Abstract
Use of the fluoroquinolone antibiotic trovafloxacin (TVX) was restricted due to idiosyncratic, drug-induced liver injury (IDILI). Previous studies demonstrated that tumor necrosis factor-alpha (TNF) and TVX interact to cause death of hepatocytes in vitro that was associated with prolonged activation of c-Jun N-terminal kinase (JNK), activation of caspases 9 and 3, and DNA damage. The purpose of this study was to explore further the mechanism by which TVX interacts with TNF to cause cytotoxicity. Treatment with TVX caused cell cycle arrest, enhanced expression of p21 and impaired proliferation, but cell death only occurred after cotreatment with TVX and TNF. Cell death involved activation of extracellular signal-related kinase (ERK), which in turn activated caspase 3 and ataxia telangiectasia and Rad3-related (ATR), both of which contributed to cytotoxicity. Cotreatment of HepG2 cells with TVX and TNF caused double-strand breaks in DNA, and ERK contributed to this effect. Inhibition of caspase activity abolished the DNA strand breaks. The data suggest a complex interaction of TVX and TNF in which TVX causes replication stress, and the downstream effects are exacerbated by TNF, leading to hepatocellular death. These results raise the possibility that IDILI from TVX results from MAPK and ATR activation in hepatocytes initiated by interaction of cytokine signaling with drug-induced replication stress.