Hyperresponsiveness in the human nasal airway: new targets for the treatment of allergic airway disease

Allergic rhinitis in children

Allergic rhinitis affects up to 40% of children but is commonly undiagnosed. Careful assessment of nasal symptoms allows for the most appropriate therapeutic options to be chosen. Allergen avoidance is often difficult in practice. Antihistamines are of limited benefit in allergic rhinitis caused by house dust mite and other perennial allergens, where symptoms, predominantly nasal obstruction, are not histamine mediated. In contrast, symptoms triggered by pollen, such as nasal itch, rhinorrhoea and sneezing, are relieved by antihistamines. Intranasal steroids are the treatment of choice for persistent moderate-severe allergic rhinitis and are more effective than antihistamines for relief of nasal obstruction. Failure to respond to intranasal medications is often caused by poor compliance or inefficient use of nasal sprays. Immunotherapy may be a useful, if expensive, option, particularly where symptoms are because of a specific pollen. The benefits of immunotherapy in house dust mite-induced rhinitis and asthma remain controversial.

Lentiviral-mediated interleukin-4 and interleukin-13 RNA interference decrease airway inflammation and hyperresponsiveness

Interleukin (IL)-4 and IL-13 are two key cytokines released from activated T helper type 2 (Th2) cells and strongly associated with asthma and allergic disease. We applied silencing of the IL-4 and IL-13 gene expression by RNA interference delivered by a lentiviral vector to evaluate the therapeutic role of IL-4 and IL13 short hairpin RNAs (shRNAs) in a murine model of asthma. Mice were sensitized with ovalbumin (OVA), and one treatment of IL-4 and IL-13 shRNA lentiviral vector (Lenti-si-IL-4 and Lenti-si-IL-13) was instilled intratracheally 48 hr before challenge. After three challenges of OVA antigen, mice were assessed for airway inflammation and hyperresponsiveness. With infection of Lenti-si-IL-4 and Lenti-si-IL-13 in EL-4 cells, both RNA and protein expressions of IL-4 and IL-13 were obviously abrogated. Furthermore, intratracheal instillation of Lenti-si-IL-4 and Lenti-si-IL-13 in OVA-immunized mice resulted in a strong inhibition of local IL-4 and IL-13 cytokine release. Treatment with Lenti-si-IL-4 and Lenti-si-IL-13 successfully alleviated OVA-induced airway eosinophilia and Th2 cell cytokine release. Finally, to determine airway hyperresponsiveness by enhanced pause and pulmonary resistance in noninvasive and invasive body plethysmography, we found that administration of Lenti-si-IL-4 and Lenti-si-IL-13 markedly decreased airway hyperresponsiveness in OVA-immunized mice. These results suggest that inhibition of IL-4 and IL-13 gene expression by shRNA lentiviral vector markedly inhibits antigen-induced airway inflammation and hyperresponsiveness in mice.

Allergic and idiopathic rhinitis: an ultrastructural study

Nasal hyperreactivity is one of the most important underlying mechanisms in both allergic (AR) and idiopathic rhinitis (IR). In order to study the pathomorphological changes in this entity, tissue samples from patients with AR, IR, and from patients without chronic inflammation were taken during nasal surgery. Primary antibodies against Substance P (SP), calcitonin gene-related peptide (CGRP), and endothelial nitric oxide synthases (NOS III) were applied and the immunocomplexes were visualized by immunocytochemistry. The nasal mucosa of patients with AR and IR showed similarities on the ultrastructural level. Neurogenic inflammation was indicated by a strong innervation pattern with sensory nerve fibers containing SP and CGRP. We could show that extensive edema and cellular infiltration might be characteristic for AR. On other hand there was no evidence of eosinophilic or NO involvement in IR. Finally, on the ultrastructural level, AR and IR showed many similarities. Based on these findings anti-inflammatory therapy modalities could be recommended for both types of rhinitis.

[Ultrastructural changes in allergic rhinitis vs. idiopathic rhinitis]

BACKGROUND

Nasal hyperreactivity is one of the most important underlying mechanisms in allergic rhinitis (AR) as well as idiopathic rhinitis (IR). The aim of the present study was to examine pathomorphological changes in nasal mucosa in these subgroups of rhinitis.

PATIENTS AND METHODS

Tissue samples of human inferior turbinates from 20 patients with AR and 16 patients with IR were taken during nasal surgery and preserved in glutaraldehyde or paraformaldehyde. Ultrathin sections of specimens from 15 patients without chronic inflammation of nasal mucosa were used as controls. Primary antibodies against substance P (SP), calcitonin-gene-related peptide (CGRP), and endothelial nitric oxide synthase (NOS III) were applied, and the immunocomplexes were visualized by an immunocytochemical staining technique using gold-labeled antibodies. Immunostained structures were photodocumented using light and transmission electron microscopy.

RESULTS

The nasal mucosa of patients with AR and IR showed similarities on the ultrastructural level. A strong innervation pattern with sensory nerve fibers containing SP and CGRP demonstrated neurogenic inflammation. Extensive edema and cellular infiltrations were found in AR. A decreased presence of eosinophils and nitric oxide was observed in IR.

CONCLUSIONS

On the ultrastructural level, AR and IR showed many similarities but also some differences. Based on these findings, anti-inflammatory therapy could be recommended for both types of rhinitis.

Pharmacological characterization of the novel histamine H3-receptor antagonist N-(3,5-dichlorophenyl)-N'-[[4-(1H-imidazol-4-ylmethyl)phenyl]-methyl]-urea (SCH 79687)

We present the pharmacological and pharmacokinetic profiles of a novel histamine H3 receptor antagonist, N-(3,5-dichlorophenyl)-N'-[[4-(1H-imidazol-4-ylmethyl)phenyl]-methyl]-urea (SCH 79687). The H3-receptor binding Ki values for SCH 79687 were 1.9 and 13 nM in the rat and guinea pig (GP), respectively. The Ki values for SCH 79687 at histamine H1 and H2 receptors were greater than 1 microM. SCH 79687 showed a 41- and 82-fold binding selectivity for the H3 receptor over alpha 2A-adrenoceptors and imidazoline I2, and >500-fold H3 selectivity compared with over 60 additional receptors. The pA2 value for SCH 79687 in the GP ileum electrical field-stimulated (EFS) contraction was 9.6 +/- 0.3. Similar H3 antagonist activity was observed in the EFS cryopreserved and fresh tissue isolated human saphenous vein (HSV) assays (pKb = 9.4 +/- 0.3 and 10.1 +/- 0.4). SCH 79687 (30 nM) did not block clonidine-induced inhibition of EFS-induced contractions in HSV. SCH 79687 (ED50 = 0.3 mg/kg i.v.) attenuated (R)-alpha-methylhistamine inhibition of sympathetic hypertensive responses in the GP. At the time of activity evaluation, the GP plasma SCH 79687 concentration was 25 ng/ml at the dose of 0.3 mg/kg i.v. In feline nasal studies, combined administration of SCH 79687 (3 mg/kg i.v.) and the H1-antagonist loratadine (3 mg/kg i.v.), at individual doses that do not produce decongestion, inhibited the compound 48/80-induced congestion by 47%. The alpha-adrenergic agonist phenylpropanolamine (PPA; 1 mg/kg i.v.) also attenuated compound 48/80 nasal responses by 42%. Unlike the H3/H1 combination that did not affect blood pressure (BP), PPA (1 mg/kg i.v.) significantly increased BP compared with control animals by a maximum of 31 mm Hg. Orally, SCH 79687 (10 mg/kg) plus loratadine (10 mg/kg) also produced decongestion without effects on BP. In pharmacokinetic studies, oral dosing with SCH 79687 in the rat (10 mg/kg) and monkey (3 mg/kg) achieved plasma Cmax and area under the curve values greater than 1.5 and 12.1 microg. h/ml, respectively. SCH 79687 is an orally active H3 antagonist with a good pharmacokinetic profile that, in combination with an H1 antagonist, demonstrates decongestant efficacy comparable with oral sympathomimetic decongestants but without hypertensive liabilities.