l-DOPA-induced dyskinesia and neuroinflammation: do microglia and astrocytes play a role?

In Parkinson's disease (PD), l-DOPA therapy leads to the emergence of motor complications including l-DOPA-induced dyskinesia (LID). LID relies on a sequence of pre- and postsynaptic neuronal events, leading to abnormal corticostriatal neurotransmission and maladaptive changes in striatal projection neurons. In recent years, additional non-neuronal mechanisms have been proposed to contribute to LID. Among these mechanisms, considerable attention has been focused on l-DOPA-induced inflammatory responses. Microglia and astrocytes are the main actors in neuroinflammatory responses, and their double role at the interface between immune and neurophysiological responses is starting to be elucidated. Both microglia and astrocytes express a multitude of neurotransmitter receptors and via the release of several soluble molecules modulate synaptic function in neuronal networks. Here we review preclinical and clinical evidence of glial overactivation by l-DOPA, supporting a role of microglia and astrocytes in the development of LID. We propose that in PD, chronically and abnormally activated microglia and astrocytes lead to an aberrant neuron-glia communication, which affect synaptic activity and neuroplasticity contributing to the development of LID.

Evidence for topographic guidance of dopaminergic axons by differential Netrin-1 expression in the striatum.

There are two main subgroups of midbrain dopaminergic (DA) neurons: the more medially located ventral tegmental area (VTA) DA neurons, which have axons that innervate the ventral-lateral (VL) striatum, and the more laterally located substantia nigra (SN) DA neurons, which preferentially degenerate in Parkinson's disease (PD) and have axons that project to the dorsal-medial (DM) striatum. DA axonal projections in the striatum are not discretely localized and they arborize widely, however they do not stray from one zone to the other so that VTA axons remain in the VL zone and SN axons in the DM zone. Here we provide evidence that Netrin-1 acts in a novel fashion to topographically pattern midbrain DA axons into these two striatal zones by means of a gradient of Netrin-1 in the striatum and by differential attraction of the axons to Netrin-1. Midbrain DA neurons are attracted to the striatum in culture and this attraction is blocked by an anti-DCC (Netrin receptor) antibody. Mechanistically, outgrowth of both VTA and SN DA axons is stimulated by Netrin-1, but the two populations of DA axons respond optimally to overlapping but distinct concentrations of Netrin-1, with SN axons preferring lower concentrations and VTA axons preferring higher concentrations. In vivo this differential preference is closely mirrored by differences in Netrin-1 expression in their respective striatal target fields. In vivo in mice lacking Netrin-1, DA axons that reach the striatum fail to segregate into two terminal zones and to fully innervate the striatum. Our results reveal novel actions for Netrin-1 and provide evidence for a mechanism through which DA axons can selectively innervate one of two terminal zones in the striatum but have free reign to arborize widely within a terminal zone.

The Barretos Cancer Hospital Animal Facility: Implementation and Results of a Dedicated Platform for Preclinical Oncology Models.

The Barretos Cancer Hospital Animal Facility (BCHAF) is a unique facility in Brazil exclusively dedicated to working with animal models for cancer research. In this article, we briefly present our modern facility and the main experiments performed, focusing on mutant strains of mice (PTCH-knockout and ApcMin mice), xenograft models, and patient-derived xenografts (PDXs). Our results show the progress and challenges in establishing these models and the need for having an appropriate representation of our cancer population to better understand tumor biology and to identify cancer biomarkers, which could be putatively targeted, allowing for personalized therapy.

Decoding the Roles of Astrocytes and Hedgehog Signaling in Medulloblastoma.

The molecular evolution of medulloblastoma is more complex than previously imagined, as emerging evidence suggests that multiple interactions between the tumor cells and components of the tumor microenvironment (TME) are important for tumor promotion and progression. The identification of several molecular networks within the TME, which interact with tumoral cells, has provided new clues to understand the tumorigenic roles of many TME components as well as potential therapeutic targets. In this review, we discuss the most recent studies regarding the roles of astrocytes in supporting sonic hedgehog (SHH) subgroup medulloblastoma (MB) and provide an overview of MB progression through SHH expression and signal transduction mechanisms into the complex tumor microenvironment. In addition, we highlight the associations between tumor and stromal cells as possible prognostic markers that could be targeted with new therapeutic strategies.

Differential behavioral and glial responses induced by dopaminergic mechanisms in the iNOS knockout mice.

The interaction between distinctive nitric oxide synthase (NOS) isoforms and the dopamine system provides new avenues to the development of pharmacological tools for the pathophysiological conditions of the dopaminergic system. Our aim was to investigate the influences of dopamine-induced effects in inducible NOS knockout (iNOS KO) mice. In order to characterize iNOS KO mice phenotype, the animals were submitted to the basal analyses of motor, sensorimotor and sensorial abilities. Pharmacological challenging of the dopaminergic system included the investigation of amphetamine-induced prepulse inhibition (PPI) disruption, haloperidol-induced catalepsy, reserpine-induced oral involuntary movements and hyperlocomotion induced by amphetamine in reserpine treated mice. The iNOS KO mice showed significant reduction of spontaneous motor activity, but there was no significant difference in sensorimotor or sensorial responses of iNOS KO mice compared to wild type (WT). Regarding the dopaminergic system, iNOS KO mice showed a significant increase of haloperidol-induced catalepsy. This effect was confirmed through an iNOS pharmacological inhibitor (1400 W) in WT mice. In addition, iNOS KO reserpine treated mice showed reduced oral involuntary movements and amphetamine-induced hyperlocomotion. Knowing that iNOS is mainly expressed in glial cells we analyzed the immunoreactivity (ir) for GFAP (astrocyte marker) and IBA-1 (microglial marker) in the striatum, an area enrolled in motor planning among other functions. iNOS KO presented reduced GFAP-ir and IBA-1-ir compared with WT. Reserpine treatment increased GFAP-ir in both WT and iNOS KO. However, these effects were slighter in iNOS KO. Activated state of microglia was increased by reserpine only in WT mice. Our results further demonstrated that the absence of iNOS interfered with dopamine-mediated behavioral and molecular responses. These results increase the understanding of the dopamine and NO system interaction, which is useful for the management of the dopamine-related pathologies.

Potential output pathways for agonistic-like responses resulting from the GABA(A) blockade of the torus semicircularis dorsalis in weakly electric fish, Gymnotus carapo.

The purpose of this study is to examine the pathways involved in the electromotor (electric organ discharge interruptions) and skeletomotor responses (defense-like) observed by blockade of GABAergic control of the torus semicircularis dorsalis (TSd) of the awake weakly electric fish Gymnotus carapo, described in a former study. Microinjection of NMDA (5 mM) into the pacemaker nucleus (PM) through a guide cannula previously implanted caused a prolonged interruption of the electric organ discharge (EOD) intermingled with reduction in frequency, similar to that described for TSd GABA(A) blockade, but without noticeable skeletomotor effects. The EOD alterations elicited by bicuculline microinjections (0.245 mM) into the TSd could be blocked or attenuated by a previous microinjection of AP-5 (0.5 mM), an NMDA antagonist, into the PM. Labeled terminals are found in the nucleus electrosensorius (nE) after injection of the biotinylated dextran amine (BDA) tracer into the TSd and into the sublemniscal prepacemaker nucleus (SPPn) subsequent to the tracer injection into the nE. Defense-like responses but not EOD interruptions are observed after microinjections of NMDA (5 mM) into the rhombencephalic reticular formation (RF), where labeled terminals are seen after BDA injection into the TSd and somata are filled after injection of the tracer into the spinal cord. In this last structure, marked fibers are seen subsequent to injection of BDA into the RF. These results suggest that two distinct pathways originate from the torus: one for EOD control, reaching PM through nE and SPPn, and the other one for skeletomotor control reaching premotor reticular neurons. Both paths could be activated by toral GABA(A) blockade.

Widespread Differential Expression of Coding Region and 3' UTR Sequences in Neurons and Other Tissues.

Mature messenger RNAs (mRNAs) consist of coding sequence (CDS) and 5' and 3' UTRs, typically expected to show similar abundance within a given neuron. Examining mRNA from defined neurons, we unexpectedly show extremely common unbalanced expression of cognate 3' UTR and CDS sequences; many genes show high 3' UTR relative to CDS, others show high CDS to 3' UTR. In situ hybridization (19 of 19 genes) shows a broad range of 3' UTR-to-CDS expression ratios across neurons and tissues. Ratios may be spatially graded or change with developmental age but are consistent across animals. Further, for two genes examined, a 3' UTR-to-CDS ratio above a particular threshold in any given neuron correlated with reduced or undetectable protein expression. Our findings raise questions about the role of isolated 3' UTR sequences in regulation of protein expression and highlight the importance of separately examining 3' UTR and CDS sequences in gene expression analyses.

Organization of the gymnotiform fish pallium in relation to learning and memory: II. Extrinsic connections.

This study describes the extrinsic connections of the dorsal telencephalon (pallium) of gymnotiform fish. We show that the afferents to the dorsolateral and dorsomedial pallial subdivisions of gymnotiform fish arise from the preglomerular complex. The preglomerular complex receives input from four clearly distinct regions: (1) descending input from the pallium itself (dorsomedial and dorsocentral subdivisions and nucleus taenia); (2) other diencephalic nuclei (centroposterior, glomerular, and anterior tuberal nuclei and nucleus of the posterior tuberculum); (3) mesencephalic sensory structures (optic tectum, dorsal and ventral torus semicircularis); and (4) basal forebrain, preoptic area, and hypothalamic nuclei. Previous studies have implicated the majority of the diencephalic and mesencephalic nuclei in electrosensory, visual, and acousticolateral functions. Here we discuss the implications of preglomerular/pallial electrosensory-associated afferents with respect to a major functional dichotomy of the electric sense. The results allow us to hypothesize that a functional distinction between electrocommunication vs. electrolocation is maintained within the input and output pathways of the gymnotiform pallium. Electrocommunication information is conveyed to the pallium through complex indirect pathways that originate in the nucleus electrosensorius, whereas electrolocation processing follows a conservative pathway inherent to all vertebrates, through the optic tectum. We hypothesize that cells responsive to communication signals do not converge onto the same targets in the preglomerular complex as cells responsive to moving objects. We also hypothesize that efferents from the dorsocentral (DC) telencephalon project to the dorsal torus semicircularis to regulate processing of electrocommunication signals, whereas DC efferents to the tectum modulate sensory control of movement.