Platelet-Mediated Metabolism of the Common Dietary Flavonoid,Quercetin

Background

Flavonoid metabolites remain in blood for periods of time potentially long enough to allow interactions with cellular components of this tissue. It is well-established that flavonoids are metabolised within the intestine and liver into methylated, sulphated and glucuronidated counterparts, which inhibit platelet function.

Methodology/Principal Findings

We demonstrate evidence suggesting platelets which contain metabolic enzymes, as an alternative location for flavonoid metabolism. Quercetin and a plasma metabolite of this compound, 4′-O-methyl quercetin (tamarixetin) were shown to gain access to the cytosolic compartment of platelets, using confocal microscopy. High performance liquid chromatography (HPLC) and mass spectrometry (MS) showed that quercetin was transformed into a compound with a mass identical to tamarixetin, suggesting that the flavonoid was methylated by catechol-O-methyl transferase (COMT) within platelets.

Conclusions/Significance

Platelets potentially mediate a third phase of flavonoid metabolism, which may impact on the regulation of the function of these cells by metabolites of these dietary compounds.     

Factors Affecting Women's Autonomous Decision Making In Research Participation Amongst Yoruba Women Of Western Nigeria

Research is a global enterprise requiring participation of both genders for generalizable knowledge; advancement of science and evidence based medical treatment. Participation of women in research is necessary to reduce the current bias that most empirical evidence is obtained from studies with men to inform health care and related policy interventions. Various factors are assumed to limit autonomy amongst the Yoruba women of western Nigeria. This paper seeks to explore the experience and understanding of autonomy by the Yoruba women in relation to research participation. Focus is on factors that affect women's autonomous decision making in research participation. An exploratory qualitative approach comprising four focus group discussions, 42 in‐depth interviews and 14 key informant interviews was used. The study permits a significant amount of triangulation, as opinions of husbands and religious leaders are also explored. Interviews and discussions were audiotaped and transcribed verbatim. Content analysis was employed for data analysis. Findings show that concepts of autonomy varied amongst the Yoruba women. Patriarchy, religion and culture are conceived to have negative impact on the autonomy of women in respect to research participation. Among the important findings are: 1) male dominance is strongly emphasized by religious leaders who should teach equality, 2) while men feel that by making decisions for women, they are protecting them, the women on the other hand see this protection as a way of limiting their autonomy. We recommend further studies to develop culturally appropriate and workable recruitment methods to increase women's participation in research.     

‘Poisonous,Filthy, Loathsome,Damnable Stuff’: The Rhetorical Ecology of Vaccination Concern

In this article, we analyze newspaper articles and advertisements mentioning vaccination from 1915 to 1922 and refer to historical studies of vaccination practices and attitudes in the early 20th century in order to assess historical continuities and discontinuities in vaccination concern. In the Progressive Era period, there were a number of themes or features that resonated with contemporary issues and circumstances: 1) fears of vaccine contamination; 2) distrust of medical professionals; 3) resistance to compulsory vaccination; and 4) the local nature of vaccination concern. Such observations help scholars and practitioners understand vaccine skepticism as longstanding, locally situated, and linked to the sociocultural contexts in which vaccination occurs and is mandated for particular segments of the population. A rhetorical approach offers a way to understand how discourses are engaged and mobilized for particular purposes in historical contexts. Historically situating vaccine hesitancy and addressing its articulation with a particular rhetorical ecology offers scholars and practitioners a robust understanding of vaccination concerns that can, and should, influence current approaches to vaccination skepticism.     

Identification of differentially expressed genes in the livers of chronically i-As-treated hamsters

Inorganic arsenic (i-As) is a human carcinogen causing skin, lung, urinary bladder, liver and kidney tumors. Chronic exposure to this naturally occurring contaminant, mainly via drinking water, is a significant worldwide environmental health concern. To explore the molecular mechanisms of arsenic hepatic injury, a differential display polymerase chain reaction (DD-PCR) screening was undertaken to identify genes with distinct expression patterns between the liver of low i-As-exposed and control animals. Golden Syrian hamsters (5-6 weeks of age) received drinking water containing 15 mg i-As/L as sodium arsenite, or unaltered water for 18 weeks. The in vivo MN test was carried out, and the frequency of micronucleated reticulocytes (MN-RETs) was scored as a measure of exposure and As-related genotoxic/carcinogenic risk. A total of 68 differentially expressed bands were identified in our initial screen, 41 of which could be assigned to specific genes. Differential level of expression of a selected number of genes was verified using real-time RT-PCR with gene-specific primers. Arsenic-altered gene expression included genes related to stress response, cellular metabolism, cell cycle regulation, telomere maintenance, cell-cell communication and signal transduction. Significant differences of MN-RET were found between treated (8.70 ± 0.02 MN/1000RETs) and control (2.5 ± 0.70 MN/1000RETs) groups (P<0.001), demonstrating both the exposure and the i-As genotoxic/carcinogenic risk. Overall, this paper reveals some possible networks involved in hepatic arsenic-related genotoxicity, carcinogenesis and diabetogenesis. Additional studies to explore further the potential implications of each candidate gene are of especial interest. The present work opens the door to new prospects for the study of i-As mechanisms taking place in the liver under chronic settings.     

Lung effector memory and activated CD4+ T cells display enhanced proliferation in surfactant protein A-deficient mice during allergen-mediated inflammation

Although many studies have shown that pulmonary surfactant protein (SP)-A functions in innate immunity, fewer studies have addressed its role in adaptive immunity and allergic hypersensitivity. We hypothesized that SP-A modulates the phenotype and prevalence of dendritic cells (DCs) and CD4(+) T cells to inhibit Th2-associated inflammatory indices associated with allergen-induced inflammation. In an OVA model of allergic hypersensitivity, SP-A(-/-) mice had greater eosinophilia, Th2-associated cytokine levels, and IgE levels compared with wild-type counterparts. Although both OVA-exposed groups had similar proportions of CD86(+) DCs and Foxp3(+) T regulatory cells, the SP-A(-/-) mice had elevated proportions of CD4(+) activated and effector memory T cells in their lungs compared with wild-type mice. Ex vivo recall stimulation of CD4(+) T cell pools demonstrated that cells from the SP-A(-/-) OVA mice had the greatest proliferative and IL-4-producing capacity, and this capability was attenuated with exogenous SP-A treatment. Additionally, tracking proliferation in vivo demonstrated that CD4(+) activated and effector memory T cells expanded to the greatest extent in the lungs of SP-A(-/-) OVA mice. Taken together, our data suggested that SP-A influences the prevalence, types, and functions of CD4(+) T cells in the lungs during allergic inflammation and that SP deficiency modifies the severity of inflammation in allergic hypersensitivity conditions like asthma.     

Identification of Critical Regions and Candidate Genes for Cardiovascular Malformations and Cardiomyopathy Associated with Deletions of Chromosome 1p36

Cardiovascular malformations and cardiomyopathy are among the most common phenotypes caused by deletions of chromosome 1p36 which affect approximately 1 in 5000 newborns. Although these cardiac-related abnormalities are a significant source of morbidity and mortality associated with 1p36 deletions, most of the individual genes that contribute to these conditions have yet to be identified. In this paper, we use a combination of clinical and molecular cytogenetic data to define five critical regions for cardiovascular malformations and two critical regions for cardiomyopathy on chromosome 1p36. Positional candidate genes which may contribute to the development of cardiovascular malformations associated with 1p36 deletions include DVL1, SKI, RERE, PDPN, SPEN, CLCNKA, ECE1, HSPG2, LUZP1, and WASF2. Similarly, haploinsufficiency of PRDM16–a gene which was recently shown to be sufficient to cause the left ventricular noncompaction–SKI, PRKCZ, RERE, UBE4B and MASP2 may contribute to the development of cardiomyopathy. When treating individuals with 1p36 deletions, or providing prognostic information to their families, physicians should take into account that 1p36 deletions which overlie these cardiac critical regions may portend to cardiovascular complications. Since several of these cardiac critical regions contain more than one positional candidate gene–and large terminal and interstitial 1p36 deletions often overlap more than one cardiac critical region–it is likely that haploinsufficiency of two or more genes contributes to the cardiac phenotypes associated with many 1p36 deletions.     

An Orthotopic Glioblastoma Mouse Model Maintaining Brain Parenchymal Physical Constraints and Suitable for Intravital Two-photon Microscopy

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumors with no curative treatments available to date.Murine models of this pathology rely on the injection of a suspension of glioma cells into the brain parenchyma following incision of the dura-mater. Whereas the cells have to be injected superficially to be accessible to intravital two-photon microscopy, superficial injections fail to recapitulate the physiopathological conditions. Indeed, escaping through the injection tract most tumor cells reach the extra-dural space where they expand abnormally fast in absence of mechanical constraints from the parenchyma.Our improvements consist not only in focally implanting a glioma spheroid rather than injecting a suspension of glioma cells in the superficial layers of the cerebral cortex but also in clogging the injection site by a cross-linked dextran gel hemi-bead that is glued to the surrounding parenchyma and sealed to dura-mater with cyanoacrylate. Altogether these measures enforce the physiological expansion and infiltration of the tumor cells inside the brain parenchyma. Craniotomy was finally closed with a glass window cemented to the skull to allow chronic imaging over weeks in absence of scar tissue development.Taking advantage of fluorescent transgenic animals grafted with fluorescent tumor cells we have shown that the dynamics of interactions occurring between glioma cells, neurons (e.g. Thy1-CFP mice) and vasculature (highlighted by an intravenous injection of a fluorescent dye) can be visualized by intravital two-photon microscopy during the progression of the disease.The possibility to image a tumor at microscopic resolution in a minimally compromised cerebral environment represents an improvement of current GBM animal models which should benefit the field of neuro-oncology and drug testing.     

Genome‐wide association study identifies loci associated with liability to alcohol and drug dependence that is associated with variability in reward‐related ventral striatum activity in African‐ and European‐Americans

Genetic influences on alcohol and drug dependence partially overlap, however, specific loci underlying this overlap remain unclear. We conducted a genome‐wide association study (GWAS) of a phenotype representing alcohol or illicit drug dependence (ANYDEP) among 7291 European‐Americans (EA; 2927 cases) and 3132 African‐Americans (AA: 1315 cases) participating in the family‐based Collaborative Study on the Genetics of Alcoholism. ANYDEP was heritable (h ² in EA = 0.60, AA = 0.37). The AA GWAS identified three regions with genome‐wide significant (GWS; P < 5E‐08) single nucleotide polymorphisms (SNPs) on chromosomes 3 (rs34066662, rs58801820) and 13 (rs75168521, rs78886294), and an insertion‐deletion on chromosome 5 (chr5:141988181). No polymorphisms reached GWS in the EA. One GWS region (chromosome 1: rs1890881) emerged from a trans‐ancestral meta‐analysis (EA + AA) of ANYDEP, and was attributable to alcohol dependence in both samples. Four genes (AA: CRKL, DZIP3, SBK3; EA: P2RX6) and four sets of genes were significantly enriched within biological pathways for hemostasis and signal transduction. GWS signals did not replicate in two independent samples but there was weak evidence for association between rs1890881 and alcohol intake in the UK Biobank. Among 118 AA and 481 EA individuals from the Duke Neurogenetics Study, rs75168521 and rs1890881 genotypes were associated with variability in reward‐related ventral striatum activation. This study identified novel loci for substance dependence and provides preliminary evidence that these variants are also associated with individual differences in neural reward reactivity. Gene discovery efforts in non‐European samples with distinct patterns of substance use may lead to the identification of novel ancestry‐specific genetic markers of risk.     

Catalytic efficiency, kinetic co-operativity of oligomeric enzymes and evolution

The catalytic performance of an enzyme, whether it is monomeric or oligomeric, depends on extra costs of energy in passing from the initial ground state to the various transition states, along the reaction co-ordinate. The improvement, during evolution, of the catalytic performance of individual subunits implies that three structural requirements are met in the course of an enzyme reaction: the unstrained enzyme subunits exist in the ground states under two conformations, one corresponding to the non-liganded state and the other to the liganded state; the inter-subunit strain is relieved in the various transition states; the subunits bound to the various transition states S not equal to, X not equal to and P not equal to have the same conformation. These structural requirements are precisely those which have been used to derive structural rate equations for polymeric enzymes. When subunits are loosely coupled, their arrangement controls the various rate constants, but not the extra costs of energy required to reach the various transition states. Moreover, one cannot expect the rate curve to display any sigmoidicity under these conditions. If subunits are tightly coupled and if the strained non-liganded and half-liganded states are destabilized with respect to the corresponding unstrained states, that is if they contain more conformational energy, the oligomeric enzyme is more catalytically efficient than the ideally isolated subunits. Moreover, if the available conformational energy of the half-liganded state is more than twice that of the non-liganded state, kinetic co-operativity is positive and the rate curve is sigmoidal. It is therefore the extent of inter-subunit strain in the half-liganded state which controls the appearance of sigmoidal kinetic behaviour. If subunits are tightly coupled but if inter-subunit strain is relieved in both the non-liganded and fully-liganded states, the half-liganded state controls both the catalytic efficiency of the enzyme and the sigmoidicity of the rate curve. Sigmoidicity and high catalytic efficiency are to be observed when this half-liganded state is destabilized relative to the corresponding unstrained state.(ABSTRACT TRUNCATED AT 400 WORDS)