Antioxidants, Oxidative Damage and Oxygen Deprivation Stress: a Review

Abstract

Oxidative stress is induced by a wide range of environmental factors including UV stress, pathogen invasion (hypersensitive reaction), herbicide action and oxygen shortage. Oxygen deprivation stress in plant cells is distinguished by three physiologically different states: transient hypoxia, anoxia and reoxygenation. Generation of reactive oxygen species (ROS) is characteristic for hypoxia and especially for reoxygenation. Of the ROS, hydrogen peroxide (H(2)O(2)) and superoxide (O(2)(.-)) are both produced in a number of cellular reactions, including the iron-catalysed Fenton reaction, and by various enzymes such as lipoxygenases, peroxidases, NADPH oxidase and xanthine oxidase. The main cellular components susceptible to damage by free radicals are lipids (peroxidation of unsaturated fatty acids in membranes), proteins (denaturation), carbohydrates and nucleic acids. Consequences of hypoxia-induced oxidative stress depend on tissue and/or species (i.e. their tolerance to anoxia), on membrane properties, on endogenous antioxidant content and on the ability to induce the response in the antioxidant system. Effective utilization of energy resources (starch, sugars) and the switch to anaerobic metabolism and the preservation of the redox status of the cell are vital for survival. The formation of ROS is prevented by an antioxidant system: low molecular mass antioxidants (ascorbic acid, glutathione, tocopherols), enzymes regenerating the reduced forms of antioxidants, and ROS-interacting enzymes such as SOD, peroxidases and catalases. In plant tissues many phenolic compounds (in addition to tocopherols) are potential antioxidants: flavonoids, tannins and lignin precursors may work as ROS-scavenging compounds. Antioxidants act as a cooperative network, employing a series of redox reactions. Interactions between ascorbic acid and glutathione, and ascorbic acid and phenolic compounds are well known. Under oxygen deprivation stress some contradictory results on the antioxidant status have been obtained. Experiments on overexpression of antioxidant production do not always result in the enhancement of the antioxidative defence, and hence increased antioxidative capacity does not always correlate positively with the degree of protection. Here we present a consideration of factors which possibly affect the effectiveness of antioxidant protection under oxygen deprivation as well as under other environmental stresses. Such aspects as compartmentalization of ROS formation and antioxidant localization, synthesis and transport of antioxidants, the ability to induce the antioxidant defense and cooperation (and/or compensation) between different antioxidant systems are the determinants of the competence of the antioxidant system.

Microcystin extracts induce ultrastructural damage and biochemical disturbance in male rabbit testis

“…Although H 2 O 2 is less reactive than other ROS in cells, it can be the source of hydroxyl radical formation through the Fenton reaction. Hydroxyl radicals, in turn, initiate LPO (Carubelli et al, 1990;Blokhina et al, 2003). The significant increase of LPO and H 2 O 2 demonstrated the excessive generation of ROS in testis caused by MCs.…”

Nitric oxide, mitochondrial hyperpolarization, and T cell activation☆

“…H 2 O 2 could leave the mitochondrion and act as a second messenger that can mediate gene transcription and cell proliferation. Induction of apoptosis or necrosis by H 2 O 2 requires transformation into an ROI, e.g., OH − , through the Fenton reaction [53].…”

Induction of Oxidative Stress by Sunflower Phytotoxins in Germinating Mustard Seeds

“…The scavenging of the superoxide radical O ÁÀ 2 À Á is achieved through an upstream enzyme, superoxide dismutase (SOD), which catalyses the dismutation of O ÁÀ 2 À Á to hydrogen peroxide (H 2 O 2 ) and plays a role in protecting cells against the toxic effects of those radicals produced in different cellular compartments (del Rio et al, 2002). Furthermore, the intracellular level of H 2 O 2 is regulated by a wide range of enzymes, the most important being catalase (CAT) (Blokhina et al, 2003). Synthesis of SOD and CAT as an adaptive response to oxidative stress has been reviewed (Mittler, 2002).…”