Abstract

Background: Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by inflammation and fibrosis of the bile ducts. CCL24 (Eotaxin-2) is a chemokine that promotes inflammation and fibrosis and is overexpressed in the liver of patients with PSC, particularly in areas with biliary injury. Previous studies showed that blocking CCL24 interferes with core pathways that contribute to PSC pathophysiology in preclinical models. These properties are unique to CCL24 and are not shared with other ligands of its cognate receptor, CCR3, like Eotaxin-1 (CCL11) and Eotaxin-3 (CCL26). In this study, we aim to further investigate the unique role of CCL24 in the pathophysiology of PSC and its association with disease-related pathways.

Methods: Sera from patients with PSC (n=45) and healthy controls (n=30) were analyzed using the Olink proximity extension assay (PEA) of 3072 proteins. Subjects’ demographics and enhanced liver fibrosis (ELF) score were documented. Serum proteomics data were analyzed according to three comparisons: (1) healthy controls vs. patients with PSC, (2) fibrosis severity in PSC patients, defined by ELF score (9.8 cutoff, defining advanced fibrosis), and (3) serum levels of CCL24 in PSC patients. Differentially expressed proteins (DEPs) were subjected to Ingenuity Pathway Analysis. Expression of protein lists was compared between healthy controls and patients with PSC, then further analyzed among patients with PSC, stratified by serum levels of CCL24, CCL11 or CCL26.

Results: Serum proteomics analysis revealed canonical pathways (such as hepatic stellate cell activation) and upstream regulators (such as IL1β) which are activated in patients with PSC, in patients with advanced fibrosis and in patients with high CCL24 levels. Additionally, protein lists related to multiple hepatotoxicity functions, such as liver fibrosis, were upregulated in patients with high CCL24 levels. Furthermore, expression of these protein lists was found to be uniquely associated with serum levels of CCL24, but not associated with CCL11 or CCL26.

Conclusion: This study provides further evidence of the critical role of CCL24 in the pathogenesis of PSC, highlighting its unique association with disease-related pathways not shared by other eotaxins. Targeting CCL24 could be a promising therapeutic strategy for the treatment of PSC, which supports the ongoing phase 2 study of CM-101, a CCL24 neutralizing antibody, in patients with PSC.