The role of nitric oxide in the neural control of nasal fluid production

Comparison of Antileukotrienes and Antihistamines in the Treatment of Allergic Rhinitis

Background

The aim of this study was to compare the effect of antileukotriene (anti-LT), antihistamine, and a combination of anti-LT and antihistamine on the symptoms and nasal resistance in allergic rhinitis patients.

Methods

We performed a placebo-controlled study, with 120 persistent, moderate to severe allergic rhinitis patients randomly selected to receive the different treatments for 4 weeks: no treatment, 10 mg of cetirizine once per day, 20 mg of zafirlukast once per day, 20 mg of zafirlukast twice per day, a combination of 20 mg of zafirlukast and 10 mg of cetirizine once per day, or a combination of 20 mg of zafirlukast twice per day and 10 mg cetirizine once per day. The nasal secretion nitric oxide (NO) concentration, nasal symptom score, and nasal resistance were measured before and after treatment.

Results

Total symptom scores improved in each treated group compared with the control group (p < 0.05). Nasal obstruction significantly improved in the anti-LT-treated groups (p < 0.05). High-dose anti-LT or the combination of low-dose anti-LT and antihistamine significantly improved allergy symptoms compared with no treatment, low-dose anti-LT, or antihistamine alone (p < 0.05). Furthermore, anti-LT decreased NO concentration in nasal secretions (p < 0.05), regardless of the dose administered.

Conclusion

These results suggest that high-dose anti-LT alone or the combination of low-dose anti-LY and antihistamine can effectively treat allergic rhinitis.

Effect of histamine on Ca(2+)-dependent signaling pathways in rat conjunctival goblet cells

PURPOSE

The purpose of this study was to determine the Ca(2+)-dependent cellular signaling pathways used by histamine to stimulate conjunctival goblet cell secretion.

METHODS

Cultured rat goblet cells were grown in RPMI 1640. Goblet cell secretion of high molecular weight glycoconjugates was measured by an enzyme-linked lectin assay. Intracellular [Ca(2+)] ([Ca(2+)](i)) was measured by loading cultured cells with the Ca(2+) sensitive dye fura-2. The level of [Ca(2+)](i) was measured using fluorescence microscopy. Extracellular regulated kinase (ERK) 2 was depleted using small interfering RNA (siRNA).

RESULTS

Histamine-stimulated conjunctival goblet cell secretion of high molecular weight glycoproteins was blocked by removal of extracellular Ca(2+) and depletion of ERK2 by siRNA. Histamine increase in [Ca(2+)](i) was desensitized by repeated addition of agonist and blocked by a phospholipase C antagonist. Histamine at higher doses increased [Ca(2+)](i) by stimulating influx of extracellular Ca(2+), but at a lower dose released Ca(2+) from intracellular stores. Activation of each histamine receptor subtype (H(1)-H(4)) increased [Ca(2+)](i) and histamine stimulation was blocked by antagonists of each receptor subtype. The H(2) receptor subtype increase in [Ca(2+)](i) was cAMP dependent.

CONCLUSIONS

We conclude that histamine activates phospholipase C to release intracellular Ca(2+) that induces the influx of extracellular Ca(2+) and activates ERK1/2 to stimulate conjunctival goblet cell mucous secretion, and that activation of all four histamine receptor subtypes can increase [Ca(2+)](i).

Increased expression of inducible nitric oxide synthase in nasal mucosae of guinea pigs with induced allergic rhinitis

BACKGROUND

Nitric oxide (NO) is produced by the action of NO synthase (NOS) isoforms and is considered an important mediator of inflammatory response including airways. In this study, the changes in the expression levels of NOS isoforms in nasal mucosae were determined in a guinea pig model of allergic rhinitis.

METHODS

An allergic rhinitis model was prepared in guinea pigs by repeated challenge with aerosolized dinitrophenylated ovalbumin antigen. Twenty-four hours after the last antigen challenge, the expression levels of NOS isoforms in nasal mucosae were determined by immunoblottings. Changes in the isometrical tension of isolated mucosal tissues of nasal septa induced by histamine were measured also.

RESULTS

Although the expression levels of endothelial NOS (eNOS) and neuronal NOS (nNOS) in nasal mucosae were not affected by the repeated antigen exposure, the inducible NOS (iNOS) level was markedly and significantly increased in the challenged animals. In isolated nasal mucosal tissues, histamine induced a concentration-dependent relaxation, which was sensitive to an H1-receptor antagonist, mepyramine, and an NOS inhibitor, L-NMMA. No significant change in the histamine responsiveness was observed between the sensitized control and repeatedly antigen-challenged groups.

CONCLUSION

The expression of three isoforms of NOS, including eNOS, nNOS, and iNOS, was presented in guinea pig nasal mucosa. A marked increase in iNOS expression in the repeatedly antigen-challenged animals suggests an important role of iNOS in the pathogenesis of allergic rhinitis. However, the pathophysiological role(s) of NO generated by iNOS in nasal allergy is still unclear.

Vasoactive intestinal peptide stimulates mucus secretion, but nitric oxide has no effect on mucus secretion in the ferret trachea

Vasoactive intestinal peptide (VIP) and nitric oxide (NO) are neurotransmitters involved in the regulation of bronchial and pulmonary vascular tone. Published studies of the effects of VIP on airway mucus secretion have yielded conflicting results. The purpose of this study was to determine the effect of VIP on mucus secretion in the ferret trachea and if this effect was influenced by NO. We used a sandwich enzyme-linked lectin assay to measure mucin secretion and a turbidimetric assay to measure lysozyme (serous cell) secretion from ferret tracheal segments. VIP (10−7 M) increased mucin secretion over 2 h. VIP (10−9 to 10−5 M) stimulated mucin secretion in a dose-dependent fashion. VIP-induced mucin secretion was partially blocked by a VIP receptor antagonist (a chimeric VIP-pituitary adenylate cyclase-activating peptide analog, VIP receptor antagonist) at a 10-fold excess concentration. At all concentrations tested, neither NG-nitro-l-arginine methyl ester, an inhibitor of NO synthase, nor S-nitroso- N-acetyl-penicillamine, an NO donor, had any significant effect on constitutive or VIP-induced mucus secretion. We conclude that VIP-stimulated mucin and lysozyme secretion was both time dependent and dose dependent and that NO neither stimulates nor inhibits mucus secretion in the ferret trachea.

Involvement of nitric oxide in pollen-induced biphasic nasal blockage in sensitised guinea pigs

We have developed a reproducible allergic rhinitis model showing biphasic nasal blockage on repetitive inhalation challenge with Japanese cedar pollen in sensitised guinea pigs. The role of nitric oxide (NO) in inducing nasal blockage was evaluated with this model. N(omega)-nitro-L-arginine methyl ester (L-NAME), a non-selective NO synthase (NOS) inhibitor, intravenously administered before the challenge, significantly inhibited both early and late nasal blockage by approximately 80% and 50%, respectively. When L-NAME treatment was performed after the challenge, the late response was inhibited by approximately 70%. This inhibition was completely reversed by co-administration of L-arginine. However, aminoguanidine and L-N(6)-(1-iminoethyl)lysine, selective inhibitors of inducible NOS, negligibly influenced the degree of nasal blockage. Meanwhile, the alpha-adrenergic agonist, naphazoline, strongly suppressed both early and late nasal blockage. These results indicate that NO, likely produced by constitutive rather than inducible NOS, plays a major role in the occurrence of biphasic nasal blockage, primarily by inducing vasodilatation.

Ultracytochemical localization of the NADPH-d activity in the human nasal respiratory mucosa in vasomotor rhinitis

OBJECTIVES

Description of the ultrastructural localization of nitric oxide synthase in the blood vessels of the nasal respiratory mucosa in patients with vasomotor rhinitis.

STUDY DESIGN

This research was conducted on seven patients--men and women, ages 20 to 45 years--suffering from vasomotor rhinitis and who had undergone surgical therapy for reduction of the inferior turbinates.

METHODS

To study the ultrastructural localization of nitric oxide synthase, NADPH-diaphorase cytochemistry was employed. Samples of the nasal mucosa were obtained from inferior turbinates.

RESULTS

The endothelial cells of the arterioles, capillaries, venules and cavernous sinuses revealed a distribution of the enzymatic activity similar to that found in unaffected subjects. A strong enzymatic activity was recognized in the smooth muscle cells of the cavernous sinuses. The smooth muscle cells of arterioles and venules were generally found to be negative to enzymatic reaction.

CONCLUSIONS

This study suggests that the vascular disorders of the vasomotor rhinitis depend, at least in part, from nitric oxide synthase induction in the smooth muscle cells of the cavernous sinuses.