Search PubMed⌕ Search

Biomedical subjects

G M Verleden

Publications and source records attributed to G M Verleden.

At least 37 records · Page 2Linked to original sources
PubMed1999

The effects of 5-HT on cholinergic contraction in human airways in vitro.

Inhaled 5-hydroxytryptamine (5-HT) causes bronchoconstriction in asthmatics, and 5-HT plasma levels are elevated in asthma. Electrical field stimulation (EFS) of human airways, in vitro, evokes cholinergic contraction mediated by the release of acetylcholine (Ach) from postganglionic cholinergic nerves. The present study investigates whether selective 5-HT agonists and antagonists can modulate EFS-induced cholinergic contraction in human airways in vitro. Human airways, obtained from resections for bronchial carcinoma or organ transplant donors, were suspended under 2-g tension, between two platinum wire electrodes, in carbogenated Krebs solution at 37 degrees C and EFS was applied (1-32 Hz, 50 V, 0.5 ms, 15 s every 4 min) to elicit cholinergic contractions. 5-HT (10 microM-0.3 mM) produced frequency- and concentration-dependent facilitation of cholinergic contraction, but did not displace the concentration/response curve to Ach. Tropisetron (1 microM), a 5-HT3 and 5-HT4 antagonist, completely blocked the facilitatory effect of 5-HT (100 microM), whereas both ondansetron (1 microM) and GR 125478D (1 microM), a selective 5-HT3 and 5-HT4 antagonist, respectively, also attenuated the 5-HT-induced enhancement of cholinergic contraction. This facilitatory effect of 5-HT was partially mimicked by both selective 5-HT3 (2-methyl-5-HT) and 5-HT4 (RS 67333 and 5-methoxytryptamine) agonists. Fluoxetine (10 microM), a 5-HT uptake inhibitor, had no effect on the 5-HT (10-100 microm) induced potentiation of cholinergic contraction. These findings suggest that 5-HT facilitates cholinergic contraction in human airways in vitro through stimulation of both prejunctional 5-HT3 and 5-HT4 receptors. This may implicate a role of 5-HT in asthma.

Acetylcholine↗
PubMed1999

Expression of monocyte chemotactic protein (MCP)-1, MCP-2, and MCP-3 by human airway smooth-muscle cells. Modulation by corticosteroids and T-helper 2 cytokines.

We have demonstrated that, in addition to their contractile function, human airway smooth-muscle cells (HASMC) are able to express and to secrete chemokines of the monocyte chemotactic protein (MCP)/ eotaxin subfamily. This group of chemokines is believed to play a fundamental role in the development of allergic airway diseases such as asthma. The expression levels of MCP (MCP-1, -2, and -3) messenger RNA (mRNA) were compared with those of regulated on activation, normal T cells expressed and secreted (RANTES) mRNA in HASMC in culture. HASMC express MCP and RANTES mRNA after stimulation with interleukin (IL)-1beta, tumor necrosis factor-alpha, and interferon-gamma. MCP mRNA was maximal at 8 h, whereas RANTES mRNA expression was delayed to 24 h after stimulation. Further, significant differences were observed in the induction patterns of MCP and RANTES mRNA expression after stimulation with the individual cytokines. Dexamethasone (DEX) significantly inhibited cytokine-induced accumulation of MCP and RANTES mRNA, in contrast to IL-4, IL-10, and IL-13, which had no inhibitory effect on cytokine-induced chemokine expression. The cytokine-induced MCP mRNA expression in HASMC was associated with MCP release, which was inhibited by DEX and post-translationally by IL-4. HASMC can actively participate in the pathogenesis of asthma by the expression and release of chemokines, which are likely to play a critical role in the generation and regulation of the inflammatory response characteristic of allergic airway diseases.

Bronchi↗
PubMed1999

Epinastine (WAL 801CL) inhibits the electrical field stimulation-induced cholinergic contraction in guinea pig and human airways in vitro.

Epinastine is an antihistamine drug with binding affinities at 5-hydroxytryptamine (5-HT) receptors. The current study was performed to investigate whether epinastine could modulate the cholinergic contraction in guinea pig and human airways in vitro. Isolated guinea pig and human airway preparations were suspended in organ baths containing modified Krebs-Henseleit solution. Electrical field stimulation was applied to elicit cholinergic contractions. Epinastine produced a concentration-dependent inhibition of the cholinergic contraction in guinea pig airways and pretreatment with methysergide (5-HT1/2/7 antagonist) significantly attenuated these inhibitory effects of epinastine. Pretreatment with tropisetron (5-HT3/4 antagonist), ketanserin (5-HT2 antagonist), SDZ216-525 (5-HT1A antagonist) or phentolamine (alpha-adrenergic antagonist) had no effect. Epinastine did not displace the concentration-response curve to acetylcholine. These results suggest that epinastine inhibits the cholinergic contraction in guinea pig airways through stimulation of prejunctional 5-hydroxytryptamine receptors, located to postganglionic cholinergic nerves. Inhibitory effects of epinastine on the cholinergic contraction in human airways in vitro were also demonstrated, which suggests that a similar mechanism might be present in human airways. The pharmacological profile of epinastine, which shows binding affinity at the 5-hydroxytryptamine7 receptor but not at the 5-hydroxytryptamine1 receptor subtypes corroborates the hypothesis that the inhibitory prejunctional 5-hydroxytryptamine receptor on cholinergic nerves is of the 5-hydroxytryptamine7 subtype.

Aged↗
PubMed1999

The effect of cigarette smoking on exhaled nitric oxide in mild steroid-naive asthmatics.

STUDY OBJECTIVES: It has been demonstrated previously that exhaled nitric oxide (eNO) is increased in steroid-naive asthmatics and that inhaled steroids reduce eNO in these patients. Cigarette smoking has also been reported to reduce the eNO in healthy volunteers. Recently a correlation has been demonstrated between eNO and airway hyperresponsiveness in steroid-naive, mild asthmatics. We hypothesized that cigarette smoking would reduce the eNO level in steroid-naive asthmatics and might, therefore, affect the correlation between eNO and airway hyperresponsiveness. DESIGN: Comparison of eNO in healthy smoking and nonsmoking volunteers with the level of eNO in steroid-naive and steroid-treated asthmatics. Correlate the eNO level with the provocative concentration of histamine causing a 20% fall in FEV1 (PC20hist) in the asthmatic smoking and nonsmoking patients. SETTING: University outpatient asthma clinic. PATIENTS AND METHODS: eNO levels and PC20hist were measured in three different asthmatic patient groups (group A = 29 steroid-naive, nonsmoking asthmatics; group B = 19 steroid-treated, nonsmoking asthmatics; and group C = 13 smoking, steroid-naive asthmatics) and in two healthy volunteer groups (group D = 18 nonsmoking; and group E = 16 smoking). RESULTS: eNO in group A was significantly increased compared with the values in groups B and D (21.8+/-12.7, 12.8+/-4.9, and 10.6+/-2.2 parts per billion [ppb], respectively). Cigarette smoking decreased eNO in healthy volunteers (7.4+/-1.8 ppb, group E) as well as in steroid-naive asthmatics (12.7+/-5.1 ppb, group C). There was a significant correlation between eNO and PC20hist in group A (r = -0.45, p < 0.05); this correlation was, however, lost in both groups B and C. CONCLUSION: Cigarette smoking and inhaled steroids reduce the eNO in patients with mild asthma to a comparable extent. Because the correlation between eNO and airway hyperresponsiveness was lost in steroid-treated and smoking, steroid-naive asthmatics, we question the value of eNO as a marker of airway inflammation, at least in mild asthmatics who are already being treated with inhaled steroids or who are currently smoking.

Administration, Inhalation↗
PubMed1998

ATP-induced Ca2+ signals in bronchial epithelial cells.

Ca2+-dependent Cl- secretion in the respiratory tract occurs physiologically or under pathophysiological conditions when inflammatory mediators are released. The mechanism of intracellular Ca2+ release was investigated in the immortalized bronchial epithelial cell line 16HBE14o-. Experiments on both intact and permeabilized cells revealed that only inositol 1,4,5-trisphosphate (InsP3) receptors and not ryanodine receptors are involved in intracellular Ca2+ release. The expression pattern of the three InsP3 receptor isoforms was assessed both at the mRNA and at the protein level. The level of expression at the mRNA level was type 3 (92.5%) >> type 2 (5.4%) > type 1 (2.1%) and this rank order was also observed at the protein level. The ATP-induced Ca2+ signals in the intact cell, consisting of abortive Ca2+ spikes or fully developed [Ca2+] rises and intracellular Ca2+ waves, were indicative of positive feedback of Ca2+ on the InsP3 receptors. Low Ca2+ concentrations stimulated and high Ca2+ concentrations inhibited InsP3-induced Ca2+ release in permeabilized 16HBE14o- cells. We localized a cytosolic Ca2+-binding site between amino acid residues 2077 and 2101 in the type-2 InsP3 receptor and between amino acids 2030 and 2050 in the type-3 InsP3 receptor by expressing the respective parts of these receptors as glutathione S-transferase fusion proteins in bacteria. We conclude that the InsP3 receptor isoforms expressed in 16HBE14o- cells (mainly type-3 and type-2) are stimulated by Ca2+ and that this phenomenon contributes to the ATP-induced Ca2+ signals in intact 16HBE14o- cells.

Adenosine Triphosphate↗
PubMed1998

Regulation of H1-receptor coupling and H1-receptor mRNA by histamine in bovine tracheal smooth muscle.

1. Pretreatment of bovine tracheal smooth muscle (BTSM) with histamine (1-100 microM, 1 h) induced a concentration-dependent desensitization of the contractile response to subsequently administered histamine, with a reduction of the maximum response of 72 +/- 8% (n = 5) following pre-exposure to 100 microM histamine. In contrast, concentration-response curves to the muscarinic agonist, methacholine were not affected following histamine pretreatment, indicating a homologous desensitization. Furthermore, concentration-response curves to NaF, a G-protein activator, were not altered following histamine pre-incubation. 2. The histamine H1-receptor (H1R) desensitization could be antagonized by mepyramine (an H1-receptor antagonist, 1 microM) but not by cimetidine (an H2-receptor antagonist, 10 microM), indicating that the desensitization occurred via stimulation of histamine H1-receptors, without evidence for the involvement of histamine H2-receptors. 3. Indomethacin (10 microM) did not block the H1R desensitization, suggesting no involvement of prostaglandins. Furthermore, histamine pre-incubation in calcium free medium still induced a functional uncoupling of H1R. 4. GF 109203X, a protein kinase C (PKC) inhibitor, and H-7, a non-selective kinase inhibitor, did not antagonize the homologous H1R desensitization. 5. The steady-state level of H1R mRNA, assessed by Northern blot analysis, was not affected by prolonged histamine exposure (100 microM, 0.5, 1, 2, 4, 16 and 24 h). 6. These results suggest that histamine induces desensitization of the H1R at the level of the receptor protein, which involves a mechanism independent of PKC, PKA, PKG and calcium influx, suggesting the involvement of a receptor-specific kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Desensitization of the histamine H1-receptor and transcriptional down-regulation of histamine H1-receptor gene expression in bovine tracheal smooth muscle.

We have investigated the role of protein kinase C (PKC) in the desensitization of histamine H1-receptors and in the expression of the histamine H1-receptor gene in airway smooth muscle. Prolonged 4beta-phorbol 12,13 dibutyrate (PDBu) pretreatment (4 h, 100 nM-1 microM) of bovine trachealis caused a concentration-dependent loss of contraction in response to histamine H1-receptor stimulation, which was associated with a concentration-dependent decrease in histamine-induced total [3H]-inositol phosphates accumulation. In contrast, the responses to sodium fluoride, a direct G-protein activator, were unalterd by PDBu (100-300 nM) pre-incubation and only slightly reduced following incubation with 1 microM PDBu. A selective PKC inhibitor, GF 109203X, partially blocked the PDBu (1 microM)-induced desensitization and completely blocked the effect of 100 nM PDBu, confirming the involvement of PKC. Binding experiments using [3H]-pyrilamine revealed a class of high-affinity binding sites within the range for the histamine H1 receptor in airway smooth muscle. PDBu (1 microM) pretreatment for 4 h did not change the number of histamine H1 receptors. PDBu (1 microM) exposure caused a time-dependent reduction in the steady-state levels of histamine H1-receptor mRNA, which was inhibited by pre-incubation with GF 109203X and by cycloheximide, a protein synthesis inhibitor. Nuclear run-on assays revealed a 50% reduction in the rate of histamine H1-receptor gene transcription after 17 h PDBu pretreatment, whereas mRNA stability was not affected by PDBu pretreatment (17 h). In conclusion, we have shown a PKC-mediated desensitization of the histamine H1-receptor in BTSM and a transcriptional down-regulation of the histamine H1-receptor gene expression, which requires new protein synthesis.

Animals↗
PubMed1998

Exhaled nitric oxide correlates with airway hyperresponsiveness in steroid-naive patients with mild asthma.

Endogenously released nitric oxide (NO) has been detected in the exhaled air of humans. Exhaled NO (NOexh) levels have been significantly increased in patients with inflammatory airways disorders such as asthma, and NOexh has been suggested to be a usable marker of airway inflammation. In the present study, NOexh levels were measured both in steroid-treated and untreated subjects with mild asthma, and were correlated with the degree of airway hyperresponsiveness (AHR), measured as the dose of histamine that produced a 20% decrease in FEV1 (PC20histamine). NOexh levels, which were significantly increased in steroid-naive patients (Group A1: NOexh = 21 +/- 11 ppb; n = 56) in comparison with levels in control subjects (Group B: NOexh = 10 +/- 2 ppb; n = 20; p < 0.001), correlated significantly with the PC20histamine (r = -0.65; p < 0.0001). The NOexh level was significantly lower in patients with chronic cough of other causes than bronchial asthma (Group A2: NOexh = 11 +/- 3 ppb; n = 18) when compared with the level in subjects with mild asthma (Group A1: p < 0.001). Therefore, the noninvasive measurement of NOexh allowed us to discriminate, among patients with respiratory complaints, between those with and without AHR. In asthmatic subjects treated with inhaled steroids, the NOexh levels were significantly lower (Group A3: NOexh = 13 +/- 5 ppb; n = 25) than in untreated subjects (Group A1; p < 0.01), and there was no relationship with the PC20histamine (r = -0.18, p = NS). These findings confirm that NOexh reflects AHR in patients with mild asthma who have not already been treated with inhaled steroids. Patients treated with inhaled steroids had an NOexh level comparable to levels in control subjects, although AHR could still be demonstrated.

Adrenergic beta-Agonists↗
PubMed1998

The effects of 8-hydroxy-2-(di-n-propylamino)tetralin on the cholinergic contraction in guinea pig and human airways in vitro.

Electrical field stimulation of guinea pig tracheal strips and human bronchial rings, in vitro, evokes a cholinergic contraction mediated by the release of acetylcholine. 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) is a 5-HT1A and 5-HT7 agonist. In this study, we have investigated whether 8-OH-DPAT could modulate the cholinergic contraction in guinea pig and human airways in vitro. 8-OH-DPAT (1 to 30 microM) produced a concentration-dependent inhibition of the cholinergic contraction in guinea pig tracheal strips with a maximal inhibition of 75.8% +/- 4. 7% (30 microM, 0.5 Hz). Pretreatment of the tissues with the 5- HT1/2/7 antagonist methysergide (10 to 30 microM) significantly attenuated the inhibitory effects of 8-OH-DPAT (10 to 30 microM) on the cholinergic contraction. Pretreatment with ketanserin (10 microM), a 5-HT2 antagonist, tropisetron (1 microM), a 5-HT3/4 antagonist, SDZ 216-525 (1 to 10 microM) and pindobind (10 microM), both selective 5-HT1A antagonists, or capsaicin (10 microM), which depletes sensory nerves from neuropeptides, had no effect on the inhibition of the cholinergic contraction by 8-OH-DPAT (10 to 30 microM). 5-carboxamidotryptamine (5-CT) (10 to 100 microM), a 5-HT1/2/7 agonist, partially mimicked the inhibitory effects of 8-OH-DPAT on the cholinergic contraction. 8-OH-DPAT (10 to 30 microM) also inhibited the cholinergic contraction in human bronchial rings in vitro with a maximal inhibition of 46.2% +/- 7.2% (30 microM, 1 Hz). SDZ 216-525 (10 microM) had no effect, whereas methysergide (30 microM) partially prevented the effect of 8-OH-DPAT in human airways. 8-OH-DPAT (30 microM) did not displace the concentration-response curve to acetylcholine (10 nM-30 mM) in guinea pig and human airways in vitro. These results suggest that 8-OH-DPAT inhibits the cholinergic contraction in guinea pig and human airways in vitro through stimulation of prejunctional atypical 5-HT receptors, possibly of the 5-HT7 subtype, located on postganglionic cholinergic nerves.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Possible recurrence of desquamative interstitial pneumonitis in a single lung transplant recipient.

Idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) is a disorder with a very poor prognosis for patients who do not respond to therapy with corticosteroids alone or in combination with immunosuppressive drugs, e.g. cyclophosphamide or azathioprine. For patients with end-stage disease, lung transplantation remains the only possibility for long-term survival. We describe a patient who received a left single lung transplant for end-stage desquamative interstitial pneumonitis. One year later, the patient again began complaining of exertional dyspnoea and a gradual decline in the transfer factor of the lung for carbon monoxide (TL,CO) was apparent. A recurrence of the primary disease in the transplanted lung was suspected on transbronchial biopsies. During treatment with high doses of steroids, a Pneumocystis carinii pneumonia developed, which was treated with co-trimoxazole. The patient completely recovered and, after a period of over 2 yrs, remained in an excellent condition, after which time he was lost from follow-up.

Adult↗
PubMed1996

Neural mechanisms and axon reflexes in asthma. Where are we?

For many years, asthma has been classified as a "neural" disease, with an imbalance between constrictor and dilator nerves being responsible for the symptomatology. Although, nowadays, asthma is recognized as an inflammatory disorder of the airways, neural mechanisms remain very important; axon reflexes, in particular, have received a lot of attention in recent years. In this commentary, an overview is given on the innervation of the airways and its relevance in asthma, and potential new insights in airways innervation are discussed. In a second part, the role of axon reflexes is highlighted. Although neuropeptides such as substance P and neurokinin A are present in human airways, where they produce many of the features characteristic of asthma, and although there is an elevation of their content in induced sputum from asthmatics, there is still no clear direct evidence for the existence of operational axon reflexes in human airways. Most of the research focused on this subject is performed in guinea pigs, where such an axon reflex clearly operates in the airways. In these animals, different receptors have been identified on C-fiber endings, which, upon stimulation, cause inhibition of neuropeptide release. Some of these receptors have also been identified on human airway nerves. Therefore, it has been suggested that modulation of axon reflexes could be of potential benefit in asthma treatment. Indeed, some drugs (e.g. sodium cromoglycate, nedocromil sodium, and ketotifen), which have been demonstrated to partially inhibit neuropeptide release in guinea pig airways, have anti-inflammatory effects on neuropeptide release in guinea pig airways, do not seem to have any anti-inflammatory effects in human asthma. Other drugs, however, such as beta2-mimetics, which have a much more pronounced inhibitory effect in asthma. In conclusion, although there is a lot of indirect evidence for the existence of axon reflex mechanisms in human airways, most of the data now available are derived from animal studies. The key question of whether axon reflexes are operational in human airways remains unanswered. Hopefully, the near future will bring a solution to this enigma with the introduction of very potent tachykinin antagonists for the treatment of human asthma.

Animals↗
PubMed1996

Epinastine (WAL 801CL) modulates the noncholinergic contraction in guinea-pig airways in vitro by a prejunctional 5-HT1-like receptor.

Electrical field stimulation (EFS) of guinea-pig airways, in vitro, evokes an excitatory nonadrenergic noncholinergic (eNANC) contraction mediated by release of tachykinins from sensory nerve endings. Epinastine (WAL 801CL) is an antihistaminic drug with binding affinity at certain other receptors, including alpha-adrenergic receptors and various serotonin (5-HT) receptor subtypes. It is used in asthma treatment; however, its mechanism of action remains to be fully defined. We have investigated whether epinastine could modulate the eNANC contraction in guinea-pig airways in vitro, and have tried to elucidate its receptor mechanism. Epinastine (0.1-100 microM) produced a concentration-dependent inhibition of the noncholinergic contraction, with a maximum inhibition of 91 +/- 7% at 100 microM. Pretreatment of the tissues with combined 5-HT1/5-HT2 antagonists, methysergide (1 microM) or methiothepin (0.1 microM), significantly attenuated the inhibitory effect of epinastine on the noncholinergic contraction. Pretreatment with tropisetron (1 microM), a 5-HT3 antagonist, ketanserin (10 microM), a 5-HT2 antagonist, thioperamide (10 microM), a histamine H3 antagonist, or phentolamine (10 microM), an alpha-adrenergic antagonist, however, had no effect. Chlorpheniramine (10 microM), another histamine H1 receptor antagonist without significant 5-HT receptor binding affinity, did not produce any inhibition of the eNANC contraction. Epinastine (100 microM) did not displace the dose-response curve to exogenously applied substance P (0.01-10 microM). These results suggest that epinastine, although identified as a 5-HT antagonist, acts as a 5-HT1 agonist and that it inhibits the noncholinergic contraction in guinea-pig airways through stimulation of a prejunctional 5-HT1-like receptor, located to sensory nerves.

Animals↗
PubMed1996

Opioids modulate the cholinergic contraction but not the nonadrenergic relaxation in guinea-pig airways in vitro.

(D-ALa2, NMePhe4, Gly-ol5) encephalin (DAMGO), a selective mu-opioid receptor agonist, has previously been demonstrated to inhibit the cholinergic and the noncholinergic contraction in guinea-pig airways. In contrast, opioids had no inhibitory effect on cholinergic neurotransmission in the upper trachea when stimulated at 8 Hz. We investigated whether DAMGO, a selective mu-opioid receptor agonist, [D-Pen 2,5] encephalin (DPDPE), a selective delta-opioid receptor agonist, and U-69593, a selective kappa-opioid receptor agonist could modulate the cholinergic contraction in the upper trachea at different frequencies of stimulation. Moreover, we have investigated whether DAMGO, DPDPE and U-69593 could also modulate the iNANC relaxation. DAMGO (1-100 microM) inhibited the cholinergic contraction in the upper trachea with a maximum inhibition of 57+/-15% at 1 Hz (n=4; p<0.05). On the other hand, DPDPE (10 microM) and U69593 (10 microM) did not produce any significant inhibition of the cholinergic contraction. Naloxone, an opioid receptor antagonist (100 microM), was able to antagonize the inhibitory effect of DAMGO (n=5; p<0.01) on the cholinergic contraction at a frequency of 2 Hz. DAMGO (10 microM) did not displace the cumulative concentration-response relationship to acetylcholine (10 nM-10 mM), (n=4; NS). This provides evidence that prejunctional mu-opioid receptors (and not delta-opioid or kappa-opioid receptors) modulate cholinergic contraction in the upper trachea. In contrast, DAMGO (10 microM) had no significant inhibitory effect on the nonadrenergic relaxation (n=4; NS) in the upper trachea. Neither DPDPE nor U-69593 had any effect on the nonadrenergic relaxation. These findings suggest that DAMGO directly inhibits the cholinergic contraction and that the opioid receptor involved in the inhibition of the cholinergic contraction in the upper trachea is of the mu-opioid type. The finding that opioids inhibit cholinergic contraction without altering NANC relaxations suggests that distinct populations of nerves mediate these two effects.

Animals↗
PubMed1994

Ketotifen modulates noncholinergic contraction in guinea pig airways in vitro by a prejunctional nonhistamine receptor.

In guinea pig airways, electrical field stimulation (50 V, 0.5 msec, 8 Hz for 20 seconds) produces a rapid contraction, which is followed by a long-lasting contraction, at least in the lower part of the trachea and in the bronchi. The latter contraction is due to the release of neuropeptides from airway sensory nerves. Ketotifen fumarate has been demonstrated to inhibit the noncholinergic contraction in guinea pig airways in vitro, but no attempt has been made to identify the receptor type. Therefore we have performed an in vitro study to investigate which receptor is responsible for the inhibitory effects of ketotifen on noncholinergic contraction in guinea pig airways. Ketotifen (3 to 100 mumol/L) produced a concentration-dependent inhibition of the noncholinergic contraction, with a maximum inhibition of 74% +/- 7% at 8 Hz stimulation (p < 0.001; n = 5). Pretreatment of the tissues with either cimetidine (10 mumol/L) or thioperamide (10 mumol/L) or phentolamine (10 mumol/L) did not prevent the inhibitory effect of ketotifen (10 mumol/L). Cetirizine (10 mumol/L), on the other hand, produced no inhibition of the noncholinergic contraction at all. Metitepine (0.1 mumol/L) and methysergide (1 mumol/L), both 5-HT1 antagonists, attenuated the inhibitory effect of ketotifen (10 mumol/L). Ketanserin (a 5-HT2 antagonist, 10 mumol/L) and tropisetron (a 5-HT3 antagonist, 1 mumol/L) had no effect. Ketoifen (100 mumol/L) did not affect the cumulative dose-response relationship to exogenous substance P (0.01 mumol/L to 10 mmol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic Fibers↗
PubMed1994

Effect of loop diuretics on cholinergic neurotransmission in human airways in vitro.

BACKGROUND: Frusemide can inhibit various indirectly acting bronchoconstrictor stimuli in asthmatic patients. Both frusemide and bumetanide also modulate airway neurotransmission in some species but there are no data on the effect of loop diuretics on neurotransmission in man. An in vitro study was performed in human airways to investigate the possible neuromodulatory action of two loop diuretics, frusemide and bumetanide, and to elucidate whether a cyclooxygenase inhibitor such as indomethacin could modulate the effect of frusemide. The effect of acetazolamide, a carbonic anhydrase inhibitor, was also investigated. METHODS: Electrical field stimulation (EFS; 40 V, 0.5 ms, 0.5-32 Hz for 15 seconds) in human airways with or without epithelium was used to induce a cholinergic contraction (n = 5 in all experiments). Indomethacin was present throughout. After obtaining a control frequency-response curve, different concentrations of diuretic were added to the organ bath and another frequency-response curve was constructed. To determine whether the effect of the diuretic was prejunctional or postjunctional a cumulative concentration-response curve to exogenous acetylcholine (Ach, 0.3 mumol/l to 10 mmol/l) was constructed in the presence of a diuretic (frusemide 1 mmol/l or bumetanide 0.1 mmol/l) or its vehicle. In some experiments indomethacin was omitted from the organ bath to investigate the possible involvement of cyclooxygenase products. RESULTS: Both frusemide (10 mumol/l to 1 mmol/l) and bumetanide (1 mumol/l to 0.1 mmol/l) produced a concentration-dependent inhibition of the EFS-induced cholinergic contraction in human airways in vitro but only in epithelium denuded tissues. Frusemide (1 mmol/l) produced a maximum inhibition of 46.3% (SE 9.9%) at 0.5 Hz and bumetanide (0.1 mmol/l 39.6 (6.2)% at 0.5 Hz. Without indomethacin in the organ bath the frusemide-induced inhibition was enhanced at 4, 8, and 16 Hz, but bumetanide-induced inhibition was not enhanced at any frequency when indomethacin was omitted. Frusemide (1 mmol/l) and bumetanide (0.1 mmol/l) had no effect on the cumulative concentration-response curve to exogenous Ach (0.3 mumol/l to 10 mmol/l). Acetazolamide (100 mumol/l) had no effect on the EFS-induced cholinergic contraction in tissues with or without epithelium. CONCLUSIONS: In human airways in vitro both frusemide and bumetanide produced a concentration-dependent inhibition of the EFS-induced cholinergic contraction. This inhibition is mediated through a prejunctional mechanism. Epithelium removal was necessary to achieve this effect. The mechanism of action of frusemide and bumetanide on airway nerves remains unclear: inhibition of the Na-K-Cl cotransporter is a possibility and, for frusemide, release of endogenous cyclooxygenase products may be involved. Carbonic anhydrase inhibition, on the other hand, is unlikely to be a factor.

Acetazolamide↗