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Toxic Responses of the Kidney
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
Cadmium toxicity results in enhanced synthesis within the liver of the metal binding protein, metallothionein. Metallothionein-cadmium complex spares cadmium toxicity to certain organs (e.g., testis), but enhances cadmium nephrotoxicity. This is accomplished by the increased renal uptake of the metallothionein-cadmium complex over the free cadmium ion. Nephrotoxicity of metallothionein-cadmium complex is localized to the proximal tubule. Pathophysiological findings are associated with reabsorption defects (glucoseurea, aminoacidurea), presence of low and high molecular weight proteins in the urine, and ion loss (phosphate). Presence of high molecular weight proteins in the urine suggests glomerular filtration defects with cadmium toxicity.
Heavy Metals
Published in Michael J. Kennish, Ecology of Estuaries: Anthropogenic Effects, 2019
The free metal ionic activity may be more important in metal toxicity of an organism than the total concentration of a metal. Metal uptake by estuarine organisms occurs via ingestion of food and particulate inorganic matter and via diffusion of dissolved metals. The metals may be stored in the skeletal structure, concretions, or intracellular matrices of an organism, and they are released in feces, eggs, and molting products. Metallothioneins and other heavy metal-binding proteins bind metal contaminants within the organism, thereby helping to control heavy metal concentrations.
Impacts of Xenobiotics on Estuarine Ecosystems
Published in Lorris G. Cockerham, Barbara S. Shane, Basic Environmental Toxicology, 2019
Metallothioneins are low molecular weight, cysteine-rich proteins with a high binding affinity for certain metals. Increased synthesis of these proteins occurs following exposure to metals, and binding of the metals to the protein reduces their toxic effects. Elevated levels of metallothioneins are found in organisms from metal-polluted sites, thus the levels can be used as a monitoring tool (Engel and Roesijadi, 1987). Toxicity by the metal is believed to occur only after the binding capacity of metallothioneins is exceeded and metals “spill over” into the metal-sensitive enzyme pool. Metallothioneins are protective mechanisms that allow organisms to be exposed to or accumulate greater concentrations of a metal without toxic effects.
Heavy metal remediation and resistance mechanism of Aeromonas, Bacillus, and Pseudomonas: A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Ali Fakhar, Bushra Gul, Ali Raza Gurmani, Shah Masaud Khan, Shafaqat Ali, Tariq Sultan, Hassan Javed Chaudhary, Mazhar Rafique, Muhammad Rizwan
Furthermore, members of Pseudomonas undergo an energy-independent and non-metabolic process by which they adsorb heavy metals through the production of biofilm EPS. Polysaccharides, proteins, and nucleic acids act as a protective layer by restricting the diffusion of heavy metals into the biofilm (Chellaiah, 2018; Izrael-Živković et al., 2018). Metalloproteins are a large group of proteins that significantly regulate metal concentration within cells (Coelho et al., 2015). They have the potential to bind Ni, Ag, Zn, Pb, Cd, and Hg with weak bonding (Pereira, 2017). Hence, for heavy metal removal through Pseudomonas, EPS are recommended as surface-active agents because of their extensive capacity (Bramhachari & Nagaraju, 2017). By means of protecting bacterial metabolic processes, metallothioneins also immobilize toxic heavy metals (Naik & Dubey, 2017).
Ozone ultrafine bubble water induces the cellular signaling involved in oxidative stress responses in human periodontal ligament fibroblasts
Published in Science and Technology of Advanced Materials, 2019
Anongwee Leewananthawet, Shinichi Arakawa, Tokuju Okano, Ryo Daitoku Kinoshita, Hiroshi Ashida, Yuichi Izumi, Toshihiko Suzuki
In RNA-seq analysis, we identified the several differentially expressed genes in OUFBW-treated cells. The most up-regulated metallothionein-1G is a member of intracellular cysteine-rich, metal-binding proteins. Metallothioneins are involved in the array of protective stress responses against various stimuli including oxidative stress [18]. The genes coding metallothioneins have many response elements for up-regulation of transcription in its promoter region that includes ARE. The transcription factor Nrf2 can bind ARE to induce cytoprotective responses to oxidative stress [16]. Therefore, the results suggest the possibility of Nrf2-mediated up-regulation of metallothioneins, which may play a role in protective stress responses against OUFBW stimulation. On the other hand, transcription factor HES1 has been reported to cooperate with retinoblastoma protein to activate transcription factor RUNX2, which is required for osteoblast differentiation and bone formation [22,23]. It may be possible that up-regulated HES1 is involved in osteoblast differentiation in periodontal ligaments. Furthermore, the c-Fos up-regulation in RNA-seq analysis is consistent with the activation MAPK pathway and the nuclear translocation of c-Fos in our study.
Investigation of metallothionein level, reduced GSH level, MDA level, and metal content in two different tissues of freshwater mussels from Atatürk Dam Lake coast, Turkey
Published in Chemistry and Ecology, 2019
Organisms in aquatic ecosystems have developed various protective mechanisms against environmental conditions and pollution [17]. Long-term exposure to environmental pollutants may cause a variety of damage to aquatic organisms [18]. The intracellular level of reactive oxygen species (ROS) in aquatic organisms can be increased in the presence of excess metal. To protect against ROS damage, organisms have developed complex antioxidants and detoxifying mechanisms that can inhibit ROS production [15,19,20]. Several biochemical markers are used to evaluate the oxidative stress in mussels that are exposed to metals [21]. Glutathione (GSH) is a tripeptide composed of glutamic acid, cysteine, and glycine amino acids. It is an intracellular antioxidant that plays an important role in xenobiotic damage, cellular defense, detoxification of drugs, and controling the release of ROS [22,23]. Malondialdehyde (MDA) is a product of lipid hydroperoxidation and is considered an important biochemical marker for chemical damage in mussels exposed to aquatic pollutants such as metals [24–26]. Metal-binding proteins such as metallothioneins (MT) are widely used as an important biochemical marker for both oxidative stress and metal toxicity. Because of their high cysteine content, they play an active role in the scavenging of free radicals [21,27]. It is also well known that they have important roles in metal homeostasis and metal detoxification because of their high affinity to metal ions [21].