Background: Augmenter of liver regeneration (ALR) protects liver from various injuries, however, the association of ALR with liver fibrosis, particularly its effect on hepatic stellate cells (HSC), remains unclear. In this study, we investigated the impact of ALR on the activation of HSC, a pivotal event in occurrence of liver fibrosis.
Methods: Liver fibrosis was induced in vivo in mice with heterozygous ALR knockdown (ALR-KD) by administration of CCl4 or bile duct ligation. The effect of ALR-KD and ALR-overexpression on liver fibrosis was studied in mice and in HSC cells as well.
Results: Hepatic collagen deposition and expression of α-smooth muscle actin (α-SMA) were significantly increased in the ALR-KD mice compared to wild-type mice. In vitro, ALR-shRNA resulted in the activation of HSC cell line (LX-2). Furthermore, ALR-shRNA promoted LX-2 cell migration, accompanied by increased filamentous actin (F-actin) assembly. The ALR-KD-mediated increase in HSC migration was associated with mitochondrial fusion, resulting in mitochondria elongation and enhancing ATP production. In contrast, ALR transfection (ALR-Tx) decelerated HSC migration and inhibited F-actin assembly, concomitantly enhancing mitochondrial fission and reducing ATP synthesis. Mechanically, stimulation of HSC migration by ALR-shRNA was attributed to the increased mitochondrial Ca2+ influx in HSCs. Treatment of ALR-shRNA-cells with Ruthenium Red (RuR), a specific inhibitor of mitochondrial calcium uniporter (MCU), significantly suppressed mitochondrial Ca2+ influx, HSC migration, mitochondrial fusion and ATP production. ALR-KD-induced HSC migration was verified in vitro in primary mouse HSCs.
Conclusion: Inhibition of ALR expression aggravates liver fibrosis, probably via promoting HSC migration and mitochondrial fusion.
Keywords: Augmenter of liver regeneration; Hepatic stellate cell; Hepatic stimulator substance; Liver fibrosis; Mitochondrial dynamics.
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