Changes Of Airway Inflammation And AHR In Late RSV Infection By LPS Or Poly(I:C) Stimulation In Mice And Its Mechanism

PART Ⅰ CHANGES OF AIRWAY INFLAMMATION AND AHR IN LATE RSV INFECTION BY LPS OR POLY(I: C) STIMULATION IN MICEObjective: Infants of RSV infection is closely associated with the subsequent recurrent wheezing and asthma in children, but the risk factors and the specific mechanism is unclear. The present study was performed to investigate the changes of airway inflammation and AHR induced by LPS and Poly(I: C) stimulation following RSV infection in this process.Methods: The mice were randomly divided into six groups: control group, LPS group, RSV group, RSV + LPS group, Poly(I: C) group and RSV + Poly(I: C) group. The mice in control group, LPS group, RSV and RSV + group were intranasally administration with LPS 10μg / 50μl PBS or PBS 50μl on the 35 th day after inoculated 100μl RSV or PBS, intranasal day, a total of four times, and specimens were collected in the 24 hours after the last intranasal(day 42); Poly(I: C) group: the mice intranasallyadministration with Poly( I: C) 10μg / 50μl PBS on the 35 th day after inoculated 100μl PBS, specimen were collected on the third day; RSV +Poly( I: C) group: the mice intranasally administration with Poly( I: C)10μg / 50μl PBS on the 35 th day after inoculated 100μl RSV, specimen were collected on the third day. Total cell and individual cells in BALF were counted, H & E staining of lung pathology and mouse AHR was detected, IFN-γ, IL-4, IL-13, MMP-9 and MMP-12 levels in BALF was tested by ELISA assay.Results: Data showed that total cell number in BALF and AHR increased in RSV + LPS group compared with the control group, LPS group and RSV group(P <0.001), inflammatory cell infiltration in lung tissue enhanced significantly than other three groups(P<0.01), MMP-12 expression in BALF was also significantly higher than the other three groups(P<0.05), compared with RSV group, while, IL-4 and IL-13 was significantly reduced(P<0.01), MMP-9 and IFN-γ have no significant difference.RSV + Poly(I: C) mice airway inflammatory cell infiltration and the total number of airway hyperresponsiveness(AHR) were significantly higher with the control group, Poly(I: C) group and RSV group(P <0.05);lung tissue pathological damage RSV + Poly(I: C) group than the control group of mice and increase the RSV group(P <0.01), while RSV + Poly(I:C) in mice BALF MMP-9 levels rose significantly compared with the other three groups higher(P <0.05), and RSV + Poly(I: C) compared with the group significantly reduced RSV alone in BALF IL-4(P <0.01), MMP-9,IFN-γ and IL-13 reduced without Significant differences.Conclusion: LPS and Poly(I: C) in the latter part of RSV infection can cause increased airway inflammation and AHR, the overpression of MMP-9 and MMP-12 may contribute to the pathogenesis of airwayinflammation and AHR.PART Ⅱ AGGRAVATION OF AIRWAY INFLAMMATION AND AHR IN LATE RSV INFECTION BY LPS STIMULATION IN MICE VIA MMP-12Objective: MMP-12 is closely related to the airway inflammation and tissue remodeling. The first part of the study found that exposure to LPS after post-RSV infection in mice, airway inflammation and AHR were significantly increased, at the same time, MMP-12 expression in BALF was also dramatically increased. These experiments further investigate the effect of MMP-12 upon the airway inflammation and AHR induced by LPS exposure in convalescence of RSV infection.Methods: The mice were given oral MMP-12 inhibitor MMP408.Mice were randomly divided into control group, RSV group, LPS group,RSV + LPS group and RSV + LPS + MMP408 group. Cell Counter counts the total number of cells and individual cell in BALF, lung function in mice substituted by airway resistance values ?(Penh), lung tissue damage and fibrin deposition were evaluated by HE staining and MASSON staining in mice after MMP-12 inhibited.Results: MMP408 successfully inhibit the expression of MMP-12 in mouse lung tissue. Compared with the RSV + LPS group, airway inflammation and AHR was significantly decreased after MMP-12 being suppressed(P <0.001), particularly, the AHR can be restored to normal level; neutrophils in BALF decreased significantly in RSV + LPS +MMP408 group, there is a growing trend lymphocytes, but no significant difference. Compared with RSV + LPS group, the infiltration ofinflammatory cells was significantly reduced can be observed after MMP-12 is suppressed in the lung tissue sections(P <0.01), meanwhile pulmonary fibrin deposition also significantly reduced(P <0.01), both of them have not returned to control levels.Conclusion: airway inflammation induced by LPS exposure in convalescence of RSV infection can be partially alleviated via inhibition of MMP-12 expression, airway inflammation, and AHR even returned to normal levels, suggesting that MMP-12 at least part involved in the pathogenic process, and it may as a therapeutic targets for intervention of airway inflammation caused by exposure to LPS in the late stage of RSV infection.