Role of melanocortin system in the zebrafish skin physiology

XIII Congress of the Iberian Association of Comparative Endocrinology - AIEC (online), 16-17 September 2021
The melanocortin system is one of the most complex hormonal systems in vertebrates. The main melanocortin peptides are the melanocyte-stimulating hormones (MSHs) and adrenocorticotropic hormone (ACTH), all of them encoded by a common precursor named proopiomelanocortin (POMC), which is expressed mainly in the pituitary. Melanocortin signaling is mediated by a family of G protein-coupled receptors. In tetrapod species, five different subtypes (MC1R-MC5R) has been characterized yet number diverges in fish species. Melanocortin signaling is mediated also by endogenous antagonists which compete with melanocortin agonist by binding to MCRs. Agouti-signaling protein (ASIP) is mainly expressed in the skin where compete by binding to MC1R whereas agouti-related protein (AGRP) is expressed in the hypothalamus to regulate energy balance by binding central MC3R and MC4R. The skin plays a crucial role in the immune function, working as a physical impediment against infestation yet also as a chemical barrier through its ability to synthesizes and secretes mucus. In addition, the skin can be considered also as part of the adaptive immune response characterized by a much more specific response to pathogens. The melanocortin system has been described to regulate inflammatory process which constitutes a key point in the defense response against the damage factors and it is an important component of the innate immune system. Our recent studies using a zebrafish strain overexpressing ASIP1 have demonstrated the participation of the melanocortin system in the regulation of skin physiology. This transgenic model thus constitutes a key opportunity to evaluate the role of the melanocortins in the skin immune response. Our results show that transgenic fish exposed to lypopolysaccharide (LPS) are capable to increase significantly the mRNA levels of pro-inflammatory skin cytokines, suggesting better immune response than wild type fish against bacterial infections
Founded by Spanish Science and Innovation Ministry, project PID2019-103969RB-C33.