Decreased Pasteur effect in platelets of aged individuals

Mitochondrial function in peripheral blood cells across the human lifespan

Mitochondrial dysfunction is considered a hallmark of aging. Up to now, a gradual decline of mitochondrial respiration with advancing age has mainly been demonstrated in human muscle tissue. A handful of studies have examined age-related mitochondrial dysfunction in human blood cells, and only with small sample sizes and mainly in platelets. In this study, we analyzed mitochondrial respiration in peripheral blood mononuclear cells (PBMCs) and platelets from 308 individuals across the human lifespan (0-86 years). In regression analyses, with adjustment for false discovery rate (FDR), we found age-related changes in respiratory measurements to be either small or absent. The main significant changes were an age-related relative decline in complex I-linked respiration and a corresponding rise of complex II-linked respiration in PBMCs. These results add to the understanding of mitochondrial dysfunction in aging and to its possible role in immune cell and platelet senescence.

Association of blood donor characteristics with in vitro platelet storage properties

BACKGROUND AND OBJECTIVE

The study was planned to determine the association of blood donor characteristics with in vitro quality of platelets.

MATERIAL AND METHODS

In the prospective observational study, a total of 85 male whole blood donors in the age group of 18-30 and 45-65 years were enrolled using purposive sampling method. Serum total cholesterol, glycosylated hemoglobin (HbA1c), and LDH levels were performed on donor pre-donation sample. Buffy coat platelet concentrates were prepared from 450 mL quadruple blood bags. Samples from platelets were taken on day one and five of storage and biochemical properties were observed.

RESULTS

Median MPV was higher in platelets from older blood donors on day five (9.8 vs 9.4, p = 0.037). Median LDH levels were also higher in platelets on day one and five from older donors (Day one: 204.5 vs 147, p = <0.000; day five: 278 vs 224, p = 0.001 respectively). Platelets from donors with high HbA1c levels had lower median pH (Day one: 7.31 vs 7.37, p = 0.024) and higher median glucose levels on day one of storage (Day one: 358 vs 311, p = 0.001). Higher median lactate levels throughout the storage period were also seen in platelets from donors with higher HbA1c levels (Day one: 7 vs 5.7, p = 0.037; Day five: 16 vs 12.2, p = 0.032). Glucose consumption (108 vs 66, p = 0.025) and lactate production (9 vs 6.4, p = 0.019) was higher in platelets from donors with higher HbA1c levels.

CONCLUSION

In vitro platelet storage properties are affected by blood donor characteristics.

Potential adverse effects of ciprofloxacin and tetracycline on ARPE-19 cell lines

Background

We aim to determine the possible adverse effects of ciprofloxacin (CPFX) and tetracycline (TETRA), as examples of bactericidal and bacteriostatic agents, respectively, on cultured human retinal pigment epithelial cells (ARPE-19).

Methods

Cells were treated with 30, 60 and 120 µg/mL of CPFX and TETRA. Cell metabolism was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. JC-1 dye (5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide) assay was conducted to measure the mitochondrial membrane potential (MMP). The level of reactive oxygen species (ROS) was measured using the -2’,7’-dichlorodihydrofluorescein diacetate assay (H2DCFDA). Quantitative real-time PCR was performed to analyse the gene expression levels associated with apoptosis (BAX, BCL2-L13, BCL2, Caspase 3, Caspase 7 and Caspase 9), inflammatory (interleukin-1β (IL-1β), IL-6, IL-33, transforming growth factor-α (TGF-α), TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4), along with the mitochondrial DNA (mtDNA) copy numbers.

Results

Results illustrated that while all three concentrations of CPFX decreased cellular viability of ARPE-19 during all incubation periods, the 120 µg/mL TETRA resulted in increased cellular viability. At 48 and 72 hours, levels of MMP and ROS decreased significantly with each antibiotic. BAX, BCL2-L13, CASP-7, CASP-9, SOD2 and GPX3 genes overexpressed by either antibiotics. There was higher expression of IL-6 and IL-1B with TETRA treatment. The level of mtDNA decreased using both treatments.

Conclusions

Clinically relevant concentrations of CPFX and TETRA have detrimental impacts on ARPE-19 cell lines in vitro, including upregulation of genes related to apoptosis, inflammation and antioxidant pathways. Additional studies are warranted to investigate if these harmful effects might be seen in retinal degeneration models in vivo.

Platelet glycolytic metabolism correlates with hemodynamic severity in pulmonary arterial hypertension

Group 1 pulmonary hypertension (PH), i.e., pulmonary arterial hypertension (PAH), is associated with a metabolic shift favoring glycolysis in cells comprising the lung vasculature as well as skeletal muscle and right heart. We sought to determine whether this metabolic switch is also detectable in circulating platelets from PAH patients. We used Seahorse Extracellular Flux to measure bioenergetics in platelets isolated from group 1 PH (PAH), group 2 PH, patients with dyspnea and normal pulmonary artery pressures, and healthy controls. We show that platelets from group 1 PH patients exhibit enhanced basal glycolysis and lower glycolytic reserve compared with platelets from healthy controls but do not differ from platelets of group 2 PH or dyspnea patients without PH. Although we were unable to identify a glycolytic phenotype unique to platelets from PAH patients, we found that platelet glycolytic metabolism correlated with hemodynamic severity only in group 1 PH patients, supporting the known link between PAH pathology and altered glycolytic metabolism and extending this association to ex vivo platelets. Pulmonary artery pressure and pulmonary vascular resistance in patients with group 1 PH were directly associated with basal platelet glycolysis and inversely associated with maximal and reserve glycolysis, suggesting that PAH progression reduces the capacity for glycolysis even while demanding an increase in glycolytic metabolism. Therefore, platelets may provide an easy-to-harvest, real-time window into the metabolic shift occurring in the lung vasculature and represent a useful surrogate for interrogating the glycolytic shift central to PAH pathology.

Assessment of platelet respiration as emerging biomarker of disease

Mitochondrial dysfunction is currently acknowledged as a central pathomechanism of most common diseases of the 21(st) century. Recently, the assessment of the bioenergetic profile of human peripheral blood cells has emerged as a novel research field with potential applications in the development of disease biomarkers. In particular, platelets have been successfully used for the ex vivo analysis of mitochondrial respiratory function in several acute and chronic pathologies. An increasing number of studies support the idea that evaluation of the bioenergetic function in circulating platelets may represent the peripheral signature of mitochondrial dysfunction in metabolically active tissues (brain, heart, liver, skeletal muscle). Accordingly, impairment of mitochondrial respiration in peripheral platelets might have potential clinical applicability as a diagnostic and prognostic tool as well as a biomarker in treatment monitoring. The aim of this minireview is to summarize current information in the field of platelet mitochondrial dysfunction in both acute and chronic diseases.

Bioenergetic Impairment in Animal and Cellular Models of Alzheimer's Disease: PARP-1 Inhibition Rescues Metabolic Dysfunctions

Amyloid-beta peptide accumulation in the brain is one of the main hallmarks of Alzheimer's disease. The amyloid aggregation process is associated with the generation of free radical species responsible for mitochondrial impairment and DNA damage that in turn activates poly(ADP-ribose)polymerase 1 (PARP-1). PARP-1 catalyzes the poly(ADP-ribosylation), a post-translational modification of proteins, cleaving the substrate NAD+ and transferring the ADP-ribose moieties to the enzyme itself or to an acceptor protein to form branched polymers of ADP-ribose. In this paper, we demonstrate that a mitochondrial dysfunction occurs in Alzheimer's transgenic mice TgCRND8, in SH-SY5Y treated with amyloid-beta and in 7PA2 cells. Moreover, PARP-1 activation contributes to the functional energetic decline affecting cytochrome oxidase IV protein levels, oxygen consumption rates, and membrane potential, resulting in cellular bioenergetic deficit. We also observed, for the first time, an increase of pyruvate kinase 2 expression, suggesting a modulation of the glycolytic pathway by PARP-1. PARP-1 inhibitors are able to restore both mitochondrial impairment and pyruvate kinase 2 expression. The overall data here presented indicate a pivotal role for this enzyme in the bioenergetic network of neuronal cells and open new perspectives for investigating molecular mechanisms underlying energy charge decline in Alzheimer's disease. In this scenario, PARP-1 inhibitors might represent a novel therapeutic intervention to rescue cellular energetic metabolism.

A study protocol for a randomised controlled trial evaluating clinical effects of platelet transfusion products: the Pathogen Reduction Evaluation and Predictive Analytical Rating Score (PREPAReS) trial

INTRODUCTION

Patients with chemotherapy-induced thrombocytopaenia frequently experience minor and sometimes severe bleeding complications. Unrestrictive availability of safe and effective blood products is presumed by treating physicians as well as patients. Pathogen reduction technology potentially offers the opportunity to enhance safety by reducing bacterial and viral contamination of platelet products along with a potential reduction of alloimmunisation in patients receiving multiple platelet transfusions.

METHODS AND ANALYSIS

To test efficacy, a randomised, single-blinded, multicentre controlled trial was designed to evaluate clinical non-inferiority of pathogen-reduced platelet concentrates treated by the Mirasol system, compared with standard plasma-stored platelet concentrates using the percentage of patients with WHO grade ≥ 2 bleeding complications as the primary endpoint. The upper limit of the 95% CI of the non-inferiority margin was chosen to be a ≤ 12.5% increase in this percentage. Bleeding symptoms are actively monitored on a daily basis. The adjudication of the bleeding grade is performed by 3 adjudicators, blinded to the platelet product randomisation as well as by an automated computer algorithm. Interim analyses evaluating bleeding complications as well as serious adverse events are performed after each batch of 60 patients. The study started in 2010 and patients will be enrolled up to a maximum of 618 patients, depending on the results of consecutive interim analyses. A flexible stopping rule was designed allowing stopping for non-inferiority or futility. Besides analysing effects of pathogen reduction on clinical efficacy, the Pathogen Reduction Evaluation and Predictive Analytical Rating Score (PREPAReS) is designed to answer several other pending questions and translational issues related to bleeding and alloimmunisation, formulated as secondary and tertiary endpoints.

ETHICS AND DISSEMINATION

Ethics approval was obtained in all 3 participating countries. Results of the main trial and each of the secondary endpoints will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NTR2106; Pre-results.

Carnosine: effect on aging-induced increase in brain regional monoamine oxidase-A activity

Aging is a natural biological process associated with several neurological disorders along with the biochemical changes in brain. Aim of the present investigation is to study the effect of carnosine (0.5-2.5μg/kg/day, i.t. for 21 consecutive days) on aging-induced changes in brain regional (cerebral cortex, hippocampus, hypothalamus and pons-medulla) mitochondrial monoamine oxidase-A (MAO-A) activity with its kinetic parameters. The results of the present study are: (1) The brain regional mitochondrial MAO-A activity and their kinetic parameters (except in Km of pons-medulla) were significantly increased with the increase of age (4-24 months), (2) Aging-induced increase of brain regional MAO-A activity including its Vmax were attenuated with higher dosages of carnosine (1.0-2.5μg/kg/day) and restored toward the activity that observed in young, though its lower dosage (0.5μg/kg/day) were ineffective in these brain regional MAO-A activity, (3) Carnosine at higher dosage in young rats, unlike aged rats significantly inhibited all the brain regional MAO-A activity by reducing their only Vmax excepting cerebral cortex, where Km was also significantly enhanced. These results suggest that carnosine attenuated the aging-induced increase of brain regional MAO-A activity by attenuating its kinetic parameters and restored toward the results of MAO-A activity that observed in corresponding brain regions of young rats.

Platelet monoamine oxidase-A activity and aging: effect of carnosine

Platelet mitochondrial MAO-A activity of male albino rats (Wistar strain) was significantly inhibited with an inhibition of its only V max during aging. This age-induced inhibition of platelet MAO-A activity became reversed following the application of higher dosages (2.0-2.5 μg/kg/day, i.t. for 21 consecutive days) of carnosine. Though carnosine at lower dosage (0.5 μg/kg/day, i.t. for 21 consecutive days) was ineffective to platelet mitochondrial MAO-A activity in both young and aged rats, at higher dosages (2.0-2.5 μg/kg/day, i.t. for 21 consecutive days) under similar condition this enzyme activity was significantly enhanced. Carnosine at 1.0 μg/kg/day, i.t. for 21 consecutive days significantly enhanced MAO-A activity only in aged (18 and 24 months) rats. These results suggest that carnosine withdraws the aging-induced inhibition of mammalian blood platelet MAO-A activity and restores its activity towards that (MAO-A activity) observed in young mammalian blood platelets.

Methods for defining distinct bioenergetic profiles in platelets, lymphocytes, monocytes, and neutrophils, and the oxidative burst from human blood

Peripheral blood mononuclear cells and platelets have long been recognized as having the potential to act as sensitive markers for mitochondrial dysfunction in a broad range of pathological conditions. However, the bioenergetic function of these cells has not been examined from the same donors, yet this is important for the selection of cell types for translational studies. Here, we demonstrate the measurement of cellular bioenergetics in isolated human monocytes, lymphocytes, and platelets, including the oxidative burst from neutrophils and monocytes from individual donors. With the exception of neutrophils, all cell types tested exhibited oxygen consumption that could be ascribed to oxidative phosphorylation with each having a distinct bioenergetic profile and distribution of respiratory chain proteins. In marked contrast, neutrophils were essentially unresponsive to mitochondrial respiratory inhibitors indicating that they have a minimal requirement for oxidative phosphorylation. In monocytes and neutrophils, we demonstrate the stimulation of the oxidative burst using phorbol 12-myristate 13-acetate and its validation in normal human subjects. Taken together, these data suggest that selection of cell type from blood cells is critical for assessing bioenergetic dysfunction and redox biology in translational research.

Ginkgo biloba extract EGb761 protects against aging-associated mitochondrial dysfunction in platelets and hippocampi of SAMP8 mice

Standardized Ginkgo biloba extract, EGb761, has been shown to possess polyvalent properties, such as anti-oxidation, anti-apoptosis and anti-inflammation. Recently, it has also been proposed to have direct protective effects on mitochondria. The effects of EGb761 make it a potential anti-aging drug. Despite that, the 'anti-aging' effect of EGb761, particularly its effect on the central nervous system, is still inconclusive. Using two age groups (3-week-old and 40-week-old) of SAMP8 mice (a senescence-accelerated strain of mice), the effects of EGb761 on mitochondrial function in platelets and hippocampi were investigated in this study. It was found that mitochondrial functions, evaluated as cytochrome c oxidase (COX) activity, mitochondrial ATP (adenosine-5'-triphosphate) content and mitochondrial glutathione (GSH) content, decreased with age. EGb761 protected against mitochondrial dysfunction in platelets of young and old mice, suggesting a peripheral effect of this herb in the prevention and treatment of age-associated degeneration. In contrast, in hippocampi, protective effects of EGb761 were observed only in the old mice, probably due to an age-associated increase in the permeability of the blood brain barrier (BBB). Therefore, while EGb761 has a potential anti-aging effect, its central effect can be affected by in vivo factors such as the BBB permeability. A better understanding of the in vivo pharmacological actions of EGb761 may contribute to a better understanding of the effectiveness and complexity of this drug.

Methamphetamine causes mitrochondrial oxidative damage in human T lymphocytes leading to functional impairment

Methamphetamine (METH) abuse is known to be associated with an inordinate rate of infections. Although many studies have described the association of METH exposure and immunosuppression, so far the underlying mechanism still remains elusive. In this study, we present evidence that METH exposure resulted in mitochondrial oxidative damage and caused dysfunction of primary human T cells. METH treatment of T lymphocytes led to a rise in intracellular calcium levels that enhanced the generation of reactive oxygen species. TCR-CD28 linked calcium mobilization and subsequent uptake by mitochondria in METH-treated T cells correlated with an increase in mitochondrion-derived superoxide. Exposure to METH-induced mitochondrial dysfunction in the form of marked decrease in mitochondrial membrane potential, increased mitochondrial mass, enhanced protein nitrosylation and diminished protein levels of complexes I, III, and IV of the electron transport chain. These changes paralleled reduced IL-2 secretion and T cell proliferative responses after TCR-CD28 stimulation indicating impaired T cell function. Furthermore, antioxidants attenuated METH-induced mitochondrial damage by preserving the protein levels of mitochondrial complexes I, III, and IV. Altogether, our data indicate that METH can cause T cell dysfunction via induction of oxidative stress and mitochondrial injury as underlying mechanism of immune impairment secondary to METH abuse.

Rule-based cell systems model of aging using feedback loop motifs mediated by stress responses

Investigating the complex systems dynamics of the aging process requires integration of a broad range of cellular processes describing damage and functional decline co-existing with adaptive and protective regulatory mechanisms. We evolve an integrated generic cell network to represent the connectivity of key cellular mechanisms structured into positive and negative feedback loop motifs centrally important for aging. The conceptual network is casted into a fuzzy-logic, hybrid-intelligent framework based on interaction rules assembled from a priori knowledge. Based upon a classical homeostatic representation of cellular energy metabolism, we first demonstrate how positive-feedback loops accelerate damage and decline consistent with a vicious cycle. This model is iteratively extended towards an adaptive response model by incorporating protective negative-feedback loop circuits. Time-lapse simulations of the adaptive response model uncover how transcriptional and translational changes, mediated by stress sensors NF-κB and mTOR, counteract accumulating damage and dysfunction by modulating mitochondrial respiration, metabolic fluxes, biosynthesis, and autophagy, crucial for cellular survival. The model allows consideration of lifespan optimization scenarios with respect to fitness criteria using a sensitivity analysis. Our work establishes a novel extendable and scalable computational approach capable to connect tractable molecular mechanisms with cellular network dynamics underlying the emerging aging phenotype.

The global process of aging disturbs a broad range of cellular mechanisms in a complex fashion and is not well understood. One important goal of computational approaches in aging is to develop integrated models in terms of a unifying aging theory, predicting progression of aging phenotypes grounded on molecular mechanisms. However, current experimental data incoherently reflects many isolated processes from a large diversity of approaches, biological model systems, and species, which makes such integration a challenging task. In an attempt to close this gap, we iteratively develop a fuzzy-logic cell systems model considering the interplay of damage, metabolism, and signaling by positive and negative feedback-loop motifs using relationships drawn from literature data. Because cellular biodynamics may be considered a complex control system, this approach seems particularly suitable. Here, we demonstrate that rule-based fuzzy-logic models provide semi-quantitative predictions that enhance our understanding of complex and interlocked molecular mechanisms and their implications on the aging physiome.

Ginkgo biloba extract EGb761 protects against mitochondrial dysfunction in platelets and hippocampi in ovariectomized rats

Using ovariectomized middle-aged rats to mimic the post-menopausal pathophysiological changes in women, we have previously demonstrated that estrogen withdrawal and age-related decrease in the functional reserve of mitochondria might co-operate to induce persistent mitochondrial dysfunction, which may be critical in inducing degenerative processes in the brain later in post-menopausal women. The standardized Ginkgo biloba extract EGb761 has long been considered a natural antioxidant. More recently it has also proposed to have direct protective effects on the mitochondria. In this work, effects of EGb761 on mitochondrial function in platelets and hippocampi of ovariectomized and sham-operated rats were investigated. It was found that EGb761 protected against the decrease of cytochrome c oxidase (COX) activity, mitochondrial ATP (adenosine-5'-triphosphate) content and mitochondrial glutathione (GSH) content in both platelets and hippocampi of ovariectomized rats, suggesting its peripheral and central effects against estrogen withdrawal-induced degeneration. In contrast, in sham-operated rats, EGb761 increased mitochondrial GSH content in platelets but failed to show similar effect on hippocampi, suggesting that EGb761 may help to enhance the functional reserve of mitochondria, but this effect was limited to the outside of the central nervous system. EGb761 displayed similar effects on platelets and hippocampi of ovariectomized rats but showed differential effects on platelets and hippocampi of sham-operated rats, possibly because estrogen withdrawal induced an increase of blood brain barrier (BBB) permeability. Therefore, while EGb761's effect may be limited to the outside of the nervous system under normal physiological conditions, EGb761 may be a potential protective agent against central neurodegeneration in post-menopausal women.

Loss of estrogen receptor beta decreases mitochondrial energetic potential and increases thrombogenicity of platelets in aged female mice

Platelets derived from aged (reproductively senescent) female mice with genetic deletion of estrogen receptor beta (betaER) are more thrombogenic than those from age-matched wild-type (WT) mice. Intracellular processes contributing to this increased thrombogenicity are not known. Experiments were designed to identify subcellular localization of estrogen receptors and evaluate both glycolytic and mitochondrial energetic processes which might affect platelet activation. Platelets and blood from aged (22-24 months) WT and estrogen receptor beta knockout (betaERKO) female mice were used in this study. Body, spleen weight, and serum concentrations of follicle-stimulating hormone and 17beta-estradiol were comparable between WT and betaERKO mice. Number of spontaneous deaths was greater in the betaERKO colony (50% compared to 30% in WT) over the course of 24 months. In resting (nonactivated) platelets, estrogen receptors did not appear to colocalize with mitochondria by immunostaining. Lactate production and mitochondrial membrane potential of intact platelets were similar in both groups of mice. However, activities of NADH dehydrogenase, cytochrome bc ( 1 ) complex, and cytochrome c oxidase of the electron transport chain were reduced in mitochondria isolated from platelets from betaERKO compared to WT mice. There were a significantly higher number of phosphatidylserine-expressing platelet-derived microvesicles in the plasma and a greater thrombin-generating capacity in betaERKO compared to WT mice. These results suggest that deficiencies in betaER affect energy metabolism of platelets resulting in greater production of circulating thrombogenic microvesicles and could potentially explain increased predisposition to thromboembolism in some elderly females.

Ginkgo biloba extract in Alzheimer's disease: from action mechanisms to medical practice

Standardized extract from the leaves of the Ginkgo biloba tree, labeled EGb761, is one of the most popular herbal supplements. Numerous preclinical studies have shown the neuroprotective effects of EGb761 and support the notion that it may be effective in the treatment and prevention of neurodegenerative disorders such as Alzheimer’s disease (AD). Despite the preclinical promise, the clinical efficacy of this drug remains elusive. In this review, possible mechanisms underlying neuroprotective actions of EGb761 are described in detail, together with a brief discussion of the problem of studying this herb clinically to verify its efficacy in the treatment and prevention of AD. Moreover, various parameters e.g., the dosage and the permeability of the blood brain barrier (BBB), impacting the outcome of the clinical effectiveness of the extract are also discussed. Overall, the findings summarized in this review suggest that, a better understanding of the neuroprotective mechanisms of EGb761 may contribute to better understanding of the effectiveness and complexity of this herb and may also be helpful for design of therapeutic strategies in future clinical practice. Therefore, in future clinical studies, different factors that could interfere with the effect of EGb761 should be considered.

Effects of beta-amyloid peptide and estrogen on platelet mitochondrial function of Sprague-Dawley rats

Beta-amyloid peptide (Abeta) peptides play a central role in the development of Alzheimer's disease. They are known to induce mitochondrial dysfunction and caspase activation, resulting in apoptosis of neuronal cells. In the present experiment, an Abeta-induced damage model of platelets was established to observe the effects of Abeta, estradiol benzoate (EB) and genistein on platelets and platelet mitochondria. It was found that after the addition of Abeta, platelet number, platelet mitochondrial membrane potential (DeltaPsim) and adenosine triphosphate (ATP) content were lowered while no protective effects of EB and genistein had been observed. The platelets could serve as a biomarker for detection of mitochondrial function and age related disease.

Ageing, oestrogen, platelets and thrombotic risk

1. Adverse thrombotic cardiovascular events increase in women coincident with the onset of menopause. 2. Age past menopause may be an important variable in defining the benefit/risk of hormone treatments. 3. Few studies have examined hormonal status as a variable of ageing using a polygenomic approach of both humoral and cellular components of the coagulation system. 4. Longitudinal studies of a global set of platelet functions that define procoagulant activity (i.e. adhesion, aggregation, secretion and thrombin production) in individuals with documented hormonal status are needed to better understand how hormonal changes associated with ageing impact thrombotic risk.

Mitochondrial dysfunction in platelets and hippocampi of senescence-accelerated mice

Senescence-accelerated mice (SAM) strains are useful models to understand the mechanisms of age-dependent degeneration. In this study, measurements of the mitochondrial membrane potential (Deltapsi(m)) of platelets and the Adenosine 5(')-triphosphate (ATP) content of hippocampi and platelets were made, and platelet mitochondria were observed in SAMP8 (faster aging mice) and SAMR1 (aging resistant control mice) at 2, 6 and 9 months of age. In addition, an Abeta-induced (Amyloid beta-protein) damage model of platelets was established. After the addition of Abeta, the Deltapsi(m) of platelets of SAMP8 at 1 and 6 months of age were measured. We found that platelet Deltapsi(m), and hippocampal and platelet ATP content of SAMP8 mice decreased at a relatively early age compared with SAMR1. The platelets of 6 month-old SAMP8 showed a tolerance to Abeta-induced damages. These results suggest that mitochondrial dysfunction might be one of the mechanisms leading to age-associated degeneration in SAMP mice at an early age and the platelets could serve as a biomarker for detection of mitochondrial function and age related disease.

Ischemic preconditioning preserves proton leakage from mitochondrial membranes but not oxidative phosphorylation during heart reperfusion

The aim of this study was to evaluate the role of mitochondria in the recovery of cardiac energetics induced by ischaemic preconditioning at reperfusion. Isolated rat hearts were aerobically perfused (control), subjected to global ischaemia and reperfusion (reperfusion), or subjected to 3 brief cycles of ischaemia/reperfusion and then to the protocol of reperfusion (preconditioning). At the end of the perfusion, antimycin A was delivered to the heart for 25 min, to inhibit mitochondrial respiration and stimulate glycolysis. The increased amount of lactate released in the coronary effluent was correlated with the number of viable cells producing this end-product of glycolysis. Preconditioned hearts released 18% more lactate than reperfused hearts (p < 0.05). This result indicates that preconditioning partially preserved cell viability, as was also evidenced by the MTT assay performed on cardiac biopsies. The difference between antimycin A-stimulated and basal lactate concentration, representing the contribution of mitochondria to the overall energetics of cardiac tissue, was also 18% more elevated in the preconditioned hearts than in the reperfused hearts (p < 0.01). The study of the respiratory function of mitochondria isolated at the end of perfusion, showed that preconditioning did not improve the oxygen-dependent production of ATP (state 3 respiration, ADP/O). On the contrary, state 4 respiration, which is related to proton leakage, was 35.0% lower in the preconditioned group than reperfusion group (p < 0.05). Thus, preconditioning ameliorates cardiac energetics by preserving cell death, but without affecting mitochondrial oxidative phosphorylation. Mitochondria can contribute to cell survival by the attenuation of proton leak from inner membrane.

Influence on mitochondria and cytotoxicity of different antibiotics administered in high concentrations on primary human osteoblasts and cell lines

Osteomyelitis, osteitis, spondylodiscitis, septic arthritis, and prosthetic joint infections still represent the worst complications of orthopedic surgery and traumatology. Successful treatment requires, besides surgical débridement, long-term systemic and high-concentration local antibiotic therapy, with possible local antibiotic concentrations of 100 microg/ml and more. In this study, we investigated the effect of 20 different antibiotics on primary human osteoblasts (PHO), the osteosarcoma cell line MG63, and the epithelial cell line HeLa. High concentrations of fluoroquinolones, macrolides, clindamycin, chloramphenicol, rifampin, tetracycline, and linezolid during 48 h of incubation inhibited proliferation and metabolic activity, whereas aminoglycosides and inhibitors of bacterial cell wall synthesis did not. Twenty percent inhibitory concentrations for proliferation of PHO were determined as 20 to 40 microg/ml for macrolides, clindamycin, and rifampin, 60 to 80 microg/ml for chloramphenicol, tetracylin, and fluoroquinolones, and 240 microg/ml for linezolid. The proliferation of the cell lines was always less inhibited. We established the measurement of extracellular lactate concentration as an indicator of glycolysis using inhibitors of the respiratory chain (antimycin A, rotenone, and sodium azide) and glycolysis (iodoacetic acid) as reference compounds, whereas inhibition of the respiratory chain increased and inhibition of glycolysis decreased lactate production. The measurement of extracellular lactate concentration revealed that fluoroquinolones, macrolides, clindamycin, rifampin, tetracycline, and especially chloramphenicol and linezolid impaired mitochondrial energetics in high concentrations. This explains partly the observed inhibition of metabolic activity and proliferation in our experiments. Because of differences in the energy metabolism, PHO provided a more sensitive model for orthopedic antibiotic usage than stable cell lines.

Mitochondrial activities of a cell line derived from thyroid Hürthle cell tumors

OBJECTIVE

We conducted a study on the functional characteristics of mitochondria in an oxyphilic thyroid tumor cell line, which may provide useful clues about Hürthle cell tumors carcinogenesis.

DESIGN

The functional study on thyroid tumors with cell oxyphilia (Hürthle cell tumors), characterized by mitochondrial hyperplasia, was carried out in XTC.UC1, and B-CPAP, an oxyphilic and nonoxyphilic thyroid tumor cell line, respectively.

MAIN OUTCOME

XTC.UC1 cell line showed higher activity of mitochondrial respiratory complexes I and II and decreased activity of complex III. The increased activity of complex I was not matched by increased expression of complex I subunits. The XTC.UC1 cells relied mostly on oxidative phosphorylation for energy conservation, although their mitochondrial energetic function was less efficient when related to mitochondrial content of the cells. Finally, the oxyphilic cell line produced significantly higher amounts of reactive oxygen species (ROS) in comparison with B-CPAP cell line.

CONCLUSION

The involvement of ROS in mitochondrial biogenesis and proliferation as well as in carcinogenesis and apoptosis indicate that differences in activity of respiratory chain components and their unbalance may be responsible for development of morphological and functional changes observed in thyroid tumors with cell oxyphilia.

Platelet characteristics change with aging: role of estrogen receptor beta

Estrogen receptor beta (betaER) is the predominant estrogen receptor in platelets. Experiments were designed to define phenotypic changes in platelets with aging following deletion of betaER (betaERKO). Blood was collected from wild-type and betaERKO female mice at 4-7 (young) and 24-25 (aged) months of age. In young animals, total number of platelets, number of platelets containing RNA (reticulated platelets), aggregation, dense body adenosine triphosphate secretion, and alpha granular secretion were the same in both groups. With aging, total number of platelets decreased but reticulated platelets increased in betaERKO mice; aggregation and dense granule adenosine triphosphate secretion decreased whereas basal expression of fibrinogen receptors increased with age in wild-type and betaERKO mice. Basal expression of P-selectin and annexin V binding increased with aging only in betaERKO mice; thrombin did not increase expression in these mice. Therefore, deletion of betaER is associated with specific platelet functions, which are expressed only with age-associated reproductive senescence.

Upregulation of human mitochondrial NADH dehydrogenase subunit 5 in intestinal epithelial cells is modulated byVibrio choleraepathogenesis

Cholera still remains an important global predicament especially in India and other developing countries. Vibrio cholerae, the etiologic agent of cholera, colonizes the small intestine and produces an enterotoxin that is largely responsible for the watery diarrheal symptoms of the disease. Using RNA arbitrarily primed PCR, ND5 a mitochondria encoded subunit of complex I of the mitochondrial respiratory chain was found to be upregulated in the human intestinal epithelial cell line Int407 following exposure to V. cholerae. The upregulation of ND5 was not observed when Int407 was infected with Escherichia coli strains. Incubation with heat-killed V. cholerae or cholera toxin or culture supernatant also showed no such upregulation indicating the involvement of live bacteria in the process. Infection of the monolayer with aflagellate non-motile mutant of V. cholerae O395 showed a very significant (59-fold) downregulation of ND5. In contrast, a remarkable upregulation of ND5 expression (200-fold) was observed in a hyperadherent icmF insertion mutant with reduced motility. V. cholerae cheY4 null mutant defective in adherence and motility also resulted in significantly reduced levels of ND5 expression while mutant with the cheY4 gene duplicated showing increased adherence and motility resulted in increased expression of ND5. These results clearly indicate that both motility and adherence to intestinal epithelial cells are possible triggering factors contributing to ND5 mRNA expression by V. cholerae. Interestingly infection with insertion mutant in the gene coding for ToxR, the master regulator of virulence in V. cholerae resulted in significant downregulation of ND5 expression. However, infection with ctxA or toxT insertion mutants did not show any significant changes in ND5 expression compared to wild-type. Almost no expression of ND5 was observed in case of mutation in the gene coding for OmpU, a ToxR activated protein. Thus, infection of Int407 with virulence mutant strains of V. cholerae revealed that the ND5 expression is modulated by the virulence of V. cholerae in a ToxT independent manner. Although no difference in the mitochondrial copy number could be detected between infected and uninfected cells, the modulation of the expression of other mitochondrial genes were also observed. Incidentally, upon V. cholerae infection, complex I activity was found to increase about 3-folds after 6 h. This is the first report of alteration in mitochondrial gene expression upon infection of a non-invasive enteric bacterium like V. cholerae showing its modulation with adherence, motility and virulence of the organism.

Coenzyme Q-dependent functions of plasma membrane in the aging process

Coenzyme Q (Q) is reduced in plasma membrane and mitochondria by NAD(P)H-dependent reductases providing reducing equivalents to maintain both respiratory chain and antioxidant protection. Reactive oxygen species (ROS) are accumulated in the aging process originating mainly in mitochondria but also in other membranes, such as plasma membrane partially by the loss of electrons from the semiquinone. The reduction of Q by NAD(P)H-dependent reductases in plasma membrane is responsible for providing its antioxidant capacity, preventing both the lipid peroxidation chain and the activation of the ceramide-dependent apoptosis pathway. Both Q content and its reductases are decreased in plasma membrane of aging mammals. Calorie restriction, which extends mammal life span, increases the content of Q in the plasma membrane and also activates Q reductases in this membrane. Both lipid peroxidation and ceramide production are decreased in the plasma membrane in calorie-restricted animals. Plasma membrane is, then, an important cellular component to control the aging process through its concentration and redox state of Q.

Biochemical analysis of respiratory function in cybrid cell lines harbouring mitochondrial DNA mutations

We analysed key biochemical features that reflect the balance between glycolysis and glucose oxidation in cybrids (cytoplasmic hybrids) harbouring a representative sample of mitochondrial DNA point mutations and deletions. The cybrids analysed had the same 143B cell nuclear background and were isogenic for the mitochondrial background. The 143B cell line and its rho(0) counterpart were used as controls. All cells analysed were in a dynamic state, and cell number, time of plating, culture medium, extracellular volume and time of harvest and assay were strictly controlled. Intra- and extra-cellular lactate and pyruvate levels were measured in homoplasmic wild-type and mutant cells, and correlated with rates of ATP synthesis and O2 consumption. In all mutant cell lines, except those with the T8993C mutation in the ATPase 6 gene, glycolysis was increased even under conditions of low glucose, as demonstrated by increased levels of extracellular lactate and pyruvate. Extracellular lactate levels were strictly and inversely correlated with rates of ATP synthesis and O2 consumption. These results show increased glycolysis and defective oxidative phosphorylation, irrespective of the type or site of the point mutation or deletion in the mitochondrial genome. The different biochemical consequences of the T8993C mutation suggest a uniquely different pathogenic mechanism for this mutation. However, the distinct clinical features associated with some of these mutations still remain to be elucidated.

Evaluation of cellular energetics by the pasteur effect in intact cardiomyoblasts and isolated perfused hearts

This work aims at exploring changes in cellular energetics by exploiting the Pasteur effect. We assumed that lactate overproduction arising from antimycin A-induced inhibition of mitochondrial respiration (delta-lactate = stimulated [lactate] -basal [lactate]) is indicative of the energy provided aerobically by the cell. Rat embryonal cardiomyocytes (H9c2), incubated with 2 micromol/L antimycin A, increased about 6 fold their lactate production in a manner linear with time and cell number. Antimycin A was also delivered to Langendorff-perfused rat hearts under control aerobic conditions or after 20 min-ischemia and 30 min-reperfusion. The test started at the end of each perfusion and lactate was measured into perfusate collected for further 25 min. A cardioplegic solution was also delivered during the test to exclude that lactate production was influenced by cardiac contraction. Control delta-lactate was 20.9 +/- 2.31 (S.E.M.) microg/mL and markedly decreased after reperfusion (7.66 +/- 0.51, p < 0.001), showing that energy production was impaired of about 70%. The determination of oxygen consumption by mitochondria isolated from reperfused hearts also suggested that the damage to the respiratory chain was similar to that evaluated by lactate overproduction (Respiratory Control Index: 75% lower than control, p < 0.001). Moreover, when delta-lactate was referred to the estimated cells which remained viable at the end of reperfusion (49.9%), it was 25% lower than control (p < 0.05). Therefore, we proposed this test as a tool for quantifying both physiological and pathological energetic modifications in living intact cardiomyocytes and in isolated and perfused hearts.

Methods to detect mitochondrial function

The bioenergetic function of mitochondria can be investigated in intact cells by a variety of methods. A simple biochemical method to compare mitochondrial oxidative phosphorylation with glycolytic ATP synthesis takes advantage of the Pasteur effect, since the amount of lactate produced under basal conditions is an indication of glycolytic ATP, while the Delta-lactate (the difference between excess lactate produced after inhibition of respiration and basal lactate) represents ATP produced anaerobically in order to compensate for decreased oxidative phosphorylation after respiratory chain inhibition. The system has been validated in a series of cells, including human platelets and lymphocytes and lines cultured in vitro. Measurement of KCN-sensitive oxygen consumption by the cells and its sensitivity to uncouplers can be good supplementary indication of mitochondrial phosphorylative capacity.

The mitochondrial production of reactive oxygen species in relation to aging and pathology

Mitochondria are known to be strong producers of reactive oxygen species (ROS) and, at the same time, particularly susceptible to the oxidative damage produced by their action on lipids, proteins, and DNA. In particular, damage to mtDNA induces alterations to the polypeptides encoded by mtDNA in the respiratory complexes, with consequent decrease of electron transfer, leading to further production of ROS and thus establishing a vicious circle of oxidative stress and energetic decline. This deficiency in mitochondrial energetic capacity is considered the cause of aging and age-related degenerative diseases. Complex I would be the enzyme most affected by ROS, since it contains seven of the 13 subunits encoded by mtDNA. Accordingly, we found that complex I activity is significantly affected by aging in rat brain and liver mitochondria as well as in human platelets. Moreover, due to its rate control over aerobic respiration, such alterations are reflected on the entire oxidative phosphorylation system. We also investigated the role of mitochondrial complex I in superoxide production and found that the one-electron donor to oxygen is most probably the Fe-S cluster N2. Short chain coenzyme Q (CoQ) analogues enhance ROS formation, presumably by mediating electron transfer from N2 to oxygen, both in bovine heart SMP and in cultured HL60 cells. Nevertheless, we have accumulated much evidence of the antioxidant role of reduced CoQ(10) in several cellular systems and demonstrated the importance of DT-diaphorase and other internal cellular reductases to reduce exogenous CoQ(10) after incorporation.

Increased transcription of mitochondrial genes for Complex I in human platelets during ageing

We studied the effect of ageing on the mRNA levels of mitochondria-encoded polypeptides in human platelets. We used quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) to investigate the expression of selected cytochrome c oxidase (COX) genes (subunits I and III) and Complex I genes (subunits reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase (ND)1 and (ND)5 in platelets from young and aged healthy subjects. Northern blot analysis confirmed the PCR results. COX I expression is higher than that of COX III in both young and aged platelets. A significant increase of transcripts for Complex I was found during ageing. On the contrary, the mRNA levels of the two COX subunits did not significantly vary during ageing.

Mitochondrial production of oxygen radical species and the role of Coenzyme Q as an antioxidant

The mitochondrial respiratory chain is a powerful source of reactive oxygen species (ROS), which is considered as the pathogenic agent of many diseases and of aging. We have investigated the role of complex I in superoxide radical production and found by the combined use of specific inhibitors of complex I that the one-electron donor to oxygen in the complex is a redox center located prior to the sites where three different types of Coenzyme Q (CoQ) competitors bind, to be identified with an Fe-S cluster, most probably N2, or possibly an ubisemiquinone intermediate insensitive to all the above inhibitors. Short-chain Coenzyme Q analogs enhance superoxide formation, presumably by mediating electron transfer from N2 to oxygen. The clinically used CoQ analog, idebenone, is particularly effective, raising doubts on its safety as a drug. Cells counteract oxidative stress by antioxidants. CoQ is the only lipophilic antioxidant to be biosynthesized. Exogenous CoQ, however, protects cells from oxidative stress by conversion into its reduced antioxidant form by cellular reductases. The plasma membrane oxidoreductase and DT-diaphorase are two such systems, likewise, they are overexpressed under oxidative stress conditions.

Apoptosis-resistant phenotype in HL-60-derived cells HCW-2 is related to changes in expression of stress-induced proteins that impact on redox status and mitochondrial metabolism

The onset of resistance to drug-induced apoptosis of tumour cells is a major problem in cancer therapy. We studied a drug-selected clone of promyelocytic HL-60 cells, called HCW-2, which display a complex resistance to a wide variety of apoptosis-inducing agents and we found that these cells show a dramatic increase in the expression of heat shock proteins (Hsps) 70 and 27, while the parental cell line does not. It is known that stress proteins such as Hsps can confer resistance to a variety of damaging agents other than heat shock, such as TNF-alpha, monocyte-induced cytotoxicity, and also play a role in resistance to chemotherapy. This elevated expression of Hsps is paralleled by an increased activity of mitochondrial metabolism and pentose phosphate pathway, this latter leading to high levels of glucose-6-phosphate dehydrogenase and, consequently, of glutathione. Thus, the apoptotic-deficient phenotype is likely because of the presence of high levels of stress response proteins and GSH, which may confer resistance to apoptotic agents, including chemotherapy drugs. Moreover, the fact that in HCW-2 cells Hsp70 are mainly localised in mitochondria may account for the increased performances of mitochondrial metabolism. These observations could have some implications for the therapy of cancer, and for the design of combined strategies that act on antioxidant defences of the neoplastic cell.

Role of mitochondria in oxidative stress and aging

The mitochondrial respiratory chain is a powerful source of reactive oxygen species (ROS), considered as the pathogenic agent of many diseases and of aging. We have investigated the role of Complex I in superoxide radical production and found by combined use of specific inhibitors of Complex I that the one-electron donor in the Complex to oxygen is a redox center located prior to the sites where three different types of coenzyme Q (CoQ) competitors bind, to be identified with an Fe-S cluster, most probably N2, or possibly an ubisemiquinone intermediate insensitive to all the above inhibitors. Short-chain coenzyme Q analogues enhance superoxide formation, presumably by mediating electron transfer from N2 to oxygen. The clinically used CoQ analogue idebenone is particularly effective, raising doubts about its safety as a drug. The mitochondrial theory of aging considers somatic mutations of mitochondrial DNA induced by ROS as the primary cause of energy decline; in rat liver mitochondria, Complex I appears to be most affected by aging and to become strongly rate limiting for electron transfer. Mitochondrial energetics is also deranged in human platelets upon aging, as demonstrated by the decreased Pasteur effect (enhancement of lactate production by respiratory inhibitors). Cells counteract oxidative stress by antioxidants: CoQ is the only lipophilic antioxidant to be biosynthesized. Exogenous CoQ, however, protects cells from oxidative stress by conversion into its reduced antioxidant form by cellular reductases. The plasma membrane oxidoreductase and DT-diaphorase are two such systems: likewise, they are overexpressed under oxidative stress conditions.