Interaction of 9,10-phenanthraquinone with dithiol causes oxidative modification of Cu,Zn-superoxide dismutase (SOD) through redox cycling

Abstract

9,10-Phenanthraquinone (9,10-PQ) is abundant in diesel exhaust particles (DEP) and causes oxidative protein modification in cells. We previously reported that redox cycling of 9,10-PQ with dithiols leads to the generation of an excess of superoxide (O₂•⁻). Cu,Zn-superoxide dismutase (Cu,Zn-SOD), which dismutates O₂•⁻ to hydrogen peroxide (H₂O₂), is sensitive to its own product, H₂O₂. In this study, incubating 9,10-PQ with dithiols, but not monothiols, for 24 hr, resulted in the conversion of native Cu,Zn-SOD to its charge isomers, some of which did not show enzyme activity. Exposing Cu,Zn-SOD to 9,10-PQ in the presence of dihydrolipoic acid (DHLA), a model for low molecular weight endogenous dithiols, caused a concentration-dependent decrease in the enzyme activity. Under these conditions, copper release from the active site and Cu,Zn-SOD oxidation were detected, the evidence for which was carbonyl formation. Experiments using agents that scavenge reactive oxygen species (ROS) indicated that the hydroxyl radical (•OH) derived from H₂O₂ plays a critical role in the fragmentation of the enzyme. The findings presented suggest that Cu,Zn-SOD readily undergoes oxidative modification associated with activity loss, caused by ROS generated by the redox cycling of 9,10-PQ with endogenous dithiols such as DHLA and, presumably, proximal protein thiols.

Interaction of Quinone-Related Electron Acceptors with Hydropersulfide Na2S2: Evidence for One-Electron Reduction Reaction

“…Because hydropersulfide possesses a high nucleophilicity and antioxidant capability, ,− the unexpected consumption of reactive sulfur species in the body might be linked to disruption of redox homeostasis. Although, there have been many reports regarding the implications of 9,10-PQ in oxidative stress-dependent toxicity in vitro and in vivo , − we have proposed a variety of redox cycle reactions of 9,10-PQ, leading to ROS production: (1) enzymes catalyzed one- and two-electron reductions of 9,10-PQ, ,, (2) interaction of 9,10-PQ with dithiols, , and now (3) one-electron reduction of 9,10-PQ by hydropersulfides. Thus, we speculate that hydropersulfides can participate in redox reactions with 9,10-PQ, possibly contributing to the toxicity of this, and other, quinones.…”

“…Furthermore, 9,10-PQ interacts with neuronal nitric oxide synthase (which has a P450 reductase domain) and inhibits its catalytic activity by shunting electrons from NADPH . In our previous study, we showed that dithiol compounds, such as dithiothreitol, 2,3-dimercapto-1-propanesulfonic acid, 2,3-dimercapto-1-propanol, and dihydrolipoic acid, but not monothiols such as GSH, cysteine, and N -acetylcysteine, also interacted with the quinone to yield 9,10-PQ •– and the corresponding thiyl radical. , …”

“…5 In our previous study, we showed that dithiol compounds, such as dithiothreitol, 2,3-dimercapto-1-propanesulfonic acid, 2,3-dimercapto-1-propanol, and dihydrolipoic acid, but not monothiols such as GSH, cysteine, and N-acetylcysteine, also interacted with the quinone to yield 9,10-PQ •− and the corresponding thiyl radical. 6,7 Recent studies have identified other thiol-derived/related species that may also have the ability to participate in the redox chemistry described above. There are hydropersulfide and hydropolysulfide species such as Cys hydropersulfide (Cys-SSH, ca.…”

Chemical toxicology of reactive species in the atmosphere: two decades of progress in an electron acceptor and an electrophile

“…Redox cycling of 9,10-phenanthrenequinone to generate reactive oxygen species 9,10-PQ, which is generated from phenanthrene through photooxidation (David and Boule, 1993), undergoes one-electron reduction by cytochrome P450 reductase in the presence of NADPH or by exogenous and endogenous dithiols to form its semiquinone radical (9,10-PQ •-), which readily reacts with molecular oxygen to yield O 2 •-and 9,10-PQ again (Fig. 2) (Kumagai et al, 1997;Koizumi et al, 2013).…”

Redox Homeostasis is Disturbed by Redox Cycling between Reactive Cysteines of Thioredoxin 1 and 9,10-Phenanthrenequinone, an Atmospheric Electron Acceptor

“…We previously reported that 9,10-PQ preferentially interacts with dithiol compounds such as dithiothreitol (DTT), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and 2,3-dimercapto-1-propanol (BAL), thereby causing ROS generation and thiol oxidation . Furthermore, we showed that 9,10-PQ undergoes redox cycling with dihydrolipoic acid (DHLA), an endogenous dithiol with low molecular weight, to produce ROS that results in oxidative damage of Cu, Zn-superoxide dismutase (Cu, Zn-SOD) . These results suggest that proximal cysteines in proteins interact with 9,10-PQ to generate excess ROS, leading to the disruption of cellular homeostasis.…”