LASS2 alleviates liver fibrosis by interacting with THBS1, TFRC, and APOE to inhibit TGF-β1 signaling and ferroptosis, and by reshaping the hepatocyte lipid secretome to suppress paracrine HSC activation.

BACKGROUND

Liver fibrosis (LF) lacks effective therapies. Longevity assurance homolog 2 (LASS2), a key ceramide synthase, contributes to liver homeostasis, but its role in LF remain unclear.

METHODS

Bioinformatics revealed LASS2 correlation with classic fibrotic factors, and its expression was assessed in fibrotic mouse livers and activated LX-2 cells. Gain- and loss-of-function studies were performed in vivo (liver-specific AAV) and in vitro (recombinant adenovirus), followed by phenotypic and mechanistic analyses. Protein interactions were mapped by proteomics and co-immunoprecipitation (co-IP), and direct interactions were validated by protein-protein docking, co-IP/Western blot, immunofluorescence colocalization, and proximity ligation assay (PLA). Hepatocyte conditioned medium (CM) experiments combined with ELISA and targeted lipidomics were performed to dissect LASS2-mediated paracrine signaling.

RESULTS

LASS2 overexpression attenuated fibrogenesis, regulated mtROS in an activation-dependent manner, promoted apoptosis in both quiescent and activated hepatic stellate cells (HSCs), and suppressed EMT. Mechanistically, LASS2 directly interacted with thrombospondin 1 (THBS1), transferrin receptor (TFRC), and apolipoprotein E (APOE). These interactions correlated with inhibition of TGF-β1/Smad2/3 signaling, remodeled lipid metabolism, coordinately suppresses ferroptosis and promotes apoptosis in activated HSCs, thereby attenuating liver fibrosis. Notably, LASS2 overexpression in hepatocytes reduced CM levels of TGF-β1 and induced global lipidomic remodeling, characterized by downregulation of pro-fibrotic lysophospholipids (LPC/LPE/LPI), phosphatidic acid (PA), and ceramides (Cer), alongside upregulation of specific sphingomyelin (SM) and BMP species, creating an anti-fibrotic paracrine milieu.

CONCLUSIONS

LASS2 acts as a dual-function metabolic-signaling integrator: it directly engages THBS1, TFRC, and APOE to control TGF-β1 signaling and ferroptosis, while also remodeling the hepatocyte-derived paracrine lipid landscape to inhibit HSC activation. Targeting LASS2 thus represents a promising anti-fibrotic strategy.