Extracellular ADP prevents neuronal apoptosis via activation of cell antioxidant enzymes and protection of mitochondrial ANT-1 |
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Authors: | A Bobba G Amadoro A Azzariti R Pizzuto A Atlante |
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Institution: | 1. Institute of Biomembranes and Bioenergetics, CNR, Bari, Italy;2. Institute of Translational Pharmacology, CNR, Roma, Italy;3. Clinical and Preclinical Pharmacology Lab, National Cancer Research Centre, Istituto Tumori G. Paolo II, Bari, Italy;4. Department of Health Sciences, University of Molise, Campobasso, Italy |
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Abstract: | Apoptosis in neuronal tissue is an efficient mechanism which contributes to both normal cell development and pathological cell death. The present study explores the effects of extracellular ADP on low K+]-induced apoptosis in rat cerebellar granule cells. ADP, released into the extracellular space in brain by multiple mechanisms, can interact with its receptor or be converted, through the actions of ectoenzymes, to adenosine. The findings reported in this paper demonstrate that ADP inhibits the proapoptotic stimulus supposedly via: i) inhibition of ROS production during early stages of apoptosis, an effect mediated by its interaction with cell receptor/s. This conclusion is validated by the increase in SOD and catalase activities as well as by the GSSG/GSH ratio value decrease, in conjunction with the drop of ROS level and the prevention of the ADP protective effect by pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS), a novel functionally selective antagonist of purine receptor; ii) safeguard of the functionality of the mitochondrial adenine nucleotide-1 translocator (ANT-1), which is early impaired during apoptosis. This effect is mediated by its plausible internalization into cell occurring as such or after its hydrolysis, by means of plasma membrane nucleotide metabolizing enzymes, and resynthesis into the cell. Moreover, the findings that ADP also protects ANT-1 from the toxic action of the two Alzheimer's disease peptides, i.e. Aβ1–42 and NH2htau, which are known to be produced in apoptotic cerebellar neurons, further corroborate the molecular mechanism of neuroprotection by ADP, herein proposed. |
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Keywords: | Act D actinomycin D AD Alzheimer's disease ADK adenylate kinase ADO adenosine ADP adenosine diphosphate AMPCP α β-methyleneadenosine 5&prime -diphosphate ANT-1 adenine nucleotide translocator AOX antioxidant Ap5A P1 P5-di(adenosine-50)penta-phosphate ASC ascorbate ATP D S ATP detecting system ATR atractyloside BME basal medium Eagle CGC cerebellar granule cell CNS central nervous system CsA cyclosporine A Cyt c cytochrome c DIV days in vitro Fe3 +-cyt c ferricytochrome c Fe2 +-cyt c ferrocytochrome c GDH glutamate dehydrogenase G6PD glucose-6-phosphate dehydrogenase GSH reduced glutathione GSSG glutathione disulfide h hours HK hexokinase MK801 (+/&minus )-5-methyl-10 11-dihydro-5H-dibenzo(a d)cyclohepten-5 10-imine hydrogen maleate NBMPR S-(4-nitrobenzyl)-6-thioinosine O2&minus superoxide anion PBS phosphate-buffered saline medium PPADS pyridoxalphosphate-6-azophenyl-2&prime 4&prime -disulfonic acid mPT mitochondrial permeability transition mPTP mitochondrial permeability transition pore RCR respiratory control ratio ROS reactive oxygen species S D standard deviation S-K25 cells control cells S-K5 cells apoptotic cells 3h-S-K5 cells apoptotic cells 3 h after the induction of apoptosis SOD superoxide dismutase SUCC succinate z-VAD z-VAD-fmk |
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