Vitiligo is an acquired depigmenting disorder characterised by the loss of functional melanocytes and of melanin from the cutaneous epidermis. A role for autoimmunity in vitiligo pathogenesis is supported by the presence of anti-melanocyte autoantibodies and autoreactive T lymphocytes in patients with the disorder. Recently, the melanin-concentrating hormone receptor 1 (MCHRI) has been identified as an autoantigen in vitiligo. The aim of this study was to characterise the properties of MCHR1 autoantibodies. The epitopes on MCHR1 that are recognised by autoantibodies in vitiligo patients were identified using recombinant receptor in radio-binding assays. Multiple regions of MCHR1, including regions between amino acids 1-138 and 139-298, were identified as binding sites for MCHR1 autoantibodies. In addition, biopanning of a phage-display MCHRI cDNA fragment library with vitiligo patient immunoglobulin G (IgG), identified more specifically the target sites of MCHRI autoantibodies. A stable Chinese hamster ovary cell line expressing MCHR1 was isolated. The cell line clearly showed expression of the receptor by flow cytometry. Stimulation of the cell line with melanin-concentrating hormone (MCH) reduced forskolinstimulated cyclic adenosine monophosphate levels and increased the levels of intracellular calcium, both indicative of MCHRI expression. Functional blocking of MCI-iR1 by receptor autoantibodies was investigated by measuring changes in intracellular calcium levels in response to MCH-stimulation of MCHRI-expressing cells that had been pre-incubated with vitiligo patient IgG. The results revealed that 10/18 (56%) of the vitiligo patient IgGs tested were able to block receptor function. In contrast, IgG from healthy controls and from patients with other autoimmune disease had no effect upon receptor function. This suggested that MCHR1 function blocking autoantibodies are specific to patients with vitiligo and are not present in patients with other autoimmune disease. The cell line expressing MCHR1 was also used to analyse MCHR1 autoantibodies for any immunological activities such as complement-fixation and antibody-dependent cell-mediated cytotoxicity (ADCC). None of the vitiligo patient sera tested appeared to have MCHRI autoantibodies that were able either to fix complement or mediate ADCC. This suggested that there are no such immunological activities against MCHR1. In conclusion, key findings from this study were that the MCHRI is an important autoantigen in vitiligo, with 56% of patients having function-blocking autoantibodies against the receptor, and that amino acids 1-138 and 139-298 are major epitopes for MCHR1 binding autoantibodies.

No description available.

Albinism is an uncommon genetic condition characterised by hypopigmentation of the hair, skin and eyes; and is associated with reduced vision, nystagmus and high refractive errors. Currently there is discrepancy in the literature in terms of the most prevalent form of refractive error in albinism. This thesis investigates refractive development in children with albinism. As nystagmus is a common feature of albinism, a group of children with Idiopathic Infantile Nystagmus (IIN) were also recruited in order to examine the effects of nystagmus on vision and refractive error. The Northern Ireland Nystagmus and Albinism (NINA) Study began in Autumn 2008 and concluded in Winter 2011. A series of retrospective, cross-sectional, prospective and imaging studies combined to explore refractive error and visual function in 105 participants (albinism n=73, IIN n=32) aged 4.5 months to 47 years. The findings were compared to published data on visually normal children and adults. The data demonstrated the following: • The most prevalent form of refractive error in albinism is hypermetropia. • High magnitudes of with- the-rule astigmatism are commonly found in albinism. • The emmetropisation process is impaired in albinism; infantile spherical and astigmatic refractive errors tend not to decrease with increasing age. • The degree of foveal hypoplasia demonstrated in albinism is related to visual acuity; poor acuity being associated with more severe hypoplasia. • The diagnoses of several individuals recruited with IIN were re-explored subsequent to their participation.

No description available.

Vitiligo is the most common skin disorder resulting in depigmentation, but high-quality research is lacking. A Cochrane review of interventions for vitiligo published in 2010 highlighted methodological limitations with existing trials; which have generally been too small and heterogeneous to inform clinical recommendations. The objective of this thesis was to improve the evidence base for the treatment of vitiligo. This PhD was funded by the National Institute for Health Research, as part of the research programme called “Setting Priorities and Reducing Uncertainties for people with Skin Diseases”. It includes the following: 1) identifying the most important research priorities for patients and clinicians, thereby informing the research agenda; 2) conducting a systematic review of outcome measures used in vitiligo trials and a survey of the most desirable outcomes for patients and clinicians; and 3) conducting a pilot double blind, randomised controlled trial (RCT) on home hand-held phototherapy in preparation of the first national multi-centre RCT for the treatment of vitiligo. For the prioritisation exercise, a total of 660 treatment uncertainties were submitted by 460 patients and clinicians. The identified priority areas included interventions such as combination of topical agents and phototherapy. The systematic review on outcome measures identified 25 different domains that had been used in previous trials. Although percentage repigmentation was measured in 96%; 48 different scales had been used. In contrast, patients and clinicians favoured the use of “cosmetically acceptable” repigmentation. Finally, a 4-month pilot trial recruited 29 participants and tested the logistics of running a future RCT. This work resulted in a commissioned call and funding of a national RCT on vitiligo (topical corticosteroids in combination with home hand-held phototherapy); the initiation of an international consensus exercise on core outcome measures for use in vitiligo trials; and informed the design and conduct of a future national RCT.

Le purinorécepteur P2X7 joue un rôle majeur dans les phénomènes de dégénérescences (Alzheimer, DMLA) et mort cellulaires. Récemment des études ont montré que l’activation basale de ce récepteur est indispensable dans le processus de cicatrisation et de prolifération cellulaire. Nous avons essayé de mieux comprendre le paradoxe de cette activation du récepteur P2X7 qui oriente vers la prolifération et même les métastases tumorales, mais aussi vers les mécanismes de dégénérescence cellulaire. L'influence du microenvironnement (Lipides, matrice extracellulaire, oxygène) apparait essentielle pour comprendre ces différents effets. Notre premier objectif a été d’étudier l’impact de la modulation du microenvironnement du récepteur P2X7 par des composants de la matrice extracellulaire. Ainsi, sur un modèle de cicatrisation cutanée, nous avons mis en évidence l’impact de la taille des fragments du hyaluronate de sodium (composant prédominant dans la matrice extracellulaire). Nos résultats ont montré que l’activation du récepteur P2X7 dépend du poids moléculaire du hyaluronate de sodium. Notre deuxième objectif a été de moduler le microenvironnement lipidique du récepteur P2X7. Nous avons sélectionné une huile riche en acides gras insaturés et avons ainsi étudié son effet sur l’activation du récepteur P2X7. Sur nos modèles de cicatrisation, nous avons mis en évidence qu’une modulation du microenvironnement lipidique du récepteur P2X7 influence son activation. D’autre part la modulation du microenvironnement lipidique sur des cellules tumorale de mélanome active les voies de dégénérescence ouvrant la perspective de nouvelles stratégies thérapeutiques. / The purinoceptor P2X7 plays a role in cytotoxic degenerative processus (Alzheimer, AMD) and cell death. Recent studies have shown that basal activation of this receptor is essential in the healing process and cell proliferation. We tried to understand the paradox that activation of P2X7 receptor that directs to the same proliferation and tumor metastasis, but also to the mechanisms of cell degeneration. The influence of the microenvironment (lipids, extracellular matrix, oxygen) appears essential to understand these effects. Our first objective was to study the impact of the modulation of P2X7 receptor microenvironment by extracellular matrix components. On cell monolayer model of wound healing we have highlighted the impact hyaluronan molecular weight (predominant component in the extracellular matrix). Our results showed that activation of P2X7 receptor is dependent on hyaluronan molecular weight. Our second objective was to modulate lipid microenvironment P2X7 receptor. We selected an oil rich in unsaturated fatty acids and thus have studied its effect on the activation of P2X7 receptor. In our models of healing and melanoma cell, we have demonstrated that modulation of lipid microenvironment affects P2X7 activation.