Relaxant Action Of Vandetanib And Ethyl Acetate Extracts From Rhizoma Imperate On Mouse Airway Smooth Muscle

The number of asthma patients worldwide is increasing year by year.Abnormal contraction of airway smooth muscle is one of the significant pathological features of asthma.At present,asthma cannot be cured.Western medicine treatment is the main clinical treatment method for asthma.There are some drugs used currently for the treatment of asthma,their long-term use will cause the body to develop drug resistance and reduce the therapeutic effect of the drug.Some patients with asthma cannot be well controlled with conventional treatment drugs.Therefore,developing new drugs is of great significance for the treatment of asthma.It was reported that molecular targeted drugs or traditional Chinese medicines have good therapeutic effects on asthma.After pre-experimental screening,we found that Vandetanib and Rhizoma imperatae extracts could relax the contracted airway smooth muscle individually.Vandetanib is a VEGFR2 inhibitor and a drug for the treatment of advanced medullary thyroid cancer.VEGF is an influencing factor closely related to airway remodeling.It needs to specifically bind to VEGFR to exert its biological effects.Rhizoma imperatae is a common Chinese medicine.Its ingredients had anti-tumor,anti-inflammatory,immunomodulatory and other pharmacological effects.It has been used in the treatment of malignant tumors and allergic dermatitis,etc.However,whether Vandetanib or Rhizoma imperatae has any effect on asthma therapy remains unknown.So,we selected the molecular target drug-Vandetanib and the traditional Chinese medicine-Rhizoma imperatae as the research objects to explore the mechanism of relaxing airway smooth muscle and their effect on asthma individually.This study aims to provide ideas and basis for the development of new drugs for asthma therapy.The first part of this study was to explore the relaxing mechanism of Vandetanib on abnormally contracted airway smooth muscle.At the tissue level,the effect of Vandetanib on mouse tracheal ring tension was detected through a tension transduction experiment.At the cellular level,a patch clamp experiment was performed to record the ion channel currents of the acutely isolated airway smooth muscle cells to reflect the effect of Vandetanib on ion channels.The results showed that Vandetanib reduced intracellular calcium ion concentration by influencing the opening of ion channels,such as VDLCC,NSCC,BK channel,and NCX,etc,thereby relaxing airway smooth muscle.At in vivo level,asthmatic mice were constructed firstly and then a series of experiments,such as airway hyperresponsiveness detection,histological observation,pathological section observation,isolated mouse tracheal rings tension detection and RT-PCR experiment were performed.These experimental results showed that Vandetanib could reduce the increasing respiratory resistance（Rrs）in asthmatic mice,reduce the tension of isolated tracheal rings in asthmatic mice,alleviate airway inflammation in asthmatic mice and reduce the expression levels of inflammatory factors such as,IL-4 and TNF.The second part of this study is to explore the relaxing mechanism of ethyl acetate extracts from Rhizoma imperate（EAERI）on the abnormally contracted airway smooth muscle.The following experiments:tension transduction experiments,the path clamp experiments to record ion channel currents,and mouse hyperresponsiveness detection were conducted.These experimental results demonstrated that EAERI inhibited VDLCC and NSCC to decrease intracellular Ca²⁺levels,thereby relaxing the pre-contracted airway smooth muscle.In addition,at in vivo level,we found that EAERI could reduce the increasing respiratory resistance（Rrs）value of mouse induced by ACh.In summary,both Vandetanib and EAERI could relax the pre-contracted mouse tracheal rings.They both reduced intracellular calcium ion concentration by affecting ion channels,such as VDLCC and NSCC,thereby relaxing airway smooth muscle.They both reduced mouse respiratory resistance（Rrs）and alleviated some symptoms related to asthma in mice.These results suggested that they both have the potential to be used in the treatment of asthma,but the underlying mechanism needs to be further explored.This study provides research ideas and data support for the development of new drugs for asthma therapy.