Deletion of Chemokine Receptor 6 Augments Ductular Reaction and Fibrosis in a Mouse Model of Cholestatic Liver Injury
Background: The chemokine CCL20 is expressed by activated cholangiocytes implicating its’ receptor, CC-chemokine receptor 6 (CCR6) in immune cell trafficking to the liver during cholestatic liver injury. In particular, the innate immune cells macrophages and neutrophils have been identified in cholestatic liver injury. Therefore, our aim was to investigate the effect of CCR6 deletion on a mouse model of 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced cholestatic liver injury. Methods: Age and gender matched WT and Ccr6-/- mice were placed on an DDC or a control diet for 21 days. Serum biochemistry, liver injury and the ductular reaction (DR) were examined by standard approaches. Gene expression by nanostring analysis and immunophenotyping of intrahepatic leukocytes (IHL) by mass cytometry were performed. Results: Unexpectedly, liver weight/body weight percentage (6.026 ± 0.13 vs 5.18 ± 0.23), serum alkaline phosphatase (646.8 ±48.88 vs 357.7 ±39.4 U/ml), alanine aminotransferase (2058 ± 377.2 vs 1140 ± 151.6 U/mL), total bilirubin (2.91 ± 0.66 vs 1.0 ± 0.12 mg/dL) were significantly greater in Ccr6-/- mice compared to WT mice on DDC diet. Ccr6-/- mice also had a more extensive DR compared to WT mice on DDC diet (5.32 ± 0.52 vs 3.44 ± 0.37 %). Sirius red (1.82 ± 0.17 vs 0.54 ± 0.13 %), desmin (3.62 ± 0.41 vs 1.63 ± 0.59 %) and alpha-smooth muscle actin (4.44 ± 0.41 vs 2.13 ± 0.27 %) stainings indicated that fibrosis was significantly increased in Ccr6-/- mice as compared to WT mice on DDC diet. Immunophenotyping of IHL revealed no difference in the total number of macrophages recruited into the liver during DDC administration. For contrast, there was a two-fold increase in the accumulation of neutrophils in the Ccr6-/- mice reared on the DDC diet as compared to the WT mice. This observation was supported by the significantly increased gene expression levels of Ltb4r1, Cfp, Cfb, Myd88, Hfe, and Stat5b suggesting an increased recruitment and survival of neutrophils in the Ccr6-/- mice. Conclusion: Genetic deletion of Ccr6 causes extensive DR, fibrosis, and upregulation of proinflammatory genes responsible for recruiting neutrophils during DDC diet-induced cholestatic liver injury in mice. These data provide novel insights into the role of the CCR6-CCL20 signaling axis in restraining neutrophil accumulation in the liver during cholestatic liver injury.
Ozturk NB, Cutshaw K, Krishnan A, Gores GJ. Deletion of chemokine receptor 6 augments ductular reaction and fibrosis in a mouse model of choestatic liver injury. Hepatology. 2022 Oct;76(S1):S1019. doi:10.1002/hep.32697.
American Association for the Study of Liver DIseases AASLD Liver Meeting 2022, November 4-8, 2022, Washington, DC.
Mayo Clinic Young Investigators Research Symposium, May 21, 2022, Rochester, MN.