Protective effects of coenzyme Q10 on cell damage induced by hydrogen peroxides in cultured skin fibroblasts

Understanding coenzyme Q

Coenzyme Q (CoQ), also known as ubiquinone, comprises a benzoquinone head group and a long isoprenoid side chain. It is thus extremely hydrophobic and resides in membranes. It is best known for its complex function as an electron transporter in the mitochondrial electron transport chain (ETC) but is also required for several other crucial cellular processes. In fact, CoQ appears to be central to the entire redox balance of the cell. Remarkably, its structure and therefore its properties have not changed from bacteria to vertebrates. In metazoans, it is synthesized in all cells and is found in most, and maybe all, biological membranes. CoQ is also known as a nutritional supplement, mostly because of its involvement with antioxidant defenses. However, whether there is any health benefit from oral consumption of CoQ is not well established. Here we review the function of CoQ as a redox-active molecule in the ETC and other enzymatic systems, its role as a prooxidant in reactive oxygen species generation, and its separate involvement in antioxidant mechanisms. We also review CoQ biosynthesis, which is particularly complex because of its extreme hydrophobicity, as well as the biological consequences of primary and secondary CoQ deficiency, including in human patients. Primary CoQ deficiency is a rare inborn condition due to mutation in CoQ biosynthetic genes. Secondary CoQ deficiency is much more common, as it accompanies a variety of pathological conditions, including mitochondrial disorders as well as aging. In this context, we discuss the importance, but also the great difficulty, of alleviating CoQ deficiency by CoQ supplementation.

Modulatory Effect of Rosmarinic Acid on H2O2-Induced Adaptive Glycolytic Response in Dermal Fibroblasts

Oxidative stress induces the adaptive response and alteration of energy metabolism across human cell types. Dermal fibroblasts shift their energy system to overload anaerobic glycolysis when exposed to sub-lethal hydrogen peroxide (H₂O₂). However, oxidative stress levels in the cells can be depleted by antioxidants, and such cellular changes can therefore be modulated. The present study aimed to investigate the modulatory effect of rosmarinic acid (a polyphenol antioxidant) against H₂O₂-induced reactive oxygen species (ROS) and the glycolytic adaptive response in fibroblasts. The results showed that H₂O₂ caused a significant ROS increase in the cells, and pre-treatment with rosmarinic acid (5-50 µM) decreased ROS significantly in the presence of glutathione. Rosmarinic acid modulated the adaptive response in H₂O₂-treated cells by decreasing glucose consumption and lactate production. The rosmarinic acid also recovered intracellular ATP and decreased NADPH production via the pentose phosphate pathway. Several glycolytic enzymes, including hexokinase-2 (HK-2), phosphofructokinase-2 (PFK-2), and lactate dehydrogenase A (LDHA), were downregulated in cells treated with rosmarinic acid. Furthermore, the key antioxidant enzymes: glutathione-disulfide reductase (GSR), glutathione peroxidase-1 (GPx-1), and peroxiredoxin-1 (Prx-1) and redox protein thioredoxin-1 (Trx-1) were upregulated in treated cells compared to control cells. To sum up, the rosmarinic acid could be used as an antioxidant against H₂O₂-induced adaptive responses in fibroblasts by modulating glucose metabolism, glycolytic genes, and GSH production. The present work indicates that rosmarinic acid holds promise in cell-based research applications for combating ROS and enhancing dermal fibroblast health.

Orally ingested ubiquinol-10 or ubiquinone-10 reaches the intestinal tract and is absorbed by the small intestine of mice mostly in its original form

Coenzyme Q10 (CoQ10) is an important lipid-soluble antioxidant and an essential component of the mitochondria. The oral bioavailability of the reduced form of CoQ10, ubiquinol-10, has been reported to be greater than that of the oxidized form of CoQ10, ubiquinone-10, in some studies. In contrast, it has also been highlighted that the oral bioavailability of ubiquinol-10 is not superior to that of ubiquinone-10 because ubiquinol-10 may be oxidized during digestion. In fact, it has not been shown which form of CoQ10 exists in the process from oral intake to absorption in the gastrointestinal tract. In this study, the amounts of ubiquinol-10 and ubiquinone-10 were measured in the gastrointestinal content and small intestine tissue after oral administration of ubiquinol-10 or ubiquinone-10 to C57BL/6J mice. The form of CoQ10 detected in the gastrointestinal content and small intestine tissue was almost the same as that when administered orally. The results of our study suggested that the orally administered ubiquinol-10 and ubiquinone-10 mostly reached the small intestine without oxidizing to ubiquinone-10 and reducing to ubiquinol-10, and both were absorbed by the small intestine tissue in almost their original forms.

The Role of Antioxidants in the Interplay between Oxidative Stress and Senescence

Cellular senescence is an irreversible state of cell cycle arrest occurring in response to stressful stimuli, such as telomere attrition, DNA damage, reactive oxygen species, and oncogenic proteins. Although beneficial and protective in several physiological processes, an excessive senescent cell burden has been involved in various pathological conditions including aging, tissue dysfunction and chronic diseases. Oxidative stress (OS) can drive senescence due to a loss of balance between pro-oxidant stimuli and antioxidant defences. Therefore, the identification and characterization of antioxidant compounds capable of preventing or counteracting the senescent phenotype is of major interest. However, despite the considerable number of studies, a comprehensive overview of the main antioxidant molecules capable of counteracting OS-induced senescence is still lacking. Here, besides a brief description of the molecular mechanisms implicated in OS-mediated aging, we review and discuss the role of enzymes, mitochondria-targeting compounds, vitamins, carotenoids, organosulfur compounds, nitrogen non-protein molecules, minerals, flavonoids, and non-flavonoids as antioxidant compounds with an anti-aging potential, therefore offering insights into innovative lifespan-extending approaches.