Ethical Implications of Pharmacogenetics – Do Slippery Slope Arguments Matter?

Pharmacogenetics is a rapidly expanding area of research exploring the relationship between inter-individual genetic variation and drug response, with the goal of developing genetically optimised therapies. Slippery slope arguments claim that a particular action should be rejected (or supported) because it might be the first step onto a slippery slope leading to undesirable (or desirable) consequences. In this article, several slippery slope arguments relevant to the context of pharmacogenetics are evaluated under consideration of underlying reasons for their popularity. The author concludes that although the examined arguments are unconvincing as slippery slope arguments, they do matter in this context. While positive slippery slope arguments serve as a driving force to fuel the development of pharmacogenetics, their negative counterparts play an important role to sensitise policy makers and the public to potential problems.     

Extending the stress‐gradient hypothesis – is competition among animals less common in harsh environments?

The role of positive interactions has become widely accepted as a mechanism shaping community dynamics. Most empirical evidence comes from plant communities and sessile marine organisms. However, evidence for the relative role of positive interactions in organizing terrestrial animal communities is more limited, and a general framework that includes positive interactions among animals is lacking. The ‘stress gradient hypothesis’ (SGH) developed by plant ecologists predicts that the balance between positive and negative interactions will vary along gradients of biotic and abiotic stress, with positive interactions being more important in stressful environments. Paralleling the SGH, stress gradients for terrestrial herbivores could be equated to inverse primary productivity gradients, so we would expect positive interactions to prevail in more stressful, low productivity environments. However, this contradicts the typical view of terrestrial animal ecology that low primary productivity systems will foster intense competition for resources among consumers. Here we use alpine herbivores as a case study to test one of the predictions of the SGH in animal communities, namely the prevalence of positive interactions in low productivity environments. We identify potential mechanisms of facilitation and review the limited number of examples of interspecific interactions among alpine herbivores to assess the role of positive and negative interactions in structuring their communities. A meta‐analysis showed no clear trend in the strength and direction of interactions among alpine herbivores. Although studies were biased towards reporting significant negative inter actions, we found no evidence of competition dominating in harsh environments. Thus, our results only partially support the SGH, but directly challenge the dominant view among animal ecologists. Clearly, a sound theoretical framework is needed to include competition, positive and neutral interactions as potential mechanisms determining the structure of animal communities under differing environmental conditions, and the stress‐gradient hypothesis can provide a solid starting point.     

How do reaction conditions affect the enantiopure synthesis of 2‐substituted‐1,4‐benzodioxane derivatives?

Several biologically active compounds structurally include the enantiopure 2‐substituted‐1,4‐benzodioxane scaffold. The straightforward racemization that affects reactions involving most of the common chemical reactives is thus a crucial issue. The developing of a completely stereo‐controlled synthetic route that does not affect the enantiomeric excess is consequently mandatory. It is also important to set up a reliable chiral HPLC method, able to follow the reaction, and to improve the synthetic performances. Here, we report the chiral investigation of two different synthons, we specifically evaluated the synthetic pathways that could be run in order to afford them, avoiding the racemization processes, which could normally occur in basic conditions. In addition, we developed peculiar chiral HPLC methods in order to resolve the enantiomers, define the enantiomeric excess, and fully characterize these compounds.     

How do digits emerge? – mathematical models of limb development

The mechanism that controls digit formation has long intrigued developmental and theoretical biologists, and many different models and mechanisms have been proposed. Here we review models of limb development with a specific focus on digit and long bone formation. Decades of experiments have revealed the basic signaling circuits that control limb development, and recent advances in imaging and molecular technologies provide us with unprecedented spatial detail and a broader view of the regulatory networks. Computational approaches are important to integrate the available information into a consistent framework that will allow us to achieve a deeper level of understanding, and that will help with the future planning and interpretation of complex experiments, paving the way to in silico genetics. Previous models of development had to be focused on very few, simple regulatory interactions. Algorithmic developments and increasing computing power now enable the generation and validation of increasingly realistic models that can be used to test old theories and uncover new mechanisms. Birth Defects Research (Part C) 102:1–12, 2014. © 2014 Wiley Periodicals, Inc.     

Role of α2‐macroglobulin in regulating amyloid β‐protein neurotoxicity: protective or detrimental factor?

alpha2-Macroglobulin (alpha2M) has been identified as a carrier protein for beta-amyloid (Abeta) decreasing fibril formation and affecting the neurotoxicity of this peptide. The alpha2-macroglobulin receptor/low density lipoprotein receptor related protein (LRP) is involved in the internalization and degradation of the alpha2M/Abeta complexes and its impairment has been reported to occur in Alzheimer's disease. Previous studies have shown alpha2M to determine an enhancement or a reduction of Abeta toxicity in different culture systems. In order to clarify the role of alpha2M in Abeta neurotoxicity, we challenged human neuroblastoma cell lines with activated alpha2M in combination with Abeta. Our results show that in neuroblastoma cells expressing high levels of LRP, the administration of activated alpha2M protects the cells from Abeta neurotoxicity. Conversely, when this receptor is not present alpha2M determines an increase in Abeta toxicity as evaluated by MTT and TUNEL assays. In LRP-negative cells transfected with the full-length human LRP, the addition of activated alpha2M resulted to be protective against Abeta-induced neurotoxicity. By means of recombinant proteins we ascribed the neurotoxic activity of alpha2M to its FP3 fragment which has been previously shown to bind and neutralize transforming growth factor-beta. These studies provide evidence for both a neuroprotective and neurotoxic role of alpha2M regulated by the expression of its receptor LRP.     

Anti‐atherosclerotic effects of vitamin E – myth or reality?

Atherosclerosis and its complications such as coronary heart disease, myocardial infarction and stroke are the leading causes of death in the developed world. High blood pressure, diabetes, smoking and a diet high in cholesterol and lipids clearly increase the likelihood of premature atherosclerosis, albeit other factors, such as the individual genetic makeup, may play an additional role. Several epidemiological studies and intervention trials have been performed with vitamin E, and some of them showed that it prevents atherosclerosis. For a long time, vitamin E was assumed to act by decreasing the oxidation of LDL, a key step in atherosclerosis initiation. However, at the cellular level, vitamin E acts by inhibition of smooth muscle cell proliferation, platelet aggregation, monocyte adhesion, oxLDL uptake and cytokine production, all reactions implied in the progression of atherosclerosis. Recent research revealed that these effects are not the result of the antioxidant activity of vitamin E, but rather of precise molecular actions of this compound. It is assumed that specific interactions of vitamin E with enzymes and proteins are at the basis of its non-antioxidant effects. Vitamin E influences the activity of several enzymes (e.g. PKC, PP2A, COX-2, 5-lipooxygenase, nitric oxide synthase, NADPH-oxidase, superoxide dismutase, phopholipase A2) and modulates the expression of genes that are involved in atherosclerosis (e.g. scavenger receptors, integrins, selectins, cytokines, cyclins). These interactions promise to reveal the biological properties of vitamin E and allow designing better strategies for the protection against atherosclerosis progression.     

Lipopolysaccharide‐induced increase in signalling in hippocampus is abrogated by IL‐10 – a role for IL‐1β?

Parenterally administered lipopolysaccharide (LPS) increases the concentration of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) in the rat hippocampus and evidence suggests that this effect plays a significant role in inhibiting long-term potentiation (LTP). The anti-inflammatory cytokine IL-10, antagonizes certain effects of IL-1beta, so if the effects of LPS are mediated through an increase in IL-1beta, it might be predicted that IL-10 would also abrogate the effect of LPS. Here, we report that IL-10 reversed the inhibitory effect of LPS on LTP and the data couple this with an inhibitory effect on the LPS-induced increase in IL-1beta. LPS treatment increased hippocampal expression of IL-1 receptor Type I protein. Consistent with the LPS-induced increases in IL-1beta concentration and receptor expression, were downstream changes which included enhanced phosphorylation of IRAK and the stress-activated kinases, JNK and p38; these LPS-induced changes were reversed by IL-10, which concurs with the idea that these events are triggered by increased activation of IL-1RI by IL-1beta. We provide evidence which indicates that LPS treatment leads to evidence of cell death and this was reversed in hippocampus prepared from LPS-treated rats which received IL-10. The evidence is therefore consistent with the idea that IL-10 acts to protect neuronal tissue from the detrimental effects induced by LPS.     

Centenarians – a useful model for healthy aging? A 29‐year follow‐up of hospitalizations among 40 000 Danes born in 1905

Centenarians surpass the current human life expectancy with about 20–25 years. However, whether centenarians represent healthy aging still remains an open question. Previous studies have been hampered by a number of methodological shortcomings such as a cross-sectional design and lack of an appropriate control group. In a longitudinal population-based cohort, it was examined whether the centenarian phenotype may be a useful model for healthy aging. The study was based on a complete follow up of 39 945 individuals alive in the Danish 1905 birth cohort on January 1, 1977 identified through the Danish Civil Registration System (DCRS). Data from the Danish Demographic Database and The Danish National Patient Register (in existence since 1977) were used. The 1905 cohort was followed up from 1977 through 2004 with respect to hospitalizations and number of hospital days. Survival status was available until December 2006. Danish centenarians from the 1905 cohort were hospitalized substantially less than their shorter-lived contemporaries at the same point in time during the years 1977 through 2004. For example, at age 71–74, the proportion of nonhospitalized centenarians was 80.5% compared with 68.4% among individuals who died in their early 80s. This trend was evident in both sexes. As a result of their lower hospitalization rates and length of stay in hospital compared with their contemporaries, who died at younger ages, Danish centenarians represent healthy agers. Centenarians constitute a useful study population in the search for fixed traits associated with exceptional longevity, such as genotype.     

How consistent is RAD‐seq divergence with DNA‐barcode based clustering in insects?

Promoted by the barcoding approach, mitochondrial DNA is more than ever used as a molecular marker to identify species boundaries. Yet, it has been repeatedly argued that it may be poorly suited for this purpose, especially in insects where mitochondria are often associated with invasive intracellular bacteria that may promote their introgression. Here, we inform this debate by assessing how divergent nuclear genomes can be when mitochondrial barcodes indicate very high proximity. To this end, we obtained RAD‐seq data from 92 barcode‐based species‐like units (operational taxonomic units [OTUs]) spanning four insect orders. In 100% of the cases, the observed median nuclear divergence was lower than 2%, a value that was recently estimated as one below which nuclear gene flow is not uncommon. These results suggest that although mitochondria may occasionally leak between species, this process is rare enough in insects to make DNA barcoding a reliable tool for clustering specimens into species‐like units.     

Can the combination of electrochemical regeneration of NAD+, selectivity of L‐α‐amino‐acid dehydrogenase,and reductive amination of α‐keto‐acid be applied to the inversion of configuration of a L‐α‐amino‐acid?

The inversion of configuration of L‐alanine can be carried out by combining its selective oxidation in the presence of NAD⁺ and L‐alanine dehydrogenase, electrochemical regeneration of the NAD⁺ at a carbon felt anode, and reductive amination of pyruvate, i.e., reduction of its imino derivative at a mercury cathode, the reaction mixture being buffered with concentrated ammonium/ammonia (1.28M / 1.28M). The dehydrogenase exhibits astonishing activity and stability under such extreme conditions of pH and ionic strength. The main drawback of the process is its slowness. At best, the complete inversion of a 10 mM solution of L‐alanine requires 140 h. A careful and detailed quantitative analysis of each of the key steps involved shows that the enzyme catalyzed oxidation is so thermodynamically uphill that it can be driven efficiently to completion only when both the coenzyme regeneration and the pyruvate reduction are very effective. The first condition is easily fulfilled. Under the best conditions, it is the rate of the chemical reaction producing the imine which controls the whole process kinetically. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 101–107, 1999.     

Phylogeny of γ‐proteobacteria: resolution of one branch of the universal tree?

The reconstruction of bacterial evolutionary relationships has proven to be a daunting task because variable mutation rates and horizontal gene transfer (HGT) among species can cause grave incongruities between phylogenetic trees based on single genes. Recently, a highly robust phylogenetic tree was constructed for 13 gamma-proteobacteria using the combined alignments of 205 conserved orthologous proteins.1 Only two proteins had incongruent tree topologies, which were attributed to HGT between Pseudomonas species and Vibrio cholerae or enterics. While the evolutionary relationships among these species appears to be resolved, further analysis suggests that HGT events with other bacterial partners likely occurred; this alters the implicit assumption of gamma-proteobacteria monophyly. Thus, any thorough reconstruction of bacterial evolution must not only choose a suitable set of molecular markers but also strive to reduce potential bias in the selection of species.