Background: Antithrombin-III (AT-III), the major inhibitor of thrombin in plasma, also has anti-inflammation property and might have positive effect on sepsis. The present study aimed to investigate the effects of AT-III on inflammatory reaction and pulmonary protection in endotoxin-induced acute lung injury (ALI) rat.
Methods: Sixty male Sprague-Dawley rats were randomly assigned equally to normal control group, ALI group, AT-III treatment group, AT-III + heparin treatment group, and heparin treatment group. The pulmonary vascular permeability index (PVPI) was measured by single nuclide tracer technique. The activity of AT-III in plasma was determined by the method of synthetic chromogenic substrata. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) levels in serum were determined by enzyme-linked immunosorbent assay. The expressions of lung tissue mitogen-activated protein kinases (ERK1/2, P38 and JNK MAPK) were determined by Western blotting.
Results: Rats had significantly improved lung histopathology in the AT-III treatment group and heparin treatment group compared with the ALI group. The PVPI of the ALI group was 0.38 + or - 0.04, significantly higher than that of the normal control group (0.20 + or - 0.02, P < 0.01), AT-III treatment group (0.30 + or - 0.04, P < 0.01) and heparin treatment group (0.28 + or - 0.04, P < 0.01) respectively. There were no significant differences of PVPI in the ALI group and AT-III + heparin treatment group. The activity of AT-III in plasma in the ALI group was (76 + or - 8)%, significantly lower than that of the normal control group ((96 + or - 11)%, P < 0.05) and AT-III treatment group ((105 + or - 17)%, P < 0.05) respectively. The serum levels of TNF-alpha and IL-6 of the ALI group were (2.770 + or - 0.373) microg/L and (1.615 + or - 0.128) ng/ml respectively, significantly higher than those of the normal control group ((0.506 + or - 0.093) microg/L and (0.233 + or - 0.047) ng/ml respectively, all P < 0.01), AT-III treatment group ((1.774 + or - 0.218) microg/L and (1.140 + or - 0145) ng/ml respectively, all P < 0.01) and heparin treatment group ((1.924 + or - 0.349) microg/L and (1.223 + or - 0.127) ng/ml respectively, all P < 0.01). The lung tissue levels of phospho-ERK1/2 and phospho-P38 MAPK expressions were markedly higher in the ALI group than in the normal control group, AT-III treatment group and heparin treatment group respectively.
Conclusions: AT-III without concomitant heparin inhibited the activation of ERK1/2 and P38 MAPK, down-regulated the levels of downstream cytokines TNF-alpha and IL-6, relieved endothelial permeability, and improved the ALI in endotoxin-induced rats. It might be helpful to administrate AT-III alone, not with concomitant heparin, to those patients with ALI and sepsis.