Intracellular metabolism and bioactivity of quercetin and its in vivo metabolites

Understanding the cellular effects of flavonoid metabolites is important for predicting which dietary flavonoids might be most beneficial in vivo. Here we investigate the bioactivity in dermal fibroblasts of the major reported in vivo metabolites of quercetin, i.e. 3'-O-methyl quercetin, 4'-O-methyl quercetin and quercetin 7-O-beta-D-glucuronide, relative to that of quercetin, in terms of their further metabolism and their resulting cytotoxic and/or cytoprotective effects in the absence and presence of oxidative stress. Uptake experiments indicate that exposure to quercetin led to the generation of two novel cellular metabolites, one characterized as a 2'-glutathionyl quercetin conjugate and another product with similar spectral characteristics but 1 mass unit lower, putatively a quinone/quinone methide. A similar product was identified in cells exposed to 3'-O-methyl quercetin, but not in the lysates of those exposed to its 4'-O-methyl counterpart, suggesting that its formation is related to oxidative metabolism. There was no uptake or metabolism of quercetin 7-O-beta-D-glucuronide by fibroblasts. Formation of oxidative metabolites may explain the observed concentration-dependent toxicity of quercetin and 3'-O-methyl quercetin, whereas the formation of a 2'-glutathionyl quercetin conjugate is interpreted as a detoxification step. Both O -methylated metabolites conferred less protection than quercetin against peroxide-induced damage, and quercetin glucuronide was ineffective. The ability to modulate cellular toxicity paralleled the ability of the compounds to decrease the level of peroxide-induced caspase-3 activation. Our data suggest that the actions of quercetin and its metabolites in vivo are mediated by intracellular metabolites.

Do in vivo terahertz imaging systems comply with safety guidelines?

Techniques for the coherent generation and detection of electromagnetic radiation in the far infrared, or terahertz, region of the electromagnetic spectrum have recently developed rapidly and may soon be applied for in vivo medical imaging. Both continuous wave and pulsed imaging systems are under development, with terahertz pulsed imaging being the more common method. Typically a pump and probe technique is used, with picosecond pulses of terahertz radiation generated from femtosecond infrared laser pulses, using an antenna or nonlinear crystal. After interaction with the subject either by transmission or reflection, coherent detection is achieved when the terahertz beam is combined with the probe laser beam. Raster scanning of the subject leads to an image data set comprising a time series representing the pulse at each pixel. A set of parametric images may be calculated, mapping the values of various parameters calculated from the shape of the pulses. A safety analysis has been performed, based on current guidelines for skin exposure to radiation of wavelengths 2.6 µm–20 mm (15 GHz–115 THz), to determine the maximum permissible exposure (MPE) for such a terahertz imaging system. The international guidelines for this range of wavelengths are drawn from two U.S. standards documents. The method for this analysis was taken from the American National Standard for the Safe Use of Lasers (ANSI Z136.1), and to ensure a conservative analysis, parameters were drawn from both this standard and from the IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields (C95.1). The calculated maximum permissible average beam power was 3 mW, indicating that typical terahertz imaging systems are safe according to the current guidelines. Further developments may however result in systems that will exceed the calculated limit. Furthermore, the published MPEs for pulsed exposures are based on measurements at shorter wavelengths and with pulses of longer duration than those used in terahertz pulsed imaging systems, so the results should be treated with caution.

Determination of the in vivo prebiotic potential of a maize based wholegrain breakfast cereal: a human feeding study

Epidemiological studies have shown an inverse relationship between risk of CVD and intake of whole grain (WG)-rich food. Regular consumption of breakfast cereals can provide not only an increase in dietary WG but also improvements to cardiovascular health. Various mechanisms have been proposed, including prebiotic modulation of the colonic microbiota. In the present study, the prebiotic activity of a maize-derived WG cereal (WGM) was evaluated in a double-blind, placebo-controlled human feeding study (n 32). For a period of 21 d, healthy men and women, mean age 32 (sd 8) years and BMI 23·3 (sd 0·58) kg/m2, consumed either 48 g/d WG cereal (WGM) or 48 g placebo cereal (non-whole grain (NWG)) in a crossover fashion. Faecal samples were collected at five points during the study on days 0, 21, 42, 63 and 84 (representing at baseline, after both treatments and both wash-out periods). Faecal bacteriology was assessed using fluorescence in situ hybridisation with 16S rRNA oligonucleotide probes specific for Bacteroides spp., Bifidobacterium spp., Clostridium histolyticum/perfringens subgroup, Lactobacillus–Enterococcus subgroup and total bacteria. After 21 d consumption of WGM, mean group levels of faecal bifidobacteria increased significantly compared with the control cereal (P = 0·001). After a 3-week wash-out period, bifidobacterial levels returned to pre-intervention levels. No statistically significant changes were observed in serum lipids, glucose or measures of faecal output. In conclusion, this WG maize-enriched breakfast cereal mediated a bifidogenic modulation of the gut microbiota, indicating a possible prebiotic mode of action

Monitoring the penetration enhancer dimethyl sulfoxide in human stratum corneum in vivo by confocal raman spectroscopy

The stratum corneum (SC) barrier typically consists of layers of corneocytes embedded in a lipid continuum that regulates barrier function. The lipid domain containing ceramides, cholesterol, and free fatty acids provides the major pathway for most drugs permeating across SC. Penetration enhancers diminish the SC barrier function. The classic enhancer is dimethyl sulfoxide (DMSO). Its mechanisms of action remain unclear, although DMSO disrupts lipid organisation and may displace protein-bound water. Here we use confocal Raman spectroscopy to probe molecular interactions between a finite (depleting) dose of DMSO and SC, as functions of depth and time, providing novel information about residence time and location of DMSO in human SC in vivo

Sustained polymeric delivery of gene silencing antisense ODNs, siRNA, DNAzymes and ribozymes: in vitro and in vivo studies

Small interfering RNA (siRNA), antisense oligonucleotides (ODNs), ribozymes and DNAzymes have emerged as sequence-specific inhibitors of gene expression that may have therapeutic potential in the treatment of a wide range of diseases. Due to their rapid degradation in vivo, the efficacy of naked gene silencing nucleic acids is relatively short lived. The entrapment of these nucleic acids within biodegradable sustained-release delivery systems may improve their stability and reduce the doses required for efficacy. In this study, we have evaluated the potential in vitro and in vivo use of biodegradable poly (d,l-lactide-co-glycolide) copolymer (PLGA) microspheres as sustained delivery devices for ODNs, ribozyme, siRNA and DNA enzymes. In addition, we investigated the release of ODN conjugates bearing 5′-end lipophilic groups. The in vitro sustained release profiles of microsphere-entrapped nucleic acids were dependent on variables such as the type of nucleic acid used, the nature of the lipophilic group, and whether the nucleic acid used was single or double stranded. For in vivo studies, whole body autoradiography was used to monitor the bio-distribution of either free tritium-labelled ODN or that entrapped within PLGA microspheres following subcutaneous administration in Balb-c mice. The majority of the radioactivity associated with free ODN was eliminated within 24 h whereas polymer-released ODN persisted in organs and at the site of administration even after seven days post-administration. Polymer microsphere released ODN exhibited a similar tissue and cellular tropism to the free ODN. Micro-autoradiography analyses of the liver and kidneys showed similar bio-distribution for polymer-released and free ODNs with the majority of radioactivity being concentrated in the proximal convoluted tubules of the kidney and in the Kupffer cells of the liver. These findings suggest that biodegradable PLGA microspheres offer a method for improving the in vivo sustained delivery of gene silencing nucleic acids, and hence are worthy of further investigation as delivery systems for these macromolecules.

Relationship between dietary-induced changes in intestinal commensal microflora and duodenojejunal myoelectric activity monitored by radiotelemetry in the rat in vivo

Interdigestive intestinal motility, and especially phase III of the migrating myoelectric/motor complex (MMC), is responsible for intestinal clearance and plays an important role in prevention of bacterial overgrowth and translocation in the gut. Yet previous results from gnotobiotic rats have shown that intestinal microflora can themselves affect the characteristics of the myoelectric activity of the gut during the interdigestive state. Given that the composition of the intestinal microflora can be altered by dietary manipulations, we investigated the effect of supplementation of the diet with synbiotics on intestinal microflora structure and the duodenojejunal myoelectric activity in the rat. To reduce animal distress caused by restraint and handling, which can itself affect GI motility, we applied radiotelemetry for duodenojejunal EMG recordings in conscious, freely moving rats. Thirty 16-month-old Spraque-Dawley rats were used. The diet for 15 rats (E group) was supplemented with chicory inulin, Lactobacillus rhamnosus and Bifidobacterium lactis. The remaining 15 rats were fed control diet without supplements (C group). Three rats from each group were implanted with three bipolar electrodes positioned at 2, 14 and 28 cm distal to the pylorus. After recovery, two 6 h recordings of duodenojejunal EMG were carried out on each operated rat. Subsequently, group C rats received feed supplements and group E rats received only control diet for 1 week, and an additional two 6 h recordings were carried out on each of these rats. Non-operated C and E rats were killed and samples of GI tract were collected for microbiological analyses. Supplementation of the diet with the pro- and prebiotics mixture increased the number of bifidobacteria, whereas it decreased the number of enterobacteria in jejunum, ileum, caecum and colon. In both caecum and colon, the dietary supplementation increased the number of total anaerobes and lactobacilli. Treatment with synbiotics increased occurrence of phase III of the MMC at all three levels of the small intestine. The propagation velocity of phase III in the whole recording segment was also increased from 3.7 +/- 0.2 to 4.4 +/- 0.2 cm min(-1) by dietary treatment. Treatment with synbiotics increased the frequency of response potentials of the propagated phase III of the MMC at both levels of the jejunum, but not in the duodenum. In both parts of the jejunum, the supplementation of the diet significantly decreased the duration of phase II of the MMC, while it did not change the duration of phase I and phase III. Using the telemetry technique it was demonstrated that changes in the gastrointestinal microflora exhibited an intestinal motility response and, more importantly, that such changes can be initiated by the addition of synbiotics to the diet.

The effect of cruciferous and leguminous sprouts on genotoxicity, in vitro and in vivo

Vegetable consumption is associated with a reduced risk of colorectal cancer, which is the second most common cancer after lung/breast cancer within Europe. Some putative protective phytochemicals are found in higher amounts in young sprouts than in mature plants. The effect of an extract of mixed cruciferous and legume sprouts on DNA damage induced by H(2)O(2) was measured in HT29 cells using single cell microgelelectrophoresis (comet). Significant antigenotoxic effect (P < or = 0.05) was observed when HT29 cells were pre-incubated with the extract (100 and 200 microL/mL) for 24 hours and then challenged with H(2)O(2). A parallel design intervention study was carried out on 10 male and 10 female healthy adult volunteers (mean age = 25.5 years) fed 113 g of cruciferous and legume sprouts daily for 14 days. The effect of the supplementation was measured on a range of parameters, including DNA damage in lymphocytes (comet), the activity of various detoxifying enzymes (glutathione S-transferase, glutathione peroxidase, and superoxide dismutase), antioxidant status using the ferric reducing ability of plasma assay, plasma antioxidants (uric acid, ascorbic acid, and alpha-tocopherol), blood lipids, plasma levels of lutein, and lycopene. A significant antigenotoxic effect against H(2)O(2)-induced DNA damage was shown in peripheral blood lymphocytes of volunteers who consumed the supplemented diet when compared with the control diet (P = 0.04). No significant induction of detoxifying enzymes was observed during the study, neither were plasma antioxidant levels or activity altered. The results support the theory that consumption of cruciferous vegetables is linked to a reduced risk of cancer via decreased damage to DNA.

Distribution, gene sequence and expression in vivo of the plasmid encoded fimbrial antigen of Salmonella serotype Enteritidis

The pefA gene which encoded the serotype associated plasmid (SAP) mediated fimbrial major subunit antigen of Salmonella enterica serotype Typhimurium shared genetic identity with 128 of 706 salmonella isolates as demonstrated by dot (colony) hybridization. Seventy-seven of 113 isolates of Typhimurium and individual isolates of serotypes Bovis-morbificans, Cholerae-suis and Enteritidis phage type 9b hybridized pefA strongly, whereas 48 isolates of Enteritidis hybridized pefA weakly and one Enteritidis isolate of phage type 14b failed to hybridize. Individual isolates of 294 serotypes and 247 individual isolates of serotype Dublin did not hybridize pefA. Southern hybridization of plasmids extracted from Enteritidis demonstrated that the pefA gene probe hybridized strongly an atypical SAP of 80 kb in size harboured by one Enteritidis isolate of phage-type 9b, whereas the typical SAP of 58 kb in size harboured by 48 Enteritidis isolates hybridized weakly. One Enteritidis isolate of phage type 14b which failed to hybridize pefA in dot (colony) hybridization experiments was demonstrated to be plasmid free. A cosmid library of Enteritidis phage type 4 expressed in Escherichia coli K12 was screened by hybridization for the presence of pef sequences. Recombinant clones which were deduced to harbour the entire pef operon elaborated a PEF-like fimbrial structure at the cell surface. The PEF-like fimbrial antigen was purified from one cosmid clone and used in western blot experiments with sera from chickens infected with Enteritidis phage-type 4. Seroconversion to the fimbrial antigen was observed which indicated that the Enteritidis PEF-like fimbrial structure was expressed at some stage during infection. Nucleotide sequence analysis demonstrated that the pefA alleles of Typhimurium and Enteritidis phage-type 4 shared 76% DNA nucleotide and 82% deduced amino acid sequence identity.

The antithrombotic effect of dextran-40 in man is due to enhanced fibrinolysis in vivo

BACKGROUND: Dextran-40 is effective in reducing postoperative Doppler-detectable embolization in patients undergoing carotid endarterectomy (CEA). Dextrans are thought to have antithrombotic and antiplatelet effects. The mode of action is unclear. In rats, dextran blocks uptake of tissue plasminogen activator (tPA) by mannose-binding receptors. Because this would have the effect of enhancing endogenous fibrinolysis, we explored this effect of dextran-40 on fibrinolysis in man. METHODS: Twenty patients undergoing endovascular stenting for abdominal aortic aneurysm were randomized to receive 100 mL of 10% dextran-40 or saline, over 1 hour, during their operation in addition to heparin. Blood samples were taken preoperatively, intraoperatively (immediately after operative procedure), and 24 hours postoperatively. Thrombi were formed in a Chandler loop and used to assess endogenous fibrinolysis over 24 hours, measured as the fall in thrombus weight, and the release of fluorescently labelled fibrinogen from the thrombus. Plasma samples were analyzed for markers of fibrinolysis; plasmin-antiplasmin (PAP), PAI-1, and t-PA, and for functional von Willebrand factor (vWF). Platelet response to thrombin and other agonists was measured by flow cytometry. RESULTS: Thrombi formed ex vivo from the intraoperative blood samples from the dextran-treated patients exhibited significantly greater fibrinolysis vs preoperative samples, seen both as a significantly greater percentage reduction in thrombus weight (from 34.7% to 70.6% reduction) and as an 175% increase in the release of fluorescence (P < .05). Fibrinolysis returned to baseline levels the next day. No change was seen in the saline-treated group. Plasma levels of PAP and PAI-1 increased significantly postoperatively in the dextran-treated group vs the saline group (P < .05). The postoperative level of functional VWF was significantly lower in the dextran-treated group vs controls. A specific reduction occurred in the platelet response to thrombin, but not to other agonists, in the intraoperative samples from the dextran-treated group (11.1% vs 37.1%; P = .022), which was not seen in the controls. CONCLUSIONS: These data are consistent with a rise in plasmin due to dextran blockade of tPA uptake in vivo, leading to enhanced fibrinolysis, cleavage of vWF and of the platelet protease-activated receptor-1 (PAR-1) thrombin receptor. This suggests that dextran exerts a combined therapeutic effect, enhancing endogenous fibrinolysis, whilst also reducing platelet adhesion to vWF and platelet activation by thrombin. The proven antithrombotic efficacy of low-dose dextran in carotid surgery may be applicable to wider therapeutic use.

In vivo study of the biocompatibility of a novel compressed collagen hydrogel scaffold for artificial corneas

The experiments were designed to evaluate the biocompatibility of a plastically compressed collagen scaffold (PCCS). The ultrastructure of the PCCS was observed via scanning electron microscopy. Twenty New Zealand white rabbits were randomly divided into experimental and control groups that received corneal pocket transplantation with PCCS and an amniotic membrane, respectively. And the contralateral eye of the implanted rabbit served as the normal group. On the 1st, 7th, 14th, 21st, 30th, 60th, 90th, and 120th postoperative day, the eyes were observed via a slit lamp. On the 120th postoperative day, the rabbit eyes were enucleated to examine the tissue compatibility of the implanted stroma. The PCCS was white and translucent. The scanning electron microscopy results showed that fibers within the PCCS were densely packed and evenly arranged. No edema, inflammation, or neovascularization was observed on ocular surface under a slit lamp and few lymphocytes were observed in the stroma of rabbit cornea after histological study. In conclusion, the PCCS has extremely high biocompatibility and is a promising corneal scaffold for an artificial cornea. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.

Aspects of in vitro and in vivo research approaches directed towards identifying probiotics and prebiotics for human use

The microbiota of the human gastrointestinal tract plays a key role in nutrition and health. Through the process of fermentation, gut bacteria metabolize various substrates (principally dietary components) to end products such as short-chain fatty acids and gases. This anaerobic metabolism is thought to contribute positively toward host daily energy requirements. However, under certain circumstances, the fermentative process may produce undesirable metabolites. This may cause the onset of gut disorders that can be manifest through both acute and chronic conditions. Moreover, the gut flora may become contaminated by transient pathogens that serve further to upset the normal community structure. There has been a recent increase in the use of dietary components that help to maintain, or even improve, the gut microflora "balance." Probiotics are live microbial feed supplements added to appropriate food vehicles (usually fermented milks), whereas prebiotics are dietary carbohydrates that have a selective metabolism in the colon and serve to increase numbers of bacteria seen as desirable. Because of their purported health-promoting properties, lactic acid-producing bacteria, including bifidobacteria, are the usual target organisms. The market value and biological potential of both approaches are enormous. This article will summarize how efficacious types can be identified.