Electroencephalogram and behavioral changes induced by histamine application into the nasal cavity and the effects of some H(1)-receptor antagonists

Intake of a fermented plant product attenuates allergic symptoms without changing systemic immune responses in a mouse model of Japanese cedar pollinosis

Background

Japanese cedar pollinosis (JCP) is one of the most prevalent allergies in Japan. Within the past few decades, many food factors have been demonstrated to suppress symptoms of pollinosis and mast cell degranulation directly or indirectly. Herein, we conducted a study to clarify the anti-allergic potency of a fermented plant product (FPP) in JCP model mice.

Methods

Mice were administered FPP, 10-fold-diluted FPP, or saline every day for 40 days by oral gavage and sensitized with major Japanese cedar pollen allergens (SBP). The numbers of sneezes were counted for 5 minutes after SBP nasal challenge. We analyzed the SBP-specific immunoglobulin titers, serum concentration of mast cell protease 1, and cytokine production from splenocytes stimulated with SBP.

Results

The numbers of sneezes by the mice administered FPP were significantly suppressed compared to those administered saline. The 10-fold-diluted FPP also suppressed the number of sneezes compared to saline, although not significantly. Serum level of mast cell protease 1 tended to be suppressed in FPP-consumed mice compared to those in saline-treated mice. The SBP-specific immunoglobulin titers and cytokine production were comparable among the groups.

Conclusions

Our results suggest that FPP intake could attenuate JCP symptoms without change of systemic immune responses.

Expression and localization of histamine H1, H2, and H3 receptors in rat olfactory epithelium

OBJECTIVE

Histamine is an important chemical mediator in the development of allergic rhinitis and plays a key role in eliciting the nasal symptoms of the disorder. Histamine may also affect smell as a neurotransmitter. However, whether histamine receptors are present in the mammalian olfactory epithelium has not yet been examined. The aim of this study was to investigate the expression and distribution of histamine H₁, H₂, and H₃ receptors in rat olfactory epithelium.

METHODS

Real-time quantitative PCR and immunohistochemical staining were performed to examine the mRNA level and protein expression and localization of histamine receptors (H₁, H₂, and H₃) in rat olfactory epithelium.

RESULTS

We demonstrated that mRNAs encoding histamine H₁, H₂, and H₃ receptors were detected in rat olfactory epithelium. Immunohistochemistry also showed strong positive staining for these receptors. Co-localization of histamine H₁, H₂, and H₃ receptors with olfactory mature protein revealed that these three histamine receptors were mainly localized in olfactory receptor neurons.

CONCLUSIONS

These findings indicate that histamine H₁, H₂, and H₃ receptors are present in rat olfactory epithelium and may play a physiological role in olfactory transmission.

Olfaction in allergic rhinitis: A systematic review

Olfactory dysfunction is a key symptom in patients with allergic rhinitis (AR). Despite the implications for quality of life, relatively few articles have tested olfactory function in their investigations. The current systematic review aimed to investigate the following 2 questions: (1) What does AR do to human olfaction? (2) How effective is the treatment of AR in restoring the sense of smell? A comprehensive literature search was performed, and human studies of any design were included. A total of 420 articles were identified, and 36 articles were considered relevant. Data indicate that the frequency of olfactory dysfunction increases with the duration of the disorder, and most studies report a frequency in the range of 20% to 40%. Although olfactory dysfunction does not appear to be very severe in patients with AR, its presence seems to increase with the severity of the disease. There is very limited evidence that antihistamines improve olfactory function. In addition, there is limited evidence that topical steroids improve the sense of smell, especially in patients with seasonal AR. This is also the case for specific immunotherapy. However, many questions remain unanswered because randomized controlled trials are infrequent and only a few studies rely on quantitative measurement of olfactory function.

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.

Role of substance P in allergic nasal symptoms in rats

The present study was undertaken to investigate the pathological role of substance P in allergic nasal symptoms in rats. The topical application of substance P caused an increase in the incidence of sneezing and nasal rubbing in a dose-dependent fashion, and at a dose of 30 nM/site it showed a significant effect. L-732,138, a tachykinin NK(1) receptor antagonist, at doses of 3 and 10 mg/kg showed a significant inhibition of the nasal signs induced by exogenous substance P in rats. In addition, L-732,138 also showed a significant inhibition of nasal behavior induced by antigen in actively sensitized rats at the same dose. On the other hand, histamine H(1) receptor antagonists, such as cyproheptadine, epinastine and olopatadine had no effect on the nasal behaviors induced by exogenous substance P, even at higher doses, indicating that exogenous substance P does not cause the degranulation of mucosal mast cells in the rat. Moreover, all the histamine H(1) receptor antagonists showed the dose-dependent inhibition of the nasal signs induced by antigen in actively sensitized rats, which revealed that the inhibition of these drugs was exhibited through the antagonistic effect on histamine H(1) receptors. Therefore, from these results, it is reasonable to conclude that substance P released from the nasal mucosa through the activation of tachykinin NK(1) receptors during the antigen antibody reaction plays an important role in allergic nasal symptoms.