Author(s)

Jeff B. Helms^1,2*, Lauren P. Saunders², Jamie Meyer², Charles J. Costa², Eric Plowman², Nick Williford¹, Matthew Corbitt¹, Jeremy P. Holden³, Craig Gatto²

¹Department of Biology, Upper Iowa University, Fayette, IA, USA.
²Division of Neuroscience and Physiology, Department of Biological Science, Illinois State University, Normal, IL, USA.
³Department of Internal Medicine, University of Wisconsin-Madison Medical Center, Madison, WI, USA.

N-acetylbenzoquinoneimine (NABQI) is a toxic metabolite of the common analgesic acetaminophen (APAP). NABQI is an electrophilic intermediate formed via the oxidation of APAP within the cytochrome P450 system. Within the normally recommended low-dose use of APAP, NABQI is a minor metabolite which is either quickly reduced back to APAP or conjugated to Glutathione (GSH) producing an innocuous by-product. However, with overdose or prolonged high-dose usage of acetaminophen, GSH levels can become depleted and the bioactive NABQI is thought to form adducts with proteins and oxidize protein sulfhydryls producing intra- and intermolecular disulfide bridges in proteins. In this work we investigated the effect of NABQI on purified kidney Na,K-ATPase to see if the clinical renal insufficiencies seen in APAP overdose may be linked to inhibition of the Na,K-ATPase. Our work has shown that NABQI does indeed inhibit the Na,K-ATPase in a dose dependent (IC₅₀ = 19.8 ± 2.9 μM) and irreversible manner. Interestingly, brief storage of NABQI at -20°C eliminates the irreversible effects of the compound, and leads to a product that remains a potent reversible inhibitor of the Na,K-ATPase (IC₅₀ = 58.7 ± 19.5 μM). Further, the reversible inhibition produced by stored NABQI competes with para-nitrop.

Na, K-ATPase, Paracetamol, N-Acetylbenzoquinoneimine, Overdose, Renal, Electrophillic

Helms, J. , Saunders, L. , Meyer, J. , Costa, C. , Plowman, E. , Williford, N. , Corbitt, M. , Holden, J. and Gatto, C. (2015) Kinetic Characterization of Na,K-ATPase Inhibition by the Acetaminophen Metabolite N-Acetylbenzoquinoneimine. Open Journal of Molecular and Integrative Physiology, 5, 1-17. doi: 10.4236/ojmip.2015.51001.