The Expression Of E-selectin In Lung Tissue Of Neonatal Rat With Acute Lung Injure And Its Clinicopathologic Significance

Objective: Acute lung injury(ALI) or acute respiratory distress syndrome(ARDS) is a common fetal disease in all age grades,and it is lack of laboratory diagnosis in neonate at present. The pulmonary vascular endothelial cell is the main target cell in the ALI,and its activation considered as an important indicator of ALI. It is an important step to trigger ALI in which the activated endothelial cell can increase leukocyte adhering and migration,and this process is closely related with the expression of adhesion molecules. E-selectin is a kind of adhesion molecules which is only expressed on the surface of activated endothelial cell,so it is considered as a good marker of endothelial cell activation. In our study we established the acute Lung injury model with lipopolysaccharide (LPS) in neonatal rats via intraperitoneal injection. Following we observed the dynamic change of E-selectin in lung and sE-selectin levels in serum to investigate the value of early diagnosis in acute lung injury of neonates. Methods: Ninety neonatal SD rats (between 6 and 7 days) were randomly divided into the control group and ALI group. The ALI group is divided with 8 subgroup(n=10 at 0.5h,1h,2h,3h,4h,8h,12h and 24h respectively) according to different sacrifice time. Rats in ALI group were injected intraperitoneally with LPS of 4mg/kg and the rats in control group were injected intraperitoneally with equal volume normal saline. The rats were sacrificed at different time points (0.5h, 1h, 2h, 3h, 4h, 8h, 12h and 24h) after the injection of LPS respectively. We observed dynamically the expression of E-selectin in lung tissue through immunohistochemistry (SABC method) while the serum sE-selectin was detected by Enzyme-linked immunosorbent assay (ELISA). In addition, the ratio of wet weight to lung dry weight of lung (wet-to-dry weight ratio, W/D), and histopathologic changes of LPS-induced lung injury were analyzed respectively.Result:1.The lung's general structure The appearance of the lung tissue in the control group appears pale pink,smooth,and elastic. The lung tissues were found hyperemia and edema at various degrees followed injection of LPS. Small pneumorrhagia just like needlepoint was observed at the 1h group. The hemorrhage became aggravated gradually between 3h and 8h,and diffuse hemorrhage at the time point of 24h.2. Changes under light microscope Rats of control group had a normal pulmonary structure. The thicker alveolar wall,interstitial edema of lung, narrower alveolar space, alveolus blood capillary engorgement can be found after 1h following LPS injection. We can also observe vascular endothelial cellular edema under high power lens. Endotheliocyte desquamated,the space between endotheliocyte widened,leucocyte mainly neutrophilic granulocyte infiltrated alveolus stroma after 4h following LPS injection. After 8 hours we found Intra-alveolar hemorrhage and RBC infiltrated alveolus stroma.3. Lung W/D ratio Compared the lung W/D ratio of ALI group with control group,we found the lung W/D ratio from 0.5h to 3h had no significance(P>0.05) while the lung W/D ratio was increase significantly from 8h to 12h(P<0.05),and the lung W/D ratio was close to the control group at 24h(P>0.05). Lung W/D ratio of neonate lung started to increase at 1hour, and reach the peak at 8hour, decreased obviously at 12h,and at 24h it basically drop to the level of the control group.4. Dynamic changes of sE-selectin in serum Compared the lung the level of soluble E-selectin of ALI group with the ones of control group,we found the level of soluble E-selectin in serum was increase significantly from 8h to 12h(P<0.05). The level of soluble E-selectin started to increase at 1hour, and reach the peak at 2hour, decreased obviously at 8h,and it basically drop to the level of the control group at 24h. There are significant difference in groups (P<0.05).5. The expression of E-selectin in the lung tissue E-selectin didn't express nearly in lung tissue of control group and E-selectin express much more in lung tissue of ALI group. It is express in arteriole, intravenous and capillary endothelium and the positive cell demonstrates buffy and yellow. The expression of E-selectin is time dependent. In ALI group the lung begin expresses E-selectin when LPS has been given to 2 hours before, reach the peak after 4 hours and decreased obviously at 8h .There was a significant difference between model 2h and 4h groups in comparison to control group.6.Correlativity between the expression of E-selectin in lung tissue and serum sE-selectin It was a positive correlation of the expression of E-selectin in lung tissue and serum sE-selectin concentration (r=0.730,P<0.01).Conclusion:1. This study proved the feasibility of acute Lung injury models in neonatal rats via lipopolysaccharide (LPS) intraperitoneal injection with a dose at 4mg/ml.2. It is increased in the expression of E-selectin in actived endothelial cell after given LPS. The time sequence of E-selectin expressed in vascular endothelial cell of the lung tissue response of ALI was obvious, which is earlier than pneumonedema.3. The expression of E-selectin which showes time sequence obviously in serum was higher than control group.The fact that there was a positive correlation of the expression of E-selectin in vascular endothelial cell of the lung tissue and in serum reflects the activation of vascular endothelial cell,which participates in inflammatory.Thus sE-selectin may prove to be a valuable diagnostic method in early ALI.