Inhibition of Membrane Lipid Peroxidation by a Radical Scavenging Mechanism: a Novel Function for Hydroxyl-Containing Ionophores

In the present study we show that K⁺/H⁺ hydroxyl-containing ionophores lasalocid-A (LAS) and nigericin (NIG) in the nanomolar concentration range, inhibit Fe²⁺-citrate and 2,2'-azobis(2-amidinopropane) di-hydrochloride (ABAP)-induced lipid peroxidation in intact rat liver mitochondria and in egg phosphatidyl-choline (PC) liposomes containing negatively charged lipids—dicetyl phosphate (DCP) or cardiolipin (CL)—and KCl as the osmotic support. In addition, monensin (MON), a hydroxyl-containing ionophore with higher affinity for Na⁺ than for K⁺, promotes a similar effect when NaCl is the osmotic support. The protective effect of the ionophores is not observed when the osmolyte is sucrose. Lipid peroxidation was evidenced by mitochondrial swelling, antimycin A-insensitive O₂ consumption, formation of thiobarbituric acid-reactive substances (TBARS), conjugated dienes, and electron paramagnetic resonance (EPR) spectra of an incorporated lipid spin probe. A time-dependent decay of spin label EPR signal is observed as a consequence of lipid peroxidation induced by both inductor systems in liposomes. Nitroxide destruction is inhibited by buty-lated hydroxytoluene, a known antioxidant, and by the hydroxyl-containing ionophores. In contrast, vali-nomycin (VAL), which does not possess alcoholic groups, does not display this protective effect. Effective order parameters (S_eff), determined from the spectra of an incorporated spin label are larger in the presence of salt and display a small increase upon addition of the ionophores, as a result of the increase of counter ion concentration at the negatively charged bilayer surface. This condition leads to increased formation of the ion-ionophore complex, the membrane binding (uncharged) species. The membrane-incorporated complex is the active species in the lipid peroxidation inhibiting process. Studies in aqueous solution (in the absence of membranes) showed that NIG and LAS, but not VAL, decrease the Fe²⁺-citrate-induced production of radicals derived from piperazine-based buffers, demonstrating their property as radical scavengers. Both Fe²⁺-citrate and ABAP promote a much more pronounced decrease of LAS fluorescence in PC/CL liposomes than in dimyristoyl phosphatidyl-choline (DMPC, saturated phospholipid)-DCP liposomes, indicating that the ionophore also scavenges lipid peroxyl radicals. A slow decrease of fluorescence is observed in the latter system, for all lipid compositions in sucrose medium, and in the absence of membranes, indicating that the primary radicals stemming from both inductors also attack the ionophore. Altogether, the data lead to the conclusion that the membrane-incorporated cation complexes of NIG, LAS and MON inhibit lipid peroxidation by blocking initiation and propagation reactions in the lipid phase via a free radical scavenging mechanism, very likely due to the presence of alcoholic hydroxyl groups in all three molecules and to the attack of the aromatic moiety of LAS.     

Phylogeny of Macroptilium (Leguminosae): morphological, biochemical and molecular evidence

Macroptilium (Benth.) Urban (Phaseoleae, Papilionoideae, Leguminosae) is an American genus of legumes, belonging to subtribe Phaseolinae along with other economically important genera, such as Vigna Savi and Phaseolus L. (the common bean genus). Cladistic analyses based on morphological, biochemical (storage seed proteins) and molecular (nuclear and plastid DNA sequences) data were performed on the 18 species currently ascribed to the genus, exploring several character weighting strategies. Equal weights, implied weighting and different transversion/transition costs were applied. The three data sets were first analyzed with separate partitions, and then combined into a single matrix. This study is the first one to analyze all the species of the genus from a cladistic point of view. In all the most parsimonious trees obtained, Macroptilium is monophyletic with excellent support values. Two monophyletic clades are recovered in almost all the analyses. Both are compound by nine species, and they constitute two sections of Macroptilium. Several interspecific relationships inside the genus are discussed. © The Willi Hennig Society 2007.     

Nonequilibrium Pathways during Electrochemical Phase Transformations in Single Crystals Revealed by Dynamic Chemical Imaging at Nanoscale Resolution

The energy density of current batteries is limited by the practical capacity of the positive electrode, which is determined by the properties of the active material and its concentration in the composite electrode architecture. The observation in dynamic conditions of electrochemical transformations creates the opportunity of identifying design rules toward reaching the theoretical limits of battery electrodes. But these observations must occur during operation and at multiple scales. They are particularly critical at the single‐particle level, where incomplete reactions and failure are prone to occur. Here, operando full‐field transmission X‐ray microscopy is coupled with X‐ray spectroscopy to follow the chemical and microstructural evolution at the nanoscale of single crystals of Li_1+xMn_2–xO₄, a technologically relevant Li‐ion battery electrode material. The onset and crystallographic directionality of a series of complex phase transitions are followed and correlated with particle fracture. The dynamic character of this study reveals the existence of nonequilibrium pathways where phases at substantially different potentials can coexist at short length scales. The results can be used to inform the engineering of particle morphologies and electrode architectures that bypass the issues observed here and lead to optimized battery electrode properties.     

Dietary Omega-3 Fatty Acid Supplementation Reduces Inflammation in Obese Pregnant Women: A Randomized Double-Blind Controlled Clinical Trial

Objective

Long-chain omega 3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) exert potent anti-inflammatory properties in humans. This study characterized the effects of omega-3 ω-3 fatty acids supplements (ω-3 FA) on the inflammatory status in the placenta and adipose tissue of overweight/obese pregnant women.

Study Design

A randomized, double-masked controlled trial was conducted in overweight/obese pregnant women that were randomly assigned to receive DHA plus EPA (2g/day) or the equivalent of a placebo twice a day from week 10–16 to term. Inflammatory pathways were characterized in: 1) adipose tissue and placenta of treated vs. untreated women; and 2) adipose and trophoblast cells cultured with long chain FAs.

Results

The sum of plasma DHA and EPA increased by 5.8 fold and ω-3 FA/ ω-6 FA ratio was 1.5 in treated vs. untreated women (p< 0.005). Plasma CRP concentrations were reduced (p<0.001). The adipose tissue and placenta of treated women exhibited a significant decrease in TLR4 adipose and placental expression as well as IL6, IL8, and TNFα In vitro, EPA and DHA suppressed the activation of TLR4, IL6, IL8 induced by palmitate in culture of adipose and trophoblast cells.

Conclusion

Supplementation of overweight/obese pregnant women with dietary ω-3 FAs for >25 weeks reduced inflammation in maternal adipose and the placental tissue. TLR4 appears as a central target of the anti-inflammatory effects at the cellular level.

Trial Registration

ClinicalTrials.gov NCT00957476     

Breast Cancer Biology and Ethnic Disparities in Breast Cancer Mortality in New Zealand: A Cohort Study

Introduction

Indigenous Māori women have a 60% higher breast cancer mortality rate compared with European women in New Zealand. We investigated differences in cancer biological characteristics and their impact on breast cancer mortality disparity between Māori and NZ European women.

Materials and Methods

Data on 2849 women with primary invasive breast cancers diagnosed between 1999 and 2012 were extracted from the Waikato Breast Cancer Register. Differences in distribution of cancer biological characteristics between Māori and NZ European women were explored adjusting for age and socioeconomic deprivation in logistic regression models. Impacts of socioeconomic deprivation, stage and cancer biological characteristics on breast cancer mortality disparity between Māori and NZ European women were explored in Cox regression models.

Results

Compared with NZ European women (n=2304), Māori women (n=429) had significantly higher rates of advanced and higher grade cancers. Māori women also had non-significantly higher rates of ER/PR negative and HER-2 positive breast cancers. Higher odds of advanced stage and higher grade remained significant for Māori after adjusting for age and deprivation. Māori women had almost a 100% higher age and deprivation adjusted breast cancer mortality hazard compared with NZ European women (HR=1.98, 1.55-2.54). Advanced stage and lower proportion of screen detected cancer in Māori explained a greater portion of the excess breast cancer mortality (HR reduction from 1.98 to 1.38), while the additional contribution through biological differences were minimal (HR reduction from 1.38 to 1.35).

Conclusions

More advanced cancer stage at diagnosis has the greatest impact while differences in biological characteristics appear to be a minor contributor for inequities in breast cancer mortality between Māori and NZ European women. Strategies aimed at reducing breast cancer mortality in Māori should focus on earlier diagnosis, which will likely have a greater impact on reducing breast cancer mortality inequity between Māori and NZ European women.     

Prevalence and Correlates of Client-Perpetrated Violence against Female Sex Workers in 13 Mexican Cities

Background

Globally, client-perpetrated violence against female sex workers (FSWs) has been associated with multiple health-related harms, including high-risk sexual behavior and increased exposure to HIV/STIs. This study examined correlates of client-perpetrated sexual, physical, and economic violence (e.g., robbery) against FSWs in 13 cities throughout Mexico.

Methods

FSWs (N = 1,089) who were enrolled in a brief, evidence-based, sexual risk reduction intervention for FSWs (Mujer Segura) were interviewed about their work context, including experiences of violence perpetrated by clients, sexual risk and substance use practices, financial need, and social supports. Three broad categories of factors (sociodemographic, work context, behavioral and social characteristics of FSWs) were examined as correlates of sexual, physical, and economic violence.

Results

The prevalence of different types of client-perpetrated violence against FSWs in the past 6 months was: sexual (11.7%), physical (11.8%), economic (16.9%), and any violence (22.6%). Greater financial need, self-identification as a street worker, and lower perceived emotional support were independently associated with all three types of violence. Alcohol use before or during sex with clients in the past month was associated with physical and sexual violence. Using drugs before or during sex with clients, injection drug use in the past month, and population size of city were associated with sexual violence only, and FSWs’ alcohol use score (AUDIT-C) was associated with economic violence only.

Conclusions

Correlates of client-perpetrated violence encompassed sociodemographic, work context, and behavioral and social factors, suggesting that approaches to violence prevention for FSWs must be multi-dimensional. Prevention could involve teaching FSWs strategies for risk avoidance in the workplace (e.g., avoiding use of alcohol with clients), enhancement of FSWs’ community-based supports, development of interventions that deliver an anti-violence curriculum to clients, and programs to address FSWs’ financial need by increasing their economic opportunities outside of the sex trade.     

Transcriptomic Identification of ADH1B as a Novel Candidate Gene for Obesity and Insulin Resistance in Human Adipose Tissue in Mexican Americans from the Veterans Administration Genetic Epidemiology Study (VAGES)

Type 2 diabetes (T2D) is a complex metabolic disease that is more prevalent in ethnic groups such as Mexican Americans, and is strongly associated with the risk factors obesity and insulin resistance. The goal of this study was to perform whole genome gene expression profiling in adipose tissue to detect common patterns of gene regulation associated with obesity and insulin resistance. We used phenotypic and genotypic data from 308 Mexican American participants from the Veterans Administration Genetic Epidemiology Study (VAGES). Basal fasting RNA was extracted from adipose tissue biopsies from a subset of 75 unrelated individuals, and gene expression data generated on the Illumina BeadArray platform. The number of gene probes with significant expression above baseline was approximately 31,000. We performed multiple regression analysis of all probes with 15 metabolic traits. Adipose tissue had 3,012 genes significantly associated with the traits of interest (false discovery rate, FDR ≤ 0.05). The significance of gene expression changes was used to select 52 genes with significant (FDR ≤ 10^-4) gene expression changes across multiple traits. Gene sets/Pathways analysis identified one gene, alcohol dehydrogenase 1B (ADH1B) that was significantly enriched (P < 10^-60) as a prime candidate for involvement in multiple relevant metabolic pathways. Illumina BeadChip derived ADH1B expression data was consistent with quantitative real time PCR data. We observed significant inverse correlations with waist circumference (2.8 x 10^-9), BMI (5.4 x 10^-6), and fasting plasma insulin (P < 0.001). These findings are consistent with a central role for ADH1B in obesity and insulin resistance and provide evidence for a novel genetic regulatory mechanism for human metabolic diseases related to these traits.     

An open-flower mutant of Melilotus alba: Potential for floral-dip transformation of a papilionoid legume with a short life cycle?

This paper describes an open-flower mutant, designated opf, that we discovered in a genetic screen of fast neutron bombardment mutants in an attempt at floral-dip transformation of Melilotus alba (Fabaceae; white sweetclover), an alternative papilionoid legume host for Sinorhizobium meliloti. The opf mutant developed flowers with reflexed sepals and petals, thereby exposing the stamens and carpel, whereas wild-type sweetclover inflorescences developed closed flowers where the young stamens and carpel remain covered during the early stages of flower development. Based on crosses with the wild type, the mutant segregated as a single, Mendelian recessive. Crosses were successful only when the opf mutant served as the female parent, suggesting that the mutant was male sterile. However, no obvious differences from wild-type stamen development were observed in the opf mutant. The anther defect was due to indehiscence. However, as the plants approached the end of their life cycle, the frequency of selfing increased. We also investigated whether the opf mutant could be transformed via Agrobacterium tumefaciens floral-dip infiltration because open flowers like those of Arabidopsis appear to be more readily transformable. However, similar to wild-type M. alba, the opf mutant is refractory to floral-dip transformation by Agrobacterium tumefaciens.