Reactive nitrogen species induce nuclear factor-κB-mediated protein degradation in skeletal muscle cells

Recently, a role for NF-κB in upregulation of proteolytic systems and protein degradation has emerged. Reactive nitrogen species (RNS) have been demonstrated to induce NF-κB activation. The aim of this study was to investigate whether RNS caused increased proteolysis in skeletal muscle cells, and whether this process was mediated through the activation of NF-κB. Fully differentiated L6 myotubes were treated with NO donor SNAP, peroxynitrite donor SIN-1, and authentic peroxynitrite, in a time-dependent manner. NF-κB activation, the activation of the ubiquitin-proteasome pathway and matrix metalloproteinases, and the levels of muscle-specific proteins (myosin heavy chain and telethonin) were investigated under the conditions of nitrosative stress. RNS donors caused NF-κB activation and increased activation of proteolytic systems, as well as the degradation of muscle-specific proteins. Antioxidant treatment, tyrosine nitration inhibition, and NF-κB molecular inhibition were proven effective in downregulation of NF-κB activation and slowing down the degradation of muscle-specific proteins. Peroxynitrite, but not NO, causes proteolytic system activation and the degradation of muscle-specific proteins in cultured myotubes, mediated through NF-κB. NF-κB inhibition by antioxidants, tyrosine nitration, and molecular inhibitors may be beneficial for decreasing the extent of muscle damage induced by RNS.