Occurrence of mast cells in relation to the distribution of nerve fibers in the rat larynx

Antigen challenge induces a supraglottic but not a subglottic edema in the rat larynx

OBJECTIVE: To examine the reaction of mast cells in the larynx of sensitized rats after allergen challenge and determine whether a type I hypersensitivity reaction can elicit a supraglottic and subglottic edema.

STUDY DESIGN: Rats were sensitized with ovalbumin (OA) and challenged 3 weeks later by intravenous injection of either OA or NaCl and perfused with glutaraldehyde. The larynges were removed and processed for light and electron microscopy. Sections from the epiglottis and subglottic region were examined.

RESULTS: In challenged animals, the connective tissue mast cells (CTMC) in the epiglottic submucosa, but not the mucosal mast cells (MMC) in epithelium, were significantly reduced compared with the case of controls, and the connective tissue was edematous. In the subglottic region, the number of both MMC and CTMC was reduced (albeit not significantly), and there was no edema in the lamina propria.

CONCLUSIONS: Allergen challenge induces a marked edema in the epiglottis but not in the subglottic area.

SIGNIFICANCE: The results indicate that the supraglottic and subglottic regions react differently to allergen challenge. (Otolaryngol Head Neck Surg 2005;132:694-700.)

Evidence for primary laryngeal inhalant allergy: a randomized, double-blinded crossover study

BACKGROUND

Despite anecdotal reports, no controlled studies to date link allergen exposure with a change in vocal function or dysphonia. The aim of this study was to determine whether allergen exposure in susceptible individuals impairs vocal function.

METHODS

The study was a prospective, double-blind, placebo-controlled study in which subjects serve as their own controls. The participants were 5 inhalant allergic adults with suspected dysphonia from allergies, without evidence of reactive lower airways based on methacholine challenge. All subjects were exposed to 2 experimental conditions in which they were challenged with (1) orally inhaled diluent placebo on 1 day, and (2) orally inhaled allergen on another day. Conditions were randomly ordered across subjects and separated by at least 48 hours. Phonatory threshold pressure (PTP) at the 80th percentile pitch was measured prior to diluent and allergen challenge, and 15 and 60 minutes postchallenge to assess potential change in vocal function after challenge testing.

RESULTS

A repeated measures ANOVA revealed a significant main effect for treatment (allergen vs placebo, p = 0.013) with greater PTP required post-allergen challenge compared to placebo and an effect size of 0.821.

CONCLUSION

A primary causal relationship between allergen exposure and impaired vocal function, as assessed by PTP, was observed in adults with documented allergy independent of asthma or nasal exposure. The current design establishes a safe model for laryngeal inhalant allergen challenge.

Short- and long-term effects of irradiation on laryngeal mucosa of the rat

Although radiotherapy is often used to treat laryngeal carcinoma, there is little information on the effects of this treatment on laryngeal structures. Rats were irradiated to the head and neck region and the larynges were studied by light- and electron-microscopy and immunohistochemistry. Ten days after irradiation, a change in the ultrastructural appearance of the granules of the subglottic glands was observed. Substance P-, bombesin- and enkephalin-like immunoreactivity was increased in local ganglionic cells and glandular nerve fibres. The mast cells were reduced in number. At examination 4 6 months after irradiation, there were no obvious differences compared with controls concerning mast-cell numbers and neuropeptide expression. The ultrastructural changes seen in the subglottic glands remained to some extent. The results show that structural changes in the subglottic glands occur concomitantly with an increased expression of certain neuropeptides in the innervation of these glands, which implies a relationship between these two parameters. The mast cells respond drastically to irradiation, but in the long run, regeneration of these cells occurs.

Is radiation-induced degranulation of mast cells in salivary glands induced by substance P?

Although DNA is the critical target for the lethal effects of irradiation, the precise mechanisms by which irradiation causes damage in tissues and biological systems is not fully understood. In the present study, the number of mast cells and the expression of the neuropeptide substance P (SP) in salivary glands were examined 10 days after a regimen of irradiation. The irradiation was given as a single dose or 5 consecutive days with daily doses of 7 Gy up to a total dose of 35 Gy. In addition, the number of mast cells and the expression of SP were examined 2 and 24 h after a single dose of 7 Gy. Immunohistochemical staining for 5-hydroxytryptamine (5-HT) and staining with avidin peroxidase and toluidine blue were used to detect mast cells. At examination 2 and 24 h after irradiation treatment, no change in the number of mast cells and the pattern of SP expression was observed. Ten days after irradiation there was a remarkable reduction in the number of mast cells in all the three glands, but there was a marked increase in the number of nerve fibers showing SP-like immunoreactivity in the parenchyme. The results show that early time-dependent alterations in the density of mast cells occur in response to irradiation, and that these changes occur concomitantly with changes in the expression of SP. Since the peripheral nervous system is a main regulator of salivary gland function, it is tempting to speculate that the nervous system interacts with mast cells via SP in modulating irradiation provoked tissue responses in salivary glands.

Contractile responses of proximal and distal trachea segments isolated from rats subjected to immunological stimulation: role of connective tissue mast cells

1. Anaphylaxis-induced contractions of proximal and distal tracheal segments isolated from 14-day ovalbumin (OA)-sensitized rats were studied. 2. OA-induced contractions in distal segments were significantly greater than those observed in proximal segments. 3. Pretreatment of the rats with compound 48/80 or with sodium cromoglycate (SCG) aerosolization significantly reduced OA-induced contractions of trachea distal segments, whereas the contractions of proximal segments were reduced only by compound 48/80. 4. Mepacrine reduced and indomethacin increased the OA-induced contractions in all tracheal segments. Nor-dihydroguaiaretic acid increased the OA-induced contractions in distal tracheal segments, whereas dazoxiben inhibited the contractions in these same segments; neither of these drugs had any effect on the contractions in proximal tracheal segments. 5. The depletion of connective tissue mast cells and subsequent in vitro treatment with indomethacin increased the OA-induced contractions in both segments. 6. We conclude that the contractions of tracheal muscle from OA-sensitized rats depends on the topographic and anatomical origin of the airway tissue. 7. Mediators released by connective tissue mast cells in proximal and distal segments play a pivotal role in this response and may account for variations in the intensity of contraction seen after the addition of OA.

Similar distribution of mast cells and substance P- and calcitonin gene-related peptide-immunoreactive nerve fibers in the adult human larynx

The mechanisms causing supraglottic and subglottic edema in the human larynx are not fully understood. Substance P (SP)- and calcitonin gene-related peptide (CGRP)-containing nerve fibers and mast cells have been suggested to induce inflammation and edema in other parts of the body. In this study of the adult human larynx the distribution of mast cells was studied in relation to SP- and CGRP-containing nerve fibers. Substance P- and CGRP-immunoreactive nerve fibers and numerous mast cells were found in the epiglottis and in the subglottic region of the larynx. Only occasional mast cells and no nerve fibers showing SP- or CGRP-like immunoreactivity were found in the vocal cords. In conclusion, the present study has shown that the distribution of nerve fibers showing SP- and CGRP-like immunoreactivity and mast cells has a similar regional variability. As the highest density of SP- and CGRP-containing nerve fibers and mast cells was present in the regions of the larynx where edema occurs, SP, CGRP, and/or mast cells might be involved in the pathogenesis of edema.

Distribution of immunocompetent cells in various areas in the normal laryngeal mucosa of the rat

The larynx can be divided into a supraglottic, a glottic and a subglottic area, each serving different functions. In many cases of laryngitis the site of infection is located in one area, leaving other areas unaffected. It seems reasonable to speculate that the underlying cause of the heterogeneous infection pattern in the larynx is the different processing of infectious agents. Therefore, the number and distribution of granulocytes, macrophages, dendritic cells, natural killer cells and T and B lymphocytes in the normal laryngeal mucosa of young rats were studied. The results show that, with the exception of granulocytes, all subpopulations were present in different numbers. Many macrophages and dendritic cells but only a few natural killer cells and T and B lymphocytes were located in the mucosa. Dendritic cells, natural killer cells and T and B lymphocytes were rarely present in the vocal fold area, whereas in the subglottic area they were present in high numbers. Thus, differences in the composition of immunocompetent cell populations between laryngeal areas were detectable.

Do nasal mast cells release histamine on stimulation with substance P in allergic rhinitis?

The effects of nasal administration of increasing doses of exogenous substance P have been studied in patients with allergic rhinitis treated with placebo or with the H1 antagonist cetirizine (10 mg twice daily for 3 days). Responses to substance P were assessed by posterior rhinomanometry (measuring nasal airway resistance) and by measure of histamine, protein and albumin production and cell recovery in nasal lavage fluids before and after challenge. Substance P induced a dose-dependent increase in nasal airway resistance which was similar after treatment with either cetirizine or placebo (maximal increase in nasal airway resistance was 4.2-fold greater than the baseline with the placebo and 4.7-fold greater than the baseline with cetirizine). No histamine release was observed. Similar increases in protein and albumin production were observed after stimulation with substance P along with the placebo (protein: from 0.35 +/- 0.11 to 3.31 +/- 0.62 mg and albumin: from 0.09 +/- 0.04 to 2.08 +/- 0.39 mg) and when combined with cetirizine treatment (proteins: from 0.42 +/- 0.09 to 3.62 +/- 0.77 and albumin: from 0.17 +/- 0.04 to 2.19 +/- 0.51 mg). After stimulation with substance P, percentages of neutrophils recovered in nasal fluids increased from 26.2 +/- 11.5 to 54.5 +/- 9.5 with the placebo and from 35.5 +/- 11.0 to 53.6 +/- 9.5 with cetirizine. Eosinophils were inconsistently found after substance P stimulation during both treatments. In conclusion, nasal response to substance P is not modified by cetirizine which suggests that the effect of substance P is not secondary to histamine release in the nose in man.

Nerve endings in the epithelium and submucosa of human epiglottis

An electron-microscopic study of the sensory innervation of human epiglottis was undertaken. The nerve supply of this structure was abundant; numerous free unmyelinated nerve endings of 2.5-3 microns were observed in the stratified epithelium of the epiglottis associated with clear cells containing mitochondria, rough endoplasmic reticulum, microtubules and dense-cored granules. The nerve and cell complex resembled a corpuscular structure, probably of a quimiosensitive character. In the submucosa, unmyelinated nerves were observed which may come from deeper myelinated trunks, and some of them entered the epithelium. Encapsulated corpuscles were also found in the submucosa. Four elements could be distinguished: nerve endings, lamellar cells, interlamellar substance, and capsule. Our observations at an ultrastructural level complete previous observations by means of light microscopy indicating that the epiglottis is a zone with an important innervation in the epithelium as well as in the submucosa. This sensory innervation probably bears a relation to reflexes, such as cough and deglution, to protect the airways.

The in vivo effect of tachykinins on airway mast cells of the rat

The tachykinins substance P (SP) and neurokinin A (NKA) have been demonstrated in sensory airway nerves of animals and man and are thought to be neurotransmitters of local axon reflexes, generated by stimuli such as cigarette smoke, dust, histamine, and bradykinin. We previously showed that intravenous SP and NKA caused bronchoconstriction in anesthetized, mechanically ventilated rats. Pharmacologic studies suggested that this occurred by an indirect mechanism, probably mediated by acetylcholine and serotonin. In this study, we demonstrate that the bronchoconstriction caused by SP and NKA in Fisher 344 rats is accompanied by a dose-dependent release of histamine and serotonin in bronchoalveolar lavage (BAL) fluid. In rats depleted of mast cell mediators by pretreatment with compound 48/80, the effects of SP and NKA on lung resistance and serotonin in BAL fluid were abolished. Local instillation of NKA in the airways caused a significant dose-dependent increase in BAL histamine. After pretreatment with thiorphan, an inhibitor of neutral endopeptidase (NEP), the bronchoconstriction and the histamine and serotonin release in BAL fluid caused by SP and NKA were enhanced. After pretreatment with a combination of thiorphan and the angiotensin-converting enzyme inhibitor captopril, NKA and SP were almost equipotent in causing bronchoconstriction and serotonin release in the airways. This study indicates that mast cells are largely involved in the bronchoconstrictor effect of intravenously administered neurokinins in rats. As in the guinea pig, NEP is involved in the termination of the bronchoconstrictor effect of tachykinins. Moreover, NEP also affects the airway histamine and serotonin release caused by these tachykinins in the Fisher 344 rat.

Distribution of SP- and CGRP-immunoreactivity in the cat's larynx

The distribution of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive (ir) fibres in the cat's larynx was investigated utilizing immunohistochemistry. Many SP- and CGRP-ir fibres with varicosities were found within and below the epithelium and along the basement membrane of the mucosa of all different regions except in the membranous portion of the vocal fold. In the subepithelium, some SP- and CGRP-ir nerve bundles and nerve fibres were recognized around the vessels and glands. In the mucosa, the pattern of distribution and the density of SR-ir fibres were similar to those of CGRP-ir fibres. These reactive fibres were denser in the supraglottic region than in the subglottic region. In the taste bud-like structures, only SP-ir fibres appeared, whereas in the motor endplates, CGRP-reaction was found exclusively. The present findings suggest that the regional distribution of SP- and CGRP-immunoreactivity might be related with sensory and autonomic innervation in the larynx.

Regulatory peptides in the human larynx and recurrent nerves

We studied the peptide-innervation of the human larynx (vocal cord, ventricular folds, epiglottis, subglottic region and the recurrent nerves) using immunocytochemical and radioimmunological methods. In the tissues of the larynx investigated, the following regulatory peptides were detected: vasoactive intestinal polypeptide (VIP), peptide histidine methionine (PHM), helospectin, neuropeptide Y (NPY), C-flanking peptide of NPY (C-PON), calcitonin gene-related peptide (CGRP), substance P and neurokinin. In the recurrent nerves only small numbers of peptide-immunoreactive nerve fibers were found. Most of them showed positive immunoreactivities with antibodies to PHM, NPY and C-PON, but only rare and scattered nerve fibers were positive for VIP-, CGRP- and substance P.