Authors:

Ahmed Bakheet

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About Paper:

Background: Lysosomes are critical for degrading cellular macromolecules, thereby maintaining cellular homeostasis. In rodents fed ethanol, lysosomes are downregulated, leading to accumulation of undegraded polymeric substrates. However, the connection between these changes in human alcohol-associated liver disease (ALD) is not fully understood. Here, we investigated lysosomal alterations in livers of human subjects with alcohol-induced hepatitis (AH) and cirrhosis (AC) to assess the role of lysosomes in ALD pathology. Methods: Livers of normal human subjects or those with AH or AC were subjected to immunostaining, RT-PCR, and Western blot (WB) analyses. Results: Compared with normal livers, mRNA levels encoding Transcription Factor EB (TFEB), which regulates autophagy and lysosome biogenesis, were elevated 4.5-fold in livers with AH and by 2.5-fold in those with AC. The upregulation of TFEB mRNA was associated with increased expression of two of its targets, PGC1α and VAT6V1H (acidifies lysosomes). In AH livers, mRNAs encoding the lysosomal-associated membrane proteins LAMP1 and LAMP2 were unchanged. However, in AC livers, both LAMP1 and LAMP2A mRNA levels were elevated, compared with normal livers. WB analyses of AH and AC liver homogenates revealed significantly higher levels of TFEB, the lysosomal protease cathepsin B (Cat B), and the lysosome damage-sensing protein Galectin-3 (Gal-3). Compared with normal livers, LAMP1 levels were lower in AH livers but were higher in AC livers. Immunostaining showed enhanced TFEB expression in both the cytoplasm and nuclei of hepatocytes of AH livers. Additionally, Cat B, Gal-3, and the autophagosome marker LC3B, showed increased staining in hepatocytes of AH livers compared with normal livers. In normal livers, LAMP1/2 and Cat B appeared as small, punctate structures, whereas in AH livers, they were larger and aggregated. In AH livers, Cat B was widely distributed throughout the entire hepatocyte, and it exhibited enhanced interaction with lipid droplet (LD) membranes. Gal-3, LC3B, and P62 were also associated with LD membranes. High colocalization of cat B and LAMP2 with Gal-3 was observed in AH livers. Conclusion: Our findings suggest that in human ALD, there is enhanced lysosome biogenesis, and this could be a response to increased processing of substrates like lipids. This may lead to lysosomal substrate accumulation, damage, and leakage, leading to hepatocyte injury, thereby contributing to ALD pathogenesis.

Source:

Auburn University / College of Veterinary Medicine / 2025

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Co-authors:

Ahmed Bakheet