褪黑素对哮喘大鼠核因子-κB表达的影响及抗炎作用

Effect of melatonin on the expression of nuclear factor-kappa B and airway inflammation in asthmatic rats

目的 探讨褪黑素 (MT)对支气管哮喘 (BA)大鼠模型肺组织核因子 κB(NF κB)表达的影响及其抗炎作用。方法 将 2 4只体重 12 0～ 170克的健康雄性SD大鼠随机分为 3组 ,每组 8只 :(1)哮喘组 :用 10 %鸡卵白蛋白 (OVA) 1ml、氢氧化铝 10 0mg无菌腹腔注入 ,2周后用 1%OVA超声雾化每天吸入激发 2 0min ,连续激发 1周致其哮喘发作 ,在每次激发前 30min腹腔注入生理盐水(NS) 1m/只。 (2 )MT组 :诱喘方法同哮喘组 ,在每次激发前 30分钟腹腔注入MT 10mg/kg。 (3)对照组 :以NS代替诱喘剂和腹腔注入药。每组分别于最后一次激发后 6h测定气道反应性 ,随后处死大鼠 ,并行支气管肺泡灌洗液 (BALF)中细胞计数、分类 ;用硝酸还原酶法测定BALF中一氧化氮(NO)含量 ,以及肺组织中诱导型一氧化氮合酶 (iNOS)和结构型一氧化氮合酶 (cNOS)活性 ;用免疫组织化学染色法观察气道上皮细胞NF κB的表达。结果 (1)MT组大鼠气道反应性及BALF中淋巴细胞、嗜酸性粒细胞数明显低于哮喘组 (P <0 .0 1) ;(2 )MT组BALF中NO含量、肺组织中iNOS低于哮喘组 (P <0 .0 1) ,且等级相关分析显示哮喘组BALF中NO含量与肺组织iNOS高度正相关 (r =0 .83P <0 .0 1) ;(3)免疫组织化学染色显示哮喘组、MT组、对照组NF

Objective Nuclear factor-kappa B (NF-κB) is a critical transcription factor governing the expression of many cytokines that are involved in the pathogenesis of inflammatory diseases, such as asthma and rheumatoid arthritis. Melatonin (MT), a relatively safe and potent antioxidant which has shown efficacy in several chronic inflammatory models, may inhibit the expression of NF-κB and therefore might have a therapeutic use in asthma. This study aimed at observing the effect of MT on the expression of NF-κB and airway inflammation in a rat model of bronchial asthma. Methods Twenty-four male Sprague-Dawley (SD) rats weighing 120 g to 170 g were randomly divided into three experimental groups (8 in each): (1) Asthmatic group: Rats were immunized on day 1 by intraperitoneal injection of 100 mg ovalbumin (OVA) in 1 ml of saline with 100 mg of alu minum hydroxide. From day 15 the animals were challenged with aerosolized OVA (1% in saline) for 20 minutes per day for 7 consecutive days. (2) MT group: OVA-sensitized rats were injected intraperitoneally with 10 mg/kg MT 30 minutes before each OVA challenge. (3) Control group: OVA for inhalation and MT for intraperitoneal injection was replaced with normal saline (NS). Airway responsiveness to aerosolized acetylcholine of 24 rats was detected six hours after the last challenge. Then the rats were lavaged and total and differentiated leukocytes counts in bronchoalveolar lavage fluid (BALF) were performed after staining with Wright-Giemsa staining. At the same time, levels of nitric oxide (NO) in BALF, inducible nitric oxide synthesis (iNOS) and constitute nitric oxide synthesis (cNOS) in the lung tissues were assessed with the use of nitrate reductase and chemical colorimetry, respectively. The expression of NF-κB in the lung tissues was observed by means of immunohistochemical staining. Results (1)After OVA challenge, there was a significant decrease in airway responsiveness, lymphocytes and eosinophils in BALF in MT group compared with asthmatic group ( P <0.01 respectively);(2) There was a significant decrease in amounts of NO -_2/ NO -_3 in the BALF and levels of iNOS in the lung tissues in MT group comparing with asthmatic group ( P <0.01 respectively);and the levels of iNOS in the lung tissues was correlated positively with NO -_2/ NO -_3 in the BALF ( P <0.01), but there were no significant differences in activity of cNOS in any of the groups analyzed.(3) There was a significant increase in expression of NF-κB in lung tissues in asthmatic group compared with the other groups ( P <0.01), and so was in MT group compared with control group ( P <0.05). Conclusions MT could partially inhibit the expression of NF-κB and down-regulate the activity of iNOS in lung tissue, decrease the production of NO in BALF. These data suggest that the inhibitory effect of MT probably play a role in decreasing airway hyperresponsiveness and airway inflammation of asthmatic rats model.