Overexpression of interferon γ-inducible protein 10 in the liver of patients with type i autoimmune hepatitis identified by suppression subtractive hybridization

Abstract

To clarify gene expression profiles in the liver may elucidate the pathogenesis of type I autoimmune hepatitis (AIH). Using suppression subtractive hybridization (SSH), we identified genes overexpressed in the liver of AIH. A small liver biopsy sample from a patient with definite AIH was available to be analyzed in our system. By mixing cDNA synthesized from this sample as a 'tester' and cDNA from a normal liver as a 'driver,' we subtracted cDNA to enrich genes overexpressed in AIH. After polymerase chain reaction (PCR) amplification and subcloning, we identified subtracted genes by sequencing 50 randomly selected clones. Only one cDNA fragment, which is identical to interferon inducible protein 10 (IP-10), was overexpressed by > 10 times in the liver of AIH, as compared with control. We confirmed IP-10 overexpression in all eight patients with AIH by reverse transcription PCR. Immunohistochemical analysis demonstrated increased IP-10 expression in hepatocytes in the liver of AIH. Reverse transcription PCR analysis of 63 liver biopsy samples with various liver diseases revealed that IP-10 expression was significantly higher in AIH (p = 0.025) and chronic hepatitis C (p = 0.0043) than in other liver diseases. Interestingly, the amount of IP-10 mRNA expression was correlated with serum ALT values in AIH (p = 0.0006), but not in chronic hepatitis C (p = 0.43). These results indicate the IP-10 expression in the liver might be used as a preferential marker of AIH, and that IP-10 has some pathophysiological roles in the liver damage of AIH.