Study On Endotoxin-induced Acute Lung Injury And The Protective Effect Of Chlorohemin In Rabbits

Object: (1) Endotoxin(ET) replicated the acute lung injury model of rabbit, so as to observe the pathophysiology changes in rabbits and investigate the mechanism of ET-induced acute lung injury.(2) The protective effect of Chlorohemin was studied in acute lung injury(ALI).Methods: Twenty four male New-Zealand rabbits were randomly assigned to three groups. Group A (control group): saline (2ml/kg) was injected through the jugular vein. Group B (ET-treated group): ALI models were replicated with intravascular endotoxin(ET) injection (700μg /kg). Group C (treatment with Chlorohemin group): intraperitoneal Chlorohemin was injected before experiment (26mg/kg, 2 /d, 2days) , the rest operation was the same with ET-treated group. The cervical intravascular saline (1ml/15min) was given during the experiment. The parameters were measured as follows:1. The basic vital signs including breath rate, heart rate , blood pressure were recorded and the arterial blood gas, oxygenation index were measured at 0 h, 0.5 h, 1 h, 2 h, 4 h.2. The neutrophilelastase(NE) concentration, Malondialdehyde(MDA) content and superoxide dismutase(SOD) activity were analyzed in blood serum at 0 h, 0.5 h, 1 h, 2 h, 4 h in three groups.3. The dry-to-wet lung weight ratio was measured after animals were sacrificed.4. The pathological changes with lung tissue was examined.5. The expression of heme oxygenase (density mean) was observed through immunohistochemical method and analyzed by Imagepro-plus 6.0 software.Results:1. Respiration: the breath was stable in group A during the experiment. After injecting ET, tachypnea appeared in group B, it was the most obvious at 0.5 h and gradually decreased later, which was still higher than normal. The tendency of respiratory change in group C was similar with that in group B. Heart rate: the heart rate was stable before and after the experiment in group A. After injecting ET, heart rate was obviously increasing and then gradually decreased to normal in group B. Blood pressure: the blood pressure in group A was above 80mmHg during the experiment. At 0.5h after injecting ET, the blood pressure in group B was definitely lower than that in group A (P<0.01) .The tendency of blood pressure in group C was descent.2. The arterial blood gas: After ET infusion, the partial pressure of oxygen and oxygenation index were decreased in group B, they degrade to 54.65mmHg and 273.250 mmHg (P<0.01,compared with group A) at 0.5h, meeting the standard of ALI and both index anastated later. The partial pressure of oxygen and oxygenation index decreased too in group C, but it did not get to the standard and definitely was higher than that in group B (P<0.01) .The partial pressure of carbon dioxide was degrading during the experiment both in group B and C.3. SOD: After ET infusion, serum SOD showed a decreasing tendency in both group B and C. Compared with group A, SOD was markedly lower at 2h, 4h (P<0.0.1) in group B. While SOD was markedly higher than that in group B at 2h, 4h in group C. MDA: After ET infusion, MDA was gradually increasing in both group B and C. Compared with group A, MDA in group B was markedly higher at 2h, 4h (P<0.01). MDA was lower than that in group B at 2h, 4h in group C, but still higher than group A.4. Serum NE: After infusion of ET, the serum NE increased gradually, it was absolutely higher compared with group A and C at lh,2h,4h(P <0.01).There is no difference between group A and C.5. The dry-to-wet lung weight ratio was significantly lower (P<0.01) in group B, there is no difference between group A and C.6. The structure of lung tissue in group A is normal. In group B, the structure of lung tissue was damaged. We could see alveolar wall thicken, alveolar septum widen, leukocyte infiltrated, microcirculation obstacle, microthrombosis and leukocyte gathered in interstitial. Pulmonary edema, alveolar hemorrhage, partial pulmonary closure and partial emphysema compensably also could been seen. The degree of these pathologic changes in group C were slight. 7. The expression of HO-1: The protein of HO-1 expressed on the trachea wall, alveolar epithelium, the vascular endothelial cell, vascular membrane and endochylema of inflammatory cells. The masculine buffy granulation of HO-1 protein of lung tissue in group A were seen by chance, the expression of HO-1 protein enhanced notably in group C, the optical density were markedly higher than other two groups (P<0.01). The optical density had no difference between group A and B.Conclusion:1. ALI models can be replicated with intravascular endotoxin(ET) injection (700(μg/kg).2. Serum MDA increased and SOD decreased in ALI by ET, oxidative stress enhanced in lung tissue.3. Serum NE heightened in ALI by ET. Pulmonary edema emerged because of destroyed air-blood barrier and increased vascular permeability by ET.4. Chlorohemin could upregulate HO-1 protein, it could antagnise oxidative stress and elastas to protect lung tissue.