Immunolocalization of corticosteroid hormone receptors in the mechanoreceptors in rat oral tissues

Abstract

Previous studies have confirmed the presence of corticosteroid receptors including mineralocorticoid (MCR) and glucocorticoid receptors (GCR) in the glia cells of both central and peripheral nervous systems. However, no report has been offered as yet on the detailed localization of these receptors in the specialized Schwann cells associated with mechanoreceptors. Thus, the present study examined the immunolocalization of MCR and GCR in the specialized Schwann cells (terminal and lamellar Schwann cells) associated with the mechanoreceptors in rat periodontal ligament and palatal mucosa by the use of immunohistochemical techniques and confocal laser scanning microscopy. It further attempted to detect the localization of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD II), a key enzyme for signal transduction via MCR. Immunostaining with antisera against GCR and MCR demonstrated intense immunoreactions in the terminal or lamellar Schwann cells but not nerve fibers associated with the periodontal and palatal mechanoreceptors. A double staining with propidium iodide and either GCR- or MCR-antiserum revealed the intranuclear and cytoplasmic localization of these receptors in the terminal Schwann cells. 11β-HSD II-immunoreactivity was found in the cytoplasm and on the nuclear envelope of the terminal Schwann cells, indicating the co-localization of MCR and 11β-HSD II in them. These findings suggest that the terminal or lamellar Schwann cells are target tissues for corticosteroid hormones. Taken together with previous reports on the functional significance of the corticosteroids, the results indicate that glucocorticoids and mineralocorticoids might be respectively involved in the proliferation and/or differentiation and Na+/K+-homeostasis in the terminal or lamellar Schwann cells associated with the mechanoreceptors.