Kazuyoshi Yamaoka

Identification and characterization of noncalcemic, tissue-selective, nonsecosteroidal vitamin D receptor modulators

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.

Localization of human airway trypsin-like protease in the airway: an immunohistochemical study

Abstract. Human airway trypsin-like protease (HAT) has been isolated from mucoid sputum of patients with chronic airway diseases. In order to clarify the cellular source of this novel protease in the human airway, we examined the localization of immunoreactive HAT in bronchial tissues obtained at surgery and fixed in 4% paraformaldehyde using an extremely sensitive immunohistochemical technique called a catalyzed signal amplification method and a monoclonal antibody against recombinant HAT. HAT immunoreactivity was demonstrated in cytoplasm of ciliated cells of bronchial epithelium and/or at the basal part of cilia. No positive reaction was found in submucosal glands or mast cells. The heterogeneous distribution of HAT immunoreactivity within the bronchial epithelium indicates that its expression might be changeable and that it might be closely related to the physiological status of the airway epithelium. Non-specific but intense reaction caused by endogenous avidin-binding activity (EABA) was selectively detected in submucosal glands, but was effectively blocked by successive treatments with avidin and biotin. These results indicate that HAT may be synthesized in the ciliated cells and that it may play some physiological roles within the epithelial layer and on the airway surface. It is necessary to keep in mind that some cells show strong EABA, especially when a highly sensitive immunohistochemical technique is applied.

Mechanisms of transcriptional repression by 1,25(OH)2 vitamin D.

Purpose of reviewVitamin D has diverse biological actions, and consequently the mechanisms behind how it regulates gene transcription are diverse. Unlike its well described positive effects on gene transcription, little is known about how vitamin D induces transcriptional repression. Recent findingsVitamin D-induced transcriptional repression of several negative vitamin D receptor target genes has been studied on a molecular level. A new class of negative vitamin D response elements, which are E-box-type motifs, bind the bHLH-type transcriptional activator (VDIR) together with a histone acetyltransferase coactivator. The vitamin D receptor, activated by vitamin D, does not directly bind to the negative vitamin D response elements, but instead associates with VDIR. This leads to the dissociation of the histone acetyltransferase coactivator and recruitment of a histone deacetylase corepressor to transrepress transcription of the target gene promoter. SummaryHistone inactivation induced by histone deacetylase co-repressors appears to facilitate vitamin D-induced transcriptional repression via the vitamin D receptor. Following vitamin D binding, structural alteration of the DNA-unbound vitamin D receptor triggers transcriptional repression. Given this, the mechanisms behind vitamin D-induced transcriptional repression are probably more complex than those of vitamin D-induced transactivation.

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

Retraction: The following article from the Journal of Bone and Mineral Research, “CDP/Cut Is an Osteoblastic Coactivator of the Vitamin D Receptor (VDR)” by Eiji Ochiai, Hirochika Kitagawa, Ichiro Takada, Sally Fujiyama, Shun Sawatsubashi, Mi‐sun Kim,Yoshihiro Mezaki, Yu Tsushima, Ken‐ichiro Takagi, Yoshiaki Azuma, Ken‐ichi Takeyama, Kazuyoshi Yamaoka, Shigeaki Kato, Takashi Kamimura, published online on December 11, 2009 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, Thomas Clemens, the American Society for Bone and Mineral Research and Wiley Periodicals, Inc. The authors have requested the retraction based on their acknowledgement that several of the figures did not reflect the observations presented.

Culture serum-induced conversion from agonist to antagonist of a Vitamin D analog, TEI-9647

The nuclear receptor for Vitamin D (VDR) mediates many of the effects of Vitamin D in target tissues by regulating gene expression. The transactivation function of ligand-bound VDR in target tissues is thought to depend on the tissue-type and the cellular-environment, but the molecular basis for these differences has not been fully understood. In this study, during characterization of TEI-9647 as a synthetic ligand for the VDR, we found that depletion of serum from the culture medium converted TEI-9647 from an antagonist to an agonist of VDR-mediated transactivation, whereas it retained antagonistic activity in the presence of serum. Consistent with these results, using a mammalian two-hybrid system, we found that TEI-9647 recruited different coactivators to the VDR in the presence and absence of serum. These findings suggest that an unknown serum factor modulates the transactivation function of the VDR.

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

Retraction: The following article from the Journal of Bone and Mineral Research, “CDP/Cut Is an Osteoblastic Coactivator of the Vitamin D Receptor (VDR)” by Eiji Ochiai, Hirochika Kitagawa, Ichiro Takada, Sally Fujiyama, Shun Sawatsubashi, Mi‐sun Kim,Yoshihiro Mezaki, Yu Tsushima, Ken‐ichiro Takagi, Yoshiaki Azuma, Ken‐ichi Takeyama, Kazuyoshi Yamaoka, Shigeaki Kato, Takashi Kamimura, published online on December 11, 2009 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, Thomas Clemens, the American Society for Bone and Mineral Research and Wiley Periodicals, Inc. The authors have requested the retraction based on their acknowledgement that several of the figures did not reflect the observations presented.