Phytochemicals cell response

A wide diversity of herbal remedies have purported abilities to stimulate defense functions. Complexes of carbohydrate and lignin, which are present in some herbs, modulate enteric immune functions (Kiyohara et al, 2000), and the changes in cytokine secretion (Matsumoto and Yamada, 2000) can trigger systemic responses. The polysaccharides present in other herbal medicines augment production of immunoglobulin (Ig) A by the Peyer s patches in the small intestine (Sakushima et al, 1997 Yu et al, 1998). The responses of the enteric immune system to lectins are variable (Pusztai 1993), and can elicit systemic responses (Lavelle et al, 2000). Other phytochemicals provide protection by inducing detoxification pathways in mucosal cells (Williamson et al, 1998). 

When human HepG2 cells were co-treated with 10 nM PhIP and with either sulforaphane or quercetin, which have reported modulating effects on the phase I and II enzymes, both phytochemicals showed dose-response effects on the formation of PhlP-DNA adducts [92]. Sulforaphane and quercetin can reduce the number of DNA adducts formed at concentrations as low as 1 and 5 pM, respectively. The proportion of adduct formation inhibited is dependant on the concentration of PhIP treatment. At low levels of PhIP treatment, for example, 100 pM, co-treatment with sulforaphane or quercetin can reduce PhIP adducts to a level that is not distinguishable from background. At higher (supra-dietary) treatment levels of PhIP, e.g., 1 pM, however, the reduction in levels of adduct formation is proportionally smaller but still significant, 30% in the case of quercetin and 10% for sulforaphane (Fig. 3). It is interesting to notice that the threshold effects of PhIP on DNA adduct formation can be modulated by sulforaphane and quercetin. 

The effect of dietary frying oil was observed in rat feeding experiments. However, to be able to screen a large number of phytochemicals and food extracts for their effect on PG formation, a macrophage cell line, RAW264.7, was used as an in vitro model (23,24). In response to lipopolysaccha-ride (EPS), COX-2 expression is induced in the macrophage (25), and the PGE produced is a well-known proinflammatory mediator (26). 

Plants often synthesize and store active phytochemicals in specific organs. For example, glandular trichomes on the surface of leaves and stems in a variety of plants provide a major site for phytochemical synthesis, storage and secretion [10]. These differentiated organs express genes of various secondary metabolic pathways, as well as proteins associated with defence responses (e.g., superoxide dismutase in tobacco leaves] [10] or sulfur metabolism in [11]). The biosynthesis of various benzylisoqui-noline-derived alkaloids in opium poppy occurs in specific cells localized in sieve elements, whereas the final products accumulate in specialized... 

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