Trovafloxacin Potentiation of Lipopolysaccharide-Induced Tumor Necrosis Factor Release from RAW 264.7 Cells Requires Extracellular Signal-Regulated Kinase and c-Jun N-Terminal Kinase s

Trovafloxacin (TVX) is a fluoroquinolone antibiotic known to cause idiosyncratic, drug-induced liver injury (IDILI) in humans. The mechanism underlying this toxicity remains unknown. Previously, an animal model of IDILI in mice revealed that TVX synergizes with inflammatory stress from bacterial lipopolysaccharide (LPS) to produce a hepatotoxic interaction. The liver injury required prolongation of the appearance of tumor necrosis factor-a (TNF) in the plasma. The results presented here describe a model of TVX/LPS coexposure in RAW 264.7 cells acting as a surrogate for TNFreleasing cells in vivo. Pretreating cells with TVX for 2 hours before LPS addition led to increased TNF protein release into culture medium in a concentrationand time-dependent manner relative to cells treated with LPS or TVX alone. During the pretreatment period, TVX increased TNF mRNA, but this was less apparent when cells were exposed to TVX after LPS addition, suggesting that the pivotal signaling events that increase TNF expression occurred during the TVX pretreatment period. Indeed, TVX exposure increased activation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase. Inhibition of either ERK or JNK decreased the TVX-mediated increase in TNF mRNA and LPS-induced TNF protein release, but p38 inhibition did not. These results demonstrated that the increased TNF appearance from TVX-LPS interaction in vivo can be reproduced in vitro and occurs in an ERKand JNK-dependent manner.