The Role of Cannabinoid-1 Receptor Ligands in the Ovalbumin-Induced Mouse Model of Allergic Asthma: Is It Related to Transient Receptor Potential Vanilloid-1 Channels?

Objectives: The aim of this study was to investigate the role of cannabinoid (CB1) receptors on airway inflammation and hypersensitivity in allergic asthma and the potential interactions with TRPV1 channels. Materials and Methods: BALB/c mice were sensitized and provoked with ovalbumin to create a model of allergic asthma. CB1 selective agonist arachidonoyl 2'-chloroethylamide (ACEA) was administered intraperitoneally at doses of 0.5, 3, and 5 mg/kg. Receptor antagonism studies were performed utilizing selective CB1 antagonists AM251 at a dose of 3 mg/kg. TRPV1 channel was selectively blocked by capsazepine at a dose of 2.5 mg/kg. Penh values were recorded in vivo by a whole-body plethysmograph under methacholine challenge. Inflammatory cell count was performed in bronchoalveolar lavage fluid (BALF). Serum levels of proinflammatory cytokines were measured by Enzyme-Linked ImmunoSorbent Assay (ELISA). Inflammation in the lung tissue was scored histopathologically. Statistical significance was determined using one-way analysis of variance or Kruskal-Wallis test and expressed as p<0.05. Results: In sensitized animals, provocation with inhaled ovalbumin increased Penh values, serum interleukin (IL)-4, IL-5, IL-13 levels, eosinophil, neutrophil, lymphocyte, macrophage counts in BALF, and inflammation in the lung tissue. ACEA applications did not significantly alter Penh values, BALF inflammatory cell levels, and histological changes related to inflammation in the lung tissue according to the disease group; however, only at a dose of 5 mg/kg, it reduced the levels of the inflammatory cytokine IL-4. AM251 decreased Penh values, eosinophil and neutrophil migration in BALF, and inflammation score of lung tissue compared with the disease group. Although BALF inflammatory cell levels and Penh values were higher in the AM251+ACEA group than in the AM251 group, the differences were insignificant. In the CPZ+ACEA group, Penh values were significantly higher, and serum IL-4 and IL-13 levels and BALF eosinophil counts were lower than that in the CPZ group. Conclusions: This study demonstrated an important role of the CB1 receptors in allergic asthma. CB1 antagonism reduced airway hyperresponsiveness and inflammation and showed immunomodulatory effects. The effect of the CB1 agonist ACEA on asthma does not appear to be related to TRPV1 channels.

Fenofibrate Attenuates Asthma Features in an Ovalbumin-induced Mouse Model Via Suppressing NF-κB Binding Activity

BACKGROUND/AIM

Asthma is a chronic inflammatory disease of the airways with a high prevalence. Asthma has a complex pathophysiology and about 5-10% of patients are not fully responsive to the currently available treatments. The aim of this study is to investigate the involvement of NF-κB in the effects of fenofibrate on a mouse model of allergic asthma.

MATERIALS AND METHODS

A total of 49 BALB/c mice were randomly distributed into 7 groups (n=7). Allergic asthma model was created by administering i.p. injections of ovalbumin on days 0, 14 and 21, followed by provocation with inhaled ovalbumin on days 28, 29 and 30. Fenofibrate was orally given in 3 different doses; 1, 10 and 30mg/kg through days 21 to 30 of the experiment. On day 31, pulmonary function test using whole body plethysmography was performed. The mice were sacrificed 24hours later. Blood samples were obtained, and serum of each sample was separated for IgE determination. Bronchoalveolar lavage fluid (BALF) and lung tissues were collected to measure IL-5 and IL-13 levels. Nuclear extracts of lung tissues were employed to assess nuclear factor kappa B (NF-κB) p65 binding activity.

RESULTS

Enhanced Pause (Penh) values were significantly increased in ovalbumin-sensitized and challenged mice (p<0.01). Administration of fenofibrate (10 and 30mg/kg) resulted in improved pulmonary function as shown by significantly lower Penh values (p<0.01). Interleukin (IL) -5 and IL-13 levels in BALF and lung tissues and immunoglobulin E (IgE) levels in serum were significantly elevated in the allergic mice. IL-5 levels in the lung tissues of mice treated with 1mg/kg fenofibrate (FEN1) group were significantly reduced (p<0.01). BALF and lung tissue IL-5 and IL-13 levels in mice treated with 10 and 30mg/kg fenofibrate, FEN10 and FEN30, respectively, were significantly diminished when compared to the ovalbumin-treated (OVA) group, whereas treatment with 1mg/kg fenofibrate resulted in insignificant changes. IgE levels in the serum of FEN30 group mice have shown a prominent reduction (p<0.01). NF-κB p65 binding activity was higher in mice sensitized and challenged with ovalbumin (p<0.01). NF-κB p65 binding activity was significantly reduced in allergic mice treated with 30mg/kg (p<0.01) fenofibrate.

CONCLUSIONS

In this study, we showed that administration of 10 and 30mg/kg fenofibrate effectively attenuated airway hyperresponsiveness and inflammation in a mouse model of allergic asthma, possibly through inhibition of NF-κB binding activity.