelets count and LDH level. In both cohorts, renal outcome was similar to patient presenting with thrombocytopenia.ConclusionHUS with normal platelets count is not infrequent. Relative to classical clinical presentation of HUS, partial HUS has similar characteristics and identical poor renal outcome and so must be treated in the same way.

Diagnostic performance of [(18)F]fluorodeoxyglucose positron emission tomography-computed tomography in cyst infection in patients with autosomal dominant polycystic kidney disease.

Cyst infection is a common complication of autosomal dominant polycystic kidney disease (ADPKD). Diagnosis is challenging with standard imaging techniques. We aimed to evaluate the diagnostic performance of [(18)F]fluorodeoxyglucose positron emission tomography-computed tomography (18-FDG PET-CT) for the diagnosis of cyst infections among ADPKD patients, in comparison with computed tomography (CT) and magnetic resonance imaging (MRI). All APKD patients who underwent 18-FDG PET-CT for suspected cyst infection between 2006 and 2013 in a French teaching hospital were included. Diagnosis of cyst infection was retained a posteriori on an index of clinical suspicion. 18-FDG PET-CT findings were was considered to be positive in cases of cyst wall hypermetabolism. CT or MRI findings were were considered to be positive in cases of cyst wall thickening (and enhancement if contrast medium was injected) and infiltration of the adjacent fat. A control group of ADPKD patients with 18-FDG PET-CT performed for other reasons was included. Thirty-two 18-FDG PET-CT scans were performed in 24 ADPKD patients with suspected cyst infection. A diagnosis of cyst infection was retained in 18 of 32 cases: 14 with positive 18-FDG PET-CT findings, and four false negatives. There were no false positives and no hypermetabolism of cyst walls in nine ADPKD control patients. 18-FDG PET-CT had a sensitivity of 77%, a specificity of 100%, and a negative predictive value of 77%. 18-FDG PET-CT allowed a differential diagnosis in three patients. In contrast, CT had a sensitivity of 7% and a negative predictive value of 35% (p <0.001 vs. 18-FDG PET-CT). Only eight MRI scans were performed. The diagnostic performance of 18-FDG PET-CT is superior to that of CT in cyst infections, for comparable radiation doses and with no injection of nephrotoxic contrast medium, in ADPKD patients.

Serum microRNAs are altered in various stages of chronic kidney disease: a preliminary study

Background MicroRNAs (miRNAs) are innovative and informative blood-based biomarkers involved in numerous pathophysiological processes. In this study and based on our previous experimental data, we investigated miR-126, miR-143, miR-145, miR-155 and miR-223 as potential circulating biomarkers for the diagnosis and prognosis of patients with chronic kidney disease (CKD). The primary objective of this study was to assess the levels of miRNA expression at various stages of CKD. Methods RNA was extracted from serum, and RT-qPCR was performed for the five miRNAs and cel-miR-39 (internal control). Results Serum levels of miR-143, -145 and -223 were elevated in patients with CKD compared with healthy controls. They were further increased in chronic haemodialysis patients, but were below control levels in renal transplant recipients. In contrast, circulating levels of miR-126 and miR-155 levels, which were also elevated in CKD patients, were lower in the haemodialysis group and even lower in the transplant group. Four of the five miRNA species were correlated with estimated glomerular filtration rate, and three were correlated with circulating uraemic toxins. Conclusions This exploratory study suggests that specific miRNAs could be biomarkers for complications of CKD, justifying further studies to link changes of miRNA levels with outcomes in CKD patients.

Trends in Survival and Renal Recovery in Patients with Multiple Myeloma or Light-Chain Amyloidosis on Chronic Dialysis

BACKGROUND AND OBJECTIVESnMonoclonal gammopathies (MGs) with renal involvement can lead to ESRD caused by myeloma cast nephropathy (MCN), immunoglobulin light chain amyloidosis (ALA), or light-chain deposition disease (LCDD). Few studies have focused on the prognosis of patients with MG on chronic dialysis. We evaluated the outcomes of patients with MG incident on chronic dialysis in France.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnAll incident patients registered in the Renal Epidemiology and Information Network Registry between 2002 and 2011 with ESRD caused by ALA, LCDD, or MCN were included. Patients survival, censored for renal transplantation, renal recovery, and loss to follow-up, as well as renal outcomes were analyzed and compared with a control group. Risk factors and causes of death were analyzed.nnnRESULTSnWe included 1459 patients, comprising 265 (18%) patients with ALA, 334 (23%) patients with LCDD, and 861 (59%) patients with MCN. Median age was 72 years, and 56% were men. Median follow-up was 13.1 months. Renal recovery was observed in 9.1% of patients and more frequent after 2006. Kidney transplantation was rare in this population (2.3%). Among 1272 patients who remained on dialysis, 67% died. Median survival on dialysis was 18.3 months. Main causes of death were malignancies (34.4%), cardiovascular diseases (18%), infections (13.3%), and cachexia (5.2%). Independent risk factors of death were age (hazard ratio [HR], 1.03 per year increase; 95% confidence interval [95% CI], 1.02 to 1.03), frailty (HR, 1.93; 95% CI, 1.58 to 2.36), congestive heart failure (HR, 1.54; 95% CI, 1.23 to 1.93), and dialysis initiation on a central catheter (HR, 1.40; 95% CI, 1.11 to 1.75). Factors associated with a lower risk of death were year of dialysis initiation (HR, 0.95 per year increase; 95% CI, 0.91 to 0.99) and high BP (HR, 0.80; 95% CI, 0.67 to 0.97).nnnCONCLUSIONSnSurvival of patients with ALA, LCDD, or MCN on chronic dialysis is poor but has improved over time. Progressive malignancy is the main cause of death in this population. Renal recovery has increased since 2006.

Aryl hydrocarbon receptor is activated in patients and mice with chronic kidney disease

Patients with chronic kidney disease (CKD) are exposed to uremic toxins and have an increased risk of cardiovascular disease. Some uremic toxins, like indoxyl sulfate, are agonists of the transcription factor aryl hydrocarbon receptor (AHR). These toxins induce a vascular procoagulant phenotype. Here we investigated AHR activation in patients with CKD and in a murine model of CKD. We performed a prospective study in 116 patients with CKD stage 3 to 5D and measured the AHR-Activating Potential of serum by bioassay. Compared to sera from healthy controls, sera from CKD patients displayed a strong AHR-Activating Potential; strongly correlated with eGFR and with the indoxyl sulfate concentration. The expression of the AHR target genes Cyp1A1 and AHRR was up-regulated in whole blood from patients with CKD. Survival analyses revealed that cardiovascular events were more frequent in CKD patients with an AHR-Activating Potential above the median. In mice with 5/6 nephrectomy, there was an increased serum AHR-Activating Potential, and an induction of Cyp1a1 mRNA in the aorta and heart, absent in AhR-/- CKD mice. After serial indoxyl sulfate injections, we observed an increase in serum AHR-AP and in expression of Cyp1a1 mRNA in aorta and heart in WT mice, but not in AhR-/- mice. Thus, the AHR pathway is activated both in patients and mice with CKD. Hence, AHR activation could be a key mechanism involved in the deleterious cardiovascular effects observed in CKD.

Indole 3-acetic acid, indoxyl sulfate and paracresyl-sulfate do not influence anemia parameters in hemodialysis patients

BackgroundThe main reason for anemia in renal failure patients is the insufficient erythropoietin production by the kidneys. Beside erythropoietin deficiency, in vitro studies have incriminated uremic toxins in the pathophysiology of anemia but clinical data are sparse. In order to assess if indole 3-acetic acid (IAA), indoxyl sulfate (IS), and paracresyl sulfate (PCS) -three protein bound uremic toxins- are clinically implicated in end-stage renal disease anemia we studied the correlation between IAA, IS and PCS plasmatic concentrations with hemoglobin and Erythropoietin Stimulating Agents (ESA) use in hemodialysis patients.MethodsBetween June and July 2014, we conducted an observational cross sectional study in two hemodialysis center. Three statistical approaches were conducted. First, we compared patients treated with ESA and those not treated. Second, we performed linear regression models between IAA, IS, and PCS plasma concentrations and hemoglobin, the ESA dose over hemoglobin ratio (ESA/Hemoglobin) or the ESA resistance index (ERI). Third, we used a polytomous logistic regression model to compare groups of patients with no/low/high ESA dose and low/high hemoglobin statuses.ResultsOverall, 240 patients were included in the study. Mean agexa0±xa0SD was 67.6xa0±xa016.0xa0years, 55.4% were men and 42.5% had diabetes mellitus.When compared with ESA treated patients, patients with no ESA had higher hemoglobin (mean 11.4xa0±xa01.1 versus 10.6xa0±xa01.2xa0g/dL; p <0.001), higher transferrin saturation (TSAT, 31.1xa0±xa016.3% versus 23.1xa0±xa011.5%; pxa0<xa00.001), less frequentlyxa0an IV iron prescription (52.1 versus 65.7%, pxa0=xa00.04) and were more frequently treated with hemodiafiltration (53.5 versus 36.7%). In univariate analysis, IAA, IS or PCS plasma concentrations did not differ between the two groups.In the linear model, IAA plasma concentration was not associated with hemoglobin, but was negatively associated with ESA/Hb (pxa0=xa00.02; Rxa0=xa00.18) and with the ERI (pxa0=xa00.03; Rxa0=xa00.17). IS was associated with none of the three anemia parameters. PCS was positively associated with hemoglobin (pxa0=xa00.03; Rxa0=xa00.14), but negatively with ESA/Hb (pxa0=xa00.03; Rxa0=xa00.17) and the ERI (pxa0=xa00.02; Rxa0=xa00.19). In multivariate analysis, the association of IAA concentration with ESA/Hb or ERI was not statistically significant, neither was the association of PCS with ESA/Hb or ERI. Identically, in the subgroup of 76 patients with no inflammation (CRP <5xa0mg/L) and no iron deficiency (TSAT >20%) linear regression between IAA, IS or PCS and any anemia parameter did not reach significance.In the third model, univariate analysis showed no intergroup significant differences for IAA and IS. Regarding PCS, the Low Hb/High ESA group had lower concentrations. However, when we compared PCS with the other significant characteristics of the five groups to the Low Hb/high ESA (our reference group), the polytomous logistic regression model didn’t show any significant difference for PCS.ConclusionsIn our study, using three different statistical models, we were unable to show any correlation between IAA, IS and PCS plasmatic concentrations and any anemia parameter in hemodialysis patients. Indolic uremic toxins and PCS have no or a very low effect on anemia parameters.

Anticorps antiphospholipides et hémodialyse : une association fréquente corrélée à la thrombose de l’abord vasculaire

Antiphospholipid antibodies (APL) are a heterogeneous family of auto-antibodies that recognize phospholipoproteins bound antigenic epitopes. APL prevalence in patients on chronic hemodialysis ranges from 11 to 37% in the literature. The association of APL with hemodialysis vascular access (VA) thrombosis has already been reported in small studies. In this single center and retrospective study, we defined the APL prevalence and APL risk factors in a large cohort of 192 hemodialysis patients. The association between history of VA thrombosis and APL presence was also analyzed. At least one type of APL was found in 38 patients (19.8%) of which 74% (n=28) had only lupus anticoagulant. Median age of APL positive patients was 68.1years vs. 71.3years in APL negative patients (P=0.02). Smoking history was associated with APL presence: 35.5% of APL positive patients had a smoking history vs only 18.3% of APL negative patients (P=0.04). The multivariate analysis showed an association between the history of VA thrombosis and patient age (HR [IC 95%]=1.04 [1.02-1.06]; P=0.001) or APL presence (HR [IC 95%]=3.03 [1.69-4.42]; P<10(-3)). In conclusion, the prevalence of APL in hemodialysis patients remains high despite hemodialysis techniques improvement: hemodiafiltration, biocompatibility improvements, ultrapure dialysis water. We report that a younger age and past history of smoking are associated with an increased risk of APL presence. The presence of APL, especially lupus anticoagulant, is associated to VA thrombosis in hemodialysis patients.