Downregulation of Stat3 Enhanced Chemokine Expression and Neutrophil Recruitment in the Peribiliary Region in Biliary Atresia

Background: Biliary atresia (BA) is an immune-related disorder, possibly with genetic predisposition. STAT3 is a key signalling molecule in inflammation. This study was to clarify the function of STAT3 in BA. Methods: STAT3 expression was examined in patients and a mouse model in which STAT3 levels were altered with a specific inhibitor or activator. Neutrophil accumulation and the levels of the neutrophil chemoattractants CXCL1 and IL-8 were determined. The effects of STAT3 inhibition in IL-8 expression were examined in human biliary epithelial cell culture. STAT3 polymorphisms were investigated in 503 BA patients and 495 controls in Southern Chinese populations. Results: STAT3 and p-STAT3 expression was reduced than that in control samples in BA liver tissue. The STAT3 inhibitor resulted in worsening mouse jaundice, body weight and mortality in the BA mice. In contrast, the STAT3 activator ameliorated the BA symptom. Extensive neutrophil accumulation together with CXCL1 upregulation, both of which were suppressed by an anti-CXCL1 antibody, was observed in the STAT3 inhibitor-treated group. Recombinant IL-8 administration increased disease severity in BA mice, and the reverse effect was shown by the STAT3 activator. Consistently, inhibiting STAT3 increased IL-8 expression in biliary epithelial cells. Furthermore, STAT3 identified was associated with BA (P=5.31E-03) through candidate gene approach. The disease risk allele (A) of rs7211777 is correlated with reduced STAT3 expression in the liver (P=8.00E-04). Conclusions: STAT3 reduction, enhanced the expression of IL-8 and CXCL1 and consequently caused accumulation of neutrophils in BA which might partially through STAT3 polymorphism reduced gene expression. Funding Statement: This work was supported by the National Natural Science Foundation of China (No. 81770510, 81671498, 81974056 and 81771629), Science and Technology Planning Project of Guangdong Province (No. 2017A020214017) and Key-Area Research and Development Program of Guangdong Province (No. 2019B020227001). Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: The study was carried out with the approval of the Ethical Committee of Guangzhou Women and Children’s Medical Center, and the informed consent was obtained from all patients recruited. Animal handling and experimental procedures were approved by the Animal Experimental Ethics Committee of the institute.