Vagotomy Affects Lipopolysaccharide-Induced Changes of Urocortin 2 Gene Expression in the Brain and on the Periphery

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Vagotomy Affects Lipopolysaccharide-Induced Changes of Urocortin 2 Gene Expression in the Brain and on the Periphery Andrej Tillinger1   · Boris Mravec1,2  Received: 22 July 2020 / Revised: 28 October 2020 / Accepted: 31 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract The corticotropin-releasing hormone family of peptides is involved in regulating the neuroendocrine stress response. Also, the vagus nerve plays an important role in the transmission of immune system-related signals to brain structures, thereby orchestrating the neuroendocrine stress response. Therefore, we investigated gene expression of urocortin 2 (Ucn2) and c-fos, a markers of neuronal activity, within the hypothalamic paraventricular nucleus (PVN), a brain structure involved in neuroendocrine and neuroimmune responses, as well as in the adrenal medulla and spleen in vagotomized rats exposed to immune challenge. In addition, markers of neuroendocrine stress response activity were investigated in the adrenal medulla, spleen, and plasma. Intraperitoneal administration of lipopolysaccharide (LPS) induced a significant increase of c-fos and Ucn2 gene expression in the PVN, and adrenal medulla as well as increases of plasma corticosterone levels. In addition, LPS administration induced a significant increase in the gene expression of tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla. In the spleen, LPS administration increased gene expression of c-fos, while gene expression of TH and PNMT was significantly reduced, and gene expression of Ucn2 was not affected. Subdiaphragmatic vagotomy significantly attenuated the LPS-induced increases of gene expression of c-fos and Ucn2 in the PVN and Ucn2 in the adrenal medulla. Our data has shown that Ucn2 may be involved in regulation of the HPA axis in response to immune challenge. In addition, our findings indicate that the effect of immune challenge on gene expression of Ucn2 is mediated by vagal pathways. Keywords  Urocortin 2 · Hypothalamus · Adrenal medulla · Corticosterone · Lipopolysaccharide · Vagus nerve

Introduction In the last decades, neuropeptides from the corticotropinreleasing hormone family, namely corticoliberine and urocortins 1–3, have emerged as central components of the neuroendocrine stress response [1]. These peptides participate in the neuroendocrine stress response at the level of the brain as well as the adrenal glands [2, 3]. The mRNA of urocortin 2 (Ucn2), a specific agonist of the CRH receptor type 2 (CRHR2), is widely distributed in peripheral tissues with high levels found in the skin and * Andrej Tillinger [email protected] 1



Institute of Experimental Endocrinology, Biomedical Research Center of the Slovak Academy of Sciences, Bratislava, Slovakia



Institute of Physiology, Faculty of Medicine, Comenius University in Bratislava, Bratislava, Slovakia

2

muscles and moderate levels found in the lungs, stomach, adrenals, ovary, spleen, and thymus. Expressio