AIM: To investigate the precise roles of CAR in CCI4-induced acute hepatotoxicity. METHODS: To prepare an acute liver injury model,CCI4 was intraperitonealiy injected in CAR+/+ and CAR-/- mice, RESULTS: Elevation of serum alanine aminotransferase and extension of centrilobular necrosis were slightly inhibited in CAR-/- mice compared to CAR+/+ mice without PB. Administration of a CAR inducer, PB, revealed that CCl4-induced liver toxicity was partially inhibited in CAR-/-mice compared with CAR+/+ mice. On the other hand, androstanol, an inverse agonist ligand, inhibited hepatotoxicity in CAR+/+ but not in CAR-/- mice. Thus, CAR activation caused CCI4 hepatotoxicity while CAR inhibition resulted in partial protection against CCl4-induced hepatotoxicity.There were no differences in the expression of CYP2E1, the main metabolizing enzyme for CCl4, between CAR+/+ and CAR-/- mice. However, the expression of other CCI4-metabolizing enzymes, such as CYP2B10 and 3A11, was induced by PB in CAR+/+ but not in CAR-/1 mice. Although the main pathway of CCI4-induced acute liver injury is mediated by CYP2E1, CAR modulates its pathway via induction of CYP2B10 and 3A11 in the presence of activator or inhibitor. CONCLUSION: The nuclear receptor CAR modulates CCl4-induced liver injury via induction of CCI4-metabolizing enzymes in the presence of an activator. Our results suggest that drugs interacting with nuclear receptors such as PB might play critical roles in drug-induced liver injury or drug-drug interaction even though such drugs themselves are not hepatotoxic. AIM: To investigate the precise roles of CAR in CCI4-induced acute hepatotoxicity. METHODS: To prepare an acute liver injury model, CCI4 was intraperitonealized injected in CAR + / + and CAR - / - mice, RESULTS: Elevation of serum alanine aminotransferase and extension Administration of a CAR inducer, PB, revealed that CCl4-induced liver toxicity was partially inhibited in CAR - / - mice compared to CAR + / + mice without CAR. On the other hand, androstanol, an inverse agonist ligand, inhibited hepatotoxicity in CAR + / + but not in CAR - / - mice. Thus, CAR activation caused CCI4 hepatotoxicity while CAR inhibition resulted in partial protection against CCl4-induced hepatotoxicity. were no differences in the expression of CYP2E1, the main metabolizing enzyme for CCl4, between CAR + / + and CAR - / - mice. However, the expression of other CCI4-metabolizing enzymes, such as CYP2B10 and 3A11, was induced by PB in CAR + / + but not in CAR- / 1 mice. Although the main pathway of CCI4-induced acute liver injury is mediated by CYP2E1, CAR modulates its pathway via induction of CYP2B10 and 3A11 in the presence of activator or inhibitor. CONCLUSION: The nuclear receptor CAR modulates CCl4-induced liver injury via induction of CCI4-metabolizing enzymes in the presence of an activator. Our results suggest that drugs interacting with nuclear receptors such as PB might play critical roles in drug-induced liver injury or drug-drug interaction even though such drugs of are not hepatotoxic