Molecular Evaluation of Vitamin D3 Receptor Agonists Designed for Topical Treatment of Skin Diseases11The authors declared not to have conflict of interest

Gasdermin A Is Required for Epidermal Cornification during Skin Barrier Regeneration and in an Atopic Dermatitis-Like Model

Atopic dermatitis is featured with impaired skin barrier. The stratum corneum and the intercellular tight junctions constitute the permeability barrier, which is essential to protect water loss in the host and prevent pathogen entry. The epidermal barrier is constantly renewed by differentiating keratinocytes through cornification, during which autophagy contributes to elimination of organelles and nucleus. The human GSDMA and its mouse homologs Gsdma1-3 are expressed in the suprabasal epidermis. Although a pyroptotic role of GSDMA/Gsdma1 in host defense against Streptococcus pyogenes has been reported, the physiological function of Gsdma1/a2/a3 in epidermal homeostasis remains elusive. Here, through repeated epidermal barrier disruption, we found that tight junction formation and stratum corneum maturation were defective in the Gsdma1/a3-deficient epidermis. Using comparative gene profiling analysis, mitochondrial respiration measurement, and in vivo tracing of mitophagy, our data indicate that Gsdma1/a3 activation leads to mitochondrial dysfunction and subsequently facilitates mitochondrial turnover and epidermal cornification. In calcipotriol (MC903)-induced atopic dermatitis-like animal model, we showed that Gsdma1/a3-deficiency selectively enhanced the T helper type 2 response. Remarkably, the GSDMA expression is reduced in the epidermis of patients with atopic dermatitis compared with that of normal individuals. Gsdma1/a3-deficiency might be involved in atopic dermatitis pathogenesis, likely through GSDMA-mediated epidermal differentiation and cornification.

Calcipotriol Attenuates Form Deprivation Myopia Through a Signaling Pathway Parallel to TGF-β2-Induced Increases in Collagen Expression

Purpose

To determine the role of calcipotriol, a vitamin D3 analogue, in myopia development and altering the expression of scleral α1 chain of type I collagen (Col1α1) in mice. We also aimed to identify if the signaling pathway mediating the above changes is different from the one involved in transforming growth factor β2 (TGF-β2)-mediated increases of COL1A1 in cultured human scleral fibroblasts (HSFs).

Methods

C57BL/6J mice were either intraperitoneally injected with calcipotriol and subjected to form deprivation (FD) or exposed to normal refractive development for 4 weeks. Scleral vitamin D receptor (Vdr) expression was knocked down using a Sub-Tenon's capsule injection of an adeno-associated virus-packaged short hairpin RNA (AAV8-shRNA). Refraction and biometric measurements evaluated myopia development. A combination of knockdown and induction strategies determined the relative contributions of the vitamin D3 and the TGF-β2 signaling pathways in modulating COL1A1 expression in HSFs.

Results

Calcipotriol injections suppressed FD-induced myopia (FDM), but it had no significant effect on normal refractive development. AAV8-shRNA injection reduced Vdr mRNA expression by 42% and shifted the refraction toward myopia (-3.15 ± 0.99D, means ± SEM) in normal eyes. In HSFs, VDR knockdown reduced calcipotriol-induced rises in COL1A1 expression, but it did not alter TGF-β2-induced increases in COL1A1 expression. Additionally, TGF-β2 augmented calcipotriol-induced rises in COL1A1 expression. TGF-β receptor (TGFBRI/II) knockdown blunted TGF-β2-induced increases in COL1A1 expression, whereas calcipotriol-induced increases in VDR and COL1A1 expression levels were unaltered.

Conclusions

Scleral vitamin D3 inhibits myopia development in mice, potentially by activating a VDR-dependent signaling pathway and increasing scleral COL1A1 expression levels.

Enhancing the production of physiologically active vitamin D3 by engineering the hydroxylase CYP105A1 and the electron transport chain

In this study, the conversion of vitamin D₃ (VD₃) to its two active forms 25(OH)VD₃ and 1α, 25(OH)₂VD₃ was carried out by engineering the hydroxylase CYP105A1 and its redox partners Fdx and Fdr. CYP105A1 and Fdx-Fdr were respectively expressed in E. coli BL21(DE3) and purified. The electron transport chain Fdx-Fdr had higher selectivity for the coenzyme NADH than NADPH. HPLC analysis showed that CYP105A1 could hydroxylate the C25 and C1α sites of VD₃ and convert VD₃ to its active forms. Finally, a one-bacterium-multi-enzyme system was constructed and used in whole-cell catalytic experiments. The results indicated that 2.491 mg/L of 25(OH)VD₃ and 0.698 mg/L of 1α, 25(OH)₂VD₃ were successfully produced under the condition of 1.0% co-solvent DMSO, 1 mM coenzyme NADH and 35 g/L biocatalyst loading. This study contributes to a basis for the industrial production of active VD₃ in future.

Calcipotriol/betamethasone dipropionate formulations for psoriasis: an overview of the options and efficacy data

INTRODUCTION

Psoriasis is a very common chronic inflammatory skin disease affecting up to 3% of the general population with 75% of the psoriasis subjects being affected by a mild form of disease. Hence, topical therapy is the most frequent employed treatment in psoriasis also because it can be easily combined with systemic therapy. In this context, calcipotriol/betamethasone dipropionate (Cal/BD) fixed-dose association represents the first-line treatment due to its efficacy and once-daily application. Different Cal/BD formulations, such as ointment, gel (topical suspension), and aerosol foam, are approved by US Food and Drug Administration.

AREAS COVERED

For this review, relevant English literature (trials, real-life studies, case series, and reviews) regarding Cal/BD different formulations efficacy in psoriasis was searched for through to 28 January 2020. The following database were consulted: PubMed, Embase, the Cochrane Library, Google Scholar, EBSCO, and clinicaltrials.gov.

EXPERT OPINION

Cal/BD formulations are efficacious treatment for psoriasis. Cal/BD aerosol foam shows a higher efficacy compared to Cal/BD ointment or gel formulations, appearing as a game-changer in psoriasis therapy not only for mild disease but also for moderate psoriasis as well as in selected severe cases in combination with systemic treatments.

Chlorpyrifos stimulates expression of vitamin D3 receptor in skin cells irradiated with UVB

Skin, the organ responsible for vitamin D synthesis, is fully exposed to many xenobiotics, e.g. polycyclic aromatic hydrocarbons and pesticides. A broad spectrum organophosphorus insecticides (OP's), such as chlorpyrifos (CPS), are commonly used in agriculture and to control domestic insects. Thus, the aim of this study was to investigate the effect of chlorpyrifos, on the expression of vitamin D₃ receptor (VDR) in human keratinocytes cell line HaCaT and fibroblasts cell line BJ. The impact of CPS and UVB radiation on cell viability were examined by Neutral Red assay. The effect of CPS on VDR expression was evaluated by RT-qPCR and flow cytometry (FC). The presented study demonstrated that exposure to CPS and UVB significantly affects the viability of HaCaT and BJ cells lines. Results also revealed that exposure to CPS induced the expression at mRNA and protein level of VDR nuclear receptor in both cell lines exposed to UVB. In HaCaT incubated with 250 μM CPS and 15 mJ/cm² UVB, the relative VDR expression was ∼2-fold higher; whereas in BJ incubated with 250 μM CPS and 20 mJ/cm², UVB was∼3-fold higher. Results from FC confirmed this result, as VDR expression increased by ~250% in HaCaT incubated with 250 μM CPS and 20 mJ/cm² UVB, and in BJ incubated with 250 μM CPS, and 20 mJ/cm² UVB cells VDR expression increased by ~190%, compared with control. It can therefore be concluded that OPs pesticide might interfere with vitamin D₃ metabolism in skin cells.

CD69 is a TGF-β/1α,25-dihydroxyvitamin D3 target gene in monocytes

CD69 is a transmembrane lectin that can be expressed on most hematopoietic cells. In monocytes, it has been functionally linked to the 5-lipoxygenase pathway in which the leukotrienes, a class of highly potent inflammatory mediators, are produced. However, regarding CD69 gene expression and its regulatory mechanisms in monocytes, only scarce data are available. Here, we report that CD69 mRNA expression, analogous to that of 5-lipoxygenase, is induced by the physiologic stimuli transforming growth factor-β (TGF-β) and 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) in monocytic cells. Comparison with T- and B-cell lines showed that the effect was specific for monocytes. CD69 expression levels were increased in a concentration-dependent manner, and kinetic analysis revealed a rapid onset of mRNA expression, indicating that CD69 is a primary TGF-β/1α,25(OH)2D3 target gene. PCR analysis of different regions of the CD69 mRNA revealed that de novo transcription was initiated and proximal and distal parts were induced concomitantly. In common with 5-lipoxygenase, no activation of 0.7 kb or ∼2.3 kb promoter fragments by TGF-β and 1α,25(OH)2D3 could be observed in transient reporter assays for CD69. Analysis of mRNA stability using a transcription inhibitor and a 3'UTR reporter construct showed that TGF-β and 1α,25(OH)2D3 do not influence CD69 mRNA stability. Functional knockdown of Smad3 clearly demonstrated that upregulation of CD69 mRNA, in contrast to 5-LO, depends on Smad3. Comparative studies with different inhibitors for mitogen activated protein kinases (MAPKs) revealed that MAPK signalling is involved in CD69 gene regulation, whereas 5-lipoxygenase gene expression was only partly affected. Mechanistically, we found evidence that CD69 gene upregulation depends on TAK1-mediated p38 activation. In summary, our data indicate that CD69 gene expression, conforming with 5-lipoxygenase, is regulated monocyte-specifically by the physiologic stimuli TGF-β and 1α,25(OH)2D3 on mRNA level, although different mechanisms account for the upregulation of each gene.

Calcipotriol delivery into the skin with PEGylated liposomes

The D-vitamin analogue calcipotriol is commonly used for topical treatment of psoriasis, but skin penetration is required for calcipotriol to reach its pharmacological target: the keratinocytes in the lower epidermis. Liposomes can enhance the delivery of drugs into the skin, but a major challenge for the development of dosage forms containing liposomes is to maintain the colloidal stability in the formulation. The purpose of this study was to investigate the effect of stabilising liposomes with the lipopolymer poly(ethylene glycol)-distearoylphosphoethanolamine (PEG-DSPE) on the physicochemical properties of the liposomes and the ability to deliver membrane-intercalated calcipotriol into the skin. Inclusion of 0.5, l and 5 mol% PEG-DSPE in the membrane enhanced the colloidal stability of the liposomes without compromising the delivery of calcipotriol from the vehicle into excised pig skin. Calcipotriol-loaded liposomes with 1 mol% PEG-DSPE did even provide for a significantly increased deposition of calcipotriol into the stratum corneum. The size of the liposomes affected the penetration of calcipotriol into the stratum corneum since small unilamellar vesicles enhanced calcipotriol penetration as compared to large multilamellar vesicles, indicating that the liposomes to some extent migrate as intact vesicles into the stratum corneum. However, calcipotriol penetrated the skin better than the lipid component of the liposomes, suggesting that at least a fraction of the drug is released from the liposomes during skin migration. In conclusion, PEGylation is therefore a promising approach for stabilising calcipotriol-containing liposomal dispersions without compromising their favourable skin accumulation properties.

Design of cyclic RKKH peptide-conjugated PEG liposomes targeting the integrin α₂β₁ receptor

Peptide conjugation to the surface of stealth liposomes has been studied for liposomal drug targeting to cells expressing specific receptors to provide a site-specific drug delivery. This study investigated the potential of peptide-conjugated liposomes for targeting cells expressing the human integrin α(2)β(1) receptor. A 12 amino acid head-to-tail cyclic peptide derived from the Jararhagin protein containing the Arg-Lys-Lys-His (RKKH)-specific binding site was conjugated to the distal ends of poly(ethylene glycol) (PEG) chains on PEGylated liposomes. Epithelial cells expressing the receptor showed increased cellular association and uptake of peptide-conjugated liposomes at 4 °C, compared to liposomes conjugated with a non-specific peptide. The interaction between cells and peptide-conjugated liposomes was significantly increased at 37 °C suggesting that a possible uptake mechanism might be energy-dependent endocytosis. In keratinocyte cell cultures, the ligand-conjugated liposomes loaded with the vitamin D(3) analogue calcipotriol induced transcription of the gene encoding the antimicrobial peptide cathelicidin, which is activated through the vitamin D(3) receptor upon binding of vitamin D(3) analogues. This suggests that the liposomes are internalized and that calcipotriol is delivered intracellularly and released in an active form. In conclusion, the 12 amino acid head-to-tail cyclic RKKH peptide seems promising for targeting of liposomes to the integrin α(2)β(1) receptor.

A Sleeping Beauty DNA transposon-based genetic sensor for functional screening of vitamin D3 analogues

Background

Analogues of vitamin D3 are extensively used in the treatment of various illnesses, such as osteoporosis, inflammatory skin diseases, and cancer. Functional testing of new vitamin D3 analogues and formulations for improved systemic and topical administration is supported by sensitive screening methods that allow a comparative evaluation of drug properties. As a new tool in functional screening of vitamin D3 analogues, we describe a genomically integratable sensor for sensitive drug detection. This system facilitates assessment of the pharmacokinetic and pharmadynamic properties of vitamin D3 analogues. The tri-cistronic genetic sensor encodes a drug-sensoring protein, a reporter protein expressed from an activated sensor-responsive promoter, and a resistance marker.

Results

The three expression cassettes, inserted in a head-to-tail orientation in a Sleeping Beauty DNA transposon vector, are efficiently inserted as a single genetic entity into the genome of cells of interest in a reaction catalyzed by the hyperactive SB100X transposase. The applicability of the sensor for screening purposes is demonstrated by the functional comparison of potent synthetic analogues of vitamin D3 designed for the treatment of psoriasis and cancer. In clones of human keratinocytes carrying from a single to numerous insertions of the vitamin D3 sensor, a sensitive sensor read-out is detected upon exposure to even low concentrations of vitamin D3 analogues. In comparative studies, the sensor unveils superior potency of new candidate drugs in comparison with analogues that are currently in clinical use.

Conclusions

Our findings demonstrate the use of the genetic sensor as a tool in first-line evaluation of new vitamin D3 analogues and pave the way for new types of drug delivery studies in sensor-transgenic animals.

Targeting of liposome-associated calcipotriol to the skin: effect of liposomal membrane fluidity and skin barrier integrity

Many dermal diseases like psoriasis are characterized by major changes in skin barrier function, which challenge the reproducible delivery of drugs into specific layers of diseased skin. The purpose of this study was to elucidate how liposomal bilayer fluidity and barrier integrity affected the delivery of liposome-associated calcipotriol to the skin. Calcipotriol-containing gel state and liquid state dipalmitoylphosphatidyl-choline:dilauroylphosphatidylcholine liposomes were prepared by extrusion. Using Langmuir monolayers, calcipotriol was shown to affect the packing of the lipid membrane. The penetration of radioactively labeled lipid and calcipotriol into pig skin was examined using the Franz diffusion cell model, and tape stripping was applied to impose an impaired barrier. Distorting the skin barrier resulted in an enhanced penetration of lipid from both gel and liquid state liposomes. In addition, increased penetration of lipid from liquid state liposomes was observed compared to gel state liposomes into barrier-impaired skin. For barrier-impaired skin, an elevated calcipotriol-to-lipid ratio was found in the receptor fluid for both liposome compositions indicating that calcipotriol is released from the vesicles. This suggests that the liposome-mediated delivery of calcipotriol to the epidermis of diseased skin is affected by the fluidity of the liposomal membrane.

Calcipotriol/betamethasone dipropionate in the treatment of psoriasis vulgaris

Psoriasis is one of the most common skin diseases. The mainstay of treatment for the vast majority of patients is topical therapy. A rising first-line treatment modality for psoriasis vulgaris is the two-compound ointment containing calcipotriol 50 mug/g plus betamethasone dipropionate 0.5 mg/g (Dovobet((R)), Daivobet((R)), Taclonex((R))), which combines a vitamin D analog and a corticosteroid. This innovative formulation preserves the activity and bioavailability of the two components and many clinical studies have demonstrated that it has a greater efficacy, tolerability, and a rapid onset of action compared with its individual ingredients or tacalcitol.

The vitamin D receptor

The vitamin D endocrine system is known for its essential role in calcium homeostasis and bone metabolism, and induces cell differentiation, inhibits cell growth, controls other hormonal systems, and modulates the immune response. Vitamin D(3) is a prohormone that is taken up by diet or synthesized in ultraviolet radiation-exposed skin and metabolically converted to the active metabolite, 1alpha,25-dihydroxyvitamin D(3). This nuclear hormone binds with high affinity the nuclear receptor vitamin D receptor. More than 3000 synthetic analogs of 1alpha,25(OH)(2)D(3) are known. This review aims to provide an overview on vitamin D signaling from the skin perspective.

Gene Regulatory Potential of Nonsteroidal Vitamin D Receptor Ligands

The seco-steroid 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] is a promising drug candidate due to its pleiotropic function including the regulation of calcium homeostasis, bone mineralization and cellular proliferation, differentiation, and apoptosis. We report here a novel class of nonsteroidal compounds, represented by the bis-aromatic molecules CD4409, CD4420, and CD4528, as ligands of the 1α,25(OH)2D3 receptor (VDR). Taking the known diphenylmethane derivative LG190178 as a reference, this study provides molecular evaluation of the interaction of nonsteroidal ligands with the VDR. All four nonsteroidal compounds were shown to induce VDR-retinoid X receptor heterodimer complex formation on a 1α,25(OH)2D3 response element, stabilize the agonistic conformation of the VDR ligand-binding domain, enable the interaction of VDR with coactivator proteins and contact with their three hydroxyl groups the same residues within the ligand-binding pocket of the VDR as 1α,25(OH)2D3. Molecular dynamics simulations demonstrated that all four nonsteroidal ligands take a shape within the ligand-binding pocket of the VDR that is very similar to that of the natural ligand. CD4528 is mimicking the natural hormone best and was found to be in vitro at least five times more potent than LG190178. In living cells, CD4528 was only two times less potent than 1α,25(OH)2D3 and induced mRNA expression of the VDR target gene CYP24 in a comparable fashion. At a noncalcemic dose of 150 μg/kg, CD4528 showed in vivo a clear induction of CYP24 expression and therefore may be used as a lead compound for the development of therapeutics against psoriasis, osteoporosis, and cancer.

Ligand-mediated conformational changes of the VDR are required for gene transactivation

The central element of the molecular switch of nuclear 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) signaling is the ligand-binding domain (LBD) of the Vitamin D receptor (VDR), which can be stabilized by 1alpha,25(OH)(2)D(3) or its analogues in to agonistic, antagonistic or inverse agonistic conformations. The positioning of helix 12 of the LBD is of most critical importance for these conformations, because it determines the distance between the charge clamp amino acids K246 and E420 that are essential for VDR-coactivator (CoA) interaction. Most VDR ligands have been identified as agonists and only a few (e.g., ZK168281 and TEI-9647) as pure or partial antagonists. Antagonists induce corepressor (CoR) dissociation from the VDR but prevent completely or partially CoA interaction and thus transactivation. Gemini is a 1alpha,25(OH)(2)D(3) analogue with two identical side chains that despite its significantly increased volume binds to the VDR and acts under most conditions as an agonist. Interestingly, supramolar CoR concentrations shift Gemini from an agonist to an inverse agonist, which actively recruits CoR to the VDR and thus mediates repression of 1alpha,25(OH)(2)D(3) target genes. Gemini is the first described (conditional) inverse agonist to an endocrine nuclear receptor (NR) and may function as a sensor for cell-specific CoA/CoR ratios.

Fixed-dose combination therapy for psoriasis

Fixed-dose combination therapy offers stable products containing two or more medications with different mechanisms of action and safety profiles. It is also convenient for patients since only one product rather than two or more needs to be applied. Topical corticosteroids are often the mainstay of therapy in psoriasis. Diprosalic and Nerisalic contain a topical corticosteroid (betamethasone dipropionate and diflucortolone, respectively) and salicylic acid. A left/right study showed that both products have comparable efficacy. It has also been shown that betamethasone dipropionate + salicylic acid ointment has similar efficacy to clobetasol and calcipotriene (calcipotriol) ointments. Betamethasone dipropionate + salicylic acid lotion has similar efficacy to clobetasol lotion. Faster improvement of scaling, itching, and redness was noted with betamethasone dipropionate + salicylic acid lotion compared with betamethasone dipropionate alone. Dovobet (Daivobet) ointment is a fixed-dose combination product containing betamethasone dipropionate and calcipotriene. Clinical studies have shown that it has greater efficacy and a faster speed of onset than the individual components or tacalcitol. Once daily and twice daily treatments have similar efficacy. Psoriasis Area and Severity Index reductions of approximately 40% after 1 week and 70% after 4 weeks of therapy were consistently noted in six large international studies involving >6000 patients. Betamethasone dipropionate + calcipotriene treatment is associated with approximately 75% less adverse cutaneous events as compared with tacalcitol, 50% less compared with calcipotriene, and a similar number as treatment with betamethasone dipropionate.

Structural evaluation of the agonistic action of a vitamin D analog with two side chains binding to the nuclear vitamin D receptor

The vitamin D receptor (VDR) is one of the endocrine members of the nuclear receptor superfamily and has a characteristic high affinity for its natural ligand 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3]. From a mechanistic point of view, the most interesting analog of 1alpha,25(OH)2D3 is the one that carries two side chains, referred to as Gemini. In this study, molecular dynamics (MD) simulations of the Gemini-VDR complex were performed that demonstrated that the binding of a ligand with a 25% increased volume does not disturb the overall structure of the ligand-binding domain (LBD). It was found that one of the two side chains takes exactly the same position as the single side chain of the natural ligand, which suggests that the molecular mechanism of the agonism of Gemini is identical to that of 1alpha,25(OH)2D3. VDR single and double point mutants at L227, A303, I313, and L397 and in vitro and ex vivo assessment of their agonistic action confirmed the predictions of the MD simulations. Moreover, it was found that the second side chain of Gemini can choose between two binding positions within the ligand-binding pocket of the VDR. These two newly identified "corners" were characterized most specifically by the amino acids pairs L227/A303 and I313/L397. Therefore, Gemini is an important model compound that allows further insight into the molecular actions of the VDR but is, in parallel, also a promising precursor for the design of even more potent 1alpha,25(OH)2D3 analogs.

Regulation of 1-alpha, 25-dihydroxyvitamin D3 on interleukin-6 and interleukin-8 induced by sulfur mustard (HD) on human skin cells

The regulatory effects of the active form of vitamin D, 1-alpha, 25-dihydroxyvitamin D3 (1-alpha, 25 (OH)2D3) were assessed on the cytokine and chemokine secretion induced by sulfur mustard on human skin fibroblasts and human epidermal keratinocytes. Stimulation of human skin fibroblasts with sulfur mustard (10(-4) M for 24 hr at 37 degrees ) resulted in approximately a 5 times increase in the secretion of interleukin-6 and over a 10 times increase for interleukin-8, which was inhibited by 1-alpha, 25 (OH)2D3, at <or=10(-9) M. 1-alpha, 25 (OH)2D3 also suppressed interleukin-8 secretion by 5 times and interleukin-6 by 4 times on sulfur mustard-stimulated human epidermal keratinocytes at concentrations <or= 10(-9) M. The effect of 1-alpha, 25 (OH)2D3 was dose-dependent for the suppression of interleukin-6 and interleukin-8 induced by sulfur mustard on human skin fibroblasts/human epidermal keratinocytes, apparent at nanomolar concentrations. Our results indicate that the suppression of these inflammatory mediators by 1-alpha, 25 (OH)2D3 is dependent on the source of the primary cultures, cell densities, and kinetics of pretreatments. In contrast to the inhibition of cytokine/chemokine production, cell proliferation was enhanced by almost 1.7 times on treated human epidermal keratinocytes with 1-alpha, 25 (OH)2D3 (1 x 10(-9) M) after sulfur mustard-stimulation (10(-4) M for 24 hr at 37 degrees C). The observed enhancement diversified based on cell density, and kinetics of pretreatment with a maximal synergism (s) observed at 1 x 10(-9) M. Photomicrographs show typical signs of cellular degeneration caused by sulfur mustard such as chromatin condensation. The observed cellular degeneration was lessened when human epidermal keratinocytes were treated with 1-alpha, 25 (OH)2D3 (2 x 10(-9) M). 1-alpha, 25(OH)2D3 could be an alternative treatment for cutaneous inflammation disorders caused by sulfur mustard because we have demonstrated its ability to suppress inflammatory mediators and enhanced cell proliferation in human skin cells stimulated with sulfur mustard.

Molecular basis of the selective activity of vitamin D analogues

More than 2,000 synthetic analogues of the biological active form of vitamin D, 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)), are presently known. Basically, all of them interfere with the molecular switch of nuclear 1alpha,25(OH)(2)D(3) signaling, which is the complex of the vitamin D receptor (VDR), the retinoid X receptor (RXR), and a 1alpha,25(OH)(2)D(3) response element (VDRE). Central element of this molecular switch is the ligand-binding domain (LBD) of the VDR, which can be stabilized by a 1alpha,25(OH)(2)D(3) analogue either in its agonistic, antagonistic, or non-agonistic conformation. The positioning of helix 12 of the LBD is of most critical importance for these conformations. In each of the three conformations, the VDR performs different protein-protein interactions, which then result in a characteristic functional profile. Most 1alpha,25(OH)(2)D(3) analogues have been identified as agonists, a few are antagonists (e.g., ZK159222 and TEI-9647), and only Gemini and some of its derivatives act under restricted conditions as non-agonists. The functional profile of some 1alpha,25(OH)(2)D(3) analogues, such as EB1089 and Gemini, can be modulated by protein and DNA interaction partners of the VDR. This provides them with some selectivity for DNA-dependent and -independent signaling pathways and VDRE structures.

Efficacy and safety of a new combination of calcipotriol and betamethasone dipropionate (once or twice daily) compared to calcipotriol (twice daily) in the treatment of psoriasis vulgaris: a randomized, double-blind, vehicle-controlled clinical trial

BACKGROUND

Calcipotriol and betamethasone dipropionate are both widely used, effective treatments for psoriasis. Vitamin D analogues and topical corticosteroids have different mechanisms of action in the treatment of psoriasis. A new vehicle has been developed in order to contain both calcipotriol (50 micro g g-1) and betamethasone dipropionate (0.5 mg g-1) in an ointment form. By using calcipotriol and a corticosteroid together, greater efficacy may be achieved than by using either compound alone.

OBJECTIVES

The present study was conducted in order to compare the clinical efficacy and safety of the combined ointment formulation used once daily with the vehicle ointment used twice daily, calcipotriol ointment used twice daily and the combined formulation used twice daily in psoriasis vulgaris.

METHODS

This was an international, multicentre, prospective, randomized, double-blind, vehicle-controlled, parallel group, 4-week study in patients with psoriasis vulgaris amenable to topical treatment. Patients were randomized to one of four treatment groups: combined formulation once daily, combined formulation twice daily, calcipotriol twice daily or vehicle twice daily. Efficacy and safety were assessed.

RESULTS

There was no statistically significant difference in the mean percentage change in the Psoriasis Area and Severity Index (PASI) from baseline to end of treatment between the two combined formulation groups, but the difference in PASI reduction was significantly higher in the combined formulation groups (68.6% once daily, 73.8% twice daily) than in both the twice daily calcipotriol group (58.8%) and the vehicle group (26.6%). Safety data showed the frequency of adverse events to be less in the combined formulation groups than in both the calcipotriol group and the vehicle group. The proportion of patients with lesional/perilesional adverse reactions was less in the combined formulation groups and vehicle group than in the calcipotriol group (9.9% combined formulation once daily, 10.6% combined formulation twice daily, 19.8% calcipotriol, 12.5% vehicle).

CONCLUSIONS

No statistically significant nor clinically relevant difference in efficacy was seen between the combined formulation used once daily and twice daily. When compared to vehicle ointment or calcipotriol ointment alone, the combined formulation was shown to be clearly more efficacious.