Vitamin D Analogs with Nitrogen Atom at C2 Substitution and Effect on Bone Formation

CYP27B1 Enzyme in Psoriasis: A Preliminary Study of Immunohistochemical Observations

Connections between vitamin D and psoriasis have been a matter of interest for the past decades, with its active metabolite, 1,25(OH)2 vitamin D, being valued for antiproliferative and immunomodulatory effects. However, none of vitamin D's actions could be possible without the CYP27B1 enzyme that bio-activates this metabolite of interest. In order to see if there is any link between the enzyme expression and the disease's particularities, we conducted a preliminary study that involved 11 skin biopsies of patients with mild (n = 4) or moderate to severe psoriasis (n = 7). The cell proliferation antigen Ki67 and the CD45RO+ marker were also assessed. Compared with healthy skin, in psoriasis, it is reported that the enzyme's expression seems to be more ubiquitous, but a clear correlation between the disease's severity and the CYP27B1 expression was, to our knowledge, lacking. We found that, in patients with very mild psoriasis, the enzyme expression was observed in the epidermal stratum basale in a similar manner as in healthy skin specimens. Contrary, for higher severity scores, a divergent result was observed, with the enzyme being either variably spread in the epidermal stratum spinosum or completely absent. Unlike malignant diseases, a significant connection between CYP27B1 and Ki67 (p = 0.313) or CYP27B1 and CD45RO+ (p = 0.657) does not seem to be relevant in psoriasis.

Robust osteogenic efficacy of 2α-heteroarylalkyl vitamin D analogue AH-1 in VDR (R270L) hereditary vitamin D-dependent rickets model rats

Active vitamin D form 1α,25-dihydroxtvitamin D₃ (1,25(OH)₂D₃) plays pivotal roles in calcium homeostasis and osteogenesis via its transcription regulation effect via binding to vitamin D receptor (VDR). Mutated VDR often causes hereditary vitamin D-dependent rickets (VDDR) type II, and patients with VDDR-II are hardly responsive to physiological doses of 1,25(OH)D₃. Current therapeutic approaches, including high doses of oral calcium and supraphysiologic doses of 1,25(OH)₂D_3, have limited success and fail to improve the quality of life of affected patients. Thus, various vitamin D analogues have been developed as therapeutic options. In our previous study, we generated genetically modified rats with mutated Vdr(R270L), an ortholog of human VDR(R274L) isolated from the patients with VDDR-II. The significant reduced affinity toward 1,25(OH)₂D₃ of rat Vdr(R270L) enabled us to evaluate biological activities of exogenous VDR ligand without 1α-hydroxy group such as 25(OH)D₃. In this study, 2α-[2-(tetrazol-2-yl)ethyl]-1α,25(OH)₂D₃ (AH-1) exerted much higher affinity for Vdr(R270L) in in vitro ligand binding assay than both 25(OH)D₃ and 1,25(OH)₂D₃. A robust osteogenic activity of AH-1 was observed in Vdr(R270L) rats. Only a 40-fold lower dose of AH-1 than that of 25(OH)D₃ was effective in ameliorating rickets symptoms in Vdr(R270L) rats. Therefore, AH-1 may be promising for the therapy of VDDR-II with VDR(R274L).

The Centennial Collection of VDR Ligands: Metabolites, Analogs, Hybrids and Non-Secosteroidal Ligands

Since the discovery of vitamin D a century ago, a great number of metabolites, analogs, hybrids and nonsteroidal VDR ligands have been developed. An enormous effort has been made to synthesize compounds which present beneficial properties while attaining lower calcium serum levels than calcitriol. This structural review covers VDR ligands published to date.