Reactive oxygen species, ROS

One of the important consequences of neuronal stimulation is increased neuronal aerobic metabolism which produces reactive oxygen species (ROS). ROS can oxidize several biomoiecules (carbohydrates, DNA, lipids, and proteins). Thus, even oxygen, which is essential for aerobic life, may be potentially toxic to cells. Addition of one electron to molecular oxygen (O,) generates a free radical [O2)) the superoxide anion. This is converted through activation of an enzyme, superoxide dismurase, to hydrogen peroxide (H-iO,), which is, in turn, the source of the hydroxyl radical (OH). Usually catalase... 

Airway inflammation is a characteristic clinical feature of asthma. The distinction between the LAR and chronic inflammation becomes more difficult as the disease progresses. Infiltrated leukocytes release ototoxic mediators such as reactive oxygen species (ROS) and cationic (basic) proteins causing epithelial damage and cyfo/cmas that perpetuate the inflammation. Sustained inflammation leads to airway hyperrespon-siveness and airway remodeling. 

Bronchial Asthma. Figure 2 Mechanisms of bronchial hyperresponsiveness. Toxic products from eosinophils [cationic peptides, reactive oxygen species (ROS)] cause epithelial injury. Nerve endings become easily accessible to mediators from mast cells, eosinophils [eosinophil-derived neurotoxin (EDN)], and neutrophils, and to airborne toxicants such as S02. Activation of nerve endings stimulates effector cells like mucosal glands and airway smooth muscle either directly or by cholinergic reflexes. 

Increased accumulation of reactive oxygen species (ROS) in biological systems. 

In the last few decades, several epidemiological studies have shown that a dietary intake of foods rich in natural antioxidants correlates with reduced risk of coronary heart disease particularly, a negative association between consumption of polyphenol-rich foods and cardiovascular diseases has been demonstrated. This association has been partially explained on the basis of the fact that polyphenols interrupt lipid peroxidation induced by reactive oxygen species (ROS). A large body of studies has shown that oxidative modification of the low-density fraction of lipoprotein (LDL) is implicated... 

The protective effects of carotenoids against chronic diseases appear to be correlated to their antioxidant capacities. Indeed, oxidative stress and reactive oxygen species (ROS) formation are at the basis of oxidative processes occurring in cardiovascular incidents, cancers, and ocular diseases. Carotenoids are then able to scavenge free radicals such as singlet molecular oxygen ( O2) and peroxyl radicals particularly, and protect cellular systems from oxidation. 

A molecule that has a prooxidant effect can be dehned as a molecule that can react with reactive oxygen species (ROS) to form compounds more deleterious to biomolecules than the ROS alone. Possible prooxidant activity of carotenoids was for the first time mentioned by Burton and Ingold. Since then, many other examples of loss of antioxidant activity or prooxidant activity have been illustrated and reviewed in the literature. Increasing oxygen partial pressure (PO2) and/or carotenoid concentration can convert a carotenoid from antioxidant to prooxidant. Thus, depending on the environment, the same molecule can exert either antioxidant or prooxidant activity. ... 

Skin inflammation induced by reactive oxygen species (ROS) an in vivo model. Br. J. Dermatol. 125, 325-329. 

Lipid peroxidation (see Fig. 17.2) is a chain reaction that can be attacked in many ways. The chain reaction can be inhibited by use of radical scavengers (chain termination). Initiation of the chain reaction can be blocked by either inhibiting synthesis. of reactive oxygen species (ROS) or by use of antioxidant enzymes like superoxide dismutase (SOD), complexes of SOD and catalase. Finally, agents that chelate iron can remove free iron and thus reduce Flaber-Weiss-mediated iron/oxygen injury. 

In addition to the QM structure of the natural terpene QMs, the reactive oxygen species (ROS) may also play a significant role in the observed biological activities. In the synthesis of taxodione and taxodone, QMs were formed from the catechol precursors through the spontaneous oxidation in the presence of silica gel.7, 8,49-51... 

Fullerene Cgo also functions efficiently as an antioxidant, actually being better than other lipid-soluble antioxidants at scavenging reactive oxygen species (ROS) (Wang et al., 1999). Water-soluble derivatives of C o, such as a poly-hydroxyl form, are able to function in the same respect in aqueous environments. 

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