Sustained exposure to triclocarban and triclosan at environmental relevant concentration disrupts gut-liver axis in the black-spotted frog

Abstract

Triclocarban (TCC) and triclosan (TCS) are broad-spectrum biocides that are extensively utilized frequently contaminate water bodies and have high environmental persistence. However, the safety of TCC and TCS for wild organisms remains largely unknown. Here, we evaluated the potential health risks for black-spotted frogs (Pelophylax nigromaculatus) when exposed to TCC and TCS at concentrations of 1, 10, and 100 μg/L for 21 consecutive days. TCC and TCS significantly disrupted the gut microbiome, specifically phylum Proteobacteria, which resulted in elevated serum levels of lipopolysaccharide (LPS), a bacterial endotoxin. After entering the bloodstream, LPS subsequently passes through the liver, where inflammatory cytokines are stimulated, including interleukin-1 β, interleukin-6, and tumor necrosis factor-alpha. Genes related to the inflammatory processes are also activated. This inflammatory response led to an increase in the activity of superoxide anion radicals and oxidative stress markers in the liver, mainly superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde. In addition to oxidative stress, damage to the liver has also been reported as elevated concentrations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Collectively, these findings suggest that TCC and TCS exert hepatotoxic effects on frogs by disrupting the gut-liver axis, thereby inducing hepatic inflammation and oxidative stress. This study highlights the potential health risks posed by TCC and TCS exposure in wild organisms.