P29

Background Skeletal muscle regeneration is governed by complex cellular signaling processes. Proliferation of skeletal myoblasts is a key initial event in muscle regeneration and has been largely related to mammalian target of rapamycin (mTOR) signal transduction mechanisms. Although the precise underlying signaling remains incompletely understood, the role of nitric oxide (NO) in cell cycle regulation is well-appreciated. Nitrite, the oxidation product of NO, is regarded as a stable source for NO-like bioactivity in cases when the oxygen-dependent NO-synthases become dysfunctional. Whether nitrite itself has the potential to affect myoblast proliferation and metabolic activity under normoxic conditions with or without activation of the NO/cyclic guanosine monophosphate (cGMP) pathway is not known. Methods The influence of nitrite and NO on C 2 C 12 myoblast proliferation was observed in cultures grown in DMEM + 10% FCS at 37 °C/5% CO 2 , with or without sodium nitrite, NO-donor DETA-NONOate, NO-scavenger cPTIO, soluble guanylatecyclase (sGC) inhibitor ODQ, or mTOR inhibitor rapamycin. Neutral red staining, propodium iodide staining for cell cycle analysis, WST-8 viability assay, mTOR phosphorylation activity assay and intracellular cGMP measuerements were performed according to modified manufacturer’s protocols. Results We here show that nitrite increases proliferation and metabolic activity of murine cultured myoblasts dose-dependently in normoxia. This effect is not abolished by the NO scavenger 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) and does not affect intracellular cGMP levels, implicating a cGMP-independent mechanism. Nitrite circumvents the rapamycin induced attenuation of myoblast proliferation and enhances mTOR phosphorylation activity. Conclusion Our results provide evidence for a novel potential physiological and therapeutic approach of nitrite in skeletal muscle regeneration processes under normoxia independent of NO and cGMP. Disclosure Nothing to disclose.