SPHK1 and inflammatory bowel disease: This was further confirmed by performing animal experiments using PF-543 (a SphK1 inhibitor), which inhibits DSS-induced colitis (Liu and Jiang, 2020), and gut-specific knockout of S1PL, which leads to increased S1P levels in the colon and aggravates IBD symptoms (Suh and Saba, 2015).