Chemokines and Chemokine Receptors Expression in Liver Inflammation

Primary Sclerosing Cholangitis (PSC) is a chronic liver disease characterized by persistent inflammation and progressive fibrosis, leading to liver failure and an increased risk of malignancy. To investigate the cellular and molecular mechanisms underlying PSC pathogenesis, we performed single-cell RNA sequencing (scRNA-seq) on liver samples from C57BL wild-type (WT) mouse and Mdr-2 knockout (KO) mice at 3 and 18 months of age. Our analysis identified significant changes in cellular composition and gene expression profiles across different liver cell populations. Notably, there was a pronounced increase in inflammatory macrophages and Kupffer cells, as well as non-immune cells such as cholangiocytes and hepatic stellate cells, which are key mediators of fibrosis. In contrast, endothelial cells exhibited minimal alterations in their proportions, indicating cell-type-specific responses to inflammation.

Chemokine receptor analysis revealed significant upregulation of CCR1, CCR2, CCR5, CXCR4, and CX3CR1, predominantly in inflammatory macrophages and Kupffer cells, while other receptors, such as CXCR3, CXCR5, and CCR7, remained unchanged. Interestingly, we found that CCR5 was uniquely expressed in Kupffer cells, whereas CCR1 was absent, despite their shared ligands (CCL3 and CCL4). This suggests a critical and specific role of CCR5 in Kupffer cell-driven inflammation and fibrogenesis. Further functional assays demonstrated that CCL3 and CCL4 secreted by Kupffer cells promoted hepatic stellate cell proliferation, implicating them in the fibrotic process.

Additionally, our study identified CCL24 as a Kupffer cell-specific chemokine with a previously unrecognized ability to bind and activate CCR5, highlighting a novel inflammatory pathway contributing to liver pathology. We also observed significant upregulation of the CXCR4/CXCL12 axis, with CXCL12 being predominantly expressed in stellate cells, suggesting an autocrine role in fibrosis. Pharmacological inhibition of CXCR4 led to a marked reduction in immune cell recruitment to the liver but paradoxically exacerbated fibrosis and inflammation, indicating complex regulatory interactions between chemokines and liver pathology.

Our findings provide novel insights into the dynamic interplay between chemokines and their receptors in liver inflammation and fibrosis, emphasizing the critical role of Kupffer cells in orchestrating immune cell recruitment and fibrogenic processes. These results highlight potential therapeutic targets, including CCR5 and CCL24, for mitigating PSC-associated liver damage.