Resveratrol modulates ATPase activity of liposome-reconstituted ABCG1

A byproduct from the Valles Calchaquíes vineyards (Argentina) rich in phenolic compounds: a tool against endemic Leishmania dissemination

Vineyard-derived pomace is a byproduct of the wine industry that can have a negative impact on the environment if it is only disposed of or used as a fertilizer. Owing to its polyphenol content, grape pomace is an alternative to biocontrol undesirable microorganisms. In the present study, we characterized the phenolic composition of red and white grape pomace from Valles Calchaquíes, Argentina, and explored its activity against Leishmania (Leishmania) amazonensis, an etiological agent of American tegumentary leishmaniasis, a neglected endemic disease in northern Argentina. Red and white pomace extracts similarly reduced Leishmania viability after a 48-h treatment, with the fractions containing a higher proportion of phenolic compounds being more active. Both extracts stimulated ATPase activity on the parasite plasma membranes, with white grape pomace having a stronger effect than red grape pomace. In addition, the extracts displayed fairly good anticholinesterase activity, which may have contributed to their anti-Leishmania activity. These results reinforce the potential applicability of grape pomace as an antimicrobial agent for the development of biopesticides.

Polyphenols extracted from Shanxi-aged vinegar exert hypolipidemic effects on OA-induced HepG2 cells via the PPARα-LXRα-ABCA1 pathway

Hyperlipidemia is one of the key risk factors causing many chronic diseases, and lowering blood lipid levels can prevent many diseases. In this paper, a hyperlipidemic cell model of oleic acid (OA) induced hepatocellular carcinoma cells (HepG2) was established using polyphenols extracted from Shanxi-aged vinegar (SAVEP). The effects of SAVEP on nuclear damage, mitochondrial membrane potential, apoptosis, cellular lipid deposition, and lipid metabolism protein expression in HepG2 hyperlipidemic cells were examined to investigate the lipid-lowering mechanism of SAVEP at the cellular level. The results showed that SAVEP could reduce the content of TC/TG index, repair the nuclear damage, reduce lipid accumulation and finally decrease the rate of apoptosis by up-regulating the expression of key proteins such as PPARα, LXRα, and ABCA1 in the process of lipid metabolism. PRACTICAL APPLICATIONS: In this thesis, the hypolipidemic activity of polyphenol extracts from Shanxi-aged vinegar was analyzed on the level of HepG2 cells. The hypolipidemic mechanism of oxidative stress, lipid metabolism and inflammatory stress was also elucidated. It provided a theoretical basis for the in-depth understanding of the hypolipidemic health effects of Shanxi-aged vinegar.

Myristic Acid Inhibits the Activity of the Bacterial ABC Transporter BmrA

ATP-binding cassette (ABC) transporters are conserved in all kingdoms of life, where they transport substrates against a concentration gradient across membranes. Some ABC transporters are known to cause multidrug resistances in humans and are able to transport chemotherapeutics across cellular membranes. Similarly, BmrA, the ABC transporter of Bacillus subtilis, is involved in excretion of certain antibiotics out of bacterial cells. Screening of extract libraries isolated from fungi revealed that the C14 fatty acid myristic acid has an inhibitory effect on the BmrA ATPase as well as the transport activity. Thus, a natural membrane constituent inhibits the BmrA activity, a finding with physiological consequences as to the activity and regulation of ABC transporter activities in biological membranes.

Human mitochondrial carnitine acylcarnitine carrier: Molecular target of dietary bioactive polyphenols from sweet cherry (Prunus avium L.)

The effect of polyphenols, recognized as the principal antioxidant and beneficial molecules introduced with the diet, extracted from sweet cherry (Prunus avium L.) on the recombinant human mitochondrial carnitine/acylcarnitine transporter (CACT) has been studied in proteoliposomes. CACT transport activity, which was strongly impaired after oxidation by atmospheric O₂ or H₂O_2, due to the formation of a disulfide bridge between cysteines 136 and 155, was restored by externally added polyphenols. CACT reduction by polyphenols was time dependent. Spectroscopic analysis of polyphenolic extracts revealed eight most represented compounds in four cultivars. Molecular docking of CACT structural omology model with the most either abundant and arguably bio-available phenolic compound (trans 3-O-feruloyl-quinic acid) of the mix, is in agreement with the experimental data since it results located in the active site close to cysteine 136 at the bottom of the translocation aqueous cavity.

Enterodiol is Actively Transported by Rat Liver Cell Membranes

The interaction of enterodiol and the well-described polyphenol epigallocatechin gallate (EGCG) with hepatic membranes has been matter of interest in the last few years. On one hand, EGCG is only able to bind to the phospholipid polar head groups, as it has been already described in synthetic lipid bilayers and erythrocyte membranes but cannot get inserted into the hydrophobic core or be transported into the lumen of membrane vesicles. On the other, enterodiol has no interaction with non-energized membranes either, but it is able to interact and even be transported upon addition of ATP. In fact, the ATPase activity undergoes a twofold increase in the presence of enterodiol but not in the presence of EGCG. This is the first report on the transport of enterodiol by liver membranes, and it may help explain the rather high blood concentrations of this estrogenic enterolignan compared to EGCG, which is extensively metabolized by the intestine and the liver. The present results suggest that a fraction of enterodiol may escape the liver inactivation by being pumped out from the hepatocytes to the bloodstream.

Differential inhibition of human erythrocyte acetylcholinesterase by polyphenols epigallocatechin-3-gallate and resveratrol. Relevance of the membrane-bound form

The activity of acetylcholinesterase (AChE) from human erythrocytes was tested in the presence of the phenolic compounds resveratrol and epigallocatechin-3-gallate (EGCG). Even though the stilbene barely changed this enzymatic activity, EGCG did inhibit AChE. Importantly, it preferentially acted on the membrane-bound enzyme rather than on its soluble form. Actually, it was shown that this flavonoid may bind to the red blood cell membrane surface, which may improve the interaction between EGCG and AChE. Therefore, caution should be taken when screening AChE inhibitors. In fact, testing compounds with the soluble form of the enzyme may underestimate the activity of some of these potential inhibitors, hence it would be advisable not to use them as a sole model system for screening. Moreover, erythrocyte AChE is proposed as a good model for these enzymatic assays. © 2016 BioFactors, 43(1):73-81, 2017.

Diverse relations between ABC transporters and lipids: An overview

It was first discovered in 1992 that P-glycoprotein (Pgp, ABCB1), an ATP binding cassette (ABC) transporter, can transport phospholipids such as phosphatidylcholine, -ethanolamine and -serine as well as glucosylceramide and glycosphingolipids. Subsequently, many other ABC transporters were identified to act as lipid transporters. For substrate transport by ABC transporters, typically a classic, alternating access model with an ATP-dependent conformational switch between a high and a low affinity substrate binding site is evoked. Transport of small hydrophilic substrates can easily be imagined this way, as the molecule can in principle enter and exit the transporter in the same orientation. Lipids on the other hand need to undergo a 180° degree turn as they translocate from one membrane leaflet to the other. Lipids and lipidated molecules are highly diverse, so there may be various ways how to achieve their flipping and flopping. Nonetheless, an increase in biophysical, biochemical and structural data is beginning to shed some light on specific aspects of lipid transport by ABC transporters. In addition, there is now abundant evidence that lipids affect ABC transporter conformation, dynamics as well as transport and ATPase activity in general. In this review, we will discuss different ways in which lipids and ABC transporters interact and how lipid translocation may be achieved with a focus on the techniques used to investigate these processes. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.

The main potentialities of resveratrol for drug delivery systems

Resveratrol (RSV), a natural polyphenol found in grapes, was found to be effective in the prevention and therapy of several diseases, however, it does have unfavourable physicochemical properties. In this context, an increasing number of studies have aimed at developing novel therapeutic systems for its delivery to overcome these disadvantages. This review focuses on the mechanisms of action and therapeutic applications. Finally, it also describes some tested formulations for RSV administration, controlled release and targeting, developed with the purpose of increasing RSV bioavailability.

Resveratrol inhibits proliferation in human colorectal carcinoma cells by inducing G1/S‑phase cell cycle arrest and apoptosis through caspase/cyclin‑CDK pathways

The present study compared the effect of resveratrol on HCT116 and Caco-2 human colon cancer cells. Annexin V/propidium iodide staining, MTT assay and western blot analysis revealed that resveratrol induced cycle arrest in the two cell lines, which was evidenced by cell cycle analysis and changes in the expression of the cell cycle proteins cyclin-dependent kinase (CDK) 2, CDK4, cyclin D1, proliferating cell nuclear antigen and P21. Furthermore, resveratrol was found to have a strong apoptosis-inducing effect, which was evidenced through the high percentage of annexin V positive cells and high protein expression of cleaved-caspase-7, cleaved-caspase-9 and cleaved-poly(ADP-ribose) polymerase in the resveratrol-treated cancer cells. In conclusion, these results demonstrated that resveratrol had greater growth inhibitory and cell cycle arrest effects on Caco-2 cells than HCT116 cells, through caspase-dependent and cyclin-CDK pathways.

Resveratrol promotes degradation of the human bile acid transporter ASBT (SLC10A2)

The sodium/bile acid co-transporter ASBT [apical sodium-dependent bile acid transporter; SLC10A2 (solute carrier family 10 member 2)] plays a key role in the enterohepatic recycling of the bile acids and indirectly contributes to cholesterol homoeostasis. ASBT inhibitors reportedly lower plasma triglyceride levels and increase HDL (high-density lipoprotein) cholesterol levels. RSV (resveratrol), a major constituent of red wine, is known to lower LDL (low-density lipoprotein) cholesterol levels, but its mechanism of action is still unclear. In the present study, we investigated the possible involvement of ASBT in RSV-mediated cholesterol-lowering effects. We demonstrate that RSV inhibits ASBT protein expression and function via a SIRT1 (sirtuin 1)-independent mechanism. The effect was specific to ASBT since other transporters involved in cholesterol homoeostasis, NTCP (SLC10A1), OSTα (SLC51A) and ABCG1 (ATP-binding cassette G1), remained unaffected. ASBT inhibition by RSV was reversed by proteasome inhibitors (MG-132 and lactacystin) and the ubiquitin inhibitor LDN57444, suggesting involvement of the ubiquitin-proteasome pathway. Immunoprecipitation revealed high levels of ubiquitinated ASBT after RSV treatment. Phosphorylation at Ser335 and Thr339 was shown previously to play a role in proteosomal degradation of rat ASBT. However, mutation at corresponding residues in rat ASBT revealed that phosphorylation does not contribute to RSV-mediated degradation of ASBT. Combined, our data indicate that RSV promotes ASBT degradation via the ubiquitin-proteasome pathway without requiring phosphorylation. We conclude that regulation of ASBT expression by RSV may have clinical relevance with regard to the observed cholesterol-lowering effects of RSV.