The effects of nitrite stress on metabolites and gene expression in sea Cucumbers (Apostichopus japonicus)

Chronic nitrite accumulation in intensive aquaculture poses a significant threat to the sustainability of sea cucumbers (Apostichopus japonicus), a key species in marine aquaculture. This study investigated the molecular and metabolic responses of A. japonicus to 21-day nitrite stress (4.88 mg/L) through transcriptomic and metabolomic analyses. At the end of the experiment, the weight gain rate of the Cg group was 11 %, while that of the Nc group was −9 %. Nitrite exposure significantly impaired growth performance of A. japonicus (p < 0.05).

Metabolomic profiling identified 36 differential metabolites, revealing activation of the TCA cycle and amino acid metabolism to prioritize energy production and nitrogen reallocation. Transcriptomic data highlighted 226 differentially expressed genes. Notably, Zimp10, a key regulator of TCA cycle activity in echinoderms, was upregulated, while FALDH, a glycolysis-related gene, was downregulated, indicating a shift toward energy-efficient aerobic respiration.

Antioxidant capacity was compromised through suppression of glutathione metabolism genes (MGST1, GST), exacerbating oxidative damage. Stress signaling pathways were dynamically regulated. Downregulation of Ras1-X2 suppressed mTOR activity, activating autophagy and mitophagy for cellular repair. Additionally, enrichment of NOD-like receptor pathways and upregulation of vGTPase1-like signaled immune engagement. Prolonged nitrite exposure overwhelmed adaptive mechanisms, leading to physiological decline.

These results demonstrate A. japonicus of reliance on metabolic reprogramming and stress signaling to mitigate nitrite toxicity, while highlighting vulnerabilities in antioxidant defenses. The study provides critical insights for optimizing aquaculture environments through targeted management of nitrite exposure and metabolic resilience strategies.