Cadmium inhibits the electron transfer chain and induces reactive oxygen species

Impact of cadmium on copepod Oithona similis at threshold concentrations: Determining safe exposure period

The level of protection by the seawater quality criteria (SWQC) of cadmium (Cd) on planktonic population remains unknown. Therefore, this study assessed the level of protection and safe exposure period of SWQC of cadmium for protection of marine life. The copepod Oithona similis exposed to the Cd at SWQC such as predicted no-effect concentration (PNEC, 0.6 μg/l), criterion continuous concentration (CCC, 1.2 μg/l), and criterion maximum concentration (CMC, 5 μg/l). The in-vivo assays with fluorescein diacetate (FDA) and 2,7-dichlorofluorescein diacetate (DC-FDA) revealed that the SWQCs are safe except for CMC for prolonged exposure. The population growth was higher at 5.4 folds in the control culture, with 4291 ± 134 ind/l, than the culture with CMC of Cd with 2403 ± 149 ind/l which is 2.7 fold growth. Protein content in copepod biomass increased between 3.27 mg/g in the control and 5.73 mg/g in CMC. Biomarker enzyme activities varied among the treatments, and higher expressions were found in CMC. Inhibition of in-vitro FDA and induced DC-FDA activities indicate the stress due to Cd toxicity. Overall, results reveal the SWQC of Cd is not safe for long-term exposure. The PNEC may ensure the protection for up to four days, CCC may be prescribed for one day, and CMC may be prescribed for one-hour exposure.

Cadmium contamination impairs alkaline tolerance in sugar beet by inhibiting carbon fixation and tryptophan metabolism

The contamination of cadmium (Cd) may overlap with alkali stress, exerting a synergistic effect on crop growth. This study examined the morphological and physiological responses of sugar beet seedlings irrigated with Cd solution (50 mM CdCl2) to alkali stress (400 mM NaHCO3). Under alkali stress, the presence of Cd exacerbated the reduction in plant growth, the maximum quantum yield of photosystem II (Fv/Fm), chlorophyll content, and osmoregulatory substances (proline, soluble sugars). Cd augmented the concentration of MDA, O2·-, and H2O2, while reducing the expression of BvPOX. Concurrently, glutathione content, ascorbate peroxidase (APX) activity, and the glutathione transferase gene (BvGST) expression were also inhibited by Cd. Cd constrained the ribulose-5P content under alkali stress and the expression of the glyceraldehyde-3-phosphate dehydrogenase gene (BvGAPDH), thereby inhibiting the Calvin cycle. Additionally, the expression of the alcohol dehydrogenase gene (BvADH) was reduced, leading to decreased sucrose and starch content. Cd also accelerated pectin metabolism. Furthermore, Cd inhibited the expression of key genes involved in melatonin synthesis (aromatic-L-amino-acid/L-tryptophan decarboxylase gene, BvDDC/BvTDC and acetylserotonin O-methyltransferase gene, BvASMT), resulting in restricted tryptophan metabolism. This study provides insights into the inhibition of carbon fixation and tryptophan metabolism induced by Cd, its effects on the growth of beets under alkaline stress conditions.

Deciphering the early responses for the cross talk between primary and secondary stressor in diazotrophic cyanobacteria Anabaena sp. PCC 7120

The present study aims to unlock the cross-protection mechanism of the diazotrophic cyanobacterium Anabaena sp. PCC 7120. Heat pre-treatment elicited a beneficial response against subsequent cadmium stress as revealed by integrated morphological, physiological, biochemical, transcript, and proteomics analyses under four sets of experimental conditions: control (C), heat (HS), cadmium (Cd), and heat + cadmium (HS + Cd). Outcomes of the present study suggested a better survival strategy shown by Anabaena sp. PCC 7120 under HS + Cd compared to Cd. According to comparative proteomics, protochlorophyllide reductase, CO2 hydration protein, and NAD(P)H quinone oxidoreductase work in concert to support the light and dark reactions of photosynthesis. Furthermore, in cross protection involvement of enzymes from pentose phosphate pathway and glycolysis for fulfilling cellular energy demand; antioxidants and antioxidant enzymes in scavenging ROS, cellular detoxification, and Cd chelation, chaperons and proteases in proper protein folding and synthesis; signaling and transporters to generate cross talk and Cd efflux were found. Increased accumulation of vegetative to heterocyst connection protein (FraH) in HS + Cd compared to Cd may be envisioned to manage better nitrogen fixation.

Genome-wide identification of the HIPPs gene family and functional validation of MsHIPP12 in enhancing cadmium tolerance in Medicago sativa

Heavy metal-associated isoprenylated plant proteins (HIPPs) are crucial for metal ion homeostasis and stress responses in plants exposed to heavy metals. They bind heavy metal ions via their HMA domains, sequestering them to prevent cellular toxicity. The C-terminal isoprenylation enhances interactions with membrane proteins, aiding in ion transport and compartmentalization. In Medicago sativa (alfalfa), we identified 23 MsHIPP genes containing conserved HMA domains and C-terminal isoprenylation motifs using bioinformatics tools. Phylogenetic analysis classified these genes into five clades, indicating functional diversity and evolutionary divergence. Promoter analysis revealed cis-regulatory elements associated with responses to light, drought, cold, abscisic acid (ABA), salicylic acid (SA), and auxin, suggesting roles in environmental adaptation. Expression profiling under drought, cold, salt, cadmium (Cd), ABA, and indole-3-acetic acid (IAA) treatments demonstrated the involvement of MsHIPPs in abiotic stress responses. Notably, overexpression of MsHIPP12 in Arabidopsis thaliana enhanced Cd tolerance by increasing antioxidant enzyme activities (APX, CAT, SOD), reducing malondialdehyde (MDA) levels, and attenuating chlorophyll degradation. These findings identify MsHIPP12 as a promising candidate gene for enhancing stress tolerance in M. sativa. This work provides valuable insights for molecular breeding strategies and phytoremediation approaches to address cadmium-contaminated soils.

Cadmium-cardiolipin disruption of respirasome assembly and redox balance through mitochondrial membrane rigidification

The environmental pollutant cadmium (Cd) poses a threat to human health through the consumption of contaminated foodstuffs culminating in chronic nephrotoxicity. Mitochondrial dysfunction and excessive reactive oxygen species (ROS) are key to Cd cellular toxicity. Cd-lipid interactions have been less considered. We hypothesized Cd binding to the inner mitochondrial membrane (IMM) phospholipid cardiolipin (CL) and membrane rigidification underlies defective electron transfer by disrupted respiratory supercomplexes (SCs). In Cd-treated rat kidney cortex (rKC) mitoplasts, laurdan (lipid-water interface), and diphenylhexatriene (hydrophobic core) revealed increased and decreased membrane fluidity, respectively. Laurdan-loaded pure CL or IMM biomimetic (40 mol % POPC, 35 mol % DOPE, 20 mol % TOCL, 5 mol % SAPI) nanoliposomes were rigidified by 25 μM Cd, which was confirmed in live-cell imaging of laurdan or di-4-ANEPPDHQ loaded human proximal convoluted tubule (HPCT) cells. Blue native gel electrophoresis evidenced ∼30% loss of I+III2+IVn SC formation after 5 μM Cd for 6 h in HPCTs, which was reversed by CL-binding drug MTP-131/SS-31/elamipretide (0.1 μM), yet α-tocopherol-insensitive. Moreover, MTP-131 attenuated Cd-induced H2O2 (∼30%) and cytochrome c release (∼25%), but not osmotic swelling, in rKC mitochondria as well as Cd-induced ROS (∼25%) in HPCTs. MTP-131 binding to IMM biomimetic nanoliposomes decreased zeta potential, prevented Cd-induced liposome size increase, and membrane rigidification reported by laurdan. Heterologous CRLS1 expression reversed Cd (5 μM, 24 h) cytotoxicity (∼25%) by MTT assay, Cd (5 μM, 3 h)-induced ROS and mitochondrial membrane rigidification by Cd (1 μM, 1 h) in HPCT cells. In summary, we report a novel mechanism for Cd toxicity in which Cd-CL interactions cause IMM rigidification, thereby disrupting correct SC assembly and increasing ROS.

Exogenous sodium nitroprusside exhibits multiple positive roles in alleviating cadmium toxicity in tobacco (Nicotiana tabacum L.)

As a donor of the gaseous signaling molecule nitric oxide (NO), sodium nitroprusside (SNP) has been shown to play a positive role in enhancing plant resistance to abiotic stress. However, its role in alleviating cadmium (Cd) toxicity in tobacco (Nicotiana tabacum L.) is not fully understood. This study found that Cd stress significantly inhibited tobacco growth. At the same time, 150 μM SNP was the most effective concentration in alleviating Cd toxicity in seedlings, restoring three stress tolerance indicators-MDA, H2O2, and proline-to control levels. Exogenous SNP mitigated Cd-induced oxidative stress by promoting the accumulation of non-enzymatic antioxidants (total phenolics and flavonoids) and activating key antioxidant enzymes (SOD, CAT, POD, APX, and GR) along with their gene expression. SNP also facilitated Cd accumulation in the root cell wall and prevented Cd translocation from roots to shoots. Additionally, SNP altered Cd's subcellular distribution, promoting its sequestration in vacuoles and cell walls, which may be related to the NO-mediated upregulation of the metallothionein gene NtMT2F and the phytochelatin gene NtPCS2. The addition of SNP significantly increased the proportion of Cd in less toxic chemical forms, with the residual Cd fraction in the Cd + SNP group reaching 7.30 %, higher than the 4.86 % in the Cd-only group. Furthermore, exogenous SNP counteracted Cd's inhibition of nitrate reductase (NR) activity, promoting endogenous NO production. This study systematically reveals the positive roles of exogenous SNP in mitigating Cd toxicity in tobacco, offering valuable insights for producing low-Cd tobacco.

Astragaloside IV attenuates cadmium induced nephrotoxicity in rats by activating Nrf2

Acute kidney injury (AKI) has become a disease of global concern due to its high morbidity and mortality. This has highlighted the need for renoprotective agents. Astragaloside IV (AS-IV) is a saponin isolated from Astragalus membranaceus with good antioxidant, anti-inflammatory and anti-tumor properties. In this study, HK2 cells and rat model were utilized to explore the protective effect of AS-IV against cadmium chloride-induced oxidative stress-induced apoptosis. CdCl2-induced apoptosis, ROS production, and mitochondrial membrane potential alterations were significantly inhibited in AS-IV -treated HK2 cells. Expression of the mitochondria-associated apoptotic proteins Cleaved-Caspase3, Cleaved-Caspase9, and Cleaved-PARP was significantly reduced after AS-IV intervention. In addition, AS-IV inhibited Rat weight loss and also alleviated the symptoms of CdCl2-induced nephrotoxicity in a rat model of CdCl2-induced kidney injury. Further experiments showed that AS-IV suppresses heavy metal Cd-induced mitochondria-mediated apoptosis by regulating the Nrf2/HO-1 pathway. In conclusion, AS-IV could protect the kidney from heavy metal-induced toxicity and could be used as a nephroprotective agent.

Interactive effects of temperature, cadmium, and hypoxia on rainbow trout (Oncorhynchus mykiss) liver mitochondrial bioenergetics

Fish in their natural environments possess elaborate mechanisms that regulate physiological function to mitigate the adverse effects of multiple environmental stressors such as temperature, metals, and hypoxia. We investigated how warm acclimation affects mitochondrial responses to Cd, hypoxia, and acute temperature shifts (heat shock and cold snap) in rainbow trout. We observed that state 3 respiration driven by complex I (CI) was resistant to the stressors while warm acclimation and Cd reduced complex I +II (CI + II) driven state 3 respiration. In contrast, state 4 (leak) respirations for both CI and CI + II were consistently stimulated by warm acclimation resulting in reduced mitochondrial coupling efficiency (respiratory control ratio [RCR]). Warm acclimation and Cd exacerbated their individual effect on leak respiration to further reduce the RCR. Moreover, the effect of warm acclimation on mitochondrial bioenergetics aligned with its inhibitory effect on activities of citrate synthase and both CI and CII. Unlike the Cd and warm acclimation combined exposure, hypoxia alone and in combination with warm acclimation and/or Cd abolished the stimulation of CI and CI + II powered leak respirations resulting in partial recovery of RCR. The response to acute temperature shifts indicated that while state 3 respiration returned to pre-acclimation level, the leak respiration did not. Overall, our findings suggest a complex in vivo interaction of multiple stressors on mitochondrial function that are not adequately predicted by their individual effects.

Fine particulate matter‑induced cardiac developmental toxicity (Review)

Fine particulate matter (PM2.5) has become an important risk factor threatening human health. Epidemiological and toxicological investigations have revealed that PM2.5 not only leads to cardiovascular dysfunction, but it also gives rise to various adverse health effects on the human body, such as cardiovascular and cerebrovascular diseases, cancers, neurodevelopmental disorders, depression and autism. PM2.5 is able to penetrate both respiratory and placental barriers, thereby resulting in negative effects on fetal development. A large body of epidemiological evidences has suggested that gestational exposure to PM2.5 increases the incidence of congenital diseases in offspring, including congenital heart defects. In addition, animal model studies have revealed that gestational exposure to PM2.5 can disrupt normal heart development in offspring, although the potential molecular mechanisms have yet to be fully elucidated. The aim of the present review was to provide a brief overview of what is currently known regarding the molecular mechanisms underlying cardiac developmental toxicity in offspring induced by gestational exposure to PM2.5.

Dynamics of metal/metalloid bioaccumulation and sensitivity in post-larvae shrimp (Macrobrachium rosenbergii) exposed to settleable atmospheric particulate matter from an industrial source

The metallurgy industry is a potent global source of particulate matter (PM) atmospheric emissions. A portion of this PM may settle in aquatic (SePM) carrying metal/metalloid particles and metallic nanoparticles. Surprisingly, this form of contamination has not received due attention from most environmental monitoring agencies. We analyzed the effect of exposure to SePM on shrimp post-larvae, a critical stage for the viability of shrimp populations and for the trophic chain. After acclimation, shrimp were exposed to contaminants using a randomized experimental design-a 4 × 4 factorial arrangement with 2 factors: exposure time (24, 48, 72, and 96 h) and SePM concentration (0.00, 0.01, 0.10, and 1.00 g L-1). The bioaccumulation of metals, contamination rates, mortality, and ROS-related biomarkers (lipid peroxidation - LPO; DNA strand breakage DNA SB and metallothionein content - MTs;) were evaluated. After contamination, the water contained 27 different metals/metalloids. Post-larvae accumulated metals, such as Cd, Pb, Al, As, Se, Sr, Zr, Ba, La, Ce, W, and Hg. However, the rise in SePM did not result in a proportional bioaccumulation rise, indicating that effective biological barriers may work for some metals. Although the different levels of SePM changed mortality dynamics, they resulted in a similar final lethality (60-80 %). SePM caused significant damage to lipids (increased LPO), genetic material (DNA SB), and increased Mts. Such effects may reflect a particularly deleterious ecological problem as it is present at such an early stage of life. These results identified a clear environmental risk since the lower level of exposure used was 102 times lower than that measured in the habitats affected by local industry. Consequently, our results emphasize the need for clear protocols for monitoring the effects of SePM in aquatic environments.

Cadmium-Induced Oxidative Damage and the Expression and Function of Mitochondrial Thioredoxin in Phascolosoma esculenta

Phascolosoma esculenta is a unique aquatic invertebrate native to China, whose habitat is highly susceptible to environmental pollution, making it an ideal model for studying aquatic toxicology. Mitochondrial thioredoxin (Trx2), a key component of the Trx system, plays an essential role in scavenging reactive oxygen species (ROS), regulating mitochondrial membrane potential, and preventing ROS-induced oxidative stress and apoptosis. This study investigated the toxicity of cadmium (Cd) on P. esculenta and the role of P. esculenta Trx2 (PeTrx2) in Cd detoxification. The results showed that Cd stress altered the activities of T-SOD and CAT, as well as the contents of GSH and MDA in the intestine. After 96 h of exposure, histological damages such as vacuolization, cell necrosis, and mitophagy were observed. Suggesting that Cd stress caused oxidative damage in P. esculenta. Furthermore, with the prolongation of stress time, the expression level of intestinal PeTrx2 mRNA initially increased and then decreased. The recombinant PeTrx2 (rPeTrx2) protein displayed dose-dependent redox activity and antioxidant capacity and enhanced Cd tolerance of Escherichia coli. After RNA interference (RNAi) with PeTrx2, significant changes in the expression of apoptosis-related genes (Caspase-3, Bax, Bcl-2, and Bcl-XL) were observed. Proving that PeTrx2 rapidly responded to Cd stress and played a vital role in mitigating Cd-induced oxidative stress and apoptosis. Our study demonstrated that PeTrx2 is a key factor for P. esculenta to endure the toxicity of Cd, providing foundational data for further exploration of the molecular mechanisms underlying heavy metal resistance in P. esculenta.

FAN1 Deletion Variant in Basenji Dogs with Fanconi Syndrome

Background: Fanconi syndrome is a disorder of renal proximal tubule transport characterized by metabolic acidosis, amino aciduria, glucosuria, and phosphaturia. There are acquired and hereditary forms of this disorder. A late-onset form of Fanconi syndrome in Basenjis was first described in 1976 and is now recognized as an inherited disease in these dogs. In part because of the late onset of disease signs, the disorder has not been eradicated from the breed by selective mating. A study was therefore undertaken to identify the molecular genetic basis of the disease so that dogs could be screened prior to breeding in order to avoid generating affected offspring. Methods: Linkage analysis within a large family of Basenjis that included both affected and unaffected individuals was performed to localize the causative variant within the genome. Significant linkage was identified between chromosome 3 (CFA3) makers and the disease phenotype. Fine mapping restricted the region to a 2.7 Mb section of CFA3. A whole genome sequence of a Basenji affected with Fanconi syndrome was generated, and the sequence data were examined for the presence of potentially deleterious homozygous variants within the mapped region. Results: A homozygous 317 bp deletion was identified in the last exon of FAN1 of the proband. 78 Basenjis of known disease status were genotyped for the deletion variant. Among these dogs, there was almost complete concordance between genotype and phenotype. The only exception was one dog that was homozygous for the deletion variant but did not exhibit signs of Fanconi syndrome. Conclusions: These data indicate that the disorder is very likely the result of FAN1 deficiency. The mechanism by which this deficiency causes the disease signs remains to be elucidated. FAN1 has endonuclease and exonuclease activity that catalyzes incisions in regions of double-stranded DNA containing interstrand crosslinks. FAN1 inactivation may cause Fanconi syndrome in Basenjis by sensitization of kidney proximal tubule cells to toxin-mediated DNA crosslinking, resulting in the accumulation of genomic and mitochondrial DNA damage in the kidney. Differential exposure to environmental toxins that promote DNA crosslink formation may explain the wide age-at-onset variability for the disorder in Basenjis.

The protective effect of glucose selenol on cadmium-induced testicular toxicity in male rat

This study aimed to investigate the protective effects of glucose selenol on cadmium (Cd)-induced testicular toxicity. Twenty-four male Sprague-Dawley (SD) rats were randomly divided into four groups. Cd was administered orally at a dose of 40 mg/L or in combination with orally administered glucose selenol at doses of 0.15 mg/L and 0.4 mg/L for 30 days. The results showed that sperm quality decreased and testicular tissue was damaged in the Cd group; Glucose selenol significantly attenuated the negative effects by improving sperm quality and reducing testicular damage. Transcriptome sequencing analysis showed that Cd stress affected spermatogenesis, sperm motility, oxidative stress, blood-testis barrier and protein metabolism. Four clusters were obtained using the R Mfuzz package, which clustered highly expressed genes under different administrations, and 36 items were enriched. Notably, protein phosphorylation was enriched in the Cd group and is considered to play a key role in the response to Cd stress. We identified fifty-six target selenium (Se) and Cd co-conversion differentially expressed genes (DEGs), including three genes relating to spermatogenesis (Dnah8, Spata31d1b, Spata31d1c). In addition, the obtained DEGs were used to construct a protein-protein interaction network, co-processed with Se and Cd, and 5 modules were constructed. Overall, the analyses of rat testicular physiology and gene expression levels offer new insights into the reproductive toxicity of Cd in rats, and provide potential application prospects for glucose selenol in alleviating the impact of Cd-induced testicular damage.

Xeroderris stuhlmannii (Taub.) Mendonça & E.P.Sousa (Fabaceae): Evidence of the antihypertensive and antioxidant activities of its leaf aqueous extract in cadmium chloride hypertensive rats

Xeroderris stuhlmannii (Fabaceae) is a medicinal reported in Cameroonian herbal medicine to treat hypertension. The aim of the study was to assess the antihypertensive and antioxidant activities of X. stuhlmannii aqueous leaf extract (AEXS) on cadmium chloride-induced hypertensive rats. The in vitro antioxidant activities of AEXS were investigated for their radical scavenging potency using 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric reducing antioxidant power (FRAP), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS), Nitric oxide (NO) and OH- assays completed with oxidative stress markers analyses. Antihypertensive activity of AEXS (35, 100, and 300 mg/kg) was assessed in CdCl2 induced-hypertensive rats. Antihypertensive activities performed include systolic (SBP), diastolic blood pressure (DBP) and heart rate (HR) variation, followed by evaluation of selected biochemical parameters in urine, blood (Alanine aminotransferase (ALT), aspartate aminotransferase (AST)), creatinine, urea and total protein) and histological examination of tissue samples (aorta, heart, kidneys and liver). The amount of the phenols of the leaf extract was estimated in mg gallic acid equivalent and identification of some compounds was done by UPLC-UV-ESI-TOF-MS. Accordingly, the identified phenols were stuhlmannione A (1), formononetin (2), stuhlmarotenoid A (3), 9-methoxymaackiain (4), 4-hydroxymaackiain (5) and 7-hydroxy-3',4'-methylenedioxy-isoflavone (6). The extract exhibited a significant (P < 0.05-0.001) decrease of SBP, DBP and HR when compare to control. AEXS also reduced (P < 0.05) serum rates of ALT, AST, and urea. The extract showed beneficial effects on alterations observed in the histological structures of the aorta, heart, kidneys and liver. AEXS highlighted high level of phenols (26.48 ± 2.89 mg GAE/g) and a strong antiradical activity on DPPH, ABTS+, OH- and NO with IC50 of 148.8 μg/mL, 27.83 μg/mL, 22.29 μg/mL, 29.84 μg/mL respectively. An optical density of 1.79 nm was obtained with FRAP test. Thus, X. stuhlmannii leaf extract has in vitro antioxidant and antihypertensive effects that may support its use against hypertension.

Melatonin as an Ameliorative Agent Against Cadmium- and Lead-Induced Toxicity in Fish: an Overview

Diverse anthropogenic activities and lack of knowledge on its consequences have promoted serious heavy metal contaminations in different aquatic systems throughout the globe. The non-biodegradable nature of most of these toxic heavy metals has increased the concern on their possible bioaccumulation in aquatic organisms as well as in other vertebrates. Among these aquatic species, fish are most sensitive to such contaminated water that not only decreases their chance of survivability in the nature but also increases the probability of biomagnifications of these heavy metals in higher order food chain. After entering the fish body, heavy metals induce detrimental changes in different vital organs by impairing multiple physiological and biochemical pathways that are essential for the species. Such alterations may include tissue damage, induction of oxidative stress, immune-suppression, endocrine disorders, uncontrolled cell proliferation, DNA damage, and even apoptosis. Although uncountable reports have explored the toxic effects of different heavy metals in diverse fish species, but surprisingly, only a few attempts have been made to ameliorate such toxic effects. Since, oxidative stress seems to be the underlying common factor in such heavy metal-induced toxicity, therefore, a potent and endogenous antioxidant with no side effect may be an appropriate therapeutic solution. Apart from summarizing the toxic effects of two important toxicants, i.e., cadmium and lead in fish, the novelty of the present treatise lies in its arguments in favor of using melatonin, an endogenous free radical scavenger and indirect antioxidant, in ameliorating the toxic effects of heavy metals in any fish species.

Interactions of binary mixtures of metals on rainbow trout (Oncorhynchus mykiss) heart mitochondrial H2O2 homeodynamics

For continuous pumping of blood, the heart needs a constant supply of energy (ATP) that is primarily met via oxidative phosphorylation in the mitochondria of cardiomyocytes. However, sustained high rates of electron transport for energy conversion redox reactions predisposes the heart to the production of reactive oxygen species (ROS) and oxidative stress. Mitochondrial ROS are fundamental drivers of responses to environmental stressors including metals but knowledge of how combinations of metals alter mitochondrial ROS homeodynamics remains sparse. We explored the effects and interactions of binary mixtures of copper (Cu), cadmium (Cd), and zinc (Zn), metals that are common contaminants of aquatic systems, on ROS (hydrogen peroxide, H2O2) homeodynamics in rainbow trout (Oncorhynchus mykiss) heart mitochondria. Isolated mitochondria were energized with glutamate-malate or succinate and exposed to a range of concentrations of the metals singly and in equimolar binary concentrations. Speciation analysis revealed that Cu was highly complexed by glutamate or Tris resulting in Cu2+ concentrations in the picomolar to nanomolar range. The concentration of Cd2+ was 7.2-7.5 % of the total while Zn2+ was 15 % and 21 % of the total during glutamate-malate and succinate oxidation, respectively. The concentration-effect relationships for Cu and Cd on mitochondrial H2O2 emission depended on the substrate while those for Zn were similar during glutamate-malate and succinate oxidation. Cu + Zn and Cu + Cd mixtures exhibited antagonistic interactions wherein Cu reduced the effects of both Cd and Zn, suggesting that Cu can mitigate oxidative distress caused by Cd or Zn. Binary combinations of the metals acted additively to reduce the rate constant and increase the half-life of H2O2 consumption while concomitantly suppressing thioredoxin reductase and stimulating glutathione peroxidase activities. Collectively, our study indicates that binary mixtures of Cu, Zn, and Cd act additively or antagonistically to modulate H2O2 homeodynamics in heart mitochondria.

The effects of cadmium on selected oxidative stress parameters and the content of photosynthetic pigments in cucumber Cucumis sativus L

BACKGROUND

Environmental pollution by cadmium (Cd) is currently a common problem in many countries, especially in highly industrialised areas. Cd present in the soil can be absorbed by plants through the root system.

AIM

The aim of the present study was to investigate the effects of cadmium on the metabolic activity of cucumber plants (Cucumis sativus L.) and the accumulation and distribution of Cd in the organs of the plants.

METHODS

Cucumber seeds (3 g) were exposed to 0.76, 1.58 or 4.17 mg Cd/L (applied as CdCl2 solutions). The activity of selected antioxidant enzymes - glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation and the content of photosynthetic pigments were determined in 6-week-old cucumber plants. In addition, intake of Cd has been determined by flame atomic absorption spectrometry (F-AAS).

RESULTS

The results show that the applied cadmium concentrations affected the activity of antioxidant enzymes. An increase in CAT activity and a decrease in SOD activity were observed in all cucumber organs analysed. GSH-Px activity increased in the roots and stems. Surprisingly, GSH-Px activity decreased in the leaves. The level of lipid peroxidation was usually unchanged (the only one statistically significant change was a decrease in the concentration of malondialdehyde in the leaves which was observed after exposure to the highest Cd concentration). The applied Cd concentrations had no effect on the content of photosynthetic pigments. The highest cadmium content was found in the roots of cucumber plants. Cd tends to accumulate in the roots and a small amount was translocated to the stems and leaves, which was confirmed with the translocation factor (TF).

CONCLUSIONS

The results indicate that the range of cadmium concentrations used, corresponding to the level of environmental pollution recorded in Europe, effectively activates the antioxidant enzyme system, without intensifying lipid peroxidation or reducing the content of photosynthetic pigments.

Cardiac Myosin and Thin Filament as Targets for Lead and Cadmium Divalent Cations

Lead and cadmium are heavy metals widely distributed in the environment and contribute significantly to cardiovascular morbidity and mortality. Using Leadmium Green dye, we have shown that lead and cadmium enter cardiomyocytes, distributing throughout the cell. Using an in vitro motility assay, we have shown that sliding velocity of actin and native thin filaments over myosin decreases with increasing concentrations of Pb2+ and Cd2+. Significantly lower concentrations of Pb2+ and Cd2+ (0.6 mM) were required to stop sliding of thin filaments over myosin compared to the stopping actin sliding over the same myosin (1.1-1.6 mM). Lower concentration of Cd2+ (1.1 mM) needed to stop actin sliding over myosin compared to the Pb2++Cd2+ combination (1.3 mM) and lead alone (1.6 mM). There were no differences found in the effects of lead and cadmium cations on relative force developed by myosin heads or number of actin filaments bound to myosin. Sliding velocity of actin over myosin in the left atrium, right and left ventricles changed equally when exposed to the same dose of the same metal. Thus, we have demonstrated for the first time that Pb2+ and Cd2+ can directly affect myosin and thin filament function, with Cd2+ exerting a more toxic influence on myosin function compared to Pb2+.

Egg White Hydrolysate Mitigates Cadmium-induced Neurological Disorders and Oxidative Damage

We aimed to investigate whether the consumption of Egg White Hydrolysate (EWH) acts on nervous system disorders induced by exposure to Cadmium (Cd) in rats. Male Wistar rats were divided into (a) Control (Ct): H2O by gavage for 28 days + H2O (i.p. - 15th - 28th day); (b) Cadmium (Cd): H2O by gavage + CdCl2 - 1 mg/kg/day (i.p. - 15th - 28th day); (c) EWH 14d: EWH 1 g/kg/day by gavage for 14 days + H2O (i.p.- 15th - 28th day); (d) Cd + EWH cotreatment (Cd + EWHco): CdCl2 + EWH for 14 days; (e) EWH 28d: EWH for 28 days; (f) EWHpre + Cd: EWH (1st - 28th day) + CdCl2 (15th - 28th day). At the beginning and the end of treatment, neuromotor performance (Neurological Deficit Scale); motor function (Rota-Rod test); ability to move and explore (Open Field test); thermal sensitivity (Hot Plate test); and state of anxiety (Elevated Maze test) were tested. The antioxidant status in the cerebral cortex and the striatum were biochemically analyzed. Cd induces anxiety, and neuromotor, and thermal sensitivity deficits. EWH consumption prevented anxiety, neuromotor deficits, and alterations in thermal sensitivity, avoiding neuromotor deficits both when the administration was performed before or during Cd exposure. Both modes of administration reduced the levels of reactive species, and the lipid peroxidation increased by Cd and improved the striatum's antioxidant capacity. Pretreatment proved to be beneficial in preventing the reduction of SOD activity in the cortex. EWH could be used as a functional food with antioxidant properties capable of preventing neurological damage induced by Cd.

Cadmium toxicity and autophagy: a review

Cadmium (Cd) is an important environmental pollutant that poses a threat to human health and represents a critical component of air pollutants, food sources, and cigarette smoke. Cd is a known carcinogen and has toxic effects on the environment and various organs in humans. Heavy metals within an organism are difficult to biodegrade, and those that enter the respiratory tract are difficult to remove. Autophagy is a key mechanism for counteracting extracellular (microorganisms and foreign bodies) or intracellular (damaged organelles and proteins that cannot be degraded by the proteasome) stress and represents a self-protective mechanism for eukaryotes against heavy metal toxicity. Autophagy maintains cellular homeostasis by isolating and gathering information about foreign chemicals associated with other molecular events. However, autophagy may trigger cell death under certain pathological conditions, including cancer. Autophagy dysfunction is one of the main mechanisms underlying Cd-induced cytotoxicity. In this review, the toxic effects of Cd-induced autophagy on different human organ systems were evaluated, with a focus on hepatotoxicity, nephrotoxicity, respiratory toxicity, and neurotoxicity. This review also highlighted the classical molecular pathways of Cd-induced autophagy, including the ROS-dependent signaling pathways, endoplasmic reticulum (ER) stress pathway, Mammalian target of rapamycin (mTOR) pathway, Beclin-1 and Bcl-2 family, and recently identified molecules associated with Cd. Moreover, research directions for Cd toxicity regarding autophagic function were proposed. This review presents the latest theories to comprehensively reveal autophagy behavior in response to Cd toxicity and proposes novel potential autophagy-targeted prevention and treatment strategies for Cd toxicity and Cd-associated diseases in humans.

Effect of cadmium on histopathological injuries and ultra-structural changes of kidney of the turtle Mauremys reevesii

This research investigated the effect of cadmium on the tissue and cell of kidney of the turtle Mauremys reevesii. Twenty turtles were injected with cadmium at 0, 7.5, 15, 30 mg/kg separately and five turtles were taken in each group at two weeks after exposure. Kidneys were immediately excised and macroscopic pathological changes were observed, then the kidneys were fixed in 4% paraformaldehyde for histopathological examination and fixed in 2.5% (v/v) glutaraldehyde for examination of ultra-structure. The tissues of kidney presented varying degrees of histopathological lesions in cadmium treated turtles by a dose-dependent manner under the light microscope. Under transmission electron microscope, renal tubules cells presented varying degrees of dose-dependent lesions. The results indicated that cadmium can cause cell damages to the kidney, in particular to the mitochondria. Mitochondria can be used as one biomarker in the monitoring of cadmium pollution and its quantitative risk assessments.

Cadmium exposure induced neuronal ferroptosis and cognitive deficits via the mtROS-ferritinophagy pathway

Exposure to environmental cadmium (Cd) is known to cause neuronal death and cognitive decline in humans. Ferroptosis, a novel iron-dependent type of regulated cell death, is involved in various neurological disorders. In the present study, Cd exposure triggered ferroptosis in the mouse hippocampus and in the HT22 murine hippocampal neuronal cell line, as indicated by significant increases in ferroptotic marker expression, intracellular iron levels, and lipid peroxidation. Interestingly, ferroptosis of hippocampal neurons in response to Cd exposure relied on the induction of autophagy since the suppression of autophagy by 3-methyladenine (3-MA) and chloroquine (CQ) substantially ameliorated Cd-induced ferroptosis. Furthermore, nuclear receptor coactivator 4 (NCOA4)-mediated degradation of ferritin was required for the Cd-induced ferroptosis of hippocampal neurons, demonstrating that NCOA4 knockdown decreased intracellular iron levels and lipid peroxidation and increased cell survival, following Cd exposure. Moreover, Cd-induced mitochondrial reactive oxygen species (mtROS) generation was essential for the ferritinophagy-mediated ferroptosis of hippocampal neurons. Importantly, pretreatment with the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively attenuated Cd-induced hippocampal neuronal death and cognitive impairment in mice. Taken together, these findings indicate that ferroptosis is a novel mechanism underlying Cd-induced neurotoxicity and cognitive impairment and that the mtROS-ferritinophagy axis modulates Cd-induced neuronal ferroptosis.

Oxidative Stress in Breast Cancer: A Biochemical Map of Reactive Oxygen Species Production

This review systematizes information about the metabolic features of breast cancer directly related to oxidative stress. It has been shown those redox changes occur at all levels and affect many regulatory systems in the human body. The features of the biochemical processes occurring in breast cancer are described, ranging from nonspecific, at first glance, and strictly biochemical to hormone-induced reactions, genetic and epigenetic regulation, which allows for a broader and deeper understanding of the principles of oncogenesis, as well as maintaining the viability of cancer cells in the mammary gland. Specific pathways of the activation of oxidative stress have been studied as a response to the overproduction of stress hormones and estrogens, and specific ways to reduce its negative impact have been described. The diversity of participants that trigger redox reactions from different sides is considered more fully: glycolytic activity in breast cancer, and the nature of consumption of amino acids and metals. The role of metals in oxidative stress is discussed in detail. They can act as both co-factors and direct participants in oxidative stress, since they are either a trigger mechanism for lipid peroxidation or capable of activating signaling pathways that affect tumorigenesis. Special attention has been paid to the genetic and epigenetic regulation of breast tumors. A complex cascade of mechanisms of epigenetic regulation is explained, which made it possible to reconsider the existing opinion about the triggers and pathways for launching the oncological process, the survival of cancer cells and their ability to localize.

Overexpression of SQUAMOSA promoter binding protein-like 4a (NtSPL4a) alleviates Cd toxicity in Nicotiana tabacum

Squamosa Promoter Binding Protein-Like (SPL) plays a crucial role in regulating plant development and combating stress, yet its mechanism in regulating resistance to Cd toxicity remains unclear. In this study, we cloned a nuclear-localized transcription factor, NtSPL4a, from the tobacco cultivar TN90. Transient co-expression results showed that miR156 significantly reduced the expression of NtSPL4a by binding to the 3'-UTR of its transcript. We obtained transgenic tobacco overexpressing NtSPL4a (including the 3'-UTR) and NtSPL4aΔ (lacking the 3'-UTR) through Agrobacterium-mediated genetic transformation. Compared to the wild type (WT), overexpression of NtSPL4a/NtSPL4aΔ shortened the flowering time and exhibited a more developed root system. The transgenic tobacco showed significantly reduced Cd content, being 85.1% (OE-NtSPL4a) and 46.7% (OE-NtSPL4aΔ) of WT, respectively. Moreover, the upregulation of NtSPL4a affected the mineral nutrient homeostasis in transgenic tobacco. Additionally, overexpression of NtSPL4a/NtSPL4aΔ effectively alleviated leaf chlorosis and oxidative stress induced by Cd toxicity. One possible reason is that the overexpression of NtSPL4a/NtSPL4aΔ can effectively promote the accumulation of non-enzymatic antioxidants. A comparative transcriptomic analysis was performed between transgenic tobacco and WT to further unravel the global impacts brought by NtSPL4a. The tobacco overexpressing NtSPL4a had 183 differentially expressed genes (77 upregulated, 106 downregulated), while the tobacco overexpressing NtSPL4aΔ had 594 differentially expressed genes (244 upregulated, 350 downregulated) compared to WT. These differentially expressed genes mainly included transcription factors, metal transport proteins, flavonoid biosynthesis pathway genes, and plant stress-related genes. Our study provides new insights into the role of the transcript factor SPL in regulating Cd tolerance.

Distinct concentration-dependent oxidative stress profiles by cadmium in a rat kidney proximal tubule cell line

Levels and chemical species of reactive oxygen/nitrogen species (ROS/RNS) determine oxidative eustress and distress. Abundance of uptake pathways and high oxygen consumption for ATP-dependent transport makes the renal proximal tubule particularly susceptible to cadmium (Cd2+)-induced oxidative stress by targeting ROS/RNS generation or antioxidant defence mechanisms, such as superoxide dismutase (SOD) or H2O2-metabolizing catalase (CAT). Though ROS/RNS are well-evidenced, the role of distinct ROS profiles in Cd2+ concentration-dependent toxicity is not clear. In renal cells, Cd2+ (10-50 µM) oxidized dihydrorhodamine 123, reaching a maximum at 2-3 h. Increases (up to fourfold) in lipid peroxidation by TBARS assay and H2O2 by Amplex Red were evident within 30 min. ROS and loss in cell viability by MTT assay with 50 µM Cd2+ could not be fully reversed by SOD mimetics Tempol and MnTBAP nor by SOD1 overexpression, whereas CAT expression and α-tocopherol were effective. SOD and CAT activities were attenuated below controls only with >6 h 50 µM Cd2+, yet augmented by up to 1.5- and 1.2-fold, respectively, by 10 µM Cd2+. Moreover, 10 µM, but not 25-50 µM Cd2+, caused 1.7-fold increase in superoxide anion (O2•-), detected by dihydroethidium, paralled by loss in cell viability, that was abolished by Tempol, MnTBAP, α-tocopherol and SOD1 or CAT overexpression. H2O2-generating NADPH oxidase 4 (NOX4) was attenuated by ~50% with 10 µM Cd2+ at 3 h compared to upregulation by 50 µM Cd2+ (~1.4-fold, 30 min), which was sustained for 24 h. In summary, O2•- predominates with low-moderate Cd2+, driving an adaptive response, whereas oxidative stress by elevated H2O2 at high Cd2+ triggers cell death signaling pathways.Highlights Different levels of reactive oxygen species are generated, depending on cadmium concentration. Superoxide anion predominates and H2O2 is suppressed with low cadmium representing oxidative eustress. High cadmium fosters H2O2 by inhibiting catalase and increasing NOX4 leading to oxidative distress. Superoxide dismutase mimetics and overexpression were less effective with high versus low cadmium. Oxidative stress profile could dictate downstream signalling pathways.

Chronic cadmium exposure impairs flight behavior by dampening flight muscle carbon metabolism in bumblebees

Cadmium pollution affects the global ecosystem because cadmium can be transferred up the food chain. The bumblebee, Bombus terrestris, is an important insect pollinator. Their foraging activity on flowers exposes them to harmful heavy metals, which damages their health and leads to massive population declines. However, the effects of chronic exposure to heavy metals on the flight performance of bumblebees have not yet been characterized. Here, we studied variation in the flight capacity of bumblebees induced by chronic cadmium exposure at field-realistic concentrations using behavioral, physiological, and molecular approaches. Chronic cadmium exposure caused a significant reduction in the duration, distance, and mean velocity of bumblebee flight. Transcriptome analysis showed that the impairment of carbon metabolism and mitochondrial dysfunction in the flight muscle were the primary causes. Physiological, biochemical, and metabolomic analyses validated disruptions in energy metabolism, and impairments in mitochondrial respiratory chain complexes activities. Histological analysis revealed muscle fiber damage and mitochondrial loss. Exogenous decanoic acid or citric acid partially restored sustained flight ability of bumblebees by mitigating muscle fiber damage and increasing energy generation. These findings provide insights into how long-term cadmium stress affects the flight ability of insects and will aid human muscle or exercise-related disease research.

Overexpression of NtGPX8a Improved Cadmium Accumulation and Tolerance in Tobacco (Nicotiana tabacum L.)

Cadmium (Cd)-induced oxidative stress detrimentally affects hyperaccumulator growth, thereby diminishing the efficacy of phytoremediation technology aimed at Cd pollution abatement. In the domain of plant antioxidant mechanisms, the role of glutathione peroxidase (GPX) in conferring Cd tolerance to tobacco (Nicotiana tabacum) remained unclear. Our investigation employed genome-wide analysis to identify 14 NtGPX genes in tobacco, revealing their organization into seven subgroups characterized by analogous conserved domain patterns. Notably, qPCR analysis highlighted NtGPX8a as markedly responsive to Cd2+ stress. Subsequent exploration through yeast two-hybridization unveiled NtGPX8a's utilization of thioredoxins AtTrxZ and AtTrxm2 as electron donors, and without interaction with AtTrx5. Introduction of NtGPX8a into Escherichia coli significantly ameliorated Cd-induced adverse effects on bacterial growth. Transgenic tobacco overexpressing NtGPX8a demonstrated significantly augmented activities of GPX, SOD, POD, and CAT under Cd2+ stress compared to the wild type (WT). Conversely, these transgenic plants exhibited markedly reduced levels of MDA, H2O2, and proline. Intriguingly, the expression of NtGPX8a in both E. coli and transgenic tobacco led to increased Cd accumulation, confirming its dual role in enhancing Cd tolerance and accumulation. Consequently, NtGPX8a emerges as a promising candidate gene for engineering transgenic hyperaccumulators endowed with robust tolerance for Cd-contaminated phytoremediation.

Using structural equation modeling to assess the genotoxic and mutagenic effects of heavy metal contamination in the freshwater ecosystems: A study involving Oreochromis niloticus in an urban river

Chemical pollutants represent a leading problem for aquatic ecosystems, as they can induce genetic, biochemical, and physiological changes in the species of these ecosystems, thus compromising their adaptability and survival. The Capibaribe River runs through the state of Pernambuco, located in Northeastern Brazil, and passes through areas of agricultural cultivation, densely populated cities, and industrial centers, primarily textiles. Despite its importance, few ecotoxicological studies have been conducted on its environment, and knowledge about pollution patterns and their effects on its biota is still being determined. The objective of this study was to evaluate the water quality and the damage supposed to be caused by pollutants on the DNA specimens of Nile tilapia (Oreochromis niloticus) obtained from seven strategic points of Capibaribe. Tilapia specimens and water were collected during the rainy and dry seasons from 2015 to 2017. The following characteristics were analyzed: physicochemical (six), metal concentration (seven), local pluviosity, micronuclei, and comet assay. The physicochemical and heavy metal analyses were exploratory, whereas the ecotoxicological analyses were hypothetical. To verify this hypothesis, we compared the groups of fish collected to the results of the micronuclei test and comet assay. We created a Structural Equation Model (SEM) to determine how each metal's micronuclei variables, damage index, pluviosity, and concentration were related. Our results demonstrated that the highest values for markers of genetic damage were detected at points with the highest heavy metal concentrations, especially iron, zinc, manganese, chromium, and cadmium. The SEM demonstrated that metals could explain the findings of the genotoxicity markers. Moreover, other pollutants, such as pesticides, should be considered, mainly where the river passes through rural areas. The results presented here demonstrate that the Capibaribe River has different degrees of contamination and confirm our hypothesis.

Mechanism of cadmium-induced nephrotoxicity

Heavy metals are found naturally in our environment and have many uses and applications in daily life. However, high concentrations of metals may be a result of pollution due to industrialization. In particular, cadmium (Cd), a white metal abundantly distributed in the terrestrial crust, is found in mines together with zinc, which accumulates after volcanic eruption or is found naturally in the sea and earth. High levels of Cd have been associated with disease. In the human body, Cd accumulates in two ways: via inhalation or consumption, mainly of plants or fish contaminated with high concentrations. Several international organizations have been working to establish the limit values of heavy metals in food, water, and the environment to avoid their toxic effects. Increased Cd levels may induce kidney, liver, or neurological diseases. Cd mainly accumulates in the kidney, causing renal disease in people exposed to moderate to high levels, which leads to the development of end-stage chronic kidney disease or death. The aim of this review is to provide an overview of Cd-induced nephrotoxicity, the mechanisms of Cd damage, and the current treatments used to reduce the toxic effects of Cd exposure.

Heavy Metal Exposure: Molecular Pathways, Clinical Implications, and Protective Strategies

Heavy metals are often found in soil and can contaminate drinking water, posing a serious threat to human health. Molecular pathways and curation therapies for mitigating heavy metal toxicity have been studied for a long time. Recent studies on oxidative stress and aging have shown that the molecular foundation of cellular damage caused by heavy metals, namely, apoptosis, endoplasmic reticulum stress, and mitochondrial stress, share the same pathways as those involved in cellular senescence and aging. In recent aging studies, many types of heavy metal exposures have been used in both cellular and animal aging models. Chelation therapy is a traditional treatment for heavy metal toxicity. However, recently, various antioxidants have been found to be effective in treating heavy metal-induced damage, shifting the research focus to investigating the interplay between antioxidants and heavy metals. In this review, we introduce the molecular basis of heavy metal-induced cellular damage and its relationship with aging, summarize its clinical implications, and discuss antioxidants and other agents with protective effects against heavy metal damage.

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Effect of lactoferrin supplement on cadmium chloride induced toxicity to male rats: Toxicopathological, ultrastructural and immunological studies

This study sought to determine whether lactoferrin supplementation could counteract the harm that cadmium (Cd) induced to the rats. The effect of Cd and lactoferrin were investigated in hematological, biochemical, histological, immunohistochemical expression and ultrastructural studies. After 30 days of treatment, rats exposed to Cd had significantly higher levels of Cd in their blood, more oxidized lipids, and less antioxidant capacity overall. Supplemental lactoferrin also significantly undoes that effect. Hematological and biochemical parameters changed along with the increase in blood Cd levels. The histological integrity of the liver, kidney, spleen, and (axillary, cervical, mesenteric and popliteal) lymph nodes that had been damaged by Cd exposure was also restored by lactoferrin supplementation. Moreover, the liver and spleen ultrastructure showed the same improvement. In addition, the spleen of Lf/Cd group showed less immunohistochemical expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in comparison to the Cd group. In conclusion, the current study showed that supplementing with lactoferrin improved immune response and restored biochemical and oxidative stability induced by Cd.

Saccharomyces cerevisiae additions normalized hemocyte differential genes expression and regulated crayfish (Procambarus clarkii) oxidative damage under cadmium stress

Because China produces the most crayfish in the world, safe solutions must be improved to mitigate the risks of ongoing heavy metal stressors accumulation. This study aimed to use Saccharomyces cerevisiae as a bioremediation agent to counteract the harmful effect of cadmium (Cd) on crayfish (Procambarus clarkia). Our study used three concentrations of S. cerevisiae on crayfish feed to assess their Cd toxicity remediation effect by measuring total antioxidant capacity (TAC) and the biomarkers related to oxidative stress like malondialdehyde (MDA), protein carbonyl derivates (PCO), and DNA-protein crosslink (DPC). A graphite furnace atomic absorption spectroscopy device was used to determine Cd contents in crayfish. Furthermore, the mRNA expression levels of lysozyme (LSZ), metallothionein (MT), and prophenoloxidase (proPO) were evaluated before and following the addition of S. cerevisiae. The results indicated that S. cerevisae at 5% supplemented in fundamental feed exhibited the best removal effect, and Cd removal rates at days 4th, 8th, 12th, and 21st were 12, 19, 29.7, and 66.45%, respectively, which were significantly higher than the basal diet of crayfish. The addition of S. cerevisiae increased TAC levels. On the other hand, it decreased MDA, PCO, and DPC, which had risen due to Cd exposure. Furthermore, it increased the expression of proPO, which was reduced by Cd exposure, and decreased the expression of LSZ and MT, acting in the opposite direction of Cd exposure alone. These findings demonstrated that feeding S. cerevisiae effectively reduces the Cd from crayfish and could be used to develop Cd-free crayfish-based foods.

Placental BCRP transporter reduces cadmium accumulation and toxicity in immortalized human trophoblasts

Cadmium (Cd) is a ubiquitous environmental metal detectable in most pregnant women. Animal and human studies demonstrate that in utero exposure to Cd reduces birth weight and impairs perinatal growth due to placental toxicity. BCRP is a prominent transporter that can efflux xenobiotics from the placenta. This study sought to investigate Cd transport and toxicity in cultured human BeWo trophoblasts with reduced expression and function of the placental barrier transporter BCRP. Knockdown (KD) of BCRP protein expression and function in BeWo trophoblasts increased the intracellular accumulation of Cd by 100% following treatment with 1 μM CdCl2. No change in the expression of Cd uptake transporters was observed between control and BCRP-KD cells. Reduced BCRP expression impaired viability of BeWo cells exposed to CdCl2 for 48 hr (BCRP-KD IC50: 11 μM, control cells IC50: 18 μM). Moreover, BCRP-KD cells were more sensitive to CdCl2-induced cytotoxicity compared to control BeWo cells. CdCl2 treatment strongly induced the expression of the metal-binding protein metallothionein (MT) in both control and BCRP-KD cells, with significantly greater MT upregulation in Cd-treated BCRP-KD cells. These data suggest that the BCRP transporter reduces Cd accumulation in syncytiotrophoblasts, which may be one mechanism to reduce subsequent toxicity to the placenta and developing fetus.

Metallomic Signatures of Lung Cancer and Chronic Obstructive Pulmonary Disease

Lung cancer (LC) is the leading cause of cancer deaths, and chronic obstructive pulmonary disease (COPD) can increase LC risk. Metallomics may provide insights into both of these tobacco-related diseases and their shared etiology. We conducted an observational study of 191 human serum samples, including those of healthy controls, LC patients, COPD patients, and patients with both COPD and LC. We found 18 elements (V, Al, As, Mn, Co, Cu, Zn, Cd, Se, W, Mo, Sb, Pb, Tl, Cr, Mg, Ni, and U) in these samples. In addition, we evaluated the elemental profiles of COPD cases of varying severity. The ratios and associations between the elements were also studied as possible signatures of the diseases. COPD severity and LC have a significant impact on the elemental composition of human serum. The severity of COPD was found to reduce the serum concentrations of As, Cd, and Tl and increased the serum concentrations of Mn and Sb compared with healthy control samples, while LC was found to increase Al, As, Mn, and Pb concentrations. This study provides new insights into the effects of LC and COPD on the human serum elemental profile that will pave the way for the potential use of elements as biomarkers for diagnosis and prognosis. It also sheds light on the potential link between the two diseases, i.e., the evolution of COPD to LC.

Mitochondria in the Spotlight: C. elegans as a Model Organism to Evaluate Xenobiotic-Induced Dysfunction

Mitochondria play a crucial role in cellular respiration, ATP production, and the regulation of various cellular processes. Mitochondrial dysfunctions have been directly linked to pathophysiological conditions, making them a significant target of interest in toxicological research. In recent years, there has been a growing need to understand the intricate effects of xenobiotics on human health, necessitating the use of effective scientific research tools. Caenorhabditis elegans (C. elegans), a nonpathogenic nematode, has emerged as a powerful tool for investigating toxic mechanisms and mitochondrial dysfunction. With remarkable genetic homology to mammals, C. elegans has been used in studies to elucidate the impact of contaminants and drugs on mitochondrial function. This review focuses on the effects of several toxic metals and metalloids, drugs of abuse and pesticides on mitochondria, highlighting the utility of C. elegans as a model organism to investigate mitochondrial dysfunction induced by xenobiotics. Mitochondrial structure, function, and dynamics are discussed, emphasizing their essential role in cellular viability and the regulation of processes such as autophagy, apoptosis, and calcium homeostasis. Additionally, specific toxins and toxicants, such as arsenic, cadmium, and manganese are examined in the context of their impact on mitochondrial function and the utility of C. elegans in elucidating the underlying mechanisms. Furthermore, we demonstrate the utilization of C. elegans as an experimental model providing a promising platform for investigating the intricate relationships between xenobiotics and mitochondrial dysfunction. This knowledge could contribute to the development of strategies to mitigate the adverse effects of contaminants and drugs of abuse, ultimately enhancing our understanding of these complex processes and promoting human health.

Selenium alleviates cadmium-induced oxidative stress, endoplasmic reticulum stress, and apoptosis in L8824 cells

Cadmium (Cd) is a toxic pollutant in industrial production that induces organ damage and apoptosis, While, selenium (Se) has the biological function of antagonizing Cd toxicity. Hence, to gain further insight into the protective mechanisms of selenium against Cd-induced damage in Ctenopharyngodon idella liver (L8824) cells, L8824 were exposed to 5 μM, 15 μM, 25 μM cadmium chloride for 24 h after pre-incubation with 25 μM sodium selenite for 9 h. Cell proliferation and morphological changes, the levels of reactive oxygen species (ROS) and antioxidant enzyme activity, mitochondrial membrane potential (MMP), endoplasmic reticulum stress (ERS)-related pathway genes expression, intracellular calcium levels and apoptosis were assessed to explore the protective effect of selenium in Cd-induced L8824 cell damage. The results showed that Cd caused decreased cell viability, ROS accumulation, reduced activity of antioxidant enzymes (SOD, CAT GPx and T-AOC) and apoptosis in L8824 cells. The incubation of Se prominently ameliorated cell proliferation, activated the Keap1-Nrf2 pathway, and restored antioxidant enzyme activity. Furthermore, the expression of grp78, perk, eif-2α, atf4, chop bax, jnk, caspase-3 and caspase-9 was significantly upregulated after Cd exposure, while the expression of bcl-2 was significantly downregulated. Se supplementation alleviated Cd-induced ERS and apoptosis. Moreover, Cd-induced elevation of intracellular Ca2+ levels were alleviated by dantrolene and 2-APB, suggesting that intracellular calcium disorders were caused by Ca2+ released by RyR and IP3R-mediated ER. The results of this study suggested that Cd could induce oxidative stress, ERS, mitochondrial damage and evoke apoptosis, whereas Se had protective effects in preventing Cd induced damage by inhibiting ERS, maintaining intracellular calcium homeostasis, enhancing the antioxidant capacity of L8824 cells and downregulating the Keap1/Nrf2 pathway.

ROS and ERK Pathway Mechanistic Approach on Hepatic Insulin Resistance After Chronic Oral Exposure to Cadmium NOAEL Dose

Cadmium is a critical toxic agent in occupational and non-occupational settings and acute and chronic environmental exposure situations that have recently been associated with metabolic disease development. Until now, the no observed adverse effect level (NOAEL) of cadmium has not been studied regarding insulin resistance development. Therefore, we aimed to monitor whether chronic oral exposure to cadmium NOAEL dose induces insulin resistance in Wistar rats and investigate if oxidative stress and/or inflammation are related. Male Wistar rats were separated into control (standard normocalorie diet + water free of cadmium) and cadmium groups (standard normocalorie diet + drinking water with 15 ppm CdCl2). At 15, 30, and 60 days, oral glucose tolerance, insulin response, and insulin resistance were analyzed using mathematical models. In the liver glycogen, triglyceride, pro- and anti-inflammatory cytokines, cadmium, zinc, metallothioneins, and redox balance were quantified. Immunoreactivity analysis of proteins involved in metabolic and mitogenic insulin signaling was performed. The results showed that a cadmium NOAEL dose after 15 days of exposure causes ROS and mitogenic arm of insulin signaling to increase while hepatic glycogen diminishes. At 30 days, Cd accumulation accentuated ROS production, hepatic triglyceride overaccumulation, and mitogenic signals that develop insulin resistance. Finally, inflammation and lipid peroxidation appear after 60 days of Cd exposure, while lipids and carbohydrate homeostasis deteriorate. In conclusion, environmental exposure to cadmium NAOEL dose causes hepatic Cd accumulation and ROS overproduction that chronically declines the antioxidant defense, deteriorates metabolic homeostasis associated with the mitogenic pathway of insulin signaling, and induces insulin resistance.

Effects of cadmium chloride and biofertilizer (Bacilar) on biochemical parameters of freshwater fish, Alburnus mossulensis

Fish in wild are often faced with various types of xenobiotics, that may display synergistic or antagonistic effects. In this study, we aim to examine how exposure to agrochemical compound (Bacilar) and cadmium (CdCl₂) alone and in combination affect biochemical parameters (lactate dehydrogenase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, alanine aminotransferase; creatine phosphokinase (CKP), cholinesterase) and oxidative stress (total antioxidant capacity, catalase, malondialdehyde and protein carbonyl concentrations) of freshwater fish Alburnus mossulensis. Fish were exposed to two concentrations of Bacilar (0.3, and 0.6 mL L^-1) and to 1 mg L^-1 cadmium chloride alone and in combination for 21 days. Results showed that fish accumulate Cd in their body, with the highest rate in individuals exposed to Cd in combination with Bacilar. Both xenobiotics in fish liver induced the activation of liver enzymes suggesting hepatotoxic effects, with the greatest impact in co-exposed groups. A significant decrease in the hepatocyte's total antioxidant capacity indicates the collapse of the antioxidant defense in fish exposed to Cd and Bacilar. A decrease in the antioxidant biomarkers was followed by increased oxidative damage of lipids and proteins. We also reported altered function in the muscle of individuals exposed to Bacilar and Cd seen as decreased activities in CKP and butyrylcholinesterase. Overall, our results point to the toxicity of both Bacilar and Cd on fish but also to their synergistic effects on Cd bioaccumulation, oxidative stress, and liver and muscle damage. This study highlights the need for evaluating the use of agrochemicals and their possible additive effects on non-target organisms.

Cadmium induced bioaccumulation, histopathology, gene regulation in fish and its amelioration - A review

Different anthropogenic activities as well as natural sources contribute enormously towards various heavy metal contaminations in aquatic habitats. Cadmium (Cd) is one of most prevalent and toxic heavy metals with a long half life. Unlike terrestrial animals, exposure of Cd in fishes may happen not only through feeds but also from its habitat water. Bioaccumulation of Cd in fishes occurs in many tissues, but mainly in gill, liver, kidney, skin, and muscle. The concentrations of Cd in fish tissues depend upon the extent and duration of Cd exposure, species and age of fishes, dietary minerals and antioxidant concentrations, and habitat water quality. Specific histopathological observations in liver, kidney, and gill are useful to understand the effects of Cd, which could help to determine the ameliorating methods to be adopted. Exposure of Cd exerts several adverse effects on general growth and development, reproductive processes, osmoregulation, morphological and histological structures, stress tolerance, and endocrine system, mainly due to changes in biological functions induced by differential expressions of several genes related to oxidative stress, apoptosis, inflammation, immunosuppressions, genotoxicity, Cd chelation and carbohydrate metabolism. Chronic biomagnifications of Cd exceeding the permitted level may be harmful not only to the fishes itself but also to humans through food chains. Amelioration of such toxic heavy metal that has been categorized as a potent carcinogenic in humans is of utmost importance. Main modes of amelioration encompas reducing oxidative damages by promoting the antioxidative defenses, decreasing Cd absorption, increasing excretion through excretory system and improving the tolerance of fishes to Cd toxicity. Many amelioration measures such as use of minerals (for example, zinc, calcium, and iron), vitamins (vitamin C, A, and E), different herbs, probiotics and other agents (taurine, bentonite, chitosan, zeolite, and metallothionein) have been explored for their effective roles to reduce Cd bioaccumulation and toxicity symptoms in fishes. The present review discusses bioaccumulation of Cd, histopathological alterations, oxidative stress, synergism-antagonism, and gene regulation in different tissues, and its amelioration measures in fishes.

The metabolism and detoxification effects of lead exposure on Aleurolyphus ovatus (Acari: Acaridae) via transcriptome analysis

Aleurolyphus ovatus Troupeau is one of the most predominant species of the Acaridae family worldwide. Recent reports have demonstrated that the accumulation of lead in stored grains and dietary items exceeds the required standards. However, the molecular mechanism of heavy metal stress on mites has not been reported. To understand the mechanism underlying the heavy metal response of A. ovatus, comparative transcriptome analysis was performed in this study using an Illumina high throughput mRNA sequencing (RNA-seq) platform. A. ovatus was fed on artificial diets containing two different concentrations of lead, namely, a low concentration of 12.5 mg/kg (LAO) and a high concentration of 100 mg/kg (HAO), while the mites in the control (NAO) group were not exposed to lead. A total of 44,362 unigenes, with an average length of 1547 bp, were identified. Of these, 996 unigenes were successfully annotated in seven functional databases. The number of differentially expressed genes (DEGs) in A. ovatus under different lead concentrations was compared. In NAO versus LAO group, including 310 up-regulated and 1580 down-regulated DEGs. In NAO versus HAO group, including 3928 up-regulated and 1761 down-regulated DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment indicated that detoxification enzyme genes were significantly expressed in pathways, such as cytochrome P450 foreign body metabolism, glutathione metabolism and drug metabolism-cytochrome pathway. The results of gene annotation and quantitative real-time PCR showed that high concentration of lead significantly stimulated the expression of metabolic detoxification enzyme genes such as glutathione S transferase (GST) and superoxide dismutase (SOD), while low concentration inhibited their expression. This study will provide a basis for the molecular mechanism of A. ovatus in response to heavy metal lead stimulation in stored grain.

Short-term exposition to acute Cadmium toxicity induces the loss of root gravitropic stimuli perception through PIN2-mediated auxin redistribution in Arabidopsis thaliana (L.) Heynh

Cadmium (Cd), one of the most widespread and water-soluble polluting heavy metals, has been widely studied on plants, even if the mechanisms underlying its phytotoxicity remain elusive. Indeed, most experiments are performed using extensive exposure time to the toxicants, not observing the primary targets affected. The present work studied Cd effects on Arabidopsis thaliana (L.) Heynh's root apical meristem (RAM) exposed for short periods (24h and 48h) to acute phytotoxic concentrations (100 and 150µM). The effects were studied through integrated morpho-histological, molecular, pharmacological and metabolomic analyses, highlighting that Cd inhibited primary root elongation by affecting the meristem zone via altering cell expansion. Moreover, Cd altered Auxin accumulation in RAM and affected PINs polar transporters particularly PIN2. In addition, we observed that high Cd concentration induced accumulation of reactive oxygen species (ROS) in roots, which resulted in an altered organization of cortical microtubules and the starch and sucrose metabolism, altering the statolith formation and, consequently, the gravitropic root response. Our results demonstrated that short Cd exposition (24h) affected cell expansion preferentially, altering auxin distribution and inducing ROS accumulation, which resulted in an alteration of gravitropic response and microtubules orientation pattern.

Oxidative Stress and Neurotoxicity of Cadmium and Zinc on Artemia franciscana

Despite not being redox-active metals, Cd and Zn can disrupt cellular redox homeostasis by acting pro-oxidatively. The aim of this study was to examine the effects of exposure to Zn (14 and 72 mg/L) and Cd (7.7 and 77 mg/L) for 24 and 48 h on oxidative and antioxidative parameters and the activity of glutathione-S-transferase in Artemia franciscana tissue. In addition, the neurotoxicity of the metals was examined by determining the activity of acetylcholinesterase (AChE). In A. franciscana tissue, Cd (0.0026 ± 0.0001 mg/L) was detected only after 48 h of exposure to 77 mg/L Cd. After 24 h, the 14- and 72-mg/L Zn treatments resulted in significant increases in the Zn concentration (0.54 ± 0.026 mg/L (p < 0.01) and 0.68 ± 0.035 (p < 0.0001), respectively) in A. franciscana tissue compared with the control level, and significant increases were also detected after 48 h (0.59 ± 0.02 (p < 0.0001) and 0.79 ± 0.015 (p < 0.0001), respectively). The malondialdehyde (MDA) concentration in the metal-treated samples was increased after 24 h of exposure, whereas after 48 h, an increase in the MDA concentration was detected only with 7.7. mg/L Cd. A significant increase in the H₂O₂ concentration after 24 h was measured only after treatment with 72 mg/L Zn. The treatment with 7.7 mg/L Cd for 24 h induced a significant increase in the AChE activity, whereas 48 h of treatment with 77 mg/L Cd and 14 mg/L Zn significantly inhibited AChE. The results indicate that lipid peroxidation resulting from metal toxicity may constitute the basis of neurotoxicity.

Toxicity mechanisms and bioavailability of copper to fish based on an adverse outcome pathway analysis

Copper (Cu) exists in a variety of forms in different aquatic environments, and affects their bioavailability. In this study we provide a systematic review on toxicity of Cu which focuses on identifying evidence in the mechanisms of Cu toxicity, and apply an adverse outcome pathway (AOP) analysis to identify multiple potential mechanisms and their interactions of Cu toxicity to fish. This analysis process included the mechanisms of behavior toxicant, oxidative toxicant, ion regulation disruption toxicity, as well as endocrine disruption toxicity. It was found that at low levels of Cu exposure, swimming, avoid predators, locating prey and other sensory functions will be impaired, and the organism will suffer from metabolic alkalosis and respiratory acidosis following the inhibition of the carbonic anhydrase active. The main pathway of acute toxicity of Cu to fish is the inhibition of the Na⁺/K⁺-ATPase enzyme, and lead to reduced intracellular sodium absorption, as well as Cu-induced increased cell permeability, in turn resulting in increased sodium ion loss, leading to cardiovascular collapse and respiratory insufficiency. The endocrine disruption toxicity of Cu to fish caused growth inhibition and reproductive reduction. In addition, there are several key pathways of Cu toxicity that are affected by hardness (e.g., Ca²⁺) and intracellular DOC concentrations, including inhibiting Cu-induction, improving branchial gas exchange, altering membrane transport functions, decreasing Na⁺ loss, and increasing Na⁺ uptake. The results of the AOP analysis will provide a robust framework for future directed research on the mechanisms of Cu toxicity.

Evaluation of the oxidative toxicity induced by lead, manganese, and cadmium using genetically modified nrf2a-mutant zebrafish

Heavy metal pollution has become a serious environmental concern and a threat to public health. Three of the most common heavy metals are cadmium (Cd), lead (Pb), and manganese (Mn). Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcription factor activated in the response to oxidative stress. In this study, mutant zebrafish with an nrf2a deletion of 7 bp were constructed by the CRISPR/Cas9 system to investigate the oxidative toxicity of these three heavy metals. The results of general toxicity tests showed that Pb exposure did not cause significant damage to mutant zebrafish compared with wild-type (WT) zebrafish. However, high Mn exposure increased mortality and malformation rates in mutant zebrafish. Of concern, Cd exposure caused significant toxic damage, including increased mortality and malformation rates, apoptosis of brain neurons, and severe locomotor behavior aberration in mutant zebrafish. The results of qRT-PCR indicated that Cd exposure could induce the activation of genes related to oxidative stress resistance in WT zebrafish, while the expression of these genes was inhibited in mutant zebrafish. This study showed that of the three heavy metals, Cd had the strongest oxidative toxicity, Mn had medium toxicity, and Pb had the weakest toxicity.

Crosstalk between Mfn2-mediated mitochondria associated membranes disorder and autophagy induced by molybdenum and cadmium in sheep heart

To investigate the crosstalk of mitochondria associated membranes (MAMs) disorder and autophagy co-induced by molybdenum (Mo) and cadmium (Cd) in sheep hearts. A total of 48 sheep were randomly divided into 4 groups: control group, Mo group, Cd group and Mo + Cd group. The intragastric administration lasted for 50 days. The results showed that Mo or/and Cd exposure could cause morphological damage, imbalance of trace elements and antioxidant function, Ca²⁺ concentration decreased markedly, and significantly increase the contents of Mo or/and Cd in myocardium. Additionally, the mRNA and protein levels of endoplasmic reticulum stress (ERS) related factors and mitochondrial biogenesis related factors were altered by Mo or/and Cd, as well as the content of ATP, inducing ERS and mitochondrial dysfunction. Meanwhile, Mo or/and Cd could lead to the alteration of expression level of MAMs-related genes and proteins, and the distance between mitochondria and endoplasmic reticulum (ER), resulting in MAMs disorder. Moreover, Mo or/and Cd exposure upregulated the mRNA and protein levels of autophagy related factors. In conclusion, our results revealed that Mo or/and Cd exposure caused ERS, mitochondrial dysfunction and structural MAMs disruption, ultimately leading to autophagy in sheep hearts, and the effects of Mo and Cd co-exposure were more obvious.

Cessation Restores Blood Pressure Levels and Endothelial Function Affected by Cadmium Exposure on Rats

Chronic cadmium exposure produces high blood pressure and endothelial damage; however, it is not known whether these effects could be reversed by interrupting the exposure to the metal. Therefore, we evaluate the systolic blood pressure (SBP) and vascular reactivity during and following chronic cadmium-exposure discontinuance. Rats received 100 mg.L^-1 cadmium chloride (CdCl₂) in the drinking water or tap water (Ct) for 30 days and/or tap water for 30 days more. The cadmium plasma content, blood pressure and vascular reactivity of isolated aorta were evaluated. Cadmium exposure increased cadmium plasma content, SBP and aorta contractile responses to phenylephrine, all reversed after suspending exposure. Endothelial removal and nitric oxide synthase (NOS) inhibition increased phenylephrine response both on control and Cd-discontinuation models. Cd-discontinuation group presented increased CAMKII and PKA protein expression, as peNOS^Ser1177. Superoxide dismutase (SOD) incubation reduced contractile response on control group, and catalase incubation enhanced the response to phenylephrine in this group. Meanwhile, both SOD2 and catalase protein expression were increased in Cd-cessation rats. Our findings provide evidence that increased SBP and endothelial dysfunction induced by Cd chronic exposure are reversed by suspending the metal exposure probably due to an improvement of antioxidant enzymes and eNOS function.

Clinical and Forensic Signs Resulting from Exposure to Heavy Metals and Other Chemical Elements of the Periodic Table

Several heavy metals and other chemical elements are natural components of the Earth's crust and their properties and toxicity have been recognized for thousands of years. Moreover, their use in industries presents a major source of environmental and occupational pollution. Therefore, this ubiquity in daily life may result in several potential exposures coming from natural sources (e.g., through food and water contamination), industrial processes, and commercial products, among others. The toxicity of most chemical elements of the periodic table accrues from their highly reactive nature, resulting in the formation of complexes with intracellular compounds that impair cellular pathways, leading to dysfunction, necrosis, and apoptosis. Nervous, gastrointestinal, hematopoietic, renal, and dermatological systems are the main targets. This manuscript aims to collect the clinical and forensic signs related to poisoning from heavy metals, such as thallium, lead, copper, mercury, iron, cadmium, and bismuth, as well as other chemical elements such as arsenic, selenium, and fluorine. Furthermore, their main sources of occupational and environmental exposure are highlighted in this review. The importance of rapid recognition is related to the fact that, through a high degree of suspicion, the clinician could rapidly initiate treatment even before the toxicological results are available, which can make a huge difference in these patients' outcomes.

Structural Characterization of Toxicologically Relevant Cd2+-L-Cysteine Complexes

The exposure of humans to Cd exerts adverse human health effects at low chronic exposure doses, but the underlying biomolecular mechanisms are incompletely understood. To gain insight into the toxicologically relevant chemistry of Cd²⁺ in the bloodstream, we employed an anion-exchange HPLC coupled to a flame atomic absorption spectrometer (FAAS) using a mobile phase of 100 mM NaCl with 5 mM Tris-buffer (pH 7.4) to resemble protein-free blood plasma. The injection of Cd²⁺ onto this HPLC-FAAS system was associated with the elution of a Cd peak that corresponded to [CdCl₃]^-/[CdCl₄]^2- complexes. The addition of 0.1-10 mM L-cysteine (Cys) to the mobile phase significantly affected the retention behavior of Cd²⁺, which was rationalized by the on-column formation of mixed CdCys_xCl_y complexes. From a toxicological point of view, the results obtained with 0.1 and 0.2 mM Cys were the most relevant because they resembled plasma concentrations. The corresponding Cd-containing (~30 μM) fractions were analyzed by X-ray absorption spectroscopy and revealed an increased sulfur coordination to Cd²⁺ when the Cys concentration was increased from 0.1 to 0.2 mM. The putative formation of these toxicologically relevant Cd species in blood plasma was implicated in the Cd uptake into target organs and underscores the notion that a better understanding of the metabolism of Cd in the bloodstream is critical to causally link human exposure with organ-based toxicological effects.