Ticlopidine-Induced Cholestatic Inflammatory Hepatitis: New Insights into Pathogenetic Mechanisms of Drug-Related Hepatotoxicity

Abstract

In immune-induced liver damage the reactive metabolites may covalently bind or alter liver proteins such as cytochrome P450 enzymes, which leads to activation of the immune system. Ticlopidine is an inhibitor of CYP2C19 human liver cytochrome. We attempted to analyse the role of cytochrome CYP2C19 genetic polymorphism in the development of ticlopidine-induced cholestatic hepatitis and relate it with the specific immune reactivity to ticlopidine, different cytokine profiles and induction of necrosis and apoptosis within the liver tissue. Three patients with cholestatic hepatitis with ticlopidine-related liver injury, 3 patients with obstructive jaundice due to choledocholithiasis, 3 patients treated with ticlopidine without liver damage and 10 healthy individuals were studied. Genotyping for the following genotypes CYP2C19 (CYP2C19*1–3) were tested after polymerase chain reaction (PCR) by restriction fragment length polymorphism (RFLP) with Sma I and BamH I enzymes. The T cell reactivity to ticlopidine was analysed by T cell proliferation assay in PBMC against ticlopidine, tetanus toxoid antigen and phytohemagglutinin on days 0, 90, 150 and 210 after therapy withdrawal. The serum levels of INF-γ, IL-2, IL-4, IL-10, TNF-α, sFas and sFasL were measured by ELISA at the same time points. Apoptosis was analysed by TUNEL assay. All patients with cholestatic hepatitis had “slow metabolizers” genotypes in contrast to other groups. The T cell reactivity to ticlopidine was present only in all the cholestatic hepatitis patients together with substantial decrease in levels of INF-γ, IL-2 and TNF-α during all of the follow-up period. Cholestatic hepatitis patients had high apoptotic index in TUNEL assay. The genetic polymorphism of the cytochrome CYP2C19 gene is directly responsible for the susceptibility to the ticlopidine-induced liver damage. Th1 type of immune reactivity plays the key role in the pathogenesis of drug-induced hepatotoxicity.