The main components of St John's Wort inhibit low-density lipoprotein atherogenic modification: A beneficial “side effect” of an OTC antidepressant drug?

Hypericin and pseudohypericin are polycyclic–phenolic structurally related compounds found in Hypericum perforatum L. (St John's wort). As hypericin has been found to bind to LDL one may assume that it can act as antioxidant of LDL lipid oxidation, a property which is of prophylactic/therapeutic interest regarding atherogenesis as LDL oxidation may play a pivotal role in the onset of atherosclerosis. Therefore, in the present paper hypericin, pseudohypericin and hyperforin, an other structurally unrelated constituent in St John's wort were tested in their ability to inhibit LDL oxidation. LDL was isolated by ultracentrifugation and oxidation was initiated either by transition metal ions (copper), tyrosyl radical (myeloperoxidase/hydrogen peroxide/tyrosine) or by endothelial cells (HUVEC). LDL modification was monitored by conjugated diene and malondialdehyde formation. The data show that all compounds (hypericin, pseudohypericin and hyperforin) at doses as low as 2.5 μmol/l are potent antioxidants in the LDL oxidation systems used. The results indicate that the derivatives found in Hypericum perforatum have possible antiatherogenic potential.     

The mechanism of oxidation-induced low-density lipoprotein aggregation: an analogy to colloidal aggregation and beyond?

Atherosclerosis is a disease initiated by lipoprotein aggregation and deposition in artery walls. In this study, the de novo low-density lipoprotein aggregation process was examined. Nine major intermediates were identified in two stages of the aggregation process. In the aggregation stage, low-density lipoprotein molecules aggregate and form nucleation units. The nucleation units chain together and form linear aggregates. The linear aggregates branch and interact with one another, forming fractals. In the fusion stage, spatially adjacent nucleation units in the fractal fuse into curved membrane surfaces, which, in turn, fuse into multilamellar or unilamellar vesicles. Alternatively, some adjacent nucleation units in the fractals assemble in a straight line and form rods. Subsequently, the rods flatten out into rough and then into smooth ribbons. Occasionally, tubular membrane vesicles are formed from the fractals. The aggregation stage seems to be analogous to colloidal aggregation and amyloid fiber formation. The fusion stage seems to be characteristic of the lipid-rich lipoproteins and is beyond colloidal aggregation and amyloid fiber formation.     

The low-density lipoprotein receptor gene family: a cellular Swiss army knife?

The low-density lipoprotein receptor gene family is an evolutionarily conserved group of cell-surface receptors produced by mammals and other organisms. Initially thought to be endocytic receptors that mediate the uptake of lipoproteins, recent findings have shown that these receptors have other roles in a range of cellular processes. Among other activities, members of this family act as signal transducers in neuronal migration processes, regulate synaptic plasticity or control vitamin homeostasis. Such multifunctionality is achieved by interaction with diverse cell-surface proteins including glycolipid-anchored receptors, G-protein-coupled receptors and ion channels. Here, we review the molecular interactions of this protein family with other cell-surface proteins that provide specificity and versatility - a versatility that may be reminiscent of a cellular Swiss army knife.     

The connections of Wnt pathway components with cell cycle and centrosome: side effects or a hidden logic?

Wnt signaling cascade has developed together with multicellularity to orchestrate the development and homeostasis of complex structures. Wnt pathway components – such as β-catenin, Dishevelled (DVL), Lrp6, and Axin-- are often dedicated proteins that emerged in evolution together with the Wnt signaling cascade and are believed to function primarily in the Wnt cascade. It is interesting to see that in recent literature many of these proteins are connected with cellular functions that are more ancient and not limited to multicellular organisms – such as cell cycle regulation, centrosome biology, or cell division. In this review, we summarize the recent literature describing this crosstalk. Specifically, we attempt to find the answers to the following questions: Is the response to Wnt ligands regulated by the cell cycle? Is the centrosome and/or cilium required to activate the Wnt pathway? How do Wnt pathway components regulate the centrosomal cycle and cilia formation and function? We critically review the evidence that describes how these connections are regulated and how they help to integrate cell-to-cell communication with the cell and the centrosomal cycle in order to achieve a fine-tuned, physiological response.     

The antihypertensive effect of peptides: a novel alternative to drugs?

Many types of bioactive peptides that inhibit angiotensin I, angiotensin I converting enzyme (ACE) and Ang II type 1 receptor (AT1) in the cardiovascular system contribute to the prevention and treatment of hypertension. These inhibitory peptides are derived from many food proteins or artificial synthetic products. Further research examining the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods. Our research also demonstrates that ACE inhibitory peptide LAP may lower blood pressure with no adverse effects.     

The renaissance of lipoprotein(a): Brave new world for preventive cardiology?

Lipoprotein(a) [Lp(a)] is a highly heritable cardiovascular risk factor. Although discovered more than 50 years ago, Lp(a) has recently re-emerged as a major focus in the fields of lipidology and preventive cardiology owing to findings from genetic studies and the possibility of lowering elevated plasma concentrations with new antisense therapy. Data from genetic, epidemiological and clinical studies have provided compelling evidence establishing Lp(a) as a causal risk factor for atherosclerotic cardiovascular disease. Nevertheless, major gaps in knowledge remain and the identification of the mechanistic processes governing both Lp(a) pathobiology and metabolism are an ongoing challenge. Furthermore, the complex structure of Lp(a) presents a major obstacle to the accurate quantification of plasma concentrations, and a universally accepted and standardized approach for measuring Lp(a) is required. Significant progress has been made in the development of novel therapeutics for selectively lowering Lp(a). However, before these therapies can be widely implemented further investigations are required to assess their efficacy, safety, and cost-efficiency in the prevention of cardiovascular events. We review recent advances in molecular and biochemical aspects, epidemiology, and pathobiology of Lp(a), and provide a contemporary update on the significance of Lp(a) in clinical medicine.“Progress lies not in enhancing what is, but in advancing toward what will be.” (Khalil Gibran)     

Pretreatment with statins improves early outcome in patients with first-ever ischaemic stroke: a pleiotropic effect of statins or a beneficial effect of hypercholesterolemia?

Background

Data from different studies suggest a favourable association between pretreatment with statins or hypercholesterolemia and outcome after ischaemic stroke. We examined whether there were differences in in-hospital mortality according to the presence or absence of statin therapy in a large population of first-ever ischaemic stroke patients and assessed the influence of statins upon early death and spontaneous neurological recovery.

Methods

In 2,082 consecutive patients with first-ever ischaemic stroke collected from a prospective hospital-based stroke registry during a period of 19 years (1986-2004), statin use or hypercholesterolemia before stroke was documented in 381 patients. On the other hand, favourable outcome defined as grades 0-2 in the modified Rankin scale was recorded in 382 patients.

Results

Early outcome was better in the presence of statin therapy or hypercholesterolemia (cholesterol levels were not measured) with significant differences between the groups with and without pretreatment with statins in in-hospital mortality (6% vs 13.3%, P = 0.001) and symptom-free (22% vs 17.5%, P = 0.025) and severe functional limitation (6.6% vs 11.5%, P = 0.002) at hospital discharge, as well as lower rates of infectious respiratory complications during hospitalization. In the logistic regression model, statin therapy was the only variable inversely associated with in-hospital death (odds ratio 0.57) and directly associated with favourable outcome (odds ratio 1.32).

Conclusions

Use of statins or hypercholesterolemia before first-ever ischaemic stroke was associated with better early outcome with a reduced mortality during hospitalization and neurological disability at hospital discharge. However, statin therapy may increase the risk of intracerebral haemorrhage, particularly in the setting of thrombolysis.

     

The ins and outs of tubulin acetylation: more than just a post-translational modification?

Microtubules are highly dynamic polymers of α/β tubulin heterodimers that play key roles in cell division and in organizing cell cytoplasm. Although they have been discovered more than two decades ago, tubulin post-translational modifications recently gained a new interest as their role was increasingly highlighted in neuron differentiation and neurodegenerative disorders. Here, we specifically focus on tubulin acetylation from its discovery to recent studies that provide new insights into how it is regulated in health and disease and how it impacts microtubule functions. Even though new mechanisms involving tubulin acetylation are regularly being uncovered, the molecular links between its location inside the microtubule lumen and its regulators and effectors is still poorly understood. This review highlights the emerging roles of tubulin acetylation in multiple cellular functions, ranging from cell motility, cell cycle progression or cell differentiation to intracellular trafficking and signalling. It also points out that tubulin acetylation should no longer be seen as a passive marker of microtubule stability, but as a broad regulator of microtubule functions.     

Decrease of memory retention in a parasitic wasp: an effect of host manipulation by Wolbachia?

Several factors, such as cold exposure, aging, the number of experiences and viral infection, have been shown to affect learning ability in different organisms. Wolbachia has been found worldwide as an arthropod parasite/mutualist symbiont in a wide range of species, including insects. Differing effects have been identified on physiology and behavior by Wolbachia. However, the effect of Wolbachia infection on the learning ability of their host had never previously been studied. The current study carried out to compare learning ability and memory duration in 2 strains of the parasitoid Trichogramma brassicae: 1 uninfected and 1 infected by Wolbachia. Both strains were able to associate the novel odors with the reward of an oviposition into a host egg. However, the percentage of females that responded to the experimental design and displayed an ability to learn in these conditions was higher in the uninfected strain. Memory duration was longer in uninfected wasps (23.8 and 21.4 h after conditioning with peppermint and lemon, respectively) than in infected wasps (18.9 and 16.2 h after conditioning with peppermint and lemon, respectively). Memory retention increased in response to the number of conditioning sessions in both strains, but memory retention was always shorter in the infected wasps than in the uninfected ones. Wolbachia infection may select for reduced memory retention because shorter memory induces infected wasps to disperse in new environments and avoid competition with uninfected wasps by forgetting cues related to previously visited environments, thus increasing transmission of Wolbachia in new environments.     

The p66shc protein: a mediator of the programmed death of an organism?

Recently knockout of the gene encoding an adaptor protein (p66shc) was shown both to prolong the life span of an animal and to prevent apoptosis of cells in response to added H2O2 (Migliaccio et al. [1999] Nature 402, 309-313). A hypothesis is put forward in which p66shc is assumed to be involved in phenoptosis, i.e., programmed death of an organism, mediated by the reactive oxygen species-dependent massive apoptosis in an organ of vital importance. The reactive oxygen species are suggested to oxidize phosphatidyl serine in the inner leaflet of the cell plasma membrane, resulting in appearance of this phospholipid in the outer membrane leaflet, an effect recognized by a special receptor and causing the p66shc phosphorylation at a serine residue. Serine-phosphorylated p66shc there is proposed to block mitosis and initiate apoptosis. The large-scale apoptosis leads to phenoptosis and, hence, shortens the life span of the organism.     

The effect of alpine ski-slopes on epigeic beetles: does even a nature-friendly management make a change?

Unique alpine ecosystems are threatened by skiing activities all over the world. We studied the effect of alpine ski-slopes on epigeic beetles by pitfall trapping in the Praděd National Nature Reserve (Czech Republic) where the management of ski-slopes has never caused any disturbance to the vegetation cover. Using a mixed modelling approach, we demonstrate a significant effect of ski-slope management on the epigeic beetle community, including its functional diversity. Beetle species responded to the ski-slope individually. We found a noticeable decline in the abundance of most species in the patches with artificially increased accumulation of snow, i.e. close to the interior edges of the ski-slopes. Above all, the ski-slopes were not preferred by relict species such as Neagolius limbolarius, Minota carpathica and Liotrichus affinis but vagile widespread carabids (Amara lunicollis, Poecilus versicolor) and herbivores associated with nitrophilous plants (Gastrophysa viridula) were more abundant on the ski-slopes. A few stenotypic carnivorous and herbivorous species were found on the ski-slopes. A high abundance of mountain herbivores such as leaf beetle Timarcha metallica reflected an increased occurrence of their host plants and carnivores such as Carabus sylvestris and Pterostichus oblongopunctatus could prefer ski-slopes due to the locally increased food supply. With respect to both uniqueness of alpine communities and to the small extent of alpine treeless zone, we recommend considering very cautiously any potential expansion of ski resorts, even those with reasonable ‘nature-friendly’ practices.     

Use of 82Br− radiotracer to study transmembrane halide flux: The effect of a tranquilizing drug,chlordiazepoxide on channel opening of a GABAA receptor

We used the short-lived radionuclide, ⁸²Br^– to follow -aminobutyrate (GABA) receptor-mediated halide exchange into membrane vesicles from rat cerebral cortex in millisecond and second time regions using quench-flow technique. The radioisotope was prepared by neutron capture [⁸¹Br^–(n,)⁸²Br^–] on irradiation of a natural isotope of bromine, ⁸¹Br^– in a neutron flux. ⁸²Br^– decays by -emission with secondary -emission. Possible advantages of ⁸²Br^– over ³⁶Cl^– in anion tracer measurements include, (a) a short lifetime (t_1/2 = 35.3 hr), which alleviates contamination and disposal problems, (b) high counting efficiency (1.54) due to the secondary radiation, (c) measurement with a -counter as well as a -counter, (d) a simple preparation not requiring subsequent purification steps giving a specific activity depending on the irradiation time. With 6 hr irradiation time the specific activity was sufficient to make measurements with <1 mm Br^–, which is less than the bromide concentration known to affect the properties of GABA_A receptor. The radiotracers, ⁸²Br^– and ³⁶Cl^– could be compared with the same solution composition. In conditions where a direct effect of binding of halide to receptor does not contribute to a difference in measured ion-flux, ⁸²Br^– was translocated only marginally faster than ³⁶Cl^–. The effect of chlordiazepoxide (CDPX) (2–250 m) on the progress of GABA (10 m)-mediated ⁸²Br^– uptake was measured in a time range of 200 msec to 20 sec using quench-flow technique. The two phases of anion exchange previously reported in this experimental model with GABA alone were observed. The rate of ⁸²Br^– exchange was increased 2.3-fold at 30–60 m CDPX and was not further increased with increasing [CDPX]. The rate of halide exchange is a measure of open channel concentration. The isotope exchange rate constant, J, in a membrane vesicle preparation, is a measure of the membrane permeability per internal volume/surface area, J = P_mA/V. Receptor desensitization rate was also increased by CDPX, but unlike the isotope exchange rate, it continued to increase up to at least 250 m CDPX.The authors thank the staff of the University of Missouri Research Reactor Center, Columbia (MURR) for their encouragement and help and for provision of [⁸²Br]NH₄Br. This work was supported in part by a grant from the Research Council of the University of Missouri Medical School and in part by the Missouri Agricultural Experiment Station (No. BCHB0307). P.S. held a Missouri Institute of Psychiatry fellowship.     

The efficiency of different salts to screen charge interactions in proteins: a Hofmeister effect?

Understanding the screening by salts of charge-charge interactions in proteins is important for at least two reasons: a), screening by intracellular salt concentration may modulate the stability and interactions of proteins in vivo; and b), the in vitro experimental estimation of the contributions from charge-charge interactions to molecular processes involving proteins is generally carried out on the basis of the salt effect on process energetics, under the assumption that these interactions are screened out by moderate salt concentrations. Here, we explore experimentally the extent to which the screening efficiency depends on the nature of the salt. To this end, we have carried out an energetic characterization of the effect of NaCl (a nondenaturing salt), guanidinium chloride (a denaturing salt), and guanidinium thiocyanate (a stronger denaturant) on the stability of the wild-type form and a T14K variant of Escherichia coli thioredoxin. Our results suggest that the efficiency of different salts to screen charge-charge interactions correlates with their denaturing strength and with the position of the constituent ions in the Hofmeister rankings. This result appears consistent with the plausible relation of the Hofmeister rankings with the extent of solute accumulation/exclusion from protein surfaces.