Microglia at the Centre of Brain Research: Accomplishments and Challenges for the Future

Nrf2 Ameliorates Sevoflurane-Induced Cognitive Deficits in Aged Mice by Inhibiting Neuroinflammation in the Hippocampus

Perioperative neurocognitive disorders (PND), common complications that occur after anesthetized surgery in elderly patients, are major challenges to our rapidly growing aging population. The transcription factor known as nuclear factor erythroid-2-related factor 2 (Nrf2) is an essential component of the cellular antioxidant response, purportedly contributing to the preservation of cognitive functions such as learning and memory. Nevertheless, the function and intracellular processes involving Nrf2 in PND remain largely unknown. Therefore, we evaluate the influence and fundamental mechanism of Nrf2 on PND in aged mice. To establish the postoperative neurocognitive dysfunction (PND) model, aged mice were subjected to anesthesia via inhalation of 3% sevoflurane for a duration of 2 h. The role of Nrf2 in PND was investigated by administering microinjections of either the adeno-associated virus (AAV)-Nrf2 vector or a null virus vector into the hippocampal CA1 region of aged mice 28 days before exposure to sevoflurane. Various assays including enzyme-linked immunosorbent assay (ELISA), immunofluorescence staining, and western blotting were employed to assess levels of pro-inflammatory cytokines, microglial activation, and the oxidative stress response. Furthermore, synaptic plasticity was evaluated through long-term potentiation (LTP) recording and Golgi staining techniques. Elevated expression of Nrf2 within the hippocampal CA1 region ameliorated sevoflurane-induced cognitive deficits, synaptic plasticity anomalies, and the oxidative stress reaction in aged mice. Furthermore, the activation of microglia and the release of pro-inflammatory cytokines (including IL-6, TNF-α, and IL-1β) within the hippocampus post-sevoflurane exposure were modulated in an Nrf2-dependent fashion. Based on the findings from present research, we conclude that Nrf2 ameliorates sevoflurane-induced cognitive dysfunction by inhibiting hippocampal neuroinflammation, thereby proposing a potential therapeutic target for PND.

Selective, Non-nucleotidic Radiotracer for P2Y12 Receptors: Design, Synthesis, Characterization, and Imaging of Brain Slices

The G protein-coupled, ADP-activated P2Y12 receptor (P2Y12R) expressed by microglial cells is involved in neuroinflammation constituting a promising biomarker. Here, we designed and characterized a potent and selective non-nucleotidic P2Y12-antagonist radioligand, [3H]PSB-22219 ([3H]18). The unlabeled compound was stable in rat liver microsomes and selective versus other ADP-activated receptors. [3H]18 displayed high-affinity binding to membrane preparations recombinantly expressing the human P2Y12R (KD = 4.57 nM), showing very low nonspecific binding. Radioligand binding assays were established and employed to characterize P2Y12Rs natively expressed in human platelet (KD = 2.53 nM), rat brain cortex (KD = 5.35 nM), and mouse microglial cell preparations (KD = 269 nM), with microglia showing extraordinarily high P2Y12R expression. Autoradiography studies allowed the visualization of human P2Y12R overexpression in the brain of a humanized rat model. The new radioligand is expected to become a useful pharmacological tool that will contribute to the development of therapeutics and radiodiagnostics targeting brain P2Y12Rs.

Neurodevelopmental Disorders Associated with Gut Microbiome Dysbiosis in Children

The formation of the human gut microbiome initiates in utero, and its maturation is established during the first 2-3 years of life. Numerous factors alter the composition of the gut microbiome and its functions, including mode of delivery, early onset of breastfeeding, exposure to antibiotics and chemicals, and maternal stress, among others. The gut microbiome-brain axis refers to the interconnection of biological networks that allow bidirectional communication between the gut microbiome and the brain, involving the nervous, endocrine, and immune systems. Evidence suggests that the gut microbiome and its metabolic byproducts are actively implicated in the regulation of the early brain development. Any disturbance during this stage may adversely affect brain functions, resulting in a variety of neurodevelopmental disorders (NDDs). In the present study, we reviewed recent evidence regarding the impact of the gut microbiome on early brain development, alongside its correlation with significant NDDs, such as autism spectrum disorder, attention-deficit/hyperactivity disorder, Tourette syndrome, cerebral palsy, fetal alcohol spectrum disorders, and genetic NDDs (Rett, Down, Angelman, and Turner syndromes). Understanding changes in the gut microbiome in NDDs may provide new chances for their treatment in the future.

Unraveling the enigma: housekeeping gene Ugt1a7c as a universal biomarker for microglia

Background

Microglia, brain resident macrophages, play multiple roles in maintaining homeostasis, including immunity, surveillance, and protecting the central nervous system through their distinct activation processes. Identifying all types of microglia-driven populations is crucial due to the presence of various phenotypes that differ based on developmental stages or activation states. During embryonic development, the E8.5 yolk sac contains erythromyeloid progenitors that go through different growth phases, eventually resulting in the formation of microglia. In addition, microglia are present in neurological diseases as a diverse population. So far, no individual biomarker for microglia has been discovered that can accurately identify and monitor their development and attributes.

Summary

Here, we highlight the newly defined biomarker of mouse microglia, UGT1A7C, which exhibits superior stability in expression during microglia development and activation compared to other known microglia biomarkers. The UGT1A7C sensing chemical probe labels all microglia in the 3xTG AD mouse model. The expression of Ugt1a7c is stable during development, with only a 4-fold variation, while other microglia biomarkers, such as Csf1r and Cx3cr1, exhibit at least a 10-fold difference. The UGT1A7C expression remains constant throughout its lifespan. In addition, the expression and activity of UGT1A7C are the same in response to different types of inflammatory activators' treatment in vitro.

Conclusion

We propose employing UGT1A7C as the representative biomarker for microglia, irrespective of their developmental state, age, or activation status. Using UGT1A7C can reduce the requirement for using multiple biomarkers, enhance the precision of microglia analysis, and even be utilized as a standard for gene/protein expression.

Identification of lncRNA-miRNA-mRNA Networks in the Lenticular Nucleus Region of the Brain Contributes to Hepatolenticular Degeneration Pathogenesis and Therapy

Long non-coding RNAs (lncRNAs) are a recently discovered group of non-coding RNAs that play a crucial role in the regulation of various human diseases, especially in the study of nervous system diseases which has garnered significant attention. However, there is limited knowledge on the identification and function of lncRNAs in hepatolenticular degeneration (HLD). The objective of this study was to identify novel lncRNAs and determine their involvement in the networks associated with HLD. We conducted a comprehensive analysis of RNA sequencing (RNA-seq) data, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and computational biology to identify novel lncRNAs and explore their potential mechanisms in HLD. We identified 212 differently expressed lncRNAs, with 98 upregulated and 114 downregulated. Additionally, 32 differently expressed mRNAs were found, with 15 upregulated and 17 downregulated. We obtained a total of 1131 pairs of co-expressed lncRNAs and mRNAs by Pearson correlation test and prediction and annotation of the lncRNA-targeted miRNA-mRNA network. The differential lncRNAs identified in this study were found to be involved in various biological functions and signaling pathways. These include translational initiation, motor learning, locomotors behavior, dioxygenase activity, integral component of postsynaptic membrane, neuroactive ligand-receptor interaction, nuclear factor-kappa B (NF-κB) signaling pathway, cholinergic synapse, sphingolipid signaling pathway, and Parkinson's disease signaling pathway, as revealed by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Six lncRNAs, including XR_001782921.1 (P < 0.01), XR_ 001780581.1 (P < 0.01), ENSMUST_00000207119 (P < 0.01), XR_865512.2 (P < 0.01), TCONS_00005916 (P < 0.01), and TCONS_00020683 (P < 0.01), showed significant differences in expression levels between the model group and normal group by RT-qPCR. Among these, four lncRNAs (TCONS_00020683, XR_865512.2, XR_001780581.1, and ENSMUST00000207119) displayed a high degree of conservation. This study provides a unique perspective for the pathogenesis and therapy of HLD by constructing the lncRNA-miRNA-mRNA network. This insight provides a foundation for future exploration in this field.

The gut-brain connection: Exploring the influence of the gut microbiota on neuroplasticity and neurodevelopmental disorders

Neuroplasticity refers to the ability of brain circuits to reorganize and change the properties of the network, resulting in alterations in brain function and behavior. It is traditionally believed that neuroplasticity is influenced by external stimuli, learning, and experience. Intriguingly, there is new evidence suggesting that endogenous signals from the body's periphery may play a role. The gut microbiota, a diverse community of microorganisms living in harmony with their host, may be able to influence plasticity through its modulation of the gut-brain axis. Interestingly, the maturation of the gut microbiota coincides with critical periods of neurodevelopment, during which neural circuits are highly plastic and potentially vulnerable. As such, dysbiosis (an imbalance in the gut microbiota composition) during early life may contribute to the disruption of normal developmental trajectories, leading to neurodevelopmental disorders. This review aims to examine the ways in which the gut microbiota can affect neuroplasticity. It will also discuss recent research linking gastrointestinal issues and bacterial dysbiosis to various neurodevelopmental disorders and their potential impact on neurological outcomes.

Transcriptomics of Parental Care in the Hypothalamic-Septal Region of Female Zebra Finch Brain

(1) Background: The objective of this study was to uncover genomic causes of parental care. Since birds do not lactate and, therefore, do not show the gene expressional changes required for lactation, we investigate gene expression associated with parenting in caring and non-caring females in an avian species, the small passerine bird zebra finch (Taeniopygia guttata). Here, we compare expression patterns in the hypothalamic–septal region since, previously, we showed that this area is activated in parenting females. (2) Methods: Transcriptome sequencing was first applied in a dissected part of the zebra finch brain related to taking care of the nestlings as compared to a control group of social pairs without nestlings. (3) Results: We found genes differentially expressed between caring and non-caring females. When introducing a log2fold change threshold of 1.5, 13 annotated genes were significantly upregulated in breeding pairs, while 39 annotated genes were downregulated. Significant enrichments of dopamine and acetylcholine biosynthetic processes were identified among upregulated pathways, while pro-opiomelanocortin and thyroid hormone pathways were downregulated, suggesting the importance of these systems in parental care. Network analysis further suggested neuro-immunological changes in mothers. (4) Conclusions: The results confirm the roles of several hypothesized major pathways in parental care, whereas novel pathways are also proposed.