Heavy-Metal-Induced Reactive Oxygen Species: Phytotoxicity and Physicochemical Changes in Plants

Abstract

As a result of the industrial revolution, anthropogenic activities have enhanced there distribution of many toxic heavy metals from the earth's crust to different environmental compartments. Environmental pollution by toxic heavy metals is increasing worldwide, and poses a rising threat to both the environment and to human health.Plants are exposed to heavy metals from various sources: mining and refining of ores, fertilizer and pesticide applications, battery chemicals, disposal of solid wastes(including sewage sludge), irrigation with wastewater, vehicular exhaust emissions and adjacent industrial activity.Heavy metals induce various morphological, physiological, and biochemical dysfunctions in plants, either directly or indirectly, and cause various damaging effects. The most frequently documented and earliest consequence of heavy metal toxicity in plants cells is the overproduction of ROS. Unlike redox-active metals such as iron and copper, heavy metals (e.g, Pb, Cd, Ni, AI, Mn and Zn) cannot generate ROS directly by participating in biological redox reactions such as Haber Weiss/Fenton reactions. However, these metals induce ROS generation via different indirect mechanisms, such as stimulating the activity of NADPH oxidases, displacing essential cations from specific binding sites of enzymes and inhibiting enzymatic activities from their affinity for -SH groups on the enzyme.Under normal conditions, ROS play several essential roles in regulating the expression of different genes. Reactive oxygen species control numerous processes like the cell cycle, plant growth, abiotic stress responses, systemic signalling, programmed cell death, pathogen defence and development. Enhanced generation of these species from heavy metal toxicity deteriorates the intrinsic antioxidant defense system of cells, and causes oxidative stress. Cells with oxidative stress display various chemical,biological and physiological toxic symptoms as a result of the interaction between ROS and biomolecules. Heavy-metal-induced ROS cause lipid peroxidation, membrane dismantling and damage to DNA, protein and carbohydrates. Plants have very well-organized defense systems, consisting of enzymatic and non-enzymatic antioxidation processes. The primary defense mechanism for heavy metal detoxification is the reduced absorption of these metals into plants or their sequestration in root cells.Secondary heavy metal tolerance mechanisms include activation of antioxidant enzymes and the binding of heavy metals by phytochelatins, glutathione and amino acids. These defense systems work in combination to manage the cascades of oxidative stress and to defend plant cells from the toxic effects of ROS.In this review, we summarized the biochemiCal processes involved in the over production of ROS as an aftermath to heavy metal exposure. We also described the ROS scavenging process that is associated with the antioxidant defense machinery.Despite considerable progress in understanding the biochemistry of ROS overproduction and scavenging, we still lack in-depth...

Oxidative stress and DNA damage induced by spinosad exposure in Spodoptera frugiperda Sf9 cells

“…Oxidative stress can be defined as the state of imbalance between prooxidant challenge and antioxidant systems, attributing to the overproduction of ROS that exceed the capacity of antioxidant defense systems (Baysal et al, 2016;Li, Jiang, Cao, Xie, & Huang, 2017). Various environmental stresses are known to enhance the ROS production, such as ultraviolet radiation, heavy metals and pesticide remnant, disturbing the cellular redox homeostasis (Ma et al, 2014;Shahid et al, 2014;Thévenod, Friedmann, Katsen, & Hauser, 2000). Increase of ROS elicits a wide variety of physiological and cellular events, including lipid peroxidation, antioxidants' depletion, and DNA damage (Chen et al, 2012;She et al, 2016;Wang, Martínez, et al, 2016).…”

Ремедіаційний Потенціал Лісоутворювальних Порід У Рекультиваційних Насадженнях

“…Масштабні роботи, повʼязані із видобутком вугілля, призводять до істотної ерозії і забруднення величезних територій (Kuznetsova et al, 2010;Alekseenko et al, 2017). Техногенний вплив призводить до глобальних порушень екологічних систем, у зв'язку з чим важливим завданням є прогноз зміни екологічних систем під впливом антропогенних факторів (Alexander, 2000;Risto et al, 2005;Shahid et al, 2014). В процесі розробки корисних копалин, зокрема, в умовах функціонування шахт, здійснюються значні порушення і забруднення земельного фонду, особливо земель сільськогосподарського призначення, виведення значних площ з користування (Allen et al, 1995;Kaar, 2002).…”

Biofabricación de nanopartículas de metales usando células vegetales o extractos de plantas

“…Faced with a stress-induced excess metal ions plants respond to various defense mechanisms such as lower income and increase the excretion of these elements by the root, complexation with metabolites, proteins or cell wall, accumulation of antioxidants and complexation and transport into the vacuole (Shahid et al, 2014). All these responses are induced and require time and energy expenditure for functional implementation.…”

“…The advantage of the formation of NPs is occurring rapidly, it depends only on the existing antioxidant potential at the time and works as an expedited response that would later be supplemented by the aforementioned adjustments that would lead to finer control and effective concentration metal ions. elementos por la raíz, la complejación con metabolitos, proteínas o la pared celular, la acumulación de antioxidantes así como el transporte y complejación en la vacuola (Shahid et al, 2014). Todas estas respuestas son inducidas y requieren de tiempo y gasto de energía para su implementación funcional.…”