Comparison of inhibitory effects between acetaminophen–glutathione conjugate and reduced glutathione in human glutathione reductase

Abstract

Acetaminophen overdose is the most frequent cause of acute liver injury. The main mechanism of acetaminophen toxicity has been attributed to oxidation of acetaminophen. The oxidation product is very reactive and reacts with glutathione generating acetaminophen-glutathione conjugate (APAP-SG). Although this conjugate has been recognized to be generally nontoxic, we have found recently that APAP-SG could produce a toxic effect. Therefore, the aim of our study was to estimate the toxicity of purified APAP-SG by characterizing the inhibitory effect in human glutathione reductase (GR) and comparing that to the inhibitory effect of the natural inhibitor reduced glutathione. We used two types of human GR: recombinant and freshly purified from red blood cells. Our results show that GR was significantly inhibited in the presence of both APAP-SG and reduced glutathione. For example, the enzyme activity of recombinant and purified GR was reduced in the presence of 4 mm APAP-SG (with 0.5 mm glutathione disulfide) by 28% and 22%, respectively. The type of enzyme inhibition was observed to be competitive in the cases of both APAP-SG and glutathione. As glutathione inhibits GR activity in cells under physiological conditions, the rate of enzyme inhibition ought to be weaker in the case of glutathione depletion that is typical of acetaminophen overdose. Notably, however, enzyme activity likely remains inhibited due to the presence of APAP-SG, which might enhance the pro-oxidative status in the cell. We conclude that our finding could reflect some other pathological mechanism that may contribute to the toxicity of acetaminophen.

Tropisetron Protects Against Acetaminophen-Induced Liver Injury via Suppressing Hepatic Oxidative Stress and Modulating the Activation of JNK/ERK MAPK Pathways

“…The increased hepatic GSH level could in part explain the hepatoprotective mechanism of tropisetron. Previous evidences showed that while the GSH content decreased below a threshold level, hepatic xanthine dehydrogenase can be converted to reversible xanthine oxidase, having an influence on superoxide radical generation and production [30, 31]. SOD is thought to be an important antioxidant enzyme, for it is closely related to the elimination of reactive oxygen species.…”

Clinical observation of the reduced glutathione in the treatment of diabetic chronic kidney disease

“…Reduced glutathione (GSH) is a tripeptide substance, including glutamate, cysteine, and glycine, which widely exists in normal cells in vivo . GSH can produce a variety of biochemical effects on cells, for example, it can be combined with a variety of chemical substances and their metabolites, and can remove the oxygen ions and other free radicals from the body . GSH, as the main metabolic regulation substance in human cells, can protect the cell membrane of liver cells, promote the activity of liver enzymes, and exhibit the detoxication and antioxidation effects .…”

“…8 GSH, as the main metabolic regulation substance in human cells, can protect the cell membrane of liver cells, promote the activity of liver enzymes, and exhibit the detoxication and antioxidation effects. 8 Currently, GSH has been used to treat CKD in clinical trials, mainly based on its role in scavenging oxygen free radicals. 9 In this study, we evaluated the effect of GSH on OS, angiogenesis factors and immune responses in diabetic CKD patients, providing new therapeutic targets for the treatment of diabetic nephropathy.…”

“…GSH can produce a variety of biochemical effects on cells, for example, it can be combined with a variety of chemical substances and their metabolites, and can remove the oxygen ions and other free radicals from the body . GSH, as the main metabolic regulation substance in human cells, can protect the cell membrane of liver cells, promote the activity of liver enzymes, and exhibit the detoxication and antioxidation effects . Currently, GSH has been used to treat CKD in clinical trials, mainly based on its role in scavenging oxygen free radicals .…”

Paracetamol-Induced Glutathione Consumption: Is There a Link With Severe COVID-19 Illness?

“…Oxidized PAC-quinone imine metabolites have also been shown to form GSH-conjugates which inhibit glutathione reductase (GR): the decreased activity of GR hampers the detoxification and antioxidant capacity of the GSH-GSSG cycle, further aggravating the pro-oxidative status in the cell (Nydlováet al, 2014).…”