A group of deltanoids (vitamin D analogs) regulate cell growth and proliferation in small cell carcinoma cell lines

A group of deltanoids has been used for studying the inhibition of cell growth and proliferation in two small cell lung carcinoma (SCLC) in vitro. The biologically active deltanoid, 1,25 dihydroxyvitamin D3 (1,25 (OH)2D3), has functions beyond its classical roles of stimulating calcium transport and serum calcium. It also causes the differentiation of a variety of precursor cells and suppresses growth. Although 1,25(OH)2D3 has an inhibitory effect on growth of certain malignant cells, its hypercalcemic effect has prevented clinical applications. Several new deltanoids, which showed comparable or even greater abilities to induce differentiation and to inhibit proliferation, have been identified. Furthermore, these synthetic deltanoids have been shown to be less effective on calcium metabolism and less hypercalcemic. We have selected four synthetic deltanoids; MC-903, 1 alpha-OH-pregnacalciferol, 19-nor-24 homo, and 19-nor-22(E). When compared with 1,25 (OH)2D3, these deltanoids showed considerable potency on cell growth and proliferation in the NCI-H82 and the NCI-H209 SCLC lines. Cells were treated with various concentrations of deltanoids. They inhibited the growth and proliferation of both SCLC cells in vitro in a time-and dose-dependent manner, as determined by cell number and 3H-thymidine uptake. 19-nor-22(E) showed an antiproliferative effect significantly comparable to 1,25(OH)2D3 in the NCI-H82 cell line 1 alpha-OH-pregnacalciferol, 19-nor-24 homo, and 19-nor-22(E) inhibited the cell growth in the NCI-H209 cells within the same significance as 1,25 (OH)2D3. The degree of the suppressive effect of the deltanoids was cell line dependent.

Tacalcitol

Tacalcitol is a vitamin D3 analogue which is available in Japan as a 2 micrograms/g ointment for twice daily application and in Western markets as a 4 micrograms/g ointment for once daily application. Tacalcitol inhibits proliferation, and induces the differentiation, of keratinocytes. In addition, it appears to modulate inflammatory and immunological mediators in the skin which may be involved in the aetiology of psoriasis. No significant systemic drug absorption occurs after application of tacalcitol to the skin. Results of clinical trials indicate that topical tacalcitol is effective in the management of stable plaque psoriasis (and possibly pustular forms of the disease), and has a similar efficacy to topical betamethasone valerate in this setting. Application of tacalcitol ointment 4 micrograms/g once daily for up to 8 weeks did not cause hypercalcaemia or hypercalciuria. Mild local skin irritation has been reported in a variable proportion of patients (< or = 12%).

Topical vitamin D3 derivatives impair the epidermal permeability barrier in normal mouse skin

BACKGROUND

Calcipotriol, 1,25(OH)2D3 and 1,24(OH)2D3 are potent drugs for the treatment of psoriasis. It has recently been published that these compounds induce epidermal hyperproliferation in hairless mouse skin.

OBJECTIVE

The aim of our study was to examine the effect of vitamin D3 derivatives on epidermal growth, keratinization and permeability barrier function in vivo.

METHODS

Calcipotriol, 1,25(OH)2D3 and 1,24(OH)2D3 in isopropanol or in an ointment formula were applied to normal hairless mouse skin. Transepidermal water loss (TEWL), a marker of cutaneous barrier function, and epidermal proliferation were determined at different time points 0-264 h after treatment. In addition, light and electron microscopy studies were performed.

RESULTS

A single treatment in solution led to a transient (2- to 3-fold) increase in TEWL after application of calcipotriol or 1,25(OH)2D3 and to a 3- to 6-fold increase in epidermal proliferation after application of each of the compounds. Repeated applications also resulted in an up to 3-fold increase in TEWL which persisted for 3 days after the end of the treatment. By light microscopy an increase in epidermal thickness was observed. There was no sign of inflammation. Electron microscopy studies showed the formation of a transitional cell zone as a sign of a premature keratinization.

CONCLUSION

These results demonstrate that in normal mouse skin vitamin D3 and its analogues disrupt the epidermal permeability barrier by induction of epidermal proliferation and premature keratinization but without morphological signs of inflammation.

Effects of 1alpha,25-dihydroxy-16ene, 23yne-vitamin D3 on osteoblastic function in human osteosarcoma SaOS-2 cells: differentiation-stage dependence and modulation by 17-beta estradiol

We compared the separate effects of 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and its analog, 1alpha,25-dihydroxy-16ene,23yne-vitamin D3 (1alpha25(OH)2-16ene,23yne-D3), as well as their interactions with 17-beta estradiol (E2) in our human osteosarcoma SaOS-2 cell models representing two stages of differentiation, the SaOS+DEX and SaOS-DEX cells. SaOS+DEX cells have been previously shown to express higher PTH-stimulated adenylate cyclase (PTH-AC) and basal alkaline phosphatase (ALP) activities compared with SaOS-DEX cells. ALP: In SaOS+DEX cells, 0.1 nmol/L analog, but not 1alpha,25(OH)2D3, increased ALP activity 1.7-fold (p < 0.05). Instead, 1 nmol/L 1alpha,25(OH)2D3 increased ALP 1.4-fold (p < 0.05). In these cells, E2 enhanced 1alpha,25(OH)2D3-stimulated ALP activity (ANOVA, F = 51.22, p <0.0001), while inhibiting the effect of the analog. [3H]-Thymidine uptake: In SaOS+DEX cells, 1alpha,25(OH)2D3 had biphasic effects (ANOVA, F = 13.08, p < 0.0001), which were not altered by E2. In contrast, the analog was stimulatory only with E2 (ANOVA, F = 3.59, p < 0.025). Osteocalcin (OC): 1alpha,25(OH)2D3 and its analog stimulated OC production in SaOS-DEX cells with smaller effects in SaOS+DEX cells. In SaOS-DEX cells, E2 enhanced the effect of 1alpha,25(OH)2D3, but not that of the analog. PTH-AC: In SaOS-DEX cells, 100 nmol/L analog inhibited PTH-AC activities by 50% (p < 0.01), whereas 1alpha,25(OH)2D3 had little effect. In SaOS+DEX cells, both compounds inhibited PTH-AC approximately 35%. E2 inhibited the effect of the analog in SaOS-DEX cells, but enhanced the effects of both compounds in SaOS+DEX cells. These results show that the analog 1alpha,25(OH)2-16ene,23yne-D3 was effective in regulating osteoblastic function; its effects were modulated by E2 and dependent upon the stage of osteoblast differentiation.

Tacalcitol (1,24(OH)2D3, TV-02) inhibits phorbol ester-induced epidermal proliferation and cutaneous inflammation, and induces epidermal differentiation in mice

In this study, we examined the cutaneous effects of tacalcitol [1,24(R)(OH)2D3] on epidermal proliferation, differentiation, and skin inflammation in vivo using hairless mice. Tacalcitol was shown to inhibit epidermal proliferation using TPA-induced ornithine decarboxylase activity and DNA synthesis as indices, and the induction of epidermal differentiation using type I transglutaminase activity as an index. Tacalcitol also displayed an antiinflammatory effect on TPA-induced inflammatory changes histopathologically. These results confirm the clinical efficacy of tacalcitol in psoriasis, and suggest that it may be efficacious in the treatment of other inflammatory skin diseases.

Metallothionein induction in calcifying growth plate cartilage chondrocytes

Metallothionein (MT) induction was studied in mineralizing cultures of chicken growth plate chondrocytes and quantitated using a Cd-saturation assay. In serum free media, MT induction was observed for Cd concentrations of 0.1 microM and greater and at Zn concentrations of 100 microM and greater. Supplementation of culture media with cysteine and/or methionine resulted in higher levels of MT induction and reduced toxicity during Cd exposure. Maximum MT induction appeared to coincide with the earliest culture stages during which important enzymes and matrix components are being synthesized. Of non-metal MT inducers tested, sodium butyrate caused a low level induction of MT while interleukin-1 had no effect on basal MT levels. 1,25-dihydroxyvitamin D increased MT induction. The steroid hormone dexamethasone caused a reduction in basal and induced MT levels. These findings suggest that MT regulation in growth plate chondrocytes differs significantly from what is known in other cell types and that this difference may be related to the mineralization of this tissue.

The effect of 1,24(R)(OH)2D3 cream and ointment on epidermal proliferation and differentiation in mice

BACKGROUND

The 1,24(R)(OH)2D3 (tacalcitol) ointment (2 micrograms/g) is available commercially as an antipsoriatic drug in Japan, but the cream preparation of tacalcitol is still under development.

OBJECTIVE

This study was conducted to compare the ability of tacalcitol cream and ointment to inhibit epidermal proliferation and induce epidermal differentiation.

METHODS

We measured the ornithine decarboxylase activity and type I transglutaminase activity as indices of proliferation and differentiation, respectively, in hairless mice.

RESULTS

These effects were statistically equal to those of the ointment preparation at the same dose, 2 micrograms/g, without inducing hypercalcemia.

CONCLUSIONS

These findings suggest that topical application of 1,24(OH)2D3 cream (2 micrograms/g) might have the same potency as the ointment formulation in the treatment of psoriasis.

Topical tacalcitol (1,24-(R)-dihydroxyvitamin D3) induces a transient increase in thymidine incorporation and calmodulin content in pig epidermis following tape stripping in vivo

Tape stripping induces transient increase in keratinocyte proliferation in vivo. The effects of tacalcitol (1,24-(R)-dihydroxyvitamin D3) ointment on the cell kinetics of pig epidermis after the tape stripping were investigated. The tacalcitol ointment (2 micrograms/g) was applied once to the back of pigs immediately after the tape stripping. The pig epidermal cell kinetics were analyzed at various times following the treatment. Tape stripping transiently increased thymidine incorporation of keratinocytes; the maximal effect was observed at 24 h. Tape stripping-induced increase in thymidine incorporation was markedly augmented by tacalcitol treatment. At 24 h following the tape stripping DNA-flow cytometry revealed an accelerated transition from G0/1 to S phase of cell cycle in tacalcitol treated epidermis. There was no significant difference, however, in mitotic counts and G2/M phase fractions between tape stripping-treated and tape stripping plus tacalcitol ointment-treated epidermis. We also measured calmodulin content of pig epidermis following the treatments. Although tape stripping slightly increased calmodulin content of pig epidermis, this was statistically not significant. Tape stripping plus tacalcitol ointment treatment resulted in a significant increase in calmodulin content at 24 h following the treatment. There was no significant difference in calmodulin content between tape stripping treated- and tape stripping plus tacalcitol-treated epidermis.

Expression of sodium-dependent phosphate (NadPi) transport in Xenopus laevis oocytes induced by mRNA from 1 alpha, 25-dihydroxyvitamin D3-treated rat osteoblast-like cells

Injection of messenger ribonucleic acid (mRNA) isolated from 1 alpha, 25-dihydroxyvitamin D3-treated osteoblast-like (PyMS) cells leads to an enhanced sodium-dependent phosphate (NadPi) transport in Xenopus laevis oocytes, when compared to untreated cells. After mRNA size fractionation, mRNA with an average size of 2.2-3.8 kilobases showed up to a 1.8-fold stimulation of NadPi transport encoding either directly a NadPi transporter(s) or proteins controlling their activity. No hybridization was observed in Northern blots with RNA from rat bone or PyMS cells with the recently cloned rat renal brush border NadPi transporter NaPi-2; hybrid depletion with a NaPi-2 antisense oligonucleotide did not abolish the PyMS mRNA-induced NadPi transport in oocytes. We present the first evidence for functional expression in Xenopus laevis oocytes of a new type of NadPi transport system in bone cells, which is different from the renal type.

Production and secretion of platelet-derived growth factor AB by cultured human keratinocytes: regulatory effects of phorbol 12-myristate 13-acetate, etretinate, 1,25-dihydroxyvitamin D3, and several cytokines

Platelet-derived growth factor (PDGF) is a potent mitogen for several mesenchymal cells and plays an important role in wound repair. Three PDGF isoforms, PDGF-AA, PDGF-BB, and PDGF-AB, have been found to be generated in various tissues. PDGF-AB production by normal human keratinocytes (NHKs), by human squamous cell carcinoma cell line (HSC-1) cells, and by human dermal fibroblasts (HDFs) was studied in the presence of agents which influence cell growth. Both NHKs and HSC-1 cells spontaneously produced and secreted PDGF-AB. NHKs grown in keratinocyte growth medium produced more PDGF-AB than did those grown in keratinocyte basic medium. Phorbol 12-myristate 13-acetate inhibited PDGF-AB production in NHKs but promoted its production in HSC-1 cells. 1,25-dihydroxyvitamin D3 up-regulated PDGF-AB production, whereas etretinate did not. High levels of calcium in the culture medium induced little change in cellular PDGF-AB levels. Prostaglandin E1 slightly inhibited PDGF-AB production, transforming growth factor beta 1 promoted PDGF-AB production and interferon-gamma, interleukin-1 alpha, and tumor necrosis factor-alpha failed to exert any influence at all. Cultured HDFs did not produce any detectable PDGF-AB. These results suggest that keratinocytes are a major source of cutaneous PDGF and that this factor may therefore play an important role in wound repair and in certain proliferative skin diseases.

Colony-stimulating factor 1 when combined with parathyroid hormone or 1,25-dihydroxyvitamin D can produce osteoclasts in cultured neonatal metatarsals from toothless (tl-osteopetrotic) rats

Toothless (tl-osteopetrotic) rats have little or no endogenous bone resorption, no marrow spaces, and very few osteoclasts and macrophages, and their live metatarsal rudiments cannot support the development of normal osteoclasts in vitro. The recent demonstration that exogenous colony-stimulating factor 1 (CSF-1) improves skeletal sclerosis and increases osteoclasts in tl rats in vivo, prompted us to explore conditions that enable osteoclasts to be formed in tl metatarsals in vitro. Coculture of neonatal tl metatarsals with CSF-1 alone produced no osteoclasts, but the addition of normal spleen and bone marrow cells and parathyroid hormone or 1,25-dihydroxyvitamin D produced osteoclasts in most cultures. Identical cultures of metatarsals from the CSF-1 deficient op/op mouse produced similar results. Within the contexts of the role of CSF-1 in osteoclastogenesis and the different biologic manifestations of osteopetrosis in these two mutations, we interpret these results to mean that other factors are required to restore osteoclast function completely in tl rats and op mice. Thus, experimental studies of these mutations are likely to provide new insights on both osteopetrosis and osteoclast biology.

1,25-Dihydroxyvitamin D3 inhibits thromboxane release from activated macrophages

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) in concentrations from 0.1 to 10 nM suppressed immunoreactive thromboxane B2 (iTXB2) release from Propionibacterium acnes (P. acnes)-elicited liver adherent cells stimulated with lipopolysaccharide (LPS, 1 microgram/ml). These suppressive effects of 1,25-(OH)2D3 were also observed in oyster glycogen-elicited peritoneal macrophages. On the contrary, it did not inhibit iTXB2 release from both resident Kupffer cells and peritoneal macrophages stimulated with the same concentration of LPS. Furthermore, 1,24(R)-dihydroxyvitamin D3 (1,24(R)-(OH)2D3), a vitamin D3 analogue, also inhibited iTXB2 release from liver adherent cells, but, another synthesized vitamin D3 analogue, 1 alpha-hydroxyvitamin D3 (1 alpha-OH-D3) tended to decrease iTXB2 release only at higher concentrations. These results suggest that active vitamin D3 analogues inhibit iTXB2 release from activated macrophages.

Expression of vacuolar H(+)-ATPase in mouse osteoclasts during in vitro differentiation

Osteoclasts express high levels of a vacuolar H(+)-adenosinetriphosphatase (H(+)-ATPase) on the ruffled membrane which they employ to dissolve bone mineral by acidifying their site of attachment on bone. The factors that control amplification of H(+)-ATPase during osteoclast differentiation are poorly understood. We examined the expression of vacuolar H(+)-ATPase in a cell culture system in which mouse spleen cells can be induced to differentiate into osteoclasts by coculture with a mouse bone marrow stromal cell line. We found that the coculture system produced active osteoclasts, identified as multinucleated cells with staining for tartrate-resistant acid phosphatase activity that formed genuine resorption pits in bone. These cells developed high levels of H(+)-ATPase expression in culture, and omission of dexamethasone or 1 alpha,25-dihydroxyvitamin D3 from the coculture system each partially suppressed the expression of H(+)-ATPase. The results demonstrate that the spleen and PA6 cell coculture system may be useful for investigating the factors that control the induction of H(+)-ATPase amplification that occurs during osteoclast differentiation.

Effects on cultured neonatal mouse calvaria of 1 alpha,25-dihydroxyvitamin D3, 26,26,26,27,27,27-hexafluoro-1 alpha,25-dihydroxyvitamin D3 and 26,26,26,27,27,27-hexafluoro-1 alpha,23S,25-trihydroxyvitamin D3

The potency of 26,26,26,27,27,27-hexafluoro-1 alpha,25-dihydroxyvitamin D3 (26,27-F6-1,25(OH)2D3) to enhance bone calcium (Ca) mobilization in vitro was higher than that of 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3). In a 48-h organ culture system using fetal rat limb bones, effects of 26,27-F6-1,25(OH)2D3 on bone resorption were similar to those of 1,25(OH)2D3. Thus, we attempted to clarify whether or not the potency of 26,27-F6-1,25(OH)2D3 in bone resorption in vitro would be higher than that of 1,25(OH)2D3. Calvarial bones from neonatal mice were used as explants and the culture period was extended to 144 from 48 h. In cultures of 0 to 48 h, both drugs increased the release of prelabeled 45Ca from cultured calvariae, in a dose-dependent manner. In cultures of 48 to 144 h, 26,27-F6-1,25(OH)2D3 was much more effective than 1,25(OH)2D3 regarding indices of bone resorption. 26,26,26,27,27,27-F6-1 alpha,23S,25-trihydroxyvitamin D3 (26,27-F6-1,23,25(OH)3D3), a main metabolite of 26,27-F6-1,25(OH)2D3 in rats, stimulated 45Ca release equipotently to 1,25(OH)2D3. In mouse bone marrow cells cultured for 7 days, the potency of 26,27-F6-1,25(OH)2D3 on osteoclast formation was much higher than 1,25(OH)2D3. These results suggest that the higher potency of 26,27-F6-1,25(OH)2D3 in bone resorption may be due at least in part to both the higher potency of 26,27-F6-1,25(OH)2D3 in osteoclast formation and the larger retention of 26,27-F6-1,23,25(OH)3D3 in calvariae.

Protective effect of vitamin D3 analogues on endotoxin shock in mice

The effect of vitamin D3 analogues on endotoxin shock in mice was investigated. Male ICR mice were orally administered vitamin D3 analogues or vehicle, accompanied by an intraperitoneal injection of endotoxin (E. Coli lipopolysaccharide, LPS, 20 mg/kg). Endotoxin caused a decrease in survival rate in a time-dependent manner. Increases in plasma immunoreactive (i) eicosanoid and hepatic malondialdehyde (MDA) levels were also observed. Administration of 1 alpha-hydroxyvitamin D3 (1 alpha-OH-D3) improved the survival rate 24 to 48 h after endotoxin treatment. The effects were markedly observed at a dose of 20 ng/kg. In addition, 1 alpha-OH-D3 restored the plasma iTXB2 and hepatic MDA levels 8 h after endotoxin injection. However, it did not affect plasma iPGE2, i6-keto-PGF1 alpha and blood iLTB4 levels. At a dose of 20 ng/kg, both 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and 1,24(R)-dihydroxyvitamin D3 (1,24(R)-(OH)2D3) restored the survival rate, the plasma iTXB2 and hepatic MDA levels. These results suggest that vitamin D3 analogues may inhibit endotoxemia through regulation of the formation of TXA2 and free radicals.

1 alpha,24R-dihydroxyvitamin D3 has an ability comparable to that of 1 alpha,25-dihydroxyvitamin D3 to induce keratinocyte differentiation

Using cultured normal human keratinocytes, we compared the activities of 1 alpha,24-dihydroxyvitamin D3 (1,25(OH)2D3), a biologically active form, in inducing cell differentiation. Treatment with 10(-6) M of 1,24R(OH)2D3 and 1,25(OH)2D3 increased the number of involucrin positive cells (differentiated from 6.4% to 24.1% and 25.1%, respectively. These results indicate that 1,24R(OH)2D3 has an ability comparable to that of 1,25(OH)2D3 to induce cell differentiation in human keratinocytes. The clinical effectiveness of 1,24R(OH)2D3 for the treatment of psoriasis may be, in part, related to its direct effect on hyperproliferative keratinocytes.

Structure-function studies on analogues of 1 alpha,25-dihydroxyvitamin D3: differential effects on leukemic cell growth, differentiation, and intestinal calcium absorption

The hormonally active form of vitamin D, 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], is an efficient stimulator of intestinal calcium absorption (ICA) and bone calcium mobilization (BCM) in humans and experimental animals and, as well, has been shown to be effective in inducing differentiation and inhibiting proliferation of leukemia cells. Thus, it has been proposed that analogues of 1,25(OH)2D3 could be synthesized which might allow for separation of biological functions, i.e., promote a differentiation of leukemia cells without a significant stimulation of ICA or BCM, both biological effects which can cause hypercalcemia in humans. Here we report the results of an evaluation of four analogues of the previously studied (Zhou et al., Blood, 74:82-92, 1989) 1 alpha,25-dihydroxy-16-ene-23-yne-vitamin D3 [1,25(OH)2-16-ene-23-yne-D3]; these analogues allowed evaluation of the consequences of (a) the presence or absence of six deuterium atoms on carbons 26 and 27 of the side chain and (b) the deletion or substitution by a fluorine atom of the 1 alpha-hydroxyl group on the A-ring. The 1,25(OH)2-16-ene-23-yne-D3 analogue was found to be 7-fold more potent than the parent 1,25(OH)2D3 with respect to (a) inhibition of clonal proliferation of HL-60 cells as well as (b) induction of differentiation of HL-60 promyelocytes. Variants of this analogue which possessed the six deuterium atoms on carbons 26 and 27 were slightly less active than the 1,25(OH)2-16-ene-yne-D3. However, replacement of the 1 alpha-hydroxyl group by a 1-fluoro group, or the absence of the 1-hydroxyl group, resulted in analogues that were somewhat less effective than the parent 1,25(OH)2D3 in achieving these biological responses but more potent as inhibitors of the renal mitochondrial 25-OH-D3-1 alpha-hydroxylase, the site of endogenous production of 1,25(OH)2D3. ICA and BCM were assessed in vivo in vitamin D-deficient chickens, and each of the analogues was markedly less potent than the standard 1,25(OH)2D3. The analogue 1,25(OH)2-16-ene-23-yne-D3 had 2% of the ICA and 3% of the BCM activity of the parent 1,25(OH)2D3. Absence of the 1 alpha-hydroxyl group or substitution of the 1-fluoro group for the 1-hydroxyl group significantly diminished both the ICA and BCM activity in comparison to 1,25(OH)2-16-ene-23-yne-D3. Receptor binding studies indicated that 1,25(OH)2-16-ene-23-yne-D3 competed about 75% as effectively as 1,25(OH)2D3 for 1,25(OH)2D3 receptors present in both chick intestinal cells and HL-60 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Production of human interleukin for DA cells (HILDA)/leukemia inhibitory factor (LIF) by activated monocytes

We demonstrate mRNA accumulation and production of HILDA/LIF by human activated Mo, monocyte-derived macrophages and myelomonocytic cell lines. Among the various stimuli tested, the synergistic combination of phorbol diester and VD3 was the most potent inducer of HILDA/LIF gene expression. The kinetics of mRNA accumulation on activated Mo showed a stimulation peak at 24 hr which declined thereafter. HILDA/LIF activity in culture supernatants was detected at 24 hr and reached a plateau at 72 hr of culture. In contrast to Mo, PBL did not accumulate HILDA/LIF mRNA upon culture with PDBu and VD3, whereas PHA and the combination of PDBu and A23187 induced HILDA/LIF mRNA accumulation and secretion in the culture supernatant. To exclude the possibility that HILDA/LIF was produced by contaminating PBL, highly enriched Mo preparations were used, which were devoid of T cells as assessed by the absence of TCR-beta chain mRNA transcripts. HILDA/LIF production by monocytic cells was further documented by the capacity of stimulated U937 cell conditioned medium to compete with 125I-labeled nHILDA/LIF for binding to its receptor on murine M1 cells. Under the synergistic effect of PDBu and VD3 stimulation, Mo-derived macrophages as well as HL-60 and U937 cell lines accumulated HILDA/LIF mRNA and produced this cytokine with identical kinetics as for Mo. Finally, we show that HILDA/LIF mRNA accumulation in U937 cells upon stimulation with PDBu, or the combination of PDBu and VD3, was inhibited in the presence of the protein synthesis inhibitor CHX. These results document for the first time that human Mo, when stimulated appropriately in vitro, can express the HILDA/LIF gene and its product, and that intermediate proteins must be newly synthesized in this process.

The effects of differentiating agents on IL-1 beta production in cultured human monocytes

Human monocytes aged in medium exhibit a decrease in LPS-induced IL-1 beta production in comparison with fresh cells. The objective of these experiments was to evaluate the effects of differentiation for 1 or 6 days in IFN-gamma, 1,25-(OH)2-vitamin D3, granulocyte-macrophage CSF, or in various combinations of these agents on both steady state IL-1 beta mRNA levels and protein production in LPS-stimulated monocytes. Monocytes preincubated in IFN-gamma for 1 day, then cultured for 24 h with LPS, exhibited similar kinetics of IL-1 beta mRNA production, but a higher peak mRNA level at 8 h after LPS stimulation, in comparison with cells cultured in medium before LPS stimulation. An increase in IL-1 beta protein production with variable secretion was noted in monocytes preincubated in IFN-gamma before stimulation with LPS. Monocytes preincubated for 1 day in 1,25-(OH)2-D3 alone or in both IFN-gamma and 1,25-(OH)2-D3 exhibited similar kinetics and peak expression of LPS-induced IL-1 beta mRNA levels as cells cultured in medium. However, monocytes preincubated for 1 day in both agents displayed a 50% or greater restoration in LPS-induced IL-1 beta synthesis and secretion in comparison with fresh cells. Granulocyte-macrophage-CSF did not augment the effects of the other differentiating agents on IL-1 beta production. Monocytes cultured over 6 days in differentiating agents failed to exhibit any restoration in LPS-induced IL-1 beta production. These in vitro-derived macrophages exhibited very low levels of both IL-1 beta mRNA and protein production under any culture condition. These results suggest that the effects of differentiating agents on LPS-induced IL-1 beta production may in part be related to the state of maturation of the monocyte. Furthermore, a repression in IL-1 beta transcription that is not reversed by exposure to differentiating agents may be acquired by monocytes as they mature into macrophages in vitro.

Mononuclear phagocytes and HSV-1 infection: increased permissivity in differentiated U937 cells is mediated by post-transcriptional regulation of viral immediate-early gene expression

Undifferentiated U937 cells are non-permissive for herpes simplex virus (HSV) infection but can be rendered permissive by treatment with phorbol myristate acetate (PMA), which causes them to differentiate to a macrophage-like phenotype. Following infection with HSV, both PMA--treated and untreated cells correctly transcribe the viral immediate-early genes at levels comparable to those observed in fully permissive cell types, but immediate-early RNA and protein are detected only in the PMA-treated cells. Hence PMA acts by relieving an early block to HSV infection caused by the rapid turnover of immediate-early RNA. This block is not caused by the production of soluble inhibitors and can also be relieved by treatment with other agents that cause macrophage differentiation such as 1, 25 dihydroxycholecalciferol. These findings therefore indicate that the non-permissivity of undifferentiated U937 cells for HSV is mediated by post-transcriptional regulation of immediate-early gene expression.

Effect on carbon lengthening at the side chain terminal of 1 alpha,25-dihydroxyvitamin D3 for calcium regulating activity

A series of analogs of 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3 (1)] with alkyl substitutions in 26- and 27-positions have been tested for their activity 1) in competing with 1,25-(OH)2D3 for binding to chick intestinal cytosol receptor, 2) in ability for formation of multinucleated cells (MNC) with various osteoclastic cell characteristics from blast cells, and 3) in stimulating bone calcium mobilization in vitamin D-deficient rats. The relative potencies of 1,25-(OH)2D3, 1 alpha,25-dihydroxy-26,27-dimethylvitamin D3 (2), 1 alpha,25-dihydroxy-26,27-diethylvitamin D3 (3), and 1 alpha,25-dihydroxy-26,27-dipropylvitamin D3 (4) in competing for intestinal cytosolic binding were 1:1.1:0.25:0.05. The similar order of the abilities on formation of the multinucleated cells in the same series was observed. In a bone calcium mobilization test with vitamin D-deficient rats, 1 alpha,25-dihydroxy-26,27-dimethylvitamin D3 showed slightly less activity than 1,25-(OH)2D3 at 12 h after administration, but long lasting activity was observed during time course experiments. 1 alpha,25-Dihydroxy-26,27-diethylvitamin D3, and 1 alpha,25-dihydroxy-26,27-dipropylvitamin D3 were found to be much less active than 1,25-(OH)2D3 in a bone calcium mobilization test.

1,24(R)-dihydroxyvitamin D3, a novel active form of vitamin D3 with high activity for inducing epidermal differentiation but decreased hypercalcemic activity

1 alpha,25-Dihydroxyvitamin D3 (1,25(OH)2D3) is known to be a hormonally active form of vitamin D3 in the regulation of intracellular and extracellular calcium levels and of differentiation of myeloid cells and epidermal keratinocytes. We found that 1 alpha,24(R)-dihydroxyvitamin D3 (1,24(OH)2D3), a novel synthetic derivative of vitamin D3, is also active in regulating the differentiation of epidermal keratinocytes. 1,24(OH)2D3 had the same affinity as 1,25(OH)2D3 for a receptor isolated from the epidermis of newborn mice. The incubation of mouse epidermal keratinocytes with 1,24(OH)2D3 induced their differentiation in a time- and dose-dependent manner, as determined by the formation of a cornified envelope and an increase in the activity of transglutaminase. 1,24(OH)2D3 inhibited DNA synthesis of epidermal keratinocytes and also increased their cytosolic calcium level. These effects of 1,24(OH)2D3 were similar to, or rather more than, those of physiologically active 1,25(OH)2D3. However, 1,24(OH)2D3 was found to cause less hypercalcemia than 1,25(OH)2D3 when administrated intravenously to rats, suggesting its possible therapeutic value in psoriasis.

Effect of 1,24R-dihydroxyvitamin D3 on the growth of human keratinocytes

The effect of 1,24R-dihydroxyvitamin D3 (1,24R(OH)2D3), a synthetic analogue of a biologically active form of vitamin D3 (1,25-dihydroxyvitamin D3, 1,25(OH)2D3), on the growth of human keratinocytes cultured in serum-free medium was investigated. The growth of cultured normal human keratinocytes was inhibited by 65% by 10(-8)M 1,24R(OH)2D3 and by 90% by 10(-7)M 1,24(OH)2D3. It inhibited cell growth almost completely at 10(-6)M. The DNA synthesis of keratinocytes was also inhibited with 1,24R(OH)2D3 by 27% at 10(-8)M, 59% at 10(-7)M, and 92% at 10(-6)M. The inhibition of cell growth and DNA synthesis were more remarkable by 1,24R(OH)2D3 than by 1,25(OH)2D3. 1,24R(OH)2D3 also inhibited the growth of keratinocytes derived from patients with psoriasis vulgaris; the growth inhibitory effect was again more remarkable with 1,24R(OH)2D3 than with 1,25(OH)2D3. The viability and protein synthesis of keratinocytes were not affected by 1,24R(OH)2D3, suggesting that the growth inhibitory effect is due to its biological activity, not to cytotoxicity. The binding of [3H]-labeled 1,25(OH)2D3 to its receptor in the cytosolic fraction of cultured keratinocytes was competitively substituted by unlabeled 1,24R(OH)2D3 as well as 1,25(OH)2D3, suggesting that 1,24R(OH)2D3 binds to the 1,25(OH)2D3 receptor. It was found that the affinity of 1,24R(OH)2D3 for the receptor was slightly higher than that of 1,25(OH)2D3. These results demonstrate that 1,24R(OH)2D3 functions as a potent growth inhibitor in vitro in human keratinocytes from both normal and psoriatic epidermis, and it possesses a higher affinity for the 1,25(OH)2D3 receptor in cultured human keratinocytes. The difference in affinity of 1,24R(OH)2D3 for the 1,25(OH)2D3 receptor correlates with its greater inhibition of keratinocyte growth than 1,25(OH)2D3. 1,24R(OH)2D3 may be useful in the treatment of psoriasis.

1,25-Dihydroxycholecalciferol and macrophage differentiation with aging

Aging is attended by both decreased levels of circulating 1,25-dihydroxy-vitamin D (1,25(OH)2D) and alterations of immune function. We have explored the relationship of these events via the effects of the steroid hormone on macrophage differentiation, using both the human leukemic cell line HL-60, which has the capacity to differentiate along a monocytic or granulocytic pathway, and authentic bone-marrow-derived macrophage precursors. When treated with 1,25(OH)2D, HL-60 cells undergo monocytic differentiation, as documented by the appearance of macrophage-specific membrane antigens and esterase activity. Also, 1,25(OH)2D increases [Ca2+]i in a slow tonic manner, an event that parallels f-Met-Leu-Phe (fMLP) receptor expression. The rise of [Ca2+]i is derived from influx of extracellular Ca2+ and is associated with increased inositol trisphosphate (IP3)-stimulated Ca2+ release from intracellular stores. On the other hand, while prevention of the 1,25(OH)2D-generated increase in [Ca2+]i leads to reduced superoxide generation, it does not block monocytic differentiation. 1,25(OH)2D also targets to authentic bone-marrow-derived macrophage precursors at all stages of differentiation. In CSF-1-dependent cells, the steroid produces doubling of expression of the mannose receptor, a macrophage-specific membrane protein, which is also expressed by differentiated osteoclasts. The macrophage-maturing effect of 1,25(OH)2D was further explored by analyzing its effect on fMLP signal transduction in HL-60 cells. While virgin HL-60 cells are unresponsive to fMLP, cells incubated for 24 h with 1,25(OH)2D respond to fMLP stimulation with a 60% increase in [Ca2+]i, and possess greater IP3-sensitive calcium stores than virgin cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of 1,25-dihydroxycholecalciferol on fracture healing and on general posttraumatic skeletal response in rats

The authors investigated the effect of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) on the local healing process following an artificial fracture of the rat tibia and on the general posttraumatic response of the skeleton to local trauma. The results showed a significant increase in dry weight of fractured tibias as compared with contralateral intact bones which was due to the newly formed callus. 1,25(OH)2D3 significantly increased the weights of tibias which can be explained by its stimulatory effect on callus formation. The uptake of 85Sr into bones resembling the metabolic pathways of calcium was significantly higher in fractured bones as compared with intact ones. 1,25(OH)2D3 significantly reduced the uptake of 85Sr. There was a significantly higher whole body retention of 85Sr in the rats with fractured bones. The administration of 1,25(OH)2D3 significantly reduced the retention of 85Sr in the fractured bone and the concomitant reduction of the whole body retention of 85Sr most likely reflected the increase in intestinal calcium absorption induced by 1,25(OH)2D3 with the consequent decrease in the specific activity of 85Sr administered in a single injection. The general posttraumatic response was reflected by increased dry weight of non-fractured bones. 1,25(OH)2D3 showed a contributory effect on this increase which may indicate that the general response consisted in increased bone formation. The uptake of 85Sr in non-fractured bones was reduced which was also most probably due to a decrease of specific activity of 85Sr. 1,25(OH)2D3 significantly accentuated the reduction of the uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

1 alpha,25(OH)2D3 exerts cytostatic effects on murine osteosarcoma cells and enhances the cytocidal effects of anticancer drugs

The effects of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), 1 alpha-hydroxyvitamin D3 (1 alpha(OH)D3), and dexamethasone on colony formation of Dunn osteosarcoma cells (TA 102 cells) were investigated. Concentrations of 1 alpha,25(OH)2D3, 1 alpha(OH)D3, and dexamethasone at which they exerted 50% reduction of the total area of TA 102 colony formation were 9 X 10(-9) M, 9 X 10(-8) M, and 5 X 10(-6) M, respectively. Effects of anticancer drugs on TA 102 cells were also investigated and concentrations needed for 50% growth inhibition (50% inhibitory concentration values) of cis-platinum, mitomycin C (MMC), methotrexate (MTX), and Adriamycin (ADR) against TA 102 cells were calculated to be 0.07 microgram/ml, 0.0008 microgram/ml, 0.0008 microgram/ml, and 0.0005 microgram/ml, respectively. The simultaneous treatment of TA 102 cells with 10(-8) M of 1 alpha,25(OH)2D3 and anticancer drugs significantly enhanced the respective inhibitory effects on colony formation. In this treatment, the IC50 value of MMC was calculated to be 6.4 X 10(-6) micrograms/ml, which was 1/160 of the expected IC50 value of MMC (8 X 10(-4) micrograms/ml). Similar synergistic effects were observed when the cells were treated with 1 alpha,25(OH)2D3 and low concentrations of cis-platinum, MTX, or ADR.

Age-dependent stimulation or inhibition of calcium release from bone cultures by 1 alpha, 25-dihydroxyvitamin D3

The effect of 1 alpha, 25-dihydroxyvitamin D3 (1 alpha, 25-(OH)2D3) on calcium release from neonatal and young adult mouse calvaria in tissue culture was studied. At concentrations from 2.6 X 10(-6) M to 2.6 X 10(-9) M, 1 alpha 25-(OH)2D3 enhanced calcium release from 5-day-old calvaria. At the same concentrations, 1 alpha, 25-(OH)2D3 either inhibited or failed to enhance calcium release from 75-day-old calvaria. Parathyroid hormone-enhanced calcium release from 75-day-old calvaria was inhibited considerably by 1 alpha, 25-(OH)2D3 at 2.6 X 10(-6) M and 2.6 X 10(-7) M. These findings suggest that cells involved in the bone resorption process may respond differently to the same stimulus at different stages in the development of the organism. This direct inhibitory effect of 1 alpha, 25-(OH)2D3 on bone resorption in cultured calvaria of older animals may explain, in part, its beneficial effect in the treatment of osteoporosis.

Effect of vitamin D metabolites on calcitriol metabolism in experimental renal failure

Previous studies from our laboratory have demonstrated that metabolic clearance rate (MCR) of calcitriol is decreased in experimental renal failure. In this experiment, we examined the effects of calcitriol, 25-hydroxyvitamin D3 (25(OH)D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) on the MCR of calcitriol in renal failure produced in rats by partial nephrectomy. The MCR of calcitriol in these rats with renal failure was significantly lower than in control rats with sham operations. Plasma concentrations of calcitriol did not differ between the rats with moderate renal failure and control rats (sham, 74.7 +/- 3.6 pg/ml, N = 7; renal failure, 67.7 +/- 6.0, N = 6; serum creatinine 0.56 +/- 0.02 mg/dl vs. 0.96 +/- 0.02); however, the levels were significantly lower in rats with severe renal failure (sham, 66.5 +/- 5.1 pg/ml, N = 7, severe renal failure, 49.6 +/- 2.1 pg/ml, N = 8; serum creatinine 0.53 +/- 0.01 mg/dl vs. 1.40 +/- 0.03). Subcutaneous infusion of calcitriol (10 ng/kg/day) in rats with severe renal failure for one week significantly increased the MCR of calcitriol (0.22 +/- .01 vs. 0.17 +/- .01 ml/min/kg, P less than 0.001). Infusion of 25(OH)D3 (600 ng/day) or 24,25(OH)2D3 (1 microgram/day) in rats with renal failure for one week also increased the MCR of calcitriol (25(OH)D3, 0.25 +/- 0.01 ml/min/kg; 24,25(OH)2D3, 0.25 +/- 0.01, both P less than 0.001) when compared to rats with renal failure infused with vehicle (0.21 +/- 0.01). Administration of 24,25(OH)2D3 significantly lowered the plasma levels of calcitriol in rats with renal failure (52.3 +/- 3.1 pg/ml, P less than 0.05) in comparison to the rats with renal failure infused with vehicle (67.7 +/- 6.0).(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of effect of 24,25-dihydroxyvitamin D3 administration on parameters of calcium metabolism

Seven patients with disordered calcium metabolism and high normal or elevated serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] were studied before and after the administration of 24,25-(OH)2D3 to determine its effects on calcium metabolism. Despite a significant increase in the mean serum 24,25-(OH)2D level [2.1 +/- 0.6 (+/- SE) to 16.7 +/- 6.2 nmol/L; P less than 0.05] after a daily dose of 20 micrograms for 1 month, there were no consistent changes in serum calcium, immunoreactive PTH, or 1,25-(OH)2D concentrations. Intestinal calcium absorption and urinary calcium excretion rose slightly during 24,25-(OH)2D administration in the majority of the patients. In the three patients in whom it was measured, serum 1,24,25-trihydroxyvitamin D levels did not change (19 +/- 5 vs. 20 +/- 5 pmol/L). We conclude that exogenous 24,25-(OH)2D3 at this dose has no significant antagonistic action on 1,25-(OH)2D and may have weak agonistic action.

Effects of vitamin D3 metabolites in ovariectomized rats

The effects of two vitamin D3 metabolites, 24R,25-dihydroxyvitamin D3 and 1 alpha,25-dihydroxyvitamin D3, were investigated in ovariectomized rats. The amount of ash in the femur on a defatted dry weight basis was significantly greater in rats treated with 1 microgram/kg 24R,25-dihydroxyvitamin D3, or 0.01 or 0.1 microgram/kg 1 alpha,25-dihydroxyvitamin D3 than in the controls. The concentration of bone gla protein in serum and amounts in the femur were significantly greater in rats treated with 1 or 10 micrograms/kg 24R,25-dihydroxyvitamin D3, but not those given 1 alpha,25-dihydroxyvitamin D3 compared with the controls. These results suggest that 24R,25-dihydroxyvitamin D3 increased bone mass probably through the stimulation of bone formation.

Vitamin D deficiency in the chick embryo: effects on prehatching motility and on the growth and differentiation of bones, muscles, and parathyroid glands

Vitamin D-deficient chicken embryos were obtained by feeding laying hens diets in which 3-7 micrograms calcitriol replaced the vitamin D3 supplement. A large proportion of the D-deficient embryos failed to complete the prehatching positional changes required to start pulmonary respiration. For this reason most of them became cyanotic and had subcutaneous edema and hemorrhages in the head and neck and died without hatching. Total as well as leg-bone and muscle weights were significantly lower in the deficient embryos than in the controls and these changes probably explain the inability of the embryos to complete the movements required to place the beak in contact with the air chamber and start pulmonary respiration. The histological study of the tibiae showed decreased mineralization with narrower trabeculae and enlarged osteoid seams; bone resorption at the inner surface was also significantly decreased. The ultrastructural study of parathyroid glands showed increased functional activity reflected by increased number and size of cisternae of rough endoplasmic reticulum. Injection of 10 ng calcitriol, 1 microgram 24,25-(OH)2D3, or 2 micrograms 25OHD3 to deficient embryos on the 14th day of incubation improved hatchability, bone and muscle weights, and both bone mineralization and resorption.

A direct effect of 24,25-(OH)2D3 and 1,25-(OH)2D3 on the modeling of fetal mice long bones in vitro

To examine the effects of 24,25-(OH)2D3 and 1,25-(OH)2D3 on fetal long bone modeling the radii and ulnae of 16 day fetal mice were grown in vitro for 2 days. Their growth, mineralization, and resorption were assessed by measuring diaphyseal length, calcium and phosphorus content, hydroxyproline-protein ratios, and the release of incorporated 45Ca. The results showed that 24,25-(OH)2D3 at concentrations of 10(-10)-10(-8) M stimulated the growth of the bones as indicated by their increased diaphyseal length, periosteal bone area, and hydroxyproline content. Calcium and phosphorus content was significantly increased; 45Ca release was unaltered. Bones incubated in media containing 10(-6) M 24,25-(OH)2D3 responded in a similar fashion to bones incubated in media containing 10(-10)-10(-8) M 1,25-(OH)2D3, with inhibition of bone growth as indicated by reduced diaphyseal length, periosteal bone area, hydroxyproline-protein ratios, and calcium and phosphorus content; 45Ca release was significantly increased. Neither metabolite affected total bone length. The results suggest a role for 24,25-(OH)2D3 in the growth of fetal mice bones in vitro and also confirm the findings from previous studies that 1,25-(OH)2D3 and high concentrations of 24,25-(OH)2D2 stimulate bone resorption.

Effects of vitamin D metabolites on collagen production and cell proliferation of growth zone and resting zone cartilage cells in vitro

Previous studies have suggested that vitamin D metabolites directly influence the differentiation and maturation of chondrocytes in calcifying cartilage. Recently, this laboratory has shown that the response of chondrocyte plasma membrane and matrix vesicle enzymes to 1,25-(OH)2D3 and 24,25-(OH)2D3 is both cell and membrane specific. The current study demonstrates that cell replication and matrix protein synthesis are also modulated by vitamin D. Confluent, third-passage growth zone (GC) and resting zone (RC) costochondral chondrocytes were incubated in medium containing 10(-13)-10(-7) M 1,25-(OH)2D3 or 10(-12)-10(-6) M 24,25-(OH)2D3. The amount of collagenase-digestible protein (CDP) secreted into the media was inversely proportional to the concentration of fetal bovine serum (FBS). At 10% FBS, greater than 80% of the CDP was incorporated into the matrix. 1,25-(OH)2D3 stimulated CDP and percentage collagen synthesis by GC cells but had no effect on the synthesis of noncollagenous protein (NCP). 1,25-(OH)2D3 inhibited CDP and percentage collagen synthesis by RC cells but did not alter NCP synthesis. [3H]thymidine incorporation was inhibited in both cell types, whether confluent or subconfluent cultures were examined. At 10(-6) and 10(-7) M 24,25-(OH)2D3, there was a significant decrease in CDP production and percentage collagen synthesis by RC cells but no effect on NCP. However, at 10(-9) and 10(-10) M hormone there was an increase in NCP production but no effect on CDP, resulting in a decrease in percentage collagen synthesis. CDP and NCP production were unaffected by 24,25-(OH)2D3 in GC cells. High concentrations of hormone inhibited [3H]thymidine incorporation in both cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of myelomonocytic U937 cells by vitamin D metabolites

Investigation of the effects of 1,25(OH)2D3 and 24,25(OH)2D3 on the proliferation and differentiation of the human myelomonocytic cell line U937 has been complemented with studies of the effect of the same metabolites on the number of nuclear receptors for 1,25(OH)2D3. Both 1,25(OH)2D3 and 24,25(OH)2D3 inhibit the proliferation of U937 cells in a dose-dependent manner. The concentrations of 24,25(OH)2D3 required to produce this effect were 100-times greater than those of 1,25(OH)2D3. Inhibition of proliferation was associated with increased expression of the CD14 and 200 kDa 63D3 antigens thus confirming differentiation of U937 towards a more mature cell type. Studies of the nuclear receptor for 1,25(OH)2D3 showed that pre-treatment of the cells with 1,25(OH)2D3 resulted in an apparent 40% decrease in the number of detectable 1,25(OH)2D3 receptors as compared to control U937 cells. This is due to the fact that the 1,25(OH)2D3 binds to U937 cell nuclei during culture and thus blocks the subsequent binding of radiolabelled 1,25(OH)2D3 used to measure the number of 1,25(OH)2D3 receptors. Measurement of the binding of unlabelled 1,25(OH)2D3 by radioimmunoassay indicated that pre-treatment of the cells with 1,25(OH)2D3 increased the capacity of U937 to bind the hormone, although measurement of these receptors by whole cell assay was prevented by the binding of 1,25(OH)2D3 itself. This effect was not observed with 24,25(OH)2D3 which was more easily displaced from binding sites by radiolabelled 1,25(OH)2D3 and it appears to act through low affinity binding to the 1,25(OH)2D3 receptor.

Free, and not total, 1,25-dihydroxyvitamin D regulates 25-hydroxyvitamin D metabolism by keratinocytes

Greater than 99% of the total circulating 1,25-dihydroxyvitamin D [1,25-(OH)2D] is bound to proteins such as the vitamin D-binding protein (DBP) and albumin; in the normal human only 0.4% of the circulating 1,25-(OH)2D is free. Although it is often assumed that only the free concentration of 1,25-(OH)2D is available to cells, this has not been demonstrated. In particular, it is not clear whether the DBPs facilitate 1,25-(OH)2D entry into target cells or serve only to transport these metabolites within the circulation. To address this question, we evaluated one of the best characterized target tissue responses to 1,25-(OH)2D, namely its ability to inhibit its own production and induce that of 24,25-(OH)2D, using one of the most sensitive cells, the human foreskin keratinocyte. We incubated keratinocytes in the presence of 1,25-(OH)2D (from 10(-11)-10(-8) M) in medium containing albumin (from 0.1-10%) or serum (from 0.1-10%) for 4 h [to inhibit the 25-hydroxyvitamin D (250HD) 1 alpha-hydroxylase] or 16 h (to induce the 250HD 24-hydroxylase) before evaluating [3H]250HD metabolism by these cells during a 1-h incubation in serum- and albumin-free medium. The free fraction of 1,25-(OH)2D was determined in each medium by centrifugal ultrafiltration and varied from 36% to 0.57% in direct proportion to the albumin or serum in the medium. Increasing the serum or albumin concentration in the medium increased the concentration of total 1,25-(OH)2D needed to inhibit its own production or stimulate that of 24,25-(OH)2D. In contrast, the concentration of free 1,25-(OH)2D needed to half-maximally inhibit its own production or induce 24,25-(OH)2D production remained constant at approximately 10(-11) M. We conclude that the free, not the total, 1,25-(OH)2D concentration regulates 250HD metabolism by keratinocytes, that DBPs do not facilitate 1,25-(OH)2D entry into the cell, and that these cells sense only free 1,25-(OH)2D.

[Role of vitamin D3 in hematology]

It has been recently shown that 1,25(OH)2D3 induces differentiation and inhibits the proliferation of normal and leukemic cells in vitro. A review of the literature and the preliminary clinical applications of this vitamin in hematology are reported.

Increased mechanical strength of the vitamin D-replete rat femur by the treatment with a large dose of 24R,25(OH)2D3

The mechanical properties of the rat femur treated with a large dose of 24R,25(OH)2D3 were examined and their relationship with the mass and mineral contents of the bone were investigated. Male Wistar rats were fed diet containing 0, 0.025, 1.25, 4.0, or 12.5 ppm 24R,25(OH)2D3 for two years starting six weeks after birth. The rats were killed and their right femurs were removed. The adhering soft tissue were stripped off. Radiographs were made of the femur and its bone mineral content was measured by single photon absorptiometry. Then a three-point bending test was done with pressure exerted in the plane of natural extension. After mechanical testing, non-decalcified cross-sections of the femur were prepared at the mid diaphysis as close to the test fracture site as possible. On x-ray images, the cortical thickness was clearly increased in groups treated with larger doses, and the mid-cortical segmental mineral content of the femur increased dose-dependently to about 150%. The mechanical parameters in the treated animals also increased significantly, strength to 120% (p less than 0.01), energy-absorption capacity to 124% (p less than 0.05), and structural stiffness to 183% (p less than 0.01). Segmental bone mineral contents showed the positive correlations with strength and structural stiffness in both the control and the 24R,25(OH)2D3 treated groups as well. We concluded that the increase in the bone density in animals administered high doses of 24R,25(OH)2D3 was accompanied by an increase in mechanical strength of the bone.

Effect of 24,25-dihydroxyvitamin D3 on 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] metabolism in vitamin D-deficient rats infused with 1,25-(OH)2D3

Previous studies revealed that administration of 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] to calcium (Ca)-deficient rats causes a dose-dependent reduction in markedly elevated serum 1,25-(OH)2D3 level. Although the results suggested that the metabolism of 1,25-(OH)2D3 was accelerated by 24,25-(OH)2D3, those experiments could not define whether the enhanced metabolism of 1,25-(OH)2D3 played a role in the reduction in the serum 1,25-(OH)2D3 level. In the present study, in order to address this issue more specifically, serum 1,25-(OH)2D3 was maintained solely by exogenous administration through miniosmotic pumps of 1,25-(OH)2D3 into vitamin D-deficient rats. Thus, by measuring the serum 1,25-(OH)2D3 concentration, the effect of 24,25-(OH)2D3 on the MCR of 1,25-(OH)2D3 could be examined. Administration of 24,25-(OH)2D3 caused a dose-dependent enhancement in the MCR of 1,25-(OH)2D3, and 1 microgram/100 g rat.day 24,25-(OH)2D3, which elevated serum 24,25-(OH)2D3 to 8.6 +/- 1.3 ng/ml, significantly increased MCR and suppressed serum levels of 1,25-(OH)2D3. The effect of 24,25-(OH)2D3 on 1,25-(OH)2D3 metabolism developed with a rapid time course, and the recovery of iv injected [1 beta-3H]1,25-(OH)2D3 in blood was significantly reduced within 1 h. In addition, there was an increase in radioactivity in the water-soluble fraction of serum as well as in urine, suggesting that 1,25-(OH)2D3 is rapidly degraded to a water-soluble metabolite(s). Furthermore, the reduction in serum 1,25-(OH)2D3 was associated with a reduction in both serum and urinary Ca levels. Because the conversion of [3H]24,25-(OH)2D3 to [3H]1,24,25-(OH)2D3 or other metabolites was minimal in these rats, 24,25-(OH)2D3 appears to act without being converted into other metabolites. These results demonstrate that 24,25-(OH)2D3 rapidly stimulates the metabolism of 1,25-(OH)2D3 and reduces its serum level. It is suggested that 24,25-(OH)2D3 plays a role in modifying serum 1,25-(OH)2D3 concentrations by affecting the metabolism of 1,25-(OH)2D3 and may have a therapeutic values in the treatment of hypercalcemia or hypercalciuria caused by 1,25-(OH)2D3 excess.

Regulation of type I collagen synthesis by 1,25-dihydroxyvitamin D3 in human osteosarcoma cells

Synthesis of type I and III collagens has been examined in MG-63 human osteosarcoma cells after treatment with the steroid hormone, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Analysis of total [3H]proline-labeled proteins and pepsin-derived collagens revealed that 1,25-(OH)2D3 selectively stimulated synthesis of alpha 1I and alpha 2I components of type I collagen after 6-12 h. Consistent with previous reports (Franceschi, R. T., Linson, C. J., Peter, T. C., and Romano, P. R. (1987) J. Biol. Chem. 262, 4165-4171), parallel increases in fibronectin synthesis were also observed. Hormonal effects were maximal (2- to 2.5-fold versus controls) after 24 h and persisted for at least 48 h. In contrast, synthesis of the alpha 1III component of type III collagen was not appreciably affected by hormone treatment. Of several vitamin D metabolites (1,25-(OH)2D3, 25-dihydroxyvitamin D3, and 24R,25-dihydroxyvitamin D3) tested for activity in stimulating type I collagen synthesis, 1,25-(OH)2D3 was found to be the most active. Analysis of collagen mRNA abundance by Northern blot hybridization indicated that both types I and III procollagen mRNAs were increased 4-fold after a 24-h exposure to 1,25-(OH)2D3. Pro alpha 1I mRNA remained elevated through the 48-h time point while pro alpha 2I and pro alpha 1III mRNAs returned to control values. These results indicate that the regulation of collagen synthesis by 1,25-(OH)2D3 is complex and may involve changes in translational efficiency as well as mRNA abundance. 1,25-(OH)2D3 also caused at least a 20-fold increase in levels of the bone-specific calcium-binding protein, osteocalcin. These results are consistent with the hypothesis that 1,25-(OH)2D3 is stimulating partial differentiation to the osteoblast phenotype in MG-63 cells.

Direct effects of 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 on growth zone and resting zone chondrocyte membrane alkaline phosphatase and phospholipase-A2 specific activities

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] and 24,25-(OH)2D3 differentially affect the specific activity of alkaline phosphatase (ALPase) and phospholipase-A2 (PLA2) of plasma membranes and extracellular matrix vesicles produced by costochondral reserve zone and growth zone cartilage chondrocytes in culture. In the present study, growth zone and cartilage and reserve zone matrix vesicles and plasma membranes were isolated from confluent chondrocyte cultures and incubated with hormone for 3 and 24 h in vitro. Addition of 1,25-(OH)2D3 to GC matrix vesicles and plasma membranes resulted in dose-dependent increases in ALPase and PLA2 specific activities in both membrane fractions. Addition of 24,25-(OH)2D3 to RC membrane fractions stimulated matrix vesicle ALPase at 10(-7) and 10(-8) M and plasma membrane ALPase at 10(-8) M only. However, 24,25-(OH)2D3 inhibited matrix vesicle and plasma membrane PLA2 activity. The effects of the vitamin D metabolites were noticed after both 3 and 24 h. Neither hormone metabolite had any effect on these enzymes in membrane fractions from cultures of neonatal rat muscle mesenchymal cells, which do not calcify their matrix in vivo. These data suggest that 1,25-(OH)2D3 and 24,25-(OH)2D3 can directly affect chondrocyte membrane enzymes without genomic influence or protein synthesis and that membrane response depends on the stage of chondrocyte differentiation. Changes in PLA2 activity may change membrane fluidity and may be a mechanism by which the hormones affect cell membranes.

Acute stimulation of creatine kinase activity by vitamin D metabolites in the developing cerebellum

There is increasing evidence that vitamin D metabolites have a developmental function. We have investigated the influence of the vitamin D status on the activity of creatine kinase in the brain. Normally fed rats show an increase in the specific activity of cerebral and cerebellar creatine kinase during postnatal development. Vitamin-D-depleted rats failed to show this normal increase. Developing cerebellum, but not cerebrum, in both vitamin D-depleted rats and in normally fed animals, responded sequentially to a single injection of a vitamin D metabolite by displaying increased creatine kinase specific activity. In 5-25-day-old rats, 24R,25-dihydroxyvitamin D-3 significantly increased creatine kinase specific activity 24 h after injection. In contrast, 1,25-dihydroxyvitamin D-3 stimulated cerebellar creatine kinase activity from 20 days after birth. A similar pattern of sequential responsiveness to vitamin D metabolites, but at an earlier age, was shown in the cerebellum of the rabbit, which is a 'perinatal brain developer' compared to the rat, a 'postnatal brain developer'. Because of the difficulty in obtaining vitamin D-depleted rabbits, studies were carried out in normally fed animals. In these rabbits, 24R,25-dihydroxyvitamin D-3 stimulated cerebellar creatine kinase activity between 6 days before birth and 9 days after birth, while 1,25-dihydroxyvitamin D-3 caused an increase in cerebellar creatine kinase specific activity from 8 days after birth. These developmental differences found in creatine kinase basal activity and responsiveness are correlated with differences in cellular growth rates, both in the rabbit and in the rat, suggesting that vitamin D metabolites may be required for optimal cerebellar development.

The influence of vitamin D metabolites on the calcification of cartilage matrix and the C-propeptide of type II collagen (chondrocalcin)

The influence of vitamin D metabolites (at 1 X 10(-10) M) on the calcification of cartilage matrix (measured by 45Ca2+ uptake) and the C-propeptide of type II collagen (measured by radioimmunoassay) has been studied using organ cultures and chondrocytes isolated from growth plates of vitamin D-deficient and -sufficient 11-day-old rats. Vitamin D-deficient rats had reduced amounts of C-propeptide in their serum and freshly isolated growth plate chondrocytes. In all chondrocytes cultured from vitamin D-deficient animals, the C-propeptide content was maximal at 24 hr whereas calcification continued to increase for up to 72 hr. In organ and chondrocyte cultures of tissue from vitamin D-sufficient rats, both 1,25-dihydroxycholecalciferol (1,25(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25(OH)2D3) were required for maximal stimulation of calcification and maximal increases in C-propeptide content. In these D-replete tissues, 24,25-(OH)2D3 had a less stimulatory effect on both calcification (organ and cell cultures) and C-propeptide (organ cultures only), while 1,25(OH)2D3 alone had no effect in cell cultures but an inhibitory effect in organ cultures. Studies of cells or tissue from growth plates of vitamin D-deficient rats demonstrated that 24,25(OH)2D3 alone produced maximal calcification and maximal increases in the C-propeptide content. 1,25(OH)2D3 generally had an inhibitory effect on both calcification and C-propeptide when used alone. In the presence of 1,25(OH)2D3, the stimulatory effect of 24,25(OH)2D3 was partly abrogated. Maximal stimulation of calcification and increases in C-propeptide by 24,25(OH)2D3 were observed at 1 X 10(-9) M and 1 X 10(-10) M. In none of these studies was there any effect on proteoglycan content.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat epiphyseal cells in culture: responsiveness to bone-seeking hormones

Cell cultures derived from young rat epiphyseal cartilage were grown for approximately 2 wk in BGJb medium supplemented with 10% fetal bovine serum to reach confluence. These cells were identified as chondrocytes as checked by morphology, the presence of alkaline phosphatase, and a positive type II collagen antibody reaction. The cells also responded to different hormonal treatment. Parathyroid hormone (PTH) increased cyclic AMP production by 50% within 15 min of treatment, whereas prostaglandin E2 (PGE2) caused an increase of 160%. Calcitonin (CT) did not affect cAMP production in these cells. DNA synthesis 24 h after hormonal treatment was increased by PTH (2.5-fold) and PGE2 (2-fold), but not by CT. Among the vitamin D metabolites, 24,25(OH)2D3 increased significantly the [3H]thymidine incorporation into DNA, whereas 1,25(OH)2D3 effect was minimal. These results provide evidence for the use of these cell cultures as a model for cartilage in vitro when studying biological and hormonal responsiveness.

Effect of vitamin D status on the activity of carbonic anhydrase in chicken epiphysis and kidney

Chickens were raised for 6 weeks from the date of hatch under red light on a vitamin D-free diet; controls were given an oral vitamin D supplement. Vitamin D-deficient animals showed decreased total serum calcium concentration and decreased DNA content in epiphysis and kidney homogenates. In calcifying epiphysis, total carbonic anhydrase (CA) activity was decreased, but activity per microgram DNA was slightly increased and specific activity was double that of the controls. Polyacrylamide gel isoelectric focusing after preparation of the enzyme showed a picture similar to that seen after parathyroid hormone (PTH) administration in chicks; therefore, this could be considered a secondary hyperparathyroidism. The CA activation was not seen in the kidney which can be explained by induction of an endogenous inhibitor protein of the cyclic AMP-dependent protein kinase exclusively in the kidney in vitamin D deficiency. In an additional experiment, chickens were raised for 3 weeks from the date of hatch under red light on a vitamin D-free diet. Daily oral substitution by different vitamin D metabolites (1,25(OH)2D3, 25OHD3, 24,25(OH)2D3) over 7 days led to CA activation compared with controls probably by restoring protein kinase activity in the kidney. Our results show that CA activity is inversely correlated with serum calcium concentrations which is in agreement with a regulatory mechanism recently proposed by us.

Effect of 24R,25-dihydroxyvitamin D3 in experimental diabetic rats

The results are presented of a controlled study in male Wistar rats into the effects of 24R,25-dihydroxyvitamin D3 on blood glucose levels, bone calcium content and ADP-induced platelet aggregation in streptozocin-induced diabetes mellitus. Blood glucose levels were shown to be decreased by 10 micrograms/kg 24R,25-dihydroxyvitamin D3. The reduced bone calcium content associated with diabetes mellitus was returned to normal levels with both 1 and 10 micrograms/kg 24R,25-dihydroxyvitamin D3. It was also shown to exhibit dose-dependent anti-platelet activity. The data suggest that 24R,25-dihydroxyvitamin D3 might have potential as a mild therapeutic agent in the treatment of osteoporosis and platelet hyperactivity associated with diabetes mellitus.

The effects of vitamin D metabolites on the plasma and matrix vesicle membranes of growth and resting cartilage cells in vitro

This study compares the effects of vitamins 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and 24,25-(OH)2D3 on populations of chondrocytes at different developmental stages. Confluent third passage chondrocytes derived from the resting zone and adjacent growth region of rat costochondral cartilage were cultured in Dulbecco's Modified Eagle's Medium containing 10% fetal bovine serum and increasing concentrations of hormone. After determination of cell number, matrix vesicles and plasma membranes were isolated by differential centrifugation. The effects of hormone on alkaline phosphatase, 5'-nucleotidase, ouabain-sensitive Na+/K+-ATPase, and phospholipid composition were dependent on vitamin D metabolite and were cell specific. Growth cartilage chondrocytes responded primarily to 1,25-(OH)2D3, whereas resting zone cells responded primarily to 24,25-(OH)2D3. 1,25-(OH)2D3 inhibited growth cartilage cell number at pharmacological concentrations and had no effect on resting cartilage cell number. In contrast, 24,25-(OH)2D3 appeared to stimulate resting cartilage cell number at physiological concentrations and inhibit these cells at pharmacological doses, but had no effect on growth cartilage chondrocytes. These data were supported by [3H]thymidine incorporation studies. 1,25-(OH)2D3 stimulated alkaline phosphatase, 5'-nucleotidase activity, and Na+/K+-ATPase activity in the matrix vesicles of growth cartilage cells. 1,25-(OH)2D3 also stimulated Na+/K+-ATPase activity in the matrix vesicles and plasma membranes of resting zone cells. Incubation with 24,25-(OH)2D3 stimulated alkaline phosphatase, 5'-nucleotidase, and Na+/K+-ATPase in the matrix vesicles produced by resting zone cells. In addition, 24,25-(OH)2D3 stimulated Na+/K+-ATPase activity in the plasma membranes of resting zone cells as well as in both matrix vesicles and plasma membranes of growth cartilage cells.

Localization of vitamin D3-responsive alkaline phosphatase in cultured chondrocytes

Alkaline phosphatase activity appears to be altered when chondrocyte cultures are incubated with 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). This study examined whether the hormone-responsive enzyme activity is associated with alkaline phosphatase-enriched extracellular membrane organelles called matrix vesicles. Confluent, third passage cultures of rat costochondral growth cartilage (GC) or resting zone chondrocytes (RC) were incubated with 1,25-(OH)2D3 or 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3) and enzyme specific activity was assayed in the cell layer or in isolated matrix vesicle and plasma membrane fractions. Alkaline phosphatase-specific activity in the matrix vesicles was enriched at least 2-fold over that of the plasma membrane and 10-fold over that of the cell layer. Matrix vesicle alkaline phosphatase was stimulated by 1,25-(OH)2D3 in GC cultures and by 24,25-(OH)2D3 in RC cultures. The cell layer failed to reveal these subtle differences. 1,25-(OH)2D3 increased GC enzyme activity but the effect was one-half that observed in the matrix vesicles alone. No effect of 1,25-(OH)2D3 on enzyme activity of the RC cell layer or of 24,25-(OH)2D3 on either GC or RC cell layers was detected. Thus, response to the metabolites is dependent on chondrocytic differentiation and is site specific: the matrix vesicle fraction is targeted and not the cells per se.