Impact of Different Methods of Induction of Cellular Hypoxia: Focus on Protein Homeostasis Signaling Pathways and Morphology of C2C12 Skeletal Muscle Cells Differentiated into Myotubes

Abstract

Hypoxia, occurring in several pathologies, has deleterious effects on skeletal muscle, in particular on protein homeostasis. Different induction methods of hypoxia are commonly used in cellular models to investigate the alterations of muscular function consecutive to hypoxic stress. However, a consensus is not clearly established concerning hypoxia induction methodology. Our aim was to compare oxygen deprivation with chemically induced hypoxia using cobalt chloride (CoCl 2 ) or desferrioxamine (DFO) on C2C12 myotubes which were either cultured in hypoxia chamber at an oxygen level of 4% or treated with CoCl 2 or DFO. For each method of hypoxia induction, we determined their impact on muscle cell morphology and on expression or activation status of key signaling proteins of synthesis and degradation pathways. The expression of HIF-1α increased whatever the method of hypoxia induction. Myotube diameter and protein content decreased exclusively for C2C12 myotubes submitted to physiological hypoxia (4% O 2 ) or treated with CoCl 2 . Results were correlated with a hypophosphorylation of key proteins regulated synthesis pathway (Akt, GSK3-β and P70S6K). Similarly, the phosphorylation of FoxO1 decreased and the autophagy-related LC3-II was overexpressed with 4% O 2 and CoCl 2 conditions. Our results demonstrated that in vitro oxygen deprivation and the use of mimetic agent such as CoCl 2 , unlike DFO, induced similar responses on myotube morphology and atrophy/hypertrophy markers. T…