Dietary polyphenols regulate endothelial function and prevent cardiovascular disease

Cell Systems to Investigate the Impact of Polyphenols on Cardiovascular Health

Polyphenols are a diverse group of micronutrients from plant origin that may serve as antioxidants and that contribute to human health in general. More specifically, many research groups have investigated their protective effect against cardiovascular diseases in several animal studies and human trials. Yet, because of the excessive processing of the polyphenol structure by human cells and the residing intestinal microbial community, which results in a large variability between the test subjects, the exact mechanisms of their protective effects are still under investigation. To this end, simplified cell culture systems have been used to decrease the inter-individual variability in mechanistic studies. In this review, we will discuss the different cell culture models that have been used so far for polyphenol research in the context of cardiovascular diseases. We will also review the current trends in cell culture research, including co-culture methodologies. Finally, we will discuss the potential of these advanced models to screen for cardiovascular effects of the large pool of bioactive polyphenols present in foods and their metabolites.

In Vitro Bioaccessibility, Human Gut Microbiota Metabolites and Hepatoprotective Potential of Chebulic Ellagitannins: A Case of Padma Hepaten® Formulation

Chebulic ellagitannins (ChET) are plant-derived polyphenols containing chebulic acid subunits, possessing a wide spectrum of biological activities that might contribute to health benefits in humans. The herbal formulation Padma Hepaten containing ChETs as the main phenolics, is used as a hepatoprotective remedy. In the present study, an in vitro dynamic model simulating gastrointestinal digestion, including dialysability, was applied to estimate the bioaccessibility of the main phenolics of Padma Hepaten. Results indicated that phenolic release was mainly achieved during the gastric phase (recovery 59.38%-97.04%), with a slight further release during intestinal digestion. Dialysis experiments showed that dialysable phenolics were 64.11% and 22.93%-26.05% of their native concentrations, respectively, for gallic acid/simple gallate esters and ellagitanins/ellagic acid, in contrast to 20.67% and 28.37%-55.35% for the same groups in the non-dialyzed part of the intestinal media. Investigation of human gut microbiota metabolites of Padma Hepaten and pure ChETs (chebulinic, chebulagic acids) established the formation of bioactive urolithins (A, B, C, D, M5). The fact of urolithin formation during microbial transformation from ChETs and ChET-containing plant material was revealed for the first time. Evaluation of the protective effect of ChETs colonic metabolites and urolithins on tert-butyl hydroperoxide (t-BHP)-induced oxidative injury in cultured rat primary hepatocytes demonstrated their significant reversion of the t-BHP-induced cell cytotoxicity, malonic dialdehyde production and lactate dehydrogenase leakage. The most potent compound was urolithin C with close values of hepatoprotection to gallic acid. The data obtained indicate that in the case of Padma Hepaten, we speculate that urolithins have the potential to play a role in the hepatic prevention against oxidative damage.

Coffee Consumption and Incidence of Subarachnoid Hemorrhage: The Jichi Medical School Cohort Study

Background

Previous studies on the association between coffee consumption and subarachnoid hemorrhage (SAH) have provided inconsistent results. We examine the risk of SAH from coffee consumption in a Japanese population.

Methods

Our analyses were based on the Jichi Medical School Cohort Study, a large-scale population-based prospective cohort study. A total of 9941 participants (3868 men and 6073 women; mean age 55 years) with no history of cardiovascular disease or carcinoma were examined. Participants were asked to choose one of five options to indicate their daily coffee consumption: none, less than 1 cup a day, 1–2 cups a day, 3–4 cups a day, or 5 or more cups a day. The incidence of SAH was assessed independently by a diagnostic committee. Cox proportional hazards models were used to calculate hazard ratios (HRs) and their 95% confidence intervals (CI) after adjustment for age and sex (HR1) and for additional potential confounders (HR2).

Results

During 10.7 years of follow-up, SAH occurred in 47 participants. When compared with the participants who consumed less than 1 cup of coffee a day, the HR of SAH was significantly higher in the group who consumed 5 or more cups a day in both models (HR1 4.49; 95% CI, 1.44–14.00; HR2 3.79; 95% CI, 1.19–12.05).

Conclusions

The present community-based cohort study showed that heavy coffee consumption was associated with an increased incidence of SAH after adjusting for age, sex, and multiple potential cardiovascular confounders.

MicroRNA-141 regulates the expression level of ICAM-1 on endothelium to decrease myocardial ischemia-reperfusion injury

A growing number of studies have suggested microRNAs (miRNAs) are involved in the modulation of myocardial ischemia-reperfusion (MI/R) injury; however, the role of endogenous miRNAs targeting endothelial cells (ECs) and its interaction with ICAM-1 in the setting of MI/R remain poorly understood. Our microarray results showed that miR-146a, miR-146b-5p, miR-155*, miR-155, miR-497, and miR-451 were significantly upregulated, whereas, miR-141 and miR-564 were significantly downregulated in the ECs challenged with TNF-α for 6 h. Real-time PCR analyses additionally validated that the expression levels of miR-146a, miR-155*, and miR-141 were consistent with the microarray results. Then, ICAM-1 was identified as a novel target of miR-141 by Target Scan software and the reporter gene system. Further functional experiments showed that elevated levels of miR-141 inhibited ICAM-1 expression and diminished leukocytes adhesion to ECs in vitro. In an in vivo murine model of MI/R injury, pretreatment with miR-141 mimics through the tail vein downregulated the expression level of ICAM-1 in heart and attenuated MI/R injury as evidenced by decreased infarct size and decline of serum cardial troponin I (cTnI) and lactate dehydrogenase (LDH) concentration. The cardioprotective effects of miR-141 mimics may be attributed to the decreased infiltration of CD11b(+) cells and F4/80(+) macrophages into ischemic myocardium tissue. In conclusion, our results demonstrate that miR-141, as a novel repressor of ICAM-1, is involved in the attenuation of MI/R injury via antithetical regulation of ICAM-1 and inflammatory cells infiltration. Thus miR-141 may constitute a new therapeutic target in the setting of ischemic heart disease.

Pterostilbene, an Active Constituent of Blueberries, Stimulates Nitric Oxide Production via Activation of Endothelial Nitric Oxide Synthase in Human Umbilical Vein Endothelial Cells

Endothelial dysfunction, a key process in development of cardiovascular diseases, is largely due to reduced nitric oxide (NO) derived from endothelial NO synthase (eNOS). Resveratrol has been reported to stimulate NO production via estrogen receptor α (ERα) activation in endothelial cells. Here, we investigated whether two natural methylated analogs of resveratrol, pterostilbene (Pts) and trans-3,5,4'-trimethoxystilbene (TMS), similarly to resveratrol, could influence endothelial NO release in human umbilical vein endothelial cells (HUVECs). In HUVECs exposed to Pts or TMS, NO production and phosphorylation of eNOS, protein kinase B (Akt), and ERα were measured by using a fluorimetric NO assay kit and Western blot analysis, respectively. Dimethylated Pts, but not trimethylated TMS, stimulated dose-dependent NO production via eNOS phosphorylation. Pts also stimulated dose-dependent phosphorylation of Akt, but not of ERα. NO production and eNOS phosphorylation in response to Pts were significantly abolished by the phosphoinositide 3-kinase (PI3K)/Akt inhibitor LY294002, but not by the ERα antagonist ICI182780. Our results suggest that Pts, but not TMS, is capable of inducing eNOS phosphorylation and the subsequent NO release, presumably, by activating PI3K/Akt pathway. The potential efficacy of Pts, an active constituent of blueberries, may aid in the prevention of cardiovascular diseases characterized by endothelial dysfunction.

Insight into the mechanism of polyphenols on the activity of HMGR by molecular docking

Statins are hypolipidemic drugs that are effective in the treatment of hypercholesterolemia by attenuating cholesterol synthesis in the liver via competitive inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Recently, dietary changes associated with drug therapy have garnered attention as novel drugs to mitigate or ameliorate hypercholesterolemia. The present study was undertaken to observe different dietary polyphenols that can bind to the active site of HMGR and inhibit it. Results from the 12 dietary polyphenols tested reveal that polyphenols can bind to HMGR and block the binding of nicotinamide adenine dinucleotide phosphate (NADP⁺). We observed that the rigidity of phenolic rings prevents the polyphenols from docking to the enzyme activity site. The presence of an ester linkage between the phenolic rings in (–)-epigallocatechin-3-gallate (EGCG) and the alkyl chain in curcumin allows them to orient in the active site of the HMGR and bind to the catalytic residues. EGCG and curcumin showed binding to the active site residues with a low GRID score, which may be a potential inhibitor of HMGR. Kaempferol showed binding to HMG-CoA, but with low binding affinity. These observations provide a rationale for the consistent hypolipidemic effect of EGCG and curcumin, which has been previously reported in several epidemiological and animal studies. Therefore, this study substantiates the mechanism of polyphenols on the activity of HMGR by molecular docking and provides the impetus for drug design involving further structure–function relationship studies.

Influence of resveratrol and dihydroquercetin inclusion into phospholipid nanopatricles on their bioavailability and specific activity

The effects of natural polyphenols, resveratrol (RES) and dihydroquercetin (DHQ), included in phospholipid nanoparticles, have been compared with free substances of RES and DHQ in in vitro and in vivo experiments. Preincubation of healthy donor plasma low density lipoproteins (LDL) with RES or DHQ included in phospholipid nanoparticles caused a more pronounced decrease in Cu2+ induced lipid oxidation compared with the free substances, and reduced the formation of lipid peroxides products. Bioavailabilities of RES and DHQ in phospholipid formulations after oral administration in rats were increased by 1.5-2 times. In an acute hypoxia model in mice prophylactic two-week administration of RES or DHQ phospholipid formulations resulted in 25% increase in survival and 1.5-fold increase in catalase activity in brain homogenates compared to free substances. Using the model of endothelial dysfunction in rats induced by L-NAME it was shown, that RES markedly attenuated the inhibition effect of L-NAME on NO synthesis. RES in phospholipid nanoparticles had the same action at a dose 10 times lower compared to free RES. Load test with resistance (clamping of the ascending aorta for 30 sec) showed that phospholipid formulation of RES possessed more pronounced protective effect due to the stimulation of endothelial NO-synthase.