Serotonin system is partially involved in immunomodulation of Nile tilapia (Oreochromis niloticus) immune cells

Abstract

Serotonin (5-hydroxytryptamine) is a well-known neurotransmitter affecting emotion, behavior, and cognition. Additionally, numerous immunomodulatory functions of serotonin have been discovered in mammals. However, the regulatory role of the serotonin system in fish immunity remains unclear. In this study, various serotonergic markers in Nile tilapia (Oreochromis niloticus) were identified and characterized. The involvement of the serotonin system during bacterial infection was investigated. Moreover, the expression characteristics and specific functions of serotonergic markers within Nile tilapia immune cells were also assessed. Overall, 22 evolutionarily conserved serotonergic marker genes in Nile tilapia were cloned and characterized. Transcriptional levels of these molecules were most abundant in the brain, and their transcripts were induced during Streptococcus agalactiae infection. Nevertheless, few serotonergic markers exist on Nile tilapia immune cells, and no distinct immunomodulation effect was observed during an immune response. The present study lays a theoretical foundation for further investigation of the immunological mechanisms in fish as well as the evolution of the serotonin system in animals.

Confocal Identification of Immune Molecules in Skin Club Cells of Zebrafish (Danio rerio, Hamilton 1882) and Their Possible Role in Immunity

“…The 5-HT expression, as already reported by Zaccone et al [ 22 ], can be associated with an immune function, since this neurotransmitter is a powerful immunomodulator involved in several biological processes, such as the stimulation of mucus production by the goblet cells of mucous membranes [ 42 ]. Further modulating social responses to stressors in fish [ 43 , 44 ], 5-HT is involved in immune mechanisms [ 45 ], regulating the inflammatory response, recruiting immune cells, and stimulating the production of cytokines [ 46 ].…”

Medulla oblongata and NCCs are central defenders against Streptococcus agalactiae infection of the tilapia brain

“…Three fish were collected post the acclimation period (at 61 st day), anesthetized using tricaine methanesulfonate (MS-222; Sigma, Darmstadt, Germany), and then euthanized. The entire brain was carefully dissected, and several distinct brain components ( 25 ), including the olfactory bulb, cerebrum, optic lobe, cerebellum, hypothalamus, and medulla oblongata, were sampled for RNA extraction. Additionally, the thin medulla oblongata was divided into two segments along the anterior-posterior axis, referred to as the anterior medulla oblongata and posterior medulla oblongata ( Supplementary Figure S1 ).…”

“…In addition, based on our previous study on the characterization of tilapia head kidney leukocytes (HKLs) through RNA-Seq in 2022 ( 25 ), the geometric mean of three universal housekeeping genes —β-actin , ef1a , and gapdh ( 26 – 28 )—were used to normalize the expression abundance of both the HKL and brain cDNA libraries.…”

“…HKL preparation was carried out following previous research from 2020 to 2023 ( 25 , 31 , 32 ). In brief, healthy fish were collected and sacrificed.…”

Gut–brain communication mediates the impact of dietary lipids on cognitive capacity

“…It conducts signals through a specific receptor 5-HTR to activate an adaptive immune response, and ultimately affects mood, behavior, and cognition. 64,65…”