Uremia accelerates both atherosclerosis and arterial calcification in apolipoprotein E knockout mice

Peritoneal Dialysis Aggravates and Accelerates Atherosclerosis in Uremic ApoE-/- Mice

BACKGROUND

Atherosclerosis is highly prevalent in people with chronic kidney disease (CKD), including those receiving peritoneal dialysis (PD). Although it is lifesaving, PD induces profound systemic inflammation, which may aggravate atherosclerosis. Therefore, the hypothesis is that this PD-induced inflammation aggravates atherosclerosis via immune cell activation.

METHODS AND RESULTS

ApoE-/- mice were subjected to a 5/6 nephrectomy to induce CKD. Three weeks later, mice were fed a high-cholesterol diet. Half of the nephrectomized mice then received daily peritoneal infusions of 3.86% Physioneal for 67 further days (CKD+PD) until the end of the experiment, and were compared with mice without CKD. Sham operated and PD-only mice were additional controls. CKD+PD mice displayed more severe atherosclerotic disease than control mice. Plaque area increased, and plaques were more advanced with a vulnerable phenotype typified by decreased collagen content and decreased fibrous cap thickness. Increased CD3+ T-cell numbers were present in plaques and perivascular adipose tissue of CKD and CKD+PD mice. Plaques of CKD+PD mice contained more iNOS+ immune cells. Spleens of CKD+PD mice showed more CD4+ central memory, terminally differentiated type 1 T-helper (Th1), Th17, and CX3C motif chemokine receptor 1+ (CX3CR1) CD4+ T-cells with less regulatory and effector T-cells.

CONCLUSIONS

PD-fluid exposure in uremic mice potentiates systemic and vascular T-cell-driven inflammation and aggravates atherosclerosis. PD polarized CD4+ T-cells toward an inflammatory Th1/Th17 phenotype, and increased CX3CR1+ CD4+ T-cells, which are associated with vascular homing in CKD-associated atherosclerosis. Targeting CD4+ T-cell activation and CX3CR1+ polarization has the potential to attenuate atherosclerosis in PD patients.

Comprehensive Analysis of 1-Year-Old Female Apolipoprotein E-Deficient Mice Reveals Advanced Atherosclerosis with Vulnerable Plaque Characteristics

Apolipoprotein E-knockout (Apoe-/-) mice constitute the most widely employed animal model of atherosclerosis. Deletion of Apoe induces profound hypercholesterolemia and promotes the development of atherosclerosis. However, despite its widespread use, the Apoe-/- mouse model remains incompletely characterized, especially at late time points and advanced disease stages. Thus, it is unclear how late atherosclerotic plaques compare to earlier ones in terms of lipid deposition, calcification, macrophage accumulation, smooth muscle cell presence, or plaque necrosis. Additionally, it is unknown how cardiac function and hemodynamic parameters are affected at late disease stages. Here, we used a comprehensive analysis based on histology, fluorescence microscopy, and Doppler ultrasonography to show that in normal chow diet-fed Apoe-/- mice, atherosclerotic lesions at the level of the aortic valve evolve from a more cellular macrophage-rich phenotype at 26 weeks to an acellular, lipid-rich, and more necrotic phenotype at 52 weeks of age, also marked by enhanced lipid deposition and calcification. Coronary artery atherosclerotic lesions are sparse at 26 weeks but ubiquitous and extensive at 52 weeks; yet, left ventricular function was not significantly affected. These findings demonstrate that atherosclerosis in Apoe-/- mice is a highly dynamic process, with atherosclerotic plaques evolving over time. At late disease stages, histopathological characteristics of increased plaque vulnerability predominate in combination with frequent and extensive coronary artery lesions, which nevertheless may not necessarily result in impaired cardiac function.

Similarities and Differences of Vascular Calcification in Diabetes and Chronic Kidney Disease

Presently, the mechanism of occurrence and development of vascular calcification (VC) is not fully understood; a range of evidence suggests a positive association between diabetes mellitus (DM) and VC. Furthermore, the increasing burden of central vascular disease in patients with chronic kidney disease (CKD) may be due, at least in part, to VC. In this review, we will review recent advances in the mechanisms of VC in the context of CKD and diabetes. The study further unveiled that VC is induced through the stimulation of pro-inflammatory factors, which in turn impairs endothelial function and triggers similar mechanisms in both disease contexts. Notably, hyperglycemia was identified as the distinctive mechanism driving calcification in DM. Conversely, in CKD, calcification is facilitated by mechanisms including mineral metabolism imbalance and the presence of uremic toxins. Additionally, we underscore the significance of investigating vascular alterations and newly identified molecular pathways as potential avenues for therapeutic intervention.

Beyond the Basics: Unraveling the Complexity of Coronary Artery Calcification

Coronary artery calcification (CAC) is mainly associated with coronary atherosclerosis, which is an indicator of coronary artery disease (CAD). CAC refers to the accumulation of calcium phosphate deposits, classified as micro- or macrocalcifications, that lead to the hardening and narrowing of the coronary arteries. CAC is a strong predictor of future cardiovascular events, such as myocardial infarction and sudden death. Our narrative review focuses on the pathophysiology of CAC, exploring its link to plaque vulnerability, genetic factors, and how race and sex can affect the condition. We also examined the connection between the gut microbiome and CAC, and the impact of genetic variants on the cellular processes involved in vascular calcification and atherogenesis. We aimed to thoroughly analyze the existing literature to improve our understanding of CAC and its potential clinical and therapeutic implications.

B- and T-lymphocyte attenuator could be a new player in accelerated atherosclerosis associated with chronic kidney disease

BACKGROUND

In chronic kidney disease (CKD), cardiovascular morbi-mortality is higher than in general population. Atherosclerotic cardiovascular disease is accelerated in CKD, but specific CKD-related risk factors for atherosclerosis are unknown.

METHODS

CKD patients from the NEFRONA study were used. We performed mRNA array from blood of patients free from atheroma plaque at baseline, with (n=10) and without (n=10) de novo atherosclerotic plaque development 2 years later. Selected mRNA candidates were validated in a bigger sample (n=148). Validated candidates were investigated in vivo in an experimental model of CKD-accelerated atherosclerosis, and in vitro in murine macrophages.

RESULTS

mRNA array analysis showed 92 up-regulated and 67 down-regulated mRNAs in samples from CKD patients with de novo plaque development. The functional analysis pointed to a paramount role of the immune response. The validation in a bigger sample confirmed that B- and T-lymphocyte co-inhibitory molecule (BTLA) down-regulation was associated with de novo plaque presence after 2 years. However, BTLA down-regulation was not found to be associated with atherosclerotic progression in patients with plaque already present at baseline. In a model of CKD-accelerated atherosclerosis, mRNA and protein expression levels of BTLA were significantly decreased in blood samples and atheroma plaques. Plaques from animals with CKD were bigger, had more infiltration of inflammatory cells, higher expression of IL6 and IL17 and less presence of collagen than plaques from control animals. Incubation of macrophages with rat uremic serum decreased BTLA expression.

CONCLUSIONS

BTLA could be a potential biomarker or therapeutic target for atherosclerosis incidence in CKD patients.

Gut microbiota-derived metabolite trimethylamine-N-oxide and stroke outcome: a systematic review

Introduction

The relationship between baseline trimethylamine N-oxide (TMAO) levels and stroke outcomes remains unclear. Therefore, this systematic review aimed to summarize the existing relevant research.

Methods

We searched for studies on the association between baseline plasma levels of TMAO and stroke outcomes in the PubMed, EMBASE, Web of Science, and Scopus databases from their inception to 12 October 2022. Two researchers independently reviewed the studies for inclusion and extracted the relevant data.

Results

Seven studies were included in the qualitative analysis. Among them, six studies reported the outcome of acute ischemic stroke (AIS) and one study of intracerebral hemorrhage (ICH), respectively. Furthermore, no study reported the outcome of subarachnoid hemorrhage. Among patients with AIS, high baseline TMAO levels were associated with unfavorable functional outcomes or mortality at 3 months, as well as a high hazard ratio of mortality, recurrence, or major adverse cardiac event. Moreover, TMAO levels showed predictive utility for unfavorable functional outcomes or mortality at 3 months. Among patients with ICH, high TMAO levels were associated with unfavorable functional outcomes at 3 months, regardless of whether the TMAO value was considered a continuous or a categorical variable.

Conclusion

Limited evidence indicates that high baseline plasma levels of TMAO may be associated with poor stroke outcomes. Further studies are warranted to confirm the relationship between TMAO and stroke outcomes.

Paradoxical reduction of plasma lipids and atherosclerosis in mice with adenine-induced chronic kidney disease and hypercholesterolemia

Background

Atherosclerotic cardiovascular disease is prevalent among patients with chronic kidney disease (CKD). In this study, we initially aimed to test whether vascular calcification associated with CKD can worsen atherosclerosis. However, a paradoxical finding emerged from attempting to test this hypothesis in a mouse model of adenine-induced CKD.

Methods

We combined adenine-induced CKD and diet-induced atherosclerosis in mice with a mutation in the low-density lipoprotein receptor gene. In the first study, mice were co-treated with 0.2% adenine in a western diet for 8 weeks to induce CKD and atherosclerosis simultaneously. In the second study, mice were pre-treated with adenine in a regular diet for 8 weeks, followed by a western diet for another 8 weeks.

Results

Co-treatment with adenine and a western diet resulted in a reduction of plasma triglycerides and cholesterol, liver lipid contents, and atherosclerosis in co-treated mice when compared with the western-only group, despite a fully penetrant CKD phenotype developed in response to adenine. In the two-step model, renal tubulointerstitial damage and polyuria persisted after the discontinuation of adenine in the adenine-pre-treated mice. The mice, however, had similar plasma triglycerides, cholesterol, liver lipid contents, and aortic root atherosclerosis after being fed a western diet, irrespective of adenine pre-treatment. Unexpectedly, adenine pre-treated mice consumed twice the calories from the diet as those not pre-treated without showing an increase in body weight.

Conclusion

The adenine-induced CKD model does not recapitulate accelerated atherosclerosis, limiting its use in pre-clinical studies. The results indicate that excessive adenine intake impacts lipid metabolism.

Overview on hydrogen sulfide-mediated suppression of vascular calcification and hemoglobin/heme-mediated vascular damage in atherosclerosis

Vulnerable atherosclerotic plaques with hemorrhage considerably contribute to cardiovascular morbidity and mortality. Calcification is the main characteristic of advanced atherosclerotic lesions and calcified aortic valve disease (CAVD). Lyses of red blood cells and hemoglobin (Hb) release occur in human hemorrhagic complicated lesions. During the interaction of cell-free Hb with plaque constituents, Hb is oxidized to ferric and ferryl states accompanied by oxidative changes of the globin moieties and heme release. Accumulation of both ferryl-Hb and metHb has been observed in atherosclerotic plaques. The oxidation hotspots in the globin chain are the cysteine and tyrosine amino acids associated with the generation of Hb dimers, tetramers and polymers. Moreover, fragmentation of Hb occurs leading to the formation of globin-derived peptides. A series of these pro-atherogenic cellular responses can be suppressed by hydrogen sulfide (H2S). Since H2S has been explored to exhibit a wide range of physiologic functions to maintain vascular homeostasis, it is not surprising that H2S may play beneficial effects in the progression of atherosclerosis. In the present review, we summarize the findings about the effects of H2S on atherosclerosis and CAVD with a special emphasis on the oxidation of Hb/heme in atherosclerotic plaque development and vascular calcification.

Quantitative Data-Independent Acquisition Mass Spectrometry Proteomics and Weighted Correlation Network Analysis of Plasma Samples for the Discovery of Chronic Kidney Disease-Specific Atherosclerosis Risk Factors

Chronic kidney disease (CKD) accelerates atherosclerosis. The mechanism of CKD-related atherosclerosis is complex, and CKD-specific risk factors may contribute to this process in addition to traditional risk factors such as hypertension, diabetes, and hypercholesterolemia. In the present study, to discover CKD-specific atherosclerosis risk factors, a total of 62 patients with different stages of kidney function were enrolled. All patients underwent coronary angiographies and the severity of coronary atherosclerosis was defined by the SYNTAX score. Patients were divided into different groups according to their kidney function levels and coronary atherosclerosis severity. Data-independent acquisition mass spectrometry was used to identify differentially expressed proteins (DEPs) in the plasma samples, and weighted correlation network analysis (WGCNA) was employed to identify significant protein modules and hub proteins related to CKD-specific atherosclerosis. The results showed that 10 DEPs associated with atherosclerosis were found in the comparative groups with modest and severe CKD. Through WGCNA, 1768 proteins were identified and 8 protein modules were established. Enrichment analyses of protein modules revealed functional clusters mainly associated with inflammation and the complement and coagulation cascade as atherosclerosis developed under CKD conditions. The results may help to better understand the mechanisms of CKD-related atherosclerosis and guide future research on developing treatments for CKD-related atherosclerosis.

Uremic Toxins and Cardiovascular Risk in Chronic Kidney Disease: What Have We Learned Recently beyond the Past Findings?

Patients with chronic kidney disease (CKD) have an elevated prevalence of atheromatous (ATH) and/or non-atheromatous (non-ATH) cardiovascular disease (CVD) due to an array of CKD-related risk factors, such as uremic toxins (UTs). Indeed, UTs have a major role in the emergence of a spectrum of CVDs, which constitute the leading cause of death in patients with end-stage renal disease. The European Uremic Toxin Work Group has identified over 100 UTs, more than 25 of which are dietary or gut-derived. Even though relationships between UTs and CVDs have been described in the literature, there are few reviews on the involvement of the most toxic compounds and the corresponding physiopathologic mechanisms. Here, we review the scientific literature on the dietary and gut-derived UTs with the greatest toxicity in vitro and in vivo. A better understanding of these toxins' roles in the elevated prevalence of CVDs among CKD patients might facilitate the development of targeted treatments. Hence, we review (i) ATH and non-ATH CVDs and the respective levels of risk in patients with CKD and (ii) the mechanisms that underlie the influence of dietary and gut-derived UTs on CVDs.

Galectin-3: A Novel Marker for the Prediction of Stroke Incidence and Clinical Prognosis

Stroke, whether ischemic or haemorrhagic, is one of the main causes of mortality and disability all over the world, which entails huge burdens in both healthcare environments as well as social and economic aspects of life. Therefore, there is a continuous search for novel reliable biomarkers that can enhance the recognition of stroke events in a timely manner and predict the clinical outcomes following a stroke event. Galectins are a group of proteins expressed by many types of cells and tissues including vasculature, certain immune cells, fibroblasts, and gastrointestinal epithelial cells. These proteins vary in their structure and configuration according to their type and have a diversity of functions according to the type of tissue they are expressed in. Among these proteins, a few studies investigated mainly the roles played by galectin-1 (Gal-1) and galectin-3 (Gal-3) in the molecular mechanisms of atherosclerosis and in brain tissue remodeling after a stroke event. In this review, we present an updated overview of the current understanding of Gal-3's functions and implications in stroke occurrence and the response of the brain tissue to stroke events, which may be a key to its utility as a predictor of stroke incidence and clinical prognosis in the future.

Dextromethorphan Reduces Oxidative Stress and Inhibits Uremic Artery Calcification

Medial vascular calcification has emerged as a key factor contributing to cardiovascular mortality in patients with chronic kidney disease (CKD). Vascular smooth muscle cells (VSMCs) with osteogenic transdifferentiation play a role in vascular calcification. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors reduce reactive oxygen species (ROS) production and calcified-medium-induced calcification of VSMCs. This study investigates the effects of dextromethorphan (DXM), an NADPH oxidase inhibitor, on vascular calcification. We used in vitro and in vivo studies to evaluate the effect of DXM on artery changes in the presence of hyperphosphatemia. The anti-vascular calcification effect of DXM was tested in adenine-fed Wistar rats. High-phosphate medium induced ROS production and calcification of VSMCs. DXM significantly attenuated the increase in ROS production, the decrease in ATP, and mitochondria membrane potential during the calcified-medium-induced VSMC calcification process (p < 0.05). The protective effect of DXM in calcified-medium-induced VSMC calcification was not further increased by NADPH oxidase inhibitors, indicating that NADPH oxidase mediates the effect of DXM. Furthermore, DXM decreased aortic calcification in Wistar rats with CKD. Our results suggest that treatment with DXM can attenuate vascular oxidative stress and ameliorate vascular calcification.

A critical re-analysis of cases of post-transplantation recurrence in genetic nephrotic syndrome

BACKGROUND

Genetic defects in podocyte proteins account for up to 30% of steroid-resistant nephrotic syndrome (SRNS) in the paediatric population. Most children with genetic SRNS are resistant to immunosuppression and at high risk of progression to stage 5 chronic kidney disease. Kidney transplantation is often the treatment of choice. The possibility of post-transplantation disease recurrence in genetic SRNS remains controversial, and poses fundamental questions about disease biology.

METHODS

We critically evaluated the published cases of post-transplantation recurrence in genetic patients, particularly testing 'mutations' against the most recent population variant databases, in order to clarify the diagnoses, and compare the clinical courses and responses to therapy.

RESULTS

Biallelic pathogenic variants in NPHS1 leading to a complete absence of nephrin were the most commonly reported and best understood instance of nephrotic syndrome occurring post-transplantation. This is an immune-mediated process driven by antibody production against the novel nephrin protein in the allograft. We also identified a number of plausible reported cases of post-transplantation recurrence involving pathogenic variants in NPHS2 (8 patients, biallelic), one in WT1 (monoallelic) and one in NUP93 (biallelic). However, the mechanism for recurrence in these cases remains unclear. Other instances of recurrence in genetic disease were difficult to interpret due to differing clinical criteria, inclusion of patients without true pathogenic variants or the influence of other factors on renal outcome.

CONCLUSIONS

Overall, post-transplantation recurrence remains very rare in patients with genetic SRNS. It appears to occur later after transplantation than in other patients and usually responds well to plasmapheresis with a good renal outcome.

Metformin prevents stroke damage in non-diabetic female mice with chronic kidney disease

Chronic kidney disease (CKD) worsens ischemic stroke severity in both patients and animals. In mice, these poorer functional outcomes are associated with decreased brain activity of AMP-activated protein kinase (AMPK), a molecule that recently emerged as a potential therapeutic target for ischemic stroke. The antidiabetic drug metformin, a well-known activator of AMPK, has improved stroke outcomes in diabetic patients with normal renal function. We investigated whether chronic metformin pre-conditioning can rescue AMPK activity and prevent stroke damage in non-diabetic mice with CKD. Eight-week-old female C57BL/6J mice were assigned to CKD or SHAM groups. CKD was induced through right kidney cortical electrocautery, followed by left total nephrectomy. Mice were then allocated to receive metformin (200 mg/kg/day) or vehicle for 5 weeks until stroke induction by transient middle cerebral artery occlusion (tMCAO). The infarct volumes were lower in CKD mice exposed to metformin than in vehicle-treated CKD mice 24 h after tMCAO. Metformin pre-conditioning of CKD mice improved their neurological score, grip strength, and prehensile abilities. It also enhanced AMPK activation, reduced apoptosis, increased neuron survival and decreased microglia/macrophage M1 signature gene expression as well as CKD-induced activation of the canonical NF-κB pathway in the ischemic lesions of CKD mice.

Combined application of rapamycin and atorvastatin improves lipid metabolism in apolipoprotein E-deficient mice with chronic kidney disease

Atherosclerosis arising from the pro-inflammatory conditions associated with chronic kidney disease (CKD) increases major cardiovascular morbidity and mortality. Rapamycin (RAPA) is known to inhibit atherosclerosis under CKD and non-CKD conditions, but it can cause dyslipidemia; thus, the co-application of lipid-lowering agents is recommended. Atorvastatin (ATV) has been widely used to reduce serum lipids levels, but its synergistic effect with RAPA in CKD remains unclear. Here, we analyzed the effect of their combined treatment on atherosclerosis stimulated by CKD in apolipoprotein E-deficient (ApoE^−/−) mice. Oil Red O staining revealed that treatment with RAPA and RAPA＋ ATV, but not ATV alone, significantly decreased the atherosclerotic lesions in the aorta and aortic sinus, compared to those seen in the control (CKD) group. The co-administration of RAPA and ATV improved the serum lipid profile and raised the expression levels of proteins involved in reverse cholesterol transport (LXRα, CYP7A1, ABCG1, PPARγ, ApoA1) in the liver. The CKD group showed increased levels of various genes encoding atherosclerosis-promoting cytokines in the spleen (Tnf-α, Il-6 and Il-1β) and aorta (Tnf-α and Il-4), and these increases were attenuated by RAPA treatment. ATV and RAPA＋ATV decreased the levels of Tnf-α and Il-1β in the spleen, but not in the aorta. Together, these results indicate that, in CKD-induced ApoE^−/− mice, RAPA significantly reduces the development of atherosclerosis by regulating the expression of inflammatory cytokines and the co-application of ATV improves lipid metabolism.

Inhibition of microbiota-dependent TMAO production attenuates chronic kidney disease in mice

Patients with chronic kidney disease (CKD) have elevated circulating levels of trimethylamine N-oxide (TMAO), a metabolite derived from gut microbes and associated with cardiovascular diseases. High circulating levels of TMAO and its dietary precursor, choline, predict increased risk for development of CKD in apparently healthy subjects, and studies in mice fed TMAO or choline suggest that TMAO can contribute to kidney impairment and renal fibrosis. Here we examined the interactions between TMAO, kidney disease, and cardiovascular disease in mouse models. We observed that while female hyperlipidemic apoE KO mice fed a 0.2% adenine diet for 14 weeks developed CKD with elevated plasma levels of TMAO, provision of a non-lethal inhibitor of gut microbial trimethylamine (TMA) production, iodomethylcholine (IMC), significantly reduced multiple markers of renal injury (plasma creatinine, cystatin C, FGF23, and TMAO), reduced histopathologic evidence of fibrosis, and markedly attenuated development of microalbuminuria. In addition, while the adenine-induced CKD model significantly increased heart weight, a surrogate marker for myocardial hypertrophy, this was largely prevented by IMC supplementation. Surprisingly, adenine feeding did not increase atherosclerosis and significantly decreased the expression of inflammatory genes in the aorta compared to the control groups, effects unrelated to TMAO levels. Our data demonstrate that inhibition of TMAO production attenuated CKD development and cardiac hypertrophy in mice, suggesting that TMAO reduction may be a novel strategy in treating CKD and its cardiovascular disease complications.

Chronic Kidney Disease-Associated Inflammation Increases the Risks of Acute Kidney Injury and Mortality after Cardiac Surgery

Cardiovascular mortality increases with decreasing renal function although the cause is yet unknown. Here, we have investigated whether low chronic inflammation in chronic kidney diseases (CKD) could contribute to increased risk for coronary artery diseases (CAD). Thus, a prospective case–control study was conducted in patients with CAD and CKD undergoing coronary artery bypass graft surgery with the aim of detecting differences in cardiovascular outcomes, epicardial adipose tissue volume, and inflammatory marker activity associated with renal dysfunction. Expression of membrane CD14 and CD16, inflammatory cytokines and chemokines, mitogen-activated protein (MAP) kinases and hsa-miR-30a-5p were analyzed in peripheral blood mononuclear cells (PBMCs). Epicardial fat volume and tissue inflammation in perivascular adipose tissue and in the aorta were also studied. In the present study, 151 patients were included, 110 with CAD (51 with CKD) and 41 nonCAD controls (15 with CKD). CKD increased the risk of cardiac surgery–associated acute kidney injury (CSA-AKI) as well as the 30-day mortality after cardiac surgery. Higher counts of CD14⁺⁺CD16⁺ monocytes were associated with vascular inflammation, with an increased expression of IL1β, and with CKD in CAD patients. Expression of hsa-miR-30a-5p was correlated with hypertension. We conclude that CKD patients show an increased risk of CSA-AKI and mortality after cardiovascular surgery, associated with the expansion of the CD14⁺⁺CD16⁺ subset of proinflammatory monocytes and with IL1β expression. We propose that inflammation associated with CKD may contribute to atherosclerosis (ATH) pathogenesis.

CSE/H2S system alleviates uremic accelerated atherosclerosis by regulating TGF-β/Smad3 pathway in 5/6 nephrectomy ApoE-/- mice

Background

Hydrogen sulfide (H₂S) has been shown to inhibit the atherosclerosis development and progression. It is produced by cystathionine γ-lyase (CSE) in the cardiovascular system. In our previous study, it has been shown that CSE/H₂S system plays a significant role in the changes of uremic accelerated atherosclerosis (UAAS), but the mechanism is not known clearly.

Methods

In this study, we explored the antagonism of CSE/H₂S system in UAAS and identified its possible signaling molecules in ApoE^−/− mice with 5/6 nephrectomy and fed with atherogenic diet. Mice were divided into sham operation group (sham group), UAAS group, sodium hydrosulfide group (UAAS+NaHS group) and propargylglycine group (UAAS+PPG group). Serum creatinine, urea nitrogen, lipid levels and lesion size of atherosclerotic plaque in the aortic roots were analyzed. Meanwhile, the expression of CSE, TGF-β and phosphorylation of Smad3 were detected.

Results

Compared with sham group, the aortic root of ApoE^−/− mice in the UAAS group developed early atherosclerosis, the levels of total cholesterol, triglyceride, low-density lipoprotein-cholesterol, serum creatinine and urea nitrogen were also higher than that in the sham group. NaHS administration can inhibit the development of atherosclerosis, but PPG administration can accelerate the atherosclerosis development. Meanwhile, the protein expression levels of CSE and TGF-β and phosphorylation of Smad3 significantly decreased in the UAAS mice. Treatment of UAAS mice with NaHS inhibited TGF-β protein expression and Smad3 phosphorylation decrease, but PPG treatment had the opposite effect.

Conclusions

The CSE/H₂S system is of great importance for treating atherosclerosis in patients with chronic kidney disease, and it may protect the vascular from atherosclerosis through the TGF-β/Smad pathway.

Risk Factors for Cardiovascular Disease in Patients Undergoing Peritoneal Dialysis

Patients on peritoneal dialysis (PD) are at high cardiovascular risk. Although some risk factors are unmodifiable (for example, age, sex, genetics), others are exacerbated in the unfriendly uremic milieu (inflammation, oxidative stress, mineral disturbances) or contribute per se to kidney disease and cardiovascular progression (diabetes mellitus, hypertension). Moreover, several factors associated with PD therapy may both increase (by altered lipid profile, hyperinsulinemia, and formation of advanced glycation end-products) and decrease (by better blood pressure control and anemia management) cardiovascular risk. The present review discusses recent findings and therapy trends in cardiovascular research on the PD population, with emphasis on the roles of inflammation, insulin resistance, homocysteinemia, dyslipidemia, vascular calcification, and genetics/epigenetics.

X-ray Micro-Computed Tomography: An Emerging Technology to Analyze Vascular Calcification in Animal Models

Vascular calcification describes the formation of mineralized tissue within the blood vessel wall, and it is highly associated with increased cardiovascular morbidity and mortality in patients with chronic kidney disease, diabetes, and atherosclerosis. In this article, we briefly review different rodent models used to study vascular calcification in vivo, and critically assess the strengths and weaknesses of the current techniques used to analyze and quantify calcification in these models, namely 2-D histology and the o-cresolphthalein assay. In light of this, we examine X-ray micro-computed tomography (µCT) as an emerging complementary tool for the analysis of vascular calcification in animal models. We demonstrate that this non-destructive technique allows us to simultaneously quantify and localize calcification in an intact vessel in 3-D, and we consider recent advances in µCT sample preparation techniques. This review also discusses the potential to combine 3-D µCT analyses with subsequent 2-D histological, immunohistochemical, and proteomic approaches in correlative microscopy workflows to obtain rich, multifaceted information on calcification volume, calcification load, and signaling mechanisms from within the same arterial segment. In conclusion we briefly discuss the potential use of µCT to visualize and measure vascular calcification in vivo in real-time.

Receptor for advanced glycation end products: a key molecule in the genesis of chronic kidney disease vascular calcification and a potential modulator of sodium phosphate co-transporter PIT-1 expression

BACKGROUND

Chronic kidney disease (CKD) is associated with increased cardiovascular mortality, frequent vascular calcification (VC) and accumulation of uraemic toxins. Advanced glycation end products and S100 proteins interact with the receptor for advanced glycation end products (RAGE). In the present work, we aimed to investigate the role(s) of RAGE in the CKD-VC process.

METHODS

Apoe-/- or Apoe-/-Ager (RAGE)-/- male mice were assigned to CKD or sham-operated groups. A high-phosphate diet was given to a subgroup of Apoe-/-and Apoe-/-Ager-/- CKD mice. Primary cultures of Ager+/+ and Ager-/- vascular smooth muscle cells (VSMCs) were established and stimulated with either vehicle, inorganic phosphate (Pi) or RAGE ligands (S100A12; 20 µM).

RESULTS

After 12 weeks of CKD we observed a significant increase in RAGE ligand (AGE and S100 proteins) concentrations in the serum of CKD Apoe-/- mice. Ager messenger RNA (mRNA) levels were 4-fold higher in CKD vessels of Apoe-/- mice. CKD Apoe-/- but not CKD Apoe-/- or Ager-/- mice displayed a marked increase in the VC surface area. Similar trends were found in the high-phosphate diet condition. mRNA levels of Runx2 significantly increased in the Apoe-/- CKD group. In vitro, stimulation of Ager+/+VSMCs with Pi or S100A12 induced mineralization and osteoblast transformation, and this was inhibited by phosphonoformic acid (Pi co-transporters inhibitor) and Ager deletion. In vivo and in vitro RAGE was necessary for regulation of the expression of Pit-1, at least in part through production of reactive oxygen species.

CONCLUSION

RAGE, through the modulation of Pit-1 expression, is a key molecule in the genesis of VC.

Reformulating Small Molecules for Cardiovascular Disease Immune Intervention: Low-Dose Combined Vitamin D/Dexamethasone Promotes IL-10 Production and Atheroprotection in Dyslipidemic Mice

The targeting of proinflammatory pathways has a prophylactic and therapeutic potential on atherosclerotic cardiovascular diseases (CVD). An alternative/complementary strategy is the promotion of endogenous atheroprotective mechanisms that are impaired during atherosclerosis progression, such as the activity of tolerogenic dendritic cells (tolDC) and regulatory T cells (Treg). There is a need to develop novel low cost, safe and effective tolDC/Treg-inducing formulations that are atheroprotective and that can be of easy translation into clinical settings. We found that apolipoprotein E-deficient (ApoE^–/–) mice treated with a low-dose combined formulation of Vitamin D and Dexamethasone (VitD/Dexa), delivered repetitively and subcutaneously (sc) promoted interleukin-10 (IL-10) production by dendritic cells and other antigen presenting cells in the lymph nodes draining the site of injection and the spleens. Expectedly, the treatment also increased the numbers of IL-10-producing CD4⁺ T cells. Concomitantly, the frequency of IFNγ-producing CD4⁺ and CD8⁺ T cells in the spleen, and the IFNγ response of splenocytes to polyclonal stimulation ex vivo were lower after VitD/Dexa treatment, indicating a reduced proatherogenic Th1 response. Interestingly, VitD/Dexa-treated mice had smaller atherosclerotic lesions, with reduced lipid content and lower inflammatory infiltrate of macrophages and T cells in the aortic root. No hypolipidemic or antioxidant effect could be detected, suggesting that a dominantly immunomodulatory mechanism of atheroprotection was engaged under the low-dose sc VitD/Dexa conditions used. Finally, no evidence of clinical, biochemical or immune toxicity was observed in treated ApoE^–/– mice and, most importantly, C57BL/6 mice latently infected with Leishmania parasites and treated with an identical VitD/Dexa dose/scheme showed no clinical or microbiological signs of disease reactivation, suggesting the absence of general immunosuppression. Altogether, these results indicate that a non-toxic, non-immunosuppressive, low-dose of VitD/Dexa, administered subcutaneously and repetitively, exerts atheroprotective effects in dyslipidemic mice, apparently due to the induction of an IL-10-producing network of lymphoid and myeloid immune cells. These well known, widely available, and inexpensive small molecules can be easily co-formulated into a simple and accessible agent with a potential use as a prophylactic or therapeutic immune intervention for CVD and other chronic inflammatory diseases.

Advanced oxidation protein products upregulate efflux transporter expression and activity through activation of the Nrf-2-mediated signaling pathway in vitro and in vivo

Clinical and benchtop studies suggest that chronic kidney disease (CKD) alters both renal and nonrenal clearance of drugs. Although studies have documented that the accumulating uremic toxins in the body under CKD conditions are humoral factors that alter the expression and/or activity of drug transporters, the specific process is poorly understood. In this study, we found that advanced oxidation protein products (AOPPs), which are a modified protein uremic toxin, could upregulate efflux transporters, including P-glycoprotein (ABCB1), multi-drug resistance-associated protein 2 (ABCC2) and breast cancer resistance protein (ABCG2) expression in CKD rat models and in HepG2 cells. Our research shows that renal function decline was associated with the accumulation of AOPPs in serum and the upregulation of efflux transporters in the liver in two rat models of CKD. In HepG2 cells, AOPPs significantly increased the expression of efflux transporters in a dose- and time-dependent manner and upregulated the mRNA expression, protein expression and activity of efflux transporters, but bovine serum albumin (BSA), a synthetic precursor of AOPPs, had no effect. This effect correlated with AOPPs activation of the nuclear factor E2-related factor 2 (Nrf-2)-mediated signaling pathway. Further investigation of the regulation of Nrf-2 by AOPPs revealed that ML385 and siNrf-2 abolished the upregulatory effects of AOPPs. These findings suggest that AOPPs upregulate ABCB1, ABCG2 and ABCC2 through Nrf-2 signaling pathways. Protein uremic toxins, such as AOPPs, may modify the nonrenal clearance of drugs in patients with CKD through effects on drug transporters.

Assessment of Thrombotic and Bleeding Tendency in Two Mouse Models of Chronic Kidney Disease: Adenine-Diet and 5/6th Nephrectomy

The coexistence of bleeding and thrombosis in patients with chronic kidney disease (CKD) is frequent and poorly understood. Mouse models are essential to understand complications of CKD and to develop new therapeutic approaches improving the health of patients. We evaluated the hemostasis in two models of renal insufficiency: adenine-diet and 5/6th nephrectomy (5/6Nx). Compared with 5/6Nx mice, mice fed with 0.25% adenine had more severe renal insufficiency and so higher levels of prothrombotic uremic toxins like indoxyl sulfate. More severe renal inflammation and fibrosis were observed in the adenine group, as demonstrated by histological and reverse transcription quantitative polymerase chain reaction experiments. Liver fibrinogen γ chain expression and level of plasma fibrinogen were increased only in adenine mice. In both CKD mouse models, tissue factor (TF) expression was increased in kidney and aorta extracts. Immunochemistry analysis of kidney sections showed that TF is localized in the vascular walls. Thrombin–antithrombin complexes were significantly increased in plasma from both adenine and 5/6Nx mice. Tail bleeding time increased significantly only in adenine mice, whereas platelet count was not significant altered. Finally, results obtained by intravital microscopy after laser-induced endothelial injury showed impaired platelet function in adenine mice and an increase in fibrin generation in 5/6Nx mice. To summarize, adenine diet causes a more severe renal insufficiency compared with 5/6Nx. The TF upregulation and the hypercoagulable state were observed in both CKD models. Bleeding tendency was observed only in the adenine model of CKD that recapitulates the whole spectrum of hemostasis abnormalities observed in advanced human CKD.

Reconsidering Garth Robinson: fluid flow and the glomerular filtration barrier

PURPOSE OF REVIEW

The goal of this review is to present recent models of the filtration barrier that may suggest mechanism-based treatments for proteinuric renal disease. The vast majority of renal failure occurs in diseases of glomerular proteinuria. The physiology of the filtration barrier remains incompletely understood, preventing invention of mechanism-based therapies. Research is currently dominated by molecular biology approaches to the kidney instead of engineering-based filtration and transport models.

RECENT FINDINGS

Reexamination of two older paradigms (basement membrane and slit diaphragm) and critical analysis of newer models may provide mechanistic insight to guide further research. We expand on our theory of podocyte-basement membrane mechanical interactions and speculate on mechanisms of action of the leading treatment for proteinuria, angiotensin blockade.

SUMMARY

Treatment of proteinuria remains largely empiric and based on inhibition of the renin-angiotensin-aldosterone system, with additional benefit from statins and vitamin D. Improved definition of transport phenomena in the capillary wall may suggest rational design of new interventions.

Macrophage galectin-3 enhances intimal translocation of vascular calcification in diabetes mellitus

The clinical risks and prognosis of diabetic vascular intimal calcification (VIC) and medial calcification (VMC) are different. This study aims to investigate the mechanism of VIC/VMC translocation. Anterior tibial arteries were collected from patients with diabetic foot amputation. The patients were then divided into VIC and VMC groups. There were plaques in all anterior tibial arteries, while the enrichment of galectin-3 in arterial plaques in the VIC group was significantly higher than that in the VMC group. Furthermore, a macrophage/vascular smooth muscle cell (VSMC) coculture system was constructed. VSMC-derived extracellular vesicles (EVs) was labeled with fluorescent probe. After macrophages were pretreated with recombinant galectin-3 protein, the migration of VSMC-derived EVs and VSMC-derived calcification was more pronounced. And anti-galectin-3 antibody can inhibit this process of EVs and calcification translocation. Then, lentivirus (LV)-treated bone marrow cells (BMCs) were transplanted into apolipoprotein E-deficient (ApoE^-/-) mice, and a diabetic atherosclerosis mouse model was constructed. After 15 wk of high-fat diet, ApoE^-/- mice transplanted with LV-shgalectin-3 BMCs exhibited medial calcification and a concentrated distribution of EVs in the media. In conclusion, upregulation of galectin-3 in macrophages promotes the migration of VSMC-derived EVs to the intima and induces diabetic vascular intimal calcification.NEW & NOTEWORTHY The clinical risk and prognosis of vascular intimal and medial calcification are different. Macrophage galectin-3 regulates the migration of vascular smooth muscle cell-derived extracellular vesicles and mediates diabetic vascular intimal/medial calcification translocation. This study may provide insights into the early intervention in diabetic vascular calcification.

Research Models for Studying Vascular Calcification

Calcification of the vessel wall contributes to high cardiovascular morbidity and mortality. Vascular calcification (VC) is a systemic disease with multifaceted contributing and inhibiting factors in an actively regulated process. The exact underlying mechanisms are not fully elucidated and reliable treatment options are lacking. Due to the complex pathophysiology, various research models exist evaluating different aspects of VC. This review aims to give an overview of the cell and animal models used so far to study the molecular processes of VC. Here, in vitro cell culture models of different origins, ex vivo settings using aortic tissue and various in vivo disease-induced animal models are summarized. They reflect different aspects and depict the (patho)physiologic mechanisms within the VC process.

Hydrogen sulfide inhibits calcification of heart valves; implications for calcific aortic valve disease

BACKGROUND AND PURPOSE

Calcification of heart valves is a frequent pathological finding in chronic kidney disease and in elderly patients. Hydrogen sulfide (H2 S) may exert anti-calcific actions. Here we investigated H2 S as an inhibitor of valvular calcification and to identify its targets in the pathogenesis.

EXPERIMENTAL APPROACH

Effects of H2 S on osteoblastic transdifferentiation of valvular interstitial cells (VIC) isolated from samples of human aortic valves were studied using immunohistochemistry and western blots. We also assessed H2S on valvular calcification in apolipoprotein E-deficient (ApoE-/- ) mice.

KEY RESULTS

In human VIC, H2 S from donor compounds (NaSH, Na2 S, GYY4137, AP67, and AP72) inhibited mineralization/osteoblastic transdifferentiation, dose-dependently in response to phosphate. Accumulation of calcium in the extracellular matrix and expression of osteocalcin and alkaline phosphatase was also inhibited. RUNX2 was not translocated to the nucleus and phosphate uptake was decreased. Pyrophosphate generation was increased via up-regulating ENPP2 and ANK1. Lowering endogenous production of H2 S by concomitant silencing of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) favoured VIC calcification. analysis of human specimens revealed higher Expression of CSE in aorta stenosis valves with calcification (AS) was higher than in valves of aortic insufficiency (AI). In contrast, tissue H2 S generation was lower in AS valves compared to AI valves. Valvular calcification in ApoE-/- mice on a high-fat diet was inhibited by H2 S.

CONCLUSIONS AND IMPLICATIONS

The endogenous CSE-CBS/H2 S system exerts anti-calcification effects in heart valves providing a novel therapeutic approach to prevent hardening of valves.

LINKED ARTICLES

This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

Calcification of the cavernosal bodies may be responsible for development of erectile dysfunction in uremic apolipoprotein E deficient (apoE-/-) mice

INTRODUCTION AND OBJECTIVE

Erectile dysfunction's physiopathology in uremia is complex and multifactorial, involving a combination of classical risk factors and specific uremia-related risk factors such as increased oxidative stress, endothelial dysfunction and inflammation. The aim of the study is to investigate the effect of chronic kidney disease (CKD) on vascular calcification and endothelial function of cavernosal bodies in apolipoprotein E deficient (apoE^-/-) mice, a well known model of erectile dysfunction.

MATERIALS AND METHODS

Eight-week-old male apoE^-/- mice were randomly assigned to the following 3 groups: (i) subtotally nephrectomised (SNX apoE^-/-, 12 mice), (ii) uninephrectomised (UNX apoE^-/-, 11 mice) or (iii) sham operated (sham-op apoE^-/-, 15 mice). At 16 weeks after surgery, aortas and penile erectile tissues were harvested for histological studies to assess atherosclerosis, vascular calcification, nitrotyrosine staining, total collagen content and macrophage staining.

RESULTS

At sacrifice, SNX and UNX mice had significantly higher serum urea, total cholesterol, and triglyceride concentrations than sham-op controls. Atherosclerotic lesions in thoracic aorta were significantly larger in uremic apoE^-/- mice than in controls. There were no atheromatous lesions in cavernosal bodies or penile artery observed in any group. However, SNX and UNX animals showed a significant increase in calcification score, collagen content and nitrotyrosine staining in cavernosal bodies when compared with controls. The degree of macrophage infiltration was comparable between the 3 groups.

CONCLUSION

In conclusion, even mild renal dysfunction, i.e., after uninephrectomy increases calcification score and aggravates endothelial function of cavernosal bodies in apoE^-/- mice and this effect might be linked to increased oxidative stress in penile endothelium.

Temporal and tissue-specific activation of aryl hydrocarbon receptor in discrete mouse models of kidney disease

Emerging evidence in animal models of chronic kidney disease (CKD) implicates Aryl Hydrocarbon Receptor (AHR) signaling as a mediator of uremic toxicity. However, details about its tissue-specific and time-dependent activation in response to various renal pathologies remain poorly defined. Here, a comprehensive analysis of AHR induction was conducted in response to discrete models of kidney diseases using a transgenic mouse line expressing the AHR responsive-promoter tethered to a β-galactosidase reporter gene. Following validation using a canonical AHR ligand (a dioxin derivative), the transgenic mice were subjected to adenine-induced and ischemia/reperfusion-induced injury models representing CKD and acute kidney injury (AKI), respectively, in humans. Indoxyl sulfate was artificially increased in mice through the drinking water and by inhibiting its excretion into the urine. Adenine-fed mice showed a distinct and significant increase in β-galactosidase in the proximal and distal renal tubules, cardiac myocytes, hepatocytes, and microvasculature in the cerebral cortex. The pattern of β-galactosidase increase coincided with the changes in serum indoxyl sulfate levels. Machine-learning-based image quantification revealed positive correlations between indoxyl sulfate levels and β-galactosidase expression in various tissues. This pattern of β-galactosidase expression was recapitulated in the indoxyl sulfate-specific model. The ischemia/reperfusion injury model showed increase in β-galactosidase in renal tubules that persisted despite reduction in serum indoxyl sulfate and blood urea nitrogen levels. Thus, our results demonstrate a relationship between AHR activation in various tissues of mice with CKD or AKI and the levels of indoxyl sulfate. This study demonstrates the use of a reporter gene mouse to probe tissue-specific manifestations of uremia in translationally relevant animal models and provide hypothesis-generating insights into the mechanism of uremic toxicity that warrant further investigation.

Molecular mechanisms of hydrogen sulfide against uremic accelerated atherosclerosis through cPKCβII/Akt signal pathway

Background

Cardiovascular disease is the most common complication and leading cause of death in maintenance hemodialysis patients. The protection mechanism of hydrogen sulfide (H₂S) and the specific role of conventional protein kinase C βII (cPKCβII)/Akt signaling pathway in the formation of atherosclerosis is still controversial.

Methods

8-week-old male ApoE^−/− mice were treated with 5/6 nephrectomy and high-fat diet to make uremia accelerated atherosclerosis (UAAS) model. Mice were divided into normal control group (control group), sham operation group (sham group), UAAS group, L-cysteine group (UAAS+L-cys group), sodium hydrosulfide group (UAAS+NaHS group), and propargylglycine group (UAAS+PPG group). Western blot was used to detect cPKCβII activation, Akt phosphorylation and endothelial nitric oxide synthase (eNOS) expression in mice aorta.

Results

The membrane translocation of cPKCβII in UAAS group was higher than sham group, and L-cys or NaHS injection could suppress the membrane translocation, but PPG treatment resulted in more membrane translocation of cPKCβII (P < 0.05, n = 6 per group). Akt phosphorylation and the eNOS expression in UAAS group was lower than sham group, and L-cys or NaHS injection could suppress the degradation of Akt phosphorylation and the eNOS expression, but PPG treatment resulted in more decrease in the Akt phosphorylation and the eNOS expression (P < 0.05, n = 6 per group).

Conclusion

Endogenous cystathionine-γ-lyase (CSE)/H₂S system protected against the formation of UAAS via cPKCβII/Akt signal pathway. The imbalance of CSE/H₂S system may participate in the formation of UAAS by affecting the expression of downstream molecule eNOS, which may be mediated by cPKCβII/Akt signaling pathway.

[Renal transplantation on vascular prosthesis]

INTRODUCTION

In front of a very calcified aortoiliac axis, renal transplantation with implantation of the artery on vascular prosthesis can be proposed. This rare intervention is considered difficult and morbid. The main objective of this work was to evaluate the overall and specific survival of the transplant in this situation. The secondary objective was the study of the complications and the evolution of the transplant's renal function.

MATERIAL AND METHODS

From a multicenter retrospective data collection of the DIVAT cohort (6 centers) added with data from 4 other transplant centers, we studied transplants with prosthetic arterial anastomosis.

RESULTS

Thirty four patients was included. The median duration of follow-up was 2.5 years. 4 patients died in the month following transplantation, 16 were hemodialysis and 9 were transfused. The median survival of the transplant was 212 days. Functional arrests of the transplant were mostly associated with nephrological degradation and return to dialysis (about 80%) while 10% were related to a death of the recipient directly attributable to renal transplantation. The surgical complications of the transplantation were marked by one arterial stenosis, one fistula and 4 urinary stenoses.

CONCLUSION

Thus, renal transplantation with arterial anastomosis on vascular prosthesis, on selected patients, offers an alternative to dialysis. A national compendium of transplanted patients on vascular prosthesis would allow a long-term follow-up of transplant's survival and define selection criteria prior to this kind of surgery.

LEVEL OF EVIDENCE

3.

Molecular imaging of endothelial activation and mineralization in a mouse model of accelerated atherosclerosis

PURPOSE

Preclinical imaging of endothelial activation and mineralization using both positron emission tomography (PET) and magnetic resonance (MR) remains scarce.

PROCEDURES

A group of uremic ApoE-/- (Ur), non-uremic ApoE-/- (NUr), and control C57Bl/6 J mice (Ctl) were investigated. Mineralization process was assessed using sodium fluoride ([18F]NaF) PET, and MR imaging combined with intravenous injection of MPIO-αVCAM-1 was used to evaluate endothelial activation. Micro- and macrocalcifications were evaluated by flame atomic absorption spectroscopy and von Kossa staining, respectively.

RESULTS

Ur mice showed an active and sustained mineralization process compared to Ctl mice (p = 0.002) using [18F]NaF PET imaging. Calcium plasma level was increased in Ur (2.54 ± 0.09 mM, n = 17) compared to NUr and Ctl mice (2.24 ± 0.01, n = 22, and 2.14 ± 0.02, n = 27, respectively; p < 0.0001). Likewise, vascular calcium content was increased in Ur (0.51 ± 0.06 μg Ca2+ per milligram of dry weight aorta, n = 11) compared to NUr (0.27 ± 0.05, n = 9, p = 0.013) and Ctl (0.28 ± 0.05, n = 11, p = 0.014). Ur mice also had a higher inflammatory state using MPIO-αVCAM-1 MR (p global = 0.01, post hoc analysis Ur vs. Ctl p = 0.003) associated with increased VCAM-1 expression (p global = 0.02). Aortic remodeling at the level of the brachiocephalic trunk, brachiocephalic trunk itself, and aortic arch in Ur mice was also demonstrated using MR.

CONCLUSIONS

Preclinical molecular imaging allowed in vivo characterization of the early phase of atherosclerosis. [18F]NaF PET showed early and sustained vascular mineralization in uremic ApoE-/- mice. MPIO-αVCAM-1 MR imaging demonstrated aortic endothelial activation, predominantly in segments with vascular remodeling.

Histopathological and proteomic analyses identify integrin-β1 as a potential mediator of phlebosclerosis in uremic patients

BACKGROUND

Patients with uremia have an excessive mortality from cardiovascular disease (CVD). Arterial remodeling is mainly responsible for uremia-induced CVD and has been well studied, yet venous remodeling is poorly understood. Here we investigate the histopathology and proteomic profiles of venous remodeling in uremic patients.

METHODS

Forearm cephalic veins were isolated from nine uremic patients during surgeries for arteriovenous fistula, and from nine healthy controls when applying surgical debridement. Hematoxylin-eosin, Masson's trichrome, von Kossa, and immunohistochemistry (IHC) against proliferating cell nuclear antigen were stained for histopathology. Isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis was executed to explore the proteome of the veins. The core regulatory protein was validated by western blot, IHC, and immunofluorescence.

RESULTS

Phlebosclerosis, characterized by intimal rarefaction and medial thickening with disordered proliferation of vascular smooth muscle cells (VSMCs), was the prominent pathological manifestation of peripheral veins in uremic patients, while inflammatory cell infiltration, atherosclerosis or calcification were not obviously detected. iTRAQ analysis showed that 350 proteins were significantly changed in phlebosclerosis of uremic patients compared with healthy controls, of which integrin-β1 (ITGβ1) exhibited the strongest regulatory ability by intermolecular interaction network analysis. The enhanced ITGβ1 expression was mainly co-expressed with the disordered proliferation of VSMCs while a little with vascular endothelial cells in the forearm cephalic veins of uremic patients.

CONCLUSIONS

Phlebosclerosis is the prominent pathological manifestation in peripheral veins of uremic patients. This pathological alteration mainly attributes to the disordered proliferation of VSMCs, which is potentially mediated by ITGβ1.

Cellular and molecular mechanisms associated with ischemic stroke severity in female mice with chronic kidney disease

Ischemic stroke is highly prevalent in chronic kidney disease (CKD) patients and has been associated with a higher risk of neurological deterioration and in-hospital mortality. To date, little is known about the processes by which CKD worsens ischemic stroke. This work aimed to investigate the cellular and molecular mechanism associated with ischemic stroke severity in an in vivo model of CKD. CKD was induced through right kidney cortical electrocautery in 8-week-old female C57BL/6 J mice followed by left total nephrectomy. Transient middle cerebral artery occlusion (tMCAO) was performed 6 weeks after left nephrectomy. Twenty-four hours after tMCAO, the infarct volumes were significantly wider in CKD than in SHAM mice. CKD mice displayed decreased neuroscore, impaired ability to remain on rotarod device, weaker muscular strength and decreased prehensile score. Apoptosis, neuronal loss, glial cells recruitment and microglia/macrophages M₁ signature genes CD32, CD86, IL-1β, IL-6, MCP1 and iNOS were significantly increased within ischemic lesions of CKD mice. This effect was associated with decreased AMP kinase phosphorylation and increased activation of the NFΚB pathway. Pharmacological targeting of AMP kinase activity, which is known to block microglia/macrophages M₁ polarization, appears promising to improve stroke recovery in CKD.

Performance Evaluation of a Dedicated Preclinical PET/CT System for the Assessment of Mineralization Process in a Mouse Model of Atherosclerosis

PURPOSE

The purpose of this study was to assess the impact of positron emission tomography/X-ray computed tomography (PET/CT) acquisition and reconstruction parameters on the assessment of mineralization process in a mouse model of atherosclerosis.

PROCEDURES

All experiments were performed on a dedicated preclinical PET/CT system. CT was evaluated using five acquisition configurations using both a tungsten wire phantom for in-plane resolution assessment and a bar pattern phantom for cross-plane resolution. Furthermore, the radiation dose of these acquisition configurations was calculated. The PET system was assessed using longitudinal line sources to determine the optimal reconstruction parameters by measuring central resolution and its coefficient of variation. An in vivo PET study was performed using uremic ApoE^-/-, non-uremic ApoE^-/-, and control mice to evaluate optimal PET reconstruction parameters for the detection of sodium [¹⁸F]fluoride (Na[¹⁸F]F) aortic uptake and for quantitative measurement of Na[¹⁸F]F bone influx (Ki) with a Patlak analysis.

RESULTS

For CT, the use of 1 × 1 and 2 × 2 binning detector mode increased both in-plane and cross-plane resolution. However, resolution improvement (163 to 62 μm for in-plane resolution) was associated with an important radiation dose increase (1.67 to 32.78 Gy). With PET, 3D-ordered subset expectation maximization (3D-OSEM) algorithm increased the central resolution compared to filtered back projection (1.42 ± 0.35 mm vs. 1.91 ± 0.08, p < 0.001). The use of 3D-OSEM with eight iterations and a zoom factor 2 yielded optimal PET resolution for preclinical study (FWHM = 0.98 mm). These PET reconstruction parameters allowed the detection of Na[¹⁸F]F aortic uptake in 3/14 ApoE^-/- mice and demonstrated a decreased Ki in uremic ApoE^-/- compared to non-uremic ApoE^-/- and control mice (p < 0.006).

CONCLUSIONS

Optimizing reconstruction parameters significantly impacted on the assessment of mineralization process in a preclinical model of accelerated atherosclerosis using Na[¹⁸F]F PET. In addition, improving the CT resolution was associated with a dramatic radiation dose increase.

Myeloperoxidase-derived oxidants damage artery wall proteins in an animal model of chronic kidney disease-accelerated atherosclerosis

Increased myeloperoxidase (MPO) levels and activity are associated with increased cardiovascular risk among individuals with chronic kidney disease (CKD). However, a lack of good animal models for examining the presence and catalytic activity of MPO in vascular lesions has impeded mechanistic studies into CKD-associated cardiovascular diseases. Here, we show for the first time that exaggerated atherosclerosis in a pathophysiologically relevant CKD mouse model is associated with increased macrophage-derived MPO activity. Male 7-week-old LDL receptor-deficient mice underwent sham (control mice) or 5/6 nephrectomy and were fed either a low-fat or high-fat, high-cholesterol diet for 24 weeks, and the extents of atherosclerosis and vascular reactivity were assessed. MPO expression and oxidation products-protein-bound oxidized tyrosine moieties 3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine-were examined with immunoassays and confirmed with mass spectrometry (MS). As anticipated, the CKD mice had significantly higher plasma creatinine, urea nitrogen, and intact parathyroid hormone along with lower hematocrit and body weight. On both the diet regimens, CKD mice did not have hypertension but had lower cholesterol and triglyceride levels than the control mice. Despite the lower cholesterol levels, CKD mice had increased aortic plaque areas, fibrosis, and luminal narrowing. They also exhibited increased MPO expression and activity (i.e. increased oxidized tyrosines) that co-localized with infiltrating lesional macrophages and diminished vascular reactivity. In summary, unlike non-CKD mouse models of atherosclerosis, CKD mice exhibit increased MPO expression and catalytic activity in atherosclerotic lesions, which co-localize with lesional macrophages. These results implicate macrophage-derived MPO in CKD-accelerated atherosclerosis.

Indoxyl Sulfate Upregulates Liver P-Glycoprotein Expression and Activity through Aryl Hydrocarbon Receptor Signaling

In patients with CKD, not only renal but also, nonrenal clearance of drugs is altered. Uremic toxins could modify the expression and/or activity of drug transporters in the liver. We tested whether the uremic toxin indoxyl sulfate (IS), an endogenous ligand of the transcription factor aryl hydrocarbon receptor, could change the expression of the following liver transporters involved in drug clearance: SLC10A1, SLC22A1, SLC22A7, SLC47A1, SLCO1B1, SLCO1B3, SLCO2B1, ABCB1, ABCB11, ABCC2, ABCC3, ABCC4, ABCC6, and ABCG2 We showed that IS increases the expression and activity of the efflux transporter P-glycoprotein (P-gp) encoded by ABCB1 in human hepatoma cells (HepG2) without modifying the expression of the other transporters. This effect depended on the aryl hydrocarbon receptor pathway. Presence of human albumin at physiologic concentration in the culture medium did not abolish the effect of IS. In two mouse models of CKD, the decline in renal function associated with the accumulation of IS in serum and the specific upregulation of Abcb1a in the liver. Additionally, among 109 heart or kidney transplant recipients with CKD, those with higher serum levels of IS needed higher doses of cyclosporin, a P-gp substrate, to obtain the cyclosporin target blood concentration. This need associated with serum levels of IS independent of renal function. These findings suggest that increased activity of P-gp could be responsible for increased hepatic cyclosporin clearance. Altogether, these results suggest that uremic toxins, such as IS, through effects on drug transporters, may modify the nonrenal clearance of drugs in patients with CKD.

Effects of apolipoprotein M in uremic atherosclerosis

BACKGROUND AND AIMS

Chronic kidney disease is characterized by uremia and causes premature death, partly due to accelerated atherosclerosis. Apolipoprotein (apo) M is a plasma carrier protein for the lipid sphingosine-1-phosphate (S1P). The Apom-S1P complex associates with HDL, and may contribute to its anti-atherosclerotic effects. The role of Apom/S1P in atherosclerosis is presently controversial and has not been explored in a uremic setting. We aimed to explore whether plasma concentrations of Apom/S1P are altered by uremia and whether Apom overexpression or deficiency affects classical and uremic atherosclerosis.

METHODS

Mild to moderate uremia was induced by subtotal nephrectomy (NX) in 86-92 Apoe-deficient mice that were either Apom-wild type, Apom-deficient, or overexpressed Apom (∼10 fold). The effects of uremia on plasma Apom/S1P and atherosclerosis were evaluated and compared to non-nephrectomized controls.

RESULTS

Uremia increased plasma Apom by ∼25%, but not S1P. Plasma S1P was elevated by ∼300% in mice overexpressing Apom, and decreased by ∼25% in Apom-deficient mice. Apom overexpression augmented aortic root atherosclerosis and plasma cholesterol. In contrast, aortic arch atherosclerosis was unaffected by the Apom genotype. There was no effect of Apom-deficiency or Apom overexpression on uremic atherosclerosis.

CONCLUSIONS

This study highlights the complexity of Apom/S1P in atherosclerosis and challenges the notion that the Apom/S1P complex is anti-atherogenic, at least in Apoe-deficient mice.

Uremia does not affect neointima formation in mice

Atherosclerotic cardiovascular disease is a major complication of chronic kidney disease (CKD). CKD leads to uremia, which modulates the phenotype of aortic smooth muscle cells (SMCs). Phenotypic modulation of SMCs plays a key role in accelerating atherosclerosis. We investigated the hypothesis that uremia potentiates neointima formation in response to vascular injury in mice. Carotid wire injury was performed on C57BL/6 wt and apolipoprotein E knockout (Apoe^−/−) mice two weeks after induction of uremia by 5/6 nephrectomy. Wire injury led to neointima formation and downregulation of genes encoding classical SMC markers (i.e., myocardin, α-smooth muscle actin, SM22-alpha, and smooth muscle myosin heavy chain) in both wt and Apoe^−/− mice. Contrary to our expectations, uremia did not potentiate neointima formation, nor did it affect intimal lesion composition as judged from magnetic resonance imaging and histological analyses. Also, there was no effect of uremia on SMC marker gene expression in the injured carotid arteries, suggesting that there may be different effects of uremia on SMCs in different vascular beds. In conclusion, uremia does not accelerate neointima formation in response to wire injury of the carotid artery in mice.

Trimethylamine N-Oxide, the Microbiome, and Heart and Kidney Disease

Trimethylamine N-oxide (TMAO) is a biologically active molecule and is a putative promoter of chronic diseases including atherosclerosis in humans. Host intestinal bacteria produce its precursor trimethylamine (TMA) from carnitine, choline, or choline-containing compounds. Most of the TMA produced is passively absorbed into portal circulation, and hepatic flavin-dependent monooxygenases (FMOs) efficiently oxidize TMA to TMAO. Both observational and experimental studies suggest a strong positive correlation between increased plasma TMAO concentrations and adverse cardiovascular events, such as myocardial infarction, stroke, and death. However, a clear mechanistic link between TMAO and such diseases is not yet validated. Therefore, it is debated whether increased TMAO concentrations are the cause or result of these diseases. Here, we have tried to review the current understanding of the properties and physiological functions of TMAO, its dietary sources, and its effects on human metabolism. Studies that describe the potential role of TMAO in the etiology of cardiovascular and other diseases are also discussed.

Urea-induced ROS accelerate senescence in endothelial progenitor cells

BACKGROUND AND AIMS

The pathogenic events responsible for the reduction of endothelial progenitor cell (EPC) number and function seen in patients with chronic renal failure (CRF) are poorly understood. Here we investigate the hypothesis that increased concentrations of urea associated with CRF increase ROS production directly in EPCs, causing abnormalities associated with coronary artery disease risk.

METHODS

Human EPCs were isolated from peripheral blood mononuclear cells of healthy donors and cultured in the presence or absence of 20 mmol/L urea.

RESULTS

Urea at concentrations seen in CRF induced ROS production in cultured EPCs. Urea-induced ROS reduced the number of endothelial cell colony forming units, uptake and binding of Dil-Ac-LDL and lectin-1, and the ability to differentiate into CD31- and vascular endothelial growth factor receptor 2-positive cells. Moreover, urea-induced ROS generation accelerated the onset of EPC senescence, leading to a senescence-associated secretory phenotype (SASP). Normalization of mitochondrial ROS production prevented each of these effects of urea.

CONCLUSIONS

These data suggest that urea itself causes both reduced EPC number and increased EPC dysfunction, thereby contributing to the pathogenesis of cardiovascular disease in CRF patients.

Mineral metabolism and cardiovascular disease in CKD

The mineral bone disorder of CKD, called Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), has a major role in the etiology and progression of cardiovascular disease in CKD patients. Since the main emphasis in CKD-MBD is on three categories (bone abnormalities, laboratory abnormalities, and vascular calcifications), we have routinely accepted ectopic cardiovascular calcifications as a central risk factor in the pathophysiology of CKD-MBD for cardiac events. However, recent compelling evidence suggests that some CKD-MBD-specific factors other than vascular calcification might contribute to the onset of cardiovascular disease. Most notable is fibroblast growth factor-23 (FGF23), which is thought to be independently associated with cardiac remodeling. Slow progression of cardiac disorders, such as vascular calcification and cardiac remodeling, characterizes cardiac disease due to CKD-MBD. In contrast, fatal arrhythmia may be induced when QT prolongation occurs with CKD-MBD treatment, such as with lower Ca dialysate or the use of calcimimetics. Sudden onset of fatal cardiac events, such as heart failure and sudden cardiac death, due to fatal arrhythmia would be another distinctive phenomenon of CKD-MBD. This may be defined as CKD-MBD-specific cardiac complex syndrome.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 μg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68⁺F4/80^-), CD4⁺, and CD8⁺ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.

Only minor differences in renal osteodystrophy features between wild-type and sclerostin knockout mice with chronic kidney disease

Renal osteodystrophy affects the majority of patients with advanced chronic kidney disease (CKD) and is characterized by progressive bone loss. This study evaluated the effects of sclerostin knockout on bone in a murine model of severe, surgically induced CKD in both sclerostin knockout and wild-type mice. Mice of both genotypes with normal kidney function served as controls. Tibiae were analyzed using micro-computed tomography, and lumbar vertebrae were analyzed by histomorphometry. Results were tested for statistical significance by 2-way ANOVA to investigate whether bone of the knockout mice reacted differently to CKD compared with bone of wild-type mice. In the tibiae, there was no difference after creation of CKD between wild-type and knockout animals for cortical thickness or cross-sectional moment of inertia. Increases in cortical porosity induced by CKD differed significantly between genotypes in the tibial metaphysis but not in the diaphysis. In the trabecular compartment, no difference in reaction to CKD between genotypes was found for bone volume, trabecular number, trabecular thickness, and trabecular separation. In the lumbar vertebrae, significant differences in response to CKD between wild-type and knockout mice were seen for both bone volume and trabecular thickness. Osteoblast parameters did not differ significantly, whereas osteoclast numbers significantly increased in the wild-type but significantly decreased in knockout mice with CKD. No differences in response to CKD between genotypes were found for bone formation rate or mineral apposition rate. Thus, complete absence of sclerostin has only minor effects on CKD-induced bone loss in mice.

T Cell CX3CR1 Mediates Excess Atherosclerotic Inflammation in Renal Impairment

Reduced kidney function increases the risk for atherosclerosis and cardiovascular death. Leukocytes in the arterial wall contribute to atherosclerotic plaque formation. We investigated the role of fractalkine receptor CX3CR1 in atherosclerotic inflammation in renal impairment. Apoe(-/-) (apolipoprotein E) CX3CR1(-/-) mice with renal impairment were protected from increased aortic atherosclerotic lesion size and macrophage accumulation. Deficiency of CX3CR1 in bone marrow, only, attenuated atherosclerosis in renal impairment in an independent atherosclerosis model of LDL receptor-deficient (LDLr(-/-)) mice as well. Analysis of inflammatory leukocytes in atherosclerotic mixed bone-marrow chimeric mice (50% wild-type/50% CX3CR1(-/-) bone marrow into LDLr(-/-) mice) showed that CX3CR1 cell intrinsically promoted aortic T cell accumulation much more than CD11b(+)CD11c(+) myeloid cell accumulation and increased IL-17-producing T cell counts. In vitro, fewer TH17 cells were obtained from CX3CR1(-/-) splenocytes than from wild-type splenocytes after polarization with IL-6, IL-23, and TGFβ Polarization of TH17 or TREG cells, or stimulation of splenocytes with TGFβ alone, increased T cell CX3CR1 reporter gene expression. Furthermore, TGFβ induced CX3CR1 mRNA expression in wild-type cells in a dose- and time-dependent manner. In atherosclerotic LDLr(-/-) mice, CX3CR1(+/-) T cells upregulated CX3CR1 and IL-17A production in renal impairment, whereas CX3CR1(-/-) T cells did not. Transfer of CX3CR1(+/-) but not Il17a(-/-) T cells into LDLr(-/-)CX3CR1(-/-) mice increased aortic lesion size and aortic CD11b(+)CD11c(+) myeloid cell accumulation in renal impairment. In summary, T cell CX3CR1 expression can be induced by TGFβ and is instrumental in enhanced atherosclerosis in renal impairment.

Seasonal variations in mood and behavior associate with common chronic diseases and symptoms in a population-based study

The purpose of this study was to assess how seasonality is associated with some of the most common non-communicable diseases (NCDs) in the general Finnish population. The global seasonality score (GSS) was used to measure the magnitude of seasonality in 4689 participants, in addition to which they reported the extent to which the seasonal variations in mood and behavior were experienced as a problem. Regression models and the odds ratios were adopted to analyze the associations adjusted for a range of covariates. Seventy percent of the participants had seasonal variations in sleep duration, social activity, mood, or energy level, and forty percent those in weight and appetite. Angina pectoris and depression were significantly associated with seasonality throughout the analysis. Hypertension, high cholesterol levels, diabetes, other (than rheumatoid) joint diseases and other (than depressive) psychological illnesses were significantly associated with experiencing a problem due to the seasonal variations, with an increase in the GSS, and with seasonal affective disorder and its subsyndromal form. The co-occurrence of the seasonal variations in mood and behavior with certain common NCDs warrants future research to have insights into the etiology and potentially shared pathways and mechanisms of action.

Signaling of Serum Amyloid A Through Receptor for Advanced Glycation End Products as a Possible Mechanism for Uremia-Related Atherosclerosis

OBJECTIVE

Cardiovascular disease is the leading cause of death in patients with end-stage renal disease. Serum amyloid A (SAA) is an acute phase protein and a binding partner for the multiligand receptor for advanced glycation end products (RAGE). We investigated the role of the interaction between SAA and RAGE in uremia-related atherogenesis.

APPROACH AND RESULTS

We used a mouse model of uremic vasculopathy, induced by 5 of 6 nephrectomy in the Apoe(-/-) background. Sham-operated mice were used as controls. Primary cultures of Ager(+/+) and Ager(-/-) vascular smooth muscle cells (VSMCs) were stimulated with recombinant SAA, S100B, or vehicle alone. Relevance to human disease was assessed with human VSMCs. The surface area of atherosclerotic lesions at the aortic roots was larger in uremic Apoe(-/-) than in sham-operated Apoe(-/-) mice (P<0.001). Furthermore, atherosclerotic lesions displayed intense immunostaining for RAGE and SAA, with a pattern similar to that of α-SMA. Ager transcript levels in the aorta were 6× higher in uremic animals than in controls (P<0.0001). Serum SAA concentrations were higher in uremic mice, not only after 4 weeks of uremia but also at 8 and 12 weeks of uremia, than in sham-operated animals. We investigated the functional role of RAGE in uremia-induced atherosclerosis further, in animals lacking RAGE. We found that the induction of uremia in Apoe(-/-) Ager(-/-) mice did not accelerate atherosclerosis. In vitro, the stimulation of Ager(+/+) but not of Ager(-/-) VSMCs with SAA or S100B significantly induced the production of reactive oxygen species, the phosphorylation of AKT and mitogen-activated protein kinase-extracellular signal-regulated kinases and cell migration. Reactive oxygen species inhibition with N-acetyl cysteine significantly inhibited both the phosphorylation of AKT and the migration of VSMCs. Similar results were obtained for human VSMCs, except that the phosphorylation of mitogen-activated protein kinase-extracellular signal-regulated kinases, rather than of AKT, was subject to specific redox-regulation by SAA and S100B. Furthermore, human aortic atherosclerotic sections were positively stained for RAGE and SAA.

CONCLUSIONS

Uremia upregulates SAA and RAGE expression in the aortic wall and in atherosclerotic lesions in mice. Ager(-/-) animals are protected against the uremia-induced acceleration of atherosclerosis. SAA modulates the functions of murine and human VSMCs in vitro in a RAGE-dependent manner. This study, therefore, identifies SAA as a potential new uremic toxin involved in uremia-related atherosclerosis through interaction with RAGE.