KU812 basophils express urocortin, CRH-R, MC1R and steroidogenic enzymes and secrete progesterone

Little is known about neuroendocrine regulation of human basophils by components of the hypothalamic-pituitary-adrenal (HPA) axis. Using the basophil cell line KU812 as an in vitro model, we show that these cells express urocortin 1-3, specific isoforms of the corticotropin-releasing hormone (CRH) receptor (CRH-R)1 and CRH-R2 but not CRH itself. The precursor for melanocortins and β-endorphin, proopiomelanocortin, was not detectable, while the melanocortin-1 receptor was present at RNA and protein level in KU812 cells. KU812 basophils furthermore expressed key enzymes involved in steroidogenesis, that is, CYP11A1, CYP17 and CYP21A2. The relevance of steroidogenic enzyme expression in KU812 cells was confirmed by showing the presence of progesterone and 17OH-progesterone in conditioned media of these cells. Our data demonstrate the expression of some but not all components of the HPA axis in human basophils. These cells are not only target cells for multiple hormones of the HPA axis but may also generate neuroendocrine mediators autonomously.