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.