Preliminary study of the genotoxic potential of homocysteine in human lymphocytes in vitro.
Homocysteine (Hcy), an immediate precursor of methionine (Met), is considered a risk factor for cardiovascular disease, Alzheimer's disease and neural tube defects. Hcy concentration is also reported to correlate positively with the micronucleus index in lymphocytes in vivo, a marker of chromosome damage. However, it is unclear whether Hcy is genotoxic or simply a biomarker of folate deficiency, a known cause of chromosome damage. We investigated whether high concentrations of Hcy are genotoxic to human lymphocytes in vitro using the cytokinesis-block micronucleus assay. Eighteen lymphocyte cultures were initiated in Met-free and serum-free RPMI 1640 medium for each of four male volunteers aged 22-23 years. At 0, 24, 44 and 72 h, cultures were spiked with L-Hcy or L-Met to achieve concentrations ranging between 50 and 400 microM. The concentration of Hcy at 96 h ranged from 19.45 +/- 2.34 to 149.02 +/- 28.16 microM in Hcy cultures and 0.91 +/- 0.17 to 2.15 +/- 0.9 microM in Met cultures spiked with 50 and 400 microM of metabolite, respectively. Forty-four hours after mitogen stimulation, cytokinesis was inhibited with cytochalasin B. After 96 h, cells were transferred to microscope slides and the frequency of micronucleated-binucleate and necrotic cells was scored. Neither Hcy (P = 0.24) nor Met (P = 0.93) had an apparent dose effect on micronucleus frequency. However, when data were pooled, micronucleus frequency was moderately higher (50.1%) in Hcy- than in Met-spiked cultures (P = 0.04; paired t-test). Hcy concentration was positively correlated with necrosis (P < 0.0005; r(2)= 0.276), however, when data were pooled, levels of necrosis were higher in Met- than in Hcy-spiked cultures (P= 0.01; paired t-test). Further research is required to define more clearly the genotoxic and cytotoxic potential of homocysteine and its metabolites.
Crott
J
J
Department of Physiology, University of Adelaide, SA 5005, Australia.
Fenech
M
M
D000328:Adult; D000704:Analysis of Variance; D002478:Cells, Cultured; D003571:Cytochalasin B / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006710:Homocysteine / Q000494:pharmacology / Q000633:toxicity*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000494:pharmacology; D015162:Micronucleus Tests; D008956:Models, Chemical; D009153:Mutagens; D009336:Necrosis; D013997:Time Factors
D009153:Mutagens; D006710:Homocysteine; D003571:Cytochalasin B; D008715:Methionine