Exploring Reactive Oxygen Species (ROS) with AAT

What are ROS?

Reactive oxygen species (ROS) are oxygen-containing molecules and are often simplified as "oxygen radicals". These can be stable molecular oxidants as well as free radicals. Since oxygen atoms contain two unpaired electrons in separate orbits of its outer electron shell, it is susceptible to radical formation. The sequential reduction of oxygen through the addition of electrons leads to the formation of a number of ROS including superoxide anion (O₂^-), hydrogen peroxide (H₂O₂), hydroxyl radical (•OH), hypochlorous acid (HOCl), peroxynitrite anion (ONOO^-), and nitric oxide (NO). 

Cellular respiration within mitochondria naturally produces ROS as a by-product, but ROS are also produced to combat viruses and bacteria [1]. ROS are also formed as intermediates of oxidoreductase enzymes and metal-catalyzed oxidation. Furthermore, cigarette smoke and other environmental toxins, such as particulate matter, are generally considered to be other sources of reactive oxygen species.

Antioxidants are the antagonists of ROS. Although ROS are associated with various pathologies such as cancer, diabetes and cardiovascular diseases, and in high concentrations can lead to oxidative stress, they are also important signaling molecules (so-called "second messengers") for the organism. They are formed by ligand-receptor interactions and act as specific messengers in signaling cascades involved, for example, in cell proliferation and differentiation [2].

The causal involvement of ROS in the above diseases is still debated, but it is considered proven that ROS in high concentrations have a harmful effect for an organism, but in small concentrations they are physiological and have health-promoting properties. This non-linear effect relationship is called "mitohormesis". This refers to a biochemical process, in which the specific induction of mitochondrial stress results in the proliferation of free radicals in the cell. However, this ultimately leads to an activation of the cell's own defense against oxygen radicals and thus represents an advantage for the organism. This physiological effect relationship was demonstrated, for example, by Matthias Blüher's group in a study in 2009 on the subject of sport and antioxidants [3].

Antioxidants prevent health-promoting effects of physical activity in humans

Sport has a health-promoting effect, no one is likely to dispute this fact. Vitamins, which include antioxidants such as vitamin C and vitamin E, are also relevant for a person's health. But if antioxidants are ingested after exercise, for example in the form of dietary supplements, they can negate the positive effect of physical exercise. In 2009, an original paper was published by Blüher et al., in which this effect was investigated [3].

Physical activity has been shown to contribute to diabetes type 2 prevention because it significantly improves glucose metabolism in the insulin-resistant state. Several mechanisms are involved in this. For example, glucose transporter expression is enhanced as well as the translocation of glucose transporters to the plasma membrane independent of insulin. In addition, exercise improves mitochondrial metabolism, and reduced mitochondrial metabolism has been functionally associated with type 2 diabetes. However, reactive oxygen species are also produced as inevitable by-products of oxidative glucose metabolism.

It is also known that muscles generate free radicals, especially during contraction and physical exertion. The group led by Matthias Blüher showed that these ROS, which are physiologically generated during physical exercise, are necessary for the insulin-sensitizing effect of physical exercise in healthy people and that antioxidants such as vitamin C and vitamin E cancel out the health-promoting effects of physical exercise and oxidative stress in humans. For this purpose, subjects were tested for the aforementioned effects for four weeks after exercise. Half of the subjects received vitamin C and vitamin E supplementation after exercise, while the other half did not. Subsequently, on the one hand, the effects on insulin sensitivity were measured using glucose infusion rates (GIR). Second, ROS defense capacity was analyzed by peroxisome proliferator-activated receptor gamma (PPAR) expression and PPAR co-activators PGC1 and PGC1.

The results showed that supplementation with antioxidants led to blockage of ROS-induced defense capacity in the subjects, and the mechanisms to improve insulin sensitivity were also blocked by the administration of vitamin C and vitamin E. These findings are consistent with the concept of mitohormesis, in which physiological ROS concentrations are beneficial to health. The working group concludes that antioxidant supplementation may preclude the health-promoting effects of exercise in humans because it blocks the ROS-activated beneficial processes (Fig. 1).

Figure 1: Antioxidant supplementation may prevent the health-promoting effects of exercise. Mitohormesis links physical exercise and subsequent reactive oxygen species formation to insulin sensitivity and antioxidant protection. Physical activity has a positive effect on insulin resistance as well as endogenous ROS defense. This effect is blocked by ingestion of antioxidants (based on Blüher et al. 2009). 

Are you looking for suitable products for your research on reactive oxygen species? Our partner AAT Bioquest offers numerous indicators, probes and assay kits for working with ROS. In the tables below you can see a selection of the corresponding products and for which oxygen species they can be used. Still not enough for you? Click on the button below to find all AAT Bioquest products related to "Cellular & Oxidative Stress":

Discover products on the subject of "Cellular & Oxidative Stress"

For more information, take a look at AAT's product brochure focusing on "Reactive Oxygen Species":

Reactive Oxygen Species (ROS) Detection

Table 1: Intracellular ROS Products Selection Guide

Table 2: ROS-selective Probes and Assay Kits

Sources:

[1] https://www.chemie.de/lexikon/Reaktive_Sauerstoffspezies.html

[2] Reactive oxygen species as intracellular messengers during cell growth and differentiation, H. Sauer, M. Wartenberg, J. Hescheler, Cell Physiol Biochem. 2001;11(4):173-86. doi: 10.1159/000047804.

[3] Blüher et al., Antioxidants prevent health-promoting effects of physical exercise in humans, 2009

Tables from AAT Bioquest: https://www.aatbio.com/catalog/reactive-oxygen-species-ros-indicators-probes-quantification-kits