Exposure to oxidative insult
(H2O2) or cigarette smoke extract (CSE)
results in a similar degree of wasting in C2C12 myotubes without
cellular inflammation
To further dissect the importance of oxidative stress on muscle
dysfunction, we compared the direct impact of a ROS,
H2O2and CSE on C2C12 myotubes. Both H2O2 and
CSE exposure resulted in a similar dose-dependent reduction in myotube
size (Figure 3A–B). Unlike that of the higher dose, the reduction in
myotube size induced by low doses of
H2O2 (5 μM) or CSE (10%) did not impact
cell viability (Figure 3C and H). In line with the presence of oxidative
stress, exposure to
H2O2(10 and 100 μM) elicited a robust expression of Nox2 which is
involved in the formation of ROS in muscle (Figure 3D) (Sakellariou et
al., 2013). Unlike that of H2O2, no
significant induction of Nox2 expression was observed under
sub-maximal dosages of CSE (Figure 3I). Meanwhile, the expression of
glutathione peroxidase 1 (Gpx1 ), a detoxifying enzyme that
scavenges H2O2, was unaltered by either
of the stimuli (Figure 3E and J). Noteworthy, the maximal concentration
of either H2O2 or CSE was capable of
eliciting a cellular inflammatory response evidenced by the increasedIl-6 gene expression (Figure 3F and K) and release of IL-6
(Figure 3G and L), but not at their respective sub-maximal
concentrations. This suggests oxidative stress accounts for some of the
deleterious effects of CSE and this oxidative stress-driven myofiber
wasting can occur without any detectable cellular inflammation
recapitulating that of our in vivo model.