Showing papers on "Zinc toxicity published in 2020"

Toxicity and bioaccumulation of Cadmium, Copper and Zinc in a direct comparison at equitoxic concentrations in common carp (Cyprinus carpio) juveniles

Abstract: The individual toxicity and bioaccumulation of cadmium, copper and zinc for common carp juveniles was evaluated in a direct comparison in two experimental setups. First, fish were exposed for 10 days to different metal concentrations in order to link metal bioaccumulation to LC50 values (concentration lethal to 50% of the animals) and incipient lethal levels (ILL, concentration where 50% survives indefinitely). Accumulated metals showed a positive dose dependent uptake for cadmium and copper, but not for zinc. Toxicity was in the order cadmium>copper>zinc with 96h LC50 values for cadmium at 0.20±0.16 μM, for copper at 0.77±0.03 μM, and for zinc at 29.89±9.03 μM respectively. For copper, the 96h exposure was sufficient to calculate the incipient lethal level and therefore 96h LC50 and ILL levels were the same, while for cadmium and zinc 5 to 6 days were needed to reach ILL resulting in slightly lower values at 0.16 μM and 28.33 μM respectively. Subsequently, a subacute exposure experiment was conducted, where carp juveniles were exposed to 2 equitoxic concentrations (10% and 50% of LC50 96 h) of the three metals for 1, 3 and 7 days. Again a significant dose-dependent increase in gill cadmium and copper, but not in zinc, was observed during the 7-day exposure. Copper clearly affected sodium levels in gill tissue, while zinc and cadmium did not significantly alter any of the gill electrolytes. The overall histopathological effects (e.g. hyperemia and hypertrophy) of the metal exposures were mild for most of the alterations. Our study showed that copper an cadmium (but not zinc) showed dose dependent metal accumulation, however this bioaccumulation was only correlated with mortality for cadmium. Metal specific alterations were reduced gill sodium levels in copper exposed fish and oedema of the primary epithelium which typically occurred in both levels of zinc exposure.

Identification of the Genetic Requirements for Zinc Tolerance and Toxicity in Saccharomyces cerevisiae.

Abstract: Zinc is essential for almost all living organisms, since it serves as a crucial cofactor for transcription factors and enzymes. However, it is toxic to cell growth when present in excess. The present work aims to investigate the toxicity mechanisms induced by zinc stress in yeast cells. To this end, 108 yeast single-gene deletion mutants were identified sensitive to 6 mM ZnCl2 through a genome-wide screen. These genes were predominantly related to the biological processes of vacuolar acidification and transport, polyphosphate metabolic process, cytosolic transport, the process utilizing autophagic mechanism. A result from the measurement of intracellular zinc content showed that 64 mutants accumulated higher intracellular zinc under zinc stress than the wild-type cells. We further measured the intracellular ROS (reactive oxygen species) levels of 108 zinc-sensitive mutants treated with 3 mM ZnCl2 We showed that the intracellular ROS levels in 51 mutants were increased by high zinc stress, suggesting their possible involvement in regulating ROS homeostasis in response to high zinc. The results also revealed that excess zinc could generate oxidative damage and then activate the expression of several antioxidant defenses genes. Taken together, the data obtained indicated that excess zinc toxicity might be mainly due to the high intracellular zinc levels and ROS levels induced by zinc stress in yeast cells. Our current findings would provide a basis to understand the molecular mechanisms of zinc toxicity in yeast cells.

Availability of Zinc Impacts Interactions between Streptococcus sanguinis and Pseudomonas aeruginosa in Coculture

Abstract: Airway infections associated with cystic fibrosis (CF) are polymicrobial. We reported previously that clinical isolates of Pseudomonas aeruginosa promote the growth of a variety of streptococcal species. To explore the mechanistic basis of this interaction, we performed a genetic screen to identify mutants of Streptococcus sanginuis SK36 whose growth was no longer enhanced by P. aeruginosa PAO1. Mutations in the zinc uptake systems of S. sanguinis SK36 reduced growth of these strains by 1 to 3 logs compared to that of wild-type S. sanguinis SK36 when grown in coculture with P. aeruginosa PAO1, and exogenous zinc (0.1 to 10 μM) rescued the coculture defect of zinc uptake mutants of S. sanguinis SK36. Zinc uptake mutants of S. sanguinis SK36 had no obvious growth defect in monoculture. Consistent with competition for zinc driving coculture dynamics, S. sanguinis SK36 grown in coculture with P. aeruginosa showed increased expression of zinc uptake genes compared to that of S. sanguinis grown alone. Strains of P. aeruginosa PAO1 defective in zinc transport also supported ∼2-fold more growth by S. sanguinis compared to that in coculture with wild-type P. aeruginosa PAO1. An analysis of 118 CF sputum samples revealed that total zinc levels varied from ∼5 to 145 μM. At relatively low zinc levels, Pseudomonas and Streptococcus spp. were found in approximately equal abundance; at higher zinc levels, we observed a decline in relative abundance of Streptococcus spp., perhaps as a result of increasing zinc toxicity. Together, our data indicate that the relative abundances of these microbes in the CF airway may be impacted by zinc levels. IMPORTANCE Polymicrobial infections in CF cases likely impact patient health, but the mechanism(s) underlying such interactions is poorly understood. Here, we show using an in vitro model system that interactions between Pseudomonas and Streptococcus are modulated by zinc availability, and clinical data are consistent with this model. Together with previous studies, our work supports a role for metal homeostasis as a key factor driving microbial interactions.

Salinity Improves Zinc Resistance in Kosteletzkya pentacarpos in Relation to a Modification in Mucilage and Polysaccharides Composition

Abstract: The halophyte plant species Kosteletzkya pentacarpos produces high amounts of mucilage which may play a role in heavy metal tolerance. The amount and composition of mucilage in K. pentacarpos exposed to zinc toxicity in the presence or in the absence of 50 mM NaCl was investigated. Exposure to 0.1 mM Zn had a detrimental impact on plants growth and water content. Most of Zn was accumulated in the roots of plants exposed to Zn toxicity both in the absence and in the presence of NaCl. Salinity, however, partially alleviated the toxicity of zinc, increasing the plant biomass and decreasing zinc absorption by the root. Crude mucilage content increased in all plant organs in response to Zn stress. Acid hydrolysis of crude mucilage extract revealed that the main neutral monosaccharide constituents were rhamnose, arabinose, galactose, and glucose. Zinc induced a rise in uronic acids in roots and stems but not in the leaves where a high constitutive proportion of uronic acids was observed. Meanwhile, changes were also observed in neutral monosaccharides component in different plant organs. Zinc stress increased the hemicellulose content, but decreased the lignin and cellulose content in the stem. Salinity slightly increased the cellulose content. We suggest that excessive zinc induces a modification in the composition and structure of polysaccharides and that mucilage may contribute to Zn tolerance through toxic ion sequestration.

Effect of salinity on zinc toxicity (ZnCl2 and ZnO nanomaterials) in the mosquitofish (Gambusia sexradiata)

Abstract: Zn is an essential trace metal in living beings. However, excessive concentrations can cause toxic effects even in the aquatic biota. Zn is widely used in different industrial sectors, which has increased its presence in aquatic environments. To assess the acute toxicity of Zn, bioassays were performed with the fish Gambusia sexradiata for a 96-h exposure using ZnCl2 (0 and 15 salinity) and ZnO nanomaterials (0 salinity). The mean lethal concentrations (LC50–96 h) for ZnCl2 were 25.36 (19.64–32.76) and 177.91 (129.39–244.63) mg Zn L−1 to 0 and 15 salinity, respectively. The increased concentration of ZnCl2 showed a dose-response relationship; similarly, the increase in salinity significantly reduces the toxicity of Zn. Characterisation of ZnO nanomaterials was carried out by FTIR, DRX, SEM, DLS and zeta potential. The FTIR spectra showed the characteristic band of Zn-O vibration at 364 cm−1, while DRX presents the hexagonal wurtzite structure with an average crystallite size of 40 nm. SEM micrographs reveal rod-like shapes with lengths and diameters of 40–350 nm and 90 nm, respectively. Agglomerates of 423 nm in water suspension were obtained by DLS and zeta potential of + 14.4 mV. Under these conditions, no mortality was observed due to the rapid flocculation/precipitation of ZnO nanomaterials, which involved brief interaction periods of Zn in the water column with the fish. Gambusia sexradiata is affected by increased Zn concentrations in hard water conditions, and salinity changes modified Zn toxicity, placing it as a suitable model for toxicity tests for this type of particles.

Zinc Poisoning - Symptoms, Causes, Treatments.

Abstract: Zinc poisoning has been reported from many parts of the world. It is one of the global health problems that affect many organs, if exposed by inhalation of zinc vapors or by consumption of contaminated food and water. Long term exposure to zinc compounds from different sources such as air, water, soil, and food, lead to toxic effects on body systems, especially digestive, respiratory, and nerve systems, and also causes cancer. Zinc levels can be determined in blood, urine, hair, and nails. Patients with zinc toxicity need chelating agents, other pharmacological treatment, protective lung ventilation, extracorporeal membrane oxygenation (ECMO), and supportive care.

Miswak (Salvadora persica) modulated the growth performance, antioxidative response, and histopathological damage induced by zinc toxicity in Nile tilapia (Oreochromis niloticus)

Abstract: In this study, Nile tilapia fingerlings with average body weight (8.6 ± 0.06 g) were exposed to zinc (Zn) toxicity and tested its amelioration with miswak (Salvadora persica L.) (SP) supplemented diet. Five fish groups were fed on diets with SP at 0, 0.25, 0.5, 1.0, and 2.0% (T1, T2, T3, T4, and T5, respectively) diet without Zn exposure, while another five groups were exposed to Zn at 7 mg/L and co-supplemented with SP at 0, 0.25, 0.5, 1.0, and 2.0 % (T6, T7, T8, T9, and T10, respectively). After 12 weeks, fish-fed 1.0% SP diet (T4) achieved the highest growth and feed performances, while the lowest one was in Zn-exposed fish (T6) (P < 0.05). T6 and T7 groups showed the most inferior carcass protein and ash contents, while T4 and T5 showed the highest lipid content (P < 0.05). The level of Zn residue increased in fish exposed to Zn (P < 0.05). Fish exposed to Zn and fed SP showed high blood urea, catalase, ALT, AST, and total superoxide dismutase (T-SOD), while the malondialdehyde (MDA) was decreased (P < 0.05). Interestingly, miswak resulted in elevated catalase and T-SOD and reduced MDA in fish without Zn exposure (P < 0.05). Zn exposure causes abnormal histopathological characteristics in gills, hepatopancreas, posterior kidney, and musculature tissues of tilapia, while fish-fed SP showed regular, healthy, and protected histopathological characters. The results suggested that SP can induce the antioxidant responses that prepare Nile tilapia for a further suppressive oxidative condition (i.e., Zn exposure).

Sensitivity of the freshwater tropical oligochaete, Branchiura sowerbyi (Beddard, 1892) to the grey list metal, Zinc

Abstract: Although the freshwater oligochaete, Branchiura sowerbyi Beddard, 1892 (Oligochaeta: Naididae: Rhyacodrilinae) has been used as an indicator organism to monitor aquatic pollution, the data on the toxic effects of the grey list metal, zinc on this worm is remained scanty. The present study was undertaken to determine the sensitivity of the worm, B. sowerbyi to zinc on the basis of 24, 48, 72 and 96h lethal concentrations (LC1, 5, 10, 15, 50, 85, 90, 95, 99) and their behavioural responses. The 96h LC50 value of zinc with 95% confidence limit to the worm was recorded as 45.48 (41.32-49.33) mg/l. The rate of mortality of the worm was significantly increased (p<0.05) with increasing concentrations and time of exposure (24, 48, 72 and 96h). The study further focussed on estimation of the toxicity factor at different time scale and possible safe level of zinc to the worm to strengthen the base line data that could be used to set up local water quality criteria (WQC) for the toxicant. The worms showed behavioural changes like clumping tendency, movement and mucous secretion with increasing concentration of the toxicant and the progress of time. The findings can be used in determination of ecological risk assessment for the worm to zinc toxicity as well as to understand its mode of action in the light of their ethological changes. Keywords: Zinc, Branchiura sowerbyi, acute toxicity, toxicity factor, safe level, behavioural responses

A Novel Zinc Chelator, 1H10, Ameliorates Experimental Autoimmune Encephalomyelitis by Modulating Zinc Toxicity and AMPK Activation.

Abstract: Previous studies in our lab revealed that chemical zinc chelation or zinc transporter 3 (ZnT3) gene deletion suppresses the clinical features and neuropathological changes associated with experimental autoimmune encephalomyelitis (EAE). In addition, although protective functions are well documented for AMP-activated protein kinase (AMPK), paradoxically, disease-promoting effects have also been demonstrated for this enzyme. Recent studies have demonstrated that AMPK contributes to zinc-induced neurotoxicity and that 1H10, an inhibitor of AMPK, reduces zinc-induced neuronal death and protects against oxidative stress, excitotoxicity, and apoptosis. Here, we sought to evaluate the therapeutic efficacy of 1H10 against myelin oligodendrocyte glycoprotein 35-55-induced EAE. 1H10 (5 μg/kg) was intraperitoneally injected once per day for the entire experimental course. Histological evaluation was performed three weeks after the initial immunization. We found that 1H10 profoundly reduced the severity of the induced EAE and that there was a remarkable suppression of demyelination, microglial activation, and immune cell infiltration. 1H10 also remarkably inhibited EAE-associated blood-brain barrier (BBB) disruption, MMP-9 activation, and aberrant synaptic zinc patch formation. Furthermore, the present study showed that long-term treatment with 1H10 also reduced the clinical course of EAE. Therefore, the present study suggests that zinc chelation and AMPK inhibition with 1H10 may have great therapeutic potential for the treatment of multiple sclerosis.

Direct and Indirect Inhibition of Salmonella Peptide Deformylase by Nitric Oxide.

Abstract: Salmonella enterica serovar Typhimurium is an intracellular pathogen that elicits nitric oxide (NO·) production by host macrophages. NO· is a potent antimicrobial mediator with diverse targets, including protein thiols and metal centers. The mobilization of zinc from metalloproteins by NO· increases the availability of free intracellular zinc, which is detrimental to bacterial cells, but the precise mechanism of zinc cytotoxicity is uncertain. Here, we show that excess zinc results in the mismetallation of the essential iron-containing enzyme peptide deformylase (PDF), thereby diminishing its activity. PDF mismetallation is observed in zinc-treated bacteria lacking the zinc exporters ZntA and ZitB and is also observed during nitrosative stress, suggesting that NO·-mediated zinc mobilization results in PDF mismetallation. However, NO· also inhibits PDF directly by S-nitrosylating the metal-binding Cys90 residue. These observations identify PDF as an essential bacterial protein that is subject to both direct and indirect inactivation by NO·, providing a novel mechanism of zinc toxicity and NO·-mediated antibacterial activity.IMPORTANCE We have previously shown that the host-derived antimicrobial mediator nitric oxide (NO·) mobilizes zinc from bacterial metalloproteins. The present study demonstrates that NO· inactivates the essential iron-containing enzyme peptide deformylase, both by promoting its mismetallation by zinc and by directly modifying its metal-binding site. We explain how free intracellular zinc is detrimental for cells and reveal a new mechanism of NO·-mediated bacterial growth inhibition that is distinct from previously known targets.

Effect of phosphorus on the toxicity of zinc to the microalga Raphidocelis subcapitata.

Abstract: The aim of this study was to evaluate the effect of phosphorus (P) on the toxicity of zinc (Zn) for the alga Raphidocelis subcapitata. P was provided in three concentrations: 2.3 x 10-4 mol L-1, 2.3 x 10-6 mol L-1 and 1.0 x 10-6 mol L-1. Algal cells were acclimated to the specific P concentrations before the start of the experiment. The chemical equilibrium software MINEQL+ 4.61 was employed to calculate the Zn2+ concentration. After acclimated, the algal cells were inoculated into media containing different Zn concentrations (0.09 x 10-6 mol L-1 to 9.08 x 10-6 mol L-1). The study showed that besides the reduction in algal growth rates, phosphorus had an important influence on the toxicity of zinc for microalga. The inhibitory Zn2+ concentration values for R. subcapitata were 2.74 x 10-6 mol L-1, 0.58 x 10-6 mol L-1 and 0.24 x 10-6 mol L-1 for the microalgae acclimated at P concentrations of 2.3 x 10-4 mol L-1, 2.3 x 10-6 mol L-1 and 1.0 x 10-6 mol L-1, respectively. Ecotoxicological studies should consider the interaction between metal concentrations and varying P values to provide realistic data of what occurs in phytoplankton communities in environments.

A Case of Copper Deficiency Myeloneuropathy Precipitated by Zinc Ingestion and Bariatric Surgery.

Abstract: In this report, we present a case of acquired copper deficiency which initially presented as progressive pain and numbness in the patient's lower extremities. The acquired copper deficiency is attributed to a previous bariatric surgery exacerbated by zinc toxicity. A 42-year-old female with a past medical history of type 2 diabetes mellitus, anemia, hypertension, bipolar disorder, attention deficit disorder, pulmonary embolus, fibromyalgia, migraine headaches, and chronic pain as well as a remote past surgical history of gastric bypass procedure presented with progressive pain and numbness in her lower extremities. The patient reported chronic use of zinc supplements. Clinical evaluation revealed abnormal neurologic exam consistent with a myeloneuropathy and anemia. A cervical spine MRI showed increased signal intensity primarily affecting the posterior columns from C2-C6. Laboratory studies confirmed low copper, low ceruloplasmin, and elevated zinc levels. This case is an example of acquired copper deficiency due to previous bariatric surgery exacerbated by zinc ingestion. With an increased prevalence of bariatric surgery, it is important to monitor patients postoperatively for neurologic symptoms potentially due to copper deficiency.

The effect of silicon (Si) on the growth and nutritional status of Schizolobium amazonicum seedlings subjected to zinc toxicity.

Abstract: Zinc is an essential element to plants. However, excessive zinc levels can severely damage them. Schizolobium amazonicum is an Amazon native species that presents desirable features to remediate environments contaminated with heavy metals. Silicon has the beneficial effect of reducing the toxicity of different contaminants. The aim of the current study is to investigate the effect of Si on the growth and nutritional status of S. amazonicum seedlings subjected to zinc toxicity. The study followed a completely randomized design at 4 x 2 factorial arrangement based on four zinc (1, 150, 300 and 600 μM) and two silicon (0 and 1.5 mM) concentrations with five repetitions for 30 days. Increasing Zn concentrations in the nutrient solution reduced the growth of the plant and Ca, P, Mg, Fe, Mn and Cu contents in plant tissues, increased S concentrations and led to higher toxicity in the roots than shoot of S. amazonicum plants. Si addition to the nutrient solution increased plant growth and the absorption of the evaluated macro and micronutrients. Si increased plant tolerance level from 42.8 to 41.3% at 600 μM Zn, which suggested that this element mitigated the phytotoxic effects of the excess of zinc. Based on the tolerance index, the species presented medium and high tolerance to the evaluated zinc doses. Bioconcentration and translocation factors have indicated the low Zn-phytoextraction capacity of S. amazonicum and suggested that the species may be promising for Zn phytostabilization purposes.

Effect of Phototherapy on Serum Zinc Level in Neonatal Jaundice

Abstract: Background: Zinc salts can reduce phototherapy duration by precipitating unconjugated bilirubin in the intestine however, zinc toxicity is an issue that must be considered. Theoretically, bilirubin reduction by phototherapy may increase serum zinc levels, making additional zinc supplementation, which cause zinc toxicity. Objectives: To evaluate serum zinc level alterations before and after phototherapy in hyperbilirubinemic newborns. Materials and Methods: A prospective cross sectional case-control study was performed at Neonatal Intensive Care Unit (NICU), Al-Azhar University Hospital, Assiut. 150 newborns aged between 2-7 days divided into 50 healthy neonates without hyperbilirubinemia (control group) and 100 neonates with physiological jaundice who required phototherapy (case group). Participants were treated according to American Academy of Pediatrics (AAP) criteria. Serum zinc level was measured before and after phototherapy. Results: The mean age of onset was approximately 2 days, while the majority of patients were females and delivered with cesarean section. The age at admission was 3.09 ± 0.57 days. In regard to our primary outcomes, serum bilirubin level was decreased significantly after phototherapy to reach 8.47 ± 1.36 mg/dl (p < 0.001). Serum zinc level was increased significantly after phototherapy to reach 75.45 ± 14.94 mcg/mL (p < 0.001). The comparison between control and study groups regarding serum zinc level showed that there was highly statistically significant difference being higher in case group compared to control group (p < 0.001). Phototherapy was associated with a significant increase in serum zinc level in neonates. Conclusions: Phototherapy increases serum zinc level by reducing bilirubin level so additional supplementation of this element can lead potentially zinc toxicity.

Correlation of the expression of metal tolerance protein genes with zinc accumulation and distribution in Malus halliana seedlings under zinc toxicity stress

Abstract: The micronutrient zinc plays an essential role in the physiological and metabolic processes in plants; however, it becomes very toxic when present in elevated amounts. To evaluate the correlation o...

Histopathological changes on etroplus maculatus (bloch, 1795) due to zinc exposure

Abstract: The contamination of the aquatic systems with heavy metals from natural and anthropogenic sources has become a global problem which poses serious threats to ecosystems and natural communities. Heavy metals get bio concentrated in organisms that may cause health problems in humans via the food chain. The heavy metal zinc causes most serious environmental contaminations and effects due to its rampant use. In this study sublethal effects of the heavy metal, zinc on the histopathological parameters in fresh water fish, Etroplus maculatus was investigated. The 96 hour LC50 value of zinc was determined by Probit analysis, that was found to be 12.4 mg/L. The liver and kidney samples were collected from fish was exposed to sublethal concentrations of zinc on 14th and 28thdays.The structural deformities observed in the liver tissue showed swelling of hepatocytes, vacuolar degeneration, necrosis, nuclear hypertrophy and cirrhosis with acute haemorrhage where as, kidney showed degenerated renal capsule and renal tubule, edema, necrosis and haemorrhage in the interstetium. The histpathological changes become prominent as the days and concentration of exposure increases. The study thus establishes that zinc is harmful to Etroplus maculatus even in sublethal concentrations and effective management strategies are to be evolved and implemented to protect our water bodies and the organisms from problems of heavy metal pollution.