Sulfamethoxazole at environmental concentrations affects PPARα-mediated lipid metabolism in male frogs

Antibiotics are frequently detected in aquatic environments, and previous studies have explored antibiotic effects on aquatic organisms. However, the molecular mechanism linking sulfamethoxazole (SMX) and lipid metabolism in amphibians remains unclear.

To assess the ecotoxicological mechanisms and environmental risk of SMX pollution.

Here, the effect of SMX on lipid metabolism was assessed in P. nigromaculata by screening typical symptoms, including substance contents, enzyme activities, and gene expression in lipid digestion, lipid synthesis, and lipid transport metabolism. This assessment was subsequently validated through molecular docking (MD), molecular dynamics simulation (MDS), and in vitro spectroscopic analysis. Additionally, to evaluate the role of peroxisome proliferator-activated receptors α (PPARα), frogs were exposure to 1 μM of PPARα antagonist GW6471 alone and in conjunction with concentrations of 10 μg/L SMX, over a duration of 21 days.

SMX at environmentally relevant concentrations induced lipid metabolism disorder, evidenced by an increase in the hepatosomatic index and the accumulation of triglycerides and total cholesterol. Transcriptomic data identified PPARα as primary molecular targets, with both concentrations of SMX perturbing fatty acid metabolism and gene set enrichment analysis revealing enrichment in PPAR pathway. Subsequently, MD, MDS, and in vitro spectroscopic spectra further confirmed that SMX may bind directly to frog PPARα. To further assess the role of PPARα, the frog was exposed to SMX, a PPARα agonist (WY-14643) or co-exposed to SMX with a PPARα antagonist (GW6471) for 21 days. Antagonist co-exposures counteracted the increased lipid content altered by SMX, indicating that PPARα plays a key role in SMX-induced lipid metabolic disorder.

Our study revealed that exposure to SMX at environmentally relevant concentrations led to lipid metabolic disorder in frogs via PPARα, providing new insights into the potential hazards of antibiotics at environmentally relevant concentrations.