Neuritogenic function of microglia in maternal immune activation and autism spectrum disorders

Sleep deprivation from mid-gestation leads to impaired of motor coordination in young offspring mice with microglia activation in the cerebellar vermis

OBJECTIVE

To investigate the effects of mid-pregnancy sleep deprivation (SD) in C57BL/6 J mice on the motor coordination of the offspring and to explore the potential mechanism of microglia activation in the cerebellar vermis of the offspring involved in the induction of impaired motor coordination development.

METHODS

C57BL/6 J pregnant mice were randomly divided into the SD and control groups. SD was implemented by the multi-platform method from first day of the middle pregnancy (gestation day 8, GD8). At postnatal day 21 (PND21), we measured the development of motor behavior and collected cerebellar vermis tissues to observe the activation of microglia by H&E staining, the expression of microglia-specific markers ionized calcium-binding adaptor molecule-1 (Iba-1) and cluster of differentiation 68 (CD68) by immunohistochemical, and interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor -α (TNF-α) by real-time quantitative PCR (RT-qPCR).

RESULTS

In the offspring of SD group, comparing to the control group, the total time of passage and the reverse crawl distance in the balance beam test, and the frequency of falls from the suspension cord was increased; with lower max rotational speed and shorter duration in the rotarod experiment. Further, we found that the microglia of cerebellar vermis tissues emerged an amoeba-like activation. The mean gray value of Iba-1 was lower, the density of positive cells of CD68 and the expression levels of IL-6 and TNF-α were increased.

CONCLUSIONS

The motor coordination of offspring is impaired, accompanying a SD from mid-pregnancy, and the cerebellar vermis showed microglia activation and pro-inflammatory response. It suggested the adverse effects of SD from mid-gestation on the development of motor coordination through the inflammatory response in the cerebellar vermis of the offspring.

Inflammation and the Potential Implication of Macrophage-Microglia Polarization in Human ASD: An Overview

Autism spectrum disorder (ASD) is a heterogeneous collection of neurodevelopmental disorders, difficult to diagnose and currently lacking treatment options. The possibility of finding reliable biomarkers useful for early identification would offer the opportunity to intervene with treatment strategies to improve the life quality of ASD patients. To date, there are many recognized risk factors for the development of ASD, both genetic and non-genetic. Although genetic and epigenetic factors may play a critical role, the extent of their contribution to ASD risk is still under study. On the other hand, non-genetic risk factors include pollution, nutrition, infection, psychological states, and lifestyle, all together known as the exposome, which impacts the mother's and fetus's life, especially during pregnancy. Pathogenic and non-pathogenic maternal immune activation (MIA) and autoimmune diseases can cause various alterations in the fetal environment, also contributing to the etiology of ASD in offspring. Activation of monocytes, macrophages, mast cells and microglia and high production of pro-inflammatory cytokines are indeed the cause of neuroinflammation, and the latter is involved in ASD's onset and development. In this review, we focused on non-genetic risk factors, especially on the connection between inflammation, macrophage polarization and ASD syndrome, MIA, and the involvement of microglia.

Microglial WNT5A supports dendritic spines maturation and neuronal firing

There is increasing evidence showing that microglia play a critical role in mediating synapse formation and spine growth, although the molecular mechanism remains elusive. Here, we demonstrate that the secreted morphogen WNT family member 5A (WNT5A) is the most abundant WNT expressed in microglia and that it promotes neuronal maturation. Co-culture of microglia with Thy1-YFP+ differentiated neurons significantly increased neuronal spine density and reduced dendritic spine turnover rate, which was diminished by silencing microglial Wnt5a in vitro. Co-cultured microglia increased post-synaptic marker PSD95 and synaptic density as determined by the co-localization of PSD95 with pre-synaptic marker VGLUT2 in vitro. The silencing of Wnt5a expression in microglia partially reduced both PSD95 and synaptic densities. Co-culture of differentiated neurons with microglia significantly enhanced neuronal firing rate as measured by multiple electrode array, which was significantly reduced by silencing microglial Wnt5a at 23 days differentiation in vitro. These findings demonstrate that microglia can mediate spine maturation and regulate neuronal excitability via WNT5A secretion indicating possible pathological roles of dysfunctional microglia in developmental disorders.

Dynamic changes in spatiotemporal transcriptome reveal maternal immune dysregulation of autism spectrum disorder

Maternal immune activation (MIA) during pregnancy is known to be an environmental risk factor for neurodevelopment and autism spectrum disorder (ASD). However, it is unclear at which fetal brain developmental windows and regions MIA induces ASD-related neurodevelopmental transcriptional abnormalities. The non-chasm differentially expressed genes (DEGs) involved in MIA inducing ASD during fetal brain developmental windows were identified by performing the differential expression analysis and comparing the common DEGs among MIA at four different gestational development windows, ASD with multiple brain regions from human patients and mouse models, and human and mouse embryonic brain developmental trajectory. The gene set and functional enrichment analyses were performing to identify MIA dysregulated ASD-related the fetal neurodevelopmental windows and brain regions and function annotations. Additionally, the networks were constructed using Cytoscape for visualization. MIA at E12.5 and E14.5 increased the risk of distinct brain regions for ASD. MIA-driven transcriptional alterations of non-chasm DEGs, during the coincidence brain developmental windows between human and mice, involving ASD-relevant synaptic components, as well as immune- and metabolism-related functions and pathways. Furthermore, a great number of non-chasm brain development-, immune-, and metabolism-related DEGs were overlapped in at least two existing ASD-associated databases, suggesting that the others could be considered as the candidate targets to construct the model mice for explaining the pathological changes of ASD when environmental factors (MIA) and gene mutation effects co-occur. Overall, our search supported that transcriptome-based MIA dysregulated the brain development-, immune-, and metabolism-related non-chasm DEGs at specific embryonic brain developmental window and region, leading to abnormal embryonic neurodevelopment, to induce the increasing risk of ASD.

Microglial Responses and Pain Behaviors Are Exacerbated by Chronic Sleep Deprivation in Rats with Chronic Pain Via Neuroinflammatory Pathways

The inflammatory response of central nervous system (CNS) and microglial activation is important in the development of pain behaviors induced by sleep deprivation. We found that chronic sleep deprivation (CSD) aggravated pain behaviors in rats with chronic pain by upregulating expression of Toll-like receptor 4 (TLR4), NOD-like receptor pyrin domain containing 3 (NLRP3), and interleukin 1β (IL-1β), which promoted microglial activation in the brain. We also found that CSD increased numbers of Iba1⁺ and TLR4⁺ cells, as well as neuronal apoptosis. Inhibitors of TLR4 and NLRP3 (TAK-242 and MCC950, respectively) reduced expression levels of inflammatory factor proteins and M1-related factor mRNA, decreased microglial activation, and relieved the hyperalgesia caused by CSD. These results suggest that CSD aggravated pain behavior in rats with chronic pain through the TLR4/NLRP3/IL-1β signaling pathway, which mediates microglial activation and promotes CNS inflammation and neuronal apoptosis.