Session Title: Pediatric Rheumatology – Pathogenesis and Genetics - Poster
Session Type: ACR Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: STING-Associated Vasculopathy with Onset in Infancy (SAVI) is a monogenic autoinflammatory interferonopathy caused by gain-of-function mutations in TMEM173/STING, a nucleic acid sensor adaptor linked to IFNβ transcription. Patients (Pts.) develop acral vasculitis and variable severity of interstitial lung disease (ILD)(Liu Y, NEJM, 2014). We hypothesized that a common STING variant modulates lung disease severity, and investigated a mechanistic role of STING in ILD.
Methods: We assessed chest computed tomography (CT) and pulmonary function tests (PFTs) in 12 SAVI pts. (N154S, V155M, V147L, V147M); lung biopsies were available for 7 pts. DNA samples were typed for the STING SNP R232H, rs1131769 (Yi G, PLoSOne 2013). Transfection studies in HEK293T cells with wildtype or “SAVI mutations” constructs on the R232 and H232 haplotypes, and stimulations of pt. fibroblast and endothelial cell lines (HUVECs) were performed. IFNB1luciferase reporter activity was assessed upon stimulation with the endogenous: 2’3’cGAMP, or the microbial: 3’3’cGAMP, c-di-AMP and c-di-GMP, STING activators. Gene expression (q-RT-PCR, RNA-seq), cytokine production, and endothelial-mesenchymal transition (endo-MT, by cell morphology and gene expression studies), were assessed.
Results: The presence of R232 in cis with the disease-causing STING mutations is associated with severe lung disease. Of 9 pts. with severe ILD, 4 pts. succumbed to pulmonary complications; all but one were homozygous for R232/R232. The pt. with no ILD was homozygous for the H232 allele (H232/H232); 2 pts. with mild ILD were heterozygous (R232/H232) for the SNP. Transfection of HEK293T cells with mutant STING on the R232 and H232 haplotypes showed increased IFNB1 expression upon stimulation with microbial stimulants but not endogenous cGAMP; which was only significant when the SAVI mutations were on the R232 but not on the H232 haplotype. Similarly, IFNB1transcription in response to exogenous stimuli in fibroblasts from 4 pts. were higher in cells with R232/R232 than in cells with H232/H232 haplotype. RNA-seq of stimulated pt. and control fibroblasts showed no expression of myofibroblast and extracellular matrix (ECM) markers ruling out that STING pathway activation would induce myofibroblast-differentiation as a mechanism for pulmonary fibrosis. Trichrome stains of SAVI lung tissues (n=2) revealed localized fibrosis around the pulmonary vessels, suggesting that STING pathway activation may induce endo-MT. Endogenous cGAMP stimulation on endothelial cells induced morphologic transition to fibroblasts with increased expression of the mesenchymal marker αSMA and the pro-fibrotic markers SLUG and TWIST. EndoMT was TGFβ independent and not induced by microbial STING stimuli. However, IFNβ significantly increased the endo-MT process over 2’3’cGAMP stimulation alone.
Conclusion: The minor allele H232 of a STING SNP confers a protective role by mitigating IFNβ responses in the context of STING activating infections while the R232 haplotype accelerates endo-MT amplified by IFNβ. Our findings suggest a novel mechanism for inducing endo-MT as a cause for the development of lung fibrosis in SAVI through endogenous STING activation.
To cite this abstract in AMA style:Almeida de Jesus A, Malle L, Yang D, Marrero B, Liu Y, Montealegre Sanchez GA, Chapelle DC, Kim H, O'Brien M, Dueckers G, Ramsey S, Fontana JR, Holland SM, Huang Y, Hill S, Santiago L, Gonzalez B, Brogan P, Brunner J, Omoyinmi E, Ramanan AV, Paller A, Jones OY, Ozen S, Brooks S, Deng Z, Boehm M, Goldbach-Mansky R, Wittkowski H. Mechanisms for the Development of Lung Fibrosis in Sting-Associated Vasculopathy with Onset in Infancy (SAVI) [abstract]. Arthritis Rheumatol. 2016; 68 (suppl 10). https://acrabstracts.org/abstract/mechanisms-for-the-development-of-lung-fibrosis-in-sting-associated-vasculopathy-with-onset-in-infancy-savi/. Accessed October 28, 2020.
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