Objective: To observe the local changes in alveoli in intravenous endotoxin induced acute lung injury (ALI) rat model after inhalation of aerosolized unfractioned heparin (UFH), and to observe its effects on coagulability, fibrinolysis and inflammatory response.
Methods: Eighty seven male Wistar rats were divided into groups according to table of random number: sham, model, heparin therapy (HT) and heparin prophylaxis (HP). Endotoxin induced ALI model was reproduced by intravenous administration of lipopolysaccharide (LPS). Rats in HP and HT groups received aerosolized UFH before and after injection with LPS respectively, while rats in both sham and model groups inhaled aerosolized normal saline. Rats in each group were respectively sacrificed at 6, 12 and 24 hours after intravenous administration of LPS, and bronchoalveolar lavage fluid (BALF) was collected. Enzyme linked immunosorbent assay was used to measure the level of thrombin antithrombin (TAT), tissue type plasminogen activator (t-PA), urokinase type plasminogen activator (u-PA), plasminogen activator inhibitor 1 (PAI-1), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) in BALF.
Results: At 6 hours after injury, the level of TAT (μg/L) in model group (3.346±0.585) was highest, that in HT group (2.764±0.100) was higher, and that in HP group (2.564±0.216) was lowest in BALF (all P<0.05). The t-PA (μg/L) concentration in HP group (3.037±0.524) was highest, that in HT group (2.494±0.191) was higher, and that in model group (1.716±0.125) was lowest (all P<0.05). Compared with model group, u-PA (μg/L) level in HP group dramatically enhanced (0.411±0.118 vs. 0.303±0.049, P<0.05). The concentration of PAI-1 (μg/L) in HP group was significantly lower than that of HT and model groups (2.296±0.246 vs. 2.597±0.425, 2.834±0.198, both P<0.05). In HP group, it was still lower than that in HT group at 12 hours (1.273±0.441 vs. 1.817±0.252, P<0.05). TNF-α (ng/L) levels in HT and HP groups were markedly lower compared with model group (68.154±3.915, 36.990±6.539 vs. 77.001±4.485) at 6 hours, and the level in HP group was lower than that in HT group (all P<0.05). TNF-α concentration in HP group was still the lowest at 12 hours (15.287±4.754), and there was significant difference compared with HT and model groups (26.756±5.336, 23.674±4.398, both P<0.05). The levels of IL-6 were not distinctively different among model, HT and HP groups at various time points.
Conclusion: It was proved that inhalation of aerosolized UFH resulted in lowering local coagulability, alleviating fibrinolytic depression, improving fibrinolysis , and attenuating inflammation in endotoxin induced ALI rat model. More prominent results will be obtained when it was use as a prophylactic measure. The optimal time of usage is 6 hours after endotoxin injection.