Liver fibrosis arises when chronic injury from viral hepatitis, alcohol, fatty liver disease, or other insults pushes hepatic stellate cells into an activated, myofibroblast-like state. In their quiescent form, these cells store vitamin A and quietly regulate blood flow through the liver’s sinusoids. When activated, they proliferate, migrate, and deposit extracellular matrix faster than it can be degraded, gradually choking the organ’s architecture into the stiff, nodular tissue of cirrhosis. Despite decades of research, no approved therapy reverses established fibrosis; treatment has largely meant removing the underlying cause and hoping the liver’s own regenerative capacity keeps pace. Praziquantel had already shown hints of anti-fibrotic activity in experimental settings, but how a drug best known for paralyzing schistosome worms could calm scar-forming liver cells remained a mystery.

To crack that mystery, the research team, led by Zhongkui Lu and Guoying Zhang of Nanjing Integrated Traditional Chinese and Western Medicine Hospital affiliated with Nanjing University of Chinese Medicine, together with colleagues at Xuzhou Medical University and Jinling Hospital, assembled potential praziquantel targets from public pharmacological databases and cross-referenced them against genes implicated in liver fibrosis. The overlap yielded 137 candidate genes. Enrichment analyses of this set pointed toward pathways involving xenobiotic metabolism and neuroactive ligand-receptor interactions, a signature consistent with the drug’s known pharmacology but also hinting at receptor-mediated effects beyond simple parasite membrane disruption.

The next step was to find the critical nodes within this network. Using the STRING database to construct a protein-protein interaction map and Cytoscape to visualize and prune it, the researchers identified six hub genes at the center of the praziquantel-fibrosis intersection: EGFR, ALB, TP53, PTGS2, ESR1, and CYP3A4. These genes span a striking range of functions, from growth factor signaling and tumor suppression to drug metabolism and hormone reception. But which of them actually matters causally for fibrosis, rather than merely being correlated with it? To answer that question, the team turned to Mendelian randomization, a statistical technique that uses naturally occurring genetic variants as instruments to test whether an exposure, here the expression or function of a candidate gene, has a causal effect on an outcome.

The Mendelian randomization analysis delivered a clear verdict for one gene. ESR1, the estrogen receptor alpha gene, showed genetically supported evidence of a protective causal role against liver fibrosis. A colocalization analysis, which tests whether the same genetic variant drives both the gene signal and the disease association in a genomic region, nominated a specific variant, rs3020404, as a plausible functional basis for the link. In other words, the population genetics did not merely suggest that ESR1 expression tracks with fibrosis severity; it suggested that inherited differences in ESR1 activity genuinely shift fibrosis risk, making the receptor a credible therapeutic target rather than a bystander.

Genetic plausibility still needed a physical mechanism, and for that the researchers turned to molecular modeling. Molecular docking placed praziquantel within ESR1’s ligand-binding pocket, and molecular dynamics simulations confirmed that the drug-receptor complex remains stable over simulated time, with the small molecule maintaining consistent contacts with the receptor. The modeling cannot prove binding in a living cell on its own, but it established that praziquantel and ESR1 are chemically compatible partners, setting the stage for functional tests.

The most revealing layer of the study came from single-cell RNA sequencing of liver tissue. Analyzing the data with the Seurat framework, the researchers mapped ESR1 expression across the liver’s cellular ecosystem and found it broadly present, but with a telling pattern: quiescent hepatic stellate cells and a cytokine-producing stellate cell subset, dubbed cyHSCs, expressed significantly higher levels of ESR1 than activated myofibroblastic stellate cells, or myHSCs. The receptor that praziquantel appears to target is most abundant precisely in the cell states that fibrosis threatens to destroy or corrupt, suggesting the drug may act by reinforcing the quiescent, non-fibrogenic identity of these cells.

To probe what ESR1 actually does inside stellate cells, the team ran virtual knockout experiments using scTenifoldKnk, a computational method that predicts how silencing a gene rewires a single-cell gene regulatory network. Removing ESR1 in silico disrupted a network whose most prominent casualties included RXFP1, EGFLAM, and several mitochondrial genome components such as MT-CO1, MT-CO2, and MT-ND4L. Pathway analysis of the perturbed genes showed strong enrichment in oxidative phosphorylation and immune signaling, including T cell receptor signaling. The picture that emerges is of ESR1 as an orchestrator of mitochondrial metabolic homeostasis and immunoregulatory signaling in stellate cells; when it is lost, the cells’ energy metabolism falters and inflammatory programs gain ground, conditions that favor fibrogenic activation.

Computational predictions, however convincing, demand wet-lab confirmation, and the researchers provided it. Working with LX-2 cells, a widely used human hepatic stellate cell line, they silenced ESR1 and tested whether praziquantel could still exert its anti-fibrotic effects. It could not, at least not fully. The loss-of-function experiments confirmed that ESR1 is functionally required for the drug’s benefit, closing the loop between network prediction, genetic causality, structural modeling, and cellular mechanism. The authors propose that praziquantel activates ESR1, which in turn maintains a protective gene network preserving mitochondrial function and immune balance in stellate cells, thereby blocking their transition into collagen-secreting myofibroblasts.

The implications extend well beyond one drug and one receptor. Repurposing praziquantel, whose safety profile is established through mass administration programs across the tropics, could dramatically shorten the path to clinical testing for an anti-fibrotic indication compared with developing a novel molecule from scratch. More broadly, the study showcases an integrative strategy, combining network pharmacology, Mendelian randomization, colocalization, molecular dynamics, single-cell transcriptomics, virtual knockout, and in vitro validation, that can elevate a computational hypothesis to a mechanistically grounded candidate therapy. ESR1 modulation itself may prove a fruitful therapeutic direction independent of praziquantel, and the identification of rs3020404 as a candidate functional variant offers a genetic handle for stratifying patients most likely to benefit. Much work remains: the findings rest heavily on human cell lines and public datasets, and animal models and clinical trials will be needed to confirm that the mechanism operates in scarred livers in living patients. But the study reframes a familiar antiparasitic as a plausible antifibrotic and hands hepatology a genetically validated, druggable target at the heart of the stellate cell’s decision to scar or stay quiet.

Subject of Research: Network pharmacology and experimental validation identifying ESR1 as the target through which praziquantel alleviates liver fibrosis

Article Title: Praziquantel targeting ESR1 to alleviate liver fibrosis: a comprehensive network analysis insight

Article References: Lu, Z., Kong, D., He, F., Lv, H., Guo, Y., Xia, X., & Zhang, G. (2026). Praziquantel targeting ESR1 to alleviate liver fibrosis: a comprehensive network analysis insight. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08941-1

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08941-1

Keywords: praziquantel, liver fibrosis, ESR1, hepatic stellate cells, Mendelian randomization, molecular docking, single-cell RNA sequencing, drug repurposing, mitochondrial function, hepatology, gene regulatory network, LX-2 cells