Experimental Research On The Mechanism Of The Effect Of Nitric Oxide Inhalation On The Inflammation-induced Lung

Background and ObjectiveThe pneumonia is one of the main causes of human deaths. The incidence of it in our country is 8 -10 times more than that in Europe and American. But the research of the disease, especially the severe pneumonia, is relatively weaker. Above 50% of the acute lung injury ( ALI) and acute respiratory distress syndrome ( ARDS) are caused by infection, and the death rate is up to 40 -50%. The antibiotic therapy can eliminate the pathogens, but is no use to the inflammation and tissue injury caused by lipopolysaccharide( LPS). How to control inflammation, reduce incidence and mortality of ALI/ARDS, are the concerns of academic circles.After the confirmation that nitric oxide( NO) is actually the endothelium -derived relaxing factor ( EDRF) , numerous studies indicate that NO involves many physiological and pathological process of our body. It is not only the vascular relaxing factor, but also an important mediator in regulating immunoreac-tions and inflammation.It has been indicated that endogenous NO plays dynamic changes and correlates with many cytokines and mediators during the inflammatory process of lung injury. In experiments, animals injected with LPS could have alleviated lung injury if given NO inhalation or NO donors at the same time. NO can prevent inflammation from occurrence and over - development, and regulates the immuno-reactions of the experimental animals to be placed in an appropriate level.The objective of this experiment is to elucidate the anti - inflammatory mechanisms of NO inhalation by using the rats model of acute lung injury.Materials and MethodsAnimal preparation: Thirty healthy male Sprague - Dawley rats were randomly divided into five groups: ① Control group: injected intravenously with 0. 9% saline, breathe the air( FiO219% ) ; ②LPS group: Injected intravenously with LPS, breathe the air(FiO219% ) ; ③LPS + INO group: injected intravenously with IPS, and two hours later put into the completely sealed box which was ventilated with the mixture of the air ( FiO219% ) and nitric oxide gas (30ppm) ;④LPS +DEX group: injected intravenously with LPS, and two hours later injected intraperitoneally with DEX, breathe the air(FiO219% ) ;⑤LPS + INO + DEX group: injected intravenously with LPS, and two hours later injected intraperitoneally with DEX, put into the completely sealed box which was ventilated with the mixture of the air(FiO219% ) and nitric oxide gas(30ppm). The treatments of INO or/and DEX were carried 2hours later after LPS injection. The experimental duration was 6 hours after LPS injection.Measurements and Methods: The arterial blood, the lung tissue and the bronchoalveloar lavage fluid ( BALF) were collected at the end of the experiment. Measurements included: wet lung weight to dry lung weight ratio (W/D) ; the concentration of the protein , white blood cell (WBC) count and the percentage of PMN in BALF; WBC count in peripheral blood; the concentrations of tumor necrosis factor - alpha(TNF - α) , interlukin - 1beta( IL - 1β) , inter-lukin - 8 (IL - 8 ) in the peripheral blood and BALF which were measured by enzyme - linked immunosorbent assay ( ELISA) ;. pathological changes of the lung tissue; the expression of NF - κB and glucocorticoid receptor(GR) in lung tissue measured by immunohistochemistry.ResultsW/D:The W/D in LPS group was significantly increased compared with that in control group( P <0.05 ). The W/D in INO or/and DEX groups was reduced compared with that in LPS group ( P < 0.05 ).WBC count in peripheral blood:This index was prominently lower in LPS group than that in control group(P <0.05 ) ,the INO or/and DEX treated groups had higher levels of WBC count than LPS group had.WBC count, percent of PMN, the concentrations of protein in BALF:These three indexes were increased notably in LPS group compared with control group ( P <0.05 ) , and decreased after therapy ( P <0.05 ) .TNF - α, IL-1β, IL - 8 in serum and BALF: The levels of these cytokines in LPS group were significantly higher than other groups( P < 0.05). After INO or/and DEX therapy, the levels dropped, but still had remarkable difference between control group( P < 0.05).Pathological changes: Histopathologic findings demonstrated interstitial and alveolar edema, hemorrhage, neutrophilic alveolitis, diffuse alveolar damage and hyaline membranes in LPS group. All these changes alleviated after thera-py.Immunohistochemical result of NF - κB: The positive percentage in the cells with nuclear staining of NF - κB p65 was significantly increased after LPS injury compared with other groups( P <0.05 ) .Immunohistochemical result of GR: The positive percentage in the cells with nuclear staining of GR had remarkable difference between LPS group and control group(P <0. 05). After therapy the positive percentage increased significantly compared with that of LPS group(P <0. 05 ) , and among the INO or/and DEX treated groups, the index in LPS + INO group was higher than that in LPS + DEX group(P<0.05).ConclusionLPS intravenous injection can establish rat model of ALI successfully.TNF -α, IL-1β, IL-8 take part in the inflammatory process of ALL INO and DEX can decrease the levels of these cytokines and alleviate the lung damage. ,During the All, the expression of NF - κB in the lung was increased, which indicates that NF - κB participates in the transcriptional regulation...