Mitochondria, aging and longevity--a new perspective

Empowering Melatonin Therapeutics with Drosophila Models

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

Tumor suppressive role of mitochondrial sirtuin 4 in induction of G2/M cell cycle arrest and apoptosis in hepatitis B virus-related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is developed from uncontrolled cell growth after the malignant transformation of hepatocytes. The hepatitis B virus (HBV) X protein (HBx) has shown to induce cell cycle progression and hepatocarcinogenesis. A sub-fraction of HBx is localized in the mitochondria. Sirtuin 4 (SIRT4), a mitochondrial protein, has been demonstrated to play a tumor-suppressive role in many cancers, including HCC. However, little is known about the association between mitochondrial HBx and SIRT4 during hepatocarcinogenesis. We aimed to investigate the clinical significance and functional role of SIRT4 in HBV-related HCC. SIRT4 expression was significantly lower in the HCC tissues collected from 30 patients with HBV-related HCC than in normal liver tissues from control patients (p < 0.0001). TCGA data analysis indicated that SIRT4 expression was also lower in patients with HBV infection than in those without, and SIRT4 levels were positively associated with better patient survival. Similarly, HCC cell lines had lower SIRT4 expression than normal liver cell lines (all p < 0.01). Among the HCC cell lines, those harbored HBV had a lower SIRT4 expression than those without HBV (p < 0.0001). In vitro experiments revealed that stable HBx transfection suppressed SIRT4 expression in both HepG2 and Huh7 cells (both p < 0.001). Ectopic SIRT4 overexpression alone could induce cellular senescence through arresting cell-cycle progression at G2/M, and inducing cell apoptosis in HCC cells. Mechanistically, SIRT4 upregulated cell-cycle governing genes p16 and p21 protein expression, suppressed CyclinB1/Cdc2 and Cdc25c which normally induce cell-cycle progression, and suppressed survivin to induce apoptosis. Our findings demonstrate the interaction between HBV and SIRT4 in the context of HCC. SIRT4 involves in G2/M DNA damage checkpoint control and genomic stability in hepatocarcinogenesis, which could be targeted for future anticancer strategies.

The Protective Effects of Levetiracetam on a Human iPSCs-Derived Spinal Muscular Atrophy Model

Spinal muscular atrophy (SMA) is an inherited disease characterized by progressive motor neuron death and subsequent muscle weakness and is caused by deletion or mutation of survival motor neuron (SMN) 1 gene. Protecting spinal motor neuron is an effective clinical strategy for SMA. The purpose of this study was to investigate the potential effect of an anti-epileptic drug levetiracetam on SMA. In the present study, we used differentiated spinal motor neurons (MNs) from SMA patient-derived induced pluripotent stem cells (SMA-iPSCs) to investigate the effect of levetiracetam. Levetiracetam promoted neurite elongation in SMA-iPSCs-MNs. TUNEL-positive spinal motor neurons were significantly reduced by levetiracetam in SMA-iPSCs-MNs. In addition, the expression level of cleaved-caspase 3 was decreased by levetiracetam in SMA-iPSCs-MNs. Furthermore, levetiracetam improved impaired mitochondrial function in SMA-iPSCs-MNs. On the other hand, levetiracetam did not affect the expression level of SMN protein in SMA-iPSCs-MNs. These findings indicate that levetiracetam has a neuroprotective effect for SMA.

Plant-derived mitochondria-targeting cysteine-rich peptide modulates cellular bioenergetics

Mitochondria are attractive therapeutic targets for developing agents to delay age-related frailty and diseases. However, few promising leads have been identified from natural products. Previously, we identified roseltide rT1, a hyperstable 27-residue cysteine-rich peptide from Hibiscus sabdariffa, as a knottin-type neutrophil elastase inhibitor. Here, we show that roseltide rT1 is also a cell-penetrating, mitochondria-targeting peptide that increases ATP production. Results from flow cytometry, live-cell imaging, pulldown assays, and genetically-modified cell lines supported that roseltide rT1 enters cells via glycosaminoglycan-dependent endocytosis, and enters the mitochondria through TOM20, a mitochondrial protein import receptor. We further showed that roseltide rT1 increases cellular ATP production via mitochondrial membrane hyperpolarization. Using biotinylated roseltide rT1 for target identification and proteomic analysis, we showed that human mitochondrial membrane ATP synthase subunit O is an intramitochondrial target. Collectively, these data support our discovery that roseltide rT1 is a first-in-class mitochondria-targeting, cysteine-rich peptide with potentials to be developed into tools to further our understanding of mitochrondria-related diseases.

The mitochondrial genome of Muga silkworm (Antheraea assamensis) and its comparative analysis with other lepidopteran insects

Muga (Antheraea assamensis) is an economically important silkmoth endemic to the states of Assam and Meghalaya in India and is the producer of the strongest known commercial silk. However, there is a scarcity of genomic and proteomic data for understanding the organism at a molecular level. Our present study is on decoding the complete mitochondrial genome (mitogenome) of A. assamensis using next generation sequencing technology and comparing it with other available lepidopteran mitogenomes. Mitogenome of A. assamensis is an AT rich circular molecule of 15,272 bp (A+T content ~80.2%). It contains 37 genes comprising of 13 protein coding genes (PCGs), 22 tRNA and 2 rRNA genes along with a 328 bp long control region. Its typical tRNA^Met-tRNA^Ile-tRNA^Gln arrangement differed from ancestral insects (tRNA^Ile-tRNA^Gln-tRNA^Met). Two PCGs cox1 and cox2 were found to have CGA and GTG as start codons, respectively as reported in some lepidopterans. Interestingly, nad4l gene showed higher transversion mutations at intra-species than inter-species level. All PCGs evolved under strong purifying selection with highest evolutionary rates observed for atp8 gene while lowest for cox1 gene. We observed the typical clover-leaf shaped secondary structures of tRNAs with a few exceptions in case of tRNA^Ser1 and tRNA^Tyr where stable DHU and TΨC loop were absent. A significant number of mismatches (35) were found to spread over 19 tRNA structures. The control region of mitogenome contained a six bp (CTTAGA/G) deletion atypical of other Antheraea species and lacked tandem repeats. Phylogenetic position of A. assamensis was consistent with the traditional taxonomic classification of Saturniidae. The complete annotated mitogenome is available in GenBank (Accession No. KU379695). To the best of our knowledge, this is the first report on complete mitogenome of A. assamensis.

Quercetin-mediated synthesis of graphene oxide-silver nanoparticle nanocomposites: a suitable alternative nanotherapy for neuroblastoma

Background

Graphene and graphene-related materials have gained substantial interest from both academia and industry for the development of unique nanomaterials for biomedical applications. Graphene oxide (GO) and silver nanoparticles (AgNPs) are a valuable platform for the development of nanocomposites, permitting the combination of nanomaterials with different physical and chemical properties to generate novel materials with improved and effective functionalities in a single platform. Therefore, this study was conducted to synthesize a graphene oxide–silver nanoparticle (GO-AgNPs) nanocomposite using the biomolecule quercetin and evaluate the potential cytotoxicity and mechanism of GO-AgNPs in human neuroblastoma cancer cells (SH-SY5Y).

Methods

The synthesized GO-AgNPs were characterized using various analytical techniques. The potential toxicities of GO-AgNPs were evaluated using a series of biochemical and cellular assays. The expression of apoptotic and anti-apoptotic genes was measured by quantitative real-time reverse transcription polymerase chain reaction. Further, apoptosis was confirmed by caspase-9/3 activity and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and GO-AgNPs-induced autophagy was also confirmed by transmission electron microscopy.

Results

The prepared GO-AgNPs exhibited significantly higher cytotoxicity toward SH-SY5Y cells than GO. GO-AgNPs induced significant cytotoxicity in SH-SY5Y cells by the loss of cell viability, inhibition of cell proliferation, increased leakage of lactate dehydrogenase, decreased level of mitochondrial membrane potential, reduced numbers of mitochondria, enhanced level of reactive oxygen species generation, increased expression of pro-apoptotic genes, and decreased expression of anti-apoptotic genes. GO-AgNPs induced caspase-9/3-dependent apoptosis via DNA fragmentation. Finally, GO-AgNPs induced accumulation of autophagosomes and autophagic vacuoles.

Conclusion

In this study, we developed an environmentally friendly, facile, dependable, and simple method for the synthesis of GO-AgNPs nanocomposites using quercetin. The synthesized GO-AgNPs exhibited enhanced cytotoxicity compared with that of GO at very low concentrations. This study not only elucidates the potential cytotoxicity against neuroblastoma cancer cells, but also reveals the molecular mechanism of toxicity.

HBx co-localizes with COXIII in HL-7702 cells to upregulate mitochondrial function and ROS generation

Hepatocellular carcinoma (HCC) is one of the most common malignant diseases, and HBx leads to the development of HBV-associated HCC. Mitochondria are key organelles that regulate apoptosis, cellular energetics and signal transduction pathways, and are the source of HBx-induced reactive oxygen species (ROS). Recent findings have shown that HBx interacts with the inner mitochondrial membrane protein, COXIII, via the yeast two-hybrid system, mating experiment and coimmunoprecipitation. The aim of the present study was to examine the co-localizaiton of HBx and COXIII in HL-7702 cells and to investigate ensuing alterations of mitochondrial function. An HL-7702 cell line stably expressing the HBx gene by lentivirus vectors was constructed. Confocal microscopy was utilized to assess the interaction between HBx protein and COXIII. Expression of COXIII, activities of cytochrome c oxidase (COX) and the mitochondrial membrane potential, which were functionally relevant to the HBx protein-COXIII interaction, were investigated in cell cultures. Moreover, the intracellular ROS levels were detected by flow cytometry. The results demonstrated that HBx co-localized with the inner mitochondrial protein, COXIII, in HL-7702 cells, causing the upregulation of COXIII protein expression as well as COX activity. However, HBx did not alter the mitochondrial membrane potential and mitochondria exhibited only slight swelling in HL-7702-HBx cells. Moreover, HBx elevated the generation of mitochondrial ROS in HL-7702-HBx cells. The main finding of the present study was that the co-localization of HBx and COXIII leads to upregulation of the mitochondrial function and ROS generation, which are associated with the oncogenesis of HBV-associated HCC.

Transmission from centenarians to their offspring of mtDNA heteroplasmy revealed by ultra-deep sequencing

The role that mtDNA heteroplasmy plays in healthy aging, familial longevity and the heritability patterns of low levels heteroplasmy in the elderly are largely unknown. We analyzed the low levels of mtDNA heteroplasmy in blood in a cohort of centenarians, their offspring and a group of offspring of non long-lived parents, characterized by a less favorable health phenotype. The aims of this study are to: (i) investigate the transmission of low level heteroplasmies in the elderly; (ii) explore the association of heteroplasmy with age and longevity and (iii) investigate heteroplasmy patterns in these three groups. We sequenced a 853 bp mtDNA fragment in 88 individuals to an average coverage of 49334-fold, using quality control filtering and triplicate PCR analysis to reduce any methodological bias, and we detected 119 heteroplasmic positions with a minor allele frequency ≥ 0.2%. The results indicate that low-level heteroplasmies are transmitted and maintained within families until extreme age. We did not find any heteroplasmic variant associated with longevity and healthy aging but we identified an unique heteroplasmy profile for each family, based on total level and positions. This familial profile suggests that heteroplasmy may contribute to familial longevity.

Circadian (about 24-hour) variation in malondialdehyde content and catalase activity of mouse erythrocytes

Lipid peroxidation is a part of normal metabolism that may cause biological molecule damage leading to the formation of several specific metabolites that include aldehydes of variable chains, such as malondialdehyde (MDA). These biological effects are controlled in vivo by a wide spectrum of enzymatic and non-enzymatic defense mechanisms among which catalase (CAT) is considered as an important regulator of oxidative stress. The present study aimed to investigate the possible relationship between the temporal patterns of the formation of MDA and the activity of CAT in the erythrocytes of mice. Twenty-four-hour studies were performed on male Swiss albino mice, 12 weeks old, synchronized to a 12:12 light: dark cycle for 3 weeks. Different and comparable groups of animals (n = 10) were sacrificed at an interval of 4 hours (1, 5, 9, 13, 17, and 21 hours after light onset (HALO)). The levels of erythrocyte MDA concentration and CAT activity both significantly (analysis of variance: F = 6.4, P < 0.002) varied according to the time of sampling under non-stressed conditions. The characteristics of the waveform describing the temporal patterns differed between the two studied variables, e.g. MDA content showing one peak (≅21 HALO) and CAT activity showing three peaks (≅9, 17, and 21 HALO). Cosinor analysis revealed a significant (adjusted Cosinor: P ≤ 0.018) circadian (τ ≅ 24 hours) rhythm in MDA level and no statistically significant rhythmicity in CAT activity. The differences and the absence of correlation between the curve patterns of erythrocyte MDA content and CAT activity under physiological conditions are hypothesized to explain that variation in lipid peroxidation may depend on several factors. Moreover, the identification of peak/trough levels of MDA accumulation in erythrocytes may reflect the degree of oxidative stress in these blood cells. In addition, the observed significant time-of-day effect suggests that, in both clinical and scientific settings, appropriate comparison of MDA production and CAT activity levels can only be achieved on data obtained at the same time of day.

The co-localization of HBx and COXIII upregulates COX-2 promoting HepG2 cell growth

HBx is a multifunctional regulator that interacts with host factors to contribute to the development of hepatocellular carcinoma. In this study, to explore the co-localization of HBx and COXIII in HepG2 cells and to investigate the molecular mechanism of HBx in HepG2 cell growth promotion, we first constructed a HepG2 cell line stably expressing the HBx gene in vitro by lentivirus vectors. In addition, we found that HBx co-localized with the inner mitochondrial protein, COXIII, in HepG2 cells by confocal laser scanning microscopy. It led to changes of mitochondrial biogenesis and morphology, including upregulation of COXIII protein expression, increased cytochrome c oxidase activity and higher mitochondrial membrane potential. The upregulation of COX-2 caused by HBx through generation of mitochondrial reactive oxygen species promoted cell growth. Thus, we conclude that co-localization of HBx and COXIII leads to upregulation of COX-2 that promotes HepG2 cell growth. Such a mechanism provides deeper insights into the molecular mechanism of HBV-associated hepatocellular carcinoma.

Mitochondrial membrane lipid remodeling in pathophysiology: a new target for diet and therapeutic interventions

Mitochondria are arbiters in the fragile balance between cell life and death. These organelles present an intricate membrane system, with a peculiar lipid composition and displaying transverse as well as lateral asymmetry. Some lipids are synthesized inside mitochondria, while others have to be imported or acquired in the form of precursors. Here, we review different processes, including external interventions (e.g., diet) and a range of biological events (apoptosis, disease and aging), which may result in alterations of mitochondrial membrane lipid content. Cardiolipin, the mitochondria lipid trademark, whose biosynthetic pathway is highly regulated, will deserve special attention in this review. The modulation of mitochondrial membrane lipid composition, especially by diet, as a therapeutic strategy for the treatment of some pathologies will be also addressed.

Apoptosis and other immune biomarkers predict influenza vaccine responsiveness

Despite the importance of the immune system in many diseases, there are currently no objective benchmarks of immunological health. In an effort to identifying such markers, we used influenza vaccination in 30 young (20-30 years) and 59 older subjects (60 to >89 years) as models for strong and weak immune responses, respectively, and assayed their serological responses to influenza strains as well as a wide variety of other parameters, including gene expression, antibodies to hemagglutinin peptides, serum cytokines, cell subset phenotypes and in vitro cytokine stimulation. Using machine learning, we identified nine variables that predict the antibody response with 84% accuracy. Two of these variables are involved in apoptosis, which positively associated with the response to vaccination and was confirmed to be a contributor to vaccine responsiveness in mice. The identification of these biomarkers provides new insights into what immune features may be most important for immune health.

Behavior genetics and postgenomics

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. According to three widely held dogmas, DNA is the unchanging template of heredity, is identical in all the cells and tissues of the body, and is the sole agent of inheritance. Rather than being an unchanging template, DNA appears subject to a good deal of environmentally induced change. Instead of identical DNA in all the cells of the body, somatic mosaicism appears to be the normal human condition. And DNA can no longer be considered the sole agent of inheritance. We now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, epigenetic regulation, DNA variability, and somatic mosaicism appear to be particularly prevalent in the human brain and probably are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period and, in particular, in enabling phenotypic plasticity in offspring. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of minimal shared maternal effects, in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology.

Expression of oxidative phosphorylation components in mitochondria of long-living Ames dwarf mice

Reduced signaling of the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) pathway is associated with extended life span in several species. Ames dwarf mice are GH-deficient and live >50% longer than wild-type littermates. Previously, we have shown that tissues from Ames mice exhibit elevated levels of antioxidative enzymes, less H(2)O(2) production, and lower oxidative damage suggesting that mitochondrial function may differ between genotypes. To explore the relationship between hormone deficiency and mitochondria in mice with extended longevity, we evaluated activity, protein, and gene expression of oxidative phosphorylation components in dwarf and wild-type mice at varying ages. Liver complex I + III activity was higher in dwarf mice compared to wild-type mice. The activity of I + III decreased between 3 and 20 months of age in both genotypes with greater declines in wild-type mice in liver and skeletal muscle. Complex IV activities in the kidney were elevated in 3- and 20-month-old dwarf mice relative to wild-type mice. In Ames mice, protein levels of the 39 kDa complex I subunit were elevated at 20 months of age when compared to wild-type mouse mitochondria for every tissue examined. Kidney and liver mitochondria from 20-month-old dwarf mice had elevated levels of both mitochondrially-encoded and nuclear-encoded complex IV proteins compared to wild-type mice (p < 0.05). Higher liver ANT1 and PGC-1α mRNA levels were also observed in dwarf mice. Overall, we found that several components of the oxidative phosphorylation (OXPHOS) system were elevated in Ames mice. Mitochondrial to nuclear DNA ratios were not different between genotypes despite the marked increase in PGC-1α levels in dwarf mice. The increased OXPHOS activities, along with lower ROS production in dwarf mice, predict enhanced mitochondrial function and efficiency, two factors likely contributing to long-life in Ames mice.

An investigation of the effects of MitoQ on human peripheral mononuclear cells

MitoQ is a ubiquinone derivative targeted to mitochondria which is known to have both antioxidant and anti-apoptotic properties within mammalian cells. Previous research has suggested that the age-related increase in oxidative DNA damage in T lymphocytes might contribute to their functional decline with age. This paper describes the impact of mitoQ on unchallenged or oxidatively challenged ex vivo human peripheral blood mononuclear cells from healthy 25-30 or 55-60 year old volunteers. When cells were challenged with hydrogen peroxide (H(2)O(2)), following mitoQ treatment (0.1-1.0 μM), the ratio of reduced to oxidized forms of glutathione increased, the levels of oxidative DNA damage decreased and there was an increase in the mitochondrial membrane potential. Low levels of mitoQ (0.1 or 0.25 μM) had no impact on endogenous DNA damage, whilst higher levels (0.5 and 1.0 μM) of mitoQ significantly reduced endogenous levels of DNA damage. The results of this investigation suggest that mitoQ may have anti-immunosenescent potential.

Long-term treatment with shengmai san-derived herbal supplement (Wei Kang Su) enhances antioxidant response in various tissues of rats with protection against carbon tetrachloride hepatotoxicity

Wei Kang Su (WKS) is a commercial herbal product based on a Chinese herbal formula, Shengmai San. Here, we investigated the effects of long-term treatment with WKS on mitochondrial antioxidant status and functional ability, as well as heat shock protein (Hsp) 25/70 production, in various tissues of rats. WKS treatment enhanced mitochondrial antioxidant status and ATP generation capacity, as well as Hsp 25/70 production in various rat tissues. WKS treatment suppressed plasma reactive oxygen metabolite levels and protected against carbon tetrachloride hepatotoxicity in rats. Long-term WKS treatment may prevent diseases by enhancing the resistance of mitochondria to oxidative stress.

Mitochondria in the elderly: Is acetylcarnitine a rejuvenator?

Endogenous acetylcarnitine is an indicator of acetyl-CoA synthesized by multiple metabolic pathways involving carbohydrates, amino acids, fatty acids, sterols, and ketone bodies, and utilized mainly by the tricarboxylic acid cycle. Acetylcarnitine supplementation has beneficial effects in elderly animals and humans, including restoration of mitochondrial content and function. These effects appear to be dose-dependent and occur even after short-term therapy. In order to set the stage for understanding the mechanism of action of acetylcarnitine, we review the metabolism and role of this compound. We suggest that acetylation of mitochondrial proteins leads to a specific increase in mitochondrial gene expression and mitochondrial protein synthesis. In the aged rat heart, this effect is translated to increased cytochrome b content, restoration of complex III activity, and oxidative phosphorylation, resulting in amelioration of the age-related mitochondrial defect.

The absence of a mitochondrial genome in rho0 yeast cells extends lifespan independently of retrograde regulation

The absence of mtDNA in rho0 yeast cells affects both respiration and mitochondrial-nuclear communication (e.g., retrograde regulation, intergenomic signaling, or pleiotropic drug resistance). Previously, it has been reported that some rho0 strains have increased replicative lifespans, attributable to the lack of respiration and retrograde regulation. Here, we have been able to confirm that rho0 cells exhibit increased replicative lifespans but have found that this is not associated with the lack of respiration or reduced oxidative stress but instead, is related to the lack of mtDNA per se in rho0 cells. Also, we find no correlation between the strength of retrograde regulation and lifespan. Furthermore, we find that pdr3- or rtg2- mutations are not responsible for lifespan extension in rho0 cells, ruling out a specific role for PDR3-pleiotropic drug resistance or RGT2-retrograde regulation pathways in the extended lifespans of rho0 cells. Surprisingly, Rtg3p, which acts downstream of Rtg2p, is required for lifespan increase in rho0 cells. Together, these findings indicate that the loss of mtDNA per se and not the lack of respiration lead to extended longevity in rho0 cells. They also suggest that Rtg3p, acting independently of retrograde regulation, mediates this effect, possibly via intergenomic signaling.

Aging impairs skeletal muscle mitochondrial bioenergetic function

This study investigated the influence of age on the functional status of mitochondria isolated from skeletal muscle of C57BL/6 mice aged 3 and 18 months. We hypothesized that skeletal muscle mitochondria isolated from aged animals will exhibit a decreased respiratory function. Mitochondrial respiratory functional measures (ie, State 3 and 4 respiration, respiratory control ratio and number of nanomoles of ADP phosphorylated by nanomoles of O(2) consumed per mitochondrion) and biochemical markers of oxidative damage (aconitase activity, protein carbonyl derivatives, sulfhydryl groups, and malondialdehyde) were measured in isolated mitochondrial suspensions. Along with traditional tests of mitochondrial function, an in vitro repetitive ADP-stimulation test was used to evaluate the mitochondrial capacity to reestablish the homeostatic balance between successive ADP stimulations. The number of mitochondria per mitochondrial suspension, calculated by transmission electron microscopy, was used to normalize functional and biochemical data. Our results confirm the existence of an age-associated decline in mitochondrial function of mixed skeletal muscle, which is significantly correlated with higher levels of mitochondrial oxidative damage.

Genome survey for loci that influence successful aging: results at 10-cM resolution

OBJECTIVE

A systematic genome survey was initiated to identify loci that affect the likelihood of reaching age 90 with preserved cognition (successful aging).

METHODS

The genome survey was conducted at 10-cM resolution for simple sequence tandem repeat polymorphisms (SSTRPs) that identify genes for Successful AGing (SAG loci) by virtue of linkage disequilibrium. Efficiency was enhanced by genotyping pools of DNA from 100 cognitively intact elders and 100 young (18-25 years) adults. The comparison groups included equal numbers of white men and women of similar ethnicity that were recruited from the southwestern Pennsylvania region.

RESULTS

Our genome survey identified nine SAG candidate loci that may influence the likelihood of reaching age 90 or more with preserved cognition. Two of the autosomal SAG loci revealed stronger allelic associations with successful aging in men than women (D1S1728, D8S264) and two were located on sex chromosomes (DXS9902, DYS390). DXS9902 resides within a predicted gene, whereas six of the SAG loci are located within regions previously reported to show linkage to other phenotypes.

CONCLUSIONS

The results of our study suggest that loci with differential effects on the successful aging of men and women may be common. The majority of the SAG candidate loci detected in this study overlap with regions previously reported to show linkage to susceptibility genes for cardiovascular disorders, psychiatric disorders, and the accumulation of tissue damage resulting from oxidative stress.

CE-LIF analysis of mitochondria using uncoated and dynamically coated capillaries

This report is the first demonstration of the use of uncoated and dynamically coated capillaries for the separation of individual mitochondria via CE. Currently, the analysis of individual mitochondria relies upon fused-silica capillaries coated with a hydrophilic polymer (e.g. poly(acryloylaminopropanol)), which is used to minimize adsorption to the capillary surface. Both uncoated fused-silica capillaries and 0.2% w/w poly(vinyl alcohol) dynamic coating solutions are used to successfully analyze isolated individual mitochondrial particles using CE-LIF. While it was possible to separate mouse liver mitochondria on an uncoated capillary, rat liver mitochondria proved to have strong adsorption characteristics that only allowed them to be adequately separated with a PVA dynamic coating or a poly(acryloylaminopropanol) (AAP) capillary. The possible causes for this adsorption are analyzed and discussed. This study shows that uncoated and dynamically coated capillaries can be used in place of AAP-coated capillaries to analyze mitochondria and suggests the use of these capillaries for the analysis of other organelles, offering a greatly simplified method for the analysis of individual organelles.

Analysis of mitochondria isolated from single cells

Bulk studies are not suitable to describe and study cell-to-cell variation, which is of high importance in biological processes such as embryogenesis, tissue differentiation, and disease. Previously, capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was used to measure the properties of organelles isolated from millions of cells. As such, these bulk measurements reported average properties for the organelles of cell populations. Similar measurements for organelles released from single cells would be highly relevant to describe the subcellular variations among cells. Toward this goal, here we introduce an approach to analyze the mitochondria released from single mammalian cells. Osteosarcoma 143B cells are labeled with either the fluorescent mitochondrion-specific 10-N-nonyl acridine orange (NAO) or via expression of the fluorescent protein DsRed2. Subsequently, a single cell is introduced into the CE-LIF capillary where the organelles are released by a combined treatment of digitonin and trypsin. After this treatment, an electric field is applied and the released organelles electromigrate toward the LIF detector. From an electropherogram, the number of detected events per cell, their individual electrophoretic mobilities, and their individual fluorescence intensities are calculated. The results obtained from DsRed2 labeling, which is retained in intact mitochondria, and NAO labeling, which labels all mitochondria, are the basis for discussion of the strengths and limitations of this single-cell approach.

Structural and functional consequences of c-N-Ras constitutively associated with intact mitochondria

We demonstrate that both c-N-Ras and c-K(B)-Ras are constitutively associated with purified mitochondria. c-K(B)-Ras is associated with the mitochondrial outer membrane, and c-N-Ras is associated with both the outer membrane and inner mitochondrial compartments. The mitochondrial morphology is abnormal in both c-N-Ras negative and K-Ras negative cells. Normal mitochondrial morphology was restored by targeting N-Ras to both the inner and outer mitochondrial compartments, or by ectopically expressing c-K(B)-Ras. Impaired mitochondrial function can result in increased CHOP and NFkappaB activity, typical for a retrograde signaling response. Both are constitutively elevated in the N-Ras negative cells, but not in the K-Ras negative background, and are restored by c-N-Ras targeted exclusively to the inner mitochondrial compartment. Surprisingly, both targeting and the ability to functionally reduce retrograde transcriptional activity were found to be independent of c-N-Ras farnesylation. Overall, these data demonstrate for the first time a (1) farnesylation independent function for c-N-Ras and (2) that N-Ras within the inner mitochondrial compartment is an essential component of the retrograde signaling system between the mitochondria and nucleus.

Mitochondrial DNA involvement in human longevity

The main message of this review can be summarized as follows: aging and longevity, as complex traits having a significant genetic component, likely depend on a number of nuclear gene variants interacting with mtDNA variability both inherited and somatic. We reviewed the data available in the literature with particular attention to human longevity, and argued that what we hypothesize for aging and longevity could have a more general relevance and be extended to other age-related complex traits such as Alzheimer's and Parkinson's diseases. The genetics which emerges for complex traits, including aging and longevity, is thus even more complicated than previously thought, as epistatic interactions between nuclear gene polymorphisms and mtDNA variability (both somatic and inherited) as well as between mtDNA somatic mutations (tissue specific) and mtDNA inherited variants (haplogroups and sub-haplogroups) must be considered as additional players capable of explaining a part of the aging and longevity phenotype. To test this hypothesis is one of the main challenge in the genetics of aging and longevity in the next future.

Chronic schisandrin B treatment improves mitochondrial antioxidant status and tissue heat shock protein production in various tissues of young adult and middle-aged rats

The effects of chronic schisandrin B (Sch B) treatment (10 mg/kg/dayx15) on mitochondrial antioxidant status and sensitivity to Ca2+-induced permeability transition, as well as tissue heat shock protein (Hsp)25/70 production were examined in various tissues (brain, heart, liver, skeletal muscle) of young adult and middle-aged female rats. Age-dependent impairment in mitochondrial antioxidant status, as assessed by levels/activities of antioxidant components (reduced glutathione, alpha-tocopherol, Se-glutathione peroxidase and Mn-superoxide dismutase) and the extent of reactive oxygen species generation in vitro, was observed in brain, heart, liver and skeletal muscle tissues. While tissue Hsp25 levels remained relatively unchanged with aging, the Hsp70 level was increased in both brain and heart tissues of middle-aged rats. Chronic Sch B treatment was able to enhance mitochondrial antioxidant status and the resistance to Ca2+-induced mitochondrial permeability transition in an age-independent manner in various tissues of rats. However, Hsp25 and Hsp70 levels were only increased in young adult rats. The Sch B-induced enhancement of mitochondrial protective parameters in the heart was associated with the protection against myocardial ischemia-reperfusion injury in both young adult and middle-aged rats. The results suggest that chronic Sch B treatment may be beneficial for reversing the mitochondrial changes with aging and enhancing the heat shock response.

Calorie restriction induces mitochondrial biogenesis and bioenergetic efficiency

Age-related accumulation of cellular damage and death has been linked to oxidative stress. Calorie restriction (CR) is the most robust, nongenetic intervention that increases lifespan and reduces the rate of aging in a variety of species. Mechanisms responsible for the antiaging effects of CR remain uncertain, but reduction of oxidative stress within mitochondria remains a major focus of research. CR is hypothesized to decrease mitochondrial electron flow and proton leaks to attenuate damage caused by reactive oxygen species. We have focused our research on a related, but different, antiaging mechanism of CR. Specifically, using both in vivo and in vitro analyses, we report that CR reduces oxidative stress at the same time that it stimulates the proliferation of mitochondria through a peroxisome proliferation-activated receptor coactivator 1 alpha signaling pathway. Moreover, mitochondria under CR conditions show less oxygen consumption, reduce membrane potential, and generate less reactive oxygen species than controls, but remarkably they are able to maintain their critical ATP production. In effect, CR can induce a peroxisome proliferation-activated receptor coactivator 1 alpha-dependent increase in mitochondria capable of efficient and balanced bioenergetics to reduce oxidative stress and attenuate age-dependent endogenous oxidative damage.

A Yang-Invigorating Chinese Herbal Formula Enhances Mitochondrial Functional Ability and Antioxidant Capacity in Various Tissues of Male and Female Rats

The practice of traditional Chinese medicine (TCM) always emphasizes the prevention of diseases and delaying the onset of senility. In this regard, the maintenance of a balance of Yin and Yang-two opposing components involved in life activities as exemplified by the antagonistic action of the sympathetic and parasympathetic nervous systems-is essential in achieving a healthy condition. Previous studies have shown that long-term treatment with a Yang-invigorating Chinese herbal formula (VI-28) could increase red cell CuZn-superoxide dismutase (SOD) activity in male human subjects. In the present study, we examined the effects of chronic VI-28 treatment (80 and 240 mg/kg/day for 30 days) on red cell CuZn-SOD activity as well as mitochondrial functional ability and antioxidant components in various tissues of male and female rats. The results indicated that VI-28 treatment increased red cell CuZn-SOD activity as well as mitochondrial ATP generation capacity, reduced glutathione and alpha-tocopherol levels, and Mn-SOD activity in brain, heart, liver, and skeletal muscle tissues in both male and female rats to varying extents. The VI-28?induced increase in mitochondrial antioxidant capacity in various tissues was evidenced by the significant reduction in the extent of reactive oxygen species generation assessed by in vitro measurement. The red cell CuZn-SOD activities correlated positively with tissue mitochondrial antioxidant component levels/activity. The beneficial effect of VI-28 treatment on mitochondrial functional ability and antioxidant capacity may have clinical implications in the prevention of age-related diseases.

Coenzyme Q10 Protects From Aging-Related Oxidative Stress and Improves Mitochondrial Function in Heart of Rats Fed a Polyunsaturated Fatty Acid (PUFA)-Rich Diet

Coenzyme Q(10) supplementation on age-related changes in oxidative stress and function of heart mitochondria in rats fed a polyunsaturated fatty acid (PUFA)-rich diet was investigated. Two groups of rats were fed for 24 months on a PUFA-rich diet, differing in supplementation or not with coenzyme Q(10). Animals were killed at 6, 12, or 24 months. Fatty-acid profile, hydroperoxides, alpha-tocopherol, coenzyme Q, catalase and glutathione peroxidase activities, and cytochromes a+a(3), b, c+c(1) and cytochrome c oxidase activity were measured. Coenzyme Q(10)-supplemented animals showed lower hydroperoxide levels; higher content and/or activity of alpha-tocopherol, coenzyme Q, and catalase; and a slightly lower decrease in mitochondrial function. According to that, previously reported positive effects of coenzyme Q supplementation on the life span of rats fed a PUFA-rich diet might be a consequence, at least in part, of a lower oxidative stress level and perhaps, to a minor extent, of a smaller decrease in mitochondrial function.

Increased mitochondrial and nuclear gene expression of cytochrome oxidase subunits I and IV in neuronal aging

To assess the role of mitochondrial metabolic competence (MMC) in neuronal aging, quantitative immunohistochemistry of cytochrome oxidase (COX) subunits I (mitochondrial-encoded) and IV (nuclear-encoded) was carried out in the cerebellar cortex of adult and old rats. The optical density (OD) values of the immunostained COX subunits I and IV were measured on an overall area of 75,000 microm(2) in the granular and molecular layers of the cerebellar cortex of each animal. In old animals, OD values of subunit I were increased by 35.5 and 34.2% in the molecular and granular layers, respectively, but only the difference found in the latter cerebellar zone was statistically significant (p < 0.05%). As regards subunit IV, old animals showed higher, not significant, densitometric values in the molecular (120.6%) and granular (126.8%) layers. The present findings sustain that gene expression of COX subunits I and IV appears not to be involved in the well-documented time-related mitochondrial decay. The proper functioning of COX depends on several factors that can affect MMC in the aging cell. In the fully assembled holoenzyme, both the subunits I and IV span the inner mitochondrial membrane. On the basis of these molecular biology data, it is reasonable to suppose that any alteration of the physicochemical features and chemical composition of the mitochondrial membranes reported to occur in aging (e.g., decreased membrane fluidity and cardiolipin content, increased cholesterol/phospholipid molar ratio and free-radical damage, etc.) may significantly affect the proper assembling of the enzyme and, in turn, its activity. Considering the reported significant decline of COX activity with advancing age, our findings further support that an adequate mitochondrial metabolic competence, while including proper nuclear and mitochondrial gene expression of subunits of the respiratory chain, relies on the overall balance among various determinants that can be differently damaged by aging and represent critical causative events responsible for the age-related functional decline of selected mitochondrial populations.

Inflamm-ageing and lifelong antigenic load as major determinants of ageing rate and longevity

Immunosenescence is the consequence of the continuous attrition caused by chronic antigenic stress. The most important characteristics of immunosenescence (accumulation of memory and effector T cells, reduction of naive T cells, shrinkage of T cell repertoire, reduction of the immunological space) are compatible with this assumption. Immunosenescence can be taken as proof that the beneficial effects of the immune system, devoted to the neutralization of harmful agents early in life, become detrimental late in life, in a period not foreseen by evolution. This perspective could explain the mechanisms of the ageing process as well as the pathogenesis of age-related diseases.

Tyrosine phosphorylation in mitochondria: a new frontier in mitochondrial signaling

Mitochondria are multifunctional organelles that participate in a range of cellular processes such as energy production, proliferation, death, and senescence. The involvement of mitochondria in such distinct aspects of cell life requires the existence of an integrated system of signals that enter and exit the organelle according to the diverse needs of the cell. The recent discovery of several protein kinases and phosphatases that localize partially or predominantly inside mitochondria opens new perspectives into the regulation of these signals. This review focuses on tyrosine phosphorylation in mitochondria. A description of the protein tyrosine kinases and phosphatases which regulate this process along with the mitochondrial tyrosine-phosphorylated proteins identified to date is followed by a discussion of the possible involvement of tyrosine phosphorylation in mitochondrial signaling and future perspectives for developments in this emerging field.

Implications of statin adverse effects in the elderly

The elderly differ from younger people in the relation of cholesterol to heart disease and mortality. Clinical trial evidence supports epidemiological findings in showing that high cholesterol weakens in its relationship to heart disease with age and loses (and in older age reverses) its relation to mortality. Randomised trial data confirm that lowering cholesterol no longer extends life in the elderly, even those at high risk of heart disease, and no evidence supports the presumption that the impact on all-cause morbidity is any more favourable. These findings increase the importance of statin adverse effects (AEs) in this group. Furthermore, the elderly may be more vulnerable to known AEs, and evidence provides cause for concern that new risks may supervene, including cancer, neurodegenerative disease and heart failure. Physiological evidence regarding the impact of statins on mitochondrial function, and mitochondrial function on ageing, support these concerns. Additionally, the impact of statin AEs (e.g., muscle and cognitive problems) may be amplified in this group. Effects may be misattributed to ageing. Even modestly lower cognitive and physical function in older elderly prognosticates increased disability, hospitalisation, institutionalisation, and mortality. Disability, once present, is less likely to recover. Because the risk for AEs is unattended by evidence of net benefit to the person, the use of statins in the elderly should be undertaken, if at all, with circumspection and close scrutiny for adverse effects.

In Vitro and In Silico Cloning of Xenopus laevis SOD2 cDNA and Its Phylogenetic Analysis

By using the methodology of both wet and dry biology (i.e., RT-PCR and cycle sequencing, and biocomputational technology, respectively) and the data obtained through the Genome Projects, we have cloned Xenopus laevis SOD2 (MnSOD) cDNA and determined its nucleotide sequence. These data and the deduced protein primary structure were compared with all the other SOD2 nucleotide and amino acid sequences from eukaryotes and prokaryotes, published in public databases. The analysis was performed by using both Clustal W, a well known and widely used program for sequence analysis, and AntiClustAl, a new algorithm recently created and implemented by our group. Our results demonstrate a very high conservation of the enzyme amino acid sequence during evolution, which proves a close structure-function relationship. This is to be expected for very ancient molecules endowed with critical biological functions, performed through a specific structural organization. The nucleotide sequence conservation is less pronounced: this too was foreseeable, due to neutral mutations and to the species-specific codon usage. The data obtained by using AntiClustAl are comparable with those produced with Clustal W, which validates this algorithm as an important new tool for biocomputational analysis. Finally, it is noteworthy that evolutionary trees, drawn by using all the available data on SOD2 nucleotide sequences and amino acid and either Clustal W or AntiClustAl, are comparable to those obtained through phylogenetic analysis based on fossil records.

The genetics of human longevity

Many of the genes that affect aging and longevity in model organisms, such as mice, fruit flies, and worms, have human homologs. This article reviews several genetic pathways that may extend lifespan through effects on aging, rather than through effects on diseases such as atherosclerosis or cancer. These include some of the genes involved in the regulation of DNA repair and nuclear structure, which cause the progeroid syndromes when mutated, as well as those that may affect telomere length, since shorter telomeres have been associated with shorter survival. Other potential longevity genes, such as sirtuins, are involved in regulating the response to cellular stress, including caloric restriction. The best-studied pathway involves insulin and insulin-like growth factor 1 signaling; mutations in homologs of these genes have extended lifespan up to sixfold in model organisms. Other potential candidates include mitochondrial DNA and the genes that regulate the inflammatory response. Despite the challenges in study design and analysis that face investigators in this area, the identification of genetic pathways that regulate longevity may suggest potential targets for therapy.

No effects of intermittent 50 Hz EMF on cytoplasmic free calcium and on the mitochondrial membrane potential in human diploid fibroblasts

The recently described increase in DNA strand breaks of cultured human diploid fibroblasts after intermittent exposure to extremely-low-frequency electromagnetic fields (ELF-EMF) of more than about 70 microT ELF-EMF is difficult to explain by a direct induction of covalent bond disruption. Therefore the hypothesis has been tested that ELF-EMF-induced DNA strand breaks might be mediated by cellular processes that cause alteration of the intracellular concentration of free calcium ([Ca2+]i) and/or the membrane potential (DeltaPsi(m)). [Ca2+]i was determined by the ratiometric fura-2 technique. Changes in DeltaPsi(m) were assessed by using the potential-dependent lipophilic cationic probe JC-1. Human fibroblasts were exposed to intermittent ELF-EMF (50 Hz, 1000 microT). Although exposure of fiboblasts to ELF-EMF resulted in a highly significant increase in DNA strand breaks as determined by the comet assay, no effect on JC-1 fluorescence emission or on [Ca2+]i has been observed when comparing exposed with sham-exposed cells. Therefore, it is suggested that ELF-EMF-induced DNA strand breaks are unlikely to be caused by intracellular changes that affect [Ca2+]i and/or DeltaPsi(m).

Bax-induced cell death of Arabidopsis is meditated through reactive oxygen-dependent and -independent processes

An Arabidopsis protoplast system was developed for dissecting plant cell death in individual cells. Bax, a mammalian pro-apoptotic member of the Bcl-2 family, induces apoptotic-like cell death in Arabidopsis. Bax accumulation in Arabidopsis mesophyll protoplasts expressing murine Bax cDNA from a glucocorticoid-inducible promoter results in cytological characteristics of apoptosis, namely DNA fragmentation, increased vacuolation, and loss of plasma membrane integrity. In vivo targeting analysis monitored using jellyfish green fluorescent protein (GFP) reporter indicated full-length Bax was localized to the mitochondria, as it does in animal cells. Deletion of the carboxyl-terminal transmembrane domain of Bax completely abolished targeting to mitochondria. Bax expression was followed by reactive oxygen species (ROS) accumulation. Treatment of protoplasts with the antioxidant N -acetyl- -cysteine (NAC) during induction of Bax expression strongly suppressed Bax-mediated ROS production and the cell death phenotype. However, some population of the ROS depleted cells still induced cell death, indicating that there is a process that Bax-mediated plant cell death is independent of ROS accumulation. Accordingly, suppression of Bax-mediated plant cell death also takes place in two different processes. Over-expression of a key redox-regulator, Arabidopsis nucleoside diphosphate kinase 2 (AtNDPK2) down-regulated ROS accumulation and suppressed Bax-mediated cell death and transient expression of Arabidopsis Bax inhibitor-1 (AtBI-1) substantially suppressed Bax-induced cell death without altering cellular ROS level. Taken together, our results collectively suggest that the Bax-mediated cell death and its suppression in plants is mediated by ROS-dependent and -independent processes.

Aging-related oxidative stress depends on dietary lipid source in rat postmitotic tissues

We investigate mitochondrial-lipid peroxidation of mitotic (liver) and postmitotic (heart and skeletal muscle) tissues of rats fed lifelong on two different lipid sources: virgin olive oil (monounsaturated fatty acids) and sunflower oil (n - 6 polyunsaturated fatty acids). Two groups of 80 rats each were fed over 24 months on a diet differing in the lipid source (virgin olive oil or sunflower oil). Twenty rats per group were killed at 6, 12, 18, and 24 months; liver, heart, and skeletal muscle mitochondria were isolated and the lipid profile, hydroperoxides, vitamin E, and ubiquinone as well as catalase activity measured. Lipid peroxidation was higher in postmitotic tissues, and sunflower oil led to a higher degree of polyunsaturation and peroxidation. The levels of alpha-tocopherol adapted to oxidative stress and preferentially accumulated during aging in heart and skeletal muscle. In conclusion, the type of dietary fat should be considered in studies on aging, since oxidative stress is directly modulated by this factor. This study confirms that postmitotic tissues are more prone to oxidative stress during aging and proposes a hypothesis to explain this phenomenon.

Variability of the SIRT3 gene, human silent information regulator Sir2 homologue, and survivorship in the elderly

The human sirtuin 3 (SIRT3) gene encodes a putative mitochondrial NAD-dependent deacetylase (SIRT3) which belongs to the evolutionary conserved family of sirtuin 2 proteins. Studies in model organisms have demonstrated that SIR2 genes control lifespan, while no data are available regarding a possible role of SIRT3 in human longevity. By analysing the genotype-specific survival function relevant to the G477T marker of SIRT3, we found that in males the TT genotype increases (p=0.0272), while the GT genotype decreases (p=0.0391) survival in the elderly. Since SIRT3 lies in a chromosomal region (11p15.5) where four genes potentially associated with longevity are located (HRAS1, Insulin-like Growth Factor 2, Proinsulin, and Tyrosine Hydroxylase) we tested for linkage-disequilibrium between G477T alleles and alleles of the above genes. The disequilibrium was not significant in any case, thus suggesting that SIRT3 itself, or a gene strictly linked to SIRT3, may have a role in human longevity.

Glutamate-induced differential mitochondrial response in young and adult rats

Excitatory amino acid glutamate is involved in neurotransmission in the nervous system but it becomes a potent neurotoxin under variety of conditions. However, the molecular mechanism of excitotoxicity is not known completely. We have studied the influence of glutamate on intracellular calcium and mitochondrial functions in cortical slices from young and adult rats. The slices from both the age groups exhibited comparable intracellular calcium changes upon glutamate stimulation. Glutamate treatment caused a decrease in adenosine 5'-diphosphate/adenosine 5'-triphosphate (ADP/ATP) and an increase in nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide reduced form (NAD/NADH) ratio in both the age groups but the magnitude and the nature of temporal change was different. Glutamate-induced decrease in ATP/ADP and increase in NAD/NADH ratio was significantly higher in slices from the adult as compared to the young rats. The slices from young rats elicited slightly higher mitochondrial depolarization than adult rats. However, the formation of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) release were significantly higher in adult rats as compared to young rats. Glutamate-induced mitochondrial depolarization, ROS formation and LDH release were highly dependent on the presence of Ca(2+) in the extracellular medium. The treatment of slices with mitochondrial inhibitors rotenone and oligomycin inhibited ROS formation and LDH release substantially. Our results suggest that the glutamate-induced increase in intracellular calcium is not the only factor responsible for neuronal cell death but the mitochondrial functions could be crucial in excitotoxicity.