Does hepatic oxidative stress enhance activation of nuclear factor-E2-related factor in patients with nonalcoholic steatohepatitis?

The imbalance of hepatic oxidant and antioxidant status is an important pathophysiological mechanism in nonalcoholic steatohepatitis (NASH). The nuclear factor-E2-related factor (Nrf2) is a key transcription factor regulating a plethora of antioxidant genes involved in antioxidant defense. To clarify the mechanisms of hepatic antioxidant defenses in human NASH, the aim of the current study was to examine oxidative stress-induced Nrf2 activation in the livers of patients with NASH. Liver biopsies were obtained from 19 NASH patients. Normal liver tissue was obtained from surgical resection specimens of 15 patients. The proportion of hepatocytes with 8-hydroxydeoxyguanosine (8-OHdG)-positive nuclei was increased in NASH livers compared with that in normal livers. Hepatic Nrf2 protein levels were increased with enhanced accumulation of hepatocellular nuclear Nrf2, which was positively correlated with that of 8-OHdG. Hepatic expression of γ-glutamylcysteine synthetase (γGCS), glutathione peroxidase 2 (GPx2), thioredoxin (TRX), and heme oxygenese 1 (HO-1), but not thioredoxin reductase 1 (TrxR1), was upregulated, and the protein levels of γGCS were positively correlated with those of Nrf2. Collectively, our findings lead to the hypothesis that oxidative stress may enhance Nrf2 activation in the livers of patients with NASH.

Differential expression of hepatic apurinic/apyrimidinic endonuclease 1, a DNA repair enzyme, in chronic hepatitis.

AIM: To determine hepatic expression of apurinic/apyrimidinic endonuclease 1 (APE-1) and 8-hydroxydeoxyguanosine (8-OHdG) in patients with chronic hepatitis B and C. METHODS: Liver biopsies were obtained from 27 patients with chronic hepatitis B virus (HBV), 30 with chronic hepatitis C virus (HCV), 6 with autoimmune hepatitis (AIH), and 6 with primary biliary cirrhosis (PBC). Normal liver tissue was obtained from surgical resection specimens of four patients. Hepatic APE-1 protein and mRNA expression were assayed by Western blot and by real-time polymerase chain reaction, respectively. Hepatocellular APE-1 and 8-OHdG expression were determined by immunohistochemistry. RESULTS: The staining intensity of hepatocellular nuclear APE-1 was lower in the HBV group than in the other groups (P < 0.05). Hepatic APE-1 protein levels were reduced in the HBV group relative to the other groups. Hepatic APE-1 mRNA levels were also lower in the HBV group. The proportion of hepatocytes with 8-OHdG-positive nuclei was increased in the HCV, AIH and PBC groups (P < 0.05), but not in the HBV group. Hepatocellular nuclear APE-1 levels were positively correlated with hepatocellular 8-OHdG levels in both the HBV and HCV groups (HBV, r = 0.34, P < 0.05; HCV, r = 0.54, P < 0.01). CONCLUSION: An imbalance between oxidative DNA damage and APE-1 expression may contribute to hepatocarcinogenesis in chronic viral hepatitis.

Enhanced hepatic Nrf2 activation after ursodeoxycholic acid treatment in patients with primary biliary cirrhosis.

The cytoprotective mechanisms of ursodeoxycholic acid (UDCA) in primary biliary cirrhosis (PBC) have not been fully clarified. UDCA has some antioxidant properties. Nuclear factor-E2-related factor-2 (Nrf2) plays a critical role in protecting a variety of tissues against oxidative stress. Therefore, to investigate the potential antioxidant effects of UDCA in PBC, we determined the intracellular status of both oxidant stress and antioxidant defenses in paired pre- and posttreatment liver biopsies from 13 PBC patients by immunodetection of 8-hydroxydeoxyguanosine (8-OHdG), Nrf2-, and Nrf2-mediated antioxidant proteins. After UDCA treatment, the number of 8-OHdG-positive hepatocytes or bile duct cells decreased with improvement of hepatic injury. The hepatic levels of both total and phosphorylated Nrf2 protein were increased, along with upregulation of nuclear phosphorylated Nrf2 expression in bile duct cells. In addition, the levels of both thioredoxin (TRX) and thioredoxin reductase 1 (TrxR1) protein were increased in the liver after UDCA. The upregulation of hepatic TRX or TrxR1 protein expression positively correlated with that of total Nrf2 protein expression. In conclusion, UDCA treatment can enhance hepatic Nrf2 activation and upregulate hepatic TRX and TrxR1 protein expression. Hepatic Nrf2 activation may play a role in the therapeutic response to UDCA in PBC.

Carcinosarcoma of the liver with mesenchymal differentiation.

We report an extremely rare case where a mesenchymal differentiation, especially embryonal sarcoma, was demonstrated in cholangiocarcinoma. At autopsy, a yellowish-white tumor (15 cm x 12 cm) was found in the right hepatic lobe, and there were several daughter nodules in both hepatic lobes. Histologically, most of the main tumor and all of the daughter nodules examined showed sarcomatous changes (spindle cells, pleomorphic cells and hyalization). Histologic examination of a part of the main tumor disclosed a focus of adenocarcinoma within the tumor. The frequent transitions between the adenocarcinomatous areas and the sarcomatous areas suggested that sarcomatous transformation occurred in the cholangiocarcinoma and then spread rapidly. Immunohistochemically, the adenocarcinomatous elements were positive for cytokeratin, carcinoembryonic antigen (CEA) and epithelial membrane antigen, and negative in the sarcomatous cells. Vimentin was positive only in the sarcomatous elements. The findings of the present case support the view that carcinosarcomas represent carcinomas that develop sarcomatous elements via metaplasia of the epithelial element.