Ligustrazine improves blood circulation by suppressing Platelet activation in a rat model of allergic asthma

•Ligustrazine suppressed bronchial hyper-responsiveness to methacholine.•Ligustrazine suppressed lung inflammation in asthmatic rats.•Ligustrazine exhibited potent immuno-modulatory and anti-inflammatory effects.•Ligustrazine improves blood circulation and ameliorated platelet activation.•Ligustrazine is a potent agent for the treatment of allergic asthma.

Chuan-xiong (Ligusticum wallichii) is a traditional herbal medicine in Eastern Asia, but the effect of its active component ligustrazine remains unclear. We explored its effect and possible mechanism in a well-characterized rat model of allergic asthma. Ligustrazine suppressed bronchial hyper-responsiveness to methacholine, and suppressed lung inflammation in asthmatic rats. Ligustrazine exhibited potent immuno-modulatory and anti-inflammatory effects: it suppressed lymphocyte and eosinophil mobilization, and reduced cytokine IL-5 and IL-13 production significantly in lung tissues from asthmatic rats (P < 0.05). Further histological examinations clearly demonstrated that ligustrazine improved blood circulation and ameliorated platelet activation, aggregation and adhesion, which induced sustained infiltration and activation of various inflammatory cells, including lymphocytes and eosinophils, followed by synthesis and release of a variety of pro-inflammatory mediators and cytokines. The present study suggests that ligustrazine is a potent agent for the treatment of allergic asthma due to its strong anti-inflammatory and immuno-modulatory properties.