Metabolites and JAK/STAT pathway were involved in the liver and spleen damage in male Wistar rats fed with mequindox.

Mequindox (MEQ) is a novel synthetic quinoxaline 1,4-dioxides antibacterial agent and growth promoter in animal husbandry. This study was to investigate whether reactive oxygen species (ROS), the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway, suppressors of cytokine signaling (SOCS) and inflammatory cytokines were involved in toxicities of MEQ. Our data demonstrated that high dose of MEQ (275 mg/kg) apparently led to tissue impairment combined with imbalance of redox in liver. In liver and spleen samples, hydroxylation metabolites and desoxymequindox were detected, directly confirming the potential link of N→O group reduction metabolism with its organ toxicity. Moreover, up-regulation of JAK/STAT, SOCS family, tumor necrosis factor (TNF-α) and interleukin-6 (IL-6) were also observed in the high-dose group. Meanwhile, significant changes of oxidative stress indices in liver were observed in the high-dose group. As for NADPH subunit, the mRNA levels of many subunits were significantly up-regulated at low doses but down-regulated in a dose-dependent manner in liver and spleen, suggesting an involvement of NADPH in MEQ metabolism and ROS generation. In conclusion, we reported the dose-dependent long-term toxicity as well as the discussion of the potential mechanism and pathways of MEQ, which raised further awareness of its toxicity following with the dose change.