| In modern society road traffic injury(RTI) has been ranking one of the major entities which threaten the health of residents. According to statistics from January to June in 2004, 211,572 victims were wounded by road traffic injury nationwide, which directly resulted in property loss up to 1,300 millions. About 55 per cent of RTI are associated to thoracic wounds, of these severe blunt thoracic wounds 10 percent to 18 percent are more likely to develop into secondary ALI or ARDS. Yet there is no way that has be clinically confirmed effectiveness for ARDS, even though we have abtained a great body of understanding in pathophysiology of ARDS.The mortality associated to ARDS is still up to 35%-65%. Therefore nowdays it is very important to study ALI and ARDS experimentally and clinically.Lung is the target organ of thoracic trauma. In the formation of ARDS the lung is also the first and the worst organ which was damaged. In the early stage of inflammantion resulting from thoracic trauma lung is the first and main place in which PMN is detained. Being the important inflammantory cells in the nonspecific defensing response and the important ingredents in the development of traumatic ARDS, PMN release excessive oxygen free radical and proteolytic enzyme if it was locally over activation and delayedly eliminated. Which consequdentlly would worsen the lung damage. Apoptosis is the safe, prompt and effective non-inflammantory way to eliminate actived PMN. Not only Apoptotic is PMN more likely to be identified and eliminated by macrophages, but its functions of degranulation andphagocytosis attenuated. Experiments demonstrate that the macrophages which has swallowed PMN excrete pre-inflammatory mediators such as transforming growth factor and prostacyclin. Published thesis suggests that in the formation of ARDS the apoptosis of PMN is depressed, however the study on its mechanism is few. This study was aimed to treat large amounts of patients suffering from ARDS secondary to RTI, but without confirmed -effective ways. In the present study we focused on PMN which is the crucial component in the development of ARDS, and explore the alterations of the apoptosis of PMN in ARDS as well as its pathogenese. Which might lay the theritical foundations for the prevention and treatment of ARDS through promoting the apoptosis of PMN by interventions.Part 1 The Establishment of Animal Model of Traumatic ARDS in RabbitsAIM To observe the changes of lung function following different impacting-variables in rabbits, aiming to establish animal model of traumatic ARDS.METHODS 65 rabbits were randomly assigned to Control group and Experimental group, experimental group was divided into subgroups according to impacting velocity: Low velocity groups (Lv, 11.06 ± 0.04 m/s), Moderate velocity groups (Mv, 16.88 ± 0.02 m/s), High velocity groups (Hv, 20.29 ± 0.03 m/s). Rabbits in the control group were sampled the lungs to determine the ratio of dry/wet and the content of total protein in Bronchoalveolar Lavage Fluid(BALF) without impacted on the right chest. The subjects in the other three groups were impacted on the right chest with different driving-velocity. Arterial blood gas was monitored before and after injury 4h, 12h, 24h, 48h, 72h respectively. The lungs were harvested toevaluate the ratio of dry/wet lung, the content of protein in BALF and pathological observation. Chest X-ray was performed for each animal in experimental groups. Expression of TNF- α was also observed in each group by immunohischemical methods.RESULTS In Lv group, 2 animals died and 1 animal represented with symptoms of ARDS. Oxygenation Index (OI) of arterial blood in 95 percent animals varied from 274mmHg to 377mmHg. Only were slight pathological changes seen. In Mv group, three animals died and five animals represented with symptoms of ARDS. OI in 75 percent of animals were more than 200mmHg. The changes of content of total protein in BALF and pathological changes in the lungs were remarkably when compared with that of Lv group, but the alteration of these variables were more slightly when compared with that of Hv group. In Hv group, eight animals were dead and 12 had ARDS symptoms. OI presented a trend of progressive reduction after injury, at 24h the average of OI drop to below 191.3mmHg, and at 72h it was 153.81mmHg. The ratio of dry/wet lung at each time-point after injury was much lower than that of control group. The content of total protein in BALF was also higher than that of Cg at each time point. Chest radiography showed diffuse immersion on bilateral lungs. Pathological observation showed congestion and edema were seen in entire right lung, as well as in some regions of the left lung, the structure of pulmonary alveolar were destroyed, large amounts of red blood cell immersed in the pulmonary alveolar, after 48h some lysed. Severe hemorrhage and edema in bilateral lungs early post-trauma. In the end stage severe exudation of inflammatory cells could be seen and typical hyaline membranes were formed. Positive expressions of TNF- α were seen in lung for three groups, particularly in HE group the result was more significant thanin the other two groups.CONCULUSION After impacted on the chest[impacting-parameters: impacting-velocity ( 20.29 ± 0.03 ) m/s, ratio of compression 20%, impacting-weight 5.7Kg], rabbits could develop into a series of clinical representations, which is severe respiratory dysfunction and could be repeated well. These representations; were highly similarities to that of Acute Respiratory Distress Syndrome in human being.Part II The Apoptosis of PMN, the Expression of COX-2 and Lung Injury following Thoracic Injury caused by High-velocity Impacted in Rabbits.Aim To explore the relation of apoptosis of PMN, the expression of Cox-2 and lung injuries following chest impacted injuries in rabbits. Methods The objects were assigned to control group and experimental group. Five rabbits were in control group and 25 rabbits were in experimental group. The average weight was (2.35 ± 0.26) kg. The rabbits in experimental group were stroke on the right thoracic wall by synchronous cardiorespiratory-triggered impactor with compression 20%, weight 5.7Kg, area 3.14cm~2 and velocity (20.29±0.03) m/s. The objects underwent similar interventions but not being stroke. At 4h, 12h, 24h, 48h and 72h after wounded five rabbits in experimental group were randomly killed. Bronchoalveolar lavage fluid and lung were sampled to evaluate the apoptosis of PMN and histological observation. The methods to determine the apoptosis were Annexin V-FITC and PI staining and flow cytometry. Chromatometry and Follin-Lowry were employed to the determination of content of total protein and albumin, the expression of COX-2 in lung, the concentration of PGE2 in Bronchoalveolar Lavage Fluid(BALF) and the index of pulmonarypermeability were evaluated. The ratio of dry/wet lung weight and respiratory burst were also evaluated in this study .Results The total number of rabbits were included in this study were 30, eventually 30 rabbits entered the results analyzing. The rate of apoptotic PMN in BALF gradually decreased as time prolonged after thoracic impacting injury(82.3 ± 12.6 vs 65.5±12.5, P<0.05). this changes was correlation with the severity of lung injury(r= -0.79 or r= 0.91). The rate of dead PMN presented a transit elevation followed by a tendency of reduction (8.1 ± 3.2 vs 21.8±4.1, 13.0 ± 3.1, P<0.05) .A persisting increase in activated PMN was seen post-trauma (9.6±1.4 vs 19.5 ± 3.6) . The ratio of dry/wet lung weight remarkably declined after injury (0.48 ± 0.07 vs 0.21 ±0.03, P<0.01) . The index of pulmonary permeability statistically increased (0.6 ± 0.2 vs 1.7 ± 0.6, P<0.01). The expression of COX-2 in lung soared after injury(5.8 ± 2.5 vs 95.7± 12.4, P<0.001), and the concentration of PGE2 in BALF were much high than that of pre-injury(2.6±1.7 vs 8.9 ± 3.1, PO.01). The pathological observations showed a great body of inflammatory cells infiltrated in the alveoli and interstitium. The pulmonary alveolar walls swelled and thickened. The alveolar structure was destroyed and typical hyaline membranes were formed.Conclusion There exist a correlation of the depression of PMN's apoptosis and the respiratory damages following thoracic trauma. The depression of PMN's apoptosis might be involved in the developing of lung injury after chest impacted injury. The expression of PMN's apoptosis might be involved in the formation of traumatic ARDS. The augmentation in the expression of COX-2 may regulate the depression of PMN's apoptosis. Part III Inhabitor of Cyclooxygenase-2 Regulating the Apoptosis of...
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