Investigation Of Mechanism Of Cell Signal Transduction And Protective Role Of Dexamethasone In Acute Lung Injury Rat

[Objective] The cell apoptosis in the lung of oleic induced acute lung injury (ALI)rat and the mechanism of its cell signal transduction are investigated. Furthermore, the role of Dexamethasone in signal transduction is discussed in early stage of ALI[Methods] (1)Establish animal model: oleic group(OG) injecting 0.25 ml/Kg oleic into remnant venous, rinsing the oleic in injection duct with 1ml saline, marking the animals, killing them by jugular venesection in 1h, 2h, 4h, 6h, 24h, respectively. Control group(CG) injecting 0.25 ml/Kg and lml saline into remnant venous. Dexamethasone oleic 2h group(DO2h) injecting 0.25 ml/Kg oleic then 1.0mg/Kg dexamethasone 15min later, killing the animals in 2h . (2)observe arterial blood gas , lung permeative index and pathology variation: analyzing arterial blood gas, calculating left lung wet/dry ratio and lung index(LI),measuring protein content in bronchial alveolar lavage fluid(BALF) and pulmonary permeability index(PPI),counting the cell numbers in BALF by microscope, observing grade of lung injury in general pathology and micro pathology. (3)Observe the cell apoptosis in lung : Fas-L protein expression was examined by immunohistochemical analysis. (4)Examine the infective factors:Projecting the Radioimmunnol method to examine the levels of TNF- α , IL-6 in the rat's serum, the lung tissue and BALF. (5) Determine expression condition of protein related to the signal transducting system inside the cells: Determining the protein expression condition of phosphoinositide3-kinase(PI3-K), extracellularsignal-regulated kinases ( ERK) and phosphorylation ERK (P-ERK) by Western blotting and immunohistochemical method. [Results] (DVariation of arterial blood gas and lung permeation after injured by oleic: PaO2 and SaC>2 became lower after being injected oleic into remnant venous and type I of respiratory failure appeared; Left lung wet/ dry and LI were higher in OG( PO.05, PO.05); protein content of BALF and PPI increased obviously ( PO.01, PO.05) ;The cell numbers in BALF increased obviously also( PO.05), most of the augmentative cell were PMN. Pulmonary edema , transparent film formation and pulmonary parenchyma were the mainly general and micro pathologic performance in OG (2)The change of cell apoptosis level in the lungs of ALI rats: The positive cell of Fas- L protein were mainly distributed in terminal thin bronchus epithelial cells, alveolar epithelial cells, pulmonary vessel endothelial cells and macrophage cell, the Fas- L was slightly expressed in the control group rats, but highly expressed in the lung of ALI rat, grain numbers and the ash degree of positive cells in OG were more than in CG ( PO.05) ; The peek value of Fas-L expression appeared in the time of 4h after rat being injured and then maintained in a higher level. (3)The variation of infective factors in ALI rat: The level of TNF- a in serum, the lung tissue and BALFincreased quickly( PO.05) after rat being injected oleic and the time of peek* value was mostly the same in serum, the lung tissue and BALF, that is thelevel of 1 h was the highest, then the level decreased gradually. Contents of IL-6 went up ( PO.05) slowly, the time of peek value was also the same in serum, the lung tissue and BALF, that is the level of 4 h is the highest, and then maintained in a higher level. (4)Variation of expression condition of protein related to the signal transduction system inside the cells in ALI: PI3-K^ ERK> P-ERK were mainly expressed in bronchus epithelial cells, alveolar epithelial cells ,pulmonary vessel endothelial cells and macrophagecells, PI3-K, ERK, P-ERK expression increased obviously in OG, P<0.05, their expression peek values appeared in 1 h or so after rat being injured by oleic. (5)The mechanism of protective role of Dexamethasone: the PaC>2 and SaO2( P<0.05) increased and pulmonary permeation were also improved after injecting dexamethasone to oleic injured rat (left lung wet/dry ratio, LI, protein content in BALF, PPI and cell numbers in BALF in DO2h were all less than OG2h, P<0.05), but Dexamethasone couldn't make the above various indexes recover to the normal level (the DO2h and CG compared, PO.05). Dexamethasone could decrease the excessive apoptosis in terminal thin bronchus epithelial cells, alveolar epithelial cells ,pulmonary vessel endothelial cells and macrophage cells (PO.05) , but couldn't make the apoptosis level recover normally, P<0.01. The level of TNF- a and IL-6 in serum, the lung tissue and BALF in DO2h were lower than OG2h, but higher than CG Dexamethasone also could inhibit the activation of PI3- K and ERK (P<0.05) and reduce their expressions, but couldn't make them recover normally (P<0.05) .[Conclusions] (Dlt was the apoptosis of bronchus epithelial cells, alveolar epithelial cells .pulmonary vessel endothelial cells and macrophage cells related to Fas-L that participated in the earlier period of ALI outbreak. (2) the level of TNF-a and IL-6 in serum, the lung tissue and BALF increased in ALI rat; TNF-a and IL-6 released in great quantities would promote bronchus epithelial cells, alveolar epithelial cells, pulmonary vessel endothelial cells and macrophage cells with Fas-L apoptosis that aggravated the lung injury. (3)Activation of ERK in bronchus epithelial cells, alveolar epithelial cells ,pulmonary vessel endothelial cells and macrophage cells may play a significant role in the process of ALI. (4)The signal transduction path of PI3-K turned to play different role in the different cell inside the lung in ALI. Its function mechanism may pass the transduction path of...