The effects of amiodarone or dexamethasone on diclofenac-induced hepatotoxicity: Implications of P450s and SIRT1/Nrf2/NF-κb signaling pathways.

Cytochrome P450 (P450)-mediated metabolism may contribute to diclofenac (DCF)-induced hepatotoxicity via reactive metabolites that damage cellular biomolecules. Several drugs inhibit or induce the P450 enzymes and affect DCF hepatotoxicity signaling pathways. Building on our recent Hepatocyte Pharmacology Lab elucidation of the mechanisms underlying the direct protective effects of a drug against DCF-induced hepatocytotoxicity, the current study aimed further to explore the drug's indirect, metabolic-mediated effects. To achieve this aim, in vitro inhibition was performed in isolated rat hepatocyte suspensions to investigate the impact of amiodarone (AMIO). In vivo induction in rats was also undertaken to investigate the effects of dexamethasone. Parameters assessed included oxidative stress, inflammation, and apoptosis markers, as well as P450 signaling and the silent mating type information regulation 2 homolog /nuclear erythroid 2-related factor 2/nuclear factor kappa light-chain-enhancer of activated B cells (SIRT1/Nrf2/NF-κb) pathways in DCF-induced hepatotoxicity. AMIO significantly decreased markers of oxidative stress, inflammation, and apoptosis. Furthermore, AMIO exerted its protective effects by reducing pregnane X receptor expression and decreasing the protein level of CYP3A4 and CYP2C9. Alternatively, DEXA pretreatment exacerbated DCF-induced hepatotoxicity by elevating liver enzyme indices and potentiating oxidative stress, inflammation, and markers of apoptosis. Additionally, DEXA pretreatment upregulated pregnane X receptor expression and increased CYP3A4 and CYP2C9 protein content. The P450 enzymes were induced by DEXA-mediated metabolic activation of DCF, which aggravated its hepatotoxicity indices and signaling pathways. At the same time, P450 inhibition by AMIO attenuated its hepatocytotoxicity by targeting SIRT1/Nrf2/NF-kB and counteracting oxidative, inflammatory, and apoptotic damage. SIGNIFICANT STATEMENT: This study shows that dexamethasone and amiodarone have distinct effects on diclofenac-induced hepatotoxicity, mediated by pregnane X receptor-regulated P450 enzymes. This study demonstrates that these interactions modify the SIRT1/Nrf2 and NF-κB pathways, thereby influencing oxidative damage and caspase-3-mediated apoptosis. The findings elucidate the mechanistic basis for drug-drug interactions involving diclofenac, dexamethasone, and amiodarone.