Parkinson’s disease (PD) is a degressive, neurodegenerative disease that affects approximately four million people worldwide. The disease is characterized by the progressive loss of midbrain dopaminergic (DAergic) neurons, which are highly related with the motor control. As the disease progresses, movement disorders appear such as tremor, rigidity, and bradykinesia, but also disorders in speech and neuropsychiatric disturbances occur.Current therapies for PD focus on symptomatic treatment, while pharmacological methods to prevent or delay the degeneration of neurons have not been discovered yet. The Nurr1 nuclear receptor, which is expressed predominantly in the substantia nigra of the midbrain, has emerged as a target for the treatment of Parkinson’s disease due to its neuroprotective action and contribution in DAergic neuron development. It has been shown that partial loss of Nurr1 function in people due to mutations leads to neuronal death. Thus, the reinforcement of Nurr1 operation via the discovery of novel potent agonists is imperative. Unfortunately, the accomplishment of this task is complicated as Nurr1 ligand binding domain (LBD) lacks a cavity for ligand binding due to the tight packing chains from several hydrophobic amino-acids in the region normally occupied by ligands in other nuclear receptors. However, the activation of Nurr1 can be feasible through heterodimer formation with Retinoid X Receptors (RXR) and especially with RXRα, which are all capable of binding ligands and therefore, mediate Nurr1 expression in midbrain. Therefore, we seek here to identify potent binders of RXRα as a means to increase Nurr1 levels. Based on the fact that multiple RXRα receptor conformations exist depending on binding of RXRα to different heterodimerization partners, we aim to increase the specificity of identified binders for the heterodimer Nurr1/RXRα. For this purpose, we describe here a new computational protocol for the selection of RXRα receptor structures that is used to perform Structure-Based Virtual Screening (SBVS) calculations for the discovery of NURR1 activators. In our study, we developed a computational protocol, where the choice of RXRα conformations for performing the SBVS is based on four criteria: (a) Pairwise comparison of the receptor conformations according to RMSD calculations, (b) analysis and clustering of RXRα structures comparing the binding-site shape and volume using SiteMap, (c) docking of a small-database of known actives for a specific heterodimer partner to the resulting shape-diverse subset of binding sites from (a) and (b) using Glide 5.8 SP and XP, and (d) retrieving representative protein conformations for the structure of interest from MD simulations using GROMACS. Virtual Screening was performed on three different subsets of RXRα receptor conformations, based on their binding to different heterodimerization partners. The final RXRα receptors to be used in SBVS were selected as mentioned above aiming to enhance the success rate and the selectivity of the hits. The Maybridge Hitfinder and Zinc databases were used in this SBVS exercise by first applying the SP filter on the full database and then the XP filter on the top 10,000 compounds of the Maybridge database and the top 40,000 compounds of the ZINC database. Compounds were selected as follows: Molecules that scored high when docked in the RXRα protein ensemble that bind to the heterodimer partner of interest and at the same time scored low for RXRα structures that bind to heterodimer partners of no interest, were selected in order to achieve selectivity. The efficiect selection was also based on their different orientation at the binding site of the various RXRα structures and different interactions with specific surrounding residues in order to maximize their selectivity potential. Finally, a post-processing step was imposed to the top-scoring compounds by using Chembioserver and FAF-Drugs2 filtering tools as well as pharmacological property prediction with the QikProp software. In vitro agonism of these compounds is still pending experimental testing. The workflow of this protocol is shown in Fig. 1. Figure 1: SBVS protocol developed for the discovery of novel selective Nurr1/RXRα agonists. / --

No description available.

Toxoplasma gondii infection is common in humans and is a significant risk factor for developing the disease schizophrenia. Genetic risk factors are likely required for the disease of schizophrenia to develop. Nurr1 – heterozygous (+/-) mice and wild-type (+/+) mice were evaluated using immune activation of astrocytes within the prefrontal cortex, dopamine levels within the striatum, and measuring the acoustic startle response reaction time by using prepulse inhibition (PPI). T. gondii infected heterozygous (+/-) mice exhibited increased GFAP expression within the prefrontal cortex. Dopamine levels within the striatum were measured and T. gondii infected wild-type (+/+) mice exhibited increased dopamine levels. The acoustic startle response reaction time was measured using PPI and T. gondii infected mice exhibited slower reaction times when compared to controls. These data demonstrate that the Nurr1 (+/-) genotype predisposes mice to T. gondii-induced alterations in behaviors that involve dopamine neurotransmission and are associated with symptoms of schizophrenia.

No description available.

Our laboratory is working with the human NTera2/D1 (NT2) cell line which have properties similar to progenitor cells in the CNS. These neural-like precursors cells can differentiate into all three major lineages - neurons, astrocytes, andoligodendrocytes. The pure neuronal population, called the hNT cells, possess characteristics of dopamine (DA) cells. In this dissertation, we performed various experiments to examine the neuronal and dopaminergic development of this cellline. We first cultured our hNT neurons with cells from the developingnigrostriatal (NS) pathway, the ventral mesencephalon and striatum, to determine their influence on survival, neuritic outgrowth, and DA phenotype. The survival ofhNT neurons was substantially greater when they were cultured with embryonicday (E) 18 cells, compared to monocultures or cocultures with either E14 orpostnatal day (P) 1 cells. The neuritic outgrowth of hNT neurons as assessed by the number of primary neurites per cell was increased when cultured with theareas of the brain from E14 and P1. The DA phenotype, as determined by the expression of the rate-limiting enzyme of DA synthesis was not increased in hNTneurons when they were cultured with primary rat cells from the NS pathway.Next we analyzed if the retinoic acid (RA)-treated hNT neurons and the NT2 precursor cells expressed three transcription factors required for development ofthe DA phenotype. We report that NT2 cells endogenously expressed Engrailed-1, Ptx3, and Nurr1 while RA treatment increased Nurr1 but down-regulated Engrailed-1 and Ptx3. Finally, lithium has been shown to stimulate neurogenesisin adult hippocampal precursors as well as influence the Wnt pathway known to be important for the induction of the DA phenotype.

No description available.

No description available.

No description available.

The contamination of seafood with methylmercury (MeHg) is a global health issue, as MeHg is a well known neurotoxin. Since dietary nutrients may interact with MeHg toxicity, and oxidative stress is one of the primary mechanisms underlying MeHg neurotoxicity, we characterized dietary antioxidant-MeHg interactions. Firstly, we used an ethnobotanical study to confirm the antioxidant activity of Northern Labrador Tea, Rhododendron tomentosum ssp. subarcticum (Tea), for the Canadian Inuit, a population with elevated MeHg exposure. Secondly, we determined the ability of Tea to ameliorate MeHg-induced toxicity in a rat perinatal exposure study. MeHg exposure (2 mg/KgBW/d) was associated with perturbed development and behaviour, elevated brain N-methyl-D-aspartate receptors, and serum lipid peroxidation. Surprisingly, Tea co-exposure (100 mg/KgBW/d) modulated MeHg’s effects on brain NMDA-R levels and lipid peroxidation, but also increased mercury serum concentrations. Thirdly, using a toxicogenomics approach we determined that MeHg exposure caused the down-regulation of Nr4a2 and its protein product Nurr1. These novel MeHg targets are implicated in developmental learning functions and were corrected with MeHg + Tea co-exposure. Lastly, we conducted a risk assessment survey and cross-sectional dietary epidemiology study in Costa Rica to further investigate dietary nutrient-MeHg interactions. Costa Rica is a Central American country with multiple sources of Hg and a high per capital fish consumption. Here, 5 of the 14 populations we studied exceeded the recommended MeHg provisional tolerable daily intake (pTDI) of 0.2 µg/KgBW/d. In Heredia the pTDI was exceeded by 34% of woman participants, primarily associated with canned tuna consumption. Interestingly, we detected that Hg body burden was significantly reduced by the consumption of antioxidant-rich dietary items. Considering our collective results, we hypothesized that MeHg toxicokinetics may be altered by dietary nutrients at the site of intestinal absorption from the disruption of gut flora, or at the site of cellular demethylation in tissues from the improvement of cellular redox state. The interaction of dietary nutrients on MeHg outcomes has a large impact on risk assessment and may provide a public health approach for managing the risk associated with MeHg exposure without reducing local fish consumption.

The contamination of seafood with methylmercury (MeHg) is a global health issue, as MeHg is a well known neurotoxin. Since dietary nutrients may interact with MeHg toxicity, and oxidative stress is one of the primary mechanisms underlying MeHg neurotoxicity, we characterized dietary antioxidant-MeHg interactions. Firstly, we used an ethnobotanical study to confirm the antioxidant activity of Northern Labrador Tea, Rhododendron tomentosum ssp. subarcticum (Tea), for the Canadian Inuit, a population with elevated MeHg exposure. Secondly, we determined the ability of Tea to ameliorate MeHg-induced toxicity in a rat perinatal exposure study. MeHg exposure (2 mg/KgBW/d) was associated with perturbed development and behaviour, elevated brain N-methyl-D-aspartate receptors, and serum lipid peroxidation. Surprisingly, Tea co-exposure (100 mg/KgBW/d) modulated MeHg’s effects on brain NMDA-R levels and lipid peroxidation, but also increased mercury serum concentrations. Thirdly, using a toxicogenomics approach we determined that MeHg exposure caused the down-regulation of Nr4a2 and its protein product Nurr1. These novel MeHg targets are implicated in developmental learning functions and were corrected with MeHg + Tea co-exposure. Lastly, we conducted a risk assessment survey and cross-sectional dietary epidemiology study in Costa Rica to further investigate dietary nutrient-MeHg interactions. Costa Rica is a Central American country with multiple sources of Hg and a high per capital fish consumption. Here, 5 of the 14 populations we studied exceeded the recommended MeHg provisional tolerable daily intake (pTDI) of 0.2 µg/KgBW/d. In Heredia the pTDI was exceeded by 34% of woman participants, primarily associated with canned tuna consumption. Interestingly, we detected that Hg body burden was significantly reduced by the consumption of antioxidant-rich dietary items. Considering our collective results, we hypothesized that MeHg toxicokinetics may be altered by dietary nutrients at the site of intestinal absorption from the disruption of gut flora, or at the site of cellular demethylation in tissues from the improvement of cellular redox state. The interaction of dietary nutrients on MeHg outcomes has a large impact on risk assessment and may provide a public health approach for managing the risk associated with MeHg exposure without reducing local fish consumption.