Effects of neuropeptides on mucociliary activity

Neuropeptide Y Reduces Nasal Epithelial T2R Bitter Taste Receptor-Stimulated Nitric Oxide Production

Bitter taste receptors (T2Rs) are G-protein-coupled receptors (GPCRs) expressed on the tongue but also in various locations throughout the body, including on motile cilia within the upper and lower airways. Within the nasal airway, T2Rs detect secreted bacterial ligands and initiate bactericidal nitric oxide (NO) responses, which also increase ciliary beat frequency (CBF) and mucociliary clearance of pathogens. Various neuropeptides, including neuropeptide tyrosine (neuropeptide Y or NPY), control physiological processes in the airway including cytokine release, fluid secretion, and ciliary beating. NPY levels and/or density of NPYergic neurons may be increased in some sinonasal diseases. We hypothesized that NPY modulates cilia-localized T2R responses in nasal epithelia. Using primary sinonasal epithelial cells cultured at air–liquid interface (ALI), we demonstrate that NPY reduces CBF through NPY2R activation of protein kinase C (PKC) and attenuates responses to T2R14 agonist apigenin. We find that NPY does not alter T2R-induced calcium elevation but does reduce T2R-stimulated NO production via a PKC-dependent process. This study extends our understanding of how T2R responses are modulated within the inflammatory environment of sinonasal diseases, which may improve our ability to effectively treat these disorders.

Mycoplasma hyopneumoniae surface-associated proteases cleave bradykinin, substance P, neurokinin A and neuropeptide Y

Mycoplasma hyopneumoniae is an economically-devastating and geographically-widespread pathogen that colonises ciliated epithelium, and destroys mucociliary function. M. hyopneumoniae devotes ~5% of its reduced genome to encode members of the P97 and P102 adhesin families that are critical for colonising epithelial cilia, but mechanisms to impair mucociliary clearance and manipulate host immune response to induce a chronic infectious state have remained elusive. Here we identified two surface exposed M. hyopneumoniae proteases, a putative Xaa-Pro aminopeptidase (MHJ_0659; PepP) and a putative oligoendopeptidase F (MHJ_0522; PepF), using immunofluorescence microscopy and two orthogonal proteomic methodologies. MHJ_0659 and MHJ_0522 were purified as polyhistidine fusion proteins and shown, using a novel MALDI-TOF MS assay, to degrade four pro-inflammatory peptides that regulate lung homeostasis; bradykinin (BK), substance P (SP), neurokinin A (NKA) and neuropeptide Y (NPY). These findings provide insight into the mechanisms used by M. hyopneumoniae to influence ciliary beat frequency, impair mucociliary clearance, and initiate a chronic infectious disease state in swine, features that are a hallmark of disease caused by this pathogen.

The Rabbit Maxillary Sinus: A Review of the Effects of Innervation on Mucociliary Activity

The stable bone walls of the maxillary sinus of the rabbit permit undisturbed recordings of the mucociliary activity by a photoelectric technique in vivo. The distribution of peptidergic neurotransmittors in the rabbit maxillary sinus was compared with their mucociliary effects on the same preparation. Nerve fibers containing neuropeptide Y were abundant around blood vessels and glands in the lamina propria. A few nerve fibers were seen just beneath the epithelium. Injections with neuropeptide Y decreased mucociliary wave frequency, the maximum decrease was about 15% for the doses 1.0 and 5.0 μg/kg. Vasoactive intestinal polypeptide (VIP) was found in the subepithelial layer and also distributed close to glands and blood vessels in the lamina propria. Administration of VIP alone did not change the mucociliary activity. However, if the rabbits were challenged with threshold doses of the mucociliary stimulant methacholine, the response to the cholinergic agonist was potentiated by VIP. Substance P (SP)-containing nerve fibers were found in the subepithelial layer, with single varicose endings sometimes penetrating into the epithelium. Challenges with SP produced a prompt increase of the mucociliary activity (the maximum increase was about 50% above baseline level), presumably due to increased chloride flux toward the lumen. Similar effects were produced by neurokinin A, which emanates from the same precursor molecule as SP. Another sensory peptide, calcitonin gene-related peptide was without effect on the mucociliary system. Our data indicate that there is a correlation between the occurrence of nerve fibers just beneath the epithelium and mucociliary effects. A localization close to the epithelium seems a logical prerequisite for epithelial effects.

Effects of Substance P and Methacholine on Mucosal Blood Flow in the Upper Airways

The aims of the present investigation were to examine the in vivo effects of substance P (SP) and methacholine on blood flow measured by laser Doppler technique in the maxillary sinus of the rabbit and in the human nasal mucosa. In the rabbit, the test substances were administered by intra-arterial catheter, and the laser Doppler probe was inserted into the maxillary sinus through a trepanation in the anterior wall. In the human nose, the laser Doppler probe was directed toward the nasal septum at the level of the anterior margin of the middle turbinate, and the test substances were administered as aerosols into the ipsilateral nostril. In the rabbit maxillary sinus, both SP and methacholine increased the blood flow, the maximum increases obtained being 13.5 ± 3.1% and 39.0 ± 5.6% after challenges with SP at 0.1 μg/kg and methacholine at 0.5 μg/kg, respectively. The rabbits displayed a decrease in blood flow after challenges at higher dosages of both SP and methacholine, accompanied by a simultaneous fall in systemic blood pressure. Atropine given IV five minutes before methacholine abolished the effects of this compound in the rabbit. The blood flow in the human nose was unaffected by saline controls, whereas it was increased both by SP and by methacholine, the increases being 34.9 ± 6.0% after challenges with SP 1.0 nmol and 119.2 ± 15.1% after challenges with methacholine 5.0 μmol. According to acoustic rhinometry, neither SP nor methacholine had, at the doses used, any effect on human nasal patency. Pretreatment with lidocaine hydrochloride spray into the human nose did not affect the increase in nasal blood flow induced by SP, but abolished the methacholine-evoked blood flow increase. Pretreatment with ipratropium bromide spray into the human nose abolished the increase in blood flow induced by methacholine. The results of the present study indicate that blood flow in the upper airways of humans and rabbits may increase due to release of SP or acetylcholine in vivo, an event that occurs after exposure to airway irritants. The vasodilation in the human nose produced by acetylcholine may be due to a neurogenic reflex, in contrast to the effect of SP.

Experience in Counting Ciliary Beat Frequency from Vital Cytologic Sampling

From a viable cytologic brush biopsy of the respiratory epithelium you can get an insight into the functional state of the epithelial cell layer, especially of the ciliated cells. We report on our experience of several hundred sampling procedures from the nasal and bronchial mucosa. The technique of the method is described, including the microphotometric apparatus to determine the ciliary beat frequency. We stress the importance of checking the ciliary beat frequency of the 10 most active cells of one preparation to get representative results. Futhermore it is decisive to watch them over a period of 10 seconds, considering the time shift of the ciliary beat frequency. Putting the cell solution into a counting chamber gives the possibility of differentiating viable and dead ciliated cells as well as squamous cells in the sample. These results proved to yield a good picture of the functional state of the sampled respiratory mucosal site.

Stimulation of Mucociliary Activity by Substance P and Capsaicin is Not Mediated by Histamine

The mucociliary activity in the rabbit maxillary sinus is stimulated by exogenous substance P and by histamine (via H1 receptors). Also, endogenous substance P released by capsaicin stimulates the mucociliary activity. A substance P-induced release of histamine has been reported. The possibility that the mucociliary stimulation by substance P is secondary to a release of histamine was investigated using a photoelectric technique. For both substance P (0.01, 0.1, and 1.0 μg/kg) and capsaicin (15 and 30 μg/kg), neither the maximum mucociliary response nor the time-course curve was affected by pretreatment with the H,-antagonist pyrilamine (4 mg/kg). It is concluded that the mucociliary effects produced by substance P and capsaicin are not secondary to a release of histamine.

Vasoactive intestinal peptide regulates sinonasal mucociliary clearance and synergizes with histamine in stimulating sinonasal fluid secretion

Mucociliary clearance (MCC) is the primary physical airway defense against inhaled pathogens and particulates. MCC depends on both proper fluid/mucus homeostasis and epithelial ciliary beating. Vasoactive intestinal peptide (VIP) is a neurotransmitter expressed in the sinonasal epithelium that is up-regulated in allergy. However, the effects of VIP on human sinonasal physiology are unknown, as are VIP's interactions with histamine, a major regulator of allergic disease. We imaged ciliary beat frequency, mucociliary transport, apical Cl(-) permeability, and airway surface liquid (ASL) height in primary human sinonasal air-liquid-interface cultures to investigate the effects of VIP and histamine. VIP stimulated an increase in ciliary beat frequency (EC50 0.5 μM; maximal increase ∼40% compared with control) and cystic fibrosis transmembrane conductance regulator (CFTR)-dependent and Na(+)K(+)2Cl(-) cotransporter-dependent fluid secretion, all requiring cAMP/PKA signaling. Histamine activated Ca(2+) signaling that increased ASL height but not ciliary beating. Low concentrations of VIP and histamine had synergistic effects on CFTR-dependent fluid secretion, revealed by increased ASL heights. An up-regulation of VIP in histamine-driven allergic rhinitis would likely enhance mucosal fluid secretion and contribute to allergic rhinorrhea. Conversely, a loss of VIP-activated secretion in patients with CF may impair mucociliary transport, contributing to increased incidences of sinonasal infections and rhinosinusitis.

Substance P and acetylcholine are co-localized in the pathway mediating mucociliary activity in Rana pipiens

Mucociliary activity is an important clearance mechanism in the respiratory system of air breathing vertebrates. Substance P (SP) and acetylcholine play a key role in the stimulation of the mucociliary transport in the frog palate. In this study, retrograde neuronal tracing was combined with immunocytochemistry for SP and choline acetyl transferase (ChAT) in the trigeminal ganglion and for neurokinin-1 receptor (NK1R) in the palate of Rana pipiens. The cells of origin of the palatine nerve were identified in the trigeminal ganglion using the retrograde tracer Fluorogold (FG). Optimal labeling of FG cells in the trigeminal ganglion was obtained at 96 h of exposure. Immunoflorescent shows that SP and acetylcholine are co-localized in 92% of the cells labeled with FG in the trigeminal ganglion. NK1 receptors were found in the membrane of epithelial and goblet cells of the palate. Ultrastructural study of the palate showed axonal-like endings with vesicles in connection with epithelial and goblet cells. These results further support the concerted action of both neurotransmitters in the regulation of mucociliary activity in the frog palate.

Substance P immunoreactive sensory axons as a subset of the total axonal population in the maxillary sinus of the rabbit: a characterization of normal and infected mucosa

Substance P (SP), one of the neuropeptides released from sensory nerves, is thought to mediate neurogenic inflammation. Although SP immunoreactive axons have been described in the sinus mucosa, no attempt has been made to characterize SP fibers as a subset of all axons present in the sinus mucosa. In addition, no study to date has characterized the changes in infected sinus mucosa. The maxillary sinus mucosa of New Zealand white rabbits was harvested from control animals and in animals with induced maxillary sinusitis. Immunohistochemical staining of the sinus mucosa for both Protein Gene Product 9.5 (PGP), a nonspecific marker for all nerves, and for SP was performed on 11 animals: 3 controls and 8 infected. In sinus mucosa from the control rabbits, <50% of all axons labeled by PGP were immunoreactive for SP. In infected mucosa, the absolute number of axons found by PGP staining decreased and nearly all of these remaining fibers were also immunoreactive for SP. We conclude that the phenotypical labeling of nerve fibers seen in normal mucosa is altered by bacterial-induced infection.

Ciliostimulatory effects mediated by nitric oxide

Ciliostimulation induced by various transmitters has been suggested to be mediated by the release of nitric oxide (NO). Freshly obtained adenoid tissue explants were pre-treated with the nitric oxide synthase (NOS) inhibitor N(G)-nitro L-arginine (L-NNA), to determine whether the ciliostimulators terbutaline, methacholine, substance P, and endothelin-1 require the release of NO to increase ciliary beat frequency (CBF) in vitro. The L-NNA pre-treatment affected the change in CBF induced by each of the ciliostimulators tested. To determine whether cyclic nucleotides also stimulate CBF by inducing the release of NO, an extra series of experiments were performed with dibutyryl cAMP and dibutyryl cGMP, and L-NNA pre-treatment. In contrast to the experiments with the various ciliostimulators, both dibutyryl cAMP and dibutyryl cGMP exerted ciliostimulatory effects that could not be inhibited by L-NNA. The present findings suggest that NO acts as an intermediate messenger in the ciliated epithelium in response to various transmitters and mediators. On the other hand, pre-treatment with the NOS inhibitor L-NNA did not affect ciliary response to the second messengers cAMP and cGMP, thus suggesting that NO dependent mechanisms do not constitute the sole pathway for the stimulation of ciliary function.

Nitric oxide is a regulator of mucociliary activity in the upper respiratory tract

The in vitro effects of the nitric oxide (NO) substrate L-arginine on ciliary beat frequency and the in vivo effects of the NO donor sodium nitroprusside (SNP) on mucociliary activity were investigated in the rabbit maxillary sinus mucosa with photoelectric techniques. L-Arginine increased ciliary beat frequency in vitro with a maximum response of 27.1% +/- 6.4% at 10(-3) mol/L, and this effect was reversibly blocked by pretreatment with the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine, whereas D-arginine had no such effect. SNP increased mucociliary activity in vivo, the peak response of 36.8% +/- 4.2% being obtained at the dose of 30.0 microg/kg. No tachyphylaxis was observed after repeat challenge with SNP. The increase in mucociliary activity caused by SNP was largely unaffected by pretreatment with the calcium channel blocker nifedipine, the cyclooxygenase inhibitor diclofenac, and the cholinergic antagonist atropine. The nonselective beta-blocker propranolol delayed the peak response of SNP to 7 to 8 minutes after challenge, compared with 1 to 2 minutes after challenge in animals without pretreatment. The results show the NO substrate L-arginine and the NO donor SNP to have ciliostimulatory effects in vitro and in vivo, respectively. The occurrence of NOS production in the sphenopalatine ganglion and sinus mucosa of the rabbit was studied by immunohistochemistry for NOS activity or nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry. The latter is an indirect sign of neuronal NOS activity. Numerous NOS-containing cell bodies were seen in the sphenopalatine ganglion; in the sinus mucosa a moderate supply of thin NOS-immunoreactive nerve fibers was seen. Taken together, the morphologic findings and the functional results indicate NO to be a regulator of mucociliary activity in upper airways.

Effect of recombinant neutral endopeptidase (EC 3.4.24.11) on neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat

The nasal mucosa harbors sensory nerves containing neuropeptides such as substance P (SP), which are released by capsaicin. The neuropeptides are degraded by peptidases, e.g., neutral endopeptidase (NEP) that is present in the nasal mucosa. We studied the effect of enzymatically active recombinant NEP (rNEP) on neuropeptide-evoked secretion of nasal fluid and plasma exudation in rats. rNEP administered intranasally (i.n.) reduced the capsaicin-evoked nasal fluid secretion but failed to reduce the secretion evoked by SP (exogenous) under the experimental conditions used. rNEP reduced the increase in nasal plasma exudation evoked by capsaicin (endogenous neuropeptides). Because rNEP reduced neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat, we suggest that peptidase activity in the nasal mucosa will determine the magnitude of the response to locally released neuropeptides.

Effects of nitric oxide on blood flow and mucociliary activity in the human nose

In an animal model, nitric oxide (NO) has been shown to increase mucociliary activity in vivo and ciliary beat frequency in vitro. The aim of the present study was to investigate the effects of NO on blood flow and mucociliary activity in the human nose. The concentration of NO in nasal air was measured with a chemiluminescence technique after nebulizing the NO donor sodium nitroprusside (SNP) at a dose of 3.0 mg into the nose in six volunteers, and was found to increase by 50.1% +/- 10.0% (mean +/- SEM; p < .001) after the SNP challenge. Blood flow measured by laser Doppler flowmetry increased by 67.3% +/- 15.5% (p < .05) after challenge with SNP at 1.0 mg, and by 75.4% +/- 18.5% at 3.0 mg (p < .01; n = 6). The higher dose, which produced no subjective side effects, was then used in the mucociliary experiments. The maximum increase in nasal mucociliary activity was 57.2% +/- 6.7% at 3.0 mg of SNP (n = 5). The findings support the view that NO regulates mucociliary activity and blood flow in the human nasal mucosa.

Effects of anti-allergic drugs on substance P (SP) and vasoactive intestinal peptide (VIP) in nasal secretions

To clarify the effects of anti-allergic drugs on substance P (SP) and vasoactive intestinal peptide (VIP) levels in nasal secretions, we employed competitive enzyme-linked immunoassays to measure concentrations of those neuropeptides in nasal secretions from 40 patients with house dust nasal allergy before and after administration of azelastine and oxatomide. One mg of azelastine and 30 mg of oxatomide were administrated twice a day for 4 weeks. Mean values of SP concentrations and ratios of SP to total protein of the nasal allergy group were significantly higher than those of the control group (p < 0.002). The VIP/total protein ratio of the allergy group was also significantly higher than that of the control group, although the VIP concentration alone was not. Mean levels of SP and VIP from patients with severe symptoms were significantly higher than those of the control group (p < 0.05), although those values were not significantly different between patients with moderate symptoms and control subjects. Azelastine and oxatomide effectively reduced SP levels in nasal secretions (p < 0.005), but they did not significantly decrease VIP levels. The reduction of SP levels was significant in patients with excellent responses to those drugs (p < 0.005), but not in patients with poor responses. These findings suggest that SP and VIP levels in nasal secretions may reflect the clinical state of nasal allergy and be one of the better parameters available for evaluating the clinical efficacy of anti-allergic drugs against nasal allergy.

Substance P enhances antigen-evoked mediator release from human nasal mucosa

Exogenous substance P (10-80 nmol/ml) induced a dose-dependent increase in nasal symptoms in asymptomatic allergics with rhinitis (n = 15) and controls (n = 8), but did not release any mediators. However, comparing the antigen-evoked release of mediators into nasal secretions with that of a substance P-pretreated antigen challenge, we found a significant enhancement of kinins, TAME esterase activity (p < 0.05-0.01), and histamine (p < 0.001, NS) 10-20 min after antigen challenge. These results suggest 1) that substance P-induced increase in nasal congestion is mediated through direct neurokinin receptor activation independently of mast cell activation, and 2) that during the allergic reaction there is a substance P-mast cell interaction that enhances the mediator response to nasal allergen challenge.

Effect of leukotriene C4 exposure on ciliated cells of the nasal mucosa

To clarify the effects of leukotriene C4 (LTC4) on human ciliated epithelium, ciliary activity of the ethmoid sinus mucosa was measured photoelectrically in tissue culture. At concentrations ranging from 10(-6)M to 10(-9)M, LTC4 showed minimal effects on the ciliated epithelium during the initial 30 minutes of exposure; thereafter, ciliary inhibition was observed in a concentration- and time-dependent manner. Irrigation of the mucosa with culture medium 15 minutes after exposure prevented the LTC4-induced ciliary inhibition. However, irrigation 60 minutes after exposure failed to inhibit 10(-8)M LTC4-induced ciliary dysfunction and mucosal damage. The LTC4-induced ciliary inhibition was blocked in the presence of FPL-55712 and/or Ly-171883, both leukotriene receptor antagonists. L-serine and sodium tetraborate complex (SBC), a gamma-glutamyl transpeptidase (gamma-GTP) inhibitor, also inhibited the LTC4-induced ciliary inhibition. These findings indicate that LTC4 is converted to LTD4 by gamma-GTP during 60 minutes of exposure, and LTC4 itself has minimal direct effects on the ciliated cells.

Signal transduction mechanisms in substance P-mediated ciliostimulation

Substance P is a neuropeptide released by afferent neurons in the respiratory tract during inflammatory reactions. It produces effects on blood vessels, bronchial smooth muscle, nasal glands, and respiratory cilia. We studied the in vitro effect of substance P on the ciliary beat frequency of human adenoid explants and its mechanism of action. Substance P was added to cultured adenoid at concentrations of 10(-10), 10(-8), 10(-6), and 10(-4) mol/L. Ciliary beat frequency was determined with phase-contrast microscopy and microphotometry. Substance P increased ciliary beat frequency a maximum of 11.9% +/- 3.8% (p < 0.01). Diclofenac (10(-6) mol/L) significantly blocked the ciliostimulatory effects of SP (p < 0.022), indicating that prostaglandin synthesis is an intermediate step in the action of substance P on ciliary beat frequency. The L-arginine analogs, NG-nitro-L-arginine methyl ester and NG-monomethyl-L-arginine, inhibit nitric oxide synthesis from L-arginine. L-Arginine analogs (10(-4) to 10(-2) mol/L) inhibited the effect of substance P (p < 0.02 at the higher concentration). This inhibition was reversed by adding L-arginine, demonstrating that nitric oxide production is a required step in substance P-induced ciliostimulation. Substance P stimulates ciliary activity in human nasal mucosa as a result of secondary production and release of endogenous prostaglandins and nitric oxide. It is likely that inflammatory disease processes that stimulate release of substance P and subsequent prostaglandin and nitric oxide production modify mucociliary transport. Pharmacologic modification of substance P and its second messengers may eventually permit regulation of this important defense mechanism and control of neurogenic inflammation.

Substance P and ciliary beat of human upper respiratory cilia in vitro

On stimulation of trigeminal nerve endings, neuropeptides are released into the nasal mucosa. Among these neuropeptides is substance P(SP). In this study, we determined the effect in vitro of SP, as well as SP together with thiorphan, a blocker of the SP-degrading enzyme neutral endopeptidase, on the ciliary beat frequency (CBF) of the human upper respiratory tract. Ciliated epithelium of human adenoid tissue was used in the experiments. The CBF was measured by means of a computer-assisted photoelectric method. Substance P(10(-8) to 10(-5) mol/L, n = 7) showed a small but statistically significant dose-dependent decrease in CBF. On perfusion with SP (10(-8)) to 10(-5) mol/L, n = 8) in combination with thiorphan, no statistically significant effect was found. We conclude that SP does not have a direct effect on ciliary activity to such an extent that it will affect mucociliary transport in vivo.

Histamine and leukotriene C4 effects on in vitro ciliary beat frequency of human upper respiratory cilia

Decreased mucociliary transport can occur in patients with type I (IgE-mediated) allergic rhinitis or allergic asthma. This study investigated if the allergic mediators histamine and leukotriene C4 (LTC4) could interfere with ciliary beat frequency (CBF) of in vitro human upper respiratory cilia and eventually result in decreased mucociliary transport. Ciliated epithelium of human adenoid tissue was used in the experiments and CBF was determined using a computer-assisted photoelectric method. Histamine in concentrations of 10(-6) - 10(-3) M (n = 12) and LTC4 as 10(-9) - 10(-6) M solutions (n = 10) showed no statistically significant dose-dependent effect on CBF in vitro.

The effects of salmeterol and salbutamol on ciliary beat frequency of cultured human bronchial epithelial cells, in vitro

Studies investigating mechanisms of mucociliary clearance have suggested that beta 2-adrenergic agents may significantly influence ciliary activity of epithelial cells and therefore play a vital role in the maintenance of functional integrity of the airways. We have cultured human bronchial epithelial cells, from surgical explants and investigated the effects of salbutamol and salmeterol, in a time- and dose-dependent manner, on the ciliary beat frequency (CBF) of these cells. Prior to and at several times after exposure to either salbutamol (10(-8) to 10(-3) M) or salmeterol (10(-8) to 10(-4) M), the epithelial cells were monitored for CBF and on the basis of data obtained from these studies, the effect of 10(-6) M propranolol was investigated in the presence of optimal concentrations of salbutamol and salmeterol. Salbutamol was optimally active at a concentration of 10(-4) M and caused a transient but significant increase in the CBF from baseline level of 8.6 +/- 0.4 to 9.6 +/- 0.5 Hz (P < 0.05), after 2 h incubation. In contrast, salmeterol was maximally active at a concentration of 10(-6) M and caused a significantly rapid and prolonged increase in CBF from a baseline value of 9.2 +/- 0.4 to 10.9 +/- 0.6 Hz (P < 0.02) and 10.6 +/- 0.8 Hz (P < 0.05) after 15 min and 24 h incubation, respectively. Propranolol (10(-6) M) abrogated the salbutamol- but not the salmeterol-induced increases in CBF.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P and vasoactive intestinal peptide in nasal secretions and plasma from patients with nasal allergy

To clarify the role of substance P (SP) and vasoactive intestinal peptide (VIP) in nasal allergy, we measured their concentrations in the nasal secretions and plasma of normal subjects and patients with nasal allergy to house dust and Japanese cedar pollen by competitive enzyme-linked immunoassay. The mean levels of SP (224 pmol/L) and VIP (41.6 pmol/L) in the nasal secretions of normal subjects were significantly higher than those in plasma (SP 3.04 pmol/L and VIP 1.04 pmol/L; p < .01). The mean levels of SP and VIP in the nasal secretions of the pollinosis group were significantly higher than those of the control group (p < .05 and p < .01), while the levels of the house dust allergy group were not higher than those of the control group. Intranasal allergen challenge significantly reduced SP levels in the nasal secretions of the allergy groups, while it did not influence VIP levels in the nasal secretions. These findings suggest that SP and VIP are actively secreted into the nose and may play an important role in the allergic reaction on the surface of the human nasal mucosa.

Substance P in the regulation of mucociliary transport in the frog palate

1. Mucociliary transport of carbon particles across the palate of anesthetized Rana pipiens was accelerated by electrical stimulation of the palatine nerve. 2. Transport was also accelerated by intracardiac injection of acetylcholine and of substance P in a dose-dependent manner. 3. Acceleration of transport by acetylcholine and by substance P was selectively blocked by atropine and by the substance P antagonist Spantide, respectively. 4. Acceleration of transport by nerve stimulation was blocked partially by atropine and by Spantide, and completely by the two administered concurrently. 5. It is concluded that nerve stimulation releases both acetylcholine and substance P or a similar neuropeptide. 6. Taken in conjunction with the literature, the data suggest that these substances are involved in the normal mechanism for stimulating mucociliary clearance of the palate in response to the presence of particles.

Vasoactive intestinal peptide stimulates ciliary motility in rabbit tracheal epithelium: modulation by neutral endopeptidase

We studied the effect of vasoactive intestinal peptide (VIP) on ciliary activity in rabbit cultured tracheal epithelium by a photoelectric method in vitro. Administration of VIP (10(-7) M) elicited an increase in ciliary beat frequency (CBF) from the baseline values of 970 +/- 52 to 1139 +/- 75 beats/min (mean +/- S.E., P less than 0.01). This ciliostimulatory effect was dose-dependent, with the maximal increase and EC50 value being 17.4 +/- 1.0% (P less than 0.05) and 6.10(-11) M, respectively. The VIP-induced increase in CBF was abolished by pretreatment of cells with [4-Cl-D-Phe6, Leu17]-VIP, a VIP receptor antagonist. The neutral endopeptidase inhibitor phosphoramidon (10(-5) M) potentiated the effect of VIP, so that the CBF dose-response curve for VIP was shifted to lower concentrations by 0.5 log U. The administration of VIP increased cyclic AMP levels in epithelial cells, an effect that was also potentiated by phosphoramidon. These results suggest that VIP may interact with its specific receptors and stimulate airway ciliary activity probably through the activation of adenylate cyclase, and that neutral endopeptidase may play a role in modulating this effect of VIP.

Stimulation of frog ciliated cells in culture by acetylcholine and substance P

1. Ciliary beat frequency in epithelial outgrowths from cultured explants of Rana pipiens palate changed markedly from second to second. 2. Acetylcholine (10(-8) to 10(-3) M) and substance P (1.35 x 10(-7) to 1.35 x 10(-5) M) increased and stabilized ciliary beat frequency. The effect of acetylcholine and part of the effect of substance P were blocked by atropine (10(-4) M). 3. Acetylcholine appears to act directly and substance P both directly and indirectly through the release of acetylcholine.

Mucociliary activity and the diving reflex

It has previously been shown that mucociliary activity in the rabbit maxillary sinus is immediately increased after short-term exposure to such airway irritants as cigarette smoke and ammonia vapor. This increase is mediated through the stimulation of capsaicin-sensitive nerve endings. Besides producing the mucociliary effect, these irritants inhibit breathing, a response characteristic of the diving reflex in mammals. Whether an increase in mucociliary activity is part of the diving reflex was investigated by injecting 0.5 mL water into the nasopharynges of anesthetized rabbits. Mucociliary and respiratory responses were compared with the effects of mechanical stimulation (ie, rotating an intranasal catheter until sneezing occurred). Water challenge produced an increase in mucociliary activity of 21.6% +/- 2.4%, a response that began approximately 10 seconds after injection. Mucociliary acceleration was completely blocked by atropine, indicating a cholinergic mechanism, but was unaffected by pretreatment with capsaicin. The respiration rate was inhibited by about 45% after challenge with water. Pretreatment with atropine and capsaicin had no effect on this reduced respiratory rate. Mechanical stimulation of the nasal mucosa accelerated mucociliary activity. This response appeared approximately 4 seconds after stimulation was begun, and occurred simultaneously with the onset of sneezing. The peak increase was 22.0% +/- 2.1%. Sneezing was followed by an increase in the respiration rate of about 40%. Pretreatment with atropine or capsaicin had no effect on respiratory responses, but did inhibit mucociliary acceleration, suggesting that the response is mediated through cholinergic effector neurons after activation of capsaicin-sensitive nerve endings.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanosensitive and beta-adrenergic control of the ciliary beat frequency of mammalian respiratory tract cells in culture

Respiratory tract ciliated cells, obtained from the rabbit trachea and maintained in culture, were sensitive to mechanical stimulation. The mechanical deformation of the cell surface induced a rapid, but transient, increase in ciliary beat frequency. In addition, the beat frequency of these ciliated cells was also increased in a dose-dependent manner by the beta-adrenergic drug isoproterenol (10(-7) to 10(-4) M) and by the calcium ionophore A23187 (10(-6) and 10(-5) M). To determine if drug and mechanosensitive activation of ciliary beat frequency arise from a common or different cellular mechanism, we investigated the effect of mechanical stimulation on beat frequency in the presence of isoproterenol or A23187. In isoproterenol (10(-8) to 10(-4) M), none of the parameters used to describe the ciliary beat frequency response to mechanical stimulation was altered. In A23187 (10(-6) M or above), the magnitude of the beat frequency response was significantly reduced or almost abolished, suggesting that mechanical stimulation acts, like A23187, to increase ciliary beat frequency by increasing intracellular calcium. Lower concentrations of A23187 had no effect. These results suggest that respiratory tract ciliated cells have at least two independent mechanisms for the control of ciliary beat frequency: one probably utilizing calcium, the other probably cAMP.

VIP potentiates cholinergic effects on the mucociliary system in the maxillary sinus

The neuropeptide vasoactive intestinal polypeptide (VIP), which is found in a population of cholinergic parasympathetic neurons in the airways, has no effects per se on mucociliary activity. In order to test the hypothesis that VIP may modulate cholinergic regulation of the mucociliary system, VIP was infused intraarterially (8.4 pmol/kg/min), and the response to challenges with methacholine in the maxillary sinus of rabbits were recorded with a photoelectric technique. Occurrence of VIP-like immunoreactivity in the rabbit maxillary sinus, maxillary nerve, and sphenopalatine ganglion was investigated. Immunoreactivity against VIP was found in nerve fibers in the subepithelial layer of the maxillary sinus and in numerous nerve cell bodies in the sphenopalatine ganglion. Infusion of VIP potentiated the mucociliary increase induced by methacholine. The mucociliary wave frequency change increased from 6.1% +/- 1.7% to 13.3% +/- 3.9% (0.01 micrograms/kg methacholine), from 11.6% +/- 3.6% to 18.8% +/- 2.2% (0.05 micrograms/kg) and from 17.0% +/- 3.0% to 27.4% +/- 3.6% (0.1 micrograms/kg). Both peak responses and response durations increased during infusions. In contrast, the vasodilating agent papaverine sulphate did not influence the mucociliary response to methacholine. The modulating effect of VIP on the mucociliary system, taken together with the morphologic observations, suggest that VIP may have a physiologic role in the regulation of the mucociliary system in the maxillary sinus.

Nasal exposure to airway irritants triggers a mucociliary defence reflex in the rabbit maxillary sinus

The effect on mucociliary (m.c.) activity in the rabbit maxillary sinus of cigarette smoke and ammonia (NH3) vapour delivered through a tracheal cannula or as nasal challenges was investigated by a photo-electric technique, and compared with simultaneously induced changes in the respiratory rate. Neither irritant had any effect on m.c. activity in the sinus after tracheo-bronchial exposure. However, the respiration rate was increased by NH3 vapour (2.5 ml, diluted 1:1 with room air) and neat cigarette smoke (10 ml) by 76.9% and 24.3% respectively (median values). In contrast, nasal challenges with both irritants increased m.c. activity by 24.1% (NH3) and 19.1% (cigarette smoke), and reduced the respiration rate by 31.0% (NH3) and 28.4% (cigarette smoke) (median values). NH3 vapour sometimes produced an apnea proper. Identical results were obtained in laryngectomized rabbits, indicating that laryngeal afferents were not involved in the responses. Moreover, topical application of the C-fibre stimulant capsaicin mimicked the effects produced by the airway irritants. It is concluded that nasal exposure to irritants triggers at least two different protective reflexes. One is the increase of m.c. activity in the upper airways involving sensory C-fibres and the other the apneic reflex of Kratschmer.

Effects of neurokinin A and calcitonin gene-related peptide on mucociliary activity in rabbit maxillary sinus

Substance P (SP) released from sensory C-fibers in the airways increases the mucociliary (m.c.) activity in the rabbit maxillary sinus. The purpose of the present study was to investigate the m.c. effects of two other neuropeptides, coexisting with SP in sensory neurones, neurokinin A (NKA) and calcitonin gene-related peptide (CGRP). NKA increased the m.c. activity dose-dependently (dose range 0.1-10.0 micrograms/kg, 88 pmol to 8.8 nmol/kg), the maximum increase being 41.9 +/- 2.6%. The effect was inhibited by pretreatment with the tachykinin antagonist (D-Pro2,D-Trp7,9)SP, but not with atropine or hexamethonium. Thus NKA released from sensory C-fibers may contribute to the non-cholinergic increase of m.c. activity observed after C-fiber stimulation. In contrast CGRP did not influence the m.c. activity. Neither did it influence the responses to NKA or SP. It is concluded that CGRP is unlikely to be involved in the control of m.c. function.

Influence of substance P on ciliary beat frequency in airway isolated preparations

The neuropeptide substance P (SP), which is released from sensory C-fibres after stimulation by chemical irritants. accelerates mucociliary activity in rabbit maxillary sinus in vivo. In order to investigate the mechanism behind this finding, we recorded ciliary beat frequency (CBF) in vitro from various respiratory explants by a photoelectric technique. It was noticed that ciliated cells from the maxillary sinus displayed a higher beating frequency than cells from the trachea and the bronchus, in that order. SP 10(-10)-10(-4) M did not influence the CBF in explants from rabbit maxillary sinus, rabbit trachea and main bronchi, guinea-pig trachea and human adenoids. Neurokinin A (NKA) 10(-6)-10(-5) M, which is also thought to be released from sensory C-fibres, did not influence the CBF in guinea-pig trachea. Neither did the C-fibre stimulant capsaicin 10(-8)-10(-4) M increase CBF in explants from human adenoids. The present findings indicate that the mucociliary effect of SP in vivo is not mediated by an effect on the cilia themselves.

Substance P and human nasal mucociliary activity

Substance P (SP), a potent inflammatory agent, has been found in sensory nerve fibres in the nasal mucosa in several experimental animals as well as in man. It may participate in the inflammatory response as part of the mucosal defence against foreign materials. In experimental animals SP has been found to increase mucociliary in airway mucosa. The present study was performed in order to find out the relationship between topically applied SP and nasal mucociliary function in humans. Thirteen healthy volunteers were challenged with 65 micrograms SP or placebo in a randomized cross over fashion and mucociliary transport time was determined each time using the saccharine dye test. The dose of SP was chosen after an open dose-response study. No statistically significant change in the mucociliary transport time was found after challenge with SP as compared to placebo. The possible reasons for this are discussed.