Effects of Multiple Dexamethasone Treatments on Aggravation of Allergic Conjunctivitis Associated with Mast Cell Hyperplasia

Abstract

Patients with allergic conjunctivitis are repeatedly exposed to allergen, leading to a chronic stage of the disease. Therefore, to elucidate mechanisms underlying the pathogenesis of this disease, we must use an experimental model in which allergic conjunctivitis develops after multiple challenges with allergen. We have developed a guinea pig model in which sensitized animals are repeatedly challenged by dropping a Japanese cedar pollen suspension onto the eye.1,2) Consequently, we found that multiple challenges aggravate the disease in proportion to the number of challenges.1,2) In addition, multiple antigen challenges increase the number of mast cells in conjunctival tissue.3) In agreement with our previous findings, 3) it has been well demonstrated that aggravation of allergic conjunctivitis is accompanied by an increased number of mast cells in human conjunctival tissue. 4,5) Although the types of mast cells that are increased in our guinea pig model have yet to be elucidated, it has been reported that among tryptase-positive, chymase-positive mast cells and tryptase-positive, chymase-negative mast cells, the predominant type increased in the conjunctival tissue of vernal conjunctivitis patients is tryptase-positive, chymase-positive mast cells. 6)On the other hand, we attempted to evaluate the effect of the anti-histaminic drug mepyramine on allergic conjunctivitis induced after the respective 1st-15th challenges in the sensitized guinea pig. Similar to other models, 7-9) we observed that mepyramine significantly suppressed responses at the 1st-5th challenges. However, allergic responses at the 7th-15th challenges were not suppressed by the compound.2) Thus, we regarded conjunctivitis responses at the 1st to approximately the 5th challenges as the acute stage, and responses at the 7th and subsequent challenges as the chronic stage. In addition, we have found that symptoms at the chronic stage were resistant to a single treatment with various pharmacologically active substances such as cysteinyl leukotriene antagonists, thromboxane A 2 antagonists, kinin antagonists, and a cyclooxygenase inhibitor. 2)In the present study, in order to determine how allergic conjunctivitis at the chronic stage can be pharmacologically controlled, we evaluated the effects of single and multiple treatments with dexamethasone on allergic responses at the acute and chronic stages. In addition, because the aggravation of allergic conjunctivitis coincides with the production of serum antigen-specific IgE 1) and the infiltration of mast cells into the conjunctival, 3) we evaluated the effects of multiple dexamethasone treatments on the levels of IgE and mast cells to assess the relationship between the aggravation of symptoms and the IgE-mast cell response. MATERIALS AND METHODSAnimals Male, 4-week-old, Hartley guinea pigs (Japan SLC, Hamamatsu, Japan) were used. This animal study was approved by the Experimental Animal Research Committee at Kyoto Pharmaceutical University.Antigen and Adjuvant Japanese cedar pollen (Cryptomeria japon...

Stimulus-Selective Regulation of Human Mast Cell Gene Expression, Degranulation and Leukotriene Production by Fluticasone and Salmeterol

“…However, mast cells respond differently to glucocorticoids when they are stimulated via receptors other than FcεRI such as G protein-coupled receptors (tachykinin receptors and complement receptors). Prednisolone inhibits SP-activated mouse peritoneal mast cell release of histamine [13] and dexamethasone inhibits mast cell hyperplasia and histamine release [44]. Although a study by Thangam et al showed that C3a-induced mast cell degranulation was not affected by dexamethasone (10 nM), human mast cells were incubated with the glucocorticoid for only 1 hr [45].…”

Effect of glucocorticoids on aquaporin-1 in guinea pigs with otitis media with effusion

“…Furthermore, we identified that dexa treatment affects AQP1 in a guinea pig model of OME. We administered dexa at a dose of 5 mg/kg since the guinea pig is relatively resistant to glucocorticoids compared with other species, including rats and mice (18). Immunoblotting revealed that dexa treatment increases the expression of AQP1 in the OME-affected ME.…”

Effect of Ganoderma lucidum on Pollen‐induced Biphasic Nasal Blockage in a Guinea Pig Model of Allergic Rhinitis

“…As previously described (Nabe et al , ; Nagata et al , ), Cry j 1‐specific IgE antibody was determined by an enzyme‐linked immunosorbent assay (ELISA) kit (Guinea pig IgE ELISA MARUPI; Dainippon Pharmaceutical Co., Osaka) using blood samples collected 3 days after the ninth inhalation challenge. Because this kit is for the measurement of guinea pig total IgE, we modified the method provided by the manufacturer to measure Cry j 1‐specific IgE.…”