The anti-inflammatory extract from leaves of Isatis tinctoria (Ze 550) inhibits dose dependently the allergen induced airway-response in sensitized mice

The extract Ze 550 obtained by means of supercritical CO2 extraction has been shown in in-vitro experiments to inhibit cyxlo-oxygenase 2, 5-lipoxygenase, NO production and to stabilise mast cells (extraction yield 0.8%). Moreover, in in-vivo models the anti-inflammatory and anti-allergic action of Ze 550 was confirmed. Since allergic diseases are accompanied by chronic inflammation the question arose whether or not the extract will also be useful in allergic asthma. A murine model of allergen-induced airways inflammation is well elaborated (6,7) with an increase in IL-4 and IL-5 in the bronchoalveolar lavage fluid (BAL), eosinophil recruitment into the lung tissue indicating that the allergic inflammation is driven by the activation of the T helper (Th) type 2 cells. Therefore the influence of Ze 550 in this model of allergic asthma was investigated. Balb/c mice were immunised subcutaneously twice at weekly intervals with 0.4ml saline containing 1µg ovalbumine (OVA) and 1.6mg alums. Intranasal challenge was repeatedly performed (3 consecutive days) under light i.v. ketamine anaesthesia by applying 50µl OVA in alum-free saline solution (10µl) or saline as control. Ze 550 was given at 10µg, 30µg and 100µg intra-nasally (in 40µl) just before the antigen challenge. The airway resistance was evaluated by whole-body plethysmography. Bronchial hyper-reactivity to aerosolized methacholine (100 mM, 1min) was investigated 24h after the last OVA challenge using whole body plethysmography. Ze 550 inhibited the methacholine induced airway hyper-responsiveness (AHR) in a dose dependent manner(10, 30 and 100µg). AL was performed by cannulating the trachea and washing 4 times with 0.5ml each of ice-cold PBS 24h after the last antigen challenge. Ze 550 again inhibited dose dependently and significantly eosinophil recruitment into BAL. Corresponding with the reduced eosinophil recruitment the EPO activity in lung tissue was also decreased. Moreover, mucus hyper-production was dose dependently inhibited by Ze 550 (10, 30, and 100µg). In BAL IL-4, IL-5 and RANTES were significantly reduced (30µg). Conclusion: Topic administration of Ze 550 into the airway prior to antigen challenge in sensitized mice reduced hyper-reactivity and Th2 cytokines IL-4 and IL-5.