Downregulation of SLC32A1 Mediates the PAI-1 Pathway in Alleviating Hepatic Stellate Cell Activation and Liver Fibrosis

Liver fibrosis (LF) is a progressive chronic liver disease characterized by excessive accumulation of extracellular matrix, which is primarily driven by the abnormal activation of hepatic stellate cells (HSCs). Gamma-aminobutyric acid (GABA) receptors have been reported to inhibit HSC activation, while solute carrier family 32 member 1 (SLC32A1), a GABA transporter protein, is speculated to be involved in LF regulation, though its specific role and underlying molecular mechanisms remain unclear. Therefore, the present study aimed to investigate the role of SLC32A1 in HSC activation and LF progression, as well as to elucidate its downstream regulatory mechanisms. Our results showed that SLC32A1 levels were elevated in LF patients. In vivo experiments demonstrated that SLC32A1 knockout alleviated CCl4-induced LF in mice. In vitro studies revealed that SLC32A1 was specifically upregulated in TGF-β1-stimulated LX-2 cells (HSCs), but not in THLE-2, THP-1, or LSECs. SLC32A1 overexpression exacerbated LX-2 activation and fibrosis, while its knockdown reversed TGF-β1-induced effects. Mechanistically, SLC32A1 promoted GABA and glycine exocytosis in LX-2 cells. However, neither exogenous nor endogenous GABA/glycine affected the reduced activation mediated by SLC32A1 knockdown, prompting investigation into alternative pathways. Among 55 differentially expressed genes, PAI-1 showed the largest difference. Critically, PAI-1 overexpression reversed the decrease in activation and fibrosis induced by SLC32A1 knockdown. Collectively, these findings demonstrate that downregulation of the SLC32A1-mediated PAI-1 pathway, rather than the GABA pathway, attenuates HSC activation and LF, highlighting SLC32A1 as a potential novel therapeutic target for LF.