The Protective Effect Of N-acetylcysteine On Pneumonia Model Of Simulated Weightlessnes S

ObjectiveIn weightlessness or simulated weightlessness, the immune function impaired, and the ability of resistance against infection reduced. N‐acetylcysteine(NAC) is commonly used as expectorant drugs clinically, on the other hand, it also be used as immune regulation, inhibition the spread of the bacteria and inflammation, and restrain of the generation of biofilm. In this study, we explored the ability of resistance to the infection of Streptococcus pneumoniae of the body during simulated weightlessness, which being set up through tail suspension. Besides this, the protective role of N‐acetylcysteine was also observed. From these, maybe we can provide a theoretical basis for the medicine and protection of infection while in weightlessness, provide the basis for aerospace Medicare.MethodsThe simulated microgravity and infected animal model: Healthy clean male Wistar rats (n=32), weight (270±20) g, randomly divided into4groups: Group A (tail suspension, infection and NAC group), Group B (tail suspension, NAC and no infection group), Group C (tail suspension, infection and no NAC group), Group D (tail suspension, no infection and no NAC group.The experiment period was9days. NAC were fed by intragastric administration on the first day, while same amount of distilled water were fed in control group. On the second day, the models of simulated weightlessness were duplicated by tail suspension method (Each rat was hung by its tail in a cage, and30degrees with the horizontal). The rats were intratracheal instilled with0.4ml suspension of streptococcus pneumoniae after tail‐suspension for3days. At the same time, no‐infection groups were intratracheal instilled with0.4ml sterile saline. At the end of experiment, the rats were killed. The leukocytes and neutrophils, CD11b and DCFH‐DA in the blood were studied. The pathology of lung tissue were also observed.Results:1. The pathological changes of rat lung: In group C, obvious congestion of the lung tissue could be observed. Some of alveolus got fusion, alveolar septum got sick, lung’s small veins and capillaries dilated and congestion. Large number of neutrophils and lymphocytes infiltrated in the interstitial, foam cells flooded in the alveolar space. Some changes like these could be find in Group A, but less severe than group C. There were pulmonary congestion in group D, and the sizes of alveolus were differ. The alveolar septa Widened, and a bit of lymphocyte and neutrophils infiltrated in the interstial. A few of the same changes but less severe could be observed in Group D.2. Streptococcus pneumoniae was got from lung tissue and BALF in the streptococcus pneumoniae group (group A,C). No bacteria grew in group B,D.3. Compared with group A and group C, neutrophile percentage were significantly higher than group B and group D. And the same trend could be observed in CD11b value, DCFH‐DA value, IL‐10and IL‐6. In group C, the value of the indexes above were the highest.Conclusion:While in weightlessness, the immune function of rat reduced, the ability of defending bacteria infection decreased. Once the lung was insulted by bacterial during weightlessness, the inflammatory response was significantly higher, the pathological changes were much more severe. NAC may have protective effect on lung infection while in weightlessness.