Frontiers in Cellular Neuroscience最新文献

Toll-like receptor 3 (TLR3) is classically known for mediating inflammatory pathways in Parkinson's disease (PD). However, the role of TLR3 in nigrostriatal degeneration in PD remains unclear. Here, we observed that TLR3 is predominantly expressed on astrocytes in the substantia nigra in both human PD brain and in rat PD models induced by intra-MFB injection of 1-methyl-4-phenylpyridinium (MPP⁺). Interestingly, Poly I: C, an activator of TLR3, significantly induced TLR3 expression on astrocytes. Treatment with Poly I: C markedly attenuated nigral dopamine neuron death in the PD rat models. The survival of dopamine neurons was accompanied by the production of ciliary neurotrophic factor and vascular endothelial growth factor-B on astrocytes in Poly I: C-treated PD rats. The attenuation of dopamine neuron death was also observed in the Poly I: C-treated AAV2-hα-syn-A53T-induced rat PD model. Our findings suggest that activating TLR3 in astrocytes could be a potential therapeutic strategy for attenuating PD progression.

[This retracts the article DOI: 10.3389/fncel.2017.00067.].

Neural regeneration remains a critical goal in regenerative medicine, especially for treating central nervous system injuries such as stroke, spinal cord injury, and neurodegenerative diseases. Mesenchymal stem cells (MSCs) have shown therapeutic potential through their capacity for differentiation and paracrine signaling; however, their clinical application is limited by low survival and engraftment rates. In this study, we investigated whether the therapeutic efficacy of human MSC (hMSC) spheroids could be enhanced through photobiomodulation (PBM). hMSCs were aggregated into three-dimensional spheroids and divided into four experimental groups: (1) untreated control spheroids, (2) spheroids treated with 660 nm PBM, (3) spheroids treated with 850 nm PBM, and (4) spheroids co-cultured with primary rat cortical neurons subjected to oxidative stress using hydrogen peroxide (H₂O₂). The PBM groups were exposed to red (660 nm) or near-infrared (NIR; 850 nm) light for 10 min. Neuronal viability and axonal regeneration were assessed. Our results demonstrated that PBM-treated hMSC spheroids significantly increased neuronal survival and axonal outgrowth compared to H₂O₂-only controls, particularly under high oxidative stress conditions. Notably, spheroids treated with 850 nm PBM exhibited the most robust neuroprotective effects. These findings suggest that PBM enhances mitochondrial activity and the secretion of neurotrophic factors by hMSC spheroids, thereby promoting neuroregeneration. This combinatorial strategy integrating PBM with 3D stem cell spheroid culture offers a promising avenue for developing advanced stem cell therapies for neurological disorders.

Introduction: Enteric glial cells (EGCs) are key regulators of gut-brain axis immunity, and their excessive activation contributes to intestinal inflammation and neuroimmune disturbances implicated in early Parkinson's disease. Oridonin, a diterpenoid compound with known anti-inflammatory and autophagy-modulating properties, has not been extensively studied in peripheral glial models. Here, we investigated the effects of oridonin on TLR4-mediated inflammatory signaling and autophagy responses in LPS-stimulated EGCs, with molecular docking used as a supportive, hypothesis-generating approach.

Methods: Rat-derived EGCs were exposed to LPS (10 μg/mL) to induce glial activation. Cells were treated with oridonin (1-5 μM) with or without the selective TLR4 inhibitor TAK-242. mRNA levels of TLR4, S100B, LC3, and beclin-1 were quantified by RT-qPCR, while caspase-1 and IL-1β protein levels were assessed by ELISA. Molecular docking was performed to explore potential interactions of oridonin and TAK-242 with the TLR4 receptor complex.

Results: LPS significantly increased TLR4 and S100B expression and upregulated the autophagy markers beclin-1 and LC3. Oridonin dose-dependently suppressed LPS-induced upregulation of TLR4 and S100B and attenuated the elevation of autophagy-related transcripts. Docking studies suggested that oridonin and TAK-242 may interact with regulatory regions of the TLR4 complex, including surface-exposed sites on the TLR4-MD-2 ectodomain and distinct sub-pockets within the intracellular TIR domain, with oridonin exhibiting a stronger predicted binding affinity. Although LPS increased TLR4 mRNA, it elicited only a modest increase in caspase-1 levels and no significant change in IL-1β levels, consistent with incomplete inflammasome activation. Whereas TAK-242 alone did not fully suppress IL-1β, combined treatment with oridonin reduced cytokine levels more effectively, suggesting complementary downstream modulation rather than direct receptor-level synergy.

Discussion: Oridonin exerts powerful anti-inflammatory and autophagy-modulating effects in EGCs by inhibiting TLR4-driven signaling, normalizing excessive autophagic responses, and limiting IL-1β output. Its dual capacity to suppress both upstream (TLR4/S100B) and downstream (caspase-1/IL-1β) components of the inflammatory cascade preserves EGC homeostasis under endotoxin stress. These findings highlight oridonin as a potential modulator of peripheral glial inflammation and support further investigation of its therapeutic potential in gut-brain axis disorders.

Protocadherins are key regulators of neurodevelopment and synaptic function, acting not only as adhesion molecules but also as synaptic hubs for intracellular signaling. Here, we uncover a novel activity-dependent signaling pathway for Pcdh9, a protocadherin linked to Autism Spectrum Disorder and Major Depressive Disorder. By combining biochemical and immunohistochemistry approaches on neuronal cultures, we show that neuronal activity triggers Matrix Metalloproteases (MMP)-dependent cleavage of PCDH9, generating a C-terminal fragment (CTF) that translocates to the nucleus. PCDH9 CTF overexpression promotes dendritic growth, increases spine density, and concomitantly strengthens excitatory synaptic transmission. These findings identify PCDH9 CTF as a novel activity-dependent signaling molecule that links synaptic activity to structural remodeling and functional modulation, suggesting a new mechanism by which synaptic activity shapes neuronal properties.

Brain sex neurosteroids have been attracted much attention, because the brain itself can synthesizes a sufficient amount of sex neurosteroids independent of circulating sex steroids. Local synthesis and action of neuro-estrogen [such as neuro-estradiol (nE2)] and neuro-androgen [such as neuro-testosterone (nT) and neuro-dihydrotestosterone (nDHT)] have become recognized as key factors in modulation of synaptic plasticity, cognitive performance, and protection of aging dependent decline of neurological functions. Unlike circulating sex steroids, these locally synthesized sex neurosteroids can directly and rapidly modulate neuronal synapses and induce potent effects on learning and memory. The properties of local neurocrine systems are significantly different from those of classical neuroendocrine systems dependent on the hypothalamic-pituitary-gonadal axis. For example, in the hippocampus, not only neuro-androgen (nT and nDHT) but also nE2 have higher concentrations than testis-derived circulating androgen (T and DHT) and ovary-derived circulating E2 (cir-E2). In addition, male nE2 concentration is higher than female nE2 at both adult stage and newborn stage during which brain masculinization occurs. Over the past decades, numerous experimental results and interpretations of sex neurosteroids have been shown. However, in several cases, these results and interpretations are mutually conflicting, and a unified understanding has not yet been achieved. Therefore, we here deeply discuss several critical and important issues toward solving complex problems to understand. We focus the following issues. First (A) Local synthesis of nE2, nT and nDHT, with particular attention to their concentrations, synthesis pathways and sex differences in rodents. Higher nE2 concentration in male hippocampus than in female in adult stage. Then (B) Comparison of modulation of long-term potentiation (LTP) by nE2 and nDHT. Stimulatory effects of nE2 on LTP which are mediated by membrane estrogen receptor ER and protein kinase signaling. Inhibitory effects of nDHT on LTP which are mediated by membrane androgen receptor AR. Third (C) Both nE2 and nDHT show the same rapid increases in dendritic spines. Their effects on spinogenesis are very different from their effects on LTP. Fourth (D) Rapid effects of nE2 and nT on cognitive behavior. Male signaling pathway may be more complex than female signaling pathway. Finally (E) Aging-dependent cognitive decline which is dependent on decrease of nT in male and nE2 in female. T-replacement therapy of male patients shows improvement in spatial cognitive decline. E2-replacement therapy improves female cognitive decline.

Haemorrhagic stroke is a devastating condition characterized by vessel rupture and free blood within the brain parenchyma or cerebrospinal fluid (CSF) filled spaces. Across the major subtypes of hemorrhagic stroke (subarachnoid, intracerebral, and intraventricular hemorrhages), the presence of blood in the CSF generates significant tissue damage in the first 72 h after the event, known as early brain injury (EBI). EBI includes neuroinflammation, blood-brain barrier breakdown and dysregulation of extracellular matrix (ECM) dynamics. ECM dysfunction has been shown to trigger fibrosis of the cortical blood vessels, limiting normal CSF circulation and resulting in the buildup of metabolic waste or the development of post-hemorrhagic hydrocephalus. Limiting or preventing this fibrosis may therefore reduce the rate of morbidity experienced by survivors, providing a potential avenue for non-surgical treatment to reduce secondary brain injury post-stroke. Despite this, current in vivo approaches fail to differentiate between the effect of blood products and secondary consequences including intracranial pressure (ICP) elevation and mass effect. Here, we describe an adult rat organotypic brain slice culture (OBSC) model of hemorrhagic stroke which enables the identification of the effect of blood products on ECM dysregulation. We demonstrate the distribution of key cell types across a time course of 0, 3 and 7 days in culture, indicating that such cultures are viable for a minimum of 7 days. Using immunofluorescence staining, Western blotting and RNA sequencing, we show that exposure of OBSCs to lysed blood markedly increases ECM deposition around cortical blood vessels. This is accompanied by dysregulation of ECM regulatory genes and upregulation of inflammation and oxidative stress-related genes, successfully recapitulating the changes seen in human stroke survivors. This versatile ex vivo model provides a translational platform to further understanding of hemorrhagic stroke pathophysiology and develop or trial novel therapeutics prior to progression to in vivo stroke studies.

Introduction: Neuropathic pain (NeP) is a major complication of spinal cord disorders that is refractory to therapy and impairs quality of life. Acute neuroinflammatory responses occur after spinal cord injury (SCI), but chronic-phase microglia/macrophage (M/M) dynamics and their involvement in degenerative compressive myelopathy (DCM) are unclear. Brain M/M may contribute to persistent NeP; however, comparative analyses of SCI and DCM are lacking. The aim of this study was to investigate M/M activation and pain-related signaling dynamics in the spinal cord and brain, and their roles in chronic NeP following SCI and DCM.

Methods: Contusive SCI was induced in C57BL/6N mice. Chronic compression was modeled using ttw/ttw mice. Motor function was assessed using the Basso Mouse Locomotor Scale. Mechanical and thermal sensitivities were evaluated. M/M activation and pain-related molecules (p-p38, p-ERK1/2) were assessed in spinal and brain regions using immunohistochemical staining. Cytokine expression was analyzed using western blotting.

Results: SCI mice showed early M/M activation at the injured site with spread to the lumbar enlargement, paralleling mechanical and thermal hypersensitivity. In DCM, M/M activation increased with compression severity, but did not extend to the lumbar enlargement. Both models showed M/M and pain-related upregulation of molecules in the hippocampus and amygdala, and thalamic activation in acute SCI or moderate-to-severe compression. Pro-inflammatory cytokines peaked acutely in SCI and under moderate compression in DCM. Anti-inflammatory cytokine induction was limited in DCM.

Discussion: Distinct neuroinflammatory patterns underlie chronic NeP in SCI and DCM. SCI shows M/M activation shifting from the injured site to the lumbar enlargement and limbic brain regions, consistent with chronic below-level pain. DCM shows localized M/M activation, but earlier hippocampal/amygdalar involvement, consistent with chronic at-level pain. These findings suggest pathology-specific therapeutic windows for targeting M/M-mediated neuroinflammation to prevent NeP.

Niemann Pick Disease Type C (NPC) is a rare neurodegenerative disease that primarily affects children. It is caused by mutations in the NPC1 or NPC2 genes, which encode proteins that transport cholesterol out of the endolysosomal organelles. Endolysosomal compartments also produce extracellular vesicles (EVs), which have emerged as key players in human disease. There is rapidly growing interest in how NPC cellular pathology impacts EV biology: of the 18 peer-reviewed publications on this topic, 13 were published within the last 5 years. Collectively, the existing literature suggests that the NPC proteins play key roles in EV biogenesis and uptake, that EV concentration and cargo are fundamentally altered in samples with NPC1/2 protein dysfunction, and that EVs may contribute to the therapeutic effects of NPC treatments. To better elucidate the connections between NPC and EVs further research is needed, especially in patient samples. Ultimately, a better understanding of the role of EVs in NPC will likely shed light on basic EV biology, related cellular neuropathologies, and a rare childhood disease that currently has no cure.

Introduction: Cerebral edema is a hallmark of lesion progression after acute ischemic stroke (AIS) and a major contributor to the evolution of spreading depolarizations (SDs). SDs trigger extracellular glutamate accumulation and excitotoxic injury, yet the mechanisms linking edema formation, glutamate dysregulation, and SD dynamics remain incompletely understood. Here, we investigated how inhibiting glial swelling and volume-regulated glutamate release, or blocking neuronal ionotropic glutamate receptors alters SD features under hypo-osmotic stress in vitro.

Methods: Acute 350-µm-thick brain slices were prepared from male Wistar rats (n = 24). Edema was induced using hypoosmotic medium (130→60 mM NaCl), and SD was triggered by hypoxia. SD evolution and extracellular glutamate levels were monitored using local field potential recordings, intrinsic optical signal imaging, and enzyme-based glutamate biosensors. Astrocyte swelling was reduced by blocking AQP4+NKCC1 (TGN-020 + bumetanide) and VRAC channels (DCPIB), while neuronal NMDA and AMPA/kainate receptors were antagonized with MK-801 + CNQX.

Results: Inhibition of AQP4, NKCC1, or VRAC channels restricted the cortical area invaded by SD, shortened SD duration, and reduced extracellular glutamate accumulation. In contrast, blockade of NMDA or AMPA/kainate receptors markedly decreased SD propagation and glutamate buildup. Both astrocytic and neuronal interventions disrupted typical SD initiation patterns, producing atypical, multifocal SD events.

Discussion: These findings demonstrate that astrocyte volume regulation and neuronal ionotropic glutamate receptors jointly shape SD characteristics under osmotic stress, identifying astrocytic water/ion homeostasis and glutamatergic signaling as potential therapeutic targets to limit excitotoxic injury in acute cerebrovascular disease.