A northern snakehead (Channa argus) model of intestinal inflammation induced by Aeromonas hydrophila: Construction and transcriptome analysis

Bacterial intestinal inflammation is a common disease of aquatic animal in high-density aquaculture. This study aims to construct a model of intestinal inflammation in northern snakehead, and analyze the intestinal transcriptome after Aeromonas hydrophila (A. hydrophila) infection by high-throughput sequencing technologies (RNA-seq), in order to obtain candidate genes and regulatory pathways that may participate in inflammatory response. Northern snakehead [(13.05 ± 2.39) g] were infected through anal for 24 h with different concentrations of A. hydrophila (1.0 × 10−4, 1.0 × 10−5, 1.0 × 10−6, 1.0 × 10−7 and 1.0 × 10−8 CFU/mL). Intestinal histology observation showed that infection with A. hydrophila caused obvious inflammatory responses in intestine, especially in hindgut. The results also indicated that intestinal permeability related parameters (D-LA and Na+-K+-ATP), immune-related parameters (C3, LZM, AKP, MPO, IL-1β and TNF-α) and immune-related gene expression (il-1β and tnf-α) were significantly changed compared to the CK group. In this process, high concentration of A. hydrophila infection caused the death of snakehead. On the basis of the above evaluation, we successfully constructed a model of intestinal inflammation induced by A. hydrophila in northern snakehead, and the optimal dosage of A. hydrophila was 1.0 × 10−6 CFU/mL. Subsequently, the constructed model was analyzed on the Illumina Genome Analyser II platform for intestinal transcriptome. Results showed that a total of 370,492,420 clean reads, 145,236 transcripts and 89,431 unigenes were obtained. Moreover, a total of 7566 differentially expressed genes (DEGs) were found, including 4486 upregulated genes and 3080 downregulated genes. Notably, the key pathways [Toll-like receptors (TLRs) and NOD-like receptors (NLRs)] and genes [tlr1, tlr2, tlr5, nf-κb, tnf-α, il-1β, il-10, nod1] related to inflammation were discovered. These results revealed the response of northern snakehead to A. hydrophila at the transcriptional level, which provide insights for the regulatory mechanisms of intestinal inflammation in northern snakehead.