ED Sciences de la Vie et de la Santé
Impact of type I interferons on melanocytes function and phenotype in vitiligo
by Ribal MERHI (Immunologie Conceptuelle, Expérimentale et Translationnelle)
The defense will take place at 14h00 - Amphithéatre Université de Bordeaux Campus Carreire, Bat BBS, RDC 2, Rue du Dr Hoffmann Martinot, 33000 Bordeaux
in front of the jury composed of
- Julien SENESCHAL - Professeur des universités - praticien hospitalier - ImmunoConcEpT CNRS UMR5164 - Directeur de these
- Christine VARON - Professeur des universités - BRIC Inserm U1312 - Examinateur
- Christine BALDESCHI - Professeur des universités - INSERM/UEVE UMR 861, I-STEM, AFM - Rapporteur
- Bouaziz JEAN-DAVID - Professeure des universités - praticienne hospitalière - Institut de recherche Saint Louis INSERM U976 HIPI - Examinateur
- Jérémy DI-DOMIZIO - Chargé de recherche - Université de Lausanne, Gilliet-LAB - Rapporteur
Type I Interferons (IFN, including IFNα and IFNβ) are implicated in the immune response in vitiligo, though their role in melanocyte loss is not fully understood. Our single-cell RNA sequencing of perilesional (PL) and non-lesional (NL) skin from active vitiligo patients showed significant upregulation of IFN-stimulated genes in melanocytes, such as IRF9, IFI6, IFI27, Mx1, and Mx2. Previous studies identified plasmacytoid dendritic cells producing IFNα in active vitiligo PL skin. Our data revealed increased IFNβ expression in the epidermis of vitiligo PL skin. TLR9 agonists, combined with heat shock protein-70 , a classical danger signal associated with vitiligo, triggered high IFNβ release by keratinocytes. Melanocytes from PL skin of active patients exhibited increased expression of the type I IFN receptor (IFNAR). In vitro stimulation with IFNα and/or IFNβ led to significant phosphorylation of STAT1, demonstrating functional IFNAR in melanocytes. Transcriptional profiling of melanocytes stimulated with IFNα and/or IFNβ revealed heightened signaling pathways related to oxidative stress, DNA damage, and cellular senescence. IFNβ alone or combined with IFNα induced senescence markers, including β-galactosidase, p16, and p21 in primary melanocyte cultures and in a 3D model of pigmented human epidermis. Immunofluorescence analyses of vitiligo PL skin showed increased p16 and p21 expression in melanocytes. Components of the senescence-associated secretory phenotype - IL-6, IL-8, CCL5, ICAM1, MMP2 - were elevated in supernatants of IFN-I-treated melanocytes. Finally, treatment of vitiligo patients with baricitinib (a JAK1 and 2 inhibitor) was associated with a decreased expression of the IFN-I response and the senescence marker p21 in melanocytes. Altogether our data highlight the potential of targeting type I IFN in patients to prevent melanocytes loss.
Anatomo-functional vulnerability of dopaminergic transmission to manipulations of vitamin A status
by Pauline COUTY (Nutrition et Neurobiologie Intégrée)
The defense will take place at 14h00 - Amphitéâtre Broca 146 rue Léo Saignat Centre Broca Nouvelle-Aquitaine 33076 Bordeaux Cedex
in front of the jury composed of
- Wojciech KREZEL - Directeur de recherche - Université Louis Pasteur de Strasbourg - Rapporteur
- Corinne BEURRIER - Chargée de recherche - Aix-Marseille Université - Rapporteur
- Patrick BOREL - Directeur de recherche - Aix-Marseille Université - Examinateur
- Elodie FINO - Chargée de recherche - Aix-Marseille Université - Examinateur
- Francis CHAOULOFF - Directeur de recherche - Université de Bordeaux - Examinateur
- Katia TOUYAROT - Maîtresse de conférences - Bordeaux INP - Directeur de these
Vitamin A deficiency during the perinatal period, caused by a vitamin A-deficient diet, remains a major public health issue, especially in developing countries. Retinoic acid (RA), the active metabolite of vitamin A, is essential for the brain development of the fetus and newborn, and plays a very important role in brain function in adulthood. By binding to its nuclear receptors, which act as transcription factors, RA regulates the expression of numerous genes, notably those involved in dopaminergic transmission within the striatum. On the other hand, reduced maternal vitamin A status during gestation or genetic polymorphisms in the retinoid signaling pathway have been associated with certain neurodevelopmental psychiatric diseases, such as schizophrenia, although the underlying mechanisms remain to be established. This is the background to this thesis, with the aim of studying the consequences of vitamin A deficiency initiated during gestation in mice on the modulation of vitamin A metabolism and its impact on the functionality of dopaminergic transmission in adult offspring. We hypothesize that hypoactivity of retinoid signaling could lead to dysfunction of dopaminergic transmission in the striatum, characteristic of certain neurodevelopmental pathologies. In this study, we show that perinatal vitamin A deficiency in mice induces hypoactivity of retinoid signaling associated with alterations in dopaminergic transmission in adult offspring, which are more pronounced in the nucleus accumbens (NAc) than in the dorsal striatum. More specifically, decreased expression of dopamine transporter (DAT) and dopamine receptor 3 (D3R) mRNA is observed in vitamin A-deficient offspring in the ventral tegmental area (VTA) and NAc, respectively. These neurobiological alterations in the mesolimbic dopaminergic transmission pathway are accompanied in deficient male offspring by an increase in motivational processes and impulsivity assessed in operant conditioning tasks, in contrast to deficient female offspring who appear to be protected. To further investigate mesolimbic transmission, we studied mesolimbic dopaminergic activity in vivo in our model, combining the dLight dopaminergic biosensor with fiber photometry. We have shown that perinatal vitamin A deficiency alters dopaminergic dynamics in vivo, leading to an increase in phasic dopamine release in the NAc during operant conditioning tasks. Finally, the causal link between alterations in mesolimbic dopaminergic transmission and the behavioral changes observed in vitamin A-deficient offspring was investigated using viral approaches (DREADDs) to manipulate the activity of dopaminergic neurons. In conclusion, this thesis demonstrates the importance of retinoid signaling, during and after the perinatal period, in maintaining the integrity of mesolimbic dopaminergic transmission. This study suggests that reduced vitamin A status in several neurodevelopmental psychiatric disorders may play a role in certains aspects of the symptomatology of these pathologies, such as motivational or impulsive disorders. Thus, nutritional supplementation with vitamin A could be envisaged as a nutritional strategy to prevent cognitive processes altered by vitamin A deficiency, in the context of these pathologies, and enable normal brain development in children.