Efficacy of theobromine in preventing intestinal CaCo-2 cell damage induced by oxysterols.

The alteration of the intestinal barrier function is currently believed to be involved in the pathogenesis of gut diseases mainly associated with the activation of inflammation processes. Diet plays an important role in the control of human gut integrity. Theobromine is a natural methylxanthine present in dark chocolate particularly abundant in cocoa bean shell. This is a polyphenol rich by-product generated in cocoa industrial processing, which is gaining value as a functional ingredient. This study aims to highlight for the first time the capability of theobromine in protecting the intestinal cell monolayer from a mixture of dietary oxysterols showing an inflammatory action in terms of IL-8 and MCP-1 overproduction. Differentiated CaCo-2 cells were treated with 60 µM oxysterol mixture and pre-incubated with 10 µM theobromine. Intestinal barrier damage was investigated in terms of tight junction claudin 1, occludin and JAM-A protein levels, matrix metalloproteinase (MMP) -2 and -9 activation and anti/pro-apoptotic protein changes. The observed cell monolayer permeability protection by theobromine may be due to its ability to inhibit the production of cytokines and MMPs that can be responsible for tight junction loss and apoptosis in intestinal cells. Our findings provide additional mechanistic hints on the healthy effect of theobromine cocoa component as an attractive natural molecule in the prevention of inflammatory gut diseases.

Postprandial Dysmetabolism and Oxidative Stress in Type 2 Diabetes: Pathogenetic Mechanisms and Therapeutic Strategies.

Postprandial dysmetabolism in type 2 diabetes (T2D) is known to impact the progression and evolution of this complex disease process. However, the underlying pathogenetic mechanisms still require full elucidation to provide guidance for disease prevention and treatment. This review focuses on the marked redox changes and inflammatory stimuli provoked by the spike in blood glucose and lipids in T2D individuals after meals. All the causes of exacerbated postprandial oxidative stress in T2D were analyzed, also considering the consequence of enhanced inflammation on vascular damage. Based on this in-depth analysis, current strategies of prevention and pharmacologic management of T2D were critically reexamined with particular emphasis on their potential redox-related rationale.

Altered Brain Cholesterol Machinery in a Down Syndrome Mouse Model: A Possible Common Feature with Alzheimer's Disease.

Down syndrome (DS) is a complex chromosomal disorder considered as a genetically determined form of Alzheimer's disease (AD). Maintenance of brain cholesterol homeostasis is essential for brain functioning and development, and its dysregulation is associated with AD neuroinflammation and oxidative damage. Brain cholesterol imbalances also likely occur in DS, concurring with the precocious AD-like neurodegeneration. In this pilot study, we analyzed, in the brain of the Ts2Cje (Ts2) mouse model of DS, the expression of genes encoding key enzymes involved in cholesterol metabolism and of the levels of cholesterol and its main precursors and products of its metabolism (i.e., oxysterols). The results showed, in Ts2 mice compared to euploid mice, the downregulation of the transcription of the genes encoding the enzymes 3-hydroxy-3-methylglutaryl-CoA reductase and 24-dehydrocholesterol reductase, the latter originally recognized as an indicator of AD, and the consequent reduction in total cholesterol levels. Moreover, the expression of genes encoding enzymes responsible for brain cholesterol oxidation and the amounts of the resulting oxysterols were modified in Ts2 mouse brains, and the levels of cholesterol autoxidation products were increased, suggesting an exacerbation of cerebral oxidative stress. We also observed an enhanced inflammatory response in Ts2 mice, underlined by the upregulation of the transcription of the genes encoding for α-interferon and interleukin-6, two cytokines whose synthesis is increased in the brains of AD patients. Overall, these results suggest that DS and AD brains share cholesterol cycle derangements and altered oxysterol levels, which may contribute to the oxidative and inflammatory events involved in both diseases.

24-Hydroxycholesterol Induces Tau Proteasome-Dependent Degradation via the SIRT1/PGC1α/Nrf2 Pathway: A Potential Mechanism to Counteract Alzheimer's Disease.

Considerable evidence indicates that cholesterol oxidation products, named oxysterols, play a key role in several events involved in Alzheimer's disease (AD) pathogenesis. Although the majority of oxysterols causes neuron dysfunction and degeneration, 24-hydroxycholesterol (24-OHC) has recently been thought to be neuroprotective also. The present study aimed at supporting this concept by exploring, in SK-N-BE neuroblastoma cells, whether 24-OHC affected the neuroprotective SIRT1/PGC1α/Nrf2 axis. We demonstrated that 24-OHC, through the up-regulation of the deacetylase SIRT1, was able to increase both PGC1α and Nrf2 expression and protein levels, as well as Nrf2 nuclear translocation. By acting on this neuroprotective pathway, 24-OHC favors tau protein clearance by triggering tau ubiquitination and subsequently its degradation through the ubiquitin-proteasome system. We also observed a modulation of SIRT1, PGC1α, and Nrf2 expression and synthesis in the brain of AD patients with the progression of the disease, suggesting their potential role in neuroprotection. These findings suggest that 24-OHC contributes to tau degradation through the up-regulation of the SIRT1/PGC1α/Nrf2 axis. Overall, the evidence points out the importance of avoiding 24-OHC loss, which can occur in the AD brain, and of limiting SIRT1, PGC1α, and Nrf2 deregulation in order to prevent the neurotoxic accumulation of hyperphosphorylated tau and counteract neurodegeneration.

Molecular signaling involved in oxysterol-induced ß1-integrin over-expression in human macrophages.

The hypercholesterolemia-atherosclerosis association is now established; hypercholesterolemia may induce vascular-cell activation, subsequently increasing expression of adhesion molecules, cytokines, chemokines, growth factors, and other key inflammatory molecules. Among inflammatory molecules expressed by vascular cells, integrins play a critical role in regulating macrophage activation and migration to the site of inflammation, by mediating cell-cell and cell-extracellular matrix interactions. The main lipid oxidation products present in oxidized LDL that may be responsible for inflammatory processes in atherogenesis, are cholesterol oxidation products, known as oxysterols. This study demonstrates the effect of an oxysterol mixture, compatible with that detectable in human hypercholesterolemic plasma, on the expression and synthesis of ß(1)-integrin in cells of the macrophage lineage. The molecular signaling whereby oxysterols induce ß(1)-integrin up-regulation is also comprehensively investigated. Over-expression of ß(1)-integrin depends on activation of classic and novel members of protein kinase C and extracellular signal-regulated kinases 1 and 2, as well as of the up-stream G-protein (Gq and G13), c-Src, and phospholipase C. In addition, the localization of ß(1)-integrin in advanced human carotid plaques is highlighted, marking its importance in atherosclerotic plaque progression.

Macrophage polarization by potential nutraceutical compounds: A strategic approach to counteract inflammation in atherosclerosis.

Chronic inflammation represents a main event in the onset and progression of atherosclerosis and is closely associated with oxidative stress in a sort of vicious circle that amplifies and sustains all stages of the disease. Key players of atherosclerosis are monocytes/macrophages. According to their pro- or anti-inflammatory phenotype and biological functions, lesional macrophages can release various mediators and enzymes, which in turn contribute to plaque progression and destabilization or, alternatively, lead to its resolution. Among the factors connected to atherosclerotic disease, lipid species carried by low density lipoproteins and pro-oxidant stimuli strongly promote inflammatory events in the vasculature, also by modulating the macrophage phenotyping. Therapies specifically aimed to balance macrophage inflammatory state are increasingly considered as powerful tools to counteract plaque formation and destabilization. In this connection, several molecules of natural origin have been recognized to be active mediators of diverse metabolic and signaling pathways regulating lipid homeostasis, redox state, and inflammation; they are, thus, considered as promising candidates to modulate macrophage responsiveness to pro-atherogenic stimuli. The current knowledge of the capability of nutraceuticals to target macrophage polarization and to counteract atherosclerotic lesion progression, based mainly on in vitro investigation, is summarized in the present review.

ApoE3 vs. ApoE4 Astrocytes: A Detailed Analysis Provides New Insights into Differences in Cholesterol Homeostasis.

The strongest genetic risk factor for sporadic Alzheimer's disease (AD) is the presence of the ε4 allele of the apolipoprotein E (ApoE) gene, the major apolipoprotein involved in brain cholesterol homeostasis. Being astrocytes the main producers of cholesterol and ApoE in the brain, we investigated the impact of the ApoE genotype on astrocyte cholesterol homeostasis. Two mouse astrocytic cell lines expressing the human ApoE3 or ApoE4 isoform were employed. Gas chromatography-mass spectrometry (GC-MS) analysis pointed out that the levels of total cholesterol, cholesterol precursors, and various oxysterols are altered in ApoE4 astrocytes. Moreover, the gene expression analysis of more than 40 lipid-related genes by qRT-PCR showed that certain genes are up-regulated (e.g., CYP27A1) and others down-regulated (e.g., PPARγ, LXRα) in ApoE4, compared to ApoE3 astrocytes. Beyond confirming the significant reduction in the levels of PPARγ, a key transcription factor involved in the maintenance of lipid homeostasis, Western blotting showed that both intracellular and secreted ApoE levels are altered in ApoE4 astrocytes, as well as the levels of receptors and transporters involved in lipid uptake/efflux (ABCA1, LDLR, LRP1, and ApoER2). Data showed that the ApoE genotype clearly affects astrocytic cholesterol homeostasis; however, further investigation is needed to clarify the mechanisms underlying these differences and the consequences on neighboring cells. Indeed, drug development aimed at restoring cholesterol homeostasis could be a potential strategy to counteract AD.

Cholesterol Dysmetabolism in Alzheimer's Disease: A Starring Role for Astrocytes?

In recent decades, the impairment of cholesterol metabolism in the pathogenesis of Alzheimer's disease (AD) has been intensively investigated, and it has been recognized to affect amyloid ß (Aß) production and clearance, tau phosphorylation, neuroinflammation and degeneration. In particular, the key role of cholesterol oxidation products, named oxysterols, has emerged. Brain cholesterol metabolism is independent from that of peripheral tissues and it must be preserved in order to guarantee cerebral functions. Among the cells that help maintain brain cholesterol homeostasis, astrocytes play a starring role since they deliver de novo synthesized cholesterol to neurons. In addition, other physiological roles of astrocytes are to modulate synaptic transmission and plasticity and support neurons providing energy. In the AD brain, astrocytes undergo significant morphological and functional changes that contribute to AD onset and development. However, the extent of this contribution and the role played by oxysterols are still unclear. Here we review the current understanding of the physiological role exerted by astrocytes in the brain and their contribution to AD pathogenesis. In particular, we focus on the impact of cholesterol dysmetabolism on astrocyte functions suggesting new potential approaches to develop therapeutic strategies aimed at counteracting AD development.

Up-regulation of PCSK6 by lipid oxidation products: A possible role in atherosclerosis.

Atherosclerosis is a degenerative disease characterized by lesions that develop in the wall of large- and medium-sized arteries due to the accumulation of low-density lipoproteins (LDLs) in the intima. A growing bulk of evidence suggests that cholesterol oxidation products, known as oxysterols, and the aldehyde 4-hydroxy-2-nonenal (HNE), the major pro-atherogenic components of oxidized LDLs, significantly contribute to atherosclerotic plaque progression and destabilization, with eventual plaque rupture. The involvement of certain members of the protein convertase subtilisin/kexin proteases (PCSKs) in atherosclerosis has been recently hypothesized. Among them, PCSK6 has been associated with plaque instability, mainly thanks to its ability to stimulate the activity of matrix metalloproteinases (MMPs) involved in extracellular matrix remodeling and to enhance inflammation. In U937 promonocytic cells and in human umbilical vein endothelial cells, an oxysterol mixture and HNE were able to up-regulate the level and activity of PCSK6, resulting in MMP-9 activation as demonstrated by PCSK6 silencing. Inflammation, enhanced by these lipid oxidation products, plays a key role in the up-regulation of PCSK6 activity as demonstrated by cell pretreatment with NS-398, with epigallocatechin gallate or with acetylsalicylic acid, all with anti-inflammatory effects. For the first time, we demonstrated that both oxysterols and HNE, which substantially accumulate in the atherosclerotic plaque, up-regulate the activity of PCSK6. Of note, we also suggest a potential association between PCSK6 activity and MMP-9 activation, pointing out that PCSK6 could contribute to atherosclerotic plaque development.

The Controversial Role of 24-S-Hydroxycholesterol in Alzheimer's Disease.

The development of Alzheimer's disease (AD) is influenced by several events, among which the dysregulation of cholesterol metabolism in the brain plays a major role. Maintenance of brain cholesterol homeostasis is essential for neuronal functioning and brain development. To maintain the steady-state level, excess brain cholesterol is converted into the more hydrophilic metabolite 24-S-hydroxycholesterol (24-OHC), also called cerebrosterol, by the neuron-specific enzyme CYP46A1. A growing bulk of evidence suggests that cholesterol oxidation products, named oxysterols, are the link connecting altered cholesterol metabolism to AD. It has been shown that the levels of some oxysterols, including 27-hydroxycholesterol, 7ß-hydroxycholesterol and 7-ketocholesterol, significantly increase in AD brains contributing to disease progression. In contrast, 24-OHC levels decrease, likely due to neuronal loss. Among the different brain oxysterols, 24-OHC is certainly the one whose role is most controversial. It is the dominant oxysterol in the brain and evidence shows that it represents a signaling molecule of great importance for brain function. However, numerous studies highlighted the potential role of 24-OHC in favoring AD development, since it promotes neuroinflammation, amyloid ß (Aß) peptide production, oxidative stress and cell death. In parallel, 24-OHC has been shown to exert several beneficial effects against AD progression, such as preventing tau hyperphosphorylation and Aß production. In this review we focus on the current knowledge of the controversial role of 24-OHC in AD pathogenesis, reporting a detailed overview of the findings about its levels in different AD biological samples and its noxious or neuroprotective effects in the brain. Given the relevant role of 24-OHC in AD pathophysiology, its targeting could be useful for disease prevention or slowing down its progression.

Protective Effect of Cocoa Bean Shell against Intestinal Damage: An Example of Byproduct Valorization.

BACKGROUND: Cocoa bean shell (CBS), a main byproduct of cocoa processing, represents a source of components such as polyphenols and methylxanthines, which have been associated with a reduced risk of several diseases. Therefore, CBS has potential application as a food ingredient. Intestinal mucosa is exposed to immune and inflammatory responses triggered by dietary agents, such as oxysterols, which derive from cholesterol oxidation and are pro-oxidant compounds able to affect intestinal function. We aimed at investigating the capability of the Forastero cultivar CBS, added or not added to ice cream, to protect against the intestinal barrier damage induced by a dietary oxysterol mixture. METHODS: Composition and antioxidant capacity of in vitro digested CBS and CBS-enriched ice cream were analyzed by high-performance liquid chromatography and 1,1-diphenyl-2-picryl-hydrazyl radical-scavenging assay, respectively. CaCo-2 cells differentiated into enterocyte-like monolayer were incubated with 60 µM oxysterol mixture in the presence of CBS formulations. RESULTS: The oxysterol mixture induced tight junction impairment, interleukin-8 and monocyte chemoattractant protein-1 cell release, and oxidative stress-related nuclear factor erythroid 2 p45-related factor 2 response Nrf2. Both CBSs protected cells from these adverse effects, probably thanks to their high phenolic content. CBS-enriched ice cream showed the highest antioxidant capacity. Theobromine, which is in high concentrations of CBS, was also tested. Although theobromine exerted no effect on Nrf2 expression, its anti-inflammatory cooperating activity in CBS effect cannot be excluded. CONCLUSIONS: Our findings suggest that CBS-enriched ice cream may be effective in the prevention of gut integrity damage associated with oxidative/inflammatory reactions.

Cholesterol oxidation products and disease: an emerging topic of interest in medicinal chemistry.

Oxysterols are a family of 27-carbon cholesterol oxidation derivatives that may be absorbed with the diet or originated endogenously. These cholesterol metabolites are now considered to be potentially involved in the initiation and progression of major chronic diseases including atherosclerosis, neurodegenerative processes, diabetes, kidney failure, and ethanol intoxication. Thus we deemed it of interest to comprehensively analyze the actual relevance of oxysterols, acting through up-regulation of inflammation, apoptosis and fibrosis, to human pathology from cell signaling to disease expression; we also review the available literature on related therapeutic prospects. Oxysterols of pathophysiologic relevance generally possess a strong pro-oxidant effect, chiefly since they activate NAD(P)H oxidases. Further, stimulation of the MEK/ERK signaling pathway appears to be a common feature of the biochemical effects of this class of compounds. Selective metabolic inhibitors of NAD(P)H oxidase and the MAPK pathway might quench or even prevent the cytotoxic effects of pathological accumulation of cholesterol oxides in cells and tissues. The marked reduction of plasma oxysterols reported for statin-based therapy is interesting: it has been associated with a lower incidence and prevalence of Alzheimer's disease (AD) and vascular dementia. Quenching reactive oxygen species' generation seems the likely mechanism exploited by statins against AD incidence and development; intervention with antioxidants might thus also be re-considered as regards molecular "integrated" prevention and possible therapy of human "multifactorial" disease processes.

A Crosstalk Between Brain Cholesterol Oxidation and Glucose Metabolism in Alzheimer's Disease.

In Alzheimer's disease (AD), both cholesterol and glucose dysmetabolism precede the onset of memory deficit and contribute to the disease's progression. It is indeed now believed that oxidized cholesterol in the form of oxysterols and altered glucose uptake are the main triggers in AD affecting production and clearance of Aß, and tau phosphorylation. However, only a few studies highlight the relationship between them, suggesting the importance of further extensive studies on this topic. Recently, a molecular link was demonstrated between cholesterol oxidative metabolism and glucose uptake in the brain. In particular, 27-hydroxycholesterol, a key linker between hypercholesterolemia and the increased AD risk, is considered a biomarker for reduced glucose metabolism. In fact, its excess increases the activity of the renin-angiotensin system in the brain, thus reducing insulin-mediated glucose uptake, which has a major impact on brain functioning. Despite this important evidence regarding the role of 27-hydroxycholesterol in regulating glucose uptake by neurons, the involvement of other cholesterol oxidation products that have been clearly demonstrated to be key players in AD cannot be ruled out. This review highlights the current understanding of the potential role of cholesterol and glucose dysmetabolism in AD progression, and the bidirectional crosstalk between these two phenomena.

Omics analysis of oxysterols to better understand their pathophysiological role.

High amounts of cholesterol have been definitely associated with the pathogenesis of several diseases, including metabolic and neurodegenerative disorders, cardiovascular diseases, and cancer. In all these pathologies the exacerbation of pro-oxidant and inflammatory responses is a consistent feature. In this scenario, species derived from enzymatic and non-enzymatic cholesterol oxidation, namely oxysterols, are strongly suspected to play a primary role. The consideration of these bioactive lipids is therefore helpful in investigating pathological mechanisms and may also acquire clinical value for the diagnosis and treatment of diseases. For this purpose and considering that a great number of oxysterols may be present together in the body, the employment of lipidomics technology certainly represents a powerful strategy for the simultaneous detection and characterization of these compounds in biological specimens. In this review, we will discuss the applicability of the lipidomics approach in the study of the association between oxysterols and diseases.

A Dietary Mixture of Oxysterols Induces In Vitro Intestinal Inflammation through TLR2/4 Activation: The Protective Effect of Cocoa Bean Shells.

BACKGROUND: Exaggerated Toll-like receptor (TLR)-mediated immune and inflammatory responses play a role in inflammatory bowel diseases. This report deals with the ability of a mixture of oxysterols widely present in cholesterol-rich foods to induce in vitro intestinal inflammation through TLR up-regulation. The anti-inflammatory action of four cocoa bean shell (CBS) extracts with different polyphenol content, was tested. METHODS: Differentiated intestinal CaCo-2 cells were treated with a dietary oxysterol mixture (Oxy-mix) (60 µM). The expression and activation of TLR2 and TLR4, as well as the production of their downstream signaling effectors IL-8, IFNß and TNFα were analyzed in the presence or absence of TLR antibodies. Honduras CBS extracts were characterized for their polyphenol contents; their anti-inflammatory action was analyzed in CaCo-2 cells treated with Oxy-mix. RESULTS: Oxysterol-dependent TLR-2 and TLR4 over-expression and activation together with cytokine induction were abolished by blocking TLRs with specific antibodies. Polyphenol-rich CBS extracts consisting of high quantities of (-)-epicatechin and tannins also prevented TLR induction. CONCLUSIONS: TLR2 and TLR4 mainly contribute to inducing oxysterol-dependent intestinal inflammation. The fractionation method of CBS allowed the recovery of fractions rich in (-)-epicatechin and tannins able to counteract oxysterol-induced inflammation, thus highlighting the beneficial biological potential of specific CBS extracts.

Lipid Oxidation Products in the Pathogenesis of Inflammation-related Gut Diseases.

BACKGROUND: A defective mucosal barrier function is the principal cause of the uncontrolled onset and progression of a number of human inflammatory gut diseases, most of which are characterized by chronic intermittent immune and inflammatory responses leading to structural intestinal damage, which can represent a potential risk for colorectal cancer development. During the active disease phase the production of pro-inflammatory cytokines and chemokines, and the induction of oxidative reactions by activated leukocytes and epithelial cells represent the main event in the intestinal inflammation. OBJECTIVE: Oxidative stress plays a key role in the development of intestinal damage. Indeed reactive oxygen species and their oxidized by-products regulate redox-sensitive signaling pathways and transcription factors, which sustain inflammation within the intestinal layer. METHODS: Polyunsaturated fatty acids and cholesterol are the principal targets of oxidative modifications. These lipids, which are cell membrane constituents or are present in food, readily undergo non-enzymatic oxidation to form chemically-reactive species that can induce a wide range of biological effects including inflammation, programmed cell death, and proliferation. RESULTS AND CONCLUSIONS: In this review we summarize the current knowledge on the role of lipid oxidation products in regulating redox pathways involved in the pathogenesis of inflammation- related gut diseases. In particular, lipid peroxidation end products, such as isoprostanes and aldehydes, and cholesterol oxidation-derived oxysterols are taken into consideration. The control of oxidative damage and consequently tissue local over-production of lipid oxidation products by using specific antioxidant and anti-inflammatory molecules in the diet may have clinical and therapeutic benefits.

Activation of the mitochondrial pathway of apoptosis by oxysterols.

A significant fraction of cholesterol that accumulates in atherosclerotic lesions is actually oxidized to yield a number of derivatives, named oxysterols, which are provided with much stronger biochemical effects than the parental compound. Of note, an increasing bulk of studies is giving evidence of accumulation of oxysterols in a number of other chronic disease processes including quite common neurodegenerative diseases. In particular, defined cholesterol oxidation products, among those of main interest in pathophysiology, may strongly activate the mitochondrial pathway of apoptotic death. Modulation by oxysterols of various pro- and anti-apoptotic molecules involved in that pathway are hereafter examined under the light of the most recent relevant literature.

HNE and cholesterol oxidation products in colorectal inflammation and carcinogenesis.

Consistent experimental data suggest the importance of inflammation-associated oxidative stress in colorectal cancer (CRC) pathogenesis. Inflammatory bowel disease with chronic intestinal inflammation is now considered a precancerous condition. Oxidative stress is an essential feature of inflammation. Activation of redox-sensitive pro-inflammatory cell signals and inflammatory mediators concur to establish a pro-tumoral environment. In this frame, lipid oxidation products, namely 4-hydroxynonenal and oxysterols, can be produced in big quantity so as to be able to exert their function as inducers of cell signaling pathways of proliferation and survival. Notably, an important source of these two compounds is represented by a high fat diet, which is undoubtedly a risk factor for inflammation and CRC development. Current evidence for the emerging implication of these two oxidized lipids in inflammation and CRC development is discussed in this review.

Derangement of intestinal epithelial cell monolayer by dietary cholesterol oxidation products.

The emerging role of the diet in the incidence of intestinal inflammatory diseases has stimulated research on the influence of eating habits with pro-inflammatory properties in inducing epithelial barrier disturbance. Cholesterol oxidation products, namely oxysterols, have been shown to promote and sustain oxidative/inflammatory reactions in human digestive tract. This work investigated in an in vitro model the potential ability of a combination of dietary oxysterols representative of a hyper-cholesterol diet to induce the loss of intestinal epithelial layer integrity. The components of the experimental mixture were the main oxysterols stemming from heat-induced cholesterol auto-oxidation, namely 7-ketocholesterol, 5α,6α-and 5ß,6ß-epoxycholesterol, 7α- and 7ß-hydroxycholesterol. These compounds added to monolayers of differentiated CaCo-2 cells in combination or singularly, caused a time-dependent induction of matrix metalloproteinases (MMP)-2 and -9, also known as gelatinases. The hyperactivation of MMP-2 and -9 was found to be associated with decreased levels of the tight junctions zonula occludens-1 (ZO-1), occludin and Junction Adhesion Molecule-A (JAM-A). Together with such a protein loss, particularly evident for ZO-1, a net perturbation of spatial localization of the three tight junctions was observed. Cell monolayer pre-treatment with the selective inhibitor of MMPs ARP100 or polyphenol (-)-epicathechin, previously shown to inhibit NADPH oxidase in the same model system, demonstrated that the decrease of the three tight junction proteins was mainly a consequence of MMPs induction, which was in turn dependent on the pro-oxidant property of the oxysterols investigated. Although further investigation on oxysterols intestinal layer damage mechanism is to be carried on, the consequent - but incomplete - prevention of oxysterols-dependent TJs alteration due to MMPs inhibition, avoided the loss of scaffold protein ZO-1, with possible significant recovery of intestinal monolayer integrity.

Early involvement of ROS overproduction in apoptosis induced by 7-ketocholesterol.

Cholesterol oxidation products are increasingly considered as much more bioactive than the parent compound in the multifactor and multistep process that characterizes atherosclerosis. In particular, 7-ketocholesterol has been reported to induce oxidative stress as well as a marked pro-apoptotic effect in vascular cells including macrophages. With the aim to investigate a possible pathogenic correlation between the two events, cultivated murine macrophages were challenged with a concentration of 7-ketocholesterol actually detectable in human vasculature. Conclusive proof was obtained of a primary role of NADPH-oxidase in the overproduction of reactive oxygen species within cells treated with the oxysterol. In addition, such oxidative burst occurred very early after cell intoxication and it was definitely demonstrated as able to lead cells to apoptotic death. In fact, two metabolic inhibitors of NADPH-oxidase and the antioxidant epicatechin very well counteracted 7-ketocholesterol-induced apoptosis by preventing the oxysterol pro-oxidant action.