Thyroid signaling in immune organs and cells of the teleost fish rainbow trout (Oncorhynchus mykiss)

• Published in: Fish & shellfish immunology Vol. 38; no. 1; pp. 166 - 174
• Main Authors: Quesada-García, A., Valdehita, A., Kropf, C., Casanova-Nakayama, A., Segner, H., Navas, J.M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-05-2014
• Subjects: Animals; Gene Expression Regulation - immunology; Head Kidney - physiology; Immune cell markers; Oncorhynchus mykiss - physiology; Propylthiouracil; Rainbow trout; Receptors, Thyrotropin - genetics; Receptors, Thyrotropin - metabolism; Signal Transduction - physiology; Spleen - physiology; Thyroid Gland - physiology; Thyroid receptors; Triiodothryronine; Propylthiouracil; Triiodothryronine; Immune cell markers; Rainbow trout; Thyroid receptors
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2014.03.016

Thyroid hormones are involved in modulating the immune system in mammals. In contrast, there is no information on the role played by these hormones in the immune system of teleost fish. Here we provide initial evidence for the presence of active thyroid signaling in immune organs and cells of teleosts. We demonstrate that immune organs (head kidney and spleen) and isolated leukocytes (from head kidney and peripheral blood) of the rainbow trout (Oncorhynchus mykiss) express both thyroid receptor α (THRA) and β (THRB). Absolute mRNA levels of THRA were significantly higher than those of THRB. THRA showed higher expression in immune organs and isolated immune cells compared to the reference organ, liver, while THRB showed the opposite. In vivo exposure of trout to triiodothryronine (T3) or the anti-thyroid agent propylthiouracil (PTU) altered THR expression in immune organs and cells. Effect of T3 and PTU over the relative expression of selected marker genes of immune cell subpopulations was also studied. Treatments changed the relative expression of markers of cytotoxic, helper and total T cells (cd4, cd8a, trb), B lymphocytes (mIgM) and macrophages (csf1r). These findings suggest that the immune system of rainbow trout is responsive to thyroid hormones.
•Immune organs and cells of the rainbow trout express both thra and thrb.•Thra is predominantly expressed in immune organs and in immune cells.•In vivo exposure to T3 and PTU alters THR expression in immune cells of juvenile rainbow trout.•Exposure to T3 and PTU also causes changes in selected molecular markers.