Imbalance in the ratio between mineralocorticoid and glucocorticoid receptors and neurodegeneration in the dentate gyrus of aged dogs

Vet World Vol.15 November-2022 Article-5

Research Article

Veterinary World, 15(11): 2543-2550

https://doi.org/10.14202/vetworld.2022.2543-2550

Shirley Jaqueline Szriber¹, Leonardo Santana Novaes², Nilton Barreto Dos Santos², Carolina Demarchi Munhoz², and Deise Carla Almeida Leite-Dellova¹

1. Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of Sao Paulo, Duque de Caxias Norte Avenue, 225, 13635-900, Pirassununga, Brazil.
2. Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Professor Lineu Prestes Avenue, 1524, Room 323, 05508-000, Sao Paulo, Brazil.

Background and Aim: Cortisol binds to mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) found in the hippocampus. The balanced expression of these receptors is essential to neuronal survival as MR and GR activations have antiapoptotic and proapoptotic effects, respectively. Given the aging changes in dogs' dentate gyrus (DG) and the possible involvement of cortisol receptors in this process, this study aimed to evaluate the expression of MR and GR and neuronal degeneration in this hippocampal region of aged dogs.

Materials and Methods: This study included cadaveric histologic hippocampus sections from 12 dogs aged 10 years and older (AG group) and six young/adult dogs aged up to 8 years (YAd group). Nissl staining and immunohistochemistry were performed to identify cells and investigate MR and GR expression, respectively. Furthermore, fluorescent labeling (fluoro- Jade B) was used to detect degenerating neurons.

Results: The AG group's polymorphic layer of the DG had a lower cell count (16%) and more degenerating neurons than the YAd group. In addition to these cellular changes, the AG group had lower MR immunoreactivity and MR-to-GR ratio. Furthermore, the lowest MR expression was associated with neuronal degeneration in the polymorphic layer of the DG of dogs.

Conclusion: An imbalance in the MR-to-GR ratio was observed in the polymorphic layer of the DG of aged dogs, along with lower MR expression and a greater number of degenerating neurons. These findings have clinical implications for understanding the decline in hippocampal memory formation associated with cognitive changes in aged dogs. Keywords: aging, canine, cortisol receptors, hippocampus, neuronal loss.

Keywords: aging, canine, cortisol receptors, hippocampus, neuronal loss.

How to cite this article: Szriber SJ, Novaes LS, Santos NB, Munhoz CD, and Leite-Dellova DCA (2022) Imbalance in the ratio between mineralocorticoid and glucocorticoid receptors and neurodegeneration in the dentate gyrus of aged dogs, Veterinary World, 15(11): 2543–2550.

Received: 20-06-2022 Accepted: 20-09-2022 Published online: 10-11-2022

Corresponding author: Shirley Jaqueline Szriber E-mail: shirley_szriber@hotmail.com

DOI: 10.14202/vetworld.2022.2543-2550

Copyright: Szriber, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.