Rifampicin and Isoniazid Induced Liver Injury via the Pregnane X Receptor

Abstract

BackgroundDrug‐induced liver injury (DILI) is a significant cause of anti‐tubercular therapy failure. Rifampicin and isoniazid co‐treatment have been shown to lead to cholestatic liver injury associated with the accumulation of protoporphyrin IX (PPIX, a heme precursor) in a human pregnane X receptor (hPXR) dependent manner in mice. Therefore, the activation of hPXR by rifampicin can lead to DILI via PPIX accumulation, thus antagonism of hPXR and modulation of PPIX transport and degradation can prevent the clinical consequences of DILI.ObjectiveUsing an hPXR mouse model and primary human hepatocytes we will induce liver toxicity and evaluate the potential of a novel small molecule inhibitor of hPXR developed by our laboratory to prevent liver injury and Mlkl activation associated with rifampicin and isoniazid treatment.MethodsPPIX accumulation was assessed by fluorescence and LC/MS/MS in human cell lines and humanized transgenic mice. hPXR target gene expression was evaluated using Western Blot and qRT‐PCR analyses in human primary cells and humanized mice. Liver injury was evaluated by analyzing mouse liver enzyme activity in sera and via histopathologic examination.ResultsALAS1/Alas1 (rate‐limiting enzyme of heme synthesis) is increased in response to isoniazid in both hPXR transgenic mice and PXR knockout mice. FECH/Fech (heme synthesis enzyme) is reduced in response to isoniazid in both mouse strains. PPIX is increased in the liver of hPXR mice treated with both rifampicin and isoniazid. Rifampicin and isoniazid co‐treatment activate necroptosis markers in hPXR mice.ConclusionsAntagonism of hPXR with a small molecule may be a viable therapeutic strategy to reduce liver injury.Support or Funding InformationFunding provided by ALSAC and NIGMS (GM 086415 & 110034)