title: Homocysteine induces DNA damage and alterations in proliferative capacity of T-lymphocytes: a model for immunosenescence?
abstract: Homocysteine (Hcy) appears to exert different effects on immune functions possibly contributing to age-related pathological states, including vascular diseases, immune dysfunction, and Alzheimer's disease. However, molecular mechanisms underlying Hcy toxicity need to be better characterized. Since T cells are a suitable model to address the possible role of replicative senescence during the in vivo aging, we investigated the effects of high Hcy concentrations on mitogen-activated lymphocytes, with regard to evaluation of DNA damage and cell cycle alterations. Cultured human peripheral blood lymphocytes were stimulated with mitogenic concanavalin A (5 microg/ml) for 48 h in the presence or absence of Hcy (1 mM). Both flow cytometric analysis and caspase-3 activity assay showed an increased rate of apoptosis in Hcy-treated lymphocyte cultures compared to controls. Further, Hcy exposure caused DNA fragmentation as evaluated by single cell gel electrophoresis showing the occurrence of comets. Cytokinesis-block micronucleus assay, performed after addition of cytochalasin B (5 microg/ml) and incubation up to 72 h, revealed a significantly higher frequency of micronucleated/binucleated cells in Hcy-treated cultures compared to controls (P < 0.001). Hcy also reduced cyclin B expression in comparison to control cultures, while cyclin D levels were not significantly affected. Cell cycle alterations, such as the inability of cells to enter into mitosis, could be related with DNA damage. These findings provided a link between perturbation of lymphocyte proliferation homeostasis and commitment towards apoptosis. Our results suggest the involvement of Hcy in the altered immune function associated with age and disease pathology.
authors.affiliation: Department of Hygiene and Public Health, University of Messina, Messina, Italy.
authors.forename: Isa
authors.initials: I
authors.lastname: Picerno
authors.forename: Cristina
authors.initials: C
authors.lastname: Chirico
authors.forename: Salvatore
authors.initials: S
authors.lastname: Condello
authors.forename: Giuseppa
authors.initials: G
authors.lastname: Visalli
authors.forename: Nadia
authors.initials: N
authors.lastname: Ferlazzo
authors.forename: Gaetano
authors.initials: G
authors.lastname: Gorgone
authors.forename: Daniela
authors.initials: D
authors.lastname: Caccamo
authors.forename: Riccardo
authors.initials: R
authors.lastname: Ientile
mesh_terms: D000375:Aging / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000276:immunology; D002453:Cell Cycle / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects / Q000276:immunology*; D020552:Comet Assay; D003208:Concanavalin A / Q000494:pharmacology; D004249:DNA Damage / Q000276:immunology*; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D006710:Homocysteine / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D048629:Micronuclei, Chromosome-Defective; D015162:Micronucleus Tests; D008934:Mitogens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism / Q000473:pathology
chemical_list: D008934:Mitogens; D006710:Homocysteine; D003208:Concanavalin A