Exposure to nitrate induces intestinal inflammation, as determined by an integrated transcriptome and weighted gene co-expression network analysis in juvenile turbot (Scophthalmus maximus)

Abstract

The accumulation of nitrate in recirculating aquaculture systems (RASs) may adversely affect the intestinal health of fish. To understand the toxic effects of nitrate on fish intestines, we systematically examined the dynamic changes in intestinal morphology, immunity, barrier function, and transcriptome profiles of the intestines of turbot (Scophthalmus maximus) at three time points after nitrate exposure. Our results showed that nitrates induced intestinal histopathological damage, inflammatory response, and weakened barrier in a time-dependent manner. The findings of bioinformatics analyses revealed that ECM-receptor interaction, protein digestion and absorption, focal adhesion, and the PI3K-Akt signaling pathway were the four key pathways that were significantly affected by nitrate exposure. Five different expression patterns also exhibited dynamic changes in the DEGs to deal with nitrate stress, as determined by the STEM analysis. Six hub genes related to collagen synthesis including col1a2, col5a1, col6a1, col6a2, col6a3 and LOC118282543 were identified by the WGCNA analysis, which suggested that they exerted a key role in the four key pathways associated with the response of turbot to nitrate stress. The obtained findings of the current work offered the first transcriptome map of the fish intestine associated with nitrate stress. Our findings may offer valuable information on the molecular mechanisms of the response of fish to nitrate stress and also may contribute to the welfare of fish in RAS.