Role of substance P in allergic nasal symptoms in rats

Effects of intranasal maropitant on clinical signs of naturally acquired upper respiratory disease in shelter cats

OBJECTIVES

The aim of this study was to test the hypothesis that intranasally administered maropitant citrate would reduce the severity of clinical signs of feline upper respiratory disease (FURD) in shelter cats with naturally acquired disease.

METHODS

Shelter cats with clinical signs of FURD were randomly assigned to receive either intranasal maropitant diluted in saline (maropitant citrate 10 mg/ml q12h, diluted 1:10 with sterile 0.9% saline) or intranasal 0.9% saline q12h for 7 days. Clinical disease severity was measured at entry into the study and again after completion of 7 days of treatment using a visual analogue scale to assess four separate clinical signs: conjunctivitis, blepharospasm, ocular discharge and nasal discharge. Total disease severity was also calculated. Cats received other medications for FURD as per standard shelter protocols, and all investigators were masked to group assignments. A Mann-Whitney U-test was performed to compare the clinical improvement score (CIS) between the treatment and control groups.

RESULTS

There were 34 cats in the maropitant treatment group; 27 cats served as placebo controls. Groups did not differ in age, sex distribution, nature of disease, administration of other medications for FURD or baseline clinical disease severity. There was no significant difference in CIS between the maropitant treatment and control groups for conjunctivitis, blepharospasm, ocular discharge, nasal discharge or total disease severity after 7 days.

CONCLUSIONS AND RELEVANCE

This study found no significant difference in outcomes for cats with FURD when treated with intranasal maropitant compared with treatment with intranasal saline. Further investigations would be required before intranasal maropitant could be recommended as the standard of care for FURD.

Evaluation of the immunity activity of glycyrrhizin in AR mice

In this study, we evaluated effect of glycyrrhizin on immunity function in allergic rhinitis (AR) mice. The AR mice model were induced by dripping ovalbumin in physiological saline (2 mg mL⁻¹, 10 μL) into the bilateral nasal cavities using a micropipette. After the AR model was induced, mice were randomly divided into six groups: the normal control, model, lycopene 20 mg kg⁻¹ (as positive control drug) group, and glycyrrhizin 10, 20, 30 mg kg⁻¹ groups. After the sensitization day 14, lycopene (20 mg/kg BW) and glycyrrhizin (10, 20 and 30 mg/kg BW) were given orally for 20 days once a day. Mice in the normal control and model groups were given saline orally once a day for 20 days. Results showed that glycyrrhizin treatment could dose-dependently significantly reduce blood immunoglobulin E (IgE), interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-6 (IL-6), nitrous oxide (NO), tumor necrosis factor-alpha (TNF-α) levels and nitrous oxide synthase (NOS) activity and enhance blood immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), interleukin-2 (IL-2) and interleukin-12 (IL-12) levels in AR mice. Furthermore, glycyrrhizin treatment could dose-dependently significantly enhance acetylcholinesterase (AchE) activity and reduce substance P (SP) level in peripheral blood and nasal mucosa of AR mice. We conclude that glycyrrhizin can improve immunity function in AR mice, suggesting a potential drug for the prevention and therapy of AR.

Participation of histamine H3 receptors in experimental allergic rhinitis of mice

The present study was performed to study the participation of histamine H(3) receptors in nasal symptoms using Sch 50971, a potent and selective agonist of the H(3) receptor. Repeated topical application of antigen caused an increase in sneezing and nasal rubbing in sensitized mice. Oral administration of Sch 50971 and imetit, specific H(3)-receptor agonists, resulted in an inhibition of nasal symptoms induced by an antigen similar to an H(1)-receptor antagonist, cetirizine. Furthermore, simultaneous use of H(3)-receptor agonists, Sch 50971 or imetit, and an H(1)-receptor antagonist, cetirizine, caused a significant inhibitory effect on nasal symptoms at doses that showed no effect when used separately. The number of eosinophils in the nasal mucosa of mice sensitized with antigen was significantly decreased by cetirizine; however, Sch 50971 and imetit had no effect on eosinophil infiltration. These results clearly indicate that H(3) receptors are involved in the etiology of nasal allergy, and the stimulation of H(3) receptors may be useful as a novel therapeutic approach in nasal allergy.

Involvement of chemical mediators in nasal allergic responses of HDC-KO mice

The present study was undertaken to investigate the involvement of chemical mediators in nasal allergic responses using histidine decarboxylase knockout (HDC-KO) mice. An allergic rhinitis model was developed in HDC-KO and wild-type mice by the intraperitoneal injection of ovalbumin, aluminum hydroxide gel and pertussis toxin. Five days later, they were boosted by a subcutaneous injection of ovalbumin into the back. From day 18 after the first immunization to day 39, intranasal sensitization with ovalbumin was performed every day and the severity of allergic rhinitis was observed by measuring nasal allergic responses and total IgE levels. It was found that the intranasal administration of antigen caused a significant increase of nasal sneezing and rubbing from day 25 to day 39 both in sensitized HDC-KO and wild-type mice. In addition, a significant elevation of total IgE levels in serum was also found both in sensitized HDC-KO and wild-type mice from day 18 to day 39 after the first immunization. L-733,060, a tachykinin NK(1) receptor antagonist at a dose of 10 mg/kg (s.c.), resulted in the dose-dependent inhibition of nasal allergic responses induced by antigen in both HDC-KO and wild-type mice. In addition, both chlorpheniramine at doses of 3 and 10 mg/kg (p.o.) and BW A868C at doses of 0.3 and 1 mg/kg (i.v.) also showed a dose-related reduction of the nasal allergic responses induced by antigen in sensitized wild-type mice. On the other hand, they had no effects on the nasal signs induced by antigen in HDC-KO mice. From these results, it was revealed that substance P induces nasal allergic responses in the mouse model of chronic allergic rhinitis through the activation of tachykinin NK(1) receptors. Therefore, it can be concluded that not only histamine, but also substance P and prostaglandin D(2), participated in the nasal allergic responses induced by antigen in mice.

Interactive effect of histamine and prostaglandin D2 on nasal allergic symptoms in rats

This study was undertaken to investigate the interactive effect of histamine and prostaglandin D(2) in nasal allergic symptoms in rats. The intranasal application of histamine at doses lower than 10 mumol/site caused no sneezing or nasal rubbing. In addition, prostaglandin D(2) also showed no significant increase in these responses, even at a dose of 10 nmol/site. On the other hand, the simultaneous instillation of histamine and prostaglandin D(2) resulted in a 1000 times more potent effect in inducing nasal symptoms than the administration of histamine alone. Thus, prostaglandin D(2) enhanced the actions of histamine in inducing sneezing and nasal rubbing in a dose-dependent manner, and significant effects were observed at doses higher than 1 nmol/site. The responses induced by the simultaneous application of histamine and prostaglandin D(2) were inhibited by chlorpheniramine, cyproheptadine, BW A868C and ramatroban. Chlorpheniramine and cyproheptadine showed the dose-related inhibition of nasal symptoms induced by the combined administration of histamine (10 nmol) and prostaglandin D(2) (10 nmol), but the effect of cyproheptadine was relatively weak compared with chlorpheniramine. Moreover, BW A868C and ramatroban also showed the inhibition of nasal symptoms induced by the simultaneous administration of histamine and prostaglandin D(2) in a dose-dependent manner. BW A868C was more potent in inhibiting the nasal symptoms than ramatroban. These results clearly indicate that prostaglandin D(2) showed a synergistic effect on sneezing and nasal rubbing induced by histamine in rats, and its effect occurred through both prostaglandin D(2) and CRTH2 (chemoattractant receptor-homologous molecule expressed on TH2 cells) receptors.