| ObjectiveAcute lung injury (ALI) is a kind of clinic syndrome with the character of permeable pulmonary edema and its serious phase is acute respiratory distress syndrome (ARDS). The mechanism of ALI/ARDS remains not clear. It was generally thought that the injured pulmonary microvascular endothelial cells (PMEC) were important factor responsible for pulmonary edema. But there is little knowledge of the role of aquaporins involved in pulmonary pathophysiologic process. Very few studies have been addressed on the expression of gene and protein of aquaporin-1, 5 or the changes of fluid transport function in lung during ALI/ARDS; It is unclear whether aquaporin-1, 5 is related to the development of pulmonary edema. Therefore, it is valuable for us to study the expression and function of aquaporin-1 in rat PMEC induced by lipopolysaccharide (LPS),tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Furthermore, we studied the mRNA and protein expression changes of aquaporin-1, 5 in acute lung injury rats induced by LPS. The aim of this research is to further clarify the pathogenesis of ALI/ARDS.Methods1. PMEC were isolated and cultured in vitro and were randomly divided into four groups: DMEM control group, LPS treated group, TNF-α treated group and IL-1β treated group. The semiquantitative RT-PCR technique was used to observe the effects of LPS, TNF-α, IL-1β on mRNA expression of AQP-1 and the immunocytochemistry method was used for determining the effects of LPS, TNF-α, IL-1β on protein expression of AQP-1 in rat PMEC. The isotope tracer technique was applied for the assay of the intra-cellular tritium water (3H2O) signal intensity in rat PMEC among the different groups.2. The model of ALI rats was established with LPS (2.5mg/kg) originated from E.coli. The rats were randomly divided into five groups: NS control group, LPS injured 2h group, LPS injured 4h group, LPS injured 6h group and LPS injured 8h group. The semiquantitative RT-PCR technique was used to observe the effects of LPS on mRNA expression of AQP-1 and AQP-5; the immunohischemistry method was used for determining the effects of LPS on protein expression of AQP-1 and AQP-5 in the lung tissues of ALI rats.Results1. Resting PMEC expressed high levels of AQP-1mRNA and AQP-1 protein. Comparing with the control groups, the expression levels of AQP-1 decreased markedly in rat PMEC treated with LPS, TNF-α and IL-1β(p<0.01).2. Resting PMEC permeated a certain quantity of tritium water. Comparing with the control groups, the permeability of tritium water weakened significantly in rat PMEC induced by LPS, TNF-α and IL-1β(p<0.01).3. In the control groups, the lung tissues of normal rats expressed high levels of AQP-1 mRNA and AQP-1 protein; the expression levels of AQP-1mRNA and AQP-1 protein declined significantly in the lung tissues of ALI rats induced by LPS(p<0.01).4. There were high expression levels of AQP-5mRNA and AQP-5 protein in the lung tissues of normal rats in the control groups; the expression levels of AQP-5mRNA and AQP-5 protein decreased remarkably in the lung tissues of ALI rats after LPS disposal(p<0.01).Conclusions1. LPS, TNF-α and IL-1β down-regulated the mRNA and protein expression levels of AQP-1 in PMEC, suggesting that the down-regulation of AQP-1 under pathological conditions may contribute to pulmonary edema by decreasing the capability of water permeability in the airspace and capillary spaces.2. The permeability of tritium water weakened remarkably in rat PMEC treated with LPS, TNF-α and IL-1β, implying that the reduction of the water transport function of AQP-1 induced by inflammatory mediator is correlated with the formation of pulmonary edema by essentially reducing the transcelluar rate of the removal of excess water from the airspace and capillary spaces.3. LPS down-regulated the mRNA and protein expression levels of AQP-1 and AQP-5 in ALI rat's lung tissues suggests that the decreased water transport function between airspace, interstitial and capillary co...
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