LPA 20:4 is a crucial factor in cholestasis-associated pruritus via activation of LPAR1

BACKGROUND: Pruritus is a common symptom in cholestatic patients. We previously reported that autotaxin (ATX) may play a role in cholestasis-associated pruritus. We further delineated the role of the ATX-lysophosphatidic acid (LPA)-LPA receptor (LPAR) axis in cholestasis-associated pruritus. METHODS: ATX activity, lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC) levels were quantified in plasma of cholestatic patients and healthy controls. Activation of LPA receptors (LPAR1-6) by plasma was studied using PRESTO-Tango for LPAR1, LPAR2, LPAR4-6 and a calcium-mobilization assay for LPAR3, and results were correlated with pruritus severity and clinical biochemical parameters. We analyzed a publicly available liver transcriptomic dataset from cholestatic patients for verification of the source of ATX. RESULTS: Cholestatic patient plasma significantly activated LPAR1 and to a lesser extent LPAR3 and LPAR4. Inhibition of autotaxin with ziritaxestat abrogated LPAR1 activation, demonstrating the central role of autotaxin in LPAR activation. Analysis of a liver transcriptomic dataset showed increased hepatic ENPP2 (ATX) expression in cholestatic patients. Plasma levels of TNFα, IL-6, IL-8 and CXCL10 in the patient cohort were also increased. Exposure of Hep3B hepatoma cells to TNFα, but not CDC, also induced ENPP2 expression. Plasma LPC levels were significantly reduced in patients with itch. Most LPA species in plasma were elevated in high-itch patients, but only LPA 20:4 levels correlated significantly with pruritus intensity. LPAR1 activation by plasma also correlated highly significantly with LPA 20:4 levels, suggesting that this is the most prominent pruritogen. CONCLUSION: Our findings provide substantial evidence for the role of the hepatic inflammation/ATX/LPA 20:4/LPAR1 axis in cholestasis-associated pruritus.