Selective COX-2 inhibitors and risk of myocardial infarction

Selective inhibitors of cyclooxygenase- 2 ( COX- 2, ` coxibs') are highly effective anti-inflammatory and analgesic drugs that exert their action by preventing the formation of prostanoids. Recently some coxibs, which were designed to exploit the advantageous effects of non- steroidal anti-inflammatory drugs while evading their side effects, have been reported to increase the risk of myocardial infarction and atherothrombotic events. This has led to the withdrawal of rofecoxib from global markets, and warnings have been issued by drug authorities about similar events during the use of celecoxib or valdecoxib/ parecoxib, bringing about questions of an inherent atherothrombotic risk of all coxibs and consequences that should be drawn by health care professionals. These questions need to be addressed in light of the known effects of selective inhibition of COX- 2 on the cardiovascular system. Although COX- 2, in contrast to the cyclooxygenase-1 ( COX- 1) isoform, is regarded as an inducible enzyme that only has a role in pathophysiological processes like pain and inflammation, experimental and clinical studies have shown that COX- 2 is constitutively expressed in tissues like the kidney or vascular endothelium, where it executes important physiological functions. COX- 2- dependent formation of prostanoids not only results in the mediation of pain or inflammatory signals but also in the maintenance of vascular integrity. Especially prostacyclin ( PGI(2)), which exerts vasodilatory and antiplatelet properties, is formed to a significant extent by COX- 2, and its levels are reduced to less than half of normal when COX- 2 is inhibited. This review outlines the rationale for the development of selective COX- 2 inhibitors and the pathophysiological consequences of selective inhibition of COX- 2 with special regard to vasoactive prostaglandins. It describes coxibs that are currently available, evaluates the current knowledge on the risk of atherothrombotic events associated with their intake and critically discusses the consequences that should be drawn from these insights. Copyright (C) 2005 S. Karger AG, Basel

Magnetofection potentiates gene delivery to cultured endothelial cells

Modification of cellular functions by overexpression of genes is increasingly practised for research of signalling pathways, but restricted by limitations of low efficiency. We investigated whether the novel technique of magnetofection (MF) could enhance gene transfer to cultured primary endothelial cells. MF of human umbilical vein endothelial cells (HUVEC) increased transfection efficiency of a luciferase reporter gene up to 360-fold compared to various conventional transfection systems. In contrast, there was only an up to 1.6-fold increase in toxicity caused by MF suggesting that the advantages of MF outbalanced the increase in toxicity. MF efficiently increased transfection efficiency using several commercially available cationic lipid transfection reagents and polyethyleneimine (PEI). Using PEI, even confluent HUVEC could be efficiently transfected to express luciferase activity. Using a green fluorescent protein vector maximum percentages of transfected cells amounted up to 38.7% while PEI without MF resulted in only 1.3% transfected cells. Likewise, in porcine aortic endothelial cells MF increased expression of a luciferase or beta-galactosidase reporter, reaching an efficiency of 37.5% of cells. MF is an effective tool for pDNA transfection of endothelial cells allowing high efficiencies. It may be of great use for investigating protein function in cell culture experiments

Sensitive superoxide detection in vascular cells by the new chemiluminescence dye L-012

The detection superoxide production in vascular cells is usually limited by a low sensitivity of available assays, We tested the applicability of the luminol derivate L-012 {[}8-amino-5-chloro-7-phenylpyridol{[}3,4-d]pyridazine-l,4(2H,3H)dione] to measure superoxide production in cultured endothelial cells (human umbilical vein endothelial cells) and rat aortic segments. Following stimulation with the protein kinase stimulator phorbol 12-myristate 13-acetate (PMA, 1 mu M) there was an 2,8-fold increase of L-012 chemiluminescence, whereas incubation with angiotensin II (100 nM) did not result in a measurable increase. Addition of vanadate (100 mu M) considerably increased the chemiluminescence (up to 17-fold) after PMA and made possible the detection of an enhanced superoxide production after stimulation with angiotensin II (by 1.7-fold). This was due to a similar to 9-fold increase in signal intensity of L-012 in the presence of vanadate, Prolonged incubation with vanadate also led to a tyrosine phosphorylation-dependent increase in superoxide formation which was predominantly produced by an NAD(P)H oxidase. Short-Term vanadate-enhanced L-012 chemiluminescence represents a highly sensitive assay making it possible to detect small changes of superoxide formation in intact vascular cells. Copyright(C) 1999 S. Karger AG. Basel

Antiplatelet drugs in cardiological practice: Established strategies and new developments

A common pathophysiological course in vascular diseases is an overwhelming activation and aggregation of blood platelets, which results in atherothrombosis. By causing the last decisive step of cerebral, coronary, or peripheral arterial ischemia thrombotic complications of atherosclerotic disease represent a major player in death cause statistics of most western countries. The development of novel therapies against platelet-dependent thrombosis and the concurrent improvement of existing therapeutic strategies thus is a paramount focus of pharmaceutical research. Currently, efficiency, dosing and indications of established antiplatelet substances are being re-evaluated, whilst new, so far unrecognized molecular targets for inhibition of platelet activity come up front. This not only allows for interesting new therapeutical options, but also widens our insight into the role platelets play in atherosclerosis in general. This article summarizes the relevant pathophysiology of platelet activation, presents current concepts in antiplatelet drug therapy, and highlights the role of platelets in vascular diseases apart from atherothrombosis

Different Modulation of the Cortical Silent Period by Two Phases of Short Interval Intracortical Inhibition

PURPOSE: To investigate the influence of 2 phases of short interval intracortical inhibition (SICI) on the cortical silent period (SP). MATERIALS AND METHODS: Single- and paired-pulse transcranial magnetic stimulations (TMSs) at 1 and 2.5ms interstimulus intervals (ISIs) were applied to the left motor cortex in 12 healthy subjects while their right hand muscles were moderately activated. Conditioning stimulation intensity was 90% of the active motor threshold (AMT). Test stimulation intensities were 120, 140, 160, 180, 200, 220, 240, 260% of the AMT and at 100% of the maximal stimulator output, the order of which was arranged randomly. The rectified electromyography area of motor evoked potential (MEP) and duration of the SP were measured off-line using a computerized program. RESULTS: At high-test stimulation intensities, MEP areas were saturated in both single- and paired-pulse stimulations, except that saturated MEPs were smaller for the paired-pulse TMS at 1ms ISI than for the other conditions. As the test stimulation intensity increased, SP was progressively prolonged in both single- and paired-pulse stimulations but was shorter in paired-pulse than single-pulse TMS. Overall, the ratio of SP duration/MEP area was comparable between single- and paired-pulse TMS except for the paired-pulse TMS at 1 ms ISI with a test stimulation intensity at 140-180% of the AMT, in which the ratio was significantly higher than in the single pulse TMS. CONCLUSION: These results suggest that 2 phases of SICI modulate MEP saturation and SP duration differently and provide additional evidence supporting the view that 2 phases of SICI are mediated by different inhibitory mechanisms.ope

Crucial role of local peroxynitrite formation in neutrophil-induced endothelial cell activation

Introduction and methods: The reaction of superoxide anions and NO not only results in a decreased availability of NO, but also leads to the formation of peroxynitrite, the role of which in the cardiovascular system is still discussed controversially. In cultured human endothelial cells, we studied whether there is a significant interaction between endothelial NO and neutrophil-derived superoxide anions in terms of endothelial peroxynitrite formation. We particularly studied whether a significantly higher redox-stress can be found in those endothelial cells directly adjacent to an activated neutrophil. Results: A considerable part of the 2,7-dihydrodichlorofluoresceine signal in endothelial cells was due to oxidation by peroxynitrite. Providing superoxide radicals by enzymatic source or by the neutrophil respiratory burst increased the fluorescence, which was attenuated by blockade of endothelial NO-synthase, suggesting that peroxynitrite was formed from neutrophil- or extracellular enzyme-derived superoxide and endothelial NO. Considerably higher fluorescence intensity was observed in endothelial cells in direct neighborhood to a neutrophil. This was particularly pronounced in the presence of a NO-donor and was accompanied by a strong activation of NF-κB and increased expression of E-selectin in these cells. Conclusion: Endothelial cells adjacent to neutrophils may have elevated levels of peroxynitrite that result in an increased expression of adhesion molecules. Such cells might represent a preferential site for adhesion and migration of additional neutrophils when simultaneously high concentrations of NO and neutrophil-derived superoxide are present

Platelet mitochondrial membrane depolarization reflects disease severity in patients with sepsis and correlates with clinical outcome

Introduction: Sepsis is still a leading cause of morbidity and mortality, even in modern times, and thrombocytopenia has been closely associated with unfavorable disease outcome. Decreases in mitochondrial membrane potential (depolarization) were found in different tissues during sepsis. Previous work suggests that mitochondrial dysfunction of platelets correlates with clinical disease activity in sepsis. However, platelet mitochondrial membrane potential (Mmp) has not been investigated in a clinical follow-up design and not with regard to disease outcome. Methods: In this study, platelet mitochondrial membrane depolarization was assessed by means of a fluorescent Mmp-Index with flow cytometry in 26 patients with sepsis compared with control patients. Platelet Mmp-Index on admission was correlated with the clinical disease scores Acute Physiology and Chronic Health Evaluation Score II (APACHE II), Sequential Organ Failure Score (SOFA), and Simplified Acute Physiology Score II (SAPS II). Finally, platelet Mmp-Index on admission and follow-up were compared in the group of sepsis survivors and nonsurvivors. Expression of the prosurvival protein Bcl-xL in platelets was quantified by immunoblotting. Results: Platelet mitochondrial membrane depolarization correlated significantly with the simultaneously assessed clinical disease severity by APACHE II (r = -0.867; P < 0.0001), SOFA (r = -0.857; P < 0.0001), and SAPS II score (r = -0.839; P < 0.0001). Patients with severe sepsis showed a significant reduction in platelet Mmp-Index compared with sepsis without organ failure (0.18 (0.12 to 0.25) versus 0.79 (0.49 to 0.85), P < 0.0006) or with the control group (0.18 (0.12 to 0.25) versus 0.89 (0.68 to 1.00), P < 0.0001). Platelet Mmp-Index remained persistently low in sepsis nonsurvivors (0.269 (0.230 to 0.305)), whereas we observed recovery of platelet Mmp-Index in the survivor group (0.9 (0.713 to 1.017)). Furthermore, the level of prosurvival protein Bcl-xL decreased in platelets during severe sepsis. Conclusion: In this study, we demonstrated that mitochondrial membrane depolarization in platelets correlates with clinical disease severity in patients with sepsis during the disease course and may be a valuable adjunct parameter to aid in the assessment of disease severity, risk stratification, and clinical outcome

Successful switching from insulin to sulfonylurea in a 3-month-old infant with diabetes due to p.G53D mutation in

Permanent neonatal diabetes mellitus is most commonly caused by mutations in the ATP-sensitive potassium channel (KATP) subunits. Prompt initiation of sulfonylurea treatment can improve glycemic control in children with KCNJ11 mutation. In this report, we present a case of permanent neonatal diabetes caused by a mutation in the KCNJ11 gene that was successfully treated via early switching of insulin to sulfonylurea treatment. A 53-day-old female infant presented with diabetic ketoacidosis. Insulin was administered for the ketoacidosis and blood glucose regulation. At 3 months of age, using genomic DNA extracted from peripheral lymphocytes, direct sequencing of KCNJ11 identified a heterozygous mutation of c.158G>A (p.G53D) and confirmed the diagnosis of permanent neonatal diabetes mellitus. Subsequently, treatment with sulfonylurea was initiated, and the insulin dose was gradually tapered. At 4 months of age, insulin therapy was discontinued, and sulfonylurea (glimepiride, 0.75 mg/kg) was administered alone. At 6 months after initiation of administration of sulfonylurea monotherapy, blood glucose control was stable, and no hypoglycemic events or developmental delays were reported. C-peptide levels increased during treatment with sulfonylurea. Early switching to sulfonylurea in infants with permanent diabetes mellitus owing to a KCNJ11 mutation could successfully help regulate glycemic control, which suggests the need for early genetic testing in patients presenting with diabetes before 6 months of age