Changes in the expression of extracellular regulated kinase (ERK 1/2) in the R6/2 mouse model of Huntington's disease after phosphodiesterase IV inhibition

The mitogen-activated protein kinases (MAPKs) superfamily comprises three major signaling pathways: the extracellular signal-regulated protein kinases (ERKs), the c-Jun N-terminal kinases or stress-activated protein kinases (JNKs/SAPKs) and the p38 family of kinases.ERK 1/2 signaling has been implicated in a number of neurodegenerative disorders, including Huntington's disease (HD). Phosphorylation patterns of ERK 1/2 and JNK are altered in cell models of HD. In this study, we aimed at studying the correlations between ERK 1/2 and the neuronal vulnerability to HD degeneration in the R6/2 transgenic mouse model of HD. Single and double-label immunofluorescence for phospho-ERK (pERK, the activated form of ERK) and for each of the striatal neuronal markers were employed on perfusion-fixed brain sections from R6/2 and wild-type mice. Moreover, Phosphodiesterase 4 inhibition through rolipram was used to study the effects on pERK expression in the different types of striatal neurons. We completed our study with western blot analysis. Our study shows that pERK levels increase with age in the medium spiny striatal neurons and in the parvalbumin interneurons, and that rolipram counteracts such increase in pERK. Conversely, cholinergic and somatostatinergic interneurons of the striatum contain higher levels of pERK in the R6/2 mice compared to the controls. Rolipram induces an increase in pERK expression in these interneurons. Thus, our study confirms and extends the concept that the expression of phosphorylated ERK 1/2 is related to neuronal vulnerability and is implicated in the pathophysiology of cell death in HD. (C) 2012 Elsevier Inc. All rights reserved

Astrocyte: physiology and pathology

A team of authors from prestigious academic schools contributed to draw up a project that would give a detailed account of astrocyte's morphology and physiology, examining thoroughly all the astrocyte's types; giving an accurate description of their morphology, location, function in the brain; and illustrating their physiology and pathology in terms of dealing with neurons through ""gliotransmitters,"" ionic channels, and membrane receptors expression. This book gives an overview of the crucial role of astrocytes in the physiology of the CNS and in the pathogenesis of several CNS disorders suggesting that the shift from a neurocentric view to one that incorporates astrocytes in disease models for drug discovery is a critical step in renewing drug development strategies to treat neurodegenerative diseases

Estradiol-induced mitogen-activated protein kinase (extracellular signal-regulated kinase 1 and 2) activity in the frog (Rana esculenta) testis

Several lines of evidence support a key role of estradiol-17β (E2) in male fertility. We have used a non-mammalian vertebrate model, the frog Rana esculenta, to investigate the regulation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) activity in the testis during the annual sexual cycle and to study whether E2 exerts a role in spermatogenesis through the regulation of ERK1/2 activity. ERK1/2 proteins are present in the cytoplasm and nucleus of the primary and secondary spermatogonia (SPG), and in the nucleus of primary spermatocytes. The annual E2 profile shows a progressive increase during active spermatogenesis with a peak in the month of June. In parallel, ERK1/2 are highly phosphorylated during the period of active spermatogenesis (from April to July) compared with the regressive period (September/October) and winter stasis (from November to March). E2 treatment induces the proliferation of primary SPG, possibly via the activation of ERK1/2, and this effect is counteracted by the anti-estrogen ICI 182-780

Modulation of nurr1 gene expression in mesencephalic dopaminergic neurones

The transcription factor/nuclear receptor Nurr1 is essential for the differentiation of midbrain dopaminergic neurones. Here we demonstrate that, during the ontogeny of rat ventral mesencephalon, nurr1 gene expression is developmentally regulated and its levels show a sharp peak between embryonic day E13 and E15, when most dopaminergic neurones differentiate. In addition, in primary cultures from embryonic rat mesencephalon, nurr1 gene follows a temporal pattern of expression comparable to that observed in vivo. We also report that exposure of embryonic mesencephalic cultures to depolarizing stimuli leads to a robust increase in nurr1 mRNA and protein. The depolarizing effect is also detected in mesencephalic cultures enriched in dopaminergic neurones by using a combination of bFGF and Sonic hedgehog. The latter further increases the number of dopaminergic neurones in these 'expanded' cultures, an effect abolished in the presence of anti-Sonic hedgehog antibodies. Our data show that nurr1 gene is highly expressed in midbrain dopaminergic neurones in a sharp temporal window and that its expression is plastic, both in vivo and in vitro. In addition we show that Sonic hedgehog can direct dopaminergic differentiation in proliferating dopaminergic neuroblasts in vitro

Ontogeny of kainate receptor gene expression in the developing rat midbrain and striatum

Kainate (KA) receptors are a family of ionotropic glutamate receptors, which mediate the excitatory synaptic transmission in various areas of the mammalian CNS. We have studied the expression pattern of the genes encoding for KA receptor subunits (Glur5-1, Glur5-2, Glur6, Glur7, KA1 and KA2) in rat prenatal (E), postnatal and adult ventral mesencephalon (MES) and striatum (STR) and in fetal midbrain primary cultures. Each receptor subunit shows a unique area- and temporal-expression pattern. In MES the onset of both Glur5 subunits is delayed when compared to the other subunits. In addition, most of the transcripts for KA subunits gradually increase during embryonic development and show a slight decrease during the first postnatal week. Differently, Glur6 and KA2 mRNAs show a sharp increase at E14.5 and decrease thereafter, reaching the lowest levels during late embryonic and postnatal development. In the STR, the gene expression of all KA subunit mRNAs is higher during embryonic development than after birth, except KA1 transcripts, that show a peak at P5. In embryonic MES primary cultures, Glur5-2, Glur6 and KA2 mRNAs are higher at the beginning of the culture when compared to older cultures, while the other subunit mRNAs do not show significant variation throughout the days in vitro. Thus, all the KA receptor subunit transcripts appear independently regulated during MES and STR development, probably contributing to the establishment of the fine tuning of the excitatory circuits reciprocally established between these CNS areas. © 2002 Elsevier Science B.V. All rights reserved

Celecoxib Inhibits Prion Protein 90-231-Mediated Pro-inflammatory Responses in Microglial Cells

Activation of microglia is a central event in the atypical inflammatory response occurring during prion encephalopathies. We report that the prion protein fragment encompassing amino acids 90–231 (PrP90-231), a model of the neurotoxic activity of the pathogenic prion protein (PrPSc), causes activation of both primary microglia cultures and N9 microglial cells in vitro. This effect was characterized by cell proliferation arrest and induction of a secretory phenotype, releasing prostaglandin E2 (PGE2) and nitric oxide (NO). Conditioned medium from PrP90-231-treated microglia induced in vitro cytotoxicity of A1 mesencephalic neurons, supporting the notion that soluble mediators released by activated microglia contributes to the neurodegeneration during prion diseases. The neuroinflammatory role of COX activity, and its potential targeting for anti-prion therapies, was tested measuring the effects of ketoprofen and celecoxib (preferential inhibitors of COX1 and COX2, respectively) on PrP90-231-induced microglial activation. Celecoxib, but not ketoprofen significantly reverted the growth arrest as well as NO and PGE2 secretion induced by PrP90-231, indicating that PrP90-231 pro-inflammatory response in microglia is mainly dependent on COX2 activation. Taken together, these data outline the importance of microglia in the neurotoxicity occurring during prion diseases and highlight the potentiality of COX2-selective inhibitors to revert microglia as adjunctive pharmacological approach to contrast the neuroinflammation-dependent neurotoxicity