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Mitochondria and the regulation of free radical damage in the eye.

ABSTRACT: Neuronal cell death can be determined by the overall level of reactive oxygen species (ROS) resulting from the combination of extrinsic sources and intrinsic production as a byproduct of oxidative phosphorylation. Key controllers of the intrinsic production of ROS are the mitochondrial uncoupling proteins (UCPs). By allowing a controlled leak of protons across the inner mitochondrial membrane activation of these proteins can decrease ROS and promote cell survival. In both primate models of Parkinson's disease and mouse models of seizures, increased activity of UCP2 significantly increased neuronal cells survival. In the retina UCP2 is expressed in many neurons and glial cells, but was not detected in rod photoreceptors. Retinal ganglion cell survival following excitotoxic damage was much greater in animals overexpressing UCP2. Traditional Chinese medicines, such as an extract of Cistanche tubulosa, may provide benefit by altering mitochondrial metabolism.

SUBMITTER: Barnstable CJ

PROVIDER: S-EPMC2798985 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Mitochondria and the regulation of free radical damage in the eye.

Barnstable Colin J CJ

Journal of ocular biology, diseases, and informatics 20090918 3

Neuronal cell death can be determined by the overall level of reactive oxygen species (ROS) resulting from the combination of extrinsic sources and intrinsic production as a byproduct of oxidative phosphorylation. Key controllers of the intrinsic production of ROS are the mitochondrial uncoupling proteins (UCPs). By allowing a controlled leak of protons across the inner mitochondrial membrane activation of these proteins can decrease ROS and promote cell survival. In both primate models of Parki ...[more]

PMID: 20046847

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Project description:The effects of elevated levels of radiation contribute to the instability of pharmaceutical formulations in space compared to those on earth. Existing technologies are ineffective at maintaining the therapeutic efficacies of drugs in space. Thus, there is an urgent need to develop novel space-hardy formulations for preserving the stability and efficacy of drug formulations. This work aims to develop a novel approach for the protection of space pharmaceutical drug molecules from the radiation-induced damage to help extend or at least preserve their structural integrity and potency. To achieve this, free radical scavenging antioxidant, Trolox was conjugated on the surface of poly-lactic-co-glycolic acid (PLGA) nanoparticles for the protection of a candidate drug, melatonin that is used as a sleep aid medication in International Space Station (ISS). Melatonin-PLGA-PLL-Trolox nanoparticle as named as PolyRad was synthesized employing single oil in water (o/w) emulsion solvent evaporation method. PolyRad is spherical in shape and has an average diameter of ~600?nm with a low polydispersity index of 0.2. PolyRad and free melatonin (control) were irradiated by UV light after being exposed to a strong oxidant, hydrogen peroxide (H2O2). Bare melatonin lost ~80% of the active structure of the drug following irradiation with UV light or treatment with H2O2. In contrast, PolyRad protected >80% of the active structure of melatonin. The ability of PolyRad to protect melatonin structure was also carried out using 0, 1, 5 and 10?Gy?gamma radiation. Gamma irradiation showed >98% active structures of melatonin encapsulated in PolyRads. Drug release and effectiveness of melatonin using PolyRad were evaluated on human umbilical vein endothelial cells (HUVEC) in vitro. Non-irradiated PolyRad demonstrated maximum drug release of ~70% after 72?h, while UV-irradiated and H2O2-treated PolyRad showed a maximum drug release of ~85%. Cytotoxicity of melatonin was carried out using both live/dead and MTT assays. Melatonin, non-radiated PolyRad and irradiated PolyRad inhibited the viability of HUVEC in a dose-dependent manner. Cell viability of melatonin, PolyRad alone without melatonin (PolyRad carrier control), non-radiated PolyRad, and irradiated PolyRad were ~98, 87, 75 and 70%, respectively at a concentration [Formula: see text] 0.01 [Formula: see text] ([Formula: see text]). Taken together, PolyRad nanoparticle provides an attractive formulation platform for preventing damage to pharmaceutical drugs in potential space mission applications.

Project description:Breakage of one strand of DNA is the most common form of DNA damage. Most damaged DNA termini require end-processing in preparation for ligation. The importance of this step is highlighted by the association of defects in the 3'-end processing enzyme tyrosyl DNA phosphodiesterase 1 (TDP1) and neurodegeneration and by the cytotoxic induction of protein-linked DNA breaks (PDBs) and oxidized nucleic acid intermediates during chemotherapy and radiotherapy. Although much is known about the repair of PDBs in the nucleus, little is known about this process in the mitochondria. We reveal that TDP1 resolves mitochondrial PDBs (mtPDBs), thereby promoting mitochondrial gene transcription. Overexpression of a toxic form of mitochondrial topoisomerase I (TOP1mt*), which generates excessive mtPDBs, results in a TDP1-dependent compensatory up-regulation of mitochondrial gene transcription. In the absence of TDP1, the imbalance in transcription of mitochondrial- and nuclear-encoded electron transport chain (ETC) subunits results in misassembly of ETC complex III. Bioenergetics profiling further reveals that TDP1 promotes oxidative phosphorylation under both basal and high energy demands. It is known that mitochondrial dysfunction results in free radical leakage and nuclear DNA damage; however, the detection of intermediates of radical damage to DNA is yet to be shown. Consequently, we report an increased accumulation of carbon-centered radicals in cells lacking TDP1, using electron spin resonance spectroscopy. Overexpression of the antioxidant enzyme superoxide dismutase 1 (SOD1) reduces carbon-centered adducts and protects TDP1-deficient cells from oxidative stress. Conversely, overexpression of the amyotrophic lateral sclerosis-associated mutant SOD1G93A leads to marked sensitivity. Whereas Tdp1 knockout mice develop normally, overexpression of SOD1G93A suggests early embryonic lethality. Together, our data show that TDP1 resolves mtPDBs, thereby regulating mitochondrial gene transcription and oxygen consumption by oxidative phosphorylation, thus conferring cellular protection against reactive oxygen species-induced damage.

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Mitochondria and the regulation of free radical damage in the eye.

Publications

Mitochondria and the regulation of free radical damage in the eye.

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