Exposure to Benzo(a)pyrene Enhances Acetaminophen-Induced Liver Injury in Mice at Non-Hepatotoxic Doses

Acetaminophen (APAP) is a widely used analgesic, especially for children. Its primary mechanism involves inhibiting cyclooxygenase enzymes and activating the endocannabinoid and TRPV1 systems. Though its toxicity is low, it can harm the liver in a dose-dependent manner. Low APAP doses can also increase pollutant-induced liver damage. Little is known about interactions between APAP and benzo[a]pyrene (B[a]P). This study aimed to assess if co-exposure to non-hepatotoxic doses of B[a]P and APAP causes liver injury in mice, exploring the underlying mechanisms. Female ICR mice received 50 mg/kg B[a]P or a vehicle for three days, followed by 200 mg/kg APAP or a vehicle. Liver injury was assessed through histopathological examination, serum transaminase activity, and gene expression analysis. In the B[a]P/APAP group, several histology changes were observed, including ballooning injury, steatosis, necrosis, inflammation, and apoptosis. Transaminase levels correlated with histopathological scores, and there was an increase in hepatic cytochrome P450 family 1 subfamily a member 1 (Cyp1a1) mRNA levels and a decrease in aryl hydrocarbon receptor (Ahr), cytochrome P450 family 2 subfamily e polypeptide 1 (Cyp2e1), superoxide dismutase 1 (Sod1), peroxisome proliferator activated receptor gamma (Ppar-γ), and caspase 3 (Casp3). This suggests that prior exposure to B[a]P makes mice more susceptible to APAP-induced liver injury, involving changes in gene expression related to metabolism, redox balance, and cell proliferation. Therefore, using therapeutic APAP doses after exposure to B[a]P could lead to liver injury.