Guido Morozzi

Cancer chemoprevention by hydroxytyrosol isolated from virgin olive oil through G1 cell cycle arrest and apoptosis.

Recent epidemiological evidence and animal studies suggest a relationship between the intake of olive oil and a reduced risk of several malignancies. The present study assesses the effect of hydroxytyrosol, a major antioxidant compound of virgin olive oil, on proliferation, apoptosis and cell cycle of tumour cells. Hydroxytyrosol inhibited proliferation of both human promyelocytic leukaemia cells HL60 and colon adenocarcinoma cells HT29 and HT29 clone 19A. The con-centrations of hydroxytyrosol which inhibited 50% of cell proliferation were ∼50 and ∼750 μmol/l for HL60 and both HT29 and HT29 clone 19A cells, respectively. At concentrations ranging from 50 to 100 μmol/l, hydroxytyrosol induced an appreciable apoptosis in HL60 cells after 24 h of incubation as evidenced by flow cytometry, fluorescence microscopy and internucleosomal DNA fragmentation. Interestingly, no effect on apoptosis was observed after similar treatment of freshly isolated human lymphocytes and polymorphonuclear cells. The DNA cell cycle analysis, quantified by flow cytometry, showed that the treatment of HL60 cells with hydroxytyrosol 50–100 μmol/l arrested the cells in the G0/G1 phase with a concomitant decrease in the cell percentage in the S and G2/M phases. These results support the hypothesis that hydroxytyrosol may exert a protective activity against cancer by arresting the cell cycle and inducing apoptosis in tumour cells, and suggest that hydroxytyrosol, an important component of virgin olive oil, may be responsible for its anticancer activity.

Effect of olive oil phenols on the production of inflammatory mediators in freshly isolated human monocytes

Recent in vitro and in vivo studies suggest that the anti-inflammatory properties of extra virgin olive oil may be involved in the prevention of chronic degenerative diseases. In this study, the ability of olive oil phenols to influence the release of superoxide anions (O2-), prostaglandin E2 (PGE2) and tumor necrosis factor α (TNFα) and the expression of cyclooxygenase2 (COX2) in human monocytes, freshly isolated from healthy donors, was investigated. O2- were measured by superoxide dismutase-inhibitable cytochrome c reduction and PGE2 and TNFα production were determined in culture medium with appropriate enzyme immunoassay kits. COX2 mRNA and protein were evaluated by quantitative reverse transcription-polymerase chain reaction and Western immunoblotting, respectively. Treatment of monocytes for 24 h with 100 μM of hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and their secoiridoid derivatives (3,4-DHPEA and p-HPEA linked to the dialdehydic form of elenolic acid: 3,4-DHPEA-EDA and p-HPEA-EDA, respectively) significantly (P<.05) inhibited the production of O2(-) as follows: 3,4-DHPEA (40%,), p-HPEA (9%), 3,4-DHPEA-EDA (25%) and p-HPEA-EDA (36%). Hydroxytyrosol also considerably reduced the expression of COX2 at both the mRNA and protein level (P<.05) and caused a clear dose-dependent reduction of PGE2 released into the culture medium (45% and 71% at 50 and 100 μM, respectively, P<.05). The COX2 mRNA was also efficiently inhibited by the secoiridoids. Moreover, it was shown that hydroxytyrosol increased the monocytes TNFα production. In addition to other chemopreventive properties, these results suggest that the health effects of olive oil phenols may be related to their ability to modulate the production of pro-inflammatory molecules, a property common to non-steroidal anti-inflammatory drugs.

Genotoxic effect of bile acids on human normal and tumour colon cells and protection by dietary antioxidants and butyrate

BackgroundColorectal cancer is the second cause of death for tumour worldwide. Among the risk factors for this disease the dietary habits seem to have a pivotal role. An elevated intake of fats causes a high release in the gut lumen of bile acids that are positively correlated with colorectal cancer, since they act as detergents and proliferation promoters. Recently, it was evidenced that bile acids can also be able to induce DNA damage.Aim of the studyIn this study the genotoxicity of deoxycholic acid (DCA) and chenodeoxycholic acid CDCA) has been evaluated in human normal colonocytes derived from 60 colon biopsies and in tumour cells. The involvement of reactive oxygen species (ROS) and the oxidative DNA damage was assessed. In addition, the protective effect exerted by both two well-known antioxidants commonly present in the diet, β-carotene and α-tocopherol, and butyrate which is known to be involved in the regulation of several cellular functions, has also been tested.MethodsThe DNA damage was evaluated by the “comet assay” or single cell gel electrophoresis (SCGE) both in its conventional use and by the Endonuclease III modified method, which allow to detect the presence of oxidized pyrimidines.ResultsBile acids (CDA and CDCA) resulted genotoxic on both normal and tumour human colon cells. The inclusion of the endonuclease III digestion step in the comet assay demonstrated that bile acids induced an oxidative DNA damage. In addition, treatment of colonocytes with bile acids in the presence of the antioxidants (β-carotene, α-tocopherol) and Na-butyrate caused a reduction of DNA damage.ConclusionOur results suggest that bile acids may be involved in the tumour initiation by inducing a DNA oxidative damage, and so add further evidences to the preventive properties of antioxidants present in the Mediterranean diet.

Production of hydrogen peroxide is responsible for the induction of apoptosis by hydroxytyrosol on HL60 cells

Hydroxytyrosol [3,4-dihydroxyphenylethanol (3,4-DHPEA)], a phenolic compound found exclusively in olive oil, exerts growth-suppressive and pro-apoptotic effects on different cancer cells. Although some molecular mechanisms involved in the pro-apoptotic activity of 3,4-DHPEA have been proposed, the initial stress signals responsible of this phenomenon are not known. Our aim was to assess the involvement of reactive oxygen species as mediators of apoptosis induced by 3,4-DHPEA on HL60 cells. Apoptosis was determined by analyzing the nuclear fragmentation by both fluorescence microscopy and flow cytometry. The externalization of phosphatidylserine was evidenced using an Annexin V-FITC kit. The concentration of H(2)O(2) in the culture medium was measured by the ferrous ion oxidation-xylenol orange method. The pro-apoptotic effect of 3,4-DHPEA (100 muM) was prevented by N-acetyl-cysteine, ascorbate, and alpha-tocopherol. Catalase suppressed the 3,4-DHPEA-induced apoptosis, while the Fe(II)-chelating reagent o-phenantroline showed no effect, suggesting the involvement of H(2)O(2 )but not of OH(*). Indeed, 3,4-DHPEA caused accumulation of H(2)O(2) in the culture medium. Tyrosol (p-hydroxyphenylethanol) and caffeic acid, compounds structurally similar to 3,4-DHPEA but not able to generate H(2)O(2), did not induce an appreciable apoptotic effect. This is the first study demonstrating that apoptosis induction by 3,4-DHPEA is mediated by the extracellular production of H(2)O(2).

Effects of dietary extra-virgin olive oil on behaviour and brain biochemical parameters in ageing rats

The aim of the present study was to verify whether extra-virgin olive oil, a dietary component naturally containing phenolic antioxidants, has the potential to protect the brain from the deleterious effects of ageing. To accomplish this goal, we used male rats fed a high-energy diet containing either maize oil, or extra-virgin olive oil with high or low phenol content (720 or 10 mg total phenols/kg oil, corresponding to a daily dose of 4 or 0.05 mg total phenols/kg body weight, respectively) from age 12 months to senescence. The measured endpoints were biochemical parameters related to oxidative stress and functional tests to evaluate motor, cognitive and emotional behaviour. Olive oil phenols did not exert major protective actions on motor and cognitive function, as we observed only a tendency to improved motor coordination on the rotarod in the old animals treated with the oil rich in phenols (40 % average increase in the time to first fall; P = 0.18). However, an interesting finding of the present study was a reduced step-through latency in the light-dark box test, found in the older animals upon treatment with the oil rich in antioxidant phenols, possibly indicating an anxiety-lowering effect. This effect was associated with decreased glutathione reductase activity and expression in the brain, a phenomenon previously associated with decreased anxiety in rodents. These results indicate a previously undetected effect of a diet containing an olive oil rich in phenols. Further studies are warranted to verify whether specific food antioxidants might also have an effect on emotional behaviour.

Anti-proliferative and pro-apoptotic activities of hydroxytyrosol on different tumour cells: the role of extracellular production of hydrogen peroxide

PurposeSeveral recently published data suggest that the anti-proliferative and pro-apoptotic properties of hydroxytyrosol [3,4-dihydroxyphenyl ethanol (3,4-DHPEA)] on HL60 cells may be mediated by the accumulation of hydrogen peroxide (H2O2) in the culture medium. The aim of this study was to clarify the role played by H2O2 in the chemopreventive activities of 3,4-DHPEA on breast (MDA and MCF-7), prostate (LNCap and PC3) and colon (SW480 and HCT116) cancer cell lines and to investigate the effects of cell culture medium components and the possible mechanisms at the basis of the H2O2-producing properties of 3,4-DHPEA.MethodsThe proliferation was measured by the MTT assay and the apoptosis by both fluorescence microscopy and flow cytometry. The concentration of H2O2 in the culture medium was measured by the ferrous ion oxidation–xylenol orange method.ResultsIt was found that the H2O2-inducing ability of 3,4-DHPEA is completely prevented by pyruvate and that the exposure of cells to conditions not supporting the H2O2 accumulation (addition of either catalase or pyruvate to the culture medium) inhibited the anti-proliferative effect of 3,4-DHPEA. Accordingly, the sensitivity of the different cell lines to the anti-proliferative effect of 3,4-DHPEA was inversely correlated with their ability to remove H2O2 from the culture medium. With regard to the mechanism by which 3,4-DHPEA causes the H2O2 accumulation, it was found that superoxide dismutase increased the H2O2 production while tyrosinase, slightly acidic pH (6,8) and absence of oxygen (O2) completely prevented this activity. In addition, different transition metal-chelating compounds did not modify the H2O2-producing activity of 3,4-DHPEA.ConclusionsThe pro-oxidant activity of 3,4-DHPEA deeply influences its ‘in vitro’ chemopreventive activities. The main initiation step in the H2O2-producing activity is the auto-oxidation of 3,4-DHPEA by O2 with the formation of the semiquinone, superoxide ions (O2−) and 2H+.

Influence of culture conditions on the DNA-damaging effect of benzene and its metabolites in human peripheral blood mononuclear cells

The DNA‐damaging ability of benzene and its metabolites on peripheral blood mononuclear cells (PBMC) has been investigated by using the alkaline comet assay. The PBMC were incubated with different compounds in two different media for 2 and 24 hr at concentrations that did not affect cell viability and the DNA damage was quantified by a computerized image analysis system. Benzene and phenol (5 mM) did not show any genotoxic activity after 2 hr of incubation in the two media tested, phosphate‐buffered saline (PBS) and RPMI containing 5% of heat‐inactivated fetal calf serum (RPMI + 5% FCS), whereas phenol was genotoxic and cytotoxic at 10 mM after 24 hr of incubation in RPMI + 5% FCS. All other benzene metabolites were genotoxic at micromolar concentrations when incubated in PBS with the following decreasing order of potency: benzenetriol, catechol, hydroquinone, and benzoquinone. When the PBMC were incubated in RPMI + 5% FCS, the effect of catechol (200–600 μM) and benzenetriol (10 μM) was reduced, whereas the genotoxicity of benzenetriol at high concentrations (50–100 μM) and hydroquinone (150–2500 μM) was not affected. In contrast, the effect of benzoquinone at 5 and 10 μM was greatly enhanced when the cells were incubated in RPMI + 5% FCS. This effect resulted mainly from the presence of serum in the medium and it was almost completely inhibited by boiling the serum (100°C, 5 min) and was partially reduced by extensive dialysis. Benzoquinone was the most damaging compound when tested under more physiological conditions, thereby supporting the general observation that it is the most myelotoxic benzene metabolite. Environ. Mol. Mutagen. 37:1–6, 2001

Deoxycholic acid and SCFA-induced apoptosis in the human tumor cell-line HT-29 and possible mechanisms

Short chain fatty acids (propionate and butyrate) and deoxycholic acid (DCA) are able to induce apoptosis in HT-29 colonic tumor cell line, but DCA induces a much higher level of apoptosis than butyrate and propionate. Mixtures of DCA with butyrate or propionate enhance the effect of the single components. Apoptosis is not affected by the PKC, PTK or de novo mRNA and protein synthesis inhibitors, so that the involvement of these enzymes and processes is ruled out. In contrast, DCA-induced apoptosis is directly related to [Ca2+]i concentration as demonstrated by the apoptosis inhibition caused by [Ca2+]i chelator BAPTA/AM.

Influence of Cultivar and Concentration of Selected Phenolic Constituents on the in Vitro Chemiopreventive Potential of Olive Oil Extracts

One of the main olive oil phenolic compounds, hydroxytyrosol (3,4-DHPEA), exerts in vitro chemopreventive activities (antiproliferative and pro-apoptotic) on tumor cells through the accumulation of H(2)O(2) in the culture medium. However, the phenol composition of virgin olive oil is complex, and 3,4-DHPEA is present at low concentrations when compared to other secoiridoids. In this study, the in vitro chemopreventive activities of complex virgin olive oil phenolic extracts (VOO-PE, derived from the four Italian cultivars Nocellara del Belice, Coratina, Ogliarola, and Taggiasca) were compared to each other and related to the amount of the single phenolic constituents. A great chemopreventive potential among the different VOO-PE was found following this order: Ogliarola > Coratina > Nocellara > Taggiasca. The antiproliferative and pro-apoptotic activities of VOO-PE were positively correlated to the secoiridoid content and negatively correlated to the concentration of both phenyl alcohols and lignans. All extracts induced H(2)O(2) accumulation in the culture medium, but this phenomenon was not responsible for their pro-apoptotic activity. When tested in a complex mixture, the olive oil phenols exerted a more potent chemopreventive effect compared to the isolated compounds, and this effect could be due either to a synergistic action of components or to any other unidentified extract constituent.

Fecal Levels of Short-Chain Fatty Acids and Bile Acids as Determinants of Colonic Mucosal Cell Proliferation in Humans

We studied the correlation between fecal levels of short-chain fatty acids (SCFA), bile acids (BA), and colonic mucosal proliferation in humans on a free diet. Subjects [n = 43: 27 men and 16 women; 61 ± 7 and 59 ± 6 (SE) yr old, respectively] were outpatients who previously underwent resection of at least two sporadic colon polyps. Mucosal proliferation was determined by [³H]thymidine incorporation in vitro in three colorectal biopsies obtained without cathartics and was expressed as labeling index (LI). BA were analyzed in feces by mass spectrometry and SCFA by gas chromatography. We found that increasing levels of BA in feces did not correlate with higher LI. On the contrary, higher levels of SCFA were significantly associated with lower LI in the colonic mucosa (P for trend = 0.02). In conclusion, in humans on a free diet, intestinal proliferation seems to be regulated by the levels of SCFA in feces and not by BA. Because a lower intestinal proliferation is associated with a decreased colon cancer risk, treatments or diets that increase colonic levels of SCFA might be beneficial for colonic mucosa.