Mechanism Of Ethanol Extract From Sedum Sarmentosum Bunge In Relaxing Airway Smooth Muscle Of Mice

Airway hyperresponsiveness?AHR?was one of the main pathological features of asthma and chronic obstructive pulmonary disease.The specific mechanism of AHR was complicated.At present,this type of disease relied only on hormonal drugs to alleviate the airway hyperresponsiveness caused by the above diseases.However,these hormonal drugs counld only alleviate the occurrence of airway hyperresponsiveness,and not be targeted against specific pathogenic factors,and easily lead to serious drug resistance and side effects.Therefore,it was necessary to develop new drugs to treat respiratory diseases such as asthma.In recent years,traditional Chinese medicine has been widely used in the treatment of diseases because of its mild action,natural ingredients and low toxicity.A large number of studies had shown that the ethanol extract of Sedum sarmentosum Bunge?ESSB?had anti-inflammatory,ani-oxidative and anti-cell-proliferation activities,but its effect on airway smooth muscle contraction had not been reported.By adding ESSB to observe the changes of mouse airway smooth muscle tension and the effect on Ca²⁺,and long-opening voltage-dependent calcium channels?LVDCCs?,non-selective cation channels?NSCCs?and calcium-activated large-conductance potassium channels(BK_Ca),the physiological mechanisms of ESSB on relaxedation activity to ASM were further clarified.The main results were as follow:1.The result confirmed that 3.98mg/mL ESSB could block L-type voltage-dependent calcium channel?LVDCCs?current and inhibited the expression of LVDCC-related genes to relax pre-contracted airway smooth muscle,and did not show significant toxic effects on tissues.Among them,the high-potassium and acetylcholine-induced airway pre-contraction,the relaxation of ESSB was dose-dependent,and the relaxation effect of high potassium was more significant?p<0.01?;at the same time,3.98 mg/mL ESSB could block the airway smooth muscle Intracellular Ca²⁺influx led to high potassium-induced airway pre-contraction.In terms of the effect on LVDCCs,the results showed that 3.98mg/mL ESSB significantly blocked the current of LVDCCs?p<0.001?;and the expression of LVDCC-related gene showed that3.98mg/mL ESSB significantly affected Cacna1c in airway smooth muscle tissue?p<0.01?.2.Further studies had shown that the relaxation of ESSB on pre-contracted airway smooth muscle was not due to the role of non-selective cation channels?NSCCs?.Among them,3.98mg/mL ESSB had no obvious blocking effect on transient receptor channel 3?TRPC3?,and it could not block NSCCs current.3.The result of this study also indicate that in exogenously stimulated?acetylcholine?activated calcium-activated K-channel(K_Ca),by addition to 10 mM TEA inhibited K_Ca opening,which led to further contraction of the airway;3.98 mg/mL ESSB was open to acetylcholine-induced K_Ca.4.For the effect of calcium-activated large conductance K channel(BK_Ca)on ESSB in airway smooth muscle,3.98 mg/mL ESSB counld significantly induce BK_Ca channel opening and relaxed the Paxiline-induced airway contraction;further Experiments showed that 3.98mg/mL ESSB significantly increased BK_Ca current and up-regulated BK?1 expression?p<0.01?.In summary,the paper demonstrated that ESSB had the effect of relaxing airway smooth muscle.The specific mechanism was to relax the LVDCCs and open calcium channels such as BK_Ca,and had little relationship with NSCCs.The above results wounld lay a solid theoretical foundation for the application of traditional Chinese medicine of Sedum sarmentosum Bunge in the treatment and prevention of respiratory diseases such as asthma,and also provide some reference for the development of monomeric compounds targeting LVDCCs and BK_Ca channels.