Effect Of Dexamethasone On Expressions Of NF-κB, MMP-9 And TIMP-1 In Asthmatic Rats

Part oneRat model of asthmaPurpose: To build stable and reproductive model of asthmatic rats. Methods: Male Wistar rats (n=18) were randomly divided into asthmatic group(n=6), dexamethasone group(n=6) and control group(n=6). All rats except control rats were sensitized with injections of 100mg OVA and 100mg aluminum hydroxide in lml saline intraperitoneally on the first day of the study(day 1). Rats were sensitized again on days 8.From day 15 to day 43(4 weeks),rats were challenged per day, each challenge being 20 min in a chamber, with free-breathing rats being exposed to 1%OVA aerosol mist produced by a Nebulizer. The rats of dexamethasone group were injected with dexamethasone(2mg/kg)intraperitoneally before each challenge . The rats of control group were sensitized and challenged with equal amounts of saline instead of OVA.The rats were anaesthetized with an intraperitoneal administration of 20% urethane solutions (2g/kg) and were placed in a supine position. After the trachea was cannulated with a 19-gauge blunt metal needle and the cervical vein was punctured , the animals were artificially ventilated by using an animal ventilator and a succession of ascending concentration of Acetylcholine in the range of10-320ug/kg was injected through the cervical vein. The airway resistances during expiratory phase were measured before and after the injections of Acetylcholine.Bronchial responsiveness was assessed by the variation of airway resistances during expiratory phase. Results: There was no difference in airway resistances during expiratory phase among the three groups.After the injection of saline, all rats had few changes in airway resistances. After the injection of 10μg/kg 20μg/kg 40μg/kg Acetylcholine, airway resistances of all rats were not doubled(compared to the airway resistances After the injection of saline, the ratio <1), After the injection of 80ug/kg Acetylcholine, airway resistances of asthmatic rats were significantly increased (the ratio>2),while there were no same reactions in dexamethasone group and control group. After the injection of 160ug/kg Acetylcholine, airway resistances of asthmatic and dexamethasone rats were significantly increased (the ratio>2),while there were no same reactions in control group.After the injection of 320ug/kg Acetylcholine, airway resistances of all rats were significantly increased especially in asthmatic group. Conclusions: Asthmatic rats were successfully established and could be used in further study. Part two Relationship between the expression of NF-kB and MMP-9 inasthmatic ratsPurpose : To observe the relationship between the activity of nuclearfactor-KB( NF-kB) and the expression of metalloproteinase-9 (MMP-9) inthe lung of asthmatic rats.Methods: Asthmatic model of rats was established.All rats wereanesthetized by 20% urethane solutions (2g/kg, intraperitoneally).Thelung was excised to collect samples for immunohistochemistry after theblood was bled. The NF-kB activity and the protein expressions ofMMP-9 were examined by immunohistochemical analysis usingpolyclonal antibodies. The pathologic changes and expression of NF-kBand MMP-9 in rats' lung were studied using light microscope andcomputer image analysis .Results: The NF-kB activity and the protein expressions of MMP-9in bronchial epithlum in asthmatic group were higher than those incontrol group(P <0.01) and dexamethasone group(P <0.05). There was asignificantly positive correlation between MMP-9 and NF-kB.Conclusions: NF-kB may partly upregulate the expression of MMP-9 inthe lung of asthmatic rats.Part threeEffect of dexamethasone on expressions of NF-kB, MMP-9 and TIMP-1 in asthmatic ratsPurpose: To observe the relationship among the expressions of nuclear factor-icB( NF-kB), metalloproteinase-9 (MMP-9)and tissue inhibitor of metalloproteinase -1 (TIMP-1 )and the effects of dexamethasone on the lung of asthmatic rats.Methods: On the basis of the model of asthma, the NF-kB activity and the protein expressions of MMP-9 and TIMP-1 were examined...