Exogenous sulphide donors modify the gene expression patterns of Atlantic salmon nasal leukocytes

Nikko Alvin R Cabillon,Carlo C Lazado

doi:10.1016/j.fsi.2021.11.005

Nikko Alvin R Cabillon, Carlo C Lazado

Open Access

https://doi.org/10.1016/j.fsi.2021.11.005

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Abstract

Hydrogen sulphide (H2S) is a known mediator of immunity, but the regulatory function of its exogenous form is not well understood in fish particularly in the mucosa. Here we report transcriptomic changes in the nasal leukocytes of Atlantic salmon (Salmo salar) following exposure to two forms of H2S donors – the salt sodium hydrosulfide (NaHS) and the organic analogue morpholin-4-ium 4-methoxyphenyl (morpholino) phosphinodithioate (GYY4137). Nasal leukocytes were exposed to three concentrations (1, 10 and 100 μM) of either of the two H2S forms for 24 h before the cells were checked for viability and collected for microarray analysis. Though cellular viability was minimally affected by the exposure to two H2S donors, GYY4137-exposed cells exhibited reduced viability compared with the NaHS group at the highest dose. The H2S-induced transcriptomic changes in the nasal leukocytes were concentration-dependent regardless of the sulphide forms. However, a larger number of differentially expressed genes (DEGs) were identified in the NaHS-exposed versus GYY4137-exposed groups across concentrations. In all comparisons, at least 53% of the DEGs identified were significantly upregulated. Gene ontology (GO) terms enriched in the lists of upregulated DEGs at higher concentrations included ferric iron binding. A comparison of the two H2S forms showed a clear grouping of different GO terms relative to concentrations. Pathway enrichment analysis revealed a significant influence in VEGF ligand-receptor interactions, oxidative stress, innate and adaptive immunity, and interleukin signalling especially at higher concentrations. Congruence analysis demonstrated that there were 16 GO terms overlapping; of these, 12 were upregulated by both sulphide donors including several involving iron binding and transport. The study offers the first molecular insights into how fish nasal leukocytes respond to exogenous H2S, and the results will be vital in resolving the regulatory function of H2S on mucosal immunity in fish.

Highlights

Olfaction is one of the oldest senses in the animal kingdom and fa cilitates odour-based identification of food, potential mating partners, dangers, and enemies; it is often the most important way of interacting with the environment [1]
A significant difference was identified between the two sulphide forms at 100 μM where cellular viability in the GYY4137 group was significantly lower than the NaHS group
In the 10 μM vs 100 μM study, we found that NaHS affected transcriptional activation of mitochondrial biogenesis and VEGFR2 mediated vascular permeability while pathways related to LAT2/NTAL/LAB on calcium mobilisation and DNA replica tion were enriched in GYY4137

Summary

Introduction

Olfaction is one of the oldest senses in the animal kingdom and fa cilitates odour-based identification of food, potential mating partners, dangers, and enemies; it is often the most important way of interacting with the environment [1]. Besides its role in olfaction, the ol factory organ has a fundamental defence function as characterised by a mucosal microenvironment with a myriad of molecular and cellular immune components [2,3]. The nasopharynx-associated lymphoid tis sue possesses B-, T-, and myeloid cells in addition to an array of innate and adaptive immune molecules [4]. These intricate layers of defence protect and maintain the balance in the nasal microenvironment, which is crucial because the olfactory organ is a portal of entry for several pathogens and is attacked by waterborne chemical stressors [3,4]. Its toxicity mechanism is via interruption of mitochondrial cellular respiration through binding to

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