Evaluation of muscarinic acetylcholine receptors type 3 in the pathogenesis of chronic inflammatory cholangiopathies

• Applicants: Dr. Julia Benckert, since 8/2023; Professor Dr. Thomas Berg; Professorin Dr. Reinhild Klein
• Subject Area: Gastroenterology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447875767

Chronic inflammatory cholangiopathies such as primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC) and immunoglobulin G4 (IgG4)-associated cholangitis (IAC) are associated with considerable morbidity and mortality. The underlying genetic, immunological and environmental pathogenetic mechanisms are largely unclear.According to the hypothesis of the so-called biliary bicarbonate umbrella by Beuers and Hohenester, hydrophobic apolar bile acids passively diffuse through the bile duct epithelium and have a potentially cholangiotoxic effect. The secretion of high HCO3 concentrations by the bile duct epithelium therefore induces an alkaline environment near the apical cell membrane, in which the bile acids deprotonate and lose their membrane passage in this hydrophilic charged form, which protects the bile duct epithelium from the toxicity of the bile acids.Muscarinic type 3 acetylcholine receptors (mAChR3) are exclusively expressed in the liver in the bile duct epithelium. Activation of basolateral mAChR3 by acetylcholine (ACh) induces bicarbonate (HCO3-) secretion into the biliary lumen. We hypothesize that dysregulated mAChR3-mediated signaling pathways may play a role in the pathogenesis of chronic inflammatory bile duct diseases.The proposed project includes different aims in the different working groups of the co-applicants in Berlin, Leipzig and Tübingen: Aim 1 includes the isolation of specific mAChR3 Auto-AK in patients as well as healthy or diseased control populations. Later on, the functionality of the mAChR3 Auto-AK will be evaluated. Aim 2 includes the analysis of sequence data from isolated mAChR3 Auto-AK in order to overexpress them monoclonally. Aim 3 includes analyzes for the expression and regulation of the different mAChR types as well as the characterization of non-neuronal ACh synthesis in primary and cultivated human bile duct epithelial cells. Aim 4 includes functional cell culture work on the importance of mAChR3-mediated signaling pathways for vitality, apoptosis, proliferation, migration and tight junction-mediated barrier function of primary and cultivated human bile duct epithelial cells. Aim 5 examines the influence of mAChR3-mediated signaling pathways on the protective bicarbonate protective shield of the bile duct epithelium. In the light of a translational approach, aim 6 examines the correlation of the results recorded in the previous subsections with the available clinical information with regard to the general clinical and paraclinical characteristics, the therapy response to the respective standard therapy as well as the consecutive long-term course of the patient depending on the individual mAChR3 Auto-AK status. Aim 7 includes analyzes of the influence of mAChR3 on immune-competent cells in vitro.

• DFG Programme: Research Grants
• International Connection: Netherlands
• Cooperation Partner: Professor Dr. Ulrich Beuers
• Ehemaliger Antragsteller: Professor Dr. Tobias Müller, until 8/2023