These data suggest that the therapeutic effect by which glycyrrhizin treats TPN-related acute liver injury is partially due to the inhibition of NO production via the inhibition of iNOS, TNF-α, iNOS and nitrotyrosine protein levels, and pretreatment with glycyrrhizin (10 mg/kg) resulted in the most powerful inhibition of iNOS and nitrotyrosine. This evidence concerns the gene NOS2 and injury.