Mitochondrial Transplantation Attenuates Cerebral Ischemia-Reperfusion Injury: Possible Involvement of Mitochondrial Component Separation

From mitochondrial dysfunction to neuroinflammation in Parkinson's disease: Pathogenesis and mitochondrial therapeutic approaches

Parkinson's disease (PD) is a prevalent and intricate neurological condition resulting from a combination of several factors, such as genetics, environment, and the natural process of aging. Degeneration of neurons in the substantia nigra pars compacta (SN) can cause motor and non-motor impairments in patients with PD. In PD's etiology, inflammation and mitochondrial dysfunction play significant roles in the disease's development. Studies of individuals with PD have revealed increased inflammation in various brain areas. Furthermore, mitochondrial dysfunction is an essential part of PD pathophysiology. Defects in the components of the mitochondrial nucleus, its membrane or internal signaling pathways, mitochondrial homeostasis, and morphological alterations in peripheral cells have been extensively documented in PD patients. According to these studies, neuroinflammation and mitochondrial dysfunction are closely connected as pathogenic conditions in neurodegenerative diseases like PD. Given the mitochondria's role in cellular homeostasis maintenance in response to membrane structural flaws or mutations in mitochondrial DNA, their dynamic nature may present therapeutic prospects in this area. Recent research investigates mitochondrial transplantation as a potential treatment for Parkinson's disease in damaged neurons. This review delves into the impact of inflammation and mitochondrial dysfunction on PD occurrence, treatment approaches, and the latest developments in mitochondrial transplantation, highlighting the potential consequences of these discoveries.

Mitochondrial transplantation in brain disorders: Achievements, methods, and challenges

Mitochondrial transplantation is a new treatment strategy aimed at repairing cellular damage by introducing healthy mitochondria into injured cells. The approach shows promise in protecting brain function in various neurological disorders such as traumatic brain injury/ischemia, neurodegenerative diseases, cognitive disorders, and cancer. These conditions are often characterized by mitochondrial dysfunction, leading to impaired energy production and neuronal death. The review highlights promising preclinical studies where mitochondrial transplantation has been shown to restore mitochondrial function, reduce inflammation, and improve cognitive and motor functions in several animal models. It also addresses significant challenges that must be overcome before this therapy can be clinically applied. Current efforts to overcome these challenges, including advancements in isolation techniques, cryopreservation methods, finding an appropriate mitochondria source, and potential delivery routes, are discussed. Considering the rising incidence of neurological disorders and the limited effectiveness of current treatments, this review offers a comprehensive overview of the current state of mitochondrial transplantation research and critically assesses the remaining obstacles. It provides valuable insights that could steer future studies and potentially lead to more effective treatments for various brain disorders.

Mitochondrion-based organellar therapies for central nervous system diseases

As most traditional drugs used to treat central nervous system (CNS) diseases have a single therapeutic target, many of them cannot treat complex diseases or diseases whose mechanism is unknown and cannot effectively reverse the root changes underlying CNS diseases. This raises the question of whether multiple functional components are involved in the complex pathological processes of CNS diseases. Organelles are the core functional units of cells, and the replacement of damaged organelles with healthy organelles allows the multitargeted and integrated modulation of cellular functions. The development of therapies that target independent functional units in the cell, specifically, organelle-based therapies, is rapidly progressing. This article comprehensively discusses the pathogenesis of mitochondrial homeostasis disorders, which involve mitochondria, one of the most important organelles in CNS diseases, and the machanisms of mitochondrion-based therapies, as well as current preclinical and clinical studies on the efficacy of therapies targeting mitochondrial to treat CNS diseases, to provide evidence for use of organelle-based treatment strategies in the future.

Mitochondrial transplantation attenuates lipopolysaccharide-induced acute respiratory distress syndrome

BACKGROUND

The mitochondria are essential organelles not only providing cellular energy in the form of ATP, but also regulating the inflammatory response and the cell death program. Mitochondrial dysfunction has been associated with various human diseases, including metabolic syndromes as well as inflammatory and neurodegenerative diseases. Acute respiratory distress syndrome (ARDS) is an acute pulmonary disorder characterized by uncontrolled alveolar inflammation, apoptotic lung epithelial/endothelial cells, and pulmonary edema. Despite the high mortality of ARDS, an effective pharmacotherapy to treat this disease has not been established yet. Therefore, identifying a novel targeted therapy for ARDS is important. Recently, exogenous mitochondrial transplantation was reported to be beneficial for treating mitochondrial dysfunction. The current study aimed to investigate the therapeutic effect of mitochondrial transplantation on ARDS in vitro and in vivo.

METHODS

Mitochondria were isolated from human stem cells. For in vitro efficacy of mitochondrial transplantation on the inflammation and cell death, murine alveolar macrophages MH-S and human pulmonary microvascular endothelial cells HPMECs were exposed to LPS, respectively. The ARDS mice model established by a single intratracheal instillation of LPS was used for in vivo efficacy of intravenously treated mitochondria.

RESULTS

Our results showed that the mitochondria isolated from human stem cells exhibited an anti-inflammatory effect against alveolar macrophages and an anti-apoptotic effect against the alveolar epithelial cells. Furthermore, intravenous mitochondrial treatment was associated with the attenuation of lung injury in the LPS-induced ARDS mice.

CONCLUSION

Dual effects of mitochondria on anti-inflammation and anti-apoptosis support the potential of mitochondrial transplantation as a novel therapeutic strategy for ARDS.

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.

Stroke studies in large animals: Prospects of mitochondrial transplantation and enhancing efficiency using hydrogels and nanoparticle-assisted delivery

One of the most frequent reasons for mortality and disability today is acute ischemic stroke, which occurs by an abrupt disruption of cerebral circulation. The intricate damage mechanism involves several factors, such as inflammatory response, disturbance of ion balance, loss of energy production, excessive reactive oxygen species and glutamate release, and finally, neuronal death. Stroke research is now carried out using several experimental models and potential therapeutics. Furthermore, studies are being conducted to address the shortcomings of clinical care. A great deal of research is being done on novel pharmacological drugs, mitochondria targeting compounds, and different approaches including brain cooling and new technologies. Still, there are many unanswered questions about disease modeling and treatment strategies. Before these new approaches may be used in therapeutic settings, they must first be tested on large animals, as most of them have been done on rodents. However, there are several limitations to large animal stroke models used for research. In this review, the damage mechanisms in acute ischemic stroke and experimental acute ischemic stroke models are addressed. The current treatment approaches and promising experimental methods such as mitochondrial transplantation, hydrogel-based interventions, and strategies like mitochondria encapsulation and chemical modification, are also examined in this work.

Bridging the gap between in vitro and in vivo models: a way forward to clinical translation of mitochondrial transplantation in acute disease states

Mitochondrial transplantation and transfer are being explored as therapeutic options in acute and chronic diseases to restore cellular function in injured tissues. To limit potential immune responses and rejection of donor mitochondria, current clinical applications have focused on delivery of autologous mitochondria. We recently convened a Mitochondrial Transplant Convergent Working Group (CWG), to explore three key issues that limit clinical translation: (1) storage of mitochondria, (2) biomaterials to enhance mitochondrial uptake, and (3) dynamic models to mimic the complex recipient tissue environment. In this review, we present a summary of CWG conclusions related to these three issues and provide an overview of pre-clinical studies aimed at building a more robust toolkit for translational trials.

Pyrroloquinoline quinone promotes human mesenchymal stem cell-derived mitochondria to improve premature ovarian insufficiency in mice through the SIRT1/ATM/p53 pathway

BACKGROUND

DNA damage and oxidative stress induced by chemotherapy are important factors in the onset of premature ovarian insufficiency (POI). Studies have shown that mitochondria derived from mesenchymal stem cells (MSC-Mito) are beneficial for age-related diseases, but their efficacy alone is limited. Pyrroloquinoline quinone (PQQ) is a potent antioxidant with significant antiaging and fertility enhancement effects. This study aimed to investigate the therapeutic effect of MSC-Mito in combination with PQQ on POI and the underlying mechanisms involved.

METHODS

A POI animal model was established in C57BL/6J mice by cyclophosphamide and busulfan. The effects of MSC-Mito and PQQ administration on the estrous cycle, ovarian pathological damage, sex hormone secretion, and oxidative stress in mice were evaluated using methods such as vaginal smears and ELISAs. Western blotting and immunohistochemistry were used to assess the expression of SIRT1, PGC-1α, and ATM/p53 pathway proteins in ovarian tissues. A cell model was constructed using KGN cells treated with phosphoramide mustard to investigate DNA damage and apoptosis through comet assays and flow cytometry. SIRT1 siRNA was transfected into KGN cells to further explore the role of the SIRT1/ATM/p53 pathway in combination therapy with MSC-Mito and PQQ for POI.

RESULTS

The combined treatment of MSC-Mito and PQQ significantly restored ovarian function and antioxidant capacity in mice with POI. This treatment also reduced the loss of follicles at various stages, improving the disrupted estrous cycle. In vitro experiments demonstrated that PQQ facilitated the proliferation of MitoTracker-labelled MSC-Mito, synergistically restoring mitochondrial function and inhibiting oxidative stress in combination with MSC-Mito. Both in vivo and in vitro, the combination of MSC-Mito and PQQ increased mitochondrial biogenesis mediated by SIRT1 and PGC-1α while inhibiting the activation of ATM and p53, consequently reducing DNA damage-mediated cell apoptosis. Furthermore, pretreatment of KGN cells with SIRT1 siRNA reversed nearly all the aforementioned changes induced by the combined treatment.

CONCLUSIONS

Our research findings indicate that PQQ facilitates MSC-Mito proliferation and, in combination with MSC-Mito, ameliorates chemotherapy-induced POI through the SIRT1/ATM/p53 signaling pathway.

Therapeutic effect of mitochondrial transplantation on burn injury

As mitochondrial damage or dysfunction is commonly observed following burn injuries, we investigated whether mitochondrial transplantation (MT) can result in therapeutic benefits in the treatment of burns. Human immortalized epidermal cells (HaCaT) and Kunming mice were used to establish a heat-injured cell model and a deep partial-thickness skin burn animal model, respectively. The cell model was established by exposing HaCaT cells to 45 or 50 °C for 10 min, after which cell proliferation was assayed using fluorescent double-staining and colony formation assays, cell migration was assessed using colloidal gold migration and scratch assays, and cell cycle progression and apoptosis were measured by flow cytometry. Histopathological staining, immunohistochemistry, nick-end labeling analysis, and enzyme-linked immunosorbent assays were used to evaluate the effects of MT on inflammation, tissue recovery, apoptosis, and scar growth in a mouse model. The therapeutic effects were observed in the heat-injured HaCaT cell model. MT promoted cell viability, colony formation, proliferation, and migration; decreased G1 phase; promoted cell division; and decreased apoptosis. Wound-healing promotion, anti-inflammation (decreased mast cell aggregation, down-regulated of TNF-α, IL-1β, IL-6, and up-regulated IL-10), acceleration of proliferation recovery (up-regulated CD34 and VEGF), apoptosis reduction, and scar formation reduction (decreased collagen I/III ratio and TGF-β1) were observed in the MT mouse model. The MT mode of action was, however, not investigated in this study. In conclusion, our data indicate that MT exerts a therapeutic effect on burn injuries both in vitro and in vivo.

Mitochondria as secretory organelles and therapeutic cargos

Mitochondria have been primarily considered intracellular organelles that are responsible for generating energy for cell survival. However, accumulating evidence suggests that mitochondria are secreted into the extracellular space under physiological and pathological conditions, and these secreted mitochondria play diverse roles by regulating metabolism, the immune response, or the differentiation/maturation in target cells. Furthermore, increasing amount of research shows the therapeutic effects of local or systemic administration of mitochondria in various disease models. These findings have led to growing interest in exploring mitochondria as potential therapeutic agents. Here, we discuss the emerging roles of mitochondria as extracellularly secreted organelles to shed light on their functions beyond energy production. Additionally, we provide information on therapeutic outcomes of mitochondrial transplantation in animal models of diseases and an update on ongoing clinical trials, underscoring the potential of using mitochondria as a novel therapeutic intervention.

Exosomal OIP5-AS1 attenuates cerebral ischemia-reperfusion injury by negatively regulating TXNIP protein stability and inhibiting neuronal pyroptosis

BACKGROUND

Cerebral ischemia-reperfusion injury (CIRI) can cause neuronal apoptosis and lead to irreversible brain injury. Numerous lncRNAs have been reported to play important roles in CIRI, but it is unclear whether these lncRNAs can function through exosomes.

METHODS

In this study, we utilized the middle cerebral artery occlusion/reperfusion (MCAO/R) animal model and the oxygen-glucose deprivation/ reoxygenation (OGD/R) cell model. RNA sequencing was performed to screen for differentially expressed lncRNAs in M2 microglia-derived exosomes (M2-Exos). RNA pull-down, RNA immunoprecipitation, co-immunoprecipitation and ubiquitination assays were used to explore the molecular mechanism of OIP5-AS1 in alleviating CIRI.

RESULTS

M2-Exos could alleviate nerve injury and pyroptosis after CIRI in vitro and in vivo. OIP5-AS1 was found to be significantly up-regulated in M2-Exos and down-regulated in OGD/R neurons, MCAO/R mice and ischemic stroke patients. In MCAO/R mice, OIP5-AS1 could reduce cerebral infarct size, cerebral edema and mNSS scores, and inhibit the expression levels of pyroptosis-related proteins in brain tissue. TXNIP was confirmed to be a reliable binding protein of OIP5-AS1. OIP5-AS1 overexpression significantly attenuated MCAO/R-induced upregulation of TXNIP at the protein level, but not at the mRNA level. OIP5-AS1 promoted the TXNIP degradation process and increased the ubiquitination of TXNIP. ITCH could bind to TXNIP. ITCH overexpression or knockdown did not alter the mRNA level of TXNIP, but negatively regulated TXNIP expression at the protein level. ITCH accelerated the degradation and ubiquitination of TXNIP, which could be attenuated by OIP5-AS1 knockdown. OIP5-AS1 could improve neuronal damage and inhibit neuronal pyroptosis through TXNIP.

CONCLUSIONS

M2-Exo-derived OIP5-AS1 can induce TXNIP ubiquitination and degradation by recruiting ITCH, negatively regulate TXNIP protein stability, inhibit neuronal pyroptosis, and attenuate CIRI.

Mitochondrial transplantation reduces lower limb ischemia-reperfusion injury by increasing skeletal muscle energy and adipocyte browning

Recent studies have shown that mitochondrial transplantation can repair lower limb IRI, but the underlying mechanism of the repair effect remains unclear. In this study, we found that in addition to being taken up by skeletal muscle cells, human umbilical cord mesenchymal stem cells (hMSCs)-derived mitochondria were also taken up by adipocytes, which was accompanied by an increase in optic atrophy 1 (OPA1) and uncoupling protein 1. Transplantation of hMSCs-derived mitochondria could not only supplement the original damaged mitochondrial function of skeletal muscle, but also promote adipocyte browning by increasing the expression of OPA1. In this process, mitochondrial transplantation can reduce cell apoptosis and repair muscle tissue, which promotes the recovery of motor function in vivo. To the best of our knowledge, there is no study on the therapeutic mechanism of mitochondrial transplantation from this perspective, which could provide a theoretical basis.

Mitochondrial transplantation and transfer: The promising method for diseases

Mitochondria are organelles that serve as the powerhouses for cellular bioenergetics in eukaryotic cells. It is responsible for mitochondrial adenosine triphosphate (ATP) generation, cell signaling and activity, calcium balance, cell survival, proliferation, apoptosis, and autophagy. Mitochondrial transplantation is a promising disease therapy that involves the recovery of mitochondrial dysfunction using isolated functioning mitochondria. The objective of the present article is to provide current knowledge on natural mitochondrial transfer processes, in vitro and in vivo applications of mitochondrial transplantation, clinical trials, and challenges associated with mitochondrial transplantation.

Effects of Mitochondrial Transplantation on Transcriptomics in a Polymicrobial Sepsis Model

Previously, we demonstrated that mitochondrial transplantation has beneficial effects in a polymicrobial sepsis model. However, the mechanism has not been fully investigated. Mitochondria have their own genes, and genomic changes in sepsis are an important issue in terms of pathophysiology, biomarkers, and therapeutic targets. To investigate the changes in transcriptomic features after mitochondrial transplantation in a polymicrobial sepsis model, we used a rat model of fecal slurry polymicrobial sepsis. Total RNA from splenocytes of sham-operated (SHAM, n = 10), sepsis-induced (SEPSIS, n = 7), and sepsis receiving mitochondrial transplantation (SEPSIS + MT, n = 8) samples was extracted and we conducted a comparative transcriptome-wide analysis between three groups. We also confirmed these results with qPCR. In terms of percentage of mitochondrial mapped reads, the SEPSIS + MT group had a significantly higher mapping ratio than the others. RT1-M2 and Cbln2 were identified as highly expressed in SEPSIS + MT compared with SEPSIS. Using SHAM expression levels as another control variable, we further identified six genes (Fxyd4, Apex2l1, Kctd4, 7SK, SNORD94, and SNORA53) that were highly expressed after sepsis induction and observed that their expression levels were attenuated by mitochondrial transplantation. Changes in transcriptomic features were identified after mitochondrial transplantation in sepsis. This might provide a hint for exploring the mechanism of mitochondrial transplantation in sepsis.

Current Advances of Mitochondrial Dysfunction and Cardiovascular Disease and Promising Therapeutic Strategies

Mitochondria are cellular power stations and essential organelles for maintaining cellular homeostasis. Dysfunctional mitochondria have emerged as a key factor in the occurrence and development of cardiovascular disease. This review focuses on advances in the relationship between mitochondrial dysfunction and cardiovascular diseases such as atherosclerosis, heart failure, myocardial ischemia reperfusion injury, and pulmonary arterial hypertension. The clinical value and challenges of mitochondria-targeted strategies, including mitochondria-targeted antioxidants, mitochondrial quality control modulators, mitochondrial function protectors, mitochondrial biogenesis promoters, and recently developed mitochondrial transplants, are also discussed.

Sirtuin-3 activates the mitochondrial unfolded protein response and reduces cerebral ischemia/reperfusion injury

Sirtuin-3 (Sirt3) deacetylates several mitochondrial proteins implicated into cerebral ischemia/reperfusion (I/R) injury. The mitochondrial unfolded protein response (UPRmt) favors mitochondrial proteostasis during various stressors. Here, we used Sirt3 transgenic mice and a transient middle cerebral artery occlusion model to evaluate the molecular basis of Sirt3 on the UPRmt during brain post-ischemic dysfunction. The present study illustrated that Sirt3 abundance was suppressed in the brain after brain ischemic abnormalities. Overexpression of Sirt3 in vivo suppressed the infarction size and attenuated neuroinflammation after brain I/R injury. Sirt3 overexpression restored neural viability by reducing mitochondrial ROS synthesis, maintaining the mitochondrial potential and improving mitochondrial adenosine triphosphate synthesis. Sirt3 overexpression protected neuronal mitochondria against brain post-ischemic malfunction via eliciting the UPRmt by the forkhead box O3 (Foxo3)/sphingosine kinase 1 (Sphk1) pathway. Inhibiting either the UPRmt or the Foxo3/Sphk1 pathway relieved the favorable influence of Sirt3 on neural function and mitochondrial behavior. In contrast, Sphk1 overexpression was sufficient to reduce the infarction size, attenuate neuroinflammation, sustain neuronal viability and prevent mitochondrial abnormalities during brain post-ischemia dysfunction. Thus, the UPRmt protects neural viability and mitochondrial homeostasis, and the Sirt3/Foxo3/Sphk1 pathway is a promosing therapeutic candidate for ischemic stroke.

Polymer-Functionalized Mitochondrial Transplantation to Fibroblasts Counteracts a Pro-Fibrotic Phenotype

Fibroblast-to-myofibroblast transition (FMT) leads to excessive extracellular matrix (ECM) deposition-a well-known hallmark of fibrotic disease. Transforming growth factor-β (TGF-β) is the primary cytokine driving FMT, and this phenotypic conversion is associated with mitochondrial dysfunction, notably a metabolic reprogramming towards enhanced glycolysis. The objective of this study was to examine whether the establishment of favorable metabolic phenotypes in TGF-β-stimulated fibroblasts could attenuate FMT. The hypothesis was that mitochondrial replenishment of TGF-β-stimulated fibroblasts would counteract a shift towards glycolytic metabolism, consequently offsetting pro-fibrotic processes. Isolated mitochondria, functionalized with a dextran and triphenylphosphonium (TPP) (Dex-TPP) polymer conjugate, were administered to fibroblasts (MRC-5 cells) stimulated with TGF-β, and effects on bioenergetics and fibrotic programming were subsequently examined. Results demonstrate that TGF-β stimulation of fibroblasts led to FMT, which was associated with enhanced glycolysis. Dex-TPP-coated mitochondria (Dex-TPP/Mt) delivery to TGF-β-stimulated fibroblasts abrogated a metabolic shift towards glycolysis and led to a reduction in reactive oxygen species (ROS) generation. Importantly, TGF-β-stimulated fibroblasts treated with Dex-TPP/Mt had lessened expression of FMT markers and ECM proteins, as well as reduced migration and proliferation. Findings highlight the potential of mitochondrial transfer, as well as other strategies involving functional reinforcement of mitochondria, as viable therapeutic modalities in fibrosis.

Mitochondrial Transfer as a Novel Therapeutic Approach in Disease Diagnosis and Treatment

Mitochondrial dysfunction is a hallmark of numerous diseases, including neurodegenerative disorders, metabolic disorders, and cancer. Mitochondrial transfer, the transfer of mitochondria from one cell to another, has recently emerged as a potential therapeutic approach for restoring mitochondrial function in diseased cells. In this review, we summarize the current understanding of mitochondrial transfer, including its mechanisms, potential therapeutic applications, and impact on cell death pathways. We also discuss the future directions and challenges in the field of mitochondrial transfer as a novel therapeutic approach in disease diagnosis and treatment.

Emerging roles of mitochondria in animal regeneration

The regeneration capacity after an injury is critical to the survival of living organisms. In animals, regeneration ability can be classified into five primary types: cellular, tissue, organ, structure, and whole-body regeneration. Multiple organelles and signaling pathways are involved in the processes of initiation, progression, and completion of regeneration. Mitochondria, as intracellular signaling platforms of pleiotropic functions in animals, have recently gained attention in animal regeneration. However, most studies to date have focused on cellular and tissue regeneration. A mechanistic understanding of the mitochondrial role in large-scale regeneration is unclear. Here, we reviewed findings related to mitochondrial involvement in animal regeneration. We outlined the evidence of mitochondrial dynamics across different animal models. Moreover, we emphasized the impact of defects and perturbation in mitochondria resulting in regeneration failure. Ultimately, we discussed the regulation of aging by mitochondria in animal regeneration and recommended this for future study. We hope this review will serve as a means to advocate for more mechanistic studies of mitochondria related to animal regeneration on different scales.

Abnormalities of glucose and lipid metabolism in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury is a common condition in cardiovascular diseases, and the mechanism of its occurrence involves multiple complex metabolic pathways and signaling pathways. Among these pathways, glucose metabolism and lipid metabolism play important roles in regulating myocardial energy metabolism. Therefore, this article focuses on the roles of glucose metabolism and lipid metabolism in myocardial ischemia-reperfusion injury, including glycolysis, glucose uptake and transport, glycogen metabolism and the pentose phosphate pathway; and triglyceride metabolism, fatty acid uptake and transport, phospholipid metabolism, lipoprotein metabolism, and cholesterol metabolism. Finally, due to the different alterations and development of glucose metabolism and lipid metabolism in myocardial ischemia-reperfusion, there are also complex interregulatory relationships between them. In the future, modulating the equilibrium between glucose metabolism and lipid metabolism in cardiomyocytes and ameliorating aberrations in myocardial energy metabolism represent highly promising novel strategies for addressing myocardial ischemia-reperfusion injury. Therefore, a comprehensive exploration of glycolipid metabolism can offer novel theoretical and clinical insights into the prevention and treatment of myocardial ischemia-reperfusion injury.

The Ketogenic Diet but not Hydroxycitric Acid Keeps Brain Mitochondria Quality Control and mtDNA Integrity Under Focal Stroke

Mitochondrial dysfunction in the ischemic brain is one of the hallmarks of stroke. Dietary interventions such as the ketogenic diet and hydroxycitric acid supplementation (a caloric restriction mimetic) may potentially protect neurons from mitochondrial damage induced by focal stroke in mice. We showed that in control mice, the ketogenic diet and the hydroxycitric acid did not impact significantly on the mtDNA integrity and expression of genes involved in the maintenance of mitochondrial quality control in the brain, liver, and kidney. The ketogenic diet changed the bacterial composition of the gut microbiome, which via the gut-brain axis may affect the increase in anxiety behavior and reduce mice mobility. The hydroxycitric acid causes mortality and suppresses mitochondrial biogenesis in the liver. Focal stroke modelling caused a significant decrease in the mtDNA copy number in both ipsilateral and contralateral brain cortex and increased the levels of mtDNA damage in the ipsilateral hemisphere. These alterations were accompanied by a decrease in the expression of some of the genes involved in maintaining mitochondrial quality control. The ketogenic diet consumption before stroke protects mtDNA in the ipsilateral cortex, probably via activation of the Nrf2 signaling. The hydroxycitric acid, on the contrary, increased stroke-induced injury. Thus, the ketogenic diet is the most preferred variant of dietetic intervention for stroke protection compared with the hydroxycitric acid supplementation. Our data confirm some reports about hydroxycitric acid toxicity, not only for the liver but also for the brain under stroke condition.

An Updated Review of Mitochondrial Transplantation as a Potential Therapeutic Strategy Against Cerebral Ischemia and Cerebral Ischemia/Reperfusion Injury

Regardless of the progress made in the pathogenesis of ischemic stroke, it remains a leading cause of adult disability and death. To date, the most effective treatment for ischemic stroke is the timely recanalization of the occluded artery. However, the short time window and reperfusion injury have greatly limited its application and efficacy. Mitochondrial dysfunction and ATP depletion have become regarded as being hallmarks of neuropathophysiology following ischemic stroke. Mitochondrial transplantation is a novel potential therapeutic intervention for ischemic stroke that has sparked widespread concern during the past few years. This review summarizes and discusses the effects of mitochondrial transplantation in in vitro and in vivo ischemic stroke models. In addition, pharmacological interventions promoting mitochondrial transplantation are reviewed and discussed. We also discuss the potential challenges to the clinical application of mitochondrial transplantation in the treatment of ischemic stroke.

Astragaloside IV alleviates stroke-triggered early brain injury by modulating neuroinflammation and ferroptosis via the Nrf2/HO-1 signaling pathway

PURPOSE

Stroke is an acute cerebrovascular disease. Astragaloside IV (AS-IV) is an active ingredient extracted from Astragalus membranaceus with an established therapeutic effect on central nervous system diseases. This study examined the neuroprotective properties and possible mechanisms of AS-IV in stroke-triggered early brain injury (EBI) in a rat transient middle cerebral artery occlusion (MCAO) model.

METHODS

The neurological scores and brain water content were analyzed. 2,3,5-triphenyl tetrazolium chloride (TTC) staining was utilized to determine the infarct volume, neuroinflammatory cytokine levels, and ferroptosis-related genes and proteins, and neuronal damage and molecular mechanisms were evaluated by terminal deoxynucleotidyl transferase dutp nick-end labeling (TUNEL) staining, western blotting, and real-time polymerase chain reaction.

RESULTS

AS-IV administration decreased the infarct volume, brain edema, neurological deficits, and inflammatory cytokines TNF-α, interleukin-1β (IL-1β), IL-6, and NF-κB, increased the levels of SLC7A11 and glutathione peroxidase 4 (GPX4), decreased lipid reactive oxygen species (ROS) levels, and prevented neuronal ferroptosis. Meanwhile, AS-IV triggered the Nrf2/HO-1 signaling pathway and alleviated ferroptosis due to the induction of stroke.

CONCLUSIONS

Hence, the findings of this research illustrate that AS-IV administration can improve delayed ischemic neurological deficits and decrease neuronal death by modulating nuroinflammation and ferroptosis via the Nrf2/HO-1 signaling pathway.

Rescuers from the Other Shore: Intercellular Mitochondrial Transfer and Its Implications in Central Nervous System Injury and Diseases

As the powerhouse and core of cellular metabolism and survival, mitochondria are the essential organelle in mammalian cells and maintain cellular homeostasis by changing their content and morphology to meet demands through mitochondrial quality control. It has been observed that mitochondria can move between cells under physiological and pathophysiological conditions, which provides a novel strategy for preserving mitochondrial homeostasis and also a therapeutic target for applications in clinical settings. Therefore, in this review, we will summarize currently known mechanisms of intercellular mitochondrial transfer, including modes, triggers, and functions. Due to the highly demanded energy and indispensable intercellular linkages of the central nervous system (CNS), we highlight the mitochondrial transfer in CNS. We also discuss future application possibilities and difficulties that need to be addressed in the treatment of CNS injury and diseases. This clarification should shed light on its potential clinical applications as a promising therapeutic target in neurological diseases. Intercellular mitochondrial transfer maintains the homeostasis of central nervous system (CNS), and its alteration is related to several neurological diseases. Supplementing exogenous mitochondrial donor cells and mitochondria, or utilizing some medications to regulate the process of transfer might mitigate the disease and injury.

Platelets Facilitate Wound Healing by Mitochondrial Transfer and Reducing Oxidative Stress in Endothelial Cells

As a critical member in wound healing, vascular endothelial cells (ECs) impaired under high levels of reactive oxygen species (ROS) would hamper neovascularization. Mitochondria transfer can reduce intracellular ROS damage under pathological condition. Meanwhile, platelets can release mitochondria and alleviate oxidative stress. However, the mechanism by which platelets promote cell survival and reduce oxidative stress damage has not been clarified. Here, first, we selected ultrasound as the best method for subsequent experiments by detecting the growth factors and mitochondria released from manipulation platelet concentrates (PCs), as well as the effect of manipulation PCs on the proliferation and migration of HUVECs. Then, we found that sonicate platelet concentrates (SPC) decreased the level of ROS in HUVECs treated with hydrogen peroxide in advance, increased mitochondrial membrane potential, and reduced apoptosis. By transmission electron microscope, we saw that two kinds of mitochondria, free or wrapped in vesicles, were released by activated platelets. In addition, we explored that platelet-derived mitochondria were transferred to HUVECs partly by means of dynamin-dependent clathrin-mediated endocytosis. Consistently, we determined that platelet-derived mitochondria reduced apoptosis of HUVECs caused by oxidative stress. What is more, we screened survivin as the target of platelet-derived mitochondria via high-throughput sequencing. Finally, we demonstrated that platelet-derived mitochondria promoted wound healing in vivo. Overall, these findings revealed that platelets are important donors of mitochondria, and platelet-derived mitochondria can promote wound healing by reducing apoptosis caused by oxidative stress in vascular endothelial cells. And survivin is a potential target. These results further expand the knowledge of the platelet function and provide new insights into the role of platelet-derived mitochondria in wound healing.

DT-010 Exerts Cardioprotective Effects by Regulating the Crosstalk between the AMPK/PGC-1α Pathway and ERp57

The AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) pathway performs a crucial role in energy metabolism and mitochondrial network. Our previous study found that DT-010, a novel danshensu (DSS) and tetramethylpyrazine (TMP) conjugate, had significant cardioprotective properties in vitro and in vivo. We also reported that ERp57 served as a major target of DSS using the chemical proteomics approach. In this article, we focus on exploring the interrelationship between the regulation of the AMPK/PGC-1α pathway and promoting ERp57 expression induced by DT-010 in tert-butylhydroperoxide- (t-BHP-) induced H9c2 cell injury. The results showed that DT-010 activated the AMPK/PGC-1α pathway and increased ERp57 protein expression. Importantly, the above phenomenon as well as the mitochondrial function can be partially reversed by siRNA-mediated ERp57 suppression. Meanwhile, silencing AMPK significantly inhibited the ERp57 expression induced by DT-010. In addition, molecular docking and kinase assay in vitro revealed that DT-010 had no direct regulation effects on AMPK activity. Taken together, DT-010 exerted cardioprotective effects by regulating the crosstalk of AMPK/PGC-1α pathway and ERp57, representing a potential therapeutic agent for ischemic heart disease.

Mitochondrial transplantation ameliorates hippocampal damage following status epilepticus

BACKGROUND

Hippocampal damage caused by status epilepticus (SE) can bring about cognitive decline and emotional disorders, which are common clinical comorbidities in patients with epilepsy. It is therefore imperative to develop a novel therapeutic strategy for protecting hippocampal damage after SE. Mitochondrial dysfunction is one of contributing factors in epilepsy. Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria, we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.

METHODS

Pilocarpine was used to induced SE in mice. SE-generated cognitive decline and emotional disorders were determined using novel object recognition, the tail suspension test, and the open field test. SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes. The metabolites underlying mitochondrial transplantation were determined using metabonomics.

RESULTS

The results showed that peripheral administration of isolated mitochondria could improve cognitive deficits and depressive and anxiety-like behaviors. Exogenous mitochondria blunted the production of reactive oxygen species, proliferation of microglia and astrocytes, and loss of neurons in the hippocampus. The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism. Among potential affected metabolites, mitochondrial transplantation decreased levels of sphingolipid (d18:1/18:0) and methylmalonic acid, and elevated levels of D-fructose-1,6-bisphosphate.

CONCLUSION

To the best of our knowledge, these findings provide the first direct experimental evidence that artificial mitochondrial transplantation is capable of ameliorating hippocampal damage following SE. These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiatric and cognitive disorders.

Mitochondrial Transplantation in Mitochondrial Medicine: Current Challenges and Future Perspectives

Mitochondrial diseases (MDs) are inherited genetic conditions characterized by pathogenic mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Current therapies are still far from being fully effective and from covering the broad spectrum of mutations in mtDNA. For example, unlike heteroplasmic conditions, MDs caused by homoplasmic mtDNA mutations do not yet benefit from advances in molecular approaches. An attractive method of providing dysfunctional cells and/or tissues with healthy mitochondria is mitochondrial transplantation. In this review, we discuss what is known about intercellular transfer of mitochondria and the methods used to transfer mitochondria both in vitro and in vivo, and we provide an outlook on future therapeutic applications. Overall, the transfer of healthy mitochondria containing wild-type mtDNA copies could induce a heteroplasmic shift even when homoplasmic mtDNA variants are present, with the aim of attenuating or preventing the progression of pathological clinical phenotypes. In summary, mitochondrial transplantation is a challenging but potentially ground-breaking option for the treatment of various mitochondrial pathologies, although several questions remain to be addressed before its application in mitochondrial medicine.

Bone Marrow Mesenchymal Stem Cell Exosomal miR-345-3p Ameliorates Cerebral Ischemia-reperfusion Injury by Targeting TRAF6

INTRODUCTION

The purpose of this study was to investigate the effects of bone marrow mesenchymal stem cells (BMSCs) exosomal miR-345-3p and tumor necrosis factor receptorassociated factor 6 (TRAF6) on cerebral ischemia reperfusion (CIR) injury. Exosomes (Exos) derived from BMSCs were isolated and identified. PC12 (rat pheochromocytoma) cells were used to establish an oxygen and glucose deprivation/reoxygenation (OGD/R) model.

METHODS

Cell counting kit-8, TUNEL staining, lactate dehydrogenase staining, RT-qPCR, and western blotting were utilized for analyzing the functions of miR-345-3p about PC12 cells. Dualluciferase reporter experiment was then to confirm the link between miR-345-3p and TRAF6. Finally, using male SD rats, the middle cerebral artery occlusion (MCAO) model was constructed. Regulation of I/R damage in MCAO rats of miR-345-3p and TRAF6 were further explored in the changes of modified neurological severity score, cerebral infarction pictures, relative infarct volume, and histopathological changes. After OGD/R treatment, neuronal apoptosis was dramatically increased. After treatment with exosomal miR-345-3p, OGD/R-induced neuroapoptosis was dramatically inhibited. Exosomal miR-345-3p inhibited OGD/R-induced neuroapoptosis by downregulating the expression of TRAF6. However, the miR-345-3p inhibitor aggravated the changes caused by OGD/R.

RESULTS

The corresponding regulations of miR-345-3p were reversed with TRAF6 overexpression. The animal experiments in vivo further verified that miR-345-3p ameliorated brain I/R injury in MCAO rats by targeting TRAF6.

CONCLUSION

This study found that BMSCs-exosomal miR-345-3p protected against CIR injury by decreasing TRAF6.

Salidroside intensifies mitochondrial function of CoCl2-damaged HT22 cells by stimulating PI3K-AKT-MAPK signaling pathway

BACKGROUND

Salidroside (Sal), an active component from Rhodiola crenulata, has been confirmed to exert neuroprotective effects against hypoxia. However, its molecular mechanisms of intensifying mitochondrial function still largely unknown. In the present study, we aimed to explore the mechanisms by which Sal heightened mitochondrial function in CoCl₂-induced HT22 hypoxic injury.

METHODS

The hypoxic condition of HT22 cells was performed by CoCl₂ stimulus. We then investigated the effects of Sal on the viability of hypoxic HT22 cells by cell counting kit-8. The contents of lactate dehydrogenase (LDH) release in cultured supernatant were detected by using commercial biochemical kit. Superoxide free radical scavenging activity, total antioxidant capacity assay kit with ferric reducing ability of plasma and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) methods were employed to detect the free radical scavenging ability and antioxidant capacity of Sal. Meanwhile, intracellular reactive oxygen species (ROS), Ca2+ and mitochondrial membrane potential (MMP) were determined by corresponding specific labeled probes. Mitochondrial morphology was tested by Mito-tracker green with confocal microscopy. Hoechst 33342 and Annexin V-FITC/propidium iodide staining were also employed to evaluate the effect of Sal on cell apoptosis. Oxygen consumption rate (OCR), real-time ATP production and proton efflux rate were measured using a Seahorse analyzer. Additionally, the potential interactions of Sal with PI3K-AKT signaling pathway-related proteins were predicted and tested by molecular docking, molecular dynamics simulation (MDS) and localized surface plasmon resonance (LSPR) techniques, respectively. Furthermore, the protein levels of p-PI3K, PI3K, p-AKT, AKT, p-JNK, JNK, p-p38 and p38 were estimated by western blot analysis.

RESULTS

Sal alleviated CoCl2-induced hypoxic injury in HT22 cells as evidenced by increased cell viability and decreased LDH release. In vitro antioxidant test confirmed that Sal had marvelous antioxidant abilities. The protected mitochondrial function by Sal treatment was illustrated by the decrease of ROS, Ca2+, mitochondrial fragment and the increase of MMP. In addition, Sal ameliorated the apoptosis of HT22 cells by decreasing Hoechst 33342 positive cells and the rate of apoptotic cells. Enhancement of energy metabolism in HT22 by Sal was demonstrated by increased OCR, real-time ATP generation and proton efflux rate. The molecular docking confirmed the potential binding of Sal to PI3K, AKT and CaMK II proteins with calculated binding energy of -1.32, -4.21 and -4.38 kcal/mol, respectively. The MDS test revealed the average hydrogen bond of complex Sal-PI3K and Sal-AKT were 0.79 and 4.46, respectively. The results of LSPR verified the potential binding of Sal to proteins PI3K, AKT and HIF-1α with affinity values of 5.20 × 10 - 3, 2.83 × 10 - 3 and 3.97 × 10 - 3 KD, respectively. Western blot analysis further argued that Sal consolidated the levels of p-PI3K and p-AKT. Meanwhile, Sal could downregulate the proteins expression of p-JNK and p-p38.

CONCLUSION

Collectively, our findings suggested that Sal can intensify mitochondrial function of CoCl2-simulated hypoxia injury in HT22 cells by stimulating PI3K-AKT-MAPK signaling pathway. Sal is a potential agent for mitochondrial protection against hypoxia with the underlying molecular mechanisms of energy metabolism being further elucidated.

The Therapeutic Potential of Mitochondria Transplantation Therapy in Neurodegenerative and Neurovascular Disorders

Neurodegenerative and neurovascular disorders affect millions of people worldwide and account for a large and increasing health burden on the general population. Thus, there is a critical need to identify potential disease-modifying treatments that can prevent or slow the disease progression. Mitochondria are highly dynamic organelles and play an important role in energy metabolism and redox homeostasis, and mitochondrial dysfunction threatens cell homeostasis, perturbs energy production, and ultimately leads to cell death and diseases. Impaired mitochondrial function has been linked to the pathogenesis of several human neurological disorders. Given the significant contribution of mitochondrial dysfunction in neurological disorders, there has been considerable interest in developing therapies that can attenuate mitochondrial abnormalities and proffer neuroprotective effects. Unfortunately, therapies that target specific components of mitochondria or oxidative stress pathways have exhibited limited translatability. To this end, mitochondrial transplantation therapy (MTT) presents a new paradigm of therapeutic intervention, which involves the supplementation of healthy mitochondria to replace the damaged mitochondria for the treatment of neurological disorders. Prior studies demonstrated that the supplementation of healthy donor mitochondria to damaged neurons promotes neuronal viability, activity, and neurite growth and has been shown to provide benefits for neural and extra-neural diseases. In this review, we discuss the significance of mitochondria and summarize an overview of the recent advances and development of MTT in neurodegenerative and neurovascular disorders, particularly Parkinson's disease, Alzheimer's disease, and stroke. The significance of MTT is emerging as they meet a critical need to develop a diseasemodifying intervention for neurodegenerative and neurovascular disorders.

BYHW Decoction Improves Cognitive Impairments in Rats with Cerebral Microinfarcts via Activation of the PKA/CREB Pathway

Cerebral microinfarcts (CMIs) are characterized by sporadic obstruction of small vessels leading to neurons death. They are associated with increased risk of cognitive impairments and may have different risk factors compared with macroinfarcts. CMIs have a high incidence and result in heavy social burden; thus, it is essential to provide reasonable treatment in clinical practice. However, there are relatively few researches on the mechanism and treatment of CMIs, and the literature is composed almost exclusively of community-or hospital based on autopsy or imageological studies focusing on elderly patients. The Bu Yang Huan Wu (BYHW) decoction, a traditional Chinese herbal formula, has long been used to treat stroke and stroke-related diseases, including cognitive impairments. We applied microsphere-induced CMI model in rats to investigate the behavioral and molecular consequences of CMIs and to determine how they were ameliorated by BYHW decoction treatment. We then used the Morris water maze, quantitative proteomics, immunohistochemistry, and other molecular assays and found that activation of the PKA/CREB pathway by BYHW decoction treatment may reverse mitochondrial dysfunction, inhibit apoptosis of hippocampal neurons, and ameliorate CMI-induced cognitive impairments in rats. Collectively, these findings confirmed the therapeutic potential of the BYHW decoction in treating cognitive impairments induced by CMIs and demonstrated a viable mechanism for its action.

Emerging Treatment Strategies for Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion injury (CI/RI) injury is a common feature of ischemic stroke which occurs when the blood supply is restored after a period of ischemia in the brain. Reduced blood-flow to the brain during CI/RI compromises neuronal cell health as a result of mitochondrial dysfunction, oxidative stress, cytokine production, inflammation and tissue damage. Reperfusion therapy during CI/RI can restore the blood flow to ischemic regions of brain which are not yet infarcted. The long-term goal of CI/RI therapy is to reduce stroke-related neuronal cell death, disability and mortality. A range of drug and interventional therapies have emerged that can alleviate CI/RI mediated oxidative stress, inflammation and apoptosis in the brain. Herein, we review recent studies on CI/RI interventions for which a mechanism of action has been described and the potential of these therapeutic modalities for future use in the clinic.

Platelet Membrane-Encapsulated MSNs Loaded with SS31 Peptide Alleviate Myocardial Ischemia-Reperfusion Injury

Clinically, antioxidant therapy is a potential strategy for myocardial ischemia-reperfusion injury (MI/RI), a common complication of acute myocardial ischemia. The H-D-Arg-Dmt-Ly-Phe-NH2 (SS31) peptide is shown to have amazing antioxidant properties, but its utilization is limited by the peptide characteristics, such as the destruction by proteases and rapid metabolism. Silica nanoparticles (MSNs) comprise an excellent material for peptide delivery, owing to the protection effect relating to peptides. Moreover, platelet membrane (PLTM) is shown to be advantageous as a coat for nanosystems because of its specific protein composition, such that a PLTM-coated nanosystem has a stealth effect in vivo, able to target injury in the cardiovascular system. Based on this feature, we designed and prepared a novel nanocarrier to target SS31 delivery. This carrier is encapsulated by a platelet membrane and loaded with SS31 peptide into MSNs. The results reveal that this delivery system can target SS31 to the injured cardiovascular site, exert antioxidant function, and alleviate MI/RI.

Hippocampal Mitochondrial Transplantation Alleviates Age-Associated Cognitive Decline via Enhancing Wnt Signaling and Neurogenesis

Gradual cognition decline and mitochondrial dysfunction are two notable changes closely associated with aging. Enhancing mitochondrial function has been assumed to be antiaging. However, most current mitochondria-promoting agents usually target 1-2 aspects of mitochondrial function. In the present study, we transplanted mitochondria isolated from young mice into the hippocampus of aged mice, which presumably boost mitochondrial function more thoroughly, examined the effects on cognition, and explored the possible underlying mechanism. Our data showed that exogenous mitochondria were efficiently internalized by nestin-positive neural progenitors in the hippocampus. Mitochondrial transplantation quickly increased ATP levels, enhanced the activity of mitochondrial complexes I, II, and IV, and decreased Tom20 expression in the hippocampus. In regard of cognitive function, mitochondria-treated mice displayed a remarkable improvement of novel object recognition and spatial memory. Utilizing the Wnt signaling reporting mouse line, TOPGAL mice, we detected activated canonical Wnt signaling in the neural progenitors of the mitochondria-treated hippocampus. Further, BrdU labeling showed that exogenous mitochondria significantly stimulated neural progenitor neurogenesis and proliferation. Taken together, our data demonstrated that exogenous mitochondria from young mice might be a novel way of rejuvenating the function of hippocampal neural progenitors to exert antiaging effects.

Reviewing the suitability of mitochondrial transplantation as therapeutic approach for pulmonary hypertension in the era of personalised medicine

Pulmonary hypertension (PH) is a fatal disease, defined as a mean pulmonary artery pressure ≥ 25 mm Hg. It is caused, in part, by mitochondrial dysfunction. Among the various biological therapies proposed to rescue mitochondrial dysfunction, evidence going back as far as 2009, suggests that mitochondrial transplantation is an alternative. Although scant, recent PH findings and other literature supports a role for mitochondrial transplantation as a therapeutic approach in the context of PH. In experimental models of PH, it confers beneficial effects that include reduced pulmonary vasoconstriction, reduced pulmonary vascular remodelling, and improved right ventricular function. It also reduces the proliferation of pulmonary artery smooth muscle cells. However, first, we must understand that more research is needed before mitochondrial transplantation can be considered an effective therapy in the clinical setting, as many of the mechanisms or potential long-term risks are still unknown. Second, the current challenges of mitochondrial transplantation are surmountable and should not deter researchers from further investigating its effectiveness and trying to overcome these challenges in creative ways.