25-Hydroxyvitamin D3 attenuates experimental periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in diabetic mice

Vitamin D has been known to be closely associated with diabetes and periodontitis while the underlying mechanism has yet to be clarified. The present study aimed to discover the effect of 25-hydroxyvitamin D3 (25-OHD3) on glycemic control and periodontal health in mice with periodontitis superimposed on experimental diabetes (known as diabetic periodontitis). We showed that 25-OHD3 intraperitoneal injection attenuated diabetic periodontitis by reducing serum fasting blood glucose, glycosylated hemoglobin and TNF-α levels, which led to decreased alveolar bone loss. Immunohistochemical staining and western blot analysis of gingival epithelia revealed that vitamin D receptor (VDR) expression was enhanced upon 25-OHD3 treatment, while toll-like receptor 4 (TLR4) expression was reduced. The expressions of Janus family kinase (JAK) 1 and signal transducer and activator of transcription (STAT) 3 as well as their phosphorylation were inhibited in gingival epithelia of diabetic periodontitis mice, whereas the expression and phosphorylation of STAT1 remained unchanged. These results suggest that 25-OHD3 could improve diabetic periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in the gingival epithelium. Our study extends the previous findings on the regulation of diabetes with periodontitis, and may also provide a potential therapy for the patients with this disease.

25-hydroxyvitamin D3 ameliorates periodontitis by modulating the expression of inflammation-associated factors in diabetic mice

Periodontitis is a complication of diabetes mellitus, and the two diseases are highly associated with the dysfunction of inflammatory mediators. 25-hydroxyvitamin D(3) (25(OH)D(3)) plays a pivotal role in inflammatory modulation, but little is known about its effects on the progression of diabetic periodontitis and the underlying mechanism. In this paper, we showed that 25(OH)D(3) ameliorated experimental periodontitis in diabetic mice. The intraperitoneal administration of 25(OH)D(3) to streptozotocin-induced diabetic mice reduced fasting glucose and serum TNF-α levels, leading to decreased alveolar bone loss. Western blot analyses of gingival epithelia showed that vitamin D receptor (VDR) and protein tyrosine phosphatase N2 (PTPN2) were upregulated, while the expression of NF-κB and the phosphorylation of Janus family kinase 1 (JAK1) were attenuated upon 25(OH)D(3) treatment. These data may provide an explanation for the therapeutic benefits and anti-inflammatory effects of 25(OH)D(3). Our findings should have important implications for the clinical therapy of diabetic periodontitis.

20S-hydroxyvitamin D3, noncalcemic product of CYP11A1 action on vitamin D3, exhibits potent antifibrogenic activity in vivo

CONTEXT

There is no effective treatment for systemic sclerosis and related fibrosing diseases. Recently the action of CYP11A1 on vitamin D(3) was shown to produce biologically active 20S-hydroxyvitamin D [20(OH)D(3)] and 20,23(OH)(2)D(3), 20,22(OH)(2)D(3), and 17,20,23(OH)(3)D(3).

OBJECTIVES

Because 20(OH)D(3) is noncalcemic (nontoxic) in vivo at very high doses, we evaluated its antifibrogenic activities both in vitro and in vivo. Because it is further metabolized by CYP11A1, we also tested preclinical utilities of its hydroxyderivatives, especially 20,23(OH)(2)D(3).

DESIGN

Human dermal fibroblasts from scleroderma and normal donors were used to test the efficiency of hydroxyvitamin D derivatives in inhibiting TGF-β1-induced collagen and hyaluronan synthesis and inhibiting cell proliferation. The in vivo activity of 20(OH)D(3) was tested using bleomycin-induced sclerosis in C57BL/6 mice.

RESULTS

20(OH)D(3) and 20,23(OH)(2)D(3) inhibited TGF-β1-induced collagen and hyaluronan synthesis similarly to 1,25(OH)(2)D(3) in cultured human fibroblasts. Also, 20(OH)D(3), 20,23(OH)(2)D(3), and 1,25(OH)(2)D(3) suppressed TGF-β1-induced expression of COL1A2, COL3A1, and hyaluronan synthase-2 mRNA, indicating that they regulate these matrix components at the transcriptional level. 20(OH)D(3), 20,23(OH)(2)D(3), 20,22(OH)(2)D(3), and 17,20,23(OH)(3)D(3) inhibited proliferation of dermal fibroblasts with comparable potency with 1,25(OH)(2)D(3), with 20(OH)D(2) being less active and 1α(OH)D(3) being almost inactive. 20,23(OH)(2)D(3) at 3 μg/kg had no effect on serum Ca(++) or fibroblast growth factor-23 levels and did not cause any noticeable signs of morbidity. 20(OH)D(3) markedly suppressed fibrogenesis in mice given sc bleomycin as demonstrated by total collagen content and hematoxylin and eosin staining of skin biopsies.

CONCLUSIONS

20(OH)D(3) is an excellent candidate for preclinical studies on scleroderma, with other CYP11A1-derived products of its metabolism deserving further testing for antibrogenic activity.

25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ promote the differentiation of human subcutaneous preadipocytes

1,25(OH)(2)D(3) inhibits adipogenesis in mouse 3T3-L1 adipocytes, but little is known about its effects or local metabolism in human adipose tissue. We showed that vitamin D receptor (VDR) and 1α-hydroxylase (CYP27B1), the enzyme that activates 25(OH)D(3) to 1,25(OH)(2)D(3), were expressed in human adipose tissues, primary preadipocytes and newly-differentiated adipocytes. Preadipocytes and newly-differentiated adipocytes were responsive to 1,25(OH)(2)D(3), as indicated by a markedly increased expression of CYP24A1, a primary VDR target. 1,25(OH)(2)D(3) enhanced adipogenesis as determined by increased expression of adipogenic markers and triglyceride accumulation (50% to 150%). The magnitude of the effect was greater in the absence of thiazolidinediones. 1,25(OH)(2)D(3) was equally effective when added after the removal of differentiation cocktail on day 3, but it had no effect when added only during the induction period (day 0-3), suggesting that 1,25(OH)(2)D(3) promoted maturation. 25(OH)D(3) also stimulated CYP24A1 expression and adipogenesis, most likely through its conversion to 1,25(OH)(2)D(3). Consistent with this possibility, incubation of preadipocytes with 25(OH)D(3) led to 1,25(OH)(2)D(3) accumulation in the media. 1,25(OH)(2)D(3) also enhanced adipogenesis in primary mouse preadipocytes. We conclude that vitamin D status may regulate human adipose tissue growth and remodeling.

25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ promote the differentiation of human subcutaneous preadipocytes

1,25(OH)₂D₃ inhibits adipogenesis in mouse 3T3-L1 adipocytes, but little is known about its effects or local metabolism in human adipose tissue. We showed that vitamin D receptor (VDR) and 1α-hydroxylase (CYP27B1), the enzyme that activates 25(OH)D₃ to 1,25(OH)₂D₃, were expressed in human adipose tissues, primary preadipocytes and newly-differentiated adipocytes. Preadipocytes and newly-differentiated adipocytes were responsive to 1,25(OH)₂D₃, as indicated by a markedly increased expression of CYP24A1, a primary VDR target. 1,25(OH)₂D₃ enhanced adipogenesis as determined by increased expression of adipogenic markers and triglyceride accumulation (50% to 150%). The magnitude of the effect was greater in the absence of thiazolidinediones. 1,25(OH)₂D₃ was equally effective when added after the removal of differentiation cocktail on day 3, but it had no effect when added only during the induction period (day 0–3), suggesting that 1,25(OH)₂D₃ promoted maturation. 25(OH)D₃ also stimulated CYP24A1 expression and adipogenesis, most likely through its conversion to 1,25(OH)₂D₃. Consistent with this possibility, incubation of preadipocytes with 25(OH)D₃ led to 1,25(OH)₂D₃ accumulation in the media. 1,25(OH)₂D₃ also enhanced adipogenesis in primary mouse preadipocytes. We conclude that vitamin D status may regulate human adipose tissue growth and remodeling.

Effects of 25-hydroxyvitamin D3 therapy on bone turnover markers and PTH levels in postmenopausal osteoporotic women treated with alendronate

OBJECTIVE

Our objective was to know the extent to which a fall in bone turnover markers is influenced by serum 25-hydroxyvitamin D (25OHD) levels in patients on alendronate (ALN) treatment.

DESIGN, PARTICIPANTS, AND SETTING

A total of 140 postmenopausal osteoporotic women were randomized to receive either ALN or ALN plus 25OHD(3) (ALN+VitD) over a 3-month period. Serum 25OHD, PTH, C-terminal telopeptide of type I collagen (CTX), and amino-terminal propeptide of type I collagen (P1NP) were measured at baseline and at the end of the 3 months.

RESULTS

25OHD rose four times above baseline levels in the ALN+VitD group, whereas no changes were seen in the ALN group. Administering ALN resulted in a significant decline in both serum CTX (53 ± 24%) and P1NP (46 ± 19%). After ALN+VitD, the fall in CTX amounted to 61 ± 20% (P = 0.06 compared with ALN) and P1NP to 50 ± 23% (P = 0.35). When patients were divided into those below and above 20 ng/ml of baseline serum 25OHD, in those below, CTX decreased by 48 ± 26% in the ALN group and by 61 ± 17% in the ALN+VitD group (P = 0.015). For P1NP, the corresponding figures were 43 ± 20 and 50 ± 23% (P = 0.2). In patients above 20 ng/ml, no differences were seen regarding CTX (58 ± 21% decrease in the ALN group and 60 ± 23% in the ALN+VitD group; P = 0.7) or P1NP (49 ± 18 and 50 ± 20%; P = 0.9).

CONCLUSIONS

Administration of 25OHD(3) is not an indispensable requirement for bisphosphonates to develop their bone antiresorptive effect. In fact, in patients with vitamin D sufficiency, no benefit is observed when the vitamin is added. However, in patients with vitamin D deficiency, an approximately 25% greater fall in the bone resorption marker CTX is seen with its administration.

25(OH)D(3) affects the maturation and function of mouse bone marrow-derived dendritic cells stimulated by Mycobacterium bovis BCG

It has been shown that vitamin D deficiency increases an individual's susceptibility to tuberculosis (TB). However, very little is known about the effect of vitamin D on the immune response to Mycobacterium tuberculosis (M. tb) in dendritic cells (DCs). Because DCs play an important role in TB infection, we investigated the phenotypic characteristics and functional capabilities of mouse bone marrow-derived dendritic cells (BMDCs) after stimulation with Bacillus Calmette-Guérin (BCG) in the presence or absence of 25(OH)D(3)(100 nM). Bone marrow cells from mice were cultured with GM-CSF (20 ng/ml) and were then treated with 25(OH)D(3) for 7 days. On day 6, 5 µg/ml of BCG (≥1.0×10(6) CFU/mg) was added to the cells for 24 hours, and on day 7, the non-adherent cells were harvested for phenotypic and functional analyses. After incubation with 25(OH)D(3), the expression levels of MHC-II and CD86 on the surface of the dendritic cells (DCs) and the ability of the DCs to stimulate proliferation of allogeneic mixed lymphocytes were lower than control cells (p<0.05). Furthermore, the level of Interleukin (IL) -4 secreted by the BMDCs in the 25(OH)D(3) culture was lower than that in the control culture (p<0.01). However, the BMDCs cultured with 25(OH)D(3) produced significantly higher levels of IL-2, IL-6, IL-10 and interferon gamma(IFN-γ) than those in the control culture (p<0.05). These findings suggest that 25(OH)D(3) modulates the immune response during mycobacterial infection by affecting the maturation and function of DCs.

A comparison of vitamin D activity in paired non-malignant and malignant human breast tissues

Links between a low vitamin D status and an increased risk of breast cancer have been observed in epidemiological studies. These links have been investigated in human tissue homogenates and cultured cell lines. We have used non-malignant, malignant and normal reduction mammoplasty breast tissues to investigate the biological and metabolic consequences of the application of vitamin D to intact ex vivo human breast tissue. Tissues were exposed to 1α,25(OH)(2)D(3) (1,25D; active metabolite) and 25(OH)D (25D; pre-metabolite). Changes in mRNA expression and protein expression after vitamin D exposure were analysed. Results indicate that while responses in normal and non-malignant breast tissues are similar between individuals, different tumour tissues are highly variable with regards to their gene expression and biological response. Collectively, malignant breast tissue responds well to active 1,25D, but not to the inactive pre-metabolite 25D. This may have consequences for the recommendation of vitamin D supplementation in breast cancer patients.

Corticosteroid use and bone mineral accretion in children with asthma: effect modification by vitamin D

BACKGROUND

The adverse effects of corticosteroids on bone mineral accretion (BMA) have been well documented. Vitamin D insufficiency, a prevalent condition in the pediatric population, has also been associated with decreased bone mineral density (BMD).

OBJECTIVE

We sought to determine whether children with asthma who have lower vitamin D levels are more susceptible to the negative effects of corticosteroids on BMD over time.

METHODS

Children aged 5 to 12 years with mild-to-moderate asthma who participated in the Childhood Asthma Management Program were followed for a mean of 4.3 years. Total doses of inhaled corticosteroids and oral corticosteroids (OCSs) were recorded, serum 25-hydroxyvitamin D3 levels were measured at the beginning of the trial, and serial dual-energy x-ray absorptiometry scans of the lumbar spine were performed. Annual BMA rates were defined as follows: [(BMD at 4 years' follow-up - BMD at baseline)/4 years].

RESULTS

BMA was calculated for 780 subjects. In boys baseline vitamin D levels significantly modified the relationship between OCSs and BMA (vitamin D × OCS interaction, P= .023). Stratification by vitamin D levels showed a decrease in BMA with increased use of OCSs in vitamin D-insufficient boys only (P< .001). Compared with vitamin D-sufficient boys, vitamin D-insufficient boys exposed to more than 2 courses of OCSs per year had twice the decrease in BMA rate (relative to boys who were OCS unexposed).

CONCLUSIONS

Vitamin D levels significantly modified the effect of OCSs on BMA in boys. Further research is needed to examine whether vitamin D supplementation in children with poorly controlled asthma might confer benefits to bone health.

20-hydroxyvitamin D₃ inhibits proliferation of cancer cells with high efficacy while being non-toxic

AIM

To define the potential utility of 20-hydroxyvitamin D(3) (20(OH)D(3)) as a tumorostatic agent, we assessed its in vitro antiproliferative activity and its in vivo toxicity.

MATERIALS AND METHODS

The antitumor activity of 20(OH)D(3) was tested against breast and liver cancer cell lines using colony formation assays. To assess in vivo toxicity, mice were injected with 5-30 μg/kg 20(OH)D(3) intraperitoneally each day for 3 weeks. Blood and organ samples were collected for clinical pathology analyses.

RESULTS

20(OH)D(3) displays similar tumorostatic activity towards MDA-MB-453 and MCF7 breast carcinomas, and HepG2 hepatocarcinoma, in a dose-dependent manner. This compound is not hypercalcemic, does not cause detectable toxicities in liver, kidney, or blood chemistry in mice at a dose as high as 30 μg/kg. In contrast, both 25(OH)D(3) and 1,25(OH)(2)D(3) caused severe hypercalcemia at a dose of 2 μg/kg.

CONCLUSION

20(OH)D(3) possesses high efficacy for inhibiting cancer cell proliferation in vitro and is non-toxic in vivo, supporting its further development as a potential anticancer therapeutic agent.

[Effect of 25-hydroxyvitamin D(3) on vitamin D receptor expression and distribution in human bronchial epithelial cells in vitro]

OBJECTIVE

To evaluate the effect of 25-hydroxyvitamin D(3) on the expression and distribution of vitamin D receptor in normal human bronchial epithelial cells.

METHODS

MTT assay was used to assess the viability of human airway epithelial cell line 16HBE following a 24-h exposure to different concentrations of 25-hydroxyvitamin D(3). Real-time quantitative PCR, Western blotting, and immunofluorescence assay were used to observe the expression and distribution of vitamin D receptor in the cells following the exposure.

RESULTS

Compared with the control cells, 16HBE cells exposed to different concentrations of 25-hydroxyvitamin D(3) exhibited no significantly increase in the expression or distribution of vitamin D receptor.

CONCLUSION

The influence of 25-hydroxyvitamin D(3) on bronchial epithelial cells might be independent of the expression and translocation of vitamin D receptor.

Age-related decline in osteoblastogenesis and 1α-hydroxylase/CYP27B1 in human mesenchymal stem cells: stimulation by parathyroid hormone

With aging, there is a decline in bone mass and in osteoblast differentiation of human mesenchymal stem cells (hMSCs) in vitro. Osteoblastogenesis can be stimulated with 1,25-dihydroxyvitamin D(3) [1,25(OH)(2) D(3) ] and, in some hMSCs, by the precursor 25-hydroxyvitamin D(3) (25OHD(3) ). CYP27B1/1α-hydroxylase activates 25OHD(3) and, to a variable degree, hMSCs express CYP27B1. In this study, we tested the hypotheses (i) that age affects responsiveness to 25OHD(3) and expression/activity of CYP27B1 in hMSCs and (ii) that parathyroid hormone (PTH) upregulates CYP27B1 in hMSCs, as it does in renal cells. There were age-related declines in osteoblastogenesis (n=8, P=0.0286) and in CYP27B1 gene expression (n=27, r= -0.498; P=0.008) in hMSCs. Unlike hMSCs from young subjects (≤50 years), hMSCs from older subjects (≥55 years) were resistant to 25OHD(3) stimulation of osteoblastogenesis. PTH1-34 (100 nm) provided hMSCs with responsiveness to 25OHD(3) (P=0.0313, Wilcoxon matched pairs test) and with two episodes of increased 1,25(OH)(2) D(3) synthesis, of cAMP response element binding protein (CREB) activation, and of CYP27B1 upregulation. Both increases in CYP27B1 expression by PTH were obliterated by CREB-siRNA or KG-501 (which specifically inhibits the downstream binding of activated CREB). Only the second period of CREB signaling was diminished by AG1024, an inhibitor of insulin-like growth factor-I receptor kinase. Thus, PTH stimulated hMSCs from elders with responsiveness to 25OHD(3) by upregulating expression/activity of CYP27B1 and did so through CREB and IGF-I pathways.

[25-hydroxyvitamin D3-induced increases of normal human airway epithelial cell permeability is not mediated by upregulated ZO-1 expression]

OBJECTIVE

To observe the effect of 25-hydroxyvitamin D3 on the permeability and ZO-1 expression in normal human airway epithelial cells.

METHODS

MTT assay was used to assess the viability of human airway epithelial cell line 16HBE following a 24-hour exposure to different concentrations of 25-hydroxy vitamin D3, and the transepithelial electrical resistance (TER) of the cell monolayer was measured using a Millicell-ERS voltohmmeter. Real-time quantitative RT-PCR was employed to determine the changes of ZO-1 mRNA expression in the cells following the exposures.

RESULTS

Exposure to 25-hydroxyvitamin D3 resulted in significantly increased permeability of 16HBE cells, but the exspression of ZO-1 showed no obvious changes. 25-hydroxyvitamin D3 at 4×10(-9) mol/L showed the strongest effect in increasing the permeability of cell monolayer.

CONCLUSION

25-hydroxyvitamin D3 increases the permeability of normal bronchial airway epithelial cell monolayer in vitro, but this effect is not mediated by upregulation of ZO-1 expression.

Direct suppression of Pth gene expression by the vitamin D prohormones doxercalciferol and calcidiol requires the vitamin D receptor

Vitamin D compounds regulate PTH at the transcriptional level, presumably via binding to the vitamin D receptor (VDR), but the exact mechanism is presently unclear. We recently reported that the several vitamin D prohormones with low VDR affinity suppressed PTH, even when their activation was inhibited, raising the possibility that their actions may be VDR independent. To test this hypothesis, we developed a novel organ culture that allowed the assessment of activities of the prohormones on PTH release from wild-type and VDR-null thyroparathyroid explants. The cultures remained viable with respect to PTH release for at least 2 weeks. Full suppression of PTH by the native vitamin D hormone, 1α,25-dihydroxyvitamin D(3) [1α,25 (OH)(2)D(3)], required 2 days, consistent with a transcriptional mechanism, and was reversible, indicating that reduced PTH was not attributable to cell death. Inhibition of PTH release by 1α,25 (OH)(2)D(3) and two prohormones, 25-hydroxyvitamin D(3) and 1α-hydroxyvitamin D(2), was observed in explants from wild-type mice but not in those from VDR-null mice. These findings 1) are the first direct demonstration of the role of the VDR in regulation of PTH by 1α,25(OH)(2)D(3), 2) confirm that the suppressive actions of the vitamin D prohormones are mediated by the VDR, and 3) introduce a novel organ culture model that allows the ex vivo study of the function of parathyroid glands from transgenic animals.

Low bone density and bone metabolism alterations in Duchenne muscular dystrophy: response to calcium and vitamin D treatment

Boys with Duchenne muscular dystrophy often have reduced bone mass and increased fracture risk. In this prospective study on 33 patients, calcifediol (25-OH vitamin D(3)) plus adjustment of dietary calcium to the recommended dose reduced bone resorption, corrected vitamin D deficiency, and increased bone mass in about two-thirds of cases.

INTRODUCTION

Low BMC and BMD and bone metabolism alterations are frequent in boys with Duchenne muscular dystrophy (DMD), especially now that long-term glucocorticosteroid (GC) treatment is the standard of care. This prospective study was designed to evaluate the effects of a first-line treatment (25-OH vitamin D(3) [calcifediol] plus adjustment of dietary calcium to the recommended daily dose) on bone.

METHODS

Thirty-three children with DMD on GC treatment were followed for 3 years: one of observation and two of treatment.

MAIN OUTCOME

spine and total body BMC and BMD increase; secondary outcome: changes in bone turnover markers (C-terminal [CTx] and N-terminal [NTx] telopeptides of procollagen type I; osteocalcin [OC]).

RESULTS

During the observation year, BMC and BMD decreased in all patients. At baseline and after 12 months, serum CTx and urinary NTx were higher than normal; OC and parathyroid hormone at the upper limit of normal; 25-OH vitamin D(3) significantly lower than normal. After 2 years of calcifediol and calcium-rich diet, BMC and BMD significantly increased in over 65% of patients, and bone metabolism parameters and turnover markers normalized in most patients (78.8%). During the observation year, there were four fractures in four patients, while during the 2 years of treatment there were two fractures in two patients.

CONCLUSIONS

Calcifediol plus adequate dietary calcium intake seems to be an effective first-line approach that controls bone turnover, corrects vitamin D deficiency, and increases BMC and BMD in most patients with DMD. Lack of response seems related to persistently high bone turnover.

Chemical synthesis of 20S-hydroxyvitamin D3, which shows antiproliferative activity

20S-hydroxyvitamin D3 (20S-(OH)D3), an in vitro product of vitamin D3 metabolism by the cytochrome P450scc, was recently isolated, identified and shown to possess antiproliferative activity without inducing hypercalcemia. The enzymatic production of 20S-(OH)D3 is tedious, expensive, and cannot meet the requirements for extensive chemical and biological studies. Here we report for the first time the chemical synthesis of 20S-(OH)D3 which exhibited biological properties characteristic of the P450scc-generated compound. Specifically, it was hydroxylated to 20,23-dihydroxyvitamin D3 and 17,20-dihydroxyvitamin D3 by P450scc and was converted to 1alpha,20-dihydroxyvitamin D3 by CYP27B1. It inhibited proliferation of human epidermal keratinocytes with lower potency than 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) in normal epidermal human keratinocytes, but with equal potency in immortalized HaCaT keratinocytes. It also stimulated VDR gene expression with similar potency to 1,25(OH)2D3, and stimulated involucrin (a marker of differentiation) and CYP24 gene expression, showing a lower potency for the latter gene than 1,25(OH)2D3. Testing performed with hamster melanoma cells demonstrated a dose-dependent inhibition of cell proliferation and colony forming capabilities similar or more pronounced than those of 1,25(OH)2D3. Thus, we have developed a chemical method for the synthesis of 20S-(OH)D3, which will allow the preparation of a series of 20S-(OH)D3 analogs to study structure-activity relationships to further optimize this class of compound for therapeutic use.

Vitamin D, calcidiol and calcitriol regulate vitamin D metabolizing enzymes in cervical and ovarian cancer cells

BACKGROUND

The vitamin D metabolizing enzymes 25-, 1α- and 24-hydroxylase are expressed in malignant cells of the cervix and the ovaries. The aim of this study was to obtain further information about the regulation of the aforementioned enzymes by vitamin D, calcidiol and calcitriol in cervical and ovarian cancer.

MATERIALS AND METHODS

The human cervical adenocarcinoma cell line HeLa and the human ovarian adenocarcinoma cell line OVCAR-3 were incubated with vitamin D, calcidiol and calcitriol. The influence of vitamin D and its metabolites on the expression of 25-, 1α- and 24-hydroxylase was assessed by real-time RT-PCR.

RESULTS

Calcitriol significantly increased the 24-hydroxylase mRNA levels in HeLa and OVCAR-3 cells. The expression of 25- and 1α-hydroxylase was not regulated in a statistically significant manner.

CONCLUSION

These results suggest that in HeLa as well as OVCAR-3 cell lines, the metabolism of vitamin D is regulated via the expression of the catabolizing 24-hydroxylase.

Exogenous versus endogenous recovery of 25-hydroxyvitamins D2 and D3 in human samples using high-performance liquid chromatography and the DiaSorin LIAISON Total-D Assay

Demand for circulating 25-hydroxyvitamin D [25(OH)D] measurements has exploded due to its relationship with many serious health problems. The present study was designed to investigate the validity of samples "spiked" with 25-hydroxyvitamin D2 [25(OH)D2] or 25-hydroxyvitamin D3 [25(OH)D3] to determine their analytical recovery by the DiaSorin LIAISON 25 OH Vitamin D Total Assay (DiaSorin Assay) and high-performance liquid chromatography (HPLC). 25(OH)D was measured in nine volunteers taking large daily doses of vitamin D2 for 2 weeks. Samples were obtained pre-supplementation and 1 week following vitamin D2. Pre-supplementation samples were used for exogenous recovery studies by adding 25(OH)D2 or 25(OH)D3. Endogenous 25(OH)D [25(OH)D2 plus 25(OH)D3] concentrations reported by the DiaSorin Assay or detected by HPLC were in excellent agreement. However, exogenously added 25(OH)D2 and 25(OH)D3 were under-recovered by the DiaSorin Assay. NIST vitamin D standards containing serum from another species (horse) or exogenous 25(OH)D2 were similarly affected when using the DiaSorin Assay. Exogenous 25(OH)D2, 25(OH)D3 or serum from other species added to human samples is inappropriate in determining the analytical recovery of vitamin D compounds when using the DiaSorin Assay. Only endogenous 25(OH)D2 and/or 25(OH)D3 contained in human blood samples should be utilized for this purpose.

Evidence for a role of prolactin in calcium homeostasis: regulation of intestinal transient receptor potential vanilloid type 6, intestinal calcium absorption, and the 25-hydroxyvitamin D(3) 1alpha hydroxylase gene by prolactin

Increased calcium transport has been observed in vitamin D-deficient pregnant and lactating rats, indicating that another factor besides 1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is involved in intestinal calcium transport. To investigate prolactin as a hormone involved in calcium homeostasis, vitamin D-deficient male mice were injected with 1,25(OH)(2)D(3), prolactin, or prolactin + 1,25(OH)(2)D(3). Prolactin alone (1 microg/g body weight 48, 24, and 4 h before termination) significantly induced duodenal transient receptor potential vanilloid type 6 (TRPV6) mRNA (4-fold) but caused no change in calbindin-D(9k). Combined treatment with 1,25(OH)(2)D(3) and prolactin resulted in an enhancement of the 1,25(OH)(2)D(3) induction of duodenal TRPV6 mRNA, calbindin-D(9k) mRNA, and an induction of duodenal calcium transport [P < 0.05 compared with 1,25(OH)(2)D(3) alone]. Because lactation is associated with an increase in circulating 1,25(OH)(2)D(3), experiments were done to determine whether prolactin also has a direct effect on induction of 25-hydroxyvitamin D(3) 1alpha hydroxylase [1alpha(OH)ase]. Using AOK B-50 cells cotransfected with the prolactin receptor and the mouse 1alpha(OH)ase promoter -1651/+22 cooperative effects between prolactin and signal transducer and activator of transcription 5 were observed in the regulation of 1alpha(OH)ase. In addition, in prolactin receptor transfected AOK B-50 cells, prolactin treatment (400 ng/ml) and signal transducer and activator of transcription 5 significantly induced 1alpha(OH)ase protein as determined by Western blot analysis. Thus, prolactin, by multiple mechanisms, including regulation of vitamin D metabolism, induction of TRPV6 mRNA, and cooperation with 1,25(OH)(2)D(3) in induction of intestinal calcium transport genes and intestinal calcium transport, can act as an important modulator of vitamin D-regulated calcium homeostasis.

1alpha,25(OH)2-Vitamin D3 stimulation of secretion via chloride channel activation in Sertoli cells

Sertoli cell secretory activities are highly dependent on ion channel functions and critical to spermatogenesis. The steroid hormone 1alpha,25(OH)2-vitamin D3 (1,25(OH)2-D3) stimulates exocytosis in different cell systems by activating a nongenotropic vitamin D receptor (VDR). Here, we described 1,25(OH)2-D3 stimulation of secretion via Cl(-) channel activation in the mouse immature Sertoli cell line TM4. 1,25(OH)2-D3 potentiation of chloride currents was dependent on hormone concentration, and correlated with a significant increase in whole-cell capacitance within 20-40 min. In addition, Cl(-) currents were potentiated by the nongenomic VDR agonist 1alpha,25(OH)2 lumisterol D3 (JN), while 1,25(OH)2-D3 potentiation of channels was suppressed by nongenomic VDR antagonist 1beta,25(OH)2-vitamin D3 (HL). Treatment of TM4 cells with PKC and PKA activators PMA and forskolin respectively, increased Cl(-) currents significantly, while PKC and PKA inhibitors Go6983 and H-89, respectively, abolished 1,25(OH)2-D3 stimulation of Cl(-) currents, suggesting phosphorylation pathways in 1,25(OH))2-D3 mediated channel responses. RT-PCR demonstrated the expression of outwardly rectifying ClC-3 channels in TM4 cells. Taken together, our results demonstrate a PKA/PKC-dependent 1,25(OH)2-D3/VDR nongenotropic pathway leading to Cl(-) channel and exocytosis activation in Sertoli cells. We conclude that 1,25(OH)2-D3 appears to be a modulator of male reproductive functions at least in part by stimulating Sertoli cell secretory functions.

Products of vitamin D3 or 7-dehydrocholesterol metabolism by cytochrome P450scc show anti-leukemia effects, having low or absent calcemic activity

Background

Cytochrome P450scc metabolizes vitamin D3 to 20-hydroxyvitamin D3 (20(OH)D3) and 20,23(OH)₂D3, as well as 1-hydroxyvitamin D3 to 1α,20-dihydroxyvitamin D3 (1,20(OH)₂D3). It also cleaves the side chain of 7-dehydrocholesterol producing 7-dehydropregnenolone (7DHP), which can be transformed to 20(OH)7DHP. UVB induces transformation of the steroidal 5,7-dienes to pregnacalciferol (pD) and a lumisterol-like compounds (pL).

Methods and Findings

To define the biological significance of these P450scc-initiated pathways, we tested the effects of their 5,7-diene precursors and secosteroidal products on leukemia cell differentiation and proliferation in comparison to 1α,25-dihydroxyvitamin D3 (1,25(OH)₂D3). These secosteroids inhibited proliferation and induced erythroid differentiation of K562 human chronic myeloid and MEL mouse leukemia cells with 20(OH)D3 and 20,23(OH)₂D3 being either equipotent or slightly less potent than 1,25(OH)₂D3, while 1,20(OH)₂D3, pD and pL compounds were slightly or moderately less potent. The compounds also inhibited proliferation and induced monocytic differentiation of HL-60 promyelocytic and U937 promonocytic human leukemia cells. Among them 1,25(OH)₂D3 was the most potent, 20(OH)D3, 20,23(OH)₂D3 and 1,20(OH)₂D3 were less active, and pD and pL compounds were the least potent. Since it had been previously proven that secosteroids without the side chain (pD) have no effect on systemic calcium levels we performed additional testing in rats and found that 20(OH)D3 had no calcemic activity at concentration as high as 1 µg/kg, whereas, 1,20(OH)₂D3 was slightly to moderately calcemic and 1,25(OH)₂D3 had strong calcemic activity.

Conclusions

We identified novel secosteroids that are excellent candidates for anti-leukemia therapy with 20(OH)D3 deserving special attention because of its relatively high potency and lack of calcemic activity.

Vitamin D metabolism and action in human bone marrow stromal cells

Vitamin D metabolites are important effectors of bone and mineral homeostasis. Extrarenal conversion of 25-hydroxyvitamin D (25OHD) to the biologically active form of vitamin D, 1 alpha,25-dihydroxyvitamin D [1,25(OH)(2)D] is catalyzed in several cell types by the 1 alpha-hydroxylase (CYP27B1), but little is known about the expression or regulation of CYP27B1 in human bones. We examined whether human bone marrow stromal cells (hMSCs, also known as mesenchymal stem cells) participate in vitamin D metabolism and whether vitamin D hydroxylases in hMSCs are influenced by the vitamin D status of the individual from whom the hMSCs were obtained. We also investigated the effects of vitamin D metabolites on osteoblast differentiation and the role of IGF-I in the regulation of CYP27B1. In a series of 27 subjects, vitamin D hydroxylases in hMSCs were expressed at different levels and were correlated with serum 25OHD, 1,25(OH)(2)D, and PTH. In vitro treatment with 25OHD up-regulated CYP27B1 and IGF-I in hMSCs; IGF-I also up-regulated CY27B1 expression and stimulated osteoblast differentiation. When hydroxylation of 25OHD was blocked by ketoconazole, a cytochrome P450 inhibitor, 25OHD was no longer able to induce CYP27B1 expression. In summary, these findings show that human bone marrow stromal cells have the molecular machinery both to metabolize and respond to vitamin D. We propose that circulating 25OHD, by virtue of its local conversion to 1,25(OH)(2)D catalyzed by basal CYP27B1 in hMSCs, amplifies vitamin D signaling through IGF-I up-regulation, which in turn induces CYP27B1 in a feed-forward mechanism to potentiate osteoblast differentiation initiated by IGF-I.

Modifying broiler diets with phytase and vitamin D metabolite (25-OH D(3)): impact on phosphorus in litter, amended soils, and runoff

Adding phytase and 25- hydroxycholecalciferol (25-OH D(3)) to broiler diets has been shown effective at reducing total P concentrations in broiler litter. This study was conducted to determine the impact of field application of broiler litter from modified diets on P solubility in litter-amended soils and P losses in runoff. Five broiler diets and their resulting litters were evaluated: a high P diet, a low P diet, each of those basal diets with phytase added, and a low P diet with phytase and 25-OH D(3) added. A field study was initiated at two sites with each of the five broiler litters and a commercial P fertilizer (triple superphosphate [TSP]) applied at the same total P rate (150 kg P ha(-1)) and a control where no P was applied. Soil P was monitored over time at two depths (0-5 cm and 0-15 cm) soils were collected in the spring and fall to perform rainfall simulation studies. Broiler litter or TSP application increased soil water-soluble P and Mehlich 3-P concentrations relative to the control, however there were no consistent differences detected between litter treatments. Results from the rainfall simulation experiments indicate that diet modification with phytase or 25-OH D(3) does not increase the potential for P losses in runoff from amended soils relative to traditional diets. Moreover, broiler diet modification to reduce excreted P could be a potentially effective method for reducing watershed scale P surpluses in areas of intensive broiler production, without raising concerns over soluble P losses from litter-amended soils.

Effects of 25-hydroxycholecalciferol and soy isoflavones supplementation on bone mineralisation of quail

1. The effects of 25-hydroxycholecalciferol (25-OH-D(3)) and soy isoflavones supplementation on performance, carcase recovery, bone mineral density, and tibia ash, Ca, P, and serum vitamin D concentrations and alkaline phosphatase activity in the Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature were evaluated. 2. A total of 270 ten-d-old Japanese quail were randomly assigned to 9 treatment groups, 6 replicates of 5 birds each in a 2 x 3 x 3 factorial arrangement of treatments. Birds were kept in a temperature-controlled room at either 22 degrees C (thermo-neutral) or 34 degrees C (heat stress) for 8 h/d (09:00-17:00 h) and given a basal (control) diet or the basal diet supplemented with one of three levels of 25-OH-D(3) (0, 250 and 500 IU/kg of diet) combined with one of three levels of soy isoflavones (0, 400 and 800 mg/kg of diet). 3. Birds kept at 34 degrees C consumed less feed and gained less weight than control birds. An increase in body weight, feed intake (and improvement in feed efficiency and carcase recovery were found in soy isoflavones and 25-OH-D(3)-supplemented quail reared under heat stress conditions. Bone mineral density, tibia ash, Ca, and P were linearly improved by 25-OH-D(3) and soy isoflavones supplementation in both thermoneutral and heat stress groups. Serum vitamin D levels and alkaline phosphatase activity were improved by 25-OH-D(3) and soy isoflavones supplementation in both thermoneutral and heat stress groups in quail. 4. In conclusion, a combination of 25-OH-D(3) and soy isoflavones supplementation to basal diet significantly improved bone mineralisation in quail.