RESUMO
Large procyanidins (more than three subunits) are not absorbed at the gastrointestinal tract but could exert local effects through their interactions with membranes. We previously showed that hexameric procyanidins (Hex), although not entering cells, interact with membranes modulating cell signaling and fate. This paper investigated if Hex, as an example of large procyanidins, can selectively interact with lipid rafts which could in part explain its biological actions. This mechanism was studied in both synthetic membranes (liposomes) and Caco-2 cells. Hex promoted Caco-2 cell membrane rigidification and dehydration, effects that were abolished upon cholesterol depletion with methyl-ß-cyclodextrin (MCD). Hex prevented lipid raft structure disruption induced by cholesterol depletion/redistribution by MCD or sodium deoxycholate. Supporting the involvement of cholesterol-Hex bonding in Hex interaction with lipid rafts, the absence of cholesterol markedly decreased the capacity of Hex to prevent deoxycholate- and Triton X-100-mediated disruption of lipid raft-like liposomes. Stressing the functional relevance of this interaction, Hex mitigated lipid raft-associated activation of the extracellular signal-regulated kinases (ERK) 1/2. Results support the capacity of a large procyanidin (Hex) to interact with membrane lipid rafts mainly through Hex-cholesterol bondings. Procyanidin-lipid raft interactions can in part explain the capacity of large procyanidins to modulate cell physiology.
Assuntos
Colesterol/metabolismo , Microdomínios da Membrana/metabolismo , Proantocianidinas/metabolismo , Western Blotting , Células CACO-2 , Detergentes , Ativação Enzimática , Humanos , Lipossomos , Sistema de Sinalização das MAP Quinases , Transdução de SinaisRESUMO
Epidemiological and intervention studies have shown that the intake of certain chocolates or cocoa products decreases blood pressure (BP) in humans. (-)-Epicatechin is the most abundant flavanol present in cocoa seeds and its derived foods. This work investigates the effects of dietary (-)-epicatechin on BP in rats that received N(ω)-nitro-l-arginine methyl ester (L-NAME) for 4 days. (-)-Epicatechin administration prevented the 42mm Hg increase in BP associated with the inhibition of NO production in a dose-dependent manner (0.2-4.0g/kg diet). This BP effect was associated with a reduction in L-NAME-mediated increase in the indexes of oxidative stress (plasma TBARS and GSSG/GSH(2) ratio) and with a restoration of the NO concentration. At the vascular level, none of the treatments modified NOS expression, but (-)-epicatechin administration avoided the L-NAME-mediated decrease in eNOS activity and increase in both superoxide anion production and NOX subunit p47(phox) expression. In summary, (-)-epicatechin was able to prevent the increase in BP and in oxidative stress and restored NO bioavailability. The fact that (-)-epicatechin is present in several plants usually consumed by humans gives the possibility of developing diets rich in those plants or pharmacological strategies using that flavonoid to diminish BP in hypertensive subjects.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Catequina/farmacologia , Hipertensão/tratamento farmacológico , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/metabolismo , Animais , Pressão Sanguínea/fisiologia , Suplementos Nutricionais , Glutationa/sangue , Dissulfeto de Glutationa/sangue , Masculino , Óxido Nítrico Sintase/biossíntese , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Vasodilatação/efeitos dos fármacosRESUMO
Hexameric procyanidins inhibit TNFalpha-induced NF-kappaB activation in Caco-2 cells. Most of the physiological actions of high molecular weight procyanidins could be limited to the gut lumen. Transcription factor NF-kappaB plays a central role in inflammation including human intestinal bowel disease. We investigated the capacity of a hexameric procyanidin fraction (Hex) to prevent tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB activation as related to oxidation and membrane interactions. In Caco-2 cells, Hex (2.5-20 microM) inhibited TNFalpha-induced NF-kappaB activation (IkappaB phosphorylation and degradation, p50 and RelA nuclear translocation, and NF-kappaB-DNA binding), inducible nitric oxide synthase expression, and cell oxidant increase. The effects on NF-kappaB activation persist beyond the period of direct exposition of cells to Hex. N-Acetylcysteine and alpha-lipoic acid inhibited TNFalpha-induced oxidant increase but did not affect NF-kappaB activation. In summary, Hex can inhibit NF-kappaB activation by interacting with the plasma membrane of intestinal cells, and through these interactions preferentially inhibits the binding of TNFalpha to its receptor and the subsequent NF-kappaB activation.