Mitochondrial Coenzyme Q Redox Homeostasis and Reactive Oxygen Species Production

Abstract

Mitochondrial coenzyme Q (mtQ) of the inner mitochondrial membrane is a redox active mobile carrier in the respiratory chain that transfers electrons between reducing dehydrogenases and oxidizing pathway(s). mtQ is also involved in mitochondrial reactive oxygen species (mtROS) formation through the mitochondrial respiratory chain. Some mtQ-binding sites related to the respiratory chain can directly form the superoxide anion from semiubiquinone radicals. On the other hand, reduced mtQ (ubiquinol, mtQH2) recycles other antioxidants and directly acts on free radicals, preventing oxidative modifications. The redox state of the mtQ pool is a central bioenergetic patameter that alters in response to changes in mitochondrial function. It reflects mitochondrial bioenergetic activity and mtROS formation level, and thus the oxidative stress associated with the mitochondria. Surprisingly, there are few studies describing a direct relationship between the mtQ redox state and mtROS production under physiological and pathological conditions. Here, we provide a first overview of what is known about the factors affecting mtQ redox homeostasis and its relationship to mtROS production. We have proposed that the level of reduction (the endogenous redox state) of mtQ may be a useful indirect marker to assess total mtROS formation. A higher mtQ reduction level (mtQH2/mtQ total ) indicates greater mtROS formation. The mtQ reduction level, and thus the mtROS formation, depends on the size of the mtQ pool and the activity of the mtQ-reducing and mtQH2-oxidizing pathway(s) of respiratory chain. We focus on a number of physiological and pathophysiological factors affecting the amount of mtQ and thus its redox homeostasis and mtROS production level.

Oxidative Phosphorylation for Aerobic Survival, but Not for Growth: The Peculiar ‘Make-Accumulate-Consume’ Strategy in Zymomonas mobilis

“…Along with activities such as those of cytochome c peroxidase that remove hydrogen peroxide, electron transport itself is a major source of ROS [46]. At a higher degree of reduction of its electron carriers, ROS production in the respiratory chain tends to increase [47]. We hypothesize that the downregulation of the respiratory promoters and the decrease in NADH oxidase activity that we see under ethanol stress are aimed primarily at minimizing respiratory ROS production.…”

Acidic fibroblast growth factor inhibits reactive oxygen species-induced epithelial–mesenchymal transdifferentiation in vascular endothelial cells via the miR-155-5p/SIRT1/Nrf2/HO-1 pathway to promote wound healing in diabetic mice

“…Mitochondria are the main sites of ROS production, and structural damage or dysfunction of these organelles can easily disrupt the in vivo balance and induce oxidative damage [ 35 ]. Harmful stimuli alter the permeability of the mitochondrial membrane, reduce membrane potential, block the transmission of the mitochondrial electron transport chain, inhibit the production of cytochrome c, inhibit the levels of adenosine triphosphate and accelerate the accumulation of total ROS in cells [ 36 ]. Based on the finding that aFGF could ameliorate oxidative stress in the wounds of animal models, this study confirmed that high glucose could induce abnormal changes in the MMP and the accumulation of mtROS and ROS in an in vitro high-glucose-induced VE cell model.…”

Complex II ambiguities—FADH2 in the electron transfer system

“…C , from ambiguous NADH-FADH 2 analogy ( 73 ) to ( D ) graphical misconception ( 58 ), as in ref. ( 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 ...…”