Inhibition of cell proliferation does not slow down echinoderm neural regeneration

BACKGROUND: Regeneration of the damaged central nervous system is one of the most interesting post-embryonic developmental phenomena. Two distinct cellular events have been implicated in supplying regenerative neurogenesis with cellular material – generation of new cells through cell proliferation and recruitment of already existing cells through cell migration. The relative contribution and importance of these two mechanisms is often unknown. METHODS: Here, we use the regenerating radial nerve cord (RNC) of the echinoderm Holothuria glaberrima as a model of extensive post-traumatic neurogenesis in the deuterostome central nervous system. To uncouple the effects of cell proliferation from those of cell migration, we treated regenerating animals with aphidicolin, a specific inhibitor of S-phase DNA replication. To monitor the effect of aphidicolin on DNA synthesis, we used BrdU immunocytochemistry. The specific radial glial marker ERG1 was used to label the regenerating RNC. Cell migration was tracked with vital staining with the lipophilic dye DiI. RESULTS: Aphidicolin treatment resulted in a significant 2.1-fold decrease in cell proliferation. In spite of this, the regenerating RNC in the treated animals did not differ in histological architecture, size and cell number from its counterpart in the control vehicle-treated animals. DiI labeling showed extensive cell migration in the RNC. Some cells migrated from as far as 2 mm away from the injury plane to contribute to the neural outgrowth. CONCLUSIONS: We suggest that inhibition of cell division in the regenerating RNC of H. glaberrima is compensated for by recruitment of cells, which migrate into the RNC outgrowth from deeper regions of the neuroepithelium. Neural regeneration in echinoderms is thus a highly regulative developmental phenomenon, in which the size of the cell pool can be controlled either by cell proliferation or cell migration, and the latter can neutralize perturbations in the former. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12983-017-0196-y) contains supplementary material, which is available to authorized users

Synchronization modulation increases transepithelial potentials in MDCK monolayers through Na/K pumps

Peer reviewedPublisher PD

Relative effects of furosemide and ethacrynic acid on ion transport and energy metabolism in slices of rat kidney-cortex

The effects of furosemide and ethacrynic acid have been studied using slices of rat kidney cortex incubated in a Ringer medium. At concentrations from 0.2–2.0 mM, furosemide had no significant effect on the tissue ATP content or on the metabolism-dependent net movements of intracellular Na + , K + and Ca 2+ . It did, however, induce an increase in the net, outward movement of Cl − ; we suggest that this may have srisen from inhibition of a Cl − accumulating mechanism. In contrast, ethacrynic acid in the same concentration range caused marked reduction of cell respiration and ATP content and virtually total inhibitition of several processes of ion transport (Na + , Cl − and Ca 2+ loss, and K + uptake). Concentrations of furosemide greater than 5 mM caused marked inhibition of energy metabolism and transport of ions, and 10 mM furosemide had quantitatively similar effects to 2 mM ethacrynic acid. Electron micrographs of kidney-cortex slices treated with the diuretics at 2 mM show that the ultrastructure was well maintained in the presence of furosemide but that ethacrynic acid caused severe structural disorganisation and necrosis. The mitochondria were generally in the orthodox configuration in the presence of furosemide, but swollen in ethacrynic acid in accord with the marked effects of 2 mM ethacrynate on mitochondrial energy metabolism. Of the effects we have detected, that of low concentrations of furosemide on Cl − movement appears to be rather specific. Higher concentrations of this agent (5 mM and above), and all concentrations of ethacrynic acid studied (0.1–5.0 mM), have several inhibitory effects which seem to result from primary inhibition of mitochondrial activities and are presumably manifestations of toxicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46309/1/210_2004_Article_BF00506264.pd

Glia-to-neuron transfer of miRNAs via extracellular vesicles: a new mechanism underlying inflammation-induced synaptic alterations

Recent evidence indicates synaptic dysfunction as an early mechanism affected in neuroinflammatory diseases, such as multiple sclerosis, which are characterized by chronic microglia activation. However, the mode(s) of action of reactive microglia in causing synaptic defects are not fully understood. In this study, we show that inflammatory microglia produce extracellular vesicles (EVs) which are enriched in a set of miRNAs that regulate the expression of key synaptic proteins. Among them, miR-146a-5p, a microglia-specific miRNA not present in hippocampal neurons, controls the expression of presynaptic synaptotagmin1 (Syt1) and postsynaptic neuroligin1 (Nlg1), an adhesion protein which play a crucial role in dendritic spine formation and synaptic stability. Using a Renilla-based sensor, we provide formal proof that inflammatory EVs transfer their miR-146a-5p cargo to neuron. By western blot and immunofluorescence analysis we show that vesicular miR-146a-5p suppresses Syt1 and Nlg1 expression in receiving neurons. Microglia-to-neuron miR-146a-5p transfer and Syt1 and Nlg1 downregulation do not occur when EV\ue2\u80\u93neuron contact is inhibited by cloaking vesicular phosphatidylserine residues and when neurons are exposed to EVs either depleted of miR-146a-5p, produced by pro-regenerative microglia, or storing inactive miR-146a-5p, produced by cells transfected with an anti-miR-146a-5p. Morphological analysis reveals that prolonged exposure to inflammatory EVs leads to significant decrease in dendritic spine density in hippocampal neurons in vivo and in primary culture, which is rescued in vitro by transfection of a miR-insensitive Nlg1 form. Dendritic spine loss is accompanied by a decrease in the density and strength of excitatory synapses, as indicated by reduced mEPSC frequency and amplitude. These findings link inflammatory microglia and enhanced EV production to loss of excitatory synapses, uncovering a previously unrecognized role for microglia-enriched miRNAs, released in association to EVs, in silencing of key synaptic genes