The harmful effect of indoxyl sulfate on neovascularization in chronic kidney disease

Influence of Hypoxia Inducible Factor-1α of Endothelial Progenitor Cells on Left Ventricular Function in Experimental Myocardial Infarction

Based on the promotion of myocardial activity via endothelial progenitor cells (EPCs) subsequent to acute myocardial infarction (AMI), our research was designed to explore the influence of excessive HIF-1α expression in expanded EPCs (eEPCs) on promotion of the activity of left ventricle subsequent to MI. Isolation of EPCs from cord blood was performed before transduction with the help of retroviral vector with or without HIF-1α expression. Transplantation was performed subsequent to ligation of the left anterior descending coronary artery in mice. Ejection fraction (EF) of left ventricle was promoted via transplantation after 2 weeks. Excessive HIF-1α expression enhanced EF of left ventricle and decreased the extent of MI. It was revealed via functional studies that excessive HIF-1α expression enhanced proliferation of EPCs triggered by low oxygen concentration and suppressed cell death in the region of infarction. Moreover, markers of endothelium CD31, VEGF, and eNOS were upregulated. Transplantation of eEPCs with excessive HIF-1α expression in AMI can promote myocardial activities by increasing differentiation, generation of vessels, proliferation of eEPCs, and suppressing cell death. The above findings propose that regulation of EPCs via HIF-1α enhances the activity as well as mobilization of EPCs, indicating that reinforcement of expression of HIF-1α is beneficial for coronary heart disease.

Targeting Uremic Toxins to Prevent Peripheral Vascular Complications in Chronic Kidney Disease

Chronic kidney disease (CKD) exhibits progressive kidney dysfunction and leads to disturbed homeostasis, including accumulation of uremic toxins, activated renin-angiotensin system, and increased oxidative stress and proinflammatory cytokines. Patients with CKD are prone to developing the peripheral vascular disease (PVD), leading to poorer outcomes than those without CKD. Cumulative evidence has showed that the synergy of uremic milieu and PVD could exaggerate vascular complications such as limb ischemia, amputation, stenosis, or thrombosis of a dialysis vascular access, and increase mortality risk. The role of uremic toxins in the pathogenesis of vascular dysfunction in CKD has been investigated. Moreover, growing evidence has shown the promising role of uremic toxins as a therapeutic target for PVD in CKD. This review focused on uremic toxins in the pathophysiology, in vitro and animal models, and current novel clinical approaches in reducing the uremic toxin to prevent peripheral vascular complications in CKD patients.

Indoxyl Sulfate and Incident Peripheral Artery Disease in Hemodialysis Patients

Peripheral artery disease (PAD) is highly prevalent among patients with chronic kidney disease (CKD) and portends a very poor prognosis. Indoxyl sulfate has been shown to induce atherothrombosis and impaired neovascularization in uremic mice. However, there is no clinical evidence regarding the role of indoxyl sulfate in PAD associated with CKD. We examined associations between indoxyl sulfate and incident symptomatic lower extremity PAD events as well as major adverse cardiovascular events (MACE) and all-cause mortality using Cox proportional hazards models in a prospective cohort of 200 hemodialysis patients free of PAD at baseline. Patients were considered as having PAD if they developed PAD symptoms confirmed by an ankle-brachial index with waveforms, duplex ultrasound or angiography, and/or major adverse limb events including revascularization and amputation. During a median follow-up of 6.5 years, 37 patients (18.5%) experienced incident symptomatic PAD. MACE occurred in 52 patients, and a total of 85 patients died. After adjusting for traditional risk factors for PAD, including age, current smoking, diabetes, and cardiovascular disease, indoxyl sulfate was significantly associated with the risk of PAD (hazard ratio (HR), 1.19 for every 10-μg/mL increase in indoxyl sulfate; 95% confidence interval (CI), 1.05–1.35). However, indoxyl sulfate was not associated with risk of MACE (HR, 1.00; 95% CI, 0.90–1.12) or death from any cause (HR, 0.98; 95% CI, 0.90–1.07). Indoxyl sulfate was associated with incident symptomatic PAD but not with MACE or all-cause mortality, suggesting that indoxyl sulfate toxicity may be unique to PAD among hemodialysis patients.

Impact of gut microbiota: How it could play roles beyond the digestive system on development of cardiovascular and renal diseases

In recent years, a significant interest in gut microbiota-host crosstalk has increased due to the involvement of gut bacteria on host health and diseases. Gut dysbiosis, a change in the gut microbiota composition alters host-microbiota interactions and induces gut immune dysregulation that have been associated with pathogenesis of several diseases, including cardiovascular diseases (CVD) and chronic kidney diseases (CKD). Gut microbiota affect the host, mainly through the immunological and metabolism-dependent and metabolism-independent pathways. In addition to these, the production of trimethylamine (TMA)/trimethylamine N-oxide (TMAO), uremic toxins and lipopolysaccharides (LPS) by gut microbiota are involved in the pathogenesis of CVD and CKD. Given the current approaches and challenges that can reshape the bacterial composition by restoring the balance between host and microbiota. In this review, we discuss the complex interplay between the gut microbiota, and the heart and the kidney, and explain the gut-cardiovascular axis and gut-kidney axis on the development and progression of cardiovascular diseases and chronic kidney diseases. In addition, we discuss the interplay between gut and kidney on hypertension or cardiovascular pathology.

Factors of microinflammation in non-diabetic chronic kidney disease: a pilot study

Background

The relationships between digestive bacterial translocation, uremic toxins, oxidative stress and microinflammation in a population of chronic kidney disease (CKD) patients without metabolic nor inflammatory disease are unknown.

Methods

Bacterial translocation, uremic toxins, oxidative stress, and inflammation were assessed by measuring plasma levels of 16S  ribosomal DNA (16S rDNA), p-cresyl sulfate (PCS), indoxyl sulfate (IS), indole acetic acid (IAA), F2-isoprostanes, hsCRP and receptor I of TNFα (RITNFα) in patients without metabolic nor inflammatory disease. 44 patients with CKD from stage IIIB to V and 14 controls with normal kidney function were included from the nephrology outpatients. 11 patients under hemodialysis (HD) were also included. Correlations between each factor and microinflammation markers were studied.

Results

16S rDNA levels were not increased in CKD patients compared to controls but were decreased in HD compared to non-HD stage V patients (4.7 (3.9–5.3) vs 8.6 (5.9–9.7) copies/μl, p = 0.002). IS, PCS and IAA levels increased in HD compared to controls (106.3 (73.3–130.4) vs 3.17 (2.4–5.1) μmol/l, p < 0.0001 for IS; 174.2 (125–227.5) vs 23.7 (13.9–52.6) μmol/l, p = 0.006 for PCS; and 3.7 (2.6–4.6) vs 1.3 (1.0–1.9) μmol/l, p = 0.0002 for IAA). Urea increased in non-HD stage V patients compared to controls (27.6 (22.7–30.9) vs 5.4 (4.8–6.4) mmol/l, p < 0.0001) and was similar in HD and in non-HD stage V (19.3 (14.0–24.0) vs 27.6 (22.7–30.9) mmol/l, p = 0.7). RITNFα levels increased in HD patients compared to controls (12.6 (9.6–13.3) vs 1.1 (1.0–1.4) ng/ml, p < 0.0001); hsCRP levels increased in non-HD stage V patients compared to controls (2.9 (1.4–8.5) vs 0.8 (0.5–1.7) mg/l, p = 0.01) and remained stable in HD patients (2.9 (1.4–8.5) vs 5.1 (0.9–11.5) mg/l, p = 1). F2-isoprostanes did not differ in CKD patients compared to controls. Among uremic toxins, IS and urea were correlated to RITNFα (r = 0.8, p < 0.0001 for both). PCS, IS and urea were higher in patients with hsCRP≧5 mg/l (p = 0.01, 0.04 and 0.001 respectively). 16S rDNA, F2-isoprostanes were not correlated to microinflammation markers in our study.

Conclusions

In CKD patients without any associated metabolic nor inflammatory disease, only PCS, IS, and urea were correlated with microinflammation. Bacterial translocation was decreased in patients under HD and was not correlated to microinflammation.

Indoxyl Sulfate, a Uremic Endotheliotoxin

Chronic kidney disease (CKD) is associated with a high prevalence of cardiovascular diseases. During CKD, the uremic toxin indoxyl sulfate (IS)—derived from tryptophan metabolism—accumulates. IS is involved in the pathophysiology of cardiovascular complications. IS can be described as an endotheliotoxin: IS induces endothelial dysfunction implicated in cardiovascular morbidity and mortality during CKD. In this review, we describe clinical and experimental evidence for IS endothelial toxicity and focus on the various molecular pathways implicated. In patients with CKD, plasma concentrations of IS correlate with cardiovascular events and mortality, with vascular calcification and atherosclerotic markers. Moreover, IS induces a prothrombotic state and impaired neovascularization. IS reduction by AST-120 reverse these abnormalities. In vitro, IS induces endothelial aryl hydrocarbon receptor (AhR) activation and proinflammatory transcription factors as NF-κB or AP-1. IS has a prooxidant effect with reduction of nitric oxide (NO) bioavailability. Finally, IS alters endothelial cell and endothelial progenitor cell migration, regeneration and control vascular smooth muscle cells proliferation. Reducing IS endothelial toxicity appears to be necessary to improve cardiovascular health in CKD patients.

CharXgen-Activated Bamboo Charcoal Encapsulated in Sodium Alginate Microsphere as the Absorbent of Uremic Toxins to Retard Kidney Function Deterioration

Indoxyl sulphate (IS) and p-cresyl sulphate (PCS) are two protein bound uraemic toxins accumulated in chronic kidney disease (CKD) and associated with adverse outcomes. The purpose of this study isto evaluate the effect of the new activated charcoal, CharXgen, on renal function protection and lowering serum uraemic toxins in CKD animal model. The physical character of CharXgen was analyzed before and after activation procedure by Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD). The effect of CharXgen on biochemistry and lowering uremic toxins was evaluated by in vitro binding assay and CKD animal model. CharXgen have high interior surface area analyzed by SEM and XRD and have been produced from local bamboo after an activation process. CharXgen was able to effectively absorb IS, p-cresol and phosphate in an in vitro gastrointestinal tract simulation study. The animal study showed that CharXgen did not cause intestine blackening. Serum albuminand liver function did not change after feeding with CharXgen. Moreover, renal function was improved in CKD rats fed with CharXgen as compared to the CKD group, and there were no significant differences in the CKD and the CKD + AST-120 groups. Serum IS and PCS were higher in the CKD group and lower in rats treated with CharXgen and AST-120. In rats treated with CharXgen, Fibroblast growth factor 23 was significantly decreased as compared to the CKD group. This change cannot be found in rats fed with AST-120.It indicates that CharXgen is a new safe and non-toxic activated charcoal having potential in attenuating renal function deterioration and lowering protein-bound uraemic toxins. Whether the introduction of this new charcoal could further have renal protection in CKD patients will need to be investigated further.

Molecular mechanisms of protein-bound uremic toxin-mediated cardiac, renal and vascular effects: underpinning intracellular targets for cardiorenal syndrome therapy

Cardiorenal syndrome (CRS) remains a global health burden with a lack of definitive and effective treatment. Protein-bound uremic toxin (PBUT) overload has been identified as a non-traditional risk factor for cardiac, renal and vascular dysfunction due to significant albumin-binding properties, rendering these solutes non-dialyzable upon the state of irreversible kidney dysfunction. Although limited, experimental studies have investigated possible mechanisms in PBUT-mediated cardiac, renal and vascular effects. The ultimate aim is to identify relevant and efficacious targets that may translate beneficial outcomes in disease models and eventually in the clinic. This review will expand on detailed knowledge on mechanisms involved in detrimental effects of PBUT, specifically affecting the heart, kidney and vasculature, and explore potential effective intracellular targets to abolish their effects in CRS initiation and/or progression.

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

Background

The 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.

Methods

Between 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.

Results

Overall, 240 patients were included in the study. Mean age ± SD was 67.6 ± 16.0 years, 55.4% were men and 42.5% had diabetes mellitus.

When compared with ESA treated patients, patients with no ESA had higher hemoglobin (mean 11.4 ± 1.1 versus 10.6 ± 1.2 g/dL; p <0.001), higher transferrin saturation (TSAT, 31.1 ± 16.3% versus 23.1 ± 11.5%; p < 0.001), less frequently an IV iron prescription (52.1 versus 65.7%, p = 0.04) 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 (p = 0.02; R = 0.18) and with the ERI (p = 0.03; R = 0.17). IS was associated with none of the three anemia parameters. PCS was positively associated with hemoglobin (p = 0.03; R = 0.14), but negatively with ESA/Hb (p = 0.03; R = 0.17) and the ERI (p = 0.02; R = 0.19). 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 <5 mg/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.

Conclusions

In 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.

Role of uremic toxin indoxyl sulfate in the progression of cardiovascular disease

The prevalence of cardiovascular disease (CVD) among patients with chronic kidney disease (CKD) is relatively high. Deterioration of renal function in CKD leads to accumulation of indoxyl sulfate, a tryptophan metabolite produced by gut microbiota. It is acknowledged that indoxyl sulfate is capable to stimulate oxidative stress, which in turn contributes to the progression of vascular disorders and its resultant coronary artery disease. Recent research have demonstrated the adverse effects of indoxyl sulfate on the heart, together with the acceleration of vascular dysfunction, suggesting that indoxyl sulfate might contribute to high prevalence of CVD in CKD. The present mini review has focused on the potential mechanisms by which indoxyl sulfate exerts this pro-oxidant effects on the cardiovascular system. The action of indoxyl sulfate are related to multiple NADPH oxidase-mediated redox signaling pathways, which have been implicated in the pathophysiology of different forms of CVD, including chronic heart failure, arrhythmia, atherosclerotic vascular disease and coronary calcification. Future therapeutic options are discussed, including modulating gut microbial flora and blocking responsible pathophysiologic pathways.