Crott J W, Fenech M
Department of Physiology, University of Adelaide, South Australia 5005, and CSIRO Human Nutrition, PO Box 10041, Gouger Street, Adelaide, SA 5000, Australia.
Carcinogenesis. 1999 Jun;20(6):1035-41. doi: 10.1093/carcin/20.6.1035.
We investigated whether high dose vitamin C influenced the viability of human lymphocytes in plasma, in the presence or absence of hydrogen peroxide (512 microM) by scoring necrotic, apoptotic and micronucleated cells using the cytokinesis-block micronucleus assay. The in vitro results showed that vitamin C (0.57-2.27 mM) on its own had no effect on the above parameters. However, in the presence of hydrogen peroxide vitamin C significantly reduced the number of dividing cells and apoptosis, and increased necrosis and micronucleated cells. A double-blind placebo controlled intervention, with a cross-over, involving 11 male subjects, aged 20-40 years, was performed to determine whether high plasma vitamin C concentration resulting from vitamin C supplementation promotes or protects against genetic damage and cell death ex vivo. Venous blood samples were collected before and after an anti-oxidant-poor diet which reduced plasma vitamin C concentrations by 15% (P < 0.05), and was followed with a 2 g vitamin C supplement, which raised plasma concentrations by 115 and 125% (0.12 mM) after 2 and 4 h, respectively (P < 0.05). Plasma collected post-vitamin C ingestion did not alter micronucleus expression or apoptosis in control or hydrogen peroxide-treated lymphocytes, but it moderately increased necrosis (P < 0.08). Analysis of combined data showed that necrotic cell frequency correlated positively with micronucleated cell frequency (r = 0.66, P < 0.0001) and negatively with apoptotic cell frequency (r = -0.81, P < 0.0001). Overall, vitamin C supplementation did not appear to cause DNA damage under normal physiological conditions nor did it protect cells against hydrogen peroxide-induced toxicity.
