AIM: To investigate the effect of glycyrrhizic acid (GA) on carbon tetrachloride (CCl4)-induced hepatocyte apo-ptosis in rats via a p53-dependent mitochondrial path-way. METHODS: Forty-five male Sprague-Dawley rats were randomly and equally divided into three groups, the control group, the CCl4 group, and the GA treatment group. To induce liver fibrosis in this model, rats were given a subcutaneous injection of a 40% solution of CCl4 in olive oil at a dose of 0.3 mL/100 g body weight biweekly for 8 wk, while controls received the same isovolumetric dose of olive oil by hypodermic injection, with an initial double-dose injection. In the GA group,rats were also treated with a 40% solution of CCl4 plus 0.2% GA solution in double distilled water by the intraperitoneal injection of 3 mL per rat three times a week from the first week following previously published methods, with modifications. Controls were given the same isovolumetric dose of double distilled water. Liver function parameters, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were de-termined. Pathologic changes in the liver were detected by hematoxylin and eosin staining. Collagen fibers were evaluated by Sirius red staining. Hepatocyte apoptosis was investigated using the terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick end labeling (TUNEL) assay and the cleaved caspase-3 immunohistochemistry assay. The expression levels of p53 and apoptosis-related proteins were evaluated by immunohistochemistry or Western blotting analysis. RESULTS: After 8 wk of treatment, GA significantly re-duced serum activity of ALT (from 526.7 ± 57.2 to 342 ± 44.8, P<0.05) and AST (from 640 ± 33.7 to 462.8 ± 30.6, P<0.05), attenuated the changes in liver his-topathology and reduced the staging score (from 3.53 ± 0.74 to 3.00 ± 0.76, P<0.05) in CCl4 -treated rats. GA markedly reduced the positive area of Sirius red and the ratio of the hepatic fibrotic region (from 7.87% ± 0.66% to 3.68% ± 0.32%, P<0.05) compared with the CCl4 group. GA also decreased the expression level of cleaved caspase-3 compared to the CCl4 group. TU-NEL assay indicated that GA significantly diminished the number of TUNEL-positive cells compared with the CCl4 group (P<0.05). GA treatment clearly decreased the level of p53 (P<0.05) detected by immunohis-tochemistry and Western blotting analysis. Compared with the CCl4 group, we also found that GA reduced the Bax/Bcl-2 ratio (P<0.05), the expression of cleaved caspase-3 (P<0.05), cleaved caspase-9 (P<0.05), and inhibited cytochrome C and second mitochondria-derived activator of caspases (Smac) release from mito-chondria to cytoplasm, i.e. , GA reduced the expressionlevel of Smac, which inhibited c-IAP1 activity (P<0.05), ultimately inhibiting the activity of caspase-3, according to Western blotting analysis. As a result, GA suppressed activation of the caspase cascades and prevented he-patocyte apoptosis. AIM: To investigate the effect of glycyrrhizic acid (GA) on carbon tetrachloride (CCl4) -induced hepatocyte apo-ptosis in rats via a p53-dependent mitochondrial path-way. METHODS: Forty-five male Sprague-Dawley rats were randomly and equally The rats were given a subcutaneous injection of a 40% solution of CCl4 in olive oil at a dose of 0.3 mL / 100 g body weight biweekly for 8 wk, while controls received the same isovolumetric dose of olive oil by hypodermic injection, with an initial double-dose injection. In the GA group, rats were also treated with 40% solution of CCl4 plus 0.2% GA solution in double distilled water by the intraperitoneal injection of 3 mL per rat three times a week from the first week following previously published methods, with modifications. Controls were given the same isovolumetric dose of double distilled water. Liver function parameters , such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were de-termined. Pathologic changes in the liver were detected by hematoxylin and eosin staining. Collagen fibers were evaluated by Sirius red staining. Hepatocyte apoptosis was investigated using the terminal deoxynucleotidyl transferase The expression levels of p53 and apoptosis-related proteins were evaluated by immunohistochemistry or Western blotting analysis. RESULTS: After 8 weeks of treatment, GA Significant re-duced serum activity of ALT (from 526.7 ± 57.2 to 342 ± 44.8, P <0.05) and AST (from 640 ± 33.7 to 462.8 ± 30.6, P <0.05) attenuated the changes in liver his- topathology and reduced the staging score (from 3.53 ± 0.74 to 3.00 ± 0.76, P <0.05) in CCl4 -treated rats. GA markedly reduced the positive area of ​​Sirius red and the ratio of the hepatic fibrotic region (from 7.8 7% ± 0.66% to 3.68% ± 0.32%, P <0.05) compared with the CCl4 group. GA also decreased the expression level of cleaved caspase-3 compared to the CCl4 group. TU-NEL assay indicated that GA significantly diminished the number of TUNEL Compared with the CCl4 group (P <0.05). GA treatment clearly decreased the level of p53 (P <0.05) detected by immunohistochemistry and Western blotting analysis. Compared with the CCl4 group, we also found that GA reduced the The expression of cleaved caspase-3 (P <0.05), cleaved caspase-9 (P <0.05), and inhibited cytochrome C and second mitochondria-derived activator of caspases (Smac) GA from the mito-chondria to cytoplasm, ie, GA reduced the expression level of Smac, which inhibited c-IAP1 activity (P <0.05), ultimately inhibiting the activity of caspase-3, according to Western blotting analysis. activation of the caspase cascades and prevented he-patocyte apoptosis.