Figure 5

PLD and PA protect L6 myotubes from dexamethasone-induced atrophy. (A) Differentiated myotubes were left untreated, or were treated with 20 μM dexamethasone alone or in the presence of GFP-, or PLD1-, or PLD2-adenovirus for 2 days. Myotube area was then assessed. Results are shown as means ± SE of n = 10. ***: different from control, p < 0.001. ⁺⁺⁺: different from dexamethasone and GFP-adenovirus treated cells, p < 0.001; NS: not significantly different from dexamethasone and GFP-adenovirus treated cells. (B) Creatine kinase activity was measured in differentiated myotubes treated as above. Means ± SE of n = 4 replicates are shown. ***: different from control, p < 0.001; ⁺⁺⁺: different from GFP-adenovirus infected cells treated with dexamethasone, p < 0.001. (C) Myotubes were infected with GFP- or PLD1-adenovirus and simultaneously treated with dexamethasone as above, in the presence or absence of FIPI. Myotube area was measured and results are shown as means ± SE of n = 5 to 10. **: different from GFP-adenovirus infected cells, p < 0.01; *: p < 0.05; ⁺⁺⁺: different from PLD1-adenovirus infected cells, p < 0.001. (D) Myotubes were treated for 2 days with 100 μM dexamethasone in the presence or absence of 100 μM PA, and myotube area was assessed. Means ± SE of n = 6 to 8 are shown. ***: different from control, p < 0.0001; ⁺⁺⁺: different from dexamethasone treated cells, p < 0.0001. (E) CK activity was measured in myotubes treated as above. Means ± SE of n = 4 are shown. ***: different from control, p < 0.0001; ⁺⁺: different from dexamethasone treated cells, p < 0.01. Note that a lower dexamethasone concentration was used in the experiments of panels A, B, C, to prevent an excessive stress of the cells submitted to an adenoviral infection.