IDDF2024-ABS-0207 S1P/S1PR4 promotes the differentiation of CD8+TRM cells aggravating bile duct injury in biliary atresia

<h3>Background</h3> Biliary atresia (BA) is the most common serious neonatal biliary disease, characterized by progressive biliary inflammation and fibrosis. We aim to comprehensively and systematically investigate the complex pathological process of BA from multiple molecular dimensions, combining transcriptomics, proteomics, metabolomics, and single-cell RNA sequencing. <h3>Methods</h3> Transcriptomic, proteomic, and metabolomic techniques were utilized for detecting and integrating the molecular characteristics of BA liver tissues. By combining single-cell RNA sequencing data, we were able to pinpoint the immune cells regulated by the abnormal metabolite in BA. <i>In vitro</i> experiments were detected to reveal the role and mechanism of the abnormal metabolite signaling pathway in the progression of BA. <i>In vivo</i>, the effect of inhibiting abnormal signaling pathway on alleviating bile duct injury and fibrosis was verified in the rotavirus type A (RRV) induced mouse model. <h3>Results</h3> We found the aberrant regulation and activation of the sphingolipid metabolism pathway was observed in BA by transcriptomic, proteomic, and metabolomic data analysis. By integrating BA single-cell RNA sequencing data, we found that Sphingosine-1-Phosphate Receptor 4 (S1PR4), a receptor of Sphingosine-1-Phosphate signaling, was primarily expressed in CX3CR1+CD8+ effector T (Teff) cells. <i>In vitro</i> experiments demonstrated that S1P promoted the migration of CX3CR1+CD8+Teff cells, and S1P/S1PR4 signaling facilitated the differentiation of CX3CR1+CD8+Teff cells into CD8+ tissue-resident memory T (TRM) cells. Co-culture of CD8+TRM cells could induce apoptosis of cholangiocytes. In the RRV mouse model, S1PR4 inhibitor could alleviate liver inflammation and fibrosis by inhibiting the accumulation of CD8+TRM cells (IDDF2024-ABS-0207 Figure 1. S1P S1PR4 promotes the differentiation of CD8 TRM cells aggravating bile duct injury in biliary atresia). <h3>Conclusions</h3> This study used multi-omics data integration to reveal aberrant regulation of the sphingolipid metabolism pathway in BA. The activated S1P/S1PR4 signaling pathway in BA liver recruited CX3CR1+CD8+Teff cells to accumulate around the cholangiocytes. S1P/S1PR4 signaling promoted the differentiation of CX3CR1+CD8+Teff cells into CD8+TRM cells, subsequently triggering apoptosis and injury of cholangiocytes, thus exacerbating the progression of BA. Targeting S1P/S1PR4 signaling activation is a promising therapeutic strategy for BA treatment.