STING signalling protects against chronic pancreatitis by modulating Th17 response.

OBJECTIVE: Chronic pancreatitis (CP) is an inflammatory disease with progressive fibrosis leading to exocrine and endocrine dysfunction. Currently, there are no approved effective therapies for CP. Stimulator of interferon genes (STING) signalling is a key innate immune sensor of DNA. In this study, we evaluated the role of STING signalling in CP.
DESIGN: We used an experimental model of CP to test the effect of STING signalling in STING wild-type and knockout mice as well as bone marrow chimaeras (BMCs). STING was activated using a pharmacological agent. Since we found changes in Th17 cells, we used neutralising and control antibodies to determine the role of IL-17A. The effect of STING signalling was further explored in IL-17A generation and we examined the effect of IL-17A on pancreatic stellate cells (PSCs). Human pancreas from patients with CP and without CP were also stained for IL-17A.
RESULTS: STING activation decreased CP-associated pancreatic inflammation and fibrosis, whereas absence of STING led to worsening of the disease. BMCs showed that leucocytes play an important role in STING signalling-mediated amelioration of experimental CP. STING deletion was associated with increased Th17 cell infiltration in the pancreas, whereas STING agonist limited this Th17 response. Importantly, anti-IL-17A antibody treatment mitigated the severity of CP in the absence of STING signalling. STING deficiency promoted Th17 polarisation and PSCs express functional IL-17 receptor by upregulating fibrosis genes. Compared with tumour margins, pancreas from patients with CP had significant increase in IL-17A+ cells.
CONCLUSION: Unlike acute pancreatitis, STING activation is protective in CP. STING signalling is important in regulating adaptive immune responses by diminishing generation of IL-17A during CP and presents a novel therapeutic target for CP. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.