Role of inflammatory macrophages and CCR9/CCL25 chemokine axis in the pathogenesis of liver injury as a therapeutic target

CCL25 contributes to the pathogenesis of D-Gal/LPS-induced acute liver failure

BACKGROUND AND AIM

Acute liver failure (ALF) is a fatal clinical syndrome of severe hepatic dysfunction. Chemokines promote liver diseases by recruiting and activating immune cells. We aimed to investigate the role of C-C chemokine ligand 25 (CCL25) in ALF.

METHODS

An ALF mouse model induced by D-galactosamine/lipopolysaccharide was evaluated through liver hematoxylin and eosin staining and serum transaminase and cytokine measurement. CCL25 expression in serum was analyzed by ELISA and in liver by immunohistochemical staining and western blot. C-C chemokine receptor 9 (CCR9)-expressing cells in the liver were identified by immunofluorescence staining. The effects of anti-CCL25 on ALF were evaluated in vivo. Cytokine expression and migration of CCL25-stimulated RAW264.7 macrophages were studied. We also investigated the role of anti-CCL25 and BMS-345541, an NF-κB signaling inhibitor, in vitro. NF-κB activation was assessed via western blot, and p65 nuclear translocation was detected using cellular immunofluorescence.

RESULTS

ALF mice showed severe histological damage and high serum levels of aminotransferase and inflammatory cytokines. Elevated CCL25 and NF-κB activation was observed in vivo. CCR9 was expressed on macrophages in ALF mouse liver. ALF was suppressed after anti-CCL25 treatment, with significant NF-κB inhibition. In vitro, CCL25 induced strong migration and cytokine release in RAW264.7 macrophages, which were eliminated by anti-CCL25 and BMS-345541. Furthermore, the NF-κB activation and p65 nuclear translocation induced by CCL25 were also inhibited by anti-CCL25 and BMS-345541.

CONCLUSION

CCL25 contributes to ALF development by inducing macrophage-mediated inflammation via activation of the NF-κB signaling.

Determination of the Binding Epitope of an Anti-Mouse CCR9 Monoclonal Antibody (C9Mab-24) Using the 1× Alanine and 2× Alanine-Substitution Method

C-C chemokine receptor 9 (CCR9) is a receptor for C-C-chemokine ligand 25 (CCL25). CCR9 is crucial in the chemotaxis of immune cells and inflammatory responses. Moreover, CCR9 is highly expressed in tumors, including several solid tumors and T-cell acute lymphoblastic leukemia. Several preclinical studies have shown that anti-CCR9 monoclonal antibodies (mAbs) exert antitumor activity. Therefore, CCR9 is an attractive target for tumor therapy. In this study, we conducted the epitope mapping of an anti-mouse CCR9 (mCCR9) mAb, C₉Mab-24 (rat IgG_2a, kappa), using the 1× alanine (1× Ala)- and 2× alanine (2× Ala)-substitution methods via enzyme-linked immunosorbent assay. We first performed the 1× Ala-substitution method using one alanine-substituted peptides of the mCCR9 N-terminus (amino acids 1-19). C₉Mab-24 did not recognize two peptides (F14A and F17A), indicating that Phe14 and Phe17 are critical for C₉Mab-24-binding to mCCR9. Furthermore, we conducted the 2× Ala-substitution method using two consecutive alanine-substituted peptides of the mCCR9 N-terminus, and showed that C₉Mab-24 did not react with four peptides (M13A-F14A, F14A-D15A, D16A-F17A, and F17A-S18A), indicating that _13-MFDDFS_-18 is involved in C₉Mab-24-binding to mCCR9. Overall, combining, the 1× Ala- or 2× Ala-scanning methods could be useful for understanding for target-antibody interaction.

The Roles of CCR9/CCL25 in Inflammation and Inflammation-Associated Diseases

Chemokine is a structure-related protein with a relatively small molecular weight, which can target cells to chemotaxis and promote inflammatory response. Inflammation plays an important role in aging. C-C chemokine receptor 9 (CCR9) and its ligand C-C chemokine ligand 25 (CCL25) are involved in the regulating the occurrence and development of various diseases, which has become a research hotspot. Early research analysis of CCR9-deficient mouse models also confirmed various physiological functions of this chemokine in inflammatory responses. Moreover, CCR9/CCL25 has been shown to play an important role in a variety of inflammation-related diseases, such as cardiovascular disease (CVD), rheumatoid arthritis, hepatitis, inflammatory bowel disease, asthma, etc. Therefore, the purpose of this review gives an overview of the recent advances in understanding the roles of CCR9/CCL25 in inflammation and inflammation-associated diseases, which will contribute to the design of future experimental studies on the potential of CCR9/CCL25 and advance the research of CCR9/CCL25 as pharmacological inflammatory targets.