Fig. 3.

MAO inhibition prevents mitochondrial dysfunction in myoblasts from patients affected by ColVI myopathies. (A) Rotenone-induced mitochondrial dysfunction. The upper, middle, and lower traces refer to the UCMD patients P1 and P2, and the BM patient B5, respectively. Myoblasts were loaded with TMRM (25 nM) to monitor the mitochondrial membrane potential by fluorescence microscopy. When indicated by arrows, rotenone (R, 2 μM) and FCCP (4 μM) were added (all traces) in the absence of further treatments (untreated) or after treatment for 40 min with pargyline (Parg-treated, 100 µM). Each trace corresponds to one cell. (B) Tyramine-induced mitochondrial dysfunction. Myoblasts from UCMD (P2 and P4), BM (P5) patients, and healthy donors (Ctrl) were incubated as described in Fig. 2A and then loaded with TMRM (25 nM). At the end of each experiment the uncoupling agent FCCP (4 μM) was added. The difference of fluorescence intensities obtained before and after FCCP is reported in the graph. Values are the mean of at least four independent experiments. *P < 0.05 for Tyr-treated vs Basal; #P < 0.05 for Parg + Tyr-treated vs Tyr-treated myoblasts. (C) CsA does not prevent mitochondrial dysfunction induced by tyramine. Myoblasts from a UCMD patient (P2) were incubated for 1 h with tyramine (Tyr, 20 µM, black bars) in the absence or in the presence of CsA (1.6 μM, as a 20 min pretreatment) or pargyline (Parg, 100 μM, as a 20 min pretreatment) and then loaded with TMRM (25 nM) to assess the mitochondrial membrane potential as described in panel B. All the treatments were also performed in the absence of tyramine (w/o Tyr, gray bars). Values are the mean of at least four independent experiments. *P < 0.05 for Tyr-treated vs Tyr-untreated myoblasts; #P < 0.05 for Parg + Tyr-treated vs Tyr-treated myoblasts.