Protective effect of mitochondrial-targeted antioxidant MitoQ against iron ion 56Fe radiation induced brain injury in mice

Space research to explore novel biochemical insights on Earth

Travel to space has overcome unprecedent technological challenges and this has resulted in transfer of these technological results on Earth to better our lives. Health technology, medical devices, and research advancements in human biology are the first beneficiaries of this transfer. The real breakthrough came with the International Space Station, which endorsed multidisciplinary international scientific collaborations and boosted the research on pathophysiological adaptation of astronauts to life on space. These studies evidenced that life in space appeared to have exposed the astronauts to an accelerated aging-related pathophysiological dysregulation across multiple systems. In this review we emphasize the interaction between several biomarkers and their alteration in concentrations/expression/function by space stress factors. These altered interactions, suggest that different biochemical and hormonal factors, and cell signals, contribute to a complex network of pathophysiological mechanisms, orchestrating the homeostatic dysregulation of various organs/metabolic pathways. The main effects of space travel on altering cell organelles biology, ultrastructure, and cross-talk, have been observed in cell aging as well as in the disruption of metabolic pathways, which are also the causal factor of rare inherited metabolic disorders, one of the major pediatric health issue. The pathophysiologic breakthrough from space research could allow the development of precision health both on Earth and Space by promoting the validation of improved biomarker-based risk scores and the exploration of new pathophysiologic hypotheses and therapeutic targets. Nonstandard abbreviations: International Space Station (ISS), Artificial Intelligence (AI), European Space Agency (ESA), National Aeronautics and Space Agency (NASA), Low Earth Orbit (LEO), high sensitive troponin (hs-cTn), high sensitive troponin I (hs-cTn I), high sensitive troponin T, Brain Natriuretic Peptide (BNP), N terminal Brain Natriuretic Peptide (NT-BNP), cardiovascular disease (CVD), parathyroid hormone (PTH), urinary hydroxyproline (uHP), urinary C- and N-terminal telopeptides (uCTX and uNTX), pyridinoline (PYD), deoxypyridinoline (DPD), half-time (HF), serum Bone Alkaline Phosphatase (sBSAP), serum Alkaline Phosphatase (sAP), Carboxy-terminal Propeptide of Type 1 Procollagen (P1CP), serum Osteocalcin (sOC)), advanced glycation end products (AGEs), glycated hemoglobin A1c (HbA1c), Insulin-like growth factor 1 (IGF1), Growth Hormone (GH), amino acid (AA), β-hydroxy-β methyl butyrate (HMB), maple syrup urine disease (MSUD), non-communicable diseases (NCDs).

Is space the final frontier for mitochondrial study?

Tweetable abstract This perspective considers several avenues for future research on mitochondrial dynamics, stress, and DNA in outer space.

Drug Discovery Targeting Post-Translational Modifications in Response to DNA Damages Induced by Space Radiation

DNA damage in astronauts induced by cosmic radiation poses a major barrier to human space exploration. Cellular responses and repair of the most lethal DNA double-strand breaks (DSBs) are crucial for genomic integrity and cell survival. Post-translational modifications (PTMs), including phosphorylation, ubiquitylation, and SUMOylation, are among the regulatory factors modulating a delicate balance and choice between predominant DSB repair pathways, such as non-homologous end joining (NHEJ) and homologous recombination (HR). In this review, we focused on the engagement of proteins in the DNA damage response (DDR) modulated by phosphorylation and ubiquitylation, including ATM, DNA-PKcs, CtIP, MDM2, and ubiquitin ligases. The involvement and function of acetylation, methylation, PARylation, and their essential proteins were also investigated, providing a repository of candidate targets for DDR regulators. However, there is a lack of radioprotectors in spite of their consideration in the discovery of radiosensitizers. We proposed new perspectives for the research and development of future agents against space radiation by the systematic integration and utilization of evolutionary strategies, including multi-omics analyses, rational computing methods, drug repositioning, and combinations of drugs and targets, which may facilitate the use of radioprotectors in practical applications in human space exploration to combat fatal radiation hazards.

Mitochondrial Stress in Metabolic Inflammation: Modest Benefits and Full Losses

Energy intake and metabolic balance are the pillars of health preservation. Overnutrition causes nonspecific, persistently low inflammatory state known as metabolic inflammation. This condition contributes to the pathophysiology of various metabolic disorders, such as atherosclerosis, obesity, diabetes mellitus, and metabolic syndrome. The mitochondria maintain the balance of energy metabolism. Excessive energy stress can lead to mitochondrial dysfunction, which promotes metabolic inflammation. The inflammatory environment further impairs mitochondrial function. Accordingly, excellent organism design keeps the body metabolically healthy in the context of mitochondrial dysfunction, and moderate mitochondrial stress can have a beneficial effect. This review summarises the research progress on the multifaceted characterisation of mitochondrial dysfunction and its role in metabolic inflammation.

Quantitative proteomic analytic approaches to identify metabolic changes in the medial prefrontal cortex of rats exposed to space radiation

NASA’s planned mission to Mars will result in astronauts being exposed to ∼350 mSv/yr of Galactic Cosmic Radiation (GCR). A growing body of data from ground-based experiments indicates that exposure to space radiation doses (approximating those that astronauts will be exposed to on a mission to Mars) impairs a variety of cognitive processes, including cognitive flexibility tasks. Some studies report that 33% of individuals may experience severe cognitive impairment. Translating the results from ground-based rodent studies into tangible risk estimates for astronauts is an enormous challenge, but it would be germane for NASA to use the vast body of data from the rodent studies to start developing appropriate countermeasures, in the expectation that some level of space radiation (SR) -induced cognitive impairment could occur in astronauts. While some targeted studies have reported radiation-induced changes in the neurotransmission properties and/or increased neuroinflammation within space radiation exposed brains, there remains little information that can be used to start the development of a mechanism-based countermeasure strategy. In this study, we have employed a robust label-free mass spectrometry (MS) -based untargeted quantitative proteomic profiling approach to characterize the composition of the medial prefrontal cortex (mPFC) proteome in rats that have been exposed to 15 cGy of 600 MeV/n28Si ions. A variety of analytical techniques were used to mine the generated expression data, which in such studies is typically hampered by low and variable sample size. We have identified several pathways and proteins whose expression alters as a result of space radiation exposure, including decreased mitochondrial function, and a further subset of proteins differs in rats that have a high level of cognitive performance after SR exposure in comparison with those that have low performance levels. While this study has provided further insight into how SR impacts upon neurophysiology, and what adaptive responses can be invoked to prevent the emergence of SR-induced cognitive impairment, the main objective of this paper is to outline strategies that can be used by others to analyze sub-optimal data sets and to identify new information.

Autophagy Inhibition Reduces Irradiation-Induced Subcortical White Matter Injury Not by Reducing Inflammation, but by Increasing Mitochondrial Fusion and Inhibiting Mitochondrial Fission

Radiotherapy is an effective tool in the treatment of malignant brain tumors, but irradiation-induced late-onset toxicity remains a major problem. The purpose of this study was to investigate if genetic inhibition of autophagy has an impact on subcortical white matter development in the juvenile mouse brain after irradiation. Ten-day-old selective neural Atg7 knockout (KO) mice and wild-type (WT) littermates were subjected to a single 6-Gy dose of whole-brain irradiation and evaluated at 5 days after irradiation. Neural Atg7 deficiency partially prevented myelin disruption compared to the WT mice after irradiation, as indicated by myelin basic protein staining. Irradiation induced oligodendrocyte progenitor cell loss in the subcortical white matter, and Atg7 deficiency partly prevented this. There was no significant change between the KO and WT mice in the number of microglia and astrocytes in the subcortical white matter after irradiation. Transcriptome analysis showed that the GO mitochondrial gene expression pathway was significantly enriched in the differentially expressed genes between the KO and WT group after irradiation. Compared with WT mice, expression of the mitochondrial fusion protein OPA1 and phosphorylation of the mitochondrial fission protein DRP1 (P-DRP1) were dramatically decreased in KO mice under physiological conditions. The protein levels of OPA1and P-DRP1 showed no differences in WT mice between the non-irradiated group and the irradiated group but had remarkably increased levels in the KO mice after irradiation. These results indicate that inhibition of autophagy reduces irradiation-induced subcortical white matter injury not by reducing inflammation, but by increasing mitochondrial fusion and inhibiting mitochondrial fission.

Neuro-consequences of the spaceflight environment

As human space exploration advances to establish a permanent presence beyond the Low Earth Orbit (LEO) with NASA's Artemis mission, researchers are striving to understand and address the health challenges of living and working in the spaceflight environment. Exposure to ionizing radiation, microgravity, isolation and other spaceflight hazards pose significant risks to astronauts. Determining neurobiological and neurobehavioral responses, understanding physiological responses under Central Nervous System (CNS) control, and identifying putative mechanisms to inform countermeasure development are critically important to ensuring brain and behavioral health of crew on long duration missions. Here we provide a detailed and comprehensive review of the effects of spaceflight and of ground-based spaceflight analogs, including simulated weightlessness, social isolation, and ionizing radiation on humans and animals. Further, we discuss dietary and non-dietary countermeasures including artificial gravity and antioxidants, among others. Significant future work is needed to ensure that neural, sensorimotor, cognitive and other physiological functions are maintained during extended deep space missions to avoid potentially catastrophic health and safety outcomes.

Progress and Promise of Nur77-based Therapeutics for Central Nervous System Disorders

Nur77 belongs to the NR4A subgroup of the nuclear receptor superfamily. Unlike other nuclear receptors, a natural ligand for Nur77 has not been identified yet. However, a few small molecules can interact with this receptor and induce a conformational change to mediate its activity. The expression and activation of Nur77 can be rapidly increased using various physiological and pathological stimuli. In vivo and in vitro studies have demonstrated its regulatory role in tissues and cells of multiple systems by means of participation in cell differentiation, apoptosis, metabolism, mitochondrial homeostasis, and other processes. Although research on Nur77 in the pathophysiology of the central nervous system (CNS) is currently limited, the present data support the fact that Nur77 is involved in many neurological disorders such as stroke, multiple sclerosis, Parkinson’s disease. This indicates that activation of Nur77 has considerable potential in treating these diseases. This review summarizes the regulatory mechanisms of Nur77 in CNS diseases and presents available evidence for its potential as targeted therapy, especially for cerebrovascular and inflammation-related CNS diseases.

Mitoquinone ameliorates cigarette smoke-induced airway inflammation and mucus hypersecretion in mice

BACKGROUND

Cigarette smoking, which induces airway inflammation and mucus hypersecretion, is a major risk factor for the development of cigarette smoke (CS)-induced airway disorders. In this study, we investigated the effects and mechanisms of mitoquinone (MitoQ), a mitochondria-targeted antioxidant, on CS-induced airway inflammation and mucus hypersecretion in mice.

METHODS

C57BL/6J mice were exposed to CS for 75 min twice daily, 5 days per week for 4 weeks. MitoQ (2.5, 5 mg/kg/day) was administered intraperitoneally 1 h before CS exposure. Bronchoalveolar lavage fluid (BALF) was obtained for cell counting and determination of pro-inflammatory cytokine levels. Lung tissue was collected for histological examination; Western blotting was used to measure levels of Mfn2, Drp1, cytochrome c, NF-κB p65, and IκBα.

RESULTS

Pretreatment with MitoQ significantly attenuated CS-induced thickening of the airway epithelium, peribronchial inflammatory cell infiltration, goblet cell hyperplasia and Muc5ac staining. The numbers of total cells, neutrophils and macrophages, as well as levels of TNF-α and IL-6 in BALF were remarkably decreased by MitoQ in a dose-dependent manner. MitoQ attenuated oxidative stress by preventing the CS-induced increase in malondialdehyde level and decrease in superoxide dismutase activity and GSH/GSSG ratio. MitoQ decreased the expression of mitochondrial fission protein Drp1 and increased that of mitochondrial fusion protein Mfn2, as well as reduced cytochrome c release into the cytosol. Furthermore, MitoQ suppressed IκBα degradation and NF-κB p65 nuclear translocation.

CONCLUSIONS

MitoQ attenuates inflammation, mucus hypersecretion, and oxidative stress induced by CS. It may exert these effects in part by modulating mitochondrial function and the NF-κB signal pathway.

Piperine Inhibits Cell Proliferation and Induces Apoptosis of Human Gastric Cancer Cells by Downregulating Phosphatidylinositol 3-Kinase (PI3K)/Akt Pathway

Background

Piperine has been reported to inhibit proliferation and induce apoptosis in various cancer cells. This study aimed to explore the efficacy and underlying mechanism of piperine in human gastric cancer.

Material/Methods

MTT assay was performed to examine the effect of piperine (concentrations of 0–300 μM) on the proliferation of human gastric cancer SNU-16 cells and normal human gastric epithelial GES-1 cells. Flow cytometry and Western blot were used to determine cell apoptosis and the expression level of protein (Cyto C, cleaved PARP, cleaved caspase-3, Bax, Bcl-2, Bad, Bcl-xl, PI3K, pPI3K, Akt, and pAkt), respectively. To further investigate the anti-tumor mechanism of piperine in SNU-16 cells, we used a small-molecule Akt activator SC79 in this study. The in vivo mechanism of piperine against gastric cancer was evaluated using a xenograft tumor model.

Results

The results showed that piperine inhibited proliferation and induced apoptosis of SNU-16 cells. Piperine upregulated the protein expression of Bax, Bad, Cyto C, cleaved PARP, and cleaved caspase-3, but downregulated the protein expression of Bcl-2, Bcl-xl, pPI3k, and pAkt. However, SC79 reversed the function of piperine on the apoptosis-related proteins. An in vivo study revealed that, compared with the control group, the tumor volume of mice treated with piperine was significantly reduced. Piperine enhanced cleaved caspase-3 expression but decreased Ki-67 expression in a dose-dependent manner. Moreover, the nontoxicity effect of piperine was confirmed by H&E staining analysis in kidney and heart tissues of mice.

Conclusions

Our findings suggest that piperine inhibits proliferation and induces apoptosis of human gastric cancer cells through inhibition of the PI3K/Akt signaling pathway.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Protective role of mitoquinone against impaired mitochondrial homeostasis in metabolic syndrome

Mitochondria control various processes in cellular metabolic homeostasis, such as adenosine triphosphate production, generation and clearance of reactive oxygen species, control of intracellular Ca²⁺ and apoptosis, and are thus a critical therapeutic target for metabolic syndrome (MetS). The mitochondrial targeted antioxidant mitoquinone (MitoQ) reduces mitochondrial oxidative stress, prevents impaired mitochondrial dynamics, and increases mitochondrial turnover by promoting autophagy (mitophagy) and mitochondrial biogenesis, which ultimately contribute to the attenuation of MetS conditions, including obesity, insulin resistance, hypertension and cardiovascular disease. The regulatory effect of MitoQ on mitochondrial homeostasis is mediated through AMPK and its downstream signaling pathways, including MTOR, SIRT1, Nrf2 and NF-κB. However, there are few reviews focusing on the critical role of MitoQ as a therapeutic agent in the treatment of MetS. The purpose of this review is to summarize the mitochondrial role in the pathogenesis of MetS, especially in obesity and type 2 diabetes, and discuss the effect and underlying mechanism of MitoQ on mitochondrial homeostasis in MetS.

Increase of mtDNA number and its mutant copies in rat brain after exposure to 150 MeV protons

Proton beam therapy is widely used for treating brain tumor. Despite the efficacy of treatment, the use of this therapy has met some limitations associated with possible damage to normal brain tissues located beyond the tumor site. In this context, the exploration of the harmful effects of protons on the normal brain tissues is of particular interest. We have investigated changes in the total mitochondrial DNA (mtDNA) copy number and identified mtDNA mutant copies in three brain regions (the hippocampus, cortex and cerebellum) of rats after irradiation their whole-head with 150 MeV protons at doses of 3 and 5 Gy. The study was performed in 2-months old male Spraque Dawley rats (n = 5 each group). The mtDNA copy numbers were determined by real-time PCR. The level of mtDNA heteroplasmy was estimated using Surveyor nuclease technology. Our results show that after head exposure to protons, levels of mtDNA copy number in three rat brain regions increase significantly as the levels of mtDNA mutant copies increase. The most significant elevation is observed in the hippocampus. In conclusion, an increase in mtDNA mutant copies may contribute to mitochondrial dysfunction accompanied by increased oxidative stress in different brain regions and promote the development of neurodegenerative diseases and the induction of carcinogenesis.

Silencing of circFoxO3 Protects HT22 Cells from Glutamate-Induced Oxidative Injury via Regulating the Mitochondrial Apoptosis Pathway

Recent studies demonstrated that FoxO3 circular RNA (circFoxO3) plays an important regulatory role in tumourigenesis and cardiomyopathy. However, the role of circFoxO3 in neurodegenerative diseases remains unknown. The aim of this study was to examine the possible role of circFoxO3 in neurodegenerative diseases and the underlying mechanisms. To model human neurodegenerative conditions, hippocampus-derived neurons were treated with glutamate. Using molecular and cellular biology approaches, we found that circFoxO3 expression was significantly higher in the glutamate treatment group than that in the control group. Furthermore, silencing of circFoxO3 protected HT22 cells from glutamate-induced oxidative injury through the inhibition of the mitochondrial apoptotic pathway. Collectively, our study demonstrates that endogenous circFoxO3 plays a key role in inducing apoptosis and neuronal cell death and may act as a novel therapeutic target for neurodegenerative diseases.

IMM-H004 therapy for permanent focal ischemic cerebral injury via CKLF1/CCR4-mediated NLRP3 inflammasome activation

Chemokine-like factor 1 (CKLF1) is a potential target for ischemic stroke therapy. The NOD-like receptor protein 3 (NLRP3) inflammasome has been postulated to mediate inflammatory responses during ischemic/reperfusion (I/R) injury. The compound IMM-H004 is a novel coumarin derivative that can improve cerebral I/R injury. This study aims to investigate the effects of IMM-H004 on ischemia stroke injury and further elucidate the molecular mechanisms. The standard pMCAO model of focal ischemia was used in this paper. Drugs were administered at 6 hours after ischemia, and behavioral assessment, euthanasia, and outcome measures were evaluated at 9 hours after ischemia. The effects of IMM-H004 on ischemic stroke injury were determined using 2,3,5-triphenyltetrazolium chloride (TTC) staining, behavioral tests, enzyme-linked immunosorbent assay (ELISA), and Nissl staining. Immunohistologic staining, immunofluorescence staining, quantitative RT-PCR (qPCR), western blotting, and coimmunoprecipitation (CO-IP) assays were used to elucidate the underlying mechanisms. IMM-H004 treatment provided significant protection against ischemia stroke through a CKLF1-dependent anti-inflammatory pathway in rats. IMM-H004 downregulated the amount of CKLF1 binding with C-C chemokine receptor type 4, further suppressing the activation of NLRP3 inflammasome and the following inflammatory response, ultimately protecting the ischemic brain. This preclinical study established the efficacy of IMM-H004 as a potential therapeutic medicine for permanent cerebral ischemia. These results support further efforts to develop IMM-H004 for human clinical trials in acute cerebral ischemia, particularly for patients who are not suitable for reperfusion therapy.

Targeting Mitochondrial Defects to Increase Longevity in Animal Models of Neurodegenerative Diseases

Bioenergetic homeostasis is a vital process maintaining cellular health and has primary importance in neuronal cells due to their high energy demand markedly at synapses. Mitochondria, the metabolic hubs of the cells, are the organelles responsible for producing energy in the form of ATP by using nutrients and oxygen. Defects in mitochondrial homeostasis result in energy deprivation and can lead to disrupted neuronal functions. Mitochondrial defects adversely contribute to the pathogenesis of neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's disease (PD). Mitochondrial defects not only include reduced ATP levels but also increased reactive oxygen species (ROS) leading to cellular damage. Here, we detail the mechanisms that lead to neuronal pathologies involving mitochondrial defects. Furthermore, we discuss how to target these mitochondrial defects in order to have beneficial effects as novel and complementary therapeutic avenues in neurodegenerative diseases. The critical evaluation of these strategies and their potential outcome can pave the way for finding novel therapies for neurodegenerative pathologies.

Exogenous hydrogen sulphide supplement accelerates skin wound healing via oxidative stress inhibition and vascular endothelial growth factor enhancement

Hydrogen sulphide (H₂ S) is an important gasotransmitter with several physiological functions. However, the roles and the detailed mechanisms of H₂ S on skin wound healing are not known well. In the present study, 129S1/SvImJ mice were intraperitoneally injected with NaHS (50 μmol/kg/d) for 2 weeks. Then, a round wound of 6 mm diameter with depth into the dermis was made. The skin wound area, blood perfusion, superoxide production, malondialdehyde (MDA) levels, total antioxidant capacity (T-AOC), expression of vascular endothelial growth factor (VEGF), dynamin-related protein 1 (DRP1) and optic atrophy 1 (OPA1) were measured. After NaHS (50 μmol/L) pre-administration for 4 hours, cell migration rate, DRP1, OPA1 and α-smooth muscle actin (α-SMA) expression, superoxide production and mitochondrial membrane potential in primary skin fibroblasts were measured. Tube formation in human umbilical vein endothelial cells (HUVECs) and cell migration in human keratinocytes were also measured. The results showed that NaHS pretreatment significantly accelerated wound healing and improved blood flow in the wound after operation. NaHS increased VEGF expression in the wound and promoted tube formation in HUVECs. Meanwhile, NaHS attenuated reactive oxygen species (ROS) production, suppressed MDA level but restored T-AOC in the wound. NaHS also promoted skin fibroblasts migration and α-SMA expression after scratch. Moreover, NaHS alleviated ROS, increased mitochondrial membrane potential, decreased DRP1 but enhanced OPA1 expression in skin fibroblasts after scratch. NaHS also accelerated human keratinocytes migration after scratch. Taken together, exogenous H₂ S supplementary accelerated the skin wound healing, which might be related to oxidative stress inhibition and VEGF enhancement.

Nicotinic ACh receptor α7 inhibits PDGF-induced migration of vascular smooth muscle cells by activating mitochondrial deacetylase sirtuin 3

BACKGROUND AND PURPOSE

PDGF-BB is an angiogenic factor involved in cardiovascular diseases. Here, we investigated the possible effects of activation of the nicotinic ACh receptor α7 subtype (α7nAChR) on PDGF-BB-induced proliferation and migration in vascular smooth muscle cells (VSMCs).

EXPERIMENTAL APPROACH

PNU-282987, a selective α7nAChR pharmacological agonist, was used to activate α7nAChR. The influences of α7nAChR activation on PDGF-BB-induced proliferation and migration, as well as the phosphorylation of focal adhesion kinase (FAK)/Src, a pro-migration signalling pathway, were determined in VSMCs. A variety of biochemical assays were applied to explore the underlying molecular mechanisms.

KEY RESULTS

PDGF-BB induced pronounced migration and proliferation of VSMCs. Activation of α7nAChRs by PNU-282987 blocked PDGF-BB-induced migration but not proliferation in wild-type (WT) VSMCs, whereas this effect was absent in α7nAChR-knockout VSMCs. Accordingly, PNU-282987 attenuated PDGF-BB-induced phosphorylation of FAK^Tyr397 and Src^Tyr416 in WT VSMCs. Mechanistically, PNU-282987 suppressed PDGF-BB-induced oxidative stress, as demonstrated by the alterations in ROS, H₂ O₂ content, superoxide anion and total antioxidant activity. A sirtuin 3 (SIRT3) inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine or shRNA-mediated SIRT3 knockdown abolished the inhibitory effect of PNU-282987. PNU-282987 did not modulate SIRT3 protein expression but enhanced mitochondrial SIRT3 deacetylase activity. In line with this action, PNU-282987 enhanced the deacetylation of mitochondrial FoxO3. Lastly, PNU-282987 corrected the PDGF-BB-induced mitochondrial dysfunction by increasing mitochondrial citrate synthase activity, ATP content and nicotinamide adenine dinucleotide pool.

CONCLUSIONS

Pharmacological activation of α7nAChRs inhibits PDGF-BB-induced VSMC migration by activating the mitochondrial deacetylase SIRT3, implying an important role for α7nAChRs in mitochondria biology and PDGF-related diseases.

LINKED ARTICLES

This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Nur77 promotes cerebral ischemia-reperfusion injury via activating INF2-mediated mitochondrial fragmentation

Mitochondrial fragmentation drastically regulates mitochondrial homeostasis in brain illness. However, the role of mitochondrial fragmentation in cerebral ischemia-reperfusion (IR) injury remains unclear. Nur77, a regulator of mitochondrial homeostasis, is associated with heart and liver IR injury, but its effects on mitochondrial function in cerebral IR injury has not been studied intensively. The aim of our study is to explore whether cerebral IR injury is modulated by Nur77 via modification of mitochondrial homeostasis. Our results indicated that Nur77 was upregulated in reperfused brain tissues. Genetic ablation of Nur77 reduced infarction area and promoted neuron survival under IR burden. Biochemical analysis demonstrated that Nur77 deletion protected mitochondrial function, attenuated mitochondrial oxidative stress, preserved mitochondrial potential, and blocked mitochondria-related cell apoptosis. In addition, we illustrated that Nur77 mediated mitochondrial damage via evoking mitochondrial fragmentation that occurred through increased mitochondrial fission and decreased fusion. Besides, our results also demonstrated that Nur77 controlled mitochondrial fragmentation via upregulating INF2 in a manner dependent on the Wnt/β-catenin pathway; inhibition of the Wnt pathway abrogated the protective effect of Nur77 deletion on reperfused-mediated neurons. Altogether, our study highlights that the pathogenesis of cerebral IR injury is associated with Nur77 activation followed by augmented mitochondrial fragmentation via an abnormal Wnt/β-catenin/INF2 pathway. Accordingly, Nur77-dependent mitochondrial fragmentation and the Wnt/β-catenin/INF2 axis may represent novel therapeutic targets to reduce cerebral IR injury.

Nurr1 exacerbates cerebral ischemia-reperfusion injury via modulating YAP-INF2-mitochondrial fission pathways

Nurr1, a nuclear transcription factor, has been linked to ischemia-reperfusion injury (IRI) in heart and kidney via modulating mitochondrial homeostasis. However, its role in cerebral ischemia-reperfusion has not been defined. In the present study, we found that cerebral IRI significantly increased the expression of Nurr1 and genetic ablation of Nurr1 attenuated the infarction area and reduced the neuron apoptosis under brain IRI burden. Functional studies have demonstrated that Nurr1 induced neuron death via activating mitochondrial fission. Aberrant mitochondrial fission promoted mitochondrial membrane potential reduction, evoked cellular oxidative stress and activated caspase-9-dependent mitochondrial apoptotic pathway. Interestingly, Nurr1 deletion alleviated fission-mediated mitochondrial damage, sustaining mitochondrial homeostasis and favoring neuron survival. Further, we found that Nurr1 deletion modulated mitochondrial fission via preventing INF2 upregulation in a manner dependent on YAP pathways. Either pharmacological blockade of YAP pathway or overexpression of INF2 abrogated the inhibitory effect of Nurr1 deletion on mitochondrial fission, leading to neuron death via mitochondrial apoptosis. Altogether, our results report that the pathogenesis of cerebral ischemia-reperfusion injury is associated with Nurr1 upregulation followed by augmented mitochondrial fission via an abnormal YAP-INF2 pathways.