GSK-3β-mediated regulation of cadmium-induced cell death and survival

The Effects of Seleno-Methionine in Cadmium-Challenged Human Primary Chondrocytes

Cadmium (Cd) is a potentially toxic element able to interfere with cellular functions and lead to disease or even death. Cd accumulation has been demonstrated in cartilage, where it can induce damage in joints. The aim of this study was to evaluate the effect of CdCl2 on primary cultures of human chondrocytes and the possible protective effect of seleno-methionine (Se-Met). Human primary articular chondrocytes were cultured and treated as follows: control groups, cells challenged with 7.5 μM and 10 μM CdCl2 alone, and cells pretreated with 10 and 20 μM Se-Met and then challenged with 7.5 μM and 10 μM CdCl2. Twenty-four hours after incubation, cell viability, histological evaluation with hematoxylin-eosin stain, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay were performed. Furthermore, reverse transcription-PCR was carried out to evaluate mRNA levels of BAX, BAK1, CASP-3, and CASP-9. After CdCl2 challenge at both doses, a reduced cell viability and an overexpression of BAX, BAK1, CASP-3, and CASP-9 genes, as well as a high number of TUNEL-positive cells, were demonstrated, all parameters becoming higher as the dose of CdCl2 was increased. The pretreatment with Se-Met lowered the expression of all considered genes, improved cell viability and morphological changes, and reduced the number of TUNEL-positive cells. It was concluded that Se-Met plays a protective role against CdCl2-induced structural and functional changes in chondrocytes in vitro, as it improved cell viability and showed a positive role in the context of the apoptotic pathways. It is therefore suggested that a translational, multifaceted approach, with plant-based diets, bioactive functional foods, nutraceuticals, micronutrients, and drugs, is possibly advisable in situations of environmental pollution caused by potentially toxic elements.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Activation of Pgk1 Results in Reduced Protein Aggregation in Diverse Neurodegenerative Conditions

The prevention of protein condensates has emerged as a new drug target to treat diverse neurodegenerative disorders. We previously reported that terazosin (TZ), a prescribed antagonist of the α1 adrenergic receptor, is an activator of phosphoglycerate kinase 1 (Pgk1) and Hsp90. In this study, we aimed to determine whether TZ prevents the formation of diverse pathological condensates in cell cultures and animal disease models. In primary neuron culture, TZ treatment reduced both the protein density and abundance of fused in sarcoma (FUS)-P525L-GFP, a disease-associated mutant form of FUS. Regarding the mechanism, we found that increased intracellular ATP levels were critical for the reduction in protein aggregate density. In addition, Hsp90 activation by TZ enhanced Hsp90 interaction with ULK1, a master regulator of autophagy. Through in vivo studies, we examined neuron-specific overexpression of tau in Drosophila, mouse models of APP/PS1 Alzheimer's disease (AD), and a rat model of multiple system atrophy (MSA) via the viral expression of α-synuclein in the striatum. TZ prevented and reversed the formation of pathological protein condensates. Together, our results suggest that activation of Pgk1 in cytosol may dissolve pathological protein aggregates via increased ATP levels and degrade these proteins via autophagy; the FUS-P525L degradation pathway in nucleus is unclear.

Potential of Quercetin to Protect Cadmium Induced Cognitive Deficits in Rats by Modulating NMDA-R Mediated Downstream Signaling and PI3K/AKT-Nrf2/ARE Signaling Pathways in Hippocampus

Exposure to cadmium, a heavy metal distributed in the environment is a cause of concern due to associated health effects in population around the world. Continuing with the leads demonstrating alterations in brain cholinergic signalling in cadmium induced cognitive deficits by us; the study is focussed to understand involvement of N-Methyl-D-aspartate receptor (NMDA-R) and its postsynaptic signalling and Nrf2-ARE pathways in hippocampus. Also, the protective potential of quercetin, a polyphenolic bioflavonoid, was assessed in cadmium induced alterations. Cadmium treatment (5 mg/kg, body weight, p.o., 28 days) decreased mRNA expression and protein levels of NMDA receptor subunits (NR1, NR2A) in rat hippocampus, compared to controls. Cadmium treated rats also exhibited decrease in levels of NMDA-R associated downstream signalling proteins (CaMKIIα, PSD-95, TrkB, BDNF, PI3K, AKT, Erk1/2, GSK3β, and CREB) and increase in levels of SynGap in hippocampus. Further, decrease in protein levels of Nrf2 and HO1 associated with increase in levels of Keap1 exhibits alterations in Nrf2/ARE signalling in hippocampus of cadmium treated rats. Degeneration of pyramidal neurons in hippocampus was also evident on cadmium treatment. Simultaneous treatment with quercetin (25 mg/kg body weight p.o., 28 days) was found to attenuate cadmium induced changes in hippocampus. The results provide novel evidence that cadmium exposure may disrupt integrity of NMDA receptors and its downstream signaling targets by affecting the Nrf2/ARE signaling pathway in hippocampus and these could contribute in cognitive deficits. It is further interesting that quercetin has the potential to protect cadmium induced changes by modulating Nrf2/ARE signaling which was effective to control NMDA-R and PI3K/AKT cell signaling pathways.

MicroRNA-429 inhibits neuroblastoma cell proliferation, migration and invasion via the NF-κB pathway

Background

MicroRNAs (miRNAs or miRs) can participate in the development and progression of neuroblastoma. Many studies have indicated that miR-429 can participate in tumor development. However, the mechanism underlying miR-429-mediated progression of neuroblastoma remains largely unclear.

Methods

Colony formation and apoptosis assays were used to determine the effect of miR-429 on cell proliferation. Its impact on cell migration was determined using the wound-healing and Transwell assays. The target gene of miR-429 was confirmed via western blotting and luciferase reporter assays. A nude mouse xenograft model with miR-429 overexpression was used to assess the effect on tumor growth.

Results

Our findings indicate that miR-429 is downregulated in neuroblastoma cell lines. We also found that it can induce apoptosis and inhibit proliferation in cells of those lines. MiR-429 can bind to the 3′-UTR of IKKβ mRNA and overexpression of IKKβ can reverse cell proliferation, blocking the effect of miR-429. Furthermore, miR-429 overexpression inhibited neuroblastoma growth in our nude mouse xenograft model.

Conclusion

We provide important insight into miR-429 as a tumor suppressor through interaction with IKKβ, which is a catalytic subunit of the IKK complex that activates NF-κB nuclear transport. Our results demonstrate that miR-429 may be a new target for the treatment of neuroblastoma.

Cadmium exposure alters steroid receptors and proinflammatory cytokine levels in endothelial cells in vitro: a potential mechanism of endocrine disruptor atherogenic effect

BACKGROUND

Cadmium (Cd) is a widespread environmental pollutant that causes alterations in human health acting as endocrine disruptor. Recent data suggest that cardiovascular system might be a contamination target tissue, since Cd is found in atheromatic plaques. Thus, the purpose of this study was to evaluate the consequence of Cd exposure of endothelial cells in vitro to evaluate detrimental effect in vascular system by a potential sex-steroid hormone receptor-dependent mechanism(s).

METHODS

To this aim, Human Umbilical Vein Endothelial Cells (HUVECs) were cultured and exposed to several concentrations of cadmium chloride (CdCl₂) for different interval times.

RESULTS

CdCl₂ exposure of HUVECs induced a significant increase of ERβ and Cyp19a1 at both mRNA and protein levels, while a drastic dose-dependent decrease of AR expression level was observed after 24 h of exposure. On the contrary, an increase of PhAR^ser308 as well as a reduction of PhGSK-3β^ser9 and PhAKT^ser473 was detected after 1 h treatment. This effect was consistently reduced by GSK inhibition. Furthermore, CdCl₂ abolished DHT-induced cell proliferation in HUVECs suggesting an antagonist-like effect of Cd on AR-mediated signaling. Remarkable, after 6 h CdCl₂-treatment, a relevant increase in TNF-α, IL-6 and IL-8 mRNA was observed and this effect was blocked by the presence of an ERβ-selective antagonist. Moreover, Cd-induced TxR1 overexpression, likely, correlated with the activation of p38 MAPK/NF-κB pathway.

CONCLUSION

In conclusion, our study demonstrates for the first time that Cd alters sex-steroid hormone receptors level and activity likely affecting intracellular signaling linked to a proinflammatory state in endothelial cells. This alteration might possibly lead to endothelial cell injury and vascular dysfunction and could be a mechanism of gender-specific atherogenic damages induced by endocrine disruptors and, thus, induce atherogenic events with increased risk of cardiovascular diseases in individuals exposed to this endocrine disruptor.