Development and preliminary validation of the patient-reported Chronic Itch Burden Scale assessing health-related quality of life in chronic pruritus.

BACKGROUND: Chronic pruritus (CP) significantly affects patients' health-related quality of life (HRQoL). Very few self-reported HRQoL questionnaires exploring CP have been developed according to international guidelines, thus limiting their use in preauthorization trials. OBJECTIVES: To develop a self-reported HRQoL questionnaire in patients with CP owing to psoriasis, atopic dermatitis, seborrhoeic dermatitis of the scalp or idiopathic dermatitis, and to explore the preliminary psychometric properties of the questionnaire. METHODS: The study was performed in France. A conceptual framework was developed based on a structured literature review and expert insight, and was improved using three focus groups involving 19 participants. A 50-item questionnaire was created and tested with 21 participants using cognitive debriefings; 11 items were removed. A cross-sectional study including 251 participants was performed to explore the preliminary psychometric properties of the 39-item questionnaire. Dimensionality was explored using principal component analysis. Cronbach's alpha and correlation coefficients (interitem, item-total score and item-dimension score) were measured. The number of items was reduced through expert consensus. RESULTS: In the 39-item version, three main dimensions were identified (Cronbach's alpha = 0·94) and all correlation coefficients were > 0·34. Upon review, 13 items were deleted owing to poor quality and six items were deleted by the team, generating a 20-item version. The questionnaire's factorial structure was best reflected with a two-dimension solution, i.e. (i) social and emotional repercussions and (ii) relation to others, fear of judgement. CONCLUSIONS: The Chronic Itch Burden Scale patient-reported questionnaire explores broad aspects of HRQoL that are relevant for patients with various skin diseases. Its good cross-sectional validity makes it useful for trials and practitioners.

Assessment of the effects of a hair lotion in women with acute telogen effluvium: a randomized controlled study.

BACKGROUND: Telogen effluvium is a hair loss disorder occurring about 3 months after a triggering event. The acute form impairs quality of life, but spontaneous recovery usually begins 3-6 months after identification and elimination of the cause, with complete recovery taking around 12 months. OBJECTIVES: To investigate the effectiveness and safety of a hair lotion containing creatine, acetyl tetrapeptide-2 and B vitamins for reducing hair loss in acute telogen effluvium. METHODS: In this open, randomized, controlled study (NCT04652232), women with acute telogen effluvium from two clinical centres were randomly allocated to receive either the lotion and a mild shampoo (intervention group), or the mild shampoo alone (controls). Hair growth parameters and hair loss were measured from phototrichograms at weeks (W) 1, 4, 8 and 16, and through investigator assessments of standardized photographs at W1 and W16. The primary criterion was the change in anagen to telogen (A/T) ratio between W1 and W16. RESULTS: One hundred women (aged 19-50 years) were included (intervention group, N = 51; controls, N = 49). Compared to baseline, the A/T ratio was higher at W16 in both groups and was significantly higher at both W4 and W8 in the intervention group, compared to only at W8 in controls. Significant decreases in telogen hair density were seen at all time points in the intervention group, compared to only at W16 in controls, and the between-group difference was significant at W8 (P = 0.0465). A larger reduction in the total number of hairs shed was observed at W8 in the intervention group (P = 0.0392). Investigator-assessed scores showed improvements in hair density for the intervention group. Global tolerance of the lotion was excellent. CONCLUSIONS: The lotion tested had a significant impact on hair loss in women with acute telogen effluvium and appeared to accelerate recovery from this condition.

Current controversies in trichology: a European expert consensus statement.

INTRODUCTION: Hair disorders are one of the most common conditions within dermatology practice but, although new diagnostic tools and therapeutic options have arisen, the management of these patients still represents a major clinical challenge. OBJECTIVE: This study aimed at gathering information and achieving consensus on relevant recommendations on the latest advances in alopecia, trichoscopy and hair dermocosmetics. METHODS: Experts of the steering committee consulted the available evidence on trichology-related areas from the past 5 years and formulated recommendations based on the evidence and their experience. A modified two-round Delphi procedure was performed among 45 European dermatologists experts in trichology to consult their degree of agreement on twenty recommendations, using a 4-point Likert scale. Consensus was defined as >80% of participants scoring either 1 (totally agree) or 2 (agree). RESULTS: In the first round of the Delphi questionnaire, 75% of the recommendations reached consensus. Those that were not agreed upon were reformulated by the steering committee and voted again after an online meeting, where consensus was achieved in all recommendations. CONCLUSIONS: All recommendations reached consensus after the two-round Delphi questionnaire and may be useful in clinical practice for dermatologists. The participants agreed that besides this consensus, further clinical studies are needed to assess the benefits of the emerging tools and treatments and to clarify the controversies that still exist in the field, aiming at improving patients' quality of life.

Effective inhibition of Th17/Th22 pathway in 2D and 3D human models of psoriasis by Celastrol enriched plant cell culture extract.

BACKGROUND: Psoriasis is an immune-mediated inflammatory disease in which the Th17 pathway is mainly involved. Systemic interventions with biologics that specifically block the Th17 pathway are effective to treat severe psoriasis. However, for efficient topical treatment, small molecules are more suitable than antibodies to penetrate and target epidermal keratinocytes, the key players in psoriasis. Celastrol, a well-described triterpene, is present in low amounts in Tripterygium wilfordii roots. By using plant cell culture (PCC), we were able to boost Celastrol production in bioreactors. Here, we evaluated immune modulator effect of Celastrol enriched extract (CEE) in Th17/Th22 psoriasis induced in 2D and 3D human models in vitro in view of its dermatological usage. METHODS: Human CD4+ T cells (hCD4), Normal Human Epidermal Keratinocytes (NHEK), micro-epidermis and reconstructed human epidermis (RHE) were preincubated with CEE and reference controls. Then, hCD4 were stimulated by anti-[CD3/CD28] while others were stimulated by Th17/22 cytokines cocktails. Psoriasis biomarkers were assessed by ELISA (hCD4 and RHE), by RT-qPCR (NHEK) or by ICH/ELISA (micro-epidermis). RESULTS: In 2D stimulated models (hCD4 and NHEK), CEE dose dependently inhibited, respectively, the expression of Th17 cytokines and psoriasis induced biomarkers. In 3D models (RHE and micro-epidermis), IL-8 expression was significantly reduced (RHE) and native phenotype was restored by CEE (micro-epidermis). CONCLUSION: These results clearly showed that Th17/Th22 cytokines, main inflammatory parameters, and psoriasis associated key biomarkers were inhibited by CEE in both 2D and 3D human in vitro models. Therefore, skin homeostasis could be restored by these modulator effects. Moreover, this high added value CEE was obtained by an ecofriendly bioprocess in contrast to traditional roots extracts. This is the first time that a well-defined CEE immune modulator has been proposed for psoriasis adjuvant care to reduce inflammation.

Tolerance and efficacy of a new celastrol-containing balm as adjunct care in psoriasis.

BACKGROUND: In patients with psoriasis, the non-lesional skin also presents abnormalities, requiring emollient application on the whole body. OBJECTIVES: To evaluate the tolerance of a new emollient balm containing celastrol, an active ingredient with anti-Th17 immunomodulatory properties used alone or in association with topical or systemic drug treatments or phototherapy, and its efficacy when used alone. METHODS: Adults with body plaque psoriasis applied the product over the whole body once a day for 4 weeks (balm used alone in 41 patients and with ongoing treatment in 50 patients). At D1, D8 ('balm alone' study) or D15 ('balm in association' study) and D29, the dermatologist rated physical and functional signs and assessed pruritus and body global lesion score (evaluating erythema, induration/thickness, scaling and dryness) in the 'balm alone' study. RESULTS: No reaction related to the product was reported, and the tolerance was deemed excellent. In the 'balm alone' study, mean pruritus intensity score significantly decreased at D8 (-39%, P < 0.001) and D29 (-60%, P < 0.001) compared with D1, together with the body global lesion score (-24% at D8 and -26% at D29, P < 0.001). In parallel, quality of life improved, as evidenced by a patient-reported outcome questionnaire. Cosmetic acceptability was good. CONCLUSION: This new emollient balm was very well tolerated by patients with body plaque psoriasis either alone or in association with drug treatment or phototherapy, which is important to ensure long-term compliance. Daily application during one month improved pruritus, physical signs and quality of life.

Dermatology today and tomorrow: from symptom control to targeted therapy.

For many decades and until recently, medical approach to dermatologic diseases has been based on the physician's ability to recognize and treat symptoms. Nowadays, advances in the understanding of the biology of diseases and in technologies for intervening against them have allowed physicians to diagnose and treat underlying disease processes rather than simply addressing the symptoms. This means that rather than addressing 'the disease in humans', physicians can now address the particular pathologic (biologic, molecular) disturbance as it presents in the individual patient, i.e., physicians now can practice something much closer to 'personalized medicine', leading to greater benefits for the patients and the health of society in general. The deeper understanding of ultraviolet radiation, the importance of photoprotection and increased knowledge about signalling pathways of melanoma and carcinoma have led to more complete care for the dermatologic patient. The current popularity for excessive exposure to the sun, without adequate application of the appropriate photoprotection remedies, is the origin of melanoma, but also for the weakening of the structure and functions of the skin. Indeed, fragility of the skin can affect humans around the world. In the senior population, this skin fragility is accompanied by pruritus, whereas atopic dermatitis is an inflammatory disease with highest prevalence in children and adolescents. Acne, the number one reason for dermatologic consultations worldwide, increases its prevalence in adolescents and in females. Senescent alopecia affects humans after menopause and andropause. The articles in this publication present an overview of the current advanced understanding of the diagnosis and therapeutic approaches in 6 fields of dermatology - dermatopaediatry and gerontodermatology, oncodermatology, hair loss, atopic dermatitis, photoprotection and acne - and thereby serve as a useful compendium of updated information and references for all healthcare professionals who see patients with presentations of the symptoms of these diseases.

Characterisation of Cutibacterium acnes phylotypes in acne and in vivo exploratory evaluation of Myrtacine®.

OBJECTIVE: Our main objective was to compare Cutibacterium acnes (C. acnes) skin colonisation in patients with mild to moderate acne versus healthy controls and secondly, to evaluate a Myrtacine® -based cream on C. acnes total population and antibioresistant Cutibacteria in patients with acne. METHODS: In 60 acne patients (Global Acne Severity Scale, GEA grades 2-3), of mean age 20 [15-30] years and in 24 age- and sex- matched healthy controls, forehead strips samplings were performed for microbiological analysis of comedones by colony forming unit (CFU) counts of global C. acnes and erythromycin (EryR) or clindamycin-resistant (ClnR) populations of Cutibacterium and determination of phylotypes by MALTI-TOF. Clinical evaluations of acne patients (GEA, lesion count, porphyrin fluorescence) were performed at baseline and after 56 days of twice-daily application of a Myrtacine® -based cream. RESULTS: We first showed (i) high and similar levels of C. acnes colonisation in superficial pilosebaceous follicles and detection of EryR and ClnR strains in both acne and control groups; (ii) different repartition of phylotypes in acne patients versus healthy control, with a predominance of phylotype IA in acne patients and a link between phylotype IA and erythromycin resistance. Besides, after treatment with the Myrtacine® -based cream in acne patients, there was no change in C. acnes total load, but a significant decrease of EryR Cutibacteria, reduced porphyrin production by C. acnes, a decrease in acne severity (GEA), associated with reduced retentional and inflammatory lesions. CONCLUSION: Cutibacterium acnes colonisation was not significantly different in acne versus control groups. Phylotype IA was predominant in acne patient and in EryR C. acnes. A Myrtacine® -based cream significantly reduced the level of EryR Cutibacteria in vivo and improved acne lesions.

Fragility of epidermis: acne and post-procedure lesional skin.

'Fragile skin', or skin with lower resistance to aggressors, can be broadly classified into four causal categories: constitutional (age-dependent or associated with specific vulnerable locations on the body, e.g. eyelids), pathological (related to disease), circumstantial (related to environmental or internal factors, e.g. stress) and iatrogenic (caused by medical interventions or treatments). In this supplement, we focus on the fourth category, the iatrogenic origin of fragile skin and the role that dermo-cosmetics can have in restoring the natural protective function of the skin following treatments for skin diseases and medical interventions. We present epidemiological data on the prevalence of fragile skin in three different geographical regions, and the results of two randomized controlled studies investigating the efficacy and tolerability of dermo-cosmetics in combination with topical acne treatment and following physical skin damage. Overall, we found that prevalence across the three regions (23% in Germany, 41% in UAE, 56% in Taiwan) reflected previous global estimates (24-53%) across skin types, with significant associations found with environmental and lifestyle factors, such as stress, humidity and pollution. The iatrogenic effects of topical acne treatments can result in poor compliance or use of over-the-counter moisturizers, which may reduce treatment efficacy. Dermo-cosmetics were found to aid in restoration of fragile skin caused by the acne topical retinoid treatment adapalene 0.1% gel, by reducing transepidermal water loss and improving skin hydration, as well as reducing the side-effects such as skin irritation that are frequently associated with topical retinoids. Additionally, dermo-cosmetic products were found to accelerate wound closure following skin damage in a laser ablation model and reduced the duration of post-procedural side-effects such as itching and burning.

A simple self-diagnosis tool to assess the prevalence of dermatoporosis in France.

IMPORTANCE: The term dermatoporosis has been proposed to describe clinical signs and functional consequences of age-related extreme skin fragility. OBJECTIVE: To create a simple dermatoporosis self-diagnosis tool (IDA: Index Dermatoporosis Assessment) and to use this tool to estimate the prevalence of dermatoporosis in France. DESIGN, SETTING AND PARTICIPANTS: A specific dermatoporosis questionnaire was developed with the help of senior dermatologists and survey experts. This questionnaire was submitted to consecutive individuals aged ≥65 years who consulted a dermatologist. At the end of the consultation, the dermatologist was asked to assess 'whether or not' dermatoporosis was present. In a second step, the final questionnaire was mailed to a representative sample of the French population aged ≥65 years in order to estimate the prevalence of dermatoporosis. RESULTS: The initial questionnaire, consisting of two modules (24 questions), was validated in 173 individuals aged ≥65 years) during a dermatologist consultation. Dermatologists diagnosed 46% of the individuals with dermatoporosis. The final validated questionnaire consisted of 14 items, 12 consisting in presence or absence of clinical signs and two items consisting of the self-assessment by individuals of skin ageing on neckline and hands (none/moderate/significant/very significant). A scoring system was generated to quote quantitatively dermatoporosis (from 0 if no sign of dermatoporosis to 20 maximal dermatoporosis). The area under the receiver operator curve was 0.8535, indicating a very good ability of the questionnaire to differentiate between individuals. A cut-off value of 11 was linked to positive and negative predictive values of 0.78 and 0.81, respectively. In a second step, using the questionnaire in a representative sample of the French population (n = 533), the estimated overall prevalence of dermatoporosis was 37.5% in French subjects aged ≥65 years [27.5% (males) vs. 43.9% (females); P < 0.05]. The estimated prevalence of dermatoporosis was twice higher in subjects with eczema or atopic dermatitis during childhood than in the population without dermatoporosis (60.6% vs. 33.4%, P < 0.001). Individuals with dermatoporosis also reported a higher prevalence of itching, long-term corticosteroid use, anticoagulant use and prior sun exposure. CONCLUSIONS AND RELEVANCE: Using a new simple dermatoporosis self-diagnosis tool, this study provides a previously unprecedented insight into the high prevalence of dermatoporosis in elderly individuals. IDA questionnaire is a short (14-item) and easy to use tool for evaluating dermatoporosis in adults and may allow an easy evaluation of each subject.

Efficacy of a Rhealba® Oat Extract-based emollient on chronic pruritus in elderly French outpatients.

BACKGROUND: Chronic pruritus, defined as itch persisting more than 6 weeks, is a debilitating problem that affects one in four elderly adults. Emollients are recommended for the management of pruritus, but evidence of efficacy is scarce. OBJECTIVE: Assess the efficacy of a Rhealba® Oat Extract-based emollient in the management of chronic pruritus in elderly outpatients. METHODS: This was a randomized, mono-centric, open-label, cross-over study in adults ≥60 years of age with xerosis associated with chronic pruritus. Subjects were randomized 1:1 to start with a 2-week non-treatment phase or a 2-week treatment phase in which they applied the emollient once or twice daily. The primary outcome was subject-assessed pruritus using an established visual analogue scale. Subjects also assessed pruritus using the 5-D itch scale. Investigators assessed xerosis using the Overall Dry Skin Score and measured hydration index by Corneometer® , desquamation by D-Squame and transepidermal water loss by Aquaflux® . RESULTS: Thirty subjects were included. Pruritus intensity on the visual analogue scale improved significantly more during the treatment phase than during the non-treatment phase (P < 0.0001). This was also observed immediately after the first product application (P < 0.0001). According to the 5-D itch scale, pruritus decreased during the treatment phase but remained stable during the non-treatment phase (P = 0.0042). At the end of the treatment phase, more than half of the subjects reported an improvement in pruritus, and 30% reported complete disappearance, whereas pruritus remained stable during the non-treatment phase (P < 0.0001). Xerosis improved significantly more during the treatment phase than during the non-treatment phase as measured by D-Squame, clinical assessment and hydration index (P < 0.0001). Transepidermal water loss did not significantly change. CONCLUSION: Daily use of a Rhealba Oat Extract-based emollient can provide relief to elderly adults who suffer from xerosis associated with chronic pruritus.

Fragility of epidermis in newborns, children and adolescents.

Within their first days of life, newborns' skin undergoes various adaptation processes needed to accommodate the transition from the wet uterine environment to the dry atmosphere. The skin of newborns and infants is considered as a physiological fragile skin, a skin with lower resistance to aggressions. Fragile skin is divided into four categories up to its origin: physiological fragile skin (age, location), pathological fragile skin (acute and chronic), circumstantial fragile skin (due to environmental extrinsic factors or intrinsic factors such as stress) and iatrogenic fragile skin. Extensive research of the past 10 years have proven evidence that at birth albeit showing a nearly perfect appearance, newborn skin is structurally and functionally immature compared to adult skin undergoing a physiological maturation process after birth at least throughout the first year of life. This article is an overview of all known data about fragility of epidermis in 'fragile populations': newborns, children and adolescents. It includes the recent pathological, pathophysiological and clinical data about fragility of epidermis in various dermatological diseases, such as atopic dermatitis, acne, rosacea, contact dermatitis, irritative dermatitis and focus on UV protection.

Fragility of epidermis and its consequence in dermatology.

The skin is the largest organ of the body, providing a protective barrier against bacteria, chemicals and physical insults while maintaining homeostasis in the internal environment. Such a barrier function the skin ensures protection against excessive water loss. The skin's immune defence consists of several facets, including immediate, non-specific mechanisms (innate immunity) and delayed, stimulus-specific responses (adaptive immunity), which contribute to fending off a wide range of potentially invasive microorganisms. This article is an overview of all known data about 'fragile skin'. Fragile skin is defined as skin with lower resistance to aggressions. Fragile skin can be classified into four categories up to its origin: physiological fragile skin (age, location), pathological fragile skin (acute and chronic), circumstantial fragile skin (due to environmental extrinsic factors or intrinsic factors such as stress) and iatrogenic fragile skin. This article includes the epidemiologic data, pathologic description of fragile skin with pathophysiological bases (mechanical and immunological role of skin barrier) and clinical description of fragile skin in atopic dermatitis, in acne, in rosacea, in psoriasis, in contact dermatitis and other dermatologic pathologies. This article includes also clinical cases and differential diagnosis of fragile skin (reactive skin) in face in adult population. In conclusion, fragile skin is very frequent worldwide and its prevalence varies between 25% and 52% in Caucasian, African and Asian population.

Amplification of amperometric biosensor responses by electrochemical substrate recycling. 3. Theoretical and experimental study of the phenol-polyphenol oxidase system immobilized in Laponite hydrogels and layer-by-layer self-assembled structures.

The amperometric response toward phenol of PPO-based rotating disk bioelectrodes is analyzed on the basis of a kinetic model taking into account internal and external mass transport effects and a CEC' electroenzymatic mechanism. Monophenolase activity of PPO catalyses the oxidation of phenol to o-quinone (step C). o-Quinone can then enter an amplification recycling process involving electrochemical reduction (step E) and enzymatic reoxidation (step C': catecholase activity). The rate-limiting steps such as monophenolase activity, catecholase recycling, permeability of the membrane, and activity and accessibility of the catalytic enzyme sites are theoretically considered and experimentally demonstrated for different electrode configurations including PPO immobilized in Laponite hydrogels and layer-by-layer self-assembled multilayers of PPO and poly(diallyldimethylammonium).

PUVA (5-methoxypsoralen plus UVA) enhances melanogenesis and modulates expression of melanogenic proteins in cultured melanocytes.

PUVA (combination of psoralens and ultraviolet A radiation) is a potent inducer of melanogenesis in normal human skin. The molecular mechanisms underlying this effect are poorly characterized. This study was undertaken to investigate the action of PUVA on melanogenesis in S91 murine melanoma cells and in cultured normal human melanocytes. Tyrosinase and DOPAchrome tautomerase (DCT) activities as well as melanin neosynthesis were measured in PUVA-treated pigment cells. To determine whether a correlation exists between PUVA-induced melanogenesis and expression of melanogenic enzymes, we analyzed the levels of tyrosinase, DCT, and tyrosinase-related protein-1 (TRP-1 or gp75) by western blotting in PUVA-treated cells. We demonstrate that UVA upregulates tyrosinase activity and melanin content with 5-methoxypsoralen at 1 microM. This phenomenon depends on the energy delivered during phototreatment. In both human and mouse cells, stimulation of melanogenesis correlated with an increase of the amount of tyrosinase. In PUVA-treated S91 cells, tyrosinase mRNA was increased, but no stimulation of DCT activity occurred in these cells, in agreement with the unchanged amount of DCT protein in cell extracts. On the contrary, in melanocytes treated with PUVA, a decrease in DCT protein was observed. Finally, the amount of TRP-1 protein was not affected by PUVA in either S91 cells or melanocytes. These results show that melanogenesis induced by PUVA is related to an increase in expression of tyrosinase. In melanocytes, melanogenesis and DCT are negatively correlated, which suggests that PUVA favors the metabolic pathway of dark-eumelanins with high UV-protective properties. This study also suggests that PUVA regulates tyrosinase, DCT, and TRP-1 expression in a noncoordinate manner.

Adhesive and migratory behaviors of nevus cells differ from those of epidermal melanocytes and are not linked to the histological type of nevus.

It has been postulated that acquired nevi undergo life span continuous evolution from junctional, presumably in radial expanding phase at the dermal epidermal junction, to compound and then to dermal nested nevi. In an attempt to correlate the morphology of nevi with biological data, we have investigated whether migratory and adhesive phenotypes of nevus cells could account for histological patterns and possible spatiotemporal changes in nevi. Nevus cells were cultured from compound and dermal nevi and compared to normal epidermal cultured melanocytes from children and adults. AR nevus cells showed similar in vitro adhesive and migratory indexes on laminin-1, laminin-5/nicein, fibronectin, or collagen IV substrates, suggesting that these intrinsic characteristics do not account for the tendency to dermal nesting and/or to radial growth along the dermal-epidermal junction. The cells from epidermal and dermal parts of compound nevi migrated similarly across a reconstituted basement membrane. The results show that intrinsic adhesive and migratory behaviors of nevus cells were not associated with a histological type of nevus. Interestingly, differences in migratory phenotype and intercellular adhesion capacities between nevus cells and normal melanocytes indicated that they could represent different melanocytic cell subpopulations. Finally, melanocytes from adults and children expressed similar levels of the same integrins as all nevus cells but showed differences in function of both alpha3 and alpha6 integrin subunits and in migratory/adhesive behaviors, which may suggest different states of melanocyte maturation.

Regulation of melanogenesis induced by 5-methoxypsoralen without ultraviolet light in murine melanoma cells.

Melanogenesis in melanoma cells can be enhanced by psoralens in the absence of UV light. Melanin biosynthesis is regulated by a number of melanocyte-specific proteins, including tyrosinase, DOPAchrome tautomerase (DCT), and tyrosinase-related protein-1 (TRP-1, gp75). To get more insight on the molecular mechanisms involved in psoralens-induced melanogenesis, we determined tyrosinase and DCT activities as well as mRNA and protein levels of tyrosinase, DCT, and TRP-1 in S91 mouse melanoma cells treated by 5-MOP. High concentration of 5-MOP (5 x 10(-5) M) induced a time-dependent increase of tyrosinase activity and melanin content, which was correlated to an increase of both mRNA and protein levels of tyrosinase. These results demonstrate that the 5-MOP stimulation of melanogenesis is related to increased tyrosinase synthesis. In addition, 5-MOP stimulated TRP-1 synthesis and induced a dose-dependent decrease of DCT activity without any modification in the expression of the protein. We explored then the signalling pathways involved in 5-MOP-induced melanogenesis and, particularly, the role of cyclic AMP and protein kinase C (PKC). A small stimulation of cyclic AMP production was observed in presence of 5-MOP. Furthermore, 1-oleoyl-2-acetylglycerol (OAG), a PKC activator, potentiated the 5-MOP stimulation of tyrosinase activity, while calphostin, a specific PKC inhibitor, inhibited the 5-MOP induction of tyrosinase activity. Phorbol-myristate acetate (PMA), described as a strong activator of PKC, inhibited also the effect of 5-MOP when used at long term. Taken together, these results demonstrate that in murine melanoma cells 5-MOP stimulates melanogenesis by increasing activity and synthesis of tyrosinase. Tyrosinase and TRP-1 expression are coordinately regulated by 5-MOP. Furthermore, a negative correlation between melanogenesis and DCT activity was observed under 5-MOP stimulation. At least, PKA and PKC systems appear to play an important role in the melanogenic effect of 5-MOP.

No high affinity melatonin binding sites are detected in murine melanoma cells and in normal human melanocytes cultured in vitro.

Saturation studies of 2-(125I)-iodomelatonin binding to membranes from normal human melanocytes, mouse melanoma cells B16F10 and amelanotic S91 revealed no specific binding. Using 2-(125I)-iodomelatonin in the concentration range of 6 to 566 pM, no high affinity melatonin binding sites were detectable in any of the cell types. Even when the concentration of radioligand was increased up to 2000 pM, specific binding was either low or absent and not reproducible. These results suggest that in the culture conditions used in this study, no high affinity melatonin binding sites are detected in pigmented cells.