Genome‐wide analysis of Toll‐like receptors in zebrafish and the effect of rearing temperature on the receptors in response to stimulated pathogen infection

Abstract

Water temperature has a major influence on the host innate immune defence and the infectivity of pathogens in ectothermic teleosts. Toll‐like receptors (TLRs) are the first and well‐characterized innate immune receptors that are conserved in vertebrates. However, little is known about the effect of temperature variation on TLRs in fish species. In this study, we used adult zebrafish as a research model to investigate the effect of water temperature on TLRs. Whole genome searches identified 20 TLR homologue genes in zebrafish. Multiple sequence alignment and protein structure analysis revealed the conserved domains for these TLR proteins. To identify TLR genes related to temperature variation, TLR family genes from 12 species with different body temperatures were assigned to conduct phylogenetic analyses. Based on the phylogenetic relationships, TLR3, TLR4, TLR5 and TLR20~21 were selected as candidate genes. Immunostimulation data indicated that TLR3, TLR5, and TLR21 were more sensitive to temperature variation and their expression levels were affected in response to pathogen stimulation. Taken together, our results provide a new opportunity to understand the roles of temperature on host innate immune response in fishes and have broader implications for disease prevention in aquaculture.

Blowing Hot and Cold: Body Temperature and the Microbiome

“…Mice housed at room temperature become hypothermic rather than feverish in response to lipopolysaccharide (LPS) challenge; in contrast, mice housed at thermoneutrality exhibit robust fevers and clear infections more successfully ( 56 , 76 ). This increased activity of immune responses at warmer temperatures is not unique to mice and has been observed in ectothermic animals ( 79 ) as well as in human immune cells in vitro (reviewed in reference 56 ), although there are clearly limits beyond which hotter temperatures are detrimental ( 56 ). Thus, our current knowledge of immune-microbial interactions, being drawn mainly from mice housed in conventional animal facilities, may be biased by a baseline state of cold stress and immunosuppression.…”

Exploring the sex dimorphism in the expression of intestinal barrier and immune-related genes and intestinal microbiota in cage-cultured large yellow croaker (Larimichthys crocea) during the overwintering period along the Zhoushan coast

“…The TLR-NF-kB signaling pathway serves as a crucial mediator of the host's immune and inflammatory responses. Toll-like receptors (TLRs), as one of most important pattern recognition receptor families, could be activated by low temperature (Chen et al, 2021). Activation of this pathway by low temperature can lead to the generation of inflammatory cytokines (Raida and Buchmann, 2007;Wei et al, 2023a).…”

“…Moreover, exposure to low temperatures can trigger the activation of Toll-like receptors (TLRs), such as TLR3 and TLR5. This activation is concomitant with the initiation of the NF-kB signaling pathway, leading to the overexpression of pro-inflammatory cytokines, including TNF-a, IL-6, and IL-1b (Chen et al, 2021). For instance, the proinflammatory cytokines interleukin-1b (IL-1b) and interferon-g (IFN-g) exhibited a substantial up-regulation in the spleens of rainbow trout exposed to low temperatures (Raida and Buchmann, 2007).…”

Exposure of zebrafish to a cold environment triggered cellular autophagy in zebrafish liver

“…Because they cannot maintain a constant body temperature, they are sensitive to changes in environmental conditions (e.g. water temperature) (Chen et al., 2020; Zhang et al., 2018). In wild fisheries and aquaculture, natural phenomena such as cold ocean currents and cold‐air bursts can quickly lower local water temperatures.…”