Neuro-Immune Cross-Talk in the Striatum: From Basal Ganglia Physiology to Circuit Dysfunction

Corrigendum: Altered expression of inflammation-associated molecules in striatum: an implication for sensitivity to heavy ion radiations

[This corrects the article DOI: 10.3389/fncel.2023.1252958.].

Functional correlates of cognitive abilities vary with age in pediatric multiple sclerosis

BACKGROUND

Pediatric multiple sclerosis (PedMS) can hamper brain maturation. Aim of this study was to assess the neuropsychological profile of PedMS patients and their resting-state functional connectivity (RS FC).

METHODS

We assessed intelligence quotient (IQ), executive speed, and language in 76 PedMS patients. On a 3.0T scanner RS FC of brain networks was estimated with a seed-based analysis (subset of 58 right-handed PedMS patients and 22 matched healthy controls). Comparisons were run between controls and PedMS (whole cohort and by age).

RESULTS

Ninety-five% of patients had normal IQ. The highest rate of failure was observed in executive speed. PedMS showed reduced RS FC in all networks than controls, especially in the basal ganglia. In younger patients (<16-year-old, n = 32) reduced RS FC in the basal ganglia, language, and sensorimotor networks associated with poorer cognitive performance (p < 0.05; r range: 0.39; 0.56). Older patients (≥16-year-old, n = 26) showed increased RS FC in the basal ganglia, default-mode, sensorimotor, executive, and language networks, associated with poorer performance in executive speed and language abilities (p < 0.05; r range: -0.40; -0.59). In both groups, lower RS FC of the caudate nucleus associated with poorer executive speed.

CONCLUSIONS

The effect of PedMS on RS FC is clinically relevant and differs according to patients' age.

Altered expression of inflammation-associated molecules in striatum: an implication for sensitivity to heavy ion radiations

Background and objective

Heavy ion radiation is one of the major hazards astronauts face during space expeditions, adversely affecting the central nervous system. Radiation causes severe damage to sensitive brain regions, especially the striatum, resulting in cognitive impairment and other physiological issues in astronauts. However, the intensity of brain damage and associated underlying molecular pathological mechanisms mediated by heavy ion radiation are still unknown. The present study is aimed to identify the damaging effect of heavy ion radiation on the striatum and associated underlying pathological mechanisms.

Materials and methods

Two parallel cohorts of rats were exposed to radiation in multiple doses and times. Cohort I was exposed to 15 Gy of 12C6+ ions radiation, whereas cohort II was exposed to 3.4 Gy and 8 Gy with 56Fe26+ ions irradiation. Physiological and behavioural tests were performed, followed by 18F-FDG-PET scans, transcriptomics analysis of the striatum, and in-vitro studies to verify the interconnection between immune cells and neurons.

Results

Both cohorts revealed more persistent striatum dysfunction than other brain regions under heavy ion radiation at multiple doses and time, exposed by physiological, behavioural, and 18F-FDG-PET scans. Transcriptomic analysis revealed that striatum dysfunction is linked with an abnormal immune system. In vitro studies demonstrated that radiation mediated diversified effects on different immune cells and sustained monocyte viability but inhibited its differentiation and migration, leading to chronic neuroinflammation in the striatum and might affect other associated brain regions.

Conclusion

Our findings suggest that striatum dysfunction under heavy ion radiation activates abnormal immune systems, leading to chronic neuroinflammation and neuronal injury.

Tourette syndrome and obsessive-compulsive disorder: A comprehensive review of structural alterations and neurological mechanisms

Currently, it is possible to study the pathogenesis of Tourette's syndrome (TS) in more detail, due to more advanced methods of neuroimaging. However, medical and surgical treatment options are limited by a lack of understanding of the nature of the disorder and its relationship to some psychiatric disorders, the most common of which is obsessive-compulsive disorder (OCD). It is believed that the origin of chronic tic disorders is based on an imbalance of excitatory and inhibitory influences in the Cortico-Striato-Thalamo-Cortical circuits (CSTC). The main CSTCs involved in the pathological process have been identified by studying structural and neurotransmitter disturbances in the interaction between the cortex and the basal ganglia. A neurotransmitter deficiency in CSTC has been demonstrated by immunohistochemical and genetic methods, but it is still not known whether it arises as a consequence of genetically determined disturbances of neuronal migration during ontogenesis or as a consequence of altered production of proteins involved in neurotransmitter production. The aim of this review is to describe current ideas about the comorbidity of TS with OCD, the involvement of CSTC in the pathogenesis of both disorders and the background of structural and neurotransmitter changes in CSTC that may serve as targets for drug and neuromodulatory treatments.

The Dysfunctional Mechanisms Throwing Tics: Structural and Functional Changes in Tourette Syndrome

Tourette Syndrome (TS) is a high-incidence multifactorial neuropsychiatric disorder characterized by motor and vocal tics co-occurring with several diverse comorbidities, including obsessive-compulsive disorder and attention-deficit hyperactivity disorder. The origin of TS is multifactorial, with strong genetic, perinatal, and immunological influences. Although almost all neurotransmettitorial systems have been implicated in TS pathophysiology, a comprehensive neurophysiological model explaining the dynamics of expression and inhibition of tics is still lacking. The genesis and maintenance of motor and non-motor aspects of TS are thought to arise from functional and/or structural modifications of the basal ganglia and related circuitry. This complex wiring involves several cortical and subcortical structures whose concerted activity controls the selection of the most appropriate reflexive and habitual motor, cognitive and emotional actions. Importantly, striatal circuits exhibit bidirectional forms of synaptic plasticity that differ in many respects from hippocampal and neocortical plasticity, including sensitivity to metaplastic molecules such as dopamine. Here, we review the available evidence about structural and functional anomalies in neural circuits which have been found in TS patients. Finally, considering what is known in the field of striatal plasticity, we discuss the role of exuberant plasticity in TS, including the prospect of future pharmacological and neuromodulation avenues.

Ameliorative effects of Fingolimod (FTY720) on microglial activation and psychosis-related behavior in short term cuprizone exposed mice

Schizophrenia is a psychiatric disorder that affects around 1% of the population in widespread populations, with severe cases leading to long-term hospitalization and necessitation of lifelong treatment. Recent studies on schizophrenia have highlighted the involvement of inflammatory and immunoregulatory mechanisms with the onset of symptoms, and the usage of anti-inflammatory treatments are being tested against periods of rapid psychosis. In the central nervous system, microglia are the innate immune population which are activated in response to a wide range of physical and psychological stress factors and produce proinflammatory mediators such as cytokines. Microglial activation and neuroinflammation has been associated to numerous psychiatric disorders including schizophrenia, especially during psychotic episodes. Thus, novel treatments which dampen microglial activation may be of great relevance in the treatment of psychiatric disorders. Fingolimod (FTY720) is a drug used as an immunosuppressive treatment to multiple sclerosis. Recent clinical trials have focused on FTY720 as a treatment for the behavioral symptoms in schizophrenia. However, the mechanisms of Fingolimod in treating the symptoms of schizophrenia are not clear. In this study we use a recently developed neuroinflammatory psychosis model in mice: cuprizone short-term exposure, to investigate the effects of FTY720 administration. FTY720 administration was able to completely alleviate methamphetamine hypersensitivity caused by cuprizone exposure. Moreover, administration of FTY720 improved multiple measures of neuroinflammation (microglial activation, cytokine production, and leucocyte infiltration). In conclusion, our results highlight the future use of FTY720 as a direct anti-inflammatory treatment against microglial activation and psychosis.

Non-competitive AMPA glutamate receptors antagonism by perampanel as a strategy to counteract hippocampal hyper-excitability and cognitive deficits in cerebral amyloidosis

Pathological accumulation of Aβ oligomers has been linked to neuronal networks hyperexcitability, potentially underpinned by glutamatergic AMPA receptors (AMPARs) dysfunction. We aimed to investigate whether the non-competitive block of AMPARs was able to counteract the alteration of hippocampal epileptic threshold, and of synaptic plasticity linked to Aβ oligomers accumulation, being this glutamate receptor a valuable specific therapeutic target. In this work, we showed that the non-competitive AMPARs antagonist perampanel (PER) which, per se, did not affect physiological synaptic transmission, was able to counteract Aβ-induced hyperexcitability. Moreover, AMPAR antagonism was able to counteract Aβ-induced hippocampal LTP impairment and hippocampal-based cognitive deficits in Aβ oligomers-injected mice, while retaining antiseizure efficacy. Beside this, AMPAR antagonism was also able to reduce the increased expression of proinflammatory cytokines in this mice model, also suggesting the presence of an anti-inflammatory activity. Thus, targeting AMPARs might be a valuable strategy to reduce both hippocampal networks hyperexcitability and synaptic plasticity deficits induced by Aβ oligomers accumulation.

Glutamatergic neurotransmission: A potential pharmacotherapeutic target for the treatment of cognitive disorders

In the mammalian brain, glutamate is regarded to be the primary excitatory neurotransmitter due to its widespread distribution and wide range of metabolic functions. Glutamate plays key roles in regulating neurogenesis, synaptogenesis, neurite outgrowth, and neuron survival in the brain. Ionotropic and metabotropic glutamate receptors, neurotransmitters, neurotensin, neurosteroids, and others co-ordinately formulate a complex glutamatergic network in the brain that maintains optimal excitatory neurotransmission. Cognitive activities are potentially synchronized by the glutamatergic activities in the brain via restoring synaptic plasticity. Dysfunctional glutamate receptors and other glutamatergic components are responsible for the aberrant glutamatergic activity in the brain that cause cognitive impairments, loss of synaptic plasticity, and neuronal damage. Thus, controlling the brain's glutamatergic transmission and modifying glutamate receptor function could be a potential therapeutic strategy for cognitive disorders. Certain drugs that regulate glutamate receptor activities have shown therapeutic promise in improving cognitive functions in preclinical and clinical studies. However, several issues regarding precise functional information of glutamatergic activity are yet to be comprehensively understood. The present article discusses the scope of developing glutamatergic systems as prospective pharmacotherapeutic targets to treat cognitive disorders. Special attention has been given to recent developments, challenges, and future prospects.

Acute intranasal treatment with nerve growth factor limits the onset of traumatic brain injury in young rats

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) comprises a primary injury directly induced by impact, which progresses into a secondary injury leading to neuroinflammation, reactive astrogliosis, and cognitive and motor damage. To date, treatment of TBI consists solely of palliative therapies that do not prevent and/or limit the outcomes of secondary damage and only stabilize the deficits. The neurotrophin, nerve growth factor (NGF), delivered to the brain parenchyma following intranasal application, could be a useful means of limiting or improving the outcomes of the secondary injury, as suggested by pre-clinical and clinical data.

EXPERIMENTAL APPROACH

We evaluated the effect of acute intranasal treatment of young (20-postnatal day) rats, with NGF in a TBI model (weight drop/close head), aggravated by hypoxic complications. Immediately after the trauma, rats were intranasally treated with human recombinant NGF (50 μg·kg^-1 ), and motor behavioural test, morphometric and biochemical assays were carried out 24 h later.

KEY RESULTS

Acute intranasal NGF prevented the onset of TBI-induced motor disabilities, and decreased reactive astrogliosis, microglial activation and IL-1β content, which after TBI develops to the same extent in the impact zone and the hypothalamus.

CONCLUSION AND IMPLICATIONS

Intranasal application of NGF was effective in decreasing the motor dysfunction and neuroinflammation in the brain of young rats in our model of TBI. This work forms an initial pre-clinical evaluation of the potential of early intranasal NGF treatment in preventing and limiting the disabling outcomes of TBI, a clinical condition that remains one of the unsolved problems of paediatric neurology.

Immunology and microbiome: Implications for motor systems

Immune-inflammatory mechanisms seem to play a relevant role in neurodegenerative disorders affecting motor systems, particularly Parkinson's disease, where activity changes in inflammatory cells and evidence of neuroinflammation in experimental models and patients is available. Amyotrophic lateral sclerosis is also characterized by neuroinflammatory changes that involve primarily glial cells, both microglia and astrocytes, as well as systemic immune dysregulation associated with more rapid progression. Similarly, the exploration of gut dysbiosis in these two prototypical neurodegenerative motor disorders is advancing rapidly. Altered composition of gut microbial constituents and related metabolic and putative functional pathways is supporting a pathophysiological link that is currently explored in preclinical, germ-free animal models. Less compelling, but still intriguing, evidence suggests that motor neurodevelopmental disorders, e.g., Tourette syndrome, are associated with abnormal trajectories of maturation that include also immune system development. Microglia has a key role also in these disorders, and new therapeutic avenues aiming at its modulation are exciting prospects. Preclinical and clinical research on the role of gut dysbiosis in Tourette syndrome and related behavioral disorders is still in its infancy, but early findings support the rationale to delve deeper into its contribution to neural and immune maturation abnormalities in its spectrum.

Ca2+-modulated photoactivatable imaging reveals neuron-astrocyte glutamatergic circuitries within the nucleus accumbens

Astrocytes are key elements of brain circuits that are involved in different aspects of the neuronal physiology relevant to brain functions. Although much effort is being made to understand how the biology of astrocytes affects brain circuits, astrocytic network heterogeneity and plasticity is still poorly defined. Here, we have combined structural and functional imaging of astrocyte activity recorded in mice using the Ca²⁺-modulated photoactivatable ratiometric integrator and specific optostimulation of glutamatergic pathways to map the functional neuron-astrocyte circuitries in the nucleus accumbens (NAc). We showed pathway-specific astrocytic responses induced by selective optostimulation of main inputs from the prefrontal cortex, basolateral amygdala, and ventral hippocampus. Furthermore, co-stimulation of glutamatergic pathways induced non-linear Ca²⁺-signaling integration, revealing integrative properties of NAc astrocytes. All these results demonstrate the existence of specific neuron-astrocyte circuits in the NAc, providing an insight to the understanding of how the NAc integrates information.

Neuron-astrocyte communication is fundamental for brain physiology, yet the heterogeneity in the functional interaction between these two elements remains poorly understood. Here we show how different neuron-astrocyte networks integrate information from distinct glutamatergic inputs.

Markers of Neuroinflammation and Apoptosis in the Temporal Lobe of Patients with Drug-Resistant Epilepsy

Abstract

Current antiepileptic strategies aim to normalize the interaction of the excitatory and inhibitory systems, which is ineffective in treating patients with drug-resistant epilepsy. Neuroinflammatory processes in the epileptic focus and its perifocal area can trigger apoptosis and also contribute to the development of drug resistance. The level of pro- and anti-apoptotic proteins (p-NF-kB, TNF-α, p53, FAS, caspase-3, caspase-9) was analyzed in intraoperative biopsies of the temporal lobe gray and white matter in the brain of patients with drug-resistant epilepsy. An increased level of pro-apoptotic proteins was revealed in the cortex and perifocal area’s white matter against the background of an imbalance of protective anti-apoptotic proteins. It appears that the activation of the extrinsic pathway of apoptosis occurs in the perifocal area, while in the epileptic focus, there are proteins responsible for the activation of the anti-apoptotic survival pathways. Active neuroinflammation in the epileptic focus and perifocal area of the temporal lobe may contribute to the development of the resistance to antiepileptic drugs and the progression of neurodegeneration in such patients.

Synaptic Dysfunction in Multiple Sclerosis: A Red Thread from Inflammation to Network Disconnection

Multiple sclerosis (MS) has been clinically considered a chronic inflammatory disease of the white matter; however, in the last decade growing evidence supported an important role of gray matter pathology as a major contributor of MS-related disability and the involvement of synaptic structures assumed a key role in the pathophysiology of the disease. Synaptic contacts are considered central units in the information flow, involved in synaptic transmission and plasticity, critical processes for the shaping and functioning of brain networks. During the course of MS, the immune system and its diffusible mediators interact with synaptic structures leading to changes in their structure and function, influencing brain network dynamics. The purpose of this review is to provide an overview of the existing literature on synaptic involvement during experimental and human MS, in order to understand the mechanisms by which synaptic failure eventually leads to brain networks alterations and contributes to disabling MS symptoms and disease progression.

Central nervous system atrophy predicts future dynamics of disability progression in a real-world multiple sclerosis cohort

Background and purpose

In an era of individualized multiple sclerosis (MS) patient management, biomarkers for accurate prediction of future clinical outcomes are needed. We aimed to evaluate the potential of short‐term magnetic resonance imaging (MRI) atrophy measures and serum neurofilament light chain (sNfL) as predictors of the dynamics of disability accumulation in relapse‐onset MS.

Methods

Brain gray and white matter, thalamic, striatal, pallidal and cervical spinal cord volumes, and lesion load were measured over three available time points (mean time span 2.24 ± 0.70 years) for 183 patients (140 relapsing‐remitting [RRMS] and 43 secondary‐progressive MS (SPMS); 123 female, age 46.4 ± 11.0 years; disease duration 15.7 ± 9.3 years), and their respective annual changes were calculated. Baseline sNfL was also measured at the third available time point for each patient. Subsequently, patients underwent annual clinical examinations over 5.4 ± 3.7 years including Expanded Disability Status Scale (EDSS) scoring, the nine‐hole peg test and the timed 25‐foot walk test.

Results

Higher annual spinal cord atrophy rates and lesion load increase predicted higher future EDSS score worsening over time in SPMS. Lower baseline thalamic volumes predicted higher walking speed worsening over time in RRMS. Lower baseline gray matter, as well as higher white matter and spinal cord atrophy rates, lesion load increase, baseline striatal volumes and baseline sNfL, predicted higher future hand dexterity worsening over time. All models showed reasonable to high prediction accuracy.

Conclusion

This study demonstrates the capability of short‐term MRI metrics to accurately predict future dynamics of disability progression in a real‐world relapse‐onset MS cohort. The present study represents a step towards the utilization of structural MRI measurements in patient care.

Alpha-Synuclein as a Prominent Actor in the Inflammatory Synaptopathy of Parkinson's Disease

Parkinson’s disease (PD) is considered the most common disorder of synucleinopathy, which is characterised by intracellular inclusions of aggregated and misfolded α-synuclein (α-syn) protein in various brain regions, and the loss of dopaminergic neurons. During the early prodromal phase of PD, synaptic alterations happen before cell death, which is linked to the synaptic accumulation of toxic α-syn specifically in the presynaptic terminals, affecting neurotransmitter release. The oligomers and protofibrils of α-syn are the most toxic species, and their overexpression impairs the distribution and activation of synaptic proteins, such as the SNARE complex, preventing neurotransmitter exocytosis and neuronal synaptic communication. In the last few years, the role of the immune system in PD has been increasingly considered. Microglial and astrocyte activation, the gene expression of proinflammatory factors, and the infiltration of immune cells from the periphery to the central nervous system (CNS) represent the main features of the inflammatory response. One of the actors of these processes is α-syn accumulation. In light of this, here, we provide a systematic review of PD-related α-syn and inflammation inter-players.