Investigation Of The Role Of Innate Immunity In Pathogenesis Of Autoimmunity-associated Pulmonary Fibrosis

Objective:Pulmonary fibrosis（PF）is a chronic,lethal,diffuse interstitial lung disease.In autoimmune diseases,such as systemic sclerosis（SSc）and primary Sjogren’s syndrome（pSS）,some patients also suffer from PF which is one of major causes of death in patients.Notably,although all SSc and pSS patients are characterized with autoimmunity,only some patients develop PF.This suggests that beside autoimmunity in general,some specific additional factors are involved in the initiation of PF.So far,the pathogenesis of the autoimmunity associated PF remains elusive,and effective therapies to PF are still missing.In this study,we aimed to explore the pathogensis of autoimmunity associated PF using genetic analysis and experimental models.Methods:To identify genetic polymorphisms associated with the status of PF in SSc,we performed a exhaustive search of the PubMed database to identify eligible studies.Then a comprehensive meta-analysis was performed by comparing PF+-SSc and PF--SSc patients to identify genetic polymorphisms associated with the status of PF in SSc.To investigate the pathogenesis of PF in pSS,we induced an animal model of pSS by immunization mice with Ro60₃16-335 peptide.Several pSS-like phenotypes were evaluated,including autoantibody production,secretion of tears and saliva,histological changes in exocrine gland and lung.To invetstigate the role of TLR4 signaling in the pathogenesis of PF in this mouse model,we first compared development of PF between C3H/HeN and C3H/HeJ mice,then investiagted the effect of a TLR4 antagonist on the development of PF.Results:Meta-analysis showed that IRF5 rs2004640（OR = 1.12;95%CI = 1.02-1.22,P = 1.39 x 10-2）,STAT4 rs7574865（OR= 1.15;95%CI = 1.07-1.47,P = 5.3 × 10-3）,CTGF G-945C（OR = 1.42;95%CI = 1.18-1.71,P = 0.0002）and IRAKI rs1059702（OR = 1.20;95%CI = 1.05-1.37,P=0.007）were associated with the status of PF in SSc patients.By contrast,TNFAIP3 rs5029939（OR = 1.13;95%CI=0.89-1.43,P =0.32）,CD226 rs763361（OR = 1.05;95%CI = 0.96-1.15,P=0.29）,CD247 rs2056626（OR= 0.93;95%CI = 0.78-1.12,P = 0.46）and IRF5 rs10488631（OR=1.04;95%CI = 0.90-1.21,P = 0.61）were not associated with PF.However,After immunization with Ro60₃16-335 peptide,C3H/HeN mice developed several pSS-like immunological and clinical features,including autoantibodies,impairment in the secretion function of exocrine glands,and pulmonary inflammation and fibrosis.By contrast,C3H/HeJ mice also developed autoantibodies,and impairment in the secretion function of exocrine glands,but pulmonary inflammation and fibrosis were absent.Sequencing of TLR4 confirmed that the C3H/HeJ mice carry a loss-of-function mutation,with Pro in C3H/HeN mice replaced by His in C3H/HeJ mice.In addition,administration of TLR4 antagonist（TAK-242）slightly modulated the severity of PF in C3H/HeN mice.Conclusion:In this study,we have identified IRF5,STAT4,CTGF and IRAKI as susceptiblity genes regulating the status of PF in SSc using meta-analysis.Further more,animal experiments have demonstrated that TLR4 signaling plays an important role in the pathogenesis of PF in mouse model of pSS.Since IRF5,STAT4,IRAK1 and TLR4 are important regulators in innate immune response,these results suggest that innate immunity contribute to the pathogenesis of autoimmunity associated PF.