IL-4 shapes microglia-dependent pruning of the cerebellum during postnatal development

Early-life IL-4 administration induces long-term changes in microglia in the cerebellum and prefrontal cortex

Microglia are crucial for brain development and their function can be impacted by postnatal insults, such as early-life allergies. These are characterized by an upregulation of interleukin (IL)-4 levels. Allergies share a strong comorbidity with Autism Spectrum Disorders (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD). We previously showed that early-life allergic asthma induces hyperactive and impulsive behaviors in mice. This phenotype was reproduced in animals administered with IL-4 in the second postnatal week. Mechanistically, elevated IL-4 levels prevented microglia-mediated engulfment of neurons in the cerebellum, resulting in a surplus of granule cells and consequent dysfunction in cerebellar connectivity. Here, we aimed to further understand the impact of early IL-4 administration in microglia of the cerebellum and the prefrontal cortex (PFC), two brain regions with protracted developmental programs and susceptible to immune system malfunction after birth. While IL-4 administration induced differential short-term effects on microglia in the cerebellum and PFC, both regions presented similar microglial features in adult mice. Although Sholl analysis did not reveal significant alterations in overall microglia morphology at postnatal day (P)10, the density of microglia was decreased in the cerebellum at this age, especially in the granular layer (GL), but remained unaltered in the PFC. Interestingly, the presence of microglia with phagocytic cups, morphological features important for whole-cell engulfment, was decreased in both regions. When assessing the long-term consequences of IL-4 administration, cerebellar and PFC microglia were hypo-ramified and exhibited increased overall density. Importantly, microglia alterations were exclusive to the GL of the cerebellum and the infralimbic region of the PFC. Our results show that postnatal elevated levels of IL-4 impair the percentage of microglia engaged in cell clearing in two brain regions with protracted developmental programs. Interestingly, IL-4-exposed microglia adapt a similar phenotype in the adult cerebellum and PFC. Our data suggest that this early-life increase in IL-4 levels is sufficient to elicit long-lasting alterations in microglia, potentially increasing cell susceptibility to later insults.

Variations in inflammatory regulators in male patients with chronic schizophrenia associated with psychopathology and cognitive deficits

BACKGROUND

Immune dysregulation has been identified as a contributing factor in the pathophysiology of schizophrenia. This study aimed to investigate variations in specific immune regulators and their correlation with psychopathology and cognitive functions in male patients with chronic schizophrenia.

METHODS

Employing a cross-sectional design, this study included 72 male patients with chronic schizophrenia. The Positive and Negative Syndrome Scale (PANSS) and the Repeatable Battery for the Assessment of Neuropsychological Status were utilized to assess psychopathology and cognitive functions, respectively.

RESULTS

Serum levels of interleukin (IL)-4, IL-10, IL-12p40, IL-13, and monocyte chemoattractant protein-1 (MCP-1) were measured. There were significantly increased levels of IL-4, IL-13, and MCP-1, alongside decreased levels of IL-10 in patients compared to controls (all P < 0.05). IL-4 levels showed a significant negative association with PANSS positive symptoms (beta=-0.222, P = 0.042). After controlling for antipsychotic medication, BMI, and smoking, this correlation was no longer significant (r=-0.232, P = 0.055). Additionally, positive correlations of IL-4 (beta = 0.297, P = 0.008), IL-13 (beta = 0.371, P = 0.001), and MCP-1 (beta = 0.280, P = 0.013) with language scores were observed. Increased levels of IL-4 (P = 0.044, OR = 1.994), IL-13 (P = 0.019, OR = 2.245), as well as IL-4 and MCP-1 interactions (P = 0.043, OR = 2.000) were positively associated with the risk of chronic schizophrenia, while lower levels of IL-10 (P = 0.003, OR = 0.2.867) were also linked to an increased risk.

CONCLUSION

The identified associations between specific immune markers and the clinical and cognitive features of chronic schizophrenia in males underscored the potential immune-mediated mechanisms underlying schizophrenia.

Increased understanding of complex neuronal circuits in the cerebellar cortex

The prevailing belief has been that the fundamental structures of cerebellar neuronal circuits, consisting of a few major neuron types, are simple and well understood. Given that the cerebellum has long been known to be crucial for motor behaviors, these simple yet organized circuit structures seemed beneficial for theoretical studies proposing neural mechanisms underlying cerebellar motor functions and learning. On the other hand, experimental studies using advanced techniques have revealed numerous structural properties that were not traditionally defined. These include subdivided neuronal types and their circuit structures, feedback pathways from output Purkinje cells, and the multidimensional organization of neuronal interactions. With the recent recognition of the cerebellar involvement in non-motor functions, it is possible that these newly identified structural properties, which are potentially capable of generating greater complexity than previously recognized, are associated with increased information capacity. This, in turn, could contribute to the wide range of cerebellar functions. However, it remains largely unknown how such structural properties contribute to cerebellar neural computations through the regulation of neuronal activity or synaptic transmissions. To promote further research into cerebellar circuit structures and their functional significance, we aim to summarize the newly identified structural properties of the cerebellar cortex and discuss future research directions concerning cerebellar circuit structures and their potential functions.

Omalizumab in combination with subcutaneous immunotherapy for the treatment of multiple allergies associated with attention-deficit/hyperactivity disorder: a case report and a literature review

We describe the case of a 10-year-old boy with asthma (AS), accompanied by allergic rhinitis (AR), food allergy (FA), and combined attention-deficit/hyperactivity disorder (ADHD), who was treated at Shanghai Renji Hospital on 11 July 2020. The efficiency of the previous treatment with salmeterol/ticlosone was poor. Treatment with montelukast sodium resulted in development of neurological symptoms. Treatment with omalizumab in combination with subcutaneous immunotherapy (SCIT) was then initiated in our department based on anti-asthmatic therapy. Symptoms of asthma were completely controlled, and FA and AR symptoms improved. The treatment regimen led to a significant improvement in ADHD symptoms and the overall quality of life of the patient. The literature search was done in the PubMed database using "attention deficit/hyperactivity disorder/ADHD" and "asthma" as keywords, and we identified 47 relevant articles. In conclusion, our results show that treating asthma with omalizumab in combination with salmeterol/ticlosone and SCIT is efficient in controlling symptoms of multiple allergies and may lead to the improvement in ADHD symptoms and the overall quality of life of pediatric patients with ADHD. While current studies suggest that allergic diseases are closely related to ADHD, there is still a lack of studies or case reports of complete treatment protocols to provide clinical clues for management of the disease.

Offspring behavioral outcomes following maternal allergic asthma in the IL-4-deficient mouse

Maternal allergic asthma (MAA) during pregnancy has been associated with increased risk of neurodevelopmental disorders in humans, and rodent studies have demonstrated that inducing a T helper-2-mediated allergic response during pregnancy leads to an offspring behavioral phenotype characterized by decreased social interaction and increased stereotypies. The interleukin (IL)-4 cytokine is hypothesized to mediate the neurobehavioral impact of MAA on offspring. Utilizing IL-4 knockout mice, this study assessed whether MAA without IL-4 signaling would still impart behavioral deficits. C57 and IL-4 knockout female mice were sensitized to ovalbumin, exposed to repeated MAA inductions, and their offspring performed social, cognitive, and motor tasks. Only C57 offspring of MAA dams displayed social and cognitive deficits, while IL-4 knockout mice showed altered motor activity compared with C57 mice. These findings highlight a key role for IL-4 signaling in MAA-induced behavioral deficits and more broadly in normal brain development.

Metabolic dynamics in astrocytes and microglia during post-natal development and their implications for autism spectrum disorders

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by elusive underlying mechanisms. Recent attention has focused on the involvement of astrocytes and microglia in ASD pathology. These glial cells play pivotal roles in maintaining neuronal homeostasis, including the regulation of metabolism. Emerging evidence suggests a potential association between ASD and inborn errors of metabolism. Therefore, gaining a comprehensive understanding of the functions of microglia and astrocytes in ASD is crucial for the development of effective therapeutic interventions. This review aims to provide a summary of the metabolism of astrocytes and microglia during post-natal development and the evidence of disrupted metabolic pathways in ASD, with particular emphasis on those potentially important for the regulation of neuronal post-natal maturation by astrocytes and microglia.