Relaxant Effect of Sodium Tanshinone IIA Sulphonate on Mouse Tracheal Smooth Muscle

Sodium tanshinone IIA sulphonate, a water-soluble derivative of tanshinone IIA, has been proven to possess versatile biological properties, but its pharmacological effect on tracheal smooth muscle remains elusive. This paper presents a study on the relaxant effect and underlying mechanisms of sodium tanshinone IIA sulphonate on mouse tracheal smooth muscle. The relaxant effect of sodium tanshinone IIA sulphonate was evaluated in mouse tracheal rings using a mechanical recording system. Intracellular Ca²⁺ concentration was measured in primary cultured tracheal smooth muscle cells using confocal imaging system. The results showed that sodium tanshinone IIA sulphonate induced dose-dependent relaxation of mouse tracheal rings in a β-adrenoceptor- and epithelium-independent manner. Pretreatment with the ATP-sensitive K⁺ channel blocker glibenclamide partly attenuated the relaxation response. Administration of sodium tanshinone IIA sulphonate notably inhibited the extracellular Ca²⁺-induced contraction. High KCl or carbachol-evoked elevation in the intracellular Ca²⁺ concentration was also abrogated by sodium tanshinone IIA sulphonate in tracheal smooth muscle cells. In conclusion, the tracheal relaxant effect of sodium tanshinone IIA sulphonate was independent of β-adrenoceptor and airway epithelium, mediated primarily by inhibition of extracellular Ca²⁺ influx via L-type voltage-dependent Ca²⁺ channels and partially by activation of the ATP-sensitive K⁺ channel. These results indicate the potential therapeutic value of sodium tanshinone IIA sulphonate for asthma treatment.