Homocysteine induces DNA damage and alterations in proliferative capacity of T-lymphocytes: a model for immunosenescence?
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.
Picerno
Isa
I
Department of Hygiene and Public Health, University of Messina, Messina, Italy.
Chirico
Cristina
C
Condello
Salvatore
S
Visalli
Giuseppa
G
Ferlazzo
Nadia
N
Gorgone
Gaetano
G
Caccamo
Daniela
D
Ientile
Riccardo
R
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
D008934:Mitogens; D006710:Homocysteine; D003208:Concanavalin A