Purinergic regulation of inflammation in liver fibrosis by ecto-nucleoside triphosphate diphosphohydrolase-3 (ENTPD3)

• Applicant: Privatdozentin Dr. Linda Feldbrügge
• Subject Area: General and Visceral Surgery
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 412957338

Liver fibrosis is caused by various chronic liver diseases, including inflammatory, toxic and metabolic diseases, and can result in liver cirrhosis and organ failure. Liver cirrhosis is among the ten most frequent causes of death in Germany. Liver transplantation remains the only therapeutic option of end-stage liver cirrhosis. Further research is needed to better understand the underlying pathophysiology, to refine non-invasive diagnostic tools and develop effective antifibrotic therapies. Liver fibrosis is characterized by excessive formation of scar tissue that replaces healthy liver cells, mainly produced by activated hepatic stellate cells that transdifferentiate into myofibroblasts. Different subsets of macrophages modulate the activation of stellate cells and thereby regulate development and resolution of fibrosis. The functions of both macrophages and stellate cells are controlled by their microenvironment that is altered by inflammatory and metabolic changes in surrounding cells, including the secretion of cytokines and metabolites into the surrounding extracellular space. Purinergic signaling by extracellular purines such as ATP and adenosine is one of the pathways that effects both macrophage phenotype and stellate cell differentiation. ATP is secreted in situations of cell stress, cell death and inflammation. Ecto-nucleoside triphosphate diphosphohydrolase-3 (ENTPD3) is a membrane-bound ecto-nucleotidase of the CD39 family that controls the concentrations of extracellular ATP and adenosine by hydrolyzing ATP and ADP to AMP which is further degraded to adenosine. ENTPD3 is expressed on macrophages and has also been observed on circulating cellular microparticles. Our preliminary data have shown that mice null for ENTPD3 develop less fibrosis when compared to wild type mice. We hypothesize that the expression of ENTPD3 on the surface of liver macrophages alters the local microenvironment by modulating extracellular purine concentrations and drives macrophages towards a more anti-fibrotic phenotype. The proposed project aims to define the underlying cellular and molecular mechanisms using global Entpd3 null mice and macrophage-specific Entpd3 knockout mice in a standard model of liver fibrosis. In vitro experiments on macrophages with and without ENTPD3 expression and co-culture experiments with hepatic stellate cells will further elucidate the mechanisms of interaction. Blockade of ENTPD3 using a monoclonal antibody will determine the potential of ENTPD3 as a therapeutic target. A cohort of patients with varying degrees of liver fibrosis will be studied for liver tissue expression of ENTPD3 and other purinergic molecules and ENTPD3 plasma activity to determine the relevance of ENTPD3 related regulation of liver fibrosis in humans and to test the value of ENTPD3 plasma activity as a non-invasive biomarker for fibrosis.

• DFG Programme: Research Grants