Neurological disorders and mitochondria

Mitochondrial redox state, bioenergetics, and calcium transport in caloric restriction: A metabolic nexus

Mitochondria congregate central reactions in energy metabolism, many of which involve electron transfer. As such, they are expected to both respond to changes in nutrient supply and demand and also provide signals that integrate energy metabolism intracellularly. In this review, we discuss how mitochondrial bioenergetics and reactive oxygen species production is impacted by dietary interventions that change nutrient availability and impact on aging, such as calorie restriction. We also discuss how dietary interventions alter mitochondrial Ca2+ transport, regulating both mitochondrial and cytosolic processes modulated by this ion. Overall, a plethora of literature data support the idea that mitochondrial oxidants and calcium transport act as integrating signals coordinating the response to changes in nutritional supply and demand in cells, tissues, and animals.

SIRT3 facilitates mitochondrial structural repair and functional recovery in rats after ischemic stroke by promoting OPA1 expression and activity

BACKGROUND

Optical atrophy 1 (OPA1), a protein accountable for mitochondrial fusion, facilitates the restoration of mitochondrial structure and function following cerebral ischemia/reperfusion (I/R) injury. The OPA1-conferred mitochondrial protection involves its expression and activity, which can be improved by SIRT3 in non-cerebral ischemia. Nevertheless, it remains obscure whether SIRT3 enhances the expression and activity of OPA1 after cerebral I/R injury.

METHODS

Mature male Sprague Dawley rats were intracranially injected with adeno-associated viral-Sirtuin-3(AAV-SIRT3) and AAV-sh_OPA1, followed by a 90-min temporary blockage of the middle cerebral artery and subsequent restoration of blood flow. Cultured cortical neurons of rats were transfected with LV-SIRT3 or LV-sh_OPA1 before a 2-h oxygen-glucose deprivation and reoxygenation. The rats and neurons were subsequently treated with a selective OPA1 activity inhibitor (MYLS22). The interaction between SIRT3 and OPA1 was assessed by molecular dynamics simulation technology and co-immunoprecipitation. The expression, function, and specific protective mechanism of SIRT3 were examined by various analyses.

RESULTS

SIRT3 interacted with OPA1 in the rat cerebral cortex before and after cerebral I/R. After cerebral I/R damage, SIRT3 upregulation increased the OPA1 expression, which enhanced deacetylation and OPA1 activity, thus alleviating cerebral infarct volume, neuronal apoptosis, oxidative pressure, and impairment in mitochondrial energy production; SIRT3 upregulation also improved neuromotor performance, repaired mitochondrial ultrastructure and membrane composition, and promoted the mitochondrial biogenesis. These neuroprotective effects were partly reversed by OPA1 expression interference and OPA1 activity inhibitor MYLS22.

CONCLUSION

In rats, SIRT3 enhances the expression and activity of OPA1, facilitating the repair of mitochondrial structure and functional recovery following cerebral I/R injury. These findings highlight that regulating SIRT3 may be a promising therapeutic strategy for ischemic stroke.

Optic disc drusen: Dystrophic calcification, a potential target for treatment

Optic disc drusen (ODD) are calcified, acellular bodies, seen in the optic nerve head of up to 2% of the population. Although seldomly affecting visual acuity, visual field defects are common, and severe, ischemic complications causing irreversible vision loss are known to occur. Different treatment strategies for ODD have been explored, but so far without success. This review focuses on the unique, calcified property of ODD, describing what we know about ODD pathogenesis and previously tried treatment strategies. In this context, we discuss current knowledge about calcium and pathological calcifications, including intracranial and ocular calcifications. We also explore some of the obstacles that must be addressed to develop a therapy centred on the concept of calcification, should calcification be identified as a pathogenic factor contributing to vision loss.

A translocation fluorescent probe for analyzing cellular physiological parameters in neurological disease models

Neurological disorders are closely linked to the alterations in cell membrane permeability (CMP) and mitochondrial membrane potential (MMP). Changes in CMP and MMP may lead to damage and death of nerve cells, thus triggering the onset and progression of neurological diseases. Therefore, monitoring the changes of these two physiological parameters not only benefits the accurate assessment of nerve cell health status, but also enables providing key information for the diagnosis and treatment of neurological diseases. However, the simultaneous monitoring of these two cellular physiological parameters is still challenging. Herein, we design and synthesize two quinolinium-carbazole-derivated fluorescent probes (OQ and PQ). As isomers, the only difference in their chemical structures is the linking position of the carbazole unit in quinoline rings. Strikingly, such a subtle difference endows OQ and PQ with significantly different organelle-staining behaviors. PQ mainly targets at the nucleus, OQ can simultaneously stain cell membranes and mitochondria in normal cells, and performs CMP and MMP-dependent translocation from the cell membrane to mitochondria then to the nucleus, thus holding great promise as an intracellular translocation probe to image the changes of CMP and MMP. After unraveling the intrinsic mechanism of their different translocation abilities by combining experiments with molecular dynamics simulations and density functional theory calculations, we successfully used OQ to monitor the continuous changes of CMP and MMP in three neurological disease-related cell models, including oxidative stress-damaged, Parkinson's disease, and virus-infected ones. Besides providing a validated imaging tool for monitoring cellular physiological parameters, this work paves a promising route for designing intracellular translocation probes to analyze cellular physiological parameters associated with various diseases.

Skeletal muscle dysfunction in amyotrophic lateral sclerosis: a mitochondrial perspective and therapeutic approaches

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease that results in the loss of motor neurons and severe skeletal muscle atrophy. The etiology of ALS is linked to skeletal muscle, which can activate a retrograde signaling cascade that destroys motor neurons. This is why satellite cells and mitochondria play a crucial role in the health and performance of skeletal muscles. This review presents current knowledge on the involvement of mitochondrial dysfunction, skeletal muscle atrophy, muscle satellite cells, and neuromuscular junction (NMJ) in ALS. It also discusses current therapeutic strategies, including exercise, drugs, stem cells, gene therapy, and the prospective use of mitochondrial transplantation as a viable therapeutic strategy.

Hypoxia and its effect on the cellular system

Eukaryotic cells utilize oxygen for different functions of cell organelles owing to cellular survival. A balanced oxygen homeostasis is an essential requirement to maintain the regulation of normal cellular systems. Any changes in the oxygen level are stressful and can alter the expression of different homeostasis regulatory genes and proteins. Lack of oxygen or hypoxia results in oxidative stress and formation of hypoxia inducible factors (HIF) and reactive oxygen species (ROS). Substantial cellular damages due to hypoxia have been reported to play a major role in various pathological conditions. There are different studies which demonstrated that the functions of cellular system are disrupted by hypoxia. Currently, study on cellular effects following hypoxia is an important field of research as it not only helps to decipher different signaling pathway modulation, but also helps to explore novel therapeutic strategies. On the basis of the beneficial effect of hypoxia preconditioning of cellular organelles, many therapeutic investigations are ongoing as a promising disease management strategy in near future. Hence, the present review discusses about the effects of hypoxia on different cellular organelles, mechanisms and their involvement in the progression of different diseases.

Traumatic Brain Injury Recovery with Photobiomodulation: Cellular Mechanisms, Clinical Evidence, and Future Potential

Traumatic Brain Injury (TBI) remains a significant global health challenge, lacking effective pharmacological treatments. This shortcoming is attributed to TBI's heterogeneous and complex pathophysiology, which includes axonal damage, mitochondrial dysfunction, oxidative stress, and persistent neuroinflammation. The objective of this study is to analyze transcranial photobiomodulation (PBM), which employs specific red to near-infrared light wavelengths to modulate brain functions, as a promising therapy to address TBI's complex pathophysiology in a single intervention. This study reviews the feasibility of this therapy, firstly by synthesizing PBM's cellular mechanisms with each identified TBI's pathophysiological aspect. The outcomes in human clinical studies are then reviewed. The findings support PBM's potential for treating TBI, notwithstanding variations in parameters such as wavelength, power density, dose, light source positioning, and pulse frequencies. Emerging data indicate that each of these parameters plays a role in the outcomes. Additionally, new research into PBM's effects on the electrical properties and polymerization dynamics of neuronal microstructures, like microtubules and tubulins, provides insights for future parameter optimization. In summary, transcranial PBM represents a multifaceted therapeutic intervention for TBI with vast potential which may be fulfilled by optimizing the parameters. Future research should investigate optimizing these parameters, which is possible by incorporating artificial intelligence.

Mitochondrial-related genes PDK2, CHDH, and ALDH5A1 served as a diagnostic signature and correlated with immune cell infiltration in ulcerative colitis

We conducted an investigation to determine the potential of mitochondrial-related genes as diagnostic biomarkers in ulcerative colitis (UC), while also examining their association with immune cell infiltration. To achieve this, we acquired four datasets pertaining to UC, which included gene expression arrays and clinical data, from the GEO database. Subsequently, we selected three signature genes (PDK2, CHDH, and ALDH5A1) to construct a diagnostic model for UC. The nomogram and ROC curves exhibited exceptional diagnostic efficacy. Following this, quantitative real-time polymerase chain reaction and western blotting assays validated the decreased mRNA and protein expression of PDK2, CHDH, and ALDH5A1 in the model of UC cells and dextran sulfate sodium salt (DSS)-induced mice colitis tissues, aligning with the findings in the risk model. This investigation suggested a negative correlation between the expression of ALDH5A1, CHDH, and PDK2 and the infiltration of M1 macrophages. Then, immunofluorescence analysis confirmed the augmented expression of CD86 in the tissue of mice subjected to DSS, while a diminished expression of ALDH5A1, CHDH, and PDK2 was observed. Consequently, it can be inferred that targeting mitochondria-associated genes, namely PDK2, CHDH, and ALDH5A1, holds potential as a viable strategy for prognostic prediction and the implementation of immune therapy for UC.

Diphenyl Diselenide Attenuates Mitochondrial Damage During Initial Hypoxia and Enhances Resistance to Recurrent Hypoxia

Hypoxia plays a significant role in the development of various cerebral diseases, many of which are associated with the potential risk of recurrence due to mitochondrial damage. Conventional drug treatments are not always effective for hypoxia-related brain diseases, necessitating the exploration of alternative compounds. In this study, we investigated the potential of diphenyl diselenide [(PhSe)2] to ameliorate locomotor impairments and mitigate brain mitochondrial dysfunction in zebrafish subjected to hypoxia. Additionally, we explored whether these improvements could confer resistance to recurrent hypoxia. Through a screening process, an appropriate dose of (PhSe)2 was determined, and animals exposed to hypoxia received a single intraperitoneal injection of 100 mg/kg of the compound or vehicle. After 1 h from the injection, evaluations were conducted on locomotor deficits, (PhSe)2 content, mitochondrial electron transport system, and mitochondrial viability in the brain. The animals were subsequently exposed to recurrent hypoxia to assess the latency time to hypoxia symptoms. The findings revealed that (PhSe)2 effectively crossed the blood-brain barrier, attenuated locomotor deficits induced by hypoxia, and improved brain mitochondrial respiration by modulating complex III. Furthermore, it enhanced mitochondrial viability in the telencephalon, contributing to greater resistance to recurrent hypoxia. These results demonstrate the beneficial effects of (PhSe)2 on both hypoxia and recurrent hypoxia, with cerebral mitochondria being a critical target of its action. Considering the involvement of brain hypoxia in numerous pathologies, (PhSe)2 should be further tested to determine its effectiveness as a potential treatment for hypoxia-related brain diseases.

Ameliorative Role of Mitochondrial Therapy in Cognitive Function of Vascular Dementia Mice

BACKGROUND

Mitochondrial dysfunction plays a vital role in the progression of vascular dementia (VaD). We hypothesized that transfer of exogenous mitochondria might be a beneficial strategy for VaD treatment.

OBJECTIVE

The study was aimed to investigate the role of mitochondrial therapy in cognitive function of VaD.

METHODS

The activity and integrity of isolated mitochondria were detected using MitoTracker and Janus Green B staining assays. After VaD mice were intravenously injected with exogenous mitochondria, Morris water maze and passive avoidance tests were used to detect cognitive function of VaD mice. Haematoxylin and eosin, Nissl, TUNEL, and Golgi staining assays were utilized to measure neuronal and synaptic injury in the hippocampus of VaD mice. Detection kits were performed to detect mitochondrial membrane potential (ΔΨ), SOD activity and the levels of ATP, ROS, and MDA in the brains of VaD mice.

RESULTS

The results showed that isolated mitochondria were intact and active. Mitochondrial therapy could ameliorate cognitive performance of VaD mice. Additionally, mitochondrial administration could attenuate hippocampal neuronal and synaptic injury, improve mitochondrial ΔΨ, ATP level and SOD activity, and reduce ROS and MDA levels in the brains of VaD mice.

CONCLUSIONS

The study reports profitable effect of mitochondrial therapy against cognitive impairment of VaD, making mitochondrial treatment become a promising therapeutic strategy for VaD.

A comprehensive review of secondary metabolites from the genus Agrocybe: Biological activities and pharmacological implications

The genus Agrocybe, situated within the Strophariaceae family, class Agaricomycetes, and phylum Basidiomycota, encompasses a myriad of species exhibiting significant biological activities. This review presents an integrative overview of the secondary metabolites derived from Agrocybe species, elucidating their respective biological activities and potential pharmacological applications. The metabolites under scrutiny encompass a diverse array of biological macromolecules, specifically polysaccharides and lectins, as well as a diverse group of 80 documented small molecular chemical constituents, classified into sterols, sesquiterpenes, volatile compounds, polyenes, and other compounds, their manifesting anti-inflammatory, anticancer, antioxidant, hepatoprotective, antimicrobial, and antidiabetic activities, these metabolites, in which polysaccharides exhibit abundant activities, underscore the potential of the Agrocybe genus as a valuable source of biologically active natural products. The present review emphasises the need for escalated research into Agrocybe, including investigations into the biosynthetic pathways of these metabolites, which could foster the development of novel pharmaceutical therapies to address various health challenges.

Natural products for the treatment of neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are among the most common diseases in older adults worldwide. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common neurodegenerative diseases, and are accompanied by cerebral cortical atrophy, neuronal loss, protein accumulation, and excessive accumulation of metal ions. Natural products exhibit outstanding performance in improving cerebral circulatory disorders, promoting cerebral haematoma absorption, repairing damaged nerve tissue, and improving damaged nerve function. In recent years, studies have shown that neuroinflammatory mechanisms and signalling pathways closely related to the occurrence and development of neurological diseases include microglial activation, nuclear factor-κB (NF-κB) pathway, mitogen activated protein kinases (MAPK) pathway, reactive oxygen pathway, nucleotide binding oligomerisation domain-like receptor protein3 (NLRP3) inflammasomes, toll-like receptor4 (TLR4) pathway, nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, and intestinal flora. Therefore, this study considered the mechanism of neurological diseases as the starting point to review the mechanism of action of natural products in the prevention and treatment of AD and PD in recent years to provide a theoretical basis for clinical prevention and treatment.

AIM

Natural products are a promising source of novel lead structures that have long been used to treat various nervous system diseases.

METHODOLOGY

This review collected literature on neurological diseases and natural products from 2012 to 2022, which were mainly searched through databases such as ScienceDirect, Springer, PubMed, SciFinder, China National Knowledge Infrastructure (CNKI), Wanfang, Google Scholar, and Baidu Academic. The following keywords were searched: neurological disorders, natural products, signalling pathway, mechanism of action.

RESULTS

This review summarises the pathogenesis of degenerative neurological diseases, recent findings on natural products used in neurodegenerative diseases, and the molecular mechanisms underlying these effects.

Proteomic analysis of gene expression in the prefrontal cortex in infant rhesus macaques after multiple sevoflurane exposures

PURPOSE

Repeated exposure of infant rhesus macaques to sevoflurane induces neurotoxicity and is associated with neurocognitive impairment in later life. We aimed to investigate the effect of repeated sevoflurane exposure on the expression of proteins in the prefrontal cortex of infant rhesus macaques by proteomics.

METHODS

Rhesus macaques were exposed to sevoflurane three times, on postnatal days 7, 21 and 35. Quantitative proteomics employing LC-MS with isobaric labeling (TMT10plex), western blotting, and transmission electron microscopy (TEM) were utilized in the studies.

RESULTS

The results of a proteomics investigation of the brain revealed that the proteins that were differentially expressed in rhesus macaques after sevoflurane exposures were associated mainly with mitochondrial respiration. Following multiple sevoflurane exposures, the prefrontal cortices of rhesus macaques exhibited increases in NDUFA8 and COX IV protein levels, while no alterations in mitochondrial morphology were observed through TEM.

CONCLUSION

Multiple exposures to sevoflurane increased the mitochondrial protein levels in rhesus macaques.

Modulating mitochondrial calcium channels (TRPM2/MCU/NCX) as a therapeutic strategy for neurodegenerative disorders

Efficient cellular communication is essential for the brain to regulate diverse functions like muscle contractions, memory formation and recall, decision-making, and task execution. This communication is facilitated by rapid signaling through electrical and chemical messengers, including voltage-gated ion channels and neurotransmitters. These messengers elicit broad responses by propagating action potentials and mediating synaptic transmission. Calcium influx and efflux are essential for releasing neurotransmitters and regulating synaptic transmission. Mitochondria, which are involved in oxidative phosphorylation, and the energy generation process, also interact with the endoplasmic reticulum to store and regulate cytoplasmic calcium levels. The number, morphology, and distribution of mitochondria in different cell types vary based on energy demands. Mitochondrial damage can cause excess reactive oxygen species (ROS) generation. Mitophagy is a selective process that targets and degrades damaged mitochondria via autophagosome-lysosome fusion. Defects in mitophagy can lead to a buildup of ROS and cell death. Numerous studies have attempted to characterize the relationship between mitochondrial dysfunction and calcium dysregulation in neurodegenerative diseases such as Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Amyotrophic lateral sclerosis, spinocerebellar ataxia, and aging. Interventional strategies to reduce mitochondrial damage and accumulation could serve as a therapeutic target, but further research is needed to unravel this potential. This review offers an overview of calcium signaling related to mitochondria in various neuronal cells. It critically examines recent findings, exploring the potential roles that mitochondrial dysfunction might play in multiple neurodegenerative diseases and aging. Furthermore, the review identifies existing gaps in knowledge to guide the direction of future research.

Sulfite Impairs Bioenergetics and Redox Status in Neonatal Rat Brain: Insights into the Early Neuropathophysiology of Isolated Sulfite Oxidase and Molybdenum Cofactor Deficiencies

Isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies are genetic diseases biochemically characterized by the toxic accumulation of sulfite in the tissues of patients, including the brain. Neurological dysfunction and brain abnormalities are commonly observed soon after birth, and some patients also have neuropathological alterations in the prenatal period (in utero). Thus, we investigated the effects of sulfite on redox and mitochondrial homeostasis, as well as signaling proteins in the cerebral cortex of rat pups. One-day-old Wistar rats received an intracerebroventricular administration of sulfite (0.5 µmol/g) or vehicle and were euthanized 30 min after injection. Sulfite administration decreased glutathione levels and glutathione S-transferase activity, and increased heme oxygenase-1 content in vivo in the cerebral cortex. Sulfite also reduced the activities of succinate dehydrogenase, creatine kinase, and respiratory chain complexes II and II-III. Furthermore, sulfite increased the cortical content of ERK1/2 and p38. These findings suggest that redox imbalance and bioenergetic impairment induced by sulfite in the brain are pathomechanisms that may contribute to the neuropathology of newborns with ISOD and MoCD. Sulfite disturbs antioxidant defenses, bioenergetics, and signaling pathways in the cerebral cortex of neonatal rats. CII: complex II; CII-III: complex II-III; CK: creatine kinase; GST: glutathione S-transferase; HO-1: heme oxygenase-1; SDH: succinate dehydrogenase; SO32-: sulfite.

Parkinson's Disease: Are PINK1 Activators Inching Closer to the Clinic?

The activation of PINK1 by small molecules has emerged as a promising strategy in treating Parkinson's disease (PD). Recent progress in this area has raised excitement around PINK1 activators as PD treatments, and herein we offer insight into these developments and their potential to deliver much needed novel PD treatments.

Mitochondrial sodium/calcium exchanger NCLX regulates glycolysis in astrocytes, impacting on cognitive performance

Intracellular Ca2+ concentrations are strictly controlled by plasma membrane transporters, the endoplasmic reticulum, and mitochondria, in which Ca2+ uptake is mediated by the mitochondrial calcium uniporter complex (MCUc), while efflux occurs mainly through the mitochondrial Na+ /Ca2+ exchanger (NCLX). RNAseq database repository searches led us to identify the Nclx transcript as highly enriched in astrocytes when compared with neurons. To assess the role of NCLX in mouse primary culture astrocytes, we inhibited its function both pharmacologically or genetically. This resulted in re-shaping of cytosolic Ca2+ signaling and a metabolic shift that increased glycolytic flux and lactate secretion in a Ca2+ -dependent manner. Interestingly, in vivo genetic deletion of NCLX in hippocampal astrocytes improved cognitive performance in behavioral tasks, whereas hippocampal neuron-specific deletion of NCLX impaired cognitive performance. These results unveil a role for NCLX as a novel modulator of astrocytic glucose metabolism, impacting on cognition.

The Role of Exercise in Maintaining Mitochondrial Proteostasis in Parkinson's Disease

Parkinson's disease (PD) is the second most common rapidly progressive neurodegenerative disease and has serious health and socio-economic consequences. Mitochondrial dysfunction is closely related to the onset and progression of PD, and the use of mitochondria as a target for PD therapy has been gaining traction in terms of both recognition and application. The disruption of mitochondrial proteostasis in the brain tissue of PD patients leads to mitochondrial dysfunction, which manifests as mitochondrial unfolded protein response, mitophagy, and mitochondrial oxidative phosphorylation. Physical exercise is important for the maintenance of human health, and has the great advantage of being a non-pharmacological therapy that is non-toxic, low-cost, and universally applicable. In this review, we investigate the relationships between exercise, mitochondrial proteostasis, and PD and explore the role and mechanisms of mitochondrial proteostasis in delaying PD through exercise.

Mitochondrial Ca2+ handling as a cell signaling hub: lessons from astrocyte function

Astrocytes are a heterogenous population of macroglial cells spread throughout the central nervous system with diverse functions, expression signatures, and intricate morphologies. Their subcellular compartments contain a distinct range of mitochondria, with functional microdomains exhibiting widespread activities, such as controlling local metabolism and Ca2+ signaling. Ca2+ is an ion of utmost importance, both physiologically and pathologically, and participates in critical central nervous system processes, including synaptic plasticity, neuron-astrocyte integration, excitotoxicity, and mitochondrial physiology and metabolism. The mitochondrial Ca2+ handling system is formed by the mitochondrial Ca2+ uniporter complex (MCUc), which mediates Ca2+ influx, and the mitochondrial Na+/Ca2+ exchanger (NCLX), responsible for most mitochondrial Ca2+ efflux, as well as additional components, including the mitochondrial permeability transition pore (mtPTP). Over the last decades, mitochondrial Ca2+ handling has been shown to be key for brain homeostasis, acting centrally in physiopathological processes such as astrogliosis, astrocyte-neuron activity integration, energy metabolism control, and neurodegeneration. In this review, we discuss the current state of knowledge regarding the mitochondrial Ca2+ handling system molecular composition, highlighting its impact on astrocytic homeostasis.

Amyotrophic lateral sclerosis: a neurodegenerative disorder poised for successful therapeutic translation

Amyotrophic lateral sclerosis (ALS) is a devastating disease caused by degeneration of motor neurons. As with all major neurodegenerative disorders, development of disease-modifying therapies has proven challenging for multiple reasons. Nevertheless, ALS is one of the few neurodegenerative diseases for which disease-modifying therapies are approved. Significant discoveries and advances have been made in ALS preclinical models, genetics, pathology, biomarkers, imaging and clinical readouts over the last 10-15 years. At the same time, novel therapeutic paradigms are being applied in areas of high unmet medical need, including neurodegenerative disorders. These developments have evolved our knowledge base, allowing identification of targeted candidate therapies for ALS with diverse mechanisms of action. In this Review, we discuss how this advanced knowledge, aligned with new approaches, can enable effective translation of therapeutic agents from preclinical studies through to clinical benefit for patients with ALS. We anticipate that this approach in ALS will also positively impact the field of drug discovery for neurodegenerative disorders more broadly.

Roles of genistein in learning and memory during aging and neurological disorders

Genistein (GEN) is a non-steroidal phytoestrogen that belongs to the isoflavone class. It is abundantly found in soy. Soy and its products are used as food components in many countries including India. The present review is focused to address roles of GEN in brain functions in the context of learning and memory as a function of aging and neurological disorders. Memory decline is one of the most disabling features observed during normal aging and age-associated neurodegenerative disorders namely Alzheimer's disease (AD) and Parkinson's disease (PD), etc. Anatomical, physiological, biochemical and molecular changes in the brain with advancement of age and pathological conditions lead to decline of cognitive functions. GEN is chemically comparable to estradiol and binds to estrogen receptors (ERs). GEN acts through ERs and mimics estrogen action. After binding to ERs, GEN regulates a plethora of brain functions including learning and memory; however detailed study still remains elusive. Due to the neuroprotective, anti-oxidative and anti-inflammatory properties, GEN is used to restore or improve memory functions in different animal models and humans. The present review may be helpful to understand roles of GEN in learning and memory during aging and neurological disorders, its direction of research and therapeutic perspectives.

CuATSM effectively ameliorates ALS patient astrocyte-mediated motor neuron toxicity in human in vitro models of amyotrophic lateral sclerosis

Patient diversity and unknown disease cause are major challenges for drug development and clinical trial design for amyotrophic lateral sclerosis (ALS). Transgenic animal models do not adequately reflect the heterogeneity of ALS. Direct reprogramming of patient fibroblasts to neuronal progenitor cells and subsequent differentiation into patient astrocytes allows rapid generation of disease relevant cell types. Thus, this methodology can facilitate compound testing in a diverse genetic background resulting in a more representative population for therapeutic evaluation. Here, we used established co-culture assays with motor neurons and reprogrammed patient skin-derived astrocytes (iAs) to evaluate the effects of (SP-4-2)-[[2,2'-(1,2-dimethyl-1,2-ethanediylidene)bis[N-methylhydrazinecarbothioamidato-κN² ,κS]](2-)]-copper (CuATSM), currently in clinical trial for ALS in Australia. Pretreatment of iAs with CuATSM had a differential effect on neuronal survival following co-culture with healthy motor neurons. Using this assay, we identified responding and non-responding cell lines for both sporadic and familial ALS (mutant SOD1 and C9ORF72). Importantly, elevated mitochondrial respiration was the common denominator in all CuATSM-responders, a metabolic phenotype not observed in non-responders. Pre-treatment of iAs with CuATSM restored mitochondrial activity to levels comparable to healthy controls. Hence, this metabolic parameter might allow selection of patient subpopulations best suited for CuATSM treatment. Moreover, CuATSM might have additional therapeutic value for mitochondrial disorders. Enhanced understanding of patient-specific cellular and molecular profiles could help improve clinical trial design in the future.

SIRT5-related desuccinylation modification of AIFM1 protects against compression-induced intervertebral disc degeneration by regulating mitochondrial homeostasis

Mitochondrial dysfunction plays a major role in the development of intervertebral disc degeneration (IDD). Sirtuin 5 (SIRT5) participates in the maintenance of mitochondrial homeostasis through its desuccinylase activity. However, it is still unclear whether succinylation or SIRT5 is involved in the impairment of mitochondria and development of IDD induced by excessive mechanical stress. Our 4D label-free quantitative proteomic results showed decreased expression of the desuccinylase SIRT5 in rat nucleus pulposus (NP) tissues under mechanical loading. Overexpression of Sirt5 effectively alleviated, whereas knockdown of Sirt5 aggravated, the apoptosis and dysfunction of NP cells under mechanical stress, consistent with the more severe IDD phenotype of Sirt5 KO mice than wild-type mice that underwent lumbar spine instability (LSI) surgery. Moreover, immunoprecipitation-coupled mass spectrometry (IP-MS) results suggested that AIFM1 was a downstream target of SIRT5, which was verified by a Co-IP assay. We further demonstrated that reduced SIRT5 expression resulted in the increased succinylation of AIFM1, which in turn abolished the interaction between AIFM1 and CHCHD4 and thus led to the reduced electron transfer chain (ETC) complex subunits in NP cells. Reduced ETC complex subunits resulted in mitochondrial dysfunction and the subsequent occurrence of IDD under mechanical stress. Finally, we validated the efficacy of treatments targeting disrupted mitochondrial protein importation by upregulating SIRT5 expression or methylene blue (MB) administration in the compression-induced rat IDD model. In conclusion, our study provides new insights into the occurrence and development of IDD and offers promising therapeutic approaches for IDD.

The Role of Mitochondria-Targeting miRNAs in Intracerebral Hemorrhage

Non-traumatic intracerebral hemorrhage (ICH) is the most common type of hemorrhagic stroke, most often occurring between the ages of 45 and 60. Arterial hypertension (AH) is most often the cause of ICH, followed by atherosclerosis, blood diseases, inflammatory changes in cerebral vessels, intoxication and vitamin deficiencies. Cerebral hemorrhage can occur by diapedesis or as a result of a ruptured vessel. AH is difficult to treat, requires surgery and can lead to disability or death. One of the important directions in the study of the pathogenesis of ICH is mitochondrial dysfunction and its regulation. The key role of mitochondrial dysfunction in AH and atherosclerosis, as well as in the development of brain damage after hemorrhage, has been acknowledged. MicroRNAs (miRNAs) are a class of non-coding RNAs (about 18-22 nucleotides) that regulate a variety of biological processes including cell differentiation, proliferation, apoptosis, etc., primarily through gene repression. There is growing evidence to support dysregulated miRNAs in various cardiovascular diseases, including ICH. Further, the realization of miRNAs within mitochondrial compartment has challenged the traditional knowledge of signaling pathways involved in the regulatory network of cardiovascular diseases. However, the role of miRNAs in mitochondrial dysfunction for ICH is still under-appreciated, with comparatively much lesser studies and investigations reported, than those in other cardiovascular diseases. In this review, we summarize the up-to-date findings on the published role miRNAs in mitochondrial function for ICH, and the potential use of miRNAs in clinical settings, such as potential therapeutic targets and non-invasive diagnostic/prognostic biomarker tools.

Isolated Mitochondrial Preparations and In organello Assays: A Powerful and Relevant Ex vivo Tool for Assessment of Brain (Patho)physiology

Mitochondria regulate multiple aspects of neuronal development, physiology, plasticity, and pathology through their regulatory roles in bioenergetic, calcium, redox, and cell survival/death signalling. While several reviews have addressed these different aspects, a comprehensive discussion focussing on the relevance of isolated brain mitochondria and their utilities in neuroscience research has been lacking. This is relevant because the employment of isolated mitochondria rather than their in situ functional evaluation, offers definitive evidence of organelle-specificity, negating the interference from extra mitochondrial cellular factors/signals. This mini-review was designed primarily to explore the commonly employed in organello analytical assays for the assessment of mitochondrial physiology and its dysfunction, with a particular focus on neuroscience research. The authors briefly discuss the methodologies for biochemical isolation of mitochondria, their quality assessment, and cryopreservation. Further, the review attempts to accumulate the key biochemical protocols for in organello assessment of a multitude of mitochondrial functions critical for neurophysiology, including assays for bioenergetic activity, calcium and redox homeostasis, and mitochondrial protein translation. The purpose of this review is not to examine each and every method or study related to the functional assessment of isolated brain mitochondria, but rather to assemble the commonly used protocols of in organello mitochondrial research in a single publication. The hope is that this review will provide a suitable platform aiding neuroscientists to choose and apply the required protocols and tools to address their particular mechanistic, diagnostic, or therapeutic question dealing within the confines of the research area of mitochondrial patho-physiology in the neuronal perspective.

Accelerated neuronal aging in vitro ∼melting watch ∼

In developed countries, the aging of the population and the associated increase in age-related diseases are causing major unresolved medical, social, and environmental matters. Therefore, research on aging has become one of the most important and urgent issues in life sciences. If the molecular mechanisms of the onset and progression of neurodegenerative diseases are elucidated, we can expect to develop disease-modifying methods to prevent neurodegeneration itself. Since the discovery of induced pluripotent stem cells (iPSCs), there has been an explosion of disease models using disease-specific iPSCs derived from patient-derived somatic cells. By inducing the differentiation of iPSCs into neurons, disease models that reflect the patient-derived pathology can be reproduced in culture dishes, and are playing an active role in elucidating new pathological mechanisms and as a platform for new drug discovery. At the same time, however, we are faced with a new problem: how to recapitulate aging in culture dishes. It has been pointed out that cells differentiated from pluripotent stem cells are juvenile, retain embryonic traits, and may not be fully mature. Therefore, attempts are being made to induce cell maturation, senescence, and stress signals through culture conditions. It has also been reported that direct conversion of fibroblasts into neurons can reproduce human neurons with an aged phenotype. Here, we outline some state-of-the-art insights into models of neuronal aging in vitro. New frontiers in which stem cells and methods for inducing differentiation of tissue regeneration can be applied to aging research are just now approaching, and we need to keep a close eye on them. These models are forefront and intended to advance our knowledge of the molecular mechanisms of aging and contribute to the development of novel therapies for human neurodegenerative diseases associated with aging.

Oxidative stress-mediated memory impairment during aging and its therapeutic intervention by natural bioactive compounds

Aging and associated neurodegenerative diseases are accompanied by the decline of several brain functions including cognitive abilities. Progressive deleterious changes at biochemical and physiological levels lead to the generation of oxidative stress, accumulation of protein aggregates, mitochondrial dysfunctions, loss of synaptic connections, and ultimately neurodegeneration and cognitive decline during aging. Oxidative stress that arises due to an imbalance between the rates of production and elimination of free radicles is the key factor for age-associated neurodegeneration and cognitive decline. Due to high energy demand, the brain is more susceptible to free radicals-mediated damages as they oxidize lipids, proteins, and nucleic acids, thereby causing an imbalance in the homeostasis of the aging brain. Animal, as well as human subject studies, showed that with almost no or few side effects, dietary interventions and plant-derived bioactive compounds could be beneficial to recovering the memory or delaying the onset of memory impairment. As the plant-derived bioactive compounds have antioxidative properties, several of them were used to recover the oxidative stress-mediated changes in the aging brain. In the present article, we review different aspects of oxidative stress-mediated cognitive change during aging and its therapeutic intervention by natural bioactive compounds.

Polyphenols for the Treatment of Ischemic Stroke: New Applications and Insights

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Currently, the main therapeutic strategy involves the use of intravenous thrombolysis to restore cerebral blood flow to prevent the transition of the penumbra to the infarct core. However, due to various limitations and complications, including the narrow time window in which this approach is effective, less than 10% of patients benefit from such therapy. Thus, there is an urgent need for alternative therapeutic strategies, with neuroprotection against the ischemic cascade response after IS being one of the most promising options. In the past few decades, polyphenolic compounds have shown great potential in animal models of IS because of their high biocompatibility and ability to target multiple ischemic cascade signaling pathways, although low bioavailability is an issue that limits the applications of several polyphenols. Here, we review the pathophysiological changes following cerebral ischemia and summarize the research progress regarding the applications of polyphenolic compounds in the treatment of IS over the past 5 years. Furthermore, we discuss several potential strategies for improving the bioavailability of polyphenolic compounds as well as some essential issues that remain to be addressed for the translation of the related therapies to the clinic.

Long-term mitochondrial stress induces early steps of Tau aggregation by increasing reactive oxygen species levels and affecting cellular proteostasis

Accumulating evidence indicates that mitochondrial dysfunction is involved in the pathogenesis of neurodegenerative diseases. Both of these conditions are often associated with an increase in protein aggregation. However, still unknown are the specific defects of mitochondrial biology that play a critical role in the development of Alzheimer’s disease, in which Tau protein aggregates are observed in the brains of some patients. Here, we report that long-term mitochondrial stress triggered Tau dimerization, which is the first step of protein aggregation. Mitochondrial dysfunction was induced in HEK293T cells that received prolonged treatment with rotenone and in HEK293T cells with the knockout of NDUFA11 protein. To monitor changes in Tau protein aggregation, we took advantage of the bimolecular fluorescence complementation assay using HEK293T cells that were transfected with plasmids that encoded Tau. Inhibition of the ISR with ISRIB induced Tau dimerization, whereas ISR activation with salubrinal, guanabenz, and sephin1 partially reversed this process. Cells that were treated with ROS scavengers, N-acetyl-l-cysteine or MitoQ, significantly reduced the amount of ROS and Tau dimerization, indicating the involvement of oxidative stress in Tau aggregation. Our results indicate that long-term mitochondrial stress may induce early steps of Tau protein aggregation by affecting oxidative balance and cellular proteostasis.

The Roles of Optogenetics and Technology in Neurobiology: A Review

Optogenetic is a technique that combines optics and genetics to control specific neurons. This technique usually uses adenoviruses that encode photosensitive protein. The adenovirus may concentrate in a specific neural region. By shining light on the target nerve region, the photosensitive protein encoded by the adenovirus is controlled. Photosensitive proteins controlled by light can selectively allow ions inside and outside the cell membrane to pass through, resulting in inhibition or activation effects. Due to the high precision and minimally invasive, optogenetics has achieved good results in many fields, especially in the field of neuron functions and neural circuits. Significant advances have also been made in the study of many clinical diseases. This review focuses on the research of optogenetics in the field of neurobiology. These include how to use optogenetics to control nerve cells, study neural circuits, and treat diseases by changing the state of neurons. We hoped that this review will give a comprehensive understanding of the progress of optogenetics in the field of neurobiology.

Mitochondrial Genetics Reinforces Multiple Layers of Interaction in Alzheimer’s Disease

Simple Summary

Nuclear DNA remains the main source of genome-wide loci association in neurodegenerative diseases, only partially accounting for the heritability of Alzheimer’s Disease (AD). In this context, mitochondrial DNA (mtDNA) is gaining more attention. Here, we investigated mitochondrial genes and genetic variants that may influence mild cognitive impairment and AD, through an integrative analysis including both differential gene expression and mitochondrial genome-wide epistasis analysis. Our results highlight important layers of interactions involving mitochondrial genetics and suggest specific molecular alterations as potential biomarkers for AD.

Abstract

Nuclear DNA has been the main source of genome-wide loci association in neurodegenerative diseases, only partially accounting for the heritability of Alzheimer’s Disease (AD). In this context, mitochondrial DNA (mtDNA) is gaining more attention. Here, we investigated mitochondrial genes and genetic variants that may influence mild cognitive impairment and AD, through an integrative analysis including differential gene expression and mitochondrial genome-wide epistasis. We assessed the expression of mitochondrial genes in different brain tissues from two public RNA-Seq databases (GEO and GTEx). Then, we analyzed mtDNA from the ADNI Cohort and investigated epistasis regarding mitochondrial variants and levels of Aβ1−42, TAU, and Phosphorylated TAU (PTAU) from cognitively healthy controls, and both mild cognitive impairment (MCI) and AD cases. We identified multiple differentially expressed mitochondrial genes in the comparisons between cognitively healthy individuals and AD patients. We also found increased protein levels in MCI and AD patients when compared to healthy controls, as well as novel candidate networks of mtDNA epistasis, which included variants in all mitochondrially-encoded oxidative phosphorylation complexes, 12S rRNA and MT-DLOOP. Our results highlight layers of potential interactions involving mitochondrial genetics and suggest specific molecular alterations as potential biomarkers for AD.

A focus on natural products for preventing and cure of mitochondrial dysfunction in Parkinson's disease

Mitochondria are considered the only source of energy production within cells. This organelle is vital for neural function and survival by producing energy (adenosine triphosphate (ATP)) and regulating intracellular calcium. Mitochondrial dysfunction, which significantly contributes to both idiopathic and familial types of Parkinson's disease (PD), depletes cellular energy, disrupts homeostasis, and induces oxidative stress, leading to cell death. In recent years several natural products have been discovered to be protective against mitochondrial dysfunction. This review discusses the role of mitochondria in the progression of PD to define the path for using natural products to prevent and/or cure PD.

MS-driven metabolic alterations are recapitulated in iPSC-derived astrocytes

Objective

Astrocytes play a significant role in the pathology of multiple sclerosis (MS). Nevertheless, for ethical reasons, most studies in these cells were performed using the Experimental Autoimmune Encephalomyelitis model. As there are significant differences between human and mouse cells, we aimed here to better characterize astrocytes from patients with MS (PwMS), focusing mainly on mitochondrial function and cell metabolism.

Methods

We obtained and characterized induced pluripotent stem cell (iPSC)‐derived astrocytes from three PwMS and three unaffected controls, and performed electron microscopy, flow cytometry, cytokine and glutamate measurements, gene expression, in situ respiration, and metabolomics. We validated our findings using a single‐nuclei RNA sequencing dataset.

Results

We detected several differences in MS astrocytes including: (i) enrichment of genes associated with neurodegeneration, (ii) increased mitochondrial fission, (iii) increased production of superoxide and MS‐related proinflammatory chemokines, (iv) impaired uptake and enhanced release of glutamate, (v) increased electron transport capacity and proton leak, in line with the increased oxidative stress, and (vi) a distinct metabolic profile, with a deficiency in amino acid catabolism and increased sphingolipid metabolism, which have already been linked to MS.

Interpretation

Here we describe the metabolic profile of iPSC‐derived astrocytes from PwMS and validate this model as a very powerful tool to study disease mechanisms and to perform non‐invasive drug targeting assays in vitro. Our findings recapitulate several disease features described in patients and provide new mechanistic insights into the metabolic rewiring of astrocytes in MS, which could be targeted in future therapeutic studies. ANN NEUROL 2022;91:652–669

The potential neuroprotective effect of diosmin in rotenone-induced model of Parkinson's disease in rats

Most treatments for Parkinson's disease (PD) focus on improving the symptoms and the dopaminergic effects; nevertheless, they cannot delay the disease progression. Diosmin (DM), a naturally occurring flavone that is obtained from citrus fruits, has demonstrated anti-apoptotic, anti-inflammatory and antioxidative properties in many diseases. This study aimed to assess the neuroprotective effects of diosmin in rotenone-induced rat model of PD and investigate its potential underlying mechanisms. A preliminary dose-response study was conducted where rats were treated with DM (50,100 and 200 mg/kg, p.o.) concomitantly with rotenone (2 mg/kg, s.c.) for 4 weeks. Catalepsy, motor impairment, spontaneous locomotion, body weight, histological examination and tyrosine hydroxylase (TH) immunoreactivity were evaluated in both the midbrains and striata of rats. Treatment with DM (200 mg/kg) showed the most promising outcome therefore, it was selected for further evaluation of α-synuclein, Bax, Bcl2, nuclear factor kappa B (NF-кB), nuclear factor erythroid 2- related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), in addition to biochemical analysis of tumor necrosis factor-α (TNF-α). Results showed that DM (200 mg/kg, p.o.) prevented rotenone-induced motor impairment, weight reduction and histological damage. Furthermore, it significantly inhibited rotenone-induced decrease in TH expression. These results were correlated with reduction in α-synuclein immunoreactivity, together with improvement of Bax/Bcl2 ratio compared to rotenone group. DM also attenuated rotenone-induced increase in NF-кB expression as well as TNF- α levels. Moreover, DM inhibited rotenone-induced upregulation of Nrf2/HO-1 pathway. Thus, the current study suggests that DM might be a promising candidate for managing the neuropathological course of PD.

Ligustilide attenuates ischemic stroke injury by promoting Drp1-mediated mitochondrial fission via activation of AMPK

BACKGROUND

Ischemic stroke is a major global cause of death and permanent disability. Studies have suggested that mitochondria play a critical role in maintaining cellular energy homeostasis and inevitably involved in neuronal damage during cerebral ischemic. Ligustilide is the main active ingredient of Angelica sinensis and Ligusticum chuanxiongs with neuroprotective activity.

PURPOSE

These study sought to exlopre the role of LIG in improving mitochondrial function and the relationship between LIG induced mitochondrial fission and mitophagy in ischemic stroke.

METHODS

Cerebral I/R injury was established by the model of Oxygen-glucose deprivation/reperfusion (OGD/R) in HT22 cells and middle cerebral artery occlusion (MCAO) in rats. Mitochondrial functions of were detected by flow cytometry and immunofluorescence, and mitochondrial fission were detected by western blots. Furthermore, we studied the role of AMPK pathway in the neuroprotective effect of LIG.

RESULTS

LIG treatment significantly increased the MMP and ATP production, decreased the reactive oxygen species (ROS) generation and Ca²⁺ overload, and further induced mitochondrial fission and mitophagy. Moreover, we found that blocking mitochondrial fission by mdivi-1 resulted in accumulation of damaged mitochondria mainly through selectively blocking mitophagy, thereby inhibiting viability of HT-22 cells after OGD/R. Also, Drp-1 inhibitor mdivi-1 increased the infarct volume and aggravated the neurological deficits after MCAO operation in vivo. Additionally, LIG triggered AMP-activated protein kinase (AMPK) pathway. AMPKα2 knockdown attenuated LIG-induced mitochondrial fission through inhibiting the expression of Drp1 and Fis1, and led to nerve cell apoptosis.

CONCLUSION

Our study indicate that LIG attenuated the injury of ischemic stroke by improving mitochondrial function and highlight the critical role of LIG in the regulation of LIG-induced mitochondrial fission and mitophagy via an AMPK-dependent manner. These findings indicate that LIG protects nerve damage against ischemic stroke by inducing Drp1-mediated mitochondrial fission via activation of AMPK signaling pathway in vivo and in vitro.

Nanomedicines, an emerging therapeutic regimen for treatment of ischemic cerebral stroke: A review

Owing to its intricate pathophysiology, cerebral stroke is a serious medical condition caused by interruption or obstruction of blood supply (blockage of vasculature) to the brain tissues which results in diminished supply of essential nutrients and oxygen (hypoxia) and ultimate necrosis of neuronal tissues. A prompt risks assessment and immediate rational therapeutic plan with proficient neuroprotection play critically important role in the effective management of this neuronal emergency. Various conventional medications are being used for treatment of acute ischemic cerebral stroke but fibrinolytic agents, alone or in combination with other agents are considered the mainstay. These clot-busting agents effectively restore blood supply (reperfusion) to ischemic regions of the brain; however, their clinical significance is hampered due to various factors such as short plasma half-life, limited distribution to brain tissues due to the presence of highly efficient physiological barrier, blood brain barrier (BBB), and lacking of target-specific delivery to the ischemic brain regions. To alleviate these issues, various types of nanomedicines such as polymeric nanoparticles (NPs), liposomes, nanoemulsion, micelles and dendrimers have been designed and evaluated. The implication of these newer therapies (nanomedicines) have revolutionized the therapeutic outcomes by improving the plasma half-life, permeation across BBB, efficient distribution to ischemic cerebral tissues and neuroprotection. Furthermore, the adaptation of some diverse techniques including PEGylation, tethering of targeting ligands on the surfaces of nanomedicines, and pH responsive features have also been pondered. The implication of these emerging adaptations have shown remarkable potential in maximizing the targeting efficiency of drugs to ischemic brain tissues, simultaneous delivery of drugs and imaging agents (for early prognosis as well as monitoring of therapy), and therapeutic outcomes such as long-term neuroprotection.

Mitochondrial morphology is associated with respiratory chain uncoupling in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is associated with unique changes in mitochondrial metabolism, including elevated respiration rates and morphological alterations. We examined electron transport chain (ETC) complex activity in fibroblasts derived from 18 children with ASD as well as mitochondrial morphology measurements in fibroblasts derived from the ASD participants and four typically developing controls. In ASD participants, symptoms severity was measured by the Social Responsiveness Scale and Aberrant Behavior Checklist. Mixed-model regression demonstrated that alterations in mitochondrial morphology were associated with both ETC Complex I+III and IV activity as well as the difference between ETC Complex I+III and IV activity. The subgroup of ASD participants with relative elevation in Complex IV activity demonstrated more typical mitochondrial morphology and milder ASD related symptoms. This study is limited by sample size given the invasive nature of obtaining fibroblasts from children. Furthermore, since mitochondrial function is heterogenous across tissues, the result may be specific to fibroblast respiration. Previous studies have separately described elevated ETC Complex IV activity and changes in mitochondrial morphology in cells derived from children with ASD but this is the first study to link these two findings in mitochondrial metabolism. The association between a difference in ETC complex I+III and IV activity and normal morphology suggests that mitochondrial in individuals with ASD may require ETC uncoupling to function optimally. Further studies should assess the molecular mechanisms behind these unique metabolic changes.Trial registration: Protocols used in this study were registered in clinicaltrials.gov as NCT02000284 and NCT02003170.

Empowering Melatonin Therapeutics with Drosophila Models

Melatonin functions as a central regulator of cell and organismal function as well as a neurohormone involved in several processes, e.g., the regulation of the circadian rhythm, sleep, aging, oxidative response, and more. As such, it holds immense pharmacological potential. Receptor-mediated melatonin function mainly occurs through MT1 and MT2, conserved amongst mammals. Other melatonin-binding proteins exist. Non-receptor-mediated activities involve regulating the mitochondrial function and antioxidant cascade, which are frequently affected by normal aging as well as disease. Several pathologies display diseased or dysfunctional mitochondria, suggesting melatonin may be used therapeutically. Drosophila models have extensively been employed to study disease pathogenesis and discover new drugs. Here, we review the multiple functions of melatonin through the lens of functional conservation and model organism research to empower potential melatonin therapeutics to treat neurodegenerative and renal diseases.

Nuclear and Mitochondrial Genome, Epigenome and Gut Microbiome: Emerging Molecular Biomarkers for Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is currently the second most common neurodegenerative disorder, burdening about 10 million elderly individuals worldwide. The multifactorial nature of PD poses a difficult obstacle for understanding the mechanisms involved in its onset and progression. Currently, diagnosis depends on the appearance of clinical signs, some of which are shared among various neurologic disorders, hindering early diagnosis. There are no effective tools to prevent PD onset, detect the disease in early stages or accurately report the risk of disease progression. Hence, there is an increasing demand for biomarkers that may identify disease onset and progression, as treatment-based medicine may not be the best approach for PD. Over the last few decades, the search for molecular markers to predict susceptibility, aid in accurate diagnosis and evaluate the progress of PD have intensified, but strategies aimed to improve individualized patient care have not yet been established.

CONCLUSIONS

Genomic variation, regulation by epigenomic mechanisms, as well as the influence of the host gut microbiome seem to have a crucial role in the onset and progress of PD, thus are considered potential biomarkers. As such, the human nuclear and mitochondrial genome, epigenome, and the host gut microbiome might be the key elements to the rise of personalized medicine for PD patients.

Queuine, a bacterial-derived hypermodified nucleobase, shows protection in in vitro models of neurodegeneration

Growing evidence suggests that human gut bacteria, which comprise the microbiome, are linked to several neurodegenerative disorders. An imbalance in the bacterial population in the gut of Parkinson's disease (PD) and Alzheimer's disease (AD) patients has been detected in several studies. This dysbiosis very likely decreases or increases microbiome-derived molecules that are protective or detrimental, respectively, to the human body and those changes are communicated to the brain through the so-called 'gut-brain-axis'. The microbiome-derived molecule queuine is a hypermodified nucleobase enriched in the brain and is exclusively produced by bacteria and salvaged by humans through their gut epithelium. Queuine replaces guanine at the wobble position (position 34) of tRNAs with GUN anticodons and promotes efficient cytoplasmic and mitochondrial mRNA translation. Queuine depletion leads to protein misfolding and activation of the endoplasmic reticulum stress and unfolded protein response pathways in mice and human cells. Protein aggregation and mitochondrial impairment are often associated with neural dysfunction and neurodegeneration. To elucidate whether queuine could facilitate protein folding and prevent aggregation and mitochondrial defects that lead to proteinopathy, we tested the effect of chemically synthesized queuine, STL-101, in several in vitro models of neurodegeneration. After neurons were pretreated with STL-101 we observed a significant decrease in hyperphosphorylated alpha-synuclein, a marker of alpha-synuclein aggregation in a PD model of synucleinopathy, as well as a decrease in tau hyperphosphorylation in an acute and a chronic model of AD. Additionally, an associated increase in neuronal survival was found in cells pretreated with STL-101 in both AD models as well as in a neurotoxic model of PD. Measurement of queuine in the plasma of 180 neurologically healthy individuals suggests that healthy humans maintain protective levels of queuine. Our work has identified a new role for queuine in neuroprotection uncovering a therapeutic potential for STL-101 in neurological disorders.

How Inflammation Pathways Contribute to Cell Death in Neuro-Muscular Disorders

Neuro-muscular disorders include a variety of diseases induced by genetic mutations resulting in muscle weakness and waste, swallowing and breathing difficulties. However, muscle alterations and nerve depletions involve specific molecular and cellular mechanisms which lead to the loss of motor-nerve or skeletal-muscle function, often due to an excessive cell death. Morphological and molecular studies demonstrated that a high number of these disorders seem characterized by an upregulated apoptosis which significantly contributes to the pathology. Cell death involvement is the consequence of some cellular processes that occur during diseases, including mitochondrial dysfunction, protein aggregation, free radical generation, excitotoxicity and inflammation. The latter represents an important mediator of disease progression, which, in the central nervous system, is known as neuroinflammation, characterized by reactive microglia and astroglia, as well the infiltration of peripheral monocytes and lymphocytes. Some of the mechanisms underlying inflammation have been linked to reactive oxygen species accumulation, which trigger mitochondrial genomic and respiratory chain instability, autophagy impairment and finally neuron or muscle cell death. This review discusses the main inflammatory pathways contributing to cell death in neuro-muscular disorders by highlighting the main mechanisms, the knowledge of which appears essential in developing therapeutic strategies to prevent the consequent neuron loss and muscle wasting.

Cytosolic aggregation of mitochondrial proteins disrupts cellular homeostasis by stimulating the aggregation of other proteins

Mitochondria are organelles with their own genomes, but they rely on the import of nuclear-encoded proteins that are translated by cytosolic ribosomes. Therefore, it is important to understand whether failures in the mitochondrial uptake of these nuclear-encoded proteins can cause proteotoxic stress and identify response mechanisms that may counteract it. Here, we report that upon impairments in mitochondrial protein import, high-risk precursor and immature forms of mitochondrial proteins form aberrant deposits in the cytosol. These deposits then cause further cytosolic accumulation and consequently aggregation of other mitochondrial proteins and disease-related proteins, including α-synuclein and amyloid β. This aggregation triggers a cytosolic protein homeostasis imbalance that is accompanied by specific molecular chaperone responses at both the transcriptomic and protein levels. Altogether, our results provide evidence that mitochondrial dysfunction, specifically protein import defects, contributes to impairments in protein homeostasis, thus revealing a possible molecular mechanism by which mitochondria are involved in neurodegenerative diseases.

Loss of MIC60 Aggravates Neuronal Death by Inducing Mitochondrial Dysfunction in a Rat Model of Intracerebral Hemorrhage

Mitochondrial damage has been reported to be a critical factor for secondary brain injury (SBI) induced by intracerebral hemorrhage (ICH). MIC60 is a key element of the mitochondrial contact site and cristae junction organizing system (MICOS), which takes a principal part in maintaining mitochondrial structure and function. The role of MIC60 and its underlying mechanisms in ICH-induced SBI are not clear, which will be investigated in this present study. To establish and emulate ICH model in vivo and in vitro, autologous blood was injected into the right basal ganglia of Sprague-Dawley (SD) rats; and primary-cultured cortical neurons were treated by oxygen hemoglobin (OxyHb). First, after ICH induction, mitochondria were damaged and exhibited mitochondrial crista-structure remodeling, and MIC60 protein levels were reduced. Furthermore, MIC60 overexpression reduced ICH-induced neuronal death both in vivo and in vitro. In addition, MIC60 upregulation reduced ICH-induced cerebral edema, neurobehavioral impairment, and cognitive dysfunction; by contrast, MIC60 knockdown had the opposite effect. Additionally, in primary-cultured neurons, MIC60 overexpression could reverse ICH-induced neuronal cell death and apoptosis, mitochondrial membrane potential collapse, and decrease of mitophagy, indicating that MIC60 overexpression can maintain the integrity of mitochondrial structures. Moreover, loss of MIC60 is after ICH-induced reduction in PINK1 levels and mislocalization of Parkin in primary-cultured neurons. Taken together, our findings suggest that MIC60 plays an important role in ICH-induced SBI and may represent a promising target for ICH therapy.

Placental endocrine insufficiency programs anxiety, deficits in cognition and atypical social behaviour in offspring

Abnormally elevated expression of the imprinted PHLDA2 gene has been reported in the placenta of human babies that are growth restricted in utero in several studies. We previously modelled this gene alteration in mice and found that just 2-fold increased expression of Phlda2 resulted in placental endocrine insufficiency. In addition, elevated Phlda2 was found to drive fetal growth restriction (FGR) of transgenic offspring and impaired maternal care by their wildtype mothers. Being born small and being exposed to suboptimal maternal care have both been associated with the increased risk of mental health disorders in human populations. In the current study we probed behavioural consequences of elevated Phlda2 for the offspring. We discovered increased anxiety-like behaviours, deficits in cognition and atypical social behaviours, with the greatest impact on male offspring. Subsequent analysis revealed alterations in the transcriptome of the adult offspring hippocampus, hypothalamus and amygdala, regions consistent with these behavioural observations. The inclusion of a group of fully wildtype controls raised in a normal maternal environment allowed us to attribute behavioural and molecular alterations to the adverse maternal environment induced by placental endocrine insufficiency rather than the specific gene change of elevated Phlda2. Our work demonstrates that a highly common alteration reported in human FGR is associated with negative behavioural outcomes later in life. Importantly, we also establish the experimental paradigm that placental endocrine insufficiency can program atypical behaviour in offspring highlighting the under-appreciated role of placental endocrine insufficiency in driving disorders of later life behaviour.

The Multifaceted Roles of Zinc in Neuronal Mitochondrial Dysfunction

Zinc is a highly abundant cation in the brain, essential for cellular functions, including transcription, enzymatic activity, and cell signaling. However, zinc can also trigger injurious cascades in neurons, contributing to the pathology of neurodegenerative diseases. Mitochondria, critical for meeting the high energy demands of the central nervous system (CNS), are a principal target of the deleterious actions of zinc. An increasing body of work suggests that intracellular zinc can, under certain circumstances, contribute to neuronal damage by inhibiting mitochondrial energy processes, including dissipation of the mitochondrial membrane potential (MMP), leading to ATP depletion. Additional consequences of zinc-mediated mitochondrial damage include reactive oxygen species (ROS) generation, mitochondrial permeability transition, and excitotoxic calcium deregulation. Zinc can also induce mitochondrial fission, resulting in mitochondrial fragmentation, as well as inhibition of mitochondrial motility. Here, we review the known mechanisms responsible for the deleterious actions of zinc on the organelle, within the context of neuronal injury associated with neurodegenerative processes. Elucidating the critical contributions of zinc-induced mitochondrial defects to neurotoxicity and neurodegeneration may provide insight into novel therapeutic targets in the clinical setting.

Unraveling the Link Between Mitochondrial Dynamics and Neuroinflammation

Neuroinflammatory and neurodegenerative diseases are a major public health problem worldwide, especially with the increase of life-expectancy observed during the last decades. For many of these diseases, we still lack a full understanding of their etiology and pathophysiology. Nonetheless their association with mitochondrial dysfunction highlights this organelle as an important player during CNS homeostasis and disease. Markers of Parkinson (PD) and Alzheimer (AD) diseases are able to induce innate immune pathways induced by alterations in mitochondrial Ca2+ homeostasis leading to neuroinflammation. Additionally, exacerbated type I IFN responses triggered by mitochondrial DNA (mtDNA), failures in mitophagy, ER-mitochondria communication and mtROS production promote neurodegeneration. On the other hand, regulation of mitochondrial dynamics is essential for CNS health maintenance and leading to the induction of IL-10 and reduction of TNF-α secretion, increased cell viability and diminished cell injury in addition to reduced oxidative stress. Thus, although previously solely seen as power suppliers to organelles and molecular processes, it is now well established that mitochondria have many other important roles, including during immune responses. Here, we discuss the importance of these mitochondrial dynamics during neuroinflammation, and how they correlate either with the amelioration or worsening of CNS disease.

Involvement of Mitochondrial Dynamics and Mitophagy in Sevoflurane-Induced Cell Toxicity

General anesthesia is a powerful and indispensable tool to ensure the accomplishment of surgical procedures or clinical examinations. Sevoflurane as an inhalational anesthetic without unpleasant odor is commonly used in clinical practice, especially for pediatric surgery. However, the toxicity caused by sevoflurane has gained growing attention. Mitochondria play a key role in maintaining cellular metabolism and survival. To maintain the stability of mitochondrial homeostasis, they are constantly going through fusion and fission. Also, damaged mitochondria need to be degraded by autophagy, termed as mitophagy. Accumulating evidence proves that sevoflurane exposure in young age could lead to cell toxicity by triggering the mitochondrial pathway of apoptosis, inducing the abnormalities of mitochondrial dynamics and mitophagy. In the present review, we focus on the current understanding of mitochondrial apoptosis, dynamics and mitophagy in cell function, the implications for cell toxicity in response to sevoflurane, and their underlying potential mechanisms.

Tavarua Deoxyriboside A and Jasplakinolide as Potential Neuroprotective Agents: Effects on Cellular Models of Oxidative Stress and Neuroinflammation

The oceans harbor a great reservoir of molecules with unknown bioactivities, which could be useful for the treatment of illnesses that nowadays have no cure, such as neurodegenerative diseases. In this work, we evaluated the neuroprotective potential of the marine Fijian compounds tavarua deoxyriboside A and jasplakinolide against oxidative stress and neuroinflammation, crucial mechanisms in neurodegeneration. Both metabolites protected SH-SY5Y human neuroblastoma cells from H₂O₂ damage, improving mitochondrial function and activating the antioxidant systems of cells. These effects were mediated by their ability of inducing Nrf2 translocation. In BV2 microglial cells activated with lipopolysaccharide, Fijian metabolites also displayed promising results, decreasing the release of proinflammatory mediators (ROS, NO, cytokines) through the reduction of gp91 and NFkB-p65 expression. Finally, we performed a coculture among both cell lines, in which treatment with compounds protected SH-SY5Y cells from activated microglia, corroborating their neuroprotective effects. These results suggest that tavarua deoxyriboside A and jasplakinolide could be used as candidate molecules for further studies against neurodegeneration.

Emerging paradigms in treating cerebral infarction with nanotheranostics: opportunities and clinical challenges

Interest is increasing in the use of nanotheranostics as diagnosis, imaging and therapeutic tools for stroke management, but movement to the clinic remains challenging.

Disruption of mitochondrial functions and oxidative stress contribute to neurologic dysfunction in organic acidurias

Organic acidurias (OADs) are inherited disorders of amino acid metabolism biochemically characterized by accumulation of short-chain carboxylic acids in tissues and biological fluids of the affected patients and clinically by predominant neurological manifestations. Some of these disorders are amenable to treatment, which significantly decreases mortality and morbidity, but it is still ineffective to prevent long-term neurologic and systemic complications. Although pathogenesis of OADs is still poorly established, recent human and animal data, such as lactic acidosis, mitochondrial morphological alterations, decreased activities of respiratory chain complexes and altered parameters of oxidative stress, found in tissues from patients and from genetic mice models with these diseases indicate that disruption of critical mitochondrial functions and oxidative stress play an important role in their pathophysiology. Furthermore, organic acids that accumulate in the most prevalent OADs were shown to compromise bioenergetics, by decreasing ATP synthesis, mitochondrial membrane potential, reducing equivalent content and calcium retention capacity, besides inducing mitochondrial swelling, reactive oxygen and nitrogen species generation and apoptosis. It is therefore presumed that secondary mitochondrial dysfunction and oxidative stress caused by major metabolites accumulating in OADs contribute to tissue damage in these pathologies.