Neurite outgrowth and differentiation of rat cortex progenitor cells are sensitive to lithium chloride at non-cytotoxic exposures

The binary combined toxicity of lithium, lead, and manganese on the proliferation of murine neural stem cells using two different models

As persistent environmental pollutants, more than thirty metals impose a potential global threat to the environment and humans, which has raised scientific concerns. Although the toxic effects of metals had been extensively studied, there is a paucity of information on their mixture toxicity. In this study, we examined the individual and binary combined toxicity of three common metals such as lithium (Li), lead (Pb), and manganese (Mn) on the proliferation of murine neural stem cells (mNSCs), respectively. Li, Pb, and Mn reduced cell proliferation at the concentration of 5.00 mM, 2.50 μM, and 5.00 μM, respectively (all p < 0.050), in a dose-dependent manner of each metal solely on mNSCs with the cytotoxicity rank as Pb > Mn > Li. Furthermore, the interactions of metal mixtures on mNSCs were determined by using response-additivity and dose-additivity models. Pb + Mn mixtures showed a more than additive effect (synergistic) of toxicity in both two methods. In the dose-additivity method, Pb + Li and Li + Mn mixtures exhibited synergistic effects in the compound with a high ratio of Li (25.0% Pb/75.0% Li, 75.0% Li/25.0% Mn), whereas they are antagonistic in the lower or equal ratio of Li (such as 75.0% Pb/25.0% Li, 25.0% Li/75.0% Mn). Besides, the interactions of Li + Mn mixtures showed some discrepancies between different endpoints. In conclusion, our study highlights the complexity of the mixtures' interaction patterns and the possible neuroprotective effect of Li under certain conditions. In the future, more research on different levels of metal mixtures, especially Li metal, is necessary to evaluate their underlying interactions and contribute to establishing risk assessment systems.

IFN-γ Enhances the Cough Reflex Sensitivity via Calcium Influx in Vagal Sensory Neurons

RATIONALE

Cough hypersensitivity syndrome is often triggered by a viral infection. The viral infection might trigger cough hypersensitivity via increasing the release of IFN-γ from T lymphocytes in the lung.

OBJECTIVES

To investigate effects of IFN-γ on the vagal sensory neurons and the cough reflex.

METHODS

Effects of IFN-γ on the cough reflex were investigated in guinea pigs. Cellular immunofluorescence imaging, calcium imaging, and patch clamp techniques were used to study effects of IFN-γ in primary cultured rat vagal sensory neurons.

MEASUREMENTS AND MAIN RESULTS

Intratracheal instillation of IFN-γ enhanced the cough response to citric acid in vivo. IFN-γ significantly increased levels of phosphorylated signal transducer and activator of transcription-1 but not phosphorylated transient receptor potential vanilloid 1 in vitro. Not only did IFN-γ enhance the response of neurons to capsaicin and electric stimulation, but also it directly induced Ca²⁺ influx, membrane depolarization, and action potentials in neurons via the Janus kinase, protein kinase A, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid pathways. However, IFN-γ did not elicit Ca²⁺ release from the endoplasmic reticulum via the phospholipase C pathway. Although IFN-γ-induced action potentials were suppressed by Ca²⁺ influx inhibitors, IFN-γ-induced Ca²⁺ influx was not altered by an inhibitor of rapid sodium channels.

CONCLUSIONS

The membrane potential in vagal sensory neurons may be depolarized by IFN-γ-induced Ca²⁺ influx. The depolarization of membrane potentials may enhance the cough reflex sensitivity and cause action potentials. IFN-γ may be a new target for treating cough hypersensitivity syndrome and postviral cough.

Gold Nanoparticle Quantitation by Whole Cell Tomography

Many proposed biomedical applications for engineered gold nanoparticles require their incorporation by mammalian cells in specific numbers and locations. Here, the number of gold nanoparticles inside of individual mammalian stem cells was characterized using fast focused ion beam-scanning electron microscopy based tomography. Enhanced optical microscopy was used to provide a multiscale map of the in vitro sample, which allows cells of interest to be identified within their local environment. Cells were then serially sectioned using a gallium ion beam and imaged using a scanning electron beam. To confirm the accuracy of single cross sections, nanoparticles in similar cross sections were imaged using transmission electron microscopy and scanning helium ion microscopy. Complete tomographic series were then used to count the nanoparticles inside of each cell and measure their spatial distribution. We investigated the influence of slice thickness on counting single particles and clusters as well as nanoparticle packing within clusters. For 60 nm citrate stabilized particles, the nanoparticle cluster packing volume is 2.15 ± 0.20 times the volume of the bare gold nanoparticles.

Citrate-stabilized gold nanoparticles as negative controls for measurements of neurite outgrowth

Gold nanoparticles (AuNPs) are promising candidates for medical diagnostics and therapeutics, due to their chemical stability, optical properties, and ease of functionalization. Citrate-stabilized reference materials also have potential as negative controls in toxicology studies of other nanoparticles. Here we examine the impact of 30 nm particles on the in vitro development of rat-cortex neural progenitor cells (NPCs), which mimic aspects of the developing neurological environment. AuNPs dispersed in a low serum culture medium initially agglomerated, but then remained stable during a three day incubation period, and agglomerated only slightly during a ten day incubation period, as determined by dynamic light scattering. Transmission electron microscopy indicated the presence of individual nanoparticles at all time points examined. Fixed cells were cross-sectioned by ion milling and imaged by scanning electronmicroscopy and helium-ion microscopy to evaluate particle incorporation. Individual nanoparticles could be resolved inside cross-sectioned cells. AuNPs were incubated with developing NPCs for ten days at concentrations of 0.5 μg/mL Au, 0.1 μg/mL Au, or 0.05 μg/mL Au. Adenosine triphosphate levels, as determined by bioluminescence measurements sensitive to low cell numbers, were not affected by AuNPs and the particles did not interfere with the assay. Multiple endpoints of neurite outgrowth were not altered by AuNPs, in particular, total neurite outgrowth per cell, a sensitive measure of neuronal development. Slide-level comparisons demonstrated the consistent response of NPCs to gold nanoparticles and a positive control chemical, neuroactive lithium. These results indicate that 30 nm citrate-stabilized AuNPs could serve as negative-control reference materials for in vitro measurements of neurite outgrowth.

DNA methylation and expression of KCNQ3 in bipolar disorder

OBJECTIVES

Accumulating evidence implicates the potassium voltage-gated channel, KQT-like subfamily, member 2 and 3 (KCNQ2 and KCNQ3) genes in the etiology of bipolar disorder (BPD). Reduced KCNQ2 or KCNQ3 gene expression might lead to a loss of inhibitory M-current and an increase in neuronal hyperexcitability in disease. The goal of the present study was to evaluate epigenetic and gene expression associations of the KCNQ2 and KCNQ3 genes with BPD.

METHODS

DNA methylation and gene expression levels of alternative transcripts of KCNQ2 and KCNQ3 capable of binding the ankyrin G (ANK3) gene were evaluated using bisulfite pyrosequencing and the quantitative real-time polymerase chain reaction in the postmortem prefrontal cortex of subjects with BPD and matched controls from the McLean Hospital. Replication analyses of DNA methylation findings were performed using prefrontal cortical DNA obtained from the Stanley Medical Research Institute.

RESULTS

Significantly lower expression was observed in KCNQ3, but not KCNQ2. DNA methylation analysis of CpGs within an alternative exonic region of KCNQ3 exon 11 demonstrated significantly lower methylation in BPD, and correlated significantly with KCNQ3 mRNA levels. Lower KCNQ3 exon 11 DNA methylation was observed in the Stanley Medical Research Institute replication cohort, although only after correcting for mood stabilizer status. Mood stabilizer treatment in rats resulted in a slight DNA methylation increase at the syntenic KCNQ3 exon 11 region, which subsequent analyses suggested could be the result of alterations in neuronal proportion.

CONCLUSION

The results of the present study suggest that epigenetic alterations in the KCNQ3 gene may be important in the etiopathogenesis of BPD and highlight the importance of controlling for medication and cellular composition-induced heterogeneity in psychiatric studies of the brain.

Plastic changes in the spinal cord in motor neuron disease

In the present paper, we analyze the cell number within lamina X at the end stage of disease in a G93A mouse model of ALS; the effects induced by lithium; the stem-cell like phenotype of lamina X cells during ALS; the differentiation of these cells towards either a glial or neuronal phenotype. In summary we found that G93A mouse model of ALS produces an increase in lamina X cells which is further augmented by lithium administration. In the absence of lithium these nestin positive stem-like cells preferentially differentiate into glia (GFAP positive), while in the presence of lithium these cells differentiate towards a neuron-like phenotype (βIII-tubulin, NeuN, and calbindin-D28K positive). These effects of lithium are observed concomitantly with attenuation in disease progression and are reminiscent of neurogenetic effects induced by lithium in the subependymal ventricular zone of the hippocampus.