Investigation of Neuregulin-1 and Glial Cell-Derived Neurotrophic Factor in Rodent Astrocytes and Microglia

Microglia in Ischemic Stroke: Pathogenesis Insights and Therapeutic Challenges

Ischemic stroke is the most common type of stroke, which is the main cause of death and disability on a global scale. As the primary immune cells in the brain that are crucial for preserving homeostasis of the central nervous system microenvironment, microglia have been found to exhibit dual or even multiple effects at different stages of ischemic stroke. The anti-inflammatory polarization of microglia and release of neurotrophic factors may provide benefits by promoting neurological recovery at the lesion in the early phase after ischemic stroke. However, the pro-inflammatory polarization of microglia and secretion of inflammatory factors in the later phase of injury may exacerbate the ischemic lesion, suggesting the therapeutic potential of modulating the balance of microglial polarization to predispose them to anti-inflammatory transformation in ischemic stroke. Microglia-mediated signaling crosstalk with other cells may also be key to improving functional outcomes following ischemic stroke. Thus, this review provides an overview of microglial functions and responses under physiological and ischemic stroke conditions, including microglial activation, polarization, and interactions with other cells. We focus on approaches that promote anti-inflammatory polarization of microglia, inhibit microglial activation, and enhance beneficial cell-to-cell interactions. These targets may hold promise for the creation of innovative therapeutic strategies.

Expression of Glial-Cell-Line-Derived Neurotrophic Factor Family Ligands in Human Intervertebral Discs

Glial-cell-line-derived neurotrophic factor (GDNF) family ligands (GFLs) contribute to the sensitization of primary afferents and are involved in the pathogenesis of inflammatory pain. The purpose of this preliminary study was to examine the expression of other GFLs (neurturin (NRTN), artemin (ARTN), persephin (PSPN)) and receptors in human IVD cells and tissues exhibiting early and advanced stages of degeneration. Human IVD cells were cultured as a monolayer after isolation from the nucleus pulposus (NP) and anulus fibrosus (AF) tissues. The mRNA expression of NRTN, ARTN, PSPN, and their receptors (GFRA2-GFRA4) was quantified using real-time PCR. Protein expression was evaluated using immunohistochemistry and Western blotting. The expression of NRTN, ARTN, PSPN, and their co-receptors (GFRA2-GFRA4) was identified in human IVD cells at both mRNA and protein levels. A trend was noted wherein the mRNA expression of ARTN, PSPN, and GFRA2 was upregulated by IL-1β treatment in a dose-dependent manner. The percentages of immunopositive cells in the advanced degenerate stage of ARTN, PSPN, and GFRA2 were significantly higher than those in the early degenerate stage. Their expression was enhanced in advanced tissue degeneration, which suggests that GFLs (ARTN and PSPN) may be involved in the pathogenesis of discogenic pain.

Nf-κb: A Target for Synchronizing the Functioning Nervous Tissue Progenitors of Different Types in Alzheimer's Disease

BACKGROUND

The efficacy of Alzheimer's disease (AD) treatment can be enhanced by developing neurogenesis regulation approaches by synchronizing regenerative-competent cell (RCCs) activity. As part of the implementation of this direction, the search for drug targets among intracellular signaling molecules is promising.

OBJECTIVE

This study aims to test the hypothesis that NF-кB inhibitors are able to synchronize the activities of different types RCCs in AD.

METHODS

The effects of NF-κB inhibitor JSH-23 on the functioning of neural stem cells (NSCs), neuronal-committed progenitors (NCPs), and neuroglial cells were studied. Individual populations of C57B1/6 mice brain cells were obtained by immunomagnetic separation. Studies were carried out under conditions of modeling β-amyloid-induced neurodegeneration (βAIN) in vitro.

RESULTS

We showed that β-amyloid (Aβ) causes divergent changes in the functioning of NSCs and NCPs. Also demonstrated that different populations of neuroglia respond differently to exposure to Aβ. These phenomena indicate a significant discoordination of the activities of various RCCs. We revealed an important role of NF-κB in the regulation of progenitor proliferation and differentiation and glial cell secretory function. It was found that the NF-κB inhibitor causes synchronization of the pro-regenerative activities of NSCs, NCPs, as well as oligodendrocytes and microglial cells in βAIN.

CONCLUSION

The results show the promise of developing a novel approach to Alzheimer's disease treatment with NF-κВ inhibitors.

Lidocaine ameliorates chronic constriction injury-induced neuropathic pain through regulating M1/M2 microglia polarization

This study is intended to explore the mechanism that lidocaine ameliorates chronic constriction injury (CCI)-induced neuropathic pain (NP) related to the polarization of M1 and M2 microglia. CCI rats were established by surgery to induce NP. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of rats were determined. Microglial line HAPI cells were polarized into M1 or M2 cells using lipopolysaccharide (LPS) or interleukin (IL)-4, respectively. Immunofluorescence staining was performed to determine the Iba1/CD86- and Iba1/CD206-positive cells. Markers of M1 and M2 microglia were assessed using flow cytometry. Real-time polymerase chain reaction and enzyme-linked immunosorbent assay were performed to detect the level of mRNA and inflammatory factors. Lidocaine ameliorates CCI-induced NP, evidenced by the markedly increased values of MWT and TWL in NP rats. Lidocaine inhibited M1 microglia polarization but promoted M2 microglia polarization in a rat model of CCI-induced NP. Besides, in the in vitro experiment, lidocaine regulated M1/M2 polarization in LPS- or IL-4-treated HAPI microglia. Lidocaine ameliorates CCI-induced NP by regulating M1/M2 microglia polarization. This study investigated the biological role of lidocaine in regulating NP in rats, which may be helpful for revealing the pathogenic mechanisms of NP and provide a potential therapeutic factor.

Astrocyte Bioenergetics and Major Psychiatric Disorders

Ongoing research continues to add new elements to the emerging picture of involvement of astrocyte energy metabolism in the pathophysiology of major psychiatric disorders, including schizophrenia, mood disorders, and addictions. This review outlines what is known about the energy metabolism in astrocytes, the most numerous cell type in the brain, and summarizes the recent work on how specific perturbations of astrocyte bioenergetics may contribute to the neuropsychiatric conditions. The role of astrocyte energy metabolism in mental health and disease is reviewed on the organism, organ, and cell level. Data arising from genomic, metabolomic, in vitro, and neurobehavioral studies is critically analyzed to suggest future directions in research and possible metabolism-focused therapeutic interventions.

The Effects of Royal Jelly Acid, 10-Hydroxy-trans-2-decenoic Acid, on Neuroinflammation and Oxidative Stress in Astrocytes Stimulated with Lipopolysaccharide and Hydrogen Peroxide

The increased prevalence of neurodegenerative diseases, especially during the COVID-19 outbreak, necessitates the search for natural immune- and cognitive-enhancing agents. 10-Hydroxy-trans-2-decenoic acid (10-H2DA), the main fatty acid of royal jelly, has several pharmacological activities. Given the fundamental role of astrocytes in regulating immune responses of the central nervous system, we used cortical astrocytes to examine the effect of 10-H2DA on the expression of genes associated with neuroinflammation and the production of neurotrophins, as well as cellular resistance to H2O2-induced cytotoxicity. Astrocytes, pretreated with a range of concentrations of 10-H2DA for 24 h, were exposed to lipopolysaccharide (LPS) for 3 h, after which the expression of proinflammatory cytokines (IL-1β, IL-6, and tumor necrosis factor-α (TNF-α)) and neurotrophic factors (BDNF, GDNF, and IGF-1) was evaluated. In the absence of LPS, 10-H2DA had no significant effect on the mRNA expression of neurotrophins or cytokines except for IL-1β, which significantly increased with low doses of 10-H2DA (3 µM). 10-H2DA (10 µM) pretreatment of LPS-stimulated cells did not significantly inhibit the expression of cytokine encoding genes; however, it significantly lowered the mRNA expression of GDNF and tended to decrease BDNF and IGF-1 expression compared with LPS alone. Additionally, 10-H2DA did not protect astrocytes against H2O2-induced oxidative stress. Our data indicate no anti-inflammatory, antioxidant, or neurotrophic effect of 10-H2DA in astrocytes undergoing inflammation or oxidative stress. The effect of IGF-1 inhibition by 10-H2DA on neuronal ketogenesis needs investigation.

Mesenchymal stem cells with modafinil (gold nanoparticles) significantly improves neurological deficits in rats after middle cerebral artery occlusion

Systemic treatments for ischemic stroke as a disease with high disability and death have been yet unsuccessful. Combined treatments can potentially cause better results in treatment of patients with Stroke. In this study we assessed the neuroprotective effect of modafinil-coated gold nanoparticles (AuNPs) and mesenchymal stem cell (MSC) in ischemic stroke rats. Stem cells and AuNPs offer great promise for new medical treatments. 60 male Wistar rats were randomly divided into five groups (12 in each group): (1) the group that developed middle cerebral artery occlusion (MCAO or ischemia), (2) the normal group (control), (3) the MCAO group that received MSC (C + MCAO), (4) the MCAO group that received MSC and modafinil (CM + MCAO), and (5) the MCAO group that received MSC and modafinil-coated AuNPs (CMN + MCAO). Middle Cerebral Artery Occlusion (MCAO) was performed by inserting a silicone coat filament in the right internal carotid artery via the external carotid artery until it reached the anterior cerebral artery. The filament was located in the internal carotid artery for 60 min and then removed. Modafinil-coated AuNPs (100 mg/kg) or Modafinil (100 mg/kg) were given to the rats as an oral gavage, once a day in the morning time. Finally, infarct volume, BDNF (Brain-derived neurotrophic factor), GDNF (Glial cell-derived neurotrophic factor), NeuN (neuronal nuclear protein) expression, and cell apoptosis in brain were analyzed. The brain infarct volume and apoptosis significantly decreased and BDNF, NeuN, and GDNF increased in C + MCAO, CM + MCAO, and CMN + MCAO groups compared to ischemia. CMN + MCAO groups did not show significant difference in these factors compared to control group. These results demonstrated that the administration of stem cells and Modafinil-coated AuNPs at the same time had a good effect on ischemic brain injuries. It happened through increasing neurotrophic factors and decreasing brain cell apoptosis.

Revisiting the Role of Neurotrophic Factors in Inflammation

The neurotrophic factors are well known for their implication in the growth and the survival of the central, sensory, enteric and parasympathetic nervous systems. Due to these properties, neurturin (NRTN) and Glial cell-derived neurotrophic factor (GDNF), which belong to the GDNF family ligands (GFLs), have been assessed in clinical trials as a treatment for neurodegenerative diseases like Parkinson’s disease. In addition, studies in favor of a functional role for GFLs outside the nervous system are accumulating. Thus, GFLs are present in several peripheral tissues, including digestive, respiratory, hematopoietic and urogenital systems, heart, blood, muscles and skin. More precisely, recent data have highlighted that different types of immune and epithelial cells (macrophages, T cells, such as, for example, mucosal-associated invariant T (MAIT) cells, innate lymphoid cells (ILC) 3, dendritic cells, mast cells, monocytes, bronchial epithelial cells, keratinocytes) have the capacity to release GFLs and express their receptors, leading to the participation in the repair of epithelial barrier damage after inflammation. Some of these mechanisms pass on to ILCs to produce cytokines (such as IL-22) that can impact gut microbiota. In addition, there are indications that NRTN could be used in the treatment of inflammatory airway diseases and it prevents the development of hyperglycemia in the diabetic rat model. On the other hand, it is suspected that the dysregulation of GFLs produces oncogenic effects. This review proposes the discussion of the biological understanding and the potential new opportunities of the GFLs, in the perspective of developing new treatments within a broad range of human diseases.

Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia

BACKGROUND

Alzheimer's disease is associated with the accumulation of intracellular Tau tangles within neurons and extracellular amyloid-β plaques in the brain parenchyma, which altogether results in synaptic loss and neurodegeneration. Extracellular concentrations of oligomers and aggregated proteins initiate microglial activation and convert their state of synaptic surveillance into a destructive inflammatory state. Although Tau oligomers have fleeting nature, they were shown to mediate neurotoxicity and microglial pro-inflammation. Due to the instability of oligomers, in vitro experiments become challenging, and hence, the stability of the full-length Tau oligomers is a major concern.

METHODS

In this study, we have prepared and stabilized hTau40^WT oligomers, which were purified by size-exclusion chromatography. The formation of the oligomers was confirmed by western blot, thioflavin-S, 8-anilinonaphthaalene-1-sulfonic acid fluorescence, and circular dichroism spectroscopy, which determine the intermolecular cross-β sheet structure and hydrophobicity. The efficiency of N9 microglial cells to phagocytose hTau40^WT oligomer and subsequent microglial activation was studied by immunofluorescence microscopy with apotome. The one-way ANOVA was performed for the statistical analysis of fluorometric assay and microscopic analysis.

RESULTS

Full-length Tau oligomers were detected in heterogeneous globular structures ranging from 5 to 50 nm as observed by high-resolution transmission electron microscopy, which was further characterized by oligomer-specific A11 antibody. Immunocytochemistry studies for oligomer treatment were evidenced with A11⁺ Iba1^high microglia, suggesting that the phagocytosis of extracellular Tau oligomers leads to microglial activation. Also, the microglia were observed with remodeled filopodia-like actin structures upon the exposure of oligomers and aggregated Tau.

CONCLUSION

The peri-membrane polymerization of actin filament and co-localization of Iba1 relate to the microglial movements for phagocytosis. Here, these findings suggest that microglia modified actin cytoskeleton for phagocytosis and rapid clearance of Tau oligomers in Alzheimer's disease condition.

Impact of Auditory Integration Therapy (AIT) on the Plasma Levels of Human Glial Cell Line-Derived Neurotrophic Factor (GDNF) in Autism Spectrum Disorder

Neurotrophic factors, including the glial cell line-derived neurotrophic factor (GDNF), are of importance for synaptic plasticity regulation, intended as the synapses' ability to strengthen or weaken their responses to differences in neuronal activity. Such plasticity is essential for sensory processing, which has been shown to be impaired in autism spectrum disorder (ASD). This study is the first to investigate the impact of auditory integration therapy (AIT) of sensory processing abnormalities in autism on plasma GDNF levels. Fifteen ASD children, aged between 5 and 12 years, were enrolled and underwent the present research study. AIT was performed throughout 10 days with a 30-min session twice a day. Before and after AIT, Childhood Autism Rating Scale (CARS), Social Responsiveness Scale (SRS), and Short Sensory Profile (SSP) scores were calculated, and plasma GDNF levels were assayed by an EIA test. A substantial decline in autistic behavior was observed after AIT in the scaling parameters used. Median plasma GDNF level was 52.142 pg/ml before AIT. This level greatly increased immediately after AIT to 242.05 pg/ml (P < 0.001). The levels were depressed to 154.00 pg/ml and 125.594 pg/ml 1 month and 3 months later, respectively, but they were still significantly higher compared with the levels before the treatment (P = 0.001, P = 0.01, respectively). There was an improvement in the measures of autism severity as an effect of AIT which induced the up-regulation of GDNF in plasma. Further research, on a large scale, is needed to evaluate if the cognitive improvement of ASD children after AIT is related or not connected to the up-regulation of GDNF.