Cadmium elicits alterations in mitochondrial morphology and functionality in C3H10T1/2Cl8 mouse embryonic fibroblasts

Morphological and metabolic changes in microglia exposed to cadmium: Cues on neurotoxic mechanisms

Microglial cells play a key role in protecting the central nervous system from pathogens and toxic compounds and are involved in the pathogenesis of different neurodegenerative diseases. Cadmium is a widespread toxic heavy metal, released into the environment at a rate of 30,000 tons/year by anthropogenic activities; it is easily uptaken by the human body through diet and cigarette smoke, as well as by occupational exposure. Once inside the body, cadmium enters the cells and substitutes to zinc and other divalent cations altering many biological functions. Its extremely long half-life makes it a serious health threat. Recent data suggest a role for heavy metals in many neurodegenerative diseases; however, the role of cadmium is still to be elucidated. In this work we report the investigation of cadmium toxicity towards murine BV2 microglial cells, a widely used model for the study of neurodegeneration. Results show that increasing cadmium concentrations increase oxidative stress, a proposed mechanism of neurodegeneration, but also that BV2 cells can keep oxidative stress under control by increasing glutathione reduction. Moreover, cadmium induces alterations of cell morphology and metabolism leading to mitochondrial impairment, without switching the cells to Warburg effect. Finally cadmium induces the release of proinflammatory cytokines, but does not markedly switch BV2 cells to M1 phenotype.

Antioxidant and Anti-Inflammatory Effect of Cinnamon (Cinnamomum verum J. Presl) Bark Extract after In Vitro Digestion Simulation

Cinnamon bark is widely used for its organoleptic features in the food context and growing evidence supports its beneficial effect on human health. The market offers an increasingly wide range of food products and supplements enriched with cinnamon extracts which are eliciting beneficial and health-promoting properties. Specifically, the extract of Cinnamomum spp. is rich in antioxidant, anti-inflammatory and anticancer biomolecules. These include widely reported cinnamic acid and some phenolic compounds, such asproanthocyanidins A and B, and kaempferol. These molecules are sensitive to physical-chemical properties (such as pH and temperature) and biological agents that act during gastric digestion, which could impair molecules' bioactivity. Therefore, in this study, the cinnamon's antioxidant and anti-inflammatory bioactivity after simulated digestion was evaluated by analyzing the chemical profile of the pure extract and digested one, as well as the cellular effect in vitro models, such as Caco2 and intestinal barrier. The results showed that the digestive process reduces the total content of polyphenols, especially tannins, while preserving other bioactive compounds such as cinnamic acid. At the functional level, the digested extract maintains an antioxidant and anti-inflammatory effect at the cellular level.

Is Cadmium Toxicity Tissue-Specific? Toxicogenomics Studies Reveal Common and Specific Pathways in Pulmonary, Hepatic, and Neuronal Cell Models

Several harmful modifications in different tissues-organs, leading to relevant diseases (e.g., liver and lung diseases, neurodegeneration) are reported after exposure to cadmium (Cd), a wide environmental contaminant. This arises the question whether any common molecular signatures and/or Cd-induced modifications might represent the building block in initiating or contributing to address the cells towards different pathological conditions. To unravel possible mechanisms of Cd tissue-specificity, we have analyzed transcriptomics data from cell models representative of three major Cd targets: pulmonary (A549), hepatic (HepG2), and neuronal (SH-SY-5Y) cells. Further, we compared common features to identify any non-specific molecular signatures. The functional analysis of dysregulated genes (gene ontology and KEGG) shows GO terms related to metabolic processes significantly enriched only in HepG2 cells. GO terms in common in the three cell models are related to metal ions stress response and detoxification processes. Results from KEGG analysis show that only one specific pathway is dysregulated in a significant way in all cell models: the mineral absorption pathway. Our data clearly indicate how the molecular mimicry of Cd and its ability to cause a general metal ions dyshomeostasis represent the initial common feature leading to different molecular signatures and alterations, possibly responsible for different pathological conditions.

Insights into Cadmium-Induced Carcinogenesis through an In Vitro Study Using C3H10T1/2Cl8 Cells: The Multifaceted Role of Mitochondria

In this paper, we report the metabolic characterization of two foci, F1 and F3, obtained at the end of Cell Transformation Assay (CTA), performed by treating C3H10T1/2Cl8 mouse embryo fibroblasts with 1 μM CdCl₂ for 24 h. The elucidation of the cadmium action mechanism can be useful both to improve the in vitro CTA and to yield insights into carcinogenesis. The metabolism of the two foci was investigated through Seahorse and enzyme activity assays; mitochondria were studied in confocal microscopy and reactive oxygen species were detected by flow cytometry. The results showed that F1 focus has higher glycolytic and TCA fluxes compared to F3 focus, and a more negative mitochondrial membrane potential, so that most ATP synthesis is performed through oxidative phosphorylation. Confocal microscopy showed mitochondria crowded in the perinuclear region. On the other hand, F3 focus showed lower metabolic rates, with ATP mainly produced by glycolysis and damaged mitochondria. Overall, our results showed that cadmium treatment induced lasting metabolic alterations in both foci. Triggered by the loss of the Pasteur effect in F1 focus and by mitochondrial impairment in F3 focus, these alterations lead to a loss of coordination among glycolysis, TCA and oxidative phosphorylation, which leads to malignant transformation.

A novel circular RNA, circPUS7 promotes cadmium-induced transformation of human bronchial epithelial cells by regulating Kirsten rat sarcoma viral oncogene homolog expression via sponging miR-770

Cadmium is a human carcinogen, which induces cancers by mechanisms that are not fully understood. Induction of oxidative stress, apoptosis resistance, genotoxic effects, and epigenetic modulations have been indicated to regulate cadmium-induced carcinogenesis. Circular RNAs are epigenetic regulators that have been recognized to play essential roles in carcinogenesis. Yet, the involvement of circular RNAs in cadmium carcinogenesis remains unclear. In this study, a novel circular RNA, circPUS7, was identified and described for the first time. CircPUS7 was significantly upregulated at week 12, 16, and 20 during the cadmium-induced transformation of human bronchial epithelial BEAS-2B cells. Knockdown of circPUS7 in cadmium-transformed BEAS-2B (T-BEAS-2B) cells significantly attenuated transformation markers including cell proliferation, migration, invasion, and anchorage-independent growth. Moreover, circPUS7 promoted malignant phenotypes by competitively binding with miR-770. Overexpression of miR-770 significantly inhibited the transformation properties of T-BEAS-2B cells while inhibition of miR-770 potently reversed the inhibitory effects of circPUS7 knockdown in proliferation, migration, invasion, and anchorage-independent growth of the T-BEAS-2B cells. Kirsten rat sarcoma viral oncogene homolog (KRAS), which was increased synchronically with circPUS7 during cadmium-induced cell transformation, was regulated by circPUS7 through sponging miR-770. In summary, our findings demonstrate that circPUS7 promotes cadmium-induced cell transformation through sponging miR-770 to regulate KRAS expression, providing a new perspective with the involvement of circular RNAs to further understand the mechanisms of cadmium carcinogenesis.

Cadmium promotes glycolysis upregulation and glutamine dependency in human neuronal cells

Cadmium is a widespread pollutant, which easily accumulates inside the human body with an estimated half-life of 25-30 years. Many data strongly suggest that it may play a role in the pathogenesis of neurodegenerative diseases. In this paper we investigated cadmium effect on human SH-SY5Y neuroblastoma cells metabolism. Results showed that, although SH-SY5Y cells already showed hyperactivated glycolysis, cadmium further increased basal glycolytic rate. Both glycolytic capacity and reserve were also increased following cadmium administration, endowing the cells with a higher compensatory glycolysis when oxidative phosphorylation was inhibited. Cadmium administration also led to an increase in glycolytic ATP production rate, paralleled by a decrease in ATP production by oxidative phosphorylation, due to an impairment of mitochondrial respiration. Moreover, following cadmium administration, mitochondria increased their dependency on glutamine, while decreasing lipids oxidation. On the whole, our data show that cadmium exacerbates the Warburg effect and promotes the use of glutamine as a substrate for lipid biosynthesis. Although increased glutamine consumption leads to an increase in glutathione level, this cannot efficiently counteract cadmium-induced oxidative stress, leading to membrane lipid peroxidation. Oxidative stress represents a serious threat for neuronal cells and our data confirm glutathione as a key defense mechanism.

Bio-indicators in cadmium toxicity: Role of HSP27 and HSP70

Heat shock proteins (HSPs) are a family of proteins that are expressed by cells in reply to stressors. The changes in concentration of HSPs could be utilized as a bio-indicator of oxidative stress caused by heavy metal. Exposure to the different heavy metals may induce or reduce the expression of different HSPs. The exposure to cadmium ion (Cd²⁺) could increase HSP70 and HSP27 over 2- to 10-fold or even more. The in vitro and in vivo models indicate that the HSP70 family is more sensitive to Cd intoxication than other HSPs. The analyses of other HSPs along with HSP70, especially HSP27, could also be useful to obtain more accurate results. In this regard, this review focuses on examining the literature to bold the futuristic uses of HSPs as bio-indicators in the initial assessment of Cd exposure risks in defined environments.