Astrocytes as Drivers and Disruptors of Behavior: New Advances in Basic Mechanisms and Therapeutic Targeting

The interplay between lipid droplets and Parkinson's disease

Lipid droplets (LDs), also known as lipid bodies, are dynamic intracellular organelles that are rich in lipids. They serve critical functions in metabolic regulation, membrane dynamics, and cellular signaling pathways. LD homeostasis plays a key role in neurotransmission, receptor activation, and neural development. Intracellular LD accumulation contributes to lipotoxicity and precedes neurodegeneration such as Parkinson's disease (PD). While recent studies have advanced our knowledge regarding how LD accumulation influences PD progression, several fundamental aspects of LD biology remain unclear. This review explores key mechanisms of LD buildup in PD pathogenesis. First, we discuss the formation and physiological roles of LD, followed by an analysis of how impaired LD generation contributes to PD development. Second, we analyze the causal relationship between LD formation and degradation. Lastly, we evaluate the therapeutic potential of LDs as diagnostic biomarkers and molecular targets for innovative neuroprotective and anti-inflammatory strategies. Thus, advancing the mechanistic understanding of LD biology can provide key insights into PD pathogenesis, facilitating the design of targeted therapies.

Lysine Demethylase 5B Alleviates Neuroinflammation in Ischemic Stroke by Repressing Steap4

Six-transmembrane epithelial antigen of prostate 4 (Steap4) has been suggested as a potential marker for reactive astrocytes. This investigation focuses on the role of Steap4 in ischemic stroke (IS) and its regulator in this context. A mouse model of IS was generated using middle cerebral artery occlusion (MCAO). Additionally, mouse astrocytes that underwent oxygen-glucose deprivation (OGD) were utilized for in vitro investigations. Steap4 was found to be upregulated in the brain of MCAO-challenged mice and OGD-challenged astrocytes. Steap4 silencing reduced infarct size and alleviated IS-associated pathological exacerbations in mice, as well as ameliorated A1 skewing of astrocytes and inflammatory cytokine secretion both in vivo and in vitro. Lysine demethylase 5B (Kdm5b), identified as an upstream regulator of Steap4, was poorly expressed in IS/OGD models. Kdm5b overexpression repressed Steap4 transcription by removing H3K4me3 modification, thus alleviating pro-inflammatory activation of astrocytes and neuroinflammation. However, Kdm5b's protective effects were diminished upon Steap4 restoration in mice or astrocytes. In conclusion, this study suggests that the loss of Kdm5b leads to aberrant upregulation of Steap4, contributing to pro-inflammatory activation of astrocytes and brain damage in IS.

Nanocarrier-based targeted drug delivery for Alzheimer's disease: addressing neuroinflammation and enhancing clinical translation

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, amyloid-beta (Aβ) aggregation, tau pathology, and chronic neuroinflammation. Among these, neuroinflammation plays a crucial role in exacerbating disease progression, making it an attractive therapeutic target. However, the presence of the blood-brain barrier (BBB) significantly limits the effective delivery of therapeutic agents to the brain, necessitating novel drug delivery strategies. Nanocarrier-based delivery systems have emerged as a promising solution to these challenges, offering targeted drug transport, enhanced BBB penetration, and improved bioavailability while minimizing systemic toxicity. This review explores the current advancements in nanocarrier-mediated drug delivery for AD, focusing on the mechanisms of neuroinflammation, the role of nanocarriers in overcoming the BBB, and their ability to modulate inflammatory pathways. Furthermore, the review discusses preclinical validation strategies and key challenges, including safety concerns, large-scale production limitations, and regulatory hurdles that must be addressed to enable clinical translation. Future perspectives emphasize the integration of nanotechnology with precision medicine, gene therapy, and artificial intelligence to optimize nanocarrier design for individualized AD treatment. By overcoming these obstacles, nanocarriers hold the potential to revolutionize therapeutic approaches for AD and other neurodegenerative diseases.

Reactive astrocytes in spinal cord injury: An analysis of heterogeneity based on temporality and spatiality, potential therapies, and limitations

Spinal cord injury (SCI) constitutes a profound central nervous system disorder characterized by significant neurological dysfunction and sensory loss below the injury site. SCI elicits a multifaceted cellular response in which the proliferation of reactive astrocytes and the ensuing diversity in their functions and phenotypes play pivotal roles within the injury microenvironment, especially during the secondary phases of the condition. This review explores the activation and heterogeneity of astrocytes following SCI. It underscores the necessity of delineating the heterogeneity among reactive astrocyte subpopulations throughout the secondary injury phase of SCI. Developing therapeutic strategies that capitalize on the beneficial properties of certain reactive astrocyte subpopulations while mitigating the adverse effects of others could have profound implications for future clinical management of SCI.

Astrocyte Dysfunctions in Obsessive Compulsive Disorder: Rethinking Neurobiology and Therapeutic Targets

Obsessive-compulsive disorder (OCD) has long been conceptualized as a neuron-centric disorder of cortico-striato-thalamo-cortical (CSTC) circuit dysregulation. However, a growing body of evidence is now reframing this narrative, placing astrocytes-once relegated to passive support roles-at the center of OCD pathophysiology. Astrocytes are critical regulators of glutamate and GABA homeostasis, calcium signaling, and synaptic plasticity, all of which are disrupted in OCD. Recent high-resolution molecular and proteomic studies reveal that specific astrocyte subpopulations, including Crym-positive astrocytes, directly shape excitatory/inhibitory balance and control perseverative behaviors by modulating presynaptic inputs from the orbitofrontal cortex. Disruptions in astrocytic neurotransmitter clearance and dopamine metabolism amplify CSTC circuit hyperactivity and reinforce compulsions. This review reframes OCD as a disorder of neuro-glial dysfunctions, proposing that targeting astrocytic signaling, metabolism, and structural plasticity may unlock transformative therapeutic strategies. By integrating human and animal data, we advocate for a glial-centric model of OCD that not only enhances mechanistic understanding but also opens new frontiers for precision treatment.

Intriguing astrocyte responses in CA1 to reduced and rehabilitated masticatory function: Dorsal and ventral distinct perspectives in adult mice

OBJECTIVE

We sought to investigate the plasticity of diet-induced changes in astrocyte morphology of stratum lacunosum-moleculare (SLM) in CA1.

DESIGN

Three diet regimes were adopted in 15 mice, from the 21st postnatal day to 6 months. The first diet regimen was pellet feed, called Hard Diet (HD). The second, with reduced masticatory, received a pellet-diet followed by a powdered-diet, and it was identified as Hard Diet/Soft Diet (HD/SD). Finally, the group with rehabilitated masticatory was named Hard Diet/Soft Diet/Hard Diet (HD/SD/HD). In the end, euthanasia and brain histological processing were performed, in which astrocytic immunoreactivity to glial-fibrillary-acidic-protein (GFAP) was tested. In reconstructed astrocytes, morphometric analysis was performed.

RESULTS

Astrocyte morphometric revealed that changes in masticatory regimens impact astrocyte morphology. In the dorsal CA1, switching from a hard diet to a soft diet led to reductions in most variables, whereas in the ventral, fewer variables were affected, highlighting regional differences in astrocyte responses. Cluster analysis further showed that diet-induced changes in astrocyte morphology were reversible in the dorsal region, but not in the ventral region, indicating a persistent impact on astrocyte diversity and complexity in the ventral even after rehabilitation. Correlation tests between astrocyte morphology and behavioral performance demonstrated disrupted relationships under masticatory stress, with effects persisting after rehabilitation.

CONCLUSION

Changes in the diet result in significant alterations in astrocyte morphology, suggesting a direct link between dietary modulation and cellular structure. Morphometric analyses revealed distinct alterations in astrocyte morphology in response to changes in the masticatory regimen, with both dorsal/ventral regions displaying notable changes. Moreover, the regional differential effects on astrocytes underscore the complexity of mastication on neuroplasticity and cognitive function.

Dynamic changes of media prefrontal cortex astrocytic activity in response to negative stimuli in male mice

Astrocytes play significant roles in regulating the central stress response. Chronic stress impairs the structure and function of astrocytes in many brain regions such as media prefrontal cortex (mPFC) in multiple neuropsychiatric conditions, but the astrocytic dynamics on the timescale of behavior remains unclear. Here, we recorded mPFC astrocytic activity in freely behaving mice and found that astrocytes are activated immediately by different aversive stimuli. Astrocyte specific GCaMP6s calcium indicator were virally expressed in mPFC astrocytes and fiber photometry experiments revealed that astrocytes are activated by tail-restraint (TRT), foot shock (FS), open arm exploration, stressor of height, predator odor and social defeat (SD) stress. ΔF/F analyses demonstrated that an unpredictable stimulus such as elevated platform stress (EPS) at the initial encounter induced the most intense and rapid changes in astrocytic calcium activity, while a predictable 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) stimulus resulted in the weakest response with a longer peak latency. In TRT, FS or SD test, a somatic stimulus led to higher average calcium activity level and faster average peak latency in repeated trails. Similar to TMT stimulus, astrocytic calcium activity in elevated plus maze (EPM) test exhibited a smaller average change in amplitude and the longest peak latency during open arm exploration. Moreover, astrocytic calcium activity exhibited different changes across behavioral states in SD tests. Our findings show that mPFC astrocytes exhibit distinct patterns of calcium activity in response to various negative stimuli, indicating that the dynamic activity of astrocytes may reflect the stress-related behavioral state under different stimulus conditions.

Astrocyte TrkB.T1 deficiency disrupts glutamatergic synaptogenesis and astrocyte-synapse interactions

Perisynaptic astrocyte processes (PAPs) contact pre- and post-synaptic elements to provide structural and functional support to synapses. Accumulating research demonstrates that the cradling of synapses by PAPs is critical for synapse formation, stabilization, and plasticity. The specific signaling pathways that govern these astrocyte-synapse interactions, however, remain to be elucidated. Herein, we demonstrate a role for the astrocyte TrkB.T1 receptor, a truncated isoform of the canonical receptor for brain derived neurotrophic factor (BDNF), in modulating astrocyte-synapse interactions and excitatory synapse development. Neuron-astrocyte co-culture studies revealed that loss of astrocyte TrkB.T1 disrupts the formation of PAPs. To elucidate the role of TrkB.T1 in synapse development, we conditionally deleted TrkB.T1 in astrocytes in mice. Synaptosome preparations were employed to probe for TrkB.T1 localization at the PAP, and confocal three-dimensional microscopy revealed a significant reduction in synapse density and astrocyte-synapse interactions across development in the absence of astrocytic TrkB.T1. These findings suggest that BDNF/TrkB.T1 signaling in astrocytes is critical for normal excitatory synapse formation in the cortex and that astrocyte TrkB.T1 serves a requisite role in astrocyte synapse interactions. Overall, this work provides new insights into the molecular mechanisms of astrocyte-mediated synaptogenesis and may have implications for understanding neurodevelopmental disorders and developing potential therapeutic targets.

Abstinence from cocaine self-administration promotes microglia pruning of astrocytes which drives cocaine-seeking behavior

Rodent drug self-administration leads to compromised ability of astrocytes to maintain glutamate homeostasis within the brain's reward circuitry, as well as reductions in surface area, volume, and synaptic colocalization of astrocyte membranes. However, the mechanisms driving astrocyte responses to cocaine are unknown. Here, we report that long-access cocaine self-administration followed by prolonged home cage abstinence results in decreased branching complexity of nucleus accumbens astrocytes, characterized by the loss of peripheral processes. Using a combination of confocal fluorescence microcopy and immuno-gold electron microscopy, we show that alterations in astrocyte structural features are driven by microglia phagocytosis, as labeled astrocyte membranes are found within microglia phagolysosomes. Inhibition of complement C3-mediated phagocytosis using the neutrophil inhibitory peptide (NIF) rescued astrocyte structure and decreased cocaine seeking behavior following cocaine self-administration and abstinence. Collectively, these results provide evidence for microglia pruning of accumbens astrocytes across cocaine abstinence which mediates cocaine craving.

Zebrafish models for studying cognitive enhancers

Cognitive decline is commonly seen both in normal aging and in neurodegenerative and neuropsychiatric diseases. Various experimental animal models represent a valuable tool to study brain cognitive processes and their deficits. Equally important is the search for novel drugs to treat cognitive deficits and improve cognitions. Complementing rodent and clinical findings, studies utilizing zebrafish (Danio rerio) are rapidly gaining popularity in translational cognitive research and neuroactive drug screening. Here, we discuss the value of zebrafish models and assays for screening nootropic (cognitive enhancer) drugs and the discovery of novel nootropics. We also discuss the existing challenges, and outline future directions of research in this field.

Unveiling the role of astrocytes in postoperative cognitive dysfunction

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by progressive cognitive decline and the accumulation of amyloid-beta plaques, tau tangles, and neuroinflammation in the brain. Postoperative cognitive dysfunction (POCD) is a prevalent and debilitating condition characterized by cognitive decline following neuroinflammation and oxidative stress induced by procedures. POCD and AD are two conditions that share similarities in the underlying mechanisms and pathophysiology. Compared to normal aging individuals, individuals with POCD are at a higher risk for developing AD. Emerging evidence suggests that astrocytes, the most abundant glial cells in the central nervous system, play a critical role in the pathogenesis of these conditions. Comprehensive functions of astrocyte in AD has been extensively explored, but very little is known about POCD may experience late-onset AD pathogenesis. Herein, in this context, we mainly explore the multifaceted roles of astrocytes in the context of POCD, highlighting their involvement in neuroinflammation, neurotransmitter regulation, synaptic plasticity and neurotrophic support, and discuss how POCD may augment the onset of AD. Additionally, we discuss potential therapeutic strategies targeting astrocytes to mitigate or prevent POCD, which hold promise for improving the quality of life for patients undergoing surgeries and against AD in the future.