Dysregulation of PGC-1α-Dependent Transcriptional Programs in Neurological and Developmental Disorders: Therapeutic Challenges and Opportunities

The effects of different durations of exposure to hypomagnetic field on the number of active mitochondria and ROS levels in the mouse hippocampus

Reactive oxygen species (ROS) are one of the potential molecules in response to a hypomagnetic field (HMF), and exposure to an HMF for eight weeks led to an increase in ROS levels in the whole hippocampus area in mice. ROS are mainly derived from the byproducts of mitochondrial metabolism. However, previous in vivo studies mostly focus on the influence of one time point of HMF exposure on the mouse hippocampus and lack comparative studies on the effects of different durations of HMF exposure on the mouse hippocampus. Here, we investigated the effects of different durations of HMF on the number of active mitochondria and ROS levels in mouse hippocampus. Compared with the geomagnetic field (GMF) group, we found that the number of active mitochondria in the hippocampus was significantly reduced during the sixth week of HMF exposure, whereas the number of active mitochondria was significantly reduced and the ROS levels was significantly increased during the eighth week of HMF exposure. The number of active mitochondria gradually decreased and ROS levels gradually increased in both GMF and HMF groups with prolonged exposure time. In addition, the expression level of the PGC-1α gene in the hippocampus, the main regulator of mitochondrial biogenesis, decreased significantly in the eighth week of HMF exposure. These results reveal that the changes in active mitochondria number and ROS levels were dependent on the durations of HMF exposure, and prolonged exposure to HMF exacerbates these changes.

Amelioration of cisplatin-induced neurodegenerative changes in rats and restoration of mitochondrial biogenesis by 6-bromoindirubin-3'-oxime: The implication of the GSK-3β/PGC1-α axis

BACKGROUND

The cognitive deficits observed after treatment with chemotherapeutic drugs are obvious clinical problems. For treating chemotherapy-induced cognitive deficits (CICD), the treatment modalities must target its underlying mechanisms. Specifically, cisplatin may activate glycogen synthase kinase-3β (GSK-3β), thereby enhancing neuronal apoptosis. 6-bromoindirubin-3'-oxime (6BIO) was not investigated previously in a model of CICD. Therefore, this investigation aimed to address the impacts of GSK3 inhibition on regulating cell signaling, which contributes to neurodegeneration and cognitive impairment.

METHODS

Thirty adult male Wistar rats were randomly allocated into control groups, while two experimental groups were exposed to repeated cisplatin injections (2 mg/kg intraperitoneally (ip), twice weekly, nine injections), termed chemobrain groups. The rats in the two experimental groups were equally divided into the chemobrain group (untreated) and the chemobrain-6BIO group (treated with 6BIO at a dose of 8.5 μg/kg ip every two days, started after the last dose of cisplatin and continued for two weeks).

RESULTS

Repeated exposure to cisplatin led to a marked decline in cognitive functions. GSK3 inhibition exerted neuroprotection by decreasing the expression of p-tau and amyloid β, thereby improving cognition. 6BIO, the GSK-3β inhibitor, restored mitochondrial biogenesis by augmenting the protein levels of PGC1-α and increasing the number of mitochondria in the cerebral cortex and hippocampus.

CONCLUSION

6BIO provided neuroprotection and exhibited anti-apoptotic and anti-oxidative effects in a rat model of chemobrain.

The Neuroprotective Flavonoids Sterubin and Fisetin Maintain Mitochondrial Health under Oxytotic/Ferroptotic Stress and Improve Bioenergetic Efficiency in HT22 Neuronal Cells

The global increase in the aging population has led to a rise in many age-related diseases with continuing unmet therapeutic needs. Research into the molecular mechanisms underlying both aging and neurodegeneration has identified promising therapeutic targets, such as the oxytosis/ferroptosis cell death pathway, in which mitochondrial dysfunction plays a critical role. This study focused on sterubin and fisetin, two flavonoids from the natural pharmacopeia previously identified as strong inhibitors of the oxytosis/ferroptosis pathway. Here, we investigated the effects of the compounds on the mitochondrial physiology in HT22 hippocampal nerve cells under oxytotic/ferroptotic stress. We show that the compounds can restore mitochondrial homeostasis at the level of redox regulation, calcium uptake, biogenesis, fusion/fission dynamics, and modulation of respiration, leading to the enhancement of bioenergetic efficiency. However, mitochondria are not required for the neuroprotective effects of sterubin and fisetin, highlighting their diverse homeostatic impacts. Sterubin and fisetin, thus, provide opportunities to expand drug development strategies for anti-oxytotic/ferroptotic agents and offer new perspectives on the intricate interplay between mitochondrial function, cellular stress, and the pathophysiology of aging and age-related neurodegenerative disorders.

Empagliflozin repurposing in Parkinson's disease; modulation of oxidative stress, neuroinflammation, AMPK/SIRT-1/PGC-1α, and wnt/β-catenin pathways

Parkinson's disease is a neuroprogressive disorder characterized by loss of dopaminergic neurons in substantia nigra pars compacta. Empagliflozin (EMPA), a SGLT-2 inhibitor, is an oral hypoglycemic agent with reported anti-inflammatory and antioxidant effects. The current study aimed to evaluate the neuroprotective effect of EMPA in rotenone-induced Parkinson's disease. Rats were randomly distributed among five groups as follows: control, rotenone (2 mg/kg), rotenone + EMPA (10 mg/kg), rotenone + EMPA (20 mg/kg), and EMPA (20 mg/kg) groups. They were treated for 30 consecutive days. Rotenone reduced locomotor activity and retention time on the rotarod performance test while elongated descent latency time. On the other side, EMPA corrected these behavioral changes. These results were confirmed by histological examination and number of intact neurons. Moreover, rotenone induced alpha-synuclein accumulation, reduced tyrosine hydroxylase expression, dopamine, 3,4-dihydroxyphenylacetic acid, and homovanillic acid concentrations. On the other side, EMPA reversed such effects induced by rotenone. Depending on previous results, EMPA (20 mg/kg) was selected for further mechanistic studies. Rotenone ameliorated superoxide dismutase and catalase activities and enhanced lipid peroxidation, interleukin-1β, and tumor necrosis factor-α levels. By contrast, EMPA opposed rotenone-induced effects on oxidative stress and inflammation. Besides, rotenone reduced the expression of pAMP-activated protein kinase (pAMPK), peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), and Sirtuin-1 (SIRT-1), as well as abrogated NAD+/NADH ratio. However, EMPA activated the AMPK/SIRT-1/PGC-1α pathway. Moreover, rotenone hindered the wnt/β-catenin pathway by reducing the wnt-3a level and β-catenin expression. On the other side, EMPA triggered activation of the wnt/β-catenin pathway. Collectively, EMPA may provide a promising solution for Parkinson's patients worldwide.

Mitochondria and Oxidative Stress as a Link between Alzheimer's Disease and Diabetes Mellitus

This review is devoted to the problems of the common features linking metabolic disorders and type 2 diabetes with the development of Alzheimer's disease. The pathogenesis of Alzheimer's disease closely intersects with the mechanisms of type 2 diabetes development, and an important risk factor for both pathologies is aging. Common pathological mechanisms include both factors in the development of oxidative stress, neuroinflammation, insulin resistance, and amyloidosis, as well as impaired mitochondrial dysfunctions and increasing cell death. The currently available drugs for the treatment of type 2 diabetes and Alzheimer's disease have limited therapeutic efficacy. It is important to note that drugs used to treat Alzheimer's disease, in particular acetylcholinesterase inhibitors, show a positive therapeutic potential in the treatment of type 2 diabetes, while drugs used in the treatment of type 2 diabetes can also prevent a number of pathologies characteristic for Alzheimer's disease. A promising direction in the search for a strategy for the treatment of type 2 diabetes and Alzheimer's disease may be the creation of complex multi-target drugs that have neuroprotective potential and affect specific common targets for type 2 diabetes and Alzheimer's disease.

The neuroprotective effect of vitamin D in Parkinson's disease: association or causation

Parkinson's disease (PD) is a chronic neurodegenerative disease (NDD) due to the degeneration of dopaminergic neurons (DNs) in the substantia nigra (SN). PD is characterized by diverse motor symptoms such as rigidity, resting tremors, and bradykinesia, and non-motor symptoms such as cognitive dysfunction and sleep disturbances. Vitamin D (VD), VD receptor (VDR), and VD metabolites are present in the brain and play a role in maintaining the development, differentiation, and functions of the DNs. VDRs exert protective effects against PD neuropathology by modulating functional capacity and DNs neurotransmission in the SN. In virtue of its anti-inflammatory and antioxidant activities, VD could be effective in the prevention and treatment of PD. VD exerts a neuroprotective effect by reducing oxidative stress and mitochondrial dysfunction, and by increasing autophagy and brain-derived neurotrophic factor (BDNF). Low VD serum level is connected with cognitive dysfunction and the development of dementia in PD. The VD-mediated cognitive augmenting effect is interrelated to the safeguarding of synaptic plasticity and modulation of neurotransmitter release. VD deficiency is linked with the severity of olfactory dysfunction which precedes the progression of symptomatic PD. However, the precise role of VD in PD remains unidentified, and there is a conflict about whether treatment with VD can ameliorate PD or not.

The master energy homeostasis regulator PGC-1α exhibits an mRNA nuclear export function

PGC-1α plays a central role in maintaining mitochondrial and energy metabolism homeostasis, linking external stimuli to transcriptional co-activation of genes involved in adaptive and age-related pathways. The carboxyl-terminus encodes a serine/arginine-rich (RS) region and an RNA recognition motif, however the RNA-processing function(s) were poorly investigated over the past 20 years. Here, we show that the RS domain of human PGC-1α directly interacts with RNA and the nuclear RNA export receptor NXF1. Inducible depletion of PGC-1α and expression of RNAi-resistant RS-deleted PGC-1α further demonstrate that its RNA/NXF1-binding activity is required for the nuclear export of some canonical mitochondrial-related mRNAs and mitochondrial homeostasis. Genome-wide investigations reveal that the nuclear export function is not strictly linked to promoter-binding, identifying in turn novel regulatory targets of PGC-1α in non-homologous end-joining and nucleocytoplasmic transport. These findings provide new directions to further elucidate the roles of PGC-1α in gene expression, metabolic disorders, aging and neurodegeneration.

Differential expression of m5C RNA methyltransferase genes NSUN6 and NSUN7 in Alzheimer's disease and traumatic brain injury

Epigenetic processes have become increasingly relevant in understanding disease-modifying mechanisms. 5-Methylcytosine methylations of DNA (5mC) and RNA (m⁵C) have functional transcriptional and RNA translational consequences and are tightly regulated by writer, reader and eraser effector proteins. To investigate the involvement of 5mC/5hmC and m⁵C effector proteins contributing to the development of dementia neuropathology, RNA sequencing data of 31 effector proteins across four brain regions was examined in 56 aged non-affected and 51 Alzheimer's disease (AD) individuals obtained from the Aging, Dementia and Traumatic Brain Injury Study. Gene expression profiles were compared between AD and controls, between neuropathological Braak and CERAD scores and in individuals with a history of traumatic brain injury (TBI). We found an increase in the DNA methylation writers DNMT1, DNMT3A and DNMT3B messenger RNA (mRNA) and a decrease in the reader UHRF1 mRNA in AD samples across three brain regions whilst the DNA erasers GADD45B and AICDA showed changes in mRNA abundance within neuropathological load groupings. RNA methylation writers NSUN6 and NSUN7 showed significant expression differences with AD and, along with the reader ALYREF, differences in expression for neuropathologic ranking. A history of TBI was associated with a significant increase in the DNA readers ZBTB4 and MeCP2 (p < 0.05) and a decrease in NSUN6 (p < 0.001) mRNA. These findings implicate regulation of protein pathways disrupted in AD and TBI via multiple pre- and post-transcriptional mechanisms including potentially acting upon transfer RNAs, enhancer RNAs as well as nuclear-cytoplasmic shuttling and cytoplasmic translational control. The targeting of such processes provides new therapeutic avenues for neurodegenerative brain conditions.

PGC 1α-Mediates Mitochondrial Damage in the Liver by Inhibiting the Mitochondrial Respiratory Chain as a Non-cholinergic Mechanism of Repeated Low-Level Soman Exposure

This work aimed to assess whether mitochondrial damage in the liver induced by subacute soman exposure is caused by peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) and whether PGC-1α regulates mitochondrial respiratory chain damage. Toxicity mechanism research may provide theoretical support for developing anti-toxic drugs in the future. First, a soman animal model was established in male Sprague-Dawley (SD) rats by subcutaneous soman injection. Then, liver damage was biochemically evaluated, and acetylcholinesterase (AChE) activity was also determined. Transmission electron microscopy (TEM) was performed to examine liver mitochondrial damage, and high-resolution respirometry was carried out for assessing mitochondrial respiration function. In addition, complex I-IV levels were quantitatively evaluated in isolated liver mitochondria by enzyme-linked immunosorbent assay (ELISA). PGC-1α levels were detected with a Jess capillary-based immunoassay device. Finally, oxidative stress was analyzed by quantifying superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), oxidized glutathione (GSSG), and reactive oxygen species (ROS) levels. Repeated low-level soman exposure did not alter AChE activity, while increasing morphological damage of liver mitochondria and liver enzyme levels in rat homogenates. Complex I, II and I + II activities were 2.33, 4.95, and 5.22 times lower after treatment compared with the control group, respectively. Among complexes I-IV, I-III decreased significantly (p < 0.05), and PGC-1α levels were 1.82 times lower after soman exposure than in the control group. Subacute soman exposure significantly increased mitochondrial ROS production, which may cause oxidate stress. These findings indicated dysregulated mitochondrial energy metabolism involves PGC-1α protein expression imbalance, revealing non-cholinergic mechanisms for soman toxicity.

PGC1α: an emerging therapeutic target for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN)-mediated paresthesias are a common complication in cancer patients undergoing chemotherapy. There are currently no treatments available to prevent or reverse CIPN. Therefore, new therapeutic targets are urgently needed to develop more effective analgesics. However, the pathogenesis of CIPN remains unclear, and the prevention and treatment strategies of CIPN are still unresolved issues in medicine. More and more studies have demonstrated that mitochondrial dysfunction has become a major factor in promoting the development and maintenance of CIPN, and peroxisome proliferator-activated receptor gamma (PPARγ) coactivator 1α (PGC1α) plays a significant role in maintaining the mitochondrial function, protecting peripheral nerves, and alleviating CIPN. In this review, we highlight the core role of PGC1α in regulating oxidative stress and maintaining normal mitochondrial function and summarize recent advances in its therapeutic effects and mechanisms in CIPN and other forms of peripheral neuropathy. Emerging studies suggest that PGC1α activation may positively impact CIPN mitigation by modulating oxidative stress, mitochondrial dysfunction, and inflammation. Therefore, novel therapeutic strategies targeting PGC1α could be a potential therapeutic target in CIPN.

The Generation of Human iPSC Lines from Three Individuals with Dravet Syndrome and Characterization of Neural Differentiation Markers in iPSC-Derived Ventral Forebrain Organoid Model

Dravet syndrome (DRVT) is a rare form of neurodevelopmental disorder with a high risk of sudden unexpected death in epilepsy (SUDEP), caused mainly (>80% cases) by mutations in the SCN1A gene, coding the Nav1.1 protein (alfa-subunit of voltage-sensitive sodium channel). Mutations in SCN1A are linked to heterogenous epileptic phenotypes of various types, severity, and patient prognosis. Here we generated iPSC lines from fibroblasts obtained from three individuals affected with DRVT carrying distinct mutations in the SCN1A gene (nonsense mutation p.Ser1516*, missense mutation p.Arg1596His, and splicing mutation c.2589+2dupT). The iPSC lines, generated with the non-integrative approach, retained the distinct SCN1A gene mutation of the donor fibroblasts and were characterized by confirming the expression of the pluripotency markers, the three-germ layer differentiation potential, the absence of exogenous vector expression, and a normal karyotype. The generated iPSC lines were used to establish ventral forebrain organoids, the most affected type of neurons in the pathology of DRVT. The DRVT organoid model will provide an additional resource for deciphering the pathology behind Nav1.1 haploinsufficiency and drug screening to remediate the functional deficits associated with the disease.

PGC-1α activity and mitochondrial dysfunction in preterm infants

Extremely low gestational age neonates (ELGANs) are born in a relatively hyperoxic environment with weak antioxidant defenses, placing them at high risk for mitochondrial dysfunction affecting multiple organ systems including the nervous, respiratory, ocular, and gastrointestinal systems. The brain and lungs are highly affected by mitochondrial dysfunction and dysregulation in the neonate, causing white matter injury (WMI) and bronchopulmonary dysplasia (BPD), respectively. Adequate mitochondrial function is important in providing sufficient energy for organ development as it relates to alveolarization and axonal myelination and decreasing oxidative stress via reactive oxygen species (ROS) and reactive nitrogen species (RNS) detoxification. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) is a master regulator of mitochondrial biogenesis and function. Since mitochondrial dysfunction is at the root of WMI and BPD pathobiology, exploring therapies that can regulate PGC-1α activity may be beneficial. This review article describes several promising therapeutic agents that can mitigate mitochondrial dysfunction through direct and indirect activation and upregulation of the PGC-1α pathway. Metformin, resveratrol, omega 3 fatty acids, montelukast, L-citrulline, and adiponectin are promising candidates that require further pre-clinical and clinical studies to understand their efficacy in decreasing the burden of disease from WMI and BPD in preterm infants.

Estrogen-related receptor gamma regulates mitochondrial and synaptic genes and modulates vulnerability to synucleinopathy

Many studies implicate mitochondrial dysfunction as a key contributor to cell loss in Parkinson disease (PD). Previous analyses of dopaminergic (DAergic) neurons from patients with Lewy-body pathology revealed a deficiency in nuclear-encoded genes for mitochondrial respiration, many of which are targets for the transcription factor estrogen-related receptor gamma (Esrrg/ERRγ). We demonstrate that deletion of ERRγ from DAergic neurons in adult mice was sufficient to cause a levodopa-responsive PD-like phenotype with reductions in mitochondrial gene expression and number, that partial deficiency of ERRγ hastens synuclein-mediated toxicity, and that ERRγ overexpression reduces inclusion load and delays synuclein-mediated cell loss. While ERRγ deletion did not fully recapitulate the transcriptional alterations observed in postmortem tissue, it caused reductions in genes involved in synaptic and mitochondrial function and autophagy. Altogether, these experiments suggest that ERRγ-deficient mice could provide a model for understanding the regulation of transcription in DAergic neurons and that amplifying ERRγ-mediated transcriptional programs should be considered as a strategy to promote DAergic maintenance in PD.

Enhanced hippocampal neurogenesis mediated by PGC-1α-activated OXPHOS after neonatal low-dose Propofol exposure

Background

Developing brain is highly plastic and can be easily affected. Growing pediatric usage of anesthetics during painless procedures has raised concerns about the effect of low-dose anesthetics on neurodevelopment. It is urgent to ascertain the neuronal effect of low-dose Propofol, a widely used anesthetic in pediatrics, on developing brains.

Methods

The behavioral tests after neonatal exposure to low-dose/high-dose Propofol in mice were conducted to clarify the cognitive effect. The nascent cells undergoing proliferation and differentiation stage in the hippocampus and cultured neural stem cells (NSCs) were further identified. In addition, single-nuclei RNA sequencing (snRNA-seq), NSCs bulk RNA-seq, and metabolism trials were performed for pathway investigation. Furthermore, small interfering RNA and stereotactic adenovirus injection were, respectively, used in NSCs and hippocampal to confirm the underlying mechanism.

Results

Behavioral tests in mice showed enhanced spatial cognitive ability after being exposed to low-dose Propofol. Activated neurogenesis was observed both in hippocampal and cultured NSCs. Moreover, transcriptome analysis of snRNA-seq, bulk RNA-seq, and metabolism trials revealed a significantly enhanced oxidative phosphorylation (OXPHOS) level in NSCs. Furthermore, PGC-1α, a master regulator in mitochondria metabolism, was found upregulated after Propofol exposure both in vivo and in vitro. Importantly, downregulation of PGC-1α remarkably prevented the effects of low-dose Propofol in activating OXPHOS and neurogenesis.

Conclusions

Taken together, this study demonstrates a novel alteration of mitochondrial function in hippocampal neurogenesis after low-dose Propofol exposure, suggesting the safety, even potentially beneficial effect, of low-dose Propofol in pediatric use.

Starting the engine of the powerhouse: mitochondrial transcription and beyond

Mitochondria are central hubs for cellular metabolism, coordinating a variety of metabolic reactions crucial for human health. Mitochondria provide most of the cellular energy via their oxidative phosphorylation (OXPHOS) system, which requires the coordinated expression of genes encoded by both the nuclear (nDNA) and mitochondrial genomes (mtDNA). Transcription of mtDNA is not only essential for the biogenesis of the OXPHOS system, but also generates RNA primers necessary to initiate mtDNA replication. Like the prokaryotic system, mitochondria have no membrane-based compartmentalization to separate the different steps of mtDNA maintenance and expression and depend entirely on nDNA-encoded factors imported into the organelle. Our understanding of mitochondrial transcription in mammalian cells has largely progressed, but the mechanisms regulating mtDNA gene expression are still poorly understood despite their profound importance for human disease. Here, we review mechanisms of mitochondrial gene expression with a focus on the recent findings in the field of mammalian mtDNA transcription and disease phenotypes caused by defects in proteins involved in this process.

Modulation of gut microbiota and markers of metabolic syndrome in mice on cholesterol and fat enriched diet by butterfly pea flower kombucha

Clitoria ternatea, with an alternative name, Butterfly pea, is increasingly being explored for medical purposes and the development of a wide range of processed products. This study aimed to incorporate Butterfly pea into an innovative probiotic drink through a symbiotic culture of bacteria and yeast (SCOBY) fermentation and to evaluate the biological activity. The benefits of the drink, referred to as butterfly pea flower kombucha (KBPF) was determined in vitro and in metabolically disorder mice that receive a diet rich in cholesterol and fat (CFED). Forty white male were categorized into four groups, i.e., A = Control/Normal Diet; B = CFED alone; C = CFED + KBPF 65 mg/kg BW (Body Weight); D = CFED + KBPF 130 mg/kg BW, and then sacrificed after 6 weeks of intervention. Seventy-nine secondary metabolite compounds were successfully identified in KBPF using LC-HRMS. In vitro studies showed the potential activity of KBPF in inhibiting not only ABTS, but also lipid (lipase) and carbohydrate (α-amylase, α-glucosidase) hydrolyzing enzymes to levels similar to acarbose control at 50–250 μg/mL. In the in vivo study, the administration of KBPF (130 mg/kg BW) significantly alleviated metabolic disorders caused by high-fat diet. Specifically, lipid profile (HDL, LDL, TC, TG), blood glucose, markers of oxidative stress (SOD liver), metabolic enzymes (lipase, amylase), and markers of inflammation (PGC-1α, TNF-α, and IL-10) were in most cases restored to normal values. Additionally, the gut microbiota community analysis showed that KBPF has a positive effect (p = 0.01) on both the Bacteroidetes phylum and the Firmicutes phylum. The new KBPF drink is a promising therapeutic functional food for preventing metabolic diseases.

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Clitoria ternatea or Butterfly pea flower processed or innovated into a functional probiotic drink, namely KBPF.

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A total of 79 Secondary metabolite compounds of KBPF were successfully identified.

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In vitro studies showed the potential activity of KBPF in inhibiting ABTS, lipase, α-glucosidase, and α-amylase.

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Administering a dose of 130 mg/kg BW KBPF was significantly promising in the alleviation of biomarker metabolic disorders with immunomodulatory effects.

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By modulating the diversity of the gut microbiome, KBPF can be a promising nutraceutical in preventing metabolic syndrome with inflammatory diseases.

Covering the Role of PGC-1α in the Nervous System

The peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a well-known transcriptional coactivator involved in mitochondrial biogenesis. PGC-1α is implicated in the pathophysiology of many neurodegenerative disorders; therefore, a deep understanding of its functioning in the nervous system may lead to the development of new therapeutic strategies. The central nervous system (CNS)-specific isoforms of PGC-1α have been recently identified, and many functions of PGC-1α are assigned to the particular cell types of the central nervous system. In the mice CNS, deficiency of PGC-1α disturbed viability and functioning of interneurons and dopaminergic neurons, followed by alterations in inhibitory signaling and behavioral dysfunction. Furthermore, in the ALS rodent model, PGC-1α protects upper motoneurons from neurodegeneration. PGC-1α is engaged in the generation of neuromuscular junctions by lower motoneurons, protection of photoreceptors, and reduction in oxidative stress in sensory neurons. Furthermore, in the glial cells, PGC-1α is essential for the maturation and proliferation of astrocytes, myelination by oligodendrocytes, and mitophagy and autophagy of microglia. PGC-1α is also necessary for synaptogenesis in the developing brain and the generation and maintenance of synapses in postnatal life. This review provides an outlook of recent studies on the role of PGC-1α in various cells in the central nervous system.

The NRF2-Dependent Transcriptional Regulation of Antioxidant Defense Pathways: Relevance for Cell Type-Specific Vulnerability to Neurodegeneration and Therapeutic Intervention

Oxidative stress has been implicated in the etiology and pathobiology of various neurodegenerative diseases. At baseline, the cells of the nervous system have the capability to regulate the genes for antioxidant defenses by engaging nuclear factor erythroid 2 (NFE2/NRF)-dependent transcriptional mechanisms, and a number of strategies have been proposed to activate these pathways to promote neuroprotection. Here, we briefly review the biology of the transcription factors of the NFE2/NRF family in the brain and provide evidence for the differential cellular localization of NFE2/NRF family members in the cells of the nervous system. We then discuss these findings in the context of the oxidative stress observed in two neurodegenerative diseases, Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), and present current strategies for activating NFE2/NRF-dependent transcription. Based on the expression of the NFE2/NRF family members in restricted populations of neurons and glia, we propose that, when designing strategies to engage these pathways for neuroprotection, the relative contributions of neuronal and non-neuronal cell types to the overall oxidative state of tissue should be considered, as well as the cell types which have the greatest intrinsic capacity for producing antioxidant enzymes.

Estrogen-related Receptor Alpha (ERRα) is Required for PGC-1α-dependent Gene Expression in the Mouse Brain

Deficiency in peroxisome proliferator-activated receptor gamma coactivator 1-alpha. (PGC-1α) expression or function is implicated in numerous neurological and psychiatric disorders. PGC-1α is required for the expression of genes involved in synchronous neurotransmitter release, axonal integrity, and metabolism, especially in parvalbumin-positive interneurons. As a transcriptional coactivator, PGC-1α requires transcription factors to specify cell-type-specific gene programs; while much is known about these factors in peripheral tissues, it is unclear if PGC-1α utilizes these same factors in neurons. Here, we identified putative transcription factors controlling PGC-1α-dependent gene expression in the brain using bioinformatics and then validated the role of the top candidate in a knockout mouse model. We transcriptionally profiled cells overexpressing PGC-1α and searched for over-represented binding motifs in the promoters of upregulated genes. Binding sites of the estrogen-related receptor (ERR) family of transcription factors were enriched, and blockade of ERRα attenuated PGC-1α-mediated induction of mitochondrial and synaptic genes in cell culture. Localization in the mouse brain revealed enrichment of ERRα expression in parvalbumin-expressing neurons with tight correlation of expression with PGC-1α across brain regions. In ERRα null mice, PGC-1α-dependent genes were reduced in multiple regions, including neocortex, hippocampus, and cerebellum, though not to the extent observed in PGC-1α null mice. Behavioral assessment revealed ambulatory hyperactivity in response to amphetamine and impairments in sensorimotor gating without the overt motor impairment characteristic of PGC-1α null mice. These data suggest that ERRα is required for normal levels of expression of PGC-1α-dependent genes in neurons but that additional factors may be involved in their regulation.

Non-Cell Autonomous and Epigenetic Mechanisms of Huntington's Disease

Huntington's disease (HD) is a rare neurodegenerative disorder caused by an expansion of CAG trinucleotide repeat located in the exon 1 of Huntingtin (HTT) gene in human chromosome 4. The HTT protein is ubiquitously expressed in the brain. Specifically, mutant HTT (mHTT) protein-mediated toxicity leads to a dramatic degeneration of the striatum among many regions of the brain. HD symptoms exhibit a major involuntary movement followed by cognitive and psychiatric dysfunctions. In this review, we address the conventional role of wild type HTT (wtHTT) and how mHTT protein disrupts the function of medium spiny neurons (MSNs). We also discuss how mHTT modulates epigenetic modifications and transcriptional pathways in MSNs. In addition, we define how non-cell autonomous pathways lead to damage and death of MSNs under HD pathological conditions. Lastly, we overview therapeutic approaches for HD. Together, understanding of precise neuropathological mechanisms of HD may improve therapeutic approaches to treat the onset and progression of HD.

PV-specific loss of the transcriptional coactivator PGC-1α slows down the evolution of epileptic activity in an acute ictogenic model

The transcriptional coactivator, PGC-1α (peroxisome proliferator-activated receptor γ coactivator 1α), plays a key role in coordinating energy requirement within cells. Its importance is reflected in the growing number of psychiatric and neurological conditions that have been associated with reduced PGC-1α levels. In cortical networks, PGC-1α is required for the induction of parvalbumin (PV) expression in interneurons, and PGC-1α deficiency affects synchronous GABAergic release. It is unknown, however, how this affects cortical excitability. We show here that knocking down PGC-1α specifically in the PV-expressing cells (PGC-1α^PV−/−) blocks the activity-dependent regulation of the synaptic proteins, SYT2 and CPLX1. More surprisingly, this cell class-specific knockout of PGC-1α appears to have a novel antiepileptic effect, as assayed in brain slices bathed in 0 Mg²⁺ media. The rate of occurrence of preictal discharges developed approximately equivalently in wild-type and PGC-1α^PV−/− brain slices, but the intensity of these discharges was lower in PGC-1α^PV−/− slices, as evident from the reduced power in the γ range and reduced firing rates in both PV interneurons and pyramidal cells during these discharges. Reflecting this reduced intensity in the preictal discharges, the PGC-1α^PV−/− brain slices experienced many more discharges before transitioning into a seizure-like event. Consequently, there was a large increase in the latency to the first seizure-like event in brain slices lacking PGC-1α in PV interneurons. We conclude that knocking down PGC-1α limits the range of PV interneuron firing and this slows the pathophysiological escalation during ictogenesis.

NEW & NOTEWORTHY Parvalbumin expressing interneurons are considered to play an important role in regulating cortical activity. We were surprised, therefore, to find that knocking down the transcriptional coactivator, PGC-1α, specifically in this class of interneurons appears to slow ictogenesis. This anti-ictogenic effect is associated with reduced activity in preictal discharges, but with a far longer period of these discharges before the first seizure-like events finally start. Thus, PGC-1α knockdown may promote schizophrenia while reducing epileptic tendencies.

The Role of PGC1α in Alzheimer's Disease and Therapeutic Interventions

The peroxisome proliferator-activated receptor co-activator-1α (PGC1α) belongs to a family of transcriptional regulators, which act as co-activators for a number of transcription factors, including PPARs, NRFs, oestrogen receptors, etc. PGC1α has been implicated in the control of mitochondrial biogenesis, the regulation of the synthesis of ROS and inflammatory cytokines, as well as genes controlling metabolic processes. The levels of PGC1α have been shown to be altered in neurodegenerative disorders. In the brains of Alzheimer's disease (AD) patients and animal models of amyloidosis, PGC1α expression was reduced compared with healthy individuals. Recently, it was shown that overexpression of PGC1α resulted in reduced amyloid-β (Aβ) generation, particularly by regulating the expression of BACE1, the rate-limiting enzyme involved in the production of Aβ. These results provide evidence pointing toward PGC1α activation as a new therapeutic avenue for AD, which has been supported by the promising observations of treatments with drugs that enhance the expression of PGC1α and gene therapy studies in animal models of AD. This review summarizes the different ways and mechanisms whereby PGC1α can be neuroprotective in AD and the pre-clinical treatments that have been explored so far.