A short treatment of cells with the lanthanide ions La3+, Ce3+, Pr3+ or Nd3+ changes the cellular chemistry into a state in which RNA replication of flaviviruses is specifically blocked without interference with host-cell multiplication

Life-On-Hold: Lanthanoids Rapidly Induce a Reversible Ametabolic State in Mammalian Cells

Simple Summary

We found that incubation with a solution containing ~50 mM neodymium (one of the rare-earth elements, REE) induces a rapid of active metabolism in mammalian cells. We have named this state REEbernation and found that the process involves a rapid replacement of calcium with neodymium in membranes and organelles of a cell, allowing it to maintain its shape and membrane integrity under extreme conditions, including vacuum. Furthermore, phosphate exchange is blocked because of non-dissolvable neodymium salts formation, which “discharged” the cell. We also showed that REEbernation is characterized by instant shutting down RNA transcriptional activity in the cells, providing an intriguing opportunity to study a snapshot of gene expression at a given time point. Finally, we found that the REEbernation state is reversible, and we could restore the metabolism and proliferation capacity of the cells. The REEbernation provides a new method to reversibly place a cell into “on-hold” mode, opening opportunities to develop protocols for biological samples fixation with a minimum effect on the omics profile for biomedical needs.

Abstract

Until now, the ability to reversibly halt cellular processes has been limited to cryopreservation and several forms of anabiosis observed in living organisms. In this paper we show that incubation of living cells with a solution containing ~50 mM neodymium induces a rapid shutdown of intracellular organelle movement and all other evidence of active metabolism. We have named this state REEbernation (derived from the terms REE (rare earth elements) and hibernation) and found that the process involves a rapid replacement of calcium with neodymium in membranes and organelles of a cell, allowing it to maintain its shape and membrane integrity under extreme conditions, such as low pressure. Furthermore, phosphate exchange is blocked as a result of non-dissolvable neodymium salts formation, which “discharged” the cell. We further showed that REEbernation is characterized by an immediate cessation of transcriptional activity in observed cells, providing an intriguing opportunity to study a snapshot of gene expression at a given time point. Finally, we found that the REEbernation state is reversible, and we could restore the metabolism and proliferation capacity of the cells. The REEbernation, in addition to being an attractive model to further investigate the basic mechanisms of cell metabolism control, also provides a new method to reversibly place a cell into “on-hold” mode, opening opportunities to develop protocols for biological samples fixation with a minimum effect on the omics profile for biomedical needs.

What is holding back the development of antiviral metallodrugs? A literature overview and implications for SARS-CoV-2 therapeutics and future viral outbreaks

In light of the Covid-19 outbreak, this review brings together historical and current literature efforts towards the development of antiviral metallodrugs. Classical compounds such as CTC-96 and auranofin are discussed in depth, as pillars for future metallodrug development. From the recent literature, both cell-based results and biophysical assays against potential viral biomolecule targets are summarized here. The comprehension of the biomolecular targets and their interactions with coordination compounds are emphasized as fundamental strategies that will foment further development of metal-based antivirals. We also discuss other possible and unexplored methods for unveiling metallodrug interactions with biomolecules related to viral replication and highlight the specific challenges involved in the development of antiviral metallodrugs.

Effects of cerium and tungsten substitution on antiviral and antibacterial properties of lanthanum molybdate

Powders of cerium (Ce)-substituted and tungsten (W)-substituted La₂Mo₂O₉ (LMO) were prepared using polymerizable complex method. Their antiviral and antibacterial performances were then evaluated using bacteriophage Qβ, bacteriophage Φ6, Escherichia coli, and Staphylococcus aureus. The obtained powders, which were almost single-phase, exhibited both antiviral and antibacterial properties. Effects of dissolved ions on their antiviral activity against bacteriophage Qβ were remarkable. A certain contribution of direct contact to the powder surface was also inferred along with the dissolved ion effect for antiviral activity against bacteriophage Φ6. Dissolved ion effects and pH values suggest that both Mo and W are in the form of polyacids. Antiviral activity against bacteriophage Φ6 was improved by substituting Ce for La in LMO. Similarly to LMO, Ce-substituted LMO exhibited hydrophobicity. Inactivation of alkaline phosphatase enzyme proteins was inferred as one mechanism of the antiviral and antibacterial activities of the obtained powders.

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Ce and W were partially substituted in La₂Mo₂O₉ (LMO).

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These powders inactivated E. coli, S. aureus, bacteriophage Qβ, and bacteriophage Φ6.

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Inactivation of alkaline phosphatase enzyme proteins on these materials was confirmed.

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Antiviral activity against bacteriophage Φ6 of LMO was improved by substituting Ce.

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Hydrophobicity and UV shielding performance were also confirmed for this material.

Development of Functional Bionanocomposites Using Cyanobacterial Polysaccharides

Cyanobacteria are regarded as very eco-friendly microreactors for the production of various biomolecules such as polysaccharides by fixing not only carbon but also nitrogen in water. Cyanobacterial polysaccharides having various functional groups such as hydroxyls, carboxyls, sulfates, etc. have the ability to interact with metals or inorganics, to create bionanocomposites. Sacran, a supergiant cyanobacterial anionic polysaccharide extracted from the extracellular matrix of Aphanothece sacrum which is mass-cultivated in freshwater, is mainly used to create functional bionanocomposites. Gel-type bionanocomposites of sacran with various metal cations are formed and showed photoresponsive functions. Metal recovery is performed from the sacran bionanocomposite gels. Sacran chains are complexed with multi-wall carbon nanotubes (MWCNT) to give viscose dispersion from which MWCNT bionanocomposites can be collected by electrophoresis. The MWCNT/sacran dispersion retains the capability of adsorbing various metal ions to form hardened hydrogel beads. Finally, natural inorganic sepiolite can be used for sacran bionanocomposites which show an efficient neodymium ion adsorption ability. Thus, cyanobacterial polysaccharides are useful for preparing eco-friendly and functional bionanocomposites with various hard materials.

Photoshrinkage in polysaccharide gels with trivalent metal ions

The giant anionic polysaccharide "sacran", which is composed of 6-deoxyhexoses, pentoses, uronic acids as well as hexoses, showed hydrophobization and insolubilization phenomena in response to ultraviolet light irradiation. The sacran solution became turbid, and microparticles were formed by photoirradiation. To visualize the results of this photoreaction, anionic polysaccharide gels cross-linked by metal cations were used. As a result, we observed that sacran-gels with trivalent metal ions gradually contracted depending on the photoirradiation energy. In contrast, alginate gels used as a comparison degraded instead of contracting. This photoshrinkage of the sacran gels may be attributed to the hydrophobization of uronic acid based on photodecarboxylation. We propose that sacran-metal ion gels can function as effective, photoresponsive gels.

Proteomic analysis of lanthanum citrate-induced apoptosis in human cervical carcinoma SiHa cells

Lanthanides possess diverse biological effect and have been shown to promote cell proliferation and induce apoptosis. Our previous studies showing that lanthanide citrate complex has significant antitumor activity in human cervical cancer HeLa cells. This study aims at determining if [LaCit(2)](3-) have the activity against another type of human cervical cancer cell line SiHa and the changes in protein expression that contribute to the mechanism(s) of [LaCit(2)](3-)-mediated apoptosis in SiHa cells. Cell growth inhibition was measured by MTT method, and apoptosis was detected by means of Hoechst 33258 staining and flow cytometry analysis. After [LaCit(2)](3-)-treatment the results show that the growth of SiHa cells was inhibited, the cells displayed typical apoptosis morphological changes, and increase in the rates of apoptosis. Using proteomics approaches, a variety of differentially expressed proteins were identified in SiHa cells before and after treatment with [LaCit(2)](3-). There were profound changes in 10 proteins relating to mitochondrial function and oxidative stress, suggesting that mitochondrial dysfunction plays a key role in [LaCit(2)](3-)-induced apoptosis. This was confirmed by a decrease in the mitochondrial transmembrane potential (Δψ(m)), and increases in H(2)O(2) generation in [LaCit(2)](3-)-treated cells. Among them the alerted proteins, Prx I, ANXA1 and TRAF5 were validated by western blotting analyses. These results suggest that there is an intrinsic molecular pathway of cell apoptosis in [LaCit(2)](3-)-treated SiHa cells. This observation is in accordance with our previous reports about the effects of [LaCit(2)](3-) and [YbCit(2)](3-) on HeLa cells and it provide a molecular mechanism underlying lanthanide citrate complex-mediated cell apoptosis.