Structural development of non-secosteroidal vitamin D receptor (VDR) ligands without any asymmetric carbon.

Non-secosteroidal VDR ligands without any assymmetric carbon were designed and synthesized based on the structure of the previously reported non-secosteroidal VDR agonist LG190178. The VDR-agonistic activity of all synthesized compounds was evaluated, and 7b emerged as a potent agonist activity with an EC50 value of 9.26 nM. Moreover, a docking simulation analysis was also performed to determine the binding mode of 7b with VDR-LBD.

Electroclinical and radiological observation of dysfunctional zones in a patient with neurosyphilis.

We report a 33-year-old Japanese man who suffered from repetitive generalized tonic-clonic seizures which were medically intractable. Neurosyphilis was serologically diagnosed in blood and cerebrospinal fluid, and penicillin G (PcG) was consequently effective. The EEG during PcG pre-treatment showed frequent right occipital spikes and right frontocentral slow waves, which disappeared after treatment. During pre-treatment, positron emission tomography with 18-fluorodeoxyglucose and Tc-99m ethyl cysteinate dimer single-photon emission computed tomography revealed occipital hypermetabolism and hyperperfusion ("hot" area) and fronto-temporo-parietal hypometabolism and hypoperfusion ("cool" area) over the right hemisphere. The spike sources of magnetoencephalography during pre-treatment were localized to "hot" areas, and the slow activities were distributed to the fronto-temporo-parietal region, corresponding to "cool" areas. The inflammatory seizure focus and reversible dysfunctional zone associated with neurosyphilis were clearly delineated using these techniques.

Synthesis of 2α- and 2ß-(3-hydroxypropyl)- 7,8-cis-14-epi-1α,25-dihydroxy-19-norvitamin D3 and their biological activity.

According to the binding mode of 14-epi-1α,25-dihydroxy-19-nortachysterol in the ligand binding domain of human vitamin D receptor (hVDR), i.e., 5,6- and 7,8-s-trans configuration that was shown by X-ray co-crystallographic analysis, 7,8-cis-locked 1α,25(OH)2D3 analogs were synthesized. In this paper, the synthesis and biological activity of 2α- and 2ß-(3-hydroxypropyl)-7,8-cis-14-epi-1α,25-dihydroxy-19-norvitamin D3 are reported. The A-ring and CD-ring precursors for the Julia-Kociensky coupling reaction to create a diene system of the target molecules were prepared using our original methods. hVDR binding affinity and osteocalcin promoter transactivation activity of the new 7,8-cis-14-epi-vitamin D3 analogs were evaluated. Interestingly, the 2ß-substituted 7,8-cis-analog was a better binder for hVDR than the 2α-isomeric counterpart.

Design and synthesis of 2α-(tetrazolylethyl)-1α,25-dihydroxyvitamin D3 as a high affinity ligand for vitamin D receptor.

X-ray cocrystallographic studies of the human vitamin D receptor (hVDR)-[2α-(3-hydroxypropyl)-1α,25-dihydroxyvitamin D3 (O1C3)] complex showed that the terminal hydroxy group of the 2α-functional group of O1C3 formed a hydrogen bond with Arg274 in the ligand binding domain (LBD) of hVDR to stabilize the complex; therefore, O1C3 showed 3-times greater binding affinity for VDR than the natural hormone. Here, the effects of a heteroaromatic ring on binding to hVDR instead of the terminal OH group of O1C3 and also on preliminary biological activities were studied. We synthesized 2α-[2-(tetrazol-2-yl)ethyl]-1α,25(OH)2D3 (1a) and its regioisomer 2α-[2-(tetrazol-1-yl)ethyl]-1α,25(OH)2D3 (1b), in which 1a showed much higher hVDR binding affinity and greater osteocalcin promoter transactivation activity in human osteosarcoma (HOS) cells than those of 1b. X-ray cocrystallographic analysis of the hVDR-1a complex showed new hydrogen bond formation between one of the nitrogen atoms of the tetrazole ring and Arg274. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Synthesis of novel C-2 substituted vitamin D derivatives having ringed side chains and their biological evaluation on bone.

Up to the present, numerous vitamin D derivatives have been synthesized, but most of them have straight side chains, and there are few publications described about in vitro and in vivo evaluations on bone by vitamin D derivatives. In our previous paper, we reported the synthesis of various C-2 substituted vitamin D derivatives (2b-2i) with a 2,2-dimethylcyclopentanone unit in the CD-ring side chains, and that the derivatives have strong activity for enhancing bone growth. On the basis of results, this time, we report the synthesis of 2α-substituted vitamin D3 derivatives with chiral cyclopentanone (3-6 and 12-16). These derivatives were obtained by Pd-coupling reaction with A-ring precursor and CD-rings precursor. We evaluated novel derivatives in vitro assays, for affinities for VDR and transactivation assays by human osteosarcoma (HOS) cells. In this research, we demonstrated that some novel vitamin D derivatives (12-MP, 13-MP, 15-MP and 16-LP) have strong transactivation activities in spite of lower affinity for VDR than 1. In addition, we also demonstrated that these derivatives have strong activities for enhancing bone growth using OVX therapeutic rats. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Synthesis of 14-epi-2α-hydroxypropoxy-1α,25-dihydroxy-19-nortachysterol and its hVDR binding.

Recently, we evaluated a novel skeleton in the vitamin D family, 14-epi-1α,25(OH)2-19-nortachysterol, and discovered its unique binding configuration in the human vitamin D receptor (VDR) with the C5,6- and C7,8-s-trans triene configuration. Because of its unprecedented form, this skeleton has a promising characteristic profile for clinical use, and also the synthesis of its derivatives should be versatile. Therefore, we synthesized the novel analog, 2α-hydroxypropoxy substituted 14-epi-1α,25(OH)2-19-nortachysterol, and evaluated its human VDR binding affinity. Although this substitution is one of the promising modification of vitamin D3 such as eldecalcitol (ED-71), it had negative effects on the binding affinity, and the compound showed lower affinity than 1α,25(OH)2D3 and its parent compound, 14-epi-1α,25(OH)2-19-nortachysterol. It was thought that the unprecedented binding configuration of this skeleton should not allow the terminal hydroxyl group of the 2α-substituent to construct effective hydrogen bond networks around the amino acid residues in the binding pocket. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Synthesis of 2α-heteroarylalkyl active vitamin d3 with therapeutic effect on enhancing bone mineral density in vivo.

2α-Heteroarylethyl-1α,25-dihydroxyvitamin D3 analogues, which were designed to form a hydrogen bond between Arg274 of human vitamin D receptor (hVDR) and a nitrogen atom of the heteroaromatic ring at the 2α-position, were synthesized. Among them, 2α-[2-(tetrazol-2-yl)ethyl]-1α,25-dihydroxyvitamin D3 showed higher osteocalcin promoter transactivation activity in human osteosarcoma (HOS) cells and a greater therapeutic effect in ovariectomized (OVX) rats, osteoporosis model animals, on enhancing bone mineral density than those of active vitamin D3. X-ray cocrystallographic analysis of the hVDR-ligand complex confirms that the new hydrogen bond formation stabilized the complex.

Design, synthesis and X-ray crystallographic study of new nonsecosteroidal vitamin D receptor ligands.

We designed and synthesized nonsecosteroidal vitamin D receptor (VDR) ligands that formed H-bonds with six amino acid residues (Tyr143, Ser233, Arg270, Ser274, His301 and His393) of the VDR ligand-binding domain. The ligand YR335 exhibited potent transcriptional activity, which was comparable to those of 1α,25-dihydroxyvitamin D(3) and YR301. The crystal structure of the complex formed between YR335 and the VDR ligand-binding domain was solved, which revealed that YR335 formed H-bonds with the six amino acid residues mentioned above.

New C15-substituted active vitamin D3.

C15-Substituted 1α,25-dihydroxyvitamin D(3) analogs were synthesized for the first time to investigate the effects of the modified CD-ring on biological activity concerning the agonistic positioning of helix-3 and helix-12 of the vitamin D receptor (VDR). X-ray cocrystallographic analysis proved that 0.6 Å shifts of the CD-ring and shrinking of the side chain were necessary to maintain the position of the 25-hydroxy group for proper interaction with helix-12. The 15-hydroxy-16-ene derivative showed higher binding affinity for hVDR than the natural hormone.

Development of 14-epi-19-nortachysterol and its unprecedented binding configuration for the human vitamin D receptor.

In the study of the synthesis of 14-epi-19-norprevitamin D(3), we found 14-epi-19-nortachysterol derivatives through C6,7-cis/trans isomerization. We also succeeded in their chemical synthesis and revealed their marked stability and potent VDR binding affinity. To the best of our knowledge, this is the first isolation of stable tachysterol analogues. Surprisingly, 14-epi-19-nortachysterol derivatives exhibited an unprecedented binding configurations for the ligand binding pocket in hVDR, C5,6-s-trans and C7,8-s-trans triene configurations, which were opposite the natural C7,8-ene-configuration of 1α,25(OH)(2)D(3).

Synthesis of 2beta-substituted-14-epi-previtamin D3 and testing of its genomic activity.

2beta-substituted analogs of 14-epi-previtamin D(3) were synthesized for the first time by the thermal isomerization of the corresponding 14-epi-vitamin D3 that were available using coupling reaction between the A-ring phosphine oxide derived from a chiral epoxide and CD-ring cis-hydrindanone. The VDR binding affinity and transactivation activity of osteocalcin promoter in HOS cells were evaluated, and the new analogs were found to be less active, 0.01-0.18% of VDR binding affinity compared with the natural hormone and EC50 1.0-9.1 nM for transactivation activity, than 14-epi-previtamin D3 with 0.5% (VDR) and EC50 0.46 nM, respectively.

CDP/cut is an osteoblastic coactivator of the vitamin D receptor (VDR).

Vitamin D plays an important role in regulating bone and calcium metabolism. The actions of vitamin D are mediated through the nuclear vitamin D receptor (VDR), and gene disruption of the VDR in mice causes skeletal disorders. However, the precise role of the VDR in each stage of osteoblastogenesis is not well understood. To address this issue, we used a biochemical approach to identify an osteoblast-specific coregulator of the VDR. Using a GST-fused VDR ligand-binding domain as bait, proteins associated with liganded VDR were purified from nuclear extracts of HOS osteoblastic cells and compared with those of HeLa cells. Among the interactants identified by mass fingerprinting, CCAAT displacement protein (CDP) was found as a novel ligand-dependent VDR interactant in HOS cells, together with other previously reported DRIP/TRAP complex components. Further biochemical analysis showed that complex formation between the VDR and CDP was distinct from the previously known DRIP/TRAP complex and the p160 family coactivator complexes. Transient expression of CDP potentiated VDR-mediated transcriptional activation in HOS cells. Furthermore, modulation of CDP expression levels in osteoblastic SaM-1 cells affected vitamin D-dependent osteoblast differentiation before the maturation (mineralization) stage. These findings suggest that CDP is a novel differentiation stage-specific coactivator of the VDR in osteoblasts.

Synthesis and biological evaluation of 4-substituted vitamin d and 14-epi-previtamin d analogs.

We synthesized the 4-hydroxy and 4-methoxy analogs of active vitamin D(3) (1alpha,25(OH)(2)D(3), 1) and its C14-epimer with the previtamin D(3) form of 14-epi-1alpha,25(OH)(2)preD(3) (14-epi-pre1). Their vitamin D receptor (VDR) binding affinity and osteocalcin promoter transactivation activity in HOS cells were evaluated, and had lower activity than the natural hormone (1) and 14-epi-pre1, respectively.

Synthesis of 2alpha-substituted-14-epi-previtamin D3 and its genomic activity.

We synthesized and isolated 2 alpha-substituted analogs of 14-epi-previtamin D3 after thermal isomerization at 80 degrees C for the first time. The VDR binding affinity and transactivation activity of osteocalcin promoter in HOS cells were evaluated, and the 2 alpha-methyl-substituted analog was found to have greater genomic activity than 14-epi-previtamin D3.

Practical synthesis and evaluation of the biological activities of 1alpha,25-dihydroxyvitamin D3 antagonists, 1alpha,25-dihydroxyvitamin D3-26,23-lactams. Designed on the basis of the helix 12-folding inhibition hypothesis.

A practical synthetic route to novel vitamin D antagonists of DLAM (1alpha,25-dihydroxyvitamin D(3)-26,23-lactam) was developed from vitamin D(2) via the 1,3-dipolar cycloaddition reaction as a key step. Six DLAM derivatives (24 compounds) with a variety of nitrogen substituents and stereochemistries at C23 and C25 were synthesized. Among these new derivatives, (23S,25S)-DLAM isomers bound effectively to VDRs and showed antagonistic activity in the HL-60 cell differentiation inhibition assay. The importance of the substituent on the nitrogen of DLAMs for antagonistic activity was also suggested by computational docking studies.

Molecular mechanism of the vitamin D antagonistic actions of (23S)-25-dehydro-1alpha-hydroxyvitamin D3-26,23-lactone depends on the primary structure of the carboxyl-terminal region of the vitamin d receptor.

We reported that (23S)-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone (TEI-9647) antagonizes vitamin D receptor (VDR)-mediated genomic actions of 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] in human cells but is agonistic in rodent cells. Human and rat VDR ligand-binding domains are similar, but differences in the C-terminal region are important for ligand binding and transactivation and might determine the agonistic/antagonistic effects of TEI-9647. We tested TEI-9647 on 1alpha,25(OH)(2)D(3) transactivation using SaOS-2 cells (human osteosarcoma) or ROS 24/1 cells (rat osteosarcoma) cotransfected with human or rodent VDR and a reporter. In both cell lines, TEI-9647 was antagonistic with wild-type human (h)VDR, but agonistic with overexpressed wild-type rat (r)VDR. VDR chimeras substituting the hVDR C-terminal region (activation function 2 domain) with corresponding rVDR residues diminished antagonism and increased agonism of TEI-9647. However, substitution of 25 C-terminal rVDR residues with corresponding hVDR residues diminished agonism and increased antagonism of TEI-9647. hVDR mutants (C403S, C410N) demonstrated that Cys403 and/or 410 was necessary for TEI-9647 antagonism of 1alpha,25(OH)(2)D(3) transactivation. These results suggest that species specificity of VDR, especially in the C-terminal region, determines the agonistic/antagonistic effects of TEI-9647 that determine, in part, VDR interactions with coactivators and emphasize the critical interaction between TEI-9647 and the two C-terminal hVDR Cys residues to mediate the antagonistic effect of TEI-9647.

Inhibition of osteoclastogenesis by a phosphodiesterase 4 inhibitor XT-611 through synergistic action with endogenous prostaglandin E2.

We examined the effect of a phosphodiesterase 4 (PDE4) inhibitor, 3,4-dipropyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-i]-purin-5-one (XT-611) on osteoclast formation in three different mouse bone-marrow cell (BMC) culture systems. We confirmed that selective inhibitors of PDE4, including XT-611, among several PDE inhibitors decreased osteoclast formation in the BMC culture system. XT-611 also inhibited osteoclast formation in co-culture of mouse bone-marrow stromal cell line ST2 and adherent cell-depleted (ACD)-BMCs. However, it did not inhibit osteoclastogenesis in culture of ACD-BMCs alone in the presence of macrophage-colony stimulating factor (M-CSF) and soluble receptor activator of NF-kappaB ligand (sRANKL). XT-611 significantly increased prostaglandin E(2) (PGE(2)) production from ST2 cells and, in combination with PGE(2), synergistically increased cAMP concentration in osteoclast progenitors. In the ST2 co-culture system, XT-611 did not influence the expression of RANKL, osteoprotegerin and RANK mRNAs. By combined treatment with XT-611 and PGE(2) of ACD-BMCs, osteoclast multinucleation was clearly inhibited with decrease in the expression of calcitonin receptor mRNA, while the expression of RANK and c-fms (an M-CSF receptor) mRNAs was unchanged. These results indicate that the PDE4 inhibitor inhibits osteoclastogenesis by acting on osteoclast progenitors synergistically with PGE(2) secreted from stromal cells, but not by influencing the cell-to-cell interaction between stromal cells and osteoclast progenitors.

Prostaglandin E2-mediated anabolic effect of a novel inhibitor of phosphodiesterase 4, XT-611, in the in vitro bone marrow culture.

UNLABELLED: The mechanism of osteoblast formation by a novel PDE4 inhibitor, XT-611, was studied in the in vitro bone marrow culture system. The compound potentiated the osteoblast differentiation through accumulation of cyclic AMP after autocrine stimulation of EP4 receptor by PGE2 in pro-osteoblastic cells. INTRODUCTION: We previously reported that inhibitors of phosphodiesterase (PDE)4 isoenzyme increase osteoblast formation in an in vitro bone marrow culture system and inhibit bone loss in animal osteoporosis models. Here we investigated the mechanism of the effect of a novel PDE4 inhibitor, 3,4-dipropyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-i]-purin-5-one (XT-611), on osteoblast formation in the in vitro bone marrow culture system. MATERIALS AND METHODS: Rodent bone marrow cells were cultured in the presence of 0.2 mM ascorbic acid phosphate ester, 1 mM beta-glycerophosphate, and 10 nM dexamethasone for 10 days. Drug treatments were done for 24 h on day 3 of culture. RESULTS: PDE4 inhibitors, including XT-611, but not PDE3 and PDE5 inhibitors, increased mineralized nodule formation in rat and mouse bone marrow cell cultures. During culture of the bone marrow cells, prostaglandin E2 (PGE2) production increased with a peak on day 4, but the increase was completely inhibited by indomethacin, an unselective cyclo-oxygenase (COX) inhibitor. Spontaneous and XT-611-induced mineralized-nodule formation was also inhibited by indomethacin and COX-2 inhibitors, in a similar potential. Alkaline phosphatase-positive nodule formation in the absence or presence of XT-611 was inhibited by an antagonist of EP4 receptor, AH23848B, and synergistically potentiated by 11-deoxy-PGE1, but it was not influenced by other EP antagonists and agonists examined. The expression of PDE4 and EP4 mRNAs was observed in bone marrow cells. The effect of XT-611 was also confirmed to involve an increase of cyclic AMP and the cyclic AMP-dependent protein kinase pathway. CONCLUSION: These results suggest that PGE2 stimulates differentiation of osteoblast progenitor cells through the EP4 receptor in an autocrine manner, and the PDE4 inhibitor potentiates the differentiation by inhibiting hydrolysis of cyclic AMP in the cells.

[A fatal case of anaphylactoid shock after administration of nonionic contrast medium].

We report a case of fatal anaphylactoid shock caused by a CT examination using nonionic contrast medium. A 79-year-old female patient was diagnosed with right recurrent nerve plasy. There was no known history of drug allergy or exposure to contrast medium. Approximately 50 seconds after contrast medium bolus injection began, the patient was noted to be apneic. Despite cardiopulmonary resucitation, the patient died. An autopsy demonstrated marked laryngeal edema and showed extensive mast cell infiltration.