An oral adsorbent, AST-120, suppresses oxidative stress in uremic rats

The AKI-to-CKD Transition: The Role of Uremic Toxins

After acute kidney injury (AKI), renal function continues to deteriorate in some patients. In a pro-inflammatory and profibrotic environment, the proximal tubules are subject to maladaptive repair. In the AKI-to-CKD transition, impaired recovery from AKI reduces tubular and glomerular filtration and leads to chronic kidney disease (CKD). Reduced kidney secretion capacity is characterized by the plasma accumulation of biologically active molecules, referred to as uremic toxins (UTs). These toxins have a role in the development of neurological, cardiovascular, bone, and renal complications of CKD. However, UTs might also cause CKD as well as be the consequence. Recent studies have shown that these molecules accumulate early in AKI and contribute to the establishment of this pro-inflammatory and profibrotic environment in the kidney. The objective of the present work was to review the mechanisms of UT toxicity that potentially contribute to the AKI-to-CKD transition in each renal compartment.

Innate Immunity System in Patients With Cardiovascular and Kidney Disease

With a global burden of 844 million, chronic kidney disease (CKD) is now considered a public health priority. Cardiovascular risk is pervasive in this population, and low-grade systemic inflammation is an established driver of adverse cardiovascular outcomes in these patients. Accelerated cellular senescence, gut microbiota-dependent immune activation, posttranslational lipoprotein modifications, neuroimmune interactions, osmotic and nonosmotic sodium accumulation, acute kidney injury, and precipitation of crystals in the kidney and the vascular system all concur in determining the unique severity of inflammation in CKD. Cohort studies documented a strong link between various biomarkers of inflammation and the risk of progression to kidney failure and cardiovascular events in patients with CKD. Interventions targeting diverse steps of the innate immune response may reduce the risk of cardiovascular and kidney disease. Among these, inhibition of IL-1β (interleukin-1 beta) signaling by canakinumab reduced the risk for cardiovascular events in patients with coronary heart disease, and this protection was equally strong in patients with and without CKD. Several old (colchicine) and new drugs targeting the innate immune system, like the IL-6 (interleukin 6) antagonist ziltivekimab, are being tested in large randomized clinical trials to thoroughly test the hypothesis that mitigating inflammation may translate into better cardiovascular and kidney outcomes in patients with CKD.

The AST-120 Recovers Uremic Toxin-Induced Cognitive Deficit via NLRP3 Inflammasome Pathway in Astrocytes and Microglia

Chronic kidney disease (CKD) is characterized by the progressive loss of renal function; moreover, CKD progression commonly leads to multiple comorbidities, including neurological dysfunction and immune disorders. CKD-triggered neuroinflammation significantly contributes to cognitive impairment. This study aimed to investigate the contribution of uremic toxins to cognitive impairment. Serum creatinine, blood urea nitrogen (BUN), indoxyl sulfate (IS), and p-cresol sulfate (PCS) levels were measured using an enzyme-linked immunosorbent assay and high-performance liquid chromatography. The creatinine, BUN, IS, and PCS levels were increased from 4 weeks after 5/6-nephrectomy in mice, which suggested that 5/6-nephrectomy could yield a CKD animal model. Further, CKD mice showed significantly increased brain and serum indoxyl sulfate levels. Immunohistochemistry analysis revealed hippocampal inflammation and NLRP3-inflammasomes in astrocytes. Further, the Y-maze and Morris water maze tests revealed learning and memory defects in CKD mice. AST-120, which is also an IS absorbent, effectively reduced serum and hippocampal IS levels as well as reversed the cognitive impairment in CKD mice. Additionally, NLRP3-knockout mice that underwent 5/6-nephrectomy showed no change in cognitive function. These findings suggested that IS is an important uremic toxin that induces NLRP3 inflammasome-mediated not only in microglia, but it also occurred in astrocytic inflammation, which subsequently causes cognitive impairment.

Uremic Toxins in the Progression of Chronic Kidney Disease and Cardiovascular Disease: Mechanisms and Therapeutic Targets

Chronic kidney disease (CKD) is a progressive loss of renal function. The gradual decline in kidney function leads to an accumulation of toxins normally cleared by the kidneys, resulting in uremia. Uremic toxins are classified into three categories: free water-soluble low-molecular-weight solutes, protein-bound solutes, and middle molecules. CKD patients have increased risk of developing cardiovascular disease (CVD), due to an assortment of CKD-specific risk factors. The accumulation of uremic toxins in the circulation and in tissues is associated with the progression of CKD and its co-morbidities, including CVD. Although numerous uremic toxins have been identified to date and many of them are believed to play a role in the progression of CKD and CVD, very few toxins have been extensively studied. The pathophysiological mechanisms of uremic toxins must be investigated further for a better understanding of their roles in disease progression and to develop therapeutic interventions against uremic toxicity. This review discusses the renal and cardiovascular toxicity of uremic toxins indoxyl sulfate, p-cresyl sulfate, hippuric acid, TMAO, ADMA, TNF-α, and IL-6. A focus is also placed on potential therapeutic targets against uremic toxicity.

AST-120, an Oral Carbon Absorbent, Protects against the Progression of Atherosclerosis in a Mouse Chronic Renal Failure Model by Preserving sFlt-1 Expression Levels

Soluble Flt-1 (sFlt-1), an endogenous antagonist of the proatherogenic cytokine placental growth factor, is decreased in chronic kidney disease (CKD), leading to atherosclerotic progression. In this study, we investigated the effect of AST-120, an oral carbon adsorbent which can remove uremic toxins, on sFlt-1 expression levels and atherosclerosis progression. Atherosclerotic apolipoprotein E-deficient mice underwent a 5/6 nephrectomy (5/6 NR) or a sham operation (sham) at 8 weeks of age and were then treated or not with oral AST-120 for 12 weeks. sFlt-1 expression levels and the degree of atherosclerosis were assessed at 22 weeks of age in each of the four groups (sham; n = 7, 5/6 NR; n = 10, sham + AST-120: n = 8, 5/6 NR + AST-120; n = 8). The expression levels of sFlt-1 mRNA in the kidney were significantly lower in the 5/6 NR group than in the sham group, but AST-120 treatment prevented this decrease in sFlt-1 levels. Similarly, the atherosclerotic plaque area of the thoracoabdominal aorta was significantly larger in the 5/6 NR group than in the sham group, and AST-120 treatment prevented this increase in atherosclerosis. AST-120 could, therefore, be used as a therapeutic to treat atherosclerosis in patients with CKD.

Effects and Safety of an Oral Adsorbent on Chronic Kidney Disease Progression: A Systematic Review and Meta-Analysis

Background: AST-120 (Kremezin), which is an oral spherical carbon adsorbent, has been reported to have the potential for retarding disease progression in patients with chronic kidney disease. We aimed to evaluate its efficacy and safety in this study. Methods: We systematically searched for randomized controlled trials published in PubMed, Embase, and Cochrane databases. The primary outcomes were the renal outcome and all-cause mortality, and the change in serum indoxyl sulfate (IS) levels. The safety outcome was also evaluated in terms of reported major adverse events. A random-effects model was used when heterogeneity was expected. Results: Eight studies providing data for 3349 patients were included in the meta-analysis. The risk ratio of renal outcome and all-cause mortality were 0.97 (95% CI: 0.88–1.07; 6 trials) and 0.94 (0.73–1.20; 5 trials), respectively. Furthermore, the weighted mean change in IS levels from baseline to the end of the study was −0.28 mg/dL (95% CI: −0.46 to −0.11; 4 trials). Conclusions: This study provides evidence that AST-120 can effectively lower IS levels but still controversial in terms of slowing disease progression and all-cause mortality. Except for dermatological events, the incidence of adverse events did not differ significantly between the AST-120 and placebo groups.

Nrf2 activator for the treatment of kidney diseases

Kidney diseases are highly prevalent worldwide, and significantly reduce the quality of life of patients, creating an urgent need for effective therapeutic modalities. Despite this significant unmet medical need, none of the drugs launched to date have demonstrated promising potential to cure kidney diseases. This is likely due to the structural complexity of the kidney as well as difficulties in setting appropriate endpoints for clinical trials and identifying appropriate therapeutic targets. Recently, an alternative endpoint for clinical trials (i.e., a 30% or 40% reduction in estimated glomerular filtration rate [eGFR] from baseline following 2-3 years of observation) has been considered in the United States, European Union, and Japan, and is expected to contribute to the progress of drug development for kidney diseases. Further, oxidative stress and inflammation are currently thought to be key factors in the progression of kidney diseases, prompting more research on drugs targeting the mechanisms related to these factors for treatment. The Kelch-like ECH-associated protein 1-nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2) system has drawn much attention in recent years for its anti-oxidative and anti-inflammatory properties, and its pharmacological potential for treatment of kidney diseases is being widely investigated in both clinical and non-clinical studies. This review summarizes the current issues in the treatment of kidney diseases, including clinical endpoints, Nrf2 activators as treatment options, and perspectives on pharmaceutical applications of Nrf2 activators.

Cardiotoxicity of Uremic Toxins: A Driver of Cardiorenal Syndrome

Cardiovascular disease (CVD) is highly prevalent in the setting of chronic kidney disease (CKD). Such coexistence of CVD and CKD—the so-called “cardiorenal or renocardiac syndrome”—contributes to exponentially increased risk of cardiovascular (CV) mortality. Uremic cardiomyopathy is a characteristic cardiac pathology commonly found in CKD. CKD patients are also predisposed to heart rhythm disorders especially atrial fibrillation. Traditional CV risk factors as well as known CKD-associated CV risk factors such as anemia are insufficient to explain CV complications in the CKD population. Accumulation of uremic retention solutes is a hallmark of impaired renal excretory function. Many of them have been considered inert solutes until their biological toxicity is unraveled and they become accepted as “uremic toxins”. Direct cardiotoxicity of uremic toxins has been increasingly demonstrated in recent years. This review offers a mechanistic insight into the pathological cardiac remodeling and dysfunction contributed by uremic toxins with a main focus on fibroblastic growth factor-23, an emerging toxin playing a central role in the chronic kidney disease–mineral bone disorder, and the two most investigated non-dialyzable protein-bound uremic toxins, indoxyl sulfate and p-cresyl sulfate. Potential therapeutic strategies that could address these toxins and their relevant mediated pathways since pre-dialysis stages are also discussed.

Effect of uremic toxin-indoxyl sulfate on the skeletal system

Chronic kidney disease-mineral bone disorders (CKD-MBD) exhibit abnormalities in the circulating mineral levels, vitamin D metabolism, and parathyroid function that contribute to the formation of a bone lesion. The uremic toxin, indoxyl sulfate (IS), accumulates in the blood in cases of renal failure and leads to bone loss. The bone and renal responses to the action of the parathyroid hormone (PTH) are progressively decreased in CKD in spite of increasing PTH levels, a condition commonly called PTH resistance. There is a high prevalence of low bone turnover or adynamic bone disease in the early stages of CKD. This could be due to the inhibition of bone turnover, such as in PTH resistance, reduced active vitamin D levels, diabetes, aluminum, and, increased IS. With an increase in IS, there is a decrease in the osteoblast Wnt/b-catenin signaling and increase in the expression of Wnt signaling inhibitors, such as sclerostin and Dickkopf-1 (DKK1). Thus, a majority of early CKD patients exhibit deterioration of bone quality owing to the action of IS, this scenario could be termed uremic osteoporosis. However, this mechanism is complicated and not fully understood. With progressive deterioration in the renal function, IS accumulates along with persistent PTH secretion, potentially leading to high-turnover bone disease because high serum PTH levels have the ability of overriding peripheral PTH resistance and other inhibitory factors of bone formation. Finally, it leads to deterioration in bone quantity with prominent bone resorption in end stage renal disease. Uremic toxins adsorbents may decelerate oxidative stress and improve bone health in CKD patients. This review article focuses on IS and bone loss in CKD patients.

Role of Uremic Toxins for Kidney, Cardiovascular, and Bone Dysfunction

With decreasing kidney function, cardiovascular disease (CVD) and mineral bone disorders frequently emerge in patients with chronic kidney disease (CKD). For these patients, in addition to the traditional risk factors, non-traditional CKD-specific risk factors are also associated with such diseases and conditions. One of these non-traditional risk factors is the accumulation of uremic toxins (UTs). In addition, the accumulation of UTs further deteriorates kidney function. Recently, a huge number of UTs have been identified. Although many experimental and clinical studies have reported associations between UTs and the progression of CKD, CVD, and bone disease, these relationships are very complex and have not been fully elucidated. Among the UTs, indoxyl sulfate, asymmetric dimethylarginine, and p-cresylsulfate have been of particular focus, up until now. In this review, we summarize the pathophysiological influences of these UTs on the kidney, cardiovascular system, and bone, and discuss the clinical data regarding the harmful effects of these UTs on diseases and conditions.

The Loss of GSTM1 Associates with Kidney Failure and Heart Failure

Glutathione S-transferase mu 1 (GSTM1) encodes an enzyme that catalyzes the conjugation of electrophilic compounds with glutathione to facilitate their degradation or excretion. The loss of one or both copies of GSTM1 is common in many populations and has been associated with CKD progression. With the hypothesis that the loss of GSTM1 is also associated with incident kidney failure and heart failure, we estimated GSTM1 copy number using exome sequencing reads in the Atherosclerosis Risk in Communities (ARIC) Study, a community-based prospective cohort of white and black participants. Overall, 51.2% and 39.8% of white participants and 25.6% and 48.5% of black participants had zero or one copy of GSTM1, respectively. Over a median follow-up of 24.6 years, 256 kidney failure events occurred in 5715 participants without prevalent kidney failure, and 1028 heart failure events occurred in 5368 participants without prevalent heart failure. In analysis adjusted for demographics, diabetes, and hypertension, having zero or one copy of GSTM1 associated with higher risk of kidney failure and heart failure (adjusted hazard ratio [95% confidence interval] for zero or one versus two copies of GSTM1: kidney failure, 1.66 [1.27 to 2.17]; heart failure, 1.16 [1.04 to 1.29]). Risk did not differ significantly between participants with zero and one copy of GSTM1 (P>0.10). In summary, the loss of GSTM1 was significantly associated with incident kidney and heart failure, independent of traditional risk factors. These results suggest GSTM1 function is a potential treatment target for the prevention of kidney and heart failure.

Anti-oxidative effect of AST-120 on kidney injury after myocardial infarction

BACKGROUND AND PURPOSE

Chronic kidney disease (CKD) is a crucial risk factor for cardiovascular disease (CVD), and combined CKD and CVD further increases morbidity and mortality. Here, we investigated effects of AST-120 on oxidative stress and kidney injury using a model of myocardial infarction (MI) in rats.

EXPERIMENTAL APPROACH

At 10 weeks, male spontaneously hypertensive rats (SHR) were divided into three groups: SHR (n = 6), MI (n = 8) and MI + AST-120 (n = 8). AST-120 administration was started at 11 weeks after MI. At 18 weeks, the rats were killed, and blood and urine, mRNA expression and renal histological analyses were performed. Echocardiography was performed before and after MI.

KEY RESULTS

At 18 weeks, the BP was significantly lower in the MI and MI+AST-120 groups than in the SHR group. Elevated levels of indoxyl sulfate (IS), one of the uremic toxins, in serum and urine were reduced by AST-120 treatment, compared with the MI group. Markers of oxidative stress in urine and serum biomarkers of kidney injury were decreased in the MI+AST-120 group compared with the other two groups. Renal expression of mRNAs for kidney injury related-markers were decreased in the MI+AST-120 group, compared with the MI group. In vitro data also supported the influence of IS on kidney injury. Immunohistological analysis showed that intrarenal oxidative stress was reduced by AST-120 administration.

CONCLUSIONS AND IMPLICATIONS

Serum IS was increased after MI and treatment with AST-120 may have protective effects on kidney injury after MI by suppressing oxidative stress.

Role of Indoxyl Sulfate as a Predisposing Factor for Atrial Fibrillation in Renal Dysfunction

Background

Renal dysfunction is a major risk factor for atrial fibrillation (AF). The uremic toxin indoxyl sulfate may contribute to the progression of cardiac fibrosis and AF substrate in renal dysfunction.

Methods and Results

Male Sprague–Dawley rats were assigned randomly to the following groups: 5/6 nephrectomy (5/6Nx) with vehicle, 5/6Nx with AST‐120, sham procedure with vehicle, and sham procedure with AST‐120. Vehicle and AST‐120 were administered for 4 weeks. Serum levels of IS were significantly increased in 5/6Nx groups. Expression of malondialdehyde, an indicator of oxidative stress, was upregulated in the left atrium of 5/6Nx groups and was accompanied by an increase in expression of NADPH oxidase 2 and 4. Monocyte‐mediated inflammatory signals such as CD68, monocyte chemoattractant protein 1, and vascular cell adhesion molecule 1 were also upregulated in 5/6Nx groups. Interstitial fibrosis was promoted heterogeneously, and expression of profibrotic indicators such as transforming growth factor β1, α‐smooth muscle actin, and collagen type 1 was upregulated in left atrium tissue of 5/6Nx groups. In cultured atrial fibroblasts, incubation with IS upregulated expression of the markers of oxidative stress, inflammation, and profibrotic factors. These results suggest the direct effects of IS on the progression of AF substrate. AF was consistently and invariably induced by atrial extrastimuli in 5/6Nx groups in electrophysiological experiments. AST‐120 treatment significantly alleviated renal dysfunction–induced oxidative stress, inflammation, and atrial fibrosis and, consequently, attenuated AF inducibility.

Conclusions

Indoxyl sulfate facilitates atrial fibrosis and AF and thus is a novel therapeutic target for prevention of renal dysfunction–induced AF.

The role of AST-120 and protein-bound uremic toxins in irritable bowel syndrome: a therapeutic perspective

AST-120 (kremezin) exhibits its favourable effects in reducing the levels of renal toxins by selective adsorption of low molecular weight substances from the intestinal lumen. So far, a vast majority of studies were focused on the role of AST-120 in the treatment of chronic kidney diseases and cardiovascular disorders, and positive therapeutic effects of the agent have already been confirmed in clinical conditions. Up to the present, there are only a few studies regarding the role of AST-120 in irritable bowel syndrome (IBS). Compelling data suggest the ability of the compound to adsorb protein-bound uremic toxins and mast cell derived mediators and to modulate the farnesoid X receptor, which is a bile acid sensor indispensable for maintaining homeostasis in the intestine. In this review we focus on the actions of AST-120 on intestinal permeability, reduction of visceral sensitivity and alteration of gut motility. We also discuss whether AST-120 can mitigate common IBS symptoms, such as abdominal pain, bloating and malfunction of the colonic transit and thus improve the quality of life of patients with IBS.

Uremic toxins, oxidative stress, and renal fibrosis: an interwined complex

The prevalence of end-stage renal diseases is currently on the rise globally, and finding the way to curb this tide is urgently needed. Tubulointerstitial fibrosis is a common pathway for essentially all the nephropathy categories known to date, and the manifestations of renal fibrosis include excessive deposition of extracellular matrix with distortion of renal microstructures and functional deterioration. Uremic toxins have been gradually found to play an important role in the development of progressive renal fibrosis, with protein-bound indoxyl sulfate, p-cresol, and p-cresyl sulfate receiving the most attention. However, the contribution of oxidative stress among the pathogenesis of uremic toxins and renal fibrosis has not been evaluated much until recently. In this review, we will discuss about the nature and sources of oxidative stress in the kidney and how uremic toxins use oxidative stress to orchestrate the processes of renal fibrosis.

N-acetylcysteine as a potential strategy to attenuate the oxidative stress induced by uremic serum in the vascular system

AIMS

Chronic kidney disease (CKD) progression is accompanied by systemic oxidative stress, which contributes to an increase in the risk of cardiovascular diseases (CVDs). N-acetylcysteine (NAC) is among the most studied antioxidants, but its therapeutic benefits in CKD-associated CVDs remain controversial. Here, we investigated whether NAC could inhibit the oxidative stress induced by uremia in vitro and in vivo.

MAIN METHODS

Endothelial and smooth muscle cells were challenged with human uremic or non-uremic sera, and the effects of a pre-treatment with 2mM NAC were evaluated. Reactive oxygen species (ROS) production, protein oxidation and total glutathione/glutathione disulfide (tGSH/GSSG) ratios were measured. Five-sixths nephrectomized or sham-operated rats were orally treated (in the drinking water) with 60 mg/kg/day NAC or not treated for 53 days. Plasma cysteine/cystine reduction potential Eh(Cyss/2Cys) was determined as a novel marker of the systemic oxidative stress.

KEY FINDINGS

NAC inhibited all the determined oxidative stress parameters, likely by increasing the tGSH/GSSG ratio, in both cell lines exposed to uremic serum. Orally administered NAC attenuated the systemic oxidative stress in uremic rats.

SIGNIFICANCE

The present results indicate that NAC, by preventing GSH depletion in vascular cells exposed to uremic serum and by attenuating the systemic oxidative stress during CKD progression, emerges as a potential strategy to prevent the oxidative stress induced by uremic toxicity in the vascular system.

DPP-4 inhibitor attenuates toxic effects of indoxyl sulfate on kidney tubular cells

Diabetic nephropathy is a common causative factor of chronic kidney disease (CKD). DPP-4 inhibitor has the ability to improve kidney function and renal microvasculature. In the present study, we investigate the deleterious effects of IS on proximal tubular cells and the protective role of DPP-4 inhibitor. Human kidney 2 (HK-2) cells were exposed to IS in the presence or absence of DPP-4 inhibitor. Effects of DPP-4 inhibitor on viability of HK-2 cells were determined by MTT assay. Reactive oxygen species (ROS) production was examined using fluorescent microscopy. Levels of cleaved caspase-3, transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA) and NF-kappaB p65 and phosphorylation of AKT and extracellular signal-regulated kinase (ERK) were detected by immunoblotting. Production of ROS and level of cleaved caspase-3 were increased by IS in a dose-dependent manner. The phosphorylation of AKT and ERK p65 were decreased alongside activation of NF-κB. Expression of TGF-β and α-SMA, were upregulated in IS-treated HK-2 cells. Treatment with DPP-4 inhibitor resulted in a significant increase in cell viability and a decrease of ROS production in IS-treated HK-2 cells. DPP-4 inhibitor restored IS-induced deactivations of AKT and ERK and inhibited activation of NF-κB in IS-treated HK-2 cells. Moreover, DPP-4 inhibitor could also attenuate IS-induced up-regulation of TGF-β and α-SMA expression. These findings suggest that DPP-4 inhibitor possesses anti-apoptotic activity to ameliorate the IS-induced renal damage, which may be partly attributed to regulating ROS/p38MAPK/ERK and PI3K-AKT pathways as well as downstream NF-κB signaling pathway.

Effect of AST-120 on Endothelial Dysfunction in Adenine-Induced Uremic Rats

Aim. Chronic kidney disease (CKD) represents endothelial dysfunction. Monocyte adhesion is recognized as the initial step of arteriosclerosis. Indoxyl sulfate (IS) is considered to be a risk factor for arteriosclerosis in CKD. Oral adsorbent AST-120 retards deterioration of renal function, reducing accumulation of IS. In the present study, we determined the monocyte adhesion in the adenine-induced uremic rats in vivo and effects of AST-120 on the adhesion molecules. Methods. Twenty-four rats were divided into control, control+AST-120, adenine, and adenine+AST-120 groups. The number of monocytes adherent to the endothelium of thoracic aorta by imaging the entire endothelial surface and the mRNA expressions of adhesion and atherosclerosis-related molecules were examined on day 49. The mRNA expressions of ICAM-1 and VCAM-1 in human umbilical vein endothelial cells were also examined. Results. Adenine increased the number of adherent monocytes, and AST-120 suppressed the increase. The monocyte adhesion was related to serum creatinine and IS in sera. Overexpression of VCAM-1 and TGF-β1 mRNA in the arterial walls was observed in uremic rats. IS induced increase of the ICAM-1 and VCAM-1 mRNA expressions in vitro. Conclusion. It appears that uremic condition introduces the monocyte adhesion to arterial wall and AST-120 might inhibit increasing of the monocyte adherence with CKD progression.

Oral adsorbent AST-120 potentiates the effect of erythropoietin-stimulating agents on Stage 5 chronic kidney disease patients: a randomized crossover study

BACKGROUND

Indoxyl sulfate (IS) suppresses erythropoietin (EPO) activity and exerts renal damage. The oral adsorbent AST-120 reduces IS load and has antioxidant and renoprotective properties; however, its roles in the treatment of anemia remain unclear in chronic kidney disease (CKD) patients.

METHODS

Fifty-one Stage 5 predialysis CKD patients with hemoglobin <10 g/dL were randomly assigned to receive two period treatments with AST-120 plus once-monthly administration of continuous EPO receptor activator (CERA, A) and CERA alone (B), with a 4-week washout period in between. Mean changes of serum creatinine, estimated glomerular filtration rate (eGFR) and hemoglobin levels from the baseline were compared between two treatments.

RESULTS

The baseline and postintervention mean creatinine levels were 5.48 and 5.36 mg/dL in the Treatment A, and 5.14 mg/dL and 5.61 g/dL in the Treatment B group, respectively (treatment effect P = 0.025, period effect P = 0.467, carryover effect P = 0.384). The baseline and postintervention mean hemoglobin levels were 9.27 and 10.47 g/dL in the Treatment A, and 9.63 g/dL and 9.54 g/dL in the Treatment B group, respectively (treatment effect P = 0.039, period effect P = 0.001, carryover effect P = 0.060). Use of AST-120 significantly reduced IS and p-cresyl sulfate (PCS) levels. Hierarchical regression showed that eGFR was an independent predictor for hemoglobin after adjustment of serum free IS and PCS levels (B = 0.049, P = 0.005).

CONCLUSIONS

Use of adjuvant AST-120 may improve renal function and hemoglobin levels than use of CERA alone in late-stage CKD patients. The change of eGFR might play an intermediate role between serum IS/PCS and improve hemoglobin levels. The finding offered insight into novel therapeutic strategies of anemia for late-stage CKD patients.

Accumulated uremic toxins attenuate bone mechanical properties in rats with chronic kidney disease

The prevalence of hip fracture is very high among patients with chronic kidney disease (CKD); however, the reason for this is unclear. We examined the effects of accumulated uremic toxins on bone chemical composition and elastic mechanical properties. Rats underwent thyroparathyroidectomy and progressive partial nephrectomy (TPTx-Nx), and were administered with vehicle or AST-120 to reduce serum indoxyl sulfate (IS) levels. Bone mechanical properties, bone mineral density (BMD), cortical bone chemical composition, and histomorphometry were determined. Storage modulus was reduced in TPTx-Nx rats compared with rats that underwent TPTx alone. BMD and histomorphometric parameters did not differ between the groups. In terms of cortical bone chemical composition, the mineral/matrix ratio and carbonate substitution was increased, whereas crystallinity was decreased in TPTx-Nx rats. The enzymatic crosslink ratio and pentosidine:matrix ratio were increased in TPTx-Nx rats. AST-120 abolished the effects of TPTx-Nx and decreased the serum IS concentration. Stepwise multiple regression analysis revealed that the pentosidine:matrix and mineral:matrix ratios were independent contributors to the storage modulus. In conclusion, the accumulated uremic toxins, including IS, seem to play an important role in deteriorating bone mechanical properties by altering the chemical composition of bone. This mechanism may account for the increased prevalence of hip fracture among patients with CKD.

CREB, NF-κB, and NADPH oxidase coordinately upregulate indoxyl sulfate-induced angiotensinogen expression in proximal tubular cells

In chronic kidney disease (CKD), indoxyl sulfate, a uremic toxin, accumulates in serum, and the expression of angiotensinogen (AGT) is upregulated in renal proximal tubular cells. The present study aimed to determine the relationship between indoxyl sulfate and the upregulation of AGT expression in proximal tubular cells. Indoxyl sulfate induced expression of AGT in rat renal cortex and in cultured human proximal tubular cells (HK-2). In proximal tubular cells, indoxyl sulfate induced phosphorylation of cAMP response element-binding protein (CREB) on Ser-133, and small interfering RNA (siRNA) specific to CREB inhibited indoxyl sulfate-induced AGT expression. Our previous study demonstrated that indoxyl sulfate activated nuclear factor-κB (NF-κB) through reactive oxygen species (ROS) production. NF-κB inhibitors (pyrrolidine dithiocarbamate and isohelenin), NF-κB p65 siRNA, an antioxidant [ N-acetylcysteine (NAC)], and a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor [diphenyleneiodonium (DPI)] suppressed indoxyl sulfate-induced AGT expression. Both NAC and DPI suppressed indoxyl sulfate-induced expression of NF-κB p65 and CREB. CREB siRNA suppressed indoxyl sulfate-induced NF-κB p65 expression, whereas both NF-κB inhibitors and NF-κB p65 siRNA prevented indoxyl sulfate-induced CREB expression. Furthermore, we focused on the expression of NADPH oxidase 4 (NOX4), because indoxyl sulfate induced NOX4 expression in vascular smooth muscle cells and vascular endothelial cells. Indoxyl sulfate induced the expression of NOX4 in proximal tubular cells, which was suppressed by NAC, DPI, NF-κB inhibitors, NF-κB p65 siRNA, and CREB siRNA. Taken together, CREB, NF-κB, and NOX4 coordinately upregulate indoxyl sulfate-induced AGT expression in proximal tubular cells.

Cardiorenal syndrome: the emerging role of protein-bound uremic toxins

Cardiorenal syndrome is a condition in which a complex interrelationship between cardiac dysfunction and renal dysfunction exists. Despite advances in treatment of both cardiovascular and kidney disease, cardiorenal syndrome remains a major global health problem. Characteristic of the pathophysiology of cardiorenal syndrome is bidirectional cross-talk; mediators/substances activated by the disease state of 1 organ can play a role in worsening dysfunction of the other by exerting their biologically harmful effects, leading to the progression of the syndrome. Accumulation of uremic toxins is a hallmark of renal excretory dysfunction. Removal of some toxins by conventional dialysis is particularly problematic because of their high protein binding. In this review, we demonstrate that protein-bound uremic toxins may play an important role in progression of cardiovascular disease in the setting of chronic kidney disease. The highly protein-bound uremic toxin indoxyl sulfate has emerged as a potent toxin adversely affecting both the kidney and heart. Direct cardiac effects of this toxin have been recently demonstrated both in vitro and in vivo. Specifically, potent fibrogenic and prohypertrophic effects, as well as oxidative stress-inducing effects, appear to play a central role in both renal and cardiac pathology. Many of these adverse effects can be suppressed by use of a gut adsorbent, AST-120. Potential mechanisms underlying indoxyl sulfate-induced cardiorenal fibrosis are discussed. Future research and clinical implications conclude this review.

Indoxyl sulfate promotes vascular smooth muscle cell senescence with upregulation of p53, p21, and prelamin A through oxidative stress

We previously demonstrated that indoxyl sulfate (IS), a uremic toxin, induces aortic calcification in hypertensive rats and induces oxidative stress and the expression of osteoblast-specific proteins in vascular smooth muscle cells. This study aimed to clarify whether IS stimulates senescence of cultured human aortic smooth muscle cells (HASMCs) and aorta in Dahl salt-sensitive hypertensive rats and whether AST-120, an oral sorbent, prevents senescence of aorta in subtotally nephrectomized uremic rats. IS increased the mRNA expression of p53 and p21 in HASMCs, whereas it did not change that of p16 and retinoblastoma protein (pRb). The IS-induced expression of p53 and p21 was suppressed by N-acetylcysteine, an antioxidant. IS promoted protein expression of p53, p21, and senescence-associated β-galactosidase (SA-β-gal) activity in HASMCs, and N-acetylcysteine and pifithrin-α,p-nitro, a p53 inhibitor, blocked these effects. IS upregulated prelamin A, a hallmark of vascular smooth muscle cell senescence, and downregulated FACE1/Zempste24 protein expression in HASMCs, and N-acetylcysteine suppressed these effects. Administration of IS to hypertensive rats increased expression of SA-β-gal, p53, p21, prelamin A, and oxidative stress markers such as 8-hydroxyl-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) in the cells embedded in the calcification area of arcuate aorta. Further, the uremic rat model showed positive staining for SA-β-gal, p53, p21, prelamin A, 8-OHdG, and MDA in the cells embedded in the calcification area of arcuate aorta, whereas AST-120 reduced the expression of these biomarkers. Taken together, IS accelerates vascular smooth muscle cell senescence with upregulation of p53, p21, and prelamin A and downregulation of FACE1 through oxidative stress.

NF-κB plays an important role in indoxyl sulfate-induced cellular senescence, fibrotic gene expression, and inhibition of proliferation in proximal tubular cells

We previously demonstrated that indoxyl sulfate induces senescence and dysfunction of proximal tubular cells by activating p53 expression. However, little is known about the role of nuclear factor (NF)-κB in these processes. The present study examines whether activation (phosphorylation) of NF-κB by indoxyl sulfate promotes senescence and dysfunction in human proximal tubular cells (HK-2 cells). Indoxyl sulfate induced phosphorylation of NF-κB p65 on Ser-276, which was suppressed by N-acetylcysteine, an antioxidant. Furthermore, indoxyl sulfate induced NF-κB p65 expression. Inhibitors of NF-κB (pyrrolidine dithiocarbamate and isohelenin) and NF-κB p65 small interfering RNA (siRNA) suppressed indoxyl sulfate-induced senescence-associated β-galactosidase activity and expression of p53, transforming growth factor (TGF)-β1, and α-smoothe muscle actin (SMA). The induction of p53 expression and p53 promoter activity by indoxyl sulfate were inhibited by pifithrin-α, p-nitro, an inhibitor of p53, whereas p53-transfected cells showed enhanced p53 promoter activity. NF-κB inhibitors suppressed indoxyl sulfate-induced p21 expression, whereas NF-κB p65 siRNA enhanced its expression. NF-κB inhibitors partially alleviated indoxyl sulfate-induced inhibition of cellular proliferation. NF-κB p65 siRNA-transfected cells showed less proliferation in the presence of indoxyl sulfate than control cells. Phosphorylated NF-κB p65 was expressed and colocalized with p53, p21, β-galactosidase, TGF-β1, and α-SMA in the kidneys of chronic renal failure (CRF) rats. AST-120, which reduces serum indoxyl sulfate level, suppressed their expression in the CRF rat kidneys. Taken together, NF-κB plays an important role in indoxyl sulfate-induced cellular senescence, fibrotic gene expression, and inhibition of proliferation in proximal tubular cells. More notably, indoxyl sulfate accelerates proximal tubular cell senescence with progression of CRF through reactive oxygen species-NF-κB-p53 pathway.

Effects of AST-120 on left ventricular mass in predialysis patients

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of death in chronic kidney disease (CKD) patients. One of the proposed mechanisms assumes that accumulated uremic toxins play an important role in the progression of CVD in CKD. Recently, it has been reported that AST-120 may attenuate progression of CVD through absorption of uremic toxins. In this study, we examined the association between the use of AST-120 and cardiac abnormalities in CKD patients.

METHODS

This was a cross-sectional study of predialysis CKD patients hospitalized in our institution between April 2008 and October 2009. We divided 107 patients into two groups based on whether AST-120 had been administered for more than 6 months (AST-120 group: n = 43) or not (control group: n = 64). Echocardiography and laboratory tests were performed for all patients; we examined the relationship between clinical characteristics and cardiac abnormalities.

RESULTS

The number of patients with left ventricular (LV) concentric change was significantly smaller in the AST-120 group than in the control group. In multivariable analysis, the administration of AST-120, gender, and pulse pressure were significantly correlated with LV concentric change.

CONCLUSIONS

Our findings suggest that AST-120 prevents the development of LV concentric change in predialysis CKD patients.

Oral adsorbent AST-120 ameliorates tubular injury in chronic renal failure patients by reducing proteinuria and oxidative stress generation

AST-120 is an oral adsorbent that attenuates the progression of chronic renal failure (CRF) and improves the prognosis of the patients under dialysis. Although tubulointerstitial injury is more important than glomerulopathy in terms of renal prognosis in patients with CRF, effect of AST-120 on tubular injury in CRF patients remains unknown. In this study, we examined whether and how AST-120 treatment could improve tubular damage in nondiabetic CRF patients. Fifty nondiabetic CRF patients were enrolled in the present study and divided into 2 groups: one was the AST-120-treated group (15 men and 10 women) and the other was the age-, sex-, and clinical variables-matched non-AST-120-treated control group. Patients were followed up for 12 months. We investigated the effects of AST-120 on serum levels of interleukin-6 (IL-6), proteinuria, and urinary excretion levels of 8-hydroxydeoxyguanosine (8-OHdG) and L-fatty acid binding protein (L-FABP), markers of oxidative stress and tubular injury, respectively. AST-120 treatment (6 g/d), but not control treatment, for 12 months significantly reduced IL-6, proteinuria, and urinary excretion levels of L-FABP and 8-OHdG, and inhibited the increase in serum creatinine in CRF patients. In univariate analyses, L-FABP levels were correlated with age, proteinuria, 8-OHdG, and IL-6. In multiple stepwise regression analysis, proteinuria and urinary 8-OHdG levels were independently related to L-FABP levels (R² = 0.605). Our present study demonstrated for the first time that AST-120 improved tubular injury in nondiabetic CRF patients. AST-120 may exert beneficial effects in CRF patients by protecting tubular damage partly via reduction of proteinuria and oxidative stress generation.

Role of oxidative stress and indoxyl sulfate in progression of cardiovascular disease in chronic kidney disease

Several abnormalities of the cardiovascular system are observed in most cases of chronic kidney disease (CKD). Mechanisms underlying these abnormalities are complicated, and several factors contribute to their pathogenesis. Of these factors, oxidative stress and uremic toxins are considered to play key roles in the progression of cardiovascular disease (CVD) in CKD. Oxidative stress increases significantly in CKD and accelerates proteinuria and renal dysfunction. In addition, oxidative stress has been reported to induce cardiac hypertrophy and fibrosis. Indoxyl sulfate, a uremic toxin, has recently been suggested to play a crucial role in the development of CVD. Recent in vitro data suggest that indoxyl sulfate increases oxidative stress. Some reports have shown that AST-120, which is an oral charcoal adsorbent, can reduce oxidative stress by lowering serum indoxyl sulfate levels. Recently, we have also demonstrated that indoxyl sulfate is associated with the production of oxidative stress, and that increased oxidative stress is significantly correlated with cardiac hypertrophy and fibrosis. Furthermore, results of our basic and clinical studies suggested that AST-120 can prevent progression of cardiac hypertrophy by reducing oxidative stress in CKD. Thus, one of the main targets of the management of CKD and CVD is the control of oxidative stress and uremic toxins, such as indoxyl sulfate.

Oral activated charcoal adsorbent (AST-120) ameliorates extent and instability of atherosclerosis accelerated by kidney disease in apolipoprotein E-deficient mice

BACKGROUND

Accelerated atherosclerosis and increased cardiovascular events are not only more common in chronic kidney disease (CKD) but are more resistant to therapeutic interventions effective in the general population. The oral charcoal adsorbent, AST-120, currently used to delay start of dialysis, reduces circulating and tissue uremic toxins, which may contribute to vasculopathy, including atherosclerosis. We, therefore, investigated whether AST-120 affects CKD-induced atherosclerosis.

METHODS

Apolipoprotein E-deficient mice, a model of atherosclerosis, underwent uninephrectomy, subtotal nephrectomy or sham operation at 8 weeks of age and were treated with AST-120 after renal ablation. Atherosclerosis and its characteristics were assessed at 25 weeks of age.

RESULTS

Uninephrectomy and subtotal nephrectomised mice had significantly increased acceleration of atherosclerosis. AST-120 treatment dramatically reduced the atherosclerotic burden in mice with kidney damage, while there was no beneficial effect in sham-operated mice. The benefit was independent of blood pressure, serum total cholesterol or creatinine clearance. AST-120 significantly decreased necrotic areas and lessened aortic deposition of the uremic toxin indoxyl sulfate without affecting lesional macrophage or collagen content. Furthermore, AST-120 lessened aortic expression of monocyte chemoattractant protein-1, tumor necrosis factor-α and interleukin-1β messenger RNA.

CONCLUSIONS

AST-120 lessens the extent of atherosclerosis induced by kidney injury and alters lesion characteristics in apolipoprotein E-deficient mice, resulting in plaques with a more stable phenotype with less necrosis and reduced inflammation.

Senescence and dysfunction of proximal tubular cells are associated with activated p53 expression by indoxyl sulfate

Various uremic toxins accumulate in patients with chronic renal failure (CRF) and one of them is indoxyl sulfate, which accelerates the progression of CRF through unknown mechanisms. The present study investigates how indoxyl sulfate promotes CRF using the proximal tubular cell line HK-2 and CRF rats. Indoxyl sulfate inhibited serum-induced cell proliferation and promoted the activation of senescence-associated β-galactosidase, a marker of cellular senescence, and the expression of α-smooth muscle actin (α-SMA), a marker of fibrosis, through inducing p53 expression and phosphorylation. Pifithrin-α, p-nitro, a p53 inhibitor, blocked these effects. Indoxyl sulfate evoked reactive oxygen species (ROS), and the antioxidant N-acetylcysteine inhibited indoxyl sulfate-induced p53 expression and phosphorylation, as well as indoxyl sulfate-induced α-SMA expression. We previously demonstrated that although cellular senescence and fibrosis are detectable in the kidneys of CRF rats, the oral adsorbent AST-120 repressed these effects. Here, we found that β-galactosidase, p53 and α-SMA were expressed and colocalized in the renal tubules of CRF rats, whereas AST-120 decreased the expression of these genes. Taken together, these findings indicate that indoxyl sulfate induces the expression and phosphorylation of p53 though ROS production, thus inhibiting cell proliferation and promoting cellular senescence and renal fibrosis.

Effects of an oral adsorbent on oxidative stress and fibronectin expression in experimental diabetic nephropathy

BACKGROUND

Previous studies have demonstrated that AST-120 (Kremezin((R))), a well-known oral adsorbent, inhibits the progression of diabetic (DM) and non-DM chronic kidney disease along with a decrease in oxidative stress. This study was undertaken to investigate whether AST-120 could reduce oxidative stress and ameliorate the development of nephropathy in experimental DM rats with normal renal function.

METHODS

Rats were injected with diluent (C, n = 16) or 65 mg/kg streptozotocin intraperitoneally (DM, n = 16), and eight rats from each group were treated with chow containing 5% AST-120. After 3 months, plasma advanced oxidation protein products (AOPP) and total malondialdehyde (MDA) levels, 24-h urinary albumin excretion, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) excretion were determined by ELISA. Glomerular endothelial nitric oxide synthase (eNOS), subunits of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (gp91phox, p47phox and p22phox), and fibronectin (FN) mRNA and protein expressions were determined by real-time PCR and western blot, respectively. In addition, dichlorodihydrofluorescein diacetate (DCF-DA) staining was performed to detect glomerular reactive oxygen species (ROS) production.

RESULTS

Compared to the C group, 24-h urinary albumin excretion was significantly higher in the DM group (P < 0.01), and AST-120 treatment significantly reduced albuminuria in DM rats (P < 0.05). Glomerular eNOS, gp91phox, p47phox and FN expression were significantly increased in DM rats compared to C rats, and these increases in DM glomeruli were significantly abrogated by AST-120 treatment (P < 0.05). The increases in plasma AOPP and MDA levels as well as renal oxidative stress in DM rats, assessed by DCF-DA staining and urinary 8-OHdG excretion rates, were also significantly attenuated by AST-120 treatment (P < 0.05).

CONCLUSION

In conclusion, the renoprotective effects of AST-120 in DM nephropathy seem to be associated with the amelioration of enhanced oxidative stress and FN expression under diabetic conditions.

Effect of a carbonaceous oral adsorbent on the progression of CKD: a multicenter, randomized, controlled trial

BACKGROUND

The carbonaceous oral adsorbent AST-120 slows the deterioration of kidney function in patients with advanced chronic kidney disease (CKD). However, information about AST-120 in patients with less severe stages of CKD is lacking.

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

75 medical facilities, 460 patients with CKD with serum creatinine (sCr) concentrations less than 5.0 mg/dL (not undergoing dialysis).

INTERVENTION

Random assignment to either a low-protein diet and antihypertensive medication in the control group or that treatment combined with AST-120 (6 g/d).

OUTCOMES & MEASUREMENTS

Composite primary end point: doubling of sCr level, increase in sCr level to 6.0 mg/dL or more, need for dialysis or transplantation, or death.

SECONDARY OUTCOMES

adverse events and changes in estimated creatinine clearance (CCr) rate, proteinuria (protein in milligrams per day), and quality of life.

RESULTS

Mean sCr level was 2.66 mg/dL and estimated CCr was 22.4 mL/min in both groups. During 56 weeks, numbers of primary end-point events (43 for control versus 42 for AST-120) and event-free survival (P = 0.9) did not differ between groups. Gastrointestinal adverse events were less common in the control group than the AST-120 group (2 versus 32 events). Estimated CCr decreased more in the control group than in the AST-120 group (-15% per year versus -12% per year, relative to the baseline value; [corrected] P = 0.001). Median proteinuria changed from protein of 1,162 to 1,167 mg/d in the control group versus 1,102 to 906 mg/d in the AST-120 group (P = 0.2).

LIMITATION

Infrequent primary end-point events.

CONCLUSION

AST-120 did not substantially slow the progression of kidney disease in patients with moderate to severe CKD during 1 year.

Oral charcoal adsorbent (AST-120) prevents progression of cardiac damage in chronic kidney disease through suppression of oxidative stress

BACKGROUND

Chronic kidney disease (CKD) is an important risk factor for cardiovascular disease (CVD). Increased oxidative stress plays a role in the pathogenesis of CVD in CKD patients. The oral charcoal adsorbent AST-120 attenuates the progression of CKD possibly by removing uraemic toxins such as indoxyl sulfate (IS), and reduces oxidative stress. We investigated the relationship between oxidative stress and cardiac damage in CKD and its prevention by AST-120.

METHODS

Male Lewis rats were administered adriamycin at 8 weeks of age, and the right kidney was removed at 12 weeks of age. From 14 weeks of age, the rats were treated daily with AST-120 (n = 8) or were untreated (control group, n = 8). At 34 weeks of age, the rats were killed and urinary and blood biochemical tests as well as cardiac histological analyses were performed.

RESULTS

At 14 weeks of age, there were no significant differences in blood pressure, renal function (creatinine clearance: 1.54 +/- 0.28 mL/min versus 1.60 +/- 0.22 mL/min), oxidative stress markers or other biochemical data between the control and AST-120 groups. At 34 weeks, despite similar blood pressure and renal function (creatinine clearance: 0.78 +/- 0.46 mL/min versus 0.75 +/- 0.54 mL/min), serum concentrations of IS and urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG), acrolein and IS were significantly lower in the AST-120 group than in the control group. Heart volume, left ventricular volume and cardiac fibrosis were significantly smaller in the experimental AST-120 group than in the control group. Immunohistological analysis revealed that the numbers of 8-OHdG- and acrolein-positive cardiomyocytes and the degrees of myocardial and perivascular fibrosis were ameliorated by AST-120 administration. The myocardial fibrosis score was significantly associated with the 8-OHdG- (r = 0.848, P < 0.001) and acrolein-positive (r = 0.812, P < 0.001) cell scores. The perivascular fibrosis score was also significantly associated with the 8-OHdG- (r = 0.906, P < 0.0001) and acrolein-positive (r = 0.789, P < 0.001) cell scores.

CONCLUSIONS

Oxidative stress is suggested to play a key role in the development of cardiac hypertrophy and fibrosis in CKD. AST-120 may suppress oxidative stress and reduce cardiac damage in CKD.

Oral adsorbent AST-120 ameliorates endothelial dysfunction independent of renal function in rats with subtotal nephrectomy

It is important to consider a strategy to halt the development of cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Oral adsorbent AST-120 retards deterioration in renal function, reducing indoxyl sulfate (IS) accumulation. The aim of this study was to determine whether AST-120 improves endothelial dysfunction by reducing oxidative/nitrative stress in a rat-CKD model. Subtotally nephrectomized (Nx) rats aged 17 weeks were divided into two groups: control rats and rats orally treated with AST-120. Two weeks after initiation of AST-120, serum and urinary IS levels, renal histological scores and endothelium-dependent vascular responses (EDVRs) in the aorta were investigated. EDVR in 5-h incubation with 250 microg ml(-1) IS was also examined in normal rat aortas. Nitrotyrosine content, mRNA expression of p47phox, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase component, and expression and phosphorylation (serine-1177) of endothelial nitric oxide synthase (eNOS) in the aorta were examined in untreated and treated Nx rats. At the end of treatment, renal function and histological scores were not different in the two groups. AST-120 prevented the elevation of serum IS level in Nx rats, reducing urinary IS excretion, and ameliorated decreased EDVR in Nx rats. Incubation with IS tended to reduce EDVR in normal aortas, albeit insignificantly. AST-120 also suppressed nitrotyrosine accumulation and inhibited p47phox expression in Nx rats. The eNOS expression and phosphorylation were similar in the two groups. In conclusion, AST-120 ameliorated endothelial dysfunction and alleviated oxidative/nitrative stress in the aorta through reduced accumulation of IS, independent of renal function, in a rat CKD model.

Long-term nebivolol administration reduces renal fibrosis and prevents endothelial dysfunction in rats with hypertension induced by renal mass reduction

OBJECTIVES

D/L-Nebivolol is a lypophilic beta1-adrenergic antagonist which is devoid of intrinsic sympathomimetic activity and can increase nitric oxide (NO) bioavailability with its subsequent vasodilating properties. The purpose of the present work was to assess the effect of long-term nebivolol administration on both renal damage and endothelial dysfunction induced by renal mass reduction (RMR) in rats. Atenolol, which does not increase NO bioavailability, was included in the study as a comparative beta-adrenoceptor antagonist.

METHODS

Rats were subjected to both right nephrectomy and surgical removal of two-thirds of the left kidney in order to retain approximately one-sixth of the total renal mass. One week after ablation, rats were distributed randomly according to the following experimental groups: control group containing RMR rats without treatment; RMR rats treated daily with nebivolol for 6 months (drinking water, 8 mg/kg per day); and RMR rats treated daily with atenolol for 6 months (drinking water, 80 mg/kg per day). A group of sham-operated animals was also included.

RESULTS

Administration of either nebivolol or atenolol similarly reduced arterial pressure in comparison with RMR untreated animals; however, animals receiving nebivolol presented lower levels of collagen type I expression as well as lower glomerular and interstitial fibrosis than those receiving atenolol. Urinary excretion of oxidative stress markers were also lower in animals receiving nebivolol than in rats treated with atenolol. Furthermore, nebivolol prevented RMR-induced endothelial dysfunction more efficiently than atenolol.

CONCLUSIONS

Nebivolol protects against renal fibrosis, oxidative stress and endothelial dysfunction better than equivalent doses, in terms of arterial pressure reduction, of atenolol in a hypertensive model of renal damage induced by RMR.

An oral adsorbent, AST-120 protects against the progression of oxidative stress by reducing the accumulation of indoxyl sulfate in the systemic circulation in renal failure

PURPOSE

The effect of AST-120, an oral adsorbent, on oxidative stress in the systemic circulation in chronic renal failure (CRF) was examined and the potential role of indoxyl sulfate (IS), an uremic toxin adsorbed by AST-120, in inducing the formation of reactive oxygen species (ROS) in the vascular system was studied, in vitro and in vivo.

MATERIALS AND METHODS

The level of oxidized albumin, a marker for oxidative stress in the systemic circulation was determined by HPLC, as previously reported. The mRNA levels of TGF-beta (1) and Oat1 were measured by quantitative RT-PCR. The IS induced ROS generation in cultured human umbilical vein endothelial cells (HUVECs) was estimated using a fluorescence microplate reader.

RESULTS

An increase in the ratio of oxidized to unoxidized albumin was determined using 5/6 nephrectomized rats (CRF rats) compared to a control group. The ratio was significantly reduced in the group that received AST-120 of 4 weeks, suggesting that AST-120 inhibits oxidative stress in CRF. An anti-oxidative effect of AST-120 was also observed in CRF rats with a similar renal function. The ratio of oxidized albumin was correlated with serum IS levels in vivo. The same relationship was also observed in CRF rats with the continued administration of IS. In addition, IS dramatically increased the generation of ROS in both a dose- and time- dependent manner in HUVEC, suggesting that accumulated IS may play an important role in enhancing intravascular oxidative stress.

CONCLUSION

We propose that AST-120 reduces IS concentrations in the blood that induces ROS production in endothelial cells, thereby inhibiting the subsequent occurrence of oxidative stress in the systemic circulation in renal failure.