title: Proteins containing oxidized amino acids induce apoptosis in human monocytes.
abstract: Cellular deposits of oxidized and aggregated proteins are hallmarks of a variety of age-related disorders, but whether such proteins contribute to pathology is not well understood. We previously reported that oxidized proteins form lipofuscin/ceroid-like bodies with a lysosomal-type distribution and up-regulate the transcription and translation of proteolytic lysosomal enzymes in cultured J774 mouse macrophages. Given the recently identified role of lysosomes in the induction of apoptosis, we have extended our studies to explore a role for oxidized proteins in apoptosis. Oxidized proteins were biosynthetically generated in situ by substituting oxidized analogues for parent amino acids. Apoptosis was measured with Annexin-V/PI (propidium iodide), TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling), MMP (mitochondrial membrane permeabilization), caspase activation and cytochrome c release, and related to lysosomal membrane permeabilization. Synthesized proteins containing the tyrosine oxidation product L-DOPA (L-3,4-dihydroxyphenylalanine) were more potent inducers of apoptosis than proteins containing the phenylalanine oxidation product o-tyrosine. Apoptosis was dependent upon incorporation of oxidized residues, as indicated by complete abrogation in cultures incubated with the non-incorporation control D-DOPA (D-3,4-dihydroxyphenylalanine) or when incorporation was competed out by parent amino acids. The findings of the present study suggest that certain oxidized proteins could play an active role in the progression of age-related disorders by contributing to LMP (lysosomal membrane permeabilization)-initiated apoptosis and may have important implications for the long-term use of L-DOPA as a therapeutic agent in Parkinson's disease.
authors.affiliation: Cell Biology Group, Heart Research Institute, 7 Eliza Street, Newtown, NSW 2042, Australia. dunlopr@hri.org.au
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Dunlop
authors.forename: Ulf T
authors.initials: UT
authors.lastname: Brunk
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rodgers
mesh_terms: D000375:Aging; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002566:Ceroid / Q000009:adverse effects; D053938:DNA Fragmentation; D004789:Enzyme Activation; D006801:Humans; D007425:Intracellular Membranes; D007980:Levodopa / Q000009:adverse effects* / Q000378:metabolism*; D008062:Lipofuscin / Q000009:adverse effects; D008247:Lysosomes; D053078:Membrane Potential, Mitochondrial; D051336:Mitochondrial Membranes; D009000:Monocytes / Q000378:metabolism*; D010084:Oxidation-Reduction; D010539:Permeability; D014176:Protein Biosynthesis; D014443:Tyrosine / Q000009:adverse effects* / Q000378:metabolism*
chemical_list: D017304:Annexin A5; D002566:Ceroid; D008062:Lipofuscin; D014443:Tyrosine; D007980:Levodopa; C026741:2-tyrosine; C505407:CASP3 protein, human; D053148:Caspase 3