| Objective To observe the protective effects of angiopoietin-1 (ang-1) on acute lung injury (ALI) induced by oleic acid at early stage in mice and to explore the expression of zonula occludens-1 (ZO-1) and VE-cadherin, meanwhile the preliminary mechanism was investigated.Methods One hundred and forty BALB/c female mice were randomly divided into 7 groups ( n=20). The ALI group (A group) was treated with oleic acid (0.2 ml/kg) intravenously to induce ALI. In the ALI + ang-1 group (B group), the mice were injected intraperitoneally with angiopoietin-1 (312.5μg/kg) at four hours later after oleic acid treatment. In the ALI + ang-1 + LY294002 group (C group), the mice were synchronously injected intraperitoneally with angiopoietin-1 (312.5μg/kg) and LY294002 (100 mg/kg) which is the phosphatidylinositol 3-kinase (PI3K) inhibitor after oleic acid treatment for four hours. In the ALI + LY294002 group (D group), the mice were injected intraperitoneally with LY294002 (100 mg/kg) at four hours later after oleic acid treatment. The control group (E group) was given normal saline (0.2 ml/kg) intravenously. In the control + LY294002 group (F group), the mice received intraperitoneal injection of LY294002 (100 mg/kg) after given with normal saline for four hours. In the control + Ang-1 (G group), the mice was treated with normal saline intravenously, and four hours later angiopoietin-1 (312.5μg/kg) was injected intraperitoneally. Then 8 hours later 10 mice were randomly taken from each group for bronchoalveolar lavage fluid (BALF) analysis including the protein level, cell count and differentials. The wet/dry weight (W/D) of the right lung, pathological changes of the left lung and the expressions of ZO-1 and VE- cadherin in lung tissues were examined for the rest mice in each group. Pathological changes of the lung tissues were examined and scored with light microscrope. The expression of ZO-1 and VE-cadherin were examined in the lung by western-blot and immunohistochemistry, their m-RNA were examined with reverse transcriptase polymerase chain reaction (RT-PCR).Results The W/D, the protein level, the total cell count and differential of polymorphonuclear leukocytes in BALF and the pathological scores were significantly decreased in the ALI + ang-1 group [4.02±0.24,(162.84±17.26)μg/ml,(33.84±2.56)×104/L,(19.78±1.64)×10~3/L,1.73±0.14] as compared to the ALI group [5.29±0.20, (227.98±13.06)μg/ml, (42.84±3.67)×10~4/L,(26.11±2.49)×10~3/L, 3.42±0.11] and to the ALI + ang-1 + LY294002 group [5.09±0.19, (211.96±19.10)μg/ml,(40.18±1.79)×10~4/L(,23.80±1.38)×10~3/L, 3.20±0.22](all P<0.05). While the expressions of ZO-1 and VE- cadherin and their m-RNA were higher than those in the ALI group and the ALI + ang-1 + LY294002 group (all P<0.05). The W/D, the protein level, the differential of polymorphonuclear leukocytes in BALF and the pathological scores in the ALI + ang-1 + LY294002 group were lower than those in the ALI group, but there were no differences of the total cell count in BALF and the expressions of ZO-1 and VE- cadherin and their m-RNA between the two groups (P>0.05). When compared to the control group, the W/D, the protein level, the total cell count and differential of polymorphonuclear leukocytes in BALF and the pathological scores of the ALI + ang-1 group were higher, and than the expressions of ZO-1 and VE- cadherin and their m-RNA were lower (all P<0.05). The above measurements of the ALI group showed no difference compared to the ALI + LY294002 group, and there also no difference among the control group, the control + Ang-1 group and the control + LY294002 group (all P>0.05).Conclusion Angiopoietin-1 is effective in relieving acute lung injury induced by oleic acid in mice at early stage and it could prevent the loss of ZO-1 and junctional VE-cadherin. The protective effect can be blocked by LY294002, the phosphatidylinositol 3-kinase (PI3K) inhibitor. Thus, angiopoietin-1 maybe maintain the expression of ZO-1 and junctional VE-cadherin through the phosphatidylinositol 3-kinase/Akt signal transduction pathway, while might be one of mechanism of protective effects of angiopoietin-1 (ang-1) on acute lung injury.
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