Research On The Role Of TLR2、TLR4in The Immunopathogenesis Of Chronic Pseudomonas Aeruginosa Lung Infection

Background and objectivePseudomonas aeruginosa is (PA) is a common opportunistic pathogen, often causinglung infections. Because of its strong ability to adapt to environment and timely changingvirulence, often makes the persistent difficulty to cure lung inflammation.Toll-likereceptors (TLRs) are a class of pathogen pattern recognition receptors (PRRs), recognizespathogen-associated molecular patterns (PAMPs),among of them TLR2and TLR4recognizes Gram-negative bacilli specific component lipopolysaccharide (LPS)，buttheir mechanism of immune injury in lung infections of chronic Pseudomonas aeruginosaare not clear. Long-term low-dose macrolide antibiotic can improve lung function andclinical symptoms in patients with chronic PA infection, but their immune mechanisms onToll-like receptors have not been explored. Therefore, in this article we will investigate therole of TLRs in the immunopathogenesis of chronic PA lung infection, and the relatedimmunomodulatory mechanism of low-dose azithromycin therapy.Methods:1. Balb/c mice were randomly divided into the airway inoculated with Pseudomonasaeruginosa (PA) agarose beads (PA group34) and sterile agarose beads (control group22).On day1、3、5、7、14after infection,six or four mice were sacrificed. Lung tissue cultures,BALF cell counts and lung pathology were observed, interleukin (interleukin, IL)-6andIL (interleukin, IL)-17in bronchoalveolar lavage fluid(BALF) were observed by ELISA.The mRNA expression of TLR2and TLR4were detected by real-time PCR. To investigate the function changes of toll like receptor2,4(TLR2,TLR4) in mice with chronicPseudomonas aeruginosa (PA) lung infection.2. Balb/c mice were inoculated with Pseudomonas agarose (PA) beads. Then sevendays after inoculation, the low-dose azithromycin (AZM) and saline treatment were givenrespectively. These mice were sacrificed on day7,10and14after modeling. IL-6and L-17levels in bronchoalveolar lavage fluid (BALF) were measured, the mRNA levels of TLR4in lung tissues were analysed, BALF cell counts, bacterial quantification and lung tissuehistology were performed. Mice in the control group were inoculated with sterile PAagarose and given saline from day7. To analysis the effect of azithromycin on TLR4expression and inflammatory factors in mice model of Pseudomonas aeruginosa (PA)pulmonary infection.Results:1. Compared with control group, IL-6, IL-17were up to the highest level of PA groupon day3significantly higher than control group, and both of them were still at high levelon day14. On day7the mRNA expression of TLR4reached a peak, while no significantchanges of TLR2existed two groups in each time.2.7days after inoculation, the airway inflammation, levels of IL-6and IL-17and themRNA levels of TLR4in PA group were significantly higher than that in control group.The IL-6、IL-17and mRNA levels of TLR4were lower in azithromycin group than insaline group on day10and14after inoculation. On day14after inoculation，the levelof IL-17in azithromycin group has down-regulated the same level of the control group.Conclusion:1.TLR4is closely related to the occurrence and development on chronicPseudomonas aeruginosa lung infection in mice，and the mechanism is that TLR4may becrucial for its development of immune and inflammatory injury.2.Low-dose azithromycin therapy modulated TLR4in airways, thereby contributingto the alleviation of airway inflammation in mice with Pseudomonas aeruginosa lunginfection.