Comparison of norepinephrine responsiveness of mucosal veins in vivo with that of isolated mucosal tissue in vitro in guinea pig nasal mucosa

Increased expression of bitter taste receptors in human allergic nasal mucosa and their contribution to the shrinkage of human nasal mucosa

OBJECTIVE

Bitter taste receptors (TAS2Rs) are expressed in the extraoral tissues, where they possess various physiological functions. This study is to characterize TAS2Rs expression in normal and allergic nasal mucosa and analyse nasal symptom after challenge with bitter tastes to evaluate their pathophysiological function in normal and allergic nasal mucosa.

METHODS

The expression levels of TAS2Rs (TAS2R4, 5, 7, 10, 14, 39, and 43) in nasal mucosa were investigated by real-time PCR, Western blot, and immunohistochemistry. The expression levels of TAS2Rs and Ca(2+) imaging in cultured epithelial cells were measured after stimulation with type 2 cytokines (IL-4, IL-5, and IL-13) or bitter tastes. Nasal symptoms in control subjects and allergic rhinitis patients using visual analogue score and acoustic rhinometry were evaluated before and after stimulation with bitter tastes. Vascular diameter of rat nasal septum was measured before and after treatment with bitter tastes.

RESULTS

TAS2Rs tested here were expressed in nasal mucosa where they were commonly distributed in superficial epithelium, submucosal glands, and endothelium. Their expression levels are increased in allergic nasal mucosa and up-regulated in cultured epithelial cells simulated with type 2 cytokines. After treatment with bitter tastes, intracellular Ca(2+) signalling was increased in cultured epithelial cells, and vascular constriction was found in rat nasal septum. Increased nasal patency was observed in human nasal mucosa without pain or sneezing.

CONCLUSION AND CLINICAL RELEVANCE

TAS2Rs are constitutively expressed in human nasal mucosa and their expression levels are increased in allergic nasal mucosa, where they could potentially contribute to shrinkage of normal and allergic nasal mucosa.

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.

Scientific rationale for the use of alpha-adrenergic agonists and glucocorticoids in the therapy of pediatric stridor

Purpose. The most common pharmacological therapies used in the treatment of stridor in children are glucocorticosteroids (GC) and alpha-adrenergic (αAR) agonists. Despite the long-standing reported efficacy of these medications, there is a paucity of data relating to their actual mechanisms of action in the upper airway. Summary. There is compelling scientific evidence supporting the use of αAR-agonists and GCs in pediatric stridor. αAR signaling and GCs regulate the vasomotor tone in the upper airway mucosa. The latter translates into better airflow dynamics, as delineated by human and nonhuman upper airway physiological models. In turn, clinical trials have demonstrated that GCs and the nonselective αAR agonist, epinephrine, improve respiratory distress scores and reduce the need for further medical care in children with stridor. Future research is needed to investigate the role of selective αAR agonists and the potential synergism of GCs and αAR-signaling in the treatment of upper airway obstruction and stridor.

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.

Regional differences in vascular responsiveness of nasal mucosae isolated from naive guinea pigs

OBJECTIVE

In the present study, the contractile response to norepinephrine (NE) and relaxing response to histamine and leukotriene D(4) (LTD(4)) were compared among the nasal mucosae of septa (S) and lateral (L) and medial turbinates (M) isolated from naive male Hartley guinea pigs.

METHODS

The isometrical tension of the isolated nasal mucosae of the above regions was measured at a resting tension of 0.5 g by using a standard organ-bath technique.

RESULTS

In each mucosal strip, NE induced a contraction in a concentration-dependent manner. A significant difference in efficacy (maximal response) of NE was found (L>M>S). In mucosal strips precontracted with NE (3x10(-5)M), both histamine and LTD(4) induced relaxing responses. The efficacy of histamine in S was significantly greater than those in L and M. The potency order of LTD(4) was L>M>S; a significant difference was observed between L and S.

CONCLUSION

In conclusion, the present study demonstrated a distinct regional difference in the response to contractile and relaxant agonists of isolated nasal mucosae of guinea pigs.