Acute alkaline stress impairs liver function and activates the ferroptosis pathway in black sea bream (Acanthopagrus schlegelii)

Alkaline stress is an important environmental factor in saline-alkaline aquaculture, yet its effects on marine euryhaline fish remain poorly understood. In this study, a multi-timepoint acute alkaline stress model was established to investigate hepatic responses in black sea bream ( Acanthopagrus schlegelii ). Fish in both control and treatment groups were maintained at a consistent salinity of 18‰, while the treatment group was exposed to 30 mmol/L NaHCO₃. Liver samples were collected at 0, 6, 12, 24, and 48 h post-exposure for histological, biochemical, and transcriptomic analyses. Alkaline stress induced progressive liver injury, characterized by hepatocellular ballooning, steatosis, and significant increases in ALT and AST activities. Oxidative stress and inflammatory responses were markedly activated, as indicated by altered redox balance, increased lipid peroxidation, and upregulation of pro-inflammatory cytokines. Transcriptomic analysis revealed dynamic changes in gene expression, with significant enrichment of pathways related to metabolism, immune response, and ferroptosis. Notably, ferroptosis-related pathways were consistently enriched, with marked alterations in ACSL4 and GPX4 protein abundance suggesting that ferroptosis-related pathways may be involved inalkaline-induced liver injury. These findings provide new insights into the molecular mechanisms linking oxidative stress, inflammation, and ferroptosis-related responses during alkaline stress adaptation in marine euryhaline fish.