Biological activity of vitamin D analogues in the skin, with special reference to antipsoriatic mechanisms

Chinese herbal medicine bath therapy for psoriasis vulgaris using topical calcipotriol as the comparator: A systematic review with meta-analysis and association rule analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Psoriasis is a chronic inflammatory skin disease. Vitamin D analogues are the first-line topical agents for the long-term management of psoriasis. Chinese herbal medicine (CHM) bath therapy is commonly employed for psoriasis. However, the effects and safety of CHM bath therapy for psoriasis vulgaris, using topical calcipotriol as the comparator, remain inconclusive. Furthermore, the combination of herbs, a distinctive feature of CHM, is essential for its therapeutic effects due to the individual and synergistic properties of the herbs involved.

AIM OF THE STUDY

The review was conducted to evaluate the effectiveness and safety of CHM bath therapy for psoriasis vulgaris, using calcipotriol as the comparator. Potential herbs and herb combinations of CHM bath therapy were also explored for further drug discovery.

MATERIALS AND METHODS

Nine databases were searched from inception until March 05, 2024. Randomised controlled trials (RCTs) investigating CHM bath therapy, using calcipotriol as the comparator, were included. Statistical analyses were performed using RevMan 5.4, Stata 12.0 and SPSS Clementine 12.0 software. The evidence certainty for outcomes was assessed using the approach proposed by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group. Moreover, association rule analysis on herbs identified in the systematic review was conducted to explore the potential herbs and herb combinations.

RESULTS

A total of 17 RCTs involving 1,379 participants were included in this systematic review. The findings of this review revealed that: 1) CHM bath therapy produced comparable effects to calcipotriol in reducing Psoriasis Area and Severity Index (PASI), Psoriasis Scalp Severity Index (PSSI), and itch visual analogue scale (VAS) at the end of the treatment phase; as well as exhibited a superior long-term effect than calcipotriol through decreasing relapse rates at the end of the follow-up phase; 2) CHM bath therapy showed an additional benefit when combined with calcipotriol in managing psoriasis vulgaris at the end of the treatment phase, in terms of PASI, PSSI, itch VAS, IL-17, IL-23, CD3+ and CD4+ T cells. The certainty of the evidence was rated as 'very low', 'low' or 'moderate' based on the GRADE assessment, considering some concerns or high risk of bias of included studies, substantial heterogeneity, and existing publication bias of some outcomes. Additionally, the proportions of participants reporting adverse events were similar in both groups. Association rule analysis of all included herbs identified 23 herb combinations including Prunus persica (L.) Batsch and Carthamus tinctorius L., as well as 11 frequently used herbs, such as Kochia scoparia (L.) Schrad., Dictamnus dasycarpus Turcz. And Sophora flavescens Ait.

CONCLUSIONS

The effects of CHM bath therapy were comparable with those of topical calcipotriol but demonstrated a longer-lasting effect. Combining CHM bath therapy with calcipotriol also provided an additional benefit for adult psoriasis vulgaris. However, the certainty of the evidence was downgraded due to the methodological limitations of included studies. To confirm the findings of this review, future investigations should involve double-blinded, placebo-controlled RCTs. Importantly, it appears worthwhile to consider further research for drug development utilising the identified herbs or herb combinations.

Self-assembled hyaluronic acid nanoparticles for the topical treatment of inflammatory skin diseases: Beyond drug carriers

Inflammatory skin diseases represent a significant health concern, affecting approximately 20-25% of the global population. These conditions not only reduce an individual's quality of life but also impose a huge burden on both humanity and society. However, addressing these challenges is hindered by their chronic nature, insufficient therapeutic effectiveness, and the propensity for recurrence and adverse side effects. Hyaluronic acid (HA) has emerged as a potential solution to these barriers, owing to its excellent attributes such as biocompatibility, non-toxicity, and targeted drug delivery. However, its practical application has been limited because endogenous hyaluronidase (HYAL) rapidly degrades HA in inflamed skin thus reducing its ability to penetrate deep into the skin. Interestingly, recent research has expanded the role of self-assembled HA-nanoparticles (HA-NPs) beyond drug carriers; they are resistant to HYAL, thereby enabling deep skin penetration, and possess inherent anti-inflammatory properties. Moreover, these abilities can be fine-tuned depending on the conditions during particle synthesis. Additionally, their role as a drug delivery system holds potential for use as a multi-target drug or hybrid drug. In conclusion, this review aims to specifically introduce and highlight the emerging potential of HA-NPs as a topical treatment for inflammatory skin conditions.

Current emerging and investigational drugs for the treatment of chronic hand eczema

INTRODUCTION

: Chronic hand eczema (CHE) is a highly prevalent, burdensome condition associated with functional impairment. Currently, topical therapeutics are the mainstay of CHE management. However, many cases are refractory to existing topical therapeutics, and the few existing systemic options are often limited in efficacy and by their side effect profiles.

AREAS COVERED

: Following a brief overview of CHE pathogenesis and existing treatments, this review will outline the mechanisms and available data on emerging and investigational drugs currently being studied in clinical trials for the treatment of CHE.

EXPERT OPINION

: Immunomodulatory drugs such as topical and systemic JAK inhibitors and Th2-targeting antibodies such as dupilumab are currently under investigation for CHE treatment, with early promise. Management of CHE will likely move toward more targeted treatments through clinical trials and away from broad immunosuppressants such as cyclosporine and methotrexate, which have previously been investigated for CHE and have more side effects. In coming years, CHE patients may benefit from a wider range of both topical and systemic therapeutics that target immune pathways relevant to the various CHE subtypes.

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.

Vitamin D and psoriasis: an update for dermatologists and nutritionists

Psoriasis is a common chronic immune-mediated inflammatory skin disease, now considered a systemic inflammatory process with several comorbidities. The skin produces vitamin D by the action of ultraviolet light. Vitamin D performs various immunomodulatory, anti-inflammatory, antioxidant and antifibrotic actions. The immunomodulatory effects of vitamin D offer opportunities to improve the treatment of several autoimmune diseases, such as psoriasis. In the literature, several significant associations are reported between low levels of vitamin D and psoriasis. Today, topical vitamin D represents an important therapeutic option due to its action on the proliferation and maturation of keratinocytes. The situation is different regarding the oral intake and integration of vitamin D in psoriasis patients. The use of vitamin D supplementation as an adjunctive treatment option in these patients is still discussed. This work aims to analyze the association between psoriasis and vitamin D levels according to dermatologists and nutritionists.

UV increases skin-derived 1α,25-dihydroxyvitamin D3 production, leading to MMP-1 expression by altering the balance of vitamin D and cholesterol synthesis from 7-dehydrocholesterol

The skin is a unique site in the human body that has the capacity to synthesize the active form of vitamin D, 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃), from 7-dehydrocholesterol (7DHC) upon UV irradiation. Keratinocytes express both 25-hydroxylase (CYP27A1 and CYP2R1) and 1α-hydroxylase (CYP27B1), critical enzymes involved in active vitamin D synthesis. Here, we investigated the effect of skin-derived 1α,25(OH)₂D₃, synthesized purely within the keratinocytes, on MMP-1 expression. Treatment of human epidermal keratinocytes with 1α,25(OH)₂D_3, but not 7DHC or 25OHD₃, significantly increased MMP-1 expression. UV irradiation increases 1α,25(OH)₂D₃ levels, and ketoconazole inhibits UV-induced production of 1α,25(OH)₂D₃. Upregulation of MMP-1 by UV was reversed by inhibition of 1α,25(OH)₂D₃ synthesis using ketoconazole or CYP27B1 siRNA. In keratinocytes, 7DHC is a substrate for both cholesterol and 1α,25(OH)₂D₃ synthesis. We demonstrated that UV irradiation leads to decreased expression of DHCR7 (7-dehydrocholesterol reductase), the enzyme that converts 7DHC to cholesterol. Inhibition of DHCR7 with its inhibitor BM15766 decreased cholesterol synthesis and increased UV-induced MMP-1 expression, which was attenuated by ketoconazole. These findings suggest that UV-induced reduction of DHCR7 leads to a decrease in cholesterol synthesis, thereby increasing 7DHC availability for 1α,25(OH)₂D₃ production, which enhances MMP-1 expression. Finally, UV irradiation in human skin in vivo significantly increased CYP27B1 mRNA and decreased DHCR7 mRNA expression. Taken together, we demonstrate here that skin-derived 1α,25(OH)₂D₃ significantly increases MMP-1 expression in human keratinocytes, a previously unappreciated function of 1α,25(OH)₂D_3. Moreover, UV irradiation upregulates the enzyme CYP27B1, which leads to 1α,25(OH)₂D₃ synthesis, but downregulates the cholesterol-producing enzyme DHCR7, both of which collectively lead to increased MMP-1 expression in human keratinocytes. This pathway may be exploited to develop a novel cutaneous anti-aging agent that blocks local cutaneous 1α,25(OH)₂D₃ synthesis.

Vitamin D and the skin: what should a dermatologist know?

Although first discovered in 1931, vitamin D has seen an increased interest in the scientific community over the past decades, including the dermatology field. Vitamin D promotes calcium and phosphorus absorption; however, the actions of vitamin D are not confined to bone. Indeed, there is now overwhelming and compelling scientific data that vitamin D plays a crucial role in a plethora of cellular function and in extra-skeletal health. Except for fatty fish livers, very few foods naturally contain vitamin D; and the major source of vitamin D comes from skin exposure to sunlight via ultraviolet B. Keratinocytes are unique in the body as not only do they provide the primary source of vitamin D for the body, but they also possess both the enzymatic machinery to metabolize the vitamin D produced to active metabolites. This has been referred to as the photoendocrine vitamin D system. Vitamin D regulates keratinocytes proliferation and differentiation; and plays a role in the defense against opportunistic infections. Multiple factors are linked to vitamin D status; and a growing number of dermatologic diseases has been linked to vitamin D status such as atopic dermatitis, psoriasis, vitiligo, and cutaneous cancers. In this article, we reviewed the potential determinants of vitamin D status, as its implications in dermatologic diseases.

Epidermolytic hyperkeratosis: clinical update

Epidermolytic hyperkeratosis (EHK), earlier termed as bullous congenital ichthyosiform erythroderma is a skin disorder characterized as an autosomal dominant and rare disorder which has been observed to affect 1 in over 200,000 infants as a consequence of a significant mutation in the genes responsible for the keratin proteins, mostly keratin 1 and 10. The features present at birth include erythema and blistering. In adults, the hallmarks include hyperkeratosis, erosions, and blisters. The major symptoms including xerosis, pruritus, and painful fissuring lead not only to cosmetic problems but also stress, inferiority complex and other psychological conditions. While clinical inspection followed by confirmatory tests including histopathology and electron microscopic assessment is used for diagnosis, treatment modalities can be further improved for better diagnosis. This article reviews subtypes of ichthyosis, with a focus on EHK, genetics behind the disease, recently reported mutations, the existing diagnostics and treatments for the same and potential of new modalities in diagnosis/treatment.

The vitamin D3 analog, maxacalcitol, reduces psoriasiform skin inflammation by inducing regulatory T cells and downregulating IL-23 and IL-17 production

BACKGROUND

Psoriasis is a Th1/Th17-mediated inflammatory dermatosis treated with topical corticosteroids and vitamin D₃ analogs (VD3 As).

OBJECTIVE

To compare the effects of a VD3 A maxacalcitol and betamethasone valerate (BV) steroid lotion on topical imiquimod (IMQ)-induced psoriasiform skin inflammation.

METHODS

Female BALB/c mice were treated with vehicle, maxacalcitol or BV lotion on the skin for 3 days, and IMQ cream for 6 days. q-PCR, H&E, immunohistochemistry and immunofluorescence studies were performed on skin samples. Additionally, mice were treated with vehicle, maxacalcitol or BV lotion for 3 days and CD4⁺CD25⁺ regulatory T cells (Tregs) and CD4⁺CD25^- cells from each group were isolated from lymph nodes. Adoptive transfer of the cells was performed on recipient mice which were treated with IMQ cream for 6 days, and skin samples were obtained for q-PCR and H&E staining.

RESULTS

Maxacalcitol and BV were comparable in regards clinical improvement, although maxacalcitol reduced the MHC Class II⁺ inflammatory cell infiltration more than BV in IMQ skin. While both treatments downregulated IL-17 A, IL-17 F, IL-22, IL-12p40, TNF-α and IL-6 mRNA expression levels, only maxacalcitol downregulated IL-23p19 expression. Significantly increased Foxp3⁺ cell infiltrations and IL-10 expression were noted in maxacalcitol-treated IMQ skin. Adoptive transfer of Treg cells from maxacalcitol-treated donor mice improved IMQ-induced inflammation clinically and histopathologically more than the recipients of Treg cells from BV-treated donor groups, showing reduced levels of inflammatory cytokines and increased IL-10 expression.

CONCLUSION

These results indicate that maxacalcitol reduces psoriasiform skin inflammation by inducing Treg cells as well as downregulating IL-23 and IL-17 production.

Molecular Mechanisms and Management of a Cutaneous Inflammatory Disorder: Psoriasis

Psoriasis is a complex chronic inflammatory cutaneous disorder. To date, robust molecular mechanisms of psoriasis have been reported. Among diverse aberrant immunopathogenetic mechanisms, the current model emphasizes the role of Th1 and the IL-23/Th17 axis, skin-resident immune cells and major signal transduction pathways involved in psoriasis. The multiple genetic risk loci for psoriasis have been rapidly revealed with the advent of a novel technology. Moreover, identifying epigenetic modifications could bridge the gap between genetic and environmental risk factors in psoriasis. This review will provide a better understanding of the pathogenesis of psoriasis by unraveling the complicated interplay among immunological abnormalities, genetic risk foci, epigenetic modification and environmental factors of psoriasis. With advances in molecular biology, diverse new targets are under investigation to manage psoriasis. The recent advances in treatment modalities for psoriasis based on targeted molecules are also discussed.

Vitamin D and its role in psoriasis: An overview of the dermatologist and nutritionist

Psoriasis is a chronic immune-mediated inflammatory skin disease. Psoriasis lesions are characterized by hyper-proliferation of epidermal keratinocytes associated with inflammatory cellular infiltrate in both dermis and epidermis. The epidermis is the natural source of vitamin D synthesis by sunlight action. Recently, a role for vitamin D in the pathogenesis of different skin diseases, including psoriasis, has been reported. Indeed, significant associations between low vitamin D status and psoriasis have been systematically observed. Due to its role in proliferation and maturation of keratinocytes, vitamin D has become an important local therapeutic option in the treatment of psoriasis. To date, the successful treatment based on adequate dietary intake of vitamin D or oral vitamin D supplementation in psoriasis represent an unmet clinical need and the evidence of its beneficial effects remains still controversial. This information is important either for Dermatologists and Nutritionists to increases the knowledge on the possible bi-directional relationships between low vitamin D status and psoriasis and on the potential usefulness of vitamin D in psoriasis with the aim not only to reduce its clinical severity, but also for delineating the risk profile for co-morbidities cardiac risk factors that may result from psoriasis. In the current review, we analyzed the possible bi-directional links between psoriatic disease and vitamin D.

Efficacy of narrowband ultraviolet B phototherapy and levels of serum vitamin D3 in psoriasis: A prospective study

INTRODUCTION

Narrowband ultraviolet B phototherapy (NBUVB) is safe and effective treatment for psoriasis. Vitamin D plays an important role in pathogenesis of psoriasis. It is known that psoriasis patients have low serum 25(OH)D levels, which increase after NBUVB. We assessed serum 25(OH)D levels, its correlation with Psoriasis Area and Severity Index (PASI), and the effect of NBUVB on 25(OH)D levels among Indian psoriasis patients.

MATERIALS AND METHODS

A prospective study comprising 30 adults with psoriasis with no major comorbidities (PASI > 10 and off-therapy >4 weeks) was conducted. PASI was estimated at baseline among patients and repeated after receiving 12 weeks of NBUVB therapy. Thirty age and gender-matched healthy controls were recruited to compare 25(OH)D levels at baseline and at 12 weeks. Patient demographic parameters, treatment dose, duration, side effects, and its impact on 25(OH)D levels and PASI were serially evaluated.

RESULTS

A total of 30 patients presenting with psoriasis and 30 healthy controls were enrolled in the study. Mean baseline PASI (M: F =19:11) among patients with mean age 36.8 (±7.7) years was 20.5 (±6.3) and all patients were either 25(OH)D deficient (n = 14) or insufficient (n = 16). Their baseline 25(OH)D levels were significantly lower than controls (25.93 nmol/L vs 47.54 nmol/L; P < 0.001). After NBUVB therapy (average cumulative dose 20.76 ± 7.1 J/cm(2); average treatment sessions 32.57 ± 1.9), there was a significant improvement in PASI as well as 25(OH)D (P < 0.05). There was no correlation between the mean improvement in PASI and 25(OH)D after 12 weeks of therapy. Twelve (40%) patients had therapy-related side effects [pruritus (n = 8), erythema (n = 4)], none had major side effects.

CONCLUSION

Improvement in PASI and serum 25(OH)D levels after NBUVB in psoriasis is significant but poorly correlated with each other. Vitamin D may not be the lone mediator of the therapeutic effects of NBUVB on psoriasis.

TNF-α increases the expression and activity of vitamin D receptor in keratinocytes: role of c-Jun N-terminal kinase

Several inflammatory mediators increase calcitriol production by epidermal keratinocytes. In turn calcitriol attenuates the keratinocyte inflammatory response. Since the effect of the in-situ generated calcitriol depends also on the sensitivity to the hormone we studied the effect of inflammatory cytokines on the response of HaCaT human keratinocytes to calcitriol by examining the expression and transcriptional activity of VDR. Treatment with TNF, but not with IL-1β or interferon γ, increased VDR protein level, while decreasing the level of its heterodimerization partner RXRα. This was associated with increased VDR mRNA levels. c-Jun N-terminal kinase, but not P38 MAPK or NFκB, was found to participate in the upregulation of VDR by TNF. The functional significance of the modulation of VDR and RXRα levels by TNF is manifested by increased induction of VDR target gene CYP24A1 by calcitriol. Calcitriol, in turn, inhibited the enhanced expression of VDR by TNF. In conclusion, the inflammatory cytokine TNF increases the response of keratinocytes to calcitriol through upregulation of its receptor VDR, which in turn is subject to negative feedback by the hormone accelerating the return of the keratinocyte vitamin D system to its basal activity. We surmise that the increased generation and sensitivity to calcitriol in keratinocytes play a role in the resolution of epidermal inflammation.

Anti-Inflammatory Effects of Tacalcitol (1,24(R)(OH)2D3, TV-02) in the Skin of TPA-Treated Hairless Mice

Tacalcitol (1,24(R)(OH)2D3, TV-02) inhibited the TPA-induced inflammatory cell infiltration (largely neutrophils) histopathologically and myeloperoxidase (MPO) activity dose-dependently. Tacalcitol inhibited the mRNA expression and protein production of TPA-induced macrophage inflammatory protein-2 (MIP-2) and KC, the functional analogue of human interleukin (IL)-8, in the skin. Immunohistochemical staining of the TPA-applied skin revealed that mast cells expressed MIP-2, whereas KC was observed in keratinocytes, fibroblasts and outer root sheath of hair follicles. Furthermore, tacalcitol inhibited TPA-induced mast cell degranulation 24 hr after application without influence on the total number of mast cells. In this study, tacalcitol was found to have an inhibitory effect on cutaneous inflammation such as inhibition of neutrophil infiltration, MIP-2 and KC production, and mast cell degranulation in TPA-treated hairless mice. These results suggest that tacalcitol modulates cutaneous inflammation as well as keratinocyte proliferation and differentiation, and the inhibitory effect of tacalcitol on cutaneous inflammation may contribute to clinical the effectiveness in the treatment of psoriasis.

Topical Vitamin D3Is Effective in Treating Senile Warts Possibly by Inducing Apoptosis

Vitamin D3 ointments containing active forms of vitamin D3 are widely used to treat inflammatory keratotic dermatoses such as psoriasis. Senile wart or seborrheic keratosis is a benign tumor which occurs mainly in the elderly. It has traditionally been treated with surgical procedures, freezing with liquid nitrogen, or laser therapy. We treated senile warts with topical vitamin D3 ointments (tacalcitol, calcipotriol or maxacalcitol). Out of 116 cases treated for 3 to 12 months, 35 (30.2%) showed complete disappearance or more than an 80% decrease in the volume of the tumor, 54 cases (46.6%) showed a decrease in the volume between 40 and 80%, and no remarkable changes or decreases of less than 40% were seen in 27 cases (23.3%). The tumors faded without any inflammatory changes such as erythema or swelling. An organ culture experiment using senile wart as a material with several concentrations of tacalcitol revealed that tacalcitol induced apoptosis in the tissue. On the other hand, only sporadic apoptotic cells were seen in the controls (p<0.001). Vitamin D3 may affect senile warts by inducing apoptosis. Clearance of senile warts, especially on exposed areas without pain, may improve the quality of life (QOL) of the elderly.

Phototherapeutic hardening modulates systemic cytokine levels in patients with polymorphic light eruption

The etiopathogenesis of polymorphic light eruption (PLE) has been linked to impaired UV-immunosuppression, Langerhans cell (LC) retention, and an absence of neutrophil infiltration into UV-exposed PLE skin. We have previously shown that photohardening restores the impaired neutrophil responsiveness to the chemoattractants leucotriene B4 and formyl-methionyl-leucyl-phenylalanin in PLE patients. The aim of this study was to investigate whether photohardening modulates baseline chemokine and cytokine levels which would alter chemoresponsiveness and hence immune function in PLE patients. Sixteen PLE patients received photohardening therapy for 4-9 weeks by 311 nm UVB. Plasma samples were taken both before and within 48 h of the penultimate phototherapeutic exposure. Plasma from these 16 patients, 8 non-irradiated PLE patients, and 14 control subjects was analyzed for IL-1β, CXCL8 (IL-8), IL-10, IL-17, TNF, CCL2 (MCP-1), CCL5 (RANTES), CCL11 (eotaxin), and CCL22 (MDC). These cytokines and chemokines were measured in early spring (March to April) and again in late spring (April to June). PLE patients had a significantly elevated level of CCL11 (p = 0.003) and IL-1β (p = 0.002) in early spring (before phototherapy). In late spring, after phototherapy, PLE patients had significantly elevated CCL2 (p = 0.002) and TNF (p = 0.002) but a trend for lowered plasma levels of CXCL8 (p = 0.021). When comparing the cytokine shifts from early to late spring, while healthy controls and non-UV-irradiated PLE patients showed an increase, PLE patients undergoing photohardening exhibited a trend for decrease in IL-1β (p = 0.012). Taken together, our results indicate that photohardening may alter the complex cytokine milieu in PLE, in particular via IL-1β, helping to normalise the pathophysiologic response to subsequent UV exposure.

Suppressive effect of calcipotriol on the induction of matrix metalloproteinase (MMP)-9 and MMP-13 in a human squamous cell carcinoma cell line

BACKGROUND

Vitamin D3 is a potent regulator of cell growth, differentiation and death, tumour invasion, and angiogenesis. Production of matrix metalloproteinase (MMP)-9 and MMP-13 by tumour cells may promote tumour growth, invasion and metastasis.

AIM

To investigate whether calcipotriol could suppress the expression of MMP-9 and MMP-13 in a human squamous cell carcinoma (SCC) cell line (DJM cells), and to examine the mechanism of modulation of MMP-9 and MMP-13 by calcipotriol in DJM cells treated with tumour necrosis factor (TNF)-α.

METHODS

Protein and mRNA levels of MMP-9 and MMP-13 were examined by ELISA and real-time PCR, respectively. Activation of signalling cascades was assessed using several inhibitors of signalling molecules and western blot analysis.

RESULTS

Production of MMP-9 and MMP-13 markedly increased when the cells were treated with TNF-α. Calcipotriol suppressed the production of MMP-9 and MMP-13 mRNA and proteins significantly, in a dose-dependent manner. Induction of MMP-9 by TNF-α was suppressed by an extracellular signal-regulated kinase (ERK) inhibitor but not by a p38 inhibitor, whereas induction of MMP-13 was inhibited by a p38 inhibitor but not by an ERK inhibitor. Calcipotriol inhibited the phosphorylation of both ERK and p38, as shown by western blotting.

CONCLUSION

Calcipotriol reduces MMP-9 and MMP-13 production through inhibiting the phosphorylation of ERK and p38, respectively.

A critical analysis of the (near) legendary status of vitamin D

Labels such as food constituent, nutrient and supplement do not convey a sense of being essential. Yet these rather mundane descriptors, even if correct, belie the true significance of vitamin D. Long believed to be merely a functioning cofactor akin to vitamin C, deficiency of this secosteroid hormone is clearly associated with morbid complications of calcium and bone mineral metabolism, and because the hormonal effects are mediated by nuclear receptors that regulate the expression of many subordinate genes, the vitamin's pleiotropic mode of action can influence numerous metabolic pathways and, possibly, a number of different diseases. Although the vitamin is under intensive investigation, much still remains unknown, even in bone health, as the identity of osteoporosis susceptibility genes remains uncertain. This article focuses on various aspects of the basic science and molecular biology of the vitamin D endocrine system. The primary goal is to critically examine the evidence supporting its role in bone metabolism, diabetes and cancer.

Randomized double-blinded placebo-controlled intra-individual trial on topical treatment with a 1,25-dihydroxyvitamin D₃ analogue in polymorphic light eruption

BACKGROUND

Polymorphic light eruption (PLE) is a very frequent photodermatosis whose pathogenesis may involve resistance to ultraviolet (UV)-induced immune suppression. Similar to UV radiation, calcitriol (1,25-dihydroxyvitamin D₃) and its analogues such as calcipotriol have been shown to exhibit immunosuppressive properties.

OBJECTIVES

We performed a randomized double-blinded placebo-controlled intraindividual half-body trial (NCT00871052) to investigate the preventive effect of a calcipotriol-containing cream in PLE.

METHODS

Thirteen patients with PLE (10 women, three men; mean age 37 years) pretreated their skin on two symmetrically located test fields with calcipotriol or placebo cream twice daily for 7 days before the start of photoprovocation testing with solar-simulated UV radiation. We established a specific PLE test score [AA + SI + 0·4 P (range 0-12), where AA is affected area score (range 0-4), SI is skin infiltration score (range 0-4) and P is pruritus score on a visual analogue scale (range 0-10)] to quantify PLE severity.

RESULTS

Photoprovocation led to PLE lesions in 12/13 (92%) patients. As shown by the PLE test score, compared with placebo calcipotrial pretreatment significantly reduced PLE symptoms in average by 32% (95% confidence interval 21-44%; P = 0·0022, exact Wilcoxon signed-rank test) throughout the observation period starting at 48 h until 144 h after the first photoprovocation exposure. At 48, 72 and 144 h calcipotriol pretreatment resulted in a lower PLE test score in 7 (58%), 9 (75%) and 10 (83%) of the 12 cases, respectively. Considering all time points together, calcipotriol diminished the PLE test score in all 12 photoprovocable patients (P = 0·0005; Wilcoxon signed-rank test).

CONCLUSIONS

These results suggest a potential therapeutic benefit of topical 1,25-dihydroxyvitamin D₃ analogues as prophylactic treatment in patients with PLE.

Vitamin D inhibits captopril-induced cell detachment and apoptosis in keratinocytes

BACKGROUND

Captopril, an angiotensin I-converting enzyme inhibitor, is a commonly prescribed antihypertensive drug. Its cutaneous side-effects include pemphigus vulgaris acantholysis and bullous pemphigoid-like cell-matrix detachment. This medication also triggers apoptosis in human keratinocytes. Calcitriol, the hormonally active vitamin D metabolite, protects keratinocytes from programmed cell death induced by various noxious stimuli.

OBJECTIVES

To examine if calcitriol protects proliferating keratinocytes from the damage inflicted by captopril.

METHODS

Autonomously proliferating HaCaT keratinocytes, used as a model for basal layer keratinocytes, were exposed to captopril. Cell detachment was examined visually by light microscopy. Cytotoxicity was assessed by Hoechst 33342 staining and lactate dehydrogenase release. Apoptotic death was assessed by monitoring caspase 3-like activity.

RESULTS

Cells exposed to captopril detached and became round. This process was accompanied by programmed cell death. From time-dependent monitoring of cell detachment and apoptosis, and examination of pan-caspase inhibitor effects on cell detachment we concluded that cell death is the consequence of cell detachment from the culture plate and not vice versa. Pretreatment with calcitriol significantly attenuated these events. The effects of calcitriol were already evident at 1 nmol L(-1) concentration of the hormone.

CONCLUSIONS

The results of this study show that calcitriol protects keratinocytes from captopril-induced cell detachment and apoptosis.

UVB-induced production of 1,25-dihydroxyvitamin D3 and vitamin D activity in human keratinocytes pretreated with a sterol delta7-reductase inhibitor

The skin fulfills an important role in the vitamin D photo-endocrine system. Epidermis is not only the site of vitamin D3 photoproduction. In addition, epidermal keratinocytes contain the vitamin D receptor (VDR) and possess 25-hydroxylase and 1alpha-hydroxylase activity indicating that all components of the vitamin D system are present. We investigated whether these components cooperate in inducing vitamin D activity upon treatment with physiological UVB doses. Upon irradiation, 24-hydroxylase mRNA was induced in keratinocytes pretreated with a sterol Delta7-reductase inhibitor (BM15766) whereby the 7-dehydrocholesterol content increased by 300-fold. Transfection experiments with a vitamin D response element containing construct confirmed VDR-dependent gene activation. Furthermore, the UVB-dependent induction of 24-hydroxylase was blocked by the cytochrome-P450 inhibitor ketoconazole. The 24-hydroxylase inducing photoproduct was transferable to unirradiated keratinocytes by medium and cellular homogenates of UVB-irradiated, BM15766-pretreated cells and was identified as 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] by high-performance liquid chromatography with tandem mass spectrometric detection. Addition of vitamin D binding protein blunted UVB-induced 24-hydroxylase suggesting the possibility of a paracrine or autocrine role for 1,25(OH)2D3. In conclusion, epidermal keratinocytes can produce vitamin D3, convert it to 1,25(OH)2D3 and respond to it upon UVB irradiation in the absence of exogenous 7-dehydrocholesterol and therefore contain a unique and complete photo-endocrine vitamin D system.

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.

Wavelength-Dependent Induction of CYP24A1-mRNA after UVB-Triggered Calcitriol Synthesis in Cultured Human Keratinocytes

Earlier investigations in our laboratory have demonstrated that UVB irradiation of cultured human keratinocytes induces the conversion of 7-dehydrocholesterol (7-DHC) to hormonally active 1alpha,25-dihydroxyvitamin D3 (calcitriol). In the research presented here, we have investigated the influence of UVB-triggered calcitriol production on gene expression of the vitamin D3 hydroxylating enzymes catabolic 25-hydroxyvitamin-D3-24-hydroxylase (CYP24A1), active vitamin-D3-25-hydroxylase (CYP27A1), and 25-hydroxyvitamin-D3-1alpha-hydroxylase (CYP27B1) using real-time PCR. Our results demonstrate a marked and wavelength-dependent induction of CYP24A1-mRNA in cultured human keratinocytes supplemented with 7-DHC, which parallels the spectral optimum at about 300 nm of calcitriol production as detected by HPLC and radioimmunoassay. Owing to the high sensitivity of real-time PCR, we provide evidence of a wavelength-dependent induction of CYP24A1-mRNA even in 7-DHC-deficient keratinocytes. Interestingly, we have found a strong but transient induction of CYP24A1-mRNA in non-irradiated keratinocytes, followed by accelerated cell proliferation. In contrast, UVB and calcitriol had no effect on gene expression of CYP27A1 and CYP27B1. We conclude from these experiments a constitutive gene expression of the vitamin D3 hydroxylases, whereas the catabolic enzyme CYP24A1 is markedly regulated by UVB, calcitriol, and perhaps cell proliferation. If confirmed at protein level, these findings could have an impact on epidermal vitamin D3 metabolism and its modulation by UVB in health and disease.

Dermal fibroblasts pretreated with a sterol Δ7-reductase inhibitor produce 25-hydroxyvitamin D3 upon UVB irradiation

As dermis is a physiological site of vitamin D3 photoproduction, the photo-endocrine vitamin D3 system was studied in dermal fibroblasts. Dermal fibroblasts contain the vitamin D receptor and induce 1alpha,25-dihydroxyvitamin D3-24-hydroxylase [CYP24] mRNA upon stimulation with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. In addition, dermal fibroblasts contain mRNA of the vitamin D3-25-hydroxylases (CYP2R1 and CYP27A1). However, we could not detect any 25-hydroxyvitamin D3 [25OHD3]-1alpha-hydroxylase mRNA in dermal fibroblasts and no CYP24 mRNA was induced upon ultraviolet [UVB] irradiation, even when endogenous 7-dehydrocholesterol content was elevated by pretreatment with the sterol Delta7-reductase inhibitor BM15766. Nevertheless, dermal fibroblasts produce inactive vitamin D3 metabolites that can be activated by epidermal keratinocytes as CYP24 mRNA is induced in epidermal keratinocytes but not in dermal fibroblasts after transfer of medium or cellular suspensions from BM15766-pretreated, UVB-irradiated fibroblasts. This CYP24 induction was UVB-dose dependent and was inhibited by ketoconazole. As revealed in a competitive binding assay, BM15766-pretreated dermal fibroblasts are able to produce 25OHD3 upon UVB irradiation, but no 1,25(OH)2D3 was detected via combined high-performance liquid chromatography radioimmunoassay. The physiological relevance of dermal vitamin D3 photoproduction and its subsequent conversion into 25OHD3 remains elusive.

The vitamin D questions: How much do you need and how should you get it?

UV radiation is a well-documented human carcinogen, indisputably linked to the current continued increased rate of skin cancer. UV radiation is also responsible for cutaneous synthesis of vitamin (vit) D3, a substance that is then sequentially hydroxylated in the liver and kidney to yield 1,25(OH)2 vit D, a hormone critical for calcium homeostasis and skeletal maintenance. Because the UV action spectra for DNA damage leading to skin cancer and for vit D photosynthesis are virtually identical, the harmful and beneficial effects of UV irradiation are inseparable. This has given rise to the argument that sun avoidance, with a goal of skin cancer prevention, may compromise vit D sufficiency. Public interest in this matter has been heightened in recent years by multiple studies correlating the level of 25-OH vit D, the readily measurable "storage" precursor form of the vit, with a variety of benefits separate from skeletal health. Although the studies are of variable quality and all alleged treatment benefits are based on dietary supplementation with vit D, not on increased sun exposure, they have been interpreted by some as support for advocating increased sun exposure of the public at large. The goal of this review is to provide a detailed, balanced, and referenced discussion of the complex literature underlying the current popular interest in vit D and sun exposure for the purpose of increasing vit D photosynthesis. We review the nomenclature, metabolism, and established functions of vit D; the evidence supporting the less well-established but purported vit D effects; the concept of vit D insufficiency; populations at risk for vit D deficiency; and finally the risk/benefit of obtaining vit D from cutaneous photosynthesis versus diet or supplementation.

Topical vitamin D3 derivatives in treating hyperkeratotic palmoplantar eczema: a report of five patients

The treatment of hyperkeratotic palmoplantar eczema is notoriously difficult. A considerable number of patients do not or only partially respond to the current treatments such as topical corticosteroids, topical keratolytics, or PUVA therapy. The purpose of this pilot study was to look for an alternative treatment for hyperkeratotic palmoplantar eczema. We treated five patients with topical vitamin D3 derivatives (calcipotriol 50 microg/g and maxacalcitol 25 microg/g ointments). The lesions almost disappeared after 2 to 8 weeks of treatment in four patients and extremely improved with a seven week treatment in one patient. No adverse effect was observed during or after the treatment, and routine laboratory investigations were within normal ranges. When relapses occurred, they responded well to retreatment. Although the study is preliminary, the results suggest that vitamin D3 derivatives offer a safe, effective alternative form of treatment for recalcitrant hyperkeratotic palmoplantar eczema.

C-25 hydroxylation of 1alpha,24(R)-dihydroxyvitamin D3 is catalyzed by 25-hydroxyvitamin D3-24-hydroxylase (CYP24A1): metabolism studies with human keratinocytes and rat recombinant CYP24A1

Recently, 25-hydroxyvitamin D3-24-hydroxylase (CYP24A1) has been shown to catalyze not only hydroxylation at C-24 but also hydroxylations at C-23 and C-26 of the secosteroid hormone 1alpha, 25-dihydroxyvitamin D3 (1alpha,25(OH)2D3). It remains to be determined whether CYP24A1 has the ability to hydroxylate vitamin D3 compounds at C-25. 1alpha,24(R)-dihydroxyvitamin D3 (1alpha,24(R)(OH)2D3) is a non-25-hydroxylated synthetic vitamin D3 analog that is presently being used as an antipsoriatic drug. In the present study, we investigated the metabolism of 1alpha,24(R)(OH)2D3 in human keratinocytes in order to examine the ability of CYP24A1 to hydroxylate 1alpha,24(R)(OH)2D3 at C-25. The results indicated that keratinocytes metabolize 1alpha,24(R)(OH)2D3 into several previously known both 25-hydroxylated and non-25-hydroxylated metabolites along with two new metabolites, namely 1alpha,23,24(OH)3D3 and 1alpha,24(OH)2-23-oxo-D3. Production of the metabolites including the 25-hydroxylated ones was detectable only when CYP24A1 activity was induced in keratinocytes 1alpha,25(OH)2D3. This finding provided indirect evidence to indicate that CYP24A1 catalyzes C-25 hydroxylation of 1alpha,24(R)(OH)2D3. The final proof for this finding was obtained through our metabolism studies using highly purified recombinant rat CYP24A1 in a reconstituted system. Incubation of this system with 1alpha,24(R)(OH)2D3 resulted in the production of both 25-hydroxylated and non-25-hydroxylated metabolites. Thus, in our present study, we identified CYP24A1 as the main enzyme responsible for the metabolism of 1alpha,24(R)(OH)2D3 in human keratinocytes, and provided unequivocal evidence to indicate that the multicatalytic enzyme CYP24A1 has the ability to hydroxylate 1alpha,24(R)(OH)2D3 at C-25.

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.

Changing paradigms in dermatology: nuclear hormone receptors

Nuclear hormone receptors (NHRs) are a family of proteins that function similarly as nuclear transcription factors. The NHR family includes glucocorticoid receptors, retinoic acid and retinoid receptors, vitamin D receptors, thyroxin receptors, and peroxisome proliferator activated receptors. These proteins are targets for some of the most commonly prescribed medications in dermatology, including corticosteroids, retinoids, and vitamin D analogues, all of which have limiting side effects. Advances in this field have led to better understanding of the mechanisms of NHR therapeutic and toxic effects, receptor subtypes, tissue distribution, and interaction with other molecules. New generations of more specific NHR ligands designed to increase therapeutic efficacy and limit adverse effects have dramatically expanded the clinical application of NHR-targeting drugs. The current understanding of NHRs and future directions for NHR ligands in dermatology are discussed.

Vitamin D enhances mitogenesis mediated by keratinocyte growth factor receptor in keratinocytes

The hormonally active vitamin D metabolite, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), and keratinocyte growth factor (KGF) belong to the network of autocrine and paracrine mediators in the skin. Both were shown to modulate keratinocyte proliferation, to reverse epidermal atrophy, to increase wound healing, and to reduce chemotherapy-induced alopecia. The overlap between their activities may suggest that vitamin D exerts some of its actions by modulation of KGF activities in the skin. This notion was examined by using HaCaT keratinocytes cultured in serum-free medium in the absence of exogenous growth factors and in the presence of the EGF receptor tyrosine kinase inhibitor AG 1478 that blocks their autonomous proliferation. These cells could be stimulated to proliferate by different fibroblast growth factors (FGFs). The relative mitogenic efficacy of basic FGF, acidic FGF, or KGF was in correlation with their affinities for the KGF receptor (KGFR). Forty-eight hour co-treatment with 1,25(OH)(2)D(3) enhanced KGFR-mediated cell proliferation in a dose dependent manner. Both ERK1/2 and c-Jun N-terminal kinase (JNK) were activated by the FGFs. Treatment with 1,25(OH)(2)D(3) increased the activation of ERK but reduced the activation of JNK. Treatment with 1,25(OH)(2)D(3) increased the levels of KGFR in the presence but not in the absence of KGF, probably due to inhibition of ligand-induced receptor degradation. Inhibition of protein kinase C with bisindolylmaleimide did not interfere with the effect of 1,25(OH)(2)D(3) on KGFR-mediated ERK activation. Our results support the notion that the paracrine KGF-KGFR system in the skin can act in concert with the autocrine vitamin D system in keratinocytes to promote keratinocyte proliferation and survival under situations of stress and injury.

Skin is an autonomous organ in synthesis, two-step activation and degradation of vitamin D(3): CYP27 in epidermis completes the set of essential vitamin D(3)-hydroxylases

The current understanding of the vitamin D(3) system shows skin as the unique site of vitamin D(3) production and liver is thought to be the main site of conversion to 25(OH)D(3). Skin is capable of activating 25(OH)D(3) via 1alpha-hydroxylation and the resulting 1alpha,25(OH)(2)D(3) plays a role in epidermal homeostasis in normal and diseased skin. It also rapidly up-regulates the major vitamin D(3) metabolizing enzyme 24-hydroxylase at the mRNA level, which is an established indicator for 1alpha,25(OH)(2)D(3)-presence. We investigated the capability of primary human keratinocytes to produce 25(OH)D(3) and subsequent metabolites from vitamin D(3). Thus, by orchestrating the entire system of production, activation and inactivation, skin could be independent of other organs in supply of hormonally active vitamin D(3). First, we demonstrated substantial conversion of (3)H-D(3) to (3)H-25(OH)D(3) in primary human keratinocytes. 25-Hydroxylation was slow, followed first order rate kinetics and was not saturable under our experimental conditions. Then we showed expression of 25-hydroxylase mRNA and compared it to levels of 1alpha-hydroxylase and 24-hydroxylase. Pre-incubation with vitamin D(3) resulted in dose and time dependent up-regulation of 24-hydroxylase mRNA, whereas neither 1alpha-hydroxylase nor 25-hydroxylase expression was affected. Since both, D(3) and 25(OH)D(3) are lacking intrinsic 24-hydroxylase-inducing capacity, up-regulation had to be the consequence of a two-step activation process via 25-hydroxylation and subsequent 1alpha-hydroxylation. 24-Hydroxylase-activities closely followed the corresponding mRNA levels. When 1alpha,25(OH)(2)D(3) itself or its precursor 25(OH)D(3) were used as inducing agents, 24-hydroxylase mRNA and enzyme activity followed a transient time course. In contrast, induction observed with physiological doses of D(3) remained high, even after a 20 h-time period. These differing characteristics may be explained by the slow but constant formation of 1alpha,25(OH)(2)D(3) from a large reservoir of D(3) in the target cell, providing constant supplies for induction.

Suppression of vitamin D receptor and induction of retinoid X receptor alpha expression during squamous differentiation of cultured keratinocytes

To gain more insight in the role of the vitamin D system in epidermal differentiation, we studied the expression of the vitamin D receptor and its heterodimeric partner retinoid X receptor alpha in cultured normal human keratinocytes during squamous differentiation, as triggered by different approaches. Northern and western blot analysis allowed us to investigate mRNA and protein levels of these nuclear receptors and of markers for growth control (c-myc, cyclin D1, p21WAF1) and differentiation (keratinocyte transglutaminase, small proline rich proteins). Growing cells to postconfluence was a potent stimulus for growth arrest and differentiation with concomitant suppression of vitamin D receptor and induction of retinoid X receptor alpha, at both the mRNA and the protein level. These changes could be prevented by concomitant treatment with epidermal growth factor or keratinocyte growth factor. Subjecting the cells to a calcium switch leading to stratification and differentiation lowered vitamin D receptor protein levels without affecting vitamin D receptor mRNA and induced both retinoid X receptor alpha mRNA and protein. Interferon-gamma and the phorbolester 12-O-tetradecanoyl phorbol 13-acetate, two well-known inducers of keratinocyte differentiation, both inhibited vitamin D receptor expression but only interferon-gamma induced retinoid X receptor alpha. The decreased vitamin D receptor expression was accompanied by reduced vitamin D responsiveness (as assessed by 24-hydroxylase mRNA induction) in postconfluent, high calcium, and 12-O-tetradecanoyl phorbol 13-acetate treated keratinocytes but not with interferon-gamma treatment. Taken together, our results associate vitamin D receptor expression with undifferentiated, proliferating keratinocytes, whereas retinoid X receptor alpha expression appears to be related to the differentiated phenotype. Therefore, proliferating and differentiating keratinocytes may be differentially targeted by active vitamin D metabolites.

1alpha,25-dihydroxycholecalciferol and cyclosporine suppress induction and promote resolution of psoriasis in human skin grafts transplanted on to SCID mice

Accumulating evidence has emphasized the importance of immunocompetent cells in determining the psoriatic phenotype. We have investigated the effect of 1alpha,25-dihydroxycholecalciferol, the naturally occurring active form of vitamin D3, cyclosporine A, and interleukin-10 on the phenotype of human psoriatic skin xenotransplants. First, psoriatic skin transplants were injected with either 1alpha,25-dihydroxy- cholecalciferol, cyclosporine A, or interleukin-10. Second, we determined the ability of autologous lymphocytes, activated in vitro using staphylococcal enterotoxin B and interleukin-2 and then exposed to either 1alpha, 25-dihydroxycholecalciferol or cyclosporine A, to induce psoriatic lesions if they were injected into the dermis of uninvolved skin grafts. We found that injections into transplanted psoriatic plaques of either 1alpha,25-dihydroxycholecalciferol or cyclosporine A, but not interleukin-10, resulted in a consistent reduction in the clinical and histologic score of psoriasis with remission towards uninvolved psoriatic skin. Injection of activated immunocytes into symptomless psoriatic skin grafts, changed the grafts towards plaque-type psoriasis with silvery scale, parakeratosis, elongated rete pegs, acanthosis, and dermal angiogenic reaction. In contrast, if activated immunocytes were exposed to 1alpha, 25-dihydroxycholecalciferol or cyclosporine A prior to injection, only minimal changes occurred. It was determined that neither staphylococcal enterotoxin B and interleukin-2 activation by itself, nor the drugs investigated, changed the CD4/CD8 ratio of activated (CD25 + ) cells. Our results are consistent with the hypothesis that psoriasis may be induced by activated T lymphocytes, and indicate that novel immunomodulatory drugs can serve to inhibit the pathogenetic ability of immunocytes in psoriasis.

Anchorage-dependent expression of the vitamin D receptor in normal human keratinocytes

Although the nuclear vitamin D receptor (VDR) is involved in the control of keratinocyte proliferation and differentiation by its ligand 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], its role in epidermal physiology remains poorly understood. Because VDR abundance reflects cellular responsiveness to 1,25(OH)2D3, we investigated VDR expression in cultured human keratinocytes and identified cell anchorage and cytoskeletal integrity as essential requirements for the maintenance of VDR levels. Suspension culture rapidly suppressed VDR expression and 1,25(OH)2D3 responsiveness (as estimated by induction of 24-hydroxylase mRNA), due to decreased transcription of the VDR gene. Concomitantly, overt growth arrest with p21WAF1 induction and cyclin D1 and c-myc suppression occurred, together with induction of differentiation markers and retinoid X receptor alpha, the heterodimeric partner for VDR. Reattachment of suspended keratinocytes to fibronectin led to a rapid restoration of VDR expression, which could be blocked by RGD peptides or a blocking anti-beta1 integrin antibody. VDR expression was also reduced by disruption of the actin cytoskeleton with cytochalasin D. Malignant keratinocytes (SCC12B2 and A431), characterized by, anchorage-independent growth, displayed a profound resistance to suspension-induced suppression of VDR, cyclin D1, and c-myc. Taken together, our results associate VDR expression [and 1,25(OH)2D3 responsiveness] with cell adhesion and an organized cytoskeleton, which are also required for cell growth of primary cells.

Current experience with tacalcitol ointment in the treatment of psoriasis

Various controlled studies have demonstrated the efficacy and safety of tacalcitol ointment (4 micrograms/g) in the treatment of psoriasis. Further data are now available from a multicentre post-marketing surveillance study involving more than 5000 outpatients. Once-daily treatment with tacalcitol resulted in a marked decrease of mean sum score (erythema, infiltration, scaling) from 6.3 to 2.7 score points in an average period of 61 days. Efficacy was assessed by dermatologists as 'very good' or 'good' in 71% of the patients. Local tolerance was stated to be 'very good' or 'good' in 94% of the patients. Only 1% of the patients experienced skin irritation. No case of hypercalcaemia was observed. Compared with conventional therapies, 52% of the patients saved up to half an hour of treatment time daily because of the once-daily application. Good local tolerance and a convenient treatment regimen may also help compliance.

Effects of calcitriol and its analogues, calcipotriol (MC 903) and 20-epi-1alpha,25-dihydroxyvitamin D3 (MC 1288), on calcium influx and DNA synthesis in cultured muscle cells

The fast actions of the secosteroid hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3; calcitriol] and the synthetic analogues calcipotriol (MC 903) and 20-epi-1alpha,25(OH)2D3 (MC 1288) on cell calcium influx were compared in rat duodenum enterocytes as well as in cells from chick embryo skeletal muscle (myoblasts) and heart (myocytes), at various concentrations (10(-12) to 10(-8) M) and treatment intervals (1-10 min). In enterocytes, at a concentration of 10(-11) M, MC 1288 was significantly more active than 1,25(OH)2D3 in rapidly stimulating 45Ca2+ uptake by enterocytes (80 vs 38% above controls, respectively), whereas MC 903 was devoid of activity. However, calcipotriol increased Ca2+ influx in myocytes and myoblasts to a greater extent than the natural hormone, whereas MC 1288 was more active only in myoblasts. Analogously to 1,25(OH)2D3, the fast MC 903- and MC 1288-induced stimulation of 45Ca2+ uptake in enterocytes and muscle cells could be blocked by both verapamil and nifedipine. In addition, MC 903 and MC 1288 were more effective than 1,25(OH)2D3 in stimulating DNA synthesis in proliferating myoblasts and in inhibiting DNA synthesis in differentiating myoblasts. The results suggest, therefore, that modifications in the side-chain of the 1,25(OH)2D3 molecule increase its ability to modulate muscle cell Ca2+ metabolism and growth. These findings are potentially relevant for the development of analogues for the treatment of vitamin D-dependent myopathies.

Photoprotective effect of calcipotriol upon skin photoreaction to UVA and UVB

It has been shown that 1,25-dihydroxyvitamin D3 has a photoprotective effect against UVB injury in mouse skin and cultured rat keratinocytes by induction of metallothionein (MT). Calcipotriol is a synthetic analogue of 1,25-dihydroxyvitamin D3 with equipotent cell regulating properties, but with a lower risk of calcium-related side effects. The aim of the present study was to see whether calcipotriol has a photoprotective property both in vitro and in vivo. We examined the effect of calcipotriol on UV-induced damage of cultured human keratinocytes through a cell viability assay, and measurement of DNA synthesis by cultured keratinocytes, on UV-induced damage of mouse skin and on minimal erythema dose (MED). We found that calcipotriol was protective against UVB-induced reduction in DNA synthetic activity of cultured keratinocytes in relatively low doses (20 and 40 mJ/cm2) of UVB. With phototesting following application of calcipotriol, five subjects among 10 healthy volunteers and three among six psoriasis patients showed an increase in MED compared with the vehicle-treated site. These findings imply that calcipotriol may be photoprotective and that more extensive studies with various doses of UV irradiation and modes of calcipotriol delivery are required.