Maria Dulce Cotrim

Angiotensin II mediates catecholamine and neuropeptide Y secretion in human adrenal chromaffin cells through the AT1 receptor

The aim of the present work was to study the effect of angiotensin II (Ang II) on catecholamines and neuropeptide Y (NPY) release in primary cultures of human adrenal chromaffin cells. Ang II stimulates norepinephrine (NE), epinephrine (EP) and NPY release from perifused chromaffin cells by 3-, 2- and 12-fold, respectively. The NPY release is more sustained than that of catecholamines. We found that the receptor-AT(2) agonist, T(2)-(Ang II 4-8)(2) has no effect on NE, EP and NPY release from chromaffin cells. We further showed that Ang II increases intracellular Ca(2+) concentration ([Ca(2+)](i)). The selective AT(1)-receptor antagonist Candesartan blocked [Ca(2+)](i) increase by Ang II, while T(2)-(Ang II 4-8)(2) was ineffective. These findings demonstrate that AT(1) stimulation induces catecholamine secretion from human adrenal chromaffin cells probably by raising cytosolic calcium.

Migraine, Serum Serotonin and Platelet 5–HT2 Receptors

In spite of recent theories about the aetiopathogenesis of migraine, serotonin continues to play a central role, explaining the efficacy of almost all migraine prophylactic drugs. In migraineurs with and without aura we measured (by HPLC-EC) the serum serotonin (5–HT) and 5–hydroxyindoleacetic acid (5–HIAA) levels between as well as during headache attacks. Between attacks of migraine with aura and at the beginning of attacks of both types of migraine the serum 5–HT and 5–HIAA concentration was significantly increased. These results were corroborated by 3H-spiperone binding to platelet membranes: in migraineurs with aura in the attack-free interval, there was a significant decrease in its Bmax, which suggests down-regulation of 5–HT2 receptors. In conclusion, we have verified that migraine with aura differs biochemically from migraine without aura.

Changes in platelet membrane fluidity of migraine patients.

Platelet membrane fluidity was measured in migraine patients, with and without aura, using the fluorescent probe TMA-DPH (1–[4–(trimethylammonium) phenyl]-6–hexa-1,3,5–triene). Polarization values for TMA-DPH were significantly higher in the platelet membranes of migraine patients (with or without aura) than in those of healthy subjects. These findings signify decreased membrane fluidity and may explain some modifications in receptors, carriers or enzymes described in platelets of migraine patients.

In vitro study of the interaction of Tilia europeae L. aqueous extract with GABAA receptors in rat brain

The interaction of GABAA receptor‐complex in rat brain was investigated in vitro with aqueous extracts obtained from the inflorescences of Tilia europeae L., using the [3H]muscimol and [3H]flunitrazepam binding techniques to synaptic membranes and the uptake of 36Cl‐ to synaptoneurosomes from cortices. The extract inhibited [3H]muscimol binding, stimulated 36ClCl‐ uptake by synaptoneurosomes and displaced at high concentrations, the [3H]flunitrazepam bound to synaptic membranes. When analysed by HPLC, the aqueous extract of Tilia europeae L. contained several amino acids, including GABA (about 100 μM). This GABA content can justify the displacement of [3H]muscimol produced by the extract but it did not increase the binding of [3H]flunitrazepam, as expected. Probably the extract contains other benzodiazepine‐like substances which displace the [3H]flunitrazepam binding and counteract the expected GABA‐induced increase in [3H]flunitrazepam binding.

Monoamine oxidase activity in blood platelets of migraine patients

Biochemical changes in platelets of migraine patients during the attacks have been reported before, however there are some conflicting results. In an attempt to define the biochemical lesion in the platelets, we have carried out a survey of platelets monoamine oxidase in migraine patients with and without aura. Platelet MAO activity in platelets from migraine patients was significantly reduced when compared with normal platelets.

Monoamine oxidase activities in human cystic and colonic arteries — influence of age

The deamination of 5-hydroxytryptamine, phenylethylamine and benzylamine by monoamine oxidases (MAO-A and B) and semicarbazide sensitive amine oxidase (SSAO) respectively has been studied in homogenates of human cystic and colonic arteries by radiochemical assays. In cystic artery the deamination is mainly carried out by SSAO with a lower participation of MAO-B. The kinetic parameters were: to MAO-B the Vmax = 15.11 +/- 0.51 nmol/mg protein.h and the Km = 78.51 +/- 5.16 microM (+/- SE) and to SSAO the Vmax = 211.70 +/- 8.75 nmol/mg protein.h and the Km = 211.51 +/- 23.27 microM (+/- SE). We could not measure MAO-A activity in our experimental conditions and also the levels of catecholamines are very low and the histological studies show a poor innervation in these tissues. In colonic artery the kinetic parameters were: to MAO-B the Vmax = 5.09 +/- 0.31 nmol/mg protein.h and the Km = 29.12 +/- 4.55 microM (+/- SE) and to SSAO the Vmax = 273.67 +/- 8.35 nmol/mg protein.h and the Km = 197.89 +/- 21.81 microM (+/- SE). In this artery we could find MAO-A in five among the nine samples studied and the kinetic parameters were: the Vmax = 14.48 +/- 0.82 nmol/mg protein.h and the Km = 136.40 +/- 25.46 microM. As we have performed the experiments with human vessels from donors with different age we could not find any relationship between the activity or affinity, in MAO-B and SSAO, with age. Nevertheless, the results show in cystic artery an increase in the affinity of MAO-B with age when we consider the female group which suggests a possible role of the hormonal condition in this behaviour.

Endothelium-dependent vasoactivity of the human internal mammary artery.

Coronary artery disease is recognized as a major health problem worldwide, particularly because of the associated morbidity and mortality. Coronary artery bypass grafting has been an established mainstay in the treatment of this disease for almost half a century and is arguably the most intensively studied surgical procedure ever undertaken. Because of its unique properties, the human internal mammary artery has long been considered the best graft to use in this type of surgery. Previous studies have shown several advantages of this graft compared with others, that is, lower incidence of atherosclerosis. However, few comparative studies on the reactivity of this artery have been published. Moreover, these studies usually focus on isolated cardiovascular risk factors rather than combined risk factors. In fact, patients who require coronary revascularization usually present multiple risk factors, which can interfere with several pathways of regulation of vascular function, namely endothelial function. Several diseases and cardiovascular risk factors have been shown to interfere with endothelial function, promoting the production of vasoconstrictors, inhibiting the production of vasodilators, or both, and thus eventually leading to endothelial dysfunction. Therefore, it is of great interest to study the endothelial function, particularly of the human internal mammary artery, in the presence of combined cardiovascular risk factors and concomitant diseases. Many techniques have been developed to assess the endothelial function, in particular, studies on isolated arteries, as well as spectroscopic, electrochemical, and immunological methods, among others.

Ultrastructural and histomorphologic properties of the internal thoracic artery: implications for coronary revascularization

Coronary artery disease represents a major health problem worldwide for which coronary artery bypass surgery remains a standard of care. Among the several grafts that are available, the internal thoracic artery (ITA) has long been considered the best as several advantages have been described compared with other vessels (e.g. saphenous vein or radial artery), namely, an absent to minor atherosclerotic development. In fact, several studies showed the presence of preatherosclerotic lesions, such as intimal and/or medial thickening, medial fibrosis, among others, in the presence of certain cardiovascular risk factors as well as established atherosclerotic lesions (i.e. type II or more lesions). This paper primarily aimed at reviewing the current knowledge on the histomorphological characteristics of ITA as well as the comparative histomorphology of ITA with other vessel grafts currently in use in coronary surgery. As some of the evidence is not clear or consensual, this paper also aimed at reviewing the main histopathological, histomorphometrical, and ultrastructural findings in ITAs from patients with known cardiovascular risk factors (e.g. aging, obesity, hypertension, diabetes, smoking, and others). As the presence of preatherosclerotic and/or atherosclerotic lesions may compromise the success of the myocardial revascularization and lead to graft failure, contributing toward the associated morbidity and/or mortality, it is essential to improve the scientific knowledge on the structural characterization of ITAs and its correlation with the cardiovascular risk profile.

Contractile effects of 3,4-methylenedioxymethamphetamine on the human internal mammary artery

Since the late 1980s numerous reports have detailed adverse reactions to the use of 3,4-methylenedioxymethamphetamine (MDMA) associated with cardiovascular collapse and sudden death, following ventricular tachycardia and hypertension. For a better understanding of the effects of MDMA on the cardiovascular system, it is critical to determine their effects at the vasculature level, including the transporter or neurotransmitter systems that are most affected at the whole range of drug doses. With this purpose in mind, the aim of our study was to evaluate the contractile effect of MDMA in the human internal mammary artery, the contribution of SERT for this effect and the responsiveness of this artery to 5-HT in the presence of MDMA. We have also studied the possible involvement of 5-HT2 receptors on the MDMA contractile effect in this human blood vessel using ketanserin. Our results showed that MDMA contracted the studied humans internal mammary artery in a SERT-independent form, through activation of 5-HT2A receptors. Considering the high plasma concentrations achieved in heavy users or in situations of acute exposure to drugs, this effect is probably involved in the cardiovascular risk profile of this psychostimulant, especially in subjects with pre-existing cardiovascular disease.

Polyphenolic characterisation and bioactivity of an Oxalis pes-caprae L. leaf extract

Abstract The present work is focused on the characterisation of the polyphenolic content of an Oxalis pes-caprae L. leaf extract and on the evaluation of its bioactivity with particular interest on its vascular activity and antioxidant potential. The polyphenolic content was characterised by HPLC-DAD and LC-MS/MS. The vascular activity was evaluated according to the influence on the serotonergic and adrenergic systems of the human internal mammary artery (HIMA). Antioxidant and neuroprotective studies were also conducted. Several luteolin and apigenin derivatives were identified as main constituents of the extract, which did not present any contractile effect nor had any effect on the serotonergic system of HIMA. However, it showed antagonistic effect on the adrenergic system, inhibiting the contraction to noradrenaline (reduction of 58.44% of maximum contraction). The extract showed antioxidant activity and standardised luteolin and apigenin derivatives showed neuroprotective potential, particularly homoorientin.