Assunta Catalano

Lycopene induces cell growth inhibition by altering mevalonate pathway and Ras signaling in cancer cell lines.

Several evidences suggest that cancer cells have abnormal cholesterol biosynthetic pathways and prenylation of small guanosine triphosphatase proteins. Tomato lycopene has been suggested to have beneficial effects against certain types of cancer, including that of prostate, although the exact molecular mechanism(s) is unknown. We tested the hypothesis that lycopene may exert its antitumor effects through changes in mevalonate pathway and in Ras activation. Incubation of the Ras-activated prostatic carcinoma LNCaP cells with a 24 h lycopene treatment (2.5-10 μM) dose dependently reduced intracellular total cholesterol by decreasing 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase expression and by inactivating Ras, as evidenced by its translocation from cell membranes to cytosol. Concomitantly, lycopene reduced the Ras-dependent activation of nuclear factor-kappaB (NF-κB). Such a reduction was parallel to an inhibition of reactive oxygen species production and to a decrease in the phosphorylation ofc-jun N-terminal kinase, extracellular signal-regulated kinase 1/2 and p38. These effects were also accompanied by an arrest of cell cycle progression and by apoptosis induction, as evidenced by a decrease in cyclin D1 and phospho-AKT levels and by an increase in p21, p27 and p53 levels and in Bax:Bcl-2 ratio. The addition of mevalonate prevented the growth-inhibitory effects of lycopene as well as its increase in Ras cytoplasmatic accumulation and the subsequent changes in NF-κB. The ability of lycopene in inhibiting HMG-CoA reductase expression and cell growth and in inactivating Ras was also found in prostate PC-3, colon HCT-116 and HT-29 and lung BEN cancer cells. These findings provide a novel mechanistic insight into the growth-inhibitory effects of lycopene in cancer.

Growth-inhibitory effects of the astaxanthin-rich alga Haematococcus pluvialis in human colon cancer cells.

The growth-inhibitory effects of the astaxanthin-rich Haematococcus pluvialis were studied in HCT-116 colon cancer cells. H. pluvialis extract (5-25 microg/ml) inhibited cell growth in a dose- and time-dependent manner, by arresting cell cycle progression and by promoting apoptosis. At 25 microg/ml of H. pluvialis extract, an increase of p53, p21(WAF-1/CIP-1) and p27 expression (220%, 160%, 250%, respectively) was observed, concomitantly with a decrease of cyclin D1 expression (58%) and AKT phosphorylation (21%). Moreover, the extract, at the same concentration, strongly up-regulated apoptosis by modifying the ratio of Bax/Bcl-2 and Bcl-XL, and increased the phosphorylation of p38, JNK, and ERK1/2 by 160%, 242%, 280%, respectively. Growth-inhibitory effects by H. pluvialis were also observed in HT-29, LS-174, WiDr, SW-480 cells. This study suggests that H. pluvialis may protect from colon cancer.

Lycopene inhibits NF-kB-mediated IL-8 expression and changes redox and PPARγ signalling in cigarette smoke-stimulated macrophages

Increasing evidence suggests that lycopene, the major carotenoid present in tomato, may be preventive against smoke-induced cell damage. However, the mechanisms of such a prevention are still unclear. The aim of this study was to investigate the role of lycopene on the production of the pro-inflammatory cytokine IL-8 induced by cigarette smoke and the possible mechanisms implicated. Therefore, human THP-1 macrophages were exposed to cigarette smoke extract (CSE), alone and following a 6-h pre-treatment with lycopene (0.5–2 µM). CSE enhanced IL-8 production in a time- and a dose-dependent manner. Lycopene pre-treatment resulted in a significant inhibition of CSE-induced IL-8 expression at both mRNA and protein levels. NF-kB controlled the transcription of IL-8 induced by CSE, since PDTC prevented such a production. Lycopene suppressed CSE-induced NF-kB DNA binding, NF-kB/p65 nuclear translocation and phosphorylation of IKKα and IkBα. Such an inhibition was accompanied by a decrease in CSE-induced ROS production and NOX-4 expression. Lycopene further inhibited CSE-induced phosphorylation of the redox-sensitive ERK1/2, JNK and p38 MAPKs. Moreover, the carotenoid increased PPARγ levels which, in turn, enhanced PTEN expression and decreased pAKT levels in CSE-exposed cells. Such effects were abolished by the PPARγ inhibitor GW9662. Taken together, our data indicate that lycopene prevented CSE-induced IL-8 production through a mechanism involving an inactivation of NF-kB. NF-kB inactivation was accompanied by an inhibition of redox signalling and an activation of PPARγ signalling. The ability of lycopene in inhibiting IL-8 production, NF-kB/p65 nuclear translocation, and redox signalling and in increasing PPARγ expression was also found in isolated rat alveolar macrophages exposed to CSE. These findings provide novel data on new molecular mechanisms by which lycopene regulates cigarette smoke-driven inflammation in human macrophages.

Lycopene prevents 7-ketocholesterol-induced oxidative stress, cell cycle arrest and apoptosis in human macrophages.

The present study was undertaken to examine whether lycopene is able to counteract 7-ketocholesterol (7-KC)-induced oxidative stress and apoptosis in human macrophages. Human THP-1 macrophages were exposed to 7-KC (10-25 microM) alone and in combination with lycopene (0.5-2 microM), and we monitored changes in cell oxidative status [reactive oxygen species (ROS) production, NOX-4, hsp70 and hsp90 expressions, 8-OHdG formation] and in cell proliferation and apoptosis. After 24 h of treatment, lycopene significantly reduced the increase in ROS production and in 8-OHdG formation induced by the oxysterol in a dose-dependent manner. Moreover, the carotenoid strongly prevented the increase of NOX-4, hsp70 and hsp90 expressions as well as the phosphorylation of the redox-sensitive p38, JNK and ERK1/2 induced by the oxysterol. The attenuation of 7-KC-induced oxidative stress by lycopene coincided with a normalization of cell growth in human macrophages. Lycopene prevented the arrest in G0/G1 phase of cell cycle induced by the oxysterol and counteracted the increased expression of p53 and p21. Concomitantly, it inhibited 7-KC-induced apoptosis, by limiting caspase-3 activation and the modulatory effects of 7-KC on AKT, Bcl-2, Bcl-xL and Bax. Comparing the effects of lycopene, beta-carotene and (5Z)-lycopene on ROS production, cell growth and apoptosis show that lycopene and its isomer were more effective than beta-carotene in counteracting the dangerous effects of 7-KC in human macrophages. Our study suggests that lycopene may act as a potential antiatherogenic agent by preventing 7-KC-induced oxidative stress and apoptosis in human macrophages.

Tomato Lycopene and Inflammatory Cascade: Basic Interactions and Clinical Implications

Lycopene, a natural carotenoid found in tomato, has been reported to possess various health benefits, such as cardiovascular and cancer preventive properties. However, the experimental basis for such health benefits is not fully understood. One of the possible mechanisms for its protective activities is by down-regulation of the inflammatory response. That includes the inhibition of pivotal pro-inflammatory mediators, such as the reduction of reactive oxygen species, the inhibition of synthesis and release of pro-inflammatory cytokines, changes in the expression of cyclooxygenase and lipoxygenase, modifications of eicosanoid synthesis, and modulation of signal transduction pathways, including that of the inducible nitric oxide synthase via its inhibitory effects on Nuclear Factor-kB (NF-kB), Activated protein-1 (AP-1) and mitogen-activated protein kinase (MAPK) signaling. Recent data suggest that lycopene also exhibits anti-inflammatory activity through induction of programmed cell death in activated immune cells. This review will discuss recent data on the control of inflammatory signaling exerted by tomato lycopene in isolated cells, in animal models and in clinical trials, focusing on the dose of the carotenoid and the biological environment in which it acts. A clear understanding of the molecular mechanisms of action of lycopene is crucial in the valuation of this molecule as a potential preventive and therapeutic agent.

Lycopene in atherosclerosis prevention: an integrated scheme of the potential mechanisms of action from cell culture studies.

Increasing evidence suggests that lycopene may protect against atherosclerosis, although, the exact mechanism(s) is still unknown. Because lycopene is an efficient antioxidant, it has been proposed for a long time that this property may be responsible for its beneficial effects. Consistent with this, the carotenoid has been demonstrated to inhibit ROS production in vitro and to protect LDL from oxidation. However, recently, other mechanisms have been evoked and include: prevention of endothelial injury; modulation of lipid metabolism through a control of cholesterol synthesis and oxysterol toxic activities; reduction of inflammatory response through changes in cytokine production; inhibition of smooth muscle cell proliferation through regulation of molecular pathways involved in cell proliferation and apoptosis. Focusing on cell culture studies, this review summarizes the experimental evidence for a role of lycopene in the different phases of atherosclerotic process.

Lycopene prevention of oxysterol-induced proinflammatory cytokine cascade in human macrophages: inhibition of NF-κB nuclear binding and increase in PPARγ expression.

It is now well accepted that oxysterols play important roles in the formation of atherosclerotic plaque, involving cytotoxic, pro-oxidant and proinflammatory processes. It has been recently suggested that tomato lycopene may act as a preventive agent in atherosclerosis, although the exact mechanism of such a protection is not clarified. The main aim of this study was to investigate whether lycopene is able to counteract oxysterol-induced proinflammatory cytokines cascade in human macrophages, limiting the formation of atherosclerotic plaque. Therefore, THP-1 macrophages were exposed to two different oxysterols, such as 7-keto-cholesterol (4-16 μM) and 25-hydroxycholesterol (2-4 μM), alone and in combination with lycopene (0.5-2 μM). Both oxysterols enhanced pro-inflammatory cytokine [interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor α) secretion and mRNA levels in a dose-dependent manner, although at different extent. These effects were associated with an increased reactive oxygen species (ROS) production through an enhanced expression of NAD(P)H oxidase. Moreover, a net increment of phosphorylation of extracellular regulated kinase 1/2, p-38 and Jun N-terminal kinase and of nuclear factor kB (NF-κB) nuclear binding was observed. Lycopene prevented oxysterol-induced increase in pro-inflammatory cytokine secretion and expression. Such an effect was accompanied by an inhibition of oxysterol-induced ROS production, mitogen-activated protein kinase phosphorylation and NF-κB activation. The inhibition of oxysterol-induced cytokine stimulation was also mimicked by the specific NF-κB inhibitor pyrrolidine dithiocarbamate. Moreover, the carotenoid increased peroxisome proliferator-activated receptor γ levels in THP-1 macrophages. Taken all together, these data bring new information on the anti-atherogenic properties of lycopene, and on its mechanisms of action in atherosclerosis prevention.

Tomato Lycopene and Lung Cancer Prevention: From Experimental to Human Studies

Increasing evidence suggests that tomato lycopene may be preventive against the formation and the development of lung cancer. Experimental studies demonstrated that lycopene may inhibit the growth of several cultured lung cancer cells and prevent lung tumorigenesis in animal models through various mechanisms, including a modulation of redox status, cell cycle arrest and/or apoptosis induction, a regulation of growth factor signaling, changes in cell growth-related enzymes, an enhancement of gap junction communication and a prevention of smoke-induced inflammation. In addition, lycopene also inhibited cell invasion, angiogenesis, and metastasis. Several lycopene metabolites have been identified, raising the question as to whether the preventive effects of lycopene on cancer risk is, at least in part, due to its metabolites. Despite these promising reports, it is difficult at the moment to directly relate available experimental data to human pathophysiology. More well controlled clinical intervention trials are needed to further clarify the exact role of lycopene in the prevention of lung cancer cell growth. Such studies should take into consideration subject selection, specific markers of analysis, the levels of carotenoids being tested, metabolism and isomerization of lycopene, interaction with other bioactive food components. This article reviews data on the cancer preventive activities of lycopene, possible mechanisms involved, and the relationship between lycopene consumption and human cancer risk.

Effect of Lycopene and Tomato Products on Cholesterol Metabolism

Background/Aims: Increased ingestion of tomato, containing lycopene, has been associated with a decreased risk for atherosclerosis, although the exact molecular mechanism is still unknown. Here we review the available evidence for a direct regulation of tomato lycopene on cholesterol metabolism using results from experimental and human studies. Results: In human macrophages lycopene dose dependently reduced intracellular total cholesterol. Such an effect was associated with a decrease in cholesterol synthesis through a reduction of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and expression, a modulation of low- density lipoprotein (LDL) receptor and acyl-coenzyme A:cholesterol acyltransferase activity. An increase in cholesterol efflux through an enhancement of ABCA1 and caveolin-1 expression was also observed. In animal models of atherosclerosis, lycopene and tomato products decreased plasma total cholesterol, LDL cholesterol and increased high-density lipoprotein cholesterol. In agreement with the experimental results, most human intervention trials analyzed show that dietary supplementation with lycopene and/or tomato products reduced plasma LDL cholesterol dependently on the dose and the time of administration. Conclusions: Although lycopene and tomato products seem to possess direct hypocholesterolemic properties, more experimental studies are needed to better understand the mechanisms involved. There is also a need for more well-designed human dietary intervention studies to better clarify the role of lycopene as a hypocholesterolemic agent.

Lycopene regulation of cholesterol synthesis and efflux in human macrophages.

Hypercholesterolemia is one of the most important risk factors for atherosclerosis, and tomato lycopene has been suggested to have beneficial effects against such a disease, although the exact molecular mechanism is unknown. We tested the hypothesis that lycopene may exert its antiatherogenic role through changes in cholesterol metabolism. Incubation of THP-1 cells with lycopene (0.5-2 μM) dose-dependently reduced intracellular total cholesterol. Such an effect was associated with a decrease in reduction of 3-hydroxy-3-methylglutaryl coenzyme A reductase expression and with an increase in ABCA1 and caveolin-1 (cav-1) expressions. In addition, lycopene enhanced RhoA levels in the cytosolic fraction, activating peroxisome proliferator-activated receptor gamma (PPARγ) and liver X receptor alpha expressions. Concomitant addition of lycopene and the PPARγ inhibitor GW9662 or lycopene and mevalonate blocked the carotenoid-induced increase in ABCA1 and cav-1 expressions. These results imply a potential role of lycopene in attenuating foam cell formation and, therefore, in preventing atherosclerosis by a cascade mechanism involving inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase, RhoA inactivation and subsequent increase in PPARγ and liver X receptor alpha activities and enhancement of ABCA1 and cav-1 expressions.