The Role of Galectin-3 in Heart Failure-The Diagnostic, Prognostic and Therapeutic Potential-Where Do We Stand?

Heart failure (HF) is a clinical syndrome with high morbidity and mortality, and its prevalence is rapidly increasing. Galectin-3 (Gal-3) is an important factor in the pathophysiology of HF, mainly due to its role in cardiac fibrosis, inflammation, and ventricular remodeling. Fibrosis is a hallmark of cardiac remodeling, HF, and atrial fibrillation development. This review aims to explore the involvement of Gal-3 in HF and its role in the pathogenesis and clinical diagnostic and prognostic significance. We report data on Gal-3 structure and molecular mechanisms of biological function crucial for HF development. Over the last decade, numerous studies have shown an association between echocardiographic and CMR biomarkers in HF and Gal-3 serum concentration. We discuss facts and concerns about Gal-3's utility in acute and chronic HF with preserved and reduced ejection fraction for diagnosis, prognosis, and risk stratification. Finally, we present attempts to use Gal-3 as a therapeutic target in HF.

PoLA/CFPiP/PCS/PSLD/PSD/PSH guidelines on diagnosis and therapy of lipid disorders in Poland 2021

In Poland there are still nearly 20 million individuals with hypercholesterolaemia, most of them are unaware of their condition; that is also why only ca. 5% of patients with familial hypercholesterolaemia have been diagnosed; that is why other rare cholesterol metabolism disorders are so rarely diagnosed in Poland. Let us hope that these guidelines, being an effect of work of experts representing 6 main scientific societies, as well as the network of PoLA lipid centers being a part of the EAS lipid centers, certification of lipidologists by PoLA, or the growing number of centers for rare diseases, with a network planned by the Ministry of Health, improvements in coordinated care for patients after myocardial infarction (KOS-Zawał), reimbursement of innovative agents, as well as introduction in Poland of an effective primary prevention program, will make improvement in relation to these unmet needs in diagnostics and treatment of lipid disorders possible.

Sirtuins and their role as physiological modulators of metabolism

The sirtuins are a family of highly evolutionary conserved NAD+-dependent deacetylases (SIRT1, 2, 3, 5). Certain human sirtuins (SIRT4, 6) have, in addition, an ADP-ribosyltransferase activity. SIRT1 and SIRT2 are located in the nucleus and cytoplasm; SIRT3 exists predominantly in mitochondria, and SIRT6 is located in the nucleus. The mammalian sirtuins have emerged as key metabolic sensors that directly link environmental nutrient signals to metabolic homeostasis. SIRT1 is involved in the regulation of gluconeogenesis and fatty acid oxidation, as well as inhibiting lipogenesis and inflammation in the liver. In addition, they contribute to the mobilization of fat in white adipose tissue, sense nutrient availability in the hypothalamus; regulate insulin secretion in the pancreas; as well as modulating the expression of genes responsible for the activity of the circadian clock in metabolic tissues. Sirtuins are implicated in a variety of cellular functions ranging from gene silencing, through the control of the cell cycle, to energy homeostasis. Caloric restriction, supported by polyphenols, including resveratrol, which is the SIRT1 activator, plays a special role in maintaining energy homeostasis. On a whole body level, the wide range of cellular activities of the sirtuins suggests that they could constitute a therapeutic target to combat obesity and related metabolic diseases. In addition, this work presents the current state of knowledge in the field of sirtuin activity in relation to nutritional status and lifespan.

Serum copeptin and copeptin/NT-proBNP ratio - new tools to differentiate takotsubo syndrome from acute myocardial infarction

BACKGROUND

Today no established biomarkers are available for the early diagnosis of takotsubo syndrome and its differentiation from ST-segment elevation myocardial infarction. We hypothesized that copeptin and copeptin/NT-proBNP ratio may serve a routine marker combination for non-invasive differentiation.

METHODS

The study compared the serum concentrations of copeptin, troponin I (TnI) and NT-proBNP in 19 consecutive women diagnosed with takotsubo syndrome according to the Mayo Clinic criteria and 10 consecutive women diagnosed with ST-segment elevation myocardial infarction.

RESULTS

Copeptin concentrations were significantly lower in patients with takotsubo syndrome than in patients with ST-segment elevation myocardial infarction. The diagnostic accuracy to distinguish takotsubo syndrome from ST-segment elevation myocardial infarction is highest for copeptin/NTproBNP ratio, copeptin/TnI at admission ratio and copeptin alone (AUC 0.8713, 0.8538, 0.8480, respectively).

CONCLUSIONS

The serum copeptin to NTproBNP ratio could be an additional tool in the non-invasive differentiation between takotsubo syndrome and ST-segment elevation myocardial infarction. However, further researches are needed.

MicroRNAs in the development of left ventricular remodeling and postmyocardial infarction heart failure

Acute myocardial infarction (AMI) induces unfavorable left ventricular remodeling (LVR), a complex process that involves molecular, cellular, and geometric alterations leading to important changes in heart structure and function. Heart failure (HF) is a frequent complication of AMI, and it remains a serious clinical, epidemiological, and economic challenge. Despite advances in the therapy and management of HF, many patients still suffer from severe symptoms. The underlying molecular mechanisms of the post‑AMI LVR are not yet fully understood. Numerous studies have indicated that dysregulation in the expression of microRNA (miRNA) molecules leads to changes in several pathological processes in the heart, which are associated with post‑AMI transition from cardiac hypertrophy to HF. In this review, we summarize the current knowledge on the role of miRNAs in the regulation of basic processes, such as excessive myocardial fibrosis, pathological cardiomyocyte hypertrophy, and myocardial cell apoptosis. Moreover, the significance of circulating miRNAs as noninvasive prognostic biomarkers in the prediction of LVR and HF after AMI has also been discussed. In conclusion, miR‑29 family members (miR‑29a and miR‑29b), miR‑150, and miR‑30a‑5p represent different groups of miRNAs, but all of them are involved in the regulation of the fundamental processes associated with post‑AMI left ventricular dysfunction and HF. Furthermore, these miRNA molecules may serve as a potential therapeutic target during disease progression.

Circulating miR-30a-5p as a prognostic biomarker of left ventricular dysfunction after acute myocardial infarction

Left ventricular (LV) dysfunction after acute myocardial infarction (AMI) is associated with an increased risk of heart failure (HF) development. Diverse microRNAs (miRNAs) have been shown to appear in the bloodstream following various cardiovascular events. The aim of this study was to identify prognostic miRNAs associated with LV dysfunction following AMI. Patients were divided into subgroups comprising patients who developed or not LV dysfunction within six months of the infarction. miRNA profiles were determined in plasma and serum samples of the patients on the first day of AMI. Levels of 14 plasma miRNAs and 16 serum miRNAs were significantly different in samples from AMI patients who later developed LV dysfunction compared to those who did not. Two miRNAs were up-regulated in both types of material. Validation in an independent group of patients, using droplet digital PCR (ddPCR) confirmed that miR-30a-5p was significantly elevated on admission in those patients who developed LV dysfunction and HF symptoms six months after AMI. A bioinformatics analysis indicated that miR-30a-5p may regulate genes involved in cardiovascular pathogenesis. This study demonstrates, for the first time, a prognostic value of circulating miR-30a-5p and its association with LV dysfunction and symptoms of HF after AMI.

Galectin-3 in Patients with Acute Heart Failure: Preliminary Report on First Polish Experience

BACKGROUND

Galectin-3 (Gal-3) as a biomarker of fibrosis and inflammation has been implicated in the development and progression of heart failure (HF) and may predict increased morbidity and mortality in society.

OBJECTIVES

In this preliminary report we investigated the utility of a novel serum marker for the diagnosis of acute HF (AHF).

MATERIAL AND METHODS

The study involved 14 AHF patients aged 67.0 ± 14.6 yrs. with left ventricular ejection fraction (LVEF) 29.29 ± 10.73%, hospitalized at the Intensive Coronary Care Unit, where the research took place. In addition, a control group consisting of 19 volunteers who were age, gender and ethnically matched to the HF group was recruited. In the study group, the concentrations of Gal-3, NT-proBNP, hsCRP and basic clinical parameters, such as prevalence of dyspnea and LVEF were determined. The concentration of Gal-3 in serum was examined by an automated quantitative test (VIDAS® Galectin-3, bioMerieux SA, France) using the ELFA technique. The survival rate was assessed after a 12-month follow-up.

RESULTS

The median (IQR) Gal-3 concentrations in patients with AHF were higher (nearly 2.1-times) than in the control group - 17.8 (10.3-27.8) ng/mL vs. 8.4 (6.5-11.0) ng/mL; p = 0.0007. In our study group, the median (IQR) of concentrations of NT-proBNP 4723 (1415-29725) pg/mL and hsCRP 10.0 (4.9-13.9) mg/L were observed. In those patients, the statistically significant correlation (Spearman's rank-correlation coefficient) between the concentrations of Gal-3 and NT-proBNP (Rs = 0.565; p = 0.035) as well as the value of LVEF and the concentration of hsCRP (Rs = -0.663; p = 0.020) were stated. The serum Gal-3 concentrations were significantly higher among the 4 HF patients (28.6%) who had died than among the HF patients who were alive after this time (n = 10) (55.6 ± 37.6 ng/mL vs. 15.0 ± 7.04 ng/mL; p = 0.005).

CONCLUSIONS

Higher expression of Gal-3 is an indicator of myocardial fibrosis and remodeling in decompensated HF. Therefore, galectin-3 seems to be an interesting and valuable marker of AHF.

Interindividual variability of atorvastatin treatment influence on the MPO gene expression in patients after acute myocardial infarction

Myeloperoxidase (MPO) and C-reactive protein (CRP) may play critical roles in generation of oxidative stress and the development of the systemic inflammatory response. The aim of the study was to determine the effect of atorvastatin therapy on the MPO gene expression and its plasma level in relation to lipids level lowering and an anti-inflammatory response in patients after acute myocardial infarction. The research material was represented by 112 samples. Thirty-eight patients with first AMI receiving atorvastatin therapy (40 mg/day) and followed up for one month were involved in the study. The relative MPO gene expression in peripheral blood mononuclear cells (PBMCs) was examined using RT-qPCR in 38 patients before-, 38 patients after-therapy and in 36 patients as the control group. The plasma concentrations of MPO and serum concentrations of biochemical parameters were determined using commercially available diagnostic tests. After one month of atorvastatin therapy, in 60.5% patients a decrease of MPO gene expression, whereas in 39.5% patients an increase, was observed. The plasma MPO levels behaved in the same way as the MPO gene expression. However, the serum lipids and CRP concentrations were significantly lower after one month of atorvastatin therapy in both groups of patients - with decreased and increased MPO gene expression. Atorvastatin exhibited a different effect on MPO gene expression and its plasma level. Short-term atorvastatin therapy resulted in lipid lowering and anti-inflammatory activity in patients after AMI, independently of its effect on MPO gene expression. The molecular mechanisms of this phenomenon are not yet defined and require further research.

Circulating microribonucleic acids miR-1, miR-21 and miR-208a in patients with symptomatic heart failure: Preliminary results

BACKGROUND

Cardiomyocytes produce a wide variety of bioactive molecules that regulate numerous physiological and pathophysiological processes. Recently, it has been recognized that changes in microribonucleic acid (miRNA) expression may lead to cardiac dysfunction.

AIMS

To assess the expression of circulating miRNAs (miR-1, miR-21 and miR-208a) in patients with symptomatic heart failure (HF), and to investigate the relationship between expression of these miRNAs and secretion of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and galectin-3.

METHODS

Thirty-five patients in New York Heart Association (NYHA) class II/III (age: 68.8 ± 13.0 years) and 26 patients in NYHA class IV (age: 72.0 ± 10.4 years) hospitalized in the intensive coronary care unit participated in the study. Serum concentrations of miRNAs were measured by quantitative real-time polymerase chain reaction. Basic biochemical assays were carried out, and NT-proBNP and galectin-3 concentrations were measured in all serum samples.

RESULTS

miR-1 was downregulated in patients with symptomatic HF and its expression decreased with severity of NYHA class (P=0.007). In contrast, overexpression of miR-21 was seen in all patients, independent of HF severity. Results suggest no miR-208a leakage into the circulation in patients with symptomatic HF. There was an inverse relationship between miR-1 expression and NT-proBNP concentration (Spearman's rank correlation coefficient [r]=-0.389; P=0.023) in patients in NYHA class II/III. Overexpression of miR-21 correlated significantly with galectin-3 concentration (r=0.422; P=0.032).

CONCLUSION

Dysregulation of miR-1 and miR-21 expression may be essential for the development of HF; miR-1 might become a biomarker for predicting HF exacerbation.

Release kinetics of circulating miRNA-208a in the early phase of myocardial infarction

BACKGROUND

The biochemical confirmation of myocardial infarction is based on cardiac troponin (cTnI or cTnT) determination. Recent scientific results suggested that microRNAs (miRNAs) might become a new biomarker of tissue injury.

AIM

To evaluate the release kinetics of circulating heart-specific miRNA-208a and also to test the hypothesis that miRNA-208a can serve as an accessible, diagnostically sensitive plasma biomarker of ST-elevation acute myocardial infarction (STEMI).

METHODS

Nineteen STEMI patients (four women and 15 men, aged 44-85 years), 12 patients with stable coronary artery disease (CAD), and eight patients with a negative observation of CAD as a control group were studied. Blood samples were collected on admission and at three, six, 12, 24, and 48 h afterwards; in the CAD and control group blood samples were taken only once. Plasma levels of miRNA-208a determined by real-time polymerase chain reaction and their relative fold changes were calculated. cTnI and creatinine kinase (CK)-MB mass were also measured in the patients’ serum samples.

RESULTS

miRNA-208a was increased in STEMI patients at the time of admission and nearly undetectable in CAD patients and controls. The peak of miRNA-208a was observed at 3 h after reperfusion (p < 0.001). The traditional biomarkers (cTnI and CK-MBmass), which increase later in comparison to miRNA-208a reaching the maximum concentrations 6 h after reperfusion, were observed. Circulating miRNA-208a levels strongly correlated with cTnI and CK-MBmass released from the infarcted area.

CONCLUSIONS

These results demonstrate that plasma miRNA-208a is an interesting and promising candidate for a new biomarker released early after onset of myocardial infarction.

Mycophenolic acid attenuates the tumour necrosis factor-α-mediated proinflammatory response in endothelial cells by blocking the MAPK/NF-κB and ROS pathways

BACKGROUND

Mycophenolate mofetil (MMF) has beneficial effects in cardiac transplant patients beyond the suppression of tissue rejection. Moreover, mycophenolic acid (MPA), its active metabolite, has been associated with positive effects on atherosclerosis in animal models. The attachment of leukocytes to the vascular endothelium and the subsequent migration of these cells into the vessel wall are early events in inflammation and atherosclerosis. The aim of this study was to investigate the effects of MPA on tumour necrosis-α (TNF-α)-induced, endothelial cell proinflammatory responses and the underlying mechanisms.

METHODS AND RESULTS

Human aortic endothelial cells (HAECs) were treated with different concentrations (primarily 50 μM) of MPA before treatment with TNF-α. The surface protein and mRNA expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were determined by flow cytometry and real-time RT-PCR, respectively. Adhesion of leukocytes to TNF-α-treated HAECs was evaluated by an adhesion assay. Activation of mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) was evaluated by measuring the levels of their phosphorylation using flow cytometry. NF-κB p65 translocation was detected by Western blotting. The production of reactive oxygen species (ROS) was determined by reduction in fluorescent 2',7'-dichlorofluorescein diacetate (H2 DCFH-DA). MPA significantly inhibits TNF-α-induced ICAM-1, VCAM-1 surface protein and mRNA expression as well as adhesion of mononuclear leukocytes to HAEC. ICAM-1 and VCAM-1 expressions were also reduced by antioxidants such as pyrrolidine dithiocarbamate, diphenylene iodonium and apocynin. MPA inhibited TNF-α-stimulated ROS generation similarly to apocynin. TNF-α increased ICAM-1 and VCAM-1 expression via c-Jun NH2 -terminal kinase (JNK), extracellular signal-regulated kinase (ERK1/2) and p38 MAPK. MPA and apocynin inhibited TNF-α-induced phosphorylation of all three MAP kinases. Furthermore, TNF-α-induced NF-κB activation was attenuated by SP600125 (JNK inhibitor), PD98059 (ERK1/2 inhibitor, SB203580 (p38 MAPK inhibitor) and MPA. MPA also inhibited TNF-α-induced nuclear translocation of NF-κB p65.

CONCLUSION

These results suggest that, in addition to the prevention of rejection, MPA may be a promising approach for the treatment of inflammatory vascular disease.

[Enantiomers: a new problem in pharmacotherapy of depression?]

Enantiomers as a optically active forms of drugs now have a big impact on most areas of pharmacotherapy. They arouse a large interest in the field of psychiatry and especially in the treatment of depression. This is due to the fact that enantiomers (chiral forms) of many drugs may have a different pharmacokinetic, pharmacological or pharmacogenetic profiles. Therefore, in many cases the use of a single enantiomer of the drug may have huge advantages over previously used forms and lead to strong improvement of the current treatments. An example is the stereoselective property of such a psychotropic drug fluoxetine as belonging to a group of selective serotonin reuptake inhibitors (SSRI).

Ischaemia modified albumin in patients with acute coronary syndrome and negative cardiac troponin I

BACKGROUND

Approximately 40-60% of patients with acute coronary syndrome (ACS) have normal cardiac troponin I (cTnI) concentrations on admission. Ischaemia modified albumin (IMA) has been suggested as a new biomarker of myocardial ischaemia.

METHODS

A total of 43 patients presenting with symptoms suggestive of ACS but with normal (< 0.1 μg/L) cTnI concentrations and 45 healthy subjects were studied. The patients from the study group were divided into two groups: STEMI (n = 28) and NSTEMI (n = 15). All these patients were undergoing percutaneous coronary intervention (PCI) with stenting. The concentrations of cTnI, myoglobin and IMA were determined on admission and 4 h after PCI.

RESULTS

Mean (SD) IMA concentrations were higher in patients with ACS (114.39 ± 25.18 U/ml) as compared to the control group (96.24 ± 6.28 U/ml, p < 0.005). IMA concentrations ≥ 104.0 U/ml demonstrated 72.1% sensitivity and 75.6% specificity for the diagnosis of ACS. The area under the receiver operator characteristic curve was 0.766 (95% CI 0.664-0.868) for ACS patients (NSTEMI + STEMI). In both groups increased median (IQR) cTnI concentration after PCI was observed (STEMI patients to 65.4 (10.9-106.9) μg/L and NSTEMI to 17.6 (0.77-84.0) μg/L). In contrast, no increase in IMA concentration was observed.

CONCLUSIONS

IMA may be a useful biomarker for the identification of ACS patients presenting with typical acute chest pain and/or abnormal electrocardiograms but negative cTnI.

Bovine corneal epithelial primary cultures as an in vitro model for ophthalmic drugs studies

In the recent years a significant development of investigations with regard to bioavailability of ocular drugs has been noticed. The corneal epithelial barrier is the main pathway for ocular penetration of topically applied ophthalmic drugs into the anterior chamber. To work out an in vitro model of bovine corneal epithelial primary cultures and exercise it for permeability research with lipophilic and hydrophilic markers, permeability coefficients estimation of the 6-carboxyfluorescein and rhodamin B was made. The corneal epithelial cultures of the 3th or 4th passage were chosen for layered culture with inserts based on the liquid-liquid interface (for the first week) and the air-liquid interface (for the two following weeks). On the 7th, 12th, 18th, 21st experiment day TER values, and on the 21st day drug permeability coefficients, were determined. The mean TER values of the 7th, 12th, 18th, 21st day of corneal epithelial culture were: 122.14, 155.14, 198.43 and; 247.43 Wcm2, respectively. The mean values of permeability coefficients on the 21st day of culture for 6-carboxyfluorescein and rhodamin B were 3.87 +/-0.10 x 10(-6)cm/s and 3.65 +/- 0.06 x 10(-6)cm/s, respectively. We state that the in vitro bovine corneal epithelial primary culture model is useful for ocular studies.

Aronia melanocarpa fruit extract exhibits anti-inflammatory activity in human aortic endothelial cells

Background

Altered expression of cell adhesion molecules (CAMs) has been implicated in a variety of chronic inflammatory conditions, including atherosclerosis. Regulation of adhesion molecule expression by specific redox-sensitive mechanisms has been reported. Additionally, it has been observed that the extract of Aronia melanocarpa (A. Melanocarpa) fruits, rich in polyphenols, exhibits potent anti-oxidant properties and displays cardioprotective activity.

Methods and results

Human aortic endothelial cells (HAECs) were pretreated with various concentrations (primarily 50 μg/mL) of Aronia Melanocarpa fruit extract prior to treatment with TNFα (10 ng/mL) for various periods of time. The surface protein and mRNA expression of ICAM-1 and VCAM-1 were determined using flow cytometry and real-time RT-PCR, respectively. Adhesion of peripheral blood mononuclear leucocytes (PBMLs) to TNFα-treated HAECs was evaluated by an adhesion assay. Activation of NF-κB was evaluated by measuring NF-κB p65 phosphorylation using flow cytometry. ROS production was determined by reduction in fluorescent 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Tested A. Melanocarpa extract significantly inhibited the expression of ICAM-1 and VCAM-1, attenuated the phosphorylation of NF-κB p65 and decreased intracellular ROS production in TNFα-treated HAECs.

Conclusion

We conclude that A. Melanocarpa fruit extract exhibits anti-inflammatory effects in HAECs by inhibiting the expression of endothelial CAMs, activation of NF-κB and production of ROS.

Trans fatty acids induce a proinflammatory response in endothelial cells through ROS-dependent nuclear factor-κB activation

It has been shown that increased intake of trans fatty acids (TFAs) is associated with a higher risk of cardiovascular disease. In this study, we have investigated the effects of linoelaidic (LA) and elaidic (EA) acids on the proinflammatory response in endothelial cells, a key step in vascular disease. Human aortic endothelial cells (HAECs) were treated with different concentrations (100 μmol/l in most experiments) of LA or EA for different periods of time. The surface protein and mRNA expression of ICAM-1 and VCAM-1 were determined by flow cytometry and real time RT-PCR, respectively. Adhesion of leukocytes to TFA-treated HAECs was evaluated by an adhesion assay. Activation of nuclear factor-κB (NF-κB) was evaluated by measuring NF-κB p65 phosphorylation using flow cytometry. ROS production was determined by the reduction of fluorescent 2',7'-dichlorofluorescein diacetate (DCFH-DA). LA treatment significantly increased protein and mRNA levels of ICAM-1 and VCAM-1, leukocyte adhesion to HAECs, phosphorylation of NF-κB and ROS generation. Similar effects were achieved for cells incubated with EA. Experiments with HAECs pretreated with pyrrolidine dithiocarbamate, an inhibitor of NF-κB, revealed that both LA and EA-mediated induction of ICAM-1 and VCAM-1 is mainly regulated by NF-κB. The ROS production induced by both of the studied acids was inhibited in the presence of diphenyleneiodonium (DPI), a NADPH oxidase inhibitor, suggesting ROS production through the activation of NADPH oxidase. Furthermore, LA or EA-induced ICAM-1 and VCAM-1 expression, activation of NF-κB and adhesion of leukocytes to HAECs were abolished in the presence of DPI.

CONCLUSION

TFAs present in our diet have a direct proinflammatory effect, which promotes leukocyte adhesion to the endothelium through ROS-dependent NF-κB activation.

Expression of platelet surface receptors and early changes in platelet function in patients with STEMI treated with abciximab and clopidogrel versus clopidogrel alone

BACKGROUND

Platelets play a crucial role in the pathogenesis of acute coronary syndromes (ACS). The efficacy of antiplatelet treatment is pivotal in the success of percutaneous coronary intervention (PCI) performed in patients with ACS.

OBJECTIVE

The aim of the study was to investigate the effects of clopidogrel with or without abciximab on the expression of platelet surface receptors and platelet function in patients with ST-segment elevation myocardial infarction (STEMI) undergoing PCI.

MATERIALS AND METHODS

Thirty patients with STEMI were included in the study. During acute primary coronary intervention, patients received aspirin (acetylsalicylic acid) and clopidogrel in a loading dose of 300mg. Clopidogrel was the only antiplatelet therapy used by nine patients (group B). Twenty-one patients (group A) received additional abciximab. Blood samples were collected and analyzed twice: before and up to 22 hours after administration of antiplatelet therapy. The platelet aggregation was established as primary platelet-related hemostasis (closure time [CT] assessed using the PFA100 system). The absolute number of platelet surface antigens as CD41a, CD42a, CD42b, CD61, and CD62P were determined by flow cytometry analysis.

RESULTS

The study revealed a statistically significant increase in CT induced by adenosine diphosphate and adrenaline (epinephrine) +130 seconds (p < 0.0001) and +94 seconds (p < 0.0001), respectively, in group A patients post-therapy. While in group B the parameters of CT did not change after treatment. In addition, the absolute number of CD41a antigens (glycoprotein [GP] IIb/IIIa) increased significantly after treatment in group A. No significant changes were observed after treatment in the expression of CD62P (P-selectin) antigens in either treatment group. There was a significant reduction in the percentage of CD62P-positive platelets in group B after antiplatelet therapy.

CONCLUSIONS

The absolute number of GP IIb/IIIa receptors increases and platelets are not activated up to 12 hours after cessation of abciximab therapy. Treatment of STEMI patients undergoing PCI with a loading dose of clopidogrel reduces the percentage of active platelets but does not influence the CT.

Significance of Aspirin and Clopidogrel Resistance in Patients Undergoing Percutaneous Coronary Interventions

Dual antiplatelet therapy (aspirin plus clopidogrel) is mandatory in patients treated with coronary stent implantation. This strategy is highly effective in prevention of stent thrombosis until its struts are covered with endothelium. However, a substantial number of patients still suffer from recurrent ischemic coronary events despite adequate antiplatelet therapy. These events fall into three categories: stent thrombosis, in stent restenosis and events related to other non-stented coronary lesions. Some data suggest that beside other local and systemic factors resistance to aspirin and clopidogrel may be a possible cause of stent thrombosis and ischemic events in patients after coronary interventions. Several mechanisms of antiplatelet drug resistance have been reported including poor compliance, interactions with other drugs, genetic polymorphism or increased platelet turnover. More research is needed to adequately assess the clinical significance and prognostic value of antiplatelet drug resistance detected by laboratory tests in patients undergoing percutaneous intervention. We review published data on mechanisms and the clinical significance of aspirin and clopidogrel resistance in patients after coronary interventions.

[Renin aldosterone profile in essential hypertension during pregnancy and after delivery]

BACKGROUND

The pathogenesis of essential hypertension (EH) is a complex multifactorial process. Little is known about the association between pregnancy and blood pressure fluctuation in women with EH. In this study we wanted to evaluate the relationship between the blood pressure (BP) and plasma renin activity (PRA) as well as serum and urine aldosterone (ALDO) levels in pregnant women with essential hypertension.

MATERIALS AND METHODS

We analyzed 84 pregnant women (97% primigravida) with EH aged 22-40 (mean 29.5 +/- 5.4) years and 60 healthy pregnant women aged 22-40 (mean 28.5 +/- 4.9) years. In women with EH, antihypertensive therapy was stopped immediately after pregnancy was confirmed. Patients with EH were divided to two groups: 1) with BP > or = 140/90 and 2) with BP > or = 140/90. PRA and ALDO as well as sodium and potassium excretion were measured three times in different periods of pregnancy: 8-12 weeks, 24-28 weeks, 34-38 weeks. In addition, both PRA and ALDO were analyzed in 4th month after delivery i.e. in the time, in which woman is reached hormonal and hemodynamic stability. PRA and ALDO were determined by RIA methods. BP was monitored by standardized method using mercury manometer.

RESULTS

PRA and ALDO concentrations in both: serum and urine were increased during pregnancy in all studied groups. No difference in kinetics of PRA and ALDO was stated between healthy pregnant women with EH. Increased was observed in women and during pregnancy. Statistically significant, the highest level of PRA was noted in fourth month after delivery in women with BP > 140/90. In this period, however, concentrations of ALDO in both serum and urine were the same in all examined women.

CONCLUSION

1. In women with EH and BP < 160/100 mm Hg during pregnancy PRA and concentration of ALDO in serum as well as ALDO excretion were the same as in healthy pregnancy women. 2. Reduction of blood pressure was observed in the group of women with the lowest PRA in fourth month after delivery. 3. PRA measured in women with EH may be a predictive parameter of BP during pregnancy.

[Role of procalcitonin in the diagnosis of uncomplicated infective endocarditis]

Infective endocarditis especially where blood culture is negative frequently causes problems in diagnosis despite of many nonspecific inflammation parameters. Procalcitonin (PCT) concentration is a new marker of severe bacterial and fungal infection. The aim of this study was to evaluate the usefulness of PCT concentration assessment in the diagnosis of uncomplicated infective endocarditis of bacterial etiology. The study group consisted of 30 patients with ongoing infective endocarditis in the course of acquired valvular heart disease. The diagnosis of bacterial endocarditis was established according to the Duke criteria on the basis of: clinical examination, laboratory investigations (inflammatory parameters, transthoracic and transesophageal echocardiography) and positive blood cultures. Patients with sepsis, concomitant infections and in an early postoperative period were excluded. Two control groups consisted of: 10 patients without endocarditis and other infections and another 10 patients without endocarditis and with an urinary tract infection. Serum procalcitonin concentrations were measured by an immunoluminometric assay (LUMItest PCT set). Mean serum PCT concentrations in patients with endocarditis (0.12 +/- 0.13, range 0-0.4 ng/ml) were significantly higher than in control group without infection (0.03 +/- 0.05, range 0-0.1 ng/ml) and higher than in control group with an urinary tract infection (0.02 +/- 0.04, range 0-0.1 ng/ml). However in 12 patients (of 30) were below sensitivity of the method and in the rest were within normal range (< 0.5 ng/ml).

CONCLUSION

Serum PCT concentration assessment seems to have no value in the diagnosis of uncomplicated infective endocarditis.

[Comparison of interleukin-6 and C-reactive protein serum concentrations assessment in diagnosis of infective endocarditis]

Serum interleukin-6 (IL-6) level might be used to aid in diagnosis of infective endocarditis (IE), especially when blood cultures are negative. One of typical acute phase proteins is C-reactive protein (CRP), often served as an additional inflammation maker. The aim of the study was to compare serum IL-6 and CRP concentrations assessment in diagnosis and monitoring of IE. The study group consisted of 40 patients with ongoing IE and valvular heart diseases. Two control groups consisted of patients with valvular heart diseases: 15 without infection and another 15 with urinary tract infection. The diagnosis of IE was established according to the Duke University criteria; in 34 patients positive blood cultures were found. Serum IL-6 and CRP were measured on three occasions after diagnosis of IE was established and during antimicrobial treatment (mean period 14 +/- 7 days) by ELISA. Usefulness of both parameters for IE diagnosis were described. Reference values were defined as 0-12.5 pg/ml for IL-6, and 0-10 mg/l for CRP. Mean concentrations of IL-6 and CRP in patients with IE (37 +/- 44.3 pg/ml and 27.1 +/- 23.9 mg/l) were significantly higher than in controls: with urinary tract infection (9.1 +/- 4.42 pg/ml and 6.95 +/- 4.39 mg/l) and without infection (3.95 +/- 1.4 pg/ml and 2.21 +/- 0.96 mg/l). CRP concentration was not significantly correlated with IL-6 (r = 0.51, p = 0.07). The significant tendency of consecutive IL-6 concentrations to decrease (from 37 +/- 44.3 to 8.7 +/- 5.7 pg/ml), without decrease of CRP (from 27.1 +/- 23.9 mg/l to 22 +/- 18.3 mg/l) was found.

CONCLUSIONS

1. Elevated serum IL-6 and CRP levels may suggest ongoing IE. 2. Sensitivity, specificity, positive and negative predictive value are nonsignificantly higher for IL-6 than CRP. 3. Combined assessment of serum IL-6 and CRP concentration has no higher value in diagnosis of IE. 4, IL-6 level decrease is faster than CRP during antimicrobial treatment, and it helps better and faster monitoring of treatment.

Hepatocyte growth factor levels in liver and blood, and post-operative liver cell proliferation in patients with benign and malignant liver tumors after partial hepatectomy

BACKGROUND

The purpose of our study was to investigate hepatocyte proliferation and the expression of hepatocyte growth factor (HGF) in liver tissue and blood from patients with benign and malignant liver tumors after partial hepatectomy.

MATERIAL/METHODS

We studied 25 consecutive patients undergoing partial hepatectomy for metastatic colorectal adenocarcinoma (15 cases) and benign liver tumors (10 cases). Immunohistochemical examination for the presence of PCNA and HGF, c-MET/HGF-receptor expression was performed on formalin-fixed samples from: a) sections of resected fragments of liver tissue remote from the tumor; b) tumor tissue; c) remnant liver, 30 min after hepatectomy; d) fine needle aspiration liver biopsy, 7 days after liver resection. Circulating HGF and the level of AFP and GGT as biomarkers for liver cell regeneration were measured in the patients' blood at the same time.

RESULTS

The proliferation rate of liver cells was higher in patients with malignant than benign liver tumors. This correlated with increased HGF in blood, but not with the expression of HGF and c-MET/HGF-R in liver tissue. The expression of HGF was detected in specimens from colorectal liver metastases.

CONCLUSIONS

The mutual interactions between tumor and other cells may influence the proliferation of hepatocytes throughout the regenerative process in patients with colorectal carcinoma metastases after partial hepatectomy.

[Mechanisms of drug metabolism--implications for drug interaction]

Most drugs undergo biotransformation before excretion by renal, biliary or other routes. The main purpose of metabolism is to make the drug, which is usually lipophilic, more water soluble. Metabolic reactions, depending upon the end product formed, can be classified as functionalisation (phase I) or conjugation (Phase II) reactions. Phase I metabolic reactions include oxidation, reduction and hydrolysis; while phase II processes are glucuronidation, sulfation, methylation, acetylation and mercapture formation. Cytochrome P-450 isozymes play a central role in metabolism of great majority of xenobiotics, as well as some endogenous substances. Many drugs can inhibit, induce and alter relative amounts of different P-450 enzymes; therefore, possibilities of drug-drug interactions exist in that one drug can influence biodisposition of another with potential clinical implications. One drug can inhibit metabolism of another, leading to excessive accumulation and toxicity. Alternatively, one drug can stimulate or induce metabolism of another drug resulting in subtherapeutic plasma levels of the later.

[Elevated levels of homocysteine in plasma as a risk factor for coronary artery disease]

This study was performed to assess the significance of association between coronary artery disease (CAD) and circulating homocysteine concentrations. 100 consecutive CAD patients (78 men and 22 women, aged 31 to 79 years) qualified for PTCA were investigated. At the time of PTCA, the risk factors for CAD and plasma for homocysteine and vitamins were obtained. The controls were without clinical evidence of coronary artery disease and hypertension (90 men and 30 women aged 32 to 81 years). Homocysteine was assayed using ELISA test. Red cell folate and plasma vitamin B12 were assayed by immunofluoroscency (Delphia test). Homocysteine concentrations were higher in patients than in controls (13.61 +/- 4.5 vs 10.99 +/- 4.49 mumol/L, p < 0.001, adjusted for age). Male patients had nonsignificantly higher homocysteine levels than females (13.94 +/- 5.21 vs 11.46 +/- 5.16 mumol/L, p = 0.05, adjusted for age). Elevated homocysteine level--defined as one in the top fifth of the control distribution > or = 12.83 mumol/L--was seen in 46% of the patients compared with 20% of the control group (p = 0.001). The odds ratio (OR) for CAD in persons with elevated homocysteine level was 3.1 (95% Cl 1.6-5.8, p < 0.001, adjusted for age). The OR for CAD of 5 mumol/L increment in homocysteine level was 2.1 (95% Cl 1.4-3.1 p < 0.001, adjusted for age). After adjustment for conventional risk factors (age, smoking, hypertension, family history of CAD, hyperlipidemia), elevated homocysteine level remained independent risk factor for CAD (OR 2.88, 95% Cl 1.1-7.8, p < 0.05). We observed inverse correlation between homocysteine and folate level (r = -0.32, p = 0.005) and between homocysteine and vitamin B12 concentrations (r = -0.24, p = 0.03), especially in men. Patients with elevated homocysteine level had lower levels of folate (629.6 +/- 241.2 nmol/L vs 735.1 +/- 252.4 nmol/L, p < 0.05), and vitamin B12 (213.6 +/- 64.4 pmol/L vs 246.6 +/- 62.3 pmol/L, p < 0.05) than patients with normal level of homocysteine. Elevated plasma homocysteine level is a strong risk factor for coronary artery disease. A 5 mumol/L increment in total homocysteine level may be associated with twofold increase of risk for the disease.

Endothelin-1 inactivating peptidase in the human kidney and urine

OBJECTIVE

Recently, an apparently novel, specific endothelin-1 inactivating metalloendopeptidase (ET-1 peptidase) has been isolated from the rat kidney. In this study we attempted to determine whether the same or a similar peptidase is present in the human kidney, and whether the enzyme is excreted into the urine. The urinary ET-1 peptidase could serve as an indirect index of the renal endothelin system, both in physiology and pathophysiology.

METHODS

Kidney specimens were obtained from part of nephrectomized kidneys unaffected by any neoplastic process from six adult patients. The enzyme was purified using differential centrifugation, detergent solubilization of the membrane proteins, ultrafiltration and nondenaturing gel electrophoresis. The enzyme activity assays were performed at pH 5.5 and 37 degrees C in the presence of increasing concentrations of unlabelled peptides and inhibitors using a fixed amount of [125I]ET-1 as substrate. The degradation extent was quantified with trichloroacetic acid precipitation and high performance liquid chromatography. The degrading activity of ET-1 was determined in urine samples from adult patients with hypertension, children with chronic renal failure and those with stable renal allograft

RESULTS

ET-1 peptidase from the human kidney displays characteristics close to that of the rat ET-1 peptidase we have recently described (J. Hypertens 1994; 12:1155-1162). The enzyme, a membrane-bound metalloendopeptidase, exhibits low electro- phoretical mobility on nondenaturing gel (Rf 0.08); it is an apparently heterologous structure comprising three enzymatically inactive subunits, it has a pH optimum at 5.5, a nanomolar range affinity to the ET-1 (KM 180 nmol/l) that is hydrolysed to two main degradation products, and a 10-100-fold lower affinity to big ET-1 (KM 11.5 micromol/l), endothelin 11 21 fragment (KM 15.3 micromol/l), endothelin antagonist Trp-Leu-Asp-Ile-Ile-Trp (KM 3.1 micromol/I), gastrin (KM 2.2 micromol/l) and cholecystokinin (KM 4.0 micromol/l). Substance P, neuropeptide Y, atrial natriuretic peptide, bradykinin, angiotensin II and enkephalin were poor substrates for the enzyme. The most powerful inhibitors of the ET-1 peptidase included thiorphan (IC50 0.28 nmol/l), phosphoramidon (IC50 0.55 nmol/l), phenanthroline (IC50 11.5 micromol/l), cyclosporin (IC50 400 micromol/l), phosphate (IC50 1.2 mmol/l), citrate (IC50 0.6 mmol/l) and aniline naphthalene sulphonic acid (IC50 0.25 mmol/l). Our data suggest that three ET-1 degrading peptidases with optimal activity at pH 4.5, 5.5 and 7.0, respectively, are excreted into the urine. The enzyme with a pH optimum 4.5 is of lysosomal origin whereas the two other enzymes correspond by their pH optima to the renal ET-1 peptidase and neutral endopeptidase. We have found statistically significant increases (P < 0.001) in the activity of both lysosomal and ET-1 peptidase in the urine in patients with hypertension and in children with chronic renal failure compared with healthy subjects or children with stable renal allograft

CONCLUSIONS

Human kidney contains an acidic, highly specific endothelin-1 inactivating metalloendopeptidase that may have a key role in the regulation of concentrations of renal and circulating endothelins. The enzyme is excreted into the urine where its activity seems to be increased in patients with hypertension and chronic renal failure; it may potentially serve as an indirect index of the renal endothelin system.

[Effect of hydroxylation polymorphism on the concentration of propranolol in the blood of humans with hyperlipidemia]

An influence of hydroxylation phenotype on the concentration of propranolol [corrected] was examined in 52 subjects with hyperlipidemia divided into 4 groups: 1--control, normolipemic, 2--hypercholesterolemic, 3--hypertriglyceridemic, and 4--mixed-form hyperlipidemic. Each study group included extensive metabolizers and one subject characterized by a poor hydroxylation phenotype. Propranolol was given intragastrically at a single dose of 80 mg [corrected]. Blood was sampled within 24 hours following the drug administration. HPLC method was used for determining blood serum concentrations of propranolol. In each study group mean blood serum concentrations of propranolol in poor metabolizers were at maximum in subject with hypertriglyceridemia, at minimum in the normolipemic one, and intermediate in hypercholesterolemic (upper) and mixed-form hyperlipidemic ones. Lipid metabolic disturbances also affected blood serum concentrations. They were the highest in hypertriglyceridemic patients, whereas in hypercholesterolemic were, in early stage of observation, even lower then in normolipemic subjects. Blood serum concentrations of propranolol [corrected] attained minimal values in patients with mixed form of hyperlipidemia. In the light of the present study we can state that hyperlipidemia modifies the blood serum concentrations of propranolol [corrected]. Although, the type of hyperlipidemia and lipophilic propranolol are not the only determinants affecting blood serum concentrations of propranolol, but also a genetic factor, i.e. hydroxylation phenotype may play an important role.

[Evaluation of the rate for reaching steady state during oral propafenone therapy in patients with ventricular arrhythmias]

We prospectively evaluated reaching of steady state and clinical efficacy of propafenone (PPF), class Ic antiarrhythmic agent, in 16 patients (pts) (age 46-69, mean 57 years) with symptomatic ventricular arrhythmias (Low class II and IV). The majority (13 pts) had coronary artery disease. Drug was administered for 7 days (daily dose: 3 x 150 mg). Efficacy was defined as > 80% reduction of ventricular premature complexes (VPC) and class IV elimination in 24-hours Holter recording. Responders were continued on PPF for 3 weeks, in non-responders dose was titrated to 900 mg a day for the next 7 days. After second Holter evaluation the treatment was continued for 2 weeks in responders group. The non-responders were switched to other drug. After 4 weeks final Holter monitoring was performed. Serum concentration of PPF and its 2 metabolites: 5-hydroxy PPF and N-depropyl PPF were determined in 2, 3, 4, 5, 6, 7th day, just before the morning dose (3 x 150 mg/day) in 9 pts.

RESULTS

Trough serum concentrations of PPF differed in high degree: 0-226 ng/ml (2nd day), 22-438 ng/ml (4th day), 42-614 ng/ml (6-7 day). An increasing tendency of serum concentrations of PPF was observed, so steady-state was not reached. This great dispersion of concentration values is because of non-linear metabolism and individual differences. Defined efficacy critetion was achieved in 62% pts, 56% for lower dose. Mean frequency of VPC was reduced by 86% in 24-hour Holter recording and per hour (p = 0.0011). Reduction of couplets/24 h was 87% (p = 0.0175). Significant prolongation of PQ (14%, p = 0.009) and QRS (13%, p = 0.0052) were observed. Changes of QT interval were not significant. One case of proarrhythmia was the cause of stopping the treatment.

CONCLUSIONS

Serum concentrations' values undermine common opinion, that steady state can be reached after 1-2 days of treatment. High dispersion of serum levels is the result of nonlinear metabolism of PPF and individual differences. In spite of this the study showed defined antiarrhythmic efficacy in 62.5% pts. In this group 90% success rate was achieved after lower dose 3 x 150 mg.

N-acetylation and hydroxylation polymorphisms in type II diabetics with microvascular disturbances

The N-acetylation and hydroxylation (CYP2D6) genetic polymorphisms were assessed in 43 healthy subjects and in 84 type II (non-insulin-dependent) diabetics. The proportions of slow and fast acetylators as well as poor and extensive metabolisers in a group of diabetics suffering from microvascular disturbances (nephropathy, retinopathy and neuropathy) were compared with the control group and with diabetics without such complications. Sulphadimidine was used as a probe for polymorphic acetylation and debrisoquine for CYP2D6. Debrisoquine and its 4-OH metabolite were assayed by means of HPLC, and sulphadimidine using a modified Bratton-Marshall procedure. The frequency of the slow phenotype (63%) was significantly higher in diabetics with microvascular disturbances than in patients without diabetic complications (P < 0.005). In patients with type II diabetes (84), only the extensive phenotype of hydroxylation was observed.

[Evaluation of vaccine potency against viral hepatitis B performed with HB-vax II vaccine in a group with an increased risk for hepatitis B]

The aim of this investigation was to established the rate of seroconversion against hepatitis B after vaccination of workers of the National Institute of Cardiology who are at increased risk. All participants were HBs-Ag, and anti-HBs negative and also had normal standard hepatic laboratory tests. Vaccination was carried out according to following scheme: the first vaccination at t = 0, the second after one month and the third after six months. Vaccine was given intramuscular. The success of vaccination was monitored by the quantitative determination of antibodies against HBs-Ag (Anti-HBs) by the ELISA method (Abbott). After each vaccination, anti-HBs formation above 10 iu/l protective level was observed in 40.7%, 85.9%, and 97.1% of immunocompetent subjects after first, second, and third vaccination respectively. The acquired anti-HBs titer varies from individual to individual but in immunocompetent subjects the level of antibodies against HBs after third vaccination was 170 fold higher then those after first vaccination. These results seems to suggest that vaccine HB-Vax-II is effective and may by recommended in pre-exposure prophylaxis against hepatitis B.

Analysis of diltiazem and desacetyldiltiazem in serum by high-performance liquid chromatography

This paper describes a simple high-performance liquid chromatographic (HPLC) method for the determination of diltiazem and desacetyldiltiazem in human serum. After basic methyl-tert-butyl ether extraction and back-extraction with hydrochloric acid, the drug and its metabolite was injected into a Supelcosil LC-CN column and the absorbance of the eluate was measured at 240 nm. The sensitivity was 5 ng/ml and the obtained precision, selectivity and stability during storage were adequate for the performed clinical studies in patients therapeutically treated with diltiazem.

Debrisoquine hydroxylation in a Polish population

The genetic polymorphism of drug oxidation mediated by cytochrome P450IID6 (CYP2D6) was determined in 154 Polish volunteers using debrisoquine as the test substance. The results showed a bimodal distribution of the debrisoquine metabolic ratio (MR). Nine persons (5.8%) with MR > 12.6 were classified as poor metabolisers (gene frequency 0.242), which is in substantial agreement with the data reported for other Caucasian populations.

Characterization of a novel, high-molecular weight, acidic, endothelin-1 inactivating metalloendopeptidase from the rat kidney

OBJECTIVE

To characterize endothelin-1 inactivating peptidase (ET-1 peptidase) recently isolated from rat kidney.

METHODS

ET-1 peptidase was purified from the membranes of whole Wistar-Kyoto (WKY) rat kidneys using differential centrifugation, detergent solubilization, ion-exchange chromatography, ultrafiltration and preparative electrophoresis. The enzyme activity in the presence of increasing concentrations of unlabelled peptides, inhibitors and other substances was determined at pH 5.5 and 37 degrees C using fixed amounts of [125I]-ET-1 as the substrate.

RESULTS

On non-denaturing gels, the purified enzyme migrated in the form of a compact, low-mobility (Rf 0.07), high relative molecular mass (approximately 250,000) protein band. During denaturing polyacrylamide gel electrophoresis this protein separated into three fractions with apparent relative molecular masses 158,000, 110,000 and 61,000. Using different buffers, the optimum pH for this enzyme was found to be 5.5. Zinc (3.7 mmol/l), nickel (4.0 mmol/l), citrate (0.6 mmol/l), phosphate (1.3 mmol/l) and barbital ions (2.5 mmol/l) inhibited ET-1 peptidase activity by 50%, whereas magnesium, calcium, cobalt, manganous, sodium and borate ions were without effect. The most powerful inhibitors of the enzyme included: phenanthroline [median inhibitory concentration (IC50) 28 mumol/l], phosphoramidon (IC50 8.0 nmol/l), thiorphan (IC50 32 nmol/l) and N-carboxymethyl-Phe-Leu (IC50 12 mumol/l). Also, bacitracin (25 mumol/l), cyclosporine A (20 mumol/l) and sodium dodecyl sulphate (0.5%) inhibited enzyme activity by 50%, whereas bestatin, puromycin, aprotinin, phenylmethylsulphonyl fluoride, amanitin (50-100 mumol/l) and cardiotoxin (25 micrograms/assay) had no effect. The Michaelis constant (Km) values of 70 and 66 nmol/l were found towards ET-1 and the ET(16-21) fragment, respectively, whereas the Km values in respect to big-ET-1, sarafotoxin S6b, sulphated cholecystokin octapeptide, gastrin, glucagon, insulin, gastric inhibitory peptide and growth hormone ranged from 1.5 to approximately 50 mumol/l. The enzyme showed no apparent affinity for enkephalins, bradykinin, angiotensins, cholecystokinin tetrapeptides and kyotorphin.

CONCLUSIONS

The present data suggest that the ET-1 peptidase that we isolated from rat kidney displays inhibitory characteristics similar to that of other known metalloendopeptidases. However, this enzyme exhibits several unique properties such as high molecular mass, an apparent complex subunits structure, pH optimum at 5.5, and very high substrate specificity towards ET-1 and the ET(16-21) fragment compared with other peptides either related or unrelated to endothelin.

Purification of endothelin-1-inactivating peptidase from the rat kidney

OBJECTIVE

To identify and purify endothelin-1-inactivating peptidase from rat tissues.

METHODS

Subcellular fractions of rat kidney, aorta, heart, lung, liver and blood cells were prepared by differential centrifugation. Kidney membrane-bound peptidase was solubilized with Triton X-100, chromatographed on the diethylaminoethyl-cellulose, ultrafiltered through a membrane of relative molecular mass 100,000 cutoff and subjected to electrophoresis on a non-denaturing polyacrylamide gel. The enzyme activity assay was performed at pH 5.5 using [125I]-endothelin-1 as the substrate. The trichloroacetic acid precipitation test, an endothelin-1 immunoreactivity assay, reverse-phase high-performance liquid chromatography and a receptor-binding assay were applied for the detection of degradation products.

RESULTS

High-activity endothelin-1-degrading peptidase coincided with the fraction from the kidney membranes of both Wistar-Kyoto and spontaneously hypertensive rats, but not with any other of the tissues that were studied. The membrane (0.5 microgram protein/assay) degraded [125I]-endothelin-1 (5-100 pmol/l) within a half-time of about 10 min at 37 degrees C. The enzyme was purified to an apparent homogeneity with non-denaturing gel electrophoresis, by which it was identified as a low-mobility (Rf 0.07) protein fraction of high relative molecular mass (> 250,000). The optimum pH was 5.5, with a little activity found outside the range 5.0-7.0. The activity of the peptidase was inhibited by 0.5 mmol/l 1,10 phenanthroline (half-maximal inhibitory concentration 0.03 mmol/l), and by 1 mmol/l EDTA, implicating a metalloenzyme. Bestatin, puromycin, phenylmethylsulphonyl fluoride and thiorphan were without effect. Unlabelled endothelin-1 inhibited the degradation of [125I]-endothelin-1 (half-maximal inhibitory concentration 100 nmol/l), whereas 100 mumol/l methionine enkephalin or angiotensin I did not. High-performance liquid chromatography analyses of the [125I]-endothelin-1 incubated with purified peptidase revealed a time-dependent accumulation of one major radioactive fraction that was soluble in trichloroacetic acid. This product (or products) was not further hydrolysed. It did not react with the endothelin antibodies or with the specific, myocardial membrane receptors.

CONCLUSION

Our data suggest that the rat kidney contains an acidic metalloproteinase of high relative molecular mass that is able to hydrolyse endothelin-1 rapidly and efficiently in vitro. The enzyme may participate in the inactivation of circulating or tissue endothelins, or both.

High-performance liquid chromatographic method for the simultaneous determination of propafenone and 5-hydroxypropafenone in human serum

A simple, rapid and sensitive high-performance liquid chromatographic method for the simultaneous determination of propafenone and 5-hydroxypropafenone in human serum is described. Method involves a single-step extraction of the drug and its metabolite with dichloromethane:2-propanol (4:1 v/v) mixture from 0.2 ml of serum. Separation of the investigated compounds on deactivated Supelcosil LC18-DB column is accomplished by ultraviolet detection at 210 nm. The limit of detection is 10 ng/ml for propafenone and 4 ng/ml for 5-hydroxypropafenone. The method is useful for the routine monitoring of propafenone and its main metabolite in serum as well as for the pharmacokinetic studies.