Chronic Contractile Activity Remediates Lysosomal Dysfunction in a Muscle Cell Lysosomal Disease Model

Lysosomes are important organelles for the degradation of unwanted biomolecules via autophagy. Lysosomal dysfunction is apparent in ageing tissues, and can cause various neurodegenerative diseases. It is imperative to understand the mechanisms and implications of lysosomal malfunction and to find strategies to ameliorate diseases. To investigate this, we induced lysosomal dysfunction with Bafilomycin A1 (BAF), a drug that hinders lysosomal acidification by blocking vATPase-mediated proton pumping, in myoblasts and myotubes. Myotubes were subjected to chronic contractile activity (CCA) to mimic "exercise" to evaluate any therapeutic potential and reversal of pathophysiology. Induced lysosomal dysfunction was evident from impaired processing of the protease cathepsin B, enhanced lysosomal accumulation and increased autophagic markers Lamp1, p62, and the LC3II/I ratio. BAF attenuated lysosomal protease degradation measured using the substrate DQ-BSA in both myoblasts and myotubes. Many of the adverse effects generated by BAF in myotubes were reversed by CCA, manifested by a decrease in immature cathepsin B, a down-regulation of Lamp1, p62, LC3II/I and partial restoration of lysosomal protein degradation enzymatic capacity. To investigate further improvements in lysosomal function in a healthy cellular model, we treated myotubes with C1, a curcumin analogue. C1 decreased Lamp1, p62 and the LC3II/I ratio, all of which indicate improved lysosomal function and autophagosome clearance with a greater lysosomal ability to degrade substrates. Additionally, C1 was able to mimic the improved mitochondrial content induced by CCA. Thus, contractile activity and curcumin analogues may provide useful therapeutic potential to resuscitate lysosomal function, improve muscle health and ameliorate lysosome-mediated diseases. NEW AND NOTEWORTHY: This study explores the potential of chronic contractile activity (CCA) in reversing the compromised lysosomes caused by the disruption of lysosomal acidification in myotubes. Remarkably, CCA mitigated the effects of Bafilomycin A1-induced lysosomal dysfunction, enhancing protease activity and increased mitochondrial content. Treatment of myotubes with the curcumin analogue C1 reduced lysosomal accumulation and enhanced mitochondrial content suggesting that contractile activity-based interventions and small-molecule modulators of lysosomal pathways may represent promising complementary strategies for treating lysosome-related diseases and enhancing muscle health.