Participation in cysteinyl leukotrienes and thromboxane A2 in nasal congestion model in Brown Norway rats

Potential synergistic effects of novel hematopoietic prostaglandin D synthase inhibitor TAS-205 and different types of anti-allergic medicine on nasal obstruction in a Guinea pig model of experimental allergic rhinitis

Nasal obstruction is one of the most bothersome symptoms of allergic rhinitis (AR) affecting sleep-related quality of life in AR patients. Although several treatments were tested to control nasal obstruction, some patients with moderate to severe AR do not respond to current treatments, including the combined administration of different types of anti-allergic medicine. Thus, new options for AR treatment are needed. This study aimed to evaluate the effects of combined treatment with a novel inhibitor of hematopoietic prostaglandin D synthase (HPGDS), TAS-205, and different types of anti-allergic medicine on nasal obstruction in AR. Firstly, we demonstrated that TAS-205 selectively inhibited prostaglandin D₂ (PGD₂) synthesis in an enzymatic assay in a cell-based assay and in vivo models of AR. Moreover, treatment with TAS-205 alone suppressed eosinophil infiltration into the nasal cavity and late phase nasal obstruction. The combined administration of TAS-205 with montelukast, a cysteinyl leukotriene receptor 1 antagonist, showed significant additive inhibitory effects on eosinophil infiltration and late phase nasal obstruction compared to treatment with each agent alone. In contrast, concomitant treatment with TAS-205 and fexofenadine, a histamine H₁ blocker, showed inhibitory effects on late phase and early phase nasal obstruction, although the magnitude of the inhibitory effects upon combined administration was comparable to that of each single treatment. These results suggest that combined treatment with an HPGDS inhibitor and different types of anti-allergic medicine may be a promising strategy to control nasal obstruction in AR patients.

Prophylactic effects of the histamine H1 receptor antagonist epinastine and the dual thromboxane A2 receptor and chemoattractant receptor-homologous molecule expressed on Th2 cells antagonist ramatroban on allergic rhinitis model in mice

The prophylactic use of anti-allergic drugs has been proposed to be effective in the treatment of seasonal allergic rhinitis in humans. However, there is little information regarding the prophylactic effect of thromboxane A(2) (TXA(2)) receptor antagonist on allergic rhinitis. Recent studies revealed that a TXA(2) receptor antagonist ramatroban could block the prostaglandin D(2) (PGD(2)) receptor and chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). In the present study, we investigated the prophylactic effects of the histamine H(1) receptor antagonist epinastine and the TXA(2) receptor antagonist ramatroban and seratrodast on mouse models of allergic rhinitis. Female BALB/c mice were sensitized by an intraperitoneal injection of ovalbumin and alum on days 0, 5, 14 and 21. Seven days later, mice were sensitized by intranasal application of ovalbumin thrice a week. Drugs were administered once a day from day 22. The severity of allergic rhinitis was assessed by determining the extent of 2 nasal allergic symptoms (sneezing and nasal rubbing). Histamine sensitivity and eosinophil infiltration into the nasal mucosa were also determined. Epinastine and ramatroban significantly reduced nasal symptoms and the number of eosinophils in the nasal mucosa. Seratrodast showed no effect on nasal symptoms and eosinophil infiltration into the nasal mucosa. In addition, histamine sensitivity was reduced by epinastine and ramatroban. These results indicate that epinastine and ramatroban induce the prophylactic effect on allergic rhinitis.

Participation of prostaglandin E2 receptor in nasal congestion of Brown Norway rats

The aim of the present study was to clarify the involvement of prostaglandin E(2) (PGE(2)) in nasal congestion in Brown Norway (BN) rats. For this purpose, we studied the effects of PGE(2) receptor (EP(1), EP(2), EP(3) and EP(4)) agonists on nasal congestion and sneezing induced by toluene 2,4-diisocyanate (TDI). Enhanced pause (Penh) was increased 1 h (early phase) and 4 h (late phase) after TDI challenge. Sulprostone (an EP(3) receptor agonist) inhibited the increase of Penh, an index of nasal congestion, in both early and late phase responses. On the other hand, PGE(1) alcohol (an EP(4) agonist) increased Penh in the early phase response. Moreover, sulprostone inhibited sneezing, an immediate response by TDI challenge. These results indicate that EP(3) receptor is responsible for the relief of nasal congestion in both early and late phase responses, and EP(4) receptor is correlated with the development of nasal congestion in the early phase response. In addition, EP(3) receptor also participates in sneezing in allergic rhinitis induced by TDI challenge in BN rats.

Pathophysiology of nasal congestion

Nasal congestion is a common symptom in rhinitis (both allergic and nonallergic), rhinosinusitis and nasal polyposis. Congestion can also be caused by physical obstruction of nasal passages and/or modulation of sensory perception. Mucosal inflammation underlies many of the specific and interrelated factors that contribute to nasal congestion, as well as other symptoms of both allergic rhinitis and rhinosinusitis. A wide range of biologically active agents (eg, histamine, tumor necrosis factor-α, interleukins, cell adhesion molecules) and cell types contribute to inflammation, which can manifest as venous engorgement, increased nasal secretions and tissue swelling/edema, ultimately leading to impaired airflow and the sensation of nasal congestion. Inflammation-induced changes in the properties of sensory afferents (eg, expression of peptides and receptors) that innervate the nose can also contribute to altered sensory perception, which may result in a subjective feeling of congestion. Increased understanding of the mechanisms underlying inflammation can facilitate improved treatment selection and the development of new therapies for congestion.