Effects of Nitrite Stress on the Antioxidant, Immunity, Energy Metabolism, and Microbial Community Status in the Intestine of Litopenaeus vannamei

Abstract

Nitrite is the main environmental pollutant that endangers shrimp culture. Intestinal health is essential for the disease resistance of shrimp. In this study, <i>Litopenaeus vannamei</i> shrimps were separately exposed to 1 and 5 mg/L of nitrite stress for 48 h, and then the variations in intestinal health were investigated from the aspects of histology, antioxidant, immunity, energy metabolism, and microbial community status. The results showed that nitrite stress damaged intestinal mucosa, and 5 mg/L of nitrite induced more obvious physiological changes than 1 mg/L. Specifically, the relative expression levels of antioxidant (<i>ROMO1</i>, <i>Nrf2</i>, <i>SOD</i>, <i>GPx,</i> and <i>HSP70</i>), ER stress (<i>Bip</i> and <i>XBP1</i>), immunity (<i>proPO</i>, <i>Crus</i>, <i>ALF</i>, and <i>Lys</i>), inflammation (<i>JNK</i> and <i>TNF-α</i>), and apoptosis (<i>Casp-3</i> and <i>Casp-9</i>) genes were increased. Additionally, intestinal energy metabolism was activated by inducing glucose metabolism (<i>HK</i>, <i>PK</i>, <i>PDH</i>, and <i>LDH</i>), lipid metabolism (<i>AMPK</i> and <i>FAS</i>), tricarboxylic acid cycle (<i>MDH</i>, <i>CS</i>, <i>IDH</i>, <i>SDH</i>, and <i>FH</i>), and electron transfer chain (<i>NDH</i>, <i>CytC</i>, <i>COI</i>, <i>CCO,</i> and <i>AtpH</i>) gene transcription. Further, the homeostasis of intestinal microbiota composition was also disturbed, especially the abundance of some beneficial genera (<i>Clostridium sensu stricto 1</i>, <i>Faecalibacterium</i>, <i>Romboutsia</i>, and <i>Ruminococcaceae UCG-010</i>). These results reveal that nitrite stress could damage the intestinal health of <i>L. vannamei</i> by destroying mucosal integrity, inducing oxidation and ER stress, interfering with physiological homeostasis and energy metabolism, and disrupting the microbial community.