The Effect And Mechanism Of Sevoflurane On Airway Inflammation And Remodeling In Asthmatic Mouse

1. Background and objectiveAsthma is a complex and chronic inflammatory disease of the lungs characterized by inflammation, airway hyper‐responsiveness, and structural remodeling. In recent years, great progress has been made in the understanding of pathogenesis related to asthma。The incidence of asthma is mostly related to two important factors, that are genetic susceptibility and environmental influence. Although great advances have been made in both the therapies and also in our understanding of its pathophysiology, the morbidity and mortality of asthma are still rising, as the environmental pollution aggravating. Meanwhile, along with the increased incidence of asthma, asthmatic patients in the proportion of patients undergoing operation also increased accordingly.Sevoflurane, a commonly used inhalational anesthetic, has been demonstrated to be useful in lessening airway responsiveness and bronchodilation in patients with asthma. Recent years, it was reported, both in domestic and foreign countries,that sevoflurane can be successfully used to treat asthmatic patients, which are refractory to routine therapeutic drug, and especially useful to infants and young children with severe asthma and persistent state. A lot of clinical researches and animal experiments show that sevoflurane can relax bronchial smooth muscle, relieve bronchodilation, and also inhibit airway hyper‐responsiveness. But, the mechanism is still unclear. Airway hyper‐responsiveness and continuous state of asthma are closely related to airway inflammation and airway remodeling.The present research is divided into two parts, and established to investigate the effect of sevoflurane on airway inflammation and airway remodeling respectively, and also to explore the underling mechanism preliminarily, using OVA sensitized and challenged acute / chronic asthmatic mice.2.ObjectivesIn the following studies, we employed OVA induced(sensitization and challenge) acute / chronic asthmatic mouse model, and investigated the effect of repeated inhalation of sevoflurane on airway inflammation and airway remodeling of asthma.3. Methods3.1 Establishment of animal modelFemale C57BL/6 mice were randomly assigned to the control group treated with saline(Control); allergic group sensitized and challenged with OVA(OVA); allergic mice treated with 3% sevoflurane in oxygen–air mixture(OVASVF); allergic mice treated with oxygen–air mixture(OVAO2). Mice were sensitized and challenged with OVA.3.2 Treatments with sevofluraneMice from group OVASVF were exposed to 3% sevoflurane for 1 hour before every challenge.3.3 Histopathology examinationTo observe the effect of sevoflurane on lung tissue pathology of asthmatic mouse, including airway inflammation and structural remodeling.3.4 Molecular biological detectionThe levels of BALF IL‐10, TNF‐α and HMGB1 and serum OVA‐specific IgE were measured by ELISA using specific kits.The paraffin‐embedded tissue sections were stained with hematoxylin and eosin(H&E) 、 periodic acid‐Schiff(PAS)、or Sirius red(SR) staining.Expression levels of tissue protein such as HMGB1、 TLR2、α‐SMA、TGF‐β and VEGF were detected using Western blotting analyses or immunohistochemistry staining.3.5 Statistical analysisData were expressed as means ± standard error of the mean(SEM). The difference among the groups was analyzed statistically by analysis of variance(ANOVA) and post hoc Bonferroni test. A P value of < 0.05 was considered statistically significant.4. Results4.1 Effect of repeated inhalation of sevoflurane on airway inflammation in acute asthma modelIn acute asthmatic mouse model,compared with the healthy controls, the numbers of differential cells and total cells increased, the levels of TNF‐α increased, the ratios of IL‐10 to TNF‐α dcreased, many inflammatory infiltrated in the peribronchial, perivascular and parenchymal regions of the lung, and the intensity of PAS staining increased in allergic mice; compared with the OVA group, the numbers of differential cells and total cells and the level of TNF‐α decreased, the ratios of IL‐10 to TNF‐α increased, the intensity of PAS staining decreased in OVASVF group, but not in the OVAO2 group.The levels of HMGB1 in BALF and the lung tissues and the levels of TLR2 in lung tissues were similar to those of the controls, but were significantly lower than that of the OVA and OVAO2 groups of mice(P<0.01).4.2 Effect of repeated inhalation of sevoflurane on airway remodeling in chronic asthma modelIn chronic asthmatic mouse model, compared with the healthy controls, much more inflammatory infiltrated in the peribronchial, perivascular and parenchymal regions of the lung, and significantly smooth muscle hyperplasia、collagen deposition and fiber hyperplasia in the lung tissues from the OVA group; compared with the OVA group, inflammatory infiltration 、smooth muscle hyperplasia、collagen deposition and fiber hyperplasia were sifnificantly decreased in OVASVF group, bur not in the OVAO2 group.Compared with the healthy controls,the levels of protein expression of α‐SMA、TGF‐β and VEGF in lung tissues significantly increased in the OVA group; compared with the OVA group, the levels of the above proteins were significantly decreased in OVASVF group, bur not in the OVAO2 group.5. Conclusions5.1Sevoflurane can inhibit airway inflammation in acute asthmatic mouse model, which may be related to the down regulation of HMGB1 and TLR2 expression.5.2Sevoflurane can inhibit airway remodeling in chronic asthmatic mouse model, which may be related to the down regulation of TGF‐β and VEGF in lung tissue.