Non-canonical adrenergic neuromodulation of motoneuron intrinsic excitability through ß-receptors in wild-type and ALS mice.

Altered neuronal excitability and synaptic inputs to motoneurons are part of the pathophysiology of Amyotrophic Lateral Sclerosis. The cAMP/PKA pathway regulates both of them but therapeutic interventions at this level are limited by the lack of knowledge about suitable pharmacological entry points. Here we used transcriptomics on microdissected and in situ motoneurons to reveal the modulation of PKA-coupled receptorome in SOD1(G93A) ALS mice, vs WT, demonstrating the dysregulation of multiple PKA-coupled GPCRs, in particular on vulnerable MNs, and the relative sparing of ß-adrenergic receptors. In vivo MN electrophysiology showed that ß2/ß3 agonists acutely increase excitability, in particular the input/output relationship, demonstrating a non-canonical adrenergic neuromodulation mediated by ß2/ß3 receptors both in WT and SOD1 mice. The excitability increase corresponds to the upregulation of immediate-early gene expression and dysregulation of ion channels transcriptome. However the ß2/ß3 neuromodulation is submitted to a strong homeostasis, since a ten days delivery of ß2/ß3 agonists results in an abolition of the excitability increase. The homeostatic response is largely caused by a substantial downregulation of PKA-coupled GPCRs in MNs from WT and SOD1 mice. Thus, ß-adrenergic receptors are physiologically involved in the regulation of MN excitability and transcriptomics, but, intriguingly, a strong homeostatic response is triggered upon chronic pharmacologic intervention.

Differential effect of ethanol intoxication on peripheral markers of cerebral injury in murine blunt traumatic brain injury.

BACKGROUND: Blood-based biomarkers have proven to be a reliable measure of the severity and outcome of traumatic brain injury (TBI) in both murine models and patients. In particular, neuron-specific enolase (NSE), neurofilament light (NFL) and S100 beta (S100B) have been investigated in the clinical setting post-injury. Ethanol intoxication (EI) remains a significant comorbidity in TBI, with 30-40% of patients having a positive blood alcohol concentration post-TBI. The effect of ethanol on blood-based biomarkers for the prognosis and diagnosis of TBI remains unclear. In this study, we investigated the effect of EI on NSE, NFL and S100B and their correlation with blood-brain barrier integrity in a murine model of TBI. METHODS: We used ultra-sensitive single-molecule array technology and enzyme-linked immunosorbent assay methods to measure NFL, NSE, S100B and claudin-5 concentrations in plasma 3 hours post-TBI. RESULTS: We showed that NFL, NSE and S100B were increased at 3 hours post-TBI. Interestingly, ethanol blood concentrations showed an inverse correlation with NSE but not with NFL or S100B. Claudin-5 levels were increased post-injury but no difference was detected compared to ethanol pretreatment. The increase in claudin-5 post-TBI was correlated with NFL but not with NSE or S100B. CONCLUSIONS: Ethanol induces an effect on biomarker release in the bloodstream that is different from TBI not influenced by alcohol. This could be the basis of investigations into humans.

Parvalbumin Interneurons Shape Neuronal Vulnerability in Blunt TBI.

Excessive excitation has been hypothesized to subsume a significant part of the acute damage occurring after traumatic brain injury (TBI). However, reduced neuronal excitability, loss of neuronal firing, and a disturbed excitation/inhibition balance have been detected. Parvalbumin (PV) interneurons are major regulators of perisomatic inhibition, principal neurons firing, and overall cortical excitability. However, their role in acute TBI pathogenic cascades is unclear. We exploited the chemogenetic Pharmacologically Selective Activation Module and Pharmacologically Selective Effector Module control of PV-Cre+ neurons and the Designer Receptors Exclusively Activated by Designer Drug (DREADD) control of principal neurons in a blunt model of TBI to explore the role of inhibition in shaping neuronal vulnerability to TBI. We demonstrated that inactivation of PV interneurons at the instance or soon after trauma enhances survival of principal neurons and reduces gliosis at 7 dpi whereas, activation of PV interneurons decreased neuronal survival. The protective effect of PV inactivation was suppressed by expressing the nuclear calcium buffer PV-nuclear localisation sequence in principal neurons, implying an activity-dependent neuroprotective signal. In fact, protective effects were obtained by increasing the excitability of principal neurons directly using DREADDs. Thus, we show that sustaining neuronal excitation in the early phases of TBI may reduce neuronal vulnerability by increasing activity-dependent survival, while excess activation of perisomatic inhibition is detrimental to neuronal integrity.

Neuroprotective effect of acute ethanol intoxication in TBI is associated to the hierarchical modulation of early transcriptional responses.

Ethanol intoxication is a risk factor for traumatic brain injury (TBI) but clinical evidence suggests that it may actually improve the prognosis of intoxicated TBI patients. We have employed a closed, weight-drop TBI model of different severity (2cm or 3cm falling height), preceded (-30min) or followed (+20min) by ethanol administration (5g/Kg). This protocol allows us to study the interaction of binge ethanol intoxication in TBI, monitoring behavioral changes, histological responses and the transcriptional regulation of a series of activity-regulated genes (immediate early genes, IEGs). We demonstrate that ethanol pretreatment before moderate TBI (2cm) significantly reduces neurological impairment and accelerates recovery. In addition, better preservation of neuronal numbers and cFos+cells was observed 7days after TBI. At transcriptional level, ethanol reduced the upregulation of a subset of IEGs encoding for transcription factors such as Atf3, c-Fos, FosB, Egr1, Egr3 and Npas4 but did not affect the upregulation of others (e.g. Gadd45b and Gadd45c). While a subset of IEGs encoding for effector proteins (such as Bdnf, InhbA and Dusp5) were downregulated by ethanol, others (such as Il-6) were unaffected. Notably, the majority of genes were sensitive to ethanol only when administered before TBI and not afterwards (the exceptions being c-Fos, Egr1 and Dusp5). Furthermore, while severe TBI (3cm) induced a qualitatively similar (but quantitatively larger) transcriptional response to moderate TBI, it was no longer sensitive to ethanol pretreatment. Thus, we have shown that a subset of the TBI-induced transcriptional responses were sensitive to ethanol intoxication at the instance of trauma (ultimately resulting in beneficial outcomes) and that the effect of ethanol was restricted to a certain time window (pre TBI treatment) and to TBI severity (moderate). This information could be critical for the translational value of ethanol in TBI and for the design of clinical studies aimed at disentangling the role of ethanol intoxication in TBI.

Acute ethanol administration results in a protective cytokine and neuroinflammatory profile in traumatic brain injury.

Ethanol intoxication is a common comorbidity in traumatic brain injury. To date, the effect of ethanol on TBI pathogenic cascades and resulting outcomes remains debated. A closed blunt weight-drop murine TBI model has been implemented to investigate behavioral (by sensorimotor and neurological tests), and neuro-immunological (by tissue cytokine arrays and immuno-histology) effects of ethanol intoxication on TBI. The effect of the occurrence of traumatic intracerebral hemorrhage was also studied. The results indicate that ethanol pretreatment results in a faster and better recovery after TBI with reduced infiltration of leukocytes and reduced microglia activation. These outcomes correspond to reduced parenchymal levels of GM-CSF, IL-6 and IL-3 and to the transient upregulation of IL-13 and VEGF, indicating an early shift in the cytokine profile towards reduced inflammation. A significant difference in the cytokine profile was still observed 24h post injury in the ethanol pretreated mice, as shown by the delayed peak in IL-6 and by the suppression of GM-CSF, IFN-γ, and IL-3. Seven days post-injury, ethanol-pretreated mice displayed a significant decrease both in CD45+ cells infiltration and in microglial activation. On the other hand, in the case of traumatic intracerebral hemorrhage, the cytokine profile was dominated by KC, CCL5, M-CSF and several interleukins and ethanol pretreatment did not produce any modification. We can thus conclude that ethanol intoxication suppresses the acute neuro-inflammatory response to TBI, an effect which is correlated with a faster and complete neurological recovery, whereas, the presence of traumatic intracerebral hemorrhage overrides the effects of ethanol.