Selective vitamin D receptor activation as anti-inflammatory target in chronic kidney disease

Salt stress perception and metabolic regulation network analysis of a marine probiotic Meyerozyma guilliermondii GXDK6

Introduction

Extremely salt-tolerant microorganisms play an important role in the development of functional metabolites or drug molecules.

Methods

In this work, the salt stress perception and metabolic regulation network of a marine probiotic Meyerozyma guilliermondii GXDK6 were investigated using integrative omics technology.

Results

Results indicated that GXDK6 could accept the salt stress signals from signal transduction proteins (e.g., phosphorelay intermediate protein YPD1), thereby contributing to regulating the differential expression of its relevant genes (e.g., CTT1, SOD) and proteins (e.g., catalase, superoxide dismutase) in response to salt stress, and increasing the salt-tolerant viability of GXDK6. Omics data also suggested that the transcription (e.g., SMD2), translation (e.g., MRPL1), and protein synthesis and processing (e.g., inner membrane protein OXA1) of upregulated RNAs may contribute to increasing the salt-tolerant survivability of GXDK6 by improving protein transport activity (e.g., Small nuclear ribonucleoprotein Sm D2), anti-apoptotic ability (e.g., 54S ribosomal protein L1), and antioxidant activity (e.g., superoxide dismutase). Moreover, up to 65.9% of the differentially expressed genes/proteins could stimulate GXDK6 to biosynthesize many salt tolerant-related metabolites (e.g., β-alanine, D-mannose) and drug molecules (e.g., deoxyspergualin, calcitriol), and were involved in the metabolic regulation of GXDK6 under high NaCl stress.

Discussion

This study provided new insights into the exploration of novel functional products and/or drugs from extremely salt-tolerant microorganisms.Graphical Abstract.

Quercetin activates vitamin D receptor and ameliorates breast cancer induced hepatic inflammation and fibrosis

Aims

To explore the hepatoprotective role of quercetin and its novel molecular mechanism of action on breast cancer associated hepatic inflammation and fibrosis via Vitamin D receptor (VDR).

Main methods

We used Ehrlich Ascites Carcinoma (mouse mammary carcinoma) model for our in-vivo experiments and human breast cancer cell lines for in-vitro assays. We inoculated 1.5 × 10⁶ Ehrlich ascites carcinoma cells into female Swiss albino mice. Quercetin (50 mg/kg) was administered intraperitoneally for 15 days. Liver enzymes activity was determined using a spectrophotometric assay. The hallmarks of inflammation and fibrosis were determined using Immunohistochemistry. The effect of quercetin on tumor formation was elucidated using human breast cancer cell lines and chick chorioallantoic membrane assay. Docking study was performed to explore the binding mode of quercetin with VDR.

Key findings

In EAC tumor-bearing mice, cell numbers, tumor volume, body weight and liver weight were dramatically increased, while they significantly decreased in mice treated with quercetin. Additionally, the peritoneal neo-angiogenesis was also significantly suppressed in the quercetin-treated mice, compared to the control. In addition, quercetin treated EAC tumor bearing mice had lower levels of liver enzymes, decreased hepatic inflammation and fibrosis compared with EAC tumor bearing mice. Docking study confirmed VDR-quercetin interaction. Furthermore, in-vitro assays and chick chorioallantoic membrane assay revealed the Vitamin D mimicking effect of quercetin.

Significance

Dietary flavonoid, quercetin could act as a promising therapeutic drug to suppress the breast cancer induced tumor angiogenesis, hepatic inflammation, and fibrosis possibly via activation of VDR.

Paricalcitol inhibits oxidative stress-induced cell senescence of the bile duct epithelium dependent on modulating Sirt1 pathway in cholestatic mice

BACKGROUND

Clinical studies indicate that vitamin D receptor (VDR) expression is reduced in primary biliary cirrhosis patient livers. However, the mechanism by which activated VDR effect cholestatic liver injury remains unclear.

METHODS

Mice were injected intraperitoneally with the VDR agonist paricalcitol or a vehicle 3 days prior to bile duct ligation (BDL) and for 5 or 28 days after surgery. The analyses of liver morphology and necrotic areas were based on H&E staining. Serum biochemical indicators of liver damage were analyzed by commercial kits. The mechanisms of paricalcitol on cholestatic liver injury were determined by Western blot analysis.

RESULTS

Paricalcitol ameliorated the BDL-induced liver damage in mice. Paricalcitol increased the proliferation of BECs to promote the repair of the bile duct. Paricalcitol also reduced the BDL-induced oxidative stress level in the mice. Mechanistic analysis revealed that paricalcitol decreased the number of SA-β-gal-positive cells and downregulated the expression of p53, p21 and p16 proteins which was associated with reducing oxidative stress. Additionally, paricalcitol exerted the inhibitory effect of cell senescence was through reducing DNA damage and promoting DNA repair. Interesting, we found that paricalcitol prevented the downregulation of oxidative stress-induced Sirt1 expression in the BDL mice and t-BHP-induced BECs models. Moreover, paricalcitol suppressed cell senescence through a Sirt1-dependent pathway. These results were confirmed by antioxidant ALCAR and the Sirt1 inhibitor EX-527.

CONCLUSION

Paricalcitol alleviated cholestatic liver injury through promoting the repair of damaged bile ducts and reducing oxidative stress-induced cell senescence of the bile duct via modulating Sirt1 pathway.

Vitamin D and Glomerulonephritis

Vitamin D presents a plethora of different functions that go beyond its role in skeletal homeostasis. It is an efficient endocrine regulator of the Renin–Angiotensin–Aldosterone System (RAAS) and erythropoiesis, exerts immunomodulatory effects, reduces the cardiovascular events and all-cause mortality. In Chronic Kidney Disease (CKD) patients, Vitamin D function is impaired; the renal hydrolyzation of its inactive form by the action of 1α-hydroxylase declines at the same pace of reduced nephron mass. Moreover, Vitamin D major carrier, the D-binding protein (DBP), is less represented due to Nephrotic Syndrome (NS), proteinuria, and the alteration of the cubilin–megalin–amnionless receptor complex in the renal proximal tubule. In Glomerulonephritis (GN), Vitamin D supplementation demonstrated to significantly reduce proteinuria and to slow kidney disease progression. It also has potent antiproliferative and immunomodulating functions, contributing to the inhibitions of kidney inflammation. Vitamin D preserves the structural integrity of the slit diaphragm guaranteeing protective effects on podocytes. Activated Vitamin D has been demonstrated to potentiate the antiproteinuric effect of RAAS inhibitors in IgA nephropathy and Lupus Nephritis, enforcing its role in the treatment of glomerulonephritis: calcitriol treatment, through Vitamin D receptor (VDR) action, can regulate the heparanase promoter activity and modulate the urokinase receptor (uPAR), guaranteeing podocyte preservation. It also controls the podocyte distribution by modulating mRNA synthesis and protein expression of nephrin and podocin. Maxalcalcitol is another promising alternative: it has about 1/600 affinity to vitamin D binding protein (DBP), compared to Calcitriol, overcoming the risk of hypercalcemia, hyperphosphatemia and calcifications, and it circulates principally in unbound form with easier availability for target tissues. Doxercalciferol, as well as paricalcitol, showed a lower incidence of hypercalcemia and hypercalciuria than Calcitriol. Paricalcitol demonstrated a significant role in suppressing RAAS genes expression: it significantly decreases angiotensinogen, renin, renin receptors, and vascular endothelial growth factor (VEGF) mRNA levels, thus reducing proteinuria and renal damage. The purpose of this article is to establish the Vitamin D role on immunomodulation, inflammatory and autoimmune processes in GN.

Vitamin D supplementation for the improvement of vascular function in patients with chronic kidney disease: a meta-analysis of randomized controlled trials

BACKGROUND

The efficacy of vitamin D on vascular function remains controversial in chronic kidney disease (CKD) patients. The aim of the present work was to perform a meta-analysis of randomized controlled trials to evaluate the efficacy of vitamin D on vascular function in CKD patients.

METHODS

We searched Medline, the Cochrane Central Register of Controlled Trials, Embase, the Science Citation Index, and clinical trial registries for randomized controlled trials comparing vitamin D with a placebo in CKD patients.

RESULTS

We included seven trials. For flow-mediated dilation (FMD), there was no significant difference between the two groups (WMD 1.66%; 95% CI - 0.2 to 3.51, p = 0.08; with significant heterogeneity, p < 0.0001, I² = 89%). We conducted a subgroup analysis. In the cholecalciferol group, compared with the placebo group, cholecalciferol significantly increased FMD (WMD 5.49%; 95% CI 4.36-6.62, p < 0.0001). In the 2 ug paricalcitol group, compared with the placebo group, paricalcitol significantly increased FMD (WMD 2.09%; 95% CI 1.28-2.9, p < 0.0001; without significant heterogeneity, p = 0.47, I² = 0%). In the 1 ug paricalcitol group, there was no significant difference between the two groups. For pulse wave velocity (PWV), vitamin D significantly decreased PWV compared with the placebo (WMD - 0.93 m/s; 95% CI - 1.71 to - 0.15, p = 0.02; without significant heterogeneity, p = 0.14, I² = 45%). For calcium (Ca) and parathyroid hormone (PTH), there was a significant difference between the vitamin D group and the placebo group. For 25-hydroxyvitamin D [25(OH)D], there was a significant difference between the inactive vitamin D group and the placebo group. For phosphorus (P), systolic blood pressure (SBP), and diastolic blood pressure (DBP), there were no significant differences between the two groups.

CONCLUSIONS

We speculate that vitamin D might be able to improve vascular function in CKD patients. The effect of vitamin D might be associated with its doses and earlier stages of the disease might respond better to vitamin D. Furthermore, trials with larger populations and longer durations are needed in order to provide more reliable evidence.

Anti-inflammatory profile of paricalcitol in kidney transplant recipients

BACKGROUND AND OBJECTIVES

Paricalcitol, a selective vitamin D receptor activator, is used to treat secondary hyperparathyroidism in kidney transplant patients. Experimental and clinical studies in non-transplant kidney disease patients have found this molecule to have anti-inflammatory properties. In this exploratory study, we evaluated the anti-inflammatory profile of paricalcitol in kidney-transplant recipients.

METHODS

Thirty one kidney transplant recipients with secondary hyperparathyroidism completed 3 months of treatment with oral paricalcitol (1μg/day). Serum concentrations and gene expression levels of inflammatory cytokines in peripheral blood mononuclear cells were analysed at the beginning and end of the study.

RESULTS

Paricalcitol significantly decreased parathyroid hormone levels with no changes in calcium and phosphorous. It also reduced serum concentrations of interleukin (IL)-6 and tumour necrosis factor-alpha (TNF-α) by 29% (P<0.05) and 9.5% (P<0.05) compared to baseline, respectively. Furthermore, gene expression levels of IL-6 and TNF-α in peripheral blood mononuclear cells decreased by 14.1% (P<0.001) and 34.1% (P<0.001), respectively. The ratios between pro-inflammatory cytokines (TNF-α and IL-6) and anti-inflammatory cytokines (IL-10), both regarding serum concentrations and gene expression, also experienced a significant reduction.

CONCLUSIONS

Paricalcitol administration to kidney transplant recipients has been found to have beneficial effects on inflammation, which may be associated with potential clinical benefits.

Early introduction of oral paricalcitol in renal transplant recipients. An open-label randomized study

In stable renal transplant recipients with hyperparathyroidism, previous studies have indicated that vitamin D agonist treatment might have anti-proteinuric effects. Animal studies indicate possible anti-fibrotic and anti-inflammatory effects. Early introduction of paricalcitol in de novo renal transplant recipients might reduce proteinuria and prevent progressive allograft fibrosis. We performed a single-center, prospective, randomized, open-label trial investigating effects of paricalcitol 2 μg/day added to standard care. Participants were included 8 weeks after engraftment and followed for 44 weeks. Primary end point was change in spot urine albumin/creatinine ratio. Exploratory microarray analyses of kidney biopsies at study end investigated potential effects on gene expression. Secondary end points included change in glomerular filtration rate (GFR), pulse wave velocity (PWV), and endothelial function measured by peripheral arterial tonometry as reactive hyperemia index (RHI). Seventy-seven de novo transplanted kidney allograft recipients were included, 37 receiving paricalcitol. Paricalcitol treatment lowered PTH levels (P = 0.01) but did not significantly reduce albuminuria (P = 0.76), change vascular parameters (PWV; P = 0.98, RHI; P = 0.33), or influence GFR (P = 0.57). Allograft gene expression was not influenced. To summarize, in newly transplanted renal allograft recipients, paricalcitol reduced PTH and was well tolerated without negatively affecting kidney function. Paricalcitol did not significantly reduce/prevent albuminuria, improve parameters of vascular health, or influence allograft gene expression.

Effect of Paricalcitol on FGF-23 and Klotho in Kidney Transplant Recipients

BACKGROUND

Paricalcitol decreases intact parathyroid hormone and the frequency of secondary hyperparathyroidism after kidney transplantation. This proof-of-concept study aimed to assess the effect of paricalcitol on fibroblast growth factor-23/KLOTHO axis in renal transplants.

METHODS

Twenty-nine subjects with secondary hyperparathyroidism received oral paricalcitol 1 μg/d for 3 months, and 8 patients matched by age, sex, and creatinine clearance, but with intact parathyroid hormone less than 100 pg/mL, were included as controls.

RESULTS

Intact parathyroid hormone decreased in paricalcitol-treated patients (P < 0.0001). Serum fibroblast growth factor-23 enhanced (P < 0.01), whereas KLOTHO concentrations showed a trend to increase (P = 0.067). KLOTHO gene expression in peripheral blood mononuclear cells increased by 45.7% in paricalcitol-treated patients (P < 0.01), without change in controls. Paricalcitol administration resulted in a median percent decrease of 56% in methylated DNA levels of KLOTHO promoter (P < 0.001). The ratio of the unmethylated/methylated KLOTHO promoter DNA did not change in controls, but it increased by 177% in paricalcitol-treated subjects (P < 0.0001). The increase in this ratio was independently associated with the change in serum KLOTHO (r = 0.55, P < 0.01) and messenger RNA expression levels (r = 0.40, P < 0.05).

CONCLUSIONS

Paricalcitol administration to renal transplant patients significantly reduced intact parathyroid hormone and increased fibroblast growth factor-23, with a trend to increase in serum KLOTHO. Paricalcitol-treated patients showed a decrease in the methylation of the KLOTHO promoter with an increment in the ratio of un-methyated/methylated DNA, which was associated with an increase of KLOTHO gene expression levels and serum KLOTHO concentrations. Long-term studies are needed to assess whether paricalcitol-induced increase in KLOTHO gene expression and serum concentrations may translate into beneficial clinical effects.

Decreased Serum 25-hydroxyvitamin D Level Causes Interventricular Septal Hypertrophy in Patients on Peritoneal Dialysis: Cardiovascular Aspects of Endogenous Vitamin D Deficiency

Introduction. In the present study, we aimed to analyze the relation of vitamin D with echocardiographic indexes in patients with end stage renal disease (ESRD) receiving renal replacement therapy (RRT). Methods. A total of 98 patients, 64 patients on hemodialysis (HD) (29F/35M, mean age 56.75 ± 18.63 years) and 34 age matched patients on peritoneal dialysis (PD) (21F/13M, mean age 58.11 ± 10.63 years), with similar duration of ESRD and RRT were enrolled into this cross-sectional study. Echocardiographic examination was performed after dialysis session at normovolemic status. Fasting blood samples were obtained before dialysis session. Results. Patients on PD and female patients in both groups had significantly lower level of 25-OH-D3 level when compared to patients on HD or male patients (p: 0.0001 and p: 0.0001). When all participants were considered, there was no significant association between 25-OH-D3 and echocardiographic parameters; however, in patients on PD, a significant negative correlation was determined between 25-OH-D3 and diastolic blood pressure, interventricular septal hypertrophy (ISH), and left ventricular mass index (LVMI) (r: −0.424, p: 0.012; r: −0.508, p: 0.004; r: 0.489, p: 0.04, resp.). Conclusion. Low serum 25-hydroxyvitamin D levels is associated with ISH and LVMI in PD patients.

Paricalcitol attenuates lipopolysaccharide-induced myocardial inflammation by regulating the NF-κB signaling pathway

Vitamin D deficiency is associated with an increased risk of cardiovascular disease, diabetes, colon and breast cancer, infectious diseases and allergies. Vascular alterations are an important pathophysiological mechanism of sepsis. Experimental data suggest that paricalcitol, a vitamin D2 analogue, exerts beneficial effects on renal inflammation and fibrosis. In the present study, we aimed to investigate the effects of paricalcitol on lipopolysaccharide (LPS)-induced myocardial inflammation and to elucidate the underlying mechanisms. We used primary cultured human umbilical vein endothelial cells for in vitro experiments, in which stimulation with tumor necrosis factor (TNF)-α was used to induce endothelial cell inflammation. For in vivo experiments, myocardial inflammation was induced by an intraperitoneal injection of 15 mg/kg LPS into C57BL6 mice pre-treated with or without 0.2 µg/kg paricalcitol. Treatment with paricalcitol suppressed the TNF-α-induced increase in the protein expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and fractalkine in endothelial cells. Treatment with paricalcitol also decreased the TNF-α-induced nuclear factor (NF)-κB binding activity. In a mouse model of LPS-induced myocardial inflammation, pre-treatment with paricalcitol prevented the LPS-induced increase in the expression of myocardial ICAM-1, phosphorylated p65 and myocardial TNF-α. Pre-treatment with paricalcitol also alleviated endotoxemia‑induced microvascular leakage in the myocardium. The findings of our study suggest that paricalcitol exerts a protective effect against LPS-induced myocardial inflammation by regulating the expression of cell adhesion molecules and TNF-α, and by improving myocardial permeability.

Vitamin D and spondyloarthritis

In cross-sectional studies, vitamin D deficiency is frequent in spondyloarthritic patients and associated with increased spondyloarthritis (SpA) activity and structural damage. Experimental studies also show that vitamin D interferes with molecular pathways critically involved in SpA, especially regarding entheseal inflammation and ossification (involving cytokines such as IL-23 and sclerostin). Vitamin D deficiency might also affect the course of the disease through periodontal and gut inflammation, leading to increased functional impairment. Therefore, Vitamin D receptor selective agonists could represent a promising therapeutic pathway in this pathology. Randomised-controlled intervention studies are required in order to further elucidate complex relationships between vitamin D deficiency and SpA.