Hyperacetylation of Cardiac Mitochondrial Proteins Is Associated with Metabolic Impairment and Sirtuin Downregulation after Chronic Total Body Irradiation of ApoE -/- Mice.

Chronic exposure to low-dose ionizing radiation is associated with an increased risk of cardiovascular disease. Alteration in energy metabolism has been suggested to contribute to radiation-induced heart pathology, mitochondrial dysfunction being a hallmark of this disease. The goal of this study was to investigate the regulatory role of acetylation in heart mitochondria in the long-term response to chronic radiation. ApoE-deficient C57Bl/6J mice were exposed to low-dose-rate (20 mGy/day) gamma radiation for 300 days, resulting in a cumulative total body dose of 6.0 Gy. Heart mitochondria were isolated and analyzed using quantitative proteomics. Radiation-induced proteome and acetylome alterations were further validated using immunoblotting, enzyme activity assays, and ELISA. In total, 71 proteins showed peptides with a changed acetylation status following irradiation. The great majority (94%) of the hyperacetylated proteins were involved in the TCA cycle, fatty acid oxidation, oxidative stress response and sirtuin pathway. The elevated acetylation patterns coincided with reduced activity of mitochondrial sirtuins, increased the level of Acetyl-CoA, and were accompanied by inactivation of major cardiac metabolic regulators PGC-1 alpha and PPAR alpha. These observations suggest that the changes in mitochondrial acetylation after irradiation is associated with impairment of heart metabolism. We propose a novel mechanism involved in the development of late cardiac damage following chronic irradiation.

A dose-dependent perturbation in cardiac energy metabolism is linked to radiation-induced ischemic heart disease in Mayak nuclear workers.

Epidemiological studies show a significant increase in ischemic heart disease (IHD) incidence associated with total external gamma-ray dose among Mayak plutonium enrichment plant workers. Our previous studies using mouse models suggest that persistent alteration of heart metabolism due to the inhibition of peroxisome proliferator-activated receptor (PPAR) alpha accompanies cardiac damage after high doses of ionising radiation. The aim of the present study was to elucidate the mechanism of radiation-induced IHD in humans. The cardiac proteome response to irradiation was analysed in Mayak workers who were exposed only to external doses of gamma rays. All participants were diagnosed during their lifetime with IHD that also was the cause of death. Label-free quantitative proteomics analysis was performed on tissue samples from the cardiac left ventricles of individuals stratified into four radiation dose groups (0 Gy, < 100 mGy, 100-500 mGy, and > 500 mGy). The groups could be separated using principal component analysis based on all proteomics features. Proteome profiling showed a dose-dependent increase in the number of downregulated mitochondrial and structural proteins. Both proteomics and immunoblotting showed decreased expression of several oxidative stress responsive proteins in the irradiated hearts. The phosphorylation of transcription factor PPAR alpha was increased in a dose-dependent manner, which is indicative of a reduction in transcriptional activity with increased radiation dose. These data suggest that chronic external radiation enhances the risk for IHD by inhibiting PPAR alpha and altering the expression of mitochondrial, structural, and antioxidant components of the heart.

Effects of local irradiation combined with sunitinib on early remodeling, mitochondria, and oxidative stress in the rat heart.

BACKGROUND AND PURPOSE: Thoracic (chemo)radiation therapy is increasingly administered with tyrosine kinase inhibitors (TKI). While TKI have adverse effects on the heart, it is unknown whether combination with other cancer therapies causes enhanced toxicity. We used an animal model to investigate whether radiation and sunitinib interact in their effects on the heart. MATERIAL AND METHODS: Male Sprague-Dawley rats received local heart irradiation (9Gy per day, 5days). Oral sunitinib (8 or 15mg/kg bodyweight per day) started on day 1 of irradiation and continued for 2weeks. Cardiac function was examined with echocardiography. Cardiac remodeling, cell death, left ventricular (LV) oxidative stress markers, mitochondrial morphology and mitochondrial permeability transition pore (mPTP) opening were assessed. RESULTS: Cardiac diameter, stroke volume, and LV volume, mass and anterior wall thickness increased in time, but only in the vehicle group. Sunitinib reduced LV inner diameter and volume in systole, which were counteracted by radiation. Sunitinib and radiation showed enhanced effects on mitochondrial morphology and mPTP opening, but not on cardiac troponin I, mast cell numbers or markers of oxidative stress. CONCLUSIONS: This study found no early enhanced effects of radiation and sunitinib on cardiac function or structure. Long-term effects remain to be determined.

A tocotrienol-enriched formulation protects against radiation-induced changes in cardiac mitochondria without modifying late cardiac function or structure.

Radiation-induced heart disease (RIHD) is a common and sometimes severe late side effect of radiation therapy for intrathoracic and chest wall tumors. We have previously shown that local heart irradiation in a rat model caused prolonged changes in mitochondrial respiration and increased susceptibility to mitochondrial permeability transition pore (mPTP) opening. Because tocotrienols are known to protect against oxidative stress-induced mitochondrial dysfunction, in this study, we examined the effects of tocotrienols on radiation-induced alterations in mitochondria, and structural and functional manifestations of RIHD. Male Sprague-Dawley rats received image-guided localized X irradiation to the heart to a total dose of 21 Gy. Twenty-four hours before irradiation, rats received a tocotrienol-enriched formulation or vehicle by oral gavage. Mitochondrial function and mitochondrial membrane parameters were studied at 2 weeks and 28 weeks after irradiation. In addition, cardiac function and histology were examined at 28 weeks. A single oral dose of the tocotrienol-enriched formulation preserved Bax/Bcl2 ratios and prevented mPTP opening and radiation-induced alterations in succinate-driven mitochondrial respiration. Nevertheless, the late effects of local heart irradiation pertaining to myocardial function and structure were not modified. Our studies suggest that a single dose of tocotrienols protects against radiation-induced mitochondrial changes, but these effects are not sufficient against long-term alterations in cardiac function or remodeling.

PPAR alpha: a novel radiation target in locally exposed Mus musculus heart revealed by quantitative proteomics.

Radiation exposure of the thorax is associated with a markedly increased risk of cardiac morbidity and mortality with a latency period of decades. Although many studies have confirmed the damaging effect of ionizing radiation on the myocardium and cardiac endothelial structure and function, the molecular mechanism behind this damage is not yet elucidated. Peroxisome proliferator-activated receptor alpha (PPAR alpha), a transcriptional regulator of lipid metabolism in heart tissue, has recently received great attention in the development of cardiovascular disease. The goal of this study was to investigate radiation-induced cardiac damage in general and the role of PPAR alpha in this process in particular. C57BL/6 mice received local heart irradiation with X-ray doses of 8 and 16 gray (Gy) at the age of 8 weeks. The mice were sacrificed 16 weeks later. Radiation-induced changes in the cardiac proteome were quantified using the Isotope Coded Protein Label (ICPL) method followed by mass spectrometry and software analysis. Significant alterations were observed in proteins involved in lipid metabolism and oxidative phosphorylation. Ionizing radiation markedly changed the phosphorylation and ubiquitination status of PPAR alpha. This was reflected as decreased expression of its target genes involved in energy metabolism and mitochondrial respiratory chain confirming the proteomics data. This study suggests that persistent alteration of cardiac metabolism due to impaired PPAR alpha activity contributes to the heart pathology after radiation.

Ionising radiation induces persistent alterations in the cardiac mitochondrial function of C57BL/6 mice 40 weeks after local heart exposure.

BACKGROUND AND PURPOSE: Radiotherapy of thoracic and chest-wall tumours increases the long-term risk of radiation-induced heart disease. The aim of this study was to investigate the long-term effect of local heart irradiation on cardiac mitochondria. METHODS: C57BL/6 and atherosclerosis-prone ApoE(-/-) mice received local heart irradiation with a single X-ray dose of 2 Gy. To investigate the low-dose effect, C57BL/6 mice also received a single heart dose of 0.2 Gy. Functional and proteomic alterations of cardiac mitochondria were evaluated after 40 weeks, compared to age-matched controls. RESULTS: The respiratory capacity of irradiated C57BL/6 cardiac mitochondria was significantly reduced at 40 weeks. In parallel, protein carbonylation was increased, suggesting enhanced oxidative stress. Considerable alterations were found in the levels of proteins of mitochondria-associated cytoskeleton, respiratory chain, ion transport and lipid metabolism. Radiation induced similar but less pronounced effects in the mitochondrial proteome of ApoE(-/-) mice. In ApoE(-/-), no significant change was observed in mitochondrial respiration or protein carbonylation. The dose of 0.2 Gy had no significant effects on cardiac mitochondria. CONCLUSION: This study suggests that ionising radiation causes non-transient alterations in cardiac mitochondria, resulting in oxidative stress that may ultimately lead to malfunctioning of the heart muscle.

Estudo dos efeitos da radioterapia no tecido cardíaco e sua associação com o metabolismo energético / Study of the effects of radiation therapy in cardiac tissue and its association with energy metabolism

Durante o tratamento radioterápico para tumores localizados na região torácica, parte do coração frequentemente é incluída no campo de tratamento e pode receber doses de radiação ionizante, significativas em relação à terapêutica. A irradiação do coração é capaz de causar importantes complicações cardíacas ao paciente, caracterizadas por alterações funcionais progressivas cerca de 10 a 20 anos após a exposição do órgão. Devido ao seu alto grau de contração e grande consumo energético, o tecido cardíaco é altamente dependente do metabolismo oxidativo que ocorre nas mitocôndrias. Danos as estas organelas podem levar ao decréscimo da produção de energia, tendo um impacto direto sobre a performance cardíaca. Ainda, ao interagir com as células, a radiação ionizante pode gerar uma série de eventos bioquímicos que conduzem a uma resposta celular complexa, em que muitas proteínas parecem estar envolvidas. Tendo em vista tais conhecimentos, o objetivo do estudo foi avaliar o aspecto ultraestrutural do tecido cardíaco, a bioenergética mitocondrial e a expressão diferencial de proteínas após irradiação. Os ensaios foram realizados em amostras de tecido cardíaco de ratos Wistar irradiados com dose única de 20 Gy direcionada ao coração. As análise tiveram início 4 e 32 semanas após irradiação. A análise ultraestrutural foi realizada através de microscopia eletrônica de transmissão. A respiração mitocondrial foi mensurada em oxígrafo, a partir das taxas de consumo de oxigênio pelas fibras cardíacas. A identificação de proteínas diferencialmente expressas foi investigada através de duas técnicas proteômicas: 2D-DIGE (2-D Fluorescence Difference Gel Electrophoresis) e uma abordagem label-free seguida de espectrometria de massas. Os resultados mostraram que os efeitos tardios da radiação incluem a degeneração das mitocôndrias e das unidades contráteis do tecido cardíaco, disfunções na cadeia respiratória mitocondrial e expressão diferencial de proteínas...

During radiotherapy for tumors located at toracic region, part of the heart is often included in the treatment field and may receive a significant ionizing radiation dose comparing to the therapeutics. Heart irradiation is able to cause substantial cardiac complications to patient, characterized by functional progressive changes from 10 to 20 years after the exposure of the organ. Because of its high level of contraction and large energetic consumption, cardiac tissue is highly depending on oxidative metabolism which happens at mitochondrias. Damage to these organelles can lead to decreased energy production, having a direct impact on cardiac performance. Even when interacting with cells, ionizing radiation can generate a series of biochemical events that lead to a complex cellular response, in many proteins seem to be involved. Given this knowledge, the aim of the study was to evaluate the ultrastructural appearance of cardiac tissue, mitochondrial bioenergetics and differential expression of proteins after irradiation. The tests were performed on samples of cardiac tissue of rats irradiated with single dose of 20 Gy directed to the heart. The analysis started 4 to 32 weeks after irradiation. The ultrastructural analysis was performed by transmission electron microscopy. Mitochondrial respiration was measured in oxigraph from rates of oxygen consumption by cardiac fibers. The identification of differentially expressed proteins was investigated using two proteomic techniques: 2D-DIGE (2-D Fluorescence Difference Gel Electrophoresis) and a label-free approach followed by mass spectrometry. The results showed that the late effects of radiation include degeneration of mitochondria and contractile units of cardiac tissue, dysfunction in the mitochondrial respiratory chain and differential expression of proteins involved in energy metabolism of carbohydrates, lipids and phosphocreatine. In general, the study showed that the cardiac irradiation damages...

Mouse lines with photo-activatable mitochondria to study mitochondrial dynamics.

Many pathological states involve dysregulation of mitochondrial fusion, fission, or transport. These dynamic events are usually studied in cells lines because of the challenges in tracking mitochondria in tissues. To investigate mitochondrial dynamics in tissues and disease models, we generated two mouse lines with photo-activatable mitochondria (PhAM). In the PhAM(floxed) line, a mitochondrially localized version of the photo-convertible fluorescent protein Dendra2 (mito-Dendra2) is targeted to the ubiquitously expressed Rosa26 locus, along with an upstream loxP-flanked termination signal. Expression of Cre in PhAM( floxed) cells results in bright mito-Dendra2 fluorescence without adverse effects on mitochondrial morphology. When crossed with Cre drivers, the PhAM(floxed) line expresses mito-Dendra2 in specific cell types, allowing mitochondria to be tracked even in tissues that have high cell density. In a second line (PhAM(excised) ), the expression of mito-Dendra2 is ubiquitous, allowing mitochondria to be analyzed in a wide range of live and fixed tissues. By using photo-conversion techniques, we directly measured mitochondrial fusion events in cultured cells as well as tissues such as skeletal muscle. These mouse lines facilitate analysis of mitochondrial dynamics in a wide spectrum of primary cells and tissues, and can be used to examine mitochondria in developmental transitions and disease states.

Label-free protein profiling of formalin-fixed paraffin-embedded (FFPE) heart tissue reveals immediate mitochondrial impairment after ionising radiation.

Qualitative proteome profiling of formalin-fixed, paraffin-embedded (FFPE) tissue is advancing the field of clinical proteomics. However, quantitative proteome analysis of FFPE tissue is hampered by the lack of an efficient labelling method. The usage of conventional protein labelling on FFPE tissue has turned out to be inefficient. Classical labelling targets lysine residues that are blocked by the formalin treatment. The aim of this study was to establish a quantitative proteomics analysis of FFPE tissue by combining the label-free approach with optimised protein extraction and separation conditions. As a model system we used FFPE heart tissue of control and exposed C57BL/6 mice after total body irradiation using a gamma ray dose of 3 gray. We identified 32 deregulated proteins (p≤0.05) in irradiated hearts 24h after the exposure. The proteomics data were further evaluated and validated by bioinformatics and immunoblotting investigation. In good agreement with our previous results using fresh-frozen tissue, the analysis indicated radiation-induced alterations in three main biological pathways: respiratory chain, lipid metabolism and pyruvate metabolism. The label-free approach enables the quantitative measurement of radiation-induced alterations in FFPE tissue and facilitates retrospective biomarker identification using clinical archives.

[The protective effects of Aduola Fuzhenglin on the heart injury induced by microwave exposure in rats].

OBJECTIVE: To study the protective effects of AduoLa Fuzhenglin(ADL) on the heart injury induced by microwave exposure in rats. METHODS: One hundred forty male Wistar rats were divided randomly into 5 groups: control, microwave radiation, 0.75 g x kg(-1) d(-1) ADL, 1.50 g x kg(-1) d(-1) ADL and 3.00 g x kg(-1) d(-1) ADL pretreatment groups. Rats in three ADL pretreatment groups were administrated by ADL per day for 2w then exposed to 30 mW/cm2 microwaves for 15 min. The left ventricle blood of rats was obtained at 7 d and 14 d after exposure to microwaves, and the blood Ca2+, AST and CK were detected with Coulter automatic biochemical analyzer, then the histological changes and ultrastructure of heart were observed under light and electron microscopes. RESULTS: At 7 d and 14 d after exposure to microwaves, the blood Ca2+, AST and CK concentrations significantly increased (P<0.05 or P<0.01) as compared with controls; Heart muscle fibers showed wavilness, endotheliocyte karyopyknosis, anachromasis; The mitochondria swelling and cavitation, intercalary dies blurred in radiation groups. The changes in 0.75 g x kg(-1) d(-1) ADL pretreatment group were similar to the radiation group, but in 1.50 g x kg(-1)d(-1) and 3.00 g x kg(-1) d(-1) ADL pretreatment groups, above indexes of rats significantly reduced as compared with microwaves group (P<0.05); also the blood Ca2+, AST, CK contents were significantly lower than those in microwave group (P<0.05); The heart showed a tendency to improve. CONCLUSION: Microwave radiation (30 mW/cm2) can cause the blood Ca2+, AST and CK turbulence, and heart injury in the histology and ultrastructure; ADL at the dosages of 1.50 g x kg(-1) d(-1) and 3.00 g x kg(-1) d(-1) has a protective effects on the heart injury induced by microwave in rats.

Dynamic modulation of Ca2+ sparks by mitochondrial oscillations in isolated guinea pig cardiomyocytes under oxidative stress.

Local control of Ca(2+)-induced Ca(2+) release (CICR) depends on the spatial organization of L-type Ca(2+) channels and ryanodine receptors (RyR) in the dyad. Analogously, Ca(2+) uptake by mitochondria is facilitated by their close proximity to the Ca(2+) release sites, a process required for stimulating oxidative phosphorylation during changes in work. Mitochondrial feedback on CICR is less well understood. Since mitochondria are a primary source of reactive oxygen species (ROS), they could potentially influence the cytosolic redox state, in turn altering RyR open probability. We have shown that self-sustained oscillations in mitochondrial inner membrane potential (ΔΨ(m)), NADH, ROS, and reduced glutathione (GSH) can be triggered by a laser flash in cardiomyocytes. Here, we employ this method to directly examine how acute changes in energy state dynamically influence resting Ca(2+) spark occurrence and properties. Two-photon laser scanning microscopy was used to monitor cytosolic Ca(2+) (or ROS), ΔΨ(m), and NADH (or GSH) simultaneously in isolated guinea pig cardiomyocytes. Resting Ca(2+) spark frequency increased with each ΔΨ(m) depolarization and decreased with ΔΨ(m) repolarization without affecting Ca(2+) spark amplitude or time-to-peak. Stabilization of mitochondrial energetics by pretreatment with the superoxide scavenger TMPyP, or by acute addition of 4'-chlorodiazepam, a mitochondrial benzodiazepine receptor antagonist that blocks the inner membrane anion channel, prevented or reversed, respectively, the increased spark frequency. Cyclosporine A did not block the ΔΨ(m) oscillations or prevent Ca(2+) spark modulation by ΔΨ(m). The results support the hypothesis that mitochondria exert an influential role on the redox environment of the Ca(2+) handling subsystem, with mechanistic implications for the pathophysiology of cardiac disease.

[The strategy of the "useful sun" improves physical endurance and structural adaptation in the myocardium].

The action of solar light transformed by special screens has been studied on CD-1 male mice. In the active control group, mice were irradiated through screens absorbing the UV-component. In the experimental group, screens transforming the UV-component into the orange-red light were used. In the active control, changes in the swimming activity, as compared to the same parameter before irradiation, were manifested much less than in animals of the experimental group. A morphological analysis showed changes in the structure of all cardiomyocyte organelles studied: the relative area of mitochondria in the experimental mice increased by more than 20% compared to intact animals (p < 0.05). A significant increase in the area of the sarcoplasmic reticulum, by 23.4% (p < 0.05), and in the volume of the myofibrillar apparatus, by 19.4% (p < 0.05), was detected. The results of our experiment show that the irradiation with using an additional orange-red component improves the physical endurance 1.5 times and initiates morphogenetic processes in cardiac muscle cells.

Photosensitization of intact heart mitochondria by the phthalocyanine Pc 4: Correlation of structural and functional deficits with cytochrome c release.

Singlet oxygen is produced by the absorption of red light by the phthalocyanine dye Pc 4, followed by energy transfer to dissolved triplet oxygen. Mitochondria preincubated with Pc 4 were illuminated by red light and the damage to mitochondrial structure and function by the generated singlet oxygen was studied. At early illumination times (3-5 min of red light exposure), State 3 respiration was inhibited (50%), whereas State 4 activity increased, resulting in effectively complete uncoupling. Individual complex activities were measured and only complex IV activity was significantly reduced and exhibited a dose response, whereas the activities of electron transport complexes I, II, and III were not significantly affected. Cytochrome c release was an increasing function of irradiation time, with 30% being released after 5 min of illumination. Mitochondrial expansion along with changes in the structure of the cristae were observed by transmission electron microscopy after 5 min of irradiation, with an increase in large vacuoles and membrane rupture occurring after more extensive exposures.

Protective role of mitochondrial unsaturated lipids on the preservation of the apoptotic ability of cytochrome C exposed to singlet oxygen.

Cytochrome c-mediated apoptosis in cells submitted to photodynamic therapy raises the question about the ability of photodynamically oxidized cytochrome c (cytc405) to trigger apoptosis as well as the effect of membranes on protein photo-oxidation. Cytochrome c was submitted to irradiation in the presence of MB+ in phosphate buffer and in the presence of four types of phosphatidylcholine/phosphatidylethanolamine/cardiolipin (PCPECL) liposomes (50/30/20%): totally saturated lipids (tsPCPECL), totally unsaturated lipids (tuPCPECL), partially unsaturated (80%) lipids, with unsaturation in the PC and PE content (puPCPECL80), and partially unsaturated (20%) lipids, with unsaturation in the CL content (puPCPECL20). Cytc405 was formed by irradiation in buffered water and in tsPCPECL and puPCPECL20 liposomes. In the presence of tuPCPECL and puPCPECL80, cytochrome c was protected from photodynamic damage (lipid-protected cytochrome c). In CL liposomes, 25% unsaturated lipids were enough to protect cytochrome c. The presence of unsaturated lipids, in amounts varying according to the liposome composition, are crucial to protect cytochrome c. Interesting findings corroborating the unsaturated lipids as cytochrome c protectors were obtained from the analysis of the lipid-oxidized derivatives of the samples. Native cytochrome c, lipid-protected cytochrome c, and cytc405 were microinjected in aortic smooth muscle cells. Apoptosis, characterized by nucleus blebbing and chromatin condensation, was detected in cells loaded with native and lipid protected cytochrome c but not in cells loaded with cytc405. These results suggest that photodynamic therapy-promoted apoptosis is feasible due to the protective effect of the mitochondrial lipids on the cytochrome c structure and function.

Mitochondrial alterations induced by 532 nm laser irradiation.

Mitochondrial alterations were monitored after low power green laser (532 nm, 30 mW) irradiation in the case of whole cells (B-14) and isolated mitochondria (from Wistar rat heart). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay products were significantly higher (by 8%) in irradiated B-14 cells as compared to non-irradiated controls. Mitochondrial transmembrane potential of B-14 cells, measured by means of a fluorescent probe 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)), significantly increased (by 13%) after exposure to green laser irradiation. Another MTT assay was used for isolated mitochondria suspensions in order to examine the effect of green laser irradiation on stimulation of processes related to oxidative phosphorylation. It revealed 31.3%-increase in MTT assay products in irradiated mitochondria as compared to controls. Laser irradiation of isolated mitochondria suspension did not significantly change 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy, indicating that mitochondrial membrane fluidity was not affected by laser light. Fluorescence emission spectra of irradiated as well as non-irradiated mitochondria suspensions showed fluorescence maximum at 635 nm, corresponding to emission of Protoporphyrin IX, which was significantly lower (by 20.7%) in irradiated sample.

A preliminary investigation into light-modulated replication of nanobacteria and heart disease.

OBJECTIVE: The purpose of this preliminary study is to evaluate the effect of various wavelengths of light on nanobacteria (NB). BACKGROUND DATA: NB and mitochondria use light for biological processes. NB have been described as multifunctional primordial nanovesicles with the potential to utilize solar energy for replication. NB produce slime, a process common to living bacteria. Slime release is an evolutionary important stress-dependent phenomenon increasing the survival chance of individual bacteria in a colony. In the cardiovascular system, stress-induced bacterial colony formation may lead to a deposition of plaque. METHODS: Cultured NB were irradiated with NASA-LEDs at different wavelengths of light: 670, 728 and 880 nm. Light intensities were about 500k Wm(-2), and energy density was 1 x 10(4) J m(-2). RESULTS: Monochromatic light clearly affected replication of NB. Maximum replication was achieved at 670 nm. CONCLUSIONS: The results indicate that suitable wavelengths of light could be instrumental in elevating the vitality level of NB, preventing the production of NB-mediated slime, and simultaneously increasing the vitality level of mitochondria. The finding could stimulate the design of cooperative therapy concepts that could reduce death caused by myocardial infarcts.

Imaging the permeability pore transition in single mitochondria.

In mitochondria the opening of a large proteinaceous pore, the "mitochondrial permeability transition pore" (MTP), is known to occur under conditions of oxidative stress and matrix calcium overload. MTP opening and the resulting cellular energy deprivation have been implicated in processes such as hypoxic cell damage, apoptosis, and neuronal excitotoxicity. Membrane potential (delta psi(m)) in single isolated heart mitochondria was measured by confocal microscopy with a voltage-sensitive fluorescent dye. Measurements in mitochondrial populations revealed a gradual loss of delta psi(m) due to the light-induced generation of free radicals. In contrast, the depolarization in individual mitochondria was fast, sometimes causing marked oscillations of delta psi(m). Rapid depolarizations were accompanied by an increased permeability of the inner mitochondrial membrane to matrix-entrapped calcein (approximately 620 Da), indicating the opening of a large membrane pore. The MTP inhibitor cyclosporin A significantly stabilized delta psi(m) in single mitochondria, thereby slowing the voltage decay in averaged recordings. We conclude that the spontaneous depolarizations were caused by repeated stochastic openings and closings of the transition pore. The data demonstrate a much more dynamic regulation of membrane permeability at the level of a single organelle than predicted from ensemble behavior of mitochondrial populations.

Mitochondrial respiratory chain features after gamma-irradiation.

Radiation provokes damage to DNA but also to membrane and protein structure. Radiolysis is a tool used very often in the study of free radical biological effects and of scavenger molecules effectiveness. Nitroimidazoles have been demonstrated to enhance the radiation effects on biological structures. The studies we have performed on isolated mitochondria irradiated, with and without nitroimidazoles, at a radiation dose equal to LD90, indicate that this treatment is not able to affect the structural and functional features investigated (ubiquinone-10, fatty acids, respiratory cytochrome levels or membrane fluidity and respiratory enzymatic activities), suggesting that an involvement of such externally produced radicals on membrane damage is unlikely. Moreover it was ascertained that the mitochondrial redox activities do not take part into the intracellular nitroimidazole reduction.

[The characteristics of the action of low-intensity laser radiation on the ultrastructure of the cardiomyocytes]. / Osobennosti deistviia nizkointensivnogo lazernogo izlucheniia na ul'trastrukturu kardiomiotsitov.

Experiments studies established hyperplastic events of cardiomyocytic subcellular structures (mitochondria, ribosomes, etc.) under the influence of low-energy infrared laser radiation at 1000 and 3000 Hz. A high biosynthesis and no destructive events were observed.