Ximelagatran increases membrane fluidity and changes membrane lipid composition in primary human hepatocytes

Effects of Bisphenol A on redox balance in red blood and sperm cells and spermatic quality in zebrafish Danio rerio

Bisphenol-A (BPA) is a potential endocrine disruptor besides being associated with oxidative damage in several vertebrate classes. In the present study we investigated oxidative effects in erythrocytes and sperm cells as well as spermatic quality in Danio rerio exposed to 14 days at BPA concentrations of 2, 10 and 100 μg/L. Organelles structure, reactive species of oxygen (ROS) and lipoperoxidation (LPO) on erythrocytes and sperm cells were measured by flow cytometry and spermatic parameters were analyzed by the computer-assisted sperm analysis (CASA) system. For both cell types, when compared with control BPA treatment induced a significant increase in ROS and LPO production causing the membrane fluidity disorder, loss of membrane integrity and mitochondrial functionality. Furthermore, it was found a significant increase in DNA fragmentation in erythrocytes of zebrafish BPA exposed. Regarding the spermatic quality, results showed lower sperm motility in animals exposed to BPA, and alterations on velocity parameters of spermatozoa. Thus, the present study concludes that BPA affects the oxidative balance of both cell types, and that can directly affects the reproductive success of the adult Danio rerio. The sensitivity of erythrocytes to oxidative damage induced by BPA was similar to sperm cells, indicating a potential use of blood cells as indicators of oxidative damage present in fish sperm.

Membranar effects exerted in vitro by polyphenols - quercetin, epigallocatechin gallate and curcumin - on HUVEC and Jurkat cells, relevant for diabetes mellitus

Polyphenols are largely studied for their beneficial action in various pathologies, but the correlation with their effects on cell membranes is still elusive. In the present study we assessed the effects exerted in vitro by quercetin, epigallocatechin gallate and curcumin on membrane fluidity and transmembrane potential of human umbilical vein endothelial cells and Jurkat T lymphoblasts, in experimental conditions mimicking diabetes mellitus, i.e. high glucose conditions or increased concentration of advanced glycation end products. Results showed that the investigated polyphenols had beneficial effects on cell membranes altered in diabetic conditions, by restoring transmembrane potential and by membrane "stiffening". Moreover, they limited the release of pro-inflammatory factors, like monocyte chemotactic protein-1. These effects were more obvious for cells exposed to advanced glycation end products specific for the late stages of diabetes. Apparently, the inhibitory action of polyphenols on lipid peroxidation was associated with a decrease of membrane fluidity. Concluding, our in vitro study highlighted the potential beneficial action of polyphenols mainly in the late stages of diabetes, exerted at the level of membrane fluidity and transmembrane potential, accompanied by an anti-inflammatory effect on endothelial and immune cells.

Quercetin and epigallocatechin gallate induce in vitro a dose-dependent stiffening and hyperpolarizing effect on the cell membrane of human mononuclear blood cells

The bioactivity of polyphenols is closely linked to their ability to interact with biological membranes. The study evaluates the in vitro effect of quercetin and epigallocatechin on the membrane anisotropy and transmembrane potential of peripheral blood mononuclear cells (PBMCs) isolated from 26 type 2 diabetes mellitus patients compared to 25 age matched controls. The in vitro assays were analyzed in correlation with the biochemical and inflammatory profile of the subjects and with insulin resistance parameters (HOMA-IR, plasma resistin) as well. For type 2 diabetes patients, the increase of HOMA-IR and resistin concentration was associated with a significant decrease of the PBMCs membrane anisotropy. The two tested polyphenols induced a dose-dependent hyperpolarizing effect and stiffening of the cell membranes for all tested subjects. Physiological levels of quercetin and epigallocatechin gallate had the tendency to normalize the PBMCs membrane anisotropy of the cells isolated from diabetes patients, bringing it to the level of cells isolated from normoglycemic ones. Epigallocatechin gallate induced higher effects compared to quercetin on the membranes isolated from subjects with higher cardiovascular risk. The decrease of membrane fluidity and the hyperpolarizing effect could explain the cardiovascular protective action of the tested compounds.

Tacrine and its analogues impair mitochondrial function and bioenergetics: a lipidomic analysis in rat brain

Tacrine is an acetylcholinesterase (AChE) inhibitor used as a cognitive enhancer in the treatment of Alzheimer's disease (AD). However, its low therapeutic efficiency and a high incidence of side effects have limited its clinical use. In this study, the molecular mechanisms underlying the impact on brain activity of tacrine and two novel tacrine analogues (T1, T2) were approached by focusing on three aspects: (i) their effects on brain cholinesterase activity; (ii) perturbations on electron transport chain enzymes activities of non-synaptic brain mitochondria; and (iii) the role of mitochondrial lipidome changes induced by these compounds on mitochondrial bioenergetics. Brain effects were evaluated 18 h after the administration of a single dose (75.6 μmol/kg) of tacrine or tacrine analogues. The three compounds promoted a significant reduction in brain AChE and butyrylcholinesterase (BuChE) activities. Additionally, tacrine was shown to be more efficient in brain AChE inhibition than T2 tacrine analogue and less active than T1 tacrine analogue, whereas BuChE inhibition followed the order: T1 > T2 > tacrine. The studies using non-synaptic brain mitochondria show that all the compounds studied disturbed brain mitochondrial bioenergetics mainly via the inhibition of complex I activity. Furthermore, the activity of complex IV is also affected by tacrine and T1 treatments while FoF(1) -ATPase is only affected by tacrine. Therefore, the compounds' toxicity as regards brain mitochondria, which follows the order: tacrine >> T1 > T2, does not correlate with their ability to inhibit brain cholinesterase enzymes. Lipidomics approaches show that phosphatidylethanolamine (PE) is the most abundant phospholipids (PL) class in non-synaptic brain mitochondria and cardiolipin (CL) present the greatest diversity of molecular species. Tacrine induced significant perturbations in the mitochondrial PL profile, which were detected by means of changes in the relative abundance of phosphatidylcholine (PC), PE, phosphatidylinositol (PI) and CL and by the presence of oxidized phosphatidylserines. Additionally, in both the T1 and T2 groups, the lipid content and molecular composition of brain mitochondria PL are perturbed to a lesser extent than in the tacrine group. Abnormalities in CL content and the amount of oxidized phosphatidylserines were associated with significant reductions in mitochondrial enzymes activities, mainly complex I. These results indicate that tacrine and its analogues impair mitochondrial function and bioenergetics, thus compromising the activity of brain cells.

Advances in anticoagulation: focus on dabigatran, an oral direct thrombin inhibitor

Dabigatran is an oral direct thrombin inhibitor with a rapid onset. Patients on dabigatran do not require coagulation monitoring. Recent prospective randomized trials have shown the efficacy of dabigatran for the prevention of venous thromboembolism after knee or hip arthroplasty and for the prevention of stroke and systemic embolism in nonvalvular atrial fibrillation. Because dabigatran is cleared principally by the kidneys, dosage adjustments are required in the setting of renal dysfunction. There currently is no reversal agent for dabigatran although hemodialysis can facilitate its rapid removal in life-threatening circumstances. The management of severe bleeding associated with dabigatran also may include the administration of a procoagulant, such as recombinant activated factor VII. Based on recent guidelines, regional anesthesia should be used cautiously in patients taking this novel oral thrombin inhibitor.

Dabigatran: An Oral Novel Potent Reversible Nonpeptide Inhibitor of Thrombin

Dabigatran is a highly selective, reversible, and potent thrombin inhibitor and is orally available as the prodrug, dabigatran etexilate. It has shown antithrombotic efficacy in animal models of thrombosis, with a rapid onset of action and predictable pharmacodynamic response. Peak plasma concentrations of dabigatran occur 1 to 2 hours after ingestion of the prodrug. The terminal half-life of dabigatran is 12 to 14 hours in elderly volunteers. Dabigatran is not metabolized by cytochrome P450 isoenzymes and does not interact with food. Dabigatran has a low potential for drug-drug interactions and is predominantly renally excreted. Dabigatran etexilate as chronic therapy effectively prevents the recurrence of venous thromboembolism and cardioembolic stroke. For the first time, it has been demonstrated clinically that there may be an effective and safe alternative to warfarin.

Lipidomics: a tool for studies of atherosclerosis

Lipids, abundant constituents of both the vascular plaque and lipoproteins, play a pivotal role in atherosclerosis. Mass spectrometry-based analysis of lipids, called lipidomics, presents a number of opportunities not only for understanding the cellular processes in health and disease but also in enabling personalized medicine. Lipidomics in its most advanced form is able to quantify hundreds of different molecular lipid species with various structural and functional roles. Unraveling this complexity will improve our understanding of diseases such as atherosclerosis at a level of detail not attainable with classical analytical methods. Improved patient selection, biomarkers for gauging treatment efficacy and safety, and translational models will be facilitated by the lipidomic deliverables. Importantly, lipid-based biomarkers and targets should lead the way as we progress toward more specialized therapeutics.