Sandra Alonso-Gil

Glycogen synthase kinase 3 inhibition promotes adult hippocampal neurogenesis in vitro and in vivo

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase originally identified as a regulator of glycogen metabolism but it also plays a pivotal role in numerous cellular functions, including differentiation, cell cycle regulation, and proliferation. The dentate gyrus of the hippocampus, together with the subventricular zone of the lateral ventricles, is one of the regions in which neurogenesis takes place in the adult brain. Here, using a chemical genetic approach that involves the use of several diverse inhibitors of GSK-3 as pharmacological tools, we show that inhibition of GSK-3 induces proliferation, migration, and differentiation of neural stem cells toward a neuronal phenotype in in vitro studies. Also, we demonstrate that inhibition of GSK-3 with the small molecule NP03112, called tideglusib, induces neurogenesis in the dentate gyrus of the hippocampus of adult rats. Taken together, our results suggest that GSK-3 should be considered as a new target molecule for modulating the production and integration of new neurons in the hippocampus as a treatment for neurodegenerative diseases or brain injury and, consequently, its inhibitors may represent new potential therapeutic drugs in neuroregenerative medicine.

Phosphodiesterase 7 Inhibition Preserves Dopaminergic Neurons in Cellular and Rodent Models of Parkinson Disease

BACKGROUND Phosphodiesterase 7 plays a major role in down-regulation of protein kinase A activity by hydrolyzing cAMP in many cell types. This cyclic nucleotide plays a key role in signal transduction in a wide variety of cellular responses. In the brain, cAMP has been implicated in learning, memory processes and other brain functions. METHODOLOGY/PRINCIPAL FINDINGS Here we show a novel function of phosphodiesterase 7 inhibition on nigrostriatal dopaminergic neuronal death. We found that S14, a heterocyclic small molecule inhibitor of phosphodiesterase 7, conferred significant neuronal protection against different insults both in the human dopaminergic cell line SH-SY5Y and in primary rat mesencephalic cultures. S14 treatment also reduced microglial activation, protected dopaminergic neurons and improved motor function in the lipopolysaccharide rat model of Parkinson disease. Finally, S14 neuroprotective effects were reversed by blocking the cAMP signaling pathways that operate through cAMP-dependent protein kinase A. CONCLUSIONS/SIGNIFICANCE Our findings demonstrate that phosphodiesterase 7 inhibition can protect dopaminergic neurons against different insults, and they provide support for the therapeutic potential of phosphodiesterase 7 inhibitors in the treatment of neurodegenerative disorders, particularly Parkinson disease.

New Melatonin–N,N-Dibenzyl(N-methyl)amine Hybrids: Potent Neurogenic Agents with Antioxidant, Cholinergic, and Neuroprotective Properties as Innovative Drugs for Alzheimer’s Disease

Here, we describe a new family of melatonin-N,N-dibenzyl(N-methyl)amine hybrids that show a balanced multifunctional profile covering neurogenic, antioxidant, cholinergic, and neuroprotective properties at low-micromolar concentrations. They promote maturation of neural stem cells into a neuronal phenotype and thus they could contribute to CNS repair. They also protect neural cells against mitochondrial oxidative stress, show antioxidant properties, and inhibit human acetylcholinesterase (AChE). Moreover, they displace propidium from the peripheral anionic site of AChE, preventing the β-amyloid aggregation promoted by AChE. In addition, they show low cell toxicity and can penetrate into the CNS. This multifunctional profile highlights these melatonin-N,N-dibenzyl(N-methyl)amine hybrids as useful prototypes in the research of innovative drugs for Alzheimers disease.

5-Imino-1,2,4-Thiadiazoles: First Small Molecules As Substrate Competitive Inhibitors of Glycogen Synthase Kinase 3

Cumulative evidence strongly supports that glycogen synthase kinase-3 (GSK-3) is a pathogenic molecule when it is up-dysregulated, emerging as an important therapeutic target in severe unmet human diseases. GSK-3 specific inhibitors might be promising effective drugs for the treatment of devastating pathologies such as neurodegenerative diseases, stroke, and mood disorders. As GSK-3 has the ability to phosphorylate primed substrates, small molecules able to bind to this site should be perfect drug candidates, able to partially block the activity of the enzyme over some specific substrates. Here, we report substituted 5-imino-1,2,4-thiadiazoles as the first small molecules able to inhibit GSK-3 in a substrate competitive manner. These compounds are cell permeable, able to decrease inflammatory activation and to selectively differentiate neural stem cells. Overall, 5-imino-1,2,4-thiadiazoles are presented here as new molecules able to decrease neuronal cell death and to increase endogenous neurogenesis blocking the GSK-3 substrate site.

Glycogen Synthase Kinase‑3 Inhibitors as Potent Therapeutic Agents for the Treatment of Parkinson Disease.

Parkinsons disease (PD) is a devastating neurodegenerative disorder characterized by degeneration of the nigrostriatal dopaminergic pathway. Because the current therapies only lead to temporary, limited improvement and have severe side effects, new approaches to treat PD need to be developed. To discover new targets for potential therapeutic intervention, a chemical genetic approach involving the use of small molecules as pharmacological tools has been implemented. First, a screening of an in-house chemical library on a well-established cellular model of PD was done followed by a detailed pharmacological analysis of the hits. Here, we report the results found for the small heterocyclic derivative called SC001, which after different enzymatic assays was revealed to be a new glycogen synthase kinase-3 (GSK-3) inhibitor with IC(50) = 3.38 ± 0.08 μM. To confirm that GSK-3 could be a good target for PD, the evaluation of a set of structurally diverse GSK-3 inhibitors as neuroprotective agents for PD was performed. Results show that inhibitors of GSK-3 have neuroprotective effects in vitro representing a new pharmacological option for the disease-modifying treatment of PD. Furthermore, we show that SC001 is able to cross the blood-brain barrier, protects dopaminergic neurons, and reduces microglia activation in in vivo models of Parkinson disease, being a good candidate for further drug development.

Effect of Phosphodiesterase 7 (PDE7) Inhibitors in Experimental Autoimmune Encephalomyelitis Mice. Discovery of a New Chemically Diverse Family of Compounds

Phosphodiesterase (PDE) 7 is involved in proinflammatory processes, being widely expressed both on lymphocytes and on certain brain regions. Specific inhibitors of PDE7 have been recently reported as potential new drugs for the treatment of neurological disorders because of their ability to increase intracellular levels of cAMP and thus to modulate the inflammatory process, as a neuroprotective well-established strategy. Multiple sclerosis is an unmet disease in which pathologies on the immune system, T-cells, and specific neural cells are involved simultaneously. Therefore, PDE7 inhibitors able to interfere with all these targets may represent an innovative therapy for this pathology. Here, we report a new chemically diverse family of heterocyclic PDE7 inhibitors, discovered and optimized by using molecular modeling studies, able to increase cAMP levels in cells, decrease inflammatory activation on primary neural cultures, and also attenuate the clinical symptoms in the experimental autoimmune encephalomyelitis (EAE) mouse model. These results led us to propose the use of PDE7 inhibitors as innovative therapeutic agents for the treatment of multiple sclerosis.

Novel N-Acetyl Bioisosteres of Melatonin: Melatonergic Receptor Pharmacology, Physicochemical Studies, and Phenotypic Assessment of Their Neurogenic Potential

Herein we present a new family of melatonin-based compounds, in which the acetamido group of melatonin has been bioisosterically replaced by a series of reversed amides and azoles, such as oxazole, 1,2,4-oxadiazole, and 1,3,4-oxadiazole, as well as other related five-membered heterocycles, namely, 1,3,4-oxadiazol(thio)ones, 1,3,4-triazol(thio)ones, and an 1,3,4-thiadiazole. New compounds were fully characterized at melatonin receptors (MT1R and MT2R), and results were rationalized by superimposition studies of their structures to the bioactive conformation of melatonin. We also found that several of these melatonin-based compounds promoted differentiation of rat neural stem cells to a neuronal phenotype in vitro, in some cases to a higher extent than melatonin. This unique profile constitutes the starting point for further pharmacological studies to assess the mechanistic pathways and the relevance of neurogenesis induced by melatonin-related structures.

Neurogenic Potential Assessment and Pharmacological Characterization of 6-Methoxy-1,2,3,4-tetrahydro-β-carboline (Pinoline) and Melatonin–Pinoline Hybrids

6-Methoxy-1,2,3,4-tetrahydro-β-carboline (pinoline) and N-acetyl-5-methoxytryptamine (melatonin) are both structurally related to 5-hydroxytryptamine (serotonin). Here we describe the design, synthesis, and characterization of a series of melatonin rigid analogues resulting from the hybridization of both pinoline and melatonin structures. The pharmacological evaluation of melatonin-pinoline hybrids comprises serotonergic and melatonergic receptors, metabolic enzymes (monoamine oxidases), antioxidant potential, the in vitro blood-brain barrier permeability, and neurogenic studies. Pinoline at trace concentrations and 2-acetyl-6-methoxy-1,2,3,4-tetrahydro-β-carboline (2) were able to stimulate early neurogenesis and neuronal maturation in an in vitro model of neural stem cells isolated from the adult rat subventricular zone. Such effects are presumably mediated via serotonergic and melatonergic stimulation, respectively.

Phosphodiesterase 7 Inhibition Induces Dopaminergic Neurogenesis in Hemiparkinsonian Rats

Parkinsons disease is characterized by a loss of dopaminergic neurons in a specific brain region, the ventral midbrain. Parkinsons disease is diagnosed when approximately 50% of the dopaminergic neurons of the substantia nigra pars compacta (SNpc) have degenerated and the others are already affected by the disease. Thus, it is conceivable that all therapeutic strategies, aimed at neuroprotection, start too late. Therefore, an urgent medical need exists to discover new pharmacological targets and novel drugs with disease‐modifying properties. In this regard, modulation of endogenous adult neurogenesis toward a dopaminergic phenotype might provide a new strategy to target Parkinsons disease by partially ameliorating the dopaminergic cell loss that occurs in this disorder. We have previously shown that a phosphodiesterase 7 (PDE7) inhibitor, S14, exerts potent neuroprotective and anti‐inflammatory effects in different rodent models of Parkinsons disease, indicating that this compound could represent a novel therapeutic agent to stop the dopaminergic cell loss that occurs during the progression of the disease. In this report we show that, in addition to its neuroprotective effect, the PDE7 inhibitor S14 is also able to induce endogenous neuroregenerative processes toward a dopaminergic phenotype. We describe a population of actively dividing cells that give rise to new neurons in the SNpc of hemiparkinsonian rats after treatment with S14. In conclusion, our data identify S14 as a novel regulator of dopaminergic neuron generation.

Microwave-assisted synthesis of hydroxyphenyl nitrones with protective action against oxidative stress.

Oxidative stress plays an important role in neuronal death in neurodegenerative disorders such as Parkinsons disease (PD). Hydroxyphenyl nitrones, derivatives of the nitrone spin trap alpha-phenyl-N-tert-butylnitrone (PBN), were synthesized and their antioxidant, anti-inflammatory and neuroprotective activity in neural cells evaluated. These hydroxyphenyl nitrones 5-7 were synthesized by reaction of the corresponding hydroxybenzaldehyde with N-tert-butyl hydroxylamine under microwave irradiation. They showed good peroxyl free radical scavenger capacities, analyzed by oxygen radical absorbance capacity (ORAC). Also inhibited peroxynitrite-mediated tyrosine nitration of alpha-synuclein in vitro and protected human neuroblastoma (SH-SY5Y) cells against SIN-1 and 6-OHDA toxicity when micromolar concentrations were used. Besides, the hydroxyphenyl nitrones evaluated showed anti-inflammatory activity modulating nitrite production in primary neural cell cultures of astrocytes and microglia treated with lipopolysaccharide (LPS), a potent inflammatory agent. These experimental data suggest a potential therapeutic use of these hydroxyphenyl nitrones against oxygen and nitrogen reactive species involved in neurodegenerative pathology.