Functional metabolomics characterizes the contribution of farnesoid X receptor in pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome

Consumption of herbal products containing pyrrolizidine alkaloids (PAs) is one of the major causes for hepatic sinusoidal obstruction syndrome (HSOS), a deadly liver disease. However, the crucial metabolic variation and biomarkers which can reflect these changes remain amphibious and thus to result in a lack of effective prevention, diagnosis and treatments against this disease. The aim of the study was to determine the impact of HSOS caused by PA exposure, and to translate metabolomics-derived biomarkers to the mechanism. In present study, cholic acid species (namely, cholic acid, taurine conjugated-cholic acid, and glycine conjugated-cholic acid) were identified as the candidate biomarkers (area under the ROC curve 0.968 [95% CI 0.908-0.994], sensitivity 83.87%, specificity 96.55%) for PA-HSOS using two independent cohorts of patients with PA-HSOS. The increased primary bile acid biosynthesis and decreased liver expression of farnesoid X receptor (FXR, which is known to inhibit bile acid biosynthesis in hepatocytes) were highlighted in PA-HSOS patients. Furtherly, a murine PA-HSOS model induced by senecionine (50 mg/kg, p.o.), a hepatotoxic PA, showed increased biosynthesis of cholic acid species via inhibition of hepatic FXR-SHP singling and treatment with the FXR agonist obeticholic acid restored the cholic acid species to the normal levels and protected mice from senecionine-induced HSOS. This work elucidates that increased levels of cholic acid species can serve as diagnostic biomarkers in PA-HSOS and targeting FXR may represent a therapeutic strategy for treating PA-HSOS in clinics.

A TMT-based shotgun proteomics uncovers overexpression of thrombospondin 1 as a contributor in pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome

Hepatic sinusoidal obstruction disease (HSOS) is a rare but life-threatening vascular liver disease. However, its underlying mechanism and molecular changes in HSOS are largely unknown, thus greatly hindering the development of its effective treatment. Hepatic sinusoidal endothelial cells (HSECs) are the primary and essential target for HSOS. A tandem mass tag-based shotgun proteomics study was performed using primary cultured HSECs from mice with HSOS induced by senecionine, a representative toxic pyrrolizidine alkaloid (PA). Dynamic changes in proteome were found at the initial period of damage and the essential role of thrombospondin 1 (TSP1) was highlighted in PA-induced HSOS. TSP1 over-expression was further confirmed in human HSECs and liver samples from patients with PA-induced HSOS. LSKL peptide, a known TSP1 inhibitor, protected mice from senecionine-induced HSOS. In addition, TSP1 was found to be covalently modified by dehydropyrrolizidine alkaloids in human HSECs and mouse livers upon senecionine treatment, thus to form the pyrrole-protein adduct. These findings provide useful information on early changes in HSECs upon PA treatment and uncover TSP1 overexpression as a contributor in PA-induced HSOS.