Autotaxin stimulates LPA2 receptor in macrophages and exacerbates dextran sulfate sodium-induced acute colitis

Autotaxin (ATX) is a secreted enzyme that hydrolyzes lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA) and choline. ATX has been implicated in multiple chronic inflammatory diseases, but little is known about its role in the development of inflammatory bowel disease (IBD). Here, we investigated how ATX contributed to intestinal inflammation during colitis. We found that ATX expression levels were upregulated in the intestines of ulcerative colitis (UC) patients in acute state as well as in the intestines of dextran sulfate sodium (DSS)-induced colitis mice, which is likely due to increased infiltration of inflammatory cells including macrophages. Intriguingly, the inhibition of ATX activity led to reduced production of inflammatory cytokines, as well as attenuated colitis. These findings suggest that ATX may display strong pro-inflammatory properties. Supporting this, treatment with recombinant mouse ATX (rmATX) increased the production of inflammatory cytokines and enzymes in mouse macrophage cell line RAW264.7 and bone marrow-derived macrophages (BMDM), whereas silencing ATX by siRNA reduced LPS-stimulated production of pro-inflammatory factors. Notably, we found that the levels of LPA2 (an LPA receptor) were dramatically upregulated in rmATX-treated RAW264.7 cells and DSS-treated mice. Gene silencing of lpa2 in RAW264.7 cells by siRNA led to reduced production of inflammatory cytokines. Moreover, adenovirus-mediated delivery of lpa2 short hairpin RNA into DSS-treated mice ameliorated colitis. Collectively, our research suggests that ATX may exacerbate DSS-induced colitis by activating LPA2 receptor in macrophages and represent a promising target for the treatment of IBD. KEY MESSAGES: Increased ATX expression and secretion in colitic colons are likely due to increased infiltration of inflammatory cells including macrophages. Recombinant ATX promotes, but ATX silencing inhibits, the production of inflammatory cytokines in LPS-stimulated RAW264.7 cells and BMDM. •LPA2 mediates the pro-inflammatory effects of ATX on macrophages. Inhibition of ATX and downregulation of LPA2 ameliorate DSS-induced colitis.