Pyrroloquinoline quinone attenuates cachexia-induced muscle atrophy via suppression of reactive oxygen species

Cachexia, a wasting syndrome, is most commonly observed in individuals with advanced cancer including lung cancer, esophageal cancer, liver cancer, etc. The characteristic sign of cachexia is muscle atrophy. To date, effective countermeasures have been still deficiency to alleviate muscle atrophy. Reactive oxygen species (ROS) are important regulators of muscle atrophy. Therefore, the effects of a naturally antioxidant, pyrroloquinoline quinone (PQQ), were explored on muscle atrophy induced by cachexia in the present study.

Tumor necrosis factor-α (TNF-α) induced C2C12 myotubes atrophy model was constructed. The atrophied C2C12 myotubes were dealt with the presence or absence of N-acetyl-L-cysteine (NAC, an antioxidant for ROS abolition) (5 mM) or PQQ (80 µM) for 24 hours. ROS content was determined by dichlorodihydrofluorescein diacetate (DCFH-DA) staining. The diameter of myotubes was analyzed by myosin heavy chain (MHC) staining. The protein levels of MHC, muscle atrophy F-box (MAFbx) and muscle RING finger-1 (MuRF-1) in each group were observed by Western blotting.

First, ROS generation was enhanced in C2C12 myotubes treated with TNF-α. NAC treatments significantly avoided the reduction in the diameter of C2C12 myotubes, and concomitantly increased MHC levels, and decreased ROS contents, MuRF1 and MAFbx levels. These data suggested that the increased ROS induced by TNF-α might play a central role in muscle wasting. PQQ (a naturally occurring antioxidant) administration inhibited C2C12 myotubes atrophy induced by TNF-α, as evidenced by the increase of the diameter of C2C12 myotubes, together with increased MHC levels and decreased ROS, MAFbx and MuRF-1 levels.

PQQ resists atrophic effect dependent on, at least in part, decreased ROS in skeletal muscle treated with TNF-α.