Z Gastroenterol 2018; 56(01): E2-E89
DOI: 10.1055/s-0037-1612684
Poster Visit Session I Fibrogenesis and Nonparenchymal Cells – Friday, January 26, 2018, 12:30pm – 1:15pm, Room 121
Georg Thieme Verlag KG Stuttgart · New York

Inability to form NLRP3 inflammasome complex leads to decreased inflammation and prevents fibrosis formation in mice after chronic bile duct ligation

M Frissen
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
L Liao
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
V Bieghs
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
K Schneider
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
A Mohs
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
E Latz
2   University Clinic Bonn, Institute for Innate Immunity, Bonn
,
A Wree
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
,
C Trautwein
1   University Clinic RWTH Aachen, Clinic for Gastroenterology, Metabolic Disorders and Internal Intensive Medicine, Aachen
› Author Affiliations
Further Information

Publication History

Publication Date:
03 January 2018 (online)

 

Background and aims:

Cholestasis causes hepatic toxicity, which leads to liver injury by cell death. Apoptotic and pyroptotic cell death is a consequence of caspase-8 and/or caspase-1 activation and is mediated by the NLRP3 inflammasome. NLRP3 activation triggers liver inflammation, fibrosis and hepatocyte pyroptosis in mice. Thus we here studied the role of NLRP3 inflammasome activation during cholestatic liver injury.

Methods:

To investigate the role of the NLRP3 inflammasome we performed bile duct ligation (BDL) in WT, NLRP3-/- and ASC-/- mice. We were interested to study the role of NLRP3 during acute (48 hours) and chronic (28 days) injury after BDL. Inflammation, fibrosis and cell death were evaluated with qPCR, IHC, IF and western blot analysis.

Results:

Acute cholestatic liver injury in NLRP3-/- mice resulted in a significantly stronger increase in serum transaminases compared to WT mice. In addition, increased hepatic inflammation, as evidenced by higher mRNA levels for TNF, IL-1b, MCP-1 and the influx of Ly6G Cd11b cells by FACS analysis, was observed in NLRP3-/- mice. The increase in liver injury can be explained by a stronger necroptotic response in NLRP3-/- mice, as shown by an increase in mitochondrial ROS and RIPK1 and 3 expression. After this initial increased response, the lack of NLRP3 expression lead to reduced serum transaminases, less inflammation and liver fibrosis. TUNEL, caspase-3 and -8 staining showed decreased cell death in NLRP3-/- mice. Furthermore, clusters of caspase-3 positive cells were observed only in WT mice 28 d after BDL, associated with pyroptosis. Since NLRP3-/- mice are unable to activate caspase-1 and cleave IL-1b, pyroptotic cell death was absent in these mice, subsequently leading to less fibrosis. Moreover, expansion of CK19 positive (progenitor/oval) cells was triggered in NLRP3-/- mice which may explain the protective phenotype in knockout mice. ASC-/- mice showed a similar but less severe phenotype as the NLRP3-/- mice, after 2 d BDL the serum transaminases and hepatic inflammation was slightly elevated compared to WT mice. In the chronic phase the ASC-/- mice were comparable to the NLRP3-/- mice, since they also lack inflammasome activation and accompanied pyroptotic cell death.

Conclusions:

During acute cholestatic liver injury lack of NLRP3 expression is associated with increased liver injury mediated by mitochondrial ROS and RIPK1 and 3 activation triggering increased necroptosis and a stronger inflammatory response. In contrast, in the chronic phase NLRP3-/- and ASC-/- mice have decreased liver injury due to reduced pyroptotic cell death leading to less inflammation and fibrosis.