VEGFR antagonists(Merck)

Children with STING‐Associated Vasculopathy with onset in Infancy (SAVI) spontaneously developed pulmonary hypertension (PH) among other sequela of inflammation. SAVI is caused by a gain‐of‐function mutation in the Stimulator of Interferon Genes (STING), a cell’s gatekeeper to cytosolic DNA through regulating type I Interferon signaling. The clinical observations suggest a role for STING in PH, yet STING‐dependent type I interferon signaling in PH has not yet been examined.

To investigate the role of STING‐dependent type I interferon signaling in chronic hypoxia (Hx)‐induced PH and chemotherapy drug Bleomycin (Blm)‐induced PH mouse model.

PH was induced for 4 weeks in wild type (WT) littermates (n=9/group) and STING deficient (STING ‐/‐ ) mice (n=9/group) with either Hx (10% oxygen) or weight‐based dosing of intraperitoneal ( i.p. ) Blm injections (0.018U.g ‐1 , twice a week). PH development was evaluated with right‐ventricular systolic pressure (RVSP, mmHg) and right‐ventricular remodeling (RV/LV+S, %). Lung tissues were collected for inflammation assessment, with flow cytometry and histologic staining (Masson Trichrome Stain (MTC) and a‐smooth muscle actin stain (aSMA)). In search for a downstream signaling, WT littermates treated with either anti‐IFNAR1antibody (aIFNAR1) or IgG (n=8/group) were subjected to similar experimental settings for evaluation of PH development. In another experiment, the gold standard Sugen Hypoxia PH model was adopted for STING ‐/‐ mice and WT littermates (n=8/group), in which the mice were treated with vascular endothelial growth factor receptor (VEGFR) antagonist, Sugen, while undergo chronic hypoxia for 4 weeks. Assessment of PH at end point was similar as outlined above. Values are meanSEM.

STING ‐/‐ mice exhibited significantly lower RVSP, compared to controls. STING ‐/‐ mice underwent chronic hypoxia exposure also showed decreased level of right‐ventricular remodeling compared to controls. Correlating with hemodynamic data, STING ‐/‐ mice displayed a lower level of lung‐infiltrated inflammatory cells. They also displayed less inflammation and collagen deposition using semiquantitative histologic measurement. Intriguingly, there was no significance difference in hemodynamic measurements as well as inflammation assessment between WT mice treated with aIFNAR and their isotype controls in both PH models, implying a STING‐independent type I interferon effect. We detect VEGF a potential underlying mechanism, as STING ‐/‐ mice are no longer protected from Hx‐induced PH when treated with Sugen, the VEGFR antagonist.

Global absence of STING provided protection against PH development secondary to chronic hypoxia and Bleomycin in mice. However, this protective effect is independent of type I interferon signaling. Interestingly, STING‐mediated VEGF expression may play a protective role against PH development.