Ectonucleotidase NTPDase2 is selectively down-regulated in biliary cirrhosis.

BACKGROUND

Portal fibroblasts are newly identified, potentially fibrogenic liver cells that are distinct from hepatic stellate cells. The ectonucleotidase* nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) is restricted to portal fibroblasts in the normal liver. However, the fate of NTPDase2 after bile duct ligation (BDL) is unknown.

AIMS: The aim of this study was to assess the effect of experimental rat and disease-mediated human biliary cirrhosis on NTPDase2 expression in the liver.

METHODS

Cirrhosis was induced in experimental rats via BDL and carbon tetrachloride (CCl4) administration. Archived human liver biopsy specimens from normal liver, primary biliary cirrhosis, or hepatitis C cirrhosis were examined. Changes in expression of NTPDase2 were determined using confocal immunofluorescence, immunoblot, and real-time polymerase chain reaction.

RESULTS

Confocal immunofluorescence demonstrated a decrease in NTPDase2 expression after BDL. Immunoblot and real-time polymerase chain reaction demonstrated a decrease in NTPDase2 expression by portal fibroblasts after BDL. No decrease in NTPDase2 protein was noted after CCl4 administration, and NTPDase2 messenger ribonucleic acid was markedly up-regulated after CCl4 administration. Confocal immunofluorescence demonstrated a shift of NTPDase2 expression from portal areas to central areas that colocalized with alpha-smooth muscle actin after CCl4 administration. In human biopsy specimens, NTPDase2 expression was lost in cirrhosis owing to primary biliary cirrhosis, whereas NTPDase2 expression was shifted to bridging fibrous bands in cirrhosis owing to hepatitis C.

CONCLUSIONS

Loss of NTPDase2 is a common pathway in both rat and human manifestations of biliary cirrhosis. Conversely, in non-biliary cirrhosis, NTPDase2 is shifted from the portal area to bridging fibrous bands. Elucidations of the mechanisms regulating NTPDase2 expression may lead to new therapeutic approaches to fibrotic liver disease.