Dietary curcumin inhibits atherosclerosis by affecting the expression of genes involved in leukocyte adhesion and transendothelial migration

Curcumin Suppresses MAPK Pathways to Reverse Tobacco Smoke-induced Gastric Epithelial-Mesenchymal Transition in Mice

Tobacco smoke (TS) has been shown to cause gastric cancer. Epithelial-mesenchymal transition (EMT) is a crucial pathophysiological process in cancer development. Mitogen-activated protein kinase (MAPK) pathways play central roles in tumorigenesis including EMT process. Curcumin is a promising chemopreventive agent for several types of cancers. In the present study, we investigated the effects of TS on MAPK pathway activation and EMT alterations in the stomach of mice, and the preventive effect of curcumin was further examined. Results showed that exposure of mice to TS for 12 weeks resulted in activation of extracellular regulated protein kinases 1 and 2 (ERK1/2), the Jun N-terminal kinase (JNK), p38, and ERK5 MAPK pathways as well as activator protein 1 (AP-1) proteins in stomach. TS reduced the mRNA and protein expression levels of the epithelial markers E-cadherin and ZO-1, while the mRNA and protein expression levels of the mesenchymal markers vimentin and N-cadherin were increased. Treatment of curcumin effectively abrogated TS-triggered gastric activation of ERK1/2 and JNK MAPK pathways, AP-1 proteins, and EMT alterations. These results suggest for the first time the protective effects of curcumin in long-term TS exposure-induced gastric MAPK activation and EMT, thus providing new insights into the pathogenesis and chemoprevention of TS-associated gastric cancer.

Nuclear Factor-κB Activation as a Pathological Mechanism of Lipid Metabolism and Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall with lipid-laden lesions, involving a complex interaction between multiple different cell types and cytokine networks. Inflammatory responses mark all stages of atherogenesis: from lipid accumulation in the intima to plaque formation and eventual rupture. One of the most important regulators of inflammation is the transcription factor nuclear factor-κB (NF-κB), which is activated through the canonical and noncanonical pathways in response to various stimuli. NF-κB has long been regarded as a proatherogenic factor, because it is implicated in multiple pathological processes during atherogenesis, including foam cell formation, vascular inflammation, proliferation of vascular smooth muscle cells, arterial calcification, and plaque progression. In contrast, inhibition of NF-κB signaling has been shown to protect against atherosclerosis. This chapter aims to discuss recent progress on the roles of NF-κB in lipid metabolism and atherosclerosis and also to highlight its potential therapeutic benefits.

Molecular analysis of curcumin-induced polarization of murine RAW264.7 macrophages

This study aimed to investigate the effects of curcumin on macrophages polarization and possible mechanism involved, and to analyze the molecular basis of its antiatherosclerosis activity. RAW264.7 macrophages (M0) and M1 macrophages were treated with curcumin at 0, 6.25, 12.5, and 25 μmol/L with or without GW9662. Using real-time polymerase chain reaction and Western blot analysis, we examined the phenotype markers of M1 [iNOS, interleukin (IL)-1β, IL-6, and MCP-1] and M2 (KLF4, FIZZ1, and MGL1] macrophages. Curcumin reduced the expression of the M1 phenotype markers and upregulated the expression of proliferator-activated receptor γ in M0 and M1 macrophages and IKBα in M1 macrophages. When M1 macrophages were incubated with curcumin and GW9662, the expression of the M1 phenotype markers was decreased, while IKBα was upregulated. The expression of the M2 phenotype markers in M0 and M1 macrophages was upregulated after the curcumin treatment. When M0 and M1 macrophages were incubated with curcumin and GW9662, the expression of the M2 phenotype markers was reduced. Curcumin inhibited the M1 inflammation phenotype as a result of the direct activation of IKBα and polarized the macrophages to become M2 phenotype through the activation of proliferator-activated receptor γ. These findings provide new clues to develop new drug therapy for atherosclerosis.

Unraveling curcumin degradation: autoxidation proceeds through spiroepoxide and vinylether intermediates en route to the main bicyclopentadione

Curcumin is a dietary anti-inflammatory and chemopreventive agent consisting of two methoxyphenol rings connected by a conjugated heptadienedione chain. Curcumin is unstable at physiological pH and rapidly degrades in an autoxidation reaction to a major bicyclopentadione product in which the 7-carbon chain has undergone oxygenation and double cyclization. Early degradation products (but not the final bicyclopentadione) mediate topoisomerase poisoning and possibly many other activities of curcumin, but it is not known how many and what autoxidation products are formed, nor their mechanism of formation. Here, using [(14)C2]curcumin as a tracer, seven novel autoxidation products, including two reaction intermediates, were isolated and identified using one- and two-dimensional NMR and mass spectrometry. The unusual spiroepoxide and vinylether reaction intermediates are precursors to the final bicyclopentadione product. A mechanism for the autoxidation of curcumin is proposed that accounts for the addition and exchange of oxygen that have been determined using (18)O2 and H2(18)O. Several of the by-products are formed from an endoperoxide intermediate via reactions that are well precedented in lipid peroxidation. The electrophilic spiroepoxide intermediate formed a stable adduct with N-acetylcysteine, suggesting that oxidative transformation is required for biological effects mediated by covalent adduction to protein thiols. The spontaneous autoxidation distinguishes curcumin among natural polyphenolic compounds of therapeutic interest; the formation of chemically diverse reactive and electrophilic products provides a novel paradigm for understanding the polypharmacological effects of curcumin.

Oleuropein or rutin consumption decreases the spontaneous development of osteoarthritis in the Hartley guinea pig

OBJECTIVE

To assess the potential protective effects of three polyphenols oleuropein, rutin and curcumin, on joint ageing and osteoarthritis (OA) development.

DESIGN

Sixty 4-week-old Dunkin-Hartley guinea pigs were randomized into four groups and received daily during 31 weeks either standard guinea pig diet (control group) or a standard guinea pig diet enriched with oleuropein (0.025%), rutin (0.5%) or rutin/curcumin (0.5%/0.25%) association. Biomarkers of OA (Coll2-1, Coll2-1NO2, Fib3-1, Fib3-2, ARGS), as well as inflammation prostaglandin E2 (PGE2) were quantified in the serum. Histological assessments of knee cartilage and synovial membrane were performed at week 4 (five young reference guinea pigs) and week 35.

RESULTS

At week 35, guinea pigs in the control group spontaneously developed significant cartilage lesions with mild synovial inflammation. The histological scores of cartilage lesions and synovitis were well correlated with the increased level of serum biomarkers. Histologically, all treatments significantly reduced the cartilage degradation score (P < 0.01), but only oleuropein significantly decreased the synovial histological score (P < 0.05) and serum PGE2 levels (P < 0.01) compared to the control group. Coll2-1 was decreased by rutin and the combination of rutin/curcumin, Fib3-1 and Fib3-2 were only decreased by the rutin/curcumin mixture, while Coll2-1NO2 was significantly decreased by all treatments (P < 0.05).

CONCLUSION

Oleuropein and rutin ± curcumin significantly slowed down the progression of spontaneous OA lesions in guinea pigs. While no additive effect was seen in the curcumin + rutin group, the differential effects of oleuropein and rutin on inflammatory and cartilage catabolic markers suggest an interesting combination for future studies in OA protection.

Beneficial effects of proanthocyanidins in the cardiac alterations induced by aldosterone in rat heart through mineralocorticoid receptor blockade

Aldosterone administration in rats results in several cardiac alterations. Previous studies have demonstrated that proanthocyanidins, phenolic bioactive compounds, have cardioprotective effects. We studied the potential beneficial effects of the proanthocyanidin-rich almond skin extract (PASE) on the cardiac alterations induced by aldosterone-salt treatment, their effects in mineralocorticoid receptor activity and we sought to confirm proanthocyanidins as the specific component of the extract involved in the beneficial cardiac effects. Male Wistar rats received aldosterone (1 mg/Kg/day) +1% NaCl for 3 weeks. Half of the animals in each group were simultaneously treated with either PASE (100 mg/Kg/day) or spironolactone (200 mg/Kg/day). The ability of PASE to act as an antagonist of the mineralocorticoid receptor was examined using a transactivation assay. High performance liquid chromatography was used to identify and to isolate proanthocyanidins. Hypertension and diastolic dysfunction induced by aldosterone were abolished by treatment with PASE. Expression of the aldosterone mediator SGK-1, together with fibrotic, inflammatory and oxidative mediators were increased by aldosterone-salt treatment; these were reduced by PASE. Aldosterone-salt induced transcriptional activity of the mineralocorticoid receptor was reduced by PASE. HPLC confirmed proanthocyanidins as the compound responsible for the beneficial effects of PASE. The effects of PASE were comparable to those seen with the mineralocorticoid antagonist, spironolactone. The observed responses in the aldosterone-salt treated rats together with the antagonism of transactivation at the mineralocorticoid receptor by PASE provides evidence that the beneficial effect of this proanthocyanidin-rich almond skin extract is via as a mineralocorticoid receptor antagonist with proanthocyanidins identified as the compounds responsible for the beneficial effects of PASE.

Epigenetic modulation in the treatment of atherosclerotic disease

Cardiovascular disease is the single largest cause of death in the western world and its incidence is on the rise globally. Atherosclerosis, characterized by the development of atheromatus plaque, can trigger luminal narrowing and upon rupture result in myocardial infarction or ischemic stroke. Epigenetic phenomena are a focus of considerable research interest due to the role they play in gene regulation. Epigenetic mechanisms such as DNA methylation and histone acetylation have been identified as potential drug targets in the treatment of cardiovascular disease. miRNAs are known to play a role in gene silencing, which has been widely investigated in cancer. In comparison, the role they play in cardiovascular disease and plaque rupture is not well understood. Nutritional epigenetic modifiers from dietary components, for instance sulforaphane found in broccoli, have been shown to suppress the pro-inflammatory response through transcription factor activation. This review will discuss current and potential epigenetic therapeutics for the treatment of cardiovascular disease, focusing on the use of miRNAs and dietary supplements such as sulforaphane and protocatechuic aldehyde.

Curcumin attenuates cardiac fibrosis in spontaneously hypertensive rats through PPAR-γ activation

AIM

To investigate the effects of curcumin (Cur) on cardiac fibrosis in spontaneously hypertensive rats (SHRs) and the mechanisms underlying the anti-fibrotic effect of Cur in rat cardiac fibroblasts (CFs) in vitro.

METHODS

SHRs were orally treated with Cur (100 mg·kg(-1)·d(-1)) or Cur (100 mg·kg(-1)·d(-1)) plus the PPAR-γ antagonist GW9662 (1 mg·kg(-1)·d(-1)) for 12 weeks. Cultured CFs were treated with angiotensin II (Ang II, 0.1 μmol/L) in vitro. The expression of relevant proteins and mRNAs was analyzed using Western blotting and real-time PCR, respectively. The expression and activity of peroxisome proliferator-activated receptor-γ (PPAR-γ) were detected using Western blotting and a DNA-binding assay, respectively.

RESULTS

Treatment of SHRs with Cur significantly decreased systolic blood pressure, blood Ang II concentration, heart weight/body weight ratio and left ventricle weight/body weight ratio, with concurrently decreased expression of connective tissue growth factor (CTGF), plasminogen activator inhibitor (PAI)-1, collagen III (Col III) and fibronectin (FN), and increased expression and activity of PPAR-γ in the left ventricle. Co-treatment with GW9662 partially abrogated the anti-fibrotic effects of Cur in SHRs. Pretreatment of CFs with Cur (5, 10, 20 μmol/L) dose-dependently inhibited Ang II-induced expression of CTGF, PAI-1, Col III and FN, and increased the expression and binding activity of PPAR-γ. Pretreatment with GW9662 partially reversed anti-fibrotic effects of Cur in vitro. Furthermore, pretreatment of CFs with Cur inhibited Ang II-induced expression of transforming growth factor-β1 (TGF-β1) and phosphorylation of Smad2/3, which were reversed by GW9662.

CONCLUSION

Cur attenuates cardiac fibrosis in SHRs and inhibits Ang II-induced production of CTGF, PAI-1 and ECM in CFs in vitro. The crosstalk between PPAR-γ and TGF-β1/Smad2/3 signaling is involved in the anti-fibrotic and anti-proliferative effects of Cur.

Oral supplementation with non-absorbable antibiotics or curcumin attenuates western diet-induced atherosclerosis and glucose intolerance in LDLR-/- mice--role of intestinal permeability and macrophage activation

Association between circulating lipopolysaccharide (LPS) and metabolic diseases (such as Type 2 Diabetes and atherosclerosis) has shifted the focus from Western diet-induced changes in gut microbiota per se to release of gut bacteria-derived products into circulation as the possible mechanism for the chronic inflammatory state underlying the development of these diseases. Under physiological conditions, an intact intestinal barrier prevents this release of LPS underscoring the importance of examining and modulating the direct effects of Western diet on intestinal barrier function. In the present study we evaluated two strategies, namely selective gut decontamination and supplementation with oral curcumin, to modulate Western-diet (WD) induced changes in intestinal barrier function and subsequent development of glucose intolerance and atherosclerosis. LDLR−/− mice were fed WD for 16 weeks and either received non-absorbable antibiotics (Neomycin and polymyxin) in drinking water for selective gut decontamination or gavaged daily with curcumin. WD significantly increased intestinal permeability as assessed by in vivo translocation of FITC-dextran and plasma LPS levels. Selective gut decontamination and supplementation with curcumin significantly attenuated the WD-induced increase in plasma LPS levels (3.32 vs 1.90 or 1.51 EU/ml, respectively) and improved intestinal barrier function at multiple levels (restoring intestinal alkaline phosphatase activity and expression of tight junction proteins, ZO-1 and Claudin-1). Consequently, both these interventions significantly reduced WD-induced glucose intolerance and atherosclerosis in LDLR−/− mice. Activation of macrophages by low levels of LPS (50 ng/ml) and its exacerbation by fatty acids is likely the mechanism by which release of trace amounts of LPS into circulation due to disruption of intestinal barrier function induces the development of these diseases. These studies not only establish the important role of intestinal barrier function, but also identify oral supplementation with curcumin as a potential therapeutic strategy to improve intestinal barrier function and prevent the development of metabolic diseases.

Curcumin inhibits EMMPRIN and MMP-9 expression through AMPK-MAPK and PKC signaling in PMA induced macrophages

In coronary arteries, plaque disruption, the major acute clinical manifestations of atherosclerosis, leads to a subsequent cardiac event, such as acute myocardial infarction (AMI) and unstable angina pectoris (UA). Numerous reports have shown that high expression of MMP-9 (matrix metalloproteinase-9), MMP-13 (matrix metalloproteinase-13) and EMMPRIN (extracellular matrix metalloproteinase induce) in monocyte/macrophage results in the plaque progression and destabilization. Curcumin exerts well-known anti-inflammatory and antioxidant effects and probably has a protective role in the atherosclerosis. The purpose of our study was to investigate the molecular mechanisms by which curcumin affects MMP-9, MMP13 and EMMPRIN in PMA (phorbol 12-myristate 13-acetate) induced macrophages. Human monocytic cells (THP-1 cells) were pretreated with curcumin or compound C for 1 h, and then induced by PMA for 48 h. Total RNA and proteins were collected for real-time PCR and Western blot analysis, respectively. In the present study, the exposure to curcumin resulted in attenuated JNK, p38, and ERK activation and decreased expression of MMP-9, MMP-13 and EMMPRIN in PMA induced macrophages. Moreover, we demonstrated that AMPK (AMP-activated protein kinase) and PKC (Protein Kinase C) was activated by PMA during monocyte/macrophage differentiation. Furthermore, curcumin reversed PMA stimulated PKC activation and suppressed the chronic activation of AMPK, which in turn reduced the expression of MMP-9, MMP-13 and EMMPRIN. Therefore, it is suggested that curcumin by inhibiting AMPK-MAPK (mitogen activated protein kinase) and PKC pathway may led to down-regulated EMMPRIN, MMP-9 and MMP-13 expression in PMA-induced THP-1 cells.

Inhibition of JNK by compound C66 prevents pathological changes of the aorta in STZ-induced diabetes

Cardiovascular diseases as leading causes of the mortality world-wide are related to diabetes. The present study was to explore the protective effect of curcumin analogue C66 on diabetes-induced pathogenic changes of aortas. Diabetes was induced in male C57BL/6 mice with a single intraperitoneal injection of streptozotocin. Diabetic mice and age-matched non-diabetic mice were randomly treated with either vehicle (Control and Diabetes), C66 (C66 and Diabetes/C66) or c-Jun N-terminal kinase (JNK) inhibitor (sp600125, JNKi and Diabetes/JNKi). All three treatments were given by gavage at 5 mg/kg every other day for 3 months. Aortic inflammation, oxidative stress, fibrosis, cell apoptosis and proliferation, Nrf2 expression and transcription were assessed by immunohistochemical staining for the protein level and real-time PCR method for mRNA level. Diabetes increased aortic wall thickness and structural derangement as well as JNK phosphorylation, all of which were attenuated by C66 treatment as JNKi did. Inhibition of JNK phosphorylation by C66 and JNKi also significantly prevented diabetes-induced increases in inflammation, oxidative and nitrative stress, apoptosis, cell proliferation and fibrosis. Furthermore, inhibition of JNK phosphorylation by C66 and JNKi significantly increased aortic Nrf2 expression and transcription function (e.g. increased expression of Nrf2-downstream genes) in normal and diabetic conditions. These results suggest that diabetes-induced pathological changes in the aorta can be protected by C66 via inhibition of JNK function, accompanied by the up-regulation of Nrf2 expression and function.

Dietary flavanols modulate the transcription of genes associated with cardiovascular pathology without changes in their DNA methylation state

Background

In a recent intervention study, the daily supplementation with 200 mg monomeric and oligomeric flavanols (MOF) from grape seeds for 8 weeks revealed a vascular health benefit in male smokers. The objective of the present study was to determine the impact of MOF consumption on the gene expression profile of leukocytes and to assess changes in DNA methylation.

Methodology/Principal Findings

Gene expression profiles were determined using whole genome microarrays (Agilent) and DNA methylation was assessed using HumanMethylation450 BeadChips (Illumina). MOF significantly modulated the expression of 864 genes. The majority of the affected genes are involved in chemotaxis, cell adhesion, cell infiltration or cytoskeleton organisation, suggesting lower immune cell adhesion to endothelial cells. This was corroborated by in vitro experiments showing that MOF exposure of monocytes attenuates their adhesion to TNF-α-stimulated endothelial cells. Nuclear factor kappa B (NF-κB) reporter gene assays confirmed that MOF decrease the activity of NF-κB. Strong inter-individual variability in the leukocytes' DNA methylation was observed. As a consequence, on group level, changes due to MOF supplementation could not be found.

Conclusion

Our study revealed that an 8 week daily supplementation with 200 mg MOF modulates the expression of genes associated with cardiovascular disease pathways without major changes of their DNA methylation state. However, strong inter-individual variation in leukocyte DNA methylation may obscure the subtle epigenetic response to dietary flavanols. Despite the lack of significant changes in DNA methylation, the modulation of gene expression appears to contribute to the observed vascular health effect of MOF in humans.

Atherosclerosis and Alzheimer--diseases with a common cause? Inflammation, oxysterols, vasculature

BACKGROUND

Aging is accompanied by increasing vulnerability to pathologies such as atherosclerosis (ATH) and Alzheimer disease (AD). Are these different pathologies, or different presentations with a similar underlying pathoetiology?

DISCUSSION

Both ATH and AD involve inflammation, macrophage infiltration, and occlusion of the vasculature. Allelic variants in common genes including APOE predispose to both diseases. In both there is strong evidence of disease association with viral and bacterial pathogens including herpes simplex and Chlamydophila. Furthermore, ablation of components of the immune system (or of bone marrow-derived macrophages alone) in animal models restricts disease development in both cases, arguing that both are accentuated by inflammatory/immune pathways. We discuss that amyloid β, a distinguishing feature of AD, also plays a key role in ATH. Several drugs, at least in mouse models, are effective in preventing the development of both ATH and AD. Given similar age-dependence, genetic underpinnings, involvement of the vasculature, association with infection, Aβ involvement, the central role of macrophages, and drug overlap, we conclude that the two conditions reflect different manifestations of a common pathoetiology.

MECHANISM

Infection and inflammation selectively induce the expression of cholesterol 25-hydroxylase (CH25H). Acutely, the production of 'immunosterol' 25-hydroxycholesterol (25OHC) defends against enveloped viruses. We present evidence that chronic macrophage CH25H upregulation leads to catalyzed esterification of sterols via 25OHC-driven allosteric activation of ACAT (acyl-CoA cholesterol acyltransferase/SOAT), intracellular accumulation of cholesteryl esters and lipid droplets, vascular occlusion, and overt disease.

SUMMARY

We postulate that AD and ATH are both caused by chronic immunologic challenge that induces CH25H expression and protection against particular infectious agents, but at the expense of longer-term pathology.

Nutritional aspects of metabolic inflammation in relation to health--insights from transcriptomic biomarkers in PBMC of fatty acids and polyphenols

Recent research has highlighted potential important interaction between metabolism and inflammation, within the context of metabolic health and nutrition, with a view to preventing diet-related disease. In addition to this, there is a paucity of evidence in relation to accurate biomarkers that are capable of reflecting this important biological interplay or relationship between metabolism and inflammation, particularly in relation to diet and health. Therefore the objective of this review is to highlight the potential role of transcriptomic approaches as a tool to capture the mechanistic basis of metabolic inflammation. Within this context, this review has focused on the potential of peripheral blood mononuclear cells transcriptomic biomarkers, because they are an accessible tissue that may reflect metabolism and subacute chronic inflammation. Also these pathways are often dysregulated in the common diet-related diseases obesity, type 2 diabetes, and cardiovascular disease, thus may be used as markers of systemic health. The review focuses on fatty acids and polyphenols, two classes of nutrients/nonnutrient food components that modulate metabolism/inflammation, which we have used as an example of a proof-of-concept with a view to understanding the extent to which transcriptomic biomarkers are related to nutritional status and/or sensitive to dietary interventions. We show that both nutritional components modulate inflammatory markers at the transcriptomic level with the capability of profiling pro- and anti-inflammatory mechanisms in a bidirectional fashion; to this end transcriptomic biomarkers may have potential within the context of metabolic inflammation. This transcriptomic biomarker approach may be a sensitive indicator of nutritional status and metabolic health.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.

miRNA as molecular target of polyphenols underlying their biological effects

Polyphenols are the most abundant antioxidants in the human diet and are widespread constituents of fruits and beverages, such as tea, coffee, and wine. Epidemiological, clinical, and animal studies support a role of polyphenols in the prevention of various chronic diseases. For a long time, their direct antioxidant effect has been reported as the mechanism responsible for the observed health properties. However, recent findings revealed that polyphenols could interact with cellular signaling cascades regulating the activity of transcription factors and consequently affecting the expression of genes. Together with this classical regulatory pathway, polyphenols have been shown to affect the expression of microRNAs (miRNA). miRNAs are small, noncoding RNAs implicated in the regulation of gene expression that control both physiological and pathological processes such as development and cancer. Furthermore, expression of miRNAs can be affected by different external stimuli including nutrients such as vitamins, lipids, and phytochemicals. In this paper, we review studies assessing modulation of miRNAs expression by dietary polyphenols that could constitute a new pathway by which these compounds may exert their health effects. Over 100 miRNAs, involved in the control of different cellular processes such as inflammation or apoptosis, were identified as modulated by polyphenols. Most of the studies were performed in vitro using different cell lines, particularly cancer cell lines, and few studies were performed in animals. From all these data, miRNAs appear as interesting mediators in regulating polyphenols' biological effects; however, further studies are needed to validate miRNA targets and particularly in physiologically relevant conditions taking into account the bioavailability of dietary polyphenols.

Vascular dysfunction in a mouse model of Rett syndrome and effects of curcumin treatment

Mutations in the coding sequence of the X-linked gene MeCP2 (Methyl CpG-binding protein) are present in around 80% of patients with Rett Syndrome, a common cause of intellectual disability in female and to date without any effective pharmacological treatment. A relevant, and so far unexplored feature of RTT patients, is a marked reduction in peripheral circulation. To investigate the relationship between loss of MeCP2 and this clinical aspect, we used the MeCP2 null mouse model B6.129SF1-MeCP2tm1Jae for functional and pharmacological studies. Functional experiments were performed on isolated resistance mesenteric vessels, mounted on a pressurized myograph. Vessels from female MeCP2(+/-) mice show a reduced endothelium-dependent relaxation, due to a reduced Nitric Oxide (NO) availability secondary to an increased Reactive Oxygen Species (ROS) generation. Such functional aspects are associated with an intravascular increase in superoxide anion production, and a decreased vascular eNOS expression. These alterations are reversed by curcumin administration (5% (w/w) dietary curcumin for 21 days), which restores endothelial NO availability, decreases intravascular ROS production and normalizes vascular eNOS gene expression. In conclusion our findings highlight alterations in the vascular/endothelial system in the absence of a correct function of MeCP2, and uncover related cellular/molecular mechanisms that are rescued by an anti-oxidant treatment.

Curcumin inhibits oxLDL-induced CD36 expression and foam cell formation through the inhibition of p38 MAPK phosphorylation

The uptake of oxidized low density lipoprotein (oxLDL) via scavenger receptors transforms macrophages into foam cells, which are a hallmark of atherosclerosis. OxLDL markedly increases the expression of the CD36 scavenger receptor. Here, we investigated whether curcumin modulate CD36 expression in oxLDL-treated RAW 264.7 murine macrophages. Our results showed that curcumin dramatically inhibits CD36 expression and foam cell formation. Furthermore, oxLDL-induced expression and activity of peroxisome proliferator-activated receptor-gamma (PPAR-γ), which is involved in CD36 expression, is also blocked in curcumin-treated cells. OxLDL activates the mitogen-activated protein kinase (MAPK) signaling transduction pathway, and p38 MAPK is associated with oxLDL-induced CD36 and PPAR-γ expression. Overexpression of dominant negative p38 MAPK blocks oxLDL-induced CD36 and PPAR-γ expression. Furthermore, curcumin markedly inhibits p38 MAPK phosphorylation. Taken together, our results suggest that curcumin modulates oxLDL-induced CD36 expression and foam cell formation via the inhibition of p38 MAPK phosphorylation in RAW 264.7 murine macrophages.

Molecular mechanisms of hypolipidemic effects of curcumin

Recent evidence suggests potential benefits from phytochemicals and micronutrients in reducing the elevated oxidative and lipid-mediated stress associated with inflammation, obesity, and atherosclerosis. These compounds may either directly scavenge reactive oxygen or nitrogen species or they may modulate the activity of signal transduction enzymes leading to changes in the expression of antioxidant genes. Alternatively, they may reduce plasma lipid levels by modulating lipid metabolic genes in tissues and thus reduce indirectly lipid-mediated oxidative and endoplasmic reticulum stress through their hypolipidemic effect. Here we review the proposed molecular mechanisms by which curcumin, a polyphenol present in the rhizomes of turmeric (Curcuma longa) spice, influences oxidative and lipid-mediated stress in the vascular system. At the molecular level, mounting experimental evidence suggests that curcumin may act chemically as scavenger of free radicals and/or influences signal transduction (e.g., Akt, AMPK) and modulates the activity of specific transcription factors (e.g., FOXO1/3a, NRF2, SREBP1/2, CREB, CREBH, PPARγ, and LXRα) that regulate the expression of genes involved in free radicals scavenging (e.g., catalase, MnSOD, and heme oxygenase-1) and lipid homeostasis (e.g., aP2/FABP4, CD36, HMG-CoA reductase, and carnitine palmitoyltransferase-I (CPT-1)). At the cellular level, curcumin may induce a mild oxidative and lipid-metabolic stress leading to an adaptive cellular stress response by hormetic stimulation of these cellular antioxidant defense systems and lipid metabolic enzymes. The resulting lower oxidative and lipid-mediated stress may not only explain the beneficial effects of curcumin on inflammation, cardiovascular, and neurodegenerative disease, but may also contribute to the increase in maximum life-span observed in animal models.

Dietary Nrf2 activators inhibit atherogenic processes

Dietary Nrf2 activators increase expression of phase 2 protein genes in cells undergoing oxidative stress resulting in a lowering of oxidative stress. Oxidative stress promotes atherogenic processes through oxidizing low density lipoproteins and promotion of inflammation through activation of nuclear factor kappa B and activation of mitogen-activated protein kinases. Nrf2 activators by decreasing oxidative stress decrease the probability of developing atherosclerotic lesions.