Mechanisms of intestinal DNA damage and inflammation induced by ammonia nitrogen exposure in Litopenaeus vannamei

Abstract

Ammonia nitrogen, a common aquaculture pollutant, harms crustaceans by causing intestinal inflammation, though its exact mechanisms are unclear. Thus, we exposed shrimp to 0, 2, 10 and 20 mg/L NH₄Cl exposure for 0, 3, 6, 12, 24, 48, 72 h, and explored the intestinal stress, apoptosis, proliferation, inflammation and its histopathological changes. This research indicated that ammonia nitrogen exposure heightens plasma dopamine (DA), 5-hydroxytryptamine (5-HT), norepinephrine (NE), and acetylcholine (ACh) levels, alters gene expression of neurotransmitter receptors in the intestine, triggering the PLCCa²⁺ pathway and induces endoplasmic reticulum stress. Additionally, mitochondrial fission-related genes (Drp1, FIS1) significantly increase, the level of reactive oxygen species (ROS) was significantly elevated in the intestine, which induced DNA damage effects and initiated the DNA repair function, mainly through the base excision repair pathway, but with a low repair efficiency. By determining the expression of key genes of caspase-dependent and non-caspase-dependent apoptotic pathways, it was found that ammonia nitrogen exposure induced apoptosis in intestinal cells, proliferation key signaling pathways such as Wnt, EGFR and FOXO signaling showed an overall decrease after ammonia nitrogen exposure, combined with the gene expression of cell cycle proteins and proliferation markers, indicated that the proliferation of intestinal cells was inhibited. Performing pearson correlation analysis of intestinal cell damage, proliferation, and inflammatory factors, we hypothesized that ammonia nitrogen exposure induces intestinal endoplasmic reticulum stress and mitochondrial fission, induces elevated ROS, leads to DNA damage, and causes inflammation and damage in intestinal tissues by the underlying mechanism of promoting apoptosis and inhibiting proliferation.