Effect Of Air Pollutants On Hospitalization Of COPD And The Role And Mechanism Of Ghrelin In Regulating Lung Injury Induced By Smoking And PM_2.5

Chronic obstructive pulmonary disease(COPD)is a serious disabling chronic lung disease,with more than 250 million cases in the world and the fourth leading cause of death in the world at present.Among Chinese adults over 40 years old,the incidence of chronic obstructive pulmonary disease is13.6%.The incidence and acute exacerbation of COPD are affected by many factors,including smoking,air pollution,infection and aging.In recent years,with the rapid development of urbanization and industrialization,the resulting air pollution has become one of the biggest health hazards in the world,with about 9 million people dying every year.The problem of air pollution has become a great concern in the society.Air pollutants mainly contain six substances harmful to public health:ozone(O?);particulates with different aerodynamic diameters(?m):PM_2.5,PM_2.5-10,PM₁₀;Nitrogen dioxide(NO₂);Sulfur dioxide(SO₂);Carbon monoxide(CO)and lead.Among them,PM_2.5with small particle size can reach the lower respiratory tract,enter the microcirculation through alveoli and then damage the health of the organism.At the same time,PM_2.5 is also the carrier of other air pollutants,such as heavy metals and hydrocarbons.A large number of epidemiological studies have shown the relationship between PM_2.5exposure and acute exacerbation of COPD and the hospitalization risk.Our previous work showed that the hospitalization rate of COPD patients with medical insurance in Shijiazhuang was positively correlated with PM_2.5exposure,with an attribution ratio of 13%.Therefore,controlling the concentration of PM_2.5 is necessary to prevent COPD and its acute exacerbation.At the same time,it is of great significance to discuss the influence of PM_2.5 on chronic diseases of respiratory system from multiple angles.Previous studies only focused on the single effect of PM_2.5 on the risk of COPD.However,the interaction between PM_2.5 and other pollutants and its influence on COPD and acute exacerbation are still unclear.In the first part of this thesis,the influence of PM_2.5 and its interaction with other air pollutants on the acute exacerbation of COPD will be discussed in depth.The research results will have great theoretical value and practical significance for reducing the death risk of COPD patients and improving their life quality.At present,the treatments for COPD mainly include antibiotics,bronchodilators,corticosteroids,oxygen supplementation and noninvasive ventilation,but they are only suitable for improving or delaying symptoms.Therefore,it is of great significance to seek effective drugs for treating COPD.Ghrelin was first discovered in stomach in 1999,which is a peptide composed of 28 amino acids.It is the endogenous ligand of growth hormone secretagogue receptor(GHSR),which is reported to be closely related to appetite.Studies have shown that the level of ghrelin in the blood of COPD patients is significantly higher than that of the control group,and it is speculated that ghrelin may be used as a biomarker with weight loss and lung dysfunction in COPD patients and addition ghrelin is beneficial to the recovery of COPD patients,but its mechanism is unclear.Persistent inflammation in bronchus is the basis of COPD.Smoking and PM_2.5 can cause inflammation in lung and promote the development of COPD.Autophagy plays an important role in the inflammatory response in lung.Some studies suggest that autophagy has bidirectional regulation on bronchial epithelial cells.However,the role of autophagy in the process of COPD induced by air pollution and cigarette extract is still unclear.In the second part of this thesis,we will focus on the effects of air pollutant PM_2.5and cigarette extracts on inflammation and autophagy in bronchial epithelial cells and lungs,and discuss the effects and mechanisms of Ghrelin on the above processes.The specific contents of the paper are as follows:Part1 Effect of PM_2.5 on the risk of exacerbation of COPD and its interaction with other atmospheric pollutants.Objective:To explore the influence of PM_2.5 on the risk of AECOPD and its interaction with other atmospheric pollutants.Methods:(1)Daily air pollutant concentration and the number of AECOPD inpatients in all tertiary hospitals were collected in Shijiazhuang from January 1,2015 to December 31,2018,followed with the construction of the time series of AECOPD inpatients and air pollutants from January 1,2015 to December 31,2018;(2)Spearman correlation analysis was made between the number of hospitalized patients with AECOPD and the daily concentration of air pollutants.(3)The generalized addictive model(GAM)combined with Poisson regression was used to explore the relationship between the number of hospitalized patients with AECOPD and the concentration of air pollutants,and natural logarithm was selected as the connection function to establish the model.(4)Distributed lag non-linear models(DLNM)was established to explore the cumulative effect and lag effect between the number of hospitalized patients with AECOPD and PM_2.5concentration;(5)The GAM model was established to analyze the interactive effect of PM_2.5 and other air pollutants on the hospitalization number of patients with AECOPD.Results:From 2015 to 2018,a total of 4,766 hospitalized patients with acute exacerbation of COPD were reported in Shijiazhuang city,with an average daily hospitalization of 3.26±2.68 and an average daily PM_2.5concentration of 85.4±73.2?g/m³.The results showed that the risk of acute exacerbation of COPD was the most highest when the value of PM_2.5 reached the maximum after 0 day delay.With the median value of PM_2.5(64?g/m³)as a reference,every 10?g/m³ increase in PM_2.5 concentration will be followed with 5.86%increase in the number of inpatients with acute exacerbation of COPD(RR=1.06,95CI=1.01-1.11),and the cumulative risk of 14 days delay will increase by 31.55%(RR=1.31,951).The results of interaction analysis showed that the number of hospitalized patients with COPD was the highest when the following pollutants exist at the same time including high PM_2.5 with moderate PM₁₀,high PM_2.5 with low CO and high SO₂,high O₃ with high NO₂(P<0.05).Conclusions:The acute exacerbation of COPD is closely related to the concentration of PM_2.5,and there is interaction between PM_2.5 and other air pollutants.Part 2: The role and mechanism of Ghrelin in regulating smoking and PM_2.5-induced lung injuryObjective: To explore the role and mechanism of Ghrelin in regulating lung and epithelial injury induced by cigarette extracts and PM_2.5.Methods:(1)Western blot and cell immunofluorescence were used to detect the effects of PM_2.5 and cigarette extracts on the expression of autophagy protein.(2)ELISA and PCR were used to detect the effects of PM_2.5 and cigarette extracts on the release of inflammatory factors from bronchial epithelial cells(16HBE).(3)Western blot,cell immunofluorescence and ELISA were used to detect the effect of Ghrelin on inflammation and autophagy induced by PM_2.5 and cigarette extracts.(4)Western blot was used to detect the effect of Ghrelin on NF-?B and AP-1 signaling pathway in 16 HBE cells induced by PM_2.5 and cigarette extracts.(5)ELISA,HE pathological staining and tissue immunofluorescence were used to detect the effects of Ghrelin on acute inflammation induced by PM_2.5 and cigarette extracts in vivo.(6)Western blot and tissue immunofluorescence were used to detect the inhibitory effect of Ghrelin on AP-1 and NF-? B.Results:(1)Expression ratio of LC3B?/LC3B?was significantly increased the in 16 HBE cells after the treatment of PM_2.5 and CSE,followed with the increase of inflammatory factors IL-6,IL-8 and mucin MUC5 AC.(2)Ghrelin could inhibit the expression of autophagy protein and release of inflammatory factors induced by PM_2.5 and CSE in a concentration-dependent manner in 16 HBE cells.(3)Ghrelin could significantly inhibit the expression of p-p65,p65,p-JUN and JUN in 16 HBE cells induced by PM_2.5 and CSE.(4)Ghrelin could significantly inhibit the number of neutrophils and inflammatory factors in alveolar lavage fluid induced by PM_2.5 and CSE,and also dramatically inhibit the pathological inflammation and the expression of MUC5 AC in lung.(5)Ghrelin could significantly inhibit the expression of AP-1 and NF-?B induced by PM_2.5 in vivo.Conclusions:(1)Exposure to PM_2.5 and CSE can enhance autophagy and increase the release of inflammatory factors in bronchial epithelial cells,and the above processes can be effectively inhibited by Ghrelin;(2)Exposure to PM_2.5 and CSE can cause acute inflammation in the lung of mice,which could be inhibited by Ghrelin administration in vivo;(3)The protective effect of Ghrelin on bronchial epithelial cells and lung injury is related to the inhibition of AP-1 and NF-?B signaling pathway.