The chemopreventive agent resveratrol stimulates cyclic AMP-dependent chloride secretion in vitro.

Resveratrol and its analogs are promising cancer chemoprevention agents, currently under investigation in clinical trials. However, patients administered other plant polyphenols experienced severe diarrhea, likely due to an increase in intracellular cyclic AMP (cAMP). Resveratrol itself raises intracellular cAMP levels in breast cancer cells in vitro. Its future use as a cancer chemopreventive agent could therefore be compromised by its severe side effects. The aim of the study was (a) to define the influence of resveratrol on intestinal Cl(-) secretion and (b) to elucidate possible intracellular transduction pathways involved. Resveratrol caused a dose- and time-dependent increase in DeltaIsc in T(84) cells. The specificity of resveratrol was confirmed by using piceatannol 100 mumol/L, the hydroxylated resveratrol analog, which did not alter DeltaIsc. A significant elevation of [cAMP](i) by resveratrol was assessed in T(84) cells. In mouse jejunum, resveratrol induced a time- and dose-dependent increase in DeltaIsc as well. In bilateral Cl(-)-free medium, as well as after inhibition of protein kinase A, resveratrol-induced DeltaIsc was reduced significantly. Preincubation of T(84) cells with butyrate 2 mmol/L (24 and 48 hours) significantly inhibited resveratrol as well as forskolin-induced Cl(-) secretion. In summary, the main mechanism of action of resveratrol in intestinal epithelia is cAMP-induced chloride secretion which can be suppressed by butyrate. It can therefore be suggested that in cancer chemoprevention, both agents should be combined to reduce an undesired side effect such as diarrhea and to benefit from the known agonistic effect of both agents on differentiation of colon cancer cells.

Molecular mechanisms of the chemopreventive effects of resveratrol and its analogs in carcinogenesis.

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a phytoalexin found in grape skins, peanuts, and red wine, has been reported to exhibit a wide range of biological and pharmacological properties. It has been speculated that dietary resveratrol could be an explanation for the so-called 'French paradox' as it may act as an antioxidant, promote nitric oxide production, inhibit platelet aggregation, and increase high-density lipoprotein cholesterol, and thereby serve as a cardioprotective agent. Recently, it has been demonstrated that resveratrol can function as a cancer chemopreventive agent, and there has been a great deal of experimental effort directed toward defining this effect. It has been shown that resveratrol and some of its analogs interfere with signal transduction pathways, modulate cell cycle-regulating proteins, and is a potent inducer of apoptosis in multiple carcinoma cell lines. This review summarizes the recent advances that have provided new insights into the molecular mechanisms underlying the promising properties of resveratrol.

Molecular mechanisms of the chemopreventive effects of resveratrol and its analogs in colorectal cancer: key role of polyamines?

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a phytoalexin found in grape skins, peanuts, and red wine, has been reported to exhibit a wide range of biological and pharmacological properties. It has been speculated that dietary resveratrol may act as an antioxidant, promote nitric oxide production, inhibit platelet aggregation, and increase high-density lipoprotein cholesterol and thereby serve as a cardioprotective agent (the so-called "French paradox"). Recently, it was demonstrated that resveratrol can function as a cancer chemopreventive agent, and there has been a great deal of experimental effort directed toward defining this effect. It has been shown that resveratrol and some of its analogues interfere with signal transduction pathways. Thus the activities of various protein kinases are inhibited, the expression of nuclear proto-oncogenes declines, and the activity of ornithine decarboxylase (ODC) is reduced. ODC, which catalyzes the rate-limiting step in the biosynthesis of polyamines, is closely linked with cellular proliferation and carcinogenesis. This review summarizes the recent advances that have provided new insights into the molecular mechanisms underlying the promising properties of resveratrol focusing on the key role of the polyamine metabolism in colorectal cancer cells.

Resveratrol-induced modification of polyamine metabolism is accompanied by induction of c-Fos.

The objective of the current study was to investigate the effect of resveratrol, a naturally occurring polyphenol with cancer chemopreventive properties, on polyamine metabolism in the human colonic adenocarcinoma cell line Caco-2. We demonstrated that inhibition of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, was due to attenuated ODC protein and mRNA levels (50-200 microM). The naturally occurring resveratrol analog piceatannol (100 microM) also diminished ODC activity, protein and mRNA levels, whereas the green tea polyphenol (-)-epigallocatechin gallate (EGCG; 100 microM) exerted only weak effects on ODC. The transcription factor c-Myc, a positive regulator of the odc gene was attenuated by resveratrol treatment and to a lesser extent by piceatannol and EGCG. S-Adenosylmethionine decarboxylase, an enzyme that synthesizes higher polyamines, was concomitantly inhibited by resveratrol and piceatannol treatment, whereas EGCG did not affect its activity. In addition resveratrol, piceatannol and EGCG enhanced spermidine/spermine N(1)-acetyltransferase activity, an enzyme that degrades polyamines in cooperation with polyamine oxidase. Intracellular levels of spermine and spermidine were not affected, whereas putrescine and N(8)-acetylspermidine concentrations increased after incubation with resveratrol. These events were paralleled by an increase of the activator protein-1 constituents c-Fos and c-Jun. Whereas DNA-binding activity of c-Jun remained unchanged, DNA-binding activity of c-Fos was significantly enhanced by resveratrol and piceatannol, but inhibited by EGCG. The data suggest that growth arrest by resveratrol is accompanied by inhibition of polyamine synthesis and increased polyamine catabolism. C-Fos seems to play a role in this context. Effects of piceatannol on polyamine synthesis were similar, but not as potent as those exerted by resveratrol.

Resveratrol enhances the differentiation induced by butyrate in caco-2 colon cancer cells.

Butyrate, a short-chain fatty acid produced in the colon by microbial fermentation of fiber, inhibits growth of colonic carcinoma cells while inducing differentiation. Resveratrol, a plant polyphenol found in red wine and peanuts, has been shown to exert chemopreventive properties on colon cancer cells. The aim of this study was to determine whether resveratrol modulates the effects of butyrate on Caco-2, a colonic adenocarcinoma cell line. The growth inhibitory effect of resveratrol (50 micromol/L) was more powerful than that of butyrate (2 mmol/L). Butyrate did not intensify the inhibition of proliferation exerted by resveratrol. Although the polyphenol enhanced the differentiation-inducing effect of butyrate, it did not elevate alkaline phosphatase activity or E-cadherin protein expression, markers of epithelial differentiation, when applied alone. Butyrate-induced transforming growth factor-beta1 secretion was inhibited by resveratrol. Treatment with the combination of resveratrol and butyrate attenuated levels of p27(Kip1), whereas resveratrol enhanced butyrate's effect on the induction of p21(Waf1/Cip1) expression. These data demonstrate a possible combined chemopreventive effect of two substances naturally occurring in the colonic lumen after ingestion of fibers and resveratrol-containing food.

Piceatannol, a natural analog of resveratrol, inhibits progression through the S phase of the cell cycle in colorectal cancer cell lines.

Piceatannol, a naturally occurring analog of resveratrol, was previously identified as the active ingredient in herbal preparations in folk medicine and as an inhibitor of p72(Syk). We studied the effects of piceatannol on growth, proliferation, differentiation and cell cycle distribution profile of the human colon carcinoma cell line Caco-2. Growth of Caco-2 and HCT-116 cells was analyzed by crystal violet assay, which demonstrated dose- and time-dependent decreases in cell numbers. Treatment of Caco-2 cells with piceatannol reduced proliferation rate. No effect on differentiation was observed. Determination of cell cycle distribution by flow cytometry revealed an accumulation of cells in the S phase. Immunoblotting demonstrated that cyclin-dependent kinases (cdk) 2 and 6, as well as cdc2 were expressed at steady-state levels, whereas cyclin D1, cyclin B1 and cdk 4 were downregulated. The abundance of p27(Kip1) was also reduced, whereas the protein level of cyclin E was enhanced. Cyclin A levels were enhanced only at concentrations up to 100 micromol/L. These changes also were observed in studies with HCT-116 cells. On the basis of our findings, piceatannol can be considered to be a promising chemopreventive or anticancer agent.