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Background and Aims: Alterations in novel immune cell subsets, such as angiogenic T cells (Tang), senescent T cells (CD4+CD28null), and monocyte subsets are associated with impaired vascular homeostasis in several inflammatory conditions. However, mediators underlying vascular deterioration in chronic kidney disease (CKD) are poorly characterized. This study assessed their role in the vascular deterioration of CKD using a broad spectrum of surrogate markers ranging from altered functionality to overt calcification.Methods: Tang (CD3+CD31+CXCR4+), CD4+CD28null cells, and monocytes [CD14/CD16 subsets and angiotensin-converting enzyme (ACE) expression] were measured in peripheral blood by flow cytometry in 33 CKD stage 5 patients undergoing peritoneal dialysis (CKD5-PD) and 15 healthy controls (HCs). Analyses were replicated in a hemodialysis cohort. Vascular surrogate markers (including adventitial vasa vasorum, pulse wave velocity, intima-media thickness, and vascular calcification) were assessed by appropriate imaging methods.Results: In CKD5-PD, decreased Tang levels (p < 0.001) were unrelated to clinical features or traditional cardiovascular (CV) risk factors but correlated negatively with troponin T levels (r = −0.550, p = 0.003). Instead, CD4+CD28null frequency was increased (p < 0.001), especially in those with vascular calcifications. Quantitative and qualitative differences were also observed within the monocyte pool, a shift toward CD16+ subsets and ACE expression being found in CKD. Equivalent results were observed in the replication cohort. Each subset associated distinctly with adverse vascular outcomes in univariate and multivariate analyses: while Tang depletion was linked to poor vascular function and subclinical atherosclerosis, increases in CD4+CD28null were associated with overt vascular thickening and calcification. Monocytes were not independently associated with vascular outcomes in CKD patients.Conclusions: Novel T cell and monocyte subsets are altered in CKD. Altered T-cell subpopulations, but not monocytes, exhibited distinct associations with different vascular outcomes in CKD. Tang are emerging biomarkers of subclinical vascular deterioration in CKD.

Background In chronic kidney disease, the activation of the renin–angiotensin–aldosterone system (RAAS) and renal inflammation stimulates renal fibrosis and the progression to end-stage renal disease. The low levels of vitamin D receptor (VDR) and its activators (VDRAs) contribute to worsen secondary hyperparathyroidism and renal fibrosis. Methods The 7/8 nephrectomy model of experimental chronic renal failure (CRF) was used to examine the anti-fibrotic effects of treatment with two VDRAs, paricalcitol and calcitriol, at equivalent doses (3/1 dose ratio) during 4 weeks. Results CRF increased the activation of the RAAS, renal inflammation and interstitial fibrosis. Paricalcitol treatment reduced renal collagen I and renal interstitial fibrosis by decreasing the activation of the RAAS through renal changes in renin, angiotensin receptor 1 (ATR1) and ATR2 mRNAs levels and renal inflammation by decreasing renal inflammatory leucocytes (CD45), a desintegrin and metaloproteinase mRNA, transforming growth factor beta mRNA and protein, and maintaining E-cadherin mRNA levels. Calcitriol showed similar trends without significant changes in most of these biomarkers. Conclusions Paricalcitol effectively attenuated the renal interstitial fibrosis induced by CRF through a combination of inhibitory actions on the RAAS, inflammation and epithelial/mesenchymal transition.

Background and Aims The stratification of early cardiovascular (CV) risk is a major unmet need in chronic kidney disease (CKD). Since angiogenic T-cells are emerging mediators of vascular homeostasis and have been linked to CV disease (CVD), this study evaluated the frequency of circulating angiogenic T-cells in CKD patients undergoing peritoneal dialysis (CKD-5D) and their potential as predictive biomarkers of CVD. Method In 30 peritoneal dialysis patients and 16 matched healthy controls (HC), we quantified: Vascular calcification (by Kauppila Index); left carotid intima media thickness (lc-IMT by ultrasound), carotid adventitial vasa vasorum density (an early marker of atherosclerosis stage, by Superb Microvascular Ultrasound Image), pulse wave velocity (a marker of vascular stiffness and dysfunction, using the Complior Analyzer), angiogenic T cell frequency in blood (by Flow cytometry) and the traditional 10-year CVD risk (using the SCORE chart). Results As expected, CKD-5D patients exhibited higher Kauppila index (p0.05) and did not correlate with Kauppila (r=-0.350, p=0.080) or lcIMT (r=-0.154, p=0.600), but strongly associated negatively with both pulse wave velocity (r=-0.734, p Conclusion Angiogenic-T cell frequency was decreased in CKD-5D patients and could be considered as biomarkers of vascular dysfunction and early atherosclerosis stage.

Inflammation is central to chronic kidney disease (CKD) pathogenesis and vascular outcomes, but the exact players remain unidentified. Since low density granulocytes (LDGs) are emerging mediators in inflammatory conditions, we aimed to evaluate whether LDGs may be altered in CKD and related to clinical outcomes as biomarkers. To his end, LDGs subsets were measured in peripheral blood by flow cytometry and confocal microscopy in 33 CKD patients undergoing peritoneal dialysis and 15 healthy controls (HC). Analyses were replicated in an additional cohort. DEF3 (marker of early granulopoiesis) gene expression on PBMCs was quantified by qPCR. Total CD15+ LDGs and both CD14lowCD16+ and CD14−CD16− subsets were expanded in CKD. The relative frequency of the CD14−CD16− subpopulation was higher among the CD15+ pool in CKD. This alteration was stable over-time. The increased CD14−CD16−CD15+ paralleled Kauppila scores and DEF3 expression, whereas no association was found with CD14lowCD16+ CD15+. Both subsets differed in their CD11b, CD10, CD35, CD31, CD62L, IFNAR1 and CD68 expression, FSC/SSC features and nuclear morphology, pointing to different origins and maturation status. In conclusion, LDGs were expanded in CKD showing a skewed distribution towards a CD14−CD16−CD15+ enrichment, in association with vascular calcification. DEF3 expression in PBMC can be a marker of LDG expansion. Fil: Rodríguez Carrio, Javier. Hospital Universitario Central de Asturias. Instituto de Investigación Sanitaria del Principado de Asturias (ISPA). Bone and Mineral Research Unit; España. Universidad de Oviedo; España Fil: Carrillo López, Natalia. Hospital Universitario Central de Asturias; España Fil: Ulloa, Catalina. Hospital Universitario Central de Asturias; España Fil: Seijo, Mariana. Hospital Universitario Central de Asturias; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; Argentina Fil: Rodríguez García, Minerva. Hospital Universitario Central de Asturias; España Fil: Rodríguez Suárez, Carmen. Hospital Universitario Central de Asturias; España Fil: Díaz-Corte, Carmen. Hospital Universitario Central de Asturias; España Fil: Cannata Andía, Jorge B.. Universidad de Oviedo; España. Hospital Universitario Central de Asturias; España Fil: Suárez, Ana. Universidad de Oviedo; España Fil: Dusso, Adriana. Hospital Universitario Central de Asturias; España

In chronic kidney disease (CKD), hyperphosphatemia-induced inflammation aggravates vascular calcification (VC) by increasing vascular smooth muscle cell (VSMC) osteogenic differentiation, ADAM17-induced renal and vascular injury, and TNFα-induction of neutral-sphingomyelinase2 (nSMase2) to release pro-calcifying exosomes. This study examined anti-inflammatory β-glucans efficacy at attenuating systemic inflammation in health, and renal and vascular injury favoring VC in hyperphosphatemic CKD. In healthy adults, dietary barley β-glucans (Bβglucans) reduced leukocyte superoxide production, inflammatory ADAM17, TNFα, nSMase2, and pro-aging/pro-inflammatory STING (Stimulator of interferon genes) gene expression without decreasing circulating inflammatory cytokines, except for γ-interferon. In hyperphosphatemic rat CKD, dietary Bβglucans reduced renal and aortic ADAM17-driven inflammation attenuating CKD-progression (higher GFR and lower serum creatinine, proteinuria, kidney inflammatory infiltration and nSMase2), and TNFα-driven increases in aortic nSMase2 and calcium deposition without improving mineral homeostasis. In VSMC, Bβglucans prevented LPS- or uremic serum-induced rapid increases in ADAM17, TNFα and nSMase2, and reduced the 13-fold higher calcium deposition induced by prolonged calcifying conditions by inhibiting osteogenic differentiation and increases in nSMase2 through Dectin1-independent actions involving Bβglucans internalization. Thus, dietary Bβglucans inhibit leukocyte superoxide production and leukocyte, renal and aortic ADAM17- and nSMase2 gene expression attenuating systemic inflammation in health, and renal injury and aortic calcification despite hyperphosphatemia in CKD. A grant to A.S.D. and M.J.M. from IRBLleida and Agrotecnio Research collaborative projects from the Consell Social at Lleida University supported initial work, Instituto de Salud Carlos III and co-funded by European Union (ERDF/FEDER) (FIS PI11/00259, PI14/01452, PI17/02181), Plan de Ciencia, Tecnología e Innovación 2013–2017 y 2018–2022 del Principado de Asturias (GRUPIN14-028, IDI-2018-000152), RedInRen from ISCIII (ISCIII-RETIC REDINREN RD16/0009). Investigator support included: NC-L by GRUPIN14-028 and IDI-2018-000152, LM-A by GRUPIN14-028, SP by FICYT; MVA and PV by Educational Grant 2 A/2015 from ERA-EDTA CKD-MBD Working Group; PV and AC by ERA-EDTA fellowships 2011 and 2012; JR-C by MINECO (“Juan de la Cierva” program, FJCI-2015-23849); A.S.D. by Asociación Investigación de Fisiología Aplicada. A.S.D. and M.J.M. are members of the Campus Iberus (Ebro Valley Campus of International Excellence).

In chronic kidney disease (CKD), the progressive loss of renal capacity to maintain the functional integrity of the vitamin D endocrine system is a major determinant of the skeletal, renal, and cardiovascular damage that markedly increases mortality rates. This chapter updates the progress in our understanding of the pathophysiology underlying CKD-induced abnormalities in the systemic and local vitamin D bioactivation to its hormonal form, 1,25-dihydroxyvitamin D or calcitriol. Special focus is directed to the molecular bases to maximize the prosurvival actions of the calcitriol/vitamin D receptor complex in CKD beyond the suppression of the PTH gene and parathyroid cell growth including: (1) The attenuation of bone loss and vascular calcification unrelated to the control of secondary hyperparathyroidism; (2) The induction of the fibroblast growth factor 23 to prevent the proaging effects of hyperphosphatemia and of an excess of active vitamin D, and (3) The simultaneous induction of the klotho gene and inhibition of its two main downregulators, hypertension, and systemic inflammation to maintain the skeletal, renal, and cardiovascular protection conferred by renal and circulating klotho.

Progressive elevations of fibroblastic growth factor 23 [FGF23] in chronic kidney disease may reduce serum 25-hydroxyvitamin D [25(OH)] and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels, via stimulation of 24-hydroxylase (Cyp24A1) mediated catabolism of these vitamin D metabolites. To test this possibility, we measured serum concentrations of 24,25-dihydroxyvitamin D [24,25(OH)2D], a product of Cyp24A1 hydroxylation of 25(OH)D, in the Col4α3 knockout mouse, a model of Alport syndrome-derived chronic kidney disease, and in patients with chronic kidney disease of variable severity. There was an inverse correlation between serum FGF23 and both 25(OH)D and 1,25(OH)2D in the mouse model but no significant relationship was observed in the cross-sectional patient cohort. The FGF23-dependent increase in Cyp24a1 mRNA expression in the mouse kidneys was consistent with the possibility that FGF23 induces vitamin D catabolism. There was, however, a reduction in serum 24,25(OH)2D levels, rather than the expected elevation, in both the mice and patients with chronic kidney disease. Low 25(OH)D and elevated FGF23 and parathyroid hormone levels were correlated with the reduced serum 24,25(OH)2D concentrations of these patients. Thus, we failed to find support for FGF23-mediated catabolism of vitamin D metabolites in chronic kidney disease assessed by 24,25(OH)2D levels.

Chronic kidney disease (CKD) progression is characterized by features of accelerated aging (bone loss, increased propensity for fractures and vascular calcification, hypertension and cardiovascular disease) and a risk of mortality 20- to 30-fold higher than in age- and gender-matched individuals with normal renal function. The progressive loss of renal capacity to maintain the functional integrity of the vitamin D endocrine system is a main determinant of the severe pro-aging features that reduce survival. The goal of this chapter is an update of the progress of the last 5 years in our understanding of the molecular pathophysiology underlying CKD-induced abnormalities in: (a) Systemic and local vitamin D bioactivation to its hormonal form, 1,25-dihydroxyvitamin D or calcitriol; (b) Classical genomic and non-genomic actions of the calcitriol/vitamin D receptor (VDR) complex that compromise survival, and (c) Synergistic VDR activation by calcitriol and its precursor, 25-hydroxyvitamin D, to counteract VDR reductions.

Si presenta un aggiornamento su: 1) la fisiopatologia della resistenza indotta dalla carbamazepina all'azione soppressiva del paracalcitolo nell'iperparatiroidismo secondario (IPTS) a malattia renale cronica (CKD); 2) l'impatto di una deficienza di vitamina D sugli effetti indesiderati della carbamazepina; 3) i benefici della supplementazione con colecalciferolo – sia da solo che in associazione con il paracalcitolo – nella prevenzione/attenuazione della soppressione dell'IPTS vitamina D-mediata; 4) la correzione appropriata della carenza di vitamina D nei pazienti con CKD in terapia antiepilettica con carbamazepina, con lo scopo di fornire al nefrologo clinico un approccio terapeutico pratico, sicuro ed efficace, per migliorare l'outcome dell'IPTS.

The integrity of the vitamin D endocrine system is essential for human health. Nutritional vitamin D deficiency in otherwise healthy individuals, associates with a higher risk of mortality for all causes, despite normal serum calcitriol. These deadly causes extend beyond the recognized adverse impact of vitamin D deficiency on calcium and phosphate homeostasis predisposing to secondary hyperparathyroidism, bone loss and vascular calcification. Vitamin D deficiency also associates with an early onset of disorders of aging, including hypertension, proteinuria, insulin resistance, immune abnormalities that enhance the propensity for viral and bacterial infections, autoimmune disorders, cancer, and multiple organ damage due to excessive systemic inflammation causing atherosclerosis, vascular stiffness, renal lesions, and impaired DNA-damage responses. The frequency and severity of all of these disorders markedly increase in chronic kidney disease (CKD) because the kidney is essential to maintain serum levels of calcitriol, the most potent endogenous endocrine activator of the vitamin D receptor (VDR), and also of 25-hydroxyvitamin D, for local rather than systemic VDR activation. The goal of this review is to update the current understanding of the pathophysiology behind the classical and non-classical actions of VDR activation that help prevent the onset and/or attenuate the progression of renal and cardiovascular damage in CKD. This knowledge is essential to identify non-invasive, sensitive and accurate biomarkers of the severity of these disorders, a first step to generate evidence-based recommendations for a safe correction of vitamin D and/or calcitriol deficiency in the course of CKD that effectively improves outcomes.

Background Vascular calcification (VC) contributes to high mortality rates in chronic kidney disease (CKD). High serum phosphate and FGF23 levels and impaired phosphaturic response to FGF23 may affect VC. Therefore, their relative contribution to abdominal aortic calcification (AAC) was examined in patients CKD stages 3–4. Methods Potential risk factors for AAC, measured by the Kauppila Index (KI), were studied in 178 patients. Results In multivariate linear analysis, AAC associated positively with age, male gender, CKD-stage, presence of carotid plaques (CP) and also with FGF23, but negatively with fractional excretion of phosphate (FEP). Intriguingly, FEP increased with similar slopes with elevations in PTH, with reductions in GFR, and also with elevations in FGF23 but the latter only in patients with none (KI = 0) or mild (KI = 1-5) AAC. Lack of a FEP-FGF23 correlation in patients with severe AAC (KI > 5) suggested a role for an impaired phosphaturic response to FGF23 but not to PTH in AAC. Logistic and zero-inflated analysis confirmed the independent association of age, CKD stage, male gender and CP with AAC, and also identified a threshold FEP/FGF23 ratio of 1/3.9, below which the chances for a patient of presenting severe AAC increased by 3-fold. Accordingly, KI remained unchanged as FEP/FGF23 ratios decreased from 1/1 to 1/3.9 but markedly increased in parallel with further reductions in FEP/FGF23 Conclusions In CKD 3–4, an impaired phosphaturic response to FGF23 with FEP/FGF23