Effects of the olive-derived polyphenol oleuropein on human health

The use of the products derived from the olive tree on human health dates back centuries. In several civilizations, the olive tree had and still has a very strong cultural and religious symbolism. Notably, the official seal and emblem of the World Health Organization features the rod of Asclepius over a world map surrounded by olive tree branches, chosen as a symbol of peace and health. Recently, accumulating experimental, clinical and epidemiological data have provided support to the traditional beliefs of the beneficial effect provided by olive derivates. In particular, the polyphenols present in olive leaves, olives, virgin (unrefined) olive oil and olive mill waste are potent antioxidant and radical scavengers with anti-tumor and anti-inflammatory properties. Here, we review the positive impact on human health of oleuropein, the most prevalent polyphenol present in olives. In addition, we provide data collected in our laboratory on the role of oleuropein in counteracting lipid accumulation in a mouse model of non-alcoholic fatty liver disease.

Benefits from dietary polyphenols for brain aging and Alzheimer's disease

Brain aging and the most diffused neurodegenerative diseases of the elderly are characterized by oxidative damage, redox metals homeostasis impairment and inflammation. Food polyphenols can counteract these alterations in vitro and are therefore suggested to have potential anti-aging and brain-protective activities, as also indicated by the results of some epidemiological studies. Despite the huge and increasing amount of the in vitro studies trying to unravel the mechanisms of action of dietary polyphenols, the research in this field is still incomplete, and questions about bioavailability, biotransformation, synergism with other dietary factors, mechanisms of the antioxidant activity, risks inherent to their possible pro-oxidant activities are still unanswered. Most of all, the capacity of the majority of these compounds to cross the blood-brain barrier and reach brain is still unknown. This commentary discusses recent data on these aspects, particularly focusing on effects of curcumin, resveratrol and catechins on Alzheimer's disease.

Environmental pollution: a tangible risk for NAFLD pathogenesis

The liver is crucial for human life, and the health of this organ often mirrors the health of the individual. The liver can be the target of several diseases, the most prevalent of which, as a consequence of development and changes in human lifestyles, is the nonalcoholic fatty liver disease (NAFLD). NAFLD is a multifactorial disease that embraces many histo-pathologic conditions and is highly linked to metabolic derangements. Technological progress and industrialization have also had the consequence of releasing pollutants in the environment, for instance pesticides or solvents, as well as by-products of discharge, such as the particulate matter. In the last decade, a growing body of evidence has emerged, shedding light on the potential impact of environmental pollutants on liver health and, in particular, on NAFLD occurrence. These contaminants have a great steatogenic potential and need to be considered as tangible NAFLD risk factors. There is an urgent need for a deeper comprehension of their molecular mechanisms of action, as well as for new lines of intervention to reduce their worldwide diffusion. This review wishes to sensitize the community to the effects of several environmental pollutants on liver health.

Copper-dependent toxicity in SH-SY5Y neuroblastoma cells involves mitochondrial damage

Treatment of SH-SY5Y human neuroblastoma cells with copper sulphate (50-300microM) in complete medium for 24h caused an increase in the level of the metal both in whole cells and in isolated mitoplasts. Toxic effects of copper resulted in the impairment of the capability of mitochondrial dehydrogenases to reduce a tetrazolium salt, and, to a lesser extent, in the loss of the integrity of the plasma membrane. The mechanism of toxicity involved the production of reactive oxygen species, amplified by the presence of ascorbate. Decreases in the levels of several mitochondrial proteins (subunits of complex I, complex V, and of the pyruvate dehydrogenase complex) were observed. These findings demonstrate that mitochondria are an early and susceptible target of copper-mediated oxidative stress in neuronal cells and support the hypothesis that mitochondrial damage triggers the neurodegenerative processes associated with copper overload in Wilson's disease.

Prediction of carotid intima-media thickness in obese patients with low prevalence of comorbidities by serum copper bioavailability

BACKGROUND AND AIM

Western societies, with growing prevalence, suffer from various metabolic diseases like obesity and hepatic steatosis, better defined as non-alcoholic fatty liver disease, or cardiovascular (CV) diseases that are strictly linked to each other. The association of their occurrence with the altered homeostasis of metals is an intriguing issue. Copper in particular was identified as key player in various metabolic derangements. On these bases, we aimed at investigating the possible association of serum copper levels with an indicator of early CV risk as the intima-media thickness (IMT) of carotid artery and its predictive value in a selected population of obese patients.

METHODS

We performed a cross-sectional study recruiting 100 obese patients characterized by a low prevalence of comorbidities. Ultrasound investigation for hepatic steatosis and IMT evaluation were performed. Serum samples were collected and then analyzed through atomic absorption spectrometry to evaluate their copper content. Possible correlations between copper bioavailability and biochemical, clinical, and anthropometric characteristics of patients were sought.

RESULTS

Age negatively predicted copper serum levels of patients (P = 0.009). However, the most interesting finding is the negative prediction of IMT by the copper serum levels (t = -2.23, P = 0.028, least absolute deviations regression). Factor analysis confirmed the aforementioned inverse correlation and highlighted the strong inverse correlation between smoking and copper serum levels.

CONCLUSION

Our data show that an altered copper bioavailability predicts early atherosclerosis as main CV risk in obese patients with hepatic steatosis detected by ultrasound, shedding some light in this pathological scenario.

Copper homeostasis as target of both consolidated and innovative strategies of anti-tumor therapy

BACKGROUND

Copper was reported to be involved in the onset and progression of cancer. Proteins in charge of copper uptake and distribution, as well as cuproenzymes, are altered in cancer. More recently, proteins involved in signaling cascades, regulating cell proliferation, and anti-apoptotic protein factors were found to interact with copper. Therefore, therapeutic strategies using copper complexing molecules have been proposed for cancer therapy and used in clinical trials.

OBJECTIVES

This review will focus on novel findings about the involvement of copper and cupro-proteins in cancer dissemination process, epithelium to mesenchymal transition and vascularization. Particularly, implication of well-established (e.g. lysil oxidase) or newly identified copper-binding proteins (e.g. MEMO1), as well as their interplay, will be discussed. Moreover, we will describe recently synthesized copper complexes, including plant-derived ones, and their efficacy in contrasting cancer development.

CONCLUSIONS

The research on the involvement of copper in cancer is still an open field. Further investigation is required to unveil the mechanisms involved in copper delivery to the novel copper-binding proteins, which may identify other possible gene and protein targets for cancer therapy.

Non-ceruloplasmin bound copper and ATP7B gene variants in Alzheimer's disease

ATP7B, a protein mainly expressed in the hepatocytes, is a copper chaperone that loads the metal into the serum copper–protein ceruloplasmin during its synthesis and also escorts superfluous copper into the bile, by a sophisticated trafficking mechanism.

Inactivation of cytochrome c oxidase by mutant SOD1s in mouse motoneuronal NSC-34 cells is independent from copper availability but is because of nitric oxide

The copper-enzyme cytochrome c oxidase (Cytox) has been indicated as a primary molecular target of mutant copper, zinc superoxide dismutase (SOD1) in familial amyotrophic lateral sclerosis (fALS); however, the mechanism underlying its inactivation is still unclear. As the toxicity of mutant SOD1s could arise from their selective recruitment to mitochondria, it is conceivable that they might compete with Cytox for the mitochondrial copper pool causing Cytox inactivation. To investigate this issue, we used mouse motoneuronal neuroblastoma x spinal cord cell line-34, stably transfected for the inducible expression of low amounts of wild-type or mutant (G93A, H46R, and H80R) human SOD1s and compared the effects observed on Cytox with those obtained by copper depletion. We demonstrated that all mutants analyzed induced cell death and decreased the Cytox activity, but not the protein content of the Cytox subunit II, at difference with copper depletion that also affected subunit II protein. Copper supplementation did not counteract mutant hSOD1s toxicity. Otherwise, the treatment of neuroblastoma x spinal cord cell line-34 expressing G93A, H46R, or H80R hSOD1 mutants, and showing constitutive expression of iNOS and nNOS, with either a NO scavenger, or NOS inhibitors prevented the inhibition of Cytox activity and rescued cell viability. These results support the involvement of NO in mutant SOD1s-induced Cytox damage, and mitochondrial toxicity.

Mitochondrial dysfunctions and altered metals homeostasis: new weapons to counteract HCV-related oxidative stress

The hepatitis C virus (HCV) infection produces several pathological effects in host organism through a wide number of molecular/metabolic pathways. Today it is worldwide accepted that oxidative stress actively participates in HCV pathology, even if the antioxidant therapies adopted until now were scarcely effective. HCV causes oxidative stress by a variety of processes, such as activation of prooxidant enzymes, weakening of antioxidant defenses, organelle damage, and metals unbalance. A focal point, in HCV-related oxidative stress onset, is the mitochondrial failure. These organelles, known to be the "power plants" of cells, have a central role in energy production, metabolism, and metals homeostasis, mainly copper and iron. Furthermore, mitochondria are direct viral targets, because many HCV proteins associate with them. They are the main intracellular free radicals producers and targets. Mitochondrial dysfunctions play a key role in the metal imbalance. This event, today overlooked, is involved in oxidative stress exacerbation and may play a role in HCV life cycle. In this review, we summarize the role of mitochondria and metals in HCV-related oxidative stress, highlighting the need to consider their deregulation in the HCV-related liver damage and in the antiviral management of patients.

Focal adhesion kinase (FAK) mediates the induction of pro-oncogenic and fibrogenic phenotypes in hepatitis C virus (HCV)-infected cells

Hepatitis C Virus (HCV) infection is one of the most common etiological factors involved in fibrosis development and its progression to hepatocellular carcinoma (HCC). The pivotal role of hepatic stellate cells (HCSs) and extracellular matrix (ECM) in fibrogenesis is now certainly accepted, while the network of molecular interactions connecting HCV is emerging as a master regulator of several biological processes including proliferation, inflammation, cytoskeleton and ECM remodeling. In this study, the effects of HCV proteins expression on liver cancer cells, both pro-invasive and pro-fibrogenic phenotypes were explored. As a model of HCV infection, we used permissive Huh7.5.1 hepatoma cells infected with JFH1-derived ccHCV. Conditioned medium from these cells was used to stimulate LX-2 cells, a line of HSCs. We found that the HCV infection of Huh7.5.1 cells decreased adhesion, increased migration and caused the delocalization of alpha-actinin from plasma membrane to cytoplasm and increased expression levels of paxillin. The treatment of LX-2 cells, with conditioned medium from HCV-infected Huh7.5.1 cells, caused an increase in cell proliferation, expression of alpha-smooth muscle actin, hyaluronic acid release and apoptosis rate measured as cleaved poly ADP-ribose polymerase (PARP). These effects were accompanied in Huh7.5.1 cells by an HCV-dependent increasing of FAK activation that physically interacts with phosphorylated paxillin and alpha-actinin, and a rising of tumor necrosis factor alpha production/release. Silencing of FAK by siRNA reverted all effects of HCV infection, both those directed on Huh7.5.1 cells, and those indirect effects on the LX-2 cells. Moreover and interestingly, FAK inhibition enhances apoptosis in HCV-conditioned LX-2 cells. In conclusion, our findings demonstrate that HCV, through FAK activation, may promote cytoskeletal reorganization and a pro-oncogenic phenotype in hepatocyte-like cells, and a fibrogenic phenotype in HSCs.

Protective effect of the Y220C mutant p53 against steatosis: good news?

Nonalcoholic fatty liver disease (NAFLD) ranges from simple steatosis to steatohepatitis, which may progress to fibrosis, and cirrhosis, leading eventually to hepatocarcinoma development. Recently, cases of hepatocarcinoma have been diagnosed in steatotic patients without nonalcoholic steatohepatitis (NASH) and cirrhosis. The p53 protein, besides its function as tumor suppressor, is emerging as an important regulator of cellular metabolism, but its role in steatosis remains unclear. We induced steatosis in HepG2 (wt-p53) and Huh7.5.1 (Y220C-mutant p53) cells using free fatty acids. We observed a different modulation of p53, different intracellular lipid content, and similar down-regulation of the de novo lipid synthesis genes but opposite modulation of the fatty acid β-oxidation pathway between HepG2 and Huh7.5.1. Accordingly, we found a diverse amount of apoptosis and reactive oxygen species between the two cell lines. Transfection of the wt-p53 in Huh7.5.1 cells reverted the different lipid metabolism behavior observed in these cells. In conclusion, unlike the wt-p53, the Y220C mutant provides a specific protection against steatosis and potentially against its progression. Our findings highlight for the first time an unknown role of a p53 mutant in the setting of steatosis. Being this mutation very frequent in human cancers, this study could be a breakthrough in explaining the occurrence of hepatocarcinoma in steatotic patients without NASH and cirrhosis.

Inverse correlation between plasma oxysterol and LDL-cholesterol levels in hepatitis C virus-infected patients

BACKGROUND

Hepatitis C virus infection is characterised by enhanced oxidative stress, which can be measured quantitatively by plasma oxysterol concentration. These molecules may affect lipid metabolism through the activation of Liver X Receptors. Hepatitis C virus exploits host lipid metabolism to facilitate its replication and diffusion. In our study we aimed to evaluate and highlight the potential pathogenetic role of oxysterols, 7-ketocholesterol and 7-β-hydroxycholesterol, in hepatitis C virus-related lipid dysmetabolism.

METHODS

The study was performed in 42 patients with chronic hepatitis C (93% genotype 1b) and 38 non-alcoholic fatty liver disease patients. Plasma oxysterols 7-ketocholesterol and 7-β-hydroxycholesterol were determined by isotope dilution gas chromatography/mass spectrometry.

RESULTS

Gas chromatography/mass spectrometry revealed higher 7-ketocholesterol (71.2 ± 77.3 vs 30.4 ± 14.5; p<0.005) and 7-β-hydroxycholesterol (23.7 ± 20.6 vs 11.5 ± 4.9; p<0.001) plasma levels in hepatitis C virus patients. Furthermore, multivariate regression analysis highlighted an inverse independent correlation between high oxysterol levels and low low-density lipoprotein cholesterol (p=0.01 for 7-β-hydroxycholesterol; p=0.02 for 7-ketocholesterol) in the hepatitis C virus group; in contrast, the non-alcoholic fatty liver disease group showed a direct correlation between oxysterol levels and low-density lipoprotein-cholesterol (p<0.001 for 7-β-hydroxycholesterol; p=0.002 for 7-ketocholesterol).

CONCLUSION

These different correlations reveal profound differences in lipid dysmetabolism between chronic hepatitis C and non-alcoholic fatty liver disease patients.

7-ketocholesterol and 5,6-secosterol modulate differently the stress-activated mitogen-activated protein kinases (MAPKs) in liver cells

Enhanced oxidative stress is a common feature of liver diseases and contributes to chronic liver disease (CLD) progression by inducing fibrogenesis during liver regeneration. Peroxidation products of cholesterol metabolism, named oxysterols, are new and reliable markers of oxidative stress in vivo. Patients affected by CLDs present high plasma levels of oxysterols, raising the question of the origin and biological relevance of these compounds in the pathophysiology of chronic liver damage. The aim of this study was to examine the molecular basis of the biological effects of oxysterols on liver-derived cells, HepG2 and Huh7. Cells were treated with different concentrations (10(-9) to 10(-5) M) of 7-ketocholesterol used as a reference, and 5,6-secosterol, a recently discovered oxysterol. FACS investigations, caspase-3 activation, and Sytox Green immunofluorescent assay showed that pathological concentrations of oxysterols induced necrosis (30-50%) after 48 h of treatment. The two analyzed compounds displayed a similar, but not identical, behavior. In fact, 5,6-secosterol, but not 7-ketocholesterol, induced cell senescence. Notably, low concentrations of 5,6-secosterol caused a sustained activation of ERK1/2, inducing cell proliferation, this unexpected behavior should be better characterized by further studies. Since enhanced oxidative stress is known to worsen liver chronic hepatitis and frequently results in overall decreased cellular survival, our data suggest the important and different role oxysterols may have in interfering with physiological liver tissue regeneration in injured human liver. Antioxidant treatment may provide a highly specific and effective mean to counteract the common consequences of oxidative stress on chronic hepatitis, such as fibrosis/cirrhosis and liver failure.

Core domain mutant Y220C of p53 protein has a key role in copper homeostasis in case of free fatty acids overload

Nonalcoholic fatty liver disease (NAFLD) is a pathology that includes a wide variety of clinical conditions ranging from simple steatosis to end-stage liver diseases. Despite the huge amount of researches, the molecular basis of NAFLD are still not fully understood. Recently, it was suggested a role for p53 in NAFLD pathogenesis. Among its targets there is Synthesis of Cytochrome c Oxidase 2 (SCO2), a copper chaperone, involved in both aerobic respiration and metal cellular excretion. Copper seems to play a role in NAFLD. It was demonstrated a low hepatic copper content in NAFLD patients, which correlates with metabolic syndrome parameters. Copper homeostasis deregulation, in fact, seems to be related to lipid metabolism alteration and insulin resistance. Here we provide evidence on the role of p53 in the modulation of copper homeostasis, in an experimental model of NAFLD. We used two different hepatoma cell lines, HepG2 and Huh 7.5.1, characterized by the presence of wt p53 and its Y220C mutant, respectively, treated with a free fatty acids (FFAs) solution. Interestingly, p53 activation correlated with the intracellular copper level maintenance. We demonstrated that, in hepatoma cell lines, core domain mutant Y220C of p53 affects the modulation of SCO2 and Copper transporter 1 (CTR1), influencing, in this way, intracellular copper homeostasis in presence of FFAs accumulation, and that the 220 residue of the protein is crucial for such control. The role of p53 we highlighted may have deep implications in clinical conditions where copper homeostasis is deregulated.

Exocycilic DNA Adducts in a Murine Model of Non-alcoholic Steatohepatitis

Introduction:

Non-alcoholic fatty liver disease is the most common hepatic disorder in Western countries. The transition from abnormal accumulation of lipids toward non-alcoholic steatohepatitis (NASH) represents a key step in the development of chronic liver pathologies. Oxidative stress and lipid peroxidation have often been proposed as mechanisms in the progression to steatohepatitis.

Methods:

We have examined the hepatic levels of exocyclic DNA adducts, indicated from 3-(2-deoxy-β-D-erythro-pentafuranosyl)pyrimido[1,2-α]purin-10(3H)-one deoxyguanosine (M₁dG) adduct, a biomarker of oxidative stress and lipid peroxidation, in a murine model of NASH using the ³²P-DNA postlabeling assay.

Results:

Our findings show that C57BL/6 mice fed with high-fat and cholesterol diet developed signs associated with NASH after eight weeks, whereas there was no evidence of steatosis in control mice. The score for steatohepatitis ranged from grade 2 to 3 for steatosis, inflammation, and fibrosis, showing that the experimental diet was able to induce pathologic alterations of the parenchyma in eight weeks. Higher levels of M₁dG adducts were detected in the livers of C57BL/6 mice which developed experimental NASH after eight weeks of high-fat and cholesterol feed, 5.6 M ₁dG ± 0.4 (SE) per 10⁶ total nucleotides, as compared to control mice, 1.6 M₁dG ± 0.4 (SE). The statistical analysis showed that the increment of oxidatively damaged DNA in mice with NASH raised on high-fat and cholesterol diet was statistically significant as compared to control mice, P=0.006.

Conclusions:

Our report suggests a link between NASH and M₁dG in experimental animals fed with a diet rich in saturated fats and cholesterol. High-fat and cholesterol may act together in inducing a broader spectrum of oxidatively damaged DNA, including exocyclic DNA adducts, that may contribute to the decline of hepatocyte functions, from disturbance of critical pathways, such as transcription and replication, triggering transient or permanent cell-cycle arrest and cell-death, up to chromosomal instability.

Copper imbalance and oxidative stress in neurodegeneration

Much experimental evidence demonstrates that the increased production of free radicals and oxidative damage due to alterations in copper homeostasis (because of either deficit or excess or aberrant coordination of the metal) are involved in the neurodegenerative processes occurring in many disorders of the central nervous system. This review outlines the systems that are involved in copper homeostasis and in the control of copper redox reactivity. The mechanisms underlying neurodegeneration in the acknowledged genetic disturbances of copper homeostasis, namely Menkes' and Wilson's diseases, and the involvement of copper in the aetiology of the major neurodegenerative disease of the aging brain, Alzheimer's disease, will be described, with particular focus on oxidative stress.