Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

https://downloads.hindawi.com/archive/2012/217037.pdf

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Environmentally induced oxidative stress in aquatic animals

“Oxidative stress” as a concept in redox biology and medicine has been formulated in 1985; at the beginning of 2015, approx. 138,000 PubMed entries show for this term. This concept has its merits and its pitfalls. Among the merits is the notion, elicited by the combined two terms of (i) aerobic metabolism as a steady-state redox balance and (ii) the associated potential strains in the balance as denoted by the term, stress, evoking biological stress responses. Current research on molecular redox switches governing oxidative stress responses is in full bloom. The fundamental importance of linking redox shifts to phosphorylation/dephosphorylation signaling is being more fully appreciated, thanks to major advances in methodology. Among the pitfalls is the fact that the underlying molecular details are to be worked out in each particular case, which is bvious for a global concept, but which is sometimes overlooked. This can lead to indiscriminate use of the term, oxidative stress, without clear relation to redox chemistry. The major role in antioxidant defense is fulfilled by antioxidant enzymes, not by small-molecule antioxidant compounds. The field of oxidative stress research embraces chemistry, biochemistry, cell biology, physiology and pathophysiology, all the way to medicine and health and disease research.

Oxidative stress: a concept in redox biology and medicine.

Hydrogen peroxide emerged as major redox metabolite operative in redox sensing, signaling and redox regulation. Generation, transport and capture of H2O2 in biological settings as well as their biological consequences can now be addressed. The present overview focuses on recent progress on metabolic sources and sinks of H2O2 and on the role of H2O2 in redox signaling under physiological conditions (1–10 nM), denoted as oxidative eustress. Higher concentrations lead to adaptive stress responses via master switches such as Nrf2/Keap1 or NF-κB. Supraphysiological concentrations of H2O2 (>100 nM) lead to damage of biomolecules, denoted as oxidative distress. Three questions are addressed: How can H2O2 be assayed in the biological setting? What are the metabolic sources and sinks of H2O2? What is the role of H2O2 in redox signaling and oxidative stress?

Hydrogen peroxide as a central redox signaling molecule in physiological oxidative stress: Oxidative eustress.

Oxic environments are hazardous. Molecular oxygen adventitiously abstracts electrons from many redox enzymes, continuously forming intracellular superoxide and hydrogen peroxide. These species can destroy the activities of metalloenzymes and the integrity of DNA, forcing organisms to protect themselves with scavenging enzymes and repair systems. Nevertheless, elevated levels of oxidants quickly poison bacteria, and both microbial competitors and hostile eukaryotic hosts exploit this vulnerability by assaulting these bacteria with peroxides or superoxide-forming antibiotics. In response, bacteria activate elegant adaptive strategies. In this Review, I summarize our current knowledge of oxidative stress in Escherichia coli, the model organism for which our understanding of damage and defence is most well developed.

The molecular mechanisms and physiological consequences of oxidative stress: lessons from a model bacterium.

Free radicals, reactive oxygen species, oxidative stress and its classification

Reactive oxygen species (ROS) are continuously produced and eliminated by living organisms normally maintaining ROS at certain steady-state levels Under some circumstances, the balance between ROS generation and elimination is disturbed leading to enhanced ROS level called "oxidative stress" The primary goal of this review is to characterize two principal mechanisms of protection against oxidative stress - regulation of membrane permeability and antioxidant potential The ancillary goals of this work are to describe up to date knowledge on the regulation of the previously mentioned mechanisms and to identify areas of prospective research and emerging directions in investigation of adaptation to oxidative stress The ubiquity for challenges leading to oxidative stress development calls for identification of common mechanisms They are cysteine residues and [Fe,S]-clusters of specific regulatory proteins The latter mechanism is realized via SoxR bacterial protein, whereas the former mechanism is involved in operation of bacterial OxyR regulon, yeast H(2)O(2)-stimulon, plant NPR1/TGA and Rap24a systems, and animal Keap1/Nrf2, NF-κB and AP-1, and others Although hundreds of studies have been carried out in the field with different taxa, the comparative analysis of adaptive response is quite incomplete and therefore, this work aims to cover a plethora of phylogenetic groups to delineate common mechanisms In addition, this article raises some questions to be elucidated and points out future directions of this research The comparative approach is used to shed light on fundamental principles and mechanisms of regulation of antioxidant systems The idea is to provide starting points from which we can develop novel tools and hypothesis to facilitate meaningful investigations in the physiology and biochemistry of organismic response to oxidative stress

Adaptive response to oxidative stress: Bacteria, fungi, plants and animals.

The purpose of this work was to evaluate the response of the antioxidant system of goldfish Carassius auratus during anoxia and reoxygenation. The exposure of goldfish to 8 h of anoxia induced a 14...

https://www.physiology.org/doi/pdf/10.1152/ajpregu.2001.280.1.R100

Volodymyr I. Lushchak

Papers

Environmentally induced oxidative stress in aquatic animals

Free radicals, reactive oxygen species, oxidative stress and its classification

Adaptive response to oxidative stress: Bacteria, fungi, plants and animals.

Oxidative stress and antioxidant defenses in goldfish Carassius auratus during anoxia and reoxygenation

Hypoxia and recovery perturb free radical processes and antioxidant potential in common carp (Cyprinus carpio) tissues.