NOD-like receptors in the human upper airways: a potential role in nasal polyposis.

BACKGROUND: Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are newly discovered cytosolic receptors belonging to the pattern-recognition receptor family. They detect various pathogen-associated molecular patterns, triggering an immune response. The knowledge about these receptors, and their role in health and disease, is limited. The aim of the present study was to characterize the expression of NOD1, NOD2, and NALP3 in the human upper airways. METHODS: Surgical samples were obtained from patients with tonsillar disease (n = 151), hypertrophic adenoids (n = 9), and nasal polyposis (n = 24). Nasal biopsies were obtained from healthy volunteers (n = 10). The expression of NOD1, NOD2, and NALP3 was analyzed using real-time PCR and immunohistochemistry. RESULTS: Expression of NOD1, NOD2, and NALP3 mRNA and protein were seen in all tissue specimens. The NLR mRNA was found to be higher in nasal polyps than in normal nasal mucosa, and local steroid treatment reduced the NLR expression in polyps. In contrast, tonsillar infection with Streptococcus pyogenes or Haemophilus influenzae did not affect the NLR expression. CONCLUSIONS: The present study demonstrates the presence of NLRs in several upper airway tissues and highlights a potential role of NLRs in chronic rhinosinusitis with polyps.

Nod1, Nod2 and Nalp3 receptors, new potential targets in treatment of allergic rhinitis?

BACKGROUND: Recently, a new set of pattern-recognition receptors, the nucleotide-binding oligomerization domain (Nod)-like receptors (NLRs), have emerged. Their activation, either by allergens or microbes, triggers an inflammatory response. The knowledge about NLRs in human airways is limited. AIM OF THE STUDY: To investigate presence of NLRs in the human nose of healthy individuals and patients with intermittent allergic rhinitis outside and during pollen season. METHODS: The expression of Nod1, Nod2, and Nalp3 in nasal biopsies was determined with real-time RT-PCR and immunohistochemistry. Cultured primary human nasal epithelial cells (HNECs) were analyzed using real-time RT-PCR and flow cytometry to further verify the presence of NLRs in the epithelium. RESULTS: Immunohistochemical analysis revealed presence of Nod1, Nod2, and Nalp3 in the nasal epithelium. This was corroborated in cultured HNECs. Patients suffering from symptomatic allergic rhinitis exhibited lower Nod1 and Nalp3 mRNA levels than both controls and patients during pollen season. Nod2 expression was found in all specimens tested, but no differences were seen between the three groups. CONCLUSION: Nod1, Nod2, and Nalp3 receptors were found to be present in the human nose. The expression of Nod1 and Nalp3 were down-regulated during pollen season among patients with allergic rhinitis. This opens up for new insights and novel therapeutic strategies in inflammatory airway disease.

Inverse relation between nasal fluid Clara Cell Protein 16 levels and symptoms and signs of rhinitis in allergen-challenged patients with intermittent allergic rhinitis.

BACKGROUND: Decreased levels of the anti-inflammatory Clara Cell Protein 16 (CC16) are found in intermittent allergic rhinitis (IAR) and asthma. In asthma this decrease has been associated with hyperreactivity and the A38G single nucleotide polymorphism (SNP). The aim of this study was to examine if IAR is associated with signs and symptoms of rhinitis and the A38G SNP. METHODS: Nasal fluid CC16 was analyzed in 20 patients with IAR before allergen challenge and 1 and 6 h after challenge, and from 28 healthy controls. The A38G SNP was analyzed in 80 patients with IAR and 106 controls. Nasal biopsies were obtained from three subjects in each group for immunohistochemical analysis of CC16. RESULTS: In the allergen-challenged patients symptoms and rhinoscopic signs of rhinitis increased after 1 h and normalized after 6 h. In contrast, nasal fluid CC16 decreased 1 h after allergen challenge and returned to baseline after 6 h. Nasal fluid CC16 levels did not differ from controls before and 6 h after challenge. Immunohistochemical investigation showed intense CC16 staining in the nasal epithelium of both patients before season and healthy controls, but weak staining in symptomatic patients during season. No significant association between the A38G SNP and IAR was found. CONCLUSION: There was an inverse relation between nasal fluid CC16 levels and symptoms and signs of rhinitis in allergen-challenged patients with IAR. However, there was no association between IAR and the A38G SNP.

Gene profiling reveals decreased expression of uteroglobin and other anti-inflammatory genes in nasal fluid cells from patients with intermittent allergic rhinitis.

BACKGROUND: Intermittent allergic rhinitis (IAR) results from interactions between a large number of pro- and anti-inflammatory mediators. Little is known about anti-inflammatory mediators in IAR. DNA microarrays allow simultaneous analysis of the whole transcriptome in a sample. OBJECTIVE: To identify anti-inflammatory transcripts in nasal fluid cells from patients with IAR during season and from healthy controls. METHODS: Nasal lavage fluids were obtained from 15 patients with symptomatic birch/and or grass pollen-induced IAR and 28 healthy controls. RNA was extracted from the nasal fluid cells and pooled into one patient- and one control pool. These were analysed with DNA microarrays containing more than 44,927 genes and variants. RESULTS: Seventeen thousand three hundred and fifty three genes were expressed in the controls and 17 928 in the patients. One thousand five hundred and seventy nine of the genes had higher expression in patients than in controls, and 1570 had lower expression in patients. Out of 189 up-regulated inflammatory genes, 187 were pro-inflammatory and two were anti-inflammatory. These genes regulated key steps of inflammation, ranging from influx of leukocytes to immunoglobulin production. By comparison, out of 49 down-regulated inflammatory genes, 36 were pro-inflammatory and 13 were anti-inflammatory. The anti-inflammatory gene that decreased most in expression in the patients was uteroglobin (also known as Clara Cell protein 16, CC16). The nasal fluid concentrations of uteroglobin protein were significantly lower in patients than in controls, 5.43+/-1.53 and 12.93+/-2.53 ng/mL, respectively (P<0.05). CONCLUSION: IAR is associated with decreased expression of uteroglobin and other anti-inflammatory genes.

Nerve growth factor enhances cholinergic innervation and contractile response to electric field stimulation in a murine in vitro model of chronic asthma.

BACKGROUND: Asthma is a chronic inflammatory disease characterized by airway hyper-responsiveness. Alterations in the neurogenic control are believed to contribute to the pathogenesis. Yet, the long-term interaction between nerves and inflammatory mediators, such as the neurotrophin nerve growth factor (NGF), are not fully understood much due to the absence of appropriate experimental assays. OBJECTIVE: To develop an ex vivo mouse organ culture assay and to investigate the effects of NGF on nerve-mediated airway contractions. METHOD: Mouse tracheal segments were cultured in periods of up to 16 days. Their contractile responses to electric field stimulation (EFS) were investigated. In addition, the effect of 4 days of NGF treatment was analysed using EFS and immunohistochemistry. RESULTS: EFS (0.2-25.6 Hz) induced reproducible and frequency-dependent cholinergic contractions of both fresh and cultured tracheal segments. The main part of the EFS response was blocked by tetrodotoxin or atropine. After 4 days in culture, regional differences appeared, with stronger EFS responses in distal than in proximal segments. More nerve fibres were seen in distal segments than in proximal segments. Treatment with NGF during 4 days of culture increased the innervation of the proximal segments, at the same time as the cholinergic contractile responses to EFS were enhanced dose-dependently. CONCLUSION: Culture of tracheal segments appears to be a suitable assay for the examination of long-term effects induced by inflammatory mediators on neurally mediated airway contractions. NGF treatment enhanced the cholinergic, nerve-dependent contractions and increased the amount of nerve fibres seen in the murine tracheal segments, suggesting a role for NGF in the development of airway hyper-responsiveness.

Increased expression of surface activation markers on neutrophils following migration into the nasal lumen.

BACKGROUND: The sequence of events following the recruitment of a free-flowing neutrophil in the peripheral circulation, via adhesion, migration and release of mediators, to a neutrophil on the surface of the nasal epithelium is a co-ordinated process. Little is known about the state of neutrophil activation following this course of events. OBJECTIVES: To investigate the expression of surface activation markers on neutrophils, reflecting activation during their recruitment to the nose, and to see whether the inflammatory process during allergic rhinitis influences this process. METHOD: Nine healthy controls and 12 patients with grass pollen-induced intermittent allergic rhinitis were investigated during the peak of the pollen season. The expression of CD11b, CD66b and CD63 on the neutrophil cell surface, as a reflection of activation, was analysed using flow cytometry. Neutrophils were derived from peripheral blood and nasal lavage fluid. In addition, eosinophil cationic protein (ECP) and myeloperoxidase (MPO) as well as L-, P- and E-selectins in the nasal lavage fluid were analysed using RIA and ELISA, respectively. RESULTS: A marked increase in the expression of all three CD markers on the neutrophil cell surface was noticed following migration from the bloodstream to the surface of the nasal mucosa. At the peak of the grass pollen season, the MPO levels increased, reflecting an increase in the total number of nasal fluid neutrophils. In parallel, the expression of CD11b was further augmented. The expression of the CDb11b was reduced on neutrophils remaining in the circulation. In addition, the level of L-selectin was reduced on neutrophils derived from the blood during allergic inflammation. CONCLUSION: Neutrophils might become activated during their transfer from the blood to the surface of the nasal mucosa, but these changes may also be due to depletion of activated neutrophils in the blood via activated endothelial/epithelial adhesion and chemoattractant measures. The increased expression of surface activation markers during allergic rhinitis suggests roles for neutrophils in the inflammatory process.

Pituitary adenylate cyclase-activating polypeptide, effects in the human nose.

BACKGROUND: Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide with strong vaso- and bronchodilator capacity. There is recent evidence that PACAP decreases the release of proinflammatory cytokines and we have previously shown that PACAP inhibits neutrophil chemotaxis in vitro, but little is known about the effects of PACAP in human upper and lower airways. OBJECTIVE: To investigate the effects of PACAP in the human upper respiratory tract focusing on vasodilatation/nasal airway resistance (NAR), neutrophil recruitment, plasma extravasation and endogenous production of IL-1-related mediators. METHODS: Surgical specimens from five patients (aged 19-55 years), obtained in conjunction with nasal surgery, were used for immunohistochemical localization of PACAP in the nasal mucosa. In seven, healthy, non-allergic, non-smoking subjects (aged 19-45 years), NAR was measured with rhinomanometry. Nasal lavage was performed, before and after intranasal application of PACAP (200 microL of a 1 microm PACAP solution in each nasal cavity), with and without the addition of histamine. Cells, albumin and IL-1-related mediators were analysed in nasal lavage. In addition, the effects on pulse, blood pressure, ECG and pulmonary function were evaluated. RESULTS: In the nasal mucosa, PACAP-like immunoreactive nerve fibres were seen close to blood vessels and seromucous glands. Application of PACAP in the nasal cavity increased NAR and augmented the increase in NAR induced by histamine. In addition, PACAP inhibited histamine-induced recruitment of neutrophils, increased plasma leakage and reduced the level of IL-1RA (an endogenously produced IL-1 receptor antagonist) in nasal lavage. Cardiovascular and pulmonary parameters were not affected. CONCLUSION: These results imply that PACAP is an important endogenous mediator in human upper airways, with a potential role as a regulator of vascular smooth muscle, secretion, plasma extravasation, neutrophil recruitment and cytokine activity.

Hemin, a heme oxygenase substrate analog, both inhibits and enhances neutrophil random migration and chemotaxis.

BACKGROUND: Carbon monoxide (CO), is an endogenously produced gas, generated by the rate-limiting enzyme heme oxygenase (HO), present in man throughout the respiratory tract. CO can elicit important physiological responses like bronchial relaxation and vasodilation. Both HO expression and CO levels in the airways increase in response to hypoxic challenge and to a wide variety of inflammatory stimuli, such as intermittent allergic rhinitis, asthma and upper respiratory tract infections. A role for CO in airway regulation and inflammation has therefore been suggested. However, information about CO-induced effects on cells involved in airway inflammation is scarce. The present study was designed to investigate if the HO substrate analog hemin could affect neutrophil random migration, and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) induced chemotaxis. METHODS: Hemin was added to and incubated with whole blood and the effects of the anticipated CO production were then evaluated on isolated neutrophils using a chemotaxis chamber. RESULTS: A biphasic dose-response curve emerged for both the neutrophil spontaneous random migration and the fMLP-induced chemotaxis. Low concentrations of hemin (10(-11) m to 10(-9) m) enhanced the migratory response, whereas higher concentrations (10(-7) m and 10(-5) m) inhibited migration. The inhibition induced by hemin on fMLP-induced migration was abolished after pre-treatment with Rp-8Br-cyclicGMPS, an inhibitor of cyclicGMP. CONCLUSIONS: The present data indicate that endogenously produced CO can affect both spontaneous and stimulated neutrophil migration, partly via a cyclicGMP-related process, hence strengthening the idea of a role for CO in airway inflammation.

Increased carbon monoxide levels in the nasal airways of subjects with a history of seasonal allergic rhinitis and in patients with upper respiratory tract infection.

BACKGROUND: Carbon monoxide (CO) has emerged as an endogenously produced gaseous mediator known to be involved in bronchial smooth muscle regulation. Increased amounts of CO have been found in exhaled air during asthma and lower airway inflammation. Recently CO has been shown to be produced in the nasal airways, but there are no reports of altered CO levels in nasal airways during inflammation. OBJECTIVE: This study was designed to investigate if CO levels increase in the human nasal airways during inflammatory conditions, such as allergy and upper airway respiratory tract infection (URTI). METHODS: CO was sampled separately from the upper and lower airways of 13 healthy control subjects, six patients with a history of allergic rhinitis and six patients with URTI. RESULTS: Nasal CO levels were increased in subjects with allergic rhinitis, compared to healthy controls (2.07 +/- 0.15 ppm, n = 6 and 1.62 +/- 0.08 ppm, n = 13, respectively, P < 0.01). CO levels were also increased in patients with URTI, compared to the same controls (1.92 +/- 0.09 ppm, n = 6, P < 0.05). Normal levels of CO were found in air from the lower airways among subjects with allergic rhinitis, whereas corresponding levels in the URTI patients were increased. CONCLUSION: The present data demonstrates that upper airway CO levels increase in parallel with different inflammatory stimuli, such as allergy and infection, suggesting a role for CO as marker or mediator of nasal inflammation.

Neuropeptide expression in the human trigeminal nucleus caudalis and in the cervical spinal cord C1 and C2.

In migraine and other primary headaches there is a strong vascular component. Besides the trigeminovascular components some of the associated symptoms point to the involvement of brain stem regions. The central limb of the trigeminal vascular pathway is its projection to the trigeminal nucleus caudalis (TNC) and to the C1-C2 levels of the spinal cord. The aim of the present study was to demonstrate the occurrence of some neurotransmitters in these regions in man. In both the TNC and in the Rexed's laminae I and II of the dorsal horns at the C1 and C2 levels there were numerous substance P immunoreactive fibres. Fibres containing calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating peptide (PACAP) were moderately dense in number. Fibres containing vasoactive intestinal peptide (VIP) or nitric oxide synthase (NOS) were not seen in the TNC or at the C1 and C2 levels of the spinal cord.

5-HT(1B) and 5-HT(1D) receptors in the human trigeminal ganglion: co-localization with calcitonin gene-related peptide, substance P and nitric oxide synthase.

5-Hydroxytryptamine (5-HT) is implicated in migraine and agonist directed against 5-HT(1B) and 5-HT(1D) receptors are commonly used as effective therapies. The antimigraine mechanisms involve the inhibition of intracranial sensory neuropeptide release. In order to determine which 5-HT(1) receptor subtypes are involved we have by immunocytochemistry examined the distribution of 5-HT(1B) and 5-HT(1D) receptors in the human trigeminal ganglia, and addressed which of them colocalize with calcitonin gene-related peptide (CGRP), substance P (SP) or nitric oxide synthase (NOS). We detected that 5-HT(1D) receptor immunoreactivity (i.r.) was predominantly expressed in medium-sized cells (86% of positive cells, 30-60 microm). About 9% of the 5-HT(1D) receptor i.r. cells were large in size (> 60 microm) and 5% were small in size (< 30 microm). In a similar pattern, 5-HT(1B) receptor i.r. was mainly expressed in medium-sized cells (81% in 30-60 microm, 15% in > 60 microm and 4% in < 30 microm). Double immunostaining was used to determine whether the 5-HT(1B) or 5-HT(1D) receptor immunoreactive cells co-localized with either CGRP, SP or NOS. Thus, 89% of the CGRP i.r. cells expressed 5-HT(1D) receptor i.r. and 65% of the CGRP positive cells were 5-HT(1B) receptor positive. Most of the 5-HT(1D) (95%) and the 5-HT(1B) (94%) receptor i.r. cells showed SP immunostaining and 83% of 5-HT(1D) receptor and 86% of 5-HT(1B) receptor i.r. cells contained NOS. In conclusion, both 5-HT(1B) and 5-HT(1D) receptors are expressed in the human trigeminal ganglion and they are mainly localized in medium-sized cells and they seem to colocalize with CGRP, SP and NOS.

The induction of carbon monoxide-mediated airway relaxation by PACAP 38 in isolated guinea pig airways.

Pituitary adenylate cyclase--activating peptide 38 (PACAP 38) displays several biologic activities relevant to obstructive airway disease. Carbon monoxide (CO) has recently emerged as a potent, endogenously produced mediator of bronchodilation. In this study, we have analyzed the occurrence of PACAP 38 and the corresponding occurrence of heme oxygenase (HO), the rate-limiting enzyme for CO production, in guinea pig trachea, using immunocytochemistry. We have also investigated whether the dilatory effects of PACAP 38 are dependent on CO, using an in vitro setup for tracheal studies. A moderate supply of PACAP-like immunoreactive nerve fibers was seen in association with tracheal smooth muscle. HO-like immunoreactivity was observed in the respiratory epithelium and in association with smooth muscle bundles. PACAP 38 induced a concentration-dependent relaxation of precontracted tracheal segments. This dilation was nearly abolished after pretreatment with zincprotoporphyrine, an inhibitor of heme oxygenase. The same effect was accomplished with Rp-8Br-cyclicGMPS, an inhibitor of cyclicGMP, whereas the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine had no effect on the PACAP 38--induced dilation. The presented data suggest that PACAP 38 can induce bronchodilation by means of a CO-dependent, cyclicGMP-related mechanism, thereby providing a link between neurotransmission and local CO release in the airway smooth muscle.

Neuropeptide localization in the "migraine generator" region of the human brainstem.

Evidence from animals and humans suggests that brainstem nuclei such as the raphe nuclei, the locus coeruleus (LC) and the periaqueductal grey matter (PAG), are involved in the pathophysiology of migraine. In order to understand possible neurotransmitters involved we have, by means of indirect immunocytochemistry, analysed these regions for the occurrence and distribution of calcitonin gene-related peptide (CGRP), substance P (SP), pituitary adenylate-cyclase activating peptide (PACAP) and vasoactive intestinal polypeptide (VIP). CGRP-immunoreactive (-ir) cell bodies, but no fibres, were found to occur in high numbers, constituting 80% of all nerve cell bodies in the LC. A smaller number of these nerve cell bodies (40%) in the LC proved to be PACAP-ir. The LC neurones also stored the vesicular monoamine transporter (VMAT)- and the C-terminal flanking peptide of neuropeptide Y (C-PON)-ir, illustrating their adrenergic nature. Double immunostaining revealed that all VMAT-and C-PON-containing neurones, in addition, stored CGRP. Immunoreactive cell bodies were not seen in the nucleus raphe magnus (NRM) or PAG. Numerous SP-ir nerve fibres were observed in the NRM, the LC and the PAG. Few PACAP-ir nerve fibres were detected in the PAG and few VIP-ir nerve fibres were seen in the NRM and the PAG.

Neuronal messengers in the human cerebral circulation.

In recent years our knowledge of the nervous control of the cerebral circulation has increased. The use of denervations and retrograde tracing in combination with immunohistochemical techniques has demonstrated that cerebral vessels are supplied with sympathetic, parasympathetic, and sensory nerve fibers and possibly central pathways containing a multiplicity of new transmitter substances in addition to the classical transmitters. The majority of these transmitters are neuropeptides. More recently it has been suggested that a gaseous transmitter, nitric oxide (NO) also could participate in the neuronal regulation of cerebral blood flow. Although little is known about the physiological actions and inter-relationships among all these putative neurotransmitters, their presence within cerebrovascular nerve fibers will make it necessary to revise our view on the mechanisms of cerebrovascular neurotransmission.

Expression of 5-HT1B receptors in human nasal mucosa.

5-HT1B receptors were discovered in human nasal mucosa using immunocytochemistry. Strong immunoreaction was seen around small blood vessels mainly confined to the smooth muscle cell layer. In contrast, no immunoreaction for 5-HT1D was seen. The possibility of local release in connection with specific target receptors suggests a role for 5-HT in the regulation of vascular tone, glandular secretion and epithelial functions and that 5-HT1B receptor agonists may be of clinical importance.

Amylin: localization, effects on cerebral arteries and on local cerebral blood flow in the cat.

Amylin and adrenomedullin are two peptides structurally related to calcitonin gene-related peptide (CGRP). We studied the occurrence of amylin in trigeminal ganglia and cerebral blood vessels of the cat with immunocytochemistry and evaluated the role of amylin and adrenomedullin in the cerebral circulation by in vitro and in vivo pharmacology. Immunocytochemistry revealed that numerous nerve cell bodies in the trigeminal ganglion contained CGRP immunoreactivity (-ir); some of these also expressed amylin-ir but none adrenomedullin-ir. There were numerous nerve fibres surrounding cerebral blood vessels that contained CGRP-ir. Occasional fibres contained amylin-ir while we observed no adrenomedullin-ir in the vessel walls. With RT-PCR and Real-Time-PCR we revealed the presence of mRNA for calcitonin receptor-like receptor (CLRL) and receptor-activity-modifying proteins (RAMPs) in cat cerebral arteries. In vitro studies revealed that amylin, adrenomedullin, and CGRP relaxed ring segments of the cat middle cerebral artery. CGRP and amylin caused concentration-dependent relaxations at low concentrations of PGF 2alpha-precontracted segment (with or without endothelium) whereas only at high concentration did adrenomedullin cause relaxation. CGRP8-37 blocked the CGRP and amylin induced relaxations in a parallel fashion. In vivo studies of amylin, adrenomedullin, and CGRP showed a brisk reproducible increase in local cerebral blood flow as examined using laser Doppler flowmetry applied to the cerebral cortex of the alpha-chloralose-anesthetized cat. The responses to amylin and CGRP were blocked by CGRP8-37. The studies suggest that there is a functional sub-set of amylin-containing trigeminal neurons which probably act via CGRP receptors.

Pituitary adenylate cyclase-activating peptide inhibits neutrophil chemotaxis.

Pituitary adenylate cyclase-activating peptide 38 (PACAP 38) is a neuropeptide that displays several biological effects of interest in the context of airway diseases such as asthma and chronic obstructive pulmonary disease. These effects include inhibition of airway and vascular smooth muscle tone as well as modulation of inflammatory cell activity. However, little is known about the effect of PACAP on granulocytes. The present study was designed to investigate if PACAP and the closely related peptide vasoactive intestinal peptide (VIP) could affect neutrophil migration. A standard 48 well chemotaxis chamber was used to assess the effects of PACAP on N-Formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced neutrophil chemotaxis and spontaneous random migration. PACAP 38 and VIP inhibited fMLP-induced human neutrophil chemotaxis. Furthermore, both peptides also exhibited a dose-related trend toward inhibiting the spontaneous, unstimulated migration of neutrophils. Since enhanced cell migration in cell chamber systems is reported to correlate with increased invasive properties in vivo, the presented inhibitory effects of PACAP 38 on neutrophil chemotaxis, supports the idea of an anti-inflammatory role for PACAP. This together with the well documented bronchodilatory capacity of PACAP might indicate a role for PACAP-agonists in future treatment of asthma and other inflammatory airway diseases.

Pituitary adenylate cyclase-activating peptide 38 a potent endogenously produced dilator of human airways.

Pituitary adenylate cyclase-activating peptide (PACAP) 38 displays several biological activities relevant to obstructive airway disease. In this study, the occurrence of PACAP 38 in human small bronchi and corresponding pulmonary arteries was analysed immunocytochemically. The dilatory effects of this peptide on the same structures were also studied in vitro. A moderate number of PACAP-like immunoreactive nerve fibres was seen in association with bronchial and vascular smooth muscle and around seromucous glands. PACAP 38 caused a concentration-dependent relaxation of precontracted bronchial and pulmonary arterial segments. The maximal relaxation was more pronounced in the airways than in the arteries, whereas the potency in both was identical. PACAP 38 caused relaxation of all segments tested (nine patients), whereas vasoactive intestinal polypeptide (VIP) failed to cause relaxation of bronchial segments from six of nine patients. Both PACAP and VIP dilated all pulmonary arterial segments tested. In conclusion, pituitary adenylate cyclase-activating peptide 38 is a potent dilator of human bronchi and is present in the human lung. Pituitary adenylate cyclase-activating peptide 38 may, therefore, play a role in the endogenous regulation of airway tone. The inhibitory effects of pituitary adenylate cyclase-activating peptide 38 are more consistent than those of the related neuropeptide vasoactive intestinal polypeptide, perhaps reflecting a difference in susceptibility to degrading enzymes.

Carbon monoxide is endogenously produced in the human nose and paranasal sinuses.

BACKGROUND: Carbon monoxide (CO) has recently emerged as an endogenously produced gaseous mediator that, like nitric oxide (NO), appears to be involved in both upper and lower airway inflammation. In healthy subjects a large part of the exhaled NO seems to originate from the nasal airways, and the paranasal sinuses have been described as a dominating site for NO production. OBJECTIVE: The current study was designed to investigate whether CO could also be produced in the nose and paranasal sinuses. METHODS: The occurrence in the nasal mucosa of the enzyme heme oxygenase, the rate limiting step for CO production, was analyzed with use of immunocytochemistry. CO in exhaled and sampled air was measured with an infrared analyzer. Forty-two healthy subjects and two patients with a tracheostoma volunteered for the study. RESULTS: Heme oxygenase-like immunoreactivity was seen in the respiratory epithelium, in connection with seromucous glands and in the vascular smooth muscle of the nose. When CO was continuously sampled from one nostril during normal breathing through the mouth, stable levels of CO could be measured within 40 seconds in all subjects tested (n = 33). Repeated measurements indicated only minor variations in the values obtained. Sampling through a drainage tube inserted into the maxillary sinus revealed CO levels comparable to the levels obtained by sampling through the nose (n = 6). Breathing through the nose increased the CO levels obtained in the exhaled air (n = 33, P <. 001). CONCLUSION: These results imply that the nose and paranasal sinuses contribute to the CO production of the human airways.

Expression of endothelin A- and B-receptors in human nasal mucosa.

Several studies have suggested an important role for the endothelin (ET) family of peptides in the vascular regulation of the nose. In addition, there is increasing evidence that ETs play a role in allergic airway inflammation. Endothelin is produced locally in the nose and mediates its effects via two distinct receptor subtypes, termed ET(A) and ET(B). Using reverse transcriptase-polymerase chain reaction, mRNAs encoding ET(A)- and ET(B)-receptors were detected in the human lower turbinate and sinus mucosa. The possibility of local release of ETs in connection with specific target receptors suggests a role for endothelin in the regulation of vascular tone, glandular secretion and epithelial functions.