Specific sequence-directed anti-bilitranslocase antibodies as a tool to detect potentially bilirubin-binding proteins in different tissues of the rat

Anthocyanins and Their Metabolites as Therapeutic Agents for Neurodegenerative Disease

Neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS), are characterized by the death of neurons within specific regions of the brain or spinal cord. While the etiology of many neurodegenerative diseases remains elusive, several factors are thought to contribute to the neurodegenerative process, such as oxidative and nitrosative stress, excitotoxicity, endoplasmic reticulum stress, protein aggregation, and neuroinflammation. These processes culminate in the death of vulnerable neuronal populations, which manifests symptomatically as cognitive and/or motor impairments. Until recently, most treatments for these disorders have targeted single aspects of disease pathology; however, this strategy has proved largely ineffective, and focus has now turned towards therapeutics which target multiple aspects underlying neurodegeneration. Anthocyanins are unique flavonoid compounds that have been shown to modulate several of the factors contributing to neuronal death, and interest in their use as therapeutics for neurodegeneration has grown in recent years. Additionally, due to observations that the bioavailability of anthocyanins is low relative to that of their metabolites, it has been proposed that anthocyanin metabolites may play a significant part in mediating the beneficial effects of an anthocyanin-rich diet. Thus, in this review, we will explore the evidence evaluating the neuroprotective and therapeutic potential of anthocyanins and their common metabolites for treating neurodegenerative diseases.

Development and evaluation of floating alginate microspheres for oral delivery of anthocyanins - A preliminary investigation

The goal of this study was to develop floating microspheres that could be used as gastroretentive systems for the delivery of anthocyanins (ACNs). These compounds are absorbed in the stomach and small intestine, and insufficient residence time in these organs could result in limited absorption and contribute to degradation. The microparticles containing freeze‐dried haskap berry extract (321.96 ± 8.35 mg cyanidin 3‐glucoside equivalents per g) were prepared by ionotropic gelation of alginate (9%, w/w) with calcium ions (CaCl₂ at 2%, w/v) in the gelation bath, with calcium carbonate as the gas‐generating compound (added at different ratios in the alginate/extract mixture). The effect of acetic acid concentration (2 and 10%, v/v) in the gelation medium was investigated. Increasing the carbonate : alginate weigh ratio from 0 to 3:4 resulted in different degrees of floatability, larger particles, higher encapsulation efficiency, and lower amount of ACN released. The power law equation fitted the experimental data well, indicating that release occurred mainly by diffusion. This is the first time floating microspheres are proposed as gastroretentive platforms for the delivery of ACNs.

Bioavailability of anthocyanins and colonic polyphenol metabolites following consumption of aronia berry extract

A single-dose pharmacokinetic trial was conducted in 6 adults to evaluate the bioavailability of anthocyanins and colonic polyphenol metabolites after consumption of 500mg aronia berry extract. UHPLC-MS methods were developed to quantitate aronia berry polyphenols and their metabolites in plasma and urine. While anthocyanins were bioavailable, microbial phenolic catabolites increased ∼10-fold more than anthocyanins in plasma and urine. Among the anthocyanins, cyanidin-3-O-galactoside was rapidly metabolized to peonidin-3-O-galactoside. Aronia polyphenols were absorbed and extensively metabolized with tmax of anthocyanins and other polyphenol catabolites from 1.0h to 6.33h in plasma and urine. Despite significant inter-individual variation in pharmacokinetic parameters, concentrations of polyphenol metabolites in plasma and urine at 24h were positively correlated with total AUC in plasma and urine (r=0.93, and r=0.98, respectively). This suggests that fasting blood and urine collections could be used to estimate polyphenol bioavailability and metabolism after aronia polyphenol consumption.

Gastroretentive systems - a proposed strategy to modulate anthocyanin release and absorption for the management of diabetes

Several reports have indicated a positive correlation between the consumption of anthocyanins (ACN) and biomarkers relating to the improvement of type 2 diabetes (T2D). However, the results from in vitro studies often do not translate into clinical evidence. Potential causes of these discrepancies are experimental conditions that lack physiological relevancy; extensive degradation of these compounds in vivo due to changes in pH and metabolism; and a short residence time in the absorption window in relation to the absorption rate. Here, gastroretentive systems (GRS) are proposed as a strategy to overcome the limitations in ACN delivery and to reduce the existing bench-to-subject gap. This review summarizes recent literature on the use of ACN for the management and control of T2D, followed by GRS platforms to promote a sustained release of ACN for increased health benefits.

Role of endothelial cell membrane transport in red wine polyphenols-induced coronary vasorelaxation: involvement of bilitranslocase

Red wine polyphenols (RWP) induce nitric oxide (NO) and endothelium-derived hyperpolarization (EDH)-mediated coronary vasodilatation involving the redox-sensitive PI3-kinase/Akt-dependent pathway in the endothelium. However, there is a gap of knowledge in explaining how bioactive polyphenols initialize their signalling pathway in endothelial cells. Here, we investigated the hypothesis that flavonoids act subsequently to their entry into the endothelium via the flavonoid membrane transporter bilitranslocase (TC 2.A.65.1.1). Thus, vascular reactivity studies were performed using isolated porcine coronary artery rings. We separately determined the NO- and EDH-mediated components of the relaxation in the presence of specific inhibitors. In either case, bilitranslocase antibodies significantly reduced the relaxations of coronary artery rings induced by RWP. Furthermore, bilitranslocase antibodies significantly reduced RWP-induced phosphorylation levels of Akt and eNOS, assessed in cultured endothelial cells from porcine coronary arteries by Western blot analysis. The present findings indicate that bilitranslocase-mediated membrane transport substantially contributes to the initial step of RWP-induced coronary vasodilatation.

Anthocyanin kinetics are dependent on anthocyanin structure

The kinetics of anthocyanin metabolism was investigated in a human feeding trial. Volunteers (n 12) consumed purple carrots containing five anthocyanin forms: cyanidin-3-(xylose-glucose-galactoside), cyanidin-3-(xylose-galactoside), cyanidin-3-(xylose-sinapoyl-glucose-galactoside), cyanidin-3-(xylose-feruloyl-glucose-galactoside) and cyanidin-3-(xylose-coumuroyl-glucose-galactoside). The purple carrots were served as three different treatments in a crossover design with a 3-week washout between treatments. Purple carrot treatments were 250 g raw carrots, 250 g cooked carrots and 500 g cooked carrots. Serial blood and urine samples were collected for 8 and 24 h after the dose, respectively, and analysed for anthocyanins. Of the anthocyanin forms ingested, four were detected in plasma and urine: cyanidin-3-(xylose-glucose-galactoside), cyanidin-3-(xylose-galactoside), cyanidin-3-(xylose-sinapoyl-glucose-galactoside) and cyanidin-3-(xylose-feruloyl-glucose-galactoside). The time courses of plasma and urine anthocyanin contents were evaluated with compartmental modelling. Results showed that absorption, gastrointestinal transit and plasma elimination are dependent on anthocyanin structure. Absorption efficiencies of acylated compounds (cyanidin-3-(xylose-sinapoyl-glucose-galactoside) and cyanidin-3-(xylose-feruloyl-glucose-galactoside)) were less than those for non-acylated anthocyanins (cyanidin-3-(xylose-glucose-galactoside) and cyanidin-3-(xylose-galactoside)). The acylated anthocyanins exhibited a shorter half-life for gastrointestinal absorption than the non-acylated anthocyanins. Fractional elimination of non-acylated compounds was slower than that for acylated anthocyanins. These results provide the first information about the kinetics of individual anthocyanins in human beings.

Plasma and urine responses are lower for acylated vs nonacylated anthocyanins from raw and cooked purple carrots

The bioavailability of acylated vs nonacylated anthocyanins and the effect of cooking and dose on the comparative bioavailability were investigated in a clinical feeding study using purple carrots as the anthocyanin source. Treatments were purple carrots as follows: 250 g raw (463 micromol of anthocyanins: 400 micromol acylated, 63 micromol nonacylated), 250 g cooked (357 micromol of anthocyanins: 308.5 micromol acylated, 48.5 micromol nonacylated), and 500 g cooked (714 micromol of anthocyanins: 617 micromol acylated, 97 micromol nonacylated). Four of the five carrot anthocyanins were found intact in plasma by 30 min after carrot consumption and peaked between 1.5 and 2.5 h. Acylation of anthocyanins resulted in an 11-14-fold decrease in anthocyanin recovery in urine and an 8-10-fold decrease in anthocyanin recovery in plasma. Cooking increased the recovery of nonacylated anthocyanins but not acylated anthocyanins. Large dose size significantly reduced recovery of both acylated and nonacylated anthocyanins, suggesting saturation of absorption mechanisms.

Anthocyanin metabolism in rats and their distribution to digestive area, kidney, and brain

Anthocyanins are present in human diet due to their wide occurrence in fruits and beverages. They possess antioxidant activities and could be involved in several health effects. The aim of this study was to investigate anthocyanin metabolism and distribution in the digestive area organs (stomach, jejunum and liver) and kidney, as well as a target tissue (brain) in rats fed with a blackberry (Rubus fruticosus L.) anthocyanin-enriched diet for 15 days. Identification and quantification of anthocyanin metabolites was carried out by HPLC-ESI-MS-MS and HPLC-DAD, respectively. The stomach exhibited only native blackberry anthocyanins (cyanidin 3-O-glucoside and cyanidin 3-O-pentose), while in other organs (jejunum, liver, and kidney) native and methylated anthocyanins as well as conjugated anthocyanidins (cyanidin and peonidin monoglucuronides) were identified. Proportions of anthocyanin derivatives differed according to the organ considered, with the liver presenting the highest proportion of methylated forms. Jejunum and plasma also contained aglycone forms. In the brain, total anthocyanin content (blackberry anthocyanins and peonidin 3-O-glucoside) reached 0.25 +/- 0.05 nmol/g of tissue (n = 6). The urinary excretion of total anthocyanins was low (0.19 +/- 0.02% of the ingested amount). Thus, organs of the digestive area indicated a metabolic pathway of anthocyanins with enzymatic conversions (methylation and/or glucurono-conjugation). Moreover, following consumption of an anthocyanin-rich diet, anthocyanins enter the brain.

Immunolocalisation of bilitranslocase in mucosecretory and parietal cells of the rat gastric mucosa

Bilitranslocase is a plasma membrane carrier localised at the vascular pole of the rat liver cell, where it mediates uptake of organic anions from the blood into the liver. This carrier is also present in the epithelium of the rat gastric mucosa, with similar molecular mass and functional properties. An immunohistochemical study reveals that both the mucus-secreting cells of the gastric pit and the H+-secreting parietal cells express bilitranslocase. These data point to a possible role of bilitranslocase and of its food-borne substrates (anthocyanins and nicotinic acid) in regulating the function and the permeability of the gastric mucosa.

The stomach as a site for anthocyanins absorption from food

The ability of anthocyanins to permeate the gastric mucosa can be suggested as a possible explanation of the fast kinetics of plasma appearance of anthocyanins in rats and humans. This paper presents an in vivo experiment aimed to prove the involvement of the stomach in the absorption of grape anthocyanins in rats. The required analytical selectivity and sensitivity was achieved by high-performance liquid chromatography, diode array detection and mass spectrometry. Malvidin 3-glucoside appeared in both portal and systemic plasma after only 6 min. The average concentrations measured in portal and systemic plasma were 0.650+/-0.162 microM and 0.234+/-0.083 microM (mean+/-S.E.M.), respectively.

The interaction of anthocyanins with bilitranslocase

Bilitranslocase (TC 2.A.65.1.1) is an organic anion membrane carrier expressed at the sinusoidal domain of the liver plasma membrane and in epithelial cells of the gastric mucosa. Its substrates are sulfobromophthalein, bilirubin, and nicotinic acid. This work reports on the identification of a new class of bilitranslocase substrates, i.e., anthocyanins. Seventeen out thes 20 compounds tested behaved as competitive inhibitors of bilitranslocase transport activity (K(I)=1.4-22 microM). Their structure-activity relationship reveals that mono- and di-glucosyl anthocyanins, the anthocyanin species occurring in food, are better ligands than the corresponding aglycones. Moreover, the first interaction of anthocyanins with the carrier occurs through hydrophilic moieties, such as the 3-glucosyl moiety and the B ring for the monoglucosides, through the 5-glucosyl moiety and the A ring for the diglucosides, and through either the B or the A ring for the aglycones. These findings suggest that bilitranslocase could play a role in the bioavailability of anthocyanins.

Immunohistochemical localization of the antioxidant enzymes biliverdin reductase and heme oxygenase-2 in human and pig gastric fundus

The intrinsic antioxidant capacities of the bile pigments biliverdin and bilirubin are increasingly recognized since both heme degradation products can exert beneficial cytoprotective effects due to their scavenging of oxygen free radicals and interaction with antioxidant vitamins. Several studies have been published on the localization of the carbon monoxide producing enzyme heme oxygenase-2 (HO-2), which concomitantly generates biliverdin; histochemical data on the distribution of biliverdin reductase (BVR), converting biliverdin to bilirubin, are still very scarce in large mammals including humans. The present study revealed by means of immunohistochemistry the presence of BVR and HO-2 in mucosal epithelial cells and in the endothelium of intramural vessels of both human and porcine gastric fundus. In addition, co-labeling with the specific neural marker protein-gene product 9.5 (PGP 9.5) demonstrated that both BVR and HO-2 were present in all intrinsic nerve cell bodies of both submucous and myenteric plexuses, while double labeling with c-Kit antibody confirmed their presence in intramuscular interstitial cells of Cajal (ICC). Our results substantiate the hypothesis that BVR, through the production of the potent antioxidant bilirubin, might be an essential component of normal physiologic gastrointestinal defense in man and pig.

Subcellular localization of bilirubin in rat brain after in vivo i.v. administration of [3H]bilirubin

Bilirubin appears to be toxic in vitro to several cellular functions localized to different subcellular compartments. It would therefore be useful to know what concentrations of bilirubin might be found in cell organelles in vivo. Rats were anesthetized and allocated to one of three groups: control, hypercarbia, and hyperosmolality. Each rat received a 5-min bolus dose of bilirubin 50 mg/kg i.v. (containing approximately 200 microCi [(3)H]bilirubin). Rats were killed 10 or 30 min after the start of the bilirubin infusion. Each brain was homogenized, and subcellular fractions were isolated by high-speed gradient centrifugation in sucrose media. The gradients were separated into aliquots of 2 mL, and the protein content was determined in each aliquot. Radioactivity was determined by scintillation counting, and the content of bilirubin per milligram of protein was calculated. Statistical comparisons were performed with Kruskal-Wallis nonparametric ANOVA. There were highly significant differences in bilirubin content per milligram of protein among subcellular compartments in all groups and at both time points. In all groups there were relatively high concentrations of bilirubin in the myelin fraction, an interesting observation in light of the theory that membranes are the primary target of bilirubin toxicity. The very high concentration of bilirubin relative to protein in cytoplasm, ribosomes, and mitochondria in the hyperosmolar group are also notable in light of data from hyperbilirubinemic animals in which changes in electrophysiology or energy metabolism only appeared after hyperosmolar opening of the blood-brain barrier. The present data may be useful in planning in vitro studies of bilirubin toxicity in cell organelles.