Butyrylcholinesterase alleviates hepatic stellate cell activation via paracrine muscarinic signalling.

BACKGROUND

Butyrylcholinesterase (BuChE) is a metabolic enzyme implicated in Alzheimer's disease, detoxification and depression. Although reduced BuChE expression is recognised in cirrhosis, its functional role in fibrogenesis remains undefined.

OBJECTIVE

We investigated whether BuChE regulates fibrosis by modulating acetylcholine (ACh) bioavailability and identified downstream cholinergic signalling.

DESIGN

BuChE expression was assessed via qPCR and immunostaining in patient biopsies. Its contribution was studied using Buche ΔHep, Buche KI/KI-Hep mice, pharmacological inhibition, mutant BuChE conditioned medium and recombinant protein. ACh release and muscarinic ACh receptor (ChRM) function were measured using patch-clamp and calcium mobilisation assay; ChRM3 role was tested via Chrm3 ΔHSC mice and AAV6-mediated overexpression.

RESULTS

BUCHE mRNA and serum activity are significantly downregulated in fibrotic patients and mice, correlating negatively with F stage and alpha-smooth muscle actin expression. BuChE is predominantly expressed in hepatocytes in the liver, which can be reduced by transforming growth factor beta or platelet-derived growth factor treatment, and its anti-fibrotic function requires enzymatic activity. Hepatocyte BuChE deletion or inhibition increases hepatic stellate cell (HSC) activation and fibrosis across multiple models, whereas overexpression is protective, establishing causality. Loss of BuChE leads to accumulation of unmetabolised ACh, which activates HSCs as a damage associated molecular pattern signal via ChRM3-NF-κB signalling. Chrm3 ΔHSC mice exhibit attenuated HSC activation and fibrosis, whereas Chrm3 overexpression promotes fibrogenesis.

CONCLUSION

Hepatocyte injury disrupts BuChE activity, causing local ACh accumulation and subsequent HSC activation via ChRM3 signalling. This newly identified cholinergic circuit drives fibrosis and represents a druggable target for therapeutic intervention.