Objective: To observe the protective effects of angiopoietin-1 on acute lung injury (ALI) induced by oleic acid at early stage in mice and to investigate the expression changes of vascular endothelial growth factor (VEGF).
Methods: Ninety-six female BALB/c mice were randomly divided into 4 groups (n = 24). The control group was given normal saline (0.9 ml/kg) intravenously. The ALI group was treated with oleic acid (0.9 ml/kg) intravenously to induce ALI. In the control + angiopoietin-1 group, the mice were injected intraperitoneally with angiopoietin-1 (312.5 microg/kg) 4 h after normal saline administration. In the ALI + angiopoietin-1 group, the mice were injected intraperitoneally with angiopoietin-1 (312.5 microg/kg) 4 h after oleic acid treatment. Then 8 h later 12 mice were randomly taken from each group for bronchoalveolar lavage fluid (BALF) analysis including the protein level, cell count and differentials, and the level of IL-6 and VEGF. The wet/dry weight (W/D) of the right lung, the level of IL-6 and VEGF in serum, pathological changes of the left lung and VEGF expressions in lung tissues were examined for the rest of mice in each group. The level of IL-6 and VEGF in both serum and BALF were measured by enzyme-linked-immunosorbent assay (ELISA). Pathological changes of the lung tissue were examined and scored with light microscrope. The expression of VEGF was immunohistochemically detected in lung tissues as integrated optic density (A) measured with Image Pro Plus 5.1 software.
Results: The W/D, the protein level, the tota1 cel1 number and differential of polymorphonuclear leukocytes in BALF, the IL-6 level in both serum and BALF, the VEGF level in serum were significantly decreased in the ALI + angiopoietin-1 group [4.09 +/- 0.14, (176 +/- 13) microg/ml, (34.4 +/- 4.1) x 10(4)/L, (19.85 +/- 3.93) x 10(3)/L, (1318 +/- 62) pg/ml, (652 +/- 17) pg/ml, (48 +/- 5) pg/ml] as compared to the ALI group [5.32 +/- 0.51, (227 +/- 12) microg/ml, (42.2 +/- 5.2) x 10(4)/L, (26.22 +/- 2.22) x 10(3)/L, (1510 +/- 117) pg/ml, (744 +/- 13) pg/ml, (74 +/- 5) pg/ml, t = 8.16, 9.92, 4.02, 4.88, 5.03, 19.18, 14.81 respectively, all P < 0.01]. Pathological scores in the ALI + angiopoietin-1 group (1.84 +/- 0.12) improved as compared to those in the ALI group (3.44 +/- 0.21, t = 24.16, P < 0.01), and the VEGF level in BALF of the ALI + angiopoietin-1 group (179 +/- 15) pg/ml was higher than that of the ALI group (140 +/- 20) pg/ml (t = 5.31, P < 0.01). The expressions of VEGF in the lung tissues indicated by A (549 +/- 72) in the ALI + angiopoietin-1 group were higher than those in the ALI group (342 +/- 85, t = 5.22, P < 0.01), but lower than those in the control group (768 +/- 111) (t = 5.35, P < 0.01). The above measurements of the control + angiopoietin-1 group showed no difference compared to the control group (t = 0.12, 0.53, 1.27, 2.28, 1.18, 0.34, 0.13, 0.25, 0.58, 0.69 respectively, all P > 0.05). Statistical analysis was done using SPSS 10.0 software. Data are expressed as mean +/- s, with statistical significance declaved for probility valaes < 0.05. LSD-t test was used for group comparison. One-factor ANOVA was used for mdlti-group comparison.
Conclusions: Angiopoietin-1 is effective in relieving the severity of acute lung injury induced by oleic acid in mice at early stage and up-regulating VEGF expression in BALF and lung tissues but down-regulating VEGF expression in serum. The results suggest that angiopoietin-1 may exert beneficial effects on ALI.