Protective effects of Ulmus davidiana var. japonica against OVA-induced murine asthma model via upregulation of heme oxygenase-1.

AIM OF THE STUDY: Traditionally, the stem and root bark of Ulmus davidiana var. japonica (Ulmaceae) are Korean herbal medicines used for anti-inflammatory and anticancer therapy. In this study, we investigated the protective effects of Ulmus davidiana var. japonica ethanolic extract (UD) in a murine asthma model. Furthermore, we determined whether heme oxygenase (HO)-1 is required for the protective activity of UD.

MATERIALS AND METHODS: Airways of ovalbumin (OVA)-sensitized mice exposed to OVA challenge developed eosinophilia, mucus hypersecretion and increased cytokine levels. UD was applied 1h prior to OVA challenge. Mice were administered UD orally at doses of 100 and 200mg/kg once daily on days 18-23. Bronchoalveolar lavage fluid (BALF) was collected 48 h after the final OVA challenge. Levels of interleukin (IL)-4 and IL-5 in BALF were measured using enzyme-linked immunosorbent assays (ELISAs). Lung tissue sections 4 microm in thickness were stained with Mayer's hematoxylin and eosin for assessment of cell infiltration and mucus production with PAS (periodic acid shift reagent) staining, in conjunction with ELISA, immunohistochemistry and Western blot analyses for HO-1 protein expression.

RESULTS AND CONCLUSION: Orally administered UD significantly inhibited the number of OVA-induced inflammatory cells and IgE production, along with reduced T-helper (Th)2 cytokine levels, such as IL-4 and IL-5, in BALF and lung tissue. In addition, UD induced a marked decrease in OVA-induced reactive oxygen species (ROS), inflammatory cell infiltration and mucus production in lung tissue. These effects were correlated with HO-1 mRNA and protein induction. Our results indicate that UD protects against OVA-induced airway inflammation, at least in part, via HO-1 upregulation.