Mechanistic insight into cadmium-induced inactivation of the Bloom protein

Adverse effects of cadmium on lymphoid organs, immune cells, and immunological responses

Humans and animals possess robust immune systems to safeguard against foreign pathogens. However, recent reports suggest a greater incidence of immunity breakdown due to exposure to environmental pollutants, with heavy metals emerging as potential candidates in such immuno-toxicological studies. While we have extensive data on the general toxicity resulting from exposure to heavy metals, comprehensive documentation of their role as immune disruptors remains scarce. Cd (Cadmium) exerts immunomodulation by interfering with immune organs and cells, leading to altered structure, physiology, and function, thereby inducing symptoms of immune deregulation, inflammation and/or autoimmunity. This review aims to summarize the link between Cd exposure and immune dysfunction, drawing from case studies on exposed human subjects, as well as research conducted on various model organisms and in-vitro culture systems.

Mechanistic Insight Into Cadmium- and Zinc-Induced Inactivation of the Candida albicans Pif1 Helicase

Zinc and cadmium are environmental contaminants that can cause disease by affecting the activity of DNA-repair proteins. In this study, we investigated the effect of Zn²⁺ and Cd²⁺ on the Candida albicans Pif1, a DNA-repair helicase that plays a critical role in ensuring genomic stability. We show that Zn2+ and Cd2+ strongly inhibit both the ATPase and the unwinding activities of CaPif1, but have no effect on its DNA binding activity. High concentrations of Cd2+ may bind to the cysteine residues of CaPif1, and its inhibition appears to be difficult to be restored by ethylene diamine tetraacetic acid, while inhibition due to Zn²⁺ can. When the two ions are at low concentrations, increasing the concentration of ATP in the reaction can appropriately weaken the inhibitory effect of Zn²⁺, while cysteine can reduce the inhibitory effect of Cd²⁺. In addition, we found that for both Cd²⁺ and Zn²⁺ the inhibition effects were nearly 100 times greater in reduced environments than in non-reducing environments. When heavy metals stimulate the body’s response, the environment of the body becomes less reducing, and thus the tolerance of CaPif1 to heavy metals will be stronger. We propose that CaPif1 may resist the toxicity of heavy metals through this mechanism. Altogether, our results provide new insights into the mechanisms by which heavy metals are toxic to DNA-repair proteins.

A Comprehensive Review on the Heavy Metal Toxicity and Sequestration in Plants

Heavy metal (HM) toxicity has become a global concern in recent years and is imposing a severe threat to the environment and human health. In the case of plants, a higher concentration of HMs, above a threshold, adversely affects cellular metabolism because of the generation of reactive oxygen species (ROS) which target the key biological molecules. Moreover, some of the HMs such as mercury and arsenic, among others, can directly alter the protein/enzyme activities by targeting their -SH group to further impede the cellular metabolism. Particularly, inhibition of photosynthesis has been reported under HM toxicity because HMs trigger the degradation of chlorophyll molecules by enhancing the chlorophyllase activity and by replacing the central Mg ion in the porphyrin ring which affects overall plant growth and yield. Consequently, plants utilize various strategies to mitigate the negative impact of HM toxicity by limiting the uptake of these HMs and their sequestration into the vacuoles with the help of various molecules including proteins such as phytochelatins, metallothionein, compatible solutes, and secondary metabolites. In this comprehensive review, we provided insights towards a wider aspect of HM toxicity, ranging from their negative impact on plant growth to the mechanisms employed by the plants to alleviate the HM toxicity and presented the molecular mechanism of HMs toxicity and sequestration in plants.

Hydrogen sulfide decreases Cd translocation from root to shoot through increasing Cd accumulation in cell wall and decreasing Cd2+ influx in Isatis indigotica

Hydrogen sulfide (H₂S), a small gaseous signalling molecule, plays a pivotal role in the plant response to heavy metal stress. Here, we revealed a novel mechanism of Isatis indigotica resistance to cadmium (Cd) stress, in which H₂S promotes Cd accumulation in the root and decreases the long-distance transport of Cd from the root to shoot. Cd significantly inhibited Isatis indigotica growth and induced the endogenous H₂S level. Application of NaHS (a H₂S donor) alleviated the effects of Cd. NaHS restriction of the translocation factor of Cd, elevated the Cd content in roots and depressed the Cd content in shoots. Cd stress decreased the cellulose and pectin contents in the cell wall, but NaHS restored the effect of Cd on the cell wall components. The Cd²⁺ fluxes were detected by noninvasive microtest technology (NMT). The data showed that NaHS pretreatment decreased the Cd²⁺ influx and proportion of the Cd content in organelles. We analyzed the effect of NaHS on the metallothionein and phytochelatin (PC) contents in roots and found that the PC and metallothionein1A (MT1A) contents were induced by NaHS. Additionally, the chemical forms of Cd²⁺ were changed by NaHS. Thus, H₂S alters the content of cell wall component, improves Cd accumulation in the cell wall, depresses Cd²⁺ transmembrane movement, induces the synthesis of metallothioneins and decreases the toxicity of intracellular Cd. Our finding has great value to reduce the loss of Isatis indigotica resulted by heavy metals stress.

Proteomic analysis of the S. cerevisiae response to the anticancer ruthenium complex KP1019

Like platinum-based chemotherapeutics, the anticancer ruthenium complex indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(iii)], or KP1019, damages DNA, induces apoptosis, and causes tumor regression in animal models. Unlike platinum-based drugs, KP1019 showed no dose-limiting toxicity in a phase I clinical trial. Despite these advances, the mechanism(s) and target(s) of KP1019 remain unclear. For example, the drug may damage DNA directly or by causing oxidative stress. Likewise, KP1019 binds cytosolic proteins, suggesting DNA is not the sole target. Here we use the budding yeast Saccharomyces cerevisiae as a model in a proteomic study of the cellular response to KP1019. Mapping protein level changes onto metabolic pathways revealed patterns consistent with elevated synthesis and/or cycling of the antioxidant glutathione, suggesting KP1019 induces oxidative stress. This result was supported by increased fluorescence of the redox-sensitive dye DCFH-DA and increased KP1019 sensitivity of yeast lacking Yap1, a master regulator of the oxidative stress response. In addition to oxidative and DNA stress, bioinformatic analysis revealed drug-dependent increases in proteins involved ribosome biogenesis, translation, and protein (re)folding. Consistent with proteotoxic effects, KP1019 increased expression of a heat-shock element (HSE) lacZ reporter. KP1019 pre-treatment also sensitized yeast to oxaliplatin, paralleling prior research showing that cancer cell lines with elevated levels of translation machinery are hypersensitive to oxaliplatin. Combined, these data suggest that one of KP1019's many targets may be protein metabolism, which opens up intriguing possibilities for combination therapy.

Alternative Pathway is Involved in Nitric Oxide-Enhanced Tolerance to Cadmium Stress in Barley Roots

Alternative pathway (AP) has been widely accepted to be involved in enhancing tolerance to various environmental stresses. In this study, the role of AP in response to cadmium (Cd) stress in two barley varieties, highland barley (Kunlun14) and barley (Ganpi6), was investigated. Results showed that the malondialdehyde (MDA) content and electrolyte leakage (EL) level under Cd stress increased in two barley varieties. The expressions of alternative oxidase (AOX) genes (mainly AOX1a), AP capacity (V_alt), and AOX protein amount were clearly induced more in Kunlun14 under Cd stress, and these parameters were further enhanced by applying sodium nitroprussid (SNP, a NO donor). Moreover, H₂O₂ and O₂⁻ contents were raised in the Cd-treated roots of two barley varieties, but they were markedly relieved by exogenous SNP. However, this mitigating effect was aggravated by salicylhydroxamic acid (SHAM, an AOX inhibitor), suggesting that AP contributes to NO-enhanced Cd stress tolerance. Further study demonstrated that the effect of SHAM application on reactive oxygen species (ROS)-related scavenging enzymes and antioxidants was minimal. These observations showed that AP exerts an indispensable function in NO-enhanced Cd stress tolerance in two barley varieties. AP was mainly responsible for regulating the ROS accumulation to maintain the homeostasis of redox state.

Levels of aqueous humor trace elements in patients with open-angle glaucoma

PURPOSE

Trace elements might play a role in the complex multifactorial pathogenesis of open-angle glaucoma. The aim of this study was to analyze concentrations of trace elements in aqueous humor samples of patients with primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEXG).

PATIENTS AND METHODS

Thirty-three aqueous humor samples were obtained from patients undergoing cataract surgery: 12 patients with POAG (age 65.3±10.50, female 8, male 4), 10 patients with PEXG (age 65.9±11.27, female 6, male 4) and 11 patients without glaucoma (age 69.5±13.70, female 7, male 4) serving as controls. Aqueous humor levels of cadmium, iron, manganese, cobalt, copper and zinc were measured by Flow-Injection-Inductively-Coupled-Plasma-Mass-Spectrometry (FI-ICP-MS).

RESULTS

From the statistical evaluation, we observed that patients with POAG had significantly higher aqueous humor levels of zinc (p=0.006) compared to controls. Increased aqueous humor levels of zinc were also observed in patients with PEXG in relation to control (p=0.0006). For iron we observed a significantly reduction in PEXG compared to control (p=0.002) and a significant difference between POAG and PEXG (p=0.0091). No significant differences were observed in aqueous humor levels of manganese, cobalt, copper, cadmium between glaucoma and control patients. No differences were seen for iron (POAG vs. controls). Analysis of trace element ratios was added.

CONCLUSION

Significant differences in aqueous humor levels of zinc and iron between glaucoma and control patients support the hypothesis that these trace elements are involved in the pathogenesis of open-angle glaucoma.

Exposure to lethal levels of benzo[a]pyrene or cadmium trigger distinct protein expression patterns in earthworms (Eisenia fetida)

Different pollutants induce distinct toxic responses in earthworms (Eisenia fetida). Here, we used proteomics techniques to compare the responses of E. fetida to exposure to the 10% lethal concentration (14d-LC₁₀) of benzo[a]pyrene (BaP) or cadmium (Cd) in natural red soil (China). BaP exposure markedly induced the expression of oxidation-reduction proteins, whereas Cd exposure mainly induced the expression of proteins involved in transcription- and translation-related processes. Furthermore, calmodulin-binding proteins were differentially expressed upon exposure to different pollutants. The calcium (Ca²⁺)-binding cytoskeletal element myosin was down-regulated upon BaP treatment, whereas the Ca²⁺-binding cytoskeletal element tropomyosin-1 was up-regulated upon Cd treatment. Some proteins exhibited opposite responses to the two pollutants. For instance, catalase (CAT) and heat shock protein 70 were up-regulated upon BaP treatment and down-regulated upon Cd treatment. A significant (p<0.05, one-way ANOVA with least-significant difference (LSD) test) increase in the level of reactive oxygen species (ROS) and CAT activity further showed that BaP mainly induces oxidative stress. Real-time PCR analysis showed that mRNA expression often did not correlate well with protein expression in earthworms subjected to Cd or BaP treatment. In addition, the expression of the gene encoding the protein metallothionein, which was not detected in the protein analysis, was induced upon Cd treatment, but slightly reduced upon BaP treatment. Therefore, BaP and Cd have distinct effects on the protein profile of E. Fetida with BaP markedly inducing ROS activity, and Cd mainly triggering genotoxicity.

CAPSULE SUMMARY

Distinct patterns of protein expression are induced in earthworms upon exposure to different pollutants; BaP markedly induces high levels of ROS, while Cd resultes in genotoxicity.

Hydrogen sulfide - cysteine cycle system enhances cadmium tolerance through alleviating cadmium-induced oxidative stress and ion toxicity in Arabidopsis roots

Cadmium (Cd²⁺) is a common toxic heavy metal ion. We investigated the roles of hydrogen sulfide (H₂S) and cysteine (Cys) in plant responses to Cd²⁺ stress. The expression of H₂S synthetic genes LCD and DES1 were induced by Cd²⁺ within 3 h, and endogenous H₂S was then rapidly released. H₂S promoted the expression of Cys synthesis-related genes SAT1 and OASA1, which led to endogenous Cys accumulation. The H₂S and Cys cycle system was stimulated by Cd²⁺ stress, and it maintained high levels in plant cells. H₂S inhibited the ROS burst by inducing alternative respiration capacity (AP) and antioxidase activity. H₂S weakened Cd²⁺ toxicity by inducing the metallothionein (MTs) genes expression. Cys promoted GSH accumulation and inhibited the ROS burst, and GSH induced the expression of phytochelatin (PCs) genes, counteracting Cd²⁺ toxicity. In summary, the H₂S and Cys cycle system played a key role in plant responses to Cd²⁺ stress. The Cd²⁺ tolerance was weakened when the cycle system was blocked in lcddes1-1 and oasa1 mutants. This paper is the first to describe the role of the H₂S and Cys cycle system in Cd²⁺ stress and to explore the relevant and specificity mechanisms of H₂S and Cys in mediating Cd²⁺ stress.