Mitochondrial fission and fusion in secondary brain damage after CNS insults

Utilizing engineered extracellular vesicles as delivery vectors in the management of ischemic stroke: a special outlook on mitochondrial delivery

Ischemic stroke is a secondary cause of mortality worldwide, imposing considerable medical and economic burdens on society. Extracellular vesicles, serving as natural nano-carriers for drug delivery, exhibit excellent biocompatibility in vivo and have significant advantages in the management of ischemic stroke. However, the uncertain distribution and rapid clearance of extracellular vesicles impede their delivery efficiency. By utilizing membrane decoration or by encapsulating therapeutic cargo within extracellular vesicles, their delivery efficacy may be greatly improved. Furthermore, previous studies have indicated that microvesicles, a subset of large-sized extracellular vesicles, can transport mitochondria to neighboring cells, thereby aiding in the restoration of mitochondrial function post-ischemic stroke. Small extracellular vesicles have also demonstrated the capability to transfer mitochondrial components, such as proteins or deoxyribonucleic acid, or their sub-components, for extracellular vesicle-based ischemic stroke therapy. In this review, we undertake a comparative analysis of the isolation techniques employed for extracellular vesicles and present an overview of the current dominant extracellular vesicle modification methodologies. Given the complex facets of treating ischemic stroke, we also delineate various extracellular vesicle modification approaches which are suited to different facets of the treatment process. Moreover, given the burgeoning interest in mitochondrial delivery, we delved into the feasibility and existing research findings on the transportation of mitochondrial fractions or intact mitochondria through small extracellular vesicles and microvesicles to offer a fresh perspective on ischemic stroke therapy.

Membrane ATPases and Mitochondrial Proteins in Fetal Cerebellum After Exposure to L-Glutamate During Gestation

L-Glutamate (L-Glu) and its salt derivatives are widely used in the food industry as flavor enhancers. Although the consumption of these compounds is generally considered safe, some studies suggest that chronically consuming L-Glu may be associated with various disorders. In this study, Wistar pregnant rats were treated daily with 1 g/L of L-Glu in their drinking water throughout the gestational period. OPA-1, DRP-1, and mitofusin 2-key proteins involved in mitochondrial fusion and fission-were analyzed by Western blot. The results showed that L-Glu exposure significantly decreased DRP-1 levels, while OPA-1 and mitofusin 2 levels were unaffected. This was accompanied by a notable decrease in mitochondrial complexes III and V. The activities of Mg2+-ATPase and Na+/K+-ATPase were also analyzed in fetal cerebellar plasma membranes. Maternal L-Glu intake significantly increased Mg2+-ATPase activity. Regarding Na+/K+-ATPase, the data showed that L-Glu exposure did not modulate the protein level or its activity. However, a positive interaction with glutamate receptors was observed in both activities, although neither AMPA nor NMDA receptors appeared to be involved. These results suggest that chronic maternal L-Glu intake during gestation modulates Mg2+-ATPase activity and protein markers of mitochondrial dynamics in the fetal cerebellum, which could affect neonatal development.

DRP1, fission and apoptosis

Mitochondrial fission is a critical physiological process in eukaryotic cells, participating in various vital activities such as mitosis, mitochondria quality control, and mitophagy. Recent studies have revealed a tight connection between mitochondrial fission and the mitochondrial metabolism, as well as apoptosis, which involves multiple cellular events and interactions between organelles. As a pivotal molecule in the process of mitochondrial fission, the function of DRP1 is regulated at multiple levels, including transcription, post-translational modifications. This review follows the guidelines for Human Gene Nomenclature and will focus on DRP1, discussing its activity regulation, its role in mitochondrial fission, and the relationship between mitochondrial fission and apoptosis.

Mitochondrial quality control disorder in neurodegenerative disorders: Potential and advantages of traditional Chinese medicines

Neurodegenerative disorders (NDDs) are prevalent chronic conditions characterized by progressive synaptic loss and pathological protein alterations. Increasing evidence suggested that mitochondrial quality control (MQC) serves as the key cellular process responsible for clearing misfolded proteins and impaired mitochondria. Herein, we provided a comprehensive analysis of the mechanisms through which MQC mediates the onset and progression of NDDs, emphasizing mitochondrial dynamic stability, the clearance of damaged mitochondria, and the generation of new mitochondria. In addition, traditional Chinese medicines (TCMs) and their active monomers targeting MQC in NDD treatment have been demonstrated. Consequently, we compiled the TCMs that show great potential in the treatment of NDDs by targeting MQC, aiming to offer novel insights and a scientific foundation for the use of MQC stabilizers in NDD prevention and treatment.

Role and therapeutic considerations of SIRT1 in epilepsy

Epilepsy is a primary study focus for scientists worldwide due to its prevalence and poor prognosis. Silent information regulator 1 (SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase, is becoming increasingly recognized for its critical role in the pathophysiology and progression of epilepsy. The treatment of epilepsy remains challenging despite the discovery of numerous factors that contribute to the development of several beneficial medications. In recent years, many microRNAs have been linked to the progression of epilepsy because they target SIRT1 mRNA. SIRT1, which protects from epilepsy, has been reported to be upregulated by several natural compounds and their derivatives. This review will summarize the latest findings about SIRT1's role in epilepsy. Results from the literature indicate that SIRT1 is a promising target for epilepsy therapy.

Naotaifang formula regulates Drp1-induced remodeling of mitochondrial dynamics following cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CIRI) has emerged as a hindrance for rehabilitation of ischemic stroke patients. Naotaifang (NTF) exhibits beneficial efficacy in alleviating inflammation and ferroptosis in vitro during CIRI. While the potential role of NTF in regulating mitochondrial dynamics in CIRI are not elucidated. This study aimed to explore the mechanism of NTF against CIRI by regulating the dynamin-related protein 1 (Drp1)-dependent mitochondrial fission/fusion. Modeling middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo to evaluate the effects of NTF on the MCAO/R-damaged neurons and the structure, dynamics and function of mitochondria. An oxygen-glucose deprivation/reperfusion (OGD/R) cell model was established to evaluate the role of NTF in OGD/R-damaged cells. Function of Drp1 in CIRI and the neuroprotection of NTF through the mitochondrial fission/fusion pathway were investigated in vivo and in vitro. The results revealed that in vivo, NTF alleviated neuron injury in a dose-dependent manner, down-regulated Drp1 and fission protein 1 (Fis1) levels, upregulated optic atrophy 1 (Opa1), mitofusin 1/2 (Mfn1 and Mfn2), facilitated mitochondrial fusion and inhibited mitochondrial fission to rescue cells from CIRI. In vitro, Drp1 overexpression inhibited mitochondrial fusion and activated mitochondrial fission, while silencing of Drp1 exhibited the opposite result. NTF rebalanced mitochondrial dynamic in the OGD/R cell model. NTF could alleviate neuron injury following CIRI by regulating the balance of mitochondrial fission and fusion. Targeting Drp1-dependent mitochondrial dynamics may represent a viable treatment strategy for addressing the issues of CIRI post ischemic stroke.

Genetic and pharmacological correction of impaired mitophagy in retinal ganglion cells rescues glaucomatous neurodegeneration

Progressive loss of retinal ganglion cells (RGCs) and degeneration of optic nerve axons are the pathological hallmarks of glaucoma. Ocular hypertension (OHT) and mitochondrial dysfunction are linked to neurodegeneration and vision loss in glaucoma. However, the exact mechanism of mitochondrial dysfunction leading to glaucomatous neurodegeneration is poorly understood. Using multiple mouse models of OHT and human eyes from normal and glaucoma donors, we show that OHT induces impaired mitophagy in RGCs, resulting in the accumulation of dysfunctional mitochondria and contributing to glaucomatous neurodegeneration. Using mitophagy reporter mice, we show that impaired mitophagy precedes glaucomatous neurodegeneration. Notably, the pharmacological rescue of impaired mitophagy via Torin-2 or genetic upregulation of RGC-specific Parkin expression restores the structural and functional integrity of RGCs and their axons in mouse models of glaucoma and ex-vivo human retinal-explant cultures. Our study indicates that impaired mitophagy contributes to mitochondrial dysfunction and oxidative stress, leading to glaucomatous neurodegeneration. Enhancing mitophagy in RGCs represents a promising therapeutic strategy to prevent glaucomatous neurodegeneration.

Sexual Dimorphism of Ethanol-Induced Mitochondrial Dynamics in Purkinje Cells

The cerebellum, a key target of ethanol's toxic effects, is associated with ataxia following alcohol consumption. However, the impact of ethanol on Purkinje cell (PC) mitochondria remains unclear. To investigate how ethanol administration affects mitochondrial dynamics in cerebellar Purkinje cells, we employed a transgenic mouse model expressing mitochondria-targeted yellow fluorescent protein in Purkinje cells (PC-mito-eYFP). Both male and female PC-mito-eYFP mice received an intraperitoneal injection of ethanol or vehicle. One hour after ethanol administration, the animals were perfusion fixed or their cerebellum tissue or isolated mitochondria were collected. Cerebellum sections were analyzed using confocal microscopy to assess changes in mitochondrial length distribution. In vivo superoxide levels were measured using dihydroethidium (DHE), and mitochondrial NAD levels were determined by high-performance liquid chromatography (HPLC). Our findings revealed a sex-dependent response to ethanol administration in mitochondrial size distribution. While male Purkinje cell mitochondria exhibited no significant changes in size, female mitochondria became more fragmented after one hour of ethanol administration. This coincided with elevated phosphorylation of the fission protein Drp1 and increased superoxide production, as measured by DHE fluorescence intensity. Similarly, mitochondrial NAD levels were significantly reduced in female mice, but no changes were observed in males. Our results demonstrate that ethanol induced mitochondrial fragmentation through increased free radical levels, due to reduced NAD and increased p-Drp1, in PC cells of the female cerebellum.

Nanoparticle targeting strategies for traumatic brain injury

Nanoparticle (NP)-based drug delivery systems hold immense potential for targeted therapy and diagnosis of neurological disorders, overcoming the limitations of conventional treatment modalities. This review explores the design considerations and functionalization strategies of NPs for precise targeting of the brain and central nervous system. This review discusses the challenges associated with drug delivery to the brain, including the blood-brain barrier and the complex heterogeneity of traumatic brain injury. We also examine the physicochemical properties of NPs, emphasizing the role of size, shape, and surface characteristics in their interactions with biological barriers and cellular uptake mechanisms. The review concludes by exploring the options of targeting ligands designed to augment NP affinity and retention to specific brain regions or cell types. Various targeting ligands are discussed for their ability to mimic receptor-ligand interaction, and brain-specific extracellular matrix components. Strategies to mimic viral mechanisms to increase uptake are discussed. Finally, the emergence of antibody, antibody fragments, and antibody mimicking peptides are discussed as promising targeting strategies. By integrating insights from these scientific fields, this review provides an understanding of NP-based targeting strategies for personalized medicine approaches to neurological disorders. The design considerations discussed here pave the way for the development of NP platforms with enhanced therapeutic efficacy and minimized off-target effects, ultimately advancing the field of neural engineering.

Therapeutic utility of Perfluorocarbon Oxygent in limiting the severity of subarachnoid hemorrhage in mice

Subarachnoid hemorrhage (SAH) is the deadliest form of hemorrhagic stroke; however, effective therapies are still lacking. Perfluorocarbons (PFCs) are lipid emulsion particles with great flexibility and their much smaller size as compared to red blood cells (RBCs) allows them to flow more efficiently within the blood circulation. Due to their ability to carry oxygen, a specific PFC-based emulsion, PFC-Oxygent, has been used as a blood substitute; however, its role in cerebral blood flow regulation is unknown. Adult C57BL/6 wildtype male mice were subjected to an endovascular perforation model of SAH followed by an intravenous (i.v.) injection of 9 ml/kg PFC-Oxygent or no treatment at 5 h after SAH. At 48 h after SAH, functional and anatomical outcomes were assessed. We found that SAH resulted in significant neurologic and motor deficits which were prevented by PFC-Oxygent treatment. We found that SAH-induced vasospasm, reduced RBC deformability, and augmented endothelial dysfunction were also restricted by PFC-Oxygent treatment. Moreover, mitochondrial activity and fusion proteins were also markedly decreased as assessed by oxidative phosphorylation (OXPHOS) after SAH. Interestingly, PFC-Oxygent treatment brought the mitochondrial activity close to the basal level. Moreover, SAH attenuated the level of phosphorylated AMP-activated protein kinase (pAMPK), whereas PFC treatment improved pAMPK levels. These data show the beneficial effects of PFC-Oxygent in limiting the severity of SAH. Further studies are needed to fully understand the mechanism through which PFC-Oxygent exerts its beneficial effects in limiting SAH severity.

Role of transcription factors, noncoding RNAs, epitranscriptomics, and epigenetics in post-ischemic neuroinflammation

Post-stroke neuroinflammation is pivotal in brain repair, yet persistent inflammation can aggravate ischemic brain damage and hamper recovery. Following stroke, specific molecules released from brain cells attract and activate central and peripheral immune cells. These immune cells subsequently release diverse inflammatory molecules within the ischemic brain, initiating a sequence of events, including activation of transcription factors in different brain cell types that modulate gene expression and influence outcomes; the interactive action of various noncoding RNAs (ncRNAs) to regulate multiple biological processes including inflammation, epitranscriptomic RNA modification that controls RNA processing, stability, and translation; and epigenetic changes including DNA methylation, hydroxymethylation, and histone modifications crucial in managing the genic response to stroke. Interactions among these events further affect post-stroke inflammation and shape the depth of ischemic brain damage and functional outcomes. We highlighted these aspects of neuroinflammation in this review and postulate that deciphering these mechanisms is pivotal for identifying therapeutic targets to alleviate post-stroke dysfunction and enhance recovery.

Role of intracranial bone marrow mesenchymal stem cells in stroke recovery: A focus on post-stroke inflammation and mitochondrial transfer

Stem cell therapy has become a hot research topic in the medical field in recent years, with enormous potential for treating a variety of diseases. In particular, bone marrow mesenchymal stem cells (BMSCs) have wide-ranging applications in the treatment of ischemic stroke, autoimmune diseases, tissue repair, and difficult-to-treat diseases. BMSCs can differentiate into multiple cell types and exhibit strong immunomodulatory properties. Although BMSCs can regulate the inflammatory response activated after stroke, the mechanism by which BMSCs regulate inflammation remains unclear and requires further study. Recently, stem cell therapy has emerged as a potentially effective approach for enhancing the recovery process following an ischemic stroke. For example, by regulating post-stroke inflammation and by transferring mitochondria to exert therapeutic effects. Therefore, this article reviews the therapeutic effects of intracranial BMSCs in regulating post-stroke inflammation and mitochondrial transfer in the treatment of stroke, providing a basis for further research.

APOE and Alzheimer's disease: Pathologic clues from transgenic Drosophila melanogaster

Alzheimer's disease (AD) is one of the most common forms of neurodegenerative diseases. Apolipoprotein E4 (ApoE4) is the main genetic risk factor in the development of late-onset AD. However, the exact mechanism underlying ApoE4-mediated neurodegeneration remains unclear. We utilized Drosophila melanogaster to examine the neurotoxic effects of various human APOE isoforms when expressed specifically in glial and neural cells. We assessed impacts on mitochondrial dynamics, ER stress, lipid metabolism, and bio-metal ion concentrations in the central nervous system (CNS) of the transgenic flies. Dachshund antibody staining revealed a reduction in the number of Kenyon cells. Behavioral investigations including ethanol tolerance and learning and memory performance demonstrated neuronal dysfunction in APOE4-expressing larvae and adult flies. Transcription level of marf and drp-1 were found to be elevated in APOE4 flies, while atf4, atf6, and xbp-1 s showed down regulation. Enhanced concentrations of triglyceride and cholesterol in the CNS were observed in APOE4 transgenic flies, with especially pronounced effects upon glial-specific expression of the gene. Spectrophotometry of brain homogenate revealed enhanced Fe++ and Zn++ ion levels in conjunction with diminished Cu++ levels upon APOE4 expression. To explore therapeutic strategies, we subjected the flies to heat-shock treatment, aiming to activate heat-shock proteins (HSPs) and assess their potential to mitigate the neurotoxic effects of APOE isoforms. The results showed potential therapeutic benefits for APOE4-expressing flies, hinting at an ability to attenuate memory deterioration. Overall, our findings suggest that APOE4 can alter lipid metabolism, bio metal ion homeostasis, and disrupt the harmonious fission-fusion balance of neuronal and glial mitochondria, ultimately inducing ER stress. These alterations mirror the main clinical manifestations of AD in patients. Therefore, our work underscores the suitability of Drosophila as a fertile model for probing the pathological roles of APOE and furthering our understanding of diverse isoform-specific functions.

Activating MC4R Promotes Functional Recovery by Repressing Oxidative Stress-Mediated AIM2 Activation Post-spinal Cord Injury

Spinal cord injury (SCI) is a destructive neurological trauma that induces permanent sensory and motor impairment as well as a deficit in autonomic physiological function. Melanocortin receptor 4 (MC4R) is a G protein-linked receptor that is extensively expressed in the neural system and contributes to inhibiting inflammation, regulating mitochondrial function, and inducing programmed cell death. However, the effect of MC4R in the modulation of oxidative stress and whether this mechanism is related to the role of absent in melanoma 2 (AIM2) in SCI are not confirmed yet. In the current study, we demonstrated that MC4R is significantly increased in the neurons of spinal cords after trauma and oxidative stimulation of cells. Further, activation of MC4R by RO27-3225 effectively improved functional recovery, inhibited AIM2 activation, maintained mitochondrial homeostasis, repressed oxidative stress, and prevented Drp1 translocation to the mitochondria. Meanwhile, treating Drp1 inhibitors would be beneficial in reducing AIM2 activation, and activating AIM2 could abolish the protective effect of MC4R on neuron homeostasis. In conclusion, we demonstrated that MC4R protects against neural injury through a novel process by inhibiting mitochondrial dysfunction, oxidative stress, as well as AIM2 activation, which may serve as an available candidate for SCI therapy.

Cadmium-induced global DNA hypermethylation promoting mitochondrial dynamics dysregulation in hippocampal neurons

Environmental cadmium exposure during pregnancy or adolescence can cause neurodevelopmental toxicity, lead to neurological impairment, and reduce cognitive abilities, such as learning and memory. However, the mechanisms by which cadmium causes neurodevelopmental toxicity and cognitive impairment are still not fully elucidated. This study used hippocampal neurons cultured in vitro to observe the impact of cadmium exposure on mitochondrial dynamics and apoptosis. Exposure to 5 μM cadmium causes degradation of hippocampal neuron cell bodies and axons, morphological destruction, low cell viability, and apoptosis increase. Cadmium exposure upregulates the expression of mitochondrial fission proteins Drp1 and Fis1, reduces the expression of mitochondrial fusion-related proteins MFN1, MFN2, and OPA1, as well as reduces the expression of PGC-1a. Mitochondrial morphology detection demonstrated that cadmium exposure changes the morphological structure of mitochondria in hippocampal neurons, increasing the number of punctate and granular mitochondria, reducing the number of tubular and reticular mitochondria, decreasing mitochondrial mass, dissipating mitochondrial membrane potential (ΔΨm), and reducing adenosine triphosphate (ATP) production. Cadmium exposure increases the global methylation level of the genome and upregulates the expression of DNMT1 and DNMT3α in hippocampal neurons. 5-Aza-CdR reduces cadmium-induced genome methylation levels in hippocampal neurons, increases the number of tubular and reticular mitochondria, and promotes cell viability. In conclusion, cadmium regulates the expression of mitochondrial dynamics-related proteins by increasing hippocampal neuron genome methylation, changing mitochondrial morphology and function, and exerting neurotoxic effects.

CircRNA and Stroke: New Insight of Potential Biomarkers and Therapeutic Targets

Stroke, the second-largest cause of death and the leading cause of disability globally, presents significant challenges in terms of prognosis and treatment. Identifying reliable prognosis biomarkers and treatment targets is crucial to address these challenges. Circular RNA (circRNA) has emerged as a promising research biomarkers and therapeutic targets because of its tissue specificity and conservation. However, the potential role of circRNA in stroke prognosis and treatment remains largely unexplored. This review briefly elucidate the mechanism underlying circRNA's involvement in stroke pathophysiology. Additionally, this review summarizes the impact of circRNA on different forms of strokes, including ischemic stroke and hemorrhagic stroke. And, this article discusses the positive effects of circRNA on promoting cerebrovascular repair and regeneration, maintaining the integrity of the blood-brain barrier (BBB), and reducing neuronal injury and immune inflammatory response. In conclusion, the significance of circRNA as a potential prognostic biomarker and a viable therapeutic target was underscored.

Variation of the 2D Pattern of Brain Proteins in Mice Infected with Taenia crassiceps ORF Strain

Some parasites are known to influence brain proteins or induce changes in the functioning of the nervous system. In this study, our objective is to demonstrate how the two-dimensional gel technique is valuable for detecting differences in protein expression and providing detailed information on changes in the brain proteome during a parasitic infection. Subsequently, we seek to understand how the parasitic infection affects the protein composition in the brain and how this may be related to changes in brain function. By analyzing de novo-expressed proteins at 2, 4, and 8 weeks post-infection compared to the brains of the control mice, we observed that proteins expressed at 2 weeks are primarily associated with neuroprotection or the initial response of the mouse brain to the infection. At 8 weeks, parasitic infection can induce oxidative stress in the brain, potentially activating signaling pathways related to the response to cellular damage. Proteins expressed at 8 weeks exhibit a pattern indicating that, as the host fails to balance the Neuro-Immuno-Endocrine network of the organism, the brain begins to undergo an apoptotic process and consequently experiences brain damage.

Saponins from Panax japonicus improve neuronal mitochondrial injury of aging rats

CONTEXT

Panax japonicus is the dried rhizome of Panax japonicus C.A. Mey. (Araliaceae). Saponins from Panax japonicus (SPJ) exhibit anti-oxidative and anti-aging effects.

OBJECTIVE

We evaluated the neuroprotective effects of SPJ on aging rats.

MATERIALS AND METHODS

Sprague-Dawley rats (18-months-old) were randomly divided into aging and SPJ groups (n = 8). Five-month-old rats were taken as the adult control (n = 8). The rats were fed a normal chow diet or the SPJ-containing diet (10 or 30 mg/kg) for 4 months. An in vitro model was established by d-galactose (d-Gal) in the SH-SY5Y cell line and pretreated with SPJ (25 and 50 µg/mL). The neuroprotection of SPJ was evaluated via Nissl staining, flow cytometry, transmission electron microscopy and Western blotting in vivo and in vitro.

RESULTS

SPJ improved the neuronal degeneration and mitochondrial morphology that are associated with aging. Meanwhile, SPJ up-regulated the protein levels of mitofusin 2 (Mfn2) and optic atrophy 1 (Opa1) and down-regulated the protein level of dynamin-like protein 1 (Drp1) in the hippocampus of aging rats (p < 0.05 or p < 0.01 vs. 22 M). The in vitro studies also demonstrated that SPJ attenuated d-Gal-induced cell senescence concomitant with the improvement in mitochondrial function; SPJ, also up-regulated the Mfn2 and Opa1 protein levels, whereas the Drp1 protein level (p < 0.05 or p < 0.01 vs. d-Gal group) was down-regulated.

DISCUSSION AND CONCLUSIONS

Further research on the elderly population will contribute to the development and utilization of SPJ for the treatment of neurodegenerative disorders.

Mitochondrial Proteomes in Neural Cells: A Systematic Review

Mitochondria are ancient endosymbiotic double membrane organelles that support a wide range of eukaryotic cell functions through energy, metabolism, and cellular control. There are over 1000 known proteins that either reside within the mitochondria or are transiently associated with it. These mitochondrial proteins represent a functional subcellular protein network (mtProteome) that is encoded by mitochondrial and nuclear genomes and significantly varies between cell types and conditions. In neurons, the high metabolic demand and differential energy requirements at the synapses are met by specific modifications to the mtProteome, resulting in alterations in the expression and functional properties of the proteins involved in energy production and quality control, including fission and fusion. The composition of mtProteomes also impacts the localization of mitochondria in axons and dendrites with a growing number of neurodegenerative diseases associated with changes in mitochondrial proteins. This review summarizes the findings on the composition and properties of mtProteomes important for mitochondrial energy production, calcium and lipid signaling, and quality control in neural cells. We highlight strategies in mass spectrometry (MS) proteomic analysis of mtProteomes from cultured cells and tissue. The research into mtProteome composition and function provides opportunities in biomarker discovery and drug development for the treatment of metabolic and neurodegenerative disease.

T817MA Regulates Mitochondrial Dynamics via Sirt1 and Arc Following Subarachnoid Hemorrhage

Spontaneous subarachnoid hemorrhage (SAH) is an acute neurologic emergency with poor outcomes, and mitochondrial dysfunction is known as one of the key pathological mechanisms underlying the SAH-induced early brain injury (EBI). 1-{3-[2-(1-benzothiophen-5-yl)ethoxy]propyl} azetidin-3-ol maleate (T817MA) is a newly synthesized neurotrophic compound that has been demonstrated to exert protective effects against brain injury. Here, we investigated the effect of T817MA in neuronal injury following experimental SAH both in vitro and in vivo. Primary cultured cortical neurons were treated with oxyhemoglobin (OxyHb) to mimic SAH in vitro, and T817MA at concentrations higher than 0.1 μM reduced OxyHb-induced neuronal injury. T817MA treatment significantly inhibited lipid peroxidation, reduced neuronal apoptosis and attenuated mitochondrial fragmentation. The results of western blot showed that T817MA markedly reduced the expression of mitochondrial fission proteins, fission protein 1 (Fis-1) and dynamin-related GTPase-1 (Drp-1), but prolonged the expression of the postsynaptic protein activity-regulated cytoskeleton-associated protein (Arc). In addition, T817MA significantly increased the expression of sirtuin 1 (Sirt1), which was accompanied by preserved enzymatic of isocitrate dehydrogenase (IDH2) and superoxide dismutase (SOD). Knockdown of Sirt1 and Arc via small interfere RNA (siRNA) transfection partially prevented the T817MA-induced protection in cortical neurons. Furthermore, treatment with T817MA in vivo significantly reduced brain damage and preserved neurological function in rats. The decreased expression of Fis-1 and Drp-1, as well as the increased expression of Arc and Sirt1 were also observed in vivo. Taken together, these data indicate that the neuroprotective agent T817MA protects against SAH-induced brain injury via Sirt1- and Arc-mediated regulation of mitochondrial dynamics.

Asialo-rhuEPO as a Potential Neuroprotectant for Ischemic Stroke Treatment

Neuroprotective drugs to protect the brain against cerebral ischemia and reperfusion (I/R) injury are urgently needed. Mammalian cell-produced recombinant human erythropoietin (rhuEPOM) has been demonstrated to have excellent neuroprotective functions in preclinical studies, but its neuroprotective properties could not be consistently translated in clinical trials. The clinical failure of rhuEPOM was thought to be mainly due to its erythropoietic activity-associated side effects. To exploit its tissue-protective property, various EPO derivatives with tissue-protective function only have been developed. Among them, asialo-rhuEPO, lacking terminal sialic acid residues, was shown to be neuroprotective but non-erythropoietic. Asialo-rhuEPO can be prepared by enzymatic removal of sialic acid residues from rhuEPOM (asialo-rhuEPOE) or by expressing human EPO gene in glycoengineered transgenic plants (asialo-rhuEPOP). Both types of asialo-rhuEPO, like rhuEPOM, displayed excellent neuroprotective effects by regulating multiple cellular pathways in cerebral I/R animal models. In this review, we describe the structure and properties of EPO and asialo-rhuEPO, summarize the progress on neuroprotective studies of asialo-rhuEPO and rhuEPOM, discuss potential reasons for the clinical failure of rhuEPOM with acute ischemic stroke patients, and advocate future studies needed to develop asialo-rhuEPO as a multimodal neuroprotectant for ischemic stroke treatment.

Phthalate induces mitochondrial injury in cerebellum through Sirt1-PGC-1α and PINK1/Parkin-mediated signal pathways

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental toxicant that is widely used in the whole world as a plasticizer that can enhance plastic properties. A number of reserarches have demonstrated that DEHP could cause varying degrees of damage to the normal function of nerve. The research aimed to investigate the mechanism of DEHP-induced cerebellar toxicity. In present study, we set DEHP-caused cerebellar injury models of quail and implied that DEHP induced cerebellar dysplasia by abnormity of Purkinje cell and reduction of cerebellar granule cell. Furthermore, the mitochondrial damage was confirmed by the swelling, cristae reduction, membrane rupture of mitochondria or even the occurrence of autophagic vacuole. To clarified DEHP-induced mitochondrial damage in cerebellum, we examined the relevant genes of mitochondrial biogenesis, mitochondrial dynamics, oxidative damage, the pathways related to Nrf2 and PINK1/Parkin in cerebellum. Based on data, it appeared that DEHP treatment had a damaging effect on the cerebellum and led to mitophagy as well as oxidative stress. In conclusion, the research indicated that DEHP-actuated mitochondrial injury has a directly relationship with mitophagy. DEHP-actuated reduced mitochondrial biogenesis and dysregulation of mitochondrial dynamics. The increase of oxidative stress damaged mitochondria, and the redundant ROS in damaged mitochondria that gave rise to cerebellar harm.

Ferulic acid attenuates high glucose-induced MAM alterations via PACS2/IP3R2/FUNDC1/VDAC1 pathway activating proapoptotic proteins and ameliorates cardiomyopathy in diabetic rats

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the severe complications of diabetes with no known biomarkers for early detection. Mitochondria-associated endoplasmic reticulum membranes (MAM) are less studied subcellular targets but an emerging area for exploration in metabolic disorders including DCM. We herein studied the role of MAMs and downstream mitochondrial functions in DCM. We also explored the efficacy of ferulic acid (FeA) against DCM via modulation of MAM and its associated signaling pathway.

METHODS

The H9c2 cardiomyoblast cells were incubated with high concentration (33 mM) of d-glucose for 48 h to create a high glucose ambience in vitro. The expression of various critical proteins of MAM, mitochondrial function, oxidative phosphorylation (OxPhos) and the genesis of apoptosis were examined. The rats fed with high fat/high fructose/streptozotocin (single dose, i.p.) were used as a diabetic model and analyzed the insulin resistance and markers of cardiac hypertrophy and apoptosis.

RESULTS

High glucose conditions caused the upregulation of MAM formation via PACS2, IP3R2, FUNDC1, and VDAC1 and decreased mitochondrial biogenesis, fusion and OxPhos. The upregulation of mitochondria-driven SMAC-HTRA2-ARTS-XIAP apoptosis and other cell death pathways indicate their critical roles in the genesis of DCM at the molecular level. The diabetic rats also showed cardiomyopathy with increased heart mass index, TNNI3K, troponin, etc. FeA effectively prevented the high glucose-induced MAM alterations and associated cellular anomalies both in vitro and in vivo.

CONCLUSION

High glucose-induced MAM distortion and subsequent mitochondrial dysfunctions act as the stem of cardiomyopathy. MAM could be explored as a potential target to treat diabetic cardiomyopathy. Also, the FeA could be an attractive nutraceutical agent for diabetic cardiomyopathy.

Peroxiredoxin-3 plays a neuroprotective role in early brain injury after experimental subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH), a type of hemorrhagic stroke, is a neurological emergency associated with a high morbidity and mortality rate. After SAH, early brain injury (EBI) is the leading cause of poor prognosis in SAH patients. Peroxiredoxins (PRDXs) are a family of sulphhydryl-dependent peroxidases. Peroxiredoxin-3 (PRDX3) is mainly located in the mitochondria of neurons, which can remove hydrogen peroxide (H2O2); however, the effect of PRDX3 on EBI after SAH remains unclear. In this study, an endovascular perforation model was used to mimic SAH in Sprague Dawley rats in vivo. The results revealed that after SAH, PRDX3 levels decreased in the neurons. PRDX3 overexpression by neuron-specific adeno-associated viruses upregulated PRDX3 levels. Furthermore, PRDX3 overexpression improved long- and short-term behavioral outcomes and alleviated neuronal impairment in rats. Nissl staining revealed that the upregulation of PRDX3 promoted cortical neuron survival. PRDX3 overexpression decreased the H2O2 content and downregulated caspase-9 expression. In conclusion, PRDX3 participates in neuronal protection by inhibiting the neuronal mitochondria-mediated death pathway; PRDX3 may be an important target for EBI intervention after SAH.

miR-181a/b downregulation: a mutation-independent therapeutic approach for inherited retinal diseases

Inherited retinal diseases (IRDs) are a group of diseases whose common landmark is progressive photoreceptor loss. The development of gene-specific therapies for IRDs is hampered by their wide genetic heterogeneity. Mitochondrial dysfunction is proving to constitute one of the key pathogenic events in IRDs; hence, approaches that enhance mitochondrial activities have a promising therapeutic potential for these conditions. We previously reported that miR-181a/b downregulation boosts mitochondrial turnover in models of primary retinal mitochondrial diseases. Here, we show that miR-181a/b silencing has a beneficial effect also in IRDs. In particular, the injection in the subretinal space of an adeno-associated viral vector (AAV) that harbors a miR-181a/b inhibitor (sponge) sequence (AAV2/8-GFP-Sponge-miR-181a/b) improves retinal morphology and visual function both in models of autosomal dominant (RHO-P347S) and of autosomal recessive (rd10) retinitis pigmentosa. Moreover, we demonstrate that miR-181a/b downregulation modulates the level of the mitochondrial fission-related protein Drp1 and rescues the mitochondrial fragmentation in RHO-P347S photoreceptors. Overall, these data support the potential use of miR-181a/b downregulation as an innovative mutation-independent therapeutic strategy for IRDs, which can be effective both to delay disease progression and to aid gene-specific therapeutic approaches.

Modulation of mitochondrial dynamics rescues cognitive function in rats with 'doxorubicin-induced chemobrain' via mitigation of mitochondrial dysfunction and neuroinflammation

Doxorubicin (DOX), an effective, extensively used chemotherapeutic drug, can cause cognitive deterioration in cancer patients. The associated debilitating neurological sequelae are referred to as chemobrain. Our recent work demonstrated that Dox treatment resulted in an imbalance in mitochondrial dynamics, ultimately culminating in cognitive decline in rats. Therefore, in this study, we aim to explore the therapeutic efficacy of a pharmacological intervention, which modulates mitochondrial dynamics using a potent mitochondrial fission inhibitor (Mdivi-1) and mitochondrial fusion promoter (M1) against Dox-induced chemobrain. In the study, male Wistar rats were randomly assigned to receive either normal saline solution or six doses of Dox (3 mg·kg-1 ) via intraperitoneal injection. Then, the Dox-treated rats were intraperitoneally given either 1% DMSO as the vehicle, Mdivi-1 (1.2 mg·kg-1 ), M1 (2 mg·kg-1 ), or a combined treatment of Mdivi-1 and M1 for 30 consecutive days. Long-term learning and memory were evaluated using the novel object location task and novel object recognition task. Following euthanasia, the rat brains were dissected to enable further molecular investigation. We demonstrated that long-term treatment with mitochondrial dynamic modulators suppressed mitochondrial fission in the hippocampus following Dox treatment, leading to an improvement in brain homeostasis. Mitochondrial dynamic modulator treatments restored cognitive function in Dox-treated rats by attenuating neuroinflammation, decreasing oxidative stress, preserving synaptic integrity, reducing potential Alzheimer's related lesions, and mitigating both apoptosis and necroptosis following Dox administration. Together, our findings suggested that mitochondrial dynamics modulators protected against Dox-induced cognitive impairment by rebalancing mitochondrial homeostasis and attenuating both oxidative and inflammatory insults.

Downregulation of SIRT3 Aggravates Lung Ischemia Reperfusion Injury by Increasing Mitochondrial Fission and Oxidative Stress through HIF-1α-Dependent Mechanisms

Lung ischemia-reperfusion injury (LIRI) is a severe multifaceted pathological condition that can lead to poor patient outcome where oxidative stress and the resulting inflammatory response can trigger and exacerbate tissue damage in LIRI patients. Sirtuin3 (SIRT3), a member of the sirtuin family, protects against oxidative stress-related diseases. However, it remains unclear if and how SIRT3 alleviates lung injury induced by ischemia/reperfusion (I/R). Our previous study showed that lung tissue structures were severely damaged at 6 h after lung I/R in mice, however, repair of the injured lung tissue was significant at 24 h. In this study, we found that both SIRT3 mRNA and protein levels were markedly increased at 24 h after lung I/R in vivo. Meanwhile, inhibition of SIRT3 aggravated lung injury and inflammation, augmented mitochondrial fission and oxidative stress and increased Hypoxia-inducible factor-1α (HIF-1α) expression in vivo. The results suggest that SIRT3 may be an upstream regulator of HIF-1α expression. Knockdown of SIRT3 resulted in excessive mitochondrial fission and increased oxidative stress in vitro, and we found that knocking down the expression of HIF-1α alleviated these changes. This suggests that the SIRT3-HIF-1α signaling pathway is involved in regulating mitochondrial function and oxidative stress. Furthermore, inhibition of dynamin-related protein 1 (Drp-1) by the inhibitor of mitophagy, Mdivi-1, blocked mitochondrial fission and alleviated oxidative stress in vitro. Taken together, our results demonstrated that downregulation of SIRT3 aggravates LIRI by increasing mitochondrial fission and oxidative stress. Activation of SIRT3 inhibits mitochondrial fission and this mechanism may serve as a new therapeutic strategy to treat LIRI.

Cell-Free Mitochondrial DNA in Acute Brain Injury

Traumatic brain injury and aneurysmal subarachnoid haemorrhage are a major cause of morbidity and mortality worldwide. Treatment options remain limited and are hampered by our understanding of the cellular and molecular mechanisms, including the inflammatory response observed in the brain. Mitochondrial DNA (mtDNA) has been shown to activate an innate inflammatory response by acting as a damage-associated molecular pattern (DAMP). Here, we show raised circulating cell-free (ccf) mtDNA levels in both cerebrospinal fluid (CSF) and serum within 48 h of brain injury. CSF ccf-mtDNA levels correlated with clinical severity and the interleukin-6 cytokine response. These findings support the use of ccf-mtDNA as a biomarker after acute brain injury linked to the inflammatory disease mechanism.

The interplay of epilepsy with impaired mitophagy and autophagy linked dementia (MAD): A review of therapeutic approaches

The duration and, age of dementia have been linked to a higher risk of seizures. The exact mechanism that drives epileptogenesis in impaired mitophagy and autophagy linked dementia (MAD) is fully defined after reviewing the Scopus, Publon, and Pubmed databases. The epileptogenesis in patients with Alzheimer's disease dementia (ADD) and Parkinson's disease dementia (PDD) is due to involvement of amyloid plaques (Aβ), phosphorylated tau (pTau), Parkin, NF-kB and NLRP3 inflammasome. Microglia, the prime protective and inflammatory cells in the brain exert crosstalk between mitophagy and inflammation. Several researchers believed that the inflammatory brain cells microglia could be a therapeutic target for the treatment of a MAD associated epilepsy. There are conventional antiepileptic drugs such as gabapentin, lamotrigine, phenytoin sodium, carbamazepine, oxcarbazepine, felbamate, lamotrigine, valproate sodium, and topiramate are prescribed by a psychiatrist to suppress seizure frequency. Also, the conventional drugs generate serious adverse effects and synergises dementia characteristics. The adverse effect of carbamazepine is neurotoxic and also, damages haemopoietic system and respiratory tract. The phenytoin treatment causes cerebellar defect and anemia. Dementia and epilepsy have a complicated relationship, thus targeting mitophagy for cure of epileptic dementia makes sense. Complementary and alternative medicine (CAM) is one of the rising strategies by many patients of the world, not only to suppress seizure frequency but also to mitigate dementia characteristics of patients. Therefore our present review focus on the interplay between epilepsy and MAD and their treatment with CAM approaches.

IGF-1 as a Potential Therapy for Spinocerebellar Ataxia Type 3

Although the effects of growth hormone (GH) therapy on spinocerebellar ataxia type 3 (SCA3) have been examined in transgenic SCA3 mice, it still poses a nonnegligible risk of cancer when used for a long term. This study investigated the efficacy of IGF-1, a downstream mediator of GH, in vivo for SCA3 treatment. IGF-1 (50 mg/kg) or saline, once a week, was intraperitoneally injected to SCA3 84Q transgenic mice harboring a human ATXN3 gene with a pathogenic expanded 84 cytosine–adenine–guanine (CAG) repeat motif at 9 months of age. Compared with the control mice harboring a 15 CAG repeat motif, the SCA3 84Q mice treated with IGF-1 for 9 months exhibited the improvement only in locomotor function and minimized degeneration of the cerebellar cortex as indicated by the survival of more Purkinje cells with a more favorable mitochondrial function along with a decrease in oxidative stress caused by DNA damage. These findings could be attributable to the inhibition of mitochondrial fission, resulting in mitochondrial fusion, and decreased immunofluorescence staining in aggresome formation and ataxin-3 mutant protein levels, possibly through the enhancement of autophagy. The findings of this study show the therapeutic potential effect of IGF-1 injection for SCA3 to prevent the exacerbation of disease progress.

Focally administered succinate improves cerebral metabolism in traumatic brain injury patients with mitochondrial dysfunction

Following traumatic brain injury (TBI), raised cerebral lactate/pyruvate ratio (LPR) reflects impaired energy metabolism. Raised LPR correlates with poor outcome and mortality following TBI. We prospectively recruited patients with TBI requiring neurocritical care and multimodal monitoring, and utilised a tiered management protocol targeting LPR. We identified patients with persistent raised LPR despite adequate cerebral glucose and oxygen provision, which we clinically classified as cerebral 'mitochondrial dysfunction' (MD). In patients with TBI and MD, we administered disodium 2,3-¹³C₂ succinate (12 mmol/L) by retrodialysis into the monitored region of the brain. We recovered ¹³C-labelled metabolites by microdialysis and utilised nuclear magnetic resonance spectroscopy (NMR) for identification and quantification.Of 33 patients with complete monitoring, 73% had MD at some point during monitoring. In 5 patients with multimodality-defined MD, succinate administration resulted in reduced LPR(-12%) and raised brain glucose(+17%). NMR of microdialysates demonstrated that the exogenous ¹³C-labelled succinate was metabolised intracellularly via the tricarboxylic acid cycle. By targeting LPR using a tiered clinical algorithm incorporating intracranial pressure, brain tissue oxygenation and microdialysis parameters, we identified MD in TBI patients requiring neurointensive care. In these, focal succinate administration improved energy metabolism, evidenced by reduction in LPR. Succinate merits further investigation for TBI therapy.

Comprehensive analysis of circRNA expression profiles in rat cerebral cortex after moderate traumatic brain injury

Traumatic brain injury is a medical event of global concern, and a growing body of research suggests that circular RNAs can play very important roles in traumatic brain injury. To explore the functions of more novel and valuable circular RNA in traumatic brain injury response, a moderate traumatic brain injury in rats was established and comprehensive analysis of circular RNA expression profiles in rat cerebral cortex was done. As a result, 301 up-regulated and 284 down-regulated circular RNAs were obtained in moderate traumatic brain injury rats, the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were performed based on the circular RNA's host genes, and a circRNA-miRNA interaction network based on differentially expressed circular RNAs was constructed. Also, four circular RNAs were validated by RT-qPCR and Sanger sequencing. This study showed that differentially expressed circular RNAs existed between rat cerebral cortex after moderate traumatic brain injury and control. And this will provide valuable information for circular RNA research in the field of traumatic brain injury.

Rethinking the necessity of low glucose intervention for cerebral ischemia/reperfusion injury

Glucose is the essential and almost exclusive metabolic fuel for the brain. Ischemic stroke caused by a blockage in one or more cerebral arteries quickly leads to a lack of regional cerebral blood supply resulting in severe glucose deprivation with subsequent induction of cellular homeostasis disturbance and eventual neuronal death. To make up ischemia-mediated adenosine 5′-triphosphate depletion, glucose in the ischemic penumbra area rapidly enters anaerobic metabolism to produce glycolytic adenosine 5′-triphosphate for cell survival. It appears that an increase in glucose in the ischemic brain would exert favorable effects. This notion is supported by in vitro studies, but generally denied by most in vivo studies. Clinical studies to manage increased blood glucose levels after stroke also failed to show any benefits or even brought out harmful effects while elevated admission blood glucose concentrations frequently correlated with poor outcomes. Surprisingly, strict glycaemic control in clinical practice also failed to yield any beneficial outcome. These controversial results from glucose management studies during the past three decades remain a challenging question of whether glucose intervention is needed for ischemic stroke care. This review provides a brief overview of the roles of cerebral glucose under normal and ischemic conditions and the results of managing glucose levels in non-diabetic patients. Moreover, the relationship between blood glucose and cerebral glucose during the ischemia/reperfusion processes and the potential benefits of low glucose supplements for non-diabetic patients are discussed.

ZFP36 protects against oxygen-glucose deprivation/reoxygenation-induced mitochondrial fragmentation and neuronal apoptosis through inhibiting NOX4-DRP1 pathway

The imbalance of mitochondrial dynamics plays an important role in the pathogenesis of cerebral ischemia/reperfusion (I/R) injury. Zinc-finger protein 36 (ZFP36) has been documented to have neuroprotective effects, however, whether ZFP36 is involved in the regulation of neuronal survival during cerebral I/R injury remains unknown. In this study, we found that the transcriptional and translational levels of ZFP36 were increased in immortalized hippocampal HT22 neuronal cells after oxygen-glucose deprivation/reoxygenation (OGD/R) treatment. ZFP36 gene silencing exacerbated OGD/R-induced dynamin-related protein 1 (DRP1) activity, mitochondrial fragmentation, oxidative stress and neuronal apoptosis, whereas ZFP36 overexpression exhibited the opposite effects. Besides, we found that NADPH oxidase 4 (NOX4) was upregulated by OGD/R, and NOX4 inhibition remarkably attenuated OGD/R-instigated DRP1 activity, mitochondrial fragmentation and neuronal apoptosis. Further study demonstrated that ZFP36 targeted NOX4 mRNA directly by binding to the AU-rich elements (AREs) in the NOX4 3'-untranslated regions (3'-UTR) and inhibited NOX4 expression. Taken together, our data indicate that ZFP36 protects against OGD/R-induced neuronal injury by inhibiting NOX4-mediated DRP1 activation and excessive mitochondrial fission. Pharmacological targeting of ZFP36 to suppress excessive mitochondrial fission may provide new therapeutic strategies in the treatment of cerebral I/R injury.

The Neuroprotective Effect of Increased PINK1 Expression Following Glutamate Excitotoxicity in Neuronal Cells

Ischemic injury in patients with stroke often leads to neuronal damage and mitochondrial dysfunction. Neuronal injury caused by ischemia can be partly attributed to glutamate (L-Glu) excitotoxicity. Previous studies have shown that PTEN-induced kinase 1 (PINK1) plays a neuroprotective role in ischemic brain injury by regulating mitochondrial integrity and function. However, there are few reports on the expression of PINK1 in L-Glu excitotoxicity models, its effect on neuronal survival, and whether PINK1 plays a protective role in stroke by regulating mitophagy. In the present study, different concentrations of L-Glu inhibited the viability of neurons. After L-Glu treatment at different times, the mRNA level, protein level, and cellular fluorescence intensity of PINK1 first increased and then decreased. Compared with normal cells, cells with low PINK1 expression enhanced the inhibitory effect of L-Glu on neuronal activity, while those with high PINK1 expression showed a protective effect on neurons by alleviating mitochondrial membrane potential loss. In addition, RAP (an autophagy activator) could increase the co-localization of the mitophagy-related proteins light chain 3 (LC3) and Tom20, whereas 3-MA (an autophagy inhibitor) exerted the opposite effect. Finally, we found that L-Glu could induce the expression of PINK1/Parkin/ LC3 in neurons at both mRNA and protein levels, while RAP could further increase their expression, and 3-MA decreased their expression. Taken together, PINK1 protects against L-Glu-induced neuronal injury by protecting mitochondrial function, and the potential protective mechanism may be closely related to the enhancement of mitophagy mediated by the PINK1/Parkin signaling pathway.

Acetylation in Mitochondria Dynamics and Neurodegeneration

Mitochondria are a unique intracellular organelle due to their evolutionary origin and multifunctional role in overall cellular physiology and pathophysiology. To meet the specific spatial metabolic demands within the cell, mitochondria are actively moving, dividing, or fusing. This process of mitochondrial dynamics is fine-tuned by a specific group of proteins and their complex post-translational modifications. In this review, we discuss the mitochondrial dynamics regulatory enzymes, their adaptor proteins, and the effect of acetylation on the activity of fusion and fission machinery as a ubiquitous response to metabolic stresses. Further, we discuss the role of intracellular cytoskeleton structures and their post-translational modifications in the modulation of mitochondrial fusion and fission. Finally, we review the role of mitochondrial dynamics dysregulation in the pathophysiology of acute brain injury and the treatment strategies based on modulation of NAD⁺-dependent deacetylation.

A Novel Plant-Produced Asialo-rhuEPO Protects Brain from Ischemic Damage Without Erythropoietic Action

Mammalian cell-produced recombinant human erythropoietin (rhuEPO^M) has been shown to be a multimodal neuroprotectant targeting an array of key pathological mechanisms in experimental stroke models. However, the rhuEPO^M clinical trials were terminated due to increased risk of thrombosis, largely ascribed to its erythropoietic function. We recently took advantage of a plant-based expression system lacking sialylation capacity to produce asialo-rhuEPO^P, a rhuEPO derivative without sialic acid residues. In the present study, we proved that asialo-rhuEPO^P is non-erythropoietic by repeated intravenous injection (44 μg/kg bw) in mice showing no increase in hemoglobin levels and red blood cell counts, and confirmed that it is non-immunogenic by measuring humoral response after immunizing the mice. We demonstrate that it is neuroprotective in a cerebral ischemia and reperfusion (I/R) mouse model, exhibiting ~ 50% reduction in cerebral infarct volume and edema, and significant improvement in neurological deficits and histopathological outcome. Our studies further revealed that asialo-rhuEPO^P, like rhuEPO^M, displays pleiotropic neuroprotective effects, including restoring I/R-interrupted mitochondrial fission and fusion proteins, preventing I/R injury-induced increase in mitophagy and autophagy markers, and inhibiting apoptosis to benefit nerve cell survival. Most importantly, asialo-rhuEPO^P lacking erythropoietic activity and immunogenicity holds great translational potential as a multimodal neuroprotectant for stroke treatment.

The unique physiological features of the broiler pectoralis major muscle as suggested by the three-dimensional ultrastructural study of mitochondria in type IIb muscle fibers

Typical skeletal muscles are composed of mixed muscle fiber types, which are classified as slow-twitch (type I) and fast-twitch (type II) fibers, whereas pectoralis major muscles (PMs) in broiler chickens are 100% composed of type IIb fast-twitch fibers. Since metabolic properties differ among muscle fiber types, the combination of muscle fiber types is involved in physiological functions and pathological conditions in skeletal muscles. In this study, using serial block-face scanning electron microscopy, we compared three-dimensional (3D) mitochondrial properties in type IIb fibers in broiler PMs and those in type I fibers of broiler gastrocnemius muscles (GMs) heterogeneously composed of slow- and fast-twitch muscle fibers. In type I fibers in the GMs, elongated mitochondria with numerous interconnections to form a substantial network among myofibrils were observed. Along with lipid droplets sandwiched by mitochondria, these features are an adaptation to effective oxidative respiration and constant oxidative damage in slow-twitch muscle fibers. In contrast, type IIb fibers in the PMs showed small and ellipsoid-shaped mitochondria with few interconnections and no lipid droplets, forming a sparse network. The mitochondrial spatial network comprises of active mitochondrial dynamics to reduce mitochondrial damage; therefore, type IIb fibers possess physiologically low capacity to maintain mitochondrial wellness due to static mitochondrial dynamics. Based on 3D mitochondrial properties, we discussed the contrasting physiological functions between type I and IIb fibers and proposed a high contractile power and low stress resistance as unique physiological properties of broiler PMs.

Protective Effects of Inhibition of Mitochondrial Fission on Organ Function After Sepsis

Sepsis-associated organ dysfunction plays a critical role in its high mortality, mainly in connection with mitochondrial dysfunction. Whether the inhibition of mitochondrial fission is beneficial to sepsis-related organ dysfunction and underlying mechanisms are unknown. Cecal ligation and puncture induced sepsis in rats and dynamic related protein 1 knockout mice, lipopolysaccharide-treated vascular smooth muscle cells and cardiomyocytes, were used to explore the effects of inhibition of mitochondrial fission and specific mechanisms. Our study showed that mitochondrial fission inhibitor Mdivi-1 could antagonize sepsis-induced organ dysfunction including heart, vascular smooth muscle, liver, kidney, and intestinal functions, and prolonged animal survival. The further study showed that mitochondrial functions such as mitochondrial membrane potential, adenosine-triphosphate contents, reactive oxygen species, superoxide dismutase and malonaldehyde were recovered after Mdivi-1 administration via improving mitochondrial morphology. And sepsis-induced inflammation and apoptosis in heart and vascular smooth muscle were alleviated through inhibition of mitochondrial fission and mitochondrial function improvement. The parameter trends in lipopolysaccharide-stimulated cardiomyocytes and vascular smooth muscle cells were similar in vivo. Dynamic related protein 1 knockout preserved sepsis-induced organ dysfunction, and the animal survival was prolonged. Taken together, this finding provides a novel effective candidate therapy for severe sepsis/septic shock and other critical clinical diseases.

Iptakalim alleviates synaptic damages via targeting mitochondrial ATP-sensitive potassium channel in depression

Synaptic plasticity damages play a crucial role in the onset and development of depression, especially in the hippocampus, which is more susceptible to stress and the most frequently studied brain region in depression. And, mitochondria have a major function in executing the complex processes of neurotransmission and plasticity. We have previously demonstrated that Iptakalim (Ipt), a new ATP-sensitive potassium (K-ATP) channel opener, could improve the depressive-like behavior in mice. But the underlying mechanisms are not well understood. The present study demonstrated that Ipt reversed depressive-like phenotype in vivo (chronic mild stress-induced mice model of depression) and in vitro (corticosterone-induced cellular model). Further study showed that Ipt could upregulate the synaptic-related proteins postsynaptic density 95 (PSD 95) and synaptophysin (SYN), and alleviated the synaptic structure damage. Moreover, Ipt could reverse the abnormal mitochondrial fission and fusion, as well as the reduced mitochondrial ATP production and collapse of mitochondrial membrane potential in depressive models. Knocking down the mitochondrial ATP-sensitive potassium (Mito-KATP) channel subunit MitoK partly blocked the above effects of Ipt. Therefore, our results reveal that Ipt can alleviate the abnormal mitochondrial dynamics and function depending on MitoK, contributing to improve synaptic plasticity and exert antidepressive effects. These findings provide a candidate compound and a novel target for antidepressive therapy.

Axotomy Induces Drp1-Dependent Fragmentation of Axonal Mitochondria

It is well established that CNS axons fail to regenerate, undergo retrograde dieback, and form dystrophic growth cones due to both intrinsic and extrinsic factors. We sought to investigate the role of axonal mitochondria in the axonal response to injury. A viral vector (AAV) containing a mitochondrially targeted fluorescent protein (mitoDsRed) as well as fluorescently tagged LC3 (GFP-LC3), an autophagosomal marker, was injected into the primary motor cortex, to label the corticospinal tract (CST), of adult rats. The axons of the CST were then injured by dorsal column lesion at C4-C5. We found that mitochondria in injured CST axons near the injury site are fragmented and fragmentation of mitochondria persists for 2 weeks before returning to pre-injury lengths. Fragmented mitochondria have consistently been shown to be dysfunctional and detrimental to cellular health. Inhibition of Drp1, the GTPase responsible for mitochondrial fission, using a specific pharmacological inhibitor (mDivi-1) blocked fragmentation. Additionally, it was determined that there is increased mitophagy in CST axons following Spinal cord injury (SCI) based on increased colocalization of mitochondria and LC3. In vitro models revealed that mitochondrial divalent ion uptake is necessary for injury-induced mitochondrial fission, as inhibiting the mitochondrial calcium uniporter (MCU) using RU360 prevented injury-induced fission. This phenomenon was also observed in vivo. These studies indicate that following the injury, both in vivo and in vitro, axonal mitochondria undergo increased fission, which may contribute to the lack of regeneration seen in CNS neurons.

IGF1R Deficiency Modulates Brain Signaling Pathways and Disturbs Mitochondria and Redox Homeostasis

Insulin-like growth factor 1 receptor (IGF1R)-mediated signaling pathways modulate important neurophysiological aspects in the central nervous system, including neurogenesis, synaptic plasticity and complex cognitive functions. In the present study, we intended to characterize the impact of IGF1R deficiency in the brain, focusing on PI3K/Akt and MAPK/ERK1/2 signaling pathways and mitochondria-related parameters. For this purpose, we used 13-week-old UBC-CreERT2; Igf1r^fl/fl male mice in which Igf1r was conditionally deleted. IGF1R deficiency caused a decrease in brain weight as well as the activation of the IR/PI3K/Akt and inhibition of the MAPK/ERK1/2/CREB signaling pathways. Despite no alterations in the activity of caspases 3 and 9, a significant alteration in phosphorylated GSK3β and an increase in phosphorylated Tau protein levels were observed. In addition, significant disturbances in mitochondrial dynamics and content and altered activity of the mitochondrial respiratory chain complexes were noticed. An increase in oxidative stress, characterized by decreased nuclear factor E2-related factor 2 (NRF2) protein levels and aconitase activity and increased H₂O₂ levels were also found in the brain of IGF1R-deficient mice. Overall, our observations confirm the complexity of IGF1R in mediating brain signaling responses and suggest that its deficiency negatively impacts brain cells homeostasis and survival by affecting mitochondria and redox homeostasis.

Phosphoglycerate Mutase 5 Knockdown Alleviates Neuronal Injury After Traumatic Brain Injury Through Drp1-Mediated Mitochondrial Dysfunction

Aims: Traumatic brain injury (TBI) is a major cause of disability and death, and a better understanding of the underlying mechanisms of mitochondrial dysfunction will provide important targets for preventing damage from neuronal insults. Phosphoglycerate mutase 5 (PGAM5) is localized to the mitochondrial outer-inner membrane contact sites, and the PGAM5-Drp1 pathway is involved in mitochondrial dysfunction and cell death. The purpose of this project was to evaluate the effects of PGAM5 on neuronal injury and mitochondrial dysfunction. Results: PGAM5 was overexpressed in mice subjected to TBI and in primary cortical neurons injured by mechanical equiaxial stretching. PGAM5 deficiency alleviated neuroinflammation, blocked Parkin, PINK1, and Drp1 translocation to mitochondria and abnormal phosphorylation of Drp1, mitochondrial ultrastructural changes, and nerve malfunction in TBI mouse model. PGAM5-shRNA (short hairpin RNA) reduced Drp1 translocation and activation, including dephosphorylation of p-Drp1 on Ser622 (human Drp1 Ser616) and phosphorylation of Drp1 on Ser643 (human Drp1 Ser637). The levels of inflammatory cytokines, the degree of mitochondrial impairment (mitochondrial membrane potential, ADP/ATP, AMP/ADP, antioxidant capacity), and neuronal injury in stretch-induced primary cortical neurons were reduced by blocking expression of PGAM5. The inhibition of PGAM5 is neuroprotective via attenuation of Drp1 activation, similar to that achieved by mitochondrial division inhibitor-1 (Mdivi1)-mediated Drp1 inhibition. Innovation and Conclusion: Our findings demonstrate the critical role of PGAM5 in progression of neuronal injury from TBI via Drp1 activation (dephosphorylation of p-Drp1 on Ser622 and phosphorylation of Drp1 on Ser643)-mediated mitochondrial dysfunction. The data may open a window for developing new drugs to prevent the neuropathology of TBI.

Impact of pediatric traumatic brain injury on hippocampal neurogenesis

Traumatic brain injury (TBI) is a major cause of mortality and morbidity in the pediatric population. With advances in medical care, the mortality rate of pediatric TBI has declined. However, more children and adolescents are living with TBI-related cognitive and emotional impairments, which negatively affects the quality of their life. Adult hippocampal neurogenesis plays an important role in cognition and mood regulation. Alterations in adult hippocampal neurogenesis are associated with a variety of neurological and neurodegenerative diseases, including TBI. Promoting endogenous hippocampal neurogenesis after TBI merits significant attention. However, TBI affects the function of neural stem/progenitor cells in the dentate gyrus of hippocampus, which results in aberrant migration and impaired dendrite development of adult-born neurons. Therefore, a better understanding of adult hippocampal neurogenesis after TBI can facilitate a more successful neuro-restoration of damage in immature brains. Secondary injuries, such as neuroinflammation and oxidative stress, exert a significant impact on hippocampal neurogenesis. Currently, a variety of therapeutic approaches have been proposed for ameliorating secondary TBI injuries. In this review, we discuss the uniqueness of pediatric TBI, adult hippocampal neurogenesis after pediatric TBI, and current efforts that promote neuroprotection to the developing brains, which can be leveraged to facilitate neuroregeneration.

Defective mitophagy in Alzheimer's disease

Alzheimer's disease (AD) is a progressive, mental illness without cure. Several years of intense research on postmortem AD brains, cell and mouse models of AD have revealed that multiple cellular changes are involved in the disease process, including mitochondrial abnormalities, synaptic damage, and glial/astrocytic activation, in addition to age-dependent accumulation of amyloid beta (Aβ) and hyperphosphorylated tau (p-tau). Synaptic damage and mitochondrial dysfunction are early cellular changes in the disease process. Healthy and functionally active mitochondria are essential for cellular functioning. Dysfunctional mitochondria play a central role in aging and AD. Mitophagy is a cellular process whereby damaged mitochondria are selectively removed from cell and mitochondrial quality and biogenesis. Mitophagy impairments cause the progressive accumulation of defective organelle and damaged mitochondria in cells. In AD, increased levels of Aβ and p-tau can induce reactive oxygen species (ROS) production, causing excessive fragmentation of mitochondria and promoting defective mitophagy. The current article discusses the latest developments of mitochondrial research and also highlights multiple types of mitophagy, including Aβ and p-tau-induced mitophagy, stress-induced mitophagy, receptor-mediated mitophagy, ubiquitin mediated mitophagy and basal mitophagy. This article also discusses the physiological states of mitochondria, including fission-fusion balance, Ca²⁺ transport, and mitochondrial transport in normal and diseased conditions. Our article summarizes current therapeutic interventions, like chemical or natural mitophagy enhancers, that influence mitophagy in AD. Our article discusses whether a partial reduction of Drp1 can be a mitophagy enhancer and a therapeutic target for mitophagy in AD and other neurological diseases.

Inorganic nitrite alters mitochondrial dynamics without overt changes in cell death and mitochondrial respiration in cardiomyoblasts under hyperglycemia

Inorganic nitrate or nitrite supplementation has been reported to demonstrate positive outcomes in rodent models of obesity and diabetes as well as in type 2 diabetic humans and even included in clinical trials pertaining to cardiovascular diseases in the recent decade. However, there are contrasting data regarding the useful and toxic effects of the anions. The primary scope of this study was to analyze the beneficial/detrimental alterations in redox status, mitochondrial dynamics and function, and cellular fitness in cardiomyoblasts inflicted by nitrite under hyperglycemic conditions compared with normoglycemia. Nitrite supplementation in H9c2 myoblasts under high glucose diminishes the Bcl-x_L expression and mitochondrial ROS levels without significant initiation of cell death or decline in total ROS levels. Concomitantly, there are tendencies towards lowering of mitochondrial membrane potential, but without noteworthy changes in mitochondrial biogenesis and respiration. The study also revealed that under high glucose stress, nitrite may alter mitochondrial dynamics by Drp1 activation possibly via Akt1-Pim1 axis. Moreover, the study revealed differential effects of Drp1 silencing and/or nitrite under the above glycemic conditions. Overall, the study warrants more research regarding the effects of nitrite therapy in cardiac cells exposed to hyperglycemia.

Mitochondrial Transfer as a Therapeutic Strategy Against Ischemic Stroke

Stroke is a debilitating disease that remains the second leading cause of death and disability worldwide. Despite accumulating knowledge of the disease pathology, treatments for stroke are limited, and clinical translation of the neuroprotective agents has not been a complete success. Accumulating evidence links mitochondrial dysfunction to brain impairments after stroke. Recent studies have implicated the important roles of healthy mitochondria in neuroprotection and neural recovery following ischemic stroke. New and convincing studies have shown that mitochondrial transfer to the damaged cells can help revive cells energetic in the recipient cells. Hence, mitochondrial transplantation has shown to replace impaired or dysfunctional mitochondria with exogenous healthy mitochondria after ischemic stroke. We highlight the potential of mitochondrial transfer by stem cells as a therapeutic strategy for the treatment of ischemic stroke. This review captures the recent advances in the mitochondrial transfer as a novel and promising treatment for ischemic stroke.

Physiological and Pathological Mitochondrial Clearance Is Related to Pectoralis Major Muscle Pathogenesis in Broilers With Wooden Breast Syndrome

Wooden breast syndrome (WB) constitutes an emerging myopathy in the pectoralis major muscle (PM) of broiler chickens, characterized by myofiber hypertrophy and degeneration along with severe fibrosis. WB pathogenesis has been considered to involve hypoxia induced by rapid growth of the PM. In this study, we focused on mitochondrial morphology and dynamics in the myofibers, as these organelles are sensitive to damage by hypoxia, and examined the effects on WB pathogenesis. Specifically, the PMs of a flock of 35 broilers at 50 days of age were evaluated. First, the severity of disease in each bird was determined by measuring histopathological indices including the fibrotic area (FA) in the muscle and circularity of myofibers (CM). These values were 29.4 ± 9.6% and 0.70 ± 0.042, respectively, showing variety among the flock. Myofiber vacuolization was observed in all birds including numerous small- or large-rimmed vacuoles, with the former consisting of ultrastructurally autophagosome-like vacuoles engulfing degenerated mitochondria. The large-rimmed vacuoles frequently occurred in the PMs with more severe FA and CM, indicating a relationship between altered autophagy/mitophagy and WB severity. Next, the expression levels of hypoxia-adaptive and mitochondrial dynamics-related genes were analyzed, and their correlations with the histopathological indices were examined. The histopathological indices were negatively correlated with the expression of vascular endothelial growth factor A (VEGFA), indicating that less angiogenesis owing to weakened hypoxia-inducible factor signaling induces more severe WB pathology. In addition, the observed negative correlation with mitochondrial dynamics-related genes implied that WB pathology deteriorates concomitant with reduced mitochondrial dynamics. Furthermore, the expression of mitochondrial dynamics-related genes showed strong positive correlation with that of VEGFA and autophagy-/mitophagy-related genes. These results revealed that the PMs of broilers possess the mechanism of physiological clearance of mitochondria damaged by the hypoxia resulting from the continuous mitochondrial dynamics and autophagy/mitophagy accompanying rapid PM growth. In turn, the altered mitochondrial clearance induced by chronic hypoxia and the accumulation of damaged mitochondria likely underly the severe pathological features of WB.

The distinctive role of tau and amyloid beta in mitochondrial dysfunction through alteration in Mfn2 and Drp1 mRNA Levels: A comparative study in Drosophila melanogaster

Alzheimer's disease (AD) is one of the most common forms of neurodegenerative diseases. Aggregation of Aβ42 and hyperphosphorylated tau are two major hallmarks of AD. Whether different forms of tau (soluble or hyperphosphorylated) or Aβ are the main culprit in the events observed in AD is still under investigation. Here, we examined the effect of wild-type, prone to hyperphosphorylation and hyperphosphorylated tau, and also Aβ42 peptide on the brain antioxidant defense system and two mitochondrial genes, Marf (homologous to human MFN2) and Drp1 involved in mitochondrial dynamics in transgenic Drosophila melanogaster. AD is an age associated disease. Therefore, the activity of antioxidant agents, CAT, SOD, and GSH levels and the mRNA levels of Marf and Drp1 were assessed in different time points of the flies lifespan. Reduction in cognitive function and antioxidant activity was observed in all transgenic flies at any time point. The most and the least effect on the eye phenotype was exerted by hyperphosphorylated tau and Aβ42, respectively. In addition, the most remarkable alteration in Marf and Drp1 mRNA levels was observed in transgenic flies expressing hyperphosphorylated tau when pan neuronal expression of transgenes was applied. However, when the disease causing gene expression was confined to the mushroom body, Marf and Drp1 mRNA levels alteration was more prominent in tau^WT and tau^E14 transgenic flies, respectively. In conclusion, in spite of antioxidant deficiency caused by different types of tau and Aβ42, it seems that tau exerts more toxic effect on the eye phenotype and mitochondrial genes regulation (Marf and Drp1). Moreover, different mechanisms seem to be involved in mitochondrial genes dysregulation when Aβ or various forms of tau are expressed.