Spatial analysis of renal acetaminophen metabolism and its modulation by 4-methylpyrazole with DESI mass spectrometry imaging.

ABSTRACT

Acute kidney injury (AKI) is a common complication in acetaminophen (APAP) overdose patients and can negatively impact prognosis. Unfortunately, N-acetylcysteine, which is the standard of care for the treatment of APAP hepatotoxicity does not prevent APAP-induced AKI. We have previously demonstrated the renal metabolism of APAP and identified fomepizole (4-methylpyrazole, 4MP) as a therapeutic option to prevent APAP-induced nephrotoxicity. However, the kidney has several functionally distinct regions, and the dose-dependent effects of APAP on renal response and regional specificity of APAP metabolism are unknown. These aspects were examined in this study using C57BL/6J mice treated with 300-1200 mg/kg APAP and mass spectrometry imaging (MSI) to provide spatial cues relevant to APAP metabolism and the effects of 4MP. We find that renal APAP metabolism and generation of the nonoxidative (APAP-GLUC and APAP-SULF) and oxidative metabolites (APAP-GSH, APAP-CYS, and APAP-NAC) were dose-dependently increased in the kidney. This was recapitulated on MSI which revealed that APAP overdose causes an accumulation of APAP and APAP GLUC in the inner medulla and APAP-CYS in the outer medulla of the kidney. APAP-GSH, APAP-NAC, and APAP-SULF were localized mainly to the outer medulla and the cortex where CYP2E1 expression was evident. Interestingly, APAP also induced a redistribution of reduced GSH, with an increase in oxidized GSH within the kidney cortex. 4MP ameliorated these region-specific variations in the formation of APAP metabolites in renal tissue sections. In conclusion, APAP metabolism has a distinct regional distribution within the kidney, the understanding of which provides insight into downstream mechanisms of APAP-induced nephrotoxicity.