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Mechanisms and Biomarkers (WG 4) page 50
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Further evidence on tomato/lycopene action have been reported by Riso et al. (1999) who
demonstrated a significant reduction in DNA damage (evaluated by the comet assay) of
lymphocytes challenged ex vivo with H2O2 after the consumption of both 60 g tomato puree
(about 16.5 mg lycopene) for 3 weeks, and 25 g tomato puree (about 7 mg lycopene) for 2
weeks (Porrini and Riso, 2000). They also found an inverse relation between DNA damage
and plasma and lymphocyte lycopene concentration (Porrini and Riso, 2000), supporting the
hypothesis of a consistent contribution of lycopene on cell protection from the oxidative
damage but not excluding the contribution of other tomato antioxidants. This inverse
relationship was also demonstrated by the cell culture group in this Network.
Protein oxidation
More research is needed to investigate the possible effect of lycopene and tomato products on
the prevention of protein oxidation as few data are available. Rao and Agarwal (1998b) found
a trend towards lower protein oxidation estimated by measuring the loss of reduced thiol
groups, after 1 week consumption of different tomato based products, as previously reported,
however this decrease was not significant.
Immunomodulation
The first site of extracellular ROS attack on the cell is the poly unsaturated fatty acid-rich cell
membrane which is very susceptible to oxidative stress. Lipid peroxidation alters membrane
fluidity (Baker and Meydani, 1994) disrupts membrane integrity and modulates cell function,
signal transduction and phagocyte response, to compromise all aspects of the immune system.
Watzl et al. (1999) recently demonstrated that 2 weeks of tomato juice consumption
significantly enhanced IL-2 and IL-4 secretion but not lymphocyte proliferation compared
with values obtained after a low carotenoid diet. However the period of depletion itself
suppressed cytokine secretion and cell proliferation, supporting an effect of restoring the
original condition more than a specific or unique effect of tomato consumption.
Plasma antioxidant capacity and other protective effect
The total peroxyl radical trapping potential of plasma (TRAP), as an index of antioxidant
capacity, should provide indication of the modification in reactivity due to increased plasma
antioxidants following an intervention with tomato products. However different authors
suggest that TRAP can not be appropriate for studying the in vivo effect of the consumption
of lipophilic antioxidant rich foods on plasma antioxidant capacity.