Reduced allergic lung inflammation by root extracts from two species of Peucedanum through inhibition of Th2 cell activation

Ethnopharmacological evidence: Peucedani Radix (PR), the root of Peucedanum praeruptorum Dunn (PPD) or Peucedanum decursivum (Miq.) Maxim. (PDM), has long been used in Korea to eliminate sputum, relieve cough, and reduce bronchus contraction. Furthermore, these therapeutic strategies are recognized as general and effective methods in western medicine as well as traditional Korean medicine. Aim of the study: To determine and compare the anti-inflammatory effects of PPD extracts (PPDE) and PDM extracts (PDME) on allergic lung inflammation, using in vivo OVA-induced airway inflammation in mice and in vitro primary cell culture systems. Materials and methods: Eight-week-old female C57BL/6 mice were placed into four groups (n=4 per group): saline control, OVA-induced allergic lung inflammation with vehicle, or PPDE (200 mg/kg) or PDME (200 mg/kg) treatment. PR extracts (PRE) were administered from 1 week before 1st OVA sensitization to the day before sacrifice. Mice were sacrificed 18 h after last OVA intra-nasal challenge followed by histological and biochemical analyses. Results: Inflammatory phenotypes were alleviated with oral administration of PRE. PRE treatment decreased mucus production in airway epithelium, inflammatory cell number, eosinophilia, type 2 cytokines, and histamine in bronchoalveolar lavage fluid (BALF). Mice with PRE administration showed diminished activated CD4 T cell (CD4(+)CD25(+) cell) and GATA-3 level in the lung. In addition, PRE treatment reduced Th2 cell activation in vitro, using Th2 polarization system. Conclusion: Our findings indicate that the anti-inflammatory effects of PRE arise from reduced Th2 cell activation and validate the clinical use of PR in traditional Korean medicine.