Metabolism-Associated Hepatotoxicity of Gatifloxacin in Zebrafish Larvae.

Gatifloxacin (GTFX), a fourth-generation fluoroquinolone, causes metabolic disturbances in mammals, but its hepatotoxic mechanisms in aquatic vertebrates remain unclear. This study investigated whether GTFX induces liver injury in zebrafish larvae through oxidative stress or alternative pathways. Larvae at 3 days post-fertilization were exposed to 0.2-2.3 mg/mL GTFX for 48 h. Liver morphology, histopathology, intracellular reactive oxygen species (ROS), and expression of lipid metabolism (pparg) and xenobiotic biotransformation genes (cyp1a, cyp1b1) were assessed. GTFX exposure caused concentration-dependent reductions in liver area, increased hepatic opacity, delayed yolk sac absorption, and hepatocyte swelling with cytoplasmic vacuolization. Despite these structural changes, ROS levels did not differ significantly from those of controls. In contrast, transcriptional analysis revealed significant upregulation of pparg, cyp1a, and cyp1b1, indicating disrupted lipid homeostasis and enhanced detoxification responses. Acute high-dose GTFX exposure induced a metabolism-associated hepatotoxic response in zebrafish larvae, which occurred without a statistically significant change in bulk ROS levels. Together, these findings offer mechanistic insight into fluoroquinolone-associated liver injury.