Differential activity of nitric oxide synthase in human nasal mucosa and polyps

The nasal decongestants oxymetazoline and xylometazoline are frequently used in the topical treatment of rhinitis and sinusitis. As nitric oxide (NO) is thought to play a role in inflammation of the upper respiratory tract, the aim of this study was to examine the in vitro effects of these compounds on the activity and the expression of NO producing enzymes, including the inducible form of NO synthase (iNOS) and the constitutive isoform of NO synthase (cNOS).Experiments concerning the effects of both compounds on enzymatic activity and enzyme induction of iNOS were performed in a lipopolysaccharide (LPS) induced rat alveolar macrophage cell line (NR8383) using the Griess assay and the 3 H-citrulline assay respectively. The effects on cNOS were examined in fresh rat synaptosomes using the 3 H-citrulline assay. The direct scavenging properties of both compounds were investigated using a amperometric NO sensor.Oxymetazoline and xylometazoline were shown to have a dose dependent inhibitory effect on total iNOS activity indicated by nitrite/nitrate formation in the Griess assay. This effect was found to be due to an inhibition of induction of the enzyme rather than inhibition of the enzyme activity, as was investigated in two separate experiments using the 3 H-citrulline assay. Inhibition of cNOS was moderate and in the same order of magnitude as the inhibition of enzymatic iNOS activity. Direct scavenging of NO could not be detected.As constitutive nitric oxide synthase activity is thought to serve beneficial physiological functions, and exaggerated inducible nitric oxide synthase activity may cause exacerbation of the inflammatory process, pharmacological treatment influencing the nitric oxide generating system should focus on inhibition of inducible nitric oxide synthase alone. The specific characteristics of these decongestants in vitro suggests suitability for this application and may indicate an additional beneficial effect in the treatment of upper respiratory tract inflammation. Eur Respir J 2000; 16: 437±444.

Section: Discussionmentioning

confidence: 99%

“…It has also been shown that considerable levels of NO metabolites are present in nasal lavage fluid of patients with house dust mite allergy [12] and that nasal polyps contain higher levels of NOS than normal nasal mucosa [13]. In addition, the exact localization of NOS in nasal mucosa has been identified [14,15].…”

mentioning

confidence: 99%

Inhibition of nitric oxide synthase by nasal decongestants

Westerveld¹,

Voss²,

Hee³

et al. 2000

“…Firstly, the normal, noninflamed nasal mucosa can itself express NOS [18] . Secondly, it has recently been shown that the epithelium of the polyps, which originate from the sinus, express the inducible type III NOS [19]. Consequently, the polyps can also generate NO and may themselves contribute to NO production.…”

Section: Discussionmentioning

confidence: 99%

Nasal nitric oxide concentration in paranasal sinus inflammatory diseases

Arnal¹,

Flores²,

Rami³

et al. 1999

125

100

In normal upper airways, nitric oxide is generated by the paranasal sinus epithelium and then diffuses into the nasal cavities. This study examined whether or not nasal NO concentration is affected by paranasal sinus inflammatory diseases.The influence of obstruction (nasal polyposis) and/or inflammation (allergy or chronic sinusitis) of the paranasal sinuses on nasal NO concentration was evaluated in nasal allergic (n=7 patients) or nonallergic (n=20) polyposis, nonallergic chronic sinusitis (n=10) and Kartagener's syndrome (n=6) and compared with control subjects (n=42). A score of alteration of the paranasal sinus (number of altered and occluded sinuses) was determined by a computed tomography scan.The nasal NO concentration in nasal nonallergic polyposis (15020 parts per billion (ppb)) was significantly decreased compared with both controls (2236 ppb, p=0.01) and polyposis with allergy (27228 ppb, p<0.0001). In each group, the nasal NO concentration was inversely correlated with the extent of tomodensitometric alteration of the paranasal sinuses. In Kartagener's syndrome, the nasal NO concentration (142 ppb) was drastically decreased compared with all other groups, despite the presence of open paranasal sinuses.Thus, the nasal NO concentration in patients with nasal polyposis appeared to be dependent on both the allergic status and the degree of obstruction of the paranasal sinuses. Eur Respir J 1999; 13: 307±312. The discovery that mammalian cells generate nitric oxide, a free radical gas previously considered merely as an atmospheric pollutant, is providing important information about many biological processes. NO is generated from arginine by a family of enzymes, the NO synthases (NOS), and acts as an autocrine and paracrine messenger [1,2]. NO also plays a major role in nonspecific host defence as a result of its antiviral and antibacterial properties. Type II NOS, initially characterized in the rodent macrophage, has been shown to be expressed only after induction by pro-inflammatory cytokines or bacterial lipopolysaccharide [1]. This isoform can be expressed by most cells involved in inflammation and is also called inducible NOS [3].Recently, LUNDBERG and coworkers [4±6] have clearly shown that most of the NO in the exhaled air of healthy subjects originates from the upper respiratory tract, with only a minor contribution from the lower airways. A type II NOS, mainly expressed in the epithelium of the paranasal sinuses, would account for most of this NO production [6]. Thus, NO could play a critical role in the physiology and pathology of the upper respiratory tract because, in addition to its role in immunity and host defence [3], NO stimulates ciliary motility [7]. Interestingly, LUNDBERG et al. [8] showed that patients with Kartagener's syndrome (referred to as an immobile cilia syndrome and characterized by situs inversus, sinusitis and bronchiectasis) had very low nasal NO concentrations. The present authors [9] and others [10] have recently shown that the nasal NO concentration in patie...

“…For the NF-kB deoxyribonucleic acid (DNA)-binding activity assay, pieces of tissue were immediately frozen in liquid nitrogen and stored at -808C. For the immunohistochemical techniques, the tissues were cut into several pieces of~5-mm thick and fixed in periodate-lysine-paraformaldehyde, frozen in Tissue-Tek1 ornithine carbamoyltransferase (OCT) medium (Miles Laboratories, Elkhart, IN, USA) and processed as previously described [13]. For epithelial cell culture, intact tissues were placed in Dulbecco's modified Eagle's medium (DMEM)/Ham's F12 medium 1:1 (Life Technologies, Merelbeke, Belgium) and immediately transported on ice to the laboratory for processing.…”

Section: Tissue Processingmentioning

confidence: 99%

“…Increasing evidence, based upon higher than normal levels of nitric oxide in the exhaled air of asthmatic patients [10,11] and prominent immunostaining for iNOS in asthmatic airway epithelium [12], suggests that the iNOS isoform may play a role in acute and chronic inflammatory airway diseases. In the upper airways, increased iNOS activity [13] and expression [14] have been shown in chronically inflamed nasal polyp tissues. Despite the reported iNOS upregulation under inflammatory conditions, exciting new findings have demonstrated that iNOS is continuously expressed in normal airway epithelium [15], implying a homeostatic role for this isoform not previously considered.…”

mentioning

confidence: 99%

Constitutive nuclear factor-kappaB activity in human upper airway tissues and nasal epithelial cells

Ramis

Bioque

Lorente³

et al. 2000

Self Cite

Respiratory epithelial cells are actively involved in the host defence and inflammatory reactions of the airways. Nuclear factor‐κB (NF‐κB) is a transcription factor that plays a pivotal role in many cellular responses to environmental changes. The inducible nitric oxide synthase (iNOS) isoform has been implicated in airway inflammation as well as in normal airway function. In this study, the hypothesis that NF‐κB may be associated with iNOS expression in airway epithelium, not only in inflammatory processes but also under physiological conditions was examined. NF‐κB deoxyribonucleic acid‐binding activity was assayed by means of electrophoretic mobility shift assay (EMSA) and iNOS expression examined using immunohistochemical techniques in healthy nasal mucosa and chronically inflamed nasal polyps. Further NF‐κB activity was assayed; by means of EMSA, in nasal epithelial cells isolated from both tissues. NF‐κB was activated in nasal polyps, but also to the same extent in healthy nasal mucosa. Uniform iNOS expression was localized within the airway epithelium in both inflamed and noninflamed tissues. Along with iNOS expression, concomitant NF‐κB activation was found in nasal epithelial cells obtained from both tissues and no differences were observed when nasal mucosa and nasal polyp were compared. These results suggest that constitutive nuclear factor‐κB and concurrent inducible nitric oxide synthase expression in epithelial cells may play a physiological role in airway function.