Expression of chemokine CXCL10 in dendritic-cell-like S100β-positive cells in rat anterior pituitary gland

Chemokines are mostly small secreted polypeptides whose signals are mediated by seven trans-membrane G-protein-coupled receptors. Their functions include the control of leukocytes and the intercellular mediation of cell migration, proliferation, and adhesion in several tissues. We have previously revealed that the CXC chemokine ligand 12 (CXCL12) and its receptor 4 (CXCR4) are expressed in the anterior pituitary gland, and that the CXCL12/CXCR4 axis evokes the migration and interconnection of S100 beta-protein-positive cells (S100 beta-positive cells), which do not produce classical anterior pituitary hormones. However, little is known of the cells producing the other CXCLs and CXCRs or of their characteristics in the anterior pituitary. We therefore examined whether CXCLs and CXCRs occurred in the rat anterior pituitary lobe. We used reverse transcription plus the polymerase chain reaction to analyze the expression of Cxcl and Cxcr and identified the cells that expressed Cxcl by in situ hybridization. Transcripts of Cxcl10 and its receptor (Cxcr3 and toll-like receptor 4, Tlr4) were clearly detected: cells expressing Cxcl10 and Tlr4 were identified amongst S100 beta-positive cells and those expressing Cxcr3 amongst adrenocorticotropic hormone (ACTH)-producing cells. We also investigated Cxcl10 expression in subpopulations of S100 beta-positive cells. We separated cultured S100 beta-positive cells into the round-type (dendritic-cell-like) and process-type (astrocyte- or epithelial-cell-like) by their adherent activity to laminin, a component of the extracellular matrix; CXCL10 was expressed only in round-type S100 beta-positive cells. Thus, CXCL10 produced by a subpopulation of S100 beta-positive cells probably exerts an autocrine/paracrine effect on S100 beta-positive cells and ACTH-producing cells in the anterior lobe.