Muriel Cario-André

Protective effects of catalase overexpression on UVB-induced apoptosis in normal human keratinocytes.

UV-induced apoptosis in keratinocytes is a highly complex process in which various molecular pathways are involved. These include the extrinsic pathway via triggering of death receptors and the intrinsic pathway via DNA damage and reactive oxygen species (ROS) formation. In this study we investigated the effect of catalase and CuZn-superoxide dismutase (SOD) overexpression on apoptosis induced by UVB exposure at room temperature or 4 °C on normal human keratinocytes. Irradiation at low temperature reduced UV-induced apoptosis by 40% in normal keratinocytes independently of any change in p53 and with a decrease in caspase-8 activation. Catalase overexpression decreased apoptosis by 40% with a reduction of caspase-9 activation accompanied by a decrease in p53. Keeping cells at low temperature and catalase overexpression had additive effects. CuZn-SOD overexpression had no significant effect on UVB-induced apoptosis. UVB induced an increase in ROS levels at two distinct stages: immediately following irradiation and around 3 h after irradiation. Catalase overexpression inhibited only the late increase in ROS levels. We conclude that catalase overexpression has a protective role against UVB irradiation by preventing DNA damage mediated by the late ROS increase.

Hematopoietic stem cell gene therapy of murine protoporphyria by methylguanine-DNA-methyltransferase-mediated in vivo drug selection

Erythropoietic protoporphyria (EPP) is an inherited defect of the ferrochelatase (FECH) gene characterized by the accumulation of toxic protoporphyrin in the liver and bone marrow resulting in severe skin photosensitivity. We previously described successful gene therapy of an animal model of the disease with erythroid-specific lentiviral vectors in the absence of preselection of corrected cells. However, the high-level of gene transfer obtained in mice is not translatable to large animal models and humans if there is no selective advantage for genetically modified hematopoietic stem cells (HSCs) in vivo. We used bicistronic SIN-lentiviral vectors coexpressing EGFP or FECH and the G156A-mutated O6-methylguanine-DNA-methyltransferase (MGMT) gene, which allowed efficient in vivo selection of transduced HSCs after O6-benzylguanine and BCNU treatment. We demonstrate for the first time that the correction and in vivo expansion of deficient transduced HSC population can be obtained by this dual gene therapy, resulting in a progressive increase of normal RBCs in EPP mice and a complete correction of skin photosensitivity. Finally, we developed a novel bipromoter SIN-lentiviral vector with a constitutive expression of MGMT gene to allow the selection of HSCs and with an erythroid-specific expression of the FECH therapeutic gene.

Segmental vitiligo as the possible expression of cutaneous somatic mosaicism : implications for common non-segmental vitiligo

Clinical findings in vitiligo challenge the widely accepted organ specific autoimmune pathomechanisms. We draw the attention to the fact that the distribution of segmental vitiligo (SV) fits in at least a subset of patients a pattern usually associated with cutaneous mosaicism. The association of SV to non‐segmental vitiligo (NSV) now confirmed by several observations indicates a continuum between the two subsets with shared predisposing genetic factors, including genes operating specifically in the skin. Some pedigrees associating SV and NSV further suggest a mechanism of loss of heterozygosity for a dominant gene controlling part of the cutaneous phenotype. The mosaic hypothesis applies only to SV and to the rare SV‐NSV association, but suggests that predisposing genetic factors in common NSV should also be searched directly in the skin. SV would be a good candidate disease to explore as a proof of principle of a new gene discovery strategy useful for multigenic disorders with organ specificity, applicable in priority to chronic inflammatory skin disorders.

Loss of epidermal hypoxia-inducible factor-1α accelerates epidermal aging and affects re-epithelialization in human and mouse

In mouse and human skin, HIF-1α is constitutively expressed in the epidermis, mainly in the basal layer. HIF-1α has been shown to have crucial systemic functions: regulation of kidney erythropoietin production in mice with constitutive HIF-1α epidermal deletion, and hypervascularity following epidermal HIF-1α overexpression. However, its local role in keratinocyte physiology has not been clearly defined. To address the function of HIF-1α in the epidermis, we used the mouse model of HIF-1α knockout targeted to keratinocytes (K14-Cre/Hif1aflox/flox). These mice had a delayed skin phenotype characterized by skin atrophy and pruritic inflammation, partly mediated by basement membrane disturbances involving laminin-332 (Ln-332) and integrins. We also investigated the relevance of results of studies in mice to human skin using reconstructed epidermis and showed that HIF-1α knockdown in human keratinocytes impairs the formation of a viable reconstructed epidermis. A diminution of keratinocyte growth potential, following HIF-1α silencing, was associated with a decreased expression of Ln-322 and α6 integrin and β1 integrin. Overall, these results indicate a role of HIF-1α in skin homeostasis especially during epidermal aging.

Altered E-Cadherin Levels and Distribution in Melanocytes Precede Clinical Manifestations of Vitiligo

Vitiligo is the most common depigmenting disorder resulting from the loss of melanocytes from the basal epidermal layer. The pathogenesis of the disease is likely multifactorial and involves autoimmune causes, as well as oxidative and mechanical stress. It is important to identify early events in vitiligo to clarify pathogenesis, improve diagnosis, and inform therapy. Here, we show that E-cadherin (Ecad), which mediates the adhesion between melanocytes and keratinocytes in the epidermis, is absent from or discontinuously distributed across melanocyte membranes of vitiligo patients long before clinical lesions appear. This abnormality is associated with the detachment of the melanocytes from the basal to the suprabasal layers in the epidermis. Using human epidermal reconstructed skin and mouse models with normal or defective Ecad expression in melanocytes, we demonstrated that Ecad is required for melanocyte adhesiveness to the basal layer under oxidative and mechanical stress, establishing a link between silent/preclinical, cell-autonomous defects in vitiligo melanocytes and known environmental stressors accelerating disease expression. Our results implicate a primary predisposing skin defect affecting melanocyte adhesiveness that, under stress conditions, leads to disappearance of melanocytes and clinical vitiligo. Melanocyte adhesiveness is thus a potential target for therapy aiming at disease stabilization.

Halo naevi and leukotrichia are strong predictors of the passage to mixed vitiligo in a subgroup of segmental vitiligo.

Backgroundu2002 Until now, segmental vitiligo has been considered as a stable entity and mixed vitiligo, the association of segmental and nonsegmental vitiligo, has been reported rarely.

Epidermal reconstructs: a new tool to study topical and systemic photoprotective molecules

In this study, we compared the effects of sunscreens and antioxidants on reconstructed epidermis made with or without melanocytes 24 h after UVB, UVA or UVA+B irradiation. For this purpose, we studied sunburn cells and cyclobutane pyrimidine dimer formation, protein and lipid oxidation, catalase and superoxide dismutase activities and vitamin E levels. Topical sunscreens protected against direct cell death and thymine dimer formation whereas their protective effect against protein and lipid oxidation and antioxidant depletion was less marked partly due to the difficulty of spreading the cream. Antioxidant molecules protected against direct cell death and protein oxidation but not against thymine dimer formation. Since topical sunscreens and systemic antioxidant protected the skin differently, we speculate that their association might protect more efficiently against UV-induced damage. This model is relevant to study systemic molecules but is less practical, due to the technical limitations of studying topical molecules.

Pre‐ vs. post‐pubertal onset of vitiligo: multivariate analysis indicates atopic diathesis association in pre‐pubertal onset vitiligo

Backgroundu2002 Limited epidemiological data exist that compare clinical features of pre‐ and post‐pubertal nonsegmental vitiligo.

A Prospective Study of Filaggrin Null Mutations in Keratoconus Patients with or without Atopic Disorders

Background: Atopic dermatitis (AD) is significantly associated with keratoconus (KC). An inherited component for KC has been suggested. Filaggrin (FLG) mutations are a strong genetic risk factor for AD. Since filaggrin is also expressed in the corneal epithelium, we hypothesized a common aetiology for ichthyosis vulgaris (IV), AD and KC. Objectives: We examined the prevalence of AD and IV in a KC population. We also studied the expression of filaggrin in normal and KC cornea and analysed 2 prevalent loss-of-function FLG alleles (R501X and 2282del4) in a KC population. Finally we examined whether the population with KC and FLG mutations had specific clinical characteristics. Results: Of 89 KC patients, 38 had current or a history of AD and/or IV. Five patients were carriers of at least 1 FLG mutant allele and had a clinical diagnosis of AD and IV with a severer KC. Conclusion: The low frequency of FLG mutations is surprising since 42.7% of our KC population had AD associated or not with IV; the expected frequency would have been 12–15%, based on our previous studies. Further studies are required to look at other possible FLG mutations or other candidate genes.

Halo Nevi Association in Nonsegmental Vitiligo Affects Age at Onset and Depigmentation Pattern

OBJECTIVEnTo compare factors associated with halo nevi with nonsegmental vitiligo (NSV) vs NSV alone.nnnDESIGNnProspective observational study in 553 patients with a confirmed diagnosis of NSV attending a vitiligo clinic between January 1, 2006, and July 1, 2010.nnnSETTINGnVitiligo Clinic at the Department of Dermatology, University Hospital Center of Bordeaux, Bordeaux, France.nnnPATIENTSnThe Vitiligo European Task Force questionnaire was informed for each patient attending the clinic with a confirmed diagnosis of NSV after the exclusion of other forms of vitiligo (focal, mucosal, and not classifiable). Thyroid function and antithyroid antibodies were screened if not obtained in the previous year.nnnMAIN OUTCOME MEASURESnExtent of disease and markers of autoimmunity or autoinflammation.nnnRESULTSnOf the 553 patients, 130 had halo nevi-NSV and 423 had NSV. Family history of premature hair graying (odds ratio, 1.74; P < .01) was positively associated with halo nevi-NSV by univariate analysis. Using multivariate analysis, age at onset younger than 18 years, phototype, total body area, localization on the trunk, involvement of hands and feet, and total staging were found to be independent factors. Age at onset younger than 18 years; phototypes I, II, and III; trunk involvement; and staging were positively associated with halo nevi-NSV, whereas this association was negative for total affected area and involvement of hands and feet.nnnCONCLUSIONSnHalo nevi association in NSV affects age at onset and depigmentation pattern and has a stronger link with familial premature hair graying, suggesting that premature hair graying may involve, at least partly, an autoimmune pathway.