长期应用尼古丁对恶唑酮诱导的实验性小鼠肠炎模型的影响及其机制探讨

Effect of long-term nicotine on oxazolone induced murine colitis model

目的 分析和探讨长期应用尼古丁对恶唑酮 (OXZ)诱导的实验性小鼠肠炎的影响以及肠黏膜和脾细胞生成细胞因子的类型。方法 采用BALB/c小鼠 ,经直肠注入OXZ制成炎症性肠病(IBD)模型 ;皮下注射尼古丁 0 .5mg·kg-1·d-1,连续 3周。将小鼠处死后 ,取出大肠及脾脏。病理组织学观察大肠黏膜改变。采用ELISA法测定大肠黏膜及脾细胞产生的干扰素γ(IFN γ)和白介素 4(IL 4)。采用流式细胞仪检测技术 (FACScan)分析脾细胞内细胞因子IFN γ和IL 4的表达。结果 尼古丁组的病理组织学计分显著低于OXZ组 (19.8比 2 3 .7,P <0 .0 2 )。与对照组比较 ,OXZ组大肠黏膜 [(185± 47)pg/ g比 (94± 14)pg/ g]和脾细胞生成的IL 4明显高于对照组 [(5 9± 12 )pg/ml比 (10± 1) pg/ml];与OXZ组比较 ,尼古丁组IL 4生成量更趋降低 [肠黏膜 :(15 7± 38) pg/ g比 (185± 47) pg/ g ,P <0 .0 5 ;脾细胞 :(5 0± 13) pg/ml比 (5 9± 12 ) pg/ml,P <0 .0 5 ]。OXZ组IFN γ/IL 4比值明显低于对照组 (黏膜 :1.10± 0 .37比 3 .40± 0 .35 ,P <0 .0 2 ;脾细胞 :2 .75± 1.90比 30 .70± 3 .90 ,P <0 .0 1) ,与尼古丁组差异无显著性 (黏膜 :1.10± 0 .37比 0 .78± 0 .14;脾细胞 :2 .75± 1.90比 0 .78± 0 .40 )。OXZ组 ,表达IL

Objective To investigate the long term effect of nicotine on oxazolone (OXZ) induced murine colitis models pathologically and analyse the cytokine profile produced by colonic mucosa and splenocytes. Methods BALB/c mice was used, colitis model was induced by intrarectal injection of oxazolone; nicotine (0.5 mg·kg -1 ·d -1 ) was injected subcutaneously for three weeks. After being sacrificed, the colon and spleen were removed. Colonic changes were examined pathologically. The IFN γ and IL4 produced by colonic mucosa and splenocytes was analyzed with ELISA. The intracellular IFN γ and IL 4 produced by splenocytes were tested by FACScan. Results In nicotine group, the histological score was significantly lower than that of OXZ group (19.8 vs 23.7, P <0.02). In the OXA group, overproduction of IL 4 by colonic mucosa [(185±47)pg/g vs (94±14)pg/g] and splenocytes [(59±12)pg/ml vs (10±1)pg/ml] was seen compared with controls. In nicotine group, a lower level of IL 4 production by colonic mucosa [(157±38)pg/g vs (185±47)pg/g, P <0.05] and splenocytes [(50±13)pg/ml vs (59±12)pg/ml, P <0.05] was noticed compared with OXZ group. The ratio of IFN γ/IL 4 was lower in OXZ group compared with controls (mucosa: 1.10±0.37 vs 3.40±0.35, P<0.02; splenocytes: 2.75±1.90 vs 30.70±3.90, P <0.01 respectively), and a further reduced level was noticed in nicotine group compared with OXZ group (mucosa: 1.10 ±0.37 vs 0.78±0.14; splenocytes: 2.75±1.90 vs 0.78±0.40 respectively). The numbers of IL 4 producing CD + 4 cells in splenocytes was 13.6 fold higher than that of IFN γ producing CD + 4 cells. Only 32% of IL 4 and 39% IFN γ producing CD + 4 cells were detected in nicotine group compared with OXZ group. Conclusion OXZ induced colitis is a Th2 type dominant (IL 4 overproduction) murine model; Long term nicotine administration ameliorate OXZ induced colitis by suppression of increased IL4.