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1.
Toxic metals and metalloids: Uptake, transport, detoxification, phytoremediation, and crop improvement for safer food.
Zhao, FJ, Tang, Z, Song, JJ, Huang, XY, Wang, P
Molecular plant. 2022;(1):27-44
Abstract
Agricultural soils are under threat of toxic metal/metalloid contamination from anthropogenic activities, leading to excessive accumulation of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in food crops that poses significant risks to human health. Understanding how these toxic metals and their methylated species are taken up, translocated, and detoxified is prerequisite to developing strategies to limit their accumulation for safer food. Toxic metals are taken up and transported across different cellular compartments and plant tissues via various transporters for essential or beneficial nutrients, e.g. As by phosphate and silicon transporters, and Cd by manganese (Mn), zinc (Zn), and iron (Fe) transporters. These transport processes are subjected to interactions with nutrients and the regulation at the transcriptional and post-translational levels. Complexation with thiol-rich compounds, such as phytochelatins, and sequestration in the vacuoles are the common mechanisms for detoxification and for limiting their translocation. A number of genes involved in toxic metal uptake, transport, and detoxification have been identified, offering targets for genetic manipulation via gene editing or transgenic technologies. Natural variations in toxic metal accumulation exist within crop germplasm, and some of the quantitative trait loci underlying these variations have been cloned, paving the way for marker-assisted breeding of low metal accumulation crops. Using plants to extract and remove toxic metals from soil is also possible, but this phytoremediation approach requires metal hyperaccumulation for efficiency. Knowledge gaps and future research needs are also discussed.
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2.
Selected Essential and Toxic Chemical Elements in Hypothyroidism-A Literature Review (2001-2021).
Błażewicz, A, Wiśniewska, P, Skórzyńska-Dziduszko, K
International journal of molecular sciences. 2021;(18)
Abstract
Thyroid hormones are known for controlling metabolism of lipids, carbohydrates, proteins, minerals, and electrolytes and for regulating body temperature. Normal thyroid status depends on the chemical/elemental composition of body fluids and tissues, which changes depending on physiological state, lifestyle and environment. A deficiency or excess of certain essential chemical elements (selenium, zinc, copper, iron or fluorine) or exposure to toxic (cadmium or lead) or potentially toxic elements (manganese or chromium) interacts with thyroid hormone synthesis and may disturb thyroid homeostasis. In our review, accessible databases (Scopus, PubMed and Web of Science) were searched for articles from 2001-2021 on the influence of selected chemical elements on the development of hypothyroidism. Our review adopted some of the strengths of a systematic review. After non-eligible reports were rejected, 29 remaining articles were reviewed. The review found that disruption of the physiological levels of elements in the body adversely affects the functioning of cells and tissues, which can lead to the development of disease.
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3.
Heavy Metals and Human Health: Possible Exposure Pathways and the Competition for Protein Binding Sites.
Witkowska, D, Słowik, J, Chilicka, K
Molecules (Basel, Switzerland). 2021;(19)
Abstract
Heavy metals enter the human body through the gastrointestinal tract, skin, or via inhalation. Toxic metals have proven to be a major threat to human health, mostly because of their ability to cause membrane and DNA damage, and to perturb protein function and enzyme activity. These metals disturb native proteins' functions by binding to free thiols or other functional groups, catalyzing the oxidation of amino acid side chains, perturbing protein folding, and/or displacing essential metal ions in enzymes. The review shows the physiological and biochemical effects of selected toxic metals interactions with proteins and enzymes. As environmental contamination by heavy metals is one of the most significant global problems, some detoxification strategies are also mentioned.
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4.
Increased Thyroid Cancer Incidence in Volcanic Areas: A Role of Increased Heavy Metals in the Environment?
Malandrino, P, Russo, M, Gianì, F, Pellegriti, G, Vigneri, P, Belfiore, A, Rizzarelli, E, Vigneri, R
International journal of molecular sciences. 2020;(10)
Abstract
Thyroid cancer incidence is significantly increased in volcanic areas, where relevant non-anthropogenic pollution with heavy metals is present in the environment. This review will discuss whether chronic lifelong exposure to slightly increased levels of metals can contribute to the increase in thyroid cancer in the residents of a volcanic area. The influence of metals on living cells depends on the physicochemical properties of the metals and their interaction with the target cell metallostasis network, which includes transporters, intracellular binding proteins, and metal-responsive elements. Very little is known about the carcinogenic potential of slightly increased metal levels on the thyroid, which might be more sensitive to mutagenic damage because of its unique biology related to iodine, which is a very reactive and strongly oxidizing agent. Different mechanisms could explain the specific carcinogenic effect of borderline/high environmental levels of metals on the thyroid, including (a) hormesis, the nonlinear response to chemicals causing important biological effects at low concentrations; (b) metal accumulation in the thyroid relative to other tissues; and (c) the specific effects of a mixture of different metals. Recent evidence related to all of these mechanisms is now available, and the data are compatible with a cause-effect relationship between increased metal levels in the environment and an increase in thyroid cancer incidence.
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5.
Mechanisms of Co, Ni, and Mn toxicity: From exposure and homeostasis to their interactions with and impact on lipids and biomembranes.
Sule, K, Umbsaar, J, Prenner, EJ
Biochimica et biophysica acta. Biomembranes. 2020;(8):183250
Abstract
Anthropogenic activity has increased human exposure to metals and resulted in metal induced toxicity. Essential trace elements like cobalt (Co), nickel (Ni), and manganese (Mn) are best known for their roles as important cofactors in many enzymes involved in signalling, metabolism, and response to oxidative stress. However, deficiencies as well as long-term overexposure to these metals can result in negative health effects. Co has been associated with cardiomyopathy, lung disease, and hearing damage, while Ni is a known carcinogen, as well as a common sensitizing metal. Mn is best classified as a neurotoxicant that causes a disorder alike to idiopathic Parkinson's disease known as Manganism. Although the mechanisms of Co, Ni, and Mn toxicity are complex and have yet to be fully elucidated, research over the years has provided useful insights into understanding metal-induced detrimental effects at the cellular and molecular level. One area of research that has been explored in less detail are metal interactions with lipids and biological membranes, which are a potentially critical target as membranes are the first point of contact for cells. This review covers the current understandings of Co, Ni and Mn toxicity, in terms of human exposure, homeostasis and mechanisms of transport, potential cellular targets, and, of primary focus, metal interactions with lipid and biomembranes. A variety of effects like membrane rigidification, leakage affecting membrane potentials, lipid phase changes, alterations in lipid metabolism and changes of cellular morphology illustrate the vast potential for metal-based membrane effects contributing to their toxicity.
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6.
Environmental influence on neurodevelopmental disorders: Potential association of heavy metal exposure and autism.
Ijomone, OM, Olung, NF, Akingbade, GT, Okoh, COA, Aschner, M
Journal of trace elements in medicine and biology : organ of the Society for Minerals and Trace Elements (GMS). 2020;:126638
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Abstract
Environmental factors have been severally established to play major roles in the pathogenesis of neurodevelopmental disorders including autism spectrum disorder (ASD). ASD is a neurodevelopmental disorder that is associated with symptoms that reduce the quality of life of affected individuals such as social interaction deficit, cognitive impairment, intellectual disabilities, restricted and repetitive behavioural patterns. ASD pathogenesis has been associated with environmental and genetic factors that alter physiologic processes during development. Here, we review literatures highlighting the environmental impact on neurodevelopmental disorders, and mechanisms by which environmental toxins may influence neurodevelopment. Furthermore, this review discusses reports highlighting neurotoxic metals (specifically, lead, mercury, cadmium, nickel and manganese) as environmental risk factors in the aetiology of ASD. This work, thus suggests that improving the environment could be vital in the management of ASD.
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7.
A Review of the Effect of Trace Metals on Freshwater Cyanobacterial Growth and Toxin Production.
Facey, JA, Apte, SC, Mitrovic, SM
Toxins. 2019;(11)
Abstract
Cyanobacterial blooms are becoming more common in freshwater systems, causing ecological degradation and human health risks through exposure to cyanotoxins. The role of phosphorus and nitrogen in cyanobacterial bloom formation is well documented and these are regularly the focus of management plans. There is also strong evidence that trace metals are required for a wide range of cellular processes, however their importance as a limiting factor of cyanobacterial growth in ecological systems is unclear. Furthermore, some studies have suggested a direct link between cyanotoxin production and some trace metals. This review synthesises current knowledge on the following: (1) the biochemical role of trace metals (particularly iron, cobalt, copper, manganese, molybdenum and zinc), (2) the growth limitation of cyanobacteria by trace metals, (3) the trace metal regulation of the phytoplankton community structure and (4) the role of trace metals in cyanotoxin production. Iron dominated the literature and regularly influenced bloom formation, with 15 of 18 studies indicating limitation or colimitation of cyanobacterial growth. A range of other trace metals were found to have a demonstrated capacity to limit cyanobacterial growth, and these metals require further study. The effect of trace metals on cyanotoxin production is equivocal and highly variable. Better understanding the role of trace metals in cyanobacterial growth and bloom formation is an essential component of freshwater management and a direction for future research.
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8.
Physiological and molecular mechanisms of heavy metal accumulation in nonmycorrhizal versus mycorrhizal plants.
Shi, W, Zhang, Y, Chen, S, Polle, A, Rennenberg, H, Luo, ZB
Plant, cell & environment. 2019;(4):1087-1103
Abstract
Uptake, translocation, detoxification, and sequestration of heavy metals (HMs) are key processes in plants to deal with excess amounts of HM. Under natural conditions, plant roots often establish ecto- and/or arbuscular-mycorrhizae with their fungal partners, thereby altering HM accumulation in host plants. This review considers the progress in understanding the physiological and molecular mechanisms involved in HM accumulation in nonmycorrhizal versus mycorrhizal plants. In nonmycorrhizal plants, HM ions in the cells can be detoxified with the aid of several chelators. Furthermore, HMs can be sequestered in cell walls, vacuoles, and the Golgi apparatus of plants. The uptake and translocation of HMs are mediated by members of ZIPs, NRAMPs, and HMAs, and HM detoxification and sequestration are mainly modulated by members of ABCs and MTPs in nonmycorrhizal plants. Mycorrhizal-induced changes in HM accumulation in plants are mainly due to HM sequestration by fungal partners and improvements in the nutritional and antioxidative status of host plants. Furthermore, mycorrhizal fungi can trigger the differential expression of genes involved in HM accumulation in both partners. Understanding the molecular mechanisms that underlie HM accumulation in mycorrhizal plants is crucial for the utilization of fungi and their host plants to remediate HM-contaminated soils.
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9.
Role of Autophagy on Heavy Metal-Induced Renal Damage and the Protective Effects of Curcumin in Autophagy and Kidney Preservation.
Avila-Rojas, SH, Lira-León, A, Aparicio-Trejo, OE, Reyes-Fermín, LM, Pedraza-Chaverri, J
Medicina (Kaunas, Lithuania). 2019;(7)
Abstract
Curcumin is a hydrophobic polyphenol compound extracted from the rhizome of turmeric. The protective effect of curcumin on kidney damage in multiple experimental models has been widely described. Its protective effect is mainly associated with its antioxidant and anti-inflammatory properties, as well as with mitochondrial function maintenance. On the other hand, occupational or environmental exposure to heavy metals is a serious public health problem. For a long time, heavy metals-induced nephrotoxicity was mainly associated with reactive oxygen species overproduction and loss of endogenous antioxidant activity. However, recent studies have shown that in addition to oxidative stress, heavy metals also suppress the autophagy flux, enhancing cell damage. Thus, natural compounds with the ability to modulate and restore autophagy flux represent a promising new therapeutic strategy. Furthermore, it has been reported in other renal damage models that curcumin's nephroprotective effects are related to its ability to regulate autophagic flow. The data indicate that curcumin modulates autophagy by classic signaling pathways (suppression of protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and/or by stimulation of adenosine monophosphate-activated protein kinase (AMPK) and extracellular signal-dependent kinase (ERK) pathways). Moreover, it allows lysosomal function preservation, which is crucial for the later stage of autophagy. However, future studies of autophagy modulation by curcumin in heavy metals-induced autophagy flux impairment are still needed.
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10.
Heavy metals in food crops: Health risks, fate, mechanisms, and management.
Rai, PK, Lee, SS, Zhang, M, Tsang, YF, Kim, KH
Environment international. 2019;:365-385
Abstract
Food security is a high-priority issue for sustainable global development both quantitatively and qualitatively. In recent decades, adverse effects of unexpected contaminants on crop quality have threatened both food security and human health. Heavy metals and metalloids (e.g., Hg, As, Pb, Cd, and Cr) can disturb human metabolomics, contributing to morbidity and even mortality. Therefore, this review focuses on and describes heavy metal contamination in soil-food crop subsystems with respect to human health risks. It also explores the possible geographical pathways of heavy metals in such subsystems. In-depth discussion is further offered on physiological/molecular translocation mechanisms involved in the uptake of metallic contaminants inside food crops. Finally, management strategies are proposed to regain sustainability in soil-food subsystems.