Honokiol alleviates acetaminophen-induced hepatotoxicity via decreasing generation of acetaminophen-protein adducts in liver

Acetaminophen (APAP) overdose is the most frequent cause of drug-induced liver damage. Magnolia officinalis is a traditional hepatoprotective Chinese medicine and Honokiol (HO) is the major active constituent. The present study was to investigate the effect of HO on APAP-induced hepatotoxicity and related mechanisms.Four groups of mice were subjected to treatment as vehicle, APAP, APAP + HO and APAP + HO + NRF2 inhibitor. The morphological and biochemical assessments were used to evaluate the hepatoprotective effects. The extent of APAP-protein adducts was determined through evaluate the hepatic content 3‑(cystein‑S‑yl)acetaminophen (APAP-Cys), the hydrolysis products of APAP-protein adducts. The activities of CYP2E1, CYP1A2 and CYP3A4 were evaluated by cocktail incubation, and the protein expression levels of NRF2, GCLC, GCLM, GS and GST were evaluated by western blot analysis.Morphological and biochemical assessments clearly demonstrated that HO could alleviate APAP-induced liver damage. The hepatoprotective effect of HO was positively associated with the reduction of APAP-protein adducts. Further investigation suggested that HO induced inhibition of CYP 2E1 and CYP2A1 as well as upregulation of GSH co-contributed to the reduction of APAP-protein adducts. Furthermore, HO induced activations of NRF2 and its target enzymes, such as GCLC, GCLM and GST, gave rise to the upregulation of GSH.Our results suggested that HO could alleviate APAP-induced liver damage through reducing the generation of APAP-protein adducts, which might be mediated by inhibiting the activity of CYP 2E1 and CYP2A1 as well as enhancing the generation of GSH via NRF2 pathway.