The Activation Of NOD1-NF-κB Signal Pathway In Lungs Of Mice Infected With Aspergillus Fumigatus

Background: Aspergillus fumigates(Af) is a ubiquitous and saprophytic fungi in the natural environment, which is a kind of important opportunist pathogen. It usually causes invasive pulmonary aspergillosis(IPA) in the immunosuppressed patients with mortality of 90%. The specific and effective methods for early diagnosis and therapy of IPA are urgently needed. The pathogenesis of IPA could be elucidated through investigating the interaction between Af with host immune system, which would provide the evidence to develop better methods for diagnosis and treatment of IPA. Innate immunity is the first barrier to fight Af, and it has been confirmed that innate immune response mediated by host cellular pattern recognition receptor(PRR) such as TLR2,TLR4 and Dectin-1 play important roles in the elimination of invaded Af. Recently, NOD1, a best studied molecule of NODs--- a newly found plasma-receptors family has been verified to play an important role in protecting early infection of bacteria. So far, its role against fungi infection is still not clear. It has been reported that NOD1 is expressed in respiratory epithelial cells and lung tissues. Its expression could be upregulated significantly by the challenge of bacteria in lungs. NOD1 deficient or mutation has a close relationship with the lung disease--- asthma. All of these suggest that NOD1 protects lungs of host from infection. , a pathogen of invading respiratory system, could interact with NOD1 to activate NOD1 signal pathway to trigger the innate immune response against Af infection in lung.Objective: To explore whether NOD1-NF-κB signal pathway is activated induced by the Af infection and its protection against Af infection ,and to make preparations for the subsequent study of its implication in immunosuppressed host infected with Af.Methods: Mice were randomly divided into two groups: infection group and the control group. The mice were sacrificed at different time points to collect their lung tissues for pathological observation of lungs tissue, cultivation of fungus, detection of MPO activity, evaluation of the expression levels of NOD1mRNA and RIP2mRNA by RT-PCR and detection of NF-κBp65 amount in nuclear and TNF-α,IL-1βlevel in cytoplasm of lung tissues via Western Blot. The datas were statistical analysed with t test between groups.Results: We established the model of normal mouse infected with Af via nose sccessfully . In the control group, Af culture was negative. Their lung tissue structures were normal, except for some trivial inflammatory cells infiltration. MPO activity,expression levels of NOD1mRNA and RIP2mRNA,NF-κBp65 amount in nuclear and TNF-α,IL-1βlevel in cytoplasm of lung tissues were all at base line level. There is no signicant difference between two groups at every two time points. The result of the infected group are as follows: (1) Af burden of lungs in the infection group stayed at a high level in the early stage of infection, and decreased remarkably at 72h, then returned to normal gradually; (2) The observation of pulmonary pathology showed inflammatory cells infiltration, hyperemia and bleeding in the infected lung of mice at 48h and 72h after being infected. The lung tissue gradually got recovered over time; (3) MPO activity was up-regulated at 24h and 48h(P<0.05) and turned to normal since 72h; (4) NOD1 mRNA reached peak at 48h and decreased gradually.RIP2mRNA expression showed two peaks at 48h and 120h in comparsion with the control, they both had a significant difference during 24~120h and 48~120h respectively(P<0.05); (5) The results of Western blot showed NF-κB,IL-1βand TNF-αexpression levels in lungs kept up-regulated remarkably till being infected 120h. and had a significant difference with the control(P<0.05), NF-κB,IL-1βexpression were at the highest level at 48h and the highest TNF-αlevel at 72h,and then dropped gradually.Conclusion:The NOD1-NF-κB signal pathway was activated by the Af infection in the murine lungs and may play a partial role in control of growth and killing of Af, suggesting that innate immune response signal pathway is likely to involve in protection against of Af.