Early endocannabinoid-mediated depolarization-induced suppression of excitation delays the appearance of the epileptic phenotype in synapsin II knockout mice.

The mechanism underlying the transition from the pre-symptomatic to the symptomatic state is a crucial aspect of epileptogenesis. SYN2 is a member of a multigene family of synaptic vesicle phosphoproteins playing a fundamental role in controlling neurotransmitter release. Human SYN2 gene mutations are associated with epilepsy and autism spectrum disorder. Mice knocked out for synapsin II (SynII KO) are prone to epileptic seizures that appear after 2 months of age. However, the involvement of the endocannabinoid system, known to regulate seizure development and propagation, in the modulation of the excitatory/inhibitory balance in the epileptic hippocampal network of SynII KO mice has not been explored. In this study, we investigated the impact of endocannabinoids on glutamatergic and GABAergic synapses at hippocampal dentate gyrus granule cells in young pre-symptomatic (1-2 months old) and adult symptomatic (5-8 months old) SynII KO mice. We observed an increase in endocannabinoid-mediated depolarization-induced suppression of excitation in young SynII KO mice, compared to age-matched wild-type controls. In contrast, the endocannabinoid-mediated depolarization-induced suppression of inhibition remained unchanged in SynII KO mice at both ages. This selective alteration of excitatory synaptic transmission was accompanied by changes in hippocampal endocannabinoid levels and cannabinoid receptor type 1 distribution among glutamatergic and GABAergic synaptic terminals contacting the granule cells of the dentate gyrus. Finally, inhibition of type-1 cannabinoid receptors in young pre-symptomatic SynII KO mice induced seizures during a tail suspension test. Our results suggest that endocannabinoids contribute to maintaining network stability in a genetic mouse model of human epilepsy.

Oxytocin Modifies the Excitability and the Action Potential Shape of the Hippocampal CA1 GABAergic Interneurons.

Oxytocin (OT) is a neuropeptide that modulates social-related behavior and cognition in the central nervous system of mammals. In the CA1 area of the hippocampus, the indirect effects of the OT on the pyramidal neurons and their role in information processing have been elucidated. However, limited data are available concerning the direct modulation exerted by OT on the CA1 interneurons (INs) expressing the oxytocin receptor (OTR). Here, we demonstrated that TGOT (Thr4,Gly7-oxytocin), a selective OTR agonist, affects not only the membrane potential and the firing frequency but also the neuronal excitability and the shape of the action potentials (APs) of these INs in mice. Furthermore, we constructed linear mixed-effects models (LMMs) to unravel the dependencies between the AP parameters and the firing frequency, also considering how TGOT can interact with them to strengthen or weaken these influences. Our analyses indicate that OT regulates the functionality of the CA1 GABAergic INs through different and independent mechanisms. Specifically, the increase in neuronal firing rate can be attributed to the depolarizing effect on the membrane potential and the related enhancement in cellular excitability by the peptide. In contrast, the significant changes in the AP shape are directly linked to oxytocinergic modulation. Importantly, these alterations in AP shape are not associated with the TGOT-induced increase in neuronal firing rate, being themselves critical for signal processing.

Prenyl Pterocarpans from Algerian Bituminaria bituminosa and Their Effects on Neuroblastoma.

The pterocarpan fraction from aerial parts of Bituminaria bituminosa was investigated for both chemical characterization and biological evaluation. Chemical studies were in accordance with the literature data on Bituminaria genus resulting in the identification of typical 4,8-prenyl pterocarpans. Three new members, bituminarins A-C (1-3), were isolated along with main bitucarpin A (4), erybraedin C (5) and erybraedin D (6) already reported from this plant. Further, biological studies evidenced antiproliferative properties of the most abundant pterocarpans 4 and 5 on neuroblastoma SH-SY5Y cell line, in agreement with previously described antiproliferative activity of these compounds against cancer cell lines other than neuroblastoma. The structure and the stereochemistry of the new molecules was determined by extensive spectroscopic analysis and chemical derivatization methods. The biological investigation was carried out by using an assay platform based on a live-cell imaging system revealing an apoptotic cell death induction.

The short-chain fatty acid acetate modulates orexin/hypocretin neurons: A novel mechanism in gut-brain axis regulation of energy homeostasis and feeding.

The short-chain fatty acids (SCFAs) acetate, propionate and butyrate, the major products of intestinal microbial fermentation of dietary fibres, are involved in fine-tuning brain functions via the gut-brain axis. However, the effects of SCFAs in the hypothalamic neuronal network regulating several autonomic-brain functions are still unknown. Using NMR spectroscopy, we detected a reduction in brain acetate concentrations in the hypothalamus of obese leptin knockout ob/ob mice compared to lean wild-type littermates. Therefore, we investigated the effect of acetate on orexin/hypocretin neurons (hereafter referred as OX or OX-A neurons), a subset of hypothalamic neurons regulating energy homeostasis, which we have characterized in previous studies to be over-activated by the lack of leptin and enhancement of endocannabinoid tone in the hypothalamus of ob/ob mice. We found that acetate reduces food-intake in concomitance with a reduction of orexin neuronal activity in ob/ob mice. This was demonstrated by evaluating food-intake behaviour and orexin-A/c-FOS immunoreactivity coupled with patch-clamp recordings in Hcrt-eGFP neurons, quantification of prepro-orexin mRNA, and immunolabeling of GPR-43, the main acetate receptor. Our data provide new insights into the mechanisms of the effects of chronic dietary supplementation with acetate, or complex carbohydrates, on energy intake and body weight, which may be partly mediated by inhibition of orexinergic neuron activity.

N-Adamantyl-1-alkyl-4-oxo-1,4-dihydroquinoline-3-carboxamide Derivatives as Fluorescent Probes to Detect Microglia Activation through the Imaging of Cannabinoid Receptor Subtype 2 (CB2R).

Cannabinoid receptor subtype 2 (CB2R) is emerging as a pivotal biomarker to identify the first steps of inflammation-based diseases such as cancer and neurodegeneration. There is an urgent need to find specific probes that may result in green and safe alternatives to the commonly used radiative technologies, to deepen the knowledge of the CB2R pathways impacting the onset of the above-mentioned pathologies. Therefore, based on one of the CB2R pharmacophores, we developed a class of fluorescent N-adamantyl-1-alkyl-4-oxo-1,4-dihydroquinoline-3-carboxamide derivatives spanning from the green to the near-infrared (NIR) regions of the light spectrum. Among the synthesized fluorescent ligands, the green-emitting compound 55 exhibited a favorable binding profile (strong CB2R affinity and high selectivity). Notably, this ligand demonstrated versatility as its use was validated in different experimental settings such as flow cytometry saturation, competitive fluorescence assays, and in vitro microglia cells mimicking inflammation states where CB2R are overexpressed.