Mitochondrial biogenesis in developing astrocytes regulates astrocyte maturation and synapse formation

Accumulation of damaged mitochondria in aging astrocytes due to mitophagy dysfunction: Implications for susceptibility to mitochondrial stress

Aging disrupts brain function, leading to cognitive decline and neurodegenerative diseases. Senescent astrocytes, a hallmark of aging, contribute to this process through unknown mechanisms. This study investigates how senescence impacts astrocytic mitochondrial dynamics, which are critical for brain health. Our research, conducted using aged mouse brains, represents the first evidence of morphologically damaged mitochondria in astrocytes, along with functional alterations in mitochondrial respiration. In vitro experiments revealed that senescent astrocytes exhibit an increase in mitochondrial fragmentation and impaired mitophagy. Concurrently, there was an upregulation of mitochondrial biogenesis, indicating a compensatory response to mitochondrial damage. Importantly, these senescent astrocytes were more susceptible to mitochondrial stress, a vulnerability reversed by rapamycin treatment. These findings suggest a potential link between senescence, impaired mitochondrial quality control, and increased susceptibility to mitochondrial stress in astrocytes. Overall, our study highlights the importance of addressing mitochondrial dysfunction and senescence-related changes in astrocytes as a promising approach for developing therapies to counter age-related neurodegeneration and improve brain health.

Mitochondrial network reorganization and transient expansion during oligodendrocyte generation

Oligodendrocyte precursor cells (OPCs) give rise to myelinating oligodendrocytes of the brain. This process persists throughout life and is essential for recovery from neurodegeneration. To better understand the cellular checkpoints that occur during oligodendrogenesis, we determined the mitochondrial distribution and morphometrics across the oligodendrocyte lineage in mouse and human cerebral cortex. During oligodendrocyte generation, mitochondrial content expands concurrently with a change in subcellular partitioning towards the distal processes. These changes are followed by an abrupt loss of mitochondria in the oligodendrocyte processes and myelin, coinciding with sheath compaction. This reorganization and extensive expansion and depletion take 3 days. Oligodendrocyte mitochondria are stationary over days while OPC mitochondrial motility is modulated by animal arousal state within minutes. Aged OPCs also display decreased mitochondrial size, volume fraction, and motility. Thus, mitochondrial dynamics are linked to oligodendrocyte generation, dynamically modified by their local microenvironment, and altered in the aging brain.

Inhibition of the mitochondrial pyruvate carrier in astrocytes reduces amyloid and tau accumulation in the 3xTgAD mouse model of Alzheimer's disease

Alzheimer's Disease (AD) is characterized by an accumulation of pathologic amyloid-beta (Aβ) and Tau proteins, neuroinflammation, metabolic changes and neuronal death. Reactive astrocytes participate in these pathophysiological processes by releasing pro-inflammatory molecules and recruiting the immune system, which further reinforces inflammation and contributes to neuronal death. Besides these neurotoxic effects, astrocytes can protect neurons by providing them with high amounts of lactate as energy fuel. Astrocytes rely on aerobic glycolysis to generate lactate by reducing pyruvate, the end product of glycolysis, through lactate dehydrogenase. Consequently, limited amounts of pyruvate enter astrocytic mitochondria through the Mitochondrial Pyruvate Carrier (MPC) to be oxidized. The MPC is a heterodimer composed of two subunits MPC1 and MPC2, the function of which in astrocytes has been poorly investigated. Here, we analyzed the role of the MPC in the pathogeny of AD, knowing that a reduction in overall glucose metabolism has been associated with a drop in cognitive performances and an accumulation of Aβ and Tau. We generated 3xTgAD mice in which MPC1 was knocked-out in astrocytes specifically and focused our study on the biochemical hallmarks of the disease, mainly Aβ and neurofibrillary tangle production. We show that inhibition of the MPC before the onset of the disease significantly reduces the quantity of Aβ and Tau aggregates in the brain of 3xTgAD mice, suggesting that acting on astrocytic glucose metabolism early on could hinder the progression of the disease.

Mitochondrial dynamics regulate cell morphology in the developing cochlea

In multicellular tissues, the size and shape of cells are intricately linked with their physiological functions. In the vertebrate auditory organ, the neurosensory epithelium develops as a mosaic of sensory hair cells (HCs), and their glial-like supporting cells, which have distinct morphologies and functional properties at different frequency positions along its tonotopic long axis. In the chick cochlea, the basilar papilla (BP), proximal (high-frequency) HCs, are larger than their distal (low-frequency) counterparts, a morphological feature essential for sound perception. Mitochondrial dynamics, which constitute the equilibrium between fusion and fission, regulate differentiation and functional refinement across a variety of cell types. We investigate this as a potential mechanism for regulating the shape of developing HCs. Using live imaging in intact BP explants, we identify distinct remodelling of mitochondrial networks in proximal compared with distal HCs. Manipulating mitochondrial dynamics in developing HCs alters their normal morphology along the proximal-distal (tonotopic) axis. Inhibition of the mitochondrial fusion machinery decreased proximal HC surface area, whereas promotion of fusion increased the distal HC surface area. We identify mitochondrial dynamics as a key regulator of HC morphology in developing inner ear epithelia.

PGC-1α/LDHA signaling facilitates glycolysis initiation to regulate mechanically induced bone remodeling under inflammatory microenvironment

The mechanosensitivity of inflammation can alter cellular mechanotransduction. However, the underlying mechanism remains unclear. This study aims to investigate the metabolic mechanism of inflammation under mechanical force to guide tissue remodeling better. Herein, we found that inflammation hindered bone remodeling under mechanical force, accompanied by a simultaneous enhancement of oxidative phosphorylation (OXPHOS) and glycolysis. The control of metabolism direction through GNE-140 and Visomitin revealed that enhanced glycolysis might act as a compensatory mechanism to resist OXPHOS-induced osteoclastogenesis by promoting osteogenesis. The inhibited osteogenesis induced by inflammatory mechanical stimuli was concomitant with a reduced expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). PGC-1α knockdown impeded osteogenesis under mechanical force and facilitated osteoclastogenesis by enhancing OXPHOS. Conversely, PGC-1α overexpression attenuated the impairment of bone remodeling by inflammatory mechanical signals through promoting glycolysis. This process benefited from the PGC-1α regulation on the transcriptional and translational activity of lactate dehydrogenase A (LDHA) and the tight control of the extracellular acidic environment. Additionally, the increased binding between PGC-1α and LDHA proteins might contribute to the glycolysis promotion within the inflammatory mechanical environment. Notably, LDHA suppression effectively eliminated the bone repair effect mediated by PGC-1α overexpression within inflammatory mechanical environments. In conclusion, this study demonstrated a novel molecular mechanism illustrating how inflammation orchestrated glucose metabolism through glycolysis and OXPHOS to affect mechanically induced bone remodeling.

Lineage-specific changes in mitochondrial properties during neural stem cell differentiation

Neural stem cells (NSCs) reside in discrete regions of the adult mammalian brain where they can differentiate into neurons, astrocytes, and oligodendrocytes. Several studies suggest that mitochondria have a major role in regulating NSC fate. Here, we evaluated mitochondrial properties throughout NSC differentiation and in lineage-specific cells. For this, we used the neurosphere assay model to isolate, expand, and differentiate mouse subventricular zone postnatal NSCs. We found that the levels of proteins involved in mitochondrial fusion (Mitofusin [Mfn] 1 and Mfn 2) increased, whereas proteins involved in fission (dynamin-related protein 1 [DRP1]) decreased along differentiation. Importantly, changes in mitochondrial dynamics correlated with distinct patterns of mitochondrial morphology in each lineage. Particularly, we found that the number of branched and unbranched mitochondria increased during astroglial and neuronal differentiation, whereas the area occupied by mitochondrial structures significantly reduced with oligodendrocyte maturation. In addition, comparing the three lineages, neurons revealed to be the most energetically flexible, whereas astrocytes presented the highest ATP content. Our work identified putative mitochondrial targets to enhance lineage-directed differentiation of mouse subventricular zone-derived NSCs.

PGC-1α in the hippocampus mediates depressive-like and stress-coping behaviours and regulates excitatory synapses in the dentate gyrus in mice

Decreased hippocampal synaptic plasticity is an important pathological change in stress-related mood disorders, including major depressive disorder. However, the underlying mechanism is unclear. PGC-1α, a transcriptional coactivator, is a key factor in synaptic plasticity. We investigated the relationships between changes in hippocampal PGC-1α expression and depressive-like and stress-coping behaviours, and whether they are related to hippocampal synapses. Adeno-associated virus was used to alter hippocampal PGC-1α expression in male C57BL/6 mice. The sucrose preference test and forced swimming test were used to assess their depressive-like and stress-coping behaviours, respectively. Immunohistochemistry and stereology were used to calculate the total number of excitatory synapses in each hippocampal subregion (the cornu ammonis (CA) 1, CA3, and dentate gyrus). Immunofluorescence was used to visualize the changes in dendritic structure. Western blotting was used to detect the expression of hippocampal PGC-1α and mitochondrial-associated proteins, such as UCP2, NRF1 and mtTFAs. Our results showed that mice with downregulated PGC-1α expression in the hippocampus exhibited depressive-like and passive stress-coping behaviours, while mice with upregulated PGC-1α in the hippocampus exhibited increased stress-coping behaviours. Moreover, the downregulation of hippocampal PGC-1α expression resulted in a decrease in the number of excitatory synapses in the DG and in the protein expression of UCP2 in the hippocampus. Alternatively, upregulation of hippocampal PGC-1α yielded the opposite results. This suggests that hippocampal PGC-1α is involved in regulating depressive-like and stress-coping behaviours and modulating the number of excitatory synapses in the DG. This provides new insight for the development of antidepressants.

Bridging metabolic syndrome and cognitive dysfunction: role of astrocytes

Metabolic syndrome (MetS) and cognitive dysfunction pose significant challenges to global health and the economy. Systemic inflammation, endocrine disruption, and autoregulatory impairment drive neurodegeneration and microcirculatory damage in MetS. Due to their unique anatomy and function, astrocytes sense and integrate multiple metabolic signals, including peripheral endocrine hormones and nutrients. Astrocytes and synapses engage in a complex dialogue of energetic and immunological interactions. Astrocytes act as a bridge between MetS and cognitive dysfunction, undergoing diverse activation in response to metabolic dysfunction. This article summarizes the alterations in astrocyte phenotypic characteristics across multiple pathological factors in MetS. It also discusses the clinical value of astrocytes as a critical pathologic diagnostic marker and potential therapeutic target for MetS-associated cognitive dysfunction.

Astrocytes at the intersection of ageing, obesity, and neurodegeneration

Once considered passive cells of the central nervous system (CNS), glia are now known to actively maintain the CNS parenchyma; in recent years, the evidence for glial functions in CNS physiology and pathophysiology has only grown. Astrocytes, a heterogeneous group of glial cells, play key roles in regulating the metabolic and inflammatory landscape of the CNS and have emerged as potential therapeutic targets for a variety of disorders. This review will outline astrocyte functions in the CNS in healthy ageing, obesity, and neurodegeneration, with a focus on the inflammatory responses and mitochondrial function, and will address therapeutic outlooks.

Exploring the effect of Anshen Dingzhi prescription on hippocampal mitochondrial signals in single prolonged stress mouse model

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE

Anshen Dingzhi prescription (ADP), which was first published in the masterpiece of traditional Chinese Medicine in the Qing Dynasty, "Yi Xue Xin Wu" (1732 CE), is documented to interrupt panic-related disorders. However, the mechanism of its action is still not clear.

AIM OF THE STUDY

This study aims to investigate the effects of ADP on post-traumatic stress disorder (PTSD)-like behaviors and explore the mechanism from perspective of sirtuin1 (SIRT1)-peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α)-dependent mitochondrial function.

MATERIALS AND METHODS

The changes of SIRT1-PGC-1α signal and mitochondrial function were evaluated in the hippocampus of mice receiving single prolonged stress (SPS). Later, the roles of this signaling pathway played in fear memory generalization and anxiety-like behavior in SPS mice was investigated using two agonists of this signaling pathway. On this basis, the effects of ADP (36.8 mg/kg) with definite therapeutic effects, on mitochondrial function were investigated and further confirmed by a SIRT1 inhibitor. Finally, the possible components of ADP targeting PGC-1α were monitored through bioinformatics.

RESULTS

Compared with control mice, SIRT1-PGC-1α signal in the hippocampus was impaired in SPS mice, accompanied with dysfunction of mitochondria and abnormal expression of synaptic proteins. The agonists of SIRT1-PGC-1α signal, ZLN005, as well as resveratrol improved the behavioral changes of mice caused by SPS, reversed the decline of proteins in SIRT1-PGC-1α signal, mitochondrial dysfunction, and the abnormal expression of synaptic proteins. The fingerprint was established for the quality control of ADP. At a dose of 36.8 mg/kg, ADP could prevent fear memory generalization and anxiety-like behavior in SPS mice. Mechanically, ADP promoted SIRT1-PGC-1α signal and repaired mitochondrial function. Importantly, SIRT1 inhibitor, selisistat eliminated the ameliorative effects of ADP on behavioral and mitochondrial function. Through molecular docking simulation, the brain-entering components of ADP, including malkangunin, Rg5, fumarine, frutinone A, celabenzine, and inermin had high binding energy with PGC-1α.

CONCLUSION

Dysfunction of SIRT1-PGC-1α-dependent mitochondrial function is attributed to SPS-triggered fear generalization and anxiety-like behavior, and ADP could improve PTSD-like behaviors likely through activating this signaling pathway.

Potassium channel modulation in macrophages sensitizes dorsal root ganglion neurons after nerve injury

Macrophages and satellite glial cells are found between injured and uninjured neurons in the lumbar dorsal root ganglia (DRG). We explored the mechanism of neuro-immune and neuron-glia crosstalk leading to hyperexcitability of DRG neurons. After spared nerve injury (SNI), CX3CR1+ resident macrophages became activated, proliferated, and increased inward-rectifying potassium channel Kir 2.1 currents. Conditioned medium (CM) by macrophages, obtained from DRG of SNI mice, sensitized small DRG neurons from naïve mice. However, treatment with CM from GFAP+ glial cells did not affect neuronal excitability. When subjected to this macrophage-derived CM, DRG neurons had increased spontaneous activity, current-evoked responses and voltage-gated NaV 1.7 and NaV 1.8 currents. Silencing Kir 2.1 in macrophages after SNI prevented the induction of neuronal hyperexcitability from their CM. Blocking vesicular exocytosis or soluble tumor necrosis factor in CM or interfering with the downstream intracellular p38 pathway in neurons, also prevented neuronal hyperexcitability. Blocking protein trafficking in neurons reduced the effect of CM, suggesting that the hyperexcitable state resulted from changes in NaV channel trafficking. These results suggest that DRG macrophages, primed by peripheral nerve injury, contribute to neuron-glia crosstalk, NaV channel dysregulation and neuronal hyperexcitability implicated in the development of neuropathic pain.

Activity-dependent compartmentalization of dendritic mitochondria morphology through local regulation of fusion-fission balance in neurons in vivo

Neuronal mitochondria play important roles beyond ATP generation, including Ca2+ uptake, and therefore have instructive roles in synaptic function and neuronal response properties. Mitochondrial morphology differs significantly between the axon and dendrites of a given neuronal subtype, but in CA1 pyramidal neurons (PNs) of the hippocampus, mitochondria within the dendritic arbor also display a remarkable degree of subcellular, layer-specific compartmentalization. In the dendrites of these neurons, mitochondria morphology ranges from highly fused and elongated in the apical tuft, to more fragmented in the apical oblique and basal dendritic compartments, and thus occupy a smaller fraction of dendritic volume than in the apical tuft. However, the molecular mechanisms underlying this striking degree of subcellular compartmentalization of mitochondria morphology are unknown, precluding the assessment of its impact on neuronal function. Here, we demonstrate that this compartment-specific morphology of dendritic mitochondria requires activity-dependent, Ca2+ and Camkk2-dependent activation of AMPK and its ability to phosphorylate two direct effectors: the pro-fission Drp1 receptor Mff and the recently identified anti-fusion, Opa1-inhibiting protein, Mtfr1l. Our study uncovers a signaling pathway underlying the subcellular compartmentalization of mitochondrial morphology in dendrites of neurons in vivo through spatially precise and activity-dependent regulation of mitochondria fission/fusion balance.

Mitochondrial metabolism in neural stem cells and implications for neurodevelopmental and neurodegenerative diseases

Mitochondria are cytoplasmic organelles having a fundamental role in the regulation of neural stem cell (NSC) fate during neural development and maintenance.During embryonic and adult neurogenesis, NSCs undergo a metabolic switch from glycolytic to oxidative phosphorylation with a rise in mitochondrial DNA (mtDNA) content, changes in mitochondria shape and size, and a physiological augmentation of mitochondrial reactive oxygen species which together drive NSCs to proliferate and differentiate. Genetic and epigenetic modifications of proteins involved in cellular differentiation (Mechanistic Target of Rapamycin), proliferation (Wingless-type), and hypoxia (Mitogen-activated protein kinase)-and all connected by the common key regulatory factor Hypoxia Inducible Factor-1A-are deemed to be responsible for the metabolic shift and, consequently, NSC fate in physiological and pathological conditions.Both primary mitochondrial dysfunction due to mutations in nuclear DNA or mtDNA or secondary mitochondrial dysfunction in oxidative phosphorylation (OXPHOS) metabolism, mitochondrial dynamics, and organelle interplay pathways can contribute to the development of neurodevelopmental or progressive neurodegenerative disorders.This review analyses the physiology and pathology of neural development starting from the available in vitro and in vivo models and highlights the current knowledge concerning key mitochondrial pathways involved in this process.

Mitochondria in the Central Nervous System in Health and Disease: The Puzzle of the Therapeutic Potential of Mitochondrial Transplantation

Mitochondria, the energy suppliers of the cells, play a central role in a variety of cellular processes essential for survival or leading to cell death. Consequently, mitochondrial dysfunction is implicated in numerous general and CNS disorders. The clinical manifestations of mitochondrial dysfunction include metabolic disorders, dysfunction of the immune system, tumorigenesis, and neuronal and behavioral abnormalities. In this review, we focus on the mitochondrial role in the CNS, which has unique characteristics and is therefore highly dependent on the mitochondria. First, we review the role of mitochondria in neuronal development, synaptogenesis, plasticity, and behavior as well as their adaptation to the intricate connections between the different cell types in the brain. Then, we review the sparse knowledge of the mechanisms of exogenous mitochondrial uptake and describe attempts to determine their half-life and transplantation long-term effects on neuronal sprouting, cellular proteome, and behavior. We further discuss the potential of mitochondrial transplantation to serve as a tool to study the causal link between mitochondria and neuronal activity and behavior. Next, we describe mitochondrial transplantation's therapeutic potential in various CNS disorders. Finally, we discuss the basic and reverse-translation challenges of this approach that currently hinder the clinical use of mitochondrial transplantation.

Metabolic dynamics in astrocytes and microglia during post-natal development and their implications for autism spectrum disorders

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by elusive underlying mechanisms. Recent attention has focused on the involvement of astrocytes and microglia in ASD pathology. These glial cells play pivotal roles in maintaining neuronal homeostasis, including the regulation of metabolism. Emerging evidence suggests a potential association between ASD and inborn errors of metabolism. Therefore, gaining a comprehensive understanding of the functions of microglia and astrocytes in ASD is crucial for the development of effective therapeutic interventions. This review aims to provide a summary of the metabolism of astrocytes and microglia during post-natal development and the evidence of disrupted metabolic pathways in ASD, with particular emphasis on those potentially important for the regulation of neuronal post-natal maturation by astrocytes and microglia.

Drosophila tweety facilitates autophagy to regulate mitochondrial homeostasis and bioenergetics in Glia

Mitochondria support the energetic demands of the cells. Autophagic turnover of mitochondria serves as a critical pathway for mitochondrial homeostasis. It is unclear how bioenergetics and autophagy are functionally connected. Here, we identify an endolysosomal membrane protein that facilitates autophagy to regulate ATP production in glia. We determined that Drosophila tweety (tty) is highly expressed in glia and localized to endolysosomes. Diminished fusion between autophagosomes and endolysosomes in tty-deficient glia was rescued by expressing the human Tweety Homolog 1 (TTYH1). Loss of tty in glia attenuated mitochondrial turnover, elevated mitochondrial oxidative stress, and impaired locomotor functions. The cellular and organismal defects were partially reversed by antioxidant treatment. We performed live-cell imaging of genetically encoded metabolite sensors to determine the impact of tty and autophagy deficiencies on glial bioenergetics. We found that tty-deficient glia exhibited reduced mitochondrial pyruvate consumption accompanied by a shift toward glycolysis for ATP production. Likewise, genetic inhibition of autophagy in glia resulted in a similar glycolytic shift in bioenergetics. Furthermore, the survival of mutant flies became more sensitive to starvation, underlining the significance of tty in the crosstalk between autophagy and bioenergetics. Together, our findings uncover the role for tty in mitochondrial homeostasis via facilitating autophagy, which determines bioenergetic balance in glia.

Reduction of inflammation and mitochondrial degeneration in mutant SOD1 mice through inhibition of voltage-gated potassium channel Kv1.3

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no effective therapy, causing progressive loss of motor neurons in the spinal cord, brainstem, and motor cortex. Regardless of its genetic or sporadic origin, there is currently no cure for ALS or therapy that can reverse or control its progression. In the present study, taking advantage of a human superoxide dismutase-1 mutant (hSOD1-G93A) mouse that recapitulates key pathological features of human ALS, we investigated the possible role of voltage-gated potassium channel Kv1.3 in disease progression. We found that chronic administration of the brain-penetrant Kv1.3 inhibitor, PAP-1 (40 mg/Kg), in early symptomatic mice (i) improves motor deficits and prolongs survival of diseased mice (ii) reduces astrocyte reactivity, microglial Kv1.3 expression, and serum pro-inflammatory soluble factors (iii) improves structural mitochondrial deficits in motor neuron mitochondria (iv) restores mitochondrial respiratory dysfunction. Taken together, these findings underscore the potential significance of Kv1.3 activity as a contributing factor to the metabolic disturbances observed in ALS. Consequently, targeting Kv1.3 presents a promising avenue for modulating disease progression, shedding new light on potential therapeutic strategies for ALS.

Astroglial Cells: Emerging Therapeutic Targets in the Management of Traumatic Brain Injury

Traumatic Brain Injury (TBI) represents a significant health concern, necessitating advanced therapeutic interventions. This detailed review explores the critical roles of astrocytes, key cellular constituents of the central nervous system (CNS), in both the pathophysiology and possible rehabilitation of TBI. Following injury, astrocytes exhibit reactive transformations, differentiating into pro-inflammatory (A1) and neuroprotective (A2) phenotypes. This paper elucidates the interactions of astrocytes with neurons, their role in neuroinflammation, and the potential for their therapeutic exploitation. Emphasized strategies encompass the utilization of endocannabinoid and calcium signaling pathways, hormone-based treatments like 17β-estradiol, biological therapies employing anti-HBGB1 monoclonal antibodies, gene therapy targeting Connexin 43, and the innovative technique of astrocyte transplantation as a means to repair damaged neural tissues.

Modulation of mitochondrial activity by sugarcane (Saccharum officinarum L.) top extract and its bioactive polyphenols: a comprehensive transcriptomics analysis in C2C12 myotubes and HepG2 hepatocytes

Age-related mitochondrial dysfunction leads to defects in cellular energy metabolism and oxidative stress defense systems, which can contribute to tissue damage and disease development. Among the key regulators responsible for mitochondrial quality control, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is an important target for mitochondrial dysfunction. We have previously reported that bioactive polyphenols extracted from sugarcane top (ST) ethanol extract (STEE) could activate neuronal energy metabolism and increase astrocyte PGC-1α transcript levels. However, their potential impact on the mitochondria activity in muscle and liver cells has not yet been investigated. To address this gap, our current study examined the effects of STEE and its polyphenols on cultured myotubes and hepatocytes in vitro. Rhodamine 123 assay revealed that the treatment with STEE and its polyphenols resulted in an increase in mitochondrial membrane potential in C2C12 myotubes. Furthermore, a comprehensive examination of gene expression patterns through transcriptome-wide microarray analysis indicated that STEE altered gene expressions related to mitochondrial functions, fatty acid metabolism, inflammatory cytokines, mitogen-activated protein kinase (MAPK) signaling, and cAMP signaling in both C2C12 myotubes and HepG2 hepatocytes. Additionally, protein-protein interaction analysis identified the PGC-1α interactive-transcription factors-targeted regulatory network of the genes regulated by STEE, and the quantitative polymerase chain reaction results confirmed that STEE and its polyphenols upregulated the transcript levels of PGC-1α in both C2C12 and HepG2 cells. These findings collectively suggest the potential beneficial effects of STEE on muscle and liver tissues and offer novel insights into the potential nutraceutical applications of this material.

Significance of quantitative analyses of the impact of heterogeneity in mitochondrial content and shape on cell differentiation

Mitochondria, classically known as the powerhouse of cells, are unique double membrane-bound multifaceted organelles carrying a genome. Mitochondrial content varies between cell types and precisely doubles within cells during each proliferating cycle. Mitochondrial content also increases to a variable degree during cell differentiation triggered after exit from the proliferating cycle. The mitochondrial content is primarily maintained by the regulation of mitochondrial biogenesis, while damaged mitochondria are eliminated from the cells by mitophagy. In any cell with a given mitochondrial content, the steady-state mitochondrial number and shape are determined by a balance between mitochondrial fission and fusion processes. The increase in mitochondrial content and alteration in mitochondrial fission and fusion are causatively linked with the process of differentiation. Here, we critically review the quantitative aspects in the detection methods of mitochondrial content and shape. Thereafter, we quantitatively link these mitochondrial properties in differentiating cells and highlight the implications of such quantitative link on stem cell functionality. Finally, we discuss an example of cell size regulation predicted from quantitative analysis of mitochondrial shape and content. To highlight the significance of quantitative analyses of these mitochondrial properties, we propose three independent rationale based hypotheses and the relevant experimental designs to test them.

Neuron-Astrocyte Interactions: A Human Perspective

This chapter explores the intricate interactions between neurons and astrocytes within the nervous system with a particular emphasis on studies conducted in human tissue or with human cells. We specifically explore how neuron-astrocyte interactions relate to processes of cellular development, morphology, migration, synapse formation, and metabolism. These findings enrich our understanding of basic neurobiology and how disruptions in these processes are relevant to human diseases.The study of human neuron-astrocyte interactions is made possible because of transformative in vitro advancements that have facilitated the generation and sustained culture of human neural cells. In addition, the rise of techniques like sequencing at single-cell resolution has enabled the exploration of numerous human cell atlases and their comparisons to other animal model systems. Thus, the innovations outlined in this chapter illuminate the convergence and divergence of neuron-astrocyte interactions across species. As technologies progress, continually more sophisticated in vitro systems will increasingly reflect in vivo environments and deepen our command of neuron-glial interactions in human biology.

Mitochondrial network reorganization and transient expansion during oligodendrocyte generation

Oligodendrocyte precursor cells (OPCs) give rise to myelinating oligodendrocytes of the central nervous system. This process persists throughout life and is essential for recovery from neurodegeneration. To better understand the cellular checkpoints that occur during oligodendrogenesis, we determined the mitochondrial distribution and morphometrics across the oligodendrocyte lineage in mouse and human cerebral cortex. During oligodendrocyte generation, mitochondrial content expanded concurrently with a change in subcellular partitioning towards the distal processes. These changes were followed by an abrupt loss of mitochondria in the oligodendrocyte processes and myelin, coinciding with sheath compaction. This reorganization and extensive expansion and depletion took 3 days. Oligodendrocyte mitochondria were stationary over days while OPC mitochondrial motility was modulated by animal arousal state within minutes. Aged OPCs also displayed decreased mitochondrial size, content, and motility. Thus, mitochondrial dynamics are linked to oligodendrocyte generation, dynamically modified by their local microenvironment, and altered in the aging brain.

Astrocytes and brain-derived neurotrophic factor (BDNF)

Astrocytes are emerging in the neuroscience field as crucial modulators of brain functions, from the molecular control of synaptic plasticity to orchestrating brain-wide circuit activity for cognitive processes. The cellular pathways through which astrocytes modulate neuronal activity and plasticity are quite diverse. In this review, we focus on neurotrophic pathways, mostly those mediated by brain-derived neurotrophic factor (BDNF). Neurotrophins are a well-known family of trophic factors with pleiotropic functions in neuronal survival, maturation and activity. Within the brain, BDNF is the most abundantly expressed and most studied of all neurotrophins. While we have detailed knowledge of the effect of BDNF on neurons, much less is known about its physiology on astroglia. However, over the last years new findings emerged demonstrating that astrocytes take an active part into BDNF physiology. In this work, we discuss the state-of-the-art knowledge about astrocytes and BDNF. Indeed, astrocytes sense extracellular BDNF through its specific TrkB receptors and activate intracellular responses that greatly vary depending on the brain area, stage of development and receptors expressed. Astrocytes also uptake and recycle BDNF / proBDNF at synapses contributing to synaptic plasticity. Finally, experimental evidence is now available describing deficits in astrocytic BDNF in several neuropathologies, suggesting that astrocytic BDNF may represent a promising target for clinical translation.

The function of astrocytes and their role in neurological diseases

Astrocytes have countless links with neurons. Previously, astrocytes were only considered a scaffold of neurons; in fact, astrocytes perform a variety of functions, including providing support for neuronal structures and energy metabolism, offering isolation and protection and influencing the formation, function and elimination of synapses. Because of these functions, astrocytes play an critical role in central nervous system (CNS) diseases. The regulation of the secretiory factors, receptors, channels and pathways of astrocytes can effectively inhibit the occurrence and development of CNS diseases, such as neuromyelitis optica (NMO), multiple sclerosis, Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease. The expression of aquaporin 4 in AS is directly related to NMO and indirectly involved in the clearance of Aβ and tau proteins in AD. Connexin 43 has a bidirectional effect on glutamate diffusion at different stages of stroke. Interestingly, astrocytes reduce the occurrence of PD through multiple effects such as secretion of related factors, mitochondrial autophagy and aquaporin 4. Therefore, this review is focused on the structure and function of astrocytes and the correlation between astrocytes and CNS diseases and drug treatment to explore the new functions of astrocytes with the astrocytes as the target. This, in turn, would provide a reference for the development of new drugs to protect neurons and promote the recovery of nerve function.

Characterisation of GFAP-Expressing Glial Cells in the Dorsal Root Ganglion after Spared Nerve Injury

Satellite glial cells (SGCs), enveloping primary sensory neurons' somas in the dorsal root ganglion (DRG), contribute to neuropathic pain upon nerve injury. Glial fibrillary acidic protein (GFAP) serves as an SGC activation marker, though its DRG satellite cell specificity is debated. We employed the hGFAP-CFP transgenic mouse line, designed for astrocyte studies, to explore its expression within the peripheral nervous system (PNS) after spared nerve injury (SNI). We used diverse immunostaining techniques, Western blot analysis, and electrophysiology to evaluate GFAP+ cell changes. Post-SNI, GFAP+ cell numbers increased without proliferation, and were found near injured ATF3+ neurons. GFAP+ FABP7+ SGCs increased, yet 75.5% of DRG GFAP+ cells lacked FABP7 expression. This suggests a significant subset of GFAP+ cells are non-myelinating Schwann cells (nmSC), indicated by their presence in the dorsal root but not in the ventral root which lacks unmyelinated fibres. Additionally, patch clamp recordings from GFAP+ FABP7-cells lacked SGC-specific Kir4.1 currents, instead displaying outward Kv currents expressing Kv1.1 and Kv1.6 channels specific to nmSCs. In conclusion, this study demonstrates increased GFAP expression in two DRG glial cell subpopulations post-SNI: GFAP+ FABP7+ SGCs and GFAP+ FABP7- nmSCs, shedding light on GFAP's specificity as an SGC marker after SNI.

PGC-1α regulates critical period onset/closure, mediating cortical plasticity

Peroxisome proliferator-activated receptor PPARγ coactivator-α (PGC-1α) is concentrated in inhibitory interneurons and plays a vital role in neuropsychiatric diseases. We previously reported some characteristic features of schizophrenia (SZ) in GABAergic neuron-specific Pgc-1alpha knockout (KO) mice (Dlx5/6-Cre: Pgc-1alphaf/f). However, there is a fundamental gap in the molecular mechanism by which the Pgc-1alpha gene is involved in the neurobehavioral abnormalities of SZ. The loss of critical period (CP) triggers-maturations of parvalbumin interneurons (PVIs) and brakes-and the formation of perineuronal nets (PNNs) implicates mistimed trajectories during adult brain development. In this study, using the Pgc-1alpha KO mouse line, we investigated the association of Pgc-1alpha gene deletion with SZ-like behavioral deficits, PVI maturation, PNN integrity and synaptic ultrastructure. These findings suggest that Pgc-1alpha gene deletion resulted in a failure of CP onset and closure, thereby prolonging cortical plasticity timing. To determine whether the manipulation of the PNN structure is a potential method of altering neuronal plasticity, GM6001, a broad-spectrum matrix metalloproteinase (MMP)-inhibitor was applied. Here we confirmed that the treatment could effectively correct the CP plasticity window and ameliorate the synaptic ultrastructure in the Pgc-1alpha KO brain. Moreover, the intervention effect on neuronal plasticity was followed by the rescue of short-term habituation deficits and the mitigation of aberrant salience, which are some characteristic features of SZ. Taken collectively, these findings suggest that the role of PGC-1α in regulating cortical plasticity is mediated, at least partially, through the regulation of CP onset/closure. Strategically introduced reinforcement of molecular brakes may be a novel preventive therapy for psychiatric disorders associated with PGC-1α dysregulation.

Peroxisom proliferator-activated receptor-γ coactivator-1α in neurodegenerative disorders: A promising therapeutic target

Neurodegenerative disorders (NDDs) are characterized by progressive loss of selectively vulnerable neuronal populations and myelin sheath, leading to behavioral and cognitive dysfunction that adversely affect the quality of life. Identifying novel therapies that attenuate the progression of NDDs would be of significance. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a widely expressed transcriptional regulator, modulates the expression of genes engaged in mitochondrial biosynthesis, metabolic regulation, and oxidative stress (OS). Emerging evidences point to the strong connection between PGC-1α and NDDs, suggesting its positive impaction on the progression of NDDs. Therefore, it is urgent to gain a deeper and broader understanding between PGC-1α and NDDs. To this end, this review presents a comprehensive overview of PGC-1α, including its basic characteristics, the post-translational modulations, as well as the interacting transcription factors. Secondly, the pathogenesis of PGC-1α in various NDDs, such as Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD) is briefly discussed. Additionally, this study summarizes the underlying mechanisms that PGC-1α is neuroprotective in NDDs via regulating neuroinflammation, OS, and mitochondrial dysfunction. Finally, we briefly outline the shortcomings of current NDDs drug therapy, and summarize the functions and potential applications of currently available PGC-1α modulators (activator or inhibitors). Generally, this review updates our insight of the important role of PGC-1α on the development of NDDs, and provides a promising therapeutic target/ drug for the treatment of NDDs.

The role of PPAR-γ in memory deficits induced by prenatal and lactation alcohol exposure in mice

Patients diagnosed with fetal alcohol spectrum disorder (FASD) show persistent cognitive disabilities, including memory deficits. However, the neurobiological substrates underlying these deficits remain unclear. Here, we show that prenatal and lactation alcohol exposure (PLAE) in mice induces FASD-like memory impairments. This is accompanied by a reduction of N-acylethanolamines (NAEs) and peroxisome proliferator-activated receptor gamma (PPAR-γ) in the hippocampus specifically in a childhood-like period (at post-natal day (PD) 25). To determine their role in memory deficits, two pharmacological approaches were performed during this specific period of early life. Thus, memory performance was tested after the repeated administration (from PD25 to PD34) of: i) URB597, to increase NAEs, with GW9662, a PPAR-γ antagonist; ii) pioglitazone, a PPAR-γ agonist. We observed that URB597 suppresses PLAE-induced memory deficits through a PPAR-γ dependent mechanism, since its effects are prevented by GW9662. Direct PPAR-γ activation, using pioglitazone, also ameliorates memory impairments. Lastly, to further investigate the region and cellular specificity, we demonstrate that an early overexpression of PPAR-γ, by means of a viral vector, in hippocampal astrocytes mitigates memory deficits induced by PLAE. Together, our data reveal that disruptions of PPAR-γ signaling during neurodevelopment contribute to PLAE-induced memory dysfunction. In turn, PPAR-γ activation during a childhood-like period is a promising therapeutic approach for memory deficits in the context of early alcohol exposure. Thus, these findings contribute to the gaining insight into the mechanisms that might underlie memory impairments in FASD patients.

Unlocking Neural Function with 3D In Vitro Models: A Technical Review of Self-Assembled, Guided, and Bioprinted Brain Organoids and Their Applications in the Study of Neurodevelopmental and Neurodegenerative Disorders

Understanding the complexities of the human brain and its associated disorders poses a significant challenge in neuroscience. Traditional research methods have limitations in replicating its intricacies, necessitating the development of in vitro models that can simulate its structure and function. Three-dimensional in vitro models, including organoids, cerebral organoids, bioprinted brain models, and functionalized brain organoids, offer promising platforms for studying human brain development, physiology, and disease. These models accurately replicate key aspects of human brain anatomy, gene expression, and cellular behavior, enabling drug discovery and toxicology studies while providing insights into human-specific phenomena not easily studied in animal models. The use of human-induced pluripotent stem cells has revolutionized the generation of 3D brain structures, with various techniques developed to generate specific brain regions. These advancements facilitate the study of brain structure development and function, overcoming previous limitations due to the scarcity of human brain samples. This technical review provides an overview of current 3D in vitro models of the human cortex, their development, characterization, and limitations, and explores the state of the art and future directions in the field, with a specific focus on their applications in studying neurodevelopmental and neurodegenerative disorders.

Astrocytic modulation of neuronal signalling

Neuronal signalling is a key element in neuronal communication and is essential for the proper functioning of the CNS. Astrocytes, the most prominent glia in the brain play a key role in modulating neuronal signalling at the molecular, synaptic, cellular, and network levels. Over the past few decades, our knowledge about astrocytes and their functioning has evolved from considering them as merely a brain glue that provides structural support to neurons, to key communication elements. Astrocytes can regulate the activity of neurons by controlling the concentrations of ions and neurotransmitters in the extracellular milieu, as well as releasing chemicals and gliotransmitters that modulate neuronal activity. The aim of this review is to summarise the main processes through which astrocytes are modulating brain function. We will systematically distinguish between direct and indirect pathways in which astrocytes affect neuronal signalling at all levels. Lastly, we will summarize pathological conditions that arise once these signalling pathways are impaired focusing on neurodegeneration.

Loss of insulin signaling in astrocytes exacerbates Alzheimer-like phenotypes in a 5xFAD mouse model

Brain insulin signaling controls peripheral energy metabolism and plays a key role in the regulation of mood and cognition. Epidemiological studies have indicated a strong connection between type 2 diabetes (T2D) and neurodegenerative disorders, especially Alzheimer's disease (AD), linked via dysregulation of insulin signaling, i.e., insulin resistance. While most studies have focused on neurons, here, we aim to understand the role of insulin signaling in astrocytes, a glial cell type highly implicated in AD pathology and AD progression. To this end, we created a mouse model by crossing 5xFAD transgenic mice, a well-recognized AD mouse model that expresses five familial AD mutations, with mice carrying a selective, inducible insulin receptor (IR) knockout in astrocytes (iGIRKO). We show that by age 6 mo, iGIRKO/5xFAD mice exhibited greater alterations in nesting, Y-maze performance, and fear response than those of mice with the 5xFAD transgenes alone. This was associated with increased Tau (T231) phosphorylation, increased Aβ plaque size, and increased association of astrocytes with plaques in the cerebral cortex as assessed using tissue CLARITY of the brain in the iGIRKO/5xFAD mice. Mechanistically, in vitro knockout of IR in primary astrocytes resulted in loss of insulin signaling, reduced ATP production and glycolic capacity, and impaired Aβ uptake both in the basal and insulin-stimulated states. Thus, insulin signaling in astrocytes plays an important role in the control of Aβ uptake, thereby contributing to AD pathology, and highlighting the potential importance of targeting insulin signaling in astrocytes as a site for therapeutics for patients with T2D and AD.

The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons

Neurons are highly dependent on mitochondrial ATP production and Ca²⁺ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.

Molecular Mechanisms of Astrocyte Involvement in Synaptogenesis and Brain Synaptic Plasticity

Astrocytes perform a wide range of important functions in the brain. As structural and functional components of synapses, astrocytes secrete various factors (proteins, lipids, small molecules, etc.) that bind to neuronal receptor and contribute to synaptogenesis and regulation of synaptic contacts. Astrocytic factors play a key role in the formation of neural networks undergoing short- and long-term synaptic morphological and functional rearrangements essential in the memory formation and behavior. The review summarizes the data on the molecular mechanisms mediating the involvement of astrocyte-secreted factors in synaptogenesis in the brain and provides up-to-date information on the role of astrocytes and astrocytic synaptogenic factors in the long-term plastic rearrangements of synaptic contacts.

Neuroinflammation and Oxidative Stress in the Pathogenesis of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder (NDD) characterized by impairments in social communication, repetitive behaviors, restricted interests, and hyperesthesia/hypesthesia caused by genetic and/or environmental factors. In recent years, inflammation and oxidative stress have been implicated in the pathogenesis of ASD. In this review, we discuss the inflammation and oxidative stress in the pathophysiology of ASD, particularly focusing on maternal immune activation (MIA). MIA is a one of the common environmental risk factors for the onset of ASD during pregnancy. It induces an immune reaction in the pregnant mother’s body, resulting in further inflammation and oxidative stress in the placenta and fetal brain. These negative factors cause neurodevelopmental impairments in the developing fetal brain and subsequently cause behavioral symptoms in the offspring. In addition, we also discuss the effects of anti-inflammatory drugs and antioxidants in basic studies on animals and clinical studies of ASD. Our review provides the latest findings and new insights into the involvements of inflammation and oxidative stress in the pathogenesis of ASD.

Nano-Brake Halts Mitochondrial Dysfunction Cascade to Alleviate Neuropathology and Rescue Alzheimer's Cognitive Deficits

Mitochondrial dysfunction has been recognized as the key pathogenesis of most neurodegenerative diseases including Alzheimer's disease (AD). The dysregulation of mitochondrial calcium ion (Ca²⁺ ) homeostasis and the mitochondrial permeability transition pore (mPTP), is a critical upstream signaling pathway that contributes to the mitochondrial dysfunction cascade in AD pathogenesis. Herein, a "two-hit braking" therapeutic strategy to synergistically halt mitochondrial Ca²⁺ overload and mPTP opening to put the mitochondrial dysfunction cascade on a brake is proposed. To achieve this goal, magnesium ion (Mg²⁺ ), a natural Ca²⁺ antagonist, and siRNA to the central mPTP regulator cyclophilin D (CypD), are co-encapsulated into the designed nano-brake; A matrix metalloproteinase 9 (MMP9) activatable cell-penetrating peptide (MAP) is anchored on the surface of nano-brake to overcome the blood-brain barrier (BBB) and realize targeted delivery to the mitochondrial dysfunction cells of the brain. Nano-brake treatment efficiently halts the mitochondrial dysfunction cascade in the cerebrovascular endothelial cells, neurons, and microglia and powerfully alleviates AD neuropathology and rescues cognitive deficits. These findings collectively demonstrate the potential of advanced design of nanotherapeutics to halt the key upstream signaling pathways of mitochondrial dysfunction to provide a powerful strategy for AD modifying therapy.

Neuroinflammation and Oxidative Stress in Individuals Affected by DiGeorge Syndrome

DiGeorge syndrome (DGS) is a rare genetic disease caused by microdeletions of the 22q11.2 region (DGS1). A haploinsufficiency at 10p level has been proposed also as a DGS cause (DGS2). Clinical manifestations are variable. The most frequent features are thymic hypoplasia or aplasia with consequent immune deficiency, cardiac malformations, hypoparathyroidism, facial and palatine abnormalities, variable degrees of cognitive impairment and psychiatric disorders. The specific aim of this descriptive report is to discuss the correlation between oxidative stress and neuroinflammation in DGS patients with microdeletions of the 22q11.2 region. The deleted chromosomic region maps various genes involved in mitochondrial metabolisms, such as DGCR8 and TXNRD2, that could lead to reactive oxygen species (ROS) increased production and antioxidant depletion. Furthermore, increased levels of ROS in mitochondria would lead to the destruction of the projection neurons in the cerebral cortex with consequent neurocognitive impairment. Finally, the increase in modified protein belonging to the family of sulfoxide compounds and hexoses, acting as inhibitors of the IV and V mitochondria complex, could result in direct ROS overproduction. Neuroinflammation in DGS individuals could be directly related to the development of the syndrome's characteristic psychiatric and cognitive disorders. In patients with psychotic disorders, the most frequent psychiatric manifestation in DGS, Th-17, Th-1 and Th-2 cells are increased with consequent elevation of proinflammatory cytokine IL-6 and IL1β. In patients with anxiety disorders, both CD3 and CD4 are increased. Some patients with autism spectrum disorders (ASDs) have an augmented level of proinflammatory cytokines IL-12, IL-6 and IL-1β, while IFNγ and the anti-inflammatory cytokine IL-10 seem to be reduced. Other data proposed that altered synaptic plasticity could be directly involved in DGS cognitive disorders. In conclusion, the use of antioxidants for restoring mitochondrial functionality in DGS could be a useful tool to protect cortical connectivity and cognitive behavior.

Metabolic perspective of astrocyte dysfunction in Alzheimer's disease and type 2 diabetes brains

The term type III diabetes (T3DM) has been proposed for Alzheimer's disease (AD) due to the shared molecular and cellular features between type 2 diabetes (T2DM) and insulin resistance-associated memory deficits and cognitive decline in elderly individuals. Astrocytes elicit neuroprotective or deleterious effects in AD progression and severity. Patients with T2DM are at a high risk of cognitive impairment, and targeting astrocytes might be promising in alleviating neurodegeneration in the diabetic brain. Recent studies focusing on cell-specific activities in the brain have revealed the important role of astrocytes in brain metabolism (e.g., glucose metabolism, lipid metabolism), neurovascular coupling, synapses, and synaptic plasticity. In this review, we discuss how astrocytes and their dysfunction result in multiple pathological and clinical features of AD and T2DM from a metabolic perspective and the potential comorbid mechanism in these two diseases from the perspective of astrocytes.

The Imbalance of Astrocytic Mitochondrial Dynamics Following Blast-Induced Traumatic Brain Injury

Mild blast-induced traumatic brain injury (bTBI) is a modality of injury that has been of major concern considering a large number of military personnel exposed to explosive blast waves. bTBI results from the propagation of high-pressure static blast forces and their subsequent energy transmission within brain tissue. Exposure to this overpressure energy causes a diffuse injury that leads to acute cell damage and, if chronic, leads to detrimental long-term cognitive deficits. The literature presents a neuro-centric approach to the role of mitochondria dynamics dysfunction in bTBI, and changes in astrocyte-specific mitochondrial dynamics have not been characterized. The balance between fission and fusion events is known as mitochondrial dynamics. As a result of fission and fusion, the mitochondrial structure is constantly altering its shape to respond to physiological stimuli or stress, which in turn affects mitochondrial function. Astrocytic mitochondria are recognized to play an essential role in overall brain metabolism, synaptic transmission, and neuron protection. Mitochondria are vulnerable to injury insults, leading to the increase in mitochondrial fission, a mechanism controlled by the GTPase dynamin-related protein (Drp1) and the phosphorylation of Drp1 at serine 616 (p-Drp1^s616). This site is critical to mediate the Drp1 translocation to mitochondria to promote fission events and consequently leads to fragmentation. An increase in mitochondrial fragmentation could have negative consequences, such as promoting an excessive generation of reactive oxygen species or triggering cytochrome c release. The aim of the present study was to characterize the unique pattern of astrocytic mitochondrial dynamics by exploring the role of DRP1 with a combination of in vitro and in vivo bTBI models. Differential remodeling of the astrocytic mitochondrial network was observed, corresponding with increases in p-Drp1^S616 four hours and seven days post-injury. Further, results showed a time-dependent reactive astrocyte phenotype transition in the rat hippocampus. This discovery can lead to innovative therapeutics targets to help prevent the secondary injury cascade after blast injury that involves mitochondria dysfunction.

Exercise and mitochondrial remodeling to prevent age-related neurodegeneration

Healthy brain activity requires precise ion and energy management creating a strong reliance on mitochondrial function. Age-related neurodegeneration leads to a decline in mitochondrial function and increased oxidative stress, with associated declines in mitochondrial mass, respiration capacity, and respiration efficiency. The interdependent processes of mitochondrial protein turnover and mitochondrial dynamics, known together as mitochondrial remodeling, play essential roles in mitochondrial health and therefore brain function. This mini-review describes the role of mitochondria in neurodegeneration and brain health, current practices for assessing both aspects of mitochondrial remodeling, and how exercise mitigates the adverse effects of aging in the brain. Exercise training elicits functional adaptations to improve brain health, and current literature strongly suggests that mitochondrial remodeling plays a vital role in these positive adaptations. Despite substantial implications that the two aspects of mitochondrial remodeling are interdependent, very few investigations have simultaneously measured mitochondrial dynamics and protein synthesis. An improved understanding of the partnership between mitochondrial protein turnover and mitochondrial dynamics will provide a better understanding of their role in both brain health and disease, as well as how they induce protection following exercise.

Proteomic analysis of spinal cord tissue in a rat model of cancer-induced bone pain

Background

Cancer-induced bone pain (CIBP) is a moderate to severe pain and seriously affects patients' quality of life. Spinal cord plays critical roles in pain generation and maintenance. Identifying differentially expressed proteins (DEPs) in spinal cord is essential to elucidate the mechanisms of cancer pain.

Methods

CIBP rat model was established by the intratibial inoculation of MRMT-1 cells. Positron emission tomography (PET) scan and transmission electron microscopy (TEM) were used to measure the stats of spinal cord in rats. Label free Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) were used to analyze the whole proteins from the lumbar spinal cord. Differentially expressed proteins (DEPs) were performed using Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and verified using Western blot and immunofluorescence assay.

Results

In the current study, CIBP rats exhibited bone damage, spontaneous pain, mechanical hyperalgesia, and impaired motor ability. In spinal cord, an hypermetabolism and functional abnormality were revealed on CIBP rats. An increase of synaptic vesicles density in active zone and a disruption of mitochondrial structure in spinal cord of CIBP rats were observed. Meanwhile, 422 DEPs, consisting of 167 up-regulated and 255 down-regulated proteins, were identified among total 1539 proteins. GO enrichment analysis indicated that the DEPs were mainly involved in catabolic process, synaptic function, and enzymic activity. KEGG pathway enrichment analysis indicated a series of pathways, including nervous system disease, hormonal signaling pathways and amino acid metabolism, were involved. Expression change of synaptic and mitochondrial related protein, such as complexin 1 (CPLX1), synaptosomal-associated protein 25 (SNAP25), synaptotagmin 1 (SYT1), aldehyde dehydrogenase isoform 1B1 (ALDH1B1), Glycine amidinotransferase (GATM) and NADH:ubiquinone oxidoreductase subunit A11 (NDUFA11), were further validated using immunofluorescence and Western blot analysis.

Conclusion

This study provides valuable information for understanding the mechanisms of CIBP, and supplies potential therapeutic targets for cancer pain.

Disruption of Astrocyte-Dependent Dopamine Control in the Developing Medial Prefrontal Cortex Leads to Excessive Grooming in Mice

BACKGROUND

Astrocytes control synaptic activity by modulating perisynaptic concentrations of ions and neurotransmitters including dopamine (DA) and, as such, could be involved in the modulating aspects of mammalian behavior.

METHODS

We produced a conditional deletion of the vesicular monoamine transporter 2 (VMAT2) specifically in astrocytes (aVMTA2cKO mice) and studied the effects of the lack of VMAT2 in prefrontal cortex (PFC) astrocytes on the regulation of DA levels, PFC circuit functions, and behavioral processes.

RESULTS

We found a significant reduction of medial PFC (mPFC) DA levels and excessive grooming and compulsive repetitive behaviors in aVMAT2cKO mice. The mice also developed a synaptic pathology, expressed through increased relative AMPA versus NMDA receptor currents in synapses of the dorsal striatum receiving inputs from the mPFC. Importantly, behavioral and synaptic phenotypes were rescued by re-expression of mPFC VMAT2 and L-DOPA treatment, showing that the deficits were driven by mPFC astrocytes that are critically involved in developmental DA homeostasis. By analyzing human tissue samples, we found that VMAT2 is expressed in human PFC astrocytes, corroborating the potential translational relevance of our observations in mice.

CONCLUSIONS

Our study shows that impairment of the astrocytic control of DA in the mPFC leads to symptoms resembling obsessive-compulsive spectrum disorders such as trichotillomania and has a profound impact on circuit function and behaviors.

Interactions between Major Bioactive Polyphenols of Sugarcane Top: Effects on Human Neural Stem Cell Differentiation and Astrocytic Maturation

Sugarcane (Saccharum officinarum L.) is a tropical plant grown for sugar production. We recently showed that sugarcane top (ST) ameliorates cognitive decline in a mouse model of accelerated aging via promoting neuronal differentiation and neuronal energy metabolism and extending the length of the astrocytic process in vitro. Since the crude extract consists of multicomponent mixtures, it is crucial to identify bioactive compounds of interest and the affected molecular targets. In the present study, we investigated the bioactivities of major polyphenols of ST, namely 3-O-caffeoylquinic acid (3CQA), 5-O-caffeoylquinic acid (5CQA), 3-O-feruloylquinic acid (3FQA), and Isoorientin (ISO), in human fetal neural stem cells (hNSCs)- an in vitro model system for studying neural development. We found that multiple polyphenols of ST contributed synergistically to stimulate neuronal differentiation of hNSCs and induce mitochondrial activity in immature astrocytes. Mono-CQAs (3CQA and 5CQA) regulated the expression of cyclins related to G1 cell cycle arrest, whereas ISO regulated basic helix-loop-helix transcription factors related to cell fate determination. Additionally, mono-CQAs activated p38 and ISO inactivated GSK3β. In hNSC-derived immature astrocytes, the compounds upregulated mRNA expression of PGC-1α, a master regulator of astrocytic mitochondrial biogenesis. Altogether, our findings suggest that synergistic interactions between major polyphenols of ST contribute to its potential for neuronal differentiation and astrocytic maturation.

Human iPSC-Derived Cortical Neurons Display Homeostatic Plasticity

Maintaining the excitability of neurons and circuits is fundamental for healthy brain functions. The global compensatory increase in excitatory synaptic strength, in response to decreased activity, is one of the main homeostatic mechanisms responsible for such regulation. This type of plasticity has been extensively characterized in rodents in vivo and in vitro, but few data exist on human neurons maturation. We have generated an in vitro cortical model system, based on differentiated human-induced pluripotent stem cells, chronically treated with tetrodotoxin, to investigate homeostatic plasticity at different developmental stages. Our findings highlight the presence of homeostatic plasticity in human cortical networks and show that the changes in synaptic strength are due to both pre- and post-synaptic mechanisms. Pre-synaptic plasticity involves the potentiation of neurotransmitter release machinery, associated to an increase in synaptic vesicle proteins expression. At the post-synaptic level, we report an increase in the expression of post-synaptic density proteins, involved in glutamatergic receptor anchoring. These results extend our understanding of neuronal homeostasis and reveal the developmental regulation of its expression in human cortical networks. Since induced pluripotent stem cell-derived neurons can be obtained from patients with neurodevelopmental and neurodegenerative diseases, our platform offers a versatile model for assessing human neural plasticity under physiological and pathological conditions.

Foundations and implications of astrocyte heterogeneity during brain development and disease

Astrocytes play crucial roles in regulating brain circuit formation and physiology. Recent technological advances have revealed unprecedented levels of astrocyte diversity encompassing molecular, morphological, and functional differences. This diversification is initiated during embryonic specification events and (in rodents) continues into the early postnatal period where it overlaps with peak synapse development and circuit refinement. In fact, several lines of evidence suggest astrocyte diversity both influences and is a consequence of molecular crosstalk among developing astrocytes and other cell types, notably neurons and their synapses. Neurological disease states exhibit additional layers of astrocyte heterogeneity, which could help shed light on these cells' key pathological roles. This review highlights recent advances in clarifying astrocyte heterogeneity and molecular/cellular crosstalk and identifies key outstanding questions.

Reduced astrocytic mGluR5 in the hippocampus is associated with stress-induced depressive-like behaviors in mice

Major depressive disorder (MDD) is one of the most common and disabling mental disorders that characterized by profound disturbances in emotional regulation, motivation, cognition, and the physiology of affected individuals. Although MDD was initially thought to be primarily triggered through neuronal dysfunction, the pathological alterations in astrocytic function have been previously reported in MDD. We report that chronic restraint stress (CRS) induces astrocyte activation and decreases expression of astrocytic mGluR5 in the hippocampal CA1 of susceptible mice exhibited depressive-like behaviors. Reducing expression of astrocytic mGluR5 in dorsal CA1 simulates CRS-induced depressive-like behaviors and impairs excitatory synaptic function in mice, while overexpression of astrocytic mGluR5 in dorsal CA1 rescues CRS-induced depressive-like traits and excitatory synaptic dysfunction. Thus, we provide direct evidence for an important role of astrocytic mGluR5 in producing the behavioral phenotypes of MDD, supporting astrocytic mGluR5 may serve as an effective therapeutic target for MDD.

Age-Associated Glia Remodeling and Mitochondrial Dysfunction in Neurodegeneration: Antioxidant Supplementation as a Possible Intervention

Aging induces substantial remodeling of glia, including density, morphology, cytokine expression, and phagocytic capacity. Alterations of glial cells, such as hypertrophy of lysosomes, endosomes and peroxisomes, and the progressive accumulation of lipofuscin, lipid droplets, and other debris have also been reported. These abnormalities have been associated with significant declines of microglial processes and reduced ability to survey the surrounding tissue, maintain synapses, and recover from injury. Similarly, aged astrocytes show reduced capacity to support metabolite transportation to neurons. In the setting of reduced glial activity, stressors and/or injury signals can trigger a coordinated action of microglia and astrocytes that may amplify neuroinflammation and contribute to the release of neurotoxic factors. Oxidative stress and proteotoxic aggregates may burst astrocyte-mediated secretion of pro-inflammatory cytokines, thus activating microglia, favoring microgliosis, and ultimately making the brain more susceptible to injury and/or neurodegeneration. Here, we discuss the contribution of microglia and astrocyte oxidative stress to neuroinflammation and neurodegeneration, highlight the pathways that may help gain insights into their molecular mechanisms, and describe the benefits of antioxidant supplementation-based strategies.

Emerging evidence for astrocyte dysfunction in schizophrenia

Schizophrenia is a complex, chronic mental health disorder whose heterogeneous genetic and neurobiological background influences early brain development, and whose precise etiology is still poorly understood. Schizophrenia is not characterized by gross brain pathology, but involves subtle pathological changes in neuronal populations and glial cells. Among the latter, astrocytes critically contribute to the regulation of early neurodevelopmental processes, and any dysfunctions in their morphological and functional maturation may lead to aberrant neurodevelopmental processes involved in the pathogenesis of schizophrenia, such as mitochondrial biogenesis, synaptogenesis, and glutamatergic and dopaminergic transmission. Studies of the mechanisms regulating astrocyte maturation may therefore improve our understanding of the cellular and molecular mechanisms underlying the pathogenesis of schizophrenia.

Maternal Inflammation During Pregnancy and Offspring Brain Development: The Role of Mitochondria

The association between maternal immune activation (MIA) during pregnancy and risk for offspring neuropsychiatric disorders has been increasingly recognized over the past several years. Among the mechanistic pathways that have been described through which maternal inflammation during pregnancy may affect fetal brain development, the role of mitochondria has received little attention. In this review, the role of mitochondria as a potential mediator of the association between MIA during pregnancy and offspring brain development and risk for psychiatric disorders will be proposed. As a basis for this postulation, convergent evidence is presented supporting the obligatory role of mitochondria in brain development, the role of mitochondria as mediators and initiators of inflammatory processes, and evidence of mitochondrial dysfunction in preclinical MIA exposure models and human neurodevelopmental disorders. Elucidating the role of mitochondria as a potential mediator of MIA-induced alterations in brain development and neurodevelopmental disease risk may not only provide new insight into the pathophysiology of mental health disorders that have their origins in exposure to infection/immune activation during pregnancy but also offer new therapeutic targets.

Revealing the Impact of Mitochondrial Fitness During Early Neural Development Using Human Brain Organoids

Mitochondrial homeostasis -including function, morphology, and inter-organelle communication- provides guidance to the intrinsic developmental programs of corticogenesis, while also being responsive to environmental and intercellular signals. Two- and three-dimensional platforms have become useful tools to interrogate the capacity of cells to generate neuronal and glia progeny in a background of metabolic dysregulation, but the mechanistic underpinnings underlying the role of mitochondria during human neurogenesis remain unexplored. Here we provide a concise overview of cortical development and the use of pluripotent stem cell models that have contributed to our understanding of mitochondrial and metabolic regulation of early human brain development. We finally discuss the effects of mitochondrial fitness dysregulation seen under stress conditions such as metabolic dysregulation, absence of developmental apoptosis, and hypoxia; and the avenues of research that can be explored with the use of brain organoids.

Synaptic Plasticity Dysfunctions in the Pathophysiology of 22q11 Deletion Syndrome: Is There a Role for Astrocytes?

The 22q11 deletion syndrome (DS) is the most common microdeletion syndrome in humans and gives a high probability of developing psychiatric disorders. Synaptic and neuronal malfunctions appear to be at the core of the symptoms presented by patients. In fact, it has long been suggested that the behavioural and cognitive impairments observed in 22q11DS are probably due to alterations in the mechanisms regulating synaptic function and plasticity. Often, synaptic changes are related to structural and functional changes observed in patients with cognitive dysfunctions, therefore suggesting that synaptic plasticity has a crucial role in the pathophysiology of the syndrome. Most interestingly, among the genes deleted in 22q11DS, six encode for mitochondrial proteins that, in mouse models, are highly expressed just after birth, when active synaptogenesis occurs, therefore indicating that mitochondrial processes are strictly related to synapse formation and maintenance of a correct synaptic signalling. Because correct synaptic functioning, not only requires correct neuronal function and metabolism, but also needs the active contribution of astrocytes, we summarize in this review recent studies showing the involvement of synaptic plasticity in the pathophysiology of 22q11DS and we discuss the relevance of mitochondria in these processes and the possible involvement of astrocytes.