Background and purpose: Alzheimer's disease (AD) is a common neurodegenerative disease characterized by a neuroinflammatory state, and to date, there is no cure and its treatment represents a large unmet clinical need. The involvement of Th17 cells in the pathogenesis of AD‐related neuroinflammation has been reported in several studies. However, the role of the cytokine, IL‐17 has not been well addressed. Herein, we investigate the effects of IL‐17 neutralizing antibody (IL‐17Ab) injected by i.c.v. or intranasal (IN) routes on amyloid‐β (Aβ)‐induced neuroinflammation and memory impairment in mice.Experimental approach: Aβ_1–42 was injected into cerebral ventricles of adult CD1 mice. These mice received IL‐17Ab via i.c.v. either at 1 h prior to Aβ_1–42 injection or IN 5 and 12 days after Aβ_1–42 injection. After 7 and 14 days of Aβ_1–42 administration, we evaluated olfactory, spatial and working memory and performed biochemical analyses on whole brain and specific brain areas.Key results: Pretreatment with IL‐17Ab, given, i.c.v., markedly reduced Aβ_1–42‐induced neurodegeneration, improved memory function, and prevented the increase of pro‐inflammatory mediators in a dose‐dependent manner at 7 and 14 days. Similarly, the double IN administration of IL‐17Ab after Aβ_1–42 injection reduced neurodegeneration, memory decline, and the levels of proinflammatory mediators and cytokines.Conclusion and implications: These findings suggest that the IL‐17Ab reduced neuroinflammation and behavioural symptoms induced by Aβ. The efficacy of IL‐17Ab IN administration in reducing Aβ_1–42 neurodegeneration points to a possible future therapeutic approach in patients with AD.Linked Articles: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc

Intrinsic homeostasis enables neuronal circuits to maintain activity levels within an appropriate range by modulating neuronal voltage‐gated conductances, but the signalling pathways involved in this process are largely unknown. We characterized the process of intrinsic homeostasis induced by sustained electrical activity in cultured hippocampal neurons based on the activation of the Repressor Element‐1 Silencing Transcription Factor/Neuron‐Restrictive Silencer Factor (REST/NRSF). We showed that 4‐aminopyridine‐induced hyperactivity enhances the expression of REST/NRSF, which in turn, reduces the expression of voltage‐gated Na+ channels, thereby decreasing the neuronal Na+ current density. This mechanism plays an important role in the downregulation of the firing activity at the single‐cell level, re‐establishing a physiological spiking activity in the entire neuronal network. Conversely, interfering with REST/NRSF expression impaired this homeostatic response. Our results identify REST/NRSF as a critical factor linking neuronal activity to the activation of intrinsic homeostasis and restoring a physiological level of activity in the entire neuronal network.

Significance: The six-layered cerebral cortex forms through tightly regulated steps including neuronal proliferation, migration, and circuitry formation. Alterations of cortical development are associated with several neurological conditions, but the underlying pathogenetic mechanisms remain largely unknown. Here, we describe the role of TBC1 domain family member 24(TBC1D24), a gene associated with syndromes combining epilepsy and cognitive deficits, in cortical development. Using an in vivo approach, we found that TBC1D24 regulates neuronal polarity, thus promoting neuronal migration and maturation. We further show that TBC1D24 exerts its function through the modulation of the activity of ADP ribosylation factor 6, a GTPase involved in membrane trafficking. Collectively, our data disclose a previously uncharacterized molecular mechanism involved in cortical development and underline how appropriate and timely neuronal positioning is essential for brain function.

The parallel fiber-Purkinje cell synapse represents the point of maximal signal divergence in the cerebellar cortex with an estimated number of about 60 billion synaptic contacts in the rat and 100,000 billions in humans. At the same time, the Purkinje cell dendritic tree is a site of remarkable convergence of more than 100,000 parallel fiber synapses. Parallel fibers activity generates fast postsynaptic currents via AMPA receptors, and slower signals, mediated by mGlu1 receptors, resulting in Purkinje cell depolarization accompanied by sharp calcium elevation within dendritic regions. Long-term depression and long-term potentiation have been widely described for the parallel fiber-Purkinje cell synapse and have been proposed as mechanisms for motor learning. The mechanisms of induction for LTP and LTD involve different signaling mechanisms within the presynaptic terminal and/or at the postsynaptic site, promoting enduring modification in the neurotransmitter release and change in responsiveness to the neurotransmitter. The parallel fiber-Purkinje cell synapse is finely modulated by several neurotransmitters, including serotonin, noradrenaline, and acetylcholine. The ability of these neuromodulators to gate LTP and LTD at the parallel fiber-Purkinje cell synapse could, at least in part, explain their effect on cerebellar-dependent learning and memory paradigms. Overall, these findings have important implications for understanding the cerebellar involvement in a series of pathological conditions, ranging from ataxia to autism. For example, parallel fiber-Purkinje cell synapse dysfunctions have been identified in several murine models of spinocerebellar ataxia (SCA) types 1, 3, 5 and 27. In some cases, the defect is specific for the AMPA receptor signaling (SCA27), while in others the mGlu1 pathway is affected (SCA1, 3, 5). Interestingly, the parallel fiber-Purkinje cell synapse has been shown to be hyper-functional in a mutant mouse model of autism spectrum disorder, with a selective deletion of Pten in Purkinje cells. However, the full range of methodological approaches, that allowed the discovery of the physiological principles of PF-PC synapse function, has not yet been completely exploited to investigate the pathophysiological mechanisms of diseases involving the cerebellum. We, therefore, propose to extend the spectrum of experimental investigations to tackle this problem.

The role of the cerebellum in Alzheimer’s disease (AD) has been neglected for a long time. Recent studies carried out using transgenic mouse models have demonstrated that amyloid-β (Aβ) is deposited in the cerebellum and affects synaptic transmission and plasticity, sometimes before plaque formation. A wide variability of motor phenotype has been observed in the different murine models of AD, without a consistent correlation with the extent of cerebellar histopathological changes or with cognitive deficits. The loss of noradrenergic drive may contribute to the impairment of cerebellar synaptic function and motor learning observed in these mice. Furthermore, cerebellar neurons, particularly granule cells, have been used as in vitro model of Aβ-induced neuronal damage. An unexpected conclusion is that the cerebellum, for a long time thought to be somehow protected from AD pathology, is actually considered as a region vulnerable to Aβ toxic damage, even at the early stage of the disease, with consequences on motor performance.