Expression And Function Of CFTR In Airway Epithelial Cells Of Acute Exacerbation Of COPD Induced By PM2.5

【Backgroud】Chronic obstructive pulmonary disease(COPD)is a heterogeneous state of the lung,which is mainly due to respiratory tract abnormalities(including bronchial and alveolar abnormalities)resulting in chronic respiratory symptoms including cough,dyspnea,coughing,and eventually irreversible,progressive airflow obstruction.The prevalence and lethality of COPD is increasing year by year,and according to relevant organizations,COPD may rank third among the common fatal diseases in 2030.There are many causes of COPD,such as genetic factors,abnormal lung development,infections,asthma,environmental factors,etc.Among the many causes,several previous studies have shown that smoking is the main factor.With the increasingly serious air pollution,people find that even if they inhale polluted air for a short time,they will have discomfort such as cough,expectoration and dyspnea.And numerous studies have shown an association between increased hospitalization,morbidity,and mortality in COPD,as well as worsening respiratory function and symptoms,and short-term exposure to ambient particulate air pollution,including PM2.5.The cystic fibrosis transmembrane conductance regulator(CFTR)is a member of the ATP-binding cassette family of membrane transport proteins.It is a Cl channel in epithelial cells regulated by phosphorylation and is expressed in many epithelial parietal membranes associated with fluid secretion and uptake.CFTR expression levels and function were found to be significantly reduced in COPD patients,and the severity was strongly correlated with thelevel of CFTR inhibition.When CFTR is dysfunctional it leads to impaired innate host defenses,resulting in increased chronic airway infection and inflammation leading to progressive lung injury and ultimately respiratory failure.Many studies have shown that PM2.5 is the inducement of acute attack of COPD,which can deposit in the lungs,activate immune response,promote the production of various cytokines and chemokines,and induce the secretion of inflammatory cells.However,there is no report about whether the expression and function of CFTR are involved in the acute exacerbation of COPD mice caused by PM2.5 exposure.【Objetctives】To explore the expression changes of cystic fibrosis transmembrane conductance regulator(CFTR)in airway epithelial cells when AECOPD occurs in mice caused by PM2.5exposure.【Methods】(1)Animal experiment: Healthy C57BL/6 mice,male,6-8 weeks old,SPF grade 24,were randomly divided into three groups: tobacco smoke exposure group(CS,n = 8),tobacco smoke exposure group+PM2.5 intervention group(CS+PM2.5,n = 8),and blank control group(CTL,n = 8).A mouse model of acute exacerbation of COPD was established by instilling PM2.5 in airway for 3 days after 90 days of CS exposure.After the modeling,the lung function of mice was detected by BUXCO small animal invasive lung function.The pathological changes of lung tissue were evaluated by HE staining.The levels of inflammatory factors such as interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),KC and mucins Muc5 ac and Muc5 b in BALF of mice were detected by ELISA to evaluate the lung inflammation in mice.Short-circuit current technique was used to measure the CFTR function of airway epithelial tissue.Lung tissue protein was extracted,and the changes of CFTR protein level in lung tissue were detected by Western blot.(2)cell experiment: 16 HBE cells were treated with tobacco smoke extract(CSE)and PM2.5.Cell culture medium was collected and the levels of IL-6 and IL-8 were measured;Western blot was used to detect the changes of CFTR protein level in lung tissue;The effect ofPM2.5 on intracellular chloride concentration([Cl-])was measured.【Result】(1)PM2.5 promoted airway inflammation,mucus hypersecretion,decreased lung function,and downregulation of CFTR expression and function in airway epithelial cells induced by CS exposure in mice(P<0.05).(2)PM2.5 intervention resulted in a further decrease in CFTR expression and a further increase in intracellular [Cl-] levels in CSE-induced 16 HBE cells(P<0.05).【Conclusions】(1)The acute exacerbation model of COPD mice was successfully established by CS exposure combined with PM2.5 airway drip: the lung function of mice decreased obviously,airway inflammation and mucus secretion increased obviously.(2)The expression and function of CFTR decreased in the acute exacerbation model of COPD mice induced by PM2.5.(3)PM2.5 promoted the expression of CFTR induced by CSE and further decreased its function.