CGRP-immunoreactive nerves in prurigo nodularis - an exploration of neurogenic inflammation

Background: The present study has explored the localization and distributio n of calcitonin gene-related peptide (CGRP)-immunoreactive (IR) nerve fiber s in prurigo nodularis, especially emphasizing its relationships to mast ce lls and eosinophils, which all are important contributors to inflammation. Methods: The exact localization of CGRP in the nerve fibers of prurigo nodu laris lesional skin has been clarified by an ultrastructural immunogold lab elling technique; and the relationships of CGRP-IR nerve fibers to tryptase -IR mast cells or eosinophil cationic protein (ECP)-IR eosinophils were als o investigated by immunofluorescence double-labelling. Results: This ultrastructural study has demonstrated that CGRP immunoreacti vity is increased in the dense-core vesicles in the axons of the prurigo no dularis lesional skin; the axons which contain CGRP are, in addition, enlar ged and have more dense-core vesicles than the axons which do not contain C GRP. The immunofluorescence investigation demonstrated that tryptase-contai ning mast cells and ECP-containing eosinophils also are significantly incre ased in the lesional skin. Conclusions: The results indicate that certain neurons increasingly express CGRP, which may dynamically result in a neurogenic inflammation in the les ional skin, through vasodilatation, and recruitment and regulation of infla mmatory cells, e.g. eosinophils and mast cells.