Effects of Magnetite Nanoparticles and Static Magnetic Field on Neural Differentiation of Pluripotent Stem Cells.

Neurodevelopmental processes of pluripotent cells, such as proliferation and differentiation, are influenced by external natural forces. Despite the presence of biogenic magnetite nanoparticles in the central nervous system and constant exposure to the Earth's magnetic fields and other sources, there is scant knowledge regarding the role of electromagnetic stimuli in neurogenesis. Moreover, emerging applications of electrical and magnetic stimulation to treat neurological disorders emphasize the relevance of understanding the impact and mechanisms behind these stimuli. Here, the effects of magnetic nanoparticles (MNPs) in polymeric coatings and the static external magnetic field (EMF) were investigated on neural induction of murine embryonic stem cells (mESCs) and human induced pluripotent stem cells (hiPSCs). The results show that the presence of 0.5% MNPs in collagen-based coatings facilitates the migration and neuronal maturation of mESCs and hiPSCs in vitro. Furthermore, the application of 0.4 Tesla EMF perpendicularly to the cell culture plane, discernibly stimulates proliferation and guide fate decisions of the pluripotent stem cells, depending on the origin of stem cells and their developmental stage. Mechanistic analysis reveals that modulation of ionic homeostasis and the expression of proteins involved in cytostructural, liposomal and cell cycle checkpoint functions provide a principal underpinning for the impact of electromagnetic stimuli on neural lineage specification and proliferation. These findings not only explore the potential of the magnetic stimuli as neural differentiation and function modulator but also highlight the risks that immoderate magnetic stimulation may affect more susceptible neurons, such as dopaminergic neurons.

Biophysical Characterization of the Nucleoside Diphosphate Kinase of Leishmania major and Effect of the P95S Mutation.

Nucleoside diphosphate kinases (NDK; EC 2.7.4.6) are enzymes required for maintaining intracellular levels of nucleosides triphosphates (NTP) through transfer the γ-phosphoryl group from a NTP to a NDP. The enzyme is associated with several biological functions including prevention of host ATP-mediated cytolysis during pathogenic infections. Here we present the biophysical characterization of NDK from Leishmania major and the effect of a mutation on the protein structure in solution. The structural stability was analyzed since this secreted protein may act in different microenvironments at various stages of the parasite life cycle. LmNDK and P95S mutant were subjected to denaturation with pH and guanidine. Structural transitions were monitored by circular dichroism and intrinsic fluorescence tryptophan emission. Our results showed that the LmNDK is more structurally stable than other described NDKs and that the catalytically active P95S mutant in the Kpn loop presented a decrease in protein stability, indicating the importance of this proline for maintenance of the LmNDK structure.