Pharmacological rescue of adult hippocampal neurogenesis in a mouse model of X-linked intellectual disability

Oligophrenin-1 (OPHN1) is a Rho GTPase activating protein whose mutations cause X-linked intellectual disability (XLID). How loss of function of Ophnl affects neuronal development is only partly understood. Here we have exploited adult hippocampal neurogenesis to dissect the steps of neuronal differentiation that are affected by Ophn1 deletion. We found that mice lacking Ophnl display a reduction in the number of newborn neurons in the dentate gyrus. A significant fraction of the Ophn1-deficient newly generated neurons failed to extend an axon towards CM, and showed an altered density of dendritic protrusions. Since Ophnl-deficient mice display overactivation of Rho-associated protein kinase (ROCK) and protein kinase A (PICA) signaling, we administered a clinically approved ROCK/PICA inhibitor (fasudil) to correct the neurogenesis defects. While administration of fasudil was not effective in rescuing axon formation, the same treatment completely restored spine density to control levels, and enhanced the long-term survival of adult-born neurons in mice lacking Ophn1. These results identify specific neurodevelopmental steps that are impacted by Ophn1 deletion, and indicate that they may be at least partially corrected by pharmacological treatment. (C) 2017 The Authors. Published by Elsevier Inc

Quantitative Kinematic Characterization of Reaching Impairments in Mice After a Stroke

Background and Objective. Kinematic analysis of reaching movements is increasingly used to evaluate upper extremity function after cerebrovascular insults in humans and has also been applied to rodent models. Such analyses can require time-consuming frame-by-frame inspections and are affected by the experimenter's bias. In this study, we introduce a semi-automated algorithm for tracking forepaw movements in mice. This methodology allows us to calculate several kinematic measures for the quantitative assessment of performance in a skilled reaching task before and after a focal cortical stroke. Methods. Mice were trained to reach for food pellets with their preferred paw until asymptotic performance was achieved. Photothrombosis was then applied to induce a focal ischemic injury in the motor cortex, contralateral to the trained limb. Mice were tested again once a week for 30 days. A high frame rate camera was used to record the movements of the paw, which was painted with a nontoxic dye. An algorithm was then applied off-line to track the trajectories and to compute kinematic measures for motor performance evaluation. Results. The tracking algorithm proved to be fast, accurate, and robust. A number of kinematic measures were identified as sensitive indicators of poststroke modifications. Based on end-point measures, ischemic mice appeared to improve their motor performance after 2 weeks. However, kinematic analysis revealed the persistence of specific trajectory adjustments up to 30 days poststroke, indicating the use of compensatory strategies. Conclusions. These results support the use of kinematic analysis in mice as a tool for both detection of poststroke functional impairments and tracking of motor improvements following rehabilitation. Similar studies could be performed in parallel with human studies to exploit the translational value of this skilled reaching analysis

The Chemokine CCL2 Mediates the Seizure-enhancing Effects of Systemic Inflammation

Epilepsy is a chronic disorder characterized by spontaneous recurrent seizures. Brain inflammation is increasingly recognized as a critical factor for seizure precipitation, but the molecular mediators of such proconvulsant effects are only partly understood. The chemokine CCL2 is one of the most elevated inflammatory mediators in patients with pharmacoresistent epilepsy, but its contribution to seizure generation remains unexplored. Here, we show, for the first time, a crucial role for CCL2 and its receptor CCR2 in seizure control. We imposed a systemic inflammatory challenge via lipopolysaccharide (LPS) administration in mice with mesial temporal lobe epilepsy. We found that LPS dramatically increased seizure frequency and upregulated the expression of many inflammatory proteins, including CCL2. To test the proconvulsant role of CCL2, we administered systemically either a CCL2 transcription inhibitor (bindarit) or a selective antagonist of the CCR2 receptor (RS102895). We found that interference with CCL2 signaling potently suppressed LPS-induced seizures. Intracerebral administration of anti-CCL2 antibodies also abrogated LPS-mediated seizure enhancement in chronically epileptic animals. Our results reveal that CCL2 is a key mediator in the molecular pathways that link peripheral inflammation with neuronal hyperexcitability

Electrophysiology of glioma: a Rho GTPase-activating protein reduces tumor growth and spares neuron structure and function

Background. Glioblastomas are the most aggressive type of brain tumor. A successful treatment should aim at halting tumor growth and protecting neuronal cells to prevent functional deficits and cognitive deterioration. Here, we exploited a Rho GTPase-activating bacterial protein toxin, cytotoxic necrotizing factor 1 (CNF1), to interfere with glioma cell growth in vitro and vivo. We also investigated whether this toxin spares neuron structure and function in peritumoral areas. Methods. We performed a microarray transcriptomic and in-depth proteomic analysis to characterize the molecular changes triggered by CNF1 in glioma cells. We also examined tumor cell senescence and growth in vehicle-and CNF1-treated glioma-bearing mice. Electrophysiological and morphological techniques were used to investigate neuronal alterations in peritumoral cortical areas. Results. Administration of CNF1 triggered molecular and morphological hallmarks of senescence in mouse and human glioma cells in vitro. CNF1 treatment in vivo induced glioma cell senescence and potently reduced tumor volumes. In peritumoral areas of glioma-bearing mice, neurons showed a shrunken dendritic arbor and severe functional alterations such as increased spontaneous activity and reduced visual responsiveness. CNF1 treatment enhanced dendritic length and improved several physiological properties of pyramidal neurons, demonstrating functional preservation of the cortical network. Conclusions. Our findings demonstrate that CNF1 reduces glioma volume while at the same time maintaining the physiological and structural properties of peritumoral neurons. These data indicate a promising strategy for the development of more effective antiglioma therapies

Neuroplastic Changes Following Brain Ischemia and their Contribution to Stroke Recovery: Novel Approaches in Neurorehabilitation

Ischemic damage to the brain triggers substantial reorganization of spared areas and pathways, which is associated with limited, spontaneous restoration of function. A better understanding of this plastic remodeling is crucial to develop more effective strategies for stroke rehabilitation. In this review article, we discuss advances in the comprehension of post-stroke network reorganization in patients and animal models. We first focus on rodent studies that have shed light on the mechanisms underlying neuronal remodeling in the perilesional area and contralesional hemisphere after motor cortex infarcts. Analysis of electrophysiological data has demonstrated brain-wide alterations in functional connectivity in both hemispheres, well beyond the infarcted area. We then illustrate the potential use of non-invasive brain stimulation (NIBS) techniques to boost recovery. We finally discuss rehabilitative protocols based on robotic devices as a tool to promote endogenous plasticity and functional restoration

Progression of motor deficits in glioma-bearing mice: impact of CNF1 therapy at symptomatic stages

Glioblastoma (GBM) is the most aggressive type of brain tumor. In this context, animal models represent excellent tools for the early detection and longitudinal mapping of neuronal dysfunction, that are critical in the preclinical validation of new therapeutic strategies. In a mouse glioma model, we developed sensitive behavioral readouts that allow early recognizing and following neurological symptoms. We injected GL261 cells into the primary motor cortex of syngenic mice and we used a battery of behavioral tests to longitudinally monitor the dysfunction induced by tumor growth. Grip strength test revealed an early onset of functional deficit associated to the glioma growth, with a significant forelimb weakness appearing 9 days after tumor inoculation. A later deficit was observed in the rotarod and in the grid walk tasks. Using this model, we found reduced tumor growth and maintenance of behavioral functions following treatment with Cytotoxic Necrotizing Factor 1 (CNF1) at a symptomatic stage. Our data provide a detailed and precise examination of how tumor growth reverberates on the behavioral functions of glioma-bearing mice, providing normative data for the study of therapeutic strategies for glioma treatment. The reduced tumor volume and robust functional sparing observed in CNF1-treated, glioma-bearing mice strengthen the notion that CNF1 delivery is a promising strategy for glioma therapy

Editorial Physiology and Plasticity of Interhemispheric Connections

The corpus callosum (CC for aficionados) is the largest fiber bundle in the brain and establishes connections between the hemispheres, and predominantly, but not solely, between the cortical areas. Functionally mysterious for a long time, it shared with the pineal gland the honor of being considered the site of the soul M. Fabri and G. Polonara provide a functional map of callosal topography by charting the BOLD signal evoked in callosal axons by taste, tactile, auditory, and visual stimuli and by motor tasks. This approach is at the frontier of what is usually obtained from BOLD signals. It provides results that are compatible with what is predicted by anatomy in the case of axons originating from primary areas, but it also shows activations that could not have been predicted from anatomy, probably due to axons originating in multisensory areas. K. E. Schmidt finds that, in the visual cortex, CC connections have a multiplicative shift of the responses and this is an interesting finding that goes beyond the old debate of whether callosal connections are excitatory or inhibitory. The finding is placed within the frame of the historical question of the general nature of callosal connections. Hubel and Wiesel V. Beaulé et al. focus on the role of CC connections in disentangling bilateral manual movements. From juvenile, to adult, to pathological conditions, the degrees of manual independence are differently modulated and this may be due to inhibitory action of callosal connections. Interestingly, inhibition between the hemispheres has been repeatedly reported for the motor functions, particularly in 2 Neural Plasticity man, although it has been observed in the visual cortex as well, where it seems to be quickly overridden by the excitatory interactions Over the last 30 years, developmental work on the CC has focused on three main themes: (i) the molecular mechanisms of axonal guidance between the hemispheres, (ii) the establishment of topographical connections, and (iii) the role of activity in the development of the connections. M. Nishikimi et al. review the first of the above themes, with special attention to the midline structures and neighboring axons. They also describe alterations in these navigational mechanisms that result in callosal dysgenesis in humans and mice. Y. Tagawa and T. Hirano review the last of the above issues and provide information on the molecular mechanisms by which spontaneous activity sculpts callosal projections. They conclude that both presynaptic and postsynaptic neuronal activities are critically involved in callosal axon development, and discuss the intracellular signaling pathways that work downstream of neuronal firing. It may be added that the overproduction and elimination of axons in development are central to the second of the themes above and continue to provide testable hypotheses on the nature of developmental plasticity of cortical connectivity Noninvasive structural and functional imaging techniques are taking an increasingly large share of brain studies, but this raises the question of how novel and more traditional, firmly established methodologies map onto each other. The CC is practically unavoidable in non-invasive structural studies, and, therefore, it can provide some general answers because of its central position in the brain, its relative "simplicity" and the amount of anatomical and functional information available. J. F. Olavarria et al. relate the critical period of callosal development, as defined by the reorganization of visual callosal connections caused by early enucleation, to the development of water diffusion parameters. This is important new information that complements the view that callosal plasticity relates to axonal maturation and differentiation. M. G. Knyazeva places callosal maturation as estimated by MRI and coherence EEG analysis, within the context of excitatory and inhibitory interactions between the hemispheres. P. Mathew et al. report data in preterm infants showing a relation between motor-specific scores and fractional anisotropy of anterior midbody of CC, the region where axons interconnecting motor areas course. Finally N. Takeuchi et al. introduce the concept of adult CC plasticity that might be elicited by trans-cranial stimulation in humans. They also discuss the use of brain stimulation techniques as a possible rehabilitation strategy to reinstate interhemispheric balance in patients with stroke