Le lobbying associatif à Bruxelles entre mobilisations unitaires et sectorielles

<p>Nuclear fractions were prepared and anti-GR (top row graphs) and anti-phospho-specific GR (middle row graphs) immunoreactivities were determined, as described in the Materials and Methods. Anti-GR and anti-phospho-GR data are presented as the mean (± SEM) immunoreactivities from PAE (n = 9–10) and SAC (n = 9–10) mice corrected to Coomassie stain. The ratio of the anti-phospho-GR to anti-total GR immunoreactivities (bottom row graphs) was calculated as described in the Materials and Methods. Total nuclear GR levels were significantly lower in the PAE mice (p = .05 for pS226 GR, left top panel; p = .008 for pS211 GR, center top panel; p = .005 for pS203 GR, right top panel). The ratio of each phospho-GR to total GR was significantly higher in the PAE (pS226 GR/total GR, p = .04; pS211 GR/total GR, p = .04; pS203 GR/total GR, p = .02). Representative Western blots are presented below.</p

Prenatal Alcohol Exposure Modifies Glucocorticoid Receptor Subcellular Distribution in the Medial Prefrontal Cortex and Impairs Frontal Cortex-Dependent Learning

<div><p>Prenatal alcohol exposure (PAE) has been shown to impair learning, memory and executive functioning in children. Perseveration, or the failure to respond adaptively to changing contingencies, is a hallmark on neurobehavioral assessment tasks for human fetal alcohol spectrum disorder (FASD). Adaptive responding is predominantly a product of the medial prefrontal cortex (mPFC) and is regulated by corticosteroids. In our mouse model of PAE we recently reported deficits in hippocampal formation-dependent learning and memory and a dysregulation of hippocampal formation glucocorticoid receptor (GR) subcellular distribution. Here, we examined the effect of PAE on frontal cortical-dependent behavior, as well as mPFC GR subcellular distribution and the levels of regulators of intracellular GR transport. PAE mice displayed significantly reduced response flexibility in a Y-maze reversal learning task. While the levels of total nuclear GR were reduced in PAE mPFC, levels of GR phosphorylated at serines 203, 211 and 226 were not significantly changed. Cytosolic, but not nuclear, MR levels were elevated in the PAE mPFC. The levels of critical GR trafficking proteins, FKBP51, Hsp90, cyclophilin 40, dynamitin and dynein intermediate chain, were altered in PAE mice, in favor of the exclusion of GR from the nucleus, indicating dysregulation of GR trafficking. Our findings suggest that there may be a link between a deficit in GR nuclear localization and frontal cortical learning deficits in prenatal alcohol-exposed mice.</p></div

Membrane levels of dynamitin (A), Dynein IC1 (B) and Dynein IC2 (C) in the medial frontal cortex of saccharin (SAC) control and prenatal alcohol exposure (PAE) offspring.

<p>Corresponding representative immunoblots are shown below the respective figures. The cytosolic fraction was prepared and immunoreactivities were determined as described in the Materials and Methods. Data are presented as mean (± SEM) immunoreactivity corrected to Coomassie stain in PAE (n = 7) and SAC (n = 7) mice. Membrane dynamitin levels were lower (p = .01) in the PAE compared to SAC offspring. Membrane dynein C-1 levels were elevated (p = .002), while dynein IC-2 levels were lower (p = .012), in the PAE compared to SAC.</p

Cytosolic levels of the FKBP51 (A), FKPB52 (B), Cyclophilin 40 (C) and Hsp90 (D) in the medial frontal cortex of saccharin (SAC) control and prenatal alcohol exposure (PAE) offspring.

<p>Corresponding representative immunoblots are shown below each figure. Cytosolic fractions were prepared, and specific immunoreactivities were determined as described in the Materials and Methods. Data are presented as mean immunoreactivity corrected to Coomassie stain ± SEM in the PAE (n = 7) and SAC (n = 7) mice. Cytosolic FKBP51 (A) levels were increased (p = .02) and cytosolic FKBP52 (B) levels were not different between the PAE and SAC mice. Cytosolic cyclophilin 40 (C) levels were lower (p = .03) in the PAE offspring compared to SAC. Cytosolic Hsp90 (D) levels (p = .02) were lower in SAC mice.</p

Cytosolic (A) and nuclear (B) levels of the mineralocorticoid receptor (MR) in the medial frontal cortex of saccharin (SAC) control and prenatal alcohol exposure (PAE) offspring.

<p>Representative immunoblots are shown below each figure. Subcellular fractions and anti-MR immunoreactivities were prepared as described in the Materials and Methods section. Data are presented as mean immunoreactivity corrected to Coomassie stain ± SEM in the PAE (n = 8–10) and SAC (n = 9–10) mice. Cytosolic MR levels were increased (p<0.05) in the PAE mice, whereas nuclear MR levels were not different in the two groups.</p

Image_2_Sex-Dependent Effects of the Histone Deacetylase Inhibitor, Sodium Valproate, on Reversal Learning After Developmental Arsenic Exposure.tif

<p>Several studies have demonstrated that exposure to arsenic in drinking water adversely affects brain development and cognitive function in adulthood. While the mechanism by which arsenic induces adverse neurological outcomes remains elusive, studies suggest a link between reduced levels of histone acetylation and impaired performance on a variety of behavioral tasks following arsenic exposure. Using our developmental arsenic exposure (DAE) paradigm, we have previously reported reduced histone acetylation and associated histone acetyltransferase enzyme expression in the frontal cortex of C57BL/6J adult male mice, with no changes observed in the female frontal cortex. In the present study, we sought to determine if DAE produced sex-dependent deficits in frontal cortical executive function using the Y-maze acquisition and reversal learning tasks, which are specific for assessing cognitive flexibility. Further, we tested whether the administration of valproic acid, a class I–IIa histone deacetylase inhibitor, was able to mitigate behavioral and biochemical changes resulting from DAE. As anticipated, DAE inhibited acquisition and reversal learning performance in adult male, but not female, mice. Valproate treatment for 2 weeks restored reversal performance in the male arsenic-exposed offspring, while not affecting female performance. Protein levels of HDACs 1, 2, and 5 were elevated following behavioral assessment but only in DAE male mice; restoration of appropriate HDAC levels occurred after valproate treatment and was concurrent with improved behavioral performance, particularly during reversal learning. Female frontal cortical levels of HDAC enzymes were not impacted by DAE or valproate treatment. Finally, mRNA expression levels of brain-derived neurotrophic factor, Bdnf, which has been implicated in the control of frontal cortical flexibility and is regulated by HDAC5, were elevated in DAE male mice and restored to normal levels following HDACi treatment. Levels of mRNA encoding glutamate receptor ionotropic NMDA type subunits, which have been linked to cognitive flexibility, were not related to the reversal learning deficit in the DAE mice and were not altered by HDACi treatments. These findings demonstrate that DAE alters frontal cortical HDAC levels and Bdnf expression in males, but not females, and that these molecular changes are associated with sex-dependent differences in cognitive flexibility in a reversal-learning task.</p