SOD2 in mitochondrial dysfunction and neurodegeneration

N-glycome analysis detects dysglycosylation missed by conventional methods in SLC39A8 deficiency

Congenital disorders of glycosylation (CDG) are a growing group of inborn metabolic disorders with multiorgan presentation. SLC39A8-CDG is a severe subtype caused by biallelic mutations in the manganese transporter SLC39A8, reducing levels of this essential cofactor for many enzymes including glycosyltransferases. The current diagnostic standard for disorders of N-glycosylation is the analysis of serum transferrin. Exome and Sanger sequencing were performed in two patients with severe neurodevelopmental phenotypes suggestive of CDG. Transferrin glycosylation was analyzed by high-performance liquid chromatography (HPLC) and isoelectric focusing in addition to comprehensive N-glycome analysis using matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS). Atomic absorption spectroscopy was used to quantify whole blood manganese levels. Both patients presented with a severe, multisystem disorder, and a complex neurological phenotype. Magnetic resonance imaging (MRI) revealed a Leigh-like syndrome with bilateral T2 hyperintensities of the basal ganglia. In patient 1, exome sequencing identified the previously undescribed homozygous variant c.608T>C [p.F203S] in SLC39A8. Patient 2 was found to be homozygous for c.112G>C [p.G38R]. Both individuals showed a reduction of whole blood manganese, though transferrin glycosylation was normal. N-glycome using MALDI-TOF MS identified an increase of the asialo-agalactosylated precursor N-glycan A2G1S1 and a decrease in bisected structures. In addition, analysis of heterozygous CDG-allele carriers identified similar but less severe glycosylation changes. Despite its reliance as a clinical gold standard, analysis of transferrin glycosylation cannot be categorically used to rule out SLC39A8-CDG. These results emphasize that SLC39A8-CDG presents as a spectrum of dysregulated glycosylation, and MS is an important tool for identifying deficiencies not detected by conventional methods.

Miro, a Rho GTPase genetically interacts with Alzheimer's disease-associated genes (Tau, Aβ42 and Appl) in Drosophila melanogaster

Miro (mitochondrial Rho GTPases), a mitochondrial outer membrane protein, facilitates mitochondrial axonal transport along the microtubules to facilitate neuronal function. It plays an important role in regulating mitochondrial dynamics (fusion and fission) and cellular energy generation. Thus, Miro might be associated with the key pathologies of several neurodegenerative diseases (NDs) including Alzheimer's disease (AD). In the present manuscript, we have demonstrated the possible genetic interaction between Miro and AD-related genes such as Tau, Aβ42 and Appl in Drosophila melanogaster Ectopic expression of Tau, Aβ42 and Appl induced a rough eye phenotype, defects in phototaxis and climbing activity, and shortened lifespan in the flies. In our study, we have observed that overexpression of Miro improves the rough eye phenotype, behavioral activities (climbing and phototaxis) and ATP level in AD model flies. Further, the improvement examined in AD-related phenotypes was correlated with decreased oxidative stress, cell death and neurodegeneration in Miro overexpressing AD model flies. Thus, the obtained results suggested that Miro genetically interacts with AD-related genes in Drosophila and has the potential to be used as a therapeutic target for the design of therapeutic strategies for NDs.This article has an associated First Person interview with the first author of the paper.

Mitochondrial Oxidative and Nitrosative Stress and Alzheimer Disease

Oxidative and nitrosative stress are widely recognized as critical factors in the pathogenesis and progression of Alzheimer disease (AD) and its earlier stage, amnestic mild cognitive impairment (MCI). A major source of free radicals that lead to oxidative and nitrosative damage is mitochondria. This review paper discusses oxidative and nitrosative stress and markers thereof in the brain, along with redox proteomics, which are techniques that have been pioneered in the Butterfield laboratory. Selected biological alterations in-and oxidative and nitrosative modifications of-mitochondria in AD and MCI and systems of relevance thereof also are presented. The review article concludes with a section on the implications of mitochondrial oxidative and nitrosative stress in MCI and AD with respect to imaging studies in and targeted therapies toward these disorders. Taken together, this review provides support for the notion that brain mitochondrial alterations in AD and MCI are key components of oxidative and nitrosative stress observed in these two disorders, and as such, they provide potentially promising therapeutic targets to slow-and hopefully one day stop-the progression of AD, which is a devastating dementing disorder.

Mitochondrial DNA and Neurodegeneration: Any Role for Dietary Antioxidants?

The maintenance of the mitochondrial function is essential in preventing and counteracting neurodegeneration. In particular, mitochondria of neuronal cells play a pivotal role in sustaining the high energetic metabolism of these cells and are especially prone to oxidative damage. Since overproduction of reactive oxygen species (ROS) is involved in the pathogenesis of neurodegeneration, dietary antioxidants have been suggested to counteract the detrimental effects of ROS and to preserve the mitochondrial function, thus slowing the progression and limiting the extent of neuronal cell loss in neurodegenerative disorders. In addition to their role in the redox-system homeostasis, mitochondria are unique organelles in that they contain their own genome (mtDNA), which acts at the interface between environmental exposures and the molecular triggers of neurodegeneration. Indeed, it has been demonstrated that mtDNA (including both genetics and, from recent evidence, epigenetics) might play relevant roles in modulating the risk for neurodegenerative disorders. This mini-review describes the link between the mitochondrial genome and cellular oxidative status, with a particular focus on neurodegeneration; moreover, it provides an overview on potential beneficial effects of antioxidants in preserving mitochondrial functions through the protection of mtDNA.

Genome-wide profiling of DNA methylation and gene expression identifies candidate genes for human diabetic neuropathy

BACKGROUND

Diabetic peripheral neuropathy (DPN) is the most common complication of type 2 diabetes (T2D). Although the cellular and molecular mechanisms of DPN are poorly understood, we and others have shown that altered gene expression and DNA methylation are implicated in disease pathogenesis. However, how DNA methylation might functionally impact gene expression and contribute to nerve damage remains unclear. Here, we analyzed genome-wide transcriptomic and methylomic profiles of sural nerves from T2D patients with DPN.

RESULTS

Unbiased clustering of transcriptomics data separated samples into groups, which correlated with HbA1c levels. Accordingly, we found 998 differentially expressed genes (DEGs) and 929 differentially methylated genes (DMGs) between the groups with the highest and lowest HbA1c levels. Functional enrichment analysis revealed that DEGs and DMGs were enriched for pathways known to play a role in DPN, including those related to the immune system, extracellular matrix (ECM), and axon guidance. To understand the interaction between the transcriptome and methylome in DPN, we performed an integrated analysis of the overlapping genes between DEGs and DMGs. Integrated functional and network analysis identified genes and pathways modulating functions such as immune response, ECM regulation, and PI3K-Akt signaling.

CONCLUSION

These results suggest for the first time that DNA methylation is a mechanism regulating gene expression in DPN. Overall, DPN patients with high HbA1c have distinct alterations in sural nerve DNA methylome and transcriptome, suggesting that optimal glycemic control in DPN patients is an important factor in maintaining epigenetic homeostasis and nerve function.

Five variants of the superoxide dismutase genes in Turkish women with polycystic ovary syndrome

INTRODUCTION

Polycystic ovary syndrome (PCOS) is one of the most common endocrine-reproductive-metabolic disorders of women at reproductive age. Many investigations have revealed that reactive oxygen species (ROS) level is significantly increased in patients with PCOS compared to healthy women.

OBJECT

The goal of the current study is to investigate the association between superoxide dismutase (SOD) variants and the risk of PCOS among Turkish women.

METHOD AND SUBJECTS

Three hundred twelve voluntary premenopausal women (148 healthy controls and 164 patients with PCOS) 18-45 years of age were include the study. All volunteers underwent physical examination and biochemical hormones evaluation. Five selected variants in SOD1 (+35 A/C (rs2234694) and SOD2 (-102 C > T, 3'UTRT > A (rs2842980), 3'UTRA > G (rs5746136), and Ala16ValC > T (rs4880) were analysed by using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method.

RESULT

3'UTRA > G and Ala16ValC > T variants showed significant differences between study groups. In the additive model of rs5746136 variant having AG and GG genotype increased the PCOS risk 2-fold (OR: 1.7, 95% CI: 1.08-2.77, p = 0.003) and 5-fold (OR: 5, 95% CI: 1.7-14.2,p = 0.003) compared to AA genotype, respectively. To have a GG + AG genotype increased the PCOS risk 2-fold (OR: 2.95% Cl: 1.2-3.1, p = 0.003) compared to AA genotype in "G" dominant model. In case of the "G" recessive model, having a GG genotype increased the PCOS risk 4-fold (OR: 3.8, 95% CI: 1.3-10.4, p = 0.01) compared to AA + AG genotype. The TT genotype of rs4880 showed almost 2-fold (OR: 1.8, 95% CI: 1.12-3.0) increased PCOS risk in the "T" recessive model.

CONCLUSION

It is quite likely that the variants which result in decreased function in the antioxidant defence mechanism related genes contribute to PCOS aetiology with inhibiting/reducing of ROS elimination.

Role of tumor suppressor molecules in genomic perturbations and damaged DNA repair involved in the pathogenesis of cancer and neurodegeneration (Review)

Genomic perturbations due to inaccurate DNA replication, including inappropriate chromosomal segregation often underlie the development of cancer and neurodegenerative diseases. The incidence of these two diseases increases with age and exhibits an inverse association. Therefore, elderly subjects with cancer exhibit a reduced risk of a neurodegenerative disease, and vice versa. Both of these diseases are associated with aging and share several risk factors. Cells have multiple mechanisms to repair DNA damage and inaccurate replication. Previous studies have demonstrated that tumor suppressor proteins serve a critical role in the DNA damage response, which may result in genomic instability and thus induction of cellular apoptosis. Tumor suppressor genes, such as phosphatase and tensin homologue deleted on chromosome 10 (PTEN), breast cancer susceptibility gene 1 (BRCA1) and TP53 reduce genomic susceptibility to cancer by repairing the damaged DNA. In addition, these genes work cooperatively to ensure the inhibition of the development of several types of cancer. PTEN, BRCA1 and TP53 have been recognized as the most frequently deleted and/or mutated genes in various types of human cancer. Recently, tumor suppressor genes have also been shown to be involved in the development of neurodegenerative diseases. The present review summarizes the recent findings of the functions of these tumor suppressors that are associated with genomic stability, and are involved in carcinogenic and neurodegenerative cell signaling. A summary is presented regarding the interactions of these tumor suppressors with their partners which results in transduction of downstream signals. The implications of these functions for cancer and neurodegenerative disease-associated biology are also highlighted.

Brain Overexpression of Uncoupling Protein-2 (UCP2) Delays Renal Damage and Stroke Occurrence in Stroke-Prone Spontaneously Hypertensive Rats

The downregulation of uncoupling protein-2 (UCP2) is associated with increased brain and kidney injury in stroke-prone spontaneously hypertensive rats (SHRSP) fed with a Japanese style hypersodic diet (JD). Systemic overexpression of UCP2 reduces organ damage in JD-fed SHRSP. We examined the effect of brain-specific UCP2 overexpression on blood pressure (BP), stroke occurrence and kidney damage in JD-fed SHRSP. Rats received a single i.c.v. injection of a lentiviral vector encoding UCP2 (LV-UCP2), or an empty vector. The brain delivery of LV-UCP2 significantly delayed the occurrence of stroke and kidney damage. The large reduction of proteinuria observed after LV-UCP2 injection was unexpected, because BP levels were unchanged. At the time of stroke, rats treated with LV-UCP2 still showed a large UCP2 upregulation in the striatum, associated with increases in OPA1 and FIS1 protein levels, and reductions in PGC1-α, SOD2, TNFα mRNA levels and NRF2 protein levels. This suggested UCP2 overexpression enhanced mitochondrial fusion and fission and reduced oxidative damage and inflammation in the striatum of JD-fed SHRSP rats. Our data suggest the existence of central mechanisms that may protect against hypertension-induced organ damage independently of BP, and strengthen the suitability of strategies aimed at enhancing UCP2 expression for the treatment of hypertensive damage.

Effect of Borrelia burgdorferi Outer Membrane Vesicles on Host Oxidative Stress Response

Outer membrane vesicles (OMVs) are spherical bodies containing proteins and nucleic acids that are released by Gram-negative bacteria, including Borrelia burgdorferi, the causative agent of Lyme disease. The functional relationship between B. burgdorferi OMVs and host neuron homeostasis is not well understood. The objective of this study was to examine how B. burgdorferi OMVs impact the host cell environment. First, an in vitro model was established by co-culturing human BE2C neuroblastoma cells with B. burgdorferi B31. B. burgdorferi was able to invade BE2C cells within 24 h. Despite internalization, BE2C cell viability and levels of apoptosis remained unchanged, but resulted in dramatically increased production of MCP-1 and MCP-2 cytokines. Elevated secretion of MCP-1 has previously been associated with changes in oxidative stress. BE2C cell mitochondrial superoxides were reduced as early as 30 min after exposure to B. burgdorferi and OMVs. To rule out whether BE2C cell antioxidant response is the cause of decline in superoxides, superoxide dismutase 2 (SOD2) gene expression was assessed. SOD2 expression was reduced upon exposure to B. burgdorferi, suggesting that B. burgdorferi might be responsible for superoxide reduction. These results suggest that B. burgdorferi modulates cell antioxidant defense and immune system reaction in response to the bacterial infection. In summary, these results show that B. burgdorferi OMVs serve to directly counter superoxide production in BE2C neurons, thereby 'priming' the host environment to support B. burgdorferi colonization.

MKP-1 Modulates Mitochondrial Transcription Factors, Oxidative Phosphorylation, and Glycolysis

Sepsis is the leading cause of death in the world. Recent reports suggest that in response to sepsis, metabolism of macrophages switches from oxidative phosphorylation to aerobic glycolysis. MAPK phosphatase (MKP)–1 (also known as DUSP1) localized in the nucleus and preferentially dephosphorylates p38 and JNK. MKP-1 controls the expression of numerous inflammatory genes and transcription factors, thereby regulating innate and adaptive immunity. MKP-1–deficient animals exhibit aberrant metabolic responses following bacterial infections with a markedly increased mortality in response to sepsis. Because metabolic reprogramming modulates immune responses to TLR-4 activation, we investigated the effect of MKP-1 deficiency on mitochondrial electron transport chains involved in oxidative phosphorylation and transcription factors regulating mitochondrial biogenesis. Mitochondrial biogenesis is regulated by three nuclear-encoded proteins, including transcription factor A (TFAM), nuclear respiratory factors (NRF-1), and peroxisome proliferator–activated receptor γ coactivator-1-α (PGC-1α). We show that MKP-1–deficient mice/ macrophages exhibit, at baseline, higher expression of oxidative phosphorylation, TFAM, PGC-1α, and NRF-1 associated with increased respiration and production of reactive oxygen species as compared with wild-type mice. Surprisingly, MKP-1–deficient mice/macrophages responded to Escherichia coli sepsis or LPS with an impaired metabolic switch; despite enhanced glycolysis, a preserved mitochondrial function and biogenesis are exhibited. Furthermore, inhibition of p38 MAPK had no significant effect on TFAM and NRF-1 either in MKP-1–deficient macrophages or in wild-type macrophages. These findings support the conclusion that MKP-1 plays an important role in regulating proteins involved in glycolysis and oxidative phosphorylation and modulates expression of mitochondrial transcription factors.

AT2R's (Angiotensin II Type 2 Receptor's) Role in Cognitive and Cerebrovascular Deficits in a Mouse Model of Alzheimer Disease

Antihypertensive medications targeting the renin-angiotensin system have lowered the incidence and progression of Alzheimer disease. Understanding how these medications function could lead to novel therapeutic strategies. AT4Rs (angiotensin IV receptors) have been associated with angiotensin receptor blockers' cognitive, cerebrovascular, and neuroinflammatory rescue in Alzheimer disease models. Yet, whether AT4Rs act alone or with AT2Rs remains unknown. Here, we investigated whether AT2Rs contribute to losartan's benefits and whether chronic AT2R activation could mimic angiotensin receptor blocker benefits in transgenic mice overexpressing familial Alzheimer disease mutations of the human APP (amyloid precursor protein). Losartan-treated mice (10 mg/kg per day, drinking water, 7 months) received intracerebroventricular (1 month) administration of vehicle or AT2R antagonist PD123319 (1.6 nmol/day). PD123319 countered losartan's benefits on spatial learning and memory, neurovascular coupling, and hampered those on oxidative stress and nitric oxide bioavailability. PD123319 did not oppose losartan's benefits on short-term memory and vasodilatory function and had no benefit on neuroinflammation or Aβ (amyloid β) pathology. Mice receiving either vehicle or selective AT2R agonist compound 21 (intracerebroventricular: 1 nmol/day, 1 month or drinking water: 10 mg/kg per day, 7 months), showed no improvement in memory, vasodilatory function, or nitric oxide bioavailability. Compound 21 treatment normalized neurovascular coupling, reduced astrogliosis independent of persisting microgliosis, and exacerbated oxidative stress in APP mice. Compound 21 reduced dense core Aβ plaques, but not diffuse plaques or Aβ species. Our findings suggest that targeting AT2Rs is not an ideal strategy for restoring Aβ-related cognitive and cerebrovascular deficits.

Targeting Evolutionary Conserved Oxidative Stress and Immunometabolic Pathways for the Treatment of Respiratory Infectious Diseases

Significance: Up until recently, metabolism has scarcely been referenced in terms of immunology. However, emerging evidence has shown that immune cells undergo an adaptation of metabolic processes, known as the metabolic switch. This switch is key to the activation, and sustained inflammatory phenotype in immune cells, which includes the production of cytokines and reactive oxygen species (ROS) that underpin infectious diseases, respiratory and cardiovascular disease, neurodegenerative disease, as well as cancer. Recent Advances: There is a burgeoning body of evidence that immunometabolism and redox biology drive infectious diseases. For example, influenza A virus (IAV) utilizes endogenous ROS production via NADPH oxidase (NOX)2-containing NOXs and mitochondria to circumvent antiviral responses. These evolutionary conserved processes are promoted by glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle that drive inflammation. Such metabolic products involve succinate, which stimulates inflammation through ROS-dependent stabilization of hypoxia-inducible factor-1α, promoting interleukin-1β production by the inflammasome. In addition, itaconate has recently gained significant attention for its role as an anti-inflammatory and antioxidant metabolite of the TCA cycle. Critical Issues: The molecular mechanisms by which immunometabolism and ROS promote viral and bacterial pathology are largely unknown. This review will provide an overview of the current paradigms with an emphasis on the roles of immunometabolism and ROS in the context of IAV infection and secondary complications due to bacterial infection such as Streptococcus pneumoniae. Future Directions: Molecular targets based on metabolic cell processes and ROS generation may provide novel and effective therapeutic strategies for IAV and associated bacterial superinfections.

Brain proteomics links oxidative stress with metabolic and cellular stress response proteins in behavioural alteration of Alzheimer's disease model rats

Alzheimer's disease (AD) impairs memory and learning related behavioural performances of the affected person. Compared with the controls, memory and learning related behavioural performances of the AD model rats followed by hippocampal proteomics had been observed in the present study. In the eight armed radial maze, altered performance of the AD rats had been observed. Using liquid chromatography coupled tandem mass spectrometry (LC-MS/MS), 822 proteins had been identified with protein threshold at 95.0%, minimum peptide of 2 and peptide threshold at 0.1% FDR. Among them, 329 proteins were differentially expressed with statistical significance (P < 0.05). Among the significantly regulated (P < 0.05) 329 proteins, 289 met the criteria of fold change (LogFC of 1.5) cut off value. Number of proteins linked with AD, oxidative stress (OS) and hypercholesterolemia was 59, 20 and 12, respectively. Number of commonly expressed proteins was 361. The highest amount of proteins differentially expressed in the AD rats were those involved in metabolic processes followed by those linked with OS. Most notable was the perturbed state of the cholesterol metabolizing proteins in the AD group. Current findings suggest that proteins associated with oxidative stress, glucose and cholesterol metabolism and cellular stress response are among the mostly affected proteins in AD subjects. Thus, novel therapeutic approaches targeting these proteins could be strategized to withstand the ever increasing global AD burden.

Tetrastigma hemsleyanum Vine Flavone Ameliorates Glutamic Acid-Induced Neurotoxicity via MAPK Pathways

Glutamic acid (Glu) is a worldwide flavor enhancer with various positive effects. However, Glu-induced neurotoxicity has been reported less. Tetrastigma hemsleyanum (TH), a rare herbal plant in China, possesses high medicinal value. More studies paid attention to tuber of TH whereas vine part (THV) attracts fewer focus. In this study, we extracted and purified flavones from THV (THVF), and UPLC-TOF/MS showed THVF was consisted of 3-caffeoylquinic acid, 5-caffeoylquinic acid, quercetin-3-O-rutinoside, and kaempferol-3-O-rutinoside. In vitro, Glu caused severe cytotoxicity, genotoxicity, mitochondrial dysfunction, and oxidative damage to rat phaeochromocytoma (PC12) cells. Conversely, THVF attenuated Glu-induced toxicity via MAPK pathways. In vivo, the neurotoxicity triggered by Glu restrained the athletic ability in Caenorhabditis elegans (C. elegans). The treatment of THVF reversed the situation induced by Glu. In a word, Glu could cause neurotoxicity and THVF owns potential neuroprotective effects both in vitro and in vivo via MAPK pathways.

Association between SOD2 V16A variant and urological cancer risk

Background: The correlation between superoxide dismutase 2 (SOD2) V16A variant and urological cancer susceptibility has been widely studied, however, with divergent results.

Results: Totally, 9,910 cancer patients and 11,239 control subjects were enrolled. V16A variant is associated with an increased susceptibility to urological cancer (A-allele vs. V-allele: OR = 1.06, 95% CI = 1.00 – 1.13, P = 0.047; AA+AV vs. VV: OR = 1.09, 95% CI = 1.02 – 1.16, P = 0.008), especially for prostate cancer (PCa). Serum SOD2 level of PCa patients with VV+VA genotypes was lower than in those with AA genotypes. SOD2 expression is downregulated in both prostate and bladder cancer, as compared to the control. Furthermore, SOD2 was found to be downregulated in more advanced PCa participants, as compared to the ones in early stages. PCa subjects with low SOD2 expression displayed a shorter disease-free survival (DFS) time compared to that of the high SOD2 expression counterparts.

Conclusions: The SOD2 V16A variant may be associated with increased urological cancer susceptibility, especially for prostate cancer.

Methods: A pooled analysis utilizing odds ratios (ORs), in silico tools and ELISA was adopted to demonstrate this association. We also used immunohistochemical staining (IHS) to assess SOD2 expression.

CircRNA Role and circRNA-Dependent Network (ceRNET) in Asthenozoospermia

The role of circRNA in reproduction is under investigation. CircRNAs are expressed in human testis, spermatozoa (SPZ), and seminal plasma. Their involvement in embryo development has also been suggested. Asthenozoospermia, a common cause of male infertility, is characterized by reduced or absent sperm motility in fresh ejaculate. While abnormal mitochondrial function, altered sperm tail, and genomic causes have been deeply investigated, the epigenetic signature of asthenozoospermic derived SPZ still remains unexplored. CircRNAs may take part in the repertoire of differentially expressed molecules in infertile men. Considering this background, we carried out a circRNA microarray, identifying a total of 9,138 transcripts, 22% of them novel based and 83.5% with an exonic structure. Using KEGG analysis, we evaluated the circRNA contribution in pathways related to mitochondrial function and sperm motility. In order to discriminate circRNAs with a differential expression in SPZ with differential morphological parameters, we separated sperm cells by Percoll gradient and analyzed their differential circRNA payload. A bioinformatic approach was then utilized to build a circRNA/miRNA/mRNA network. With the aim to demonstrate a dynamic contribution of circRNAs to the sperm epigenetic signature, we verified their modulation as a consequence of an oral amino acid supplementation, efficacious in improving SPZ motility.

Comparative iTRAQ proteomics revealed proteins associated with lobed fin regeneration in Bichirs

Background

Polypterus senegalus can fully regenerate its pectoral lobed fins, including a complex endoskeleton, with remarkable precision. However, despite the enormous potential of this species for use in medical research, its regeneration mechanisms remain largely unknown.

Methods

To identify the differentially expressed proteins (DEPs) during the early stages of lobed fin regeneration in P. senegalus, we performed a differential proteomic analysis using isobaric tag for relative and absolute quantitation (iTRAQ) approach based quantitative proteome from the pectoral lobed fins at 3 time points. Furthermore, we validated the changes in protein expression with multiple-reaction monitoring (MRM) analysis.

Results

The experiment yielded a total of 3177 proteins and 15,091 unique peptides including 1006 non-redundant (nr) DEPs. Of these, 592 were upregulated while 349 were downregulated after lobed fin amputation when compared to the original tissue. Bioinformatics analyses showed that the DEPs were mainly associated with Ribosome and RNA transport, metabolic, ECM-receptor interaction, Golgi and endoplasmic reticulum, DNA replication, and Regulation of actin cytoskeleton.

Conclusions

To our knowledge, this is the first proteomic research to investigate alterations in protein levels and affected pathways in bichirs’ lobe-fin/limb regeneration. In addition, our study demonstrated a highly dynamic regulation during lobed fin regeneration in P. senegalus. These results not only provide a comprehensive dataset on differentially expressed proteins during the early stages of lobe-fin/limb regeneration but also advance our understanding of the molecular mechanisms underlying lobe-fin/limb regeneration.

Ubiquitin Subproteome of Brain Mitochondria and Its Changes Induced by Experimental Parkinsonism and Action of Neuroprotectors

The review summarizes the data of our research and published studies on the ubiquitination of brain mitochondrial proteins and its changes during the development of experimental parkinsonism and administration of the neuroprotector isatin (indole-2,3-dione) with special attention to the mitochondrial ubiquitin-conjugating system and location of ubiquitinated proteins in these organelles. Incubation of brain mitochondrial fraction with biotinylated ubiquitin in vitro resulted in the incorporation of biotinylated ubiquitin in both mitochondrial and mitochondria-associated proteins. According to the interactome analysis, the identified non-ubiquitinated proteins are able to form tight complexes with ubiquitinated proteins or their partners and components of mitochondrial membranes, in which interactions of ubiquitin chains with the ubiquitin-binding protein domains play an important role. The studies of endogenous ubiquitination in the total brain mitochondrial fraction of C57Bl mice performed in different laboratories have shown that mitochondrial proteins represent about 30% of all ubiquitinated proteins. However, comparison of brain subproteomes of mitochondrial ubiquitinated proteins reported in the literature revealed significant differences both in their composition and involvement of identified ubiquitinated proteins in biological processes listed in the Gene Ontology database. The development of experimental parkinsonism in C57Bl mice induced by a single-dose administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) resulted in a decrease in the total number of mitochondrial ubiquitinated proteins and increase in the number of oxidized mitochondrial proteins containing the ubiquitin signature (K-ε-GG). Comparison of ubiquitinated proteins associated with the mouse brain mitochondrial fraction and mouse brain mitochondrial proteins bound to the proteasome ubiquitin receptor (Rpn10 subunit) did not reveal any common proteins. This suggests that ubiquitination of brain mitochondrial proteins is not directly related to their degradation in the proteasomes. Proteomic profiling of brain isatin-binding proteins identified enzymes involved in the ubiquitin-conjugating system functioning. Mapping of the identified isatin-binding proteins to known metabolic pathways indicates their participation in the parkin (E3 ubiquitin ligase)-associated pathway (CH000000947). The functional links involving brain mitochondrial ubiquitinated proteins were found only in the group of animals with the MPTP-induced parkinsonism, but not in animals treated with MPTP/isatin or isatin only. This suggests that the neuroprotective effect of isatin may be associated with the impaired functional relationships of proteins targeted to subsequent degradation.

Exploring the kidney hazard of exposure to mercuric chloride in mice:Disorder of mitochondrial dynamics induces oxidative stress and results in apoptosis

Mercury is one of the 10 toxic chemicals with major public health concerns. Continuous exposure to low levels of heavy metals including mercury is related to renal injury, especially in children. This study investigated the possible molecular mechanism of inorganic mercury-induced kidney injury. Twenty eight Kunming mice were divided into four groups (n = 7), and treated with 0, 20, 40, 80 mg/L mercuric chloride (HgCl₂) in drinking water for 16 weeks respectively. All the HgCl₂ exposure mice displayed different degrees of renal injury, which was diagnosed by hematoxylin and eosin stain, biochemical analysis, and ultrastructure examination. The treatment of HgCl₂ inhibited the silent information regulator two ortholog 1 (Sirt1)/peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) signaling pathway and resulted the disorder of mitochondrial dynamics, as evidenced by the increasing expression of dynamin-related protein 1 and decreasing expression of mitofusin 2. Meanwhile, HgCl₂ inhibited the nuclear factor erythroid 2-related factor 2 (Nrf2) axis. The abnormality of mitochondrial dynamics and the suppression of Nrf2 axis exacerbated oxidative stress, and then induced cell apoptosis. These findings demonstrated that the disorder of mitochondrial dynamics induced by HgCl₂ activated oxidative stress, and further resulted in renal apoptosis through inhibiting the Sirt1/PGC-1α signaling pathway and the Nrf2 axis.

Prenatal ambient air pollution exposure and SOD2 promoter methylation in maternal and cord blood

The evidence is increasing that prenatal air pollutant exposure contributes to elevated oxidative stress in children, but the underlying mechanism is unclear. A pilot study was conducted in China to explore the associations between prenatal ambient air pollution exposure and superoxide dismutase 2 (SOD2) promoter methylation in maternal and cord blood. After detection and analyses, SOD2 promoter methylation levels in umbilical cord blood were elevated as maternal SOD2 promoter methylation levels increased. In addition, the SOD2 promoter methylation levels in umbilical cord blood were positively associated with the particulate matter 10 (PM₁₀) exposure concentrations during the entire pregnancy and the second trimester. In maternal peripheral blood, the SOD2 promoter methylation levels were positively associated with the exposure concentrations of PM₁₀ (during the entire pregnancy and the second trimester) and nitrogen dioxide (NO₂) (during the first trimester of pregnancy), whereas the levels were negatively associated with the exposure concentrations of NO₂ during the third trimester of pregnancy. Additionally, interaction analyses revealed that the maternal SOD2 promoter methylation level and sulfur dioxide (SO₂) exposure (during the entire pregnancy and the third trimester), as well as NO₂ exposure (during the third trimester of pregnancy), had an interaction effect on the SOD2 promoter methylation level in umbilical cord blood. Furthermore, mediation analysis revealed that the associations between SOD2 promoter methylation in umbilical cord blood and PM₁₀ exposure during the entire pregnancy and the second trimester were partly mediated by maternal SOD2 promoter methylation. In conclusion, prenatal exposure to air pollutants was significantly associated with SOD2 promoter methylation levels in umbilical cord blood, and this association may be affected by SOD2 promoter methylation levels in maternal peripheral blood. These associations may be one of the mechanisms by which prenatal air pollutant exposure leads to oxidative stress in newborns.

mTOR hyperactivation in Down Syndrome underlies deficits in autophagy induction, autophagosome formation, and mitophagy

Down syndrome (DS), a complex genetic disorder caused by chromosome 21 trisomy, is associated with mitochondrial dysfunction leading to the accumulation of damaged mitochondria. Here we report that mitophagy, a form of selective autophagy activated to clear damaged mitochondria is deficient in primary human fibroblasts derived from individuals with DS leading to accumulation of damaged mitochondria with consequent increases in oxidative stress. We identified two molecular bases for this mitophagy deficiency: PINK1/PARKIN impairment and abnormal suppression of macroautophagy. First, strongly downregulated PARKIN and the mitophagic adaptor protein SQSTM1/p62 delays PINK1 activation to impair mitophagy induction after mitochondrial depolarization by CCCP or antimycin A plus oligomycin. Secondly, mTOR is strongly hyper-activated, which globally suppresses macroautophagy induction and the transcriptional expression of proteins critical for autophagosome formation such as ATG7, ATG3 and FOXO1. Notably, inhibition of mTOR complex 1 (mTORC1) and complex 2 (mTORC2) using AZD8055 (AZD) restores autophagy flux, PARKIN/PINK initiation of mitophagy, and the clearance of damaged mitochondria by mitophagy. These results recommend mTORC1-mTORC2 inhibition as a promising candidate therapeutic strategy for Down Syndrome.

Reactive Oxygen Species Are Key Mediators of Demyelination in Canine Distemper Leukoencephalitis but not in Theiler's Murine Encephalomyelitis

(1) Background: Canine distemper virus (CDV)-induced demyelinating leukoencephalitis (CDV-DL) in dogs and Theiler’s murine encephalomyelitis (TME) virus (TMEV)-induced demyelinating leukomyelitis (TMEV-DL) are virus-induced demyelinating conditions mimicking Multiple Sclerosis (MS). Reactive oxygen species (ROS) can induce the degradation of lipids and nucleic acids to characteristic metabolites such as oxidized lipids, malondialdehyde, and 8-hydroxyguanosine. The hypothesis of this study is that ROS are key effector molecules in the pathogenesis of myelin membrane breakdown in CDV-DL and TMEV-DL. (2) Methods: ROS metabolites and antioxidative enzymes were assessed using immunofluorescence in cerebellar lesions of naturally CDV-infected dogs and spinal cord tissue of TMEV-infected mice. The transcription of selected genes involved in ROS generation and detoxification was analyzed using gene-expression microarrays in CDV-DL and TMEV-DL. (3) Results: Immunofluorescence revealed increased amounts of oxidized lipids, malondialdehyde, and 8-hydroxyguanosine in CDV-DL while TMEV-infected mice did not reveal marked changes. In contrast, microarray-analysis showed an upregulated gene expression associated with ROS generation in both diseases. (4) Conclusion: In summary, the present study demonstrates a similar upregulation of gene-expression of ROS generation in CDV-DL and TMEV-DL. However, immunofluorescence revealed increased accumulation of ROS metabolites exclusively in CDV-DL. These results suggest differences in the pathogenesis of demyelination in these two animal models.

NF-κB/c-Rel deficiency causes Parkinson's disease-like prodromal symptoms and progressive pathology in mice

Background

Parkinson’s disease (PD), the most common neurodegenerative movement disorder, is characterized by dopaminergic nigrostriatal neuron loss and brain accumulation of Lewy bodies, protein aggregates mainly composed of α-synuclein. We reported that mice deficient for NF-κB/c-Rel (c-rel^-/-) develop a late-onset parkinsonism. At 18 months of age, c-rel^-/- mice showed nigrostriatal degeneration and accumulation of α-synuclein aggregates associated with a motor impairment responsive to L-DOPA administration. Being c-Rel protein a transcriptional regulator for mitochondrial anti-oxidant and antiapoptotic factors, it has been inferred that its deficiency may affect the resilience of “energy demanding” nigral dopaminergic neurons to the aging process.

PD patients manifest a prodromal syndrome that includes olfactory and gastrointestinal dysfunctions years before the frank degeneration of nigrostriatal neurons and appearance of motor symptoms. According to the Braak staging, the onset of non-motor and motor symptoms relates to progressive ascendant diffusion of α-synuclein pathology in the brain. The aim of this study was to identify whether c-rel^-/- deficiency is associated with the onset of premotor signs of PD and spatio-temporal progression of cerebral α-synuclein deposition.

Methods

Intestinal and olfactory functions, intestine and brain α-synuclein deposition as well as striatal alterations, were assessed in c-rel^-/- and control mice from 2 to 18 months of age.

Results

From 2 months of age, c-rel^-/- mice displayed intestinal constipation and increasing olfactory impairment. At 2 months, c-rel^-/- mice exhibited a mild α-synuclein accumulation in the distal colon. Moreover, they developed an age-dependent deposition of fibrillary α-synuclein that, starting at 5 months from the olfactory bulbs, dorsal motor nucleus of vagus and locus coeruleus, reached the substantia nigra at 12 months. At this age, the α-synuclein pathology associated with a drop of dopamine transporter in the striatum that anticipated by 6 months the axonal degeneration. From 12 months onwards oxidative/nitrosative stress developed in the striatum in parallel with altered expression of mitochondrial homeostasis regulators in the substantia nigra.

Conclusions

In c-rel^-/- mice, reproducing a parkinsonian progressive pathology with non-motor and motor symptoms, a Braak-like pattern of brain ascending α-synuclein deposition occurs. The peculiar phenotype of c-rel^-/- mice envisages a potential contribution of c-Rel dysregulation to the pathogenesis of PD.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0154-z) contains supplementary material, which is available to authorized users.

Reduced lifespan of mice lacking catalase correlates with altered lipid metabolism without oxidative damage or premature aging

The relationship between the mechanisms that underlie longevity and aging and the metabolic alterations due to feeding conditions has not been completely defined. In the present work, through the deletion of the gene encoding catalase, hydrogen peroxide (H₂O₂) was uncovered as a relevant regulator of longevity and of liver metabolism. Mice lacking catalase (Cat^-/-) fed ad libitum with a regular diet showed a shorter lifespan than wild type mice, which correlated with reduced body weight, blood glucose levels and liver fat accumulation, but not with increased oxidative damage or consistent premature aging. High fat diet (HFD) and fasting increased oxidative damage in the liver of wild type animals but, unexpectedly, this was not the case for that of Cat^-/- mice. Interestingly, although HFD feeding similarly increased the body weight of Cat^-/- and wild-type mice, hyperglycemia and liver steatosis did not develop in the former. Fat accumulation due to fasting, on the other hand, was diminished in mice lacking catalase, which correlated with increased risk of death and low ketone body blood levels. Alteration in expression of some metabolic genes in livers of catalase deficient mice was consistent with reduced lipogenesis. Specifically, Pparγ2 expression up-regulation in response to a HFD and down-regulation upon fasting was lower and higher, respectively, in livers of Cat^-/- than of wild type mice, and a marked decay was observed during Cat^-/- mice aging. We propose that catalase regulates lipid metabolism in the liver by an evolutionary conserved mechanism that is determinant of lifespan without affecting general oxidative damage.

Efficacy and Mechanism of Panax Ginseng in Experimental Stroke

Stroke is one of the leading causes of death and long-term disability worldwide. However, effective therapeutic approaches are still limited. The disruption of blood supply triggers complicated temporal and spatial events involving hemodynamic, biochemical, and neurophysiologic changes, eventually leading to pathological disturbance and diverse clinical symptoms. Ginseng (Panax ginseng), a popular herb distributed in East Asia, has been extensively used as medicinal and nutritional supplements for a variety of disorders worldwide. In recent years, ginseng has displayed attractive beneficial effects in distinct neurological disorders including stroke, involving multiple protective mechanisms. In this article, we reviewed the literature on ginseng studies in the experimental stroke field, particularly focusing on the in vivo evidence on the preventive or therapeutic efficacy and mechanisms of ginseng and ginsenosides in various stroke models of mice and rats. We also summarized the efficacy and underlying mechanisms of ginseng and ginsenosides on short- and long-term stroke outcomes.

Trans sodium crocetinate alleviates ischemia/reperfusion-induced myocardial oxidative stress and apoptosis via the SIRT3/FOXO3a/SOD2 signaling pathway

Trans sodium crocetinate (TSC) has been reported to exert a protective effect against cerebral ischemia/reperfusion (I/R) injury. However, whether TSC protects against myocardial ischemia/reperfusion (MI/R) injury remains unknown. Herein, we found that TSC treatment reduced myocardial infract size and elevated serum LDH and CK activities of MI/R rats. TSC administration attenuated oxidative stress in MI/R rats and H9C2 cells exposed to oxygen glucose deprivation/reperfusion (OGD/R). TSC administration relieved I/R-induced myocardial apoptosis in vivo and in vitro, as evidenced by reduced number of TUNEL positive cells, accompanying with marked decreases in caspase-3 activity and Bax protein level and an increase in Bcl-2 protein level. TSC treatment markedly increased SIRT3 activity and SIRT3 and SOD2 protein levels, and could also diminished the phosphorylation of FOXO3a protein. Additionally, TSC treatment attenuated the acetylation of FOXO3a and SOD2 protein. But, these effects were obviously blocked by SIRT3 knockdown. Besides, SIRT3 knockdown blocked the cardioprotective effect of TSC on OGD/R-induced oxidative stress, apoptosis and mitochondrial dysfunction in vitro. In summary, TSC alleviates I/R-induced myocardial oxidative stress and apoptosis via the SIRT3/FOXO3a/SOD2 signaling pathway. Our study suggests that TSC may become a novel drug for the treatment of MI/R injury.

Molecular Toxicological Mechanisms of Synthetic Cathinones on C2C12 Myoblasts

Synthetic cathinones are popular psychoactive substances that may cause skeletal muscle damage. In addition to indirect sympathomimetic myotoxicity, these substances could be directly myotoxic. Since studies in myocytes are currently lacking, the aim of the present study was to investigate potential toxicological effects by synthetic cathinones on C2C12 myoblasts (mouse skeletal muscle cell line). We exposed C2C12 myoblasts to 3-methylmethcathinone, 4-methylmethcathinone (mephedrone), 3,4-methylenedioxymethcathinone (methylone), 3,4-methylenedioxypyrovalerone (MDPV), alpha-pyrrolidinovalerophenone (α-PVP), and naphthylpyrovalerone (naphyrone) for 1 or 24 h before cell membrane integrity, ATP content, mitochondrial oxygen consumption, and mitochondrial superoxide production was measured. 3,4-Methylenedioxymethamphetamine (MDMA) was included as a reference compound. All investigated synthetic cathinones, as well as MDMA, impaired cell membrane integrity, depleted ATP levels, and increased mitochondrial superoxide concentrations in a concentration-dependent manner in the range of 50–2000 μM. The two pyrovalerone derivatives α-PVP and naphyrone, and MDMA, additionally impaired basal and maximal cellular respiration, suggesting mitochondrial dysfunction. Alpha-PVP inhibited complex I, naphyrone complex II, and MDMA complex I and III, whereas complex IV was not affected. We conclude that, in addition to sympathetic nervous system effects and strenuous muscle exercise, direct effects of some cathinones on skeletal muscle mitochondria may contribute to myotoxicity in susceptible synthetic cathinone drugs users.

Mitochondria-Derived Vesicles Deliver Antimicrobial Reactive Oxygen Species to Control Phagosome-Localized Staphylococcus aureus

Pathogenic bacteria taken up into the macrophage phagosome are the target of many anti-microbial mechanisms. Although mitochondria-derived antimicrobial effectors like reactive oxygen species (mROS) aid in bacterial killing, it is unclear how these effectors reach bacteria within the phagosomal lumen. We show here that endoplasmic reticulum stress triggered upon methicillin-resistant Staphylococcus aureus (MRSA) infection induces mROS that are delivered to bacteria-containing phagosomes via mitochondria-derived vesicles (MDVs). The endoplasmic reticulum stress sensor IRE1α induces mROS, specifically hydrogen peroxide (mH₂O₂), upon MRSA infection. MRSA infection also stimulates the generation of MDVs, which require the mitochondrial stress response factor Parkin, and contributes to mH₂O₂ accumulation in bacteria-containing phagosomes. Accumulation of phagosomal H₂O₂ requires Toll-like receptor signaling and the mitochondrial enzyme superoxide dismutase-2 (Sod2), which is delivered to phagosomes by MDVs. Sod2 depletion compromises mH₂O₂ production and bacterial killing. Thus, mitochondrial redox capacity enhances macrophage antimicrobial function by delivering mitochondria-derived effector molecules into bacteria-containing phagosomes.

Endurance training on rodent brain antioxidant capacity: A meta-analysis

The influence of physical exercise on brain antioxidant defense mechanisms has been studied. Nevertheless, the effect of training volume on the brain`s redox balance remains unclear. In this meta-analysis, we compared the effect of training volume on antioxidant enzymatic resource and lipid peroxidation on various brain regions. The activities of the enzymes glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) and the levels of thiobarbituric acid reactive substances (TBARS) were also evaluated. The effects of training periods (weeks) and exercise duration were compared. Meta-analysis revealed that protocols over 8 weeks were associated with an increase in SOD (p =  0.0008) and CAT activities (p =  0.0001). Exercise durations for 30 and 60 min were associated with higher CAT activity (p =  0.04). Joint analysis revealed that moderate physical exercise over 4 and 8 weeks promoted a healthy enzymatic balance. However, high volumes of exercise over 8 weeks were associated with the increased antioxidant enzymatic activity, indicating higher reactive oxygen species (ROS) levels. The data also indicated that there is still limited research and inaccurate information, on the safety conditions of training periods that simulate tests of ultra resistance in humans.

Sodium tanshinone IIA sulfonate protects ARPE-19 cells against oxidative stress by inhibiting autophagy and apoptosis

Oxidative stress in retinal pigment epithelium (RPE) is considered to be a major contributor to the development and progression of age-related macular degeneration (AMD). Previous investigations have shown that sodium tanshinone IIA sulfonate (STS) can alleviate oxidative stress in haemorrhagic shock-induced organ damage and cigarette smoke-induced chronic obstructive pulmonary disease in mice. However, whether STS has a protective effect in ARPE-19 cells under oxidative stress and its exact mechanisms have not yet been fully elucidated. In the present study, we utilized H₂O₂ to establish an oxidative stress environment. Our findings show that STS activated the PI3K/AKT/mTOR pathway to inhibit autophagy and diminished the expression of the autophagic proteins Beclin 1, ATG3, ATG7 and ATG9 in ARPE-19 cells under oxidative stress. Detection of the intrinsic apoptosis-related factors BAX, mitochondrial membrane potential (MMP), caspase-9, caspase-3 and BCL-2, as well as the extrinsic apoptosis-related factors c-FLIP, v-FLIP and caspase-8, confirmed that STS inhibited the intrinsic and extrinsic apoptotic pathways, and attenuated apoptosis in ARPE-19 cells under oxidative stress conditions. These findings shed new light on the protective effects of STS in ARPE-19 cells and its mechanisms under oxidative stress to provide novel and promising therapeutic strategies for AMD.

Crucial role of protein oligomerization in the pathogenesis of Alzheimer's and Parkinson's diseases

Misfolding and aggregation of the proteins amyloid-β, tau and alpha-synuclein is the predominant pathology underlying the neurodegenerative disorders, Alzheimer's and Parkinson's disease. While end stage insoluble products of aggregation have been well characterised in human and animal models of disease, accumulating evidence from biophysical, cellular and in vivo studies has shown that soluble intermediates of aggregation, or oligomers, may be the key species that mediate toxicity and underlie seeding and spreading in disease. Here, we review the process of protein misfolding, and the intrinsic and extrinsic processes that cause the native states of the key aggregating proteins to undergo conformational change to form oligomers and ultimately fibrils. We discuss the structural features of the key toxic intermediate, and describe the putative mechanisms by which oligomers may cause cell toxicity. Finally, we explore the potential therapeutic approaches raised by the oligomer hypothesis in neurodegenerative disease.

Sirtuin 1 Mediates Hydrogen Sulfide-induced Cytoprotection Effects in Neonatal Mouse Cardiomyocytes

Background:

Current knowledge indicates that oxidative damage and the following inflammation is pivotal pathway for myocardial cell death. In recent decades, hydrogen sulfide (H₂S) has been identified as a novel endogenous vasodilator and neuromodulator due to its antioxidation capacity. However, whether H₂S pretreatment in neonatal mouse cardiomyocytes is a protection effect against oxidative stress remains elusive.

Methods:

Primary neonatal mouse cardiomyocytes were isolated and cultured, subsequently, pretreated with the H₂S donor, sodium hydrosulfide (NaHS). Cell viability, lactate dehydrogenase (LDH) release, and reactive oxygen species (ROS) production are evaluated. The levels of superoxide dismutase (Sod2) and Sirtuin 1 (Sirt1), a deacetylation enzyme, were detected by Western blotting. The statistics was performed using independent-sample t-test.

Results:

NaHS (100 μmol/L) had no toxicity to primary neonatal mouse cardiomyocytes. Furthermore, NaHS pretreatment significantly improved neonatal mouse cardiomyocytes survival after H₂O₂-induced cell death, indicated by the decrease in LDH release (40.00 ± 2.65% vs. 65.33 ± 4.33%, P < 0.01) and ROS production (1.90 ± 0.33 vs. 4.56 ± 0.56, P < 0.05), and that the salubrious effect was accompanied by the upregulation of Sod2 expression. In addition, the study showed that NaHS pretreatment improved mitochondrial DNA number in neonatal mouse cardiomyocyte. Furthermore, the result demonstrated NaHS increased the expression of Sirt1 in neonatal mouse cardiomyocyte. Ex 527, an inhibitor of Sirt1, could attenuate these effects of NaHS-induced Sod2 expression and mtDNA number increase, furthermore, abrogate the cytoprotective effects of NaHS for neonatal mouse cardiomyocytes.

Conclusion:

Sirt1 mediated H₂S-induced cytoprotection effects in neonatal mouse cardiomyocytes.

13 reasons why the brain is susceptible to oxidative stress

The human brain consumes 20% of the total basal oxygen (O2) budget to support ATP intensive neuronal activity. Without sufficient O2 to support ATP demands, neuronal activity fails, such that, even transient ischemia is neurodegenerative. While the essentiality of O2 to brain function is clear, how oxidative stress causes neurodegeneration is ambiguous. Ambiguity exists because many of the reasons why the brain is susceptible to oxidative stress remain obscure. Many are erroneously understood as the deleterious result of adventitious O2 derived free radical and non-radical species generation. To understand how many reasons underpin oxidative stress, one must first re-cast free radical and non-radical species in a positive light because their deliberate generation enables the brain to achieve critical functions (e.g. synaptic plasticity) through redox signalling (i.e. positive functionality). Using free radicals and non-radical derivatives to signal sensitises the brain to oxidative stress when redox signalling goes awry (i.e. negative functionality). To advance mechanistic understanding, we rationalise 13 reasons why the brain is susceptible to oxidative stress. Key reasons include inter alia unsaturated lipid enrichment, mitochondria, calcium, glutamate, modest antioxidant defence, redox active transition metals and neurotransmitter auto-oxidation. We review RNA oxidation as an underappreciated cause of oxidative stress. The complex interplay between each reason dictates neuronal susceptibility to oxidative stress in a dynamic context and neural identity dependent manner. Our discourse sets the stage for investigators to interrogate the biochemical basis of oxidative stress in the brain in health and disease.

Altered homeostasis of trace elements in the blood of SCA2 patients

Spinocerebellar ataxia type 2 (SCA2) is a neurological disorder characterized by cerebellar dysfunction. The possible association between metals and neurodegenerative diseases is under constant investigation, with particular focus on their involvement in oxidative stress and their potential role as biomarkers of these pathologies. Whole blood samples of SCA2 patients and of healthy individuals were subjected to multi-elemental analysis by inductively coupled plasma-mass spectrometry (ICP-MS). Reduced levels of manganese and copper were found in SCA2 patients, while zinc and vanadium concentrations were significantly higher in patients compared to controls. Copper, manganese and zinc are cofactors of many enzymes (such as superoxide dismutase, SOD) involved in the cellular antioxidant response, whereas vanadium is a transition metal able to produce reactive radicals. A marked decrease of the antioxidant response has been previously reported in SCA2 patients. We suggest that an unbalance of transitional elements in the blood may reflect altered antioxidant homeostasis in SCA2 patients and could constitute a future peripheral biomarker for this disease. In addition, we suggest a possible role of vanadium in the altered lipid metabolism of SCA2 patients.

Implications of PI3K/AKT/PTEN Signaling on Superoxide Dismutases Expression and in the Pathogenesis of Alzheimer's Disease

Alzheimer’s disease is a neurodegenerative sickness, where the speed of personal disease progression differs prominently due to genetic and environmental factors such as life style. Alzheimer’s disease is described by the construction of neuronal plaques and neurofibrillary tangles composed of phosphorylated tau protein. Mitochondrial dysfunction may be a noticeable feature of Alzheimer’s disease and increased production of reactive oxygen species has long been described. Superoxide dismutases (SODs) protect from excess reactive oxygen species to form less reactive hydrogen peroxide. It is suggested that SODs can play a protective role in neurodegeneration. In addition, PI3K/AKT pathway has been shown to play a critical role on the neuroprotection and inhibiting apoptosis via the enhancing expression of the SODs. This pathway appears to be crucial in Alzheimer’s disease because it is related to the tau protein hyper-phosphorylation. Dietary supplementation of several ordinary compounds may provide a novel therapeutic approach to brain disorders by modulating the function of the PI3K/AKT pathway. Understanding these systems may offer a better efficacy of new therapeutic approaches. In this review, we summarize recent progresses on the involvement of the SODs and PI3K/AKT pathway in neuroprotective signaling against Alzheimer’s disease.

Long-lived rodents reveal signatures of positive selection in genes associated with lifespan

The genetics of lifespan determination is poorly understood. Most research has been done on short-lived animals and it is unclear if these insights can be transferred to long-lived mammals like humans. Some African mole-rats (Bathyergidae) have life expectancies that are multiple times higher than similar sized and phylogenetically closely related rodents. To gain new insights into genetic mechanisms determining mammalian lifespans, we obtained genomic and transcriptomic data from 17 rodent species and scanned eleven evolutionary branches associated with the evolution of enhanced longevity for positively selected genes (PSGs). Indicating relevance for aging, the set of 250 identified PSGs showed in liver of long-lived naked mole-rats and short-lived rats an expression pattern that fits the antagonistic pleiotropy theory of aging. Moreover, we found the PSGs to be enriched for genes known to be related to aging. Among these enrichments were “cellular respiration” and “metal ion homeostasis”, as well as functional terms associated with processes regulated by the mTOR pathway: translation, autophagy and inflammation. Remarkably, among PSGs are RHEB, a regulator of mTOR, and IGF1, both central components of aging-relevant pathways, as well as genes yet unknown to be aging-associated but representing convincing functional candidates, e.g. RHEBL1, AMHR2, PSMG1 and AGER. Exemplary protein homology modeling suggests functional consequences for amino acid changes under positive selection. Therefore, we conclude that our results provide a meaningful resource for follow-up studies to mechanistically link identified genes and amino acids under positive selection to aging and lifespan determination.

As an adaption to different environments rodents have evolved a wide range of lifespans. While most rodents are short-lived, along several phylogenetic branches long-lived species evolved. This provided us a unique opportunity to search for genes that are associated with enhanced longevity in mammals. Towards this, we computationally compared gene sequences of exceptional long-lived rodent species (like the naked mole-rat and chinchilla) and short-lived rodents (like rat and mouse) and identified those which evolved exceptional fast. As natural selection acts in parallel on a multitude of phenotypes, only a subset of the identified genes is probably associated with enhanced longevity. Applying several tests, we ensured that the dataset is related to aging. We conclude that lifespan extension in rodents can be attributed to changes in their defense against free radicals, iron homeostasis as well as cellular respiration and translation as central parts of the growth program. This confirms aging theories assuming a tradeoff between fast growth and long lifespan. Moreover, our study offers a meaningful resource of targets, i.e. genes and specific positions therein, for functional follow-up studies on their potential roles in the determination of lifespan–regardless whether they are currently known to be aging-related or not.

Susceptibility to Oxidative Stress Is Determined by Genetic Background in Neuronal Cell Cultures

Traumatic brain injury (TBI) leads to a deleterious and multifactorial secondary inflammatory response in the brain. Oxidative stress from the inflammation likely contributes to the brain damage although it is unclear to which extent. A largely unexplored approach is to consider phenotypic regulation of oxidative stress levels. Genetic polymorphism influences inflammation in the central nervous system and it is possible that the antioxidative response differs between phenotypes and affects the severity of the secondary injury. We therefore compared the antioxidative response in inbred rat strains dark agouti (DA) to piebald viral glaxo (PVG). DA has high susceptibility to inflammatory challenges and PVG is protected. Primary neuronal cell cultures were exposed to peroxynitrite (ONOO^-), nitric oxide (NO), superoxide (O₂^-), and 4-hydroxynonenal (4-HNE). Our findings demonstrated a phenotypic control of the neuronal antioxidative response, specific to manganese O₂^- dismutase (MnSOD). DA neurons had increased levels of MnSOD, equal levels of peroxiredoxin 5 (PRDX5), decreased oxidative stress markers 3-nitrotyrosine (3-NT) and 4-HNE and decreased neuronal death detected by lactate dehydrogenase (LDH) release after 24 h, and higher oxidative stress levels by CellROX than PVG after 2 h. It is possible that DA neurons had a phenotypic adaptation to a fiercer inflammatory environment. ONOO^- was confirmed as the most powerful oxidative damage mediator, while 4-HNE caused few oxidative effects. Inducible NO synthase (iNOS) was not induced, suggesting that inflammatory, while not oxidative stimulation was required. These findings indicate that phenotypic antioxidative regulation affects the secondary inflammation, which should be considered in future individualized treatments and when evaluating antioxidative pharmacological interventions.

Mitochondrial Molecular Abnormalities Revealed by Proteomic Analysis of Hippocampal Organelles of Mice Triple Transgenic for Alzheimer Disease

Mitochondrial dysfunction is implicated in the pathogenesis of Alzheimer's disease (AD). However, the precise mitochondrial molecular deficits in AD remain poorly understood. Mitochondrial and nuclear proteomic analysis in mature male triple transgenic AD mice (PS1M146V/APPSwe/TauP301L) by two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) coupled with MALDI-TOF-MS/MS, bio-informatics analysis and immunofluorescent staining were performed in this study. In addition to impaired spatial memory impairment and intracellular accumulation of amyloid 1-42 (Aβ1-42) in the 3xTg-AD mice, a well-accepted mouse model of the human disease, we also found significantly increased DNA oxidative damage in entorhinal cortex, hippocampal CA1, CA3 and dental gyrus (DG), as evidenced by the positive staining of 8-hydroxyguanosine, a biomarker of mild cognitive impairment early in AD. We identified significant differences in 27 hippocampal mitochondrial proteins (11 increased and 16 decreased), and 37 hippocampal nuclear proteins (12 increased and 25 decreased) in 3xTg-AD mice compared with the wild-type (WT) mice. Differentially expressed mitochondrial and nuclear proteins were mainly involved in energy metabolism (>55%), synapses, DNA damage, apoptosis and oxidative stress. Two proteins were differentially expressed in both hippocampal mitochondria and nuclei, namely electron transport chain (ETC)-related protein ATP synthase subunit d (ATP5H) was significantly decreased, and apoptosis-related dynamin-1 (DYN1), a pre-synaptic and mitochondrial division-regulated protein that was significantly increased. In sum, perturbations of hippocampus mitochondrial energy metabolism-related proteins responsible for ATP generation via oxidation phosphorylation (OXPHOS), especially nuclear-encoded OXPHOS proteins, correlated with the amyloid-associated cognitive deficits of this murine AD model. The molecular changes in respiratory chain-related proteins and DYN1 may represent novel biomarkers of AD.

The Antioxidant Effect of Rosmarinic Acid by Different Delivery Routes in the Animal Model of Noise-Induced Hearing Loss

HYPOTHESIS

Trans-tympanic Rosmarinic Acid (RA), as compared with the systemic administration, protects against noise-induced auditory hair cell and hearing losses in rats in vivo.

BACKGROUND

ROS production, lipoperoxidative damage, and an imbalance of antioxidant defences play a significant role in noise-induced hearing loss. Several molecules with antioxidant properties have been tested to restore redox homeostasis; however, drug delivery system represents a challenge for their effectiveness. In our model, acute and intense noise exposure induces hearing loss, hair cell death, and oxidative stress, with an increase in superoxide production and over-expression of lipid peroxidation in cochlear structures.

METHODS

RA was administrated in male Wistar rats by trans-tympanic (20 μl) and systemic (10 mg/kg) modality. In systemic administration, RA was injected 1 hour before noise exposure and once daily for the following 3 days. ABRs were measured before and at days 1, 3, 7, and 30 after noise exposure. Rhodamine-phalloidin staining, dihydroethidium and 8-isoprostane immunostainings were performed to assess and quantify outer hair cells loss, superoxide production, and lipid peroxidation in the different experimental groups.

RESULTS

Systemic RA administration significantly decreased noise-induced hearing loss and the improvement of auditory function was paralleled by a significant reduction in cochlear oxidative stress. The trans-tympanic modality of drug administration showed a similar degree of protection both at the functional and morphological levels.

CONCLUSION

The effectiveness of RA given via trans-tympanic injection could be interesting for the future application of this minimally-invasive procedure in the treatment of ROS-induced hearing loss.

Sex differences in brain mitochondrial metabolism: influence of endogenous steroids and stroke

Steroids are neuroprotective and a growing body of evidence indicates that mitochondria are a potential target of their effects. The mitochondria are the site of cellular energy synthesis, regulate oxidative stress and play a key role in cell death after brain injury and neurodegenerative diseases. After providing a summary of the literature on the general functions of mitochondria and the effects of sex steroid administrations on mitochondrial metabolism, we summarise and discuss our recent findings concerning sex differences in brain mitochondrial function under physiological and pathological conditions. To analyse the influence of endogenous sex steroids, the oxidative phosphorylation system, mitochondrial oxidative stress and brain steroid levels were compared between male and female mice, either intact or gonadectomised. The results obtained show that females have higher a mitochondrial respiration and lower oxidative stress compared to males and also that these differences were suppressed by ovariectomy but not orchidectomy. We have also shown that the decrease in brain mitochondrial respiration induced by ischaemia/reperfusion is different according to sex. In both sexes, treatment with progesterone reduced the ischaemia/reperfusion-induced mitochondrial alterations. Our findings indicate sex differences in brain mitochondrial function under physiological conditions, as well as after stroke, and identify mitochondria as a target of the neuroprotective properties of progesterone. Thus, it is necessary to investigate sex specificity in brain physiopathological mechanisms, especially when mitochondria impairment is involved.

The Interrelation between Reactive Oxygen Species and Autophagy in Neurological Disorders

Neurological function deficits due to cerebral ischemia or neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) have long been considered a thorny issue in clinical treatment. Recovery after neurologic impairment is fairly limited, which poses a major threat to health and quality of life. Accumulating evidences support that ROS and autophagy are both implicated in the onset and development of neurological disorders. Notably, oxidative stress triggered by excess of ROS not only puts the brain in a vulnerable state but also enhances the virulence of other pathogenic factors, just like mitochondrial dysfunction, which is described as the culprit of nerve cell damage. Nevertheless, autophagy is proposed as a subtle cellular defense mode against destructive stimulus by timely removal of damaged and cytotoxic substance. Emerging evidence suggests that the interplay of ROS and autophagy may establish a determinant role in the modulation of neuronal homeostasis. However, the underlying regulatory mechanisms are still largely unexplored. This review sets out to afford an overview of the crosstalk between ROS and autophagy and discusses relevant molecular mechanisms in cerebral ischemia, AD, and PD, so as to provide new insights into promising therapeutic targets for the abovementioned neurological conditions.

Severe oxidative stress in an acute inflammatory demyelinating model in the rhesus monkey

Oxidative stress is increasingly implicated as a co-factor of tissue injury in inflammatory/demyelinating disorders of the central nervous system (CNS), such as multiple sclerosis (MS). While rodent experimental autoimmune encephalomyelitis (EAE) models diverge from human demyelinating disorders with respect to limited oxidative injury, we observed that in a non-human primate (NHP) model for MS, namely EAE in the common marmoset, key pathological features of the disease were recapitulated, including oxidative tissue injury. Here, we investigated the presence of oxidative injury in another NHP EAE model, i.e. in rhesus macaques, which yields an acute demyelinating disease, which may more closely resemble acute disseminated encephalomyelitis (ADEM) than MS. Rhesus monkey EAE diverges from marmoset EAE by abundant neutrophil recruitment into the CNS and destructive injury to white matter. This difference prompted us to investigate to which extent the oxidative pathway features elicited in MS and marmoset EAE are reflected in the acute rhesus monkey EAE model. The rhesus EAE brain was characterized by widespread demyelination and active lesions containing numerous phagocytic cells and to a lesser extent T cells. We observed induction of the oxidative stress pathway, including injury, with a predilection of p22phox expression in neutrophils and macrophages/microglia. In addition, changes in iron were observed. These results indicate that pathogenic mechanisms in the rhesus EAE model may differ from the marmoset EAE and MS brain due to the neutrophil involvement, but may in the end lead to similar induction of oxidative stress and injury.

Chronic traumatic encephalopathy-integration of canonical traumatic brain injury secondary injury mechanisms with tau pathology

In recent years, a new neurodegenerative tauopathy labeled Chronic Traumatic Encephalopathy (CTE), has been identified that is believed to be primarily a sequela of repeated mild traumatic brain injury (TBI), often referred to as concussion, that occurs in athletes participating in contact sports (e.g. boxing, American football, Australian football, rugby, soccer, ice hockey) or in military combatants, especially after blast-induced injuries. Since the identification of CTE, and its neuropathological finding of deposits of hyperphosphorylated tau protein, mechanistic attention has been on lumping the disorder together with various other non-traumatic neurodegenerative tauopathies. Indeed, brains from suspected CTE cases that have come to autopsy have been confirmed to have deposits of hyperphosphorylated tau in locations that make its anatomical distribution distinct for other tauopathies. The fact that these individuals experienced repetitive TBI episodes during their athletic or military careers suggests that the secondary injury mechanisms that have been extensively characterized in acute TBI preclinical models, and in TBI patients, including glutamate excitotoxicity, intracellular calcium overload, mitochondrial dysfunction, free radical-induced oxidative damage and neuroinflammation, may contribute to the brain damage associated with CTE. Thus, the current review begins with an in depth analysis of what is known about the tau protein and its functions and dysfunctions followed by a discussion of the major TBI secondary injury mechanisms, and how the latter have been shown to contribute to tau pathology. The value of this review is that it might lead to improved neuroprotective strategies for either prophylactically attenuating the development of CTE or slowing its progression.

The antiepileptic drug levetiracetam promotes neuroblast differentiation and expression of superoxide dismutase in the mouse hippocampal dentate gyrus via PI3K/Akt signalling

Levetiracetam (LEV), a second-generation antiepileptic drug, is commonly prescribed to treat certain types of seizures. Few studies have investigated the effects of LEV on hippocampal neurogenesis and its related mechanisms. In the present study, we investigated the effects of LEV on cell proliferation and neuronal differentiation in the mouse hippocampal dentate gyrus (DG). We here demonstrate a dose-dependent increase in Ki-67-immunoreactive cells in the subgranular zone of the DG in LEV-treated mice, and doublecortin-immunoreactive cells were also significantly increased in the hippocampal DG of mice treated with LEV. The above results indicate that LEV could improve cell proliferation and neuroblast differentiation in the hippocampus. In addition, we also found that LEV treatment improved superoxide dismutase (SOD)2, catalase and Gpx-1 levels and increased phosphatidylinositol 3-kinase (PI3K) and phosphorylated Akt protein levels in the hippocampus. Further investigation of the molecular mechanisms underlying these effects revealed that PC12 cell was blocked by a pharmacological inhibitor of PI3K (LY294002), and that LEV treatment rapidly activated PI3K/Akt and SOD2, catalase and Gpx-1. In brief, our results indicate that LEV enhanced cell proliferation and neuroblast differentiation by increasing the expression of antioxidants and PI3K and the level of phosphorylated Akt in the mouse hippocampus.

Chronic Ethanol Metabolism Inhibits Hepatic Mitochondrial Superoxide Dismutase via Lysine Acetylation

BACKGROUND

Chronic ethanol (EtOH) consumption is a major cause of liver disease worldwide. Oxidative stress is a known consequence of EtOH metabolism and is thought to contribute significantly to alcoholic liver disease (ALD). Therefore, elucidating pathways leading to sustained oxidative stress and downstream redox imbalances may reveal how EtOH consumption leads to ALD. Recent studies suggest that EtOH metabolism impacts mitochondrial antioxidant processes through a number of proteomic alterations, including hyperacetylation of key antioxidant proteins.

METHODS

To elucidate mechanisms of EtOH-induced hepatic oxidative stress, we investigate a role for protein hyperacetylation in modulating mitochondrial superoxide dismutase (SOD2) structure and function in a 6-week Lieber-DeCarli murine model of EtOH consumption. Our experimental approach includes immunoblotting immunohistochemistry (IHC), activity assays, mass spectrometry, and in silico modeling.

RESULTS

We found that EtOH metabolism significantly increased the acetylation of SOD2 at 2 functionally relevant lysine sites, K68 and K122, resulting in a 40% decrease in enzyme activity while overall SOD2 abundance was unchanged. In vitro studies also reveal which lysine residues are more susceptible to acetylation. IHC analysis demonstrates that SOD2 hyperacetylation occurs near zone 3 within the liver, which is the main EtOH-metabolizing region of the liver.

CONCLUSIONS

Overall, the findings presented in this study support a role for EtOH-induced lysine acetylation as an adverse posttranslational modification within the mitochondria that directly impacts SOD2 charge state and activity. Last, the data presented here indicate that protein hyperacetylation may be a major factor contributing to an imbalance in hepatic redox homeostasis due to chronic EtOH metabolism.

Glaucoma may be a non-memory manifestation of Alzheimer's disease in older people

BACKGROUND

The purpose of this paper was to examine whether glaucoma could be a non-memory manifestation of Alzheimer's disease in older people.

METHODS

We conducted a population-based, retrospective, case-control study to analyze the database of the Taiwan National Health Insurance Program. There were 1,351 subjects ≥65 years old with newly diagnosed Alzheimer's disease as the cases, and 5,329 subjects without any type of dementias as the controls during 2000-2011. The odds ratio (OR) and 95% confidence interval (CI) for the risk of Alzheimer's disease associated with glaucoma was estimated by the multivariable unconditional logistic regression model.

RESULTS

After controlling for confounders, the multivariable logistic regression model demonstrated that the adjusted OR of Alzheimer's disease was 1.50 in subjects with glaucoma (95% CI 1.19, 1.89), compared to subjects without glaucoma.

CONCLUSIONS

Older people with glaucoma are associated with 1.5-fold increased odds of Alzheimer's disease in Taiwan. Glaucoma may be a non-memory manifestation of Alzheimer's disease in older people. Further research is needed to confirm this issue.