Apelin effects on lipopolysaccharide-increased pulmonary permeability in rats.

MATERIAL AND METHOD: Pretreatment with apelin-13 (AP-13, 2 mg/kg, i.p.), sodium butyrate (BUT, 200 mg/kg, s.c.) and N-acetyl-L-cysteine (NAC, 150 mg/kg, s.c.), all reduced the LPS-induced vascular leak measured as Evans blue extravasation, in rats lung tissue when compared to intranasal LPS (10 mg/100 mL) administered alone. RESULTS: Although there is a significant difference either between AP-13 and BUT on one hand, and NAC and BUT on the other hand pretreatments, there is no significant difference between AP-13 and NAC pretreatments. Firstly, apelin-13 pretreatment might justify its effects through the modulation of endothelial layer functions. We recently demonstrated that AP-13 could diminish the endothelial dysfunction of pulmonary vein from both ovalbumin sensitized rats and rats with pulmonary hypertension. Furthermore, pretreatment with AP-13 + BUT, AP-13+NAC as well as BUT+ NAC reduced the LPS-induced vascular leak when compared to LPS alone. The reduction effects of BUT and NAC association were higher than those of either BUT or NAC alone. These synergistic effects might be associated to different and additive mechanisms of action of BUT and NAC. Thus, BUT might be primarily effective on macrophage migration and secondarily on activation and cytokine secretion by macrophages and NAC might be primarily effective on macrophages activation. Furthermore, since there are no significant effects between AP-13, NAC and AP-13+NAC we can conclude that AP-13 and NAC effects might be mediated through the same mechanisms (with the possible involvement of nuclear transcription factor NF-kB).

Ghrelin and Ang 1-7 have cumulative vasodilatory effects on pulmonary vessels.

UNLABELLED: Ghrelin is an orexigenic hormone that has been shown to have vasodilator effects. Angiotensin 1-7 (Ang 1-7) is a bioactive component of the renin-angiotensin system and may play an important role in the regulation of cardiovascular homeostasis. AIM: The aim of this study was to investigate the interaction between ghrelin and a better known vasodilatator, Ang 1-7. MATERIAL AND METHOD: The dose-dependent relaxing effects of ghrelin were assessed on pulmonary artery rings of male Wistar rats with intact endothelium in the absence or the presence of Ang 1-7. Ang 1-7 was added in the organ bath with 5 minutes before N(G)-nitro L-arginine methyl ester (L-NAME, 1 micro/M) and indomethacin administration in the presence of cumulative doses of ghrelin. RESULTS: Our results showed that Ang 1-7 could improve and restore vasorelaxant effects of ghrelin on rat pulmonary rings with intact endothelium. CONCLUSION: Vasodilatatory actions of ghrelin are potentiated by Ang 1-7 and mediated by local synthesis of prostaglandins and nitric oxide.

Adenosine involvement on bronchial reactivity modulation by diesel exhaust.

UNLABELLED: In recent decades, epidemiologic investigations have suggested a strong relationship between air pollution and an increase in the prevalence of allergic rhinitis and asthma. AIM: To investigate the possible involvement of adenosine (AD) in bronchomotor effects of diesel exhaust (DE). MATERIAL AND METHOD: Isolated bronchi from ovalbumin (OVA) sensitized rats were challenged in presence or absence of diesel exhaust extract (DEE). AD was delivered on organ bath before or after DEE, at concentrations did not produce significantly contractile effects. RESULTS: AD (0.1 microM) pre-treatment increased bronchomotor effects of DEE: amplified the bronchoconstrictor effects of OVA with more than 35% and decreased Emax of terbutaline induced bronchorelaxation of acetylcholine (Ach) preconstricted bronchial rings (up to 20%), but did not significantly modify ACh-induced contractions. OVA-induced contractions, ACh-induced contractions and terbutaline-induced relaxations have not been significantly modified as compare with DEE alone. On the other hand, DEE amplified AD (cumulative doses) contractile effects. CONCLUSION: These results confirmed our initial hypothesis that AD could partial mediate or at least, modulate DEE effects on airway reactivity.

[New insight into nitric oxide involvement in regulation of airways smooth muscle tone]. / New insight into nitric oxide involvement in regulation of airways smooth muscle tone.

UNLABELLED: All three isoforms of NO synthases (NOS) were localised in the lung and are involved in regulation of airways and pulmonary vessels smooth muscle tone and inflammatory response. The participation of nitric oxide in the regulation of airways smooth muscle has not been understood yet. MATERIAL AND METHOD: We studied age-related variation of NO secretion on three lots of bronchi rats: young (4-6 weeks), adults (2-3 months), old (12-14 months). The implied of NO synthesis on airways smooth muscle tone was indirectly investigated by blocking NOS with N(omega)-nitro-L-arginine methyl ester (L-NAME). RESULTS: Pre-treatment of isolated bronchi rings with 0.1 mM L-NAME amplified both tonic contractions induced by cumulative doses of acetylcholine (0.1 nM - 1mM) and various doses of angiotensin II (10 nM - 10 eM). L-NAME actions were lower on old than young rats: at least two times for ACh and three times for Ang II. These results suggest that NO actions decrease with age. Decrease of NO activity on airways was described in pathological states like asthma. CONCLUSIONS: Decrease of NO activity would generate increase of airway smooth muscle tone and would explain partially aging changes on airway reactivity.

[Interactions between angiotensin II and theophylline on isolated rat bronchi]. / Interactiunea angiotensina II--teofilina pe inele de bronhie de sobolan.

UNLABELLED: For more than half of century physicians are using theophylline for the treatment of obstructive pulmonary diseases. Because our previously results suggested the amplification of intrapulmonary renin angiotensin system (RAS) on ovalbumin (OVA) induced airway hyperresponsiveness we studied the interaction between theophylline and angiotensin II (Ang II) on normal versus sensitized rats. MATERIALS AND METHODS: we used main left bronchial rings mounted in wire myograph to assess the effects of Ang II and theophylline on airway smooth muscle. RESULTS: On both normal and OVA sensitized rats theophylline did not significantly modify either Ang II contractile effects or Ang II amplification of acetylcholine (ACh)-induced bronchoconstriction. On the other hand, on sensitized rat after antigen challenge, theophylline pretreatment reduced Ang II inhibition of terbutaline--induced relaxation of bronchial rings precontracted with ACh, increasing both EC50 and E(max) of terbutaline effects with 22.04 +/- 3.48% and 19.48 +/- 1.67%, respectively. CONCLUSION: These findings suggested that, in addition to bronchodilatory and antiinflammatory actions, theophylline could block some effects of intrapulmonary RAS activated in pathologically states as antigen sensitization and challenge.

Contractile effects of angiotensinogen and its multiple metabolization pathways on vessel walls.

The contractile effects of angiotensinogen (Aogen) and its metabolization pathways were studied on rat renal vein (RRV), rat pulmonary artery (RPA) and human umbilical vein (HUV) rings. Experiments were made in the presence or in the absence of pepstatin A (a renin inhibitor, 10 microM), captopril (an ACE inhibitor, 10 microM), chymostatin (a chymase inhibitor, 10 microM), amastatin (an aminopeptidase-A and -M inhibitor) or losartan (a specific AT1 blocker, 10 microM). On all rings, Aogen-induced contractions were reduced by pepstatin A or captopril, amplified by amastatin and blocked by losartan. Chymostatin had a stronger inhibitory effect than captopril on HUV and simultaneous administering of chymostatin and captopril prevented Aogen contractile effects on HUV. It is suggested that all studied vessels possess a local renin-angiotensin system and possibility of angiotensin II production within the vessel walls using various and species-dependent enzymatic pathways.

Interactions between angiotensin I and acetylcholine on rat left main bronchial rings.

Angiotensin (Ang) II is known to amplified bronchoconstriction induced by acetylcholine (ACh). On the other hand all the components of renin angiotensin system were located on lungs. Contractile effects of Ang I (the precursor of Ang II) and interactions between Ang I and ACh on rat bronchial rings were characterize using angiotensin II type 1 (AT1) receptor antagonist (losartan), angiotensin converting enzyme (ACE) inhibitors (captopril and teprotide) and chymase inhibitor (chymostatin). We found that Ang I has contractile effects and amplified ACh-induced contractions. Blocking of AT1 receptors with 10 mM losartan significantly reduced 10 mM Ang I contractile effects (12.79 +/- 9.59% from 167.62 +/- 8.92%; p<0.05). Pre-treatment with 1 mM teprotide reduced 10 mM Ang I-induced contractions (35.68 +/- 7.83%; p>0.05). Captopril and teprotide only reduced Ang I actions. This suggested that both types of Ang I effects were mediated by AT1 receptors, but possibly conversion of Ang I into Ang II were not significantly dependent by ACE or chymase.

Are multiple angiotensin receptor types involved in angiotensin (1-7) actions on isolated rat portal vein.

Angiotensin (1-7) [Ang (1-7)] is a bioactive component of the renin angiotensin system. Ang (1-7) may interact with angiotensin type 1 (AT1) or type 2 (AT2) receptors and with Ang (1-7) - specific receptors. We examined the interactions between different doses of Ang (1-7) (1 nM-1 microM) and angiotensin II (Ang II) (10 and 100 nM) on isolated rat portal vein. In endothelium-denuded portal vein rings, Ang (1-7) inhibited contractile effects induced by Ang II. The effects of Ang (1-7) were modified by indomethacin, N(G)-nitro-L-arginine methyl ester (L-NAME), (D-Ala7)-Angiotensin (1-7) (H-2888) and losartan. Our results suggest that on rat isolated portal vein rings without endothelium, Ang (1-7) reduces Ang II-induced contractions by acting mostly on Ang (1-7) specific receptors, and this effect is mediated by vasodilatatory prostaglandins. At high concentrations, Ang (1-7) effects are mediated by AT1-receptors, though to a lesser extent than by Ang (1-7) specific receptors.

New bioactive angiotensins formation pathways and functional involvements.

After a brief review of the actual knowledge concerning the circulating and tissue Renin-Angiotensin System (RAS) as a unitary hormonal system, the cognitive acquisitions regarding the formation and action mechanisms of the new biologically active angiotensins will be presented. The review of the enzymatic pathways for their synthesis and inactivation, as metabolism products of angiotensin II (1-8), will be followed by the presentation of the main physio-pharmacological actions of angiotensin III (2-8), angiotensin IV (3-8) and angiotensin (1-7). The functional involvements of the cerebral angiotensin IV in what concerns its possible participation in the normal neurochemical processes of memory and in the neurodegenerative processes of Alzheimer disease will be exposed, together with the vasodilating effects of angiotensin (1-7) as counteracting factor for the constricting effects of angiotensin II. The data concerning the bioactive fragments of angiotensin II will be accompanied by those regarding its implication in the cardiovascular modeling and the induction of oxidative stress, inflammation, atherogenesis, etc. In their turn, personal researches bring new experimental evidences in favor of interactions between angiotensin (1-7) and angiotensin II within the rat thoracic aorta. Biphasic, dose-dependent effects were observed for angiotensin (1-7), induced both through nitric oxide, kinins and prostaglandin release for counteracting the vasoconstricting effects of angiotensin II and the modulation of its own vasodilator action.

Are polyamines involved in the contractile effects of angiotensin II in the rat aorta? (Polyamines and angiotensin II in rat aorta).

Angiotensin II (AII) is a central factor involved in the pathophysiology of arterial hypertension and atherosclerosis. On the other hand, polyamines represent a family of organic cations with low molecular weight, playing intracellular regulatory roles essential for the cellular growth and differentiation. The cellular contents, the synthesis and the transport of polyamines are increased following the actions of AII, as well as of other cellular growth factors. Our results show that the administration of polyamines as pre-treatment modulates the contractile effects of extracellular AII (80 nM). This modulation is concentration-dependent and dual: the lower concentrations amplify and the higher concentrations reduce the effects of AII in the isolated rat aorta rings without endothelium. Moreover, DL-alpha-Difluoromethylomithine (DFMO), a specific inhibitor of ornithine decarboxylase, does not significantly modify the contractile effects of AII. Thus, these data suggest that polyamines generated through this metabolic pathway are not involved in the contractile effects of AII in rat aortic vascular smooth muscle.

[Cytosolic calcium dynamics and smooth muscle contraction.III Plasmalemmal calcium fluxes]. / Dinamica citosolica a calciului si contractia muschiului neted. III. Fluxuri de calciu plasmalemale.

Smooth muscle contractile activity depends upon cytosolic Ca2+, the Ca(2+)-sensitivity of actin-myosin interaction and several auxiliary mechanisms. This section presents the plasmalemmal Ca2+ fluxes in relation with the functional structure of their supportive proteins and the contractile impact. Summaries of classical data are accompanied by examples of recent advances. Ca2+ influx occurs mainly via the L and T types of voltage-operated Ca2+ channels, the store-operated Ca2+ channels and the non-selective cation channels (operated by membrane receptors or mechanical stimuli). The plasmalemmal Ca2+ ATPase and Na/Ca antiport function to limit increases in cytosolic Ca2+; Na/Ca effect is opposite when driven to operate in the reverse mode.

[Polyamines antagonizing angiotensin II contractile effects in isolated rat aorta]. / Antagonizarea efectelor contractile ale angiotensinei II de catre poliamine la nivelul aortei izolate de sobolan.

Our study showed that the administration in pre-treatment of some polyamines (especially spermine and spermidine and almost null agmatine, putrescine and cadaverine) reduced the contractile effects of angiotensin II (Ang II) in isolated rat aorta. These effects might not be associated to the interference of clathrin coated vesicles (coated pits) formation or caveolae interaction (and thus to Ang II internalization through AT1 receptors). In contrast, these effects seem to be due to the interaction with voltage-gated membrane Ca2+ channels. Therefore, the alteration of transmembrane Ca2+ fluxes does not exclude the involvement of internalization process through coated pits or caveolae, since the endocytosis mediated by these phenomena essentially needs Ca2+. In addition, the inhibitory effects are dependent on the number of positive charges of the polyamine molecules.

[Interactions between angiotensin-(1-7)and angiotensin II in isolated rat portal vein]. / Interactiuni ale Angiotensinei-(1-7) cu Angiotensina II la nivelul venei porte izolate de sobolan.

Our preliminary data show for the first time the interaction between angiotensin-(1-7) (Ang-(1-7)) and angiotensin II (Ang II, 10 nM) in isolated rat portal vein. Very low concentrations (10 nM) of Ang-(1-7) have marked functional antagonizing effects on Ang II-induced contractions. High concentrations of Ang-(1-7) (1-10 mM) do not affect the effects of Ang II. The effects of low concentration Ang-(1-7) might be associated to the interaction with Ang-(1-7) specific receptors and the own contractile effects (approximatively 28%) at high concentrations might be assign to the interaction with angiotensin specific receptors AT1. But, the lack of effects of Ang-(1-7) high concentrations on Ang II-induced contractions hardly might be associated to the interaction with AT1 receptors. Although losartan was entirely blocking the Ang-(1-7) effects, there is in the literature a series of data showing that Ang-(1-7) specific receptors (or a subtype of Ang-(1-7) receptors) might be sensible (with possible high affinity) to losartan. Additional experiments are thus necessary to further clarify these interactions.

[Effects of polyamine-loaded liposomes on liver mitochondrial permeability transition]. / Efectele poliaminelor încarcate în lipozomi asupra permeabilitatii tranzitorii mitocondriale (PTM) hepatice.

The objective of the present study was represented by the effects of polyamineloaded liposomes on hepatic mitochondrial permeability transition (MPT). MPT was appreciated through the swelling of the isolated guinea-pig liver mithocondria induced by Ca2+, at 540 nm, using a diode-array 8452 UV-VIS spectrophotometer and a General Purpose software (Hewlett-Packard). Polyamines encapsulated in liposomes might inhibit the appearance of MPT induced by Ca2+, directly proportional to electrical charge: spermine > spermidine > putrescine > cadaverine. Thus, together with some previous data, it was observed that spermine may modulate hepatic MPT from the exterior, as well as from the interior of mitochondria. Moreover, spermidine and putrescine may also modulate MPT from the interior of mitochondria at low doses, and from the exterior only at high doses. The changes in mitochondrial membranes lipid composition (as done by control liposomes) are slightly influencing the MPT. The increase in membrane rigidity through the use of 40% cholesterol-enriched liposomes is drastically decreasing the appearance and development of MPT.

[Cytosolic calcium dynamics and smooth muscle contraction(II): Reticular calcium fluxes]. / Dinamica citosolica a calciului si contractia muschiului neted (II): Fluxuri de calciu reticulare.

The contractile status of smooth muscle depends upon cytosolic Ca2+, the Ca(2+)-sensitivity of actin-myosin interaction and various calcium-independent mechanisms. This second part of our overview is devoted to the complex involvement of endoplasmic reticulum in the cytosolic Ca2+ signals related to smooth muscle contractile activity, with a focus on the functional structure of reticular membrane proteins that ensure the respective Ca2+ fluxes. Ca2+ release is activated by cytosolic Ca2+, involving reticular channels called inositol triphosphate receptors and ryanodine receptors. Beside calcium and inositol triphosphate, cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate have recently emerged as intracellular signals that activate Ca2+ release. The reticular Ca2+ pump is essential both for the control of cytosolic Ca2+ and for the preservation of reticular stores.

Pepstatin A is inducing contractile effects on isolated rat aorta rings.

In a series of experiments dealing with the effects of angiotensin I (AI) and angiotensinogen on isolated rat aorta we observed that pepstatin A was able to induce contractile effects by itself. The endothelin pathway was excluded by the inhibitory effects of captopril, chymostatin and amastatin. In addition, few preliminary experiments showed that the contractile effects of pepstatin A were inhibited by the pretreatment with losartan, an antagonist of AT1 angiotensin receptors. Pepstatin A-induced contractile effects on isolated rat aorta were inhibited with high potency by captopril, chymostatin and amastatin and were totally blocked by captopril + amastatin and captopril + chymostatin. Finally, we concluded that the pepstatin A-induced contractile effects on isolated rat aorta rings are dependent on an angiotensinogen vascular pool, compulsory involve an angiotensin-converting enzyme-1 (ACE-1) mediated pathway and one or more non-classical pathways for the generation of angiotensin peptides. Further experiments are necessary to elucidate the mechanisms associated to pepstatin A-induced effects.