Retinoids in psoriasis and disorders of keratinization

Combining Isotretinoin and Topical Cholesterol/Atorvastatin in the Treatment of Linear Porokeratosis: A Case Report

Linear porokeratosis (LP) is an epidermal keratinization disorder manifesting in the form of annular plaques with an atrophic center and hyperkeratotic margins. Although rare, LP carries a significant risk of skin cancer. Histological examination usually reveals the cornoid lamella, a parakeratosis column visualized in the outer layer of the epidermis. First-line treatment of LP is retinoids. However, the effects of combination therapy of isotretinoin and topical statins on LP are not well-understood. Herein, we attempted treatment with both isotretinoin and 2% cholesterol/atorvastatin ointment, with considerable improvement observed using the former but not the latter. These findings suggest that 2% topical cholesterol/atorvastatin treatment may not carry any additional benefits, even if used alongside retinoids. Further studies are needed to assess the potential effects of statins on LP.

Vulvar Lichen Sclerosus from Pathophysiology to Therapeutic Approaches: Evidence and Prospects

Vulvar lichen sclerosus (VLS) is a chronic, distressing, inflammatory disease with an enormous impact on quality of life. Treatment goals are relieving symptoms, reversing signs and preventing anatomical changes. Despite the availability of numerous therapeutic options, treatment outcome may not be entirely satisfactory and a definitive cure does not exist. This may be due to the fact that the exact VLS etiopathogenesis remains unknown. The objectives of this paper were to review the most up-to-date knowledge on VLS etiopathogenesis and to consider the available therapies through the lens of a plausible pathogenetic model. An electronic search on both VLS etiopathogenesis and its treatment was performed using the National Library of Medicine PubMed database. Based on current knowledge, it is conceivable that various, heterogeneous environmental factors acting on a genetic background trigger an autoimmune, Th-1 response, which leads to a chronic inflammatory state. This, in turn, can determine both tissue and micro-vascular injury and activation of signaling pathways involved in fibroblast and collagen metabolism. This pathogenetic sequence may explain the effectiveness of anti-inflammatory treatments, mostly topical corticosteroids, in improving VLS clinical-pathological changes. Further deepening of the disease pathways will presumably allow key mediators to become new therapeutic targets and optimize the available treatments.

Combined Transcriptomic Analysis Revealed AKR1B10 Played an Important Role in Psoriasis through the Dysregulated Lipid Pathway and Overproliferation of Keratinocyte

RNA-seq has enabled in-depth analysis of the pathogenesis of psoriasis on the transcriptomic level, and many biomarkers have been discovered to be related to the immune response, lipid metabolism, and keratinocyte proliferation. However, few studies have combined analysis from various datasets. In this study, we integrated different psoriasis RNA-seq datasets to reveal the pathogenesis of psoriasis through the analysis of differentially expressed genes (DEGs), pathway analysis, and functional annotation. The revealed biomarkers were further validated through proliferation phenotypes. The results showed that DEGs were functionally related to lipid metabolism and keratinocyte differentiation dysregulation. The results also showed new biomarkers, such as AKR1B10 and PLA2G gene families, as well as pathways that include the PPAR signaling pathway, cytokine-cytokine receptor interaction, alpha-linoleic acid metabolism, and glycosphingolipid biosynthesis. Using siRNA knockdown assays, we further validated the role that the AKR1B10 gene plays in proliferation. Our study demonstrated not only the dysfunction of the AKR1B10 gene in lipid metabolizing but also its important role in the overproliferation and migration of keratinocyte, which provided evidence for further therapeutic uses for psoriasis.

Primary Localized Cutaneous Amyloidosis: A Systematic Treatment Review

BACKGROUND

Primary localized cutaneous amyloidosis (PLCA) is characterized by extracellular deposition of heterogenic amyloid proteins in the skin without systemic involvement. Lichen amyloidosis, macular amyloidosis, and (primary localized cutaneous) nodular amyloidosis are different subtypes of PLCA.

OBJECTIVE

The aim of this study was to review the current reported treatment options for PLCA.

METHODS

This systematic review was based on a search in the PubMed database for English and German articles from 1985 to 2016.

RESULTS

Reports on the treatment of PLCA were limited predominantly to case reports or small case series. There were a few clinical trials but these lacked control groups. A variety of treatment options for PLCA were reported including retinoids, corticosteroids, cyclophosphamide, cyclosporine, amitriptyline, colchicine, cepharanthin, tacrolimus, dimethyl sulfoxide, vitamin D₃ analogs, capsaicin, menthol, hydrocolloid dressings, surgical modalities, laser treatment, and phototherapy.

CONCLUSION

No definitive recommendation of preferable treatment procedures can be made based on the analyzed literature. Randomized controlled trials are needed to offer patients an evidence-based therapy with high-quality standardized treatment regimens for PLCA.

Treatment of Porokeratosis: A Systematic Review

BACKGROUND

Porokeratosis (PK) is a rare skin disease of unknown etiology. It consists of a keratinization disorder, which may appear in several clinical forms and can undergo malignant transformation. The histopathological hallmark of PK is the cornoid lamella. While many topical, systemic, and surgical treatment modalities for PK have been described, no randomized controlled trials have been performed yet. Because of a lack of treatment standards for PK, European and international guidelines cannot be created.

OBJECTIVE

The aim of this systematic review is to outline options for treating PK.

METHODS

We performed a systematic literature search in an electronic database for published literature. A total of 88 articles fulfilling our inclusion criteria were found.

RESULTS

There were no randomized controlled trials on the treatment of PK, but mainly case reports and case series. Porokeratosis of Mibelli showed the best outcomes after treatment with imiquimod cream and linear PK responded well to topical or systemic retinoids. Topical vitamin D acid derivatives may be the best therapeutic option for disseminated PK. Surgical interventions and cryotherapy may be preferred in areas where the use of topical agents is difficult or contraindicated.

CONCLUSION

To offer patients with PK an evidence-based high-quality standardized therapy, randomized controlled trials are needed.

Two Egyptian cases of lipoid proteinosis successfully treated with acitretin

BACKGROUND

Lipoid proteinosis (Urbach-Wiethe disease) is a rare progressive autosomal recessive disorder, characterized histologically by deposition of periodic acid Schiff-positive, diastase resistant, hyaline-like material into the skin, upper aerodigestive tract, and internal organs.

MAIN OBSERVATION

We report two cases of lipoid proteinosis. A 2-year-old girl presented with vesiculobullous skin lesions on her face, trunk, extremities and scalp, inability to protrude the tongue and hoarseness of voice that appeared few months after birth. The other case is a 4-year-old girl, who presented with waxy papules on face and trunk, hoarseness of voice and enlarged lips and tongue. The lesions healed leaving pitted scars in both cases. Based on clinical, histopathological and laryngoscopy findings, lipoid proteinosis was diagnosed in both cases. Acitretin was started in a dose of 0.5 mg/kg/day in every child. Complete remission of cutaneous lesions and improvement of the hoarseness was observed after one year.

CONCLUSION

Acitretin may be benificial for treatment of mucosal and cutaneous lesions in lipoid proteinosis.

Novel retinoic acid 4-hydroxylase (CYP26) inhibitors based on a 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl scaffold

Retinoic acid (RA), the biologically active metabolite of vitamin A, is used medicinally for the treatment of hyperproliferative diseases including dermatological conditions and cancer. The antiproliferative effects of RA have been well documented as well as the limitations owing to toxicity and the development of resistance to RA therapy. RA metabolism inhibitors (RAMBAs or CYP26 inhibitors) are attracting increasing interest as an alternative method for enhancing endogenous levels of retinoic acid in the treatment of hyperproliferative disease. Here the synthesis and inhibitory activity of novel 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl derivatives in a MCF-7 CYP26A1 microsomal assay are described. The most promising inhibitor methyl 2,2-dimethyl-3-(4-(phenylamino)phenyl)-3-(1H-1,2,4-triazol-1-yl)propanoate (6) exhibited an IC(50) of 13 nM (compared with standards Liarozole IC(50) 540 nM and R116010 IC(50) 10 nM) and was further evaluated for CYP selectivity using a panel of CYP with >100-fold selectivity for CYP26 compared with CYP1A2, 2C9 and 2D6 observed and 15-fold selectivity compared with CYP3A4. The results demonstrate the potential for further development of these potent inhibitors.

Synthesis and biological evaluation of 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-[4-(naphthalen-2-ylamino)phenyl]propyl derivatives as small molecule inhibitors of retinoic acid 4-hydroxylase (CYP26)

The synthesis and potent inhibitory activity of novel 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(naphthalen-2-ylamino)phenyl)propyl derivatives vs a MCF-7 CYP26A1 microsomal assay is described. This study focused on the effect of modifying the heme binding azole group and the flexible C3 chain on inhibitory activity and selectivity. The most promising inhibitor 2,2-dimethyl-3-[4-(naphthalen-2-ylamino)-phenyl]-3-[1,2,4]triazol-1-yl-propionic acid methyl ester (17) (IC(50) = 0.35 nM as compared with liarozole IC(50) = 540 nM and R116010 IC(50) = 10 nM) was evaluated for CYP selectivity and hepatic stability. Compounds with CYP26 inhibitory IC(50) values ≤50 nM enhanced the biological activity of exogenous ATRA, as evidenced by a 3.7-5.8-fold increase in CYP26A1 mRNA in SH-SY5Y neuroblastoma cells as compared with ATRA alone. All compounds demonstrated an activity comparable with or better than R116010, and the induction correlated well with CYP26 inhibition data. These studies highlight the promising activity profile of this novel CYP26 inhibitor and suggest it as an appropriate candidate for future development.

Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis

BACKGROUND

Despite reported antiproliferative activity of vitamin A and its common use for cancer, there is no comprehensive synthesis of its safety and efficacy in lung cancers. To address this issue we conducted a systematic review of the safety and efficacy of vitamin A for the treatment and prevention of lung cancers.

METHODS AND FINDINGS

Two independent reviewers searched six electronic databases from inception to July 2009 for clinical, observational, and preclinical evidence pertaining to the safety and efficacy of vitamin A and related retinoids for lung cancers. 248 studies were included for full review and analysis. Five RCTs assessed treatment of lung cancers, three assessed primary prevention, and three looked at secondary prevention of lung cancers. Five surrogate studies, 26 phase I/II, 32 observational, and 67 preclinical studies were also included. 107 studies were included for interactions between vitamin A and chemo- or radiation-therapy. Although some studies demonstrated benefits, there was insufficient evidence overall to support the use of vitamin A or related retinoids for the treatment or prevention of lung cancers. Retinyl palmitate combined with beta carotene increased risk of lung cancer in smokers in the large CARET trial. Pooling of three studies pertaining to treatment and three studies on secondary prevention revealed no significant effects on response rate, second primary tumor, recurrence, 5-year survival, and mortality. There was a small improvement in event free survival associated with vitamin A compared to controls, RR 1.24 (95% CI 1.13-1.35). The synthetic rexinoid bexarotene increased survival significantly among a subset of patients in two RCTs (p<0.014, <0.087).

CONCLUSIONS

There is a lack of evidence to support the use of naturally occurring retinoids for the treatment and prevention of lung cancers. The rexinoid bexarotene may hold promise for use among a subset of patients, and deserves further study.

Pathogenesis of the cutaneous phenotype in inherited disorders of cholesterol metabolism: Therapeutic implications for topical treatment of these disorders

Molecular geneticists tend to conceptualize disease pathogenesis from the mutated gene outward, an approach that does not take into account the impact of barrier requirements in determining disease phenotype. An ‘outside-to-inside’ perspective has provided quite different explanations for the ichthyoses, including several of the disorders of distal cholesterol metabolism. Elucidation of responsible pathogenic mechanisms also is pointing to appropriate, pathogenesis (pathway)-based therapeutic strategies. In the case of the lipid metabolic disorders, it takes full advantage of new molecular, genetic and cellular pathogenesis information to correct or bypass the metabolic abnormality. This approach fully exploits the unique accessibility of the skin to a topical approach. Moreover, since it will utilize topical lipids and lipid-soluble, and often generic, lipid-soluble drugs, these treatments should be readily transported across the stratum corneum. If successful, this approach could initiate an entirely new departure for the therapy of the ichthyoses. Finally, because these agents are relatively safe and inexpensive, this form of treatment has the potential to be widely-deployed, even in the developing world.

Isotretinoin in the treatment of multiple benign pilomatrixomas in a mixed-breed dog

An 18-month-old cross-breed dog developed multiple skin nodules, which over 8 months had increased in size and number. Biopsy samples were submitted for histopathological examination and revealed multiple benign pilomatrixomas. The dog was treated with 1 mg kg(-1) isotretinoin daily, which led to a stabilization of the size and number of the lesions. Attempts to lower the dosage to an every other day regimen led to an increase in the nodules' size and number. Monthly complete blood count and chemistry tests and Schirmer tear tests were performed to monitor any adverse effects of the retinoid treatment. No adverse effects were noted. To the authors' knowledge, this is the first report of multiple pilomatrixomas arising in a young dog and successfully controlled with oral retinoids.

Promoter activity of the retinoic acid receptor gene in theCiona intestinalis embryo

Retinoic acid regulates development of many chordate-specific characteristics. The genes encoding retinoic acid receptors (RARs) were isolated only from chordates. In the present study, a genomic DNA fragment containing the promoter region of the RAR gene (Ci-RAR) in the protochordate Ciona intestinalis was isolated. The transgene containing 1,326 bp of the Ci-RAR 5' flanking region was expressed in the epidermis, central nervous system, and muscle. The sequence element necessary for expression in the epidermis seemed to be subdivided into two elements. One was required for activation in the dorsal midline epidermis and the other for the rest of the epidermis. The element responsible for activation in the central nervous system was characterized by putative binding sites for Fox, Ets, and GATA transcription factors. An E-box sequence was required for the transgene expression in the tail muscle cells.

Peroxisome proliferator-activated receptor (PPAR)-beta/delta stimulates differentiation and lipid accumulation in keratinocytes

Peroxisome proliferator-activated receptor (PPAR) are nuclear hormone receptors that are activated by endogenous lipid metabolites. Previous studies have demonstrated that PPAR-alpha activation stimulates keratinocyte differentiation in vitro and in vivo, is anti-inflammatory, and improves barrier homeostasis. Recent studies have shown that PPAR-beta/delta activation induces keratinocyte differentiation in vitro. This study demonstrated that topical treatment of mice with a selective PPAR-beta/delta agonist (GW1514) in vivo had pro-differentiating effects, was anti-inflammatory, improved barrier homeostasis, and stimulated differentiation in a disease model of epidermal hyperproliferation [corrected]. In contrast to PPAR-alpha activation, PPAR-beta/deltain vivo did not display anti-proliferative or pro-apoptotic effects. The pro-differentiating effects persisted in mice lacking PPAR-alpha, but were decreased in mice deficient in retinoid X receptor-alpha, the major heterodimerization partner of PPAR. Furthermore, in vitro PPAR-beta/delta activation, aside from stimulating differentiation-related genes, additionally induced adipose differentiation-related protein (ADRP) and fasting induced adipose factor (FIAF) mRNA in cultures keratinocytes, which was paralleled by increased oil red O staining indicative of lipid accumulation, the bulk of which were triglycerides (TG). Comparison of differentially expressed genes between PPAR-beta/delta and PPAR-alpha activation revealed distinct profiles. Together, these studies indicate that PPAR-beta/delta activation stimulates keratinocyte differentiation, is anti-inflammatory, improves barrier homeostasis, and stimulates TG accumulation in keratinocytes.

Nukleäre Hormonrezeptoren: Interventionsmöglichkeiten jenseits von Glukokortikoiden, Retinoiden und Vitamin D

Nuclear hormone receptors are ligand-dependent transcription factors. The class of nuclear hormone receptors that form heterodimers with retinoid X receptor includes members that are well established targets of current dermatological therapeutics such as the retinoic acid receptor (RAR) and the vitamin D receptor (VDR) as well as more recently discovered receptors including the peroxisome proliferator-activated receptors (PPAR) and the liver X receptor (LXR). After ligand activation (often lipid metabolites), these intracellular receptors exert their functions by binding to specific response elements in regulatory sequences of target genes, preferentially those involved in differentiation, energy expenditure and lipid metabolism. A number of selective activators has been developed by combinational chemistry, initially for their anti-diabetic and lipid lowering properties as well as their ability to regulate bile acid and drug metabolism. However, these activators also have marked effects on cutaneous homeostasis. Therefore, these compounds have important implications for dermatological therapy. In this review, the clinical implications of the more recently discovered members of the nuclear hormone receptor family are discussed.

Oral liarozole in the treatment of palmoplantar pustular psoriasis: a randomized, double-blind, placebo-controlled study

BACKGROUND

Palmoplantar pustular psoriasis (PPP) is a chronic, relapsing condition often recalcitrant to therapy. Synthetic retinoids have been found to be efficacious in the treatment of PPP, but their use is limited by side-effects. Liarozole is an imidazole-like compound that inhibits the retinoic acid (RA) 4-hydroxylase-mediated breakdown of all-trans RA, causing elevation of plasma and cutaneous levels of RA. Thus liarozole acts as a retinoid-mimetic drug. Liarozole has already been found to be effective in the treatment of retinoid-responsive conditions such as chronic plaque psoriasis and ichthyoses.

OBJECTIVES

To assess the efficacy and side-effect profile of liarozole in the treatment of PPP.

METHODS

We performed a double-blind, randomized, placebo-controlled trial of oral liarozole 75 mg twice daily for 12 weeks in the treatment of PPP. The trial was conducted at two centres and involved 15 patients.

RESULTS

Using the PPP Area and Severity Index we found a statistically significant (P = 0.02) improvement in PPP in subjects on liarozole (median 3, range 1.8-14.1) as compared with placebo (median 12.1, range 5-18) by the end of the treatment phase. There was also a statistically significant difference (P = 0.006) in the number of fresh pustules after treatment for the two study groups (liarozole median 2, range 0-18; placebo median 38, range 2-75). The severity of disease (on a scale of 0-8) between the two groups was significantly different at the end of treatment (liarozole median 1, range 1-5; placebo median 3, range 2-6; P = 0.04). No patients withdrew from the trial because of adverse events. The most commonly reported side-effects were pruritus, cheilitis and xerosis but these were rarely severe and resolved rapidly on discontinuation of treatment. Laboratory results, including haematology, liver function tests and serum cholesterol and triglycerides were not significantly different between the liarozole and placebo groups.

CONCLUSIONS

The results of this pilot study suggest that liarozole 75 mg twice daily is an effective and well-tolerated therapy for PPP. In addition, the pharmacokinetics of liarozole may help to circumvent side-effects associated with synthetic retinoids and allow its use in premenopausal women.

Safety issues in isotretinoin therapy

Isotretinoin (Accutane, Roche Laboratories Inc, Nutley, NJ) is an important drug, not only for the treatment of severe acne, but also for other diagnoses and in chemoprevention settings. Because the use of isotretinoin is increasing, it is important for physicians to be aware of the adverse events, toxicities, and management issues related to its use. The most important issue is that of congenital defects, which has resulted in new pregnancy prevention policies and programs implemented by the manufacturer. A relatively new concern is that of depression associated with isotretinoin use, also resulting in new policies placed by the manufacturer and the FDA. The most common adverse effects observed during treatment are mucocutaneous and ocular in nature, but laboratory abnormalities and effects in the nervous, musculoskeletal, gastrointestinal, pulmonary, hematologic, and other systems are also described. Additionally, potential drug interactions, follow-up, and toxicity prevention measures are discussed.

The influence of retinoic acid and retinoic acid derivatives on beta2 integrins and L-selectin expression in HL-60 cells in vitro

A decreased expression of the beta2-integrin CD11b molecules on peripheral neutrophils from patients with pustular psoriasis occurred during treatment with retinoid compounds. Since this effect could not be mimicked in vitro with isolated peripheral neutrophils, the effect of retinoid compounds on cell differentiation was investigated. The promyelocytic cell line, HL60, was used to study what effect different retinoid compounds had on the cell surface expression of CD11b and L-selectin (CD62L) molecules, complement-mediated phagocytosis, adhesion and the oxidative burst. Retinoid-differentiated cells showed a significantly lower expression of CD11b and CD62L, and a decreased phagocytosis and oxidative burst compared to DMSO-differentiated HL60 cells or peripheral blood neutrophils. The diminished expression of beta2-integrins or L-selectin did not affect their adhesion to non-activated or lipopolysaccharide-activated endothelial cells in vitro but may however affect adhesion to vascular endothelium under shear forces during blood flow. These results suggest that retinoid treatment could affect several early steps in the inflammatory process.

Regulation of vascular endothelial growth factor expression in human keratinocytes by retinoids

Vascular endothelial growth factor (VEGF) is overexpressed in hyperproliferative diseases, such as psoriasis and cancers, which are characterized by increased angiogenesis. Experimentally, VEGF overexpression can be induced by the treatment of cell cultures and biological tissues with phorbol esters, such as 12-O-tetradecanoylphorbol-13-acetate (TPA). Using normal human keratinocytes in conventional cultures and skin grafted onto nude mice in vivo, we show that retinoids can inhibit TPA-mediated VEGF gene induction at the transcriptional level. Because retinoids are biologically active either by interacting with the nuclear retinoic acid receptors or by interfering with the activator protein 1 (AP1) transcription factor, we studied the effect of the retinoic acid derivative CD 2409, which exhibits strong anti-AP1 activity but does not bind to the known retinoic acid receptors in vitro. The results demonstrate that the inhibition of VEGF expression by retinoids only depends on their anti-AP1 activity and does not require gene transactivation via retinoic acid response elements. Because the VEGF promoter contains four potential AP1 binding sites, we used different promoter constructs to identify the functional site responsible for TPA induction and retinoid inhibition. This site turned out to be localized at position -621 of the 5' flanking region of the VEGF gene.

Retinoic acid suppresses intimal hyperplasia and prevents vessel remodeling following arterial injury

Vitamin A and its derivatives (retinoids) are capable of inhibiting vascular smooth muscle cell proliferation in vitro. The present study examines the effect of two retinoids, all-trans retinoic acid and 13-cis retinoic acid, on intimal hyperplasia following arterial injury. After receiving varying doses of all-trans retinoic acid or 13-cis retinoic acid, 78 male Sprague-Dawley rats underwent standard balloon catheter denudation of the left common carotid artery. Morphometric analysis and immunohistochemistry for proliferating cell nuclear antigen was performed at early and late time points. Intimal/medial ratios were reduced in a dose-dependent fashion for animals treated with all-trans retinoic acid (P = 0.001) and 13-cis retinoic acid (P = 0.004). Proliferating cell nuclear antigen labeling indices were reduced after treatment with all-trans retinoic acid and 13-cis retinoic acid at early time points post-injury. At a dose of 10 mg/kg, both all-trans retinoic acid and 13-cis retinoic acid inhibited vessel remodeling as measured by increases in luminal diameter (P < 0.05) and external elastic lamina (P < 0.05). Retinoids are an attractive clinical option for the treatment of restenosis following angioplasty and arterial surgery.

Etretinate Therapy for Refractory Sclerodermatous Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (GVHD) is the most common late complication of allogeneic bone marrow transplantation (BMT). The sclerodermatous form of the disease is often refractory to standard treatment modalities. Based on reports of response to etretinate, a synthetic retinoid, among patients with scleroderma, we have added etretinate to the treatment regimen of 32 patients with refractory sclerodermatous chronic GVHD. This case series is comprised mainly of patients who had chronic GVHD of long duration (median of 30 months before the initiation of etretinate). Most had failed to respond to three or more agents before etretinate treatment was started. Clinical response was assessed after 3 months of therapy. Five patients did not complete a 3-month trial. Among the 27 patients evaluable for response, 20 showed improvement including softening of the skin, flattening of cutaneous lesions, increased range of motion, and improved performance status. Four showed no response after 3 months of therapy and 3 had progression of their sclerosis. Overall, etretinate has been fairly well tolerated in our patients, with skin breakdown and/or ulceration leading to its discontinuation in 6 patients. We believe the results in our patients are encouraging and suggest that further evaluation of etretinate in the treatment of sclerodermatous chronic GVHD is warranted.

Etretinate Therapy for Refractory Sclerodermatous Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (GVHD) is the most common late complication of allogeneic bone marrow transplantation (BMT). The sclerodermatous form of the disease is often refractory to standard treatment modalities. Based on reports of response to etretinate, a synthetic retinoid, among patients with scleroderma, we have added etretinate to the treatment regimen of 32 patients with refractory sclerodermatous chronic GVHD. This case series is comprised mainly of patients who had chronic GVHD of long duration (median of 30 months before the initiation of etretinate). Most had failed to respond to three or more agents before etretinate treatment was started. Clinical response was assessed after 3 months of therapy. Five patients did not complete a 3-month trial. Among the 27 patients evaluable for response, 20 showed improvement including softening of the skin, flattening of cutaneous lesions, increased range of motion, and improved performance status. Four showed no response after 3 months of therapy and 3 had progression of their sclerosis. Overall, etretinate has been fairly well tolerated in our patients, with skin breakdown and/or ulceration leading to its discontinuation in 6 patients. We believe the results in our patients are encouraging and suggest that further evaluation of etretinate in the treatment of sclerodermatous chronic GVHD is warranted.

Rational design of receptor-selective retinoids

Orally administered retinoids can be associated with significant adverse effects because of high systemic exposure and a lack of receptor selectivity. Targeting the diseased tissue and improving the selectivity of the retinoid-receptor interaction to activate only those discrete pathways required for efficacy may minimize adverse effects. First- and second-generation retinoids contain several alternating single and double bonds that confer great conformational flexibility, allowing the molecules to adopt a variety of shapes and creating the potential to interact with multiple receptors. We hypothesized that, by designing a more rigid conformational structure, the receptor selectivity of retinoids could be improved and their therapeutic index enhanced. This strategy has resulted in the development of tazarotene. The receptor selectivity of tazarotene, together with its topical delivery, ensures a targeted action on psoriatic keratinocytes.

Etretinate in the management of harlequin siblings

Harlequin fetus is the severe form of congenital ichthyosis. There are very few reports of babies with this condition surviving the first few weeks of life. We treated two siblings who lived for 22 months and six weeks respectively. We started treatment with oral etretinate every early in their lives and achieved good improvement in the skin condition of these babies.

All-trans retinoic acid blocks the antiproliferative prodifferentiating actions of 1,25-dihydroxyvitamin D3 in normal human keratinocytes

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] and all-trans retinoic acid (RA), the active metabolites of vitamins D and A respectively, regulate the proliferation and differentiation of keratinocytes. Both the vitamin D receptor (VDR) and the retinoic acid receptor family (RAR) bind to DNA response elements as heterodimers with the retinoic X receptor (RXR), suggesting that there are pathways of action that are shared by both compounds. Therefore, we examined the interactions of 1,25(OH)2D3 and RA upon the proliferation and differentiation of normal human keratinocytes (NHK) and of a squamous cell carcinoma cell line, SCC4. Although both 1,25(OH)2D3 and RA were each able to inhibit NHK proliferation in a dose-dependent manner, when they were administered in combination, proliferation was stimulated, suggesting mutual antagonism. In contrast, SCC4 cells proved insensitive in terms of proliferation to 1,25(OH)2D3 and to all but the highest concentration (10(-6) M) of RA. 1,25(OH)2D3 exerted a biphasic effect on transglutaminase (TGase) and involucrin (INV) mRNA levels, with maximal stimulation at 10(-9) M. RA inhibited TGase and INV mRNA levels and antagonized the stimulation by 1,25(OH)2D3. A similar pattern was observed for TGase protein, but, RA, which, by itself, reduced INV, markedly enhanced the ability of 1,25(OH)2D3 to raise INV levels, possibly by inhibiting 1,25(OH)2D3-stimulated TGase activity and cross-linking of soluble INV into the insoluble cornified envelope (CE). Thus, in NHK cells, RA antagonizes the antiproliferative prodifferentiating actions of 1,25(OH)2D3, but assessment of a single marker, such as INV protein, may be misleading.

Systemic treatment of severe psoriasis

Severe psoriasis presents a difficult therapeutic challenge. Some modalities such as synthetic retinoids, phototherapy and methotrexate have been available for many years and need reappraisal, cyclosporin has only recently become available and requires careful administration. In this article we focus on the therapeutic modalities available to the dermatologist in Australia.

Tazarotene--first of a new generation of receptor-selective retinoids

Tazarotene is a topically applied retinoid that targets the skin, the site of the fundamental defect(s) in psoriasis, modulating the major causes of the disease and achieving sustained efficacy. In vitro, binding of tazarotenic acid has been demonstrated to retinoic acid receptors (RARs), the probable molecular target of retinoid action in adult human skin, but not to retinoid X receptors (RXRs). In gene activation assays, tazarotene is selective for the RAR beta and RAR gamma subtypes. This selectivity could theoretically limit undesirable effects at the receptor level. In vitro, animal and clinical evidence reveals that topical tazarotene modulates all three pathogenic factors in psoriasis: abnormal keratinocyte differentiation, hyperproliferation, and increased expression of inflammatory markers. Tazarotene is minimally absorbed systemically after topical administration. Tazarotene is rapidly metabolized by esterase metabolism to its active free-acid form, tazarotenic acid, which has a relatively short elimination half-life (1-2 h). The pharmacokinetic profile of tazarotenic acid is predictable, with no significant accumulation. In preclinical toxicity studies, high topical doses produced only reversible topical irritation, and lower doses were well tolerated. Topical doses were neither carcinogenic nor teratogenic, had no effect on fertility or general reproduction, and were not phototoxic, sensitizing, or photoallergenic. The pharmacological selectivity of tazarotene and limited systemic exposure result in minimal systemic effects, while the lesser cytotoxic effects (relative to other retinoids) result in reduced local effects.

Inhibition of the metabolism of endogenous retinoic acid as treatment for severe psoriasis: an open study with oral liarozole

Retinoids derived from retinol or beta-carotene are inactivated, among other ways, by enzymes belonging to the P450 cytochrome group. Liarozole, an imidazole-containing compound, is known to be a potent inhibitor of the cytochrome P450-mediated metabolism of all-trans retinoic acid. As a result, increased levels of this retinoid are found in skin and plasma. Therefore, in the treatment of psoriasis, therapeutic effects may be expected with liarozole which are similar to those observed with synthetic retinoids. In an open study, oral liarozole was given at a daily dose of 75 mg b.i.d., for 12 weeks to 31 patients with severe psoriasis. After 1 month, this dosage could be increased to 150 mg b.i.d. if there was no improvement or only moderate improvement. Initially, the effect of liarozole was mainly on scaling. A decrease in the Psoriasis Area and Severity Index (PASI) score of 45% at week 4, of 69% at week 8 and of 77% at week 12 was obtained, compared with baseline. A further decrease in the PASI score of up to 87% was observed in the 16 patients who were allowed to continue treatment for a maximum period of 12 months. An excellent or good improvement was noted in 77% of the patients within 12 weeks of starting treatment. This response rate had increased to 88% by the last follow-up visit. Nearly all patients (29 of 31) experienced adverse reactions, such as dry oral mucosa, headache and itching. These were mostly mild and transient, but four patients dropped out of the study because of an adverse event. Haematological, biochemical and cardiovascular parameters were not significantly influenced by liarozole. Six patients showed an increase in triglycerides, which normalized in three of four patients during further treatment. The results of this pilot study suggest that, at doses of 75-150 mg b.i.d., liarozole is an active antipsoriatic drug, and may be a useful addition to the existing therapeutic armamentarium. Controlled studies should be performed to compare liarozole with standard oral treatments.

Therapeutic progress. II: Treatment of psoriasis

Treatment of psoriasis is rapidly changing with improved understanding of the pathogenesis of the disease. Newer topical preparations such as calcipotriol and immunosuppressive agents such as cyclosporin A and FK506 are having a major impact on the therapy of psoriasis. This article reviews the conventional therapies and newer agents used in the treatment of this common dermatosis.