Effects Of Vitamin D3 Analogs Research Articles

Clinical effect of vitamin D3 analogues is not inactivated by subsequent UV exposure

Combining phototherapy with topical vitamin D3 analogues is a useful therapy for the treatment of psoriasis by reducing the cumulative UV dose required for clearance of lesions. Experimental investigations demonstrated that calcipotriol is degraded by UV radiation, and suggested that calcipotriol should be applied after phototherapy but not immediately before. Calcipotriol or maxacalcitol ointment was topically applied to psoriatic plaques of six patients immediately before or after phototherapy on the right or left side of the body, respectively. Topical application of vitamin D3 analogues either before or after irradiation by psoralen and UVA radiation (PUVA) or narrow-band (NB)-UVB showed exactly similar effects in all patients. Therapeutic effects of vitamin D3 analogues are not clinically inactivated by subsequent irradiation with PUVA or NB-UVB phototherapy.

Autocrine TGFβ signaling mediates vitamin D3 analog‐induced growth inhibition in breast cells

In this study, we address whether TGFbeta signaling mediates vitamin D3 analog-induced growth inhibition in nonmalignant and malignant breast cells. Normal mammary epithelial cells (184), immortalized nonmalignant mammary epithelial cells (184A1 and MCF10A), and breast cancer cells (early passage MCF7: MCF7E) were sensitive to the inhibitory effects of vitamin D3 analogs (EB1089 and MC1288) while late passage MCF7 breast cancer (MCF7L) cells were relatively resistant. A similar pattern of sensitivity to TGFbeta was observed with these cells. Thus, the sensitivity to the vitamin D3 analogs correlated with the sensitivity to TGFbeta. MCF7L TGFbetaRII-transfected cells, which have autocrine TGFbeta activity, were more sensitive to EB1089 than MCF7L cells. TGFbeta neutralizing antibody was found to block the inhibitory effects of these analogs. These results are consistent with the idea that autocrine TGFbeta signaling mediates the anti-proliferative effects of the vitamin D3 analogs in these cells. The expression of TGFbeta isoforms and/or TGFbeta receptors was induced by the analogs in the vitamin D3 and TGFbeta sensitive cells. Vitamin D3 analogs did not induce TGFbeta or TGFbeta receptor expression in the resistant MCF7L cells. Therefore, EB1089 induces autocrine TGFbeta activity through increasing expression of TGFbeta isoforms and/or TGFbeta receptors. In addition, EB1089 induced nuclear VDR protein levels in the sensitive 184A1 cells but not in the resistant MCF7L cells. 184A1 cells were more sensitive to EB1089-induced VDR-dependent transactivation than MCF7L cells as measured by a luciferase reporter construct containing the VDRE, indicating a defect of VDR signaling in MCF7L cells. Smad3, a TGFbeta signaling mediator, coactivated VDR-dependent transactivation in 184A1 cells but not in MCF7L cells. These results indicate that Smad3 coactivates VDR to further enhance TGFbeta signaling and vitamin D3 signaling in the sensitive 184A1 cells. The results also indicate that Smad3 is not of itself sufficient to coactivate VDR in TGFbeta/vitamin D3 resistant MCF7L cells and other factors are required. We found that the PI 3-kinase pathway inhibitor LY29004 inhibited the synergy of TGFbeta and EB1089 on VDR-dependent transactivation activity. This indicates that the crosstalk between TGFbeta and vitamin D signaling is also PI 3-kinase pathway dependent.

In vivo effects of vitamin D3 analogues

Several in vivo studies have been carried out on the effect of vitamin D3 analogues on epidermal proliferation, keratinization and inflammation in psoriasis. Vitamin D3 analogues have a pronounced effect on epidermal proliferation, keratinization and accumulation of neutrophils in psoriatic lesional skin. Of these effects the antiproliferative effect proved to be a sustained and prolonged action of vitamin D3 analogues.

Vitamin D3 analogs and their 24-Oxo metabolites equally inhibit clonal proliferation of a variety of cancer cells but have differing molecular effects

The seco-steroid hormone, 1 alpha, 25 dihydroxyvitamin D3 (1 alpha,25(OH)2D3) binds to a specific nuclear receptor that acts as a ligand-inducible transcription factor. The resulting genomic effects include partial arrest in G0/G1 of the cell cycle and induction of differentiation; these effects have been observed in various types of cancer. Recently, we produced enzymatically the natural 24-oxo metabolites of 1 alpha,25(OH)2D3 and two of its potent synthetic analogs (1 alpha,25-(OH)2-16-ene-D3 and 1 alpha,25-(OH)2-20-epi-D3) using a rat kidney perfusion system. We have found that the 24-oxo metabolites of both 1 alpha,25(OH)2D3 and its analogs have either the same or greater antiproliferative activity against various cancer cells as their parental compounds. Notably, two cell lines (DU-145 (prostate cancer) and MDA-MB-436 [breast cancer]) that were extremely resistant to the antiproliferative effects of vitamin D3 analogs displayed greater sensitivity towards the 24-oxo metabolite of the vitamin D3 analog. Similarly, the 24-oxo metabolites had the capacity to induce differentiation and apoptosis and to diminish the proportion of cells in S phase. Most interestingly, while the analog 1 alpha,25(OH)2-20-epi-D3 induced expression of BRCA1 in MCF-7 breast cancer cells; its 24-oxo metabolite dramatically suppressed BRAC1 expression. Thus, we have shown for the first time that the various biological activities produced by the hormone 1 alpha,25(OH)2D3 and some of its analogs may represent a combination of actions by the hormone 1 alpha,25(OH)2D3 and its natural 24-oxo metabolites.

The in vitro effect of vitamin D3 analogue EB-1089 on a human prostate cancer cell line (PC-3).

To determine the effect of vitamin D3 analogue (EB-1089) on the growth and proliferation of a prostate cancer cell line (PC-3). PC-3 cells (10(4) cells per well) were plated into 24-well tissue culture plates. After 24 h, the culture medium was replaced with one containing the vitamin D3 analogue EB-1089; a control treatment using only replacement medium was conducted in parallel. Cell proliferation was measured by the incorporation of 3H-thymidine 7 and 12 days after the addition of the vitamin D3 analogue. Cells were precipitated with 5% trichloroacetic acid and the radioactivity determined using a scintillation counter. Each experiment was performed at least five times. There was a significant dose-dependent inhibition of cell growth after 7 and 12 days of treatment with EB-1089, varying from 40 to 70% of the 3H-thymidine incorporation by controls, respectively. The maximum inhibition occurred with 0.1 micromol/L EB-1089 on day 7 and day 12 (both P < 0.01). Longer incubation times appeared to have a greater effect when higher concentrations of EB-1089 were used. These in vitro studies have shown that the vitamin D3 analogue EB-1089 can significantly reduce the growth rate of the prostate cancer cell line PC-3. This would support the hypothesis that deficiency of vitamin D increases the risk of prostate cancer and further in vivo testing of vitamin D is warranted for its potential role in active therapy.

Vitamin D analog 25‐(OH)‐16,23E‐diene‐26,27‐hexafluoro‐vitamin D3 induces differentiation of HL60 cells with minimal effects on cellular calcium homeostasis

Numerous vitamin D3 analogs (VDAs) can inhibit the proliferation of cells from several types of human malignancies. The physiologically active form of vitamin D3, 1,25-dihydroxyvitamin D3(1,25D3), is formed by successive hydroxylations of cholecalciferol at the 25 and 1α positions. In this study we examined the effects of the absence of the 1α(OH) group, introduction of a double bond in position 16, and further modifications at the 23, 26, and 27 positions in the side chain on the potency of the VDAs. The parameters studied were the rapidity of the induction of monocytic differentiation, the cell cycle traverse, and the effects of VDAs on intracellular calcium homeostasis in HL60 cells. The results show that (1) 1,25D3 derivatives which lack the 1α(OH) group have little differentiation-inducing activity, (2) hexafluorination (6F) of the terminal methyl groups in the side chain partially restores the activity of 1α-desoxy compounds and potentiates the activity of 1α hydroxylated compounds, and (3) 25-(OH)-16,23E-diene-26,27-hexafluoro-vitamin D3 (Ro25-9887) alone among the twelve compounds tested induces differentiation with only minimal changes in the basal levels of intracellular calcium and store-dependent calcium influx in HL60 cells. Addition of 1α(OH) group to this compound increases its differentiation-inducing activity but also elevates basal calcium level. The results suggest that altered calcium homeostasis is not an obligatory component of HL60 leukemia cell differentiation, and that Ro25-9887 and related VDAs may be suitable for testing as components of anti-leukemic therapy. © 1996 Wiley-Liss, Inc.

Vitamin D analog 25-(OH)-16,23E-Diene-26,27-hexafluoro-vitamin D3 induces differentiation of HL60 cells with minimal effects on cellular calcium homeostasis.

Numerous vitamin D3 analogs (VDAs) can inhibit the proliferation of cells from several types of human malignancies. The physiologically active form of vitamin D3, 1,25-dihydroxyvitamin D3(1,25D3), is formed by successive hydroxylations of cholecalciferol at the 25 and 1 alpha positions. In this study we examined the effects of the absence of the 1 alpha (OH) group, introduction of a double bond in position 16, and further modifications at the 23, 26, and 27 positions in the side chain on the potency of the VDAs. The parameters studied were the rapidity of the induction of monocytic differentiation, the cell cycle traverse, and the effects of VDAs on intracellular calcium homeostasis in HL60 cells. The results show that (1) 1,25D3 derivatives which lace the 1 alpha (OH) group have little differentiation-inducing activity, (2) hexafluorination (6F) of the terminal methyl groups in the side chain partially restores the activity of 1 alpha-desoxy compounds and potentiates the activity of 1 alpha hydroxylated compounds, and (3) 25-(OH)-16,23E-diene-26,27-hexafluoro-vitamin D2 (Ro25-9887) alone among the twelve compounds tested induces differentiation with only minimal changes in the basal levels of intracellular calcium and store-dependent calcium influx in HL60 cells. Addition of 1 alpha (OH) group to this compound increases its differentiation-inducing activity but also elevates basal calcium level. The results suggest that altered calcium homeostasis is not an obligatory component of HL60 leukemia cell differentiation, and that Ro25-9887 and related VDAs may be suitable for testing as components of anti-leukemic therapy.

Vitamin D analog 25-(OH)-16,23E-diene-26,27-hexafluoro-vitamin D3 induces differentiation of HL60 cells with minimal effects on cellular calcium homeostasis

Numerous vitamin D3 analogs (VDAs) can inhibit the proliferation of cells from several types of human malignancies. The physiologically active form of vitamin D3, 1,25-dihydroxyvitamin D3(1,25D3), is formed by successive hydroxylations of cholecalciferol at the 25 and 1 alpha positions. In this study we examined the effects of the absence of the 1 alpha (OH) group, introduction of a double bond in position 16, and further modifications at the 23, 26, and 27 positions in the side chain on the potency of the VDAs. The parameters studied were the rapidity of the induction of monocytic differentiation, the cell cycle traverse, and the effects of VDAs on intracellular calcium homeostasis in HL60 cells. The results show that (1) 1,25D3 derivatives which lace the 1 alpha (OH) group have little differentiation-inducing activity, (2) hexafluorination (6F) of the terminal methyl groups in the side chain partially restores the activity of 1 alpha-desoxy compounds and potentiates the activity of 1 alpha hydroxylated compounds, and (3) 25-(OH)-16,23E-diene-26,27-hexafluoro-vitamin D2 (Ro25-9887) alone among the twelve compounds tested induces differentiation with only minimal changes in the basal levels of intracellular calcium and store-dependent calcium influx in HL60 cells. Addition of 1 alpha (OH) group to this compound increases its differentiation-inducing activity but also elevates basal calcium level. The results suggest that altered calcium homeostasis is not an obligatory component of HL60 leukemia cell differentiation, and that Ro25-9887 and related VDAs may be suitable for testing as components of anti-leukemic therapy.

Direct effects of vitamin D3 analogues on G-protein mediated signalling systems in rat osteosarcoma cells and rat pituitary adenoma cells.

In normal rats treated with 1,25(OH)2D3 or 24,25(OH)2D3, serum Ca2+, ALP, PRL and GH are significantly altered. In order to study the primary effect of vitamin D3 analogues on target organ function, rat UMR 106 osteosarcoma and GH3 pituitary adenoma cells in monolayer culture were exposed accordingly. Surprisingly, prolonged exposure of these cell lines to physiological levels of either 1,25(OH)2D3 or 24,25(OH)2D3 did not significantly affect the secretory parameters (ALP, PRL or GH) tested. However, 1,25(OH)2D3 exposure significantly reduced PTH- and Gpp(NH)p-elicited AC as well as Gpp(NH)p-stimulated PLC activities in the UMR 106 cells. These changes were accompanied by an increase and decrease in the membrane contents of the G-protein subunits G36 beta and Gq/11 alpha, respectively. In contrast, 24,25(OH)2D3 remained without significant biological effect on these signalling systems despite concomitantly augmented levels of G36 beta. TRH- and Gpp(NH)p-elicited PLC activities in the GH3 cells were significantly reduced by 1,25(OH)2D3 with a concurrent reduction in cellular amounts of Gq/11 alpha, however, 24,25(OH)2D3 did not significantly alter any signalling systems nor G-proteins analyzed. It is concluded that the osteoblastic and pituitary cell secretion of ALP, PRL and GH remain unaffected by the presence of 1,25(OH)2D3 and 24,25(OH)2D3, despite distinct alterations in components of G-protein mediated signalling pathways. Hence, other factors like ambient Ca2+ may be responsible for the perturbed secretory patterns of ALP and PRL seen in vitamin D3 treated rats.

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.

P-526 - Effect of vitamin D3 analogues on interleukin 1 (IL-1) production in mice.

P-526 - Effect of vitamin D3 analogues on interleukin 1 (IL-1) production in mice.

P-527 - Inhibitory effect of vitamin D3 analogues on immunologically induced liver injuries in mice.

P-527 - Inhibitory effect of vitamin D3 analogues on immunologically induced liver injuries in mice.