title: Nitrite circumvents canonical cGMP signaling to enhance proliferation of myocyte precursor cells.
abstract: Skeletal muscle tissue has a remarkable high regenerative capacity. The underlying cellular events are governed by complex signaling processes, and the proliferation of skeletal myoblasts is a key initial event. The role of nitric oxide (NO) in cell cycle regulation is well-appreciated. Nitrite, an NO oxidation product, is a stable source for NO-like bioactivity particularly in cases when oxygen shortage compromises NO-synthases activity. Although numerous studies suggest that nitrite effects are largely related to NO-dependent signaling, emerging evidence also implicates that nitrite itself can activate protein pathways albeit under physiological, normoxic conditions. This includes a recently demonstrated cyclic guanosine monophosphate-(cGMP)-independent enhancement of endothelial cell proliferation. Whether nitrite itself has the potential to affect myoblast proliferation and metabolism with or without activation of the canonical NO/cGMP pathway to subsequently support muscle cell regeneration is not known. Here we show that nitrite increases proliferation and metabolic activity of murine cultured myoblasts dose-dependently. This effect is not abolished by the NO scavenger 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimida-zoline-1-oxyl-3 oxide and does not affect intracellular cGMP levels, implicating a cGMP-independent mechanism. Nitrite circumvents the rapamycin induced attenuation of myoblast proliferation and enhances mTOR activity. 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.
authors.affiliation: Division of Cardiology, Pulmonology and Vascular Medicine, Department of Medicine, Medical Faculty, University Hospital Duesseldorf, Moorenstrasse 5, 40225, Düsseldorf, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Totzeck
authors.forename: Andreas
authors.initials: A
authors.lastname: Schicho
authors.forename: Pia
authors.initials: P
authors.lastname: Stock
authors.forename: Malte
authors.initials: M
authors.lastname: Kelm
authors.forename: Tienush
authors.initials: T
authors.lastname: Rassaf
authors.forename: Ulrike B
authors.initials: UB
authors.lastname: Hendgen-Cotta
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D006152:Cyclic GMP / Q000378:metabolism*; D051379:Mice; D032342:Muscle Cells / Q000166:cytology* / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology; D012977:Sodium Nitrite / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D009569:Nitric Oxide; D058570:TOR Serine-Threonine Kinases; D006152:Cyclic GMP; D012977:Sodium Nitrite; D020123:Sirolimus