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International Journal of Molecular... Jun 2024Neuropathic pain, which refers to pain caused by a lesion or disease of the somatosensory system, represents a wide variety of peripheral or central disorders. Treating... (Review)
Review
Neuropathic pain, which refers to pain caused by a lesion or disease of the somatosensory system, represents a wide variety of peripheral or central disorders. Treating neuropathic pain is quite demanding, primarily because of its intricate underlying etiological mechanisms. The central nervous system relies on microglia to maintain balance, as they are associated with serving primary immune responses in the brain next to cell communication. Ferroptosis, driven by phospholipid peroxidation and regulated by iron, is a vital mechanism of cell death regulation. Neuroinflammation can be triggered by ferroptosis in microglia, which contributes to the release of inflammatory cytokines. Conversely, neuroinflammation can induce iron accumulation in microglia, resulting in microglial ferroptosis. Accumulating evidence suggests that neuroinflammation, characterized by glial cell activation and the release of inflammatory substances, significantly exacerbates the development of neuropathic pain. By inhibiting microglial ferroptosis, it may be possible to prevent neuroinflammation and subsequently alleviate neuropathic pain. The activation of the homopentameric α7 subtype of the neuronal nicotinic acetylcholine receptor (α7nAChR) has the potential to suppress microglial activation, transitioning M1 microglia to an M2 phenotype, facilitating the release of anti-inflammatory factors, and ultimately reducing neuropathic pain. Recent years have witnessed a growing recognition of the regulatory role of α7nAChR in ferroptosis, which could be a potential target for treating neuropathic pain. This review summarizes the mechanisms related to α7nAChR and the progress of ferroptosis in neuropathic pain according to recent research. Such an exploration will help to elucidate the relationship between α7nAChR, ferroptosis, and neuroinflammation and provide new insights into neuropathic pain management.
Topics: Ferroptosis; Neuralgia; Humans; Animals; Neuroinflammatory Diseases; Microglia; alpha7 Nicotinic Acetylcholine Receptor; Inflammation
PubMed: 38928421
DOI: 10.3390/ijms25126716 -
International Journal of Molecular... Jun 2024The present study examined how P2X7 receptor knockout (KO) modulates central post-stroke pain (CPSP) induced by lesions of the ventrobasal complex (VBC) of the thalamus...
The present study examined how P2X7 receptor knockout (KO) modulates central post-stroke pain (CPSP) induced by lesions of the ventrobasal complex (VBC) of the thalamus in behaviors, molecular levels, and electrical recording tests. Following the experimental procedure, the wild-type and P2X7 receptor KO mice were injected with 10 mU/0.2 μL type IV collagenase in the VBC of the thalamus to induce an animal model of stroke-like thalamic hemorrhage. Behavioral data showed that the CPSP group induced thermal and mechanical pain. The P2X7 receptor KO group showed reduced thermal and mechanical pain responses compared to the CPSP group. Molecular assessments revealed that the CPSP group had lower expression of NeuN and KCC2 and higher expression of GFAP, IBA1, and BDNF. The P2X7 KO group showed lower expression of GFAP, IBA1, and BDNF but nonsignificant differences in KCC2 expression than the CPSP group. The expression of NKCC1, GABAa receptor, and TrkB did not differ significantly between the control, CPSP, and P2X7 receptor KO groups. Muscimol, a GABAa agonist, application increased multiunit numbers for monitoring many neurons and [Cl] outflux in the cytosol in the CPSP group, while P2X7 receptor KO reduced multiunit activity and increased [Cl] influx compared to the CPSP group. P2X4 receptor expression was significantly decreased in the 100 kDa but not the 50 kDa site in the P2X7 receptor KO group. Altogether, the P2X7 hypothesis of CPSP was proposed, wherein P2X7 receptor KO altered the CPSP pain responses, numbers of astrocytes and microglia, CSD amplitude of the anterior cingulate cortex and the medial dorsal thalamus, BDNF expression, [Cl] influx, and P2X4 expression in 100 kDa with P2X7 receptors. The present findings have implications for the clinical treatment of CPSP symptoms.
Topics: Animals; Receptors, Purinergic P2X7; Mice; Mice, Knockout; Stroke; K Cl- Cotransporters; Male; Pain; Disease Models, Animal; Brain-Derived Neurotrophic Factor; Symporters; Mice, Inbred C57BL; Neurons; Muscimol; Glial Fibrillary Acidic Protein; Thalamus
PubMed: 38928280
DOI: 10.3390/ijms25126577 -
International Journal of Molecular... Jun 2024Clinical treatment options to combat Encephalopathy of Prematurity (EoP) are still lacking. We, and others, have proposed (intranasal) mesenchymal stem cells (MSCs) as a...
Clinical treatment options to combat Encephalopathy of Prematurity (EoP) are still lacking. We, and others, have proposed (intranasal) mesenchymal stem cells (MSCs) as a potent therapeutic strategy to boost white matter repair in the injured preterm brain. Using a double-hit mouse model of diffuse white matter injury, we previously showed that the efficacy of MSC treatment was time dependent, with a significant decrease in functional and histological improvements after the postponement of cell administration. In this follow-up study, we aimed to investigate the mechanisms underlying this loss of therapeutic efficacy. Additionally, we optimized the regenerative potential of MSCs by means of genetic engineering with the transient hypersecretion of beneficial factors, in order to prolong the treatment window. Though the cerebral expression of known chemoattractants was stable over time, the migration of MSCs to the injured brain was partially impaired. Moreover, using a primary oligodendrocyte (OL) culture, we showed that the rescue of injured OLs was reduced after delayed MSC coculture. Cocultures of modified MSCs, hypersecreting IGF1, LIF, IL11, or IL10, with primary microglia and OLs, revealed a superior treatment efficacy over naïve MSCs. Additionally, we showed that the delayed intranasal administration of IGF1-, LIF-, or IL11-hypersecreting MSCs, improved myelination and the functional outcome in EoP mice. In conclusion, the impaired migration and regenerative capacity of intranasally applied MSCs likely underlie the observed loss of efficacy after delayed treatment. The intranasal administration of IGF1-, LIF-, or IL11-hypersecreting MSCs, is a promising optimization strategy to prolong the window for effective MSC treatment in preterm infants with EoP.
Topics: Animals; Mesenchymal Stem Cells; Mice; Mesenchymal Stem Cell Transplantation; Secretome; Disease Models, Animal; Oligodendroglia; Humans; Coculture Techniques; Microglia; Mice, Inbred C57BL
PubMed: 38928201
DOI: 10.3390/ijms25126494 -
International Journal of Molecular... Jun 2024Neurogenesis is the process by which new brain cells are formed. This crucial event emerges during embryonic life and proceeds in adulthood, and it could be influenced...
Neurogenesis is the process by which new brain cells are formed. This crucial event emerges during embryonic life and proceeds in adulthood, and it could be influenced by environmental pollution. Non-combustion-derived magnetite represents a portion of the coarse particulate matter (PM) contributing to air and water pollution in urban settings. Studies on humans have reported that magnetite and other iron oxides have significant damaging effects at a central level, where these particles accumulate and promote oxidative stress. Similarly, magnetite nanoparticles can cross the placenta and damage the embryo brain during development, but the impact on neurogenesis is still unknown. Furthermore, an abnormal Fe cation concentration in cells and tissues might promote reactive oxygen species (ROS) generation and has been associated with multiple neurodegenerative conditions. In the present study, we used zebrafish as an in vivo system to analyze the specific effects of magnetite on embryonic neurogenesis. First, we characterized magnetite using mineralogical and spectroscopic analyses. Embryos treated with magnetite at sub-lethal concentrations showed a dose-response increase in ROS in the brain, which was accompanied by a massive decrease in antioxidant genes (, , , and ). In addition, a higher number of apoptotic cells was observed in embryos treated with magnetite. Next, interestingly, embryos exposed to magnetite displayed a decrease in neural staminal progenitors (, , and markers) and a neuronal marker (). Finally, we observed significative increases in (specific microglia marker) and interleukin-1b (), confirming a status of inflammation in the brain embryos treated with magnetite. Our study represents the very first in vivo evidence concerning the effects of magnetite on brain development.
Topics: Animals; Zebrafish; Neurogenesis; Ferrosoferric Oxide; Embryo, Nonmammalian; Reactive Oxygen Species; Oxidative Stress; Brain; Apoptosis; Magnetite Nanoparticles
PubMed: 38928164
DOI: 10.3390/ijms25126459 -
Biomedicines May 2024Abnormal aggregation of α-synuclein is the hallmark of neurodegenerative diseases, classified as α-synucleinopathies, primarily occurring sporadically. Their onset is...
SARS-CoV-2 Spike Protein 1 Causes Aggregation of α-Synuclein via Microglia-Induced Inflammation and Production of Mitochondrial ROS: Potential Therapeutic Applications of Metformin.
Abnormal aggregation of α-synuclein is the hallmark of neurodegenerative diseases, classified as α-synucleinopathies, primarily occurring sporadically. Their onset is associated with an interaction between genetic susceptibility and environmental factors such as neurotoxins, oxidative stress, inflammation, and viral infections. Recently, evidence has suggested an association between neurological complications in long COVID (sometimes referred to as 'post-acute sequelae of COVID-19') and α-synucleinopathies, but its underlying mechanisms are not completely understood. In this study, we first showed that SARS-CoV-2 Spike protein 1 (S1) induces α-synuclein aggregation associated with activation of microglial cells in the rodent model. In vitro, we demonstrated that S1 increases aggregation of α-synuclein in BE(2)M-17 dopaminergic neurons via BV-2 microglia-mediated inflammatory responses. We also identified that S1 directly affects aggregation of α-synuclein in dopaminergic neurons through increasing mitochondrial ROS, though only under conditions of sufficient α-Syn accumulation. In addition, we observed a synergistic effect between S1 and the neurotoxin MPP+ S1 treatment. Combined with a low dose of MPP+, it boosted α-synuclein aggregation and mitochondrial ROS production compared to S1 or the MPP+ treatment group. Furthermore, we evaluated the therapeutic effects of metformin. The treatment of metformin suppressed the S1-induced inflammatory response and α-synucleinopathy. Our findings demonstrate that S1 promotes α-synucleinopathy via both microglia-mediated inflammation and mitochondrial ROS, and they provide pathological insights, as well as a foundation for the clinical management of α-synucleinopathies and the onset of neurological symptoms after the COVID-19 outbreak.
PubMed: 38927430
DOI: 10.3390/biomedicines12061223 -
Alzheimer's Research & Therapy Jun 2024The soluble triggering receptor expressed on myeloid cells 2 (sTREM2) in cerebrospinal fluid (CSF) is considered a biomarker of microglia activity. The objective of this...
BACKGROUND
The soluble triggering receptor expressed on myeloid cells 2 (sTREM2) in cerebrospinal fluid (CSF) is considered a biomarker of microglia activity. The objective of this study was to investigate the trajectory of CSF sTREM2 levels over time and examine its association with sex.
METHODS
A total of 1,017 participants from the Alzheimer's Disease Neuroimaging Initiative Study (ADNI) with at least one CSF sTREM2 record were included. The trajectory of CSF sTREM2 was analyzed using a growth curve model. The association between CSF sTREM2 levels and sex was assessed using linear mixed-effect models.
RESULTS
CSF sTREM2 levels were increased with age over time (P < 0.0001). No significant sex difference was observed in sTREM2 levels across the entire sample; however, among the APOE ε4 allele carriers, women exhibited significantly higher sTREM2 levels than men (β = 0.146, P = 0.002).
CONCLUSION
Our findings highlight the association between CSF sTREM2 levels and age-related increments, underscoring the potential influence of aging on sTREM2 dynamics. Furthermore, our observations indicate a noteworthy association between sex and CSF sTREM2 levels, particularly in individuals carrying the APOE ε4 allele.
Topics: Humans; Alzheimer Disease; Female; Male; Membrane Glycoproteins; Receptors, Immunologic; Aged; Longitudinal Studies; Neuroimaging; Biomarkers; Aged, 80 and over; Apolipoprotein E4; Aging; Sex Characteristics; Middle Aged
PubMed: 38926894
DOI: 10.1186/s13195-024-01506-8 -
BMC Neuroscience Jun 2024Astrocytes are the most abundant cell type of the central nervous system and are fundamentally involved in homeostasis, neuroprotection, and synaptic plasticity. This...
BACKGROUND
Astrocytes are the most abundant cell type of the central nervous system and are fundamentally involved in homeostasis, neuroprotection, and synaptic plasticity. This regulatory function of astrocytes on their neighboring cells in the healthy brain is subject of current research. In the ischemic brain we assume disease specific differences in astrocytic acting. The renin-angiotensin-aldosterone system regulates arterial blood pressure through endothelial cells and perivascular musculature. Moreover, astrocytes express angiotensin II type 1 and 2 receptors. However, their role in astrocytic function has not yet been fully elucidated. We hypothesized that the angiotensin II receptors impact astrocyte function as revealed in an in vitro system mimicking cerebral ischemia. Astrocytes derived from neonatal wistar rats were exposed to telmisartan (angiotensin II type 1 receptor-blocker) or PD123319 (angiotensin II type 2 receptor-blocker) under normal conditions (control) or deprivation from oxygen and glucose. Conditioned medium (CM) of astrocytes was harvested to elucidate astrocyte-mediated indirect effects on microglia and cortical neurons.
RESULT
The blockade of angiotensin II type 1 receptor by telmisartan increased the survival of astrocytes during ischemic conditions in vitro without affecting their proliferation rate or disturbing their expression of S100A10, a marker of activation. The inhibition of the angiotensin II type 2 receptor pathway by PD123319 resulted in both increased expression of S100A10 and proliferation rate. The CM of telmisartan-treated astrocytes reduced the expression of pro-inflammatory mediators with simultaneous increase of anti-inflammatory markers in microglia. Increased neuronal activity was observed after treatment of neurons with CM of telmisartan- as well as PD123319-stimulated astrocytes.
CONCLUSION
Data show that angiotensin II receptors have functional relevance for astrocytes that differs in healthy and ischemic conditions and effects surrounding microglia and neuronal activity via secretory signals. Above that, this work emphasizes the strong interference of the different cells in the CNS and that targeting astrocytes might serve as a therapeutic strategy to influence the acting of glia-neuronal network in de- and regenerative context.
Topics: Animals; Astrocytes; Rats, Wistar; Microglia; Receptor, Angiotensin, Type 2; Telmisartan; Angiotensin II Type 1 Receptor Blockers; Neurons; Receptor, Angiotensin, Type 1; Ischemic Stroke; Angiotensin II Type 2 Receptor Blockers; Rats; Cells, Cultured; Pyridines; Imidazoles; Animals, Newborn; Benzimidazoles; Cell Communication
PubMed: 38926677
DOI: 10.1186/s12868-024-00876-x -
Nature Communications Jun 2024Acute brain slices represent a workhorse model for studying the central nervous system (CNS) from nanoscale events to complex circuits. While slice preparation...
Acute brain slices represent a workhorse model for studying the central nervous system (CNS) from nanoscale events to complex circuits. While slice preparation inherently involves tissue damage, it is unclear how microglia, the main immune cells and damage sensors of the CNS react to this injury and shape neuronal activity ex vivo. To this end, we investigated microglial phenotypes and contribution to network organization and functioning in acute brain slices. We reveal time-dependent microglial phenotype changes influenced by complex extracellular ATP dynamics through P2Y12R and CX3CR1 signalling, which is sustained for hours in ex vivo mouse brain slices. Downregulation of P2Y12R and changes of microglia-neuron interactions occur in line with alterations in the number of excitatory and inhibitory synapses over time. Importantly, functional microglia modulate synapse sprouting, while microglial dysfunction results in markedly impaired ripple activity both ex vivo and in vivo. Collectively, our data suggest that microglia are modulators of complex neuronal networks with important roles to maintain neuronal network integrity and activity. We suggest that slice preparation can be used to model time-dependent changes of microglia-neuron interactions to reveal how microglia shape neuronal circuits in physiological and pathological conditions.
Topics: Animals; Microglia; Adenosine Triphosphate; Mice; Neurons; CX3C Chemokine Receptor 1; Receptors, Purinergic P2Y12; Brain; Synapses; Mice, Inbred C57BL; Phenotype; Male; Signal Transduction
PubMed: 38926390
DOI: 10.1038/s41467-024-49773-1 -
ENeuro Jun 2024Microglia carry out important functions as the resident macrophages of the brain. To study their role in health and disease, the research community needs tools to...
Microglia carry out important functions as the resident macrophages of the brain. To study their role in health and disease, the research community needs tools to genetically modify them with maximum completeness in a manner that distinguishes them from closely related cell-types, such as monocytes. While currently available tamoxifen-inducible CreERT2 lines are able to achieve the differentiation from other cells, the field needs improved and publicly available constitutively active Cre lines, especially ones with favorable efficiency and specificity profiles for studies where high recombination efficiency is imperative and where tamoxifen administration is contraindicated. Here, we leverage the microglia-specific gene to generate mice expressing Cre. Using genomic methods, we show correct positioning of the transgene and intact microglia homeostasis in mice. Crossing mice to four different reporters, we demonstrate highly efficient recombination in microglia across differentially sensitive loxP alleles in different genomic contexts, indicating robust applicability of the line. Further, we show that microglia recombine a loxP reporter during early embryonic development, supporting the use of the line for developmental studies. Finally, using immunofluorescence and flow cytometry, we reveal that most border associated macrophages (BAMs) are also targeted whereas only few liver and spleen macrophages and virtually no white blood cell subsets exhibit Cre activity, distinguishing this line from another publicly available Cre line, (MMRRC). mice are immediately available (JAX Stock #036591) and serve as a valuable addition to the community's microglia toolbox by providing highly efficient constitutive Cre activity with excellent specificity, particularly for studies where tamoxifen administration is undesirable. The microglia toolbox is continuously growing with more transgenic lines and most recently even viral tools becoming available. When selecting a Cre driver line, investigators must weigh relative strengths and weaknesses of available lines and carefully make the best choice for their given application. These tradeoffs include (1) availability and ease of employment, (2) chromosomal positioning of Cre with respect to the floxed allele (should not be on the same chromosome for conditional knockout studies), (3) activity level of a given Cre line and thus completeness of recombination across the microglia population, (4) specificity with respect to acceptable off-target cell types and tissues, (5) temporal aspects including earliest onset of Cre expression or inducibility, (6) robustness in disease contexts, and (7) potential perturbation of microglia homeostasis through Cre itself or disruption of the targeting locus. Considering these tradeoffs, it is evident that there may not be a one-size-fits all solution but an application-based preference for a mouse line in the diverse repertoire of microglia tools. mice are an excellent addition to this toolbox.
PubMed: 38926085
DOI: 10.1523/ENEURO.0549-23.2024 -
Brain, Behavior, and Immunity Jun 2024Older patients with spinal cord injury (SCI) have different features with regard to neurological characteristics after injury. Recent large-scale longitudinal...
Older patients with spinal cord injury (SCI) have different features with regard to neurological characteristics after injury. Recent large-scale longitudinal population-based studies showed that individuals with SCI are at a higher risk of developing dementia than non-SCI patients, indicating that SCI is a potential risk factor for dementia. Aging is known to potentiate inflammation and neurodegeneration at the injured site leading to impaired recovery from SCI. However, no research has been aimed at studying the mechanisms of SCI-mediated cognitive impairment in the elderly. The present study examined neurobehavioral and molecular changes in the brain and the underlying mechanisms associated with brain dysfunction in aged C57BL/6 male mice using a contusion SCI model. At 2 months post-injury, aged mice displayed worse performance in locomotor, cognitive and depressive-like behavioral tests compared to young adult animals. Histopathology in injured spinal cord tissue was exacerbated in aged SCI mice. In the brain, transcriptomic analysis with NanoString neuropathology panel identified activated microglia and dysregulated autophagy as the most significantly altered pathways by both age and injury. These findings were further validated by flow cytometry, which demonstrated increased myeloid and lymphocytes infiltration at both the injured site and brain of aged mice. Moreover, SCI in aged mice altered microglial function and dysregulated autophagy in microglia, resulting in worsened neurodegeneration. Taken together, our data indicate that old age exacerbates neuropathological changes in both the injured spinal cord and remote brain regions leading to poorer functional outcomes, at least in part, through altered inflammation and autophagy function.
PubMed: 38925420
DOI: 10.1016/j.bbi.2024.06.023