Paricalcitol Research Articles

Paricalcitol ameliorates diabetic nephropathy by promoting EETs and M2 macrophage polarization and inhibiting inflammation by regulating VDR/CYP2J2 axis.

Previous studies have shown that paricalcitol (PA) has a protective effect on the kidneys. However, the exact molecular mechanism by which PA affects diabetic nephropathy (DN) progression remains uncertain. PBMCs of patients with DN were isolated, and CYP2J2 and VDR levels were detected by qPCR. Pearson correlation analysis was utilized to detect the relationship between uACR and CYP2J2 and VDR and between CYP2J2 and VDR. The protective effects of PA on DN have been examined by TUNEL, HE staining, ELISA, and Flow cytometry assays in STZ-induced mice. Moreover, THP-1 cells were stimulated with HG/LPS for invitro studies. ELISA, qPCR, western blot, and Flow cytometry assays were utilized to assess the effects of PA on DN progression by regulating CYP2J2. The interaction between CYP2J2 and VDR was analyzed by CHIP-qPCR and luciferase experiments. CYP2J2 and VDR levels were downregulated and uACR level was upregulated in DN patients. CYP2J2 and VDR were positively correlated in PBMCs. Both CYP2J2 and VDR are inversely correlated with uACR. Moreover, after PA treatment, 11, 12-EET levels increased, inflammatory factor levels decreased, and M2 macrophage polarization was promoted in STZ-induced mice and HG/LPS-triggered THP-1 cells. Depletion of CYP2J2 and VDR decreased 11, 12-EET level, enhanced inflammatory factor levels, and inhibited M2 macrophage polarization, which were reversed by CYP2J2 overexpression in HG/LPS-treated cells. Furthermore, VDR bound to the CYP2J2 promoter and promoted CYP2J2 transcriptional expression. The present work pointed out a new use for PA to inhibit DN progression by increasing EET level, inhibiting inflammatory response, and inducing M2 macrophage polarization via regulating the VDR/CYP2J2 axis.

Electrocardiographic, biochemical, and scintigraphic evidence for the cardioprotective effect of paricalcitol and vitamin D3 on doxorubicin-induced acute cardiotoxicity in rats.

We aimed to investigate the possible cardioprotective effects of paricalcitol (PR), its vitamin Dreceptor agonist, and vitamin D3 (VIT-D3) on an experimental model of doxorubicin (DX) cardiotoxicity by 99mTc-PYP scintigraphy, electrocardiographic (ECG) and biochemical methods. Forty-two male Wistar/Albino rats (250‒300 g; aged 10‒12 weeks) were randomly separated into six groups, namely into control (CN), doxorubicin (DX), paricalcitol (PR), vitamin D3 (VIT-D3), paricalcitol + doxorubicin (PR+DX), and vitamin D3 + doxorubicin (VIT-D3+DX) groups. Cardiotoxicity was induced by three doses of DX (18 mg/kg, i.p.) at 24-hour intervals on days 18, 19 and 20. PR (0.5 ug/ kg, i.p) and VIT-D3 (5,000IU/kg, i.p) were injected for 20 days before and after the application of DX (18 mg/kg, i.p.). On day 21 of the experiment, biochemical parameters [tumor necrosis factor TNF-alpha (TNF-α); interleukin-6 (IL-6), nitric oxide (NO), and cardiac troponin T(cTnT)], as well as ECG and scintigraphic (99mTc-PYP) features were assessed. Compared to CN, DX significantly raised TNF-α, IL-6, and NO in heart tissue, cTnT in serum, 99mTc-PYP uptake in the myocardium, and ECG parameters, specifically QRS complex duration, QT interval duration, and ST-segment amplitude, while also reducing heart rate (p<0.001). Pretreatment with PR and VIT-D3 mitigated these abnormalities produced by DX in the heart (p<0.001). Results show that vitamin Dreceptor agonist paricalcitol and vitamin Dprotect against DX-induced cardiotoxicity through anti-inflammatory and antioxidant effects (Fig. 4, Ref. 59). Text in PDF www.elis.sk Keywords: paricalcitol, doxorubicin, vitamin D, ECG, 99mTc-PYP scintigraphy, cardiotoxicity, inflammation.

VDR Activation Attenuates Renal Tubular Epithelial Cell Ferroptosis by Regulating Nrf2/HO-1 Signaling Pathway in Diabetic Nephropathy.

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes. Ferroptosis, a new form of cell death, plays a crucial role in the pathogenesis of DN. Renal tubular injury triggered by ferroptosis might be essential in this process. Numerous studies demonstratethat the vitamin D receptor (VDR) exerts beneficial effects by suppressing ferroptosis. However, the underlying mechanism has not been fully elucidated. Thus, they verified the nephroprotective effect of VDR activation and explored the mechanism by which VDR activation suppressed ferroptosis in db/db mice and high glucose-cultured proximal tubular epithelial cells (PTECs). Paricalcitol (PAR) is a VDR agonist that can mitigate kidney injury and prevent renal dysfunction. PAR treatment could inhibit ferroptosis of PTECs through decreasing iron content, increasing glutathione (GSH) levels, reducing malondialdehyde (MDA) generation, decreasing the expression of positive ferroptosis mediator transferrin receptor 1 (TFR-1), and enhancing the expression of negative ferroptosis mediators including ferritin heavy chain (FTH-1), glutathione peroxidase 4 (GPX4), and cystine/glutamate antiporter solute carrier family 7 member 11(SLC7A11). Mechanistically, VDR activation upregulated the NFE2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway to suppress ferroptosis in PTECs. These findings suggested that VDR activation inhibited ferroptosis of PTECs in DN via modulating the Nrf2/HO-1 signaling pathway.

Paricalcitol and Extended Release Calcifediol for Treatment of Secondary Hyperparathyroidism in Non-Dialysis Chronic Kidney Disease: Results From a Network Meta-Analysis.

Secondary hyperparathyroidism (SHPT) is a complication of chronic kidney disease (CKD) affecting mineral and bone metabolism and characterized by excessive parathyroid hormone (PTH) production and parathyroid hyperplasia. The objective of this analysis was to compare the efficacy and adverse effects of extended release calcifediol (ERC) and paricalcitol (PCT) by assessing their effect on biomarkers PTH, calcium and Phosphate in patients with non-dialysis CKD (ND CKD). A systematic literature research (SLR) was performed in PubMed to identify randomized control trials (RCTs). Quality assessment was done with the GRADE method. The effects of ERC vs PCT were compared using random effects in a frequentist setting. Nine RCTs comprising 1426 patients were included in the analyses. The analyses were performed on two overlapping networks, due to non-reporting of outcomes in some of the included studies. No head-to-head trials were identified. No statistically significant differences in PTH reduction were found between PCT and ERC. Treatment with PCT showed statistically significant increases in calcium compared to ERC (0.2 mg/dl increase, 95% CI: -0.37 to -0.05 mg/dl). No differences in effects on phosphate were observed. This NMA showed that ERC is comparable in lowering PTH levels vs PCT. ERC displayed avoidance of potentially clinically relevant increases in serum calcium, offering an effective and well tolerated treatment option for the management of SHPT in patients with ND CKD.

Vitamin D Receptor Regulates Autophagy to Inhibit Apoptosis and Promote Proliferation in Hepatocyte Injury.

Oxidative stress is an important mechanism in liver ischemia/reperfusion (I/R) injury. Hepatocyte apoptosis and proliferation occur in parallel with liver I/R injury, and the degree of apoptosis and proliferation determines the effects on hepatocytes. Vitamin D receptor (VDR) can lessen liver I/R injury, but previous studies focused mostly on inflammation and immunity. H2O2 was used to induce hepatocyte injury. Before treatment with H2O2, Hep-3B cells were pretreated with paricalcitol (PC) and siRNA-VDR. Rapamycin and chloroquine were also applied in the study. The number of apoptotic cells was measured with an annexin V (AV) -fluorescein isothiocyanate apoptosis detection kit. Expression of proteins was measured by western blotting. As compared with the H2O2+Hep-3B group, levels of AV/PI, cleaved caspase-3, and p62 were lower, and expression levels of Bcl-2, proliferating cell nuclear antigen, and VDR were higher, in the PC+H2O2+Hep-3B group. When the VDR gene was silenced by siRNA-VDR in the siRNA-VDR+H2O2+Hep-3B group, expressions of AV/PI, cleaved caspase-3, and p62 were upregulated, and expressions of Bcl-2, proliferating cell nuclear antigen, and VDR were downregulated, as compared with values for the siRNA-NC+H2O2+Hep-3B group. Treatment with rapamycin or chloroquine partially reversed the effect of PC and siRNA-VDR on apoptosis and proliferation. VDR mediates hepatocyte apoptosis and proliferation through autophagy.

SMAD3 interacts with vitamin D receptor and affects vitamin D-mediated oxidative stress to ameliorate cerebral ischaemia-reperfusion injury.

Cerebral ischaemia/reperfusion (I/R) injury is caused by blood flow restoration after an ischaemic insult, and effective treatments targeting I/R injury are still insufficient. Oxidative stress plays a critical role in the pathogenesis of cerebral I/R injury. This study investigated whether vitamin D receptor (VDR) could inhibit oxidative stress caused by cerebral I/R injury and explored the detailed mechanism. VDR was highly expressed in brain tissues of mice with cerebral I/R injury. Pretreatment with the active vitamin D calcitriol and synthetic vitamin D analogue paricalcitol (PC) reduced autophagy and apoptosis, improved neurological deficits and decreased infarct size in mice after cerebral I/R. Calcitriol or PC upregulated VDR expression to prevent cerebral I/R injury by affecting oxidative stress. Silencing of VDR reversed the protective effects of calcitriol or PC on brain tissues in mice with cerebral I/R. The bioinformatics analysis revealed that VDR interacted with SMAD family member 3 (SMAD3). It was validated through the chromatin immunoprecipitation assay that SMAD3 can bind to the VDR promoter and VDR can bind to the SMAD3 promoter. Collectively, these findings provide evidence that reciprocal activation between SMAD3 and VDR transcription factors defines vitamin D-mediated oxidative stress to prevent cerebral I/R injury.

Abstract 6367: Activation of vitamin D/VDR signaling reverses gemcitabine resistance of pancreatic cancer cells through inhibition of MUC1 expression

Abstract Objective: Pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis, largely due to its resistance to currently available therapies. Identifying the determinants of and signaling pathways regulating this resistance is essential for the development of effective therapeutic modalities to improve the outcome of PDA. The purpose of this study is to define the role of vitamin D/VDR signaling and underlying mechanisms in PDA pathogenesis and therapeutic resistance. Materials &amp; Methods: We used an unbiased reverse phase protein array (RPPA) to identify Vitamin D3 downstream molecules; we also used a variety of cellular and molecular biological approaches to determine the impact of vitamin D/VDR signaling on the expression of MUC1 mucin and the cellular response to gemcitabine treatment in PDA cells. We used in vivo experimental systems to determine the effect of combination use of gemcitabine with Vitamin D analogue on pancreatic tumorigenicity. Additionally, we used ultra-high resolution mass spectrometry (HRMS) to analyze the relative abundance of intracellular dFdCTP in tumor tissue samples. Results: We identified that MUC1 protein expression was significantly reduced in AsPC-1 human pancreatic cancer cells after treatment with vitamin D3 or its analogue calcipotriol (Cal) by the RPPA analysis, which was further confirmed in MiaPaca-2 and Colo357 pancreatic cancer cells. VDR negatively regulated MUC1 expression in pancreatic cancer cells in both gain- and loss-of-function assays. We established gemcitabine (Gem) resistant AsPC-1-GemR and Colo357-GemR cells and found that AsPC-1-GemR and Colo357-GemR cells had much lower levels of VDR but higher levels of MUC1 protein expression compared to their parental cells, Vitamin D3 or its analogue significantly induced VDR and inhibited MUC1 expression in AsPC-1-GemR and Colo357-GemR cells, and sensitized the resistant cells to gemcitabine treatment. The results of siRNA knockdown experiments indicated that inhibition of MUC1 expression was essential for Cal’s sensitization of PDA cells to Gem treatment in vitro. In keeping with these findings, administration of the Vitamin D3 analogue, paricalcitol (PA) significantly enhanced the therapeutic efficacy of Gem compared to chemotherapy alone in xenograft and syngeneic mouse models of pancreatic cancer without any significant systemic toxicity. The improved combination treatment correlated with increased intratumoral concentration of dFdCTP, the biological active metabolite of gemcitabine. Conclusions: This study reveals a previously unidentified vitamin D/VDR-MUC1 signaling pathway involved in the regulation of gemcitabine resistance of PDA. Our results suggest that combinational therapies which include targeted activation of vitamin D/VDR signaling may improve the outcomes of patients with PDA. Citation Format: Daoyan Wei, Margarete Hafley, Liang Wang, Yi Liu, Peiying Yang, Xiangsheng Zuo, Robert S. Bresalier. Activation of vitamin D/VDR signaling reverses gemcitabine resistance of pancreatic cancer cells through inhibition of MUC1 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6367.

Activation of vitamin D receptor inhibits Tau phosphorylation is associated with reduction of iron accumulation in APP/PS1 transgenic mice

Vitamin D deficiency and iron accumulation are prevalent in the brains of Alzheimer's disease (AD) patients, however, whether Vitamin D has a role in the regulations of iron metabolism in the condition of AD remains unknown. Our previous studies revealed that vitamin D deficiency promotes β-amyloid (Aβ) deposition in the APP/PS1 mouse brains, while supplemented with a specific agonist of vitamin D receptor (VDR), paricalcitol (PAL), significantly reduced Aβ production via promoting the lysosomal degradation of β-site APP cleavage enzyme 1 (BACE1). In this study, our data suggested that activation of VDR by PAL significantly reduced the iron accumulation in the cortex and hippocampus of APP/PS1 mice through downregulation of Transferrin receptor (TFR) by reducing iron-regulatory protein 2 (IRP2) expression. Furthermore, activation of VDR effectively reduced the phosphorylations of Tau at Ser396 and Thr181 sites via inhibiting the GSK3β phosphorylation (Tyr216). Taken together, our data suggest that activation of VDR could inhibit the phosphorylations of Tau possibly by repressing the iron accumulation-induced upregulation of GSK3β activity in the brains of APP/PS1 mice. Thus, activation of VDR may be an effective strategy for treating AD.

Effect of Early and Delayed Commencement of Paricalcitol in Combination with Enalapril on the Progression of Experimental Polycystic Kidney Disease.

Vitamin D secosteroids are intranuclear regulators of cellular growth and suppress the renin-angiotensin system. The aim of this study was to test the hypothesis that the vitamin D receptor agonist, paricalcitol (PC), either alone or with enalapril (E) (an angiotensin-converting enzyme inhibitor), reduces the progression of polycystic kidney disease. Preventative treatment of Lewis polycystic kidney (LPK) and Lewis control rats with PC (0.2 μg/kg i.p. 5 days/week) or vehicle from postnatal weeks 3 to 10 did not alter kidney enlargement. To evaluate the efficacy in established disease, LPK rats received either PC (0.8 μg/kg i.p; 3 days/week), vehicle, E (50 mg/L in water) or the combination of PC + E from weeks 10 to 20. In established disease, PC also did not alter the progression of kidney enlargement, kidney cyst growth or decline in renal function in LPK rats. Moreover, the higher dose of PC was associated with increased serum calcium and weight loss. However, in established disease, the combination of PC + E reduced systolic blood pressure and heart-body weight ratio compared to vehicle and E alone (p < 0.05). In conclusion, the combination of PC + E attenuated cardiovascular disease but caused hypercalcaemia and did not alter kidney cyst growth in LPK rats.

Evaluation of the protective effect of paricalcitol and vitamin D3 at doxorubicin nephrotoxicity in rats with 99mTechnetium-dimercaptosuccinic acid renal scintigraphy and biochemical methods.

The present study aimed to examine the effect of paricalcitol (PRC) and vitamin D3 (vit D3) on doxorubicin (DOX)-induced nephrotoxicity in rats. Forty-two Wistar rats were randomly categorized into six groups: control; 2) PRC(0.5 µg/kg) and 3) vit D3(5.000 IU/kg) administered for 14 days; 4) DOX, 18 mg/kg administered on the 12th, 13th and 14th days of the study; 5) PRC (0.5 µg/kg, +DOX(18 mg/kg); vit D3(5.000 IU)+DOX(18 mg/kg). On the 15th day of the experiment, 99mTc-DMSA uptake level and biochemical parameter in serum and tissue were assay. Activities of 99mTechnetium-Dimercaptosuccinic Acid (99mTc-DMSA) were lower in groups receiving DOX and/or PRC+DOX, vit D3+DOX than in control groups. The 99mTc-DMSA level in the group PRC+DOX and vit D3+DOX were importantly higher than DOX group. DOX caused an important increase in blood urea nitrogen (BUN), creatinine, Tumor Necrosis Factor-α(TNF- α), interleukin-6(IL-6) and nitric oxide(NO) levels compared to control groups. However, PRC and vit D3 pretreatments lowered them. Uptake of 99mTc-DMSA level was higher in groups PRC+DOX than in vit D3+DOX group. Administration of PRC and vit D3 alone did not change alterations all of parameters. The results indicated that PRC administration protects kidney in DOX-induced nephrotoxic rats. In addition, PRC has a stronger nephroprotective effect than vit D3.

Antifibrotic effects of hypocalcemic vitamin D analogs in murine and human hepatic stellate cells and in the CCl4 mouse model

Liver cirrhosis is a life-threatening consequence of liver fibrosis. The aim of this study was to investigate the antifibrotic potential of clinically available vitamin D analogs compared to that of calcitriol in vitro and in vivo. Murine hepatic stellate cells, Kupffer cells, and human LX-2 cells were treated with vitamin D analogs, and the profibrotic behavior of these cells was studied. In vivo liver fibrosis was induced using CCl4 until measurable fibrosis was established. Animals were then treated with calcitriol and paricalcitol. Vitamin D and its analogs showed antifibrotic effects in vitro. Treatment with active vitamin D (calcitriol, CAL) and its analogs reduced the protein expression of α-smooth muscle actin (α-SMA) in mHSC. In human LX-2 cells alfacalcidol reduced transforming growth factor-β (TGF-β) induced platelet-derived growth factor receptor-β protein expression and contractility while paricalcitol (PCT), in its equipotent dose to CAL, reduced TGF-β induced α-SMA protein expression, and ACTA2 and TGF-β mRNA expression. No effects of a treatment with vitamin D and its analogs were observed in Kupffer cells. In vivo, PCT-treated mice had significantly lower calcium levels than CAL-treated mice. CAL and PCT reduced the hepatic infiltration of CD11b-positive cells and alanine transaminase levels, while PCT but not CAL significantly inhibited fibrosis progression, with a favorable side effect profile in the CCl4 model. We conclude that hypocalcemic vitamin D analogs should be considered in future studies investigating vitamin D for the treatment of liver fibrosis.

Effects of vitamin D and paricalcitol on epileptogenesis and behavioral properties of WAG/Rij rats with absence epilepsy

AimVitamin D (Vit D) has been considered as a neurosteroid and has a pivotal role in neuroprotection including epilepsy. Vit D regulator acts via a Vit D receptor (VDR). WAG/Rij rats have a genetically epileptic model of absence epilepsy with comorbidity of depression. The aim of the present study was to investigate the effect of Vit D and paricalcitol (PRC) on WAG/Rij rats. Material and methodsSixty-three male WAG/Rij rats and seven male Wistar rats were used. The effects of acute and chronic treatment with Vit D (5.000 and 60.000 IU/kg, i.p) and PRC (0.5, 5 and 10 μg/kg, i.p) on absence seizures, and related psychiatric comorbidity were investigated in WAG/Rij rats. Depression-like behavior was assayed by using the forced swimming test (FST) and; anxiety-like behavior by using the open field test (OFT). ResultsAcute Vit D treatments (5.000 and 60.000 IU/kg) similarly reduced the number and duration of spike-wave discharges (SWDs) and showed anxiolytic-antidepressive effect whereas there were no significant changes in other measured parameters between the daily and the bolus dose of Vit D. Acute administration of PRC (0.5, 5 and 10 μg/kg) showed anti-convulsive and anxiolytic-antidepressive effect. The dose (0.5 μg/kg) of PRC was the most effective dose. Chronic treatment was more effective than acute therapy in all parameters. ConclusionThe results of the present study demonstrate that Vit D and PRC have antiepileptic and anxiolytic-antidepressive effects on the absence epilepsy in WAG/Rij rats.

Paricalcitol accelerates BACE1 lysosomal degradation and inhibits calpain-1 dependent neuronal loss in APP/PS1 transgenic mice.

BackgroundRecent studies have revealed that vitamin D deficiency may increase the risk of Alzheimer's disease, and vitamin D supplementation may be effective strategy to ameliorate the neurodegenerative process in Alzheimer's disease patients. Paricalcitol (PAL), a low-calcemic vitamin D receptor agonist, is clinically used to treat secondary hyperparathyroidism. However, the potential application of PAL for treating neurodegenerative disorders remains unexplored.MethodsThe APP/PS1 mice were intraperitoneally injected with PAL or vehicle every other day for 15 weeks. The β-amyloid (Aβ) production was confirmed using immunostaining and enzyme linked immunosorbent assay. The underlying mechanism was verified by western blot and immunostaining in vivo and in vitro.FindingsLong-term PAL treatment clearly reduced β-amyloid (Aβ) generation and neuronal loss in APP/PS1 transgenic mouse brains. PAL stimulated the expression of low-density lipoprotein receptor-related protein 1 (LRP1) possibly through inhibiting sterol regulatory element binding protein-2 (SREBP2); PAL also promoted LRP1-mediated β-site APP cleavage enzyme 1 (BACE1) transport to late endosomes, thus increasing the lysosomal degradation of BACE1. Furthermore, PAL diminished 8-hydroxyguanosine (8-OHdG) generation in neuronal mitochondria via enhancing base excision repair (BER), resulting in the attenuation of calpain-1-mediated neuronal loss.InterpretationThe present data demonstrate that PAL can reduce Aβ generation through accelerating BACE1 lysosomal degradation and can inhibit neuronal loss through suppressing mitochondrial 8-OHdG generation. Hence, PAL might be a promising agent for treating Alzheimer's disease.FundThis study was financially supported by the Natural Science Foundation of China (U1608282).

Paricalcitol Accelerates BACE1 Lysosomal Degradation and Inhibits Calpain-1 Dependent Neuronal Loss in APP/PS1 Transgenic Mice

Abstract Background Recent studies have revealed that vitamin D deficiency may increase the risk of Alzheimer's disease, and vitamin D supplementation may be effective strategy to ameliorate the neurodegenerative process in Alzheimer's disease patients. Paricalcitol (PAL), a low-calcemic vitamin D receptor agonist, is clinically used to treat secondary hyperparathyroidism. However, the potential application of PAL for treating neurodegenerative disorders remains unexplored. Methods The APP/PS1 mice were intraperitoneally injected with PAL or vehicle every other day for 15 weeks. The β-amyloid (Aβ) production was confirmed using immunostaining and enzyme linked immunosorbent assay. The underlying mechanism was verified by western blot and immunostaining in vivo and in vitro. Findings Long-term PAL treatment clearly reduced β-amyloid (Aβ) generation and neuronal loss in APP/PS1 transgenic mouse brains. PAL stimulated the expression of low-density lipoprotein receptor-related protein 1 (LRP1) possibly through inhibiting sterol regulatory element binding protein-2 (SREBP2); PAL also promoted LRP1-mediated β-site APP cleavage enzyme 1 (BACE1) transport to late endosomes, thus increasing the lysosomal degradation of BACE1. Furthermore, PAL diminished 8-hydroxyguanosine (8-OHdG) generation in neuronal mitochondria via enhancing base excision repair (BER), resulting in the attenuation of calpain-1-mediated neuronal loss. Interpretation The present data demonstrate that PAL can reduce Aβ generation through accelerating BACE1 lysosomal degradation and can inhibit neuronal loss through suppressing mitochondrial 8-OHdG generation. Hence, PAL might be a promising agent for treating Alzheimer's disease. Fund This study was financially supported by the Natural Science Foundation of China (U1608282).

Vitamin D receptor activation raises soluble thrombomodulin levels in chronic kidney disease patients: a double blind, randomized trial.

Thrombomodulin (TM) is a proteoglycan highly represented in the endothelial glycocalix that regulates the haemostasis and the endothelial response to inflammation. High soluble TM levels underlie a lower risk for coronary heart disease in population studies. Activation of vitamin D receptor (VDR) upregulates TM, but the effect of this intervention on soluble TM has never been tested in chronic kidney disease (CKD) patients. We performed a post hoc analysis of a 12 weeks double blind, randomized, placebo-controlled trial testing the effect of VDR activation by paricalcitol (PCT) on endothelium-dependent flow-mediated vasodilatation (FMD) in the forearm (ClinicalTrials.gov identifier: NCT01680198). Circulating TM was measured in the whole CKD population [88 patients: PCT n = 44; placebo n = 44] that took part into this trial. Soluble TM at baseline was inversely related to the glomerular filtration rate (r = -0.65, P < 0.001) and to FMD (Spearman's ρ = -0.29, P = 0.01). Alongside the expected effects on bone mineral biomarkers, PCT produced a consistent rise (P = 0.005) in TM levels, from a median value of 8446.0 pg/mL [interquartile range (IQR): 6227.8-10 910.8 pg/mL] to 9127.5 pg/mL (6393.0-11 287.3 pg/mL) while placebo had no effect (between-groups difference P = 0.008). TM levels re-approached baseline values 2 weeks after stopping PCT. TM changes across the trial paralleled simultaneous changes in FMD. VDR activation by PCT raises TM levels and FMD and such effects are rapidly reversible after stopping the treatment. The TM rise induced by PCT is a possible mechanism whereby improvement in endothelial function by VDR activation may favourably impact upon vascular health in CKD patients.

Paricalcitol and albuminuria: tread carefully

Paricalcitol and albuminuria: tread carefully

Experimental Autoimmune Encephalomyelitis Is Successfully Controlled by Epicutaneous Administration of MOG Plus Vitamin D Analog.

Multiple sclerosis (MS) is an inflammatory and demyelinating disorder of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) has been widely employed to evaluate new strategies to control MS, including procedures to induce immunological tolerance. Considering that skin exposure to protein antigens can induce tolerance and that vitamin D analogs conserve immunomodulatory potential and are less toxic, we investigated the efficacy of epicutaneous application of a myelin oligodendrocyte glycoprotein peptide (MOG35–55) associated with paricalcitol (PARI) on EAE development. Three and 11 days after EAE induction, C57BL/6 mice were treated with an occlusive patch containing MOG plus PARI. Clinical parameters were daily assessed, whereas immunological and histological evaluations were performed during the acute EAE phase. MOG and MOG + PARI significantly controlled disease development reducing weight loss and clinical score. Moreover, MOG and MOG + PARI reduced the inflammatory process and preserved the myelin sheath in the CNS. High percentages of Foxp3+ regulatory T cells (Tregs) and lower MHCII fluorescence intensity in dendritic cells in draining lymph nodes were concomitantly observed. MOG + PARI association was, however, more efficient being able to reduce disease incidence and clinical scores more significantly than MOG or PARI alone. This experimental group also displayed a higher ratio between mRNA expression for Foxp3 and RORc and a higher percentage of Foxp3+ cells in the CNS. Modulation of activation markers observed in microglial cells eluted from EAE treated mice were confirmed by in vitro studies with the BV-2 microglial cell line. The results show that MOG + PARI association applied by an epicutaneous route controlled EAE development. Protective involved mechanisms include mainly a higher proportion of Tregs and also a direct immunomodulatory effect of PARI on microglial cells.

Paricalcitol Versus Calcifediol for Treating Hyperparathyroidism in Kidney Transplant Recipients

IntroductionSecondary hyperparathyroidism (SHPT) and vitamin D deficiency are common at kidney transplantation and are associated with some early and late complications. This study was designed to evaluate whether paricalcitol was more effective than nutritional vitamin D for controlling SHPT in de novo kidney allograft recipients.MethodsThis was a 6-month, investigator-initiated, multicenter, open-label, randomized clinical trial. Patients with pretransplantation iPTH between 250 and 600 pg/ml and calcium <10 mg/dl were randomized to paricalcitol (PAR) or calcifediol (CAL). The intention-to-treat population (PAR: n = 46; CAL: n = 47) was used for the analysis. The primary endpoint was the percentage of patients with serum iPTH >110 pg/ml at 6 months. Secondary endpoints were bone mineral metabolism, renal function, and allograft protocol biopsies.ResultsThe primary outcome occurred in 19.6% of patients in the PAR group and 36.2% of patients in the CAL group (P = 0.07). However, there was a higher percentage of patients with iPTH <70 pg/ml in the PAR group than in the CAL group (63.4% vs. 37.2%; P = 0.03). No differences were observed in bone turnover biomarkers and bone mineral density. The estimated glomerular filtration rate was significantly higher in the CAL group than in the PAR group without differences in albuminuria. In protocol biopsies, interstitial fibrosis and tubular atrophy tended to be higher in the PAR group than in the CAL group (48% vs. 23.8%; P = 0.09). Both medications were well tolerated.ConclusionBoth PAR and CAL reduced iPTH, but PAR was associated with a higher proportion of patients with iPTH <70 pg/ml. These results do not support the use of PAR to treat posttransplantation hyperparathyroidism.

High phosphate induces a pro-inflammatory response by vascular smooth muscle cells and modulation by vitamin D derivatives

In chronic kidney disease patients, high phosphate (HP) levels are associated with cardiovascular disease, the major cause of morbidity and mortality. Since serum phosphate has been independently correlated with inflammation, the present study aimed to investigate an independent direct effect of HP as a pro-inflammatory factor in VSMCs. A possible modulatory effect of vitamin D (VitD) was also investigated. The study was performed in an in vitro model of human aortic smooth muscle cells (HASMCs). Incubation of cells in an HP (3.3 mM) medium caused an increased expression of the pro-inflammatory mediators intercellular adhesion molecule 1 (ICAM-1), interleukins (ILs) IL-1β, IL-6, IL-8 and tumour necrosis factor α (TNF-α) (not corroborated at the protein levels for ICAM-1), as well as an increase in reactive oxygen/nitrogen species (ROS/RNS) production. This was accompanied by the activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signalling as demonstrated by the increase in the nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells protein 65 (p65-NF-κΒ) assessed by Western blotting and confocal microscopy. Since all these events were attenuated by an antioxidant pre-incubation with the radical scavenger Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), it is suggested that the inflammatory response is upstream mediated by the ROS/RNS-induced activation of NF-κΒ. Addition of paricalcitol (PC) 3·10-8 M to cells in HP prevented the phosphate induced ROS/RNS increase, the activation of NF-κΒ and the cytokine up-regulation. A bimodal effect was observed, however, for different calcitriol (CTR) concentrations, 10-10 and 10-12 M attenuated but 10-8 M stimulated this phosphate induced pro-oxidative and pro-inflammatory response. Therefore, these findings provide novel mechanisms whereby HP may directly favour vascular dysfunctions and new insights into the protective effects exerted by VitD derivatives.

Regulatory effect of vitamin D on the expression of occludin in the intestinal epithelial cells of neonatal rats with necrotizing enterocolitis

Objective To investigate the expression of occludin in the intestinal epithelial cells of neonatal rats with necrotizing enterocolitis (NEC). The influence of vitamin D on NEC and the expression of occludin was also explored. Methods Sixty neonatal Wistar rats from different litters were divided into four groups 48 hours after birth: 10 in the breast-fed+ control group, 10 in the breast-fed + vitamin D group, 20 in the NEC+ control group and 20 in the NEC+ vitamin D group.In groups with NEC, neonatal rats were separated from their mothers and treated with rat milk substitute+ hypoxia+ hypothermia.In groups with vitamin D treatment, paricalcitol was given through intraperitoneal injection 30 minutes before, one day and two days after the induction of NEC.The tissue was harvested from the ileum of the rats 72 hours after induction of NEC.Microscopically, the tissue was assessed according to the Nadler scoring system.The expression and location of occludin was observed after immunofluorescence staining.Western blotting was performed and quantified to compare the expression of occludin among groups. Results In NEC rats, the intestinal structure was destructed.Separation of the submucosal or muscular layer, discharge or disappearance of the villa was accompanied by necrosis of the intestinal cells.Vitamin D treatment could significantly alleviate those changes, with the Nadler score 1.70±0.21 compared to 2.90±0.23 without vitamin D treatment(P<0.01). The expression of occludin was decreased in NEC rats and vitamin D could partly rescue this decrease(P<0.01). The distribution of occludin was sparse and discontinuous in NEC rats while after vitamin D treatment, the distribution was maintained even and continuous. Conclusion The expression of occludin in intestinal epithelial cells is significantly reduced in NEC rat.Vitamin D treatment may inhibit the development of NEC by maintaining the expression of occludin. Key words: Occludin; Intestinal epithelial cells; Vitamin D; Necrotizing enterocolitis