Proteomic characterization of the possible molecular targets of pyrrolizidine alkaloid isoline-induced hepatotoxicity.

Pyrrolizidine alkaloids (PAs) are distributed in plants worldwide including medicinal herbs or teas. In the present study, we investigated the effects of isoline, which is a retronecine-type PA isolated from traditional Chinese medicinal herb Ligularia duciformis, on mouse liver proteins by using proteomic approaches. Firstly, our results showed that 110mg/kg isoline increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in serum, and hepatic tissue pathological observation further confirmed isoline-induced liver injury. Proteomic analysis showed that the liver samples from mice of isoline group demonstrated about 13 differentially expressed proteins compared with normal group, and those proteins may be involved in isoline-induced liver injury in mice. Next, all these 13 protein spots were identified by MALDI-TOF-TOF MS or LTQ MS; and among them 9 differentially expressed proteins are involved in the process of oxidative stress or cellular energy metabolism. Further lipid peroxidation analysis and ATPase assay confirmed the existing of oxidative injury induced by isoline and consequent disruption of energy metabolism. Furthermore, an in silico drug target searching program INVDOCK identified 2 potential protein targets of isoline, and the results are in support of proteomic analysis. In summary, the possible signaling molecules related with isoline-induced liver injury were demonstrated in this study.