Diet supplementation for 5 weeks with polyphenol-rich cereals improves several functions and the redox state of mouse leucocytes

BACKGROUND: Cereals naturally contain a great variety of polyphenols, which exert a wide range of physiological effects both in vitro and in vivo. Many of their protective effects, including an improvement of the function and redox state of immune cells in unhealthy or aged subjects come from their properties as powerful antioxidant compounds. However, whether cereal-based dietary supplementation positively affects the immune function and cellular redox state of healthy subjects remains unclear. AIM OF THE STUDY: To investigate the effects of supplementation (20% wt/wt) for 5 weeks with four different cereal fractions on healthy mice. METHODS: Several parameters of function and redox state of peritoneal leukocytes were measured. The cereals, named B (wheat germ), C (buckwheat flour), D (fine rice bran) and E (wheat middlings) contained different amounts of gallic acid, p-hydroxybenzoic acid, vanillic acid, sinapic acid, p-coumaric acid, ferulic acid, quercetin, catechin, rutin and oryzanol as major polyphenols. RESULTS: In general, all cereal fractions caused an improvement of the leukocyte parameters studied such as chemotaxis capacity, microbicidal activity, lymphoproliferative response to mitogens, interleukin-2 (IL-2) and tumor necrosis factor (TNFα) release, as well as oxidized glutathione (GSSG), GSSG/GSH ratio, catalase (CAT) activity and lipid oxidative damage. We observed similar effects among the cereal fractions. CONCLUSIONS: The results suggest that some of these effects may due, at least partially, to the antioxidant activity of the polyphenols naturally present in cereals. Since an appropriate function of the leukocytes has been proposed as marker of the health state, a short-term intake of cereals seems to be sufficient to exert a benefit in the health of the general population. However, further studies are needed to assess the optimal doses and to find out which active polyphenols are able to mediate the observed physiological effects before recommending their regular consumption

Plasmodium falciparum: Differential Selection of Drug Resistance Alleles in Contiguous Urban and Peri-Urban Areas of Brazzaville, Republic of Congo

The African continent is currently experiencing rapid population growth, with rising urbanization increasing the percentage of the population living in large towns and cities. We studied the impact of the degree of urbanization on the population genetics of Plasmodium falciparum in urban and peri-urban areas in and around the city of Brazzaville, Republic of Congo. This field setting, which incorporates local health centers situated in areas of varying urbanization, is of interest as it allows the characterization of malaria parasites from areas where the human, parasite, and mosquito populations are shared, but where differences in the degree of urbanization (leading to dramatic differences in transmission intensity) cause the pattern of malaria transmission to differ greatly. We have investigated how these differences in transmission intensity affect parasite genetic diversity, including the amount of genetic polymorphism in each area, the degree of linkage disequilibrium within the populations, and the prevalence and frequency of drug resistance markers. To determine parasite population structure, heterozygosity and linkage disequilibrium, we typed eight microsatellite markers and performed haplotype analysis of the msp1 gene by PCR. Mutations known to be associated with resistance to the antimalarial drugs chloroquine and pyrimethamine were determined by sequencing the relevant portions of the crt and dhfr genes, respectively. We found that parasite genetic diversity was comparable between the two sites, with high levels of polymorphism being maintained in both areas despite dramatic differences in transmission intensity. Crucially, we found that the frequencies of genetic markers of drug resistance against pyrimethamine and chloroquine differed significantly between the sites, indicative of differing selection pressures in the two areas

Toxicological aspects of the use of phenolic compounds in disease prevention

The consumption of a diet low in fat and enhanced by fruits and vegetables, especially rich in phenolic compounds, may reduce risks of many civilization diseases. The use of traditional medicines, mainly derived from plant sources, has become an attractive segment in the management of many lifestyle diseases. Concerning the application of dietary supplements (based on phenolic compounds) in common practice, the ongoing debate over possible adverse effects of certain nutrients and dosage levels is of great importance. Since dietary supplements are not classified as drugs, their potential toxicities and interactions have not been thoroughly evaluated. First, this review will introduce phenolic compounds as natural substances beneficial for human health. Second, the potential dual mode of action of flavonoids will be outlined. Third, potential deleterious impacts of phenolic compounds utilization will be discussed: pro-oxidant and estrogenic activities, cancerogenic potential, cytotoxic effects, apoptosis induction and flavonoid-drug interaction. Finally, future trends within the research field will be indicated

CD4-Specific Designed Ankyrin Repeat Proteins Are Novel Potent HIV Entry Inhibitors with Unique Characteristics

Here, we describe the generation of a novel type of HIV entry inhibitor using the recently developed Designed Ankyrin Repeat Protein (DARPin) technology. DARPin proteins specific for human CD4 were selected from a DARPin DNA library using ribosome display. Selected pool members interacted specifically with CD4 and competed with gp120 for binding to CD4. DARPin proteins derived in the initial selection series inhibited HIV in a dose-dependent manner, but showed a relatively high variability in their capacity to block replication of patient isolates on primary CD4 T cells. In consequence, a second series of CD4-specific DARPins with improved affinity for CD4 was generated. These 2nd series DARPins potently inhibit infection of genetically divergent (subtype B and C) HIV isolates in the low nanomolar range, independent of coreceptor usage. Importantly, the actions of the CD4 binding DARPins were highly specific: no effect on cell viability or activation, CD4 memory cell function, or interference with CD4-independent virus entry was observed. These novel CD4 targeting molecules described here combine the unique characteristics of DARPins—high physical stability, specificity and low production costs—with the capacity to potently block HIV entry, rendering them promising candidates for microbicide development

Involvement of nitric oxide (NO) in signal transduction of stomatal opening

The stomatal aperture responds to a range of stimuli including light, humidity, CO2, growth regulators and air pollutants. Many papers have conclusively shown that complex signal transduction pathways in guard cells are involved in the regulation of stomatal movements (Schroeder et al 2001; Zeiger 1990). Howerver, the molecular mechanisms for sensing this variety of stimuli has not yet been revealed. Recent papers have suggested that hydrogen peroxide (H2O2) is involved in abscisic acid-induced stomatal closing (Pei et al 2000). H2O2 is a reactive oxygen species (ROS) that can diffuse across lipid bilayers, thereby functioning as an intra- and intercellular signaling molecule in plants and animals (Corpas et al 2001; Finkel 1998). In addition to ROS, NO has attracted considerable interest as another diffusable signaling molecule in animal cells. NO is produced within animal cells and exhibits diverse physiological functions including signal transduction, enzyme regulation and immune response (Knowles and Moncada 1994). It is now evident that NO plays essential roles in animal physiology. Although there is an increasing number of reports indicating that NO could also participate in many physiological responses of plants: pathogen response, programmed cell death and growth (Delledonne et al 1998; Durner and Klessig 1999), our understanding of NO in plants is still very limited. Here we demonstrate that NO is involved in the signal transduction mechanisms for stomatal opening

Nitrate reductase as a producer of nitric oxide in plants : temperature-dependence of the enzymatic active nitrogen formation

Nitric oxide (NO) has long been recognized as a harmful air pollutant that can be produced through industrial activities. After the discovery of NO synthase (NOS, EC 1.14.13.39) that produces NO during the conversion of L-arginine to L-citrulline, our view of NO has been drastically changed from a harmful pollutant to an important signal messenger in animal cells (Yamasaki, 2000). In contrast to the large body of knowledge on functions of NO in animal systems, however, little is known in plant systems. Recent studies have suggested that NO is involved in a broad spectrum of physiological responses, including pathogen response, programmed cell death, germination, phytoalexin production and ethylene emission (Bolwell, 1999; Wendehenne, 2001). Although NOS inhibitor experiments using N-nitro-L-arginine (L-NNA), NG-monomethyl-L-arginine (L-NMMA) or NG-nitro-L-arigine-methyl ester (L-NAME) have suggested the existence of a mammalian-type NOS in plants, no plant NOS gene has been conclusively identified to date. Furthermore, no homologue of mammalian-type NOS has been found in the genome of Arabidopsis thaliana. Thus, the presence of mammalian-type NOS in plants remains a subject to be clarified and the mechanism for NO production in plant cells has not yet been confirmed. It has been sometimes reported that several plant and algal species emit NO when nitrate or nitrite is supplied in darkness. In the legume plant Glycine max, the constitutive nitrate reductase (cNR) was identified to produce NO (Dean and Harper, 1986). Harper and coworkers have suggested that NO would be produced from nitrite by the activity of cNR (Dean and Harper, 1988). Normally, NR is the rate-limiting step enzyme of nitrate assimilation in plants and algae, catalyzing the reduction of nitrate (NO3-) to nitrite (NO2-). The NO producing activity had been considered a unique characteristic of cNR that is only distributed in the Phaseolus tribe of the family leguminosae (Dean and Harper, 1988). We have recently shown in vitro evidence that maize inducible NR (iNR) is also capable of producing NO though one electron reduction of nitrite (Yamasaki et al., 1999). A similar nitrite-dependent NO production catalyzed by NR has been reported in bacteria and fungi (Yamasaki, 2000). These results suggest that NO producing acitivity of NR is a more general feature than was previously thought (Yamasaki, 2000). Here we demonstrate that production of active nitrogen species (NO and ONOO-) by NR is strongly temperature-dependent

Nitric oxide suppresses the energy transduction of plant mitochondria

Plant mitochondria are known to possess two respiratory electron transport pathways, i.e. the cytochrome and alternative pathways. The cytochrome pathway, which ends at cytochrome c oxidase (COX), is almost identical to the respiratory electron transport pathway in animal mitochondria. The alternative pathway, which ends at alternative oxidase (AOX), is unique in plants, fungi and parasitic protozoa. Although thermogenesis has been considered as a possible role for alternative pathway. the physiological significance of this non-energy producing pathways is not fully understood. Millar and Day (1996) have proposed that the alternative pathway may play an important role in preventing oxidative damage induced by nitric oxide (NO). Nitric Oxide (NO) is a free radical that can act as a signal messenger in animal cells (Packer 1996). It has been known that NO sometimes disturbs the energy transduction system in animal mitochondria by inhibiting the activity of COX (Brookes e al. 1999), In contrast to extensive knowledge on biochemistry and physiology on NO in animal systems, the source and role of NO in plants have been not yet confirmed. We have recently revealed that plant nitrate reductase (NR) is capable of converting nitrite to NO in the presence of NADH (Yamasaki, Sakihama 2000; Yamasaki 2000). NR is a key enzyme in nitrate assimilation pathway. By using the NR-catalyzed NO production system, here we demonstrate in vitro effects of NO on the energy transduction system of mitochondria. The results presented in this study provide substantial evidence to confirm that the plant alternative pathway is resistant to NO