SARS冠状病毒N蛋白致大鼠肺部炎症及糖皮质激素对其的作用

目的探讨严重急性呼吸综合征(SARS)冠状病毒N蛋白所致大鼠肺部炎症反应及糖皮质激素(以下简称激素)对其的调节作用。方法24只SD大鼠随机分为4组,每组6只;A组大鼠气管内滴入无菌生理盐水0.2ml,B组(6h)、C组(24h)大鼠气管内滴入SARS病毒N蛋白溶液0.2ml,D组大鼠气管内滴入SARS病毒N蛋白溶液0.2ml的同时腹腔内注射10mg/kg地塞米松。测4组大鼠外周血、支气管肺泡灌洗液(BALF)中WBC总数及分类;测4组大鼠肺组织湿/干(W/D)比值;观察4组大鼠肺组织病理学变化;ELISA测4组大鼠血清及BALF中IL6、IL10、转化生长因子(TGF)β1水平。结果(1)外周血淋巴细胞比例C组较A组低(P<0.05),D组较A、C组均低(P值均小于0.01);D组WBC总数较A、C组均低(P<0.01)。BALF中WBC总数C组较A组高(P<0.05),D组较C组低(P<0.05);B、C组BALF中肺泡巨噬细胞占98%～99%。(2)肺脏W/D比值B、C组较A组高(P<0.05),D组较C组低(P<0.01)。(3)肺组织病理学变化:B、C组大鼠肺泡间隔明显增宽,有较多的炎性细胞渗出,包括中性粒细胞、淋巴细胞、单核细胞、成纤维细胞等,血管充血、淤血,有的支气管腔内有炎性细胞渗出,C组变化较B组无明显加重;D组大鼠肺组织炎性反应较B、C组减轻,肺泡间隔变薄,炎性细胞渗出减少。(4)血清及BALF中IL6、IL10、TGFβ1水平B组较A组高(P<0.01),C组进一步升高(P<0.01),D组较C组低(P<0.01)。结论SARS冠状病毒N蛋白具有致病性,能够引起大鼠肺部炎症反应和(或)急性肺损伤,肺损伤与促炎性细胞因子、抗炎性细胞因子的升高及失衡有关;激素可有效地减轻SARS冠状病毒N蛋白所致的肺部炎症反应。

A study of pulmonary inflammatory reaction induced by N-protein of SARS-CoV in rat models and effects of glucocorticoids on it

OBJECTIVE: To study the pulmonary inflammatory reaction induced by N-protein of SARS-CoV in rat models and the effects of glucocorticoids on the inflammatory reaction. METHODS: The pulmonary inflammatory reaction in rat models were induced by intratracheal instillation of N-protein of SARS-CoV with a dose of 0.2 mg/kg. The rats were randomly divided into four groups: normal saline control group (Nc group), N-protein group 1 (P1 group, 6 h), N-protein group 2 (P2 group, 24 h), and N-protein + dexamethasone group (P + D group, dexamethasone 10 mg/kg intraperitoneally). The blood samples, bronchial alveolar lavage fluid (BALF) and lung tissue were collected after challenge. The cytological and histopathologic changes of lung tissues were observed and the wet/dry ratios (W/D) of lung tissue were determined. The interleukin (IL)-6, IL-10 and transforming growth factor-beta1 (TGF-beta1) of serum and BALF were measured by ELISA. RESULTS: (1) Compared with the percentage of peripheral blood lymphocytes in Nc group (68.42 +/- 13.07)%], that in P2 group (50.50 +/- 14.36)%] was significantly decreased (P < 0.05); compared with Nc group and P2 group, that in P + D group was furthermore significantly decreased (P < 0.01). Compared with the total WBC of peripheral blood in Nc group (5.86 +/- 2.25) x 10(9)] and P2 group (4.83 +/- 1.49) x 10(9)], that in P + D group (1.96 +/- 1.30) x 10(9)] was significantly decreased (P < 0.01). (2) Compared with the total WBC of BALF in Nc group (95 +/- 29) x 10(7)], that in P2 group (160 +/- 60) x 10(7)] was significantly increased (P < 0.05); but compared with P2 group, that in P + D group (62 +/- 23) x 10(7)] was significantly decreased (P < 0.05). Analysis of BALF differential cell counts showed that the majority of cells were alveolar macrophages in all groups. (3) The W/D ratios of lung tissue in both P1 and P2 group (5.18 +/- 0.29) and (5.19 +/- 0.34), respectively] after N-protein challenge were significantly increased than that in Nc groups (4.77 +/- 0.27), P < 0.05]; the W/D ratio in P + D group (4.70 +/- 0.18) was significantly decreased than that in P2 group (P < 0.01). (4) Compared with Nc group, the levels of IL-6, IL-10, TGF-beta1 in both serum and BALF of P1 group were significantly increased (P < 0.01), and the levels of these cytokines in P2 group were significantly higher than those in P1 group (P < 0.01), but significantly lower in P + D group compared with P2 group (P < 0.01). CONCLUSIONS: The N-protein of SARS-CoV had pathogenicity and could induce obvious pulmonary inflammatory reaction and acute lung injury, which were related to the increase and imbalance of pro-inflammatory and anti-inflammatory cytokines. Glucocorticoids could effectively alleviate the pulmonary inflammatory reaction induced by N-protein of SARS-CoV.