Ischemia-reperfusion injury during experimental heart transplantation. Evaluation of trimetazidine's cytoprotective effect

INTRODUCTION AND OBJECTIVES: The objectives of this study were to analyze the ischemia-reperfusion injury due to free radicals that occurs during heart transplantation and to determine the potential cytoprotective effect of trimetazidine. MATERIAL AND METHOD: A total of 21 orthotopic heart transplantations were performed in pigs. We divided the experimental animals into 2 groups: in group A (n=11),standard myocardial protection was used; in group B (n=10), trimetazidine was added to the cardioplegic solution used to protect the donor heart and to the solution administered to the recipient prior to release of the aortic clamp (trimetazidine, 10(-5) mol/L), and recipients were pretreated with trimetazidine, 2.5 mg/kg. Blood samples were taken from the recipients coronary sinus at three times: at baseline, during ischemia, and during reperfusion. We measured the levels of malondialdehyde, a marker of lipid peroxidation, and of several antioxidants: glutathione peroxidase, glutathione reductase, superoxide dismutase, alpha-tocopherol, and retinol. The total antioxidant status was also determined. RESULTS: Malondialdehyde production and enzymatic antioxidant activity rose during ischemia and reperfusion, while the retinol level decreased. The increases in malondialdehyde level and glutathione peroxidase activity that occurred between baseline and reperfusion were significantly higher in group A. CONCLUSIONS. The degree of lipid peroxidation and the level of activity of intracellular antioxidant mechanisms increased progressively throughout transplantation. Trimetazidine had a cytoprotective effect. It ameliorated free radical-induced reperfusion injury and modified the response pattern of several defense mechanisms.     

The BDNF gene: exemplifying complexity in Ca2+ -dependent gene expression

Over the last 20 years, great effort has been made to decipher the molecular mechanisms used by cells to transform a cytosolic Ca2+ signal into specific, finely-controlled changes in gene expression. Several previous reviews addressed the variety of regulatory mechanisms that participate in Ca2+ -dependent gene expression in neurons (Carafoli et al., 2001; Mellstrom and Naranjo 2001; West et al., 2001). Nevertheless, recent discoveries have revealed new players and new interactions that tune this process. In this review, we will use the four promoters that regulate the expression of the brain-derived neurotrophic factor (BDNF) gene as a magnificent scenario in which these mechanisms intermingle to show the complexity of Ca2+ -dependent gene expression.     

Effects of in vitro glycation on Fe3+ binding and Fe3+ isoforms of transferrin

BACKGROUND: In diabetes, protein function is altered by glycation, but the impact on the Fe3+ binding and antioxidant functions of transferrin (Tf) is largely unknown. The aim of the present study was to investigate the effects of glycation on the distribution of Fe3+ on the two Fe3+ -binding sites of Tf. METHODS: In vitro glycation of Tf was accomplished by preincubation with glucose for 14 days. Tf was loaded with Fe3+ compounds to achieve theoretical Tf Fe3+ saturations of 32%, 64%, and 96% (monitored by spectrophotometry). Fe3+ -Tf isoforms were separated by isoelectric focusing. RESULTS: Fe3+ binding was highest when Tf was incubated with Fe:nitrilotriacetic acid and reached a steady state overnight. Increasing the Fe3+ load led to a shift of isoform profile toward the diferric form (Fe2-Tf): in freshly prepared Tf, Fe2-Tf represented 6%, 30%, and 66% of all isoforms at 32%, 64%, and 96% theoretical Fe3+ saturation, respectively. Fe3+ was equally distributed to the monoferric Tf forms with Fe3+ bound to the amino (Fe1N-Tf) and carboxy termini (Fe1C-Tf). Glycation decreased binding of Fe3+ to Tf (monitored at 450 nm). At low theoretical Fe3+ saturation (32%), glycation increased the mean (SD) proportion of Fe2-Tf: 18 (3)% in the presence of 33.3 mmol/L glucose vs 12 (4)% with 0 mmol/L glucose (P = 0.01). In contrast, at 96% theoretical Fe3+ saturation, Fe2-Tf decreased linearly with increasing glycation (r = 0.97; P = 0.008). Preincubation, independent of glycation, favored the Fe1N-Tf isoform at 64% theoretical Fe3+ saturation [27 (0.7)% vs 23 (1.1)% of the Fe1C-Tf isoform; P = 0.009]. CONCLUSIONS: Glycation impairs Fe3+ binding and affects Fe3+ -Tf isoform distribution depending on concentration. The diagnostic implications of these results need further elucidation in clinical studies.     

Fibrosis in hypertensive heart disease: role of the renin-angiotensin-aldosterone system

Structural homogeneity of cardiac tissue is governed by mechanical and humoral factors that regulate cell growth, apoptosis, phenotype, and extracellular matrix turnover. ANGII has endocrine, autocrine, and paracrine properties that influence the behavior of cardiac cells and matrix by AT1 receptor binding. Various paradigms have been suggested, including ANGII-mediated up-regulation of collagen types I and III formation and deposition in cardiac conditions, such as HHD. A growing body of evidence, however, deals with the potential role of aldosterone, either local or systemic, in inducing cardiac fibrosis. Aldosterone might also mediate the profibrotic actions of ANGII. To reduce the risk of heart failure that accompanies HHD, its adverse structural remodeling (eg, myocardial hypertrophy and fibrosis) must be targeted for pharmacologic intervention. Cardioprotective agents must reverse not only the exaggerated growth of cardiac cells, but also regress existing abnormalities in fibrillar collagen. Available experimental and clinical data suggest that agents interfering with ACE, the AT1 receptor, or the mineralocorticoid receptor may provide such a cardioprotective effect.     

Factors related to experiencing respiratory failure in cases of opiate overdose for which care was provided in an open setting. Barcelona, Spain

BACKGROUND: To determine the factors associated with respiratory arrest in opiate overdoses (coma, pupillary miosis, respiratory depression, and response to naloxone) among injecting drug users in the Can Tunis quarter of Barcelona. METHODS: We ran a transversal observational study where all overdoses assisted between March, 2001 and June, 2002. After overdose treatment, data were collected using a standard questionnaire, including: patients' sociodemographic data, opiate and other substances' use prior to overdose, clinical signs and symptoms presented, and medical intervention received, by way of a standardised questionnaire. Logistic regression was used as a tool for analysis. RESULTS: Of 222 opiate overdose cases, 60.8% showed respiratory arrest. Of all risk factors tested, only prior abstinence heroin abstinence for 2 weeks or longer days (OR=1.893; p=0.04), and no previous consumption of benzodiazepines (OR:0.462; p=0.017), proved to have a statistically significant association with suffering a respiratory arrest. Concomitant use of alcohol, cocaine or methadone appeared not associated with suffering respiratory arrest in opiate overdose. CONCLUSIONS: The main risk factor for respiratory arrest in opiate overdoses was a prior abstinence period of more than 2 weeks. Benzodiazepines use was associated with absence of respiratory arrest in overdose cases. Alcohol or methadone use, as well as the use of larger quantities of heroin, was not associated with suffering respiratory arrest in opiate overdoses. A study of other factors, not included in this study, and that could interfere with our results, should be considered for their possible relationship to benzodiazepine use as well as to absence of respiratory arrest in overdose cases.     

Proteomics for nasal secretion analysis

Since the completion of the human genome, the interest of the scientific community has evolved toward understanding the human proteome. The genomic and proteomic data will facilitate our understanding of the functions of proteins in diseases and the discovery of novel drug target proteins and biomarkers of diseases. Highly sensitive analytic techniques are necessary to study the complexity of biologic samples. The key to any proteomics experiment is to reduce the complexity of the sample before mass spectrometry (MS) analysis. Numerous separation techniques have been used, including one- and two-dimensional gel electrophoresis, chromatography, and affinity techniques. MS has become a powerful method for analyzing biologic samples. This review does not cover all aspects of proteomics, but is intended to give an introductory explanation of the technology using the example of the proteomics of nasal secretions.     

Beta-amyloid25-35 inhibits glutamate uptake in cultured neurons and astrocytes: modulation of uptake as a survival mechanism

Glutamate transporters are vulnerable to oxidants resulting in reduced uptake function. We have studied the effects of beta-amyloid(25-35) (beta A(25-35)) on [(3)H]-glutamate uptake on cortical neuron or astrocyte cultures in comparison with a scrambled peptide (SCR) and dihydrokainic acid (DHK), a prototypic uptake inhibitor. beta A(25-35) was more potent than DHK in inhibiting glutamate uptake and the effects of both were more marked on astrocytes than on neurons. At 24 h, beta A(25-35) dose-dependently (0.5-15 microM) increased glutamate levels in media from neuron cultures. DHK only enhanced extracellular glutamate at the highest concentration tested (2500 microM). beta A(25-35) induced gradual neurotoxicity (0.1-50 microM) over time. Exposure to beta A(25-35) resulted in increased uptake in astrocytes (0.25-5 microM) and neurons (0.5-15 microM) surviving its toxic effects. However, exposure to DHK (2.5-2500 microM) did not induce neurotoxicity nor modulated uptake. These results indicate that, while inhibition of glutamate uptake may be involved in the neurotoxic effects of beta A(25-35), enhancement of uptake may be a survival mechanism following exposure to beta A(25-35).