Inhaled atrial natriuretic peptide and asthmatic airways

Contentious role of 'Good Adiponectin' in pulmonary and cardiovascular diseases: Is adiponectin directed therapy a boon or a bane?

After two decades of its discovery, numerous facts of adiponectin (APN) biology has been uncovered, yet, APN remains an elusive adipokine. Findings from clinical studies and animal models established APN's ameliorative role in cardiovascular disease (CVD) and pulmonary disease (PD) but the same condition is prognostic for mortality in the same set of patients which cornered APN towards a dubious state. A repertoire of mechanisms associated with the positive association of APN in both lean/cachectic or obese CVD and PD patients from past publications are evaluated. Newer pharmacological agent may be explored to regulate elevated blood APN concentration in COPD or CHF patients whereas administration of recombinant APN as well as growth hormone may augment blood APN concentration in obese subjects associated with low blood and intracellular APN concentration. However, some APN directed therapy in clinical as well as in pre-clinical setup has pronounced some contentious effects. After reviewing the mechanisms of the contentious role of APN functioning in pathologic conditions of CVD and PD in both lean and obese conditions, the authors came to conclusion that APN directed therapy may be utilized with caution keeping in mind the different age group, sex and the different CVD as well as pulmonary diseases they are suffering from.

Influence of atrial natriuretic peptide, brain natriuretic peptide and urodilatin on the histamine-induced bronchoconstriction in the conscious guinea pig

The influence of human atrial natriuretic peptide (ANP) and of two related peptides, human brain natriuretic peptide (BNP) and urodilatin (URO) on the bronchoconstriction induced by inhalation of histamine in conscious, non-anaesthetized guinea pigs was tested.Changes in lung function were registered using two independent methods, one operating in a closed body-plethysmographic system, the other in an open system based on the time lag of air flow curves. The peptides were infused (0.25 ml/min) into the jugular vein for a period from 10 min before until 15 min after the histamine inhalation.ANP displayed virtually no effect on the bronchoconstriction. URO showed some inibition at 1280ng kg(-1) min(-1), but not at lower doses. BNP (640ng kg(-1) min(-1)) inhibited the bronchoconstriction markedly for the total registration period.It can be concluded from these results that BNP exerts bronchoprotective effects in the conscious guinea pig, which are superior to those of ANP or URO.

Bronchodilator effect of infused B-type natriuretic peptide in asthma

STUDY OBJECTIVE

To determine the bronchodilator effect of recombinant human B-type natriuretic peptide (BNP; nesiritide) on patients with asthma.

DESIGN

A prospective, open-label study.

SETTING

Outpatient setting.

PATIENTS

Eight adult patients with asthma confirmed by > 12% and > 200 mL increase in FEV1 after bronchodilator inhalation.

INTERVENTIONS

An IV nesiritide bolus, 2 microg/kg, followed by continuous infusion for a total of 3 h at escalating doses of 0.01, 0.02, and 0.03 microg/kg/min for 1 h each as tolerated.

MEASUREMENTS

Spirometry and forced oscillation technique (FOT) measurements were both obtained at baseline and every 30 min during the infusion. Two doses of albuterol, 90 microg, inhalation via metered-dose inhaler were then administered at the end of nesiritide infusion, followed by repeat spirometry and FOT measurements after 30 min. Primary end points were FEV1 and FVC changes after the nesiritide infusion for 3 h. Wilcoxon signed-ranks tests were used to compare the effects of nesiritide and albuterol.

RESULTS

Baseline measurements (mean +/- SD) were as follows: FEV1, 1.89 +/- 0.87 L; FVC, 3.02 +/- 0.99 L; respiratory resistance at 5 Hz (Rrs5), 10.3 +/- 3.85 cm H2O . s/L; and mean respiratory resistance at 5 to 20 Hz, 7.56 +/- 1.92 cm H2O/L/s. Mean baseline serum BNP level was 27 +/- 27 pg/mL. After 180 min of nesiritide infusion, the following measurements showed significant changes: FEV1 increased to 2.41 +/- 0.78 L (mean increase, 520 mL), p = 0.012; FVC increased to 3.65 +/- 1.05 L (mean increase, 630 mL), p = 0.017; and Rrs5 decreased to 8.24 +/- 4.02 cm H2O/L/s, p = 0.017. After albuterol, there were no further significant changes in these measurements.

CONCLUSION

IV nesiritide is an effective bronchodilator in patients with asthma.

Guanylyl cyclases, nitric oxide, natriuretic peptides, and airway smooth muscle function

Airway smooth muscle (ASM) plays an important role in asthma pathophysiology through its contractile and proliferative functions. The cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) are second messengers capable of mediating the effects of a variety of drugs and hormones. There is a large body of evidence to support the hypothesis that cAMP is a mediator of the ASM's relaxant effects of drugs, such as beta2-adrenoceptor agonists, in human airways. Although most attention has been paid to this second messenger and the signal transduction pathways it activates, recent evidence suggests that cGMP is also an important second messenger in ASM with important relaxant and antiproliferative effects. Here, we review the regulation and function of cGMP in ASM and discuss the implications for asthma pathophysiology and therapeutics. Recent studies suggest that activators of soluble and particulate guanylyl cyclases, such as nitric oxide donors and natriuretic peptides, have both relaxant and antiproliferative effects that are mediated through cGMP-dependent and cGMP-independent pathways. Abnormalities in these pathways may contribute to asthma pathophysiology, and therapeutic manipulation may complement the effects of beta2-adrenoceptor agonists.

Atrial natriuretic peptide gene transfer by means of intranasal administration attenuates airway reactivity in a mouse model of allergic sensitization

Atrial natriuretic peptide (ANP) is a bronchodilator; however, the short half-life of ANP in vivo limited its therapeutic utility to treat asthma. The efficacy of intranasally administered plasmid DNA-expressing ANP (pANP; amino acid 99-126; Acc. No. XM131840) on the prevention of allergen-induced airway hyperresponsiveness (AHR) was examined in this study by using a mouse model of asthma. Ovalbumin-sensitized mice were treated with pANP versus control plasmids, and AHR was monitored after ovalbumin challenge for 5 weeks on 10-day intervals starting 4 days after gene transfer. Mice administered pANP demonstrated significantly less AHR for 20 days after treatment. The results demonstrate that pANP gene transfer protects against AHR and might be useful in the treatment of asthma.

Effect of inhaled thiorphan, a neutral endopeptidase inhibitor, on the bronchodilator response to inhaled atrial natriuretic peptide (ANP)

BACKGROUND

The hormone atrial natriuretic peptide (ANP) causes bronchodilation and partially protects against direct and indirect bronchial challenges. Both in vitro and in vivo studies have found that the protective effect of ANP against bronchoconstriction is enhanced by inhibition of the enzyme neutral endopeptidase (NEP). It was hypothesised that pretreatment with thiorphan, an NEP inhibitor, might enhance the bronchodilator response to inhaled ANP.

METHODS

In a randomised double blind placebo controlled crossover study, six asthmatic patients (one woman) of mean (SD) age 47.3 (3.8) years and forced expiratory volume in one second (FEV1) 1.91 (0.42) 1, 55 (3.8)% predicted, were studied. All were shown at screening to have at least a 25% improvement in FEV1 to inhaled salbutamol. On five study visits the patients received either thiorphan 1 mg (in 2 ml) followed by ANP 5 mg or placebo (saline), or placebo (saline) followed by ANP (5 mg), placebo or salbutamol 5 mg. Spirometric parameters were measured after each inhalation and thereafter for the next two hours.

RESULTS

ANP alone caused a bronchodilator response up to 15 minutes when compared with placebo or thiorphan alone with a mean (SE) change in FEV1 of 16.8 (8.1)% and 16.1 (6.8)% at 10 and 15 minutes from baseline, respectively. Prior inhalation of thiorphan prolonged the duration of the bronchodilator effect of ANP up to 60 minutes with a mean (SE) change in FEV1 of 23.1 (3.4)% at 60 minutes. There was no difference in the maximum degree of bronchodilation following the administration of ANP alone compared with the combination of thiorphan and ANP. The degree and duration of the bronchodilator response produced by ANP, or the combination of the NEP inhibitor and ANP, were less than that produced by salbutamol.

CONCLUSIONS

These results confirm that, at least in part, the bronchodilator response to inhaled ANP is modulated by NEP. Analogues of ANP which are stable to NEP may have greater bronchodilator activity than ANP in the treatment of asthma.

Effects of intradermal injection of atrial natriuretic peptide

Atrial natriuretic peptide (ANP) causes mast cell degranulation in rats in vivo and in vitro but is bronchodilator in humans. The aim of this study was to investigate the wheal and flare dose-response to intradermal injection of alpha-human ANP in normal humans. Eight normal subjects received five 30 microliters injections containing 1, 10, 39, 78, 117 pmol ANP and one each of normal saline, histamine 675 pmol and substance P 30 pmol. Maximum ANP flare response was greater but not significantly than that to saline at 1.55 +/- 0.6 (mean +/- s.e. mean) compared with 0.42 +/- 0.17 cm2, but much less than to histamine 9.86 +/- 0.97 or to substance P 12.5 +/- 1.2. Maximum ANP wheal response was significantly greater than that to saline at 0.38 +/- 0.08 compared with 0.18 +/- 0.05 cm2 (difference between means 0.20, 95% CI 0.05, 0.35), but much less than to histamine 0.75 +/- 0.06 or to substance P 1.05 +/- 0.08 cm2. No dose-response to ANP was demonstrated, though responses to the highest dose differed significantly from those to the lowest dose studied. We conclude that human cutaneous responses to ANP differ from those of animals and that the skin is less responsive than other tissues in humans.

Bronchodilator and pre-protective effects of urodilatin in bovine bronchi in vitro: comparison with atrial natriuretic peptide

1. This study examined the activity and mechanisms of action of urodilatin in bovine bronchi. For comparison, the ability of urodilatin to evoke bronchodilatation or protect against subsequent challenge was compared to that of the closely related peptide alpha-human atrial natriuretic peptide (ANP). 2. Urodilatin reversed methacholine-evoked contraction in a concentration-dependent manner in bovine bronchi. In the absence of any attempt to prevent degradation by neutral endopeptidases, urodilatin was more potent than ANP in this tissue. 3. The bronchodilator properties of urodilatin were significantly augmented by the neutral endopeptidase inhibitor, phosphoramidon (3.68 x 10(-5) M). This provides evidence for at least partial degradation of urodilatin by neutral endopeptidases. With phosphoramidon present, urodilatin and ANP were equipotent. 4. In the presence of phosphoramidon (3.68 x 10(-5) M), pre-incubation with urodilatin (10(-6) M) had a protective effect against subsequent methacholine-induced contraction. This action of urodilatin was quantitatively similar to that of ANP in the presence of this endopeptidase inhibitor. 5. The actions of urodilatin appear to involve ATP-sensitive K+ channels since tolbutamide (10(-6) - 10(-5) M) significantly attenuated the relaxations induced by this peptide. 6. Small conductance Ca(2+)-activated K+ channels seem likewise to be implicated in the actions of urodilatin since blockade of these channels with apamin (10(-7) - 10(-6) M) resulted in a marked attenuation of urodilatin-evoked responses. 7. The presence of charybdotoxin (10-9 M-10-M) had no significant effect on subsequent responses tourodilatin suggesting that large conductance Ca2+-activated K+ channels are not involved in the relaxations evoked by this peptide.8. In the presence of phosphoramidon (3.68 x 10-5 M), urodilatin (10-6 M) evoked elevation of cyclic GMP levels within bovine bronchial tissue. Levels of cyclic GMP increased significantly within 5-10 s in response to this peptide and preceded the initiation of relaxant responses. Maximum increases in cyclic GMP levels were reached within 5 min; the time required for maximal relaxation evoked by this peptide.9. In conclusion, urodilatin, like ANP reversed and protected against, subsequent methacholine-induced bronchoconstriction; an action enhanced by the presence of phosphoramidon (3.68 x 1O-5 M).Associated with these actions of urodilatin was a rise in cyclic GMP levels as well as the opening of ATP-sensitive K+ and small conductance Ca2+-activated K+ channels.

The interaction of alpha-human atrial natriuretic peptide (ANP) with salbutamol, sodium nitroprusside and isosorbide dinitrate in human bronchial smooth muscle

1. Contractions in human bronchial rings evoked by methacholine (10(-6) M) were reversed by single contractions of alpha-human atrial natriuretic peptide (10(-6) M), salbutamol (10(-6) M), sodium nitroprusside (10(-6) M) or isosorbide dinitrate (4.2 x 10(-5) M) and the extent of the relaxations compared. The activity of combinations of ANP with salbutamol, sodium nitroprusside and isosorbide dinitrate were compared with those for each agonist alone. 2. ANP and salbutamol were equipotent in reversing methacholine-evoked contraction and, in combination these agonists evoked an additive response. ANP and sodium nitroprusside also evoked similar degrees of relaxation and were additive, as were ANP and isosorbide dinitrate; however, with isosorbide dinitrate a higher concentration was required to evoke the same degree of relaxation as ANP, sodium nitroprusside or salbutamol. 3. Cumulative concentration-response curves to methacholine (10(-9)-3 x 10(-4) M) were examined in the presence and absence of the above bronchodilator substances, alone and in combination allowing their abilities to protect against contraction to be compared. ANP (10(-6) M) and salbutamol (10(-6) M) each attenuated subsequent contractions evoked by methacholine, an ability not shared with sodium nitroprusside (10(-6) M) or isosorbide dinitrate (4.2 x 10(-5) M). Indeed at lower concentrations of methacholine (< 3 x 10(-7) M), sodium nitroprusside evoked a paradoxical enhancement of methacholine-evoked contractions. 4. In combination, ANP and salbutamol attenuated contractions evoked by methacholine to a significantly greater degree than that seen with either agonist alone, whilst a combination of ANP and sodium nitroprusside evoked no greater effect than that seen with ANP alone. By contrast, isosorbide dinitrate and ANP together evoked a greater inhibition than ANP alone.5 These results suggest that a combination of agents such as ANP and salbutamol evokes a greater effect than either alone, both in reversing and protecting against methacholine-evoked contractions.Such combinations may be of benefit in the treatment of patients, allowing lower doses of drug to be used. Combinations of ANP and isosorbide dinitrate may likewise be of interest; however, the mechanism underlying the enhancement of ANP responses by isosorbide dinitrate requires further study.

Effect of inhaled atrial natriuretic peptide on methacholine induced bronchoconstriction in asthma

We have previously demonstrated that intravenous and inhaled atrial natriuretic peptide (ANP) significantly inhibits histamine induced bronchoconstriction in asthmatic patients. The current study was designed to determine whether inhaled ANP was also able to inhibit the effects of methacholine. Eight atopic asthmatic patients (five women) were studied: mean (SD) age 38.2 (8.3) years flow expiratory volume per second (FEV1) 2.97 (0.60) litres, equivalent to 92 (13) % of the predicted. Each had demonstrated at least mild bronchial hyperreactivity to inhaled methacholine at screening (geometric mean PC20 1.02 mg/ml; range 0.11-6.54 mg/ml). Patients attended for 3 study days and after baseline spirometry received 3.5 ml saline (placebo), 0.1 mg ANP or 1 mg ANP (ANP dissolved in 3.5 ml saline) in a randomized, double-blind manner via a Mizer aerosol conservation device. Aerosolization took approximately 9 min and FEV1 was repeated at 0.5, 1.5 and 3 min after completion. Immediately thereafter each patient received a 2 min inhalation of methacholine at a dose individually calculated to give a 25% fall in FEV1 (as extrapolated at their initial screening visit) and the FEV1 was followed over the next 20 min. Mean (SEM)% FEV1 did not change significantly after ANP being -4.3 (1.7), -3.2 (2.7) and -2.4 (1.2) after placebo, 0.1 mg ANP and 1 mg ANP respectively. The mean (SEM) maximum fall in FEV1 after methacholine was as follows: placebo 26.9 (5.7)%, 0.1 mg ANP 18.2 (4.3)% and 1.0 mg 11.2 (2.7)% (P < 0.05 placebo vs 1 mg ANP). These results demonstrate that ANP offers significant protection against methacholine induced bronchoconstriction in asthmatic patients.

Bronchodilator, cardiovascular, and cyclic guanylyl monophosphate response to high-dose infused atrial natriuretic peptide in asthma

Atrial natriuretic peptide (ANP) has bronchodilator and vasodilator properties thought to be mediated through the generation of cyclic guanylyl monophosphate (cGMP). The current study was designed to examine the effects of infused ANP on respiratory (FEV1), cardiovascular (blood pressure and pulse), and metabolic (plasma cGMP) function in asthmatic patients. Eight patients with a mean +/- SD age of 45.6 +/- 8.2 yr and mean FEV1 of 56.4 +/- 15.4% of predicted were studied using a randomized double-blind crossover design. On one study day after baseline measurements (FEV1, blood pressure, pulse, and plasma cGMP), ANP was infused for 20-min periods at 5 pmol/kg/min and at 25 pmol/kg/min; a placebo (saline) inhalation was then administered. On the other day the placebo infusion was followed by inhalation of 5 mg albuterol. Measurements were repeated at the end of each 20-min period. The highest rate of ANP infusion increased the FEV1 by 0.50 +/- 0.09 L compared with 0.09 +/- 0.05 after the placebo infusion (p < 0.001). The increase in FEV1 produced by ANP plus placebo inhalation (0.50 +/- 0.28 L) was similar to that produced by placebo infusion plus albuterol inhalation (0.61 +/- 0.30 L). There was no clinically significant fall in systolic or diastolic blood pressure (torr) at the 25 pmol/kg/min infusion rate. The mean basal cGMP was 602 +/- 242 fmol/ml and increased to 5,883 +/- 1,460 and 21,182 +/- 2,509 with the two rates of ANP infusion.(ABSTRACT TRUNCATED AT 250 WORDS)