Fig.2.

The p53 inhibitor pifithrin-alpha decreased both spontaneous and staurosporine-induced caspase activity in MDC1A myogenic cells. A. Cultures of MDC1A (red lines) and healthy control (green lines) myogenic cells were incubated with pifithrin-alpha at the indicated concentrations and assayed for caspase 3/7 (DEVDase) enzymatic activity after four days in differentiation medium. Caspase values were normalized so that the average of the untreated healthy controls = 1. Error bars = SE; ^**P < 0.01 by ANOVA to compare values at 0, 10μM, and 25μM; n = 3 for cells of each individual donor. B. As indicated, cells were either left untreated or treated with 25μM pifithrin-alpha as in panel A either without staurosporine (STS) or with staurosporine at 1μM for the final 4.5 h prior to harvest. Pifithrin-alpha treatment reduced both spontaneous and staurosporine-induced caspase activity in MDC1A cultures. Error bars = SE; ^**P < 0.01 by ANOVA; n as indicated. Healthy control cells included 15Vbic, 16Ubic, and 21Ubic. MDC1A cells included 38/03, 50/04, and 96/04. C, D. Treatment with staurosporine (+STS) at 1μM for 4.5 h hours generated morphological abnormalities of nuclei (blue) including blebbing and fragmentation (e.g., arrows in panel C) and disrupted the striated organization of myosin heavy chain (MyHC, green) in MDC1A (50/04) cultures (panel C). However, these staurosporine-induced changes were largely eliminated when the p53 inhibitor pifithrin-alpha (+pifithrin-α) at 25μM was included in combination with staurosporine (panel D). Bar in panel C = 20μm.