Susceptibility of Human Platelets, Monocytes, and Neutrophils Bioenergetics to Acetaminophen

Acetaminophen (APAP) is a common over-the-counter pain reliever with high hepatotoxic potential. Although APAP hepatotoxicity has been recognized for years, the mechanisms remain elusive. APAP is metabolized to N-acetyl-p-benzoquinone imine (NAPQI) by cytochrome p450 and conjugated with GSH for detoxification, causing oxidative stress that impairs mitochondrial function. In a previous study, we found that APAP decreases rat hepatocyte respiration, and this effect is exacerbated in alcohol-treated rats. Recently, it has been reported that following APAP overdose, platelets and monocytes accumulate in the liver contributing to hepatotoxicity. In the present study, we report the inhibition of mitochondrial function of platelets and monocytes, as well as the oxidative burst capacity of monocytes and neutrophils treated with APAP. Platelets, monocytes, and neutrophils were isolated from blood of healthy human volunteers. The cells were seeded into XF96 microplates and treated with APAP in a dose-response manner for 30 min prior to mitochondrial stress test (MST). In platelets and monocytes, APAP decreases mitochondrial function in a dose-dependent manner revealed by decreased basal oxygen consumption rates (OCR), as well as decreased maximal OCR, reserve capacity, and ATP-linked OCR. In addition to MST, we tested the platelets activation with 0.2 U/ml of thombin, and monocytes and neutrophiles oxidative burst measured following activation with phorbol 12-myristate 13-acetate (PMA). APAP (5 mM) completly abolished thrombin-activation of platelets. Similarly, APAP inhibited the oxidative burst in neutrophils in a dose-dependent manner. Taken together, these data show that within an hour, APAP causes significant bioenergetic changes of platelets, monocytes and decreases the oxidative burst magnitude of neutrophils and monocytes. This work was supported by National Institute of Health grants R21AA023273 (to VDU and AS).