Mitochondrial protein S-nitrosation protects against ischemia reperfusion-induced denervation at neuromuscular junction in skeletal muscle

Abstract

Deterioration of neuromuscular junction (NMJ) integrity and function is causal to muscle atrophy and frailty, ultimately hindering quality of life and increasing the risk of death. In particular, NMJ is vulnerable to ischemia reperfusion (IR) injury when blood flow is restricted followed by restoration. However, little is known about the underlying mechanism(s) and hence the lack of effective interventions. New evidence suggests that mitochondrial oxidative stress plays a causal role in IR injury, which can be precluded by enhancing mitochondrial protein S-nitrosation (SNO). To elucidate the role of IR and mitochondrial protein SNO in skeletal muscle, we utilized a clinically relevant model and showed that IR resulted in significant muscle and motor nerve injuries with evidence of elevated muscle creatine kinase in the serum, denervation at NMJ, myofiber degeneration and regeneration, as well as muscle atrophy. Interestingly, we observed that neuromuscular transmission improved prior to muscle recovery, suggesting the importance of the motor nerve in muscle functional recovery. Injection of a mitochondria-targeted S-nitrosation enhancing agent, MitoSNO, into ischemic muscle prior to reperfusion reduced mitochondrial oxidative stress in the motor nerve and NMJ, attenuated denervation at NMJ, and resulted in accelerated functional recovery of the muscle. These findings demonstrate that enhancing mitochondrial protein SNO protects against IR-induced denervation at NMJ in skeletal muscle and accelerates functional regeneration. This could be an efficacious intervention for protecting neuromuscular injury under the condition of IR and other related pathological conditions.

Critical Limb Ischemia Induces Remodeling of Skeletal Muscle Motor Unit and Myonuclear- and Mitochondrial-Domains

“…Analogously, ischemic insults, which disrupt the perfusion to skeletal muscle, delays the initial response to injury and influences the outcome of muscle regeneration, as demonstrated by the continuous regeneration 56 days following HLI. While previous reports have shown a delayed and prolonged regenerative response to ischemia through centrally nucleated fibers up to day 14 [12], accreted myonuclei up to day 14 [40], and denervation up to day 28 [20], our data indicates that the regeneration of these niche components are sustained for at least 56 days. Nonetheless, in order to discern when these ischemic tissues are fully repaired, further testing with extended time points is required.…”

“…In support of this notion, some of the axonal guidance factors are known to possess angiogenic properties [17], and other well-known angiogenic factors, such as vascular endothelial growth factor (VEGF), guide Schwann cell-mediated peripheral nerve regeneration [18]. As such, when blood flow is restricted in ischemic injury, motor neurons undergo rapid Wallerian degeneration, and their regenerative response is activated [19,20]. Moreover, a recent report showed that the regeneration of the motor neuron and its corresponding neuromuscular synapses are in part linked to an increase in activation of MuSC and myogenesis [21].…”

Mitochondrial ROS cause motor deficits induced by synaptic inactivity: Implications for synapse pruning

“…MnTnBuOE-2-PyP 5+ blocked mitochondrial ROS to significantly reduce MitoPQ induced motor deficits; suggesting mitochondrial ROS production is the key proximal event. A related corollary: MitoSNO rescues ischemia-reperfusion injury induced denervation by blocking mitochondrial ROS [76] .…”

When motor unit expansion in ageing muscle fails, atrophy ensues

“…Whereas a recent study suggests neuromuscular junction alterations (e.g. fragmentation of the acetylcholine receptor cluster on the muscle fibre) do not occur with ageing in human muscle (Jones et al 2017), the results of this recent study are confounded by the source material which largely came from the amputated limbs of individuals with a history of peripheral vascular disease, noting that ischaemia-reperfusion is known to cause neuromuscular junction degeneration (Tu et al 2017;Wilson et al 2018). Indeed, other studies of neuromuscular junction morphology with ageing in human skeletal muscle (Oda, 1984;Wokke et al 1990) have observed similar fragmentation patterns to that seen in rodent models of ageing (Valdez et al 2012).…”

“…; Wilson et al . ). Indeed, other studies of neuromuscular junction morphology with ageing in human skeletal muscle (Oda, ; Wokke et al .…”