Alzheimer's disease, Kuf's disease, tellurium and selenium

Associations between multiple urinary metals and metabolic syndrome: Exploring the mediating role of liver function in Chinese community-dwelling elderly

BACKGROUND

Multiple metals exposure has been revealed to be related to metabolic syndrome (MetS). However, the associations and interactions between multiple metals exposure and MetS are remains controversial, and the potential mechanism of the above-mentioned is still unclear.

METHODS

The associations between urinary metals and the MetS were analyzed by multivariable logistic regression model and restricted cubic spline (RCS). Bayesian kernel machine regression (BKMR) model and quantile-based g-computation (qgcomp) were applied to explore the mixed exposure and interaction effect of metals. Mediation analysis was used to explore the role of liver function.

RESULTS

In the single metal model, multiple metals were significantly associated with MetS. RCS analysis further verified the associations between 8 metals and MetS. BKMR model and qgcomp showed that zinc (Zn), iron (Fe), and tellurium (Te) were the main factors affecting the overall effect. In addition, mediation analysis indicated that serum alanine aminotransferase (ALT) mediated 21.54% and 13.29% in the associations of vanadium (V) and Zn with the risk of MetS, respectively.

CONCLUSIONS

Elevated urinary concentration of Zn, V, Te, copper (Cu), molybdenum (Mo), and thallium (Tl) were related to the increased risk of MetS. Conversely, Fe and selenium (Se) may be protective factors for MetS in mixed exposure. Liver function may play a key role in the association of V and Zn exposure with MetS.

Mitochondrial Neurodegenerative Diseases: Three Mitochondrial Ribosomal Proteins as Intermediate Stage in the Pathway That Associates Damaged Genes with Alzheimer's and Parkinson's

Currently, numerous research endeavors are dedicated to unraveling the intricate nature of neurodegenerative diseases. These conditions are characterized by the gradual and progressive impairment of specific neuronal systems that exhibit anatomical or physiological connections. In particular, in the last twenty years, remarkable efforts have been made to elucidate neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. However, despite extensive research endeavors, no cure or effective treatment has been discovered thus far. With the emergence of studies shedding light on the contribution of mitochondria to the onset and advancement of mitochondrial neurodegenerative disorders, researchers are now directing their investigations toward the development of therapies. These therapies include molecules designed to protect mitochondria and neurons from the detrimental effects of aging, as well as mutant proteins. Our objective is to discuss and evaluate the recent discovery of three mitochondrial ribosomal proteins linked to Alzheimer's and Parkinson's diseases. These proteins represent an intermediate stage in the pathway connecting damaged genes to the two mitochondrial neurological pathologies. This discovery potentially could open new avenues for the production of medicinal substances with curative potential for the treatment of these diseases.

Mitochondrial ribosomal protein genes connected with Alzheimer's and tellurite toxicity

Mitochondrial diseases are a group of genetic disorders characterized by dysfunctional mitochondria. Within eukaryotic cells, mitochondria contain their own ribosomes, which synthesize small amounts of proteins, all of which are essential for the biogenesis of the oxidative phosphorylation system. The ribosome is an evolutionarily conserved macromolecular machine in nature both from a structural and functional point of view, universally responsible for the synthesis of proteins. Among the diseases afflicting humans, those of ribosomal origin - either cytoplasmic ribosomes (80S) or mitochondrial ribosomes (70S) - are relevant. These are inherited or acquired diseases most commonly caused by either ribosomal protein haploinsufficiency or defects in ribosome biogenesis. Here we review the scientific literature about the recent advances on changes in mitochondrial ribosomal structural and assembly proteins that are implicated in primary mitochondrial diseases and neurodegenerative disorders, and their possible connection with metalloid pollution and toxicity, with a focus on MRPL44, NAM9 (MNA6) and GEP3 (MTG3), whose lack or defect was associated with resistance to tellurite. Finally, we illustrate the suitability of yeast Saccharomyces cerevisiae (S.cerevisiae) and the nematode Caenorhabditis elegans (C.elegans) as model organisms for studying mitochondrial ribosome dysfunctions including those involved in human diseases.

Mitochondrial ribosomal proteins involved in tellurite resistance in yeast Saccharomyces cerevisiae

A considerable body of evidence links together mitochondrial dysfunctions, toxic action of metalloid oxyanions, and system and neurodegenerative disorders. In this study we have used the model yeast Saccharomyces cerevisiae to investigate the genetic determinants associated with tellurite resistance/sensitivity. Nitrosoguanidine-induced K₂TeO₃-resistant mutants were isolated, and one of these mutants, named Sc57-Te₅^R, was characterized. Both random spore analysis and tetrad analysis and growth of heterozygous (Te^S/Te₅^R) diploid from Sc57-Te₅^R mutant revealed that nuclear and recessive mutation(s) was responsible for the resistance. To get insight into the mechanisms responsible for K₂TeO₃-resistance, RNA microarray analyses were performed with K₂TeO₃-treated and untreated Sc57-Te₅^R cells. A total of 372 differentially expressed loci were identified corresponding to 6.37% of the S. cerevisiae transcriptome. Of these, 288 transcripts were up-regulated upon K₂TeO₃ treatment. About half of up-regulated transcripts were associated with the following molecular functions: oxidoreductase activity, structural constituent of cell wall, transporter activity. Comparative whole-genome sequencing allowed us to identify nucleotide variants distinguishing Sc57-Te₅^R from parental strain Sc57. We detected 15 CDS-inactivating mutations, and found that 3 of them affected genes coding mitochondrial ribosomal proteins (MRPL44 and NAM9) and mitochondrial ribosomal biogenesis (GEP3) pointing out to alteration of mitochondrial ribosome as main determinant of tellurite resistance.

Induction of S-Phase Arrest in Human Glioma Cells by Selenocysteine, a Natural Selenium-Containing Agent Via Triggering Reactive Oxygen Species-Mediated DNA Damage and Modulating MAPKs and AKT Pathways

Selenocysteine (SeC) a natural available selenoamino acid exhibits novel anticancer activities against human cancer cell lines. However, the growth inhibitory effect and mechanism of SeC in human glioma cells remain unclear. The present study reveals that SeC time- and dose-dependently inhibited U251 and U87 human glioma cells growth by induction of S-phase cell cycle arrest, followed by the marked decrease of cyclin A. SeC-induced S-phase arrest was achieved by inducing DNA damage through triggering generation of reactive oxygen species (ROS) and superoxide anion, with concomitant increase of TUNEL-positive cells and induction of p21waf1/Cip1 and p53. SeC treatment also caused the activation of p38MAPK, JNK and ERK, and inactivation of AKT. Four inhibitors of MAPKs and AKT pathways further confirmed their roles in SeC-induced S-phase arrest in human glioma cells. Our findings advance the understanding on the molecular mechanisms of SeC in human glioma management.

Evaluation of tellurium toxicity in transformed and non-transformed human colon cells

Diphenyl ditelluride (DPDT) and tellurium tetrachloride (TeCl(4)) were evaluated for toxicity in transformed (HT-29, Caco-2) and non-transformed colon cells (CCD-18Co). Significant decreases in viability were observed with DPDT exposure in HT-29 (62.5-1000 μM), Caco-2 (31.25-1000 μM) and CCD-18Co cells (500-1000 μM) and with TeCl(4) in HT-29 (31.25-1000 μM), Caco-2 (31.25-1000 μM) and CCD-18Co cells (500-1000 μM). Light microscopy confirmed viability analysis. Significant increases in caspase 3/7 and 9 activity were observed with DPDT in HT-29 (500-1000 μM) and CCD-18Co cells (1000 μM) indicating apoptosis. No significant increases in caspases were seen with TeCl(4) indicating necrosis. Apoptosis or necrosis was confirmed with fluorescent staining (FITC-Annexin, Hoechst 33342 and Ethidium Homodimer). Significant decreases in GSH/GSSG ratio were observed with DPDT in HT-29 (62.5-1000 μM), and CCD-18Co cells (1000 μM) and with TeCl(4) in HT-29 (62.5-1000 μM) and CCD-18Co cells (250-1000 μM). We concluded that cells treated with DPDT resulted in apoptosis and TeCl(4) treatment in necrosis. GSH/GSSG ratio shifts indicate oxidative mechanisms are involved.

Tellurium-induced cognitive deficits in rats are related to neuropathological changes in the central nervous system

The effects of sodium tellurite 0.1 and 0.4 mg/kg were assessed in the Morris water maze. Two days after treatment rats were tested for acquisition (posttreatment days 3-6) and on seventh day on a spatial retention task. Tellurium treatment was found to cause significant impairment in retention of the spatial learning task. Locomotor disturbances were not the cause of the observed effects. Ultrastructural observations showed neuropathological changes in hippocampus subfields and prefrontal cortex with swelling of synapses, astrocytes and astrocytic processes around the vessels in the cerebral cortex neuropil. Severity of the observed changes in glial-neuronal unit was in correlation with the extent of learning impairment. A direct injury of Schwann cells with the secondary myoclasis was noted in the sciatic nerve. Our results indicate that acute treatment with sodium tellurite results in impairment of learning and spatial memory.

Scavenger receptor class B type I expression and elemental analysis in cerebellum and parietal cortex regions of the Alzheimer's disease brain

Metal ions play an important role in health and disease by influencing cellular biochemical pathways. The increased concentrations of some metal ions may have cytotoxic effects through their ability to oxidatively modify biomolecules, which may cause oxidative stress-induced brain cell death leading to neurodegenerative disorders observed in Alzheimer's disease (AD). We therefore performed elemental analysis of human brain tissues by a sophisticated method of inductively coupled plasma mass spectrometry (ICP-MS) in two regions of the AD brain, the parietal cortex and cerebellum, and compared them with the age-matched control. Our analysis shows the differential distribution of some metal ions in the two regions of the brain. Most importantly, Si, Sn, Al and Mn showed significantly higher levels in the parietal cortex of the AD brain compared to the control. The other metal ions showing moderate increases in the parietal cortex were Na, Te, Cr, Fe and B. Since these metal ions can modify lipoproteins in the brain and modified lipoproteins are taken up by scavenger receptors class B type I (SR-BI), we also determined the presence of SR-BI in the parietal cortex and cerebellum regions of the control and AD brains using a sensitive method, the reverse transcriptase-polymerase chain reaction. Our results suggest that SR-BI are present in the parietal cortex as well as in the cerebellum of the control and AD brains, suggesting that the presence of SR-BI may be involved in the uptake of oxidatively modified lipoproteins and beta-amyloid (Abeta) protein complexed with apoE, suggesting implications in the progression of late onset AD and other neurodegenerative disorders characterized by the deposition of insoluble aggregates observed in the AD brain.

Essentiality of selenium in the human body: relationship with different diseases

In the present review different aspects related to the essential element selenium in the human organism are considered. A large number of human studies have been performed in order to improve knowledge on the influence of this element in the origin and development of several degenerative diseases. Selenium deficiencies among human beings as well as animals are being recognized worldwide to be related to a number of pathologies. This element has also the special characteristic that the range between its essential and toxic character is very close, and consequently daily dietary intake should be appropriately monitored in individuals. Nevertheless, nowadays there is still a lot of controversy about the optimum dietary level of this element in order to cure or to prevent the appearance of diseases such as cirrhosis, cancer, diabetes, or cardiovascular pathologies. Results obtained in several animal and epidemiological studies have indicated that Se could constitute a dietary factor with protective action against several degenerative diseases.