Parthenolide sensitizes cells to X-ray-induced cell killing through inhibition of NF-kappaB and split-dose repair

Human cancers have multiple alterations in cell signaling pathways that promote resistance to cytotoxic therapy such as X rays. Parthenolide is a sesquiterpene lactone that has been shown to inhibit several pro-survival cell signaling pathways, induce apoptosis, and enhance chemotherapy-induced cell killing. We investigated whether parthenolide would enhance X-ray-induced cell killing in radiation resistant, NF-kappaB-activated CGL1 cells. Treatment with 5 microM parthenolide for 48 to 72 h inhibited constitutive NF-kappaB binding and cell growth, reduced plating efficiency, and induced apoptosis through stabilization of p53 (TP53), induction of the pro-apoptosis protein BAX, and phosphorylation of BID. Parthenolide also enhanced radiation-induced cell killing, increasing the X-ray sensitivity of CGL1 cells by a dose modification factor of 1.6. Flow cytometry revealed that parthenolide reduced the percentage of X-ray-resistant S-phase cells due to induction of p21 waf1/cip1 (CDKN1A) and the onset of G1/S and G2/M blocks, but depletion of radioresistant S-phase cells does not explain the observed X-ray sensitization. Further studies demonstrated that the enhancement of X-ray-induced cell killing by parthenolide is due to inhibition of split-dose repair.     

Hunting of Mammals Reduces Seed Removal and Dispersal of the Afrotropical Tree Antrocaryon klaineanum (Anacardiaceae)

Throughout the tropics, mammalian seed dispersers are being driven to local extinction by intense hunting pressure, generating concern not only about the loss of these species, but also about the consequences for the plants they disperse. We compared two rain forest sites in Cameroon—one with heavy hunting pressure and one protected from hunting—to appraise the loss of mammalian seed dispersers and to assess the impact of this loss on seed removal and seed dispersal of Antrocaryon klaineanum (Anacardiaceae), a mammal-dispersed tree. Surveys of arboreal frugivores indicate that three of the five monkey species, as well as chimpanzee and gorilla, have been extirpated from the hunted forest. Diaspore counts underneath A. klaineanum adults (six trees per site) indicate that seed removal is severely reduced in the hunted forest. Finally, genetic maternity exclusion analysis (using 3–7 nuclear microsatellite loci) of maternally inherited endocarp tissue from diaspores collected under the canopies of 12 fruiting "mother" trees (six trees per site) revealed that seed dispersal in the hunted forest is also greatly reduced. In the hunted forest with reduced mammal dispersal agents, only 1 of the 53 assayed endocarps (2%) did not match the mother and was determined to be from a dispersed diaspore. By contrast, in the protected forest, 20 of the 48 assayed endocarps (42%) were from dispersed diaspores. This study provides strong evidence that loss of dispersal agents can lead to reduced seed removal and loss of seed dispersal, disrupting the seed dispersal cycle.     

Macaronesia: a source of hidden genetic diversity for post‐glacial recolonization of western Europe in the leafy liverwort Radula lindenbergiana

Aim Bryophytes exhibit apparently low rates of endemism in Macaronesia and differ from angiosperms in their diversity patterns by the widespread occurrence of endemics within and among archipelagos. This paper investigates the phylogeography of the leafy liverwort Radula lindenbergiana to determine: (1) whether or not morphologically cryptic diversification has occurred in Macaronesia, and (2) the relationships between Macaronesian and continental populations. Location Macaronesia, Europe, Africa. Methods Eighty‐four samples were collected across the species’ distribution range and sequenced at four chloroplast DNA (cpDNA) loci (atpB–rbcL, trnG, trnL and rps4). Phylogenetic reconstructions and Bayesian ancestral area reconstructions were used in combination with population genetics statistics (H, N_ST, F_ST) to describe the pattern of present genetic diversity in R. lindenbergiana and infer its biogeographic history. Results Patterns of genetic diversity in R. lindenbergiana exhibit a striking westwards gradient, wherein haplotype (0.90) and nucleotide (0.0038 ± 0.0019) diversity peak in Macaronesia, with a substantial endemic component. We found 20.9% of the genetic variance between biogeographic regions, and most pairwise F_ST comparisons between regions are significantly different from zero. The global N_ST (0.78) is significantly higher than the global F_ST (0.20), providing evidence for the presence of phylogeographic signal in the data. Ancestral area reconstructions suggest that the haplotypes currently found in western Europe share a Macaronesian common ancestor. Main conclusions The haplotype diversification exhibited by R. lindenbergiana in Macaronesia is comparable to that reported for many angiosperm groups at the species level. The apparent lack of radiation among Macaronesian bryophytes may thus reflect the reduced morphology of bryophytes in comparison with angiosperms. The high diversity found among Macaronesian haplotypes, especially in Madeira and the Canary Islands, and the significant N_ST/F_ST ratio between Macaronesia and all the other biogeographic regions (an indication that mutation rate exceeds dispersal rates) suggest that Macaronesian archipelagos could have served as a refugium during the Quaternary glaciations. Many haplotypes currently found in Europe share a Macaronesian common ancestor, and this further suggests that Macaronesia might have played a key role in the back‐colonization of the continent.     

Response surface optimization for joint contact model evaluation

When optimization is used to evaluate a joint contact model's ability to reproduce experimental measurements, the high computational cost of repeated contact analysis can be a limiting factor. This paper presents a computationally-efficient response surface optimization methodology to address this limitation. Quadratic response surfaces were fit to contact quantities (contact force, maximum pressure, average pressure, and contact area) predicted by a discrete element contact model of the tibiofemoral joint for various combinations of material modulus and relative bone pose (i.e., position and orientation). The response surfaces were then used as surrogates for costly contact analyses in optimizations that minimized differences between measured and predicted contact quantities. The methodology was evaluated theoretically using six sets of synthetic (i.e., computer-generated) contact data, and practically using one set of experimental contact data. For the synthetic cases, the response surface optimizations recovered all contact quantities to within 3.4% error. For the experimental case, they matched all contact quantities to within 6.3% error except for maximum contact pressure, which was in error by up to 50%. Response surface optimization provides rapid evaluation of joint contact models within a limited range of relative bone poses and can help identify potential weaknesses in contact model formulation and/or experimental data quality.     

Characterization of the Cardiac Overexpression of HSPB2 Reveals Mitochondrial and Myogenic Roles Supported by a Cardiac HspB2 Interactome

Small Heat Shock Proteins (sHSPs) are molecular chaperones that transiently interact with other proteins, thereby assisting with quality control of proper protein folding and/or degradation. They are also recruited to protect cells from a variety of stresses in response to extreme heat, heavy metals, and oxidative-reductive stress. Although ten human sHSPs have been identified, their likely diverse biological functions remain an enigma in health and disease, and much less is known about non-redundant roles in selective cells and tissues. Herein, we set out to comprehensively characterize the cardiac-restricted Heat Shock Protein B-2 (HspB2), which exhibited ischemic cardioprotection in transgenic overexpressing mice including reduced infarct size and maintenance of ATP levels. Global yeast two-hybrid analysis using HspB2 (bait) and a human cardiac library (prey) coupled with co-immunoprecipitation studies for mitochondrial target validation revealed the first HspB2 “cardiac interactome” to contain many myofibril and mitochondrial-binding partners consistent with the overexpression phenotype. This interactome has been submitted to the Biological General Repository for Interaction Datasets (BioGRID). A related sHSP chaperone HspB5 had only partially overlapping binding partners, supporting specificity of the interactome as well as non-redundant roles reported for these sHSPs. Evidence that the cardiac yeast two-hybrid HspB2 interactome targets resident mitochondrial client proteins is consistent with the role of HspB2 in maintaining ATP levels and suggests new chaperone-dependent functions for metabolic homeostasis. One of the HspB2 targets, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), has reported roles in HspB2 associated phenotypes including cardiac ATP production, mitochondrial function, and apoptosis, and was validated as a potential client protein of HspB2 through chaperone assays. From the clientele and phenotypes identified herein, it is tempting to speculate that small molecule activators of HspB2 might be deployed to mitigate mitochondrial related diseases such as cardiomyopathy and neurodegenerative disease.     

Landscape fragmentation affects responses of avian communities to climate change

Forecasting the consequences of climate change is contingent upon our understanding of the relationship between biodiversity patterns and climatic variability. While the impacts of climate change on individual species have been well‐documented, there is a paucity of studies on climate‐mediated changes in community dynamics. Our objectives were to investigate the relationship between temporal turnover in avian biodiversity and changes in climatic conditions and to assess the role of landscape fragmentation in affecting this relationship. We hypothesized that community turnover would be highest in regions experiencing the most pronounced changes in climate and that these patterns would be reduced in human‐dominated landscapes. To test this hypothesis, we quantified temporal turnover in avian communities over a 20‐year period using data from the New York State Breeding Atlases collected during 1980–1985 and 2000–2005. We applied Bayesian spatially varying intercept models to evaluate the relationship between temporal turnover and temporal trends in climatic conditions and landscape fragmentation. We found that models including interaction terms between climate change and landscape fragmentation were superior to models without the interaction terms, suggesting that the relationship between avian community turnover and changes in climatic conditions was affected by the level of landscape fragmentation. Specifically, we found weaker associations between temporal turnover and climatic change in regions with prevalent habitat fragmentation. We suggest that avian communities in fragmented landscapes are more robust to climate change than communities found in contiguous habitats because they are comprised of species with wider thermal niches and thus are less susceptible to shifts in climatic variability. We conclude that highly fragmented regions are likely to undergo less pronounced changes in composition and structure of faunal communities as a result of climate change, whereas those changes are likely to be greater in contiguous and unfragmented habitats.     

Expression of the mRNA encoding truncated PPARα does not correlate with hepatic insensitivity to peroxisome proliferators

Two alternatively spliced forms of human PPAR mRNA, PPAR1 and PPAR2, have been identified. PPAR1 mRNA gives rise to an active PPAR protein while PPAR2 mRNA gives rise to a form of PPAR which lacks the ligand-binding domain. PPAR2 is unable to activate a peroxisome proliferator response element (PPRE) reporter gene construct in transient transfection assays. Both PPAR1 and PPAR2 mRNA are present in human liver, kidney, testes, heart, small intestine, and smooth muscle. In human liver, PPAR2 mRNA abundance is approximately half that of PPAR1 mRNA; a correlation analysis of PPAR1 and PPAR2 mRNA mass revealed an r-value of 0.75 (n = 18). Additional studies with intact liver from various species, showed that the PPAR2/PPAR1 mRNA ratios in rat, rabbit, and mouse liver were less than 0.10; significantly lower than the 0.3 and 0.5 ratios observed in monkey and human livers, respectively. To determine if a high PPAR2/PPAR1 mRNA ratio was associated with insensitivity to peroxisome proliferators, we treated human, rat, and rabbit hepatocytes with WY14643, a potent PPARa activator, and measured acyl CoA oxidase (ACO) mRNA levels. Rat ACO mRNA levels increased markedly in response to WY14643 while human and rabbit hepatocytes were unresponsive. Thus, although the PPAR2/PPAR1 mRNA ratio is low in rabbits, this species is not responsive to peroxisome proliferators. Further studies with male and female rats, which vary significantly in their response to peroxisome proliferators, showed little difference in the ratio of PPAR2/PPAR1 mRNA. These data suggest that selective PPAR2 mRNA expression is not the basis for differential species or gender responses to peroxisome proliferators.     

S-Nitrosothiol measurements in biological systems

S-Nitrosothiol (SNO) cysteine modifications are regulated signaling reactions that dramatically affect, and are affected by, protein conformation. The lability of the SNO bond can make SNO-modified proteins cumbersome to measure accurately. Here, we review methodologies for detecting SNO modifications in biology. There are three caveats. (1) Many assays for biological SNOs are used near the limit of detection: standard curves must be in the biologically relevant concentration range. (2) The assays that are most reliable are those that modify SNO protein or peptide chemistry the least. (3) Each result should be quantitatively validated using more than one assay. Improved assays are needed and are in development.