Julija Erhardt

Modulation of recombinant GABA(A) receptors by neurosteroid dehydroepiandrosterone sulfate.

Aim: To investigate whether long-term exposure to the neurosteroid dehydroepiandrosterone sulfate (DHEAS) induces adaptive changes of GABA_A receptors related to the development of tolerance and dependence. Methods: We compared the parameters of [³H]DHEAS binding and the effects of DHEAS on [³H]flunitrazepam binding in the membranes of HEK 293 cells, nontransfected or stably transfected with recombinant α₁β₂γ_2S GABA_A receptors. In HEK 293 cells expressing α₁β₂γ_2S GABA_A receptors, we investigated the effects of long-term DHEAS treatment on the [³H]flunitrazepam and [³H]t-butylbicycloorthobenzoate ([³H]TBOB) binding and on their modulation with GABA. Results: DHEAS behaves as an allosteric antagonist of the recombinant α₁β₂γ_2S GABA_A receptors expressed in HEK 293 cells. Exposure of cells to 100 µmol/l DHEAS for 48 h did not change the number or affinity of benzodiazepine and convulsive binding sites. Long-term DHEAS treatment failed to affect functional allosteric interactions between GABA_A receptor binding sites, as evidenced by an unchanged ability of GABA to stimulate or to inhibit [³H]flunitrazepam and [³H]TBOB binding, respectively. Conclusion: The findings that prolonged DHEAS treatment does not produce changes in GABA_A receptor expression and functional coupling, assumed to underlie the development of tolerance and dependence, might have importance in the long-term therapy necessary for the observed beneficial effects of DHEAS.

Effects of acute and chronic administration of neurosteroid dehydroepiandrosterone sulfate on neuronal excitability in mice

Background Neurosteroid dehydroepiandrosterone sulfate (DHEAS) has been associated with important brain functions, including neuronal survival, memory, and behavior, showing therapeutic potential in various neuropsychiatric and cognitive disorders. However, the antagonistic effects of DHEAS on γ-amino-butyric acidA receptors and its facilitatory action on glutamatergic neurotransmission might lead to enhanced brain excitability and seizures and thus limit DHEAS therapeutic applications. The aim of this study was to investigate possible age and sex differences in the neuronal excitability of the mice following acute and chronic DHEAS administration. Methods DHEAS was administered intraperitoneally in male and female adult and old mice either acutely or repeatedly once daily for 4 weeks in a 10 mg/kg dose. To investigate the potential proconvulsant properties of DHEAS, we studied the effects of acute and chronic DHEAS treatment on picrotoxin-, pentylentetrazole-, and N-methyl-D-aspartate-induced seizures in mice. The effects of acute and chronic DHEAS administration on the locomotor activity, motor coordination, and body weight of the mice were also studied. We also investigated the effects of DHEAS treatment on [3H]flunitrazepam binding to the mouse brain membranes. Results DHEAS did not modify the locomotor activity, motor coordination, body weight, and brain [3H]flunitrazepam binding of male and female mice. The results failed to demonstrate significant effects of single- and long-term DHEAS treatment on the convulsive susceptibility in both adult and aged mice of both sexes. However, small but significant changes regarding sex differences in the susceptibility to seizures were observed following DHEAS administration to mice. Conclusion Although our findings suggest that DHEAS treatment might be safe for various potential therapeutic applications in adult as well as in old age, they also support subtle interaction of DHEAS with male and female hormonal status, which may underline observed sex differences in the relationship between DHEAS and various health outcomes.

MIgGGly (mouse IgG glycosylation analysis) - a high-throughput method for studying Fc-linked IgG N-glycosylation in mice with nanoUPLC-ESI-MS

Immunoglobulin G (IgG) N-glycosylation is crucial for its effector functions. It is a complex trait, and large sample sets are needed to discover multiple genetic factors that underlie it. While in humans such high-throughput studies of IgG N-glycans became usual, only one has been carried out in mice. Here we describe and validate a method for the relative quantification of IgG Fc-linked N-glycans in a subclass-specific manner using nano-reverse phase liquid chromatography coupled with mass-spectrometry (nanoRP-LC-MS) applied to murine IgG. High-throughput data processing is ensured by the LaCyTools software. We have shown that IgG isolation procedure is the main source of technical variation in the current protocol. The major glycoforms were quantified reliably with coefficients of variation below 6% for all the analytes with relative abundances above 5%. We have applied our method to a sample set of 3 inbred strains: BALB/c, C57BL/6 and C3H and observed differences in subclass-specific and strain-specific N-glycosylation of IgG, suggesting a significant genetic component in the regulation of Fc-linked IgG N-glycosylation.

New tools for neuroenhancement - what about neuroethics?

In addition to the widely adopted and widespread pharmacological treatments for neuroenhancement, in the last decade there have emerged several nonpharmacological treatments. These methods treat the brain with a magnetic field or an electrical current and induce neuromodulatory and/or neurostimulatory effects.In addition to safety, several other ethical issues include issues of implicit and explicit coercion, value systems, fairness and hard work, possible changes in users’ identity and personality.The real question is not whether we can stop the use of these devices, but whether they are taking us in an unexpected direction with unanticipated consequences.