Endothelial aging may be induced early in pathological situations. The uremic toxins indoxyl sulfate (IS) and p-cresol (PC) accumulate in the plasma of chronic kidney disease (CKD) patients, causing accelerated endothelial aging, increased cardiovascular events and mortality. However, the mechanisms by which uremic toxins exert their deleterious effects on endothelial aging are not yet fully known. Thus, the aim of the present study is to determine the effects of IS and PC on endothelial damage and early senescence in cultured human umbilical vein endothelial cells (HUVECs). Hence, we establish an in vitro model of endothelial damage mediated by different passages of HUVECs and stimulated with different concentrations of IS and PC to evaluate functional effects on the vascular endothelium. We observe that cell passage-induced senescence is associated with apoptosis, ROS production and decreased endothelial proliferative capacity. Similarly, we observe that IS and PC cause premature aging in a dose-dependent manner, altering HUVECs’ regenerative capacity, and decreasing their cell migration and potential to form vascular structures in vitro. In conclusion, IS and PC cause accelerated aging in HUVECs, thus contributing to endothelial dysfunction associated with CKD progression.

Atherosclerosis is initiated by the activation of endothelial cells that allows monocyte adhesion and transmigration through the vascular wall. The accumulation of uremic toxins such as indoxyl sulphate (IS) and p-cresol (PC) has been associated with atherosclerosis. Currently, miRNAs play a crucial role in the regulation of monocyte activation, adhesion, and trans-endothelial migration. The aim of the present study is to evaluate the effect of IS and PC on monocyte adhesion and migration processes in monocytes co-cultured with endothelial cells as well as to determine the underlying mechanisms. The incubation of HUVECs and THP-1 cells with both IS and PC toxins resulted in an increased migratory capacity of THP-1 cells. Furthermore, the exposure of THP-1 cells to both uremic toxins resulted in the upregulation of BMP-2 and miRNAs-126-3p, -146b-5p, and -223-3p, as well as the activation of nuclear factor kappa B (NF-κB) and a decrease in its inhibitor IĸB. Uremic toxins, such as IS and PC, enhance the migratory and adhesion capacity of THP-1 cells to the vascular endothelium. These toxins, particularly PC, contribute significantly to uremia-associated vascular disease by increasing in THP-1 cells the expression of BMP-2, NF-κB, and key miRNAs associated with the development of atherosclerotic vascular diseases.

Chronic kidney disease (CKD) is associated with gut microbiota alterations that contribute to increased inflammation and the generation of uremic toxins and may worsen the disease progression. While probiotics may improve the pro-inflammatory cytokine profile, their effects on mineral metabolism, vascular calcification (VC), and CKD progression remain unclear. We aimed to evaluate the impact of a commercial probiotic (Probimel) supplementation on kidney function, mineral metabolism, inflammation and VC in both an experimental rat model and patients with advanced CKD and VC. The experimental model of VC was performed through 5/6 nephrectomy (Nx), a high-phosphate diet, and calcitriol. Animals were divided into three groups: Sham, Nephrectomy, and Nephrectomy + Probiotic. In the exploratory clinical study, 23 patients with advanced stage 5 CKD and VC were randomized and either received or did not receive daily probiotics for 6 months. Kidney function, mineral metabolism, uremic toxins, inflammation, VC, and fecal microbiota were evaluated. Probiotic supplementation decreased interleukin-6 (IL-6) and interpheron-γ (IFN-γ) and levels of the uremic toxin, indoxyl sulfate (IS), in the experimental model. However, no clear evidence of improvement in kidney function or vascular calcification was observed in either rats or patients with this probiotic. Under our experimental and clinical conditions, the selected probiotic did not modify key parameters related to CKD progression or VC.

Background: Chronic kidney disease (CKD) is associated with early disturbances in mineral metabolism that contribute to bone fragility. Secondary hyperparathyroidism is a key component of chronic kidney disease–mineral and bone disorder (CKD-MBD) and may affect bone even during the early stages of CKD. This study evaluated the association between serum parathyroid hormone (PTH) concentrations and bone mineral density (BMD) in patients with stage 3 CKD. Methods: A multicenter cross-sectional observational study was conducted in 203 patients with stage 3 CKD. Blood and 24 h urine samples were collected to measure creatinine, calcium, phosphate, magnesium, 25-hydroxyvitamin D, fibroblast growth factor 23 (FGF23), and PTH. Bone mineral density was assessed by dual-energy X-ray absorptiometry (DXA). Associations between serum PTH concentrations and BMD were analyzed. Results: Elevated serum PTH concentrations were associated with lower femoral BMD and less favorable femoral T-scores, whereas no significant associations were observed at the lumbar spine. Serum PTH concentrations were inversely correlated with femoral BMD and femoral T-scores. Patients with reduced femoral BMD also showed higher FGF23 concentrations and lower renal function, while serum calcium, phosphate, magnesium, and 25-hydroxyvitamin D concentrations did not differ significantly among the groups. Conclusions: Elevated serum PTH concentrations were associated with reduced femoral BMD in patients with stage 3 CKD, supporting preferential early involvement of cortical bone. Serum PTH may represent an accessible biomarker for the early identification of patients at increased risk of cortical bone loss before conventional biochemical abnormalities become clinically apparent.

The progression of chronic kidney disease (CKD) entails the development of complications, such as anemia and disturbances in mineral homeostasis, among others, and both of them have been shown to be closely related. In fact, high phosphorus (P) and excessive production of fibroblast growth factor 23 (FGF23) are hallmarks of the mineral alterations found in CKD, both of which have been associated with the development of anemia. The objective of this study was to evaluate whether the modulation of P load may impact the severity of CKD-related anemia as well as to separate the effects of FGF23 from those of P by the administration of an AntiFGF23 antibody while also investigating the involvement of hypoxia-inducible factor (HIF) signaling in these actions. To address this objective, we used a CKD model based on 5/6 nephrectomy (Nx). In a first experiment, CKD rats received diets with 0.2, 0.6, or 1.2% of P for 4 weeks. In a second study, Nx rats fed a 1.2% P diet were treated with an AntiFGF23 antibody for the same period. In an additional experiment, the effect of the exogenous administration of FGF23 and AntiFGF23 was evaluated. In all the experiments, we analyzed the hematological status, parameters of renal function and mineral metabolism, and HIF signaling. In CKD, the increase in P load was associated with an expected progressive elevation in FGF23 and an aggravation of anemia. In a situation of uremia with high P load, the neutralization of FGF23 restored hematological alterations while producing a significant inhibition in renal HIF1Alpha. In the absence of renal damage, the administration of recombinant FGF23 produced a decrease in serum iron and reticulocytes without changes in HIF signaling. In conclusion, progressive and concomitant increases in P and FGF23 produce an aggravation of anemia of renal origin. In this setting, the normalization of hematological parameters induced by FGF23 blockade is associated with the inhibition of renal HIF signaling. Thus, the implementation of FGF23-targeting therapies might constitute an additional strategy for the clinical management of CKD-related anemia.