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Published on: March 10, 2017
Nlrp3 Activation Induces Il-18 Synthesis and Affects the Epithelial Barrier Function in Reactive Cholangiocytes
Luca Maroni1, Laura Agostinelli1, Stefania Saccomanno1
1Department of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy.
Abstract:
Microbial products are thought to influence the progression of cholangiopathies, in particular primary sclerosing cholangitis (PSC). Inflammasomes are molecular platforms that respond to microbial products through the synthesis of proinflammatory cytokines. We investigated the role of inflammasome activation in cholangiocyte response to injury. Nucleotide-binding oligomerization domain (NOD)-like receptor family, pyrin domain-containing protein 3 (Nlrp3) expression was tested in cholangiocytes of normal and cholestatic livers. Effects of Nlrp3 activation induced by incubation with lipopolysaccharide and ATP was studied in vitro in normal and siRNA-Nlrp3 knocked-down cholangiocytes. Wild-type and Nlrp3 knockout (Nlrp3-/-) mice were fed 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; a model of sclerosing cholangitis) for 4 weeks. Nlrp3 and its components were overexpressed in cholangiocytes of mice subjected to DDC and in patients affected by PSC. In vitro, Nlrp3 activation stimulated expression of Il-18 but not of Il-1β and Il-6. Nlrp3 activation had no effect on cholangiocyte proliferation but significantly decreased the expression of Zonulin-1 and E-cadherin, whereas Nlrp3 knockdown increased the permeability of cholangiocyte monolayers. In vivo, the DDC-stimulated number of cytokeratin-19-positive cells in the liver of wild-type animals was slightly reduced in Nlrp3-/- mice, and expression of E-cadherin was reestablished. In conclusion, Nlrp3 is expressed in reactive cholangiocytes, in both murine models and patients with PSC. Activation of Nlrp3 leads to synthesis of proinflammatory cytokines and influences epithelial integrity of cholangiocytes.
Insights
The inflammasome Nlrp3 (NOD-like receptor family, pyrin domain-containing protein 3) is activated in cholangiocytes during liver injury and primary sclerosing cholangitis (PSC). Nlrp3 activation impacts cytokine production and epithelial barrier function in cholangiocytes.
Area of Science:
- Hepatology
- Immunology
- Cell Biology
Background:
- Microbial products influence cholangiopathies like primary sclerosing cholangitis (PSC).
- Inflammasomes, such as Nlrp3 (NOD-like receptor family, pyrin domain-containing protein 3), are key responders to microbial stimuli, producing proinflammatory cytokines.
- The role of inflammasome activation in cholangiocyte injury remains to be fully elucidated.
Purpose of the Study:
- To investigate the role and impact of inflammasome activation, specifically Nlrp3, in cholangiocyte response to injury.
- To analyze Nlrp3 expression in normal, cholestatic, and PSC-affected livers.
- To determine the effects of Nlrp3 activation on cholangiocyte function in vitro and in vivo.
Main Methods:
- Assessed Nlrp3 expression in cholangiocytes from normal, cholestatic, and PSC livers.
- Studied Nlrp3 activation effects in vitro using lipopolysaccharide and ATP in normal and Nlrp3-knockdown cholangiocytes.
- Utilized a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced sclerosing cholangitis model in wild-type and Nlrp3 knockout (Nlrp3-/-) mice.
Main Results:
- Nlrp3 was overexpressed in reactive cholangiocytes in DDC-treated mice and PSC patients.
- In vitro, Nlrp3 activation induced IL-18 and decreased Zonulin-1 and E-cadherin expression, increasing cholangiocyte monolayer permeability.
- In vivo, Nlrp3 deficiency in mice partially reduced DDC-induced cholangiocyte proliferation and restored E-cadherin expression.
Conclusions:
- Nlrp3 is expressed in reactive cholangiocytes during liver injury and PSC.
- Nlrp3 activation contributes to proinflammatory cytokine synthesis and affects cholangiocyte epithelial integrity.
- Targeting Nlrp3 may offer a therapeutic strategy for cholangiopathies.
