Free Radical Biology & Medicine, Vol. 31, No. 11, pp. 1287–1312, 2001

Abstract
Reactive oxygen species (ROS) are known mediators of intracellular signaling cascades. Excessive production of ROS may, however, lead to oxidative stress, loss of cell function, and ultimately apoptosis or necrosis. A balance between oxidant and antioxidant intracellular systems is hence vital for cell function, regulation, and adaptation to diverse growth conditions. Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous oxidoreductase system with antioxidant and redox regulatory roles. In mammals, extracellular forms of Trx also have cytokine-like effects. Mammalian TrxR has a highly reactive active site selenocysteine residue resulting in a profound reductive capacity, reducing several substrates in addition to Trx. Due to the reactivity of TrxR, the enzyme is inhibited by many clinically used electrophilic compounds including nitrosoureas, aurothioglucose, platinum compounds, and retinoic acid derivatives. The properties of TrxR in combination with the functions of Trx position this system at the core of cellular thiol redox control and antioxidant defense. In this review, we focus on the reactions of the Trx system with ROS molecules and different cellular antioxidant enzymes. We summarize the TrxR-catalyzed regeneration of several antioxidant compounds, including ascorbic acid (vitamin C), selenium-containing substances, lipoic acid, and ubiquinone (Q10). We also discuss the general cellular effects of TrxR inhibition. Dinitrohalobenzenes constitute a unique class of immunostimulatory TrxR inhibitors and we consider the immunomodulatory effects of dinitrohalobenzene compounds in view of their reactions with the Trx system.

Keywords: Thioredoxin; Thioredoxin reductase; Redox regulation; Inflammation; Oxidative stress; Antioxidant; Dinitrohalobenzene; Reactive oxygen species; Free radicals

Erciyes Tıp Dergisi (Erciyes Medical Journal) 2009;31(4):369-375

Grape (Vitis Vinifera), one of the most widely consumed fruit worldwide, contain many bioactive constituents including flavonoids, polyphenols, anthocyanins and stibene derivatives resveratrol. Scientific studies have shown that grape extracts especially grape seed and skin have biological and therapeutic effects such as antioxidative, anticarcinogenic, antimicrobial, antiviral, antiaging, antiinflammatory, antidiabetic activities as well as having cardioprotective, hepatoprotective and neuroprotective effects. These results confirm that grapes widely accepted as benefical for human health to treat and prevent from diseases. This review focuses on the bioactive components and antioxidative effects of grape.

Clinica Chimica Acta 390 (2008) 1–11

As the red cell emerges from the bone marrow, it loses its nucleus, ribosomes, and mitochondria and therefore all capacity for protein synthesis. However, because of the high O2 tension in arterial blood and heme Fe content, reactive oxygen species (ROS) are continuously produced within red cells. Erythrocytes transport large amount of oxygen over their lifespan resulting in oxidative stress. Various factors can lead to the generation of oxidizing radicals such as O2•−, H2O2, HO• in erythrocytes. Evidence indicates that many physiological and pathological conditions such as aging, inflammation, eryptosis develop through ROS action. As such, red cells have potent antioxidant protection consisting of enzymatic and nonenzymatic pathways that modify highly ROS into substantially less reactive intermediates.

The object of this review is to shed light on the role of ROS both at physiological and pathological levels and the structural requirements of antioxidants for appreciable radical-scavenging activity. Obviously, much is still to be discovered before we clearly understand mechanisms of free radical systems in erythrocytes. Ongoing trends in the field are recognition of undetermined oxidant/antioxidant interactions and elucidation of important signaling networks in radical metabolism.