Effects Of Air Mixed Pollutants On The Expression Of HO-1in The Lung Of Rats

In recent years, air pollution was increasing seriously and could induce injury tohuman health. Air pollutants were complex components, and formed from a varietypollutants. The main pollutants in the pollutant particles were the particulate matter（PM10） which diameter was less than10um. Recent studies were found that particulatematter which diameter was less than2.5um （PM2.5） could enter the lung tissue andblood deeply. PM2.5was more harmful to the human body. On the other hand, with thedevelopment of the rapid industry and people’s living standard, energy consumptionand the emission of CO、NO₂、SO₂were increased.In the heme degradation process, HO-1acts as a rate limiting enzyme andproduces bilirubin, ferritin and carbon monoxide （CO）, and the protective system ismediated by the physiologic activities of these products. Since heme oxygenase-1（HO-1） is known to protect lung tissue against various kinds of oxidative stress,increased expression of HO-1in thought to reflect oxidative stress. Expression ofHO-1is significantly induced by oxidative stress such as ultraviolet rays, heat shock,endotoxin and cytokine. Increased HO-1expression has also been reported in humaninterstitial pneumonia and cystic fibrosis.Objective:In order to determine whether HO-1were involved in lung injury caused byexposure to mixed pollutants or not. We investigated the heme oxygenase-1geneexpression in lung injury caused by exposure to simulated atmospheric pollution. Weused a rat model in which animals were exposure to simulated atmospheric pollution.We investigated the morphological changes and histological changes in the lungsfollowing exposure to simulated atmospheric pollution. Then, we analyzed theexpression of HO-1mRNA and protein in the lungs of rats, and the activity of HO-1. Methods:30Wistar rats were randomly divided into three experimental groups （3d，7d,1Mgroup） and three control groups （control3d，control7d, control1M group）.5rats eachgroup respectively. Rats were anesthetized by ether. Either1ml saline or1ml PM2.5suspension （10mg/1ml saline） was administered to the animal intratracheally. The dayafter administration, experimental animals were inhaled with air mixture of whichconcentrations of SO₂、NO₂、CO were15,12,400mg/m3for4hours everyday. Thecontrol groups were fed in normal air. Rats were killed in4d,8d and31d aftercontamination. Rats were operated and right middle lung lob were taken out. TheRNA and proteins were extracted from the lung, and the expression of HO-1mRNAand protein were detected by RT-PCR and Western blotting. The left lung was inflatedand fixed by intratracheal instillation of4%paraformaldehyde and theimmunostaining for HO-1was performed. The liver tissue of control animals wereprepared by homogenization for determine the activity of HO-1.Result:1. Histopathological findingsIn the experimental animals, after7d and30d after exposure, congestion andedema of lung tissue were observed compared with control groups. Infiltration ofinflammatory cells （mainly neutrophils and alveolar macrophages） was party observedin these experimental animals （7d and30d after exposure）. After30d exposure bymixed pollutants, proliferation of fibrous tissue was detected in the lung slide ofexperimental animals compared with control groups（p＜0.05）.2. Gene expression of HO-1mRNAIn control animals, the expression of HO-1mRNA was very low duringexperiment period. Significent increased expression of HO-1mRNA was detected inthe mixed pollutants-exposed groups after7d and30d compared with control groups（p＜0.05）.3. Expression of HO-1proteinIn control animals, the expression of HO-1protein was very low during experiment. Significent increased expression of HO-1protein was detected in themixed pollutants-exposed groups at7d and30d following exposure compared withcontrol groups（p＜0.05）.1. Immunohistochemical staining for HO-1geneIn the control groups, there are less HO-1-positive cells in the lung slides. In theexperimental groups, at7d and30d after administration, the HO-1-positive cells werefound in some alveolar and bronchial epithelial cells compared with control groups（p＜0.05）.2. Activity of HO-1proteinThe activity of HO-1protein in the mixed pollutants-exposed groups at7d and30d were higher than control groups. There were significant different betweenexperimental groups （30d） and control groups（p＜0.05）.Conclusion:1. In the normal lung tissues of rats, the expression of HO-1mRNA and proteinwere very low.2. In the experimental groups, increased expression of HO-1mRNA and proteinwas detected in the mixed pollutants-exposed groups at7d and30d after exposurecompared with control groups.3. Significant histopathological changes and higher expression of HO-1mRNAand protein were detected in the mixed pollutants-exposed groups at30d afterexposure compared with control groups. The activity of HO-1protein wassignificantly increased at this time-point.