Expression of nitric oxide synthases in nasal mucosa from a mouse model of allergic rhinitis

Overexpression of Inducible Nitric Oxide Synthase in Allergic and Nonallergic Nasal Polyp

Sinonasal polyps are very common benign lesions of the nasal mucosa. Most of nasal polyps (NP) are idiopathic, and the pathophysiology of this disease is still incompletely understood. Nitric oxide (NO) is a reactive molecule generated by nitric oxide synthase (NOS). NO has been identified as an important mediator in airway function and pathogenesis of several respiratory system diseases. Histological and genetical expression of iNOS was detected to evaluate the role of NO in the pathogenesis of allergic (ANP) and nonallergic nasal polyps (NANP). Forty patients with nasal polyps (20 allergic and 20 nonallergic) were identified by history, clinical examination, and investigation. NPs were obtained from the middle turbinate (MT) during concha bullosa surgery. Twenty normal MT nasal tissues were taken as the control from patients undergoing concha bullosa surgery, without any evidence of allergy or inflammation. A nasal polyp specimen from each patient was subjected for immune-histochemical study followed by histological examination to detect the expression of iNOS. RT-PCR was used to evaluate the iNOS gene expression in isolated tissues. The expression of iNOS in both epithelial and stromal layers was greater in NP than in MT tissues. The ANP group showed more iNOS expression than those of the NANP group. The relative mRNA levels of iNOS gene were significantly higher in ANP (2.5-fold) compared to the normal (1.02-fold, P < 0.001) and NANP (1.5-fold, P < 0.01) groups. NP exhibited a significantly high expression of iNOS at both histological and genetical levels. NO might be an essential factor in the life history of NP. Further studies in a larger sample size are required to explain the probable mechanisms of NO in pathogenesis of NP.

Elevated guanylate cyclase and cyclic-guanosine monophosphate-dependent protein kinase levels in nasal mucosae of antigen-challenged rats

OBJECTIVE

In patients with severe allergic rhinitis, the most serious symptom is rhinostenosis, which is considered to be induced by a dilatation of plexus cavernosum. The vascular relaxing responses to chemical mediators are mainly mediated by the production of nitric oxide (NO). However, the exact mechanism(s) in nasal venoresponsiveness of allergic rhinitis is not fully understood. In the present study, we investigated the roles of soluble guanylate cyclase (sGC) and cyclic-guanosine monophosphate (c-GMP)-dependent protein kinase G (PKG) in venodilatation of nasal mucosae of antigen-challenged rats.

METHODS

Actively sensitized rats were repeatedly challenged with aerosolized antigen (2,4-dinitrophenylated Ascaris suum). Twenty-four hours after the final antigen challenge, nasal septum mucosa was exposed surgically and observed directly in vivo under a stereoscopic microscope. The sodium nitroprusside (SNP) and 8-Br-cGMP (a PKG activator) were administered into arterial injection, and the venous diameters of nasal mucosa were observed.

RESULTS

The intra-arterial injections of SNP and 8-Br-cGMP-induced venodilatation were significantly augmented in the nasal mucosae of repeatedly antigen-challenged rats. Furthermore, protein expressions of sGC and PKG were significantly increased in nasal mucosae of the antigen-challenged rats.

CONCLUSION

The present findings suggest the idea that the promoted cGMP/PKG pathway may be involved in the enhanced NO-induced venodilatation in nasal mucosae of antigen-challenged rats.

Expression of nitric oxide synthases in leukocytes in nasal polyps

BACKGROUND

Nitric oxide (NO) has various roles in airway physiology and pathophysiology. Monitoring exhaled NO levels is increasingly common to measure airways inflammation and inhaled NO studied for its therapeutic value in premature infants and adult respiratory distress syndrome. NO is produced by 3 isoforms of NO synthase (NOS1, 2, 3), and each can play distinct and perhaps overlapping roles in the airways. However, the distribution, regulation, and functions of NOS in various cells in the upper airways, particularly in leukocytes, are incompletely understood.

OBJECTIVE

To characterize the expression of NOS isoforms in leukocytes in normal middle turbinate tissues (MT) and in inflammatory nasal tissue (nasal polyps, NP).

METHODS

Normal MT tissue was collected from surgical specimens that were to be discarded. The NP samples were from surgical tissue archives of 15 patients with chronic rhinosinusitis. Isoforms of NOS in cells were identified by double immunostaining using NOS isoform-specific and leukocyte-specific (mast cell, eosinophil, macrophage, neutrophil, or T cell) antibodies.

RESULTS

The proportion of total cells below the epithelium that were positive for each isoform of NOS was higher in NP than in MT. Each isoform of NOS was found in all leukocyte populations studied, and there were significant differences in the percentage of leukocytes expressing NOS isoforms between MT and NP.

CONCLUSION

All isoforms of NOS are expressed in leukocytes in MT and NP, and their expression varies among leukocyte types. Our data provide a basis to investigate the regulation, cell distribution, and distinct functions of NOS isoforms in normal and inflamed nasal tissues.

Augmented venous responsiveness to leukotriene D(4) in nasal septal mucosae of repeatedly antigen-challenged rats

One possible mechanism of the nasal obstruction observed in allergic rhinitis is thought to be a dilatation of veins in nasal mucosa, although the exact mechanism(s) is not fully understood. An involvement of cysteinyl leukotrienes (CysLTs) in the nasal obstruction has also been suggested. In addition to the specific antigen-induced nasal symptoms, nasal hyperresponsiveness to non-specific stimuli is one of the characteristic features of patients with allergic rhinitis. Augmentation of LTD(4)-induced venodilatation (a part of nasal hyperresponsiveness) of nasal mucosae in antigen-challenged rats was investigated. The LTD(4)-induced venodilatation was significantly increased in antigen-challenged rats, although venodilatation by application of LTD(4) was not induced in nasal mucosae of control rats. The LTD(4)-induced venodilatation was significantly inhibited by pretreatment with L-NMMA [an inhibitor of nitrix oxide synthase (NOS)]. Although mRNA of CysLT1 receptor of nasal mucosa was within control level, the LTD(4)-induced production of NOx in nasal cavity was augmented in repeatedly antigen challenge rats. In addition, the level of iNOS mRNA was also significantly augmented in nasal mucosae of repeatedly antigen-challenged rats. Interestingly, sodium nitroprusside (SNP; an NO donor)-induced venodilatation itself was significantly augmented in nasal mucosae of repeatedly antigen challenge rats. In conclusion, we here suggest that the sensitivity of venodilatation to LTD(4) was augmented in nasal mucosae of challenged rats. Therein, not only increased NO production but also enhanced NO responsiveness might be involved in the development of nasal hyperresponsiveness in allergic rhinitis.

Involvements of cysteinyl leukotrienes and nitric oxide in antigen-induced venodilatation of nasal mucosa in sensitized rats in vivo

To determine an in vivo venodilatation of nasal mucosa, which is thought to be one of the causes of nasal obstruction in allergic rhinitis, venous diameters of nasal septa were directly measured in anesthetized rats. An application of antigen to nasal mucosa of sensitized rats caused an increase in diameters of mucosal veins, that is, venodilatation: the maximal response (about 20% increase in diameters) was observed at 55 min after antigen challenge. The antigen-induced increase in venous diameter of nasal mucosa was significantly inhibited by pretreatment with a cysteinyl leukotrienes (CysLTs) receptor antagonist, SR2640, and a nitric oxide (NO) synthase inhibitor, N(G)-monomethyl-L-arginine, indicating that CysLTs and NO might be involved in the venodilatation of nasal mucosa induced by antigen challenge. Blocking the action of CysLTs and NO might be therefore useful for the therapy of nasal obstruction in allergic rhinitis.

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.

Effects of 1400W, a potent selective inducible NOS inhibitor, on histamine- and leukotriene D4-induced relaxation of isolated guinea pig nasal mucosa

To clarify the role of inducible nitric oxide synthase (iNOS) in the relaxation of nasal vasculature, the effects of a potent selective iNOS inhibitor, N-[(3-aminomethyl)benzyl]acetamidine (1400W), on histamine- and leukotriene D4 (LTD4)-induced relaxations of isolated nasal septal mucosae were examined in naive guinea pigs. In addition to eNOS and nNOS, Western blots demonstrated a distinct expression of iNOS in nasal mucosal tissues of naive guinea pigs. In isolated nasal septal mucosae precontracted with norepinephrine (3 x 10(-5)M), both histamine (10(-7)-10(-3)M) and LTD4 (10(-10)-10(-7)M) exhibited relaxations, which were inhibited by a NOS inhibitor NG-monomethyl-L-arginine (L-NMMA; 10(-4)M). The inhibitory effect of L-NMMA was reversed by L-arginine (10(-3)M), indicating that the relaxations induced by histamine and LTD4 are mediated by NO. Furthermore, both the histamine- and LTD4-induced relaxations were also significantly attenuated by 1400W (10(-5)M). These findings suggest an involvement of NO generated by iNOS in agonist-induced relaxation of nasal mucosal vasculature in naive guinea pigs.

Nasal Obstruction as a Common Side-Effect of Sildenafil Citrate

Sildenafil citrate is an effective oral drug for erectile dysfunction. The main action of sildenafil is the enhancement of the effect of nitric oxide (NO) by inhibiting the cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase-5 (PDE-5), an enzyme responsible for degradation of cGMP. NO is also present in the nasal mucosa and is responsible for vasodilation causing congestion and nasal obstruction. The aim of this study was to detect the effect of sildenafil on nasal mucosa in terms of nasal obstruction. A total of 16 patients presented to urology clinic suffering from impotence and medicated with sildenafil were included in the study. Before and after oral administration of 50 mg sildenafil, in all of the patients the nasal patency was examined by active anterior rhinomanometry (a method of assessing nasal resistance) using air pressure of 150 Pascal. In addition, all patients were asked about their sensation of nasal patency to detect the symptomatic nasal obstruction. There was a significant decrease in nasal air flow values (cm(3)/s) (p < 0.05). Except for three cases, all patients indicated that they had the sensation of nasal obstruction after the use of sildenafil (p < 0.05). Nasal obstruction is a common complaint for the patients using Sildenafil.

Second-hand smoke increases nitric oxide and alters the IgE response in a murine model of allergic aspergillosis

This study was performed to determine the effects of environmental tobacco smoke (ETS) on nitric oxide (NO) and immunoglobulin (Ig) production in a murine model of allergic bronchopulmonary aspergillosis (ABPA). Adult BALB/c mice were exposed to aged and diluted sidestream cigarette smoke from day 0 through day 43 to simulate “second-hand smoke”. During exposure, mice were sensitized to soluble Aspergillus fumigatus (Af) antigen intranasally between day 14 and 24. All Af sensitized mice in ambient air (Af + AIR) made elevated levels of IgE, IgG1, IgM, IgG2a and IgA. Af sensitized mice housed in ETS (Af + ETS) made similar levels of immunoglobulins except for IgE that was significantly reduced in the serum and bronchoalveolar lavage (BAL). However, immunohistochemical evaluation of the lung revealed a marked accumulation of IgE positive cells in the lung parenchyma of these Af + ETS mice. LPS stimulation of BAL cells revealed elevated levels of NO in the Af + AIR group, which was further enhanced in the Af+ETS group. In vitro restimulation of the BAL cells on day 45 showed a TH0 response with elevated levels of IL3, 4, 5, 10 and IFN-γ. However, by day 28 the response shifted such that TH2 cytokines increased while IFN-γ decreased. The Af + ETS group showed markedly reduced levels in all cytokines tested, including the inflammatory cytokine IL6, when compared to the Af+AIR group. These results demonstrate that ETS affects ABPA by further enhancing the NO production and reduces the TH2 and the inflammatory cytokines while altering the pattern of IgE responses.

Mediators of inflammation in the early and the late phase of allergic rhinitis

PURPOSE OF REVIEW

This review provides the reader with an overview of the early and the late phase of the immediate allergic reaction. Furthermore, recent publications are presented that could reveal important new insights into the mechanisms of allergic inflammation.

RECENT FINDINGS

Recent work on the possible roles of nerve growth factor, nitric oxide synthases, several CC chemokines and other mediators is presented.

SUMMARY

Allergic rhinitis is characterized by the clinical symptoms of sneezing, itching, rhinorrhea, and nasal congestion. Frequently, these are accompanied by eye, ear and throat symptoms or postnasal drip. The symptoms arise as a result of inflammation induced by IgE-mediated immune response to a specific allergen. Inflammatory mediators are released and cells are activated and recruited to the mucosa. In this review, early and late phase responses of the allergic type I reaction are described, including the different cell types and mediators involved. Special attention is paid to new inflammatory processes to provide the reader with recent information.

Endothelial nitric oxide synthase/soluble guanylate cyclase system in human nasal polyps

The aim of our study was to analyze the level of expression of the endothelial nitric oxide synthase (eNOS)/soluble guanylate cyclase (sGC) system in nasal polyps and control nasal mucosae. The study was performed in polyps from 15 patients and nasal mucosae from 11 subjects operated on the nasal septum (control group). The expression of endothelial nitric oxide synthase (eNOS) and soluble guanylate cyclase (sGC) was determined in nasal mucosae. Western blot analysis demonstrated that eNOS protein was overexpressed in the nasal polyps with respect to control nasal mucosae. Immunohistochemistry also demonstrated that the vascular endothelium of nasal polyps contained higher amounts of eNOS protein than control nasal mucosae. Moreover, the beta(1) subunit of sGC was also overexpressed in the nasal polyps, which was associated with an increased content of cyclic GMP in the nasal polyps with respect to nasal control mucosae. In human nasal polyposis, there is an overexpression of the eNOS/sGC system. Further studies are needed to assess whether this overexpression is involved in the genesis of nasal polyposis.