| ObjectiveTo establish rat asthma model;to study the effect of HO-1 on allergic airway inflammation in animal model; to observe the relationship between HO-1 and IL-10 in asthma; to explore the mechanism of HO-1 in allergic airway inflammation.MethodsMale Sprague-Dawley(SD)rats (4 weeks) were given an intraperitoneal injection of 1 ml 10% OVA complexed with 10% aluminum hydroxide gel and the killed Bacillus pertussis on days 0. Two weeks after the sensitization, the rats inhaled 2% OVA to sensitize their airways. Forty male SD rats were randomly divided equally into five groups. The rats of each group received the HO-1 inductor hemin (Porphyrin Products),an inhibitor of HO activity zinc protoporphyrin IX (ZnPP) or Dexamethasone (DXM) respectively, given intraperitoneally before the challenges. All the rats of the different groups were killed 24 h after the last challenge for assessment. Bronchial alveolar lavage fluid (BALF) was acquired to count the number of cells and the percentage of eosinophil.IL-10 level in BALF supernatant was determined by an ELISA test. The examination of histology, and immunohistochemistry was also performed to evaluate the airway inflammation and the expression of HO-1. The correlation between HO-1 and IL-10 was also performed.Results1. The evaluation of asthma model: The rats treated by OVA appeared visible respiratory distress signs (polypnea, contraction of accessory respiratory muscles, and cyanose).Compared with control rats, the rats treated by OVA appeared typical airway inflammation and their percentage of eosinophil was increased obviously(P<0.01),which indicated that the rat asthma model was established successfully. There was less appearance in group hemin and group DXM rats compared with OVA-sensitized/challenged rats. However, there was no difference between group OVA and group ZnPP.2. The detection of pathologic histology: Airway inflammation responses including eosinophil infiltration were significantly increased in OVA, hemin, ZnPP, or DXM -treated rats as compared with control rat. But these parameters were significantly lower in group hemin and group DXM than those in group OVA and group ZnPP.3. The assessment of cytological in bronchoalveolar lavage fluids(BALF) suggested that the number of cells and percentage of eosinophil in BALF of rats treated by hemin or DXM were significantly less than those in group OVA and group ZnPP rats (P<0.05). However, there was no significant difference between group OVA and group ZnPP(P>0.05).There was no significant difference between group hemin and group DXM, too(P>0.05). 4. Immunohistochemistry showed that the expression of HO-1 was up-regulated in OVA-treated rat compared with group control, administration of hemin or DXM could significantly increase the expression of HO-1 as compared with group OVA(P<0.01). However, there was no significant difference between group ZnPP and group OVA (P>0.05). There was no significant difference between group hemin and group DXM, too(P>0.05). HO-1 was mainly expressed in macrophage, airway epithelial cells and smooth muscle cells.5. The level of interleukin 10 (IL-10) in BALF of OVA treated rat was obviously decreased compared with control rats (P<0.05), but enhanced significantly after rat treated by hemin or DXM as compared with group OVA (P<0.01) .However, the expression of IL-10 in group ZnPP had no significant difference compared with group OVA (P>0.05).Moreover, there was no significant difference between group hemin and group DXM, too(P>0.05).6. The expression trend of HO-1 was similar with that of IL-10 in different groups. The related coefficient of the Spearman was r=0.718, P<0.01(2-tailed), which showed that the correlation was significant. It suggested that the level of HO-1 and IL-10 had high positive linear correlation.Conclusion1. OVA complexed with immunoadjuvant aluminum hydroxide gel and the killed Bacillus pertussis could successfully establish an asthma model of rat.2. The expression of HO-1 protein increased significantly within the lung tissue of asthma.3. HO-1 was mainly expressed in macrophage and airway epithelial cells.4. Either HO-1 inductor hemin or DXM could augment the expression of HO-1.5. HO-1 had significant role of anti-inflammation in animal model.6. The anti-inflammation role of hemin was similar with that of DXM.7. There existed positive correlation between the expression of HO-1 and the level of anti-inflammatory cytokine IL-10.
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