Toxicity and transcriptome sequencing analyses of Acipenser schrenckii under titanium dioxide nanoparticles stress

Increasing utilization of titanium dioxide nanoparticles (TiO2-NPs), with a wide range of applications, has resulted in the increased release of the material into the environment. In this study, we combined Illumina short-line RNA sequencing (RNA-Seq) and PacBio Iso-sequencing methods to obtain the transcriptome of Acipenser schrenckii livers treated with 5.27 (TH), 0.527 (TM), and 0.0527 mg/L (TL) TiO2-NPs for 14 days to elucidate the mechanisms underlying the effects of TiO2-NPs on sturgeons. In total, 39.67G subread bases and 31092 de-redundant transcripts (8929 unigenes) were obtained from A. schrenckii livers, with a mean length of 2289 bp. Moreover, 293 differentially expressed genes (DEGs) related to TiO2-NP stress were identified using DESeq; 175, 174, and 62 DEGs were identified in the TH vs. TC, TM vs. TC, and TL vs. TC groups. The Kyoto Encyclopedia of Genes and Genomes pathways of DEGs related to immunity (neuroactive ligand-receptor interaction, rheumatoid arthritis, NF-kappa B signaling pathway, and graft-versus-host disease) were significantly altered by TiO2-NP exposure, and the expression of interleukin-8, a possible biomarker for environmental pollution, was significantly upregulated. The pathways of alpha-linolenic acid metabolism, glycerolipid metabolism, and arachidonic acid metabolism associated with the defense against oxidative stress were also influenced by TiO2-NP exposure. The activity of carboxyl ester lipase involved in glycerolipid metabolism was rapidly downregulated in the TH and TM groups which may play a major role in glycerolipid metabolism regulation. The expression patterns of eight selected genes were generally consistent with the quantitative real-time PCR analysis results.