Stereospecific Inhibition of Ethanol Potentiation on Glycine Receptor by M554 Stereoisomers.

Blocking the interaction between the Gßγ protein and the glycine receptor (GlyR) has emerged as a promising pharmacological strategy to treat acute alcohol intoxication by inhibiting ethanol potentiation on GlyR. M554 is a recently discovered small molecule capable of binding to Gßγ with potent in vitro and in vivo inhibitory activity. This compound has been tested as a mixture of diastereomers, and no information is available concerning the stereospecific activity of each species, which is critical to pursue efforts on lead optimization and drug development. In this work, we explored the differential activity of four M554 stereoisomers by in silico molecular dynamics simulations and electrophysiological experiments. Our results revealed that the (R,R)-M554 stereoisomer is a promising lead compound that inhibits ethanol potentiation of GlyR.

Prevention of Synaptic Alterations and Neurotoxic Effects of PAMAM Dendrimers by Surface Functionalization.

One of the most studied nanocarriers for drug delivery are polyamidoamine (PAMAM) dendrimers. However, the alterations produced by PAMAM dendrimers in neuronal function have not been thoroughly investigated, and important aspects such as effects on synaptic transmission remain unexplored. We focused on the neuronal activity disruption induced by dendrimers and the possibility to prevent these effects by surface chemical modifications. Therefore, we studied the effects of fourth generation PAMAM with unmodified positively charged surface (G4) in hippocampal neurons, and compared the results with dendrimers functionalized in 25% of their surface groups with folate (PFO25) and polyethylene glycol (PPEG25). G4 dendrimers significantly reduced cell viability at 1 µM, which was attenuated by both chemical modifications, PPEG25 being the less cytotoxic. Patch clamp recordings demonstrated that G4 induced a 7.5-fold increment in capacitive currents as a measure of membrane permeability. Moreover, treatment with this dendrimer increased intracellular Ca2+ by 8-fold with a complete disruption of transients pattern, having as consequence that G4 treatment increased the synaptic vesicle release and frequency of synaptic events by 2.4- and 3-fold, respectively. PFO25 and PPEG25 treatments did not alter membrane permeability, total Ca2+ intake, synaptic vesicle release or synaptic activity frequency. These results demonstrate that cationic G4 dendrimers have neurotoxic effects and induce alterations in normal synaptic activity, which are generated by the augmentation of membrane permeability and a subsequent intracellular Ca2+ increase. Interestingly, these toxic effects and synaptic alterations are prevented by the modification of 25% of PAMAM surface with either folate or polyethylene glycol.