Oxysterol, 5α-cholestan-3-one, modulates a contractile response to ß2-adrenoceptor stimulation in the mouse atria: Involvement of NO signaling.

AIM: Atrial ß2-adrenoceptors provide an important mechanism for regulation of cardiac function and changes in their downstream signaling are involved in processes underlying heart disorders. We have investigated the mechanism by which the cholesterol metabolite 5α-cholestan-3-one (5ɑCh3) modulates inotropic effect of ß2-adrenoceptor agonist fenoterol. MAIN METHODS: Atria from mice were electrically stimulated and changes in contraction amplitude in response to fenoterol were studied in 5ɑCh3-pretreated samples. Intracellular Ca2+ and NO levels were estimated using fluorescent dyes Fluo-4 and DAF-FM, respectively. KEY FINDINGS: By itself 5αCh3 that appears in the circulation under some pathological conditions had a negligible influence on contraction, Ca2+-transient and NO production. However, pretreatment with 5αCh3 markedly attenuated the positive inotropic effect of fenoterol which was accompanied by an increase in the NO synthesis. Unexpectedly, the oxysterol also augmented an enhancement of Ca2+-transient amplitude in response to fenoterol. Under conditions of a pharmacological inhibition of Gi-protein/Akt/NO synthase/protein kinase G signaling, 5αCh3 augmented the inotropic effect of fenoterol. Herein, Akt antagonist suppressed the increase in NO production, while inhibition of NO synthesis did not modify the increased amplitude of the Ca2+-transient. Along similar lines, enrichment of plasma membranes with cholesterol reduced the stimulatory effect of 5αCh3 on ß2-adrenoceptor-evoked NO production, but not on the Ca2+-transient amplitude, leading to an elevation of the positive inotropic response to fenoterol. SIGNIFICANCE: These data suggest that 5ɑCh3 potentiates the effect of pharmacological ß2-adrenoceptor activation on both NO production and Ca2+ transient via independent mechanisms, thereby affecting the positive inotropy.

Nociceptin inhibits vanilloid TRPV-1-mediated neurosensitization induced by fenoterol in human isolated bronchi.

Chronic exposure to beta(2)-adrenoceptor agonists, especially fenoterol, has been shown to increase smooth muscle contraction to endothelin-1 in human bronchi partly through tachykinin-mediated pathways. The purpose of this work was to further investigate the role of sensory nerves in fenoterol-induced sensitization of human airways and the effect of nociceptin, a nociceptin/orphanin FQ (NOP) receptor agonist, on the increase in contraction after fenoterol exposure. Human bronchi from 62 patients were sensitized to endothelin-1 by prolonged incubation with fenoterol (0.1 microM, 15 h). The sensitizing effect of fenoterol was inhibited by high concentration of capsaicin (10 microM, 30 min before fenoterol sensitization), which induces depletion of mediators from sensory nerves, or co-incubation of fenoterol and capsazepine (1 microM), a vanilloid TRPV-1 receptor antagonist. Moreover, short pretreatment of bronchi with capsaicin (10 microM) or capsazepine (1 microM) after sensitization by fenoterol decreased the rise in smooth muscle contraction to endothelin-1. Nociceptin (1 microM) also inhibited the increased contraction in fenoterol-sensitized bronchi. Tertiapin (10 microM), an inhibitor of the inward-rectifier K(+) channels, but not naloxone (0.1 microM), a DOP/KOP/MOP receptor antagonist, prevented the inhibitory effect of nociceptin. In conclusion, fenoterol induces sensitization of human isolated bronchi to endothelin-1 in part through the stimulation of the vanilloid TRPV-1 receptor on tachykininergic sensory nerves. Nociceptin inhibits airway hyperresponsiveness via NOP receptor activation. This effect involves inward-rectifier K(+) channels.

SR 142801, a tachykinin NK(3) receptor antagonist, prevents beta(2)-adrenoceptor agonist-induced hyperresponsiveness to neurokinin A in guinea-pig isolated trachea.

We investigated whether fenoterol was able to enhance contractile responsiveness to neurokinin A (NKA) on the guinea-pig isolated trachea. We then studied the effects of two inhibitors of nuclear factor kappa B (NFkappaB), gliotoxin and pyrrolidine dithiocarbamate, and of the tachykinin NK(1), NK(2) and NK(3) receptor antagonists, SR 140333, SR 48968 and SR 142801 and determined whether tachykinin receptor gene expression was up-regulated in the trachea after exposure to fenoterol. Fenoterol (0.1 microM, 15 h, 21 degrees C) induced an increased contractile response to NKA (mean of difference in maximal tension between control and fenoterol +/- S.E.M; +0.47 +/- 0.14 g, n = 26, P < 0.01). This hyperresponsiveness was strongly reduced by co-incubation with gliotoxin (0.1 microg/ml) or pyrrolidine dithiocarbamate (0.1 mM) and abolished by SR 140333 (0.1 microM) and SR 142801 (0.1 microM). SR 48968 (0.1 microM) diminished the tracheal contractility to NKA but failed to reduce the hyperreactivity induced by fenoterol. Tachykinin NK(1) receptor (NK(1)R), NK(2) receptor (NK(2)R) and NK(3) receptor (NK(3)R) gene expression was analyzed by semiquantitative RT-PCR. Compared to control tissues, NK(1)R and NK(2)R mRNA expression was increased by about 1.6-fold and 1.4-fold, respectively, in tissues treated with fenoterol. We were unable to detect the presence of NK(3)R mRNA in the guinea-pig trachea. In conclusion, fenoterol induces tracheal hyperresponsiveness to NKA and an up-regulation of NK(1)R and NK(2)R gene expression. The hyperresponsiveness implicates the NFkappaB pathway and is abolished by tachykinin NK(1) (SR 140333) and NK(3) (SR 142801) receptor antagonists.

Role of cyclic AMP in the modulation of IgE production by the beta 2-adrenoceptor agonist, fenoterol.

We have previously demonstrated that the beta 2-adrenoceptor agonist, salbutamol, potentiates the effect of interleukin-4 (IL-4) on immunoglobulin E (IgE) production by human peripheral blood mononuclear cells (PBMC). This study was undertaken to further define the activities of these drugs and the role of cyclic-adenosine monophosphate (cAMP) in the modulation of IgE production. Our results indicate that fenoterol (1 microM) potentiated IL-4-induced IgE production and IgE messenger ribonucleic acid (mRNA) expression. Moreover, this effect was associated with an increase in intracellular cAMP levels. The activities of this drug on IgE production were mimicked by cell permeable cAMP analogues, such as dibutyryl-cAMP (db-cAMP) (100 microM) or Sp-AMP (10 microM). The potentiating effect of fenoterol on IgE production was markedly inhibited in the presence of protein kinase A (PKA) inhibitors: H8 (10 microM) and Rp-AMP (10 microM), suggesting that its effects are likely to depend on the activation of the cAMP pathway. Additionally, the potentiating effect of fenoterol was also blocked in the presence of indomethacin. Fenoterol potentiated IL-4-induced IgE production from purified B-cells activated through their CD40 antigen. This effect was associated with an increase in cellular viability. Therefore, the activities of this drug on PBMC are likely to be mediated by the activation of another cellular type. Taken together, these results show that fenoterol potentiates the IL-4-induced IgE production via the cAMP pathway, but that this enhancement could not be explained by a direct effect on B-lymphocytes.

[Prenatal effect of fenoterol (Partusisten) on the heart in the presence of verapamil]. / Pränatale Herzwirkungen des Fenoterol (Partusisten) in Gegenwart von Verapamil.

The effect of fenoterol and fenoterol + verapamil on fetal hearts obtained from termination of pregnancy and surviving in nutrient solution was investigated. In 10--20-week-old fetal hearts, under the influence of fenoterol, a concentration-dependent increase was observed in spontaneous rate and contractility. A close linear correlation was found between the fetal age and the tachycardiac effect of the drug. The positive chronotropic and inotropic effect of fenoterol was significantly decreased by a therapeutically meaningful concentration (20 micrograms/l) of verapamil. The results are in favour of the suggestion that the inhibition by verapamil of the in utero fetal tachycardiac effect of fenoterol might occur, at least in part, in the fetal heart itself.

The costo-uterine muscle of the rat contains a homogeneous population of beta-adrenoceptors.

The effects of two selective beta-adrenoceptor antagonists on the inhibitory responses to some sympathomimetic amines of electrically-stimulated preparations of costo-uterine muscle, taken from virgin rats, have been examined quantitatively. pA2 values for the antagonist, atenolol (beta 1-selective) and ICI 118,551 (beta 2-selective) were obtained using as agonists, fenoterol (beta 2-selective agonist) and noradrenaline (alpha- and beta-adrenoceptor agonist, beta 1-selective); and in addition, with ICI 118,551 only, isoprenaline (beta-agonist, non-selective) and adrenaline (alpha- and beta-adrenoceptor agonist, beta 2-selective). Catecholamine uptake mechanisms and alpha-adrenoceptors were not blocked in any of these experiments. Atenolol competitively antagonized the effects of fenoterol and noradrenaline to a similar extent, the pA2 values being 5.4 and 5.7, respectively. ICI 118,551 competitively antagonized the effects of fenoterol, isoprenaline, adrenaline and noradrenaline to a similar extent; pA2 values ranged from 8.7 with noradrenaline to 9.1 with isoprenaline. These results extend our previous observations which indicated that the adrenoceptors mediating inhibition of electrically-evoked contractions of costo-uterine muscle of the virgin rat are homogeneous and of the beta 2-subtype. The potency of the beta 1-selective agonist RO 363 in producing inhibition of electrically-evoked contractions of this tissue was also examined. RO 363 was 200 times less potent than isoprenaline but was a full agonist. This indicates that there is efficient coupling between beta 2-adrenoceptor activation and tissue response in this non-innervated preparation.

Effect of fenoterol on immunological release of leukotrienes and histamine from human lung in vitro: selective antagonism by beta-adrenoceptor antagonists.

The inhibitory effects of fenoterol, a beta 2-adrenoceptor agonist, on the release of SRS-A leukotrienes and histamine from chopped human lung tissue were measured and selective beta-adrenoceptor antagonists used to investigate the nature of the receptors involved. Fenoterol 0.01-1.0 microM inhibited the antigen-induced release of SRS-A and histamine, but not the release induced by the calcium ionophore A23187. Propranolol 0.1 and 1.0 microM and butoxamine 10 and 100 microM significantly antagonized the effects of fenoterol 0.1 microM on SRS-A and histamine at concentrations which affect (beta 2-adrenoceptors, while atenolol 0.1 to 10 microM showed no antagonism at concentrations which affect beta 1-adrenoceptors. These results suggest that adrenoceptors in human lung which modulate the immunological release of SRS-A leukotrienes are of the beta 2-subtype as for histamine release.

[The cardiac hazard of tocolysis and antagonising possibilities. I. The haemodynamic situation of the patient during tocolysis/Protection of the myocardium by means of cardioselective beta-blockade. Experimental results (author's transl)]. / Das kardiale Risiko bei Tokolyse und Möglich-keiten zu dessen Antagonisierung. I. Mitteilung: Zur hämodynamischen Situation der tokolysierten Patientin/Kardioprotektion durch Kardioselektive beta-blocker. Tierexperimentelle Ergebnisse.

7 mongrel dogs underwent general anaesthesia and thoracotomy. For the assessment of the haemodynamic situation the following parameters were measured: Left ventricular and aortic pressure, coronary flow, oxygen-saturation in the coronary sinus, pulmonal arterial pressure, central venous pressure, heart rate. From these measurements cardiac output volume and myocardial oxygen consumption could be calculated. Using an ultrasound transit-time method regional myocardial function could be assessed. After the establishment of these measurements Fenoterol has been given in an increasing dosage up to the upper therapeutical range. Then additionally the cardioselective beta-antagonist Metoprolol was administered stepwise up to a total dose of 1.2 mg/kg body weight. The measurements proved evidence, that a relatively small dose of 0,2-0,4 mg Metoprolol/kg body weight is sufficient to compensate the haemodynamic situation impaired by Fenoterol, esp. the rise in myocardial oxygen consumption.

[Treatment of premature labour and antagonization of the side effects of tocolytic therapy with verapamil (author's transl)]. / Die Behandlung der vorzeitigen Wehentätigkeit und Antagonisierung der Nebenwirkungen der tokolytischen Therapie mit Verapamil.

167 cases of threatened premature birth were treated with Fenoterol, Fenoterol + Verapamil and Ritodrine. In 70-79% of cases a newborn of over 2500 g was achieved. In 70-76% it was possible to prolong the pregnancy for over 7 days and in 61-64% a gestation age of 37 weeks and more was reached. Special attention was paid to the facts as to whether the general side effects of Fenoterol can be antagonized with Verapamil.