La neurofibromatose de type 1 (NF1) constitue la maladie autosomique dominante la plus fréquente avec une incidence d’environ 1 naissance pour 3500. Les manifestations cliniques les plus courantes sont neurocutanées et se caractérisent par une hyperpigmentation générale diffuse avec une impression de peau brune, des tâches hyperpigmentées dites tâches café-au-lait, des tumeurs bénignes de la gaine des nerfs périphériques appelées neurofibromes et des troubles neurologiques. Le gène NF1, responsable de la maladie est un gène suppresseur de tumeur qui code pour la neurofibromine. Les mécanismes moléculaires associés à l’altération de la pigmentation chez ces patients restent jusqu’ici inconnus. Nous avons étudié cette question grâce à la mise en place au laboratoire d’un protocole de différenciation des cellules souches pluripotentes en mélanocytes et l’accès à deux lignées de cellules souches embryonnaires porteuses de la mutation causale de NF1 (hESC-NF1). Dans cette étude, nous avons montré qu’une perte d’expression de la neurofibromine dans les mélanocytes dérivés de hESC-NF1 reproduisait le phénotype d’hyperpigmentation généralisée et pouvait mimer la formation des tâches « café au lait ». L’analyse des mécanismes moléculaires associés à ce phénotype pathologique montre que les mélanocytes NF1 présentent une dérégulation des voies de signalisation AMPc et ERK conduisant à l’augmentation de la mélanogenèse. Le phénotype hyperpigmentaire des mélanocytes NF1 a pu être corrigé grâce à l’utilisation d’inhibiteurs pharmacologiques spécifiques de la voie AMPc, de la voie ERK et de la mélanogenèse. En parallèle, afin de pouvoir envisager une approche de thérapie cellulaire à partir des mélanocytes dérivés de cellules pluripotentes pour le traitement de maladies associées à une hypopigmentation d’origine génétiques ou non, un protocole de différenciation fondé sur une application séquentielle de cytokines permettant de diriger de manière spécifique les cellules souches pluripotentes en mélanocytes a été développé au laboratoire. Des mélanocytes fonctionnels ont été obtenus en 30 jours en engagement la différenciation des cellules souches vers la crête neurale afin d’induire l’émergence de précurseurs de mélanocytes par l’action de molécules telles que la BMP4, l’acide ascorbique, l’endotheline 3, le SCF et un activateur de WNT3a (CHIR99021L’ensemble de ce travail a permis de valider la pertinence de l’utilisation des cellules souches pluripotentes porteuses de maladie génétique ou pour le traitement de maladies hyper ou hypopigmentaire par des approches de modélisation pathologique et de criblage pharmacologique ou par des approches de thérapie cellulaire. / Neurofibromatosis type 1 is one of the most common autosomal dominant diseases (1/3500). Café-au-lait” macules (CALMs); overall skin hyperpigmentation, neurofibromas (benign tumors resulting from Schwann cell proliferation) and deficits cognitive are the mains clinical manifestations. NF1 is caused by mutations in a tumor suppressor gene that encodes neurofibromin, a functional RAS-GTPase-activating protein (RAS-GAP). Neurofibromin down-regulates RAS signaling by accelerating the conversion of active RAS-GTP to inactive RAS-GDP. The resulting decreased expression of neurofibromin leads to activation of several important downstream signaling pathways, including MEK/MAPK, AKT/mTOR and cAMP-mediated protein kinase A pathways. In order to better understand molecular mechanisms linking neurofibromin and associated manifestations in the pathology, mouse models have been established. However, these models don’t reproduce systematically cutaneous manifestations associated with NF1. To overcome this issue, we take advantage that pluripotent stem cells possess the capacity of self-renew and are able to differentiate into a wide variety of cell types. A growing number of examples illustrate how such cells, retrieved from genetically selected donors carrying the causal mutation of a monogenic disorder, may reproduce disease-associated phenotypes. Two human embryonic stem cell lines derived from embryos characterized as mutant-gene carriers for NF1 during a pre-implantation diagnosis procedure were differentiated into a pure and proliferative melanocytes, in order to explore mechanisms associated with hyperpigmentation and “café-au-lait” macules associated with NF1. In this study, we demonstrated that NF1 melanocytes reproduce the hyperpigmentation phenotype in vitro, and further characterized the link between loss of heterozygosity and the typical “café au lait” macules that appear over the general hyperpigmentation. Molecular mechanisms associated with these pathological phenotypes correlate with an increased activity of cyclic AMP-mediated protein kinase A and ERK1/2 signaling pathways, leading to increase of melanogenesis. Finally, the hyperpigmentation phenotype could be rescued by using specific inhibitors of these signaling pathways. In parallel, to consider a cell therapy approach from melanocytes derived from pluripotent cells for the treatment of hypopigmentation disorders related to the death or dysfunction of melanocytes such as Griscelli or Vitiligo syndromes, a differentiation protocol based on sequential application of molecules to specifically induce the differentiation of pluripotent stem cells into melanocytes was developed in the laboratory. Functional melanocytes were obtained in 30 days by the commitment of pluripotent stem cells into melanocytes precursors via neural crest state by the action of molecules such as BMP4, ascorbic acid, endothelin 3, SCF and an activator of Wnt3a (CHIR99021). All of this work has validated the appropriateness of the use of pluripotent stem cells carring genetic mutations or not to treat hyper or hypopigmentation disease by identified pharmoclogical treatment or by a cell therapy approach.

Introdução: A hiperpigmentação periocular (HPPO) está entre as queixas mais comuns nos pacientes com queixas estéticas. Apesar de muito prevalente, não há relatos sobre as características dermatoscópicas de HPPO. Objetivos: Determinar os diferentes padrões das estruturas das HPPO utilizando o dermatoscópio de luz polarizada e compará-los aos encontrados com exame realizado por videodermatoscópio de contato com luz não-polarizada. Métodos: Trinta e três pacientes com HPPO tiveram os padrões dermoscópicos relacionadas à pigmentação , às estruturas vasculares e à gravidade global examinados e descritos com o uso do dermatoscópio de luz polarizada . Estes resultados foram comparados com os encontrados na região malar ipsilateral. Posteriormente, o mesmo observador avaliou as mesmas áreas anatômicas utilizando o videodermatoscopio digital. As imagens geradas pelo videodermatoscopio também foram analisadas por outro observador independente cegado. Resultados: Entre as características dermatoscópicas mais prevalentes na área periocular estão as máculas melanóticas e as estruturas vasculares, vasos especialmente arboriformes e lineares. Na dermatoscopia de luz polarizada , a HPPO apresentou maior freqüência de máculas melanóticas e estruturas vasculares em comparação com a área malar (respectivamente 30/33 ( 90,9%) x 26 /33 (78,9%) p = 0,024 e 32 /33 (97%) x 25 /33 (75,7%) p = 0,094). A correlação entre a dermatoscopia com luz polarizada e a dermatoscopia de luz não polarizada foi moderada a alta para as mesmas estruturas (valores de kappa , respectivamente, 0,58 e 0,66) . A análise entre os diferentes observadores utilizando a dermatoscopia de contato de luz não-polarizada também mostrou alta concordância para a presença de máculas melanóticas e estruturas vasculares ( valores de kappa , respectivamente, 0,62 e 0,66). Conclusões: A HPPO possui um padrão dermatoscópico baseado na presença de máculas melanóticas e diferentes graus de estruturas vasculares. A dermatoscopia de luz polarizada e a videodermatoscopia de contato de luz não-polarizada são métodos úteis e equiparáveis na avaliação da área periocular. / Background: Periocular hyperpigmentation (POH) is among the most common complaints in patients with cosmetic concerns. Despite its high prevalence, there are no reports on dermoscopic features of POH. Objectives: To determine the different patterns of POH structures by using a polarized-light dermatoscope and compare them to patterns found with the use of a nonpolarized light contact videodermoscopy. Methods: Thirty-three patients with POH had dermoscopic patterns related to pigmentation, vascular structures and global severity examined and described with the use of polarized-light dermoscopy. These findings were initially compared to those from the ipsilateral malar region. Later, the same observer assessed the same anatomic areas using digital videodermatoscopy. The images generated by videodermatoscopy were also analyzed by a blind independent observer. Results: Among the most prevalent dermoscopic features in the periocular area are melanotic macules and vascular structures, especially arboriform and linear vessels. In polarized light dermoscopy, the HPPO showed higher frequency of melanotic macules and vascular structures compared to the malar area. (respectively 30/33 (90.9%) x 26/33 (78,9%) p = 0.024 and 32/33 (97%) x 25/33 (75.7%) p = 0,094) The correlation between the polarized light dermoscopy and non-polarized light dermoscopy was moderate to high for the same structures (kappa values, respectively, 0.58 and 0.66). The analysis between different observers using non-polarized contact dermoscopy also showed high concordance for the presence of melanotic macules and vascular structures (kappa values, respectively, 0.62 and 0.66). Conclusions: POH shows a dermoscopic pattern based on the presence of melanotic macules and different degrees of vascular structures. Polarized light and non-polarized contact dermoscopy are useful and equivalent methods for the evaluation of the periocular area.

Introdução: A hiperpigmentação periocular (HPPO) está entre as queixas mais comuns nos pacientes com queixas estéticas. Apesar de muito prevalente, não há relatos sobre as características dermatoscópicas de HPPO. Objetivos: Determinar os diferentes padrões das estruturas das HPPO utilizando o dermatoscópio de luz polarizada e compará-los aos encontrados com exame realizado por videodermatoscópio de contato com luz não-polarizada. Métodos: Trinta e três pacientes com HPPO tiveram os padrões dermoscópicos relacionadas à pigmentação , às estruturas vasculares e à gravidade global examinados e descritos com o uso do dermatoscópio de luz polarizada . Estes resultados foram comparados com os encontrados na região malar ipsilateral. Posteriormente, o mesmo observador avaliou as mesmas áreas anatômicas utilizando o videodermatoscopio digital. As imagens geradas pelo videodermatoscopio também foram analisadas por outro observador independente cegado. Resultados: Entre as características dermatoscópicas mais prevalentes na área periocular estão as máculas melanóticas e as estruturas vasculares, vasos especialmente arboriformes e lineares. Na dermatoscopia de luz polarizada , a HPPO apresentou maior freqüência de máculas melanóticas e estruturas vasculares em comparação com a área malar (respectivamente 30/33 ( 90,9%) x 26 /33 (78,9%) p = 0,024 e 32 /33 (97%) x 25 /33 (75,7%) p = 0,094). A correlação entre a dermatoscopia com luz polarizada e a dermatoscopia de luz não polarizada foi moderada a alta para as mesmas estruturas (valores de kappa , respectivamente, 0,58 e 0,66) . A análise entre os diferentes observadores utilizando a dermatoscopia de contato de luz não-polarizada também mostrou alta concordância para a presença de máculas melanóticas e estruturas vasculares ( valores de kappa , respectivamente, 0,62 e 0,66). Conclusões: A HPPO possui um padrão dermatoscópico baseado na presença de máculas melanóticas e diferentes graus de estruturas vasculares. A dermatoscopia de luz polarizada e a videodermatoscopia de contato de luz não-polarizada são métodos úteis e equiparáveis na avaliação da área periocular. / Background: Periocular hyperpigmentation (POH) is among the most common complaints in patients with cosmetic concerns. Despite its high prevalence, there are no reports on dermoscopic features of POH. Objectives: To determine the different patterns of POH structures by using a polarized-light dermatoscope and compare them to patterns found with the use of a nonpolarized light contact videodermoscopy. Methods: Thirty-three patients with POH had dermoscopic patterns related to pigmentation, vascular structures and global severity examined and described with the use of polarized-light dermoscopy. These findings were initially compared to those from the ipsilateral malar region. Later, the same observer assessed the same anatomic areas using digital videodermatoscopy. The images generated by videodermatoscopy were also analyzed by a blind independent observer. Results: Among the most prevalent dermoscopic features in the periocular area are melanotic macules and vascular structures, especially arboriform and linear vessels. In polarized light dermoscopy, the HPPO showed higher frequency of melanotic macules and vascular structures compared to the malar area. (respectively 30/33 (90.9%) x 26/33 (78,9%) p = 0.024 and 32/33 (97%) x 25/33 (75.7%) p = 0,094) The correlation between the polarized light dermoscopy and non-polarized light dermoscopy was moderate to high for the same structures (kappa values, respectively, 0.58 and 0.66). The analysis between different observers using non-polarized contact dermoscopy also showed high concordance for the presence of melanotic macules and vascular structures (kappa values, respectively, 0.62 and 0.66). Conclusions: POH shows a dermoscopic pattern based on the presence of melanotic macules and different degrees of vascular structures. Polarized light and non-polarized contact dermoscopy are useful and equivalent methods for the evaluation of the periocular area.

Introdução: A hiperpigmentação periocular (HPPO) está entre as queixas mais comuns nos pacientes com queixas estéticas. Apesar de muito prevalente, não há relatos sobre as características dermatoscópicas de HPPO. Objetivos: Determinar os diferentes padrões das estruturas das HPPO utilizando o dermatoscópio de luz polarizada e compará-los aos encontrados com exame realizado por videodermatoscópio de contato com luz não-polarizada. Métodos: Trinta e três pacientes com HPPO tiveram os padrões dermoscópicos relacionadas à pigmentação , às estruturas vasculares e à gravidade global examinados e descritos com o uso do dermatoscópio de luz polarizada . Estes resultados foram comparados com os encontrados na região malar ipsilateral. Posteriormente, o mesmo observador avaliou as mesmas áreas anatômicas utilizando o videodermatoscopio digital. As imagens geradas pelo videodermatoscopio também foram analisadas por outro observador independente cegado. Resultados: Entre as características dermatoscópicas mais prevalentes na área periocular estão as máculas melanóticas e as estruturas vasculares, vasos especialmente arboriformes e lineares. Na dermatoscopia de luz polarizada , a HPPO apresentou maior freqüência de máculas melanóticas e estruturas vasculares em comparação com a área malar (respectivamente 30/33 ( 90,9%) x 26 /33 (78,9%) p = 0,024 e 32 /33 (97%) x 25 /33 (75,7%) p = 0,094). A correlação entre a dermatoscopia com luz polarizada e a dermatoscopia de luz não polarizada foi moderada a alta para as mesmas estruturas (valores de kappa , respectivamente, 0,58 e 0,66) . A análise entre os diferentes observadores utilizando a dermatoscopia de contato de luz não-polarizada também mostrou alta concordância para a presença de máculas melanóticas e estruturas vasculares ( valores de kappa , respectivamente, 0,62 e 0,66). Conclusões: A HPPO possui um padrão dermatoscópico baseado na presença de máculas melanóticas e diferentes graus de estruturas vasculares. A dermatoscopia de luz polarizada e a videodermatoscopia de contato de luz não-polarizada são métodos úteis e equiparáveis na avaliação da área periocular. / Background: Periocular hyperpigmentation (POH) is among the most common complaints in patients with cosmetic concerns. Despite its high prevalence, there are no reports on dermoscopic features of POH. Objectives: To determine the different patterns of POH structures by using a polarized-light dermatoscope and compare them to patterns found with the use of a nonpolarized light contact videodermoscopy. Methods: Thirty-three patients with POH had dermoscopic patterns related to pigmentation, vascular structures and global severity examined and described with the use of polarized-light dermoscopy. These findings were initially compared to those from the ipsilateral malar region. Later, the same observer assessed the same anatomic areas using digital videodermatoscopy. The images generated by videodermatoscopy were also analyzed by a blind independent observer. Results: Among the most prevalent dermoscopic features in the periocular area are melanotic macules and vascular structures, especially arboriform and linear vessels. In polarized light dermoscopy, the HPPO showed higher frequency of melanotic macules and vascular structures compared to the malar area. (respectively 30/33 (90.9%) x 26/33 (78,9%) p = 0.024 and 32/33 (97%) x 25/33 (75.7%) p = 0,094) The correlation between the polarized light dermoscopy and non-polarized light dermoscopy was moderate to high for the same structures (kappa values, respectively, 0.58 and 0.66). The analysis between different observers using non-polarized contact dermoscopy also showed high concordance for the presence of melanotic macules and vascular structures (kappa values, respectively, 0.62 and 0.66). Conclusions: POH shows a dermoscopic pattern based on the presence of melanotic macules and different degrees of vascular structures. Polarized light and non-polarized contact dermoscopy are useful and equivalent methods for the evaluation of the periocular area.

Hyperpigmentation is a common dermatological complaint that can have profound effect on appearance and quality of life.  Disorders of hyperpigmentation comprise a large group of skin conditions characterized by an increase of melanin production, increase in density of active melanocytes, abnormal melanin distribution, and/or deposition of exogenous pigments. This cross-sectional study was conducted to evaluate the impact hyperpigmentation disorders on health-related quality of life and to better understand patient knowledge, approaches, and experiences. The study was conducted on 298 consenting adult patients with a skin related disorder of hyperpigmentation who sought dermatological care at Boston Medical Center (BMC) or East Boston Neighborhood Health Center (EBNHC) from February of 2015 to March of 2016. Patients were anonymously surveyed in order to collect an assortment of information including demographic characteristics, skin condition, health practices, knowledge base, and health-related quality of life (HRQoL) measured with the Dermatology Life Quality Index (DLQI) (Finlay and Khan 1994) and SDIEQ, a five-item , non-validated, brief health-related quality of life questionnaire (A. Taylor et al. 2008). Disease severity was assessed by Melasma Area Severity Index (MASI), Post Acne Hyperpigmentation Index (PAHPI) and body surface area when appropriate. The mean overall DLQI was 6.56 (SD 5.35). In sub-analysis, the mean DLQI in those diagnosed with post-inflammatory hyperpigmentation was 7.89 (SD 0.61), melasma 6.75 (SD 0.45), and other hyperpigmentation disorders 4.5 (SD 0.55). The disease type and duration were both factors associated with a change in DLQI scores. The factors associated with a higher likelihood of patients’ knowledge of their diagnosis included a higher level of formal education, younger age, longer duration of having the condition, and current use of sunscreen, which were found to have 2.4, 2, 3.7, and 2.4 significantly higher odds of knowing their diagnosis, respectively. This study found that the overall impact of hyperpigmentation on health-related quality of life (HRQoL) was small to moderate; however, about 22% reported a very large affect on quality of life. Patients with post-inflammatory hyperpigmentation (PIH) and melasma have significantly lower quality of life when compared with other hyperpigmentation disorders. MASI had a significantly weak correlation with DLQI and SDIEQ, demonstrating that disease severity does not predict patient perception and impact on quality of life.

Philosophiae Doctor - PhD / Dyspigmentation is one of the commonest dermatological presenting complaints from patients, particularly hyperpigmentation. Hyperpigmentation can cause dangerous psychological and emotional impact on self-perception and health quality of lives of people affected. However, of all the diseases encountered globally, epidemiological data has shown that skin diseases account for almost 34% of all the diseases and these dermatological disorders have gotten worse over time. The gold standard for treatment of hyperpigmentation is hydroquinone. Despite its efficacy, hydroquinone and other current modalities of treatments are associated with some side effects. There are a number of natural products derived from medicinal plants that have proven to be an abundant source of biologically active compounds and a lot of these have served as the basis for the development of new lead chemicals for pharmaceutical. The present study focused on screening of selected South African plants (Maclura pomifera, Otholobium fruticans, Phyylica ericoides, Psoralea aphylla, Rhynchosia villosa, and Serruria furcellata) for their antimelanogenic potentials. Methanol and ethyl acetate were used for the extraction of plant materials. Standard methods were employed for evaluation of cytotoxicity of the methanolic leaf extracts (MLE), ethyl acetate leaf extracts (ELE) and melanin synthesis potentials on B16 melanoma cells. To elucidate mechanisms of melanin reduction action, intracellular tyrosinase activity was determined by measuring the rate of L-DOPA oxidation. Tyrosinase activity was assessed further with dihydroxyphenylalanine (DOPA) staining. The mode of action was further determined by evaluating reactive oxygen species (ROS) and expressions of melanogenesis gene using qPCR. The results showed that O. fruticans and S. furcellata reduced melanin synthesis without cytotoxicity. O. fruticans inhibited tyrosinase activity, increased ROS and suppressed the expression of TYR, TRP-1, TRP-2/Dopachrome tautomerase, MITF, MC1R but upregulated β-Catenin. S. furcellata stimulated tyrosinase activity and did not increase ROS. It upregulated the expression of TYR, TRP-1, TRP-2, and MC1R while MITF and β-Catenin were suppressed. The results showed that O. fruticans reduced melanin synthesis via cAMP pathway while S. furcellata reduced the synthesis via possibly degradation of melanin pigment. The present study on O. fruticans and S. furcellata has shown that leaves of these plants are candidate anti-melanogenic agents. However, more work still needs to be done to elucidate other possible mechanisms that are relevant to antimelanogenic effects of these two plants. / 2020-08-31

Orientador: Mary Luci de Souza Queiroz / Tese (doutorado) - Universidade Estadual de Campinas. Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-12T09:49:02Z (GMT). No. of bitstreams: 1 Eberlin_Samara_D.pdf: 2378892 bytes, checksum: 98a7ab7699a5cebee6b0d53463f9f52c (MD5) Previous issue date: 2008 / Resumo: Desordens periorbitais (DPO) é um nome atribuído a um conjunto de disfunções estéticas caracterizadas por alterações na coloração e na forma das pálpebras. As principais manifestações observadas são, hipercromia da região infraorbital, formação de bolsas de gordura, de edema e de rugas finas. A hipercromia ocorre em função de um distúrbio microvascular que pode gerar a formação de edema e alteração da tonalidade da pele. A formação de bolsas de gordura é caracterizada por uma hipertrofia nos adipócitos devido ao acúmulo de triacilglicerol intracelular. Pela ação deletéria da radiação UV observa-se a degradação do tecido conectivo, o que é refletido através do aparecimento de rugas ao redor dos olhos. Neste trabalho, avaliamos a possível aplicação da associação dos extratos hidroglicólicos de Pfaffia paniculata e Ptychopetalum olacoides (AEHPPPO) na prevenção e tratamento da DPO. Os resultados clínicos obtidos demonstraram que AEHPPPO promoveu uma redução da hipercromia, do edema e das linhas finas de expressão na região periorbital. Estes efeitos podem ser atribuídos àqueles observados in vitro, onde AEHPPPO demonstrou atividades antioxidante, antiinflamatória, estimuladora da síntese dos componentes da matriz extracelular e do metabolismo do tecido adiposo. Estes resultados nos levam a sugerir que este composto poderia ser utilizado como uma alternativa eficaz em produtos para o cuidados da pele, particularmente aqueles destinados à região dos olhos, com o propósito de prevenir ou minimizar a presença da hipercromia, bolsas e rugas finas nesta área específica. / Abstract: Despite the frequency in which occurs, little has been written in scientific literature on the treatment of periorbital disorders (POD). POD are characterized by alterations in color and shape of the upper and lower eyelids, manifested by hyperpigmentation ("dark circles") and puffiness resulted by fat and fluid accumulation. It has been reported that darkening around the eyes is caused by a process of postinflammatory hemodynamic congestion, characterized by melanin and hemoglobin accumulation. The puffiness caused by orbital adipose tissue is due to an overload of triacylglycerol in the adipocyte, probably as a consequence of circulatory disturbance. Another consequence of the inflammatory process is the local edema due to capillary vasodilatation, which is caused by the release of inflammatory mediators. In addition, POD is usually accompanied by local wrinkling formation, due to deterioration of extracellular matrix (ECM), especially provoked by UV radiation exposure. In this work, we have demonstrated the effects of Pfaffia paniculata/Ptychopetalum olacoides-associated compound (PPLAC) as a dermocosmetic active in the clinical improvement of periorbital disorders. The clinical evaluation showed significant improvements in skin hyperchromia, edema and flaccidity in periorbital area. These clinical observations were also confirmed by in vitro studies, which demonstrated anti-inflammatory, antioxidant and lipolytic effects, besides the ability to stimulate ECM compounds production. Our results clearly encourage the use of this compound as an adjuvant to eyecare dermocosmetics products with the purpose to reduce the local bruised appearance and puffiness improvement. / Doutorado / Doutor em Farmacologia

>Magister Scientiae - MSc / Hyperpigmentation disorders such as melasma, freckles and black-pigmented spots on the surface of the skin are often a result of increased over production and accumulation of melanin pigments in the skin. In melanin biogenesis, tyrosinase is the key enzyme that catalysis the synthesis of melanin, thus the most effective and easiest way to reduce melanin synthesis is by inhibiting tyrosinase. There are a large number of reported tyrosinase inhibitors, their identification and isolation from natural sources is highly important because when natural tyrosinase inhibitors are identified in natural sources, their production is relatively low in cost. Tyrosinase inhibitors are highly sought in the cosmetic industry because of their skin – whitening effects. Most common used tyrosinase inhibitors are kojic acid (KA), arbutin, hydroquinone and ascorbic acid. However, these inhibitors have side effects and lack clinical efficiency. These facts led us to focus our research work on the exploration of natural tyrosinase inhibitors. Due to the therapeutic potential of medical plants researchers are not only concerned with validating ethnopharmacological usage of plants, but also with identification, isolation and characterization of bioactive components. Sutherlandia frutescens and Psoralea aphylla are both examples of indigenous fynbos species, which have been applied by indigenous people for the benefit of their medicinal properties.

Les problèmes d’hyperpigmentation cutanée sont caractérisés par l’apparition de taches brunes foncées, distribuées irrégulièrement sur la peau, généralement sur les zones photo-exposées. Ce problème largement répandu est la conséquence de plusieurs perturbations cutanées d’une ampleur autant physiologique qu’esthétique. Les rayonnements ultraviolets (UV) jouent un rôle important dans la mélanogenèse mais sont aussi à l’origine de plusieurs dérèglements physiologiques des mélanocytes induisant ainsi leur mal-fonctionnement.L’application d’un écran solaire est un moyen très efficace pour la protection contre les UV et la prévention des problèmes d’hyperpigmentation cutanée. Pour la première fois, nous avons pu mettre en place une nouvelle méthode in vitro pour la détermination du facteur de protection solaire (SPF) d’un écran en utilisant le film Gafchromic® EBT3 comme substrat et en se basant sur le changement de couleur du substrat. La variation de couleur est évaluée par spectroscopie ultraviolet-visible et est rapportée à l’absorbance du film après son exposition à un simulateur de soleil.En plus, nous nous sommes intéressés à la recherche de principes actifs extraits de plantes pour la régulation des problèmes d’hyperpigmentation cutanée. Pour ce, des huiles essentielles (HE) ont été extraites à partir de cinq plantes indigènes ou endémiques au Liban et leur composition analysée par chromatographie en phase gazeuse couplée à la spectrométrie de masse (GC-MS). Leurs effets moléculaires sur les structures cutanées ont été déterminés par analyses in tubo et in vitro. Les analyses enzymatiques in tubo ont permis de détecter une activité anti tyrosinase importante des deux HE d’Origanum syriacum et Origanum ehrenbergii. Cette activité a été liée à la composition phytochimique de chaque HE et a été attribuée au composé majoritaire, le carvacrol. Les études in vitro sur des cultures de mélanocytes ont permis de déterminer une diminution significative de la production de la mélanine en présence des HE et du carvacrol. Nous avons pu établir un lien entre les deux études pour déterminer le mécanisme d’action du carvacrol. Il s’agit d’une inhibition compétitive où le carvacrol se lie à la tyrosinase pour suivre une série d’oxydations enzymatiques bloquant ainsi l’oxydation de la tyrosine et causant un dérèglement de la mélanogenèse.Notre étude est la première à démontrer l’activité anti tyrosinase des HE d’O. syriacum et d’O. ehrenbergii. La complémentarité entre les tests d’efficacité et les analyses GC-MS nous a permis d’attribuer l’activité anti tyrosinase au carvacrol qui agit par inhibition compétitive.Ainsi, l’application de protecteur solaire associée à l’application cutanée de régulateurs de la mélanogenèse pourrait être une solution efficace pour les problèmes d’hyperpigmentation cutanée. / Hyperpigmentation disorders are characterized by an irregular distribution of dark spots on the skin, mainly on photo-exposed skin areas. This widespread problem is the result of several skin disorders leading to many physiological and aesthetic perturbations. Ultraviolet (UV) radiations play an important role in melanogenesis. However, they are also the source of several physiological disorders that induce a malfunctioning of melanocytes.The application of sunscreen is a very effective UV protection method and it is considered a main factor in the prevention of skin hyperpigmentation problems. One of the novelties in our research is that, for the first time, we were able to establish a new in vitro method for the determination of the sun protection factor (SPF) of a sunscreen, using EBT3 Gafchromic® film as a substrate. Our method relied on the color change of the substrate that was evaluated by UV-visible spectrophotometric measurements and valued by the absorbance of the film exposed to a solar simulator.In addition, we were interested in discovering new plant-derived active ingredients for the regulation of skin hyperpigmentation disorders. For this process, five essential oils (EO) of indigenous or endemic plants to Lebanon were extracted and their composition was studied by gas chromatography coupled to mass spectrometry (GC-MS). We studied as well their molecular effects on cutaneous structures by in tubo and in vitro analysis. In tubo enzymatic analysis allowed us to identify an important anti tyrosinase activity of the two EO of Origanum syriacum and Origanum ehrenbergii. This activity was linked to the phytochemical composition of the EO and was assigned to the presence of their main component, carvacrol. In vitro cell cultures of melanocytes enabled us to determine a significant reduction in the melanin production in the presence of the EOs and carvacrol. Furthermore, we were able to define the mechanism of action of carvacrol by linking both in tubo and in vitro studies: carvacrol binds to tyrosinase and undergoes a series of oxidation reactions, thus preventing the oxidation of tyrosine. This mechanism is called competitive inhibition and it disturbs the regular pathway of melanogenesis.Our study is the first to demonstrate the anti tyrosinase activity of the EO of O. syriacum and O. ehrenbergii. The complementarity between efficacy tests and the phytochemical GC-MS analysis was our tool to discover that tyrosinase inhibition is mainly due to the presence of carvacrol that acts by competitive inhibition.Thus, the application of a sunscreen paired with the application of cutaneous melanogenesis regulator could be an effective solution for skin hyperpigmentation disorders.

Made available in DSpace on 2016-08-10T10:29:43Z (GMT). No. of bitstreams: 1 TACIANA FRIZON.pdf: 1007171 bytes, checksum: e139c3cba6711bcac003708dd8fedecf (MD5) Previous issue date: 2010-03-19 / There are many pathological changes of skin color classified into hereditary and acquired hyper-pigmentation. The depigmetant drugs mostly used in the treatment of skin hyperpigmentation are zelaic acid, phytic acid, ascorbic acid, kojic acid, tretinoin and hydroquinone. However, hydroquinone is mainly used in masterful formulations; primarily in the handling of creams, therefore, it deserves special attention. This study had the objective of analyzing the molecular behavior of hydroquinone. The constant use of hydroquinone in dermatology and compounding pharmacies justify the studies that may evaluate the aspects of its manipulation, the main types of skin hyper-pigmentation, and the addressing questions about the physical chemistry of the drug, increased stability for about three to six months in compounding pharmacies, the composition, the filling, the conservation and proper use of hydroquinone by the patients. Usually hydroquinone concentration used in preparations can reach up to 10% and as a vehicle several basis are used, including hydro-alcoholic solution. The use of a base such as cetostearyl alcohol and an emulsifier non-ionic as the polysorbate, the use of opaque labels, pH defined between 6,0 and 6,5, avoid the presence of oxygen, use water with high level of purity, metal less and use of antioxidants sodium metabisulfite, will slow the oxidatation process and extend the validation date for six months. / Há várias alterações patológicas da coloração da pele que estão classificadas em hipercromia hereditárias e adquiridas. Os medicamentos despigmetantes mais utilizados no tratamento da hiperpigmentação cutânea são: ácido azeláico, ácido fítico, ácido ascórbico, ácido kójico, tretinoína, ácido glicólico e hidroquinona. No entanto, a hidroquinona é mais utilizada em formulações magistrais, principalmente, na manipulação de cremes e, portanto, merece destaque. O presente trabalho teve por objetivo analisar o comportamento molecular da hidroquinona. O seu uso constante na dermatologia e em farmácias magistrais justifica os estudos que possam avaliar aspectos de sua manipulação, os principais tipos de hiperpigmentação cutânea e, abordar questões sobre as propriedades físico-química desse fármaco, e o aumento da estabilidade de três para seis meses em farmácia magistral, a composição, o envase, a conservação e o uso adequado da hidroquinona pelos pacientes. Sua concentração usual em preparações magistrais pode atingir até 10% utilizando como veículo diversas bases, inclusive solução hidroalcoólica. A utilização de uma base como o alcoocetoestearílico e um emulsionante não iônico como o polissorbato, o uso de embalagens opacas, pH definido entre 6,0 a 6,5, evitar a presença de oxigênio, utilizar água com alto grau de pureza, sem metais e o uso do antioxidantes metabissulfito de sódio, vão retardam o processo oxidativo e ampliam o prazo de validade para seis meses.